“pseudo-atomic” operations in C++

Question

So I\'m aware that nothing is atomic in C++. But I\'m trying to figure out if there are any \"pseudo-atomic\" assumptions I can make. The reason is that I want to avoid using

Answer 1

My answer is going to be frustrating: No, No, No, No, and No.

1-4) The compiler is allowed to do ANYTHING it pleases with a variable it writes to. It may store temporary values in it, so long as ends up doing something that would do the same thing as that thread executing in a vacuum. ANYTHING is valid

5) Nope, no guarantee. If a variable is not atomic, and you write to it on one thread, and read or write to it on another, it is a race case. The spec declares such race cases to be undefined behavior, and absolutely anything goes. That being said, you will be hard pressed to find a compiler that does not give you 7 or 8, but it IS legal for a compiler to give you something else.

I always refer to this highly comical explanation of race cases.

http://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong