title: std::call_once, when should it be used?
body: <p>The <a href="https://en.cppreference.com/w/cpp/thread/call_once" rel="nofollow noreferrer"><code>std::call_once</code> function</a>, introduced in C++11, ensures a callable is called exactly one time, in a thread safe manner.</p>
  <p>Since this can be achieved by other means - when should <code>std::call_once</code> be used? What type of problems is it intended to address?</p>
  <p>Please provide examples.</p>