Program received signal SIGSEGV, Segmentation fault.
0x00007ffff646b411 in _IO_vfprintf_internal (s=0x7fffffffbf70, format=<value optimized out>, ap=0x7fffffffc190) at vfprintf.c:1601
1601    vfprintf.c: No such file or directory.                                                                                    
        in vfprintf.c                                                                                                             
(gdb) bt                                                                                                                          
#0  0x00007ffff646b411 in _IO_vfprintf_internal (s=0x7fffffffbf70, format=<value optimized out>, ap=0x7fffffffc190) at vfprintf.c:1601
#1  0x00007ffff648c722 in _IO_vsnprintf (string=0x660a70 "", maxlen=<value optimized out>, format=0x7ffff6ed201c "%s%.*s",
    args=0x7fffffffc190) at vsnprintf.c:120
#2  0x000000000040b3e4 in sofia_log_handler (logdata=0x633e00, format=0x7ffff6ed201c "%s%.*s", args=0x7fffffffc190)
    at telepathy-sofiasip.c:58
#3  0x00007ffff6e7edca in su_vllog (log=0x7ffff710fdc0, level=0, fmt=0x7ffff6ed201c "%s%.*s", ap=0x7fffffffc190) at su_log.c:137
#4  0x00007ffff6e7ec0d in su_log (fmt=0x7ffff6ed201c "%s%.*s") at su_log.c:95
#5  0x00007ffff6e92d77 in tport_log_msg (self=0x653890, msg=0x65ebf0, what=0x7ffff6ed1521 "send", via=0x7ffff6ed151e "to", now=...)
    at tport_logging.c:256
#6  0x00007ffff6e8da8c in tport_send_msg (self=0x653890, msg=0x65ebf0, tpn=0x7fffffffccb0, cc=0x0) at tport.c:3409
#7  0x00007ffff6e8d6c9 in tport_prepare_and_send (self=0x653890, msg=0x65ebf0, tpn=0x7fffffffccb0, cc=0x0, mtu=0) at tport.c:3342
#8  0x00007ffff6e8d531 in tport_tsend (self=0x653890, msg=0x65ebf0, _tpn=0x65f7d8, tag=0x7ffff7105ea0, value=0) at tport.c:3304
#9  0x00007ffff6df61bb in outgoing_send (orq=0x65f700, retransmit=0) at nta.c:7955
#10 0x00007ffff6df5e04 in outgoing_send_via (orq=0x65f700, tp=0x653890) at nta.c:7888
#11 0x00007ffff6df5ae1 in outgoing_prepare_send (orq=0x65f700) at nta.c:7825
#12 0x00007ffff6dfd61a in outgoing_query_results (orq=0x65f700, sq=0x65fa30, results=0x7fffffffd048, rlen=1) at nta.c:10449
#13 0x00007ffff6dfd402 in outgoing_answer_a (orq=0x65f700, q=0x0, answers=0x65f970) at nta.c:10400
#14 0x00007ffff6dfd038 in outgoing_query_a (orq=0x65f700, sq=0x65fa30) at nta.c:10340
#15 0x00007ffff6dfbc8a in outgoing_query_all (orq=0x65f700) at nta.c:9944
#16 0x00007ffff6dfbba5 in outgoing_make_a_aaaa_query (orq=0x65f700) at nta.c:9915
#17 0x00007ffff6dfb228 in outgoing_resolve_next (orq=0x65f700) at nta.c:9687
#18 0x00007ffff6dfca21 in outgoing_answer_srv (orq=0x65f700, q=0x0, answers=0x65f970) at nta.c:10235
#19 0x00007ffff6dfc4f8 in outgoing_query_srv (orq=0x65f700, sq=0x65f9e0) at nta.c:10135


Something to note: the stuff that's passed into sofia_log_handler as args looks a bit like this (note that s is longer than n):
(gdb) up 5
#5  0x00007ffff6e92d77 in tport_log_msg (self=0x653890, msg=0x65ebf0, what=0x7ffff6ed1521 "send", via=0x7ffff6ed151e "to", now=...)
    at tport_logging.c:256
256           su_log("%s%.*s", linelen > 0 ? "" : "   ", (int)n, s);
(gdb) printf "%s", s
Authorization: Digest username="alsuren", realm="opensips.org", nonce="4b8fe96600014291c4301c2919913bee7dceb99f65fa93cd", algorithm=MD5, uri="sip:opensips.org", response="c240d4a640be78ddacdc794e121d9af9"
Content-Length: 0

(gdb) printf "%s", s+n

Content-Length: 0
(gdb)