Description of problem: On F11 GDB started to backtrace past clone() thread_start. This was workarounded in GDB by code matching pattern which changed with gcc44. The workaround in GDB could be dropped as the upstream DWARF based patch now works in F11 and its Fedora specific removal can be stopped. Originally it was incompatible with libgcc unwinder (although I did not find the specific patch which did fix it). Version-Release number of selected component (if applicable): glibc-2.9.90-11.{x86_64,i?86} gdb-6.8.50.20090302-10.fc11.x86_64 How reproducible: Always. Steps to Reproduce: $ gdb -q ./threadit (gdb) b start Breakpoint 1 at 0x400628: file threadit.c, line 31. (gdb) r [...] (gdb) bt Actual results: #0 start (arg=0x0) at threadit.c:31 #1 0x00000000009a087a in start_thread () from /lib64/libpthread.so.0 #2 0x00007ffff7d5b4cd in clone () from /lib64/libc.so.6 #3 0x0000000000000000 in ?? () (gdb) Expected results: #0 start (arg=0x0) at threadit.c:31 #1 0x00000000009a087a in start_thread () from /lib64/libpthread.so.0 #2 0x00007ffff7d5b4cd in clone () from /lib64/libc.so.6 (gdb) Additional info: The removal is by: * Thu Dec 14 2006 Jakub Jelinek <jakub> 2.5.90-13 - revert i?86/x86_64 clone CFI temporarily glibc-fedora.patch +++ glibc-20090320T1944-fedora/sysdeps/unix/sysv/linux/i386/clone.S 14 Dec 2006 09:06:34 -0000 1.22.2.6 +++ glibc-20090320T1944-fedora/sysdeps/unix/sysv/linux/x86_64/clone.S 14 Dec 2006 09:06:34 -0000 1.4.2.4 It was discussed at: http://sourceware.org/ml/libc-alpha/2006-11/msg00082.html http://sourceware.org/ml/libc-alpha/2006-12/threads.html#00008 GDB regression on: gdb.threads/bt-clone-stop.exp glibc scratch build test: http://koji.fedoraproject.org/scratch/jkratoch/task_1253117/ With no regressions for: grep -i 'make:.*error' *.log It breaks upstream libunwind for its testcase: {G,L}test-concurrent But Fedora libunwind has no (maybe one minor) regressions probably due to its: http://sources.redhat.com/cgi-bin/cvsweb.cgi/frysk-imports/libunwind/src/dwarf/Gparser.c.diff?r1=1.3&r2=1.4&cvsroot=frysk libunwind.non-ia64 is currently used only by Frysk now. Tested that the testcase: ------------------------------------------------------------------------------ #include <pthread.h> #include <execinfo.h> #include <stdio.h> #include <unistd.h> void * tf (void *arg) { void *buf[512]; int i = backtrace (buf, 512); printf ("%d\n", i); backtrace_symbols_fd (buf, i, STDOUT_FILENO); return NULL; } int main (void) { pthread_t th; pthread_create (&th, NULL, tf, NULL); pthread_join (th, NULL); return 0; } ------------------------------------------------------------------------------ unwinds fine on x86_64+i686: 3 ./clone-testcase[0x400692] /lib64/libpthread.so.0[0x11687a] /lib64/libc.so.6(clone+0x6d)[0x6e04cd] and that it really loops with the glibc scratch build o RHEL-5.2: 512 ./clone-testcase[0x40065b] .../glibc-2.9.90-11cfiundef.x86_64/lib64/libpthread.so.0[0x2b1babcc887a] .../glibc-2.9.90-11cfiundef.x86_64/lib64/libc.so.6(clone+0x6d)[0x2b1babfbd4cd] .../glibc-2.9.90-11cfiundef.x86_64/lib64/libc.so.6(clone+0x6d)[0x2b1babfbd4cd] .../glibc-2.9.90-11cfiundef.x86_64/lib64/libc.so.6(clone+0x6d)[0x2b1babfbd4cd] [...] .../glibc-2.9.90-11cfiundef.x86_64/lib64/libc.so.6(clone+0x6d)[0x2b1babfbd4cd] <stop> If the patch removal stays in glibc sure I can update the workaround in GDB.
To my knowledge GCC unwinder still treats DW_CFA_undefined exactly the same as DW_CFA_same_value, so this really can't be removed, it breaks a lot of stuff. I guess I should revive the http://gcc.gnu.org/ml/gcc/2006-12/msg00312.html patch, but I'll need support for that from Roland/you/drow.
This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle. Changing version to '11'. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping
What is the status of this?
The GCC change is now in upstream GCC 4.4.0+ (and of course Fedora GCC 4.4-RH too), so in theory this could be reverted even on the glibc side.
Fixed in rawhide.