Where is ptrdiff_t defined in C?
It's defined in
That header defines the integral types
wchar_t, the functional macro
offsetof, and the constant macro
It is defined by the POSIX standard: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html Where the type is exactly may be implemetation-specific, but interface is stddef.h