The Microsoft Visual C++ compilers have the EnterCriticalSection and ExitCriticalSection objects to allow for synchronization between threads.

What is the GCC equivalent?

I see references around to __sync_synchronize along with __scoped_lock

In fact I see mention of a number of atomic __sync functions along with a number of __atomic ones.

I actually have been using __sync_fetch_and_add for my atomic increment Should I be using __atomic_add_dispatch instead? What's the difference?

Which ones should I be using? Are there some constructs in C++ that I can use in both the latest version of GCC and Visual C++ 2010 that are available as I'm going to be writing some cross platform code.

I see boost has some functions available, but for various reasons I'm not allowed to use boost under windows.

On Linux (and other Unixen) you need to use PThreads, or Posix Threads. There is no equivalent to Critical Sections on Windows; use a Mutex instead.

EDIT: See first comment below -- apparently Posix Mutexes are the same as Win32 Critical Sections in that they are bound to a single process.