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

int x = 0, y = 0;
int a, b, c, d;

void *thread0( void *arg ) {
    y = 1;
    a = x;
    c = y;
    return 0;
}

void *thread1( void *arg ) {
    x = 1;
    b = y;
    d = x;
    return 0;
}

int main() {
    pthread_t t0, t1;
    pthread_create( &t0, 0, thread0, 0 );
    pthread_create( &t1, 0, thread1, 0 );
    pthread_join( t0, 0 );
    pthread_join( t1, 0 );
    printf( "a = %d, b = %d, c = %d, d = %d", a, b, c, d );
    assert( a != 0 || b != 0 );
}