View source for cpp/language/declarations

===Declarators===
{{spar|init-declarator-list}} is a comma-separated sequence of one or more {{spar|init-declarators}}, which have the following syntax:

{{sdsc begin}}
{{sdsc|num=1|1=
{{spar|declarator}} {{spar optional|initializer}}
}}
{{sdsc|num=2|notes={{mark since c++20}}|1=
{{spar|declarator}} {{spar|requires-clause}}
}}
{{sdsc end}}

{{par begin}}
{{par|{{spar|declarator}}|the declarator}}
{{par|{{spar|initializer}}|optional initializer (except where required, such as when initializing references or const objects). See {{rlp|initialization|Initialization}} for details.}}
{{par|{{spar|requires-clause}}|{{rlp|constraints#Requires clauses|a requires-clause}}, which adds a {{rlp|constraints|constraint}} to a {{rlp|function|function declaration}}}}
{{par end}}

Each {{spar|init-declarator}} in an init-declarator sequence {{c|S D1, D2, D3;}} is processed as if it were a standalone declaration with the same specifiers: {{c|S D1; S D2; S D3;}}.

Each declarator introduces exactly one object, reference, function, or (for typedef declarations) type alias, whose type is provided by {{spar|decl-specifier-seq}} and optionally modified by operators such as {{c|&}} (reference to) or {{c|[]}} (array of) or {{c|()}} (function returning) in the declarator. These operators can be applied recursively, as shown below.

A {{spar|declarator}} is one of the following:
{{sdsc begin}}
{{sdsc|num=1|1=
{{spar|unqualified-id}} {{spar optional|attr}}
}}
{{sdsc|num=2|1=
{{spar|qualified-id}} {{spar optional|attr}}
}}
{{sdsc|num=3|notes={{mark since c++11}}|1=
{{ttb|...}} {{spar|identifier}} {{spar optional|attr}}
}}
{{sdsc|num=4|1=
{{ttb|*}} {{spar optional|attr}} {{spar optional|cv}} {{spar|declarator}}
}}
{{sdsc|num=5|1=
{{spar|nested-name-specifier}} {{ttb|*}} {{spar optional|attr}} {{spar optional|cv}} {{spar|declarator}}
}}
{{sdsc|num=6|1=
{{ttb|&}} {{spar optional|attr}} {{spar|declarator}}
}}
{{sdsc|num=7|notes={{mark since c++11}}|1=
{{ttb|&&}} {{spar optional|attr}} {{spar|declarator}}
}}
{{sdsc|num=8|1=
{{spar|noptr-declarator}} {{ttb|[}} {{spar optional|constexpr}} {{ttb|]}} {{spar optional|attr}}
}}
{{sdsc|num=9|1=
{{spar|noptr-declarator}} {{ttb|(}} {{spar|parameter-list}} {{ttb|)}} {{spar optional|cv}} {{spar optional|ref}} {{spar optional|except}} {{spar optional|attr}}
}}
{{sdsc end}}

@1@ The {{rlp|name}} that is declared.
@2@ A declarator that uses a {{rlp|identifiers#Qualified identifiers|qualified identifier}} ({{spar|qualified-id}}) defines or redeclares a previously declared {{rlp|namespace#Namespaces|namespace member}} or {{rlp|classes|class member}}.
@3@ {{rlp|parameter pack|Parameter pack}}, only appears in {{rlp|function#Parameter list|parameter declarations}}.
@4@ {{rlp|pointer|Pointer declarator}}: the declaration {{c|S * D;}} declares {{tt|D}} as a pointer to the type determined by {{spar|decl-specifier-seq}} {{tt|S}}.
@5@ {{rlp|pointer|Pointer to member declaration}}: the declaration {{c|S C::* D;}} declares {{tt|D}} as a pointer to member of {{tt|C}} of type determined by {{spar|decl-specifier-seq}} {{tt|S}}. {{spar|nested-name-specifier}} is a {{rlp|identifiers#Qualified identifiers|sequence of names and scope resolution operators {{ttb|::}}}}
@6@ {{rlp|reference|Lvalue reference declarator}}: the declaration {{c|S & D;}} declares {{tt|D}} as an lvalue reference to the type determined by {{spar|decl-specifier-seq}} {{tt|S}}.
@7@ {{rlp|reference|Rvalue reference declarator}}: the declaration {{c|S && D;}} declares {{tt|D}} as an rvalue reference to the type determined by {{spar|decl-specifier-seq}} {{tt|S}}.
@8@ {{rlp|array|Array declarator}}. {{spar|noptr-declarator}} any valid declarator, but if it begins with *, &, or &&, it has to be surrounded by parentheses.
@9@ {{rlp|function|Function declarator}}. {{spar|noptr-declarator}} any valid declarator, but if it begins with *, &, or &&, it has to be surrounded by parentheses. {{rev inl|since=c++11|It may end with the optional trailing return type.}}

{{rrev|since=c++11|
In all cases, {{spar|attr}} is an optional sequence of {{rlp|attributes}}. When appearing immediately after the identifier, it applies to the object being declared.
}}

{{spar|cv}} is a sequence of {{rlp|cv|const and volatile}} qualifiers, where either qualifier may appear at most once in the sequence.

{{todo|explain declaration name hiding rules; how a variable/function declaration hides a class (but not a typedef) with the same name}}