(gdb) bt
#0  0x001b31e3 in _int_malloc () from /lib/libc.so.6
#1  0x001b3ffd in calloc () from /lib/libc.so.6
#2  0x0807f7bd in ast_channel_alloc (needqueue=1, state=0, cid_num=0xb752d564 "0", cid_name=0xb752d503 "025388103", 
    acctcode=0x8141360 "", exten=0xb752d50d "972527655681", context=0xb752d4bf "rm1", amaflag=0, name_fmt=0x7c1496 "SIP/%s-%08x")
    at /usr/src/asterisk-1.4.18/include/asterisk/utils.h:359
#3  0x007722e6 in sip_new (i=0xb7512dc8, state=0, title=<value optimized out>) at chan_sip.c:3961
#4  0x007b3cdf in handle_request_invite (p=0xb7512dc8, req=0xb7a7cf1c, debug=0, seqno=102, sin=0xb7a7e240, recount=0xb7a7e250, 
    e=0xb7a7d13f "sip:972527655681@ngn4.client.pins.net", nounlock=0xb7a7e254) at chan_sip.c:13896
#5  0x007b6937 in handle_request (p=0xb7512dc8, req=0xb7a7cf1c, sin=0xb7a7e240, recount=0xb7a7e250, nounlock=0xb7a7e254)
    at chan_sip.c:15241
#6  0x007b80de in sipsock_read (id=0x90af740, fd=14, events=1, ignore=0x0) at chan_sip.c:15388
#7  0x080a95d0 in ast_io_wait (ioc=0x90ada18, howlong=1000) at io.c:279
#8  0x00793569 in do_monitor (data=0x0) at chan_sip.c:15601
#9  0x080f8f4b in dummy_start (data=0x90b2210) at utils.c:852
#10 0x002c245b in start_thread () from /lib/libpthread.so.0
#11 0x0021a24e in clone () from /lib/libc.so.6
(gdb)