I'm not seeing it: int sum(int a, int b) { return a + b; } _Static_assert(sum(1,2) == 3, "message"); gcc -c -O x.c x.c:2:17: error: expressio

I'm not seeing it: int sum(int a, int b) { return a + b; } _Static_assert(sum(1,2) == 3, "message"); gcc -c -O x.c x.c:2:17: error: expression in static assertion is not constant _Static_assert(sum(1,2) == 3, "message");