Literal types: 0x1ull vs 0x1llu

Question

My gcc compiler allows me to define an unsigned long long (i.e. 64-bit) literal as

#define A_LITERAL 0x1ull

--- or ---

Answer 1

Both are allowed by the C standard (section 6.4.4.1).

The unsigned suffix u can be before or after the long l (or long long (ll)) suffix.