Is this function with atomic thread-safe

Question

I am trying to learn how to use atomic :)

class foo {
  static std::atomic<uint32_t> count_;
  uint32 increase_and_get() {
    uint32 t = count_++;
    return t;
  }
}

Is the function increase_and_get() thread-safe?

Answer 1

Yes, it is safe: the increment is atomic, and the local t cannot be altered by concurrent threads. You can further simplify your code to eliminate the temporary variable altogether:

uint32 increase_and_get() {
    return count_++;
}

Answer 2

Yes, it would be threadsafe. Assuming of course there are no bugs in the std::atomic implementation - but it's not usually hard to get right.

This is exactly what std::atomic is meant to do.