./myfile/lib/libmy.a(my.o): In function `ZN4My6My_t4initERKNS0_10Settings_tE': C:/Boost/include/boost-1_34_1/boost/filesystem/path.hpp:302: undefined reference to `boost::filesystem::detail::status_api(std::string const&, unsigned int&)' ./myfile/lib/libmy.a(my.o): In function `_tcf_0': C:/CPW/cs_classes/./myfile/include/myerror.h:186: undefined reference to `boost::filesystem::detail::get_current_path_api(std::string&)' i build boost linking to a built boost filesystem file using mingw 3.4.5 including option. -l"boost_filesystem-mgw34-1_34_1" this is line 302 of path.hpp "const external_string_type external_file_string() const { return Traits::to_external( *this, file_string() ); }" "