I'm trying to compile simple code using utf8_codecvt_facet: // ---- UTF8.cpp starts ------------------------------ #include <iostream> #include <fstream> #include <string> #include <locale> #include <boost/program_options/detail/utf8_codecvt_facet.hpp> using namespace std; int main() { locale loc; locale utf8loc(loc, new boost::program_options::detail::utf8_codecvt_facet()); wifstream f; f.imbue(utf8loc); f.open("UTF8.txt", ios::binary); wstring s; f >> s; f.close(); return 0; } // ---- UTF8.cpp ends ------------------------------ It works OK with VC 8.0 (both building Boost and this code with VC 8.0). But I get linker errors with VC 7.1 (both building Boost and this code with VC 7.1): UFT8.obj : error LNK2001: unresolved external symbol "protected: virtual int __thiscall boost::program_options::detail::utf8_codecvt_facet::do_out(int &,unsigned short const *,unsigned short const *,unsigned short const * &,char *,char *,char * &)const " (?do_out@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBG1AAPBGPAD3AAPAD@Z) UFT8.obj : error LNK2001: unresolved external symbol "protected: virtual int __thiscall boost::program_options::detail::utf8_codecvt_facet::do_in(int &,char const *,char const *,char const * &,unsigned short *,unsigned short *,unsigned short * &)const " (?do_in@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBD1AAPBDPAG3AAPAG@Z) As a linker tells me the reference is: ?do_in@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBD1AAPBDPAG3AAPAG@Z But library (auto-linked libboost_program_options-vc71-sgd-1_33_1.lib) contains: ?do_in@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBD1AAPBDPA_W3AAPA_W@Z When I add Boost/libs/program_options/src/utf8_codecvt_facet.cpp to my VC 7.1 project, the sample code builds fine. The question is how to build this code under VC 7.1? Is it needed to rebuild Boost's libboost_program_options-vc71-*-1_33_1.lib with some compiler options to get ?do_in@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBD1AAPBDPAG3AAPAG@Z export or to build code above with some options to get ?do_in@utf8_codecvt_facet@detail@program_options@boost@@MBEHAAHPBD1AAPBDPA_W3AAPA_W@Z reference?