const error_category& stream_category() noexcept;
Returns: A reference to an object of a type derived from class error_category. All calls to this function return references to the same object.
The object's default_error_condition and equivalent virtual functions behave as specified for the class error_category. The object's name virtual function returns a pointer to the string "stream".
error_code make_error_code(stream_errc e) noexcept;
Returns: error_code(static_cast<int>(e), stream_category()).
error_condition make_error_condition(stream_errc e) noexcept;
Returns: error_condition(static_cast<int>(e), stream_category()).