setting a gdb exit breakpoint not working?

user_189270 0
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I've set breakpoints on exit and _exit and my program (multithreaded app, running on linux 2.6.16.46-0.12 sles10), is somehow still exiting in a way I can't locate

(gdb) c
...
[New Thread 47513671297344 (LWP 15279)]
[New Thread 47513667103040 (LWP 15280)]
[New Thread 47513662908736 (LWP 15281)]

Program exited with code 0177.
(gdb)

the exit functions reside in libc so there's no deferred load shared library issues. Anybody know of some other mysterious trigger for exit that can't be caught?

EDIT: the problem is now academic only. I tried binary search debugging, backing out a subset of my changes (the problem went away). After I applied them again in sequence, I can no longer repro the problem, even with things restored to the original state.

EDIT2: I found one reason for this sort of error recently, which may have been the original source for this problem. For historical reasons our product uses the evil linker flag -Bsymbolic. Among the side effects of this is that when a symbol is undefined but called, the GLIBC runtime linker will bomb in exactly this way, and you see it in the debugger as a process exited with 0177. When the runtime linker aborts this way, I'd guess it makes the syscall to _exit directly (rather than using the C runtime library exit() or _exit()). That would be consistent with the fact that I was unable to catch this with an the exit breakpoints in the debugger.

gdb unix linux
3 Answers

It might be that you have some lazy references unresolved in some shared library loaded into process. I have exactly the same situation that "someone somewhere" exited process and that appeared to be unresolved reference.

Check your process with "ldd -r" option.

Looks like ld.so or whatever does lazy resolving of some symbols to uniform exit function (which should be abort IMHO).

My situation:

$ ldd ./program
undefined symbol: XXXX  (/usr/lib/libYYY.so)

$./program
program: started! 
...
<program is running regardless of undefined references>

Now exit appeared when I've invoked some scenario that used function that was undefined. It always exited with exitcode=127 and gdb reported 0177.

user_2694480
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