#include <stdio.h>

#define STATIC_ASSERT(COND) typedef char static_assertion_##__LINE__[(COND) ? 1 : -1]
#define ENSURE_SIZE(structure, size) STATIC_ASSERT(sizeof(structure) == size)

typedef struct
{
	unsigned a : 1;
	unsigned b : 1;
} foo;
ENSURE_SIZE(foo, sizeof(unsigned));

int main(void) {
	return 0;
}