#include <assert.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
char *pointers[2];
pthread_barrier_t bar;
void *thread_main(void *n) {
char local;
unsigned long id = (unsigned long)n;
pointers[id] = &local;
pthread_barrier_wait(&bar);
pthread_barrier_wait(&bar);
return NULL;
}
int main(int argc, char **argv) {
assert(argc >= 2);
char t = argv[1][0];
pthread_t threads[2];
pthread_barrier_init(&bar, NULL, 3);
pthread_create(&threads[0], 0, thread_main, (void *)0);
pthread_create(&threads[1], 0, thread_main, (void *)1);
pthread_barrier_wait(&bar);
if (t == 'a') {
unsigned r = pointers[0] - pointers[1];
} else {
char local;
char *parent_pointer = &local;
unsigned r = parent_pointer - pointers[0];
}
pthread_barrier_wait(&bar);
pthread_join(threads[0], 0);
pthread_join(threads[1], 0);
pthread_barrier_destroy(&bar);
return 0;
}