(gdb) bt
#0  0x00007f7cb110aa75 in raise () from /lib/libc.so.6
#1  0x00007f7cb110e5c0 in abort () from /lib/libc.so.6
#2  0x00007f7cb11444fb in ?? () from /lib/libc.so.6
#3  0x00007f7cb114e5b6 in ?? () from /lib/libc.so.6
#4  0x00007f7cb1154e53 in free () from /lib/libc.so.6
#5  0x00000000004fc700 in ast_logger_unregister_level (name=0x7f7cac30eb6f "FAX") at logger.c:1426
#6  0x00007f7cac30be3a in unload_module () at res_fax.c:2718
#7  0x00000000004f155d in ast_module_shutdown () at loader.c:491
#8  0x0000000000440516 in quit_handler (num=0, niceness=1, safeshutdown=1, restart=0) at asterisk.c:1646
#9  0x00000000004410a5 in handle_stop_gracefully (e=0x82bcb0, cmd=-4, a=0x7f7c7d7767b0) at asterisk.c:1893
#10 0x000000000049a96a in ast_cli_command_full (uid=0, gid=0, fd=38, s=0x7f7c7d7768c0 "core stop gracefully") at cli.c:2474
#11 0x000000000049ab81 in ast_cli_command_multiple_full (uid=0, gid=0, fd=38, size=21, s=0x7f7c7d776b3f "core stop gracefully") at cli.c:2497
#12 0x000000000043f044 in netconsole (vconsole=0x899ae0) at asterisk.c:1265
#13 0x0000000000584e7c in dummy_start (data=0x2b5a858) at utils.c:974
#14 0x00007f7cb36e39ca in start_thread () from /lib/libpthread.so.0
#15 0x00007f7cb11bd6fd in clone () from /lib/libc.so.6
#16 0x0000000000000000 in ?? ()