The attribute-token deprecated can be used to mark names and entities whose use is still allowed, but is discouraged for some reason. [ Note: In particular, deprecated is appropriate for names and entities that are deemed obsolescent or unsafe. — end note ] It shall appear at most once in each attribute-list. An attribute-argument-clause may be present and, if present, it shall have the form:
( string-literal )
[ Note: The string-literal in the attribute-argument-clause could be used to explain the rationale for deprecation and/or to suggest a replacing entity. — end note ]
The attribute may be applied to the declaration of a class, a typedef-name, a variable, a non-static data member, a function, a namespace, an enumeration, an enumerator, or a template specialization.
A name or entity declared without the deprecated attribute can later be redeclared with the attribute and vice-versa. [ Note: Thus, an entity initially declared without the attribute can be marked as deprecated by a subsequent redeclaration. However, after an entity is marked as deprecated, later redeclarations do not un-deprecate the entity. — end note ] Redeclarations using different forms of the attribute (with or without the attribute-argument-clause or with different attribute-argument-clauses) are allowed.
[ Note: Implementations may use the deprecated attribute to produce a diagnostic message in case the program refers to a name or entity other than to declare it, after a declaration that specifies the attribute. The diagnostic message may include the text provided within the attribute-argument-clause of any deprecated attribute applied to the name or entity. — end note ]