gcc/testsuite/gcc.dg/atomic/pr81316.c

/* { dg-do run } */
/* { dg-options "-pthread" } */
/* { dg-require-effective-target pthread } */

#include <pthread.h>
#include <stdlib.h>

static _Atomic int sem1;

static void *f(void *va)
{
  void **p = va;
  while (!__atomic_load_n(&sem1, __ATOMIC_ACQUIRE))
    sched_yield ();
  exit(!*p);
}

int main(int argc)
{
  void *p = 0;
  pthread_t thr;
  if (pthread_create(&thr, 0, f, &p))
    return 2;
  // GCC used to RTL-DSE this store
  p = &p;
  __atomic_store_n(&sem1, 1, __ATOMIC_RELEASE);
  int r = -1;
  while (r < 0)
    {
      sched_yield ();
      asm("":"+r"(r));
    }
  return r;
}