It appears the following code has a warning detected by GCC4.7.2: /boost/include/boost-1_52/boost/property_tree/detail/ptree_utils.hpp: In instantiation of 'std::string boost::property_tree::detail::narrow(const Ch*) [with Ch = wchar_t; std::string = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]': /boost/include/boost-1_52/boost/property_tree/string_path.hpp:64:36: required from here /boost/include/boost-1_52/boost/property_tree/detail/ptree_utils.hpp:76:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] boost-1_52\boost\property_tree\detail\ptree_utils.hpp (Starting line 70): template<class Ch> std::string narrow(const Ch *text) { std::string result; while (*text) { if (*text < 0 || *text > (std::numeric_limits<char>::max)()) Shouldn't it be: template<class Ch> std::string narrow(const Ch *text) { std::string result; while (*text) { if (*text < 0 || *text > (std::numeric_limits<Ch>::max)()) Code to reproduce this warning (just the include): #include <boost/property_tree/ptree.hpp>