Hi Developers When using the boost.thread package as a dll under vc7.1, one gets for each reference of boost::mutex the C4275 warning for the inherited noncopyable class (in fact 5 times, one for mutex, one for timed_mutex, one for try_mutex, one for thread, and one for thread_group!!) c:\boost\include\boost-1_32\boost\thread\mutex.hpp(34) : warning C4275: non - DLL-interface 'boost::noncopyable_::noncopyable' used as base for DLL-interface 'boost::mutex' In order to avoid such warning, it would be nice to redefine -- again(sic) -- the BOOST_DECL macro and put it as a decorator for all dependent classes used by the boost libraries that could be generated as a dll.(thread, regex, filesystem, and so on). With the empty string as default value in boost/config.hpp, it would the responsability of each boost libraries to setup BOOST_DECL to the correct value when using it as a dll. Cheers Francis ANDRE