(gdb) bt
#0  0xa7ba6947 in raise () from /lib/tls/libc.so.6
#1  0xa7ba80c9 in abort () from /lib/tls/libc.so.6
#2  0xa7bdbfda in __fsetlocking () from /lib/tls/libc.so.6
#3  0xa7be389f in mallopt () from /lib/tls/libc.so.6
#4  0xa7be3942 in free () from /lib/tls/libc.so.6
#5  0xa7e8a407 in opbx_verbose (fmt=0xa7f0f898 "    -- Executing %s(\"%s\", \"%s\") %s\n")
    at logger.c:918
#6  0xa7eb82e3 in pbx_extension_helper (c=0x82832c8, con=0x0, context=0x828346c "faxout",
    exten=0x8283560 "h", priority=2, label=0x0, callerid=0x0, action=1) at pbx.c:1832
#7  0xa7eba22f in __opbx_pbx_run (c=0x82832c8) at pbx.c:2610
#8  0xa7eba847 in opbx_pbx_run (c=0x82832c8) at pbx.c:2715
#9  0xa7ebb968 in opbx_pbx_outgoing_exten (type=0x8245d44 "SIP", format=64, data=0x8245e44,
    timeout=30000, context=0x8246244 "faxout", exten=0x8246144 "s", priority=1, reason=0xa6bab448,
    sync=2, cid_num=0x8246348 "", cid_name=0x8246448 "", vars=0x81ae108, channel=0x0) at pbx.c:5196
#10 0xa65b255b in attempt_thread (data=0x8245c30) at pbx_spool.c:266
#11 0xa7e160bd in start_thread () from /lib/tls/libpthread.so.0
#12 0xa7c498fe in clone () from /lib/tls/libc.so.6
(gdb)