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Sergio Durigan Junior 6d62641c83 Fix Python completion when using the "complete" command
This patch is related to PR python/16699, and is an improvement over the
patch posted here:

  <https://sourceware.org/ml/gdb-patches/2014-03/msg00301.html>

Keith noticed that, when using the "complete" command on GDB to complete
a Python command, some strange things could happen.  In order to
understand what can go wrong, I need to explain how the Python
completion mechanism works.

When the user requests a completion of a Python command by using TAB,
GDB will first try to determine the right set of "brkchars" that will be
used when doing the completion.  This is done by actually calling the
"complete" method of the Python class.  Then, when we already know the
"brkchars" that will be used, we call the "complete" method again, for
the same values.

If you read the thread mentioned above, you will see that one of the
design decisions was to make the "cmdpy_completer_helper" (which is the
function the does the actual calling of the "complete" method) cache the
first result of the completion, since this result will be used in the
second call, to do the actual completion.

The problem is that the "complete" command does not process the
brkchars, and the current Python completion mechanism (improved by the
patch mentioned above) relies on GDB trying to determine the brkchars,
and then doing the completion itself.  Therefore, when we use the
"complete" command instead of doing a TAB-completion on GDB, there is a
scenario where we can use the invalid cache of a previous Python command
that was completed before.  For example:

  (gdb) A <TAB>
  (gdb) complete B
  B value1
  B value10
  B value2
  B value3
  B value4
  B value5
  B value6
  B value7
  B value8
  B value9
  (gdb) B <TAB>
  comp1   comp2   comp4   comp6   comp8
  comp10  comp3   comp5   comp7   comp9

Here, we see that "complete B " gave a different result than "B <TAB>".
The reason for that is because "A <TAB>" was called before, and its
completion results were "value*", so when GDB tried to "complete B " it
wrongly answered with the results for A.  The problem here is using a
wrong cache (A's cache) for completing B.

We tried to come up with a solution that would preserve the caching
mechanism, but it wasn't really possible.  So I decided to completely
remove the cache, and doing the method calling twice for every
completion.  This is not optimal, but I do not think it will impact
users noticeably.

It is worth mentioning another small issue that I found.  The code was
doing:

  wordobj = PyUnicode_Decode (word, sizeof (word), host_charset (), NULL);

which is totally wrong, because using "sizeof" here will lead to always
the same result.  So I changed this to use "strlen".  The testcase also
catches this problem.

Keith kindly expanded the existing testcase to cover the problem
described above, and everything is passing.

gdb/ChangeLog:
2015-04-08  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR python/16699
	* python/py-cmd.c (cmdpy_completer_helper): Adjust function to not
	use a caching mechanism.  Adjust comments and code to reflect
	that.  Replace 'sizeof' by 'strlen' when fetching 'wordobj'.
	(cmdpy_completer_handle_brkchars): Adjust call to
	cmdpy_completer_helper.  Call Py_XDECREF for 'resultobj'.
	(cmdpy_completer): Likewise.

gdb/testsuite/ChangeLog:
2015-04-08  Keith Seitz  <keiths@redhat.com>

	PR python/16699
	* gdb.python/py-completion.exp: New tests for completion.
	* gdb.python/py-completion.py (CompleteLimit1): New class.
	(CompleteLimit2): Likewise.
	(CompleteLimit3): Likewise.
	(CompleteLimit4): Likewise.
	(CompleteLimit5): Likewise.
	(CompleteLimit6): Likewise.
	(CompleteLimit7): Likewise.
2015-04-08 18:27:10 -04:00
bfd Work around a GCC uninitialized warning bug 2015-04-08 09:27:27 -07:00
binutils Add SHF_COMPRESSED support to gas and objcopy 2015-04-08 07:54:09 -07:00
config Set zlibdir/zlibinc with top_builddir/top_srcdir 2015-04-02 05:43:07 -07:00
cpu or1k: add missing l.msync, l.psync and l.psync instructions. 2014-07-20 20:26:09 +03:00
elfcpp Add chdr_size, Chdr, Chdr_write and Chdr_data 2015-04-08 10:29:40 -07:00
etc PR external/{16327,16328}: Remove etc/configure.texi and etc/standards.texi. 2014-06-27 11:33:25 +02:00
gas Add SHF_COMPRESSED support to gas and objcopy 2015-04-08 07:54:09 -07:00
gdb Fix Python completion when using the "complete" command 2015-04-08 18:27:10 -04:00
gold Add AArch32 support for arm gold linker. 2015-04-07 17:21:27 -07:00
gprof Regenerate Makeile.in file for copyright update 2015-01-02 22:27:27 +10:30
include Add Elf_Internal_Chdr and ElfXX_External_Chdr 2015-04-03 12:50:10 -07:00
intl
ld Skip empty EMULATION_NAME 2015-04-08 09:46:50 -07:00
libdecnumber Another part of fixing "make TAGS". 2015-01-22 21:07:31 +02:00
libiberty strerror.c: Do not declare sys_nerr or sys_errlist if already macros 2015-01-19 16:29:07 +01:00
opcodes x86: Use individual prefix control for each opcode. 2015-04-06 19:33:01 +03:00
readline Fix executable indicator in file name completion on Windows. 2014-12-30 21:14:25 +02:00
sim sim: move sim-engine.o/sim-hrw.o to the common list 2015-04-06 23:56:47 -04:00
texinfo
zlib Add missing ChangeLog entry 2015-03-31 13:15:01 -07:00
.cvsignore
.gitattributes Add a .gitattributes file for use with git-merge-changelog 2014-07-25 18:07:23 -04:00
.gitignore
ChangeLog Add --with-system-zlib to top level configure 2015-04-01 04:57:28 -07:00
compile Update from upstream Automake 2014-11-16 13:43:48 +01:00
config-ml.in Sync config-ml.in with GCC trunk 2015-03-17 05:15:34 -07:00
config.guess Update config.guess and config.sub to the latest upstream version 2015-03-30 16:28:14 -04:00
config.rpath
config.sub Update config.guess and config.sub to the latest upstream version 2015-03-30 16:28:14 -04:00
configure Add --with-system-zlib to top level configure 2015-04-01 04:57:28 -07:00
configure.ac Add --with-system-zlib to top level configure 2015-04-01 04:57:28 -07:00
COPYING
COPYING3
COPYING3.LIB
COPYING.LIB
COPYING.LIBGLOSS
COPYING.NEWLIB
depcomp Update from upstream Automake 2014-11-16 13:43:48 +01:00
djunpack.bat
install-sh Update from upstream Automake 2014-11-16 13:43:48 +01:00
libtool.m4 Update libtool.m4 from GCC trunk 2014-11-24 09:14:09 -08:00
lt~obsolete.m4
ltgcc.m4
ltmain.sh
ltoptions.m4
ltsugar.m4
ltversion.m4
MAINTAINERS Update description of ownership of files in include/ 2014-11-04 16:14:14 -08:00
Makefile.def Make all-bfd depend on all-zlib 2015-03-30 10:18:34 -07:00
Makefile.in Make all-bfd depend on all-zlib 2015-03-30 10:18:34 -07:00
Makefile.tpl Update top-level files from GCC trunk 2015-03-16 09:12:37 -07:00
makefile.vms
missing Update from upstream Automake 2014-11-16 13:43:48 +01:00
mkdep
mkinstalldirs Update from upstream Automake 2014-11-16 13:43:48 +01:00
move-if-change Update `move-if-change' from gnulib 2014-11-16 17:04:02 +01:00
README
README-maintainer-mode
setup.com
src-release.sh Remove --with-target-subdir=. --disable-multilib 2015-03-31 13:13:13 -07:00
symlink-tree
ylwrap Update from upstream Automake 2014-11-16 13:43:48 +01:00

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This directory contains various GNU compilers, assemblers, linkers, 
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