Hi, What is the status of boost/smart_ptr/detail/sp_counted_base_aix.hpp? It is not #included by default in sp_counted_base_aix.hpp. Is it safe to use or is it just an exprerimental version? We have a multiplatform application and I am trying to make some improvements for it on AIX platform. One candidate right now is to utilize sp_counted_base_aix.hpp (boost/smart_ptr/detail/sp_counted_base_aix.hpp). It implements atomic counter without (pthread) mutexes. Using it improves performance of our app up to 10%. But sp_counted_base_aix.hpp is not used by default. I had to add an #ifed to sp_counted_base.hpp to make it work. I tested the implementation with a small sample program that copied and removed shared_ptrs in multiple threads and it works. But I am still concerned. How widely is this AIX specific implementation used? How risky is it for us to use it? Best regards Vojtech