This is actually an error for me since I have "warnings as errors" turned on. For the Dinkumware lib, type_info::operator== and operator!= return int instead of bool. This causes problems with the any_bridge_compare class in named_slot_map.hpp template<typename Compare, typename Key> class any_bridge_compare { ... bool operator()(const any& k1, const any& k2) const { if (k1.type() == typeid(front_type)) return k2.type() != typeid(front_type); -------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This results in warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning) I recommend changing the line in question to: return !(k2.type() == typeid(front_type)); -- Eric Niebler Boost Consulting www.boost-consulting.com