(gdb) bt
#0  0x00550402 in __kernel_vsyscall ()
#1  0x0027ac00 in raise () from /lib/libc.so.6
#2  0x0027c451 in abort () from /lib/libc.so.6
#3  0x002b01fb in __libc_message () from /lib/libc.so.6
#4  0x002b7f5d in _int_free () from /lib/libc.so.6
#5  0x002bb5b0 in free () from /lib/libc.so.6
#6  0x004540c8 in vm_execmain (chan=0x9299008, data=0xb7c42f58) at app_voicemail.c:5565
#7  0x0808f349 in pbx_extension_helper (c=0x9299008, con=<value optimized out>, context=<value optimized out>, 
    exten=0x929924c "4000", priority=2, label=0x0, callerid=0x927a598 "233", action=1) at pbx.c:574
#8  0x080910a8 in __ast_pbx_run (c=0x9299008) at pbx.c:2250
#9  0x08091cdc in pbx_thread (data=0x9299008) at pbx.c:2537
#10 0x003c52db in start_thread () from /lib/libpthread.so.0
#11 0x0031f12e in clone () from /lib/libc.so.6