[_kst_]

Well, you can certainly think of "long" and "short" as adjectives, but the grammar doesn't treat them that way.

"long", "short", "signed", "unsigned", "int", "float", and "double" are all type specifiers. The language specification includes an exhaustive list of the valid combinations of type specifiers, including which ones refer to the same type. The specifiers can legally appear in an order. For example, "short", "signed short", and "int short signed", among others, all refer to the same type. (They're referred to as "multisets" because "long" and "long long" are distinct.)