I'm using VC2008 to build a library which uses boost::system. This library is then used in a COM DLL. When I build the COM DLL in 'Release mode' I get these link errors: ----------------------------------------- EuroATLib.lib(EuroATLib.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __stdcall boost::system::get_system_category(void)" (?get_system_category@system@boost@@YGABVerror_category@12@XZ) EuroATLib.lib(EuroATLib.obj) : error LNK2001: unresolved external symbol "class boost::system::error_category const & __stdcall boost::system::get_generic_category(void)" (?get_generic_category@system@boost@@YGABVerror_category@12@XZ) EuroATLib.lib(ATDispatcher.obj) : error LNK2001: unresolved external symbol "bool __stdcall boost::this_thread::interruptible_wait(void *,struct boost::detail::timeout)" (?interruptible_wait@this_thread@boost@@YG_NPAXUtimeout@detail@2@@Z) ----------------------------------------- I think the problem is in the calling convention that in COM is __stdcall while the boost::system uses __cdecl. What I don't understand is why when I build the COM DLL in 'Debug mode' it works! I've checked the VC linker settings and it seems ok. Any suggestions? Thanks, Daniele.