Hi Beman, I noticed the following in v3 whie hunting down a bug in my unit test: # ifdef BOOST_WINDOWS_API const std::string string() const { return string(codecvt()); } const std::string string(const codecvt_type& cvt) const; // string_type is std::wstring, so there is no conversion const std::wstring& wstring() const { return m_pathname; } const std::wstring& wstring(const codecvt_type&) const { return m_pathname; } # else // BOOST_POSIX_API // string_type is std::string, so there is no conversion const std::string& string() const { return m_pathname; } const std::string& string(const codecvt_type&) const; const std::wstring wstring() const { return wstring(codecvt()); } const std::wstring wstring(const codecvt_type& cvt) const # endif I can understand, that it is more efficient to return a reference when a referenec can be formed. However, consider const std::string& ext = iter->path().extension().string(); This is fine on windows, as a temporary is returned, and its lifetime is extended; on linux, extension() returns a temp path object, from where we get a reference. I'm not a 100% sure, but I think the C++ standard does not guarantee that this path object be kept alive. The net efffect is a crash on linux. I'm not sure its a great idea to have different reference-ness on the return types here. It could lead to other subtle differences. kind regards -Thorsten