I use the library (libnids) in my program. I call the nids_run function from the library, which continues to work until I explicitly call nids_exit.
My program processes SIGINT and calls nids_exit. The interrupt handler returns normally, but sometimes, before the library returns the control to my program, I get segfault. This backtrace gdb gives me:
#0 0x00007ffff6498b2a in ?? () from /usr/lib/libpcap.so.1
#1 0x00007ffff649bee1 in pcap_loop () from /usr/lib/libpcap.so.1
#2 0x00007ffff77bae66 in nids_run () from /usr/lib/libnids.so.1.24
#3 0x0000000000401e92 in main (argc=3, argv=0x7fffffffebf8) at eve.c:139
What is the best strategy for finding a problem? Should I somehow debug libpcap?
UPDATE:
As ArjunShankar said, I ran my program under Valgrind. This is part of the output:
==7504== Invalid read of size 4
==7504== at 0x654EDC1: ??? (in /usr/lib/libpcap.so.1.2.1)
==7504== by 0x6551EE0: pcap_loop (in /usr/lib/libpcap.so.1.2.1)
==7504== by 0x5250E65: nids_run (in /usr/lib/libnids.so.1.24)
==7504== by 0x401E91: main (eve.c:139)
==7504== Address 0x70eece8 is 40 bytes inside a block of size 768 free'd
==7504== at 0x4C29A9E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==7504== by 0x5250DEB: nids_exit (in /usr/lib/libnids.so.1.24)
==7504== by 0x4026D0: signal_handler (signalhandling.c:17)
==7504== by 0x5B6313F: ??? (in /lib/libpthread-2.15.so)
==7504== by 0x5B5FC60: pthread_cond_timedwait@@GLIBC_2.3.2 (in /lib/libpthread-2.15.so)
==7504== by 0x58E37D4: g_cond_wait_until (in /usr/lib/libglib-2.0.so.0.3200.1)
==7504== by 0x587E2C0: ??? (in /usr/lib/libglib-2.0.so.0.3200.1)
==7504== by 0x587E909: g_async_queue_timeout_pop (in /usr/lib/libglib-2.0.so.0.3200.1)
==7504== by 0x4022D2: analyzer_thread_func (analyzers.c:93)
==7504== by 0x58CA0C4: ??? (in /usr/lib/libglib-2.0.so.0.3200.1)
==7504== by 0x5B5BE0D: start_thread (in /lib/libpthread-2.15.so)
Further information can be found at: http://pastebin.com/93gkSScS