(gdb) bt
#0  0x00a55e90 in rawmemchr () from /lib/libc.so.6
#1  0x00a4b69d in _IO_str_init_static_internal () from /lib/libc.so.6
#2  0x00a40eb3 in vsscanf () from /lib/libc.so.6
#3  0x00a3c3fe in sscanf () from /lib/libc.so.6
#4  0x05a25c2c in func_header_read (chan=0x9ed0240, function=0x6566eb0 "SIP_HEADER", data=0x6566ebb "X-Test-Header",
    buf=0x6565ea0 "", len=4096) at chan_sip.c:10912
#5  0x080b6c9e in ast_func_read (chan=0x9ed0240, function=0x6566eb0 "SIP_HEADER", workspace=0x6565ea0 "", len=4096)
    at pbx.c:1417
#6  0x080b9213 in pbx_substitute_variables_helper_full (c=0x9ed0240, headp=0x9ed0534, cp1=Variable "cp1" is not available.
) at pbx.c:1535
#7  0x080ba422 in pbx_extension_helper (c=0x9ed0240, con=0x0, context=0x9ed03c0 "pre-process", exten=0x9ed0410 "1234",
    priority=1, label=0x0, callerid=0x9eb9088 "012345678", action=E_SPAWN) at pbx.c:1615
#8  0x080bc16c in __ast_pbx_run (c=0x9ed0240) at pbx.c:2161
#9  0x080bd0ce in pbx_thread (data=0x9ed0240) at pbx.c:2472
#10 0x080e6f3b in dummy_start (data=0x9ed07d8) at utils.c:538
#11 0x00cab40b in start_thread () from /lib/libpthread.so.0
#12 0x00ab2b7e in clone () from /lib/libc.so.6
(gdb) bt full
#0  0x00a55e90 in rawmemchr () from /lib/libc.so.6
No symbol table info available.
#1  0x00a4b69d in _IO_str_init_static_internal () from /lib/libc.so.6
No symbol table info available.
#2  0x00a40eb3 in vsscanf () from /lib/libc.so.6
No symbol table info available.
#3  0x00a3c3fe in sscanf () from /lib/libc.so.6
No symbol table info available.
#4  0x05a25c2c in func_header_read (chan=0x9ed0240, function=0x6566eb0 "SIP_HEADER", data=0x6566ebb "X-Test-Header",
    buf=0x6565ea0 "", len=4096) at chan_sip.c:10912
        p = Variable "p" is not available.
(gdb)