Gcc exit status codes

Question

I've noticed that when running gcc, if the compile failes, most of the time it returns an exit status code of '1'. However, it sometimes returns a status code of '4' (for example, if the input file does not exist). I haven't been able to find anything in the gcc documentation that covers what different error codes might mean -- does anyone know of any?

Answer 1

According to the official documentation of the command line switch -pass-exit-codes:

Normally the gcc program exits with the code of 1 if any phase of the compiler returns a non-success return code. If you specify -pass-exit-codes, the gcc program instead returns with the numerically highest error produced by any phase returning an error indication. The C, C++, and Fortran front ends return 4 if an internal compiler error is encountered.