If you are developing, `gcc -g` while compiling(or CFLAGS += g), and loading the core with gdb does give a very good idea of what went wrong.

It is a lucky scenario when you actually get a core and one taken at the exactly right time. Unfortunately there are some pointer bugs that are hard to find even with Valgrind.

Buffer overflows do not produce cores, they just sit there until a determined cracker makes use of them. And a dangling pointer might still access memory that looks valid both to OS and memcheck.