Are volatile reads and writes atomic on Windows+VisualC?

Question

There are a couple of questions on this site asking whether using a volatile variable for atomic / multithreaded access is possible: See here, here, or here for

Answer 1

A bit off-topic, but let's have a go anyway.

... there are the docs for The Interlocked* functions, especially InterlockedExchange which takes a volatile(!) variable ...

If you think about this:

void foo(int volatile*);

Does it say:

• the argument must be a pointer to a volatile int, or
• the argument may as well be a pointer to a volatile int?

The latter is the correct answer, since the function can be passed both pointers to volatile and non-volatile int's.

Hence, the fact that InterlockedExchangeX() has its argument volatile-qualified does not imply that it must operate on volatile integers only.