Method message

include/win/boost/system/error_code.hpp:357–357

      const error_category &  category() const BOOST_SYSTEM_NOEXCEPT { return *m_cat; }
      error_condition         default_error_condition() const BOOST_SYSTEM_NOEXCEPT  { return m_cat->default_error_condition(value()); }
      std::string             message() const  { return m_cat->message(value()); }

      typedef void (*unspecified_bool_type)();
      static void unspecified_bool_true() {}