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GDB recently gained the ability to print a backtrace when a fatal signal is encountered. This backtrace is produced using the backtrace and backtrace_symbols_fd API available in glibc. However, in order for this API to actually map addresses to symbol names it is required that the application (GDB) be compiled with -rdynamic, which GDB is not by default. As a result, the backtrace produced often looks like this: Fatal signal: Bus error ----- Backtrace ----- ./gdb/gdb[0x80ec00] ./gdb/gdb[0x80ed56] /lib64/libc.so.6(+0x3c6b0)[0x7fc2ce1936b0] /lib64/libc.so.6(__poll+0x4f)[0x7fc2ce24da5f] ./gdb/gdb[0x15495ba] ./gdb/gdb[0x15489b8] ./gdb/gdb[0x9b794d] ./gdb/gdb[0x9b7a6d] ./gdb/gdb[0x9b943b] ./gdb/gdb[0x9b94a1] ./gdb/gdb[0x4175dd] /lib64/libc.so.6(__libc_start_main+0xf3)[0x7fc2ce17e1a3] ./gdb/gdb[0x4174de] --------------------- This is OK if you have access to the exact same build of GDB, you can manually map the addresses back to symbols, however, it is next to useless if all you have is a backtrace copied into a bug report. GCC uses libbacktrace for printing a backtrace when it encounters an error. In recent commits I added this library into the binutils-gdb repository, and in this commit I allow this library to be used by GDB. Now (when GDB is compiled with debug information) the backtrace looks like this: ----- Backtrace ----- 0x80ee08 gdb_internal_backtrace ../../src/gdb/event-top.c:989 0x80ef0b handle_fatal_signal ../../src/gdb/event-top.c:1036 0x7f24539dd6af ??? 0x7f2453a97a5f ??? 0x154976f gdb_wait_for_event ../../src/gdbsupport/event-loop.cc:613 0x1548b6d _Z16gdb_do_one_eventv ../../src/gdbsupport/event-loop.cc:237 0x9b7b02 start_event_loop ../../src/gdb/main.c:421 0x9b7c22 captured_command_loop ../../src/gdb/main.c:481 0x9b95f0 captured_main ../../src/gdb/main.c:1353 0x9b9656 _Z8gdb_mainP18captured_main_args ../../src/gdb/main.c:1368 0x4175ec main ../../src/gdb/gdb.c:32 --------------------- Which seems much more useful. Use of libbacktrace is optional. If GDB is configured with --disable-libbacktrace then the libbacktrace directory will not be built, and GDB will not try to use this library. In this case GDB would try to use the old backtrace and backtrace_symbols_fd API. All of the functions related to writing the backtrace of GDB itself have been moved into the new files gdb/by-utils.{c,h}. |
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bfd | ||
binutils | ||
config | ||
contrib | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gdbserver | ||
gdbsupport | ||
gnulib | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libbacktrace | ||
libctf | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
zlib | ||
.cvsignore | ||
.gitattributes | ||
.gitignore | ||
ar-lib | ||
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 | ||
multilib.am | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release.sh | ||
symlink-tree | ||
test-driver | ||
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.