One inconvenience in multithreaded programs is that we must practically secure every data structure they modify, with mutexes or other measures that protect from uncontrolled concurrent modification.
One data structure that is typically used very often for printing is std::cout. If multiple threads access cout concurrently, then the output will appear in interesting mixed patterns on the terminal. In order to prevent this, we would need to write our own function that prints in a concurrency-safe fashion.
We are going to learn how to provide a cout wrapper that consists of minimal code itself and that is as comfortable to use as cout.
