CODEWITHSUNDEEP
multithreadingqtdebugginggdbcoredump
dargaud
dargaud

Reputation: 2581

QThread dumps core

I'm looking at a program that crashes, leading to a useless (or so it seems) core dump. I didn't write the program but I'm trying to find what may be the cause.

First strange thing is that the core dump is named after QThread instead of my executable itself.

Then inside the backtrace, there's no hint at line numbers of the program itself:

$ gdb acqui ../../appli/core.QThread.31667.1448795278
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `./acqui'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00007fcf4a1ce107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007fcf4a1ce107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007fcf4a1cf4e8 in __GI_abort () at abort.c:89
#2  0x00007fcf4aab9b3d in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007fcf4aab7bb6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007fcf4aab7c01 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007fcf4aab7e69 in __cxa_rethrow () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x00007fcf4b8707db in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#7  0x00007fcf4b764e99 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#8  0x00007fcf4b76770f in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9  0x00007fcf4ad6c0a4 in start_thread (arg=0x7fcf0b7fe700) at pthread_create.c:309
#10 0x00007fcf4a27f04d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
(gdb) info threads
  Id   Target Id         Frame 
  16   Thread 0x7fcf297fa700 (LWP 31676) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  15   Thread 0x7fcf28ff9700 (LWP 60474) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  14   Thread 0x7fcf08ff9700 (LWP 60516) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  13   Thread 0x7fcf0bfff700 (LWP 60513) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  12   Thread 0x7fcf3932c700 (LWP 60494) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  11   Thread 0x7fcf29ffb700 (LWP 60444) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  10   Thread 0x7fcf39b2d700 (LWP 31668) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  9    Thread 0x7fcf2affd700 (LWP 31673) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  8    Thread 0x7fcf2bfff700 (LWP 31671) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  7    Thread 0x7fcf38b2b700 (LWP 60432) syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  6    Thread 0x7fcf2a7fc700 (LWP 31674) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  5    Thread 0x7fcf4d4f9780 (LWP 31667) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  4    Thread 0x7fcf097fa700 (LWP 60430) pthread_cond_timedwait@@GLIBC_2.3.2 ()
    at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
  3    Thread 0x7fcf09ffb700 (LWP 31682) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
  2    Thread 0x7fcf0affd700 (LWP 31680) 0x00007fcf4a27650d in poll () at ../sysdeps/unix/syscall-template.S:81
* 1    Thread 0x7fcf0b7fe700 (LWP 31679) 0x00007fcf4a1ce107 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56

I'm at a loss as to where to start. Is it a problem in using QThread ? Something else ? How can I enable more (or better) debugging info ? The program itself is compiled with -g -ggdb.

Upvotes: 1

Views: 731

Answers (1)

Tom Tromey
Tom Tromey

Reputation: 22539

This part:

#4  0x00007fcf4aab7c01 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007fcf4aab7e69 in __cxa_rethrow () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6

... means that the code in question is re-throwing an exception, but there is no exception handler for it. So, the runtime calls std::terminate.

This is a programming error, though exactly what to do depends on your libraries and program -- maybe not re-throw, maybe install an outermost exception handler and log a message, etc.

Upvotes: 1

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