c = 0;

thread 1:
{
  a = 1;
  b.store(2, memory_order_relaxed);
  c.store(3, memory_order_release);
}

thread 2:
{
  while (c.load(memory_order_acquire) != 3)
    ;
  // 以下 assert 永远不会失败
  assert(a == 1 && b == 2);
  assert(b.load(memory_order_relaxed) == 2);
}