Do I need to synchronize primitives in C++

Question

I have a volatile bool 'play' flag in my class that is being set by one thread and being read by another thread.

Do I need to synchronize the calls to that flag? for example in this function:

void stop() 
{
   play = false;
}

In windows they have the _InterlockedExchange and OSX has OSAtomicAdd64Barrier, I've seen those functions being used with shared primitives, do I need them?

Thank you

Answer 1

Yes, and volatile does not in any way imply thread safe or atomic. Use std::mutex and std::unique_lock etc if you can, not the platform specifics. std::atomic is good choice -- maybe even best in this case.