error_code make_error_code(io_errc e);
Returns: error_code(static_cast<int>(e), iostream_category()).
error_condition make_error_condition(io_errc e);
Returns: error_condition(static_cast<int>(e), iostream_category()).
const error_category& iostream_category();
Returns: A reference to an object of a type derived from class error_category.
The object's default_error_condition and equivalent virtual functions shall behave as specified for the class error_category. The object's name virtual function shall return a pointer to the string "iostream".