[dcl.attr.deprecated]

# 9 Declarations [[dcl]](./#dcl)

## 9.13 Attributes [[dcl.attr]](dcl.attr#deprecated)

### 9.13.4 Deprecated attribute [dcl.attr.deprecated]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/declarations.tex#L9715)

The [*attribute-token*](dcl.attr.grammar#nt:attribute-token "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]") deprecated can be used to mark names and entities
whose use is still allowed, but is discouraged for some reason[.](#1.sentence-1)

[*Note [1](#note-1)*:

In particular,deprecated is appropriate for names and entities that are deemed obsolescent or
unsafe[.](#1.sentence-2)

— *end note*]

An[*attribute-argument-clause*](dcl.attr.grammar#nt:attribute-argument-clause "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]") may be present and, if present, it shall have the form:

( [*unevaluated-string*](lex.string.uneval#nt:unevaluated-string "5.13.6 Unevaluated strings [lex.string.uneval]") )

[*Note [2](#note-2)*:

The [*unevaluated-string*](lex.string.uneval#nt:unevaluated-string "5.13.6 Unevaluated strings [lex.string.uneval]") in the [*attribute-argument-clause*](dcl.attr.grammar#nt:attribute-argument-clause "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]") can be used to explain the rationale for deprecation and/or to suggest a replacing entity[.](#1.sentence-3)

— *end note*]

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/declarations.tex#L9733)

The attribute may be applied to the declaration of
a class,
a type alias,
a variable,
a non-static data member,
a function,
a namespace,
an enumeration,
an enumerator,
a concept, or
a template specialization[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/declarations.tex#L9746)

An entity declared without the deprecated attribute can later be redeclared
with the attribute and vice-versa[.](#3.sentence-1)

[*Note [3](#note-3)*:

Thus, an entity initially declared without the
attribute can be marked as deprecated by a subsequent redeclaration[.](#3.sentence-2)

However, after an entity
is marked as deprecated, later redeclarations do not un-deprecate the entity[.](#3.sentence-3)

— *end note*]

Redeclarations using different forms of the attribute (with or without the[*attribute-argument-clause*](dcl.attr.grammar#nt:attribute-argument-clause "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]") or with different[*attribute-argument-clause*](dcl.attr.grammar#nt:attribute-argument-clause "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]")*s*) are allowed[.](#3.sentence-4)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/declarations.tex#L9758)

*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[.](#4.sentence-1)

The diagnostic message should include the text provided
within the [*attribute-argument-clause*](dcl.attr.grammar#nt:attribute-argument-clause "9.13.1 Attribute syntax and semantics [dcl.attr.grammar]") of any deprecated attribute applied
to the name or entity[.](#4.sentence-2)

The value of
a [*has-attribute-expression*](cpp.cond#nt:has-attribute-expression "15.2 Conditional inclusion [cpp.cond]") for the deprecated attribute
should be 0 unless the implementation can issue such diagnostic messages[.](#4.sentence-3)