The boost::swap utility (svn/boost/trunk/boost/utility/swap.hpp) still may call std::swap when the user has added a custom swap function to the namespace of the user's type, because of some compiler bugs regarding argument-dependent lookup (ADL). This issue will occur when using GCC 3.3.1, Intel C++ 8.1, MSVC 7.1, or Borland, as indicated by regression failures of "specialized_in_global" and/or "specialized_in_other" for those specific compilers: http://www.boost.org/development/tests/trunk/developer/utility-swap_.html Those compilers typically fail to do ADL within boost::swap's internal helper function, boost_swap_impl::swap_impl<T>: template<class T> void swap_impl(T& left, T& right) { using std::swap; swap(left,right); // <-- Some compiles don't do ADL here! } What about removing the the using-declaration, "using std::swap;", and adding an extra function, boost_swap_impl::swap<T>? Which would directly call std::swap, as follows: namespace boost_swap_impl { template<class T> void swap(T& left, T& right) { std::swap(left,right); } } After doing so, MSVC 7.1 (2003) will pass both "specialized_in_global" and "specialized_in_other", while it never did before. Borland will pass "specialized_in_other" for the first time, as I tested locally on BCC 5.8.4. Who knows, maybe it will also improve the regression results of GCC 3.3.1 and Intel C++ 8.1... :-) Moreover, I think that such a workaround could also be useful to other Boost libraries, when they would start to use the boost::swap utility. For example, it could solve some swap related regression failures of boost::optional. What do you think? Would it be okay to commit this change to the trunk? Hereby the patch I would like to apply. Kind regards, -- Niels Dekker http://www.xs4all.nl/~nd/dekkerware Scientific programmer at LKEB, Leiden University Medical Center