Question

From what I’ve read from Herb Sutter and others you would think that volatile and concurrent programming were completely orthogonal concepts, at least as far as C/C++ are concerned.

However, in GCC implementation all of std::atomic‘s member functions have the volatile qualifier. The same is true in Anthony Williams’s implementation of std::atomic.

So what’s deal, do my atomic<> variables need be volatile or not?

Answer 1

Why is the volatile qualifier used throughout std::atomic?

So that volatile objects can also be atomic. See here:

The relevant quote is

The functions and operations are defined to work with volatile objects, so that variables that should be volatile can also be atomic. The volatile qualifier, however, is not required for atomicity.

Do my atomic<> variables need to be volatile or not?

No, atomic objects don’t have to be volatile.