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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="decltype.html" title="cpp/language/decltype"><span class="t-lines"><span>decltype</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="alignas.html" title="cpp/language/alignas"><span class="t-lines"><span>alignas</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="cv.html" title="cpp/language/cv"><span class="t-lines"><span>const/volatile</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="elaborated_type_specifier.html" title="cpp/language/elaborated type specifier"> elaborated type specifier</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="attributes.html" title="cpp/language/attributes"> attributes </a><span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv-h2"><td colspan="5"> Declarators </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="reference.html" title="cpp/language/reference"> reference </a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="pointer.html" title="cpp/language/pointer"> pointer </a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="array.html" title="cpp/language/array"> array </a> </td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h2"><td colspan="5"> Block declarations </td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> simple-declaration</strong> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="type_alias.html" title="cpp/language/type alias"> alias declaration</a><span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="namespace_alias.html" title="cpp/language/namespace alias"> namespace alias definition </a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="using_declaration.html" title="cpp/language/using declaration"> using-declaration</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="namespace.html#Using-directives" title="cpp/language/namespace"> using-directive</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_assert.html" title="cpp/language/static assert"> static_assert declaration</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="asm.html" title="cpp/language/asm"> asm-definition</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="enum.html" title="cpp/language/enum"> opaque enum declaration</a><span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv-h2"><td colspan="5"> Other declarations </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="namespace.html" title="cpp/language/namespace"> namespace definition</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function.html" title="cpp/language/function"> function declaration</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="class_template.html" title="cpp/language/class template"> class template declaration</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function_template.html" title="cpp/language/function template"> function template declaration</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="class_template.html#Explicit_instantiation" title="cpp/language/class template"> explicit template instantiation</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="template_specialization.html" title="cpp/language/template specialization"> explicit template specialization</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="language_linkage.html" title="cpp/language/language linkage"> linkage specification</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> attribute declaration</strong> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"> empty declaration</strong> </td></tr>
</table></div></td></tr>
</table></div>
</div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/language/declarations/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p><i>Declarations</i> introduce (or re-introduce) names into the C++ program. Each kind of entity is declared differently. <a href="definition.html" title="cpp/language/definition">Definitions</a> are declarations that are sufficient to use the entity identified by the name.
</p><p>A declaration is one of the following:
</p>
<ul><li> <a href="function.html" title="cpp/language/function">Function declaration</a>
</li><li> <a href="templates.html" title="cpp/language/templates">Template declaration</a>
</li><li> <a href="class_template.html#Explicit_instantiation" title="cpp/language/class template">Explicit template instantiation</a>
</li><li> <a href="template_specialization.html" title="cpp/language/template specialization">Explicit template specialization</a>
</li><li> <a href="namespace.html" title="cpp/language/namespace">Namespace definition</a>
</li><li> <a href="language_linkage.html" title="cpp/language/language linkage">Linkage specification</a>
</li><li> Attribute declaration (<span class="t-spar"><a href="attributes.html" title="cpp/language/attributes">attr</a></span> <code><b>;</b></code>) <span class="t-mark-rev t-since-cxx11">(since C++11)</span>
</li><li> Empty declaration (<code><b>;</b></code>)
</li><li> Block declaration (a declaration that can appear inside a <a href="statements.html#Compound_statement" title="cpp/language/statements">block</a>), which, in turn, can be one of the following:
</li></ul>
<dl><dd><ul><li><a href="asm.html" title="cpp/language/asm">asm definition</a>
</li><li><a href="type_alias.html" title="cpp/language/type alias">type alias declaration</a>
</li><li><a href="namespace_alias.html" title="cpp/language/namespace alias">namespace alias definition</a>
</li><li><a href="using_declaration.html" title="cpp/language/using declaration">using declaration</a>
</li><li><a href="namespace.html#Using-directives" title="cpp/language/namespace">using directive</a>
</li><li><a href="static_assert.html" title="cpp/language/static assert">static_assert</a> declaration
</li><li><a href="enum.html" title="cpp/language/enum">opaque enum declaration</a>
</li><li>simple declaration
</li></ul>
</dd></dl>
<p>Simple declaration is a statement that introduces, creates, and optionally initializes one or several identifiers, typically variables.
</p>
<table class="t-sdsc-begin">
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">decl-specifier-seq</span><span class="t-mark">(optional)</span> <span class="t-spar">init-declarator-list</span><span class="t-mark">(optional)</span> <code><b>;</b></code>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<table class="t-par-begin">
<tr class="t-par">
<td> <span class="t-spar">attr</span><span class="t-mark-rev t-since-cxx11">(C++11)</span>
</td>
<td> -
</td>
<td> optional sequence of any number of <a href="attributes.html" title="cpp/language/attributes">attributes</a>
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">decl-specifier-seq</span>
</td>
<td> -
</td>
<td> sequence of type specifiers including the type name. It is only optional in the declarations of constructors, destructors, and user-defined type <a href="cast_operator.html" title="cpp/language/cast operator">conversion functions</a>
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">init-declarator-list</span>
</td>
<td> -
</td>
<td> comma-separated list of <i>declarators</i> with optional <i>initializers</i>. Init-declarator-list is optional when declaring a named class/struct/union or a named enumeration
</td></tr></table>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="declarations.html#Specifiers"><span class="tocnumber">1</span> <span class="toctext">Specifiers</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="declarations.html#Declarators"><span class="tocnumber">2</span> <span class="toctext">Declarators</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="declarations.html#Notes"><span class="tocnumber">3</span> <span class="toctext">Notes</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="declarations.html#Examples"><span class="tocnumber">4</span> <span class="toctext">Examples</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/declarations&action=edit&section=1" title="Edit section: Specifiers">edit</a>]</span> <span class="mw-headline" id="Specifiers">Specifiers</span></h3>
<p><span class="t-spar">decl-specifier-seq</span> is a sequence of the following whitespace-separated specifiers:
</p>
<ul><li> <a href="typedef.html" title="cpp/language/typedef">typedef specifier</a>. If present, the entire declaration is a <a href="typedef.html" title="cpp/language/typedef">typedef declaration</a> and each declarator introduces a new type name, not an object or a function.
</li><li> function specifier (<a href="../keyword/inline.html" title="cpp/keyword/inline">inline</a>, <a href="../keyword/virtual.html" title="cpp/keyword/virtual">virtual</a>, <a href="../keyword/explicit.html" title="cpp/keyword/explicit">explicit</a>), only allowed in <a href="function.html" title="cpp/language/function">function declarations</a>
</li><li> <a href="friend.html" title="cpp/language/friend">friend specifier</a>, allowed in class and function declarations.
</li><li> <a href="constexpr.html" title="cpp/language/constexpr">constexpr specifier</a>, only allowed in variable definitions, function and function template declarations, and the declaration of static data members of literal type.
</li><li> <a href="storage_duration.html" title="cpp/language/storage duration">storage class specifier</a> (<a href="../keyword/register.html" title="cpp/keyword/register">register</a>, <a href="../keyword/static.html" title="cpp/keyword/static">static</a>, <span class="t-rev-inl t-since-cxx11"><span><a href="../keyword/thread_local.html" title="cpp/keyword/thread local">thread_local</a></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>, <a href="../keyword/extern.html" title="cpp/keyword/extern">extern</a>, <a href="../keyword/mutable.html" title="cpp/keyword/mutable">mutable</a>). Only one storage class specifier is allowed, except that <code>thread_local</code> may appear together with <code>extern</code> or <code>static</code>.
</li><li> <span class="t-spar">type-specifier-seq</span>, i.e. a sequence of type specifiers, which can be any one of the following:
</li></ul>
<dl><dd><ul><li> <a href="class.html" title="cpp/language/class">class specifier</a>
</li><li> <a href="enum.html" title="cpp/language/enum">enum specifier</a>
</li><li> simple type specifier
</li></ul>
<dl><dd><ul><li>any keyword that names a <a href="types.html" title="cpp/language/types">fundamental type</a>: <a href="../keyword/char.html" title="cpp/keyword/char">char</a><span class="t-rev-inl t-since-cxx11"><span>, <a href="../keyword/char16_t.html" title="cpp/keyword/char16 t">char16_t</a>, <a href="../keyword/char32_t.html" title="cpp/keyword/char32 t">char32_t</a></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span>, <a href="../keyword/wchar_t.html" title="cpp/keyword/wchar t">wchar_t</a>, <a href="../keyword/bool.html" title="cpp/keyword/bool">bool</a>, <a href="../keyword/short.html" title="cpp/keyword/short">short</a>, <a href="../keyword/int.html" title="cpp/keyword/int">int</a>, <a href="../keyword/long.html" title="cpp/keyword/long">long</a>, <a href="../keyword/signed.html" title="cpp/keyword/signed">signed</a>, <a href="../keyword/unsigned.html" title="cpp/keyword/unsigned">unsigned</a>, <a href="../keyword/float.html" title="cpp/keyword/float">float</a>, <a href="../keyword/double.html" title="cpp/keyword/double">double</a>, <a href="../keyword/void.html" title="cpp/keyword/void">void</a>
</li></ul>
</dd></dl>
</dd></dl>
<table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<dl><dd><dl><dd><ul><li><a href="auto.html" title="cpp/language/auto">auto</a>
</li><li><a href="decltype.html" title="cpp/language/decltype">decltype specifier</a>
</li></ul>
</dd></dl>
</dd></dl>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr></table>
<dl><dd><dl><dd><ul><li> previously declared class name (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>)
</li><li> previously declared enum name (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>)
</li><li> previously declared <a href="typedef.html" title="cpp/language/typedef">typedef-name</a><span class="t-rev-inl t-since-cxx11"><span> or <a href="type_alias.html" title="cpp/language/type alias">type alias</a></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span> (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>)
</li><li> template name with template arguments (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>, optionally using <a href="dependent_name.html" title="cpp/language/dependent name">template disambiguator</a>)
</li></ul>
</dd></dl>
<ul><li> <a href="elaborated_type_specifier.html" title="cpp/language/elaborated type specifier">elaborated type specifier</a>
</li></ul>
<dl><dd><ul><li> the keyword <a href="../keyword/class.html" title="cpp/keyword/class">class</a>, <a href="../keyword/struct.html" title="cpp/keyword/struct">struct</a>, or <a href="../keyword/union.html" title="cpp/keyword/union">union</a>, followed by the identifier (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>), previously defined as the name of a class, struct, or union.
</li><li> the keyword <a href="../keyword/class.html" title="cpp/keyword/class">class</a>, <a href="../keyword/struct.html" title="cpp/keyword/struct">struct</a>, or <a href="../keyword/union.html" title="cpp/keyword/union">union</a>, followed by template name with template arguments (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>, optionally using <a href="dependent_name.html" title="cpp/language/dependent name">template disambiguator</a>), previously defined as the name of a class template.
</li><li> the keyword <a href="../keyword/enum.html" title="cpp/keyword/enum">enum</a> followed by the identifier (optionally <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">qualified</a>), previously declared as the name of an enumeration.
</li></ul>
</dd></dl>
<ul><li> <a href="dependent_name.html" title="cpp/language/dependent name">typename specifier</a>
</li><li> <a href="cv.html" title="cpp/language/cv">cv qualifier</a>
</li></ul>
</dd><dd>only one type specifier is allowed in a decl-specifier-seq, with the following exceptions:
</dd><dd>- <code>const</code> can be combined with any type specifier except itself.
</dd><dd>- <code>volatile</code> can be combined with any type specifier except itself.
</dd><dd>- <code>signed</code> or <code>unsigned</code> can be combined with <code>char</code>, <code>long</code>, <code>short</code>, or <code>int</code>.
</dd><dd>- <code>short</code> or <code>long</code> can be combined with <code>int</code>.
</dd><dd>- <code>long</code> can be combined with <code>double</code>.
</dd></dl>
<table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<dl><dd>- <code>long</code> can be combined with <code>long</code>.
</dd></dl>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr></table>
<p><a href="attributes.html" title="cpp/language/attributes">Attributes</a> may appear in decl-specifier-seq, in which case they apply to the type determined by the preceding specifiers.
</p>
<table class="t-rev-begin">
<tr class="t-rev t-since-cxx17"><td>
<p>The only specifier that is allowed to appear twice in a <span class="t-spar">decl-specifier-seq</span> is <code>long</code> (which can appear twice in a row. All other repeats, such as <code>const static const</code>, or <code>virtual inline virtual</code> are errors.
</p>
</td>
<td><span class="t-mark-rev t-since-cxx17">(since C++17)</span></td></tr>
</table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/declarations&action=edit&section=2" title="Edit section: Declarators">edit</a>]</span> <span class="mw-headline" id="Declarators">Declarators</span></h3>
<p><span class="t-spar">init-declarator-seq</span> is a comma-separated sequence of one or more <span class="t-spar">init-declarators</span>, which have the following syntax:
</p>
<table class="t-sdsc-begin">
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">declarator</span> <span class="t-spar">initializer</span><span class="t-mark">(optional)</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<table class="t-par-begin">
<tr class="t-par">
<td> <span class="t-spar">declarator</span>
</td>
<td> -
</td>
<td> the declarator
</td></tr>
<tr class="t-par">
<td> <span class="t-spar">initializer</span>
</td>
<td> -
</td>
<td> optional initializer (except where required, such as when initializing references or const objects). See <a href="initialization.html" title="cpp/language/initialization">Initialization</a> for details.
</td></tr></table>
<p>Each <span class="t-spar">init-declaractor</span> in a init-declarator sequence <span class="t-c"><span class="mw-geshi cpp source-cpp">S D1, D2, D3<span class="sy4">;</span></span></span> is processed as if it were a standalone declaration with the same specifiers: <span class="t-c"><span class="mw-geshi cpp source-cpp">S D1<span class="sy4">;</span> S D2<span class="sy4">;</span> S D3<span class="sy4">;</span></span></span>.
</p><p>Each declarator introduces exactly one object, function, or (for typedef declarations) type alias, whose type is provided by <span class="t-spar">decl-specifier-seq</span> and optionally modified by operators such as <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">&</span></span></span> (reference to) or <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span><span class="br0">]</span></span></span> (array of) or <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="br0">)</span></span></span> (function returning) in the declarator. These operators can be applied recursively, as shown below.
</p><p>A <span class="t-spar">declarator</span> is one of the following:
</p>
<table class="t-sdsc-begin">
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">name</span> <span class="t-spar">attr</span><span class="t-mark">(optional)</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">qualified-id</span> <span class="t-spar">attr</span><span class="t-mark">(optional)</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>...</b></code> <span class="t-spar">identifier</span> <span class="t-spar">attr</span><span class="t-mark">(optional)</span>
</td>
<td> (3)
</td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span>
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>*</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">cv</span><span class="t-mark">(optional)</span> <span class="t-spar">declarator</span>
</td>
<td> (4)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">nested-name-specifier</span> <code><b>*</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">cv</span><span class="t-mark">(optional)</span> <span class="t-spar">declarator</span>
</td>
<td> (5)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>&</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">declarator</span>
</td>
<td> (6)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <code><b>&&</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">declarator</span>
</td>
<td> (7)
</td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span>
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">noptr-declarator</span> <code><b>[</b></code> <span class="t-spar">constexpr</span><span class="t-mark">(optional)</span> <code><b>]</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span>
</td>
<td> (8)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">noptr-declarator</span> <code><b>(</b></code> <span class="t-spar">parameter-list</span> <code><b>)</b></code> <span class="t-spar">cv</span><span class="t-mark">(optional)</span> <span class="t-spar">ref</span><span class="t-mark">(optional)</span> <span class="t-spar">except</span><span class="t-mark">(optional)</span> <span class="t-spar">attr</span><span class="t-mark">(optional)</span>
</td>
<td> (9)
</td>
<td class="t-sdsc-nopad">
</td></tr>
<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<div class="t-li1"><span class="t-li">1)</span> The <a href="name.html" title="cpp/language/name" class="mw-redirect">name</a> that is declared. A declarator that consist of just a name, declares an entity of exactly the type provided by <span class="t-spar">decl-specifier-seq</span>.</div>
<div class="t-li1"><span class="t-li">2)</span> A previously declared name can be re-declared in a different scope.</div>
<div class="t-li1"><span class="t-li">3)</span> <a href="parameter_pack.html" title="cpp/language/parameter pack">Parameter pack</a>, only appears in function parameter lists for variadic function templates.</div>
<div class="t-li1"><span class="t-li">4)</span> <a href="pointer.html" title="cpp/language/pointer">Pointer declarator</a>: the declaration <span class="t-c"><span class="mw-geshi cpp source-cpp">S <span class="sy2">*</span> D<span class="sy4">;</span></span></span> declares <code>D</code> as a pointer to the type determined by <span class="t-spar">decl-specifier-seq</span> <code>S</code>.</div>
<div class="t-li1"><span class="t-li">5)</span> <a href="pointer.html" title="cpp/language/pointer">Pointer to member declaration</a>: the declaration <span class="t-c"><span class="mw-geshi cpp source-cpp">S C<span class="sy4">::</span><span class="sy2">*</span> D<span class="sy4">;</span></span></span> declares <code>D</code> as a pointer to member of <code>C</code> of type determined by <span class="t-spar">decl-specifier-seq</span> <code>S</code>. <span class="t-spar">nested-name-specifier</span> is a <a href="name.html#Qualified_identifiers" title="cpp/language/identifiers">sequence of names and scope resolution operators <code><b>::</b></code></a></div>
<div class="t-li1"><span class="t-li">6)</span> <a href="reference.html" title="cpp/language/reference">Lvalue reference declarator</a>: the declaration <span class="t-c"><span class="mw-geshi cpp source-cpp">S <span class="sy3">&</span> D<span class="sy4">;</span></span></span> declares the object <code>D</code> with type lvalue reference to the type determined by <span class="t-spar">decl-specifier-seq</span> <code>S</code>.</div>
<div class="t-li1"><span class="t-li">7)</span> <a href="reference.html" title="cpp/language/reference">Rvalue reference declarator</a>: the declaration <span class="t-c"><span class="mw-geshi cpp source-cpp">S <span class="sy3">&&</span> D<span class="sy4">;</span></span></span> declares the object <code>D</code> with type rvalue reference to the type determined by <span class="t-spar">decl-specifier-seq</span> <code>S</code>.</div>
<div class="t-li1"><span class="t-li">8)</span> <a href="array.html" title="cpp/language/array">Array declarator</a>. <span class="t-spar">noptr-declarator</span> any valid declarator, but if it begins with *, &, or &&, it has to be surrounded by parentheses.</div>
<div class="t-li1"><span class="t-li">9)</span> <a href="function.html" title="cpp/language/function">Function declarator</a>. <span class="t-spar">noptr-declarator</span> any valid declarator, but if it begins with *, &, or &&, it has to be surrounded by parentheses. Note that the outermost function declarator may end with the optional trailing return type. </div>
<p>In all cases, <span class="t-spar">attr</span> is an optional sequence of <a href="attributes.html" title="cpp/language/attributes">attributes</a>. When appearing immediately after the identifier, it applies to the object being declared.
</p><p><span class="t-spar">cv</span> is a sequence of <a href="cv.html" title="cpp/language/cv">const and volatile</a> qualifiers, where either qualifier may appear at most once in the sequence.
</p>
<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style=""><tr><td class="mbox-empty-cell"></td><td class="mbox-text" style="">This section is incomplete<br />Reason: explain declaration name hiding rules; how a variable/function declaration hides a class (but not a typedef) with the same name </td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/declarations&action=edit&section=3" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span></h3>
<p>When a block declaration appears <a href="statements.html#Compound_statement" title="cpp/language/statements">inside a block</a>, and an identifier introduced by a declaration was previously declared in an outer block, the <a href="scope.html" title="cpp/language/scope">outer declaration is hidden</a> for the remainder of the block.
</p><p>If a declaration introduces a variable with automatic storage duration, it is initialized when its declaration statement is executed. All automatic variables declared in a block are destroyed on exit from the block (regardless how the block is exited: via <a href="exceptions.html" title="cpp/language/exceptions">exception</a>, <a href="goto.html" title="cpp/language/goto">goto</a>, or by reaching its end), in order opposite to their order of initialization.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/language/declarations&action=edit&section=4" title="Edit section: Examples">edit</a>]</span> <span class="mw-headline" id="Examples">Examples</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">class</span> C <span class="br0">{</span>
<a href="../string/basic_string.html"><span class="kw1042">std::<span class="me2">string</span></span></a> member<span class="sy4">;</span> <span class="co1">// decl-specifier-seq is "std::string"</span>
<span class="co1">// declarator is "member"</span>
<span class="br0">}</span> obj, <span class="sy2">*</span>pObj<span class="br0">(</span><span class="sy3">&</span>obj<span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// decl-specifier-seq is "class C { std::string member; }"</span>
<span class="co1">// declarator "obj" defines an object of type C</span>
<span class="co1">// declarator "*pObj(&obj)" declares and initializes a pointer to C</span>
 
<span class="kw4">int</span> a <span class="sy1">=</span> <span class="nu0">1</span>, <span class="sy2">*</span>p <span class="sy1">=</span> <a href="../types/NULL.html"><span class="kw103">NULL</span></a>, f<span class="br0">(</span><span class="br0">)</span>, <span class="br0">(</span><span class="sy2">*</span>pf<span class="br0">)</span><span class="br0">(</span><span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// decl-specifier-seq is int</span>
<span class="co1">// declarator a=1 defines and initializes a variable of type int</span>
<span class="co1">// declarator *p=NULL defines and initializes a variable of type int*</span>
<span class="co1">// declarator (f)() declares (but doesn't define)</span>
<span class="co1">// a function taking no arguments and returning int</span>
<span class="co1">// declarator (*pf)(double) defines a pointer to function</span>
<span class="co1">// taking double and returning int</span>
 
<span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">(</span><span class="sy2">*</span>foo<span class="br0">)</span><span class="br0">(</span><span class="kw4">double</span><span class="br0">)</span><span class="br0">)</span><span class="br0">[</span><span class="nu0">3</span><span class="br0">]</span> <span class="sy1">=</span> <a href="../types/NULL.html"><span class="kw103">NULL</span></a><span class="sy4">;</span>
<span class="co1">// decl-specifier-seq is int</span>
<span class="co1">// 1. declarator "(*(*foo)(double))[3]" is an array declarator:</span>
<span class="co1">// the type declared is "/nested declarator/ array of 3 int"</span>
<span class="co1">// 2. the nested declarator is "*(*foo)(double))", which is a pointer declarator</span>
<span class="co1">// the type declared is "/nested declarator/ pointer to array of 3 int"</span>
<span class="co1">// 3. the nested declarator is "(*foo)(double)", which is a function declarator</span>
<span class="co1">// the type declared is "/nested declarator/ function taking double and returning</span>
<span class="co1">// pointer to array of 3 int"</span>
<span class="co1">// 4. the nested declarator is "(*foo)" which is a (parenthesized, as required by</span>
<span class="co1">// function declarator syntax) pointer declarator.</span>
<span class="co1">// the type declared is "/nested declarator/ pointer to function taking double</span>
<span class="co1">// and returning pointer to array of 3 int"</span>
<span class="co1">// 5. the nested declarator is "foo", which is an identifier.</span>
<span class="co1">// The declaration declares the object foo of type "pointer to function taking double </span>
<span class="co1">// and returning pointer to array of 3 int"</span>
<span class="co1">// The initializer "= NULL" provides the initial value of this pointer.</span></pre></div></div>
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