9 Declarations [dcl.dcl]

9.12 Attributes [dcl.attr]

9.12.5 Deprecated attribute [dcl.attr.deprecated]

1
#
The attribute-token deprecated can be used to mark names and entities whose use is still allowed, but is discouraged for some reason.
[Note 1: 
In particular, deprecated is appropriate for names and entities that are deemed obsolescent or unsafe.
— end note]
An attribute-argument-clause may be present and, if present, it shall have the form:
( unevaluated-string )
[Note 2: 
The unevaluated-string in the attribute-argument-clause can be used to explain the rationale for deprecation and/or to suggest a replacing entity.
— end note]
2
#
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, a concept, or a template specialization.
3
#
An entity declared without the deprecated attribute can later be redeclared with the attribute and vice-versa.
[Note 3: 
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.
4
#
Recommended practice: Implementations should 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 should include the text provided within the attribute-argument-clause of any deprecated attribute applied to the name or entity.
The value of a has-attribute-expression for the deprecated attribute should be 0 unless the implementation can issue such diagnostic messages.