Examples of atomic primitives and their cross platform implementations
Test by running 'make && ./cas'
The compare_and_swap(*ptr, oldvalue, newvalue) implements the CAS atomic primitive. This uses __sync_bool_compare_and_swap gcc builtin if available, falling back to inline assembly if not, and uses InterlockCompareExchange if on Windows.
The fetch_and_add(*ptr, value) implements the FAA atomic primitive. This uses __sync_fetch_and_add gcc builtin if available, falling back to inline x86 assembly if not, and uses InterlockedExchangeAdd on Windows (NOTE: I've just realised this might be the wrong method to use, will need to check when I get back onto a Windows machine).
Tested on OS X (Intel __amd64__)
Tested on Windows 7 with MSVC 2k13 _WIN32
Tested on Ubuntu 13.10 (Kernel 3.11.0-12-generic) (Intel x86_64)