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Compiling GDB with a recent GCC exposes a problem:
../../gdb/typeprint.c: In function 'void whatis_exp(const char*, int)':
../../gdb/typeprint.c:515:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
real_type = value_rtti_type (val, &full, &top, &using_enc);
~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The warning is correct. There are indeed code paths that use
uninitialized 'val', leading to crashes. Inside the
value_rtti_indirect_type/value_rtti_type calls here in whatis_exp:
if (opts.objectprint)
{
if (((TYPE_CODE (type) == TYPE_CODE_PTR) || TYPE_IS_REFERENCE (type))
&& (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_STRUCT))
real_type = value_rtti_indirect_type (val, &full, &top, &using_enc);
else if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
real_type = value_rtti_type (val, &full, &top, &using_enc);
}
We reach those calls above with "set print object on", and then with
any of:
(gdb) whatis struct some_structure_type
(gdb) whatis struct some_structure_type *
(gdb) whatis struct some_structure_type &
because "whatis" with a type argument enters this branch:
/* The behavior of "whatis" depends on whether the user
expression names a type directly, or a language expression
(including variable names). If the former, then "whatis"
strips one level of typedefs, only. If an expression,
"whatis" prints the type of the expression without stripping
any typedef level. "ptype" always strips all levels of
typedefs. */
if (show == -1 && expr->elts[0].opcode == OP_TYPE)
{
which does not initialize VAL. Trying the above triggers crashes like
this:
(gdb) set print object on
(gdb) whatis some_structure_type
Thread 1 "gdb" received signal SIGSEGV, Segmentation fault.
0x00000000005dda90 in check_typedef (type=0x6120736573756170) at src/gdb/gdbtypes.c:2388
2388 int instance_flags = TYPE_INSTANCE_FLAGS (type);
...
This is a regression caused by a recent-ish refactoring of the code on
'whatis_exp', introduced by:
commit
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| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| zlib | ||
| .cvsignore | ||
| .gitattributes | ||
| .gitignore | ||
| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| makefile.vms | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release.sh | ||
| symlink-tree | ||
| ylwrap | ||
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.