[bug #29642] gdb: breakpoints in triggered in other threads result in SIGTRAP

[Carl Fredrik Hammar]

URL:
  <http://savannah.gnu.org/bugs/?29642>

                 Summary: gdb: breakpoints in triggered in other threads
result in SIGTRAP
                 Project: The GNU Hurd
            Submitted by: hammy
            Submitted on: Thu 22 Apr 2010 04:38:30 PM CEST
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
         Reproducibility: None
              Size (loc): None
         Planned Release: None
                  Effort: 0.00
Wiki-like text discussion box: 

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Details:

When debugging a multithreaded program with gdb, breakpoints triggered in
separate threads results in a SIGTRAP as if it was a regular terminating
signal.  For instance, with the program:


#include <pthread.h>

void *
foo (void *arg)
{
  return NULL;
}

int
main (int argc, char *argv[])
{
  pthread_t t;

  pthread_create (&t, NULL, foo, NULL);
  pthread_join (t, NULL);
}



the bug can be like this:


(gdb) break main
Breakpoint 1 at 0x8048507: file /home/cfhammar/src/hurd-test/gdb-threads.c,
line 14.
(gdb) break foo
Breakpoint 2 at 0x80484f7: file /home/cfhammar/src/hurd-test/gdb-threads.c,
line 6.
(gdb) run
Starting program: /home/cfhammar/test/hurd-test/gdb-threads 
[New Thread 423.5]

Breakpoint 1, main (argc=1, argv=0x15ffdc8)
    at /home/cfhammar/src/hurd-test/gdb-threads.c:14
14        pthread_create (&t, NULL, foo, NULL);
(gdb) continue
Continuing.
[New Thread 423.6]

Program received signal SIGTRAP, Trace/breakpoint trap.
0x01057d8c in mach_msg_trap ()
    at
/home/buildd/build/chroot-unstable/home/buildd/byhand/eglibc-2.10.2/build-tree/hurd-i386-libc/mach/mach_msg_trap.S:2
2      
/home/buildd/build/chroot-unstable/home/buildd/byhand/eglibc-2.10.2/build-tree/hurd-i386-libc/mach/mach_msg_trap.S:
No such file or directory.
        in
/home/buildd/build/chroot-unstable/home/buildd/byhand/eglibc-2.10.2/build-tree/hurd-i386-libc/mach/mach_msg_trap.S
Current language:  auto
The current source language is "auto; currently asm".



There are no problems when all the breakpoints are in main().  I have
only tested with gdb 7.0.1-2 from Debian.





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