You may not always have gdb(1) at hand. Here are a couple of other options at your disposal.

#1 Use addr2line to get the crash location

$ cat badmem.c
void function_c() { int *i = (int*)0xdeadbeef; *i = 123; } // <-- line 1
void function_b() { function_c(); }
void function_a() { function_b(); }
int main() { function_a(); return 0; }
$ gcc -g badmem.c -o badmem
$ ./badmem
Segmentation fault

No core dump? You can still get some info.

$ tail -n1 /var/log/syslog
... badmem[1171]: segfault at deadbeef ip 00000000004004da sp 00007fff8825dcd0 error 6 in badmem[400000+1000]
$ echo 00000000004004da | addr2line -Cfe ./badmem
function_c
/home/walter/srcelf/bt/badmem ...

Sometimes you want a backtrace or a core dump from a process that you do not want to stall. This could concern a multithreaded application of which some threads are still doing important work (like handling customer calls). Firing up gdb would halt the process for as long as you're getting info, and raising a SIGABRT to get a core dump has the negative side-effect of killing the process. Neither is acceptable in a production environment.

In comes the handy gdb(1) option -ex. See this hanging.c example that we will examine while leaving it running.

int c ...