Question

I posted other question: What type should I use for binary representation of C enum?, and by the answer, I have to know my compiler’s enum data-type.

What’s the data-type of C enum on Clang compiler?

Answer 1

Like most (all, maybe) C compilers, the size of an enumerated type can vary. Here’s an example program and its output:

#include <stdio.h>

typedef enum
{
  val1 = 0x12
} type1;

typedef enum
{
  val2 = 0x123456789
} type2;

int main(int argc, char **argv)
{
  printf("1: %zu\n2: %zu\n", sizeof(type1), sizeof(type2));
  return 0;
}

Output:

1: 4
2: 8

All that the standard requires is:

The choice of type is implementation-defined, but shall be capable of representing the values of all the members of the enumeration.

A quick web search didn’t turn up a clang manual that specified its behaviour, but one is almost certainly out there somewhere.