#include <stdio.h>

typedef struct { int counter; } atomic_t; /* NB: no "volatile" */

#define ATOMIC_INIT(i)	{ (i) }

#define atomic_read(v)		((v)->counter)

static __inline__ int atomic_add_return(int i, atomic_t *v)
{
	int __i = i;

	__asm__ __volatile__(
		"lock; xaddl %0, %1;"
		:"=r"(i)
		:"m"(v->counter), "0"(i));
/*	__asm__ __volatile__(
		"lock; xaddl %0, %1"
		:"+r" (i), "+m" (v->counter)
		: : "memory"); */
	return i + __i;
}

int main (void) {
	atomic_t a = ATOMIC_INIT(0);
	int x;

	x = atomic_add_return (1, &a);
	if ((x!=1) || (atomic_read(&a)!=1))
		printf("fail: %i, %i\n", x, atomic_read(&a));
}