llvm-project/compiler-rt/test/tsan/atomic_stack.cc

// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
#include "test.h"

int Global;

void *Thread1(void *x) {
  barrier_wait(&barrier);
  __atomic_fetch_add(&Global, 1, __ATOMIC_RELAXED);
  return NULL;
}

void *Thread2(void *x) {
  Global++;
  barrier_wait(&barrier);
  return NULL;
}

int main() {
  barrier_init(&barrier, 2);
  pthread_t t[2];
  pthread_create(&t[0], NULL, Thread1, NULL);
  pthread_create(&t[1], NULL, Thread2, NULL);
  pthread_join(t[0], NULL);
  pthread_join(t[1], NULL);
}

// CHECK: WARNING: ThreadSanitizer: data race
// CHECK:   Atomic write of size 4
// CHECK:     #0 __tsan_atomic32_fetch_add
// CHECK:     #1 Thread1