214 lines
8.3 KiB
Plaintext
Executable File
214 lines
8.3 KiB
Plaintext
Executable File
GDB 4.0 -- what has changed since 3.5?
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* New Facilities
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Wide output is wrapped at good places to make the output more
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readable.
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Gdb now supports cross-debugging from a host machine of one type to a
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target machine of another type. Communication with the target system
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is over serial lines. The ``target'' command handles connecting to the
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remote system; the ``load'' command will download a program into the
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remote system. It also supports debugging of realtime processes
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running under VxWorks, using SunRPC Remote Procedure Calls over TCP/IP
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to talk to a debugger stub on the target system.
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New CPUs supported include the AMD 29000 and Intel 960.
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GDB now reads object files and symbol tables via a ``binary file''
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library, which allows a single copy of GDB to debug programs of multiple
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object file types such as a.out and coff.
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There is now a GDB reference card in "gdbrc.tex".
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* Control-Variable user interface simplified
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All variables that control the operation of the debugger can be set
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by the ``set'' command, and displayed by the ``show'' command.
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For example, ``set prompt new-gdb=>'' will change your prompt to new-gdb=>.
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``Show prompt'' produces the response:
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Gdb's prompt is new-gdb=>.
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What follows are the NEW set commands. The command ``help set'' will
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print a complete list of old and new set commands. ``help set FOO''
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will give a longer description of the variable FOO.
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confirm on/off: Enables warning questions for operations that are
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hard to recover from, e.g. rerunning the program while
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it is already running. Default is ON.
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editing on/off: Enables EMACS style command line editing
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of input. Previous lines can be recalled with
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control-P, the current line can be edited with control-B,
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you can search for commands with control-R, etc.
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Default is ON.
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history filename NAME: NAME is where the gdb command history
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will be stored. The default is .gdb_history,
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or the value of the environment variable
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GDBHISTFILE.
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history size N: The size, in commands, of the command history. The
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default is 256, or the value of the environment variable
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HISTSIZE.
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history write on/off: If this value is set to ON, the history file will
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be saved after exiting gdb. If set to OFF, the
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file will not be saved. The default is OFF.
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history expansion on/off: If this value is set to ON, then csh-like
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history expansion will be performed on
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command line input. The default is OFF.
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radix N: Sets the default radix for input and output. It can be set
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to 8, 10, or 16. Note that the argument to "radix" is interpreted
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in the current radix, so "set radix 10" is always a no-op.
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screen-height N: This integer value is the number of lines on a page. Default
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is 24, the current `stty rows'' setting, or the ``li#''
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setting from the termcap entry matching the environment
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variable TERM.
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screen-width N: This integer value is the number of characters on a line.
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Default is 80, the current `stty cols'' setting, or the ``co#''
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setting from the termcap entry matching the environment
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variable TERM.
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Note: ``set screensize'' is obsolete. Use ``set height'' and
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``set width'' instead.
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print address on/off: Print memory addresses in various command displays,
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such as stack traces and structure values. Gdb looks
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more ``symbolic'' if you turn this off; it looks more
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``machine level'' with it on. Default is ON.
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print array on/off: Prettyprint arrays. New convenient format! Default
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is OFF.
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print demangle on/off: Print C++ symbols in "source" form if on,
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"raw" form if off.
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print asm-demangle on/off: Same, for assembler level printouts
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like instructions.
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print vtbl on/off: Prettyprint C++ virtual function tables. Default is OFF.
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* Support for Epoch Environment.
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The epoch environment is a version of Emacs v18 with windowing. One
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new command, ``inspect'', is identical to ``print'', except that if you
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are running in the epoch environment, the value is printed in its own
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window.
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* Support for Shared Libraries
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GDB can now debug programs and core files that use SunOS shared libraries.
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Symbols from a shared library cannot be referenced
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before the shared library has been linked with the program (this
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happens after you type ``run'' and before the function main() is entered).
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At any time after this linking (including when examining core files
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from dynamically linked programs), gdb reads the symbols from each
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shared library when you type the ``sharedlibrary'' command.
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It can be abbreviated ``share''.
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sharedlibrary REGEXP: Load shared object library symbols for files
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matching a unix regular expression. No argument
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indicates to load symbols for all shared libraries.
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info sharedlibrary: Status of loaded shared libraries.
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* Watchpoints
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A watchpoint stops execution of a program whenever the value of an
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expression changes. Checking for this slows down execution
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tremendously whenever you are in the scope of the expression, but is
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quite useful for catching tough ``bit-spreader'' or pointer misuse
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problems. Some machines such as the 386 have hardware for doing this
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more quickly, and future versions of gdb will use this hardware.
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watch EXP: Set a watchpoint (breakpoint) for an expression.
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info watchpoints: Information about your watchpoints.
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delete N: Deletes watchpoint number N (same as breakpoints).
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disable N: Temporarily turns off watchpoint number N (same as breakpoints).
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enable N: Re-enables watchpoint number N (same as breakpoints).
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* C++ multiple inheritance
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When used with a GCC version 2 compiler, GDB supports multiple inheritance
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for C++ programs.
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* C++ exception handling
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Gdb now supports limited C++ exception handling. Besides the existing
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ability to breakpoint on an exception handler, gdb can breakpoint on
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the raising of an exception (before the stack is peeled back to the
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handler's context).
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catch FOO: If there is a FOO exception handler in the dynamic scope,
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set a breakpoint to catch exceptions which may be raised there.
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Multiple exceptions (``catch foo bar baz'') may be caught.
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info catch: Lists all exceptions which may be caught in the
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current stack frame.
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* Minor command changes
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The command ``call func (arg, arg, ...)'' now acts like the print
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command, except it does not print or save a value if the function's result
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is void. This is similar to dbx usage.
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The ``up'' and ``down'' commands now always print the frame they end up
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at; ``up-silently'' and `down-silently'' can be used in scripts to change
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frames without printing.
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* New directory command
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'dir' now adds directories to the FRONT of the source search path.
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The path starts off empty. Source files that contain debug information
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about the directory in which they were compiled can be found even
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with an empty path; GCC includes this information. If GDB can't find
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your source file in the current directory, type "dir .".
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* Features removed in this release
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``info types'' has been removed, since it printed builtin types in a
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confusing fashion, and did not do useful things with typedefs. ``ptype''
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or ``whatis'' are more useful commands for dealing with types..
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* Configuring GDB for compilation
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For normal use, type ``config.gdb host''. Hosts now handled are:
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3b1 altos altosgas arm bigmips convex hp300bsd hp300hpux i386v i386v-g
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i386v32 i386v32-g isi littlemips m88k merlin news news1000 none np1 pn
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pyramid sun2os3 sun2os4 sun386 sun3os3 sun3os4 sun4os3 sun4os4 symmetry
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umax vax
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Type config.gdb +host to get a full description of each host.
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You can now build gdb conveniently for several architectures from the
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same sources. If config.gdb is run from a subdirectory, it configures
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the Makefile to use source files from '..'. Each subdirectory can be
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indpendently configured. An explicit source file directory can also
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be specified with the +srcdir=xxx option. Due to obscure search rules
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in the C preprocessor, if you have previously built gdb in the main
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directory, run 'make cleanconfig' in the top level directory before
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building it in a subdirectory.
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GDB now handles cross debugging. If you are remotely debugging between
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two different machines, type ``config.gdb host target''.
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Host is the machine where gdb will run; target is the machine
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where the program that you are debugging will run.
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Type config.gdb +target to get a full description of each target.
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