Not that I'm defending autoconf (I dislike it a lot), but POSIX is also ignorant sometimes, so it shouldn't be treated dogmatically - e.g., google for the sockl

Not that I'm defending autoconf (I dislike it a lot), but POSIX is also ignorant sometimes, so it shouldn't be treated dogmatically - e.g., google for the socklen_t confusion. Other than that, the real world isn't black and white either. Although many unixen claim to be POSIX compliant, based on my experience they are mostly POSIX-ish. And there's also no guarantee for sizeof(size_t) being a platform's word size.