#include <stdio.h>

void compare(int a)
{
	printf("%x\n", a);
}

struct X {
	int a:12;
	int b:1;
};

void foo(struct X* x)
{
	compare(x->a);
}

int main() {
	struct X x;
	x.a = 0xfab;
	foo(&x);
}