pthreads_atom.c

#include <pthread.h>
#include <stdio.h>

#define atomic_int_add(ptr, val) __sync_add_and_fetch(&ptr, val)

int counter = 0;

void* worker(void* val){
    int i;
#ifdef ATOMIC
    for (i = 0; i < 500; i++) { printf("%d\n", atomic_int_add(counter, 1));}
#else
    for (i = 0; i < 500; i++) { printf("%d\n", ++counter);}
#endif
}

int main() {
    int i;
    pthread_t threads[2];

    for (i = 0 ; i < 10; i++)
	pthread_create(&threads[i], NULL, worker, NULL);
    for (i = 0 ; i < 10; i++)
	pthread_join(threads[i], NULL);

    return 0;
}