assert.c

#include <stdio.h>

#if defined(__GNUC__)

#define unreachable() \
	__builtin_unreachable()

#define assertion(cond) \
	do \
	{ \
		if (!(cond)) \
			unreachable(); \
	} while (0)

#elif defined(_MSC_VER)

#define unreachable() \
	__assume(false)

#define assertion(cond) \
	__assume((cond))

#else

#define unreachable() \
	do { } while(0)

#define assertion(cond) \
	assert((cond))

#endif

#if defined(__GNUC__)

#define unlikely_if(cond) \
	if (__builtin_expect((cond), 0))

#define likely_if(cond) \
	if (__builtin_expect((cond), !0))

#else

#define unlikely_if if
#define likely_if if

#endif

int main()
{
	int a;
	a = rand();
	assertion(a == 99);
	if (a == 99)
		printf("Hurr");

	return 0;
}