Eh, the portability is actually getting a lot better nowadays. Most consumer and server processors being released in the last few years support double-world com

Eh, the portability is actually getting a lot better nowadays. Most consumer and server processors being released in the last few years support double-world compare and swap. Atomic increment, load, store, etc. are also pretty widespread now. The key is like someone said above that you cannot make your code ambiguous. In C++ especially, the atomic primitives can compile to different instructions depending on how you use them so it's important to be very explicit. One thing that can be a pain is memory fences. The guarantees can be different on different CPUs so you can run into weird bugs. In my case, generally I compile to target particular CPUs on servers we own so it's not a big deal. But I can imagine for consumer software this can be a huge pain.