[Boost-users] atomic_count overflow/underflow behaviour

What is the behaviour of boost::detail::atomic_count overflow? I realize that overflow for a signed long is undefined, but it is possible that each platform-specific atomic increment operator handles overflow in some documented way, which in sum would constitute a defined behaviour for atomic_count overflow. Documenting this behaviour (along with that of underflow, which is presumably the same) in the atomic_count documentation would be extremely helpful.