Carsten Raas:
Did you rebuild date_time itself with this change?
Yes, I did.
I followed the hint of Peter Dimov in http://lists.boost.org/Archives/boost/2008/04/135521.php
That's very odd. It's true that Datetime uses shared_ptr, and that shared_ptr uses __sync_fetch_and_add on some platforms, but it shouldn't on Intel x64 because: #elif defined(__GNUC__) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 ) && !defined( __arm__ ) && !defined( __hppa ) && ( !defined( __INTEL_COMPILER ) || defined( __ia64__ ) ) # include <boost/detail/sp_counted_base_sync.hpp> so I've no idea where the reference to __sync_fetch_and_add comes from. Can you try rebuilding Datetime with #define __sync_fetch_and_add ERROR and see what in Boost is trying to make use of it? (The other alternative is that libstdc++ itself is using __sync_fetch_and_add in a header.)