Enumerator Attributes

GCC allows attributes to be set on enumerators. See Attribute Syntax, for details of the exact syntax for using attributes. Other attributes are available for functions (see Declaring Attributes of Functions), variables (see Specifying Attributes of Variables), labels (see Label Attributes), statements (see Statement Attributes), and for types (see Specifying Attributes of Types).

This example uses the deprecated enumerator attribute to indicate the oldval enumerator is deprecated:

enum E {
  oldval __attribute__((deprecated)),
  newval
};

int
fn (void)
{
  return oldval;
}

deprecated

The deprecated attribute results in a warning if the enumerator is used anywhere in the source file. This is useful when identifying enumerators that are expected to be removed in a future version of a program. The warning also includes the location of the declaration of the deprecated enumerator, to enable users to easily find further information about why the enumerator is deprecated, or what they should do instead. Note that the warnings only occurs for uses.

unavailable

The unavailable attribute results in an error if the enumerator is used anywhere in the source file. In other respects it behaves in the same manner as the deprecated attribute.