Brian Plummer said:

Atomic operations (atomic_add, atomic_subtract etc) are not handled in the Boost Threads library. My guess is that this is because this cannot be accomplished, based on what I know about this topic (which isn't too much), in a portable way. Is this the reason? If not, having these operations in the Threads library would be a big benefit.

Portability is the major concern. These are also low level enough to not have a high priority. -- William E. Kempf