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While working on another issue relating to GDB's use of the Python
Pygments package for disassembly styling I noticed an issue in the
case where the Pygments package raises an exception.
The intention of the current code is that, should the Pygments package
raise an exception, GDB will disable future attempts to call into the
Pygments code. This was intended to prevent repeated errors during
disassembly if, for some reason, the Pygments code isn't working.
Since the Pygments based styling was added, GDB now supports
disassembly styling using libopcodes, but this is only available for
some architectures. For architectures not covered by libopcodes
Pygments is still the only option.
What I observed is that, if I disable the libopcodes styling, then
setup GDB so that the Pygments based styling code will indicate an
error (by returning None), GDB does, as expected, stop using the
Pygments based styling. However, the libopcodes based styling will
instead be used, despite this feature having been disabled.
The problem is that the disassembler output is produced into a
string_file buffer. When we are using Pygments, this buffer is
created without styling support. However, when Pygments fails, we
recreate the buffer with styling support.
The problem is that we should only recreate the buffer with styling
support only if libopcodes styling is enabled. This was an oversight
in commit:
commit 4cbe4ca5da
Date: Mon Feb 14 14:40:52 2022 +0000
gdb: add support for disassembler styling using libopcodes
This commit:
1. Factors out some of the condition checking logic into two new
helper functions use_ext_lang_for_styling and
use_libopcodes_for_styling,
2. Reorders gdb_disassembler::m_buffer and gdb_disassembler::m_dest,
this allows these fields to be initialised m_dest first, which means
that the new condition checking functions can rely on m_dest being
set, even when called from the gdb_disassembler constructor,
3. Make use of the new condition checking functions each time
m_buffer is initialised,
4. Add a new test that forces the Python disassembler styling
function to return None, this will cause GDB to disable use of
Pygments for styling, and
5. When we reinitialise m_buffer, and re-disassemble the
instruction, call reset the in-comment flag. If the instruction
being disassembler ends in a comment then the first disassembly pass
will have set the in-comment flag to true. This shouldn't be a
problem as we will only be using Pygments, and thus performing a
re-disassembly pass, if libopcodes is disabled, so the in-comment
flag will never be checked, even if it is set incorrectly. However,
I think that having the flag set correctly is a good thing, even if
we don't check it (you never know what future uses might come up).
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.