Program crashes and core files

On Unix platforms if a program crashes a so called "core file" is created. It contains the memory status of the program when it crashed. This information can be used for post-mortem debugging using a debugger like gdb.

For best debugging results a program needs to be compiled with debugging turned on. This creates additional debugging instructions in the object code of the program and preserves all symbol and line information. This allows a debugger to show the proper source code pieces.

man gcc lists a large number of debugging and optimization options. Some compilers do not allow mixing debugging and optimization.