Hi, The Boost 1.54 smart_ptr atomic API code only supports the IBM xlC compiler under AIX. The attached patch make it also support the gcc compiler. I wanted to fill in a ticket for it on https://svn.boost.org/trac/boost/newticket but for some reason the ticket was classified as a spam by Trac. Anyone could help me here? One issue is the _sync*() APIs doesn't work when built optimized with GCC 4.8.0 on AIX 6.1 and 7.1 (and so the patch assume they don't work with all versions of GCC on AIX), so the patch undefine BOOST_SP_HAS_SYNC to prevent using those APIs. Another issue is the builtins.h file that Boost uses is missing, because it is installed as part of xlC. Under gcc, this patch will define assembly versions of the 2 builtins that are used in sp_counted_base_aix.hpp. Hope this gets through, -- Florent