For the changing of the std::string allocator, I retypedef the std::string to my string, just like this: namespace MyNamespace { template<typename Elem, typename Traits> class basic_string : public std::basic_string<Elem, Traits, STLAllocator<Elem> > { // reimplement the typedefs and constructors. }; typedef basic_string<char, std::char_traits<char> > string; typedef basic_string<wchar_t, std::char_traits<wchar_t> > wstring; } So I want the boost::filesystem use my own string type, but I met some problem: The code like this: namespace MyNamespace { struct path_traits; typedef boost::filesystem::basic_path<string, path_traits> path; typedef boost::filesystem::basic_path<wstring, path_traits> wpath; struct path_traits { typedef string internal_string_type; typedef string external_string_type; static external_string_type to_external( const path &, const internal_string_type & src ) { return src; } static internal_string_type to_internal( const external_string_type & src ) { return src; } }; typedef boost::filesystem::basic_recursive_directory_iterator<path> recursive_directory_iterator; typedef boost::filesystem::basic_recursive_directory_iterator<wpath> wrecursive_directory_iterator; } namespace boost { namespace filesystem { template<> struct is_basic_path<MyNamespace::path> { BOOST_STATIC_CONSTANT( bool, value = true ); }; template<> struct is_basic_path<MyNamespace::wpath> { BOOST_STATIC_CONSTANT( bool, value = true ); }; } } namespace MyNamespace { inline bool is_directory( const path & ph ) { return boost::filesystem::is_directory<path>( ph ); } inline bool is_directory( const wpath & ph ) { return boost::filesystem::is_directory<wpath>( ph ); } } For replace all the function is a huge work, and in this way I can not replace it for I met this function: BOOST_FILESYSTEM_DECL file_status status_api( const std::string & ph, system::error_code & ec ); Maybe this way is too bother, I think there must be an easy way to replace the string. Is there any way to resolve this? Thank you.