It's neither: sizeof belongs in its own category of unary compile-time(-ish) operators, whose only other member is _Alignof. If you're so inclined, you might

It's neither: sizeof belongs in its own category of unary compile-time(-ish) operators, whose only other member is _Alignof. If you're so inclined, you might add _Generic and _Pragma to that mix as well, but they aren't really a close fit.