I know a lot of people say "Boost is awful", but Boost provides the same atomic interfaces: http://www.boost.org/doc/libs/1_60_0/doc/html/atomic.html. Quoting from the introduction:

"Boost.Atomic is a library that provides atomic data types and operations on these data types, as well as memory ordering constraints required for coordinating multiple threads through atomic variables. It implements the interface as defined by the C++11 standard, but makes this feature available for platforms lacking system/compiler support for this particular C++11 feature."