43692 lines
1.5 MiB
43692 lines
1.5 MiB
\input texinfo @c -*-texinfo-*-
|
||
@c Copyright (C) 1988-2018 Free Software Foundation, Inc.
|
||
@c
|
||
@c %**start of header
|
||
@c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
|
||
@c of @set vars. However, you can override filename with makeinfo -o.
|
||
@setfilename gdb.info
|
||
@c
|
||
@c man begin INCLUDE
|
||
@include gdb-cfg.texi
|
||
@c man end
|
||
@c
|
||
@settitle Debugging with @value{GDBN}
|
||
@setchapternewpage odd
|
||
@c %**end of header
|
||
|
||
@iftex
|
||
@c @smallbook
|
||
@c @cropmarks
|
||
@end iftex
|
||
|
||
@finalout
|
||
@c To avoid file-name clashes between index.html and Index.html, when
|
||
@c the manual is produced on a Posix host and then moved to a
|
||
@c case-insensitive filesystem (e.g., MS-Windows), we separate the
|
||
@c indices into two: Concept Index and all the rest.
|
||
@syncodeindex ky fn
|
||
@syncodeindex tp fn
|
||
|
||
@c readline appendices use @vindex, @findex and @ftable,
|
||
@c annotate.texi and gdbmi use @findex.
|
||
@syncodeindex vr fn
|
||
|
||
@c !!set GDB manual's edition---not the same as GDB version!
|
||
@c This is updated by GNU Press.
|
||
@set EDITION Tenth
|
||
|
||
@c !!set GDB edit command default editor
|
||
@set EDITOR /bin/ex
|
||
|
||
@c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
|
||
|
||
@c This is a dir.info fragment to support semi-automated addition of
|
||
@c manuals to an info tree.
|
||
@dircategory Software development
|
||
@direntry
|
||
* Gdb: (gdb). The GNU debugger.
|
||
* gdbserver: (gdb) Server. The GNU debugging server.
|
||
@end direntry
|
||
|
||
@copying
|
||
@c man begin COPYRIGHT
|
||
Copyright @copyright{} 1988-2018 Free Software Foundation, Inc.
|
||
|
||
Permission is granted to copy, distribute and/or modify this document
|
||
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
any later version published by the Free Software Foundation; with the
|
||
Invariant Sections being ``Free Software'' and ``Free Software Needs
|
||
Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
|
||
and with the Back-Cover Texts as in (a) below.
|
||
|
||
(a) The FSF's Back-Cover Text is: ``You are free to copy and modify
|
||
this GNU Manual. Buying copies from GNU Press supports the FSF in
|
||
developing GNU and promoting software freedom.''
|
||
@c man end
|
||
@end copying
|
||
|
||
@ifnottex
|
||
This file documents the @sc{gnu} debugger @value{GDBN}.
|
||
|
||
This is the @value{EDITION} Edition, of @cite{Debugging with
|
||
@value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
|
||
@ifset VERSION_PACKAGE
|
||
@value{VERSION_PACKAGE}
|
||
@end ifset
|
||
Version @value{GDBVN}.
|
||
|
||
@insertcopying
|
||
@end ifnottex
|
||
|
||
@titlepage
|
||
@title Debugging with @value{GDBN}
|
||
@subtitle The @sc{gnu} Source-Level Debugger
|
||
@sp 1
|
||
@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
|
||
@ifset VERSION_PACKAGE
|
||
@sp 1
|
||
@subtitle @value{VERSION_PACKAGE}
|
||
@end ifset
|
||
@author Richard Stallman, Roland Pesch, Stan Shebs, et al.
|
||
@page
|
||
@tex
|
||
{\parskip=0pt
|
||
\hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
|
||
\hfill {\it Debugging with @value{GDBN}}\par
|
||
\hfill \TeX{}info \texinfoversion\par
|
||
}
|
||
@end tex
|
||
|
||
@vskip 0pt plus 1filll
|
||
Published by the Free Software Foundation @*
|
||
51 Franklin Street, Fifth Floor,
|
||
Boston, MA 02110-1301, USA@*
|
||
ISBN 978-0-9831592-3-0 @*
|
||
|
||
@insertcopying
|
||
@end titlepage
|
||
@page
|
||
|
||
@ifnottex
|
||
@node Top, Summary, (dir), (dir)
|
||
|
||
@top Debugging with @value{GDBN}
|
||
|
||
This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
|
||
|
||
This is the @value{EDITION} Edition, for @value{GDBN}
|
||
@ifset VERSION_PACKAGE
|
||
@value{VERSION_PACKAGE}
|
||
@end ifset
|
||
Version @value{GDBVN}.
|
||
|
||
Copyright (C) 1988-2018 Free Software Foundation, Inc.
|
||
|
||
This edition of the GDB manual is dedicated to the memory of Fred
|
||
Fish. Fred was a long-standing contributor to GDB and to Free
|
||
software in general. We will miss him.
|
||
|
||
@menu
|
||
* Summary:: Summary of @value{GDBN}
|
||
* Sample Session:: A sample @value{GDBN} session
|
||
|
||
* Invocation:: Getting in and out of @value{GDBN}
|
||
* Commands:: @value{GDBN} commands
|
||
* Running:: Running programs under @value{GDBN}
|
||
* Stopping:: Stopping and continuing
|
||
* Reverse Execution:: Running programs backward
|
||
* Process Record and Replay:: Recording inferior's execution and replaying it
|
||
* Stack:: Examining the stack
|
||
* Source:: Examining source files
|
||
* Data:: Examining data
|
||
* Optimized Code:: Debugging optimized code
|
||
* Macros:: Preprocessor Macros
|
||
* Tracepoints:: Debugging remote targets non-intrusively
|
||
* Overlays:: Debugging programs that use overlays
|
||
|
||
* Languages:: Using @value{GDBN} with different languages
|
||
|
||
* Symbols:: Examining the symbol table
|
||
* Altering:: Altering execution
|
||
* GDB Files:: @value{GDBN} files
|
||
* Targets:: Specifying a debugging target
|
||
* Remote Debugging:: Debugging remote programs
|
||
* Configurations:: Configuration-specific information
|
||
* Controlling GDB:: Controlling @value{GDBN}
|
||
* Extending GDB:: Extending @value{GDBN}
|
||
* Interpreters:: Command Interpreters
|
||
* TUI:: @value{GDBN} Text User Interface
|
||
* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
|
||
* GDB/MI:: @value{GDBN}'s Machine Interface.
|
||
* Annotations:: @value{GDBN}'s annotation interface.
|
||
* JIT Interface:: Using the JIT debugging interface.
|
||
* In-Process Agent:: In-Process Agent
|
||
|
||
* GDB Bugs:: Reporting bugs in @value{GDBN}
|
||
|
||
@ifset SYSTEM_READLINE
|
||
* Command Line Editing: (rluserman). Command Line Editing
|
||
* Using History Interactively: (history). Using History Interactively
|
||
@end ifset
|
||
@ifclear SYSTEM_READLINE
|
||
* Command Line Editing:: Command Line Editing
|
||
* Using History Interactively:: Using History Interactively
|
||
@end ifclear
|
||
* In Memoriam:: In Memoriam
|
||
* Formatting Documentation:: How to format and print @value{GDBN} documentation
|
||
* Installing GDB:: Installing GDB
|
||
* Maintenance Commands:: Maintenance Commands
|
||
* Remote Protocol:: GDB Remote Serial Protocol
|
||
* Agent Expressions:: The GDB Agent Expression Mechanism
|
||
* Target Descriptions:: How targets can describe themselves to
|
||
@value{GDBN}
|
||
* Operating System Information:: Getting additional information from
|
||
the operating system
|
||
* Trace File Format:: GDB trace file format
|
||
* Index Section Format:: .gdb_index section format
|
||
* Man Pages:: Manual pages
|
||
* Copying:: GNU General Public License says
|
||
how you can copy and share GDB
|
||
* GNU Free Documentation License:: The license for this documentation
|
||
* Concept Index:: Index of @value{GDBN} concepts
|
||
* Command and Variable Index:: Index of @value{GDBN} commands, variables,
|
||
functions, and Python data types
|
||
@end menu
|
||
|
||
@end ifnottex
|
||
|
||
@contents
|
||
|
||
@node Summary
|
||
@unnumbered Summary of @value{GDBN}
|
||
|
||
The purpose of a debugger such as @value{GDBN} is to allow you to see what is
|
||
going on ``inside'' another program while it executes---or what another
|
||
program was doing at the moment it crashed.
|
||
|
||
@value{GDBN} can do four main kinds of things (plus other things in support of
|
||
these) to help you catch bugs in the act:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Start your program, specifying anything that might affect its behavior.
|
||
|
||
@item
|
||
Make your program stop on specified conditions.
|
||
|
||
@item
|
||
Examine what has happened, when your program has stopped.
|
||
|
||
@item
|
||
Change things in your program, so you can experiment with correcting the
|
||
effects of one bug and go on to learn about another.
|
||
@end itemize
|
||
|
||
You can use @value{GDBN} to debug programs written in C and C@t{++}.
|
||
For more information, see @ref{Supported Languages,,Supported Languages}.
|
||
For more information, see @ref{C,,C and C++}.
|
||
|
||
Support for D is partial. For information on D, see
|
||
@ref{D,,D}.
|
||
|
||
@cindex Modula-2
|
||
Support for Modula-2 is partial. For information on Modula-2, see
|
||
@ref{Modula-2,,Modula-2}.
|
||
|
||
Support for OpenCL C is partial. For information on OpenCL C, see
|
||
@ref{OpenCL C,,OpenCL C}.
|
||
|
||
@cindex Pascal
|
||
Debugging Pascal programs which use sets, subranges, file variables, or
|
||
nested functions does not currently work. @value{GDBN} does not support
|
||
entering expressions, printing values, or similar features using Pascal
|
||
syntax.
|
||
|
||
@cindex Fortran
|
||
@value{GDBN} can be used to debug programs written in Fortran, although
|
||
it may be necessary to refer to some variables with a trailing
|
||
underscore.
|
||
|
||
@value{GDBN} can be used to debug programs written in Objective-C,
|
||
using either the Apple/NeXT or the GNU Objective-C runtime.
|
||
|
||
@menu
|
||
* Free Software:: Freely redistributable software
|
||
* Free Documentation:: Free Software Needs Free Documentation
|
||
* Contributors:: Contributors to GDB
|
||
@end menu
|
||
|
||
@node Free Software
|
||
@unnumberedsec Free Software
|
||
|
||
@value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
|
||
General Public License
|
||
(GPL). The GPL gives you the freedom to copy or adapt a licensed
|
||
program---but every person getting a copy also gets with it the
|
||
freedom to modify that copy (which means that they must get access to
|
||
the source code), and the freedom to distribute further copies.
|
||
Typical software companies use copyrights to limit your freedoms; the
|
||
Free Software Foundation uses the GPL to preserve these freedoms.
|
||
|
||
Fundamentally, the General Public License is a license which says that
|
||
you have these freedoms and that you cannot take these freedoms away
|
||
from anyone else.
|
||
|
||
@node Free Documentation
|
||
@unnumberedsec Free Software Needs Free Documentation
|
||
|
||
The biggest deficiency in the free software community today is not in
|
||
the software---it is the lack of good free documentation that we can
|
||
include with the free software. Many of our most important
|
||
programs do not come with free reference manuals and free introductory
|
||
texts. Documentation is an essential part of any software package;
|
||
when an important free software package does not come with a free
|
||
manual and a free tutorial, that is a major gap. We have many such
|
||
gaps today.
|
||
|
||
Consider Perl, for instance. The tutorial manuals that people
|
||
normally use are non-free. How did this come about? Because the
|
||
authors of those manuals published them with restrictive terms---no
|
||
copying, no modification, source files not available---which exclude
|
||
them from the free software world.
|
||
|
||
That wasn't the first time this sort of thing happened, and it was far
|
||
from the last. Many times we have heard a GNU user eagerly describe a
|
||
manual that he is writing, his intended contribution to the community,
|
||
only to learn that he had ruined everything by signing a publication
|
||
contract to make it non-free.
|
||
|
||
Free documentation, like free software, is a matter of freedom, not
|
||
price. The problem with the non-free manual is not that publishers
|
||
charge a price for printed copies---that in itself is fine. (The Free
|
||
Software Foundation sells printed copies of manuals, too.) The
|
||
problem is the restrictions on the use of the manual. Free manuals
|
||
are available in source code form, and give you permission to copy and
|
||
modify. Non-free manuals do not allow this.
|
||
|
||
The criteria of freedom for a free manual are roughly the same as for
|
||
free software. Redistribution (including the normal kinds of
|
||
commercial redistribution) must be permitted, so that the manual can
|
||
accompany every copy of the program, both on-line and on paper.
|
||
|
||
Permission for modification of the technical content is crucial too.
|
||
When people modify the software, adding or changing features, if they
|
||
are conscientious they will change the manual too---so they can
|
||
provide accurate and clear documentation for the modified program. A
|
||
manual that leaves you no choice but to write a new manual to document
|
||
a changed version of the program is not really available to our
|
||
community.
|
||
|
||
Some kinds of limits on the way modification is handled are
|
||
acceptable. For example, requirements to preserve the original
|
||
author's copyright notice, the distribution terms, or the list of
|
||
authors, are ok. It is also no problem to require modified versions
|
||
to include notice that they were modified. Even entire sections that
|
||
may not be deleted or changed are acceptable, as long as they deal
|
||
with nontechnical topics (like this one). These kinds of restrictions
|
||
are acceptable because they don't obstruct the community's normal use
|
||
of the manual.
|
||
|
||
However, it must be possible to modify all the @emph{technical}
|
||
content of the manual, and then distribute the result in all the usual
|
||
media, through all the usual channels. Otherwise, the restrictions
|
||
obstruct the use of the manual, it is not free, and we need another
|
||
manual to replace it.
|
||
|
||
Please spread the word about this issue. Our community continues to
|
||
lose manuals to proprietary publishing. If we spread the word that
|
||
free software needs free reference manuals and free tutorials, perhaps
|
||
the next person who wants to contribute by writing documentation will
|
||
realize, before it is too late, that only free manuals contribute to
|
||
the free software community.
|
||
|
||
If you are writing documentation, please insist on publishing it under
|
||
the GNU Free Documentation License or another free documentation
|
||
license. Remember that this decision requires your approval---you
|
||
don't have to let the publisher decide. Some commercial publishers
|
||
will use a free license if you insist, but they will not propose the
|
||
option; it is up to you to raise the issue and say firmly that this is
|
||
what you want. If the publisher you are dealing with refuses, please
|
||
try other publishers. If you're not sure whether a proposed license
|
||
is free, write to @email{licensing@@gnu.org}.
|
||
|
||
You can encourage commercial publishers to sell more free, copylefted
|
||
manuals and tutorials by buying them, and particularly by buying
|
||
copies from the publishers that paid for their writing or for major
|
||
improvements. Meanwhile, try to avoid buying non-free documentation
|
||
at all. Check the distribution terms of a manual before you buy it,
|
||
and insist that whoever seeks your business must respect your freedom.
|
||
Check the history of the book, and try to reward the publishers that
|
||
have paid or pay the authors to work on it.
|
||
|
||
The Free Software Foundation maintains a list of free documentation
|
||
published by other publishers, at
|
||
@url{http://www.fsf.org/doc/other-free-books.html}.
|
||
|
||
@node Contributors
|
||
@unnumberedsec Contributors to @value{GDBN}
|
||
|
||
Richard Stallman was the original author of @value{GDBN}, and of many
|
||
other @sc{gnu} programs. Many others have contributed to its
|
||
development. This section attempts to credit major contributors. One
|
||
of the virtues of free software is that everyone is free to contribute
|
||
to it; with regret, we cannot actually acknowledge everyone here. The
|
||
file @file{ChangeLog} in the @value{GDBN} distribution approximates a
|
||
blow-by-blow account.
|
||
|
||
Changes much prior to version 2.0 are lost in the mists of time.
|
||
|
||
@quotation
|
||
@emph{Plea:} Additions to this section are particularly welcome. If you
|
||
or your friends (or enemies, to be evenhanded) have been unfairly
|
||
omitted from this list, we would like to add your names!
|
||
@end quotation
|
||
|
||
So that they may not regard their many labors as thankless, we
|
||
particularly thank those who shepherded @value{GDBN} through major
|
||
releases:
|
||
Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
|
||
Jim Blandy (release 4.18);
|
||
Jason Molenda (release 4.17);
|
||
Stan Shebs (release 4.14);
|
||
Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
|
||
Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
|
||
John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
|
||
Jim Kingdon (releases 3.5, 3.4, and 3.3);
|
||
and Randy Smith (releases 3.2, 3.1, and 3.0).
|
||
|
||
Richard Stallman, assisted at various times by Peter TerMaat, Chris
|
||
Hanson, and Richard Mlynarik, handled releases through 2.8.
|
||
|
||
Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
|
||
in @value{GDBN}, with significant additional contributions from Per
|
||
Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
|
||
demangler. Early work on C@t{++} was by Peter TerMaat (who also did
|
||
much general update work leading to release 3.0).
|
||
|
||
@value{GDBN} uses the BFD subroutine library to examine multiple
|
||
object-file formats; BFD was a joint project of David V.
|
||
Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
|
||
|
||
David Johnson wrote the original COFF support; Pace Willison did
|
||
the original support for encapsulated COFF.
|
||
|
||
Brent Benson of Harris Computer Systems contributed DWARF 2 support.
|
||
|
||
Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
|
||
Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
|
||
support.
|
||
Jean-Daniel Fekete contributed Sun 386i support.
|
||
Chris Hanson improved the HP9000 support.
|
||
Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
|
||
David Johnson contributed Encore Umax support.
|
||
Jyrki Kuoppala contributed Altos 3068 support.
|
||
Jeff Law contributed HP PA and SOM support.
|
||
Keith Packard contributed NS32K support.
|
||
Doug Rabson contributed Acorn Risc Machine support.
|
||
Bob Rusk contributed Harris Nighthawk CX-UX support.
|
||
Chris Smith contributed Convex support (and Fortran debugging).
|
||
Jonathan Stone contributed Pyramid support.
|
||
Michael Tiemann contributed SPARC support.
|
||
Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
|
||
Pace Willison contributed Intel 386 support.
|
||
Jay Vosburgh contributed Symmetry support.
|
||
Marko Mlinar contributed OpenRISC 1000 support.
|
||
|
||
Andreas Schwab contributed M68K @sc{gnu}/Linux support.
|
||
|
||
Rich Schaefer and Peter Schauer helped with support of SunOS shared
|
||
libraries.
|
||
|
||
Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
|
||
about several machine instruction sets.
|
||
|
||
Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
|
||
remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
|
||
contributed remote debugging modules for the i960, VxWorks, A29K UDI,
|
||
and RDI targets, respectively.
|
||
|
||
Brian Fox is the author of the readline libraries providing
|
||
command-line editing and command history.
|
||
|
||
Andrew Beers of SUNY Buffalo wrote the language-switching code, the
|
||
Modula-2 support, and contributed the Languages chapter of this manual.
|
||
|
||
Fred Fish wrote most of the support for Unix System Vr4.
|
||
He also enhanced the command-completion support to cover C@t{++} overloaded
|
||
symbols.
|
||
|
||
Hitachi America (now Renesas America), Ltd. sponsored the support for
|
||
H8/300, H8/500, and Super-H processors.
|
||
|
||
NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
|
||
|
||
Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
|
||
processors.
|
||
|
||
Toshiba sponsored the support for the TX39 Mips processor.
|
||
|
||
Matsushita sponsored the support for the MN10200 and MN10300 processors.
|
||
|
||
Fujitsu sponsored the support for SPARClite and FR30 processors.
|
||
|
||
Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
|
||
watchpoints.
|
||
|
||
Michael Snyder added support for tracepoints.
|
||
|
||
Stu Grossman wrote gdbserver.
|
||
|
||
Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
|
||
nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
|
||
|
||
The following people at the Hewlett-Packard Company contributed
|
||
support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
|
||
(narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
|
||
compiler, and the Text User Interface (nee Terminal User Interface):
|
||
Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
|
||
Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
|
||
provided HP-specific information in this manual.
|
||
|
||
DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
|
||
Robert Hoehne made significant contributions to the DJGPP port.
|
||
|
||
Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
|
||
development since 1991. Cygnus engineers who have worked on @value{GDBN}
|
||
fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
|
||
Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
|
||
Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
|
||
Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
|
||
Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
|
||
addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
|
||
JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
|
||
Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
|
||
Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
|
||
Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
|
||
Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
|
||
Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
|
||
Zuhn have made contributions both large and small.
|
||
|
||
Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
|
||
Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
|
||
|
||
Jim Blandy added support for preprocessor macros, while working for Red
|
||
Hat.
|
||
|
||
Andrew Cagney designed @value{GDBN}'s architecture vector. Many
|
||
people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
|
||
Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
|
||
Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
|
||
Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
|
||
with the migration of old architectures to this new framework.
|
||
|
||
Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
|
||
unwinder framework, this consisting of a fresh new design featuring
|
||
frame IDs, independent frame sniffers, and the sentinel frame. Mark
|
||
Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
|
||
libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
|
||
trad unwinders. The architecture-specific changes, each involving a
|
||
complete rewrite of the architecture's frame code, were carried out by
|
||
Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
|
||
Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
|
||
Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
|
||
Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
|
||
Weigand.
|
||
|
||
Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
|
||
Tensilica, Inc.@: contributed support for Xtensa processors. Others
|
||
who have worked on the Xtensa port of @value{GDBN} in the past include
|
||
Steve Tjiang, John Newlin, and Scott Foehner.
|
||
|
||
Michael Eager and staff of Xilinx, Inc., contributed support for the
|
||
Xilinx MicroBlaze architecture.
|
||
|
||
Initial support for the FreeBSD/mips target and native configuration
|
||
was developed by SRI International and the University of Cambridge
|
||
Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
|
||
("CTSRD"), as part of the DARPA CRASH research programme.
|
||
|
||
The original port to the OpenRISC 1000 is believed to be due to
|
||
Alessandro Forin and Per Bothner. More recent ports have been the work
|
||
of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
|
||
Stafford Horne.
|
||
|
||
@node Sample Session
|
||
@chapter A Sample @value{GDBN} Session
|
||
|
||
You can use this manual at your leisure to read all about @value{GDBN}.
|
||
However, a handful of commands are enough to get started using the
|
||
debugger. This chapter illustrates those commands.
|
||
|
||
@iftex
|
||
In this sample session, we emphasize user input like this: @b{input},
|
||
to make it easier to pick out from the surrounding output.
|
||
@end iftex
|
||
|
||
@c FIXME: this example may not be appropriate for some configs, where
|
||
@c FIXME...primary interest is in remote use.
|
||
|
||
One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
|
||
processor) exhibits the following bug: sometimes, when we change its
|
||
quote strings from the default, the commands used to capture one macro
|
||
definition within another stop working. In the following short @code{m4}
|
||
session, we define a macro @code{foo} which expands to @code{0000}; we
|
||
then use the @code{m4} built-in @code{defn} to define @code{bar} as the
|
||
same thing. However, when we change the open quote string to
|
||
@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
|
||
procedure fails to define a new synonym @code{baz}:
|
||
|
||
@smallexample
|
||
$ @b{cd gnu/m4}
|
||
$ @b{./m4}
|
||
@b{define(foo,0000)}
|
||
|
||
@b{foo}
|
||
0000
|
||
@b{define(bar,defn(`foo'))}
|
||
|
||
@b{bar}
|
||
0000
|
||
@b{changequote(<QUOTE>,<UNQUOTE>)}
|
||
|
||
@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
|
||
@b{baz}
|
||
@b{Ctrl-d}
|
||
m4: End of input: 0: fatal error: EOF in string
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Let us use @value{GDBN} to try to see what is going on.
|
||
|
||
@smallexample
|
||
$ @b{@value{GDBP} m4}
|
||
@c FIXME: this falsifies the exact text played out, to permit smallbook
|
||
@c FIXME... format to come out better.
|
||
@value{GDBN} is free software and you are welcome to distribute copies
|
||
of it under certain conditions; type "show copying" to see
|
||
the conditions.
|
||
There is absolutely no warranty for @value{GDBN}; type "show warranty"
|
||
for details.
|
||
|
||
@value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@value{GDBN} reads only enough symbol data to know where to find the
|
||
rest when needed; as a result, the first prompt comes up very quickly.
|
||
We now tell @value{GDBN} to use a narrower display width than usual, so
|
||
that examples fit in this manual.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{set width 70}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
We need to see how the @code{m4} built-in @code{changequote} works.
|
||
Having looked at the source, we know the relevant subroutine is
|
||
@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
|
||
@code{break} command.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{break m4_changequote}
|
||
Breakpoint 1 at 0x62f4: file builtin.c, line 879.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Using the @code{run} command, we start @code{m4} running under @value{GDBN}
|
||
control; as long as control does not reach the @code{m4_changequote}
|
||
subroutine, the program runs as usual:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{run}
|
||
Starting program: /work/Editorial/gdb/gnu/m4/m4
|
||
@b{define(foo,0000)}
|
||
|
||
@b{foo}
|
||
0000
|
||
@end smallexample
|
||
|
||
@noindent
|
||
To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
|
||
suspends execution of @code{m4}, displaying information about the
|
||
context where it stops.
|
||
|
||
@smallexample
|
||
@b{changequote(<QUOTE>,<UNQUOTE>)}
|
||
|
||
Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
|
||
at builtin.c:879
|
||
879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Now we use the command @code{n} (@code{next}) to advance execution to
|
||
the next line of the current function.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{n}
|
||
882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
|
||
: nil,
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@code{set_quotes} looks like a promising subroutine. We can go into it
|
||
by using the command @code{s} (@code{step}) instead of @code{next}.
|
||
@code{step} goes to the next line to be executed in @emph{any}
|
||
subroutine, so it steps into @code{set_quotes}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{s}
|
||
set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
|
||
at input.c:530
|
||
530 if (lquote != def_lquote)
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The display that shows the subroutine where @code{m4} is now
|
||
suspended (and its arguments) is called a stack frame display. It
|
||
shows a summary of the stack. We can use the @code{backtrace}
|
||
command (which can also be spelled @code{bt}), to see where we are
|
||
in the stack as a whole: the @code{backtrace} command displays a
|
||
stack frame for each active subroutine.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{bt}
|
||
#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
|
||
at input.c:530
|
||
#1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
|
||
at builtin.c:882
|
||
#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
|
||
#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
|
||
at macro.c:71
|
||
#4 0x79dc in expand_input () at macro.c:40
|
||
#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
|
||
@end smallexample
|
||
|
||
@noindent
|
||
We step through a few more lines to see what happens. The first two
|
||
times, we can use @samp{s}; the next two times we use @code{n} to avoid
|
||
falling into the @code{xstrdup} subroutine.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{s}
|
||
0x3b5c 532 if (rquote != def_rquote)
|
||
(@value{GDBP}) @b{s}
|
||
0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
|
||
def_lquote : xstrdup(lq);
|
||
(@value{GDBP}) @b{n}
|
||
536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
|
||
: xstrdup(rq);
|
||
(@value{GDBP}) @b{n}
|
||
538 len_lquote = strlen(rquote);
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The last line displayed looks a little odd; we can examine the variables
|
||
@code{lquote} and @code{rquote} to see if they are in fact the new left
|
||
and right quotes we specified. We use the command @code{p}
|
||
(@code{print}) to see their values.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{p lquote}
|
||
$1 = 0x35d40 "<QUOTE>"
|
||
(@value{GDBP}) @b{p rquote}
|
||
$2 = 0x35d50 "<UNQUOTE>"
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@code{lquote} and @code{rquote} are indeed the new left and right quotes.
|
||
To look at some context, we can display ten lines of source
|
||
surrounding the current line with the @code{l} (@code{list}) command.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{l}
|
||
533 xfree(rquote);
|
||
534
|
||
535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
|
||
: xstrdup (lq);
|
||
536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
|
||
: xstrdup (rq);
|
||
537
|
||
538 len_lquote = strlen(rquote);
|
||
539 len_rquote = strlen(lquote);
|
||
540 @}
|
||
541
|
||
542 void
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Let us step past the two lines that set @code{len_lquote} and
|
||
@code{len_rquote}, and then examine the values of those variables.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{n}
|
||
539 len_rquote = strlen(lquote);
|
||
(@value{GDBP}) @b{n}
|
||
540 @}
|
||
(@value{GDBP}) @b{p len_lquote}
|
||
$3 = 9
|
||
(@value{GDBP}) @b{p len_rquote}
|
||
$4 = 7
|
||
@end smallexample
|
||
|
||
@noindent
|
||
That certainly looks wrong, assuming @code{len_lquote} and
|
||
@code{len_rquote} are meant to be the lengths of @code{lquote} and
|
||
@code{rquote} respectively. We can set them to better values using
|
||
the @code{p} command, since it can print the value of
|
||
any expression---and that expression can include subroutine calls and
|
||
assignments.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{p len_lquote=strlen(lquote)}
|
||
$5 = 7
|
||
(@value{GDBP}) @b{p len_rquote=strlen(rquote)}
|
||
$6 = 9
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Is that enough to fix the problem of using the new quotes with the
|
||
@code{m4} built-in @code{defn}? We can allow @code{m4} to continue
|
||
executing with the @code{c} (@code{continue}) command, and then try the
|
||
example that caused trouble initially:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{c}
|
||
Continuing.
|
||
|
||
@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
|
||
|
||
baz
|
||
0000
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Success! The new quotes now work just as well as the default ones. The
|
||
problem seems to have been just the two typos defining the wrong
|
||
lengths. We allow @code{m4} exit by giving it an EOF as input:
|
||
|
||
@smallexample
|
||
@b{Ctrl-d}
|
||
Program exited normally.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The message @samp{Program exited normally.} is from @value{GDBN}; it
|
||
indicates @code{m4} has finished executing. We can end our @value{GDBN}
|
||
session with the @value{GDBN} @code{quit} command.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{quit}
|
||
@end smallexample
|
||
|
||
@node Invocation
|
||
@chapter Getting In and Out of @value{GDBN}
|
||
|
||
This chapter discusses how to start @value{GDBN}, and how to get out of it.
|
||
The essentials are:
|
||
@itemize @bullet
|
||
@item
|
||
type @samp{@value{GDBP}} to start @value{GDBN}.
|
||
@item
|
||
type @kbd{quit} or @kbd{Ctrl-d} to exit.
|
||
@end itemize
|
||
|
||
@menu
|
||
* Invoking GDB:: How to start @value{GDBN}
|
||
* Quitting GDB:: How to quit @value{GDBN}
|
||
* Shell Commands:: How to use shell commands inside @value{GDBN}
|
||
* Logging Output:: How to log @value{GDBN}'s output to a file
|
||
@end menu
|
||
|
||
@node Invoking GDB
|
||
@section Invoking @value{GDBN}
|
||
|
||
Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
|
||
@value{GDBN} reads commands from the terminal until you tell it to exit.
|
||
|
||
You can also run @code{@value{GDBP}} with a variety of arguments and options,
|
||
to specify more of your debugging environment at the outset.
|
||
|
||
The command-line options described here are designed
|
||
to cover a variety of situations; in some environments, some of these
|
||
options may effectively be unavailable.
|
||
|
||
The most usual way to start @value{GDBN} is with one argument,
|
||
specifying an executable program:
|
||
|
||
@smallexample
|
||
@value{GDBP} @var{program}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can also start with both an executable program and a core file
|
||
specified:
|
||
|
||
@smallexample
|
||
@value{GDBP} @var{program} @var{core}
|
||
@end smallexample
|
||
|
||
You can, instead, specify a process ID as a second argument, if you want
|
||
to debug a running process:
|
||
|
||
@smallexample
|
||
@value{GDBP} @var{program} 1234
|
||
@end smallexample
|
||
|
||
@noindent
|
||
would attach @value{GDBN} to process @code{1234} (unless you also have a file
|
||
named @file{1234}; @value{GDBN} does check for a core file first).
|
||
|
||
Taking advantage of the second command-line argument requires a fairly
|
||
complete operating system; when you use @value{GDBN} as a remote
|
||
debugger attached to a bare board, there may not be any notion of
|
||
``process'', and there is often no way to get a core dump. @value{GDBN}
|
||
will warn you if it is unable to attach or to read core dumps.
|
||
|
||
You can optionally have @code{@value{GDBP}} pass any arguments after the
|
||
executable file to the inferior using @code{--args}. This option stops
|
||
option processing.
|
||
@smallexample
|
||
@value{GDBP} --args gcc -O2 -c foo.c
|
||
@end smallexample
|
||
This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
|
||
@code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
|
||
|
||
You can run @code{@value{GDBP}} without printing the front material, which describes
|
||
@value{GDBN}'s non-warranty, by specifying @code{--silent}
|
||
(or @code{-q}/@code{--quiet}):
|
||
|
||
@smallexample
|
||
@value{GDBP} --silent
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can further control how @value{GDBN} starts up by using command-line
|
||
options. @value{GDBN} itself can remind you of the options available.
|
||
|
||
@noindent
|
||
Type
|
||
|
||
@smallexample
|
||
@value{GDBP} -help
|
||
@end smallexample
|
||
|
||
@noindent
|
||
to display all available options and briefly describe their use
|
||
(@samp{@value{GDBP} -h} is a shorter equivalent).
|
||
|
||
All options and command line arguments you give are processed
|
||
in sequential order. The order makes a difference when the
|
||
@samp{-x} option is used.
|
||
|
||
|
||
@menu
|
||
* File Options:: Choosing files
|
||
* Mode Options:: Choosing modes
|
||
* Startup:: What @value{GDBN} does during startup
|
||
@end menu
|
||
|
||
@node File Options
|
||
@subsection Choosing Files
|
||
|
||
When @value{GDBN} starts, it reads any arguments other than options as
|
||
specifying an executable file and core file (or process ID). This is
|
||
the same as if the arguments were specified by the @samp{-se} and
|
||
@samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
|
||
first argument that does not have an associated option flag as
|
||
equivalent to the @samp{-se} option followed by that argument; and the
|
||
second argument that does not have an associated option flag, if any, as
|
||
equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
|
||
If the second argument begins with a decimal digit, @value{GDBN} will
|
||
first attempt to attach to it as a process, and if that fails, attempt
|
||
to open it as a corefile. If you have a corefile whose name begins with
|
||
a digit, you can prevent @value{GDBN} from treating it as a pid by
|
||
prefixing it with @file{./}, e.g.@: @file{./12345}.
|
||
|
||
If @value{GDBN} has not been configured to included core file support,
|
||
such as for most embedded targets, then it will complain about a second
|
||
argument and ignore it.
|
||
|
||
Many options have both long and short forms; both are shown in the
|
||
following list. @value{GDBN} also recognizes the long forms if you truncate
|
||
them, so long as enough of the option is present to be unambiguous.
|
||
(If you prefer, you can flag option arguments with @samp{--} rather
|
||
than @samp{-}, though we illustrate the more usual convention.)
|
||
|
||
@c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
|
||
@c way, both those who look for -foo and --foo in the index, will find
|
||
@c it.
|
||
|
||
@table @code
|
||
@item -symbols @var{file}
|
||
@itemx -s @var{file}
|
||
@cindex @code{--symbols}
|
||
@cindex @code{-s}
|
||
Read symbol table from file @var{file}.
|
||
|
||
@item -exec @var{file}
|
||
@itemx -e @var{file}
|
||
@cindex @code{--exec}
|
||
@cindex @code{-e}
|
||
Use file @var{file} as the executable file to execute when appropriate,
|
||
and for examining pure data in conjunction with a core dump.
|
||
|
||
@item -se @var{file}
|
||
@cindex @code{--se}
|
||
Read symbol table from file @var{file} and use it as the executable
|
||
file.
|
||
|
||
@item -core @var{file}
|
||
@itemx -c @var{file}
|
||
@cindex @code{--core}
|
||
@cindex @code{-c}
|
||
Use file @var{file} as a core dump to examine.
|
||
|
||
@item -pid @var{number}
|
||
@itemx -p @var{number}
|
||
@cindex @code{--pid}
|
||
@cindex @code{-p}
|
||
Connect to process ID @var{number}, as with the @code{attach} command.
|
||
|
||
@item -command @var{file}
|
||
@itemx -x @var{file}
|
||
@cindex @code{--command}
|
||
@cindex @code{-x}
|
||
Execute commands from file @var{file}. The contents of this file is
|
||
evaluated exactly as the @code{source} command would.
|
||
@xref{Command Files,, Command files}.
|
||
|
||
@item -eval-command @var{command}
|
||
@itemx -ex @var{command}
|
||
@cindex @code{--eval-command}
|
||
@cindex @code{-ex}
|
||
Execute a single @value{GDBN} command.
|
||
|
||
This option may be used multiple times to call multiple commands. It may
|
||
also be interleaved with @samp{-command} as required.
|
||
|
||
@smallexample
|
||
@value{GDBP} -ex 'target sim' -ex 'load' \
|
||
-x setbreakpoints -ex 'run' a.out
|
||
@end smallexample
|
||
|
||
@item -init-command @var{file}
|
||
@itemx -ix @var{file}
|
||
@cindex @code{--init-command}
|
||
@cindex @code{-ix}
|
||
Execute commands from file @var{file} before loading the inferior (but
|
||
after loading gdbinit files).
|
||
@xref{Startup}.
|
||
|
||
@item -init-eval-command @var{command}
|
||
@itemx -iex @var{command}
|
||
@cindex @code{--init-eval-command}
|
||
@cindex @code{-iex}
|
||
Execute a single @value{GDBN} command before loading the inferior (but
|
||
after loading gdbinit files).
|
||
@xref{Startup}.
|
||
|
||
@item -directory @var{directory}
|
||
@itemx -d @var{directory}
|
||
@cindex @code{--directory}
|
||
@cindex @code{-d}
|
||
Add @var{directory} to the path to search for source and script files.
|
||
|
||
@item -r
|
||
@itemx -readnow
|
||
@cindex @code{--readnow}
|
||
@cindex @code{-r}
|
||
Read each symbol file's entire symbol table immediately, rather than
|
||
the default, which is to read it incrementally as it is needed.
|
||
This makes startup slower, but makes future operations faster.
|
||
|
||
@item --readnever
|
||
@anchor{--readnever}
|
||
@cindex @code{--readnever}, command-line option
|
||
Do not read each symbol file's symbolic debug information. This makes
|
||
startup faster but at the expense of not being able to perform
|
||
symbolic debugging. DWARF unwind information is also not read,
|
||
meaning backtraces may become incomplete or inaccurate. One use of
|
||
this is when a user simply wants to do the following sequence: attach,
|
||
dump core, detach. Loading the debugging information in this case is
|
||
an unnecessary cause of delay.
|
||
@end table
|
||
|
||
@node Mode Options
|
||
@subsection Choosing Modes
|
||
|
||
You can run @value{GDBN} in various alternative modes---for example, in
|
||
batch mode or quiet mode.
|
||
|
||
@table @code
|
||
@anchor{-nx}
|
||
@item -nx
|
||
@itemx -n
|
||
@cindex @code{--nx}
|
||
@cindex @code{-n}
|
||
Do not execute commands found in any initialization file.
|
||
There are three init files, loaded in the following order:
|
||
|
||
@table @code
|
||
@item @file{system.gdbinit}
|
||
This is the system-wide init file.
|
||
Its location is specified with the @code{--with-system-gdbinit}
|
||
configure option (@pxref{System-wide configuration}).
|
||
It is loaded first when @value{GDBN} starts, before command line options
|
||
have been processed.
|
||
@item @file{~/.gdbinit}
|
||
This is the init file in your home directory.
|
||
It is loaded next, after @file{system.gdbinit}, and before
|
||
command options have been processed.
|
||
@item @file{./.gdbinit}
|
||
This is the init file in the current directory.
|
||
It is loaded last, after command line options other than @code{-x} and
|
||
@code{-ex} have been processed. Command line options @code{-x} and
|
||
@code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
|
||
@end table
|
||
|
||
For further documentation on startup processing, @xref{Startup}.
|
||
For documentation on how to write command files,
|
||
@xref{Command Files,,Command Files}.
|
||
|
||
@anchor{-nh}
|
||
@item -nh
|
||
@cindex @code{--nh}
|
||
Do not execute commands found in @file{~/.gdbinit}, the init file
|
||
in your home directory.
|
||
@xref{Startup}.
|
||
|
||
@item -quiet
|
||
@itemx -silent
|
||
@itemx -q
|
||
@cindex @code{--quiet}
|
||
@cindex @code{--silent}
|
||
@cindex @code{-q}
|
||
``Quiet''. Do not print the introductory and copyright messages. These
|
||
messages are also suppressed in batch mode.
|
||
|
||
@item -batch
|
||
@cindex @code{--batch}
|
||
Run in batch mode. Exit with status @code{0} after processing all the
|
||
command files specified with @samp{-x} (and all commands from
|
||
initialization files, if not inhibited with @samp{-n}). Exit with
|
||
nonzero status if an error occurs in executing the @value{GDBN} commands
|
||
in the command files. Batch mode also disables pagination, sets unlimited
|
||
terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
|
||
off} were in effect (@pxref{Messages/Warnings}).
|
||
|
||
Batch mode may be useful for running @value{GDBN} as a filter, for
|
||
example to download and run a program on another computer; in order to
|
||
make this more useful, the message
|
||
|
||
@smallexample
|
||
Program exited normally.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
(which is ordinarily issued whenever a program running under
|
||
@value{GDBN} control terminates) is not issued when running in batch
|
||
mode.
|
||
|
||
@item -batch-silent
|
||
@cindex @code{--batch-silent}
|
||
Run in batch mode exactly like @samp{-batch}, but totally silently. All
|
||
@value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
|
||
unaffected). This is much quieter than @samp{-silent} and would be useless
|
||
for an interactive session.
|
||
|
||
This is particularly useful when using targets that give @samp{Loading section}
|
||
messages, for example.
|
||
|
||
Note that targets that give their output via @value{GDBN}, as opposed to
|
||
writing directly to @code{stdout}, will also be made silent.
|
||
|
||
@item -return-child-result
|
||
@cindex @code{--return-child-result}
|
||
The return code from @value{GDBN} will be the return code from the child
|
||
process (the process being debugged), with the following exceptions:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
@value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
|
||
internal error. In this case the exit code is the same as it would have been
|
||
without @samp{-return-child-result}.
|
||
@item
|
||
The user quits with an explicit value. E.g., @samp{quit 1}.
|
||
@item
|
||
The child process never runs, or is not allowed to terminate, in which case
|
||
the exit code will be -1.
|
||
@end itemize
|
||
|
||
This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
|
||
when @value{GDBN} is being used as a remote program loader or simulator
|
||
interface.
|
||
|
||
@item -nowindows
|
||
@itemx -nw
|
||
@cindex @code{--nowindows}
|
||
@cindex @code{-nw}
|
||
``No windows''. If @value{GDBN} comes with a graphical user interface
|
||
(GUI) built in, then this option tells @value{GDBN} to only use the command-line
|
||
interface. If no GUI is available, this option has no effect.
|
||
|
||
@item -windows
|
||
@itemx -w
|
||
@cindex @code{--windows}
|
||
@cindex @code{-w}
|
||
If @value{GDBN} includes a GUI, then this option requires it to be
|
||
used if possible.
|
||
|
||
@item -cd @var{directory}
|
||
@cindex @code{--cd}
|
||
Run @value{GDBN} using @var{directory} as its working directory,
|
||
instead of the current directory.
|
||
|
||
@item -data-directory @var{directory}
|
||
@itemx -D @var{directory}
|
||
@cindex @code{--data-directory}
|
||
@cindex @code{-D}
|
||
Run @value{GDBN} using @var{directory} as its data directory.
|
||
The data directory is where @value{GDBN} searches for its
|
||
auxiliary files. @xref{Data Files}.
|
||
|
||
@item -fullname
|
||
@itemx -f
|
||
@cindex @code{--fullname}
|
||
@cindex @code{-f}
|
||
@sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
|
||
subprocess. It tells @value{GDBN} to output the full file name and line
|
||
number in a standard, recognizable fashion each time a stack frame is
|
||
displayed (which includes each time your program stops). This
|
||
recognizable format looks like two @samp{\032} characters, followed by
|
||
the file name, line number and character position separated by colons,
|
||
and a newline. The Emacs-to-@value{GDBN} interface program uses the two
|
||
@samp{\032} characters as a signal to display the source code for the
|
||
frame.
|
||
|
||
@item -annotate @var{level}
|
||
@cindex @code{--annotate}
|
||
This option sets the @dfn{annotation level} inside @value{GDBN}. Its
|
||
effect is identical to using @samp{set annotate @var{level}}
|
||
(@pxref{Annotations}). The annotation @var{level} controls how much
|
||
information @value{GDBN} prints together with its prompt, values of
|
||
expressions, source lines, and other types of output. Level 0 is the
|
||
normal, level 1 is for use when @value{GDBN} is run as a subprocess of
|
||
@sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
|
||
that control @value{GDBN}, and level 2 has been deprecated.
|
||
|
||
The annotation mechanism has largely been superseded by @sc{gdb/mi}
|
||
(@pxref{GDB/MI}).
|
||
|
||
@item --args
|
||
@cindex @code{--args}
|
||
Change interpretation of command line so that arguments following the
|
||
executable file are passed as command line arguments to the inferior.
|
||
This option stops option processing.
|
||
|
||
@item -baud @var{bps}
|
||
@itemx -b @var{bps}
|
||
@cindex @code{--baud}
|
||
@cindex @code{-b}
|
||
Set the line speed (baud rate or bits per second) of any serial
|
||
interface used by @value{GDBN} for remote debugging.
|
||
|
||
@item -l @var{timeout}
|
||
@cindex @code{-l}
|
||
Set the timeout (in seconds) of any communication used by @value{GDBN}
|
||
for remote debugging.
|
||
|
||
@item -tty @var{device}
|
||
@itemx -t @var{device}
|
||
@cindex @code{--tty}
|
||
@cindex @code{-t}
|
||
Run using @var{device} for your program's standard input and output.
|
||
@c FIXME: kingdon thinks there is more to -tty. Investigate.
|
||
|
||
@c resolve the situation of these eventually
|
||
@item -tui
|
||
@cindex @code{--tui}
|
||
Activate the @dfn{Text User Interface} when starting. The Text User
|
||
Interface manages several text windows on the terminal, showing
|
||
source, assembly, registers and @value{GDBN} command outputs
|
||
(@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
|
||
option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
|
||
Using @value{GDBN} under @sc{gnu} Emacs}).
|
||
|
||
@item -interpreter @var{interp}
|
||
@cindex @code{--interpreter}
|
||
Use the interpreter @var{interp} for interface with the controlling
|
||
program or device. This option is meant to be set by programs which
|
||
communicate with @value{GDBN} using it as a back end.
|
||
@xref{Interpreters, , Command Interpreters}.
|
||
|
||
@samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
|
||
@value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
|
||
The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
|
||
previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
|
||
selected with @samp{--interpreter=mi1}, is deprecated. Earlier
|
||
@sc{gdb/mi} interfaces are no longer supported.
|
||
|
||
@item -write
|
||
@cindex @code{--write}
|
||
Open the executable and core files for both reading and writing. This
|
||
is equivalent to the @samp{set write on} command inside @value{GDBN}
|
||
(@pxref{Patching}).
|
||
|
||
@item -statistics
|
||
@cindex @code{--statistics}
|
||
This option causes @value{GDBN} to print statistics about time and
|
||
memory usage after it completes each command and returns to the prompt.
|
||
|
||
@item -version
|
||
@cindex @code{--version}
|
||
This option causes @value{GDBN} to print its version number and
|
||
no-warranty blurb, and exit.
|
||
|
||
@item -configuration
|
||
@cindex @code{--configuration}
|
||
This option causes @value{GDBN} to print details about its build-time
|
||
configuration parameters, and then exit. These details can be
|
||
important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
|
||
|
||
@end table
|
||
|
||
@node Startup
|
||
@subsection What @value{GDBN} Does During Startup
|
||
@cindex @value{GDBN} startup
|
||
|
||
Here's the description of what @value{GDBN} does during session startup:
|
||
|
||
@enumerate
|
||
@item
|
||
Sets up the command interpreter as specified by the command line
|
||
(@pxref{Mode Options, interpreter}).
|
||
|
||
@item
|
||
@cindex init file
|
||
Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
|
||
used when building @value{GDBN}; @pxref{System-wide configuration,
|
||
,System-wide configuration and settings}) and executes all the commands in
|
||
that file.
|
||
|
||
@anchor{Home Directory Init File}
|
||
@item
|
||
Reads the init file (if any) in your home directory@footnote{On
|
||
DOS/Windows systems, the home directory is the one pointed to by the
|
||
@code{HOME} environment variable.} and executes all the commands in
|
||
that file.
|
||
|
||
@anchor{Option -init-eval-command}
|
||
@item
|
||
Executes commands and command files specified by the @samp{-iex} and
|
||
@samp{-ix} options in their specified order. Usually you should use the
|
||
@samp{-ex} and @samp{-x} options instead, but this way you can apply
|
||
settings before @value{GDBN} init files get executed and before inferior
|
||
gets loaded.
|
||
|
||
@item
|
||
Processes command line options and operands.
|
||
|
||
@anchor{Init File in the Current Directory during Startup}
|
||
@item
|
||
Reads and executes the commands from init file (if any) in the current
|
||
working directory as long as @samp{set auto-load local-gdbinit} is set to
|
||
@samp{on} (@pxref{Init File in the Current Directory}).
|
||
This is only done if the current directory is
|
||
different from your home directory. Thus, you can have more than one
|
||
init file, one generic in your home directory, and another, specific
|
||
to the program you are debugging, in the directory where you invoke
|
||
@value{GDBN}.
|
||
|
||
@item
|
||
If the command line specified a program to debug, or a process to
|
||
attach to, or a core file, @value{GDBN} loads any auto-loaded
|
||
scripts provided for the program or for its loaded shared libraries.
|
||
@xref{Auto-loading}.
|
||
|
||
If you wish to disable the auto-loading during startup,
|
||
you must do something like the following:
|
||
|
||
@smallexample
|
||
$ gdb -iex "set auto-load python-scripts off" myprogram
|
||
@end smallexample
|
||
|
||
Option @samp{-ex} does not work because the auto-loading is then turned
|
||
off too late.
|
||
|
||
@item
|
||
Executes commands and command files specified by the @samp{-ex} and
|
||
@samp{-x} options in their specified order. @xref{Command Files}, for
|
||
more details about @value{GDBN} command files.
|
||
|
||
@item
|
||
Reads the command history recorded in the @dfn{history file}.
|
||
@xref{Command History}, for more details about the command history and the
|
||
files where @value{GDBN} records it.
|
||
@end enumerate
|
||
|
||
Init files use the same syntax as @dfn{command files} (@pxref{Command
|
||
Files}) and are processed by @value{GDBN} in the same way. The init
|
||
file in your home directory can set options (such as @samp{set
|
||
complaints}) that affect subsequent processing of command line options
|
||
and operands. Init files are not executed if you use the @samp{-nx}
|
||
option (@pxref{Mode Options, ,Choosing Modes}).
|
||
|
||
To display the list of init files loaded by gdb at startup, you
|
||
can use @kbd{gdb --help}.
|
||
|
||
@cindex init file name
|
||
@cindex @file{.gdbinit}
|
||
@cindex @file{gdb.ini}
|
||
The @value{GDBN} init files are normally called @file{.gdbinit}.
|
||
The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
|
||
the limitations of file names imposed by DOS filesystems. The Windows
|
||
port of @value{GDBN} uses the standard name, but if it finds a
|
||
@file{gdb.ini} file in your home directory, it warns you about that
|
||
and suggests to rename the file to the standard name.
|
||
|
||
|
||
@node Quitting GDB
|
||
@section Quitting @value{GDBN}
|
||
@cindex exiting @value{GDBN}
|
||
@cindex leaving @value{GDBN}
|
||
|
||
@table @code
|
||
@kindex quit @r{[}@var{expression}@r{]}
|
||
@kindex q @r{(@code{quit})}
|
||
@item quit @r{[}@var{expression}@r{]}
|
||
@itemx q
|
||
To exit @value{GDBN}, use the @code{quit} command (abbreviated
|
||
@code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
|
||
do not supply @var{expression}, @value{GDBN} will terminate normally;
|
||
otherwise it will terminate using the result of @var{expression} as the
|
||
error code.
|
||
@end table
|
||
|
||
@cindex interrupt
|
||
An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
|
||
terminates the action of any @value{GDBN} command that is in progress and
|
||
returns to @value{GDBN} command level. It is safe to type the interrupt
|
||
character at any time because @value{GDBN} does not allow it to take effect
|
||
until a time when it is safe.
|
||
|
||
If you have been using @value{GDBN} to control an attached process or
|
||
device, you can release it with the @code{detach} command
|
||
(@pxref{Attach, ,Debugging an Already-running Process}).
|
||
|
||
@node Shell Commands
|
||
@section Shell Commands
|
||
|
||
If you need to execute occasional shell commands during your
|
||
debugging session, there is no need to leave or suspend @value{GDBN}; you can
|
||
just use the @code{shell} command.
|
||
|
||
@table @code
|
||
@kindex shell
|
||
@kindex !
|
||
@cindex shell escape
|
||
@item shell @var{command-string}
|
||
@itemx !@var{command-string}
|
||
Invoke a standard shell to execute @var{command-string}.
|
||
Note that no space is needed between @code{!} and @var{command-string}.
|
||
If it exists, the environment variable @code{SHELL} determines which
|
||
shell to run. Otherwise @value{GDBN} uses the default shell
|
||
(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
|
||
@end table
|
||
|
||
The utility @code{make} is often needed in development environments.
|
||
You do not have to use the @code{shell} command for this purpose in
|
||
@value{GDBN}:
|
||
|
||
@table @code
|
||
@kindex make
|
||
@cindex calling make
|
||
@item make @var{make-args}
|
||
Execute the @code{make} program with the specified
|
||
arguments. This is equivalent to @samp{shell make @var{make-args}}.
|
||
@end table
|
||
|
||
@node Logging Output
|
||
@section Logging Output
|
||
@cindex logging @value{GDBN} output
|
||
@cindex save @value{GDBN} output to a file
|
||
|
||
You may want to save the output of @value{GDBN} commands to a file.
|
||
There are several commands to control @value{GDBN}'s logging.
|
||
|
||
@table @code
|
||
@kindex set logging
|
||
@item set logging on
|
||
Enable logging.
|
||
@item set logging off
|
||
Disable logging.
|
||
@cindex logging file name
|
||
@item set logging file @var{file}
|
||
Change the name of the current logfile. The default logfile is @file{gdb.txt}.
|
||
@item set logging overwrite [on|off]
|
||
By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
|
||
you want @code{set logging on} to overwrite the logfile instead.
|
||
@item set logging redirect [on|off]
|
||
By default, @value{GDBN} output will go to both the terminal and the logfile.
|
||
Set @code{redirect} if you want output to go only to the log file.
|
||
@kindex show logging
|
||
@item show logging
|
||
Show the current values of the logging settings.
|
||
@end table
|
||
|
||
@node Commands
|
||
@chapter @value{GDBN} Commands
|
||
|
||
You can abbreviate a @value{GDBN} command to the first few letters of the command
|
||
name, if that abbreviation is unambiguous; and you can repeat certain
|
||
@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
|
||
key to get @value{GDBN} to fill out the rest of a word in a command (or to
|
||
show you the alternatives available, if there is more than one possibility).
|
||
|
||
@menu
|
||
* Command Syntax:: How to give commands to @value{GDBN}
|
||
* Completion:: Command completion
|
||
* Help:: How to ask @value{GDBN} for help
|
||
@end menu
|
||
|
||
@node Command Syntax
|
||
@section Command Syntax
|
||
|
||
A @value{GDBN} command is a single line of input. There is no limit on
|
||
how long it can be. It starts with a command name, which is followed by
|
||
arguments whose meaning depends on the command name. For example, the
|
||
command @code{step} accepts an argument which is the number of times to
|
||
step, as in @samp{step 5}. You can also use the @code{step} command
|
||
with no arguments. Some commands do not allow any arguments.
|
||
|
||
@cindex abbreviation
|
||
@value{GDBN} command names may always be truncated if that abbreviation is
|
||
unambiguous. Other possible command abbreviations are listed in the
|
||
documentation for individual commands. In some cases, even ambiguous
|
||
abbreviations are allowed; for example, @code{s} is specially defined as
|
||
equivalent to @code{step} even though there are other commands whose
|
||
names start with @code{s}. You can test abbreviations by using them as
|
||
arguments to the @code{help} command.
|
||
|
||
@cindex repeating commands
|
||
@kindex RET @r{(repeat last command)}
|
||
A blank line as input to @value{GDBN} (typing just @key{RET}) means to
|
||
repeat the previous command. Certain commands (for example, @code{run})
|
||
will not repeat this way; these are commands whose unintentional
|
||
repetition might cause trouble and which you are unlikely to want to
|
||
repeat. User-defined commands can disable this feature; see
|
||
@ref{Define, dont-repeat}.
|
||
|
||
The @code{list} and @code{x} commands, when you repeat them with
|
||
@key{RET}, construct new arguments rather than repeating
|
||
exactly as typed. This permits easy scanning of source or memory.
|
||
|
||
@value{GDBN} can also use @key{RET} in another way: to partition lengthy
|
||
output, in a way similar to the common utility @code{more}
|
||
(@pxref{Screen Size,,Screen Size}). Since it is easy to press one
|
||
@key{RET} too many in this situation, @value{GDBN} disables command
|
||
repetition after any command that generates this sort of display.
|
||
|
||
@kindex # @r{(a comment)}
|
||
@cindex comment
|
||
Any text from a @kbd{#} to the end of the line is a comment; it does
|
||
nothing. This is useful mainly in command files (@pxref{Command
|
||
Files,,Command Files}).
|
||
|
||
@cindex repeating command sequences
|
||
@kindex Ctrl-o @r{(operate-and-get-next)}
|
||
The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
|
||
commands. This command accepts the current line, like @key{RET}, and
|
||
then fetches the next line relative to the current line from the history
|
||
for editing.
|
||
|
||
@node Completion
|
||
@section Command Completion
|
||
|
||
@cindex completion
|
||
@cindex word completion
|
||
@value{GDBN} can fill in the rest of a word in a command for you, if there is
|
||
only one possibility; it can also show you what the valid possibilities
|
||
are for the next word in a command, at any time. This works for @value{GDBN}
|
||
commands, @value{GDBN} subcommands, and the names of symbols in your program.
|
||
|
||
Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
|
||
of a word. If there is only one possibility, @value{GDBN} fills in the
|
||
word, and waits for you to finish the command (or press @key{RET} to
|
||
enter it). For example, if you type
|
||
|
||
@c FIXME "@key" does not distinguish its argument sufficiently to permit
|
||
@c complete accuracy in these examples; space introduced for clarity.
|
||
@c If texinfo enhancements make it unnecessary, it would be nice to
|
||
@c replace " @key" by "@key" in the following...
|
||
@smallexample
|
||
(@value{GDBP}) info bre @key{TAB}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
|
||
the only @code{info} subcommand beginning with @samp{bre}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info breakpoints
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can either press @key{RET} at this point, to run the @code{info
|
||
breakpoints} command, or backspace and enter something else, if
|
||
@samp{breakpoints} does not look like the command you expected. (If you
|
||
were sure you wanted @code{info breakpoints} in the first place, you
|
||
might as well just type @key{RET} immediately after @samp{info bre},
|
||
to exploit command abbreviations rather than command completion).
|
||
|
||
If there is more than one possibility for the next word when you press
|
||
@key{TAB}, @value{GDBN} sounds a bell. You can either supply more
|
||
characters and try again, or just press @key{TAB} a second time;
|
||
@value{GDBN} displays all the possible completions for that word. For
|
||
example, you might want to set a breakpoint on a subroutine whose name
|
||
begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
|
||
just sounds the bell. Typing @key{TAB} again displays all the
|
||
function names in your program that begin with those characters, for
|
||
example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) b make_ @key{TAB}
|
||
@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
|
||
make_a_section_from_file make_environ
|
||
make_abs_section make_function_type
|
||
make_blockvector make_pointer_type
|
||
make_cleanup make_reference_type
|
||
make_command make_symbol_completion_list
|
||
(@value{GDBP}) b make_
|
||
@end smallexample
|
||
|
||
@noindent
|
||
After displaying the available possibilities, @value{GDBN} copies your
|
||
partial input (@samp{b make_} in the example) so you can finish the
|
||
command.
|
||
|
||
If you just want to see the list of alternatives in the first place, you
|
||
can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
|
||
means @kbd{@key{META} ?}. You can type this either by holding down a
|
||
key designated as the @key{META} shift on your keyboard (if there is
|
||
one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
|
||
|
||
If the number of possible completions is large, @value{GDBN} will
|
||
print as much of the list as it has collected, as well as a message
|
||
indicating that the list may be truncated.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) b m@key{TAB}@key{TAB}
|
||
main
|
||
<... the rest of the possible completions ...>
|
||
*** List may be truncated, max-completions reached. ***
|
||
(@value{GDBP}) b m
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This behavior can be controlled with the following commands:
|
||
|
||
@table @code
|
||
@kindex set max-completions
|
||
@item set max-completions @var{limit}
|
||
@itemx set max-completions unlimited
|
||
Set the maximum number of completion candidates. @value{GDBN} will
|
||
stop looking for more completions once it collects this many candidates.
|
||
This is useful when completing on things like function names as collecting
|
||
all the possible candidates can be time consuming.
|
||
The default value is 200. A value of zero disables tab-completion.
|
||
Note that setting either no limit or a very large limit can make
|
||
completion slow.
|
||
@kindex show max-completions
|
||
@item show max-completions
|
||
Show the maximum number of candidates that @value{GDBN} will collect and show
|
||
during completion.
|
||
@end table
|
||
|
||
@cindex quotes in commands
|
||
@cindex completion of quoted strings
|
||
Sometimes the string you need, while logically a ``word'', may contain
|
||
parentheses or other characters that @value{GDBN} normally excludes from
|
||
its notion of a word. To permit word completion to work in this
|
||
situation, you may enclose words in @code{'} (single quote marks) in
|
||
@value{GDBN} commands.
|
||
|
||
A likely situation where you might need this is in typing an
|
||
expression that involves a C@t{++} symbol name with template
|
||
parameters. This is because when completing expressions, GDB treats
|
||
the @samp{<} character as word delimiter, assuming that it's the
|
||
less-than comparison operator (@pxref{C Operators, , C and C@t{++}
|
||
Operators}).
|
||
|
||
For example, when you want to call a C@t{++} template function
|
||
interactively using the @code{print} or @code{call} commands, you may
|
||
need to distinguish whether you mean the version of @code{name} that
|
||
was specialized for @code{int}, @code{name<int>()}, or the version
|
||
that was specialized for @code{float}, @code{name<float>()}. To use
|
||
the word-completion facilities in this situation, type a single quote
|
||
@code{'} at the beginning of the function name. This alerts
|
||
@value{GDBN} that it may need to consider more information than usual
|
||
when you press @key{TAB} or @kbd{M-?} to request word completion:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p 'func< @kbd{M-?}
|
||
func<int>() func<float>()
|
||
(@value{GDBP}) p 'func<
|
||
@end smallexample
|
||
|
||
When setting breakpoints however (@pxref{Specify Location}), you don't
|
||
usually need to type a quote before the function name, because
|
||
@value{GDBN} understands that you want to set a breakpoint on a
|
||
function:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) b func< @kbd{M-?}
|
||
func<int>() func<float>()
|
||
(@value{GDBP}) b func<
|
||
@end smallexample
|
||
|
||
This is true even in the case of typing the name of C@t{++} overloaded
|
||
functions (multiple definitions of the same function, distinguished by
|
||
argument type). For example, when you want to set a breakpoint you
|
||
don't need to distinguish whether you mean the version of @code{name}
|
||
that takes an @code{int} parameter, @code{name(int)}, or the version
|
||
that takes a @code{float} parameter, @code{name(float)}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) b bubble( @kbd{M-?}
|
||
bubble(int) bubble(double)
|
||
(@value{GDBP}) b bubble(dou @kbd{M-?}
|
||
bubble(double)
|
||
@end smallexample
|
||
|
||
See @ref{quoting names} for a description of other scenarios that
|
||
require quoting.
|
||
|
||
For more information about overloaded functions, see @ref{C Plus Plus
|
||
Expressions, ,C@t{++} Expressions}. You can use the command @code{set
|
||
overload-resolution off} to disable overload resolution;
|
||
see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
|
||
|
||
@cindex completion of structure field names
|
||
@cindex structure field name completion
|
||
@cindex completion of union field names
|
||
@cindex union field name completion
|
||
When completing in an expression which looks up a field in a
|
||
structure, @value{GDBN} also tries@footnote{The completer can be
|
||
confused by certain kinds of invalid expressions. Also, it only
|
||
examines the static type of the expression, not the dynamic type.} to
|
||
limit completions to the field names available in the type of the
|
||
left-hand-side:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p gdb_stdout.@kbd{M-?}
|
||
magic to_fputs to_rewind
|
||
to_data to_isatty to_write
|
||
to_delete to_put to_write_async_safe
|
||
to_flush to_read
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This is because the @code{gdb_stdout} is a variable of the type
|
||
@code{struct ui_file} that is defined in @value{GDBN} sources as
|
||
follows:
|
||
|
||
@smallexample
|
||
struct ui_file
|
||
@{
|
||
int *magic;
|
||
ui_file_flush_ftype *to_flush;
|
||
ui_file_write_ftype *to_write;
|
||
ui_file_write_async_safe_ftype *to_write_async_safe;
|
||
ui_file_fputs_ftype *to_fputs;
|
||
ui_file_read_ftype *to_read;
|
||
ui_file_delete_ftype *to_delete;
|
||
ui_file_isatty_ftype *to_isatty;
|
||
ui_file_rewind_ftype *to_rewind;
|
||
ui_file_put_ftype *to_put;
|
||
void *to_data;
|
||
@}
|
||
@end smallexample
|
||
|
||
|
||
@node Help
|
||
@section Getting Help
|
||
@cindex online documentation
|
||
@kindex help
|
||
|
||
You can always ask @value{GDBN} itself for information on its commands,
|
||
using the command @code{help}.
|
||
|
||
@table @code
|
||
@kindex h @r{(@code{help})}
|
||
@item help
|
||
@itemx h
|
||
You can use @code{help} (abbreviated @code{h}) with no arguments to
|
||
display a short list of named classes of commands:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) help
|
||
List of classes of commands:
|
||
|
||
aliases -- Aliases of other commands
|
||
breakpoints -- Making program stop at certain points
|
||
data -- Examining data
|
||
files -- Specifying and examining files
|
||
internals -- Maintenance commands
|
||
obscure -- Obscure features
|
||
running -- Running the program
|
||
stack -- Examining the stack
|
||
status -- Status inquiries
|
||
support -- Support facilities
|
||
tracepoints -- Tracing of program execution without
|
||
stopping the program
|
||
user-defined -- User-defined commands
|
||
|
||
Type "help" followed by a class name for a list of
|
||
commands in that class.
|
||
Type "help" followed by command name for full
|
||
documentation.
|
||
Command name abbreviations are allowed if unambiguous.
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
@c the above line break eliminates huge line overfull...
|
||
|
||
@item help @var{class}
|
||
Using one of the general help classes as an argument, you can get a
|
||
list of the individual commands in that class. For example, here is the
|
||
help display for the class @code{status}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) help status
|
||
Status inquiries.
|
||
|
||
List of commands:
|
||
|
||
@c Line break in "show" line falsifies real output, but needed
|
||
@c to fit in smallbook page size.
|
||
info -- Generic command for showing things
|
||
about the program being debugged
|
||
show -- Generic command for showing things
|
||
about the debugger
|
||
|
||
Type "help" followed by command name for full
|
||
documentation.
|
||
Command name abbreviations are allowed if unambiguous.
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@item help @var{command}
|
||
With a command name as @code{help} argument, @value{GDBN} displays a
|
||
short paragraph on how to use that command.
|
||
|
||
@kindex apropos
|
||
@item apropos @var{args}
|
||
The @code{apropos} command searches through all of the @value{GDBN}
|
||
commands, and their documentation, for the regular expression specified in
|
||
@var{args}. It prints out all matches found. For example:
|
||
|
||
@smallexample
|
||
apropos alias
|
||
@end smallexample
|
||
|
||
@noindent
|
||
results in:
|
||
|
||
@smallexample
|
||
@c @group
|
||
alias -- Define a new command that is an alias of an existing command
|
||
aliases -- Aliases of other commands
|
||
d -- Delete some breakpoints or auto-display expressions
|
||
del -- Delete some breakpoints or auto-display expressions
|
||
delete -- Delete some breakpoints or auto-display expressions
|
||
@c @end group
|
||
@end smallexample
|
||
|
||
@kindex complete
|
||
@item complete @var{args}
|
||
The @code{complete @var{args}} command lists all the possible completions
|
||
for the beginning of a command. Use @var{args} to specify the beginning of the
|
||
command you want completed. For example:
|
||
|
||
@smallexample
|
||
complete i
|
||
@end smallexample
|
||
|
||
@noindent results in:
|
||
|
||
@smallexample
|
||
@group
|
||
if
|
||
ignore
|
||
info
|
||
inspect
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent This is intended for use by @sc{gnu} Emacs.
|
||
@end table
|
||
|
||
In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
|
||
and @code{show} to inquire about the state of your program, or the state
|
||
of @value{GDBN} itself. Each command supports many topics of inquiry; this
|
||
manual introduces each of them in the appropriate context. The listings
|
||
under @code{info} and under @code{show} in the Command, Variable, and
|
||
Function Index point to all the sub-commands. @xref{Command and Variable
|
||
Index}.
|
||
|
||
@c @group
|
||
@table @code
|
||
@kindex info
|
||
@kindex i @r{(@code{info})}
|
||
@item info
|
||
This command (abbreviated @code{i}) is for describing the state of your
|
||
program. For example, you can show the arguments passed to a function
|
||
with @code{info args}, list the registers currently in use with @code{info
|
||
registers}, or list the breakpoints you have set with @code{info breakpoints}.
|
||
You can get a complete list of the @code{info} sub-commands with
|
||
@w{@code{help info}}.
|
||
|
||
@kindex set
|
||
@item set
|
||
You can assign the result of an expression to an environment variable with
|
||
@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
|
||
@code{set prompt $}.
|
||
|
||
@kindex show
|
||
@item show
|
||
In contrast to @code{info}, @code{show} is for describing the state of
|
||
@value{GDBN} itself.
|
||
You can change most of the things you can @code{show}, by using the
|
||
related command @code{set}; for example, you can control what number
|
||
system is used for displays with @code{set radix}, or simply inquire
|
||
which is currently in use with @code{show radix}.
|
||
|
||
@kindex info set
|
||
To display all the settable parameters and their current
|
||
values, you can use @code{show} with no arguments; you may also use
|
||
@code{info set}. Both commands produce the same display.
|
||
@c FIXME: "info set" violates the rule that "info" is for state of
|
||
@c FIXME...program. Ck w/ GNU: "info set" to be called something else,
|
||
@c FIXME...or change desc of rule---eg "state of prog and debugging session"?
|
||
@end table
|
||
@c @end group
|
||
|
||
Here are several miscellaneous @code{show} subcommands, all of which are
|
||
exceptional in lacking corresponding @code{set} commands:
|
||
|
||
@table @code
|
||
@kindex show version
|
||
@cindex @value{GDBN} version number
|
||
@item show version
|
||
Show what version of @value{GDBN} is running. You should include this
|
||
information in @value{GDBN} bug-reports. If multiple versions of
|
||
@value{GDBN} are in use at your site, you may need to determine which
|
||
version of @value{GDBN} you are running; as @value{GDBN} evolves, new
|
||
commands are introduced, and old ones may wither away. Also, many
|
||
system vendors ship variant versions of @value{GDBN}, and there are
|
||
variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
|
||
The version number is the same as the one announced when you start
|
||
@value{GDBN}.
|
||
|
||
@kindex show copying
|
||
@kindex info copying
|
||
@cindex display @value{GDBN} copyright
|
||
@item show copying
|
||
@itemx info copying
|
||
Display information about permission for copying @value{GDBN}.
|
||
|
||
@kindex show warranty
|
||
@kindex info warranty
|
||
@item show warranty
|
||
@itemx info warranty
|
||
Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
|
||
if your version of @value{GDBN} comes with one.
|
||
|
||
@kindex show configuration
|
||
@item show configuration
|
||
Display detailed information about the way @value{GDBN} was configured
|
||
when it was built. This displays the optional arguments passed to the
|
||
@file{configure} script and also configuration parameters detected
|
||
automatically by @command{configure}. When reporting a @value{GDBN}
|
||
bug (@pxref{GDB Bugs}), it is important to include this information in
|
||
your report.
|
||
|
||
@end table
|
||
|
||
@node Running
|
||
@chapter Running Programs Under @value{GDBN}
|
||
|
||
When you run a program under @value{GDBN}, you must first generate
|
||
debugging information when you compile it.
|
||
|
||
You may start @value{GDBN} with its arguments, if any, in an environment
|
||
of your choice. If you are doing native debugging, you may redirect
|
||
your program's input and output, debug an already running process, or
|
||
kill a child process.
|
||
|
||
@menu
|
||
* Compilation:: Compiling for debugging
|
||
* Starting:: Starting your program
|
||
* Arguments:: Your program's arguments
|
||
* Environment:: Your program's environment
|
||
|
||
* Working Directory:: Your program's working directory
|
||
* Input/Output:: Your program's input and output
|
||
* Attach:: Debugging an already-running process
|
||
* Kill Process:: Killing the child process
|
||
|
||
* Inferiors and Programs:: Debugging multiple inferiors and programs
|
||
* Threads:: Debugging programs with multiple threads
|
||
* Forks:: Debugging forks
|
||
* Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
|
||
@end menu
|
||
|
||
@node Compilation
|
||
@section Compiling for Debugging
|
||
|
||
In order to debug a program effectively, you need to generate
|
||
debugging information when you compile it. This debugging information
|
||
is stored in the object file; it describes the data type of each
|
||
variable or function and the correspondence between source line numbers
|
||
and addresses in the executable code.
|
||
|
||
To request debugging information, specify the @samp{-g} option when you run
|
||
the compiler.
|
||
|
||
Programs that are to be shipped to your customers are compiled with
|
||
optimizations, using the @samp{-O} compiler option. However, some
|
||
compilers are unable to handle the @samp{-g} and @samp{-O} options
|
||
together. Using those compilers, you cannot generate optimized
|
||
executables containing debugging information.
|
||
|
||
@value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
|
||
without @samp{-O}, making it possible to debug optimized code. We
|
||
recommend that you @emph{always} use @samp{-g} whenever you compile a
|
||
program. You may think your program is correct, but there is no sense
|
||
in pushing your luck. For more information, see @ref{Optimized Code}.
|
||
|
||
Older versions of the @sc{gnu} C compiler permitted a variant option
|
||
@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
|
||
format; if your @sc{gnu} C compiler has this option, do not use it.
|
||
|
||
@value{GDBN} knows about preprocessor macros and can show you their
|
||
expansion (@pxref{Macros}). Most compilers do not include information
|
||
about preprocessor macros in the debugging information if you specify
|
||
the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
|
||
the @sc{gnu} C compiler, provides macro information if you are using
|
||
the DWARF debugging format, and specify the option @option{-g3}.
|
||
|
||
@xref{Debugging Options,,Options for Debugging Your Program or GCC,
|
||
gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
|
||
information on @value{NGCC} options affecting debug information.
|
||
|
||
You will have the best debugging experience if you use the latest
|
||
version of the DWARF debugging format that your compiler supports.
|
||
DWARF is currently the most expressive and best supported debugging
|
||
format in @value{GDBN}.
|
||
|
||
@need 2000
|
||
@node Starting
|
||
@section Starting your Program
|
||
@cindex starting
|
||
@cindex running
|
||
|
||
@table @code
|
||
@kindex run
|
||
@kindex r @r{(@code{run})}
|
||
@item run
|
||
@itemx r
|
||
Use the @code{run} command to start your program under @value{GDBN}.
|
||
You must first specify the program name with an argument to
|
||
@value{GDBN} (@pxref{Invocation, ,Getting In and Out of
|
||
@value{GDBN}}), or by using the @code{file} or @code{exec-file}
|
||
command (@pxref{Files, ,Commands to Specify Files}).
|
||
|
||
@end table
|
||
|
||
If you are running your program in an execution environment that
|
||
supports processes, @code{run} creates an inferior process and makes
|
||
that process run your program. In some environments without processes,
|
||
@code{run} jumps to the start of your program. Other targets,
|
||
like @samp{remote}, are always running. If you get an error
|
||
message like this one:
|
||
|
||
@smallexample
|
||
The "remote" target does not support "run".
|
||
Try "help target" or "continue".
|
||
@end smallexample
|
||
|
||
@noindent
|
||
then use @code{continue} to run your program. You may need @code{load}
|
||
first (@pxref{load}).
|
||
|
||
The execution of a program is affected by certain information it
|
||
receives from its superior. @value{GDBN} provides ways to specify this
|
||
information, which you must do @emph{before} starting your program. (You
|
||
can change it after starting your program, but such changes only affect
|
||
your program the next time you start it.) This information may be
|
||
divided into four categories:
|
||
|
||
@table @asis
|
||
@item The @emph{arguments.}
|
||
Specify the arguments to give your program as the arguments of the
|
||
@code{run} command. If a shell is available on your target, the shell
|
||
is used to pass the arguments, so that you may use normal conventions
|
||
(such as wildcard expansion or variable substitution) in describing
|
||
the arguments.
|
||
In Unix systems, you can control which shell is used with the
|
||
@code{SHELL} environment variable. If you do not define @code{SHELL},
|
||
@value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
|
||
use of any shell with the @code{set startup-with-shell} command (see
|
||
below for details).
|
||
|
||
@item The @emph{environment.}
|
||
Your program normally inherits its environment from @value{GDBN}, but you can
|
||
use the @value{GDBN} commands @code{set environment} and @code{unset
|
||
environment} to change parts of the environment that affect
|
||
your program. @xref{Environment, ,Your Program's Environment}.
|
||
|
||
@item The @emph{working directory.}
|
||
You can set your program's working directory with the command
|
||
@kbd{set cwd}. If you do not set any working directory with this
|
||
command, your program will inherit @value{GDBN}'s working directory if
|
||
native debugging, or the remote server's working directory if remote
|
||
debugging. @xref{Working Directory, ,Your Program's Working
|
||
Directory}.
|
||
|
||
@item The @emph{standard input and output.}
|
||
Your program normally uses the same device for standard input and
|
||
standard output as @value{GDBN} is using. You can redirect input and output
|
||
in the @code{run} command line, or you can use the @code{tty} command to
|
||
set a different device for your program.
|
||
@xref{Input/Output, ,Your Program's Input and Output}.
|
||
|
||
@cindex pipes
|
||
@emph{Warning:} While input and output redirection work, you cannot use
|
||
pipes to pass the output of the program you are debugging to another
|
||
program; if you attempt this, @value{GDBN} is likely to wind up debugging the
|
||
wrong program.
|
||
@end table
|
||
|
||
When you issue the @code{run} command, your program begins to execute
|
||
immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
|
||
of how to arrange for your program to stop. Once your program has
|
||
stopped, you may call functions in your program, using the @code{print}
|
||
or @code{call} commands. @xref{Data, ,Examining Data}.
|
||
|
||
If the modification time of your symbol file has changed since the last
|
||
time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
|
||
table, and reads it again. When it does this, @value{GDBN} tries to retain
|
||
your current breakpoints.
|
||
|
||
@table @code
|
||
@kindex start
|
||
@item start
|
||
@cindex run to main procedure
|
||
The name of the main procedure can vary from language to language.
|
||
With C or C@t{++}, the main procedure name is always @code{main}, but
|
||
other languages such as Ada do not require a specific name for their
|
||
main procedure. The debugger provides a convenient way to start the
|
||
execution of the program and to stop at the beginning of the main
|
||
procedure, depending on the language used.
|
||
|
||
The @samp{start} command does the equivalent of setting a temporary
|
||
breakpoint at the beginning of the main procedure and then invoking
|
||
the @samp{run} command.
|
||
|
||
@cindex elaboration phase
|
||
Some programs contain an @dfn{elaboration} phase where some startup code is
|
||
executed before the main procedure is called. This depends on the
|
||
languages used to write your program. In C@t{++}, for instance,
|
||
constructors for static and global objects are executed before
|
||
@code{main} is called. It is therefore possible that the debugger stops
|
||
before reaching the main procedure. However, the temporary breakpoint
|
||
will remain to halt execution.
|
||
|
||
Specify the arguments to give to your program as arguments to the
|
||
@samp{start} command. These arguments will be given verbatim to the
|
||
underlying @samp{run} command. Note that the same arguments will be
|
||
reused if no argument is provided during subsequent calls to
|
||
@samp{start} or @samp{run}.
|
||
|
||
It is sometimes necessary to debug the program during elaboration. In
|
||
these cases, using the @code{start} command would stop the execution
|
||
of your program too late, as the program would have already completed
|
||
the elaboration phase. Under these circumstances, either insert
|
||
breakpoints in your elaboration code before running your program or
|
||
use the @code{starti} command.
|
||
|
||
@kindex starti
|
||
@item starti
|
||
@cindex run to first instruction
|
||
The @samp{starti} command does the equivalent of setting a temporary
|
||
breakpoint at the first instruction of a program's execution and then
|
||
invoking the @samp{run} command. For programs containing an
|
||
elaboration phase, the @code{starti} command will stop execution at
|
||
the start of the elaboration phase.
|
||
|
||
@anchor{set exec-wrapper}
|
||
@kindex set exec-wrapper
|
||
@item set exec-wrapper @var{wrapper}
|
||
@itemx show exec-wrapper
|
||
@itemx unset exec-wrapper
|
||
When @samp{exec-wrapper} is set, the specified wrapper is used to
|
||
launch programs for debugging. @value{GDBN} starts your program
|
||
with a shell command of the form @kbd{exec @var{wrapper}
|
||
@var{program}}. Quoting is added to @var{program} and its
|
||
arguments, but not to @var{wrapper}, so you should add quotes if
|
||
appropriate for your shell. The wrapper runs until it executes
|
||
your program, and then @value{GDBN} takes control.
|
||
|
||
You can use any program that eventually calls @code{execve} with
|
||
its arguments as a wrapper. Several standard Unix utilities do
|
||
this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
|
||
with @code{exec "$@@"} will also work.
|
||
|
||
For example, you can use @code{env} to pass an environment variable to
|
||
the debugged program, without setting the variable in your shell's
|
||
environment:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
|
||
(@value{GDBP}) run
|
||
@end smallexample
|
||
|
||
This command is available when debugging locally on most targets, excluding
|
||
@sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
|
||
|
||
@kindex set startup-with-shell
|
||
@anchor{set startup-with-shell}
|
||
@item set startup-with-shell
|
||
@itemx set startup-with-shell on
|
||
@itemx set startup-with-shell off
|
||
@itemx show startup-with-shell
|
||
On Unix systems, by default, if a shell is available on your target,
|
||
@value{GDBN}) uses it to start your program. Arguments of the
|
||
@code{run} command are passed to the shell, which does variable
|
||
substitution, expands wildcard characters and performs redirection of
|
||
I/O. In some circumstances, it may be useful to disable such use of a
|
||
shell, for example, when debugging the shell itself or diagnosing
|
||
startup failures such as:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) run
|
||
Starting program: ./a.out
|
||
During startup program terminated with signal SIGSEGV, Segmentation fault.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
which indicates the shell or the wrapper specified with
|
||
@samp{exec-wrapper} crashed, not your program. Most often, this is
|
||
caused by something odd in your shell's non-interactive mode
|
||
initialization file---such as @file{.cshrc} for C-shell,
|
||
$@file{.zshenv} for the Z shell, or the file specified in the
|
||
@samp{BASH_ENV} environment variable for BASH.
|
||
|
||
@anchor{set auto-connect-native-target}
|
||
@kindex set auto-connect-native-target
|
||
@item set auto-connect-native-target
|
||
@itemx set auto-connect-native-target on
|
||
@itemx set auto-connect-native-target off
|
||
@itemx show auto-connect-native-target
|
||
|
||
By default, if not connected to any target yet (e.g., with
|
||
@code{target remote}), the @code{run} command starts your program as a
|
||
native process under @value{GDBN}, on your local machine. If you're
|
||
sure you don't want to debug programs on your local machine, you can
|
||
tell @value{GDBN} to not connect to the native target automatically
|
||
with the @code{set auto-connect-native-target off} command.
|
||
|
||
If @code{on}, which is the default, and if @value{GDBN} is not
|
||
connected to a target already, the @code{run} command automaticaly
|
||
connects to the native target, if one is available.
|
||
|
||
If @code{off}, and if @value{GDBN} is not connected to a target
|
||
already, the @code{run} command fails with an error:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) run
|
||
Don't know how to run. Try "help target".
|
||
@end smallexample
|
||
|
||
If @value{GDBN} is already connected to a target, @value{GDBN} always
|
||
uses it with the @code{run} command.
|
||
|
||
In any case, you can explicitly connect to the native target with the
|
||
@code{target native} command. For example,
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set auto-connect-native-target off
|
||
(@value{GDBP}) run
|
||
Don't know how to run. Try "help target".
|
||
(@value{GDBP}) target native
|
||
(@value{GDBP}) run
|
||
Starting program: ./a.out
|
||
[Inferior 1 (process 10421) exited normally]
|
||
@end smallexample
|
||
|
||
In case you connected explicitly to the @code{native} target,
|
||
@value{GDBN} remains connected even if all inferiors exit, ready for
|
||
the next @code{run} command. Use the @code{disconnect} command to
|
||
disconnect.
|
||
|
||
Examples of other commands that likewise respect the
|
||
@code{auto-connect-native-target} setting: @code{attach}, @code{info
|
||
proc}, @code{info os}.
|
||
|
||
@kindex set disable-randomization
|
||
@item set disable-randomization
|
||
@itemx set disable-randomization on
|
||
This option (enabled by default in @value{GDBN}) will turn off the native
|
||
randomization of the virtual address space of the started program. This option
|
||
is useful for multiple debugging sessions to make the execution better
|
||
reproducible and memory addresses reusable across debugging sessions.
|
||
|
||
This feature is implemented only on certain targets, including @sc{gnu}/Linux.
|
||
On @sc{gnu}/Linux you can get the same behavior using
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set exec-wrapper setarch `uname -m` -R
|
||
@end smallexample
|
||
|
||
@item set disable-randomization off
|
||
Leave the behavior of the started executable unchanged. Some bugs rear their
|
||
ugly heads only when the program is loaded at certain addresses. If your bug
|
||
disappears when you run the program under @value{GDBN}, that might be because
|
||
@value{GDBN} by default disables the address randomization on platforms, such
|
||
as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
|
||
disable-randomization off} to try to reproduce such elusive bugs.
|
||
|
||
On targets where it is available, virtual address space randomization
|
||
protects the programs against certain kinds of security attacks. In these
|
||
cases the attacker needs to know the exact location of a concrete executable
|
||
code. Randomizing its location makes it impossible to inject jumps misusing
|
||
a code at its expected addresses.
|
||
|
||
Prelinking shared libraries provides a startup performance advantage but it
|
||
makes addresses in these libraries predictable for privileged processes by
|
||
having just unprivileged access at the target system. Reading the shared
|
||
library binary gives enough information for assembling the malicious code
|
||
misusing it. Still even a prelinked shared library can get loaded at a new
|
||
random address just requiring the regular relocation process during the
|
||
startup. Shared libraries not already prelinked are always loaded at
|
||
a randomly chosen address.
|
||
|
||
Position independent executables (PIE) contain position independent code
|
||
similar to the shared libraries and therefore such executables get loaded at
|
||
a randomly chosen address upon startup. PIE executables always load even
|
||
already prelinked shared libraries at a random address. You can build such
|
||
executable using @command{gcc -fPIE -pie}.
|
||
|
||
Heap (malloc storage), stack and custom mmap areas are always placed randomly
|
||
(as long as the randomization is enabled).
|
||
|
||
@item show disable-randomization
|
||
Show the current setting of the explicit disable of the native randomization of
|
||
the virtual address space of the started program.
|
||
|
||
@end table
|
||
|
||
@node Arguments
|
||
@section Your Program's Arguments
|
||
|
||
@cindex arguments (to your program)
|
||
The arguments to your program can be specified by the arguments of the
|
||
@code{run} command.
|
||
They are passed to a shell, which expands wildcard characters and
|
||
performs redirection of I/O, and thence to your program. Your
|
||
@code{SHELL} environment variable (if it exists) specifies what shell
|
||
@value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
|
||
the default shell (@file{/bin/sh} on Unix).
|
||
|
||
On non-Unix systems, the program is usually invoked directly by
|
||
@value{GDBN}, which emulates I/O redirection via the appropriate system
|
||
calls, and the wildcard characters are expanded by the startup code of
|
||
the program, not by the shell.
|
||
|
||
@code{run} with no arguments uses the same arguments used by the previous
|
||
@code{run}, or those set by the @code{set args} command.
|
||
|
||
@table @code
|
||
@kindex set args
|
||
@item set args
|
||
Specify the arguments to be used the next time your program is run. If
|
||
@code{set args} has no arguments, @code{run} executes your program
|
||
with no arguments. Once you have run your program with arguments,
|
||
using @code{set args} before the next @code{run} is the only way to run
|
||
it again without arguments.
|
||
|
||
@kindex show args
|
||
@item show args
|
||
Show the arguments to give your program when it is started.
|
||
@end table
|
||
|
||
@node Environment
|
||
@section Your Program's Environment
|
||
|
||
@cindex environment (of your program)
|
||
The @dfn{environment} consists of a set of environment variables and
|
||
their values. Environment variables conventionally record such things as
|
||
your user name, your home directory, your terminal type, and your search
|
||
path for programs to run. Usually you set up environment variables with
|
||
the shell and they are inherited by all the other programs you run. When
|
||
debugging, it can be useful to try running your program with a modified
|
||
environment without having to start @value{GDBN} over again.
|
||
|
||
@table @code
|
||
@kindex path
|
||
@item path @var{directory}
|
||
Add @var{directory} to the front of the @code{PATH} environment variable
|
||
(the search path for executables) that will be passed to your program.
|
||
The value of @code{PATH} used by @value{GDBN} does not change.
|
||
You may specify several directory names, separated by whitespace or by a
|
||
system-dependent separator character (@samp{:} on Unix, @samp{;} on
|
||
MS-DOS and MS-Windows). If @var{directory} is already in the path, it
|
||
is moved to the front, so it is searched sooner.
|
||
|
||
You can use the string @samp{$cwd} to refer to whatever is the current
|
||
working directory at the time @value{GDBN} searches the path. If you
|
||
use @samp{.} instead, it refers to the directory where you executed the
|
||
@code{path} command. @value{GDBN} replaces @samp{.} in the
|
||
@var{directory} argument (with the current path) before adding
|
||
@var{directory} to the search path.
|
||
@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
|
||
@c document that, since repeating it would be a no-op.
|
||
|
||
@kindex show paths
|
||
@item show paths
|
||
Display the list of search paths for executables (the @code{PATH}
|
||
environment variable).
|
||
|
||
@kindex show environment
|
||
@item show environment @r{[}@var{varname}@r{]}
|
||
Print the value of environment variable @var{varname} to be given to
|
||
your program when it starts. If you do not supply @var{varname},
|
||
print the names and values of all environment variables to be given to
|
||
your program. You can abbreviate @code{environment} as @code{env}.
|
||
|
||
@kindex set environment
|
||
@anchor{set environment}
|
||
@item set environment @var{varname} @r{[}=@var{value}@r{]}
|
||
Set environment variable @var{varname} to @var{value}. The value
|
||
changes for your program (and the shell @value{GDBN} uses to launch
|
||
it), not for @value{GDBN} itself. The @var{value} may be any string; the
|
||
values of environment variables are just strings, and any
|
||
interpretation is supplied by your program itself. The @var{value}
|
||
parameter is optional; if it is eliminated, the variable is set to a
|
||
null value.
|
||
@c "any string" here does not include leading, trailing
|
||
@c blanks. Gnu asks: does anyone care?
|
||
|
||
For example, this command:
|
||
|
||
@smallexample
|
||
set env USER = foo
|
||
@end smallexample
|
||
|
||
@noindent
|
||
tells the debugged program, when subsequently run, that its user is named
|
||
@samp{foo}. (The spaces around @samp{=} are used for clarity here; they
|
||
are not actually required.)
|
||
|
||
Note that on Unix systems, @value{GDBN} runs your program via a shell,
|
||
which also inherits the environment set with @code{set environment}.
|
||
If necessary, you can avoid that by using the @samp{env} program as a
|
||
wrapper instead of using @code{set environment}. @xref{set
|
||
exec-wrapper}, for an example doing just that.
|
||
|
||
Environment variables that are set by the user are also transmitted to
|
||
@command{gdbserver} to be used when starting the remote inferior.
|
||
@pxref{QEnvironmentHexEncoded}.
|
||
|
||
@kindex unset environment
|
||
@anchor{unset environment}
|
||
@item unset environment @var{varname}
|
||
Remove variable @var{varname} from the environment to be passed to your
|
||
program. This is different from @samp{set env @var{varname} =};
|
||
@code{unset environment} removes the variable from the environment,
|
||
rather than assigning it an empty value.
|
||
|
||
Environment variables that are unset by the user are also unset on
|
||
@command{gdbserver} when starting the remote inferior.
|
||
@pxref{QEnvironmentUnset}.
|
||
@end table
|
||
|
||
@emph{Warning:} On Unix systems, @value{GDBN} runs your program using
|
||
the shell indicated by your @code{SHELL} environment variable if it
|
||
exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
|
||
names a shell that runs an initialization file when started
|
||
non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
|
||
for the Z shell, or the file specified in the @samp{BASH_ENV}
|
||
environment variable for BASH---any variables you set in that file
|
||
affect your program. You may wish to move setting of environment
|
||
variables to files that are only run when you sign on, such as
|
||
@file{.login} or @file{.profile}.
|
||
|
||
@node Working Directory
|
||
@section Your Program's Working Directory
|
||
|
||
@cindex working directory (of your program)
|
||
Each time you start your program with @code{run}, the inferior will be
|
||
initialized with the current working directory specified by the
|
||
@kbd{set cwd} command. If no directory has been specified by this
|
||
command, then the inferior will inherit @value{GDBN}'s current working
|
||
directory as its working directory if native debugging, or it will
|
||
inherit the remote server's current working directory if remote
|
||
debugging.
|
||
|
||
@table @code
|
||
@kindex set cwd
|
||
@cindex change inferior's working directory
|
||
@anchor{set cwd command}
|
||
@item set cwd @r{[}@var{directory}@r{]}
|
||
Set the inferior's working directory to @var{directory}, which will be
|
||
@code{glob}-expanded in order to resolve tildes (@file{~}). If no
|
||
argument has been specified, the command clears the setting and resets
|
||
it to an empty state. This setting has no effect on @value{GDBN}'s
|
||
working directory, and it only takes effect the next time you start
|
||
the inferior. The @file{~} in @var{directory} is a short for the
|
||
@dfn{home directory}, usually pointed to by the @env{HOME} environment
|
||
variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
|
||
uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
|
||
fallback.
|
||
|
||
You can also change @value{GDBN}'s current working directory by using
|
||
the @code{cd} command.
|
||
@xref{cd command}.
|
||
|
||
@kindex show cwd
|
||
@cindex show inferior's working directory
|
||
@item show cwd
|
||
Show the inferior's working directory. If no directory has been
|
||
specified by @kbd{set cwd}, then the default inferior's working
|
||
directory is the same as @value{GDBN}'s working directory.
|
||
|
||
@kindex cd
|
||
@cindex change @value{GDBN}'s working directory
|
||
@anchor{cd command}
|
||
@item cd @r{[}@var{directory}@r{]}
|
||
Set the @value{GDBN} working directory to @var{directory}. If not
|
||
given, @var{directory} uses @file{'~'}.
|
||
|
||
The @value{GDBN} working directory serves as a default for the
|
||
commands that specify files for @value{GDBN} to operate on.
|
||
@xref{Files, ,Commands to Specify Files}.
|
||
@xref{set cwd command}.
|
||
|
||
@kindex pwd
|
||
@item pwd
|
||
Print the @value{GDBN} working directory.
|
||
@end table
|
||
|
||
It is generally impossible to find the current working directory of
|
||
the process being debugged (since a program can change its directory
|
||
during its run). If you work on a system where @value{GDBN} supports
|
||
the @code{info proc} command (@pxref{Process Information}), you can
|
||
use the @code{info proc} command to find out the
|
||
current working directory of the debuggee.
|
||
|
||
@node Input/Output
|
||
@section Your Program's Input and Output
|
||
|
||
@cindex redirection
|
||
@cindex i/o
|
||
@cindex terminal
|
||
By default, the program you run under @value{GDBN} does input and output to
|
||
the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
|
||
to its own terminal modes to interact with you, but it records the terminal
|
||
modes your program was using and switches back to them when you continue
|
||
running your program.
|
||
|
||
@table @code
|
||
@kindex info terminal
|
||
@item info terminal
|
||
Displays information recorded by @value{GDBN} about the terminal modes your
|
||
program is using.
|
||
@end table
|
||
|
||
You can redirect your program's input and/or output using shell
|
||
redirection with the @code{run} command. For example,
|
||
|
||
@smallexample
|
||
run > outfile
|
||
@end smallexample
|
||
|
||
@noindent
|
||
starts your program, diverting its output to the file @file{outfile}.
|
||
|
||
@kindex tty
|
||
@cindex controlling terminal
|
||
Another way to specify where your program should do input and output is
|
||
with the @code{tty} command. This command accepts a file name as
|
||
argument, and causes this file to be the default for future @code{run}
|
||
commands. It also resets the controlling terminal for the child
|
||
process, for future @code{run} commands. For example,
|
||
|
||
@smallexample
|
||
tty /dev/ttyb
|
||
@end smallexample
|
||
|
||
@noindent
|
||
directs that processes started with subsequent @code{run} commands
|
||
default to do input and output on the terminal @file{/dev/ttyb} and have
|
||
that as their controlling terminal.
|
||
|
||
An explicit redirection in @code{run} overrides the @code{tty} command's
|
||
effect on the input/output device, but not its effect on the controlling
|
||
terminal.
|
||
|
||
When you use the @code{tty} command or redirect input in the @code{run}
|
||
command, only the input @emph{for your program} is affected. The input
|
||
for @value{GDBN} still comes from your terminal. @code{tty} is an alias
|
||
for @code{set inferior-tty}.
|
||
|
||
@cindex inferior tty
|
||
@cindex set inferior controlling terminal
|
||
You can use the @code{show inferior-tty} command to tell @value{GDBN} to
|
||
display the name of the terminal that will be used for future runs of your
|
||
program.
|
||
|
||
@table @code
|
||
@item set inferior-tty [ @var{tty} ]
|
||
@kindex set inferior-tty
|
||
Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
|
||
restores the default behavior, which is to use the same terminal as
|
||
@value{GDBN}.
|
||
|
||
@item show inferior-tty
|
||
@kindex show inferior-tty
|
||
Show the current tty for the program being debugged.
|
||
@end table
|
||
|
||
@node Attach
|
||
@section Debugging an Already-running Process
|
||
@kindex attach
|
||
@cindex attach
|
||
|
||
@table @code
|
||
@item attach @var{process-id}
|
||
This command attaches to a running process---one that was started
|
||
outside @value{GDBN}. (@code{info files} shows your active
|
||
targets.) The command takes as argument a process ID. The usual way to
|
||
find out the @var{process-id} of a Unix process is with the @code{ps} utility,
|
||
or with the @samp{jobs -l} shell command.
|
||
|
||
@code{attach} does not repeat if you press @key{RET} a second time after
|
||
executing the command.
|
||
@end table
|
||
|
||
To use @code{attach}, your program must be running in an environment
|
||
which supports processes; for example, @code{attach} does not work for
|
||
programs on bare-board targets that lack an operating system. You must
|
||
also have permission to send the process a signal.
|
||
|
||
When you use @code{attach}, the debugger finds the program running in
|
||
the process first by looking in the current working directory, then (if
|
||
the program is not found) by using the source file search path
|
||
(@pxref{Source Path, ,Specifying Source Directories}). You can also use
|
||
the @code{file} command to load the program. @xref{Files, ,Commands to
|
||
Specify Files}.
|
||
|
||
The first thing @value{GDBN} does after arranging to debug the specified
|
||
process is to stop it. You can examine and modify an attached process
|
||
with all the @value{GDBN} commands that are ordinarily available when
|
||
you start processes with @code{run}. You can insert breakpoints; you
|
||
can step and continue; you can modify storage. If you would rather the
|
||
process continue running, you may use the @code{continue} command after
|
||
attaching @value{GDBN} to the process.
|
||
|
||
@table @code
|
||
@kindex detach
|
||
@item detach
|
||
When you have finished debugging the attached process, you can use the
|
||
@code{detach} command to release it from @value{GDBN} control. Detaching
|
||
the process continues its execution. After the @code{detach} command,
|
||
that process and @value{GDBN} become completely independent once more, and you
|
||
are ready to @code{attach} another process or start one with @code{run}.
|
||
@code{detach} does not repeat if you press @key{RET} again after
|
||
executing the command.
|
||
@end table
|
||
|
||
If you exit @value{GDBN} while you have an attached process, you detach
|
||
that process. If you use the @code{run} command, you kill that process.
|
||
By default, @value{GDBN} asks for confirmation if you try to do either of these
|
||
things; you can control whether or not you need to confirm by using the
|
||
@code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
|
||
Messages}).
|
||
|
||
@node Kill Process
|
||
@section Killing the Child Process
|
||
|
||
@table @code
|
||
@kindex kill
|
||
@item kill
|
||
Kill the child process in which your program is running under @value{GDBN}.
|
||
@end table
|
||
|
||
This command is useful if you wish to debug a core dump instead of a
|
||
running process. @value{GDBN} ignores any core dump file while your program
|
||
is running.
|
||
|
||
On some operating systems, a program cannot be executed outside @value{GDBN}
|
||
while you have breakpoints set on it inside @value{GDBN}. You can use the
|
||
@code{kill} command in this situation to permit running your program
|
||
outside the debugger.
|
||
|
||
The @code{kill} command is also useful if you wish to recompile and
|
||
relink your program, since on many systems it is impossible to modify an
|
||
executable file while it is running in a process. In this case, when you
|
||
next type @code{run}, @value{GDBN} notices that the file has changed, and
|
||
reads the symbol table again (while trying to preserve your current
|
||
breakpoint settings).
|
||
|
||
@node Inferiors and Programs
|
||
@section Debugging Multiple Inferiors and Programs
|
||
|
||
@value{GDBN} lets you run and debug multiple programs in a single
|
||
session. In addition, @value{GDBN} on some systems may let you run
|
||
several programs simultaneously (otherwise you have to exit from one
|
||
before starting another). In the most general case, you can have
|
||
multiple threads of execution in each of multiple processes, launched
|
||
from multiple executables.
|
||
|
||
@cindex inferior
|
||
@value{GDBN} represents the state of each program execution with an
|
||
object called an @dfn{inferior}. An inferior typically corresponds to
|
||
a process, but is more general and applies also to targets that do not
|
||
have processes. Inferiors may be created before a process runs, and
|
||
may be retained after a process exits. Inferiors have unique
|
||
identifiers that are different from process ids. Usually each
|
||
inferior will also have its own distinct address space, although some
|
||
embedded targets may have several inferiors running in different parts
|
||
of a single address space. Each inferior may in turn have multiple
|
||
threads running in it.
|
||
|
||
To find out what inferiors exist at any moment, use @w{@code{info
|
||
inferiors}}:
|
||
|
||
@table @code
|
||
@kindex info inferiors
|
||
@item info inferiors
|
||
Print a list of all inferiors currently being managed by @value{GDBN}.
|
||
|
||
@value{GDBN} displays for each inferior (in this order):
|
||
|
||
@enumerate
|
||
@item
|
||
the inferior number assigned by @value{GDBN}
|
||
|
||
@item
|
||
the target system's inferior identifier
|
||
|
||
@item
|
||
the name of the executable the inferior is running.
|
||
|
||
@end enumerate
|
||
|
||
@noindent
|
||
An asterisk @samp{*} preceding the @value{GDBN} inferior number
|
||
indicates the current inferior.
|
||
|
||
For example,
|
||
@end table
|
||
@c end table here to get a little more width for example
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info inferiors
|
||
Num Description Executable
|
||
2 process 2307 hello
|
||
* 1 process 3401 goodbye
|
||
@end smallexample
|
||
|
||
To switch focus between inferiors, use the @code{inferior} command:
|
||
|
||
@table @code
|
||
@kindex inferior @var{infno}
|
||
@item inferior @var{infno}
|
||
Make inferior number @var{infno} the current inferior. The argument
|
||
@var{infno} is the inferior number assigned by @value{GDBN}, as shown
|
||
in the first field of the @samp{info inferiors} display.
|
||
@end table
|
||
|
||
@vindex $_inferior@r{, convenience variable}
|
||
The debugger convenience variable @samp{$_inferior} contains the
|
||
number of the current inferior. You may find this useful in writing
|
||
breakpoint conditional expressions, command scripts, and so forth.
|
||
@xref{Convenience Vars,, Convenience Variables}, for general
|
||
information on convenience variables.
|
||
|
||
You can get multiple executables into a debugging session via the
|
||
@code{add-inferior} and @w{@code{clone-inferior}} commands. On some
|
||
systems @value{GDBN} can add inferiors to the debug session
|
||
automatically by following calls to @code{fork} and @code{exec}. To
|
||
remove inferiors from the debugging session use the
|
||
@w{@code{remove-inferiors}} command.
|
||
|
||
@table @code
|
||
@kindex add-inferior
|
||
@item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
|
||
Adds @var{n} inferiors to be run using @var{executable} as the
|
||
executable; @var{n} defaults to 1. If no executable is specified,
|
||
the inferiors begins empty, with no program. You can still assign or
|
||
change the program assigned to the inferior at any time by using the
|
||
@code{file} command with the executable name as its argument.
|
||
|
||
@kindex clone-inferior
|
||
@item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
|
||
Adds @var{n} inferiors ready to execute the same program as inferior
|
||
@var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
|
||
number of the current inferior. This is a convenient command when you
|
||
want to run another instance of the inferior you are debugging.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info inferiors
|
||
Num Description Executable
|
||
* 1 process 29964 helloworld
|
||
(@value{GDBP}) clone-inferior
|
||
Added inferior 2.
|
||
1 inferiors added.
|
||
(@value{GDBP}) info inferiors
|
||
Num Description Executable
|
||
2 <null> helloworld
|
||
* 1 process 29964 helloworld
|
||
@end smallexample
|
||
|
||
You can now simply switch focus to inferior 2 and run it.
|
||
|
||
@kindex remove-inferiors
|
||
@item remove-inferiors @var{infno}@dots{}
|
||
Removes the inferior or inferiors @var{infno}@dots{}. It is not
|
||
possible to remove an inferior that is running with this command. For
|
||
those, use the @code{kill} or @code{detach} command first.
|
||
|
||
@end table
|
||
|
||
To quit debugging one of the running inferiors that is not the current
|
||
inferior, you can either detach from it by using the @w{@code{detach
|
||
inferior}} command (allowing it to run independently), or kill it
|
||
using the @w{@code{kill inferiors}} command:
|
||
|
||
@table @code
|
||
@kindex detach inferiors @var{infno}@dots{}
|
||
@item detach inferior @var{infno}@dots{}
|
||
Detach from the inferior or inferiors identified by @value{GDBN}
|
||
inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
|
||
still stays on the list of inferiors shown by @code{info inferiors},
|
||
but its Description will show @samp{<null>}.
|
||
|
||
@kindex kill inferiors @var{infno}@dots{}
|
||
@item kill inferiors @var{infno}@dots{}
|
||
Kill the inferior or inferiors identified by @value{GDBN} inferior
|
||
number(s) @var{infno}@dots{}. Note that the inferior's entry still
|
||
stays on the list of inferiors shown by @code{info inferiors}, but its
|
||
Description will show @samp{<null>}.
|
||
@end table
|
||
|
||
After the successful completion of a command such as @code{detach},
|
||
@code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
|
||
a normal process exit, the inferior is still valid and listed with
|
||
@code{info inferiors}, ready to be restarted.
|
||
|
||
|
||
To be notified when inferiors are started or exit under @value{GDBN}'s
|
||
control use @w{@code{set print inferior-events}}:
|
||
|
||
@table @code
|
||
@kindex set print inferior-events
|
||
@cindex print messages on inferior start and exit
|
||
@item set print inferior-events
|
||
@itemx set print inferior-events on
|
||
@itemx set print inferior-events off
|
||
The @code{set print inferior-events} command allows you to enable or
|
||
disable printing of messages when @value{GDBN} notices that new
|
||
inferiors have started or that inferiors have exited or have been
|
||
detached. By default, these messages will not be printed.
|
||
|
||
@kindex show print inferior-events
|
||
@item show print inferior-events
|
||
Show whether messages will be printed when @value{GDBN} detects that
|
||
inferiors have started, exited or have been detached.
|
||
@end table
|
||
|
||
Many commands will work the same with multiple programs as with a
|
||
single program: e.g., @code{print myglobal} will simply display the
|
||
value of @code{myglobal} in the current inferior.
|
||
|
||
|
||
Occasionaly, when debugging @value{GDBN} itself, it may be useful to
|
||
get more info about the relationship of inferiors, programs, address
|
||
spaces in a debug session. You can do that with the @w{@code{maint
|
||
info program-spaces}} command.
|
||
|
||
@table @code
|
||
@kindex maint info program-spaces
|
||
@item maint info program-spaces
|
||
Print a list of all program spaces currently being managed by
|
||
@value{GDBN}.
|
||
|
||
@value{GDBN} displays for each program space (in this order):
|
||
|
||
@enumerate
|
||
@item
|
||
the program space number assigned by @value{GDBN}
|
||
|
||
@item
|
||
the name of the executable loaded into the program space, with e.g.,
|
||
the @code{file} command.
|
||
|
||
@end enumerate
|
||
|
||
@noindent
|
||
An asterisk @samp{*} preceding the @value{GDBN} program space number
|
||
indicates the current program space.
|
||
|
||
In addition, below each program space line, @value{GDBN} prints extra
|
||
information that isn't suitable to display in tabular form. For
|
||
example, the list of inferiors bound to the program space.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) maint info program-spaces
|
||
Id Executable
|
||
* 1 hello
|
||
2 goodbye
|
||
Bound inferiors: ID 1 (process 21561)
|
||
@end smallexample
|
||
|
||
Here we can see that no inferior is running the program @code{hello},
|
||
while @code{process 21561} is running the program @code{goodbye}. On
|
||
some targets, it is possible that multiple inferiors are bound to the
|
||
same program space. The most common example is that of debugging both
|
||
the parent and child processes of a @code{vfork} call. For example,
|
||
|
||
@smallexample
|
||
(@value{GDBP}) maint info program-spaces
|
||
Id Executable
|
||
* 1 vfork-test
|
||
Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
|
||
@end smallexample
|
||
|
||
Here, both inferior 2 and inferior 1 are running in the same program
|
||
space as a result of inferior 1 having executed a @code{vfork} call.
|
||
@end table
|
||
|
||
@node Threads
|
||
@section Debugging Programs with Multiple Threads
|
||
|
||
@cindex threads of execution
|
||
@cindex multiple threads
|
||
@cindex switching threads
|
||
In some operating systems, such as GNU/Linux and Solaris, a single program
|
||
may have more than one @dfn{thread} of execution. The precise semantics
|
||
of threads differ from one operating system to another, but in general
|
||
the threads of a single program are akin to multiple processes---except
|
||
that they share one address space (that is, they can all examine and
|
||
modify the same variables). On the other hand, each thread has its own
|
||
registers and execution stack, and perhaps private memory.
|
||
|
||
@value{GDBN} provides these facilities for debugging multi-thread
|
||
programs:
|
||
|
||
@itemize @bullet
|
||
@item automatic notification of new threads
|
||
@item @samp{thread @var{thread-id}}, a command to switch among threads
|
||
@item @samp{info threads}, a command to inquire about existing threads
|
||
@item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
|
||
a command to apply a command to a list of threads
|
||
@item thread-specific breakpoints
|
||
@item @samp{set print thread-events}, which controls printing of
|
||
messages on thread start and exit.
|
||
@item @samp{set libthread-db-search-path @var{path}}, which lets
|
||
the user specify which @code{libthread_db} to use if the default choice
|
||
isn't compatible with the program.
|
||
@end itemize
|
||
|
||
@cindex focus of debugging
|
||
@cindex current thread
|
||
The @value{GDBN} thread debugging facility allows you to observe all
|
||
threads while your program runs---but whenever @value{GDBN} takes
|
||
control, one thread in particular is always the focus of debugging.
|
||
This thread is called the @dfn{current thread}. Debugging commands show
|
||
program information from the perspective of the current thread.
|
||
|
||
@cindex @code{New} @var{systag} message
|
||
@cindex thread identifier (system)
|
||
@c FIXME-implementors!! It would be more helpful if the [New...] message
|
||
@c included GDB's numeric thread handle, so you could just go to that
|
||
@c thread without first checking `info threads'.
|
||
Whenever @value{GDBN} detects a new thread in your program, it displays
|
||
the target system's identification for the thread with a message in the
|
||
form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
|
||
whose form varies depending on the particular system. For example, on
|
||
@sc{gnu}/Linux, you might see
|
||
|
||
@smallexample
|
||
[New Thread 0x41e02940 (LWP 25582)]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
when @value{GDBN} notices a new thread. In contrast, on other systems,
|
||
the @var{systag} is simply something like @samp{process 368}, with no
|
||
further qualifier.
|
||
|
||
@c FIXME!! (1) Does the [New...] message appear even for the very first
|
||
@c thread of a program, or does it only appear for the
|
||
@c second---i.e.@: when it becomes obvious we have a multithread
|
||
@c program?
|
||
@c (2) *Is* there necessarily a first thread always? Or do some
|
||
@c multithread systems permit starting a program with multiple
|
||
@c threads ab initio?
|
||
|
||
@anchor{thread numbers}
|
||
@cindex thread number, per inferior
|
||
@cindex thread identifier (GDB)
|
||
For debugging purposes, @value{GDBN} associates its own thread number
|
||
---always a single integer---with each thread of an inferior. This
|
||
number is unique between all threads of an inferior, but not unique
|
||
between threads of different inferiors.
|
||
|
||
@cindex qualified thread ID
|
||
You can refer to a given thread in an inferior using the qualified
|
||
@var{inferior-num}.@var{thread-num} syntax, also known as
|
||
@dfn{qualified thread ID}, with @var{inferior-num} being the inferior
|
||
number and @var{thread-num} being the thread number of the given
|
||
inferior. For example, thread @code{2.3} refers to thread number 3 of
|
||
inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
|
||
then @value{GDBN} infers you're referring to a thread of the current
|
||
inferior.
|
||
|
||
Until you create a second inferior, @value{GDBN} does not show the
|
||
@var{inferior-num} part of thread IDs, even though you can always use
|
||
the full @var{inferior-num}.@var{thread-num} form to refer to threads
|
||
of inferior 1, the initial inferior.
|
||
|
||
@anchor{thread ID lists}
|
||
@cindex thread ID lists
|
||
Some commands accept a space-separated @dfn{thread ID list} as
|
||
argument. A list element can be:
|
||
|
||
@enumerate
|
||
@item
|
||
A thread ID as shown in the first field of the @samp{info threads}
|
||
display, with or without an inferior qualifier. E.g., @samp{2.1} or
|
||
@samp{1}.
|
||
|
||
@item
|
||
A range of thread numbers, again with or without an inferior
|
||
qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
|
||
@var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
|
||
|
||
@item
|
||
All threads of an inferior, specified with a star wildcard, with or
|
||
without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
|
||
@samp{1.*}) or @code{*}. The former refers to all threads of the
|
||
given inferior, and the latter form without an inferior qualifier
|
||
refers to all threads of the current inferior.
|
||
|
||
@end enumerate
|
||
|
||
For example, if the current inferior is 1, and inferior 7 has one
|
||
thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
|
||
includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
|
||
7 to 9 of inferior 6 and all threads of inferior 7. That is, in
|
||
expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
|
||
7.1}.
|
||
|
||
|
||
@anchor{global thread numbers}
|
||
@cindex global thread number
|
||
@cindex global thread identifier (GDB)
|
||
In addition to a @emph{per-inferior} number, each thread is also
|
||
assigned a unique @emph{global} number, also known as @dfn{global
|
||
thread ID}, a single integer. Unlike the thread number component of
|
||
the thread ID, no two threads have the same global ID, even when
|
||
you're debugging multiple inferiors.
|
||
|
||
From @value{GDBN}'s perspective, a process always has at least one
|
||
thread. In other words, @value{GDBN} assigns a thread number to the
|
||
program's ``main thread'' even if the program is not multi-threaded.
|
||
|
||
@vindex $_thread@r{, convenience variable}
|
||
@vindex $_gthread@r{, convenience variable}
|
||
The debugger convenience variables @samp{$_thread} and
|
||
@samp{$_gthread} contain, respectively, the per-inferior thread number
|
||
and the global thread number of the current thread. You may find this
|
||
useful in writing breakpoint conditional expressions, command scripts,
|
||
and so forth. @xref{Convenience Vars,, Convenience Variables}, for
|
||
general information on convenience variables.
|
||
|
||
If @value{GDBN} detects the program is multi-threaded, it augments the
|
||
usual message about stopping at a breakpoint with the ID and name of
|
||
the thread that hit the breakpoint.
|
||
|
||
@smallexample
|
||
Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
|
||
@end smallexample
|
||
|
||
Likewise when the program receives a signal:
|
||
|
||
@smallexample
|
||
Thread 1 "main" received signal SIGINT, Interrupt.
|
||
@end smallexample
|
||
|
||
@table @code
|
||
@kindex info threads
|
||
@item info threads @r{[}@var{thread-id-list}@r{]}
|
||
|
||
Display information about one or more threads. With no arguments
|
||
displays information about all threads. You can specify the list of
|
||
threads that you want to display using the thread ID list syntax
|
||
(@pxref{thread ID lists}).
|
||
|
||
@value{GDBN} displays for each thread (in this order):
|
||
|
||
@enumerate
|
||
@item
|
||
the per-inferior thread number assigned by @value{GDBN}
|
||
|
||
@item
|
||
the global thread number assigned by @value{GDBN}, if the @samp{-gid}
|
||
option was specified
|
||
|
||
@item
|
||
the target system's thread identifier (@var{systag})
|
||
|
||
@item
|
||
the thread's name, if one is known. A thread can either be named by
|
||
the user (see @code{thread name}, below), or, in some cases, by the
|
||
program itself.
|
||
|
||
@item
|
||
the current stack frame summary for that thread
|
||
@end enumerate
|
||
|
||
@noindent
|
||
An asterisk @samp{*} to the left of the @value{GDBN} thread number
|
||
indicates the current thread.
|
||
|
||
For example,
|
||
@end table
|
||
@c end table here to get a little more width for example
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info threads
|
||
Id Target Id Frame
|
||
* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
|
||
2 process 35 thread 23 0x34e5 in sigpause ()
|
||
3 process 35 thread 27 0x34e5 in sigpause ()
|
||
at threadtest.c:68
|
||
@end smallexample
|
||
|
||
If you're debugging multiple inferiors, @value{GDBN} displays thread
|
||
IDs using the qualified @var{inferior-num}.@var{thread-num} format.
|
||
Otherwise, only @var{thread-num} is shown.
|
||
|
||
If you specify the @samp{-gid} option, @value{GDBN} displays a column
|
||
indicating each thread's global thread ID:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info threads
|
||
Id GId Target Id Frame
|
||
1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
|
||
1.2 3 process 35 thread 23 0x34e5 in sigpause ()
|
||
1.3 4 process 35 thread 27 0x34e5 in sigpause ()
|
||
* 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
|
||
@end smallexample
|
||
|
||
On Solaris, you can display more information about user threads with a
|
||
Solaris-specific command:
|
||
|
||
@table @code
|
||
@item maint info sol-threads
|
||
@kindex maint info sol-threads
|
||
@cindex thread info (Solaris)
|
||
Display info on Solaris user threads.
|
||
@end table
|
||
|
||
@table @code
|
||
@kindex thread @var{thread-id}
|
||
@item thread @var{thread-id}
|
||
Make thread ID @var{thread-id} the current thread. The command
|
||
argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
|
||
the first field of the @samp{info threads} display, with or without an
|
||
inferior qualifier (e.g., @samp{2.1} or @samp{1}).
|
||
|
||
@value{GDBN} responds by displaying the system identifier of the
|
||
thread you selected, and its current stack frame summary:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) thread 2
|
||
[Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
|
||
#0 some_function (ignore=0x0) at example.c:8
|
||
8 printf ("hello\n");
|
||
@end smallexample
|
||
|
||
@noindent
|
||
As with the @samp{[New @dots{}]} message, the form of the text after
|
||
@samp{Switching to} depends on your system's conventions for identifying
|
||
threads.
|
||
|
||
@kindex thread apply
|
||
@cindex apply command to several threads
|
||
@item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
|
||
The @code{thread apply} command allows you to apply the named
|
||
@var{command} to one or more threads. Specify the threads that you
|
||
want affected using the thread ID list syntax (@pxref{thread ID
|
||
lists}), or specify @code{all} to apply to all threads. To apply a
|
||
command to all threads in descending order, type @kbd{thread apply all
|
||
@var{command}}. To apply a command to all threads in ascending order,
|
||
type @kbd{thread apply all -ascending @var{command}}.
|
||
|
||
|
||
@kindex thread name
|
||
@cindex name a thread
|
||
@item thread name [@var{name}]
|
||
This command assigns a name to the current thread. If no argument is
|
||
given, any existing user-specified name is removed. The thread name
|
||
appears in the @samp{info threads} display.
|
||
|
||
On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
|
||
determine the name of the thread as given by the OS. On these
|
||
systems, a name specified with @samp{thread name} will override the
|
||
system-give name, and removing the user-specified name will cause
|
||
@value{GDBN} to once again display the system-specified name.
|
||
|
||
@kindex thread find
|
||
@cindex search for a thread
|
||
@item thread find [@var{regexp}]
|
||
Search for and display thread ids whose name or @var{systag}
|
||
matches the supplied regular expression.
|
||
|
||
As well as being the complement to the @samp{thread name} command,
|
||
this command also allows you to identify a thread by its target
|
||
@var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
|
||
is the LWP id.
|
||
|
||
@smallexample
|
||
(@value{GDBN}) thread find 26688
|
||
Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
|
||
(@value{GDBN}) info thread 4
|
||
Id Target Id Frame
|
||
4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
|
||
@end smallexample
|
||
|
||
@kindex set print thread-events
|
||
@cindex print messages on thread start and exit
|
||
@item set print thread-events
|
||
@itemx set print thread-events on
|
||
@itemx set print thread-events off
|
||
The @code{set print thread-events} command allows you to enable or
|
||
disable printing of messages when @value{GDBN} notices that new threads have
|
||
started or that threads have exited. By default, these messages will
|
||
be printed if detection of these events is supported by the target.
|
||
Note that these messages cannot be disabled on all targets.
|
||
|
||
@kindex show print thread-events
|
||
@item show print thread-events
|
||
Show whether messages will be printed when @value{GDBN} detects that threads
|
||
have started and exited.
|
||
@end table
|
||
|
||
@xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
|
||
more information about how @value{GDBN} behaves when you stop and start
|
||
programs with multiple threads.
|
||
|
||
@xref{Set Watchpoints,,Setting Watchpoints}, for information about
|
||
watchpoints in programs with multiple threads.
|
||
|
||
@anchor{set libthread-db-search-path}
|
||
@table @code
|
||
@kindex set libthread-db-search-path
|
||
@cindex search path for @code{libthread_db}
|
||
@item set libthread-db-search-path @r{[}@var{path}@r{]}
|
||
If this variable is set, @var{path} is a colon-separated list of
|
||
directories @value{GDBN} will use to search for @code{libthread_db}.
|
||
If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
|
||
its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
|
||
Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
|
||
macro.
|
||
|
||
On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
|
||
@code{libthread_db} library to obtain information about threads in the
|
||
inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
|
||
to find @code{libthread_db}. @value{GDBN} also consults first if inferior
|
||
specific thread debugging library loading is enabled
|
||
by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
|
||
|
||
A special entry @samp{$sdir} for @samp{libthread-db-search-path}
|
||
refers to the default system directories that are
|
||
normally searched for loading shared libraries. The @samp{$sdir} entry
|
||
is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
|
||
(@pxref{libthread_db.so.1 file}).
|
||
|
||
A special entry @samp{$pdir} for @samp{libthread-db-search-path}
|
||
refers to the directory from which @code{libpthread}
|
||
was loaded in the inferior process.
|
||
|
||
For any @code{libthread_db} library @value{GDBN} finds in above directories,
|
||
@value{GDBN} attempts to initialize it with the current inferior process.
|
||
If this initialization fails (which could happen because of a version
|
||
mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
|
||
will unload @code{libthread_db}, and continue with the next directory.
|
||
If none of @code{libthread_db} libraries initialize successfully,
|
||
@value{GDBN} will issue a warning and thread debugging will be disabled.
|
||
|
||
Setting @code{libthread-db-search-path} is currently implemented
|
||
only on some platforms.
|
||
|
||
@kindex show libthread-db-search-path
|
||
@item show libthread-db-search-path
|
||
Display current libthread_db search path.
|
||
|
||
@kindex set debug libthread-db
|
||
@kindex show debug libthread-db
|
||
@cindex debugging @code{libthread_db}
|
||
@item set debug libthread-db
|
||
@itemx show debug libthread-db
|
||
Turns on or off display of @code{libthread_db}-related events.
|
||
Use @code{1} to enable, @code{0} to disable.
|
||
@end table
|
||
|
||
@node Forks
|
||
@section Debugging Forks
|
||
|
||
@cindex fork, debugging programs which call
|
||
@cindex multiple processes
|
||
@cindex processes, multiple
|
||
On most systems, @value{GDBN} has no special support for debugging
|
||
programs which create additional processes using the @code{fork}
|
||
function. When a program forks, @value{GDBN} will continue to debug the
|
||
parent process and the child process will run unimpeded. If you have
|
||
set a breakpoint in any code which the child then executes, the child
|
||
will get a @code{SIGTRAP} signal which (unless it catches the signal)
|
||
will cause it to terminate.
|
||
|
||
However, if you want to debug the child process there is a workaround
|
||
which isn't too painful. Put a call to @code{sleep} in the code which
|
||
the child process executes after the fork. It may be useful to sleep
|
||
only if a certain environment variable is set, or a certain file exists,
|
||
so that the delay need not occur when you don't want to run @value{GDBN}
|
||
on the child. While the child is sleeping, use the @code{ps} program to
|
||
get its process ID. Then tell @value{GDBN} (a new invocation of
|
||
@value{GDBN} if you are also debugging the parent process) to attach to
|
||
the child process (@pxref{Attach}). From that point on you can debug
|
||
the child process just like any other process which you attached to.
|
||
|
||
On some systems, @value{GDBN} provides support for debugging programs
|
||
that create additional processes using the @code{fork} or @code{vfork}
|
||
functions. On @sc{gnu}/Linux platforms, this feature is supported
|
||
with kernel version 2.5.46 and later.
|
||
|
||
The fork debugging commands are supported in native mode and when
|
||
connected to @code{gdbserver} in either @code{target remote} mode or
|
||
@code{target extended-remote} mode.
|
||
|
||
By default, when a program forks, @value{GDBN} will continue to debug
|
||
the parent process and the child process will run unimpeded.
|
||
|
||
If you want to follow the child process instead of the parent process,
|
||
use the command @w{@code{set follow-fork-mode}}.
|
||
|
||
@table @code
|
||
@kindex set follow-fork-mode
|
||
@item set follow-fork-mode @var{mode}
|
||
Set the debugger response to a program call of @code{fork} or
|
||
@code{vfork}. A call to @code{fork} or @code{vfork} creates a new
|
||
process. The @var{mode} argument can be:
|
||
|
||
@table @code
|
||
@item parent
|
||
The original process is debugged after a fork. The child process runs
|
||
unimpeded. This is the default.
|
||
|
||
@item child
|
||
The new process is debugged after a fork. The parent process runs
|
||
unimpeded.
|
||
|
||
@end table
|
||
|
||
@kindex show follow-fork-mode
|
||
@item show follow-fork-mode
|
||
Display the current debugger response to a @code{fork} or @code{vfork} call.
|
||
@end table
|
||
|
||
@cindex debugging multiple processes
|
||
On Linux, if you want to debug both the parent and child processes, use the
|
||
command @w{@code{set detach-on-fork}}.
|
||
|
||
@table @code
|
||
@kindex set detach-on-fork
|
||
@item set detach-on-fork @var{mode}
|
||
Tells gdb whether to detach one of the processes after a fork, or
|
||
retain debugger control over them both.
|
||
|
||
@table @code
|
||
@item on
|
||
The child process (or parent process, depending on the value of
|
||
@code{follow-fork-mode}) will be detached and allowed to run
|
||
independently. This is the default.
|
||
|
||
@item off
|
||
Both processes will be held under the control of @value{GDBN}.
|
||
One process (child or parent, depending on the value of
|
||
@code{follow-fork-mode}) is debugged as usual, while the other
|
||
is held suspended.
|
||
|
||
@end table
|
||
|
||
@kindex show detach-on-fork
|
||
@item show detach-on-fork
|
||
Show whether detach-on-fork mode is on/off.
|
||
@end table
|
||
|
||
If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
|
||
will retain control of all forked processes (including nested forks).
|
||
You can list the forked processes under the control of @value{GDBN} by
|
||
using the @w{@code{info inferiors}} command, and switch from one fork
|
||
to another by using the @code{inferior} command (@pxref{Inferiors and
|
||
Programs, ,Debugging Multiple Inferiors and Programs}).
|
||
|
||
To quit debugging one of the forked processes, you can either detach
|
||
from it by using the @w{@code{detach inferiors}} command (allowing it
|
||
to run independently), or kill it using the @w{@code{kill inferiors}}
|
||
command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
|
||
and Programs}.
|
||
|
||
If you ask to debug a child process and a @code{vfork} is followed by an
|
||
@code{exec}, @value{GDBN} executes the new target up to the first
|
||
breakpoint in the new target. If you have a breakpoint set on
|
||
@code{main} in your original program, the breakpoint will also be set on
|
||
the child process's @code{main}.
|
||
|
||
On some systems, when a child process is spawned by @code{vfork}, you
|
||
cannot debug the child or parent until an @code{exec} call completes.
|
||
|
||
If you issue a @code{run} command to @value{GDBN} after an @code{exec}
|
||
call executes, the new target restarts. To restart the parent
|
||
process, use the @code{file} command with the parent executable name
|
||
as its argument. By default, after an @code{exec} call executes,
|
||
@value{GDBN} discards the symbols of the previous executable image.
|
||
You can change this behaviour with the @w{@code{set follow-exec-mode}}
|
||
command.
|
||
|
||
@table @code
|
||
@kindex set follow-exec-mode
|
||
@item set follow-exec-mode @var{mode}
|
||
|
||
Set debugger response to a program call of @code{exec}. An
|
||
@code{exec} call replaces the program image of a process.
|
||
|
||
@code{follow-exec-mode} can be:
|
||
|
||
@table @code
|
||
@item new
|
||
@value{GDBN} creates a new inferior and rebinds the process to this
|
||
new inferior. The program the process was running before the
|
||
@code{exec} call can be restarted afterwards by restarting the
|
||
original inferior.
|
||
|
||
For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info inferiors
|
||
(gdb) info inferior
|
||
Id Description Executable
|
||
* 1 <null> prog1
|
||
(@value{GDBP}) run
|
||
process 12020 is executing new program: prog2
|
||
Program exited normally.
|
||
(@value{GDBP}) info inferiors
|
||
Id Description Executable
|
||
1 <null> prog1
|
||
* 2 <null> prog2
|
||
@end smallexample
|
||
|
||
@item same
|
||
@value{GDBN} keeps the process bound to the same inferior. The new
|
||
executable image replaces the previous executable loaded in the
|
||
inferior. Restarting the inferior after the @code{exec} call, with
|
||
e.g., the @code{run} command, restarts the executable the process was
|
||
running after the @code{exec} call. This is the default mode.
|
||
|
||
For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info inferiors
|
||
Id Description Executable
|
||
* 1 <null> prog1
|
||
(@value{GDBP}) run
|
||
process 12020 is executing new program: prog2
|
||
Program exited normally.
|
||
(@value{GDBP}) info inferiors
|
||
Id Description Executable
|
||
* 1 <null> prog2
|
||
@end smallexample
|
||
|
||
@end table
|
||
@end table
|
||
|
||
@code{follow-exec-mode} is supported in native mode and
|
||
@code{target extended-remote} mode.
|
||
|
||
You can use the @code{catch} command to make @value{GDBN} stop whenever
|
||
a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
|
||
Catchpoints, ,Setting Catchpoints}.
|
||
|
||
@node Checkpoint/Restart
|
||
@section Setting a @emph{Bookmark} to Return to Later
|
||
|
||
@cindex checkpoint
|
||
@cindex restart
|
||
@cindex bookmark
|
||
@cindex snapshot of a process
|
||
@cindex rewind program state
|
||
|
||
On certain operating systems@footnote{Currently, only
|
||
@sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
|
||
program's state, called a @dfn{checkpoint}, and come back to it
|
||
later.
|
||
|
||
Returning to a checkpoint effectively undoes everything that has
|
||
happened in the program since the @code{checkpoint} was saved. This
|
||
includes changes in memory, registers, and even (within some limits)
|
||
system state. Effectively, it is like going back in time to the
|
||
moment when the checkpoint was saved.
|
||
|
||
Thus, if you're stepping thru a program and you think you're
|
||
getting close to the point where things go wrong, you can save
|
||
a checkpoint. Then, if you accidentally go too far and miss
|
||
the critical statement, instead of having to restart your program
|
||
from the beginning, you can just go back to the checkpoint and
|
||
start again from there.
|
||
|
||
This can be especially useful if it takes a lot of time or
|
||
steps to reach the point where you think the bug occurs.
|
||
|
||
To use the @code{checkpoint}/@code{restart} method of debugging:
|
||
|
||
@table @code
|
||
@kindex checkpoint
|
||
@item checkpoint
|
||
Save a snapshot of the debugged program's current execution state.
|
||
The @code{checkpoint} command takes no arguments, but each checkpoint
|
||
is assigned a small integer id, similar to a breakpoint id.
|
||
|
||
@kindex info checkpoints
|
||
@item info checkpoints
|
||
List the checkpoints that have been saved in the current debugging
|
||
session. For each checkpoint, the following information will be
|
||
listed:
|
||
|
||
@table @code
|
||
@item Checkpoint ID
|
||
@item Process ID
|
||
@item Code Address
|
||
@item Source line, or label
|
||
@end table
|
||
|
||
@kindex restart @var{checkpoint-id}
|
||
@item restart @var{checkpoint-id}
|
||
Restore the program state that was saved as checkpoint number
|
||
@var{checkpoint-id}. All program variables, registers, stack frames
|
||
etc.@: will be returned to the values that they had when the checkpoint
|
||
was saved. In essence, gdb will ``wind back the clock'' to the point
|
||
in time when the checkpoint was saved.
|
||
|
||
Note that breakpoints, @value{GDBN} variables, command history etc.
|
||
are not affected by restoring a checkpoint. In general, a checkpoint
|
||
only restores things that reside in the program being debugged, not in
|
||
the debugger.
|
||
|
||
@kindex delete checkpoint @var{checkpoint-id}
|
||
@item delete checkpoint @var{checkpoint-id}
|
||
Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
|
||
|
||
@end table
|
||
|
||
Returning to a previously saved checkpoint will restore the user state
|
||
of the program being debugged, plus a significant subset of the system
|
||
(OS) state, including file pointers. It won't ``un-write'' data from
|
||
a file, but it will rewind the file pointer to the previous location,
|
||
so that the previously written data can be overwritten. For files
|
||
opened in read mode, the pointer will also be restored so that the
|
||
previously read data can be read again.
|
||
|
||
Of course, characters that have been sent to a printer (or other
|
||
external device) cannot be ``snatched back'', and characters received
|
||
from eg.@: a serial device can be removed from internal program buffers,
|
||
but they cannot be ``pushed back'' into the serial pipeline, ready to
|
||
be received again. Similarly, the actual contents of files that have
|
||
been changed cannot be restored (at this time).
|
||
|
||
However, within those constraints, you actually can ``rewind'' your
|
||
program to a previously saved point in time, and begin debugging it
|
||
again --- and you can change the course of events so as to debug a
|
||
different execution path this time.
|
||
|
||
@cindex checkpoints and process id
|
||
Finally, there is one bit of internal program state that will be
|
||
different when you return to a checkpoint --- the program's process
|
||
id. Each checkpoint will have a unique process id (or @var{pid}),
|
||
and each will be different from the program's original @var{pid}.
|
||
If your program has saved a local copy of its process id, this could
|
||
potentially pose a problem.
|
||
|
||
@subsection A Non-obvious Benefit of Using Checkpoints
|
||
|
||
On some systems such as @sc{gnu}/Linux, address space randomization
|
||
is performed on new processes for security reasons. This makes it
|
||
difficult or impossible to set a breakpoint, or watchpoint, on an
|
||
absolute address if you have to restart the program, since the
|
||
absolute location of a symbol will change from one execution to the
|
||
next.
|
||
|
||
A checkpoint, however, is an @emph{identical} copy of a process.
|
||
Therefore if you create a checkpoint at (eg.@:) the start of main,
|
||
and simply return to that checkpoint instead of restarting the
|
||
process, you can avoid the effects of address randomization and
|
||
your symbols will all stay in the same place.
|
||
|
||
@node Stopping
|
||
@chapter Stopping and Continuing
|
||
|
||
The principal purposes of using a debugger are so that you can stop your
|
||
program before it terminates; or so that, if your program runs into
|
||
trouble, you can investigate and find out why.
|
||
|
||
Inside @value{GDBN}, your program may stop for any of several reasons,
|
||
such as a signal, a breakpoint, or reaching a new line after a
|
||
@value{GDBN} command such as @code{step}. You may then examine and
|
||
change variables, set new breakpoints or remove old ones, and then
|
||
continue execution. Usually, the messages shown by @value{GDBN} provide
|
||
ample explanation of the status of your program---but you can also
|
||
explicitly request this information at any time.
|
||
|
||
@table @code
|
||
@kindex info program
|
||
@item info program
|
||
Display information about the status of your program: whether it is
|
||
running or not, what process it is, and why it stopped.
|
||
@end table
|
||
|
||
@menu
|
||
* Breakpoints:: Breakpoints, watchpoints, and catchpoints
|
||
* Continuing and Stepping:: Resuming execution
|
||
* Skipping Over Functions and Files::
|
||
Skipping over functions and files
|
||
* Signals:: Signals
|
||
* Thread Stops:: Stopping and starting multi-thread programs
|
||
@end menu
|
||
|
||
@node Breakpoints
|
||
@section Breakpoints, Watchpoints, and Catchpoints
|
||
|
||
@cindex breakpoints
|
||
A @dfn{breakpoint} makes your program stop whenever a certain point in
|
||
the program is reached. For each breakpoint, you can add conditions to
|
||
control in finer detail whether your program stops. You can set
|
||
breakpoints with the @code{break} command and its variants (@pxref{Set
|
||
Breaks, ,Setting Breakpoints}), to specify the place where your program
|
||
should stop by line number, function name or exact address in the
|
||
program.
|
||
|
||
On some systems, you can set breakpoints in shared libraries before
|
||
the executable is run.
|
||
|
||
@cindex watchpoints
|
||
@cindex data breakpoints
|
||
@cindex memory tracing
|
||
@cindex breakpoint on memory address
|
||
@cindex breakpoint on variable modification
|
||
A @dfn{watchpoint} is a special breakpoint that stops your program
|
||
when the value of an expression changes. The expression may be a value
|
||
of a variable, or it could involve values of one or more variables
|
||
combined by operators, such as @samp{a + b}. This is sometimes called
|
||
@dfn{data breakpoints}. You must use a different command to set
|
||
watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
|
||
from that, you can manage a watchpoint like any other breakpoint: you
|
||
enable, disable, and delete both breakpoints and watchpoints using the
|
||
same commands.
|
||
|
||
You can arrange to have values from your program displayed automatically
|
||
whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
|
||
Automatic Display}.
|
||
|
||
@cindex catchpoints
|
||
@cindex breakpoint on events
|
||
A @dfn{catchpoint} is another special breakpoint that stops your program
|
||
when a certain kind of event occurs, such as the throwing of a C@t{++}
|
||
exception or the loading of a library. As with watchpoints, you use a
|
||
different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
|
||
Catchpoints}), but aside from that, you can manage a catchpoint like any
|
||
other breakpoint. (To stop when your program receives a signal, use the
|
||
@code{handle} command; see @ref{Signals, ,Signals}.)
|
||
|
||
@cindex breakpoint numbers
|
||
@cindex numbers for breakpoints
|
||
@value{GDBN} assigns a number to each breakpoint, watchpoint, or
|
||
catchpoint when you create it; these numbers are successive integers
|
||
starting with one. In many of the commands for controlling various
|
||
features of breakpoints you use the breakpoint number to say which
|
||
breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
|
||
@dfn{disabled}; if disabled, it has no effect on your program until you
|
||
enable it again.
|
||
|
||
@cindex breakpoint ranges
|
||
@cindex breakpoint lists
|
||
@cindex ranges of breakpoints
|
||
@cindex lists of breakpoints
|
||
Some @value{GDBN} commands accept a space-separated list of breakpoints
|
||
on which to operate. A list element can be either a single breakpoint number,
|
||
like @samp{5}, or a range of such numbers, like @samp{5-7}.
|
||
When a breakpoint list is given to a command, all breakpoints in that list
|
||
are operated on.
|
||
|
||
@menu
|
||
* Set Breaks:: Setting breakpoints
|
||
* Set Watchpoints:: Setting watchpoints
|
||
* Set Catchpoints:: Setting catchpoints
|
||
* Delete Breaks:: Deleting breakpoints
|
||
* Disabling:: Disabling breakpoints
|
||
* Conditions:: Break conditions
|
||
* Break Commands:: Breakpoint command lists
|
||
* Dynamic Printf:: Dynamic printf
|
||
* Save Breakpoints:: How to save breakpoints in a file
|
||
* Static Probe Points:: Listing static probe points
|
||
* Error in Breakpoints:: ``Cannot insert breakpoints''
|
||
* Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
|
||
@end menu
|
||
|
||
@node Set Breaks
|
||
@subsection Setting Breakpoints
|
||
|
||
@c FIXME LMB what does GDB do if no code on line of breakpt?
|
||
@c consider in particular declaration with/without initialization.
|
||
@c
|
||
@c FIXME 2 is there stuff on this already? break at fun start, already init?
|
||
|
||
@kindex break
|
||
@kindex b @r{(@code{break})}
|
||
@vindex $bpnum@r{, convenience variable}
|
||
@cindex latest breakpoint
|
||
Breakpoints are set with the @code{break} command (abbreviated
|
||
@code{b}). The debugger convenience variable @samp{$bpnum} records the
|
||
number of the breakpoint you've set most recently; see @ref{Convenience
|
||
Vars,, Convenience Variables}, for a discussion of what you can do with
|
||
convenience variables.
|
||
|
||
@table @code
|
||
@item break @var{location}
|
||
Set a breakpoint at the given @var{location}, which can specify a
|
||
function name, a line number, or an address of an instruction.
|
||
(@xref{Specify Location}, for a list of all the possible ways to
|
||
specify a @var{location}.) The breakpoint will stop your program just
|
||
before it executes any of the code in the specified @var{location}.
|
||
|
||
When using source languages that permit overloading of symbols, such as
|
||
C@t{++}, a function name may refer to more than one possible place to break.
|
||
@xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
|
||
that situation.
|
||
|
||
It is also possible to insert a breakpoint that will stop the program
|
||
only if a specific thread (@pxref{Thread-Specific Breakpoints})
|
||
or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
|
||
|
||
@item break
|
||
When called without any arguments, @code{break} sets a breakpoint at
|
||
the next instruction to be executed in the selected stack frame
|
||
(@pxref{Stack, ,Examining the Stack}). In any selected frame but the
|
||
innermost, this makes your program stop as soon as control
|
||
returns to that frame. This is similar to the effect of a
|
||
@code{finish} command in the frame inside the selected frame---except
|
||
that @code{finish} does not leave an active breakpoint. If you use
|
||
@code{break} without an argument in the innermost frame, @value{GDBN} stops
|
||
the next time it reaches the current location; this may be useful
|
||
inside loops.
|
||
|
||
@value{GDBN} normally ignores breakpoints when it resumes execution, until at
|
||
least one instruction has been executed. If it did not do this, you
|
||
would be unable to proceed past a breakpoint without first disabling the
|
||
breakpoint. This rule applies whether or not the breakpoint already
|
||
existed when your program stopped.
|
||
|
||
@item break @dots{} if @var{cond}
|
||
Set a breakpoint with condition @var{cond}; evaluate the expression
|
||
@var{cond} each time the breakpoint is reached, and stop only if the
|
||
value is nonzero---that is, if @var{cond} evaluates as true.
|
||
@samp{@dots{}} stands for one of the possible arguments described
|
||
above (or no argument) specifying where to break. @xref{Conditions,
|
||
,Break Conditions}, for more information on breakpoint conditions.
|
||
|
||
@kindex tbreak
|
||
@item tbreak @var{args}
|
||
Set a breakpoint enabled only for one stop. The @var{args} are the
|
||
same as for the @code{break} command, and the breakpoint is set in the same
|
||
way, but the breakpoint is automatically deleted after the first time your
|
||
program stops there. @xref{Disabling, ,Disabling Breakpoints}.
|
||
|
||
@kindex hbreak
|
||
@cindex hardware breakpoints
|
||
@item hbreak @var{args}
|
||
Set a hardware-assisted breakpoint. The @var{args} are the same as for the
|
||
@code{break} command and the breakpoint is set in the same way, but the
|
||
breakpoint requires hardware support and some target hardware may not
|
||
have this support. The main purpose of this is EPROM/ROM code
|
||
debugging, so you can set a breakpoint at an instruction without
|
||
changing the instruction. This can be used with the new trap-generation
|
||
provided by SPARClite DSU and most x86-based targets. These targets
|
||
will generate traps when a program accesses some data or instruction
|
||
address that is assigned to the debug registers. However the hardware
|
||
breakpoint registers can take a limited number of breakpoints. For
|
||
example, on the DSU, only two data breakpoints can be set at a time, and
|
||
@value{GDBN} will reject this command if more than two are used. Delete
|
||
or disable unused hardware breakpoints before setting new ones
|
||
(@pxref{Disabling, ,Disabling Breakpoints}).
|
||
@xref{Conditions, ,Break Conditions}.
|
||
For remote targets, you can restrict the number of hardware
|
||
breakpoints @value{GDBN} will use, see @ref{set remote
|
||
hardware-breakpoint-limit}.
|
||
|
||
@kindex thbreak
|
||
@item thbreak @var{args}
|
||
Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
|
||
are the same as for the @code{hbreak} command and the breakpoint is set in
|
||
the same way. However, like the @code{tbreak} command,
|
||
the breakpoint is automatically deleted after the
|
||
first time your program stops there. Also, like the @code{hbreak}
|
||
command, the breakpoint requires hardware support and some target hardware
|
||
may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
|
||
See also @ref{Conditions, ,Break Conditions}.
|
||
|
||
@kindex rbreak
|
||
@cindex regular expression
|
||
@cindex breakpoints at functions matching a regexp
|
||
@cindex set breakpoints in many functions
|
||
@item rbreak @var{regex}
|
||
Set breakpoints on all functions matching the regular expression
|
||
@var{regex}. This command sets an unconditional breakpoint on all
|
||
matches, printing a list of all breakpoints it set. Once these
|
||
breakpoints are set, they are treated just like the breakpoints set with
|
||
the @code{break} command. You can delete them, disable them, or make
|
||
them conditional the same way as any other breakpoint.
|
||
|
||
The syntax of the regular expression is the standard one used with tools
|
||
like @file{grep}. Note that this is different from the syntax used by
|
||
shells, so for instance @code{foo*} matches all functions that include
|
||
an @code{fo} followed by zero or more @code{o}s. There is an implicit
|
||
@code{.*} leading and trailing the regular expression you supply, so to
|
||
match only functions that begin with @code{foo}, use @code{^foo}.
|
||
|
||
@cindex non-member C@t{++} functions, set breakpoint in
|
||
When debugging C@t{++} programs, @code{rbreak} is useful for setting
|
||
breakpoints on overloaded functions that are not members of any special
|
||
classes.
|
||
|
||
@cindex set breakpoints on all functions
|
||
The @code{rbreak} command can be used to set breakpoints in
|
||
@strong{all} the functions in a program, like this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) rbreak .
|
||
@end smallexample
|
||
|
||
@item rbreak @var{file}:@var{regex}
|
||
If @code{rbreak} is called with a filename qualification, it limits
|
||
the search for functions matching the given regular expression to the
|
||
specified @var{file}. This can be used, for example, to set breakpoints on
|
||
every function in a given file:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) rbreak file.c:.
|
||
@end smallexample
|
||
|
||
The colon separating the filename qualifier from the regex may
|
||
optionally be surrounded by spaces.
|
||
|
||
@kindex info breakpoints
|
||
@cindex @code{$_} and @code{info breakpoints}
|
||
@item info breakpoints @r{[}@var{list}@dots{}@r{]}
|
||
@itemx info break @r{[}@var{list}@dots{}@r{]}
|
||
Print a table of all breakpoints, watchpoints, and catchpoints set and
|
||
not deleted. Optional argument @var{n} means print information only
|
||
about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
|
||
For each breakpoint, following columns are printed:
|
||
|
||
@table @emph
|
||
@item Breakpoint Numbers
|
||
@item Type
|
||
Breakpoint, watchpoint, or catchpoint.
|
||
@item Disposition
|
||
Whether the breakpoint is marked to be disabled or deleted when hit.
|
||
@item Enabled or Disabled
|
||
Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
|
||
that are not enabled.
|
||
@item Address
|
||
Where the breakpoint is in your program, as a memory address. For a
|
||
pending breakpoint whose address is not yet known, this field will
|
||
contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
|
||
library that has the symbol or line referred by breakpoint is loaded.
|
||
See below for details. A breakpoint with several locations will
|
||
have @samp{<MULTIPLE>} in this field---see below for details.
|
||
@item What
|
||
Where the breakpoint is in the source for your program, as a file and
|
||
line number. For a pending breakpoint, the original string passed to
|
||
the breakpoint command will be listed as it cannot be resolved until
|
||
the appropriate shared library is loaded in the future.
|
||
@end table
|
||
|
||
@noindent
|
||
If a breakpoint is conditional, there are two evaluation modes: ``host'' and
|
||
``target''. If mode is ``host'', breakpoint condition evaluation is done by
|
||
@value{GDBN} on the host's side. If it is ``target'', then the condition
|
||
is evaluated by the target. The @code{info break} command shows
|
||
the condition on the line following the affected breakpoint, together with
|
||
its condition evaluation mode in between parentheses.
|
||
|
||
Breakpoint commands, if any, are listed after that. A pending breakpoint is
|
||
allowed to have a condition specified for it. The condition is not parsed for
|
||
validity until a shared library is loaded that allows the pending
|
||
breakpoint to resolve to a valid location.
|
||
|
||
@noindent
|
||
@code{info break} with a breakpoint
|
||
number @var{n} as argument lists only that breakpoint. The
|
||
convenience variable @code{$_} and the default examining-address for
|
||
the @code{x} command are set to the address of the last breakpoint
|
||
listed (@pxref{Memory, ,Examining Memory}).
|
||
|
||
@noindent
|
||
@code{info break} displays a count of the number of times the breakpoint
|
||
has been hit. This is especially useful in conjunction with the
|
||
@code{ignore} command. You can ignore a large number of breakpoint
|
||
hits, look at the breakpoint info to see how many times the breakpoint
|
||
was hit, and then run again, ignoring one less than that number. This
|
||
will get you quickly to the last hit of that breakpoint.
|
||
|
||
@noindent
|
||
For a breakpoints with an enable count (xref) greater than 1,
|
||
@code{info break} also displays that count.
|
||
|
||
@end table
|
||
|
||
@value{GDBN} allows you to set any number of breakpoints at the same place in
|
||
your program. There is nothing silly or meaningless about this. When
|
||
the breakpoints are conditional, this is even useful
|
||
(@pxref{Conditions, ,Break Conditions}).
|
||
|
||
@cindex multiple locations, breakpoints
|
||
@cindex breakpoints, multiple locations
|
||
It is possible that a breakpoint corresponds to several locations
|
||
in your program. Examples of this situation are:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Multiple functions in the program may have the same name.
|
||
|
||
@item
|
||
For a C@t{++} constructor, the @value{NGCC} compiler generates several
|
||
instances of the function body, used in different cases.
|
||
|
||
@item
|
||
For a C@t{++} template function, a given line in the function can
|
||
correspond to any number of instantiations.
|
||
|
||
@item
|
||
For an inlined function, a given source line can correspond to
|
||
several places where that function is inlined.
|
||
@end itemize
|
||
|
||
In all those cases, @value{GDBN} will insert a breakpoint at all
|
||
the relevant locations.
|
||
|
||
A breakpoint with multiple locations is displayed in the breakpoint
|
||
table using several rows---one header row, followed by one row for
|
||
each breakpoint location. The header row has @samp{<MULTIPLE>} in the
|
||
address column. The rows for individual locations contain the actual
|
||
addresses for locations, and show the functions to which those
|
||
locations belong. The number column for a location is of the form
|
||
@var{breakpoint-number}.@var{location-number}.
|
||
|
||
For example:
|
||
|
||
@smallexample
|
||
Num Type Disp Enb Address What
|
||
1 breakpoint keep y <MULTIPLE>
|
||
stop only if i==1
|
||
breakpoint already hit 1 time
|
||
1.1 y 0x080486a2 in void foo<int>() at t.cc:8
|
||
1.2 y 0x080486ca in void foo<double>() at t.cc:8
|
||
@end smallexample
|
||
|
||
You cannot delete the individual locations from a breakpoint. However,
|
||
each location can be individually enabled or disabled by passing
|
||
@var{breakpoint-number}.@var{location-number} as argument to the
|
||
@code{enable} and @code{disable} commands. It's also possible to
|
||
@code{enable} and @code{disable} a range of @var{location-number}
|
||
locations using a @var{breakpoint-number} and two @var{location-number}s,
|
||
in increasing order, separated by a hyphen, like
|
||
@kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
|
||
in which case @value{GDBN} acts on all the locations in the range (inclusive).
|
||
Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
|
||
all of the locations that belong to that breakpoint.
|
||
|
||
@cindex pending breakpoints
|
||
It's quite common to have a breakpoint inside a shared library.
|
||
Shared libraries can be loaded and unloaded explicitly,
|
||
and possibly repeatedly, as the program is executed. To support
|
||
this use case, @value{GDBN} updates breakpoint locations whenever
|
||
any shared library is loaded or unloaded. Typically, you would
|
||
set a breakpoint in a shared library at the beginning of your
|
||
debugging session, when the library is not loaded, and when the
|
||
symbols from the library are not available. When you try to set
|
||
breakpoint, @value{GDBN} will ask you if you want to set
|
||
a so called @dfn{pending breakpoint}---breakpoint whose address
|
||
is not yet resolved.
|
||
|
||
After the program is run, whenever a new shared library is loaded,
|
||
@value{GDBN} reevaluates all the breakpoints. When a newly loaded
|
||
shared library contains the symbol or line referred to by some
|
||
pending breakpoint, that breakpoint is resolved and becomes an
|
||
ordinary breakpoint. When a library is unloaded, all breakpoints
|
||
that refer to its symbols or source lines become pending again.
|
||
|
||
This logic works for breakpoints with multiple locations, too. For
|
||
example, if you have a breakpoint in a C@t{++} template function, and
|
||
a newly loaded shared library has an instantiation of that template,
|
||
a new location is added to the list of locations for the breakpoint.
|
||
|
||
Except for having unresolved address, pending breakpoints do not
|
||
differ from regular breakpoints. You can set conditions or commands,
|
||
enable and disable them and perform other breakpoint operations.
|
||
|
||
@value{GDBN} provides some additional commands for controlling what
|
||
happens when the @samp{break} command cannot resolve breakpoint
|
||
address specification to an address:
|
||
|
||
@kindex set breakpoint pending
|
||
@kindex show breakpoint pending
|
||
@table @code
|
||
@item set breakpoint pending auto
|
||
This is the default behavior. When @value{GDBN} cannot find the breakpoint
|
||
location, it queries you whether a pending breakpoint should be created.
|
||
|
||
@item set breakpoint pending on
|
||
This indicates that an unrecognized breakpoint location should automatically
|
||
result in a pending breakpoint being created.
|
||
|
||
@item set breakpoint pending off
|
||
This indicates that pending breakpoints are not to be created. Any
|
||
unrecognized breakpoint location results in an error. This setting does
|
||
not affect any pending breakpoints previously created.
|
||
|
||
@item show breakpoint pending
|
||
Show the current behavior setting for creating pending breakpoints.
|
||
@end table
|
||
|
||
The settings above only affect the @code{break} command and its
|
||
variants. Once breakpoint is set, it will be automatically updated
|
||
as shared libraries are loaded and unloaded.
|
||
|
||
@cindex automatic hardware breakpoints
|
||
For some targets, @value{GDBN} can automatically decide if hardware or
|
||
software breakpoints should be used, depending on whether the
|
||
breakpoint address is read-only or read-write. This applies to
|
||
breakpoints set with the @code{break} command as well as to internal
|
||
breakpoints set by commands like @code{next} and @code{finish}. For
|
||
breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
|
||
breakpoints.
|
||
|
||
You can control this automatic behaviour with the following commands:
|
||
|
||
@kindex set breakpoint auto-hw
|
||
@kindex show breakpoint auto-hw
|
||
@table @code
|
||
@item set breakpoint auto-hw on
|
||
This is the default behavior. When @value{GDBN} sets a breakpoint, it
|
||
will try to use the target memory map to decide if software or hardware
|
||
breakpoint must be used.
|
||
|
||
@item set breakpoint auto-hw off
|
||
This indicates @value{GDBN} should not automatically select breakpoint
|
||
type. If the target provides a memory map, @value{GDBN} will warn when
|
||
trying to set software breakpoint at a read-only address.
|
||
@end table
|
||
|
||
@value{GDBN} normally implements breakpoints by replacing the program code
|
||
at the breakpoint address with a special instruction, which, when
|
||
executed, given control to the debugger. By default, the program
|
||
code is so modified only when the program is resumed. As soon as
|
||
the program stops, @value{GDBN} restores the original instructions. This
|
||
behaviour guards against leaving breakpoints inserted in the
|
||
target should gdb abrubptly disconnect. However, with slow remote
|
||
targets, inserting and removing breakpoint can reduce the performance.
|
||
This behavior can be controlled with the following commands::
|
||
|
||
@kindex set breakpoint always-inserted
|
||
@kindex show breakpoint always-inserted
|
||
@table @code
|
||
@item set breakpoint always-inserted off
|
||
All breakpoints, including newly added by the user, are inserted in
|
||
the target only when the target is resumed. All breakpoints are
|
||
removed from the target when it stops. This is the default mode.
|
||
|
||
@item set breakpoint always-inserted on
|
||
Causes all breakpoints to be inserted in the target at all times. If
|
||
the user adds a new breakpoint, or changes an existing breakpoint, the
|
||
breakpoints in the target are updated immediately. A breakpoint is
|
||
removed from the target only when breakpoint itself is deleted.
|
||
@end table
|
||
|
||
@value{GDBN} handles conditional breakpoints by evaluating these conditions
|
||
when a breakpoint breaks. If the condition is true, then the process being
|
||
debugged stops, otherwise the process is resumed.
|
||
|
||
If the target supports evaluating conditions on its end, @value{GDBN} may
|
||
download the breakpoint, together with its conditions, to it.
|
||
|
||
This feature can be controlled via the following commands:
|
||
|
||
@kindex set breakpoint condition-evaluation
|
||
@kindex show breakpoint condition-evaluation
|
||
@table @code
|
||
@item set breakpoint condition-evaluation host
|
||
This option commands @value{GDBN} to evaluate the breakpoint
|
||
conditions on the host's side. Unconditional breakpoints are sent to
|
||
the target which in turn receives the triggers and reports them back to GDB
|
||
for condition evaluation. This is the standard evaluation mode.
|
||
|
||
@item set breakpoint condition-evaluation target
|
||
This option commands @value{GDBN} to download breakpoint conditions
|
||
to the target at the moment of their insertion. The target
|
||
is responsible for evaluating the conditional expression and reporting
|
||
breakpoint stop events back to @value{GDBN} whenever the condition
|
||
is true. Due to limitations of target-side evaluation, some conditions
|
||
cannot be evaluated there, e.g., conditions that depend on local data
|
||
that is only known to the host. Examples include
|
||
conditional expressions involving convenience variables, complex types
|
||
that cannot be handled by the agent expression parser and expressions
|
||
that are too long to be sent over to the target, specially when the
|
||
target is a remote system. In these cases, the conditions will be
|
||
evaluated by @value{GDBN}.
|
||
|
||
@item set breakpoint condition-evaluation auto
|
||
This is the default mode. If the target supports evaluating breakpoint
|
||
conditions on its end, @value{GDBN} will download breakpoint conditions to
|
||
the target (limitations mentioned previously apply). If the target does
|
||
not support breakpoint condition evaluation, then @value{GDBN} will fallback
|
||
to evaluating all these conditions on the host's side.
|
||
@end table
|
||
|
||
|
||
@cindex negative breakpoint numbers
|
||
@cindex internal @value{GDBN} breakpoints
|
||
@value{GDBN} itself sometimes sets breakpoints in your program for
|
||
special purposes, such as proper handling of @code{longjmp} (in C
|
||
programs). These internal breakpoints are assigned negative numbers,
|
||
starting with @code{-1}; @samp{info breakpoints} does not display them.
|
||
You can see these breakpoints with the @value{GDBN} maintenance command
|
||
@samp{maint info breakpoints} (@pxref{maint info breakpoints}).
|
||
|
||
|
||
@node Set Watchpoints
|
||
@subsection Setting Watchpoints
|
||
|
||
@cindex setting watchpoints
|
||
You can use a watchpoint to stop execution whenever the value of an
|
||
expression changes, without having to predict a particular place where
|
||
this may happen. (This is sometimes called a @dfn{data breakpoint}.)
|
||
The expression may be as simple as the value of a single variable, or
|
||
as complex as many variables combined by operators. Examples include:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
A reference to the value of a single variable.
|
||
|
||
@item
|
||
An address cast to an appropriate data type. For example,
|
||
@samp{*(int *)0x12345678} will watch a 4-byte region at the specified
|
||
address (assuming an @code{int} occupies 4 bytes).
|
||
|
||
@item
|
||
An arbitrarily complex expression, such as @samp{a*b + c/d}. The
|
||
expression can use any operators valid in the program's native
|
||
language (@pxref{Languages}).
|
||
@end itemize
|
||
|
||
You can set a watchpoint on an expression even if the expression can
|
||
not be evaluated yet. For instance, you can set a watchpoint on
|
||
@samp{*global_ptr} before @samp{global_ptr} is initialized.
|
||
@value{GDBN} will stop when your program sets @samp{global_ptr} and
|
||
the expression produces a valid value. If the expression becomes
|
||
valid in some other way than changing a variable (e.g.@: if the memory
|
||
pointed to by @samp{*global_ptr} becomes readable as the result of a
|
||
@code{malloc} call), @value{GDBN} may not stop until the next time
|
||
the expression changes.
|
||
|
||
@cindex software watchpoints
|
||
@cindex hardware watchpoints
|
||
Depending on your system, watchpoints may be implemented in software or
|
||
hardware. @value{GDBN} does software watchpointing by single-stepping your
|
||
program and testing the variable's value each time, which is hundreds of
|
||
times slower than normal execution. (But this may still be worth it, to
|
||
catch errors where you have no clue what part of your program is the
|
||
culprit.)
|
||
|
||
On some systems, such as most PowerPC or x86-based targets,
|
||
@value{GDBN} includes support for hardware watchpoints, which do not
|
||
slow down the running of your program.
|
||
|
||
@table @code
|
||
@kindex watch
|
||
@item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
|
||
Set a watchpoint for an expression. @value{GDBN} will break when the
|
||
expression @var{expr} is written into by the program and its value
|
||
changes. The simplest (and the most popular) use of this command is
|
||
to watch the value of a single variable:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) watch foo
|
||
@end smallexample
|
||
|
||
If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
|
||
argument, @value{GDBN} breaks only when the thread identified by
|
||
@var{thread-id} changes the value of @var{expr}. If any other threads
|
||
change the value of @var{expr}, @value{GDBN} will not break. Note
|
||
that watchpoints restricted to a single thread in this way only work
|
||
with Hardware Watchpoints.
|
||
|
||
Ordinarily a watchpoint respects the scope of variables in @var{expr}
|
||
(see below). The @code{-location} argument tells @value{GDBN} to
|
||
instead watch the memory referred to by @var{expr}. In this case,
|
||
@value{GDBN} will evaluate @var{expr}, take the address of the result,
|
||
and watch the memory at that address. The type of the result is used
|
||
to determine the size of the watched memory. If the expression's
|
||
result does not have an address, then @value{GDBN} will print an
|
||
error.
|
||
|
||
The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
|
||
of masked watchpoints, if the current architecture supports this
|
||
feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
|
||
Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
|
||
to an address to watch. The mask specifies that some bits of an address
|
||
(the bits which are reset in the mask) should be ignored when matching
|
||
the address accessed by the inferior against the watchpoint address.
|
||
Thus, a masked watchpoint watches many addresses simultaneously---those
|
||
addresses whose unmasked bits are identical to the unmasked bits in the
|
||
watchpoint address. The @code{mask} argument implies @code{-location}.
|
||
Examples:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) watch foo mask 0xffff00ff
|
||
(@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
|
||
@end smallexample
|
||
|
||
@kindex rwatch
|
||
@item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
|
||
Set a watchpoint that will break when the value of @var{expr} is read
|
||
by the program.
|
||
|
||
@kindex awatch
|
||
@item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
|
||
Set a watchpoint that will break when @var{expr} is either read from
|
||
or written into by the program.
|
||
|
||
@kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
|
||
@item info watchpoints @r{[}@var{list}@dots{}@r{]}
|
||
This command prints a list of watchpoints, using the same format as
|
||
@code{info break} (@pxref{Set Breaks}).
|
||
@end table
|
||
|
||
If you watch for a change in a numerically entered address you need to
|
||
dereference it, as the address itself is just a constant number which will
|
||
never change. @value{GDBN} refuses to create a watchpoint that watches
|
||
a never-changing value:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) watch 0x600850
|
||
Cannot watch constant value 0x600850.
|
||
(@value{GDBP}) watch *(int *) 0x600850
|
||
Watchpoint 1: *(int *) 6293584
|
||
@end smallexample
|
||
|
||
@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
|
||
watchpoints execute very quickly, and the debugger reports a change in
|
||
value at the exact instruction where the change occurs. If @value{GDBN}
|
||
cannot set a hardware watchpoint, it sets a software watchpoint, which
|
||
executes more slowly and reports the change in value at the next
|
||
@emph{statement}, not the instruction, after the change occurs.
|
||
|
||
@cindex use only software watchpoints
|
||
You can force @value{GDBN} to use only software watchpoints with the
|
||
@kbd{set can-use-hw-watchpoints 0} command. With this variable set to
|
||
zero, @value{GDBN} will never try to use hardware watchpoints, even if
|
||
the underlying system supports them. (Note that hardware-assisted
|
||
watchpoints that were set @emph{before} setting
|
||
@code{can-use-hw-watchpoints} to zero will still use the hardware
|
||
mechanism of watching expression values.)
|
||
|
||
@table @code
|
||
@item set can-use-hw-watchpoints
|
||
@kindex set can-use-hw-watchpoints
|
||
Set whether or not to use hardware watchpoints.
|
||
|
||
@item show can-use-hw-watchpoints
|
||
@kindex show can-use-hw-watchpoints
|
||
Show the current mode of using hardware watchpoints.
|
||
@end table
|
||
|
||
For remote targets, you can restrict the number of hardware
|
||
watchpoints @value{GDBN} will use, see @ref{set remote
|
||
hardware-breakpoint-limit}.
|
||
|
||
When you issue the @code{watch} command, @value{GDBN} reports
|
||
|
||
@smallexample
|
||
Hardware watchpoint @var{num}: @var{expr}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
if it was able to set a hardware watchpoint.
|
||
|
||
Currently, the @code{awatch} and @code{rwatch} commands can only set
|
||
hardware watchpoints, because accesses to data that don't change the
|
||
value of the watched expression cannot be detected without examining
|
||
every instruction as it is being executed, and @value{GDBN} does not do
|
||
that currently. If @value{GDBN} finds that it is unable to set a
|
||
hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
|
||
will print a message like this:
|
||
|
||
@smallexample
|
||
Expression cannot be implemented with read/access watchpoint.
|
||
@end smallexample
|
||
|
||
Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
|
||
data type of the watched expression is wider than what a hardware
|
||
watchpoint on the target machine can handle. For example, some systems
|
||
can only watch regions that are up to 4 bytes wide; on such systems you
|
||
cannot set hardware watchpoints for an expression that yields a
|
||
double-precision floating-point number (which is typically 8 bytes
|
||
wide). As a work-around, it might be possible to break the large region
|
||
into a series of smaller ones and watch them with separate watchpoints.
|
||
|
||
If you set too many hardware watchpoints, @value{GDBN} might be unable
|
||
to insert all of them when you resume the execution of your program.
|
||
Since the precise number of active watchpoints is unknown until such
|
||
time as the program is about to be resumed, @value{GDBN} might not be
|
||
able to warn you about this when you set the watchpoints, and the
|
||
warning will be printed only when the program is resumed:
|
||
|
||
@smallexample
|
||
Hardware watchpoint @var{num}: Could not insert watchpoint
|
||
@end smallexample
|
||
|
||
@noindent
|
||
If this happens, delete or disable some of the watchpoints.
|
||
|
||
Watching complex expressions that reference many variables can also
|
||
exhaust the resources available for hardware-assisted watchpoints.
|
||
That's because @value{GDBN} needs to watch every variable in the
|
||
expression with separately allocated resources.
|
||
|
||
If you call a function interactively using @code{print} or @code{call},
|
||
any watchpoints you have set will be inactive until @value{GDBN} reaches another
|
||
kind of breakpoint or the call completes.
|
||
|
||
@value{GDBN} automatically deletes watchpoints that watch local
|
||
(automatic) variables, or expressions that involve such variables, when
|
||
they go out of scope, that is, when the execution leaves the block in
|
||
which these variables were defined. In particular, when the program
|
||
being debugged terminates, @emph{all} local variables go out of scope,
|
||
and so only watchpoints that watch global variables remain set. If you
|
||
rerun the program, you will need to set all such watchpoints again. One
|
||
way of doing that would be to set a code breakpoint at the entry to the
|
||
@code{main} function and when it breaks, set all the watchpoints.
|
||
|
||
@cindex watchpoints and threads
|
||
@cindex threads and watchpoints
|
||
In multi-threaded programs, watchpoints will detect changes to the
|
||
watched expression from every thread.
|
||
|
||
@quotation
|
||
@emph{Warning:} In multi-threaded programs, software watchpoints
|
||
have only limited usefulness. If @value{GDBN} creates a software
|
||
watchpoint, it can only watch the value of an expression @emph{in a
|
||
single thread}. If you are confident that the expression can only
|
||
change due to the current thread's activity (and if you are also
|
||
confident that no other thread can become current), then you can use
|
||
software watchpoints as usual. However, @value{GDBN} may not notice
|
||
when a non-current thread's activity changes the expression. (Hardware
|
||
watchpoints, in contrast, watch an expression in all threads.)
|
||
@end quotation
|
||
|
||
@xref{set remote hardware-watchpoint-limit}.
|
||
|
||
@node Set Catchpoints
|
||
@subsection Setting Catchpoints
|
||
@cindex catchpoints, setting
|
||
@cindex exception handlers
|
||
@cindex event handling
|
||
|
||
You can use @dfn{catchpoints} to cause the debugger to stop for certain
|
||
kinds of program events, such as C@t{++} exceptions or the loading of a
|
||
shared library. Use the @code{catch} command to set a catchpoint.
|
||
|
||
@table @code
|
||
@kindex catch
|
||
@item catch @var{event}
|
||
Stop when @var{event} occurs. The @var{event} can be any of the following:
|
||
|
||
@table @code
|
||
@item throw @r{[}@var{regexp}@r{]}
|
||
@itemx rethrow @r{[}@var{regexp}@r{]}
|
||
@itemx catch @r{[}@var{regexp}@r{]}
|
||
@kindex catch throw
|
||
@kindex catch rethrow
|
||
@kindex catch catch
|
||
@cindex stop on C@t{++} exceptions
|
||
The throwing, re-throwing, or catching of a C@t{++} exception.
|
||
|
||
If @var{regexp} is given, then only exceptions whose type matches the
|
||
regular expression will be caught.
|
||
|
||
@vindex $_exception@r{, convenience variable}
|
||
The convenience variable @code{$_exception} is available at an
|
||
exception-related catchpoint, on some systems. This holds the
|
||
exception being thrown.
|
||
|
||
There are currently some limitations to C@t{++} exception handling in
|
||
@value{GDBN}:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The support for these commands is system-dependent. Currently, only
|
||
systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
|
||
supported.
|
||
|
||
@item
|
||
The regular expression feature and the @code{$_exception} convenience
|
||
variable rely on the presence of some SDT probes in @code{libstdc++}.
|
||
If these probes are not present, then these features cannot be used.
|
||
These probes were first available in the GCC 4.8 release, but whether
|
||
or not they are available in your GCC also depends on how it was
|
||
built.
|
||
|
||
@item
|
||
The @code{$_exception} convenience variable is only valid at the
|
||
instruction at which an exception-related catchpoint is set.
|
||
|
||
@item
|
||
When an exception-related catchpoint is hit, @value{GDBN} stops at a
|
||
location in the system library which implements runtime exception
|
||
support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
|
||
(@pxref{Selection}) to get to your code.
|
||
|
||
@item
|
||
If you call a function interactively, @value{GDBN} normally returns
|
||
control to you when the function has finished executing. If the call
|
||
raises an exception, however, the call may bypass the mechanism that
|
||
returns control to you and cause your program either to abort or to
|
||
simply continue running until it hits a breakpoint, catches a signal
|
||
that @value{GDBN} is listening for, or exits. This is the case even if
|
||
you set a catchpoint for the exception; catchpoints on exceptions are
|
||
disabled within interactive calls. @xref{Calling}, for information on
|
||
controlling this with @code{set unwind-on-terminating-exception}.
|
||
|
||
@item
|
||
You cannot raise an exception interactively.
|
||
|
||
@item
|
||
You cannot install an exception handler interactively.
|
||
@end itemize
|
||
|
||
@item exception
|
||
@kindex catch exception
|
||
@cindex Ada exception catching
|
||
@cindex catch Ada exceptions
|
||
An Ada exception being raised. If an exception name is specified
|
||
at the end of the command (eg @code{catch exception Program_Error}),
|
||
the debugger will stop only when this specific exception is raised.
|
||
Otherwise, the debugger stops execution when any Ada exception is raised.
|
||
|
||
When inserting an exception catchpoint on a user-defined exception whose
|
||
name is identical to one of the exceptions defined by the language, the
|
||
fully qualified name must be used as the exception name. Otherwise,
|
||
@value{GDBN} will assume that it should stop on the pre-defined exception
|
||
rather than the user-defined one. For instance, assuming an exception
|
||
called @code{Constraint_Error} is defined in package @code{Pck}, then
|
||
the command to use to catch such exceptions is @kbd{catch exception
|
||
Pck.Constraint_Error}.
|
||
|
||
@item handlers
|
||
@kindex catch handlers
|
||
@cindex Ada exception handlers catching
|
||
@cindex catch Ada exceptions when handled
|
||
An Ada exception being handled. If an exception name is
|
||
specified at the end of the command
|
||
(eg @kbd{catch handlers Program_Error}), the debugger will stop
|
||
only when this specific exception is handled.
|
||
Otherwise, the debugger stops execution when any Ada exception is handled.
|
||
|
||
When inserting a handlers catchpoint on a user-defined
|
||
exception whose name is identical to one of the exceptions
|
||
defined by the language, the fully qualified name must be used
|
||
as the exception name. Otherwise, @value{GDBN} will assume that it
|
||
should stop on the pre-defined exception rather than the
|
||
user-defined one. For instance, assuming an exception called
|
||
@code{Constraint_Error} is defined in package @code{Pck}, then the
|
||
command to use to catch such exceptions handling is
|
||
@kbd{catch handlers Pck.Constraint_Error}.
|
||
|
||
@item exception unhandled
|
||
@kindex catch exception unhandled
|
||
An exception that was raised but is not handled by the program.
|
||
|
||
@item assert
|
||
@kindex catch assert
|
||
A failed Ada assertion.
|
||
|
||
@item exec
|
||
@kindex catch exec
|
||
@cindex break on fork/exec
|
||
A call to @code{exec}.
|
||
|
||
@item syscall
|
||
@itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
|
||
@kindex catch syscall
|
||
@cindex break on a system call.
|
||
A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
|
||
syscall is a mechanism for application programs to request a service
|
||
from the operating system (OS) or one of the OS system services.
|
||
@value{GDBN} can catch some or all of the syscalls issued by the
|
||
debuggee, and show the related information for each syscall. If no
|
||
argument is specified, calls to and returns from all system calls
|
||
will be caught.
|
||
|
||
@var{name} can be any system call name that is valid for the
|
||
underlying OS. Just what syscalls are valid depends on the OS. On
|
||
GNU and Unix systems, you can find the full list of valid syscall
|
||
names on @file{/usr/include/asm/unistd.h}.
|
||
|
||
@c For MS-Windows, the syscall names and the corresponding numbers
|
||
@c can be found, e.g., on this URL:
|
||
@c http://www.metasploit.com/users/opcode/syscalls.html
|
||
@c but we don't support Windows syscalls yet.
|
||
|
||
Normally, @value{GDBN} knows in advance which syscalls are valid for
|
||
each OS, so you can use the @value{GDBN} command-line completion
|
||
facilities (@pxref{Completion,, command completion}) to list the
|
||
available choices.
|
||
|
||
You may also specify the system call numerically. A syscall's
|
||
number is the value passed to the OS's syscall dispatcher to
|
||
identify the requested service. When you specify the syscall by its
|
||
name, @value{GDBN} uses its database of syscalls to convert the name
|
||
into the corresponding numeric code, but using the number directly
|
||
may be useful if @value{GDBN}'s database does not have the complete
|
||
list of syscalls on your system (e.g., because @value{GDBN} lags
|
||
behind the OS upgrades).
|
||
|
||
You may specify a group of related syscalls to be caught at once using
|
||
the @code{group:} syntax (@code{g:} is a shorter equivalent). For
|
||
instance, on some platforms @value{GDBN} allows you to catch all
|
||
network related syscalls, by passing the argument @code{group:network}
|
||
to @code{catch syscall}. Note that not all syscall groups are
|
||
available in every system. You can use the command completion
|
||
facilities (@pxref{Completion,, command completion}) to list the
|
||
syscall groups available on your environment.
|
||
|
||
The example below illustrates how this command works if you don't provide
|
||
arguments to it:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall
|
||
Catchpoint 1 (syscall)
|
||
(@value{GDBP}) r
|
||
Starting program: /tmp/catch-syscall
|
||
|
||
Catchpoint 1 (call to syscall 'close'), \
|
||
0xffffe424 in __kernel_vsyscall ()
|
||
(@value{GDBP}) c
|
||
Continuing.
|
||
|
||
Catchpoint 1 (returned from syscall 'close'), \
|
||
0xffffe424 in __kernel_vsyscall ()
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
Here is an example of catching a system call by name:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall chroot
|
||
Catchpoint 1 (syscall 'chroot' [61])
|
||
(@value{GDBP}) r
|
||
Starting program: /tmp/catch-syscall
|
||
|
||
Catchpoint 1 (call to syscall 'chroot'), \
|
||
0xffffe424 in __kernel_vsyscall ()
|
||
(@value{GDBP}) c
|
||
Continuing.
|
||
|
||
Catchpoint 1 (returned from syscall 'chroot'), \
|
||
0xffffe424 in __kernel_vsyscall ()
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
An example of specifying a system call numerically. In the case
|
||
below, the syscall number has a corresponding entry in the XML
|
||
file, so @value{GDBN} finds its name and prints it:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall 252
|
||
Catchpoint 1 (syscall(s) 'exit_group')
|
||
(@value{GDBP}) r
|
||
Starting program: /tmp/catch-syscall
|
||
|
||
Catchpoint 1 (call to syscall 'exit_group'), \
|
||
0xffffe424 in __kernel_vsyscall ()
|
||
(@value{GDBP}) c
|
||
Continuing.
|
||
|
||
Program exited normally.
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
Here is an example of catching a syscall group:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall group:process
|
||
Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
|
||
'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
|
||
'exit_group' [252] 'waitid' [284] 'unshare' [310])
|
||
(@value{GDBP}) r
|
||
Starting program: /tmp/catch-syscall
|
||
|
||
Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
|
||
from /lib64/ld-linux-x86-64.so.2
|
||
|
||
(@value{GDBP}) c
|
||
Continuing.
|
||
@end smallexample
|
||
|
||
However, there can be situations when there is no corresponding name
|
||
in XML file for that syscall number. In this case, @value{GDBN} prints
|
||
a warning message saying that it was not able to find the syscall name,
|
||
but the catchpoint will be set anyway. See the example below:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall 764
|
||
warning: The number '764' does not represent a known syscall.
|
||
Catchpoint 2 (syscall 764)
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
If you configure @value{GDBN} using the @samp{--without-expat} option,
|
||
it will not be able to display syscall names. Also, if your
|
||
architecture does not have an XML file describing its system calls,
|
||
you will not be able to see the syscall names. It is important to
|
||
notice that these two features are used for accessing the syscall
|
||
name database. In either case, you will see a warning like this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall
|
||
warning: Could not open "syscalls/i386-linux.xml"
|
||
warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
|
||
GDB will not be able to display syscall names.
|
||
Catchpoint 1 (syscall)
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
Of course, the file name will change depending on your architecture and system.
|
||
|
||
Still using the example above, you can also try to catch a syscall by its
|
||
number. In this case, you would see something like:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) catch syscall 252
|
||
Catchpoint 1 (syscall(s) 252)
|
||
@end smallexample
|
||
|
||
Again, in this case @value{GDBN} would not be able to display syscall's names.
|
||
|
||
@item fork
|
||
@kindex catch fork
|
||
A call to @code{fork}.
|
||
|
||
@item vfork
|
||
@kindex catch vfork
|
||
A call to @code{vfork}.
|
||
|
||
@item load @r{[}regexp@r{]}
|
||
@itemx unload @r{[}regexp@r{]}
|
||
@kindex catch load
|
||
@kindex catch unload
|
||
The loading or unloading of a shared library. If @var{regexp} is
|
||
given, then the catchpoint will stop only if the regular expression
|
||
matches one of the affected libraries.
|
||
|
||
@item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
|
||
@kindex catch signal
|
||
The delivery of a signal.
|
||
|
||
With no arguments, this catchpoint will catch any signal that is not
|
||
used internally by @value{GDBN}, specifically, all signals except
|
||
@samp{SIGTRAP} and @samp{SIGINT}.
|
||
|
||
With the argument @samp{all}, all signals, including those used by
|
||
@value{GDBN}, will be caught. This argument cannot be used with other
|
||
signal names.
|
||
|
||
Otherwise, the arguments are a list of signal names as given to
|
||
@code{handle} (@pxref{Signals}). Only signals specified in this list
|
||
will be caught.
|
||
|
||
One reason that @code{catch signal} can be more useful than
|
||
@code{handle} is that you can attach commands and conditions to the
|
||
catchpoint.
|
||
|
||
When a signal is caught by a catchpoint, the signal's @code{stop} and
|
||
@code{print} settings, as specified by @code{handle}, are ignored.
|
||
However, whether the signal is still delivered to the inferior depends
|
||
on the @code{pass} setting; this can be changed in the catchpoint's
|
||
commands.
|
||
|
||
@end table
|
||
|
||
@item tcatch @var{event}
|
||
@kindex tcatch
|
||
Set a catchpoint that is enabled only for one stop. The catchpoint is
|
||
automatically deleted after the first time the event is caught.
|
||
|
||
@end table
|
||
|
||
Use the @code{info break} command to list the current catchpoints.
|
||
|
||
|
||
@node Delete Breaks
|
||
@subsection Deleting Breakpoints
|
||
|
||
@cindex clearing breakpoints, watchpoints, catchpoints
|
||
@cindex deleting breakpoints, watchpoints, catchpoints
|
||
It is often necessary to eliminate a breakpoint, watchpoint, or
|
||
catchpoint once it has done its job and you no longer want your program
|
||
to stop there. This is called @dfn{deleting} the breakpoint. A
|
||
breakpoint that has been deleted no longer exists; it is forgotten.
|
||
|
||
With the @code{clear} command you can delete breakpoints according to
|
||
where they are in your program. With the @code{delete} command you can
|
||
delete individual breakpoints, watchpoints, or catchpoints by specifying
|
||
their breakpoint numbers.
|
||
|
||
It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
|
||
automatically ignores breakpoints on the first instruction to be executed
|
||
when you continue execution without changing the execution address.
|
||
|
||
@table @code
|
||
@kindex clear
|
||
@item clear
|
||
Delete any breakpoints at the next instruction to be executed in the
|
||
selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
|
||
the innermost frame is selected, this is a good way to delete a
|
||
breakpoint where your program just stopped.
|
||
|
||
@item clear @var{location}
|
||
Delete any breakpoints set at the specified @var{location}.
|
||
@xref{Specify Location}, for the various forms of @var{location}; the
|
||
most useful ones are listed below:
|
||
|
||
@table @code
|
||
@item clear @var{function}
|
||
@itemx clear @var{filename}:@var{function}
|
||
Delete any breakpoints set at entry to the named @var{function}.
|
||
|
||
@item clear @var{linenum}
|
||
@itemx clear @var{filename}:@var{linenum}
|
||
Delete any breakpoints set at or within the code of the specified
|
||
@var{linenum} of the specified @var{filename}.
|
||
@end table
|
||
|
||
@cindex delete breakpoints
|
||
@kindex delete
|
||
@kindex d @r{(@code{delete})}
|
||
@item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
|
||
Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
|
||
list specified as argument. If no argument is specified, delete all
|
||
breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
|
||
confirm off}). You can abbreviate this command as @code{d}.
|
||
@end table
|
||
|
||
@node Disabling
|
||
@subsection Disabling Breakpoints
|
||
|
||
@cindex enable/disable a breakpoint
|
||
Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
|
||
prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
|
||
it had been deleted, but remembers the information on the breakpoint so
|
||
that you can @dfn{enable} it again later.
|
||
|
||
You disable and enable breakpoints, watchpoints, and catchpoints with
|
||
the @code{enable} and @code{disable} commands, optionally specifying
|
||
one or more breakpoint numbers as arguments. Use @code{info break} to
|
||
print a list of all breakpoints, watchpoints, and catchpoints if you
|
||
do not know which numbers to use.
|
||
|
||
Disabling and enabling a breakpoint that has multiple locations
|
||
affects all of its locations.
|
||
|
||
A breakpoint, watchpoint, or catchpoint can have any of several
|
||
different states of enablement:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Enabled. The breakpoint stops your program. A breakpoint set
|
||
with the @code{break} command starts out in this state.
|
||
@item
|
||
Disabled. The breakpoint has no effect on your program.
|
||
@item
|
||
Enabled once. The breakpoint stops your program, but then becomes
|
||
disabled.
|
||
@item
|
||
Enabled for a count. The breakpoint stops your program for the next
|
||
N times, then becomes disabled.
|
||
@item
|
||
Enabled for deletion. The breakpoint stops your program, but
|
||
immediately after it does so it is deleted permanently. A breakpoint
|
||
set with the @code{tbreak} command starts out in this state.
|
||
@end itemize
|
||
|
||
You can use the following commands to enable or disable breakpoints,
|
||
watchpoints, and catchpoints:
|
||
|
||
@table @code
|
||
@kindex disable
|
||
@kindex dis @r{(@code{disable})}
|
||
@item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
|
||
Disable the specified breakpoints---or all breakpoints, if none are
|
||
listed. A disabled breakpoint has no effect but is not forgotten. All
|
||
options such as ignore-counts, conditions and commands are remembered in
|
||
case the breakpoint is enabled again later. You may abbreviate
|
||
@code{disable} as @code{dis}.
|
||
|
||
@kindex enable
|
||
@item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
|
||
Enable the specified breakpoints (or all defined breakpoints). They
|
||
become effective once again in stopping your program.
|
||
|
||
@item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
|
||
Enable the specified breakpoints temporarily. @value{GDBN} disables any
|
||
of these breakpoints immediately after stopping your program.
|
||
|
||
@item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
|
||
Enable the specified breakpoints temporarily. @value{GDBN} records
|
||
@var{count} with each of the specified breakpoints, and decrements a
|
||
breakpoint's count when it is hit. When any count reaches 0,
|
||
@value{GDBN} disables that breakpoint. If a breakpoint has an ignore
|
||
count (@pxref{Conditions, ,Break Conditions}), that will be
|
||
decremented to 0 before @var{count} is affected.
|
||
|
||
@item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
|
||
Enable the specified breakpoints to work once, then die. @value{GDBN}
|
||
deletes any of these breakpoints as soon as your program stops there.
|
||
Breakpoints set by the @code{tbreak} command start out in this state.
|
||
@end table
|
||
|
||
@c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
|
||
@c confusing: tbreak is also initially enabled.
|
||
Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
|
||
,Setting Breakpoints}), breakpoints that you set are initially enabled;
|
||
subsequently, they become disabled or enabled only when you use one of
|
||
the commands above. (The command @code{until} can set and delete a
|
||
breakpoint of its own, but it does not change the state of your other
|
||
breakpoints; see @ref{Continuing and Stepping, ,Continuing and
|
||
Stepping}.)
|
||
|
||
@node Conditions
|
||
@subsection Break Conditions
|
||
@cindex conditional breakpoints
|
||
@cindex breakpoint conditions
|
||
|
||
@c FIXME what is scope of break condition expr? Context where wanted?
|
||
@c in particular for a watchpoint?
|
||
The simplest sort of breakpoint breaks every time your program reaches a
|
||
specified place. You can also specify a @dfn{condition} for a
|
||
breakpoint. A condition is just a Boolean expression in your
|
||
programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
|
||
a condition evaluates the expression each time your program reaches it,
|
||
and your program stops only if the condition is @emph{true}.
|
||
|
||
This is the converse of using assertions for program validation; in that
|
||
situation, you want to stop when the assertion is violated---that is,
|
||
when the condition is false. In C, if you want to test an assertion expressed
|
||
by the condition @var{assert}, you should set the condition
|
||
@samp{! @var{assert}} on the appropriate breakpoint.
|
||
|
||
Conditions are also accepted for watchpoints; you may not need them,
|
||
since a watchpoint is inspecting the value of an expression anyhow---but
|
||
it might be simpler, say, to just set a watchpoint on a variable name,
|
||
and specify a condition that tests whether the new value is an interesting
|
||
one.
|
||
|
||
Break conditions can have side effects, and may even call functions in
|
||
your program. This can be useful, for example, to activate functions
|
||
that log program progress, or to use your own print functions to
|
||
format special data structures. The effects are completely predictable
|
||
unless there is another enabled breakpoint at the same address. (In
|
||
that case, @value{GDBN} might see the other breakpoint first and stop your
|
||
program without checking the condition of this one.) Note that
|
||
breakpoint commands are usually more convenient and flexible than break
|
||
conditions for the
|
||
purpose of performing side effects when a breakpoint is reached
|
||
(@pxref{Break Commands, ,Breakpoint Command Lists}).
|
||
|
||
Breakpoint conditions can also be evaluated on the target's side if
|
||
the target supports it. Instead of evaluating the conditions locally,
|
||
@value{GDBN} encodes the expression into an agent expression
|
||
(@pxref{Agent Expressions}) suitable for execution on the target,
|
||
independently of @value{GDBN}. Global variables become raw memory
|
||
locations, locals become stack accesses, and so forth.
|
||
|
||
In this case, @value{GDBN} will only be notified of a breakpoint trigger
|
||
when its condition evaluates to true. This mechanism may provide faster
|
||
response times depending on the performance characteristics of the target
|
||
since it does not need to keep @value{GDBN} informed about
|
||
every breakpoint trigger, even those with false conditions.
|
||
|
||
Break conditions can be specified when a breakpoint is set, by using
|
||
@samp{if} in the arguments to the @code{break} command. @xref{Set
|
||
Breaks, ,Setting Breakpoints}. They can also be changed at any time
|
||
with the @code{condition} command.
|
||
|
||
You can also use the @code{if} keyword with the @code{watch} command.
|
||
The @code{catch} command does not recognize the @code{if} keyword;
|
||
@code{condition} is the only way to impose a further condition on a
|
||
catchpoint.
|
||
|
||
@table @code
|
||
@kindex condition
|
||
@item condition @var{bnum} @var{expression}
|
||
Specify @var{expression} as the break condition for breakpoint,
|
||
watchpoint, or catchpoint number @var{bnum}. After you set a condition,
|
||
breakpoint @var{bnum} stops your program only if the value of
|
||
@var{expression} is true (nonzero, in C). When you use
|
||
@code{condition}, @value{GDBN} checks @var{expression} immediately for
|
||
syntactic correctness, and to determine whether symbols in it have
|
||
referents in the context of your breakpoint. If @var{expression} uses
|
||
symbols not referenced in the context of the breakpoint, @value{GDBN}
|
||
prints an error message:
|
||
|
||
@smallexample
|
||
No symbol "foo" in current context.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@value{GDBN} does
|
||
not actually evaluate @var{expression} at the time the @code{condition}
|
||
command (or a command that sets a breakpoint with a condition, like
|
||
@code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
|
||
|
||
@item condition @var{bnum}
|
||
Remove the condition from breakpoint number @var{bnum}. It becomes
|
||
an ordinary unconditional breakpoint.
|
||
@end table
|
||
|
||
@cindex ignore count (of breakpoint)
|
||
A special case of a breakpoint condition is to stop only when the
|
||
breakpoint has been reached a certain number of times. This is so
|
||
useful that there is a special way to do it, using the @dfn{ignore
|
||
count} of the breakpoint. Every breakpoint has an ignore count, which
|
||
is an integer. Most of the time, the ignore count is zero, and
|
||
therefore has no effect. But if your program reaches a breakpoint whose
|
||
ignore count is positive, then instead of stopping, it just decrements
|
||
the ignore count by one and continues. As a result, if the ignore count
|
||
value is @var{n}, the breakpoint does not stop the next @var{n} times
|
||
your program reaches it.
|
||
|
||
@table @code
|
||
@kindex ignore
|
||
@item ignore @var{bnum} @var{count}
|
||
Set the ignore count of breakpoint number @var{bnum} to @var{count}.
|
||
The next @var{count} times the breakpoint is reached, your program's
|
||
execution does not stop; other than to decrement the ignore count, @value{GDBN}
|
||
takes no action.
|
||
|
||
To make the breakpoint stop the next time it is reached, specify
|
||
a count of zero.
|
||
|
||
When you use @code{continue} to resume execution of your program from a
|
||
breakpoint, you can specify an ignore count directly as an argument to
|
||
@code{continue}, rather than using @code{ignore}. @xref{Continuing and
|
||
Stepping,,Continuing and Stepping}.
|
||
|
||
If a breakpoint has a positive ignore count and a condition, the
|
||
condition is not checked. Once the ignore count reaches zero,
|
||
@value{GDBN} resumes checking the condition.
|
||
|
||
You could achieve the effect of the ignore count with a condition such
|
||
as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
|
||
is decremented each time. @xref{Convenience Vars, ,Convenience
|
||
Variables}.
|
||
@end table
|
||
|
||
Ignore counts apply to breakpoints, watchpoints, and catchpoints.
|
||
|
||
|
||
@node Break Commands
|
||
@subsection Breakpoint Command Lists
|
||
|
||
@cindex breakpoint commands
|
||
You can give any breakpoint (or watchpoint or catchpoint) a series of
|
||
commands to execute when your program stops due to that breakpoint. For
|
||
example, you might want to print the values of certain expressions, or
|
||
enable other breakpoints.
|
||
|
||
@table @code
|
||
@kindex commands
|
||
@kindex end@r{ (breakpoint commands)}
|
||
@item commands @r{[}@var{list}@dots{}@r{]}
|
||
@itemx @dots{} @var{command-list} @dots{}
|
||
@itemx end
|
||
Specify a list of commands for the given breakpoints. The commands
|
||
themselves appear on the following lines. Type a line containing just
|
||
@code{end} to terminate the commands.
|
||
|
||
To remove all commands from a breakpoint, type @code{commands} and
|
||
follow it immediately with @code{end}; that is, give no commands.
|
||
|
||
With no argument, @code{commands} refers to the last breakpoint,
|
||
watchpoint, or catchpoint set (not to the breakpoint most recently
|
||
encountered). If the most recent breakpoints were set with a single
|
||
command, then the @code{commands} will apply to all the breakpoints
|
||
set by that command. This applies to breakpoints set by
|
||
@code{rbreak}, and also applies when a single @code{break} command
|
||
creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
|
||
Expressions}).
|
||
@end table
|
||
|
||
Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
|
||
disabled within a @var{command-list}.
|
||
|
||
You can use breakpoint commands to start your program up again. Simply
|
||
use the @code{continue} command, or @code{step}, or any other command
|
||
that resumes execution.
|
||
|
||
Any other commands in the command list, after a command that resumes
|
||
execution, are ignored. This is because any time you resume execution
|
||
(even with a simple @code{next} or @code{step}), you may encounter
|
||
another breakpoint---which could have its own command list, leading to
|
||
ambiguities about which list to execute.
|
||
|
||
@kindex silent
|
||
If the first command you specify in a command list is @code{silent}, the
|
||
usual message about stopping at a breakpoint is not printed. This may
|
||
be desirable for breakpoints that are to print a specific message and
|
||
then continue. If none of the remaining commands print anything, you
|
||
see no sign that the breakpoint was reached. @code{silent} is
|
||
meaningful only at the beginning of a breakpoint command list.
|
||
|
||
The commands @code{echo}, @code{output}, and @code{printf} allow you to
|
||
print precisely controlled output, and are often useful in silent
|
||
breakpoints. @xref{Output, ,Commands for Controlled Output}.
|
||
|
||
For example, here is how you could use breakpoint commands to print the
|
||
value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
|
||
|
||
@smallexample
|
||
break foo if x>0
|
||
commands
|
||
silent
|
||
printf "x is %d\n",x
|
||
cont
|
||
end
|
||
@end smallexample
|
||
|
||
One application for breakpoint commands is to compensate for one bug so
|
||
you can test for another. Put a breakpoint just after the erroneous line
|
||
of code, give it a condition to detect the case in which something
|
||
erroneous has been done, and give it commands to assign correct values
|
||
to any variables that need them. End with the @code{continue} command
|
||
so that your program does not stop, and start with the @code{silent}
|
||
command so that no output is produced. Here is an example:
|
||
|
||
@smallexample
|
||
break 403
|
||
commands
|
||
silent
|
||
set x = y + 4
|
||
cont
|
||
end
|
||
@end smallexample
|
||
|
||
@node Dynamic Printf
|
||
@subsection Dynamic Printf
|
||
|
||
@cindex dynamic printf
|
||
@cindex dprintf
|
||
The dynamic printf command @code{dprintf} combines a breakpoint with
|
||
formatted printing of your program's data to give you the effect of
|
||
inserting @code{printf} calls into your program on-the-fly, without
|
||
having to recompile it.
|
||
|
||
In its most basic form, the output goes to the GDB console. However,
|
||
you can set the variable @code{dprintf-style} for alternate handling.
|
||
For instance, you can ask to format the output by calling your
|
||
program's @code{printf} function. This has the advantage that the
|
||
characters go to the program's output device, so they can recorded in
|
||
redirects to files and so forth.
|
||
|
||
If you are doing remote debugging with a stub or agent, you can also
|
||
ask to have the printf handled by the remote agent. In addition to
|
||
ensuring that the output goes to the remote program's device along
|
||
with any other output the program might produce, you can also ask that
|
||
the dprintf remain active even after disconnecting from the remote
|
||
target. Using the stub/agent is also more efficient, as it can do
|
||
everything without needing to communicate with @value{GDBN}.
|
||
|
||
@table @code
|
||
@kindex dprintf
|
||
@item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
|
||
Whenever execution reaches @var{location}, print the values of one or
|
||
more @var{expressions} under the control of the string @var{template}.
|
||
To print several values, separate them with commas.
|
||
|
||
@item set dprintf-style @var{style}
|
||
Set the dprintf output to be handled in one of several different
|
||
styles enumerated below. A change of style affects all existing
|
||
dynamic printfs immediately. (If you need individual control over the
|
||
print commands, simply define normal breakpoints with
|
||
explicitly-supplied command lists.)
|
||
|
||
@table @code
|
||
@item gdb
|
||
@kindex dprintf-style gdb
|
||
Handle the output using the @value{GDBN} @code{printf} command.
|
||
|
||
@item call
|
||
@kindex dprintf-style call
|
||
Handle the output by calling a function in your program (normally
|
||
@code{printf}).
|
||
|
||
@item agent
|
||
@kindex dprintf-style agent
|
||
Have the remote debugging agent (such as @code{gdbserver}) handle
|
||
the output itself. This style is only available for agents that
|
||
support running commands on the target.
|
||
@end table
|
||
|
||
@item set dprintf-function @var{function}
|
||
Set the function to call if the dprintf style is @code{call}. By
|
||
default its value is @code{printf}. You may set it to any expression.
|
||
that @value{GDBN} can evaluate to a function, as per the @code{call}
|
||
command.
|
||
|
||
@item set dprintf-channel @var{channel}
|
||
Set a ``channel'' for dprintf. If set to a non-empty value,
|
||
@value{GDBN} will evaluate it as an expression and pass the result as
|
||
a first argument to the @code{dprintf-function}, in the manner of
|
||
@code{fprintf} and similar functions. Otherwise, the dprintf format
|
||
string will be the first argument, in the manner of @code{printf}.
|
||
|
||
As an example, if you wanted @code{dprintf} output to go to a logfile
|
||
that is a standard I/O stream assigned to the variable @code{mylog},
|
||
you could do the following:
|
||
|
||
@example
|
||
(gdb) set dprintf-style call
|
||
(gdb) set dprintf-function fprintf
|
||
(gdb) set dprintf-channel mylog
|
||
(gdb) dprintf 25,"at line 25, glob=%d\n",glob
|
||
Dprintf 1 at 0x123456: file main.c, line 25.
|
||
(gdb) info break
|
||
1 dprintf keep y 0x00123456 in main at main.c:25
|
||
call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
|
||
continue
|
||
(gdb)
|
||
@end example
|
||
|
||
Note that the @code{info break} displays the dynamic printf commands
|
||
as normal breakpoint commands; you can thus easily see the effect of
|
||
the variable settings.
|
||
|
||
@item set disconnected-dprintf on
|
||
@itemx set disconnected-dprintf off
|
||
@kindex set disconnected-dprintf
|
||
Choose whether @code{dprintf} commands should continue to run if
|
||
@value{GDBN} has disconnected from the target. This only applies
|
||
if the @code{dprintf-style} is @code{agent}.
|
||
|
||
@item show disconnected-dprintf off
|
||
@kindex show disconnected-dprintf
|
||
Show the current choice for disconnected @code{dprintf}.
|
||
|
||
@end table
|
||
|
||
@value{GDBN} does not check the validity of function and channel,
|
||
relying on you to supply values that are meaningful for the contexts
|
||
in which they are being used. For instance, the function and channel
|
||
may be the values of local variables, but if that is the case, then
|
||
all enabled dynamic prints must be at locations within the scope of
|
||
those locals. If evaluation fails, @value{GDBN} will report an error.
|
||
|
||
@node Save Breakpoints
|
||
@subsection How to save breakpoints to a file
|
||
|
||
To save breakpoint definitions to a file use the @w{@code{save
|
||
breakpoints}} command.
|
||
|
||
@table @code
|
||
@kindex save breakpoints
|
||
@cindex save breakpoints to a file for future sessions
|
||
@item save breakpoints [@var{filename}]
|
||
This command saves all current breakpoint definitions together with
|
||
their commands and ignore counts, into a file @file{@var{filename}}
|
||
suitable for use in a later debugging session. This includes all
|
||
types of breakpoints (breakpoints, watchpoints, catchpoints,
|
||
tracepoints). To read the saved breakpoint definitions, use the
|
||
@code{source} command (@pxref{Command Files}). Note that watchpoints
|
||
with expressions involving local variables may fail to be recreated
|
||
because it may not be possible to access the context where the
|
||
watchpoint is valid anymore. Because the saved breakpoint definitions
|
||
are simply a sequence of @value{GDBN} commands that recreate the
|
||
breakpoints, you can edit the file in your favorite editing program,
|
||
and remove the breakpoint definitions you're not interested in, or
|
||
that can no longer be recreated.
|
||
@end table
|
||
|
||
@node Static Probe Points
|
||
@subsection Static Probe Points
|
||
|
||
@cindex static probe point, SystemTap
|
||
@cindex static probe point, DTrace
|
||
@value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
|
||
for Statically Defined Tracing, and the probes are designed to have a tiny
|
||
runtime code and data footprint, and no dynamic relocations.
|
||
|
||
Currently, the following types of probes are supported on
|
||
ELF-compatible systems:
|
||
|
||
@itemize @bullet
|
||
|
||
@item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
|
||
@acronym{SDT} probes@footnote{See
|
||
@uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
|
||
for more information on how to add @code{SystemTap} @acronym{SDT}
|
||
probes in your applications.}. @code{SystemTap} probes are usable
|
||
from assembly, C and C@t{++} languages@footnote{See
|
||
@uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
|
||
for a good reference on how the @acronym{SDT} probes are implemented.}.
|
||
|
||
@item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
|
||
@acronym{USDT} probes. @code{DTrace} probes are usable from C and
|
||
C@t{++} languages.
|
||
@end itemize
|
||
|
||
@cindex semaphores on static probe points
|
||
Some @code{SystemTap} probes have an associated semaphore variable;
|
||
for instance, this happens automatically if you defined your probe
|
||
using a DTrace-style @file{.d} file. If your probe has a semaphore,
|
||
@value{GDBN} will automatically enable it when you specify a
|
||
breakpoint using the @samp{-probe-stap} notation. But, if you put a
|
||
breakpoint at a probe's location by some other method (e.g.,
|
||
@code{break file:line}), then @value{GDBN} will not automatically set
|
||
the semaphore. @code{DTrace} probes do not support semaphores.
|
||
|
||
You can examine the available static static probes using @code{info
|
||
probes}, with optional arguments:
|
||
|
||
@table @code
|
||
@kindex info probes
|
||
@item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
|
||
If given, @var{type} is either @code{stap} for listing
|
||
@code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
|
||
probes. If omitted all probes are listed regardless of their types.
|
||
|
||
If given, @var{provider} is a regular expression used to match against provider
|
||
names when selecting which probes to list. If omitted, probes by all
|
||
probes from all providers are listed.
|
||
|
||
If given, @var{name} is a regular expression to match against probe names
|
||
when selecting which probes to list. If omitted, probe names are not
|
||
considered when deciding whether to display them.
|
||
|
||
If given, @var{objfile} is a regular expression used to select which
|
||
object files (executable or shared libraries) to examine. If not
|
||
given, all object files are considered.
|
||
|
||
@item info probes all
|
||
List the available static probes, from all types.
|
||
@end table
|
||
|
||
@cindex enabling and disabling probes
|
||
Some probe points can be enabled and/or disabled. The effect of
|
||
enabling or disabling a probe depends on the type of probe being
|
||
handled. Some @code{DTrace} probes can be enabled or
|
||
disabled, but @code{SystemTap} probes cannot be disabled.
|
||
|
||
You can enable (or disable) one or more probes using the following
|
||
commands, with optional arguments:
|
||
|
||
@table @code
|
||
@kindex enable probes
|
||
@item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
|
||
If given, @var{provider} is a regular expression used to match against
|
||
provider names when selecting which probes to enable. If omitted,
|
||
all probes from all providers are enabled.
|
||
|
||
If given, @var{name} is a regular expression to match against probe
|
||
names when selecting which probes to enable. If omitted, probe names
|
||
are not considered when deciding whether to enable them.
|
||
|
||
If given, @var{objfile} is a regular expression used to select which
|
||
object files (executable or shared libraries) to examine. If not
|
||
given, all object files are considered.
|
||
|
||
@kindex disable probes
|
||
@item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
|
||
See the @code{enable probes} command above for a description of the
|
||
optional arguments accepted by this command.
|
||
@end table
|
||
|
||
@vindex $_probe_arg@r{, convenience variable}
|
||
A probe may specify up to twelve arguments. These are available at the
|
||
point at which the probe is defined---that is, when the current PC is
|
||
at the probe's location. The arguments are available using the
|
||
convenience variables (@pxref{Convenience Vars})
|
||
@code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
|
||
probes each probe argument is an integer of the appropriate size;
|
||
types are not preserved. In @code{DTrace} probes types are preserved
|
||
provided that they are recognized as such by @value{GDBN}; otherwise
|
||
the value of the probe argument will be a long integer. The
|
||
convenience variable @code{$_probe_argc} holds the number of arguments
|
||
at the current probe point.
|
||
|
||
These variables are always available, but attempts to access them at
|
||
any location other than a probe point will cause @value{GDBN} to give
|
||
an error message.
|
||
|
||
|
||
@c @ifclear BARETARGET
|
||
@node Error in Breakpoints
|
||
@subsection ``Cannot insert breakpoints''
|
||
|
||
If you request too many active hardware-assisted breakpoints and
|
||
watchpoints, you will see this error message:
|
||
|
||
@c FIXME: the precise wording of this message may change; the relevant
|
||
@c source change is not committed yet (Sep 3, 1999).
|
||
@smallexample
|
||
Stopped; cannot insert breakpoints.
|
||
You may have requested too many hardware breakpoints and watchpoints.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This message is printed when you attempt to resume the program, since
|
||
only then @value{GDBN} knows exactly how many hardware breakpoints and
|
||
watchpoints it needs to insert.
|
||
|
||
When this message is printed, you need to disable or remove some of the
|
||
hardware-assisted breakpoints and watchpoints, and then continue.
|
||
|
||
@node Breakpoint-related Warnings
|
||
@subsection ``Breakpoint address adjusted...''
|
||
@cindex breakpoint address adjusted
|
||
|
||
Some processor architectures place constraints on the addresses at
|
||
which breakpoints may be placed. For architectures thus constrained,
|
||
@value{GDBN} will attempt to adjust the breakpoint's address to comply
|
||
with the constraints dictated by the architecture.
|
||
|
||
One example of such an architecture is the Fujitsu FR-V. The FR-V is
|
||
a VLIW architecture in which a number of RISC-like instructions may be
|
||
bundled together for parallel execution. The FR-V architecture
|
||
constrains the location of a breakpoint instruction within such a
|
||
bundle to the instruction with the lowest address. @value{GDBN}
|
||
honors this constraint by adjusting a breakpoint's address to the
|
||
first in the bundle.
|
||
|
||
It is not uncommon for optimized code to have bundles which contain
|
||
instructions from different source statements, thus it may happen that
|
||
a breakpoint's address will be adjusted from one source statement to
|
||
another. Since this adjustment may significantly alter @value{GDBN}'s
|
||
breakpoint related behavior from what the user expects, a warning is
|
||
printed when the breakpoint is first set and also when the breakpoint
|
||
is hit.
|
||
|
||
A warning like the one below is printed when setting a breakpoint
|
||
that's been subject to address adjustment:
|
||
|
||
@smallexample
|
||
warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
|
||
@end smallexample
|
||
|
||
Such warnings are printed both for user settable and @value{GDBN}'s
|
||
internal breakpoints. If you see one of these warnings, you should
|
||
verify that a breakpoint set at the adjusted address will have the
|
||
desired affect. If not, the breakpoint in question may be removed and
|
||
other breakpoints may be set which will have the desired behavior.
|
||
E.g., it may be sufficient to place the breakpoint at a later
|
||
instruction. A conditional breakpoint may also be useful in some
|
||
cases to prevent the breakpoint from triggering too often.
|
||
|
||
@value{GDBN} will also issue a warning when stopping at one of these
|
||
adjusted breakpoints:
|
||
|
||
@smallexample
|
||
warning: Breakpoint 1 address previously adjusted from 0x00010414
|
||
to 0x00010410.
|
||
@end smallexample
|
||
|
||
When this warning is encountered, it may be too late to take remedial
|
||
action except in cases where the breakpoint is hit earlier or more
|
||
frequently than expected.
|
||
|
||
@node Continuing and Stepping
|
||
@section Continuing and Stepping
|
||
|
||
@cindex stepping
|
||
@cindex continuing
|
||
@cindex resuming execution
|
||
@dfn{Continuing} means resuming program execution until your program
|
||
completes normally. In contrast, @dfn{stepping} means executing just
|
||
one more ``step'' of your program, where ``step'' may mean either one
|
||
line of source code, or one machine instruction (depending on what
|
||
particular command you use). Either when continuing or when stepping,
|
||
your program may stop even sooner, due to a breakpoint or a signal. (If
|
||
it stops due to a signal, you may want to use @code{handle}, or use
|
||
@samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
|
||
or you may step into the signal's handler (@pxref{stepping and signal
|
||
handlers}).)
|
||
|
||
@table @code
|
||
@kindex continue
|
||
@kindex c @r{(@code{continue})}
|
||
@kindex fg @r{(resume foreground execution)}
|
||
@item continue @r{[}@var{ignore-count}@r{]}
|
||
@itemx c @r{[}@var{ignore-count}@r{]}
|
||
@itemx fg @r{[}@var{ignore-count}@r{]}
|
||
Resume program execution, at the address where your program last stopped;
|
||
any breakpoints set at that address are bypassed. The optional argument
|
||
@var{ignore-count} allows you to specify a further number of times to
|
||
ignore a breakpoint at this location; its effect is like that of
|
||
@code{ignore} (@pxref{Conditions, ,Break Conditions}).
|
||
|
||
The argument @var{ignore-count} is meaningful only when your program
|
||
stopped due to a breakpoint. At other times, the argument to
|
||
@code{continue} is ignored.
|
||
|
||
The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
|
||
debugged program is deemed to be the foreground program) are provided
|
||
purely for convenience, and have exactly the same behavior as
|
||
@code{continue}.
|
||
@end table
|
||
|
||
To resume execution at a different place, you can use @code{return}
|
||
(@pxref{Returning, ,Returning from a Function}) to go back to the
|
||
calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
|
||
Different Address}) to go to an arbitrary location in your program.
|
||
|
||
A typical technique for using stepping is to set a breakpoint
|
||
(@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
|
||
beginning of the function or the section of your program where a problem
|
||
is believed to lie, run your program until it stops at that breakpoint,
|
||
and then step through the suspect area, examining the variables that are
|
||
interesting, until you see the problem happen.
|
||
|
||
@table @code
|
||
@kindex step
|
||
@kindex s @r{(@code{step})}
|
||
@item step
|
||
Continue running your program until control reaches a different source
|
||
line, then stop it and return control to @value{GDBN}. This command is
|
||
abbreviated @code{s}.
|
||
|
||
@quotation
|
||
@c "without debugging information" is imprecise; actually "without line
|
||
@c numbers in the debugging information". (gcc -g1 has debugging info but
|
||
@c not line numbers). But it seems complex to try to make that
|
||
@c distinction here.
|
||
@emph{Warning:} If you use the @code{step} command while control is
|
||
within a function that was compiled without debugging information,
|
||
execution proceeds until control reaches a function that does have
|
||
debugging information. Likewise, it will not step into a function which
|
||
is compiled without debugging information. To step through functions
|
||
without debugging information, use the @code{stepi} command, described
|
||
below.
|
||
@end quotation
|
||
|
||
The @code{step} command only stops at the first instruction of a source
|
||
line. This prevents the multiple stops that could otherwise occur in
|
||
@code{switch} statements, @code{for} loops, etc. @code{step} continues
|
||
to stop if a function that has debugging information is called within
|
||
the line. In other words, @code{step} @emph{steps inside} any functions
|
||
called within the line.
|
||
|
||
Also, the @code{step} command only enters a function if there is line
|
||
number information for the function. Otherwise it acts like the
|
||
@code{next} command. This avoids problems when using @code{cc -gl}
|
||
on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
|
||
was any debugging information about the routine.
|
||
|
||
@item step @var{count}
|
||
Continue running as in @code{step}, but do so @var{count} times. If a
|
||
breakpoint is reached, or a signal not related to stepping occurs before
|
||
@var{count} steps, stepping stops right away.
|
||
|
||
@kindex next
|
||
@kindex n @r{(@code{next})}
|
||
@item next @r{[}@var{count}@r{]}
|
||
Continue to the next source line in the current (innermost) stack frame.
|
||
This is similar to @code{step}, but function calls that appear within
|
||
the line of code are executed without stopping. Execution stops when
|
||
control reaches a different line of code at the original stack level
|
||
that was executing when you gave the @code{next} command. This command
|
||
is abbreviated @code{n}.
|
||
|
||
An argument @var{count} is a repeat count, as for @code{step}.
|
||
|
||
|
||
@c FIX ME!! Do we delete this, or is there a way it fits in with
|
||
@c the following paragraph? --- Vctoria
|
||
@c
|
||
@c @code{next} within a function that lacks debugging information acts like
|
||
@c @code{step}, but any function calls appearing within the code of the
|
||
@c function are executed without stopping.
|
||
|
||
The @code{next} command only stops at the first instruction of a
|
||
source line. This prevents multiple stops that could otherwise occur in
|
||
@code{switch} statements, @code{for} loops, etc.
|
||
|
||
@kindex set step-mode
|
||
@item set step-mode
|
||
@cindex functions without line info, and stepping
|
||
@cindex stepping into functions with no line info
|
||
@itemx set step-mode on
|
||
The @code{set step-mode on} command causes the @code{step} command to
|
||
stop at the first instruction of a function which contains no debug line
|
||
information rather than stepping over it.
|
||
|
||
This is useful in cases where you may be interested in inspecting the
|
||
machine instructions of a function which has no symbolic info and do not
|
||
want @value{GDBN} to automatically skip over this function.
|
||
|
||
@item set step-mode off
|
||
Causes the @code{step} command to step over any functions which contains no
|
||
debug information. This is the default.
|
||
|
||
@item show step-mode
|
||
Show whether @value{GDBN} will stop in or step over functions without
|
||
source line debug information.
|
||
|
||
@kindex finish
|
||
@kindex fin @r{(@code{finish})}
|
||
@item finish
|
||
Continue running until just after function in the selected stack frame
|
||
returns. Print the returned value (if any). This command can be
|
||
abbreviated as @code{fin}.
|
||
|
||
Contrast this with the @code{return} command (@pxref{Returning,
|
||
,Returning from a Function}).
|
||
|
||
@kindex until
|
||
@kindex u @r{(@code{until})}
|
||
@cindex run until specified location
|
||
@item until
|
||
@itemx u
|
||
Continue running until a source line past the current line, in the
|
||
current stack frame, is reached. This command is used to avoid single
|
||
stepping through a loop more than once. It is like the @code{next}
|
||
command, except that when @code{until} encounters a jump, it
|
||
automatically continues execution until the program counter is greater
|
||
than the address of the jump.
|
||
|
||
This means that when you reach the end of a loop after single stepping
|
||
though it, @code{until} makes your program continue execution until it
|
||
exits the loop. In contrast, a @code{next} command at the end of a loop
|
||
simply steps back to the beginning of the loop, which forces you to step
|
||
through the next iteration.
|
||
|
||
@code{until} always stops your program if it attempts to exit the current
|
||
stack frame.
|
||
|
||
@code{until} may produce somewhat counterintuitive results if the order
|
||
of machine code does not match the order of the source lines. For
|
||
example, in the following excerpt from a debugging session, the @code{f}
|
||
(@code{frame}) command shows that execution is stopped at line
|
||
@code{206}; yet when we use @code{until}, we get to line @code{195}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) f
|
||
#0 main (argc=4, argv=0xf7fffae8) at m4.c:206
|
||
206 expand_input();
|
||
(@value{GDBP}) until
|
||
195 for ( ; argc > 0; NEXTARG) @{
|
||
@end smallexample
|
||
|
||
This happened because, for execution efficiency, the compiler had
|
||
generated code for the loop closure test at the end, rather than the
|
||
start, of the loop---even though the test in a C @code{for}-loop is
|
||
written before the body of the loop. The @code{until} command appeared
|
||
to step back to the beginning of the loop when it advanced to this
|
||
expression; however, it has not really gone to an earlier
|
||
statement---not in terms of the actual machine code.
|
||
|
||
@code{until} with no argument works by means of single
|
||
instruction stepping, and hence is slower than @code{until} with an
|
||
argument.
|
||
|
||
@item until @var{location}
|
||
@itemx u @var{location}
|
||
Continue running your program until either the specified @var{location} is
|
||
reached, or the current stack frame returns. The location is any of
|
||
the forms described in @ref{Specify Location}.
|
||
This form of the command uses temporary breakpoints, and
|
||
hence is quicker than @code{until} without an argument. The specified
|
||
location is actually reached only if it is in the current frame. This
|
||
implies that @code{until} can be used to skip over recursive function
|
||
invocations. For instance in the code below, if the current location is
|
||
line @code{96}, issuing @code{until 99} will execute the program up to
|
||
line @code{99} in the same invocation of factorial, i.e., after the inner
|
||
invocations have returned.
|
||
|
||
@smallexample
|
||
94 int factorial (int value)
|
||
95 @{
|
||
96 if (value > 1) @{
|
||
97 value *= factorial (value - 1);
|
||
98 @}
|
||
99 return (value);
|
||
100 @}
|
||
@end smallexample
|
||
|
||
|
||
@kindex advance @var{location}
|
||
@item advance @var{location}
|
||
Continue running the program up to the given @var{location}. An argument is
|
||
required, which should be of one of the forms described in
|
||
@ref{Specify Location}.
|
||
Execution will also stop upon exit from the current stack
|
||
frame. This command is similar to @code{until}, but @code{advance} will
|
||
not skip over recursive function calls, and the target location doesn't
|
||
have to be in the same frame as the current one.
|
||
|
||
|
||
@kindex stepi
|
||
@kindex si @r{(@code{stepi})}
|
||
@item stepi
|
||
@itemx stepi @var{arg}
|
||
@itemx si
|
||
Execute one machine instruction, then stop and return to the debugger.
|
||
|
||
It is often useful to do @samp{display/i $pc} when stepping by machine
|
||
instructions. This makes @value{GDBN} automatically display the next
|
||
instruction to be executed, each time your program stops. @xref{Auto
|
||
Display,, Automatic Display}.
|
||
|
||
An argument is a repeat count, as in @code{step}.
|
||
|
||
@need 750
|
||
@kindex nexti
|
||
@kindex ni @r{(@code{nexti})}
|
||
@item nexti
|
||
@itemx nexti @var{arg}
|
||
@itemx ni
|
||
Execute one machine instruction, but if it is a function call,
|
||
proceed until the function returns.
|
||
|
||
An argument is a repeat count, as in @code{next}.
|
||
|
||
@end table
|
||
|
||
@anchor{range stepping}
|
||
@cindex range stepping
|
||
@cindex target-assisted range stepping
|
||
By default, and if available, @value{GDBN} makes use of
|
||
target-assisted @dfn{range stepping}. In other words, whenever you
|
||
use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
|
||
tells the target to step the corresponding range of instruction
|
||
addresses instead of issuing multiple single-steps. This speeds up
|
||
line stepping, particularly for remote targets. Ideally, there should
|
||
be no reason you would want to turn range stepping off. However, it's
|
||
possible that a bug in the debug info, a bug in the remote stub (for
|
||
remote targets), or even a bug in @value{GDBN} could make line
|
||
stepping behave incorrectly when target-assisted range stepping is
|
||
enabled. You can use the following command to turn off range stepping
|
||
if necessary:
|
||
|
||
@table @code
|
||
@kindex set range-stepping
|
||
@kindex show range-stepping
|
||
@item set range-stepping
|
||
@itemx show range-stepping
|
||
Control whether range stepping is enabled.
|
||
|
||
If @code{on}, and the target supports it, @value{GDBN} tells the
|
||
target to step a range of addresses itself, instead of issuing
|
||
multiple single-steps. If @code{off}, @value{GDBN} always issues
|
||
single-steps, even if range stepping is supported by the target. The
|
||
default is @code{on}.
|
||
|
||
@end table
|
||
|
||
@node Skipping Over Functions and Files
|
||
@section Skipping Over Functions and Files
|
||
@cindex skipping over functions and files
|
||
|
||
The program you are debugging may contain some functions which are
|
||
uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
|
||
skip a function, all functions in a file or a particular function in
|
||
a particular file when stepping.
|
||
|
||
For example, consider the following C function:
|
||
|
||
@smallexample
|
||
101 int func()
|
||
102 @{
|
||
103 foo(boring());
|
||
104 bar(boring());
|
||
105 @}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
|
||
are not interested in stepping through @code{boring}. If you run @code{step}
|
||
at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
|
||
step over both @code{foo} and @code{boring}!
|
||
|
||
One solution is to @code{step} into @code{boring} and use the @code{finish}
|
||
command to immediately exit it. But this can become tedious if @code{boring}
|
||
is called from many places.
|
||
|
||
A more flexible solution is to execute @kbd{skip boring}. This instructs
|
||
@value{GDBN} never to step into @code{boring}. Now when you execute
|
||
@code{step} at line 103, you'll step over @code{boring} and directly into
|
||
@code{foo}.
|
||
|
||
Functions may be skipped by providing either a function name, linespec
|
||
(@pxref{Specify Location}), regular expression that matches the function's
|
||
name, file name or a @code{glob}-style pattern that matches the file name.
|
||
|
||
On Posix systems the form of the regular expression is
|
||
``Extended Regular Expressions''. See for example @samp{man 7 regex}
|
||
on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
|
||
expression is whatever is provided by the @code{regcomp} function of
|
||
the underlying system.
|
||
See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
|
||
description of @code{glob}-style patterns.
|
||
|
||
@table @code
|
||
@kindex skip
|
||
@item skip @r{[}@var{options}@r{]}
|
||
The basic form of the @code{skip} command takes zero or more options
|
||
that specify what to skip.
|
||
The @var{options} argument is any useful combination of the following:
|
||
|
||
@table @code
|
||
@item -file @var{file}
|
||
@itemx -fi @var{file}
|
||
Functions in @var{file} will be skipped over when stepping.
|
||
|
||
@item -gfile @var{file-glob-pattern}
|
||
@itemx -gfi @var{file-glob-pattern}
|
||
@cindex skipping over files via glob-style patterns
|
||
Functions in files matching @var{file-glob-pattern} will be skipped
|
||
over when stepping.
|
||
|
||
@smallexample
|
||
(gdb) skip -gfi utils/*.c
|
||
@end smallexample
|
||
|
||
@item -function @var{linespec}
|
||
@itemx -fu @var{linespec}
|
||
Functions named by @var{linespec} or the function containing the line
|
||
named by @var{linespec} will be skipped over when stepping.
|
||
@xref{Specify Location}.
|
||
|
||
@item -rfunction @var{regexp}
|
||
@itemx -rfu @var{regexp}
|
||
@cindex skipping over functions via regular expressions
|
||
Functions whose name matches @var{regexp} will be skipped over when stepping.
|
||
|
||
This form is useful for complex function names.
|
||
For example, there is generally no need to step into C@t{++} @code{std::string}
|
||
constructors or destructors. Plus with C@t{++} templates it can be hard to
|
||
write out the full name of the function, and often it doesn't matter what
|
||
the template arguments are. Specifying the function to be skipped as a
|
||
regular expression makes this easier.
|
||
|
||
@smallexample
|
||
(gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
|
||
@end smallexample
|
||
|
||
If you want to skip every templated C@t{++} constructor and destructor
|
||
in the @code{std} namespace you can do:
|
||
|
||
@smallexample
|
||
(gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
|
||
@end smallexample
|
||
@end table
|
||
|
||
If no options are specified, the function you're currently debugging
|
||
will be skipped.
|
||
|
||
@kindex skip function
|
||
@item skip function @r{[}@var{linespec}@r{]}
|
||
After running this command, the function named by @var{linespec} or the
|
||
function containing the line named by @var{linespec} will be skipped over when
|
||
stepping. @xref{Specify Location}.
|
||
|
||
If you do not specify @var{linespec}, the function you're currently debugging
|
||
will be skipped.
|
||
|
||
(If you have a function called @code{file} that you want to skip, use
|
||
@kbd{skip function file}.)
|
||
|
||
@kindex skip file
|
||
@item skip file @r{[}@var{filename}@r{]}
|
||
After running this command, any function whose source lives in @var{filename}
|
||
will be skipped over when stepping.
|
||
|
||
@smallexample
|
||
(gdb) skip file boring.c
|
||
File boring.c will be skipped when stepping.
|
||
@end smallexample
|
||
|
||
If you do not specify @var{filename}, functions whose source lives in the file
|
||
you're currently debugging will be skipped.
|
||
@end table
|
||
|
||
Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
|
||
These are the commands for managing your list of skips:
|
||
|
||
@table @code
|
||
@kindex info skip
|
||
@item info skip @r{[}@var{range}@r{]}
|
||
Print details about the specified skip(s). If @var{range} is not specified,
|
||
print a table with details about all functions and files marked for skipping.
|
||
@code{info skip} prints the following information about each skip:
|
||
|
||
@table @emph
|
||
@item Identifier
|
||
A number identifying this skip.
|
||
@item Enabled or Disabled
|
||
Enabled skips are marked with @samp{y}.
|
||
Disabled skips are marked with @samp{n}.
|
||
@item Glob
|
||
If the file name is a @samp{glob} pattern this is @samp{y}.
|
||
Otherwise it is @samp{n}.
|
||
@item File
|
||
The name or @samp{glob} pattern of the file to be skipped.
|
||
If no file is specified this is @samp{<none>}.
|
||
@item RE
|
||
If the function name is a @samp{regular expression} this is @samp{y}.
|
||
Otherwise it is @samp{n}.
|
||
@item Function
|
||
The name or regular expression of the function to skip.
|
||
If no function is specified this is @samp{<none>}.
|
||
@end table
|
||
|
||
@kindex skip delete
|
||
@item skip delete @r{[}@var{range}@r{]}
|
||
Delete the specified skip(s). If @var{range} is not specified, delete all
|
||
skips.
|
||
|
||
@kindex skip enable
|
||
@item skip enable @r{[}@var{range}@r{]}
|
||
Enable the specified skip(s). If @var{range} is not specified, enable all
|
||
skips.
|
||
|
||
@kindex skip disable
|
||
@item skip disable @r{[}@var{range}@r{]}
|
||
Disable the specified skip(s). If @var{range} is not specified, disable all
|
||
skips.
|
||
|
||
@end table
|
||
|
||
@node Signals
|
||
@section Signals
|
||
@cindex signals
|
||
|
||
A signal is an asynchronous event that can happen in a program. The
|
||
operating system defines the possible kinds of signals, and gives each
|
||
kind a name and a number. For example, in Unix @code{SIGINT} is the
|
||
signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
|
||
@code{SIGSEGV} is the signal a program gets from referencing a place in
|
||
memory far away from all the areas in use; @code{SIGALRM} occurs when
|
||
the alarm clock timer goes off (which happens only if your program has
|
||
requested an alarm).
|
||
|
||
@cindex fatal signals
|
||
Some signals, including @code{SIGALRM}, are a normal part of the
|
||
functioning of your program. Others, such as @code{SIGSEGV}, indicate
|
||
errors; these signals are @dfn{fatal} (they kill your program immediately) if the
|
||
program has not specified in advance some other way to handle the signal.
|
||
@code{SIGINT} does not indicate an error in your program, but it is normally
|
||
fatal so it can carry out the purpose of the interrupt: to kill the program.
|
||
|
||
@value{GDBN} has the ability to detect any occurrence of a signal in your
|
||
program. You can tell @value{GDBN} in advance what to do for each kind of
|
||
signal.
|
||
|
||
@cindex handling signals
|
||
Normally, @value{GDBN} is set up to let the non-erroneous signals like
|
||
@code{SIGALRM} be silently passed to your program
|
||
(so as not to interfere with their role in the program's functioning)
|
||
but to stop your program immediately whenever an error signal happens.
|
||
You can change these settings with the @code{handle} command.
|
||
|
||
@table @code
|
||
@kindex info signals
|
||
@kindex info handle
|
||
@item info signals
|
||
@itemx info handle
|
||
Print a table of all the kinds of signals and how @value{GDBN} has been told to
|
||
handle each one. You can use this to see the signal numbers of all
|
||
the defined types of signals.
|
||
|
||
@item info signals @var{sig}
|
||
Similar, but print information only about the specified signal number.
|
||
|
||
@code{info handle} is an alias for @code{info signals}.
|
||
|
||
@item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
|
||
Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
|
||
for details about this command.
|
||
|
||
@kindex handle
|
||
@item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
|
||
Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
|
||
can be the number of a signal or its name (with or without the
|
||
@samp{SIG} at the beginning); a list of signal numbers of the form
|
||
@samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
|
||
known signals. Optional arguments @var{keywords}, described below,
|
||
say what change to make.
|
||
@end table
|
||
|
||
@c @group
|
||
The keywords allowed by the @code{handle} command can be abbreviated.
|
||
Their full names are:
|
||
|
||
@table @code
|
||
@item nostop
|
||
@value{GDBN} should not stop your program when this signal happens. It may
|
||
still print a message telling you that the signal has come in.
|
||
|
||
@item stop
|
||
@value{GDBN} should stop your program when this signal happens. This implies
|
||
the @code{print} keyword as well.
|
||
|
||
@item print
|
||
@value{GDBN} should print a message when this signal happens.
|
||
|
||
@item noprint
|
||
@value{GDBN} should not mention the occurrence of the signal at all. This
|
||
implies the @code{nostop} keyword as well.
|
||
|
||
@item pass
|
||
@itemx noignore
|
||
@value{GDBN} should allow your program to see this signal; your program
|
||
can handle the signal, or else it may terminate if the signal is fatal
|
||
and not handled. @code{pass} and @code{noignore} are synonyms.
|
||
|
||
@item nopass
|
||
@itemx ignore
|
||
@value{GDBN} should not allow your program to see this signal.
|
||
@code{nopass} and @code{ignore} are synonyms.
|
||
@end table
|
||
@c @end group
|
||
|
||
When a signal stops your program, the signal is not visible to the
|
||
program until you
|
||
continue. Your program sees the signal then, if @code{pass} is in
|
||
effect for the signal in question @emph{at that time}. In other words,
|
||
after @value{GDBN} reports a signal, you can use the @code{handle}
|
||
command with @code{pass} or @code{nopass} to control whether your
|
||
program sees that signal when you continue.
|
||
|
||
The default is set to @code{nostop}, @code{noprint}, @code{pass} for
|
||
non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
|
||
@code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
|
||
erroneous signals.
|
||
|
||
You can also use the @code{signal} command to prevent your program from
|
||
seeing a signal, or cause it to see a signal it normally would not see,
|
||
or to give it any signal at any time. For example, if your program stopped
|
||
due to some sort of memory reference error, you might store correct
|
||
values into the erroneous variables and continue, hoping to see more
|
||
execution; but your program would probably terminate immediately as
|
||
a result of the fatal signal once it saw the signal. To prevent this,
|
||
you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
|
||
Program a Signal}.
|
||
|
||
@cindex stepping and signal handlers
|
||
@anchor{stepping and signal handlers}
|
||
|
||
@value{GDBN} optimizes for stepping the mainline code. If a signal
|
||
that has @code{handle nostop} and @code{handle pass} set arrives while
|
||
a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
|
||
in progress, @value{GDBN} lets the signal handler run and then resumes
|
||
stepping the mainline code once the signal handler returns. In other
|
||
words, @value{GDBN} steps over the signal handler. This prevents
|
||
signals that you've specified as not interesting (with @code{handle
|
||
nostop}) from changing the focus of debugging unexpectedly. Note that
|
||
the signal handler itself may still hit a breakpoint, stop for another
|
||
signal that has @code{handle stop} in effect, or for any other event
|
||
that normally results in stopping the stepping command sooner. Also
|
||
note that @value{GDBN} still informs you that the program received a
|
||
signal if @code{handle print} is set.
|
||
|
||
@anchor{stepping into signal handlers}
|
||
|
||
If you set @code{handle pass} for a signal, and your program sets up a
|
||
handler for it, then issuing a stepping command, such as @code{step}
|
||
or @code{stepi}, when your program is stopped due to the signal will
|
||
step @emph{into} the signal handler (if the target supports that).
|
||
|
||
Likewise, if you use the @code{queue-signal} command to queue a signal
|
||
to be delivered to the current thread when execution of the thread
|
||
resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
|
||
stepping command will step into the signal handler.
|
||
|
||
Here's an example, using @code{stepi} to step to the first instruction
|
||
of @code{SIGUSR1}'s handler:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) handle SIGUSR1
|
||
Signal Stop Print Pass to program Description
|
||
SIGUSR1 Yes Yes Yes User defined signal 1
|
||
(@value{GDBP}) c
|
||
Continuing.
|
||
|
||
Program received signal SIGUSR1, User defined signal 1.
|
||
main () sigusr1.c:28
|
||
28 p = 0;
|
||
(@value{GDBP}) si
|
||
sigusr1_handler () at sigusr1.c:9
|
||
9 @{
|
||
@end smallexample
|
||
|
||
The same, but using @code{queue-signal} instead of waiting for the
|
||
program to receive the signal first:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) n
|
||
28 p = 0;
|
||
(@value{GDBP}) queue-signal SIGUSR1
|
||
(@value{GDBP}) si
|
||
sigusr1_handler () at sigusr1.c:9
|
||
9 @{
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@cindex extra signal information
|
||
@anchor{extra signal information}
|
||
|
||
On some targets, @value{GDBN} can inspect extra signal information
|
||
associated with the intercepted signal, before it is actually
|
||
delivered to the program being debugged. This information is exported
|
||
by the convenience variable @code{$_siginfo}, and consists of data
|
||
that is passed by the kernel to the signal handler at the time of the
|
||
receipt of a signal. The data type of the information itself is
|
||
target dependent. You can see the data type using the @code{ptype
|
||
$_siginfo} command. On Unix systems, it typically corresponds to the
|
||
standard @code{siginfo_t} type, as defined in the @file{signal.h}
|
||
system header.
|
||
|
||
Here's an example, on a @sc{gnu}/Linux system, printing the stray
|
||
referenced address that raised a segmentation fault.
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) continue
|
||
Program received signal SIGSEGV, Segmentation fault.
|
||
0x0000000000400766 in main ()
|
||
69 *(int *)p = 0;
|
||
(@value{GDBP}) ptype $_siginfo
|
||
type = struct @{
|
||
int si_signo;
|
||
int si_errno;
|
||
int si_code;
|
||
union @{
|
||
int _pad[28];
|
||
struct @{...@} _kill;
|
||
struct @{...@} _timer;
|
||
struct @{...@} _rt;
|
||
struct @{...@} _sigchld;
|
||
struct @{...@} _sigfault;
|
||
struct @{...@} _sigpoll;
|
||
@} _sifields;
|
||
@}
|
||
(@value{GDBP}) ptype $_siginfo._sifields._sigfault
|
||
type = struct @{
|
||
void *si_addr;
|
||
@}
|
||
(@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
|
||
$1 = (void *) 0x7ffff7ff7000
|
||
@end group
|
||
@end smallexample
|
||
|
||
Depending on target support, @code{$_siginfo} may also be writable.
|
||
|
||
@cindex Intel MPX boundary violations
|
||
@cindex boundary violations, Intel MPX
|
||
On some targets, a @code{SIGSEGV} can be caused by a boundary
|
||
violation, i.e., accessing an address outside of the allowed range.
|
||
In those cases @value{GDBN} may displays additional information,
|
||
depending on how @value{GDBN} has been told to handle the signal.
|
||
With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
|
||
kind: "Upper" or "Lower", the memory address accessed and the
|
||
bounds, while with @code{handle nostop SIGSEGV} no additional
|
||
information is displayed.
|
||
|
||
The usual output of a segfault is:
|
||
@smallexample
|
||
Program received signal SIGSEGV, Segmentation fault
|
||
0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
|
||
68 value = *(p + len);
|
||
@end smallexample
|
||
|
||
While a bound violation is presented as:
|
||
@smallexample
|
||
Program received signal SIGSEGV, Segmentation fault
|
||
Upper bound violation while accessing address 0x7fffffffc3b3
|
||
Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
|
||
0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
|
||
68 value = *(p + len);
|
||
@end smallexample
|
||
|
||
@node Thread Stops
|
||
@section Stopping and Starting Multi-thread Programs
|
||
|
||
@cindex stopped threads
|
||
@cindex threads, stopped
|
||
|
||
@cindex continuing threads
|
||
@cindex threads, continuing
|
||
|
||
@value{GDBN} supports debugging programs with multiple threads
|
||
(@pxref{Threads,, Debugging Programs with Multiple Threads}). There
|
||
are two modes of controlling execution of your program within the
|
||
debugger. In the default mode, referred to as @dfn{all-stop mode},
|
||
when any thread in your program stops (for example, at a breakpoint
|
||
or while being stepped), all other threads in the program are also stopped by
|
||
@value{GDBN}. On some targets, @value{GDBN} also supports
|
||
@dfn{non-stop mode}, in which other threads can continue to run freely while
|
||
you examine the stopped thread in the debugger.
|
||
|
||
@menu
|
||
* All-Stop Mode:: All threads stop when GDB takes control
|
||
* Non-Stop Mode:: Other threads continue to execute
|
||
* Background Execution:: Running your program asynchronously
|
||
* Thread-Specific Breakpoints:: Controlling breakpoints
|
||
* Interrupted System Calls:: GDB may interfere with system calls
|
||
* Observer Mode:: GDB does not alter program behavior
|
||
@end menu
|
||
|
||
@node All-Stop Mode
|
||
@subsection All-Stop Mode
|
||
|
||
@cindex all-stop mode
|
||
|
||
In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
|
||
@emph{all} threads of execution stop, not just the current thread. This
|
||
allows you to examine the overall state of the program, including
|
||
switching between threads, without worrying that things may change
|
||
underfoot.
|
||
|
||
Conversely, whenever you restart the program, @emph{all} threads start
|
||
executing. @emph{This is true even when single-stepping} with commands
|
||
like @code{step} or @code{next}.
|
||
|
||
In particular, @value{GDBN} cannot single-step all threads in lockstep.
|
||
Since thread scheduling is up to your debugging target's operating
|
||
system (not controlled by @value{GDBN}), other threads may
|
||
execute more than one statement while the current thread completes a
|
||
single step. Moreover, in general other threads stop in the middle of a
|
||
statement, rather than at a clean statement boundary, when the program
|
||
stops.
|
||
|
||
You might even find your program stopped in another thread after
|
||
continuing or even single-stepping. This happens whenever some other
|
||
thread runs into a breakpoint, a signal, or an exception before the
|
||
first thread completes whatever you requested.
|
||
|
||
@cindex automatic thread selection
|
||
@cindex switching threads automatically
|
||
@cindex threads, automatic switching
|
||
Whenever @value{GDBN} stops your program, due to a breakpoint or a
|
||
signal, it automatically selects the thread where that breakpoint or
|
||
signal happened. @value{GDBN} alerts you to the context switch with a
|
||
message such as @samp{[Switching to Thread @var{n}]} to identify the
|
||
thread.
|
||
|
||
On some OSes, you can modify @value{GDBN}'s default behavior by
|
||
locking the OS scheduler to allow only a single thread to run.
|
||
|
||
@table @code
|
||
@item set scheduler-locking @var{mode}
|
||
@cindex scheduler locking mode
|
||
@cindex lock scheduler
|
||
Set the scheduler locking mode. It applies to normal execution,
|
||
record mode, and replay mode. If it is @code{off}, then there is no
|
||
locking and any thread may run at any time. If @code{on}, then only
|
||
the current thread may run when the inferior is resumed. The
|
||
@code{step} mode optimizes for single-stepping; it prevents other
|
||
threads from preempting the current thread while you are stepping, so
|
||
that the focus of debugging does not change unexpectedly. Other
|
||
threads never get a chance to run when you step, and they are
|
||
completely free to run when you use commands like @samp{continue},
|
||
@samp{until}, or @samp{finish}. However, unless another thread hits a
|
||
breakpoint during its timeslice, @value{GDBN} does not change the
|
||
current thread away from the thread that you are debugging. The
|
||
@code{replay} mode behaves like @code{off} in record mode and like
|
||
@code{on} in replay mode.
|
||
|
||
@item show scheduler-locking
|
||
Display the current scheduler locking mode.
|
||
@end table
|
||
|
||
@cindex resume threads of multiple processes simultaneously
|
||
By default, when you issue one of the execution commands such as
|
||
@code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
|
||
threads of the current inferior to run. For example, if @value{GDBN}
|
||
is attached to two inferiors, each with two threads, the
|
||
@code{continue} command resumes only the two threads of the current
|
||
inferior. This is useful, for example, when you debug a program that
|
||
forks and you want to hold the parent stopped (so that, for instance,
|
||
it doesn't run to exit), while you debug the child. In other
|
||
situations, you may not be interested in inspecting the current state
|
||
of any of the processes @value{GDBN} is attached to, and you may want
|
||
to resume them all until some breakpoint is hit. In the latter case,
|
||
you can instruct @value{GDBN} to allow all threads of all the
|
||
inferiors to run with the @w{@code{set schedule-multiple}} command.
|
||
|
||
@table @code
|
||
@kindex set schedule-multiple
|
||
@item set schedule-multiple
|
||
Set the mode for allowing threads of multiple processes to be resumed
|
||
when an execution command is issued. When @code{on}, all threads of
|
||
all processes are allowed to run. When @code{off}, only the threads
|
||
of the current process are resumed. The default is @code{off}. The
|
||
@code{scheduler-locking} mode takes precedence when set to @code{on},
|
||
or while you are stepping and set to @code{step}.
|
||
|
||
@item show schedule-multiple
|
||
Display the current mode for resuming the execution of threads of
|
||
multiple processes.
|
||
@end table
|
||
|
||
@node Non-Stop Mode
|
||
@subsection Non-Stop Mode
|
||
|
||
@cindex non-stop mode
|
||
|
||
@c This section is really only a place-holder, and needs to be expanded
|
||
@c with more details.
|
||
|
||
For some multi-threaded targets, @value{GDBN} supports an optional
|
||
mode of operation in which you can examine stopped program threads in
|
||
the debugger while other threads continue to execute freely. This
|
||
minimizes intrusion when debugging live systems, such as programs
|
||
where some threads have real-time constraints or must continue to
|
||
respond to external events. This is referred to as @dfn{non-stop} mode.
|
||
|
||
In non-stop mode, when a thread stops to report a debugging event,
|
||
@emph{only} that thread is stopped; @value{GDBN} does not stop other
|
||
threads as well, in contrast to the all-stop mode behavior. Additionally,
|
||
execution commands such as @code{continue} and @code{step} apply by default
|
||
only to the current thread in non-stop mode, rather than all threads as
|
||
in all-stop mode. This allows you to control threads explicitly in
|
||
ways that are not possible in all-stop mode --- for example, stepping
|
||
one thread while allowing others to run freely, stepping
|
||
one thread while holding all others stopped, or stepping several threads
|
||
independently and simultaneously.
|
||
|
||
To enter non-stop mode, use this sequence of commands before you run
|
||
or attach to your program:
|
||
|
||
@smallexample
|
||
# If using the CLI, pagination breaks non-stop.
|
||
set pagination off
|
||
|
||
# Finally, turn it on!
|
||
set non-stop on
|
||
@end smallexample
|
||
|
||
You can use these commands to manipulate the non-stop mode setting:
|
||
|
||
@table @code
|
||
@kindex set non-stop
|
||
@item set non-stop on
|
||
Enable selection of non-stop mode.
|
||
@item set non-stop off
|
||
Disable selection of non-stop mode.
|
||
@kindex show non-stop
|
||
@item show non-stop
|
||
Show the current non-stop enablement setting.
|
||
@end table
|
||
|
||
Note these commands only reflect whether non-stop mode is enabled,
|
||
not whether the currently-executing program is being run in non-stop mode.
|
||
In particular, the @code{set non-stop} preference is only consulted when
|
||
@value{GDBN} starts or connects to the target program, and it is generally
|
||
not possible to switch modes once debugging has started. Furthermore,
|
||
since not all targets support non-stop mode, even when you have enabled
|
||
non-stop mode, @value{GDBN} may still fall back to all-stop operation by
|
||
default.
|
||
|
||
In non-stop mode, all execution commands apply only to the current thread
|
||
by default. That is, @code{continue} only continues one thread.
|
||
To continue all threads, issue @code{continue -a} or @code{c -a}.
|
||
|
||
You can use @value{GDBN}'s background execution commands
|
||
(@pxref{Background Execution}) to run some threads in the background
|
||
while you continue to examine or step others from @value{GDBN}.
|
||
The MI execution commands (@pxref{GDB/MI Program Execution}) are
|
||
always executed asynchronously in non-stop mode.
|
||
|
||
Suspending execution is done with the @code{interrupt} command when
|
||
running in the background, or @kbd{Ctrl-c} during foreground execution.
|
||
In all-stop mode, this stops the whole process;
|
||
but in non-stop mode the interrupt applies only to the current thread.
|
||
To stop the whole program, use @code{interrupt -a}.
|
||
|
||
Other execution commands do not currently support the @code{-a} option.
|
||
|
||
In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
|
||
that thread current, as it does in all-stop mode. This is because the
|
||
thread stop notifications are asynchronous with respect to @value{GDBN}'s
|
||
command interpreter, and it would be confusing if @value{GDBN} unexpectedly
|
||
changed to a different thread just as you entered a command to operate on the
|
||
previously current thread.
|
||
|
||
@node Background Execution
|
||
@subsection Background Execution
|
||
|
||
@cindex foreground execution
|
||
@cindex background execution
|
||
@cindex asynchronous execution
|
||
@cindex execution, foreground, background and asynchronous
|
||
|
||
@value{GDBN}'s execution commands have two variants: the normal
|
||
foreground (synchronous) behavior, and a background
|
||
(asynchronous) behavior. In foreground execution, @value{GDBN} waits for
|
||
the program to report that some thread has stopped before prompting for
|
||
another command. In background execution, @value{GDBN} immediately gives
|
||
a command prompt so that you can issue other commands while your program runs.
|
||
|
||
If the target doesn't support async mode, @value{GDBN} issues an error
|
||
message if you attempt to use the background execution commands.
|
||
|
||
To specify background execution, add a @code{&} to the command. For example,
|
||
the background form of the @code{continue} command is @code{continue&}, or
|
||
just @code{c&}. The execution commands that accept background execution
|
||
are:
|
||
|
||
@table @code
|
||
@kindex run&
|
||
@item run
|
||
@xref{Starting, , Starting your Program}.
|
||
|
||
@item attach
|
||
@kindex attach&
|
||
@xref{Attach, , Debugging an Already-running Process}.
|
||
|
||
@item step
|
||
@kindex step&
|
||
@xref{Continuing and Stepping, step}.
|
||
|
||
@item stepi
|
||
@kindex stepi&
|
||
@xref{Continuing and Stepping, stepi}.
|
||
|
||
@item next
|
||
@kindex next&
|
||
@xref{Continuing and Stepping, next}.
|
||
|
||
@item nexti
|
||
@kindex nexti&
|
||
@xref{Continuing and Stepping, nexti}.
|
||
|
||
@item continue
|
||
@kindex continue&
|
||
@xref{Continuing and Stepping, continue}.
|
||
|
||
@item finish
|
||
@kindex finish&
|
||
@xref{Continuing and Stepping, finish}.
|
||
|
||
@item until
|
||
@kindex until&
|
||
@xref{Continuing and Stepping, until}.
|
||
|
||
@end table
|
||
|
||
Background execution is especially useful in conjunction with non-stop
|
||
mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
|
||
However, you can also use these commands in the normal all-stop mode with
|
||
the restriction that you cannot issue another execution command until the
|
||
previous one finishes. Examples of commands that are valid in all-stop
|
||
mode while the program is running include @code{help} and @code{info break}.
|
||
|
||
You can interrupt your program while it is running in the background by
|
||
using the @code{interrupt} command.
|
||
|
||
@table @code
|
||
@kindex interrupt
|
||
@item interrupt
|
||
@itemx interrupt -a
|
||
|
||
Suspend execution of the running program. In all-stop mode,
|
||
@code{interrupt} stops the whole process, but in non-stop mode, it stops
|
||
only the current thread. To stop the whole program in non-stop mode,
|
||
use @code{interrupt -a}.
|
||
@end table
|
||
|
||
@node Thread-Specific Breakpoints
|
||
@subsection Thread-Specific Breakpoints
|
||
|
||
When your program has multiple threads (@pxref{Threads,, Debugging
|
||
Programs with Multiple Threads}), you can choose whether to set
|
||
breakpoints on all threads, or on a particular thread.
|
||
|
||
@table @code
|
||
@cindex breakpoints and threads
|
||
@cindex thread breakpoints
|
||
@kindex break @dots{} thread @var{thread-id}
|
||
@item break @var{location} thread @var{thread-id}
|
||
@itemx break @var{location} thread @var{thread-id} if @dots{}
|
||
@var{location} specifies source lines; there are several ways of
|
||
writing them (@pxref{Specify Location}), but the effect is always to
|
||
specify some source line.
|
||
|
||
Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
|
||
to specify that you only want @value{GDBN} to stop the program when a
|
||
particular thread reaches this breakpoint. The @var{thread-id} specifier
|
||
is one of the thread identifiers assigned by @value{GDBN}, shown
|
||
in the first column of the @samp{info threads} display.
|
||
|
||
If you do not specify @samp{thread @var{thread-id}} when you set a
|
||
breakpoint, the breakpoint applies to @emph{all} threads of your
|
||
program.
|
||
|
||
You can use the @code{thread} qualifier on conditional breakpoints as
|
||
well; in this case, place @samp{thread @var{thread-id}} before or
|
||
after the breakpoint condition, like this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
|
||
@end smallexample
|
||
|
||
@end table
|
||
|
||
Thread-specific breakpoints are automatically deleted when
|
||
@value{GDBN} detects the corresponding thread is no longer in the
|
||
thread list. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) c
|
||
Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
|
||
@end smallexample
|
||
|
||
There are several ways for a thread to disappear, such as a regular
|
||
thread exit, but also when you detach from the process with the
|
||
@code{detach} command (@pxref{Attach, ,Debugging an Already-running
|
||
Process}), or if @value{GDBN} loses the remote connection
|
||
(@pxref{Remote Debugging}), etc. Note that with some targets,
|
||
@value{GDBN} is only able to detect a thread has exited when the user
|
||
explictly asks for the thread list with the @code{info threads}
|
||
command.
|
||
|
||
@node Interrupted System Calls
|
||
@subsection Interrupted System Calls
|
||
|
||
@cindex thread breakpoints and system calls
|
||
@cindex system calls and thread breakpoints
|
||
@cindex premature return from system calls
|
||
There is an unfortunate side effect when using @value{GDBN} to debug
|
||
multi-threaded programs. If one thread stops for a
|
||
breakpoint, or for some other reason, and another thread is blocked in a
|
||
system call, then the system call may return prematurely. This is a
|
||
consequence of the interaction between multiple threads and the signals
|
||
that @value{GDBN} uses to implement breakpoints and other events that
|
||
stop execution.
|
||
|
||
To handle this problem, your program should check the return value of
|
||
each system call and react appropriately. This is good programming
|
||
style anyways.
|
||
|
||
For example, do not write code like this:
|
||
|
||
@smallexample
|
||
sleep (10);
|
||
@end smallexample
|
||
|
||
The call to @code{sleep} will return early if a different thread stops
|
||
at a breakpoint or for some other reason.
|
||
|
||
Instead, write this:
|
||
|
||
@smallexample
|
||
int unslept = 10;
|
||
while (unslept > 0)
|
||
unslept = sleep (unslept);
|
||
@end smallexample
|
||
|
||
A system call is allowed to return early, so the system is still
|
||
conforming to its specification. But @value{GDBN} does cause your
|
||
multi-threaded program to behave differently than it would without
|
||
@value{GDBN}.
|
||
|
||
Also, @value{GDBN} uses internal breakpoints in the thread library to
|
||
monitor certain events such as thread creation and thread destruction.
|
||
When such an event happens, a system call in another thread may return
|
||
prematurely, even though your program does not appear to stop.
|
||
|
||
@node Observer Mode
|
||
@subsection Observer Mode
|
||
|
||
If you want to build on non-stop mode and observe program behavior
|
||
without any chance of disruption by @value{GDBN}, you can set
|
||
variables to disable all of the debugger's attempts to modify state,
|
||
whether by writing memory, inserting breakpoints, etc. These operate
|
||
at a low level, intercepting operations from all commands.
|
||
|
||
When all of these are set to @code{off}, then @value{GDBN} is said to
|
||
be @dfn{observer mode}. As a convenience, the variable
|
||
@code{observer} can be set to disable these, plus enable non-stop
|
||
mode.
|
||
|
||
Note that @value{GDBN} will not prevent you from making nonsensical
|
||
combinations of these settings. For instance, if you have enabled
|
||
@code{may-insert-breakpoints} but disabled @code{may-write-memory},
|
||
then breakpoints that work by writing trap instructions into the code
|
||
stream will still not be able to be placed.
|
||
|
||
@table @code
|
||
|
||
@kindex observer
|
||
@item set observer on
|
||
@itemx set observer off
|
||
When set to @code{on}, this disables all the permission variables
|
||
below (except for @code{insert-fast-tracepoints}), plus enables
|
||
non-stop debugging. Setting this to @code{off} switches back to
|
||
normal debugging, though remaining in non-stop mode.
|
||
|
||
@item show observer
|
||
Show whether observer mode is on or off.
|
||
|
||
@kindex may-write-registers
|
||
@item set may-write-registers on
|
||
@itemx set may-write-registers off
|
||
This controls whether @value{GDBN} will attempt to alter the values of
|
||
registers, such as with assignment expressions in @code{print}, or the
|
||
@code{jump} command. It defaults to @code{on}.
|
||
|
||
@item show may-write-registers
|
||
Show the current permission to write registers.
|
||
|
||
@kindex may-write-memory
|
||
@item set may-write-memory on
|
||
@itemx set may-write-memory off
|
||
This controls whether @value{GDBN} will attempt to alter the contents
|
||
of memory, such as with assignment expressions in @code{print}. It
|
||
defaults to @code{on}.
|
||
|
||
@item show may-write-memory
|
||
Show the current permission to write memory.
|
||
|
||
@kindex may-insert-breakpoints
|
||
@item set may-insert-breakpoints on
|
||
@itemx set may-insert-breakpoints off
|
||
This controls whether @value{GDBN} will attempt to insert breakpoints.
|
||
This affects all breakpoints, including internal breakpoints defined
|
||
by @value{GDBN}. It defaults to @code{on}.
|
||
|
||
@item show may-insert-breakpoints
|
||
Show the current permission to insert breakpoints.
|
||
|
||
@kindex may-insert-tracepoints
|
||
@item set may-insert-tracepoints on
|
||
@itemx set may-insert-tracepoints off
|
||
This controls whether @value{GDBN} will attempt to insert (regular)
|
||
tracepoints at the beginning of a tracing experiment. It affects only
|
||
non-fast tracepoints, fast tracepoints being under the control of
|
||
@code{may-insert-fast-tracepoints}. It defaults to @code{on}.
|
||
|
||
@item show may-insert-tracepoints
|
||
Show the current permission to insert tracepoints.
|
||
|
||
@kindex may-insert-fast-tracepoints
|
||
@item set may-insert-fast-tracepoints on
|
||
@itemx set may-insert-fast-tracepoints off
|
||
This controls whether @value{GDBN} will attempt to insert fast
|
||
tracepoints at the beginning of a tracing experiment. It affects only
|
||
fast tracepoints, regular (non-fast) tracepoints being under the
|
||
control of @code{may-insert-tracepoints}. It defaults to @code{on}.
|
||
|
||
@item show may-insert-fast-tracepoints
|
||
Show the current permission to insert fast tracepoints.
|
||
|
||
@kindex may-interrupt
|
||
@item set may-interrupt on
|
||
@itemx set may-interrupt off
|
||
This controls whether @value{GDBN} will attempt to interrupt or stop
|
||
program execution. When this variable is @code{off}, the
|
||
@code{interrupt} command will have no effect, nor will
|
||
@kbd{Ctrl-c}. It defaults to @code{on}.
|
||
|
||
@item show may-interrupt
|
||
Show the current permission to interrupt or stop the program.
|
||
|
||
@end table
|
||
|
||
@node Reverse Execution
|
||
@chapter Running programs backward
|
||
@cindex reverse execution
|
||
@cindex running programs backward
|
||
|
||
When you are debugging a program, it is not unusual to realize that
|
||
you have gone too far, and some event of interest has already happened.
|
||
If the target environment supports it, @value{GDBN} can allow you to
|
||
``rewind'' the program by running it backward.
|
||
|
||
A target environment that supports reverse execution should be able
|
||
to ``undo'' the changes in machine state that have taken place as the
|
||
program was executing normally. Variables, registers etc.@: should
|
||
revert to their previous values. Obviously this requires a great
|
||
deal of sophistication on the part of the target environment; not
|
||
all target environments can support reverse execution.
|
||
|
||
When a program is executed in reverse, the instructions that
|
||
have most recently been executed are ``un-executed'', in reverse
|
||
order. The program counter runs backward, following the previous
|
||
thread of execution in reverse. As each instruction is ``un-executed'',
|
||
the values of memory and/or registers that were changed by that
|
||
instruction are reverted to their previous states. After executing
|
||
a piece of source code in reverse, all side effects of that code
|
||
should be ``undone'', and all variables should be returned to their
|
||
prior values@footnote{
|
||
Note that some side effects are easier to undo than others. For instance,
|
||
memory and registers are relatively easy, but device I/O is hard. Some
|
||
targets may be able undo things like device I/O, and some may not.
|
||
|
||
The contract between @value{GDBN} and the reverse executing target
|
||
requires only that the target do something reasonable when
|
||
@value{GDBN} tells it to execute backwards, and then report the
|
||
results back to @value{GDBN}. Whatever the target reports back to
|
||
@value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
|
||
assumes that the memory and registers that the target reports are in a
|
||
consistant state, but @value{GDBN} accepts whatever it is given.
|
||
}.
|
||
|
||
If you are debugging in a target environment that supports
|
||
reverse execution, @value{GDBN} provides the following commands.
|
||
|
||
@table @code
|
||
@kindex reverse-continue
|
||
@kindex rc @r{(@code{reverse-continue})}
|
||
@item reverse-continue @r{[}@var{ignore-count}@r{]}
|
||
@itemx rc @r{[}@var{ignore-count}@r{]}
|
||
Beginning at the point where your program last stopped, start executing
|
||
in reverse. Reverse execution will stop for breakpoints and synchronous
|
||
exceptions (signals), just like normal execution. Behavior of
|
||
asynchronous signals depends on the target environment.
|
||
|
||
@kindex reverse-step
|
||
@kindex rs @r{(@code{step})}
|
||
@item reverse-step @r{[}@var{count}@r{]}
|
||
Run the program backward until control reaches the start of a
|
||
different source line; then stop it, and return control to @value{GDBN}.
|
||
|
||
Like the @code{step} command, @code{reverse-step} will only stop
|
||
at the beginning of a source line. It ``un-executes'' the previously
|
||
executed source line. If the previous source line included calls to
|
||
debuggable functions, @code{reverse-step} will step (backward) into
|
||
the called function, stopping at the beginning of the @emph{last}
|
||
statement in the called function (typically a return statement).
|
||
|
||
Also, as with the @code{step} command, if non-debuggable functions are
|
||
called, @code{reverse-step} will run thru them backward without stopping.
|
||
|
||
@kindex reverse-stepi
|
||
@kindex rsi @r{(@code{reverse-stepi})}
|
||
@item reverse-stepi @r{[}@var{count}@r{]}
|
||
Reverse-execute one machine instruction. Note that the instruction
|
||
to be reverse-executed is @emph{not} the one pointed to by the program
|
||
counter, but the instruction executed prior to that one. For instance,
|
||
if the last instruction was a jump, @code{reverse-stepi} will take you
|
||
back from the destination of the jump to the jump instruction itself.
|
||
|
||
@kindex reverse-next
|
||
@kindex rn @r{(@code{reverse-next})}
|
||
@item reverse-next @r{[}@var{count}@r{]}
|
||
Run backward to the beginning of the previous line executed in
|
||
the current (innermost) stack frame. If the line contains function
|
||
calls, they will be ``un-executed'' without stopping. Starting from
|
||
the first line of a function, @code{reverse-next} will take you back
|
||
to the caller of that function, @emph{before} the function was called,
|
||
just as the normal @code{next} command would take you from the last
|
||
line of a function back to its return to its caller
|
||
@footnote{Unless the code is too heavily optimized.}.
|
||
|
||
@kindex reverse-nexti
|
||
@kindex rni @r{(@code{reverse-nexti})}
|
||
@item reverse-nexti @r{[}@var{count}@r{]}
|
||
Like @code{nexti}, @code{reverse-nexti} executes a single instruction
|
||
in reverse, except that called functions are ``un-executed'' atomically.
|
||
That is, if the previously executed instruction was a return from
|
||
another function, @code{reverse-nexti} will continue to execute
|
||
in reverse until the call to that function (from the current stack
|
||
frame) is reached.
|
||
|
||
@kindex reverse-finish
|
||
@item reverse-finish
|
||
Just as the @code{finish} command takes you to the point where the
|
||
current function returns, @code{reverse-finish} takes you to the point
|
||
where it was called. Instead of ending up at the end of the current
|
||
function invocation, you end up at the beginning.
|
||
|
||
@kindex set exec-direction
|
||
@item set exec-direction
|
||
Set the direction of target execution.
|
||
@item set exec-direction reverse
|
||
@cindex execute forward or backward in time
|
||
@value{GDBN} will perform all execution commands in reverse, until the
|
||
exec-direction mode is changed to ``forward''. Affected commands include
|
||
@code{step, stepi, next, nexti, continue, and finish}. The @code{return}
|
||
command cannot be used in reverse mode.
|
||
@item set exec-direction forward
|
||
@value{GDBN} will perform all execution commands in the normal fashion.
|
||
This is the default.
|
||
@end table
|
||
|
||
|
||
@node Process Record and Replay
|
||
@chapter Recording Inferior's Execution and Replaying It
|
||
@cindex process record and replay
|
||
@cindex recording inferior's execution and replaying it
|
||
|
||
On some platforms, @value{GDBN} provides a special @dfn{process record
|
||
and replay} target that can record a log of the process execution, and
|
||
replay it later with both forward and reverse execution commands.
|
||
|
||
@cindex replay mode
|
||
When this target is in use, if the execution log includes the record
|
||
for the next instruction, @value{GDBN} will debug in @dfn{replay
|
||
mode}. In the replay mode, the inferior does not really execute code
|
||
instructions. Instead, all the events that normally happen during
|
||
code execution are taken from the execution log. While code is not
|
||
really executed in replay mode, the values of registers (including the
|
||
program counter register) and the memory of the inferior are still
|
||
changed as they normally would. Their contents are taken from the
|
||
execution log.
|
||
|
||
@cindex record mode
|
||
If the record for the next instruction is not in the execution log,
|
||
@value{GDBN} will debug in @dfn{record mode}. In this mode, the
|
||
inferior executes normally, and @value{GDBN} records the execution log
|
||
for future replay.
|
||
|
||
The process record and replay target supports reverse execution
|
||
(@pxref{Reverse Execution}), even if the platform on which the
|
||
inferior runs does not. However, the reverse execution is limited in
|
||
this case by the range of the instructions recorded in the execution
|
||
log. In other words, reverse execution on platforms that don't
|
||
support it directly can only be done in the replay mode.
|
||
|
||
When debugging in the reverse direction, @value{GDBN} will work in
|
||
replay mode as long as the execution log includes the record for the
|
||
previous instruction; otherwise, it will work in record mode, if the
|
||
platform supports reverse execution, or stop if not.
|
||
|
||
For architecture environments that support process record and replay,
|
||
@value{GDBN} provides the following commands:
|
||
|
||
@table @code
|
||
@kindex target record
|
||
@kindex target record-full
|
||
@kindex target record-btrace
|
||
@kindex record
|
||
@kindex record full
|
||
@kindex record btrace
|
||
@kindex record btrace bts
|
||
@kindex record btrace pt
|
||
@kindex record bts
|
||
@kindex record pt
|
||
@kindex rec
|
||
@kindex rec full
|
||
@kindex rec btrace
|
||
@kindex rec btrace bts
|
||
@kindex rec btrace pt
|
||
@kindex rec bts
|
||
@kindex rec pt
|
||
@item record @var{method}
|
||
This command starts the process record and replay target. The
|
||
recording method can be specified as parameter. Without a parameter
|
||
the command uses the @code{full} recording method. The following
|
||
recording methods are available:
|
||
|
||
@table @code
|
||
@item full
|
||
Full record/replay recording using @value{GDBN}'s software record and
|
||
replay implementation. This method allows replaying and reverse
|
||
execution.
|
||
|
||
@item btrace @var{format}
|
||
Hardware-supported instruction recording. This method does not record
|
||
data. Further, the data is collected in a ring buffer so old data will
|
||
be overwritten when the buffer is full. It allows limited reverse
|
||
execution. Variables and registers are not available during reverse
|
||
execution. In remote debugging, recording continues on disconnect.
|
||
Recorded data can be inspected after reconnecting. The recording may
|
||
be stopped using @code{record stop}.
|
||
|
||
The recording format can be specified as parameter. Without a parameter
|
||
the command chooses the recording format. The following recording
|
||
formats are available:
|
||
|
||
@table @code
|
||
@item bts
|
||
@cindex branch trace store
|
||
Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
|
||
this format, the processor stores a from/to record for each executed
|
||
branch in the btrace ring buffer.
|
||
|
||
@item pt
|
||
@cindex Intel Processor Trace
|
||
Use the @dfn{Intel Processor Trace} recording format. In this
|
||
format, the processor stores the execution trace in a compressed form
|
||
that is afterwards decoded by @value{GDBN}.
|
||
|
||
The trace can be recorded with very low overhead. The compressed
|
||
trace format also allows small trace buffers to already contain a big
|
||
number of instructions compared to @acronym{BTS}.
|
||
|
||
Decoding the recorded execution trace, on the other hand, is more
|
||
expensive than decoding @acronym{BTS} trace. This is mostly due to the
|
||
increased number of instructions to process. You should increase the
|
||
buffer-size with care.
|
||
@end table
|
||
|
||
Not all recording formats may be available on all processors.
|
||
@end table
|
||
|
||
The process record and replay target can only debug a process that is
|
||
already running. Therefore, you need first to start the process with
|
||
the @kbd{run} or @kbd{start} commands, and then start the recording
|
||
with the @kbd{record @var{method}} command.
|
||
|
||
@cindex displaced stepping, and process record and replay
|
||
Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
|
||
will be automatically disabled when process record and replay target
|
||
is started. That's because the process record and replay target
|
||
doesn't support displaced stepping.
|
||
|
||
@cindex non-stop mode, and process record and replay
|
||
@cindex asynchronous execution, and process record and replay
|
||
If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
|
||
the asynchronous execution mode (@pxref{Background Execution}), not
|
||
all recording methods are available. The @code{full} recording method
|
||
does not support these two modes.
|
||
|
||
@kindex record stop
|
||
@kindex rec s
|
||
@item record stop
|
||
Stop the process record and replay target. When process record and
|
||
replay target stops, the entire execution log will be deleted and the
|
||
inferior will either be terminated, or will remain in its final state.
|
||
|
||
When you stop the process record and replay target in record mode (at
|
||
the end of the execution log), the inferior will be stopped at the
|
||
next instruction that would have been recorded. In other words, if
|
||
you record for a while and then stop recording, the inferior process
|
||
will be left in the same state as if the recording never happened.
|
||
|
||
On the other hand, if the process record and replay target is stopped
|
||
while in replay mode (that is, not at the end of the execution log,
|
||
but at some earlier point), the inferior process will become ``live''
|
||
at that earlier state, and it will then be possible to continue the
|
||
usual ``live'' debugging of the process from that state.
|
||
|
||
When the inferior process exits, or @value{GDBN} detaches from it,
|
||
process record and replay target will automatically stop itself.
|
||
|
||
@kindex record goto
|
||
@item record goto
|
||
Go to a specific location in the execution log. There are several
|
||
ways to specify the location to go to:
|
||
|
||
@table @code
|
||
@item record goto begin
|
||
@itemx record goto start
|
||
Go to the beginning of the execution log.
|
||
|
||
@item record goto end
|
||
Go to the end of the execution log.
|
||
|
||
@item record goto @var{n}
|
||
Go to instruction number @var{n} in the execution log.
|
||
@end table
|
||
|
||
@kindex record save
|
||
@item record save @var{filename}
|
||
Save the execution log to a file @file{@var{filename}}.
|
||
Default filename is @file{gdb_record.@var{process_id}}, where
|
||
@var{process_id} is the process ID of the inferior.
|
||
|
||
This command may not be available for all recording methods.
|
||
|
||
@kindex record restore
|
||
@item record restore @var{filename}
|
||
Restore the execution log from a file @file{@var{filename}}.
|
||
File must have been created with @code{record save}.
|
||
|
||
@kindex set record full
|
||
@item set record full insn-number-max @var{limit}
|
||
@itemx set record full insn-number-max unlimited
|
||
Set the limit of instructions to be recorded for the @code{full}
|
||
recording method. Default value is 200000.
|
||
|
||
If @var{limit} is a positive number, then @value{GDBN} will start
|
||
deleting instructions from the log once the number of the record
|
||
instructions becomes greater than @var{limit}. For every new recorded
|
||
instruction, @value{GDBN} will delete the earliest recorded
|
||
instruction to keep the number of recorded instructions at the limit.
|
||
(Since deleting recorded instructions loses information, @value{GDBN}
|
||
lets you control what happens when the limit is reached, by means of
|
||
the @code{stop-at-limit} option, described below.)
|
||
|
||
If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
|
||
delete recorded instructions from the execution log. The number of
|
||
recorded instructions is limited only by the available memory.
|
||
|
||
@kindex show record full
|
||
@item show record full insn-number-max
|
||
Show the limit of instructions to be recorded with the @code{full}
|
||
recording method.
|
||
|
||
@item set record full stop-at-limit
|
||
Control the behavior of the @code{full} recording method when the
|
||
number of recorded instructions reaches the limit. If ON (the
|
||
default), @value{GDBN} will stop when the limit is reached for the
|
||
first time and ask you whether you want to stop the inferior or
|
||
continue running it and recording the execution log. If you decide
|
||
to continue recording, each new recorded instruction will cause the
|
||
oldest one to be deleted.
|
||
|
||
If this option is OFF, @value{GDBN} will automatically delete the
|
||
oldest record to make room for each new one, without asking.
|
||
|
||
@item show record full stop-at-limit
|
||
Show the current setting of @code{stop-at-limit}.
|
||
|
||
@item set record full memory-query
|
||
Control the behavior when @value{GDBN} is unable to record memory
|
||
changes caused by an instruction for the @code{full} recording method.
|
||
If ON, @value{GDBN} will query whether to stop the inferior in that
|
||
case.
|
||
|
||
If this option is OFF (the default), @value{GDBN} will automatically
|
||
ignore the effect of such instructions on memory. Later, when
|
||
@value{GDBN} replays this execution log, it will mark the log of this
|
||
instruction as not accessible, and it will not affect the replay
|
||
results.
|
||
|
||
@item show record full memory-query
|
||
Show the current setting of @code{memory-query}.
|
||
|
||
@kindex set record btrace
|
||
The @code{btrace} record target does not trace data. As a
|
||
convenience, when replaying, @value{GDBN} reads read-only memory off
|
||
the live program directly, assuming that the addresses of the
|
||
read-only areas don't change. This for example makes it possible to
|
||
disassemble code while replaying, but not to print variables.
|
||
In some cases, being able to inspect variables might be useful.
|
||
You can use the following command for that:
|
||
|
||
@item set record btrace replay-memory-access
|
||
Control the behavior of the @code{btrace} recording method when
|
||
accessing memory during replay. If @code{read-only} (the default),
|
||
@value{GDBN} will only allow accesses to read-only memory.
|
||
If @code{read-write}, @value{GDBN} will allow accesses to read-only
|
||
and to read-write memory. Beware that the accessed memory corresponds
|
||
to the live target and not necessarily to the current replay
|
||
position.
|
||
|
||
@item set record btrace cpu @var{identifier}
|
||
Set the processor to be used for enabling workarounds for processor
|
||
errata when decoding the trace.
|
||
|
||
Processor errata are defects in processor operation, caused by its
|
||
design or manufacture. They can cause a trace not to match the
|
||
specification. This, in turn, may cause trace decode to fail.
|
||
@value{GDBN} can detect erroneous trace packets and correct them, thus
|
||
avoiding the decoding failures. These corrections are known as
|
||
@dfn{errata workarounds}, and are enabled based on the processor on
|
||
which the trace was recorded.
|
||
|
||
By default, @value{GDBN} attempts to detect the processor
|
||
automatically, and apply the necessary workarounds for it. However,
|
||
you may need to specify the processor if @value{GDBN} does not yet
|
||
support it. This command allows you to do that, and also allows to
|
||
disable the workarounds.
|
||
|
||
The argument @var{identifier} identifies the @sc{cpu} and is of the
|
||
form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
|
||
there are two special identifiers, @code{none} and @code{auto}
|
||
(default).
|
||
|
||
The following vendor identifiers and corresponding processor
|
||
identifiers are currently supported:
|
||
|
||
@multitable @columnfractions .1 .9
|
||
|
||
@item @code{intel}
|
||
@tab @var{family}/@var{model}[/@var{stepping}]
|
||
|
||
@end multitable
|
||
|
||
On GNU/Linux systems, the processor @var{family}, @var{model}, and
|
||
@var{stepping} can be obtained from @code{/proc/cpuinfo}.
|
||
|
||
If @var{identifier} is @code{auto}, enable errata workarounds for the
|
||
processor on which the trace was recorded. If @var{identifier} is
|
||
@code{none}, errata workarounds are disabled.
|
||
|
||
For example, when using an old @value{GDBN} on a new system, decode
|
||
may fail because @value{GDBN} does not support the new processor. It
|
||
often suffices to specify an older processor that @value{GDBN}
|
||
supports.
|
||
|
||
@smallexample
|
||
(gdb) info record
|
||
Active record target: record-btrace
|
||
Recording format: Intel Processor Trace.
|
||
Buffer size: 16kB.
|
||
Failed to configure the Intel Processor Trace decoder: unknown cpu.
|
||
(gdb) set record btrace cpu intel:6/158
|
||
(gdb) info record
|
||
Active record target: record-btrace
|
||
Recording format: Intel Processor Trace.
|
||
Buffer size: 16kB.
|
||
Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
|
||
@end smallexample
|
||
|
||
@kindex show record btrace
|
||
@item show record btrace replay-memory-access
|
||
Show the current setting of @code{replay-memory-access}.
|
||
|
||
@item show record btrace cpu
|
||
Show the processor to be used for enabling trace decode errata
|
||
workarounds.
|
||
|
||
@kindex set record btrace bts
|
||
@item set record btrace bts buffer-size @var{size}
|
||
@itemx set record btrace bts buffer-size unlimited
|
||
Set the requested ring buffer size for branch tracing in @acronym{BTS}
|
||
format. Default is 64KB.
|
||
|
||
If @var{size} is a positive number, then @value{GDBN} will try to
|
||
allocate a buffer of at least @var{size} bytes for each new thread
|
||
that uses the btrace recording method and the @acronym{BTS} format.
|
||
The actually obtained buffer size may differ from the requested
|
||
@var{size}. Use the @code{info record} command to see the actual
|
||
buffer size for each thread that uses the btrace recording method and
|
||
the @acronym{BTS} format.
|
||
|
||
If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
|
||
allocate a buffer of 4MB.
|
||
|
||
Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
|
||
also need longer to process the branch trace data before it can be used.
|
||
|
||
@item show record btrace bts buffer-size @var{size}
|
||
Show the current setting of the requested ring buffer size for branch
|
||
tracing in @acronym{BTS} format.
|
||
|
||
@kindex set record btrace pt
|
||
@item set record btrace pt buffer-size @var{size}
|
||
@itemx set record btrace pt buffer-size unlimited
|
||
Set the requested ring buffer size for branch tracing in Intel
|
||
Processor Trace format. Default is 16KB.
|
||
|
||
If @var{size} is a positive number, then @value{GDBN} will try to
|
||
allocate a buffer of at least @var{size} bytes for each new thread
|
||
that uses the btrace recording method and the Intel Processor Trace
|
||
format. The actually obtained buffer size may differ from the
|
||
requested @var{size}. Use the @code{info record} command to see the
|
||
actual buffer size for each thread.
|
||
|
||
If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
|
||
allocate a buffer of 4MB.
|
||
|
||
Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
|
||
also need longer to process the branch trace data before it can be used.
|
||
|
||
@item show record btrace pt buffer-size @var{size}
|
||
Show the current setting of the requested ring buffer size for branch
|
||
tracing in Intel Processor Trace format.
|
||
|
||
@kindex info record
|
||
@item info record
|
||
Show various statistics about the recording depending on the recording
|
||
method:
|
||
|
||
@table @code
|
||
@item full
|
||
For the @code{full} recording method, it shows the state of process
|
||
record and its in-memory execution log buffer, including:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Whether in record mode or replay mode.
|
||
@item
|
||
Lowest recorded instruction number (counting from when the current execution log started recording instructions).
|
||
@item
|
||
Highest recorded instruction number.
|
||
@item
|
||
Current instruction about to be replayed (if in replay mode).
|
||
@item
|
||
Number of instructions contained in the execution log.
|
||
@item
|
||
Maximum number of instructions that may be contained in the execution log.
|
||
@end itemize
|
||
|
||
@item btrace
|
||
For the @code{btrace} recording method, it shows:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Recording format.
|
||
@item
|
||
Number of instructions that have been recorded.
|
||
@item
|
||
Number of blocks of sequential control-flow formed by the recorded
|
||
instructions.
|
||
@item
|
||
Whether in record mode or replay mode.
|
||
@end itemize
|
||
|
||
For the @code{bts} recording format, it also shows:
|
||
@itemize @bullet
|
||
@item
|
||
Size of the perf ring buffer.
|
||
@end itemize
|
||
|
||
For the @code{pt} recording format, it also shows:
|
||
@itemize @bullet
|
||
@item
|
||
Size of the perf ring buffer.
|
||
@end itemize
|
||
@end table
|
||
|
||
@kindex record delete
|
||
@kindex rec del
|
||
@item record delete
|
||
When record target runs in replay mode (``in the past''), delete the
|
||
subsequent execution log and begin to record a new execution log starting
|
||
from the current address. This means you will abandon the previously
|
||
recorded ``future'' and begin recording a new ``future''.
|
||
|
||
@kindex record instruction-history
|
||
@kindex rec instruction-history
|
||
@item record instruction-history
|
||
Disassembles instructions from the recorded execution log. By
|
||
default, ten instructions are disassembled. This can be changed using
|
||
the @code{set record instruction-history-size} command. Instructions
|
||
are printed in execution order.
|
||
|
||
It can also print mixed source+disassembly if you specify the the
|
||
@code{/m} or @code{/s} modifier, and print the raw instructions in hex
|
||
as well as in symbolic form by specifying the @code{/r} modifier.
|
||
|
||
The current position marker is printed for the instruction at the
|
||
current program counter value. This instruction can appear multiple
|
||
times in the trace and the current position marker will be printed
|
||
every time. To omit the current position marker, specify the
|
||
@code{/p} modifier.
|
||
|
||
To better align the printed instructions when the trace contains
|
||
instructions from more than one function, the function name may be
|
||
omitted by specifying the @code{/f} modifier.
|
||
|
||
Speculatively executed instructions are prefixed with @samp{?}. This
|
||
feature is not available for all recording formats.
|
||
|
||
There are several ways to specify what part of the execution log to
|
||
disassemble:
|
||
|
||
@table @code
|
||
@item record instruction-history @var{insn}
|
||
Disassembles ten instructions starting from instruction number
|
||
@var{insn}.
|
||
|
||
@item record instruction-history @var{insn}, +/-@var{n}
|
||
Disassembles @var{n} instructions around instruction number
|
||
@var{insn}. If @var{n} is preceded with @code{+}, disassembles
|
||
@var{n} instructions after instruction number @var{insn}. If
|
||
@var{n} is preceded with @code{-}, disassembles @var{n}
|
||
instructions before instruction number @var{insn}.
|
||
|
||
@item record instruction-history
|
||
Disassembles ten more instructions after the last disassembly.
|
||
|
||
@item record instruction-history -
|
||
Disassembles ten more instructions before the last disassembly.
|
||
|
||
@item record instruction-history @var{begin}, @var{end}
|
||
Disassembles instructions beginning with instruction number
|
||
@var{begin} until instruction number @var{end}. The instruction
|
||
number @var{end} is included.
|
||
@end table
|
||
|
||
This command may not be available for all recording methods.
|
||
|
||
@kindex set record
|
||
@item set record instruction-history-size @var{size}
|
||
@itemx set record instruction-history-size unlimited
|
||
Define how many instructions to disassemble in the @code{record
|
||
instruction-history} command. The default value is 10.
|
||
A @var{size} of @code{unlimited} means unlimited instructions.
|
||
|
||
@kindex show record
|
||
@item show record instruction-history-size
|
||
Show how many instructions to disassemble in the @code{record
|
||
instruction-history} command.
|
||
|
||
@kindex record function-call-history
|
||
@kindex rec function-call-history
|
||
@item record function-call-history
|
||
Prints the execution history at function granularity. It prints one
|
||
line for each sequence of instructions that belong to the same
|
||
function giving the name of that function, the source lines
|
||
for this instruction sequence (if the @code{/l} modifier is
|
||
specified), and the instructions numbers that form the sequence (if
|
||
the @code{/i} modifier is specified). The function names are indented
|
||
to reflect the call stack depth if the @code{/c} modifier is
|
||
specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
|
||
given together.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{list 1, 10}
|
||
1 void foo (void)
|
||
2 @{
|
||
3 @}
|
||
4
|
||
5 void bar (void)
|
||
6 @{
|
||
7 ...
|
||
8 foo ();
|
||
9 ...
|
||
10 @}
|
||
(@value{GDBP}) @b{record function-call-history /ilc}
|
||
1 bar inst 1,4 at foo.c:6,8
|
||
2 foo inst 5,10 at foo.c:2,3
|
||
3 bar inst 11,13 at foo.c:9,10
|
||
@end smallexample
|
||
|
||
By default, ten lines are printed. This can be changed using the
|
||
@code{set record function-call-history-size} command. Functions are
|
||
printed in execution order. There are several ways to specify what
|
||
to print:
|
||
|
||
@table @code
|
||
@item record function-call-history @var{func}
|
||
Prints ten functions starting from function number @var{func}.
|
||
|
||
@item record function-call-history @var{func}, +/-@var{n}
|
||
Prints @var{n} functions around function number @var{func}. If
|
||
@var{n} is preceded with @code{+}, prints @var{n} functions after
|
||
function number @var{func}. If @var{n} is preceded with @code{-},
|
||
prints @var{n} functions before function number @var{func}.
|
||
|
||
@item record function-call-history
|
||
Prints ten more functions after the last ten-line print.
|
||
|
||
@item record function-call-history -
|
||
Prints ten more functions before the last ten-line print.
|
||
|
||
@item record function-call-history @var{begin}, @var{end}
|
||
Prints functions beginning with function number @var{begin} until
|
||
function number @var{end}. The function number @var{end} is included.
|
||
@end table
|
||
|
||
This command may not be available for all recording methods.
|
||
|
||
@item set record function-call-history-size @var{size}
|
||
@itemx set record function-call-history-size unlimited
|
||
Define how many lines to print in the
|
||
@code{record function-call-history} command. The default value is 10.
|
||
A size of @code{unlimited} means unlimited lines.
|
||
|
||
@item show record function-call-history-size
|
||
Show how many lines to print in the
|
||
@code{record function-call-history} command.
|
||
@end table
|
||
|
||
|
||
@node Stack
|
||
@chapter Examining the Stack
|
||
|
||
When your program has stopped, the first thing you need to know is where it
|
||
stopped and how it got there.
|
||
|
||
@cindex call stack
|
||
Each time your program performs a function call, information about the call
|
||
is generated.
|
||
That information includes the location of the call in your program,
|
||
the arguments of the call,
|
||
and the local variables of the function being called.
|
||
The information is saved in a block of data called a @dfn{stack frame}.
|
||
The stack frames are allocated in a region of memory called the @dfn{call
|
||
stack}.
|
||
|
||
When your program stops, the @value{GDBN} commands for examining the
|
||
stack allow you to see all of this information.
|
||
|
||
@cindex selected frame
|
||
One of the stack frames is @dfn{selected} by @value{GDBN} and many
|
||
@value{GDBN} commands refer implicitly to the selected frame. In
|
||
particular, whenever you ask @value{GDBN} for the value of a variable in
|
||
your program, the value is found in the selected frame. There are
|
||
special @value{GDBN} commands to select whichever frame you are
|
||
interested in. @xref{Selection, ,Selecting a Frame}.
|
||
|
||
When your program stops, @value{GDBN} automatically selects the
|
||
currently executing frame and describes it briefly, similar to the
|
||
@code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
|
||
|
||
@menu
|
||
* Frames:: Stack frames
|
||
* Backtrace:: Backtraces
|
||
* Selection:: Selecting a frame
|
||
* Frame Info:: Information on a frame
|
||
* Frame Filter Management:: Managing frame filters
|
||
|
||
@end menu
|
||
|
||
@node Frames
|
||
@section Stack Frames
|
||
|
||
@cindex frame, definition
|
||
@cindex stack frame
|
||
The call stack is divided up into contiguous pieces called @dfn{stack
|
||
frames}, or @dfn{frames} for short; each frame is the data associated
|
||
with one call to one function. The frame contains the arguments given
|
||
to the function, the function's local variables, and the address at
|
||
which the function is executing.
|
||
|
||
@cindex initial frame
|
||
@cindex outermost frame
|
||
@cindex innermost frame
|
||
When your program is started, the stack has only one frame, that of the
|
||
function @code{main}. This is called the @dfn{initial} frame or the
|
||
@dfn{outermost} frame. Each time a function is called, a new frame is
|
||
made. Each time a function returns, the frame for that function invocation
|
||
is eliminated. If a function is recursive, there can be many frames for
|
||
the same function. The frame for the function in which execution is
|
||
actually occurring is called the @dfn{innermost} frame. This is the most
|
||
recently created of all the stack frames that still exist.
|
||
|
||
@cindex frame pointer
|
||
Inside your program, stack frames are identified by their addresses. A
|
||
stack frame consists of many bytes, each of which has its own address; each
|
||
kind of computer has a convention for choosing one byte whose
|
||
address serves as the address of the frame. Usually this address is kept
|
||
in a register called the @dfn{frame pointer register}
|
||
(@pxref{Registers, $fp}) while execution is going on in that frame.
|
||
|
||
@cindex frame number
|
||
@value{GDBN} assigns numbers to all existing stack frames, starting with
|
||
zero for the innermost frame, one for the frame that called it,
|
||
and so on upward. These numbers do not really exist in your program;
|
||
they are assigned by @value{GDBN} to give you a way of designating stack
|
||
frames in @value{GDBN} commands.
|
||
|
||
@c The -fomit-frame-pointer below perennially causes hbox overflow
|
||
@c underflow problems.
|
||
@cindex frameless execution
|
||
Some compilers provide a way to compile functions so that they operate
|
||
without stack frames. (For example, the @value{NGCC} option
|
||
@smallexample
|
||
@samp{-fomit-frame-pointer}
|
||
@end smallexample
|
||
generates functions without a frame.)
|
||
This is occasionally done with heavily used library functions to save
|
||
the frame setup time. @value{GDBN} has limited facilities for dealing
|
||
with these function invocations. If the innermost function invocation
|
||
has no stack frame, @value{GDBN} nevertheless regards it as though
|
||
it had a separate frame, which is numbered zero as usual, allowing
|
||
correct tracing of the function call chain. However, @value{GDBN} has
|
||
no provision for frameless functions elsewhere in the stack.
|
||
|
||
@node Backtrace
|
||
@section Backtraces
|
||
|
||
@cindex traceback
|
||
@cindex call stack traces
|
||
A backtrace is a summary of how your program got where it is. It shows one
|
||
line per frame, for many frames, starting with the currently executing
|
||
frame (frame zero), followed by its caller (frame one), and on up the
|
||
stack.
|
||
|
||
@anchor{backtrace-command}
|
||
@kindex backtrace
|
||
@kindex bt @r{(@code{backtrace})}
|
||
To print a backtrace of the entire stack, use the @code{backtrace}
|
||
command, or its alias @code{bt}. This command will print one line per
|
||
frame for frames in the stack. By default, all stack frames are
|
||
printed. You can stop the backtrace at any time by typing the system
|
||
interrupt character, normally @kbd{Ctrl-c}.
|
||
|
||
@table @code
|
||
@item backtrace [@var{args}@dots{}]
|
||
@itemx bt [@var{args}@dots{}]
|
||
Print the backtrace of the entire stack. The optional @var{args} can
|
||
be one of the following:
|
||
|
||
@table @code
|
||
@item @var{n}
|
||
@itemx @var{n}
|
||
Print only the innermost @var{n} frames, where @var{n} is a positive
|
||
number.
|
||
|
||
@item -@var{n}
|
||
@itemx -@var{n}
|
||
Print only the outermost @var{n} frames, where @var{n} is a positive
|
||
number.
|
||
|
||
@item full
|
||
Print the values of the local variables also. This can be combined
|
||
with a number to limit the number of frames shown.
|
||
|
||
@item no-filters
|
||
Do not run Python frame filters on this backtrace. @xref{Frame
|
||
Filter API}, for more information. Additionally use @ref{disable
|
||
frame-filter all} to turn off all frame filters. This is only
|
||
relevant when @value{GDBN} has been configured with @code{Python}
|
||
support.
|
||
|
||
@item hide
|
||
A Python frame filter might decide to ``elide'' some frames. Normally
|
||
such elided frames are still printed, but they are indented relative
|
||
to the filtered frames that cause them to be elided. The @code{hide}
|
||
option causes elided frames to not be printed at all.
|
||
@end table
|
||
@end table
|
||
|
||
@kindex where
|
||
@kindex info stack
|
||
The names @code{where} and @code{info stack} (abbreviated @code{info s})
|
||
are additional aliases for @code{backtrace}.
|
||
|
||
@cindex multiple threads, backtrace
|
||
In a multi-threaded program, @value{GDBN} by default shows the
|
||
backtrace only for the current thread. To display the backtrace for
|
||
several or all of the threads, use the command @code{thread apply}
|
||
(@pxref{Threads, thread apply}). For example, if you type @kbd{thread
|
||
apply all backtrace}, @value{GDBN} will display the backtrace for all
|
||
the threads; this is handy when you debug a core dump of a
|
||
multi-threaded program.
|
||
|
||
Each line in the backtrace shows the frame number and the function name.
|
||
The program counter value is also shown---unless you use @code{set
|
||
print address off}. The backtrace also shows the source file name and
|
||
line number, as well as the arguments to the function. The program
|
||
counter value is omitted if it is at the beginning of the code for that
|
||
line number.
|
||
|
||
Here is an example of a backtrace. It was made with the command
|
||
@samp{bt 3}, so it shows the innermost three frames.
|
||
|
||
@smallexample
|
||
@group
|
||
#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
|
||
at builtin.c:993
|
||
#1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
|
||
#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
|
||
at macro.c:71
|
||
(More stack frames follow...)
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The display for frame zero does not begin with a program counter
|
||
value, indicating that your program has stopped at the beginning of the
|
||
code for line @code{993} of @code{builtin.c}.
|
||
|
||
@noindent
|
||
The value of parameter @code{data} in frame 1 has been replaced by
|
||
@code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
|
||
only if it is a scalar (integer, pointer, enumeration, etc). See command
|
||
@kbd{set print frame-arguments} in @ref{Print Settings} for more details
|
||
on how to configure the way function parameter values are printed.
|
||
|
||
@cindex optimized out, in backtrace
|
||
@cindex function call arguments, optimized out
|
||
If your program was compiled with optimizations, some compilers will
|
||
optimize away arguments passed to functions if those arguments are
|
||
never used after the call. Such optimizations generate code that
|
||
passes arguments through registers, but doesn't store those arguments
|
||
in the stack frame. @value{GDBN} has no way of displaying such
|
||
arguments in stack frames other than the innermost one. Here's what
|
||
such a backtrace might look like:
|
||
|
||
@smallexample
|
||
@group
|
||
#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
|
||
at builtin.c:993
|
||
#1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
|
||
#2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
|
||
at macro.c:71
|
||
(More stack frames follow...)
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The values of arguments that were not saved in their stack frames are
|
||
shown as @samp{<optimized out>}.
|
||
|
||
If you need to display the values of such optimized-out arguments,
|
||
either deduce that from other variables whose values depend on the one
|
||
you are interested in, or recompile without optimizations.
|
||
|
||
@cindex backtrace beyond @code{main} function
|
||
@cindex program entry point
|
||
@cindex startup code, and backtrace
|
||
Most programs have a standard user entry point---a place where system
|
||
libraries and startup code transition into user code. For C this is
|
||
@code{main}@footnote{
|
||
Note that embedded programs (the so-called ``free-standing''
|
||
environment) are not required to have a @code{main} function as the
|
||
entry point. They could even have multiple entry points.}.
|
||
When @value{GDBN} finds the entry function in a backtrace
|
||
it will terminate the backtrace, to avoid tracing into highly
|
||
system-specific (and generally uninteresting) code.
|
||
|
||
If you need to examine the startup code, or limit the number of levels
|
||
in a backtrace, you can change this behavior:
|
||
|
||
@table @code
|
||
@item set backtrace past-main
|
||
@itemx set backtrace past-main on
|
||
@kindex set backtrace
|
||
Backtraces will continue past the user entry point.
|
||
|
||
@item set backtrace past-main off
|
||
Backtraces will stop when they encounter the user entry point. This is the
|
||
default.
|
||
|
||
@item show backtrace past-main
|
||
@kindex show backtrace
|
||
Display the current user entry point backtrace policy.
|
||
|
||
@item set backtrace past-entry
|
||
@itemx set backtrace past-entry on
|
||
Backtraces will continue past the internal entry point of an application.
|
||
This entry point is encoded by the linker when the application is built,
|
||
and is likely before the user entry point @code{main} (or equivalent) is called.
|
||
|
||
@item set backtrace past-entry off
|
||
Backtraces will stop when they encounter the internal entry point of an
|
||
application. This is the default.
|
||
|
||
@item show backtrace past-entry
|
||
Display the current internal entry point backtrace policy.
|
||
|
||
@item set backtrace limit @var{n}
|
||
@itemx set backtrace limit 0
|
||
@itemx set backtrace limit unlimited
|
||
@cindex backtrace limit
|
||
Limit the backtrace to @var{n} levels. A value of @code{unlimited}
|
||
or zero means unlimited levels.
|
||
|
||
@item show backtrace limit
|
||
Display the current limit on backtrace levels.
|
||
@end table
|
||
|
||
You can control how file names are displayed.
|
||
|
||
@table @code
|
||
@item set filename-display
|
||
@itemx set filename-display relative
|
||
@cindex filename-display
|
||
Display file names relative to the compilation directory. This is the default.
|
||
|
||
@item set filename-display basename
|
||
Display only basename of a filename.
|
||
|
||
@item set filename-display absolute
|
||
Display an absolute filename.
|
||
|
||
@item show filename-display
|
||
Show the current way to display filenames.
|
||
@end table
|
||
|
||
@node Selection
|
||
@section Selecting a Frame
|
||
|
||
Most commands for examining the stack and other data in your program work on
|
||
whichever stack frame is selected at the moment. Here are the commands for
|
||
selecting a stack frame; all of them finish by printing a brief description
|
||
of the stack frame just selected.
|
||
|
||
@table @code
|
||
@kindex frame@r{, selecting}
|
||
@kindex f @r{(@code{frame})}
|
||
@item frame @var{n}
|
||
@itemx f @var{n}
|
||
Select frame number @var{n}. Recall that frame zero is the innermost
|
||
(currently executing) frame, frame one is the frame that called the
|
||
innermost one, and so on. The highest-numbered frame is the one for
|
||
@code{main}.
|
||
|
||
@item frame @var{stack-addr} [ @var{pc-addr} ]
|
||
@itemx f @var{stack-addr} [ @var{pc-addr} ]
|
||
Select the frame at address @var{stack-addr}. This is useful mainly if the
|
||
chaining of stack frames has been damaged by a bug, making it
|
||
impossible for @value{GDBN} to assign numbers properly to all frames. In
|
||
addition, this can be useful when your program has multiple stacks and
|
||
switches between them. The optional @var{pc-addr} can also be given to
|
||
specify the value of PC for the stack frame.
|
||
|
||
@kindex up
|
||
@item up @var{n}
|
||
Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
|
||
numbers @var{n}, this advances toward the outermost frame, to higher
|
||
frame numbers, to frames that have existed longer.
|
||
|
||
@kindex down
|
||
@kindex do @r{(@code{down})}
|
||
@item down @var{n}
|
||
Move @var{n} frames down the stack; @var{n} defaults to 1. For
|
||
positive numbers @var{n}, this advances toward the innermost frame, to
|
||
lower frame numbers, to frames that were created more recently.
|
||
You may abbreviate @code{down} as @code{do}.
|
||
@end table
|
||
|
||
All of these commands end by printing two lines of output describing the
|
||
frame. The first line shows the frame number, the function name, the
|
||
arguments, and the source file and line number of execution in that
|
||
frame. The second line shows the text of that source line.
|
||
|
||
@need 1000
|
||
For example:
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) up
|
||
#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
|
||
at env.c:10
|
||
10 read_input_file (argv[i]);
|
||
@end group
|
||
@end smallexample
|
||
|
||
After such a printout, the @code{list} command with no arguments
|
||
prints ten lines centered on the point of execution in the frame.
|
||
You can also edit the program at the point of execution with your favorite
|
||
editing program by typing @code{edit}.
|
||
@xref{List, ,Printing Source Lines},
|
||
for details.
|
||
|
||
@table @code
|
||
@kindex select-frame
|
||
@item select-frame
|
||
The @code{select-frame} command is a variant of @code{frame} that does
|
||
not display the new frame after selecting it. This command is
|
||
intended primarily for use in @value{GDBN} command scripts, where the
|
||
output might be unnecessary and distracting.
|
||
|
||
@kindex down-silently
|
||
@kindex up-silently
|
||
@item up-silently @var{n}
|
||
@itemx down-silently @var{n}
|
||
These two commands are variants of @code{up} and @code{down},
|
||
respectively; they differ in that they do their work silently, without
|
||
causing display of the new frame. They are intended primarily for use
|
||
in @value{GDBN} command scripts, where the output might be unnecessary and
|
||
distracting.
|
||
@end table
|
||
|
||
@node Frame Info
|
||
@section Information About a Frame
|
||
|
||
There are several other commands to print information about the selected
|
||
stack frame.
|
||
|
||
@table @code
|
||
@item frame
|
||
@itemx f
|
||
When used without any argument, this command does not change which
|
||
frame is selected, but prints a brief description of the currently
|
||
selected stack frame. It can be abbreviated @code{f}. With an
|
||
argument, this command is used to select a stack frame.
|
||
@xref{Selection, ,Selecting a Frame}.
|
||
|
||
@kindex info frame
|
||
@kindex info f @r{(@code{info frame})}
|
||
@item info frame
|
||
@itemx info f
|
||
This command prints a verbose description of the selected stack frame,
|
||
including:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
the address of the frame
|
||
@item
|
||
the address of the next frame down (called by this frame)
|
||
@item
|
||
the address of the next frame up (caller of this frame)
|
||
@item
|
||
the language in which the source code corresponding to this frame is written
|
||
@item
|
||
the address of the frame's arguments
|
||
@item
|
||
the address of the frame's local variables
|
||
@item
|
||
the program counter saved in it (the address of execution in the caller frame)
|
||
@item
|
||
which registers were saved in the frame
|
||
@end itemize
|
||
|
||
@noindent The verbose description is useful when
|
||
something has gone wrong that has made the stack format fail to fit
|
||
the usual conventions.
|
||
|
||
@item info frame @var{addr}
|
||
@itemx info f @var{addr}
|
||
Print a verbose description of the frame at address @var{addr}, without
|
||
selecting that frame. The selected frame remains unchanged by this
|
||
command. This requires the same kind of address (more than one for some
|
||
architectures) that you specify in the @code{frame} command.
|
||
@xref{Selection, ,Selecting a Frame}.
|
||
|
||
@kindex info args
|
||
@item info args
|
||
Print the arguments of the selected frame, each on a separate line.
|
||
|
||
@item info locals
|
||
@kindex info locals
|
||
Print the local variables of the selected frame, each on a separate
|
||
line. These are all variables (declared either static or automatic)
|
||
accessible at the point of execution of the selected frame.
|
||
|
||
@end table
|
||
|
||
@node Frame Filter Management
|
||
@section Management of Frame Filters.
|
||
@cindex managing frame filters
|
||
|
||
Frame filters are Python based utilities to manage and decorate the
|
||
output of frames. @xref{Frame Filter API}, for further information.
|
||
|
||
Managing frame filters is performed by several commands available
|
||
within @value{GDBN}, detailed here.
|
||
|
||
@table @code
|
||
@kindex info frame-filter
|
||
@item info frame-filter
|
||
Print a list of installed frame filters from all dictionaries, showing
|
||
their name, priority and enabled status.
|
||
|
||
@kindex disable frame-filter
|
||
@anchor{disable frame-filter all}
|
||
@item disable frame-filter @var{filter-dictionary} @var{filter-name}
|
||
Disable a frame filter in the dictionary matching
|
||
@var{filter-dictionary} and @var{filter-name}. The
|
||
@var{filter-dictionary} may be @code{all}, @code{global},
|
||
@code{progspace}, or the name of the object file where the frame filter
|
||
dictionary resides. When @code{all} is specified, all frame filters
|
||
across all dictionaries are disabled. The @var{filter-name} is the name
|
||
of the frame filter and is used when @code{all} is not the option for
|
||
@var{filter-dictionary}. A disabled frame-filter is not deleted, it
|
||
may be enabled again later.
|
||
|
||
@kindex enable frame-filter
|
||
@item enable frame-filter @var{filter-dictionary} @var{filter-name}
|
||
Enable a frame filter in the dictionary matching
|
||
@var{filter-dictionary} and @var{filter-name}. The
|
||
@var{filter-dictionary} may be @code{all}, @code{global},
|
||
@code{progspace} or the name of the object file where the frame filter
|
||
dictionary resides. When @code{all} is specified, all frame filters across
|
||
all dictionaries are enabled. The @var{filter-name} is the name of the frame
|
||
filter and is used when @code{all} is not the option for
|
||
@var{filter-dictionary}.
|
||
|
||
Example:
|
||
|
||
@smallexample
|
||
(gdb) info frame-filter
|
||
|
||
global frame-filters:
|
||
Priority Enabled Name
|
||
1000 No PrimaryFunctionFilter
|
||
100 Yes Reverse
|
||
|
||
progspace /build/test frame-filters:
|
||
Priority Enabled Name
|
||
100 Yes ProgspaceFilter
|
||
|
||
objfile /build/test frame-filters:
|
||
Priority Enabled Name
|
||
999 Yes BuildProgra Filter
|
||
|
||
(gdb) disable frame-filter /build/test BuildProgramFilter
|
||
(gdb) info frame-filter
|
||
|
||
global frame-filters:
|
||
Priority Enabled Name
|
||
1000 No PrimaryFunctionFilter
|
||
100 Yes Reverse
|
||
|
||
progspace /build/test frame-filters:
|
||
Priority Enabled Name
|
||
100 Yes ProgspaceFilter
|
||
|
||
objfile /build/test frame-filters:
|
||
Priority Enabled Name
|
||
999 No BuildProgramFilter
|
||
|
||
(gdb) enable frame-filter global PrimaryFunctionFilter
|
||
(gdb) info frame-filter
|
||
|
||
global frame-filters:
|
||
Priority Enabled Name
|
||
1000 Yes PrimaryFunctionFilter
|
||
100 Yes Reverse
|
||
|
||
progspace /build/test frame-filters:
|
||
Priority Enabled Name
|
||
100 Yes ProgspaceFilter
|
||
|
||
objfile /build/test frame-filters:
|
||
Priority Enabled Name
|
||
999 No BuildProgramFilter
|
||
@end smallexample
|
||
|
||
@kindex set frame-filter priority
|
||
@item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
|
||
Set the @var{priority} of a frame filter in the dictionary matching
|
||
@var{filter-dictionary}, and the frame filter name matching
|
||
@var{filter-name}. The @var{filter-dictionary} may be @code{global},
|
||
@code{progspace} or the name of the object file where the frame filter
|
||
dictionary resides. The @var{priority} is an integer.
|
||
|
||
@kindex show frame-filter priority
|
||
@item show frame-filter priority @var{filter-dictionary} @var{filter-name}
|
||
Show the @var{priority} of a frame filter in the dictionary matching
|
||
@var{filter-dictionary}, and the frame filter name matching
|
||
@var{filter-name}. The @var{filter-dictionary} may be @code{global},
|
||
@code{progspace} or the name of the object file where the frame filter
|
||
dictionary resides.
|
||
|
||
Example:
|
||
|
||
@smallexample
|
||
(gdb) info frame-filter
|
||
|
||
global frame-filters:
|
||
Priority Enabled Name
|
||
1000 Yes PrimaryFunctionFilter
|
||
100 Yes Reverse
|
||
|
||
progspace /build/test frame-filters:
|
||
Priority Enabled Name
|
||
100 Yes ProgspaceFilter
|
||
|
||
objfile /build/test frame-filters:
|
||
Priority Enabled Name
|
||
999 No BuildProgramFilter
|
||
|
||
(gdb) set frame-filter priority global Reverse 50
|
||
(gdb) info frame-filter
|
||
|
||
global frame-filters:
|
||
Priority Enabled Name
|
||
1000 Yes PrimaryFunctionFilter
|
||
50 Yes Reverse
|
||
|
||
progspace /build/test frame-filters:
|
||
Priority Enabled Name
|
||
100 Yes ProgspaceFilter
|
||
|
||
objfile /build/test frame-filters:
|
||
Priority Enabled Name
|
||
999 No BuildProgramFilter
|
||
@end smallexample
|
||
@end table
|
||
|
||
@node Source
|
||
@chapter Examining Source Files
|
||
|
||
@value{GDBN} can print parts of your program's source, since the debugging
|
||
information recorded in the program tells @value{GDBN} what source files were
|
||
used to build it. When your program stops, @value{GDBN} spontaneously prints
|
||
the line where it stopped. Likewise, when you select a stack frame
|
||
(@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
|
||
execution in that frame has stopped. You can print other portions of
|
||
source files by explicit command.
|
||
|
||
If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
|
||
prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
|
||
@value{GDBN} under @sc{gnu} Emacs}.
|
||
|
||
@menu
|
||
* List:: Printing source lines
|
||
* Specify Location:: How to specify code locations
|
||
* Edit:: Editing source files
|
||
* Search:: Searching source files
|
||
* Source Path:: Specifying source directories
|
||
* Machine Code:: Source and machine code
|
||
@end menu
|
||
|
||
@node List
|
||
@section Printing Source Lines
|
||
|
||
@kindex list
|
||
@kindex l @r{(@code{list})}
|
||
To print lines from a source file, use the @code{list} command
|
||
(abbreviated @code{l}). By default, ten lines are printed.
|
||
There are several ways to specify what part of the file you want to
|
||
print; see @ref{Specify Location}, for the full list.
|
||
|
||
Here are the forms of the @code{list} command most commonly used:
|
||
|
||
@table @code
|
||
@item list @var{linenum}
|
||
Print lines centered around line number @var{linenum} in the
|
||
current source file.
|
||
|
||
@item list @var{function}
|
||
Print lines centered around the beginning of function
|
||
@var{function}.
|
||
|
||
@item list
|
||
Print more lines. If the last lines printed were printed with a
|
||
@code{list} command, this prints lines following the last lines
|
||
printed; however, if the last line printed was a solitary line printed
|
||
as part of displaying a stack frame (@pxref{Stack, ,Examining the
|
||
Stack}), this prints lines centered around that line.
|
||
|
||
@item list -
|
||
Print lines just before the lines last printed.
|
||
@end table
|
||
|
||
@cindex @code{list}, how many lines to display
|
||
By default, @value{GDBN} prints ten source lines with any of these forms of
|
||
the @code{list} command. You can change this using @code{set listsize}:
|
||
|
||
@table @code
|
||
@kindex set listsize
|
||
@item set listsize @var{count}
|
||
@itemx set listsize unlimited
|
||
Make the @code{list} command display @var{count} source lines (unless
|
||
the @code{list} argument explicitly specifies some other number).
|
||
Setting @var{count} to @code{unlimited} or 0 means there's no limit.
|
||
|
||
@kindex show listsize
|
||
@item show listsize
|
||
Display the number of lines that @code{list} prints.
|
||
@end table
|
||
|
||
Repeating a @code{list} command with @key{RET} discards the argument,
|
||
so it is equivalent to typing just @code{list}. This is more useful
|
||
than listing the same lines again. An exception is made for an
|
||
argument of @samp{-}; that argument is preserved in repetition so that
|
||
each repetition moves up in the source file.
|
||
|
||
In general, the @code{list} command expects you to supply zero, one or two
|
||
@dfn{locations}. Locations specify source lines; there are several ways
|
||
of writing them (@pxref{Specify Location}), but the effect is always
|
||
to specify some source line.
|
||
|
||
Here is a complete description of the possible arguments for @code{list}:
|
||
|
||
@table @code
|
||
@item list @var{location}
|
||
Print lines centered around the line specified by @var{location}.
|
||
|
||
@item list @var{first},@var{last}
|
||
Print lines from @var{first} to @var{last}. Both arguments are
|
||
locations. When a @code{list} command has two locations, and the
|
||
source file of the second location is omitted, this refers to
|
||
the same source file as the first location.
|
||
|
||
@item list ,@var{last}
|
||
Print lines ending with @var{last}.
|
||
|
||
@item list @var{first},
|
||
Print lines starting with @var{first}.
|
||
|
||
@item list +
|
||
Print lines just after the lines last printed.
|
||
|
||
@item list -
|
||
Print lines just before the lines last printed.
|
||
|
||
@item list
|
||
As described in the preceding table.
|
||
@end table
|
||
|
||
@node Specify Location
|
||
@section Specifying a Location
|
||
@cindex specifying location
|
||
@cindex location
|
||
@cindex source location
|
||
|
||
@menu
|
||
* Linespec Locations:: Linespec locations
|
||
* Explicit Locations:: Explicit locations
|
||
* Address Locations:: Address locations
|
||
@end menu
|
||
|
||
Several @value{GDBN} commands accept arguments that specify a location
|
||
of your program's code. Since @value{GDBN} is a source-level
|
||
debugger, a location usually specifies some line in the source code.
|
||
Locations may be specified using three different formats:
|
||
linespec locations, explicit locations, or address locations.
|
||
|
||
@node Linespec Locations
|
||
@subsection Linespec Locations
|
||
@cindex linespec locations
|
||
|
||
A @dfn{linespec} is a colon-separated list of source location parameters such
|
||
as file name, function name, etc. Here are all the different ways of
|
||
specifying a linespec:
|
||
|
||
@table @code
|
||
@item @var{linenum}
|
||
Specifies the line number @var{linenum} of the current source file.
|
||
|
||
@item -@var{offset}
|
||
@itemx +@var{offset}
|
||
Specifies the line @var{offset} lines before or after the @dfn{current
|
||
line}. For the @code{list} command, the current line is the last one
|
||
printed; for the breakpoint commands, this is the line at which
|
||
execution stopped in the currently selected @dfn{stack frame}
|
||
(@pxref{Frames, ,Frames}, for a description of stack frames.) When
|
||
used as the second of the two linespecs in a @code{list} command,
|
||
this specifies the line @var{offset} lines up or down from the first
|
||
linespec.
|
||
|
||
@item @var{filename}:@var{linenum}
|
||
Specifies the line @var{linenum} in the source file @var{filename}.
|
||
If @var{filename} is a relative file name, then it will match any
|
||
source file name with the same trailing components. For example, if
|
||
@var{filename} is @samp{gcc/expr.c}, then it will match source file
|
||
name of @file{/build/trunk/gcc/expr.c}, but not
|
||
@file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
|
||
|
||
@item @var{function}
|
||
Specifies the line that begins the body of the function @var{function}.
|
||
For example, in C, this is the line with the open brace.
|
||
|
||
By default, in C@t{++} and Ada, @var{function} is interpreted as
|
||
specifying all functions named @var{function} in all scopes. For
|
||
C@t{++}, this means in all namespaces and classes. For Ada, this
|
||
means in all packages.
|
||
|
||
For example, assuming a program with C@t{++} symbols named
|
||
@code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
|
||
func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
|
||
|
||
Commands that accept a linespec let you override this with the
|
||
@code{-qualified} option. For example, @w{@kbd{break -qualified
|
||
func}} sets a breakpoint on a free-function named @code{func} ignoring
|
||
any C@t{++} class methods and namespace functions called @code{func}.
|
||
|
||
@xref{Explicit Locations}.
|
||
|
||
@item @var{function}:@var{label}
|
||
Specifies the line where @var{label} appears in @var{function}.
|
||
|
||
@item @var{filename}:@var{function}
|
||
Specifies the line that begins the body of the function @var{function}
|
||
in the file @var{filename}. You only need the file name with a
|
||
function name to avoid ambiguity when there are identically named
|
||
functions in different source files.
|
||
|
||
@item @var{label}
|
||
Specifies the line at which the label named @var{label} appears
|
||
in the function corresponding to the currently selected stack frame.
|
||
If there is no current selected stack frame (for instance, if the inferior
|
||
is not running), then @value{GDBN} will not search for a label.
|
||
|
||
@cindex breakpoint at static probe point
|
||
@item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
|
||
The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
|
||
applications to embed static probes. @xref{Static Probe Points}, for more
|
||
information on finding and using static probes. This form of linespec
|
||
specifies the location of such a static probe.
|
||
|
||
If @var{objfile} is given, only probes coming from that shared library
|
||
or executable matching @var{objfile} as a regular expression are considered.
|
||
If @var{provider} is given, then only probes from that provider are considered.
|
||
If several probes match the spec, @value{GDBN} will insert a breakpoint at
|
||
each one of those probes.
|
||
@end table
|
||
|
||
@node Explicit Locations
|
||
@subsection Explicit Locations
|
||
@cindex explicit locations
|
||
|
||
@dfn{Explicit locations} allow the user to directly specify the source
|
||
location's parameters using option-value pairs.
|
||
|
||
Explicit locations are useful when several functions, labels, or
|
||
file names have the same name (base name for files) in the program's
|
||
sources. In these cases, explicit locations point to the source
|
||
line you meant more accurately and unambiguously. Also, using
|
||
explicit locations might be faster in large programs.
|
||
|
||
For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
|
||
defined in the file named @file{foo} or the label @code{bar} in a function
|
||
named @code{foo}. @value{GDBN} must search either the file system or
|
||
the symbol table to know.
|
||
|
||
The list of valid explicit location options is summarized in the
|
||
following table:
|
||
|
||
@table @code
|
||
@item -source @var{filename}
|
||
The value specifies the source file name. To differentiate between
|
||
files with the same base name, prepend as many directories as is necessary
|
||
to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
|
||
@value{GDBN} will use the first file it finds with the given base
|
||
name. This option requires the use of either @code{-function} or @code{-line}.
|
||
|
||
@item -function @var{function}
|
||
The value specifies the name of a function. Operations
|
||
on function locations unmodified by other options (such as @code{-label}
|
||
or @code{-line}) refer to the line that begins the body of the function.
|
||
In C, for example, this is the line with the open brace.
|
||
|
||
By default, in C@t{++} and Ada, @var{function} is interpreted as
|
||
specifying all functions named @var{function} in all scopes. For
|
||
C@t{++}, this means in all namespaces and classes. For Ada, this
|
||
means in all packages.
|
||
|
||
For example, assuming a program with C@t{++} symbols named
|
||
@code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
|
||
-function func}} and @w{@kbd{break -function B::func}} set a
|
||
breakpoint on both symbols.
|
||
|
||
You can use the @kbd{-qualified} flag to override this (see below).
|
||
|
||
@item -qualified
|
||
|
||
This flag makes @value{GDBN} interpret a function name specified with
|
||
@kbd{-function} as a complete fully-qualified name.
|
||
|
||
For example, assuming a C@t{++} program with symbols named
|
||
@code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
|
||
-function B::func}} command sets a breakpoint on @code{B::func}, only.
|
||
|
||
(Note: the @kbd{-qualified} option can precede a linespec as well
|
||
(@pxref{Linespec Locations}), so the particular example above could be
|
||
simplified as @w{@kbd{break -qualified B::func}}.)
|
||
|
||
@item -label @var{label}
|
||
The value specifies the name of a label. When the function
|
||
name is not specified, the label is searched in the function of the currently
|
||
selected stack frame.
|
||
|
||
@item -line @var{number}
|
||
The value specifies a line offset for the location. The offset may either
|
||
be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
|
||
the command. When specified without any other options, the line offset is
|
||
relative to the current line.
|
||
@end table
|
||
|
||
Explicit location options may be abbreviated by omitting any non-unique
|
||
trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
|
||
|
||
@node Address Locations
|
||
@subsection Address Locations
|
||
@cindex address locations
|
||
|
||
@dfn{Address locations} indicate a specific program address. They have
|
||
the generalized form *@var{address}.
|
||
|
||
For line-oriented commands, such as @code{list} and @code{edit}, this
|
||
specifies a source line that contains @var{address}. For @code{break} and
|
||
other breakpoint-oriented commands, this can be used to set breakpoints in
|
||
parts of your program which do not have debugging information or
|
||
source files.
|
||
|
||
Here @var{address} may be any expression valid in the current working
|
||
language (@pxref{Languages, working language}) that specifies a code
|
||
address. In addition, as a convenience, @value{GDBN} extends the
|
||
semantics of expressions used in locations to cover several situations
|
||
that frequently occur during debugging. Here are the various forms
|
||
of @var{address}:
|
||
|
||
@table @code
|
||
@item @var{expression}
|
||
Any expression valid in the current working language.
|
||
|
||
@item @var{funcaddr}
|
||
An address of a function or procedure derived from its name. In C,
|
||
C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
|
||
simply the function's name @var{function} (and actually a special case
|
||
of a valid expression). In Pascal and Modula-2, this is
|
||
@code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
|
||
(although the Pascal form also works).
|
||
|
||
This form specifies the address of the function's first instruction,
|
||
before the stack frame and arguments have been set up.
|
||
|
||
@item '@var{filename}':@var{funcaddr}
|
||
Like @var{funcaddr} above, but also specifies the name of the source
|
||
file explicitly. This is useful if the name of the function does not
|
||
specify the function unambiguously, e.g., if there are several
|
||
functions with identical names in different source files.
|
||
@end table
|
||
|
||
@node Edit
|
||
@section Editing Source Files
|
||
@cindex editing source files
|
||
|
||
@kindex edit
|
||
@kindex e @r{(@code{edit})}
|
||
To edit the lines in a source file, use the @code{edit} command.
|
||
The editing program of your choice
|
||
is invoked with the current line set to
|
||
the active line in the program.
|
||
Alternatively, there are several ways to specify what part of the file you
|
||
want to print if you want to see other parts of the program:
|
||
|
||
@table @code
|
||
@item edit @var{location}
|
||
Edit the source file specified by @code{location}. Editing starts at
|
||
that @var{location}, e.g., at the specified source line of the
|
||
specified file. @xref{Specify Location}, for all the possible forms
|
||
of the @var{location} argument; here are the forms of the @code{edit}
|
||
command most commonly used:
|
||
|
||
@table @code
|
||
@item edit @var{number}
|
||
Edit the current source file with @var{number} as the active line number.
|
||
|
||
@item edit @var{function}
|
||
Edit the file containing @var{function} at the beginning of its definition.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@subsection Choosing your Editor
|
||
You can customize @value{GDBN} to use any editor you want
|
||
@footnote{
|
||
The only restriction is that your editor (say @code{ex}), recognizes the
|
||
following command-line syntax:
|
||
@smallexample
|
||
ex +@var{number} file
|
||
@end smallexample
|
||
The optional numeric value +@var{number} specifies the number of the line in
|
||
the file where to start editing.}.
|
||
By default, it is @file{@value{EDITOR}}, but you can change this
|
||
by setting the environment variable @code{EDITOR} before using
|
||
@value{GDBN}. For example, to configure @value{GDBN} to use the
|
||
@code{vi} editor, you could use these commands with the @code{sh} shell:
|
||
@smallexample
|
||
EDITOR=/usr/bin/vi
|
||
export EDITOR
|
||
gdb @dots{}
|
||
@end smallexample
|
||
or in the @code{csh} shell,
|
||
@smallexample
|
||
setenv EDITOR /usr/bin/vi
|
||
gdb @dots{}
|
||
@end smallexample
|
||
|
||
@node Search
|
||
@section Searching Source Files
|
||
@cindex searching source files
|
||
|
||
There are two commands for searching through the current source file for a
|
||
regular expression.
|
||
|
||
@table @code
|
||
@kindex search
|
||
@kindex forward-search
|
||
@kindex fo @r{(@code{forward-search})}
|
||
@item forward-search @var{regexp}
|
||
@itemx search @var{regexp}
|
||
The command @samp{forward-search @var{regexp}} checks each line,
|
||
starting with the one following the last line listed, for a match for
|
||
@var{regexp}. It lists the line that is found. You can use the
|
||
synonym @samp{search @var{regexp}} or abbreviate the command name as
|
||
@code{fo}.
|
||
|
||
@kindex reverse-search
|
||
@item reverse-search @var{regexp}
|
||
The command @samp{reverse-search @var{regexp}} checks each line, starting
|
||
with the one before the last line listed and going backward, for a match
|
||
for @var{regexp}. It lists the line that is found. You can abbreviate
|
||
this command as @code{rev}.
|
||
@end table
|
||
|
||
@node Source Path
|
||
@section Specifying Source Directories
|
||
|
||
@cindex source path
|
||
@cindex directories for source files
|
||
Executable programs sometimes do not record the directories of the source
|
||
files from which they were compiled, just the names. Even when they do,
|
||
the directories could be moved between the compilation and your debugging
|
||
session. @value{GDBN} has a list of directories to search for source files;
|
||
this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
|
||
it tries all the directories in the list, in the order they are present
|
||
in the list, until it finds a file with the desired name.
|
||
|
||
For example, suppose an executable references the file
|
||
@file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
|
||
@file{/mnt/cross}. The file is first looked up literally; if this
|
||
fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
|
||
fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
|
||
message is printed. @value{GDBN} does not look up the parts of the
|
||
source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
|
||
Likewise, the subdirectories of the source path are not searched: if
|
||
the source path is @file{/mnt/cross}, and the binary refers to
|
||
@file{foo.c}, @value{GDBN} would not find it under
|
||
@file{/mnt/cross/usr/src/foo-1.0/lib}.
|
||
|
||
Plain file names, relative file names with leading directories, file
|
||
names containing dots, etc.@: are all treated as described above; for
|
||
instance, if the source path is @file{/mnt/cross}, and the source file
|
||
is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
|
||
@file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
|
||
that---@file{/mnt/cross/foo.c}.
|
||
|
||
Note that the executable search path is @emph{not} used to locate the
|
||
source files.
|
||
|
||
Whenever you reset or rearrange the source path, @value{GDBN} clears out
|
||
any information it has cached about where source files are found and where
|
||
each line is in the file.
|
||
|
||
@kindex directory
|
||
@kindex dir
|
||
When you start @value{GDBN}, its source path includes only @samp{cdir}
|
||
and @samp{cwd}, in that order.
|
||
To add other directories, use the @code{directory} command.
|
||
|
||
The search path is used to find both program source files and @value{GDBN}
|
||
script files (read using the @samp{-command} option and @samp{source} command).
|
||
|
||
In addition to the source path, @value{GDBN} provides a set of commands
|
||
that manage a list of source path substitution rules. A @dfn{substitution
|
||
rule} specifies how to rewrite source directories stored in the program's
|
||
debug information in case the sources were moved to a different
|
||
directory between compilation and debugging. A rule is made of
|
||
two strings, the first specifying what needs to be rewritten in
|
||
the path, and the second specifying how it should be rewritten.
|
||
In @ref{set substitute-path}, we name these two parts @var{from} and
|
||
@var{to} respectively. @value{GDBN} does a simple string replacement
|
||
of @var{from} with @var{to} at the start of the directory part of the
|
||
source file name, and uses that result instead of the original file
|
||
name to look up the sources.
|
||
|
||
Using the previous example, suppose the @file{foo-1.0} tree has been
|
||
moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
|
||
@value{GDBN} to replace @file{/usr/src} in all source path names with
|
||
@file{/mnt/cross}. The first lookup will then be
|
||
@file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
|
||
of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
|
||
substitution rule, use the @code{set substitute-path} command
|
||
(@pxref{set substitute-path}).
|
||
|
||
To avoid unexpected substitution results, a rule is applied only if the
|
||
@var{from} part of the directory name ends at a directory separator.
|
||
For instance, a rule substituting @file{/usr/source} into
|
||
@file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
|
||
not to @file{/usr/sourceware/foo-2.0}. And because the substitution
|
||
is applied only at the beginning of the directory name, this rule will
|
||
not be applied to @file{/root/usr/source/baz.c} either.
|
||
|
||
In many cases, you can achieve the same result using the @code{directory}
|
||
command. However, @code{set substitute-path} can be more efficient in
|
||
the case where the sources are organized in a complex tree with multiple
|
||
subdirectories. With the @code{directory} command, you need to add each
|
||
subdirectory of your project. If you moved the entire tree while
|
||
preserving its internal organization, then @code{set substitute-path}
|
||
allows you to direct the debugger to all the sources with one single
|
||
command.
|
||
|
||
@code{set substitute-path} is also more than just a shortcut command.
|
||
The source path is only used if the file at the original location no
|
||
longer exists. On the other hand, @code{set substitute-path} modifies
|
||
the debugger behavior to look at the rewritten location instead. So, if
|
||
for any reason a source file that is not relevant to your executable is
|
||
located at the original location, a substitution rule is the only
|
||
method available to point @value{GDBN} at the new location.
|
||
|
||
@cindex @samp{--with-relocated-sources}
|
||
@cindex default source path substitution
|
||
You can configure a default source path substitution rule by
|
||
configuring @value{GDBN} with the
|
||
@samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
|
||
should be the name of a directory under @value{GDBN}'s configured
|
||
prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
|
||
directory names in debug information under @var{dir} will be adjusted
|
||
automatically if the installed @value{GDBN} is moved to a new
|
||
location. This is useful if @value{GDBN}, libraries or executables
|
||
with debug information and corresponding source code are being moved
|
||
together.
|
||
|
||
@table @code
|
||
@item directory @var{dirname} @dots{}
|
||
@item dir @var{dirname} @dots{}
|
||
Add directory @var{dirname} to the front of the source path. Several
|
||
directory names may be given to this command, separated by @samp{:}
|
||
(@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
|
||
part of absolute file names) or
|
||
whitespace. You may specify a directory that is already in the source
|
||
path; this moves it forward, so @value{GDBN} searches it sooner.
|
||
|
||
@kindex cdir
|
||
@kindex cwd
|
||
@vindex $cdir@r{, convenience variable}
|
||
@vindex $cwd@r{, convenience variable}
|
||
@cindex compilation directory
|
||
@cindex current directory
|
||
@cindex working directory
|
||
@cindex directory, current
|
||
@cindex directory, compilation
|
||
You can use the string @samp{$cdir} to refer to the compilation
|
||
directory (if one is recorded), and @samp{$cwd} to refer to the current
|
||
working directory. @samp{$cwd} is not the same as @samp{.}---the former
|
||
tracks the current working directory as it changes during your @value{GDBN}
|
||
session, while the latter is immediately expanded to the current
|
||
directory at the time you add an entry to the source path.
|
||
|
||
@item directory
|
||
Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
|
||
|
||
@c RET-repeat for @code{directory} is explicitly disabled, but since
|
||
@c repeating it would be a no-op we do not say that. (thanks to RMS)
|
||
|
||
@item set directories @var{path-list}
|
||
@kindex set directories
|
||
Set the source path to @var{path-list}.
|
||
@samp{$cdir:$cwd} are added if missing.
|
||
|
||
@item show directories
|
||
@kindex show directories
|
||
Print the source path: show which directories it contains.
|
||
|
||
@anchor{set substitute-path}
|
||
@item set substitute-path @var{from} @var{to}
|
||
@kindex set substitute-path
|
||
Define a source path substitution rule, and add it at the end of the
|
||
current list of existing substitution rules. If a rule with the same
|
||
@var{from} was already defined, then the old rule is also deleted.
|
||
|
||
For example, if the file @file{/foo/bar/baz.c} was moved to
|
||
@file{/mnt/cross/baz.c}, then the command
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set substitute-path /foo/bar /mnt/cross
|
||
@end smallexample
|
||
|
||
@noindent
|
||
will tell @value{GDBN} to replace @samp{/foo/bar} with
|
||
@samp{/mnt/cross}, which will allow @value{GDBN} to find the file
|
||
@file{baz.c} even though it was moved.
|
||
|
||
In the case when more than one substitution rule have been defined,
|
||
the rules are evaluated one by one in the order where they have been
|
||
defined. The first one matching, if any, is selected to perform
|
||
the substitution.
|
||
|
||
For instance, if we had entered the following commands:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set substitute-path /usr/src/include /mnt/include
|
||
(@value{GDBP}) set substitute-path /usr/src /mnt/src
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
|
||
@file{/mnt/include/defs.h} by using the first rule. However, it would
|
||
use the second rule to rewrite @file{/usr/src/lib/foo.c} into
|
||
@file{/mnt/src/lib/foo.c}.
|
||
|
||
|
||
@item unset substitute-path [path]
|
||
@kindex unset substitute-path
|
||
If a path is specified, search the current list of substitution rules
|
||
for a rule that would rewrite that path. Delete that rule if found.
|
||
A warning is emitted by the debugger if no rule could be found.
|
||
|
||
If no path is specified, then all substitution rules are deleted.
|
||
|
||
@item show substitute-path [path]
|
||
@kindex show substitute-path
|
||
If a path is specified, then print the source path substitution rule
|
||
which would rewrite that path, if any.
|
||
|
||
If no path is specified, then print all existing source path substitution
|
||
rules.
|
||
|
||
@end table
|
||
|
||
If your source path is cluttered with directories that are no longer of
|
||
interest, @value{GDBN} may sometimes cause confusion by finding the wrong
|
||
versions of source. You can correct the situation as follows:
|
||
|
||
@enumerate
|
||
@item
|
||
Use @code{directory} with no argument to reset the source path to its default value.
|
||
|
||
@item
|
||
Use @code{directory} with suitable arguments to reinstall the
|
||
directories you want in the source path. You can add all the
|
||
directories in one command.
|
||
@end enumerate
|
||
|
||
@node Machine Code
|
||
@section Source and Machine Code
|
||
@cindex source line and its code address
|
||
|
||
You can use the command @code{info line} to map source lines to program
|
||
addresses (and vice versa), and the command @code{disassemble} to display
|
||
a range of addresses as machine instructions. You can use the command
|
||
@code{set disassemble-next-line} to set whether to disassemble next
|
||
source line when execution stops. When run under @sc{gnu} Emacs
|
||
mode, the @code{info line} command causes the arrow to point to the
|
||
line specified. Also, @code{info line} prints addresses in symbolic form as
|
||
well as hex.
|
||
|
||
@table @code
|
||
@kindex info line
|
||
@item info line
|
||
@itemx info line @var{location}
|
||
Print the starting and ending addresses of the compiled code for
|
||
source line @var{location}. You can specify source lines in any of
|
||
the ways documented in @ref{Specify Location}. With no @var{location}
|
||
information about the current source line is printed.
|
||
@end table
|
||
|
||
For example, we can use @code{info line} to discover the location of
|
||
the object code for the first line of function
|
||
@code{m4_changequote}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info line m4_changequote
|
||
Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
|
||
ends at 0x6350 <m4_changequote+4>.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@cindex code address and its source line
|
||
We can also inquire (using @code{*@var{addr}} as the form for
|
||
@var{location}) what source line covers a particular address:
|
||
@smallexample
|
||
(@value{GDBP}) info line *0x63ff
|
||
Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
|
||
ends at 0x6404 <m4_changequote+184>.
|
||
@end smallexample
|
||
|
||
@cindex @code{$_} and @code{info line}
|
||
@cindex @code{x} command, default address
|
||
@kindex x@r{(examine), and} info line
|
||
After @code{info line}, the default address for the @code{x} command
|
||
is changed to the starting address of the line, so that @samp{x/i} is
|
||
sufficient to begin examining the machine code (@pxref{Memory,
|
||
,Examining Memory}). Also, this address is saved as the value of the
|
||
convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
|
||
Variables}).
|
||
|
||
@cindex info line, repeated calls
|
||
After @code{info line}, using @code{info line} again without
|
||
specifying a location will display information about the next source
|
||
line.
|
||
|
||
@table @code
|
||
@kindex disassemble
|
||
@cindex assembly instructions
|
||
@cindex instructions, assembly
|
||
@cindex machine instructions
|
||
@cindex listing machine instructions
|
||
@item disassemble
|
||
@itemx disassemble /m
|
||
@itemx disassemble /s
|
||
@itemx disassemble /r
|
||
This specialized command dumps a range of memory as machine
|
||
instructions. It can also print mixed source+disassembly by specifying
|
||
the @code{/m} or @code{/s} modifier and print the raw instructions in hex
|
||
as well as in symbolic form by specifying the @code{/r} modifier.
|
||
The default memory range is the function surrounding the
|
||
program counter of the selected frame. A single argument to this
|
||
command is a program counter value; @value{GDBN} dumps the function
|
||
surrounding this value. When two arguments are given, they should
|
||
be separated by a comma, possibly surrounded by whitespace. The
|
||
arguments specify a range of addresses to dump, in one of two forms:
|
||
|
||
@table @code
|
||
@item @var{start},@var{end}
|
||
the addresses from @var{start} (inclusive) to @var{end} (exclusive)
|
||
@item @var{start},+@var{length}
|
||
the addresses from @var{start} (inclusive) to
|
||
@code{@var{start}+@var{length}} (exclusive).
|
||
@end table
|
||
|
||
@noindent
|
||
When 2 arguments are specified, the name of the function is also
|
||
printed (since there could be several functions in the given range).
|
||
|
||
The argument(s) can be any expression yielding a numeric value, such as
|
||
@samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
|
||
|
||
If the range of memory being disassembled contains current program counter,
|
||
the instruction at that location is shown with a @code{=>} marker.
|
||
@end table
|
||
|
||
The following example shows the disassembly of a range of addresses of
|
||
HP PA-RISC 2.0 code:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) disas 0x32c4, 0x32e4
|
||
Dump of assembler code from 0x32c4 to 0x32e4:
|
||
0x32c4 <main+204>: addil 0,dp
|
||
0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
|
||
0x32cc <main+212>: ldil 0x3000,r31
|
||
0x32d0 <main+216>: ble 0x3f8(sr4,r31)
|
||
0x32d4 <main+220>: ldo 0(r31),rp
|
||
0x32d8 <main+224>: addil -0x800,dp
|
||
0x32dc <main+228>: ldo 0x588(r1),r26
|
||
0x32e0 <main+232>: ldil 0x3000,r31
|
||
End of assembler dump.
|
||
@end smallexample
|
||
|
||
Here is an example showing mixed source+assembly for Intel x86
|
||
with @code{/m} or @code{/s}, when the program is stopped just after
|
||
function prologue in a non-optimized function with no inline code.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) disas /m main
|
||
Dump of assembler code for function main:
|
||
5 @{
|
||
0x08048330 <+0>: push %ebp
|
||
0x08048331 <+1>: mov %esp,%ebp
|
||
0x08048333 <+3>: sub $0x8,%esp
|
||
0x08048336 <+6>: and $0xfffffff0,%esp
|
||
0x08048339 <+9>: sub $0x10,%esp
|
||
|
||
6 printf ("Hello.\n");
|
||
=> 0x0804833c <+12>: movl $0x8048440,(%esp)
|
||
0x08048343 <+19>: call 0x8048284 <puts@@plt>
|
||
|
||
7 return 0;
|
||
8 @}
|
||
0x08048348 <+24>: mov $0x0,%eax
|
||
0x0804834d <+29>: leave
|
||
0x0804834e <+30>: ret
|
||
|
||
End of assembler dump.
|
||
@end smallexample
|
||
|
||
The @code{/m} option is deprecated as its output is not useful when
|
||
there is either inlined code or re-ordered code.
|
||
The @code{/s} option is the preferred choice.
|
||
Here is an example for AMD x86-64 showing the difference between
|
||
@code{/m} output and @code{/s} output.
|
||
This example has one inline function defined in a header file,
|
||
and the code is compiled with @samp{-O2} optimization.
|
||
Note how the @code{/m} output is missing the disassembly of
|
||
several instructions that are present in the @code{/s} output.
|
||
|
||
@file{foo.h}:
|
||
|
||
@smallexample
|
||
int
|
||
foo (int a)
|
||
@{
|
||
if (a < 0)
|
||
return a * 2;
|
||
if (a == 0)
|
||
return 1;
|
||
return a + 10;
|
||
@}
|
||
@end smallexample
|
||
|
||
@file{foo.c}:
|
||
|
||
@smallexample
|
||
#include "foo.h"
|
||
volatile int x, y;
|
||
int
|
||
main ()
|
||
@{
|
||
x = foo (y);
|
||
return 0;
|
||
@}
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) disas /m main
|
||
Dump of assembler code for function main:
|
||
5 @{
|
||
|
||
6 x = foo (y);
|
||
0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
|
||
0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
|
||
|
||
7 return 0;
|
||
8 @}
|
||
0x000000000040041d <+29>: xor %eax,%eax
|
||
0x000000000040041f <+31>: retq
|
||
0x0000000000400420 <+32>: add %eax,%eax
|
||
0x0000000000400422 <+34>: jmp 0x400417 <main+23>
|
||
|
||
End of assembler dump.
|
||
(@value{GDBP}) disas /s main
|
||
Dump of assembler code for function main:
|
||
foo.c:
|
||
5 @{
|
||
6 x = foo (y);
|
||
0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
|
||
|
||
foo.h:
|
||
4 if (a < 0)
|
||
0x0000000000400406 <+6>: test %eax,%eax
|
||
0x0000000000400408 <+8>: js 0x400420 <main+32>
|
||
|
||
6 if (a == 0)
|
||
7 return 1;
|
||
8 return a + 10;
|
||
0x000000000040040a <+10>: lea 0xa(%rax),%edx
|
||
0x000000000040040d <+13>: test %eax,%eax
|
||
0x000000000040040f <+15>: mov $0x1,%eax
|
||
0x0000000000400414 <+20>: cmovne %edx,%eax
|
||
|
||
foo.c:
|
||
6 x = foo (y);
|
||
0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
|
||
|
||
7 return 0;
|
||
8 @}
|
||
0x000000000040041d <+29>: xor %eax,%eax
|
||
0x000000000040041f <+31>: retq
|
||
|
||
foo.h:
|
||
5 return a * 2;
|
||
0x0000000000400420 <+32>: add %eax,%eax
|
||
0x0000000000400422 <+34>: jmp 0x400417 <main+23>
|
||
End of assembler dump.
|
||
@end smallexample
|
||
|
||
Here is another example showing raw instructions in hex for AMD x86-64,
|
||
|
||
@smallexample
|
||
(gdb) disas /r 0x400281,+10
|
||
Dump of assembler code from 0x400281 to 0x40028b:
|
||
0x0000000000400281: 38 36 cmp %dh,(%rsi)
|
||
0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
|
||
0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
|
||
0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
|
||
End of assembler dump.
|
||
@end smallexample
|
||
|
||
Addresses cannot be specified as a location (@pxref{Specify Location}).
|
||
So, for example, if you want to disassemble function @code{bar}
|
||
in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
|
||
and not @samp{disassemble foo.c:bar}.
|
||
|
||
Some architectures have more than one commonly-used set of instruction
|
||
mnemonics or other syntax.
|
||
|
||
For programs that were dynamically linked and use shared libraries,
|
||
instructions that call functions or branch to locations in the shared
|
||
libraries might show a seemingly bogus location---it's actually a
|
||
location of the relocation table. On some architectures, @value{GDBN}
|
||
might be able to resolve these to actual function names.
|
||
|
||
@table @code
|
||
@kindex set disassembler-options
|
||
@cindex disassembler options
|
||
@item set disassembler-options @var{option1}[,@var{option2}@dots{}]
|
||
This command controls the passing of target specific information to
|
||
the disassembler. For a list of valid options, please refer to the
|
||
@code{-M}/@code{--disassembler-options} section of the @samp{objdump}
|
||
manual and/or the output of @kbd{objdump --help}
|
||
(@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
|
||
The default value is the empty string.
|
||
|
||
If it is necessary to specify more than one disassembler option, then
|
||
multiple options can be placed together into a comma separated list.
|
||
Currently this command is only supported on targets ARM, PowerPC
|
||
and S/390.
|
||
|
||
@kindex show disassembler-options
|
||
@item show disassembler-options
|
||
Show the current setting of the disassembler options.
|
||
@end table
|
||
|
||
@table @code
|
||
@kindex set disassembly-flavor
|
||
@cindex Intel disassembly flavor
|
||
@cindex AT&T disassembly flavor
|
||
@item set disassembly-flavor @var{instruction-set}
|
||
Select the instruction set to use when disassembling the
|
||
program via the @code{disassemble} or @code{x/i} commands.
|
||
|
||
Currently this command is only defined for the Intel x86 family. You
|
||
can set @var{instruction-set} to either @code{intel} or @code{att}.
|
||
The default is @code{att}, the AT&T flavor used by default by Unix
|
||
assemblers for x86-based targets.
|
||
|
||
@kindex show disassembly-flavor
|
||
@item show disassembly-flavor
|
||
Show the current setting of the disassembly flavor.
|
||
@end table
|
||
|
||
@table @code
|
||
@kindex set disassemble-next-line
|
||
@kindex show disassemble-next-line
|
||
@item set disassemble-next-line
|
||
@itemx show disassemble-next-line
|
||
Control whether or not @value{GDBN} will disassemble the next source
|
||
line or instruction when execution stops. If ON, @value{GDBN} will
|
||
display disassembly of the next source line when execution of the
|
||
program being debugged stops. This is @emph{in addition} to
|
||
displaying the source line itself, which @value{GDBN} always does if
|
||
possible. If the next source line cannot be displayed for some reason
|
||
(e.g., if @value{GDBN} cannot find the source file, or there's no line
|
||
info in the debug info), @value{GDBN} will display disassembly of the
|
||
next @emph{instruction} instead of showing the next source line. If
|
||
AUTO, @value{GDBN} will display disassembly of next instruction only
|
||
if the source line cannot be displayed. This setting causes
|
||
@value{GDBN} to display some feedback when you step through a function
|
||
with no line info or whose source file is unavailable. The default is
|
||
OFF, which means never display the disassembly of the next line or
|
||
instruction.
|
||
@end table
|
||
|
||
|
||
@node Data
|
||
@chapter Examining Data
|
||
|
||
@cindex printing data
|
||
@cindex examining data
|
||
@kindex print
|
||
@kindex inspect
|
||
The usual way to examine data in your program is with the @code{print}
|
||
command (abbreviated @code{p}), or its synonym @code{inspect}. It
|
||
evaluates and prints the value of an expression of the language your
|
||
program is written in (@pxref{Languages, ,Using @value{GDBN} with
|
||
Different Languages}). It may also print the expression using a
|
||
Python-based pretty-printer (@pxref{Pretty Printing}).
|
||
|
||
@table @code
|
||
@item print @var{expr}
|
||
@itemx print /@var{f} @var{expr}
|
||
@var{expr} is an expression (in the source language). By default the
|
||
value of @var{expr} is printed in a format appropriate to its data type;
|
||
you can choose a different format by specifying @samp{/@var{f}}, where
|
||
@var{f} is a letter specifying the format; see @ref{Output Formats,,Output
|
||
Formats}.
|
||
|
||
@item print
|
||
@itemx print /@var{f}
|
||
@cindex reprint the last value
|
||
If you omit @var{expr}, @value{GDBN} displays the last value again (from the
|
||
@dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
|
||
conveniently inspect the same value in an alternative format.
|
||
@end table
|
||
|
||
A more low-level way of examining data is with the @code{x} command.
|
||
It examines data in memory at a specified address and prints it in a
|
||
specified format. @xref{Memory, ,Examining Memory}.
|
||
|
||
If you are interested in information about types, or about how the
|
||
fields of a struct or a class are declared, use the @code{ptype @var{exp}}
|
||
command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
|
||
Table}.
|
||
|
||
@cindex exploring hierarchical data structures
|
||
@kindex explore
|
||
Another way of examining values of expressions and type information is
|
||
through the Python extension command @code{explore} (available only if
|
||
the @value{GDBN} build is configured with @code{--with-python}). It
|
||
offers an interactive way to start at the highest level (or, the most
|
||
abstract level) of the data type of an expression (or, the data type
|
||
itself) and explore all the way down to leaf scalar values/fields
|
||
embedded in the higher level data types.
|
||
|
||
@table @code
|
||
@item explore @var{arg}
|
||
@var{arg} is either an expression (in the source language), or a type
|
||
visible in the current context of the program being debugged.
|
||
@end table
|
||
|
||
The working of the @code{explore} command can be illustrated with an
|
||
example. If a data type @code{struct ComplexStruct} is defined in your
|
||
C program as
|
||
|
||
@smallexample
|
||
struct SimpleStruct
|
||
@{
|
||
int i;
|
||
double d;
|
||
@};
|
||
|
||
struct ComplexStruct
|
||
@{
|
||
struct SimpleStruct *ss_p;
|
||
int arr[10];
|
||
@};
|
||
@end smallexample
|
||
|
||
@noindent
|
||
followed by variable declarations as
|
||
|
||
@smallexample
|
||
struct SimpleStruct ss = @{ 10, 1.11 @};
|
||
struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
|
||
@end smallexample
|
||
|
||
@noindent
|
||
then, the value of the variable @code{cs} can be explored using the
|
||
@code{explore} command as follows.
|
||
|
||
@smallexample
|
||
(gdb) explore cs
|
||
The value of `cs' is a struct/class of type `struct ComplexStruct' with
|
||
the following fields:
|
||
|
||
ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
|
||
arr = <Enter 1 to explore this field of type `int [10]'>
|
||
|
||
Enter the field number of choice:
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Since the fields of @code{cs} are not scalar values, you are being
|
||
prompted to chose the field you want to explore. Let's say you choose
|
||
the field @code{ss_p} by entering @code{0}. Then, since this field is a
|
||
pointer, you will be asked if it is pointing to a single value. From
|
||
the declaration of @code{cs} above, it is indeed pointing to a single
|
||
value, hence you enter @code{y}. If you enter @code{n}, then you will
|
||
be asked if it were pointing to an array of values, in which case this
|
||
field will be explored as if it were an array.
|
||
|
||
@smallexample
|
||
`cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
|
||
Continue exploring it as a pointer to a single value [y/n]: y
|
||
The value of `*(cs.ss_p)' is a struct/class of type `struct
|
||
SimpleStruct' with the following fields:
|
||
|
||
i = 10 .. (Value of type `int')
|
||
d = 1.1100000000000001 .. (Value of type `double')
|
||
|
||
Press enter to return to parent value:
|
||
@end smallexample
|
||
|
||
@noindent
|
||
If the field @code{arr} of @code{cs} was chosen for exploration by
|
||
entering @code{1} earlier, then since it is as array, you will be
|
||
prompted to enter the index of the element in the array that you want
|
||
to explore.
|
||
|
||
@smallexample
|
||
`cs.arr' is an array of `int'.
|
||
Enter the index of the element you want to explore in `cs.arr': 5
|
||
|
||
`(cs.arr)[5]' is a scalar value of type `int'.
|
||
|
||
(cs.arr)[5] = 4
|
||
|
||
Press enter to return to parent value:
|
||
@end smallexample
|
||
|
||
In general, at any stage of exploration, you can go deeper towards the
|
||
leaf values by responding to the prompts appropriately, or hit the
|
||
return key to return to the enclosing data structure (the @i{higher}
|
||
level data structure).
|
||
|
||
Similar to exploring values, you can use the @code{explore} command to
|
||
explore types. Instead of specifying a value (which is typically a
|
||
variable name or an expression valid in the current context of the
|
||
program being debugged), you specify a type name. If you consider the
|
||
same example as above, your can explore the type
|
||
@code{struct ComplexStruct} by passing the argument
|
||
@code{struct ComplexStruct} to the @code{explore} command.
|
||
|
||
@smallexample
|
||
(gdb) explore struct ComplexStruct
|
||
@end smallexample
|
||
|
||
@noindent
|
||
By responding to the prompts appropriately in the subsequent interactive
|
||
session, you can explore the type @code{struct ComplexStruct} in a
|
||
manner similar to how the value @code{cs} was explored in the above
|
||
example.
|
||
|
||
The @code{explore} command also has two sub-commands,
|
||
@code{explore value} and @code{explore type}. The former sub-command is
|
||
a way to explicitly specify that value exploration of the argument is
|
||
being invoked, while the latter is a way to explicitly specify that type
|
||
exploration of the argument is being invoked.
|
||
|
||
@table @code
|
||
@item explore value @var{expr}
|
||
@cindex explore value
|
||
This sub-command of @code{explore} explores the value of the
|
||
expression @var{expr} (if @var{expr} is an expression valid in the
|
||
current context of the program being debugged). The behavior of this
|
||
command is identical to that of the behavior of the @code{explore}
|
||
command being passed the argument @var{expr}.
|
||
|
||
@item explore type @var{arg}
|
||
@cindex explore type
|
||
This sub-command of @code{explore} explores the type of @var{arg} (if
|
||
@var{arg} is a type visible in the current context of program being
|
||
debugged), or the type of the value/expression @var{arg} (if @var{arg}
|
||
is an expression valid in the current context of the program being
|
||
debugged). If @var{arg} is a type, then the behavior of this command is
|
||
identical to that of the @code{explore} command being passed the
|
||
argument @var{arg}. If @var{arg} is an expression, then the behavior of
|
||
this command will be identical to that of the @code{explore} command
|
||
being passed the type of @var{arg} as the argument.
|
||
@end table
|
||
|
||
@menu
|
||
* Expressions:: Expressions
|
||
* Ambiguous Expressions:: Ambiguous Expressions
|
||
* Variables:: Program variables
|
||
* Arrays:: Artificial arrays
|
||
* Output Formats:: Output formats
|
||
* Memory:: Examining memory
|
||
* Auto Display:: Automatic display
|
||
* Print Settings:: Print settings
|
||
* Pretty Printing:: Python pretty printing
|
||
* Value History:: Value history
|
||
* Convenience Vars:: Convenience variables
|
||
* Convenience Funs:: Convenience functions
|
||
* Registers:: Registers
|
||
* Floating Point Hardware:: Floating point hardware
|
||
* Vector Unit:: Vector Unit
|
||
* OS Information:: Auxiliary data provided by operating system
|
||
* Memory Region Attributes:: Memory region attributes
|
||
* Dump/Restore Files:: Copy between memory and a file
|
||
* Core File Generation:: Cause a program dump its core
|
||
* Character Sets:: Debugging programs that use a different
|
||
character set than GDB does
|
||
* Caching Target Data:: Data caching for targets
|
||
* Searching Memory:: Searching memory for a sequence of bytes
|
||
* Value Sizes:: Managing memory allocated for values
|
||
@end menu
|
||
|
||
@node Expressions
|
||
@section Expressions
|
||
|
||
@cindex expressions
|
||
@code{print} and many other @value{GDBN} commands accept an expression and
|
||
compute its value. Any kind of constant, variable or operator defined
|
||
by the programming language you are using is valid in an expression in
|
||
@value{GDBN}. This includes conditional expressions, function calls,
|
||
casts, and string constants. It also includes preprocessor macros, if
|
||
you compiled your program to include this information; see
|
||
@ref{Compilation}.
|
||
|
||
@cindex arrays in expressions
|
||
@value{GDBN} supports array constants in expressions input by
|
||
the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
|
||
you can use the command @code{print @{1, 2, 3@}} to create an array
|
||
of three integers. If you pass an array to a function or assign it
|
||
to a program variable, @value{GDBN} copies the array to memory that
|
||
is @code{malloc}ed in the target program.
|
||
|
||
Because C is so widespread, most of the expressions shown in examples in
|
||
this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
|
||
Languages}, for information on how to use expressions in other
|
||
languages.
|
||
|
||
In this section, we discuss operators that you can use in @value{GDBN}
|
||
expressions regardless of your programming language.
|
||
|
||
@cindex casts, in expressions
|
||
Casts are supported in all languages, not just in C, because it is so
|
||
useful to cast a number into a pointer in order to examine a structure
|
||
at that address in memory.
|
||
@c FIXME: casts supported---Mod2 true?
|
||
|
||
@value{GDBN} supports these operators, in addition to those common
|
||
to programming languages:
|
||
|
||
@table @code
|
||
@item @@
|
||
@samp{@@} is a binary operator for treating parts of memory as arrays.
|
||
@xref{Arrays, ,Artificial Arrays}, for more information.
|
||
|
||
@item ::
|
||
@samp{::} allows you to specify a variable in terms of the file or
|
||
function where it is defined. @xref{Variables, ,Program Variables}.
|
||
|
||
@cindex @{@var{type}@}
|
||
@cindex type casting memory
|
||
@cindex memory, viewing as typed object
|
||
@cindex casts, to view memory
|
||
@item @{@var{type}@} @var{addr}
|
||
Refers to an object of type @var{type} stored at address @var{addr} in
|
||
memory. The address @var{addr} may be any expression whose value is
|
||
an integer or pointer (but parentheses are required around binary
|
||
operators, just as in a cast). This construct is allowed regardless
|
||
of what kind of data is normally supposed to reside at @var{addr}.
|
||
@end table
|
||
|
||
@node Ambiguous Expressions
|
||
@section Ambiguous Expressions
|
||
@cindex ambiguous expressions
|
||
|
||
Expressions can sometimes contain some ambiguous elements. For instance,
|
||
some programming languages (notably Ada, C@t{++} and Objective-C) permit
|
||
a single function name to be defined several times, for application in
|
||
different contexts. This is called @dfn{overloading}. Another example
|
||
involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
|
||
templates and is typically instantiated several times, resulting in
|
||
the same function name being defined in different contexts.
|
||
|
||
In some cases and depending on the language, it is possible to adjust
|
||
the expression to remove the ambiguity. For instance in C@t{++}, you
|
||
can specify the signature of the function you want to break on, as in
|
||
@kbd{break @var{function}(@var{types})}. In Ada, using the fully
|
||
qualified name of your function often makes the expression unambiguous
|
||
as well.
|
||
|
||
When an ambiguity that needs to be resolved is detected, the debugger
|
||
has the capability to display a menu of numbered choices for each
|
||
possibility, and then waits for the selection with the prompt @samp{>}.
|
||
The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
|
||
aborts the current command. If the command in which the expression was
|
||
used allows more than one choice to be selected, the next option in the
|
||
menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
|
||
choices.
|
||
|
||
For example, the following session excerpt shows an attempt to set a
|
||
breakpoint at the overloaded symbol @code{String::after}.
|
||
We choose three particular definitions of that function name:
|
||
|
||
@c FIXME! This is likely to change to show arg type lists, at least
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) b String::after
|
||
[0] cancel
|
||
[1] all
|
||
[2] file:String.cc; line number:867
|
||
[3] file:String.cc; line number:860
|
||
[4] file:String.cc; line number:875
|
||
[5] file:String.cc; line number:853
|
||
[6] file:String.cc; line number:846
|
||
[7] file:String.cc; line number:735
|
||
> 2 4 6
|
||
Breakpoint 1 at 0xb26c: file String.cc, line 867.
|
||
Breakpoint 2 at 0xb344: file String.cc, line 875.
|
||
Breakpoint 3 at 0xafcc: file String.cc, line 846.
|
||
Multiple breakpoints were set.
|
||
Use the "delete" command to delete unwanted
|
||
breakpoints.
|
||
(@value{GDBP})
|
||
@end group
|
||
@end smallexample
|
||
|
||
@table @code
|
||
@kindex set multiple-symbols
|
||
@item set multiple-symbols @var{mode}
|
||
@cindex multiple-symbols menu
|
||
|
||
This option allows you to adjust the debugger behavior when an expression
|
||
is ambiguous.
|
||
|
||
By default, @var{mode} is set to @code{all}. If the command with which
|
||
the expression is used allows more than one choice, then @value{GDBN}
|
||
automatically selects all possible choices. For instance, inserting
|
||
a breakpoint on a function using an ambiguous name results in a breakpoint
|
||
inserted on each possible match. However, if a unique choice must be made,
|
||
then @value{GDBN} uses the menu to help you disambiguate the expression.
|
||
For instance, printing the address of an overloaded function will result
|
||
in the use of the menu.
|
||
|
||
When @var{mode} is set to @code{ask}, the debugger always uses the menu
|
||
when an ambiguity is detected.
|
||
|
||
Finally, when @var{mode} is set to @code{cancel}, the debugger reports
|
||
an error due to the ambiguity and the command is aborted.
|
||
|
||
@kindex show multiple-symbols
|
||
@item show multiple-symbols
|
||
Show the current value of the @code{multiple-symbols} setting.
|
||
@end table
|
||
|
||
@node Variables
|
||
@section Program Variables
|
||
|
||
The most common kind of expression to use is the name of a variable
|
||
in your program.
|
||
|
||
Variables in expressions are understood in the selected stack frame
|
||
(@pxref{Selection, ,Selecting a Frame}); they must be either:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
global (or file-static)
|
||
@end itemize
|
||
|
||
@noindent or
|
||
|
||
@itemize @bullet
|
||
@item
|
||
visible according to the scope rules of the
|
||
programming language from the point of execution in that frame
|
||
@end itemize
|
||
|
||
@noindent This means that in the function
|
||
|
||
@smallexample
|
||
foo (a)
|
||
int a;
|
||
@{
|
||
bar (a);
|
||
@{
|
||
int b = test ();
|
||
bar (b);
|
||
@}
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
you can examine and use the variable @code{a} whenever your program is
|
||
executing within the function @code{foo}, but you can only use or
|
||
examine the variable @code{b} while your program is executing inside
|
||
the block where @code{b} is declared.
|
||
|
||
@cindex variable name conflict
|
||
There is an exception: you can refer to a variable or function whose
|
||
scope is a single source file even if the current execution point is not
|
||
in this file. But it is possible to have more than one such variable or
|
||
function with the same name (in different source files). If that
|
||
happens, referring to that name has unpredictable effects. If you wish,
|
||
you can specify a static variable in a particular function or file by
|
||
using the colon-colon (@code{::}) notation:
|
||
|
||
@cindex colon-colon, context for variables/functions
|
||
@ifnotinfo
|
||
@c info cannot cope with a :: index entry, but why deprive hard copy readers?
|
||
@cindex @code{::}, context for variables/functions
|
||
@end ifnotinfo
|
||
@smallexample
|
||
@var{file}::@var{variable}
|
||
@var{function}::@var{variable}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Here @var{file} or @var{function} is the name of the context for the
|
||
static @var{variable}. In the case of file names, you can use quotes to
|
||
make sure @value{GDBN} parses the file name as a single word---for example,
|
||
to print a global value of @code{x} defined in @file{f2.c}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p 'f2.c'::x
|
||
@end smallexample
|
||
|
||
The @code{::} notation is normally used for referring to
|
||
static variables, since you typically disambiguate uses of local variables
|
||
in functions by selecting the appropriate frame and using the
|
||
simple name of the variable. However, you may also use this notation
|
||
to refer to local variables in frames enclosing the selected frame:
|
||
|
||
@smallexample
|
||
void
|
||
foo (int a)
|
||
@{
|
||
if (a < 10)
|
||
bar (a);
|
||
else
|
||
process (a); /* Stop here */
|
||
@}
|
||
|
||
int
|
||
bar (int a)
|
||
@{
|
||
foo (a + 5);
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
For example, if there is a breakpoint at the commented line,
|
||
here is what you might see
|
||
when the program stops after executing the call @code{bar(0)}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p a
|
||
$1 = 10
|
||
(@value{GDBP}) p bar::a
|
||
$2 = 5
|
||
(@value{GDBP}) up 2
|
||
#2 0x080483d0 in foo (a=5) at foobar.c:12
|
||
(@value{GDBP}) p a
|
||
$3 = 5
|
||
(@value{GDBP}) p bar::a
|
||
$4 = 0
|
||
@end smallexample
|
||
|
||
@cindex C@t{++} scope resolution
|
||
These uses of @samp{::} are very rarely in conflict with the very
|
||
similar use of the same notation in C@t{++}. When they are in
|
||
conflict, the C@t{++} meaning takes precedence; however, this can be
|
||
overridden by quoting the file or function name with single quotes.
|
||
|
||
For example, suppose the program is stopped in a method of a class
|
||
that has a field named @code{includefile}, and there is also an
|
||
include file named @file{includefile} that defines a variable,
|
||
@code{some_global}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p includefile
|
||
$1 = 23
|
||
(@value{GDBP}) p includefile::some_global
|
||
A syntax error in expression, near `'.
|
||
(@value{GDBP}) p 'includefile'::some_global
|
||
$2 = 27
|
||
@end smallexample
|
||
|
||
@cindex wrong values
|
||
@cindex variable values, wrong
|
||
@cindex function entry/exit, wrong values of variables
|
||
@cindex optimized code, wrong values of variables
|
||
@quotation
|
||
@emph{Warning:} Occasionally, a local variable may appear to have the
|
||
wrong value at certain points in a function---just after entry to a new
|
||
scope, and just before exit.
|
||
@end quotation
|
||
You may see this problem when you are stepping by machine instructions.
|
||
This is because, on most machines, it takes more than one instruction to
|
||
set up a stack frame (including local variable definitions); if you are
|
||
stepping by machine instructions, variables may appear to have the wrong
|
||
values until the stack frame is completely built. On exit, it usually
|
||
also takes more than one machine instruction to destroy a stack frame;
|
||
after you begin stepping through that group of instructions, local
|
||
variable definitions may be gone.
|
||
|
||
This may also happen when the compiler does significant optimizations.
|
||
To be sure of always seeing accurate values, turn off all optimization
|
||
when compiling.
|
||
|
||
@cindex ``No symbol "foo" in current context''
|
||
Another possible effect of compiler optimizations is to optimize
|
||
unused variables out of existence, or assign variables to registers (as
|
||
opposed to memory addresses). Depending on the support for such cases
|
||
offered by the debug info format used by the compiler, @value{GDBN}
|
||
might not be able to display values for such local variables. If that
|
||
happens, @value{GDBN} will print a message like this:
|
||
|
||
@smallexample
|
||
No symbol "foo" in current context.
|
||
@end smallexample
|
||
|
||
To solve such problems, either recompile without optimizations, or use a
|
||
different debug info format, if the compiler supports several such
|
||
formats. @xref{Compilation}, for more information on choosing compiler
|
||
options. @xref{C, ,C and C@t{++}}, for more information about debug
|
||
info formats that are best suited to C@t{++} programs.
|
||
|
||
If you ask to print an object whose contents are unknown to
|
||
@value{GDBN}, e.g., because its data type is not completely specified
|
||
by the debug information, @value{GDBN} will say @samp{<incomplete
|
||
type>}. @xref{Symbols, incomplete type}, for more about this.
|
||
|
||
@cindex no debug info variables
|
||
If you try to examine or use the value of a (global) variable for
|
||
which @value{GDBN} has no type information, e.g., because the program
|
||
includes no debug information, @value{GDBN} displays an error message.
|
||
@xref{Symbols, unknown type}, for more about unknown types. If you
|
||
cast the variable to its declared type, @value{GDBN} gets the
|
||
variable's value using the cast-to type as the variable's type. For
|
||
example, in a C program:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p var
|
||
'var' has unknown type; cast it to its declared type
|
||
(@value{GDBP}) p (float) var
|
||
$1 = 3.14
|
||
@end smallexample
|
||
|
||
If you append @kbd{@@entry} string to a function parameter name you get its
|
||
value at the time the function got called. If the value is not available an
|
||
error message is printed. Entry values are available only with some compilers.
|
||
Entry values are normally also printed at the function parameter list according
|
||
to @ref{set print entry-values}.
|
||
|
||
@smallexample
|
||
Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
|
||
29 i++;
|
||
(gdb) next
|
||
30 e (i);
|
||
(gdb) print i
|
||
$1 = 31
|
||
(gdb) print i@@entry
|
||
$2 = 30
|
||
@end smallexample
|
||
|
||
Strings are identified as arrays of @code{char} values without specified
|
||
signedness. Arrays of either @code{signed char} or @code{unsigned char} get
|
||
printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
|
||
@code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
|
||
defines literal string type @code{"char"} as @code{char} without a sign.
|
||
For program code
|
||
|
||
@smallexample
|
||
char var0[] = "A";
|
||
signed char var1[] = "A";
|
||
@end smallexample
|
||
|
||
You get during debugging
|
||
@smallexample
|
||
(gdb) print var0
|
||
$1 = "A"
|
||
(gdb) print var1
|
||
$2 = @{65 'A', 0 '\0'@}
|
||
@end smallexample
|
||
|
||
@node Arrays
|
||
@section Artificial Arrays
|
||
|
||
@cindex artificial array
|
||
@cindex arrays
|
||
@kindex @@@r{, referencing memory as an array}
|
||
It is often useful to print out several successive objects of the
|
||
same type in memory; a section of an array, or an array of
|
||
dynamically determined size for which only a pointer exists in the
|
||
program.
|
||
|
||
You can do this by referring to a contiguous span of memory as an
|
||
@dfn{artificial array}, using the binary operator @samp{@@}. The left
|
||
operand of @samp{@@} should be the first element of the desired array
|
||
and be an individual object. The right operand should be the desired length
|
||
of the array. The result is an array value whose elements are all of
|
||
the type of the left argument. The first element is actually the left
|
||
argument; the second element comes from bytes of memory immediately
|
||
following those that hold the first element, and so on. Here is an
|
||
example. If a program says
|
||
|
||
@smallexample
|
||
int *array = (int *) malloc (len * sizeof (int));
|
||
@end smallexample
|
||
|
||
@noindent
|
||
you can print the contents of @code{array} with
|
||
|
||
@smallexample
|
||
p *array@@len
|
||
@end smallexample
|
||
|
||
The left operand of @samp{@@} must reside in memory. Array values made
|
||
with @samp{@@} in this way behave just like other arrays in terms of
|
||
subscripting, and are coerced to pointers when used in expressions.
|
||
Artificial arrays most often appear in expressions via the value history
|
||
(@pxref{Value History, ,Value History}), after printing one out.
|
||
|
||
Another way to create an artificial array is to use a cast.
|
||
This re-interprets a value as if it were an array.
|
||
The value need not be in memory:
|
||
@smallexample
|
||
(@value{GDBP}) p/x (short[2])0x12345678
|
||
$1 = @{0x1234, 0x5678@}
|
||
@end smallexample
|
||
|
||
As a convenience, if you leave the array length out (as in
|
||
@samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
|
||
the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
|
||
@smallexample
|
||
(@value{GDBP}) p/x (short[])0x12345678
|
||
$2 = @{0x1234, 0x5678@}
|
||
@end smallexample
|
||
|
||
Sometimes the artificial array mechanism is not quite enough; in
|
||
moderately complex data structures, the elements of interest may not
|
||
actually be adjacent---for example, if you are interested in the values
|
||
of pointers in an array. One useful work-around in this situation is
|
||
to use a convenience variable (@pxref{Convenience Vars, ,Convenience
|
||
Variables}) as a counter in an expression that prints the first
|
||
interesting value, and then repeat that expression via @key{RET}. For
|
||
instance, suppose you have an array @code{dtab} of pointers to
|
||
structures, and you are interested in the values of a field @code{fv}
|
||
in each structure. Here is an example of what you might type:
|
||
|
||
@smallexample
|
||
set $i = 0
|
||
p dtab[$i++]->fv
|
||
@key{RET}
|
||
@key{RET}
|
||
@dots{}
|
||
@end smallexample
|
||
|
||
@node Output Formats
|
||
@section Output Formats
|
||
|
||
@cindex formatted output
|
||
@cindex output formats
|
||
By default, @value{GDBN} prints a value according to its data type. Sometimes
|
||
this is not what you want. For example, you might want to print a number
|
||
in hex, or a pointer in decimal. Or you might want to view data in memory
|
||
at a certain address as a character string or as an instruction. To do
|
||
these things, specify an @dfn{output format} when you print a value.
|
||
|
||
The simplest use of output formats is to say how to print a value
|
||
already computed. This is done by starting the arguments of the
|
||
@code{print} command with a slash and a format letter. The format
|
||
letters supported are:
|
||
|
||
@table @code
|
||
@item x
|
||
Regard the bits of the value as an integer, and print the integer in
|
||
hexadecimal.
|
||
|
||
@item d
|
||
Print as integer in signed decimal.
|
||
|
||
@item u
|
||
Print as integer in unsigned decimal.
|
||
|
||
@item o
|
||
Print as integer in octal.
|
||
|
||
@item t
|
||
Print as integer in binary. The letter @samp{t} stands for ``two''.
|
||
@footnote{@samp{b} cannot be used because these format letters are also
|
||
used with the @code{x} command, where @samp{b} stands for ``byte'';
|
||
see @ref{Memory,,Examining Memory}.}
|
||
|
||
@item a
|
||
@cindex unknown address, locating
|
||
@cindex locate address
|
||
Print as an address, both absolute in hexadecimal and as an offset from
|
||
the nearest preceding symbol. You can use this format used to discover
|
||
where (in what function) an unknown address is located:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p/a 0x54320
|
||
$3 = 0x54320 <_initialize_vx+396>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The command @code{info symbol 0x54320} yields similar results.
|
||
@xref{Symbols, info symbol}.
|
||
|
||
@item c
|
||
Regard as an integer and print it as a character constant. This
|
||
prints both the numerical value and its character representation. The
|
||
character representation is replaced with the octal escape @samp{\nnn}
|
||
for characters outside the 7-bit @sc{ascii} range.
|
||
|
||
Without this format, @value{GDBN} displays @code{char},
|
||
@w{@code{unsigned char}}, and @w{@code{signed char}} data as character
|
||
constants. Single-byte members of vectors are displayed as integer
|
||
data.
|
||
|
||
@item f
|
||
Regard the bits of the value as a floating point number and print
|
||
using typical floating point syntax.
|
||
|
||
@item s
|
||
@cindex printing strings
|
||
@cindex printing byte arrays
|
||
Regard as a string, if possible. With this format, pointers to single-byte
|
||
data are displayed as null-terminated strings and arrays of single-byte data
|
||
are displayed as fixed-length strings. Other values are displayed in their
|
||
natural types.
|
||
|
||
Without this format, @value{GDBN} displays pointers to and arrays of
|
||
@code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
|
||
strings. Single-byte members of a vector are displayed as an integer
|
||
array.
|
||
|
||
@item z
|
||
Like @samp{x} formatting, the value is treated as an integer and
|
||
printed as hexadecimal, but leading zeros are printed to pad the value
|
||
to the size of the integer type.
|
||
|
||
@item r
|
||
@cindex raw printing
|
||
Print using the @samp{raw} formatting. By default, @value{GDBN} will
|
||
use a Python-based pretty-printer, if one is available (@pxref{Pretty
|
||
Printing}). This typically results in a higher-level display of the
|
||
value's contents. The @samp{r} format bypasses any Python
|
||
pretty-printer which might exist.
|
||
@end table
|
||
|
||
For example, to print the program counter in hex (@pxref{Registers}), type
|
||
|
||
@smallexample
|
||
p/x $pc
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Note that no space is required before the slash; this is because command
|
||
names in @value{GDBN} cannot contain a slash.
|
||
|
||
To reprint the last value in the value history with a different format,
|
||
you can use the @code{print} command with just a format and no
|
||
expression. For example, @samp{p/x} reprints the last value in hex.
|
||
|
||
@node Memory
|
||
@section Examining Memory
|
||
|
||
You can use the command @code{x} (for ``examine'') to examine memory in
|
||
any of several formats, independently of your program's data types.
|
||
|
||
@cindex examining memory
|
||
@table @code
|
||
@kindex x @r{(examine memory)}
|
||
@item x/@var{nfu} @var{addr}
|
||
@itemx x @var{addr}
|
||
@itemx x
|
||
Use the @code{x} command to examine memory.
|
||
@end table
|
||
|
||
@var{n}, @var{f}, and @var{u} are all optional parameters that specify how
|
||
much memory to display and how to format it; @var{addr} is an
|
||
expression giving the address where you want to start displaying memory.
|
||
If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
|
||
Several commands set convenient defaults for @var{addr}.
|
||
|
||
@table @r
|
||
@item @var{n}, the repeat count
|
||
The repeat count is a decimal integer; the default is 1. It specifies
|
||
how much memory (counting by units @var{u}) to display. If a negative
|
||
number is specified, memory is examined backward from @var{addr}.
|
||
@c This really is **decimal**; unaffected by 'set radix' as of GDB
|
||
@c 4.1.2.
|
||
|
||
@item @var{f}, the display format
|
||
The display format is one of the formats used by @code{print}
|
||
(@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
|
||
@samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
|
||
The default is @samp{x} (hexadecimal) initially. The default changes
|
||
each time you use either @code{x} or @code{print}.
|
||
|
||
@item @var{u}, the unit size
|
||
The unit size is any of
|
||
|
||
@table @code
|
||
@item b
|
||
Bytes.
|
||
@item h
|
||
Halfwords (two bytes).
|
||
@item w
|
||
Words (four bytes). This is the initial default.
|
||
@item g
|
||
Giant words (eight bytes).
|
||
@end table
|
||
|
||
Each time you specify a unit size with @code{x}, that size becomes the
|
||
default unit the next time you use @code{x}. For the @samp{i} format,
|
||
the unit size is ignored and is normally not written. For the @samp{s} format,
|
||
the unit size defaults to @samp{b}, unless it is explicitly given.
|
||
Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
|
||
32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
|
||
Note that the results depend on the programming language of the
|
||
current compilation unit. If the language is C, the @samp{s}
|
||
modifier will use the UTF-16 encoding while @samp{w} will use
|
||
UTF-32. The encoding is set by the programming language and cannot
|
||
be altered.
|
||
|
||
@item @var{addr}, starting display address
|
||
@var{addr} is the address where you want @value{GDBN} to begin displaying
|
||
memory. The expression need not have a pointer value (though it may);
|
||
it is always interpreted as an integer address of a byte of memory.
|
||
@xref{Expressions, ,Expressions}, for more information on expressions. The default for
|
||
@var{addr} is usually just after the last address examined---but several
|
||
other commands also set the default address: @code{info breakpoints} (to
|
||
the address of the last breakpoint listed), @code{info line} (to the
|
||
starting address of a line), and @code{print} (if you use it to display
|
||
a value from memory).
|
||
@end table
|
||
|
||
For example, @samp{x/3uh 0x54320} is a request to display three halfwords
|
||
(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
|
||
starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
|
||
words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
|
||
@pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
|
||
|
||
You can also specify a negative repeat count to examine memory backward
|
||
from the given address. For example, @samp{x/-3uh 0x54320} prints three
|
||
halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
|
||
|
||
Since the letters indicating unit sizes are all distinct from the
|
||
letters specifying output formats, you do not have to remember whether
|
||
unit size or format comes first; either order works. The output
|
||
specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
|
||
(However, the count @var{n} must come first; @samp{wx4} does not work.)
|
||
|
||
Even though the unit size @var{u} is ignored for the formats @samp{s}
|
||
and @samp{i}, you might still want to use a count @var{n}; for example,
|
||
@samp{3i} specifies that you want to see three machine instructions,
|
||
including any operands. For convenience, especially when used with
|
||
the @code{display} command, the @samp{i} format also prints branch delay
|
||
slot instructions, if any, beyond the count specified, which immediately
|
||
follow the last instruction that is within the count. The command
|
||
@code{disassemble} gives an alternative way of inspecting machine
|
||
instructions; see @ref{Machine Code,,Source and Machine Code}.
|
||
|
||
If a negative repeat count is specified for the formats @samp{s} or @samp{i},
|
||
the command displays null-terminated strings or instructions before the given
|
||
address as many as the absolute value of the given number. For the @samp{i}
|
||
format, we use line number information in the debug info to accurately locate
|
||
instruction boundaries while disassembling backward. If line info is not
|
||
available, the command stops examining memory with an error message.
|
||
|
||
All the defaults for the arguments to @code{x} are designed to make it
|
||
easy to continue scanning memory with minimal specifications each time
|
||
you use @code{x}. For example, after you have inspected three machine
|
||
instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
|
||
with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
|
||
the repeat count @var{n} is used again; the other arguments default as
|
||
for successive uses of @code{x}.
|
||
|
||
When examining machine instructions, the instruction at current program
|
||
counter is shown with a @code{=>} marker. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) x/5i $pc-6
|
||
0x804837f <main+11>: mov %esp,%ebp
|
||
0x8048381 <main+13>: push %ecx
|
||
0x8048382 <main+14>: sub $0x4,%esp
|
||
=> 0x8048385 <main+17>: movl $0x8048460,(%esp)
|
||
0x804838c <main+24>: call 0x80482d4 <puts@@plt>
|
||
@end smallexample
|
||
|
||
@cindex @code{$_}, @code{$__}, and value history
|
||
The addresses and contents printed by the @code{x} command are not saved
|
||
in the value history because there is often too much of them and they
|
||
would get in the way. Instead, @value{GDBN} makes these values available for
|
||
subsequent use in expressions as values of the convenience variables
|
||
@code{$_} and @code{$__}. After an @code{x} command, the last address
|
||
examined is available for use in expressions in the convenience variable
|
||
@code{$_}. The contents of that address, as examined, are available in
|
||
the convenience variable @code{$__}.
|
||
|
||
If the @code{x} command has a repeat count, the address and contents saved
|
||
are from the last memory unit printed; this is not the same as the last
|
||
address printed if several units were printed on the last line of output.
|
||
|
||
@anchor{addressable memory unit}
|
||
@cindex addressable memory unit
|
||
Most targets have an addressable memory unit size of 8 bits. This means
|
||
that to each memory address are associated 8 bits of data. Some
|
||
targets, however, have other addressable memory unit sizes.
|
||
Within @value{GDBN} and this document, the term
|
||
@dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
|
||
when explicitly referring to a chunk of data of that size. The word
|
||
@dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
|
||
the addressable memory unit size of the target. For most systems,
|
||
addressable memory unit is a synonym of byte.
|
||
|
||
@cindex remote memory comparison
|
||
@cindex target memory comparison
|
||
@cindex verify remote memory image
|
||
@cindex verify target memory image
|
||
When you are debugging a program running on a remote target machine
|
||
(@pxref{Remote Debugging}), you may wish to verify the program's image
|
||
in the remote machine's memory against the executable file you
|
||
downloaded to the target. Or, on any target, you may want to check
|
||
whether the program has corrupted its own read-only sections. The
|
||
@code{compare-sections} command is provided for such situations.
|
||
|
||
@table @code
|
||
@kindex compare-sections
|
||
@item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
|
||
Compare the data of a loadable section @var{section-name} in the
|
||
executable file of the program being debugged with the same section in
|
||
the target machine's memory, and report any mismatches. With no
|
||
arguments, compares all loadable sections. With an argument of
|
||
@code{-r}, compares all loadable read-only sections.
|
||
|
||
Note: for remote targets, this command can be accelerated if the
|
||
target supports computing the CRC checksum of a block of memory
|
||
(@pxref{qCRC packet}).
|
||
@end table
|
||
|
||
@node Auto Display
|
||
@section Automatic Display
|
||
@cindex automatic display
|
||
@cindex display of expressions
|
||
|
||
If you find that you want to print the value of an expression frequently
|
||
(to see how it changes), you might want to add it to the @dfn{automatic
|
||
display list} so that @value{GDBN} prints its value each time your program stops.
|
||
Each expression added to the list is given a number to identify it;
|
||
to remove an expression from the list, you specify that number.
|
||
The automatic display looks like this:
|
||
|
||
@smallexample
|
||
2: foo = 38
|
||
3: bar[5] = (struct hack *) 0x3804
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This display shows item numbers, expressions and their current values. As with
|
||
displays you request manually using @code{x} or @code{print}, you can
|
||
specify the output format you prefer; in fact, @code{display} decides
|
||
whether to use @code{print} or @code{x} depending your format
|
||
specification---it uses @code{x} if you specify either the @samp{i}
|
||
or @samp{s} format, or a unit size; otherwise it uses @code{print}.
|
||
|
||
@table @code
|
||
@kindex display
|
||
@item display @var{expr}
|
||
Add the expression @var{expr} to the list of expressions to display
|
||
each time your program stops. @xref{Expressions, ,Expressions}.
|
||
|
||
@code{display} does not repeat if you press @key{RET} again after using it.
|
||
|
||
@item display/@var{fmt} @var{expr}
|
||
For @var{fmt} specifying only a display format and not a size or
|
||
count, add the expression @var{expr} to the auto-display list but
|
||
arrange to display it each time in the specified format @var{fmt}.
|
||
@xref{Output Formats,,Output Formats}.
|
||
|
||
@item display/@var{fmt} @var{addr}
|
||
For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
|
||
number of units, add the expression @var{addr} as a memory address to
|
||
be examined each time your program stops. Examining means in effect
|
||
doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
|
||
@end table
|
||
|
||
For example, @samp{display/i $pc} can be helpful, to see the machine
|
||
instruction about to be executed each time execution stops (@samp{$pc}
|
||
is a common name for the program counter; @pxref{Registers, ,Registers}).
|
||
|
||
@table @code
|
||
@kindex delete display
|
||
@kindex undisplay
|
||
@item undisplay @var{dnums}@dots{}
|
||
@itemx delete display @var{dnums}@dots{}
|
||
Remove items from the list of expressions to display. Specify the
|
||
numbers of the displays that you want affected with the command
|
||
argument @var{dnums}. It can be a single display number, one of the
|
||
numbers shown in the first field of the @samp{info display} display;
|
||
or it could be a range of display numbers, as in @code{2-4}.
|
||
|
||
@code{undisplay} does not repeat if you press @key{RET} after using it.
|
||
(Otherwise you would just get the error @samp{No display number @dots{}}.)
|
||
|
||
@kindex disable display
|
||
@item disable display @var{dnums}@dots{}
|
||
Disable the display of item numbers @var{dnums}. A disabled display
|
||
item is not printed automatically, but is not forgotten. It may be
|
||
enabled again later. Specify the numbers of the displays that you
|
||
want affected with the command argument @var{dnums}. It can be a
|
||
single display number, one of the numbers shown in the first field of
|
||
the @samp{info display} display; or it could be a range of display
|
||
numbers, as in @code{2-4}.
|
||
|
||
@kindex enable display
|
||
@item enable display @var{dnums}@dots{}
|
||
Enable display of item numbers @var{dnums}. It becomes effective once
|
||
again in auto display of its expression, until you specify otherwise.
|
||
Specify the numbers of the displays that you want affected with the
|
||
command argument @var{dnums}. It can be a single display number, one
|
||
of the numbers shown in the first field of the @samp{info display}
|
||
display; or it could be a range of display numbers, as in @code{2-4}.
|
||
|
||
@item display
|
||
Display the current values of the expressions on the list, just as is
|
||
done when your program stops.
|
||
|
||
@kindex info display
|
||
@item info display
|
||
Print the list of expressions previously set up to display
|
||
automatically, each one with its item number, but without showing the
|
||
values. This includes disabled expressions, which are marked as such.
|
||
It also includes expressions which would not be displayed right now
|
||
because they refer to automatic variables not currently available.
|
||
@end table
|
||
|
||
@cindex display disabled out of scope
|
||
If a display expression refers to local variables, then it does not make
|
||
sense outside the lexical context for which it was set up. Such an
|
||
expression is disabled when execution enters a context where one of its
|
||
variables is not defined. For example, if you give the command
|
||
@code{display last_char} while inside a function with an argument
|
||
@code{last_char}, @value{GDBN} displays this argument while your program
|
||
continues to stop inside that function. When it stops elsewhere---where
|
||
there is no variable @code{last_char}---the display is disabled
|
||
automatically. The next time your program stops where @code{last_char}
|
||
is meaningful, you can enable the display expression once again.
|
||
|
||
@node Print Settings
|
||
@section Print Settings
|
||
|
||
@cindex format options
|
||
@cindex print settings
|
||
@value{GDBN} provides the following ways to control how arrays, structures,
|
||
and symbols are printed.
|
||
|
||
@noindent
|
||
These settings are useful for debugging programs in any language:
|
||
|
||
@table @code
|
||
@kindex set print
|
||
@item set print address
|
||
@itemx set print address on
|
||
@cindex print/don't print memory addresses
|
||
@value{GDBN} prints memory addresses showing the location of stack
|
||
traces, structure values, pointer values, breakpoints, and so forth,
|
||
even when it also displays the contents of those addresses. The default
|
||
is @code{on}. For example, this is what a stack frame display looks like with
|
||
@code{set print address on}:
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) f
|
||
#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
|
||
at input.c:530
|
||
530 if (lquote != def_lquote)
|
||
@end group
|
||
@end smallexample
|
||
|
||
@item set print address off
|
||
Do not print addresses when displaying their contents. For example,
|
||
this is the same stack frame displayed with @code{set print address off}:
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) set print addr off
|
||
(@value{GDBP}) f
|
||
#0 set_quotes (lq="<<", rq=">>") at input.c:530
|
||
530 if (lquote != def_lquote)
|
||
@end group
|
||
@end smallexample
|
||
|
||
You can use @samp{set print address off} to eliminate all machine
|
||
dependent displays from the @value{GDBN} interface. For example, with
|
||
@code{print address off}, you should get the same text for backtraces on
|
||
all machines---whether or not they involve pointer arguments.
|
||
|
||
@kindex show print
|
||
@item show print address
|
||
Show whether or not addresses are to be printed.
|
||
@end table
|
||
|
||
When @value{GDBN} prints a symbolic address, it normally prints the
|
||
closest earlier symbol plus an offset. If that symbol does not uniquely
|
||
identify the address (for example, it is a name whose scope is a single
|
||
source file), you may need to clarify. One way to do this is with
|
||
@code{info line}, for example @samp{info line *0x4537}. Alternately,
|
||
you can set @value{GDBN} to print the source file and line number when
|
||
it prints a symbolic address:
|
||
|
||
@table @code
|
||
@item set print symbol-filename on
|
||
@cindex source file and line of a symbol
|
||
@cindex symbol, source file and line
|
||
Tell @value{GDBN} to print the source file name and line number of a
|
||
symbol in the symbolic form of an address.
|
||
|
||
@item set print symbol-filename off
|
||
Do not print source file name and line number of a symbol. This is the
|
||
default.
|
||
|
||
@item show print symbol-filename
|
||
Show whether or not @value{GDBN} will print the source file name and
|
||
line number of a symbol in the symbolic form of an address.
|
||
@end table
|
||
|
||
Another situation where it is helpful to show symbol filenames and line
|
||
numbers is when disassembling code; @value{GDBN} shows you the line
|
||
number and source file that corresponds to each instruction.
|
||
|
||
Also, you may wish to see the symbolic form only if the address being
|
||
printed is reasonably close to the closest earlier symbol:
|
||
|
||
@table @code
|
||
@item set print max-symbolic-offset @var{max-offset}
|
||
@itemx set print max-symbolic-offset unlimited
|
||
@cindex maximum value for offset of closest symbol
|
||
Tell @value{GDBN} to only display the symbolic form of an address if the
|
||
offset between the closest earlier symbol and the address is less than
|
||
@var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
|
||
to always print the symbolic form of an address if any symbol precedes
|
||
it. Zero is equivalent to @code{unlimited}.
|
||
|
||
@item show print max-symbolic-offset
|
||
Ask how large the maximum offset is that @value{GDBN} prints in a
|
||
symbolic address.
|
||
@end table
|
||
|
||
@cindex wild pointer, interpreting
|
||
@cindex pointer, finding referent
|
||
If you have a pointer and you are not sure where it points, try
|
||
@samp{set print symbol-filename on}. Then you can determine the name
|
||
and source file location of the variable where it points, using
|
||
@samp{p/a @var{pointer}}. This interprets the address in symbolic form.
|
||
For example, here @value{GDBN} shows that a variable @code{ptt} points
|
||
at another variable @code{t}, defined in @file{hi2.c}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set print symbol-filename on
|
||
(@value{GDBP}) p/a ptt
|
||
$4 = 0xe008 <t in hi2.c>
|
||
@end smallexample
|
||
|
||
@quotation
|
||
@emph{Warning:} For pointers that point to a local variable, @samp{p/a}
|
||
does not show the symbol name and filename of the referent, even with
|
||
the appropriate @code{set print} options turned on.
|
||
@end quotation
|
||
|
||
You can also enable @samp{/a}-like formatting all the time using
|
||
@samp{set print symbol on}:
|
||
|
||
@table @code
|
||
@item set print symbol on
|
||
Tell @value{GDBN} to print the symbol corresponding to an address, if
|
||
one exists.
|
||
|
||
@item set print symbol off
|
||
Tell @value{GDBN} not to print the symbol corresponding to an
|
||
address. In this mode, @value{GDBN} will still print the symbol
|
||
corresponding to pointers to functions. This is the default.
|
||
|
||
@item show print symbol
|
||
Show whether @value{GDBN} will display the symbol corresponding to an
|
||
address.
|
||
@end table
|
||
|
||
Other settings control how different kinds of objects are printed:
|
||
|
||
@table @code
|
||
@item set print array
|
||
@itemx set print array on
|
||
@cindex pretty print arrays
|
||
Pretty print arrays. This format is more convenient to read,
|
||
but uses more space. The default is off.
|
||
|
||
@item set print array off
|
||
Return to compressed format for arrays.
|
||
|
||
@item show print array
|
||
Show whether compressed or pretty format is selected for displaying
|
||
arrays.
|
||
|
||
@cindex print array indexes
|
||
@item set print array-indexes
|
||
@itemx set print array-indexes on
|
||
Print the index of each element when displaying arrays. May be more
|
||
convenient to locate a given element in the array or quickly find the
|
||
index of a given element in that printed array. The default is off.
|
||
|
||
@item set print array-indexes off
|
||
Stop printing element indexes when displaying arrays.
|
||
|
||
@item show print array-indexes
|
||
Show whether the index of each element is printed when displaying
|
||
arrays.
|
||
|
||
@item set print elements @var{number-of-elements}
|
||
@itemx set print elements unlimited
|
||
@cindex number of array elements to print
|
||
@cindex limit on number of printed array elements
|
||
Set a limit on how many elements of an array @value{GDBN} will print.
|
||
If @value{GDBN} is printing a large array, it stops printing after it has
|
||
printed the number of elements set by the @code{set print elements} command.
|
||
This limit also applies to the display of strings.
|
||
When @value{GDBN} starts, this limit is set to 200.
|
||
Setting @var{number-of-elements} to @code{unlimited} or zero means
|
||
that the number of elements to print is unlimited.
|
||
|
||
@item show print elements
|
||
Display the number of elements of a large array that @value{GDBN} will print.
|
||
If the number is 0, then the printing is unlimited.
|
||
|
||
@item set print frame-arguments @var{value}
|
||
@kindex set print frame-arguments
|
||
@cindex printing frame argument values
|
||
@cindex print all frame argument values
|
||
@cindex print frame argument values for scalars only
|
||
@cindex do not print frame argument values
|
||
This command allows to control how the values of arguments are printed
|
||
when the debugger prints a frame (@pxref{Frames}). The possible
|
||
values are:
|
||
|
||
@table @code
|
||
@item all
|
||
The values of all arguments are printed.
|
||
|
||
@item scalars
|
||
Print the value of an argument only if it is a scalar. The value of more
|
||
complex arguments such as arrays, structures, unions, etc, is replaced
|
||
by @code{@dots{}}. This is the default. Here is an example where
|
||
only scalar arguments are shown:
|
||
|
||
@smallexample
|
||
#1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
|
||
at frame-args.c:23
|
||
@end smallexample
|
||
|
||
@item none
|
||
None of the argument values are printed. Instead, the value of each argument
|
||
is replaced by @code{@dots{}}. In this case, the example above now becomes:
|
||
|
||
@smallexample
|
||
#1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
|
||
at frame-args.c:23
|
||
@end smallexample
|
||
@end table
|
||
|
||
By default, only scalar arguments are printed. This command can be used
|
||
to configure the debugger to print the value of all arguments, regardless
|
||
of their type. However, it is often advantageous to not print the value
|
||
of more complex parameters. For instance, it reduces the amount of
|
||
information printed in each frame, making the backtrace more readable.
|
||
Also, it improves performance when displaying Ada frames, because
|
||
the computation of large arguments can sometimes be CPU-intensive,
|
||
especially in large applications. Setting @code{print frame-arguments}
|
||
to @code{scalars} (the default) or @code{none} avoids this computation,
|
||
thus speeding up the display of each Ada frame.
|
||
|
||
@item show print frame-arguments
|
||
Show how the value of arguments should be displayed when printing a frame.
|
||
|
||
@item set print raw frame-arguments on
|
||
Print frame arguments in raw, non pretty-printed, form.
|
||
|
||
@item set print raw frame-arguments off
|
||
Print frame arguments in pretty-printed form, if there is a pretty-printer
|
||
for the value (@pxref{Pretty Printing}),
|
||
otherwise print the value in raw form.
|
||
This is the default.
|
||
|
||
@item show print raw frame-arguments
|
||
Show whether to print frame arguments in raw form.
|
||
|
||
@anchor{set print entry-values}
|
||
@item set print entry-values @var{value}
|
||
@kindex set print entry-values
|
||
Set printing of frame argument values at function entry. In some cases
|
||
@value{GDBN} can determine the value of function argument which was passed by
|
||
the function caller, even if the value was modified inside the called function
|
||
and therefore is different. With optimized code, the current value could be
|
||
unavailable, but the entry value may still be known.
|
||
|
||
The default value is @code{default} (see below for its description). Older
|
||
@value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
|
||
this feature will behave in the @code{default} setting the same way as with the
|
||
@code{no} setting.
|
||
|
||
This functionality is currently supported only by DWARF 2 debugging format and
|
||
the compiler has to produce @samp{DW_TAG_call_site} tags. With
|
||
@value{NGCC}, you need to specify @option{-O -g} during compilation, to get
|
||
this information.
|
||
|
||
The @var{value} parameter can be one of the following:
|
||
|
||
@table @code
|
||
@item no
|
||
Print only actual parameter values, never print values from function entry
|
||
point.
|
||
@smallexample
|
||
#0 equal (val=5)
|
||
#0 different (val=6)
|
||
#0 lost (val=<optimized out>)
|
||
#0 born (val=10)
|
||
#0 invalid (val=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item only
|
||
Print only parameter values from function entry point. The actual parameter
|
||
values are never printed.
|
||
@smallexample
|
||
#0 equal (val@@entry=5)
|
||
#0 different (val@@entry=5)
|
||
#0 lost (val@@entry=5)
|
||
#0 born (val@@entry=<optimized out>)
|
||
#0 invalid (val@@entry=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item preferred
|
||
Print only parameter values from function entry point. If value from function
|
||
entry point is not known while the actual value is known, print the actual
|
||
value for such parameter.
|
||
@smallexample
|
||
#0 equal (val@@entry=5)
|
||
#0 different (val@@entry=5)
|
||
#0 lost (val@@entry=5)
|
||
#0 born (val=10)
|
||
#0 invalid (val@@entry=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item if-needed
|
||
Print actual parameter values. If actual parameter value is not known while
|
||
value from function entry point is known, print the entry point value for such
|
||
parameter.
|
||
@smallexample
|
||
#0 equal (val=5)
|
||
#0 different (val=6)
|
||
#0 lost (val@@entry=5)
|
||
#0 born (val=10)
|
||
#0 invalid (val=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item both
|
||
Always print both the actual parameter value and its value from function entry
|
||
point, even if values of one or both are not available due to compiler
|
||
optimizations.
|
||
@smallexample
|
||
#0 equal (val=5, val@@entry=5)
|
||
#0 different (val=6, val@@entry=5)
|
||
#0 lost (val=<optimized out>, val@@entry=5)
|
||
#0 born (val=10, val@@entry=<optimized out>)
|
||
#0 invalid (val=<optimized out>, val@@entry=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item compact
|
||
Print the actual parameter value if it is known and also its value from
|
||
function entry point if it is known. If neither is known, print for the actual
|
||
value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
|
||
values are known and identical, print the shortened
|
||
@code{param=param@@entry=VALUE} notation.
|
||
@smallexample
|
||
#0 equal (val=val@@entry=5)
|
||
#0 different (val=6, val@@entry=5)
|
||
#0 lost (val@@entry=5)
|
||
#0 born (val=10)
|
||
#0 invalid (val=<optimized out>)
|
||
@end smallexample
|
||
|
||
@item default
|
||
Always print the actual parameter value. Print also its value from function
|
||
entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
|
||
if both values are known and identical, print the shortened
|
||
@code{param=param@@entry=VALUE} notation.
|
||
@smallexample
|
||
#0 equal (val=val@@entry=5)
|
||
#0 different (val=6, val@@entry=5)
|
||
#0 lost (val=<optimized out>, val@@entry=5)
|
||
#0 born (val=10)
|
||
#0 invalid (val=<optimized out>)
|
||
@end smallexample
|
||
@end table
|
||
|
||
For analysis messages on possible failures of frame argument values at function
|
||
entry resolution see @ref{set debug entry-values}.
|
||
|
||
@item show print entry-values
|
||
Show the method being used for printing of frame argument values at function
|
||
entry.
|
||
|
||
@item set print repeats @var{number-of-repeats}
|
||
@itemx set print repeats unlimited
|
||
@cindex repeated array elements
|
||
Set the threshold for suppressing display of repeated array
|
||
elements. When the number of consecutive identical elements of an
|
||
array exceeds the threshold, @value{GDBN} prints the string
|
||
@code{"<repeats @var{n} times>"}, where @var{n} is the number of
|
||
identical repetitions, instead of displaying the identical elements
|
||
themselves. Setting the threshold to @code{unlimited} or zero will
|
||
cause all elements to be individually printed. The default threshold
|
||
is 10.
|
||
|
||
@item show print repeats
|
||
Display the current threshold for printing repeated identical
|
||
elements.
|
||
|
||
@item set print null-stop
|
||
@cindex @sc{null} elements in arrays
|
||
Cause @value{GDBN} to stop printing the characters of an array when the first
|
||
@sc{null} is encountered. This is useful when large arrays actually
|
||
contain only short strings.
|
||
The default is off.
|
||
|
||
@item show print null-stop
|
||
Show whether @value{GDBN} stops printing an array on the first
|
||
@sc{null} character.
|
||
|
||
@item set print pretty on
|
||
@cindex print structures in indented form
|
||
@cindex indentation in structure display
|
||
Cause @value{GDBN} to print structures in an indented format with one member
|
||
per line, like this:
|
||
|
||
@smallexample
|
||
@group
|
||
$1 = @{
|
||
next = 0x0,
|
||
flags = @{
|
||
sweet = 1,
|
||
sour = 1
|
||
@},
|
||
meat = 0x54 "Pork"
|
||
@}
|
||
@end group
|
||
@end smallexample
|
||
|
||
@item set print pretty off
|
||
Cause @value{GDBN} to print structures in a compact format, like this:
|
||
|
||
@smallexample
|
||
@group
|
||
$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
|
||
meat = 0x54 "Pork"@}
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This is the default format.
|
||
|
||
@item show print pretty
|
||
Show which format @value{GDBN} is using to print structures.
|
||
|
||
@item set print sevenbit-strings on
|
||
@cindex eight-bit characters in strings
|
||
@cindex octal escapes in strings
|
||
Print using only seven-bit characters; if this option is set,
|
||
@value{GDBN} displays any eight-bit characters (in strings or
|
||
character values) using the notation @code{\}@var{nnn}. This setting is
|
||
best if you are working in English (@sc{ascii}) and you use the
|
||
high-order bit of characters as a marker or ``meta'' bit.
|
||
|
||
@item set print sevenbit-strings off
|
||
Print full eight-bit characters. This allows the use of more
|
||
international character sets, and is the default.
|
||
|
||
@item show print sevenbit-strings
|
||
Show whether or not @value{GDBN} is printing only seven-bit characters.
|
||
|
||
@item set print union on
|
||
@cindex unions in structures, printing
|
||
Tell @value{GDBN} to print unions which are contained in structures
|
||
and other unions. This is the default setting.
|
||
|
||
@item set print union off
|
||
Tell @value{GDBN} not to print unions which are contained in
|
||
structures and other unions. @value{GDBN} will print @code{"@{...@}"}
|
||
instead.
|
||
|
||
@item show print union
|
||
Ask @value{GDBN} whether or not it will print unions which are contained in
|
||
structures and other unions.
|
||
|
||
For example, given the declarations
|
||
|
||
@smallexample
|
||
typedef enum @{Tree, Bug@} Species;
|
||
typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
|
||
typedef enum @{Caterpillar, Cocoon, Butterfly@}
|
||
Bug_forms;
|
||
|
||
struct thing @{
|
||
Species it;
|
||
union @{
|
||
Tree_forms tree;
|
||
Bug_forms bug;
|
||
@} form;
|
||
@};
|
||
|
||
struct thing foo = @{Tree, @{Acorn@}@};
|
||
@end smallexample
|
||
|
||
@noindent
|
||
with @code{set print union on} in effect @samp{p foo} would print
|
||
|
||
@smallexample
|
||
$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and with @code{set print union off} in effect it would print
|
||
|
||
@smallexample
|
||
$1 = @{it = Tree, form = @{...@}@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@code{set print union} affects programs written in C-like languages
|
||
and in Pascal.
|
||
@end table
|
||
|
||
@need 1000
|
||
@noindent
|
||
These settings are of interest when debugging C@t{++} programs:
|
||
|
||
@table @code
|
||
@cindex demangling C@t{++} names
|
||
@item set print demangle
|
||
@itemx set print demangle on
|
||
Print C@t{++} names in their source form rather than in the encoded
|
||
(``mangled'') form passed to the assembler and linker for type-safe
|
||
linkage. The default is on.
|
||
|
||
@item show print demangle
|
||
Show whether C@t{++} names are printed in mangled or demangled form.
|
||
|
||
@item set print asm-demangle
|
||
@itemx set print asm-demangle on
|
||
Print C@t{++} names in their source form rather than their mangled form, even
|
||
in assembler code printouts such as instruction disassemblies.
|
||
The default is off.
|
||
|
||
@item show print asm-demangle
|
||
Show whether C@t{++} names in assembly listings are printed in mangled
|
||
or demangled form.
|
||
|
||
@cindex C@t{++} symbol decoding style
|
||
@cindex symbol decoding style, C@t{++}
|
||
@kindex set demangle-style
|
||
@item set demangle-style @var{style}
|
||
Choose among several encoding schemes used by different compilers to
|
||
represent C@t{++} names. The choices for @var{style} are currently:
|
||
|
||
@table @code
|
||
@item auto
|
||
Allow @value{GDBN} to choose a decoding style by inspecting your program.
|
||
This is the default.
|
||
|
||
@item gnu
|
||
Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
|
||
|
||
@item hp
|
||
Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
|
||
|
||
@item lucid
|
||
Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
|
||
|
||
@item arm
|
||
Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
|
||
@strong{Warning:} this setting alone is not sufficient to allow
|
||
debugging @code{cfront}-generated executables. @value{GDBN} would
|
||
require further enhancement to permit that.
|
||
|
||
@end table
|
||
If you omit @var{style}, you will see a list of possible formats.
|
||
|
||
@item show demangle-style
|
||
Display the encoding style currently in use for decoding C@t{++} symbols.
|
||
|
||
@item set print object
|
||
@itemx set print object on
|
||
@cindex derived type of an object, printing
|
||
@cindex display derived types
|
||
When displaying a pointer to an object, identify the @emph{actual}
|
||
(derived) type of the object rather than the @emph{declared} type, using
|
||
the virtual function table. Note that the virtual function table is
|
||
required---this feature can only work for objects that have run-time
|
||
type identification; a single virtual method in the object's declared
|
||
type is sufficient. Note that this setting is also taken into account when
|
||
working with variable objects via MI (@pxref{GDB/MI}).
|
||
|
||
@item set print object off
|
||
Display only the declared type of objects, without reference to the
|
||
virtual function table. This is the default setting.
|
||
|
||
@item show print object
|
||
Show whether actual, or declared, object types are displayed.
|
||
|
||
@item set print static-members
|
||
@itemx set print static-members on
|
||
@cindex static members of C@t{++} objects
|
||
Print static members when displaying a C@t{++} object. The default is on.
|
||
|
||
@item set print static-members off
|
||
Do not print static members when displaying a C@t{++} object.
|
||
|
||
@item show print static-members
|
||
Show whether C@t{++} static members are printed or not.
|
||
|
||
@item set print pascal_static-members
|
||
@itemx set print pascal_static-members on
|
||
@cindex static members of Pascal objects
|
||
@cindex Pascal objects, static members display
|
||
Print static members when displaying a Pascal object. The default is on.
|
||
|
||
@item set print pascal_static-members off
|
||
Do not print static members when displaying a Pascal object.
|
||
|
||
@item show print pascal_static-members
|
||
Show whether Pascal static members are printed or not.
|
||
|
||
@c These don't work with HP ANSI C++ yet.
|
||
@item set print vtbl
|
||
@itemx set print vtbl on
|
||
@cindex pretty print C@t{++} virtual function tables
|
||
@cindex virtual functions (C@t{++}) display
|
||
@cindex VTBL display
|
||
Pretty print C@t{++} virtual function tables. The default is off.
|
||
(The @code{vtbl} commands do not work on programs compiled with the HP
|
||
ANSI C@t{++} compiler (@code{aCC}).)
|
||
|
||
@item set print vtbl off
|
||
Do not pretty print C@t{++} virtual function tables.
|
||
|
||
@item show print vtbl
|
||
Show whether C@t{++} virtual function tables are pretty printed, or not.
|
||
@end table
|
||
|
||
@node Pretty Printing
|
||
@section Pretty Printing
|
||
|
||
@value{GDBN} provides a mechanism to allow pretty-printing of values using
|
||
Python code. It greatly simplifies the display of complex objects. This
|
||
mechanism works for both MI and the CLI.
|
||
|
||
@menu
|
||
* Pretty-Printer Introduction:: Introduction to pretty-printers
|
||
* Pretty-Printer Example:: An example pretty-printer
|
||
* Pretty-Printer Commands:: Pretty-printer commands
|
||
@end menu
|
||
|
||
@node Pretty-Printer Introduction
|
||
@subsection Pretty-Printer Introduction
|
||
|
||
When @value{GDBN} prints a value, it first sees if there is a pretty-printer
|
||
registered for the value. If there is then @value{GDBN} invokes the
|
||
pretty-printer to print the value. Otherwise the value is printed normally.
|
||
|
||
Pretty-printers are normally named. This makes them easy to manage.
|
||
The @samp{info pretty-printer} command will list all the installed
|
||
pretty-printers with their names.
|
||
If a pretty-printer can handle multiple data types, then its
|
||
@dfn{subprinters} are the printers for the individual data types.
|
||
Each such subprinter has its own name.
|
||
The format of the name is @var{printer-name};@var{subprinter-name}.
|
||
|
||
Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
|
||
Typically they are automatically loaded and registered when the corresponding
|
||
debug information is loaded, thus making them available without having to
|
||
do anything special.
|
||
|
||
There are three places where a pretty-printer can be registered.
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Pretty-printers registered globally are available when debugging
|
||
all inferiors.
|
||
|
||
@item
|
||
Pretty-printers registered with a program space are available only
|
||
when debugging that program.
|
||
@xref{Progspaces In Python}, for more details on program spaces in Python.
|
||
|
||
@item
|
||
Pretty-printers registered with an objfile are loaded and unloaded
|
||
with the corresponding objfile (e.g., shared library).
|
||
@xref{Objfiles In Python}, for more details on objfiles in Python.
|
||
@end itemize
|
||
|
||
@xref{Selecting Pretty-Printers}, for further information on how
|
||
pretty-printers are selected,
|
||
|
||
@xref{Writing a Pretty-Printer}, for implementing pretty printers
|
||
for new types.
|
||
|
||
@node Pretty-Printer Example
|
||
@subsection Pretty-Printer Example
|
||
|
||
Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print s
|
||
$1 = @{
|
||
static npos = 4294967295,
|
||
_M_dataplus = @{
|
||
<std::allocator<char>> = @{
|
||
<__gnu_cxx::new_allocator<char>> = @{
|
||
<No data fields>@}, <No data fields>
|
||
@},
|
||
members of std::basic_string<char, std::char_traits<char>,
|
||
std::allocator<char> >::_Alloc_hider:
|
||
_M_p = 0x804a014 "abcd"
|
||
@}
|
||
@}
|
||
@end smallexample
|
||
|
||
With a pretty-printer for @code{std::string} only the contents are printed:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print s
|
||
$2 = "abcd"
|
||
@end smallexample
|
||
|
||
@node Pretty-Printer Commands
|
||
@subsection Pretty-Printer Commands
|
||
@cindex pretty-printer commands
|
||
|
||
@table @code
|
||
@kindex info pretty-printer
|
||
@item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
|
||
Print the list of installed pretty-printers.
|
||
This includes disabled pretty-printers, which are marked as such.
|
||
|
||
@var{object-regexp} is a regular expression matching the objects
|
||
whose pretty-printers to list.
|
||
Objects can be @code{global}, the program space's file
|
||
(@pxref{Progspaces In Python}),
|
||
and the object files within that program space (@pxref{Objfiles In Python}).
|
||
@xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
|
||
looks up a printer from these three objects.
|
||
|
||
@var{name-regexp} is a regular expression matching the name of the printers
|
||
to list.
|
||
|
||
@kindex disable pretty-printer
|
||
@item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
|
||
Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
|
||
A disabled pretty-printer is not forgotten, it may be enabled again later.
|
||
|
||
@kindex enable pretty-printer
|
||
@item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
|
||
Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
|
||
@end table
|
||
|
||
Example:
|
||
|
||
Suppose we have three pretty-printers installed: one from library1.so
|
||
named @code{foo} that prints objects of type @code{foo}, and
|
||
another from library2.so named @code{bar} that prints two types of objects,
|
||
@code{bar1} and @code{bar2}.
|
||
|
||
@smallexample
|
||
(gdb) info pretty-printer
|
||
library1.so:
|
||
foo
|
||
library2.so:
|
||
bar
|
||
bar1
|
||
bar2
|
||
(gdb) info pretty-printer library2
|
||
library2.so:
|
||
bar
|
||
bar1
|
||
bar2
|
||
(gdb) disable pretty-printer library1
|
||
1 printer disabled
|
||
2 of 3 printers enabled
|
||
(gdb) info pretty-printer
|
||
library1.so:
|
||
foo [disabled]
|
||
library2.so:
|
||
bar
|
||
bar1
|
||
bar2
|
||
(gdb) disable pretty-printer library2 bar:bar1
|
||
1 printer disabled
|
||
1 of 3 printers enabled
|
||
(gdb) info pretty-printer library2
|
||
library1.so:
|
||
foo [disabled]
|
||
library2.so:
|
||
bar
|
||
bar1 [disabled]
|
||
bar2
|
||
(gdb) disable pretty-printer library2 bar
|
||
1 printer disabled
|
||
0 of 3 printers enabled
|
||
(gdb) info pretty-printer library2
|
||
library1.so:
|
||
foo [disabled]
|
||
library2.so:
|
||
bar [disabled]
|
||
bar1 [disabled]
|
||
bar2
|
||
@end smallexample
|
||
|
||
Note that for @code{bar} the entire printer can be disabled,
|
||
as can each individual subprinter.
|
||
|
||
@node Value History
|
||
@section Value History
|
||
|
||
@cindex value history
|
||
@cindex history of values printed by @value{GDBN}
|
||
Values printed by the @code{print} command are saved in the @value{GDBN}
|
||
@dfn{value history}. This allows you to refer to them in other expressions.
|
||
Values are kept until the symbol table is re-read or discarded
|
||
(for example with the @code{file} or @code{symbol-file} commands).
|
||
When the symbol table changes, the value history is discarded,
|
||
since the values may contain pointers back to the types defined in the
|
||
symbol table.
|
||
|
||
@cindex @code{$}
|
||
@cindex @code{$$}
|
||
@cindex history number
|
||
The values printed are given @dfn{history numbers} by which you can
|
||
refer to them. These are successive integers starting with one.
|
||
@code{print} shows you the history number assigned to a value by
|
||
printing @samp{$@var{num} = } before the value; here @var{num} is the
|
||
history number.
|
||
|
||
To refer to any previous value, use @samp{$} followed by the value's
|
||
history number. The way @code{print} labels its output is designed to
|
||
remind you of this. Just @code{$} refers to the most recent value in
|
||
the history, and @code{$$} refers to the value before that.
|
||
@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
|
||
is the value just prior to @code{$$}, @code{$$1} is equivalent to
|
||
@code{$$}, and @code{$$0} is equivalent to @code{$}.
|
||
|
||
For example, suppose you have just printed a pointer to a structure and
|
||
want to see the contents of the structure. It suffices to type
|
||
|
||
@smallexample
|
||
p *$
|
||
@end smallexample
|
||
|
||
If you have a chain of structures where the component @code{next} points
|
||
to the next one, you can print the contents of the next one with this:
|
||
|
||
@smallexample
|
||
p *$.next
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can print successive links in the chain by repeating this
|
||
command---which you can do by just typing @key{RET}.
|
||
|
||
Note that the history records values, not expressions. If the value of
|
||
@code{x} is 4 and you type these commands:
|
||
|
||
@smallexample
|
||
print x
|
||
set x=5
|
||
@end smallexample
|
||
|
||
@noindent
|
||
then the value recorded in the value history by the @code{print} command
|
||
remains 4 even though the value of @code{x} has changed.
|
||
|
||
@table @code
|
||
@kindex show values
|
||
@item show values
|
||
Print the last ten values in the value history, with their item numbers.
|
||
This is like @samp{p@ $$9} repeated ten times, except that @code{show
|
||
values} does not change the history.
|
||
|
||
@item show values @var{n}
|
||
Print ten history values centered on history item number @var{n}.
|
||
|
||
@item show values +
|
||
Print ten history values just after the values last printed. If no more
|
||
values are available, @code{show values +} produces no display.
|
||
@end table
|
||
|
||
Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
|
||
same effect as @samp{show values +}.
|
||
|
||
@node Convenience Vars
|
||
@section Convenience Variables
|
||
|
||
@cindex convenience variables
|
||
@cindex user-defined variables
|
||
@value{GDBN} provides @dfn{convenience variables} that you can use within
|
||
@value{GDBN} to hold on to a value and refer to it later. These variables
|
||
exist entirely within @value{GDBN}; they are not part of your program, and
|
||
setting a convenience variable has no direct effect on further execution
|
||
of your program. That is why you can use them freely.
|
||
|
||
Convenience variables are prefixed with @samp{$}. Any name preceded by
|
||
@samp{$} can be used for a convenience variable, unless it is one of
|
||
the predefined machine-specific register names (@pxref{Registers, ,Registers}).
|
||
(Value history references, in contrast, are @emph{numbers} preceded
|
||
by @samp{$}. @xref{Value History, ,Value History}.)
|
||
|
||
You can save a value in a convenience variable with an assignment
|
||
expression, just as you would set a variable in your program.
|
||
For example:
|
||
|
||
@smallexample
|
||
set $foo = *object_ptr
|
||
@end smallexample
|
||
|
||
@noindent
|
||
would save in @code{$foo} the value contained in the object pointed to by
|
||
@code{object_ptr}.
|
||
|
||
Using a convenience variable for the first time creates it, but its
|
||
value is @code{void} until you assign a new value. You can alter the
|
||
value with another assignment at any time.
|
||
|
||
Convenience variables have no fixed types. You can assign a convenience
|
||
variable any type of value, including structures and arrays, even if
|
||
that variable already has a value of a different type. The convenience
|
||
variable, when used as an expression, has the type of its current value.
|
||
|
||
@table @code
|
||
@kindex show convenience
|
||
@cindex show all user variables and functions
|
||
@item show convenience
|
||
Print a list of convenience variables used so far, and their values,
|
||
as well as a list of the convenience functions.
|
||
Abbreviated @code{show conv}.
|
||
|
||
@kindex init-if-undefined
|
||
@cindex convenience variables, initializing
|
||
@item init-if-undefined $@var{variable} = @var{expression}
|
||
Set a convenience variable if it has not already been set. This is useful
|
||
for user-defined commands that keep some state. It is similar, in concept,
|
||
to using local static variables with initializers in C (except that
|
||
convenience variables are global). It can also be used to allow users to
|
||
override default values used in a command script.
|
||
|
||
If the variable is already defined then the expression is not evaluated so
|
||
any side-effects do not occur.
|
||
@end table
|
||
|
||
One of the ways to use a convenience variable is as a counter to be
|
||
incremented or a pointer to be advanced. For example, to print
|
||
a field from successive elements of an array of structures:
|
||
|
||
@smallexample
|
||
set $i = 0
|
||
print bar[$i++]->contents
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Repeat that command by typing @key{RET}.
|
||
|
||
Some convenience variables are created automatically by @value{GDBN} and given
|
||
values likely to be useful.
|
||
|
||
@table @code
|
||
@vindex $_@r{, convenience variable}
|
||
@item $_
|
||
The variable @code{$_} is automatically set by the @code{x} command to
|
||
the last address examined (@pxref{Memory, ,Examining Memory}). Other
|
||
commands which provide a default address for @code{x} to examine also
|
||
set @code{$_} to that address; these commands include @code{info line}
|
||
and @code{info breakpoint}. The type of @code{$_} is @code{void *}
|
||
except when set by the @code{x} command, in which case it is a pointer
|
||
to the type of @code{$__}.
|
||
|
||
@vindex $__@r{, convenience variable}
|
||
@item $__
|
||
The variable @code{$__} is automatically set by the @code{x} command
|
||
to the value found in the last address examined. Its type is chosen
|
||
to match the format in which the data was printed.
|
||
|
||
@item $_exitcode
|
||
@vindex $_exitcode@r{, convenience variable}
|
||
When the program being debugged terminates normally, @value{GDBN}
|
||
automatically sets this variable to the exit code of the program, and
|
||
resets @code{$_exitsignal} to @code{void}.
|
||
|
||
@item $_exitsignal
|
||
@vindex $_exitsignal@r{, convenience variable}
|
||
When the program being debugged dies due to an uncaught signal,
|
||
@value{GDBN} automatically sets this variable to that signal's number,
|
||
and resets @code{$_exitcode} to @code{void}.
|
||
|
||
To distinguish between whether the program being debugged has exited
|
||
(i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
|
||
@code{$_exitsignal} is not @code{void}), the convenience function
|
||
@code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
|
||
Functions}). For example, considering the following source code:
|
||
|
||
@smallexample
|
||
#include <signal.h>
|
||
|
||
int
|
||
main (int argc, char *argv[])
|
||
@{
|
||
raise (SIGALRM);
|
||
return 0;
|
||
@}
|
||
@end smallexample
|
||
|
||
A valid way of telling whether the program being debugged has exited
|
||
or signalled would be:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) define has_exited_or_signalled
|
||
Type commands for definition of ``has_exited_or_signalled''.
|
||
End with a line saying just ``end''.
|
||
>if $_isvoid ($_exitsignal)
|
||
>echo The program has exited\n
|
||
>else
|
||
>echo The program has signalled\n
|
||
>end
|
||
>end
|
||
(@value{GDBP}) run
|
||
Starting program:
|
||
|
||
Program terminated with signal SIGALRM, Alarm clock.
|
||
The program no longer exists.
|
||
(@value{GDBP}) has_exited_or_signalled
|
||
The program has signalled
|
||
@end smallexample
|
||
|
||
As can be seen, @value{GDBN} correctly informs that the program being
|
||
debugged has signalled, since it calls @code{raise} and raises a
|
||
@code{SIGALRM} signal. If the program being debugged had not called
|
||
@code{raise}, then @value{GDBN} would report a normal exit:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) has_exited_or_signalled
|
||
The program has exited
|
||
@end smallexample
|
||
|
||
@item $_exception
|
||
The variable @code{$_exception} is set to the exception object being
|
||
thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
|
||
|
||
@item $_probe_argc
|
||
@itemx $_probe_arg0@dots{}$_probe_arg11
|
||
Arguments to a static probe. @xref{Static Probe Points}.
|
||
|
||
@item $_sdata
|
||
@vindex $_sdata@r{, inspect, convenience variable}
|
||
The variable @code{$_sdata} contains extra collected static tracepoint
|
||
data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
|
||
@code{$_sdata} could be empty, if not inspecting a trace buffer, or
|
||
if extra static tracepoint data has not been collected.
|
||
|
||
@item $_siginfo
|
||
@vindex $_siginfo@r{, convenience variable}
|
||
The variable @code{$_siginfo} contains extra signal information
|
||
(@pxref{extra signal information}). Note that @code{$_siginfo}
|
||
could be empty, if the application has not yet received any signals.
|
||
For example, it will be empty before you execute the @code{run} command.
|
||
|
||
@item $_tlb
|
||
@vindex $_tlb@r{, convenience variable}
|
||
The variable @code{$_tlb} is automatically set when debugging
|
||
applications running on MS-Windows in native mode or connected to
|
||
gdbserver that supports the @code{qGetTIBAddr} request.
|
||
@xref{General Query Packets}.
|
||
This variable contains the address of the thread information block.
|
||
|
||
@item $_inferior
|
||
The number of the current inferior. @xref{Inferiors and
|
||
Programs, ,Debugging Multiple Inferiors and Programs}.
|
||
|
||
@item $_thread
|
||
The thread number of the current thread. @xref{thread numbers}.
|
||
|
||
@item $_gthread
|
||
The global number of the current thread. @xref{global thread numbers}.
|
||
|
||
@end table
|
||
|
||
@node Convenience Funs
|
||
@section Convenience Functions
|
||
|
||
@cindex convenience functions
|
||
@value{GDBN} also supplies some @dfn{convenience functions}. These
|
||
have a syntax similar to convenience variables. A convenience
|
||
function can be used in an expression just like an ordinary function;
|
||
however, a convenience function is implemented internally to
|
||
@value{GDBN}.
|
||
|
||
These functions do not require @value{GDBN} to be configured with
|
||
@code{Python} support, which means that they are always available.
|
||
|
||
@table @code
|
||
|
||
@item $_isvoid (@var{expr})
|
||
@findex $_isvoid@r{, convenience function}
|
||
Return one if the expression @var{expr} is @code{void}. Otherwise it
|
||
returns zero.
|
||
|
||
A @code{void} expression is an expression where the type of the result
|
||
is @code{void}. For example, you can examine a convenience variable
|
||
(see @ref{Convenience Vars,, Convenience Variables}) to check whether
|
||
it is @code{void}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print $_exitcode
|
||
$1 = void
|
||
(@value{GDBP}) print $_isvoid ($_exitcode)
|
||
$2 = 1
|
||
(@value{GDBP}) run
|
||
Starting program: ./a.out
|
||
[Inferior 1 (process 29572) exited normally]
|
||
(@value{GDBP}) print $_exitcode
|
||
$3 = 0
|
||
(@value{GDBP}) print $_isvoid ($_exitcode)
|
||
$4 = 0
|
||
@end smallexample
|
||
|
||
In the example above, we used @code{$_isvoid} to check whether
|
||
@code{$_exitcode} is @code{void} before and after the execution of the
|
||
program being debugged. Before the execution there is no exit code to
|
||
be examined, therefore @code{$_exitcode} is @code{void}. After the
|
||
execution the program being debugged returned zero, therefore
|
||
@code{$_exitcode} is zero, which means that it is not @code{void}
|
||
anymore.
|
||
|
||
The @code{void} expression can also be a call of a function from the
|
||
program being debugged. For example, given the following function:
|
||
|
||
@smallexample
|
||
void
|
||
foo (void)
|
||
@{
|
||
@}
|
||
@end smallexample
|
||
|
||
The result of calling it inside @value{GDBN} is @code{void}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print foo ()
|
||
$1 = void
|
||
(@value{GDBP}) print $_isvoid (foo ())
|
||
$2 = 1
|
||
(@value{GDBP}) set $v = foo ()
|
||
(@value{GDBP}) print $v
|
||
$3 = void
|
||
(@value{GDBP}) print $_isvoid ($v)
|
||
$4 = 1
|
||
@end smallexample
|
||
|
||
@end table
|
||
|
||
These functions require @value{GDBN} to be configured with
|
||
@code{Python} support.
|
||
|
||
@table @code
|
||
|
||
@item $_memeq(@var{buf1}, @var{buf2}, @var{length})
|
||
@findex $_memeq@r{, convenience function}
|
||
Returns one if the @var{length} bytes at the addresses given by
|
||
@var{buf1} and @var{buf2} are equal.
|
||
Otherwise it returns zero.
|
||
|
||
@item $_regex(@var{str}, @var{regex})
|
||
@findex $_regex@r{, convenience function}
|
||
Returns one if the string @var{str} matches the regular expression
|
||
@var{regex}. Otherwise it returns zero.
|
||
The syntax of the regular expression is that specified by @code{Python}'s
|
||
regular expression support.
|
||
|
||
@item $_streq(@var{str1}, @var{str2})
|
||
@findex $_streq@r{, convenience function}
|
||
Returns one if the strings @var{str1} and @var{str2} are equal.
|
||
Otherwise it returns zero.
|
||
|
||
@item $_strlen(@var{str})
|
||
@findex $_strlen@r{, convenience function}
|
||
Returns the length of string @var{str}.
|
||
|
||
@item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
|
||
@findex $_caller_is@r{, convenience function}
|
||
Returns one if the calling function's name is equal to @var{name}.
|
||
Otherwise it returns zero.
|
||
|
||
If the optional argument @var{number_of_frames} is provided,
|
||
it is the number of frames up in the stack to look.
|
||
The default is 1.
|
||
|
||
Example:
|
||
|
||
@smallexample
|
||
(gdb) backtrace
|
||
#0 bottom_func ()
|
||
at testsuite/gdb.python/py-caller-is.c:21
|
||
#1 0x00000000004005a0 in middle_func ()
|
||
at testsuite/gdb.python/py-caller-is.c:27
|
||
#2 0x00000000004005ab in top_func ()
|
||
at testsuite/gdb.python/py-caller-is.c:33
|
||
#3 0x00000000004005b6 in main ()
|
||
at testsuite/gdb.python/py-caller-is.c:39
|
||
(gdb) print $_caller_is ("middle_func")
|
||
$1 = 1
|
||
(gdb) print $_caller_is ("top_func", 2)
|
||
$1 = 1
|
||
@end smallexample
|
||
|
||
@item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
|
||
@findex $_caller_matches@r{, convenience function}
|
||
Returns one if the calling function's name matches the regular expression
|
||
@var{regexp}. Otherwise it returns zero.
|
||
|
||
If the optional argument @var{number_of_frames} is provided,
|
||
it is the number of frames up in the stack to look.
|
||
The default is 1.
|
||
|
||
@item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
|
||
@findex $_any_caller_is@r{, convenience function}
|
||
Returns one if any calling function's name is equal to @var{name}.
|
||
Otherwise it returns zero.
|
||
|
||
If the optional argument @var{number_of_frames} is provided,
|
||
it is the number of frames up in the stack to look.
|
||
The default is 1.
|
||
|
||
This function differs from @code{$_caller_is} in that this function
|
||
checks all stack frames from the immediate caller to the frame specified
|
||
by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
|
||
frame specified by @var{number_of_frames}.
|
||
|
||
@item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
|
||
@findex $_any_caller_matches@r{, convenience function}
|
||
Returns one if any calling function's name matches the regular expression
|
||
@var{regexp}. Otherwise it returns zero.
|
||
|
||
If the optional argument @var{number_of_frames} is provided,
|
||
it is the number of frames up in the stack to look.
|
||
The default is 1.
|
||
|
||
This function differs from @code{$_caller_matches} in that this function
|
||
checks all stack frames from the immediate caller to the frame specified
|
||
by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
|
||
frame specified by @var{number_of_frames}.
|
||
|
||
@item $_as_string(@var{value})
|
||
@findex $_as_string@r{, convenience function}
|
||
Return the string representation of @var{value}.
|
||
|
||
This function is useful to obtain the textual label (enumerator) of an
|
||
enumeration value. For example, assuming the variable @var{node} is of
|
||
an enumerated type:
|
||
|
||
@smallexample
|
||
(gdb) printf "Visiting node of type %s\n", $_as_string(node)
|
||
Visiting node of type NODE_INTEGER
|
||
@end smallexample
|
||
|
||
@end table
|
||
|
||
@value{GDBN} provides the ability to list and get help on
|
||
convenience functions.
|
||
|
||
@table @code
|
||
@item help function
|
||
@kindex help function
|
||
@cindex show all convenience functions
|
||
Print a list of all convenience functions.
|
||
@end table
|
||
|
||
@node Registers
|
||
@section Registers
|
||
|
||
@cindex registers
|
||
You can refer to machine register contents, in expressions, as variables
|
||
with names starting with @samp{$}. The names of registers are different
|
||
for each machine; use @code{info registers} to see the names used on
|
||
your machine.
|
||
|
||
@table @code
|
||
@kindex info registers
|
||
@item info registers
|
||
Print the names and values of all registers except floating-point
|
||
and vector registers (in the selected stack frame).
|
||
|
||
@kindex info all-registers
|
||
@cindex floating point registers
|
||
@item info all-registers
|
||
Print the names and values of all registers, including floating-point
|
||
and vector registers (in the selected stack frame).
|
||
|
||
@item info registers @var{reggroup} @dots{}
|
||
Print the name and value of the registers in each of the specified
|
||
@var{reggroup}s. The @var{reggoup} can be any of those returned by
|
||
@code{maint print reggroups} (@pxref{Maintenance Commands}).
|
||
|
||
@item info registers @var{regname} @dots{}
|
||
Print the @dfn{relativized} value of each specified register @var{regname}.
|
||
As discussed in detail below, register values are normally relative to
|
||
the selected stack frame. The @var{regname} may be any register name valid on
|
||
the machine you are using, with or without the initial @samp{$}.
|
||
@end table
|
||
|
||
@anchor{standard registers}
|
||
@cindex stack pointer register
|
||
@cindex program counter register
|
||
@cindex process status register
|
||
@cindex frame pointer register
|
||
@cindex standard registers
|
||
@value{GDBN} has four ``standard'' register names that are available (in
|
||
expressions) on most machines---whenever they do not conflict with an
|
||
architecture's canonical mnemonics for registers. The register names
|
||
@code{$pc} and @code{$sp} are used for the program counter register and
|
||
the stack pointer. @code{$fp} is used for a register that contains a
|
||
pointer to the current stack frame, and @code{$ps} is used for a
|
||
register that contains the processor status. For example,
|
||
you could print the program counter in hex with
|
||
|
||
@smallexample
|
||
p/x $pc
|
||
@end smallexample
|
||
|
||
@noindent
|
||
or print the instruction to be executed next with
|
||
|
||
@smallexample
|
||
x/i $pc
|
||
@end smallexample
|
||
|
||
@noindent
|
||
or add four to the stack pointer@footnote{This is a way of removing
|
||
one word from the stack, on machines where stacks grow downward in
|
||
memory (most machines, nowadays). This assumes that the innermost
|
||
stack frame is selected; setting @code{$sp} is not allowed when other
|
||
stack frames are selected. To pop entire frames off the stack,
|
||
regardless of machine architecture, use @code{return};
|
||
see @ref{Returning, ,Returning from a Function}.} with
|
||
|
||
@smallexample
|
||
set $sp += 4
|
||
@end smallexample
|
||
|
||
Whenever possible, these four standard register names are available on
|
||
your machine even though the machine has different canonical mnemonics,
|
||
so long as there is no conflict. The @code{info registers} command
|
||
shows the canonical names. For example, on the SPARC, @code{info
|
||
registers} displays the processor status register as @code{$psr} but you
|
||
can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
|
||
is an alias for the @sc{eflags} register.
|
||
|
||
@value{GDBN} always considers the contents of an ordinary register as an
|
||
integer when the register is examined in this way. Some machines have
|
||
special registers which can hold nothing but floating point; these
|
||
registers are considered to have floating point values. There is no way
|
||
to refer to the contents of an ordinary register as floating point value
|
||
(although you can @emph{print} it as a floating point value with
|
||
@samp{print/f $@var{regname}}).
|
||
|
||
Some registers have distinct ``raw'' and ``virtual'' data formats. This
|
||
means that the data format in which the register contents are saved by
|
||
the operating system is not the same one that your program normally
|
||
sees. For example, the registers of the 68881 floating point
|
||
coprocessor are always saved in ``extended'' (raw) format, but all C
|
||
programs expect to work with ``double'' (virtual) format. In such
|
||
cases, @value{GDBN} normally works with the virtual format only (the format
|
||
that makes sense for your program), but the @code{info registers} command
|
||
prints the data in both formats.
|
||
|
||
@cindex SSE registers (x86)
|
||
@cindex MMX registers (x86)
|
||
Some machines have special registers whose contents can be interpreted
|
||
in several different ways. For example, modern x86-based machines
|
||
have SSE and MMX registers that can hold several values packed
|
||
together in several different formats. @value{GDBN} refers to such
|
||
registers in @code{struct} notation:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print $xmm1
|
||
$1 = @{
|
||
v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
|
||
v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
|
||
v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
|
||
v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
|
||
v4_int32 = @{0, 20657912, 11, 13@},
|
||
v2_int64 = @{88725056443645952, 55834574859@},
|
||
uint128 = 0x0000000d0000000b013b36f800000000
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
To set values of such registers, you need to tell @value{GDBN} which
|
||
view of the register you wish to change, as if you were assigning
|
||
value to a @code{struct} member:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
|
||
@end smallexample
|
||
|
||
Normally, register values are relative to the selected stack frame
|
||
(@pxref{Selection, ,Selecting a Frame}). This means that you get the
|
||
value that the register would contain if all stack frames farther in
|
||
were exited and their saved registers restored. In order to see the
|
||
true contents of hardware registers, you must select the innermost
|
||
frame (with @samp{frame 0}).
|
||
|
||
@cindex caller-saved registers
|
||
@cindex call-clobbered registers
|
||
@cindex volatile registers
|
||
@cindex <not saved> values
|
||
Usually ABIs reserve some registers as not needed to be saved by the
|
||
callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
|
||
registers). It may therefore not be possible for @value{GDBN} to know
|
||
the value a register had before the call (in other words, in the outer
|
||
frame), if the register value has since been changed by the callee.
|
||
@value{GDBN} tries to deduce where the inner frame saved
|
||
(``callee-saved'') registers, from the debug info, unwind info, or the
|
||
machine code generated by your compiler. If some register is not
|
||
saved, and @value{GDBN} knows the register is ``caller-saved'' (via
|
||
its own knowledge of the ABI, or because the debug/unwind info
|
||
explicitly says the register's value is undefined), @value{GDBN}
|
||
displays @w{@samp{<not saved>}} as the register's value. With targets
|
||
that @value{GDBN} has no knowledge of the register saving convention,
|
||
if a register was not saved by the callee, then its value and location
|
||
in the outer frame are assumed to be the same of the inner frame.
|
||
This is usually harmless, because if the register is call-clobbered,
|
||
the caller either does not care what is in the register after the
|
||
call, or has code to restore the value that it does care about. Note,
|
||
however, that if you change such a register in the outer frame, you
|
||
may also be affecting the inner frame. Also, the more ``outer'' the
|
||
frame is you're looking at, the more likely a call-clobbered
|
||
register's value is to be wrong, in the sense that it doesn't actually
|
||
represent the value the register had just before the call.
|
||
|
||
@node Floating Point Hardware
|
||
@section Floating Point Hardware
|
||
@cindex floating point
|
||
|
||
Depending on the configuration, @value{GDBN} may be able to give
|
||
you more information about the status of the floating point hardware.
|
||
|
||
@table @code
|
||
@kindex info float
|
||
@item info float
|
||
Display hardware-dependent information about the floating
|
||
point unit. The exact contents and layout vary depending on the
|
||
floating point chip. Currently, @samp{info float} is supported on
|
||
the ARM and x86 machines.
|
||
@end table
|
||
|
||
@node Vector Unit
|
||
@section Vector Unit
|
||
@cindex vector unit
|
||
|
||
Depending on the configuration, @value{GDBN} may be able to give you
|
||
more information about the status of the vector unit.
|
||
|
||
@table @code
|
||
@kindex info vector
|
||
@item info vector
|
||
Display information about the vector unit. The exact contents and
|
||
layout vary depending on the hardware.
|
||
@end table
|
||
|
||
@node OS Information
|
||
@section Operating System Auxiliary Information
|
||
@cindex OS information
|
||
|
||
@value{GDBN} provides interfaces to useful OS facilities that can help
|
||
you debug your program.
|
||
|
||
@cindex auxiliary vector
|
||
@cindex vector, auxiliary
|
||
Some operating systems supply an @dfn{auxiliary vector} to programs at
|
||
startup. This is akin to the arguments and environment that you
|
||
specify for a program, but contains a system-dependent variety of
|
||
binary values that tell system libraries important details about the
|
||
hardware, operating system, and process. Each value's purpose is
|
||
identified by an integer tag; the meanings are well-known but system-specific.
|
||
Depending on the configuration and operating system facilities,
|
||
@value{GDBN} may be able to show you this information. For remote
|
||
targets, this functionality may further depend on the remote stub's
|
||
support of the @samp{qXfer:auxv:read} packet, see
|
||
@ref{qXfer auxiliary vector read}.
|
||
|
||
@table @code
|
||
@kindex info auxv
|
||
@item info auxv
|
||
Display the auxiliary vector of the inferior, which can be either a
|
||
live process or a core dump file. @value{GDBN} prints each tag value
|
||
numerically, and also shows names and text descriptions for recognized
|
||
tags. Some values in the vector are numbers, some bit masks, and some
|
||
pointers to strings or other data. @value{GDBN} displays each value in the
|
||
most appropriate form for a recognized tag, and in hexadecimal for
|
||
an unrecognized tag.
|
||
@end table
|
||
|
||
On some targets, @value{GDBN} can access operating system-specific
|
||
information and show it to you. The types of information available
|
||
will differ depending on the type of operating system running on the
|
||
target. The mechanism used to fetch the data is described in
|
||
@ref{Operating System Information}. For remote targets, this
|
||
functionality depends on the remote stub's support of the
|
||
@samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
|
||
|
||
@table @code
|
||
@kindex info os
|
||
@item info os @var{infotype}
|
||
|
||
Display OS information of the requested type.
|
||
|
||
On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
|
||
|
||
@anchor{linux info os infotypes}
|
||
@table @code
|
||
@kindex info os cpus
|
||
@item cpus
|
||
Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
|
||
the available fields from /proc/cpuinfo. For each supported architecture
|
||
different fields are available. Two common entries are processor which gives
|
||
CPU number and bogomips; a system constant that is calculated during
|
||
kernel initialization.
|
||
|
||
@kindex info os files
|
||
@item files
|
||
Display the list of open file descriptors on the target. For each
|
||
file descriptor, @value{GDBN} prints the identifier of the process
|
||
owning the descriptor, the command of the owning process, the value
|
||
of the descriptor, and the target of the descriptor.
|
||
|
||
@kindex info os modules
|
||
@item modules
|
||
Display the list of all loaded kernel modules on the target. For each
|
||
module, @value{GDBN} prints the module name, the size of the module in
|
||
bytes, the number of times the module is used, the dependencies of the
|
||
module, the status of the module, and the address of the loaded module
|
||
in memory.
|
||
|
||
@kindex info os msg
|
||
@item msg
|
||
Display the list of all System V message queues on the target. For each
|
||
message queue, @value{GDBN} prints the message queue key, the message
|
||
queue identifier, the access permissions, the current number of bytes
|
||
on the queue, the current number of messages on the queue, the processes
|
||
that last sent and received a message on the queue, the user and group
|
||
of the owner and creator of the message queue, the times at which a
|
||
message was last sent and received on the queue, and the time at which
|
||
the message queue was last changed.
|
||
|
||
@kindex info os processes
|
||
@item processes
|
||
Display the list of processes on the target. For each process,
|
||
@value{GDBN} prints the process identifier, the name of the user, the
|
||
command corresponding to the process, and the list of processor cores
|
||
that the process is currently running on. (To understand what these
|
||
properties mean, for this and the following info types, please consult
|
||
the general @sc{gnu}/Linux documentation.)
|
||
|
||
@kindex info os procgroups
|
||
@item procgroups
|
||
Display the list of process groups on the target. For each process,
|
||
@value{GDBN} prints the identifier of the process group that it belongs
|
||
to, the command corresponding to the process group leader, the process
|
||
identifier, and the command line of the process. The list is sorted
|
||
first by the process group identifier, then by the process identifier,
|
||
so that processes belonging to the same process group are grouped together
|
||
and the process group leader is listed first.
|
||
|
||
@kindex info os semaphores
|
||
@item semaphores
|
||
Display the list of all System V semaphore sets on the target. For each
|
||
semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
|
||
set identifier, the access permissions, the number of semaphores in the
|
||
set, the user and group of the owner and creator of the semaphore set,
|
||
and the times at which the semaphore set was operated upon and changed.
|
||
|
||
@kindex info os shm
|
||
@item shm
|
||
Display the list of all System V shared-memory regions on the target.
|
||
For each shared-memory region, @value{GDBN} prints the region key,
|
||
the shared-memory identifier, the access permissions, the size of the
|
||
region, the process that created the region, the process that last
|
||
attached to or detached from the region, the current number of live
|
||
attaches to the region, and the times at which the region was last
|
||
attached to, detach from, and changed.
|
||
|
||
@kindex info os sockets
|
||
@item sockets
|
||
Display the list of Internet-domain sockets on the target. For each
|
||
socket, @value{GDBN} prints the address and port of the local and
|
||
remote endpoints, the current state of the connection, the creator of
|
||
the socket, the IP address family of the socket, and the type of the
|
||
connection.
|
||
|
||
@kindex info os threads
|
||
@item threads
|
||
Display the list of threads running on the target. For each thread,
|
||
@value{GDBN} prints the identifier of the process that the thread
|
||
belongs to, the command of the process, the thread identifier, and the
|
||
processor core that it is currently running on. The main thread of a
|
||
process is not listed.
|
||
@end table
|
||
|
||
@item info os
|
||
If @var{infotype} is omitted, then list the possible values for
|
||
@var{infotype} and the kind of OS information available for each
|
||
@var{infotype}. If the target does not return a list of possible
|
||
types, this command will report an error.
|
||
@end table
|
||
|
||
@node Memory Region Attributes
|
||
@section Memory Region Attributes
|
||
@cindex memory region attributes
|
||
|
||
@dfn{Memory region attributes} allow you to describe special handling
|
||
required by regions of your target's memory. @value{GDBN} uses
|
||
attributes to determine whether to allow certain types of memory
|
||
accesses; whether to use specific width accesses; and whether to cache
|
||
target memory. By default the description of memory regions is
|
||
fetched from the target (if the current target supports this), but the
|
||
user can override the fetched regions.
|
||
|
||
Defined memory regions can be individually enabled and disabled. When a
|
||
memory region is disabled, @value{GDBN} uses the default attributes when
|
||
accessing memory in that region. Similarly, if no memory regions have
|
||
been defined, @value{GDBN} uses the default attributes when accessing
|
||
all memory.
|
||
|
||
When a memory region is defined, it is given a number to identify it;
|
||
to enable, disable, or remove a memory region, you specify that number.
|
||
|
||
@table @code
|
||
@kindex mem
|
||
@item mem @var{lower} @var{upper} @var{attributes}@dots{}
|
||
Define a memory region bounded by @var{lower} and @var{upper} with
|
||
attributes @var{attributes}@dots{}, and add it to the list of regions
|
||
monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
|
||
case: it is treated as the target's maximum memory address.
|
||
(0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
|
||
|
||
@item mem auto
|
||
Discard any user changes to the memory regions and use target-supplied
|
||
regions, if available, or no regions if the target does not support.
|
||
|
||
@kindex delete mem
|
||
@item delete mem @var{nums}@dots{}
|
||
Remove memory regions @var{nums}@dots{} from the list of regions
|
||
monitored by @value{GDBN}.
|
||
|
||
@kindex disable mem
|
||
@item disable mem @var{nums}@dots{}
|
||
Disable monitoring of memory regions @var{nums}@dots{}.
|
||
A disabled memory region is not forgotten.
|
||
It may be enabled again later.
|
||
|
||
@kindex enable mem
|
||
@item enable mem @var{nums}@dots{}
|
||
Enable monitoring of memory regions @var{nums}@dots{}.
|
||
|
||
@kindex info mem
|
||
@item info mem
|
||
Print a table of all defined memory regions, with the following columns
|
||
for each region:
|
||
|
||
@table @emph
|
||
@item Memory Region Number
|
||
@item Enabled or Disabled.
|
||
Enabled memory regions are marked with @samp{y}.
|
||
Disabled memory regions are marked with @samp{n}.
|
||
|
||
@item Lo Address
|
||
The address defining the inclusive lower bound of the memory region.
|
||
|
||
@item Hi Address
|
||
The address defining the exclusive upper bound of the memory region.
|
||
|
||
@item Attributes
|
||
The list of attributes set for this memory region.
|
||
@end table
|
||
@end table
|
||
|
||
|
||
@subsection Attributes
|
||
|
||
@subsubsection Memory Access Mode
|
||
The access mode attributes set whether @value{GDBN} may make read or
|
||
write accesses to a memory region.
|
||
|
||
While these attributes prevent @value{GDBN} from performing invalid
|
||
memory accesses, they do nothing to prevent the target system, I/O DMA,
|
||
etc.@: from accessing memory.
|
||
|
||
@table @code
|
||
@item ro
|
||
Memory is read only.
|
||
@item wo
|
||
Memory is write only.
|
||
@item rw
|
||
Memory is read/write. This is the default.
|
||
@end table
|
||
|
||
@subsubsection Memory Access Size
|
||
The access size attribute tells @value{GDBN} to use specific sized
|
||
accesses in the memory region. Often memory mapped device registers
|
||
require specific sized accesses. If no access size attribute is
|
||
specified, @value{GDBN} may use accesses of any size.
|
||
|
||
@table @code
|
||
@item 8
|
||
Use 8 bit memory accesses.
|
||
@item 16
|
||
Use 16 bit memory accesses.
|
||
@item 32
|
||
Use 32 bit memory accesses.
|
||
@item 64
|
||
Use 64 bit memory accesses.
|
||
@end table
|
||
|
||
@c @subsubsection Hardware/Software Breakpoints
|
||
@c The hardware/software breakpoint attributes set whether @value{GDBN}
|
||
@c will use hardware or software breakpoints for the internal breakpoints
|
||
@c used by the step, next, finish, until, etc. commands.
|
||
@c
|
||
@c @table @code
|
||
@c @item hwbreak
|
||
@c Always use hardware breakpoints
|
||
@c @item swbreak (default)
|
||
@c @end table
|
||
|
||
@subsubsection Data Cache
|
||
The data cache attributes set whether @value{GDBN} will cache target
|
||
memory. While this generally improves performance by reducing debug
|
||
protocol overhead, it can lead to incorrect results because @value{GDBN}
|
||
does not know about volatile variables or memory mapped device
|
||
registers.
|
||
|
||
@table @code
|
||
@item cache
|
||
Enable @value{GDBN} to cache target memory.
|
||
@item nocache
|
||
Disable @value{GDBN} from caching target memory. This is the default.
|
||
@end table
|
||
|
||
@subsection Memory Access Checking
|
||
@value{GDBN} can be instructed to refuse accesses to memory that is
|
||
not explicitly described. This can be useful if accessing such
|
||
regions has undesired effects for a specific target, or to provide
|
||
better error checking. The following commands control this behaviour.
|
||
|
||
@table @code
|
||
@kindex set mem inaccessible-by-default
|
||
@item set mem inaccessible-by-default [on|off]
|
||
If @code{on} is specified, make @value{GDBN} treat memory not
|
||
explicitly described by the memory ranges as non-existent and refuse accesses
|
||
to such memory. The checks are only performed if there's at least one
|
||
memory range defined. If @code{off} is specified, make @value{GDBN}
|
||
treat the memory not explicitly described by the memory ranges as RAM.
|
||
The default value is @code{on}.
|
||
@kindex show mem inaccessible-by-default
|
||
@item show mem inaccessible-by-default
|
||
Show the current handling of accesses to unknown memory.
|
||
@end table
|
||
|
||
|
||
@c @subsubsection Memory Write Verification
|
||
@c The memory write verification attributes set whether @value{GDBN}
|
||
@c will re-reads data after each write to verify the write was successful.
|
||
@c
|
||
@c @table @code
|
||
@c @item verify
|
||
@c @item noverify (default)
|
||
@c @end table
|
||
|
||
@node Dump/Restore Files
|
||
@section Copy Between Memory and a File
|
||
@cindex dump/restore files
|
||
@cindex append data to a file
|
||
@cindex dump data to a file
|
||
@cindex restore data from a file
|
||
|
||
You can use the commands @code{dump}, @code{append}, and
|
||
@code{restore} to copy data between target memory and a file. The
|
||
@code{dump} and @code{append} commands write data to a file, and the
|
||
@code{restore} command reads data from a file back into the inferior's
|
||
memory. Files may be in binary, Motorola S-record, Intel hex,
|
||
Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
|
||
append to binary files, and cannot read from Verilog Hex files.
|
||
|
||
@table @code
|
||
|
||
@kindex dump
|
||
@item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
|
||
@itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
|
||
Dump the contents of memory from @var{start_addr} to @var{end_addr},
|
||
or the value of @var{expr}, to @var{filename} in the given format.
|
||
|
||
The @var{format} parameter may be any one of:
|
||
@table @code
|
||
@item binary
|
||
Raw binary form.
|
||
@item ihex
|
||
Intel hex format.
|
||
@item srec
|
||
Motorola S-record format.
|
||
@item tekhex
|
||
Tektronix Hex format.
|
||
@item verilog
|
||
Verilog Hex format.
|
||
@end table
|
||
|
||
@value{GDBN} uses the same definitions of these formats as the
|
||
@sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
|
||
@var{format} is omitted, @value{GDBN} dumps the data in raw binary
|
||
form.
|
||
|
||
@kindex append
|
||
@item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
|
||
@itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
|
||
Append the contents of memory from @var{start_addr} to @var{end_addr},
|
||
or the value of @var{expr}, to the file @var{filename}, in raw binary form.
|
||
(@value{GDBN} can only append data to files in raw binary form.)
|
||
|
||
@kindex restore
|
||
@item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
|
||
Restore the contents of file @var{filename} into memory. The
|
||
@code{restore} command can automatically recognize any known @sc{bfd}
|
||
file format, except for raw binary. To restore a raw binary file you
|
||
must specify the optional keyword @code{binary} after the filename.
|
||
|
||
If @var{bias} is non-zero, its value will be added to the addresses
|
||
contained in the file. Binary files always start at address zero, so
|
||
they will be restored at address @var{bias}. Other bfd files have
|
||
a built-in location; they will be restored at offset @var{bias}
|
||
from that location.
|
||
|
||
If @var{start} and/or @var{end} are non-zero, then only data between
|
||
file offset @var{start} and file offset @var{end} will be restored.
|
||
These offsets are relative to the addresses in the file, before
|
||
the @var{bias} argument is applied.
|
||
|
||
@end table
|
||
|
||
@node Core File Generation
|
||
@section How to Produce a Core File from Your Program
|
||
@cindex dump core from inferior
|
||
|
||
A @dfn{core file} or @dfn{core dump} is a file that records the memory
|
||
image of a running process and its process status (register values
|
||
etc.). Its primary use is post-mortem debugging of a program that
|
||
crashed while it ran outside a debugger. A program that crashes
|
||
automatically produces a core file, unless this feature is disabled by
|
||
the user. @xref{Files}, for information on invoking @value{GDBN} in
|
||
the post-mortem debugging mode.
|
||
|
||
Occasionally, you may wish to produce a core file of the program you
|
||
are debugging in order to preserve a snapshot of its state.
|
||
@value{GDBN} has a special command for that.
|
||
|
||
@table @code
|
||
@kindex gcore
|
||
@kindex generate-core-file
|
||
@item generate-core-file [@var{file}]
|
||
@itemx gcore [@var{file}]
|
||
Produce a core dump of the inferior process. The optional argument
|
||
@var{file} specifies the file name where to put the core dump. If not
|
||
specified, the file name defaults to @file{core.@var{pid}}, where
|
||
@var{pid} is the inferior process ID.
|
||
|
||
Note that this command is implemented only for some systems (as of
|
||
this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
|
||
|
||
On @sc{gnu}/Linux, this command can take into account the value of the
|
||
file @file{/proc/@var{pid}/coredump_filter} when generating the core
|
||
dump (@pxref{set use-coredump-filter}), and by default honors the
|
||
@code{VM_DONTDUMP} flag for mappings where it is present in the file
|
||
@file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
|
||
|
||
@kindex set use-coredump-filter
|
||
@anchor{set use-coredump-filter}
|
||
@item set use-coredump-filter on
|
||
@itemx set use-coredump-filter off
|
||
Enable or disable the use of the file
|
||
@file{/proc/@var{pid}/coredump_filter} when generating core dump
|
||
files. This file is used by the Linux kernel to decide what types of
|
||
memory mappings will be dumped or ignored when generating a core dump
|
||
file. @var{pid} is the process ID of a currently running process.
|
||
|
||
To make use of this feature, you have to write in the
|
||
@file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
|
||
which is a bit mask representing the memory mapping types. If a bit
|
||
is set in the bit mask, then the memory mappings of the corresponding
|
||
types will be dumped; otherwise, they will be ignored. This
|
||
configuration is inherited by child processes. For more information
|
||
about the bits that can be set in the
|
||
@file{/proc/@var{pid}/coredump_filter} file, please refer to the
|
||
manpage of @code{core(5)}.
|
||
|
||
By default, this option is @code{on}. If this option is turned
|
||
@code{off}, @value{GDBN} does not read the @file{coredump_filter} file
|
||
and instead uses the same default value as the Linux kernel in order
|
||
to decide which pages will be dumped in the core dump file. This
|
||
value is currently @code{0x33}, which means that bits @code{0}
|
||
(anonymous private mappings), @code{1} (anonymous shared mappings),
|
||
@code{4} (ELF headers) and @code{5} (private huge pages) are active.
|
||
This will cause these memory mappings to be dumped automatically.
|
||
|
||
@kindex set dump-excluded-mappings
|
||
@anchor{set dump-excluded-mappings}
|
||
@item set dump-excluded-mappings on
|
||
@itemx set dump-excluded-mappings off
|
||
If @code{on} is specified, @value{GDBN} will dump memory mappings
|
||
marked with the @code{VM_DONTDUMP} flag. This flag is represented in
|
||
the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
|
||
|
||
The default value is @code{off}.
|
||
@end table
|
||
|
||
@node Character Sets
|
||
@section Character Sets
|
||
@cindex character sets
|
||
@cindex charset
|
||
@cindex translating between character sets
|
||
@cindex host character set
|
||
@cindex target character set
|
||
|
||
If the program you are debugging uses a different character set to
|
||
represent characters and strings than the one @value{GDBN} uses itself,
|
||
@value{GDBN} can automatically translate between the character sets for
|
||
you. The character set @value{GDBN} uses we call the @dfn{host
|
||
character set}; the one the inferior program uses we call the
|
||
@dfn{target character set}.
|
||
|
||
For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
|
||
uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
|
||
remote protocol (@pxref{Remote Debugging}) to debug a program
|
||
running on an IBM mainframe, which uses the @sc{ebcdic} character set,
|
||
then the host character set is Latin-1, and the target character set is
|
||
@sc{ebcdic}. If you give @value{GDBN} the command @code{set
|
||
target-charset EBCDIC-US}, then @value{GDBN} translates between
|
||
@sc{ebcdic} and Latin 1 as you print character or string values, or use
|
||
character and string literals in expressions.
|
||
|
||
@value{GDBN} has no way to automatically recognize which character set
|
||
the inferior program uses; you must tell it, using the @code{set
|
||
target-charset} command, described below.
|
||
|
||
Here are the commands for controlling @value{GDBN}'s character set
|
||
support:
|
||
|
||
@table @code
|
||
@item set target-charset @var{charset}
|
||
@kindex set target-charset
|
||
Set the current target character set to @var{charset}. To display the
|
||
list of supported target character sets, type
|
||
@kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
|
||
|
||
@item set host-charset @var{charset}
|
||
@kindex set host-charset
|
||
Set the current host character set to @var{charset}.
|
||
|
||
By default, @value{GDBN} uses a host character set appropriate to the
|
||
system it is running on; you can override that default using the
|
||
@code{set host-charset} command. On some systems, @value{GDBN} cannot
|
||
automatically determine the appropriate host character set. In this
|
||
case, @value{GDBN} uses @samp{UTF-8}.
|
||
|
||
@value{GDBN} can only use certain character sets as its host character
|
||
set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
|
||
@value{GDBN} will list the host character sets it supports.
|
||
|
||
@item set charset @var{charset}
|
||
@kindex set charset
|
||
Set the current host and target character sets to @var{charset}. As
|
||
above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
|
||
@value{GDBN} will list the names of the character sets that can be used
|
||
for both host and target.
|
||
|
||
@item show charset
|
||
@kindex show charset
|
||
Show the names of the current host and target character sets.
|
||
|
||
@item show host-charset
|
||
@kindex show host-charset
|
||
Show the name of the current host character set.
|
||
|
||
@item show target-charset
|
||
@kindex show target-charset
|
||
Show the name of the current target character set.
|
||
|
||
@item set target-wide-charset @var{charset}
|
||
@kindex set target-wide-charset
|
||
Set the current target's wide character set to @var{charset}. This is
|
||
the character set used by the target's @code{wchar_t} type. To
|
||
display the list of supported wide character sets, type
|
||
@kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
|
||
|
||
@item show target-wide-charset
|
||
@kindex show target-wide-charset
|
||
Show the name of the current target's wide character set.
|
||
@end table
|
||
|
||
Here is an example of @value{GDBN}'s character set support in action.
|
||
Assume that the following source code has been placed in the file
|
||
@file{charset-test.c}:
|
||
|
||
@smallexample
|
||
#include <stdio.h>
|
||
|
||
char ascii_hello[]
|
||
= @{72, 101, 108, 108, 111, 44, 32, 119,
|
||
111, 114, 108, 100, 33, 10, 0@};
|
||
char ibm1047_hello[]
|
||
= @{200, 133, 147, 147, 150, 107, 64, 166,
|
||
150, 153, 147, 132, 90, 37, 0@};
|
||
|
||
main ()
|
||
@{
|
||
printf ("Hello, world!\n");
|
||
@}
|
||
@end smallexample
|
||
|
||
In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
|
||
containing the string @samp{Hello, world!} followed by a newline,
|
||
encoded in the @sc{ascii} and @sc{ibm1047} character sets.
|
||
|
||
We compile the program, and invoke the debugger on it:
|
||
|
||
@smallexample
|
||
$ gcc -g charset-test.c -o charset-test
|
||
$ gdb -nw charset-test
|
||
GNU gdb 2001-12-19-cvs
|
||
Copyright 2001 Free Software Foundation, Inc.
|
||
@dots{}
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
We can use the @code{show charset} command to see what character sets
|
||
@value{GDBN} is currently using to interpret and display characters and
|
||
strings:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) show charset
|
||
The current host and target character set is `ISO-8859-1'.
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
For the sake of printing this manual, let's use @sc{ascii} as our
|
||
initial character set:
|
||
@smallexample
|
||
(@value{GDBP}) set charset ASCII
|
||
(@value{GDBP}) show charset
|
||
The current host and target character set is `ASCII'.
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
Let's assume that @sc{ascii} is indeed the correct character set for our
|
||
host system --- in other words, let's assume that if @value{GDBN} prints
|
||
characters using the @sc{ascii} character set, our terminal will display
|
||
them properly. Since our current target character set is also
|
||
@sc{ascii}, the contents of @code{ascii_hello} print legibly:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print ascii_hello
|
||
$1 = 0x401698 "Hello, world!\n"
|
||
(@value{GDBP}) print ascii_hello[0]
|
||
$2 = 72 'H'
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@value{GDBN} uses the target character set for character and string
|
||
literals you use in expressions:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print '+'
|
||
$3 = 43 '+'
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
The @sc{ascii} character set uses the number 43 to encode the @samp{+}
|
||
character.
|
||
|
||
@value{GDBN} relies on the user to tell it which character set the
|
||
target program uses. If we print @code{ibm1047_hello} while our target
|
||
character set is still @sc{ascii}, we get jibberish:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print ibm1047_hello
|
||
$4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
|
||
(@value{GDBP}) print ibm1047_hello[0]
|
||
$5 = 200 '\310'
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
|
||
@value{GDBN} tells us the character sets it supports:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set target-charset
|
||
ASCII EBCDIC-US IBM1047 ISO-8859-1
|
||
(@value{GDBP}) set target-charset
|
||
@end smallexample
|
||
|
||
We can select @sc{ibm1047} as our target character set, and examine the
|
||
program's strings again. Now the @sc{ascii} string is wrong, but
|
||
@value{GDBN} translates the contents of @code{ibm1047_hello} from the
|
||
target character set, @sc{ibm1047}, to the host character set,
|
||
@sc{ascii}, and they display correctly:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set target-charset IBM1047
|
||
(@value{GDBP}) show charset
|
||
The current host character set is `ASCII'.
|
||
The current target character set is `IBM1047'.
|
||
(@value{GDBP}) print ascii_hello
|
||
$6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
|
||
(@value{GDBP}) print ascii_hello[0]
|
||
$7 = 72 '\110'
|
||
(@value{GDBP}) print ibm1047_hello
|
||
$8 = 0x4016a8 "Hello, world!\n"
|
||
(@value{GDBP}) print ibm1047_hello[0]
|
||
$9 = 200 'H'
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
As above, @value{GDBN} uses the target character set for character and
|
||
string literals you use in expressions:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print '+'
|
||
$10 = 78 '+'
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
|
||
character.
|
||
|
||
@node Caching Target Data
|
||
@section Caching Data of Targets
|
||
@cindex caching data of targets
|
||
|
||
@value{GDBN} caches data exchanged between the debugger and a target.
|
||
Each cache is associated with the address space of the inferior.
|
||
@xref{Inferiors and Programs}, about inferior and address space.
|
||
Such caching generally improves performance in remote debugging
|
||
(@pxref{Remote Debugging}), because it reduces the overhead of the
|
||
remote protocol by bundling memory reads and writes into large chunks.
|
||
Unfortunately, simply caching everything would lead to incorrect results,
|
||
since @value{GDBN} does not necessarily know anything about volatile
|
||
values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
|
||
(@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
|
||
is executing.
|
||
Therefore, by default, @value{GDBN} only caches data
|
||
known to be on the stack@footnote{In non-stop mode, it is moderately
|
||
rare for a running thread to modify the stack of a stopped thread
|
||
in a way that would interfere with a backtrace, and caching of
|
||
stack reads provides a significant speed up of remote backtraces.} or
|
||
in the code segment.
|
||
Other regions of memory can be explicitly marked as
|
||
cacheable; @pxref{Memory Region Attributes}.
|
||
|
||
@table @code
|
||
@kindex set remotecache
|
||
@item set remotecache on
|
||
@itemx set remotecache off
|
||
This option no longer does anything; it exists for compatibility
|
||
with old scripts.
|
||
|
||
@kindex show remotecache
|
||
@item show remotecache
|
||
Show the current state of the obsolete remotecache flag.
|
||
|
||
@kindex set stack-cache
|
||
@item set stack-cache on
|
||
@itemx set stack-cache off
|
||
Enable or disable caching of stack accesses. When @code{on}, use
|
||
caching. By default, this option is @code{on}.
|
||
|
||
@kindex show stack-cache
|
||
@item show stack-cache
|
||
Show the current state of data caching for memory accesses.
|
||
|
||
@kindex set code-cache
|
||
@item set code-cache on
|
||
@itemx set code-cache off
|
||
Enable or disable caching of code segment accesses. When @code{on},
|
||
use caching. By default, this option is @code{on}. This improves
|
||
performance of disassembly in remote debugging.
|
||
|
||
@kindex show code-cache
|
||
@item show code-cache
|
||
Show the current state of target memory cache for code segment
|
||
accesses.
|
||
|
||
@kindex info dcache
|
||
@item info dcache @r{[}line@r{]}
|
||
Print the information about the performance of data cache of the
|
||
current inferior's address space. The information displayed
|
||
includes the dcache width and depth, and for each cache line, its
|
||
number, address, and how many times it was referenced. This
|
||
command is useful for debugging the data cache operation.
|
||
|
||
If a line number is specified, the contents of that line will be
|
||
printed in hex.
|
||
|
||
@item set dcache size @var{size}
|
||
@cindex dcache size
|
||
@kindex set dcache size
|
||
Set maximum number of entries in dcache (dcache depth above).
|
||
|
||
@item set dcache line-size @var{line-size}
|
||
@cindex dcache line-size
|
||
@kindex set dcache line-size
|
||
Set number of bytes each dcache entry caches (dcache width above).
|
||
Must be a power of 2.
|
||
|
||
@item show dcache size
|
||
@kindex show dcache size
|
||
Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
|
||
|
||
@item show dcache line-size
|
||
@kindex show dcache line-size
|
||
Show default size of dcache lines.
|
||
|
||
@end table
|
||
|
||
@node Searching Memory
|
||
@section Search Memory
|
||
@cindex searching memory
|
||
|
||
Memory can be searched for a particular sequence of bytes with the
|
||
@code{find} command.
|
||
|
||
@table @code
|
||
@kindex find
|
||
@item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
|
||
@itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
|
||
Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
|
||
etc. The search begins at address @var{start_addr} and continues for either
|
||
@var{len} bytes or through to @var{end_addr} inclusive.
|
||
@end table
|
||
|
||
@var{s} and @var{n} are optional parameters.
|
||
They may be specified in either order, apart or together.
|
||
|
||
@table @r
|
||
@item @var{s}, search query size
|
||
The size of each search query value.
|
||
|
||
@table @code
|
||
@item b
|
||
bytes
|
||
@item h
|
||
halfwords (two bytes)
|
||
@item w
|
||
words (four bytes)
|
||
@item g
|
||
giant words (eight bytes)
|
||
@end table
|
||
|
||
All values are interpreted in the current language.
|
||
This means, for example, that if the current source language is C/C@t{++}
|
||
then searching for the string ``hello'' includes the trailing '\0'.
|
||
The null terminator can be removed from searching by using casts,
|
||
e.g.: @samp{@{char[5]@}"hello"}.
|
||
|
||
If the value size is not specified, it is taken from the
|
||
value's type in the current language.
|
||
This is useful when one wants to specify the search
|
||
pattern as a mixture of types.
|
||
Note that this means, for example, that in the case of C-like languages
|
||
a search for an untyped 0x42 will search for @samp{(int) 0x42}
|
||
which is typically four bytes.
|
||
|
||
@item @var{n}, maximum number of finds
|
||
The maximum number of matches to print. The default is to print all finds.
|
||
@end table
|
||
|
||
You can use strings as search values. Quote them with double-quotes
|
||
(@code{"}).
|
||
The string value is copied into the search pattern byte by byte,
|
||
regardless of the endianness of the target and the size specification.
|
||
|
||
The address of each match found is printed as well as a count of the
|
||
number of matches found.
|
||
|
||
The address of the last value found is stored in convenience variable
|
||
@samp{$_}.
|
||
A count of the number of matches is stored in @samp{$numfound}.
|
||
|
||
For example, if stopped at the @code{printf} in this function:
|
||
|
||
@smallexample
|
||
void
|
||
hello ()
|
||
@{
|
||
static char hello[] = "hello-hello";
|
||
static struct @{ char c; short s; int i; @}
|
||
__attribute__ ((packed)) mixed
|
||
= @{ 'c', 0x1234, 0x87654321 @};
|
||
printf ("%s\n", hello);
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
you get during debugging:
|
||
|
||
@smallexample
|
||
(gdb) find &hello[0], +sizeof(hello), "hello"
|
||
0x804956d <hello.1620+6>
|
||
1 pattern found
|
||
(gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
|
||
0x8049567 <hello.1620>
|
||
0x804956d <hello.1620+6>
|
||
2 patterns found.
|
||
(gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
|
||
0x8049567 <hello.1620>
|
||
0x804956d <hello.1620+6>
|
||
2 patterns found.
|
||
(gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
|
||
0x8049567 <hello.1620>
|
||
1 pattern found
|
||
(gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
|
||
0x8049560 <mixed.1625>
|
||
1 pattern found
|
||
(gdb) print $numfound
|
||
$1 = 1
|
||
(gdb) print $_
|
||
$2 = (void *) 0x8049560
|
||
@end smallexample
|
||
|
||
@node Value Sizes
|
||
@section Value Sizes
|
||
|
||
Whenever @value{GDBN} prints a value memory will be allocated within
|
||
@value{GDBN} to hold the contents of the value. It is possible in
|
||
some languages with dynamic typing systems, that an invalid program
|
||
may indicate a value that is incorrectly large, this in turn may cause
|
||
@value{GDBN} to try and allocate an overly large ammount of memory.
|
||
|
||
@table @code
|
||
@kindex set max-value-size
|
||
@item set max-value-size @var{bytes}
|
||
@itemx set max-value-size unlimited
|
||
Set the maximum size of memory that @value{GDBN} will allocate for the
|
||
contents of a value to @var{bytes}, trying to display a value that
|
||
requires more memory than that will result in an error.
|
||
|
||
Setting this variable does not effect values that have already been
|
||
allocated within @value{GDBN}, only future allocations.
|
||
|
||
There's a minimum size that @code{max-value-size} can be set to in
|
||
order that @value{GDBN} can still operate correctly, this minimum is
|
||
currently 16 bytes.
|
||
|
||
The limit applies to the results of some subexpressions as well as to
|
||
complete expressions. For example, an expression denoting a simple
|
||
integer component, such as @code{x.y.z}, may fail if the size of
|
||
@var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
|
||
@value{GDBN} is sometimes clever; the expression @code{A[i]}, where
|
||
@var{A} is an array variable with non-constant size, will generally
|
||
succeed regardless of the bounds on @var{A}, as long as the component
|
||
size is less than @var{bytes}.
|
||
|
||
The default value of @code{max-value-size} is currently 64k.
|
||
|
||
@kindex show max-value-size
|
||
@item show max-value-size
|
||
Show the maximum size of memory, in bytes, that @value{GDBN} will
|
||
allocate for the contents of a value.
|
||
@end table
|
||
|
||
@node Optimized Code
|
||
@chapter Debugging Optimized Code
|
||
@cindex optimized code, debugging
|
||
@cindex debugging optimized code
|
||
|
||
Almost all compilers support optimization. With optimization
|
||
disabled, the compiler generates assembly code that corresponds
|
||
directly to your source code, in a simplistic way. As the compiler
|
||
applies more powerful optimizations, the generated assembly code
|
||
diverges from your original source code. With help from debugging
|
||
information generated by the compiler, @value{GDBN} can map from
|
||
the running program back to constructs from your original source.
|
||
|
||
@value{GDBN} is more accurate with optimization disabled. If you
|
||
can recompile without optimization, it is easier to follow the
|
||
progress of your program during debugging. But, there are many cases
|
||
where you may need to debug an optimized version.
|
||
|
||
When you debug a program compiled with @samp{-g -O}, remember that the
|
||
optimizer has rearranged your code; the debugger shows you what is
|
||
really there. Do not be too surprised when the execution path does not
|
||
exactly match your source file! An extreme example: if you define a
|
||
variable, but never use it, @value{GDBN} never sees that
|
||
variable---because the compiler optimizes it out of existence.
|
||
|
||
Some things do not work as well with @samp{-g -O} as with just
|
||
@samp{-g}, particularly on machines with instruction scheduling. If in
|
||
doubt, recompile with @samp{-g} alone, and if this fixes the problem,
|
||
please report it to us as a bug (including a test case!).
|
||
@xref{Variables}, for more information about debugging optimized code.
|
||
|
||
@menu
|
||
* Inline Functions:: How @value{GDBN} presents inlining
|
||
* Tail Call Frames:: @value{GDBN} analysis of jumps to functions
|
||
@end menu
|
||
|
||
@node Inline Functions
|
||
@section Inline Functions
|
||
@cindex inline functions, debugging
|
||
|
||
@dfn{Inlining} is an optimization that inserts a copy of the function
|
||
body directly at each call site, instead of jumping to a shared
|
||
routine. @value{GDBN} displays inlined functions just like
|
||
non-inlined functions. They appear in backtraces. You can view their
|
||
arguments and local variables, step into them with @code{step}, skip
|
||
them with @code{next}, and escape from them with @code{finish}.
|
||
You can check whether a function was inlined by using the
|
||
@code{info frame} command.
|
||
|
||
For @value{GDBN} to support inlined functions, the compiler must
|
||
record information about inlining in the debug information ---
|
||
@value{NGCC} using the @sc{dwarf 2} format does this, and several
|
||
other compilers do also. @value{GDBN} only supports inlined functions
|
||
when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
|
||
do not emit two required attributes (@samp{DW_AT_call_file} and
|
||
@samp{DW_AT_call_line}); @value{GDBN} does not display inlined
|
||
function calls with earlier versions of @value{NGCC}. It instead
|
||
displays the arguments and local variables of inlined functions as
|
||
local variables in the caller.
|
||
|
||
The body of an inlined function is directly included at its call site;
|
||
unlike a non-inlined function, there are no instructions devoted to
|
||
the call. @value{GDBN} still pretends that the call site and the
|
||
start of the inlined function are different instructions. Stepping to
|
||
the call site shows the call site, and then stepping again shows
|
||
the first line of the inlined function, even though no additional
|
||
instructions are executed.
|
||
|
||
This makes source-level debugging much clearer; you can see both the
|
||
context of the call and then the effect of the call. Only stepping by
|
||
a single instruction using @code{stepi} or @code{nexti} does not do
|
||
this; single instruction steps always show the inlined body.
|
||
|
||
There are some ways that @value{GDBN} does not pretend that inlined
|
||
function calls are the same as normal calls:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Setting breakpoints at the call site of an inlined function may not
|
||
work, because the call site does not contain any code. @value{GDBN}
|
||
may incorrectly move the breakpoint to the next line of the enclosing
|
||
function, after the call. This limitation will be removed in a future
|
||
version of @value{GDBN}; until then, set a breakpoint on an earlier line
|
||
or inside the inlined function instead.
|
||
|
||
@item
|
||
@value{GDBN} cannot locate the return value of inlined calls after
|
||
using the @code{finish} command. This is a limitation of compiler-generated
|
||
debugging information; after @code{finish}, you can step to the next line
|
||
and print a variable where your program stored the return value.
|
||
|
||
@end itemize
|
||
|
||
@node Tail Call Frames
|
||
@section Tail Call Frames
|
||
@cindex tail call frames, debugging
|
||
|
||
Function @code{B} can call function @code{C} in its very last statement. In
|
||
unoptimized compilation the call of @code{C} is immediately followed by return
|
||
instruction at the end of @code{B} code. Optimizing compiler may replace the
|
||
call and return in function @code{B} into one jump to function @code{C}
|
||
instead. Such use of a jump instruction is called @dfn{tail call}.
|
||
|
||
During execution of function @code{C}, there will be no indication in the
|
||
function call stack frames that it was tail-called from @code{B}. If function
|
||
@code{A} regularly calls function @code{B} which tail-calls function @code{C},
|
||
then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
|
||
some cases @value{GDBN} can determine that @code{C} was tail-called from
|
||
@code{B}, and it will then create fictitious call frame for that, with the
|
||
return address set up as if @code{B} called @code{C} normally.
|
||
|
||
This functionality is currently supported only by DWARF 2 debugging format and
|
||
the compiler has to produce @samp{DW_TAG_call_site} tags. With
|
||
@value{NGCC}, you need to specify @option{-O -g} during compilation, to get
|
||
this information.
|
||
|
||
@kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
|
||
kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
|
||
|
||
@smallexample
|
||
(gdb) x/i $pc - 2
|
||
0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
|
||
(gdb) info frame
|
||
Stack level 1, frame at 0x7fffffffda30:
|
||
rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
|
||
tail call frame, caller of frame at 0x7fffffffda30
|
||
source language c++.
|
||
Arglist at unknown address.
|
||
Locals at unknown address, Previous frame's sp is 0x7fffffffda30
|
||
@end smallexample
|
||
|
||
The detection of all the possible code path executions can find them ambiguous.
|
||
There is no execution history stored (possible @ref{Reverse Execution} is never
|
||
used for this purpose) and the last known caller could have reached the known
|
||
callee by multiple different jump sequences. In such case @value{GDBN} still
|
||
tries to show at least all the unambiguous top tail callers and all the
|
||
unambiguous bottom tail calees, if any.
|
||
|
||
@table @code
|
||
@anchor{set debug entry-values}
|
||
@item set debug entry-values
|
||
@kindex set debug entry-values
|
||
When set to on, enables printing of analysis messages for both frame argument
|
||
values at function entry and tail calls. It will show all the possible valid
|
||
tail calls code paths it has considered. It will also print the intersection
|
||
of them with the final unambiguous (possibly partial or even empty) code path
|
||
result.
|
||
|
||
@item show debug entry-values
|
||
@kindex show debug entry-values
|
||
Show the current state of analysis messages printing for both frame argument
|
||
values at function entry and tail calls.
|
||
@end table
|
||
|
||
The analysis messages for tail calls can for example show why the virtual tail
|
||
call frame for function @code{c} has not been recognized (due to the indirect
|
||
reference by variable @code{x}):
|
||
|
||
@smallexample
|
||
static void __attribute__((noinline, noclone)) c (void);
|
||
void (*x) (void) = c;
|
||
static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
|
||
static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
|
||
int main (void) @{ x (); return 0; @}
|
||
|
||
Breakpoint 1, DW_OP_entry_value resolving cannot find
|
||
DW_TAG_call_site 0x40039a in main
|
||
a () at t.c:3
|
||
3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
|
||
(gdb) bt
|
||
#0 a () at t.c:3
|
||
#1 0x000000000040039a in main () at t.c:5
|
||
@end smallexample
|
||
|
||
Another possibility is an ambiguous virtual tail call frames resolution:
|
||
|
||
@smallexample
|
||
int i;
|
||
static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
|
||
static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
|
||
static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
|
||
static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
|
||
static void __attribute__((noinline, noclone)) b (void)
|
||
@{ if (i) c (); else e (); @}
|
||
static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
|
||
int main (void) @{ a (); return 0; @}
|
||
|
||
tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
|
||
tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
|
||
tailcall: reduced: 0x4004d2(a) |
|
||
(gdb) bt
|
||
#0 f () at t.c:2
|
||
#1 0x00000000004004d2 in a () at t.c:8
|
||
#2 0x0000000000400395 in main () at t.c:9
|
||
@end smallexample
|
||
|
||
@set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
|
||
@set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
|
||
|
||
@c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
|
||
@ifset HAVE_MAKEINFO_CLICK
|
||
@set ARROW @click{}
|
||
@set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
|
||
@set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
|
||
@end ifset
|
||
@ifclear HAVE_MAKEINFO_CLICK
|
||
@set ARROW ->
|
||
@set CALLSEQ1B @value{CALLSEQ1A}
|
||
@set CALLSEQ2B @value{CALLSEQ2A}
|
||
@end ifclear
|
||
|
||
Frames #0 and #2 are real, #1 is a virtual tail call frame.
|
||
The code can have possible execution paths @value{CALLSEQ1B} or
|
||
@value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
|
||
|
||
@code{initial:} state shows some random possible calling sequence @value{GDBN}
|
||
has found. It then finds another possible calling sequcen - that one is
|
||
prefixed by @code{compare:}. The non-ambiguous intersection of these two is
|
||
printed as the @code{reduced:} calling sequence. That one could have many
|
||
futher @code{compare:} and @code{reduced:} statements as long as there remain
|
||
any non-ambiguous sequence entries.
|
||
|
||
For the frame of function @code{b} in both cases there are different possible
|
||
@code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
|
||
also ambigous. The only non-ambiguous frame is the one for function @code{a},
|
||
therefore this one is displayed to the user while the ambiguous frames are
|
||
omitted.
|
||
|
||
There can be also reasons why printing of frame argument values at function
|
||
entry may fail:
|
||
|
||
@smallexample
|
||
int v;
|
||
static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
|
||
static void __attribute__((noinline, noclone)) a (int i);
|
||
static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
|
||
static void __attribute__((noinline, noclone)) a (int i)
|
||
@{ if (i) b (i - 1); else c (0); @}
|
||
int main (void) @{ a (5); return 0; @}
|
||
|
||
(gdb) bt
|
||
#0 c (i=i@@entry=0) at t.c:2
|
||
#1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
|
||
function "a" at 0x400420 can call itself via tail calls
|
||
i=<optimized out>) at t.c:6
|
||
#2 0x000000000040036e in main () at t.c:7
|
||
@end smallexample
|
||
|
||
@value{GDBN} cannot find out from the inferior state if and how many times did
|
||
function @code{a} call itself (via function @code{b}) as these calls would be
|
||
tail calls. Such tail calls would modify thue @code{i} variable, therefore
|
||
@value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
|
||
prints @code{<optimized out>} instead.
|
||
|
||
@node Macros
|
||
@chapter C Preprocessor Macros
|
||
|
||
Some languages, such as C and C@t{++}, provide a way to define and invoke
|
||
``preprocessor macros'' which expand into strings of tokens.
|
||
@value{GDBN} can evaluate expressions containing macro invocations, show
|
||
the result of macro expansion, and show a macro's definition, including
|
||
where it was defined.
|
||
|
||
You may need to compile your program specially to provide @value{GDBN}
|
||
with information about preprocessor macros. Most compilers do not
|
||
include macros in their debugging information, even when you compile
|
||
with the @option{-g} flag. @xref{Compilation}.
|
||
|
||
A program may define a macro at one point, remove that definition later,
|
||
and then provide a different definition after that. Thus, at different
|
||
points in the program, a macro may have different definitions, or have
|
||
no definition at all. If there is a current stack frame, @value{GDBN}
|
||
uses the macros in scope at that frame's source code line. Otherwise,
|
||
@value{GDBN} uses the macros in scope at the current listing location;
|
||
see @ref{List}.
|
||
|
||
Whenever @value{GDBN} evaluates an expression, it always expands any
|
||
macro invocations present in the expression. @value{GDBN} also provides
|
||
the following commands for working with macros explicitly.
|
||
|
||
@table @code
|
||
|
||
@kindex macro expand
|
||
@cindex macro expansion, showing the results of preprocessor
|
||
@cindex preprocessor macro expansion, showing the results of
|
||
@cindex expanding preprocessor macros
|
||
@item macro expand @var{expression}
|
||
@itemx macro exp @var{expression}
|
||
Show the results of expanding all preprocessor macro invocations in
|
||
@var{expression}. Since @value{GDBN} simply expands macros, but does
|
||
not parse the result, @var{expression} need not be a valid expression;
|
||
it can be any string of tokens.
|
||
|
||
@kindex macro exp1
|
||
@item macro expand-once @var{expression}
|
||
@itemx macro exp1 @var{expression}
|
||
@cindex expand macro once
|
||
@i{(This command is not yet implemented.)} Show the results of
|
||
expanding those preprocessor macro invocations that appear explicitly in
|
||
@var{expression}. Macro invocations appearing in that expansion are
|
||
left unchanged. This command allows you to see the effect of a
|
||
particular macro more clearly, without being confused by further
|
||
expansions. Since @value{GDBN} simply expands macros, but does not
|
||
parse the result, @var{expression} need not be a valid expression; it
|
||
can be any string of tokens.
|
||
|
||
@kindex info macro
|
||
@cindex macro definition, showing
|
||
@cindex definition of a macro, showing
|
||
@cindex macros, from debug info
|
||
@item info macro [-a|-all] [--] @var{macro}
|
||
Show the current definition or all definitions of the named @var{macro},
|
||
and describe the source location or compiler command-line where that
|
||
definition was established. The optional double dash is to signify the end of
|
||
argument processing and the beginning of @var{macro} for non C-like macros where
|
||
the macro may begin with a hyphen.
|
||
|
||
@kindex info macros
|
||
@item info macros @var{location}
|
||
Show all macro definitions that are in effect at the location specified
|
||
by @var{location}, and describe the source location or compiler
|
||
command-line where those definitions were established.
|
||
|
||
@kindex macro define
|
||
@cindex user-defined macros
|
||
@cindex defining macros interactively
|
||
@cindex macros, user-defined
|
||
@item macro define @var{macro} @var{replacement-list}
|
||
@itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
|
||
Introduce a definition for a preprocessor macro named @var{macro},
|
||
invocations of which are replaced by the tokens given in
|
||
@var{replacement-list}. The first form of this command defines an
|
||
``object-like'' macro, which takes no arguments; the second form
|
||
defines a ``function-like'' macro, which takes the arguments given in
|
||
@var{arglist}.
|
||
|
||
A definition introduced by this command is in scope in every
|
||
expression evaluated in @value{GDBN}, until it is removed with the
|
||
@code{macro undef} command, described below. The definition overrides
|
||
all definitions for @var{macro} present in the program being debugged,
|
||
as well as any previous user-supplied definition.
|
||
|
||
@kindex macro undef
|
||
@item macro undef @var{macro}
|
||
Remove any user-supplied definition for the macro named @var{macro}.
|
||
This command only affects definitions provided with the @code{macro
|
||
define} command, described above; it cannot remove definitions present
|
||
in the program being debugged.
|
||
|
||
@kindex macro list
|
||
@item macro list
|
||
List all the macros defined using the @code{macro define} command.
|
||
@end table
|
||
|
||
@cindex macros, example of debugging with
|
||
Here is a transcript showing the above commands in action. First, we
|
||
show our source files:
|
||
|
||
@smallexample
|
||
$ cat sample.c
|
||
#include <stdio.h>
|
||
#include "sample.h"
|
||
|
||
#define M 42
|
||
#define ADD(x) (M + x)
|
||
|
||
main ()
|
||
@{
|
||
#define N 28
|
||
printf ("Hello, world!\n");
|
||
#undef N
|
||
printf ("We're so creative.\n");
|
||
#define N 1729
|
||
printf ("Goodbye, world!\n");
|
||
@}
|
||
$ cat sample.h
|
||
#define Q <
|
||
$
|
||
@end smallexample
|
||
|
||
Now, we compile the program using the @sc{gnu} C compiler,
|
||
@value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
|
||
minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
|
||
and @option{-gdwarf-4}; we recommend always choosing the most recent
|
||
version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
|
||
includes information about preprocessor macros in the debugging
|
||
information.
|
||
|
||
@smallexample
|
||
$ gcc -gdwarf-2 -g3 sample.c -o sample
|
||
$
|
||
@end smallexample
|
||
|
||
Now, we start @value{GDBN} on our sample program:
|
||
|
||
@smallexample
|
||
$ gdb -nw sample
|
||
GNU gdb 2002-05-06-cvs
|
||
Copyright 2002 Free Software Foundation, Inc.
|
||
GDB is free software, @dots{}
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
We can expand macros and examine their definitions, even when the
|
||
program is not running. @value{GDBN} uses the current listing position
|
||
to decide which macro definitions are in scope:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) list main
|
||
3
|
||
4 #define M 42
|
||
5 #define ADD(x) (M + x)
|
||
6
|
||
7 main ()
|
||
8 @{
|
||
9 #define N 28
|
||
10 printf ("Hello, world!\n");
|
||
11 #undef N
|
||
12 printf ("We're so creative.\n");
|
||
(@value{GDBP}) info macro ADD
|
||
Defined at /home/jimb/gdb/macros/play/sample.c:5
|
||
#define ADD(x) (M + x)
|
||
(@value{GDBP}) info macro Q
|
||
Defined at /home/jimb/gdb/macros/play/sample.h:1
|
||
included at /home/jimb/gdb/macros/play/sample.c:2
|
||
#define Q <
|
||
(@value{GDBP}) macro expand ADD(1)
|
||
expands to: (42 + 1)
|
||
(@value{GDBP}) macro expand-once ADD(1)
|
||
expands to: once (M + 1)
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
In the example above, note that @code{macro expand-once} expands only
|
||
the macro invocation explicit in the original text --- the invocation of
|
||
@code{ADD} --- but does not expand the invocation of the macro @code{M},
|
||
which was introduced by @code{ADD}.
|
||
|
||
Once the program is running, @value{GDBN} uses the macro definitions in
|
||
force at the source line of the current stack frame:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) break main
|
||
Breakpoint 1 at 0x8048370: file sample.c, line 10.
|
||
(@value{GDBP}) run
|
||
Starting program: /home/jimb/gdb/macros/play/sample
|
||
|
||
Breakpoint 1, main () at sample.c:10
|
||
10 printf ("Hello, world!\n");
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
At line 10, the definition of the macro @code{N} at line 9 is in force:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info macro N
|
||
Defined at /home/jimb/gdb/macros/play/sample.c:9
|
||
#define N 28
|
||
(@value{GDBP}) macro expand N Q M
|
||
expands to: 28 < 42
|
||
(@value{GDBP}) print N Q M
|
||
$1 = 1
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
As we step over directives that remove @code{N}'s definition, and then
|
||
give it a new definition, @value{GDBN} finds the definition (or lack
|
||
thereof) in force at each point:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) next
|
||
Hello, world!
|
||
12 printf ("We're so creative.\n");
|
||
(@value{GDBP}) info macro N
|
||
The symbol `N' has no definition as a C/C++ preprocessor macro
|
||
at /home/jimb/gdb/macros/play/sample.c:12
|
||
(@value{GDBP}) next
|
||
We're so creative.
|
||
14 printf ("Goodbye, world!\n");
|
||
(@value{GDBP}) info macro N
|
||
Defined at /home/jimb/gdb/macros/play/sample.c:13
|
||
#define N 1729
|
||
(@value{GDBP}) macro expand N Q M
|
||
expands to: 1729 < 42
|
||
(@value{GDBP}) print N Q M
|
||
$2 = 0
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
In addition to source files, macros can be defined on the compilation command
|
||
line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
|
||
such a way, @value{GDBN} displays the location of their definition as line zero
|
||
of the source file submitted to the compiler.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info macro __STDC__
|
||
Defined at /home/jimb/gdb/macros/play/sample.c:0
|
||
-D__STDC__=1
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
|
||
@node Tracepoints
|
||
@chapter Tracepoints
|
||
@c This chapter is based on the documentation written by Michael
|
||
@c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
|
||
|
||
@cindex tracepoints
|
||
In some applications, it is not feasible for the debugger to interrupt
|
||
the program's execution long enough for the developer to learn
|
||
anything helpful about its behavior. If the program's correctness
|
||
depends on its real-time behavior, delays introduced by a debugger
|
||
might cause the program to change its behavior drastically, or perhaps
|
||
fail, even when the code itself is correct. It is useful to be able
|
||
to observe the program's behavior without interrupting it.
|
||
|
||
Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
|
||
specify locations in the program, called @dfn{tracepoints}, and
|
||
arbitrary expressions to evaluate when those tracepoints are reached.
|
||
Later, using the @code{tfind} command, you can examine the values
|
||
those expressions had when the program hit the tracepoints. The
|
||
expressions may also denote objects in memory---structures or arrays,
|
||
for example---whose values @value{GDBN} should record; while visiting
|
||
a particular tracepoint, you may inspect those objects as if they were
|
||
in memory at that moment. However, because @value{GDBN} records these
|
||
values without interacting with you, it can do so quickly and
|
||
unobtrusively, hopefully not disturbing the program's behavior.
|
||
|
||
The tracepoint facility is currently available only for remote
|
||
targets. @xref{Targets}. In addition, your remote target must know
|
||
how to collect trace data. This functionality is implemented in the
|
||
remote stub; however, none of the stubs distributed with @value{GDBN}
|
||
support tracepoints as of this writing. The format of the remote
|
||
packets used to implement tracepoints are described in @ref{Tracepoint
|
||
Packets}.
|
||
|
||
It is also possible to get trace data from a file, in a manner reminiscent
|
||
of corefiles; you specify the filename, and use @code{tfind} to search
|
||
through the file. @xref{Trace Files}, for more details.
|
||
|
||
This chapter describes the tracepoint commands and features.
|
||
|
||
@menu
|
||
* Set Tracepoints::
|
||
* Analyze Collected Data::
|
||
* Tracepoint Variables::
|
||
* Trace Files::
|
||
@end menu
|
||
|
||
@node Set Tracepoints
|
||
@section Commands to Set Tracepoints
|
||
|
||
Before running such a @dfn{trace experiment}, an arbitrary number of
|
||
tracepoints can be set. A tracepoint is actually a special type of
|
||
breakpoint (@pxref{Set Breaks}), so you can manipulate it using
|
||
standard breakpoint commands. For instance, as with breakpoints,
|
||
tracepoint numbers are successive integers starting from one, and many
|
||
of the commands associated with tracepoints take the tracepoint number
|
||
as their argument, to identify which tracepoint to work on.
|
||
|
||
For each tracepoint, you can specify, in advance, some arbitrary set
|
||
of data that you want the target to collect in the trace buffer when
|
||
it hits that tracepoint. The collected data can include registers,
|
||
local variables, or global data. Later, you can use @value{GDBN}
|
||
commands to examine the values these data had at the time the
|
||
tracepoint was hit.
|
||
|
||
Tracepoints do not support every breakpoint feature. Ignore counts on
|
||
tracepoints have no effect, and tracepoints cannot run @value{GDBN}
|
||
commands when they are hit. Tracepoints may not be thread-specific
|
||
either.
|
||
|
||
@cindex fast tracepoints
|
||
Some targets may support @dfn{fast tracepoints}, which are inserted in
|
||
a different way (such as with a jump instead of a trap), that is
|
||
faster but possibly restricted in where they may be installed.
|
||
|
||
@cindex static tracepoints
|
||
@cindex markers, static tracepoints
|
||
@cindex probing markers, static tracepoints
|
||
Regular and fast tracepoints are dynamic tracing facilities, meaning
|
||
that they can be used to insert tracepoints at (almost) any location
|
||
in the target. Some targets may also support controlling @dfn{static
|
||
tracepoints} from @value{GDBN}. With static tracing, a set of
|
||
instrumentation points, also known as @dfn{markers}, are embedded in
|
||
the target program, and can be activated or deactivated by name or
|
||
address. These are usually placed at locations which facilitate
|
||
investigating what the target is actually doing. @value{GDBN}'s
|
||
support for static tracing includes being able to list instrumentation
|
||
points, and attach them with @value{GDBN} defined high level
|
||
tracepoints that expose the whole range of convenience of
|
||
@value{GDBN}'s tracepoints support. Namely, support for collecting
|
||
registers values and values of global or local (to the instrumentation
|
||
point) variables; tracepoint conditions and trace state variables.
|
||
The act of installing a @value{GDBN} static tracepoint on an
|
||
instrumentation point, or marker, is referred to as @dfn{probing} a
|
||
static tracepoint marker.
|
||
|
||
@code{gdbserver} supports tracepoints on some target systems.
|
||
@xref{Server,,Tracepoints support in @code{gdbserver}}.
|
||
|
||
This section describes commands to set tracepoints and associated
|
||
conditions and actions.
|
||
|
||
@menu
|
||
* Create and Delete Tracepoints::
|
||
* Enable and Disable Tracepoints::
|
||
* Tracepoint Passcounts::
|
||
* Tracepoint Conditions::
|
||
* Trace State Variables::
|
||
* Tracepoint Actions::
|
||
* Listing Tracepoints::
|
||
* Listing Static Tracepoint Markers::
|
||
* Starting and Stopping Trace Experiments::
|
||
* Tracepoint Restrictions::
|
||
@end menu
|
||
|
||
@node Create and Delete Tracepoints
|
||
@subsection Create and Delete Tracepoints
|
||
|
||
@table @code
|
||
@cindex set tracepoint
|
||
@kindex trace
|
||
@item trace @var{location}
|
||
The @code{trace} command is very similar to the @code{break} command.
|
||
Its argument @var{location} can be any valid location.
|
||
@xref{Specify Location}. The @code{trace} command defines a tracepoint,
|
||
which is a point in the target program where the debugger will briefly stop,
|
||
collect some data, and then allow the program to continue. Setting a tracepoint
|
||
or changing its actions takes effect immediately if the remote stub
|
||
supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
|
||
in tracing}).
|
||
If remote stub doesn't support the @samp{InstallInTrace} feature, all
|
||
these changes don't take effect until the next @code{tstart}
|
||
command, and once a trace experiment is running, further changes will
|
||
not have any effect until the next trace experiment starts. In addition,
|
||
@value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
|
||
address is not yet resolved. (This is similar to pending breakpoints.)
|
||
Pending tracepoints are not downloaded to the target and not installed
|
||
until they are resolved. The resolution of pending tracepoints requires
|
||
@value{GDBN} support---when debugging with the remote target, and
|
||
@value{GDBN} disconnects from the remote stub (@pxref{disconnected
|
||
tracing}), pending tracepoints can not be resolved (and downloaded to
|
||
the remote stub) while @value{GDBN} is disconnected.
|
||
|
||
Here are some examples of using the @code{trace} command:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{trace foo.c:121} // a source file and line number
|
||
|
||
(@value{GDBP}) @b{trace +2} // 2 lines forward
|
||
|
||
(@value{GDBP}) @b{trace my_function} // first source line of function
|
||
|
||
(@value{GDBP}) @b{trace *my_function} // EXACT start address of function
|
||
|
||
(@value{GDBP}) @b{trace *0x2117c4} // an address
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can abbreviate @code{trace} as @code{tr}.
|
||
|
||
@item trace @var{location} if @var{cond}
|
||
Set a tracepoint with condition @var{cond}; evaluate the expression
|
||
@var{cond} each time the tracepoint is reached, and collect data only
|
||
if the value is nonzero---that is, if @var{cond} evaluates as true.
|
||
@xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
|
||
information on tracepoint conditions.
|
||
|
||
@item ftrace @var{location} [ if @var{cond} ]
|
||
@cindex set fast tracepoint
|
||
@cindex fast tracepoints, setting
|
||
@kindex ftrace
|
||
The @code{ftrace} command sets a fast tracepoint. For targets that
|
||
support them, fast tracepoints will use a more efficient but possibly
|
||
less general technique to trigger data collection, such as a jump
|
||
instruction instead of a trap, or some sort of hardware support. It
|
||
may not be possible to create a fast tracepoint at the desired
|
||
location, in which case the command will exit with an explanatory
|
||
message.
|
||
|
||
@value{GDBN} handles arguments to @code{ftrace} exactly as for
|
||
@code{trace}.
|
||
|
||
On 32-bit x86-architecture systems, fast tracepoints normally need to
|
||
be placed at an instruction that is 5 bytes or longer, but can be
|
||
placed at 4-byte instructions if the low 64K of memory of the target
|
||
program is available to install trampolines. Some Unix-type systems,
|
||
such as @sc{gnu}/Linux, exclude low addresses from the program's
|
||
address space; but for instance with the Linux kernel it is possible
|
||
to let @value{GDBN} use this area by doing a @command{sysctl} command
|
||
to set the @code{mmap_min_addr} kernel parameter, as in
|
||
|
||
@example
|
||
sudo sysctl -w vm.mmap_min_addr=32768
|
||
@end example
|
||
|
||
@noindent
|
||
which sets the low address to 32K, which leaves plenty of room for
|
||
trampolines. The minimum address should be set to a page boundary.
|
||
|
||
@item strace @var{location} [ if @var{cond} ]
|
||
@cindex set static tracepoint
|
||
@cindex static tracepoints, setting
|
||
@cindex probe static tracepoint marker
|
||
@kindex strace
|
||
The @code{strace} command sets a static tracepoint. For targets that
|
||
support it, setting a static tracepoint probes a static
|
||
instrumentation point, or marker, found at @var{location}. It may not
|
||
be possible to set a static tracepoint at the desired location, in
|
||
which case the command will exit with an explanatory message.
|
||
|
||
@value{GDBN} handles arguments to @code{strace} exactly as for
|
||
@code{trace}, with the addition that the user can also specify
|
||
@code{-m @var{marker}} as @var{location}. This probes the marker
|
||
identified by the @var{marker} string identifier. This identifier
|
||
depends on the static tracepoint backend library your program is
|
||
using. You can find all the marker identifiers in the @samp{ID} field
|
||
of the @code{info static-tracepoint-markers} command output.
|
||
@xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
|
||
Markers}. For example, in the following small program using the UST
|
||
tracing engine:
|
||
|
||
@smallexample
|
||
main ()
|
||
@{
|
||
trace_mark(ust, bar33, "str %s", "FOOBAZ");
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
the marker id is composed of joining the first two arguments to the
|
||
@code{trace_mark} call with a slash, which translates to:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info static-tracepoint-markers
|
||
Cnt Enb ID Address What
|
||
1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
|
||
Data: "str %s"
|
||
[etc...]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
so you may probe the marker above with:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) strace -m ust/bar33
|
||
@end smallexample
|
||
|
||
Static tracepoints accept an extra collect action --- @code{collect
|
||
$_sdata}. This collects arbitrary user data passed in the probe point
|
||
call to the tracing library. In the UST example above, you'll see
|
||
that the third argument to @code{trace_mark} is a printf-like format
|
||
string. The user data is then the result of running that formating
|
||
string against the following arguments. Note that @code{info
|
||
static-tracepoint-markers} command output lists that format string in
|
||
the @samp{Data:} field.
|
||
|
||
You can inspect this data when analyzing the trace buffer, by printing
|
||
the $_sdata variable like any other variable available to
|
||
@value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
|
||
|
||
@vindex $tpnum
|
||
@cindex last tracepoint number
|
||
@cindex recent tracepoint number
|
||
@cindex tracepoint number
|
||
The convenience variable @code{$tpnum} records the tracepoint number
|
||
of the most recently set tracepoint.
|
||
|
||
@kindex delete tracepoint
|
||
@cindex tracepoint deletion
|
||
@item delete tracepoint @r{[}@var{num}@r{]}
|
||
Permanently delete one or more tracepoints. With no argument, the
|
||
default is to delete all tracepoints. Note that the regular
|
||
@code{delete} command can remove tracepoints also.
|
||
|
||
Examples:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
|
||
|
||
(@value{GDBP}) @b{delete trace} // remove all tracepoints
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You can abbreviate this command as @code{del tr}.
|
||
@end table
|
||
|
||
@node Enable and Disable Tracepoints
|
||
@subsection Enable and Disable Tracepoints
|
||
|
||
These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
|
||
|
||
@table @code
|
||
@kindex disable tracepoint
|
||
@item disable tracepoint @r{[}@var{num}@r{]}
|
||
Disable tracepoint @var{num}, or all tracepoints if no argument
|
||
@var{num} is given. A disabled tracepoint will have no effect during
|
||
a trace experiment, but it is not forgotten. You can re-enable
|
||
a disabled tracepoint using the @code{enable tracepoint} command.
|
||
If the command is issued during a trace experiment and the debug target
|
||
has support for disabling tracepoints during a trace experiment, then the
|
||
change will be effective immediately. Otherwise, it will be applied to the
|
||
next trace experiment.
|
||
|
||
@kindex enable tracepoint
|
||
@item enable tracepoint @r{[}@var{num}@r{]}
|
||
Enable tracepoint @var{num}, or all tracepoints. If this command is
|
||
issued during a trace experiment and the debug target supports enabling
|
||
tracepoints during a trace experiment, then the enabled tracepoints will
|
||
become effective immediately. Otherwise, they will become effective the
|
||
next time a trace experiment is run.
|
||
@end table
|
||
|
||
@node Tracepoint Passcounts
|
||
@subsection Tracepoint Passcounts
|
||
|
||
@table @code
|
||
@kindex passcount
|
||
@cindex tracepoint pass count
|
||
@item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
|
||
Set the @dfn{passcount} of a tracepoint. The passcount is a way to
|
||
automatically stop a trace experiment. If a tracepoint's passcount is
|
||
@var{n}, then the trace experiment will be automatically stopped on
|
||
the @var{n}'th time that tracepoint is hit. If the tracepoint number
|
||
@var{num} is not specified, the @code{passcount} command sets the
|
||
passcount of the most recently defined tracepoint. If no passcount is
|
||
given, the trace experiment will run until stopped explicitly by the
|
||
user.
|
||
|
||
Examples:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
|
||
@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
|
||
|
||
(@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
|
||
@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
|
||
(@value{GDBP}) @b{trace foo}
|
||
(@value{GDBP}) @b{pass 3}
|
||
(@value{GDBP}) @b{trace bar}
|
||
(@value{GDBP}) @b{pass 2}
|
||
(@value{GDBP}) @b{trace baz}
|
||
(@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
|
||
@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
|
||
@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
|
||
@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
|
||
@end smallexample
|
||
@end table
|
||
|
||
@node Tracepoint Conditions
|
||
@subsection Tracepoint Conditions
|
||
@cindex conditional tracepoints
|
||
@cindex tracepoint conditions
|
||
|
||
The simplest sort of tracepoint collects data every time your program
|
||
reaches a specified place. You can also specify a @dfn{condition} for
|
||
a tracepoint. A condition is just a Boolean expression in your
|
||
programming language (@pxref{Expressions, ,Expressions}). A
|
||
tracepoint with a condition evaluates the expression each time your
|
||
program reaches it, and data collection happens only if the condition
|
||
is true.
|
||
|
||
Tracepoint conditions can be specified when a tracepoint is set, by
|
||
using @samp{if} in the arguments to the @code{trace} command.
|
||
@xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
|
||
also be set or changed at any time with the @code{condition} command,
|
||
just as with breakpoints.
|
||
|
||
Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
|
||
the conditional expression itself. Instead, @value{GDBN} encodes the
|
||
expression into an agent expression (@pxref{Agent Expressions})
|
||
suitable for execution on the target, independently of @value{GDBN}.
|
||
Global variables become raw memory locations, locals become stack
|
||
accesses, and so forth.
|
||
|
||
For instance, suppose you have a function that is usually called
|
||
frequently, but should not be called after an error has occurred. You
|
||
could use the following tracepoint command to collect data about calls
|
||
of that function that happen while the error code is propagating
|
||
through the program; an unconditional tracepoint could end up
|
||
collecting thousands of useless trace frames that you would have to
|
||
search through.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
|
||
@end smallexample
|
||
|
||
@node Trace State Variables
|
||
@subsection Trace State Variables
|
||
@cindex trace state variables
|
||
|
||
A @dfn{trace state variable} is a special type of variable that is
|
||
created and managed by target-side code. The syntax is the same as
|
||
that for GDB's convenience variables (a string prefixed with ``$''),
|
||
but they are stored on the target. They must be created explicitly,
|
||
using a @code{tvariable} command. They are always 64-bit signed
|
||
integers.
|
||
|
||
Trace state variables are remembered by @value{GDBN}, and downloaded
|
||
to the target along with tracepoint information when the trace
|
||
experiment starts. There are no intrinsic limits on the number of
|
||
trace state variables, beyond memory limitations of the target.
|
||
|
||
@cindex convenience variables, and trace state variables
|
||
Although trace state variables are managed by the target, you can use
|
||
them in print commands and expressions as if they were convenience
|
||
variables; @value{GDBN} will get the current value from the target
|
||
while the trace experiment is running. Trace state variables share
|
||
the same namespace as other ``$'' variables, which means that you
|
||
cannot have trace state variables with names like @code{$23} or
|
||
@code{$pc}, nor can you have a trace state variable and a convenience
|
||
variable with the same name.
|
||
|
||
@table @code
|
||
|
||
@item tvariable $@var{name} [ = @var{expression} ]
|
||
@kindex tvariable
|
||
The @code{tvariable} command creates a new trace state variable named
|
||
@code{$@var{name}}, and optionally gives it an initial value of
|
||
@var{expression}. The @var{expression} is evaluated when this command is
|
||
entered; the result will be converted to an integer if possible,
|
||
otherwise @value{GDBN} will report an error. A subsequent
|
||
@code{tvariable} command specifying the same name does not create a
|
||
variable, but instead assigns the supplied initial value to the
|
||
existing variable of that name, overwriting any previous initial
|
||
value. The default initial value is 0.
|
||
|
||
@item info tvariables
|
||
@kindex info tvariables
|
||
List all the trace state variables along with their initial values.
|
||
Their current values may also be displayed, if the trace experiment is
|
||
currently running.
|
||
|
||
@item delete tvariable @r{[} $@var{name} @dots{} @r{]}
|
||
@kindex delete tvariable
|
||
Delete the given trace state variables, or all of them if no arguments
|
||
are specified.
|
||
|
||
@end table
|
||
|
||
@node Tracepoint Actions
|
||
@subsection Tracepoint Action Lists
|
||
|
||
@table @code
|
||
@kindex actions
|
||
@cindex tracepoint actions
|
||
@item actions @r{[}@var{num}@r{]}
|
||
This command will prompt for a list of actions to be taken when the
|
||
tracepoint is hit. If the tracepoint number @var{num} is not
|
||
specified, this command sets the actions for the one that was most
|
||
recently defined (so that you can define a tracepoint and then say
|
||
@code{actions} without bothering about its number). You specify the
|
||
actions themselves on the following lines, one action at a time, and
|
||
terminate the actions list with a line containing just @code{end}. So
|
||
far, the only defined actions are @code{collect}, @code{teval}, and
|
||
@code{while-stepping}.
|
||
|
||
@code{actions} is actually equivalent to @code{commands} (@pxref{Break
|
||
Commands, ,Breakpoint Command Lists}), except that only the defined
|
||
actions are allowed; any other @value{GDBN} command is rejected.
|
||
|
||
@cindex remove actions from a tracepoint
|
||
To remove all actions from a tracepoint, type @samp{actions @var{num}}
|
||
and follow it immediately with @samp{end}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{collect @var{data}} // collect some data
|
||
|
||
(@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
|
||
|
||
(@value{GDBP}) @b{end} // signals the end of actions.
|
||
@end smallexample
|
||
|
||
In the following example, the action list begins with @code{collect}
|
||
commands indicating the things to be collected when the tracepoint is
|
||
hit. Then, in order to single-step and collect additional data
|
||
following the tracepoint, a @code{while-stepping} command is used,
|
||
followed by the list of things to be collected after each step in a
|
||
sequence of single steps. The @code{while-stepping} command is
|
||
terminated by its own separate @code{end} command. Lastly, the action
|
||
list is terminated by an @code{end} command.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{trace foo}
|
||
(@value{GDBP}) @b{actions}
|
||
Enter actions for tracepoint 1, one per line:
|
||
> collect bar,baz
|
||
> collect $regs
|
||
> while-stepping 12
|
||
> collect $pc, arr[i]
|
||
> end
|
||
end
|
||
@end smallexample
|
||
|
||
@kindex collect @r{(tracepoints)}
|
||
@item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
|
||
Collect values of the given expressions when the tracepoint is hit.
|
||
This command accepts a comma-separated list of any valid expressions.
|
||
In addition to global, static, or local variables, the following
|
||
special arguments are supported:
|
||
|
||
@table @code
|
||
@item $regs
|
||
Collect all registers.
|
||
|
||
@item $args
|
||
Collect all function arguments.
|
||
|
||
@item $locals
|
||
Collect all local variables.
|
||
|
||
@item $_ret
|
||
Collect the return address. This is helpful if you want to see more
|
||
of a backtrace.
|
||
|
||
@emph{Note:} The return address location can not always be reliably
|
||
determined up front, and the wrong address / registers may end up
|
||
collected instead. On some architectures the reliability is higher
|
||
for tracepoints at function entry, while on others it's the opposite.
|
||
When this happens, backtracing will stop because the return address is
|
||
found unavailable (unless another collect rule happened to match it).
|
||
|
||
@item $_probe_argc
|
||
Collects the number of arguments from the static probe at which the
|
||
tracepoint is located.
|
||
@xref{Static Probe Points}.
|
||
|
||
@item $_probe_arg@var{n}
|
||
@var{n} is an integer between 0 and 11. Collects the @var{n}th argument
|
||
from the static probe at which the tracepoint is located.
|
||
@xref{Static Probe Points}.
|
||
|
||
@item $_sdata
|
||
@vindex $_sdata@r{, collect}
|
||
Collect static tracepoint marker specific data. Only available for
|
||
static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
|
||
Lists}. On the UST static tracepoints library backend, an
|
||
instrumentation point resembles a @code{printf} function call. The
|
||
tracing library is able to collect user specified data formatted to a
|
||
character string using the format provided by the programmer that
|
||
instrumented the program. Other backends have similar mechanisms.
|
||
Here's an example of a UST marker call:
|
||
|
||
@smallexample
|
||
const char master_name[] = "$your_name";
|
||
trace_mark(channel1, marker1, "hello %s", master_name)
|
||
@end smallexample
|
||
|
||
In this case, collecting @code{$_sdata} collects the string
|
||
@samp{hello $yourname}. When analyzing the trace buffer, you can
|
||
inspect @samp{$_sdata} like any other variable available to
|
||
@value{GDBN}.
|
||
@end table
|
||
|
||
You can give several consecutive @code{collect} commands, each one
|
||
with a single argument, or one @code{collect} command with several
|
||
arguments separated by commas; the effect is the same.
|
||
|
||
The optional @var{mods} changes the usual handling of the arguments.
|
||
@code{s} requests that pointers to chars be handled as strings, in
|
||
particular collecting the contents of the memory being pointed at, up
|
||
to the first zero. The upper bound is by default the value of the
|
||
@code{print elements} variable; if @code{s} is followed by a decimal
|
||
number, that is the upper bound instead. So for instance
|
||
@samp{collect/s25 mystr} collects as many as 25 characters at
|
||
@samp{mystr}.
|
||
|
||
The command @code{info scope} (@pxref{Symbols, info scope}) is
|
||
particularly useful for figuring out what data to collect.
|
||
|
||
@kindex teval @r{(tracepoints)}
|
||
@item teval @var{expr1}, @var{expr2}, @dots{}
|
||
Evaluate the given expressions when the tracepoint is hit. This
|
||
command accepts a comma-separated list of expressions. The results
|
||
are discarded, so this is mainly useful for assigning values to trace
|
||
state variables (@pxref{Trace State Variables}) without adding those
|
||
values to the trace buffer, as would be the case if the @code{collect}
|
||
action were used.
|
||
|
||
@kindex while-stepping @r{(tracepoints)}
|
||
@item while-stepping @var{n}
|
||
Perform @var{n} single-step instruction traces after the tracepoint,
|
||
collecting new data after each step. The @code{while-stepping}
|
||
command is followed by the list of what to collect while stepping
|
||
(followed by its own @code{end} command):
|
||
|
||
@smallexample
|
||
> while-stepping 12
|
||
> collect $regs, myglobal
|
||
> end
|
||
>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Note that @code{$pc} is not automatically collected by
|
||
@code{while-stepping}; you need to explicitly collect that register if
|
||
you need it. You may abbreviate @code{while-stepping} as @code{ws} or
|
||
@code{stepping}.
|
||
|
||
@item set default-collect @var{expr1}, @var{expr2}, @dots{}
|
||
@kindex set default-collect
|
||
@cindex default collection action
|
||
This variable is a list of expressions to collect at each tracepoint
|
||
hit. It is effectively an additional @code{collect} action prepended
|
||
to every tracepoint action list. The expressions are parsed
|
||
individually for each tracepoint, so for instance a variable named
|
||
@code{xyz} may be interpreted as a global for one tracepoint, and a
|
||
local for another, as appropriate to the tracepoint's location.
|
||
|
||
@item show default-collect
|
||
@kindex show default-collect
|
||
Show the list of expressions that are collected by default at each
|
||
tracepoint hit.
|
||
|
||
@end table
|
||
|
||
@node Listing Tracepoints
|
||
@subsection Listing Tracepoints
|
||
|
||
@table @code
|
||
@kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
|
||
@kindex info tp @r{[}@var{n}@dots{}@r{]}
|
||
@cindex information about tracepoints
|
||
@item info tracepoints @r{[}@var{num}@dots{}@r{]}
|
||
Display information about the tracepoint @var{num}. If you don't
|
||
specify a tracepoint number, displays information about all the
|
||
tracepoints defined so far. The format is similar to that used for
|
||
@code{info breakpoints}; in fact, @code{info tracepoints} is the same
|
||
command, simply restricting itself to tracepoints.
|
||
|
||
A tracepoint's listing may include additional information specific to
|
||
tracing:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
its passcount as given by the @code{passcount @var{n}} command
|
||
|
||
@item
|
||
the state about installed on target of each location
|
||
@end itemize
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{info trace}
|
||
Num Type Disp Enb Address What
|
||
1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
|
||
while-stepping 20
|
||
collect globfoo, $regs
|
||
end
|
||
collect globfoo2
|
||
end
|
||
pass count 1200
|
||
2 tracepoint keep y <MULTIPLE>
|
||
collect $eip
|
||
2.1 y 0x0804859c in func4 at change-loc.h:35
|
||
installed on target
|
||
2.2 y 0xb7ffc480 in func4 at change-loc.h:35
|
||
installed on target
|
||
2.3 y <PENDING> set_tracepoint
|
||
3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
|
||
not installed on target
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This command can be abbreviated @code{info tp}.
|
||
@end table
|
||
|
||
@node Listing Static Tracepoint Markers
|
||
@subsection Listing Static Tracepoint Markers
|
||
|
||
@table @code
|
||
@kindex info static-tracepoint-markers
|
||
@cindex information about static tracepoint markers
|
||
@item info static-tracepoint-markers
|
||
Display information about all static tracepoint markers defined in the
|
||
program.
|
||
|
||
For each marker, the following columns are printed:
|
||
|
||
@table @emph
|
||
@item Count
|
||
An incrementing counter, output to help readability. This is not a
|
||
stable identifier.
|
||
@item ID
|
||
The marker ID, as reported by the target.
|
||
@item Enabled or Disabled
|
||
Probed markers are tagged with @samp{y}. @samp{n} identifies marks
|
||
that are not enabled.
|
||
@item Address
|
||
Where the marker is in your program, as a memory address.
|
||
@item What
|
||
Where the marker is in the source for your program, as a file and line
|
||
number. If the debug information included in the program does not
|
||
allow @value{GDBN} to locate the source of the marker, this column
|
||
will be left blank.
|
||
@end table
|
||
|
||
@noindent
|
||
In addition, the following information may be printed for each marker:
|
||
|
||
@table @emph
|
||
@item Data
|
||
User data passed to the tracing library by the marker call. In the
|
||
UST backend, this is the format string passed as argument to the
|
||
marker call.
|
||
@item Static tracepoints probing the marker
|
||
The list of static tracepoints attached to the marker.
|
||
@end table
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info static-tracepoint-markers
|
||
Cnt ID Enb Address What
|
||
1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
|
||
Data: number1 %d number2 %d
|
||
Probed by static tracepoints: #2
|
||
2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
|
||
Data: str %s
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
@end table
|
||
|
||
@node Starting and Stopping Trace Experiments
|
||
@subsection Starting and Stopping Trace Experiments
|
||
|
||
@table @code
|
||
@kindex tstart [ @var{notes} ]
|
||
@cindex start a new trace experiment
|
||
@cindex collected data discarded
|
||
@item tstart
|
||
This command starts the trace experiment, and begins collecting data.
|
||
It has the side effect of discarding all the data collected in the
|
||
trace buffer during the previous trace experiment. If any arguments
|
||
are supplied, they are taken as a note and stored with the trace
|
||
experiment's state. The notes may be arbitrary text, and are
|
||
especially useful with disconnected tracing in a multi-user context;
|
||
the notes can explain what the trace is doing, supply user contact
|
||
information, and so forth.
|
||
|
||
@kindex tstop [ @var{notes} ]
|
||
@cindex stop a running trace experiment
|
||
@item tstop
|
||
This command stops the trace experiment. If any arguments are
|
||
supplied, they are recorded with the experiment as a note. This is
|
||
useful if you are stopping a trace started by someone else, for
|
||
instance if the trace is interfering with the system's behavior and
|
||
needs to be stopped quickly.
|
||
|
||
@strong{Note}: a trace experiment and data collection may stop
|
||
automatically if any tracepoint's passcount is reached
|
||
(@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
|
||
|
||
@kindex tstatus
|
||
@cindex status of trace data collection
|
||
@cindex trace experiment, status of
|
||
@item tstatus
|
||
This command displays the status of the current trace data
|
||
collection.
|
||
@end table
|
||
|
||
Here is an example of the commands we described so far:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{trace gdb_c_test}
|
||
(@value{GDBP}) @b{actions}
|
||
Enter actions for tracepoint #1, one per line.
|
||
> collect $regs,$locals,$args
|
||
> while-stepping 11
|
||
> collect $regs
|
||
> end
|
||
> end
|
||
(@value{GDBP}) @b{tstart}
|
||
[time passes @dots{}]
|
||
(@value{GDBP}) @b{tstop}
|
||
@end smallexample
|
||
|
||
@anchor{disconnected tracing}
|
||
@cindex disconnected tracing
|
||
You can choose to continue running the trace experiment even if
|
||
@value{GDBN} disconnects from the target, voluntarily or
|
||
involuntarily. For commands such as @code{detach}, the debugger will
|
||
ask what you want to do with the trace. But for unexpected
|
||
terminations (@value{GDBN} crash, network outage), it would be
|
||
unfortunate to lose hard-won trace data, so the variable
|
||
@code{disconnected-tracing} lets you decide whether the trace should
|
||
continue running without @value{GDBN}.
|
||
|
||
@table @code
|
||
@item set disconnected-tracing on
|
||
@itemx set disconnected-tracing off
|
||
@kindex set disconnected-tracing
|
||
Choose whether a tracing run should continue to run if @value{GDBN}
|
||
has disconnected from the target. Note that @code{detach} or
|
||
@code{quit} will ask you directly what to do about a running trace no
|
||
matter what this variable's setting, so the variable is mainly useful
|
||
for handling unexpected situations, such as loss of the network.
|
||
|
||
@item show disconnected-tracing
|
||
@kindex show disconnected-tracing
|
||
Show the current choice for disconnected tracing.
|
||
|
||
@end table
|
||
|
||
When you reconnect to the target, the trace experiment may or may not
|
||
still be running; it might have filled the trace buffer in the
|
||
meantime, or stopped for one of the other reasons. If it is running,
|
||
it will continue after reconnection.
|
||
|
||
Upon reconnection, the target will upload information about the
|
||
tracepoints in effect. @value{GDBN} will then compare that
|
||
information to the set of tracepoints currently defined, and attempt
|
||
to match them up, allowing for the possibility that the numbers may
|
||
have changed due to creation and deletion in the meantime. If one of
|
||
the target's tracepoints does not match any in @value{GDBN}, the
|
||
debugger will create a new tracepoint, so that you have a number with
|
||
which to specify that tracepoint. This matching-up process is
|
||
necessarily heuristic, and it may result in useless tracepoints being
|
||
created; you may simply delete them if they are of no use.
|
||
|
||
@cindex circular trace buffer
|
||
If your target agent supports a @dfn{circular trace buffer}, then you
|
||
can run a trace experiment indefinitely without filling the trace
|
||
buffer; when space runs out, the agent deletes already-collected trace
|
||
frames, oldest first, until there is enough room to continue
|
||
collecting. This is especially useful if your tracepoints are being
|
||
hit too often, and your trace gets terminated prematurely because the
|
||
buffer is full. To ask for a circular trace buffer, simply set
|
||
@samp{circular-trace-buffer} to on. You can set this at any time,
|
||
including during tracing; if the agent can do it, it will change
|
||
buffer handling on the fly, otherwise it will not take effect until
|
||
the next run.
|
||
|
||
@table @code
|
||
@item set circular-trace-buffer on
|
||
@itemx set circular-trace-buffer off
|
||
@kindex set circular-trace-buffer
|
||
Choose whether a tracing run should use a linear or circular buffer
|
||
for trace data. A linear buffer will not lose any trace data, but may
|
||
fill up prematurely, while a circular buffer will discard old trace
|
||
data, but it will have always room for the latest tracepoint hits.
|
||
|
||
@item show circular-trace-buffer
|
||
@kindex show circular-trace-buffer
|
||
Show the current choice for the trace buffer. Note that this may not
|
||
match the agent's current buffer handling, nor is it guaranteed to
|
||
match the setting that might have been in effect during a past run,
|
||
for instance if you are looking at frames from a trace file.
|
||
|
||
@end table
|
||
|
||
@table @code
|
||
@item set trace-buffer-size @var{n}
|
||
@itemx set trace-buffer-size unlimited
|
||
@kindex set trace-buffer-size
|
||
Request that the target use a trace buffer of @var{n} bytes. Not all
|
||
targets will honor the request; they may have a compiled-in size for
|
||
the trace buffer, or some other limitation. Set to a value of
|
||
@code{unlimited} or @code{-1} to let the target use whatever size it
|
||
likes. This is also the default.
|
||
|
||
@item show trace-buffer-size
|
||
@kindex show trace-buffer-size
|
||
Show the current requested size for the trace buffer. Note that this
|
||
will only match the actual size if the target supports size-setting,
|
||
and was able to handle the requested size. For instance, if the
|
||
target can only change buffer size between runs, this variable will
|
||
not reflect the change until the next run starts. Use @code{tstatus}
|
||
to get a report of the actual buffer size.
|
||
@end table
|
||
|
||
@table @code
|
||
@item set trace-user @var{text}
|
||
@kindex set trace-user
|
||
|
||
@item show trace-user
|
||
@kindex show trace-user
|
||
|
||
@item set trace-notes @var{text}
|
||
@kindex set trace-notes
|
||
Set the trace run's notes.
|
||
|
||
@item show trace-notes
|
||
@kindex show trace-notes
|
||
Show the trace run's notes.
|
||
|
||
@item set trace-stop-notes @var{text}
|
||
@kindex set trace-stop-notes
|
||
Set the trace run's stop notes. The handling of the note is as for
|
||
@code{tstop} arguments; the set command is convenient way to fix a
|
||
stop note that is mistaken or incomplete.
|
||
|
||
@item show trace-stop-notes
|
||
@kindex show trace-stop-notes
|
||
Show the trace run's stop notes.
|
||
|
||
@end table
|
||
|
||
@node Tracepoint Restrictions
|
||
@subsection Tracepoint Restrictions
|
||
|
||
@cindex tracepoint restrictions
|
||
There are a number of restrictions on the use of tracepoints. As
|
||
described above, tracepoint data gathering occurs on the target
|
||
without interaction from @value{GDBN}. Thus the full capabilities of
|
||
the debugger are not available during data gathering, and then at data
|
||
examination time, you will be limited by only having what was
|
||
collected. The following items describe some common problems, but it
|
||
is not exhaustive, and you may run into additional difficulties not
|
||
mentioned here.
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Tracepoint expressions are intended to gather objects (lvalues). Thus
|
||
the full flexibility of GDB's expression evaluator is not available.
|
||
You cannot call functions, cast objects to aggregate types, access
|
||
convenience variables or modify values (except by assignment to trace
|
||
state variables). Some language features may implicitly call
|
||
functions (for instance Objective-C fields with accessors), and therefore
|
||
cannot be collected either.
|
||
|
||
@item
|
||
Collection of local variables, either individually or in bulk with
|
||
@code{$locals} or @code{$args}, during @code{while-stepping} may
|
||
behave erratically. The stepping action may enter a new scope (for
|
||
instance by stepping into a function), or the location of the variable
|
||
may change (for instance it is loaded into a register). The
|
||
tracepoint data recorded uses the location information for the
|
||
variables that is correct for the tracepoint location. When the
|
||
tracepoint is created, it is not possible, in general, to determine
|
||
where the steps of a @code{while-stepping} sequence will advance the
|
||
program---particularly if a conditional branch is stepped.
|
||
|
||
@item
|
||
Collection of an incompletely-initialized or partially-destroyed object
|
||
may result in something that @value{GDBN} cannot display, or displays
|
||
in a misleading way.
|
||
|
||
@item
|
||
When @value{GDBN} displays a pointer to character it automatically
|
||
dereferences the pointer to also display characters of the string
|
||
being pointed to. However, collecting the pointer during tracing does
|
||
not automatically collect the string. You need to explicitly
|
||
dereference the pointer and provide size information if you want to
|
||
collect not only the pointer, but the memory pointed to. For example,
|
||
@code{*ptr@@50} can be used to collect the 50 element array pointed to
|
||
by @code{ptr}.
|
||
|
||
@item
|
||
It is not possible to collect a complete stack backtrace at a
|
||
tracepoint. Instead, you may collect the registers and a few hundred
|
||
bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
|
||
(adjust to use the name of the actual stack pointer register on your
|
||
target architecture, and the amount of stack you wish to capture).
|
||
Then the @code{backtrace} command will show a partial backtrace when
|
||
using a trace frame. The number of stack frames that can be examined
|
||
depends on the sizes of the frames in the collected stack. Note that
|
||
if you ask for a block so large that it goes past the bottom of the
|
||
stack, the target agent may report an error trying to read from an
|
||
invalid address.
|
||
|
||
@item
|
||
If you do not collect registers at a tracepoint, @value{GDBN} can
|
||
infer that the value of @code{$pc} must be the same as the address of
|
||
the tracepoint and use that when you are looking at a trace frame
|
||
for that tracepoint. However, this cannot work if the tracepoint has
|
||
multiple locations (for instance if it was set in a function that was
|
||
inlined), or if it has a @code{while-stepping} loop. In those cases
|
||
@value{GDBN} will warn you that it can't infer @code{$pc}, and default
|
||
it to zero.
|
||
|
||
@end itemize
|
||
|
||
@node Analyze Collected Data
|
||
@section Using the Collected Data
|
||
|
||
After the tracepoint experiment ends, you use @value{GDBN} commands
|
||
for examining the trace data. The basic idea is that each tracepoint
|
||
collects a trace @dfn{snapshot} every time it is hit and another
|
||
snapshot every time it single-steps. All these snapshots are
|
||
consecutively numbered from zero and go into a buffer, and you can
|
||
examine them later. The way you examine them is to @dfn{focus} on a
|
||
specific trace snapshot. When the remote stub is focused on a trace
|
||
snapshot, it will respond to all @value{GDBN} requests for memory and
|
||
registers by reading from the buffer which belongs to that snapshot,
|
||
rather than from @emph{real} memory or registers of the program being
|
||
debugged. This means that @strong{all} @value{GDBN} commands
|
||
(@code{print}, @code{info registers}, @code{backtrace}, etc.) will
|
||
behave as if we were currently debugging the program state as it was
|
||
when the tracepoint occurred. Any requests for data that are not in
|
||
the buffer will fail.
|
||
|
||
@menu
|
||
* tfind:: How to select a trace snapshot
|
||
* tdump:: How to display all data for a snapshot
|
||
* save tracepoints:: How to save tracepoints for a future run
|
||
@end menu
|
||
|
||
@node tfind
|
||
@subsection @code{tfind @var{n}}
|
||
|
||
@kindex tfind
|
||
@cindex select trace snapshot
|
||
@cindex find trace snapshot
|
||
The basic command for selecting a trace snapshot from the buffer is
|
||
@code{tfind @var{n}}, which finds trace snapshot number @var{n},
|
||
counting from zero. If no argument @var{n} is given, the next
|
||
snapshot is selected.
|
||
|
||
Here are the various forms of using the @code{tfind} command.
|
||
|
||
@table @code
|
||
@item tfind start
|
||
Find the first snapshot in the buffer. This is a synonym for
|
||
@code{tfind 0} (since 0 is the number of the first snapshot).
|
||
|
||
@item tfind none
|
||
Stop debugging trace snapshots, resume @emph{live} debugging.
|
||
|
||
@item tfind end
|
||
Same as @samp{tfind none}.
|
||
|
||
@item tfind
|
||
No argument means find the next trace snapshot or find the first
|
||
one if no trace snapshot is selected.
|
||
|
||
@item tfind -
|
||
Find the previous trace snapshot before the current one. This permits
|
||
retracing earlier steps.
|
||
|
||
@item tfind tracepoint @var{num}
|
||
Find the next snapshot associated with tracepoint @var{num}. Search
|
||
proceeds forward from the last examined trace snapshot. If no
|
||
argument @var{num} is given, it means find the next snapshot collected
|
||
for the same tracepoint as the current snapshot.
|
||
|
||
@item tfind pc @var{addr}
|
||
Find the next snapshot associated with the value @var{addr} of the
|
||
program counter. Search proceeds forward from the last examined trace
|
||
snapshot. If no argument @var{addr} is given, it means find the next
|
||
snapshot with the same value of PC as the current snapshot.
|
||
|
||
@item tfind outside @var{addr1}, @var{addr2}
|
||
Find the next snapshot whose PC is outside the given range of
|
||
addresses (exclusive).
|
||
|
||
@item tfind range @var{addr1}, @var{addr2}
|
||
Find the next snapshot whose PC is between @var{addr1} and
|
||
@var{addr2} (inclusive).
|
||
|
||
@item tfind line @r{[}@var{file}:@r{]}@var{n}
|
||
Find the next snapshot associated with the source line @var{n}. If
|
||
the optional argument @var{file} is given, refer to line @var{n} in
|
||
that source file. Search proceeds forward from the last examined
|
||
trace snapshot. If no argument @var{n} is given, it means find the
|
||
next line other than the one currently being examined; thus saying
|
||
@code{tfind line} repeatedly can appear to have the same effect as
|
||
stepping from line to line in a @emph{live} debugging session.
|
||
@end table
|
||
|
||
The default arguments for the @code{tfind} commands are specifically
|
||
designed to make it easy to scan through the trace buffer. For
|
||
instance, @code{tfind} with no argument selects the next trace
|
||
snapshot, and @code{tfind -} with no argument selects the previous
|
||
trace snapshot. So, by giving one @code{tfind} command, and then
|
||
simply hitting @key{RET} repeatedly you can examine all the trace
|
||
snapshots in order. Or, by saying @code{tfind -} and then hitting
|
||
@key{RET} repeatedly you can examine the snapshots in reverse order.
|
||
The @code{tfind line} command with no argument selects the snapshot
|
||
for the next source line executed. The @code{tfind pc} command with
|
||
no argument selects the next snapshot with the same program counter
|
||
(PC) as the current frame. The @code{tfind tracepoint} command with
|
||
no argument selects the next trace snapshot collected by the same
|
||
tracepoint as the current one.
|
||
|
||
In addition to letting you scan through the trace buffer manually,
|
||
these commands make it easy to construct @value{GDBN} scripts that
|
||
scan through the trace buffer and print out whatever collected data
|
||
you are interested in. Thus, if we want to examine the PC, FP, and SP
|
||
registers from each trace frame in the buffer, we can say this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{tfind start}
|
||
(@value{GDBP}) @b{while ($trace_frame != -1)}
|
||
> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
|
||
$trace_frame, $pc, $sp, $fp
|
||
> tfind
|
||
> end
|
||
|
||
Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
|
||
Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
|
||
Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
|
||
Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
|
||
Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
|
||
Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
|
||
Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
|
||
Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
|
||
Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
|
||
Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
|
||
Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
|
||
@end smallexample
|
||
|
||
Or, if we want to examine the variable @code{X} at each source line in
|
||
the buffer:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{tfind start}
|
||
(@value{GDBP}) @b{while ($trace_frame != -1)}
|
||
> printf "Frame %d, X == %d\n", $trace_frame, X
|
||
> tfind line
|
||
> end
|
||
|
||
Frame 0, X = 1
|
||
Frame 7, X = 2
|
||
Frame 13, X = 255
|
||
@end smallexample
|
||
|
||
@node tdump
|
||
@subsection @code{tdump}
|
||
@kindex tdump
|
||
@cindex dump all data collected at tracepoint
|
||
@cindex tracepoint data, display
|
||
|
||
This command takes no arguments. It prints all the data collected at
|
||
the current trace snapshot.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{trace 444}
|
||
(@value{GDBP}) @b{actions}
|
||
Enter actions for tracepoint #2, one per line:
|
||
> collect $regs, $locals, $args, gdb_long_test
|
||
> end
|
||
|
||
(@value{GDBP}) @b{tstart}
|
||
|
||
(@value{GDBP}) @b{tfind line 444}
|
||
#0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
|
||
at gdb_test.c:444
|
||
444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
|
||
|
||
(@value{GDBP}) @b{tdump}
|
||
Data collected at tracepoint 2, trace frame 1:
|
||
d0 0xc4aa0085 -995491707
|
||
d1 0x18 24
|
||
d2 0x80 128
|
||
d3 0x33 51
|
||
d4 0x71aea3d 119204413
|
||
d5 0x22 34
|
||
d6 0xe0 224
|
||
d7 0x380035 3670069
|
||
a0 0x19e24a 1696330
|
||
a1 0x3000668 50333288
|
||
a2 0x100 256
|
||
a3 0x322000 3284992
|
||
a4 0x3000698 50333336
|
||
a5 0x1ad3cc 1758156
|
||
fp 0x30bf3c 0x30bf3c
|
||
sp 0x30bf34 0x30bf34
|
||
ps 0x0 0
|
||
pc 0x20b2c8 0x20b2c8
|
||
fpcontrol 0x0 0
|
||
fpstatus 0x0 0
|
||
fpiaddr 0x0 0
|
||
p = 0x20e5b4 "gdb-test"
|
||
p1 = (void *) 0x11
|
||
p2 = (void *) 0x22
|
||
p3 = (void *) 0x33
|
||
p4 = (void *) 0x44
|
||
p5 = (void *) 0x55
|
||
p6 = (void *) 0x66
|
||
gdb_long_test = 17 '\021'
|
||
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@code{tdump} works by scanning the tracepoint's current collection
|
||
actions and printing the value of each expression listed. So
|
||
@code{tdump} can fail, if after a run, you change the tracepoint's
|
||
actions to mention variables that were not collected during the run.
|
||
|
||
Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
|
||
uses the collected value of @code{$pc} to distinguish between trace
|
||
frames that were collected at the tracepoint hit, and frames that were
|
||
collected while stepping. This allows it to correctly choose whether
|
||
to display the basic list of collections, or the collections from the
|
||
body of the while-stepping loop. However, if @code{$pc} was not collected,
|
||
then @code{tdump} will always attempt to dump using the basic collection
|
||
list, and may fail if a while-stepping frame does not include all the
|
||
same data that is collected at the tracepoint hit.
|
||
@c This is getting pretty arcane, example would be good.
|
||
|
||
@node save tracepoints
|
||
@subsection @code{save tracepoints @var{filename}}
|
||
@kindex save tracepoints
|
||
@kindex save-tracepoints
|
||
@cindex save tracepoints for future sessions
|
||
|
||
This command saves all current tracepoint definitions together with
|
||
their actions and passcounts, into a file @file{@var{filename}}
|
||
suitable for use in a later debugging session. To read the saved
|
||
tracepoint definitions, use the @code{source} command (@pxref{Command
|
||
Files}). The @w{@code{save-tracepoints}} command is a deprecated
|
||
alias for @w{@code{save tracepoints}}
|
||
|
||
@node Tracepoint Variables
|
||
@section Convenience Variables for Tracepoints
|
||
@cindex tracepoint variables
|
||
@cindex convenience variables for tracepoints
|
||
|
||
@table @code
|
||
@vindex $trace_frame
|
||
@item (int) $trace_frame
|
||
The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
|
||
snapshot is selected.
|
||
|
||
@vindex $tracepoint
|
||
@item (int) $tracepoint
|
||
The tracepoint for the current trace snapshot.
|
||
|
||
@vindex $trace_line
|
||
@item (int) $trace_line
|
||
The line number for the current trace snapshot.
|
||
|
||
@vindex $trace_file
|
||
@item (char []) $trace_file
|
||
The source file for the current trace snapshot.
|
||
|
||
@vindex $trace_func
|
||
@item (char []) $trace_func
|
||
The name of the function containing @code{$tracepoint}.
|
||
@end table
|
||
|
||
Note: @code{$trace_file} is not suitable for use in @code{printf},
|
||
use @code{output} instead.
|
||
|
||
Here's a simple example of using these convenience variables for
|
||
stepping through all the trace snapshots and printing some of their
|
||
data. Note that these are not the same as trace state variables,
|
||
which are managed by the target.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{tfind start}
|
||
|
||
(@value{GDBP}) @b{while $trace_frame != -1}
|
||
> output $trace_file
|
||
> printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
|
||
> tfind
|
||
> end
|
||
@end smallexample
|
||
|
||
@node Trace Files
|
||
@section Using Trace Files
|
||
@cindex trace files
|
||
|
||
In some situations, the target running a trace experiment may no
|
||
longer be available; perhaps it crashed, or the hardware was needed
|
||
for a different activity. To handle these cases, you can arrange to
|
||
dump the trace data into a file, and later use that file as a source
|
||
of trace data, via the @code{target tfile} command.
|
||
|
||
@table @code
|
||
|
||
@kindex tsave
|
||
@item tsave [ -r ] @var{filename}
|
||
@itemx tsave [-ctf] @var{dirname}
|
||
Save the trace data to @var{filename}. By default, this command
|
||
assumes that @var{filename} refers to the host filesystem, so if
|
||
necessary @value{GDBN} will copy raw trace data up from the target and
|
||
then save it. If the target supports it, you can also supply the
|
||
optional argument @code{-r} (``remote'') to direct the target to save
|
||
the data directly into @var{filename} in its own filesystem, which may be
|
||
more efficient if the trace buffer is very large. (Note, however, that
|
||
@code{target tfile} can only read from files accessible to the host.)
|
||
By default, this command will save trace frame in tfile format.
|
||
You can supply the optional argument @code{-ctf} to save data in CTF
|
||
format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
|
||
that can be shared by multiple debugging and tracing tools. Please go to
|
||
@indicateurl{http://www.efficios.com/ctf} to get more information.
|
||
|
||
@kindex target tfile
|
||
@kindex tfile
|
||
@kindex target ctf
|
||
@kindex ctf
|
||
@item target tfile @var{filename}
|
||
@itemx target ctf @var{dirname}
|
||
Use the file named @var{filename} or directory named @var{dirname} as
|
||
a source of trace data. Commands that examine data work as they do with
|
||
a live target, but it is not possible to run any new trace experiments.
|
||
@code{tstatus} will report the state of the trace run at the moment
|
||
the data was saved, as well as the current trace frame you are examining.
|
||
Both @var{filename} and @var{dirname} must be on a filesystem accessible to
|
||
the host.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) target ctf ctf.ctf
|
||
(@value{GDBP}) tfind
|
||
Found trace frame 0, tracepoint 2
|
||
39 ++a; /* set tracepoint 1 here */
|
||
(@value{GDBP}) tdump
|
||
Data collected at tracepoint 2, trace frame 0:
|
||
i = 0
|
||
a = 0
|
||
b = 1 '\001'
|
||
c = @{"123", "456", "789", "123", "456", "789"@}
|
||
d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
|
||
(@value{GDBP}) p b
|
||
$1 = 1
|
||
@end smallexample
|
||
|
||
@end table
|
||
|
||
@node Overlays
|
||
@chapter Debugging Programs That Use Overlays
|
||
@cindex overlays
|
||
|
||
If your program is too large to fit completely in your target system's
|
||
memory, you can sometimes use @dfn{overlays} to work around this
|
||
problem. @value{GDBN} provides some support for debugging programs that
|
||
use overlays.
|
||
|
||
@menu
|
||
* How Overlays Work:: A general explanation of overlays.
|
||
* Overlay Commands:: Managing overlays in @value{GDBN}.
|
||
* Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
|
||
mapped by asking the inferior.
|
||
* Overlay Sample Program:: A sample program using overlays.
|
||
@end menu
|
||
|
||
@node How Overlays Work
|
||
@section How Overlays Work
|
||
@cindex mapped overlays
|
||
@cindex unmapped overlays
|
||
@cindex load address, overlay's
|
||
@cindex mapped address
|
||
@cindex overlay area
|
||
|
||
Suppose you have a computer whose instruction address space is only 64
|
||
kilobytes long, but which has much more memory which can be accessed by
|
||
other means: special instructions, segment registers, or memory
|
||
management hardware, for example. Suppose further that you want to
|
||
adapt a program which is larger than 64 kilobytes to run on this system.
|
||
|
||
One solution is to identify modules of your program which are relatively
|
||
independent, and need not call each other directly; call these modules
|
||
@dfn{overlays}. Separate the overlays from the main program, and place
|
||
their machine code in the larger memory. Place your main program in
|
||
instruction memory, but leave at least enough space there to hold the
|
||
largest overlay as well.
|
||
|
||
Now, to call a function located in an overlay, you must first copy that
|
||
overlay's machine code from the large memory into the space set aside
|
||
for it in the instruction memory, and then jump to its entry point
|
||
there.
|
||
|
||
@c NB: In the below the mapped area's size is greater or equal to the
|
||
@c size of all overlays. This is intentional to remind the developer
|
||
@c that overlays don't necessarily need to be the same size.
|
||
|
||
@smallexample
|
||
@group
|
||
Data Instruction Larger
|
||
Address Space Address Space Address Space
|
||
+-----------+ +-----------+ +-----------+
|
||
| | | | | |
|
||
+-----------+ +-----------+ +-----------+<-- overlay 1
|
||
| program | | main | .----| overlay 1 | load address
|
||
| variables | | program | | +-----------+
|
||
| and heap | | | | | |
|
||
+-----------+ | | | +-----------+<-- overlay 2
|
||
| | +-----------+ | | | load address
|
||
+-----------+ | | | .-| overlay 2 |
|
||
| | | | | |
|
||
mapped --->+-----------+ | | +-----------+
|
||
address | | | | | |
|
||
| overlay | <-' | | |
|
||
| area | <---' +-----------+<-- overlay 3
|
||
| | <---. | | load address
|
||
+-----------+ `--| overlay 3 |
|
||
| | | |
|
||
+-----------+ | |
|
||
+-----------+
|
||
| |
|
||
+-----------+
|
||
|
||
@anchor{A code overlay}A code overlay
|
||
@end group
|
||
@end smallexample
|
||
|
||
The diagram (@pxref{A code overlay}) shows a system with separate data
|
||
and instruction address spaces. To map an overlay, the program copies
|
||
its code from the larger address space to the instruction address space.
|
||
Since the overlays shown here all use the same mapped address, only one
|
||
may be mapped at a time. For a system with a single address space for
|
||
data and instructions, the diagram would be similar, except that the
|
||
program variables and heap would share an address space with the main
|
||
program and the overlay area.
|
||
|
||
An overlay loaded into instruction memory and ready for use is called a
|
||
@dfn{mapped} overlay; its @dfn{mapped address} is its address in the
|
||
instruction memory. An overlay not present (or only partially present)
|
||
in instruction memory is called @dfn{unmapped}; its @dfn{load address}
|
||
is its address in the larger memory. The mapped address is also called
|
||
the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
|
||
called the @dfn{load memory address}, or @dfn{LMA}.
|
||
|
||
Unfortunately, overlays are not a completely transparent way to adapt a
|
||
program to limited instruction memory. They introduce a new set of
|
||
global constraints you must keep in mind as you design your program:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Before calling or returning to a function in an overlay, your program
|
||
must make sure that overlay is actually mapped. Otherwise, the call or
|
||
return will transfer control to the right address, but in the wrong
|
||
overlay, and your program will probably crash.
|
||
|
||
@item
|
||
If the process of mapping an overlay is expensive on your system, you
|
||
will need to choose your overlays carefully to minimize their effect on
|
||
your program's performance.
|
||
|
||
@item
|
||
The executable file you load onto your system must contain each
|
||
overlay's instructions, appearing at the overlay's load address, not its
|
||
mapped address. However, each overlay's instructions must be relocated
|
||
and its symbols defined as if the overlay were at its mapped address.
|
||
You can use GNU linker scripts to specify different load and relocation
|
||
addresses for pieces of your program; see @ref{Overlay Description,,,
|
||
ld.info, Using ld: the GNU linker}.
|
||
|
||
@item
|
||
The procedure for loading executable files onto your system must be able
|
||
to load their contents into the larger address space as well as the
|
||
instruction and data spaces.
|
||
|
||
@end itemize
|
||
|
||
The overlay system described above is rather simple, and could be
|
||
improved in many ways:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
If your system has suitable bank switch registers or memory management
|
||
hardware, you could use those facilities to make an overlay's load area
|
||
contents simply appear at their mapped address in instruction space.
|
||
This would probably be faster than copying the overlay to its mapped
|
||
area in the usual way.
|
||
|
||
@item
|
||
If your overlays are small enough, you could set aside more than one
|
||
overlay area, and have more than one overlay mapped at a time.
|
||
|
||
@item
|
||
You can use overlays to manage data, as well as instructions. In
|
||
general, data overlays are even less transparent to your design than
|
||
code overlays: whereas code overlays only require care when you call or
|
||
return to functions, data overlays require care every time you access
|
||
the data. Also, if you change the contents of a data overlay, you
|
||
must copy its contents back out to its load address before you can copy a
|
||
different data overlay into the same mapped area.
|
||
|
||
@end itemize
|
||
|
||
|
||
@node Overlay Commands
|
||
@section Overlay Commands
|
||
|
||
To use @value{GDBN}'s overlay support, each overlay in your program must
|
||
correspond to a separate section of the executable file. The section's
|
||
virtual memory address and load memory address must be the overlay's
|
||
mapped and load addresses. Identifying overlays with sections allows
|
||
@value{GDBN} to determine the appropriate address of a function or
|
||
variable, depending on whether the overlay is mapped or not.
|
||
|
||
@value{GDBN}'s overlay commands all start with the word @code{overlay};
|
||
you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
|
||
|
||
@table @code
|
||
@item overlay off
|
||
@kindex overlay
|
||
Disable @value{GDBN}'s overlay support. When overlay support is
|
||
disabled, @value{GDBN} assumes that all functions and variables are
|
||
always present at their mapped addresses. By default, @value{GDBN}'s
|
||
overlay support is disabled.
|
||
|
||
@item overlay manual
|
||
@cindex manual overlay debugging
|
||
Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
|
||
relies on you to tell it which overlays are mapped, and which are not,
|
||
using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
|
||
commands described below.
|
||
|
||
@item overlay map-overlay @var{overlay}
|
||
@itemx overlay map @var{overlay}
|
||
@cindex map an overlay
|
||
Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
|
||
be the name of the object file section containing the overlay. When an
|
||
overlay is mapped, @value{GDBN} assumes it can find the overlay's
|
||
functions and variables at their mapped addresses. @value{GDBN} assumes
|
||
that any other overlays whose mapped ranges overlap that of
|
||
@var{overlay} are now unmapped.
|
||
|
||
@item overlay unmap-overlay @var{overlay}
|
||
@itemx overlay unmap @var{overlay}
|
||
@cindex unmap an overlay
|
||
Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
|
||
must be the name of the object file section containing the overlay.
|
||
When an overlay is unmapped, @value{GDBN} assumes it can find the
|
||
overlay's functions and variables at their load addresses.
|
||
|
||
@item overlay auto
|
||
Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
|
||
consults a data structure the overlay manager maintains in the inferior
|
||
to see which overlays are mapped. For details, see @ref{Automatic
|
||
Overlay Debugging}.
|
||
|
||
@item overlay load-target
|
||
@itemx overlay load
|
||
@cindex reloading the overlay table
|
||
Re-read the overlay table from the inferior. Normally, @value{GDBN}
|
||
re-reads the table @value{GDBN} automatically each time the inferior
|
||
stops, so this command should only be necessary if you have changed the
|
||
overlay mapping yourself using @value{GDBN}. This command is only
|
||
useful when using automatic overlay debugging.
|
||
|
||
@item overlay list-overlays
|
||
@itemx overlay list
|
||
@cindex listing mapped overlays
|
||
Display a list of the overlays currently mapped, along with their mapped
|
||
addresses, load addresses, and sizes.
|
||
|
||
@end table
|
||
|
||
Normally, when @value{GDBN} prints a code address, it includes the name
|
||
of the function the address falls in:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print main
|
||
$3 = @{int ()@} 0x11a0 <main>
|
||
@end smallexample
|
||
@noindent
|
||
When overlay debugging is enabled, @value{GDBN} recognizes code in
|
||
unmapped overlays, and prints the names of unmapped functions with
|
||
asterisks around them. For example, if @code{foo} is a function in an
|
||
unmapped overlay, @value{GDBN} prints it this way:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) overlay list
|
||
No sections are mapped.
|
||
(@value{GDBP}) print foo
|
||
$5 = @{int (int)@} 0x100000 <*foo*>
|
||
@end smallexample
|
||
@noindent
|
||
When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
|
||
name normally:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) overlay list
|
||
Section .ov.foo.text, loaded at 0x100000 - 0x100034,
|
||
mapped at 0x1016 - 0x104a
|
||
(@value{GDBP}) print foo
|
||
$6 = @{int (int)@} 0x1016 <foo>
|
||
@end smallexample
|
||
|
||
When overlay debugging is enabled, @value{GDBN} can find the correct
|
||
address for functions and variables in an overlay, whether or not the
|
||
overlay is mapped. This allows most @value{GDBN} commands, like
|
||
@code{break} and @code{disassemble}, to work normally, even on unmapped
|
||
code. However, @value{GDBN}'s breakpoint support has some limitations:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
@cindex breakpoints in overlays
|
||
@cindex overlays, setting breakpoints in
|
||
You can set breakpoints in functions in unmapped overlays, as long as
|
||
@value{GDBN} can write to the overlay at its load address.
|
||
@item
|
||
@value{GDBN} can not set hardware or simulator-based breakpoints in
|
||
unmapped overlays. However, if you set a breakpoint at the end of your
|
||
overlay manager (and tell @value{GDBN} which overlays are now mapped, if
|
||
you are using manual overlay management), @value{GDBN} will re-set its
|
||
breakpoints properly.
|
||
@end itemize
|
||
|
||
|
||
@node Automatic Overlay Debugging
|
||
@section Automatic Overlay Debugging
|
||
@cindex automatic overlay debugging
|
||
|
||
@value{GDBN} can automatically track which overlays are mapped and which
|
||
are not, given some simple co-operation from the overlay manager in the
|
||
inferior. If you enable automatic overlay debugging with the
|
||
@code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
|
||
looks in the inferior's memory for certain variables describing the
|
||
current state of the overlays.
|
||
|
||
Here are the variables your overlay manager must define to support
|
||
@value{GDBN}'s automatic overlay debugging:
|
||
|
||
@table @asis
|
||
|
||
@item @code{_ovly_table}:
|
||
This variable must be an array of the following structures:
|
||
|
||
@smallexample
|
||
struct
|
||
@{
|
||
/* The overlay's mapped address. */
|
||
unsigned long vma;
|
||
|
||
/* The size of the overlay, in bytes. */
|
||
unsigned long size;
|
||
|
||
/* The overlay's load address. */
|
||
unsigned long lma;
|
||
|
||
/* Non-zero if the overlay is currently mapped;
|
||
zero otherwise. */
|
||
unsigned long mapped;
|
||
@}
|
||
@end smallexample
|
||
|
||
@item @code{_novlys}:
|
||
This variable must be a four-byte signed integer, holding the total
|
||
number of elements in @code{_ovly_table}.
|
||
|
||
@end table
|
||
|
||
To decide whether a particular overlay is mapped or not, @value{GDBN}
|
||
looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
|
||
@code{lma} members equal the VMA and LMA of the overlay's section in the
|
||
executable file. When @value{GDBN} finds a matching entry, it consults
|
||
the entry's @code{mapped} member to determine whether the overlay is
|
||
currently mapped.
|
||
|
||
In addition, your overlay manager may define a function called
|
||
@code{_ovly_debug_event}. If this function is defined, @value{GDBN}
|
||
will silently set a breakpoint there. If the overlay manager then
|
||
calls this function whenever it has changed the overlay table, this
|
||
will enable @value{GDBN} to accurately keep track of which overlays
|
||
are in program memory, and update any breakpoints that may be set
|
||
in overlays. This will allow breakpoints to work even if the
|
||
overlays are kept in ROM or other non-writable memory while they
|
||
are not being executed.
|
||
|
||
@node Overlay Sample Program
|
||
@section Overlay Sample Program
|
||
@cindex overlay example program
|
||
|
||
When linking a program which uses overlays, you must place the overlays
|
||
at their load addresses, while relocating them to run at their mapped
|
||
addresses. To do this, you must write a linker script (@pxref{Overlay
|
||
Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
|
||
since linker scripts are specific to a particular host system, target
|
||
architecture, and target memory layout, this manual cannot provide
|
||
portable sample code demonstrating @value{GDBN}'s overlay support.
|
||
|
||
However, the @value{GDBN} source distribution does contain an overlaid
|
||
program, with linker scripts for a few systems, as part of its test
|
||
suite. The program consists of the following files from
|
||
@file{gdb/testsuite/gdb.base}:
|
||
|
||
@table @file
|
||
@item overlays.c
|
||
The main program file.
|
||
@item ovlymgr.c
|
||
A simple overlay manager, used by @file{overlays.c}.
|
||
@item foo.c
|
||
@itemx bar.c
|
||
@itemx baz.c
|
||
@itemx grbx.c
|
||
Overlay modules, loaded and used by @file{overlays.c}.
|
||
@item d10v.ld
|
||
@itemx m32r.ld
|
||
Linker scripts for linking the test program on the @code{d10v-elf}
|
||
and @code{m32r-elf} targets.
|
||
@end table
|
||
|
||
You can build the test program using the @code{d10v-elf} GCC
|
||
cross-compiler like this:
|
||
|
||
@smallexample
|
||
$ d10v-elf-gcc -g -c overlays.c
|
||
$ d10v-elf-gcc -g -c ovlymgr.c
|
||
$ d10v-elf-gcc -g -c foo.c
|
||
$ d10v-elf-gcc -g -c bar.c
|
||
$ d10v-elf-gcc -g -c baz.c
|
||
$ d10v-elf-gcc -g -c grbx.c
|
||
$ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
|
||
baz.o grbx.o -Wl,-Td10v.ld -o overlays
|
||
@end smallexample
|
||
|
||
The build process is identical for any other architecture, except that
|
||
you must substitute the appropriate compiler and linker script for the
|
||
target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
|
||
|
||
|
||
@node Languages
|
||
@chapter Using @value{GDBN} with Different Languages
|
||
@cindex languages
|
||
|
||
Although programming languages generally have common aspects, they are
|
||
rarely expressed in the same manner. For instance, in ANSI C,
|
||
dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
|
||
Modula-2, it is accomplished by @code{p^}. Values can also be
|
||
represented (and displayed) differently. Hex numbers in C appear as
|
||
@samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
|
||
|
||
@cindex working language
|
||
Language-specific information is built into @value{GDBN} for some languages,
|
||
allowing you to express operations like the above in your program's
|
||
native language, and allowing @value{GDBN} to output values in a manner
|
||
consistent with the syntax of your program's native language. The
|
||
language you use to build expressions is called the @dfn{working
|
||
language}.
|
||
|
||
@menu
|
||
* Setting:: Switching between source languages
|
||
* Show:: Displaying the language
|
||
* Checks:: Type and range checks
|
||
* Supported Languages:: Supported languages
|
||
* Unsupported Languages:: Unsupported languages
|
||
@end menu
|
||
|
||
@node Setting
|
||
@section Switching Between Source Languages
|
||
|
||
There are two ways to control the working language---either have @value{GDBN}
|
||
set it automatically, or select it manually yourself. You can use the
|
||
@code{set language} command for either purpose. On startup, @value{GDBN}
|
||
defaults to setting the language automatically. The working language is
|
||
used to determine how expressions you type are interpreted, how values
|
||
are printed, etc.
|
||
|
||
In addition to the working language, every source file that
|
||
@value{GDBN} knows about has its own working language. For some object
|
||
file formats, the compiler might indicate which language a particular
|
||
source file is in. However, most of the time @value{GDBN} infers the
|
||
language from the name of the file. The language of a source file
|
||
controls whether C@t{++} names are demangled---this way @code{backtrace} can
|
||
show each frame appropriately for its own language. There is no way to
|
||
set the language of a source file from within @value{GDBN}, but you can
|
||
set the language associated with a filename extension. @xref{Show, ,
|
||
Displaying the Language}.
|
||
|
||
This is most commonly a problem when you use a program, such
|
||
as @code{cfront} or @code{f2c}, that generates C but is written in
|
||
another language. In that case, make the
|
||
program use @code{#line} directives in its C output; that way
|
||
@value{GDBN} will know the correct language of the source code of the original
|
||
program, and will display that source code, not the generated C code.
|
||
|
||
@menu
|
||
* Filenames:: Filename extensions and languages.
|
||
* Manually:: Setting the working language manually
|
||
* Automatically:: Having @value{GDBN} infer the source language
|
||
@end menu
|
||
|
||
@node Filenames
|
||
@subsection List of Filename Extensions and Languages
|
||
|
||
If a source file name ends in one of the following extensions, then
|
||
@value{GDBN} infers that its language is the one indicated.
|
||
|
||
@table @file
|
||
@item .ada
|
||
@itemx .ads
|
||
@itemx .adb
|
||
@itemx .a
|
||
Ada source file.
|
||
|
||
@item .c
|
||
C source file
|
||
|
||
@item .C
|
||
@itemx .cc
|
||
@itemx .cp
|
||
@itemx .cpp
|
||
@itemx .cxx
|
||
@itemx .c++
|
||
C@t{++} source file
|
||
|
||
@item .d
|
||
D source file
|
||
|
||
@item .m
|
||
Objective-C source file
|
||
|
||
@item .f
|
||
@itemx .F
|
||
Fortran source file
|
||
|
||
@item .mod
|
||
Modula-2 source file
|
||
|
||
@item .s
|
||
@itemx .S
|
||
Assembler source file. This actually behaves almost like C, but
|
||
@value{GDBN} does not skip over function prologues when stepping.
|
||
@end table
|
||
|
||
In addition, you may set the language associated with a filename
|
||
extension. @xref{Show, , Displaying the Language}.
|
||
|
||
@node Manually
|
||
@subsection Setting the Working Language
|
||
|
||
If you allow @value{GDBN} to set the language automatically,
|
||
expressions are interpreted the same way in your debugging session and
|
||
your program.
|
||
|
||
@kindex set language
|
||
If you wish, you may set the language manually. To do this, issue the
|
||
command @samp{set language @var{lang}}, where @var{lang} is the name of
|
||
a language, such as
|
||
@code{c} or @code{modula-2}.
|
||
For a list of the supported languages, type @samp{set language}.
|
||
|
||
Setting the language manually prevents @value{GDBN} from updating the working
|
||
language automatically. This can lead to confusion if you try
|
||
to debug a program when the working language is not the same as the
|
||
source language, when an expression is acceptable to both
|
||
languages---but means different things. For instance, if the current
|
||
source file were written in C, and @value{GDBN} was parsing Modula-2, a
|
||
command such as:
|
||
|
||
@smallexample
|
||
print a = b + c
|
||
@end smallexample
|
||
|
||
@noindent
|
||
might not have the effect you intended. In C, this means to add
|
||
@code{b} and @code{c} and place the result in @code{a}. The result
|
||
printed would be the value of @code{a}. In Modula-2, this means to compare
|
||
@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
|
||
|
||
@node Automatically
|
||
@subsection Having @value{GDBN} Infer the Source Language
|
||
|
||
To have @value{GDBN} set the working language automatically, use
|
||
@samp{set language local} or @samp{set language auto}. @value{GDBN}
|
||
then infers the working language. That is, when your program stops in a
|
||
frame (usually by encountering a breakpoint), @value{GDBN} sets the
|
||
working language to the language recorded for the function in that
|
||
frame. If the language for a frame is unknown (that is, if the function
|
||
or block corresponding to the frame was defined in a source file that
|
||
does not have a recognized extension), the current working language is
|
||
not changed, and @value{GDBN} issues a warning.
|
||
|
||
This may not seem necessary for most programs, which are written
|
||
entirely in one source language. However, program modules and libraries
|
||
written in one source language can be used by a main program written in
|
||
a different source language. Using @samp{set language auto} in this
|
||
case frees you from having to set the working language manually.
|
||
|
||
@node Show
|
||
@section Displaying the Language
|
||
|
||
The following commands help you find out which language is the
|
||
working language, and also what language source files were written in.
|
||
|
||
@table @code
|
||
@item show language
|
||
@anchor{show language}
|
||
@kindex show language
|
||
Display the current working language. This is the
|
||
language you can use with commands such as @code{print} to
|
||
build and compute expressions that may involve variables in your program.
|
||
|
||
@item info frame
|
||
@kindex info frame@r{, show the source language}
|
||
Display the source language for this frame. This language becomes the
|
||
working language if you use an identifier from this frame.
|
||
@xref{Frame Info, ,Information about a Frame}, to identify the other
|
||
information listed here.
|
||
|
||
@item info source
|
||
@kindex info source@r{, show the source language}
|
||
Display the source language of this source file.
|
||
@xref{Symbols, ,Examining the Symbol Table}, to identify the other
|
||
information listed here.
|
||
@end table
|
||
|
||
In unusual circumstances, you may have source files with extensions
|
||
not in the standard list. You can then set the extension associated
|
||
with a language explicitly:
|
||
|
||
@table @code
|
||
@item set extension-language @var{ext} @var{language}
|
||
@kindex set extension-language
|
||
Tell @value{GDBN} that source files with extension @var{ext} are to be
|
||
assumed as written in the source language @var{language}.
|
||
|
||
@item info extensions
|
||
@kindex info extensions
|
||
List all the filename extensions and the associated languages.
|
||
@end table
|
||
|
||
@node Checks
|
||
@section Type and Range Checking
|
||
|
||
Some languages are designed to guard you against making seemingly common
|
||
errors through a series of compile- and run-time checks. These include
|
||
checking the type of arguments to functions and operators and making
|
||
sure mathematical overflows are caught at run time. Checks such as
|
||
these help to ensure a program's correctness once it has been compiled
|
||
by eliminating type mismatches and providing active checks for range
|
||
errors when your program is running.
|
||
|
||
By default @value{GDBN} checks for these errors according to the
|
||
rules of the current source language. Although @value{GDBN} does not check
|
||
the statements in your program, it can check expressions entered directly
|
||
into @value{GDBN} for evaluation via the @code{print} command, for example.
|
||
|
||
@menu
|
||
* Type Checking:: An overview of type checking
|
||
* Range Checking:: An overview of range checking
|
||
@end menu
|
||
|
||
@cindex type checking
|
||
@cindex checks, type
|
||
@node Type Checking
|
||
@subsection An Overview of Type Checking
|
||
|
||
Some languages, such as C and C@t{++}, are strongly typed, meaning that the
|
||
arguments to operators and functions have to be of the correct type,
|
||
otherwise an error occurs. These checks prevent type mismatch
|
||
errors from ever causing any run-time problems. For example,
|
||
|
||
@smallexample
|
||
int klass::my_method(char *b) @{ return b ? 1 : 2; @}
|
||
|
||
(@value{GDBP}) print obj.my_method (0)
|
||
$1 = 2
|
||
@exdent but
|
||
(@value{GDBP}) print obj.my_method (0x1234)
|
||
Cannot resolve method klass::my_method to any overloaded instance
|
||
@end smallexample
|
||
|
||
The second example fails because in C@t{++} the integer constant
|
||
@samp{0x1234} is not type-compatible with the pointer parameter type.
|
||
|
||
For the expressions you use in @value{GDBN} commands, you can tell
|
||
@value{GDBN} to not enforce strict type checking or
|
||
to treat any mismatches as errors and abandon the expression;
|
||
When type checking is disabled, @value{GDBN} successfully evaluates
|
||
expressions like the second example above.
|
||
|
||
Even if type checking is off, there may be other reasons
|
||
related to type that prevent @value{GDBN} from evaluating an expression.
|
||
For instance, @value{GDBN} does not know how to add an @code{int} and
|
||
a @code{struct foo}. These particular type errors have nothing to do
|
||
with the language in use and usually arise from expressions which make
|
||
little sense to evaluate anyway.
|
||
|
||
@value{GDBN} provides some additional commands for controlling type checking:
|
||
|
||
@kindex set check type
|
||
@kindex show check type
|
||
@table @code
|
||
@item set check type on
|
||
@itemx set check type off
|
||
Set strict type checking on or off. If any type mismatches occur in
|
||
evaluating an expression while type checking is on, @value{GDBN} prints a
|
||
message and aborts evaluation of the expression.
|
||
|
||
@item show check type
|
||
Show the current setting of type checking and whether @value{GDBN}
|
||
is enforcing strict type checking rules.
|
||
@end table
|
||
|
||
@cindex range checking
|
||
@cindex checks, range
|
||
@node Range Checking
|
||
@subsection An Overview of Range Checking
|
||
|
||
In some languages (such as Modula-2), it is an error to exceed the
|
||
bounds of a type; this is enforced with run-time checks. Such range
|
||
checking is meant to ensure program correctness by making sure
|
||
computations do not overflow, or indices on an array element access do
|
||
not exceed the bounds of the array.
|
||
|
||
For expressions you use in @value{GDBN} commands, you can tell
|
||
@value{GDBN} to treat range errors in one of three ways: ignore them,
|
||
always treat them as errors and abandon the expression, or issue
|
||
warnings but evaluate the expression anyway.
|
||
|
||
A range error can result from numerical overflow, from exceeding an
|
||
array index bound, or when you type a constant that is not a member
|
||
of any type. Some languages, however, do not treat overflows as an
|
||
error. In many implementations of C, mathematical overflow causes the
|
||
result to ``wrap around'' to lower values---for example, if @var{m} is
|
||
the largest integer value, and @var{s} is the smallest, then
|
||
|
||
@smallexample
|
||
@var{m} + 1 @result{} @var{s}
|
||
@end smallexample
|
||
|
||
This, too, is specific to individual languages, and in some cases
|
||
specific to individual compilers or machines. @xref{Supported Languages, ,
|
||
Supported Languages}, for further details on specific languages.
|
||
|
||
@value{GDBN} provides some additional commands for controlling the range checker:
|
||
|
||
@kindex set check range
|
||
@kindex show check range
|
||
@table @code
|
||
@item set check range auto
|
||
Set range checking on or off based on the current working language.
|
||
@xref{Supported Languages, ,Supported Languages}, for the default settings for
|
||
each language.
|
||
|
||
@item set check range on
|
||
@itemx set check range off
|
||
Set range checking on or off, overriding the default setting for the
|
||
current working language. A warning is issued if the setting does not
|
||
match the language default. If a range error occurs and range checking is on,
|
||
then a message is printed and evaluation of the expression is aborted.
|
||
|
||
@item set check range warn
|
||
Output messages when the @value{GDBN} range checker detects a range error,
|
||
but attempt to evaluate the expression anyway. Evaluating the
|
||
expression may still be impossible for other reasons, such as accessing
|
||
memory that the process does not own (a typical example from many Unix
|
||
systems).
|
||
|
||
@item show range
|
||
Show the current setting of the range checker, and whether or not it is
|
||
being set automatically by @value{GDBN}.
|
||
@end table
|
||
|
||
@node Supported Languages
|
||
@section Supported Languages
|
||
|
||
@value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
|
||
OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
|
||
@c This is false ...
|
||
Some @value{GDBN} features may be used in expressions regardless of the
|
||
language you use: the @value{GDBN} @code{@@} and @code{::} operators,
|
||
and the @samp{@{type@}addr} construct (@pxref{Expressions,
|
||
,Expressions}) can be used with the constructs of any supported
|
||
language.
|
||
|
||
The following sections detail to what degree each source language is
|
||
supported by @value{GDBN}. These sections are not meant to be language
|
||
tutorials or references, but serve only as a reference guide to what the
|
||
@value{GDBN} expression parser accepts, and what input and output
|
||
formats should look like for different languages. There are many good
|
||
books written on each of these languages; please look to these for a
|
||
language reference or tutorial.
|
||
|
||
@menu
|
||
* C:: C and C@t{++}
|
||
* D:: D
|
||
* Go:: Go
|
||
* Objective-C:: Objective-C
|
||
* OpenCL C:: OpenCL C
|
||
* Fortran:: Fortran
|
||
* Pascal:: Pascal
|
||
* Rust:: Rust
|
||
* Modula-2:: Modula-2
|
||
* Ada:: Ada
|
||
@end menu
|
||
|
||
@node C
|
||
@subsection C and C@t{++}
|
||
|
||
@cindex C and C@t{++}
|
||
@cindex expressions in C or C@t{++}
|
||
|
||
Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
|
||
to both languages. Whenever this is the case, we discuss those languages
|
||
together.
|
||
|
||
@cindex C@t{++}
|
||
@cindex @code{g++}, @sc{gnu} C@t{++} compiler
|
||
@cindex @sc{gnu} C@t{++}
|
||
The C@t{++} debugging facilities are jointly implemented by the C@t{++}
|
||
compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
|
||
effectively, you must compile your C@t{++} programs with a supported
|
||
C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
|
||
compiler (@code{aCC}).
|
||
|
||
@menu
|
||
* C Operators:: C and C@t{++} operators
|
||
* C Constants:: C and C@t{++} constants
|
||
* C Plus Plus Expressions:: C@t{++} expressions
|
||
* C Defaults:: Default settings for C and C@t{++}
|
||
* C Checks:: C and C@t{++} type and range checks
|
||
* Debugging C:: @value{GDBN} and C
|
||
* Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
|
||
* Decimal Floating Point:: Numbers in Decimal Floating Point format
|
||
@end menu
|
||
|
||
@node C Operators
|
||
@subsubsection C and C@t{++} Operators
|
||
|
||
@cindex C and C@t{++} operators
|
||
|
||
Operators must be defined on values of specific types. For instance,
|
||
@code{+} is defined on numbers, but not on structures. Operators are
|
||
often defined on groups of types.
|
||
|
||
For the purposes of C and C@t{++}, the following definitions hold:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
@emph{Integral types} include @code{int} with any of its storage-class
|
||
specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
|
||
|
||
@item
|
||
@emph{Floating-point types} include @code{float}, @code{double}, and
|
||
@code{long double} (if supported by the target platform).
|
||
|
||
@item
|
||
@emph{Pointer types} include all types defined as @code{(@var{type} *)}.
|
||
|
||
@item
|
||
@emph{Scalar types} include all of the above.
|
||
|
||
@end itemize
|
||
|
||
@noindent
|
||
The following operators are supported. They are listed here
|
||
in order of increasing precedence:
|
||
|
||
@table @code
|
||
@item ,
|
||
The comma or sequencing operator. Expressions in a comma-separated list
|
||
are evaluated from left to right, with the result of the entire
|
||
expression being the last expression evaluated.
|
||
|
||
@item =
|
||
Assignment. The value of an assignment expression is the value
|
||
assigned. Defined on scalar types.
|
||
|
||
@item @var{op}=
|
||
Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
|
||
and translated to @w{@code{@var{a} = @var{a op b}}}.
|
||
@w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
|
||
@var{op} is any one of the operators @code{|}, @code{^}, @code{&},
|
||
@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
|
||
|
||
@item ?:
|
||
The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
|
||
of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
|
||
should be of an integral type.
|
||
|
||
@item ||
|
||
Logical @sc{or}. Defined on integral types.
|
||
|
||
@item &&
|
||
Logical @sc{and}. Defined on integral types.
|
||
|
||
@item |
|
||
Bitwise @sc{or}. Defined on integral types.
|
||
|
||
@item ^
|
||
Bitwise exclusive-@sc{or}. Defined on integral types.
|
||
|
||
@item &
|
||
Bitwise @sc{and}. Defined on integral types.
|
||
|
||
@item ==@r{, }!=
|
||
Equality and inequality. Defined on scalar types. The value of these
|
||
expressions is 0 for false and non-zero for true.
|
||
|
||
@item <@r{, }>@r{, }<=@r{, }>=
|
||
Less than, greater than, less than or equal, greater than or equal.
|
||
Defined on scalar types. The value of these expressions is 0 for false
|
||
and non-zero for true.
|
||
|
||
@item <<@r{, }>>
|
||
left shift, and right shift. Defined on integral types.
|
||
|
||
@item @@
|
||
The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
|
||
|
||
@item +@r{, }-
|
||
Addition and subtraction. Defined on integral types, floating-point types and
|
||
pointer types.
|
||
|
||
@item *@r{, }/@r{, }%
|
||
Multiplication, division, and modulus. Multiplication and division are
|
||
defined on integral and floating-point types. Modulus is defined on
|
||
integral types.
|
||
|
||
@item ++@r{, }--
|
||
Increment and decrement. When appearing before a variable, the
|
||
operation is performed before the variable is used in an expression;
|
||
when appearing after it, the variable's value is used before the
|
||
operation takes place.
|
||
|
||
@item *
|
||
Pointer dereferencing. Defined on pointer types. Same precedence as
|
||
@code{++}.
|
||
|
||
@item &
|
||
Address operator. Defined on variables. Same precedence as @code{++}.
|
||
|
||
For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
|
||
allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
|
||
to examine the address
|
||
where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
|
||
stored.
|
||
|
||
@item -
|
||
Negative. Defined on integral and floating-point types. Same
|
||
precedence as @code{++}.
|
||
|
||
@item !
|
||
Logical negation. Defined on integral types. Same precedence as
|
||
@code{++}.
|
||
|
||
@item ~
|
||
Bitwise complement operator. Defined on integral types. Same precedence as
|
||
@code{++}.
|
||
|
||
|
||
@item .@r{, }->
|
||
Structure member, and pointer-to-structure member. For convenience,
|
||
@value{GDBN} regards the two as equivalent, choosing whether to dereference a
|
||
pointer based on the stored type information.
|
||
Defined on @code{struct} and @code{union} data.
|
||
|
||
@item .*@r{, }->*
|
||
Dereferences of pointers to members.
|
||
|
||
@item []
|
||
Array indexing. @code{@var{a}[@var{i}]} is defined as
|
||
@code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
|
||
|
||
@item ()
|
||
Function parameter list. Same precedence as @code{->}.
|
||
|
||
@item ::
|
||
C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
|
||
and @code{class} types.
|
||
|
||
@item ::
|
||
Doubled colons also represent the @value{GDBN} scope operator
|
||
(@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
|
||
above.
|
||
@end table
|
||
|
||
If an operator is redefined in the user code, @value{GDBN} usually
|
||
attempts to invoke the redefined version instead of using the operator's
|
||
predefined meaning.
|
||
|
||
@node C Constants
|
||
@subsubsection C and C@t{++} Constants
|
||
|
||
@cindex C and C@t{++} constants
|
||
|
||
@value{GDBN} allows you to express the constants of C and C@t{++} in the
|
||
following ways:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Integer constants are a sequence of digits. Octal constants are
|
||
specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
|
||
by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
|
||
@samp{l}, specifying that the constant should be treated as a
|
||
@code{long} value.
|
||
|
||
@item
|
||
Floating point constants are a sequence of digits, followed by a decimal
|
||
point, followed by a sequence of digits, and optionally followed by an
|
||
exponent. An exponent is of the form:
|
||
@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
|
||
sequence of digits. The @samp{+} is optional for positive exponents.
|
||
A floating-point constant may also end with a letter @samp{f} or
|
||
@samp{F}, specifying that the constant should be treated as being of
|
||
the @code{float} (as opposed to the default @code{double}) type; or with
|
||
a letter @samp{l} or @samp{L}, which specifies a @code{long double}
|
||
constant.
|
||
|
||
@item
|
||
Enumerated constants consist of enumerated identifiers, or their
|
||
integral equivalents.
|
||
|
||
@item
|
||
Character constants are a single character surrounded by single quotes
|
||
(@code{'}), or a number---the ordinal value of the corresponding character
|
||
(usually its @sc{ascii} value). Within quotes, the single character may
|
||
be represented by a letter or by @dfn{escape sequences}, which are of
|
||
the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
|
||
of the character's ordinal value; or of the form @samp{\@var{x}}, where
|
||
@samp{@var{x}} is a predefined special character---for example,
|
||
@samp{\n} for newline.
|
||
|
||
Wide character constants can be written by prefixing a character
|
||
constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
|
||
form of @samp{x}. The target wide character set is used when
|
||
computing the value of this constant (@pxref{Character Sets}).
|
||
|
||
@item
|
||
String constants are a sequence of character constants surrounded by
|
||
double quotes (@code{"}). Any valid character constant (as described
|
||
above) may appear. Double quotes within the string must be preceded by
|
||
a backslash, so for instance @samp{"a\"b'c"} is a string of five
|
||
characters.
|
||
|
||
Wide string constants can be written by prefixing a string constant
|
||
with @samp{L}, as in C. The target wide character set is used when
|
||
computing the value of this constant (@pxref{Character Sets}).
|
||
|
||
@item
|
||
Pointer constants are an integral value. You can also write pointers
|
||
to constants using the C operator @samp{&}.
|
||
|
||
@item
|
||
Array constants are comma-separated lists surrounded by braces @samp{@{}
|
||
and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
|
||
integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
|
||
and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
|
||
@end itemize
|
||
|
||
@node C Plus Plus Expressions
|
||
@subsubsection C@t{++} Expressions
|
||
|
||
@cindex expressions in C@t{++}
|
||
@value{GDBN} expression handling can interpret most C@t{++} expressions.
|
||
|
||
@cindex debugging C@t{++} programs
|
||
@cindex C@t{++} compilers
|
||
@cindex debug formats and C@t{++}
|
||
@cindex @value{NGCC} and C@t{++}
|
||
@quotation
|
||
@emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
|
||
the proper compiler and the proper debug format. Currently,
|
||
@value{GDBN} works best when debugging C@t{++} code that is compiled
|
||
with the most recent version of @value{NGCC} possible. The DWARF
|
||
debugging format is preferred; @value{NGCC} defaults to this on most
|
||
popular platforms. Other compilers and/or debug formats are likely to
|
||
work badly or not at all when using @value{GDBN} to debug C@t{++}
|
||
code. @xref{Compilation}.
|
||
@end quotation
|
||
|
||
@enumerate
|
||
|
||
@cindex member functions
|
||
@item
|
||
Member function calls are allowed; you can use expressions like
|
||
|
||
@smallexample
|
||
count = aml->GetOriginal(x, y)
|
||
@end smallexample
|
||
|
||
@vindex this@r{, inside C@t{++} member functions}
|
||
@cindex namespace in C@t{++}
|
||
@item
|
||
While a member function is active (in the selected stack frame), your
|
||
expressions have the same namespace available as the member function;
|
||
that is, @value{GDBN} allows implicit references to the class instance
|
||
pointer @code{this} following the same rules as C@t{++}. @code{using}
|
||
declarations in the current scope are also respected by @value{GDBN}.
|
||
|
||
@cindex call overloaded functions
|
||
@cindex overloaded functions, calling
|
||
@cindex type conversions in C@t{++}
|
||
@item
|
||
You can call overloaded functions; @value{GDBN} resolves the function
|
||
call to the right definition, with some restrictions. @value{GDBN} does not
|
||
perform overload resolution involving user-defined type conversions,
|
||
calls to constructors, or instantiations of templates that do not exist
|
||
in the program. It also cannot handle ellipsis argument lists or
|
||
default arguments.
|
||
|
||
It does perform integral conversions and promotions, floating-point
|
||
promotions, arithmetic conversions, pointer conversions, conversions of
|
||
class objects to base classes, and standard conversions such as those of
|
||
functions or arrays to pointers; it requires an exact match on the
|
||
number of function arguments.
|
||
|
||
Overload resolution is always performed, unless you have specified
|
||
@code{set overload-resolution off}. @xref{Debugging C Plus Plus,
|
||
,@value{GDBN} Features for C@t{++}}.
|
||
|
||
You must specify @code{set overload-resolution off} in order to use an
|
||
explicit function signature to call an overloaded function, as in
|
||
@smallexample
|
||
p 'foo(char,int)'('x', 13)
|
||
@end smallexample
|
||
|
||
The @value{GDBN} command-completion facility can simplify this;
|
||
see @ref{Completion, ,Command Completion}.
|
||
|
||
@cindex reference declarations
|
||
@item
|
||
@value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
|
||
references; you can use them in expressions just as you do in C@t{++}
|
||
source---they are automatically dereferenced.
|
||
|
||
In the parameter list shown when @value{GDBN} displays a frame, the values of
|
||
reference variables are not displayed (unlike other variables); this
|
||
avoids clutter, since references are often used for large structures.
|
||
The @emph{address} of a reference variable is always shown, unless
|
||
you have specified @samp{set print address off}.
|
||
|
||
@item
|
||
@value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
|
||
expressions can use it just as expressions in your program do. Since
|
||
one scope may be defined in another, you can use @code{::} repeatedly if
|
||
necessary, for example in an expression like
|
||
@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
|
||
resolving name scope by reference to source files, in both C and C@t{++}
|
||
debugging (@pxref{Variables, ,Program Variables}).
|
||
|
||
@item
|
||
@value{GDBN} performs argument-dependent lookup, following the C@t{++}
|
||
specification.
|
||
@end enumerate
|
||
|
||
@node C Defaults
|
||
@subsubsection C and C@t{++} Defaults
|
||
|
||
@cindex C and C@t{++} defaults
|
||
|
||
If you allow @value{GDBN} to set range checking automatically, it
|
||
defaults to @code{off} whenever the working language changes to
|
||
C or C@t{++}. This happens regardless of whether you or @value{GDBN}
|
||
selects the working language.
|
||
|
||
If you allow @value{GDBN} to set the language automatically, it
|
||
recognizes source files whose names end with @file{.c}, @file{.C}, or
|
||
@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
|
||
these files, it sets the working language to C or C@t{++}.
|
||
@xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
|
||
for further details.
|
||
|
||
@node C Checks
|
||
@subsubsection C and C@t{++} Type and Range Checks
|
||
|
||
@cindex C and C@t{++} checks
|
||
|
||
By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
|
||
checking is used. However, if you turn type checking off, @value{GDBN}
|
||
will allow certain non-standard conversions, such as promoting integer
|
||
constants to pointers.
|
||
|
||
Range checking, if turned on, is done on mathematical operations. Array
|
||
indices are not checked, since they are often used to index a pointer
|
||
that is not itself an array.
|
||
|
||
@node Debugging C
|
||
@subsubsection @value{GDBN} and C
|
||
|
||
The @code{set print union} and @code{show print union} commands apply to
|
||
the @code{union} type. When set to @samp{on}, any @code{union} that is
|
||
inside a @code{struct} or @code{class} is also printed. Otherwise, it
|
||
appears as @samp{@{...@}}.
|
||
|
||
The @code{@@} operator aids in the debugging of dynamic arrays, formed
|
||
with pointers and a memory allocation function. @xref{Expressions,
|
||
,Expressions}.
|
||
|
||
@node Debugging C Plus Plus
|
||
@subsubsection @value{GDBN} Features for C@t{++}
|
||
|
||
@cindex commands for C@t{++}
|
||
|
||
Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
|
||
designed specifically for use with C@t{++}. Here is a summary:
|
||
|
||
@table @code
|
||
@cindex break in overloaded functions
|
||
@item @r{breakpoint menus}
|
||
When you want a breakpoint in a function whose name is overloaded,
|
||
@value{GDBN} has the capability to display a menu of possible breakpoint
|
||
locations to help you specify which function definition you want.
|
||
@xref{Ambiguous Expressions,,Ambiguous Expressions}.
|
||
|
||
@cindex overloading in C@t{++}
|
||
@item rbreak @var{regex}
|
||
Setting breakpoints using regular expressions is helpful for setting
|
||
breakpoints on overloaded functions that are not members of any special
|
||
classes.
|
||
@xref{Set Breaks, ,Setting Breakpoints}.
|
||
|
||
@cindex C@t{++} exception handling
|
||
@item catch throw
|
||
@itemx catch rethrow
|
||
@itemx catch catch
|
||
Debug C@t{++} exception handling using these commands. @xref{Set
|
||
Catchpoints, , Setting Catchpoints}.
|
||
|
||
@cindex inheritance
|
||
@item ptype @var{typename}
|
||
Print inheritance relationships as well as other information for type
|
||
@var{typename}.
|
||
@xref{Symbols, ,Examining the Symbol Table}.
|
||
|
||
@item info vtbl @var{expression}.
|
||
The @code{info vtbl} command can be used to display the virtual
|
||
method tables of the object computed by @var{expression}. This shows
|
||
one entry per virtual table; there may be multiple virtual tables when
|
||
multiple inheritance is in use.
|
||
|
||
@cindex C@t{++} demangling
|
||
@item demangle @var{name}
|
||
Demangle @var{name}.
|
||
@xref{Symbols}, for a more complete description of the @code{demangle} command.
|
||
|
||
@cindex C@t{++} symbol display
|
||
@item set print demangle
|
||
@itemx show print demangle
|
||
@itemx set print asm-demangle
|
||
@itemx show print asm-demangle
|
||
Control whether C@t{++} symbols display in their source form, both when
|
||
displaying code as C@t{++} source and when displaying disassemblies.
|
||
@xref{Print Settings, ,Print Settings}.
|
||
|
||
@item set print object
|
||
@itemx show print object
|
||
Choose whether to print derived (actual) or declared types of objects.
|
||
@xref{Print Settings, ,Print Settings}.
|
||
|
||
@item set print vtbl
|
||
@itemx show print vtbl
|
||
Control the format for printing virtual function tables.
|
||
@xref{Print Settings, ,Print Settings}.
|
||
(The @code{vtbl} commands do not work on programs compiled with the HP
|
||
ANSI C@t{++} compiler (@code{aCC}).)
|
||
|
||
@kindex set overload-resolution
|
||
@cindex overloaded functions, overload resolution
|
||
@item set overload-resolution on
|
||
Enable overload resolution for C@t{++} expression evaluation. The default
|
||
is on. For overloaded functions, @value{GDBN} evaluates the arguments
|
||
and searches for a function whose signature matches the argument types,
|
||
using the standard C@t{++} conversion rules (see @ref{C Plus Plus
|
||
Expressions, ,C@t{++} Expressions}, for details).
|
||
If it cannot find a match, it emits a message.
|
||
|
||
@item set overload-resolution off
|
||
Disable overload resolution for C@t{++} expression evaluation. For
|
||
overloaded functions that are not class member functions, @value{GDBN}
|
||
chooses the first function of the specified name that it finds in the
|
||
symbol table, whether or not its arguments are of the correct type. For
|
||
overloaded functions that are class member functions, @value{GDBN}
|
||
searches for a function whose signature @emph{exactly} matches the
|
||
argument types.
|
||
|
||
@kindex show overload-resolution
|
||
@item show overload-resolution
|
||
Show the current setting of overload resolution.
|
||
|
||
@item @r{Overloaded symbol names}
|
||
You can specify a particular definition of an overloaded symbol, using
|
||
the same notation that is used to declare such symbols in C@t{++}: type
|
||
@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
|
||
also use the @value{GDBN} command-line word completion facilities to list the
|
||
available choices, or to finish the type list for you.
|
||
@xref{Completion,, Command Completion}, for details on how to do this.
|
||
|
||
@item @r{Breakpoints in functions with ABI tags}
|
||
|
||
The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
|
||
correspond to changes in the ABI of a type, function, or variable that
|
||
would not otherwise be reflected in a mangled name. See
|
||
@url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
|
||
for more detail.
|
||
|
||
The ABI tags are visible in C@t{++} demangled names. For example, a
|
||
function that returns a std::string:
|
||
|
||
@smallexample
|
||
std::string function(int);
|
||
@end smallexample
|
||
|
||
@noindent
|
||
when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
|
||
tag, and @value{GDBN} displays the symbol like this:
|
||
|
||
@smallexample
|
||
function[abi:cxx11](int)
|
||
@end smallexample
|
||
|
||
You can set a breakpoint on such functions simply as if they had no
|
||
tag. For example:
|
||
|
||
@smallexample
|
||
(gdb) b function(int)
|
||
Breakpoint 2 at 0x40060d: file main.cc, line 10.
|
||
(gdb) info breakpoints
|
||
Num Type Disp Enb Address What
|
||
1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
|
||
at main.cc:10
|
||
@end smallexample
|
||
|
||
On the rare occasion you need to disambiguate between different ABI
|
||
tags, you can do so by simply including the ABI tag in the function
|
||
name, like:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) b ambiguous[abi:other_tag](int)
|
||
@end smallexample
|
||
@end table
|
||
|
||
@node Decimal Floating Point
|
||
@subsubsection Decimal Floating Point format
|
||
@cindex decimal floating point format
|
||
|
||
@value{GDBN} can examine, set and perform computations with numbers in
|
||
decimal floating point format, which in the C language correspond to the
|
||
@code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
|
||
specified by the extension to support decimal floating-point arithmetic.
|
||
|
||
There are two encodings in use, depending on the architecture: BID (Binary
|
||
Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
|
||
PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
|
||
configured target.
|
||
|
||
Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
|
||
to manipulate decimal floating point numbers, it is not possible to convert
|
||
(using a cast, for example) integers wider than 32-bit to decimal float.
|
||
|
||
In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
|
||
point computations, error checking in decimal float operations ignores
|
||
underflow, overflow and divide by zero exceptions.
|
||
|
||
In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
|
||
to inspect @code{_Decimal128} values stored in floating point registers.
|
||
See @ref{PowerPC,,PowerPC} for more details.
|
||
|
||
@node D
|
||
@subsection D
|
||
|
||
@cindex D
|
||
@value{GDBN} can be used to debug programs written in D and compiled with
|
||
GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
|
||
specific feature --- dynamic arrays.
|
||
|
||
@node Go
|
||
@subsection Go
|
||
|
||
@cindex Go (programming language)
|
||
@value{GDBN} can be used to debug programs written in Go and compiled with
|
||
@file{gccgo} or @file{6g} compilers.
|
||
|
||
Here is a summary of the Go-specific features and restrictions:
|
||
|
||
@table @code
|
||
@cindex current Go package
|
||
@item The current Go package
|
||
The name of the current package does not need to be specified when
|
||
specifying global variables and functions.
|
||
|
||
For example, given the program:
|
||
|
||
@example
|
||
package main
|
||
var myglob = "Shall we?"
|
||
func main () @{
|
||
// ...
|
||
@}
|
||
@end example
|
||
|
||
When stopped inside @code{main} either of these work:
|
||
|
||
@example
|
||
(gdb) p myglob
|
||
(gdb) p main.myglob
|
||
@end example
|
||
|
||
@cindex builtin Go types
|
||
@item Builtin Go types
|
||
The @code{string} type is recognized by @value{GDBN} and is printed
|
||
as a string.
|
||
|
||
@cindex builtin Go functions
|
||
@item Builtin Go functions
|
||
The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
|
||
function and handles it internally.
|
||
|
||
@cindex restrictions on Go expressions
|
||
@item Restrictions on Go expressions
|
||
All Go operators are supported except @code{&^}.
|
||
The Go @code{_} ``blank identifier'' is not supported.
|
||
Automatic dereferencing of pointers is not supported.
|
||
@end table
|
||
|
||
@node Objective-C
|
||
@subsection Objective-C
|
||
|
||
@cindex Objective-C
|
||
This section provides information about some commands and command
|
||
options that are useful for debugging Objective-C code. See also
|
||
@ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
|
||
few more commands specific to Objective-C support.
|
||
|
||
@menu
|
||
* Method Names in Commands::
|
||
* The Print Command with Objective-C::
|
||
@end menu
|
||
|
||
@node Method Names in Commands
|
||
@subsubsection Method Names in Commands
|
||
|
||
The following commands have been extended to accept Objective-C method
|
||
names as line specifications:
|
||
|
||
@kindex clear@r{, and Objective-C}
|
||
@kindex break@r{, and Objective-C}
|
||
@kindex info line@r{, and Objective-C}
|
||
@kindex jump@r{, and Objective-C}
|
||
@kindex list@r{, and Objective-C}
|
||
@itemize
|
||
@item @code{clear}
|
||
@item @code{break}
|
||
@item @code{info line}
|
||
@item @code{jump}
|
||
@item @code{list}
|
||
@end itemize
|
||
|
||
A fully qualified Objective-C method name is specified as
|
||
|
||
@smallexample
|
||
-[@var{Class} @var{methodName}]
|
||
@end smallexample
|
||
|
||
where the minus sign is used to indicate an instance method and a
|
||
plus sign (not shown) is used to indicate a class method. The class
|
||
name @var{Class} and method name @var{methodName} are enclosed in
|
||
brackets, similar to the way messages are specified in Objective-C
|
||
source code. For example, to set a breakpoint at the @code{create}
|
||
instance method of class @code{Fruit} in the program currently being
|
||
debugged, enter:
|
||
|
||
@smallexample
|
||
break -[Fruit create]
|
||
@end smallexample
|
||
|
||
To list ten program lines around the @code{initialize} class method,
|
||
enter:
|
||
|
||
@smallexample
|
||
list +[NSText initialize]
|
||
@end smallexample
|
||
|
||
In the current version of @value{GDBN}, the plus or minus sign is
|
||
required. In future versions of @value{GDBN}, the plus or minus
|
||
sign will be optional, but you can use it to narrow the search. It
|
||
is also possible to specify just a method name:
|
||
|
||
@smallexample
|
||
break create
|
||
@end smallexample
|
||
|
||
You must specify the complete method name, including any colons. If
|
||
your program's source files contain more than one @code{create} method,
|
||
you'll be presented with a numbered list of classes that implement that
|
||
method. Indicate your choice by number, or type @samp{0} to exit if
|
||
none apply.
|
||
|
||
As another example, to clear a breakpoint established at the
|
||
@code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
|
||
|
||
@smallexample
|
||
clear -[NSWindow makeKeyAndOrderFront:]
|
||
@end smallexample
|
||
|
||
@node The Print Command with Objective-C
|
||
@subsubsection The Print Command With Objective-C
|
||
@cindex Objective-C, print objects
|
||
@kindex print-object
|
||
@kindex po @r{(@code{print-object})}
|
||
|
||
The print command has also been extended to accept methods. For example:
|
||
|
||
@smallexample
|
||
print -[@var{object} hash]
|
||
@end smallexample
|
||
|
||
@cindex print an Objective-C object description
|
||
@cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
|
||
@noindent
|
||
will tell @value{GDBN} to send the @code{hash} message to @var{object}
|
||
and print the result. Also, an additional command has been added,
|
||
@code{print-object} or @code{po} for short, which is meant to print
|
||
the description of an object. However, this command may only work
|
||
with certain Objective-C libraries that have a particular hook
|
||
function, @code{_NSPrintForDebugger}, defined.
|
||
|
||
@node OpenCL C
|
||
@subsection OpenCL C
|
||
|
||
@cindex OpenCL C
|
||
This section provides information about @value{GDBN}s OpenCL C support.
|
||
|
||
@menu
|
||
* OpenCL C Datatypes::
|
||
* OpenCL C Expressions::
|
||
* OpenCL C Operators::
|
||
@end menu
|
||
|
||
@node OpenCL C Datatypes
|
||
@subsubsection OpenCL C Datatypes
|
||
|
||
@cindex OpenCL C Datatypes
|
||
@value{GDBN} supports the builtin scalar and vector datatypes specified
|
||
by OpenCL 1.1. In addition the half- and double-precision floating point
|
||
data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
|
||
extensions are also known to @value{GDBN}.
|
||
|
||
@node OpenCL C Expressions
|
||
@subsubsection OpenCL C Expressions
|
||
|
||
@cindex OpenCL C Expressions
|
||
@value{GDBN} supports accesses to vector components including the access as
|
||
lvalue where possible. Since OpenCL C is based on C99 most C expressions
|
||
supported by @value{GDBN} can be used as well.
|
||
|
||
@node OpenCL C Operators
|
||
@subsubsection OpenCL C Operators
|
||
|
||
@cindex OpenCL C Operators
|
||
@value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
|
||
vector data types.
|
||
|
||
@node Fortran
|
||
@subsection Fortran
|
||
@cindex Fortran-specific support in @value{GDBN}
|
||
|
||
@value{GDBN} can be used to debug programs written in Fortran, but it
|
||
currently supports only the features of Fortran 77 language.
|
||
|
||
@cindex trailing underscore, in Fortran symbols
|
||
Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
|
||
among them) append an underscore to the names of variables and
|
||
functions. When you debug programs compiled by those compilers, you
|
||
will need to refer to variables and functions with a trailing
|
||
underscore.
|
||
|
||
@menu
|
||
* Fortran Operators:: Fortran operators and expressions
|
||
* Fortran Defaults:: Default settings for Fortran
|
||
* Special Fortran Commands:: Special @value{GDBN} commands for Fortran
|
||
@end menu
|
||
|
||
@node Fortran Operators
|
||
@subsubsection Fortran Operators and Expressions
|
||
|
||
@cindex Fortran operators and expressions
|
||
|
||
Operators must be defined on values of specific types. For instance,
|
||
@code{+} is defined on numbers, but not on characters or other non-
|
||
arithmetic types. Operators are often defined on groups of types.
|
||
|
||
@table @code
|
||
@item **
|
||
The exponentiation operator. It raises the first operand to the power
|
||
of the second one.
|
||
|
||
@item :
|
||
The range operator. Normally used in the form of array(low:high) to
|
||
represent a section of array.
|
||
|
||
@item %
|
||
The access component operator. Normally used to access elements in derived
|
||
types. Also suitable for unions. As unions aren't part of regular Fortran,
|
||
this can only happen when accessing a register that uses a gdbarch-defined
|
||
union type.
|
||
@end table
|
||
|
||
@node Fortran Defaults
|
||
@subsubsection Fortran Defaults
|
||
|
||
@cindex Fortran Defaults
|
||
|
||
Fortran symbols are usually case-insensitive, so @value{GDBN} by
|
||
default uses case-insensitive matches for Fortran symbols. You can
|
||
change that with the @samp{set case-insensitive} command, see
|
||
@ref{Symbols}, for the details.
|
||
|
||
@node Special Fortran Commands
|
||
@subsubsection Special Fortran Commands
|
||
|
||
@cindex Special Fortran commands
|
||
|
||
@value{GDBN} has some commands to support Fortran-specific features,
|
||
such as displaying common blocks.
|
||
|
||
@table @code
|
||
@cindex @code{COMMON} blocks, Fortran
|
||
@kindex info common
|
||
@item info common @r{[}@var{common-name}@r{]}
|
||
This command prints the values contained in the Fortran @code{COMMON}
|
||
block whose name is @var{common-name}. With no argument, the names of
|
||
all @code{COMMON} blocks visible at the current program location are
|
||
printed.
|
||
@end table
|
||
|
||
@node Pascal
|
||
@subsection Pascal
|
||
|
||
@cindex Pascal support in @value{GDBN}, limitations
|
||
Debugging Pascal programs which use sets, subranges, file variables, or
|
||
nested functions does not currently work. @value{GDBN} does not support
|
||
entering expressions, printing values, or similar features using Pascal
|
||
syntax.
|
||
|
||
The Pascal-specific command @code{set print pascal_static-members}
|
||
controls whether static members of Pascal objects are displayed.
|
||
@xref{Print Settings, pascal_static-members}.
|
||
|
||
@node Rust
|
||
@subsection Rust
|
||
|
||
@value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
|
||
Programming Language}. Type- and value-printing, and expression
|
||
parsing, are reasonably complete. However, there are a few
|
||
peculiarities and holes to be aware of.
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Linespecs (@pxref{Specify Location}) are never relative to the current
|
||
crate. Instead, they act as if there were a global namespace of
|
||
crates, somewhat similar to the way @code{extern crate} behaves.
|
||
|
||
That is, if @value{GDBN} is stopped at a breakpoint in a function in
|
||
crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
|
||
to set a breakpoint in a function named @samp{f} in a crate named
|
||
@samp{B}.
|
||
|
||
As a consequence of this approach, linespecs also cannot refer to
|
||
items using @samp{self::} or @samp{super::}.
|
||
|
||
@item
|
||
Because @value{GDBN} implements Rust name-lookup semantics in
|
||
expressions, it will sometimes prepend the current crate to a name.
|
||
For example, if @value{GDBN} is stopped at a breakpoint in the crate
|
||
@samp{K}, then @code{print ::x::y} will try to find the symbol
|
||
@samp{K::x::y}.
|
||
|
||
However, since it is useful to be able to refer to other crates when
|
||
debugging, @value{GDBN} provides the @code{extern} extension to
|
||
circumvent this. To use the extension, just put @code{extern} before
|
||
a path expression to refer to the otherwise unavailable ``global''
|
||
scope.
|
||
|
||
In the above example, if you wanted to refer to the symbol @samp{y} in
|
||
the crate @samp{x}, you would use @code{print extern x::y}.
|
||
|
||
@item
|
||
The Rust expression evaluator does not support ``statement-like''
|
||
expressions such as @code{if} or @code{match}, or lambda expressions.
|
||
|
||
@item
|
||
Tuple expressions are not implemented.
|
||
|
||
@item
|
||
The Rust expression evaluator does not currently implement the
|
||
@code{Drop} trait. Objects that may be created by the evaluator will
|
||
never be destroyed.
|
||
|
||
@item
|
||
@value{GDBN} does not implement type inference for generics. In order
|
||
to call generic functions or otherwise refer to generic items, you
|
||
will have to specify the type parameters manually.
|
||
|
||
@item
|
||
@value{GDBN} currently uses the C@t{++} demangler for Rust. In most
|
||
cases this does not cause any problems. However, in an expression
|
||
context, completing a generic function name will give syntactically
|
||
invalid results. This happens because Rust requires the @samp{::}
|
||
operator between the function name and its generic arguments. For
|
||
example, @value{GDBN} might provide a completion like
|
||
@code{crate::f<u32>}, where the parser would require
|
||
@code{crate::f::<u32>}.
|
||
|
||
@item
|
||
As of this writing, the Rust compiler (version 1.8) has a few holes in
|
||
the debugging information it generates. These holes prevent certain
|
||
features from being implemented by @value{GDBN}:
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Method calls cannot be made via traits.
|
||
|
||
@item
|
||
Operator overloading is not implemented.
|
||
|
||
@item
|
||
When debugging in a monomorphized function, you cannot use the generic
|
||
type names.
|
||
|
||
@item
|
||
The type @code{Self} is not available.
|
||
|
||
@item
|
||
@code{use} statements are not available, so some names may not be
|
||
available in the crate.
|
||
@end itemize
|
||
@end itemize
|
||
|
||
@node Modula-2
|
||
@subsection Modula-2
|
||
|
||
@cindex Modula-2, @value{GDBN} support
|
||
|
||
The extensions made to @value{GDBN} to support Modula-2 only support
|
||
output from the @sc{gnu} Modula-2 compiler (which is currently being
|
||
developed). Other Modula-2 compilers are not currently supported, and
|
||
attempting to debug executables produced by them is most likely
|
||
to give an error as @value{GDBN} reads in the executable's symbol
|
||
table.
|
||
|
||
@cindex expressions in Modula-2
|
||
@menu
|
||
* M2 Operators:: Built-in operators
|
||
* Built-In Func/Proc:: Built-in functions and procedures
|
||
* M2 Constants:: Modula-2 constants
|
||
* M2 Types:: Modula-2 types
|
||
* M2 Defaults:: Default settings for Modula-2
|
||
* Deviations:: Deviations from standard Modula-2
|
||
* M2 Checks:: Modula-2 type and range checks
|
||
* M2 Scope:: The scope operators @code{::} and @code{.}
|
||
* GDB/M2:: @value{GDBN} and Modula-2
|
||
@end menu
|
||
|
||
@node M2 Operators
|
||
@subsubsection Operators
|
||
@cindex Modula-2 operators
|
||
|
||
Operators must be defined on values of specific types. For instance,
|
||
@code{+} is defined on numbers, but not on structures. Operators are
|
||
often defined on groups of types. For the purposes of Modula-2, the
|
||
following definitions hold:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
|
||
their subranges.
|
||
|
||
@item
|
||
@emph{Character types} consist of @code{CHAR} and its subranges.
|
||
|
||
@item
|
||
@emph{Floating-point types} consist of @code{REAL}.
|
||
|
||
@item
|
||
@emph{Pointer types} consist of anything declared as @code{POINTER TO
|
||
@var{type}}.
|
||
|
||
@item
|
||
@emph{Scalar types} consist of all of the above.
|
||
|
||
@item
|
||
@emph{Set types} consist of @code{SET} and @code{BITSET} types.
|
||
|
||
@item
|
||
@emph{Boolean types} consist of @code{BOOLEAN}.
|
||
@end itemize
|
||
|
||
@noindent
|
||
The following operators are supported, and appear in order of
|
||
increasing precedence:
|
||
|
||
@table @code
|
||
@item ,
|
||
Function argument or array index separator.
|
||
|
||
@item :=
|
||
Assignment. The value of @var{var} @code{:=} @var{value} is
|
||
@var{value}.
|
||
|
||
@item <@r{, }>
|
||
Less than, greater than on integral, floating-point, or enumerated
|
||
types.
|
||
|
||
@item <=@r{, }>=
|
||
Less than or equal to, greater than or equal to
|
||
on integral, floating-point and enumerated types, or set inclusion on
|
||
set types. Same precedence as @code{<}.
|
||
|
||
@item =@r{, }<>@r{, }#
|
||
Equality and two ways of expressing inequality, valid on scalar types.
|
||
Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
|
||
available for inequality, since @code{#} conflicts with the script
|
||
comment character.
|
||
|
||
@item IN
|
||
Set membership. Defined on set types and the types of their members.
|
||
Same precedence as @code{<}.
|
||
|
||
@item OR
|
||
Boolean disjunction. Defined on boolean types.
|
||
|
||
@item AND@r{, }&
|
||
Boolean conjunction. Defined on boolean types.
|
||
|
||
@item @@
|
||
The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
|
||
|
||
@item +@r{, }-
|
||
Addition and subtraction on integral and floating-point types, or union
|
||
and difference on set types.
|
||
|
||
@item *
|
||
Multiplication on integral and floating-point types, or set intersection
|
||
on set types.
|
||
|
||
@item /
|
||
Division on floating-point types, or symmetric set difference on set
|
||
types. Same precedence as @code{*}.
|
||
|
||
@item DIV@r{, }MOD
|
||
Integer division and remainder. Defined on integral types. Same
|
||
precedence as @code{*}.
|
||
|
||
@item -
|
||
Negative. Defined on @code{INTEGER} and @code{REAL} data.
|
||
|
||
@item ^
|
||
Pointer dereferencing. Defined on pointer types.
|
||
|
||
@item NOT
|
||
Boolean negation. Defined on boolean types. Same precedence as
|
||
@code{^}.
|
||
|
||
@item .
|
||
@code{RECORD} field selector. Defined on @code{RECORD} data. Same
|
||
precedence as @code{^}.
|
||
|
||
@item []
|
||
Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
|
||
|
||
@item ()
|
||
Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
|
||
as @code{^}.
|
||
|
||
@item ::@r{, }.
|
||
@value{GDBN} and Modula-2 scope operators.
|
||
@end table
|
||
|
||
@quotation
|
||
@emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
|
||
treats the use of the operator @code{IN}, or the use of operators
|
||
@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
|
||
@code{<=}, and @code{>=} on sets as an error.
|
||
@end quotation
|
||
|
||
|
||
@node Built-In Func/Proc
|
||
@subsubsection Built-in Functions and Procedures
|
||
@cindex Modula-2 built-ins
|
||
|
||
Modula-2 also makes available several built-in procedures and functions.
|
||
In describing these, the following metavariables are used:
|
||
|
||
@table @var
|
||
|
||
@item a
|
||
represents an @code{ARRAY} variable.
|
||
|
||
@item c
|
||
represents a @code{CHAR} constant or variable.
|
||
|
||
@item i
|
||
represents a variable or constant of integral type.
|
||
|
||
@item m
|
||
represents an identifier that belongs to a set. Generally used in the
|
||
same function with the metavariable @var{s}. The type of @var{s} should
|
||
be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
|
||
|
||
@item n
|
||
represents a variable or constant of integral or floating-point type.
|
||
|
||
@item r
|
||
represents a variable or constant of floating-point type.
|
||
|
||
@item t
|
||
represents a type.
|
||
|
||
@item v
|
||
represents a variable.
|
||
|
||
@item x
|
||
represents a variable or constant of one of many types. See the
|
||
explanation of the function for details.
|
||
@end table
|
||
|
||
All Modula-2 built-in procedures also return a result, described below.
|
||
|
||
@table @code
|
||
@item ABS(@var{n})
|
||
Returns the absolute value of @var{n}.
|
||
|
||
@item CAP(@var{c})
|
||
If @var{c} is a lower case letter, it returns its upper case
|
||
equivalent, otherwise it returns its argument.
|
||
|
||
@item CHR(@var{i})
|
||
Returns the character whose ordinal value is @var{i}.
|
||
|
||
@item DEC(@var{v})
|
||
Decrements the value in the variable @var{v} by one. Returns the new value.
|
||
|
||
@item DEC(@var{v},@var{i})
|
||
Decrements the value in the variable @var{v} by @var{i}. Returns the
|
||
new value.
|
||
|
||
@item EXCL(@var{m},@var{s})
|
||
Removes the element @var{m} from the set @var{s}. Returns the new
|
||
set.
|
||
|
||
@item FLOAT(@var{i})
|
||
Returns the floating point equivalent of the integer @var{i}.
|
||
|
||
@item HIGH(@var{a})
|
||
Returns the index of the last member of @var{a}.
|
||
|
||
@item INC(@var{v})
|
||
Increments the value in the variable @var{v} by one. Returns the new value.
|
||
|
||
@item INC(@var{v},@var{i})
|
||
Increments the value in the variable @var{v} by @var{i}. Returns the
|
||
new value.
|
||
|
||
@item INCL(@var{m},@var{s})
|
||
Adds the element @var{m} to the set @var{s} if it is not already
|
||
there. Returns the new set.
|
||
|
||
@item MAX(@var{t})
|
||
Returns the maximum value of the type @var{t}.
|
||
|
||
@item MIN(@var{t})
|
||
Returns the minimum value of the type @var{t}.
|
||
|
||
@item ODD(@var{i})
|
||
Returns boolean TRUE if @var{i} is an odd number.
|
||
|
||
@item ORD(@var{x})
|
||
Returns the ordinal value of its argument. For example, the ordinal
|
||
value of a character is its @sc{ascii} value (on machines supporting
|
||
the @sc{ascii} character set). The argument @var{x} must be of an
|
||
ordered type, which include integral, character and enumerated types.
|
||
|
||
@item SIZE(@var{x})
|
||
Returns the size of its argument. The argument @var{x} can be a
|
||
variable or a type.
|
||
|
||
@item TRUNC(@var{r})
|
||
Returns the integral part of @var{r}.
|
||
|
||
@item TSIZE(@var{x})
|
||
Returns the size of its argument. The argument @var{x} can be a
|
||
variable or a type.
|
||
|
||
@item VAL(@var{t},@var{i})
|
||
Returns the member of the type @var{t} whose ordinal value is @var{i}.
|
||
@end table
|
||
|
||
@quotation
|
||
@emph{Warning:} Sets and their operations are not yet supported, so
|
||
@value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
|
||
an error.
|
||
@end quotation
|
||
|
||
@cindex Modula-2 constants
|
||
@node M2 Constants
|
||
@subsubsection Constants
|
||
|
||
@value{GDBN} allows you to express the constants of Modula-2 in the following
|
||
ways:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Integer constants are simply a sequence of digits. When used in an
|
||
expression, a constant is interpreted to be type-compatible with the
|
||
rest of the expression. Hexadecimal integers are specified by a
|
||
trailing @samp{H}, and octal integers by a trailing @samp{B}.
|
||
|
||
@item
|
||
Floating point constants appear as a sequence of digits, followed by a
|
||
decimal point and another sequence of digits. An optional exponent can
|
||
then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
|
||
@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
|
||
digits of the floating point constant must be valid decimal (base 10)
|
||
digits.
|
||
|
||
@item
|
||
Character constants consist of a single character enclosed by a pair of
|
||
like quotes, either single (@code{'}) or double (@code{"}). They may
|
||
also be expressed by their ordinal value (their @sc{ascii} value, usually)
|
||
followed by a @samp{C}.
|
||
|
||
@item
|
||
String constants consist of a sequence of characters enclosed by a
|
||
pair of like quotes, either single (@code{'}) or double (@code{"}).
|
||
Escape sequences in the style of C are also allowed. @xref{C
|
||
Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
|
||
sequences.
|
||
|
||
@item
|
||
Enumerated constants consist of an enumerated identifier.
|
||
|
||
@item
|
||
Boolean constants consist of the identifiers @code{TRUE} and
|
||
@code{FALSE}.
|
||
|
||
@item
|
||
Pointer constants consist of integral values only.
|
||
|
||
@item
|
||
Set constants are not yet supported.
|
||
@end itemize
|
||
|
||
@node M2 Types
|
||
@subsubsection Modula-2 Types
|
||
@cindex Modula-2 types
|
||
|
||
Currently @value{GDBN} can print the following data types in Modula-2
|
||
syntax: array types, record types, set types, pointer types, procedure
|
||
types, enumerated types, subrange types and base types. You can also
|
||
print the contents of variables declared using these type.
|
||
This section gives a number of simple source code examples together with
|
||
sample @value{GDBN} sessions.
|
||
|
||
The first example contains the following section of code:
|
||
|
||
@smallexample
|
||
VAR
|
||
s: SET OF CHAR ;
|
||
r: [20..40] ;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and you can request @value{GDBN} to interrogate the type and value of
|
||
@code{r} and @code{s}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print s
|
||
@{'A'..'C', 'Z'@}
|
||
(@value{GDBP}) ptype s
|
||
SET OF CHAR
|
||
(@value{GDBP}) print r
|
||
21
|
||
(@value{GDBP}) ptype r
|
||
[20..40]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Likewise if your source code declares @code{s} as:
|
||
|
||
@smallexample
|
||
VAR
|
||
s: SET ['A'..'Z'] ;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
then you may query the type of @code{s} by:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype s
|
||
type = SET ['A'..'Z']
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Note that at present you cannot interactively manipulate set
|
||
expressions using the debugger.
|
||
|
||
The following example shows how you might declare an array in Modula-2
|
||
and how you can interact with @value{GDBN} to print its type and contents:
|
||
|
||
@smallexample
|
||
VAR
|
||
s: ARRAY [-10..10] OF CHAR ;
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype s
|
||
ARRAY [-10..10] OF CHAR
|
||
@end smallexample
|
||
|
||
Note that the array handling is not yet complete and although the type
|
||
is printed correctly, expression handling still assumes that all
|
||
arrays have a lower bound of zero and not @code{-10} as in the example
|
||
above.
|
||
|
||
Here are some more type related Modula-2 examples:
|
||
|
||
@smallexample
|
||
TYPE
|
||
colour = (blue, red, yellow, green) ;
|
||
t = [blue..yellow] ;
|
||
VAR
|
||
s: t ;
|
||
BEGIN
|
||
s := blue ;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The @value{GDBN} interaction shows how you can query the data type
|
||
and value of a variable.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print s
|
||
$1 = blue
|
||
(@value{GDBP}) ptype t
|
||
type = [blue..yellow]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
In this example a Modula-2 array is declared and its contents
|
||
displayed. Observe that the contents are written in the same way as
|
||
their @code{C} counterparts.
|
||
|
||
@smallexample
|
||
VAR
|
||
s: ARRAY [1..5] OF CARDINAL ;
|
||
BEGIN
|
||
s[1] := 1 ;
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print s
|
||
$1 = @{1, 0, 0, 0, 0@}
|
||
(@value{GDBP}) ptype s
|
||
type = ARRAY [1..5] OF CARDINAL
|
||
@end smallexample
|
||
|
||
The Modula-2 language interface to @value{GDBN} also understands
|
||
pointer types as shown in this example:
|
||
|
||
@smallexample
|
||
VAR
|
||
s: POINTER TO ARRAY [1..5] OF CARDINAL ;
|
||
BEGIN
|
||
NEW(s) ;
|
||
s^[1] := 1 ;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and you can request that @value{GDBN} describes the type of @code{s}.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype s
|
||
type = POINTER TO ARRAY [1..5] OF CARDINAL
|
||
@end smallexample
|
||
|
||
@value{GDBN} handles compound types as we can see in this example.
|
||
Here we combine array types, record types, pointer types and subrange
|
||
types:
|
||
|
||
@smallexample
|
||
TYPE
|
||
foo = RECORD
|
||
f1: CARDINAL ;
|
||
f2: CHAR ;
|
||
f3: myarray ;
|
||
END ;
|
||
|
||
myarray = ARRAY myrange OF CARDINAL ;
|
||
myrange = [-2..2] ;
|
||
VAR
|
||
s: POINTER TO ARRAY myrange OF foo ;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and you can ask @value{GDBN} to describe the type of @code{s} as shown
|
||
below.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype s
|
||
type = POINTER TO ARRAY [-2..2] OF foo = RECORD
|
||
f1 : CARDINAL;
|
||
f2 : CHAR;
|
||
f3 : ARRAY [-2..2] OF CARDINAL;
|
||
END
|
||
@end smallexample
|
||
|
||
@node M2 Defaults
|
||
@subsubsection Modula-2 Defaults
|
||
@cindex Modula-2 defaults
|
||
|
||
If type and range checking are set automatically by @value{GDBN}, they
|
||
both default to @code{on} whenever the working language changes to
|
||
Modula-2. This happens regardless of whether you or @value{GDBN}
|
||
selected the working language.
|
||
|
||
If you allow @value{GDBN} to set the language automatically, then entering
|
||
code compiled from a file whose name ends with @file{.mod} sets the
|
||
working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
|
||
Infer the Source Language}, for further details.
|
||
|
||
@node Deviations
|
||
@subsubsection Deviations from Standard Modula-2
|
||
@cindex Modula-2, deviations from
|
||
|
||
A few changes have been made to make Modula-2 programs easier to debug.
|
||
This is done primarily via loosening its type strictness:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Unlike in standard Modula-2, pointer constants can be formed by
|
||
integers. This allows you to modify pointer variables during
|
||
debugging. (In standard Modula-2, the actual address contained in a
|
||
pointer variable is hidden from you; it can only be modified
|
||
through direct assignment to another pointer variable or expression that
|
||
returned a pointer.)
|
||
|
||
@item
|
||
C escape sequences can be used in strings and characters to represent
|
||
non-printable characters. @value{GDBN} prints out strings with these
|
||
escape sequences embedded. Single non-printable characters are
|
||
printed using the @samp{CHR(@var{nnn})} format.
|
||
|
||
@item
|
||
The assignment operator (@code{:=}) returns the value of its right-hand
|
||
argument.
|
||
|
||
@item
|
||
All built-in procedures both modify @emph{and} return their argument.
|
||
@end itemize
|
||
|
||
@node M2 Checks
|
||
@subsubsection Modula-2 Type and Range Checks
|
||
@cindex Modula-2 checks
|
||
|
||
@quotation
|
||
@emph{Warning:} in this release, @value{GDBN} does not yet perform type or
|
||
range checking.
|
||
@end quotation
|
||
@c FIXME remove warning when type/range checks added
|
||
|
||
@value{GDBN} considers two Modula-2 variables type equivalent if:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
They are of types that have been declared equivalent via a @code{TYPE
|
||
@var{t1} = @var{t2}} statement
|
||
|
||
@item
|
||
They have been declared on the same line. (Note: This is true of the
|
||
@sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
|
||
@end itemize
|
||
|
||
As long as type checking is enabled, any attempt to combine variables
|
||
whose types are not equivalent is an error.
|
||
|
||
Range checking is done on all mathematical operations, assignment, array
|
||
index bounds, and all built-in functions and procedures.
|
||
|
||
@node M2 Scope
|
||
@subsubsection The Scope Operators @code{::} and @code{.}
|
||
@cindex scope
|
||
@cindex @code{.}, Modula-2 scope operator
|
||
@cindex colon, doubled as scope operator
|
||
@ifinfo
|
||
@vindex colon-colon@r{, in Modula-2}
|
||
@c Info cannot handle :: but TeX can.
|
||
@end ifinfo
|
||
@ifnotinfo
|
||
@vindex ::@r{, in Modula-2}
|
||
@end ifnotinfo
|
||
|
||
There are a few subtle differences between the Modula-2 scope operator
|
||
(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
|
||
similar syntax:
|
||
|
||
@smallexample
|
||
|
||
@var{module} . @var{id}
|
||
@var{scope} :: @var{id}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where @var{scope} is the name of a module or a procedure,
|
||
@var{module} the name of a module, and @var{id} is any declared
|
||
identifier within your program, except another module.
|
||
|
||
Using the @code{::} operator makes @value{GDBN} search the scope
|
||
specified by @var{scope} for the identifier @var{id}. If it is not
|
||
found in the specified scope, then @value{GDBN} searches all scopes
|
||
enclosing the one specified by @var{scope}.
|
||
|
||
Using the @code{.} operator makes @value{GDBN} search the current scope for
|
||
the identifier specified by @var{id} that was imported from the
|
||
definition module specified by @var{module}. With this operator, it is
|
||
an error if the identifier @var{id} was not imported from definition
|
||
module @var{module}, or if @var{id} is not an identifier in
|
||
@var{module}.
|
||
|
||
@node GDB/M2
|
||
@subsubsection @value{GDBN} and Modula-2
|
||
|
||
Some @value{GDBN} commands have little use when debugging Modula-2 programs.
|
||
Five subcommands of @code{set print} and @code{show print} apply
|
||
specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
|
||
@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
|
||
apply to C@t{++}, and the last to the C @code{union} type, which has no direct
|
||
analogue in Modula-2.
|
||
|
||
The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
|
||
with any language, is not useful with Modula-2. Its
|
||
intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
|
||
created in Modula-2 as they can in C or C@t{++}. However, because an
|
||
address can be specified by an integral constant, the construct
|
||
@samp{@{@var{type}@}@var{adrexp}} is still useful.
|
||
|
||
@cindex @code{#} in Modula-2
|
||
In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
|
||
interpreted as the beginning of a comment. Use @code{<>} instead.
|
||
|
||
@node Ada
|
||
@subsection Ada
|
||
@cindex Ada
|
||
|
||
The extensions made to @value{GDBN} for Ada only support
|
||
output from the @sc{gnu} Ada (GNAT) compiler.
|
||
Other Ada compilers are not currently supported, and
|
||
attempting to debug executables produced by them is most likely
|
||
to be difficult.
|
||
|
||
|
||
@cindex expressions in Ada
|
||
@menu
|
||
* Ada Mode Intro:: General remarks on the Ada syntax
|
||
and semantics supported by Ada mode
|
||
in @value{GDBN}.
|
||
* Omissions from Ada:: Restrictions on the Ada expression syntax.
|
||
* Additions to Ada:: Extensions of the Ada expression syntax.
|
||
* Overloading support for Ada:: Support for expressions involving overloaded
|
||
subprograms.
|
||
* Stopping Before Main Program:: Debugging the program during elaboration.
|
||
* Ada Exceptions:: Ada Exceptions
|
||
* Ada Tasks:: Listing and setting breakpoints in tasks.
|
||
* Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
|
||
* Ravenscar Profile:: Tasking Support when using the Ravenscar
|
||
Profile
|
||
* Ada Settings:: New settable GDB parameters for Ada.
|
||
* Ada Glitches:: Known peculiarities of Ada mode.
|
||
@end menu
|
||
|
||
@node Ada Mode Intro
|
||
@subsubsection Introduction
|
||
@cindex Ada mode, general
|
||
|
||
The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
|
||
syntax, with some extensions.
|
||
The philosophy behind the design of this subset is
|
||
|
||
@itemize @bullet
|
||
@item
|
||
That @value{GDBN} should provide basic literals and access to operations for
|
||
arithmetic, dereferencing, field selection, indexing, and subprogram calls,
|
||
leaving more sophisticated computations to subprograms written into the
|
||
program (which therefore may be called from @value{GDBN}).
|
||
|
||
@item
|
||
That type safety and strict adherence to Ada language restrictions
|
||
are not particularly important to the @value{GDBN} user.
|
||
|
||
@item
|
||
That brevity is important to the @value{GDBN} user.
|
||
@end itemize
|
||
|
||
Thus, for brevity, the debugger acts as if all names declared in
|
||
user-written packages are directly visible, even if they are not visible
|
||
according to Ada rules, thus making it unnecessary to fully qualify most
|
||
names with their packages, regardless of context. Where this causes
|
||
ambiguity, @value{GDBN} asks the user's intent.
|
||
|
||
The debugger will start in Ada mode if it detects an Ada main program.
|
||
As for other languages, it will enter Ada mode when stopped in a program that
|
||
was translated from an Ada source file.
|
||
|
||
While in Ada mode, you may use `@t{--}' for comments. This is useful
|
||
mostly for documenting command files. The standard @value{GDBN} comment
|
||
(@samp{#}) still works at the beginning of a line in Ada mode, but not in the
|
||
middle (to allow based literals).
|
||
|
||
@node Omissions from Ada
|
||
@subsubsection Omissions from Ada
|
||
@cindex Ada, omissions from
|
||
|
||
Here are the notable omissions from the subset:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Only a subset of the attributes are supported:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@t{'First}, @t{'Last}, and @t{'Length}
|
||
on array objects (not on types and subtypes).
|
||
|
||
@item
|
||
@t{'Min} and @t{'Max}.
|
||
|
||
@item
|
||
@t{'Pos} and @t{'Val}.
|
||
|
||
@item
|
||
@t{'Tag}.
|
||
|
||
@item
|
||
@t{'Range} on array objects (not subtypes), but only as the right
|
||
operand of the membership (@code{in}) operator.
|
||
|
||
@item
|
||
@t{'Access}, @t{'Unchecked_Access}, and
|
||
@t{'Unrestricted_Access} (a GNAT extension).
|
||
|
||
@item
|
||
@t{'Address}.
|
||
@end itemize
|
||
|
||
@item
|
||
The names in
|
||
@code{Characters.Latin_1} are not available and
|
||
concatenation is not implemented. Thus, escape characters in strings are
|
||
not currently available.
|
||
|
||
@item
|
||
Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
|
||
equality of representations. They will generally work correctly
|
||
for strings and arrays whose elements have integer or enumeration types.
|
||
They may not work correctly for arrays whose element
|
||
types have user-defined equality, for arrays of real values
|
||
(in particular, IEEE-conformant floating point, because of negative
|
||
zeroes and NaNs), and for arrays whose elements contain unused bits with
|
||
indeterminate values.
|
||
|
||
@item
|
||
The other component-by-component array operations (@code{and}, @code{or},
|
||
@code{xor}, @code{not}, and relational tests other than equality)
|
||
are not implemented.
|
||
|
||
@item
|
||
@cindex array aggregates (Ada)
|
||
@cindex record aggregates (Ada)
|
||
@cindex aggregates (Ada)
|
||
There is limited support for array and record aggregates. They are
|
||
permitted only on the right sides of assignments, as in these examples:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
|
||
(@value{GDBP}) set An_Array := (1, others => 0)
|
||
(@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
|
||
(@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
|
||
(@value{GDBP}) set A_Record := (1, "Peter", True);
|
||
(@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
|
||
@end smallexample
|
||
|
||
Changing a
|
||
discriminant's value by assigning an aggregate has an
|
||
undefined effect if that discriminant is used within the record.
|
||
However, you can first modify discriminants by directly assigning to
|
||
them (which normally would not be allowed in Ada), and then performing an
|
||
aggregate assignment. For example, given a variable @code{A_Rec}
|
||
declared to have a type such as:
|
||
|
||
@smallexample
|
||
type Rec (Len : Small_Integer := 0) is record
|
||
Id : Integer;
|
||
Vals : IntArray (1 .. Len);
|
||
end record;
|
||
@end smallexample
|
||
|
||
you can assign a value with a different size of @code{Vals} with two
|
||
assignments:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set A_Rec.Len := 4
|
||
(@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
|
||
@end smallexample
|
||
|
||
As this example also illustrates, @value{GDBN} is very loose about the usual
|
||
rules concerning aggregates. You may leave out some of the
|
||
components of an array or record aggregate (such as the @code{Len}
|
||
component in the assignment to @code{A_Rec} above); they will retain their
|
||
original values upon assignment. You may freely use dynamic values as
|
||
indices in component associations. You may even use overlapping or
|
||
redundant component associations, although which component values are
|
||
assigned in such cases is not defined.
|
||
|
||
@item
|
||
Calls to dispatching subprograms are not implemented.
|
||
|
||
@item
|
||
The overloading algorithm is much more limited (i.e., less selective)
|
||
than that of real Ada. It makes only limited use of the context in
|
||
which a subexpression appears to resolve its meaning, and it is much
|
||
looser in its rules for allowing type matches. As a result, some
|
||
function calls will be ambiguous, and the user will be asked to choose
|
||
the proper resolution.
|
||
|
||
@item
|
||
The @code{new} operator is not implemented.
|
||
|
||
@item
|
||
Entry calls are not implemented.
|
||
|
||
@item
|
||
Aside from printing, arithmetic operations on the native VAX floating-point
|
||
formats are not supported.
|
||
|
||
@item
|
||
It is not possible to slice a packed array.
|
||
|
||
@item
|
||
The names @code{True} and @code{False}, when not part of a qualified name,
|
||
are interpreted as if implicitly prefixed by @code{Standard}, regardless of
|
||
context.
|
||
Should your program
|
||
redefine these names in a package or procedure (at best a dubious practice),
|
||
you will have to use fully qualified names to access their new definitions.
|
||
@end itemize
|
||
|
||
@node Additions to Ada
|
||
@subsubsection Additions to Ada
|
||
@cindex Ada, deviations from
|
||
|
||
As it does for other languages, @value{GDBN} makes certain generic
|
||
extensions to Ada (@pxref{Expressions}):
|
||
|
||
@itemize @bullet
|
||
@item
|
||
If the expression @var{E} is a variable residing in memory (typically
|
||
a local variable or array element) and @var{N} is a positive integer,
|
||
then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
|
||
@var{N}-1 adjacent variables following it in memory as an array. In
|
||
Ada, this operator is generally not necessary, since its prime use is
|
||
in displaying parts of an array, and slicing will usually do this in
|
||
Ada. However, there are occasional uses when debugging programs in
|
||
which certain debugging information has been optimized away.
|
||
|
||
@item
|
||
@code{@var{B}::@var{var}} means ``the variable named @var{var} that
|
||
appears in function or file @var{B}.'' When @var{B} is a file name,
|
||
you must typically surround it in single quotes.
|
||
|
||
@item
|
||
The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
|
||
@var{type} that appears at address @var{addr}.''
|
||
|
||
@item
|
||
A name starting with @samp{$} is a convenience variable
|
||
(@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
|
||
@end itemize
|
||
|
||
In addition, @value{GDBN} provides a few other shortcuts and outright
|
||
additions specific to Ada:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The assignment statement is allowed as an expression, returning
|
||
its right-hand operand as its value. Thus, you may enter
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set x := y + 3
|
||
(@value{GDBP}) print A(tmp := y + 1)
|
||
@end smallexample
|
||
|
||
@item
|
||
The semicolon is allowed as an ``operator,'' returning as its value
|
||
the value of its right-hand operand.
|
||
This allows, for example,
|
||
complex conditional breaks:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) break f
|
||
(@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
|
||
@end smallexample
|
||
|
||
@item
|
||
Rather than use catenation and symbolic character names to introduce special
|
||
characters into strings, one may instead use a special bracket notation,
|
||
which is also used to print strings. A sequence of characters of the form
|
||
@samp{["@var{XX}"]} within a string or character literal denotes the
|
||
(single) character whose numeric encoding is @var{XX} in hexadecimal. The
|
||
sequence of characters @samp{["""]} also denotes a single quotation mark
|
||
in strings. For example,
|
||
@smallexample
|
||
"One line.["0a"]Next line.["0a"]"
|
||
@end smallexample
|
||
@noindent
|
||
contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
|
||
after each period.
|
||
|
||
@item
|
||
The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
|
||
@t{'Max} is optional (and is ignored in any case). For example, it is valid
|
||
to write
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print 'max(x, y)
|
||
@end smallexample
|
||
|
||
@item
|
||
When printing arrays, @value{GDBN} uses positional notation when the
|
||
array has a lower bound of 1, and uses a modified named notation otherwise.
|
||
For example, a one-dimensional array of three integers with a lower bound
|
||
of 3 might print as
|
||
|
||
@smallexample
|
||
(3 => 10, 17, 1)
|
||
@end smallexample
|
||
|
||
@noindent
|
||
That is, in contrast to valid Ada, only the first component has a @code{=>}
|
||
clause.
|
||
|
||
@item
|
||
You may abbreviate attributes in expressions with any unique,
|
||
multi-character subsequence of
|
||
their names (an exact match gets preference).
|
||
For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
|
||
in place of @t{a'length}.
|
||
|
||
@item
|
||
@cindex quoting Ada internal identifiers
|
||
Since Ada is case-insensitive, the debugger normally maps identifiers you type
|
||
to lower case. The GNAT compiler uses upper-case characters for
|
||
some of its internal identifiers, which are normally of no interest to users.
|
||
For the rare occasions when you actually have to look at them,
|
||
enclose them in angle brackets to avoid the lower-case mapping.
|
||
For example,
|
||
@smallexample
|
||
(@value{GDBP}) print <JMPBUF_SAVE>[0]
|
||
@end smallexample
|
||
|
||
@item
|
||
Printing an object of class-wide type or dereferencing an
|
||
access-to-class-wide value will display all the components of the object's
|
||
specific type (as indicated by its run-time tag). Likewise, component
|
||
selection on such a value will operate on the specific type of the
|
||
object.
|
||
|
||
@end itemize
|
||
|
||
@node Overloading support for Ada
|
||
@subsubsection Overloading support for Ada
|
||
@cindex overloading, Ada
|
||
|
||
The debugger supports limited overloading. Given a subprogram call in which
|
||
the function symbol has multiple definitions, it will use the number of
|
||
actual parameters and some information about their types to attempt to narrow
|
||
the set of definitions. It also makes very limited use of context, preferring
|
||
procedures to functions in the context of the @code{call} command, and
|
||
functions to procedures elsewhere.
|
||
|
||
If, after narrowing, the set of matching definitions still contains more than
|
||
one definition, @value{GDBN} will display a menu to query which one it should
|
||
use, for instance:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print f(1)
|
||
Multiple matches for f
|
||
[0] cancel
|
||
[1] foo.f (integer) return boolean at foo.adb:23
|
||
[2] foo.f (foo.new_integer) return boolean at foo.adb:28
|
||
>
|
||
@end smallexample
|
||
|
||
In this case, just select one menu entry either to cancel expression evaluation
|
||
(type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
|
||
instance (type the corresponding number and press @key{RET}).
|
||
|
||
Here are a couple of commands to customize @value{GDBN}'s behavior in this
|
||
case:
|
||
|
||
@table @code
|
||
|
||
@kindex set ada print-signatures
|
||
@item set ada print-signatures
|
||
Control whether parameter types and return types are displayed in overloads
|
||
selection menus. It is @code{on} by default.
|
||
@xref{Overloading support for Ada}.
|
||
|
||
@kindex show ada print-signatures
|
||
@item show ada print-signatures
|
||
Show the current setting for displaying parameter types and return types in
|
||
overloads selection menu.
|
||
@xref{Overloading support for Ada}.
|
||
|
||
@end table
|
||
|
||
@node Stopping Before Main Program
|
||
@subsubsection Stopping at the Very Beginning
|
||
|
||
@cindex breakpointing Ada elaboration code
|
||
It is sometimes necessary to debug the program during elaboration, and
|
||
before reaching the main procedure.
|
||
As defined in the Ada Reference
|
||
Manual, the elaboration code is invoked from a procedure called
|
||
@code{adainit}. To run your program up to the beginning of
|
||
elaboration, simply use the following two commands:
|
||
@code{tbreak adainit} and @code{run}.
|
||
|
||
@node Ada Exceptions
|
||
@subsubsection Ada Exceptions
|
||
|
||
A command is provided to list all Ada exceptions:
|
||
|
||
@table @code
|
||
@kindex info exceptions
|
||
@item info exceptions
|
||
@itemx info exceptions @var{regexp}
|
||
The @code{info exceptions} command allows you to list all Ada exceptions
|
||
defined within the program being debugged, as well as their addresses.
|
||
With a regular expression, @var{regexp}, as argument, only those exceptions
|
||
whose names match @var{regexp} are listed.
|
||
@end table
|
||
|
||
Below is a small example, showing how the command can be used, first
|
||
without argument, and next with a regular expression passed as an
|
||
argument.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info exceptions
|
||
All defined Ada exceptions:
|
||
constraint_error: 0x613da0
|
||
program_error: 0x613d20
|
||
storage_error: 0x613ce0
|
||
tasking_error: 0x613ca0
|
||
const.aint_global_e: 0x613b00
|
||
(@value{GDBP}) info exceptions const.aint
|
||
All Ada exceptions matching regular expression "const.aint":
|
||
constraint_error: 0x613da0
|
||
const.aint_global_e: 0x613b00
|
||
@end smallexample
|
||
|
||
It is also possible to ask @value{GDBN} to stop your program's execution
|
||
when an exception is raised. For more details, see @ref{Set Catchpoints}.
|
||
|
||
@node Ada Tasks
|
||
@subsubsection Extensions for Ada Tasks
|
||
@cindex Ada, tasking
|
||
|
||
Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
|
||
@value{GDBN} provides the following task-related commands:
|
||
|
||
@table @code
|
||
@kindex info tasks
|
||
@item info tasks
|
||
This command shows a list of current Ada tasks, as in the following example:
|
||
|
||
|
||
@smallexample
|
||
@iftex
|
||
@leftskip=0.5cm
|
||
@end iftex
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 8088000 0 15 Child Activation Wait main_task
|
||
2 80a4000 1 15 Accept Statement b
|
||
3 809a800 1 15 Child Activation Wait a
|
||
* 4 80ae800 3 15 Runnable c
|
||
|
||
@end smallexample
|
||
|
||
@noindent
|
||
In this listing, the asterisk before the last task indicates it to be the
|
||
task currently being inspected.
|
||
|
||
@table @asis
|
||
@item ID
|
||
Represents @value{GDBN}'s internal task number.
|
||
|
||
@item TID
|
||
The Ada task ID.
|
||
|
||
@item P-ID
|
||
The parent's task ID (@value{GDBN}'s internal task number).
|
||
|
||
@item Pri
|
||
The base priority of the task.
|
||
|
||
@item State
|
||
Current state of the task.
|
||
|
||
@table @code
|
||
@item Unactivated
|
||
The task has been created but has not been activated. It cannot be
|
||
executing.
|
||
|
||
@item Runnable
|
||
The task is not blocked for any reason known to Ada. (It may be waiting
|
||
for a mutex, though.) It is conceptually "executing" in normal mode.
|
||
|
||
@item Terminated
|
||
The task is terminated, in the sense of ARM 9.3 (5). Any dependents
|
||
that were waiting on terminate alternatives have been awakened and have
|
||
terminated themselves.
|
||
|
||
@item Child Activation Wait
|
||
The task is waiting for created tasks to complete activation.
|
||
|
||
@item Accept Statement
|
||
The task is waiting on an accept or selective wait statement.
|
||
|
||
@item Waiting on entry call
|
||
The task is waiting on an entry call.
|
||
|
||
@item Async Select Wait
|
||
The task is waiting to start the abortable part of an asynchronous
|
||
select statement.
|
||
|
||
@item Delay Sleep
|
||
The task is waiting on a select statement with only a delay
|
||
alternative open.
|
||
|
||
@item Child Termination Wait
|
||
The task is sleeping having completed a master within itself, and is
|
||
waiting for the tasks dependent on that master to become terminated or
|
||
waiting on a terminate Phase.
|
||
|
||
@item Wait Child in Term Alt
|
||
The task is sleeping waiting for tasks on terminate alternatives to
|
||
finish terminating.
|
||
|
||
@item Accepting RV with @var{taskno}
|
||
The task is accepting a rendez-vous with the task @var{taskno}.
|
||
@end table
|
||
|
||
@item Name
|
||
Name of the task in the program.
|
||
|
||
@end table
|
||
|
||
@kindex info task @var{taskno}
|
||
@item info task @var{taskno}
|
||
This command shows detailled informations on the specified task, as in
|
||
the following example:
|
||
@smallexample
|
||
@iftex
|
||
@leftskip=0.5cm
|
||
@end iftex
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 8077880 0 15 Child Activation Wait main_task
|
||
* 2 807c468 1 15 Runnable task_1
|
||
(@value{GDBP}) info task 2
|
||
Ada Task: 0x807c468
|
||
Name: task_1
|
||
Thread: 0x807f378
|
||
Parent: 1 (main_task)
|
||
Base Priority: 15
|
||
State: Runnable
|
||
@end smallexample
|
||
|
||
@item task
|
||
@kindex task@r{ (Ada)}
|
||
@cindex current Ada task ID
|
||
This command prints the ID of the current task.
|
||
|
||
@smallexample
|
||
@iftex
|
||
@leftskip=0.5cm
|
||
@end iftex
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 8077870 0 15 Child Activation Wait main_task
|
||
* 2 807c458 1 15 Runnable t
|
||
(@value{GDBP}) task
|
||
[Current task is 2]
|
||
@end smallexample
|
||
|
||
@item task @var{taskno}
|
||
@cindex Ada task switching
|
||
This command is like the @code{thread @var{thread-id}}
|
||
command (@pxref{Threads}). It switches the context of debugging
|
||
from the current task to the given task.
|
||
|
||
@smallexample
|
||
@iftex
|
||
@leftskip=0.5cm
|
||
@end iftex
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 8077870 0 15 Child Activation Wait main_task
|
||
* 2 807c458 1 15 Runnable t
|
||
(@value{GDBP}) task 1
|
||
[Switching to task 1]
|
||
#0 0x8067726 in pthread_cond_wait ()
|
||
(@value{GDBP}) bt
|
||
#0 0x8067726 in pthread_cond_wait ()
|
||
#1 0x8056714 in system.os_interface.pthread_cond_wait ()
|
||
#2 0x805cb63 in system.task_primitives.operations.sleep ()
|
||
#3 0x806153e in system.tasking.stages.activate_tasks ()
|
||
#4 0x804aacc in un () at un.adb:5
|
||
@end smallexample
|
||
|
||
@item break @var{location} task @var{taskno}
|
||
@itemx break @var{location} task @var{taskno} if @dots{}
|
||
@cindex breakpoints and tasks, in Ada
|
||
@cindex task breakpoints, in Ada
|
||
@kindex break @dots{} task @var{taskno}@r{ (Ada)}
|
||
These commands are like the @code{break @dots{} thread @dots{}}
|
||
command (@pxref{Thread Stops}). The
|
||
@var{location} argument specifies source lines, as described
|
||
in @ref{Specify Location}.
|
||
|
||
Use the qualifier @samp{task @var{taskno}} with a breakpoint command
|
||
to specify that you only want @value{GDBN} to stop the program when a
|
||
particular Ada task reaches this breakpoint. The @var{taskno} is one of the
|
||
numeric task identifiers assigned by @value{GDBN}, shown in the first
|
||
column of the @samp{info tasks} display.
|
||
|
||
If you do not specify @samp{task @var{taskno}} when you set a
|
||
breakpoint, the breakpoint applies to @emph{all} tasks of your
|
||
program.
|
||
|
||
You can use the @code{task} qualifier on conditional breakpoints as
|
||
well; in this case, place @samp{task @var{taskno}} before the
|
||
breakpoint condition (before the @code{if}).
|
||
|
||
For example,
|
||
|
||
@smallexample
|
||
@iftex
|
||
@leftskip=0.5cm
|
||
@end iftex
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 140022020 0 15 Child Activation Wait main_task
|
||
2 140045060 1 15 Accept/Select Wait t2
|
||
3 140044840 1 15 Runnable t1
|
||
* 4 140056040 1 15 Runnable t3
|
||
(@value{GDBP}) b 15 task 2
|
||
Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
|
||
(@value{GDBP}) cont
|
||
Continuing.
|
||
task # 1 running
|
||
task # 2 running
|
||
|
||
Breakpoint 5, test_task_debug () at test_task_debug.adb:15
|
||
15 flush;
|
||
(@value{GDBP}) info tasks
|
||
ID TID P-ID Pri State Name
|
||
1 140022020 0 15 Child Activation Wait main_task
|
||
* 2 140045060 1 15 Runnable t2
|
||
3 140044840 1 15 Runnable t1
|
||
4 140056040 1 15 Delay Sleep t3
|
||
@end smallexample
|
||
@end table
|
||
|
||
@node Ada Tasks and Core Files
|
||
@subsubsection Tasking Support when Debugging Core Files
|
||
@cindex Ada tasking and core file debugging
|
||
|
||
When inspecting a core file, as opposed to debugging a live program,
|
||
tasking support may be limited or even unavailable, depending on
|
||
the platform being used.
|
||
For instance, on x86-linux, the list of tasks is available, but task
|
||
switching is not supported.
|
||
|
||
On certain platforms, the debugger needs to perform some
|
||
memory writes in order to provide Ada tasking support. When inspecting
|
||
a core file, this means that the core file must be opened with read-write
|
||
privileges, using the command @samp{"set write on"} (@pxref{Patching}).
|
||
Under these circumstances, you should make a backup copy of the core
|
||
file before inspecting it with @value{GDBN}.
|
||
|
||
@node Ravenscar Profile
|
||
@subsubsection Tasking Support when using the Ravenscar Profile
|
||
@cindex Ravenscar Profile
|
||
|
||
The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
|
||
specifically designed for systems with safety-critical real-time
|
||
requirements.
|
||
|
||
@table @code
|
||
@kindex set ravenscar task-switching on
|
||
@cindex task switching with program using Ravenscar Profile
|
||
@item set ravenscar task-switching on
|
||
Allows task switching when debugging a program that uses the Ravenscar
|
||
Profile. This is the default.
|
||
|
||
@kindex set ravenscar task-switching off
|
||
@item set ravenscar task-switching off
|
||
Turn off task switching when debugging a program that uses the Ravenscar
|
||
Profile. This is mostly intended to disable the code that adds support
|
||
for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
|
||
the Ravenscar runtime is preventing @value{GDBN} from working properly.
|
||
To be effective, this command should be run before the program is started.
|
||
|
||
@kindex show ravenscar task-switching
|
||
@item show ravenscar task-switching
|
||
Show whether it is possible to switch from task to task in a program
|
||
using the Ravenscar Profile.
|
||
|
||
@end table
|
||
|
||
@node Ada Settings
|
||
@subsubsection Ada Settings
|
||
@cindex Ada settings
|
||
|
||
@table @code
|
||
@kindex set varsize-limit
|
||
@item set varsize-limit @var{size}
|
||
Prevent @value{GDBN} from attempting to evaluate objects whose size
|
||
is above the given limit (@var{size}) when those sizes are computed
|
||
from run-time quantities. This is typically the case when the object
|
||
has a variable size, such as an array whose bounds are not known at
|
||
compile time for example. Setting @var{size} to @code{unlimited}
|
||
removes the size limitation. By default, the limit is about 65KB.
|
||
|
||
The purpose of having such a limit is to prevent @value{GDBN} from
|
||
trying to grab enormous chunks of virtual memory when asked to evaluate
|
||
a quantity whose bounds have been corrupted or have not yet been fully
|
||
initialized. The limit applies to the results of some subexpressions
|
||
as well as to complete expressions. For example, an expression denoting
|
||
a simple integer component, such as @code{x.y.z}, may fail if the size of
|
||
@code{x.y} is variable and exceeds @code{size}. On the other hand,
|
||
@value{GDBN} is sometimes clever; the expression @code{A(i)}, where
|
||
@code{A} is an array variable with non-constant size, will generally
|
||
succeed regardless of the bounds on @code{A}, as long as the component
|
||
size is less than @var{size}.
|
||
|
||
@kindex show varsize-limit
|
||
@item show varsize-limit
|
||
Show the limit on types whose size is determined by run-time quantities.
|
||
@end table
|
||
|
||
@node Ada Glitches
|
||
@subsubsection Known Peculiarities of Ada Mode
|
||
@cindex Ada, problems
|
||
|
||
Besides the omissions listed previously (@pxref{Omissions from Ada}),
|
||
we know of several problems with and limitations of Ada mode in
|
||
@value{GDBN},
|
||
some of which will be fixed with planned future releases of the debugger
|
||
and the GNU Ada compiler.
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Static constants that the compiler chooses not to materialize as objects in
|
||
storage are invisible to the debugger.
|
||
|
||
@item
|
||
Named parameter associations in function argument lists are ignored (the
|
||
argument lists are treated as positional).
|
||
|
||
@item
|
||
Many useful library packages are currently invisible to the debugger.
|
||
|
||
@item
|
||
Fixed-point arithmetic, conversions, input, and output is carried out using
|
||
floating-point arithmetic, and may give results that only approximate those on
|
||
the host machine.
|
||
|
||
@item
|
||
The GNAT compiler never generates the prefix @code{Standard} for any of
|
||
the standard symbols defined by the Ada language. @value{GDBN} knows about
|
||
this: it will strip the prefix from names when you use it, and will never
|
||
look for a name you have so qualified among local symbols, nor match against
|
||
symbols in other packages or subprograms. If you have
|
||
defined entities anywhere in your program other than parameters and
|
||
local variables whose simple names match names in @code{Standard},
|
||
GNAT's lack of qualification here can cause confusion. When this happens,
|
||
you can usually resolve the confusion
|
||
by qualifying the problematic names with package
|
||
@code{Standard} explicitly.
|
||
@end itemize
|
||
|
||
Older versions of the compiler sometimes generate erroneous debugging
|
||
information, resulting in the debugger incorrectly printing the value
|
||
of affected entities. In some cases, the debugger is able to work
|
||
around an issue automatically. In other cases, the debugger is able
|
||
to work around the issue, but the work-around has to be specifically
|
||
enabled.
|
||
|
||
@kindex set ada trust-PAD-over-XVS
|
||
@kindex show ada trust-PAD-over-XVS
|
||
@table @code
|
||
|
||
@item set ada trust-PAD-over-XVS on
|
||
Configure GDB to strictly follow the GNAT encoding when computing the
|
||
value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
|
||
types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
|
||
a complete description of the encoding used by the GNAT compiler).
|
||
This is the default.
|
||
|
||
@item set ada trust-PAD-over-XVS off
|
||
This is related to the encoding using by the GNAT compiler. If @value{GDBN}
|
||
sometimes prints the wrong value for certain entities, changing @code{ada
|
||
trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
|
||
the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
|
||
@code{off}, but this incurs a slight performance penalty, so it is
|
||
recommended to leave this setting to @code{on} unless necessary.
|
||
|
||
@end table
|
||
|
||
@cindex GNAT descriptive types
|
||
@cindex GNAT encoding
|
||
Internally, the debugger also relies on the compiler following a number
|
||
of conventions known as the @samp{GNAT Encoding}, all documented in
|
||
@file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
|
||
how the debugging information should be generated for certain types.
|
||
In particular, this convention makes use of @dfn{descriptive types},
|
||
which are artificial types generated purely to help the debugger.
|
||
|
||
These encodings were defined at a time when the debugging information
|
||
format used was not powerful enough to describe some of the more complex
|
||
types available in Ada. Since DWARF allows us to express nearly all
|
||
Ada features, the long-term goal is to slowly replace these descriptive
|
||
types by their pure DWARF equivalent. To facilitate that transition,
|
||
a new maintenance option is available to force the debugger to ignore
|
||
those descriptive types. It allows the user to quickly evaluate how
|
||
well @value{GDBN} works without them.
|
||
|
||
@table @code
|
||
|
||
@kindex maint ada set ignore-descriptive-types
|
||
@item maintenance ada set ignore-descriptive-types [on|off]
|
||
Control whether the debugger should ignore descriptive types.
|
||
The default is not to ignore descriptives types (@code{off}).
|
||
|
||
@kindex maint ada show ignore-descriptive-types
|
||
@item maintenance ada show ignore-descriptive-types
|
||
Show if descriptive types are ignored by @value{GDBN}.
|
||
|
||
@end table
|
||
|
||
@node Unsupported Languages
|
||
@section Unsupported Languages
|
||
|
||
@cindex unsupported languages
|
||
@cindex minimal language
|
||
In addition to the other fully-supported programming languages,
|
||
@value{GDBN} also provides a pseudo-language, called @code{minimal}.
|
||
It does not represent a real programming language, but provides a set
|
||
of capabilities close to what the C or assembly languages provide.
|
||
This should allow most simple operations to be performed while debugging
|
||
an application that uses a language currently not supported by @value{GDBN}.
|
||
|
||
If the language is set to @code{auto}, @value{GDBN} will automatically
|
||
select this language if the current frame corresponds to an unsupported
|
||
language.
|
||
|
||
@node Symbols
|
||
@chapter Examining the Symbol Table
|
||
|
||
The commands described in this chapter allow you to inquire about the
|
||
symbols (names of variables, functions and types) defined in your
|
||
program. This information is inherent in the text of your program and
|
||
does not change as your program executes. @value{GDBN} finds it in your
|
||
program's symbol table, in the file indicated when you started @value{GDBN}
|
||
(@pxref{File Options, ,Choosing Files}), or by one of the
|
||
file-management commands (@pxref{Files, ,Commands to Specify Files}).
|
||
|
||
@cindex symbol names
|
||
@cindex names of symbols
|
||
@cindex quoting names
|
||
@anchor{quoting names}
|
||
Occasionally, you may need to refer to symbols that contain unusual
|
||
characters, which @value{GDBN} ordinarily treats as word delimiters. The
|
||
most frequent case is in referring to static variables in other
|
||
source files (@pxref{Variables,,Program Variables}). File names
|
||
are recorded in object files as debugging symbols, but @value{GDBN} would
|
||
ordinarily parse a typical file name, like @file{foo.c}, as the three words
|
||
@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
|
||
@samp{foo.c} as a single symbol, enclose it in single quotes; for example,
|
||
|
||
@smallexample
|
||
p 'foo.c'::x
|
||
@end smallexample
|
||
|
||
@noindent
|
||
looks up the value of @code{x} in the scope of the file @file{foo.c}.
|
||
|
||
@table @code
|
||
@cindex case-insensitive symbol names
|
||
@cindex case sensitivity in symbol names
|
||
@kindex set case-sensitive
|
||
@item set case-sensitive on
|
||
@itemx set case-sensitive off
|
||
@itemx set case-sensitive auto
|
||
Normally, when @value{GDBN} looks up symbols, it matches their names
|
||
with case sensitivity determined by the current source language.
|
||
Occasionally, you may wish to control that. The command @code{set
|
||
case-sensitive} lets you do that by specifying @code{on} for
|
||
case-sensitive matches or @code{off} for case-insensitive ones. If
|
||
you specify @code{auto}, case sensitivity is reset to the default
|
||
suitable for the source language. The default is case-sensitive
|
||
matches for all languages except for Fortran, for which the default is
|
||
case-insensitive matches.
|
||
|
||
@kindex show case-sensitive
|
||
@item show case-sensitive
|
||
This command shows the current setting of case sensitivity for symbols
|
||
lookups.
|
||
|
||
@kindex set print type methods
|
||
@item set print type methods
|
||
@itemx set print type methods on
|
||
@itemx set print type methods off
|
||
Normally, when @value{GDBN} prints a class, it displays any methods
|
||
declared in that class. You can control this behavior either by
|
||
passing the appropriate flag to @code{ptype}, or using @command{set
|
||
print type methods}. Specifying @code{on} will cause @value{GDBN} to
|
||
display the methods; this is the default. Specifying @code{off} will
|
||
cause @value{GDBN} to omit the methods.
|
||
|
||
@kindex show print type methods
|
||
@item show print type methods
|
||
This command shows the current setting of method display when printing
|
||
classes.
|
||
|
||
@kindex set print type nested-type-limit
|
||
@item set print type nested-type-limit @var{limit}
|
||
@itemx set print type nested-type-limit unlimited
|
||
Set the limit of displayed nested types that the type printer will
|
||
show. A @var{limit} of @code{unlimited} or @code{-1} will show all
|
||
nested definitions. By default, the type printer will not show any nested
|
||
types defined in classes.
|
||
|
||
@kindex show print type nested-type-limit
|
||
@item show print type nested-type-limit
|
||
This command shows the current display limit of nested types when
|
||
printing classes.
|
||
|
||
@kindex set print type typedefs
|
||
@item set print type typedefs
|
||
@itemx set print type typedefs on
|
||
@itemx set print type typedefs off
|
||
|
||
Normally, when @value{GDBN} prints a class, it displays any typedefs
|
||
defined in that class. You can control this behavior either by
|
||
passing the appropriate flag to @code{ptype}, or using @command{set
|
||
print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
|
||
display the typedef definitions; this is the default. Specifying
|
||
@code{off} will cause @value{GDBN} to omit the typedef definitions.
|
||
Note that this controls whether the typedef definition itself is
|
||
printed, not whether typedef names are substituted when printing other
|
||
types.
|
||
|
||
@kindex show print type typedefs
|
||
@item show print type typedefs
|
||
This command shows the current setting of typedef display when
|
||
printing classes.
|
||
|
||
@kindex info address
|
||
@cindex address of a symbol
|
||
@item info address @var{symbol}
|
||
Describe where the data for @var{symbol} is stored. For a register
|
||
variable, this says which register it is kept in. For a non-register
|
||
local variable, this prints the stack-frame offset at which the variable
|
||
is always stored.
|
||
|
||
Note the contrast with @samp{print &@var{symbol}}, which does not work
|
||
at all for a register variable, and for a stack local variable prints
|
||
the exact address of the current instantiation of the variable.
|
||
|
||
@kindex info symbol
|
||
@cindex symbol from address
|
||
@cindex closest symbol and offset for an address
|
||
@item info symbol @var{addr}
|
||
Print the name of a symbol which is stored at the address @var{addr}.
|
||
If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
|
||
nearest symbol and an offset from it:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info symbol 0x54320
|
||
_initialize_vx + 396 in section .text
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This is the opposite of the @code{info address} command. You can use
|
||
it to find out the name of a variable or a function given its address.
|
||
|
||
For dynamically linked executables, the name of executable or shared
|
||
library containing the symbol is also printed:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info symbol 0x400225
|
||
_start + 5 in section .text of /tmp/a.out
|
||
(@value{GDBP}) info symbol 0x2aaaac2811cf
|
||
__read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
|
||
@end smallexample
|
||
|
||
@kindex demangle
|
||
@cindex demangle
|
||
@item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
|
||
Demangle @var{name}.
|
||
If @var{language} is provided it is the name of the language to demangle
|
||
@var{name} in. Otherwise @var{name} is demangled in the current language.
|
||
|
||
The @samp{--} option specifies the end of options,
|
||
and is useful when @var{name} begins with a dash.
|
||
|
||
The parameter @code{demangle-style} specifies how to interpret the kind
|
||
of mangling used. @xref{Print Settings}.
|
||
|
||
@kindex whatis
|
||
@item whatis[/@var{flags}] [@var{arg}]
|
||
Print the data type of @var{arg}, which can be either an expression
|
||
or a name of a data type. With no argument, print the data type of
|
||
@code{$}, the last value in the value history.
|
||
|
||
If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
|
||
is not actually evaluated, and any side-effecting operations (such as
|
||
assignments or function calls) inside it do not take place.
|
||
|
||
If @var{arg} is a variable or an expression, @code{whatis} prints its
|
||
literal type as it is used in the source code. If the type was
|
||
defined using a @code{typedef}, @code{whatis} will @emph{not} print
|
||
the data type underlying the @code{typedef}. If the type of the
|
||
variable or the expression is a compound data type, such as
|
||
@code{struct} or @code{class}, @code{whatis} never prints their
|
||
fields or methods. It just prints the @code{struct}/@code{class}
|
||
name (a.k.a.@: its @dfn{tag}). If you want to see the members of
|
||
such a compound data type, use @code{ptype}.
|
||
|
||
If @var{arg} is a type name that was defined using @code{typedef},
|
||
@code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
|
||
Unrolling means that @code{whatis} will show the underlying type used
|
||
in the @code{typedef} declaration of @var{arg}. However, if that
|
||
underlying type is also a @code{typedef}, @code{whatis} will not
|
||
unroll it.
|
||
|
||
For C code, the type names may also have the form @samp{class
|
||
@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
|
||
@var{union-tag}} or @samp{enum @var{enum-tag}}.
|
||
|
||
@var{flags} can be used to modify how the type is displayed.
|
||
Available flags are:
|
||
|
||
@table @code
|
||
@item r
|
||
Display in ``raw'' form. Normally, @value{GDBN} substitutes template
|
||
parameters and typedefs defined in a class when printing the class'
|
||
members. The @code{/r} flag disables this.
|
||
|
||
@item m
|
||
Do not print methods defined in the class.
|
||
|
||
@item M
|
||
Print methods defined in the class. This is the default, but the flag
|
||
exists in case you change the default with @command{set print type methods}.
|
||
|
||
@item t
|
||
Do not print typedefs defined in the class. Note that this controls
|
||
whether the typedef definition itself is printed, not whether typedef
|
||
names are substituted when printing other types.
|
||
|
||
@item T
|
||
Print typedefs defined in the class. This is the default, but the flag
|
||
exists in case you change the default with @command{set print type typedefs}.
|
||
|
||
@item o
|
||
Print the offsets and sizes of fields in a struct, similar to what the
|
||
@command{pahole} tool does. This option implies the @code{/tm} flags.
|
||
|
||
For example, given the following declarations:
|
||
|
||
@smallexample
|
||
struct tuv
|
||
@{
|
||
int a1;
|
||
char *a2;
|
||
int a3;
|
||
@};
|
||
|
||
struct xyz
|
||
@{
|
||
int f1;
|
||
char f2;
|
||
void *f3;
|
||
struct tuv f4;
|
||
@};
|
||
|
||
union qwe
|
||
@{
|
||
struct tuv fff1;
|
||
struct xyz fff2;
|
||
@};
|
||
|
||
struct tyu
|
||
@{
|
||
int a1 : 1;
|
||
int a2 : 3;
|
||
int a3 : 23;
|
||
char a4 : 2;
|
||
int64_t a5;
|
||
int a6 : 5;
|
||
int64_t a7 : 3;
|
||
@};
|
||
@end smallexample
|
||
|
||
Issuing a @kbd{ptype /o struct tuv} command would print:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype /o struct tuv
|
||
/* offset | size */ type = struct tuv @{
|
||
/* 0 | 4 */ int a1;
|
||
/* XXX 4-byte hole */
|
||
/* 8 | 8 */ char *a2;
|
||
/* 16 | 4 */ int a3;
|
||
|
||
/* total size (bytes): 24 */
|
||
@}
|
||
@end smallexample
|
||
|
||
Notice the format of the first column of comments. There, you can
|
||
find two parts separated by the @samp{|} character: the @emph{offset},
|
||
which indicates where the field is located inside the struct, in
|
||
bytes, and the @emph{size} of the field. Another interesting line is
|
||
the marker of a @emph{hole} in the struct, indicating that it may be
|
||
possible to pack the struct and make it use less space by reorganizing
|
||
its fields.
|
||
|
||
It is also possible to print offsets inside an union:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype /o union qwe
|
||
/* offset | size */ type = union qwe @{
|
||
/* 24 */ struct tuv @{
|
||
/* 0 | 4 */ int a1;
|
||
/* XXX 4-byte hole */
|
||
/* 8 | 8 */ char *a2;
|
||
/* 16 | 4 */ int a3;
|
||
|
||
/* total size (bytes): 24 */
|
||
@} fff1;
|
||
/* 40 */ struct xyz @{
|
||
/* 0 | 4 */ int f1;
|
||
/* 4 | 1 */ char f2;
|
||
/* XXX 3-byte hole */
|
||
/* 8 | 8 */ void *f3;
|
||
/* 16 | 24 */ struct tuv @{
|
||
/* 16 | 4 */ int a1;
|
||
/* XXX 4-byte hole */
|
||
/* 24 | 8 */ char *a2;
|
||
/* 32 | 4 */ int a3;
|
||
|
||
/* total size (bytes): 24 */
|
||
@} f4;
|
||
|
||
/* total size (bytes): 40 */
|
||
@} fff2;
|
||
|
||
/* total size (bytes): 40 */
|
||
@}
|
||
@end smallexample
|
||
|
||
In this case, since @code{struct tuv} and @code{struct xyz} occupy the
|
||
same space (because we are dealing with an union), the offset is not
|
||
printed for them. However, you can still examine the offset of each
|
||
of these structures' fields.
|
||
|
||
Another useful scenario is printing the offsets of a struct containing
|
||
bitfields:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype /o struct tyu
|
||
/* offset | size */ type = struct tyu @{
|
||
/* 0:31 | 4 */ int a1 : 1;
|
||
/* 0:28 | 4 */ int a2 : 3;
|
||
/* 0: 5 | 4 */ int a3 : 23;
|
||
/* 3: 3 | 1 */ signed char a4 : 2;
|
||
/* XXX 3-bit hole */
|
||
/* XXX 4-byte hole */
|
||
/* 8 | 8 */ int64_t a5;
|
||
/* 16:27 | 4 */ int a6 : 5;
|
||
/* 16:56 | 8 */ int64_t a7 : 3;
|
||
|
||
/* total size (bytes): 24 */
|
||
@}
|
||
@end smallexample
|
||
|
||
Note how the offset information is now extended to also include how
|
||
many bits are left to be used in each bitfield.
|
||
@end table
|
||
|
||
@kindex ptype
|
||
@item ptype[/@var{flags}] [@var{arg}]
|
||
@code{ptype} accepts the same arguments as @code{whatis}, but prints a
|
||
detailed description of the type, instead of just the name of the type.
|
||
@xref{Expressions, ,Expressions}.
|
||
|
||
Contrary to @code{whatis}, @code{ptype} always unrolls any
|
||
@code{typedef}s in its argument declaration, whether the argument is
|
||
a variable, expression, or a data type. This means that @code{ptype}
|
||
of a variable or an expression will not print literally its type as
|
||
present in the source code---use @code{whatis} for that. @code{typedef}s at
|
||
the pointer or reference targets are also unrolled. Only @code{typedef}s of
|
||
fields, methods and inner @code{class typedef}s of @code{struct}s,
|
||
@code{class}es and @code{union}s are not unrolled even with @code{ptype}.
|
||
|
||
For example, for this variable declaration:
|
||
|
||
@smallexample
|
||
typedef double real_t;
|
||
struct complex @{ real_t real; double imag; @};
|
||
typedef struct complex complex_t;
|
||
complex_t var;
|
||
real_t *real_pointer_var;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
the two commands give this output:
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) whatis var
|
||
type = complex_t
|
||
(@value{GDBP}) ptype var
|
||
type = struct complex @{
|
||
real_t real;
|
||
double imag;
|
||
@}
|
||
(@value{GDBP}) whatis complex_t
|
||
type = struct complex
|
||
(@value{GDBP}) whatis struct complex
|
||
type = struct complex
|
||
(@value{GDBP}) ptype struct complex
|
||
type = struct complex @{
|
||
real_t real;
|
||
double imag;
|
||
@}
|
||
(@value{GDBP}) whatis real_pointer_var
|
||
type = real_t *
|
||
(@value{GDBP}) ptype real_pointer_var
|
||
type = double *
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent
|
||
As with @code{whatis}, using @code{ptype} without an argument refers to
|
||
the type of @code{$}, the last value in the value history.
|
||
|
||
@cindex incomplete type
|
||
Sometimes, programs use opaque data types or incomplete specifications
|
||
of complex data structure. If the debug information included in the
|
||
program does not allow @value{GDBN} to display a full declaration of
|
||
the data type, it will say @samp{<incomplete type>}. For example,
|
||
given these declarations:
|
||
|
||
@smallexample
|
||
struct foo;
|
||
struct foo *fooptr;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
but no definition for @code{struct foo} itself, @value{GDBN} will say:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype foo
|
||
$1 = <incomplete type>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
``Incomplete type'' is C terminology for data types that are not
|
||
completely specified.
|
||
|
||
@cindex unknown type
|
||
Othertimes, information about a variable's type is completely absent
|
||
from the debug information included in the program. This most often
|
||
happens when the program or library where the variable is defined
|
||
includes no debug information at all. @value{GDBN} knows the variable
|
||
exists from inspecting the linker/loader symbol table (e.g., the ELF
|
||
dynamic symbol table), but such symbols do not contain type
|
||
information. Inspecting the type of a (global) variable for which
|
||
@value{GDBN} has no type information shows:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) ptype var
|
||
type = <data variable, no debug info>
|
||
@end smallexample
|
||
|
||
@xref{Variables, no debug info variables}, for how to print the values
|
||
of such variables.
|
||
|
||
@kindex info types
|
||
@item info types @var{regexp}
|
||
@itemx info types
|
||
Print a brief description of all types whose names match the regular
|
||
expression @var{regexp} (or all types in your program, if you supply
|
||
no argument). Each complete typename is matched as though it were a
|
||
complete line; thus, @samp{i type value} gives information on all
|
||
types in your program whose names include the string @code{value}, but
|
||
@samp{i type ^value$} gives information only on types whose complete
|
||
name is @code{value}.
|
||
|
||
This command differs from @code{ptype} in two ways: first, like
|
||
@code{whatis}, it does not print a detailed description; second, it
|
||
lists all source files and line numbers where a type is defined.
|
||
|
||
@kindex info type-printers
|
||
@item info type-printers
|
||
Versions of @value{GDBN} that ship with Python scripting enabled may
|
||
have ``type printers'' available. When using @command{ptype} or
|
||
@command{whatis}, these printers are consulted when the name of a type
|
||
is needed. @xref{Type Printing API}, for more information on writing
|
||
type printers.
|
||
|
||
@code{info type-printers} displays all the available type printers.
|
||
|
||
@kindex enable type-printer
|
||
@kindex disable type-printer
|
||
@item enable type-printer @var{name}@dots{}
|
||
@item disable type-printer @var{name}@dots{}
|
||
These commands can be used to enable or disable type printers.
|
||
|
||
@kindex info scope
|
||
@cindex local variables
|
||
@item info scope @var{location}
|
||
List all the variables local to a particular scope. This command
|
||
accepts a @var{location} argument---a function name, a source line, or
|
||
an address preceded by a @samp{*}, and prints all the variables local
|
||
to the scope defined by that location. (@xref{Specify Location}, for
|
||
details about supported forms of @var{location}.) For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{info scope command_line_handler}
|
||
Scope for command_line_handler:
|
||
Symbol rl is an argument at stack/frame offset 8, length 4.
|
||
Symbol linebuffer is in static storage at address 0x150a18, length 4.
|
||
Symbol linelength is in static storage at address 0x150a1c, length 4.
|
||
Symbol p is a local variable in register $esi, length 4.
|
||
Symbol p1 is a local variable in register $ebx, length 4.
|
||
Symbol nline is a local variable in register $edx, length 4.
|
||
Symbol repeat is a local variable at frame offset -8, length 4.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This command is especially useful for determining what data to collect
|
||
during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
|
||
collect}.
|
||
|
||
@kindex info source
|
||
@item info source
|
||
Show information about the current source file---that is, the source file for
|
||
the function containing the current point of execution:
|
||
@itemize @bullet
|
||
@item
|
||
the name of the source file, and the directory containing it,
|
||
@item
|
||
the directory it was compiled in,
|
||
@item
|
||
its length, in lines,
|
||
@item
|
||
which programming language it is written in,
|
||
@item
|
||
if the debug information provides it, the program that compiled the file
|
||
(which may include, e.g., the compiler version and command line arguments),
|
||
@item
|
||
whether the executable includes debugging information for that file, and
|
||
if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
|
||
@item
|
||
whether the debugging information includes information about
|
||
preprocessor macros.
|
||
@end itemize
|
||
|
||
|
||
@kindex info sources
|
||
@item info sources
|
||
Print the names of all source files in your program for which there is
|
||
debugging information, organized into two lists: files whose symbols
|
||
have already been read, and files whose symbols will be read when needed.
|
||
|
||
@kindex info functions
|
||
@item info functions
|
||
Print the names and data types of all defined functions.
|
||
Similarly to @samp{info types}, this command groups its output by source
|
||
files and annotates each function definition with its source line
|
||
number.
|
||
|
||
@item info functions @var{regexp}
|
||
Like @samp{info functions}, but only print the names and data types of
|
||
functions whose names contain a match for regular expression
|
||
@var{regexp}. Thus, @samp{info fun step} finds all functions whose
|
||
names include @code{step}; @samp{info fun ^step} finds those whose names
|
||
start with @code{step}. If a function name contains characters that
|
||
conflict with the regular expression language (e.g.@:
|
||
@samp{operator*()}), they may be quoted with a backslash.
|
||
|
||
@kindex info variables
|
||
@item info variables
|
||
Print the names and data types of all variables that are defined
|
||
outside of functions (i.e.@: excluding local variables).
|
||
The printed variables are grouped by source files and annotated with
|
||
their respective source line numbers.
|
||
|
||
@item info variables @var{regexp}
|
||
Like @kbd{info variables}, but only print the names and data types of
|
||
non-local variables whose names contain a match for regular expression
|
||
@var{regexp}.
|
||
|
||
@kindex info classes
|
||
@cindex Objective-C, classes and selectors
|
||
@item info classes
|
||
@itemx info classes @var{regexp}
|
||
Display all Objective-C classes in your program, or
|
||
(with the @var{regexp} argument) all those matching a particular regular
|
||
expression.
|
||
|
||
@kindex info selectors
|
||
@item info selectors
|
||
@itemx info selectors @var{regexp}
|
||
Display all Objective-C selectors in your program, or
|
||
(with the @var{regexp} argument) all those matching a particular regular
|
||
expression.
|
||
|
||
@ignore
|
||
This was never implemented.
|
||
@kindex info methods
|
||
@item info methods
|
||
@itemx info methods @var{regexp}
|
||
The @code{info methods} command permits the user to examine all defined
|
||
methods within C@t{++} program, or (with the @var{regexp} argument) a
|
||
specific set of methods found in the various C@t{++} classes. Many
|
||
C@t{++} classes provide a large number of methods. Thus, the output
|
||
from the @code{ptype} command can be overwhelming and hard to use. The
|
||
@code{info-methods} command filters the methods, printing only those
|
||
which match the regular-expression @var{regexp}.
|
||
@end ignore
|
||
|
||
@cindex opaque data types
|
||
@kindex set opaque-type-resolution
|
||
@item set opaque-type-resolution on
|
||
Tell @value{GDBN} to resolve opaque types. An opaque type is a type
|
||
declared as a pointer to a @code{struct}, @code{class}, or
|
||
@code{union}---for example, @code{struct MyType *}---that is used in one
|
||
source file although the full declaration of @code{struct MyType} is in
|
||
another source file. The default is on.
|
||
|
||
A change in the setting of this subcommand will not take effect until
|
||
the next time symbols for a file are loaded.
|
||
|
||
@item set opaque-type-resolution off
|
||
Tell @value{GDBN} not to resolve opaque types. In this case, the type
|
||
is printed as follows:
|
||
@smallexample
|
||
@{<no data fields>@}
|
||
@end smallexample
|
||
|
||
@kindex show opaque-type-resolution
|
||
@item show opaque-type-resolution
|
||
Show whether opaque types are resolved or not.
|
||
|
||
@kindex set print symbol-loading
|
||
@cindex print messages when symbols are loaded
|
||
@item set print symbol-loading
|
||
@itemx set print symbol-loading full
|
||
@itemx set print symbol-loading brief
|
||
@itemx set print symbol-loading off
|
||
The @code{set print symbol-loading} command allows you to control the
|
||
printing of messages when @value{GDBN} loads symbol information.
|
||
By default a message is printed for the executable and one for each
|
||
shared library, and normally this is what you want. However, when
|
||
debugging apps with large numbers of shared libraries these messages
|
||
can be annoying.
|
||
When set to @code{brief} a message is printed for each executable,
|
||
and when @value{GDBN} loads a collection of shared libraries at once
|
||
it will only print one message regardless of the number of shared
|
||
libraries. When set to @code{off} no messages are printed.
|
||
|
||
@kindex show print symbol-loading
|
||
@item show print symbol-loading
|
||
Show whether messages will be printed when a @value{GDBN} command
|
||
entered from the keyboard causes symbol information to be loaded.
|
||
|
||
@kindex maint print symbols
|
||
@cindex symbol dump
|
||
@kindex maint print psymbols
|
||
@cindex partial symbol dump
|
||
@kindex maint print msymbols
|
||
@cindex minimal symbol dump
|
||
@item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
|
||
@itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
|
||
@itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
|
||
@itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
|
||
@itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
|
||
Write a dump of debugging symbol data into the file @var{filename} or
|
||
the terminal if @var{filename} is unspecified.
|
||
If @code{-objfile @var{objfile}} is specified, only dump symbols for
|
||
that objfile.
|
||
If @code{-pc @var{address}} is specified, only dump symbols for the file
|
||
with code at that address. Note that @var{address} may be a symbol like
|
||
@code{main}.
|
||
If @code{-source @var{source}} is specified, only dump symbols for that
|
||
source file.
|
||
|
||
These commands are used to debug the @value{GDBN} symbol-reading code.
|
||
These commands do not modify internal @value{GDBN} state, therefore
|
||
@samp{maint print symbols} will only print symbols for already expanded symbol
|
||
tables.
|
||
You can use the command @code{info sources} to find out which files these are.
|
||
If you use @samp{maint print psymbols} instead, the dump shows information
|
||
about symbols that @value{GDBN} only knows partially---that is, symbols
|
||
defined in files that @value{GDBN} has skimmed, but not yet read completely.
|
||
Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
|
||
``ELF symbols''.
|
||
|
||
@xref{Files, ,Commands to Specify Files}, for a discussion of how
|
||
@value{GDBN} reads symbols (in the description of @code{symbol-file}).
|
||
|
||
@kindex maint info symtabs
|
||
@kindex maint info psymtabs
|
||
@cindex listing @value{GDBN}'s internal symbol tables
|
||
@cindex symbol tables, listing @value{GDBN}'s internal
|
||
@cindex full symbol tables, listing @value{GDBN}'s internal
|
||
@cindex partial symbol tables, listing @value{GDBN}'s internal
|
||
@item maint info symtabs @r{[} @var{regexp} @r{]}
|
||
@itemx maint info psymtabs @r{[} @var{regexp} @r{]}
|
||
|
||
List the @code{struct symtab} or @code{struct partial_symtab}
|
||
structures whose names match @var{regexp}. If @var{regexp} is not
|
||
given, list them all. The output includes expressions which you can
|
||
copy into a @value{GDBN} debugging this one to examine a particular
|
||
structure in more detail. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) maint info psymtabs dwarf2read
|
||
@{ objfile /home/gnu/build/gdb/gdb
|
||
((struct objfile *) 0x82e69d0)
|
||
@{ psymtab /home/gnu/src/gdb/dwarf2read.c
|
||
((struct partial_symtab *) 0x8474b10)
|
||
readin no
|
||
fullname (null)
|
||
text addresses 0x814d3c8 -- 0x8158074
|
||
globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
|
||
statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
|
||
dependencies (none)
|
||
@}
|
||
@}
|
||
(@value{GDBP}) maint info symtabs
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
@noindent
|
||
We see that there is one partial symbol table whose filename contains
|
||
the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
|
||
and we see that @value{GDBN} has not read in any symtabs yet at all.
|
||
If we set a breakpoint on a function, that will cause @value{GDBN} to
|
||
read the symtab for the compilation unit containing that function:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) break dwarf2_psymtab_to_symtab
|
||
Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
|
||
line 1574.
|
||
(@value{GDBP}) maint info symtabs
|
||
@{ objfile /home/gnu/build/gdb/gdb
|
||
((struct objfile *) 0x82e69d0)
|
||
@{ symtab /home/gnu/src/gdb/dwarf2read.c
|
||
((struct symtab *) 0x86c1f38)
|
||
dirname (null)
|
||
fullname (null)
|
||
blockvector ((struct blockvector *) 0x86c1bd0) (primary)
|
||
linetable ((struct linetable *) 0x8370fa0)
|
||
debugformat DWARF 2
|
||
@}
|
||
@}
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@kindex maint info line-table
|
||
@cindex listing @value{GDBN}'s internal line tables
|
||
@cindex line tables, listing @value{GDBN}'s internal
|
||
@item maint info line-table @r{[} @var{regexp} @r{]}
|
||
|
||
List the @code{struct linetable} from all @code{struct symtab}
|
||
instances whose name matches @var{regexp}. If @var{regexp} is not
|
||
given, list the @code{struct linetable} from all @code{struct symtab}.
|
||
|
||
@kindex maint set symbol-cache-size
|
||
@cindex symbol cache size
|
||
@item maint set symbol-cache-size @var{size}
|
||
Set the size of the symbol cache to @var{size}.
|
||
The default size is intended to be good enough for debugging
|
||
most applications. This option exists to allow for experimenting
|
||
with different sizes.
|
||
|
||
@kindex maint show symbol-cache-size
|
||
@item maint show symbol-cache-size
|
||
Show the size of the symbol cache.
|
||
|
||
@kindex maint print symbol-cache
|
||
@cindex symbol cache, printing its contents
|
||
@item maint print symbol-cache
|
||
Print the contents of the symbol cache.
|
||
This is useful when debugging symbol cache issues.
|
||
|
||
@kindex maint print symbol-cache-statistics
|
||
@cindex symbol cache, printing usage statistics
|
||
@item maint print symbol-cache-statistics
|
||
Print symbol cache usage statistics.
|
||
This helps determine how well the cache is being utilized.
|
||
|
||
@kindex maint flush-symbol-cache
|
||
@cindex symbol cache, flushing
|
||
@item maint flush-symbol-cache
|
||
Flush the contents of the symbol cache, all entries are removed.
|
||
This command is useful when debugging the symbol cache.
|
||
It is also useful when collecting performance data.
|
||
|
||
@end table
|
||
|
||
@node Altering
|
||
@chapter Altering Execution
|
||
|
||
Once you think you have found an error in your program, you might want to
|
||
find out for certain whether correcting the apparent error would lead to
|
||
correct results in the rest of the run. You can find the answer by
|
||
experiment, using the @value{GDBN} features for altering execution of the
|
||
program.
|
||
|
||
For example, you can store new values into variables or memory
|
||
locations, give your program a signal, restart it at a different
|
||
address, or even return prematurely from a function.
|
||
|
||
@menu
|
||
* Assignment:: Assignment to variables
|
||
* Jumping:: Continuing at a different address
|
||
* Signaling:: Giving your program a signal
|
||
* Returning:: Returning from a function
|
||
* Calling:: Calling your program's functions
|
||
* Patching:: Patching your program
|
||
* Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
|
||
@end menu
|
||
|
||
@node Assignment
|
||
@section Assignment to Variables
|
||
|
||
@cindex assignment
|
||
@cindex setting variables
|
||
To alter the value of a variable, evaluate an assignment expression.
|
||
@xref{Expressions, ,Expressions}. For example,
|
||
|
||
@smallexample
|
||
print x=4
|
||
@end smallexample
|
||
|
||
@noindent
|
||
stores the value 4 into the variable @code{x}, and then prints the
|
||
value of the assignment expression (which is 4).
|
||
@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
|
||
information on operators in supported languages.
|
||
|
||
@kindex set variable
|
||
@cindex variables, setting
|
||
If you are not interested in seeing the value of the assignment, use the
|
||
@code{set} command instead of the @code{print} command. @code{set} is
|
||
really the same as @code{print} except that the expression's value is
|
||
not printed and is not put in the value history (@pxref{Value History,
|
||
,Value History}). The expression is evaluated only for its effects.
|
||
|
||
If the beginning of the argument string of the @code{set} command
|
||
appears identical to a @code{set} subcommand, use the @code{set
|
||
variable} command instead of just @code{set}. This command is identical
|
||
to @code{set} except for its lack of subcommands. For example, if your
|
||
program has a variable @code{width}, you get an error if you try to set
|
||
a new value with just @samp{set width=13}, because @value{GDBN} has the
|
||
command @code{set width}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) whatis width
|
||
type = double
|
||
(@value{GDBP}) p width
|
||
$4 = 13
|
||
(@value{GDBP}) set width=47
|
||
Invalid syntax in expression.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The invalid expression, of course, is @samp{=47}. In
|
||
order to actually set the program's variable @code{width}, use
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set var width=47
|
||
@end smallexample
|
||
|
||
Because the @code{set} command has many subcommands that can conflict
|
||
with the names of program variables, it is a good idea to use the
|
||
@code{set variable} command instead of just @code{set}. For example, if
|
||
your program has a variable @code{g}, you run into problems if you try
|
||
to set a new value with just @samp{set g=4}, because @value{GDBN} has
|
||
the command @code{set gnutarget}, abbreviated @code{set g}:
|
||
|
||
@smallexample
|
||
@group
|
||
(@value{GDBP}) whatis g
|
||
type = double
|
||
(@value{GDBP}) p g
|
||
$1 = 1
|
||
(@value{GDBP}) set g=4
|
||
(@value{GDBP}) p g
|
||
$2 = 1
|
||
(@value{GDBP}) r
|
||
The program being debugged has been started already.
|
||
Start it from the beginning? (y or n) y
|
||
Starting program: /home/smith/cc_progs/a.out
|
||
"/home/smith/cc_progs/a.out": can't open to read symbols:
|
||
Invalid bfd target.
|
||
(@value{GDBP}) show g
|
||
The current BFD target is "=4".
|
||
@end group
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The program variable @code{g} did not change, and you silently set the
|
||
@code{gnutarget} to an invalid value. In order to set the variable
|
||
@code{g}, use
|
||
|
||
@smallexample
|
||
(@value{GDBP}) set var g=4
|
||
@end smallexample
|
||
|
||
@value{GDBN} allows more implicit conversions in assignments than C; you can
|
||
freely store an integer value into a pointer variable or vice versa,
|
||
and you can convert any structure to any other structure that is the
|
||
same length or shorter.
|
||
@comment FIXME: how do structs align/pad in these conversions?
|
||
@comment /doc@cygnus.com 18dec1990
|
||
|
||
To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
|
||
construct to generate a value of specified type at a specified address
|
||
(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
|
||
to memory location @code{0x83040} as an integer (which implies a certain size
|
||
and representation in memory), and
|
||
|
||
@smallexample
|
||
set @{int@}0x83040 = 4
|
||
@end smallexample
|
||
|
||
@noindent
|
||
stores the value 4 into that memory location.
|
||
|
||
@node Jumping
|
||
@section Continuing at a Different Address
|
||
|
||
Ordinarily, when you continue your program, you do so at the place where
|
||
it stopped, with the @code{continue} command. You can instead continue at
|
||
an address of your own choosing, with the following commands:
|
||
|
||
@table @code
|
||
@kindex jump
|
||
@kindex j @r{(@code{jump})}
|
||
@item jump @var{location}
|
||
@itemx j @var{location}
|
||
Resume execution at @var{location}. Execution stops again immediately
|
||
if there is a breakpoint there. @xref{Specify Location}, for a description
|
||
of the different forms of @var{location}. It is common
|
||
practice to use the @code{tbreak} command in conjunction with
|
||
@code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
|
||
|
||
The @code{jump} command does not change the current stack frame, or
|
||
the stack pointer, or the contents of any memory location or any
|
||
register other than the program counter. If @var{location} is in
|
||
a different function from the one currently executing, the results may
|
||
be bizarre if the two functions expect different patterns of arguments or
|
||
of local variables. For this reason, the @code{jump} command requests
|
||
confirmation if the specified line is not in the function currently
|
||
executing. However, even bizarre results are predictable if you are
|
||
well acquainted with the machine-language code of your program.
|
||
@end table
|
||
|
||
On many systems, you can get much the same effect as the @code{jump}
|
||
command by storing a new value into the register @code{$pc}. The
|
||
difference is that this does not start your program running; it only
|
||
changes the address of where it @emph{will} run when you continue. For
|
||
example,
|
||
|
||
@smallexample
|
||
set $pc = 0x485
|
||
@end smallexample
|
||
|
||
@noindent
|
||
makes the next @code{continue} command or stepping command execute at
|
||
address @code{0x485}, rather than at the address where your program stopped.
|
||
@xref{Continuing and Stepping, ,Continuing and Stepping}.
|
||
|
||
The most common occasion to use the @code{jump} command is to back
|
||
up---perhaps with more breakpoints set---over a portion of a program
|
||
that has already executed, in order to examine its execution in more
|
||
detail.
|
||
|
||
@c @group
|
||
@node Signaling
|
||
@section Giving your Program a Signal
|
||
@cindex deliver a signal to a program
|
||
|
||
@table @code
|
||
@kindex signal
|
||
@item signal @var{signal}
|
||
Resume execution where your program is stopped, but immediately give it the
|
||
signal @var{signal}. The @var{signal} can be the name or the number of a
|
||
signal. For example, on many systems @code{signal 2} and @code{signal
|
||
SIGINT} are both ways of sending an interrupt signal.
|
||
|
||
Alternatively, if @var{signal} is zero, continue execution without
|
||
giving a signal. This is useful when your program stopped on account of
|
||
a signal and would ordinarily see the signal when resumed with the
|
||
@code{continue} command; @samp{signal 0} causes it to resume without a
|
||
signal.
|
||
|
||
@emph{Note:} When resuming a multi-threaded program, @var{signal} is
|
||
delivered to the currently selected thread, not the thread that last
|
||
reported a stop. This includes the situation where a thread was
|
||
stopped due to a signal. So if you want to continue execution
|
||
suppressing the signal that stopped a thread, you should select that
|
||
same thread before issuing the @samp{signal 0} command. If you issue
|
||
the @samp{signal 0} command with another thread as the selected one,
|
||
@value{GDBN} detects that and asks for confirmation.
|
||
|
||
Invoking the @code{signal} command is not the same as invoking the
|
||
@code{kill} utility from the shell. Sending a signal with @code{kill}
|
||
causes @value{GDBN} to decide what to do with the signal depending on
|
||
the signal handling tables (@pxref{Signals}). The @code{signal} command
|
||
passes the signal directly to your program.
|
||
|
||
@code{signal} does not repeat when you press @key{RET} a second time
|
||
after executing the command.
|
||
|
||
@kindex queue-signal
|
||
@item queue-signal @var{signal}
|
||
Queue @var{signal} to be delivered immediately to the current thread
|
||
when execution of the thread resumes. The @var{signal} can be the name or
|
||
the number of a signal. For example, on many systems @code{signal 2} and
|
||
@code{signal SIGINT} are both ways of sending an interrupt signal.
|
||
The handling of the signal must be set to pass the signal to the program,
|
||
otherwise @value{GDBN} will report an error.
|
||
You can control the handling of signals from @value{GDBN} with the
|
||
@code{handle} command (@pxref{Signals}).
|
||
|
||
Alternatively, if @var{signal} is zero, any currently queued signal
|
||
for the current thread is discarded and when execution resumes no signal
|
||
will be delivered. This is useful when your program stopped on account
|
||
of a signal and would ordinarily see the signal when resumed with the
|
||
@code{continue} command.
|
||
|
||
This command differs from the @code{signal} command in that the signal
|
||
is just queued, execution is not resumed. And @code{queue-signal} cannot
|
||
be used to pass a signal whose handling state has been set to @code{nopass}
|
||
(@pxref{Signals}).
|
||
@end table
|
||
@c @end group
|
||
|
||
@xref{stepping into signal handlers}, for information on how stepping
|
||
commands behave when the thread has a signal queued.
|
||
|
||
@node Returning
|
||
@section Returning from a Function
|
||
|
||
@table @code
|
||
@cindex returning from a function
|
||
@kindex return
|
||
@item return
|
||
@itemx return @var{expression}
|
||
You can cancel execution of a function call with the @code{return}
|
||
command. If you give an
|
||
@var{expression} argument, its value is used as the function's return
|
||
value.
|
||
@end table
|
||
|
||
When you use @code{return}, @value{GDBN} discards the selected stack frame
|
||
(and all frames within it). You can think of this as making the
|
||
discarded frame return prematurely. If you wish to specify a value to
|
||
be returned, give that value as the argument to @code{return}.
|
||
|
||
This pops the selected stack frame (@pxref{Selection, ,Selecting a
|
||
Frame}), and any other frames inside of it, leaving its caller as the
|
||
innermost remaining frame. That frame becomes selected. The
|
||
specified value is stored in the registers used for returning values
|
||
of functions.
|
||
|
||
The @code{return} command does not resume execution; it leaves the
|
||
program stopped in the state that would exist if the function had just
|
||
returned. In contrast, the @code{finish} command (@pxref{Continuing
|
||
and Stepping, ,Continuing and Stepping}) resumes execution until the
|
||
selected stack frame returns naturally.
|
||
|
||
@value{GDBN} needs to know how the @var{expression} argument should be set for
|
||
the inferior. The concrete registers assignment depends on the OS ABI and the
|
||
type being returned by the selected stack frame. For example it is common for
|
||
OS ABI to return floating point values in FPU registers while integer values in
|
||
CPU registers. Still some ABIs return even floating point values in CPU
|
||
registers. Larger integer widths (such as @code{long long int}) also have
|
||
specific placement rules. @value{GDBN} already knows the OS ABI from its
|
||
current target so it needs to find out also the type being returned to make the
|
||
assignment into the right register(s).
|
||
|
||
Normally, the selected stack frame has debug info. @value{GDBN} will always
|
||
use the debug info instead of the implicit type of @var{expression} when the
|
||
debug info is available. For example, if you type @kbd{return -1}, and the
|
||
function in the current stack frame is declared to return a @code{long long
|
||
int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
|
||
into a @code{long long int}:
|
||
|
||
@smallexample
|
||
Breakpoint 1, func () at gdb.base/return-nodebug.c:29
|
||
29 return 31;
|
||
(@value{GDBP}) return -1
|
||
Make func return now? (y or n) y
|
||
#0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
|
||
43 printf ("result=%lld\n", func ());
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
However, if the selected stack frame does not have a debug info, e.g., if the
|
||
function was compiled without debug info, @value{GDBN} has to find out the type
|
||
to return from user. Specifying a different type by mistake may set the value
|
||
in different inferior registers than the caller code expects. For example,
|
||
typing @kbd{return -1} with its implicit type @code{int} would set only a part
|
||
of a @code{long long int} result for a debug info less function (on 32-bit
|
||
architectures). Therefore the user is required to specify the return type by
|
||
an appropriate cast explicitly:
|
||
|
||
@smallexample
|
||
Breakpoint 2, 0x0040050b in func ()
|
||
(@value{GDBP}) return -1
|
||
Return value type not available for selected stack frame.
|
||
Please use an explicit cast of the value to return.
|
||
(@value{GDBP}) return (long long int) -1
|
||
Make selected stack frame return now? (y or n) y
|
||
#0 0x00400526 in main ()
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@node Calling
|
||
@section Calling Program Functions
|
||
|
||
@table @code
|
||
@cindex calling functions
|
||
@cindex inferior functions, calling
|
||
@item print @var{expr}
|
||
Evaluate the expression @var{expr} and display the resulting value.
|
||
The expression may include calls to functions in the program being
|
||
debugged.
|
||
|
||
@kindex call
|
||
@item call @var{expr}
|
||
Evaluate the expression @var{expr} without displaying @code{void}
|
||
returned values.
|
||
|
||
You can use this variant of the @code{print} command if you want to
|
||
execute a function from your program that does not return anything
|
||
(a.k.a.@: @dfn{a void function}), but without cluttering the output
|
||
with @code{void} returned values that @value{GDBN} will otherwise
|
||
print. If the result is not void, it is printed and saved in the
|
||
value history.
|
||
@end table
|
||
|
||
It is possible for the function you call via the @code{print} or
|
||
@code{call} command to generate a signal (e.g., if there's a bug in
|
||
the function, or if you passed it incorrect arguments). What happens
|
||
in that case is controlled by the @code{set unwindonsignal} command.
|
||
|
||
Similarly, with a C@t{++} program it is possible for the function you
|
||
call via the @code{print} or @code{call} command to generate an
|
||
exception that is not handled due to the constraints of the dummy
|
||
frame. In this case, any exception that is raised in the frame, but has
|
||
an out-of-frame exception handler will not be found. GDB builds a
|
||
dummy-frame for the inferior function call, and the unwinder cannot
|
||
seek for exception handlers outside of this dummy-frame. What happens
|
||
in that case is controlled by the
|
||
@code{set unwind-on-terminating-exception} command.
|
||
|
||
@table @code
|
||
@item set unwindonsignal
|
||
@kindex set unwindonsignal
|
||
@cindex unwind stack in called functions
|
||
@cindex call dummy stack unwinding
|
||
Set unwinding of the stack if a signal is received while in a function
|
||
that @value{GDBN} called in the program being debugged. If set to on,
|
||
@value{GDBN} unwinds the stack it created for the call and restores
|
||
the context to what it was before the call. If set to off (the
|
||
default), @value{GDBN} stops in the frame where the signal was
|
||
received.
|
||
|
||
@item show unwindonsignal
|
||
@kindex show unwindonsignal
|
||
Show the current setting of stack unwinding in the functions called by
|
||
@value{GDBN}.
|
||
|
||
@item set unwind-on-terminating-exception
|
||
@kindex set unwind-on-terminating-exception
|
||
@cindex unwind stack in called functions with unhandled exceptions
|
||
@cindex call dummy stack unwinding on unhandled exception.
|
||
Set unwinding of the stack if a C@t{++} exception is raised, but left
|
||
unhandled while in a function that @value{GDBN} called in the program being
|
||
debugged. If set to on (the default), @value{GDBN} unwinds the stack
|
||
it created for the call and restores the context to what it was before
|
||
the call. If set to off, @value{GDBN} the exception is delivered to
|
||
the default C@t{++} exception handler and the inferior terminated.
|
||
|
||
@item show unwind-on-terminating-exception
|
||
@kindex show unwind-on-terminating-exception
|
||
Show the current setting of stack unwinding in the functions called by
|
||
@value{GDBN}.
|
||
|
||
@end table
|
||
|
||
@subsection Calling functions with no debug info
|
||
|
||
@cindex no debug info functions
|
||
Sometimes, a function you wish to call is missing debug information.
|
||
In such case, @value{GDBN} does not know the type of the function,
|
||
including the types of the function's parameters. To avoid calling
|
||
the inferior function incorrectly, which could result in the called
|
||
function functioning erroneously and even crash, @value{GDBN} refuses
|
||
to call the function unless you tell it the type of the function.
|
||
|
||
For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
|
||
to do that. The simplest is to cast the call to the function's
|
||
declared return type. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p getenv ("PATH")
|
||
'getenv' has unknown return type; cast the call to its declared return type
|
||
(@value{GDBP}) p (char *) getenv ("PATH")
|
||
$1 = 0x7fffffffe7ba "/usr/local/bin:/"...
|
||
@end smallexample
|
||
|
||
Casting the return type of a no-debug function is equivalent to
|
||
casting the function to a pointer to a prototyped function that has a
|
||
prototype that matches the types of the passed-in arguments, and
|
||
calling that. I.e., the call above is equivalent to:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and given this prototyped C or C++ function with float parameters:
|
||
|
||
@smallexample
|
||
float multiply (float v1, float v2) @{ return v1 * v2; @}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
these calls are equivalent:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p (float) multiply (2.0f, 3.0f)
|
||
(@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
|
||
@end smallexample
|
||
|
||
If the function you wish to call is declared as unprototyped (i.e.@:
|
||
old K&R style), you must use the cast-to-function-pointer syntax, so
|
||
that @value{GDBN} knows that it needs to apply default argument
|
||
promotions (promote float arguments to double). @xref{ABI, float
|
||
promotion}. For example, given this unprototyped C function with
|
||
float parameters, and no debug info:
|
||
|
||
@smallexample
|
||
float
|
||
multiply_noproto (v1, v2)
|
||
float v1, v2;
|
||
@{
|
||
return v1 * v2;
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
you call it like this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
|
||
@end smallexample
|
||
|
||
@node Patching
|
||
@section Patching Programs
|
||
|
||
@cindex patching binaries
|
||
@cindex writing into executables
|
||
@cindex writing into corefiles
|
||
|
||
By default, @value{GDBN} opens the file containing your program's
|
||
executable code (or the corefile) read-only. This prevents accidental
|
||
alterations to machine code; but it also prevents you from intentionally
|
||
patching your program's binary.
|
||
|
||
If you'd like to be able to patch the binary, you can specify that
|
||
explicitly with the @code{set write} command. For example, you might
|
||
want to turn on internal debugging flags, or even to make emergency
|
||
repairs.
|
||
|
||
@table @code
|
||
@kindex set write
|
||
@item set write on
|
||
@itemx set write off
|
||
If you specify @samp{set write on}, @value{GDBN} opens executable and
|
||
core files for both reading and writing; if you specify @kbd{set write
|
||
off} (the default), @value{GDBN} opens them read-only.
|
||
|
||
If you have already loaded a file, you must load it again (using the
|
||
@code{exec-file} or @code{core-file} command) after changing @code{set
|
||
write}, for your new setting to take effect.
|
||
|
||
@item show write
|
||
@kindex show write
|
||
Display whether executable files and core files are opened for writing
|
||
as well as reading.
|
||
@end table
|
||
|
||
@node Compiling and Injecting Code
|
||
@section Compiling and injecting code in @value{GDBN}
|
||
@cindex injecting code
|
||
@cindex writing into executables
|
||
@cindex compiling code
|
||
|
||
@value{GDBN} supports on-demand compilation and code injection into
|
||
programs running under @value{GDBN}. GCC 5.0 or higher built with
|
||
@file{libcc1.so} must be installed for this functionality to be enabled.
|
||
This functionality is implemented with the following commands.
|
||
|
||
@table @code
|
||
@kindex compile code
|
||
@item compile code @var{source-code}
|
||
@itemx compile code -raw @var{--} @var{source-code}
|
||
Compile @var{source-code} with the compiler language found as the current
|
||
language in @value{GDBN} (@pxref{Languages}). If compilation and
|
||
injection is not supported with the current language specified in
|
||
@value{GDBN}, or the compiler does not support this feature, an error
|
||
message will be printed. If @var{source-code} compiles and links
|
||
successfully, @value{GDBN} will load the object-code emitted,
|
||
and execute it within the context of the currently selected inferior.
|
||
It is important to note that the compiled code is executed immediately.
|
||
After execution, the compiled code is removed from @value{GDBN} and any
|
||
new types or variables you have defined will be deleted.
|
||
|
||
The command allows you to specify @var{source-code} in two ways.
|
||
The simplest method is to provide a single line of code to the command.
|
||
E.g.:
|
||
|
||
@smallexample
|
||
compile code printf ("hello world\n");
|
||
@end smallexample
|
||
|
||
If you specify options on the command line as well as source code, they
|
||
may conflict. The @samp{--} delimiter can be used to separate options
|
||
from actual source code. E.g.:
|
||
|
||
@smallexample
|
||
compile code -r -- printf ("hello world\n");
|
||
@end smallexample
|
||
|
||
Alternatively you can enter source code as multiple lines of text. To
|
||
enter this mode, invoke the @samp{compile code} command without any text
|
||
following the command. This will start the multiple-line editor and
|
||
allow you to type as many lines of source code as required. When you
|
||
have completed typing, enter @samp{end} on its own line to exit the
|
||
editor.
|
||
|
||
@smallexample
|
||
compile code
|
||
>printf ("hello\n");
|
||
>printf ("world\n");
|
||
>end
|
||
@end smallexample
|
||
|
||
Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
|
||
provided @var{source-code} in a callable scope. In this case, you must
|
||
specify the entry point of the code by defining a function named
|
||
@code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
|
||
inferior. Using @samp{-raw} option may be needed for example when
|
||
@var{source-code} requires @samp{#include} lines which may conflict with
|
||
inferior symbols otherwise.
|
||
|
||
@kindex compile file
|
||
@item compile file @var{filename}
|
||
@itemx compile file -raw @var{filename}
|
||
Like @code{compile code}, but take the source code from @var{filename}.
|
||
|
||
@smallexample
|
||
compile file /home/user/example.c
|
||
@end smallexample
|
||
@end table
|
||
|
||
@table @code
|
||
@item compile print @var{expr}
|
||
@itemx compile print /@var{f} @var{expr}
|
||
Compile and execute @var{expr} with the compiler language found as the
|
||
current language in @value{GDBN} (@pxref{Languages}). By default the
|
||
value of @var{expr} is printed in a format appropriate to its data type;
|
||
you can choose a different format by specifying @samp{/@var{f}}, where
|
||
@var{f} is a letter specifying the format; see @ref{Output Formats,,Output
|
||
Formats}.
|
||
|
||
@item compile print
|
||
@itemx compile print /@var{f}
|
||
@cindex reprint the last value
|
||
Alternatively you can enter the expression (source code producing it) as
|
||
multiple lines of text. To enter this mode, invoke the @samp{compile print}
|
||
command without any text following the command. This will start the
|
||
multiple-line editor.
|
||
@end table
|
||
|
||
@noindent
|
||
The process of compiling and injecting the code can be inspected using:
|
||
|
||
@table @code
|
||
@anchor{set debug compile}
|
||
@item set debug compile
|
||
@cindex compile command debugging info
|
||
Turns on or off display of @value{GDBN} process of compiling and
|
||
injecting the code. The default is off.
|
||
|
||
@item show debug compile
|
||
Displays the current state of displaying @value{GDBN} process of
|
||
compiling and injecting the code.
|
||
@end table
|
||
|
||
@subsection Compilation options for the @code{compile} command
|
||
|
||
@value{GDBN} needs to specify the right compilation options for the code
|
||
to be injected, in part to make its ABI compatible with the inferior
|
||
and in part to make the injected code compatible with @value{GDBN}'s
|
||
injecting process.
|
||
|
||
@noindent
|
||
The options used, in increasing precedence:
|
||
|
||
@table @asis
|
||
@item target architecture and OS options (@code{gdbarch})
|
||
These options depend on target processor type and target operating
|
||
system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
|
||
(@code{-m64}) compilation option.
|
||
|
||
@item compilation options recorded in the target
|
||
@value{NGCC} (since version 4.7) stores the options used for compilation
|
||
into @code{DW_AT_producer} part of DWARF debugging information according
|
||
to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
|
||
explicitly specify @code{-g} during inferior compilation otherwise
|
||
@value{NGCC} produces no DWARF. This feature is only relevant for
|
||
platforms where @code{-g} produces DWARF by default, otherwise one may
|
||
try to enforce DWARF by using @code{-gdwarf-4}.
|
||
|
||
@item compilation options set by @code{set compile-args}
|
||
@end table
|
||
|
||
@noindent
|
||
You can override compilation options using the following command:
|
||
|
||
@table @code
|
||
@item set compile-args
|
||
@cindex compile command options override
|
||
Set compilation options used for compiling and injecting code with the
|
||
@code{compile} commands. These options override any conflicting ones
|
||
from the target architecture and/or options stored during inferior
|
||
compilation.
|
||
|
||
@item show compile-args
|
||
Displays the current state of compilation options override.
|
||
This does not show all the options actually used during compilation,
|
||
use @ref{set debug compile} for that.
|
||
@end table
|
||
|
||
@subsection Caveats when using the @code{compile} command
|
||
|
||
There are a few caveats to keep in mind when using the @code{compile}
|
||
command. As the caveats are different per language, the table below
|
||
highlights specific issues on a per language basis.
|
||
|
||
@table @asis
|
||
@item C code examples and caveats
|
||
When the language in @value{GDBN} is set to @samp{C}, the compiler will
|
||
attempt to compile the source code with a @samp{C} compiler. The source
|
||
code provided to the @code{compile} command will have much the same
|
||
access to variables and types as it normally would if it were part of
|
||
the program currently being debugged in @value{GDBN}.
|
||
|
||
Below is a sample program that forms the basis of the examples that
|
||
follow. This program has been compiled and loaded into @value{GDBN},
|
||
much like any other normal debugging session.
|
||
|
||
@smallexample
|
||
void function1 (void)
|
||
@{
|
||
int i = 42;
|
||
printf ("function 1\n");
|
||
@}
|
||
|
||
void function2 (void)
|
||
@{
|
||
int j = 12;
|
||
function1 ();
|
||
@}
|
||
|
||
int main(void)
|
||
@{
|
||
int k = 6;
|
||
int *p;
|
||
function2 ();
|
||
return 0;
|
||
@}
|
||
@end smallexample
|
||
|
||
For the purposes of the examples in this section, the program above has
|
||
been compiled, loaded into @value{GDBN}, stopped at the function
|
||
@code{main}, and @value{GDBN} is awaiting input from the user.
|
||
|
||
To access variables and types for any program in @value{GDBN}, the
|
||
program must be compiled and packaged with debug information. The
|
||
@code{compile} command is not an exception to this rule. Without debug
|
||
information, you can still use the @code{compile} command, but you will
|
||
be very limited in what variables and types you can access.
|
||
|
||
So with that in mind, the example above has been compiled with debug
|
||
information enabled. The @code{compile} command will have access to
|
||
all variables and types (except those that may have been optimized
|
||
out). Currently, as @value{GDBN} has stopped the program in the
|
||
@code{main} function, the @code{compile} command would have access to
|
||
the variable @code{k}. You could invoke the @code{compile} command
|
||
and type some source code to set the value of @code{k}. You can also
|
||
read it, or do anything with that variable you would normally do in
|
||
@code{C}. Be aware that changes to inferior variables in the
|
||
@code{compile} command are persistent. In the following example:
|
||
|
||
@smallexample
|
||
compile code k = 3;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
the variable @code{k} is now 3. It will retain that value until
|
||
something else in the example program changes it, or another
|
||
@code{compile} command changes it.
|
||
|
||
Normal scope and access rules apply to source code compiled and
|
||
injected by the @code{compile} command. In the example, the variables
|
||
@code{j} and @code{k} are not accessible yet, because the program is
|
||
currently stopped in the @code{main} function, where these variables
|
||
are not in scope. Therefore, the following command
|
||
|
||
@smallexample
|
||
compile code j = 3;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
will result in a compilation error message.
|
||
|
||
Once the program is continued, execution will bring these variables in
|
||
scope, and they will become accessible; then the code you specify via
|
||
the @code{compile} command will be able to access them.
|
||
|
||
You can create variables and types with the @code{compile} command as
|
||
part of your source code. Variables and types that are created as part
|
||
of the @code{compile} command are not visible to the rest of the program for
|
||
the duration of its run. This example is valid:
|
||
|
||
@smallexample
|
||
compile code int ff = 5; printf ("ff is %d\n", ff);
|
||
@end smallexample
|
||
|
||
However, if you were to type the following into @value{GDBN} after that
|
||
command has completed:
|
||
|
||
@smallexample
|
||
compile code printf ("ff is %d\n'', ff);
|
||
@end smallexample
|
||
|
||
@noindent
|
||
a compiler error would be raised as the variable @code{ff} no longer
|
||
exists. Object code generated and injected by the @code{compile}
|
||
command is removed when its execution ends. Caution is advised
|
||
when assigning to program variables values of variables created by the
|
||
code submitted to the @code{compile} command. This example is valid:
|
||
|
||
@smallexample
|
||
compile code int ff = 5; k = ff;
|
||
@end smallexample
|
||
|
||
The value of the variable @code{ff} is assigned to @code{k}. The variable
|
||
@code{k} does not require the existence of @code{ff} to maintain the value
|
||
it has been assigned. However, pointers require particular care in
|
||
assignment. If the source code compiled with the @code{compile} command
|
||
changed the address of a pointer in the example program, perhaps to a
|
||
variable created in the @code{compile} command, that pointer would point
|
||
to an invalid location when the command exits. The following example
|
||
would likely cause issues with your debugged program:
|
||
|
||
@smallexample
|
||
compile code int ff = 5; p = &ff;
|
||
@end smallexample
|
||
|
||
In this example, @code{p} would point to @code{ff} when the
|
||
@code{compile} command is executing the source code provided to it.
|
||
However, as variables in the (example) program persist with their
|
||
assigned values, the variable @code{p} would point to an invalid
|
||
location when the command exists. A general rule should be followed
|
||
in that you should either assign @code{NULL} to any assigned pointers,
|
||
or restore a valid location to the pointer before the command exits.
|
||
|
||
Similar caution must be exercised with any structs, unions, and typedefs
|
||
defined in @code{compile} command. Types defined in the @code{compile}
|
||
command will no longer be available in the next @code{compile} command.
|
||
Therefore, if you cast a variable to a type defined in the
|
||
@code{compile} command, care must be taken to ensure that any future
|
||
need to resolve the type can be achieved.
|
||
|
||
@smallexample
|
||
(gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
|
||
(gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
|
||
gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
|
||
Compilation failed.
|
||
(gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
|
||
42
|
||
@end smallexample
|
||
|
||
Variables that have been optimized away by the compiler are not
|
||
accessible to the code submitted to the @code{compile} command.
|
||
Access to those variables will generate a compiler error which @value{GDBN}
|
||
will print to the console.
|
||
@end table
|
||
|
||
@subsection Compiler search for the @code{compile} command
|
||
|
||
@value{GDBN} needs to find @value{NGCC} for the inferior being debugged
|
||
which may not be obvious for remote targets of different architecture
|
||
than where @value{GDBN} is running. Environment variable @code{PATH} on
|
||
@value{GDBN} host is searched for @value{NGCC} binary matching the
|
||
target architecture and operating system. This search can be overriden
|
||
by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
|
||
taken from shell that executed @value{GDBN}, it is not the value set by
|
||
@value{GDBN} command @code{set environment}). @xref{Environment}.
|
||
|
||
|
||
Specifically @code{PATH} is searched for binaries matching regular expression
|
||
@code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
|
||
debugged. @var{arch} is processor name --- multiarch is supported, so for
|
||
example both @code{i386} and @code{x86_64} targets look for pattern
|
||
@code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
|
||
for pattern @code{s390x?}. @var{os} is currently supported only for
|
||
pattern @code{linux(-gnu)?}.
|
||
|
||
On Posix hosts the compiler driver @value{GDBN} needs to find also
|
||
shared library @file{libcc1.so} from the compiler. It is searched in
|
||
default shared library search path (overridable with usual environment
|
||
variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
|
||
compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
|
||
according to the installation of the found compiler --- as possibly
|
||
specified by the @code{set compile-gcc} command.
|
||
|
||
@table @code
|
||
@item set compile-gcc
|
||
@cindex compile command driver filename override
|
||
Set compilation command used for compiling and injecting code with the
|
||
@code{compile} commands. If this option is not set (it is set to
|
||
an empty string), the search described above will occur --- that is the
|
||
default.
|
||
|
||
@item show compile-gcc
|
||
Displays the current compile command @value{NGCC} driver filename.
|
||
If set, it is the main command @command{gcc}, found usually for example
|
||
under name @file{x86_64-linux-gnu-gcc}.
|
||
@end table
|
||
|
||
@node GDB Files
|
||
@chapter @value{GDBN} Files
|
||
|
||
@value{GDBN} needs to know the file name of the program to be debugged,
|
||
both in order to read its symbol table and in order to start your
|
||
program. To debug a core dump of a previous run, you must also tell
|
||
@value{GDBN} the name of the core dump file.
|
||
|
||
@menu
|
||
* Files:: Commands to specify files
|
||
* File Caching:: Information about @value{GDBN}'s file caching
|
||
* Separate Debug Files:: Debugging information in separate files
|
||
* MiniDebugInfo:: Debugging information in a special section
|
||
* Index Files:: Index files speed up GDB
|
||
* Symbol Errors:: Errors reading symbol files
|
||
* Data Files:: GDB data files
|
||
@end menu
|
||
|
||
@node Files
|
||
@section Commands to Specify Files
|
||
|
||
@cindex symbol table
|
||
@cindex core dump file
|
||
|
||
You may want to specify executable and core dump file names. The usual
|
||
way to do this is at start-up time, using the arguments to
|
||
@value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
|
||
Out of @value{GDBN}}).
|
||
|
||
Occasionally it is necessary to change to a different file during a
|
||
@value{GDBN} session. Or you may run @value{GDBN} and forget to
|
||
specify a file you want to use. Or you are debugging a remote target
|
||
via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
|
||
Program}). In these situations the @value{GDBN} commands to specify
|
||
new files are useful.
|
||
|
||
@table @code
|
||
@cindex executable file
|
||
@kindex file
|
||
@item file @var{filename}
|
||
Use @var{filename} as the program to be debugged. It is read for its
|
||
symbols and for the contents of pure memory. It is also the program
|
||
executed when you use the @code{run} command. If you do not specify a
|
||
directory and the file is not found in the @value{GDBN} working directory,
|
||
@value{GDBN} uses the environment variable @code{PATH} as a list of
|
||
directories to search, just as the shell does when looking for a program
|
||
to run. You can change the value of this variable, for both @value{GDBN}
|
||
and your program, using the @code{path} command.
|
||
|
||
@cindex unlinked object files
|
||
@cindex patching object files
|
||
You can load unlinked object @file{.o} files into @value{GDBN} using
|
||
the @code{file} command. You will not be able to ``run'' an object
|
||
file, but you can disassemble functions and inspect variables. Also,
|
||
if the underlying BFD functionality supports it, you could use
|
||
@kbd{gdb -write} to patch object files using this technique. Note
|
||
that @value{GDBN} can neither interpret nor modify relocations in this
|
||
case, so branches and some initialized variables will appear to go to
|
||
the wrong place. But this feature is still handy from time to time.
|
||
|
||
@item file
|
||
@code{file} with no argument makes @value{GDBN} discard any information it
|
||
has on both executable file and the symbol table.
|
||
|
||
@kindex exec-file
|
||
@item exec-file @r{[} @var{filename} @r{]}
|
||
Specify that the program to be run (but not the symbol table) is found
|
||
in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
|
||
if necessary to locate your program. Omitting @var{filename} means to
|
||
discard information on the executable file.
|
||
|
||
@kindex symbol-file
|
||
@item symbol-file @r{[} @var{filename} @r{]}
|
||
Read symbol table information from file @var{filename}. @code{PATH} is
|
||
searched when necessary. Use the @code{file} command to get both symbol
|
||
table and program to run from the same file.
|
||
|
||
@code{symbol-file} with no argument clears out @value{GDBN} information on your
|
||
program's symbol table.
|
||
|
||
The @code{symbol-file} command causes @value{GDBN} to forget the contents of
|
||
some breakpoints and auto-display expressions. This is because they may
|
||
contain pointers to the internal data recording symbols and data types,
|
||
which are part of the old symbol table data being discarded inside
|
||
@value{GDBN}.
|
||
|
||
@code{symbol-file} does not repeat if you press @key{RET} again after
|
||
executing it once.
|
||
|
||
When @value{GDBN} is configured for a particular environment, it
|
||
understands debugging information in whatever format is the standard
|
||
generated for that environment; you may use either a @sc{gnu} compiler, or
|
||
other compilers that adhere to the local conventions.
|
||
Best results are usually obtained from @sc{gnu} compilers; for example,
|
||
using @code{@value{NGCC}} you can generate debugging information for
|
||
optimized code.
|
||
|
||
For most kinds of object files, with the exception of old SVR3 systems
|
||
using COFF, the @code{symbol-file} command does not normally read the
|
||
symbol table in full right away. Instead, it scans the symbol table
|
||
quickly to find which source files and which symbols are present. The
|
||
details are read later, one source file at a time, as they are needed.
|
||
|
||
The purpose of this two-stage reading strategy is to make @value{GDBN}
|
||
start up faster. For the most part, it is invisible except for
|
||
occasional pauses while the symbol table details for a particular source
|
||
file are being read. (The @code{set verbose} command can turn these
|
||
pauses into messages if desired. @xref{Messages/Warnings, ,Optional
|
||
Warnings and Messages}.)
|
||
|
||
We have not implemented the two-stage strategy for COFF yet. When the
|
||
symbol table is stored in COFF format, @code{symbol-file} reads the
|
||
symbol table data in full right away. Note that ``stabs-in-COFF''
|
||
still does the two-stage strategy, since the debug info is actually
|
||
in stabs format.
|
||
|
||
@kindex readnow
|
||
@cindex reading symbols immediately
|
||
@cindex symbols, reading immediately
|
||
@item symbol-file @r{[} -readnow @r{]} @var{filename}
|
||
@itemx file @r{[} -readnow @r{]} @var{filename}
|
||
You can override the @value{GDBN} two-stage strategy for reading symbol
|
||
tables by using the @samp{-readnow} option with any of the commands that
|
||
load symbol table information, if you want to be sure @value{GDBN} has the
|
||
entire symbol table available.
|
||
|
||
@cindex @code{-readnever}, option for symbol-file command
|
||
@cindex never read symbols
|
||
@cindex symbols, never read
|
||
@item symbol-file @r{[} -readnever @r{]} @var{filename}
|
||
@itemx file @r{[} -readnever @r{]} @var{filename}
|
||
You can instruct @value{GDBN} to never read the symbolic information
|
||
contained in @var{filename} by using the @samp{-readnever} option.
|
||
@xref{--readnever}.
|
||
|
||
@c FIXME: for now no mention of directories, since this seems to be in
|
||
@c flux. 13mar1992 status is that in theory GDB would look either in
|
||
@c current dir or in same dir as myprog; but issues like competing
|
||
@c GDB's, or clutter in system dirs, mean that in practice right now
|
||
@c only current dir is used. FFish says maybe a special GDB hierarchy
|
||
@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
|
||
@c files.
|
||
|
||
@kindex core-file
|
||
@item core-file @r{[}@var{filename}@r{]}
|
||
@itemx core
|
||
Specify the whereabouts of a core dump file to be used as the ``contents
|
||
of memory''. Traditionally, core files contain only some parts of the
|
||
address space of the process that generated them; @value{GDBN} can access the
|
||
executable file itself for other parts.
|
||
|
||
@code{core-file} with no argument specifies that no core file is
|
||
to be used.
|
||
|
||
Note that the core file is ignored when your program is actually running
|
||
under @value{GDBN}. So, if you have been running your program and you
|
||
wish to debug a core file instead, you must kill the subprocess in which
|
||
the program is running. To do this, use the @code{kill} command
|
||
(@pxref{Kill Process, ,Killing the Child Process}).
|
||
|
||
@kindex add-symbol-file
|
||
@cindex dynamic linking
|
||
@item add-symbol-file @var{filename} @var{address}
|
||
@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
|
||
@itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
|
||
The @code{add-symbol-file} command reads additional symbol table
|
||
information from the file @var{filename}. You would use this command
|
||
when @var{filename} has been dynamically loaded (by some other means)
|
||
into the program that is running. The @var{address} should give the memory
|
||
address at which the file has been loaded; @value{GDBN} cannot figure
|
||
this out for itself. You can additionally specify an arbitrary number
|
||
of @samp{-s @var{section} @var{address}} pairs, to give an explicit
|
||
section name and base address for that section. You can specify any
|
||
@var{address} as an expression.
|
||
|
||
The symbol table of the file @var{filename} is added to the symbol table
|
||
originally read with the @code{symbol-file} command. You can use the
|
||
@code{add-symbol-file} command any number of times; the new symbol data
|
||
thus read is kept in addition to the old.
|
||
|
||
Changes can be reverted using the command @code{remove-symbol-file}.
|
||
|
||
@cindex relocatable object files, reading symbols from
|
||
@cindex object files, relocatable, reading symbols from
|
||
@cindex reading symbols from relocatable object files
|
||
@cindex symbols, reading from relocatable object files
|
||
@cindex @file{.o} files, reading symbols from
|
||
Although @var{filename} is typically a shared library file, an
|
||
executable file, or some other object file which has been fully
|
||
relocated for loading into a process, you can also load symbolic
|
||
information from relocatable @file{.o} files, as long as:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
the file's symbolic information refers only to linker symbols defined in
|
||
that file, not to symbols defined by other object files,
|
||
@item
|
||
every section the file's symbolic information refers to has actually
|
||
been loaded into the inferior, as it appears in the file, and
|
||
@item
|
||
you can determine the address at which every section was loaded, and
|
||
provide these to the @code{add-symbol-file} command.
|
||
@end itemize
|
||
|
||
@noindent
|
||
Some embedded operating systems, like Sun Chorus and VxWorks, can load
|
||
relocatable files into an already running program; such systems
|
||
typically make the requirements above easy to meet. However, it's
|
||
important to recognize that many native systems use complex link
|
||
procedures (@code{.linkonce} section factoring and C@t{++} constructor table
|
||
assembly, for example) that make the requirements difficult to meet. In
|
||
general, one cannot assume that using @code{add-symbol-file} to read a
|
||
relocatable object file's symbolic information will have the same effect
|
||
as linking the relocatable object file into the program in the normal
|
||
way.
|
||
|
||
@code{add-symbol-file} does not repeat if you press @key{RET} after using it.
|
||
|
||
@kindex remove-symbol-file
|
||
@item remove-symbol-file @var{filename}
|
||
@item remove-symbol-file -a @var{address}
|
||
Remove a symbol file added via the @code{add-symbol-file} command. The
|
||
file to remove can be identified by its @var{filename} or by an @var{address}
|
||
that lies within the boundaries of this symbol file in memory. Example:
|
||
|
||
@smallexample
|
||
(gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
|
||
add symbol table from file "/home/user/gdb/mylib.so" at
|
||
.text_addr = 0x7ffff7ff9480
|
||
(y or n) y
|
||
Reading symbols from /home/user/gdb/mylib.so...done.
|
||
(gdb) remove-symbol-file -a 0x7ffff7ff9480
|
||
Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
|
||
|
||
@kindex add-symbol-file-from-memory
|
||
@cindex @code{syscall DSO}
|
||
@cindex load symbols from memory
|
||
@item add-symbol-file-from-memory @var{address}
|
||
Load symbols from the given @var{address} in a dynamically loaded
|
||
object file whose image is mapped directly into the inferior's memory.
|
||
For example, the Linux kernel maps a @code{syscall DSO} into each
|
||
process's address space; this DSO provides kernel-specific code for
|
||
some system calls. The argument can be any expression whose
|
||
evaluation yields the address of the file's shared object file header.
|
||
For this command to work, you must have used @code{symbol-file} or
|
||
@code{exec-file} commands in advance.
|
||
|
||
@kindex section
|
||
@item section @var{section} @var{addr}
|
||
The @code{section} command changes the base address of the named
|
||
@var{section} of the exec file to @var{addr}. This can be used if the
|
||
exec file does not contain section addresses, (such as in the
|
||
@code{a.out} format), or when the addresses specified in the file
|
||
itself are wrong. Each section must be changed separately. The
|
||
@code{info files} command, described below, lists all the sections and
|
||
their addresses.
|
||
|
||
@kindex info files
|
||
@kindex info target
|
||
@item info files
|
||
@itemx info target
|
||
@code{info files} and @code{info target} are synonymous; both print the
|
||
current target (@pxref{Targets, ,Specifying a Debugging Target}),
|
||
including the names of the executable and core dump files currently in
|
||
use by @value{GDBN}, and the files from which symbols were loaded. The
|
||
command @code{help target} lists all possible targets rather than
|
||
current ones.
|
||
|
||
@kindex maint info sections
|
||
@item maint info sections
|
||
Another command that can give you extra information about program sections
|
||
is @code{maint info sections}. In addition to the section information
|
||
displayed by @code{info files}, this command displays the flags and file
|
||
offset of each section in the executable and core dump files. In addition,
|
||
@code{maint info sections} provides the following command options (which
|
||
may be arbitrarily combined):
|
||
|
||
@table @code
|
||
@item ALLOBJ
|
||
Display sections for all loaded object files, including shared libraries.
|
||
@item @var{sections}
|
||
Display info only for named @var{sections}.
|
||
@item @var{section-flags}
|
||
Display info only for sections for which @var{section-flags} are true.
|
||
The section flags that @value{GDBN} currently knows about are:
|
||
@table @code
|
||
@item ALLOC
|
||
Section will have space allocated in the process when loaded.
|
||
Set for all sections except those containing debug information.
|
||
@item LOAD
|
||
Section will be loaded from the file into the child process memory.
|
||
Set for pre-initialized code and data, clear for @code{.bss} sections.
|
||
@item RELOC
|
||
Section needs to be relocated before loading.
|
||
@item READONLY
|
||
Section cannot be modified by the child process.
|
||
@item CODE
|
||
Section contains executable code only.
|
||
@item DATA
|
||
Section contains data only (no executable code).
|
||
@item ROM
|
||
Section will reside in ROM.
|
||
@item CONSTRUCTOR
|
||
Section contains data for constructor/destructor lists.
|
||
@item HAS_CONTENTS
|
||
Section is not empty.
|
||
@item NEVER_LOAD
|
||
An instruction to the linker to not output the section.
|
||
@item COFF_SHARED_LIBRARY
|
||
A notification to the linker that the section contains
|
||
COFF shared library information.
|
||
@item IS_COMMON
|
||
Section contains common symbols.
|
||
@end table
|
||
@end table
|
||
@kindex set trust-readonly-sections
|
||
@cindex read-only sections
|
||
@item set trust-readonly-sections on
|
||
Tell @value{GDBN} that readonly sections in your object file
|
||
really are read-only (i.e.@: that their contents will not change).
|
||
In that case, @value{GDBN} can fetch values from these sections
|
||
out of the object file, rather than from the target program.
|
||
For some targets (notably embedded ones), this can be a significant
|
||
enhancement to debugging performance.
|
||
|
||
The default is off.
|
||
|
||
@item set trust-readonly-sections off
|
||
Tell @value{GDBN} not to trust readonly sections. This means that
|
||
the contents of the section might change while the program is running,
|
||
and must therefore be fetched from the target when needed.
|
||
|
||
@item show trust-readonly-sections
|
||
Show the current setting of trusting readonly sections.
|
||
@end table
|
||
|
||
All file-specifying commands allow both absolute and relative file names
|
||
as arguments. @value{GDBN} always converts the file name to an absolute file
|
||
name and remembers it that way.
|
||
|
||
@cindex shared libraries
|
||
@anchor{Shared Libraries}
|
||
@value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
|
||
Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
|
||
DSBT (TIC6X) shared libraries.
|
||
|
||
On MS-Windows @value{GDBN} must be linked with the Expat library to support
|
||
shared libraries. @xref{Expat}.
|
||
|
||
@value{GDBN} automatically loads symbol definitions from shared libraries
|
||
when you use the @code{run} command, or when you examine a core file.
|
||
(Before you issue the @code{run} command, @value{GDBN} does not understand
|
||
references to a function in a shared library, however---unless you are
|
||
debugging a core file).
|
||
|
||
@c FIXME: some @value{GDBN} release may permit some refs to undef
|
||
@c FIXME...symbols---eg in a break cmd---assuming they are from a shared
|
||
@c FIXME...lib; check this from time to time when updating manual
|
||
|
||
There are times, however, when you may wish to not automatically load
|
||
symbol definitions from shared libraries, such as when they are
|
||
particularly large or there are many of them.
|
||
|
||
To control the automatic loading of shared library symbols, use the
|
||
commands:
|
||
|
||
@table @code
|
||
@kindex set auto-solib-add
|
||
@item set auto-solib-add @var{mode}
|
||
If @var{mode} is @code{on}, symbols from all shared object libraries
|
||
will be loaded automatically when the inferior begins execution, you
|
||
attach to an independently started inferior, or when the dynamic linker
|
||
informs @value{GDBN} that a new library has been loaded. If @var{mode}
|
||
is @code{off}, symbols must be loaded manually, using the
|
||
@code{sharedlibrary} command. The default value is @code{on}.
|
||
|
||
@cindex memory used for symbol tables
|
||
If your program uses lots of shared libraries with debug info that
|
||
takes large amounts of memory, you can decrease the @value{GDBN}
|
||
memory footprint by preventing it from automatically loading the
|
||
symbols from shared libraries. To that end, type @kbd{set
|
||
auto-solib-add off} before running the inferior, then load each
|
||
library whose debug symbols you do need with @kbd{sharedlibrary
|
||
@var{regexp}}, where @var{regexp} is a regular expression that matches
|
||
the libraries whose symbols you want to be loaded.
|
||
|
||
@kindex show auto-solib-add
|
||
@item show auto-solib-add
|
||
Display the current autoloading mode.
|
||
@end table
|
||
|
||
@cindex load shared library
|
||
To explicitly load shared library symbols, use the @code{sharedlibrary}
|
||
command:
|
||
|
||
@table @code
|
||
@kindex info sharedlibrary
|
||
@kindex info share
|
||
@item info share @var{regex}
|
||
@itemx info sharedlibrary @var{regex}
|
||
Print the names of the shared libraries which are currently loaded
|
||
that match @var{regex}. If @var{regex} is omitted then print
|
||
all shared libraries that are loaded.
|
||
|
||
@kindex info dll
|
||
@item info dll @var{regex}
|
||
This is an alias of @code{info sharedlibrary}.
|
||
|
||
@kindex sharedlibrary
|
||
@kindex share
|
||
@item sharedlibrary @var{regex}
|
||
@itemx share @var{regex}
|
||
Load shared object library symbols for files matching a
|
||
Unix regular expression.
|
||
As with files loaded automatically, it only loads shared libraries
|
||
required by your program for a core file or after typing @code{run}. If
|
||
@var{regex} is omitted all shared libraries required by your program are
|
||
loaded.
|
||
|
||
@item nosharedlibrary
|
||
@kindex nosharedlibrary
|
||
@cindex unload symbols from shared libraries
|
||
Unload all shared object library symbols. This discards all symbols
|
||
that have been loaded from all shared libraries. Symbols from shared
|
||
libraries that were loaded by explicit user requests are not
|
||
discarded.
|
||
@end table
|
||
|
||
Sometimes you may wish that @value{GDBN} stops and gives you control
|
||
when any of shared library events happen. The best way to do this is
|
||
to use @code{catch load} and @code{catch unload} (@pxref{Set
|
||
Catchpoints}).
|
||
|
||
@value{GDBN} also supports the the @code{set stop-on-solib-events}
|
||
command for this. This command exists for historical reasons. It is
|
||
less useful than setting a catchpoint, because it does not allow for
|
||
conditions or commands as a catchpoint does.
|
||
|
||
@table @code
|
||
@item set stop-on-solib-events
|
||
@kindex set stop-on-solib-events
|
||
This command controls whether @value{GDBN} should give you control
|
||
when the dynamic linker notifies it about some shared library event.
|
||
The most common event of interest is loading or unloading of a new
|
||
shared library.
|
||
|
||
@item show stop-on-solib-events
|
||
@kindex show stop-on-solib-events
|
||
Show whether @value{GDBN} stops and gives you control when shared
|
||
library events happen.
|
||
@end table
|
||
|
||
Shared libraries are also supported in many cross or remote debugging
|
||
configurations. @value{GDBN} needs to have access to the target's libraries;
|
||
this can be accomplished either by providing copies of the libraries
|
||
on the host system, or by asking @value{GDBN} to automatically retrieve the
|
||
libraries from the target. If copies of the target libraries are
|
||
provided, they need to be the same as the target libraries, although the
|
||
copies on the target can be stripped as long as the copies on the host are
|
||
not.
|
||
|
||
@cindex where to look for shared libraries
|
||
For remote debugging, you need to tell @value{GDBN} where the target
|
||
libraries are, so that it can load the correct copies---otherwise, it
|
||
may try to load the host's libraries. @value{GDBN} has two variables
|
||
to specify the search directories for target libraries.
|
||
|
||
@table @code
|
||
@cindex prefix for executable and shared library file names
|
||
@cindex system root, alternate
|
||
@kindex set solib-absolute-prefix
|
||
@kindex set sysroot
|
||
@item set sysroot @var{path}
|
||
Use @var{path} as the system root for the program being debugged. Any
|
||
absolute shared library paths will be prefixed with @var{path}; many
|
||
runtime loaders store the absolute paths to the shared library in the
|
||
target program's memory. When starting processes remotely, and when
|
||
attaching to already-running processes (local or remote), their
|
||
executable filenames will be prefixed with @var{path} if reported to
|
||
@value{GDBN} as absolute by the operating system. If you use
|
||
@code{set sysroot} to find executables and shared libraries, they need
|
||
to be laid out in the same way that they are on the target, with
|
||
e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
|
||
@var{path}.
|
||
|
||
If @var{path} starts with the sequence @file{target:} and the target
|
||
system is remote then @value{GDBN} will retrieve the target binaries
|
||
from the remote system. This is only supported when using a remote
|
||
target that supports the @code{remote get} command (@pxref{File
|
||
Transfer,,Sending files to a remote system}). The part of @var{path}
|
||
following the initial @file{target:} (if present) is used as system
|
||
root prefix on the remote file system. If @var{path} starts with the
|
||
sequence @file{remote:} this is converted to the sequence
|
||
@file{target:} by @code{set sysroot}@footnote{Historically the
|
||
functionality to retrieve binaries from the remote system was
|
||
provided by prefixing @var{path} with @file{remote:}}. If you want
|
||
to specify a local system root using a directory that happens to be
|
||
named @file{target:} or @file{remote:}, you need to use some
|
||
equivalent variant of the name like @file{./target:}.
|
||
|
||
For targets with an MS-DOS based filesystem, such as MS-Windows and
|
||
SymbianOS, @value{GDBN} tries prefixing a few variants of the target
|
||
absolute file name with @var{path}. But first, on Unix hosts,
|
||
@value{GDBN} converts all backslash directory separators into forward
|
||
slashes, because the backslash is not a directory separator on Unix:
|
||
|
||
@smallexample
|
||
c:\foo\bar.dll @result{} c:/foo/bar.dll
|
||
@end smallexample
|
||
|
||
Then, @value{GDBN} attempts prefixing the target file name with
|
||
@var{path}, and looks for the resulting file name in the host file
|
||
system:
|
||
|
||
@smallexample
|
||
c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
|
||
@end smallexample
|
||
|
||
If that does not find the binary, @value{GDBN} tries removing
|
||
the @samp{:} character from the drive spec, both for convenience, and,
|
||
for the case of the host file system not supporting file names with
|
||
colons:
|
||
|
||
@smallexample
|
||
c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
|
||
@end smallexample
|
||
|
||
This makes it possible to have a system root that mirrors a target
|
||
with more than one drive. E.g., you may want to setup your local
|
||
copies of the target system shared libraries like so (note @samp{c} vs
|
||
@samp{z}):
|
||
|
||
@smallexample
|
||
@file{/path/to/sysroot/c/sys/bin/foo.dll}
|
||
@file{/path/to/sysroot/c/sys/bin/bar.dll}
|
||
@file{/path/to/sysroot/z/sys/bin/bar.dll}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
and point the system root at @file{/path/to/sysroot}, so that
|
||
@value{GDBN} can find the correct copies of both
|
||
@file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
|
||
|
||
If that still does not find the binary, @value{GDBN} tries
|
||
removing the whole drive spec from the target file name:
|
||
|
||
@smallexample
|
||
c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
|
||
@end smallexample
|
||
|
||
This last lookup makes it possible to not care about the drive name,
|
||
if you don't want or need to.
|
||
|
||
The @code{set solib-absolute-prefix} command is an alias for @code{set
|
||
sysroot}.
|
||
|
||
@cindex default system root
|
||
@cindex @samp{--with-sysroot}
|
||
You can set the default system root by using the configure-time
|
||
@samp{--with-sysroot} option. If the system root is inside
|
||
@value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
|
||
@samp{--exec-prefix}), then the default system root will be updated
|
||
automatically if the installed @value{GDBN} is moved to a new
|
||
location.
|
||
|
||
@kindex show sysroot
|
||
@item show sysroot
|
||
Display the current executable and shared library prefix.
|
||
|
||
@kindex set solib-search-path
|
||
@item set solib-search-path @var{path}
|
||
If this variable is set, @var{path} is a colon-separated list of
|
||
directories to search for shared libraries. @samp{solib-search-path}
|
||
is used after @samp{sysroot} fails to locate the library, or if the
|
||
path to the library is relative instead of absolute. If you want to
|
||
use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
|
||
@samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
|
||
finding your host's libraries. @samp{sysroot} is preferred; setting
|
||
it to a nonexistent directory may interfere with automatic loading
|
||
of shared library symbols.
|
||
|
||
@kindex show solib-search-path
|
||
@item show solib-search-path
|
||
Display the current shared library search path.
|
||
|
||
@cindex DOS file-name semantics of file names.
|
||
@kindex set target-file-system-kind (unix|dos-based|auto)
|
||
@kindex show target-file-system-kind
|
||
@item set target-file-system-kind @var{kind}
|
||
Set assumed file system kind for target reported file names.
|
||
|
||
Shared library file names as reported by the target system may not
|
||
make sense as is on the system @value{GDBN} is running on. For
|
||
example, when remote debugging a target that has MS-DOS based file
|
||
system semantics, from a Unix host, the target may be reporting to
|
||
@value{GDBN} a list of loaded shared libraries with file names such as
|
||
@file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
|
||
drive letters, so the @samp{c:\} prefix is not normally understood as
|
||
indicating an absolute file name, and neither is the backslash
|
||
normally considered a directory separator character. In that case,
|
||
the native file system would interpret this whole absolute file name
|
||
as a relative file name with no directory components. This would make
|
||
it impossible to point @value{GDBN} at a copy of the remote target's
|
||
shared libraries on the host using @code{set sysroot}, and impractical
|
||
with @code{set solib-search-path}. Setting
|
||
@code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
|
||
to interpret such file names similarly to how the target would, and to
|
||
map them to file names valid on @value{GDBN}'s native file system
|
||
semantics. The value of @var{kind} can be @code{"auto"}, in addition
|
||
to one of the supported file system kinds. In that case, @value{GDBN}
|
||
tries to determine the appropriate file system variant based on the
|
||
current target's operating system (@pxref{ABI, ,Configuring the
|
||
Current ABI}). The supported file system settings are:
|
||
|
||
@table @code
|
||
@item unix
|
||
Instruct @value{GDBN} to assume the target file system is of Unix
|
||
kind. Only file names starting the forward slash (@samp{/}) character
|
||
are considered absolute, and the directory separator character is also
|
||
the forward slash.
|
||
|
||
@item dos-based
|
||
Instruct @value{GDBN} to assume the target file system is DOS based.
|
||
File names starting with either a forward slash, or a drive letter
|
||
followed by a colon (e.g., @samp{c:}), are considered absolute, and
|
||
both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
|
||
considered directory separators.
|
||
|
||
@item auto
|
||
Instruct @value{GDBN} to use the file system kind associated with the
|
||
target operating system (@pxref{ABI, ,Configuring the Current ABI}).
|
||
This is the default.
|
||
@end table
|
||
@end table
|
||
|
||
@cindex file name canonicalization
|
||
@cindex base name differences
|
||
When processing file names provided by the user, @value{GDBN}
|
||
frequently needs to compare them to the file names recorded in the
|
||
program's debug info. Normally, @value{GDBN} compares just the
|
||
@dfn{base names} of the files as strings, which is reasonably fast
|
||
even for very large programs. (The base name of a file is the last
|
||
portion of its name, after stripping all the leading directories.)
|
||
This shortcut in comparison is based upon the assumption that files
|
||
cannot have more than one base name. This is usually true, but
|
||
references to files that use symlinks or similar filesystem
|
||
facilities violate that assumption. If your program records files
|
||
using such facilities, or if you provide file names to @value{GDBN}
|
||
using symlinks etc., you can set @code{basenames-may-differ} to
|
||
@code{true} to instruct @value{GDBN} to completely canonicalize each
|
||
pair of file names it needs to compare. This will make file-name
|
||
comparisons accurate, but at a price of a significant slowdown.
|
||
|
||
@table @code
|
||
@item set basenames-may-differ
|
||
@kindex set basenames-may-differ
|
||
Set whether a source file may have multiple base names.
|
||
|
||
@item show basenames-may-differ
|
||
@kindex show basenames-may-differ
|
||
Show whether a source file may have multiple base names.
|
||
@end table
|
||
|
||
@node File Caching
|
||
@section File Caching
|
||
@cindex caching of opened files
|
||
@cindex caching of bfd objects
|
||
|
||
To speed up file loading, and reduce memory usage, @value{GDBN} will
|
||
reuse the @code{bfd} objects used to track open files. @xref{Top, ,
|
||
BFD, bfd, The Binary File Descriptor Library}. The following commands
|
||
allow visibility and control of the caching behavior.
|
||
|
||
@table @code
|
||
@kindex maint info bfds
|
||
@item maint info bfds
|
||
This prints information about each @code{bfd} object that is known to
|
||
@value{GDBN}.
|
||
|
||
@kindex maint set bfd-sharing
|
||
@kindex maint show bfd-sharing
|
||
@kindex bfd caching
|
||
@item maint set bfd-sharing
|
||
@item maint show bfd-sharing
|
||
Control whether @code{bfd} objects can be shared. When sharing is
|
||
enabled @value{GDBN} reuses already open @code{bfd} objects rather
|
||
than reopening the same file. Turning sharing off does not cause
|
||
already shared @code{bfd} objects to be unshared, but all future files
|
||
that are opened will create a new @code{bfd} object. Similarly,
|
||
re-enabling sharing does not cause multiple existing @code{bfd}
|
||
objects to be collapsed into a single shared @code{bfd} object.
|
||
|
||
@kindex set debug bfd-cache @var{level}
|
||
@kindex bfd caching
|
||
@item set debug bfd-cache @var{level}
|
||
Turns on debugging of the bfd cache, setting the level to @var{level}.
|
||
|
||
@kindex show debug bfd-cache
|
||
@kindex bfd caching
|
||
@item show debug bfd-cache
|
||
Show the current debugging level of the bfd cache.
|
||
@end table
|
||
|
||
@node Separate Debug Files
|
||
@section Debugging Information in Separate Files
|
||
@cindex separate debugging information files
|
||
@cindex debugging information in separate files
|
||
@cindex @file{.debug} subdirectories
|
||
@cindex debugging information directory, global
|
||
@cindex global debugging information directories
|
||
@cindex build ID, and separate debugging files
|
||
@cindex @file{.build-id} directory
|
||
|
||
@value{GDBN} allows you to put a program's debugging information in a
|
||
file separate from the executable itself, in a way that allows
|
||
@value{GDBN} to find and load the debugging information automatically.
|
||
Since debugging information can be very large---sometimes larger
|
||
than the executable code itself---some systems distribute debugging
|
||
information for their executables in separate files, which users can
|
||
install only when they need to debug a problem.
|
||
|
||
@value{GDBN} supports two ways of specifying the separate debug info
|
||
file:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The executable contains a @dfn{debug link} that specifies the name of
|
||
the separate debug info file. The separate debug file's name is
|
||
usually @file{@var{executable}.debug}, where @var{executable} is the
|
||
name of the corresponding executable file without leading directories
|
||
(e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
|
||
debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
|
||
checksum for the debug file, which @value{GDBN} uses to validate that
|
||
the executable and the debug file came from the same build.
|
||
|
||
@item
|
||
The executable contains a @dfn{build ID}, a unique bit string that is
|
||
also present in the corresponding debug info file. (This is supported
|
||
only on some operating systems, when using the ELF or PE file formats
|
||
for binary files and the @sc{gnu} Binutils.) For more details about
|
||
this feature, see the description of the @option{--build-id}
|
||
command-line option in @ref{Options, , Command Line Options, ld.info,
|
||
The GNU Linker}. The debug info file's name is not specified
|
||
explicitly by the build ID, but can be computed from the build ID, see
|
||
below.
|
||
@end itemize
|
||
|
||
Depending on the way the debug info file is specified, @value{GDBN}
|
||
uses two different methods of looking for the debug file:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
For the ``debug link'' method, @value{GDBN} looks up the named file in
|
||
the directory of the executable file, then in a subdirectory of that
|
||
directory named @file{.debug}, and finally under each one of the global debug
|
||
directories, in a subdirectory whose name is identical to the leading
|
||
directories of the executable's absolute file name.
|
||
|
||
@item
|
||
For the ``build ID'' method, @value{GDBN} looks in the
|
||
@file{.build-id} subdirectory of each one of the global debug directories for
|
||
a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
|
||
first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
|
||
are the rest of the bit string. (Real build ID strings are 32 or more
|
||
hex characters, not 10.)
|
||
@end itemize
|
||
|
||
So, for example, suppose you ask @value{GDBN} to debug
|
||
@file{/usr/bin/ls}, which has a debug link that specifies the
|
||
file @file{ls.debug}, and a build ID whose value in hex is
|
||
@code{abcdef1234}. If the list of the global debug directories includes
|
||
@file{/usr/lib/debug}, then @value{GDBN} will look for the following
|
||
debug information files, in the indicated order:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
|
||
@item
|
||
@file{/usr/bin/ls.debug}
|
||
@item
|
||
@file{/usr/bin/.debug/ls.debug}
|
||
@item
|
||
@file{/usr/lib/debug/usr/bin/ls.debug}.
|
||
@end itemize
|
||
|
||
@anchor{debug-file-directory}
|
||
Global debugging info directories default to what is set by @value{GDBN}
|
||
configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
|
||
you can also set the global debugging info directories, and view the list
|
||
@value{GDBN} is currently using.
|
||
|
||
@table @code
|
||
|
||
@kindex set debug-file-directory
|
||
@item set debug-file-directory @var{directories}
|
||
Set the directories which @value{GDBN} searches for separate debugging
|
||
information files to @var{directory}. Multiple path components can be set
|
||
concatenating them by a path separator.
|
||
|
||
@kindex show debug-file-directory
|
||
@item show debug-file-directory
|
||
Show the directories @value{GDBN} searches for separate debugging
|
||
information files.
|
||
|
||
@end table
|
||
|
||
@cindex @code{.gnu_debuglink} sections
|
||
@cindex debug link sections
|
||
A debug link is a special section of the executable file named
|
||
@code{.gnu_debuglink}. The section must contain:
|
||
|
||
@itemize
|
||
@item
|
||
A filename, with any leading directory components removed, followed by
|
||
a zero byte,
|
||
@item
|
||
zero to three bytes of padding, as needed to reach the next four-byte
|
||
boundary within the section, and
|
||
@item
|
||
a four-byte CRC checksum, stored in the same endianness used for the
|
||
executable file itself. The checksum is computed on the debugging
|
||
information file's full contents by the function given below, passing
|
||
zero as the @var{crc} argument.
|
||
@end itemize
|
||
|
||
Any executable file format can carry a debug link, as long as it can
|
||
contain a section named @code{.gnu_debuglink} with the contents
|
||
described above.
|
||
|
||
@cindex @code{.note.gnu.build-id} sections
|
||
@cindex build ID sections
|
||
The build ID is a special section in the executable file (and in other
|
||
ELF binary files that @value{GDBN} may consider). This section is
|
||
often named @code{.note.gnu.build-id}, but that name is not mandatory.
|
||
It contains unique identification for the built files---the ID remains
|
||
the same across multiple builds of the same build tree. The default
|
||
algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
|
||
content for the build ID string. The same section with an identical
|
||
value is present in the original built binary with symbols, in its
|
||
stripped variant, and in the separate debugging information file.
|
||
|
||
The debugging information file itself should be an ordinary
|
||
executable, containing a full set of linker symbols, sections, and
|
||
debugging information. The sections of the debugging information file
|
||
should have the same names, addresses, and sizes as the original file,
|
||
but they need not contain any data---much like a @code{.bss} section
|
||
in an ordinary executable.
|
||
|
||
The @sc{gnu} binary utilities (Binutils) package includes the
|
||
@samp{objcopy} utility that can produce
|
||
the separated executable / debugging information file pairs using the
|
||
following commands:
|
||
|
||
@smallexample
|
||
@kbd{objcopy --only-keep-debug foo foo.debug}
|
||
@kbd{strip -g foo}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
These commands remove the debugging
|
||
information from the executable file @file{foo} and place it in the file
|
||
@file{foo.debug}. You can use the first, second or both methods to link the
|
||
two files:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The debug link method needs the following additional command to also leave
|
||
behind a debug link in @file{foo}:
|
||
|
||
@smallexample
|
||
@kbd{objcopy --add-gnu-debuglink=foo.debug foo}
|
||
@end smallexample
|
||
|
||
Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
|
||
a version of the @code{strip} command such that the command @kbd{strip foo -f
|
||
foo.debug} has the same functionality as the two @code{objcopy} commands and
|
||
the @code{ln -s} command above, together.
|
||
|
||
@item
|
||
Build ID gets embedded into the main executable using @code{ld --build-id} or
|
||
the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
|
||
compatibility fixes for debug files separation are present in @sc{gnu} binary
|
||
utilities (Binutils) package since version 2.18.
|
||
@end itemize
|
||
|
||
@noindent
|
||
|
||
@cindex CRC algorithm definition
|
||
The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
|
||
IEEE 802.3 using the polynomial:
|
||
|
||
@c TexInfo requires naked braces for multi-digit exponents for Tex
|
||
@c output, but this causes HTML output to barf. HTML has to be set using
|
||
@c raw commands. So we end up having to specify this equation in 2
|
||
@c different ways!
|
||
@ifhtml
|
||
@display
|
||
@html
|
||
<em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
|
||
+ <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
|
||
@end html
|
||
@end display
|
||
@end ifhtml
|
||
@ifnothtml
|
||
@display
|
||
@math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
|
||
@math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
|
||
@end display
|
||
@end ifnothtml
|
||
|
||
The function is computed byte at a time, taking the least
|
||
significant bit of each byte first. The initial pattern
|
||
@code{0xffffffff} is used, to ensure leading zeros affect the CRC and
|
||
the final result is inverted to ensure trailing zeros also affect the
|
||
CRC.
|
||
|
||
@emph{Note:} This is the same CRC polynomial as used in handling the
|
||
@dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
|
||
However in the case of the Remote Serial Protocol, the CRC is computed
|
||
@emph{most} significant bit first, and the result is not inverted, so
|
||
trailing zeros have no effect on the CRC value.
|
||
|
||
To complete the description, we show below the code of the function
|
||
which produces the CRC used in @code{.gnu_debuglink}. Inverting the
|
||
initially supplied @code{crc} argument means that an initial call to
|
||
this function passing in zero will start computing the CRC using
|
||
@code{0xffffffff}.
|
||
|
||
@kindex gnu_debuglink_crc32
|
||
@smallexample
|
||
unsigned long
|
||
gnu_debuglink_crc32 (unsigned long crc,
|
||
unsigned char *buf, size_t len)
|
||
@{
|
||
static const unsigned long crc32_table[256] =
|
||
@{
|
||
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
|
||
0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
|
||
0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
|
||
0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
|
||
0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
|
||
0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
|
||
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
|
||
0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
|
||
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
|
||
0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
|
||
0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
|
||
0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
|
||
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
|
||
0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
|
||
0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
|
||
0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
|
||
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
|
||
0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
|
||
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
|
||
0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
|
||
0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
|
||
0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
|
||
0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
|
||
0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
|
||
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
|
||
0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
|
||
0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
|
||
0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
|
||
0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
|
||
0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
|
||
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
|
||
0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
|
||
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
|
||
0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
|
||
0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
|
||
0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
|
||
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
|
||
0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
|
||
0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
|
||
0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
|
||
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
|
||
0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
|
||
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
|
||
0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
|
||
0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
|
||
0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
|
||
0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
|
||
0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
|
||
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
|
||
0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
|
||
0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
|
||
0x2d02ef8d
|
||
@};
|
||
unsigned char *end;
|
||
|
||
crc = ~crc & 0xffffffff;
|
||
for (end = buf + len; buf < end; ++buf)
|
||
crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
|
||
return ~crc & 0xffffffff;
|
||
@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This computation does not apply to the ``build ID'' method.
|
||
|
||
@node MiniDebugInfo
|
||
@section Debugging information in a special section
|
||
@cindex separate debug sections
|
||
@cindex @samp{.gnu_debugdata} section
|
||
|
||
Some systems ship pre-built executables and libraries that have a
|
||
special @samp{.gnu_debugdata} section. This feature is called
|
||
@dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
|
||
is used to supply extra symbols for backtraces.
|
||
|
||
The intent of this section is to provide extra minimal debugging
|
||
information for use in simple backtraces. It is not intended to be a
|
||
replacement for full separate debugging information (@pxref{Separate
|
||
Debug Files}). The example below shows the intended use; however,
|
||
@value{GDBN} does not currently put restrictions on what sort of
|
||
debugging information might be included in the section.
|
||
|
||
@value{GDBN} has support for this extension. If the section exists,
|
||
then it is used provided that no other source of debugging information
|
||
can be found, and that @value{GDBN} was configured with LZMA support.
|
||
|
||
This section can be easily created using @command{objcopy} and other
|
||
standard utilities:
|
||
|
||
@smallexample
|
||
# Extract the dynamic symbols from the main binary, there is no need
|
||
# to also have these in the normal symbol table.
|
||
nm -D @var{binary} --format=posix --defined-only \
|
||
| awk '@{ print $1 @}' | sort > dynsyms
|
||
|
||
# Extract all the text (i.e. function) symbols from the debuginfo.
|
||
# (Note that we actually also accept "D" symbols, for the benefit
|
||
# of platforms like PowerPC64 that use function descriptors.)
|
||
nm @var{binary} --format=posix --defined-only \
|
||
| awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
|
||
| sort > funcsyms
|
||
|
||
# Keep all the function symbols not already in the dynamic symbol
|
||
# table.
|
||
comm -13 dynsyms funcsyms > keep_symbols
|
||
|
||
# Separate full debug info into debug binary.
|
||
objcopy --only-keep-debug @var{binary} debug
|
||
|
||
# Copy the full debuginfo, keeping only a minimal set of symbols and
|
||
# removing some unnecessary sections.
|
||
objcopy -S --remove-section .gdb_index --remove-section .comment \
|
||
--keep-symbols=keep_symbols debug mini_debuginfo
|
||
|
||
# Drop the full debug info from the original binary.
|
||
strip --strip-all -R .comment @var{binary}
|
||
|
||
# Inject the compressed data into the .gnu_debugdata section of the
|
||
# original binary.
|
||
xz mini_debuginfo
|
||
objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
|
||
@end smallexample
|
||
|
||
@node Index Files
|
||
@section Index Files Speed Up @value{GDBN}
|
||
@cindex index files
|
||
@cindex @samp{.gdb_index} section
|
||
|
||
When @value{GDBN} finds a symbol file, it scans the symbols in the
|
||
file in order to construct an internal symbol table. This lets most
|
||
@value{GDBN} operations work quickly---at the cost of a delay early
|
||
on. For large programs, this delay can be quite lengthy, so
|
||
@value{GDBN} provides a way to build an index, which speeds up
|
||
startup.
|
||
|
||
For convenience, @value{GDBN} comes with a program,
|
||
@command{gdb-add-index}, which can be used to add the index to a
|
||
symbol file. It takes the symbol file as its only argument:
|
||
|
||
@smallexample
|
||
$ gdb-add-index symfile
|
||
@end smallexample
|
||
|
||
@xref{gdb-add-index}.
|
||
|
||
It is also possible to do the work manually. Here is what
|
||
@command{gdb-add-index} does behind the curtains.
|
||
|
||
The index is stored as a section in the symbol file. @value{GDBN} can
|
||
write the index to a file, then you can put it into the symbol file
|
||
using @command{objcopy}.
|
||
|
||
To create an index file, use the @code{save gdb-index} command:
|
||
|
||
@table @code
|
||
@item save gdb-index [-dwarf-5] @var{directory}
|
||
@kindex save gdb-index
|
||
Create index files for all symbol files currently known by
|
||
@value{GDBN}. For each known @var{symbol-file}, this command by
|
||
default creates it produces a single file
|
||
@file{@var{symbol-file}.gdb-index}. If you invoke this command with
|
||
the @option{-dwarf-5} option, it produces 2 files:
|
||
@file{@var{symbol-file}.debug_names} and
|
||
@file{@var{symbol-file}.debug_str}. The files are created in the
|
||
given @var{directory}.
|
||
@end table
|
||
|
||
Once you have created an index file you can merge it into your symbol
|
||
file, here named @file{symfile}, using @command{objcopy}:
|
||
|
||
@smallexample
|
||
$ objcopy --add-section .gdb_index=symfile.gdb-index \
|
||
--set-section-flags .gdb_index=readonly symfile symfile
|
||
@end smallexample
|
||
|
||
Or for @code{-dwarf-5}:
|
||
|
||
@smallexample
|
||
$ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
|
||
$ cat symfile.debug_str >>symfile.debug_str.new
|
||
$ objcopy --add-section .debug_names=symfile.gdb-index \
|
||
--set-section-flags .debug_names=readonly \
|
||
--update-section .debug_str=symfile.debug_str.new symfile symfile
|
||
@end smallexample
|
||
|
||
@value{GDBN} will normally ignore older versions of @file{.gdb_index}
|
||
sections that have been deprecated. Usually they are deprecated because
|
||
they are missing a new feature or have performance issues.
|
||
To tell @value{GDBN} to use a deprecated index section anyway
|
||
specify @code{set use-deprecated-index-sections on}.
|
||
The default is @code{off}.
|
||
This can speed up startup, but may result in some functionality being lost.
|
||
@xref{Index Section Format}.
|
||
|
||
@emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
|
||
must be done before gdb reads the file. The following will not work:
|
||
|
||
@smallexample
|
||
$ gdb -ex "set use-deprecated-index-sections on" <program>
|
||
@end smallexample
|
||
|
||
Instead you must do, for example,
|
||
|
||
@smallexample
|
||
$ gdb -iex "set use-deprecated-index-sections on" <program>
|
||
@end smallexample
|
||
|
||
There are currently some limitation on indices. They only work when
|
||
for DWARF debugging information, not stabs. And, they do not
|
||
currently work for programs using Ada.
|
||
|
||
@node Symbol Errors
|
||
@section Errors Reading Symbol Files
|
||
|
||
While reading a symbol file, @value{GDBN} occasionally encounters problems,
|
||
such as symbol types it does not recognize, or known bugs in compiler
|
||
output. By default, @value{GDBN} does not notify you of such problems, since
|
||
they are relatively common and primarily of interest to people
|
||
debugging compilers. If you are interested in seeing information
|
||
about ill-constructed symbol tables, you can either ask @value{GDBN} to print
|
||
only one message about each such type of problem, no matter how many
|
||
times the problem occurs; or you can ask @value{GDBN} to print more messages,
|
||
to see how many times the problems occur, with the @code{set
|
||
complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
|
||
Messages}).
|
||
|
||
The messages currently printed, and their meanings, include:
|
||
|
||
@table @code
|
||
@item inner block not inside outer block in @var{symbol}
|
||
|
||
The symbol information shows where symbol scopes begin and end
|
||
(such as at the start of a function or a block of statements). This
|
||
error indicates that an inner scope block is not fully contained
|
||
in its outer scope blocks.
|
||
|
||
@value{GDBN} circumvents the problem by treating the inner block as if it had
|
||
the same scope as the outer block. In the error message, @var{symbol}
|
||
may be shown as ``@code{(don't know)}'' if the outer block is not a
|
||
function.
|
||
|
||
@item block at @var{address} out of order
|
||
|
||
The symbol information for symbol scope blocks should occur in
|
||
order of increasing addresses. This error indicates that it does not
|
||
do so.
|
||
|
||
@value{GDBN} does not circumvent this problem, and has trouble
|
||
locating symbols in the source file whose symbols it is reading. (You
|
||
can often determine what source file is affected by specifying
|
||
@code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
|
||
Messages}.)
|
||
|
||
@item bad block start address patched
|
||
|
||
The symbol information for a symbol scope block has a start address
|
||
smaller than the address of the preceding source line. This is known
|
||
to occur in the SunOS 4.1.1 (and earlier) C compiler.
|
||
|
||
@value{GDBN} circumvents the problem by treating the symbol scope block as
|
||
starting on the previous source line.
|
||
|
||
@item bad string table offset in symbol @var{n}
|
||
|
||
@cindex foo
|
||
Symbol number @var{n} contains a pointer into the string table which is
|
||
larger than the size of the string table.
|
||
|
||
@value{GDBN} circumvents the problem by considering the symbol to have the
|
||
name @code{foo}, which may cause other problems if many symbols end up
|
||
with this name.
|
||
|
||
@item unknown symbol type @code{0x@var{nn}}
|
||
|
||
The symbol information contains new data types that @value{GDBN} does
|
||
not yet know how to read. @code{0x@var{nn}} is the symbol type of the
|
||
uncomprehended information, in hexadecimal.
|
||
|
||
@value{GDBN} circumvents the error by ignoring this symbol information.
|
||
This usually allows you to debug your program, though certain symbols
|
||
are not accessible. If you encounter such a problem and feel like
|
||
debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
|
||
on @code{complain}, then go up to the function @code{read_dbx_symtab}
|
||
and examine @code{*bufp} to see the symbol.
|
||
|
||
@item stub type has NULL name
|
||
|
||
@value{GDBN} could not find the full definition for a struct or class.
|
||
|
||
@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
|
||
The symbol information for a C@t{++} member function is missing some
|
||
information that recent versions of the compiler should have output for
|
||
it.
|
||
|
||
@item info mismatch between compiler and debugger
|
||
|
||
@value{GDBN} could not parse a type specification output by the compiler.
|
||
|
||
@end table
|
||
|
||
@node Data Files
|
||
@section GDB Data Files
|
||
|
||
@cindex prefix for data files
|
||
@value{GDBN} will sometimes read an auxiliary data file. These files
|
||
are kept in a directory known as the @dfn{data directory}.
|
||
|
||
You can set the data directory's name, and view the name @value{GDBN}
|
||
is currently using.
|
||
|
||
@table @code
|
||
@kindex set data-directory
|
||
@item set data-directory @var{directory}
|
||
Set the directory which @value{GDBN} searches for auxiliary data files
|
||
to @var{directory}.
|
||
|
||
@kindex show data-directory
|
||
@item show data-directory
|
||
Show the directory @value{GDBN} searches for auxiliary data files.
|
||
@end table
|
||
|
||
@cindex default data directory
|
||
@cindex @samp{--with-gdb-datadir}
|
||
You can set the default data directory by using the configure-time
|
||
@samp{--with-gdb-datadir} option. If the data directory is inside
|
||
@value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
|
||
@samp{--exec-prefix}), then the default data directory will be updated
|
||
automatically if the installed @value{GDBN} is moved to a new
|
||
location.
|
||
|
||
The data directory may also be specified with the
|
||
@code{--data-directory} command line option.
|
||
@xref{Mode Options}.
|
||
|
||
@node Targets
|
||
@chapter Specifying a Debugging Target
|
||
|
||
@cindex debugging target
|
||
A @dfn{target} is the execution environment occupied by your program.
|
||
|
||
Often, @value{GDBN} runs in the same host environment as your program;
|
||
in that case, the debugging target is specified as a side effect when
|
||
you use the @code{file} or @code{core} commands. When you need more
|
||
flexibility---for example, running @value{GDBN} on a physically separate
|
||
host, or controlling a standalone system over a serial port or a
|
||
realtime system over a TCP/IP connection---you can use the @code{target}
|
||
command to specify one of the target types configured for @value{GDBN}
|
||
(@pxref{Target Commands, ,Commands for Managing Targets}).
|
||
|
||
@cindex target architecture
|
||
It is possible to build @value{GDBN} for several different @dfn{target
|
||
architectures}. When @value{GDBN} is built like that, you can choose
|
||
one of the available architectures with the @kbd{set architecture}
|
||
command.
|
||
|
||
@table @code
|
||
@kindex set architecture
|
||
@kindex show architecture
|
||
@item set architecture @var{arch}
|
||
This command sets the current target architecture to @var{arch}. The
|
||
value of @var{arch} can be @code{"auto"}, in addition to one of the
|
||
supported architectures.
|
||
|
||
@item show architecture
|
||
Show the current target architecture.
|
||
|
||
@item set processor
|
||
@itemx processor
|
||
@kindex set processor
|
||
@kindex show processor
|
||
These are alias commands for, respectively, @code{set architecture}
|
||
and @code{show architecture}.
|
||
@end table
|
||
|
||
@menu
|
||
* Active Targets:: Active targets
|
||
* Target Commands:: Commands for managing targets
|
||
* Byte Order:: Choosing target byte order
|
||
@end menu
|
||
|
||
@node Active Targets
|
||
@section Active Targets
|
||
|
||
@cindex stacking targets
|
||
@cindex active targets
|
||
@cindex multiple targets
|
||
|
||
There are multiple classes of targets such as: processes, executable files or
|
||
recording sessions. Core files belong to the process class, making core file
|
||
and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
|
||
on multiple active targets, one in each class. This allows you to (for
|
||
example) start a process and inspect its activity, while still having access to
|
||
the executable file after the process finishes. Or if you start process
|
||
recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
|
||
presented a virtual layer of the recording target, while the process target
|
||
remains stopped at the chronologically last point of the process execution.
|
||
|
||
Use the @code{core-file} and @code{exec-file} commands to select a new core
|
||
file or executable target (@pxref{Files, ,Commands to Specify Files}). To
|
||
specify as a target a process that is already running, use the @code{attach}
|
||
command (@pxref{Attach, ,Debugging an Already-running Process}).
|
||
|
||
@node Target Commands
|
||
@section Commands for Managing Targets
|
||
|
||
@table @code
|
||
@item target @var{type} @var{parameters}
|
||
Connects the @value{GDBN} host environment to a target machine or
|
||
process. A target is typically a protocol for talking to debugging
|
||
facilities. You use the argument @var{type} to specify the type or
|
||
protocol of the target machine.
|
||
|
||
Further @var{parameters} are interpreted by the target protocol, but
|
||
typically include things like device names or host names to connect
|
||
with, process numbers, and baud rates.
|
||
|
||
The @code{target} command does not repeat if you press @key{RET} again
|
||
after executing the command.
|
||
|
||
@kindex help target
|
||
@item help target
|
||
Displays the names of all targets available. To display targets
|
||
currently selected, use either @code{info target} or @code{info files}
|
||
(@pxref{Files, ,Commands to Specify Files}).
|
||
|
||
@item help target @var{name}
|
||
Describe a particular target, including any parameters necessary to
|
||
select it.
|
||
|
||
@kindex set gnutarget
|
||
@item set gnutarget @var{args}
|
||
@value{GDBN} uses its own library BFD to read your files. @value{GDBN}
|
||
knows whether it is reading an @dfn{executable},
|
||
a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
|
||
with the @code{set gnutarget} command. Unlike most @code{target} commands,
|
||
with @code{gnutarget} the @code{target} refers to a program, not a machine.
|
||
|
||
@quotation
|
||
@emph{Warning:} To specify a file format with @code{set gnutarget},
|
||
you must know the actual BFD name.
|
||
@end quotation
|
||
|
||
@noindent
|
||
@xref{Files, , Commands to Specify Files}.
|
||
|
||
@kindex show gnutarget
|
||
@item show gnutarget
|
||
Use the @code{show gnutarget} command to display what file format
|
||
@code{gnutarget} is set to read. If you have not set @code{gnutarget},
|
||
@value{GDBN} will determine the file format for each file automatically,
|
||
and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
|
||
@end table
|
||
|
||
@cindex common targets
|
||
Here are some common targets (available, or not, depending on the GDB
|
||
configuration):
|
||
|
||
@table @code
|
||
@kindex target
|
||
@item target exec @var{program}
|
||
@cindex executable file target
|
||
An executable file. @samp{target exec @var{program}} is the same as
|
||
@samp{exec-file @var{program}}.
|
||
|
||
@item target core @var{filename}
|
||
@cindex core dump file target
|
||
A core dump file. @samp{target core @var{filename}} is the same as
|
||
@samp{core-file @var{filename}}.
|
||
|
||
@item target remote @var{medium}
|
||
@cindex remote target
|
||
A remote system connected to @value{GDBN} via a serial line or network
|
||
connection. This command tells @value{GDBN} to use its own remote
|
||
protocol over @var{medium} for debugging. @xref{Remote Debugging}.
|
||
|
||
For example, if you have a board connected to @file{/dev/ttya} on the
|
||
machine running @value{GDBN}, you could say:
|
||
|
||
@smallexample
|
||
target remote /dev/ttya
|
||
@end smallexample
|
||
|
||
@code{target remote} supports the @code{load} command. This is only
|
||
useful if you have some other way of getting the stub to the target
|
||
system, and you can put it somewhere in memory where it won't get
|
||
clobbered by the download.
|
||
|
||
@item target sim @r{[}@var{simargs}@r{]} @dots{}
|
||
@cindex built-in simulator target
|
||
Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
|
||
In general,
|
||
@smallexample
|
||
target sim
|
||
load
|
||
run
|
||
@end smallexample
|
||
@noindent
|
||
works; however, you cannot assume that a specific memory map, device
|
||
drivers, or even basic I/O is available, although some simulators do
|
||
provide these. For info about any processor-specific simulator details,
|
||
see the appropriate section in @ref{Embedded Processors, ,Embedded
|
||
Processors}.
|
||
|
||
@item target native
|
||
@cindex native target
|
||
Setup for local/native process debugging. Useful to make the
|
||
@code{run} command spawn native processes (likewise @code{attach},
|
||
etc.@:) even when @code{set auto-connect-native-target} is @code{off}
|
||
(@pxref{set auto-connect-native-target}).
|
||
|
||
@end table
|
||
|
||
Different targets are available on different configurations of @value{GDBN};
|
||
your configuration may have more or fewer targets.
|
||
|
||
Many remote targets require you to download the executable's code once
|
||
you've successfully established a connection. You may wish to control
|
||
various aspects of this process.
|
||
|
||
@table @code
|
||
|
||
@item set hash
|
||
@kindex set hash@r{, for remote monitors}
|
||
@cindex hash mark while downloading
|
||
This command controls whether a hash mark @samp{#} is displayed while
|
||
downloading a file to the remote monitor. If on, a hash mark is
|
||
displayed after each S-record is successfully downloaded to the
|
||
monitor.
|
||
|
||
@item show hash
|
||
@kindex show hash@r{, for remote monitors}
|
||
Show the current status of displaying the hash mark.
|
||
|
||
@item set debug monitor
|
||
@kindex set debug monitor
|
||
@cindex display remote monitor communications
|
||
Enable or disable display of communications messages between
|
||
@value{GDBN} and the remote monitor.
|
||
|
||
@item show debug monitor
|
||
@kindex show debug monitor
|
||
Show the current status of displaying communications between
|
||
@value{GDBN} and the remote monitor.
|
||
@end table
|
||
|
||
@table @code
|
||
|
||
@kindex load @var{filename} @var{offset}
|
||
@item load @var{filename} @var{offset}
|
||
@anchor{load}
|
||
Depending on what remote debugging facilities are configured into
|
||
@value{GDBN}, the @code{load} command may be available. Where it exists, it
|
||
is meant to make @var{filename} (an executable) available for debugging
|
||
on the remote system---by downloading, or dynamic linking, for example.
|
||
@code{load} also records the @var{filename} symbol table in @value{GDBN}, like
|
||
the @code{add-symbol-file} command.
|
||
|
||
If your @value{GDBN} does not have a @code{load} command, attempting to
|
||
execute it gets the error message ``@code{You can't do that when your
|
||
target is @dots{}}''
|
||
|
||
The file is loaded at whatever address is specified in the executable.
|
||
For some object file formats, you can specify the load address when you
|
||
link the program; for other formats, like a.out, the object file format
|
||
specifies a fixed address.
|
||
@c FIXME! This would be a good place for an xref to the GNU linker doc.
|
||
|
||
It is also possible to tell @value{GDBN} to load the executable file at a
|
||
specific offset described by the optional argument @var{offset}. When
|
||
@var{offset} is provided, @var{filename} must also be provided.
|
||
|
||
Depending on the remote side capabilities, @value{GDBN} may be able to
|
||
load programs into flash memory.
|
||
|
||
@code{load} does not repeat if you press @key{RET} again after using it.
|
||
@end table
|
||
|
||
@table @code
|
||
|
||
@kindex flash-erase
|
||
@item flash-erase
|
||
@anchor{flash-erase}
|
||
|
||
Erases all known flash memory regions on the target.
|
||
|
||
@end table
|
||
|
||
@node Byte Order
|
||
@section Choosing Target Byte Order
|
||
|
||
@cindex choosing target byte order
|
||
@cindex target byte order
|
||
|
||
Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
|
||
offer the ability to run either big-endian or little-endian byte
|
||
orders. Usually the executable or symbol will include a bit to
|
||
designate the endian-ness, and you will not need to worry about
|
||
which to use. However, you may still find it useful to adjust
|
||
@value{GDBN}'s idea of processor endian-ness manually.
|
||
|
||
@table @code
|
||
@kindex set endian
|
||
@item set endian big
|
||
Instruct @value{GDBN} to assume the target is big-endian.
|
||
|
||
@item set endian little
|
||
Instruct @value{GDBN} to assume the target is little-endian.
|
||
|
||
@item set endian auto
|
||
Instruct @value{GDBN} to use the byte order associated with the
|
||
executable.
|
||
|
||
@item show endian
|
||
Display @value{GDBN}'s current idea of the target byte order.
|
||
|
||
@end table
|
||
|
||
Note that these commands merely adjust interpretation of symbolic
|
||
data on the host, and that they have absolutely no effect on the
|
||
target system.
|
||
|
||
|
||
@node Remote Debugging
|
||
@chapter Debugging Remote Programs
|
||
@cindex remote debugging
|
||
|
||
If you are trying to debug a program running on a machine that cannot run
|
||
@value{GDBN} in the usual way, it is often useful to use remote debugging.
|
||
For example, you might use remote debugging on an operating system kernel,
|
||
or on a small system which does not have a general purpose operating system
|
||
powerful enough to run a full-featured debugger.
|
||
|
||
Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
|
||
to make this work with particular debugging targets. In addition,
|
||
@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
|
||
but not specific to any particular target system) which you can use if you
|
||
write the remote stubs---the code that runs on the remote system to
|
||
communicate with @value{GDBN}.
|
||
|
||
Other remote targets may be available in your
|
||
configuration of @value{GDBN}; use @code{help target} to list them.
|
||
|
||
@menu
|
||
* Connecting:: Connecting to a remote target
|
||
* File Transfer:: Sending files to a remote system
|
||
* Server:: Using the gdbserver program
|
||
* Remote Configuration:: Remote configuration
|
||
* Remote Stub:: Implementing a remote stub
|
||
@end menu
|
||
|
||
@node Connecting
|
||
@section Connecting to a Remote Target
|
||
@cindex remote debugging, connecting
|
||
@cindex @code{gdbserver}, connecting
|
||
@cindex remote debugging, types of connections
|
||
@cindex @code{gdbserver}, types of connections
|
||
@cindex @code{gdbserver}, @code{target remote} mode
|
||
@cindex @code{gdbserver}, @code{target extended-remote} mode
|
||
|
||
This section describes how to connect to a remote target, including the
|
||
types of connections and their differences, how to set up executable and
|
||
symbol files on the host and target, and the commands used for
|
||
connecting to and disconnecting from the remote target.
|
||
|
||
@subsection Types of Remote Connections
|
||
|
||
@value{GDBN} supports two types of remote connections, @code{target remote}
|
||
mode and @code{target extended-remote} mode. Note that many remote targets
|
||
support only @code{target remote} mode. There are several major
|
||
differences between the two types of connections, enumerated here:
|
||
|
||
@table @asis
|
||
|
||
@cindex remote debugging, detach and program exit
|
||
@item Result of detach or program exit
|
||
@strong{With target remote mode:} When the debugged program exits or you
|
||
detach from it, @value{GDBN} disconnects from the target. When using
|
||
@code{gdbserver}, @code{gdbserver} will exit.
|
||
|
||
@strong{With target extended-remote mode:} When the debugged program exits or
|
||
you detach from it, @value{GDBN} remains connected to the target, even
|
||
though no program is running. You can rerun the program, attach to a
|
||
running program, or use @code{monitor} commands specific to the target.
|
||
|
||
When using @code{gdbserver} in this case, it does not exit unless it was
|
||
invoked using the @option{--once} option. If the @option{--once} option
|
||
was not used, you can ask @code{gdbserver} to exit using the
|
||
@code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
|
||
|
||
@item Specifying the program to debug
|
||
For both connection types you use the @code{file} command to specify the
|
||
program on the host system. If you are using @code{gdbserver} there are
|
||
some differences in how to specify the location of the program on the
|
||
target.
|
||
|
||
@strong{With target remote mode:} You must either specify the program to debug
|
||
on the @code{gdbserver} command line or use the @option{--attach} option
|
||
(@pxref{Attaching to a program,,Attaching to a Running Program}).
|
||
|
||
@cindex @option{--multi}, @code{gdbserver} option
|
||
@strong{With target extended-remote mode:} You may specify the program to debug
|
||
on the @code{gdbserver} command line, or you can load the program or attach
|
||
to it using @value{GDBN} commands after connecting to @code{gdbserver}.
|
||
|
||
@anchor{--multi Option in Types of Remote Connnections}
|
||
You can start @code{gdbserver} without supplying an initial command to run
|
||
or process ID to attach. To do this, use the @option{--multi} command line
|
||
option. Then you can connect using @code{target extended-remote} and start
|
||
the program you want to debug (see below for details on using the
|
||
@code{run} command in this scenario). Note that the conditions under which
|
||
@code{gdbserver} terminates depend on how @value{GDBN} connects to it
|
||
(@code{target remote} or @code{target extended-remote}). The
|
||
@option{--multi} option to @code{gdbserver} has no influence on that.
|
||
|
||
@item The @code{run} command
|
||
@strong{With target remote mode:} The @code{run} command is not
|
||
supported. Once a connection has been established, you can use all
|
||
the usual @value{GDBN} commands to examine and change data. The
|
||
remote program is already running, so you can use commands like
|
||
@kbd{step} and @kbd{continue}.
|
||
|
||
@strong{With target extended-remote mode:} The @code{run} command is
|
||
supported. The @code{run} command uses the value set by
|
||
@code{set remote exec-file} (@pxref{set remote exec-file}) to select
|
||
the program to run. Command line arguments are supported, except for
|
||
wildcard expansion and I/O redirection (@pxref{Arguments}).
|
||
|
||
If you specify the program to debug on the command line, then the
|
||
@code{run} command is not required to start execution, and you can
|
||
resume using commands like @kbd{step} and @kbd{continue} as with
|
||
@code{target remote} mode.
|
||
|
||
@anchor{Attaching in Types of Remote Connections}
|
||
@item Attaching
|
||
@strong{With target remote mode:} The @value{GDBN} command @code{attach} is
|
||
not supported. To attach to a running program using @code{gdbserver}, you
|
||
must use the @option{--attach} option (@pxref{Running gdbserver}).
|
||
|
||
@strong{With target extended-remote mode:} To attach to a running program,
|
||
you may use the @code{attach} command after the connection has been
|
||
established. If you are using @code{gdbserver}, you may also invoke
|
||
@code{gdbserver} using the @option{--attach} option
|
||
(@pxref{Running gdbserver}).
|
||
|
||
@end table
|
||
|
||
@anchor{Host and target files}
|
||
@subsection Host and Target Files
|
||
@cindex remote debugging, symbol files
|
||
@cindex symbol files, remote debugging
|
||
|
||
@value{GDBN}, running on the host, needs access to symbol and debugging
|
||
information for your program running on the target. This requires
|
||
access to an unstripped copy of your program, and possibly any associated
|
||
symbol files. Note that this section applies equally to both @code{target
|
||
remote} mode and @code{target extended-remote} mode.
|
||
|
||
Some remote targets (@pxref{qXfer executable filename read}, and
|
||
@pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
|
||
the same connection used to communicate with @value{GDBN}. With such a
|
||
target, if the remote program is unstripped, the only command you need is
|
||
@code{target remote} (or @code{target extended-remote}).
|
||
|
||
If the remote program is stripped, or the target does not support remote
|
||
program file access, start up @value{GDBN} using the name of the local
|
||
unstripped copy of your program as the first argument, or use the
|
||
@code{file} command. Use @code{set sysroot} to specify the location (on
|
||
the host) of target libraries (unless your @value{GDBN} was compiled with
|
||
the correct sysroot using @code{--with-sysroot}). Alternatively, you
|
||
may use @code{set solib-search-path} to specify how @value{GDBN} locates
|
||
target libraries.
|
||
|
||
The symbol file and target libraries must exactly match the executable
|
||
and libraries on the target, with one exception: the files on the host
|
||
system should not be stripped, even if the files on the target system
|
||
are. Mismatched or missing files will lead to confusing results
|
||
during debugging. On @sc{gnu}/Linux targets, mismatched or missing
|
||
files may also prevent @code{gdbserver} from debugging multi-threaded
|
||
programs.
|
||
|
||
@subsection Remote Connection Commands
|
||
@cindex remote connection commands
|
||
@value{GDBN} can communicate with the target over a serial line, or
|
||
over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
|
||
each case, @value{GDBN} uses the same protocol for debugging your
|
||
program; only the medium carrying the debugging packets varies. The
|
||
@code{target remote} and @code{target extended-remote} commands
|
||
establish a connection to the target. Both commands accept the same
|
||
arguments, which indicate the medium to use:
|
||
|
||
@table @code
|
||
|
||
@item target remote @var{serial-device}
|
||
@itemx target extended-remote @var{serial-device}
|
||
@cindex serial line, @code{target remote}
|
||
Use @var{serial-device} to communicate with the target. For example,
|
||
to use a serial line connected to the device named @file{/dev/ttyb}:
|
||
|
||
@smallexample
|
||
target remote /dev/ttyb
|
||
@end smallexample
|
||
|
||
If you're using a serial line, you may want to give @value{GDBN} the
|
||
@samp{--baud} option, or use the @code{set serial baud} command
|
||
(@pxref{Remote Configuration, set serial baud}) before the
|
||
@code{target} command.
|
||
|
||
@item target remote @code{@var{host}:@var{port}}
|
||
@itemx target remote @code{tcp:@var{host}:@var{port}}
|
||
@itemx target extended-remote @code{@var{host}:@var{port}}
|
||
@itemx target extended-remote @code{tcp:@var{host}:@var{port}}
|
||
@cindex @acronym{TCP} port, @code{target remote}
|
||
Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
|
||
The @var{host} may be either a host name or a numeric @acronym{IP}
|
||
address; @var{port} must be a decimal number. The @var{host} could be
|
||
the target machine itself, if it is directly connected to the net, or
|
||
it might be a terminal server which in turn has a serial line to the
|
||
target.
|
||
|
||
For example, to connect to port 2828 on a terminal server named
|
||
@code{manyfarms}:
|
||
|
||
@smallexample
|
||
target remote manyfarms:2828
|
||
@end smallexample
|
||
|
||
If your remote target is actually running on the same machine as your
|
||
debugger session (e.g.@: a simulator for your target running on the
|
||
same host), you can omit the hostname. For example, to connect to
|
||
port 1234 on your local machine:
|
||
|
||
@smallexample
|
||
target remote :1234
|
||
@end smallexample
|
||
@noindent
|
||
|
||
Note that the colon is still required here.
|
||
|
||
@item target remote @code{udp:@var{host}:@var{port}}
|
||
@itemx target extended-remote @code{udp:@var{host}:@var{port}}
|
||
@cindex @acronym{UDP} port, @code{target remote}
|
||
Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
|
||
connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
|
||
|
||
@smallexample
|
||
target remote udp:manyfarms:2828
|
||
@end smallexample
|
||
|
||
When using a @acronym{UDP} connection for remote debugging, you should
|
||
keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
|
||
can silently drop packets on busy or unreliable networks, which will
|
||
cause havoc with your debugging session.
|
||
|
||
@item target remote | @var{command}
|
||
@itemx target extended-remote | @var{command}
|
||
@cindex pipe, @code{target remote} to
|
||
Run @var{command} in the background and communicate with it using a
|
||
pipe. The @var{command} is a shell command, to be parsed and expanded
|
||
by the system's command shell, @code{/bin/sh}; it should expect remote
|
||
protocol packets on its standard input, and send replies on its
|
||
standard output. You could use this to run a stand-alone simulator
|
||
that speaks the remote debugging protocol, to make net connections
|
||
using programs like @code{ssh}, or for other similar tricks.
|
||
|
||
If @var{command} closes its standard output (perhaps by exiting),
|
||
@value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
|
||
program has already exited, this will have no effect.)
|
||
|
||
@end table
|
||
|
||
@cindex interrupting remote programs
|
||
@cindex remote programs, interrupting
|
||
Whenever @value{GDBN} is waiting for the remote program, if you type the
|
||
interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
|
||
program. This may or may not succeed, depending in part on the hardware
|
||
and the serial drivers the remote system uses. If you type the
|
||
interrupt character once again, @value{GDBN} displays this prompt:
|
||
|
||
@smallexample
|
||
Interrupted while waiting for the program.
|
||
Give up (and stop debugging it)? (y or n)
|
||
@end smallexample
|
||
|
||
In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
|
||
the remote debugging session. (If you decide you want to try again later,
|
||
you can use @kbd{target remote} again to connect once more.) If you type
|
||
@kbd{n}, @value{GDBN} goes back to waiting.
|
||
|
||
In @code{target extended-remote} mode, typing @kbd{n} will leave
|
||
@value{GDBN} connected to the target.
|
||
|
||
@table @code
|
||
@kindex detach (remote)
|
||
@item detach
|
||
When you have finished debugging the remote program, you can use the
|
||
@code{detach} command to release it from @value{GDBN} control.
|
||
Detaching from the target normally resumes its execution, but the results
|
||
will depend on your particular remote stub. After the @code{detach}
|
||
command in @code{target remote} mode, @value{GDBN} is free to connect to
|
||
another target. In @code{target extended-remote} mode, @value{GDBN} is
|
||
still connected to the target.
|
||
|
||
@kindex disconnect
|
||
@item disconnect
|
||
The @code{disconnect} command closes the connection to the target, and
|
||
the target is generally not resumed. It will wait for @value{GDBN}
|
||
(this instance or another one) to connect and continue debugging. After
|
||
the @code{disconnect} command, @value{GDBN} is again free to connect to
|
||
another target.
|
||
|
||
@cindex send command to remote monitor
|
||
@cindex extend @value{GDBN} for remote targets
|
||
@cindex add new commands for external monitor
|
||
@kindex monitor
|
||
@item monitor @var{cmd}
|
||
This command allows you to send arbitrary commands directly to the
|
||
remote monitor. Since @value{GDBN} doesn't care about the commands it
|
||
sends like this, this command is the way to extend @value{GDBN}---you
|
||
can add new commands that only the external monitor will understand
|
||
and implement.
|
||
@end table
|
||
|
||
@node File Transfer
|
||
@section Sending files to a remote system
|
||
@cindex remote target, file transfer
|
||
@cindex file transfer
|
||
@cindex sending files to remote systems
|
||
|
||
Some remote targets offer the ability to transfer files over the same
|
||
connection used to communicate with @value{GDBN}. This is convenient
|
||
for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
|
||
running @code{gdbserver} over a network interface. For other targets,
|
||
e.g.@: embedded devices with only a single serial port, this may be
|
||
the only way to upload or download files.
|
||
|
||
Not all remote targets support these commands.
|
||
|
||
@table @code
|
||
@kindex remote put
|
||
@item remote put @var{hostfile} @var{targetfile}
|
||
Copy file @var{hostfile} from the host system (the machine running
|
||
@value{GDBN}) to @var{targetfile} on the target system.
|
||
|
||
@kindex remote get
|
||
@item remote get @var{targetfile} @var{hostfile}
|
||
Copy file @var{targetfile} from the target system to @var{hostfile}
|
||
on the host system.
|
||
|
||
@kindex remote delete
|
||
@item remote delete @var{targetfile}
|
||
Delete @var{targetfile} from the target system.
|
||
|
||
@end table
|
||
|
||
@node Server
|
||
@section Using the @code{gdbserver} Program
|
||
|
||
@kindex gdbserver
|
||
@cindex remote connection without stubs
|
||
@code{gdbserver} is a control program for Unix-like systems, which
|
||
allows you to connect your program with a remote @value{GDBN} via
|
||
@code{target remote} or @code{target extended-remote}---but without
|
||
linking in the usual debugging stub.
|
||
|
||
@code{gdbserver} is not a complete replacement for the debugging stubs,
|
||
because it requires essentially the same operating-system facilities
|
||
that @value{GDBN} itself does. In fact, a system that can run
|
||
@code{gdbserver} to connect to a remote @value{GDBN} could also run
|
||
@value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
|
||
because it is a much smaller program than @value{GDBN} itself. It is
|
||
also easier to port than all of @value{GDBN}, so you may be able to get
|
||
started more quickly on a new system by using @code{gdbserver}.
|
||
Finally, if you develop code for real-time systems, you may find that
|
||
the tradeoffs involved in real-time operation make it more convenient to
|
||
do as much development work as possible on another system, for example
|
||
by cross-compiling. You can use @code{gdbserver} to make a similar
|
||
choice for debugging.
|
||
|
||
@value{GDBN} and @code{gdbserver} communicate via either a serial line
|
||
or a TCP connection, using the standard @value{GDBN} remote serial
|
||
protocol.
|
||
|
||
@quotation
|
||
@emph{Warning:} @code{gdbserver} does not have any built-in security.
|
||
Do not run @code{gdbserver} connected to any public network; a
|
||
@value{GDBN} connection to @code{gdbserver} provides access to the
|
||
target system with the same privileges as the user running
|
||
@code{gdbserver}.
|
||
@end quotation
|
||
|
||
@anchor{Running gdbserver}
|
||
@subsection Running @code{gdbserver}
|
||
@cindex arguments, to @code{gdbserver}
|
||
@cindex @code{gdbserver}, command-line arguments
|
||
|
||
Run @code{gdbserver} on the target system. You need a copy of the
|
||
program you want to debug, including any libraries it requires.
|
||
@code{gdbserver} does not need your program's symbol table, so you can
|
||
strip the program if necessary to save space. @value{GDBN} on the host
|
||
system does all the symbol handling.
|
||
|
||
To use the server, you must tell it how to communicate with @value{GDBN};
|
||
the name of your program; and the arguments for your program. The usual
|
||
syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
|
||
@end smallexample
|
||
|
||
@var{comm} is either a device name (to use a serial line), or a TCP
|
||
hostname and portnumber, or @code{-} or @code{stdio} to use
|
||
stdin/stdout of @code{gdbserver}.
|
||
For example, to debug Emacs with the argument
|
||
@samp{foo.txt} and communicate with @value{GDBN} over the serial port
|
||
@file{/dev/com1}:
|
||
|
||
@smallexample
|
||
target> gdbserver /dev/com1 emacs foo.txt
|
||
@end smallexample
|
||
|
||
@code{gdbserver} waits passively for the host @value{GDBN} to communicate
|
||
with it.
|
||
|
||
To use a TCP connection instead of a serial line:
|
||
|
||
@smallexample
|
||
target> gdbserver host:2345 emacs foo.txt
|
||
@end smallexample
|
||
|
||
The only difference from the previous example is the first argument,
|
||
specifying that you are communicating with the host @value{GDBN} via
|
||
TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
|
||
expect a TCP connection from machine @samp{host} to local TCP port 2345.
|
||
(Currently, the @samp{host} part is ignored.) You can choose any number
|
||
you want for the port number as long as it does not conflict with any
|
||
TCP ports already in use on the target system (for example, @code{23} is
|
||
reserved for @code{telnet}).@footnote{If you choose a port number that
|
||
conflicts with another service, @code{gdbserver} prints an error message
|
||
and exits.} You must use the same port number with the host @value{GDBN}
|
||
@code{target remote} command.
|
||
|
||
The @code{stdio} connection is useful when starting @code{gdbserver}
|
||
with ssh:
|
||
|
||
@smallexample
|
||
(gdb) target remote | ssh -T hostname gdbserver - hello
|
||
@end smallexample
|
||
|
||
The @samp{-T} option to ssh is provided because we don't need a remote pty,
|
||
and we don't want escape-character handling. Ssh does this by default when
|
||
a command is provided, the flag is provided to make it explicit.
|
||
You could elide it if you want to.
|
||
|
||
Programs started with stdio-connected gdbserver have @file{/dev/null} for
|
||
@code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
|
||
display through a pipe connected to gdbserver.
|
||
Both @code{stdout} and @code{stderr} use the same pipe.
|
||
|
||
@anchor{Attaching to a program}
|
||
@subsubsection Attaching to a Running Program
|
||
@cindex attach to a program, @code{gdbserver}
|
||
@cindex @option{--attach}, @code{gdbserver} option
|
||
|
||
On some targets, @code{gdbserver} can also attach to running programs.
|
||
This is accomplished via the @code{--attach} argument. The syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver --attach @var{comm} @var{pid}
|
||
@end smallexample
|
||
|
||
@var{pid} is the process ID of a currently running process. It isn't
|
||
necessary to point @code{gdbserver} at a binary for the running process.
|
||
|
||
In @code{target extended-remote} mode, you can also attach using the
|
||
@value{GDBN} attach command
|
||
(@pxref{Attaching in Types of Remote Connections}).
|
||
|
||
@pindex pidof
|
||
You can debug processes by name instead of process ID if your target has the
|
||
@code{pidof} utility:
|
||
|
||
@smallexample
|
||
target> gdbserver --attach @var{comm} `pidof @var{program}`
|
||
@end smallexample
|
||
|
||
In case more than one copy of @var{program} is running, or @var{program}
|
||
has multiple threads, most versions of @code{pidof} support the
|
||
@code{-s} option to only return the first process ID.
|
||
|
||
@subsubsection TCP port allocation lifecycle of @code{gdbserver}
|
||
|
||
This section applies only when @code{gdbserver} is run to listen on a TCP
|
||
port.
|
||
|
||
@code{gdbserver} normally terminates after all of its debugged processes have
|
||
terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
|
||
extended-remote}, @code{gdbserver} stays running even with no processes left.
|
||
@value{GDBN} normally terminates the spawned debugged process on its exit,
|
||
which normally also terminates @code{gdbserver} in the @kbd{target remote}
|
||
mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
|
||
cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
|
||
stays running even in the @kbd{target remote} mode.
|
||
|
||
When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
|
||
Such reconnecting is useful for features like @ref{disconnected tracing}. For
|
||
completeness, at most one @value{GDBN} can be connected at a time.
|
||
|
||
@cindex @option{--once}, @code{gdbserver} option
|
||
By default, @code{gdbserver} keeps the listening TCP port open, so that
|
||
subsequent connections are possible. However, if you start @code{gdbserver}
|
||
with the @option{--once} option, it will stop listening for any further
|
||
connection attempts after connecting to the first @value{GDBN} session. This
|
||
means no further connections to @code{gdbserver} will be possible after the
|
||
first one. It also means @code{gdbserver} will terminate after the first
|
||
connection with remote @value{GDBN} has closed, even for unexpectedly closed
|
||
connections and even in the @kbd{target extended-remote} mode. The
|
||
@option{--once} option allows reusing the same port number for connecting to
|
||
multiple instances of @code{gdbserver} running on the same host, since each
|
||
instance closes its port after the first connection.
|
||
|
||
@anchor{Other Command-Line Arguments for gdbserver}
|
||
@subsubsection Other Command-Line Arguments for @code{gdbserver}
|
||
|
||
You can use the @option{--multi} option to start @code{gdbserver} without
|
||
specifying a program to debug or a process to attach to. Then you can
|
||
attach in @code{target extended-remote} mode and run or attach to a
|
||
program. For more information,
|
||
@pxref{--multi Option in Types of Remote Connnections}.
|
||
|
||
@cindex @option{--debug}, @code{gdbserver} option
|
||
The @option{--debug} option tells @code{gdbserver} to display extra
|
||
status information about the debugging process.
|
||
@cindex @option{--remote-debug}, @code{gdbserver} option
|
||
The @option{--remote-debug} option tells @code{gdbserver} to display
|
||
remote protocol debug output. These options are intended for
|
||
@code{gdbserver} development and for bug reports to the developers.
|
||
|
||
@cindex @option{--debug-format}, @code{gdbserver} option
|
||
The @option{--debug-format=option1[,option2,...]} option tells
|
||
@code{gdbserver} to include additional information in each output.
|
||
Possible options are:
|
||
|
||
@table @code
|
||
@item none
|
||
Turn off all extra information in debugging output.
|
||
@item all
|
||
Turn on all extra information in debugging output.
|
||
@item timestamps
|
||
Include a timestamp in each line of debugging output.
|
||
@end table
|
||
|
||
Options are processed in order. Thus, for example, if @option{none}
|
||
appears last then no additional information is added to debugging output.
|
||
|
||
@cindex @option{--wrapper}, @code{gdbserver} option
|
||
The @option{--wrapper} option specifies a wrapper to launch programs
|
||
for debugging. The option should be followed by the name of the
|
||
wrapper, then any command-line arguments to pass to the wrapper, then
|
||
@kbd{--} indicating the end of the wrapper arguments.
|
||
|
||
@code{gdbserver} runs the specified wrapper program with a combined
|
||
command line including the wrapper arguments, then the name of the
|
||
program to debug, then any arguments to the program. The wrapper
|
||
runs until it executes your program, and then @value{GDBN} gains control.
|
||
|
||
You can use any program that eventually calls @code{execve} with
|
||
its arguments as a wrapper. Several standard Unix utilities do
|
||
this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
|
||
with @code{exec "$@@"} will also work.
|
||
|
||
For example, you can use @code{env} to pass an environment variable to
|
||
the debugged program, without setting the variable in @code{gdbserver}'s
|
||
environment:
|
||
|
||
@smallexample
|
||
$ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
|
||
@end smallexample
|
||
|
||
@cindex @option{--selftest}
|
||
The @option{--selftest} option runs the self tests in @code{gdbserver}:
|
||
|
||
@smallexample
|
||
$ gdbserver --selftest
|
||
Ran 2 unit tests, 0 failed
|
||
@end smallexample
|
||
|
||
These tests are disabled in release.
|
||
@subsection Connecting to @code{gdbserver}
|
||
|
||
The basic procedure for connecting to the remote target is:
|
||
@itemize
|
||
|
||
@item
|
||
Run @value{GDBN} on the host system.
|
||
|
||
@item
|
||
Make sure you have the necessary symbol files
|
||
(@pxref{Host and target files}).
|
||
Load symbols for your application using the @code{file} command before you
|
||
connect. Use @code{set sysroot} to locate target libraries (unless your
|
||
@value{GDBN} was compiled with the correct sysroot using
|
||
@code{--with-sysroot}).
|
||
|
||
@item
|
||
Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
|
||
For TCP connections, you must start up @code{gdbserver} prior to using
|
||
the @code{target} command. Otherwise you may get an error whose
|
||
text depends on the host system, but which usually looks something like
|
||
@samp{Connection refused}. Don't use the @code{load}
|
||
command in @value{GDBN} when using @code{target remote} mode, since the
|
||
program is already on the target.
|
||
|
||
@end itemize
|
||
|
||
@anchor{Monitor Commands for gdbserver}
|
||
@subsection Monitor Commands for @code{gdbserver}
|
||
@cindex monitor commands, for @code{gdbserver}
|
||
|
||
During a @value{GDBN} session using @code{gdbserver}, you can use the
|
||
@code{monitor} command to send special requests to @code{gdbserver}.
|
||
Here are the available commands.
|
||
|
||
@table @code
|
||
@item monitor help
|
||
List the available monitor commands.
|
||
|
||
@item monitor set debug 0
|
||
@itemx monitor set debug 1
|
||
Disable or enable general debugging messages.
|
||
|
||
@item monitor set remote-debug 0
|
||
@itemx monitor set remote-debug 1
|
||
Disable or enable specific debugging messages associated with the remote
|
||
protocol (@pxref{Remote Protocol}).
|
||
|
||
@item monitor set debug-format option1@r{[},option2,...@r{]}
|
||
Specify additional text to add to debugging messages.
|
||
Possible options are:
|
||
|
||
@table @code
|
||
@item none
|
||
Turn off all extra information in debugging output.
|
||
@item all
|
||
Turn on all extra information in debugging output.
|
||
@item timestamps
|
||
Include a timestamp in each line of debugging output.
|
||
@end table
|
||
|
||
Options are processed in order. Thus, for example, if @option{none}
|
||
appears last then no additional information is added to debugging output.
|
||
|
||
@item monitor set libthread-db-search-path [PATH]
|
||
@cindex gdbserver, search path for @code{libthread_db}
|
||
When this command is issued, @var{path} is a colon-separated list of
|
||
directories to search for @code{libthread_db} (@pxref{Threads,,set
|
||
libthread-db-search-path}). If you omit @var{path},
|
||
@samp{libthread-db-search-path} will be reset to its default value.
|
||
|
||
The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
|
||
not supported in @code{gdbserver}.
|
||
|
||
@item monitor exit
|
||
Tell gdbserver to exit immediately. This command should be followed by
|
||
@code{disconnect} to close the debugging session. @code{gdbserver} will
|
||
detach from any attached processes and kill any processes it created.
|
||
Use @code{monitor exit} to terminate @code{gdbserver} at the end
|
||
of a multi-process mode debug session.
|
||
|
||
@end table
|
||
|
||
@subsection Tracepoints support in @code{gdbserver}
|
||
@cindex tracepoints support in @code{gdbserver}
|
||
|
||
On some targets, @code{gdbserver} supports tracepoints, fast
|
||
tracepoints and static tracepoints.
|
||
|
||
For fast or static tracepoints to work, a special library called the
|
||
@dfn{in-process agent} (IPA), must be loaded in the inferior process.
|
||
This library is built and distributed as an integral part of
|
||
@code{gdbserver}. In addition, support for static tracepoints
|
||
requires building the in-process agent library with static tracepoints
|
||
support. At present, the UST (LTTng Userspace Tracer,
|
||
@url{http://lttng.org/ust}) tracing engine is supported. This support
|
||
is automatically available if UST development headers are found in the
|
||
standard include path when @code{gdbserver} is built, or if
|
||
@code{gdbserver} was explicitly configured using @option{--with-ust}
|
||
to point at such headers. You can explicitly disable the support
|
||
using @option{--with-ust=no}.
|
||
|
||
There are several ways to load the in-process agent in your program:
|
||
|
||
@table @code
|
||
@item Specifying it as dependency at link time
|
||
|
||
You can link your program dynamically with the in-process agent
|
||
library. On most systems, this is accomplished by adding
|
||
@code{-linproctrace} to the link command.
|
||
|
||
@item Using the system's preloading mechanisms
|
||
|
||
You can force loading the in-process agent at startup time by using
|
||
your system's support for preloading shared libraries. Many Unixes
|
||
support the concept of preloading user defined libraries. In most
|
||
cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
|
||
in the environment. See also the description of @code{gdbserver}'s
|
||
@option{--wrapper} command line option.
|
||
|
||
@item Using @value{GDBN} to force loading the agent at run time
|
||
|
||
On some systems, you can force the inferior to load a shared library,
|
||
by calling a dynamic loader function in the inferior that takes care
|
||
of dynamically looking up and loading a shared library. On most Unix
|
||
systems, the function is @code{dlopen}. You'll use the @code{call}
|
||
command for that. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) call dlopen ("libinproctrace.so", ...)
|
||
@end smallexample
|
||
|
||
Note that on most Unix systems, for the @code{dlopen} function to be
|
||
available, the program needs to be linked with @code{-ldl}.
|
||
@end table
|
||
|
||
On systems that have a userspace dynamic loader, like most Unix
|
||
systems, when you connect to @code{gdbserver} using @code{target
|
||
remote}, you'll find that the program is stopped at the dynamic
|
||
loader's entry point, and no shared library has been loaded in the
|
||
program's address space yet, including the in-process agent. In that
|
||
case, before being able to use any of the fast or static tracepoints
|
||
features, you need to let the loader run and load the shared
|
||
libraries. The simplest way to do that is to run the program to the
|
||
main procedure. E.g., if debugging a C or C@t{++} program, start
|
||
@code{gdbserver} like so:
|
||
|
||
@smallexample
|
||
$ gdbserver :9999 myprogram
|
||
@end smallexample
|
||
|
||
Start GDB and connect to @code{gdbserver} like so, and run to main:
|
||
|
||
@smallexample
|
||
$ gdb myprogram
|
||
(@value{GDBP}) target remote myhost:9999
|
||
0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
|
||
(@value{GDBP}) b main
|
||
(@value{GDBP}) continue
|
||
@end smallexample
|
||
|
||
The in-process tracing agent library should now be loaded into the
|
||
process; you can confirm it with the @code{info sharedlibrary}
|
||
command, which will list @file{libinproctrace.so} as loaded in the
|
||
process. You are now ready to install fast tracepoints, list static
|
||
tracepoint markers, probe static tracepoints markers, and start
|
||
tracing.
|
||
|
||
@node Remote Configuration
|
||
@section Remote Configuration
|
||
|
||
@kindex set remote
|
||
@kindex show remote
|
||
This section documents the configuration options available when
|
||
debugging remote programs. For the options related to the File I/O
|
||
extensions of the remote protocol, see @ref{system,
|
||
system-call-allowed}.
|
||
|
||
@table @code
|
||
@item set remoteaddresssize @var{bits}
|
||
@cindex address size for remote targets
|
||
@cindex bits in remote address
|
||
Set the maximum size of address in a memory packet to the specified
|
||
number of bits. @value{GDBN} will mask off the address bits above
|
||
that number, when it passes addresses to the remote target. The
|
||
default value is the number of bits in the target's address.
|
||
|
||
@item show remoteaddresssize
|
||
Show the current value of remote address size in bits.
|
||
|
||
@item set serial baud @var{n}
|
||
@cindex baud rate for remote targets
|
||
Set the baud rate for the remote serial I/O to @var{n} baud. The
|
||
value is used to set the speed of the serial port used for debugging
|
||
remote targets.
|
||
|
||
@item show serial baud
|
||
Show the current speed of the remote connection.
|
||
|
||
@item set serial parity @var{parity}
|
||
Set the parity for the remote serial I/O. Supported values of @var{parity} are:
|
||
@code{even}, @code{none}, and @code{odd}. The default is @code{none}.
|
||
|
||
@item show serial parity
|
||
Show the current parity of the serial port.
|
||
|
||
@item set remotebreak
|
||
@cindex interrupt remote programs
|
||
@cindex BREAK signal instead of Ctrl-C
|
||
@anchor{set remotebreak}
|
||
If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
|
||
when you type @kbd{Ctrl-c} to interrupt the program running
|
||
on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
|
||
character instead. The default is off, since most remote systems
|
||
expect to see @samp{Ctrl-C} as the interrupt signal.
|
||
|
||
@item show remotebreak
|
||
Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
|
||
interrupt the remote program.
|
||
|
||
@item set remoteflow on
|
||
@itemx set remoteflow off
|
||
@kindex set remoteflow
|
||
Enable or disable hardware flow control (@code{RTS}/@code{CTS})
|
||
on the serial port used to communicate to the remote target.
|
||
|
||
@item show remoteflow
|
||
@kindex show remoteflow
|
||
Show the current setting of hardware flow control.
|
||
|
||
@item set remotelogbase @var{base}
|
||
Set the base (a.k.a.@: radix) of logging serial protocol
|
||
communications to @var{base}. Supported values of @var{base} are:
|
||
@code{ascii}, @code{octal}, and @code{hex}. The default is
|
||
@code{ascii}.
|
||
|
||
@item show remotelogbase
|
||
Show the current setting of the radix for logging remote serial
|
||
protocol.
|
||
|
||
@item set remotelogfile @var{file}
|
||
@cindex record serial communications on file
|
||
Record remote serial communications on the named @var{file}. The
|
||
default is not to record at all.
|
||
|
||
@item show remotelogfile.
|
||
Show the current setting of the file name on which to record the
|
||
serial communications.
|
||
|
||
@item set remotetimeout @var{num}
|
||
@cindex timeout for serial communications
|
||
@cindex remote timeout
|
||
Set the timeout limit to wait for the remote target to respond to
|
||
@var{num} seconds. The default is 2 seconds.
|
||
|
||
@item show remotetimeout
|
||
Show the current number of seconds to wait for the remote target
|
||
responses.
|
||
|
||
@cindex limit hardware breakpoints and watchpoints
|
||
@cindex remote target, limit break- and watchpoints
|
||
@anchor{set remote hardware-watchpoint-limit}
|
||
@anchor{set remote hardware-breakpoint-limit}
|
||
@item set remote hardware-watchpoint-limit @var{limit}
|
||
@itemx set remote hardware-breakpoint-limit @var{limit}
|
||
Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
|
||
watchpoints. A limit of -1, the default, is treated as unlimited.
|
||
|
||
@cindex limit hardware watchpoints length
|
||
@cindex remote target, limit watchpoints length
|
||
@anchor{set remote hardware-watchpoint-length-limit}
|
||
@item set remote hardware-watchpoint-length-limit @var{limit}
|
||
Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
|
||
a remote hardware watchpoint. A limit of -1, the default, is treated
|
||
as unlimited.
|
||
|
||
@item show remote hardware-watchpoint-length-limit
|
||
Show the current limit (in bytes) of the maximum length of
|
||
a remote hardware watchpoint.
|
||
|
||
@item set remote exec-file @var{filename}
|
||
@itemx show remote exec-file
|
||
@anchor{set remote exec-file}
|
||
@cindex executable file, for remote target
|
||
Select the file used for @code{run} with @code{target
|
||
extended-remote}. This should be set to a filename valid on the
|
||
target system. If it is not set, the target will use a default
|
||
filename (e.g.@: the last program run).
|
||
|
||
@item set remote interrupt-sequence
|
||
@cindex interrupt remote programs
|
||
@cindex select Ctrl-C, BREAK or BREAK-g
|
||
Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
|
||
@samp{BREAK-g} as the
|
||
sequence to the remote target in order to interrupt the execution.
|
||
@samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
|
||
is high level of serial line for some certain time.
|
||
Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
|
||
It is @code{BREAK} signal followed by character @code{g}.
|
||
|
||
@item show interrupt-sequence
|
||
Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
|
||
is sent by @value{GDBN} to interrupt the remote program.
|
||
@code{BREAK-g} is BREAK signal followed by @code{g} and
|
||
also known as Magic SysRq g.
|
||
|
||
@item set remote interrupt-on-connect
|
||
@cindex send interrupt-sequence on start
|
||
Specify whether interrupt-sequence is sent to remote target when
|
||
@value{GDBN} connects to it. This is mostly needed when you debug
|
||
Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
|
||
which is known as Magic SysRq g in order to connect @value{GDBN}.
|
||
|
||
@item show interrupt-on-connect
|
||
Show whether interrupt-sequence is sent
|
||
to remote target when @value{GDBN} connects to it.
|
||
|
||
@kindex set tcp
|
||
@kindex show tcp
|
||
@item set tcp auto-retry on
|
||
@cindex auto-retry, for remote TCP target
|
||
Enable auto-retry for remote TCP connections. This is useful if the remote
|
||
debugging agent is launched in parallel with @value{GDBN}; there is a race
|
||
condition because the agent may not become ready to accept the connection
|
||
before @value{GDBN} attempts to connect. When auto-retry is
|
||
enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
|
||
to establish the connection using the timeout specified by
|
||
@code{set tcp connect-timeout}.
|
||
|
||
@item set tcp auto-retry off
|
||
Do not auto-retry failed TCP connections.
|
||
|
||
@item show tcp auto-retry
|
||
Show the current auto-retry setting.
|
||
|
||
@item set tcp connect-timeout @var{seconds}
|
||
@itemx set tcp connect-timeout unlimited
|
||
@cindex connection timeout, for remote TCP target
|
||
@cindex timeout, for remote target connection
|
||
Set the timeout for establishing a TCP connection to the remote target to
|
||
@var{seconds}. The timeout affects both polling to retry failed connections
|
||
(enabled by @code{set tcp auto-retry on}) and waiting for connections
|
||
that are merely slow to complete, and represents an approximate cumulative
|
||
value. If @var{seconds} is @code{unlimited}, there is no timeout and
|
||
@value{GDBN} will keep attempting to establish a connection forever,
|
||
unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
|
||
|
||
@item show tcp connect-timeout
|
||
Show the current connection timeout setting.
|
||
@end table
|
||
|
||
@cindex remote packets, enabling and disabling
|
||
The @value{GDBN} remote protocol autodetects the packets supported by
|
||
your debugging stub. If you need to override the autodetection, you
|
||
can use these commands to enable or disable individual packets. Each
|
||
packet can be set to @samp{on} (the remote target supports this
|
||
packet), @samp{off} (the remote target does not support this packet),
|
||
or @samp{auto} (detect remote target support for this packet). They
|
||
all default to @samp{auto}. For more information about each packet,
|
||
see @ref{Remote Protocol}.
|
||
|
||
During normal use, you should not have to use any of these commands.
|
||
If you do, that may be a bug in your remote debugging stub, or a bug
|
||
in @value{GDBN}. You may want to report the problem to the
|
||
@value{GDBN} developers.
|
||
|
||
For each packet @var{name}, the command to enable or disable the
|
||
packet is @code{set remote @var{name}-packet}. The available settings
|
||
are:
|
||
|
||
@multitable @columnfractions 0.28 0.32 0.25
|
||
@item Command Name
|
||
@tab Remote Packet
|
||
@tab Related Features
|
||
|
||
@item @code{fetch-register}
|
||
@tab @code{p}
|
||
@tab @code{info registers}
|
||
|
||
@item @code{set-register}
|
||
@tab @code{P}
|
||
@tab @code{set}
|
||
|
||
@item @code{binary-download}
|
||
@tab @code{X}
|
||
@tab @code{load}, @code{set}
|
||
|
||
@item @code{read-aux-vector}
|
||
@tab @code{qXfer:auxv:read}
|
||
@tab @code{info auxv}
|
||
|
||
@item @code{symbol-lookup}
|
||
@tab @code{qSymbol}
|
||
@tab Detecting multiple threads
|
||
|
||
@item @code{attach}
|
||
@tab @code{vAttach}
|
||
@tab @code{attach}
|
||
|
||
@item @code{verbose-resume}
|
||
@tab @code{vCont}
|
||
@tab Stepping or resuming multiple threads
|
||
|
||
@item @code{run}
|
||
@tab @code{vRun}
|
||
@tab @code{run}
|
||
|
||
@item @code{software-breakpoint}
|
||
@tab @code{Z0}
|
||
@tab @code{break}
|
||
|
||
@item @code{hardware-breakpoint}
|
||
@tab @code{Z1}
|
||
@tab @code{hbreak}
|
||
|
||
@item @code{write-watchpoint}
|
||
@tab @code{Z2}
|
||
@tab @code{watch}
|
||
|
||
@item @code{read-watchpoint}
|
||
@tab @code{Z3}
|
||
@tab @code{rwatch}
|
||
|
||
@item @code{access-watchpoint}
|
||
@tab @code{Z4}
|
||
@tab @code{awatch}
|
||
|
||
@item @code{pid-to-exec-file}
|
||
@tab @code{qXfer:exec-file:read}
|
||
@tab @code{attach}, @code{run}
|
||
|
||
@item @code{target-features}
|
||
@tab @code{qXfer:features:read}
|
||
@tab @code{set architecture}
|
||
|
||
@item @code{library-info}
|
||
@tab @code{qXfer:libraries:read}
|
||
@tab @code{info sharedlibrary}
|
||
|
||
@item @code{memory-map}
|
||
@tab @code{qXfer:memory-map:read}
|
||
@tab @code{info mem}
|
||
|
||
@item @code{read-sdata-object}
|
||
@tab @code{qXfer:sdata:read}
|
||
@tab @code{print $_sdata}
|
||
|
||
@item @code{read-spu-object}
|
||
@tab @code{qXfer:spu:read}
|
||
@tab @code{info spu}
|
||
|
||
@item @code{write-spu-object}
|
||
@tab @code{qXfer:spu:write}
|
||
@tab @code{info spu}
|
||
|
||
@item @code{read-siginfo-object}
|
||
@tab @code{qXfer:siginfo:read}
|
||
@tab @code{print $_siginfo}
|
||
|
||
@item @code{write-siginfo-object}
|
||
@tab @code{qXfer:siginfo:write}
|
||
@tab @code{set $_siginfo}
|
||
|
||
@item @code{threads}
|
||
@tab @code{qXfer:threads:read}
|
||
@tab @code{info threads}
|
||
|
||
@item @code{get-thread-local-@*storage-address}
|
||
@tab @code{qGetTLSAddr}
|
||
@tab Displaying @code{__thread} variables
|
||
|
||
@item @code{get-thread-information-block-address}
|
||
@tab @code{qGetTIBAddr}
|
||
@tab Display MS-Windows Thread Information Block.
|
||
|
||
@item @code{search-memory}
|
||
@tab @code{qSearch:memory}
|
||
@tab @code{find}
|
||
|
||
@item @code{supported-packets}
|
||
@tab @code{qSupported}
|
||
@tab Remote communications parameters
|
||
|
||
@item @code{catch-syscalls}
|
||
@tab @code{QCatchSyscalls}
|
||
@tab @code{catch syscall}
|
||
|
||
@item @code{pass-signals}
|
||
@tab @code{QPassSignals}
|
||
@tab @code{handle @var{signal}}
|
||
|
||
@item @code{program-signals}
|
||
@tab @code{QProgramSignals}
|
||
@tab @code{handle @var{signal}}
|
||
|
||
@item @code{hostio-close-packet}
|
||
@tab @code{vFile:close}
|
||
@tab @code{remote get}, @code{remote put}
|
||
|
||
@item @code{hostio-open-packet}
|
||
@tab @code{vFile:open}
|
||
@tab @code{remote get}, @code{remote put}
|
||
|
||
@item @code{hostio-pread-packet}
|
||
@tab @code{vFile:pread}
|
||
@tab @code{remote get}, @code{remote put}
|
||
|
||
@item @code{hostio-pwrite-packet}
|
||
@tab @code{vFile:pwrite}
|
||
@tab @code{remote get}, @code{remote put}
|
||
|
||
@item @code{hostio-unlink-packet}
|
||
@tab @code{vFile:unlink}
|
||
@tab @code{remote delete}
|
||
|
||
@item @code{hostio-readlink-packet}
|
||
@tab @code{vFile:readlink}
|
||
@tab Host I/O
|
||
|
||
@item @code{hostio-fstat-packet}
|
||
@tab @code{vFile:fstat}
|
||
@tab Host I/O
|
||
|
||
@item @code{hostio-setfs-packet}
|
||
@tab @code{vFile:setfs}
|
||
@tab Host I/O
|
||
|
||
@item @code{noack-packet}
|
||
@tab @code{QStartNoAckMode}
|
||
@tab Packet acknowledgment
|
||
|
||
@item @code{osdata}
|
||
@tab @code{qXfer:osdata:read}
|
||
@tab @code{info os}
|
||
|
||
@item @code{query-attached}
|
||
@tab @code{qAttached}
|
||
@tab Querying remote process attach state.
|
||
|
||
@item @code{trace-buffer-size}
|
||
@tab @code{QTBuffer:size}
|
||
@tab @code{set trace-buffer-size}
|
||
|
||
@item @code{trace-status}
|
||
@tab @code{qTStatus}
|
||
@tab @code{tstatus}
|
||
|
||
@item @code{traceframe-info}
|
||
@tab @code{qXfer:traceframe-info:read}
|
||
@tab Traceframe info
|
||
|
||
@item @code{install-in-trace}
|
||
@tab @code{InstallInTrace}
|
||
@tab Install tracepoint in tracing
|
||
|
||
@item @code{disable-randomization}
|
||
@tab @code{QDisableRandomization}
|
||
@tab @code{set disable-randomization}
|
||
|
||
@item @code{startup-with-shell}
|
||
@tab @code{QStartupWithShell}
|
||
@tab @code{set startup-with-shell}
|
||
|
||
@item @code{environment-hex-encoded}
|
||
@tab @code{QEnvironmentHexEncoded}
|
||
@tab @code{set environment}
|
||
|
||
@item @code{environment-unset}
|
||
@tab @code{QEnvironmentUnset}
|
||
@tab @code{unset environment}
|
||
|
||
@item @code{environment-reset}
|
||
@tab @code{QEnvironmentReset}
|
||
@tab @code{Reset the inferior environment (i.e., unset user-set variables)}
|
||
|
||
@item @code{set-working-dir}
|
||
@tab @code{QSetWorkingDir}
|
||
@tab @code{set cwd}
|
||
|
||
@item @code{conditional-breakpoints-packet}
|
||
@tab @code{Z0 and Z1}
|
||
@tab @code{Support for target-side breakpoint condition evaluation}
|
||
|
||
@item @code{multiprocess-extensions}
|
||
@tab @code{multiprocess extensions}
|
||
@tab Debug multiple processes and remote process PID awareness
|
||
|
||
@item @code{swbreak-feature}
|
||
@tab @code{swbreak stop reason}
|
||
@tab @code{break}
|
||
|
||
@item @code{hwbreak-feature}
|
||
@tab @code{hwbreak stop reason}
|
||
@tab @code{hbreak}
|
||
|
||
@item @code{fork-event-feature}
|
||
@tab @code{fork stop reason}
|
||
@tab @code{fork}
|
||
|
||
@item @code{vfork-event-feature}
|
||
@tab @code{vfork stop reason}
|
||
@tab @code{vfork}
|
||
|
||
@item @code{exec-event-feature}
|
||
@tab @code{exec stop reason}
|
||
@tab @code{exec}
|
||
|
||
@item @code{thread-events}
|
||
@tab @code{QThreadEvents}
|
||
@tab Tracking thread lifetime.
|
||
|
||
@item @code{no-resumed-stop-reply}
|
||
@tab @code{no resumed thread left stop reply}
|
||
@tab Tracking thread lifetime.
|
||
|
||
@end multitable
|
||
|
||
@node Remote Stub
|
||
@section Implementing a Remote Stub
|
||
|
||
@cindex debugging stub, example
|
||
@cindex remote stub, example
|
||
@cindex stub example, remote debugging
|
||
The stub files provided with @value{GDBN} implement the target side of the
|
||
communication protocol, and the @value{GDBN} side is implemented in the
|
||
@value{GDBN} source file @file{remote.c}. Normally, you can simply allow
|
||
these subroutines to communicate, and ignore the details. (If you're
|
||
implementing your own stub file, you can still ignore the details: start
|
||
with one of the existing stub files. @file{sparc-stub.c} is the best
|
||
organized, and therefore the easiest to read.)
|
||
|
||
@cindex remote serial debugging, overview
|
||
To debug a program running on another machine (the debugging
|
||
@dfn{target} machine), you must first arrange for all the usual
|
||
prerequisites for the program to run by itself. For example, for a C
|
||
program, you need:
|
||
|
||
@enumerate
|
||
@item
|
||
A startup routine to set up the C runtime environment; these usually
|
||
have a name like @file{crt0}. The startup routine may be supplied by
|
||
your hardware supplier, or you may have to write your own.
|
||
|
||
@item
|
||
A C subroutine library to support your program's
|
||
subroutine calls, notably managing input and output.
|
||
|
||
@item
|
||
A way of getting your program to the other machine---for example, a
|
||
download program. These are often supplied by the hardware
|
||
manufacturer, but you may have to write your own from hardware
|
||
documentation.
|
||
@end enumerate
|
||
|
||
The next step is to arrange for your program to use a serial port to
|
||
communicate with the machine where @value{GDBN} is running (the @dfn{host}
|
||
machine). In general terms, the scheme looks like this:
|
||
|
||
@table @emph
|
||
@item On the host,
|
||
@value{GDBN} already understands how to use this protocol; when everything
|
||
else is set up, you can simply use the @samp{target remote} command
|
||
(@pxref{Targets,,Specifying a Debugging Target}).
|
||
|
||
@item On the target,
|
||
you must link with your program a few special-purpose subroutines that
|
||
implement the @value{GDBN} remote serial protocol. The file containing these
|
||
subroutines is called a @dfn{debugging stub}.
|
||
|
||
On certain remote targets, you can use an auxiliary program
|
||
@code{gdbserver} instead of linking a stub into your program.
|
||
@xref{Server,,Using the @code{gdbserver} Program}, for details.
|
||
@end table
|
||
|
||
The debugging stub is specific to the architecture of the remote
|
||
machine; for example, use @file{sparc-stub.c} to debug programs on
|
||
@sc{sparc} boards.
|
||
|
||
@cindex remote serial stub list
|
||
These working remote stubs are distributed with @value{GDBN}:
|
||
|
||
@table @code
|
||
|
||
@item i386-stub.c
|
||
@cindex @file{i386-stub.c}
|
||
@cindex Intel
|
||
@cindex i386
|
||
For Intel 386 and compatible architectures.
|
||
|
||
@item m68k-stub.c
|
||
@cindex @file{m68k-stub.c}
|
||
@cindex Motorola 680x0
|
||
@cindex m680x0
|
||
For Motorola 680x0 architectures.
|
||
|
||
@item sh-stub.c
|
||
@cindex @file{sh-stub.c}
|
||
@cindex Renesas
|
||
@cindex SH
|
||
For Renesas SH architectures.
|
||
|
||
@item sparc-stub.c
|
||
@cindex @file{sparc-stub.c}
|
||
@cindex Sparc
|
||
For @sc{sparc} architectures.
|
||
|
||
@item sparcl-stub.c
|
||
@cindex @file{sparcl-stub.c}
|
||
@cindex Fujitsu
|
||
@cindex SparcLite
|
||
For Fujitsu @sc{sparclite} architectures.
|
||
|
||
@end table
|
||
|
||
The @file{README} file in the @value{GDBN} distribution may list other
|
||
recently added stubs.
|
||
|
||
@menu
|
||
* Stub Contents:: What the stub can do for you
|
||
* Bootstrapping:: What you must do for the stub
|
||
* Debug Session:: Putting it all together
|
||
@end menu
|
||
|
||
@node Stub Contents
|
||
@subsection What the Stub Can Do for You
|
||
|
||
@cindex remote serial stub
|
||
The debugging stub for your architecture supplies these three
|
||
subroutines:
|
||
|
||
@table @code
|
||
@item set_debug_traps
|
||
@findex set_debug_traps
|
||
@cindex remote serial stub, initialization
|
||
This routine arranges for @code{handle_exception} to run when your
|
||
program stops. You must call this subroutine explicitly in your
|
||
program's startup code.
|
||
|
||
@item handle_exception
|
||
@findex handle_exception
|
||
@cindex remote serial stub, main routine
|
||
This is the central workhorse, but your program never calls it
|
||
explicitly---the setup code arranges for @code{handle_exception} to
|
||
run when a trap is triggered.
|
||
|
||
@code{handle_exception} takes control when your program stops during
|
||
execution (for example, on a breakpoint), and mediates communications
|
||
with @value{GDBN} on the host machine. This is where the communications
|
||
protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
|
||
representative on the target machine. It begins by sending summary
|
||
information on the state of your program, then continues to execute,
|
||
retrieving and transmitting any information @value{GDBN} needs, until you
|
||
execute a @value{GDBN} command that makes your program resume; at that point,
|
||
@code{handle_exception} returns control to your own code on the target
|
||
machine.
|
||
|
||
@item breakpoint
|
||
@cindex @code{breakpoint} subroutine, remote
|
||
Use this auxiliary subroutine to make your program contain a
|
||
breakpoint. Depending on the particular situation, this may be the only
|
||
way for @value{GDBN} to get control. For instance, if your target
|
||
machine has some sort of interrupt button, you won't need to call this;
|
||
pressing the interrupt button transfers control to
|
||
@code{handle_exception}---in effect, to @value{GDBN}. On some machines,
|
||
simply receiving characters on the serial port may also trigger a trap;
|
||
again, in that situation, you don't need to call @code{breakpoint} from
|
||
your own program---simply running @samp{target remote} from the host
|
||
@value{GDBN} session gets control.
|
||
|
||
Call @code{breakpoint} if none of these is true, or if you simply want
|
||
to make certain your program stops at a predetermined point for the
|
||
start of your debugging session.
|
||
@end table
|
||
|
||
@node Bootstrapping
|
||
@subsection What You Must Do for the Stub
|
||
|
||
@cindex remote stub, support routines
|
||
The debugging stubs that come with @value{GDBN} are set up for a particular
|
||
chip architecture, but they have no information about the rest of your
|
||
debugging target machine.
|
||
|
||
First of all you need to tell the stub how to communicate with the
|
||
serial port.
|
||
|
||
@table @code
|
||
@item int getDebugChar()
|
||
@findex getDebugChar
|
||
Write this subroutine to read a single character from the serial port.
|
||
It may be identical to @code{getchar} for your target system; a
|
||
different name is used to allow you to distinguish the two if you wish.
|
||
|
||
@item void putDebugChar(int)
|
||
@findex putDebugChar
|
||
Write this subroutine to write a single character to the serial port.
|
||
It may be identical to @code{putchar} for your target system; a
|
||
different name is used to allow you to distinguish the two if you wish.
|
||
@end table
|
||
|
||
@cindex control C, and remote debugging
|
||
@cindex interrupting remote targets
|
||
If you want @value{GDBN} to be able to stop your program while it is
|
||
running, you need to use an interrupt-driven serial driver, and arrange
|
||
for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
|
||
character). That is the character which @value{GDBN} uses to tell the
|
||
remote system to stop.
|
||
|
||
Getting the debugging target to return the proper status to @value{GDBN}
|
||
probably requires changes to the standard stub; one quick and dirty way
|
||
is to just execute a breakpoint instruction (the ``dirty'' part is that
|
||
@value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
|
||
|
||
Other routines you need to supply are:
|
||
|
||
@table @code
|
||
@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
|
||
@findex exceptionHandler
|
||
Write this function to install @var{exception_address} in the exception
|
||
handling tables. You need to do this because the stub does not have any
|
||
way of knowing what the exception handling tables on your target system
|
||
are like (for example, the processor's table might be in @sc{rom},
|
||
containing entries which point to a table in @sc{ram}).
|
||
The @var{exception_number} specifies the exception which should be changed;
|
||
its meaning is architecture-dependent (for example, different numbers
|
||
might represent divide by zero, misaligned access, etc). When this
|
||
exception occurs, control should be transferred directly to
|
||
@var{exception_address}, and the processor state (stack, registers,
|
||
and so on) should be just as it is when a processor exception occurs. So if
|
||
you want to use a jump instruction to reach @var{exception_address}, it
|
||
should be a simple jump, not a jump to subroutine.
|
||
|
||
For the 386, @var{exception_address} should be installed as an interrupt
|
||
gate so that interrupts are masked while the handler runs. The gate
|
||
should be at privilege level 0 (the most privileged level). The
|
||
@sc{sparc} and 68k stubs are able to mask interrupts themselves without
|
||
help from @code{exceptionHandler}.
|
||
|
||
@item void flush_i_cache()
|
||
@findex flush_i_cache
|
||
On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
|
||
instruction cache, if any, on your target machine. If there is no
|
||
instruction cache, this subroutine may be a no-op.
|
||
|
||
On target machines that have instruction caches, @value{GDBN} requires this
|
||
function to make certain that the state of your program is stable.
|
||
@end table
|
||
|
||
@noindent
|
||
You must also make sure this library routine is available:
|
||
|
||
@table @code
|
||
@item void *memset(void *, int, int)
|
||
@findex memset
|
||
This is the standard library function @code{memset} that sets an area of
|
||
memory to a known value. If you have one of the free versions of
|
||
@code{libc.a}, @code{memset} can be found there; otherwise, you must
|
||
either obtain it from your hardware manufacturer, or write your own.
|
||
@end table
|
||
|
||
If you do not use the GNU C compiler, you may need other standard
|
||
library subroutines as well; this varies from one stub to another,
|
||
but in general the stubs are likely to use any of the common library
|
||
subroutines which @code{@value{NGCC}} generates as inline code.
|
||
|
||
|
||
@node Debug Session
|
||
@subsection Putting it All Together
|
||
|
||
@cindex remote serial debugging summary
|
||
In summary, when your program is ready to debug, you must follow these
|
||
steps.
|
||
|
||
@enumerate
|
||
@item
|
||
Make sure you have defined the supporting low-level routines
|
||
(@pxref{Bootstrapping,,What You Must Do for the Stub}):
|
||
@display
|
||
@code{getDebugChar}, @code{putDebugChar},
|
||
@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
|
||
@end display
|
||
|
||
@item
|
||
Insert these lines in your program's startup code, before the main
|
||
procedure is called:
|
||
|
||
@smallexample
|
||
set_debug_traps();
|
||
breakpoint();
|
||
@end smallexample
|
||
|
||
On some machines, when a breakpoint trap is raised, the hardware
|
||
automatically makes the PC point to the instruction after the
|
||
breakpoint. If your machine doesn't do that, you may need to adjust
|
||
@code{handle_exception} to arrange for it to return to the instruction
|
||
after the breakpoint on this first invocation, so that your program
|
||
doesn't keep hitting the initial breakpoint instead of making
|
||
progress.
|
||
|
||
@item
|
||
For the 680x0 stub only, you need to provide a variable called
|
||
@code{exceptionHook}. Normally you just use:
|
||
|
||
@smallexample
|
||
void (*exceptionHook)() = 0;
|
||
@end smallexample
|
||
|
||
@noindent
|
||
but if before calling @code{set_debug_traps}, you set it to point to a
|
||
function in your program, that function is called when
|
||
@code{@value{GDBN}} continues after stopping on a trap (for example, bus
|
||
error). The function indicated by @code{exceptionHook} is called with
|
||
one parameter: an @code{int} which is the exception number.
|
||
|
||
@item
|
||
Compile and link together: your program, the @value{GDBN} debugging stub for
|
||
your target architecture, and the supporting subroutines.
|
||
|
||
@item
|
||
Make sure you have a serial connection between your target machine and
|
||
the @value{GDBN} host, and identify the serial port on the host.
|
||
|
||
@item
|
||
@c The "remote" target now provides a `load' command, so we should
|
||
@c document that. FIXME.
|
||
Download your program to your target machine (or get it there by
|
||
whatever means the manufacturer provides), and start it.
|
||
|
||
@item
|
||
Start @value{GDBN} on the host, and connect to the target
|
||
(@pxref{Connecting,,Connecting to a Remote Target}).
|
||
|
||
@end enumerate
|
||
|
||
@node Configurations
|
||
@chapter Configuration-Specific Information
|
||
|
||
While nearly all @value{GDBN} commands are available for all native and
|
||
cross versions of the debugger, there are some exceptions. This chapter
|
||
describes things that are only available in certain configurations.
|
||
|
||
There are three major categories of configurations: native
|
||
configurations, where the host and target are the same, embedded
|
||
operating system configurations, which are usually the same for several
|
||
different processor architectures, and bare embedded processors, which
|
||
are quite different from each other.
|
||
|
||
@menu
|
||
* Native::
|
||
* Embedded OS::
|
||
* Embedded Processors::
|
||
* Architectures::
|
||
@end menu
|
||
|
||
@node Native
|
||
@section Native
|
||
|
||
This section describes details specific to particular native
|
||
configurations.
|
||
|
||
@menu
|
||
* BSD libkvm Interface:: Debugging BSD kernel memory images
|
||
* Process Information:: Process information
|
||
* DJGPP Native:: Features specific to the DJGPP port
|
||
* Cygwin Native:: Features specific to the Cygwin port
|
||
* Hurd Native:: Features specific to @sc{gnu} Hurd
|
||
* Darwin:: Features specific to Darwin
|
||
@end menu
|
||
|
||
@node BSD libkvm Interface
|
||
@subsection BSD libkvm Interface
|
||
|
||
@cindex libkvm
|
||
@cindex kernel memory image
|
||
@cindex kernel crash dump
|
||
|
||
BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
|
||
interface that provides a uniform interface for accessing kernel virtual
|
||
memory images, including live systems and crash dumps. @value{GDBN}
|
||
uses this interface to allow you to debug live kernels and kernel crash
|
||
dumps on many native BSD configurations. This is implemented as a
|
||
special @code{kvm} debugging target. For debugging a live system, load
|
||
the currently running kernel into @value{GDBN} and connect to the
|
||
@code{kvm} target:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{target kvm}
|
||
@end smallexample
|
||
|
||
For debugging crash dumps, provide the file name of the crash dump as an
|
||
argument:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @b{target kvm /var/crash/bsd.0}
|
||
@end smallexample
|
||
|
||
Once connected to the @code{kvm} target, the following commands are
|
||
available:
|
||
|
||
@table @code
|
||
@kindex kvm
|
||
@item kvm pcb
|
||
Set current context from the @dfn{Process Control Block} (PCB) address.
|
||
|
||
@item kvm proc
|
||
Set current context from proc address. This command isn't available on
|
||
modern FreeBSD systems.
|
||
@end table
|
||
|
||
@node Process Information
|
||
@subsection Process Information
|
||
@cindex /proc
|
||
@cindex examine process image
|
||
@cindex process info via @file{/proc}
|
||
|
||
Some operating systems provide interfaces to fetch additional
|
||
information about running processes beyond memory and per-thread
|
||
register state. If @value{GDBN} is configured for an operating system
|
||
with a supported interface, the command @code{info proc} is available
|
||
to report information about the process running your program, or about
|
||
any process running on your system.
|
||
|
||
One supported interface is a facility called @samp{/proc} that can be
|
||
used to examine the image of a running process using file-system
|
||
subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
|
||
systems.
|
||
|
||
On FreeBSD systems, system control nodes are used to query process
|
||
information.
|
||
|
||
In addition, some systems may provide additional process information
|
||
in core files. Note that a core file may include a subset of the
|
||
information available from a live process. Process information is
|
||
currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
|
||
systems.
|
||
|
||
@table @code
|
||
@kindex info proc
|
||
@cindex process ID
|
||
@item info proc
|
||
@itemx info proc @var{process-id}
|
||
Summarize available information about any running process. If a
|
||
process ID is specified by @var{process-id}, display information about
|
||
that process; otherwise display information about the program being
|
||
debugged. The summary includes the debugged process ID, the command
|
||
line used to invoke it, its current working directory, and its
|
||
executable file's absolute file name.
|
||
|
||
On some systems, @var{process-id} can be of the form
|
||
@samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
|
||
within a process. If the optional @var{pid} part is missing, it means
|
||
a thread from the process being debugged (the leading @samp{/} still
|
||
needs to be present, or else @value{GDBN} will interpret the number as
|
||
a process ID rather than a thread ID).
|
||
|
||
@item info proc cmdline
|
||
@cindex info proc cmdline
|
||
Show the original command line of the process. This command is
|
||
supported on @sc{gnu}/Linux and FreeBSD.
|
||
|
||
@item info proc cwd
|
||
@cindex info proc cwd
|
||
Show the current working directory of the process. This command is
|
||
supported on @sc{gnu}/Linux and FreeBSD.
|
||
|
||
@item info proc exe
|
||
@cindex info proc exe
|
||
Show the name of executable of the process. This command is supported
|
||
on @sc{gnu}/Linux and FreeBSD.
|
||
|
||
@item info proc mappings
|
||
@cindex memory address space mappings
|
||
Report the memory address space ranges accessible in the program. On
|
||
Solaris and FreeBSD systems, each memory range includes information on
|
||
whether the process has read, write, or execute access rights to each
|
||
range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
|
||
includes the object file which is mapped to that range.
|
||
|
||
@item info proc stat
|
||
@itemx info proc status
|
||
@cindex process detailed status information
|
||
Show additional process-related information, including the user ID and
|
||
group ID; virtual memory usage; the signals that are pending, blocked,
|
||
and ignored; its TTY; its consumption of system and user time; its
|
||
stack size; its @samp{nice} value; etc. These commands are supported
|
||
on @sc{gnu}/Linux and FreeBSD.
|
||
|
||
For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
|
||
information (type @kbd{man 5 proc} from your shell prompt).
|
||
|
||
For FreeBSD systems, @code{info proc stat} is an alias for @code{info
|
||
proc status}.
|
||
|
||
@item info proc all
|
||
Show all the information about the process described under all of the
|
||
above @code{info proc} subcommands.
|
||
|
||
@ignore
|
||
@comment These sub-options of 'info proc' were not included when
|
||
@comment procfs.c was re-written. Keep their descriptions around
|
||
@comment against the day when someone finds the time to put them back in.
|
||
@kindex info proc times
|
||
@item info proc times
|
||
Starting time, user CPU time, and system CPU time for your program and
|
||
its children.
|
||
|
||
@kindex info proc id
|
||
@item info proc id
|
||
Report on the process IDs related to your program: its own process ID,
|
||
the ID of its parent, the process group ID, and the session ID.
|
||
@end ignore
|
||
|
||
@item set procfs-trace
|
||
@kindex set procfs-trace
|
||
@cindex @code{procfs} API calls
|
||
This command enables and disables tracing of @code{procfs} API calls.
|
||
|
||
@item show procfs-trace
|
||
@kindex show procfs-trace
|
||
Show the current state of @code{procfs} API call tracing.
|
||
|
||
@item set procfs-file @var{file}
|
||
@kindex set procfs-file
|
||
Tell @value{GDBN} to write @code{procfs} API trace to the named
|
||
@var{file}. @value{GDBN} appends the trace info to the previous
|
||
contents of the file. The default is to display the trace on the
|
||
standard output.
|
||
|
||
@item show procfs-file
|
||
@kindex show procfs-file
|
||
Show the file to which @code{procfs} API trace is written.
|
||
|
||
@item proc-trace-entry
|
||
@itemx proc-trace-exit
|
||
@itemx proc-untrace-entry
|
||
@itemx proc-untrace-exit
|
||
@kindex proc-trace-entry
|
||
@kindex proc-trace-exit
|
||
@kindex proc-untrace-entry
|
||
@kindex proc-untrace-exit
|
||
These commands enable and disable tracing of entries into and exits
|
||
from the @code{syscall} interface.
|
||
|
||
@item info pidlist
|
||
@kindex info pidlist
|
||
@cindex process list, QNX Neutrino
|
||
For QNX Neutrino only, this command displays the list of all the
|
||
processes and all the threads within each process.
|
||
|
||
@item info meminfo
|
||
@kindex info meminfo
|
||
@cindex mapinfo list, QNX Neutrino
|
||
For QNX Neutrino only, this command displays the list of all mapinfos.
|
||
@end table
|
||
|
||
@node DJGPP Native
|
||
@subsection Features for Debugging @sc{djgpp} Programs
|
||
@cindex @sc{djgpp} debugging
|
||
@cindex native @sc{djgpp} debugging
|
||
@cindex MS-DOS-specific commands
|
||
|
||
@cindex DPMI
|
||
@sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
|
||
MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
|
||
that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
|
||
top of real-mode DOS systems and their emulations.
|
||
|
||
@value{GDBN} supports native debugging of @sc{djgpp} programs, and
|
||
defines a few commands specific to the @sc{djgpp} port. This
|
||
subsection describes those commands.
|
||
|
||
@table @code
|
||
@kindex info dos
|
||
@item info dos
|
||
This is a prefix of @sc{djgpp}-specific commands which print
|
||
information about the target system and important OS structures.
|
||
|
||
@kindex sysinfo
|
||
@cindex MS-DOS system info
|
||
@cindex free memory information (MS-DOS)
|
||
@item info dos sysinfo
|
||
This command displays assorted information about the underlying
|
||
platform: the CPU type and features, the OS version and flavor, the
|
||
DPMI version, and the available conventional and DPMI memory.
|
||
|
||
@cindex GDT
|
||
@cindex LDT
|
||
@cindex IDT
|
||
@cindex segment descriptor tables
|
||
@cindex descriptor tables display
|
||
@item info dos gdt
|
||
@itemx info dos ldt
|
||
@itemx info dos idt
|
||
These 3 commands display entries from, respectively, Global, Local,
|
||
and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
|
||
tables are data structures which store a descriptor for each segment
|
||
that is currently in use. The segment's selector is an index into a
|
||
descriptor table; the table entry for that index holds the
|
||
descriptor's base address and limit, and its attributes and access
|
||
rights.
|
||
|
||
A typical @sc{djgpp} program uses 3 segments: a code segment, a data
|
||
segment (used for both data and the stack), and a DOS segment (which
|
||
allows access to DOS/BIOS data structures and absolute addresses in
|
||
conventional memory). However, the DPMI host will usually define
|
||
additional segments in order to support the DPMI environment.
|
||
|
||
@cindex garbled pointers
|
||
These commands allow to display entries from the descriptor tables.
|
||
Without an argument, all entries from the specified table are
|
||
displayed. An argument, which should be an integer expression, means
|
||
display a single entry whose index is given by the argument. For
|
||
example, here's a convenient way to display information about the
|
||
debugged program's data segment:
|
||
|
||
@smallexample
|
||
@exdent @code{(@value{GDBP}) info dos ldt $ds}
|
||
@exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This comes in handy when you want to see whether a pointer is outside
|
||
the data segment's limit (i.e.@: @dfn{garbled}).
|
||
|
||
@cindex page tables display (MS-DOS)
|
||
@item info dos pde
|
||
@itemx info dos pte
|
||
These two commands display entries from, respectively, the Page
|
||
Directory and the Page Tables. Page Directories and Page Tables are
|
||
data structures which control how virtual memory addresses are mapped
|
||
into physical addresses. A Page Table includes an entry for every
|
||
page of memory that is mapped into the program's address space; there
|
||
may be several Page Tables, each one holding up to 4096 entries. A
|
||
Page Directory has up to 4096 entries, one each for every Page Table
|
||
that is currently in use.
|
||
|
||
Without an argument, @kbd{info dos pde} displays the entire Page
|
||
Directory, and @kbd{info dos pte} displays all the entries in all of
|
||
the Page Tables. An argument, an integer expression, given to the
|
||
@kbd{info dos pde} command means display only that entry from the Page
|
||
Directory table. An argument given to the @kbd{info dos pte} command
|
||
means display entries from a single Page Table, the one pointed to by
|
||
the specified entry in the Page Directory.
|
||
|
||
@cindex direct memory access (DMA) on MS-DOS
|
||
These commands are useful when your program uses @dfn{DMA} (Direct
|
||
Memory Access), which needs physical addresses to program the DMA
|
||
controller.
|
||
|
||
These commands are supported only with some DPMI servers.
|
||
|
||
@cindex physical address from linear address
|
||
@item info dos address-pte @var{addr}
|
||
This command displays the Page Table entry for a specified linear
|
||
address. The argument @var{addr} is a linear address which should
|
||
already have the appropriate segment's base address added to it,
|
||
because this command accepts addresses which may belong to @emph{any}
|
||
segment. For example, here's how to display the Page Table entry for
|
||
the page where a variable @code{i} is stored:
|
||
|
||
@smallexample
|
||
@exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
|
||
@exdent @code{Page Table entry for address 0x11a00d30:}
|
||
@exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This says that @code{i} is stored at offset @code{0xd30} from the page
|
||
whose physical base address is @code{0x02698000}, and shows all the
|
||
attributes of that page.
|
||
|
||
Note that you must cast the addresses of variables to a @code{char *},
|
||
since otherwise the value of @code{__djgpp_base_address}, the base
|
||
address of all variables and functions in a @sc{djgpp} program, will
|
||
be added using the rules of C pointer arithmetics: if @code{i} is
|
||
declared an @code{int}, @value{GDBN} will add 4 times the value of
|
||
@code{__djgpp_base_address} to the address of @code{i}.
|
||
|
||
Here's another example, it displays the Page Table entry for the
|
||
transfer buffer:
|
||
|
||
@smallexample
|
||
@exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
|
||
@exdent @code{Page Table entry for address 0x29110:}
|
||
@exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
(The @code{+ 3} offset is because the transfer buffer's address is the
|
||
3rd member of the @code{_go32_info_block} structure.) The output
|
||
clearly shows that this DPMI server maps the addresses in conventional
|
||
memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
|
||
linear (@code{0x29110}) addresses are identical.
|
||
|
||
This command is supported only with some DPMI servers.
|
||
@end table
|
||
|
||
@cindex DOS serial data link, remote debugging
|
||
In addition to native debugging, the DJGPP port supports remote
|
||
debugging via a serial data link. The following commands are specific
|
||
to remote serial debugging in the DJGPP port of @value{GDBN}.
|
||
|
||
@table @code
|
||
@kindex set com1base
|
||
@kindex set com1irq
|
||
@kindex set com2base
|
||
@kindex set com2irq
|
||
@kindex set com3base
|
||
@kindex set com3irq
|
||
@kindex set com4base
|
||
@kindex set com4irq
|
||
@item set com1base @var{addr}
|
||
This command sets the base I/O port address of the @file{COM1} serial
|
||
port.
|
||
|
||
@item set com1irq @var{irq}
|
||
This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
|
||
for the @file{COM1} serial port.
|
||
|
||
There are similar commands @samp{set com2base}, @samp{set com3irq},
|
||
etc.@: for setting the port address and the @code{IRQ} lines for the
|
||
other 3 COM ports.
|
||
|
||
@kindex show com1base
|
||
@kindex show com1irq
|
||
@kindex show com2base
|
||
@kindex show com2irq
|
||
@kindex show com3base
|
||
@kindex show com3irq
|
||
@kindex show com4base
|
||
@kindex show com4irq
|
||
The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
|
||
display the current settings of the base address and the @code{IRQ}
|
||
lines used by the COM ports.
|
||
|
||
@item info serial
|
||
@kindex info serial
|
||
@cindex DOS serial port status
|
||
This command prints the status of the 4 DOS serial ports. For each
|
||
port, it prints whether it's active or not, its I/O base address and
|
||
IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
|
||
counts of various errors encountered so far.
|
||
@end table
|
||
|
||
|
||
@node Cygwin Native
|
||
@subsection Features for Debugging MS Windows PE Executables
|
||
@cindex MS Windows debugging
|
||
@cindex native Cygwin debugging
|
||
@cindex Cygwin-specific commands
|
||
|
||
@value{GDBN} supports native debugging of MS Windows programs, including
|
||
DLLs with and without symbolic debugging information.
|
||
|
||
@cindex Ctrl-BREAK, MS-Windows
|
||
@cindex interrupt debuggee on MS-Windows
|
||
MS-Windows programs that call @code{SetConsoleMode} to switch off the
|
||
special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
|
||
by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
|
||
supports @kbd{C-@key{BREAK}} as an alternative interrupt key
|
||
sequence, which can be used to interrupt the debuggee even if it
|
||
ignores @kbd{C-c}.
|
||
|
||
There are various additional Cygwin-specific commands, described in
|
||
this section. Working with DLLs that have no debugging symbols is
|
||
described in @ref{Non-debug DLL Symbols}.
|
||
|
||
@table @code
|
||
@kindex info w32
|
||
@item info w32
|
||
This is a prefix of MS Windows-specific commands which print
|
||
information about the target system and important OS structures.
|
||
|
||
@item info w32 selector
|
||
This command displays information returned by
|
||
the Win32 API @code{GetThreadSelectorEntry} function.
|
||
It takes an optional argument that is evaluated to
|
||
a long value to give the information about this given selector.
|
||
Without argument, this command displays information
|
||
about the six segment registers.
|
||
|
||
@item info w32 thread-information-block
|
||
This command displays thread specific information stored in the
|
||
Thread Information Block (readable on the X86 CPU family using @code{$fs}
|
||
selector for 32-bit programs and @code{$gs} for 64-bit programs).
|
||
|
||
@kindex signal-event
|
||
@item signal-event @var{id}
|
||
This command signals an event with user-provided @var{id}. Used to resume
|
||
crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
|
||
|
||
To use it, create or edit the following keys in
|
||
@code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
|
||
@code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
|
||
(for x86_64 versions):
|
||
|
||
@itemize @minus
|
||
@item
|
||
@code{Debugger} (REG_SZ) --- a command to launch the debugger.
|
||
Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
|
||
"attach %ld" -ex "signal-event %ld" -ex "continue"}.
|
||
|
||
The first @code{%ld} will be replaced by the process ID of the
|
||
crashing process, the second @code{%ld} will be replaced by the ID of
|
||
the event that blocks the crashing process, waiting for @value{GDBN}
|
||
to attach.
|
||
|
||
@item
|
||
@code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
|
||
make the system run debugger specified by the Debugger key
|
||
automatically, @code{0} will cause a dialog box with ``OK'' and
|
||
``Cancel'' buttons to appear, which allows the user to either
|
||
terminate the crashing process (OK) or debug it (Cancel).
|
||
@end itemize
|
||
|
||
@kindex set cygwin-exceptions
|
||
@cindex debugging the Cygwin DLL
|
||
@cindex Cygwin DLL, debugging
|
||
@item set cygwin-exceptions @var{mode}
|
||
If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
|
||
happen inside the Cygwin DLL. If @var{mode} is @code{off},
|
||
@value{GDBN} will delay recognition of exceptions, and may ignore some
|
||
exceptions which seem to be caused by internal Cygwin DLL
|
||
``bookkeeping''. This option is meant primarily for debugging the
|
||
Cygwin DLL itself; the default value is @code{off} to avoid annoying
|
||
@value{GDBN} users with false @code{SIGSEGV} signals.
|
||
|
||
@kindex show cygwin-exceptions
|
||
@item show cygwin-exceptions
|
||
Displays whether @value{GDBN} will break on exceptions that happen
|
||
inside the Cygwin DLL itself.
|
||
|
||
@kindex set new-console
|
||
@item set new-console @var{mode}
|
||
If @var{mode} is @code{on} the debuggee will
|
||
be started in a new console on next start.
|
||
If @var{mode} is @code{off}, the debuggee will
|
||
be started in the same console as the debugger.
|
||
|
||
@kindex show new-console
|
||
@item show new-console
|
||
Displays whether a new console is used
|
||
when the debuggee is started.
|
||
|
||
@kindex set new-group
|
||
@item set new-group @var{mode}
|
||
This boolean value controls whether the debuggee should
|
||
start a new group or stay in the same group as the debugger.
|
||
This affects the way the Windows OS handles
|
||
@samp{Ctrl-C}.
|
||
|
||
@kindex show new-group
|
||
@item show new-group
|
||
Displays current value of new-group boolean.
|
||
|
||
@kindex set debugevents
|
||
@item set debugevents
|
||
This boolean value adds debug output concerning kernel events related
|
||
to the debuggee seen by the debugger. This includes events that
|
||
signal thread and process creation and exit, DLL loading and
|
||
unloading, console interrupts, and debugging messages produced by the
|
||
Windows @code{OutputDebugString} API call.
|
||
|
||
@kindex set debugexec
|
||
@item set debugexec
|
||
This boolean value adds debug output concerning execute events
|
||
(such as resume thread) seen by the debugger.
|
||
|
||
@kindex set debugexceptions
|
||
@item set debugexceptions
|
||
This boolean value adds debug output concerning exceptions in the
|
||
debuggee seen by the debugger.
|
||
|
||
@kindex set debugmemory
|
||
@item set debugmemory
|
||
This boolean value adds debug output concerning debuggee memory reads
|
||
and writes by the debugger.
|
||
|
||
@kindex set shell
|
||
@item set shell
|
||
This boolean values specifies whether the debuggee is called
|
||
via a shell or directly (default value is on).
|
||
|
||
@kindex show shell
|
||
@item show shell
|
||
Displays if the debuggee will be started with a shell.
|
||
|
||
@end table
|
||
|
||
@menu
|
||
* Non-debug DLL Symbols:: Support for DLLs without debugging symbols
|
||
@end menu
|
||
|
||
@node Non-debug DLL Symbols
|
||
@subsubsection Support for DLLs without Debugging Symbols
|
||
@cindex DLLs with no debugging symbols
|
||
@cindex Minimal symbols and DLLs
|
||
|
||
Very often on windows, some of the DLLs that your program relies on do
|
||
not include symbolic debugging information (for example,
|
||
@file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
|
||
symbols in a DLL, it relies on the minimal amount of symbolic
|
||
information contained in the DLL's export table. This section
|
||
describes working with such symbols, known internally to @value{GDBN} as
|
||
``minimal symbols''.
|
||
|
||
Note that before the debugged program has started execution, no DLLs
|
||
will have been loaded. The easiest way around this problem is simply to
|
||
start the program --- either by setting a breakpoint or letting the
|
||
program run once to completion.
|
||
|
||
@subsubsection DLL Name Prefixes
|
||
|
||
In keeping with the naming conventions used by the Microsoft debugging
|
||
tools, DLL export symbols are made available with a prefix based on the
|
||
DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
|
||
also entered into the symbol table, so @code{CreateFileA} is often
|
||
sufficient. In some cases there will be name clashes within a program
|
||
(particularly if the executable itself includes full debugging symbols)
|
||
necessitating the use of the fully qualified name when referring to the
|
||
contents of the DLL. Use single-quotes around the name to avoid the
|
||
exclamation mark (``!'') being interpreted as a language operator.
|
||
|
||
Note that the internal name of the DLL may be all upper-case, even
|
||
though the file name of the DLL is lower-case, or vice-versa. Since
|
||
symbols within @value{GDBN} are @emph{case-sensitive} this may cause
|
||
some confusion. If in doubt, try the @code{info functions} and
|
||
@code{info variables} commands or even @code{maint print msymbols}
|
||
(@pxref{Symbols}). Here's an example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info function CreateFileA
|
||
All functions matching regular expression "CreateFileA":
|
||
|
||
Non-debugging symbols:
|
||
0x77e885f4 CreateFileA
|
||
0x77e885f4 KERNEL32!CreateFileA
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) info function !
|
||
All functions matching regular expression "!":
|
||
|
||
Non-debugging symbols:
|
||
0x6100114c cygwin1!__assert
|
||
0x61004034 cygwin1!_dll_crt0@@0
|
||
0x61004240 cygwin1!dll_crt0(per_process *)
|
||
[etc...]
|
||
@end smallexample
|
||
|
||
@subsubsection Working with Minimal Symbols
|
||
|
||
Symbols extracted from a DLL's export table do not contain very much
|
||
type information. All that @value{GDBN} can do is guess whether a symbol
|
||
refers to a function or variable depending on the linker section that
|
||
contains the symbol. Also note that the actual contents of the memory
|
||
contained in a DLL are not available unless the program is running. This
|
||
means that you cannot examine the contents of a variable or disassemble
|
||
a function within a DLL without a running program.
|
||
|
||
Variables are generally treated as pointers and dereferenced
|
||
automatically. For this reason, it is often necessary to prefix a
|
||
variable name with the address-of operator (``&'') and provide explicit
|
||
type information in the command. Here's an example of the type of
|
||
problem:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print 'cygwin1!__argv'
|
||
'cygwin1!__argv' has unknown type; cast it to its declared type
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) x 'cygwin1!__argv'
|
||
'cygwin1!__argv' has unknown type; cast it to its declared type
|
||
@end smallexample
|
||
|
||
And two possible solutions:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
|
||
$2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(@value{GDBP}) x/2x &'cygwin1!__argv'
|
||
0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
|
||
(@value{GDBP}) x/x 0x10021608
|
||
0x10021608: 0x0022fd98
|
||
(@value{GDBP}) x/s 0x0022fd98
|
||
0x22fd98: "/cygdrive/c/mydirectory/myprogram"
|
||
@end smallexample
|
||
|
||
Setting a break point within a DLL is possible even before the program
|
||
starts execution. However, under these circumstances, @value{GDBN} can't
|
||
examine the initial instructions of the function in order to skip the
|
||
function's frame set-up code. You can work around this by using ``*&''
|
||
to set the breakpoint at a raw memory address:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) break *&'python22!PyOS_Readline'
|
||
Breakpoint 1 at 0x1e04eff0
|
||
@end smallexample
|
||
|
||
The author of these extensions is not entirely convinced that setting a
|
||
break point within a shared DLL like @file{kernel32.dll} is completely
|
||
safe.
|
||
|
||
@node Hurd Native
|
||
@subsection Commands Specific to @sc{gnu} Hurd Systems
|
||
@cindex @sc{gnu} Hurd debugging
|
||
|
||
This subsection describes @value{GDBN} commands specific to the
|
||
@sc{gnu} Hurd native debugging.
|
||
|
||
@table @code
|
||
@item set signals
|
||
@itemx set sigs
|
||
@kindex set signals@r{, Hurd command}
|
||
@kindex set sigs@r{, Hurd command}
|
||
This command toggles the state of inferior signal interception by
|
||
@value{GDBN}. Mach exceptions, such as breakpoint traps, are not
|
||
affected by this command. @code{sigs} is a shorthand alias for
|
||
@code{signals}.
|
||
|
||
@item show signals
|
||
@itemx show sigs
|
||
@kindex show signals@r{, Hurd command}
|
||
@kindex show sigs@r{, Hurd command}
|
||
Show the current state of intercepting inferior's signals.
|
||
|
||
@item set signal-thread
|
||
@itemx set sigthread
|
||
@kindex set signal-thread
|
||
@kindex set sigthread
|
||
This command tells @value{GDBN} which thread is the @code{libc} signal
|
||
thread. That thread is run when a signal is delivered to a running
|
||
process. @code{set sigthread} is the shorthand alias of @code{set
|
||
signal-thread}.
|
||
|
||
@item show signal-thread
|
||
@itemx show sigthread
|
||
@kindex show signal-thread
|
||
@kindex show sigthread
|
||
These two commands show which thread will run when the inferior is
|
||
delivered a signal.
|
||
|
||
@item set stopped
|
||
@kindex set stopped@r{, Hurd command}
|
||
This commands tells @value{GDBN} that the inferior process is stopped,
|
||
as with the @code{SIGSTOP} signal. The stopped process can be
|
||
continued by delivering a signal to it.
|
||
|
||
@item show stopped
|
||
@kindex show stopped@r{, Hurd command}
|
||
This command shows whether @value{GDBN} thinks the debuggee is
|
||
stopped.
|
||
|
||
@item set exceptions
|
||
@kindex set exceptions@r{, Hurd command}
|
||
Use this command to turn off trapping of exceptions in the inferior.
|
||
When exception trapping is off, neither breakpoints nor
|
||
single-stepping will work. To restore the default, set exception
|
||
trapping on.
|
||
|
||
@item show exceptions
|
||
@kindex show exceptions@r{, Hurd command}
|
||
Show the current state of trapping exceptions in the inferior.
|
||
|
||
@item set task pause
|
||
@kindex set task@r{, Hurd commands}
|
||
@cindex task attributes (@sc{gnu} Hurd)
|
||
@cindex pause current task (@sc{gnu} Hurd)
|
||
This command toggles task suspension when @value{GDBN} has control.
|
||
Setting it to on takes effect immediately, and the task is suspended
|
||
whenever @value{GDBN} gets control. Setting it to off will take
|
||
effect the next time the inferior is continued. If this option is set
|
||
to off, you can use @code{set thread default pause on} or @code{set
|
||
thread pause on} (see below) to pause individual threads.
|
||
|
||
@item show task pause
|
||
@kindex show task@r{, Hurd commands}
|
||
Show the current state of task suspension.
|
||
|
||
@item set task detach-suspend-count
|
||
@cindex task suspend count
|
||
@cindex detach from task, @sc{gnu} Hurd
|
||
This command sets the suspend count the task will be left with when
|
||
@value{GDBN} detaches from it.
|
||
|
||
@item show task detach-suspend-count
|
||
Show the suspend count the task will be left with when detaching.
|
||
|
||
@item set task exception-port
|
||
@itemx set task excp
|
||
@cindex task exception port, @sc{gnu} Hurd
|
||
This command sets the task exception port to which @value{GDBN} will
|
||
forward exceptions. The argument should be the value of the @dfn{send
|
||
rights} of the task. @code{set task excp} is a shorthand alias.
|
||
|
||
@item set noninvasive
|
||
@cindex noninvasive task options
|
||
This command switches @value{GDBN} to a mode that is the least
|
||
invasive as far as interfering with the inferior is concerned. This
|
||
is the same as using @code{set task pause}, @code{set exceptions}, and
|
||
@code{set signals} to values opposite to the defaults.
|
||
|
||
@item info send-rights
|
||
@itemx info receive-rights
|
||
@itemx info port-rights
|
||
@itemx info port-sets
|
||
@itemx info dead-names
|
||
@itemx info ports
|
||
@itemx info psets
|
||
@cindex send rights, @sc{gnu} Hurd
|
||
@cindex receive rights, @sc{gnu} Hurd
|
||
@cindex port rights, @sc{gnu} Hurd
|
||
@cindex port sets, @sc{gnu} Hurd
|
||
@cindex dead names, @sc{gnu} Hurd
|
||
These commands display information about, respectively, send rights,
|
||
receive rights, port rights, port sets, and dead names of a task.
|
||
There are also shorthand aliases: @code{info ports} for @code{info
|
||
port-rights} and @code{info psets} for @code{info port-sets}.
|
||
|
||
@item set thread pause
|
||
@kindex set thread@r{, Hurd command}
|
||
@cindex thread properties, @sc{gnu} Hurd
|
||
@cindex pause current thread (@sc{gnu} Hurd)
|
||
This command toggles current thread suspension when @value{GDBN} has
|
||
control. Setting it to on takes effect immediately, and the current
|
||
thread is suspended whenever @value{GDBN} gets control. Setting it to
|
||
off will take effect the next time the inferior is continued.
|
||
Normally, this command has no effect, since when @value{GDBN} has
|
||
control, the whole task is suspended. However, if you used @code{set
|
||
task pause off} (see above), this command comes in handy to suspend
|
||
only the current thread.
|
||
|
||
@item show thread pause
|
||
@kindex show thread@r{, Hurd command}
|
||
This command shows the state of current thread suspension.
|
||
|
||
@item set thread run
|
||
This command sets whether the current thread is allowed to run.
|
||
|
||
@item show thread run
|
||
Show whether the current thread is allowed to run.
|
||
|
||
@item set thread detach-suspend-count
|
||
@cindex thread suspend count, @sc{gnu} Hurd
|
||
@cindex detach from thread, @sc{gnu} Hurd
|
||
This command sets the suspend count @value{GDBN} will leave on a
|
||
thread when detaching. This number is relative to the suspend count
|
||
found by @value{GDBN} when it notices the thread; use @code{set thread
|
||
takeover-suspend-count} to force it to an absolute value.
|
||
|
||
@item show thread detach-suspend-count
|
||
Show the suspend count @value{GDBN} will leave on the thread when
|
||
detaching.
|
||
|
||
@item set thread exception-port
|
||
@itemx set thread excp
|
||
Set the thread exception port to which to forward exceptions. This
|
||
overrides the port set by @code{set task exception-port} (see above).
|
||
@code{set thread excp} is the shorthand alias.
|
||
|
||
@item set thread takeover-suspend-count
|
||
Normally, @value{GDBN}'s thread suspend counts are relative to the
|
||
value @value{GDBN} finds when it notices each thread. This command
|
||
changes the suspend counts to be absolute instead.
|
||
|
||
@item set thread default
|
||
@itemx show thread default
|
||
@cindex thread default settings, @sc{gnu} Hurd
|
||
Each of the above @code{set thread} commands has a @code{set thread
|
||
default} counterpart (e.g., @code{set thread default pause}, @code{set
|
||
thread default exception-port}, etc.). The @code{thread default}
|
||
variety of commands sets the default thread properties for all
|
||
threads; you can then change the properties of individual threads with
|
||
the non-default commands.
|
||
@end table
|
||
|
||
@node Darwin
|
||
@subsection Darwin
|
||
@cindex Darwin
|
||
|
||
@value{GDBN} provides the following commands specific to the Darwin target:
|
||
|
||
@table @code
|
||
@item set debug darwin @var{num}
|
||
@kindex set debug darwin
|
||
When set to a non zero value, enables debugging messages specific to
|
||
the Darwin support. Higher values produce more verbose output.
|
||
|
||
@item show debug darwin
|
||
@kindex show debug darwin
|
||
Show the current state of Darwin messages.
|
||
|
||
@item set debug mach-o @var{num}
|
||
@kindex set debug mach-o
|
||
When set to a non zero value, enables debugging messages while
|
||
@value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
|
||
file format used on Darwin for object and executable files.) Higher
|
||
values produce more verbose output. This is a command to diagnose
|
||
problems internal to @value{GDBN} and should not be needed in normal
|
||
usage.
|
||
|
||
@item show debug mach-o
|
||
@kindex show debug mach-o
|
||
Show the current state of Mach-O file messages.
|
||
|
||
@item set mach-exceptions on
|
||
@itemx set mach-exceptions off
|
||
@kindex set mach-exceptions
|
||
On Darwin, faults are first reported as a Mach exception and are then
|
||
mapped to a Posix signal. Use this command to turn on trapping of
|
||
Mach exceptions in the inferior. This might be sometimes useful to
|
||
better understand the cause of a fault. The default is off.
|
||
|
||
@item show mach-exceptions
|
||
@kindex show mach-exceptions
|
||
Show the current state of exceptions trapping.
|
||
@end table
|
||
|
||
|
||
@node Embedded OS
|
||
@section Embedded Operating Systems
|
||
|
||
This section describes configurations involving the debugging of
|
||
embedded operating systems that are available for several different
|
||
architectures.
|
||
|
||
@value{GDBN} includes the ability to debug programs running on
|
||
various real-time operating systems.
|
||
|
||
@node Embedded Processors
|
||
@section Embedded Processors
|
||
|
||
This section goes into details specific to particular embedded
|
||
configurations.
|
||
|
||
@cindex send command to simulator
|
||
Whenever a specific embedded processor has a simulator, @value{GDBN}
|
||
allows to send an arbitrary command to the simulator.
|
||
|
||
@table @code
|
||
@item sim @var{command}
|
||
@kindex sim@r{, a command}
|
||
Send an arbitrary @var{command} string to the simulator. Consult the
|
||
documentation for the specific simulator in use for information about
|
||
acceptable commands.
|
||
@end table
|
||
|
||
|
||
@menu
|
||
* ARC:: Synopsys ARC
|
||
* ARM:: ARM
|
||
* M68K:: Motorola M68K
|
||
* MicroBlaze:: Xilinx MicroBlaze
|
||
* MIPS Embedded:: MIPS Embedded
|
||
* OpenRISC 1000:: OpenRISC 1000 (or1k)
|
||
* PowerPC Embedded:: PowerPC Embedded
|
||
* AVR:: Atmel AVR
|
||
* CRIS:: CRIS
|
||
* Super-H:: Renesas Super-H
|
||
@end menu
|
||
|
||
@node ARC
|
||
@subsection Synopsys ARC
|
||
@cindex Synopsys ARC
|
||
@cindex ARC specific commands
|
||
@cindex ARC600
|
||
@cindex ARC700
|
||
@cindex ARC EM
|
||
@cindex ARC HS
|
||
|
||
@value{GDBN} provides the following ARC-specific commands:
|
||
|
||
@table @code
|
||
@item set debug arc
|
||
@kindex set debug arc
|
||
Control the level of ARC specific debug messages. Use 0 for no messages (the
|
||
default), 1 for debug messages, and 2 for even more debug messages.
|
||
|
||
@item show debug arc
|
||
@kindex show debug arc
|
||
Show the level of ARC specific debugging in operation.
|
||
|
||
@item maint print arc arc-instruction @var{address}
|
||
@kindex maint print arc arc-instruction
|
||
Print internal disassembler information about instruction at a given address.
|
||
|
||
@end table
|
||
|
||
@node ARM
|
||
@subsection ARM
|
||
|
||
@value{GDBN} provides the following ARM-specific commands:
|
||
|
||
@table @code
|
||
@item set arm disassembler
|
||
@kindex set arm
|
||
This commands selects from a list of disassembly styles. The
|
||
@code{"std"} style is the standard style.
|
||
|
||
@item show arm disassembler
|
||
@kindex show arm
|
||
Show the current disassembly style.
|
||
|
||
@item set arm apcs32
|
||
@cindex ARM 32-bit mode
|
||
This command toggles ARM operation mode between 32-bit and 26-bit.
|
||
|
||
@item show arm apcs32
|
||
Display the current usage of the ARM 32-bit mode.
|
||
|
||
@item set arm fpu @var{fputype}
|
||
This command sets the ARM floating-point unit (FPU) type. The
|
||
argument @var{fputype} can be one of these:
|
||
|
||
@table @code
|
||
@item auto
|
||
Determine the FPU type by querying the OS ABI.
|
||
@item softfpa
|
||
Software FPU, with mixed-endian doubles on little-endian ARM
|
||
processors.
|
||
@item fpa
|
||
GCC-compiled FPA co-processor.
|
||
@item softvfp
|
||
Software FPU with pure-endian doubles.
|
||
@item vfp
|
||
VFP co-processor.
|
||
@end table
|
||
|
||
@item show arm fpu
|
||
Show the current type of the FPU.
|
||
|
||
@item set arm abi
|
||
This command forces @value{GDBN} to use the specified ABI.
|
||
|
||
@item show arm abi
|
||
Show the currently used ABI.
|
||
|
||
@item set arm fallback-mode (arm|thumb|auto)
|
||
@value{GDBN} uses the symbol table, when available, to determine
|
||
whether instructions are ARM or Thumb. This command controls
|
||
@value{GDBN}'s default behavior when the symbol table is not
|
||
available. The default is @samp{auto}, which causes @value{GDBN} to
|
||
use the current execution mode (from the @code{T} bit in the @code{CPSR}
|
||
register).
|
||
|
||
@item show arm fallback-mode
|
||
Show the current fallback instruction mode.
|
||
|
||
@item set arm force-mode (arm|thumb|auto)
|
||
This command overrides use of the symbol table to determine whether
|
||
instructions are ARM or Thumb. The default is @samp{auto}, which
|
||
causes @value{GDBN} to use the symbol table and then the setting
|
||
of @samp{set arm fallback-mode}.
|
||
|
||
@item show arm force-mode
|
||
Show the current forced instruction mode.
|
||
|
||
@item set debug arm
|
||
Toggle whether to display ARM-specific debugging messages from the ARM
|
||
target support subsystem.
|
||
|
||
@item show debug arm
|
||
Show whether ARM-specific debugging messages are enabled.
|
||
@end table
|
||
|
||
@table @code
|
||
@item target sim @r{[}@var{simargs}@r{]} @dots{}
|
||
The @value{GDBN} ARM simulator accepts the following optional arguments.
|
||
|
||
@table @code
|
||
@item --swi-support=@var{type}
|
||
Tell the simulator which SWI interfaces to support. The argument
|
||
@var{type} may be a comma separated list of the following values.
|
||
The default value is @code{all}.
|
||
|
||
@table @code
|
||
@item none
|
||
@item demon
|
||
@item angel
|
||
@item redboot
|
||
@item all
|
||
@end table
|
||
@end table
|
||
@end table
|
||
|
||
@node M68K
|
||
@subsection M68k
|
||
|
||
The Motorola m68k configuration includes ColdFire support.
|
||
|
||
@node MicroBlaze
|
||
@subsection MicroBlaze
|
||
@cindex Xilinx MicroBlaze
|
||
@cindex XMD, Xilinx Microprocessor Debugger
|
||
|
||
The MicroBlaze is a soft-core processor supported on various Xilinx
|
||
FPGAs, such as Spartan or Virtex series. Boards with these processors
|
||
usually have JTAG ports which connect to a host system running the Xilinx
|
||
Embedded Development Kit (EDK) or Software Development Kit (SDK).
|
||
This host system is used to download the configuration bitstream to
|
||
the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
|
||
communicates with the target board using the JTAG interface and
|
||
presents a @code{gdbserver} interface to the board. By default
|
||
@code{xmd} uses port @code{1234}. (While it is possible to change
|
||
this default port, it requires the use of undocumented @code{xmd}
|
||
commands. Contact Xilinx support if you need to do this.)
|
||
|
||
Use these GDB commands to connect to the MicroBlaze target processor.
|
||
|
||
@table @code
|
||
@item target remote :1234
|
||
Use this command to connect to the target if you are running @value{GDBN}
|
||
on the same system as @code{xmd}.
|
||
|
||
@item target remote @var{xmd-host}:1234
|
||
Use this command to connect to the target if it is connected to @code{xmd}
|
||
running on a different system named @var{xmd-host}.
|
||
|
||
@item load
|
||
Use this command to download a program to the MicroBlaze target.
|
||
|
||
@item set debug microblaze @var{n}
|
||
Enable MicroBlaze-specific debugging messages if non-zero.
|
||
|
||
@item show debug microblaze @var{n}
|
||
Show MicroBlaze-specific debugging level.
|
||
@end table
|
||
|
||
@node MIPS Embedded
|
||
@subsection @acronym{MIPS} Embedded
|
||
|
||
@noindent
|
||
@value{GDBN} supports these special commands for @acronym{MIPS} targets:
|
||
|
||
@table @code
|
||
@item set mipsfpu double
|
||
@itemx set mipsfpu single
|
||
@itemx set mipsfpu none
|
||
@itemx set mipsfpu auto
|
||
@itemx show mipsfpu
|
||
@kindex set mipsfpu
|
||
@kindex show mipsfpu
|
||
@cindex @acronym{MIPS} remote floating point
|
||
@cindex floating point, @acronym{MIPS} remote
|
||
If your target board does not support the @acronym{MIPS} floating point
|
||
coprocessor, you should use the command @samp{set mipsfpu none} (if you
|
||
need this, you may wish to put the command in your @value{GDBN} init
|
||
file). This tells @value{GDBN} how to find the return value of
|
||
functions which return floating point values. It also allows
|
||
@value{GDBN} to avoid saving the floating point registers when calling
|
||
functions on the board. If you are using a floating point coprocessor
|
||
with only single precision floating point support, as on the @sc{r4650}
|
||
processor, use the command @samp{set mipsfpu single}. The default
|
||
double precision floating point coprocessor may be selected using
|
||
@samp{set mipsfpu double}.
|
||
|
||
In previous versions the only choices were double precision or no
|
||
floating point, so @samp{set mipsfpu on} will select double precision
|
||
and @samp{set mipsfpu off} will select no floating point.
|
||
|
||
As usual, you can inquire about the @code{mipsfpu} variable with
|
||
@samp{show mipsfpu}.
|
||
@end table
|
||
|
||
@node OpenRISC 1000
|
||
@subsection OpenRISC 1000
|
||
@cindex OpenRISC 1000
|
||
|
||
@noindent
|
||
The OpenRISC 1000 provides a free RISC instruction set architecture. It is
|
||
mainly provided as a soft-core which can run on Xilinx, Altera and other
|
||
FPGA's.
|
||
|
||
@value{GDBN} for OpenRISC supports the below commands when connecting to
|
||
a target:
|
||
|
||
@table @code
|
||
|
||
@kindex target sim
|
||
@item target sim
|
||
|
||
Runs the builtin CPU simulator which can run very basic
|
||
programs but does not support most hardware functions like MMU.
|
||
For more complex use cases the user is advised to run an external
|
||
target, and connect using @samp{target remote}.
|
||
|
||
Example: @code{target sim}
|
||
|
||
@item set debug or1k
|
||
Toggle whether to display OpenRISC-specific debugging messages from the
|
||
OpenRISC target support subsystem.
|
||
|
||
@item show debug or1k
|
||
Show whether OpenRISC-specific debugging messages are enabled.
|
||
@end table
|
||
|
||
@node PowerPC Embedded
|
||
@subsection PowerPC Embedded
|
||
|
||
@cindex DVC register
|
||
@value{GDBN} supports using the DVC (Data Value Compare) register to
|
||
implement in hardware simple hardware watchpoint conditions of the form:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
|
||
if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
|
||
@end smallexample
|
||
|
||
The DVC register will be automatically used when @value{GDBN} detects
|
||
such pattern in a condition expression, and the created watchpoint uses one
|
||
debug register (either the @code{exact-watchpoints} option is on and the
|
||
variable is scalar, or the variable has a length of one byte). This feature
|
||
is available in native @value{GDBN} running on a Linux kernel version 2.6.34
|
||
or newer.
|
||
|
||
When running on PowerPC embedded processors, @value{GDBN} automatically uses
|
||
ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
|
||
in which case watchpoints using only one debug register are created when
|
||
watching variables of scalar types.
|
||
|
||
You can create an artificial array to watch an arbitrary memory
|
||
region using one of the following commands (@pxref{Expressions}):
|
||
|
||
@smallexample
|
||
(@value{GDBP}) watch *((char *) @var{address})@@@var{length}
|
||
(@value{GDBP}) watch @{char[@var{length}]@} @var{address}
|
||
@end smallexample
|
||
|
||
PowerPC embedded processors support masked watchpoints. See the discussion
|
||
about the @code{mask} argument in @ref{Set Watchpoints}.
|
||
|
||
@cindex ranged breakpoint
|
||
PowerPC embedded processors support hardware accelerated
|
||
@dfn{ranged breakpoints}. A ranged breakpoint stops execution of
|
||
the inferior whenever it executes an instruction at any address within
|
||
the range it specifies. To set a ranged breakpoint in @value{GDBN},
|
||
use the @code{break-range} command.
|
||
|
||
@value{GDBN} provides the following PowerPC-specific commands:
|
||
|
||
@table @code
|
||
@kindex break-range
|
||
@item break-range @var{start-location}, @var{end-location}
|
||
Set a breakpoint for an address range given by
|
||
@var{start-location} and @var{end-location}, which can specify a function name,
|
||
a line number, an offset of lines from the current line or from the start
|
||
location, or an address of an instruction (see @ref{Specify Location},
|
||
for a list of all the possible ways to specify a @var{location}.)
|
||
The breakpoint will stop execution of the inferior whenever it
|
||
executes an instruction at any address within the specified range,
|
||
(including @var{start-location} and @var{end-location}.)
|
||
|
||
@kindex set powerpc
|
||
@item set powerpc soft-float
|
||
@itemx show powerpc soft-float
|
||
Force @value{GDBN} to use (or not use) a software floating point calling
|
||
convention. By default, @value{GDBN} selects the calling convention based
|
||
on the selected architecture and the provided executable file.
|
||
|
||
@item set powerpc vector-abi
|
||
@itemx show powerpc vector-abi
|
||
Force @value{GDBN} to use the specified calling convention for vector
|
||
arguments and return values. The valid options are @samp{auto};
|
||
@samp{generic}, to avoid vector registers even if they are present;
|
||
@samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
|
||
registers. By default, @value{GDBN} selects the calling convention
|
||
based on the selected architecture and the provided executable file.
|
||
|
||
@item set powerpc exact-watchpoints
|
||
@itemx show powerpc exact-watchpoints
|
||
Allow @value{GDBN} to use only one debug register when watching a variable
|
||
of scalar type, thus assuming that the variable is accessed through the
|
||
address of its first byte.
|
||
|
||
@end table
|
||
|
||
@node AVR
|
||
@subsection Atmel AVR
|
||
@cindex AVR
|
||
|
||
When configured for debugging the Atmel AVR, @value{GDBN} supports the
|
||
following AVR-specific commands:
|
||
|
||
@table @code
|
||
@item info io_registers
|
||
@kindex info io_registers@r{, AVR}
|
||
@cindex I/O registers (Atmel AVR)
|
||
This command displays information about the AVR I/O registers. For
|
||
each register, @value{GDBN} prints its number and value.
|
||
@end table
|
||
|
||
@node CRIS
|
||
@subsection CRIS
|
||
@cindex CRIS
|
||
|
||
When configured for debugging CRIS, @value{GDBN} provides the
|
||
following CRIS-specific commands:
|
||
|
||
@table @code
|
||
@item set cris-version @var{ver}
|
||
@cindex CRIS version
|
||
Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
|
||
The CRIS version affects register names and sizes. This command is useful in
|
||
case autodetection of the CRIS version fails.
|
||
|
||
@item show cris-version
|
||
Show the current CRIS version.
|
||
|
||
@item set cris-dwarf2-cfi
|
||
@cindex DWARF-2 CFI and CRIS
|
||
Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
|
||
Change to @samp{off} when using @code{gcc-cris} whose version is below
|
||
@code{R59}.
|
||
|
||
@item show cris-dwarf2-cfi
|
||
Show the current state of using DWARF-2 CFI.
|
||
|
||
@item set cris-mode @var{mode}
|
||
@cindex CRIS mode
|
||
Set the current CRIS mode to @var{mode}. It should only be changed when
|
||
debugging in guru mode, in which case it should be set to
|
||
@samp{guru} (the default is @samp{normal}).
|
||
|
||
@item show cris-mode
|
||
Show the current CRIS mode.
|
||
@end table
|
||
|
||
@node Super-H
|
||
@subsection Renesas Super-H
|
||
@cindex Super-H
|
||
|
||
For the Renesas Super-H processor, @value{GDBN} provides these
|
||
commands:
|
||
|
||
@table @code
|
||
@item set sh calling-convention @var{convention}
|
||
@kindex set sh calling-convention
|
||
Set the calling-convention used when calling functions from @value{GDBN}.
|
||
Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
|
||
With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
|
||
convention. If the DWARF-2 information of the called function specifies
|
||
that the function follows the Renesas calling convention, the function
|
||
is called using the Renesas calling convention. If the calling convention
|
||
is set to @samp{renesas}, the Renesas calling convention is always used,
|
||
regardless of the DWARF-2 information. This can be used to override the
|
||
default of @samp{gcc} if debug information is missing, or the compiler
|
||
does not emit the DWARF-2 calling convention entry for a function.
|
||
|
||
@item show sh calling-convention
|
||
@kindex show sh calling-convention
|
||
Show the current calling convention setting.
|
||
|
||
@end table
|
||
|
||
|
||
@node Architectures
|
||
@section Architectures
|
||
|
||
This section describes characteristics of architectures that affect
|
||
all uses of @value{GDBN} with the architecture, both native and cross.
|
||
|
||
@menu
|
||
* AArch64::
|
||
* i386::
|
||
* Alpha::
|
||
* MIPS::
|
||
* HPPA:: HP PA architecture
|
||
* SPU:: Cell Broadband Engine SPU architecture
|
||
* PowerPC::
|
||
* Nios II::
|
||
* Sparc64::
|
||
@end menu
|
||
|
||
@node AArch64
|
||
@subsection AArch64
|
||
@cindex AArch64 support
|
||
|
||
When @value{GDBN} is debugging the AArch64 architecture, it provides the
|
||
following special commands:
|
||
|
||
@table @code
|
||
@item set debug aarch64
|
||
@kindex set debug aarch64
|
||
This command determines whether AArch64 architecture-specific debugging
|
||
messages are to be displayed.
|
||
|
||
@item show debug aarch64
|
||
Show whether AArch64 debugging messages are displayed.
|
||
|
||
@end table
|
||
|
||
@node i386
|
||
@subsection x86 Architecture-specific Issues
|
||
|
||
@table @code
|
||
@item set struct-convention @var{mode}
|
||
@kindex set struct-convention
|
||
@cindex struct return convention
|
||
@cindex struct/union returned in registers
|
||
Set the convention used by the inferior to return @code{struct}s and
|
||
@code{union}s from functions to @var{mode}. Possible values of
|
||
@var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
|
||
default). @code{"default"} or @code{"pcc"} means that @code{struct}s
|
||
are returned on the stack, while @code{"reg"} means that a
|
||
@code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
|
||
be returned in a register.
|
||
|
||
@item show struct-convention
|
||
@kindex show struct-convention
|
||
Show the current setting of the convention to return @code{struct}s
|
||
from functions.
|
||
@end table
|
||
|
||
|
||
@subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
|
||
@cindex Intel Memory Protection Extensions (MPX).
|
||
|
||
Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
|
||
@footnote{The register named with capital letters represent the architecture
|
||
registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
|
||
which are the lower bound and upper bound. Bounds are effective addresses or
|
||
memory locations. The upper bounds are architecturally represented in 1's
|
||
complement form. A bound having lower bound = 0, and upper bound = 0
|
||
(1's complement of all bits set) will allow access to the entire address space.
|
||
|
||
@samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
|
||
through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
|
||
display the upper bound performing the complement of one operation on the
|
||
upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
|
||
@value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
|
||
can also be noted that the upper bounds are inclusive.
|
||
|
||
As an example, assume that the register BND0 holds bounds for a pointer having
|
||
access allowed for the range between 0x32 and 0x71. The values present on
|
||
bnd0raw and bnd registers are presented as follows:
|
||
|
||
@smallexample
|
||
bnd0raw = @{0x32, 0xffffffff8e@}
|
||
bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
|
||
@end smallexample
|
||
|
||
This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
|
||
change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
|
||
counterpart. When the bnd0@dots{}bnd3 registers are displayed via
|
||
Python, the display includes the memory size, in bits, accessible to
|
||
the pointer.
|
||
|
||
Bounds can also be stored in bounds tables, which are stored in
|
||
application memory. These tables store bounds for pointers by specifying
|
||
the bounds pointer's value along with its bounds. Evaluating and changing
|
||
bounds located in bound tables is therefore interesting while investigating
|
||
bugs on MPX context. @value{GDBN} provides commands for this purpose:
|
||
|
||
@table @code
|
||
@item show mpx bound @var{pointer}
|
||
@kindex show mpx bound
|
||
Display bounds of the given @var{pointer}.
|
||
|
||
@item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
|
||
@kindex set mpx bound
|
||
Set the bounds of a pointer in the bound table.
|
||
This command takes three parameters: @var{pointer} is the pointers
|
||
whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
|
||
for lower and upper bounds respectively.
|
||
@end table
|
||
|
||
When you call an inferior function on an Intel MPX enabled program,
|
||
GDB sets the inferior's bound registers to the init (disabled) state
|
||
before calling the function. As a consequence, bounds checks for the
|
||
pointer arguments passed to the function will always pass.
|
||
|
||
This is necessary because when you call an inferior function, the
|
||
program is usually in the middle of the execution of other function.
|
||
Since at that point bound registers are in an arbitrary state, not
|
||
clearing them would lead to random bound violations in the called
|
||
function.
|
||
|
||
You can still examine the influence of the bound registers on the
|
||
execution of the called function by stopping the execution of the
|
||
called function at its prologue, setting bound registers, and
|
||
continuing the execution. For example:
|
||
|
||
@smallexample
|
||
$ break *upper
|
||
Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
|
||
$ print upper (a, b, c, d, 1)
|
||
Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
|
||
$ print $bnd0
|
||
@{lbound = 0x0, ubound = ffffffff@} : size -1
|
||
@end smallexample
|
||
|
||
At this last step the value of bnd0 can be changed for investigation of bound
|
||
violations caused along the execution of the call. In order to know how to
|
||
set the bound registers or bound table for the call consult the ABI.
|
||
|
||
@node Alpha
|
||
@subsection Alpha
|
||
|
||
See the following section.
|
||
|
||
@node MIPS
|
||
@subsection @acronym{MIPS}
|
||
|
||
@cindex stack on Alpha
|
||
@cindex stack on @acronym{MIPS}
|
||
@cindex Alpha stack
|
||
@cindex @acronym{MIPS} stack
|
||
Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
|
||
sometimes requires @value{GDBN} to search backward in the object code to
|
||
find the beginning of a function.
|
||
|
||
@cindex response time, @acronym{MIPS} debugging
|
||
To improve response time (especially for embedded applications, where
|
||
@value{GDBN} may be restricted to a slow serial line for this search)
|
||
you may want to limit the size of this search, using one of these
|
||
commands:
|
||
|
||
@table @code
|
||
@cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
|
||
@item set heuristic-fence-post @var{limit}
|
||
Restrict @value{GDBN} to examining at most @var{limit} bytes in its
|
||
search for the beginning of a function. A value of @var{0} (the
|
||
default) means there is no limit. However, except for @var{0}, the
|
||
larger the limit the more bytes @code{heuristic-fence-post} must search
|
||
and therefore the longer it takes to run. You should only need to use
|
||
this command when debugging a stripped executable.
|
||
|
||
@item show heuristic-fence-post
|
||
Display the current limit.
|
||
@end table
|
||
|
||
@noindent
|
||
These commands are available @emph{only} when @value{GDBN} is configured
|
||
for debugging programs on Alpha or @acronym{MIPS} processors.
|
||
|
||
Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
|
||
programs:
|
||
|
||
@table @code
|
||
@item set mips abi @var{arg}
|
||
@kindex set mips abi
|
||
@cindex set ABI for @acronym{MIPS}
|
||
Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
|
||
values of @var{arg} are:
|
||
|
||
@table @samp
|
||
@item auto
|
||
The default ABI associated with the current binary (this is the
|
||
default).
|
||
@item o32
|
||
@item o64
|
||
@item n32
|
||
@item n64
|
||
@item eabi32
|
||
@item eabi64
|
||
@end table
|
||
|
||
@item show mips abi
|
||
@kindex show mips abi
|
||
Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
|
||
|
||
@item set mips compression @var{arg}
|
||
@kindex set mips compression
|
||
@cindex code compression, @acronym{MIPS}
|
||
Tell @value{GDBN} which @acronym{MIPS} compressed
|
||
@acronym{ISA, Instruction Set Architecture} encoding is used by the
|
||
inferior. @value{GDBN} uses this for code disassembly and other
|
||
internal interpretation purposes. This setting is only referred to
|
||
when no executable has been associated with the debugging session or
|
||
the executable does not provide information about the encoding it uses.
|
||
Otherwise this setting is automatically updated from information
|
||
provided by the executable.
|
||
|
||
Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
|
||
The default compressed @acronym{ISA} encoding is @samp{mips16}, as
|
||
executables containing @acronym{MIPS16} code frequently are not
|
||
identified as such.
|
||
|
||
This setting is ``sticky''; that is, it retains its value across
|
||
debugging sessions until reset either explicitly with this command or
|
||
implicitly from an executable.
|
||
|
||
The compiler and/or assembler typically add symbol table annotations to
|
||
identify functions compiled for the @acronym{MIPS16} or
|
||
@acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
|
||
are present, @value{GDBN} uses them in preference to the global
|
||
compressed @acronym{ISA} encoding setting.
|
||
|
||
@item show mips compression
|
||
@kindex show mips compression
|
||
Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
|
||
@value{GDBN} to debug the inferior.
|
||
|
||
@item set mipsfpu
|
||
@itemx show mipsfpu
|
||
@xref{MIPS Embedded, set mipsfpu}.
|
||
|
||
@item set mips mask-address @var{arg}
|
||
@kindex set mips mask-address
|
||
@cindex @acronym{MIPS} addresses, masking
|
||
This command determines whether the most-significant 32 bits of 64-bit
|
||
@acronym{MIPS} addresses are masked off. The argument @var{arg} can be
|
||
@samp{on}, @samp{off}, or @samp{auto}. The latter is the default
|
||
setting, which lets @value{GDBN} determine the correct value.
|
||
|
||
@item show mips mask-address
|
||
@kindex show mips mask-address
|
||
Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
|
||
not.
|
||
|
||
@item set remote-mips64-transfers-32bit-regs
|
||
@kindex set remote-mips64-transfers-32bit-regs
|
||
This command controls compatibility with 64-bit @acronym{MIPS} targets that
|
||
transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
|
||
that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
|
||
and 64 bits for other registers, set this option to @samp{on}.
|
||
|
||
@item show remote-mips64-transfers-32bit-regs
|
||
@kindex show remote-mips64-transfers-32bit-regs
|
||
Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
|
||
|
||
@item set debug mips
|
||
@kindex set debug mips
|
||
This command turns on and off debugging messages for the @acronym{MIPS}-specific
|
||
target code in @value{GDBN}.
|
||
|
||
@item show debug mips
|
||
@kindex show debug mips
|
||
Show the current setting of @acronym{MIPS} debugging messages.
|
||
@end table
|
||
|
||
|
||
@node HPPA
|
||
@subsection HPPA
|
||
@cindex HPPA support
|
||
|
||
When @value{GDBN} is debugging the HP PA architecture, it provides the
|
||
following special commands:
|
||
|
||
@table @code
|
||
@item set debug hppa
|
||
@kindex set debug hppa
|
||
This command determines whether HPPA architecture-specific debugging
|
||
messages are to be displayed.
|
||
|
||
@item show debug hppa
|
||
Show whether HPPA debugging messages are displayed.
|
||
|
||
@item maint print unwind @var{address}
|
||
@kindex maint print unwind@r{, HPPA}
|
||
This command displays the contents of the unwind table entry at the
|
||
given @var{address}.
|
||
|
||
@end table
|
||
|
||
|
||
@node SPU
|
||
@subsection Cell Broadband Engine SPU architecture
|
||
@cindex Cell Broadband Engine
|
||
@cindex SPU
|
||
|
||
When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
|
||
it provides the following special commands:
|
||
|
||
@table @code
|
||
@item info spu event
|
||
@kindex info spu
|
||
Display SPU event facility status. Shows current event mask
|
||
and pending event status.
|
||
|
||
@item info spu signal
|
||
Display SPU signal notification facility status. Shows pending
|
||
signal-control word and signal notification mode of both signal
|
||
notification channels.
|
||
|
||
@item info spu mailbox
|
||
Display SPU mailbox facility status. Shows all pending entries,
|
||
in order of processing, in each of the SPU Write Outbound,
|
||
SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
|
||
|
||
@item info spu dma
|
||
Display MFC DMA status. Shows all pending commands in the MFC
|
||
DMA queue. For each entry, opcode, tag, class IDs, effective
|
||
and local store addresses and transfer size are shown.
|
||
|
||
@item info spu proxydma
|
||
Display MFC Proxy-DMA status. Shows all pending commands in the MFC
|
||
Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
|
||
and local store addresses and transfer size are shown.
|
||
|
||
@end table
|
||
|
||
When @value{GDBN} is debugging a combined PowerPC/SPU application
|
||
on the Cell Broadband Engine, it provides in addition the following
|
||
special commands:
|
||
|
||
@table @code
|
||
@item set spu stop-on-load @var{arg}
|
||
@kindex set spu
|
||
Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
|
||
will give control to the user when a new SPE thread enters its @code{main}
|
||
function. The default is @code{off}.
|
||
|
||
@item show spu stop-on-load
|
||
@kindex show spu
|
||
Show whether to stop for new SPE threads.
|
||
|
||
@item set spu auto-flush-cache @var{arg}
|
||
Set whether to automatically flush the software-managed cache. When set to
|
||
@code{on}, @value{GDBN} will automatically cause the SPE software-managed
|
||
cache to be flushed whenever SPE execution stops. This provides a consistent
|
||
view of PowerPC memory that is accessed via the cache. If an application
|
||
does not use the software-managed cache, this option has no effect.
|
||
|
||
@item show spu auto-flush-cache
|
||
Show whether to automatically flush the software-managed cache.
|
||
|
||
@end table
|
||
|
||
@node PowerPC
|
||
@subsection PowerPC
|
||
@cindex PowerPC architecture
|
||
|
||
When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
|
||
pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
|
||
numbers stored in the floating point registers. These values must be stored
|
||
in two consecutive registers, always starting at an even register like
|
||
@code{f0} or @code{f2}.
|
||
|
||
The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
|
||
by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
|
||
@code{f2} and @code{f3} for @code{$dl1} and so on.
|
||
|
||
For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
|
||
wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
|
||
|
||
@node Nios II
|
||
@subsection Nios II
|
||
@cindex Nios II architecture
|
||
|
||
When @value{GDBN} is debugging the Nios II architecture,
|
||
it provides the following special commands:
|
||
|
||
@table @code
|
||
|
||
@item set debug nios2
|
||
@kindex set debug nios2
|
||
This command turns on and off debugging messages for the Nios II
|
||
target code in @value{GDBN}.
|
||
|
||
@item show debug nios2
|
||
@kindex show debug nios2
|
||
Show the current setting of Nios II debugging messages.
|
||
@end table
|
||
|
||
@node Sparc64
|
||
@subsection Sparc64
|
||
@cindex Sparc64 support
|
||
@cindex Application Data Integrity
|
||
@subsubsection ADI Support
|
||
|
||
The M7 processor supports an Application Data Integrity (ADI) feature that
|
||
detects invalid data accesses. When software allocates memory and enables
|
||
ADI on the allocated memory, it chooses a 4-bit version number, sets the
|
||
version in the upper 4 bits of the 64-bit pointer to that data, and stores
|
||
the 4-bit version in every cacheline of that data. Hardware saves the latter
|
||
in spare bits in the cache and memory hierarchy. On each load and store,
|
||
the processor compares the upper 4 VA (virtual address) bits to the
|
||
cacheline's version. If there is a mismatch, the processor generates a
|
||
version mismatch trap which can be either precise or disrupting. The trap
|
||
is an error condition which the kernel delivers to the process as a SIGSEGV
|
||
signal.
|
||
|
||
Note that only 64-bit applications can use ADI and need to be built with
|
||
ADI-enabled.
|
||
|
||
Values of the ADI version tags, which are in granularity of a
|
||
cacheline (64 bytes), can be viewed or modified.
|
||
|
||
|
||
@table @code
|
||
@kindex adi examine
|
||
@item adi (examine | x) [ / @var{n} ] @var{addr}
|
||
|
||
The @code{adi examine} command displays the value of one ADI version tag per
|
||
cacheline.
|
||
|
||
@var{n} is a decimal integer specifying the number in bytes; the default
|
||
is 1. It specifies how much ADI version information, at the ratio of 1:ADI
|
||
block size, to display.
|
||
|
||
@var{addr} is the address in user address space where you want @value{GDBN}
|
||
to begin displaying the ADI version tags.
|
||
|
||
Below is an example of displaying ADI versions of variable "shmaddr".
|
||
|
||
@smallexample
|
||
(@value{GDBP}) adi x/100 shmaddr
|
||
0xfff800010002c000: 0 0
|
||
@end smallexample
|
||
|
||
@kindex adi assign
|
||
@item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
|
||
|
||
The @code{adi assign} command is used to assign new ADI version tag
|
||
to an address.
|
||
|
||
@var{n} is a decimal integer specifying the number in bytes;
|
||
the default is 1. It specifies how much ADI version information, at the
|
||
ratio of 1:ADI block size, to modify.
|
||
|
||
@var{addr} is the address in user address space where you want @value{GDBN}
|
||
to begin modifying the ADI version tags.
|
||
|
||
@var{tag} is the new ADI version tag.
|
||
|
||
For example, do the following to modify then verify ADI versions of
|
||
variable "shmaddr":
|
||
|
||
@smallexample
|
||
(@value{GDBP}) adi a/100 shmaddr = 7
|
||
(@value{GDBP}) adi x/100 shmaddr
|
||
0xfff800010002c000: 7 7
|
||
@end smallexample
|
||
|
||
@end table
|
||
|
||
@node Controlling GDB
|
||
@chapter Controlling @value{GDBN}
|
||
|
||
You can alter the way @value{GDBN} interacts with you by using the
|
||
@code{set} command. For commands controlling how @value{GDBN} displays
|
||
data, see @ref{Print Settings, ,Print Settings}. Other settings are
|
||
described here.
|
||
|
||
@menu
|
||
* Prompt:: Prompt
|
||
* Editing:: Command editing
|
||
* Command History:: Command history
|
||
* Screen Size:: Screen size
|
||
* Numbers:: Numbers
|
||
* ABI:: Configuring the current ABI
|
||
* Auto-loading:: Automatically loading associated files
|
||
* Messages/Warnings:: Optional warnings and messages
|
||
* Debugging Output:: Optional messages about internal happenings
|
||
* Other Misc Settings:: Other Miscellaneous Settings
|
||
@end menu
|
||
|
||
@node Prompt
|
||
@section Prompt
|
||
|
||
@cindex prompt
|
||
|
||
@value{GDBN} indicates its readiness to read a command by printing a string
|
||
called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
|
||
can change the prompt string with the @code{set prompt} command. For
|
||
instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
|
||
the prompt in one of the @value{GDBN} sessions so that you can always tell
|
||
which one you are talking to.
|
||
|
||
@emph{Note:} @code{set prompt} does not add a space for you after the
|
||
prompt you set. This allows you to set a prompt which ends in a space
|
||
or a prompt that does not.
|
||
|
||
@table @code
|
||
@kindex set prompt
|
||
@item set prompt @var{newprompt}
|
||
Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
|
||
|
||
@kindex show prompt
|
||
@item show prompt
|
||
Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
|
||
@end table
|
||
|
||
Versions of @value{GDBN} that ship with Python scripting enabled have
|
||
prompt extensions. The commands for interacting with these extensions
|
||
are:
|
||
|
||
@table @code
|
||
@kindex set extended-prompt
|
||
@item set extended-prompt @var{prompt}
|
||
Set an extended prompt that allows for substitutions.
|
||
@xref{gdb.prompt}, for a list of escape sequences that can be used for
|
||
substitution. Any escape sequences specified as part of the prompt
|
||
string are replaced with the corresponding strings each time the prompt
|
||
is displayed.
|
||
|
||
For example:
|
||
|
||
@smallexample
|
||
set extended-prompt Current working directory: \w (gdb)
|
||
@end smallexample
|
||
|
||
Note that when an extended-prompt is set, it takes control of the
|
||
@var{prompt_hook} hook. @xref{prompt_hook}, for further information.
|
||
|
||
@kindex show extended-prompt
|
||
@item show extended-prompt
|
||
Prints the extended prompt. Any escape sequences specified as part of
|
||
the prompt string with @code{set extended-prompt}, are replaced with the
|
||
corresponding strings each time the prompt is displayed.
|
||
@end table
|
||
|
||
@node Editing
|
||
@section Command Editing
|
||
@cindex readline
|
||
@cindex command line editing
|
||
|
||
@value{GDBN} reads its input commands via the @dfn{Readline} interface. This
|
||
@sc{gnu} library provides consistent behavior for programs which provide a
|
||
command line interface to the user. Advantages are @sc{gnu} Emacs-style
|
||
or @dfn{vi}-style inline editing of commands, @code{csh}-like history
|
||
substitution, and a storage and recall of command history across
|
||
debugging sessions.
|
||
|
||
You may control the behavior of command line editing in @value{GDBN} with the
|
||
command @code{set}.
|
||
|
||
@table @code
|
||
@kindex set editing
|
||
@cindex editing
|
||
@item set editing
|
||
@itemx set editing on
|
||
Enable command line editing (enabled by default).
|
||
|
||
@item set editing off
|
||
Disable command line editing.
|
||
|
||
@kindex show editing
|
||
@item show editing
|
||
Show whether command line editing is enabled.
|
||
@end table
|
||
|
||
@ifset SYSTEM_READLINE
|
||
@xref{Command Line Editing, , , rluserman, GNU Readline Library},
|
||
@end ifset
|
||
@ifclear SYSTEM_READLINE
|
||
@xref{Command Line Editing},
|
||
@end ifclear
|
||
for more details about the Readline
|
||
interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
|
||
encouraged to read that chapter.
|
||
|
||
@node Command History
|
||
@section Command History
|
||
@cindex command history
|
||
|
||
@value{GDBN} can keep track of the commands you type during your
|
||
debugging sessions, so that you can be certain of precisely what
|
||
happened. Use these commands to manage the @value{GDBN} command
|
||
history facility.
|
||
|
||
@value{GDBN} uses the @sc{gnu} History library, a part of the Readline
|
||
package, to provide the history facility.
|
||
@ifset SYSTEM_READLINE
|
||
@xref{Using History Interactively, , , history, GNU History Library},
|
||
@end ifset
|
||
@ifclear SYSTEM_READLINE
|
||
@xref{Using History Interactively},
|
||
@end ifclear
|
||
for the detailed description of the History library.
|
||
|
||
To issue a command to @value{GDBN} without affecting certain aspects of
|
||
the state which is seen by users, prefix it with @samp{server }
|
||
(@pxref{Server Prefix}). This
|
||
means that this command will not affect the command history, nor will it
|
||
affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
|
||
pressed on a line by itself.
|
||
|
||
@cindex @code{server}, command prefix
|
||
The server prefix does not affect the recording of values into the value
|
||
history; to print a value without recording it into the value history,
|
||
use the @code{output} command instead of the @code{print} command.
|
||
|
||
Here is the description of @value{GDBN} commands related to command
|
||
history.
|
||
|
||
@table @code
|
||
@cindex history substitution
|
||
@cindex history file
|
||
@kindex set history filename
|
||
@cindex @env{GDBHISTFILE}, environment variable
|
||
@item set history filename @var{fname}
|
||
Set the name of the @value{GDBN} command history file to @var{fname}.
|
||
This is the file where @value{GDBN} reads an initial command history
|
||
list, and where it writes the command history from this session when it
|
||
exits. You can access this list through history expansion or through
|
||
the history command editing characters listed below. This file defaults
|
||
to the value of the environment variable @code{GDBHISTFILE}, or to
|
||
@file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
|
||
is not set.
|
||
|
||
@cindex save command history
|
||
@kindex set history save
|
||
@item set history save
|
||
@itemx set history save on
|
||
Record command history in a file, whose name may be specified with the
|
||
@code{set history filename} command. By default, this option is disabled.
|
||
|
||
@item set history save off
|
||
Stop recording command history in a file.
|
||
|
||
@cindex history size
|
||
@kindex set history size
|
||
@cindex @env{GDBHISTSIZE}, environment variable
|
||
@item set history size @var{size}
|
||
@itemx set history size unlimited
|
||
Set the number of commands which @value{GDBN} keeps in its history list.
|
||
This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
|
||
to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
|
||
are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
|
||
either a negative number or the empty string, then the number of commands
|
||
@value{GDBN} keeps in the history list is unlimited.
|
||
|
||
@cindex remove duplicate history
|
||
@kindex set history remove-duplicates
|
||
@item set history remove-duplicates @var{count}
|
||
@itemx set history remove-duplicates unlimited
|
||
Control the removal of duplicate history entries in the command history list.
|
||
If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
|
||
history entries and remove the first entry that is a duplicate of the current
|
||
entry being added to the command history list. If @var{count} is
|
||
@code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
|
||
removal of duplicate history entries is disabled.
|
||
|
||
Only history entries added during the current session are considered for
|
||
removal. This option is set to 0 by default.
|
||
|
||
@end table
|
||
|
||
History expansion assigns special meaning to the character @kbd{!}.
|
||
@ifset SYSTEM_READLINE
|
||
@xref{Event Designators, , , history, GNU History Library},
|
||
@end ifset
|
||
@ifclear SYSTEM_READLINE
|
||
@xref{Event Designators},
|
||
@end ifclear
|
||
for more details.
|
||
|
||
@cindex history expansion, turn on/off
|
||
Since @kbd{!} is also the logical not operator in C, history expansion
|
||
is off by default. If you decide to enable history expansion with the
|
||
@code{set history expansion on} command, you may sometimes need to
|
||
follow @kbd{!} (when it is used as logical not, in an expression) with
|
||
a space or a tab to prevent it from being expanded. The readline
|
||
history facilities do not attempt substitution on the strings
|
||
@kbd{!=} and @kbd{!(}, even when history expansion is enabled.
|
||
|
||
The commands to control history expansion are:
|
||
|
||
@table @code
|
||
@item set history expansion on
|
||
@itemx set history expansion
|
||
@kindex set history expansion
|
||
Enable history expansion. History expansion is off by default.
|
||
|
||
@item set history expansion off
|
||
Disable history expansion.
|
||
|
||
@c @group
|
||
@kindex show history
|
||
@item show history
|
||
@itemx show history filename
|
||
@itemx show history save
|
||
@itemx show history size
|
||
@itemx show history expansion
|
||
These commands display the state of the @value{GDBN} history parameters.
|
||
@code{show history} by itself displays all four states.
|
||
@c @end group
|
||
@end table
|
||
|
||
@table @code
|
||
@kindex show commands
|
||
@cindex show last commands
|
||
@cindex display command history
|
||
@item show commands
|
||
Display the last ten commands in the command history.
|
||
|
||
@item show commands @var{n}
|
||
Print ten commands centered on command number @var{n}.
|
||
|
||
@item show commands +
|
||
Print ten commands just after the commands last printed.
|
||
@end table
|
||
|
||
@node Screen Size
|
||
@section Screen Size
|
||
@cindex size of screen
|
||
@cindex screen size
|
||
@cindex pagination
|
||
@cindex page size
|
||
@cindex pauses in output
|
||
|
||
Certain commands to @value{GDBN} may produce large amounts of
|
||
information output to the screen. To help you read all of it,
|
||
@value{GDBN} pauses and asks you for input at the end of each page of
|
||
output. Type @key{RET} when you want to continue the output, or @kbd{q}
|
||
to discard the remaining output. Also, the screen width setting
|
||
determines when to wrap lines of output. Depending on what is being
|
||
printed, @value{GDBN} tries to break the line at a readable place,
|
||
rather than simply letting it overflow onto the following line.
|
||
|
||
Normally @value{GDBN} knows the size of the screen from the terminal
|
||
driver software. For example, on Unix @value{GDBN} uses the termcap data base
|
||
together with the value of the @code{TERM} environment variable and the
|
||
@code{stty rows} and @code{stty cols} settings. If this is not correct,
|
||
you can override it with the @code{set height} and @code{set
|
||
width} commands:
|
||
|
||
@table @code
|
||
@kindex set height
|
||
@kindex set width
|
||
@kindex show width
|
||
@kindex show height
|
||
@item set height @var{lpp}
|
||
@itemx set height unlimited
|
||
@itemx show height
|
||
@itemx set width @var{cpl}
|
||
@itemx set width unlimited
|
||
@itemx show width
|
||
These @code{set} commands specify a screen height of @var{lpp} lines and
|
||
a screen width of @var{cpl} characters. The associated @code{show}
|
||
commands display the current settings.
|
||
|
||
If you specify a height of either @code{unlimited} or zero lines,
|
||
@value{GDBN} does not pause during output no matter how long the
|
||
output is. This is useful if output is to a file or to an editor
|
||
buffer.
|
||
|
||
Likewise, you can specify @samp{set width unlimited} or @samp{set
|
||
width 0} to prevent @value{GDBN} from wrapping its output.
|
||
|
||
@item set pagination on
|
||
@itemx set pagination off
|
||
@kindex set pagination
|
||
Turn the output pagination on or off; the default is on. Turning
|
||
pagination off is the alternative to @code{set height unlimited}. Note that
|
||
running @value{GDBN} with the @option{--batch} option (@pxref{Mode
|
||
Options, -batch}) also automatically disables pagination.
|
||
|
||
@item show pagination
|
||
@kindex show pagination
|
||
Show the current pagination mode.
|
||
@end table
|
||
|
||
@node Numbers
|
||
@section Numbers
|
||
@cindex number representation
|
||
@cindex entering numbers
|
||
|
||
You can always enter numbers in octal, decimal, or hexadecimal in
|
||
@value{GDBN} by the usual conventions: octal numbers begin with
|
||
@samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
|
||
begin with @samp{0x}. Numbers that neither begin with @samp{0} or
|
||
@samp{0x}, nor end with a @samp{.} are, by default, entered in base
|
||
10; likewise, the default display for numbers---when no particular
|
||
format is specified---is base 10. You can change the default base for
|
||
both input and output with the commands described below.
|
||
|
||
@table @code
|
||
@kindex set input-radix
|
||
@item set input-radix @var{base}
|
||
Set the default base for numeric input. Supported choices
|
||
for @var{base} are decimal 8, 10, or 16. The base must itself be
|
||
specified either unambiguously or using the current input radix; for
|
||
example, any of
|
||
|
||
@smallexample
|
||
set input-radix 012
|
||
set input-radix 10.
|
||
set input-radix 0xa
|
||
@end smallexample
|
||
|
||
@noindent
|
||
sets the input base to decimal. On the other hand, @samp{set input-radix 10}
|
||
leaves the input radix unchanged, no matter what it was, since
|
||
@samp{10}, being without any leading or trailing signs of its base, is
|
||
interpreted in the current radix. Thus, if the current radix is 16,
|
||
@samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
|
||
change the radix.
|
||
|
||
@kindex set output-radix
|
||
@item set output-radix @var{base}
|
||
Set the default base for numeric display. Supported choices
|
||
for @var{base} are decimal 8, 10, or 16. The base must itself be
|
||
specified either unambiguously or using the current input radix.
|
||
|
||
@kindex show input-radix
|
||
@item show input-radix
|
||
Display the current default base for numeric input.
|
||
|
||
@kindex show output-radix
|
||
@item show output-radix
|
||
Display the current default base for numeric display.
|
||
|
||
@item set radix @r{[}@var{base}@r{]}
|
||
@itemx show radix
|
||
@kindex set radix
|
||
@kindex show radix
|
||
These commands set and show the default base for both input and output
|
||
of numbers. @code{set radix} sets the radix of input and output to
|
||
the same base; without an argument, it resets the radix back to its
|
||
default value of 10.
|
||
|
||
@end table
|
||
|
||
@node ABI
|
||
@section Configuring the Current ABI
|
||
|
||
@value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
|
||
application automatically. However, sometimes you need to override its
|
||
conclusions. Use these commands to manage @value{GDBN}'s view of the
|
||
current ABI.
|
||
|
||
@cindex OS ABI
|
||
@kindex set osabi
|
||
@kindex show osabi
|
||
@cindex Newlib OS ABI and its influence on the longjmp handling
|
||
|
||
One @value{GDBN} configuration can debug binaries for multiple operating
|
||
system targets, either via remote debugging or native emulation.
|
||
@value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
|
||
but you can override its conclusion using the @code{set osabi} command.
|
||
One example where this is useful is in debugging of binaries which use
|
||
an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
|
||
not have the same identifying marks that the standard C library for your
|
||
platform provides.
|
||
|
||
When @value{GDBN} is debugging the AArch64 architecture, it provides a
|
||
``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
|
||
@code{longjmp} when debugging binaries that use the @sc{newlib} C library.
|
||
The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
|
||
|
||
@table @code
|
||
@item show osabi
|
||
Show the OS ABI currently in use.
|
||
|
||
@item set osabi
|
||
With no argument, show the list of registered available OS ABI's.
|
||
|
||
@item set osabi @var{abi}
|
||
Set the current OS ABI to @var{abi}.
|
||
@end table
|
||
|
||
@cindex float promotion
|
||
|
||
Generally, the way that an argument of type @code{float} is passed to a
|
||
function depends on whether the function is prototyped. For a prototyped
|
||
(i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
|
||
according to the architecture's convention for @code{float}. For unprototyped
|
||
(i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
|
||
@code{double} and then passed.
|
||
|
||
Unfortunately, some forms of debug information do not reliably indicate whether
|
||
a function is prototyped. If @value{GDBN} calls a function that is not marked
|
||
as prototyped, it consults @kbd{set coerce-float-to-double}.
|
||
|
||
@table @code
|
||
@kindex set coerce-float-to-double
|
||
@item set coerce-float-to-double
|
||
@itemx set coerce-float-to-double on
|
||
Arguments of type @code{float} will be promoted to @code{double} when passed
|
||
to an unprototyped function. This is the default setting.
|
||
|
||
@item set coerce-float-to-double off
|
||
Arguments of type @code{float} will be passed directly to unprototyped
|
||
functions.
|
||
|
||
@kindex show coerce-float-to-double
|
||
@item show coerce-float-to-double
|
||
Show the current setting of promoting @code{float} to @code{double}.
|
||
@end table
|
||
|
||
@kindex set cp-abi
|
||
@kindex show cp-abi
|
||
@value{GDBN} needs to know the ABI used for your program's C@t{++}
|
||
objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
|
||
used to build your application. @value{GDBN} only fully supports
|
||
programs with a single C@t{++} ABI; if your program contains code using
|
||
multiple C@t{++} ABI's or if @value{GDBN} can not identify your
|
||
program's ABI correctly, you can tell @value{GDBN} which ABI to use.
|
||
Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
|
||
before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
|
||
``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
|
||
use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
|
||
``auto''.
|
||
|
||
@table @code
|
||
@item show cp-abi
|
||
Show the C@t{++} ABI currently in use.
|
||
|
||
@item set cp-abi
|
||
With no argument, show the list of supported C@t{++} ABI's.
|
||
|
||
@item set cp-abi @var{abi}
|
||
@itemx set cp-abi auto
|
||
Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
|
||
@end table
|
||
|
||
@node Auto-loading
|
||
@section Automatically loading associated files
|
||
@cindex auto-loading
|
||
|
||
@value{GDBN} sometimes reads files with commands and settings automatically,
|
||
without being explicitly told so by the user. We call this feature
|
||
@dfn{auto-loading}. While auto-loading is useful for automatically adapting
|
||
@value{GDBN} to the needs of your project, it can sometimes produce unexpected
|
||
results or introduce security risks (e.g., if the file comes from untrusted
|
||
sources).
|
||
|
||
@menu
|
||
* Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
|
||
* libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
|
||
|
||
* Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
|
||
* Auto-loading verbose mode:: @samp{set/show debug auto-load}
|
||
@end menu
|
||
|
||
There are various kinds of files @value{GDBN} can automatically load.
|
||
In addition to these files, @value{GDBN} supports auto-loading code written
|
||
in various extension languages. @xref{Auto-loading extensions}.
|
||
|
||
Note that loading of these associated files (including the local @file{.gdbinit}
|
||
file) requires accordingly configured @code{auto-load safe-path}
|
||
(@pxref{Auto-loading safe path}).
|
||
|
||
For these reasons, @value{GDBN} includes commands and options to let you
|
||
control when to auto-load files and which files should be auto-loaded.
|
||
|
||
@table @code
|
||
@anchor{set auto-load off}
|
||
@kindex set auto-load off
|
||
@item set auto-load off
|
||
Globally disable loading of all auto-loaded files.
|
||
You may want to use this command with the @samp{-iex} option
|
||
(@pxref{Option -init-eval-command}) such as:
|
||
@smallexample
|
||
$ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
|
||
@end smallexample
|
||
|
||
Be aware that system init file (@pxref{System-wide configuration})
|
||
and init files from your home directory (@pxref{Home Directory Init File})
|
||
still get read (as they come from generally trusted directories).
|
||
To prevent @value{GDBN} from auto-loading even those init files, use the
|
||
@option{-nx} option (@pxref{Mode Options}), in addition to
|
||
@code{set auto-load no}.
|
||
|
||
@anchor{show auto-load}
|
||
@kindex show auto-load
|
||
@item show auto-load
|
||
Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
|
||
or disabled.
|
||
|
||
@smallexample
|
||
(gdb) show auto-load
|
||
gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
|
||
libthread-db: Auto-loading of inferior specific libthread_db is on.
|
||
local-gdbinit: Auto-loading of .gdbinit script from current directory
|
||
is on.
|
||
python-scripts: Auto-loading of Python scripts is on.
|
||
safe-path: List of directories from which it is safe to auto-load files
|
||
is $debugdir:$datadir/auto-load.
|
||
scripts-directory: List of directories from which to load auto-loaded scripts
|
||
is $debugdir:$datadir/auto-load.
|
||
@end smallexample
|
||
|
||
@anchor{info auto-load}
|
||
@kindex info auto-load
|
||
@item info auto-load
|
||
Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
|
||
not.
|
||
|
||
@smallexample
|
||
(gdb) info auto-load
|
||
gdb-scripts:
|
||
Loaded Script
|
||
Yes /home/user/gdb/gdb-gdb.gdb
|
||
libthread-db: No auto-loaded libthread-db.
|
||
local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
|
||
loaded.
|
||
python-scripts:
|
||
Loaded Script
|
||
Yes /home/user/gdb/gdb-gdb.py
|
||
@end smallexample
|
||
@end table
|
||
|
||
These are @value{GDBN} control commands for the auto-loading:
|
||
|
||
@multitable @columnfractions .5 .5
|
||
@item @xref{set auto-load off}.
|
||
@tab Disable auto-loading globally.
|
||
@item @xref{show auto-load}.
|
||
@tab Show setting of all kinds of files.
|
||
@item @xref{info auto-load}.
|
||
@tab Show state of all kinds of files.
|
||
@item @xref{set auto-load gdb-scripts}.
|
||
@tab Control for @value{GDBN} command scripts.
|
||
@item @xref{show auto-load gdb-scripts}.
|
||
@tab Show setting of @value{GDBN} command scripts.
|
||
@item @xref{info auto-load gdb-scripts}.
|
||
@tab Show state of @value{GDBN} command scripts.
|
||
@item @xref{set auto-load python-scripts}.
|
||
@tab Control for @value{GDBN} Python scripts.
|
||
@item @xref{show auto-load python-scripts}.
|
||
@tab Show setting of @value{GDBN} Python scripts.
|
||
@item @xref{info auto-load python-scripts}.
|
||
@tab Show state of @value{GDBN} Python scripts.
|
||
@item @xref{set auto-load guile-scripts}.
|
||
@tab Control for @value{GDBN} Guile scripts.
|
||
@item @xref{show auto-load guile-scripts}.
|
||
@tab Show setting of @value{GDBN} Guile scripts.
|
||
@item @xref{info auto-load guile-scripts}.
|
||
@tab Show state of @value{GDBN} Guile scripts.
|
||
@item @xref{set auto-load scripts-directory}.
|
||
@tab Control for @value{GDBN} auto-loaded scripts location.
|
||
@item @xref{show auto-load scripts-directory}.
|
||
@tab Show @value{GDBN} auto-loaded scripts location.
|
||
@item @xref{add-auto-load-scripts-directory}.
|
||
@tab Add directory for auto-loaded scripts location list.
|
||
@item @xref{set auto-load local-gdbinit}.
|
||
@tab Control for init file in the current directory.
|
||
@item @xref{show auto-load local-gdbinit}.
|
||
@tab Show setting of init file in the current directory.
|
||
@item @xref{info auto-load local-gdbinit}.
|
||
@tab Show state of init file in the current directory.
|
||
@item @xref{set auto-load libthread-db}.
|
||
@tab Control for thread debugging library.
|
||
@item @xref{show auto-load libthread-db}.
|
||
@tab Show setting of thread debugging library.
|
||
@item @xref{info auto-load libthread-db}.
|
||
@tab Show state of thread debugging library.
|
||
@item @xref{set auto-load safe-path}.
|
||
@tab Control directories trusted for automatic loading.
|
||
@item @xref{show auto-load safe-path}.
|
||
@tab Show directories trusted for automatic loading.
|
||
@item @xref{add-auto-load-safe-path}.
|
||
@tab Add directory trusted for automatic loading.
|
||
@end multitable
|
||
|
||
@node Init File in the Current Directory
|
||
@subsection Automatically loading init file in the current directory
|
||
@cindex auto-loading init file in the current directory
|
||
|
||
By default, @value{GDBN} reads and executes the canned sequences of commands
|
||
from init file (if any) in the current working directory,
|
||
see @ref{Init File in the Current Directory during Startup}.
|
||
|
||
Note that loading of this local @file{.gdbinit} file also requires accordingly
|
||
configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
|
||
@table @code
|
||
@anchor{set auto-load local-gdbinit}
|
||
@kindex set auto-load local-gdbinit
|
||
@item set auto-load local-gdbinit [on|off]
|
||
Enable or disable the auto-loading of canned sequences of commands
|
||
(@pxref{Sequences}) found in init file in the current directory.
|
||
|
||
@anchor{show auto-load local-gdbinit}
|
||
@kindex show auto-load local-gdbinit
|
||
@item show auto-load local-gdbinit
|
||
Show whether auto-loading of canned sequences of commands from init file in the
|
||
current directory is enabled or disabled.
|
||
|
||
@anchor{info auto-load local-gdbinit}
|
||
@kindex info auto-load local-gdbinit
|
||
@item info auto-load local-gdbinit
|
||
Print whether canned sequences of commands from init file in the
|
||
current directory have been auto-loaded.
|
||
@end table
|
||
|
||
@node libthread_db.so.1 file
|
||
@subsection Automatically loading thread debugging library
|
||
@cindex auto-loading libthread_db.so.1
|
||
|
||
This feature is currently present only on @sc{gnu}/Linux native hosts.
|
||
|
||
@value{GDBN} reads in some cases thread debugging library from places specific
|
||
to the inferior (@pxref{set libthread-db-search-path}).
|
||
|
||
The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
|
||
without checking this @samp{set auto-load libthread-db} switch as system
|
||
libraries have to be trusted in general. In all other cases of
|
||
@samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
|
||
auto-load libthread-db} is enabled before trying to open such thread debugging
|
||
library.
|
||
|
||
Note that loading of this debugging library also requires accordingly configured
|
||
@code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
|
||
@table @code
|
||
@anchor{set auto-load libthread-db}
|
||
@kindex set auto-load libthread-db
|
||
@item set auto-load libthread-db [on|off]
|
||
Enable or disable the auto-loading of inferior specific thread debugging library.
|
||
|
||
@anchor{show auto-load libthread-db}
|
||
@kindex show auto-load libthread-db
|
||
@item show auto-load libthread-db
|
||
Show whether auto-loading of inferior specific thread debugging library is
|
||
enabled or disabled.
|
||
|
||
@anchor{info auto-load libthread-db}
|
||
@kindex info auto-load libthread-db
|
||
@item info auto-load libthread-db
|
||
Print the list of all loaded inferior specific thread debugging libraries and
|
||
for each such library print list of inferior @var{pid}s using it.
|
||
@end table
|
||
|
||
@node Auto-loading safe path
|
||
@subsection Security restriction for auto-loading
|
||
@cindex auto-loading safe-path
|
||
|
||
As the files of inferior can come from untrusted source (such as submitted by
|
||
an application user) @value{GDBN} does not always load any files automatically.
|
||
@value{GDBN} provides the @samp{set auto-load safe-path} setting to list
|
||
directories trusted for loading files not explicitly requested by user.
|
||
Each directory can also be a shell wildcard pattern.
|
||
|
||
If the path is not set properly you will see a warning and the file will not
|
||
get loaded:
|
||
|
||
@smallexample
|
||
$ ./gdb -q ./gdb
|
||
Reading symbols from /home/user/gdb/gdb...done.
|
||
warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
|
||
declined by your `auto-load safe-path' set
|
||
to "$debugdir:$datadir/auto-load".
|
||
warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
|
||
declined by your `auto-load safe-path' set
|
||
to "$debugdir:$datadir/auto-load".
|
||
@end smallexample
|
||
|
||
@noindent
|
||
To instruct @value{GDBN} to go ahead and use the init files anyway,
|
||
invoke @value{GDBN} like this:
|
||
|
||
@smallexample
|
||
$ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
|
||
@end smallexample
|
||
|
||
The list of trusted directories is controlled by the following commands:
|
||
|
||
@table @code
|
||
@anchor{set auto-load safe-path}
|
||
@kindex set auto-load safe-path
|
||
@item set auto-load safe-path @r{[}@var{directories}@r{]}
|
||
Set the list of directories (and their subdirectories) trusted for automatic
|
||
loading and execution of scripts. You can also enter a specific trusted file.
|
||
Each directory can also be a shell wildcard pattern; wildcards do not match
|
||
directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
|
||
(@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
|
||
If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
|
||
its default value as specified during @value{GDBN} compilation.
|
||
|
||
The list of directories uses path separator (@samp{:} on GNU and Unix
|
||
systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
|
||
to the @env{PATH} environment variable.
|
||
|
||
@anchor{show auto-load safe-path}
|
||
@kindex show auto-load safe-path
|
||
@item show auto-load safe-path
|
||
Show the list of directories trusted for automatic loading and execution of
|
||
scripts.
|
||
|
||
@anchor{add-auto-load-safe-path}
|
||
@kindex add-auto-load-safe-path
|
||
@item add-auto-load-safe-path
|
||
Add an entry (or list of entries) to the list of directories trusted for
|
||
automatic loading and execution of scripts. Multiple entries may be delimited
|
||
by the host platform path separator in use.
|
||
@end table
|
||
|
||
This variable defaults to what @code{--with-auto-load-dir} has been configured
|
||
to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
|
||
substitution applies the same as for @ref{set auto-load scripts-directory}.
|
||
The default @code{set auto-load safe-path} value can be also overriden by
|
||
@value{GDBN} configuration option @option{--with-auto-load-safe-path}.
|
||
|
||
Setting this variable to @file{/} disables this security protection,
|
||
corresponding @value{GDBN} configuration option is
|
||
@option{--without-auto-load-safe-path}.
|
||
This variable is supposed to be set to the system directories writable by the
|
||
system superuser only. Users can add their source directories in init files in
|
||
their home directories (@pxref{Home Directory Init File}). See also deprecated
|
||
init file in the current directory
|
||
(@pxref{Init File in the Current Directory during Startup}).
|
||
|
||
To force @value{GDBN} to load the files it declined to load in the previous
|
||
example, you could use one of the following ways:
|
||
|
||
@table @asis
|
||
@item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
|
||
Specify this trusted directory (or a file) as additional component of the list.
|
||
You have to specify also any existing directories displayed by
|
||
by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
|
||
|
||
@item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
|
||
Specify this directory as in the previous case but just for a single
|
||
@value{GDBN} session.
|
||
|
||
@item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
|
||
Disable auto-loading safety for a single @value{GDBN} session.
|
||
This assumes all the files you debug during this @value{GDBN} session will come
|
||
from trusted sources.
|
||
|
||
@item @kbd{./configure --without-auto-load-safe-path}
|
||
During compilation of @value{GDBN} you may disable any auto-loading safety.
|
||
This assumes all the files you will ever debug with this @value{GDBN} come from
|
||
trusted sources.
|
||
@end table
|
||
|
||
On the other hand you can also explicitly forbid automatic files loading which
|
||
also suppresses any such warning messages:
|
||
|
||
@table @asis
|
||
@item @kbd{gdb -iex "set auto-load no" @dots{}}
|
||
You can use @value{GDBN} command-line option for a single @value{GDBN} session.
|
||
|
||
@item @file{~/.gdbinit}: @samp{set auto-load no}
|
||
Disable auto-loading globally for the user
|
||
(@pxref{Home Directory Init File}). While it is improbable, you could also
|
||
use system init file instead (@pxref{System-wide configuration}).
|
||
@end table
|
||
|
||
This setting applies to the file names as entered by user. If no entry matches
|
||
@value{GDBN} tries as a last resort to also resolve all the file names into
|
||
their canonical form (typically resolving symbolic links) and compare the
|
||
entries again. @value{GDBN} already canonicalizes most of the filenames on its
|
||
own before starting the comparison so a canonical form of directories is
|
||
recommended to be entered.
|
||
|
||
@node Auto-loading verbose mode
|
||
@subsection Displaying files tried for auto-load
|
||
@cindex auto-loading verbose mode
|
||
|
||
For better visibility of all the file locations where you can place scripts to
|
||
be auto-loaded with inferior --- or to protect yourself against accidental
|
||
execution of untrusted scripts --- @value{GDBN} provides a feature for printing
|
||
all the files attempted to be loaded. Both existing and non-existing files may
|
||
be printed.
|
||
|
||
For example the list of directories from which it is safe to auto-load files
|
||
(@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
|
||
may not be too obvious while setting it up.
|
||
|
||
@smallexample
|
||
(gdb) set debug auto-load on
|
||
(gdb) file ~/src/t/true
|
||
auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
|
||
for objfile "/tmp/true".
|
||
auto-load: Updating directories of "/usr:/opt".
|
||
auto-load: Using directory "/usr".
|
||
auto-load: Using directory "/opt".
|
||
warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
|
||
by your `auto-load safe-path' set to "/usr:/opt".
|
||
@end smallexample
|
||
|
||
@table @code
|
||
@anchor{set debug auto-load}
|
||
@kindex set debug auto-load
|
||
@item set debug auto-load [on|off]
|
||
Set whether to print the filenames attempted to be auto-loaded.
|
||
|
||
@anchor{show debug auto-load}
|
||
@kindex show debug auto-load
|
||
@item show debug auto-load
|
||
Show whether printing of the filenames attempted to be auto-loaded is turned
|
||
on or off.
|
||
@end table
|
||
|
||
@node Messages/Warnings
|
||
@section Optional Warnings and Messages
|
||
|
||
@cindex verbose operation
|
||
@cindex optional warnings
|
||
By default, @value{GDBN} is silent about its inner workings. If you are
|
||
running on a slow machine, you may want to use the @code{set verbose}
|
||
command. This makes @value{GDBN} tell you when it does a lengthy
|
||
internal operation, so you will not think it has crashed.
|
||
|
||
Currently, the messages controlled by @code{set verbose} are those
|
||
which announce that the symbol table for a source file is being read;
|
||
see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
|
||
|
||
@table @code
|
||
@kindex set verbose
|
||
@item set verbose on
|
||
Enables @value{GDBN} output of certain informational messages.
|
||
|
||
@item set verbose off
|
||
Disables @value{GDBN} output of certain informational messages.
|
||
|
||
@kindex show verbose
|
||
@item show verbose
|
||
Displays whether @code{set verbose} is on or off.
|
||
@end table
|
||
|
||
By default, if @value{GDBN} encounters bugs in the symbol table of an
|
||
object file, it is silent; but if you are debugging a compiler, you may
|
||
find this information useful (@pxref{Symbol Errors, ,Errors Reading
|
||
Symbol Files}).
|
||
|
||
@table @code
|
||
|
||
@kindex set complaints
|
||
@item set complaints @var{limit}
|
||
Permits @value{GDBN} to output @var{limit} complaints about each type of
|
||
unusual symbols before becoming silent about the problem. Set
|
||
@var{limit} to zero to suppress all complaints; set it to a large number
|
||
to prevent complaints from being suppressed.
|
||
|
||
@kindex show complaints
|
||
@item show complaints
|
||
Displays how many symbol complaints @value{GDBN} is permitted to produce.
|
||
|
||
@end table
|
||
|
||
@anchor{confirmation requests}
|
||
By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
|
||
lot of stupid questions to confirm certain commands. For example, if
|
||
you try to run a program which is already running:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) run
|
||
The program being debugged has been started already.
|
||
Start it from the beginning? (y or n)
|
||
@end smallexample
|
||
|
||
If you are willing to unflinchingly face the consequences of your own
|
||
commands, you can disable this ``feature'':
|
||
|
||
@table @code
|
||
|
||
@kindex set confirm
|
||
@cindex flinching
|
||
@cindex confirmation
|
||
@cindex stupid questions
|
||
@item set confirm off
|
||
Disables confirmation requests. Note that running @value{GDBN} with
|
||
the @option{--batch} option (@pxref{Mode Options, -batch}) also
|
||
automatically disables confirmation requests.
|
||
|
||
@item set confirm on
|
||
Enables confirmation requests (the default).
|
||
|
||
@kindex show confirm
|
||
@item show confirm
|
||
Displays state of confirmation requests.
|
||
|
||
@end table
|
||
|
||
@cindex command tracing
|
||
If you need to debug user-defined commands or sourced files you may find it
|
||
useful to enable @dfn{command tracing}. In this mode each command will be
|
||
printed as it is executed, prefixed with one or more @samp{+} symbols, the
|
||
quantity denoting the call depth of each command.
|
||
|
||
@table @code
|
||
@kindex set trace-commands
|
||
@cindex command scripts, debugging
|
||
@item set trace-commands on
|
||
Enable command tracing.
|
||
@item set trace-commands off
|
||
Disable command tracing.
|
||
@item show trace-commands
|
||
Display the current state of command tracing.
|
||
@end table
|
||
|
||
@node Debugging Output
|
||
@section Optional Messages about Internal Happenings
|
||
@cindex optional debugging messages
|
||
|
||
@value{GDBN} has commands that enable optional debugging messages from
|
||
various @value{GDBN} subsystems; normally these commands are of
|
||
interest to @value{GDBN} maintainers, or when reporting a bug. This
|
||
section documents those commands.
|
||
|
||
@table @code
|
||
@kindex set exec-done-display
|
||
@item set exec-done-display
|
||
Turns on or off the notification of asynchronous commands'
|
||
completion. When on, @value{GDBN} will print a message when an
|
||
asynchronous command finishes its execution. The default is off.
|
||
@kindex show exec-done-display
|
||
@item show exec-done-display
|
||
Displays the current setting of asynchronous command completion
|
||
notification.
|
||
@kindex set debug
|
||
@cindex ARM AArch64
|
||
@item set debug aarch64
|
||
Turns on or off display of debugging messages related to ARM AArch64.
|
||
The default is off.
|
||
@kindex show debug
|
||
@item show debug aarch64
|
||
Displays the current state of displaying debugging messages related to
|
||
ARM AArch64.
|
||
@cindex gdbarch debugging info
|
||
@cindex architecture debugging info
|
||
@item set debug arch
|
||
Turns on or off display of gdbarch debugging info. The default is off
|
||
@item show debug arch
|
||
Displays the current state of displaying gdbarch debugging info.
|
||
@item set debug aix-solib
|
||
@cindex AIX shared library debugging
|
||
Control display of debugging messages from the AIX shared library
|
||
support module. The default is off.
|
||
@item show debug aix-thread
|
||
Show the current state of displaying AIX shared library debugging messages.
|
||
@item set debug aix-thread
|
||
@cindex AIX threads
|
||
Display debugging messages about inner workings of the AIX thread
|
||
module.
|
||
@item show debug aix-thread
|
||
Show the current state of AIX thread debugging info display.
|
||
@item set debug check-physname
|
||
@cindex physname
|
||
Check the results of the ``physname'' computation. When reading DWARF
|
||
debugging information for C@t{++}, @value{GDBN} attempts to compute
|
||
each entity's name. @value{GDBN} can do this computation in two
|
||
different ways, depending on exactly what information is present.
|
||
When enabled, this setting causes @value{GDBN} to compute the names
|
||
both ways and display any discrepancies.
|
||
@item show debug check-physname
|
||
Show the current state of ``physname'' checking.
|
||
@item set debug coff-pe-read
|
||
@cindex COFF/PE exported symbols
|
||
Control display of debugging messages related to reading of COFF/PE
|
||
exported symbols. The default is off.
|
||
@item show debug coff-pe-read
|
||
Displays the current state of displaying debugging messages related to
|
||
reading of COFF/PE exported symbols.
|
||
@item set debug dwarf-die
|
||
@cindex DWARF DIEs
|
||
Dump DWARF DIEs after they are read in.
|
||
The value is the number of nesting levels to print.
|
||
A value of zero turns off the display.
|
||
@item show debug dwarf-die
|
||
Show the current state of DWARF DIE debugging.
|
||
@item set debug dwarf-line
|
||
@cindex DWARF Line Tables
|
||
Turns on or off display of debugging messages related to reading
|
||
DWARF line tables. The default is 0 (off).
|
||
A value of 1 provides basic information.
|
||
A value greater than 1 provides more verbose information.
|
||
@item show debug dwarf-line
|
||
Show the current state of DWARF line table debugging.
|
||
@item set debug dwarf-read
|
||
@cindex DWARF Reading
|
||
Turns on or off display of debugging messages related to reading
|
||
DWARF debug info. The default is 0 (off).
|
||
A value of 1 provides basic information.
|
||
A value greater than 1 provides more verbose information.
|
||
@item show debug dwarf-read
|
||
Show the current state of DWARF reader debugging.
|
||
@item set debug displaced
|
||
@cindex displaced stepping debugging info
|
||
Turns on or off display of @value{GDBN} debugging info for the
|
||
displaced stepping support. The default is off.
|
||
@item show debug displaced
|
||
Displays the current state of displaying @value{GDBN} debugging info
|
||
related to displaced stepping.
|
||
@item set debug event
|
||
@cindex event debugging info
|
||
Turns on or off display of @value{GDBN} event debugging info. The
|
||
default is off.
|
||
@item show debug event
|
||
Displays the current state of displaying @value{GDBN} event debugging
|
||
info.
|
||
@item set debug expression
|
||
@cindex expression debugging info
|
||
Turns on or off display of debugging info about @value{GDBN}
|
||
expression parsing. The default is off.
|
||
@item show debug expression
|
||
Displays the current state of displaying debugging info about
|
||
@value{GDBN} expression parsing.
|
||
@item set debug fbsd-lwp
|
||
@cindex FreeBSD LWP debug messages
|
||
Turns on or off debugging messages from the FreeBSD LWP debug support.
|
||
@item show debug fbsd-lwp
|
||
Show the current state of FreeBSD LWP debugging messages.
|
||
@item set debug fbsd-nat
|
||
@cindex FreeBSD native target debug messages
|
||
Turns on or off debugging messages from the FreeBSD native target.
|
||
@item show debug fbsd-nat
|
||
Show the current state of FreeBSD native target debugging messages.
|
||
@item set debug frame
|
||
@cindex frame debugging info
|
||
Turns on or off display of @value{GDBN} frame debugging info. The
|
||
default is off.
|
||
@item show debug frame
|
||
Displays the current state of displaying @value{GDBN} frame debugging
|
||
info.
|
||
@item set debug gnu-nat
|
||
@cindex @sc{gnu}/Hurd debug messages
|
||
Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
|
||
@item show debug gnu-nat
|
||
Show the current state of @sc{gnu}/Hurd debugging messages.
|
||
@item set debug infrun
|
||
@cindex inferior debugging info
|
||
Turns on or off display of @value{GDBN} debugging info for running the inferior.
|
||
The default is off. @file{infrun.c} contains GDB's runtime state machine used
|
||
for implementing operations such as single-stepping the inferior.
|
||
@item show debug infrun
|
||
Displays the current state of @value{GDBN} inferior debugging.
|
||
@item set debug jit
|
||
@cindex just-in-time compilation, debugging messages
|
||
Turn on or off debugging messages from JIT debug support.
|
||
@item show debug jit
|
||
Displays the current state of @value{GDBN} JIT debugging.
|
||
@item set debug lin-lwp
|
||
@cindex @sc{gnu}/Linux LWP debug messages
|
||
@cindex Linux lightweight processes
|
||
Turn on or off debugging messages from the Linux LWP debug support.
|
||
@item show debug lin-lwp
|
||
Show the current state of Linux LWP debugging messages.
|
||
@item set debug linux-namespaces
|
||
@cindex @sc{gnu}/Linux namespaces debug messages
|
||
Turn on or off debugging messages from the Linux namespaces debug support.
|
||
@item show debug linux-namespaces
|
||
Show the current state of Linux namespaces debugging messages.
|
||
@item set debug mach-o
|
||
@cindex Mach-O symbols processing
|
||
Control display of debugging messages related to Mach-O symbols
|
||
processing. The default is off.
|
||
@item show debug mach-o
|
||
Displays the current state of displaying debugging messages related to
|
||
reading of COFF/PE exported symbols.
|
||
@item set debug notification
|
||
@cindex remote async notification debugging info
|
||
Turn on or off debugging messages about remote async notification.
|
||
The default is off.
|
||
@item show debug notification
|
||
Displays the current state of remote async notification debugging messages.
|
||
@item set debug observer
|
||
@cindex observer debugging info
|
||
Turns on or off display of @value{GDBN} observer debugging. This
|
||
includes info such as the notification of observable events.
|
||
@item show debug observer
|
||
Displays the current state of observer debugging.
|
||
@item set debug overload
|
||
@cindex C@t{++} overload debugging info
|
||
Turns on or off display of @value{GDBN} C@t{++} overload debugging
|
||
info. This includes info such as ranking of functions, etc. The default
|
||
is off.
|
||
@item show debug overload
|
||
Displays the current state of displaying @value{GDBN} C@t{++} overload
|
||
debugging info.
|
||
@cindex expression parser, debugging info
|
||
@cindex debug expression parser
|
||
@item set debug parser
|
||
Turns on or off the display of expression parser debugging output.
|
||
Internally, this sets the @code{yydebug} variable in the expression
|
||
parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
|
||
details. The default is off.
|
||
@item show debug parser
|
||
Show the current state of expression parser debugging.
|
||
@cindex packets, reporting on stdout
|
||
@cindex serial connections, debugging
|
||
@cindex debug remote protocol
|
||
@cindex remote protocol debugging
|
||
@cindex display remote packets
|
||
@item set debug remote
|
||
Turns on or off display of reports on all packets sent back and forth across
|
||
the serial line to the remote machine. The info is printed on the
|
||
@value{GDBN} standard output stream. The default is off.
|
||
@item show debug remote
|
||
Displays the state of display of remote packets.
|
||
|
||
@item set debug separate-debug-file
|
||
Turns on or off display of debug output about separate debug file search.
|
||
@item show debug separate-debug-file
|
||
Displays the state of separate debug file search debug output.
|
||
|
||
@item set debug serial
|
||
Turns on or off display of @value{GDBN} serial debugging info. The
|
||
default is off.
|
||
@item show debug serial
|
||
Displays the current state of displaying @value{GDBN} serial debugging
|
||
info.
|
||
@item set debug solib-frv
|
||
@cindex FR-V shared-library debugging
|
||
Turn on or off debugging messages for FR-V shared-library code.
|
||
@item show debug solib-frv
|
||
Display the current state of FR-V shared-library code debugging
|
||
messages.
|
||
@item set debug symbol-lookup
|
||
@cindex symbol lookup
|
||
Turns on or off display of debugging messages related to symbol lookup.
|
||
The default is 0 (off).
|
||
A value of 1 provides basic information.
|
||
A value greater than 1 provides more verbose information.
|
||
@item show debug symbol-lookup
|
||
Show the current state of symbol lookup debugging messages.
|
||
@item set debug symfile
|
||
@cindex symbol file functions
|
||
Turns on or off display of debugging messages related to symbol file functions.
|
||
The default is off. @xref{Files}.
|
||
@item show debug symfile
|
||
Show the current state of symbol file debugging messages.
|
||
@item set debug symtab-create
|
||
@cindex symbol table creation
|
||
Turns on or off display of debugging messages related to symbol table creation.
|
||
The default is 0 (off).
|
||
A value of 1 provides basic information.
|
||
A value greater than 1 provides more verbose information.
|
||
@item show debug symtab-create
|
||
Show the current state of symbol table creation debugging.
|
||
@item set debug target
|
||
@cindex target debugging info
|
||
Turns on or off display of @value{GDBN} target debugging info. This info
|
||
includes what is going on at the target level of GDB, as it happens. The
|
||
default is 0. Set it to 1 to track events, and to 2 to also track the
|
||
value of large memory transfers.
|
||
@item show debug target
|
||
Displays the current state of displaying @value{GDBN} target debugging
|
||
info.
|
||
@item set debug timestamp
|
||
@cindex timestampping debugging info
|
||
Turns on or off display of timestamps with @value{GDBN} debugging info.
|
||
When enabled, seconds and microseconds are displayed before each debugging
|
||
message.
|
||
@item show debug timestamp
|
||
Displays the current state of displaying timestamps with @value{GDBN}
|
||
debugging info.
|
||
@item set debug varobj
|
||
@cindex variable object debugging info
|
||
Turns on or off display of @value{GDBN} variable object debugging
|
||
info. The default is off.
|
||
@item show debug varobj
|
||
Displays the current state of displaying @value{GDBN} variable object
|
||
debugging info.
|
||
@item set debug xml
|
||
@cindex XML parser debugging
|
||
Turn on or off debugging messages for built-in XML parsers.
|
||
@item show debug xml
|
||
Displays the current state of XML debugging messages.
|
||
@end table
|
||
|
||
@node Other Misc Settings
|
||
@section Other Miscellaneous Settings
|
||
@cindex miscellaneous settings
|
||
|
||
@table @code
|
||
@kindex set interactive-mode
|
||
@item set interactive-mode
|
||
If @code{on}, forces @value{GDBN} to assume that GDB was started
|
||
in a terminal. In practice, this means that @value{GDBN} should wait
|
||
for the user to answer queries generated by commands entered at
|
||
the command prompt. If @code{off}, forces @value{GDBN} to operate
|
||
in the opposite mode, and it uses the default answers to all queries.
|
||
If @code{auto} (the default), @value{GDBN} tries to determine whether
|
||
its standard input is a terminal, and works in interactive-mode if it
|
||
is, non-interactively otherwise.
|
||
|
||
In the vast majority of cases, the debugger should be able to guess
|
||
correctly which mode should be used. But this setting can be useful
|
||
in certain specific cases, such as running a MinGW @value{GDBN}
|
||
inside a cygwin window.
|
||
|
||
@kindex show interactive-mode
|
||
@item show interactive-mode
|
||
Displays whether the debugger is operating in interactive mode or not.
|
||
@end table
|
||
|
||
@node Extending GDB
|
||
@chapter Extending @value{GDBN}
|
||
@cindex extending GDB
|
||
|
||
@value{GDBN} provides several mechanisms for extension.
|
||
@value{GDBN} also provides the ability to automatically load
|
||
extensions when it reads a file for debugging. This allows the
|
||
user to automatically customize @value{GDBN} for the program
|
||
being debugged.
|
||
|
||
@menu
|
||
* Sequences:: Canned Sequences of @value{GDBN} Commands
|
||
* Python:: Extending @value{GDBN} using Python
|
||
* Guile:: Extending @value{GDBN} using Guile
|
||
* Auto-loading extensions:: Automatically loading extensions
|
||
* Multiple Extension Languages:: Working with multiple extension languages
|
||
* Aliases:: Creating new spellings of existing commands
|
||
@end menu
|
||
|
||
To facilitate the use of extension languages, @value{GDBN} is capable
|
||
of evaluating the contents of a file. When doing so, @value{GDBN}
|
||
can recognize which extension language is being used by looking at
|
||
the filename extension. Files with an unrecognized filename extension
|
||
are always treated as a @value{GDBN} Command Files.
|
||
@xref{Command Files,, Command files}.
|
||
|
||
You can control how @value{GDBN} evaluates these files with the following
|
||
setting:
|
||
|
||
@table @code
|
||
@kindex set script-extension
|
||
@kindex show script-extension
|
||
@item set script-extension off
|
||
All scripts are always evaluated as @value{GDBN} Command Files.
|
||
|
||
@item set script-extension soft
|
||
The debugger determines the scripting language based on filename
|
||
extension. If this scripting language is supported, @value{GDBN}
|
||
evaluates the script using that language. Otherwise, it evaluates
|
||
the file as a @value{GDBN} Command File.
|
||
|
||
@item set script-extension strict
|
||
The debugger determines the scripting language based on filename
|
||
extension, and evaluates the script using that language. If the
|
||
language is not supported, then the evaluation fails.
|
||
|
||
@item show script-extension
|
||
Display the current value of the @code{script-extension} option.
|
||
|
||
@end table
|
||
|
||
@node Sequences
|
||
@section Canned Sequences of Commands
|
||
|
||
Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
|
||
Command Lists}), @value{GDBN} provides two ways to store sequences of
|
||
commands for execution as a unit: user-defined commands and command
|
||
files.
|
||
|
||
@menu
|
||
* Define:: How to define your own commands
|
||
* Hooks:: Hooks for user-defined commands
|
||
* Command Files:: How to write scripts of commands to be stored in a file
|
||
* Output:: Commands for controlled output
|
||
* Auto-loading sequences:: Controlling auto-loaded command files
|
||
@end menu
|
||
|
||
@node Define
|
||
@subsection User-defined Commands
|
||
|
||
@cindex user-defined command
|
||
@cindex arguments, to user-defined commands
|
||
A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
|
||
which you assign a new name as a command. This is done with the
|
||
@code{define} command. User commands may accept an unlimited number of arguments
|
||
separated by whitespace. Arguments are accessed within the user command
|
||
via @code{$arg0@dots{}$argN}. A trivial example:
|
||
|
||
@smallexample
|
||
define adder
|
||
print $arg0 + $arg1 + $arg2
|
||
end
|
||
@end smallexample
|
||
|
||
@noindent
|
||
To execute the command use:
|
||
|
||
@smallexample
|
||
adder 1 2 3
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This defines the command @code{adder}, which prints the sum of
|
||
its three arguments. Note the arguments are text substitutions, so they may
|
||
reference variables, use complex expressions, or even perform inferior
|
||
functions calls.
|
||
|
||
@cindex argument count in user-defined commands
|
||
@cindex how many arguments (user-defined commands)
|
||
In addition, @code{$argc} may be used to find out how many arguments have
|
||
been passed.
|
||
|
||
@smallexample
|
||
define adder
|
||
if $argc == 2
|
||
print $arg0 + $arg1
|
||
end
|
||
if $argc == 3
|
||
print $arg0 + $arg1 + $arg2
|
||
end
|
||
end
|
||
@end smallexample
|
||
|
||
Combining with the @code{eval} command (@pxref{eval}) makes it easier
|
||
to process a variable number of arguments:
|
||
|
||
@smallexample
|
||
define adder
|
||
set $i = 0
|
||
set $sum = 0
|
||
while $i < $argc
|
||
eval "set $sum = $sum + $arg%d", $i
|
||
set $i = $i + 1
|
||
end
|
||
print $sum
|
||
end
|
||
@end smallexample
|
||
|
||
@table @code
|
||
|
||
@kindex define
|
||
@item define @var{commandname}
|
||
Define a command named @var{commandname}. If there is already a command
|
||
by that name, you are asked to confirm that you want to redefine it.
|
||
The argument @var{commandname} may be a bare command name consisting of letters,
|
||
numbers, dashes, and underscores. It may also start with any predefined
|
||
prefix command. For example, @samp{define target my-target} creates
|
||
a user-defined @samp{target my-target} command.
|
||
|
||
The definition of the command is made up of other @value{GDBN} command lines,
|
||
which are given following the @code{define} command. The end of these
|
||
commands is marked by a line containing @code{end}.
|
||
|
||
@kindex document
|
||
@kindex end@r{ (user-defined commands)}
|
||
@item document @var{commandname}
|
||
Document the user-defined command @var{commandname}, so that it can be
|
||
accessed by @code{help}. The command @var{commandname} must already be
|
||
defined. This command reads lines of documentation just as @code{define}
|
||
reads the lines of the command definition, ending with @code{end}.
|
||
After the @code{document} command is finished, @code{help} on command
|
||
@var{commandname} displays the documentation you have written.
|
||
|
||
You may use the @code{document} command again to change the
|
||
documentation of a command. Redefining the command with @code{define}
|
||
does not change the documentation.
|
||
|
||
@kindex dont-repeat
|
||
@cindex don't repeat command
|
||
@item dont-repeat
|
||
Used inside a user-defined command, this tells @value{GDBN} that this
|
||
command should not be repeated when the user hits @key{RET}
|
||
(@pxref{Command Syntax, repeat last command}).
|
||
|
||
@kindex help user-defined
|
||
@item help user-defined
|
||
List all user-defined commands and all python commands defined in class
|
||
COMAND_USER. The first line of the documentation or docstring is
|
||
included (if any).
|
||
|
||
@kindex show user
|
||
@item show user
|
||
@itemx show user @var{commandname}
|
||
Display the @value{GDBN} commands used to define @var{commandname} (but
|
||
not its documentation). If no @var{commandname} is given, display the
|
||
definitions for all user-defined commands.
|
||
This does not work for user-defined python commands.
|
||
|
||
@cindex infinite recursion in user-defined commands
|
||
@kindex show max-user-call-depth
|
||
@kindex set max-user-call-depth
|
||
@item show max-user-call-depth
|
||
@itemx set max-user-call-depth
|
||
The value of @code{max-user-call-depth} controls how many recursion
|
||
levels are allowed in user-defined commands before @value{GDBN} suspects an
|
||
infinite recursion and aborts the command.
|
||
This does not apply to user-defined python commands.
|
||
@end table
|
||
|
||
In addition to the above commands, user-defined commands frequently
|
||
use control flow commands, described in @ref{Command Files}.
|
||
|
||
When user-defined commands are executed, the
|
||
commands of the definition are not printed. An error in any command
|
||
stops execution of the user-defined command.
|
||
|
||
If used interactively, commands that would ask for confirmation proceed
|
||
without asking when used inside a user-defined command. Many @value{GDBN}
|
||
commands that normally print messages to say what they are doing omit the
|
||
messages when used in a user-defined command.
|
||
|
||
@node Hooks
|
||
@subsection User-defined Command Hooks
|
||
@cindex command hooks
|
||
@cindex hooks, for commands
|
||
@cindex hooks, pre-command
|
||
|
||
@kindex hook
|
||
You may define @dfn{hooks}, which are a special kind of user-defined
|
||
command. Whenever you run the command @samp{foo}, if the user-defined
|
||
command @samp{hook-foo} exists, it is executed (with no arguments)
|
||
before that command.
|
||
|
||
@cindex hooks, post-command
|
||
@kindex hookpost
|
||
A hook may also be defined which is run after the command you executed.
|
||
Whenever you run the command @samp{foo}, if the user-defined command
|
||
@samp{hookpost-foo} exists, it is executed (with no arguments) after
|
||
that command. Post-execution hooks may exist simultaneously with
|
||
pre-execution hooks, for the same command.
|
||
|
||
It is valid for a hook to call the command which it hooks. If this
|
||
occurs, the hook is not re-executed, thereby avoiding infinite recursion.
|
||
|
||
@c It would be nice if hookpost could be passed a parameter indicating
|
||
@c if the command it hooks executed properly or not. FIXME!
|
||
|
||
@kindex stop@r{, a pseudo-command}
|
||
In addition, a pseudo-command, @samp{stop} exists. Defining
|
||
(@samp{hook-stop}) makes the associated commands execute every time
|
||
execution stops in your program: before breakpoint commands are run,
|
||
displays are printed, or the stack frame is printed.
|
||
|
||
For example, to ignore @code{SIGALRM} signals while
|
||
single-stepping, but treat them normally during normal execution,
|
||
you could define:
|
||
|
||
@smallexample
|
||
define hook-stop
|
||
handle SIGALRM nopass
|
||
end
|
||
|
||
define hook-run
|
||
handle SIGALRM pass
|
||
end
|
||
|
||
define hook-continue
|
||
handle SIGALRM pass
|
||
end
|
||
@end smallexample
|
||
|
||
As a further example, to hook at the beginning and end of the @code{echo}
|
||
command, and to add extra text to the beginning and end of the message,
|
||
you could define:
|
||
|
||
@smallexample
|
||
define hook-echo
|
||
echo <<<---
|
||
end
|
||
|
||
define hookpost-echo
|
||
echo --->>>\n
|
||
end
|
||
|
||
(@value{GDBP}) echo Hello World
|
||
<<<---Hello World--->>>
|
||
(@value{GDBP})
|
||
|
||
@end smallexample
|
||
|
||
You can define a hook for any single-word command in @value{GDBN}, but
|
||
not for command aliases; you should define a hook for the basic command
|
||
name, e.g.@: @code{backtrace} rather than @code{bt}.
|
||
@c FIXME! So how does Joe User discover whether a command is an alias
|
||
@c or not?
|
||
You can hook a multi-word command by adding @code{hook-} or
|
||
@code{hookpost-} to the last word of the command, e.g.@:
|
||
@samp{define target hook-remote} to add a hook to @samp{target remote}.
|
||
|
||
If an error occurs during the execution of your hook, execution of
|
||
@value{GDBN} commands stops and @value{GDBN} issues a prompt
|
||
(before the command that you actually typed had a chance to run).
|
||
|
||
If you try to define a hook which does not match any known command, you
|
||
get a warning from the @code{define} command.
|
||
|
||
@node Command Files
|
||
@subsection Command Files
|
||
|
||
@cindex command files
|
||
@cindex scripting commands
|
||
A command file for @value{GDBN} is a text file made of lines that are
|
||
@value{GDBN} commands. Comments (lines starting with @kbd{#}) may
|
||
also be included. An empty line in a command file does nothing; it
|
||
does not mean to repeat the last command, as it would from the
|
||
terminal.
|
||
|
||
You can request the execution of a command file with the @code{source}
|
||
command. Note that the @code{source} command is also used to evaluate
|
||
scripts that are not Command Files. The exact behavior can be configured
|
||
using the @code{script-extension} setting.
|
||
@xref{Extending GDB,, Extending GDB}.
|
||
|
||
@table @code
|
||
@kindex source
|
||
@cindex execute commands from a file
|
||
@item source [-s] [-v] @var{filename}
|
||
Execute the command file @var{filename}.
|
||
@end table
|
||
|
||
The lines in a command file are generally executed sequentially,
|
||
unless the order of execution is changed by one of the
|
||
@emph{flow-control commands} described below. The commands are not
|
||
printed as they are executed. An error in any command terminates
|
||
execution of the command file and control is returned to the console.
|
||
|
||
@value{GDBN} first searches for @var{filename} in the current directory.
|
||
If the file is not found there, and @var{filename} does not specify a
|
||
directory, then @value{GDBN} also looks for the file on the source search path
|
||
(specified with the @samp{directory} command);
|
||
except that @file{$cdir} is not searched because the compilation directory
|
||
is not relevant to scripts.
|
||
|
||
If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
|
||
on the search path even if @var{filename} specifies a directory.
|
||
The search is done by appending @var{filename} to each element of the
|
||
search path. So, for example, if @var{filename} is @file{mylib/myscript}
|
||
and the search path contains @file{/home/user} then @value{GDBN} will
|
||
look for the script @file{/home/user/mylib/myscript}.
|
||
The search is also done if @var{filename} is an absolute path.
|
||
For example, if @var{filename} is @file{/tmp/myscript} and
|
||
the search path contains @file{/home/user} then @value{GDBN} will
|
||
look for the script @file{/home/user/tmp/myscript}.
|
||
For DOS-like systems, if @var{filename} contains a drive specification,
|
||
it is stripped before concatenation. For example, if @var{filename} is
|
||
@file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
|
||
will look for the script @file{c:/tmp/myscript}.
|
||
|
||
If @code{-v}, for verbose mode, is given then @value{GDBN} displays
|
||
each command as it is executed. The option must be given before
|
||
@var{filename}, and is interpreted as part of the filename anywhere else.
|
||
|
||
Commands that would ask for confirmation if used interactively proceed
|
||
without asking when used in a command file. Many @value{GDBN} commands that
|
||
normally print messages to say what they are doing omit the messages
|
||
when called from command files.
|
||
|
||
@value{GDBN} also accepts command input from standard input. In this
|
||
mode, normal output goes to standard output and error output goes to
|
||
standard error. Errors in a command file supplied on standard input do
|
||
not terminate execution of the command file---execution continues with
|
||
the next command.
|
||
|
||
@smallexample
|
||
gdb < cmds > log 2>&1
|
||
@end smallexample
|
||
|
||
(The syntax above will vary depending on the shell used.) This example
|
||
will execute commands from the file @file{cmds}. All output and errors
|
||
would be directed to @file{log}.
|
||
|
||
Since commands stored on command files tend to be more general than
|
||
commands typed interactively, they frequently need to deal with
|
||
complicated situations, such as different or unexpected values of
|
||
variables and symbols, changes in how the program being debugged is
|
||
built, etc. @value{GDBN} provides a set of flow-control commands to
|
||
deal with these complexities. Using these commands, you can write
|
||
complex scripts that loop over data structures, execute commands
|
||
conditionally, etc.
|
||
|
||
@table @code
|
||
@kindex if
|
||
@kindex else
|
||
@item if
|
||
@itemx else
|
||
This command allows to include in your script conditionally executed
|
||
commands. The @code{if} command takes a single argument, which is an
|
||
expression to evaluate. It is followed by a series of commands that
|
||
are executed only if the expression is true (its value is nonzero).
|
||
There can then optionally be an @code{else} line, followed by a series
|
||
of commands that are only executed if the expression was false. The
|
||
end of the list is marked by a line containing @code{end}.
|
||
|
||
@kindex while
|
||
@item while
|
||
This command allows to write loops. Its syntax is similar to
|
||
@code{if}: the command takes a single argument, which is an expression
|
||
to evaluate, and must be followed by the commands to execute, one per
|
||
line, terminated by an @code{end}. These commands are called the
|
||
@dfn{body} of the loop. The commands in the body of @code{while} are
|
||
executed repeatedly as long as the expression evaluates to true.
|
||
|
||
@kindex loop_break
|
||
@item loop_break
|
||
This command exits the @code{while} loop in whose body it is included.
|
||
Execution of the script continues after that @code{while}s @code{end}
|
||
line.
|
||
|
||
@kindex loop_continue
|
||
@item loop_continue
|
||
This command skips the execution of the rest of the body of commands
|
||
in the @code{while} loop in whose body it is included. Execution
|
||
branches to the beginning of the @code{while} loop, where it evaluates
|
||
the controlling expression.
|
||
|
||
@kindex end@r{ (if/else/while commands)}
|
||
@item end
|
||
Terminate the block of commands that are the body of @code{if},
|
||
@code{else}, or @code{while} flow-control commands.
|
||
@end table
|
||
|
||
|
||
@node Output
|
||
@subsection Commands for Controlled Output
|
||
|
||
During the execution of a command file or a user-defined command, normal
|
||
@value{GDBN} output is suppressed; the only output that appears is what is
|
||
explicitly printed by the commands in the definition. This section
|
||
describes three commands useful for generating exactly the output you
|
||
want.
|
||
|
||
@table @code
|
||
@kindex echo
|
||
@item echo @var{text}
|
||
@c I do not consider backslash-space a standard C escape sequence
|
||
@c because it is not in ANSI.
|
||
Print @var{text}. Nonprinting characters can be included in
|
||
@var{text} using C escape sequences, such as @samp{\n} to print a
|
||
newline. @strong{No newline is printed unless you specify one.}
|
||
In addition to the standard C escape sequences, a backslash followed
|
||
by a space stands for a space. This is useful for displaying a
|
||
string with spaces at the beginning or the end, since leading and
|
||
trailing spaces are otherwise trimmed from all arguments.
|
||
To print @samp{@w{ }and foo =@w{ }}, use the command
|
||
@samp{echo \@w{ }and foo = \@w{ }}.
|
||
|
||
A backslash at the end of @var{text} can be used, as in C, to continue
|
||
the command onto subsequent lines. For example,
|
||
|
||
@smallexample
|
||
echo This is some text\n\
|
||
which is continued\n\
|
||
onto several lines.\n
|
||
@end smallexample
|
||
|
||
produces the same output as
|
||
|
||
@smallexample
|
||
echo This is some text\n
|
||
echo which is continued\n
|
||
echo onto several lines.\n
|
||
@end smallexample
|
||
|
||
@kindex output
|
||
@item output @var{expression}
|
||
Print the value of @var{expression} and nothing but that value: no
|
||
newlines, no @samp{$@var{nn} = }. The value is not entered in the
|
||
value history either. @xref{Expressions, ,Expressions}, for more information
|
||
on expressions.
|
||
|
||
@item output/@var{fmt} @var{expression}
|
||
Print the value of @var{expression} in format @var{fmt}. You can use
|
||
the same formats as for @code{print}. @xref{Output Formats,,Output
|
||
Formats}, for more information.
|
||
|
||
@kindex printf
|
||
@item printf @var{template}, @var{expressions}@dots{}
|
||
Print the values of one or more @var{expressions} under the control of
|
||
the string @var{template}. To print several values, make
|
||
@var{expressions} be a comma-separated list of individual expressions,
|
||
which may be either numbers or pointers. Their values are printed as
|
||
specified by @var{template}, exactly as a C program would do by
|
||
executing the code below:
|
||
|
||
@smallexample
|
||
printf (@var{template}, @var{expressions}@dots{});
|
||
@end smallexample
|
||
|
||
As in @code{C} @code{printf}, ordinary characters in @var{template}
|
||
are printed verbatim, while @dfn{conversion specification} introduced
|
||
by the @samp{%} character cause subsequent @var{expressions} to be
|
||
evaluated, their values converted and formatted according to type and
|
||
style information encoded in the conversion specifications, and then
|
||
printed.
|
||
|
||
For example, you can print two values in hex like this:
|
||
|
||
@smallexample
|
||
printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
|
||
@end smallexample
|
||
|
||
@code{printf} supports all the standard @code{C} conversion
|
||
specifications, including the flags and modifiers between the @samp{%}
|
||
character and the conversion letter, with the following exceptions:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The argument-ordering modifiers, such as @samp{2$}, are not supported.
|
||
|
||
@item
|
||
The modifier @samp{*} is not supported for specifying precision or
|
||
width.
|
||
|
||
@item
|
||
The @samp{'} flag (for separation of digits into groups according to
|
||
@code{LC_NUMERIC'}) is not supported.
|
||
|
||
@item
|
||
The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
|
||
supported.
|
||
|
||
@item
|
||
The conversion letter @samp{n} (as in @samp{%n}) is not supported.
|
||
|
||
@item
|
||
The conversion letters @samp{a} and @samp{A} are not supported.
|
||
@end itemize
|
||
|
||
@noindent
|
||
Note that the @samp{ll} type modifier is supported only if the
|
||
underlying @code{C} implementation used to build @value{GDBN} supports
|
||
the @code{long long int} type, and the @samp{L} type modifier is
|
||
supported only if @code{long double} type is available.
|
||
|
||
As in @code{C}, @code{printf} supports simple backslash-escape
|
||
sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
|
||
@samp{\a}, and @samp{\f}, that consist of backslash followed by a
|
||
single character. Octal and hexadecimal escape sequences are not
|
||
supported.
|
||
|
||
Additionally, @code{printf} supports conversion specifications for DFP
|
||
(@dfn{Decimal Floating Point}) types using the following length modifiers
|
||
together with a floating point specifier.
|
||
letters:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
@samp{H} for printing @code{Decimal32} types.
|
||
|
||
@item
|
||
@samp{D} for printing @code{Decimal64} types.
|
||
|
||
@item
|
||
@samp{DD} for printing @code{Decimal128} types.
|
||
@end itemize
|
||
|
||
If the underlying @code{C} implementation used to build @value{GDBN} has
|
||
support for the three length modifiers for DFP types, other modifiers
|
||
such as width and precision will also be available for @value{GDBN} to use.
|
||
|
||
In case there is no such @code{C} support, no additional modifiers will be
|
||
available and the value will be printed in the standard way.
|
||
|
||
Here's an example of printing DFP types using the above conversion letters:
|
||
@smallexample
|
||
printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
|
||
@end smallexample
|
||
|
||
@anchor{eval}
|
||
@kindex eval
|
||
@item eval @var{template}, @var{expressions}@dots{}
|
||
Convert the values of one or more @var{expressions} under the control of
|
||
the string @var{template} to a command line, and call it.
|
||
|
||
@end table
|
||
|
||
@node Auto-loading sequences
|
||
@subsection Controlling auto-loading native @value{GDBN} scripts
|
||
@cindex native script auto-loading
|
||
|
||
When a new object file is read (for example, due to the @code{file}
|
||
command, or because the inferior has loaded a shared library),
|
||
@value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
|
||
@xref{Auto-loading extensions}.
|
||
|
||
Auto-loading can be enabled or disabled,
|
||
and the list of auto-loaded scripts can be printed.
|
||
|
||
@table @code
|
||
@anchor{set auto-load gdb-scripts}
|
||
@kindex set auto-load gdb-scripts
|
||
@item set auto-load gdb-scripts [on|off]
|
||
Enable or disable the auto-loading of canned sequences of commands scripts.
|
||
|
||
@anchor{show auto-load gdb-scripts}
|
||
@kindex show auto-load gdb-scripts
|
||
@item show auto-load gdb-scripts
|
||
Show whether auto-loading of canned sequences of commands scripts is enabled or
|
||
disabled.
|
||
|
||
@anchor{info auto-load gdb-scripts}
|
||
@kindex info auto-load gdb-scripts
|
||
@cindex print list of auto-loaded canned sequences of commands scripts
|
||
@item info auto-load gdb-scripts [@var{regexp}]
|
||
Print the list of all canned sequences of commands scripts that @value{GDBN}
|
||
auto-loaded.
|
||
@end table
|
||
|
||
If @var{regexp} is supplied only canned sequences of commands scripts with
|
||
matching names are printed.
|
||
|
||
@c Python docs live in a separate file.
|
||
@include python.texi
|
||
|
||
@c Guile docs live in a separate file.
|
||
@include guile.texi
|
||
|
||
@node Auto-loading extensions
|
||
@section Auto-loading extensions
|
||
@cindex auto-loading extensions
|
||
|
||
@value{GDBN} provides two mechanisms for automatically loading extensions
|
||
when a new object file is read (for example, due to the @code{file}
|
||
command, or because the inferior has loaded a shared library):
|
||
@file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
|
||
section of modern file formats like ELF.
|
||
|
||
@menu
|
||
* objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
|
||
* .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
|
||
* Which flavor to choose?::
|
||
@end menu
|
||
|
||
The auto-loading feature is useful for supplying application-specific
|
||
debugging commands and features.
|
||
|
||
Auto-loading can be enabled or disabled,
|
||
and the list of auto-loaded scripts can be printed.
|
||
See the @samp{auto-loading} section of each extension language
|
||
for more information.
|
||
For @value{GDBN} command files see @ref{Auto-loading sequences}.
|
||
For Python files see @ref{Python Auto-loading}.
|
||
|
||
Note that loading of this script file also requires accordingly configured
|
||
@code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
|
||
@node objfile-gdbdotext file
|
||
@subsection The @file{@var{objfile}-gdb.@var{ext}} file
|
||
@cindex @file{@var{objfile}-gdb.gdb}
|
||
@cindex @file{@var{objfile}-gdb.py}
|
||
@cindex @file{@var{objfile}-gdb.scm}
|
||
|
||
When a new object file is read, @value{GDBN} looks for a file named
|
||
@file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
|
||
where @var{objfile} is the object file's name and
|
||
where @var{ext} is the file extension for the extension language:
|
||
|
||
@table @code
|
||
@item @file{@var{objfile}-gdb.gdb}
|
||
GDB's own command language
|
||
@item @file{@var{objfile}-gdb.py}
|
||
Python
|
||
@item @file{@var{objfile}-gdb.scm}
|
||
Guile
|
||
@end table
|
||
|
||
@var{script-name} is formed by ensuring that the file name of @var{objfile}
|
||
is absolute, following all symlinks, and resolving @code{.} and @code{..}
|
||
components, and appending the @file{-gdb.@var{ext}} suffix.
|
||
If this file exists and is readable, @value{GDBN} will evaluate it as a
|
||
script in the specified extension language.
|
||
|
||
If this file does not exist, then @value{GDBN} will look for
|
||
@var{script-name} file in all of the directories as specified below.
|
||
|
||
Note that loading of these files requires an accordingly configured
|
||
@code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
|
||
For object files using @file{.exe} suffix @value{GDBN} tries to load first the
|
||
scripts normally according to its @file{.exe} filename. But if no scripts are
|
||
found @value{GDBN} also tries script filenames matching the object file without
|
||
its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
|
||
is attempted on any platform. This makes the script filenames compatible
|
||
between Unix and MS-Windows hosts.
|
||
|
||
@table @code
|
||
@anchor{set auto-load scripts-directory}
|
||
@kindex set auto-load scripts-directory
|
||
@item set auto-load scripts-directory @r{[}@var{directories}@r{]}
|
||
Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
|
||
may be delimited by the host platform path separator in use
|
||
(@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
|
||
|
||
Each entry here needs to be covered also by the security setting
|
||
@code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
|
||
|
||
@anchor{with-auto-load-dir}
|
||
This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
|
||
@code{set auto-load safe-path} value can be also overriden by @value{GDBN}
|
||
configuration option @option{--with-auto-load-dir}.
|
||
|
||
Any reference to @file{$debugdir} will get replaced by
|
||
@var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
|
||
reference to @file{$datadir} will get replaced by @var{data-directory} which is
|
||
determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
|
||
@file{$datadir} must be placed as a directory component --- either alone or
|
||
delimited by @file{/} or @file{\} directory separators, depending on the host
|
||
platform.
|
||
|
||
The list of directories uses path separator (@samp{:} on GNU and Unix
|
||
systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
|
||
to the @env{PATH} environment variable.
|
||
|
||
@anchor{show auto-load scripts-directory}
|
||
@kindex show auto-load scripts-directory
|
||
@item show auto-load scripts-directory
|
||
Show @value{GDBN} auto-loaded scripts location.
|
||
|
||
@anchor{add-auto-load-scripts-directory}
|
||
@kindex add-auto-load-scripts-directory
|
||
@item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
|
||
Add an entry (or list of entries) to the list of auto-loaded scripts locations.
|
||
Multiple entries may be delimited by the host platform path separator in use.
|
||
@end table
|
||
|
||
@value{GDBN} does not track which files it has already auto-loaded this way.
|
||
@value{GDBN} will load the associated script every time the corresponding
|
||
@var{objfile} is opened.
|
||
So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
|
||
is evaluated more than once.
|
||
|
||
@node dotdebug_gdb_scripts section
|
||
@subsection The @code{.debug_gdb_scripts} section
|
||
@cindex @code{.debug_gdb_scripts} section
|
||
|
||
For systems using file formats like ELF and COFF,
|
||
when @value{GDBN} loads a new object file
|
||
it will look for a special section named @code{.debug_gdb_scripts}.
|
||
If this section exists, its contents is a list of null-terminated entries
|
||
specifying scripts to load. Each entry begins with a non-null prefix byte that
|
||
specifies the kind of entry, typically the extension language and whether the
|
||
script is in a file or inlined in @code{.debug_gdb_scripts}.
|
||
|
||
The following entries are supported:
|
||
|
||
@table @code
|
||
@item SECTION_SCRIPT_ID_PYTHON_FILE = 1
|
||
@item SECTION_SCRIPT_ID_SCHEME_FILE = 3
|
||
@item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
|
||
@item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
|
||
@end table
|
||
|
||
@subsubsection Script File Entries
|
||
|
||
If the entry specifies a file, @value{GDBN} will look for the file first
|
||
in the current directory and then along the source search path
|
||
(@pxref{Source Path, ,Specifying Source Directories}),
|
||
except that @file{$cdir} is not searched, since the compilation
|
||
directory is not relevant to scripts.
|
||
|
||
File entries can be placed in section @code{.debug_gdb_scripts} with,
|
||
for example, this GCC macro for Python scripts.
|
||
|
||
@example
|
||
/* Note: The "MS" section flags are to remove duplicates. */
|
||
#define DEFINE_GDB_PY_SCRIPT(script_name) \
|
||
asm("\
|
||
.pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
|
||
.byte 1 /* Python */\n\
|
||
.asciz \"" script_name "\"\n\
|
||
.popsection \n\
|
||
");
|
||
@end example
|
||
|
||
@noindent
|
||
For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
|
||
Then one can reference the macro in a header or source file like this:
|
||
|
||
@example
|
||
DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
|
||
@end example
|
||
|
||
The script name may include directories if desired.
|
||
|
||
Note that loading of this script file also requires accordingly configured
|
||
@code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
|
||
If the macro invocation is put in a header, any application or library
|
||
using this header will get a reference to the specified script,
|
||
and with the use of @code{"MS"} attributes on the section, the linker
|
||
will remove duplicates.
|
||
|
||
@subsubsection Script Text Entries
|
||
|
||
Script text entries allow to put the executable script in the entry
|
||
itself instead of loading it from a file.
|
||
The first line of the entry, everything after the prefix byte and up to
|
||
the first newline (@code{0xa}) character, is the script name, and must not
|
||
contain any kind of space character, e.g., spaces or tabs.
|
||
The rest of the entry, up to the trailing null byte, is the script to
|
||
execute in the specified language. The name needs to be unique among
|
||
all script names, as @value{GDBN} executes each script only once based
|
||
on its name.
|
||
|
||
Here is an example from file @file{py-section-script.c} in the @value{GDBN}
|
||
testsuite.
|
||
|
||
@example
|
||
#include "symcat.h"
|
||
#include "gdb/section-scripts.h"
|
||
asm(
|
||
".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
|
||
".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
|
||
".ascii \"gdb.inlined-script\\n\"\n"
|
||
".ascii \"class test_cmd (gdb.Command):\\n\"\n"
|
||
".ascii \" def __init__ (self):\\n\"\n"
|
||
".ascii \" super (test_cmd, self).__init__ ("
|
||
"\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
|
||
".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
|
||
".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
|
||
".ascii \"test_cmd ()\\n\"\n"
|
||
".byte 0\n"
|
||
".popsection\n"
|
||
);
|
||
@end example
|
||
|
||
Loading of inlined scripts requires a properly configured
|
||
@code{auto-load safe-path} (@pxref{Auto-loading safe path}).
|
||
The path to specify in @code{auto-load safe-path} is the path of the file
|
||
containing the @code{.debug_gdb_scripts} section.
|
||
|
||
@node Which flavor to choose?
|
||
@subsection Which flavor to choose?
|
||
|
||
Given the multiple ways of auto-loading extensions, it might not always
|
||
be clear which one to choose. This section provides some guidance.
|
||
|
||
@noindent
|
||
Benefits of the @file{-gdb.@var{ext}} way:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Can be used with file formats that don't support multiple sections.
|
||
|
||
@item
|
||
Ease of finding scripts for public libraries.
|
||
|
||
Scripts specified in the @code{.debug_gdb_scripts} section are searched for
|
||
in the source search path.
|
||
For publicly installed libraries, e.g., @file{libstdc++}, there typically
|
||
isn't a source directory in which to find the script.
|
||
|
||
@item
|
||
Doesn't require source code additions.
|
||
@end itemize
|
||
|
||
@noindent
|
||
Benefits of the @code{.debug_gdb_scripts} way:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Works with static linking.
|
||
|
||
Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
|
||
trigger their loading. When an application is statically linked the only
|
||
objfile available is the executable, and it is cumbersome to attach all the
|
||
scripts from all the input libraries to the executable's
|
||
@file{-gdb.@var{ext}} script.
|
||
|
||
@item
|
||
Works with classes that are entirely inlined.
|
||
|
||
Some classes can be entirely inlined, and thus there may not be an associated
|
||
shared library to attach a @file{-gdb.@var{ext}} script to.
|
||
|
||
@item
|
||
Scripts needn't be copied out of the source tree.
|
||
|
||
In some circumstances, apps can be built out of large collections of internal
|
||
libraries, and the build infrastructure necessary to install the
|
||
@file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
|
||
cumbersome. It may be easier to specify the scripts in the
|
||
@code{.debug_gdb_scripts} section as relative paths, and add a path to the
|
||
top of the source tree to the source search path.
|
||
@end itemize
|
||
|
||
@node Multiple Extension Languages
|
||
@section Multiple Extension Languages
|
||
|
||
The Guile and Python extension languages do not share any state,
|
||
and generally do not interfere with each other.
|
||
There are some things to be aware of, however.
|
||
|
||
@subsection Python comes first
|
||
|
||
Python was @value{GDBN}'s first extension language, and to avoid breaking
|
||
existing behaviour Python comes first. This is generally solved by the
|
||
``first one wins'' principle. @value{GDBN} maintains a list of enabled
|
||
extension languages, and when it makes a call to an extension language,
|
||
(say to pretty-print a value), it tries each in turn until an extension
|
||
language indicates it has performed the request (e.g., has returned the
|
||
pretty-printed form of a value).
|
||
This extends to errors while performing such requests: If an error happens
|
||
while, for example, trying to pretty-print an object then the error is
|
||
reported and any following extension languages are not tried.
|
||
|
||
@node Aliases
|
||
@section Creating new spellings of existing commands
|
||
@cindex aliases for commands
|
||
|
||
It is often useful to define alternate spellings of existing commands.
|
||
For example, if a new @value{GDBN} command defined in Python has
|
||
a long name to type, it is handy to have an abbreviated version of it
|
||
that involves less typing.
|
||
|
||
@value{GDBN} itself uses aliases. For example @samp{s} is an alias
|
||
of the @samp{step} command even though it is otherwise an ambiguous
|
||
abbreviation of other commands like @samp{set} and @samp{show}.
|
||
|
||
Aliases are also used to provide shortened or more common versions
|
||
of multi-word commands. For example, @value{GDBN} provides the
|
||
@samp{tty} alias of the @samp{set inferior-tty} command.
|
||
|
||
You can define a new alias with the @samp{alias} command.
|
||
|
||
@table @code
|
||
|
||
@kindex alias
|
||
@item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
|
||
|
||
@end table
|
||
|
||
@var{ALIAS} specifies the name of the new alias.
|
||
Each word of @var{ALIAS} must consist of letters, numbers, dashes and
|
||
underscores.
|
||
|
||
@var{COMMAND} specifies the name of an existing command
|
||
that is being aliased.
|
||
|
||
The @samp{-a} option specifies that the new alias is an abbreviation
|
||
of the command. Abbreviations are not shown in command
|
||
lists displayed by the @samp{help} command.
|
||
|
||
The @samp{--} option specifies the end of options,
|
||
and is useful when @var{ALIAS} begins with a dash.
|
||
|
||
Here is a simple example showing how to make an abbreviation
|
||
of a command so that there is less to type.
|
||
Suppose you were tired of typing @samp{disas}, the current
|
||
shortest unambiguous abbreviation of the @samp{disassemble} command
|
||
and you wanted an even shorter version named @samp{di}.
|
||
The following will accomplish this.
|
||
|
||
@smallexample
|
||
(gdb) alias -a di = disas
|
||
@end smallexample
|
||
|
||
Note that aliases are different from user-defined commands.
|
||
With a user-defined command, you also need to write documentation
|
||
for it with the @samp{document} command.
|
||
An alias automatically picks up the documentation of the existing command.
|
||
|
||
Here is an example where we make @samp{elms} an abbreviation of
|
||
@samp{elements} in the @samp{set print elements} command.
|
||
This is to show that you can make an abbreviation of any part
|
||
of a command.
|
||
|
||
@smallexample
|
||
(gdb) alias -a set print elms = set print elements
|
||
(gdb) alias -a show print elms = show print elements
|
||
(gdb) set p elms 20
|
||
(gdb) show p elms
|
||
Limit on string chars or array elements to print is 200.
|
||
@end smallexample
|
||
|
||
Note that if you are defining an alias of a @samp{set} command,
|
||
and you want to have an alias for the corresponding @samp{show}
|
||
command, then you need to define the latter separately.
|
||
|
||
Unambiguously abbreviated commands are allowed in @var{COMMAND} and
|
||
@var{ALIAS}, just as they are normally.
|
||
|
||
@smallexample
|
||
(gdb) alias -a set pr elms = set p ele
|
||
@end smallexample
|
||
|
||
Finally, here is an example showing the creation of a one word
|
||
alias for a more complex command.
|
||
This creates alias @samp{spe} of the command @samp{set print elements}.
|
||
|
||
@smallexample
|
||
(gdb) alias spe = set print elements
|
||
(gdb) spe 20
|
||
@end smallexample
|
||
|
||
@node Interpreters
|
||
@chapter Command Interpreters
|
||
@cindex command interpreters
|
||
|
||
@value{GDBN} supports multiple command interpreters, and some command
|
||
infrastructure to allow users or user interface writers to switch
|
||
between interpreters or run commands in other interpreters.
|
||
|
||
@value{GDBN} currently supports two command interpreters, the console
|
||
interpreter (sometimes called the command-line interpreter or @sc{cli})
|
||
and the machine interface interpreter (or @sc{gdb/mi}). This manual
|
||
describes both of these interfaces in great detail.
|
||
|
||
By default, @value{GDBN} will start with the console interpreter.
|
||
However, the user may choose to start @value{GDBN} with another
|
||
interpreter by specifying the @option{-i} or @option{--interpreter}
|
||
startup options. Defined interpreters include:
|
||
|
||
@table @code
|
||
@item console
|
||
@cindex console interpreter
|
||
The traditional console or command-line interpreter. This is the most often
|
||
used interpreter with @value{GDBN}. With no interpreter specified at runtime,
|
||
@value{GDBN} will use this interpreter.
|
||
|
||
@item mi
|
||
@cindex mi interpreter
|
||
The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
|
||
by programs wishing to use @value{GDBN} as a backend for a debugger GUI
|
||
or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
|
||
Interface}.
|
||
|
||
@item mi2
|
||
@cindex mi2 interpreter
|
||
The current @sc{gdb/mi} interface.
|
||
|
||
@item mi1
|
||
@cindex mi1 interpreter
|
||
The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
|
||
|
||
@end table
|
||
|
||
@cindex invoke another interpreter
|
||
|
||
@kindex interpreter-exec
|
||
You may execute commands in any interpreter from the current
|
||
interpreter using the appropriate command. If you are running the
|
||
console interpreter, simply use the @code{interpreter-exec} command:
|
||
|
||
@smallexample
|
||
interpreter-exec mi "-data-list-register-names"
|
||
@end smallexample
|
||
|
||
@sc{gdb/mi} has a similar command, although it is only available in versions of
|
||
@value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
|
||
|
||
Note that @code{interpreter-exec} only changes the interpreter for the
|
||
duration of the specified command. It does not change the interpreter
|
||
permanently.
|
||
|
||
@cindex start a new independent interpreter
|
||
|
||
Although you may only choose a single interpreter at startup, it is
|
||
possible to run an independent interpreter on a specified input/output
|
||
device (usually a tty).
|
||
|
||
For example, consider a debugger GUI or IDE that wants to provide a
|
||
@value{GDBN} console view. It may do so by embedding a terminal
|
||
emulator widget in its GUI, starting @value{GDBN} in the traditional
|
||
command-line mode with stdin/stdout/stderr redirected to that
|
||
terminal, and then creating an MI interpreter running on a specified
|
||
input/output device. The console interpreter created by @value{GDBN}
|
||
at startup handles commands the user types in the terminal widget,
|
||
while the GUI controls and synchronizes state with @value{GDBN} using
|
||
the separate MI interpreter.
|
||
|
||
To start a new secondary @dfn{user interface} running MI, use the
|
||
@code{new-ui} command:
|
||
|
||
@kindex new-ui
|
||
@cindex new user interface
|
||
@smallexample
|
||
new-ui @var{interpreter} @var{tty}
|
||
@end smallexample
|
||
|
||
The @var{interpreter} parameter specifies the interpreter to run.
|
||
This accepts the same values as the @code{interpreter-exec} command.
|
||
For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
|
||
@var{tty} parameter specifies the name of the bidirectional file the
|
||
interpreter uses for input/output, usually the name of a
|
||
pseudoterminal slave on Unix systems. For example:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) new-ui mi /dev/pts/9
|
||
@end smallexample
|
||
|
||
@noindent
|
||
runs an MI interpreter on @file{/dev/pts/9}.
|
||
|
||
@node TUI
|
||
@chapter @value{GDBN} Text User Interface
|
||
@cindex TUI
|
||
@cindex Text User Interface
|
||
|
||
@menu
|
||
* TUI Overview:: TUI overview
|
||
* TUI Keys:: TUI key bindings
|
||
* TUI Single Key Mode:: TUI single key mode
|
||
* TUI Commands:: TUI-specific commands
|
||
* TUI Configuration:: TUI configuration variables
|
||
@end menu
|
||
|
||
The @value{GDBN} Text User Interface (TUI) is a terminal
|
||
interface which uses the @code{curses} library to show the source
|
||
file, the assembly output, the program registers and @value{GDBN}
|
||
commands in separate text windows. The TUI mode is supported only
|
||
on platforms where a suitable version of the @code{curses} library
|
||
is available.
|
||
|
||
The TUI mode is enabled by default when you invoke @value{GDBN} as
|
||
@samp{@value{GDBP} -tui}.
|
||
You can also switch in and out of TUI mode while @value{GDBN} runs by
|
||
using various TUI commands and key bindings, such as @command{tui
|
||
enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
|
||
@ref{TUI Keys, ,TUI Key Bindings}.
|
||
|
||
@node TUI Overview
|
||
@section TUI Overview
|
||
|
||
In TUI mode, @value{GDBN} can display several text windows:
|
||
|
||
@table @emph
|
||
@item command
|
||
This window is the @value{GDBN} command window with the @value{GDBN}
|
||
prompt and the @value{GDBN} output. The @value{GDBN} input is still
|
||
managed using readline.
|
||
|
||
@item source
|
||
The source window shows the source file of the program. The current
|
||
line and active breakpoints are displayed in this window.
|
||
|
||
@item assembly
|
||
The assembly window shows the disassembly output of the program.
|
||
|
||
@item register
|
||
This window shows the processor registers. Registers are highlighted
|
||
when their values change.
|
||
@end table
|
||
|
||
The source and assembly windows show the current program position
|
||
by highlighting the current line and marking it with a @samp{>} marker.
|
||
Breakpoints are indicated with two markers. The first marker
|
||
indicates the breakpoint type:
|
||
|
||
@table @code
|
||
@item B
|
||
Breakpoint which was hit at least once.
|
||
|
||
@item b
|
||
Breakpoint which was never hit.
|
||
|
||
@item H
|
||
Hardware breakpoint which was hit at least once.
|
||
|
||
@item h
|
||
Hardware breakpoint which was never hit.
|
||
@end table
|
||
|
||
The second marker indicates whether the breakpoint is enabled or not:
|
||
|
||
@table @code
|
||
@item +
|
||
Breakpoint is enabled.
|
||
|
||
@item -
|
||
Breakpoint is disabled.
|
||
@end table
|
||
|
||
The source, assembly and register windows are updated when the current
|
||
thread changes, when the frame changes, or when the program counter
|
||
changes.
|
||
|
||
These windows are not all visible at the same time. The command
|
||
window is always visible. The others can be arranged in several
|
||
layouts:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
source only,
|
||
|
||
@item
|
||
assembly only,
|
||
|
||
@item
|
||
source and assembly,
|
||
|
||
@item
|
||
source and registers, or
|
||
|
||
@item
|
||
assembly and registers.
|
||
@end itemize
|
||
|
||
A status line above the command window shows the following information:
|
||
|
||
@table @emph
|
||
@item target
|
||
Indicates the current @value{GDBN} target.
|
||
(@pxref{Targets, ,Specifying a Debugging Target}).
|
||
|
||
@item process
|
||
Gives the current process or thread number.
|
||
When no process is being debugged, this field is set to @code{No process}.
|
||
|
||
@item function
|
||
Gives the current function name for the selected frame.
|
||
The name is demangled if demangling is turned on (@pxref{Print Settings}).
|
||
When there is no symbol corresponding to the current program counter,
|
||
the string @code{??} is displayed.
|
||
|
||
@item line
|
||
Indicates the current line number for the selected frame.
|
||
When the current line number is not known, the string @code{??} is displayed.
|
||
|
||
@item pc
|
||
Indicates the current program counter address.
|
||
@end table
|
||
|
||
@node TUI Keys
|
||
@section TUI Key Bindings
|
||
@cindex TUI key bindings
|
||
|
||
The TUI installs several key bindings in the readline keymaps
|
||
@ifset SYSTEM_READLINE
|
||
(@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
|
||
@end ifset
|
||
@ifclear SYSTEM_READLINE
|
||
(@pxref{Command Line Editing}).
|
||
@end ifclear
|
||
The following key bindings are installed for both TUI mode and the
|
||
@value{GDBN} standard mode.
|
||
|
||
@table @kbd
|
||
@kindex C-x C-a
|
||
@item C-x C-a
|
||
@kindex C-x a
|
||
@itemx C-x a
|
||
@kindex C-x A
|
||
@itemx C-x A
|
||
Enter or leave the TUI mode. When leaving the TUI mode,
|
||
the curses window management stops and @value{GDBN} operates using
|
||
its standard mode, writing on the terminal directly. When reentering
|
||
the TUI mode, control is given back to the curses windows.
|
||
The screen is then refreshed.
|
||
|
||
@kindex C-x 1
|
||
@item C-x 1
|
||
Use a TUI layout with only one window. The layout will
|
||
either be @samp{source} or @samp{assembly}. When the TUI mode
|
||
is not active, it will switch to the TUI mode.
|
||
|
||
Think of this key binding as the Emacs @kbd{C-x 1} binding.
|
||
|
||
@kindex C-x 2
|
||
@item C-x 2
|
||
Use a TUI layout with at least two windows. When the current
|
||
layout already has two windows, the next layout with two windows is used.
|
||
When a new layout is chosen, one window will always be common to the
|
||
previous layout and the new one.
|
||
|
||
Think of it as the Emacs @kbd{C-x 2} binding.
|
||
|
||
@kindex C-x o
|
||
@item C-x o
|
||
Change the active window. The TUI associates several key bindings
|
||
(like scrolling and arrow keys) with the active window. This command
|
||
gives the focus to the next TUI window.
|
||
|
||
Think of it as the Emacs @kbd{C-x o} binding.
|
||
|
||
@kindex C-x s
|
||
@item C-x s
|
||
Switch in and out of the TUI SingleKey mode that binds single
|
||
keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
|
||
@end table
|
||
|
||
The following key bindings only work in the TUI mode:
|
||
|
||
@table @asis
|
||
@kindex PgUp
|
||
@item @key{PgUp}
|
||
Scroll the active window one page up.
|
||
|
||
@kindex PgDn
|
||
@item @key{PgDn}
|
||
Scroll the active window one page down.
|
||
|
||
@kindex Up
|
||
@item @key{Up}
|
||
Scroll the active window one line up.
|
||
|
||
@kindex Down
|
||
@item @key{Down}
|
||
Scroll the active window one line down.
|
||
|
||
@kindex Left
|
||
@item @key{Left}
|
||
Scroll the active window one column left.
|
||
|
||
@kindex Right
|
||
@item @key{Right}
|
||
Scroll the active window one column right.
|
||
|
||
@kindex C-L
|
||
@item @kbd{C-L}
|
||
Refresh the screen.
|
||
@end table
|
||
|
||
Because the arrow keys scroll the active window in the TUI mode, they
|
||
are not available for their normal use by readline unless the command
|
||
window has the focus. When another window is active, you must use
|
||
other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
|
||
and @kbd{C-f} to control the command window.
|
||
|
||
@node TUI Single Key Mode
|
||
@section TUI Single Key Mode
|
||
@cindex TUI single key mode
|
||
|
||
The TUI also provides a @dfn{SingleKey} mode, which binds several
|
||
frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
|
||
switch into this mode, where the following key bindings are used:
|
||
|
||
@table @kbd
|
||
@kindex c @r{(SingleKey TUI key)}
|
||
@item c
|
||
continue
|
||
|
||
@kindex d @r{(SingleKey TUI key)}
|
||
@item d
|
||
down
|
||
|
||
@kindex f @r{(SingleKey TUI key)}
|
||
@item f
|
||
finish
|
||
|
||
@kindex n @r{(SingleKey TUI key)}
|
||
@item n
|
||
next
|
||
|
||
@kindex o @r{(SingleKey TUI key)}
|
||
@item o
|
||
nexti. The shortcut letter @samp{o} stands for ``step Over''.
|
||
|
||
@kindex q @r{(SingleKey TUI key)}
|
||
@item q
|
||
exit the SingleKey mode.
|
||
|
||
@kindex r @r{(SingleKey TUI key)}
|
||
@item r
|
||
run
|
||
|
||
@kindex s @r{(SingleKey TUI key)}
|
||
@item s
|
||
step
|
||
|
||
@kindex i @r{(SingleKey TUI key)}
|
||
@item i
|
||
stepi. The shortcut letter @samp{i} stands for ``step Into''.
|
||
|
||
@kindex u @r{(SingleKey TUI key)}
|
||
@item u
|
||
up
|
||
|
||
@kindex v @r{(SingleKey TUI key)}
|
||
@item v
|
||
info locals
|
||
|
||
@kindex w @r{(SingleKey TUI key)}
|
||
@item w
|
||
where
|
||
@end table
|
||
|
||
Other keys temporarily switch to the @value{GDBN} command prompt.
|
||
The key that was pressed is inserted in the editing buffer so that
|
||
it is possible to type most @value{GDBN} commands without interaction
|
||
with the TUI SingleKey mode. Once the command is entered the TUI
|
||
SingleKey mode is restored. The only way to permanently leave
|
||
this mode is by typing @kbd{q} or @kbd{C-x s}.
|
||
|
||
|
||
@node TUI Commands
|
||
@section TUI-specific Commands
|
||
@cindex TUI commands
|
||
|
||
The TUI has specific commands to control the text windows.
|
||
These commands are always available, even when @value{GDBN} is not in
|
||
the TUI mode. When @value{GDBN} is in the standard mode, most
|
||
of these commands will automatically switch to the TUI mode.
|
||
|
||
Note that if @value{GDBN}'s @code{stdout} is not connected to a
|
||
terminal, or @value{GDBN} has been started with the machine interface
|
||
interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
|
||
these commands will fail with an error, because it would not be
|
||
possible or desirable to enable curses window management.
|
||
|
||
@table @code
|
||
@item tui enable
|
||
@kindex tui enable
|
||
Activate TUI mode. The last active TUI window layout will be used if
|
||
TUI mode has prevsiouly been used in the current debugging session,
|
||
otherwise a default layout is used.
|
||
|
||
@item tui disable
|
||
@kindex tui disable
|
||
Disable TUI mode, returning to the console interpreter.
|
||
|
||
@item info win
|
||
@kindex info win
|
||
List and give the size of all displayed windows.
|
||
|
||
@item layout @var{name}
|
||
@kindex layout
|
||
Changes which TUI windows are displayed. In each layout the command
|
||
window is always displayed, the @var{name} parameter controls which
|
||
additional windows are displayed, and can be any of the following:
|
||
|
||
@table @code
|
||
@item next
|
||
Display the next layout.
|
||
|
||
@item prev
|
||
Display the previous layout.
|
||
|
||
@item src
|
||
Display the source and command windows.
|
||
|
||
@item asm
|
||
Display the assembly and command windows.
|
||
|
||
@item split
|
||
Display the source, assembly, and command windows.
|
||
|
||
@item regs
|
||
When in @code{src} layout display the register, source, and command
|
||
windows. When in @code{asm} or @code{split} layout display the
|
||
register, assembler, and command windows.
|
||
@end table
|
||
|
||
@item focus @var{name}
|
||
@kindex focus
|
||
Changes which TUI window is currently active for scrolling. The
|
||
@var{name} parameter can be any of the following:
|
||
|
||
@table @code
|
||
@item next
|
||
Make the next window active for scrolling.
|
||
|
||
@item prev
|
||
Make the previous window active for scrolling.
|
||
|
||
@item src
|
||
Make the source window active for scrolling.
|
||
|
||
@item asm
|
||
Make the assembly window active for scrolling.
|
||
|
||
@item regs
|
||
Make the register window active for scrolling.
|
||
|
||
@item cmd
|
||
Make the command window active for scrolling.
|
||
@end table
|
||
|
||
@item refresh
|
||
@kindex refresh
|
||
Refresh the screen. This is similar to typing @kbd{C-L}.
|
||
|
||
@item tui reg @var{group}
|
||
@kindex tui reg
|
||
Changes the register group displayed in the tui register window to
|
||
@var{group}. If the register window is not currently displayed this
|
||
command will cause the register window to be displayed. The list of
|
||
register groups, as well as their order is target specific. The
|
||
following groups are available on most targets:
|
||
@table @code
|
||
@item next
|
||
Repeatedly selecting this group will cause the display to cycle
|
||
through all of the available register groups.
|
||
|
||
@item prev
|
||
Repeatedly selecting this group will cause the display to cycle
|
||
through all of the available register groups in the reverse order to
|
||
@var{next}.
|
||
|
||
@item general
|
||
Display the general registers.
|
||
@item float
|
||
Display the floating point registers.
|
||
@item system
|
||
Display the system registers.
|
||
@item vector
|
||
Display the vector registers.
|
||
@item all
|
||
Display all registers.
|
||
@end table
|
||
|
||
@item update
|
||
@kindex update
|
||
Update the source window and the current execution point.
|
||
|
||
@item winheight @var{name} +@var{count}
|
||
@itemx winheight @var{name} -@var{count}
|
||
@kindex winheight
|
||
Change the height of the window @var{name} by @var{count}
|
||
lines. Positive counts increase the height, while negative counts
|
||
decrease it. The @var{name} parameter can be one of @code{src} (the
|
||
source window), @code{cmd} (the command window), @code{asm} (the
|
||
disassembly window), or @code{regs} (the register display window).
|
||
|
||
@item tabset @var{nchars}
|
||
@kindex tabset
|
||
Set the width of tab stops to be @var{nchars} characters. This
|
||
setting affects the display of TAB characters in the source and
|
||
assembly windows.
|
||
@end table
|
||
|
||
@node TUI Configuration
|
||
@section TUI Configuration Variables
|
||
@cindex TUI configuration variables
|
||
|
||
Several configuration variables control the appearance of TUI windows.
|
||
|
||
@table @code
|
||
@item set tui border-kind @var{kind}
|
||
@kindex set tui border-kind
|
||
Select the border appearance for the source, assembly and register windows.
|
||
The possible values are the following:
|
||
@table @code
|
||
@item space
|
||
Use a space character to draw the border.
|
||
|
||
@item ascii
|
||
Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
|
||
|
||
@item acs
|
||
Use the Alternate Character Set to draw the border. The border is
|
||
drawn using character line graphics if the terminal supports them.
|
||
@end table
|
||
|
||
@item set tui border-mode @var{mode}
|
||
@kindex set tui border-mode
|
||
@itemx set tui active-border-mode @var{mode}
|
||
@kindex set tui active-border-mode
|
||
Select the display attributes for the borders of the inactive windows
|
||
or the active window. The @var{mode} can be one of the following:
|
||
@table @code
|
||
@item normal
|
||
Use normal attributes to display the border.
|
||
|
||
@item standout
|
||
Use standout mode.
|
||
|
||
@item reverse
|
||
Use reverse video mode.
|
||
|
||
@item half
|
||
Use half bright mode.
|
||
|
||
@item half-standout
|
||
Use half bright and standout mode.
|
||
|
||
@item bold
|
||
Use extra bright or bold mode.
|
||
|
||
@item bold-standout
|
||
Use extra bright or bold and standout mode.
|
||
@end table
|
||
@end table
|
||
|
||
@node Emacs
|
||
@chapter Using @value{GDBN} under @sc{gnu} Emacs
|
||
|
||
@cindex Emacs
|
||
@cindex @sc{gnu} Emacs
|
||
A special interface allows you to use @sc{gnu} Emacs to view (and
|
||
edit) the source files for the program you are debugging with
|
||
@value{GDBN}.
|
||
|
||
To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
|
||
executable file you want to debug as an argument. This command starts
|
||
@value{GDBN} as a subprocess of Emacs, with input and output through a newly
|
||
created Emacs buffer.
|
||
@c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
|
||
|
||
Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
|
||
things:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
All ``terminal'' input and output goes through an Emacs buffer, called
|
||
the GUD buffer.
|
||
|
||
This applies both to @value{GDBN} commands and their output, and to the input
|
||
and output done by the program you are debugging.
|
||
|
||
This is useful because it means that you can copy the text of previous
|
||
commands and input them again; you can even use parts of the output
|
||
in this way.
|
||
|
||
All the facilities of Emacs' Shell mode are available for interacting
|
||
with your program. In particular, you can send signals the usual
|
||
way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
|
||
stop.
|
||
|
||
@item
|
||
@value{GDBN} displays source code through Emacs.
|
||
|
||
Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
|
||
source file for that frame and puts an arrow (@samp{=>}) at the
|
||
left margin of the current line. Emacs uses a separate buffer for
|
||
source display, and splits the screen to show both your @value{GDBN} session
|
||
and the source.
|
||
|
||
Explicit @value{GDBN} @code{list} or search commands still produce output as
|
||
usual, but you probably have no reason to use them from Emacs.
|
||
@end itemize
|
||
|
||
We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
|
||
a graphical mode, enabled by default, which provides further buffers
|
||
that can control the execution and describe the state of your program.
|
||
@xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
|
||
|
||
If you specify an absolute file name when prompted for the @kbd{M-x
|
||
gdb} argument, then Emacs sets your current working directory to where
|
||
your program resides. If you only specify the file name, then Emacs
|
||
sets your current working directory to the directory associated
|
||
with the previous buffer. In this case, @value{GDBN} may find your
|
||
program by searching your environment's @code{PATH} variable, but on
|
||
some operating systems it might not find the source. So, although the
|
||
@value{GDBN} input and output session proceeds normally, the auxiliary
|
||
buffer does not display the current source and line of execution.
|
||
|
||
The initial working directory of @value{GDBN} is printed on the top
|
||
line of the GUD buffer and this serves as a default for the commands
|
||
that specify files for @value{GDBN} to operate on. @xref{Files,
|
||
,Commands to Specify Files}.
|
||
|
||
By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
|
||
need to call @value{GDBN} by a different name (for example, if you
|
||
keep several configurations around, with different names) you can
|
||
customize the Emacs variable @code{gud-gdb-command-name} to run the
|
||
one you want.
|
||
|
||
In the GUD buffer, you can use these special Emacs commands in
|
||
addition to the standard Shell mode commands:
|
||
|
||
@table @kbd
|
||
@item C-h m
|
||
Describe the features of Emacs' GUD Mode.
|
||
|
||
@item C-c C-s
|
||
Execute to another source line, like the @value{GDBN} @code{step} command; also
|
||
update the display window to show the current file and location.
|
||
|
||
@item C-c C-n
|
||
Execute to next source line in this function, skipping all function
|
||
calls, like the @value{GDBN} @code{next} command. Then update the display window
|
||
to show the current file and location.
|
||
|
||
@item C-c C-i
|
||
Execute one instruction, like the @value{GDBN} @code{stepi} command; update
|
||
display window accordingly.
|
||
|
||
@item C-c C-f
|
||
Execute until exit from the selected stack frame, like the @value{GDBN}
|
||
@code{finish} command.
|
||
|
||
@item C-c C-r
|
||
Continue execution of your program, like the @value{GDBN} @code{continue}
|
||
command.
|
||
|
||
@item C-c <
|
||
Go up the number of frames indicated by the numeric argument
|
||
(@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
|
||
like the @value{GDBN} @code{up} command.
|
||
|
||
@item C-c >
|
||
Go down the number of frames indicated by the numeric argument, like the
|
||
@value{GDBN} @code{down} command.
|
||
@end table
|
||
|
||
In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
|
||
tells @value{GDBN} to set a breakpoint on the source line point is on.
|
||
|
||
In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
|
||
separate frame which shows a backtrace when the GUD buffer is current.
|
||
Move point to any frame in the stack and type @key{RET} to make it
|
||
become the current frame and display the associated source in the
|
||
source buffer. Alternatively, click @kbd{Mouse-2} to make the
|
||
selected frame become the current one. In graphical mode, the
|
||
speedbar displays watch expressions.
|
||
|
||
If you accidentally delete the source-display buffer, an easy way to get
|
||
it back is to type the command @code{f} in the @value{GDBN} buffer, to
|
||
request a frame display; when you run under Emacs, this recreates
|
||
the source buffer if necessary to show you the context of the current
|
||
frame.
|
||
|
||
The source files displayed in Emacs are in ordinary Emacs buffers
|
||
which are visiting the source files in the usual way. You can edit
|
||
the files with these buffers if you wish; but keep in mind that @value{GDBN}
|
||
communicates with Emacs in terms of line numbers. If you add or
|
||
delete lines from the text, the line numbers that @value{GDBN} knows cease
|
||
to correspond properly with the code.
|
||
|
||
A more detailed description of Emacs' interaction with @value{GDBN} is
|
||
given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
|
||
Emacs Manual}).
|
||
|
||
@node GDB/MI
|
||
@chapter The @sc{gdb/mi} Interface
|
||
|
||
@unnumberedsec Function and Purpose
|
||
|
||
@cindex @sc{gdb/mi}, its purpose
|
||
@sc{gdb/mi} is a line based machine oriented text interface to
|
||
@value{GDBN} and is activated by specifying using the
|
||
@option{--interpreter} command line option (@pxref{Mode Options}). It
|
||
is specifically intended to support the development of systems which
|
||
use the debugger as just one small component of a larger system.
|
||
|
||
This chapter is a specification of the @sc{gdb/mi} interface. It is written
|
||
in the form of a reference manual.
|
||
|
||
Note that @sc{gdb/mi} is still under construction, so some of the
|
||
features described below are incomplete and subject to change
|
||
(@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
|
||
|
||
@unnumberedsec Notation and Terminology
|
||
|
||
@cindex notational conventions, for @sc{gdb/mi}
|
||
This chapter uses the following notation:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
@code{|} separates two alternatives.
|
||
|
||
@item
|
||
@code{[ @var{something} ]} indicates that @var{something} is optional:
|
||
it may or may not be given.
|
||
|
||
@item
|
||
@code{( @var{group} )*} means that @var{group} inside the parentheses
|
||
may repeat zero or more times.
|
||
|
||
@item
|
||
@code{( @var{group} )+} means that @var{group} inside the parentheses
|
||
may repeat one or more times.
|
||
|
||
@item
|
||
@code{"@var{string}"} means a literal @var{string}.
|
||
@end itemize
|
||
|
||
@ignore
|
||
@heading Dependencies
|
||
@end ignore
|
||
|
||
@menu
|
||
* GDB/MI General Design::
|
||
* GDB/MI Command Syntax::
|
||
* GDB/MI Compatibility with CLI::
|
||
* GDB/MI Development and Front Ends::
|
||
* GDB/MI Output Records::
|
||
* GDB/MI Simple Examples::
|
||
* GDB/MI Command Description Format::
|
||
* GDB/MI Breakpoint Commands::
|
||
* GDB/MI Catchpoint Commands::
|
||
* GDB/MI Program Context::
|
||
* GDB/MI Thread Commands::
|
||
* GDB/MI Ada Tasking Commands::
|
||
* GDB/MI Program Execution::
|
||
* GDB/MI Stack Manipulation::
|
||
* GDB/MI Variable Objects::
|
||
* GDB/MI Data Manipulation::
|
||
* GDB/MI Tracepoint Commands::
|
||
* GDB/MI Symbol Query::
|
||
* GDB/MI File Commands::
|
||
@ignore
|
||
* GDB/MI Kod Commands::
|
||
* GDB/MI Memory Overlay Commands::
|
||
* GDB/MI Signal Handling Commands::
|
||
@end ignore
|
||
* GDB/MI Target Manipulation::
|
||
* GDB/MI File Transfer Commands::
|
||
* GDB/MI Ada Exceptions Commands::
|
||
* GDB/MI Support Commands::
|
||
* GDB/MI Miscellaneous Commands::
|
||
@end menu
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI General Design
|
||
@section @sc{gdb/mi} General Design
|
||
@cindex GDB/MI General Design
|
||
|
||
Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
|
||
parts---commands sent to @value{GDBN}, responses to those commands
|
||
and notifications. Each command results in exactly one response,
|
||
indicating either successful completion of the command, or an error.
|
||
For the commands that do not resume the target, the response contains the
|
||
requested information. For the commands that resume the target, the
|
||
response only indicates whether the target was successfully resumed.
|
||
Notifications is the mechanism for reporting changes in the state of the
|
||
target, or in @value{GDBN} state, that cannot conveniently be associated with
|
||
a command and reported as part of that command response.
|
||
|
||
The important examples of notifications are:
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Exec notifications. These are used to report changes in
|
||
target state---when a target is resumed, or stopped. It would not
|
||
be feasible to include this information in response of resuming
|
||
commands, because one resume commands can result in multiple events in
|
||
different threads. Also, quite some time may pass before any event
|
||
happens in the target, while a frontend needs to know whether the resuming
|
||
command itself was successfully executed.
|
||
|
||
@item
|
||
Console output, and status notifications. Console output
|
||
notifications are used to report output of CLI commands, as well as
|
||
diagnostics for other commands. Status notifications are used to
|
||
report the progress of a long-running operation. Naturally, including
|
||
this information in command response would mean no output is produced
|
||
until the command is finished, which is undesirable.
|
||
|
||
@item
|
||
General notifications. Commands may have various side effects on
|
||
the @value{GDBN} or target state beyond their official purpose. For example,
|
||
a command may change the selected thread. Although such changes can
|
||
be included in command response, using notification allows for more
|
||
orthogonal frontend design.
|
||
|
||
@end itemize
|
||
|
||
There's no guarantee that whenever an MI command reports an error,
|
||
@value{GDBN} or the target are in any specific state, and especially,
|
||
the state is not reverted to the state before the MI command was
|
||
processed. Therefore, whenever an MI command results in an error,
|
||
we recommend that the frontend refreshes all the information shown in
|
||
the user interface.
|
||
|
||
|
||
@menu
|
||
* Context management::
|
||
* Asynchronous and non-stop modes::
|
||
* Thread groups::
|
||
@end menu
|
||
|
||
@node Context management
|
||
@subsection Context management
|
||
|
||
@subsubsection Threads and Frames
|
||
|
||
In most cases when @value{GDBN} accesses the target, this access is
|
||
done in context of a specific thread and frame (@pxref{Frames}).
|
||
Often, even when accessing global data, the target requires that a thread
|
||
be specified. The CLI interface maintains the selected thread and frame,
|
||
and supplies them to target on each command. This is convenient,
|
||
because a command line user would not want to specify that information
|
||
explicitly on each command, and because user interacts with
|
||
@value{GDBN} via a single terminal, so no confusion is possible as
|
||
to what thread and frame are the current ones.
|
||
|
||
In the case of MI, the concept of selected thread and frame is less
|
||
useful. First, a frontend can easily remember this information
|
||
itself. Second, a graphical frontend can have more than one window,
|
||
each one used for debugging a different thread, and the frontend might
|
||
want to access additional threads for internal purposes. This
|
||
increases the risk that by relying on implicitly selected thread, the
|
||
frontend may be operating on a wrong one. Therefore, each MI command
|
||
should explicitly specify which thread and frame to operate on. To
|
||
make it possible, each MI command accepts the @samp{--thread} and
|
||
@samp{--frame} options, the value to each is @value{GDBN} global
|
||
identifier for thread and frame to operate on.
|
||
|
||
Usually, each top-level window in a frontend allows the user to select
|
||
a thread and a frame, and remembers the user selection for further
|
||
operations. However, in some cases @value{GDBN} may suggest that the
|
||
current thread or frame be changed. For example, when stopping on a
|
||
breakpoint it is reasonable to switch to the thread where breakpoint is
|
||
hit. For another example, if the user issues the CLI @samp{thread} or
|
||
@samp{frame} commands via the frontend, it is desirable to change the
|
||
frontend's selection to the one specified by user. @value{GDBN}
|
||
communicates the suggestion to change current thread and frame using the
|
||
@samp{=thread-selected} notification.
|
||
|
||
Note that historically, MI shares the selected thread with CLI, so
|
||
frontends used the @code{-thread-select} to execute commands in the
|
||
right context. However, getting this to work right is cumbersome. The
|
||
simplest way is for frontend to emit @code{-thread-select} command
|
||
before every command. This doubles the number of commands that need
|
||
to be sent. The alternative approach is to suppress @code{-thread-select}
|
||
if the selected thread in @value{GDBN} is supposed to be identical to the
|
||
thread the frontend wants to operate on. However, getting this
|
||
optimization right can be tricky. In particular, if the frontend
|
||
sends several commands to @value{GDBN}, and one of the commands changes the
|
||
selected thread, then the behaviour of subsequent commands will
|
||
change. So, a frontend should either wait for response from such
|
||
problematic commands, or explicitly add @code{-thread-select} for
|
||
all subsequent commands. No frontend is known to do this exactly
|
||
right, so it is suggested to just always pass the @samp{--thread} and
|
||
@samp{--frame} options.
|
||
|
||
@subsubsection Language
|
||
|
||
The execution of several commands depends on which language is selected.
|
||
By default, the current language (@pxref{show language}) is used.
|
||
But for commands known to be language-sensitive, it is recommended
|
||
to use the @samp{--language} option. This option takes one argument,
|
||
which is the name of the language to use while executing the command.
|
||
For instance:
|
||
|
||
@smallexample
|
||
-data-evaluate-expression --language c "sizeof (void*)"
|
||
^done,value="4"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
The valid language names are the same names accepted by the
|
||
@samp{set language} command (@pxref{Manually}), excluding @samp{auto},
|
||
@samp{local} or @samp{unknown}.
|
||
|
||
@node Asynchronous and non-stop modes
|
||
@subsection Asynchronous command execution and non-stop mode
|
||
|
||
On some targets, @value{GDBN} is capable of processing MI commands
|
||
even while the target is running. This is called @dfn{asynchronous
|
||
command execution} (@pxref{Background Execution}). The frontend may
|
||
specify a preferrence for asynchronous execution using the
|
||
@code{-gdb-set mi-async 1} command, which should be emitted before
|
||
either running the executable or attaching to the target. After the
|
||
frontend has started the executable or attached to the target, it can
|
||
find if asynchronous execution is enabled using the
|
||
@code{-list-target-features} command.
|
||
|
||
@table @code
|
||
@item -gdb-set mi-async on
|
||
@item -gdb-set mi-async off
|
||
Set whether MI is in asynchronous mode.
|
||
|
||
When @code{off}, which is the default, MI execution commands (e.g.,
|
||
@code{-exec-continue}) are foreground commands, and @value{GDBN} waits
|
||
for the program to stop before processing further commands.
|
||
|
||
When @code{on}, MI execution commands are background execution
|
||
commands (e.g., @code{-exec-continue} becomes the equivalent of the
|
||
@code{c&} CLI command), and so @value{GDBN} is capable of processing
|
||
MI commands even while the target is running.
|
||
|
||
@item -gdb-show mi-async
|
||
Show whether MI asynchronous mode is enabled.
|
||
@end table
|
||
|
||
Note: In @value{GDBN} version 7.7 and earlier, this option was called
|
||
@code{target-async} instead of @code{mi-async}, and it had the effect
|
||
of both putting MI in asynchronous mode and making CLI background
|
||
commands possible. CLI background commands are now always possible
|
||
``out of the box'' if the target supports them. The old spelling is
|
||
kept as a deprecated alias for backwards compatibility.
|
||
|
||
Even if @value{GDBN} can accept a command while target is running,
|
||
many commands that access the target do not work when the target is
|
||
running. Therefore, asynchronous command execution is most useful
|
||
when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
|
||
it is possible to examine the state of one thread, while other threads
|
||
are running.
|
||
|
||
When a given thread is running, MI commands that try to access the
|
||
target in the context of that thread may not work, or may work only on
|
||
some targets. In particular, commands that try to operate on thread's
|
||
stack will not work, on any target. Commands that read memory, or
|
||
modify breakpoints, may work or not work, depending on the target. Note
|
||
that even commands that operate on global state, such as @code{print},
|
||
@code{set}, and breakpoint commands, still access the target in the
|
||
context of a specific thread, so frontend should try to find a
|
||
stopped thread and perform the operation on that thread (using the
|
||
@samp{--thread} option).
|
||
|
||
Which commands will work in the context of a running thread is
|
||
highly target dependent. However, the two commands
|
||
@code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
|
||
to find the state of a thread, will always work.
|
||
|
||
@node Thread groups
|
||
@subsection Thread groups
|
||
@value{GDBN} may be used to debug several processes at the same time.
|
||
On some platfroms, @value{GDBN} may support debugging of several
|
||
hardware systems, each one having several cores with several different
|
||
processes running on each core. This section describes the MI
|
||
mechanism to support such debugging scenarios.
|
||
|
||
The key observation is that regardless of the structure of the
|
||
target, MI can have a global list of threads, because most commands that
|
||
accept the @samp{--thread} option do not need to know what process that
|
||
thread belongs to. Therefore, it is not necessary to introduce
|
||
neither additional @samp{--process} option, nor an notion of the
|
||
current process in the MI interface. The only strictly new feature
|
||
that is required is the ability to find how the threads are grouped
|
||
into processes.
|
||
|
||
To allow the user to discover such grouping, and to support arbitrary
|
||
hierarchy of machines/cores/processes, MI introduces the concept of a
|
||
@dfn{thread group}. Thread group is a collection of threads and other
|
||
thread groups. A thread group always has a string identifier, a type,
|
||
and may have additional attributes specific to the type. A new
|
||
command, @code{-list-thread-groups}, returns the list of top-level
|
||
thread groups, which correspond to processes that @value{GDBN} is
|
||
debugging at the moment. By passing an identifier of a thread group
|
||
to the @code{-list-thread-groups} command, it is possible to obtain
|
||
the members of specific thread group.
|
||
|
||
To allow the user to easily discover processes, and other objects, he
|
||
wishes to debug, a concept of @dfn{available thread group} is
|
||
introduced. Available thread group is an thread group that
|
||
@value{GDBN} is not debugging, but that can be attached to, using the
|
||
@code{-target-attach} command. The list of available top-level thread
|
||
groups can be obtained using @samp{-list-thread-groups --available}.
|
||
In general, the content of a thread group may be only retrieved only
|
||
after attaching to that thread group.
|
||
|
||
Thread groups are related to inferiors (@pxref{Inferiors and
|
||
Programs}). Each inferior corresponds to a thread group of a special
|
||
type @samp{process}, and some additional operations are permitted on
|
||
such thread groups.
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Command Syntax
|
||
@section @sc{gdb/mi} Command Syntax
|
||
|
||
@menu
|
||
* GDB/MI Input Syntax::
|
||
* GDB/MI Output Syntax::
|
||
@end menu
|
||
|
||
@node GDB/MI Input Syntax
|
||
@subsection @sc{gdb/mi} Input Syntax
|
||
|
||
@cindex input syntax for @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, input syntax
|
||
@table @code
|
||
@item @var{command} @expansion{}
|
||
@code{@var{cli-command} | @var{mi-command}}
|
||
|
||
@item @var{cli-command} @expansion{}
|
||
@code{[ @var{token} ] @var{cli-command} @var{nl}}, where
|
||
@var{cli-command} is any existing @value{GDBN} CLI command.
|
||
|
||
@item @var{mi-command} @expansion{}
|
||
@code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
|
||
@code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
|
||
|
||
@item @var{token} @expansion{}
|
||
"any sequence of digits"
|
||
|
||
@item @var{option} @expansion{}
|
||
@code{"-" @var{parameter} [ " " @var{parameter} ]}
|
||
|
||
@item @var{parameter} @expansion{}
|
||
@code{@var{non-blank-sequence} | @var{c-string}}
|
||
|
||
@item @var{operation} @expansion{}
|
||
@emph{any of the operations described in this chapter}
|
||
|
||
@item @var{non-blank-sequence} @expansion{}
|
||
@emph{anything, provided it doesn't contain special characters such as
|
||
"-", @var{nl}, """ and of course " "}
|
||
|
||
@item @var{c-string} @expansion{}
|
||
@code{""" @var{seven-bit-iso-c-string-content} """}
|
||
|
||
@item @var{nl} @expansion{}
|
||
@code{CR | CR-LF}
|
||
@end table
|
||
|
||
@noindent
|
||
Notes:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The CLI commands are still handled by the @sc{mi} interpreter; their
|
||
output is described below.
|
||
|
||
@item
|
||
The @code{@var{token}}, when present, is passed back when the command
|
||
finishes.
|
||
|
||
@item
|
||
Some @sc{mi} commands accept optional arguments as part of the parameter
|
||
list. Each option is identified by a leading @samp{-} (dash) and may be
|
||
followed by an optional argument parameter. Options occur first in the
|
||
parameter list and can be delimited from normal parameters using
|
||
@samp{--} (this is useful when some parameters begin with a dash).
|
||
@end itemize
|
||
|
||
Pragmatics:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
We want easy access to the existing CLI syntax (for debugging).
|
||
|
||
@item
|
||
We want it to be easy to spot a @sc{mi} operation.
|
||
@end itemize
|
||
|
||
@node GDB/MI Output Syntax
|
||
@subsection @sc{gdb/mi} Output Syntax
|
||
|
||
@cindex output syntax of @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, output syntax
|
||
The output from @sc{gdb/mi} consists of zero or more out-of-band records
|
||
followed, optionally, by a single result record. This result record
|
||
is for the most recent command. The sequence of output records is
|
||
terminated by @samp{(gdb)}.
|
||
|
||
If an input command was prefixed with a @code{@var{token}} then the
|
||
corresponding output for that command will also be prefixed by that same
|
||
@var{token}.
|
||
|
||
@table @code
|
||
@item @var{output} @expansion{}
|
||
@code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
|
||
|
||
@item @var{result-record} @expansion{}
|
||
@code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
|
||
|
||
@item @var{out-of-band-record} @expansion{}
|
||
@code{@var{async-record} | @var{stream-record}}
|
||
|
||
@item @var{async-record} @expansion{}
|
||
@code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
|
||
|
||
@item @var{exec-async-output} @expansion{}
|
||
@code{[ @var{token} ] "*" @var{async-output nl}}
|
||
|
||
@item @var{status-async-output} @expansion{}
|
||
@code{[ @var{token} ] "+" @var{async-output nl}}
|
||
|
||
@item @var{notify-async-output} @expansion{}
|
||
@code{[ @var{token} ] "=" @var{async-output nl}}
|
||
|
||
@item @var{async-output} @expansion{}
|
||
@code{@var{async-class} ( "," @var{result} )*}
|
||
|
||
@item @var{result-class} @expansion{}
|
||
@code{"done" | "running" | "connected" | "error" | "exit"}
|
||
|
||
@item @var{async-class} @expansion{}
|
||
@code{"stopped" | @var{others}} (where @var{others} will be added
|
||
depending on the needs---this is still in development).
|
||
|
||
@item @var{result} @expansion{}
|
||
@code{ @var{variable} "=" @var{value}}
|
||
|
||
@item @var{variable} @expansion{}
|
||
@code{ @var{string} }
|
||
|
||
@item @var{value} @expansion{}
|
||
@code{ @var{const} | @var{tuple} | @var{list} }
|
||
|
||
@item @var{const} @expansion{}
|
||
@code{@var{c-string}}
|
||
|
||
@item @var{tuple} @expansion{}
|
||
@code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
|
||
|
||
@item @var{list} @expansion{}
|
||
@code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
|
||
@var{result} ( "," @var{result} )* "]" }
|
||
|
||
@item @var{stream-record} @expansion{}
|
||
@code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
|
||
|
||
@item @var{console-stream-output} @expansion{}
|
||
@code{"~" @var{c-string nl}}
|
||
|
||
@item @var{target-stream-output} @expansion{}
|
||
@code{"@@" @var{c-string nl}}
|
||
|
||
@item @var{log-stream-output} @expansion{}
|
||
@code{"&" @var{c-string nl}}
|
||
|
||
@item @var{nl} @expansion{}
|
||
@code{CR | CR-LF}
|
||
|
||
@item @var{token} @expansion{}
|
||
@emph{any sequence of digits}.
|
||
@end table
|
||
|
||
@noindent
|
||
Notes:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
All output sequences end in a single line containing a period.
|
||
|
||
@item
|
||
The @code{@var{token}} is from the corresponding request. Note that
|
||
for all async output, while the token is allowed by the grammar and
|
||
may be output by future versions of @value{GDBN} for select async
|
||
output messages, it is generally omitted. Frontends should treat
|
||
all async output as reporting general changes in the state of the
|
||
target and there should be no need to associate async output to any
|
||
prior command.
|
||
|
||
@item
|
||
@cindex status output in @sc{gdb/mi}
|
||
@var{status-async-output} contains on-going status information about the
|
||
progress of a slow operation. It can be discarded. All status output is
|
||
prefixed by @samp{+}.
|
||
|
||
@item
|
||
@cindex async output in @sc{gdb/mi}
|
||
@var{exec-async-output} contains asynchronous state change on the target
|
||
(stopped, started, disappeared). All async output is prefixed by
|
||
@samp{*}.
|
||
|
||
@item
|
||
@cindex notify output in @sc{gdb/mi}
|
||
@var{notify-async-output} contains supplementary information that the
|
||
client should handle (e.g., a new breakpoint information). All notify
|
||
output is prefixed by @samp{=}.
|
||
|
||
@item
|
||
@cindex console output in @sc{gdb/mi}
|
||
@var{console-stream-output} is output that should be displayed as is in the
|
||
console. It is the textual response to a CLI command. All the console
|
||
output is prefixed by @samp{~}.
|
||
|
||
@item
|
||
@cindex target output in @sc{gdb/mi}
|
||
@var{target-stream-output} is the output produced by the target program.
|
||
All the target output is prefixed by @samp{@@}.
|
||
|
||
@item
|
||
@cindex log output in @sc{gdb/mi}
|
||
@var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
|
||
instance messages that should be displayed as part of an error log. All
|
||
the log output is prefixed by @samp{&}.
|
||
|
||
@item
|
||
@cindex list output in @sc{gdb/mi}
|
||
New @sc{gdb/mi} commands should only output @var{lists} containing
|
||
@var{values}.
|
||
|
||
|
||
@end itemize
|
||
|
||
@xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
|
||
details about the various output records.
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Compatibility with CLI
|
||
@section @sc{gdb/mi} Compatibility with CLI
|
||
|
||
@cindex compatibility, @sc{gdb/mi} and CLI
|
||
@cindex @sc{gdb/mi}, compatibility with CLI
|
||
|
||
For the developers convenience CLI commands can be entered directly,
|
||
but there may be some unexpected behaviour. For example, commands
|
||
that query the user will behave as if the user replied yes, breakpoint
|
||
command lists are not executed and some CLI commands, such as
|
||
@code{if}, @code{when} and @code{define}, prompt for further input with
|
||
@samp{>}, which is not valid MI output.
|
||
|
||
This feature may be removed at some stage in the future and it is
|
||
recommended that front ends use the @code{-interpreter-exec} command
|
||
(@pxref{-interpreter-exec}).
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Development and Front Ends
|
||
@section @sc{gdb/mi} Development and Front Ends
|
||
@cindex @sc{gdb/mi} development
|
||
|
||
The application which takes the MI output and presents the state of the
|
||
program being debugged to the user is called a @dfn{front end}.
|
||
|
||
Although @sc{gdb/mi} is still incomplete, it is currently being used
|
||
by a variety of front ends to @value{GDBN}. This makes it difficult
|
||
to introduce new functionality without breaking existing usage. This
|
||
section tries to minimize the problems by describing how the protocol
|
||
might change.
|
||
|
||
Some changes in MI need not break a carefully designed front end, and
|
||
for these the MI version will remain unchanged. The following is a
|
||
list of changes that may occur within one level, so front ends should
|
||
parse MI output in a way that can handle them:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
New MI commands may be added.
|
||
|
||
@item
|
||
New fields may be added to the output of any MI command.
|
||
|
||
@item
|
||
The range of values for fields with specified values, e.g.,
|
||
@code{in_scope} (@pxref{-var-update}) may be extended.
|
||
|
||
@c The format of field's content e.g type prefix, may change so parse it
|
||
@c at your own risk. Yes, in general?
|
||
|
||
@c The order of fields may change? Shouldn't really matter but it might
|
||
@c resolve inconsistencies.
|
||
@end itemize
|
||
|
||
If the changes are likely to break front ends, the MI version level
|
||
will be increased by one. This will allow the front end to parse the
|
||
output according to the MI version. Apart from mi0, new versions of
|
||
@value{GDBN} will not support old versions of MI and it will be the
|
||
responsibility of the front end to work with the new one.
|
||
|
||
@c Starting with mi3, add a new command -mi-version that prints the MI
|
||
@c version?
|
||
|
||
The best way to avoid unexpected changes in MI that might break your front
|
||
end is to make your project known to @value{GDBN} developers and
|
||
follow development on @email{gdb@@sourceware.org} and
|
||
@email{gdb-patches@@sourceware.org}.
|
||
@cindex mailing lists
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Output Records
|
||
@section @sc{gdb/mi} Output Records
|
||
|
||
@menu
|
||
* GDB/MI Result Records::
|
||
* GDB/MI Stream Records::
|
||
* GDB/MI Async Records::
|
||
* GDB/MI Breakpoint Information::
|
||
* GDB/MI Frame Information::
|
||
* GDB/MI Thread Information::
|
||
* GDB/MI Ada Exception Information::
|
||
@end menu
|
||
|
||
@node GDB/MI Result Records
|
||
@subsection @sc{gdb/mi} Result Records
|
||
|
||
@cindex result records in @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, result records
|
||
In addition to a number of out-of-band notifications, the response to a
|
||
@sc{gdb/mi} command includes one of the following result indications:
|
||
|
||
@table @code
|
||
@findex ^done
|
||
@item "^done" [ "," @var{results} ]
|
||
The synchronous operation was successful, @code{@var{results}} are the return
|
||
values.
|
||
|
||
@item "^running"
|
||
@findex ^running
|
||
This result record is equivalent to @samp{^done}. Historically, it
|
||
was output instead of @samp{^done} if the command has resumed the
|
||
target. This behaviour is maintained for backward compatibility, but
|
||
all frontends should treat @samp{^done} and @samp{^running}
|
||
identically and rely on the @samp{*running} output record to determine
|
||
which threads are resumed.
|
||
|
||
@item "^connected"
|
||
@findex ^connected
|
||
@value{GDBN} has connected to a remote target.
|
||
|
||
@item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
|
||
@findex ^error
|
||
The operation failed. The @code{msg=@var{c-string}} variable contains
|
||
the corresponding error message.
|
||
|
||
If present, the @code{code=@var{c-string}} variable provides an error
|
||
code on which consumers can rely on to detect the corresponding
|
||
error condition. At present, only one error code is defined:
|
||
|
||
@table @samp
|
||
@item "undefined-command"
|
||
Indicates that the command causing the error does not exist.
|
||
@end table
|
||
|
||
@item "^exit"
|
||
@findex ^exit
|
||
@value{GDBN} has terminated.
|
||
|
||
@end table
|
||
|
||
@node GDB/MI Stream Records
|
||
@subsection @sc{gdb/mi} Stream Records
|
||
|
||
@cindex @sc{gdb/mi}, stream records
|
||
@cindex stream records in @sc{gdb/mi}
|
||
@value{GDBN} internally maintains a number of output streams: the console, the
|
||
target, and the log. The output intended for each of these streams is
|
||
funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
|
||
|
||
Each stream record begins with a unique @dfn{prefix character} which
|
||
identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
|
||
Syntax}). In addition to the prefix, each stream record contains a
|
||
@code{@var{string-output}}. This is either raw text (with an implicit new
|
||
line) or a quoted C string (which does not contain an implicit newline).
|
||
|
||
@table @code
|
||
@item "~" @var{string-output}
|
||
The console output stream contains text that should be displayed in the
|
||
CLI console window. It contains the textual responses to CLI commands.
|
||
|
||
@item "@@" @var{string-output}
|
||
The target output stream contains any textual output from the running
|
||
target. This is only present when GDB's event loop is truly
|
||
asynchronous, which is currently only the case for remote targets.
|
||
|
||
@item "&" @var{string-output}
|
||
The log stream contains debugging messages being produced by @value{GDBN}'s
|
||
internals.
|
||
@end table
|
||
|
||
@node GDB/MI Async Records
|
||
@subsection @sc{gdb/mi} Async Records
|
||
|
||
@cindex async records in @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, async records
|
||
@dfn{Async} records are used to notify the @sc{gdb/mi} client of
|
||
additional changes that have occurred. Those changes can either be a
|
||
consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
|
||
target activity (e.g., target stopped).
|
||
|
||
The following is the list of possible async records:
|
||
|
||
@table @code
|
||
|
||
@item *running,thread-id="@var{thread}"
|
||
The target is now running. The @var{thread} field can be the global
|
||
thread ID of the the thread that is now running, and it can be
|
||
@samp{all} if all threads are running. The frontend should assume
|
||
that no interaction with a running thread is possible after this
|
||
notification is produced. The frontend should not assume that this
|
||
notification is output only once for any command. @value{GDBN} may
|
||
emit this notification several times, either for different threads,
|
||
because it cannot resume all threads together, or even for a single
|
||
thread, if the thread must be stepped though some code before letting
|
||
it run freely.
|
||
|
||
@item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
|
||
The target has stopped. The @var{reason} field can have one of the
|
||
following values:
|
||
|
||
@table @code
|
||
@item breakpoint-hit
|
||
A breakpoint was reached.
|
||
@item watchpoint-trigger
|
||
A watchpoint was triggered.
|
||
@item read-watchpoint-trigger
|
||
A read watchpoint was triggered.
|
||
@item access-watchpoint-trigger
|
||
An access watchpoint was triggered.
|
||
@item function-finished
|
||
An -exec-finish or similar CLI command was accomplished.
|
||
@item location-reached
|
||
An -exec-until or similar CLI command was accomplished.
|
||
@item watchpoint-scope
|
||
A watchpoint has gone out of scope.
|
||
@item end-stepping-range
|
||
An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
|
||
similar CLI command was accomplished.
|
||
@item exited-signalled
|
||
The inferior exited because of a signal.
|
||
@item exited
|
||
The inferior exited.
|
||
@item exited-normally
|
||
The inferior exited normally.
|
||
@item signal-received
|
||
A signal was received by the inferior.
|
||
@item solib-event
|
||
The inferior has stopped due to a library being loaded or unloaded.
|
||
This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
|
||
set or when a @code{catch load} or @code{catch unload} catchpoint is
|
||
in use (@pxref{Set Catchpoints}).
|
||
@item fork
|
||
The inferior has forked. This is reported when @code{catch fork}
|
||
(@pxref{Set Catchpoints}) has been used.
|
||
@item vfork
|
||
The inferior has vforked. This is reported in when @code{catch vfork}
|
||
(@pxref{Set Catchpoints}) has been used.
|
||
@item syscall-entry
|
||
The inferior entered a system call. This is reported when @code{catch
|
||
syscall} (@pxref{Set Catchpoints}) has been used.
|
||
@item syscall-return
|
||
The inferior returned from a system call. This is reported when
|
||
@code{catch syscall} (@pxref{Set Catchpoints}) has been used.
|
||
@item exec
|
||
The inferior called @code{exec}. This is reported when @code{catch exec}
|
||
(@pxref{Set Catchpoints}) has been used.
|
||
@end table
|
||
|
||
The @var{id} field identifies the global thread ID of the thread
|
||
that directly caused the stop -- for example by hitting a breakpoint.
|
||
Depending on whether all-stop
|
||
mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
|
||
stop all threads, or only the thread that directly triggered the stop.
|
||
If all threads are stopped, the @var{stopped} field will have the
|
||
value of @code{"all"}. Otherwise, the value of the @var{stopped}
|
||
field will be a list of thread identifiers. Presently, this list will
|
||
always include a single thread, but frontend should be prepared to see
|
||
several threads in the list. The @var{core} field reports the
|
||
processor core on which the stop event has happened. This field may be absent
|
||
if such information is not available.
|
||
|
||
@item =thread-group-added,id="@var{id}"
|
||
@itemx =thread-group-removed,id="@var{id}"
|
||
A thread group was either added or removed. The @var{id} field
|
||
contains the @value{GDBN} identifier of the thread group. When a thread
|
||
group is added, it generally might not be associated with a running
|
||
process. When a thread group is removed, its id becomes invalid and
|
||
cannot be used in any way.
|
||
|
||
@item =thread-group-started,id="@var{id}",pid="@var{pid}"
|
||
A thread group became associated with a running program,
|
||
either because the program was just started or the thread group
|
||
was attached to a program. The @var{id} field contains the
|
||
@value{GDBN} identifier of the thread group. The @var{pid} field
|
||
contains process identifier, specific to the operating system.
|
||
|
||
@item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
|
||
A thread group is no longer associated with a running program,
|
||
either because the program has exited, or because it was detached
|
||
from. The @var{id} field contains the @value{GDBN} identifier of the
|
||
thread group. The @var{code} field is the exit code of the inferior; it exists
|
||
only when the inferior exited with some code.
|
||
|
||
@item =thread-created,id="@var{id}",group-id="@var{gid}"
|
||
@itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
|
||
A thread either was created, or has exited. The @var{id} field
|
||
contains the global @value{GDBN} identifier of the thread. The @var{gid}
|
||
field identifies the thread group this thread belongs to.
|
||
|
||
@item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
|
||
Informs that the selected thread or frame were changed. This notification
|
||
is not emitted as result of the @code{-thread-select} or
|
||
@code{-stack-select-frame} commands, but is emitted whenever an MI command
|
||
that is not documented to change the selected thread and frame actually
|
||
changes them. In particular, invoking, directly or indirectly
|
||
(via user-defined command), the CLI @code{thread} or @code{frame} commands,
|
||
will generate this notification. Changing the thread or frame from another
|
||
user interface (see @ref{Interpreters}) will also generate this notification.
|
||
|
||
The @var{frame} field is only present if the newly selected thread is
|
||
stopped. See @ref{GDB/MI Frame Information} for the format of its value.
|
||
|
||
We suggest that in response to this notification, front ends
|
||
highlight the selected thread and cause subsequent commands to apply to
|
||
that thread.
|
||
|
||
@item =library-loaded,...
|
||
Reports that a new library file was loaded by the program. This
|
||
notification has 5 fields---@var{id}, @var{target-name},
|
||
@var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
|
||
opaque identifier of the library. For remote debugging case,
|
||
@var{target-name} and @var{host-name} fields give the name of the
|
||
library file on the target, and on the host respectively. For native
|
||
debugging, both those fields have the same value. The
|
||
@var{symbols-loaded} field is emitted only for backward compatibility
|
||
and should not be relied on to convey any useful information. The
|
||
@var{thread-group} field, if present, specifies the id of the thread
|
||
group in whose context the library was loaded. If the field is
|
||
absent, it means the library was loaded in the context of all present
|
||
thread groups. The @var{ranges} field specifies the ranges of addresses belonging
|
||
to this library.
|
||
|
||
@item =library-unloaded,...
|
||
Reports that a library was unloaded by the program. This notification
|
||
has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
|
||
the same meaning as for the @code{=library-loaded} notification.
|
||
The @var{thread-group} field, if present, specifies the id of the
|
||
thread group in whose context the library was unloaded. If the field is
|
||
absent, it means the library was unloaded in the context of all present
|
||
thread groups.
|
||
|
||
@item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
|
||
@itemx =traceframe-changed,end
|
||
Reports that the trace frame was changed and its new number is
|
||
@var{tfnum}. The number of the tracepoint associated with this trace
|
||
frame is @var{tpnum}.
|
||
|
||
@item =tsv-created,name=@var{name},initial=@var{initial}
|
||
Reports that the new trace state variable @var{name} is created with
|
||
initial value @var{initial}.
|
||
|
||
@item =tsv-deleted,name=@var{name}
|
||
@itemx =tsv-deleted
|
||
Reports that the trace state variable @var{name} is deleted or all
|
||
trace state variables are deleted.
|
||
|
||
@item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
|
||
Reports that the trace state variable @var{name} is modified with
|
||
the initial value @var{initial}. The current value @var{current} of
|
||
trace state variable is optional and is reported if the current
|
||
value of trace state variable is known.
|
||
|
||
@item =breakpoint-created,bkpt=@{...@}
|
||
@itemx =breakpoint-modified,bkpt=@{...@}
|
||
@itemx =breakpoint-deleted,id=@var{number}
|
||
Reports that a breakpoint was created, modified, or deleted,
|
||
respectively. Only user-visible breakpoints are reported to the MI
|
||
user.
|
||
|
||
The @var{bkpt} argument is of the same form as returned by the various
|
||
breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
|
||
@var{number} is the ordinal number of the breakpoint.
|
||
|
||
Note that if a breakpoint is emitted in the result record of a
|
||
command, then it will not also be emitted in an async record.
|
||
|
||
@item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
|
||
@itemx =record-stopped,thread-group="@var{id}"
|
||
Execution log recording was either started or stopped on an
|
||
inferior. The @var{id} is the @value{GDBN} identifier of the thread
|
||
group corresponding to the affected inferior.
|
||
|
||
The @var{method} field indicates the method used to record execution. If the
|
||
method in use supports multiple recording formats, @var{format} will be present
|
||
and contain the currently used format. @xref{Process Record and Replay},
|
||
for existing method and format values.
|
||
|
||
@item =cmd-param-changed,param=@var{param},value=@var{value}
|
||
Reports that a parameter of the command @code{set @var{param}} is
|
||
changed to @var{value}. In the multi-word @code{set} command,
|
||
the @var{param} is the whole parameter list to @code{set} command.
|
||
For example, In command @code{set check type on}, @var{param}
|
||
is @code{check type} and @var{value} is @code{on}.
|
||
|
||
@item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
|
||
Reports that bytes from @var{addr} to @var{data} + @var{len} were
|
||
written in an inferior. The @var{id} is the identifier of the
|
||
thread group corresponding to the affected inferior. The optional
|
||
@code{type="code"} part is reported if the memory written to holds
|
||
executable code.
|
||
@end table
|
||
|
||
@node GDB/MI Breakpoint Information
|
||
@subsection @sc{gdb/mi} Breakpoint Information
|
||
|
||
When @value{GDBN} reports information about a breakpoint, a
|
||
tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
|
||
following fields:
|
||
|
||
@table @code
|
||
@item number
|
||
The breakpoint number. For a breakpoint that represents one location
|
||
of a multi-location breakpoint, this will be a dotted pair, like
|
||
@samp{1.2}.
|
||
|
||
@item type
|
||
The type of the breakpoint. For ordinary breakpoints this will be
|
||
@samp{breakpoint}, but many values are possible.
|
||
|
||
@item catch-type
|
||
If the type of the breakpoint is @samp{catchpoint}, then this
|
||
indicates the exact type of catchpoint.
|
||
|
||
@item disp
|
||
This is the breakpoint disposition---either @samp{del}, meaning that
|
||
the breakpoint will be deleted at the next stop, or @samp{keep},
|
||
meaning that the breakpoint will not be deleted.
|
||
|
||
@item enabled
|
||
This indicates whether the breakpoint is enabled, in which case the
|
||
value is @samp{y}, or disabled, in which case the value is @samp{n}.
|
||
Note that this is not the same as the field @code{enable}.
|
||
|
||
@item addr
|
||
The address of the breakpoint. This may be a hexidecimal number,
|
||
giving the address; or the string @samp{<PENDING>}, for a pending
|
||
breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
|
||
multiple locations. This field will not be present if no address can
|
||
be determined. For example, a watchpoint does not have an address.
|
||
|
||
@item func
|
||
If known, the function in which the breakpoint appears.
|
||
If not known, this field is not present.
|
||
|
||
@item filename
|
||
The name of the source file which contains this function, if known.
|
||
If not known, this field is not present.
|
||
|
||
@item fullname
|
||
The full file name of the source file which contains this function, if
|
||
known. If not known, this field is not present.
|
||
|
||
@item line
|
||
The line number at which this breakpoint appears, if known.
|
||
If not known, this field is not present.
|
||
|
||
@item at
|
||
If the source file is not known, this field may be provided. If
|
||
provided, this holds the address of the breakpoint, possibly followed
|
||
by a symbol name.
|
||
|
||
@item pending
|
||
If this breakpoint is pending, this field is present and holds the
|
||
text used to set the breakpoint, as entered by the user.
|
||
|
||
@item evaluated-by
|
||
Where this breakpoint's condition is evaluated, either @samp{host} or
|
||
@samp{target}.
|
||
|
||
@item thread
|
||
If this is a thread-specific breakpoint, then this identifies the
|
||
thread in which the breakpoint can trigger.
|
||
|
||
@item task
|
||
If this breakpoint is restricted to a particular Ada task, then this
|
||
field will hold the task identifier.
|
||
|
||
@item cond
|
||
If the breakpoint is conditional, this is the condition expression.
|
||
|
||
@item ignore
|
||
The ignore count of the breakpoint.
|
||
|
||
@item enable
|
||
The enable count of the breakpoint.
|
||
|
||
@item traceframe-usage
|
||
FIXME.
|
||
|
||
@item static-tracepoint-marker-string-id
|
||
For a static tracepoint, the name of the static tracepoint marker.
|
||
|
||
@item mask
|
||
For a masked watchpoint, this is the mask.
|
||
|
||
@item pass
|
||
A tracepoint's pass count.
|
||
|
||
@item original-location
|
||
The location of the breakpoint as originally specified by the user.
|
||
This field is optional.
|
||
|
||
@item times
|
||
The number of times the breakpoint has been hit.
|
||
|
||
@item installed
|
||
This field is only given for tracepoints. This is either @samp{y},
|
||
meaning that the tracepoint is installed, or @samp{n}, meaning that it
|
||
is not.
|
||
|
||
@item what
|
||
Some extra data, the exact contents of which are type-dependent.
|
||
|
||
@end table
|
||
|
||
For example, here is what the output of @code{-break-insert}
|
||
(@pxref{GDB/MI Breakpoint Commands}) might be:
|
||
|
||
@smallexample
|
||
-> -break-insert main
|
||
<- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x08048564",func="main",file="myprog.c",
|
||
fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
|
||
times="0"@}
|
||
<- (gdb)
|
||
@end smallexample
|
||
|
||
@node GDB/MI Frame Information
|
||
@subsection @sc{gdb/mi} Frame Information
|
||
|
||
Response from many MI commands includes an information about stack
|
||
frame. This information is a tuple that may have the following
|
||
fields:
|
||
|
||
@table @code
|
||
@item level
|
||
The level of the stack frame. The innermost frame has the level of
|
||
zero. This field is always present.
|
||
|
||
@item func
|
||
The name of the function corresponding to the frame. This field may
|
||
be absent if @value{GDBN} is unable to determine the function name.
|
||
|
||
@item addr
|
||
The code address for the frame. This field is always present.
|
||
|
||
@item file
|
||
The name of the source files that correspond to the frame's code
|
||
address. This field may be absent.
|
||
|
||
@item line
|
||
The source line corresponding to the frames' code address. This field
|
||
may be absent.
|
||
|
||
@item from
|
||
The name of the binary file (either executable or shared library) the
|
||
corresponds to the frame's code address. This field may be absent.
|
||
|
||
@end table
|
||
|
||
@node GDB/MI Thread Information
|
||
@subsection @sc{gdb/mi} Thread Information
|
||
|
||
Whenever @value{GDBN} has to report an information about a thread, it
|
||
uses a tuple with the following fields. The fields are always present unless
|
||
stated otherwise.
|
||
|
||
@table @code
|
||
@item id
|
||
The global numeric id assigned to the thread by @value{GDBN}.
|
||
|
||
@item target-id
|
||
The target-specific string identifying the thread.
|
||
|
||
@item details
|
||
Additional information about the thread provided by the target.
|
||
It is supposed to be human-readable and not interpreted by the
|
||
frontend. This field is optional.
|
||
|
||
@item name
|
||
The name of the thread. If the user specified a name using the
|
||
@code{thread name} command, then this name is given. Otherwise, if
|
||
@value{GDBN} can extract the thread name from the target, then that
|
||
name is given. If @value{GDBN} cannot find the thread name, then this
|
||
field is omitted.
|
||
|
||
@item state
|
||
The execution state of the thread, either @samp{stopped} or @samp{running},
|
||
depending on whether the thread is presently running.
|
||
|
||
@item frame
|
||
The stack frame currently executing in the thread. This field is only present
|
||
if the thread is stopped. Its format is documented in
|
||
@ref{GDB/MI Frame Information}.
|
||
|
||
@item core
|
||
The value of this field is an integer number of the processor core the
|
||
thread was last seen on. This field is optional.
|
||
@end table
|
||
|
||
@node GDB/MI Ada Exception Information
|
||
@subsection @sc{gdb/mi} Ada Exception Information
|
||
|
||
Whenever a @code{*stopped} record is emitted because the program
|
||
stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
|
||
@value{GDBN} provides the name of the exception that was raised via
|
||
the @code{exception-name} field. Also, for exceptions that were raised
|
||
with an exception message, @value{GDBN} provides that message via
|
||
the @code{exception-message} field.
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Simple Examples
|
||
@section Simple Examples of @sc{gdb/mi} Interaction
|
||
@cindex @sc{gdb/mi}, simple examples
|
||
|
||
This subsection presents several simple examples of interaction using
|
||
the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
|
||
following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
|
||
the output received from @sc{gdb/mi}.
|
||
|
||
Note the line breaks shown in the examples are here only for
|
||
readability, they don't appear in the real output.
|
||
|
||
@subheading Setting a Breakpoint
|
||
|
||
Setting a breakpoint generates synchronous output which contains detailed
|
||
information of the breakpoint.
|
||
|
||
@smallexample
|
||
-> -break-insert main
|
||
<- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x08048564",func="main",file="myprog.c",
|
||
fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
|
||
times="0"@}
|
||
<- (gdb)
|
||
@end smallexample
|
||
|
||
@subheading Program Execution
|
||
|
||
Program execution generates asynchronous records and MI gives the
|
||
reason that execution stopped.
|
||
|
||
@smallexample
|
||
-> -exec-run
|
||
<- ^running
|
||
<- (gdb)
|
||
<- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
|
||
frame=@{addr="0x08048564",func="main",
|
||
args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
|
||
file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
|
||
<- (gdb)
|
||
-> -exec-continue
|
||
<- ^running
|
||
<- (gdb)
|
||
<- *stopped,reason="exited-normally"
|
||
<- (gdb)
|
||
@end smallexample
|
||
|
||
@subheading Quitting @value{GDBN}
|
||
|
||
Quitting @value{GDBN} just prints the result class @samp{^exit}.
|
||
|
||
@smallexample
|
||
-> (gdb)
|
||
<- -gdb-exit
|
||
<- ^exit
|
||
@end smallexample
|
||
|
||
Please note that @samp{^exit} is printed immediately, but it might
|
||
take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
|
||
performs necessary cleanups, including killing programs being debugged
|
||
or disconnecting from debug hardware, so the frontend should wait till
|
||
@value{GDBN} exits and should only forcibly kill @value{GDBN} if it
|
||
fails to exit in reasonable time.
|
||
|
||
@subheading A Bad Command
|
||
|
||
Here's what happens if you pass a non-existent command:
|
||
|
||
@smallexample
|
||
-> -rubbish
|
||
<- ^error,msg="Undefined MI command: rubbish"
|
||
<- (gdb)
|
||
@end smallexample
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Command Description Format
|
||
@section @sc{gdb/mi} Command Description Format
|
||
|
||
The remaining sections describe blocks of commands. Each block of
|
||
commands is laid out in a fashion similar to this section.
|
||
|
||
@subheading Motivation
|
||
|
||
The motivation for this collection of commands.
|
||
|
||
@subheading Introduction
|
||
|
||
A brief introduction to this collection of commands as a whole.
|
||
|
||
@subheading Commands
|
||
|
||
For each command in the block, the following is described:
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-command @var{args}@dots{}
|
||
@end smallexample
|
||
|
||
@subsubheading Result
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} CLI command(s), if any.
|
||
|
||
@subsubheading Example
|
||
|
||
Example(s) formatted for readability. Some of the described commands have
|
||
not been implemented yet and these are labeled N.A.@: (not available).
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Breakpoint Commands
|
||
@section @sc{gdb/mi} Breakpoint Commands
|
||
|
||
@cindex breakpoint commands for @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, breakpoint commands
|
||
This section documents @sc{gdb/mi} commands for manipulating
|
||
breakpoints.
|
||
|
||
@subheading The @code{-break-after} Command
|
||
@findex -break-after
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-after @var{number} @var{count}
|
||
@end smallexample
|
||
|
||
The breakpoint number @var{number} is not in effect until it has been
|
||
hit @var{count} times. To see how this is reflected in the output of
|
||
the @samp{-break-list} command, see the description of the
|
||
@samp{-break-list} command below.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{ignore}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-insert main
|
||
^done,bkpt=@{number="1",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x000100d0",func="main",file="hello.c",
|
||
fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
|
||
times="0"@}
|
||
(gdb)
|
||
-break-after 1 3
|
||
~
|
||
^done
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
|
||
line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@ignore
|
||
@subheading The @code{-break-catch} Command
|
||
@findex -break-catch
|
||
@end ignore
|
||
|
||
@subheading The @code{-break-commands} Command
|
||
@findex -break-commands
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-commands @var{number} [ @var{command1} ... @var{commandN} ]
|
||
@end smallexample
|
||
|
||
Specifies the CLI commands that should be executed when breakpoint
|
||
@var{number} is hit. The parameters @var{command1} to @var{commandN}
|
||
are the commands. If no command is specified, any previously-set
|
||
commands are cleared. @xref{Break Commands}. Typical use of this
|
||
functionality is tracing a program, that is, printing of values of
|
||
some variables whenever breakpoint is hit and then continuing.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{commands}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-insert main
|
||
^done,bkpt=@{number="1",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x000100d0",func="main",file="hello.c",
|
||
fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
|
||
times="0"@}
|
||
(gdb)
|
||
-break-commands 1 "print v" "continue"
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-condition} Command
|
||
@findex -break-condition
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-condition @var{number} @var{expr}
|
||
@end smallexample
|
||
|
||
Breakpoint @var{number} will stop the program only if the condition in
|
||
@var{expr} is true. The condition becomes part of the
|
||
@samp{-break-list} output (see the description of the @samp{-break-list}
|
||
command below).
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{condition}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-condition 1 1
|
||
^done
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
|
||
line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-delete} Command
|
||
@findex -break-delete
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-delete ( @var{breakpoint} )+
|
||
@end smallexample
|
||
|
||
Delete the breakpoint(s) whose number(s) are specified in the argument
|
||
list. This is obviously reflected in the breakpoint list.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{delete}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-delete 1
|
||
^done
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-disable} Command
|
||
@findex -break-disable
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-disable ( @var{breakpoint} )+
|
||
@end smallexample
|
||
|
||
Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
|
||
break list is now set to @samp{n} for the named @var{breakpoint}(s).
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{disable}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-disable 2
|
||
^done
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
|
||
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
|
||
line="5",thread-groups=["i1"],times="0"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-enable} Command
|
||
@findex -break-enable
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-enable ( @var{breakpoint} )+
|
||
@end smallexample
|
||
|
||
Enable (previously disabled) @var{breakpoint}(s).
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{enable}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-enable 2
|
||
^done
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
|
||
line="5",thread-groups=["i1"],times="0"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-info} Command
|
||
@findex -break-info
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-info @var{breakpoint}
|
||
@end smallexample
|
||
|
||
@c REDUNDANT???
|
||
Get information about a single breakpoint.
|
||
|
||
The result is a table of breakpoints. @xref{GDB/MI Breakpoint
|
||
Information}, for details on the format of each breakpoint in the
|
||
table.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
@subheading The @code{-break-insert} Command
|
||
@findex -break-insert
|
||
@anchor{-break-insert}
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
|
||
[ -c @var{condition} ] [ -i @var{ignore-count} ]
|
||
[ -p @var{thread-id} ] [ @var{location} ]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
If specified, @var{location}, can be one of:
|
||
|
||
@table @var
|
||
@item linespec location
|
||
A linespec location. @xref{Linespec Locations}.
|
||
|
||
@item explicit location
|
||
An explicit location. @sc{gdb/mi} explicit locations are
|
||
analogous to the CLI's explicit locations using the option names
|
||
listed below. @xref{Explicit Locations}.
|
||
|
||
@table @samp
|
||
@item --source @var{filename}
|
||
The source file name of the location. This option requires the use
|
||
of either @samp{--function} or @samp{--line}.
|
||
|
||
@item --function @var{function}
|
||
The name of a function or method.
|
||
|
||
@item --label @var{label}
|
||
The name of a label.
|
||
|
||
@item --line @var{lineoffset}
|
||
An absolute or relative line offset from the start of the location.
|
||
@end table
|
||
|
||
@item address location
|
||
An address location, *@var{address}. @xref{Address Locations}.
|
||
@end table
|
||
|
||
@noindent
|
||
The possible optional parameters of this command are:
|
||
|
||
@table @samp
|
||
@item -t
|
||
Insert a temporary breakpoint.
|
||
@item -h
|
||
Insert a hardware breakpoint.
|
||
@item -f
|
||
If @var{location} cannot be parsed (for example if it
|
||
refers to unknown files or functions), create a pending
|
||
breakpoint. Without this flag, @value{GDBN} will report
|
||
an error, and won't create a breakpoint, if @var{location}
|
||
cannot be parsed.
|
||
@item -d
|
||
Create a disabled breakpoint.
|
||
@item -a
|
||
Create a tracepoint. @xref{Tracepoints}. When this parameter
|
||
is used together with @samp{-h}, a fast tracepoint is created.
|
||
@item -c @var{condition}
|
||
Make the breakpoint conditional on @var{condition}.
|
||
@item -i @var{ignore-count}
|
||
Initialize the @var{ignore-count}.
|
||
@item -p @var{thread-id}
|
||
Restrict the breakpoint to the thread with the specified global
|
||
@var{thread-id}.
|
||
@end table
|
||
|
||
@subsubheading Result
|
||
|
||
@xref{GDB/MI Breakpoint Information}, for details on the format of the
|
||
resulting breakpoint.
|
||
|
||
Note: this format is open to change.
|
||
@c An out-of-band breakpoint instead of part of the result?
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
|
||
@samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-insert main
|
||
^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
|
||
fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
|
||
times="0"@}
|
||
(gdb)
|
||
-break-insert -t foo
|
||
^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
|
||
fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
|
||
times="0"@}
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x0001072c", func="main",file="recursive2.c",
|
||
fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
|
||
times="0"@},
|
||
bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
|
||
addr="0x00010774",func="foo",file="recursive2.c",
|
||
fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
|
||
times="0"@}]@}
|
||
(gdb)
|
||
@c -break-insert -r foo.*
|
||
@c ~int foo(int, int);
|
||
@c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
|
||
@c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
|
||
@c times="0"@}
|
||
@c (gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-dprintf-insert} Command
|
||
@findex -dprintf-insert
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-dprintf-insert [ -t ] [ -f ] [ -d ]
|
||
[ -c @var{condition} ] [ -i @var{ignore-count} ]
|
||
[ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
|
||
[ @var{argument} ]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
If supplied, @var{location} may be specified the same way as for
|
||
the @code{-break-insert} command. @xref{-break-insert}.
|
||
|
||
The possible optional parameters of this command are:
|
||
|
||
@table @samp
|
||
@item -t
|
||
Insert a temporary breakpoint.
|
||
@item -f
|
||
If @var{location} cannot be parsed (for example, if it
|
||
refers to unknown files or functions), create a pending
|
||
breakpoint. Without this flag, @value{GDBN} will report
|
||
an error, and won't create a breakpoint, if @var{location}
|
||
cannot be parsed.
|
||
@item -d
|
||
Create a disabled breakpoint.
|
||
@item -c @var{condition}
|
||
Make the breakpoint conditional on @var{condition}.
|
||
@item -i @var{ignore-count}
|
||
Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
|
||
to @var{ignore-count}.
|
||
@item -p @var{thread-id}
|
||
Restrict the breakpoint to the thread with the specified global
|
||
@var{thread-id}.
|
||
@end table
|
||
|
||
@subsubheading Result
|
||
|
||
@xref{GDB/MI Breakpoint Information}, for details on the format of the
|
||
resulting breakpoint.
|
||
|
||
@c An out-of-band breakpoint instead of part of the result?
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{dprintf}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
4-dprintf-insert foo "At foo entry\n"
|
||
4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
|
||
addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
|
||
fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
|
||
times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
|
||
original-location="foo"@}
|
||
(gdb)
|
||
5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
|
||
5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
|
||
addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
|
||
fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
|
||
times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
|
||
original-location="mi-dprintf.c:26"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-list} Command
|
||
@findex -break-list
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-list
|
||
@end smallexample
|
||
|
||
Displays the list of inserted breakpoints, showing the following fields:
|
||
|
||
@table @samp
|
||
@item Number
|
||
number of the breakpoint
|
||
@item Type
|
||
type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
|
||
@item Disposition
|
||
should the breakpoint be deleted or disabled when it is hit: @samp{keep}
|
||
or @samp{nokeep}
|
||
@item Enabled
|
||
is the breakpoint enabled or no: @samp{y} or @samp{n}
|
||
@item Address
|
||
memory location at which the breakpoint is set
|
||
@item What
|
||
logical location of the breakpoint, expressed by function name, file
|
||
name, line number
|
||
@item Thread-groups
|
||
list of thread groups to which this breakpoint applies
|
||
@item Times
|
||
number of times the breakpoint has been hit
|
||
@end table
|
||
|
||
If there are no breakpoints or watchpoints, the @code{BreakpointTable}
|
||
@code{body} field is an empty list.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info break}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
|
||
times="0"@},
|
||
bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
|
||
line="13",thread-groups=["i1"],times="0"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Here's an example of the result when there are no breakpoints:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-break-passcount} Command
|
||
@findex -break-passcount
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-passcount @var{tracepoint-number} @var{passcount}
|
||
@end smallexample
|
||
|
||
Set the passcount for tracepoint @var{tracepoint-number} to
|
||
@var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
|
||
is not a tracepoint, error is emitted. This corresponds to CLI
|
||
command @samp{passcount}.
|
||
|
||
@subheading The @code{-break-watch} Command
|
||
@findex -break-watch
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-break-watch [ -a | -r ]
|
||
@end smallexample
|
||
|
||
Create a watchpoint. With the @samp{-a} option it will create an
|
||
@dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
|
||
read from or on a write to the memory location. With the @samp{-r}
|
||
option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
|
||
trigger only when the memory location is accessed for reading. Without
|
||
either of the options, the watchpoint created is a regular watchpoint,
|
||
i.e., it will trigger when the memory location is accessed for writing.
|
||
@xref{Set Watchpoints, , Setting Watchpoints}.
|
||
|
||
Note that @samp{-break-list} will report a single list of watchpoints and
|
||
breakpoints inserted.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
|
||
@samp{rwatch}.
|
||
|
||
@subsubheading Example
|
||
|
||
Setting a watchpoint on a variable in the @code{main} function:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-watch x
|
||
^done,wpt=@{number="2",exp="x"@}
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
|
||
value=@{old="-268439212",new="55"@},
|
||
frame=@{func="main",args=[],file="recursive2.c",
|
||
fullname="/home/foo/bar/recursive2.c",line="5"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
|
||
the program execution twice: first for the variable changing value, then
|
||
for the watchpoint going out of scope.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-watch C
|
||
^done,wpt=@{number="5",exp="C"@}
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="watchpoint-trigger",
|
||
wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
|
||
frame=@{func="callee4",args=[],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="watchpoint-scope",wpnum="5",
|
||
frame=@{func="callee3",args=[@{name="strarg",
|
||
value="0x11940 \"A string argument.\""@}],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Listing breakpoints and watchpoints, at different points in the program
|
||
execution. Note that once the watchpoint goes out of scope, it is
|
||
deleted.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-watch C
|
||
^done,wpt=@{number="2",exp="C"@}
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x00010734",func="callee4",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
|
||
times="1"@},
|
||
bkpt=@{number="2",type="watchpoint",disp="keep",
|
||
enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
|
||
value=@{old="-276895068",new="3"@},
|
||
frame=@{func="callee4",args=[],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x00010734",func="callee4",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
|
||
times="1"@},
|
||
bkpt=@{number="2",type="watchpoint",disp="keep",
|
||
enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
^done,reason="watchpoint-scope",wpnum="2",
|
||
frame=@{func="callee3",args=[@{name="strarg",
|
||
value="0x11940 \"A string argument.\""@}],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
|
||
(gdb)
|
||
-break-list
|
||
^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
|
||
hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
|
||
@{width="14",alignment="-1",col_name="type",colhdr="Type"@},
|
||
@{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
|
||
@{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
|
||
@{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
|
||
@{width="40",alignment="2",col_name="what",colhdr="What"@}],
|
||
body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x00010734",func="callee4",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
|
||
thread-groups=["i1"],times="1"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Catchpoint Commands
|
||
@section @sc{gdb/mi} Catchpoint Commands
|
||
|
||
This section documents @sc{gdb/mi} commands for manipulating
|
||
catchpoints.
|
||
|
||
@menu
|
||
* Shared Library GDB/MI Catchpoint Commands::
|
||
* Ada Exception GDB/MI Catchpoint Commands::
|
||
@end menu
|
||
|
||
@node Shared Library GDB/MI Catchpoint Commands
|
||
@subsection Shared Library @sc{gdb/mi} Catchpoints
|
||
|
||
@subheading The @code{-catch-load} Command
|
||
@findex -catch-load
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-catch-load [ -t ] [ -d ] @var{regexp}
|
||
@end smallexample
|
||
|
||
Add a catchpoint for library load events. If the @samp{-t} option is used,
|
||
the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
|
||
Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
|
||
in a disabled state. The @samp{regexp} argument is a regular
|
||
expression used to match the name of the loaded library.
|
||
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{catch load}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-catch-load -t foo.so
|
||
^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
|
||
what="load of library matching foo.so",catch-type="load",times="0"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-catch-unload} Command
|
||
@findex -catch-unload
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-catch-unload [ -t ] [ -d ] @var{regexp}
|
||
@end smallexample
|
||
|
||
Add a catchpoint for library unload events. If the @samp{-t} option is
|
||
used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
|
||
Breakpoints}). If the @samp{-d} option is used, the catchpoint is
|
||
created in a disabled state. The @samp{regexp} argument is a regular
|
||
expression used to match the name of the unloaded library.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{catch unload}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-catch-unload -d bar.so
|
||
^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
|
||
what="load of library matching bar.so",catch-type="unload",times="0"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@node Ada Exception GDB/MI Catchpoint Commands
|
||
@subsection Ada Exception @sc{gdb/mi} Catchpoints
|
||
|
||
The following @sc{gdb/mi} commands can be used to create catchpoints
|
||
that stop the execution when Ada exceptions are being raised.
|
||
|
||
@subheading The @code{-catch-assert} Command
|
||
@findex -catch-assert
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-catch-assert [ -c @var{condition}] [ -d ] [ -t ]
|
||
@end smallexample
|
||
|
||
Add a catchpoint for failed Ada assertions.
|
||
|
||
The possible optional parameters for this command are:
|
||
|
||
@table @samp
|
||
@item -c @var{condition}
|
||
Make the catchpoint conditional on @var{condition}.
|
||
@item -d
|
||
Create a disabled catchpoint.
|
||
@item -t
|
||
Create a temporary catchpoint.
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{catch assert}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-catch-assert
|
||
^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
|
||
thread-groups=["i1"],times="0",
|
||
original-location="__gnat_debug_raise_assert_failure"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-catch-exception} Command
|
||
@findex -catch-exception
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
|
||
[ -t ] [ -u ]
|
||
@end smallexample
|
||
|
||
Add a catchpoint stopping when Ada exceptions are raised.
|
||
By default, the command stops the program when any Ada exception
|
||
gets raised. But it is also possible, by using some of the
|
||
optional parameters described below, to create more selective
|
||
catchpoints.
|
||
|
||
The possible optional parameters for this command are:
|
||
|
||
@table @samp
|
||
@item -c @var{condition}
|
||
Make the catchpoint conditional on @var{condition}.
|
||
@item -d
|
||
Create a disabled catchpoint.
|
||
@item -e @var{exception-name}
|
||
Only stop when @var{exception-name} is raised. This option cannot
|
||
be used combined with @samp{-u}.
|
||
@item -t
|
||
Create a temporary catchpoint.
|
||
@item -u
|
||
Stop only when an unhandled exception gets raised. This option
|
||
cannot be used combined with @samp{-e}.
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{catch exception}
|
||
and @samp{catch exception unhandled}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-catch-exception -e Program_Error
|
||
^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x0000000000404874",
|
||
what="`Program_Error' Ada exception", thread-groups=["i1"],
|
||
times="0",original-location="__gnat_debug_raise_exception"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-catch-handlers} Command
|
||
@findex -catch-handlers
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
|
||
[ -t ]
|
||
@end smallexample
|
||
|
||
Add a catchpoint stopping when Ada exceptions are handled.
|
||
By default, the command stops the program when any Ada exception
|
||
gets handled. But it is also possible, by using some of the
|
||
optional parameters described below, to create more selective
|
||
catchpoints.
|
||
|
||
The possible optional parameters for this command are:
|
||
|
||
@table @samp
|
||
@item -c @var{condition}
|
||
Make the catchpoint conditional on @var{condition}.
|
||
@item -d
|
||
Create a disabled catchpoint.
|
||
@item -e @var{exception-name}
|
||
Only stop when @var{exception-name} is handled.
|
||
@item -t
|
||
Create a temporary catchpoint.
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{catch handlers}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-catch-handlers -e Constraint_Error
|
||
^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
|
||
enabled="y",addr="0x0000000000402f68",
|
||
what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
|
||
times="0",original-location="__gnat_begin_handler"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Program Context
|
||
@section @sc{gdb/mi} Program Context
|
||
|
||
@subheading The @code{-exec-arguments} Command
|
||
@findex -exec-arguments
|
||
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-arguments @var{args}
|
||
@end smallexample
|
||
|
||
Set the inferior program arguments, to be used in the next
|
||
@samp{-exec-run}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{set args}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-arguments -v word
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-exec-show-arguments} Command
|
||
@findex -exec-show-arguments
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-show-arguments
|
||
@end smallexample
|
||
|
||
Print the arguments of the program.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{show args}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-environment-cd} Command
|
||
@findex -environment-cd
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-environment-cd @var{pathdir}
|
||
@end smallexample
|
||
|
||
Set @value{GDBN}'s working directory.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{cd}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-environment-directory} Command
|
||
@findex -environment-directory
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-environment-directory [ -r ] [ @var{pathdir} ]+
|
||
@end smallexample
|
||
|
||
Add directories @var{pathdir} to beginning of search path for source files.
|
||
If the @samp{-r} option is used, the search path is reset to the default
|
||
search path. If directories @var{pathdir} are supplied in addition to the
|
||
@samp{-r} option, the search path is first reset and then addition
|
||
occurs as normal.
|
||
Multiple directories may be specified, separated by blanks. Specifying
|
||
multiple directories in a single command
|
||
results in the directories added to the beginning of the
|
||
search path in the same order they were presented in the command.
|
||
If blanks are needed as
|
||
part of a directory name, double-quotes should be used around
|
||
the name. In the command output, the path will show up separated
|
||
by the system directory-separator character. The directory-separator
|
||
character must not be used
|
||
in any directory name.
|
||
If no directories are specified, the current search path is displayed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{dir}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
|
||
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
|
||
(gdb)
|
||
-environment-directory ""
|
||
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
|
||
(gdb)
|
||
-environment-directory -r /home/jjohnstn/src/gdb /usr/src
|
||
^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
|
||
(gdb)
|
||
-environment-directory -r
|
||
^done,source-path="$cdir:$cwd"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-environment-path} Command
|
||
@findex -environment-path
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-environment-path [ -r ] [ @var{pathdir} ]+
|
||
@end smallexample
|
||
|
||
Add directories @var{pathdir} to beginning of search path for object files.
|
||
If the @samp{-r} option is used, the search path is reset to the original
|
||
search path that existed at gdb start-up. If directories @var{pathdir} are
|
||
supplied in addition to the
|
||
@samp{-r} option, the search path is first reset and then addition
|
||
occurs as normal.
|
||
Multiple directories may be specified, separated by blanks. Specifying
|
||
multiple directories in a single command
|
||
results in the directories added to the beginning of the
|
||
search path in the same order they were presented in the command.
|
||
If blanks are needed as
|
||
part of a directory name, double-quotes should be used around
|
||
the name. In the command output, the path will show up separated
|
||
by the system directory-separator character. The directory-separator
|
||
character must not be used
|
||
in any directory name.
|
||
If no directories are specified, the current path is displayed.
|
||
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{path}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-environment-path
|
||
^done,path="/usr/bin"
|
||
(gdb)
|
||
-environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
|
||
^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
|
||
(gdb)
|
||
-environment-path -r /usr/local/bin
|
||
^done,path="/usr/local/bin:/usr/bin"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-environment-pwd} Command
|
||
@findex -environment-pwd
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-environment-pwd
|
||
@end smallexample
|
||
|
||
Show the current working directory.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{pwd}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-environment-pwd
|
||
^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Thread Commands
|
||
@section @sc{gdb/mi} Thread Commands
|
||
|
||
|
||
@subheading The @code{-thread-info} Command
|
||
@findex -thread-info
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-thread-info [ @var{thread-id} ]
|
||
@end smallexample
|
||
|
||
Reports information about either a specific thread, if the
|
||
@var{thread-id} parameter is present, or about all threads.
|
||
@var{thread-id} is the thread's global thread ID. When printing
|
||
information about all threads, also reports the global ID of the
|
||
current thread.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @samp{info thread} command prints the same information
|
||
about all threads.
|
||
|
||
@subsubheading Result
|
||
|
||
The result contains the following attributes:
|
||
|
||
@table @samp
|
||
@item threads
|
||
A list of threads. The format of the elements of the list is described in
|
||
@ref{GDB/MI Thread Information}.
|
||
|
||
@item current-thread-id
|
||
The global id of the currently selected thread. This field is omitted if there
|
||
is no selected thread (for example, when the selected inferior is not running,
|
||
and therefore has no threads) or if a @var{thread-id} argument was passed to
|
||
the command.
|
||
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-thread-info
|
||
^done,threads=[
|
||
@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
|
||
frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
|
||
args=[]@},state="running"@},
|
||
@{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
|
||
frame=@{level="0",addr="0x0804891f",func="foo",
|
||
args=[@{name="i",value="10"@}],
|
||
file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
|
||
state="running"@}],
|
||
current-thread-id="1"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-thread-list-ids} Command
|
||
@findex -thread-list-ids
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-thread-list-ids
|
||
@end smallexample
|
||
|
||
Produces a list of the currently known global @value{GDBN} thread ids.
|
||
At the end of the list it also prints the total number of such
|
||
threads.
|
||
|
||
This command is retained for historical reasons, the
|
||
@code{-thread-info} command should be used instead.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
Part of @samp{info threads} supplies the same information.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-thread-list-ids
|
||
^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
|
||
current-thread-id="1",number-of-threads="3"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-thread-select} Command
|
||
@findex -thread-select
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-thread-select @var{thread-id}
|
||
@end smallexample
|
||
|
||
Make thread with global thread number @var{thread-id} the current
|
||
thread. It prints the number of the new current thread, and the
|
||
topmost frame for that thread.
|
||
|
||
This command is deprecated in favor of explicitly using the
|
||
@samp{--thread} option to each command.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{thread}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-next
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",thread-id="2",line="187",
|
||
file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
|
||
(gdb)
|
||
-thread-list-ids
|
||
^done,
|
||
thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
|
||
number-of-threads="3"
|
||
(gdb)
|
||
-thread-select 3
|
||
^done,new-thread-id="3",
|
||
frame=@{level="0",func="vprintf",
|
||
args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
|
||
@{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Ada Tasking Commands
|
||
@section @sc{gdb/mi} Ada Tasking Commands
|
||
|
||
@subheading The @code{-ada-task-info} Command
|
||
@findex -ada-task-info
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-ada-task-info [ @var{task-id} ]
|
||
@end smallexample
|
||
|
||
Reports information about either a specific Ada task, if the
|
||
@var{task-id} parameter is present, or about all Ada tasks.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @samp{info tasks} command prints the same information
|
||
about all Ada tasks (@pxref{Ada Tasks}).
|
||
|
||
@subsubheading Result
|
||
|
||
The result is a table of Ada tasks. The following columns are
|
||
defined for each Ada task:
|
||
|
||
@table @samp
|
||
@item current
|
||
This field exists only for the current thread. It has the value @samp{*}.
|
||
|
||
@item id
|
||
The identifier that @value{GDBN} uses to refer to the Ada task.
|
||
|
||
@item task-id
|
||
The identifier that the target uses to refer to the Ada task.
|
||
|
||
@item thread-id
|
||
The global thread identifier of the thread corresponding to the Ada
|
||
task.
|
||
|
||
This field should always exist, as Ada tasks are always implemented
|
||
on top of a thread. But if @value{GDBN} cannot find this corresponding
|
||
thread for any reason, the field is omitted.
|
||
|
||
@item parent-id
|
||
This field exists only when the task was created by another task.
|
||
In this case, it provides the ID of the parent task.
|
||
|
||
@item priority
|
||
The base priority of the task.
|
||
|
||
@item state
|
||
The current state of the task. For a detailed description of the
|
||
possible states, see @ref{Ada Tasks}.
|
||
|
||
@item name
|
||
The name of the task.
|
||
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-ada-task-info
|
||
^done,tasks=@{nr_rows="3",nr_cols="8",
|
||
hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
|
||
@{width="3",alignment="1",col_name="id",colhdr="ID"@},
|
||
@{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
|
||
@{width="4",alignment="1",col_name="thread-id",colhdr=""@},
|
||
@{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
|
||
@{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
|
||
@{width="22",alignment="-1",col_name="state",colhdr="State"@},
|
||
@{width="1",alignment="2",col_name="name",colhdr="Name"@}],
|
||
body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
|
||
state="Child Termination Wait",name="main_task"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Program Execution
|
||
@section @sc{gdb/mi} Program Execution
|
||
|
||
These are the asynchronous commands which generate the out-of-band
|
||
record @samp{*stopped}. Currently @value{GDBN} only really executes
|
||
asynchronously with remote targets and this interaction is mimicked in
|
||
other cases.
|
||
|
||
@subheading The @code{-exec-continue} Command
|
||
@findex -exec-continue
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-continue [--reverse] [--all|--thread-group N]
|
||
@end smallexample
|
||
|
||
Resumes the execution of the inferior program, which will continue
|
||
to execute until it reaches a debugger stop event. If the
|
||
@samp{--reverse} option is specified, execution resumes in reverse until
|
||
it reaches a stop event. Stop events may include
|
||
@itemize @bullet
|
||
@item
|
||
breakpoints or watchpoints
|
||
@item
|
||
signals or exceptions
|
||
@item
|
||
the end of the process (or its beginning under @samp{--reverse})
|
||
@item
|
||
the end or beginning of a replay log if one is being used.
|
||
@end itemize
|
||
In all-stop mode (@pxref{All-Stop
|
||
Mode}), may resume only one thread, or all threads, depending on the
|
||
value of the @samp{scheduler-locking} variable. If @samp{--all} is
|
||
specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
|
||
ignored in all-stop mode. If the @samp{--thread-group} options is
|
||
specified, then all threads in that thread group are resumed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} corresponding is @samp{continue}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-exec-continue
|
||
^running
|
||
(gdb)
|
||
@@Hello world
|
||
*stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
|
||
func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
|
||
line="13"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-finish} Command
|
||
@findex -exec-finish
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-finish [--reverse]
|
||
@end smallexample
|
||
|
||
Resumes the execution of the inferior program until the current
|
||
function is exited. Displays the results returned by the function.
|
||
If the @samp{--reverse} option is specified, resumes the reverse
|
||
execution of the inferior program until the point where current
|
||
function was called.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{finish}.
|
||
|
||
@subsubheading Example
|
||
|
||
Function returning @code{void}.
|
||
|
||
@smallexample
|
||
-exec-finish
|
||
^running
|
||
(gdb)
|
||
@@hello from foo
|
||
*stopped,reason="function-finished",frame=@{func="main",args=[],
|
||
file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Function returning other than @code{void}. The name of the internal
|
||
@value{GDBN} variable storing the result is printed, together with the
|
||
value itself.
|
||
|
||
@smallexample
|
||
-exec-finish
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
|
||
args=[@{name="a",value="1"],@{name="b",value="9"@}@},
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
gdb-result-var="$1",return-value="0"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-interrupt} Command
|
||
@findex -exec-interrupt
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-interrupt [--all|--thread-group N]
|
||
@end smallexample
|
||
|
||
Interrupts the background execution of the target. Note how the token
|
||
associated with the stop message is the one for the execution command
|
||
that has been interrupted. The token for the interrupt itself only
|
||
appears in the @samp{^done} output. If the user is trying to
|
||
interrupt a non-running program, an error message will be printed.
|
||
|
||
Note that when asynchronous execution is enabled, this command is
|
||
asynchronous just like other execution commands. That is, first the
|
||
@samp{^done} response will be printed, and the target stop will be
|
||
reported after that using the @samp{*stopped} notification.
|
||
|
||
In non-stop mode, only the context thread is interrupted by default.
|
||
All threads (in all inferiors) will be interrupted if the
|
||
@samp{--all} option is specified. If the @samp{--thread-group}
|
||
option is specified, all threads in that group will be interrupted.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{interrupt}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
111-exec-continue
|
||
111^running
|
||
|
||
(gdb)
|
||
222-exec-interrupt
|
||
222^done
|
||
(gdb)
|
||
111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
|
||
frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
|
||
fullname="/home/foo/bar/try.c",line="13"@}
|
||
(gdb)
|
||
|
||
(gdb)
|
||
-exec-interrupt
|
||
^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-exec-jump} Command
|
||
@findex -exec-jump
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-jump @var{location}
|
||
@end smallexample
|
||
|
||
Resumes execution of the inferior program at the location specified by
|
||
parameter. @xref{Specify Location}, for a description of the
|
||
different forms of @var{location}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{jump}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-exec-jump foo.c:10
|
||
*running,thread-id="all"
|
||
^running
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-next} Command
|
||
@findex -exec-next
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-next [--reverse]
|
||
@end smallexample
|
||
|
||
Resumes execution of the inferior program, stopping when the beginning
|
||
of the next source line is reached.
|
||
|
||
If the @samp{--reverse} option is specified, resumes reverse execution
|
||
of the inferior program, stopping at the beginning of the previous
|
||
source line. If you issue this command on the first line of a
|
||
function, it will take you back to the caller of that function, to the
|
||
source line where the function was called.
|
||
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{next}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-exec-next
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",line="8",file="hello.c"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-next-instruction} Command
|
||
@findex -exec-next-instruction
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-next-instruction [--reverse]
|
||
@end smallexample
|
||
|
||
Executes one machine instruction. If the instruction is a function
|
||
call, continues until the function returns. If the program stops at an
|
||
instruction in the middle of a source line, the address will be
|
||
printed as well.
|
||
|
||
If the @samp{--reverse} option is specified, resumes reverse execution
|
||
of the inferior program, stopping at the previous instruction. If the
|
||
previously executed instruction was a return from another function,
|
||
it will continue to execute in reverse until the call to that function
|
||
(from the current stack frame) is reached.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{nexti}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-next-instruction
|
||
^running
|
||
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",
|
||
addr="0x000100d4",line="5",file="hello.c"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-return} Command
|
||
@findex -exec-return
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-return
|
||
@end smallexample
|
||
|
||
Makes current function return immediately. Doesn't execute the inferior.
|
||
Displays the new current frame.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{return}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
200-break-insert callee4
|
||
200^done,bkpt=@{number="1",addr="0x00010734",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
|
||
(gdb)
|
||
000-exec-run
|
||
000^running
|
||
(gdb)
|
||
000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
|
||
frame=@{func="callee4",args=[],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
|
||
(gdb)
|
||
205-break-delete
|
||
205^done
|
||
(gdb)
|
||
111-exec-return
|
||
111^done,frame=@{level="0",func="callee3",
|
||
args=[@{name="strarg",
|
||
value="0x11940 \"A string argument.\""@}],
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-run} Command
|
||
@findex -exec-run
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-run [ --all | --thread-group N ] [ --start ]
|
||
@end smallexample
|
||
|
||
Starts execution of the inferior from the beginning. The inferior
|
||
executes until either a breakpoint is encountered or the program
|
||
exits. In the latter case the output will include an exit code, if
|
||
the program has exited exceptionally.
|
||
|
||
When neither the @samp{--all} nor the @samp{--thread-group} option
|
||
is specified, the current inferior is started. If the
|
||
@samp{--thread-group} option is specified, it should refer to a thread
|
||
group of type @samp{process}, and that thread group will be started.
|
||
If the @samp{--all} option is specified, then all inferiors will be started.
|
||
|
||
Using the @samp{--start} option instructs the debugger to stop
|
||
the execution at the start of the inferior's main subprogram,
|
||
following the same behavior as the @code{start} command
|
||
(@pxref{Starting}).
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{run}.
|
||
|
||
@subsubheading Examples
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-break-insert main
|
||
^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
|
||
(gdb)
|
||
-exec-run
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
|
||
frame=@{func="main",args=[],file="recursive2.c",
|
||
fullname="/home/foo/bar/recursive2.c",line="4"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Program exited normally:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-run
|
||
^running
|
||
(gdb)
|
||
x = 55
|
||
*stopped,reason="exited-normally"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Program exited exceptionally:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-run
|
||
^running
|
||
(gdb)
|
||
x = 55
|
||
*stopped,reason="exited",exit-code="01"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Another way the program can terminate is if it receives a signal such as
|
||
@code{SIGINT}. In this case, @sc{gdb/mi} displays this:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
*stopped,reason="exited-signalled",signal-name="SIGINT",
|
||
signal-meaning="Interrupt"
|
||
@end smallexample
|
||
|
||
|
||
@c @subheading -exec-signal
|
||
|
||
|
||
@subheading The @code{-exec-step} Command
|
||
@findex -exec-step
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-step [--reverse]
|
||
@end smallexample
|
||
|
||
Resumes execution of the inferior program, stopping when the beginning
|
||
of the next source line is reached, if the next source line is not a
|
||
function call. If it is, stop at the first instruction of the called
|
||
function. If the @samp{--reverse} option is specified, resumes reverse
|
||
execution of the inferior program, stopping at the beginning of the
|
||
previously executed source line.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{step}.
|
||
|
||
@subsubheading Example
|
||
|
||
Stepping into a function:
|
||
|
||
@smallexample
|
||
-exec-step
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",
|
||
frame=@{func="foo",args=[@{name="a",value="10"@},
|
||
@{name="b",value="0"@}],file="recursive2.c",
|
||
fullname="/home/foo/bar/recursive2.c",line="11"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Regular stepping:
|
||
|
||
@smallexample
|
||
-exec-step
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",line="14",file="recursive2.c"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-step-instruction} Command
|
||
@findex -exec-step-instruction
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-step-instruction [--reverse]
|
||
@end smallexample
|
||
|
||
Resumes the inferior which executes one machine instruction. If the
|
||
@samp{--reverse} option is specified, resumes reverse execution of the
|
||
inferior program, stopping at the previously executed instruction.
|
||
The output, once @value{GDBN} has stopped, will vary depending on
|
||
whether we have stopped in the middle of a source line or not. In the
|
||
former case, the address at which the program stopped will be printed
|
||
as well.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{stepi}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-step-instruction
|
||
^running
|
||
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",
|
||
frame=@{func="foo",args=[],file="try.c",
|
||
fullname="/home/foo/bar/try.c",line="10"@}
|
||
(gdb)
|
||
-exec-step-instruction
|
||
^running
|
||
|
||
(gdb)
|
||
*stopped,reason="end-stepping-range",
|
||
frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
|
||
fullname="/home/foo/bar/try.c",line="10"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-exec-until} Command
|
||
@findex -exec-until
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-until [ @var{location} ]
|
||
@end smallexample
|
||
|
||
Executes the inferior until the @var{location} specified in the
|
||
argument is reached. If there is no argument, the inferior executes
|
||
until a source line greater than the current one is reached. The
|
||
reason for stopping in this case will be @samp{location-reached}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{until}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-until recursive2.c:6
|
||
^running
|
||
(gdb)
|
||
x = 55
|
||
*stopped,reason="location-reached",frame=@{func="main",args=[],
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@ignore
|
||
@subheading -file-clear
|
||
Is this going away????
|
||
@end ignore
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Stack Manipulation
|
||
@section @sc{gdb/mi} Stack Manipulation Commands
|
||
|
||
@subheading The @code{-enable-frame-filters} Command
|
||
@findex -enable-frame-filters
|
||
|
||
@smallexample
|
||
-enable-frame-filters
|
||
@end smallexample
|
||
|
||
@value{GDBN} allows Python-based frame filters to affect the output of
|
||
the MI commands relating to stack traces. As there is no way to
|
||
implement this in a fully backward-compatible way, a front end must
|
||
request that this functionality be enabled.
|
||
|
||
Once enabled, this feature cannot be disabled.
|
||
|
||
Note that if Python support has not been compiled into @value{GDBN},
|
||
this command will still succeed (and do nothing).
|
||
|
||
@subheading The @code{-stack-info-frame} Command
|
||
@findex -stack-info-frame
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-info-frame
|
||
@end smallexample
|
||
|
||
Get info on the selected frame.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
|
||
(without arguments).
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-info-frame
|
||
^done,frame=@{level="1",addr="0x0001076c",func="callee3",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-stack-info-depth} Command
|
||
@findex -stack-info-depth
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-info-depth [ @var{max-depth} ]
|
||
@end smallexample
|
||
|
||
Return the depth of the stack. If the integer argument @var{max-depth}
|
||
is specified, do not count beyond @var{max-depth} frames.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There's no equivalent @value{GDBN} command.
|
||
|
||
@subsubheading Example
|
||
|
||
For a stack with frame levels 0 through 11:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-info-depth
|
||
^done,depth="12"
|
||
(gdb)
|
||
-stack-info-depth 4
|
||
^done,depth="4"
|
||
(gdb)
|
||
-stack-info-depth 12
|
||
^done,depth="12"
|
||
(gdb)
|
||
-stack-info-depth 11
|
||
^done,depth="11"
|
||
(gdb)
|
||
-stack-info-depth 13
|
||
^done,depth="12"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@anchor{-stack-list-arguments}
|
||
@subheading The @code{-stack-list-arguments} Command
|
||
@findex -stack-list-arguments
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
|
||
[ @var{low-frame} @var{high-frame} ]
|
||
@end smallexample
|
||
|
||
Display a list of the arguments for the frames between @var{low-frame}
|
||
and @var{high-frame} (inclusive). If @var{low-frame} and
|
||
@var{high-frame} are not provided, list the arguments for the whole
|
||
call stack. If the two arguments are equal, show the single frame
|
||
at the corresponding level. It is an error if @var{low-frame} is
|
||
larger than the actual number of frames. On the other hand,
|
||
@var{high-frame} may be larger than the actual number of frames, in
|
||
which case only existing frames will be returned.
|
||
|
||
If @var{print-values} is 0 or @code{--no-values}, print only the names of
|
||
the variables; if it is 1 or @code{--all-values}, print also their
|
||
values; and if it is 2 or @code{--simple-values}, print the name,
|
||
type and value for simple data types, and the name and type for arrays,
|
||
structures and unions. If the option @code{--no-frame-filters} is
|
||
supplied, then Python frame filters will not be executed.
|
||
|
||
If the @code{--skip-unavailable} option is specified, arguments that
|
||
are not available are not listed. Partially available arguments
|
||
are still displayed, however.
|
||
|
||
Use of this command to obtain arguments in a single frame is
|
||
deprecated in favor of the @samp{-stack-list-variables} command.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@value{GDBN} does not have an equivalent command. @code{gdbtk} has a
|
||
@samp{gdb_get_args} command which partially overlaps with the
|
||
functionality of @samp{-stack-list-arguments}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-frames
|
||
^done,
|
||
stack=[
|
||
frame=@{level="0",addr="0x00010734",func="callee4",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
|
||
frame=@{level="1",addr="0x0001076c",func="callee3",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
|
||
frame=@{level="2",addr="0x0001078c",func="callee2",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
|
||
frame=@{level="3",addr="0x000107b4",func="callee1",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
|
||
frame=@{level="4",addr="0x000107e0",func="main",
|
||
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
|
||
(gdb)
|
||
-stack-list-arguments 0
|
||
^done,
|
||
stack-args=[
|
||
frame=@{level="0",args=[]@},
|
||
frame=@{level="1",args=[name="strarg"]@},
|
||
frame=@{level="2",args=[name="intarg",name="strarg"]@},
|
||
frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
|
||
frame=@{level="4",args=[]@}]
|
||
(gdb)
|
||
-stack-list-arguments 1
|
||
^done,
|
||
stack-args=[
|
||
frame=@{level="0",args=[]@},
|
||
frame=@{level="1",
|
||
args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
|
||
frame=@{level="2",args=[
|
||
@{name="intarg",value="2"@},
|
||
@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
|
||
@{frame=@{level="3",args=[
|
||
@{name="intarg",value="2"@},
|
||
@{name="strarg",value="0x11940 \"A string argument.\""@},
|
||
@{name="fltarg",value="3.5"@}]@},
|
||
frame=@{level="4",args=[]@}]
|
||
(gdb)
|
||
-stack-list-arguments 0 2 2
|
||
^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
|
||
(gdb)
|
||
-stack-list-arguments 1 2 2
|
||
^done,stack-args=[frame=@{level="2",
|
||
args=[@{name="intarg",value="2"@},
|
||
@{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c @subheading -stack-list-exception-handlers
|
||
|
||
|
||
@anchor{-stack-list-frames}
|
||
@subheading The @code{-stack-list-frames} Command
|
||
@findex -stack-list-frames
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
|
||
@end smallexample
|
||
|
||
List the frames currently on the stack. For each frame it displays the
|
||
following info:
|
||
|
||
@table @samp
|
||
@item @var{level}
|
||
The frame number, 0 being the topmost frame, i.e., the innermost function.
|
||
@item @var{addr}
|
||
The @code{$pc} value for that frame.
|
||
@item @var{func}
|
||
Function name.
|
||
@item @var{file}
|
||
File name of the source file where the function lives.
|
||
@item @var{fullname}
|
||
The full file name of the source file where the function lives.
|
||
@item @var{line}
|
||
Line number corresponding to the @code{$pc}.
|
||
@item @var{from}
|
||
The shared library where this function is defined. This is only given
|
||
if the frame's function is not known.
|
||
@end table
|
||
|
||
If invoked without arguments, this command prints a backtrace for the
|
||
whole stack. If given two integer arguments, it shows the frames whose
|
||
levels are between the two arguments (inclusive). If the two arguments
|
||
are equal, it shows the single frame at the corresponding level. It is
|
||
an error if @var{low-frame} is larger than the actual number of
|
||
frames. On the other hand, @var{high-frame} may be larger than the
|
||
actual number of frames, in which case only existing frames will be
|
||
returned. If the option @code{--no-frame-filters} is supplied, then
|
||
Python frame filters will not be executed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
|
||
|
||
@subsubheading Example
|
||
|
||
Full stack backtrace:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-frames
|
||
^done,stack=
|
||
[frame=@{level="0",addr="0x0001076c",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
|
||
frame=@{level="1",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="2",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="3",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="4",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="5",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="6",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="7",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="8",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="9",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="10",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="11",addr="0x00010738",func="main",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Show frames between @var{low_frame} and @var{high_frame}:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-frames 3 5
|
||
^done,stack=
|
||
[frame=@{level="3",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="4",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
|
||
frame=@{level="5",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Show a single frame:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-frames 3 3
|
||
^done,stack=
|
||
[frame=@{level="3",addr="0x000107a4",func="foo",
|
||
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-stack-list-locals} Command
|
||
@findex -stack-list-locals
|
||
@anchor{-stack-list-locals}
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
|
||
@end smallexample
|
||
|
||
Display the local variable names for the selected frame. If
|
||
@var{print-values} is 0 or @code{--no-values}, print only the names of
|
||
the variables; if it is 1 or @code{--all-values}, print also their
|
||
values; and if it is 2 or @code{--simple-values}, print the name,
|
||
type and value for simple data types, and the name and type for arrays,
|
||
structures and unions. In this last case, a frontend can immediately
|
||
display the value of simple data types and create variable objects for
|
||
other data types when the user wishes to explore their values in
|
||
more detail. If the option @code{--no-frame-filters} is supplied, then
|
||
Python frame filters will not be executed.
|
||
|
||
If the @code{--skip-unavailable} option is specified, local variables
|
||
that are not available are not listed. Partially available local
|
||
variables are still displayed, however.
|
||
|
||
This command is deprecated in favor of the
|
||
@samp{-stack-list-variables} command.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-locals 0
|
||
^done,locals=[name="A",name="B",name="C"]
|
||
(gdb)
|
||
-stack-list-locals --all-values
|
||
^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
|
||
@{name="C",value="@{1, 2, 3@}"@}]
|
||
-stack-list-locals --simple-values
|
||
^done,locals=[@{name="A",type="int",value="1"@},
|
||
@{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@anchor{-stack-list-variables}
|
||
@subheading The @code{-stack-list-variables} Command
|
||
@findex -stack-list-variables
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
|
||
@end smallexample
|
||
|
||
Display the names of local variables and function arguments for the selected frame. If
|
||
@var{print-values} is 0 or @code{--no-values}, print only the names of
|
||
the variables; if it is 1 or @code{--all-values}, print also their
|
||
values; and if it is 2 or @code{--simple-values}, print the name,
|
||
type and value for simple data types, and the name and type for arrays,
|
||
structures and unions. If the option @code{--no-frame-filters} is
|
||
supplied, then Python frame filters will not be executed.
|
||
|
||
If the @code{--skip-unavailable} option is specified, local variables
|
||
and arguments that are not available are not listed. Partially
|
||
available arguments and local variables are still displayed, however.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-list-variables --thread 1 --frame 0 --all-values
|
||
^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-stack-select-frame} Command
|
||
@findex -stack-select-frame
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-stack-select-frame @var{framenum}
|
||
@end smallexample
|
||
|
||
Change the selected frame. Select a different frame @var{framenum} on
|
||
the stack.
|
||
|
||
This command in deprecated in favor of passing the @samp{--frame}
|
||
option to every command.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
|
||
@samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-stack-select-frame 2
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Variable Objects
|
||
@section @sc{gdb/mi} Variable Objects
|
||
|
||
@ignore
|
||
|
||
@subheading Motivation for Variable Objects in @sc{gdb/mi}
|
||
|
||
For the implementation of a variable debugger window (locals, watched
|
||
expressions, etc.), we are proposing the adaptation of the existing code
|
||
used by @code{Insight}.
|
||
|
||
The two main reasons for that are:
|
||
|
||
@enumerate 1
|
||
@item
|
||
It has been proven in practice (it is already on its second generation).
|
||
|
||
@item
|
||
It will shorten development time (needless to say how important it is
|
||
now).
|
||
@end enumerate
|
||
|
||
The original interface was designed to be used by Tcl code, so it was
|
||
slightly changed so it could be used through @sc{gdb/mi}. This section
|
||
describes the @sc{gdb/mi} operations that will be available and gives some
|
||
hints about their use.
|
||
|
||
@emph{Note}: In addition to the set of operations described here, we
|
||
expect the @sc{gui} implementation of a variable window to require, at
|
||
least, the following operations:
|
||
|
||
@itemize @bullet
|
||
@item @code{-gdb-show} @code{output-radix}
|
||
@item @code{-stack-list-arguments}
|
||
@item @code{-stack-list-locals}
|
||
@item @code{-stack-select-frame}
|
||
@end itemize
|
||
|
||
@end ignore
|
||
|
||
@subheading Introduction to Variable Objects
|
||
|
||
@cindex variable objects in @sc{gdb/mi}
|
||
|
||
Variable objects are "object-oriented" MI interface for examining and
|
||
changing values of expressions. Unlike some other MI interfaces that
|
||
work with expressions, variable objects are specifically designed for
|
||
simple and efficient presentation in the frontend. A variable object
|
||
is identified by string name. When a variable object is created, the
|
||
frontend specifies the expression for that variable object. The
|
||
expression can be a simple variable, or it can be an arbitrary complex
|
||
expression, and can even involve CPU registers. After creating a
|
||
variable object, the frontend can invoke other variable object
|
||
operations---for example to obtain or change the value of a variable
|
||
object, or to change display format.
|
||
|
||
Variable objects have hierarchical tree structure. Any variable object
|
||
that corresponds to a composite type, such as structure in C, has
|
||
a number of child variable objects, for example corresponding to each
|
||
element of a structure. A child variable object can itself have
|
||
children, recursively. Recursion ends when we reach
|
||
leaf variable objects, which always have built-in types. Child variable
|
||
objects are created only by explicit request, so if a frontend
|
||
is not interested in the children of a particular variable object, no
|
||
child will be created.
|
||
|
||
For a leaf variable object it is possible to obtain its value as a
|
||
string, or set the value from a string. String value can be also
|
||
obtained for a non-leaf variable object, but it's generally a string
|
||
that only indicates the type of the object, and does not list its
|
||
contents. Assignment to a non-leaf variable object is not allowed.
|
||
|
||
A frontend does not need to read the values of all variable objects each time
|
||
the program stops. Instead, MI provides an update command that lists all
|
||
variable objects whose values has changed since the last update
|
||
operation. This considerably reduces the amount of data that must
|
||
be transferred to the frontend. As noted above, children variable
|
||
objects are created on demand, and only leaf variable objects have a
|
||
real value. As result, gdb will read target memory only for leaf
|
||
variables that frontend has created.
|
||
|
||
The automatic update is not always desirable. For example, a frontend
|
||
might want to keep a value of some expression for future reference,
|
||
and never update it. For another example, fetching memory is
|
||
relatively slow for embedded targets, so a frontend might want
|
||
to disable automatic update for the variables that are either not
|
||
visible on the screen, or ``closed''. This is possible using so
|
||
called ``frozen variable objects''. Such variable objects are never
|
||
implicitly updated.
|
||
|
||
Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
|
||
fixed variable object, the expression is parsed when the variable
|
||
object is created, including associating identifiers to specific
|
||
variables. The meaning of expression never changes. For a floating
|
||
variable object the values of variables whose names appear in the
|
||
expressions are re-evaluated every time in the context of the current
|
||
frame. Consider this example:
|
||
|
||
@smallexample
|
||
void do_work(...)
|
||
@{
|
||
struct work_state state;
|
||
|
||
if (...)
|
||
do_work(...);
|
||
@}
|
||
@end smallexample
|
||
|
||
If a fixed variable object for the @code{state} variable is created in
|
||
this function, and we enter the recursive call, the variable
|
||
object will report the value of @code{state} in the top-level
|
||
@code{do_work} invocation. On the other hand, a floating variable
|
||
object will report the value of @code{state} in the current frame.
|
||
|
||
If an expression specified when creating a fixed variable object
|
||
refers to a local variable, the variable object becomes bound to the
|
||
thread and frame in which the variable object is created. When such
|
||
variable object is updated, @value{GDBN} makes sure that the
|
||
thread/frame combination the variable object is bound to still exists,
|
||
and re-evaluates the variable object in context of that thread/frame.
|
||
|
||
The following is the complete set of @sc{gdb/mi} operations defined to
|
||
access this functionality:
|
||
|
||
@multitable @columnfractions .4 .6
|
||
@item @strong{Operation}
|
||
@tab @strong{Description}
|
||
|
||
@item @code{-enable-pretty-printing}
|
||
@tab enable Python-based pretty-printing
|
||
@item @code{-var-create}
|
||
@tab create a variable object
|
||
@item @code{-var-delete}
|
||
@tab delete the variable object and/or its children
|
||
@item @code{-var-set-format}
|
||
@tab set the display format of this variable
|
||
@item @code{-var-show-format}
|
||
@tab show the display format of this variable
|
||
@item @code{-var-info-num-children}
|
||
@tab tells how many children this object has
|
||
@item @code{-var-list-children}
|
||
@tab return a list of the object's children
|
||
@item @code{-var-info-type}
|
||
@tab show the type of this variable object
|
||
@item @code{-var-info-expression}
|
||
@tab print parent-relative expression that this variable object represents
|
||
@item @code{-var-info-path-expression}
|
||
@tab print full expression that this variable object represents
|
||
@item @code{-var-show-attributes}
|
||
@tab is this variable editable? does it exist here?
|
||
@item @code{-var-evaluate-expression}
|
||
@tab get the value of this variable
|
||
@item @code{-var-assign}
|
||
@tab set the value of this variable
|
||
@item @code{-var-update}
|
||
@tab update the variable and its children
|
||
@item @code{-var-set-frozen}
|
||
@tab set frozeness attribute
|
||
@item @code{-var-set-update-range}
|
||
@tab set range of children to display on update
|
||
@end multitable
|
||
|
||
In the next subsection we describe each operation in detail and suggest
|
||
how it can be used.
|
||
|
||
@subheading Description And Use of Operations on Variable Objects
|
||
|
||
@subheading The @code{-enable-pretty-printing} Command
|
||
@findex -enable-pretty-printing
|
||
|
||
@smallexample
|
||
-enable-pretty-printing
|
||
@end smallexample
|
||
|
||
@value{GDBN} allows Python-based visualizers to affect the output of the
|
||
MI variable object commands. However, because there was no way to
|
||
implement this in a fully backward-compatible way, a front end must
|
||
request that this functionality be enabled.
|
||
|
||
Once enabled, this feature cannot be disabled.
|
||
|
||
Note that if Python support has not been compiled into @value{GDBN},
|
||
this command will still succeed (and do nothing).
|
||
|
||
This feature is currently (as of @value{GDBN} 7.0) experimental, and
|
||
may work differently in future versions of @value{GDBN}.
|
||
|
||
@subheading The @code{-var-create} Command
|
||
@findex -var-create
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-create @{@var{name} | "-"@}
|
||
@{@var{frame-addr} | "*" | "@@"@} @var{expression}
|
||
@end smallexample
|
||
|
||
This operation creates a variable object, which allows the monitoring of
|
||
a variable, the result of an expression, a memory cell or a CPU
|
||
register.
|
||
|
||
The @var{name} parameter is the string by which the object can be
|
||
referenced. It must be unique. If @samp{-} is specified, the varobj
|
||
system will generate a string ``varNNNNNN'' automatically. It will be
|
||
unique provided that one does not specify @var{name} of that format.
|
||
The command fails if a duplicate name is found.
|
||
|
||
The frame under which the expression should be evaluated can be
|
||
specified by @var{frame-addr}. A @samp{*} indicates that the current
|
||
frame should be used. A @samp{@@} indicates that a floating variable
|
||
object must be created.
|
||
|
||
@var{expression} is any expression valid on the current language set (must not
|
||
begin with a @samp{*}), or one of the following:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
@samp{*@var{addr}}, where @var{addr} is the address of a memory cell
|
||
|
||
@item
|
||
@samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
|
||
|
||
@item
|
||
@samp{$@var{regname}} --- a CPU register name
|
||
@end itemize
|
||
|
||
@cindex dynamic varobj
|
||
A varobj's contents may be provided by a Python-based pretty-printer. In this
|
||
case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
|
||
have slightly different semantics in some cases. If the
|
||
@code{-enable-pretty-printing} command is not sent, then @value{GDBN}
|
||
will never create a dynamic varobj. This ensures backward
|
||
compatibility for existing clients.
|
||
|
||
@subsubheading Result
|
||
|
||
This operation returns attributes of the newly-created varobj. These
|
||
are:
|
||
|
||
@table @samp
|
||
@item name
|
||
The name of the varobj.
|
||
|
||
@item numchild
|
||
The number of children of the varobj. This number is not necessarily
|
||
reliable for a dynamic varobj. Instead, you must examine the
|
||
@samp{has_more} attribute.
|
||
|
||
@item value
|
||
The varobj's scalar value. For a varobj whose type is some sort of
|
||
aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
|
||
will not be interesting.
|
||
|
||
@item type
|
||
The varobj's type. This is a string representation of the type, as
|
||
would be printed by the @value{GDBN} CLI. If @samp{print object}
|
||
(@pxref{Print Settings, set print object}) is set to @code{on}, the
|
||
@emph{actual} (derived) type of the object is shown rather than the
|
||
@emph{declared} one.
|
||
|
||
@item thread-id
|
||
If a variable object is bound to a specific thread, then this is the
|
||
thread's global identifier.
|
||
|
||
@item has_more
|
||
For a dynamic varobj, this indicates whether there appear to be any
|
||
children available. For a non-dynamic varobj, this will be 0.
|
||
|
||
@item dynamic
|
||
This attribute will be present and have the value @samp{1} if the
|
||
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
|
||
then this attribute will not be present.
|
||
|
||
@item displayhint
|
||
A dynamic varobj can supply a display hint to the front end. The
|
||
value comes directly from the Python pretty-printer object's
|
||
@code{display_hint} method. @xref{Pretty Printing API}.
|
||
@end table
|
||
|
||
Typical output will look like this:
|
||
|
||
@smallexample
|
||
name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
|
||
has_more="@var{has_more}"
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-var-delete} Command
|
||
@findex -var-delete
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-delete [ -c ] @var{name}
|
||
@end smallexample
|
||
|
||
Deletes a previously created variable object and all of its children.
|
||
With the @samp{-c} option, just deletes the children.
|
||
|
||
Returns an error if the object @var{name} is not found.
|
||
|
||
|
||
@subheading The @code{-var-set-format} Command
|
||
@findex -var-set-format
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-set-format @var{name} @var{format-spec}
|
||
@end smallexample
|
||
|
||
Sets the output format for the value of the object @var{name} to be
|
||
@var{format-spec}.
|
||
|
||
@anchor{-var-set-format}
|
||
The syntax for the @var{format-spec} is as follows:
|
||
|
||
@smallexample
|
||
@var{format-spec} @expansion{}
|
||
@{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
|
||
@end smallexample
|
||
|
||
The natural format is the default format choosen automatically
|
||
based on the variable type (like decimal for an @code{int}, hex
|
||
for pointers, etc.).
|
||
|
||
The zero-hexadecimal format has a representation similar to hexadecimal
|
||
but with padding zeroes to the left of the value. For example, a 32-bit
|
||
hexadecimal value of 0x1234 would be represented as 0x00001234 in the
|
||
zero-hexadecimal format.
|
||
|
||
For a variable with children, the format is set only on the
|
||
variable itself, and the children are not affected.
|
||
|
||
@subheading The @code{-var-show-format} Command
|
||
@findex -var-show-format
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-show-format @var{name}
|
||
@end smallexample
|
||
|
||
Returns the format used to display the value of the object @var{name}.
|
||
|
||
@smallexample
|
||
@var{format} @expansion{}
|
||
@var{format-spec}
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-var-info-num-children} Command
|
||
@findex -var-info-num-children
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-info-num-children @var{name}
|
||
@end smallexample
|
||
|
||
Returns the number of children of a variable object @var{name}:
|
||
|
||
@smallexample
|
||
numchild=@var{n}
|
||
@end smallexample
|
||
|
||
Note that this number is not completely reliable for a dynamic varobj.
|
||
It will return the current number of children, but more children may
|
||
be available.
|
||
|
||
|
||
@subheading The @code{-var-list-children} Command
|
||
@findex -var-list-children
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
|
||
@end smallexample
|
||
@anchor{-var-list-children}
|
||
|
||
Return a list of the children of the specified variable object and
|
||
create variable objects for them, if they do not already exist. With
|
||
a single argument or if @var{print-values} has a value of 0 or
|
||
@code{--no-values}, print only the names of the variables; if
|
||
@var{print-values} is 1 or @code{--all-values}, also print their
|
||
values; and if it is 2 or @code{--simple-values} print the name and
|
||
value for simple data types and just the name for arrays, structures
|
||
and unions.
|
||
|
||
@var{from} and @var{to}, if specified, indicate the range of children
|
||
to report. If @var{from} or @var{to} is less than zero, the range is
|
||
reset and all children will be reported. Otherwise, children starting
|
||
at @var{from} (zero-based) and up to and excluding @var{to} will be
|
||
reported.
|
||
|
||
If a child range is requested, it will only affect the current call to
|
||
@code{-var-list-children}, but not future calls to @code{-var-update}.
|
||
For this, you must instead use @code{-var-set-update-range}. The
|
||
intent of this approach is to enable a front end to implement any
|
||
update approach it likes; for example, scrolling a view may cause the
|
||
front end to request more children with @code{-var-list-children}, and
|
||
then the front end could call @code{-var-set-update-range} with a
|
||
different range to ensure that future updates are restricted to just
|
||
the visible items.
|
||
|
||
For each child the following results are returned:
|
||
|
||
@table @var
|
||
|
||
@item name
|
||
Name of the variable object created for this child.
|
||
|
||
@item exp
|
||
The expression to be shown to the user by the front end to designate this child.
|
||
For example this may be the name of a structure member.
|
||
|
||
For a dynamic varobj, this value cannot be used to form an
|
||
expression. There is no way to do this at all with a dynamic varobj.
|
||
|
||
For C/C@t{++} structures there are several pseudo children returned to
|
||
designate access qualifiers. For these pseudo children @var{exp} is
|
||
@samp{public}, @samp{private}, or @samp{protected}. In this case the
|
||
type and value are not present.
|
||
|
||
A dynamic varobj will not report the access qualifying
|
||
pseudo-children, regardless of the language. This information is not
|
||
available at all with a dynamic varobj.
|
||
|
||
@item numchild
|
||
Number of children this child has. For a dynamic varobj, this will be
|
||
0.
|
||
|
||
@item type
|
||
The type of the child. If @samp{print object}
|
||
(@pxref{Print Settings, set print object}) is set to @code{on}, the
|
||
@emph{actual} (derived) type of the object is shown rather than the
|
||
@emph{declared} one.
|
||
|
||
@item value
|
||
If values were requested, this is the value.
|
||
|
||
@item thread-id
|
||
If this variable object is associated with a thread, this is the
|
||
thread's global thread id. Otherwise this result is not present.
|
||
|
||
@item frozen
|
||
If the variable object is frozen, this variable will be present with a value of 1.
|
||
|
||
@item displayhint
|
||
A dynamic varobj can supply a display hint to the front end. The
|
||
value comes directly from the Python pretty-printer object's
|
||
@code{display_hint} method. @xref{Pretty Printing API}.
|
||
|
||
@item dynamic
|
||
This attribute will be present and have the value @samp{1} if the
|
||
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
|
||
then this attribute will not be present.
|
||
|
||
@end table
|
||
|
||
The result may have its own attributes:
|
||
|
||
@table @samp
|
||
@item displayhint
|
||
A dynamic varobj can supply a display hint to the front end. The
|
||
value comes directly from the Python pretty-printer object's
|
||
@code{display_hint} method. @xref{Pretty Printing API}.
|
||
|
||
@item has_more
|
||
This is an integer attribute which is nonzero if there are children
|
||
remaining after the end of the selected range.
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-list-children n
|
||
^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
|
||
numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
|
||
(gdb)
|
||
-var-list-children --all-values n
|
||
^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
|
||
numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-var-info-type} Command
|
||
@findex -var-info-type
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-info-type @var{name}
|
||
@end smallexample
|
||
|
||
Returns the type of the specified variable @var{name}. The type is
|
||
returned as a string in the same format as it is output by the
|
||
@value{GDBN} CLI:
|
||
|
||
@smallexample
|
||
type=@var{typename}
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-var-info-expression} Command
|
||
@findex -var-info-expression
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-info-expression @var{name}
|
||
@end smallexample
|
||
|
||
Returns a string that is suitable for presenting this
|
||
variable object in user interface. The string is generally
|
||
not valid expression in the current language, and cannot be evaluated.
|
||
|
||
For example, if @code{a} is an array, and variable object
|
||
@code{A} was created for @code{a}, then we'll get this output:
|
||
|
||
@smallexample
|
||
(gdb) -var-info-expression A.1
|
||
^done,lang="C",exp="1"
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Here, the value of @code{lang} is the language name, which can be
|
||
found in @ref{Supported Languages}.
|
||
|
||
Note that the output of the @code{-var-list-children} command also
|
||
includes those expressions, so the @code{-var-info-expression} command
|
||
is of limited use.
|
||
|
||
@subheading The @code{-var-info-path-expression} Command
|
||
@findex -var-info-path-expression
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-info-path-expression @var{name}
|
||
@end smallexample
|
||
|
||
Returns an expression that can be evaluated in the current
|
||
context and will yield the same value that a variable object has.
|
||
Compare this with the @code{-var-info-expression} command, which
|
||
result can be used only for UI presentation. Typical use of
|
||
the @code{-var-info-path-expression} command is creating a
|
||
watchpoint from a variable object.
|
||
|
||
This command is currently not valid for children of a dynamic varobj,
|
||
and will give an error when invoked on one.
|
||
|
||
For example, suppose @code{C} is a C@t{++} class, derived from class
|
||
@code{Base}, and that the @code{Base} class has a member called
|
||
@code{m_size}. Assume a variable @code{c} is has the type of
|
||
@code{C} and a variable object @code{C} was created for variable
|
||
@code{c}. Then, we'll get this output:
|
||
@smallexample
|
||
(gdb) -var-info-path-expression C.Base.public.m_size
|
||
^done,path_expr=((Base)c).m_size)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-var-show-attributes} Command
|
||
@findex -var-show-attributes
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-show-attributes @var{name}
|
||
@end smallexample
|
||
|
||
List attributes of the specified variable object @var{name}:
|
||
|
||
@smallexample
|
||
status=@var{attr} [ ( ,@var{attr} )* ]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
|
||
|
||
@subheading The @code{-var-evaluate-expression} Command
|
||
@findex -var-evaluate-expression
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-evaluate-expression [-f @var{format-spec}] @var{name}
|
||
@end smallexample
|
||
|
||
Evaluates the expression that is represented by the specified variable
|
||
object and returns its value as a string. The format of the string
|
||
can be specified with the @samp{-f} option. The possible values of
|
||
this option are the same as for @code{-var-set-format}
|
||
(@pxref{-var-set-format}). If the @samp{-f} option is not specified,
|
||
the current display format will be used. The current display format
|
||
can be changed using the @code{-var-set-format} command.
|
||
|
||
@smallexample
|
||
value=@var{value}
|
||
@end smallexample
|
||
|
||
Note that one must invoke @code{-var-list-children} for a variable
|
||
before the value of a child variable can be evaluated.
|
||
|
||
@subheading The @code{-var-assign} Command
|
||
@findex -var-assign
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-assign @var{name} @var{expression}
|
||
@end smallexample
|
||
|
||
Assigns the value of @var{expression} to the variable object specified
|
||
by @var{name}. The object must be @samp{editable}. If the variable's
|
||
value is altered by the assign, the variable will show up in any
|
||
subsequent @code{-var-update} list.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-assign var1 3
|
||
^done,value="3"
|
||
(gdb)
|
||
-var-update *
|
||
^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-var-update} Command
|
||
@findex -var-update
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-update [@var{print-values}] @{@var{name} | "*"@}
|
||
@end smallexample
|
||
|
||
Reevaluate the expressions corresponding to the variable object
|
||
@var{name} and all its direct and indirect children, and return the
|
||
list of variable objects whose values have changed; @var{name} must
|
||
be a root variable object. Here, ``changed'' means that the result of
|
||
@code{-var-evaluate-expression} before and after the
|
||
@code{-var-update} is different. If @samp{*} is used as the variable
|
||
object names, all existing variable objects are updated, except
|
||
for frozen ones (@pxref{-var-set-frozen}). The option
|
||
@var{print-values} determines whether both names and values, or just
|
||
names are printed. The possible values of this option are the same
|
||
as for @code{-var-list-children} (@pxref{-var-list-children}). It is
|
||
recommended to use the @samp{--all-values} option, to reduce the
|
||
number of MI commands needed on each program stop.
|
||
|
||
With the @samp{*} parameter, if a variable object is bound to a
|
||
currently running thread, it will not be updated, without any
|
||
diagnostic.
|
||
|
||
If @code{-var-set-update-range} was previously used on a varobj, then
|
||
only the selected range of children will be reported.
|
||
|
||
@code{-var-update} reports all the changed varobjs in a tuple named
|
||
@samp{changelist}.
|
||
|
||
Each item in the change list is itself a tuple holding:
|
||
|
||
@table @samp
|
||
@item name
|
||
The name of the varobj.
|
||
|
||
@item value
|
||
If values were requested for this update, then this field will be
|
||
present and will hold the value of the varobj.
|
||
|
||
@item in_scope
|
||
@anchor{-var-update}
|
||
This field is a string which may take one of three values:
|
||
|
||
@table @code
|
||
@item "true"
|
||
The variable object's current value is valid.
|
||
|
||
@item "false"
|
||
The variable object does not currently hold a valid value but it may
|
||
hold one in the future if its associated expression comes back into
|
||
scope.
|
||
|
||
@item "invalid"
|
||
The variable object no longer holds a valid value.
|
||
This can occur when the executable file being debugged has changed,
|
||
either through recompilation or by using the @value{GDBN} @code{file}
|
||
command. The front end should normally choose to delete these variable
|
||
objects.
|
||
@end table
|
||
|
||
In the future new values may be added to this list so the front should
|
||
be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
|
||
|
||
@item type_changed
|
||
This is only present if the varobj is still valid. If the type
|
||
changed, then this will be the string @samp{true}; otherwise it will
|
||
be @samp{false}.
|
||
|
||
When a varobj's type changes, its children are also likely to have
|
||
become incorrect. Therefore, the varobj's children are automatically
|
||
deleted when this attribute is @samp{true}. Also, the varobj's update
|
||
range, when set using the @code{-var-set-update-range} command, is
|
||
unset.
|
||
|
||
@item new_type
|
||
If the varobj's type changed, then this field will be present and will
|
||
hold the new type.
|
||
|
||
@item new_num_children
|
||
For a dynamic varobj, if the number of children changed, or if the
|
||
type changed, this will be the new number of children.
|
||
|
||
The @samp{numchild} field in other varobj responses is generally not
|
||
valid for a dynamic varobj -- it will show the number of children that
|
||
@value{GDBN} knows about, but because dynamic varobjs lazily
|
||
instantiate their children, this will not reflect the number of
|
||
children which may be available.
|
||
|
||
The @samp{new_num_children} attribute only reports changes to the
|
||
number of children known by @value{GDBN}. This is the only way to
|
||
detect whether an update has removed children (which necessarily can
|
||
only happen at the end of the update range).
|
||
|
||
@item displayhint
|
||
The display hint, if any.
|
||
|
||
@item has_more
|
||
This is an integer value, which will be 1 if there are more children
|
||
available outside the varobj's update range.
|
||
|
||
@item dynamic
|
||
This attribute will be present and have the value @samp{1} if the
|
||
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
|
||
then this attribute will not be present.
|
||
|
||
@item new_children
|
||
If new children were added to a dynamic varobj within the selected
|
||
update range (as set by @code{-var-set-update-range}), then they will
|
||
be listed in this attribute.
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-assign var1 3
|
||
^done,value="3"
|
||
(gdb)
|
||
-var-update --all-values var1
|
||
^done,changelist=[@{name="var1",value="3",in_scope="true",
|
||
type_changed="false"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-var-set-frozen} Command
|
||
@findex -var-set-frozen
|
||
@anchor{-var-set-frozen}
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-set-frozen @var{name} @var{flag}
|
||
@end smallexample
|
||
|
||
Set the frozenness flag on the variable object @var{name}. The
|
||
@var{flag} parameter should be either @samp{1} to make the variable
|
||
frozen or @samp{0} to make it unfrozen. If a variable object is
|
||
frozen, then neither itself, nor any of its children, are
|
||
implicitly updated by @code{-var-update} of
|
||
a parent variable or by @code{-var-update *}. Only
|
||
@code{-var-update} of the variable itself will update its value and
|
||
values of its children. After a variable object is unfrozen, it is
|
||
implicitly updated by all subsequent @code{-var-update} operations.
|
||
Unfreezing a variable does not update it, only subsequent
|
||
@code{-var-update} does.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-set-frozen V 1
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-var-set-update-range} command
|
||
@findex -var-set-update-range
|
||
@anchor{-var-set-update-range}
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-set-update-range @var{name} @var{from} @var{to}
|
||
@end smallexample
|
||
|
||
Set the range of children to be returned by future invocations of
|
||
@code{-var-update}.
|
||
|
||
@var{from} and @var{to} indicate the range of children to report. If
|
||
@var{from} or @var{to} is less than zero, the range is reset and all
|
||
children will be reported. Otherwise, children starting at @var{from}
|
||
(zero-based) and up to and excluding @var{to} will be reported.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-set-update-range V 1 2
|
||
^done
|
||
@end smallexample
|
||
|
||
@subheading The @code{-var-set-visualizer} command
|
||
@findex -var-set-visualizer
|
||
@anchor{-var-set-visualizer}
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-var-set-visualizer @var{name} @var{visualizer}
|
||
@end smallexample
|
||
|
||
Set a visualizer for the variable object @var{name}.
|
||
|
||
@var{visualizer} is the visualizer to use. The special value
|
||
@samp{None} means to disable any visualizer in use.
|
||
|
||
If not @samp{None}, @var{visualizer} must be a Python expression.
|
||
This expression must evaluate to a callable object which accepts a
|
||
single argument. @value{GDBN} will call this object with the value of
|
||
the varobj @var{name} as an argument (this is done so that the same
|
||
Python pretty-printing code can be used for both the CLI and MI).
|
||
When called, this object must return an object which conforms to the
|
||
pretty-printing interface (@pxref{Pretty Printing API}).
|
||
|
||
The pre-defined function @code{gdb.default_visualizer} may be used to
|
||
select a visualizer by following the built-in process
|
||
(@pxref{Selecting Pretty-Printers}). This is done automatically when
|
||
a varobj is created, and so ordinarily is not needed.
|
||
|
||
This feature is only available if Python support is enabled. The MI
|
||
command @code{-list-features} (@pxref{GDB/MI Support Commands})
|
||
can be used to check this.
|
||
|
||
@subsubheading Example
|
||
|
||
Resetting the visualizer:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-set-visualizer V None
|
||
^done
|
||
@end smallexample
|
||
|
||
Reselecting the default (type-based) visualizer:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-set-visualizer V gdb.default_visualizer
|
||
^done
|
||
@end smallexample
|
||
|
||
Suppose @code{SomeClass} is a visualizer class. A lambda expression
|
||
can be used to instantiate this class for a varobj:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-var-set-visualizer V "lambda val: SomeClass()"
|
||
^done
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Data Manipulation
|
||
@section @sc{gdb/mi} Data Manipulation
|
||
|
||
@cindex data manipulation, in @sc{gdb/mi}
|
||
@cindex @sc{gdb/mi}, data manipulation
|
||
This section describes the @sc{gdb/mi} commands that manipulate data:
|
||
examine memory and registers, evaluate expressions, etc.
|
||
|
||
For details about what an addressable memory unit is,
|
||
@pxref{addressable memory unit}.
|
||
|
||
@c REMOVED FROM THE INTERFACE.
|
||
@c @subheading -data-assign
|
||
@c Change the value of a program variable. Plenty of side effects.
|
||
@c @subsubheading GDB Command
|
||
@c set variable
|
||
@c @subsubheading Example
|
||
@c N.A.
|
||
|
||
@subheading The @code{-data-disassemble} Command
|
||
@findex -data-disassemble
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-disassemble
|
||
[ -s @var{start-addr} -e @var{end-addr} ]
|
||
| [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
|
||
-- @var{mode}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Where:
|
||
|
||
@table @samp
|
||
@item @var{start-addr}
|
||
is the beginning address (or @code{$pc})
|
||
@item @var{end-addr}
|
||
is the end address
|
||
@item @var{filename}
|
||
is the name of the file to disassemble
|
||
@item @var{linenum}
|
||
is the line number to disassemble around
|
||
@item @var{lines}
|
||
is the number of disassembly lines to be produced. If it is -1,
|
||
the whole function will be disassembled, in case no @var{end-addr} is
|
||
specified. If @var{end-addr} is specified as a non-zero value, and
|
||
@var{lines} is lower than the number of disassembly lines between
|
||
@var{start-addr} and @var{end-addr}, only @var{lines} lines are
|
||
displayed; if @var{lines} is higher than the number of lines between
|
||
@var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
|
||
are displayed.
|
||
@item @var{mode}
|
||
is one of:
|
||
@itemize @bullet
|
||
@item 0 disassembly only
|
||
@item 1 mixed source and disassembly (deprecated)
|
||
@item 2 disassembly with raw opcodes
|
||
@item 3 mixed source and disassembly with raw opcodes (deprecated)
|
||
@item 4 mixed source and disassembly
|
||
@item 5 mixed source and disassembly with raw opcodes
|
||
@end itemize
|
||
|
||
Modes 1 and 3 are deprecated. The output is ``source centric''
|
||
which hasn't proved useful in practice.
|
||
@xref{Machine Code}, for a discussion of the difference between
|
||
@code{/m} and @code{/s} output of the @code{disassemble} command.
|
||
@end table
|
||
|
||
@subsubheading Result
|
||
|
||
The result of the @code{-data-disassemble} command will be a list named
|
||
@samp{asm_insns}, the contents of this list depend on the @var{mode}
|
||
used with the @code{-data-disassemble} command.
|
||
|
||
For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
|
||
following fields:
|
||
|
||
@table @code
|
||
@item address
|
||
The address at which this instruction was disassembled.
|
||
|
||
@item func-name
|
||
The name of the function this instruction is within.
|
||
|
||
@item offset
|
||
The decimal offset in bytes from the start of @samp{func-name}.
|
||
|
||
@item inst
|
||
The text disassembly for this @samp{address}.
|
||
|
||
@item opcodes
|
||
This field is only present for modes 2, 3 and 5. This contains the raw opcode
|
||
bytes for the @samp{inst} field.
|
||
|
||
@end table
|
||
|
||
For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
|
||
@samp{src_and_asm_line}, each of which has the following fields:
|
||
|
||
@table @code
|
||
@item line
|
||
The line number within @samp{file}.
|
||
|
||
@item file
|
||
The file name from the compilation unit. This might be an absolute
|
||
file name or a relative file name depending on the compile command
|
||
used.
|
||
|
||
@item fullname
|
||
Absolute file name of @samp{file}. It is converted to a canonical form
|
||
using the source file search path
|
||
(@pxref{Source Path, ,Specifying Source Directories})
|
||
and after resolving all the symbolic links.
|
||
|
||
If the source file is not found this field will contain the path as
|
||
present in the debug information.
|
||
|
||
@item line_asm_insn
|
||
This is a list of tuples containing the disassembly for @samp{line} in
|
||
@samp{file}. The fields of each tuple are the same as for
|
||
@code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
|
||
@samp{func-name}, @samp{offset}, @samp{inst}, and optionally
|
||
@samp{opcodes}.
|
||
|
||
@end table
|
||
|
||
Note that whatever included in the @samp{inst} field, is not
|
||
manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
|
||
adjust its format.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{disassemble}.
|
||
|
||
@subsubheading Example
|
||
|
||
Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-disassemble -s $pc -e "$pc + 20" -- 0
|
||
^done,
|
||
asm_insns=[
|
||
@{address="0x000107c0",func-name="main",offset="4",
|
||
inst="mov 2, %o0"@},
|
||
@{address="0x000107c4",func-name="main",offset="8",
|
||
inst="sethi %hi(0x11800), %o2"@},
|
||
@{address="0x000107c8",func-name="main",offset="12",
|
||
inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
|
||
@{address="0x000107cc",func-name="main",offset="16",
|
||
inst="sethi %hi(0x11800), %o2"@},
|
||
@{address="0x000107d0",func-name="main",offset="20",
|
||
inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Disassemble the whole @code{main} function. Line 32 is part of
|
||
@code{main}.
|
||
|
||
@smallexample
|
||
-data-disassemble -f basics.c -l 32 -- 0
|
||
^done,asm_insns=[
|
||
@{address="0x000107bc",func-name="main",offset="0",
|
||
inst="save %sp, -112, %sp"@},
|
||
@{address="0x000107c0",func-name="main",offset="4",
|
||
inst="mov 2, %o0"@},
|
||
@{address="0x000107c4",func-name="main",offset="8",
|
||
inst="sethi %hi(0x11800), %o2"@},
|
||
[@dots{}]
|
||
@{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
|
||
@{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Disassemble 3 instructions from the start of @code{main}:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-disassemble -f basics.c -l 32 -n 3 -- 0
|
||
^done,asm_insns=[
|
||
@{address="0x000107bc",func-name="main",offset="0",
|
||
inst="save %sp, -112, %sp"@},
|
||
@{address="0x000107c0",func-name="main",offset="4",
|
||
inst="mov 2, %o0"@},
|
||
@{address="0x000107c4",func-name="main",offset="8",
|
||
inst="sethi %hi(0x11800), %o2"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Disassemble 3 instructions from the start of @code{main} in mixed mode:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-disassemble -f basics.c -l 32 -n 3 -- 1
|
||
^done,asm_insns=[
|
||
src_and_asm_line=@{line="31",
|
||
file="../../../src/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
|
||
line_asm_insn=[@{address="0x000107bc",
|
||
func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
|
||
src_and_asm_line=@{line="32",
|
||
file="../../../src/gdb/testsuite/gdb.mi/basics.c",
|
||
fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
|
||
line_asm_insn=[@{address="0x000107c0",
|
||
func-name="main",offset="4",inst="mov 2, %o0"@},
|
||
@{address="0x000107c4",func-name="main",offset="8",
|
||
inst="sethi %hi(0x11800), %o2"@}]@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-data-evaluate-expression} Command
|
||
@findex -data-evaluate-expression
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-evaluate-expression @var{expr}
|
||
@end smallexample
|
||
|
||
Evaluate @var{expr} as an expression. The expression could contain an
|
||
inferior function call. The function call will execute synchronously.
|
||
If the expression contains spaces, it must be enclosed in double quotes.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
|
||
@samp{call}. In @code{gdbtk} only, there's a corresponding
|
||
@samp{gdb_eval} command.
|
||
|
||
@subsubheading Example
|
||
|
||
In the following example, the numbers that precede the commands are the
|
||
@dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
|
||
Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
|
||
output.
|
||
|
||
@smallexample
|
||
211-data-evaluate-expression A
|
||
211^done,value="1"
|
||
(gdb)
|
||
311-data-evaluate-expression &A
|
||
311^done,value="0xefffeb7c"
|
||
(gdb)
|
||
411-data-evaluate-expression A+3
|
||
411^done,value="4"
|
||
(gdb)
|
||
511-data-evaluate-expression "A + 3"
|
||
511^done,value="4"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-data-list-changed-registers} Command
|
||
@findex -data-list-changed-registers
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-list-changed-registers
|
||
@end smallexample
|
||
|
||
Display a list of the registers that have changed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
|
||
has the corresponding command @samp{gdb_changed_register_list}.
|
||
|
||
@subsubheading Example
|
||
|
||
On a PPC MBX board:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-exec-continue
|
||
^running
|
||
|
||
(gdb)
|
||
*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
|
||
func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
|
||
line="5"@}
|
||
(gdb)
|
||
-data-list-changed-registers
|
||
^done,changed-registers=["0","1","2","4","5","6","7","8","9",
|
||
"10","11","13","14","15","16","17","18","19","20","21","22","23",
|
||
"24","25","26","27","28","30","31","64","65","66","67","69"]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-data-list-register-names} Command
|
||
@findex -data-list-register-names
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-list-register-names [ ( @var{regno} )+ ]
|
||
@end smallexample
|
||
|
||
Show a list of register names for the current target. If no arguments
|
||
are given, it shows a list of the names of all the registers. If
|
||
integer numbers are given as arguments, it will print a list of the
|
||
names of the registers corresponding to the arguments. To ensure
|
||
consistency between a register name and its number, the output list may
|
||
include empty register names.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@value{GDBN} does not have a command which corresponds to
|
||
@samp{-data-list-register-names}. In @code{gdbtk} there is a
|
||
corresponding command @samp{gdb_regnames}.
|
||
|
||
@subsubheading Example
|
||
|
||
For the PPC MBX board:
|
||
@smallexample
|
||
(gdb)
|
||
-data-list-register-names
|
||
^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
|
||
"r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
|
||
"r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
|
||
"r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
|
||
"f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
|
||
"f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
|
||
"", "pc","ps","cr","lr","ctr","xer"]
|
||
(gdb)
|
||
-data-list-register-names 1 2 3
|
||
^done,register-names=["r1","r2","r3"]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-data-list-register-values} Command
|
||
@findex -data-list-register-values
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-list-register-values
|
||
[ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
|
||
@end smallexample
|
||
|
||
Display the registers' contents. The format according to which the
|
||
registers' contents are to be returned is given by @var{fmt}, followed
|
||
by an optional list of numbers specifying the registers to display. A
|
||
missing list of numbers indicates that the contents of all the
|
||
registers must be returned. The @code{--skip-unavailable} option
|
||
indicates that only the available registers are to be returned.
|
||
|
||
Allowed formats for @var{fmt} are:
|
||
|
||
@table @code
|
||
@item x
|
||
Hexadecimal
|
||
@item o
|
||
Octal
|
||
@item t
|
||
Binary
|
||
@item d
|
||
Decimal
|
||
@item r
|
||
Raw
|
||
@item N
|
||
Natural
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
|
||
all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
|
||
|
||
@subsubheading Example
|
||
|
||
For a PPC MBX board (note: line breaks are for readability only, they
|
||
don't appear in the actual output):
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-list-register-values r 64 65
|
||
^done,register-values=[@{number="64",value="0xfe00a300"@},
|
||
@{number="65",value="0x00029002"@}]
|
||
(gdb)
|
||
-data-list-register-values x
|
||
^done,register-values=[@{number="0",value="0xfe0043c8"@},
|
||
@{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
|
||
@{number="3",value="0x0"@},@{number="4",value="0xa"@},
|
||
@{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
|
||
@{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
|
||
@{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
|
||
@{number="11",value="0x1"@},@{number="12",value="0x0"@},
|
||
@{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
|
||
@{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
|
||
@{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
|
||
@{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
|
||
@{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
|
||
@{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
|
||
@{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
|
||
@{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
|
||
@{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
|
||
@{number="31",value="0x0"@},@{number="32",value="0x0"@},
|
||
@{number="33",value="0x0"@},@{number="34",value="0x0"@},
|
||
@{number="35",value="0x0"@},@{number="36",value="0x0"@},
|
||
@{number="37",value="0x0"@},@{number="38",value="0x0"@},
|
||
@{number="39",value="0x0"@},@{number="40",value="0x0"@},
|
||
@{number="41",value="0x0"@},@{number="42",value="0x0"@},
|
||
@{number="43",value="0x0"@},@{number="44",value="0x0"@},
|
||
@{number="45",value="0x0"@},@{number="46",value="0x0"@},
|
||
@{number="47",value="0x0"@},@{number="48",value="0x0"@},
|
||
@{number="49",value="0x0"@},@{number="50",value="0x0"@},
|
||
@{number="51",value="0x0"@},@{number="52",value="0x0"@},
|
||
@{number="53",value="0x0"@},@{number="54",value="0x0"@},
|
||
@{number="55",value="0x0"@},@{number="56",value="0x0"@},
|
||
@{number="57",value="0x0"@},@{number="58",value="0x0"@},
|
||
@{number="59",value="0x0"@},@{number="60",value="0x0"@},
|
||
@{number="61",value="0x0"@},@{number="62",value="0x0"@},
|
||
@{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
|
||
@{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
|
||
@{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
|
||
@{number="69",value="0x20002b03"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-data-read-memory} Command
|
||
@findex -data-read-memory
|
||
|
||
This command is deprecated, use @code{-data-read-memory-bytes} instead.
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-read-memory [ -o @var{byte-offset} ]
|
||
@var{address} @var{word-format} @var{word-size}
|
||
@var{nr-rows} @var{nr-cols} [ @var{aschar} ]
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where:
|
||
|
||
@table @samp
|
||
@item @var{address}
|
||
An expression specifying the address of the first memory word to be
|
||
read. Complex expressions containing embedded white space should be
|
||
quoted using the C convention.
|
||
|
||
@item @var{word-format}
|
||
The format to be used to print the memory words. The notation is the
|
||
same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
|
||
,Output Formats}).
|
||
|
||
@item @var{word-size}
|
||
The size of each memory word in bytes.
|
||
|
||
@item @var{nr-rows}
|
||
The number of rows in the output table.
|
||
|
||
@item @var{nr-cols}
|
||
The number of columns in the output table.
|
||
|
||
@item @var{aschar}
|
||
If present, indicates that each row should include an @sc{ascii} dump. The
|
||
value of @var{aschar} is used as a padding character when a byte is not a
|
||
member of the printable @sc{ascii} character set (printable @sc{ascii}
|
||
characters are those whose code is between 32 and 126, inclusively).
|
||
|
||
@item @var{byte-offset}
|
||
An offset to add to the @var{address} before fetching memory.
|
||
@end table
|
||
|
||
This command displays memory contents as a table of @var{nr-rows} by
|
||
@var{nr-cols} words, each word being @var{word-size} bytes. In total,
|
||
@code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
|
||
(returned as @samp{total-bytes}). Should less than the requested number
|
||
of bytes be returned by the target, the missing words are identified
|
||
using @samp{N/A}. The number of bytes read from the target is returned
|
||
in @samp{nr-bytes} and the starting address used to read memory in
|
||
@samp{addr}.
|
||
|
||
The address of the next/previous row or page is available in
|
||
@samp{next-row} and @samp{prev-row}, @samp{next-page} and
|
||
@samp{prev-page}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
|
||
@samp{gdb_get_mem} memory read command.
|
||
|
||
@subsubheading Example
|
||
|
||
Read six bytes of memory starting at @code{bytes+6} but then offset by
|
||
@code{-6} bytes. Format as three rows of two columns. One byte per
|
||
word. Display each word in hex.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
9-data-read-memory -o -6 -- bytes+6 x 1 3 2
|
||
9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
|
||
next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
|
||
prev-page="0x0000138a",memory=[
|
||
@{addr="0x00001390",data=["0x00","0x01"]@},
|
||
@{addr="0x00001392",data=["0x02","0x03"]@},
|
||
@{addr="0x00001394",data=["0x04","0x05"]@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Read two bytes of memory starting at address @code{shorts + 64} and
|
||
display as a single word formatted in decimal.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
5-data-read-memory shorts+64 d 2 1 1
|
||
5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
|
||
next-row="0x00001512",prev-row="0x0000150e",
|
||
next-page="0x00001512",prev-page="0x0000150e",memory=[
|
||
@{addr="0x00001510",data=["128"]@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Read thirty two bytes of memory starting at @code{bytes+16} and format
|
||
as eight rows of four columns. Include a string encoding with @samp{x}
|
||
used as the non-printable character.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
4-data-read-memory bytes+16 x 1 8 4 x
|
||
4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
|
||
next-row="0x000013c0",prev-row="0x0000139c",
|
||
next-page="0x000013c0",prev-page="0x00001380",memory=[
|
||
@{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
|
||
@{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
|
||
@{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
|
||
@{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
|
||
@{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
|
||
@{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
|
||
@{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
|
||
@{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-data-read-memory-bytes} Command
|
||
@findex -data-read-memory-bytes
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-read-memory-bytes [ -o @var{offset} ]
|
||
@var{address} @var{count}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where:
|
||
|
||
@table @samp
|
||
@item @var{address}
|
||
An expression specifying the address of the first addressable memory unit
|
||
to be read. Complex expressions containing embedded white space should be
|
||
quoted using the C convention.
|
||
|
||
@item @var{count}
|
||
The number of addressable memory units to read. This should be an integer
|
||
literal.
|
||
|
||
@item @var{offset}
|
||
The offset relative to @var{address} at which to start reading. This
|
||
should be an integer literal. This option is provided so that a frontend
|
||
is not required to first evaluate address and then perform address
|
||
arithmetics itself.
|
||
|
||
@end table
|
||
|
||
This command attempts to read all accessible memory regions in the
|
||
specified range. First, all regions marked as unreadable in the memory
|
||
map (if one is defined) will be skipped. @xref{Memory Region
|
||
Attributes}. Second, @value{GDBN} will attempt to read the remaining
|
||
regions. For each one, if reading full region results in an errors,
|
||
@value{GDBN} will try to read a subset of the region.
|
||
|
||
In general, every single memory unit in the region may be readable or not,
|
||
and the only way to read every readable unit is to try a read at
|
||
every address, which is not practical. Therefore, @value{GDBN} will
|
||
attempt to read all accessible memory units at either beginning or the end
|
||
of the region, using a binary division scheme. This heuristic works
|
||
well for reading accross a memory map boundary. Note that if a region
|
||
has a readable range that is neither at the beginning or the end,
|
||
@value{GDBN} will not read it.
|
||
|
||
The result record (@pxref{GDB/MI Result Records}) that is output of
|
||
the command includes a field named @samp{memory} whose content is a
|
||
list of tuples. Each tuple represent a successfully read memory block
|
||
and has the following fields:
|
||
|
||
@table @code
|
||
@item begin
|
||
The start address of the memory block, as hexadecimal literal.
|
||
|
||
@item end
|
||
The end address of the memory block, as hexadecimal literal.
|
||
|
||
@item offset
|
||
The offset of the memory block, as hexadecimal literal, relative to
|
||
the start address passed to @code{-data-read-memory-bytes}.
|
||
|
||
@item contents
|
||
The contents of the memory block, in hex.
|
||
|
||
@end table
|
||
|
||
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{x}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-read-memory-bytes &a 10
|
||
^done,memory=[@{begin="0xbffff154",offset="0x00000000",
|
||
end="0xbffff15e",
|
||
contents="01000000020000000300"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-data-write-memory-bytes} Command
|
||
@findex -data-write-memory-bytes
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-data-write-memory-bytes @var{address} @var{contents}
|
||
-data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where:
|
||
|
||
@table @samp
|
||
@item @var{address}
|
||
An expression specifying the address of the first addressable memory unit
|
||
to be written. Complex expressions containing embedded white space should
|
||
be quoted using the C convention.
|
||
|
||
@item @var{contents}
|
||
The hex-encoded data to write. It is an error if @var{contents} does
|
||
not represent an integral number of addressable memory units.
|
||
|
||
@item @var{count}
|
||
Optional argument indicating the number of addressable memory units to be
|
||
written. If @var{count} is greater than @var{contents}' length,
|
||
@value{GDBN} will repeatedly write @var{contents} until it fills
|
||
@var{count} memory units.
|
||
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There's no corresponding @value{GDBN} command.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-write-memory-bytes &a "aabbccdd"
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-data-write-memory-bytes &a "aabbccdd" 16e
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Tracepoint Commands
|
||
@section @sc{gdb/mi} Tracepoint Commands
|
||
|
||
The commands defined in this section implement MI support for
|
||
tracepoints. For detailed introduction, see @ref{Tracepoints}.
|
||
|
||
@subheading The @code{-trace-find} Command
|
||
@findex -trace-find
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-find @var{mode} [@var{parameters}@dots{}]
|
||
@end smallexample
|
||
|
||
Find a trace frame using criteria defined by @var{mode} and
|
||
@var{parameters}. The following table lists permissible
|
||
modes and their parameters. For details of operation, see @ref{tfind}.
|
||
|
||
@table @samp
|
||
|
||
@item none
|
||
No parameters are required. Stops examining trace frames.
|
||
|
||
@item frame-number
|
||
An integer is required as parameter. Selects tracepoint frame with
|
||
that index.
|
||
|
||
@item tracepoint-number
|
||
An integer is required as parameter. Finds next
|
||
trace frame that corresponds to tracepoint with the specified number.
|
||
|
||
@item pc
|
||
An address is required as parameter. Finds
|
||
next trace frame that corresponds to any tracepoint at the specified
|
||
address.
|
||
|
||
@item pc-inside-range
|
||
Two addresses are required as parameters. Finds next trace
|
||
frame that corresponds to a tracepoint at an address inside the
|
||
specified range. Both bounds are considered to be inside the range.
|
||
|
||
@item pc-outside-range
|
||
Two addresses are required as parameters. Finds
|
||
next trace frame that corresponds to a tracepoint at an address outside
|
||
the specified range. Both bounds are considered to be inside the range.
|
||
|
||
@item line
|
||
Line specification is required as parameter. @xref{Specify Location}.
|
||
Finds next trace frame that corresponds to a tracepoint at
|
||
the specified location.
|
||
|
||
@end table
|
||
|
||
If @samp{none} was passed as @var{mode}, the response does not
|
||
have fields. Otherwise, the response may have the following fields:
|
||
|
||
@table @samp
|
||
@item found
|
||
This field has either @samp{0} or @samp{1} as the value, depending
|
||
on whether a matching tracepoint was found.
|
||
|
||
@item traceframe
|
||
The index of the found traceframe. This field is present iff
|
||
the @samp{found} field has value of @samp{1}.
|
||
|
||
@item tracepoint
|
||
The index of the found tracepoint. This field is present iff
|
||
the @samp{found} field has value of @samp{1}.
|
||
|
||
@item frame
|
||
The information about the frame corresponding to the found trace
|
||
frame. This field is present only if a trace frame was found.
|
||
@xref{GDB/MI Frame Information}, for description of this field.
|
||
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tfind}.
|
||
|
||
@subheading -trace-define-variable
|
||
@findex -trace-define-variable
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-define-variable @var{name} [ @var{value} ]
|
||
@end smallexample
|
||
|
||
Create trace variable @var{name} if it does not exist. If
|
||
@var{value} is specified, sets the initial value of the specified
|
||
trace variable to that value. Note that the @var{name} should start
|
||
with the @samp{$} character.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tvariable}.
|
||
|
||
@subheading The @code{-trace-frame-collected} Command
|
||
@findex -trace-frame-collected
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-frame-collected
|
||
[--var-print-values @var{var_pval}]
|
||
[--comp-print-values @var{comp_pval}]
|
||
[--registers-format @var{regformat}]
|
||
[--memory-contents]
|
||
@end smallexample
|
||
|
||
This command returns the set of collected objects, register names,
|
||
trace state variable names, memory ranges and computed expressions
|
||
that have been collected at a particular trace frame. The optional
|
||
parameters to the command affect the output format in different ways.
|
||
See the output description table below for more details.
|
||
|
||
The reported names can be used in the normal manner to create
|
||
varobjs and inspect the objects themselves. The items returned by
|
||
this command are categorized so that it is clear which is a variable,
|
||
which is a register, which is a trace state variable, which is a
|
||
memory range and which is a computed expression.
|
||
|
||
For instance, if the actions were
|
||
@smallexample
|
||
collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
|
||
collect *(int*)0xaf02bef0@@40
|
||
@end smallexample
|
||
|
||
@noindent
|
||
the object collected in its entirety would be @code{myVar}. The
|
||
object @code{myArray} would be partially collected, because only the
|
||
element at index @code{myIndex} would be collected. The remaining
|
||
objects would be computed expressions.
|
||
|
||
An example output would be:
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-trace-frame-collected
|
||
^done,
|
||
explicit-variables=[@{name="myVar",value="1"@}],
|
||
computed-expressions=[@{name="myArray[myIndex]",value="0"@},
|
||
@{name="myObj.field",value="0"@},
|
||
@{name="myPtr->field",value="1"@},
|
||
@{name="myCount + 2",value="3"@},
|
||
@{name="$tvar1 + 1",value="43970027"@}],
|
||
registers=[@{number="0",value="0x7fe2c6e79ec8"@},
|
||
@{number="1",value="0x0"@},
|
||
@{number="2",value="0x4"@},
|
||
...
|
||
@{number="125",value="0x0"@}],
|
||
tvars=[@{name="$tvar1",current="43970026"@}],
|
||
memory=[@{address="0x0000000000602264",length="4"@},
|
||
@{address="0x0000000000615bc0",length="4"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
Where:
|
||
|
||
@table @code
|
||
@item explicit-variables
|
||
The set of objects that have been collected in their entirety (as
|
||
opposed to collecting just a few elements of an array or a few struct
|
||
members). For each object, its name and value are printed.
|
||
The @code{--var-print-values} option affects how or whether the value
|
||
field is output. If @var{var_pval} is 0, then print only the names;
|
||
if it is 1, print also their values; and if it is 2, print the name,
|
||
type and value for simple data types, and the name and type for
|
||
arrays, structures and unions.
|
||
|
||
@item computed-expressions
|
||
The set of computed expressions that have been collected at the
|
||
current trace frame. The @code{--comp-print-values} option affects
|
||
this set like the @code{--var-print-values} option affects the
|
||
@code{explicit-variables} set. See above.
|
||
|
||
@item registers
|
||
The registers that have been collected at the current trace frame.
|
||
For each register collected, the name and current value are returned.
|
||
The value is formatted according to the @code{--registers-format}
|
||
option. See the @command{-data-list-register-values} command for a
|
||
list of the allowed formats. The default is @samp{x}.
|
||
|
||
@item tvars
|
||
The trace state variables that have been collected at the current
|
||
trace frame. For each trace state variable collected, the name and
|
||
current value are returned.
|
||
|
||
@item memory
|
||
The set of memory ranges that have been collected at the current trace
|
||
frame. Its content is a list of tuples. Each tuple represents a
|
||
collected memory range and has the following fields:
|
||
|
||
@table @code
|
||
@item address
|
||
The start address of the memory range, as hexadecimal literal.
|
||
|
||
@item length
|
||
The length of the memory range, as decimal literal.
|
||
|
||
@item contents
|
||
The contents of the memory block, in hex. This field is only present
|
||
if the @code{--memory-contents} option is specified.
|
||
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There is no corresponding @value{GDBN} command.
|
||
|
||
@subsubheading Example
|
||
|
||
@subheading -trace-list-variables
|
||
@findex -trace-list-variables
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-list-variables
|
||
@end smallexample
|
||
|
||
Return a table of all defined trace variables. Each element of the
|
||
table has the following fields:
|
||
|
||
@table @samp
|
||
@item name
|
||
The name of the trace variable. This field is always present.
|
||
|
||
@item initial
|
||
The initial value. This is a 64-bit signed integer. This
|
||
field is always present.
|
||
|
||
@item current
|
||
The value the trace variable has at the moment. This is a 64-bit
|
||
signed integer. This field is absent iff current value is
|
||
not defined, for example if the trace was never run, or is
|
||
presently running.
|
||
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tvariables}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-trace-list-variables
|
||
^done,trace-variables=@{nr_rows="1",nr_cols="3",
|
||
hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
|
||
@{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
|
||
@{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
|
||
body=[variable=@{name="$trace_timestamp",initial="0"@}
|
||
variable=@{name="$foo",initial="10",current="15"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading -trace-save
|
||
@findex -trace-save
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-save [ -r ] [ -ctf ] @var{filename}
|
||
@end smallexample
|
||
|
||
Saves the collected trace data to @var{filename}. Without the
|
||
@samp{-r} option, the data is downloaded from the target and saved
|
||
in a local file. With the @samp{-r} option the target is asked
|
||
to perform the save.
|
||
|
||
By default, this command will save the trace in the tfile format. You can
|
||
supply the optional @samp{-ctf} argument to save it the CTF format. See
|
||
@ref{Trace Files} for more information about CTF.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tsave}.
|
||
|
||
|
||
@subheading -trace-start
|
||
@findex -trace-start
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-start
|
||
@end smallexample
|
||
|
||
Starts a tracing experiment. The result of this command does not
|
||
have any fields.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tstart}.
|
||
|
||
@subheading -trace-status
|
||
@findex -trace-status
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-status
|
||
@end smallexample
|
||
|
||
Obtains the status of a tracing experiment. The result may include
|
||
the following fields:
|
||
|
||
@table @samp
|
||
|
||
@item supported
|
||
May have a value of either @samp{0}, when no tracing operations are
|
||
supported, @samp{1}, when all tracing operations are supported, or
|
||
@samp{file} when examining trace file. In the latter case, examining
|
||
of trace frame is possible but new tracing experiement cannot be
|
||
started. This field is always present.
|
||
|
||
@item running
|
||
May have a value of either @samp{0} or @samp{1} depending on whether
|
||
tracing experiement is in progress on target. This field is present
|
||
if @samp{supported} field is not @samp{0}.
|
||
|
||
@item stop-reason
|
||
Report the reason why the tracing was stopped last time. This field
|
||
may be absent iff tracing was never stopped on target yet. The
|
||
value of @samp{request} means the tracing was stopped as result of
|
||
the @code{-trace-stop} command. The value of @samp{overflow} means
|
||
the tracing buffer is full. The value of @samp{disconnection} means
|
||
tracing was automatically stopped when @value{GDBN} has disconnected.
|
||
The value of @samp{passcount} means tracing was stopped when a
|
||
tracepoint was passed a maximal number of times for that tracepoint.
|
||
This field is present if @samp{supported} field is not @samp{0}.
|
||
|
||
@item stopping-tracepoint
|
||
The number of tracepoint whose passcount as exceeded. This field is
|
||
present iff the @samp{stop-reason} field has the value of
|
||
@samp{passcount}.
|
||
|
||
@item frames
|
||
@itemx frames-created
|
||
The @samp{frames} field is a count of the total number of trace frames
|
||
in the trace buffer, while @samp{frames-created} is the total created
|
||
during the run, including ones that were discarded, such as when a
|
||
circular trace buffer filled up. Both fields are optional.
|
||
|
||
@item buffer-size
|
||
@itemx buffer-free
|
||
These fields tell the current size of the tracing buffer and the
|
||
remaining space. These fields are optional.
|
||
|
||
@item circular
|
||
The value of the circular trace buffer flag. @code{1} means that the
|
||
trace buffer is circular and old trace frames will be discarded if
|
||
necessary to make room, @code{0} means that the trace buffer is linear
|
||
and may fill up.
|
||
|
||
@item disconnected
|
||
The value of the disconnected tracing flag. @code{1} means that
|
||
tracing will continue after @value{GDBN} disconnects, @code{0} means
|
||
that the trace run will stop.
|
||
|
||
@item trace-file
|
||
The filename of the trace file being examined. This field is
|
||
optional, and only present when examining a trace file.
|
||
|
||
@end table
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tstatus}.
|
||
|
||
@subheading -trace-stop
|
||
@findex -trace-stop
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-trace-stop
|
||
@end smallexample
|
||
|
||
Stops a tracing experiment. The result of this command has the same
|
||
fields as @code{-trace-status}, except that the @samp{supported} and
|
||
@samp{running} fields are not output.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{tstop}.
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Symbol Query
|
||
@section @sc{gdb/mi} Symbol Query Commands
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-symbol-info-address} Command
|
||
@findex -symbol-info-address
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-info-address @var{symbol}
|
||
@end smallexample
|
||
|
||
Describe where @var{symbol} is stored.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info address}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-info-file} Command
|
||
@findex -symbol-info-file
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-info-file
|
||
@end smallexample
|
||
|
||
Show the file for the symbol.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There's no equivalent @value{GDBN} command. @code{gdbtk} has
|
||
@samp{gdb_find_file}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-info-function} Command
|
||
@findex -symbol-info-function
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-info-function
|
||
@end smallexample
|
||
|
||
Show which function the symbol lives in.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@samp{gdb_get_function} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-info-line} Command
|
||
@findex -symbol-info-line
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-info-line
|
||
@end smallexample
|
||
|
||
Show the core addresses of the code for a source line.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info line}.
|
||
@code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-info-symbol} Command
|
||
@findex -symbol-info-symbol
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-info-symbol @var{addr}
|
||
@end smallexample
|
||
|
||
Describe what symbol is at location @var{addr}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info symbol}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-list-functions} Command
|
||
@findex -symbol-list-functions
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-list-functions
|
||
@end smallexample
|
||
|
||
List the functions in the executable.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
|
||
@samp{gdb_search} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-symbol-list-lines} Command
|
||
@findex -symbol-list-lines
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-list-lines @var{filename}
|
||
@end smallexample
|
||
|
||
Print the list of lines that contain code and their associated program
|
||
addresses for the given source filename. The entries are sorted in
|
||
ascending PC order.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There is no corresponding @value{GDBN} command.
|
||
|
||
@subsubheading Example
|
||
@smallexample
|
||
(gdb)
|
||
-symbol-list-lines basics.c
|
||
^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-symbol-list-types} Command
|
||
@findex -symbol-list-types
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-list-types
|
||
@end smallexample
|
||
|
||
List all the type names.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding commands are @samp{info types} in @value{GDBN},
|
||
@samp{gdb_search} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-list-variables} Command
|
||
@findex -symbol-list-variables
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-list-variables
|
||
@end smallexample
|
||
|
||
List all the global and static variable names.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-locate} Command
|
||
@findex -symbol-locate
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-locate
|
||
@end smallexample
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
@samp{gdb_loc} in @code{gdbtk}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-symbol-type} Command
|
||
@findex -symbol-type
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-symbol-type @var{variable}
|
||
@end smallexample
|
||
|
||
Show type of @var{variable}.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
|
||
@samp{gdb_obj_variable}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI File Commands
|
||
@section @sc{gdb/mi} File Commands
|
||
|
||
This section describes the GDB/MI commands to specify executable file names
|
||
and to read in and obtain symbol table information.
|
||
|
||
@subheading The @code{-file-exec-and-symbols} Command
|
||
@findex -file-exec-and-symbols
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-exec-and-symbols @var{file}
|
||
@end smallexample
|
||
|
||
Specify the executable file to be debugged. This file is the one from
|
||
which the symbol table is also read. If no file is specified, the
|
||
command clears the executable and symbol information. If breakpoints
|
||
are set when using this command with no arguments, @value{GDBN} will produce
|
||
error messages. Otherwise, no output is produced, except a completion
|
||
notification.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{file}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-file-exec-file} Command
|
||
@findex -file-exec-file
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-exec-file @var{file}
|
||
@end smallexample
|
||
|
||
Specify the executable file to be debugged. Unlike
|
||
@samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
|
||
from this file. If used without argument, @value{GDBN} clears the information
|
||
about the executable file. No output is produced, except a completion
|
||
notification.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{exec-file}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-file-list-exec-sections} Command
|
||
@findex -file-list-exec-sections
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-list-exec-sections
|
||
@end smallexample
|
||
|
||
List the sections of the current executable file.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @value{GDBN} command @samp{info file} shows, among the rest, the same
|
||
information as this command. @code{gdbtk} has a corresponding command
|
||
@samp{gdb_load_info}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-file-list-exec-source-file} Command
|
||
@findex -file-list-exec-source-file
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-list-exec-source-file
|
||
@end smallexample
|
||
|
||
List the line number, the current source file, and the absolute path
|
||
to the current source file for the current executable. The macro
|
||
information field has a value of @samp{1} or @samp{0} depending on
|
||
whether or not the file includes preprocessor macro information.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @value{GDBN} equivalent is @samp{info source}
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
123-file-list-exec-source-file
|
||
123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-file-list-exec-source-files} Command
|
||
@findex -file-list-exec-source-files
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-list-exec-source-files
|
||
@end smallexample
|
||
|
||
List the source files for the current executable.
|
||
|
||
It will always output both the filename and fullname (absolute file
|
||
name) of a source file.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @value{GDBN} equivalent is @samp{info sources}.
|
||
@code{gdbtk} has an analogous command @samp{gdb_listfiles}.
|
||
|
||
@subsubheading Example
|
||
@smallexample
|
||
(gdb)
|
||
-file-list-exec-source-files
|
||
^done,files=[
|
||
@{file=foo.c,fullname=/home/foo.c@},
|
||
@{file=/home/bar.c,fullname=/home/bar.c@},
|
||
@{file=gdb_could_not_find_fullpath.c@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-file-list-shared-libraries} Command
|
||
@findex -file-list-shared-libraries
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-list-shared-libraries [ @var{regexp} ]
|
||
@end smallexample
|
||
|
||
List the shared libraries in the program.
|
||
With a regular expression @var{regexp}, only those libraries whose
|
||
names match @var{regexp} are listed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info shared}. The fields
|
||
have a similar meaning to the @code{=library-loaded} notification.
|
||
The @code{ranges} field specifies the multiple segments belonging to this
|
||
library. Each range has the following fields:
|
||
|
||
@table @samp
|
||
@item from
|
||
The address defining the inclusive lower bound of the segment.
|
||
@item to
|
||
The address defining the exclusive upper bound of the segment.
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
@smallexample
|
||
(gdb)
|
||
-file-list-exec-source-files
|
||
^done,shared-libraries=[
|
||
@{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
|
||
@{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-file-list-symbol-files} Command
|
||
@findex -file-list-symbol-files
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-list-symbol-files
|
||
@end smallexample
|
||
|
||
List symbol files.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info file} (part of it).
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-file-symbol-file} Command
|
||
@findex -file-symbol-file
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-file-symbol-file @var{file}
|
||
@end smallexample
|
||
|
||
Read symbol table info from the specified @var{file} argument. When
|
||
used without arguments, clears @value{GDBN}'s symbol table info. No output is
|
||
produced, except for a completion notification.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{symbol-file}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@ignore
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Memory Overlay Commands
|
||
@section @sc{gdb/mi} Memory Overlay Commands
|
||
|
||
The memory overlay commands are not implemented.
|
||
|
||
@c @subheading -overlay-auto
|
||
|
||
@c @subheading -overlay-list-mapping-state
|
||
|
||
@c @subheading -overlay-list-overlays
|
||
|
||
@c @subheading -overlay-map
|
||
|
||
@c @subheading -overlay-off
|
||
|
||
@c @subheading -overlay-on
|
||
|
||
@c @subheading -overlay-unmap
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Signal Handling Commands
|
||
@section @sc{gdb/mi} Signal Handling Commands
|
||
|
||
Signal handling commands are not implemented.
|
||
|
||
@c @subheading -signal-handle
|
||
|
||
@c @subheading -signal-list-handle-actions
|
||
|
||
@c @subheading -signal-list-signal-types
|
||
@end ignore
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Target Manipulation
|
||
@section @sc{gdb/mi} Target Manipulation Commands
|
||
|
||
|
||
@subheading The @code{-target-attach} Command
|
||
@findex -target-attach
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-attach @var{pid} | @var{gid} | @var{file}
|
||
@end smallexample
|
||
|
||
Attach to a process @var{pid} or a file @var{file} outside of
|
||
@value{GDBN}, or a thread group @var{gid}. If attaching to a thread
|
||
group, the id previously returned by
|
||
@samp{-list-thread-groups --available} must be used.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{attach}.
|
||
|
||
@subsubheading Example
|
||
@smallexample
|
||
(gdb)
|
||
-target-attach 34
|
||
=thread-created,id="1"
|
||
*stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@ignore
|
||
@subheading The @code{-target-compare-sections} Command
|
||
@findex -target-compare-sections
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-compare-sections [ @var{section} ]
|
||
@end smallexample
|
||
|
||
Compare data of section @var{section} on target to the exec file.
|
||
Without the argument, all sections are compared.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @value{GDBN} equivalent is @samp{compare-sections}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-target-detach} Command
|
||
@findex -target-detach
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-detach [ @var{pid} | @var{gid} ]
|
||
@end smallexample
|
||
|
||
Detach from the remote target which normally resumes its execution.
|
||
If either @var{pid} or @var{gid} is specified, detaches from either
|
||
the specified process, or specified thread group. There's no output.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{detach}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-detach
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-target-disconnect} Command
|
||
@findex -target-disconnect
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-disconnect
|
||
@end smallexample
|
||
|
||
Disconnect from the remote target. There's no output and the target is
|
||
generally not resumed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{disconnect}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-disconnect
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-target-download} Command
|
||
@findex -target-download
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-download
|
||
@end smallexample
|
||
|
||
Loads the executable onto the remote target.
|
||
It prints out an update message every half second, which includes the fields:
|
||
|
||
@table @samp
|
||
@item section
|
||
The name of the section.
|
||
@item section-sent
|
||
The size of what has been sent so far for that section.
|
||
@item section-size
|
||
The size of the section.
|
||
@item total-sent
|
||
The total size of what was sent so far (the current and the previous sections).
|
||
@item total-size
|
||
The size of the overall executable to download.
|
||
@end table
|
||
|
||
@noindent
|
||
Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
|
||
@sc{gdb/mi} Output Syntax}).
|
||
|
||
In addition, it prints the name and size of the sections, as they are
|
||
downloaded. These messages include the following fields:
|
||
|
||
@table @samp
|
||
@item section
|
||
The name of the section.
|
||
@item section-size
|
||
The size of the section.
|
||
@item total-size
|
||
The size of the overall executable to download.
|
||
@end table
|
||
|
||
@noindent
|
||
At the end, a summary is printed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{load}.
|
||
|
||
@subsubheading Example
|
||
|
||
Note: each status message appears on a single line. Here the messages
|
||
have been broken down so that they can fit onto a page.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-download
|
||
+download,@{section=".text",section-size="6668",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="512",section-size="6668",
|
||
total-sent="512",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="1024",section-size="6668",
|
||
total-sent="1024",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="1536",section-size="6668",
|
||
total-sent="1536",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="2048",section-size="6668",
|
||
total-sent="2048",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="2560",section-size="6668",
|
||
total-sent="2560",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="3072",section-size="6668",
|
||
total-sent="3072",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="3584",section-size="6668",
|
||
total-sent="3584",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="4096",section-size="6668",
|
||
total-sent="4096",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="4608",section-size="6668",
|
||
total-sent="4608",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="5120",section-size="6668",
|
||
total-sent="5120",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="5632",section-size="6668",
|
||
total-sent="5632",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="6144",section-size="6668",
|
||
total-sent="6144",total-size="9880"@}
|
||
+download,@{section=".text",section-sent="6656",section-size="6668",
|
||
total-sent="6656",total-size="9880"@}
|
||
+download,@{section=".init",section-size="28",total-size="9880"@}
|
||
+download,@{section=".fini",section-size="28",total-size="9880"@}
|
||
+download,@{section=".data",section-size="3156",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="512",section-size="3156",
|
||
total-sent="7236",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="1024",section-size="3156",
|
||
total-sent="7748",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="1536",section-size="3156",
|
||
total-sent="8260",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="2048",section-size="3156",
|
||
total-sent="8772",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="2560",section-size="3156",
|
||
total-sent="9284",total-size="9880"@}
|
||
+download,@{section=".data",section-sent="3072",section-size="3156",
|
||
total-sent="9796",total-size="9880"@}
|
||
^done,address="0x10004",load-size="9880",transfer-rate="6586",
|
||
write-rate="429"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-target-exec-status} Command
|
||
@findex -target-exec-status
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-exec-status
|
||
@end smallexample
|
||
|
||
Provide information on the state of the target (whether it is running or
|
||
not, for instance).
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There's no equivalent @value{GDBN} command.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-target-list-available-targets} Command
|
||
@findex -target-list-available-targets
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-list-available-targets
|
||
@end smallexample
|
||
|
||
List the possible targets to connect to.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{help target}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-target-list-current-targets} Command
|
||
@findex -target-list-current-targets
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-list-current-targets
|
||
@end smallexample
|
||
|
||
Describe the current target.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding information is printed by @samp{info file} (among
|
||
other things).
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
|
||
@subheading The @code{-target-list-parameters} Command
|
||
@findex -target-list-parameters
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-list-parameters
|
||
@end smallexample
|
||
|
||
@c ????
|
||
@end ignore
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
No equivalent.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
|
||
@subheading The @code{-target-flash-erase} Command
|
||
@findex -target-flash-erase
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-flash-erase
|
||
@end smallexample
|
||
|
||
Erases all known flash memory regions on the target.
|
||
|
||
The corresponding @value{GDBN} command is @samp{flash-erase}.
|
||
|
||
The output is a list of flash regions that have been erased, with starting
|
||
addresses and memory region sizes.
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-flash-erase
|
||
^done,erased-regions=@{address="0x0",size="0x40000"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-target-select} Command
|
||
@findex -target-select
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-select @var{type} @var{parameters @dots{}}
|
||
@end smallexample
|
||
|
||
Connect @value{GDBN} to the remote target. This command takes two args:
|
||
|
||
@table @samp
|
||
@item @var{type}
|
||
The type of target, for instance @samp{remote}, etc.
|
||
@item @var{parameters}
|
||
Device names, host names and the like. @xref{Target Commands, ,
|
||
Commands for Managing Targets}, for more details.
|
||
@end table
|
||
|
||
The output is a connection notification, followed by the address at
|
||
which the target program is, in the following form:
|
||
|
||
@smallexample
|
||
^connected,addr="@var{address}",func="@var{function name}",
|
||
args=[@var{arg list}]
|
||
@end smallexample
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{target}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-select remote /dev/ttya
|
||
^connected,addr="0xfe00a300",func="??",args=[]
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI File Transfer Commands
|
||
@section @sc{gdb/mi} File Transfer Commands
|
||
|
||
|
||
@subheading The @code{-target-file-put} Command
|
||
@findex -target-file-put
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-file-put @var{hostfile} @var{targetfile}
|
||
@end smallexample
|
||
|
||
Copy file @var{hostfile} from the host system (the machine running
|
||
@value{GDBN}) to @var{targetfile} on the target system.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{remote put}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-file-put localfile remotefile
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-target-file-get} Command
|
||
@findex -target-file-get
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-file-get @var{targetfile} @var{hostfile}
|
||
@end smallexample
|
||
|
||
Copy file @var{targetfile} from the target system to @var{hostfile}
|
||
on the host system.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{remote get}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-file-get remotefile localfile
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-target-file-delete} Command
|
||
@findex -target-file-delete
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-target-file-delete @var{targetfile}
|
||
@end smallexample
|
||
|
||
Delete @var{targetfile} from the target system.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{remote delete}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-target-file-delete remotefile
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Ada Exceptions Commands
|
||
@section Ada Exceptions @sc{gdb/mi} Commands
|
||
|
||
@subheading The @code{-info-ada-exceptions} Command
|
||
@findex -info-ada-exceptions
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-info-ada-exceptions [ @var{regexp}]
|
||
@end smallexample
|
||
|
||
List all Ada exceptions defined within the program being debugged.
|
||
With a regular expression @var{regexp}, only those exceptions whose
|
||
names match @var{regexp} are listed.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info exceptions}.
|
||
|
||
@subsubheading Result
|
||
|
||
The result is a table of Ada exceptions. The following columns are
|
||
defined for each exception:
|
||
|
||
@table @samp
|
||
@item name
|
||
The name of the exception.
|
||
|
||
@item address
|
||
The address of the exception.
|
||
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
-info-ada-exceptions aint
|
||
^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
|
||
hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
|
||
@{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
|
||
body=[@{name="constraint_error",address="0x0000000000613da0"@},
|
||
@{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
|
||
@end smallexample
|
||
|
||
@subheading Catching Ada Exceptions
|
||
|
||
The commands describing how to ask @value{GDBN} to stop when a program
|
||
raises an exception are described at @ref{Ada Exception GDB/MI
|
||
Catchpoint Commands}.
|
||
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Support Commands
|
||
@section @sc{gdb/mi} Support Commands
|
||
|
||
Since new commands and features get regularly added to @sc{gdb/mi},
|
||
some commands are available to help front-ends query the debugger
|
||
about support for these capabilities. Similarly, it is also possible
|
||
to query @value{GDBN} about target support of certain features.
|
||
|
||
@subheading The @code{-info-gdb-mi-command} Command
|
||
@cindex @code{-info-gdb-mi-command}
|
||
@findex -info-gdb-mi-command
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-info-gdb-mi-command @var{cmd_name}
|
||
@end smallexample
|
||
|
||
Query support for the @sc{gdb/mi} command named @var{cmd_name}.
|
||
|
||
Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
|
||
is technically not part of the command name (@pxref{GDB/MI Input
|
||
Syntax}), and thus should be omitted in @var{cmd_name}. However,
|
||
for ease of use, this command also accepts the form with the leading
|
||
dash.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
There is no corresponding @value{GDBN} command.
|
||
|
||
@subsubheading Result
|
||
|
||
The result is a tuple. There is currently only one field:
|
||
|
||
@table @samp
|
||
@item exists
|
||
This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
|
||
@code{"false"} otherwise.
|
||
|
||
@end table
|
||
|
||
@subsubheading Example
|
||
|
||
Here is an example where the @sc{gdb/mi} command does not exist:
|
||
|
||
@smallexample
|
||
-info-gdb-mi-command unsupported-command
|
||
^done,command=@{exists="false"@}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
And here is an example where the @sc{gdb/mi} command is known
|
||
to the debugger:
|
||
|
||
@smallexample
|
||
-info-gdb-mi-command symbol-list-lines
|
||
^done,command=@{exists="true"@}
|
||
@end smallexample
|
||
|
||
@subheading The @code{-list-features} Command
|
||
@findex -list-features
|
||
@cindex supported @sc{gdb/mi} features, list
|
||
|
||
Returns a list of particular features of the MI protocol that
|
||
this version of gdb implements. A feature can be a command,
|
||
or a new field in an output of some command, or even an
|
||
important bugfix. While a frontend can sometimes detect presence
|
||
of a feature at runtime, it is easier to perform detection at debugger
|
||
startup.
|
||
|
||
The command returns a list of strings, with each string naming an
|
||
available feature. Each returned string is just a name, it does not
|
||
have any internal structure. The list of possible feature names
|
||
is given below.
|
||
|
||
Example output:
|
||
|
||
@smallexample
|
||
(gdb) -list-features
|
||
^done,result=["feature1","feature2"]
|
||
@end smallexample
|
||
|
||
The current list of features is:
|
||
|
||
@ftable @samp
|
||
@item frozen-varobjs
|
||
Indicates support for the @code{-var-set-frozen} command, as well
|
||
as possible presense of the @code{frozen} field in the output
|
||
of @code{-varobj-create}.
|
||
@item pending-breakpoints
|
||
Indicates support for the @option{-f} option to the @code{-break-insert}
|
||
command.
|
||
@item python
|
||
Indicates Python scripting support, Python-based
|
||
pretty-printing commands, and possible presence of the
|
||
@samp{display_hint} field in the output of @code{-var-list-children}
|
||
@item thread-info
|
||
Indicates support for the @code{-thread-info} command.
|
||
@item data-read-memory-bytes
|
||
Indicates support for the @code{-data-read-memory-bytes} and the
|
||
@code{-data-write-memory-bytes} commands.
|
||
@item breakpoint-notifications
|
||
Indicates that changes to breakpoints and breakpoints created via the
|
||
CLI will be announced via async records.
|
||
@item ada-task-info
|
||
Indicates support for the @code{-ada-task-info} command.
|
||
@item language-option
|
||
Indicates that all @sc{gdb/mi} commands accept the @option{--language}
|
||
option (@pxref{Context management}).
|
||
@item info-gdb-mi-command
|
||
Indicates support for the @code{-info-gdb-mi-command} command.
|
||
@item undefined-command-error-code
|
||
Indicates support for the "undefined-command" error code in error result
|
||
records, produced when trying to execute an undefined @sc{gdb/mi} command
|
||
(@pxref{GDB/MI Result Records}).
|
||
@item exec-run-start-option
|
||
Indicates that the @code{-exec-run} command supports the @option{--start}
|
||
option (@pxref{GDB/MI Program Execution}).
|
||
@end ftable
|
||
|
||
@subheading The @code{-list-target-features} Command
|
||
@findex -list-target-features
|
||
|
||
Returns a list of particular features that are supported by the
|
||
target. Those features affect the permitted MI commands, but
|
||
unlike the features reported by the @code{-list-features} command, the
|
||
features depend on which target GDB is using at the moment. Whenever
|
||
a target can change, due to commands such as @code{-target-select},
|
||
@code{-target-attach} or @code{-exec-run}, the list of target features
|
||
may change, and the frontend should obtain it again.
|
||
Example output:
|
||
|
||
@smallexample
|
||
(gdb) -list-target-features
|
||
^done,result=["async"]
|
||
@end smallexample
|
||
|
||
The current list of features is:
|
||
|
||
@table @samp
|
||
@item async
|
||
Indicates that the target is capable of asynchronous command
|
||
execution, which means that @value{GDBN} will accept further commands
|
||
while the target is running.
|
||
|
||
@item reverse
|
||
Indicates that the target is capable of reverse execution.
|
||
@xref{Reverse Execution}, for more information.
|
||
|
||
@end table
|
||
|
||
@c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||
@node GDB/MI Miscellaneous Commands
|
||
@section Miscellaneous @sc{gdb/mi} Commands
|
||
|
||
@c @subheading -gdb-complete
|
||
|
||
@subheading The @code{-gdb-exit} Command
|
||
@findex -gdb-exit
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-gdb-exit
|
||
@end smallexample
|
||
|
||
Exit @value{GDBN} immediately.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
Approximately corresponds to @samp{quit}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-gdb-exit
|
||
^exit
|
||
@end smallexample
|
||
|
||
|
||
@ignore
|
||
@subheading The @code{-exec-abort} Command
|
||
@findex -exec-abort
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-exec-abort
|
||
@end smallexample
|
||
|
||
Kill the inferior running program.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{kill}.
|
||
|
||
@subsubheading Example
|
||
N.A.
|
||
@end ignore
|
||
|
||
|
||
@subheading The @code{-gdb-set} Command
|
||
@findex -gdb-set
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-gdb-set
|
||
@end smallexample
|
||
|
||
Set an internal @value{GDBN} variable.
|
||
@c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{set}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-gdb-set $foo=3
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
|
||
@subheading The @code{-gdb-show} Command
|
||
@findex -gdb-show
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-gdb-show
|
||
@end smallexample
|
||
|
||
Show the current value of a @value{GDBN} variable.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{show}.
|
||
|
||
@subsubheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-gdb-show annotate
|
||
^done,value="0"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@c @subheading -gdb-source
|
||
|
||
|
||
@subheading The @code{-gdb-version} Command
|
||
@findex -gdb-version
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-gdb-version
|
||
@end smallexample
|
||
|
||
Show version information for @value{GDBN}. Used mostly in testing.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
|
||
default shows this information when you start an interactive session.
|
||
|
||
@subsubheading Example
|
||
|
||
@c This example modifies the actual output from GDB to avoid overfull
|
||
@c box in TeX.
|
||
@smallexample
|
||
(gdb)
|
||
-gdb-version
|
||
~GNU gdb 5.2.1
|
||
~Copyright 2000 Free Software Foundation, Inc.
|
||
~GDB is free software, covered by the GNU General Public License, and
|
||
~you are welcome to change it and/or distribute copies of it under
|
||
~ certain conditions.
|
||
~Type "show copying" to see the conditions.
|
||
~There is absolutely no warranty for GDB. Type "show warranty" for
|
||
~ details.
|
||
~This GDB was configured as
|
||
"--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-list-thread-groups} Command
|
||
@findex -list-thread-groups
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
|
||
@end smallexample
|
||
|
||
Lists thread groups (@pxref{Thread groups}). When a single thread
|
||
group is passed as the argument, lists the children of that group.
|
||
When several thread group are passed, lists information about those
|
||
thread groups. Without any parameters, lists information about all
|
||
top-level thread groups.
|
||
|
||
Normally, thread groups that are being debugged are reported.
|
||
With the @samp{--available} option, @value{GDBN} reports thread groups
|
||
available on the target.
|
||
|
||
The output of this command may have either a @samp{threads} result or
|
||
a @samp{groups} result. The @samp{thread} result has a list of tuples
|
||
as value, with each tuple describing a thread (@pxref{GDB/MI Thread
|
||
Information}). The @samp{groups} result has a list of tuples as value,
|
||
each tuple describing a thread group. If top-level groups are
|
||
requested (that is, no parameter is passed), or when several groups
|
||
are passed, the output always has a @samp{groups} result. The format
|
||
of the @samp{group} result is described below.
|
||
|
||
To reduce the number of roundtrips it's possible to list thread groups
|
||
together with their children, by passing the @samp{--recurse} option
|
||
and the recursion depth. Presently, only recursion depth of 1 is
|
||
permitted. If this option is present, then every reported thread group
|
||
will also include its children, either as @samp{group} or
|
||
@samp{threads} field.
|
||
|
||
In general, any combination of option and parameters is permitted, with
|
||
the following caveats:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
When a single thread group is passed, the output will typically
|
||
be the @samp{threads} result. Because threads may not contain
|
||
anything, the @samp{recurse} option will be ignored.
|
||
|
||
@item
|
||
When the @samp{--available} option is passed, limited information may
|
||
be available. In particular, the list of threads of a process might
|
||
be inaccessible. Further, specifying specific thread groups might
|
||
not give any performance advantage over listing all thread groups.
|
||
The frontend should assume that @samp{-list-thread-groups --available}
|
||
is always an expensive operation and cache the results.
|
||
|
||
@end itemize
|
||
|
||
The @samp{groups} result is a list of tuples, where each tuple may
|
||
have the following fields:
|
||
|
||
@table @code
|
||
@item id
|
||
Identifier of the thread group. This field is always present.
|
||
The identifier is an opaque string; frontends should not try to
|
||
convert it to an integer, even though it might look like one.
|
||
|
||
@item type
|
||
The type of the thread group. At present, only @samp{process} is a
|
||
valid type.
|
||
|
||
@item pid
|
||
The target-specific process identifier. This field is only present
|
||
for thread groups of type @samp{process} and only if the process exists.
|
||
|
||
@item exit-code
|
||
The exit code of this group's last exited thread, formatted in octal.
|
||
This field is only present for thread groups of type @samp{process} and
|
||
only if the process is not running.
|
||
|
||
@item num_children
|
||
The number of children this thread group has. This field may be
|
||
absent for an available thread group.
|
||
|
||
@item threads
|
||
This field has a list of tuples as value, each tuple describing a
|
||
thread. It may be present if the @samp{--recurse} option is
|
||
specified, and it's actually possible to obtain the threads.
|
||
|
||
@item cores
|
||
This field is a list of integers, each identifying a core that one
|
||
thread of the group is running on. This field may be absent if
|
||
such information is not available.
|
||
|
||
@item executable
|
||
The name of the executable file that corresponds to this thread group.
|
||
The field is only present for thread groups of type @samp{process},
|
||
and only if there is a corresponding executable file.
|
||
|
||
@end table
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
@value{GDBP}
|
||
-list-thread-groups
|
||
^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
|
||
-list-thread-groups 17
|
||
^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
|
||
frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
|
||
@{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
|
||
frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
|
||
file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
|
||
-list-thread-groups --available
|
||
^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
|
||
-list-thread-groups --available --recurse 1
|
||
^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
|
||
threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
|
||
@{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
|
||
-list-thread-groups --available --recurse 1 17 18
|
||
^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
|
||
threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
|
||
@{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
|
||
@end smallexample
|
||
|
||
@subheading The @code{-info-os} Command
|
||
@findex -info-os
|
||
|
||
@subsubheading Synopsis
|
||
|
||
@smallexample
|
||
-info-os [ @var{type} ]
|
||
@end smallexample
|
||
|
||
If no argument is supplied, the command returns a table of available
|
||
operating-system-specific information types. If one of these types is
|
||
supplied as an argument @var{type}, then the command returns a table
|
||
of data of that type.
|
||
|
||
The types of information available depend on the target operating
|
||
system.
|
||
|
||
@subsubheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{info os}.
|
||
|
||
@subsubheading Example
|
||
|
||
When run on a @sc{gnu}/Linux system, the output will look something
|
||
like this:
|
||
|
||
@smallexample
|
||
@value{GDBP}
|
||
-info-os
|
||
^done,OSDataTable=@{nr_rows="10",nr_cols="3",
|
||
hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
|
||
@{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
|
||
@{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
|
||
body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
|
||
col2="CPUs"@},
|
||
item=@{col0="files",col1="Listing of all file descriptors",
|
||
col2="File descriptors"@},
|
||
item=@{col0="modules",col1="Listing of all loaded kernel modules",
|
||
col2="Kernel modules"@},
|
||
item=@{col0="msg",col1="Listing of all message queues",
|
||
col2="Message queues"@},
|
||
item=@{col0="processes",col1="Listing of all processes",
|
||
col2="Processes"@},
|
||
item=@{col0="procgroups",col1="Listing of all process groups",
|
||
col2="Process groups"@},
|
||
item=@{col0="semaphores",col1="Listing of all semaphores",
|
||
col2="Semaphores"@},
|
||
item=@{col0="shm",col1="Listing of all shared-memory regions",
|
||
col2="Shared-memory regions"@},
|
||
item=@{col0="sockets",col1="Listing of all internet-domain sockets",
|
||
col2="Sockets"@},
|
||
item=@{col0="threads",col1="Listing of all threads",
|
||
col2="Threads"@}]
|
||
@value{GDBP}
|
||
-info-os processes
|
||
^done,OSDataTable=@{nr_rows="190",nr_cols="4",
|
||
hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
|
||
@{width="10",alignment="-1",col_name="col1",colhdr="user"@},
|
||
@{width="10",alignment="-1",col_name="col2",colhdr="command"@},
|
||
@{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
|
||
body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
|
||
item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
|
||
item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
|
||
...
|
||
item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
|
||
item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
(Note that the MI output here includes a @code{"Title"} column that
|
||
does not appear in command-line @code{info os}; this column is useful
|
||
for MI clients that want to enumerate the types of data, such as in a
|
||
popup menu, but is needless clutter on the command line, and
|
||
@code{info os} omits it.)
|
||
|
||
@subheading The @code{-add-inferior} Command
|
||
@findex -add-inferior
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-add-inferior
|
||
@end smallexample
|
||
|
||
Creates a new inferior (@pxref{Inferiors and Programs}). The created
|
||
inferior is not associated with any executable. Such association may
|
||
be established with the @samp{-file-exec-and-symbols} command
|
||
(@pxref{GDB/MI File Commands}). The command response has a single
|
||
field, @samp{inferior}, whose value is the identifier of the
|
||
thread group corresponding to the new inferior.
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
@value{GDBP}
|
||
-add-inferior
|
||
^done,inferior="i3"
|
||
@end smallexample
|
||
|
||
@subheading The @code{-interpreter-exec} Command
|
||
@findex -interpreter-exec
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-interpreter-exec @var{interpreter} @var{command}
|
||
@end smallexample
|
||
@anchor{-interpreter-exec}
|
||
|
||
Execute the specified @var{command} in the given @var{interpreter}.
|
||
|
||
@subheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{interpreter-exec}.
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-interpreter-exec console "break main"
|
||
&"During symbol reading, couldn't parse type; debugger out of date?.\n"
|
||
&"During symbol reading, bad structure-type format.\n"
|
||
~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-inferior-tty-set} Command
|
||
@findex -inferior-tty-set
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-inferior-tty-set /dev/pts/1
|
||
@end smallexample
|
||
|
||
Set terminal for future runs of the program being debugged.
|
||
|
||
@subheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-inferior-tty-set /dev/pts/1
|
||
^done
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-inferior-tty-show} Command
|
||
@findex -inferior-tty-show
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-inferior-tty-show
|
||
@end smallexample
|
||
|
||
Show terminal for future runs of program being debugged.
|
||
|
||
@subheading @value{GDBN} Command
|
||
|
||
The corresponding @value{GDBN} command is @samp{show inferior-tty}.
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-inferior-tty-set /dev/pts/1
|
||
^done
|
||
(gdb)
|
||
-inferior-tty-show
|
||
^done,inferior_tty_terminal="/dev/pts/1"
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@subheading The @code{-enable-timings} Command
|
||
@findex -enable-timings
|
||
|
||
@subheading Synopsis
|
||
|
||
@smallexample
|
||
-enable-timings [yes | no]
|
||
@end smallexample
|
||
|
||
Toggle the printing of the wallclock, user and system times for an MI
|
||
command as a field in its output. This command is to help frontend
|
||
developers optimize the performance of their code. No argument is
|
||
equivalent to @samp{yes}.
|
||
|
||
@subheading @value{GDBN} Command
|
||
|
||
No equivalent.
|
||
|
||
@subheading Example
|
||
|
||
@smallexample
|
||
(gdb)
|
||
-enable-timings
|
||
^done
|
||
(gdb)
|
||
-break-insert main
|
||
^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
|
||
addr="0x080484ed",func="main",file="myprog.c",
|
||
fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
|
||
times="0"@},
|
||
time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
|
||
(gdb)
|
||
-enable-timings no
|
||
^done
|
||
(gdb)
|
||
-exec-run
|
||
^running
|
||
(gdb)
|
||
*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
|
||
frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
|
||
@{name="argv",value="0xbfb60364"@}],file="myprog.c",
|
||
fullname="/home/nickrob/myprog.c",line="73"@}
|
||
(gdb)
|
||
@end smallexample
|
||
|
||
@node Annotations
|
||
@chapter @value{GDBN} Annotations
|
||
|
||
This chapter describes annotations in @value{GDBN}. Annotations were
|
||
designed to interface @value{GDBN} to graphical user interfaces or other
|
||
similar programs which want to interact with @value{GDBN} at a
|
||
relatively high level.
|
||
|
||
The annotation mechanism has largely been superseded by @sc{gdb/mi}
|
||
(@pxref{GDB/MI}).
|
||
|
||
@ignore
|
||
This is Edition @value{EDITION}, @value{DATE}.
|
||
@end ignore
|
||
|
||
@menu
|
||
* Annotations Overview:: What annotations are; the general syntax.
|
||
* Server Prefix:: Issuing a command without affecting user state.
|
||
* Prompting:: Annotations marking @value{GDBN}'s need for input.
|
||
* Errors:: Annotations for error messages.
|
||
* Invalidation:: Some annotations describe things now invalid.
|
||
* Annotations for Running::
|
||
Whether the program is running, how it stopped, etc.
|
||
* Source Annotations:: Annotations describing source code.
|
||
@end menu
|
||
|
||
@node Annotations Overview
|
||
@section What is an Annotation?
|
||
@cindex annotations
|
||
|
||
Annotations start with a newline character, two @samp{control-z}
|
||
characters, and the name of the annotation. If there is no additional
|
||
information associated with this annotation, the name of the annotation
|
||
is followed immediately by a newline. If there is additional
|
||
information, the name of the annotation is followed by a space, the
|
||
additional information, and a newline. The additional information
|
||
cannot contain newline characters.
|
||
|
||
Any output not beginning with a newline and two @samp{control-z}
|
||
characters denotes literal output from @value{GDBN}. Currently there is
|
||
no need for @value{GDBN} to output a newline followed by two
|
||
@samp{control-z} characters, but if there was such a need, the
|
||
annotations could be extended with an @samp{escape} annotation which
|
||
means those three characters as output.
|
||
|
||
The annotation @var{level}, which is specified using the
|
||
@option{--annotate} command line option (@pxref{Mode Options}), controls
|
||
how much information @value{GDBN} prints together with its prompt,
|
||
values of expressions, source lines, and other types of output. Level 0
|
||
is for no annotations, level 1 is for use when @value{GDBN} is run as a
|
||
subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
|
||
for programs that control @value{GDBN}, and level 2 annotations have
|
||
been made obsolete (@pxref{Limitations, , Limitations of the Annotation
|
||
Interface, annotate, GDB's Obsolete Annotations}).
|
||
|
||
@table @code
|
||
@kindex set annotate
|
||
@item set annotate @var{level}
|
||
The @value{GDBN} command @code{set annotate} sets the level of
|
||
annotations to the specified @var{level}.
|
||
|
||
@item show annotate
|
||
@kindex show annotate
|
||
Show the current annotation level.
|
||
@end table
|
||
|
||
This chapter describes level 3 annotations.
|
||
|
||
A simple example of starting up @value{GDBN} with annotations is:
|
||
|
||
@smallexample
|
||
$ @kbd{gdb --annotate=3}
|
||
GNU gdb 6.0
|
||
Copyright 2003 Free Software Foundation, Inc.
|
||
GDB is free software, covered by the GNU General Public License,
|
||
and you are welcome to change it and/or distribute copies of it
|
||
under certain conditions.
|
||
Type "show copying" to see the conditions.
|
||
There is absolutely no warranty for GDB. Type "show warranty"
|
||
for details.
|
||
This GDB was configured as "i386-pc-linux-gnu"
|
||
|
||
^Z^Zpre-prompt
|
||
(@value{GDBP})
|
||
^Z^Zprompt
|
||
@kbd{quit}
|
||
|
||
^Z^Zpost-prompt
|
||
$
|
||
@end smallexample
|
||
|
||
Here @samp{quit} is input to @value{GDBN}; the rest is output from
|
||
@value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
|
||
denotes a @samp{control-z} character) are annotations; the rest is
|
||
output from @value{GDBN}.
|
||
|
||
@node Server Prefix
|
||
@section The Server Prefix
|
||
@cindex server prefix
|
||
|
||
If you prefix a command with @samp{server } then it will not affect
|
||
the command history, nor will it affect @value{GDBN}'s notion of which
|
||
command to repeat if @key{RET} is pressed on a line by itself. This
|
||
means that commands can be run behind a user's back by a front-end in
|
||
a transparent manner.
|
||
|
||
The @code{server } prefix does not affect the recording of values into
|
||
the value history; to print a value without recording it into the
|
||
value history, use the @code{output} command instead of the
|
||
@code{print} command.
|
||
|
||
Using this prefix also disables confirmation requests
|
||
(@pxref{confirmation requests}).
|
||
|
||
@node Prompting
|
||
@section Annotation for @value{GDBN} Input
|
||
|
||
@cindex annotations for prompts
|
||
When @value{GDBN} prompts for input, it annotates this fact so it is possible
|
||
to know when to send output, when the output from a given command is
|
||
over, etc.
|
||
|
||
Different kinds of input each have a different @dfn{input type}. Each
|
||
input type has three annotations: a @code{pre-} annotation, which
|
||
denotes the beginning of any prompt which is being output, a plain
|
||
annotation, which denotes the end of the prompt, and then a @code{post-}
|
||
annotation which denotes the end of any echo which may (or may not) be
|
||
associated with the input. For example, the @code{prompt} input type
|
||
features the following annotations:
|
||
|
||
@smallexample
|
||
^Z^Zpre-prompt
|
||
^Z^Zprompt
|
||
^Z^Zpost-prompt
|
||
@end smallexample
|
||
|
||
The input types are
|
||
|
||
@table @code
|
||
@findex pre-prompt annotation
|
||
@findex prompt annotation
|
||
@findex post-prompt annotation
|
||
@item prompt
|
||
When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
|
||
|
||
@findex pre-commands annotation
|
||
@findex commands annotation
|
||
@findex post-commands annotation
|
||
@item commands
|
||
When @value{GDBN} prompts for a set of commands, like in the @code{commands}
|
||
command. The annotations are repeated for each command which is input.
|
||
|
||
@findex pre-overload-choice annotation
|
||
@findex overload-choice annotation
|
||
@findex post-overload-choice annotation
|
||
@item overload-choice
|
||
When @value{GDBN} wants the user to select between various overloaded functions.
|
||
|
||
@findex pre-query annotation
|
||
@findex query annotation
|
||
@findex post-query annotation
|
||
@item query
|
||
When @value{GDBN} wants the user to confirm a potentially dangerous operation.
|
||
|
||
@findex pre-prompt-for-continue annotation
|
||
@findex prompt-for-continue annotation
|
||
@findex post-prompt-for-continue annotation
|
||
@item prompt-for-continue
|
||
When @value{GDBN} is asking the user to press return to continue. Note: Don't
|
||
expect this to work well; instead use @code{set height 0} to disable
|
||
prompting. This is because the counting of lines is buggy in the
|
||
presence of annotations.
|
||
@end table
|
||
|
||
@node Errors
|
||
@section Errors
|
||
@cindex annotations for errors, warnings and interrupts
|
||
|
||
@findex quit annotation
|
||
@smallexample
|
||
^Z^Zquit
|
||
@end smallexample
|
||
|
||
This annotation occurs right before @value{GDBN} responds to an interrupt.
|
||
|
||
@findex error annotation
|
||
@smallexample
|
||
^Z^Zerror
|
||
@end smallexample
|
||
|
||
This annotation occurs right before @value{GDBN} responds to an error.
|
||
|
||
Quit and error annotations indicate that any annotations which @value{GDBN} was
|
||
in the middle of may end abruptly. For example, if a
|
||
@code{value-history-begin} annotation is followed by a @code{error}, one
|
||
cannot expect to receive the matching @code{value-history-end}. One
|
||
cannot expect not to receive it either, however; an error annotation
|
||
does not necessarily mean that @value{GDBN} is immediately returning all the way
|
||
to the top level.
|
||
|
||
@findex error-begin annotation
|
||
A quit or error annotation may be preceded by
|
||
|
||
@smallexample
|
||
^Z^Zerror-begin
|
||
@end smallexample
|
||
|
||
Any output between that and the quit or error annotation is the error
|
||
message.
|
||
|
||
Warning messages are not yet annotated.
|
||
@c If we want to change that, need to fix warning(), type_error(),
|
||
@c range_error(), and possibly other places.
|
||
|
||
@node Invalidation
|
||
@section Invalidation Notices
|
||
|
||
@cindex annotations for invalidation messages
|
||
The following annotations say that certain pieces of state may have
|
||
changed.
|
||
|
||
@table @code
|
||
@findex frames-invalid annotation
|
||
@item ^Z^Zframes-invalid
|
||
|
||
The frames (for example, output from the @code{backtrace} command) may
|
||
have changed.
|
||
|
||
@findex breakpoints-invalid annotation
|
||
@item ^Z^Zbreakpoints-invalid
|
||
|
||
The breakpoints may have changed. For example, the user just added or
|
||
deleted a breakpoint.
|
||
@end table
|
||
|
||
@node Annotations for Running
|
||
@section Running the Program
|
||
@cindex annotations for running programs
|
||
|
||
@findex starting annotation
|
||
@findex stopping annotation
|
||
When the program starts executing due to a @value{GDBN} command such as
|
||
@code{step} or @code{continue},
|
||
|
||
@smallexample
|
||
^Z^Zstarting
|
||
@end smallexample
|
||
|
||
is output. When the program stops,
|
||
|
||
@smallexample
|
||
^Z^Zstopped
|
||
@end smallexample
|
||
|
||
is output. Before the @code{stopped} annotation, a variety of
|
||
annotations describe how the program stopped.
|
||
|
||
@table @code
|
||
@findex exited annotation
|
||
@item ^Z^Zexited @var{exit-status}
|
||
The program exited, and @var{exit-status} is the exit status (zero for
|
||
successful exit, otherwise nonzero).
|
||
|
||
@findex signalled annotation
|
||
@findex signal-name annotation
|
||
@findex signal-name-end annotation
|
||
@findex signal-string annotation
|
||
@findex signal-string-end annotation
|
||
@item ^Z^Zsignalled
|
||
The program exited with a signal. After the @code{^Z^Zsignalled}, the
|
||
annotation continues:
|
||
|
||
@smallexample
|
||
@var{intro-text}
|
||
^Z^Zsignal-name
|
||
@var{name}
|
||
^Z^Zsignal-name-end
|
||
@var{middle-text}
|
||
^Z^Zsignal-string
|
||
@var{string}
|
||
^Z^Zsignal-string-end
|
||
@var{end-text}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where @var{name} is the name of the signal, such as @code{SIGILL} or
|
||
@code{SIGSEGV}, and @var{string} is the explanation of the signal, such
|
||
as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
|
||
@var{intro-text}, @var{middle-text}, and @var{end-text} are for the
|
||
user's benefit and have no particular format.
|
||
|
||
@findex signal annotation
|
||
@item ^Z^Zsignal
|
||
The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
|
||
just saying that the program received the signal, not that it was
|
||
terminated with it.
|
||
|
||
@findex breakpoint annotation
|
||
@item ^Z^Zbreakpoint @var{number}
|
||
The program hit breakpoint number @var{number}.
|
||
|
||
@findex watchpoint annotation
|
||
@item ^Z^Zwatchpoint @var{number}
|
||
The program hit watchpoint number @var{number}.
|
||
@end table
|
||
|
||
@node Source Annotations
|
||
@section Displaying Source
|
||
@cindex annotations for source display
|
||
|
||
@findex source annotation
|
||
The following annotation is used instead of displaying source code:
|
||
|
||
@smallexample
|
||
^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
|
||
@end smallexample
|
||
|
||
where @var{filename} is an absolute file name indicating which source
|
||
file, @var{line} is the line number within that file (where 1 is the
|
||
first line in the file), @var{character} is the character position
|
||
within the file (where 0 is the first character in the file) (for most
|
||
debug formats this will necessarily point to the beginning of a line),
|
||
@var{middle} is @samp{middle} if @var{addr} is in the middle of the
|
||
line, or @samp{beg} if @var{addr} is at the beginning of the line, and
|
||
@var{addr} is the address in the target program associated with the
|
||
source which is being displayed. The @var{addr} is in the form @samp{0x}
|
||
followed by one or more lowercase hex digits (note that this does not
|
||
depend on the language).
|
||
|
||
@node JIT Interface
|
||
@chapter JIT Compilation Interface
|
||
@cindex just-in-time compilation
|
||
@cindex JIT compilation interface
|
||
|
||
This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
|
||
interface. A JIT compiler is a program or library that generates native
|
||
executable code at runtime and executes it, usually in order to achieve good
|
||
performance while maintaining platform independence.
|
||
|
||
Programs that use JIT compilation are normally difficult to debug because
|
||
portions of their code are generated at runtime, instead of being loaded from
|
||
object files, which is where @value{GDBN} normally finds the program's symbols
|
||
and debug information. In order to debug programs that use JIT compilation,
|
||
@value{GDBN} has an interface that allows the program to register in-memory
|
||
symbol files with @value{GDBN} at runtime.
|
||
|
||
If you are using @value{GDBN} to debug a program that uses this interface, then
|
||
it should work transparently so long as you have not stripped the binary. If
|
||
you are developing a JIT compiler, then the interface is documented in the rest
|
||
of this chapter. At this time, the only known client of this interface is the
|
||
LLVM JIT.
|
||
|
||
Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
|
||
JIT compiler communicates with @value{GDBN} by writing data into a global
|
||
variable and calling a fuction at a well-known symbol. When @value{GDBN}
|
||
attaches, it reads a linked list of symbol files from the global variable to
|
||
find existing code, and puts a breakpoint in the function so that it can find
|
||
out about additional code.
|
||
|
||
@menu
|
||
* Declarations:: Relevant C struct declarations
|
||
* Registering Code:: Steps to register code
|
||
* Unregistering Code:: Steps to unregister code
|
||
* Custom Debug Info:: Emit debug information in a custom format
|
||
@end menu
|
||
|
||
@node Declarations
|
||
@section JIT Declarations
|
||
|
||
These are the relevant struct declarations that a C program should include to
|
||
implement the interface:
|
||
|
||
@smallexample
|
||
typedef enum
|
||
@{
|
||
JIT_NOACTION = 0,
|
||
JIT_REGISTER_FN,
|
||
JIT_UNREGISTER_FN
|
||
@} jit_actions_t;
|
||
|
||
struct jit_code_entry
|
||
@{
|
||
struct jit_code_entry *next_entry;
|
||
struct jit_code_entry *prev_entry;
|
||
const char *symfile_addr;
|
||
uint64_t symfile_size;
|
||
@};
|
||
|
||
struct jit_descriptor
|
||
@{
|
||
uint32_t version;
|
||
/* This type should be jit_actions_t, but we use uint32_t
|
||
to be explicit about the bitwidth. */
|
||
uint32_t action_flag;
|
||
struct jit_code_entry *relevant_entry;
|
||
struct jit_code_entry *first_entry;
|
||
@};
|
||
|
||
/* GDB puts a breakpoint in this function. */
|
||
void __attribute__((noinline)) __jit_debug_register_code() @{ @};
|
||
|
||
/* Make sure to specify the version statically, because the
|
||
debugger may check the version before we can set it. */
|
||
struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
|
||
@end smallexample
|
||
|
||
If the JIT is multi-threaded, then it is important that the JIT synchronize any
|
||
modifications to this global data properly, which can easily be done by putting
|
||
a global mutex around modifications to these structures.
|
||
|
||
@node Registering Code
|
||
@section Registering Code
|
||
|
||
To register code with @value{GDBN}, the JIT should follow this protocol:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Generate an object file in memory with symbols and other desired debug
|
||
information. The file must include the virtual addresses of the sections.
|
||
|
||
@item
|
||
Create a code entry for the file, which gives the start and size of the symbol
|
||
file.
|
||
|
||
@item
|
||
Add it to the linked list in the JIT descriptor.
|
||
|
||
@item
|
||
Point the relevant_entry field of the descriptor at the entry.
|
||
|
||
@item
|
||
Set @code{action_flag} to @code{JIT_REGISTER} and call
|
||
@code{__jit_debug_register_code}.
|
||
@end itemize
|
||
|
||
When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
|
||
@code{relevant_entry} pointer so it doesn't have to walk the list looking for
|
||
new code. However, the linked list must still be maintained in order to allow
|
||
@value{GDBN} to attach to a running process and still find the symbol files.
|
||
|
||
@node Unregistering Code
|
||
@section Unregistering Code
|
||
|
||
If code is freed, then the JIT should use the following protocol:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Remove the code entry corresponding to the code from the linked list.
|
||
|
||
@item
|
||
Point the @code{relevant_entry} field of the descriptor at the code entry.
|
||
|
||
@item
|
||
Set @code{action_flag} to @code{JIT_UNREGISTER} and call
|
||
@code{__jit_debug_register_code}.
|
||
@end itemize
|
||
|
||
If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
|
||
and the JIT will leak the memory used for the associated symbol files.
|
||
|
||
@node Custom Debug Info
|
||
@section Custom Debug Info
|
||
@cindex custom JIT debug info
|
||
@cindex JIT debug info reader
|
||
|
||
Generating debug information in platform-native file formats (like ELF
|
||
or COFF) may be an overkill for JIT compilers; especially if all the
|
||
debug info is used for is displaying a meaningful backtrace. The
|
||
issue can be resolved by having the JIT writers decide on a debug info
|
||
format and also provide a reader that parses the debug info generated
|
||
by the JIT compiler. This section gives a brief overview on writing
|
||
such a parser. More specific details can be found in the source file
|
||
@file{gdb/jit-reader.in}, which is also installed as a header at
|
||
@file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
|
||
|
||
The reader is implemented as a shared object (so this functionality is
|
||
not available on platforms which don't allow loading shared objects at
|
||
runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
|
||
@code{jit-reader-unload} are provided, to be used to load and unload
|
||
the readers from a preconfigured directory. Once loaded, the shared
|
||
object is used the parse the debug information emitted by the JIT
|
||
compiler.
|
||
|
||
@menu
|
||
* Using JIT Debug Info Readers:: How to use supplied readers correctly
|
||
* Writing JIT Debug Info Readers:: Creating a debug-info reader
|
||
@end menu
|
||
|
||
@node Using JIT Debug Info Readers
|
||
@subsection Using JIT Debug Info Readers
|
||
@kindex jit-reader-load
|
||
@kindex jit-reader-unload
|
||
|
||
Readers can be loaded and unloaded using the @code{jit-reader-load}
|
||
and @code{jit-reader-unload} commands.
|
||
|
||
@table @code
|
||
@item jit-reader-load @var{reader}
|
||
Load the JIT reader named @var{reader}, which is a shared
|
||
object specified as either an absolute or a relative file name. In
|
||
the latter case, @value{GDBN} will try to load the reader from a
|
||
pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
|
||
system (here @var{libdir} is the system library directory, often
|
||
@file{/usr/local/lib}).
|
||
|
||
Only one reader can be active at a time; trying to load a second
|
||
reader when one is already loaded will result in @value{GDBN}
|
||
reporting an error. A new JIT reader can be loaded by first unloading
|
||
the current one using @code{jit-reader-unload} and then invoking
|
||
@code{jit-reader-load}.
|
||
|
||
@item jit-reader-unload
|
||
Unload the currently loaded JIT reader.
|
||
|
||
@end table
|
||
|
||
@node Writing JIT Debug Info Readers
|
||
@subsection Writing JIT Debug Info Readers
|
||
@cindex writing JIT debug info readers
|
||
|
||
As mentioned, a reader is essentially a shared object conforming to a
|
||
certain ABI. This ABI is described in @file{jit-reader.h}.
|
||
|
||
@file{jit-reader.h} defines the structures, macros and functions
|
||
required to write a reader. It is installed (along with
|
||
@value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
|
||
the system include directory.
|
||
|
||
Readers need to be released under a GPL compatible license. A reader
|
||
can be declared as released under such a license by placing the macro
|
||
@code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
|
||
|
||
The entry point for readers is the symbol @code{gdb_init_reader},
|
||
which is expected to be a function with the prototype
|
||
|
||
@findex gdb_init_reader
|
||
@smallexample
|
||
extern struct gdb_reader_funcs *gdb_init_reader (void);
|
||
@end smallexample
|
||
|
||
@cindex @code{struct gdb_reader_funcs}
|
||
|
||
@code{struct gdb_reader_funcs} contains a set of pointers to callback
|
||
functions. These functions are executed to read the debug info
|
||
generated by the JIT compiler (@code{read}), to unwind stack frames
|
||
(@code{unwind}) and to create canonical frame IDs
|
||
(@code{get_Frame_id}). It also has a callback that is called when the
|
||
reader is being unloaded (@code{destroy}). The struct looks like this
|
||
|
||
@smallexample
|
||
struct gdb_reader_funcs
|
||
@{
|
||
/* Must be set to GDB_READER_INTERFACE_VERSION. */
|
||
int reader_version;
|
||
|
||
/* For use by the reader. */
|
||
void *priv_data;
|
||
|
||
gdb_read_debug_info *read;
|
||
gdb_unwind_frame *unwind;
|
||
gdb_get_frame_id *get_frame_id;
|
||
gdb_destroy_reader *destroy;
|
||
@};
|
||
@end smallexample
|
||
|
||
@cindex @code{struct gdb_symbol_callbacks}
|
||
@cindex @code{struct gdb_unwind_callbacks}
|
||
|
||
The callbacks are provided with another set of callbacks by
|
||
@value{GDBN} to do their job. For @code{read}, these callbacks are
|
||
passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
|
||
and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
|
||
@code{struct gdb_symbol_callbacks} has callbacks to create new object
|
||
files and new symbol tables inside those object files. @code{struct
|
||
gdb_unwind_callbacks} has callbacks to read registers off the current
|
||
frame and to write out the values of the registers in the previous
|
||
frame. Both have a callback (@code{target_read}) to read bytes off the
|
||
target's address space.
|
||
|
||
@node In-Process Agent
|
||
@chapter In-Process Agent
|
||
@cindex debugging agent
|
||
The traditional debugging model is conceptually low-speed, but works fine,
|
||
because most bugs can be reproduced in debugging-mode execution. However,
|
||
as multi-core or many-core processors are becoming mainstream, and
|
||
multi-threaded programs become more and more popular, there should be more
|
||
and more bugs that only manifest themselves at normal-mode execution, for
|
||
example, thread races, because debugger's interference with the program's
|
||
timing may conceal the bugs. On the other hand, in some applications,
|
||
it is not feasible for the debugger to interrupt the program's execution
|
||
long enough for the developer to learn anything helpful about its behavior.
|
||
If the program's correctness depends on its real-time behavior, delays
|
||
introduced by a debugger might cause the program to fail, even when the
|
||
code itself is correct. It is useful to be able to observe the program's
|
||
behavior without interrupting it.
|
||
|
||
Therefore, traditional debugging model is too intrusive to reproduce
|
||
some bugs. In order to reduce the interference with the program, we can
|
||
reduce the number of operations performed by debugger. The
|
||
@dfn{In-Process Agent}, a shared library, is running within the same
|
||
process with inferior, and is able to perform some debugging operations
|
||
itself. As a result, debugger is only involved when necessary, and
|
||
performance of debugging can be improved accordingly. Note that
|
||
interference with program can be reduced but can't be removed completely,
|
||
because the in-process agent will still stop or slow down the program.
|
||
|
||
The in-process agent can interpret and execute Agent Expressions
|
||
(@pxref{Agent Expressions}) during performing debugging operations. The
|
||
agent expressions can be used for different purposes, such as collecting
|
||
data in tracepoints, and condition evaluation in breakpoints.
|
||
|
||
@anchor{Control Agent}
|
||
You can control whether the in-process agent is used as an aid for
|
||
debugging with the following commands:
|
||
|
||
@table @code
|
||
@kindex set agent on
|
||
@item set agent on
|
||
Causes the in-process agent to perform some operations on behalf of the
|
||
debugger. Just which operations requested by the user will be done
|
||
by the in-process agent depends on the its capabilities. For example,
|
||
if you request to evaluate breakpoint conditions in the in-process agent,
|
||
and the in-process agent has such capability as well, then breakpoint
|
||
conditions will be evaluated in the in-process agent.
|
||
|
||
@kindex set agent off
|
||
@item set agent off
|
||
Disables execution of debugging operations by the in-process agent. All
|
||
of the operations will be performed by @value{GDBN}.
|
||
|
||
@kindex show agent
|
||
@item show agent
|
||
Display the current setting of execution of debugging operations by
|
||
the in-process agent.
|
||
@end table
|
||
|
||
@menu
|
||
* In-Process Agent Protocol::
|
||
@end menu
|
||
|
||
@node In-Process Agent Protocol
|
||
@section In-Process Agent Protocol
|
||
@cindex in-process agent protocol
|
||
|
||
The in-process agent is able to communicate with both @value{GDBN} and
|
||
GDBserver (@pxref{In-Process Agent}). This section documents the protocol
|
||
used for communications between @value{GDBN} or GDBserver and the IPA.
|
||
In general, @value{GDBN} or GDBserver sends commands
|
||
(@pxref{IPA Protocol Commands}) and data to in-process agent, and then
|
||
in-process agent replies back with the return result of the command, or
|
||
some other information. The data sent to in-process agent is composed
|
||
of primitive data types, such as 4-byte or 8-byte type, and composite
|
||
types, which are called objects (@pxref{IPA Protocol Objects}).
|
||
|
||
@menu
|
||
* IPA Protocol Objects::
|
||
* IPA Protocol Commands::
|
||
@end menu
|
||
|
||
@node IPA Protocol Objects
|
||
@subsection IPA Protocol Objects
|
||
@cindex ipa protocol objects
|
||
|
||
The commands sent to and results received from agent may contain some
|
||
complex data types called @dfn{objects}.
|
||
|
||
The in-process agent is running on the same machine with @value{GDBN}
|
||
or GDBserver, so it doesn't have to handle as much differences between
|
||
two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
|
||
However, there are still some differences of two ends in two processes:
|
||
|
||
@enumerate
|
||
@item
|
||
word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
|
||
compiled as a 64-bit executable, while in-process agent is a 32-bit one.
|
||
@item
|
||
ABI. Some machines may have multiple types of ABI, @value{GDBN} or
|
||
GDBserver is compiled with one, and in-process agent is compiled with
|
||
the other one.
|
||
@end enumerate
|
||
|
||
Here are the IPA Protocol Objects:
|
||
|
||
@enumerate
|
||
@item
|
||
agent expression object. It represents an agent expression
|
||
(@pxref{Agent Expressions}).
|
||
@anchor{agent expression object}
|
||
@item
|
||
tracepoint action object. It represents a tracepoint action
|
||
(@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
|
||
memory, static trace data and to evaluate expression.
|
||
@anchor{tracepoint action object}
|
||
@item
|
||
tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
|
||
@anchor{tracepoint object}
|
||
|
||
@end enumerate
|
||
|
||
The following table describes important attributes of each IPA protocol
|
||
object:
|
||
|
||
@multitable @columnfractions .30 .20 .50
|
||
@headitem Name @tab Size @tab Description
|
||
@item @emph{agent expression object} @tab @tab
|
||
@item length @tab 4 @tab length of bytes code
|
||
@item byte code @tab @var{length} @tab contents of byte code
|
||
@item @emph{tracepoint action for collecting memory} @tab @tab
|
||
@item 'M' @tab 1 @tab type of tracepoint action
|
||
@item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
|
||
address of the lowest byte to collect, otherwise @var{addr} is the offset
|
||
of @var{basereg} for memory collecting.
|
||
@item len @tab 8 @tab length of memory for collecting
|
||
@item basereg @tab 4 @tab the register number containing the starting
|
||
memory address for collecting.
|
||
@item @emph{tracepoint action for collecting registers} @tab @tab
|
||
@item 'R' @tab 1 @tab type of tracepoint action
|
||
@item @emph{tracepoint action for collecting static trace data} @tab @tab
|
||
@item 'L' @tab 1 @tab type of tracepoint action
|
||
@item @emph{tracepoint action for expression evaluation} @tab @tab
|
||
@item 'X' @tab 1 @tab type of tracepoint action
|
||
@item agent expression @tab length of @tab @ref{agent expression object}
|
||
@item @emph{tracepoint object} @tab @tab
|
||
@item number @tab 4 @tab number of tracepoint
|
||
@item address @tab 8 @tab address of tracepoint inserted on
|
||
@item type @tab 4 @tab type of tracepoint
|
||
@item enabled @tab 1 @tab enable or disable of tracepoint
|
||
@item step_count @tab 8 @tab step
|
||
@item pass_count @tab 8 @tab pass
|
||
@item numactions @tab 4 @tab number of tracepoint actions
|
||
@item hit count @tab 8 @tab hit count
|
||
@item trace frame usage @tab 8 @tab trace frame usage
|
||
@item compiled_cond @tab 8 @tab compiled condition
|
||
@item orig_size @tab 8 @tab orig size
|
||
@item condition @tab 4 if condition is NULL otherwise length of
|
||
@ref{agent expression object}
|
||
@tab zero if condition is NULL, otherwise is
|
||
@ref{agent expression object}
|
||
@item actions @tab variable
|
||
@tab numactions number of @ref{tracepoint action object}
|
||
@end multitable
|
||
|
||
@node IPA Protocol Commands
|
||
@subsection IPA Protocol Commands
|
||
@cindex ipa protocol commands
|
||
|
||
The spaces in each command are delimiters to ease reading this commands
|
||
specification. They don't exist in real commands.
|
||
|
||
@table @samp
|
||
|
||
@item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
|
||
Installs a new fast tracepoint described by @var{tracepoint_object}
|
||
(@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
|
||
head of @dfn{jumppad}, which is used to jump to data collection routine
|
||
in IPA finally.
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
|
||
@var{target_address} is address of tracepoint in the inferior.
|
||
The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
|
||
@var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
|
||
The @var{fjump} contains a sequence of instructions jump to jumppad entry.
|
||
The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
|
||
@item E @var{NN}
|
||
for an error
|
||
|
||
@end table
|
||
|
||
@item close
|
||
Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
|
||
is about to kill inferiors.
|
||
|
||
@item qTfSTM
|
||
@xref{qTfSTM}.
|
||
@item qTsSTM
|
||
@xref{qTsSTM}.
|
||
@item qTSTMat
|
||
@xref{qTSTMat}.
|
||
@item probe_marker_at:@var{address}
|
||
Asks in-process agent to probe the marker at @var{address}.
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
@item unprobe_marker_at:@var{address}
|
||
Asks in-process agent to unprobe the marker at @var{address}.
|
||
@end table
|
||
|
||
@node GDB Bugs
|
||
@chapter Reporting Bugs in @value{GDBN}
|
||
@cindex bugs in @value{GDBN}
|
||
@cindex reporting bugs in @value{GDBN}
|
||
|
||
Your bug reports play an essential role in making @value{GDBN} reliable.
|
||
|
||
Reporting a bug may help you by bringing a solution to your problem, or it
|
||
may not. But in any case the principal function of a bug report is to help
|
||
the entire community by making the next version of @value{GDBN} work better. Bug
|
||
reports are your contribution to the maintenance of @value{GDBN}.
|
||
|
||
In order for a bug report to serve its purpose, you must include the
|
||
information that enables us to fix the bug.
|
||
|
||
@menu
|
||
* Bug Criteria:: Have you found a bug?
|
||
* Bug Reporting:: How to report bugs
|
||
@end menu
|
||
|
||
@node Bug Criteria
|
||
@section Have You Found a Bug?
|
||
@cindex bug criteria
|
||
|
||
If you are not sure whether you have found a bug, here are some guidelines:
|
||
|
||
@itemize @bullet
|
||
@cindex fatal signal
|
||
@cindex debugger crash
|
||
@cindex crash of debugger
|
||
@item
|
||
If the debugger gets a fatal signal, for any input whatever, that is a
|
||
@value{GDBN} bug. Reliable debuggers never crash.
|
||
|
||
@cindex error on valid input
|
||
@item
|
||
If @value{GDBN} produces an error message for valid input, that is a
|
||
bug. (Note that if you're cross debugging, the problem may also be
|
||
somewhere in the connection to the target.)
|
||
|
||
@cindex invalid input
|
||
@item
|
||
If @value{GDBN} does not produce an error message for invalid input,
|
||
that is a bug. However, you should note that your idea of
|
||
``invalid input'' might be our idea of ``an extension'' or ``support
|
||
for traditional practice''.
|
||
|
||
@item
|
||
If you are an experienced user of debugging tools, your suggestions
|
||
for improvement of @value{GDBN} are welcome in any case.
|
||
@end itemize
|
||
|
||
@node Bug Reporting
|
||
@section How to Report Bugs
|
||
@cindex bug reports
|
||
@cindex @value{GDBN} bugs, reporting
|
||
|
||
A number of companies and individuals offer support for @sc{gnu} products.
|
||
If you obtained @value{GDBN} from a support organization, we recommend you
|
||
contact that organization first.
|
||
|
||
You can find contact information for many support companies and
|
||
individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
|
||
distribution.
|
||
@c should add a web page ref...
|
||
|
||
@ifset BUGURL
|
||
@ifset BUGURL_DEFAULT
|
||
In any event, we also recommend that you submit bug reports for
|
||
@value{GDBN}. The preferred method is to submit them directly using
|
||
@uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
|
||
page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
|
||
be used.
|
||
|
||
@strong{Do not send bug reports to @samp{info-gdb}, or to
|
||
@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
|
||
not want to receive bug reports. Those that do have arranged to receive
|
||
@samp{bug-gdb}.
|
||
|
||
The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
|
||
serves as a repeater. The mailing list and the newsgroup carry exactly
|
||
the same messages. Often people think of posting bug reports to the
|
||
newsgroup instead of mailing them. This appears to work, but it has one
|
||
problem which can be crucial: a newsgroup posting often lacks a mail
|
||
path back to the sender. Thus, if we need to ask for more information,
|
||
we may be unable to reach you. For this reason, it is better to send
|
||
bug reports to the mailing list.
|
||
@end ifset
|
||
@ifclear BUGURL_DEFAULT
|
||
In any event, we also recommend that you submit bug reports for
|
||
@value{GDBN} to @value{BUGURL}.
|
||
@end ifclear
|
||
@end ifset
|
||
|
||
The fundamental principle of reporting bugs usefully is this:
|
||
@strong{report all the facts}. If you are not sure whether to state a
|
||
fact or leave it out, state it!
|
||
|
||
Often people omit facts because they think they know what causes the
|
||
problem and assume that some details do not matter. Thus, you might
|
||
assume that the name of the variable you use in an example does not matter.
|
||
Well, probably it does not, but one cannot be sure. Perhaps the bug is a
|
||
stray memory reference which happens to fetch from the location where that
|
||
name is stored in memory; perhaps, if the name were different, the contents
|
||
of that location would fool the debugger into doing the right thing despite
|
||
the bug. Play it safe and give a specific, complete example. That is the
|
||
easiest thing for you to do, and the most helpful.
|
||
|
||
Keep in mind that the purpose of a bug report is to enable us to fix the
|
||
bug. It may be that the bug has been reported previously, but neither
|
||
you nor we can know that unless your bug report is complete and
|
||
self-contained.
|
||
|
||
Sometimes people give a few sketchy facts and ask, ``Does this ring a
|
||
bell?'' Those bug reports are useless, and we urge everyone to
|
||
@emph{refuse to respond to them} except to chide the sender to report
|
||
bugs properly.
|
||
|
||
To enable us to fix the bug, you should include all these things:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The version of @value{GDBN}. @value{GDBN} announces it if you start
|
||
with no arguments; you can also print it at any time using @code{show
|
||
version}.
|
||
|
||
Without this, we will not know whether there is any point in looking for
|
||
the bug in the current version of @value{GDBN}.
|
||
|
||
@item
|
||
The type of machine you are using, and the operating system name and
|
||
version number.
|
||
|
||
@item
|
||
The details of the @value{GDBN} build-time configuration.
|
||
@value{GDBN} shows these details if you invoke it with the
|
||
@option{--configuration} command-line option, or if you type
|
||
@code{show configuration} at @value{GDBN}'s prompt.
|
||
|
||
@item
|
||
What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
|
||
``@value{GCC}--2.8.1''.
|
||
|
||
@item
|
||
What compiler (and its version) was used to compile the program you are
|
||
debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
|
||
C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
|
||
to get this information; for other compilers, see the documentation for
|
||
those compilers.
|
||
|
||
@item
|
||
The command arguments you gave the compiler to compile your example and
|
||
observe the bug. For example, did you use @samp{-O}? To guarantee
|
||
you will not omit something important, list them all. A copy of the
|
||
Makefile (or the output from make) is sufficient.
|
||
|
||
If we were to try to guess the arguments, we would probably guess wrong
|
||
and then we might not encounter the bug.
|
||
|
||
@item
|
||
A complete input script, and all necessary source files, that will
|
||
reproduce the bug.
|
||
|
||
@item
|
||
A description of what behavior you observe that you believe is
|
||
incorrect. For example, ``It gets a fatal signal.''
|
||
|
||
Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
|
||
will certainly notice it. But if the bug is incorrect output, we might
|
||
not notice unless it is glaringly wrong. You might as well not give us
|
||
a chance to make a mistake.
|
||
|
||
Even if the problem you experience is a fatal signal, you should still
|
||
say so explicitly. Suppose something strange is going on, such as, your
|
||
copy of @value{GDBN} is out of synch, or you have encountered a bug in
|
||
the C library on your system. (This has happened!) Your copy might
|
||
crash and ours would not. If you told us to expect a crash, then when
|
||
ours fails to crash, we would know that the bug was not happening for
|
||
us. If you had not told us to expect a crash, then we would not be able
|
||
to draw any conclusion from our observations.
|
||
|
||
@pindex script
|
||
@cindex recording a session script
|
||
To collect all this information, you can use a session recording program
|
||
such as @command{script}, which is available on many Unix systems.
|
||
Just run your @value{GDBN} session inside @command{script} and then
|
||
include the @file{typescript} file with your bug report.
|
||
|
||
Another way to record a @value{GDBN} session is to run @value{GDBN}
|
||
inside Emacs and then save the entire buffer to a file.
|
||
|
||
@item
|
||
If you wish to suggest changes to the @value{GDBN} source, send us context
|
||
diffs. If you even discuss something in the @value{GDBN} source, refer to
|
||
it by context, not by line number.
|
||
|
||
The line numbers in our development sources will not match those in your
|
||
sources. Your line numbers would convey no useful information to us.
|
||
|
||
@end itemize
|
||
|
||
Here are some things that are not necessary:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
A description of the envelope of the bug.
|
||
|
||
Often people who encounter a bug spend a lot of time investigating
|
||
which changes to the input file will make the bug go away and which
|
||
changes will not affect it.
|
||
|
||
This is often time consuming and not very useful, because the way we
|
||
will find the bug is by running a single example under the debugger
|
||
with breakpoints, not by pure deduction from a series of examples.
|
||
We recommend that you save your time for something else.
|
||
|
||
Of course, if you can find a simpler example to report @emph{instead}
|
||
of the original one, that is a convenience for us. Errors in the
|
||
output will be easier to spot, running under the debugger will take
|
||
less time, and so on.
|
||
|
||
However, simplification is not vital; if you do not want to do this,
|
||
report the bug anyway and send us the entire test case you used.
|
||
|
||
@item
|
||
A patch for the bug.
|
||
|
||
A patch for the bug does help us if it is a good one. But do not omit
|
||
the necessary information, such as the test case, on the assumption that
|
||
a patch is all we need. We might see problems with your patch and decide
|
||
to fix the problem another way, or we might not understand it at all.
|
||
|
||
Sometimes with a program as complicated as @value{GDBN} it is very hard to
|
||
construct an example that will make the program follow a certain path
|
||
through the code. If you do not send us the example, we will not be able
|
||
to construct one, so we will not be able to verify that the bug is fixed.
|
||
|
||
And if we cannot understand what bug you are trying to fix, or why your
|
||
patch should be an improvement, we will not install it. A test case will
|
||
help us to understand.
|
||
|
||
@item
|
||
A guess about what the bug is or what it depends on.
|
||
|
||
Such guesses are usually wrong. Even we cannot guess right about such
|
||
things without first using the debugger to find the facts.
|
||
@end itemize
|
||
|
||
@c The readline documentation is distributed with the readline code
|
||
@c and consists of the two following files:
|
||
@c rluser.texi
|
||
@c hsuser.texi
|
||
@c Use -I with makeinfo to point to the appropriate directory,
|
||
@c environment var TEXINPUTS with TeX.
|
||
@ifclear SYSTEM_READLINE
|
||
@include rluser.texi
|
||
@include hsuser.texi
|
||
@end ifclear
|
||
|
||
@node In Memoriam
|
||
@appendix In Memoriam
|
||
|
||
The @value{GDBN} project mourns the loss of the following long-time
|
||
contributors:
|
||
|
||
@table @code
|
||
@item Fred Fish
|
||
Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
|
||
to Free Software in general. Outside of @value{GDBN}, he was known in
|
||
the Amiga world for his series of Fish Disks, and the GeekGadget project.
|
||
|
||
@item Michael Snyder
|
||
Michael was one of the Global Maintainers of the @value{GDBN} project,
|
||
with contributions recorded as early as 1996, until 2011. In addition
|
||
to his day to day participation, he was a large driving force behind
|
||
adding Reverse Debugging to @value{GDBN}.
|
||
@end table
|
||
|
||
Beyond their technical contributions to the project, they were also
|
||
enjoyable members of the Free Software Community. We will miss them.
|
||
|
||
@node Formatting Documentation
|
||
@appendix Formatting Documentation
|
||
|
||
@cindex @value{GDBN} reference card
|
||
@cindex reference card
|
||
The @value{GDBN} 4 release includes an already-formatted reference card, ready
|
||
for printing with PostScript or Ghostscript, in the @file{gdb}
|
||
subdirectory of the main source directory@footnote{In
|
||
@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
|
||
release.}. If you can use PostScript or Ghostscript with your printer,
|
||
you can print the reference card immediately with @file{refcard.ps}.
|
||
|
||
The release also includes the source for the reference card. You
|
||
can format it, using @TeX{}, by typing:
|
||
|
||
@smallexample
|
||
make refcard.dvi
|
||
@end smallexample
|
||
|
||
The @value{GDBN} reference card is designed to print in @dfn{landscape}
|
||
mode on US ``letter'' size paper;
|
||
that is, on a sheet 11 inches wide by 8.5 inches
|
||
high. You will need to specify this form of printing as an option to
|
||
your @sc{dvi} output program.
|
||
|
||
@cindex documentation
|
||
|
||
All the documentation for @value{GDBN} comes as part of the machine-readable
|
||
distribution. The documentation is written in Texinfo format, which is
|
||
a documentation system that uses a single source file to produce both
|
||
on-line information and a printed manual. You can use one of the Info
|
||
formatting commands to create the on-line version of the documentation
|
||
and @TeX{} (or @code{texi2roff}) to typeset the printed version.
|
||
|
||
@value{GDBN} includes an already formatted copy of the on-line Info
|
||
version of this manual in the @file{gdb} subdirectory. The main Info
|
||
file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
|
||
subordinate files matching @samp{gdb.info*} in the same directory. If
|
||
necessary, you can print out these files, or read them with any editor;
|
||
but they are easier to read using the @code{info} subsystem in @sc{gnu}
|
||
Emacs or the standalone @code{info} program, available as part of the
|
||
@sc{gnu} Texinfo distribution.
|
||
|
||
If you want to format these Info files yourself, you need one of the
|
||
Info formatting programs, such as @code{texinfo-format-buffer} or
|
||
@code{makeinfo}.
|
||
|
||
If you have @code{makeinfo} installed, and are in the top level
|
||
@value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
|
||
version @value{GDBVN}), you can make the Info file by typing:
|
||
|
||
@smallexample
|
||
cd gdb
|
||
make gdb.info
|
||
@end smallexample
|
||
|
||
If you want to typeset and print copies of this manual, you need @TeX{},
|
||
a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
|
||
Texinfo definitions file.
|
||
|
||
@TeX{} is a typesetting program; it does not print files directly, but
|
||
produces output files called @sc{dvi} files. To print a typeset
|
||
document, you need a program to print @sc{dvi} files. If your system
|
||
has @TeX{} installed, chances are it has such a program. The precise
|
||
command to use depends on your system; @kbd{lpr -d} is common; another
|
||
(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
|
||
require a file name without any extension or a @samp{.dvi} extension.
|
||
|
||
@TeX{} also requires a macro definitions file called
|
||
@file{texinfo.tex}. This file tells @TeX{} how to typeset a document
|
||
written in Texinfo format. On its own, @TeX{} cannot either read or
|
||
typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
|
||
and is located in the @file{gdb-@var{version-number}/texinfo}
|
||
directory.
|
||
|
||
If you have @TeX{} and a @sc{dvi} printer program installed, you can
|
||
typeset and print this manual. First switch to the @file{gdb}
|
||
subdirectory of the main source directory (for example, to
|
||
@file{gdb-@value{GDBVN}/gdb}) and type:
|
||
|
||
@smallexample
|
||
make gdb.dvi
|
||
@end smallexample
|
||
|
||
Then give @file{gdb.dvi} to your @sc{dvi} printing program.
|
||
|
||
@node Installing GDB
|
||
@appendix Installing @value{GDBN}
|
||
@cindex installation
|
||
|
||
@menu
|
||
* Requirements:: Requirements for building @value{GDBN}
|
||
* Running Configure:: Invoking the @value{GDBN} @file{configure} script
|
||
* Separate Objdir:: Compiling @value{GDBN} in another directory
|
||
* Config Names:: Specifying names for hosts and targets
|
||
* Configure Options:: Summary of options for configure
|
||
* System-wide configuration:: Having a system-wide init file
|
||
@end menu
|
||
|
||
@node Requirements
|
||
@section Requirements for Building @value{GDBN}
|
||
@cindex building @value{GDBN}, requirements for
|
||
|
||
Building @value{GDBN} requires various tools and packages to be available.
|
||
Other packages will be used only if they are found.
|
||
|
||
@heading Tools/Packages Necessary for Building @value{GDBN}
|
||
@table @asis
|
||
@item ISO C90 compiler
|
||
@value{GDBN} is written in ISO C90. It should be buildable with any
|
||
working C90 compiler, e.g.@: GCC.
|
||
|
||
@end table
|
||
|
||
@heading Tools/Packages Optional for Building @value{GDBN}
|
||
@table @asis
|
||
@item Expat
|
||
@anchor{Expat}
|
||
@value{GDBN} can use the Expat XML parsing library. This library may be
|
||
included with your operating system distribution; if it is not, you
|
||
can get the latest version from @url{http://expat.sourceforge.net}.
|
||
The @file{configure} script will search for this library in several
|
||
standard locations; if it is installed in an unusual path, you can
|
||
use the @option{--with-libexpat-prefix} option to specify its location.
|
||
|
||
Expat is used for:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Remote protocol memory maps (@pxref{Memory Map Format})
|
||
@item
|
||
Target descriptions (@pxref{Target Descriptions})
|
||
@item
|
||
Remote shared library lists (@xref{Library List Format},
|
||
or alternatively @pxref{Library List Format for SVR4 Targets})
|
||
@item
|
||
MS-Windows shared libraries (@pxref{Shared Libraries})
|
||
@item
|
||
Traceframe info (@pxref{Traceframe Info Format})
|
||
@item
|
||
Branch trace (@pxref{Branch Trace Format},
|
||
@pxref{Branch Trace Configuration Format})
|
||
@end itemize
|
||
|
||
@item MPFR
|
||
@anchor{MPFR}
|
||
@value{GDBN} can use the GNU MPFR multiple-precision floating-point
|
||
library. This library may be included with your operating system
|
||
distribution; if it is not, you can get the latest version from
|
||
@url{http://www.mpfr.org}. The @file{configure} script will search
|
||
for this library in several standard locations; if it is installed
|
||
in an unusual path, you can use the @option{--with-libmpfr-prefix}
|
||
option to specify its location.
|
||
|
||
GNU MPFR is used to emulate target floating-point arithmetic during
|
||
expression evaluation when the target uses different floating-point
|
||
formats than the host. If GNU MPFR it is not available, @value{GDBN}
|
||
will fall back to using host floating-point arithmetic.
|
||
|
||
@item zlib
|
||
@cindex compressed debug sections
|
||
@value{GDBN} will use the @samp{zlib} library, if available, to read
|
||
compressed debug sections. Some linkers, such as GNU gold, are capable
|
||
of producing binaries with compressed debug sections. If @value{GDBN}
|
||
is compiled with @samp{zlib}, it will be able to read the debug
|
||
information in such binaries.
|
||
|
||
The @samp{zlib} library is likely included with your operating system
|
||
distribution; if it is not, you can get the latest version from
|
||
@url{http://zlib.net}.
|
||
|
||
@item iconv
|
||
@value{GDBN}'s features related to character sets (@pxref{Character
|
||
Sets}) require a functioning @code{iconv} implementation. If you are
|
||
on a GNU system, then this is provided by the GNU C Library. Some
|
||
other systems also provide a working @code{iconv}.
|
||
|
||
If @value{GDBN} is using the @code{iconv} program which is installed
|
||
in a non-standard place, you will need to tell @value{GDBN} where to find it.
|
||
This is done with @option{--with-iconv-bin} which specifies the
|
||
directory that contains the @code{iconv} program.
|
||
|
||
On systems without @code{iconv}, you can install GNU Libiconv. If you
|
||
have previously installed Libiconv, you can use the
|
||
@option{--with-libiconv-prefix} option to configure.
|
||
|
||
@value{GDBN}'s top-level @file{configure} and @file{Makefile} will
|
||
arrange to build Libiconv if a directory named @file{libiconv} appears
|
||
in the top-most source directory. If Libiconv is built this way, and
|
||
if the operating system does not provide a suitable @code{iconv}
|
||
implementation, then the just-built library will automatically be used
|
||
by @value{GDBN}. One easy way to set this up is to download GNU
|
||
Libiconv, unpack it, and then rename the directory holding the
|
||
Libiconv source code to @samp{libiconv}.
|
||
@end table
|
||
|
||
@node Running Configure
|
||
@section Invoking the @value{GDBN} @file{configure} Script
|
||
@cindex configuring @value{GDBN}
|
||
@value{GDBN} comes with a @file{configure} script that automates the process
|
||
of preparing @value{GDBN} for installation; you can then use @code{make} to
|
||
build the @code{gdb} program.
|
||
@iftex
|
||
@c irrelevant in info file; it's as current as the code it lives with.
|
||
@footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
|
||
look at the @file{README} file in the sources; we may have improved the
|
||
installation procedures since publishing this manual.}
|
||
@end iftex
|
||
|
||
The @value{GDBN} distribution includes all the source code you need for
|
||
@value{GDBN} in a single directory, whose name is usually composed by
|
||
appending the version number to @samp{gdb}.
|
||
|
||
For example, the @value{GDBN} version @value{GDBVN} distribution is in the
|
||
@file{gdb-@value{GDBVN}} directory. That directory contains:
|
||
|
||
@table @code
|
||
@item gdb-@value{GDBVN}/configure @r{(and supporting files)}
|
||
script for configuring @value{GDBN} and all its supporting libraries
|
||
|
||
@item gdb-@value{GDBVN}/gdb
|
||
the source specific to @value{GDBN} itself
|
||
|
||
@item gdb-@value{GDBVN}/bfd
|
||
source for the Binary File Descriptor library
|
||
|
||
@item gdb-@value{GDBVN}/include
|
||
@sc{gnu} include files
|
||
|
||
@item gdb-@value{GDBVN}/libiberty
|
||
source for the @samp{-liberty} free software library
|
||
|
||
@item gdb-@value{GDBVN}/opcodes
|
||
source for the library of opcode tables and disassemblers
|
||
|
||
@item gdb-@value{GDBVN}/readline
|
||
source for the @sc{gnu} command-line interface
|
||
|
||
@item gdb-@value{GDBVN}/glob
|
||
source for the @sc{gnu} filename pattern-matching subroutine
|
||
|
||
@item gdb-@value{GDBVN}/mmalloc
|
||
source for the @sc{gnu} memory-mapped malloc package
|
||
@end table
|
||
|
||
The simplest way to configure and build @value{GDBN} is to run @file{configure}
|
||
from the @file{gdb-@var{version-number}} source directory, which in
|
||
this example is the @file{gdb-@value{GDBVN}} directory.
|
||
|
||
First switch to the @file{gdb-@var{version-number}} source directory
|
||
if you are not already in it; then run @file{configure}. Pass the
|
||
identifier for the platform on which @value{GDBN} will run as an
|
||
argument.
|
||
|
||
For example:
|
||
|
||
@smallexample
|
||
cd gdb-@value{GDBVN}
|
||
./configure @var{host}
|
||
make
|
||
@end smallexample
|
||
|
||
@noindent
|
||
where @var{host} is an identifier such as @samp{sun4} or
|
||
@samp{decstation}, that identifies the platform where @value{GDBN} will run.
|
||
(You can often leave off @var{host}; @file{configure} tries to guess the
|
||
correct value by examining your system.)
|
||
|
||
Running @samp{configure @var{host}} and then running @code{make} builds the
|
||
@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
|
||
libraries, then @code{gdb} itself. The configured source files, and the
|
||
binaries, are left in the corresponding source directories.
|
||
|
||
@need 750
|
||
@file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
|
||
system does not recognize this automatically when you run a different
|
||
shell, you may need to run @code{sh} on it explicitly:
|
||
|
||
@smallexample
|
||
sh configure @var{host}
|
||
@end smallexample
|
||
|
||
If you run @file{configure} from a directory that contains source
|
||
directories for multiple libraries or programs, such as the
|
||
@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
|
||
@file{configure}
|
||
creates configuration files for every directory level underneath (unless
|
||
you tell it not to, with the @samp{--norecursion} option).
|
||
|
||
You should run the @file{configure} script from the top directory in the
|
||
source tree, the @file{gdb-@var{version-number}} directory. If you run
|
||
@file{configure} from one of the subdirectories, you will configure only
|
||
that subdirectory. That is usually not what you want. In particular,
|
||
if you run the first @file{configure} from the @file{gdb} subdirectory
|
||
of the @file{gdb-@var{version-number}} directory, you will omit the
|
||
configuration of @file{bfd}, @file{readline}, and other sibling
|
||
directories of the @file{gdb} subdirectory. This leads to build errors
|
||
about missing include files such as @file{bfd/bfd.h}.
|
||
|
||
You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
|
||
However, you should make sure that the shell on your path (named by
|
||
the @samp{SHELL} environment variable) is publicly readable. Remember
|
||
that @value{GDBN} uses the shell to start your program---some systems refuse to
|
||
let @value{GDBN} debug child processes whose programs are not readable.
|
||
|
||
@node Separate Objdir
|
||
@section Compiling @value{GDBN} in Another Directory
|
||
|
||
If you want to run @value{GDBN} versions for several host or target machines,
|
||
you need a different @code{gdb} compiled for each combination of
|
||
host and target. @file{configure} is designed to make this easy by
|
||
allowing you to generate each configuration in a separate subdirectory,
|
||
rather than in the source directory. If your @code{make} program
|
||
handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
|
||
@code{make} in each of these directories builds the @code{gdb}
|
||
program specified there.
|
||
|
||
To build @code{gdb} in a separate directory, run @file{configure}
|
||
with the @samp{--srcdir} option to specify where to find the source.
|
||
(You also need to specify a path to find @file{configure}
|
||
itself from your working directory. If the path to @file{configure}
|
||
would be the same as the argument to @samp{--srcdir}, you can leave out
|
||
the @samp{--srcdir} option; it is assumed.)
|
||
|
||
For example, with version @value{GDBVN}, you can build @value{GDBN} in a
|
||
separate directory for a Sun 4 like this:
|
||
|
||
@smallexample
|
||
@group
|
||
cd gdb-@value{GDBVN}
|
||
mkdir ../gdb-sun4
|
||
cd ../gdb-sun4
|
||
../gdb-@value{GDBVN}/configure sun4
|
||
make
|
||
@end group
|
||
@end smallexample
|
||
|
||
When @file{configure} builds a configuration using a remote source
|
||
directory, it creates a tree for the binaries with the same structure
|
||
(and using the same names) as the tree under the source directory. In
|
||
the example, you'd find the Sun 4 library @file{libiberty.a} in the
|
||
directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
|
||
@file{gdb-sun4/gdb}.
|
||
|
||
Make sure that your path to the @file{configure} script has just one
|
||
instance of @file{gdb} in it. If your path to @file{configure} looks
|
||
like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
|
||
one subdirectory of @value{GDBN}, not the whole package. This leads to
|
||
build errors about missing include files such as @file{bfd/bfd.h}.
|
||
|
||
One popular reason to build several @value{GDBN} configurations in separate
|
||
directories is to configure @value{GDBN} for cross-compiling (where
|
||
@value{GDBN} runs on one machine---the @dfn{host}---while debugging
|
||
programs that run on another machine---the @dfn{target}).
|
||
You specify a cross-debugging target by
|
||
giving the @samp{--target=@var{target}} option to @file{configure}.
|
||
|
||
When you run @code{make} to build a program or library, you must run
|
||
it in a configured directory---whatever directory you were in when you
|
||
called @file{configure} (or one of its subdirectories).
|
||
|
||
The @code{Makefile} that @file{configure} generates in each source
|
||
directory also runs recursively. If you type @code{make} in a source
|
||
directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
|
||
directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
|
||
will build all the required libraries, and then build GDB.
|
||
|
||
When you have multiple hosts or targets configured in separate
|
||
directories, you can run @code{make} on them in parallel (for example,
|
||
if they are NFS-mounted on each of the hosts); they will not interfere
|
||
with each other.
|
||
|
||
@node Config Names
|
||
@section Specifying Names for Hosts and Targets
|
||
|
||
The specifications used for hosts and targets in the @file{configure}
|
||
script are based on a three-part naming scheme, but some short predefined
|
||
aliases are also supported. The full naming scheme encodes three pieces
|
||
of information in the following pattern:
|
||
|
||
@smallexample
|
||
@var{architecture}-@var{vendor}-@var{os}
|
||
@end smallexample
|
||
|
||
For example, you can use the alias @code{sun4} as a @var{host} argument,
|
||
or as the value for @var{target} in a @code{--target=@var{target}}
|
||
option. The equivalent full name is @samp{sparc-sun-sunos4}.
|
||
|
||
The @file{configure} script accompanying @value{GDBN} does not provide
|
||
any query facility to list all supported host and target names or
|
||
aliases. @file{configure} calls the Bourne shell script
|
||
@code{config.sub} to map abbreviations to full names; you can read the
|
||
script, if you wish, or you can use it to test your guesses on
|
||
abbreviations---for example:
|
||
|
||
@smallexample
|
||
% sh config.sub i386-linux
|
||
i386-pc-linux-gnu
|
||
% sh config.sub alpha-linux
|
||
alpha-unknown-linux-gnu
|
||
% sh config.sub hp9k700
|
||
hppa1.1-hp-hpux
|
||
% sh config.sub sun4
|
||
sparc-sun-sunos4.1.1
|
||
% sh config.sub sun3
|
||
m68k-sun-sunos4.1.1
|
||
% sh config.sub i986v
|
||
Invalid configuration `i986v': machine `i986v' not recognized
|
||
@end smallexample
|
||
|
||
@noindent
|
||
@code{config.sub} is also distributed in the @value{GDBN} source
|
||
directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
|
||
|
||
@node Configure Options
|
||
@section @file{configure} Options
|
||
|
||
Here is a summary of the @file{configure} options and arguments that
|
||
are most often useful for building @value{GDBN}. @file{configure} also has
|
||
several other options not listed here. @inforef{What Configure
|
||
Does,,configure.info}, for a full explanation of @file{configure}.
|
||
|
||
@smallexample
|
||
configure @r{[}--help@r{]}
|
||
@r{[}--prefix=@var{dir}@r{]}
|
||
@r{[}--exec-prefix=@var{dir}@r{]}
|
||
@r{[}--srcdir=@var{dirname}@r{]}
|
||
@r{[}--norecursion@r{]} @r{[}--rm@r{]}
|
||
@r{[}--target=@var{target}@r{]}
|
||
@var{host}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
You may introduce options with a single @samp{-} rather than
|
||
@samp{--} if you prefer; but you may abbreviate option names if you use
|
||
@samp{--}.
|
||
|
||
@table @code
|
||
@item --help
|
||
Display a quick summary of how to invoke @file{configure}.
|
||
|
||
@item --prefix=@var{dir}
|
||
Configure the source to install programs and files under directory
|
||
@file{@var{dir}}.
|
||
|
||
@item --exec-prefix=@var{dir}
|
||
Configure the source to install programs under directory
|
||
@file{@var{dir}}.
|
||
|
||
@c avoid splitting the warning from the explanation:
|
||
@need 2000
|
||
@item --srcdir=@var{dirname}
|
||
@strong{Warning: using this option requires @sc{gnu} @code{make}, or another
|
||
@code{make} that implements the @code{VPATH} feature.}@*
|
||
Use this option to make configurations in directories separate from the
|
||
@value{GDBN} source directories. Among other things, you can use this to
|
||
build (or maintain) several configurations simultaneously, in separate
|
||
directories. @file{configure} writes configuration-specific files in
|
||
the current directory, but arranges for them to use the source in the
|
||
directory @var{dirname}. @file{configure} creates directories under
|
||
the working directory in parallel to the source directories below
|
||
@var{dirname}.
|
||
|
||
@item --norecursion
|
||
Configure only the directory level where @file{configure} is executed; do not
|
||
propagate configuration to subdirectories.
|
||
|
||
@item --target=@var{target}
|
||
Configure @value{GDBN} for cross-debugging programs running on the specified
|
||
@var{target}. Without this option, @value{GDBN} is configured to debug
|
||
programs that run on the same machine (@var{host}) as @value{GDBN} itself.
|
||
|
||
There is no convenient way to generate a list of all available targets.
|
||
|
||
@item @var{host} @dots{}
|
||
Configure @value{GDBN} to run on the specified @var{host}.
|
||
|
||
There is no convenient way to generate a list of all available hosts.
|
||
@end table
|
||
|
||
There are many other options available as well, but they are generally
|
||
needed for special purposes only.
|
||
|
||
@node System-wide configuration
|
||
@section System-wide configuration and settings
|
||
@cindex system-wide init file
|
||
|
||
@value{GDBN} can be configured to have a system-wide init file;
|
||
this file will be read and executed at startup (@pxref{Startup, , What
|
||
@value{GDBN} does during startup}).
|
||
|
||
Here is the corresponding configure option:
|
||
|
||
@table @code
|
||
@item --with-system-gdbinit=@var{file}
|
||
Specify that the default location of the system-wide init file is
|
||
@var{file}.
|
||
@end table
|
||
|
||
If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
|
||
it may be subject to relocation. Two possible cases:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
If the default location of this init file contains @file{$prefix},
|
||
it will be subject to relocation. Suppose that the configure options
|
||
are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
|
||
if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
|
||
init file is looked for as @file{$install/etc/gdbinit} instead of
|
||
@file{$prefix/etc/gdbinit}.
|
||
|
||
@item
|
||
By contrast, if the default location does not contain the prefix,
|
||
it will not be relocated. E.g.@: if @value{GDBN} has been configured with
|
||
@option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
|
||
then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
|
||
wherever @value{GDBN} is installed.
|
||
@end itemize
|
||
|
||
If the configured location of the system-wide init file (as given by the
|
||
@option{--with-system-gdbinit} option at configure time) is in the
|
||
data-directory (as specified by @option{--with-gdb-datadir} at configure
|
||
time) or in one of its subdirectories, then @value{GDBN} will look for the
|
||
system-wide init file in the directory specified by the
|
||
@option{--data-directory} command-line option.
|
||
Note that the system-wide init file is only read once, during @value{GDBN}
|
||
initialization. If the data-directory is changed after @value{GDBN} has
|
||
started with the @code{set data-directory} command, the file will not be
|
||
reread.
|
||
|
||
@menu
|
||
* System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
|
||
@end menu
|
||
|
||
@node System-wide Configuration Scripts
|
||
@subsection Installed System-wide Configuration Scripts
|
||
@cindex system-wide configuration scripts
|
||
|
||
The @file{system-gdbinit} directory, located inside the data-directory
|
||
(as specified by @option{--with-gdb-datadir} at configure time) contains
|
||
a number of scripts which can be used as system-wide init files. To
|
||
automatically source those scripts at startup, @value{GDBN} should be
|
||
configured with @option{--with-system-gdbinit}. Otherwise, any user
|
||
should be able to source them by hand as needed.
|
||
|
||
The following scripts are currently available:
|
||
@itemize @bullet
|
||
|
||
@item @file{elinos.py}
|
||
@pindex elinos.py
|
||
@cindex ELinOS system-wide configuration script
|
||
This script is useful when debugging a program on an ELinOS target.
|
||
It takes advantage of the environment variables defined in a standard
|
||
ELinOS environment in order to determine the location of the system
|
||
shared libraries, and then sets the @samp{solib-absolute-prefix}
|
||
and @samp{solib-search-path} variables appropriately.
|
||
|
||
@item @file{wrs-linux.py}
|
||
@pindex wrs-linux.py
|
||
@cindex Wind River Linux system-wide configuration script
|
||
This script is useful when debugging a program on a target running
|
||
Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
|
||
the host-side sysroot used by the target system.
|
||
|
||
@end itemize
|
||
|
||
@node Maintenance Commands
|
||
@appendix Maintenance Commands
|
||
@cindex maintenance commands
|
||
@cindex internal commands
|
||
|
||
In addition to commands intended for @value{GDBN} users, @value{GDBN}
|
||
includes a number of commands intended for @value{GDBN} developers,
|
||
that are not documented elsewhere in this manual. These commands are
|
||
provided here for reference. (For commands that turn on debugging
|
||
messages, see @ref{Debugging Output}.)
|
||
|
||
@table @code
|
||
@kindex maint agent
|
||
@kindex maint agent-eval
|
||
@item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
|
||
@itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
|
||
Translate the given @var{expression} into remote agent bytecodes.
|
||
This command is useful for debugging the Agent Expression mechanism
|
||
(@pxref{Agent Expressions}). The @samp{agent} version produces an
|
||
expression useful for data collection, such as by tracepoints, while
|
||
@samp{maint agent-eval} produces an expression that evaluates directly
|
||
to a result. For instance, a collection expression for @code{globa +
|
||
globb} will include bytecodes to record four bytes of memory at each
|
||
of the addresses of @code{globa} and @code{globb}, while discarding
|
||
the result of the addition, while an evaluation expression will do the
|
||
addition and return the sum.
|
||
If @code{-at} is given, generate remote agent bytecode for @var{location}.
|
||
If not, generate remote agent bytecode for current frame PC address.
|
||
|
||
@kindex maint agent-printf
|
||
@item maint agent-printf @var{format},@var{expr},...
|
||
Translate the given format string and list of argument expressions
|
||
into remote agent bytecodes and display them as a disassembled list.
|
||
This command is useful for debugging the agent version of dynamic
|
||
printf (@pxref{Dynamic Printf}).
|
||
|
||
@kindex maint info breakpoints
|
||
@item @anchor{maint info breakpoints}maint info breakpoints
|
||
Using the same format as @samp{info breakpoints}, display both the
|
||
breakpoints you've set explicitly, and those @value{GDBN} is using for
|
||
internal purposes. Internal breakpoints are shown with negative
|
||
breakpoint numbers. The type column identifies what kind of breakpoint
|
||
is shown:
|
||
|
||
@table @code
|
||
@item breakpoint
|
||
Normal, explicitly set breakpoint.
|
||
|
||
@item watchpoint
|
||
Normal, explicitly set watchpoint.
|
||
|
||
@item longjmp
|
||
Internal breakpoint, used to handle correctly stepping through
|
||
@code{longjmp} calls.
|
||
|
||
@item longjmp resume
|
||
Internal breakpoint at the target of a @code{longjmp}.
|
||
|
||
@item until
|
||
Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
|
||
|
||
@item finish
|
||
Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
|
||
|
||
@item shlib events
|
||
Shared library events.
|
||
|
||
@end table
|
||
|
||
@kindex maint info btrace
|
||
@item maint info btrace
|
||
Pint information about raw branch tracing data.
|
||
|
||
@kindex maint btrace packet-history
|
||
@item maint btrace packet-history
|
||
Print the raw branch trace packets that are used to compute the
|
||
execution history for the @samp{record btrace} command. Both the
|
||
information and the format in which it is printed depend on the btrace
|
||
recording format.
|
||
|
||
@table @code
|
||
@item bts
|
||
For the BTS recording format, print a list of blocks of sequential
|
||
code. For each block, the following information is printed:
|
||
|
||
@table @asis
|
||
@item Block number
|
||
Newer blocks have higher numbers. The oldest block has number zero.
|
||
@item Lowest @samp{PC}
|
||
@item Highest @samp{PC}
|
||
@end table
|
||
|
||
@item pt
|
||
For the Intel Processor Trace recording format, print a list of
|
||
Intel Processor Trace packets. For each packet, the following
|
||
information is printed:
|
||
|
||
@table @asis
|
||
@item Packet number
|
||
Newer packets have higher numbers. The oldest packet has number zero.
|
||
@item Trace offset
|
||
The packet's offset in the trace stream.
|
||
@item Packet opcode and payload
|
||
@end table
|
||
@end table
|
||
|
||
@kindex maint btrace clear-packet-history
|
||
@item maint btrace clear-packet-history
|
||
Discards the cached packet history printed by the @samp{maint btrace
|
||
packet-history} command. The history will be computed again when
|
||
needed.
|
||
|
||
@kindex maint btrace clear
|
||
@item maint btrace clear
|
||
Discard the branch trace data. The data will be fetched anew and the
|
||
branch trace will be recomputed when needed.
|
||
|
||
This implicitly truncates the branch trace to a single branch trace
|
||
buffer. When updating branch trace incrementally, the branch trace
|
||
available to @value{GDBN} may be bigger than a single branch trace
|
||
buffer.
|
||
|
||
@kindex maint set btrace pt skip-pad
|
||
@item maint set btrace pt skip-pad
|
||
@kindex maint show btrace pt skip-pad
|
||
@item maint show btrace pt skip-pad
|
||
Control whether @value{GDBN} will skip PAD packets when computing the
|
||
packet history.
|
||
|
||
@kindex set displaced-stepping
|
||
@kindex show displaced-stepping
|
||
@cindex displaced stepping support
|
||
@cindex out-of-line single-stepping
|
||
@item set displaced-stepping
|
||
@itemx show displaced-stepping
|
||
Control whether or not @value{GDBN} will do @dfn{displaced stepping}
|
||
if the target supports it. Displaced stepping is a way to single-step
|
||
over breakpoints without removing them from the inferior, by executing
|
||
an out-of-line copy of the instruction that was originally at the
|
||
breakpoint location. It is also known as out-of-line single-stepping.
|
||
|
||
@table @code
|
||
@item set displaced-stepping on
|
||
If the target architecture supports it, @value{GDBN} will use
|
||
displaced stepping to step over breakpoints.
|
||
|
||
@item set displaced-stepping off
|
||
@value{GDBN} will not use displaced stepping to step over breakpoints,
|
||
even if such is supported by the target architecture.
|
||
|
||
@cindex non-stop mode, and @samp{set displaced-stepping}
|
||
@item set displaced-stepping auto
|
||
This is the default mode. @value{GDBN} will use displaced stepping
|
||
only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
|
||
architecture supports displaced stepping.
|
||
@end table
|
||
|
||
@kindex maint check-psymtabs
|
||
@item maint check-psymtabs
|
||
Check the consistency of currently expanded psymtabs versus symtabs.
|
||
Use this to check, for example, whether a symbol is in one but not the other.
|
||
|
||
@kindex maint check-symtabs
|
||
@item maint check-symtabs
|
||
Check the consistency of currently expanded symtabs.
|
||
|
||
@kindex maint expand-symtabs
|
||
@item maint expand-symtabs [@var{regexp}]
|
||
Expand symbol tables.
|
||
If @var{regexp} is specified, only expand symbol tables for file
|
||
names matching @var{regexp}.
|
||
|
||
@kindex maint set catch-demangler-crashes
|
||
@kindex maint show catch-demangler-crashes
|
||
@cindex demangler crashes
|
||
@item maint set catch-demangler-crashes [on|off]
|
||
@itemx maint show catch-demangler-crashes
|
||
Control whether @value{GDBN} should attempt to catch crashes in the
|
||
symbol name demangler. The default is to attempt to catch crashes.
|
||
If enabled, the first time a crash is caught, a core file is created,
|
||
the offending symbol is displayed and the user is presented with the
|
||
option to terminate the current session.
|
||
|
||
@kindex maint cplus first_component
|
||
@item maint cplus first_component @var{name}
|
||
Print the first C@t{++} class/namespace component of @var{name}.
|
||
|
||
@kindex maint cplus namespace
|
||
@item maint cplus namespace
|
||
Print the list of possible C@t{++} namespaces.
|
||
|
||
@kindex maint deprecate
|
||
@kindex maint undeprecate
|
||
@cindex deprecated commands
|
||
@item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
|
||
@itemx maint undeprecate @var{command}
|
||
Deprecate or undeprecate the named @var{command}. Deprecated commands
|
||
cause @value{GDBN} to issue a warning when you use them. The optional
|
||
argument @var{replacement} says which newer command should be used in
|
||
favor of the deprecated one; if it is given, @value{GDBN} will mention
|
||
the replacement as part of the warning.
|
||
|
||
@kindex maint dump-me
|
||
@item maint dump-me
|
||
@cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
|
||
Cause a fatal signal in the debugger and force it to dump its core.
|
||
This is supported only on systems which support aborting a program
|
||
with the @code{SIGQUIT} signal.
|
||
|
||
@kindex maint internal-error
|
||
@kindex maint internal-warning
|
||
@kindex maint demangler-warning
|
||
@cindex demangler crashes
|
||
@item maint internal-error @r{[}@var{message-text}@r{]}
|
||
@itemx maint internal-warning @r{[}@var{message-text}@r{]}
|
||
@itemx maint demangler-warning @r{[}@var{message-text}@r{]}
|
||
|
||
Cause @value{GDBN} to call the internal function @code{internal_error},
|
||
@code{internal_warning} or @code{demangler_warning} and hence behave
|
||
as though an internal problem has been detected. In addition to
|
||
reporting the internal problem, these functions give the user the
|
||
opportunity to either quit @value{GDBN} or (for @code{internal_error}
|
||
and @code{internal_warning}) create a core file of the current
|
||
@value{GDBN} session.
|
||
|
||
These commands take an optional parameter @var{message-text} that is
|
||
used as the text of the error or warning message.
|
||
|
||
Here's an example of using @code{internal-error}:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
|
||
@dots{}/maint.c:121: internal-error: testing, 1, 2
|
||
A problem internal to GDB has been detected. Further
|
||
debugging may prove unreliable.
|
||
Quit this debugging session? (y or n) @kbd{n}
|
||
Create a core file? (y or n) @kbd{n}
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
@cindex @value{GDBN} internal error
|
||
@cindex internal errors, control of @value{GDBN} behavior
|
||
@cindex demangler crashes
|
||
|
||
@kindex maint set internal-error
|
||
@kindex maint show internal-error
|
||
@kindex maint set internal-warning
|
||
@kindex maint show internal-warning
|
||
@kindex maint set demangler-warning
|
||
@kindex maint show demangler-warning
|
||
@item maint set internal-error @var{action} [ask|yes|no]
|
||
@itemx maint show internal-error @var{action}
|
||
@itemx maint set internal-warning @var{action} [ask|yes|no]
|
||
@itemx maint show internal-warning @var{action}
|
||
@itemx maint set demangler-warning @var{action} [ask|yes|no]
|
||
@itemx maint show demangler-warning @var{action}
|
||
When @value{GDBN} reports an internal problem (error or warning) it
|
||
gives the user the opportunity to both quit @value{GDBN} and create a
|
||
core file of the current @value{GDBN} session. These commands let you
|
||
override the default behaviour for each particular @var{action},
|
||
described in the table below.
|
||
|
||
@table @samp
|
||
@item quit
|
||
You can specify that @value{GDBN} should always (yes) or never (no)
|
||
quit. The default is to ask the user what to do.
|
||
|
||
@item corefile
|
||
You can specify that @value{GDBN} should always (yes) or never (no)
|
||
create a core file. The default is to ask the user what to do. Note
|
||
that there is no @code{corefile} option for @code{demangler-warning}:
|
||
demangler warnings always create a core file and this cannot be
|
||
disabled.
|
||
@end table
|
||
|
||
@kindex maint packet
|
||
@item maint packet @var{text}
|
||
If @value{GDBN} is talking to an inferior via the serial protocol,
|
||
then this command sends the string @var{text} to the inferior, and
|
||
displays the response packet. @value{GDBN} supplies the initial
|
||
@samp{$} character, the terminating @samp{#} character, and the
|
||
checksum.
|
||
|
||
@kindex maint print architecture
|
||
@item maint print architecture @r{[}@var{file}@r{]}
|
||
Print the entire architecture configuration. The optional argument
|
||
@var{file} names the file where the output goes.
|
||
|
||
@kindex maint print c-tdesc @r{[}@var{file}@r{]}
|
||
@item maint print c-tdesc
|
||
Print the target description (@pxref{Target Descriptions}) as
|
||
a C source file. By default, the target description is for the current
|
||
target, but if the optional argument @var{file} is provided, that file
|
||
is used to produce the description. The @var{file} should be an XML
|
||
document, of the form described in @ref{Target Description Format}.
|
||
The created source file is built into @value{GDBN} when @value{GDBN} is
|
||
built again. This command is used by developers after they add or
|
||
modify XML target descriptions.
|
||
|
||
@kindex maint check xml-descriptions
|
||
@item maint check xml-descriptions @var{dir}
|
||
Check that the target descriptions dynamically created by @value{GDBN}
|
||
equal the descriptions created from XML files found in @var{dir}.
|
||
|
||
@kindex maint print dummy-frames
|
||
@item maint print dummy-frames
|
||
Prints the contents of @value{GDBN}'s internal dummy-frame stack.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @kbd{b add}
|
||
@dots{}
|
||
(@value{GDBP}) @kbd{print add(2,3)}
|
||
Breakpoint 2, add (a=2, b=3) at @dots{}
|
||
58 return (a + b);
|
||
The program being debugged stopped while in a function called from GDB.
|
||
@dots{}
|
||
(@value{GDBP}) @kbd{maint print dummy-frames}
|
||
0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
|
||
(@value{GDBP})
|
||
@end smallexample
|
||
|
||
Takes an optional file parameter.
|
||
|
||
@kindex maint print registers
|
||
@kindex maint print raw-registers
|
||
@kindex maint print cooked-registers
|
||
@kindex maint print register-groups
|
||
@kindex maint print remote-registers
|
||
@item maint print registers @r{[}@var{file}@r{]}
|
||
@itemx maint print raw-registers @r{[}@var{file}@r{]}
|
||
@itemx maint print cooked-registers @r{[}@var{file}@r{]}
|
||
@itemx maint print register-groups @r{[}@var{file}@r{]}
|
||
@itemx maint print remote-registers @r{[}@var{file}@r{]}
|
||
Print @value{GDBN}'s internal register data structures.
|
||
|
||
The command @code{maint print raw-registers} includes the contents of
|
||
the raw register cache; the command @code{maint print
|
||
cooked-registers} includes the (cooked) value of all registers,
|
||
including registers which aren't available on the target nor visible
|
||
to user; the command @code{maint print register-groups} includes the
|
||
groups that each register is a member of; and the command @code{maint
|
||
print remote-registers} includes the remote target's register numbers
|
||
and offsets in the `G' packets.
|
||
|
||
These commands take an optional parameter, a file name to which to
|
||
write the information.
|
||
|
||
@kindex maint print reggroups
|
||
@item maint print reggroups @r{[}@var{file}@r{]}
|
||
Print @value{GDBN}'s internal register group data structures. The
|
||
optional argument @var{file} tells to what file to write the
|
||
information.
|
||
|
||
The register groups info looks like this:
|
||
|
||
@smallexample
|
||
(@value{GDBP}) @kbd{maint print reggroups}
|
||
Group Type
|
||
general user
|
||
float user
|
||
all user
|
||
vector user
|
||
system user
|
||
save internal
|
||
restore internal
|
||
@end smallexample
|
||
|
||
@kindex flushregs
|
||
@item flushregs
|
||
This command forces @value{GDBN} to flush its internal register cache.
|
||
|
||
@kindex maint print objfiles
|
||
@cindex info for known object files
|
||
@item maint print objfiles @r{[}@var{regexp}@r{]}
|
||
Print a dump of all known object files.
|
||
If @var{regexp} is specified, only print object files whose names
|
||
match @var{regexp}. For each object file, this command prints its name,
|
||
address in memory, and all of its psymtabs and symtabs.
|
||
|
||
@kindex maint print user-registers
|
||
@cindex user registers
|
||
@item maint print user-registers
|
||
List all currently available @dfn{user registers}. User registers
|
||
typically provide alternate names for actual hardware registers. They
|
||
include the four ``standard'' registers @code{$fp}, @code{$pc},
|
||
@code{$sp}, and @code{$ps}. @xref{standard registers}. User
|
||
registers can be used in expressions in the same way as the canonical
|
||
register names, but only the latter are listed by the @code{info
|
||
registers} and @code{maint print registers} commands.
|
||
|
||
@kindex maint print section-scripts
|
||
@cindex info for known .debug_gdb_scripts-loaded scripts
|
||
@item maint print section-scripts [@var{regexp}]
|
||
Print a dump of scripts specified in the @code{.debug_gdb_section} section.
|
||
If @var{regexp} is specified, only print scripts loaded by object files
|
||
matching @var{regexp}.
|
||
For each script, this command prints its name as specified in the objfile,
|
||
and the full path if known.
|
||
@xref{dotdebug_gdb_scripts section}.
|
||
|
||
@kindex maint print statistics
|
||
@cindex bcache statistics
|
||
@item maint print statistics
|
||
This command prints, for each object file in the program, various data
|
||
about that object file followed by the byte cache (@dfn{bcache})
|
||
statistics for the object file. The objfile data includes the number
|
||
of minimal, partial, full, and stabs symbols, the number of types
|
||
defined by the objfile, the number of as yet unexpanded psym tables,
|
||
the number of line tables and string tables, and the amount of memory
|
||
used by the various tables. The bcache statistics include the counts,
|
||
sizes, and counts of duplicates of all and unique objects, max,
|
||
average, and median entry size, total memory used and its overhead and
|
||
savings, and various measures of the hash table size and chain
|
||
lengths.
|
||
|
||
@kindex maint print target-stack
|
||
@cindex target stack description
|
||
@item maint print target-stack
|
||
A @dfn{target} is an interface between the debugger and a particular
|
||
kind of file or process. Targets can be stacked in @dfn{strata},
|
||
so that more than one target can potentially respond to a request.
|
||
In particular, memory accesses will walk down the stack of targets
|
||
until they find a target that is interested in handling that particular
|
||
address.
|
||
|
||
This command prints a short description of each layer that was pushed on
|
||
the @dfn{target stack}, starting from the top layer down to the bottom one.
|
||
|
||
@kindex maint print type
|
||
@cindex type chain of a data type
|
||
@item maint print type @var{expr}
|
||
Print the type chain for a type specified by @var{expr}. The argument
|
||
can be either a type name or a symbol. If it is a symbol, the type of
|
||
that symbol is described. The type chain produced by this command is
|
||
a recursive definition of the data type as stored in @value{GDBN}'s
|
||
data structures, including its flags and contained types.
|
||
|
||
@kindex maint selftest
|
||
@cindex self tests
|
||
@item maint selftest @r{[}@var{filter}@r{]}
|
||
Run any self tests that were compiled in to @value{GDBN}. This will
|
||
print a message showing how many tests were run, and how many failed.
|
||
If a @var{filter} is passed, only the tests with @var{filter} in their
|
||
name will by ran.
|
||
|
||
@kindex "maint info selftests"
|
||
@cindex self tests
|
||
@item maint info selftests
|
||
List the selftests compiled in to @value{GDBN}.
|
||
|
||
@kindex maint set dwarf always-disassemble
|
||
@kindex maint show dwarf always-disassemble
|
||
@item maint set dwarf always-disassemble
|
||
@item maint show dwarf always-disassemble
|
||
Control the behavior of @code{info address} when using DWARF debugging
|
||
information.
|
||
|
||
The default is @code{off}, which means that @value{GDBN} should try to
|
||
describe a variable's location in an easily readable format. When
|
||
@code{on}, @value{GDBN} will instead display the DWARF location
|
||
expression in an assembly-like format. Note that some locations are
|
||
too complex for @value{GDBN} to describe simply; in this case you will
|
||
always see the disassembly form.
|
||
|
||
Here is an example of the resulting disassembly:
|
||
|
||
@smallexample
|
||
(gdb) info addr argc
|
||
Symbol "argc" is a complex DWARF expression:
|
||
1: DW_OP_fbreg 0
|
||
@end smallexample
|
||
|
||
For more information on these expressions, see
|
||
@uref{http://www.dwarfstd.org/, the DWARF standard}.
|
||
|
||
@kindex maint set dwarf max-cache-age
|
||
@kindex maint show dwarf max-cache-age
|
||
@item maint set dwarf max-cache-age
|
||
@itemx maint show dwarf max-cache-age
|
||
Control the DWARF compilation unit cache.
|
||
|
||
@cindex DWARF compilation units cache
|
||
In object files with inter-compilation-unit references, such as those
|
||
produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
|
||
reader needs to frequently refer to previously read compilation units.
|
||
This setting controls how long a compilation unit will remain in the
|
||
cache if it is not referenced. A higher limit means that cached
|
||
compilation units will be stored in memory longer, and more total
|
||
memory will be used. Setting it to zero disables caching, which will
|
||
slow down @value{GDBN} startup, but reduce memory consumption.
|
||
|
||
@kindex maint set profile
|
||
@kindex maint show profile
|
||
@cindex profiling GDB
|
||
@item maint set profile
|
||
@itemx maint show profile
|
||
Control profiling of @value{GDBN}.
|
||
|
||
Profiling will be disabled until you use the @samp{maint set profile}
|
||
command to enable it. When you enable profiling, the system will begin
|
||
collecting timing and execution count data; when you disable profiling or
|
||
exit @value{GDBN}, the results will be written to a log file. Remember that
|
||
if you use profiling, @value{GDBN} will overwrite the profiling log file
|
||
(often called @file{gmon.out}). If you have a record of important profiling
|
||
data in a @file{gmon.out} file, be sure to move it to a safe location.
|
||
|
||
Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
|
||
compiled with the @samp{-pg} compiler option.
|
||
|
||
@kindex maint set show-debug-regs
|
||
@kindex maint show show-debug-regs
|
||
@cindex hardware debug registers
|
||
@item maint set show-debug-regs
|
||
@itemx maint show show-debug-regs
|
||
Control whether to show variables that mirror the hardware debug
|
||
registers. Use @code{on} to enable, @code{off} to disable. If
|
||
enabled, the debug registers values are shown when @value{GDBN} inserts or
|
||
removes a hardware breakpoint or watchpoint, and when the inferior
|
||
triggers a hardware-assisted breakpoint or watchpoint.
|
||
|
||
@kindex maint set show-all-tib
|
||
@kindex maint show show-all-tib
|
||
@item maint set show-all-tib
|
||
@itemx maint show show-all-tib
|
||
Control whether to show all non zero areas within a 1k block starting
|
||
at thread local base, when using the @samp{info w32 thread-information-block}
|
||
command.
|
||
|
||
@kindex maint set target-async
|
||
@kindex maint show target-async
|
||
@item maint set target-async
|
||
@itemx maint show target-async
|
||
This controls whether @value{GDBN} targets operate in synchronous or
|
||
asynchronous mode (@pxref{Background Execution}). Normally the
|
||
default is asynchronous, if it is available; but this can be changed
|
||
to more easily debug problems occurring only in synchronous mode.
|
||
|
||
@kindex maint set target-non-stop @var{mode} [on|off|auto]
|
||
@kindex maint show target-non-stop
|
||
@item maint set target-non-stop
|
||
@itemx maint show target-non-stop
|
||
|
||
This controls whether @value{GDBN} targets always operate in non-stop
|
||
mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
|
||
Mode}). The default is @code{auto}, meaning non-stop mode is enabled
|
||
if supported by the target.
|
||
|
||
@table @code
|
||
@item maint set target-non-stop auto
|
||
This is the default mode. @value{GDBN} controls the target in
|
||
non-stop mode if the target supports it.
|
||
|
||
@item maint set target-non-stop on
|
||
@value{GDBN} controls the target in non-stop mode even if the target
|
||
does not indicate support.
|
||
|
||
@item maint set target-non-stop off
|
||
@value{GDBN} does not control the target in non-stop mode even if the
|
||
target supports it.
|
||
@end table
|
||
|
||
@kindex maint set per-command
|
||
@kindex maint show per-command
|
||
@item maint set per-command
|
||
@itemx maint show per-command
|
||
@cindex resources used by commands
|
||
|
||
@value{GDBN} can display the resources used by each command.
|
||
This is useful in debugging performance problems.
|
||
|
||
@table @code
|
||
@item maint set per-command space [on|off]
|
||
@itemx maint show per-command space
|
||
Enable or disable the printing of the memory used by GDB for each command.
|
||
If enabled, @value{GDBN} will display how much memory each command
|
||
took, following the command's own output.
|
||
This can also be requested by invoking @value{GDBN} with the
|
||
@option{--statistics} command-line switch (@pxref{Mode Options}).
|
||
|
||
@item maint set per-command time [on|off]
|
||
@itemx maint show per-command time
|
||
Enable or disable the printing of the execution time of @value{GDBN}
|
||
for each command.
|
||
If enabled, @value{GDBN} will display how much time it
|
||
took to execute each command, following the command's own output.
|
||
Both CPU time and wallclock time are printed.
|
||
Printing both is useful when trying to determine whether the cost is
|
||
CPU or, e.g., disk/network latency.
|
||
Note that the CPU time printed is for @value{GDBN} only, it does not include
|
||
the execution time of the inferior because there's no mechanism currently
|
||
to compute how much time was spent by @value{GDBN} and how much time was
|
||
spent by the program been debugged.
|
||
This can also be requested by invoking @value{GDBN} with the
|
||
@option{--statistics} command-line switch (@pxref{Mode Options}).
|
||
|
||
@item maint set per-command symtab [on|off]
|
||
@itemx maint show per-command symtab
|
||
Enable or disable the printing of basic symbol table statistics
|
||
for each command.
|
||
If enabled, @value{GDBN} will display the following information:
|
||
|
||
@enumerate a
|
||
@item
|
||
number of symbol tables
|
||
@item
|
||
number of primary symbol tables
|
||
@item
|
||
number of blocks in the blockvector
|
||
@end enumerate
|
||
@end table
|
||
|
||
@kindex maint space
|
||
@cindex memory used by commands
|
||
@item maint space @var{value}
|
||
An alias for @code{maint set per-command space}.
|
||
A non-zero value enables it, zero disables it.
|
||
|
||
@kindex maint time
|
||
@cindex time of command execution
|
||
@item maint time @var{value}
|
||
An alias for @code{maint set per-command time}.
|
||
A non-zero value enables it, zero disables it.
|
||
|
||
@kindex maint translate-address
|
||
@item maint translate-address @r{[}@var{section}@r{]} @var{addr}
|
||
Find the symbol stored at the location specified by the address
|
||
@var{addr} and an optional section name @var{section}. If found,
|
||
@value{GDBN} prints the name of the closest symbol and an offset from
|
||
the symbol's location to the specified address. This is similar to
|
||
the @code{info address} command (@pxref{Symbols}), except that this
|
||
command also allows to find symbols in other sections.
|
||
|
||
If section was not specified, the section in which the symbol was found
|
||
is also printed. For dynamically linked executables, the name of
|
||
executable or shared library containing the symbol is printed as well.
|
||
|
||
@end table
|
||
|
||
The following command is useful for non-interactive invocations of
|
||
@value{GDBN}, such as in the test suite.
|
||
|
||
@table @code
|
||
@item set watchdog @var{nsec}
|
||
@kindex set watchdog
|
||
@cindex watchdog timer
|
||
@cindex timeout for commands
|
||
Set the maximum number of seconds @value{GDBN} will wait for the
|
||
target operation to finish. If this time expires, @value{GDBN}
|
||
reports and error and the command is aborted.
|
||
|
||
@item show watchdog
|
||
Show the current setting of the target wait timeout.
|
||
@end table
|
||
|
||
@node Remote Protocol
|
||
@appendix @value{GDBN} Remote Serial Protocol
|
||
|
||
@menu
|
||
* Overview::
|
||
* Packets::
|
||
* Stop Reply Packets::
|
||
* General Query Packets::
|
||
* Architecture-Specific Protocol Details::
|
||
* Tracepoint Packets::
|
||
* Host I/O Packets::
|
||
* Interrupts::
|
||
* Notification Packets::
|
||
* Remote Non-Stop::
|
||
* Packet Acknowledgment::
|
||
* Examples::
|
||
* File-I/O Remote Protocol Extension::
|
||
* Library List Format::
|
||
* Library List Format for SVR4 Targets::
|
||
* Memory Map Format::
|
||
* Thread List Format::
|
||
* Traceframe Info Format::
|
||
* Branch Trace Format::
|
||
* Branch Trace Configuration Format::
|
||
@end menu
|
||
|
||
@node Overview
|
||
@section Overview
|
||
|
||
There may be occasions when you need to know something about the
|
||
protocol---for example, if there is only one serial port to your target
|
||
machine, you might want your program to do something special if it
|
||
recognizes a packet meant for @value{GDBN}.
|
||
|
||
In the examples below, @samp{->} and @samp{<-} are used to indicate
|
||
transmitted and received data, respectively.
|
||
|
||
@cindex protocol, @value{GDBN} remote serial
|
||
@cindex serial protocol, @value{GDBN} remote
|
||
@cindex remote serial protocol
|
||
All @value{GDBN} commands and responses (other than acknowledgments
|
||
and notifications, see @ref{Notification Packets}) are sent as a
|
||
@var{packet}. A @var{packet} is introduced with the character
|
||
@samp{$}, the actual @var{packet-data}, and the terminating character
|
||
@samp{#} followed by a two-digit @var{checksum}:
|
||
|
||
@smallexample
|
||
@code{$}@var{packet-data}@code{#}@var{checksum}
|
||
@end smallexample
|
||
@noindent
|
||
|
||
@cindex checksum, for @value{GDBN} remote
|
||
@noindent
|
||
The two-digit @var{checksum} is computed as the modulo 256 sum of all
|
||
characters between the leading @samp{$} and the trailing @samp{#} (an
|
||
eight bit unsigned checksum).
|
||
|
||
Implementors should note that prior to @value{GDBN} 5.0 the protocol
|
||
specification also included an optional two-digit @var{sequence-id}:
|
||
|
||
@smallexample
|
||
@code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
|
||
@end smallexample
|
||
|
||
@cindex sequence-id, for @value{GDBN} remote
|
||
@noindent
|
||
That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
|
||
has never output @var{sequence-id}s. Stubs that handle packets added
|
||
since @value{GDBN} 5.0 must not accept @var{sequence-id}.
|
||
|
||
When either the host or the target machine receives a packet, the first
|
||
response expected is an acknowledgment: either @samp{+} (to indicate
|
||
the package was received correctly) or @samp{-} (to request
|
||
retransmission):
|
||
|
||
@smallexample
|
||
-> @code{$}@var{packet-data}@code{#}@var{checksum}
|
||
<- @code{+}
|
||
@end smallexample
|
||
@noindent
|
||
|
||
The @samp{+}/@samp{-} acknowledgments can be disabled
|
||
once a connection is established.
|
||
@xref{Packet Acknowledgment}, for details.
|
||
|
||
The host (@value{GDBN}) sends @var{command}s, and the target (the
|
||
debugging stub incorporated in your program) sends a @var{response}. In
|
||
the case of step and continue @var{command}s, the response is only sent
|
||
when the operation has completed, and the target has again stopped all
|
||
threads in all attached processes. This is the default all-stop mode
|
||
behavior, but the remote protocol also supports @value{GDBN}'s non-stop
|
||
execution mode; see @ref{Remote Non-Stop}, for details.
|
||
|
||
@var{packet-data} consists of a sequence of characters with the
|
||
exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
|
||
exceptions).
|
||
|
||
@cindex remote protocol, field separator
|
||
Fields within the packet should be separated using @samp{,} @samp{;} or
|
||
@samp{:}. Except where otherwise noted all numbers are represented in
|
||
@sc{hex} with leading zeros suppressed.
|
||
|
||
Implementors should note that prior to @value{GDBN} 5.0, the character
|
||
@samp{:} could not appear as the third character in a packet (as it
|
||
would potentially conflict with the @var{sequence-id}).
|
||
|
||
@cindex remote protocol, binary data
|
||
@anchor{Binary Data}
|
||
Binary data in most packets is encoded either as two hexadecimal
|
||
digits per byte of binary data. This allowed the traditional remote
|
||
protocol to work over connections which were only seven-bit clean.
|
||
Some packets designed more recently assume an eight-bit clean
|
||
connection, and use a more efficient encoding to send and receive
|
||
binary data.
|
||
|
||
The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
|
||
as an escape character. Any escaped byte is transmitted as the escape
|
||
character followed by the original character XORed with @code{0x20}.
|
||
For example, the byte @code{0x7d} would be transmitted as the two
|
||
bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
|
||
@code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
|
||
@samp{@}}) must always be escaped. Responses sent by the stub
|
||
must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
|
||
is not interpreted as the start of a run-length encoded sequence
|
||
(described next).
|
||
|
||
Response @var{data} can be run-length encoded to save space.
|
||
Run-length encoding replaces runs of identical characters with one
|
||
instance of the repeated character, followed by a @samp{*} and a
|
||
repeat count. The repeat count is itself sent encoded, to avoid
|
||
binary characters in @var{data}: a value of @var{n} is sent as
|
||
@code{@var{n}+29}. For a repeat count greater or equal to 3, this
|
||
produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
|
||
code 32) for a repeat count of 3. (This is because run-length
|
||
encoding starts to win for counts 3 or more.) Thus, for example,
|
||
@samp{0* } is a run-length encoding of ``0000'': the space character
|
||
after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
|
||
3}} more times.
|
||
|
||
The printable characters @samp{#} and @samp{$} or with a numeric value
|
||
greater than 126 must not be used. Runs of six repeats (@samp{#}) or
|
||
seven repeats (@samp{$}) can be expanded using a repeat count of only
|
||
five (@samp{"}). For example, @samp{00000000} can be encoded as
|
||
@samp{0*"00}.
|
||
|
||
The error response returned for some packets includes a two character
|
||
error number. That number is not well defined.
|
||
|
||
@cindex empty response, for unsupported packets
|
||
For any @var{command} not supported by the stub, an empty response
|
||
(@samp{$#00}) should be returned. That way it is possible to extend the
|
||
protocol. A newer @value{GDBN} can tell if a packet is supported based
|
||
on that response.
|
||
|
||
At a minimum, a stub is required to support the @samp{g} and @samp{G}
|
||
commands for register access, and the @samp{m} and @samp{M} commands
|
||
for memory access. Stubs that only control single-threaded targets
|
||
can implement run control with the @samp{c} (continue), and @samp{s}
|
||
(step) commands. Stubs that support multi-threading targets should
|
||
support the @samp{vCont} command. All other commands are optional.
|
||
|
||
@node Packets
|
||
@section Packets
|
||
|
||
The following table provides a complete list of all currently defined
|
||
@var{command}s and their corresponding response @var{data}.
|
||
@xref{File-I/O Remote Protocol Extension}, for details about the File
|
||
I/O extension of the remote protocol.
|
||
|
||
Each packet's description has a template showing the packet's overall
|
||
syntax, followed by an explanation of the packet's meaning. We
|
||
include spaces in some of the templates for clarity; these are not
|
||
part of the packet's syntax. No @value{GDBN} packet uses spaces to
|
||
separate its components. For example, a template like @samp{foo
|
||
@var{bar} @var{baz}} describes a packet beginning with the three ASCII
|
||
bytes @samp{foo}, followed by a @var{bar}, followed directly by a
|
||
@var{baz}. @value{GDBN} does not transmit a space character between the
|
||
@samp{foo} and the @var{bar}, or between the @var{bar} and the
|
||
@var{baz}.
|
||
|
||
@cindex @var{thread-id}, in remote protocol
|
||
@anchor{thread-id syntax}
|
||
Several packets and replies include a @var{thread-id} field to identify
|
||
a thread. Normally these are positive numbers with a target-specific
|
||
interpretation, formatted as big-endian hex strings. A @var{thread-id}
|
||
can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
|
||
pick any thread.
|
||
|
||
In addition, the remote protocol supports a multiprocess feature in
|
||
which the @var{thread-id} syntax is extended to optionally include both
|
||
process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
|
||
The @var{pid} (process) and @var{tid} (thread) components each have the
|
||
format described above: a positive number with target-specific
|
||
interpretation formatted as a big-endian hex string, literal @samp{-1}
|
||
to indicate all processes or threads (respectively), or @samp{0} to
|
||
indicate an arbitrary process or thread. Specifying just a process, as
|
||
@samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
|
||
error to specify all processes but a specific thread, such as
|
||
@samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
|
||
for those packets and replies explicitly documented to include a process
|
||
ID, rather than a @var{thread-id}.
|
||
|
||
The multiprocess @var{thread-id} syntax extensions are only used if both
|
||
@value{GDBN} and the stub report support for the @samp{multiprocess}
|
||
feature using @samp{qSupported}. @xref{multiprocess extensions}, for
|
||
more information.
|
||
|
||
Note that all packet forms beginning with an upper- or lower-case
|
||
letter, other than those described here, are reserved for future use.
|
||
|
||
Here are the packet descriptions.
|
||
|
||
@table @samp
|
||
|
||
@item !
|
||
@cindex @samp{!} packet
|
||
@anchor{extended mode}
|
||
Enable extended mode. In extended mode, the remote server is made
|
||
persistent. The @samp{R} packet is used to restart the program being
|
||
debugged.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The remote target both supports and has enabled extended mode.
|
||
@end table
|
||
|
||
@item ?
|
||
@cindex @samp{?} packet
|
||
@anchor{? packet}
|
||
Indicate the reason the target halted. The reply is the same as for
|
||
step and continue. This packet has a special interpretation when the
|
||
target is in non-stop mode; see @ref{Remote Non-Stop}.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item A @var{arglen},@var{argnum},@var{arg},@dots{}
|
||
@cindex @samp{A} packet
|
||
Initialized @code{argv[]} array passed into program. @var{arglen}
|
||
specifies the number of bytes in the hex encoded byte stream
|
||
@var{arg}. See @code{gdbserver} for more details.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The arguments were set.
|
||
@item E @var{NN}
|
||
An error occurred.
|
||
@end table
|
||
|
||
@item b @var{baud}
|
||
@cindex @samp{b} packet
|
||
(Don't use this packet; its behavior is not well-defined.)
|
||
Change the serial line speed to @var{baud}.
|
||
|
||
JTC: @emph{When does the transport layer state change? When it's
|
||
received, or after the ACK is transmitted. In either case, there are
|
||
problems if the command or the acknowledgment packet is dropped.}
|
||
|
||
Stan: @emph{If people really wanted to add something like this, and get
|
||
it working for the first time, they ought to modify ser-unix.c to send
|
||
some kind of out-of-band message to a specially-setup stub and have the
|
||
switch happen "in between" packets, so that from remote protocol's point
|
||
of view, nothing actually happened.}
|
||
|
||
@item B @var{addr},@var{mode}
|
||
@cindex @samp{B} packet
|
||
Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
|
||
breakpoint at @var{addr}.
|
||
|
||
Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
|
||
(@pxref{insert breakpoint or watchpoint packet}).
|
||
|
||
@cindex @samp{bc} packet
|
||
@anchor{bc}
|
||
@item bc
|
||
Backward continue. Execute the target system in reverse. No parameter.
|
||
@xref{Reverse Execution}, for more information.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@cindex @samp{bs} packet
|
||
@anchor{bs}
|
||
@item bs
|
||
Backward single step. Execute one instruction in reverse. No parameter.
|
||
@xref{Reverse Execution}, for more information.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item c @r{[}@var{addr}@r{]}
|
||
@cindex @samp{c} packet
|
||
Continue at @var{addr}, which is the address to resume. If @var{addr}
|
||
is omitted, resume at current address.
|
||
|
||
This packet is deprecated for multi-threading support. @xref{vCont
|
||
packet}.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item C @var{sig}@r{[};@var{addr}@r{]}
|
||
@cindex @samp{C} packet
|
||
Continue with signal @var{sig} (hex signal number). If
|
||
@samp{;@var{addr}} is omitted, resume at same address.
|
||
|
||
This packet is deprecated for multi-threading support. @xref{vCont
|
||
packet}.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item d
|
||
@cindex @samp{d} packet
|
||
Toggle debug flag.
|
||
|
||
Don't use this packet; instead, define a general set packet
|
||
(@pxref{General Query Packets}).
|
||
|
||
@item D
|
||
@itemx D;@var{pid}
|
||
@cindex @samp{D} packet
|
||
The first form of the packet is used to detach @value{GDBN} from the
|
||
remote system. It is sent to the remote target
|
||
before @value{GDBN} disconnects via the @code{detach} command.
|
||
|
||
The second form, including a process ID, is used when multiprocess
|
||
protocol extensions are enabled (@pxref{multiprocess extensions}), to
|
||
detach only a specific process. The @var{pid} is specified as a
|
||
big-endian hex string.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item F @var{RC},@var{EE},@var{CF};@var{XX}
|
||
@cindex @samp{F} packet
|
||
A reply from @value{GDBN} to an @samp{F} packet sent by the target.
|
||
This is part of the File-I/O protocol extension. @xref{File-I/O
|
||
Remote Protocol Extension}, for the specification.
|
||
|
||
@item g
|
||
@anchor{read registers packet}
|
||
@cindex @samp{g} packet
|
||
Read general registers.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX@dots{}}
|
||
Each byte of register data is described by two hex digits. The bytes
|
||
with the register are transmitted in target byte order. The size of
|
||
each register and their position within the @samp{g} packet are
|
||
determined by the @value{GDBN} internal gdbarch functions
|
||
@code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
|
||
|
||
When reading registers from a trace frame (@pxref{Analyze Collected
|
||
Data,,Using the Collected Data}), the stub may also return a string of
|
||
literal @samp{x}'s in place of the register data digits, to indicate
|
||
that the corresponding register has not been collected, thus its value
|
||
is unavailable. For example, for an architecture with 4 registers of
|
||
4 bytes each, the following reply indicates to @value{GDBN} that
|
||
registers 0 and 2 have not been collected, while registers 1 and 3
|
||
have been collected, and both have zero value:
|
||
|
||
@smallexample
|
||
-> @code{g}
|
||
<- @code{xxxxxxxx00000000xxxxxxxx00000000}
|
||
@end smallexample
|
||
|
||
@item E @var{NN}
|
||
for an error.
|
||
@end table
|
||
|
||
@item G @var{XX@dots{}}
|
||
@cindex @samp{G} packet
|
||
Write general registers. @xref{read registers packet}, for a
|
||
description of the @var{XX@dots{}} data.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item H @var{op} @var{thread-id}
|
||
@cindex @samp{H} packet
|
||
Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
|
||
@samp{G}, et.al.). Depending on the operation to be performed, @var{op}
|
||
should be @samp{c} for step and continue operations (note that this
|
||
is deprecated, supporting the @samp{vCont} command is a better
|
||
option), and @samp{g} for other operations. The thread designator
|
||
@var{thread-id} has the format and interpretation described in
|
||
@ref{thread-id syntax}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@c FIXME: JTC:
|
||
@c 'H': How restrictive (or permissive) is the thread model. If a
|
||
@c thread is selected and stopped, are other threads allowed
|
||
@c to continue to execute? As I mentioned above, I think the
|
||
@c semantics of each command when a thread is selected must be
|
||
@c described. For example:
|
||
@c
|
||
@c 'g': If the stub supports threads and a specific thread is
|
||
@c selected, returns the register block from that thread;
|
||
@c otherwise returns current registers.
|
||
@c
|
||
@c 'G' If the stub supports threads and a specific thread is
|
||
@c selected, sets the registers of the register block of
|
||
@c that thread; otherwise sets current registers.
|
||
|
||
@item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
|
||
@anchor{cycle step packet}
|
||
@cindex @samp{i} packet
|
||
Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
|
||
present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
|
||
step starting at that address.
|
||
|
||
@item I
|
||
@cindex @samp{I} packet
|
||
Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
|
||
step packet}.
|
||
|
||
@item k
|
||
@cindex @samp{k} packet
|
||
Kill request.
|
||
|
||
The exact effect of this packet is not specified.
|
||
|
||
For a bare-metal target, it may power cycle or reset the target
|
||
system. For that reason, the @samp{k} packet has no reply.
|
||
|
||
For a single-process target, it may kill that process if possible.
|
||
|
||
A multiple-process target may choose to kill just one process, or all
|
||
that are under @value{GDBN}'s control. For more precise control, use
|
||
the vKill packet (@pxref{vKill packet}).
|
||
|
||
If the target system immediately closes the connection in response to
|
||
@samp{k}, @value{GDBN} does not consider the lack of packet
|
||
acknowledgment to be an error, and assumes the kill was successful.
|
||
|
||
If connected using @kbd{target extended-remote}, and the target does
|
||
not close the connection in response to a kill request, @value{GDBN}
|
||
probes the target state as if a new connection was opened
|
||
(@pxref{? packet}).
|
||
|
||
@item m @var{addr},@var{length}
|
||
@cindex @samp{m} packet
|
||
Read @var{length} addressable memory units starting at address @var{addr}
|
||
(@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
|
||
any particular boundary.
|
||
|
||
The stub need not use any particular size or alignment when gathering
|
||
data from memory for the response; even if @var{addr} is word-aligned
|
||
and @var{length} is a multiple of the word size, the stub is free to
|
||
use byte accesses, or not. For this reason, this packet may not be
|
||
suitable for accessing memory-mapped I/O devices.
|
||
@cindex alignment of remote memory accesses
|
||
@cindex size of remote memory accesses
|
||
@cindex memory, alignment and size of remote accesses
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX@dots{}}
|
||
Memory contents; each byte is transmitted as a two-digit hexadecimal number.
|
||
The reply may contain fewer addressable memory units than requested if the
|
||
server was able to read only part of the region of memory.
|
||
@item E @var{NN}
|
||
@var{NN} is errno
|
||
@end table
|
||
|
||
@item M @var{addr},@var{length}:@var{XX@dots{}}
|
||
@cindex @samp{M} packet
|
||
Write @var{length} addressable memory units starting at address @var{addr}
|
||
(@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
|
||
byte is transmitted as a two-digit hexadecimal number.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error (this includes the case where only part of the data was
|
||
written).
|
||
@end table
|
||
|
||
@item p @var{n}
|
||
@cindex @samp{p} packet
|
||
Read the value of register @var{n}; @var{n} is in hex.
|
||
@xref{read registers packet}, for a description of how the returned
|
||
register value is encoded.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX@dots{}}
|
||
the register's value
|
||
@item E @var{NN}
|
||
for an error
|
||
@item @w{}
|
||
Indicating an unrecognized @var{query}.
|
||
@end table
|
||
|
||
@item P @var{n@dots{}}=@var{r@dots{}}
|
||
@anchor{write register packet}
|
||
@cindex @samp{P} packet
|
||
Write register @var{n@dots{}} with value @var{r@dots{}}. The register
|
||
number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
|
||
digits for each byte in the register (target byte order).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item q @var{name} @var{params}@dots{}
|
||
@itemx Q @var{name} @var{params}@dots{}
|
||
@cindex @samp{q} packet
|
||
@cindex @samp{Q} packet
|
||
General query (@samp{q}) and set (@samp{Q}). These packets are
|
||
described fully in @ref{General Query Packets}.
|
||
|
||
@item r
|
||
@cindex @samp{r} packet
|
||
Reset the entire system.
|
||
|
||
Don't use this packet; use the @samp{R} packet instead.
|
||
|
||
@item R @var{XX}
|
||
@cindex @samp{R} packet
|
||
Restart the program being debugged. The @var{XX}, while needed, is ignored.
|
||
This packet is only available in extended mode (@pxref{extended mode}).
|
||
|
||
The @samp{R} packet has no reply.
|
||
|
||
@item s @r{[}@var{addr}@r{]}
|
||
@cindex @samp{s} packet
|
||
Single step, resuming at @var{addr}. If
|
||
@var{addr} is omitted, resume at same address.
|
||
|
||
This packet is deprecated for multi-threading support. @xref{vCont
|
||
packet}.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item S @var{sig}@r{[};@var{addr}@r{]}
|
||
@anchor{step with signal packet}
|
||
@cindex @samp{S} packet
|
||
Step with signal. This is analogous to the @samp{C} packet, but
|
||
requests a single-step, rather than a normal resumption of execution.
|
||
|
||
This packet is deprecated for multi-threading support. @xref{vCont
|
||
packet}.
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item t @var{addr}:@var{PP},@var{MM}
|
||
@cindex @samp{t} packet
|
||
Search backwards starting at address @var{addr} for a match with pattern
|
||
@var{PP} and mask @var{MM}, both of which are are 4 byte long.
|
||
There must be at least 3 digits in @var{addr}.
|
||
|
||
@item T @var{thread-id}
|
||
@cindex @samp{T} packet
|
||
Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
thread is still alive
|
||
@item E @var{NN}
|
||
thread is dead
|
||
@end table
|
||
|
||
@item v
|
||
Packets starting with @samp{v} are identified by a multi-letter name,
|
||
up to the first @samp{;} or @samp{?} (or the end of the packet).
|
||
|
||
@item vAttach;@var{pid}
|
||
@cindex @samp{vAttach} packet
|
||
Attach to a new process with the specified process ID @var{pid}.
|
||
The process ID is a
|
||
hexadecimal integer identifying the process. In all-stop mode, all
|
||
threads in the attached process are stopped; in non-stop mode, it may be
|
||
attached without being stopped if that is supported by the target.
|
||
|
||
@c In non-stop mode, on a successful vAttach, the stub should set the
|
||
@c current thread to a thread of the newly-attached process. After
|
||
@c attaching, GDB queries for the attached process's thread ID with qC.
|
||
@c Also note that, from a user perspective, whether or not the
|
||
@c target is stopped on attach in non-stop mode depends on whether you
|
||
@c use the foreground or background version of the attach command, not
|
||
@c on what vAttach does; GDB does the right thing with respect to either
|
||
@c stopping or restarting threads.
|
||
|
||
This packet is only available in extended mode (@pxref{extended mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item E @var{nn}
|
||
for an error
|
||
@item @r{Any stop packet}
|
||
for success in all-stop mode (@pxref{Stop Reply Packets})
|
||
@item OK
|
||
for success in non-stop mode (@pxref{Remote Non-Stop})
|
||
@end table
|
||
|
||
@item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
|
||
@cindex @samp{vCont} packet
|
||
@anchor{vCont packet}
|
||
Resume the inferior, specifying different actions for each thread.
|
||
|
||
For each inferior thread, the leftmost action with a matching
|
||
@var{thread-id} is applied. Threads that don't match any action
|
||
remain in their current state. Thread IDs are specified using the
|
||
syntax described in @ref{thread-id syntax}. If multiprocess
|
||
extensions (@pxref{multiprocess extensions}) are supported, actions
|
||
can be specified to match all threads in a process by using the
|
||
@samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
|
||
@var{thread-id} matches all threads. Specifying no actions is an
|
||
error.
|
||
|
||
Currently supported actions are:
|
||
|
||
@table @samp
|
||
@item c
|
||
Continue.
|
||
@item C @var{sig}
|
||
Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
|
||
@item s
|
||
Step.
|
||
@item S @var{sig}
|
||
Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
|
||
@item t
|
||
Stop.
|
||
@item r @var{start},@var{end}
|
||
Step once, and then keep stepping as long as the thread stops at
|
||
addresses between @var{start} (inclusive) and @var{end} (exclusive).
|
||
The remote stub reports a stop reply when either the thread goes out
|
||
of the range or is stopped due to an unrelated reason, such as hitting
|
||
a breakpoint. @xref{range stepping}.
|
||
|
||
If the range is empty (@var{start} == @var{end}), then the action
|
||
becomes equivalent to the @samp{s} action. In other words,
|
||
single-step once, and report the stop (even if the stepped instruction
|
||
jumps to @var{start}).
|
||
|
||
(A stop reply may be sent at any point even if the PC is still within
|
||
the stepping range; for example, it is valid to implement this packet
|
||
in a degenerate way as a single instruction step operation.)
|
||
|
||
@end table
|
||
|
||
The optional argument @var{addr} normally associated with the
|
||
@samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
|
||
not supported in @samp{vCont}.
|
||
|
||
The @samp{t} action is only relevant in non-stop mode
|
||
(@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
|
||
A stop reply should be generated for any affected thread not already stopped.
|
||
When a thread is stopped by means of a @samp{t} action,
|
||
the corresponding stop reply should indicate that the thread has stopped with
|
||
signal @samp{0}, regardless of whether the target uses some other signal
|
||
as an implementation detail.
|
||
|
||
The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
|
||
@samp{r} actions for threads that are already running. Conversely,
|
||
the server must ignore @samp{t} actions for threads that are already
|
||
stopped.
|
||
|
||
@emph{Note:} In non-stop mode, a thread is considered running until
|
||
@value{GDBN} acknowleges an asynchronous stop notification for it with
|
||
the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
|
||
|
||
The stub must support @samp{vCont} if it reports support for
|
||
multiprocess extensions (@pxref{multiprocess extensions}).
|
||
|
||
Reply:
|
||
@xref{Stop Reply Packets}, for the reply specifications.
|
||
|
||
@item vCont?
|
||
@cindex @samp{vCont?} packet
|
||
Request a list of actions supported by the @samp{vCont} packet.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item vCont@r{[};@var{action}@dots{}@r{]}
|
||
The @samp{vCont} packet is supported. Each @var{action} is a supported
|
||
command in the @samp{vCont} packet.
|
||
@item @w{}
|
||
The @samp{vCont} packet is not supported.
|
||
@end table
|
||
|
||
@anchor{vCtrlC packet}
|
||
@item vCtrlC
|
||
@cindex @samp{vCtrlC} packet
|
||
Interrupt remote target as if a control-C was pressed on the remote
|
||
terminal. This is the equivalent to reacting to the @code{^C}
|
||
(@samp{\003}, the control-C character) character in all-stop mode
|
||
while the target is running, except this works in non-stop mode.
|
||
@xref{interrupting remote targets}, for more info on the all-stop
|
||
variant.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item E @var{nn}
|
||
for an error
|
||
@item OK
|
||
for success
|
||
@end table
|
||
|
||
@item vFile:@var{operation}:@var{parameter}@dots{}
|
||
@cindex @samp{vFile} packet
|
||
Perform a file operation on the target system. For details,
|
||
see @ref{Host I/O Packets}.
|
||
|
||
@item vFlashErase:@var{addr},@var{length}
|
||
@cindex @samp{vFlashErase} packet
|
||
Direct the stub to erase @var{length} bytes of flash starting at
|
||
@var{addr}. The region may enclose any number of flash blocks, but
|
||
its start and end must fall on block boundaries, as indicated by the
|
||
flash block size appearing in the memory map (@pxref{Memory Map
|
||
Format}). @value{GDBN} groups flash memory programming operations
|
||
together, and sends a @samp{vFlashDone} request after each group; the
|
||
stub is allowed to delay erase operation until the @samp{vFlashDone}
|
||
packet is received.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item vFlashWrite:@var{addr}:@var{XX@dots{}}
|
||
@cindex @samp{vFlashWrite} packet
|
||
Direct the stub to write data to flash address @var{addr}. The data
|
||
is passed in binary form using the same encoding as for the @samp{X}
|
||
packet (@pxref{Binary Data}). The memory ranges specified by
|
||
@samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
|
||
not overlap, and must appear in order of increasing addresses
|
||
(although @samp{vFlashErase} packets for higher addresses may already
|
||
have been received; the ordering is guaranteed only between
|
||
@samp{vFlashWrite} packets). If a packet writes to an address that was
|
||
neither erased by a preceding @samp{vFlashErase} packet nor by some other
|
||
target-specific method, the results are unpredictable.
|
||
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E.memtype
|
||
for vFlashWrite addressing non-flash memory
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item vFlashDone
|
||
@cindex @samp{vFlashDone} packet
|
||
Indicate to the stub that flash programming operation is finished.
|
||
The stub is permitted to delay or batch the effects of a group of
|
||
@samp{vFlashErase} and @samp{vFlashWrite} packets until a
|
||
@samp{vFlashDone} packet is received. The contents of the affected
|
||
regions of flash memory are unpredictable until the @samp{vFlashDone}
|
||
request is completed.
|
||
|
||
@item vKill;@var{pid}
|
||
@cindex @samp{vKill} packet
|
||
@anchor{vKill packet}
|
||
Kill the process with the specified process ID @var{pid}, which is a
|
||
hexadecimal integer identifying the process. This packet is used in
|
||
preference to @samp{k} when multiprocess protocol extensions are
|
||
supported; see @ref{multiprocess extensions}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item E @var{nn}
|
||
for an error
|
||
@item OK
|
||
for success
|
||
@end table
|
||
|
||
@item vMustReplyEmpty
|
||
@cindex @samp{vMustReplyEmpty} packet
|
||
The correct reply to an unknown @samp{v} packet is to return the empty
|
||
string, however, some older versions of @command{gdbserver} would
|
||
incorrectly return @samp{OK} for unknown @samp{v} packets.
|
||
|
||
The @samp{vMustReplyEmpty} is used as a feature test to check how
|
||
@command{gdbserver} handles unknown packets, it is important that this
|
||
packet be handled in the same way as other unknown @samp{v} packets.
|
||
If this packet is handled differently to other unknown @samp{v}
|
||
packets then it is possile that @value{GDBN} may run into problems in
|
||
other areas, specifically around use of @samp{vFile:setfs:}.
|
||
|
||
@item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
|
||
@cindex @samp{vRun} packet
|
||
Run the program @var{filename}, passing it each @var{argument} on its
|
||
command line. The file and arguments are hex-encoded strings. If
|
||
@var{filename} is an empty string, the stub may use a default program
|
||
(e.g.@: the last program run). The program is created in the stopped
|
||
state.
|
||
|
||
@c FIXME: What about non-stop mode?
|
||
|
||
This packet is only available in extended mode (@pxref{extended mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item E @var{nn}
|
||
for an error
|
||
@item @r{Any stop packet}
|
||
for success (@pxref{Stop Reply Packets})
|
||
@end table
|
||
|
||
@item vStopped
|
||
@cindex @samp{vStopped} packet
|
||
@xref{Notification Packets}.
|
||
|
||
@item X @var{addr},@var{length}:@var{XX@dots{}}
|
||
@anchor{X packet}
|
||
@cindex @samp{X} packet
|
||
Write data to memory, where the data is transmitted in binary.
|
||
Memory is specified by its address @var{addr} and number of addressable memory
|
||
units @var{length} (@pxref{addressable memory unit});
|
||
@samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
for success
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item z @var{type},@var{addr},@var{kind}
|
||
@itemx Z @var{type},@var{addr},@var{kind}
|
||
@anchor{insert breakpoint or watchpoint packet}
|
||
@cindex @samp{z} packet
|
||
@cindex @samp{Z} packets
|
||
Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
|
||
watchpoint starting at address @var{address} of kind @var{kind}.
|
||
|
||
Each breakpoint and watchpoint packet @var{type} is documented
|
||
separately.
|
||
|
||
@emph{Implementation notes: A remote target shall return an empty string
|
||
for an unrecognized breakpoint or watchpoint packet @var{type}. A
|
||
remote target shall support either both or neither of a given
|
||
@samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
|
||
avoid potential problems with duplicate packets, the operations should
|
||
be implemented in an idempotent way.}
|
||
|
||
@item z0,@var{addr},@var{kind}
|
||
@itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
|
||
@cindex @samp{z0} packet
|
||
@cindex @samp{Z0} packet
|
||
Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
|
||
@var{addr} of type @var{kind}.
|
||
|
||
A software breakpoint is implemented by replacing the instruction at
|
||
@var{addr} with a software breakpoint or trap instruction. The
|
||
@var{kind} is target-specific and typically indicates the size of the
|
||
breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
|
||
@sc{mips} can insert either a 2 or 4 byte breakpoint. Some
|
||
architectures have additional meanings for @var{kind}
|
||
(@pxref{Architecture-Specific Protocol Details}); if no
|
||
architecture-specific value is being used, it should be @samp{0}.
|
||
@var{kind} is hex-encoded. @var{cond_list} is an optional list of
|
||
conditional expressions in bytecode form that should be evaluated on
|
||
the target's side. These are the conditions that should be taken into
|
||
consideration when deciding if the breakpoint trigger should be
|
||
reported back to @value{GDBN}.
|
||
|
||
See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
|
||
for how to best report a software breakpoint event to @value{GDBN}.
|
||
|
||
The @var{cond_list} parameter is comprised of a series of expressions,
|
||
concatenated without separators. Each expression has the following form:
|
||
|
||
@table @samp
|
||
|
||
@item X @var{len},@var{expr}
|
||
@var{len} is the length of the bytecode expression and @var{expr} is the
|
||
actual conditional expression in bytecode form.
|
||
|
||
@end table
|
||
|
||
The optional @var{cmd_list} parameter introduces commands that may be
|
||
run on the target, rather than being reported back to @value{GDBN}.
|
||
The parameter starts with a numeric flag @var{persist}; if the flag is
|
||
nonzero, then the breakpoint may remain active and the commands
|
||
continue to be run even when @value{GDBN} disconnects from the target.
|
||
Following this flag is a series of expressions concatenated with no
|
||
separators. Each expression has the following form:
|
||
|
||
@table @samp
|
||
|
||
@item X @var{len},@var{expr}
|
||
@var{len} is the length of the bytecode expression and @var{expr} is the
|
||
actual commands expression in bytecode form.
|
||
|
||
@end table
|
||
|
||
@emph{Implementation note: It is possible for a target to copy or move
|
||
code that contains software breakpoints (e.g., when implementing
|
||
overlays). The behavior of this packet, in the presence of such a
|
||
target, is not defined.}
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
success
|
||
@item @w{}
|
||
not supported
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item z1,@var{addr},@var{kind}
|
||
@itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
|
||
@cindex @samp{z1} packet
|
||
@cindex @samp{Z1} packet
|
||
Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
|
||
address @var{addr}.
|
||
|
||
A hardware breakpoint is implemented using a mechanism that is not
|
||
dependent on being able to modify the target's memory. The
|
||
@var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
|
||
same meaning as in @samp{Z0} packets.
|
||
|
||
@emph{Implementation note: A hardware breakpoint is not affected by code
|
||
movement.}
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
success
|
||
@item @w{}
|
||
not supported
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item z2,@var{addr},@var{kind}
|
||
@itemx Z2,@var{addr},@var{kind}
|
||
@cindex @samp{z2} packet
|
||
@cindex @samp{Z2} packet
|
||
Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
|
||
The number of bytes to watch is specified by @var{kind}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
success
|
||
@item @w{}
|
||
not supported
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item z3,@var{addr},@var{kind}
|
||
@itemx Z3,@var{addr},@var{kind}
|
||
@cindex @samp{z3} packet
|
||
@cindex @samp{Z3} packet
|
||
Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
|
||
The number of bytes to watch is specified by @var{kind}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
success
|
||
@item @w{}
|
||
not supported
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@item z4,@var{addr},@var{kind}
|
||
@itemx Z4,@var{addr},@var{kind}
|
||
@cindex @samp{z4} packet
|
||
@cindex @samp{Z4} packet
|
||
Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
|
||
The number of bytes to watch is specified by @var{kind}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
success
|
||
@item @w{}
|
||
not supported
|
||
@item E @var{NN}
|
||
for an error
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node Stop Reply Packets
|
||
@section Stop Reply Packets
|
||
@cindex stop reply packets
|
||
|
||
The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
|
||
@samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
|
||
receive any of the below as a reply. Except for @samp{?}
|
||
and @samp{vStopped}, that reply is only returned
|
||
when the target halts. In the below the exact meaning of @dfn{signal
|
||
number} is defined by the header @file{include/gdb/signals.h} in the
|
||
@value{GDBN} source code.
|
||
|
||
In non-stop mode, the server will simply reply @samp{OK} to commands
|
||
such as @samp{vCont}; any stop will be the subject of a future
|
||
notification. @xref{Remote Non-Stop}.
|
||
|
||
As in the description of request packets, we include spaces in the
|
||
reply templates for clarity; these are not part of the reply packet's
|
||
syntax. No @value{GDBN} stop reply packet uses spaces to separate its
|
||
components.
|
||
|
||
@table @samp
|
||
|
||
@item S @var{AA}
|
||
The program received signal number @var{AA} (a two-digit hexadecimal
|
||
number). This is equivalent to a @samp{T} response with no
|
||
@var{n}:@var{r} pairs.
|
||
|
||
@item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
|
||
@cindex @samp{T} packet reply
|
||
The program received signal number @var{AA} (a two-digit hexadecimal
|
||
number). This is equivalent to an @samp{S} response, except that the
|
||
@samp{@var{n}:@var{r}} pairs can carry values of important registers
|
||
and other information directly in the stop reply packet, reducing
|
||
round-trip latency. Single-step and breakpoint traps are reported
|
||
this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
If @var{n} is a hexadecimal number, it is a register number, and the
|
||
corresponding @var{r} gives that register's value. The data @var{r} is a
|
||
series of bytes in target byte order, with each byte given by a
|
||
two-digit hex number.
|
||
|
||
@item
|
||
If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
|
||
the stopped thread, as specified in @ref{thread-id syntax}.
|
||
|
||
@item
|
||
If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
|
||
the core on which the stop event was detected.
|
||
|
||
@item
|
||
If @var{n} is a recognized @dfn{stop reason}, it describes a more
|
||
specific event that stopped the target. The currently defined stop
|
||
reasons are listed below. The @var{aa} should be @samp{05}, the trap
|
||
signal. At most one stop reason should be present.
|
||
|
||
@item
|
||
Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
|
||
and go on to the next; this allows us to extend the protocol in the
|
||
future.
|
||
@end itemize
|
||
|
||
The currently defined stop reasons are:
|
||
|
||
@table @samp
|
||
@item watch
|
||
@itemx rwatch
|
||
@itemx awatch
|
||
The packet indicates a watchpoint hit, and @var{r} is the data address, in
|
||
hex.
|
||
|
||
@item syscall_entry
|
||
@itemx syscall_return
|
||
The packet indicates a syscall entry or return, and @var{r} is the
|
||
syscall number, in hex.
|
||
|
||
@cindex shared library events, remote reply
|
||
@item library
|
||
The packet indicates that the loaded libraries have changed.
|
||
@value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
|
||
list of loaded libraries. The @var{r} part is ignored.
|
||
|
||
@cindex replay log events, remote reply
|
||
@item replaylog
|
||
The packet indicates that the target cannot continue replaying
|
||
logged execution events, because it has reached the end (or the
|
||
beginning when executing backward) of the log. The value of @var{r}
|
||
will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
|
||
for more information.
|
||
|
||
@item swbreak
|
||
@anchor{swbreak stop reason}
|
||
The packet indicates a software breakpoint instruction was executed,
|
||
irrespective of whether it was @value{GDBN} that planted the
|
||
breakpoint or the breakpoint is hardcoded in the program. The @var{r}
|
||
part must be left empty.
|
||
|
||
On some architectures, such as x86, at the architecture level, when a
|
||
breakpoint instruction executes the program counter points at the
|
||
breakpoint address plus an offset. On such targets, the stub is
|
||
responsible for adjusting the PC to point back at the breakpoint
|
||
address.
|
||
|
||
This packet should not be sent by default; older @value{GDBN} versions
|
||
did not support it. @value{GDBN} requests it, by supplying an
|
||
appropriate @samp{qSupported} feature (@pxref{qSupported}). The
|
||
remote stub must also supply the appropriate @samp{qSupported} feature
|
||
indicating support.
|
||
|
||
This packet is required for correct non-stop mode operation.
|
||
|
||
@item hwbreak
|
||
The packet indicates the target stopped for a hardware breakpoint.
|
||
The @var{r} part must be left empty.
|
||
|
||
The same remarks about @samp{qSupported} and non-stop mode above
|
||
apply.
|
||
|
||
@cindex fork events, remote reply
|
||
@item fork
|
||
The packet indicates that @code{fork} was called, and @var{r}
|
||
is the thread ID of the new child process. Refer to
|
||
@ref{thread-id syntax} for the format of the @var{thread-id}
|
||
field. This packet is only applicable to targets that support
|
||
fork events.
|
||
|
||
This packet should not be sent by default; older @value{GDBN} versions
|
||
did not support it. @value{GDBN} requests it, by supplying an
|
||
appropriate @samp{qSupported} feature (@pxref{qSupported}). The
|
||
remote stub must also supply the appropriate @samp{qSupported} feature
|
||
indicating support.
|
||
|
||
@cindex vfork events, remote reply
|
||
@item vfork
|
||
The packet indicates that @code{vfork} was called, and @var{r}
|
||
is the thread ID of the new child process. Refer to
|
||
@ref{thread-id syntax} for the format of the @var{thread-id}
|
||
field. This packet is only applicable to targets that support
|
||
vfork events.
|
||
|
||
This packet should not be sent by default; older @value{GDBN} versions
|
||
did not support it. @value{GDBN} requests it, by supplying an
|
||
appropriate @samp{qSupported} feature (@pxref{qSupported}). The
|
||
remote stub must also supply the appropriate @samp{qSupported} feature
|
||
indicating support.
|
||
|
||
@cindex vforkdone events, remote reply
|
||
@item vforkdone
|
||
The packet indicates that a child process created by a vfork
|
||
has either called @code{exec} or terminated, so that the
|
||
address spaces of the parent and child process are no longer
|
||
shared. The @var{r} part is ignored. This packet is only
|
||
applicable to targets that support vforkdone events.
|
||
|
||
This packet should not be sent by default; older @value{GDBN} versions
|
||
did not support it. @value{GDBN} requests it, by supplying an
|
||
appropriate @samp{qSupported} feature (@pxref{qSupported}). The
|
||
remote stub must also supply the appropriate @samp{qSupported} feature
|
||
indicating support.
|
||
|
||
@cindex exec events, remote reply
|
||
@item exec
|
||
The packet indicates that @code{execve} was called, and @var{r}
|
||
is the absolute pathname of the file that was executed, in hex.
|
||
This packet is only applicable to targets that support exec events.
|
||
|
||
This packet should not be sent by default; older @value{GDBN} versions
|
||
did not support it. @value{GDBN} requests it, by supplying an
|
||
appropriate @samp{qSupported} feature (@pxref{qSupported}). The
|
||
remote stub must also supply the appropriate @samp{qSupported} feature
|
||
indicating support.
|
||
|
||
@cindex thread create event, remote reply
|
||
@anchor{thread create event}
|
||
@item create
|
||
The packet indicates that the thread was just created. The new thread
|
||
is stopped until @value{GDBN} sets it running with a resumption packet
|
||
(@pxref{vCont packet}). This packet should not be sent by default;
|
||
@value{GDBN} requests it with the @ref{QThreadEvents} packet. See
|
||
also the @samp{w} (@pxref{thread exit event}) remote reply below. The
|
||
@var{r} part is ignored.
|
||
|
||
@end table
|
||
|
||
@item W @var{AA}
|
||
@itemx W @var{AA} ; process:@var{pid}
|
||
The process exited, and @var{AA} is the exit status. This is only
|
||
applicable to certain targets.
|
||
|
||
The second form of the response, including the process ID of the
|
||
exited process, can be used only when @value{GDBN} has reported
|
||
support for multiprocess protocol extensions; see @ref{multiprocess
|
||
extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
|
||
hex strings.
|
||
|
||
@item X @var{AA}
|
||
@itemx X @var{AA} ; process:@var{pid}
|
||
The process terminated with signal @var{AA}.
|
||
|
||
The second form of the response, including the process ID of the
|
||
terminated process, can be used only when @value{GDBN} has reported
|
||
support for multiprocess protocol extensions; see @ref{multiprocess
|
||
extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
|
||
hex strings.
|
||
|
||
@anchor{thread exit event}
|
||
@cindex thread exit event, remote reply
|
||
@item w @var{AA} ; @var{tid}
|
||
|
||
The thread exited, and @var{AA} is the exit status. This response
|
||
should not be sent by default; @value{GDBN} requests it with the
|
||
@ref{QThreadEvents} packet. See also @ref{thread create event} above.
|
||
@var{AA} is formatted as a big-endian hex string.
|
||
|
||
@item N
|
||
There are no resumed threads left in the target. In other words, even
|
||
though the process is alive, the last resumed thread has exited. For
|
||
example, say the target process has two threads: thread 1 and thread
|
||
2. The client leaves thread 1 stopped, and resumes thread 2, which
|
||
subsequently exits. At this point, even though the process is still
|
||
alive, and thus no @samp{W} stop reply is sent, no thread is actually
|
||
executing either. The @samp{N} stop reply thus informs the client
|
||
that it can stop waiting for stop replies. This packet should not be
|
||
sent by default; older @value{GDBN} versions did not support it.
|
||
@value{GDBN} requests it, by supplying an appropriate
|
||
@samp{qSupported} feature (@pxref{qSupported}). The remote stub must
|
||
also supply the appropriate @samp{qSupported} feature indicating
|
||
support.
|
||
|
||
@item O @var{XX}@dots{}
|
||
@samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
|
||
written as the program's console output. This can happen at any time
|
||
while the program is running and the debugger should continue to wait
|
||
for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
|
||
|
||
@item F @var{call-id},@var{parameter}@dots{}
|
||
@var{call-id} is the identifier which says which host system call should
|
||
be called. This is just the name of the function. Translation into the
|
||
correct system call is only applicable as it's defined in @value{GDBN}.
|
||
@xref{File-I/O Remote Protocol Extension}, for a list of implemented
|
||
system calls.
|
||
|
||
@samp{@var{parameter}@dots{}} is a list of parameters as defined for
|
||
this very system call.
|
||
|
||
The target replies with this packet when it expects @value{GDBN} to
|
||
call a host system call on behalf of the target. @value{GDBN} replies
|
||
with an appropriate @samp{F} packet and keeps up waiting for the next
|
||
reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
|
||
or @samp{s} action is expected to be continued. @xref{File-I/O Remote
|
||
Protocol Extension}, for more details.
|
||
|
||
@end table
|
||
|
||
@node General Query Packets
|
||
@section General Query Packets
|
||
@cindex remote query requests
|
||
|
||
Packets starting with @samp{q} are @dfn{general query packets};
|
||
packets starting with @samp{Q} are @dfn{general set packets}. General
|
||
query and set packets are a semi-unified form for retrieving and
|
||
sending information to and from the stub.
|
||
|
||
The initial letter of a query or set packet is followed by a name
|
||
indicating what sort of thing the packet applies to. For example,
|
||
@value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
|
||
definitions with the stub. These packet names follow some
|
||
conventions:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The name must not contain commas, colons or semicolons.
|
||
@item
|
||
Most @value{GDBN} query and set packets have a leading upper case
|
||
letter.
|
||
@item
|
||
The names of custom vendor packets should use a company prefix, in
|
||
lower case, followed by a period. For example, packets designed at
|
||
the Acme Corporation might begin with @samp{qacme.foo} (for querying
|
||
foos) or @samp{Qacme.bar} (for setting bars).
|
||
@end itemize
|
||
|
||
The name of a query or set packet should be separated from any
|
||
parameters by a @samp{:}; the parameters themselves should be
|
||
separated by @samp{,} or @samp{;}. Stubs must be careful to match the
|
||
full packet name, and check for a separator or the end of the packet,
|
||
in case two packet names share a common prefix. New packets should not begin
|
||
with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
|
||
packets predate these conventions, and have arguments without any terminator
|
||
for the packet name; we suspect they are in widespread use in places that
|
||
are difficult to upgrade. The @samp{qC} packet has no arguments, but some
|
||
existing stubs (e.g.@: RedBoot) are known to not check for the end of the
|
||
packet.}.
|
||
|
||
Like the descriptions of the other packets, each description here
|
||
has a template showing the packet's overall syntax, followed by an
|
||
explanation of the packet's meaning. We include spaces in some of the
|
||
templates for clarity; these are not part of the packet's syntax. No
|
||
@value{GDBN} packet uses spaces to separate its components.
|
||
|
||
Here are the currently defined query and set packets:
|
||
|
||
@table @samp
|
||
|
||
@item QAgent:1
|
||
@itemx QAgent:0
|
||
Turn on or off the agent as a helper to perform some debugging operations
|
||
delegated from @value{GDBN} (@pxref{Control Agent}).
|
||
|
||
@item QAllow:@var{op}:@var{val}@dots{}
|
||
@cindex @samp{QAllow} packet
|
||
Specify which operations @value{GDBN} expects to request of the
|
||
target, as a semicolon-separated list of operation name and value
|
||
pairs. Possible values for @var{op} include @samp{WriteReg},
|
||
@samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
|
||
@samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
|
||
indicating that @value{GDBN} will not request the operation, or 1,
|
||
indicating that it may. (The target can then use this to set up its
|
||
own internals optimally, for instance if the debugger never expects to
|
||
insert breakpoints, it may not need to install its own trap handler.)
|
||
|
||
@item qC
|
||
@cindex current thread, remote request
|
||
@cindex @samp{qC} packet
|
||
Return the current thread ID.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item QC @var{thread-id}
|
||
Where @var{thread-id} is a thread ID as documented in
|
||
@ref{thread-id syntax}.
|
||
@item @r{(anything else)}
|
||
Any other reply implies the old thread ID.
|
||
@end table
|
||
|
||
@item qCRC:@var{addr},@var{length}
|
||
@cindex CRC of memory block, remote request
|
||
@cindex @samp{qCRC} packet
|
||
@anchor{qCRC packet}
|
||
Compute the CRC checksum of a block of memory using CRC-32 defined in
|
||
IEEE 802.3. The CRC is computed byte at a time, taking the most
|
||
significant bit of each byte first. The initial pattern code
|
||
@code{0xffffffff} is used to ensure leading zeros affect the CRC.
|
||
|
||
@emph{Note:} This is the same CRC used in validating separate debug
|
||
files (@pxref{Separate Debug Files, , Debugging Information in Separate
|
||
Files}). However the algorithm is slightly different. When validating
|
||
separate debug files, the CRC is computed taking the @emph{least}
|
||
significant bit of each byte first, and the final result is inverted to
|
||
detect trailing zeros.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item E @var{NN}
|
||
An error (such as memory fault)
|
||
@item C @var{crc32}
|
||
The specified memory region's checksum is @var{crc32}.
|
||
@end table
|
||
|
||
@item QDisableRandomization:@var{value}
|
||
@cindex disable address space randomization, remote request
|
||
@cindex @samp{QDisableRandomization} packet
|
||
Some target operating systems will randomize the virtual address space
|
||
of the inferior process as a security feature, but provide a feature
|
||
to disable such randomization, e.g.@: to allow for a more deterministic
|
||
debugging experience. On such systems, this packet with a @var{value}
|
||
of 1 directs the target to disable address space randomization for
|
||
processes subsequently started via @samp{vRun} packets, while a packet
|
||
with a @var{value} of 0 tells the target to enable address space
|
||
randomization.
|
||
|
||
This packet is only available in extended mode (@pxref{extended mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QDisableRandomization} is not supported
|
||
by the stub.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
This should only be done on targets that actually support disabling
|
||
address space randomization.
|
||
|
||
@item QStartupWithShell:@var{value}
|
||
@cindex startup with shell, remote request
|
||
@cindex @samp{QStartupWithShell} packet
|
||
On UNIX-like targets, it is possible to start the inferior using a
|
||
shell program. This is the default behavior on both @value{GDBN} and
|
||
@command{gdbserver} (@pxref{set startup-with-shell}). This packet is
|
||
used to inform @command{gdbserver} whether it should start the
|
||
inferior using a shell or not.
|
||
|
||
If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
|
||
to start the inferior. If @var{value} is @samp{1},
|
||
@command{gdbserver} will use a shell to start the inferior. All other
|
||
values are considered an error.
|
||
|
||
This packet is only available in extended mode (@pxref{extended
|
||
mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}). This should only be done on targets that
|
||
actually support starting the inferior using a shell.
|
||
|
||
Use of this packet is controlled by the @code{set startup-with-shell}
|
||
command; @pxref{set startup-with-shell}.
|
||
|
||
@item QEnvironmentHexEncoded:@var{hex-value}
|
||
@anchor{QEnvironmentHexEncoded}
|
||
@cindex set environment variable, remote request
|
||
@cindex @samp{QEnvironmentHexEncoded} packet
|
||
On UNIX-like targets, it is possible to set environment variables that
|
||
will be passed to the inferior during the startup process. This
|
||
packet is used to inform @command{gdbserver} of an environment
|
||
variable that has been defined by the user on @value{GDBN} (@pxref{set
|
||
environment}).
|
||
|
||
The packet is composed by @var{hex-value}, an hex encoded
|
||
representation of the @var{name=value} format representing an
|
||
environment variable. The name of the environment variable is
|
||
represented by @var{name}, and the value to be assigned to the
|
||
environment variable is represented by @var{value}. If the variable
|
||
has no value (i.e., the value is @code{null}), then @var{value} will
|
||
not be present.
|
||
|
||
This packet is only available in extended mode (@pxref{extended
|
||
mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}). This should only be done on targets that
|
||
actually support passing environment variables to the starting
|
||
inferior.
|
||
|
||
This packet is related to the @code{set environment} command;
|
||
@pxref{set environment}.
|
||
|
||
@item QEnvironmentUnset:@var{hex-value}
|
||
@anchor{QEnvironmentUnset}
|
||
@cindex unset environment variable, remote request
|
||
@cindex @samp{QEnvironmentUnset} packet
|
||
On UNIX-like targets, it is possible to unset environment variables
|
||
before starting the inferior in the remote target. This packet is
|
||
used to inform @command{gdbserver} of an environment variable that has
|
||
been unset by the user on @value{GDBN} (@pxref{unset environment}).
|
||
|
||
The packet is composed by @var{hex-value}, an hex encoded
|
||
representation of the name of the environment variable to be unset.
|
||
|
||
This packet is only available in extended mode (@pxref{extended
|
||
mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}). This should only be done on targets that
|
||
actually support passing environment variables to the starting
|
||
inferior.
|
||
|
||
This packet is related to the @code{unset environment} command;
|
||
@pxref{unset environment}.
|
||
|
||
@item QEnvironmentReset
|
||
@anchor{QEnvironmentReset}
|
||
@cindex reset environment, remote request
|
||
@cindex @samp{QEnvironmentReset} packet
|
||
On UNIX-like targets, this packet is used to reset the state of
|
||
environment variables in the remote target before starting the
|
||
inferior. In this context, reset means unsetting all environment
|
||
variables that were previously set by the user (i.e., were not
|
||
initially present in the environment). It is sent to
|
||
@command{gdbserver} before the @samp{QEnvironmentHexEncoded}
|
||
(@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
|
||
(@pxref{QEnvironmentUnset}) packets.
|
||
|
||
This packet is only available in extended mode (@pxref{extended
|
||
mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}). This should only be done on targets that
|
||
actually support passing environment variables to the starting
|
||
inferior.
|
||
|
||
@item QSetWorkingDir:@r{[}@var{directory}@r{]}
|
||
@anchor{QSetWorkingDir packet}
|
||
@cindex set working directory, remote request
|
||
@cindex @samp{QSetWorkingDir} packet
|
||
This packet is used to inform the remote server of the intended
|
||
current working directory for programs that are going to be executed.
|
||
|
||
The packet is composed by @var{directory}, an hex encoded
|
||
representation of the directory that the remote inferior will use as
|
||
its current working directory. If @var{directory} is an empty string,
|
||
the remote server should reset the inferior's current working
|
||
directory to its original, empty value.
|
||
|
||
This packet is only available in extended mode (@pxref{extended
|
||
mode}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
@end table
|
||
|
||
@item qfThreadInfo
|
||
@itemx qsThreadInfo
|
||
@cindex list active threads, remote request
|
||
@cindex @samp{qfThreadInfo} packet
|
||
@cindex @samp{qsThreadInfo} packet
|
||
Obtain a list of all active thread IDs from the target (OS). Since there
|
||
may be too many active threads to fit into one reply packet, this query
|
||
works iteratively: it may require more than one query/reply sequence to
|
||
obtain the entire list of threads. The first query of the sequence will
|
||
be the @samp{qfThreadInfo} query; subsequent queries in the
|
||
sequence will be the @samp{qsThreadInfo} query.
|
||
|
||
NOTE: This packet replaces the @samp{qL} query (see below).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item m @var{thread-id}
|
||
A single thread ID
|
||
@item m @var{thread-id},@var{thread-id}@dots{}
|
||
a comma-separated list of thread IDs
|
||
@item l
|
||
(lower case letter @samp{L}) denotes end of list.
|
||
@end table
|
||
|
||
In response to each query, the target will reply with a list of one or
|
||
more thread IDs, separated by commas.
|
||
@value{GDBN} will respond to each reply with a request for more thread
|
||
ids (using the @samp{qs} form of the query), until the target responds
|
||
with @samp{l} (lower-case ell, for @dfn{last}).
|
||
Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
|
||
fields.
|
||
|
||
@emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
|
||
initial connection with the remote target, and the very first thread ID
|
||
mentioned in the reply will be stopped by @value{GDBN} in a subsequent
|
||
message. Therefore, the stub should ensure that the first thread ID in
|
||
the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
|
||
|
||
@item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
|
||
@cindex get thread-local storage address, remote request
|
||
@cindex @samp{qGetTLSAddr} packet
|
||
Fetch the address associated with thread local storage specified
|
||
by @var{thread-id}, @var{offset}, and @var{lm}.
|
||
|
||
@var{thread-id} is the thread ID associated with the
|
||
thread for which to fetch the TLS address. @xref{thread-id syntax}.
|
||
|
||
@var{offset} is the (big endian, hex encoded) offset associated with the
|
||
thread local variable. (This offset is obtained from the debug
|
||
information associated with the variable.)
|
||
|
||
@var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
|
||
load module associated with the thread local storage. For example,
|
||
a @sc{gnu}/Linux system will pass the link map address of the shared
|
||
object associated with the thread local storage under consideration.
|
||
Other operating environments may choose to represent the load module
|
||
differently, so the precise meaning of this parameter will vary.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX}@dots{}
|
||
Hex encoded (big endian) bytes representing the address of the thread
|
||
local storage requested.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
|
||
@end table
|
||
|
||
@item qGetTIBAddr:@var{thread-id}
|
||
@cindex get thread information block address
|
||
@cindex @samp{qGetTIBAddr} packet
|
||
Fetch address of the Windows OS specific Thread Information Block.
|
||
|
||
@var{thread-id} is the thread ID associated with the thread.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX}@dots{}
|
||
Hex encoded (big endian) bytes representing the linear address of the
|
||
thread information block.
|
||
|
||
@item E @var{nn}
|
||
An error occured. This means that either the thread was not found, or the
|
||
address could not be retrieved.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
|
||
@end table
|
||
|
||
@item qL @var{startflag} @var{threadcount} @var{nextthread}
|
||
Obtain thread information from RTOS. Where: @var{startflag} (one hex
|
||
digit) is one to indicate the first query and zero to indicate a
|
||
subsequent query; @var{threadcount} (two hex digits) is the maximum
|
||
number of threads the response packet can contain; and @var{nextthread}
|
||
(eight hex digits), for subsequent queries (@var{startflag} is zero), is
|
||
returned in the response as @var{argthread}.
|
||
|
||
Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
|
||
Where: @var{count} (two hex digits) is the number of threads being
|
||
returned; @var{done} (one hex digit) is zero to indicate more threads
|
||
and one indicates no further threads; @var{argthreadid} (eight hex
|
||
digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
|
||
is a sequence of thread IDs, @var{threadid} (eight hex
|
||
digits), from the target. See @code{remote.c:parse_threadlist_response()}.
|
||
@end table
|
||
|
||
@item qOffsets
|
||
@cindex section offsets, remote request
|
||
@cindex @samp{qOffsets} packet
|
||
Get section offsets that the target used when relocating the downloaded
|
||
image.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
|
||
Relocate the @code{Text} section by @var{xxx} from its original address.
|
||
Relocate the @code{Data} section by @var{yyy} from its original address.
|
||
If the object file format provides segment information (e.g.@: @sc{elf}
|
||
@samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
|
||
segments by the supplied offsets.
|
||
|
||
@emph{Note: while a @code{Bss} offset may be included in the response,
|
||
@value{GDBN} ignores this and instead applies the @code{Data} offset
|
||
to the @code{Bss} section.}
|
||
|
||
@item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
|
||
Relocate the first segment of the object file, which conventionally
|
||
contains program code, to a starting address of @var{xxx}. If
|
||
@samp{DataSeg} is specified, relocate the second segment, which
|
||
conventionally contains modifiable data, to a starting address of
|
||
@var{yyy}. @value{GDBN} will report an error if the object file
|
||
does not contain segment information, or does not contain at least
|
||
as many segments as mentioned in the reply. Extra segments are
|
||
kept at fixed offsets relative to the last relocated segment.
|
||
@end table
|
||
|
||
@item qP @var{mode} @var{thread-id}
|
||
@cindex thread information, remote request
|
||
@cindex @samp{qP} packet
|
||
Returns information on @var{thread-id}. Where: @var{mode} is a hex
|
||
encoded 32 bit mode; @var{thread-id} is a thread ID
|
||
(@pxref{thread-id syntax}).
|
||
|
||
Don't use this packet; use the @samp{qThreadExtraInfo} query instead
|
||
(see below).
|
||
|
||
Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
|
||
|
||
@item QNonStop:1
|
||
@itemx QNonStop:0
|
||
@cindex non-stop mode, remote request
|
||
@cindex @samp{QNonStop} packet
|
||
@anchor{QNonStop}
|
||
Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
|
||
@xref{Remote Non-Stop}, for more information.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QNonStop} is not supported by
|
||
the stub.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
Use of this packet is controlled by the @code{set non-stop} command;
|
||
@pxref{Non-Stop Mode}.
|
||
|
||
@item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
|
||
@itemx QCatchSyscalls:0
|
||
@cindex catch syscalls from inferior, remote request
|
||
@cindex @samp{QCatchSyscalls} packet
|
||
@anchor{QCatchSyscalls}
|
||
Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
|
||
catching syscalls from the inferior process.
|
||
|
||
For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
|
||
in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
|
||
is listed, every system call should be reported.
|
||
|
||
Note that if a syscall not in the list is reported, @value{GDBN} will
|
||
still filter the event according to its own list from all corresponding
|
||
@code{catch syscall} commands. However, it is more efficient to only
|
||
report the requested syscalls.
|
||
|
||
Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
|
||
@samp{QCatchSyscalls:1} list is completely replaced by the new list.
|
||
|
||
If the inferior process execs, the state of @samp{QCatchSyscalls} is
|
||
kept for the new process too. On targets where exec may affect syscall
|
||
numbers, for example with exec between 32 and 64-bit processes, the
|
||
client should send a new packet with the new syscall list.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. @var{nn} are hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QCatchSyscalls} is not supported by
|
||
the stub.
|
||
@end table
|
||
|
||
Use of this packet is controlled by the @code{set remote catch-syscalls}
|
||
command (@pxref{Remote Configuration, set remote catch-syscalls}).
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
|
||
@cindex pass signals to inferior, remote request
|
||
@cindex @samp{QPassSignals} packet
|
||
@anchor{QPassSignals}
|
||
Each listed @var{signal} should be passed directly to the inferior process.
|
||
Signals are numbered identically to continue packets and stop replies
|
||
(@pxref{Stop Reply Packets}). Each @var{signal} list item should be
|
||
strictly greater than the previous item. These signals do not need to stop
|
||
the inferior, or be reported to @value{GDBN}. All other signals should be
|
||
reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
|
||
combine; any earlier @samp{QPassSignals} list is completely replaced by the
|
||
new list. This packet improves performance when using @samp{handle
|
||
@var{signal} nostop noprint pass}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QPassSignals} is not supported by
|
||
the stub.
|
||
@end table
|
||
|
||
Use of this packet is controlled by the @code{set remote pass-signals}
|
||
command (@pxref{Remote Configuration, set remote pass-signals}).
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
|
||
@cindex signals the inferior may see, remote request
|
||
@cindex @samp{QProgramSignals} packet
|
||
@anchor{QProgramSignals}
|
||
Each listed @var{signal} may be delivered to the inferior process.
|
||
Others should be silently discarded.
|
||
|
||
In some cases, the remote stub may need to decide whether to deliver a
|
||
signal to the program or not without @value{GDBN} involvement. One
|
||
example of that is while detaching --- the program's threads may have
|
||
stopped for signals that haven't yet had a chance of being reported to
|
||
@value{GDBN}, and so the remote stub can use the signal list specified
|
||
by this packet to know whether to deliver or ignore those pending
|
||
signals.
|
||
|
||
This does not influence whether to deliver a signal as requested by a
|
||
resumption packet (@pxref{vCont packet}).
|
||
|
||
Signals are numbered identically to continue packets and stop replies
|
||
(@pxref{Stop Reply Packets}). Each @var{signal} list item should be
|
||
strictly greater than the previous item. Multiple
|
||
@samp{QProgramSignals} packets do not combine; any earlier
|
||
@samp{QProgramSignals} list is completely replaced by the new list.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QProgramSignals} is not supported
|
||
by the stub.
|
||
@end table
|
||
|
||
Use of this packet is controlled by the @code{set remote program-signals}
|
||
command (@pxref{Remote Configuration, set remote program-signals}).
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@anchor{QThreadEvents}
|
||
@item QThreadEvents:1
|
||
@itemx QThreadEvents:0
|
||
@cindex thread create/exit events, remote request
|
||
@cindex @samp{QThreadEvents} packet
|
||
|
||
Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
|
||
reporting of thread create and exit events. @xref{thread create
|
||
event}, for the reply specifications. For example, this is used in
|
||
non-stop mode when @value{GDBN} stops a set of threads and
|
||
synchronously waits for the their corresponding stop replies. Without
|
||
exit events, if one of the threads exits, @value{GDBN} would hang
|
||
forever not knowing that it should no longer expect a stop for that
|
||
same thread. @value{GDBN} does not enable this feature unless the
|
||
stub reports that it supports it by including @samp{QThreadEvents+} in
|
||
its @samp{qSupported} reply.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The request succeeded.
|
||
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
|
||
@item @w{}
|
||
An empty reply indicates that @samp{QThreadEvents} is not supported by
|
||
the stub.
|
||
@end table
|
||
|
||
Use of this packet is controlled by the @code{set remote thread-events}
|
||
command (@pxref{Remote Configuration, set remote thread-events}).
|
||
|
||
@item qRcmd,@var{command}
|
||
@cindex execute remote command, remote request
|
||
@cindex @samp{qRcmd} packet
|
||
@var{command} (hex encoded) is passed to the local interpreter for
|
||
execution. Invalid commands should be reported using the output
|
||
string. Before the final result packet, the target may also respond
|
||
with a number of intermediate @samp{O@var{output}} console output
|
||
packets. @emph{Implementors should note that providing access to a
|
||
stubs's interpreter may have security implications}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
A command response with no output.
|
||
@item @var{OUTPUT}
|
||
A command response with the hex encoded output string @var{OUTPUT}.
|
||
@item E @var{NN}
|
||
Indicate a badly formed request.
|
||
@item @w{}
|
||
An empty reply indicates that @samp{qRcmd} is not recognized.
|
||
@end table
|
||
|
||
(Note that the @code{qRcmd} packet's name is separated from the
|
||
command by a @samp{,}, not a @samp{:}, contrary to the naming
|
||
conventions above. Please don't use this packet as a model for new
|
||
packets.)
|
||
|
||
@item qSearch:memory:@var{address};@var{length};@var{search-pattern}
|
||
@cindex searching memory, in remote debugging
|
||
@ifnotinfo
|
||
@cindex @samp{qSearch:memory} packet
|
||
@end ifnotinfo
|
||
@cindex @samp{qSearch memory} packet
|
||
@anchor{qSearch memory}
|
||
Search @var{length} bytes at @var{address} for @var{search-pattern}.
|
||
Both @var{address} and @var{length} are encoded in hex;
|
||
@var{search-pattern} is a sequence of bytes, also hex encoded.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item 0
|
||
The pattern was not found.
|
||
@item 1,address
|
||
The pattern was found at @var{address}.
|
||
@item E @var{NN}
|
||
A badly formed request or an error was encountered while searching memory.
|
||
@item @w{}
|
||
An empty reply indicates that @samp{qSearch:memory} is not recognized.
|
||
@end table
|
||
|
||
@item QStartNoAckMode
|
||
@cindex @samp{QStartNoAckMode} packet
|
||
@anchor{QStartNoAckMode}
|
||
Request that the remote stub disable the normal @samp{+}/@samp{-}
|
||
protocol acknowledgments (@pxref{Packet Acknowledgment}).
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The stub has switched to no-acknowledgment mode.
|
||
@value{GDBN} acknowledges this reponse,
|
||
but neither the stub nor @value{GDBN} shall send or expect further
|
||
@samp{+}/@samp{-} acknowledgments in the current connection.
|
||
@item @w{}
|
||
An empty reply indicates that the stub does not support no-acknowledgment mode.
|
||
@end table
|
||
|
||
@item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
|
||
@cindex supported packets, remote query
|
||
@cindex features of the remote protocol
|
||
@cindex @samp{qSupported} packet
|
||
@anchor{qSupported}
|
||
Tell the remote stub about features supported by @value{GDBN}, and
|
||
query the stub for features it supports. This packet allows
|
||
@value{GDBN} and the remote stub to take advantage of each others'
|
||
features. @samp{qSupported} also consolidates multiple feature probes
|
||
at startup, to improve @value{GDBN} performance---a single larger
|
||
packet performs better than multiple smaller probe packets on
|
||
high-latency links. Some features may enable behavior which must not
|
||
be on by default, e.g.@: because it would confuse older clients or
|
||
stubs. Other features may describe packets which could be
|
||
automatically probed for, but are not. These features must be
|
||
reported before @value{GDBN} will use them. This ``default
|
||
unsupported'' behavior is not appropriate for all packets, but it
|
||
helps to keep the initial connection time under control with new
|
||
versions of @value{GDBN} which support increasing numbers of packets.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
|
||
The stub supports or does not support each returned @var{stubfeature},
|
||
depending on the form of each @var{stubfeature} (see below for the
|
||
possible forms).
|
||
@item @w{}
|
||
An empty reply indicates that @samp{qSupported} is not recognized,
|
||
or that no features needed to be reported to @value{GDBN}.
|
||
@end table
|
||
|
||
The allowed forms for each feature (either a @var{gdbfeature} in the
|
||
@samp{qSupported} packet, or a @var{stubfeature} in the response)
|
||
are:
|
||
|
||
@table @samp
|
||
@item @var{name}=@var{value}
|
||
The remote protocol feature @var{name} is supported, and associated
|
||
with the specified @var{value}. The format of @var{value} depends
|
||
on the feature, but it must not include a semicolon.
|
||
@item @var{name}+
|
||
The remote protocol feature @var{name} is supported, and does not
|
||
need an associated value.
|
||
@item @var{name}-
|
||
The remote protocol feature @var{name} is not supported.
|
||
@item @var{name}?
|
||
The remote protocol feature @var{name} may be supported, and
|
||
@value{GDBN} should auto-detect support in some other way when it is
|
||
needed. This form will not be used for @var{gdbfeature} notifications,
|
||
but may be used for @var{stubfeature} responses.
|
||
@end table
|
||
|
||
Whenever the stub receives a @samp{qSupported} request, the
|
||
supplied set of @value{GDBN} features should override any previous
|
||
request. This allows @value{GDBN} to put the stub in a known
|
||
state, even if the stub had previously been communicating with
|
||
a different version of @value{GDBN}.
|
||
|
||
The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
|
||
are defined:
|
||
|
||
@table @samp
|
||
@item multiprocess
|
||
This feature indicates whether @value{GDBN} supports multiprocess
|
||
extensions to the remote protocol. @value{GDBN} does not use such
|
||
extensions unless the stub also reports that it supports them by
|
||
including @samp{multiprocess+} in its @samp{qSupported} reply.
|
||
@xref{multiprocess extensions}, for details.
|
||
|
||
@item xmlRegisters
|
||
This feature indicates that @value{GDBN} supports the XML target
|
||
description. If the stub sees @samp{xmlRegisters=} with target
|
||
specific strings separated by a comma, it will report register
|
||
description.
|
||
|
||
@item qRelocInsn
|
||
This feature indicates whether @value{GDBN} supports the
|
||
@samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
|
||
instruction reply packet}).
|
||
|
||
@item swbreak
|
||
This feature indicates whether @value{GDBN} supports the swbreak stop
|
||
reason in stop replies. @xref{swbreak stop reason}, for details.
|
||
|
||
@item hwbreak
|
||
This feature indicates whether @value{GDBN} supports the hwbreak stop
|
||
reason in stop replies. @xref{swbreak stop reason}, for details.
|
||
|
||
@item fork-events
|
||
This feature indicates whether @value{GDBN} supports fork event
|
||
extensions to the remote protocol. @value{GDBN} does not use such
|
||
extensions unless the stub also reports that it supports them by
|
||
including @samp{fork-events+} in its @samp{qSupported} reply.
|
||
|
||
@item vfork-events
|
||
This feature indicates whether @value{GDBN} supports vfork event
|
||
extensions to the remote protocol. @value{GDBN} does not use such
|
||
extensions unless the stub also reports that it supports them by
|
||
including @samp{vfork-events+} in its @samp{qSupported} reply.
|
||
|
||
@item exec-events
|
||
This feature indicates whether @value{GDBN} supports exec event
|
||
extensions to the remote protocol. @value{GDBN} does not use such
|
||
extensions unless the stub also reports that it supports them by
|
||
including @samp{exec-events+} in its @samp{qSupported} reply.
|
||
|
||
@item vContSupported
|
||
This feature indicates whether @value{GDBN} wants to know the
|
||
supported actions in the reply to @samp{vCont?} packet.
|
||
@end table
|
||
|
||
Stubs should ignore any unknown values for
|
||
@var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
|
||
packet supports receiving packets of unlimited length (earlier
|
||
versions of @value{GDBN} may reject overly long responses). Additional values
|
||
for @var{gdbfeature} may be defined in the future to let the stub take
|
||
advantage of new features in @value{GDBN}, e.g.@: incompatible
|
||
improvements in the remote protocol---the @samp{multiprocess} feature is
|
||
an example of such a feature. The stub's reply should be independent
|
||
of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
|
||
describes all the features it supports, and then the stub replies with
|
||
all the features it supports.
|
||
|
||
Similarly, @value{GDBN} will silently ignore unrecognized stub feature
|
||
responses, as long as each response uses one of the standard forms.
|
||
|
||
Some features are flags. A stub which supports a flag feature
|
||
should respond with a @samp{+} form response. Other features
|
||
require values, and the stub should respond with an @samp{=}
|
||
form response.
|
||
|
||
Each feature has a default value, which @value{GDBN} will use if
|
||
@samp{qSupported} is not available or if the feature is not mentioned
|
||
in the @samp{qSupported} response. The default values are fixed; a
|
||
stub is free to omit any feature responses that match the defaults.
|
||
|
||
Not all features can be probed, but for those which can, the probing
|
||
mechanism is useful: in some cases, a stub's internal
|
||
architecture may not allow the protocol layer to know some information
|
||
about the underlying target in advance. This is especially common in
|
||
stubs which may be configured for multiple targets.
|
||
|
||
These are the currently defined stub features and their properties:
|
||
|
||
@multitable @columnfractions 0.35 0.2 0.12 0.2
|
||
@c NOTE: The first row should be @headitem, but we do not yet require
|
||
@c a new enough version of Texinfo (4.7) to use @headitem.
|
||
@item Feature Name
|
||
@tab Value Required
|
||
@tab Default
|
||
@tab Probe Allowed
|
||
|
||
@item @samp{PacketSize}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{qXfer:auxv:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:btrace:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:btrace-conf:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:exec-file:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:features:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:libraries:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:libraries-svr4:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{augmented-libraries-svr4-read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{qXfer:memory-map:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:sdata:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:spu:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:spu:write}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:siginfo:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:siginfo:write}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:threads:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:traceframe-info:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:uib:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{qXfer:fdpic:read}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{Qbtrace:off}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{Qbtrace:bts}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{Qbtrace:pt}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{Qbtrace-conf:bts:size}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{Qbtrace-conf:pt:size}
|
||
@tab Yes
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{QNonStop}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{QCatchSyscalls}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{QPassSignals}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{QStartNoAckMode}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab Yes
|
||
|
||
@item @samp{multiprocess}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{ConditionalBreakpoints}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{ConditionalTracepoints}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{ReverseContinue}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{ReverseStep}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{TracepointSource}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{QAgent}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{QAllow}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{QDisableRandomization}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{EnableDisableTracepoints}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{QTBuffer:size}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{tracenz}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{BreakpointCommands}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{swbreak}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{hwbreak}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{fork-events}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{vfork-events}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{exec-events}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{QThreadEvents}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@item @samp{no-resumed}
|
||
@tab No
|
||
@tab @samp{-}
|
||
@tab No
|
||
|
||
@end multitable
|
||
|
||
These are the currently defined stub features, in more detail:
|
||
|
||
@table @samp
|
||
@cindex packet size, remote protocol
|
||
@item PacketSize=@var{bytes}
|
||
The remote stub can accept packets up to at least @var{bytes} in
|
||
length. @value{GDBN} will send packets up to this size for bulk
|
||
transfers, and will never send larger packets. This is a limit on the
|
||
data characters in the packet, including the frame and checksum.
|
||
There is no trailing NUL byte in a remote protocol packet; if the stub
|
||
stores packets in a NUL-terminated format, it should allow an extra
|
||
byte in its buffer for the NUL. If this stub feature is not supported,
|
||
@value{GDBN} guesses based on the size of the @samp{g} packet response.
|
||
|
||
@item qXfer:auxv:read
|
||
The remote stub understands the @samp{qXfer:auxv:read} packet
|
||
(@pxref{qXfer auxiliary vector read}).
|
||
|
||
@item qXfer:btrace:read
|
||
The remote stub understands the @samp{qXfer:btrace:read}
|
||
packet (@pxref{qXfer btrace read}).
|
||
|
||
@item qXfer:btrace-conf:read
|
||
The remote stub understands the @samp{qXfer:btrace-conf:read}
|
||
packet (@pxref{qXfer btrace-conf read}).
|
||
|
||
@item qXfer:exec-file:read
|
||
The remote stub understands the @samp{qXfer:exec-file:read} packet
|
||
(@pxref{qXfer executable filename read}).
|
||
|
||
@item qXfer:features:read
|
||
The remote stub understands the @samp{qXfer:features:read} packet
|
||
(@pxref{qXfer target description read}).
|
||
|
||
@item qXfer:libraries:read
|
||
The remote stub understands the @samp{qXfer:libraries:read} packet
|
||
(@pxref{qXfer library list read}).
|
||
|
||
@item qXfer:libraries-svr4:read
|
||
The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
|
||
(@pxref{qXfer svr4 library list read}).
|
||
|
||
@item augmented-libraries-svr4-read
|
||
The remote stub understands the augmented form of the
|
||
@samp{qXfer:libraries-svr4:read} packet
|
||
(@pxref{qXfer svr4 library list read}).
|
||
|
||
@item qXfer:memory-map:read
|
||
The remote stub understands the @samp{qXfer:memory-map:read} packet
|
||
(@pxref{qXfer memory map read}).
|
||
|
||
@item qXfer:sdata:read
|
||
The remote stub understands the @samp{qXfer:sdata:read} packet
|
||
(@pxref{qXfer sdata read}).
|
||
|
||
@item qXfer:spu:read
|
||
The remote stub understands the @samp{qXfer:spu:read} packet
|
||
(@pxref{qXfer spu read}).
|
||
|
||
@item qXfer:spu:write
|
||
The remote stub understands the @samp{qXfer:spu:write} packet
|
||
(@pxref{qXfer spu write}).
|
||
|
||
@item qXfer:siginfo:read
|
||
The remote stub understands the @samp{qXfer:siginfo:read} packet
|
||
(@pxref{qXfer siginfo read}).
|
||
|
||
@item qXfer:siginfo:write
|
||
The remote stub understands the @samp{qXfer:siginfo:write} packet
|
||
(@pxref{qXfer siginfo write}).
|
||
|
||
@item qXfer:threads:read
|
||
The remote stub understands the @samp{qXfer:threads:read} packet
|
||
(@pxref{qXfer threads read}).
|
||
|
||
@item qXfer:traceframe-info:read
|
||
The remote stub understands the @samp{qXfer:traceframe-info:read}
|
||
packet (@pxref{qXfer traceframe info read}).
|
||
|
||
@item qXfer:uib:read
|
||
The remote stub understands the @samp{qXfer:uib:read}
|
||
packet (@pxref{qXfer unwind info block}).
|
||
|
||
@item qXfer:fdpic:read
|
||
The remote stub understands the @samp{qXfer:fdpic:read}
|
||
packet (@pxref{qXfer fdpic loadmap read}).
|
||
|
||
@item QNonStop
|
||
The remote stub understands the @samp{QNonStop} packet
|
||
(@pxref{QNonStop}).
|
||
|
||
@item QCatchSyscalls
|
||
The remote stub understands the @samp{QCatchSyscalls} packet
|
||
(@pxref{QCatchSyscalls}).
|
||
|
||
@item QPassSignals
|
||
The remote stub understands the @samp{QPassSignals} packet
|
||
(@pxref{QPassSignals}).
|
||
|
||
@item QStartNoAckMode
|
||
The remote stub understands the @samp{QStartNoAckMode} packet and
|
||
prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
|
||
|
||
@item multiprocess
|
||
@anchor{multiprocess extensions}
|
||
@cindex multiprocess extensions, in remote protocol
|
||
The remote stub understands the multiprocess extensions to the remote
|
||
protocol syntax. The multiprocess extensions affect the syntax of
|
||
thread IDs in both packets and replies (@pxref{thread-id syntax}), and
|
||
add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
|
||
replies. Note that reporting this feature indicates support for the
|
||
syntactic extensions only, not that the stub necessarily supports
|
||
debugging of more than one process at a time. The stub must not use
|
||
multiprocess extensions in packet replies unless @value{GDBN} has also
|
||
indicated it supports them in its @samp{qSupported} request.
|
||
|
||
@item qXfer:osdata:read
|
||
The remote stub understands the @samp{qXfer:osdata:read} packet
|
||
((@pxref{qXfer osdata read}).
|
||
|
||
@item ConditionalBreakpoints
|
||
The target accepts and implements evaluation of conditional expressions
|
||
defined for breakpoints. The target will only report breakpoint triggers
|
||
when such conditions are true (@pxref{Conditions, ,Break Conditions}).
|
||
|
||
@item ConditionalTracepoints
|
||
The remote stub accepts and implements conditional expressions defined
|
||
for tracepoints (@pxref{Tracepoint Conditions}).
|
||
|
||
@item ReverseContinue
|
||
The remote stub accepts and implements the reverse continue packet
|
||
(@pxref{bc}).
|
||
|
||
@item ReverseStep
|
||
The remote stub accepts and implements the reverse step packet
|
||
(@pxref{bs}).
|
||
|
||
@item TracepointSource
|
||
The remote stub understands the @samp{QTDPsrc} packet that supplies
|
||
the source form of tracepoint definitions.
|
||
|
||
@item QAgent
|
||
The remote stub understands the @samp{QAgent} packet.
|
||
|
||
@item QAllow
|
||
The remote stub understands the @samp{QAllow} packet.
|
||
|
||
@item QDisableRandomization
|
||
The remote stub understands the @samp{QDisableRandomization} packet.
|
||
|
||
@item StaticTracepoint
|
||
@cindex static tracepoints, in remote protocol
|
||
The remote stub supports static tracepoints.
|
||
|
||
@item InstallInTrace
|
||
@anchor{install tracepoint in tracing}
|
||
The remote stub supports installing tracepoint in tracing.
|
||
|
||
@item EnableDisableTracepoints
|
||
The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
|
||
@samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
|
||
to be enabled and disabled while a trace experiment is running.
|
||
|
||
@item QTBuffer:size
|
||
The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
|
||
packet that allows to change the size of the trace buffer.
|
||
|
||
@item tracenz
|
||
@cindex string tracing, in remote protocol
|
||
The remote stub supports the @samp{tracenz} bytecode for collecting strings.
|
||
See @ref{Bytecode Descriptions} for details about the bytecode.
|
||
|
||
@item BreakpointCommands
|
||
@cindex breakpoint commands, in remote protocol
|
||
The remote stub supports running a breakpoint's command list itself,
|
||
rather than reporting the hit to @value{GDBN}.
|
||
|
||
@item Qbtrace:off
|
||
The remote stub understands the @samp{Qbtrace:off} packet.
|
||
|
||
@item Qbtrace:bts
|
||
The remote stub understands the @samp{Qbtrace:bts} packet.
|
||
|
||
@item Qbtrace:pt
|
||
The remote stub understands the @samp{Qbtrace:pt} packet.
|
||
|
||
@item Qbtrace-conf:bts:size
|
||
The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
|
||
|
||
@item Qbtrace-conf:pt:size
|
||
The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
|
||
|
||
@item swbreak
|
||
The remote stub reports the @samp{swbreak} stop reason for memory
|
||
breakpoints.
|
||
|
||
@item hwbreak
|
||
The remote stub reports the @samp{hwbreak} stop reason for hardware
|
||
breakpoints.
|
||
|
||
@item fork-events
|
||
The remote stub reports the @samp{fork} stop reason for fork events.
|
||
|
||
@item vfork-events
|
||
The remote stub reports the @samp{vfork} stop reason for vfork events
|
||
and vforkdone events.
|
||
|
||
@item exec-events
|
||
The remote stub reports the @samp{exec} stop reason for exec events.
|
||
|
||
@item vContSupported
|
||
The remote stub reports the supported actions in the reply to
|
||
@samp{vCont?} packet.
|
||
|
||
@item QThreadEvents
|
||
The remote stub understands the @samp{QThreadEvents} packet.
|
||
|
||
@item no-resumed
|
||
The remote stub reports the @samp{N} stop reply.
|
||
|
||
@end table
|
||
|
||
@item qSymbol::
|
||
@cindex symbol lookup, remote request
|
||
@cindex @samp{qSymbol} packet
|
||
Notify the target that @value{GDBN} is prepared to serve symbol lookup
|
||
requests. Accept requests from the target for the values of symbols.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The target does not need to look up any (more) symbols.
|
||
@item qSymbol:@var{sym_name}
|
||
The target requests the value of symbol @var{sym_name} (hex encoded).
|
||
@value{GDBN} may provide the value by using the
|
||
@samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
|
||
below.
|
||
@end table
|
||
|
||
@item qSymbol:@var{sym_value}:@var{sym_name}
|
||
Set the value of @var{sym_name} to @var{sym_value}.
|
||
|
||
@var{sym_name} (hex encoded) is the name of a symbol whose value the
|
||
target has previously requested.
|
||
|
||
@var{sym_value} (hex) is the value for symbol @var{sym_name}. If
|
||
@value{GDBN} cannot supply a value for @var{sym_name}, then this field
|
||
will be empty.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The target does not need to look up any (more) symbols.
|
||
@item qSymbol:@var{sym_name}
|
||
The target requests the value of a new symbol @var{sym_name} (hex
|
||
encoded). @value{GDBN} will continue to supply the values of symbols
|
||
(if available), until the target ceases to request them.
|
||
@end table
|
||
|
||
@item qTBuffer
|
||
@itemx QTBuffer
|
||
@itemx QTDisconnected
|
||
@itemx QTDP
|
||
@itemx QTDPsrc
|
||
@itemx QTDV
|
||
@itemx qTfP
|
||
@itemx qTfV
|
||
@itemx QTFrame
|
||
@itemx qTMinFTPILen
|
||
|
||
@xref{Tracepoint Packets}.
|
||
|
||
@item qThreadExtraInfo,@var{thread-id}
|
||
@cindex thread attributes info, remote request
|
||
@cindex @samp{qThreadExtraInfo} packet
|
||
Obtain from the target OS a printable string description of thread
|
||
attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
|
||
for the forms of @var{thread-id}. This
|
||
string may contain anything that the target OS thinks is interesting
|
||
for @value{GDBN} to tell the user about the thread. The string is
|
||
displayed in @value{GDBN}'s @code{info threads} display. Some
|
||
examples of possible thread extra info strings are @samp{Runnable}, or
|
||
@samp{Blocked on Mutex}.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{XX}@dots{}
|
||
Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
|
||
comprising the printable string containing the extra information about
|
||
the thread's attributes.
|
||
@end table
|
||
|
||
(Note that the @code{qThreadExtraInfo} packet's name is separated from
|
||
the command by a @samp{,}, not a @samp{:}, contrary to the naming
|
||
conventions above. Please don't use this packet as a model for new
|
||
packets.)
|
||
|
||
@item QTNotes
|
||
@itemx qTP
|
||
@itemx QTSave
|
||
@itemx qTsP
|
||
@itemx qTsV
|
||
@itemx QTStart
|
||
@itemx QTStop
|
||
@itemx QTEnable
|
||
@itemx QTDisable
|
||
@itemx QTinit
|
||
@itemx QTro
|
||
@itemx qTStatus
|
||
@itemx qTV
|
||
@itemx qTfSTM
|
||
@itemx qTsSTM
|
||
@itemx qTSTMat
|
||
@xref{Tracepoint Packets}.
|
||
|
||
@item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
|
||
@cindex read special object, remote request
|
||
@cindex @samp{qXfer} packet
|
||
@anchor{qXfer read}
|
||
Read uninterpreted bytes from the target's special data area
|
||
identified by the keyword @var{object}. Request @var{length} bytes
|
||
starting at @var{offset} bytes into the data. The content and
|
||
encoding of @var{annex} is specific to @var{object}; it can supply
|
||
additional details about what data to access.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item m @var{data}
|
||
Data @var{data} (@pxref{Binary Data}) has been read from the
|
||
target. There may be more data at a higher address (although
|
||
it is permitted to return @samp{m} even for the last valid
|
||
block of data, as long as at least one byte of data was read).
|
||
It is possible for @var{data} to have fewer bytes than the @var{length} in the
|
||
request.
|
||
|
||
@item l @var{data}
|
||
Data @var{data} (@pxref{Binary Data}) has been read from the target.
|
||
There is no more data to be read. It is possible for @var{data} to
|
||
have fewer bytes than the @var{length} in the request.
|
||
|
||
@item l
|
||
The @var{offset} in the request is at the end of the data.
|
||
There is no more data to be read.
|
||
|
||
@item E00
|
||
The request was malformed, or @var{annex} was invalid.
|
||
|
||
@item E @var{nn}
|
||
The offset was invalid, or there was an error encountered reading the data.
|
||
The @var{nn} part is a hex-encoded @code{errno} value.
|
||
|
||
@item @w{}
|
||
An empty reply indicates the @var{object} string was not recognized by
|
||
the stub, or that the object does not support reading.
|
||
@end table
|
||
|
||
Here are the specific requests of this form defined so far. All the
|
||
@samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
|
||
formats, listed above.
|
||
|
||
@table @samp
|
||
@item qXfer:auxv:read::@var{offset},@var{length}
|
||
@anchor{qXfer auxiliary vector read}
|
||
Access the target's @dfn{auxiliary vector}. @xref{OS Information,
|
||
auxiliary vector}. Note @var{annex} must be empty.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer btrace read}
|
||
|
||
Return a description of the current branch trace.
|
||
@xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
|
||
packet may have one of the following values:
|
||
|
||
@table @code
|
||
@item all
|
||
Returns all available branch trace.
|
||
|
||
@item new
|
||
Returns all available branch trace if the branch trace changed since
|
||
the last read request.
|
||
|
||
@item delta
|
||
Returns the new branch trace since the last read request. Adds a new
|
||
block to the end of the trace that begins at zero and ends at the source
|
||
location of the first branch in the trace buffer. This extra block is
|
||
used to stitch traces together.
|
||
|
||
If the trace buffer overflowed, returns an error indicating the overflow.
|
||
@end table
|
||
|
||
This packet is not probed by default; the remote stub must request it
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:btrace-conf:read::@var{offset},@var{length}
|
||
@anchor{qXfer btrace-conf read}
|
||
|
||
Return a description of the current branch trace configuration.
|
||
@xref{Branch Trace Configuration Format}.
|
||
|
||
This packet is not probed by default; the remote stub must request it
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer executable filename read}
|
||
Return the full absolute name of the file that was executed to create
|
||
a process running on the remote system. The annex specifies the
|
||
numeric process ID of the process to query, encoded as a hexadecimal
|
||
number. If the annex part is empty the remote stub should return the
|
||
filename corresponding to the currently executing process.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:features:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer target description read}
|
||
Access the @dfn{target description}. @xref{Target Descriptions}. The
|
||
annex specifies which XML document to access. The main description is
|
||
always loaded from the @samp{target.xml} annex.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer library list read}
|
||
Access the target's list of loaded libraries. @xref{Library List Format}.
|
||
The annex part of the generic @samp{qXfer} packet must be empty
|
||
(@pxref{qXfer read}).
|
||
|
||
Targets which maintain a list of libraries in the program's memory do
|
||
not need to implement this packet; it is designed for platforms where
|
||
the operating system manages the list of loaded libraries.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer svr4 library list read}
|
||
Access the target's list of loaded libraries when the target is an SVR4
|
||
platform. @xref{Library List Format for SVR4 Targets}. The annex part
|
||
of the generic @samp{qXfer} packet must be empty unless the remote
|
||
stub indicated it supports the augmented form of this packet
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qXfer read}, @ref{qSupported}).
|
||
|
||
This packet is optional for better performance on SVR4 targets.
|
||
@value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
If the remote stub indicates it supports the augmented form of this
|
||
packet then the annex part of the generic @samp{qXfer} packet may
|
||
contain a semicolon-separated list of @samp{@var{name}=@var{value}}
|
||
arguments. The currently supported arguments are:
|
||
|
||
@table @code
|
||
@item start=@var{address}
|
||
A hexadecimal number specifying the address of the @samp{struct
|
||
link_map} to start reading the library list from. If unset or zero
|
||
then the first @samp{struct link_map} in the library list will be
|
||
chosen as the starting point.
|
||
|
||
@item prev=@var{address}
|
||
A hexadecimal number specifying the address of the @samp{struct
|
||
link_map} immediately preceding the @samp{struct link_map}
|
||
specified by the @samp{start} argument. If unset or zero then
|
||
the remote stub will expect that no @samp{struct link_map}
|
||
exists prior to the starting point.
|
||
|
||
@end table
|
||
|
||
Arguments that are not understood by the remote stub will be silently
|
||
ignored.
|
||
|
||
@item qXfer:memory-map:read::@var{offset},@var{length}
|
||
@anchor{qXfer memory map read}
|
||
Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
|
||
annex part of the generic @samp{qXfer} packet must be empty
|
||
(@pxref{qXfer read}).
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:sdata:read::@var{offset},@var{length}
|
||
@anchor{qXfer sdata read}
|
||
|
||
Read contents of the extra collected static tracepoint marker
|
||
information. The annex part of the generic @samp{qXfer} packet must
|
||
be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
|
||
Action Lists}.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}).
|
||
|
||
@item qXfer:siginfo:read::@var{offset},@var{length}
|
||
@anchor{qXfer siginfo read}
|
||
Read contents of the extra signal information on the target
|
||
system. The annex part of the generic @samp{qXfer} packet must be
|
||
empty (@pxref{qXfer read}).
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}).
|
||
|
||
@item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer spu read}
|
||
Read contents of an @code{spufs} file on the target system. The
|
||
annex specifies which file to read; it must be of the form
|
||
@file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
|
||
in the target process, and @var{name} identifes the @code{spufs} file
|
||
in that context to be accessed.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}).
|
||
|
||
@item qXfer:threads:read::@var{offset},@var{length}
|
||
@anchor{qXfer threads read}
|
||
Access the list of threads on target. @xref{Thread List Format}. The
|
||
annex part of the generic @samp{qXfer} packet must be empty
|
||
(@pxref{qXfer read}).
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:traceframe-info:read::@var{offset},@var{length}
|
||
@anchor{qXfer traceframe info read}
|
||
|
||
Return a description of the current traceframe's contents.
|
||
@xref{Traceframe Info Format}. The annex part of the generic
|
||
@samp{qXfer} packet must be empty (@pxref{qXfer read}).
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
|
||
@anchor{qXfer unwind info block}
|
||
|
||
Return the unwind information block for @var{pc}. This packet is used
|
||
on OpenVMS/ia64 to ask the kernel unwind information.
|
||
|
||
This packet is not probed by default.
|
||
|
||
@item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
|
||
@anchor{qXfer fdpic loadmap read}
|
||
Read contents of @code{loadmap}s on the target system. The
|
||
annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
|
||
executable @code{loadmap} or interpreter @code{loadmap} to read.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@item qXfer:osdata:read::@var{offset},@var{length}
|
||
@anchor{qXfer osdata read}
|
||
Access the target's @dfn{operating system information}.
|
||
@xref{Operating System Information}.
|
||
|
||
@end table
|
||
|
||
@item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
|
||
@cindex write data into object, remote request
|
||
@anchor{qXfer write}
|
||
Write uninterpreted bytes into the target's special data area
|
||
identified by the keyword @var{object}, starting at @var{offset} bytes
|
||
into the data. The binary-encoded data (@pxref{Binary Data}) to be
|
||
written is given by @var{data}@dots{}. The content and encoding of @var{annex}
|
||
is specific to @var{object}; it can supply additional details about what data
|
||
to access.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item @var{nn}
|
||
@var{nn} (hex encoded) is the number of bytes written.
|
||
This may be fewer bytes than supplied in the request.
|
||
|
||
@item E00
|
||
The request was malformed, or @var{annex} was invalid.
|
||
|
||
@item E @var{nn}
|
||
The offset was invalid, or there was an error encountered writing the data.
|
||
The @var{nn} part is a hex-encoded @code{errno} value.
|
||
|
||
@item @w{}
|
||
An empty reply indicates the @var{object} string was not
|
||
recognized by the stub, or that the object does not support writing.
|
||
@end table
|
||
|
||
Here are the specific requests of this form defined so far. All the
|
||
@samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
|
||
formats, listed above.
|
||
|
||
@table @samp
|
||
@item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
|
||
@anchor{qXfer siginfo write}
|
||
Write @var{data} to the extra signal information on the target system.
|
||
The annex part of the generic @samp{qXfer} packet must be
|
||
empty (@pxref{qXfer write}).
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response
|
||
(@pxref{qSupported}).
|
||
|
||
@item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
|
||
@anchor{qXfer spu write}
|
||
Write @var{data} to an @code{spufs} file on the target system. The
|
||
annex specifies which file to write; it must be of the form
|
||
@file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
|
||
in the target process, and @var{name} identifes the @code{spufs} file
|
||
in that context to be accessed.
|
||
|
||
This packet is not probed by default; the remote stub must request it,
|
||
by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
|
||
@end table
|
||
|
||
@item qXfer:@var{object}:@var{operation}:@dots{}
|
||
Requests of this form may be added in the future. When a stub does
|
||
not recognize the @var{object} keyword, or its support for
|
||
@var{object} does not recognize the @var{operation} keyword, the stub
|
||
must respond with an empty packet.
|
||
|
||
@item qAttached:@var{pid}
|
||
@cindex query attached, remote request
|
||
@cindex @samp{qAttached} packet
|
||
Return an indication of whether the remote server attached to an
|
||
existing process or created a new process. When the multiprocess
|
||
protocol extensions are supported (@pxref{multiprocess extensions}),
|
||
@var{pid} is an integer in hexadecimal format identifying the target
|
||
process. Otherwise, @value{GDBN} will omit the @var{pid} field and
|
||
the query packet will be simplified as @samp{qAttached}.
|
||
|
||
This query is used, for example, to know whether the remote process
|
||
should be detached or killed when a @value{GDBN} session is ended with
|
||
the @code{quit} command.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item 1
|
||
The remote server attached to an existing process.
|
||
@item 0
|
||
The remote server created a new process.
|
||
@item E @var{NN}
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@item Qbtrace:bts
|
||
Enable branch tracing for the current thread using Branch Trace Store.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
Branch tracing has been enabled.
|
||
@item E.errtext
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@item Qbtrace:pt
|
||
Enable branch tracing for the current thread using Intel Processor Trace.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
Branch tracing has been enabled.
|
||
@item E.errtext
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@item Qbtrace:off
|
||
Disable branch tracing for the current thread.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
Branch tracing has been disabled.
|
||
@item E.errtext
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@item Qbtrace-conf:bts:size=@var{value}
|
||
Set the requested ring buffer size for new threads that use the
|
||
btrace recording method in bts format.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The ring buffer size has been set.
|
||
@item E.errtext
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@item Qbtrace-conf:pt:size=@var{value}
|
||
Set the requested ring buffer size for new threads that use the
|
||
btrace recording method in pt format.
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item OK
|
||
The ring buffer size has been set.
|
||
@item E.errtext
|
||
A badly formed request or an error was encountered.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node Architecture-Specific Protocol Details
|
||
@section Architecture-Specific Protocol Details
|
||
|
||
This section describes how the remote protocol is applied to specific
|
||
target architectures. Also see @ref{Standard Target Features}, for
|
||
details of XML target descriptions for each architecture.
|
||
|
||
@menu
|
||
* ARM-Specific Protocol Details::
|
||
* MIPS-Specific Protocol Details::
|
||
@end menu
|
||
|
||
@node ARM-Specific Protocol Details
|
||
@subsection @acronym{ARM}-specific Protocol Details
|
||
|
||
@menu
|
||
* ARM Breakpoint Kinds::
|
||
@end menu
|
||
|
||
@node ARM Breakpoint Kinds
|
||
@subsubsection @acronym{ARM} Breakpoint Kinds
|
||
@cindex breakpoint kinds, @acronym{ARM}
|
||
|
||
These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
|
||
|
||
@table @r
|
||
|
||
@item 2
|
||
16-bit Thumb mode breakpoint.
|
||
|
||
@item 3
|
||
32-bit Thumb mode (Thumb-2) breakpoint.
|
||
|
||
@item 4
|
||
32-bit @acronym{ARM} mode breakpoint.
|
||
|
||
@end table
|
||
|
||
@node MIPS-Specific Protocol Details
|
||
@subsection @acronym{MIPS}-specific Protocol Details
|
||
|
||
@menu
|
||
* MIPS Register packet Format::
|
||
* MIPS Breakpoint Kinds::
|
||
@end menu
|
||
|
||
@node MIPS Register packet Format
|
||
@subsubsection @acronym{MIPS} Register Packet Format
|
||
@cindex register packet format, @acronym{MIPS}
|
||
|
||
The following @code{g}/@code{G} packets have previously been defined.
|
||
In the below, some thirty-two bit registers are transferred as
|
||
sixty-four bits. Those registers should be zero/sign extended (which?)
|
||
to fill the space allocated. Register bytes are transferred in target
|
||
byte order. The two nibbles within a register byte are transferred
|
||
most-significant -- least-significant.
|
||
|
||
@table @r
|
||
|
||
@item MIPS32
|
||
All registers are transferred as thirty-two bit quantities in the order:
|
||
32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
|
||
registers; fsr; fir; fp.
|
||
|
||
@item MIPS64
|
||
All registers are transferred as sixty-four bit quantities (including
|
||
thirty-two bit registers such as @code{sr}). The ordering is the same
|
||
as @code{MIPS32}.
|
||
|
||
@end table
|
||
|
||
@node MIPS Breakpoint Kinds
|
||
@subsubsection @acronym{MIPS} Breakpoint Kinds
|
||
@cindex breakpoint kinds, @acronym{MIPS}
|
||
|
||
These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
|
||
|
||
@table @r
|
||
|
||
@item 2
|
||
16-bit @acronym{MIPS16} mode breakpoint.
|
||
|
||
@item 3
|
||
16-bit @acronym{microMIPS} mode breakpoint.
|
||
|
||
@item 4
|
||
32-bit standard @acronym{MIPS} mode breakpoint.
|
||
|
||
@item 5
|
||
32-bit @acronym{microMIPS} mode breakpoint.
|
||
|
||
@end table
|
||
|
||
@node Tracepoint Packets
|
||
@section Tracepoint Packets
|
||
@cindex tracepoint packets
|
||
@cindex packets, tracepoint
|
||
|
||
Here we describe the packets @value{GDBN} uses to implement
|
||
tracepoints (@pxref{Tracepoints}).
|
||
|
||
@table @samp
|
||
|
||
@item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
|
||
@cindex @samp{QTDP} packet
|
||
Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
|
||
is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
|
||
the tracepoint is disabled. The @var{step} gives the tracepoint's step
|
||
count, and @var{pass} gives its pass count. If an @samp{F} is present,
|
||
then the tracepoint is to be a fast tracepoint, and the @var{flen} is
|
||
the number of bytes that the target should copy elsewhere to make room
|
||
for the tracepoint. If an @samp{X} is present, it introduces a
|
||
tracepoint condition, which consists of a hexadecimal length, followed
|
||
by a comma and hex-encoded bytes, in a manner similar to action
|
||
encodings as described below. If the trailing @samp{-} is present,
|
||
further @samp{QTDP} packets will follow to specify this tracepoint's
|
||
actions.
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item OK
|
||
The packet was understood and carried out.
|
||
@item qRelocInsn
|
||
@xref{Tracepoint Packets,,Relocate instruction reply packet}.
|
||
@item @w{}
|
||
The packet was not recognized.
|
||
@end table
|
||
|
||
@item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
|
||
Define actions to be taken when a tracepoint is hit. The @var{n} and
|
||
@var{addr} must be the same as in the initial @samp{QTDP} packet for
|
||
this tracepoint. This packet may only be sent immediately after
|
||
another @samp{QTDP} packet that ended with a @samp{-}. If the
|
||
trailing @samp{-} is present, further @samp{QTDP} packets will follow,
|
||
specifying more actions for this tracepoint.
|
||
|
||
In the series of action packets for a given tracepoint, at most one
|
||
can have an @samp{S} before its first @var{action}. If such a packet
|
||
is sent, it and the following packets define ``while-stepping''
|
||
actions. Any prior packets define ordinary actions --- that is, those
|
||
taken when the tracepoint is first hit. If no action packet has an
|
||
@samp{S}, then all the packets in the series specify ordinary
|
||
tracepoint actions.
|
||
|
||
The @samp{@var{action}@dots{}} portion of the packet is a series of
|
||
actions, concatenated without separators. Each action has one of the
|
||
following forms:
|
||
|
||
@table @samp
|
||
|
||
@item R @var{mask}
|
||
Collect the registers whose bits are set in @var{mask},
|
||
a hexadecimal number whose @var{i}'th bit is set if register number
|
||
@var{i} should be collected. (The least significant bit is numbered
|
||
zero.) Note that @var{mask} may be any number of digits long; it may
|
||
not fit in a 32-bit word.
|
||
|
||
@item M @var{basereg},@var{offset},@var{len}
|
||
Collect @var{len} bytes of memory starting at the address in register
|
||
number @var{basereg}, plus @var{offset}. If @var{basereg} is
|
||
@samp{-1}, then the range has a fixed address: @var{offset} is the
|
||
address of the lowest byte to collect. The @var{basereg},
|
||
@var{offset}, and @var{len} parameters are all unsigned hexadecimal
|
||
values (the @samp{-1} value for @var{basereg} is a special case).
|
||
|
||
@item X @var{len},@var{expr}
|
||
Evaluate @var{expr}, whose length is @var{len}, and collect memory as
|
||
it directs. The agent expression @var{expr} is as described in
|
||
@ref{Agent Expressions}. Each byte of the expression is encoded as a
|
||
two-digit hex number in the packet; @var{len} is the number of bytes
|
||
in the expression (and thus one-half the number of hex digits in the
|
||
packet).
|
||
|
||
@end table
|
||
|
||
Any number of actions may be packed together in a single @samp{QTDP}
|
||
packet, as long as the packet does not exceed the maximum packet
|
||
length (400 bytes, for many stubs). There may be only one @samp{R}
|
||
action per tracepoint, and it must precede any @samp{M} or @samp{X}
|
||
actions. Any registers referred to by @samp{M} and @samp{X} actions
|
||
must be collected by a preceding @samp{R} action. (The
|
||
``while-stepping'' actions are treated as if they were attached to a
|
||
separate tracepoint, as far as these restrictions are concerned.)
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item OK
|
||
The packet was understood and carried out.
|
||
@item qRelocInsn
|
||
@xref{Tracepoint Packets,,Relocate instruction reply packet}.
|
||
@item @w{}
|
||
The packet was not recognized.
|
||
@end table
|
||
|
||
@item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
|
||
@cindex @samp{QTDPsrc} packet
|
||
Specify a source string of tracepoint @var{n} at address @var{addr}.
|
||
This is useful to get accurate reproduction of the tracepoints
|
||
originally downloaded at the beginning of the trace run. The @var{type}
|
||
is the name of the tracepoint part, such as @samp{cond} for the
|
||
tracepoint's conditional expression (see below for a list of types), while
|
||
@var{bytes} is the string, encoded in hexadecimal.
|
||
|
||
@var{start} is the offset of the @var{bytes} within the overall source
|
||
string, while @var{slen} is the total length of the source string.
|
||
This is intended for handling source strings that are longer than will
|
||
fit in a single packet.
|
||
@c Add detailed example when this info is moved into a dedicated
|
||
@c tracepoint descriptions section.
|
||
|
||
The available string types are @samp{at} for the location,
|
||
@samp{cond} for the conditional, and @samp{cmd} for an action command.
|
||
@value{GDBN} sends a separate packet for each command in the action
|
||
list, in the same order in which the commands are stored in the list.
|
||
|
||
The target does not need to do anything with source strings except
|
||
report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
|
||
query packets.
|
||
|
||
Although this packet is optional, and @value{GDBN} will only send it
|
||
if the target replies with @samp{TracepointSource} @xref{General
|
||
Query Packets}, it makes both disconnected tracing and trace files
|
||
much easier to use. Otherwise the user must be careful that the
|
||
tracepoints in effect while looking at trace frames are identical to
|
||
the ones in effect during the trace run; even a small discrepancy
|
||
could cause @samp{tdump} not to work, or a particular trace frame not
|
||
be found.
|
||
|
||
@item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
|
||
@cindex define trace state variable, remote request
|
||
@cindex @samp{QTDV} packet
|
||
Create a new trace state variable, number @var{n}, with an initial
|
||
value of @var{value}, which is a 64-bit signed integer. Both @var{n}
|
||
and @var{value} are encoded as hexadecimal values. @value{GDBN} has
|
||
the option of not using this packet for initial values of zero; the
|
||
target should simply create the trace state variables as they are
|
||
mentioned in expressions. The value @var{builtin} should be 1 (one)
|
||
if the trace state variable is builtin and 0 (zero) if it is not builtin.
|
||
@value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
|
||
@samp{qTsV} packet had it set. The contents of @var{name} is the
|
||
hex-encoded name (without the leading @samp{$}) of the trace state
|
||
variable.
|
||
|
||
@item QTFrame:@var{n}
|
||
@cindex @samp{QTFrame} packet
|
||
Select the @var{n}'th tracepoint frame from the buffer, and use the
|
||
register and memory contents recorded there to answer subsequent
|
||
request packets from @value{GDBN}.
|
||
|
||
A successful reply from the stub indicates that the stub has found the
|
||
requested frame. The response is a series of parts, concatenated
|
||
without separators, describing the frame we selected. Each part has
|
||
one of the following forms:
|
||
|
||
@table @samp
|
||
@item F @var{f}
|
||
The selected frame is number @var{n} in the trace frame buffer;
|
||
@var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
|
||
was no frame matching the criteria in the request packet.
|
||
|
||
@item T @var{t}
|
||
The selected trace frame records a hit of tracepoint number @var{t};
|
||
@var{t} is a hexadecimal number.
|
||
|
||
@end table
|
||
|
||
@item QTFrame:pc:@var{addr}
|
||
Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
|
||
currently selected frame whose PC is @var{addr};
|
||
@var{addr} is a hexadecimal number.
|
||
|
||
@item QTFrame:tdp:@var{t}
|
||
Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
|
||
currently selected frame that is a hit of tracepoint @var{t}; @var{t}
|
||
is a hexadecimal number.
|
||
|
||
@item QTFrame:range:@var{start}:@var{end}
|
||
Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
|
||
currently selected frame whose PC is between @var{start} (inclusive)
|
||
and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
|
||
numbers.
|
||
|
||
@item QTFrame:outside:@var{start}:@var{end}
|
||
Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
|
||
frame @emph{outside} the given range of addresses (exclusive).
|
||
|
||
@item qTMinFTPILen
|
||
@cindex @samp{qTMinFTPILen} packet
|
||
This packet requests the minimum length of instruction at which a fast
|
||
tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
|
||
the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
|
||
it depends on the target system being able to create trampolines in
|
||
the first 64K of memory, which might or might not be possible for that
|
||
system. So the reply to this packet will be 4 if it is able to
|
||
arrange for that.
|
||
|
||
Replies:
|
||
|
||
@table @samp
|
||
@item 0
|
||
The minimum instruction length is currently unknown.
|
||
@item @var{length}
|
||
The minimum instruction length is @var{length}, where @var{length}
|
||
is a hexadecimal number greater or equal to 1. A reply
|
||
of 1 means that a fast tracepoint may be placed on any instruction
|
||
regardless of size.
|
||
@item E
|
||
An error has occurred.
|
||
@item @w{}
|
||
An empty reply indicates that the request is not supported by the stub.
|
||
@end table
|
||
|
||
@item QTStart
|
||
@cindex @samp{QTStart} packet
|
||
Begin the tracepoint experiment. Begin collecting data from
|
||
tracepoint hits in the trace frame buffer. This packet supports the
|
||
@samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
|
||
instruction reply packet}).
|
||
|
||
@item QTStop
|
||
@cindex @samp{QTStop} packet
|
||
End the tracepoint experiment. Stop collecting trace frames.
|
||
|
||
@item QTEnable:@var{n}:@var{addr}
|
||
@anchor{QTEnable}
|
||
@cindex @samp{QTEnable} packet
|
||
Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
|
||
experiment. If the tracepoint was previously disabled, then collection
|
||
of data from it will resume.
|
||
|
||
@item QTDisable:@var{n}:@var{addr}
|
||
@anchor{QTDisable}
|
||
@cindex @samp{QTDisable} packet
|
||
Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
|
||
experiment. No more data will be collected from the tracepoint unless
|
||
@samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
|
||
|
||
@item QTinit
|
||
@cindex @samp{QTinit} packet
|
||
Clear the table of tracepoints, and empty the trace frame buffer.
|
||
|
||
@item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
|
||
@cindex @samp{QTro} packet
|
||
Establish the given ranges of memory as ``transparent''. The stub
|
||
will answer requests for these ranges from memory's current contents,
|
||
if they were not collected as part of the tracepoint hit.
|
||
|
||
@value{GDBN} uses this to mark read-only regions of memory, like those
|
||
containing program code. Since these areas never change, they should
|
||
still have the same contents they did when the tracepoint was hit, so
|
||
there's no reason for the stub to refuse to provide their contents.
|
||
|
||
@item QTDisconnected:@var{value}
|
||
@cindex @samp{QTDisconnected} packet
|
||
Set the choice to what to do with the tracing run when @value{GDBN}
|
||
disconnects from the target. A @var{value} of 1 directs the target to
|
||
continue the tracing run, while 0 tells the target to stop tracing if
|
||
@value{GDBN} is no longer in the picture.
|
||
|
||
@item qTStatus
|
||
@cindex @samp{qTStatus} packet
|
||
Ask the stub if there is a trace experiment running right now.
|
||
|
||
The reply has the form:
|
||
|
||
@table @samp
|
||
|
||
@item T@var{running}@r{[};@var{field}@r{]}@dots{}
|
||
@var{running} is a single digit @code{1} if the trace is presently
|
||
running, or @code{0} if not. It is followed by semicolon-separated
|
||
optional fields that an agent may use to report additional status.
|
||
|
||
@end table
|
||
|
||
If the trace is not running, the agent may report any of several
|
||
explanations as one of the optional fields:
|
||
|
||
@table @samp
|
||
|
||
@item tnotrun:0
|
||
No trace has been run yet.
|
||
|
||
@item tstop[:@var{text}]:0
|
||
The trace was stopped by a user-originated stop command. The optional
|
||
@var{text} field is a user-supplied string supplied as part of the
|
||
stop command (for instance, an explanation of why the trace was
|
||
stopped manually). It is hex-encoded.
|
||
|
||
@item tfull:0
|
||
The trace stopped because the trace buffer filled up.
|
||
|
||
@item tdisconnected:0
|
||
The trace stopped because @value{GDBN} disconnected from the target.
|
||
|
||
@item tpasscount:@var{tpnum}
|
||
The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
|
||
|
||
@item terror:@var{text}:@var{tpnum}
|
||
The trace stopped because tracepoint @var{tpnum} had an error. The
|
||
string @var{text} is available to describe the nature of the error
|
||
(for instance, a divide by zero in the condition expression); it
|
||
is hex encoded.
|
||
|
||
@item tunknown:0
|
||
The trace stopped for some other reason.
|
||
|
||
@end table
|
||
|
||
Additional optional fields supply statistical and other information.
|
||
Although not required, they are extremely useful for users monitoring
|
||
the progress of a trace run. If a trace has stopped, and these
|
||
numbers are reported, they must reflect the state of the just-stopped
|
||
trace.
|
||
|
||
@table @samp
|
||
|
||
@item tframes:@var{n}
|
||
The number of trace frames in the buffer.
|
||
|
||
@item tcreated:@var{n}
|
||
The total number of trace frames created during the run. This may
|
||
be larger than the trace frame count, if the buffer is circular.
|
||
|
||
@item tsize:@var{n}
|
||
The total size of the trace buffer, in bytes.
|
||
|
||
@item tfree:@var{n}
|
||
The number of bytes still unused in the buffer.
|
||
|
||
@item circular:@var{n}
|
||
The value of the circular trace buffer flag. @code{1} means that the
|
||
trace buffer is circular and old trace frames will be discarded if
|
||
necessary to make room, @code{0} means that the trace buffer is linear
|
||
and may fill up.
|
||
|
||
@item disconn:@var{n}
|
||
The value of the disconnected tracing flag. @code{1} means that
|
||
tracing will continue after @value{GDBN} disconnects, @code{0} means
|
||
that the trace run will stop.
|
||
|
||
@end table
|
||
|
||
@item qTP:@var{tp}:@var{addr}
|
||
@cindex tracepoint status, remote request
|
||
@cindex @samp{qTP} packet
|
||
Ask the stub for the current state of tracepoint number @var{tp} at
|
||
address @var{addr}.
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item V@var{hits}:@var{usage}
|
||
The tracepoint has been hit @var{hits} times so far during the trace
|
||
run, and accounts for @var{usage} in the trace buffer. Note that
|
||
@code{while-stepping} steps are not counted as separate hits, but the
|
||
steps' space consumption is added into the usage number.
|
||
|
||
@end table
|
||
|
||
@item qTV:@var{var}
|
||
@cindex trace state variable value, remote request
|
||
@cindex @samp{qTV} packet
|
||
Ask the stub for the value of the trace state variable number @var{var}.
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item V@var{value}
|
||
The value of the variable is @var{value}. This will be the current
|
||
value of the variable if the user is examining a running target, or a
|
||
saved value if the variable was collected in the trace frame that the
|
||
user is looking at. Note that multiple requests may result in
|
||
different reply values, such as when requesting values while the
|
||
program is running.
|
||
|
||
@item U
|
||
The value of the variable is unknown. This would occur, for example,
|
||
if the user is examining a trace frame in which the requested variable
|
||
was not collected.
|
||
@end table
|
||
|
||
@item qTfP
|
||
@cindex @samp{qTfP} packet
|
||
@itemx qTsP
|
||
@cindex @samp{qTsP} packet
|
||
These packets request data about tracepoints that are being used by
|
||
the target. @value{GDBN} sends @code{qTfP} to get the first piece
|
||
of data, and multiple @code{qTsP} to get additional pieces. Replies
|
||
to these packets generally take the form of the @code{QTDP} packets
|
||
that define tracepoints. (FIXME add detailed syntax)
|
||
|
||
@item qTfV
|
||
@cindex @samp{qTfV} packet
|
||
@itemx qTsV
|
||
@cindex @samp{qTsV} packet
|
||
These packets request data about trace state variables that are on the
|
||
target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
|
||
and multiple @code{qTsV} to get additional variables. Replies to
|
||
these packets follow the syntax of the @code{QTDV} packets that define
|
||
trace state variables.
|
||
|
||
@item qTfSTM
|
||
@itemx qTsSTM
|
||
@anchor{qTfSTM}
|
||
@anchor{qTsSTM}
|
||
@cindex @samp{qTfSTM} packet
|
||
@cindex @samp{qTsSTM} packet
|
||
These packets request data about static tracepoint markers that exist
|
||
in the target program. @value{GDBN} sends @code{qTfSTM} to get the
|
||
first piece of data, and multiple @code{qTsSTM} to get additional
|
||
pieces. Replies to these packets take the following form:
|
||
|
||
Reply:
|
||
@table @samp
|
||
@item m @var{address}:@var{id}:@var{extra}
|
||
A single marker
|
||
@item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
|
||
a comma-separated list of markers
|
||
@item l
|
||
(lower case letter @samp{L}) denotes end of list.
|
||
@item E @var{nn}
|
||
An error occurred. The error number @var{nn} is given as hex digits.
|
||
@item @w{}
|
||
An empty reply indicates that the request is not supported by the
|
||
stub.
|
||
@end table
|
||
|
||
The @var{address} is encoded in hex;
|
||
@var{id} and @var{extra} are strings encoded in hex.
|
||
|
||
In response to each query, the target will reply with a list of one or
|
||
more markers, separated by commas. @value{GDBN} will respond to each
|
||
reply with a request for more markers (using the @samp{qs} form of the
|
||
query), until the target responds with @samp{l} (lower-case ell, for
|
||
@dfn{last}).
|
||
|
||
@item qTSTMat:@var{address}
|
||
@anchor{qTSTMat}
|
||
@cindex @samp{qTSTMat} packet
|
||
This packets requests data about static tracepoint markers in the
|
||
target program at @var{address}. Replies to this packet follow the
|
||
syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
|
||
tracepoint markers.
|
||
|
||
@item QTSave:@var{filename}
|
||
@cindex @samp{QTSave} packet
|
||
This packet directs the target to save trace data to the file name
|
||
@var{filename} in the target's filesystem. The @var{filename} is encoded
|
||
as a hex string; the interpretation of the file name (relative vs
|
||
absolute, wild cards, etc) is up to the target.
|
||
|
||
@item qTBuffer:@var{offset},@var{len}
|
||
@cindex @samp{qTBuffer} packet
|
||
Return up to @var{len} bytes of the current contents of trace buffer,
|
||
starting at @var{offset}. The trace buffer is treated as if it were
|
||
a contiguous collection of traceframes, as per the trace file format.
|
||
The reply consists as many hex-encoded bytes as the target can deliver
|
||
in a packet; it is not an error to return fewer than were asked for.
|
||
A reply consisting of just @code{l} indicates that no bytes are
|
||
available.
|
||
|
||
@item QTBuffer:circular:@var{value}
|
||
This packet directs the target to use a circular trace buffer if
|
||
@var{value} is 1, or a linear buffer if the value is 0.
|
||
|
||
@item QTBuffer:size:@var{size}
|
||
@anchor{QTBuffer-size}
|
||
@cindex @samp{QTBuffer size} packet
|
||
This packet directs the target to make the trace buffer be of size
|
||
@var{size} if possible. A value of @code{-1} tells the target to
|
||
use whatever size it prefers.
|
||
|
||
@item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
|
||
@cindex @samp{QTNotes} packet
|
||
This packet adds optional textual notes to the trace run. Allowable
|
||
types include @code{user}, @code{notes}, and @code{tstop}, the
|
||
@var{text} fields are arbitrary strings, hex-encoded.
|
||
|
||
@end table
|
||
|
||
@subsection Relocate instruction reply packet
|
||
When installing fast tracepoints in memory, the target may need to
|
||
relocate the instruction currently at the tracepoint address to a
|
||
different address in memory. For most instructions, a simple copy is
|
||
enough, but, for example, call instructions that implicitly push the
|
||
return address on the stack, and relative branches or other
|
||
PC-relative instructions require offset adjustment, so that the effect
|
||
of executing the instruction at a different address is the same as if
|
||
it had executed in the original location.
|
||
|
||
In response to several of the tracepoint packets, the target may also
|
||
respond with a number of intermediate @samp{qRelocInsn} request
|
||
packets before the final result packet, to have @value{GDBN} handle
|
||
this relocation operation. If a packet supports this mechanism, its
|
||
documentation will explicitly say so. See for example the above
|
||
descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
|
||
format of the request is:
|
||
|
||
@table @samp
|
||
@item qRelocInsn:@var{from};@var{to}
|
||
|
||
This requests @value{GDBN} to copy instruction at address @var{from}
|
||
to address @var{to}, possibly adjusted so that executing the
|
||
instruction at @var{to} has the same effect as executing it at
|
||
@var{from}. @value{GDBN} writes the adjusted instruction to target
|
||
memory starting at @var{to}.
|
||
@end table
|
||
|
||
Replies:
|
||
@table @samp
|
||
@item qRelocInsn:@var{adjusted_size}
|
||
Informs the stub the relocation is complete. The @var{adjusted_size} is
|
||
the length in bytes of resulting relocated instruction sequence.
|
||
@item E @var{NN}
|
||
A badly formed request was detected, or an error was encountered while
|
||
relocating the instruction.
|
||
@end table
|
||
|
||
@node Host I/O Packets
|
||
@section Host I/O Packets
|
||
@cindex Host I/O, remote protocol
|
||
@cindex file transfer, remote protocol
|
||
|
||
The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
|
||
operations on the far side of a remote link. For example, Host I/O is
|
||
used to upload and download files to a remote target with its own
|
||
filesystem. Host I/O uses the same constant values and data structure
|
||
layout as the target-initiated File-I/O protocol. However, the
|
||
Host I/O packets are structured differently. The target-initiated
|
||
protocol relies on target memory to store parameters and buffers.
|
||
Host I/O requests are initiated by @value{GDBN}, and the
|
||
target's memory is not involved. @xref{File-I/O Remote Protocol
|
||
Extension}, for more details on the target-initiated protocol.
|
||
|
||
The Host I/O request packets all encode a single operation along with
|
||
its arguments. They have this format:
|
||
|
||
@table @samp
|
||
|
||
@item vFile:@var{operation}: @var{parameter}@dots{}
|
||
@var{operation} is the name of the particular request; the target
|
||
should compare the entire packet name up to the second colon when checking
|
||
for a supported operation. The format of @var{parameter} depends on
|
||
the operation. Numbers are always passed in hexadecimal. Negative
|
||
numbers have an explicit minus sign (i.e.@: two's complement is not
|
||
used). Strings (e.g.@: filenames) are encoded as a series of
|
||
hexadecimal bytes. The last argument to a system call may be a
|
||
buffer of escaped binary data (@pxref{Binary Data}).
|
||
|
||
@end table
|
||
|
||
The valid responses to Host I/O packets are:
|
||
|
||
@table @samp
|
||
|
||
@item F @var{result} [, @var{errno}] [; @var{attachment}]
|
||
@var{result} is the integer value returned by this operation, usually
|
||
non-negative for success and -1 for errors. If an error has occured,
|
||
@var{errno} will be included in the result specifying a
|
||
value defined by the File-I/O protocol (@pxref{Errno Values}). For
|
||
operations which return data, @var{attachment} supplies the data as a
|
||
binary buffer. Binary buffers in response packets are escaped in the
|
||
normal way (@pxref{Binary Data}). See the individual packet
|
||
documentation for the interpretation of @var{result} and
|
||
@var{attachment}.
|
||
|
||
@item @w{}
|
||
An empty response indicates that this operation is not recognized.
|
||
|
||
@end table
|
||
|
||
These are the supported Host I/O operations:
|
||
|
||
@table @samp
|
||
@item vFile:open: @var{filename}, @var{flags}, @var{mode}
|
||
Open a file at @var{filename} and return a file descriptor for it, or
|
||
return -1 if an error occurs. The @var{filename} is a string,
|
||
@var{flags} is an integer indicating a mask of open flags
|
||
(@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
|
||
of mode bits to use if the file is created (@pxref{mode_t Values}).
|
||
@xref{open}, for details of the open flags and mode values.
|
||
|
||
@item vFile:close: @var{fd}
|
||
Close the open file corresponding to @var{fd} and return 0, or
|
||
-1 if an error occurs.
|
||
|
||
@item vFile:pread: @var{fd}, @var{count}, @var{offset}
|
||
Read data from the open file corresponding to @var{fd}. Up to
|
||
@var{count} bytes will be read from the file, starting at @var{offset}
|
||
relative to the start of the file. The target may read fewer bytes;
|
||
common reasons include packet size limits and an end-of-file
|
||
condition. The number of bytes read is returned. Zero should only be
|
||
returned for a successful read at the end of the file, or if
|
||
@var{count} was zero.
|
||
|
||
The data read should be returned as a binary attachment on success.
|
||
If zero bytes were read, the response should include an empty binary
|
||
attachment (i.e.@: a trailing semicolon). The return value is the
|
||
number of target bytes read; the binary attachment may be longer if
|
||
some characters were escaped.
|
||
|
||
@item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
|
||
Write @var{data} (a binary buffer) to the open file corresponding
|
||
to @var{fd}. Start the write at @var{offset} from the start of the
|
||
file. Unlike many @code{write} system calls, there is no
|
||
separate @var{count} argument; the length of @var{data} in the
|
||
packet is used. @samp{vFile:write} returns the number of bytes written,
|
||
which may be shorter than the length of @var{data}, or -1 if an
|
||
error occurred.
|
||
|
||
@item vFile:fstat: @var{fd}
|
||
Get information about the open file corresponding to @var{fd}.
|
||
On success the information is returned as a binary attachment
|
||
and the return value is the size of this attachment in bytes.
|
||
If an error occurs the return value is -1. The format of the
|
||
returned binary attachment is as described in @ref{struct stat}.
|
||
|
||
@item vFile:unlink: @var{filename}
|
||
Delete the file at @var{filename} on the target. Return 0,
|
||
or -1 if an error occurs. The @var{filename} is a string.
|
||
|
||
@item vFile:readlink: @var{filename}
|
||
Read value of symbolic link @var{filename} on the target. Return
|
||
the number of bytes read, or -1 if an error occurs.
|
||
|
||
The data read should be returned as a binary attachment on success.
|
||
If zero bytes were read, the response should include an empty binary
|
||
attachment (i.e.@: a trailing semicolon). The return value is the
|
||
number of target bytes read; the binary attachment may be longer if
|
||
some characters were escaped.
|
||
|
||
@item vFile:setfs: @var{pid}
|
||
Select the filesystem on which @code{vFile} operations with
|
||
@var{filename} arguments will operate. This is required for
|
||
@value{GDBN} to be able to access files on remote targets where
|
||
the remote stub does not share a common filesystem with the
|
||
inferior(s).
|
||
|
||
If @var{pid} is nonzero, select the filesystem as seen by process
|
||
@var{pid}. If @var{pid} is zero, select the filesystem as seen by
|
||
the remote stub. Return 0 on success, or -1 if an error occurs.
|
||
If @code{vFile:setfs:} indicates success, the selected filesystem
|
||
remains selected until the next successful @code{vFile:setfs:}
|
||
operation.
|
||
|
||
@end table
|
||
|
||
@node Interrupts
|
||
@section Interrupts
|
||
@cindex interrupts (remote protocol)
|
||
@anchor{interrupting remote targets}
|
||
|
||
In all-stop mode, when a program on the remote target is running,
|
||
@value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
|
||
@code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
|
||
is specified via @value{GDBN}'s @samp{interrupt-sequence}.
|
||
|
||
The precise meaning of @code{BREAK} is defined by the transport
|
||
mechanism and may, in fact, be undefined. @value{GDBN} does not
|
||
currently define a @code{BREAK} mechanism for any of the network
|
||
interfaces except for TCP, in which case @value{GDBN} sends the
|
||
@code{telnet} BREAK sequence.
|
||
|
||
@samp{Ctrl-C}, on the other hand, is defined and implemented for all
|
||
transport mechanisms. It is represented by sending the single byte
|
||
@code{0x03} without any of the usual packet overhead described in
|
||
the Overview section (@pxref{Overview}). When a @code{0x03} byte is
|
||
transmitted as part of a packet, it is considered to be packet data
|
||
and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
|
||
(@pxref{X packet}), used for binary downloads, may include an unescaped
|
||
@code{0x03} as part of its packet.
|
||
|
||
@code{BREAK} followed by @code{g} is also known as Magic SysRq g.
|
||
When Linux kernel receives this sequence from serial port,
|
||
it stops execution and connects to gdb.
|
||
|
||
In non-stop mode, because packet resumptions are asynchronous
|
||
(@pxref{vCont packet}), @value{GDBN} is always free to send a remote
|
||
command to the remote stub, even when the target is running. For that
|
||
reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
|
||
packet}) with the usual packet framing instead of the single byte
|
||
@code{0x03}.
|
||
|
||
Stubs are not required to recognize these interrupt mechanisms and the
|
||
precise meaning associated with receipt of the interrupt is
|
||
implementation defined. If the target supports debugging of multiple
|
||
threads and/or processes, it should attempt to interrupt all
|
||
currently-executing threads and processes.
|
||
If the stub is successful at interrupting the
|
||
running program, it should send one of the stop
|
||
reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
|
||
of successfully stopping the program in all-stop mode, and a stop reply
|
||
for each stopped thread in non-stop mode.
|
||
Interrupts received while the
|
||
program is stopped are queued and the program will be interrupted when
|
||
it is resumed next time.
|
||
|
||
@node Notification Packets
|
||
@section Notification Packets
|
||
@cindex notification packets
|
||
@cindex packets, notification
|
||
|
||
The @value{GDBN} remote serial protocol includes @dfn{notifications},
|
||
packets that require no acknowledgment. Both the GDB and the stub
|
||
may send notifications (although the only notifications defined at
|
||
present are sent by the stub). Notifications carry information
|
||
without incurring the round-trip latency of an acknowledgment, and so
|
||
are useful for low-impact communications where occasional packet loss
|
||
is not a problem.
|
||
|
||
A notification packet has the form @samp{% @var{data} #
|
||
@var{checksum}}, where @var{data} is the content of the notification,
|
||
and @var{checksum} is a checksum of @var{data}, computed and formatted
|
||
as for ordinary @value{GDBN} packets. A notification's @var{data}
|
||
never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
|
||
receiving a notification, the recipient sends no @samp{+} or @samp{-}
|
||
to acknowledge the notification's receipt or to report its corruption.
|
||
|
||
Every notification's @var{data} begins with a name, which contains no
|
||
colon characters, followed by a colon character.
|
||
|
||
Recipients should silently ignore corrupted notifications and
|
||
notifications they do not understand. Recipients should restart
|
||
timeout periods on receipt of a well-formed notification, whether or
|
||
not they understand it.
|
||
|
||
Senders should only send the notifications described here when this
|
||
protocol description specifies that they are permitted. In the
|
||
future, we may extend the protocol to permit existing notifications in
|
||
new contexts; this rule helps older senders avoid confusing newer
|
||
recipients.
|
||
|
||
(Older versions of @value{GDBN} ignore bytes received until they see
|
||
the @samp{$} byte that begins an ordinary packet, so new stubs may
|
||
transmit notifications without fear of confusing older clients. There
|
||
are no notifications defined for @value{GDBN} to send at the moment, but we
|
||
assume that most older stubs would ignore them, as well.)
|
||
|
||
Each notification is comprised of three parts:
|
||
@table @samp
|
||
@item @var{name}:@var{event}
|
||
The notification packet is sent by the side that initiates the
|
||
exchange (currently, only the stub does that), with @var{event}
|
||
carrying the specific information about the notification, and
|
||
@var{name} specifying the name of the notification.
|
||
@item @var{ack}
|
||
The acknowledge sent by the other side, usually @value{GDBN}, to
|
||
acknowledge the exchange and request the event.
|
||
@end table
|
||
|
||
The purpose of an asynchronous notification mechanism is to report to
|
||
@value{GDBN} that something interesting happened in the remote stub.
|
||
|
||
The remote stub may send notification @var{name}:@var{event}
|
||
at any time, but @value{GDBN} acknowledges the notification when
|
||
appropriate. The notification event is pending before @value{GDBN}
|
||
acknowledges. Only one notification at a time may be pending; if
|
||
additional events occur before @value{GDBN} has acknowledged the
|
||
previous notification, they must be queued by the stub for later
|
||
synchronous transmission in response to @var{ack} packets from
|
||
@value{GDBN}. Because the notification mechanism is unreliable,
|
||
the stub is permitted to resend a notification if it believes
|
||
@value{GDBN} may not have received it.
|
||
|
||
Specifically, notifications may appear when @value{GDBN} is not
|
||
otherwise reading input from the stub, or when @value{GDBN} is
|
||
expecting to read a normal synchronous response or a
|
||
@samp{+}/@samp{-} acknowledgment to a packet it has sent.
|
||
Notification packets are distinct from any other communication from
|
||
the stub so there is no ambiguity.
|
||
|
||
After receiving a notification, @value{GDBN} shall acknowledge it by
|
||
sending a @var{ack} packet as a regular, synchronous request to the
|
||
stub. Such acknowledgment is not required to happen immediately, as
|
||
@value{GDBN} is permitted to send other, unrelated packets to the
|
||
stub first, which the stub should process normally.
|
||
|
||
Upon receiving a @var{ack} packet, if the stub has other queued
|
||
events to report to @value{GDBN}, it shall respond by sending a
|
||
normal @var{event}. @value{GDBN} shall then send another @var{ack}
|
||
packet to solicit further responses; again, it is permitted to send
|
||
other, unrelated packets as well which the stub should process
|
||
normally.
|
||
|
||
If the stub receives a @var{ack} packet and there are no additional
|
||
@var{event} to report, the stub shall return an @samp{OK} response.
|
||
At this point, @value{GDBN} has finished processing a notification
|
||
and the stub has completed sending any queued events. @value{GDBN}
|
||
won't accept any new notifications until the final @samp{OK} is
|
||
received . If further notification events occur, the stub shall send
|
||
a new notification, @value{GDBN} shall accept the notification, and
|
||
the process shall be repeated.
|
||
|
||
The process of asynchronous notification can be illustrated by the
|
||
following example:
|
||
@smallexample
|
||
<- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
|
||
@code{...}
|
||
-> @code{vStopped}
|
||
<- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
|
||
-> @code{vStopped}
|
||
<- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
|
||
-> @code{vStopped}
|
||
<- @code{OK}
|
||
@end smallexample
|
||
|
||
The following notifications are defined:
|
||
@multitable @columnfractions 0.12 0.12 0.38 0.38
|
||
|
||
@item Notification
|
||
@tab Ack
|
||
@tab Event
|
||
@tab Description
|
||
|
||
@item Stop
|
||
@tab vStopped
|
||
@tab @var{reply}. The @var{reply} has the form of a stop reply, as
|
||
described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
|
||
for information on how these notifications are acknowledged by
|
||
@value{GDBN}.
|
||
@tab Report an asynchronous stop event in non-stop mode.
|
||
|
||
@end multitable
|
||
|
||
@node Remote Non-Stop
|
||
@section Remote Protocol Support for Non-Stop Mode
|
||
|
||
@value{GDBN}'s remote protocol supports non-stop debugging of
|
||
multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
|
||
supports non-stop mode, it should report that to @value{GDBN} by including
|
||
@samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
|
||
|
||
@value{GDBN} typically sends a @samp{QNonStop} packet only when
|
||
establishing a new connection with the stub. Entering non-stop mode
|
||
does not alter the state of any currently-running threads, but targets
|
||
must stop all threads in any already-attached processes when entering
|
||
all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
|
||
probe the target state after a mode change.
|
||
|
||
In non-stop mode, when an attached process encounters an event that
|
||
would otherwise be reported with a stop reply, it uses the
|
||
asynchronous notification mechanism (@pxref{Notification Packets}) to
|
||
inform @value{GDBN}. In contrast to all-stop mode, where all threads
|
||
in all processes are stopped when a stop reply is sent, in non-stop
|
||
mode only the thread reporting the stop event is stopped. That is,
|
||
when reporting a @samp{S} or @samp{T} response to indicate completion
|
||
of a step operation, hitting a breakpoint, or a fault, only the
|
||
affected thread is stopped; any other still-running threads continue
|
||
to run. When reporting a @samp{W} or @samp{X} response, all running
|
||
threads belonging to other attached processes continue to run.
|
||
|
||
In non-stop mode, the target shall respond to the @samp{?} packet as
|
||
follows. First, any incomplete stop reply notification/@samp{vStopped}
|
||
sequence in progress is abandoned. The target must begin a new
|
||
sequence reporting stop events for all stopped threads, whether or not
|
||
it has previously reported those events to @value{GDBN}. The first
|
||
stop reply is sent as a synchronous reply to the @samp{?} packet, and
|
||
subsequent stop replies are sent as responses to @samp{vStopped} packets
|
||
using the mechanism described above. The target must not send
|
||
asynchronous stop reply notifications until the sequence is complete.
|
||
If all threads are running when the target receives the @samp{?} packet,
|
||
or if the target is not attached to any process, it shall respond
|
||
@samp{OK}.
|
||
|
||
If the stub supports non-stop mode, it should also support the
|
||
@samp{swbreak} stop reason if software breakpoints are supported, and
|
||
the @samp{hwbreak} stop reason if hardware breakpoints are supported
|
||
(@pxref{swbreak stop reason}). This is because given the asynchronous
|
||
nature of non-stop mode, between the time a thread hits a breakpoint
|
||
and the time the event is finally processed by @value{GDBN}, the
|
||
breakpoint may have already been removed from the target. Due to
|
||
this, @value{GDBN} needs to be able to tell whether a trap stop was
|
||
caused by a delayed breakpoint event, which should be ignored, as
|
||
opposed to a random trap signal, which should be reported to the user.
|
||
Note the @samp{swbreak} feature implies that the target is responsible
|
||
for adjusting the PC when a software breakpoint triggers, if
|
||
necessary, such as on the x86 architecture.
|
||
|
||
@node Packet Acknowledgment
|
||
@section Packet Acknowledgment
|
||
|
||
@cindex acknowledgment, for @value{GDBN} remote
|
||
@cindex packet acknowledgment, for @value{GDBN} remote
|
||
By default, when either the host or the target machine receives a packet,
|
||
the first response expected is an acknowledgment: either @samp{+} (to indicate
|
||
the package was received correctly) or @samp{-} (to request retransmission).
|
||
This mechanism allows the @value{GDBN} remote protocol to operate over
|
||
unreliable transport mechanisms, such as a serial line.
|
||
|
||
In cases where the transport mechanism is itself reliable (such as a pipe or
|
||
TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
|
||
It may be desirable to disable them in that case to reduce communication
|
||
overhead, or for other reasons. This can be accomplished by means of the
|
||
@samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
|
||
|
||
When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
|
||
expect @samp{+}/@samp{-} protocol acknowledgments. The packet
|
||
and response format still includes the normal checksum, as described in
|
||
@ref{Overview}, but the checksum may be ignored by the receiver.
|
||
|
||
If the stub supports @samp{QStartNoAckMode} and prefers to operate in
|
||
no-acknowledgment mode, it should report that to @value{GDBN}
|
||
by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
|
||
@pxref{qSupported}.
|
||
If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
|
||
disabled via the @code{set remote noack-packet off} command
|
||
(@pxref{Remote Configuration}),
|
||
@value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
|
||
Only then may the stub actually turn off packet acknowledgments.
|
||
@value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
|
||
response, which can be safely ignored by the stub.
|
||
|
||
Note that @code{set remote noack-packet} command only affects negotiation
|
||
between @value{GDBN} and the stub when subsequent connections are made;
|
||
it does not affect the protocol acknowledgment state for any current
|
||
connection.
|
||
Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
|
||
new connection is established,
|
||
there is also no protocol request to re-enable the acknowledgments
|
||
for the current connection, once disabled.
|
||
|
||
@node Examples
|
||
@section Examples
|
||
|
||
Example sequence of a target being re-started. Notice how the restart
|
||
does not get any direct output:
|
||
|
||
@smallexample
|
||
-> @code{R00}
|
||
<- @code{+}
|
||
@emph{target restarts}
|
||
-> @code{?}
|
||
<- @code{+}
|
||
<- @code{T001:1234123412341234}
|
||
-> @code{+}
|
||
@end smallexample
|
||
|
||
Example sequence of a target being stepped by a single instruction:
|
||
|
||
@smallexample
|
||
-> @code{G1445@dots{}}
|
||
<- @code{+}
|
||
-> @code{s}
|
||
<- @code{+}
|
||
@emph{time passes}
|
||
<- @code{T001:1234123412341234}
|
||
-> @code{+}
|
||
-> @code{g}
|
||
<- @code{+}
|
||
<- @code{1455@dots{}}
|
||
-> @code{+}
|
||
@end smallexample
|
||
|
||
@node File-I/O Remote Protocol Extension
|
||
@section File-I/O Remote Protocol Extension
|
||
@cindex File-I/O remote protocol extension
|
||
|
||
@menu
|
||
* File-I/O Overview::
|
||
* Protocol Basics::
|
||
* The F Request Packet::
|
||
* The F Reply Packet::
|
||
* The Ctrl-C Message::
|
||
* Console I/O::
|
||
* List of Supported Calls::
|
||
* Protocol-specific Representation of Datatypes::
|
||
* Constants::
|
||
* File-I/O Examples::
|
||
@end menu
|
||
|
||
@node File-I/O Overview
|
||
@subsection File-I/O Overview
|
||
@cindex file-i/o overview
|
||
|
||
The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
|
||
target to use the host's file system and console I/O to perform various
|
||
system calls. System calls on the target system are translated into a
|
||
remote protocol packet to the host system, which then performs the needed
|
||
actions and returns a response packet to the target system.
|
||
This simulates file system operations even on targets that lack file systems.
|
||
|
||
The protocol is defined to be independent of both the host and target systems.
|
||
It uses its own internal representation of datatypes and values. Both
|
||
@value{GDBN} and the target's @value{GDBN} stub are responsible for
|
||
translating the system-dependent value representations into the internal
|
||
protocol representations when data is transmitted.
|
||
|
||
The communication is synchronous. A system call is possible only when
|
||
@value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
|
||
or @samp{s} packets. While @value{GDBN} handles the request for a system call,
|
||
the target is stopped to allow deterministic access to the target's
|
||
memory. Therefore File-I/O is not interruptible by target signals. On
|
||
the other hand, it is possible to interrupt File-I/O by a user interrupt
|
||
(@samp{Ctrl-C}) within @value{GDBN}.
|
||
|
||
The target's request to perform a host system call does not finish
|
||
the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
|
||
after finishing the system call, the target returns to continuing the
|
||
previous activity (continue, step). No additional continue or step
|
||
request from @value{GDBN} is required.
|
||
|
||
@smallexample
|
||
(@value{GDBP}) continue
|
||
<- target requests 'system call X'
|
||
target is stopped, @value{GDBN} executes system call
|
||
-> @value{GDBN} returns result
|
||
... target continues, @value{GDBN} returns to wait for the target
|
||
<- target hits breakpoint and sends a Txx packet
|
||
@end smallexample
|
||
|
||
The protocol only supports I/O on the console and to regular files on
|
||
the host file system. Character or block special devices, pipes,
|
||
named pipes, sockets or any other communication method on the host
|
||
system are not supported by this protocol.
|
||
|
||
File I/O is not supported in non-stop mode.
|
||
|
||
@node Protocol Basics
|
||
@subsection Protocol Basics
|
||
@cindex protocol basics, file-i/o
|
||
|
||
The File-I/O protocol uses the @code{F} packet as the request as well
|
||
as reply packet. Since a File-I/O system call can only occur when
|
||
@value{GDBN} is waiting for a response from the continuing or stepping target,
|
||
the File-I/O request is a reply that @value{GDBN} has to expect as a result
|
||
of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
|
||
This @code{F} packet contains all information needed to allow @value{GDBN}
|
||
to call the appropriate host system call:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
A unique identifier for the requested system call.
|
||
|
||
@item
|
||
All parameters to the system call. Pointers are given as addresses
|
||
in the target memory address space. Pointers to strings are given as
|
||
pointer/length pair. Numerical values are given as they are.
|
||
Numerical control flags are given in a protocol-specific representation.
|
||
|
||
@end itemize
|
||
|
||
At this point, @value{GDBN} has to perform the following actions.
|
||
|
||
@itemize @bullet
|
||
@item
|
||
If the parameters include pointer values to data needed as input to a
|
||
system call, @value{GDBN} requests this data from the target with a
|
||
standard @code{m} packet request. This additional communication has to be
|
||
expected by the target implementation and is handled as any other @code{m}
|
||
packet.
|
||
|
||
@item
|
||
@value{GDBN} translates all value from protocol representation to host
|
||
representation as needed. Datatypes are coerced into the host types.
|
||
|
||
@item
|
||
@value{GDBN} calls the system call.
|
||
|
||
@item
|
||
It then coerces datatypes back to protocol representation.
|
||
|
||
@item
|
||
If the system call is expected to return data in buffer space specified
|
||
by pointer parameters to the call, the data is transmitted to the
|
||
target using a @code{M} or @code{X} packet. This packet has to be expected
|
||
by the target implementation and is handled as any other @code{M} or @code{X}
|
||
packet.
|
||
|
||
@end itemize
|
||
|
||
Eventually @value{GDBN} replies with another @code{F} packet which contains all
|
||
necessary information for the target to continue. This at least contains
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Return value.
|
||
|
||
@item
|
||
@code{errno}, if has been changed by the system call.
|
||
|
||
@item
|
||
``Ctrl-C'' flag.
|
||
|
||
@end itemize
|
||
|
||
After having done the needed type and value coercion, the target continues
|
||
the latest continue or step action.
|
||
|
||
@node The F Request Packet
|
||
@subsection The @code{F} Request Packet
|
||
@cindex file-i/o request packet
|
||
@cindex @code{F} request packet
|
||
|
||
The @code{F} request packet has the following format:
|
||
|
||
@table @samp
|
||
@item F@var{call-id},@var{parameter@dots{}}
|
||
|
||
@var{call-id} is the identifier to indicate the host system call to be called.
|
||
This is just the name of the function.
|
||
|
||
@var{parameter@dots{}} are the parameters to the system call.
|
||
Parameters are hexadecimal integer values, either the actual values in case
|
||
of scalar datatypes, pointers to target buffer space in case of compound
|
||
datatypes and unspecified memory areas, or pointer/length pairs in case
|
||
of string parameters. These are appended to the @var{call-id} as a
|
||
comma-delimited list. All values are transmitted in ASCII
|
||
string representation, pointer/length pairs separated by a slash.
|
||
|
||
@end table
|
||
|
||
|
||
|
||
@node The F Reply Packet
|
||
@subsection The @code{F} Reply Packet
|
||
@cindex file-i/o reply packet
|
||
@cindex @code{F} reply packet
|
||
|
||
The @code{F} reply packet has the following format:
|
||
|
||
@table @samp
|
||
|
||
@item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
|
||
|
||
@var{retcode} is the return code of the system call as hexadecimal value.
|
||
|
||
@var{errno} is the @code{errno} set by the call, in protocol-specific
|
||
representation.
|
||
This parameter can be omitted if the call was successful.
|
||
|
||
@var{Ctrl-C flag} is only sent if the user requested a break. In this
|
||
case, @var{errno} must be sent as well, even if the call was successful.
|
||
The @var{Ctrl-C flag} itself consists of the character @samp{C}:
|
||
|
||
@smallexample
|
||
F0,0,C
|
||
@end smallexample
|
||
|
||
@noindent
|
||
or, if the call was interrupted before the host call has been performed:
|
||
|
||
@smallexample
|
||
F-1,4,C
|
||
@end smallexample
|
||
|
||
@noindent
|
||
assuming 4 is the protocol-specific representation of @code{EINTR}.
|
||
|
||
@end table
|
||
|
||
|
||
@node The Ctrl-C Message
|
||
@subsection The @samp{Ctrl-C} Message
|
||
@cindex ctrl-c message, in file-i/o protocol
|
||
|
||
If the @samp{Ctrl-C} flag is set in the @value{GDBN}
|
||
reply packet (@pxref{The F Reply Packet}),
|
||
the target should behave as if it had
|
||
gotten a break message. The meaning for the target is ``system call
|
||
interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
|
||
(as with a break message) and return to @value{GDBN} with a @code{T02}
|
||
packet.
|
||
|
||
It's important for the target to know in which
|
||
state the system call was interrupted. There are two possible cases:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The system call hasn't been performed on the host yet.
|
||
|
||
@item
|
||
The system call on the host has been finished.
|
||
|
||
@end itemize
|
||
|
||
These two states can be distinguished by the target by the value of the
|
||
returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
|
||
call hasn't been performed. This is equivalent to the @code{EINTR} handling
|
||
on POSIX systems. In any other case, the target may presume that the
|
||
system call has been finished --- successfully or not --- and should behave
|
||
as if the break message arrived right after the system call.
|
||
|
||
@value{GDBN} must behave reliably. If the system call has not been called
|
||
yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
|
||
@code{errno} in the packet. If the system call on the host has been finished
|
||
before the user requests a break, the full action must be finished by
|
||
@value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
|
||
The @code{F} packet may only be sent when either nothing has happened
|
||
or the full action has been completed.
|
||
|
||
@node Console I/O
|
||
@subsection Console I/O
|
||
@cindex console i/o as part of file-i/o
|
||
|
||
By default and if not explicitly closed by the target system, the file
|
||
descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
|
||
on the @value{GDBN} console is handled as any other file output operation
|
||
(@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
|
||
by @value{GDBN} so that after the target read request from file descriptor
|
||
0 all following typing is buffered until either one of the following
|
||
conditions is met:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
|
||
@code{read}
|
||
system call is treated as finished.
|
||
|
||
@item
|
||
The user presses @key{RET}. This is treated as end of input with a trailing
|
||
newline.
|
||
|
||
@item
|
||
The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
|
||
character (neither newline nor @samp{Ctrl-D}) is appended to the input.
|
||
|
||
@end itemize
|
||
|
||
If the user has typed more characters than fit in the buffer given to
|
||
the @code{read} call, the trailing characters are buffered in @value{GDBN} until
|
||
either another @code{read(0, @dots{})} is requested by the target, or debugging
|
||
is stopped at the user's request.
|
||
|
||
|
||
@node List of Supported Calls
|
||
@subsection List of Supported Calls
|
||
@cindex list of supported file-i/o calls
|
||
|
||
@menu
|
||
* open::
|
||
* close::
|
||
* read::
|
||
* write::
|
||
* lseek::
|
||
* rename::
|
||
* unlink::
|
||
* stat/fstat::
|
||
* gettimeofday::
|
||
* isatty::
|
||
* system::
|
||
@end menu
|
||
|
||
@node open
|
||
@unnumberedsubsubsec open
|
||
@cindex open, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int open(const char *pathname, int flags);
|
||
int open(const char *pathname, int flags, mode_t mode);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
|
||
|
||
@noindent
|
||
@var{flags} is the bitwise @code{OR} of the following values:
|
||
|
||
@table @code
|
||
@item O_CREAT
|
||
If the file does not exist it will be created. The host
|
||
rules apply as far as file ownership and time stamps
|
||
are concerned.
|
||
|
||
@item O_EXCL
|
||
When used with @code{O_CREAT}, if the file already exists it is
|
||
an error and open() fails.
|
||
|
||
@item O_TRUNC
|
||
If the file already exists and the open mode allows
|
||
writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
|
||
truncated to zero length.
|
||
|
||
@item O_APPEND
|
||
The file is opened in append mode.
|
||
|
||
@item O_RDONLY
|
||
The file is opened for reading only.
|
||
|
||
@item O_WRONLY
|
||
The file is opened for writing only.
|
||
|
||
@item O_RDWR
|
||
The file is opened for reading and writing.
|
||
@end table
|
||
|
||
@noindent
|
||
Other bits are silently ignored.
|
||
|
||
|
||
@noindent
|
||
@var{mode} is the bitwise @code{OR} of the following values:
|
||
|
||
@table @code
|
||
@item S_IRUSR
|
||
User has read permission.
|
||
|
||
@item S_IWUSR
|
||
User has write permission.
|
||
|
||
@item S_IRGRP
|
||
Group has read permission.
|
||
|
||
@item S_IWGRP
|
||
Group has write permission.
|
||
|
||
@item S_IROTH
|
||
Others have read permission.
|
||
|
||
@item S_IWOTH
|
||
Others have write permission.
|
||
@end table
|
||
|
||
@noindent
|
||
Other bits are silently ignored.
|
||
|
||
|
||
@item Return value:
|
||
@code{open} returns the new file descriptor or -1 if an error
|
||
occurred.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EEXIST
|
||
@var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
|
||
|
||
@item EISDIR
|
||
@var{pathname} refers to a directory.
|
||
|
||
@item EACCES
|
||
The requested access is not allowed.
|
||
|
||
@item ENAMETOOLONG
|
||
@var{pathname} was too long.
|
||
|
||
@item ENOENT
|
||
A directory component in @var{pathname} does not exist.
|
||
|
||
@item ENODEV
|
||
@var{pathname} refers to a device, pipe, named pipe or socket.
|
||
|
||
@item EROFS
|
||
@var{pathname} refers to a file on a read-only filesystem and
|
||
write access was requested.
|
||
|
||
@item EFAULT
|
||
@var{pathname} is an invalid pointer value.
|
||
|
||
@item ENOSPC
|
||
No space on device to create the file.
|
||
|
||
@item EMFILE
|
||
The process already has the maximum number of files open.
|
||
|
||
@item ENFILE
|
||
The limit on the total number of files open on the system
|
||
has been reached.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node close
|
||
@unnumberedsubsubsec close
|
||
@cindex close, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int close(int fd);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fclose,@var{fd}}
|
||
|
||
@item Return value:
|
||
@code{close} returns zero on success, or -1 if an error occurred.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EBADF
|
||
@var{fd} isn't a valid open file descriptor.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node read
|
||
@unnumberedsubsubsec read
|
||
@cindex read, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int read(int fd, void *buf, unsigned int count);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fread,@var{fd},@var{bufptr},@var{count}}
|
||
|
||
@item Return value:
|
||
On success, the number of bytes read is returned.
|
||
Zero indicates end of file. If count is zero, read
|
||
returns zero as well. On error, -1 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EBADF
|
||
@var{fd} is not a valid file descriptor or is not open for
|
||
reading.
|
||
|
||
@item EFAULT
|
||
@var{bufptr} is an invalid pointer value.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node write
|
||
@unnumberedsubsubsec write
|
||
@cindex write, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int write(int fd, const void *buf, unsigned int count);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
|
||
|
||
@item Return value:
|
||
On success, the number of bytes written are returned.
|
||
Zero indicates nothing was written. On error, -1
|
||
is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EBADF
|
||
@var{fd} is not a valid file descriptor or is not open for
|
||
writing.
|
||
|
||
@item EFAULT
|
||
@var{bufptr} is an invalid pointer value.
|
||
|
||
@item EFBIG
|
||
An attempt was made to write a file that exceeds the
|
||
host-specific maximum file size allowed.
|
||
|
||
@item ENOSPC
|
||
No space on device to write the data.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node lseek
|
||
@unnumberedsubsubsec lseek
|
||
@cindex lseek, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
long lseek (int fd, long offset, int flag);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Flseek,@var{fd},@var{offset},@var{flag}}
|
||
|
||
@var{flag} is one of:
|
||
|
||
@table @code
|
||
@item SEEK_SET
|
||
The offset is set to @var{offset} bytes.
|
||
|
||
@item SEEK_CUR
|
||
The offset is set to its current location plus @var{offset}
|
||
bytes.
|
||
|
||
@item SEEK_END
|
||
The offset is set to the size of the file plus @var{offset}
|
||
bytes.
|
||
@end table
|
||
|
||
@item Return value:
|
||
On success, the resulting unsigned offset in bytes from
|
||
the beginning of the file is returned. Otherwise, a
|
||
value of -1 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EBADF
|
||
@var{fd} is not a valid open file descriptor.
|
||
|
||
@item ESPIPE
|
||
@var{fd} is associated with the @value{GDBN} console.
|
||
|
||
@item EINVAL
|
||
@var{flag} is not a proper value.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node rename
|
||
@unnumberedsubsubsec rename
|
||
@cindex rename, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int rename(const char *oldpath, const char *newpath);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
|
||
|
||
@item Return value:
|
||
On success, zero is returned. On error, -1 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EISDIR
|
||
@var{newpath} is an existing directory, but @var{oldpath} is not a
|
||
directory.
|
||
|
||
@item EEXIST
|
||
@var{newpath} is a non-empty directory.
|
||
|
||
@item EBUSY
|
||
@var{oldpath} or @var{newpath} is a directory that is in use by some
|
||
process.
|
||
|
||
@item EINVAL
|
||
An attempt was made to make a directory a subdirectory
|
||
of itself.
|
||
|
||
@item ENOTDIR
|
||
A component used as a directory in @var{oldpath} or new
|
||
path is not a directory. Or @var{oldpath} is a directory
|
||
and @var{newpath} exists but is not a directory.
|
||
|
||
@item EFAULT
|
||
@var{oldpathptr} or @var{newpathptr} are invalid pointer values.
|
||
|
||
@item EACCES
|
||
No access to the file or the path of the file.
|
||
|
||
@item ENAMETOOLONG
|
||
|
||
@var{oldpath} or @var{newpath} was too long.
|
||
|
||
@item ENOENT
|
||
A directory component in @var{oldpath} or @var{newpath} does not exist.
|
||
|
||
@item EROFS
|
||
The file is on a read-only filesystem.
|
||
|
||
@item ENOSPC
|
||
The device containing the file has no room for the new
|
||
directory entry.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node unlink
|
||
@unnumberedsubsubsec unlink
|
||
@cindex unlink, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int unlink(const char *pathname);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Funlink,@var{pathnameptr}/@var{len}}
|
||
|
||
@item Return value:
|
||
On success, zero is returned. On error, -1 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EACCES
|
||
No access to the file or the path of the file.
|
||
|
||
@item EPERM
|
||
The system does not allow unlinking of directories.
|
||
|
||
@item EBUSY
|
||
The file @var{pathname} cannot be unlinked because it's
|
||
being used by another process.
|
||
|
||
@item EFAULT
|
||
@var{pathnameptr} is an invalid pointer value.
|
||
|
||
@item ENAMETOOLONG
|
||
@var{pathname} was too long.
|
||
|
||
@item ENOENT
|
||
A directory component in @var{pathname} does not exist.
|
||
|
||
@item ENOTDIR
|
||
A component of the path is not a directory.
|
||
|
||
@item EROFS
|
||
The file is on a read-only filesystem.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node stat/fstat
|
||
@unnumberedsubsubsec stat/fstat
|
||
@cindex fstat, file-i/o system call
|
||
@cindex stat, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int stat(const char *pathname, struct stat *buf);
|
||
int fstat(int fd, struct stat *buf);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
|
||
@samp{Ffstat,@var{fd},@var{bufptr}}
|
||
|
||
@item Return value:
|
||
On success, zero is returned. On error, -1 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EBADF
|
||
@var{fd} is not a valid open file.
|
||
|
||
@item ENOENT
|
||
A directory component in @var{pathname} does not exist or the
|
||
path is an empty string.
|
||
|
||
@item ENOTDIR
|
||
A component of the path is not a directory.
|
||
|
||
@item EFAULT
|
||
@var{pathnameptr} is an invalid pointer value.
|
||
|
||
@item EACCES
|
||
No access to the file or the path of the file.
|
||
|
||
@item ENAMETOOLONG
|
||
@var{pathname} was too long.
|
||
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node gettimeofday
|
||
@unnumberedsubsubsec gettimeofday
|
||
@cindex gettimeofday, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int gettimeofday(struct timeval *tv, void *tz);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
|
||
|
||
@item Return value:
|
||
On success, 0 is returned, -1 otherwise.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EINVAL
|
||
@var{tz} is a non-NULL pointer.
|
||
|
||
@item EFAULT
|
||
@var{tvptr} and/or @var{tzptr} is an invalid pointer value.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@node isatty
|
||
@unnumberedsubsubsec isatty
|
||
@cindex isatty, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int isatty(int fd);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fisatty,@var{fd}}
|
||
|
||
@item Return value:
|
||
Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
Note that the @code{isatty} call is treated as a special case: it returns
|
||
1 to the target if the file descriptor is attached
|
||
to the @value{GDBN} console, 0 otherwise. Implementing through system calls
|
||
would require implementing @code{ioctl} and would be more complex than
|
||
needed.
|
||
|
||
|
||
@node system
|
||
@unnumberedsubsubsec system
|
||
@cindex system, file-i/o system call
|
||
|
||
@table @asis
|
||
@item Synopsis:
|
||
@smallexample
|
||
int system(const char *command);
|
||
@end smallexample
|
||
|
||
@item Request:
|
||
@samp{Fsystem,@var{commandptr}/@var{len}}
|
||
|
||
@item Return value:
|
||
If @var{len} is zero, the return value indicates whether a shell is
|
||
available. A zero return value indicates a shell is not available.
|
||
For non-zero @var{len}, the value returned is -1 on error and the
|
||
return status of the command otherwise. Only the exit status of the
|
||
command is returned, which is extracted from the host's @code{system}
|
||
return value by calling @code{WEXITSTATUS(retval)}. In case
|
||
@file{/bin/sh} could not be executed, 127 is returned.
|
||
|
||
@item Errors:
|
||
|
||
@table @code
|
||
@item EINTR
|
||
The call was interrupted by the user.
|
||
@end table
|
||
|
||
@end table
|
||
|
||
@value{GDBN} takes over the full task of calling the necessary host calls
|
||
to perform the @code{system} call. The return value of @code{system} on
|
||
the host is simplified before it's returned
|
||
to the target. Any termination signal information from the child process
|
||
is discarded, and the return value consists
|
||
entirely of the exit status of the called command.
|
||
|
||
Due to security concerns, the @code{system} call is by default refused
|
||
by @value{GDBN}. The user has to allow this call explicitly with the
|
||
@code{set remote system-call-allowed 1} command.
|
||
|
||
@table @code
|
||
@item set remote system-call-allowed
|
||
@kindex set remote system-call-allowed
|
||
Control whether to allow the @code{system} calls in the File I/O
|
||
protocol for the remote target. The default is zero (disabled).
|
||
|
||
@item show remote system-call-allowed
|
||
@kindex show remote system-call-allowed
|
||
Show whether the @code{system} calls are allowed in the File I/O
|
||
protocol.
|
||
@end table
|
||
|
||
@node Protocol-specific Representation of Datatypes
|
||
@subsection Protocol-specific Representation of Datatypes
|
||
@cindex protocol-specific representation of datatypes, in file-i/o protocol
|
||
|
||
@menu
|
||
* Integral Datatypes::
|
||
* Pointer Values::
|
||
* Memory Transfer::
|
||
* struct stat::
|
||
* struct timeval::
|
||
@end menu
|
||
|
||
@node Integral Datatypes
|
||
@unnumberedsubsubsec Integral Datatypes
|
||
@cindex integral datatypes, in file-i/o protocol
|
||
|
||
The integral datatypes used in the system calls are @code{int},
|
||
@code{unsigned int}, @code{long}, @code{unsigned long},
|
||
@code{mode_t}, and @code{time_t}.
|
||
|
||
@code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
|
||
implemented as 32 bit values in this protocol.
|
||
|
||
@code{long} and @code{unsigned long} are implemented as 64 bit types.
|
||
|
||
@xref{Limits}, for corresponding MIN and MAX values (similar to those
|
||
in @file{limits.h}) to allow range checking on host and target.
|
||
|
||
@code{time_t} datatypes are defined as seconds since the Epoch.
|
||
|
||
All integral datatypes transferred as part of a memory read or write of a
|
||
structured datatype e.g.@: a @code{struct stat} have to be given in big endian
|
||
byte order.
|
||
|
||
@node Pointer Values
|
||
@unnumberedsubsubsec Pointer Values
|
||
@cindex pointer values, in file-i/o protocol
|
||
|
||
Pointers to target data are transmitted as they are. An exception
|
||
is made for pointers to buffers for which the length isn't
|
||
transmitted as part of the function call, namely strings. Strings
|
||
are transmitted as a pointer/length pair, both as hex values, e.g.@:
|
||
|
||
@smallexample
|
||
@code{1aaf/12}
|
||
@end smallexample
|
||
|
||
@noindent
|
||
which is a pointer to data of length 18 bytes at position 0x1aaf.
|
||
The length is defined as the full string length in bytes, including
|
||
the trailing null byte. For example, the string @code{"hello world"}
|
||
at address 0x123456 is transmitted as
|
||
|
||
@smallexample
|
||
@code{123456/d}
|
||
@end smallexample
|
||
|
||
@node Memory Transfer
|
||
@unnumberedsubsubsec Memory Transfer
|
||
@cindex memory transfer, in file-i/o protocol
|
||
|
||
Structured data which is transferred using a memory read or write (for
|
||
example, a @code{struct stat}) is expected to be in a protocol-specific format
|
||
with all scalar multibyte datatypes being big endian. Translation to
|
||
this representation needs to be done both by the target before the @code{F}
|
||
packet is sent, and by @value{GDBN} before
|
||
it transfers memory to the target. Transferred pointers to structured
|
||
data should point to the already-coerced data at any time.
|
||
|
||
|
||
@node struct stat
|
||
@unnumberedsubsubsec struct stat
|
||
@cindex struct stat, in file-i/o protocol
|
||
|
||
The buffer of type @code{struct stat} used by the target and @value{GDBN}
|
||
is defined as follows:
|
||
|
||
@smallexample
|
||
struct stat @{
|
||
unsigned int st_dev; /* device */
|
||
unsigned int st_ino; /* inode */
|
||
mode_t st_mode; /* protection */
|
||
unsigned int st_nlink; /* number of hard links */
|
||
unsigned int st_uid; /* user ID of owner */
|
||
unsigned int st_gid; /* group ID of owner */
|
||
unsigned int st_rdev; /* device type (if inode device) */
|
||
unsigned long st_size; /* total size, in bytes */
|
||
unsigned long st_blksize; /* blocksize for filesystem I/O */
|
||
unsigned long st_blocks; /* number of blocks allocated */
|
||
time_t st_atime; /* time of last access */
|
||
time_t st_mtime; /* time of last modification */
|
||
time_t st_ctime; /* time of last change */
|
||
@};
|
||
@end smallexample
|
||
|
||
The integral datatypes conform to the definitions given in the
|
||
appropriate section (see @ref{Integral Datatypes}, for details) so this
|
||
structure is of size 64 bytes.
|
||
|
||
The values of several fields have a restricted meaning and/or
|
||
range of values.
|
||
|
||
@table @code
|
||
|
||
@item st_dev
|
||
A value of 0 represents a file, 1 the console.
|
||
|
||
@item st_ino
|
||
No valid meaning for the target. Transmitted unchanged.
|
||
|
||
@item st_mode
|
||
Valid mode bits are described in @ref{Constants}. Any other
|
||
bits have currently no meaning for the target.
|
||
|
||
@item st_uid
|
||
@itemx st_gid
|
||
@itemx st_rdev
|
||
No valid meaning for the target. Transmitted unchanged.
|
||
|
||
@item st_atime
|
||
@itemx st_mtime
|
||
@itemx st_ctime
|
||
These values have a host and file system dependent
|
||
accuracy. Especially on Windows hosts, the file system may not
|
||
support exact timing values.
|
||
@end table
|
||
|
||
The target gets a @code{struct stat} of the above representation and is
|
||
responsible for coercing it to the target representation before
|
||
continuing.
|
||
|
||
Note that due to size differences between the host, target, and protocol
|
||
representations of @code{struct stat} members, these members could eventually
|
||
get truncated on the target.
|
||
|
||
@node struct timeval
|
||
@unnumberedsubsubsec struct timeval
|
||
@cindex struct timeval, in file-i/o protocol
|
||
|
||
The buffer of type @code{struct timeval} used by the File-I/O protocol
|
||
is defined as follows:
|
||
|
||
@smallexample
|
||
struct timeval @{
|
||
time_t tv_sec; /* second */
|
||
long tv_usec; /* microsecond */
|
||
@};
|
||
@end smallexample
|
||
|
||
The integral datatypes conform to the definitions given in the
|
||
appropriate section (see @ref{Integral Datatypes}, for details) so this
|
||
structure is of size 8 bytes.
|
||
|
||
@node Constants
|
||
@subsection Constants
|
||
@cindex constants, in file-i/o protocol
|
||
|
||
The following values are used for the constants inside of the
|
||
protocol. @value{GDBN} and target are responsible for translating these
|
||
values before and after the call as needed.
|
||
|
||
@menu
|
||
* Open Flags::
|
||
* mode_t Values::
|
||
* Errno Values::
|
||
* Lseek Flags::
|
||
* Limits::
|
||
@end menu
|
||
|
||
@node Open Flags
|
||
@unnumberedsubsubsec Open Flags
|
||
@cindex open flags, in file-i/o protocol
|
||
|
||
All values are given in hexadecimal representation.
|
||
|
||
@smallexample
|
||
O_RDONLY 0x0
|
||
O_WRONLY 0x1
|
||
O_RDWR 0x2
|
||
O_APPEND 0x8
|
||
O_CREAT 0x200
|
||
O_TRUNC 0x400
|
||
O_EXCL 0x800
|
||
@end smallexample
|
||
|
||
@node mode_t Values
|
||
@unnumberedsubsubsec mode_t Values
|
||
@cindex mode_t values, in file-i/o protocol
|
||
|
||
All values are given in octal representation.
|
||
|
||
@smallexample
|
||
S_IFREG 0100000
|
||
S_IFDIR 040000
|
||
S_IRUSR 0400
|
||
S_IWUSR 0200
|
||
S_IXUSR 0100
|
||
S_IRGRP 040
|
||
S_IWGRP 020
|
||
S_IXGRP 010
|
||
S_IROTH 04
|
||
S_IWOTH 02
|
||
S_IXOTH 01
|
||
@end smallexample
|
||
|
||
@node Errno Values
|
||
@unnumberedsubsubsec Errno Values
|
||
@cindex errno values, in file-i/o protocol
|
||
|
||
All values are given in decimal representation.
|
||
|
||
@smallexample
|
||
EPERM 1
|
||
ENOENT 2
|
||
EINTR 4
|
||
EBADF 9
|
||
EACCES 13
|
||
EFAULT 14
|
||
EBUSY 16
|
||
EEXIST 17
|
||
ENODEV 19
|
||
ENOTDIR 20
|
||
EISDIR 21
|
||
EINVAL 22
|
||
ENFILE 23
|
||
EMFILE 24
|
||
EFBIG 27
|
||
ENOSPC 28
|
||
ESPIPE 29
|
||
EROFS 30
|
||
ENAMETOOLONG 91
|
||
EUNKNOWN 9999
|
||
@end smallexample
|
||
|
||
@code{EUNKNOWN} is used as a fallback error value if a host system returns
|
||
any error value not in the list of supported error numbers.
|
||
|
||
@node Lseek Flags
|
||
@unnumberedsubsubsec Lseek Flags
|
||
@cindex lseek flags, in file-i/o protocol
|
||
|
||
@smallexample
|
||
SEEK_SET 0
|
||
SEEK_CUR 1
|
||
SEEK_END 2
|
||
@end smallexample
|
||
|
||
@node Limits
|
||
@unnumberedsubsubsec Limits
|
||
@cindex limits, in file-i/o protocol
|
||
|
||
All values are given in decimal representation.
|
||
|
||
@smallexample
|
||
INT_MIN -2147483648
|
||
INT_MAX 2147483647
|
||
UINT_MAX 4294967295
|
||
LONG_MIN -9223372036854775808
|
||
LONG_MAX 9223372036854775807
|
||
ULONG_MAX 18446744073709551615
|
||
@end smallexample
|
||
|
||
@node File-I/O Examples
|
||
@subsection File-I/O Examples
|
||
@cindex file-i/o examples
|
||
|
||
Example sequence of a write call, file descriptor 3, buffer is at target
|
||
address 0x1234, 6 bytes should be written:
|
||
|
||
@smallexample
|
||
<- @code{Fwrite,3,1234,6}
|
||
@emph{request memory read from target}
|
||
-> @code{m1234,6}
|
||
<- XXXXXX
|
||
@emph{return "6 bytes written"}
|
||
-> @code{F6}
|
||
@end smallexample
|
||
|
||
Example sequence of a read call, file descriptor 3, buffer is at target
|
||
address 0x1234, 6 bytes should be read:
|
||
|
||
@smallexample
|
||
<- @code{Fread,3,1234,6}
|
||
@emph{request memory write to target}
|
||
-> @code{X1234,6:XXXXXX}
|
||
@emph{return "6 bytes read"}
|
||
-> @code{F6}
|
||
@end smallexample
|
||
|
||
Example sequence of a read call, call fails on the host due to invalid
|
||
file descriptor (@code{EBADF}):
|
||
|
||
@smallexample
|
||
<- @code{Fread,3,1234,6}
|
||
-> @code{F-1,9}
|
||
@end smallexample
|
||
|
||
Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
|
||
host is called:
|
||
|
||
@smallexample
|
||
<- @code{Fread,3,1234,6}
|
||
-> @code{F-1,4,C}
|
||
<- @code{T02}
|
||
@end smallexample
|
||
|
||
Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
|
||
host is called:
|
||
|
||
@smallexample
|
||
<- @code{Fread,3,1234,6}
|
||
-> @code{X1234,6:XXXXXX}
|
||
<- @code{T02}
|
||
@end smallexample
|
||
|
||
@node Library List Format
|
||
@section Library List Format
|
||
@cindex library list format, remote protocol
|
||
|
||
On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
|
||
same process as your application to manage libraries. In this case,
|
||
@value{GDBN} can use the loader's symbol table and normal memory
|
||
operations to maintain a list of shared libraries. On other
|
||
platforms, the operating system manages loaded libraries.
|
||
@value{GDBN} can not retrieve the list of currently loaded libraries
|
||
through memory operations, so it uses the @samp{qXfer:libraries:read}
|
||
packet (@pxref{qXfer library list read}) instead. The remote stub
|
||
queries the target's operating system and reports which libraries
|
||
are loaded.
|
||
|
||
The @samp{qXfer:libraries:read} packet returns an XML document which
|
||
lists loaded libraries and their offsets. Each library has an
|
||
associated name and one or more segment or section base addresses,
|
||
which report where the library was loaded in memory.
|
||
|
||
For the common case of libraries that are fully linked binaries, the
|
||
library should have a list of segments. If the target supports
|
||
dynamic linking of a relocatable object file, its library XML element
|
||
should instead include a list of allocated sections. The segment or
|
||
section bases are start addresses, not relocation offsets; they do not
|
||
depend on the library's link-time base addresses.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
library lists. @xref{Expat}.
|
||
|
||
A simple memory map, with one loaded library relocated by a single
|
||
offset, looks like this:
|
||
|
||
@smallexample
|
||
<library-list>
|
||
<library name="/lib/libc.so.6">
|
||
<segment address="0x10000000"/>
|
||
</library>
|
||
</library-list>
|
||
@end smallexample
|
||
|
||
Another simple memory map, with one loaded library with three
|
||
allocated sections (.text, .data, .bss), looks like this:
|
||
|
||
@smallexample
|
||
<library-list>
|
||
<library name="sharedlib.o">
|
||
<section address="0x10000000"/>
|
||
<section address="0x20000000"/>
|
||
<section address="0x30000000"/>
|
||
</library>
|
||
</library-list>
|
||
@end smallexample
|
||
|
||
The format of a library list is described by this DTD:
|
||
|
||
@smallexample
|
||
<!-- library-list: Root element with versioning -->
|
||
<!ELEMENT library-list (library)*>
|
||
<!ATTLIST library-list version CDATA #FIXED "1.0">
|
||
<!ELEMENT library (segment*, section*)>
|
||
<!ATTLIST library name CDATA #REQUIRED>
|
||
<!ELEMENT segment EMPTY>
|
||
<!ATTLIST segment address CDATA #REQUIRED>
|
||
<!ELEMENT section EMPTY>
|
||
<!ATTLIST section address CDATA #REQUIRED>
|
||
@end smallexample
|
||
|
||
In addition, segments and section descriptors cannot be mixed within a
|
||
single library element, and you must supply at least one segment or
|
||
section for each library.
|
||
|
||
@node Library List Format for SVR4 Targets
|
||
@section Library List Format for SVR4 Targets
|
||
@cindex library list format, remote protocol
|
||
|
||
On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
|
||
(e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
|
||
shared libraries. Still a special library list provided by this packet is
|
||
more efficient for the @value{GDBN} remote protocol.
|
||
|
||
The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
|
||
loaded libraries and their SVR4 linker parameters. For each library on SVR4
|
||
target, the following parameters are reported:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@code{name}, the absolute file name from the @code{l_name} field of
|
||
@code{struct link_map}.
|
||
@item
|
||
@code{lm} with address of @code{struct link_map} used for TLS
|
||
(Thread Local Storage) access.
|
||
@item
|
||
@code{l_addr}, the displacement as read from the field @code{l_addr} of
|
||
@code{struct link_map}. For prelinked libraries this is not an absolute
|
||
memory address. It is a displacement of absolute memory address against
|
||
address the file was prelinked to during the library load.
|
||
@item
|
||
@code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
|
||
@end itemize
|
||
|
||
Additionally the single @code{main-lm} attribute specifies address of
|
||
@code{struct link_map} used for the main executable. This parameter is used
|
||
for TLS access and its presence is optional.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
SVR4 library lists. @xref{Expat}.
|
||
|
||
A simple memory map, with two loaded libraries (which do not use prelink),
|
||
looks like this:
|
||
|
||
@smallexample
|
||
<library-list-svr4 version="1.0" main-lm="0xe4f8f8">
|
||
<library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
|
||
l_ld="0xe4eefc"/>
|
||
<library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
|
||
l_ld="0x152350"/>
|
||
</library-list-svr>
|
||
@end smallexample
|
||
|
||
The format of an SVR4 library list is described by this DTD:
|
||
|
||
@smallexample
|
||
<!-- library-list-svr4: Root element with versioning -->
|
||
<!ELEMENT library-list-svr4 (library)*>
|
||
<!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
|
||
<!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
|
||
<!ELEMENT library EMPTY>
|
||
<!ATTLIST library name CDATA #REQUIRED>
|
||
<!ATTLIST library lm CDATA #REQUIRED>
|
||
<!ATTLIST library l_addr CDATA #REQUIRED>
|
||
<!ATTLIST library l_ld CDATA #REQUIRED>
|
||
@end smallexample
|
||
|
||
@node Memory Map Format
|
||
@section Memory Map Format
|
||
@cindex memory map format
|
||
|
||
To be able to write into flash memory, @value{GDBN} needs to obtain a
|
||
memory map from the target. This section describes the format of the
|
||
memory map.
|
||
|
||
The memory map is obtained using the @samp{qXfer:memory-map:read}
|
||
(@pxref{qXfer memory map read}) packet and is an XML document that
|
||
lists memory regions.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
memory maps. @xref{Expat}.
|
||
|
||
The top-level structure of the document is shown below:
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<!DOCTYPE memory-map
|
||
PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
|
||
"http://sourceware.org/gdb/gdb-memory-map.dtd">
|
||
<memory-map>
|
||
region...
|
||
</memory-map>
|
||
@end smallexample
|
||
|
||
Each region can be either:
|
||
|
||
@itemize
|
||
|
||
@item
|
||
A region of RAM starting at @var{addr} and extending for @var{length}
|
||
bytes from there:
|
||
|
||
@smallexample
|
||
<memory type="ram" start="@var{addr}" length="@var{length}"/>
|
||
@end smallexample
|
||
|
||
|
||
@item
|
||
A region of read-only memory:
|
||
|
||
@smallexample
|
||
<memory type="rom" start="@var{addr}" length="@var{length}"/>
|
||
@end smallexample
|
||
|
||
|
||
@item
|
||
A region of flash memory, with erasure blocks @var{blocksize}
|
||
bytes in length:
|
||
|
||
@smallexample
|
||
<memory type="flash" start="@var{addr}" length="@var{length}">
|
||
<property name="blocksize">@var{blocksize}</property>
|
||
</memory>
|
||
@end smallexample
|
||
|
||
@end itemize
|
||
|
||
Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
|
||
by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
|
||
packets to write to addresses in such ranges.
|
||
|
||
The formal DTD for memory map format is given below:
|
||
|
||
@smallexample
|
||
<!-- ................................................... -->
|
||
<!-- Memory Map XML DTD ................................ -->
|
||
<!-- File: memory-map.dtd .............................. -->
|
||
<!-- .................................... .............. -->
|
||
<!-- memory-map.dtd -->
|
||
<!-- memory-map: Root element with versioning -->
|
||
<!ELEMENT memory-map (memory)*>
|
||
<!ATTLIST memory-map version CDATA #FIXED "1.0.0">
|
||
<!ELEMENT memory (property)*>
|
||
<!-- memory: Specifies a memory region,
|
||
and its type, or device. -->
|
||
<!ATTLIST memory type (ram|rom|flash) #REQUIRED
|
||
start CDATA #REQUIRED
|
||
length CDATA #REQUIRED>
|
||
<!-- property: Generic attribute tag -->
|
||
<!ELEMENT property (#PCDATA | property)*>
|
||
<!ATTLIST property name (blocksize) #REQUIRED>
|
||
@end smallexample
|
||
|
||
@node Thread List Format
|
||
@section Thread List Format
|
||
@cindex thread list format
|
||
|
||
To efficiently update the list of threads and their attributes,
|
||
@value{GDBN} issues the @samp{qXfer:threads:read} packet
|
||
(@pxref{qXfer threads read}) and obtains the XML document with
|
||
the following structure:
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<threads>
|
||
<thread id="id" core="0" name="name">
|
||
... description ...
|
||
</thread>
|
||
</threads>
|
||
@end smallexample
|
||
|
||
Each @samp{thread} element must have the @samp{id} attribute that
|
||
identifies the thread (@pxref{thread-id syntax}). The
|
||
@samp{core} attribute, if present, specifies which processor core
|
||
the thread was last executing on. The @samp{name} attribute, if
|
||
present, specifies the human-readable name of the thread. The content
|
||
of the of @samp{thread} element is interpreted as human-readable
|
||
auxiliary information. The @samp{handle} attribute, if present,
|
||
is a hex encoded representation of the thread handle.
|
||
|
||
|
||
@node Traceframe Info Format
|
||
@section Traceframe Info Format
|
||
@cindex traceframe info format
|
||
|
||
To be able to know which objects in the inferior can be examined when
|
||
inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
|
||
memory ranges, registers and trace state variables that have been
|
||
collected in a traceframe.
|
||
|
||
This list is obtained using the @samp{qXfer:traceframe-info:read}
|
||
(@pxref{qXfer traceframe info read}) packet and is an XML document.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
traceframe info discovery. @xref{Expat}.
|
||
|
||
The top-level structure of the document is shown below:
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<!DOCTYPE traceframe-info
|
||
PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
|
||
"http://sourceware.org/gdb/gdb-traceframe-info.dtd">
|
||
<traceframe-info>
|
||
block...
|
||
</traceframe-info>
|
||
@end smallexample
|
||
|
||
Each traceframe block can be either:
|
||
|
||
@itemize
|
||
|
||
@item
|
||
A region of collected memory starting at @var{addr} and extending for
|
||
@var{length} bytes from there:
|
||
|
||
@smallexample
|
||
<memory start="@var{addr}" length="@var{length}"/>
|
||
@end smallexample
|
||
|
||
@item
|
||
A block indicating trace state variable numbered @var{number} has been
|
||
collected:
|
||
|
||
@smallexample
|
||
<tvar id="@var{number}"/>
|
||
@end smallexample
|
||
|
||
@end itemize
|
||
|
||
The formal DTD for the traceframe info format is given below:
|
||
|
||
@smallexample
|
||
<!ELEMENT traceframe-info (memory | tvar)* >
|
||
<!ATTLIST traceframe-info version CDATA #FIXED "1.0">
|
||
|
||
<!ELEMENT memory EMPTY>
|
||
<!ATTLIST memory start CDATA #REQUIRED
|
||
length CDATA #REQUIRED>
|
||
<!ELEMENT tvar>
|
||
<!ATTLIST tvar id CDATA #REQUIRED>
|
||
@end smallexample
|
||
|
||
@node Branch Trace Format
|
||
@section Branch Trace Format
|
||
@cindex branch trace format
|
||
|
||
In order to display the branch trace of an inferior thread,
|
||
@value{GDBN} needs to obtain the list of branches. This list is
|
||
represented as list of sequential code blocks that are connected via
|
||
branches. The code in each block has been executed sequentially.
|
||
|
||
This list is obtained using the @samp{qXfer:btrace:read}
|
||
(@pxref{qXfer btrace read}) packet and is an XML document.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
traceframe info discovery. @xref{Expat}.
|
||
|
||
The top-level structure of the document is shown below:
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<!DOCTYPE btrace
|
||
PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
|
||
"http://sourceware.org/gdb/gdb-btrace.dtd">
|
||
<btrace>
|
||
block...
|
||
</btrace>
|
||
@end smallexample
|
||
|
||
@itemize
|
||
|
||
@item
|
||
A block of sequentially executed instructions starting at @var{begin}
|
||
and ending at @var{end}:
|
||
|
||
@smallexample
|
||
<block begin="@var{begin}" end="@var{end}"/>
|
||
@end smallexample
|
||
|
||
@end itemize
|
||
|
||
The formal DTD for the branch trace format is given below:
|
||
|
||
@smallexample
|
||
<!ELEMENT btrace (block* | pt) >
|
||
<!ATTLIST btrace version CDATA #FIXED "1.0">
|
||
|
||
<!ELEMENT block EMPTY>
|
||
<!ATTLIST block begin CDATA #REQUIRED
|
||
end CDATA #REQUIRED>
|
||
|
||
<!ELEMENT pt (pt-config?, raw?)>
|
||
|
||
<!ELEMENT pt-config (cpu?)>
|
||
|
||
<!ELEMENT cpu EMPTY>
|
||
<!ATTLIST cpu vendor CDATA #REQUIRED
|
||
family CDATA #REQUIRED
|
||
model CDATA #REQUIRED
|
||
stepping CDATA #REQUIRED>
|
||
|
||
<!ELEMENT raw (#PCDATA)>
|
||
@end smallexample
|
||
|
||
@node Branch Trace Configuration Format
|
||
@section Branch Trace Configuration Format
|
||
@cindex branch trace configuration format
|
||
|
||
For each inferior thread, @value{GDBN} can obtain the branch trace
|
||
configuration using the @samp{qXfer:btrace-conf:read}
|
||
(@pxref{qXfer btrace-conf read}) packet.
|
||
|
||
The configuration describes the branch trace format and configuration
|
||
settings for that format. The following information is described:
|
||
|
||
@table @code
|
||
@item bts
|
||
This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
|
||
@table @code
|
||
@item size
|
||
The size of the @acronym{BTS} ring buffer in bytes.
|
||
@end table
|
||
@item pt
|
||
This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
|
||
PT}) format.
|
||
@table @code
|
||
@item size
|
||
The size of the @acronym{Intel PT} ring buffer in bytes.
|
||
@end table
|
||
@end table
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
branch trace configuration discovery. @xref{Expat}.
|
||
|
||
The formal DTD for the branch trace configuration format is given below:
|
||
|
||
@smallexample
|
||
<!ELEMENT btrace-conf (bts?, pt?)>
|
||
<!ATTLIST btrace-conf version CDATA #FIXED "1.0">
|
||
|
||
<!ELEMENT bts EMPTY>
|
||
<!ATTLIST bts size CDATA #IMPLIED>
|
||
|
||
<!ELEMENT pt EMPTY>
|
||
<!ATTLIST pt size CDATA #IMPLIED>
|
||
@end smallexample
|
||
|
||
@include agentexpr.texi
|
||
|
||
@node Target Descriptions
|
||
@appendix Target Descriptions
|
||
@cindex target descriptions
|
||
|
||
One of the challenges of using @value{GDBN} to debug embedded systems
|
||
is that there are so many minor variants of each processor
|
||
architecture in use. It is common practice for vendors to start with
|
||
a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
|
||
and then make changes to adapt it to a particular market niche. Some
|
||
architectures have hundreds of variants, available from dozens of
|
||
vendors. This leads to a number of problems:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
With so many different customized processors, it is difficult for
|
||
the @value{GDBN} maintainers to keep up with the changes.
|
||
@item
|
||
Since individual variants may have short lifetimes or limited
|
||
audiences, it may not be worthwhile to carry information about every
|
||
variant in the @value{GDBN} source tree.
|
||
@item
|
||
When @value{GDBN} does support the architecture of the embedded system
|
||
at hand, the task of finding the correct architecture name to give the
|
||
@command{set architecture} command can be error-prone.
|
||
@end itemize
|
||
|
||
To address these problems, the @value{GDBN} remote protocol allows a
|
||
target system to not only identify itself to @value{GDBN}, but to
|
||
actually describe its own features. This lets @value{GDBN} support
|
||
processor variants it has never seen before --- to the extent that the
|
||
descriptions are accurate, and that @value{GDBN} understands them.
|
||
|
||
@value{GDBN} must be linked with the Expat library to support XML
|
||
target descriptions. @xref{Expat}.
|
||
|
||
@menu
|
||
* Retrieving Descriptions:: How descriptions are fetched from a target.
|
||
* Target Description Format:: The contents of a target description.
|
||
* Predefined Target Types:: Standard types available for target
|
||
descriptions.
|
||
* Enum Target Types:: How to define enum target types.
|
||
* Standard Target Features:: Features @value{GDBN} knows about.
|
||
@end menu
|
||
|
||
@node Retrieving Descriptions
|
||
@section Retrieving Descriptions
|
||
|
||
Target descriptions can be read from the target automatically, or
|
||
specified by the user manually. The default behavior is to read the
|
||
description from the target. @value{GDBN} retrieves it via the remote
|
||
protocol using @samp{qXfer} requests (@pxref{General Query Packets,
|
||
qXfer}). The @var{annex} in the @samp{qXfer} packet will be
|
||
@samp{target.xml}. The contents of the @samp{target.xml} annex are an
|
||
XML document, of the form described in @ref{Target Description
|
||
Format}.
|
||
|
||
Alternatively, you can specify a file to read for the target description.
|
||
If a file is set, the target will not be queried. The commands to
|
||
specify a file are:
|
||
|
||
@table @code
|
||
@cindex set tdesc filename
|
||
@item set tdesc filename @var{path}
|
||
Read the target description from @var{path}.
|
||
|
||
@cindex unset tdesc filename
|
||
@item unset tdesc filename
|
||
Do not read the XML target description from a file. @value{GDBN}
|
||
will use the description supplied by the current target.
|
||
|
||
@cindex show tdesc filename
|
||
@item show tdesc filename
|
||
Show the filename to read for a target description, if any.
|
||
@end table
|
||
|
||
|
||
@node Target Description Format
|
||
@section Target Description Format
|
||
@cindex target descriptions, XML format
|
||
|
||
A target description annex is an @uref{http://www.w3.org/XML/, XML}
|
||
document which complies with the Document Type Definition provided in
|
||
the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
|
||
means you can use generally available tools like @command{xmllint} to
|
||
check that your feature descriptions are well-formed and valid.
|
||
However, to help people unfamiliar with XML write descriptions for
|
||
their targets, we also describe the grammar here.
|
||
|
||
Target descriptions can identify the architecture of the remote target
|
||
and (for some architectures) provide information about custom register
|
||
sets. They can also identify the OS ABI of the remote target.
|
||
@value{GDBN} can use this information to autoconfigure for your
|
||
target, or to warn you if you connect to an unsupported target.
|
||
|
||
Here is a simple target description:
|
||
|
||
@smallexample
|
||
<target version="1.0">
|
||
<architecture>i386:x86-64</architecture>
|
||
</target>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
This minimal description only says that the target uses
|
||
the x86-64 architecture.
|
||
|
||
A target description has the following overall form, with [ ] marking
|
||
optional elements and @dots{} marking repeatable elements. The elements
|
||
are explained further below.
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<!DOCTYPE target SYSTEM "gdb-target.dtd">
|
||
<target version="1.0">
|
||
@r{[}@var{architecture}@r{]}
|
||
@r{[}@var{osabi}@r{]}
|
||
@r{[}@var{compatible}@r{]}
|
||
@r{[}@var{feature}@dots{}@r{]}
|
||
</target>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The description is generally insensitive to whitespace and line
|
||
breaks, under the usual common-sense rules. The XML version
|
||
declaration and document type declaration can generally be omitted
|
||
(@value{GDBN} does not require them), but specifying them may be
|
||
useful for XML validation tools. The @samp{version} attribute for
|
||
@samp{<target>} may also be omitted, but we recommend
|
||
including it; if future versions of @value{GDBN} use an incompatible
|
||
revision of @file{gdb-target.dtd}, they will detect and report
|
||
the version mismatch.
|
||
|
||
@subsection Inclusion
|
||
@cindex target descriptions, inclusion
|
||
@cindex XInclude
|
||
@ifnotinfo
|
||
@cindex <xi:include>
|
||
@end ifnotinfo
|
||
|
||
It can sometimes be valuable to split a target description up into
|
||
several different annexes, either for organizational purposes, or to
|
||
share files between different possible target descriptions. You can
|
||
divide a description into multiple files by replacing any element of
|
||
the target description with an inclusion directive of the form:
|
||
|
||
@smallexample
|
||
<xi:include href="@var{document}"/>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
When @value{GDBN} encounters an element of this form, it will retrieve
|
||
the named XML @var{document}, and replace the inclusion directive with
|
||
the contents of that document. If the current description was read
|
||
using @samp{qXfer}, then so will be the included document;
|
||
@var{document} will be interpreted as the name of an annex. If the
|
||
current description was read from a file, @value{GDBN} will look for
|
||
@var{document} as a file in the same directory where it found the
|
||
original description.
|
||
|
||
@subsection Architecture
|
||
@cindex <architecture>
|
||
|
||
An @samp{<architecture>} element has this form:
|
||
|
||
@smallexample
|
||
<architecture>@var{arch}</architecture>
|
||
@end smallexample
|
||
|
||
@var{arch} is one of the architectures from the set accepted by
|
||
@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
|
||
|
||
@subsection OS ABI
|
||
@cindex @code{<osabi>}
|
||
|
||
This optional field was introduced in @value{GDBN} version 7.0.
|
||
Previous versions of @value{GDBN} ignore it.
|
||
|
||
An @samp{<osabi>} element has this form:
|
||
|
||
@smallexample
|
||
<osabi>@var{abi-name}</osabi>
|
||
@end smallexample
|
||
|
||
@var{abi-name} is an OS ABI name from the same selection accepted by
|
||
@w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
|
||
|
||
@subsection Compatible Architecture
|
||
@cindex @code{<compatible>}
|
||
|
||
This optional field was introduced in @value{GDBN} version 7.0.
|
||
Previous versions of @value{GDBN} ignore it.
|
||
|
||
A @samp{<compatible>} element has this form:
|
||
|
||
@smallexample
|
||
<compatible>@var{arch}</compatible>
|
||
@end smallexample
|
||
|
||
@var{arch} is one of the architectures from the set accepted by
|
||
@code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
|
||
|
||
A @samp{<compatible>} element is used to specify that the target
|
||
is able to run binaries in some other than the main target architecture
|
||
given by the @samp{<architecture>} element. For example, on the
|
||
Cell Broadband Engine, the main architecture is @code{powerpc:common}
|
||
or @code{powerpc:common64}, but the system is able to run binaries
|
||
in the @code{spu} architecture as well. The way to describe this
|
||
capability with @samp{<compatible>} is as follows:
|
||
|
||
@smallexample
|
||
<architecture>powerpc:common</architecture>
|
||
<compatible>spu</compatible>
|
||
@end smallexample
|
||
|
||
@subsection Features
|
||
@cindex <feature>
|
||
|
||
Each @samp{<feature>} describes some logical portion of the target
|
||
system. Features are currently used to describe available CPU
|
||
registers and the types of their contents. A @samp{<feature>} element
|
||
has this form:
|
||
|
||
@smallexample
|
||
<feature name="@var{name}">
|
||
@r{[}@var{type}@dots{}@r{]}
|
||
@var{reg}@dots{}
|
||
</feature>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
Each feature's name should be unique within the description. The name
|
||
of a feature does not matter unless @value{GDBN} has some special
|
||
knowledge of the contents of that feature; if it does, the feature
|
||
should have its standard name. @xref{Standard Target Features}.
|
||
|
||
@subsection Types
|
||
|
||
Any register's value is a collection of bits which @value{GDBN} must
|
||
interpret. The default interpretation is a two's complement integer,
|
||
but other types can be requested by name in the register description.
|
||
Some predefined types are provided by @value{GDBN} (@pxref{Predefined
|
||
Target Types}), and the description can define additional composite
|
||
and enum types.
|
||
|
||
Each type element must have an @samp{id} attribute, which gives
|
||
a unique (within the containing @samp{<feature>}) name to the type.
|
||
Types must be defined before they are used.
|
||
|
||
@cindex <vector>
|
||
Some targets offer vector registers, which can be treated as arrays
|
||
of scalar elements. These types are written as @samp{<vector>} elements,
|
||
specifying the array element type, @var{type}, and the number of elements,
|
||
@var{count}:
|
||
|
||
@smallexample
|
||
<vector id="@var{id}" type="@var{type}" count="@var{count}"/>
|
||
@end smallexample
|
||
|
||
@cindex <union>
|
||
If a register's value is usefully viewed in multiple ways, define it
|
||
with a union type containing the useful representations. The
|
||
@samp{<union>} element contains one or more @samp{<field>} elements,
|
||
each of which has a @var{name} and a @var{type}:
|
||
|
||
@smallexample
|
||
<union id="@var{id}">
|
||
<field name="@var{name}" type="@var{type}"/>
|
||
@dots{}
|
||
</union>
|
||
@end smallexample
|
||
|
||
@cindex <struct>
|
||
@cindex <flags>
|
||
If a register's value is composed from several separate values, define
|
||
it with either a structure type or a flags type.
|
||
A flags type may only contain bitfields.
|
||
A structure type may either contain only bitfields or contain no bitfields.
|
||
If the value contains only bitfields, its total size in bytes must be
|
||
specified.
|
||
|
||
Non-bitfield values have a @var{name} and @var{type}.
|
||
|
||
@smallexample
|
||
<struct id="@var{id}">
|
||
<field name="@var{name}" type="@var{type}"/>
|
||
@dots{}
|
||
</struct>
|
||
@end smallexample
|
||
|
||
Both @var{name} and @var{type} values are required.
|
||
No implicit padding is added.
|
||
|
||
Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
|
||
|
||
@smallexample
|
||
<struct id="@var{id}" size="@var{size}">
|
||
<field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
|
||
@dots{}
|
||
</struct>
|
||
@end smallexample
|
||
|
||
@smallexample
|
||
<flags id="@var{id}" size="@var{size}">
|
||
<field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
|
||
@dots{}
|
||
</flags>
|
||
@end smallexample
|
||
|
||
The @var{name} value is required.
|
||
Bitfield values may be named with the empty string, @samp{""},
|
||
in which case the field is ``filler'' and its value is not printed.
|
||
Not all bits need to be specified, so ``filler'' fields are optional.
|
||
|
||
The @var{start} and @var{end} values are required, and @var{type}
|
||
is optional.
|
||
The field's @var{start} must be less than or equal to its @var{end},
|
||
and zero represents the least significant bit.
|
||
|
||
The default value of @var{type} is @code{bool} for single bit fields,
|
||
and an unsigned integer otherwise.
|
||
|
||
Which to choose? Structures or flags?
|
||
|
||
Registers defined with @samp{flags} have these advantages over
|
||
defining them with @samp{struct}:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Arithmetic may be performed on them as if they were integers.
|
||
@item
|
||
They are printed in a more readable fashion.
|
||
@end itemize
|
||
|
||
Registers defined with @samp{struct} have one advantage over
|
||
defining them with @samp{flags}:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
One can fetch individual fields like in @samp{C}.
|
||
|
||
@smallexample
|
||
(gdb) print $my_struct_reg.field3
|
||
$1 = 42
|
||
@end smallexample
|
||
|
||
@end itemize
|
||
|
||
@subsection Registers
|
||
@cindex <reg>
|
||
|
||
Each register is represented as an element with this form:
|
||
|
||
@smallexample
|
||
<reg name="@var{name}"
|
||
bitsize="@var{size}"
|
||
@r{[}regnum="@var{num}"@r{]}
|
||
@r{[}save-restore="@var{save-restore}"@r{]}
|
||
@r{[}type="@var{type}"@r{]}
|
||
@r{[}group="@var{group}"@r{]}/>
|
||
@end smallexample
|
||
|
||
@noindent
|
||
The components are as follows:
|
||
|
||
@table @var
|
||
|
||
@item name
|
||
The register's name; it must be unique within the target description.
|
||
|
||
@item bitsize
|
||
The register's size, in bits.
|
||
|
||
@item regnum
|
||
The register's number. If omitted, a register's number is one greater
|
||
than that of the previous register (either in the current feature or in
|
||
a preceding feature); the first register in the target description
|
||
defaults to zero. This register number is used to read or write
|
||
the register; e.g.@: it is used in the remote @code{p} and @code{P}
|
||
packets, and registers appear in the @code{g} and @code{G} packets
|
||
in order of increasing register number.
|
||
|
||
@item save-restore
|
||
Whether the register should be preserved across inferior function
|
||
calls; this must be either @code{yes} or @code{no}. The default is
|
||
@code{yes}, which is appropriate for most registers except for
|
||
some system control registers; this is not related to the target's
|
||
ABI.
|
||
|
||
@item type
|
||
The type of the register. It may be a predefined type, a type
|
||
defined in the current feature, or one of the special types @code{int}
|
||
and @code{float}. @code{int} is an integer type of the correct size
|
||
for @var{bitsize}, and @code{float} is a floating point type (in the
|
||
architecture's normal floating point format) of the correct size for
|
||
@var{bitsize}. The default is @code{int}.
|
||
|
||
@item group
|
||
The register group to which this register belongs. It can be one of the
|
||
standard register groups @code{general}, @code{float}, @code{vector} or an
|
||
arbitrary string. Group names should be limited to alphanumeric characters.
|
||
If a group name is made up of multiple words the words may be separated by
|
||
hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
|
||
@var{group} is specified, @value{GDBN} will not display the register in
|
||
@code{info registers}.
|
||
|
||
@end table
|
||
|
||
@node Predefined Target Types
|
||
@section Predefined Target Types
|
||
@cindex target descriptions, predefined types
|
||
|
||
Type definitions in the self-description can build up composite types
|
||
from basic building blocks, but can not define fundamental types. Instead,
|
||
standard identifiers are provided by @value{GDBN} for the fundamental
|
||
types. The currently supported types are:
|
||
|
||
@table @code
|
||
|
||
@item bool
|
||
Boolean type, occupying a single bit.
|
||
|
||
@item int8
|
||
@itemx int16
|
||
@itemx int32
|
||
@itemx int64
|
||
@itemx int128
|
||
Signed integer types holding the specified number of bits.
|
||
|
||
@item uint8
|
||
@itemx uint16
|
||
@itemx uint32
|
||
@itemx uint64
|
||
@itemx uint128
|
||
Unsigned integer types holding the specified number of bits.
|
||
|
||
@item code_ptr
|
||
@itemx data_ptr
|
||
Pointers to unspecified code and data. The program counter and
|
||
any dedicated return address register may be marked as code
|
||
pointers; printing a code pointer converts it into a symbolic
|
||
address. The stack pointer and any dedicated address registers
|
||
may be marked as data pointers.
|
||
|
||
@item ieee_single
|
||
Single precision IEEE floating point.
|
||
|
||
@item ieee_double
|
||
Double precision IEEE floating point.
|
||
|
||
@item arm_fpa_ext
|
||
The 12-byte extended precision format used by ARM FPA registers.
|
||
|
||
@item i387_ext
|
||
The 10-byte extended precision format used by x87 registers.
|
||
|
||
@item i386_eflags
|
||
32bit @sc{eflags} register used by x86.
|
||
|
||
@item i386_mxcsr
|
||
32bit @sc{mxcsr} register used by x86.
|
||
|
||
@end table
|
||
|
||
@node Enum Target Types
|
||
@section Enum Target Types
|
||
@cindex target descriptions, enum types
|
||
|
||
Enum target types are useful in @samp{struct} and @samp{flags}
|
||
register descriptions. @xref{Target Description Format}.
|
||
|
||
Enum types have a name, size and a list of name/value pairs.
|
||
|
||
@smallexample
|
||
<enum id="@var{id}" size="@var{size}">
|
||
<evalue name="@var{name}" value="@var{value}"/>
|
||
@dots{}
|
||
</enum>
|
||
@end smallexample
|
||
|
||
Enums must be defined before they are used.
|
||
|
||
@smallexample
|
||
<enum id="levels_type" size="4">
|
||
<evalue name="low" value="0"/>
|
||
<evalue name="high" value="1"/>
|
||
</enum>
|
||
<flags id="flags_type" size="4">
|
||
<field name="X" start="0"/>
|
||
<field name="LEVEL" start="1" end="1" type="levels_type"/>
|
||
</flags>
|
||
<reg name="flags" bitsize="32" type="flags_type"/>
|
||
@end smallexample
|
||
|
||
Given that description, a value of 3 for the @samp{flags} register
|
||
would be printed as:
|
||
|
||
@smallexample
|
||
(gdb) info register flags
|
||
flags 0x3 [ X LEVEL=high ]
|
||
@end smallexample
|
||
|
||
@node Standard Target Features
|
||
@section Standard Target Features
|
||
@cindex target descriptions, standard features
|
||
|
||
A target description must contain either no registers or all the
|
||
target's registers. If the description contains no registers, then
|
||
@value{GDBN} will assume a default register layout, selected based on
|
||
the architecture. If the description contains any registers, the
|
||
default layout will not be used; the standard registers must be
|
||
described in the target description, in such a way that @value{GDBN}
|
||
can recognize them.
|
||
|
||
This is accomplished by giving specific names to feature elements
|
||
which contain standard registers. @value{GDBN} will look for features
|
||
with those names and verify that they contain the expected registers;
|
||
if any known feature is missing required registers, or if any required
|
||
feature is missing, @value{GDBN} will reject the target
|
||
description. You can add additional registers to any of the
|
||
standard features --- @value{GDBN} will display them just as if
|
||
they were added to an unrecognized feature.
|
||
|
||
This section lists the known features and their expected contents.
|
||
Sample XML documents for these features are included in the
|
||
@value{GDBN} source tree, in the directory @file{gdb/features}.
|
||
|
||
Names recognized by @value{GDBN} should include the name of the
|
||
company or organization which selected the name, and the overall
|
||
architecture to which the feature applies; so e.g.@: the feature
|
||
containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
|
||
|
||
The names of registers are not case sensitive for the purpose
|
||
of recognizing standard features, but @value{GDBN} will only display
|
||
registers using the capitalization used in the description.
|
||
|
||
@menu
|
||
* AArch64 Features::
|
||
* ARC Features::
|
||
* ARM Features::
|
||
* i386 Features::
|
||
* MicroBlaze Features::
|
||
* MIPS Features::
|
||
* M68K Features::
|
||
* NDS32 Features::
|
||
* Nios II Features::
|
||
* OpenRISC 1000 Features::
|
||
* PowerPC Features::
|
||
* S/390 and System z Features::
|
||
* Sparc Features::
|
||
* TIC6x Features::
|
||
@end menu
|
||
|
||
|
||
@node AArch64 Features
|
||
@subsection AArch64 Features
|
||
@cindex target descriptions, AArch64 features
|
||
|
||
The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
|
||
targets. It should contain registers @samp{x0} through @samp{x30},
|
||
@samp{sp}, @samp{pc}, and @samp{cpsr}.
|
||
|
||
The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
|
||
it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
|
||
and @samp{fpcr}.
|
||
|
||
@node ARC Features
|
||
@subsection ARC Features
|
||
@cindex target descriptions, ARC Features
|
||
|
||
ARC processors are highly configurable, so even core registers and their number
|
||
are not completely predetermined. In addition flags and PC registers which are
|
||
important to @value{GDBN} are not ``core'' registers in ARC. It is required
|
||
that one of the core registers features is present.
|
||
@samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
|
||
|
||
The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
|
||
targets with a normal register file. It should contain registers @samp{r0}
|
||
through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
|
||
@samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
|
||
and any of extension core registers @samp{r32} through @samp{r59/acch}.
|
||
@samp{ilink} and extension core registers are not available to read/write, when
|
||
debugging GNU/Linux applications, thus @samp{ilink} is made optional.
|
||
|
||
The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
|
||
ARC HS targets with a reduced register file. It should contain registers
|
||
@samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
|
||
@samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
|
||
This feature may contain register @samp{ilink} and any of extension core
|
||
registers @samp{r32} through @samp{r59/acch}.
|
||
|
||
The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
|
||
targets with a normal register file. It should contain registers @samp{r0}
|
||
through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
|
||
@samp{lp_count} and @samp{pcl}. This feature may contain registers
|
||
@samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
|
||
through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
|
||
registers are not available when debugging GNU/Linux applications. The only
|
||
difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
|
||
@samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
|
||
ARC v2, but @samp{ilink2} is optional on ARCompact.
|
||
|
||
The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
|
||
targets. It should contain registers @samp{pc} and @samp{status32}.
|
||
|
||
@node ARM Features
|
||
@subsection ARM Features
|
||
@cindex target descriptions, ARM features
|
||
|
||
The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
|
||
ARM targets.
|
||
It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
|
||
@samp{lr}, @samp{pc}, and @samp{cpsr}.
|
||
|
||
For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
|
||
feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
|
||
registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
|
||
and @samp{xpsr}.
|
||
|
||
The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
|
||
should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
|
||
|
||
The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
|
||
it should contain at least registers @samp{wR0} through @samp{wR15} and
|
||
@samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
|
||
@samp{wCSSF}, and @samp{wCASF} registers are optional.
|
||
|
||
The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
|
||
should contain at least registers @samp{d0} through @samp{d15}. If
|
||
they are present, @samp{d16} through @samp{d31} should also be included.
|
||
@value{GDBN} will synthesize the single-precision registers from
|
||
halves of the double-precision registers.
|
||
|
||
The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
|
||
need to contain registers; it instructs @value{GDBN} to display the
|
||
VFP double-precision registers as vectors and to synthesize the
|
||
quad-precision registers from pairs of double-precision registers.
|
||
If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
|
||
be present and include 32 double-precision registers.
|
||
|
||
@node i386 Features
|
||
@subsection i386 Features
|
||
@cindex target descriptions, i386 features
|
||
|
||
The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
|
||
targets. It should describe the following registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{eax} through @samp{edi} plus @samp{eip} for i386
|
||
@item
|
||
@samp{rax} through @samp{r15} plus @samp{rip} for amd64
|
||
@item
|
||
@samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
|
||
@samp{fs}, @samp{gs}
|
||
@item
|
||
@samp{st0} through @samp{st7}
|
||
@item
|
||
@samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
|
||
@samp{foseg}, @samp{fooff} and @samp{fop}
|
||
@end itemize
|
||
|
||
The register sets may be different, depending on the target.
|
||
|
||
The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
|
||
describe registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{xmm0} through @samp{xmm7} for i386
|
||
@item
|
||
@samp{xmm0} through @samp{xmm15} for amd64
|
||
@item
|
||
@samp{mxcsr}
|
||
@end itemize
|
||
|
||
The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
|
||
@samp{org.gnu.gdb.i386.sse} feature. It should
|
||
describe the upper 128 bits of @sc{ymm} registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{ymm0h} through @samp{ymm7h} for i386
|
||
@item
|
||
@samp{ymm0h} through @samp{ymm15h} for amd64
|
||
@end itemize
|
||
|
||
The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
|
||
Memory Protection Extension (MPX). It should describe the following registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
|
||
@item
|
||
@samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
|
||
@end itemize
|
||
|
||
The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
|
||
describe a single register, @samp{orig_eax}.
|
||
|
||
The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
|
||
describe two system registers: @samp{fs_base} and @samp{gs_base}.
|
||
|
||
The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
|
||
@samp{org.gnu.gdb.i386.avx} feature. It should
|
||
describe additional @sc{xmm} registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
|
||
@end itemize
|
||
|
||
It should describe the upper 128 bits of additional @sc{ymm} registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
|
||
@end itemize
|
||
|
||
It should
|
||
describe the upper 256 bits of @sc{zmm} registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{zmm0h} through @samp{zmm7h} for i386.
|
||
@item
|
||
@samp{zmm0h} through @samp{zmm15h} for amd64.
|
||
@end itemize
|
||
|
||
It should
|
||
describe the additional @sc{zmm} registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
|
||
@end itemize
|
||
|
||
The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
|
||
describe a single register, @samp{pkru}. It is a 32-bit register
|
||
valid for i386 and amd64.
|
||
|
||
@node MicroBlaze Features
|
||
@subsection MicroBlaze Features
|
||
@cindex target descriptions, MicroBlaze features
|
||
|
||
The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
|
||
targets. It should contain registers @samp{r0} through @samp{r31},
|
||
@samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
|
||
@samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
|
||
@samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
|
||
|
||
The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
|
||
If present, it should contain registers @samp{rshr} and @samp{rslr}
|
||
|
||
@node MIPS Features
|
||
@subsection @acronym{MIPS} Features
|
||
@cindex target descriptions, @acronym{MIPS} features
|
||
|
||
The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
|
||
It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
|
||
@samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
|
||
on the target.
|
||
|
||
The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
|
||
contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
|
||
registers. They may be 32-bit or 64-bit depending on the target.
|
||
|
||
The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
|
||
it may be optional in a future version of @value{GDBN}. It should
|
||
contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
|
||
@samp{fir}. They may be 32-bit or 64-bit depending on the target.
|
||
|
||
The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
|
||
contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
|
||
@samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
|
||
be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
|
||
|
||
The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
|
||
contain a single register, @samp{restart}, which is used by the
|
||
Linux kernel to control restartable syscalls.
|
||
|
||
@node M68K Features
|
||
@subsection M68K Features
|
||
@cindex target descriptions, M68K features
|
||
|
||
@table @code
|
||
@item @samp{org.gnu.gdb.m68k.core}
|
||
@itemx @samp{org.gnu.gdb.coldfire.core}
|
||
@itemx @samp{org.gnu.gdb.fido.core}
|
||
One of those features must be always present.
|
||
The feature that is present determines which flavor of m68k is
|
||
used. The feature that is present should contain registers
|
||
@samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
|
||
@samp{sp}, @samp{ps} and @samp{pc}.
|
||
|
||
@item @samp{org.gnu.gdb.coldfire.fp}
|
||
This feature is optional. If present, it should contain registers
|
||
@samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
|
||
@samp{fpiaddr}.
|
||
@end table
|
||
|
||
@node NDS32 Features
|
||
@subsection NDS32 Features
|
||
@cindex target descriptions, NDS32 features
|
||
|
||
The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
|
||
targets. It should contain at least registers @samp{r0} through
|
||
@samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
|
||
and @samp{pc}.
|
||
|
||
The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
|
||
it should contain 64-bit double-precision floating-point registers
|
||
@samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
|
||
@samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
|
||
|
||
@emph{Note:} The first sixteen 64-bit double-precision floating-point
|
||
registers are overlapped with the thirty-two 32-bit single-precision
|
||
floating-point registers. The 32-bit single-precision registers, if
|
||
not being listed explicitly, will be synthesized from halves of the
|
||
overlapping 64-bit double-precision registers. Listing 32-bit
|
||
single-precision registers explicitly is deprecated, and the
|
||
support to it could be totally removed some day.
|
||
|
||
@node Nios II Features
|
||
@subsection Nios II Features
|
||
@cindex target descriptions, Nios II features
|
||
|
||
The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
|
||
targets. It should contain the 32 core registers (@samp{zero},
|
||
@samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
|
||
@samp{pc}, and the 16 control registers (@samp{status} through
|
||
@samp{mpuacc}).
|
||
|
||
@node OpenRISC 1000 Features
|
||
@subsection Openrisc 1000 Features
|
||
@cindex target descriptions, OpenRISC 1000 features
|
||
|
||
The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
|
||
targets. It should contain the 32 general purpose registers (@samp{r0}
|
||
through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
|
||
|
||
@node PowerPC Features
|
||
@subsection PowerPC Features
|
||
@cindex target descriptions, PowerPC features
|
||
|
||
The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
|
||
targets. It should contain registers @samp{r0} through @samp{r31},
|
||
@samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
|
||
@samp{xer}. They may be 32-bit or 64-bit depending on the target.
|
||
|
||
The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
|
||
contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
|
||
|
||
The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
|
||
contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
|
||
and @samp{vrsave}.
|
||
|
||
The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
|
||
contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
|
||
will combine these registers with the floating point registers
|
||
(@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
|
||
through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
|
||
through @samp{vs63}, the set of vector registers for POWER7.
|
||
|
||
The @samp{org.gnu.gdb.power.spe} feature is optional. It should
|
||
contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
|
||
@samp{spefscr}. SPE targets should provide 32-bit registers in
|
||
@samp{org.gnu.gdb.power.core} and provide the upper halves in
|
||
@samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
|
||
these to present registers @samp{ev0} through @samp{ev31} to the
|
||
user.
|
||
|
||
@node S/390 and System z Features
|
||
@subsection S/390 and System z Features
|
||
@cindex target descriptions, S/390 features
|
||
@cindex target descriptions, System z features
|
||
|
||
The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
|
||
System z targets. It should contain the PSW and the 16 general
|
||
registers. In particular, System z targets should provide the 64-bit
|
||
registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
|
||
S/390 targets should provide the 32-bit versions of these registers.
|
||
A System z target that runs in 31-bit addressing mode should provide
|
||
32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
|
||
register's upper halves @samp{r0h} through @samp{r15h}, and their
|
||
lower halves @samp{r0l} through @samp{r15l}.
|
||
|
||
The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
|
||
contain the 64-bit registers @samp{f0} through @samp{f15}, and
|
||
@samp{fpc}.
|
||
|
||
The @samp{org.gnu.gdb.s390.acr} feature is required. It should
|
||
contain the 32-bit registers @samp{acr0} through @samp{acr15}.
|
||
|
||
The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
|
||
contain the register @samp{orig_r2}, which is 64-bit wide on System z
|
||
targets and 32-bit otherwise. In addition, the feature may contain
|
||
the @samp{last_break} register, whose width depends on the addressing
|
||
mode, as well as the @samp{system_call} register, which is always
|
||
32-bit wide.
|
||
|
||
The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
|
||
contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
|
||
@samp{atia}, and @samp{tr0} through @samp{tr15}.
|
||
|
||
The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
|
||
64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
|
||
combined by @value{GDBN} with the floating point registers @samp{f0}
|
||
through @samp{f15} to present the 128-bit wide vector registers
|
||
@samp{v0} through @samp{v15}. In addition, this feature should
|
||
contain the 128-bit wide vector registers @samp{v16} through
|
||
@samp{v31}.
|
||
|
||
The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
|
||
the 64-bit wide guarded-storage-control registers @samp{gsd},
|
||
@samp{gssm}, and @samp{gsepla}.
|
||
|
||
The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
|
||
the 64-bit wide guarded-storage broadcast control registers
|
||
@samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
|
||
|
||
@node Sparc Features
|
||
@subsection Sparc Features
|
||
@cindex target descriptions, sparc32 features
|
||
@cindex target descriptions, sparc64 features
|
||
The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
|
||
targets. It should describe the following registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{g0} through @samp{g7}
|
||
@item
|
||
@samp{o0} through @samp{o7}
|
||
@item
|
||
@samp{l0} through @samp{l7}
|
||
@item
|
||
@samp{i0} through @samp{i7}
|
||
@end itemize
|
||
|
||
They may be 32-bit or 64-bit depending on the target.
|
||
|
||
Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
|
||
targets. It should describe the following registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{f0} through @samp{f31}
|
||
@item
|
||
@samp{f32} through @samp{f62} for sparc64
|
||
@end itemize
|
||
|
||
The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
|
||
targets. It should describe the following registers:
|
||
|
||
@itemize @minus
|
||
@item
|
||
@samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
|
||
@samp{fsr}, and @samp{csr} for sparc32
|
||
@item
|
||
@samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
|
||
for sparc64
|
||
@end itemize
|
||
|
||
@node TIC6x Features
|
||
@subsection TMS320C6x Features
|
||
@cindex target descriptions, TIC6x features
|
||
@cindex target descriptions, TMS320C6x features
|
||
The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
|
||
targets. It should contain registers @samp{A0} through @samp{A15},
|
||
registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
|
||
|
||
The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
|
||
contain registers @samp{A16} through @samp{A31} and @samp{B16}
|
||
through @samp{B31}.
|
||
|
||
The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
|
||
contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
|
||
|
||
@node Operating System Information
|
||
@appendix Operating System Information
|
||
@cindex operating system information
|
||
|
||
@menu
|
||
* Process list::
|
||
@end menu
|
||
|
||
Users of @value{GDBN} often wish to obtain information about the state of
|
||
the operating system running on the target---for example the list of
|
||
processes, or the list of open files. This section describes the
|
||
mechanism that makes it possible. This mechanism is similar to the
|
||
target features mechanism (@pxref{Target Descriptions}), but focuses
|
||
on a different aspect of target.
|
||
|
||
Operating system information is retrived from the target via the
|
||
remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
|
||
read}). The object name in the request should be @samp{osdata}, and
|
||
the @var{annex} identifies the data to be fetched.
|
||
|
||
@node Process list
|
||
@appendixsection Process list
|
||
@cindex operating system information, process list
|
||
|
||
When requesting the process list, the @var{annex} field in the
|
||
@samp{qXfer} request should be @samp{processes}. The returned data is
|
||
an XML document. The formal syntax of this document is defined in
|
||
@file{gdb/features/osdata.dtd}.
|
||
|
||
An example document is:
|
||
|
||
@smallexample
|
||
<?xml version="1.0"?>
|
||
<!DOCTYPE target SYSTEM "osdata.dtd">
|
||
<osdata type="processes">
|
||
<item>
|
||
<column name="pid">1</column>
|
||
<column name="user">root</column>
|
||
<column name="command">/sbin/init</column>
|
||
<column name="cores">1,2,3</column>
|
||
</item>
|
||
</osdata>
|
||
@end smallexample
|
||
|
||
Each item should include a column whose name is @samp{pid}. The value
|
||
of that column should identify the process on the target. The
|
||
@samp{user} and @samp{command} columns are optional, and will be
|
||
displayed by @value{GDBN}. The @samp{cores} column, if present,
|
||
should contain a comma-separated list of cores that this process
|
||
is running on. Target may provide additional columns,
|
||
which @value{GDBN} currently ignores.
|
||
|
||
@node Trace File Format
|
||
@appendix Trace File Format
|
||
@cindex trace file format
|
||
|
||
The trace file comes in three parts: a header, a textual description
|
||
section, and a trace frame section with binary data.
|
||
|
||
The header has the form @code{\x7fTRACE0\n}. The first byte is
|
||
@code{0x7f} so as to indicate that the file contains binary data,
|
||
while the @code{0} is a version number that may have different values
|
||
in the future.
|
||
|
||
The description section consists of multiple lines of @sc{ascii} text
|
||
separated by newline characters (@code{0xa}). The lines may include a
|
||
variety of optional descriptive or context-setting information, such
|
||
as tracepoint definitions or register set size. @value{GDBN} will
|
||
ignore any line that it does not recognize. An empty line marks the end
|
||
of this section.
|
||
|
||
@table @code
|
||
@item R @var{size}
|
||
Specifies the size of a register block in bytes. This is equal to the
|
||
size of a @code{g} packet payload in the remote protocol. @var{size}
|
||
is an ascii decimal number. There should be only one such line in
|
||
a single trace file.
|
||
|
||
@item status @var{status}
|
||
Trace status. @var{status} has the same format as a @code{qTStatus}
|
||
remote packet reply. There should be only one such line in a single trace
|
||
file.
|
||
|
||
@item tp @var{payload}
|
||
Tracepoint definition. The @var{payload} has the same format as
|
||
@code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
|
||
may take multiple lines of definition, corresponding to the multiple
|
||
reply packets.
|
||
|
||
@item tsv @var{payload}
|
||
Trace state variable definition. The @var{payload} has the same format as
|
||
@code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
|
||
may take multiple lines of definition, corresponding to the multiple
|
||
reply packets.
|
||
|
||
@item tdesc @var{payload}
|
||
Target description in XML format. The @var{payload} is a single line of
|
||
the XML file. All such lines should be concatenated together to get
|
||
the original XML file. This file is in the same format as @code{qXfer}
|
||
@code{features} payload, and corresponds to the main @code{target.xml}
|
||
file. Includes are not allowed.
|
||
|
||
@end table
|
||
|
||
The trace frame section consists of a number of consecutive frames.
|
||
Each frame begins with a two-byte tracepoint number, followed by a
|
||
four-byte size giving the amount of data in the frame. The data in
|
||
the frame consists of a number of blocks, each introduced by a
|
||
character indicating its type (at least register, memory, and trace
|
||
state variable). The data in this section is raw binary, not a
|
||
hexadecimal or other encoding; its endianness matches the target's
|
||
endianness.
|
||
|
||
@c FIXME bi-arch may require endianness/arch info in description section
|
||
|
||
@table @code
|
||
@item R @var{bytes}
|
||
Register block. The number and ordering of bytes matches that of a
|
||
@code{g} packet in the remote protocol. Note that these are the
|
||
actual bytes, in target order, not a hexadecimal encoding.
|
||
|
||
@item M @var{address} @var{length} @var{bytes}...
|
||
Memory block. This is a contiguous block of memory, at the 8-byte
|
||
address @var{address}, with a 2-byte length @var{length}, followed by
|
||
@var{length} bytes.
|
||
|
||
@item V @var{number} @var{value}
|
||
Trace state variable block. This records the 8-byte signed value
|
||
@var{value} of trace state variable numbered @var{number}.
|
||
|
||
@end table
|
||
|
||
Future enhancements of the trace file format may include additional types
|
||
of blocks.
|
||
|
||
@node Index Section Format
|
||
@appendix @code{.gdb_index} section format
|
||
@cindex .gdb_index section format
|
||
@cindex index section format
|
||
|
||
This section documents the index section that is created by @code{save
|
||
gdb-index} (@pxref{Index Files}). The index section is
|
||
DWARF-specific; some knowledge of DWARF is assumed in this
|
||
description.
|
||
|
||
The mapped index file format is designed to be directly
|
||
@code{mmap}able on any architecture. In most cases, a datum is
|
||
represented using a little-endian 32-bit integer value, called an
|
||
@code{offset_type}. Big endian machines must byte-swap the values
|
||
before using them. Exceptions to this rule are noted. The data is
|
||
laid out such that alignment is always respected.
|
||
|
||
A mapped index consists of several areas, laid out in order.
|
||
|
||
@enumerate
|
||
@item
|
||
The file header. This is a sequence of values, of @code{offset_type}
|
||
unless otherwise noted:
|
||
|
||
@enumerate
|
||
@item
|
||
The version number, currently 8. Versions 1, 2 and 3 are obsolete.
|
||
Version 4 uses a different hashing function from versions 5 and 6.
|
||
Version 6 includes symbols for inlined functions, whereas versions 4
|
||
and 5 do not. Version 7 adds attributes to the CU indices in the
|
||
symbol table. Version 8 specifies that symbols from DWARF type units
|
||
(@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
|
||
compilation unit (@samp{DW_TAG_comp_unit}) using the type.
|
||
|
||
@value{GDBN} will only read version 4, 5, or 6 indices
|
||
by specifying @code{set use-deprecated-index-sections on}.
|
||
GDB has a workaround for potentially broken version 7 indices so it is
|
||
currently not flagged as deprecated.
|
||
|
||
@item
|
||
The offset, from the start of the file, of the CU list.
|
||
|
||
@item
|
||
The offset, from the start of the file, of the types CU list. Note
|
||
that this area can be empty, in which case this offset will be equal
|
||
to the next offset.
|
||
|
||
@item
|
||
The offset, from the start of the file, of the address area.
|
||
|
||
@item
|
||
The offset, from the start of the file, of the symbol table.
|
||
|
||
@item
|
||
The offset, from the start of the file, of the constant pool.
|
||
@end enumerate
|
||
|
||
@item
|
||
The CU list. This is a sequence of pairs of 64-bit little-endian
|
||
values, sorted by the CU offset. The first element in each pair is
|
||
the offset of a CU in the @code{.debug_info} section. The second
|
||
element in each pair is the length of that CU. References to a CU
|
||
elsewhere in the map are done using a CU index, which is just the
|
||
0-based index into this table. Note that if there are type CUs, then
|
||
conceptually CUs and type CUs form a single list for the purposes of
|
||
CU indices.
|
||
|
||
@item
|
||
The types CU list. This is a sequence of triplets of 64-bit
|
||
little-endian values. In a triplet, the first value is the CU offset,
|
||
the second value is the type offset in the CU, and the third value is
|
||
the type signature. The types CU list is not sorted.
|
||
|
||
@item
|
||
The address area. The address area consists of a sequence of address
|
||
entries. Each address entry has three elements:
|
||
|
||
@enumerate
|
||
@item
|
||
The low address. This is a 64-bit little-endian value.
|
||
|
||
@item
|
||
The high address. This is a 64-bit little-endian value. Like
|
||
@code{DW_AT_high_pc}, the value is one byte beyond the end.
|
||
|
||
@item
|
||
The CU index. This is an @code{offset_type} value.
|
||
@end enumerate
|
||
|
||
@item
|
||
The symbol table. This is an open-addressed hash table. The size of
|
||
the hash table is always a power of 2.
|
||
|
||
Each slot in the hash table consists of a pair of @code{offset_type}
|
||
values. The first value is the offset of the symbol's name in the
|
||
constant pool. The second value is the offset of the CU vector in the
|
||
constant pool.
|
||
|
||
If both values are 0, then this slot in the hash table is empty. This
|
||
is ok because while 0 is a valid constant pool index, it cannot be a
|
||
valid index for both a string and a CU vector.
|
||
|
||
The hash value for a table entry is computed by applying an
|
||
iterative hash function to the symbol's name. Starting with an
|
||
initial value of @code{r = 0}, each (unsigned) character @samp{c} in
|
||
the string is incorporated into the hash using the formula depending on the
|
||
index version:
|
||
|
||
@table @asis
|
||
@item Version 4
|
||
The formula is @code{r = r * 67 + c - 113}.
|
||
|
||
@item Versions 5 to 7
|
||
The formula is @code{r = r * 67 + tolower (c) - 113}.
|
||
@end table
|
||
|
||
The terminating @samp{\0} is not incorporated into the hash.
|
||
|
||
The step size used in the hash table is computed via
|
||
@code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
|
||
value, and @samp{size} is the size of the hash table. The step size
|
||
is used to find the next candidate slot when handling a hash
|
||
collision.
|
||
|
||
The names of C@t{++} symbols in the hash table are canonicalized. We
|
||
don't currently have a simple description of the canonicalization
|
||
algorithm; if you intend to create new index sections, you must read
|
||
the code.
|
||
|
||
@item
|
||
The constant pool. This is simply a bunch of bytes. It is organized
|
||
so that alignment is correct: CU vectors are stored first, followed by
|
||
strings.
|
||
|
||
A CU vector in the constant pool is a sequence of @code{offset_type}
|
||
values. The first value is the number of CU indices in the vector.
|
||
Each subsequent value is the index and symbol attributes of a CU in
|
||
the CU list. This element in the hash table is used to indicate which
|
||
CUs define the symbol and how the symbol is used.
|
||
See below for the format of each CU index+attributes entry.
|
||
|
||
A string in the constant pool is zero-terminated.
|
||
@end enumerate
|
||
|
||
Attributes were added to CU index values in @code{.gdb_index} version 7.
|
||
If a symbol has multiple uses within a CU then there is one
|
||
CU index+attributes value for each use.
|
||
|
||
The format of each CU index+attributes entry is as follows
|
||
(bit 0 = LSB):
|
||
|
||
@table @asis
|
||
|
||
@item Bits 0-23
|
||
This is the index of the CU in the CU list.
|
||
@item Bits 24-27
|
||
These bits are reserved for future purposes and must be zero.
|
||
@item Bits 28-30
|
||
The kind of the symbol in the CU.
|
||
|
||
@table @asis
|
||
@item 0
|
||
This value is reserved and should not be used.
|
||
By reserving zero the full @code{offset_type} value is backwards compatible
|
||
with previous versions of the index.
|
||
@item 1
|
||
The symbol is a type.
|
||
@item 2
|
||
The symbol is a variable or an enum value.
|
||
@item 3
|
||
The symbol is a function.
|
||
@item 4
|
||
Any other kind of symbol.
|
||
@item 5,6,7
|
||
These values are reserved.
|
||
@end table
|
||
|
||
@item Bit 31
|
||
This bit is zero if the value is global and one if it is static.
|
||
|
||
The determination of whether a symbol is global or static is complicated.
|
||
The authorative reference is the file @file{dwarf2read.c} in
|
||
@value{GDBN} sources.
|
||
|
||
@end table
|
||
|
||
This pseudo-code describes the computation of a symbol's kind and
|
||
global/static attributes in the index.
|
||
|
||
@smallexample
|
||
is_external = get_attribute (die, DW_AT_external);
|
||
language = get_attribute (cu_die, DW_AT_language);
|
||
switch (die->tag)
|
||
@{
|
||
case DW_TAG_typedef:
|
||
case DW_TAG_base_type:
|
||
case DW_TAG_subrange_type:
|
||
kind = TYPE;
|
||
is_static = 1;
|
||
break;
|
||
case DW_TAG_enumerator:
|
||
kind = VARIABLE;
|
||
is_static = language != CPLUS;
|
||
break;
|
||
case DW_TAG_subprogram:
|
||
kind = FUNCTION;
|
||
is_static = ! (is_external || language == ADA);
|
||
break;
|
||
case DW_TAG_constant:
|
||
kind = VARIABLE;
|
||
is_static = ! is_external;
|
||
break;
|
||
case DW_TAG_variable:
|
||
kind = VARIABLE;
|
||
is_static = ! is_external;
|
||
break;
|
||
case DW_TAG_namespace:
|
||
kind = TYPE;
|
||
is_static = 0;
|
||
break;
|
||
case DW_TAG_class_type:
|
||
case DW_TAG_interface_type:
|
||
case DW_TAG_structure_type:
|
||
case DW_TAG_union_type:
|
||
case DW_TAG_enumeration_type:
|
||
kind = TYPE;
|
||
is_static = language != CPLUS;
|
||
break;
|
||
default:
|
||
assert (0);
|
||
@}
|
||
@end smallexample
|
||
|
||
@node Man Pages
|
||
@appendix Manual pages
|
||
@cindex Man pages
|
||
|
||
@menu
|
||
* gdb man:: The GNU Debugger man page
|
||
* gdbserver man:: Remote Server for the GNU Debugger man page
|
||
* gcore man:: Generate a core file of a running program
|
||
* gdbinit man:: gdbinit scripts
|
||
* gdb-add-index man:: Add index files to speed up GDB
|
||
@end menu
|
||
|
||
@node gdb man
|
||
@heading gdb man
|
||
|
||
@c man title gdb The GNU Debugger
|
||
|
||
@c man begin SYNOPSIS gdb
|
||
gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
|
||
[@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
|
||
[@option{-b}@w{ }@var{bps}]
|
||
[@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
|
||
[@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
|
||
[@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
|
||
[@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
|
||
[@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
|
||
@c man end
|
||
|
||
@c man begin DESCRIPTION gdb
|
||
The purpose of a debugger such as @value{GDBN} is to allow you to see what is
|
||
going on ``inside'' another program while it executes -- or what another
|
||
program was doing at the moment it crashed.
|
||
|
||
@value{GDBN} can do four main kinds of things (plus other things in support of
|
||
these) to help you catch bugs in the act:
|
||
|
||
@itemize @bullet
|
||
@item
|
||
Start your program, specifying anything that might affect its behavior.
|
||
|
||
@item
|
||
Make your program stop on specified conditions.
|
||
|
||
@item
|
||
Examine what has happened, when your program has stopped.
|
||
|
||
@item
|
||
Change things in your program, so you can experiment with correcting the
|
||
effects of one bug and go on to learn about another.
|
||
@end itemize
|
||
|
||
You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
|
||
Modula-2.
|
||
|
||
@value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
|
||
commands from the terminal until you tell it to exit with the @value{GDBN}
|
||
command @code{quit}. You can get online help from @value{GDBN} itself
|
||
by using the command @code{help}.
|
||
|
||
You can run @code{gdb} with no arguments or options; but the most
|
||
usual way to start @value{GDBN} is with one argument or two, specifying an
|
||
executable program as the argument:
|
||
|
||
@smallexample
|
||
gdb program
|
||
@end smallexample
|
||
|
||
You can also start with both an executable program and a core file specified:
|
||
|
||
@smallexample
|
||
gdb program core
|
||
@end smallexample
|
||
|
||
You can, instead, specify a process ID as a second argument, if you want
|
||
to debug a running process:
|
||
|
||
@smallexample
|
||
gdb program 1234
|
||
gdb -p 1234
|
||
@end smallexample
|
||
|
||
@noindent
|
||
would attach @value{GDBN} to process @code{1234} (unless you also have a file
|
||
named @file{1234}; @value{GDBN} does check for a core file first).
|
||
With option @option{-p} you can omit the @var{program} filename.
|
||
|
||
Here are some of the most frequently needed @value{GDBN} commands:
|
||
|
||
@c pod2man highlights the right hand side of the @item lines.
|
||
@table @env
|
||
@item break [@var{file}:]@var{function}
|
||
Set a breakpoint at @var{function} (in @var{file}).
|
||
|
||
@item run [@var{arglist}]
|
||
Start your program (with @var{arglist}, if specified).
|
||
|
||
@item bt
|
||
Backtrace: display the program stack.
|
||
|
||
@item print @var{expr}
|
||
Display the value of an expression.
|
||
|
||
@item c
|
||
Continue running your program (after stopping, e.g. at a breakpoint).
|
||
|
||
@item next
|
||
Execute next program line (after stopping); step @emph{over} any
|
||
function calls in the line.
|
||
|
||
@item edit [@var{file}:]@var{function}
|
||
look at the program line where it is presently stopped.
|
||
|
||
@item list [@var{file}:]@var{function}
|
||
type the text of the program in the vicinity of where it is presently stopped.
|
||
|
||
@item step
|
||
Execute next program line (after stopping); step @emph{into} any
|
||
function calls in the line.
|
||
|
||
@item help [@var{name}]
|
||
Show information about @value{GDBN} command @var{name}, or general information
|
||
about using @value{GDBN}.
|
||
|
||
@item quit
|
||
Exit from @value{GDBN}.
|
||
@end table
|
||
|
||
@ifset man
|
||
For full details on @value{GDBN},
|
||
see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
by Richard M. Stallman and Roland H. Pesch. The same text is available online
|
||
as the @code{gdb} entry in the @code{info} program.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@c man begin OPTIONS gdb
|
||
Any arguments other than options specify an executable
|
||
file and core file (or process ID); that is, the first argument
|
||
encountered with no
|
||
associated option flag is equivalent to a @option{-se} option, and the second,
|
||
if any, is equivalent to a @option{-c} option if it's the name of a file.
|
||
Many options have
|
||
both long and short forms; both are shown here. The long forms are also
|
||
recognized if you truncate them, so long as enough of the option is
|
||
present to be unambiguous. (If you prefer, you can flag option
|
||
arguments with @option{+} rather than @option{-}, though we illustrate the
|
||
more usual convention.)
|
||
|
||
All the options and command line arguments you give are processed
|
||
in sequential order. The order makes a difference when the @option{-x}
|
||
option is used.
|
||
|
||
@table @env
|
||
@item -help
|
||
@itemx -h
|
||
List all options, with brief explanations.
|
||
|
||
@item -symbols=@var{file}
|
||
@itemx -s @var{file}
|
||
Read symbol table from file @var{file}.
|
||
|
||
@item -write
|
||
Enable writing into executable and core files.
|
||
|
||
@item -exec=@var{file}
|
||
@itemx -e @var{file}
|
||
Use file @var{file} as the executable file to execute when
|
||
appropriate, and for examining pure data in conjunction with a core
|
||
dump.
|
||
|
||
@item -se=@var{file}
|
||
Read symbol table from file @var{file} and use it as the executable
|
||
file.
|
||
|
||
@item -core=@var{file}
|
||
@itemx -c @var{file}
|
||
Use file @var{file} as a core dump to examine.
|
||
|
||
@item -command=@var{file}
|
||
@itemx -x @var{file}
|
||
Execute @value{GDBN} commands from file @var{file}.
|
||
|
||
@item -ex @var{command}
|
||
Execute given @value{GDBN} @var{command}.
|
||
|
||
@item -directory=@var{directory}
|
||
@itemx -d @var{directory}
|
||
Add @var{directory} to the path to search for source files.
|
||
|
||
@item -nh
|
||
Do not execute commands from @file{~/.gdbinit}.
|
||
|
||
@item -nx
|
||
@itemx -n
|
||
Do not execute commands from any @file{.gdbinit} initialization files.
|
||
|
||
@item -quiet
|
||
@itemx -q
|
||
``Quiet''. Do not print the introductory and copyright messages. These
|
||
messages are also suppressed in batch mode.
|
||
|
||
@item -batch
|
||
Run in batch mode. Exit with status @code{0} after processing all the command
|
||
files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
|
||
Exit with nonzero status if an error occurs in executing the @value{GDBN}
|
||
commands in the command files.
|
||
|
||
Batch mode may be useful for running @value{GDBN} as a filter, for example to
|
||
download and run a program on another computer; in order to make this
|
||
more useful, the message
|
||
|
||
@smallexample
|
||
Program exited normally.
|
||
@end smallexample
|
||
|
||
@noindent
|
||
(which is ordinarily issued whenever a program running under @value{GDBN} control
|
||
terminates) is not issued when running in batch mode.
|
||
|
||
@item -cd=@var{directory}
|
||
Run @value{GDBN} using @var{directory} as its working directory,
|
||
instead of the current directory.
|
||
|
||
@item -fullname
|
||
@itemx -f
|
||
Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
|
||
@value{GDBN} to output the full file name and line number in a standard,
|
||
recognizable fashion each time a stack frame is displayed (which
|
||
includes each time the program stops). This recognizable format looks
|
||
like two @samp{\032} characters, followed by the file name, line number
|
||
and character position separated by colons, and a newline. The
|
||
Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
|
||
characters as a signal to display the source code for the frame.
|
||
|
||
@item -b @var{bps}
|
||
Set the line speed (baud rate or bits per second) of any serial
|
||
interface used by @value{GDBN} for remote debugging.
|
||
|
||
@item -tty=@var{device}
|
||
Run using @var{device} for your program's standard input and output.
|
||
@end table
|
||
@c man end
|
||
|
||
@c man begin SEEALSO gdb
|
||
@ifset man
|
||
The full documentation for @value{GDBN} is maintained as a Texinfo manual.
|
||
If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
|
||
documentation are properly installed at your site, the command
|
||
|
||
@smallexample
|
||
info gdb
|
||
@end smallexample
|
||
|
||
@noindent
|
||
should give you access to the complete manual.
|
||
|
||
@cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
Richard M. Stallman and Roland H. Pesch, July 1991.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@node gdbserver man
|
||
@heading gdbserver man
|
||
|
||
@c man title gdbserver Remote Server for the GNU Debugger
|
||
@format
|
||
@c man begin SYNOPSIS gdbserver
|
||
gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
|
||
|
||
gdbserver --attach @var{comm} @var{pid}
|
||
|
||
gdbserver --multi @var{comm}
|
||
@c man end
|
||
@end format
|
||
|
||
@c man begin DESCRIPTION gdbserver
|
||
@command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
|
||
than the one which is running the program being debugged.
|
||
|
||
@ifclear man
|
||
@subheading Usage (server (target) side)
|
||
@end ifclear
|
||
@ifset man
|
||
Usage (server (target) side):
|
||
@end ifset
|
||
|
||
First, you need to have a copy of the program you want to debug put onto
|
||
the target system. The program can be stripped to save space if needed, as
|
||
@command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
|
||
the @value{GDBN} running on the host system.
|
||
|
||
To use the server, you log on to the target system, and run the @command{gdbserver}
|
||
program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
|
||
your program, and (c) its arguments. The general syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver @var{comm} @var{program} [@var{args} ...]
|
||
@end smallexample
|
||
|
||
For example, using a serial port, you might say:
|
||
|
||
@smallexample
|
||
@ifset man
|
||
@c @file would wrap it as F</dev/com1>.
|
||
target> gdbserver /dev/com1 emacs foo.txt
|
||
@end ifset
|
||
@ifclear man
|
||
target> gdbserver @file{/dev/com1} emacs foo.txt
|
||
@end ifclear
|
||
@end smallexample
|
||
|
||
This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
|
||
to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
|
||
waits patiently for the host @value{GDBN} to communicate with it.
|
||
|
||
To use a TCP connection, you could say:
|
||
|
||
@smallexample
|
||
target> gdbserver host:2345 emacs foo.txt
|
||
@end smallexample
|
||
|
||
This says pretty much the same thing as the last example, except that we are
|
||
going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
|
||
that we are expecting to see a TCP connection from @code{host} to local TCP port
|
||
2345. (Currently, the @code{host} part is ignored.) You can choose any number you
|
||
want for the port number as long as it does not conflict with any existing TCP
|
||
ports on the target system. This same port number must be used in the host
|
||
@value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
|
||
you chose a port number that conflicts with another service, @command{gdbserver} will
|
||
print an error message and exit.
|
||
|
||
@command{gdbserver} can also attach to running programs.
|
||
This is accomplished via the @option{--attach} argument. The syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver --attach @var{comm} @var{pid}
|
||
@end smallexample
|
||
|
||
@var{pid} is the process ID of a currently running process. It isn't
|
||
necessary to point @command{gdbserver} at a binary for the running process.
|
||
|
||
To start @code{gdbserver} without supplying an initial command to run
|
||
or process ID to attach, use the @option{--multi} command line option.
|
||
In such case you should connect using @kbd{target extended-remote} to start
|
||
the program you want to debug.
|
||
|
||
@smallexample
|
||
target> gdbserver --multi @var{comm}
|
||
@end smallexample
|
||
|
||
@ifclear man
|
||
@subheading Usage (host side)
|
||
@end ifclear
|
||
@ifset man
|
||
Usage (host side):
|
||
@end ifset
|
||
|
||
You need an unstripped copy of the target program on your host system, since
|
||
@value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
|
||
would, with the target program as the first argument. (You may need to use the
|
||
@option{--baud} option if the serial line is running at anything except 9600 baud.)
|
||
That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
|
||
new command you need to know about is @code{target remote}
|
||
(or @code{target extended-remote}). Its argument is either
|
||
a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
|
||
descriptor. For example:
|
||
|
||
@smallexample
|
||
@ifset man
|
||
@c @file would wrap it as F</dev/ttyb>.
|
||
(gdb) target remote /dev/ttyb
|
||
@end ifset
|
||
@ifclear man
|
||
(gdb) target remote @file{/dev/ttyb}
|
||
@end ifclear
|
||
@end smallexample
|
||
|
||
@noindent
|
||
communicates with the server via serial line @file{/dev/ttyb}, and:
|
||
|
||
@smallexample
|
||
(gdb) target remote the-target:2345
|
||
@end smallexample
|
||
|
||
@noindent
|
||
communicates via a TCP connection to port 2345 on host `the-target', where
|
||
you previously started up @command{gdbserver} with the same port number. Note that for
|
||
TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
|
||
command, otherwise you may get an error that looks something like
|
||
`Connection refused'.
|
||
|
||
@command{gdbserver} can also debug multiple inferiors at once,
|
||
described in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{Inferiors and Programs}
|
||
-- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{Inferiors and Programs}.
|
||
@end ifclear
|
||
In such case use the @code{extended-remote} @value{GDBN} command variant:
|
||
|
||
@smallexample
|
||
(gdb) target extended-remote the-target:2345
|
||
@end smallexample
|
||
|
||
The @command{gdbserver} option @option{--multi} may or may not be used in such
|
||
case.
|
||
@c man end
|
||
|
||
@c man begin OPTIONS gdbserver
|
||
There are three different modes for invoking @command{gdbserver}:
|
||
|
||
@itemize @bullet
|
||
|
||
@item
|
||
Debug a specific program specified by its program name:
|
||
|
||
@smallexample
|
||
gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
|
||
@end smallexample
|
||
|
||
The @var{comm} parameter specifies how should the server communicate
|
||
with @value{GDBN}; it is either a device name (to use a serial line),
|
||
a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
|
||
stdin/stdout of @code{gdbserver}. Specify the name of the program to
|
||
debug in @var{prog}. Any remaining arguments will be passed to the
|
||
program verbatim. When the program exits, @value{GDBN} will close the
|
||
connection, and @code{gdbserver} will exit.
|
||
|
||
@item
|
||
Debug a specific program by specifying the process ID of a running
|
||
program:
|
||
|
||
@smallexample
|
||
gdbserver --attach @var{comm} @var{pid}
|
||
@end smallexample
|
||
|
||
The @var{comm} parameter is as described above. Supply the process ID
|
||
of a running program in @var{pid}; @value{GDBN} will do everything
|
||
else. Like with the previous mode, when the process @var{pid} exits,
|
||
@value{GDBN} will close the connection, and @code{gdbserver} will exit.
|
||
|
||
@item
|
||
Multi-process mode -- debug more than one program/process:
|
||
|
||
@smallexample
|
||
gdbserver --multi @var{comm}
|
||
@end smallexample
|
||
|
||
In this mode, @value{GDBN} can instruct @command{gdbserver} which
|
||
command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
|
||
close the connection when a process being debugged exits, so you can
|
||
debug several processes in the same session.
|
||
@end itemize
|
||
|
||
In each of the modes you may specify these options:
|
||
|
||
@table @env
|
||
|
||
@item --help
|
||
List all options, with brief explanations.
|
||
|
||
@item --version
|
||
This option causes @command{gdbserver} to print its version number and exit.
|
||
|
||
@item --attach
|
||
@command{gdbserver} will attach to a running program. The syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver --attach @var{comm} @var{pid}
|
||
@end smallexample
|
||
|
||
@var{pid} is the process ID of a currently running process. It isn't
|
||
necessary to point @command{gdbserver} at a binary for the running process.
|
||
|
||
@item --multi
|
||
To start @code{gdbserver} without supplying an initial command to run
|
||
or process ID to attach, use this command line option.
|
||
Then you can connect using @kbd{target extended-remote} and start
|
||
the program you want to debug. The syntax is:
|
||
|
||
@smallexample
|
||
target> gdbserver --multi @var{comm}
|
||
@end smallexample
|
||
|
||
@item --debug
|
||
Instruct @code{gdbserver} to display extra status information about the debugging
|
||
process.
|
||
This option is intended for @code{gdbserver} development and for bug reports to
|
||
the developers.
|
||
|
||
@item --remote-debug
|
||
Instruct @code{gdbserver} to display remote protocol debug output.
|
||
This option is intended for @code{gdbserver} development and for bug reports to
|
||
the developers.
|
||
|
||
@item --debug-format=option1@r{[},option2,...@r{]}
|
||
Instruct @code{gdbserver} to include extra information in each line
|
||
of debugging output.
|
||
@xref{Other Command-Line Arguments for gdbserver}.
|
||
|
||
@item --wrapper
|
||
Specify a wrapper to launch programs
|
||
for debugging. The option should be followed by the name of the
|
||
wrapper, then any command-line arguments to pass to the wrapper, then
|
||
@kbd{--} indicating the end of the wrapper arguments.
|
||
|
||
@item --once
|
||
By default, @command{gdbserver} keeps the listening TCP port open, so that
|
||
additional connections are possible. However, if you start @code{gdbserver}
|
||
with the @option{--once} option, it will stop listening for any further
|
||
connection attempts after connecting to the first @value{GDBN} session.
|
||
|
||
@c --disable-packet is not documented for users.
|
||
|
||
@c --disable-randomization and --no-disable-randomization are superseded by
|
||
@c QDisableRandomization.
|
||
|
||
@end table
|
||
@c man end
|
||
|
||
@c man begin SEEALSO gdbserver
|
||
@ifset man
|
||
The full documentation for @value{GDBN} is maintained as a Texinfo manual.
|
||
If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
|
||
documentation are properly installed at your site, the command
|
||
|
||
@smallexample
|
||
info gdb
|
||
@end smallexample
|
||
|
||
should give you access to the complete manual.
|
||
|
||
@cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
Richard M. Stallman and Roland H. Pesch, July 1991.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@node gcore man
|
||
@heading gcore
|
||
|
||
@c man title gcore Generate a core file of a running program
|
||
|
||
@format
|
||
@c man begin SYNOPSIS gcore
|
||
gcore [-a] [-o @var{filename}] @var{pid}
|
||
@c man end
|
||
@end format
|
||
|
||
@c man begin DESCRIPTION gcore
|
||
Generate a core dump of a running program with process ID @var{pid}.
|
||
Produced file is equivalent to a kernel produced core file as if the process
|
||
crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
|
||
limit). Unlike after a crash, after @command{gcore} the program remains
|
||
running without any change.
|
||
@c man end
|
||
|
||
@c man begin OPTIONS gcore
|
||
@table @env
|
||
@item -a
|
||
Dump all memory mappings. The actual effect of this option depends on
|
||
the Operating System. On @sc{gnu}/Linux, it will disable
|
||
@code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
|
||
enable @code{dump-excluded-mappings} (@pxref{set
|
||
dump-excluded-mappings}).
|
||
|
||
@item -o @var{filename}
|
||
The optional argument
|
||
@var{filename} specifies the file name where to put the core dump.
|
||
If not specified, the file name defaults to @file{core.@var{pid}},
|
||
where @var{pid} is the running program process ID.
|
||
@end table
|
||
@c man end
|
||
|
||
@c man begin SEEALSO gcore
|
||
@ifset man
|
||
The full documentation for @value{GDBN} is maintained as a Texinfo manual.
|
||
If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
|
||
documentation are properly installed at your site, the command
|
||
|
||
@smallexample
|
||
info gdb
|
||
@end smallexample
|
||
|
||
@noindent
|
||
should give you access to the complete manual.
|
||
|
||
@cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
Richard M. Stallman and Roland H. Pesch, July 1991.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@node gdbinit man
|
||
@heading gdbinit
|
||
|
||
@c man title gdbinit GDB initialization scripts
|
||
|
||
@format
|
||
@c man begin SYNOPSIS gdbinit
|
||
@ifset SYSTEM_GDBINIT
|
||
@value{SYSTEM_GDBINIT}
|
||
@end ifset
|
||
|
||
~/.gdbinit
|
||
|
||
./.gdbinit
|
||
@c man end
|
||
@end format
|
||
|
||
@c man begin DESCRIPTION gdbinit
|
||
These files contain @value{GDBN} commands to automatically execute during
|
||
@value{GDBN} startup. The lines of contents are canned sequences of commands,
|
||
described in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{Sequences}
|
||
-- shell command @code{info -f gdb -n Sequences}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{Sequences}.
|
||
@end ifclear
|
||
|
||
Please read more in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{Startup}
|
||
-- shell command @code{info -f gdb -n Startup}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{Startup}.
|
||
@end ifclear
|
||
|
||
@table @env
|
||
@ifset SYSTEM_GDBINIT
|
||
@item @value{SYSTEM_GDBINIT}
|
||
@end ifset
|
||
@ifclear SYSTEM_GDBINIT
|
||
@item (not enabled with @code{--with-system-gdbinit} during compilation)
|
||
@end ifclear
|
||
System-wide initialization file. It is executed unless user specified
|
||
@value{GDBN} option @code{-nx} or @code{-n}.
|
||
See more in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{System-wide configuration}
|
||
-- shell command @code{info -f gdb -n 'System-wide configuration'}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{System-wide configuration}.
|
||
@end ifclear
|
||
|
||
@item ~/.gdbinit
|
||
User initialization file. It is executed unless user specified
|
||
@value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
|
||
|
||
@item ./.gdbinit
|
||
Initialization file for current directory. It may need to be enabled with
|
||
@value{GDBN} security command @code{set auto-load local-gdbinit}.
|
||
See more in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{Init File in the Current Directory}
|
||
-- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{Init File in the Current Directory}.
|
||
@end ifclear
|
||
@end table
|
||
@c man end
|
||
|
||
@c man begin SEEALSO gdbinit
|
||
@ifset man
|
||
gdb(1), @code{info -f gdb -n Startup}
|
||
|
||
The full documentation for @value{GDBN} is maintained as a Texinfo manual.
|
||
If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
|
||
documentation are properly installed at your site, the command
|
||
|
||
@smallexample
|
||
info gdb
|
||
@end smallexample
|
||
|
||
should give you access to the complete manual.
|
||
|
||
@cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
Richard M. Stallman and Roland H. Pesch, July 1991.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@node gdb-add-index man
|
||
@heading gdb-add-index
|
||
@pindex gdb-add-index
|
||
@anchor{gdb-add-index}
|
||
|
||
@c man title gdb-add-index Add index files to speed up GDB
|
||
|
||
@c man begin SYNOPSIS gdb-add-index
|
||
gdb-add-index @var{filename}
|
||
@c man end
|
||
|
||
@c man begin DESCRIPTION gdb-add-index
|
||
When @value{GDBN} finds a symbol file, it scans the symbols in the
|
||
file in order to construct an internal symbol table. This lets most
|
||
@value{GDBN} operations work quickly--at the cost of a delay early on.
|
||
For large programs, this delay can be quite lengthy, so @value{GDBN}
|
||
provides a way to build an index, which speeds up startup.
|
||
|
||
To determine whether a file contains such an index, use the command
|
||
@kbd{readelf -S filename}: the index is stored in a section named
|
||
@code{.gdb_index}. The index file can only be produced on systems
|
||
which use ELF binaries and DWARF debug information (i.e., sections
|
||
named @code{.debug_*}).
|
||
|
||
@command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
|
||
in the @env{PATH} environment variable. If you want to use different
|
||
versions of these programs, you can specify them through the
|
||
@env{GDB} and @env{OBJDUMP} environment variables.
|
||
|
||
See more in
|
||
@ifset man
|
||
the @value{GDBN} manual in node @code{Index Files}
|
||
-- shell command @kbd{info -f gdb -n "Index Files"}.
|
||
@end ifset
|
||
@ifclear man
|
||
@ref{Index Files}.
|
||
@end ifclear
|
||
@c man end
|
||
|
||
@c man begin SEEALSO gdb-add-index
|
||
@ifset man
|
||
The full documentation for @value{GDBN} is maintained as a Texinfo manual.
|
||
If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
|
||
documentation are properly installed at your site, the command
|
||
|
||
@smallexample
|
||
info gdb
|
||
@end smallexample
|
||
|
||
should give you access to the complete manual.
|
||
|
||
@cite{Using GDB: A Guide to the GNU Source-Level Debugger},
|
||
Richard M. Stallman and Roland H. Pesch, July 1991.
|
||
@end ifset
|
||
@c man end
|
||
|
||
@include gpl.texi
|
||
|
||
@node GNU Free Documentation License
|
||
@appendix GNU Free Documentation License
|
||
@include fdl.texi
|
||
|
||
@node Concept Index
|
||
@unnumbered Concept Index
|
||
|
||
@printindex cp
|
||
|
||
@node Command and Variable Index
|
||
@unnumbered Command, Variable, and Function Index
|
||
|
||
@printindex fn
|
||
|
||
@tex
|
||
% I think something like @@colophon should be in texinfo. In the
|
||
% meantime:
|
||
\long\def\colophon{\hbox to0pt{}\vfill
|
||
\centerline{The body of this manual is set in}
|
||
\centerline{\fontname\tenrm,}
|
||
\centerline{with headings in {\bf\fontname\tenbf}}
|
||
\centerline{and examples in {\tt\fontname\tentt}.}
|
||
\centerline{{\it\fontname\tenit\/},}
|
||
\centerline{{\bf\fontname\tenbf}, and}
|
||
\centerline{{\sl\fontname\tensl\/}}
|
||
\centerline{are used for emphasis.}\vfill}
|
||
\page\colophon
|
||
% Blame: doc@@cygnus.com, 1991.
|
||
@end tex
|
||
|
||
@bye
|