[wizeman]

> C does not guarantee a 64 bit type exists.

Isn't (signed/unsigned) 'long long int' mandatory since C99?

It says: 'There are five standard signed integer types, designated as signed char, short int, int, long int, and long long int'.

My cursory search for 'long long' in the standard didn't find anything about it being optional...

[morelisp]

You appear to be correct, though in my defense I didn't give a version and I have definitely been stuck on such a compiler long after 1999. (And I suspect they're still over-represented for 32 bit systems.)