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), 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.