(gdb) break *0x972

With frame filters and decorators, GDB lets you rewrite the output of the where command. That's quite convenient, except that it doesn't work well in one situation (that I could not clearly understand ...):

(gdb) where no-filters # <--- notice the option here
#0  do_spin () at .../gcc-5.2.0/libgomp/config/linux/wait.h:55
#1  do_wait () at ...gcc-5.2.0//libgomp/config/linux/wait.h:64
#2  gomp_team_barrier_wait_end (...) at .../libgomp/config/linux/bar.c:112
#3  0x00007ffff7bd8966 in GOMP_barrier () at gomp_preload.c:49
#4  0x0000000000400a19 in main._omp_fn.0 () at parallel-demo.c:10
#5  0x00007ffff7bd89e4 in GOMP_parallel_trampoline (...) at gomp_preload.c:62
#6  0x00007ffff79c442e in gomp_thread_start () at .../libgomp/team.c:118
#7  0x00007ffff7bd8ce8 in pthread_create_trampoline () at pthread_preload.c:33
#8  0x00007ffff779f4a4 in start_thread () from /usr/lib/libpthread.so.0
#9  0x00007ffff74dd13d in clone () from /usr/lib/libc.so.6

becomes:

(gdb) where
#0  gomp_team_barrier_wait_end () at .../libgomp/config/linux/wait.h:55
#1  gomp_team_barrier_wait_end () at .../libgomp/config/linux/wait.h:64
#2  #pragma omp barrier () at parallel-demo.c:10
#4  #parallel zone #1 of main () at parallel-demo.c:10

Many frames are gone, that's my cleanup, some function names have been changed, that's my OpenMP work ... but the function name of frame #0 and #1 are inconsistent. It should not read gomp_team_barrier_wait_end but rather do_spin and do_wait, respectively.

I don't know what's special about these functions, they're inlined, but that's not enough to explain and recreate the problem ...

Anyway, I found that the inconsistency boils down to two lines:

(gdb) frame 0
(gdb) pi print(gdb.selected_frame().function())
gomp_team_barrier_wait_end # wrong
(gdb) pi print(gdb.selected_frame().name())    
do_spin # right

So to solve my problem, I add a frame decorator that picks up the frame name instead of its function symbol:

class BugFixFrame(gdb.frames.FrameDecorator):
    def function(self): 
        return self.inferior_frame().name() 

class BugFixFrameFilter:
    def __init__(self):
        self.enabled = True
        self.priority = 99999

    def filter(self, frames):
        for frame in frames:
            yield BugFixFrame(frame)

gdb.frame_filters["Bug fix frame filter"] = BugFixFrameFilter()

and I now have my clean and correct callstack:

(gdb) where                                                          
#0  do_spin (val=0, addr=0x602104) at .../libgomp/config/linux/wait.h:55
#1  do_wait (val=0, addr=0x602104) at .../libgomp/config/linux/wait.h:64
#2  #pragma omp barrier () at parallel-demo.c:10
#4  #parallel zone #1 of main () at parallel-demo.c:10

I've submitted a bug report as PR/19225.