Atomic/not-atomic mix, any guarantees?

Question

Let's I have GUI thread with code like this:

std::vector<int> vec;
std::atomic<bool> data_ready{false};
std::thread th([&data_ready, &vec]() {
   //we get data
   vec.push_back(something);
   data_ready = true;
});
draw_progress_dialog();
while (!data_ready) {
  process_not_user_events();
  sleep_a_little();
}
//is it here safe to use vec?

As you see I not protect "vec" by any kind of lock, but I not use "vec" in two thread at the same moment, the only problem is memory access reodering,

Is it impossible according to C++11 standard that some modifications in "vec" happens after "data_ready = true;"?

It is not clear (for me) from documentation, is it memory ordering relevant only for other atomics, or not.

Plus question, is "default" memory order is what I want, or have to change memory model?

Answer 1

只要你使用的内存顺序至少是获取/释放（这是默认值），你就可以保证在将标志设置为true之前看到写入线程所做的所有更新（不仅仅是原子变量的更新）你可以尽快阅读。

是的，这很好。