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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="../type_trait_variable_templates.html" title="cpp/experimental/type trait variable templates"><span class="t-lines"><span>variable templates for type traits</span></span></a></div></div></td></tr>
</table></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/experimental/lib_extensions/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../weak_ptr.html" title="cpp/experimental/weak ptr"><tt>std::experimental::weak_ptr</tt></a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>weak_ptr::weak_ptr</span></span></strong></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <a href="../weak_ptr.html#identical-weak_ptr" title="cpp/experimental/weak ptr"> Members and non-members identical to those of <code>std::weak_ptr</code></a></td></tr>
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<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> weak_ptr<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (1) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl t-since-libfund_ts">
<td> <div><span class="mw-geshi cpp source-cpp">weak_ptr<span class="br0">(</span> <span class="kw4">const</span> weak_ptr<span class="sy3">&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (2) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl t-since-libfund_ts">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span> <br />
weak_ptr<span class="br0">(</span> <span class="kw4">const</span> weak_ptr<span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (2) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl t-since-libfund_ts">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span> <br />
weak_ptr<span class="br0">(</span> <span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">experimental</span><span class="sy4">::</span><span class="me2">shared_ptr</span><span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (2) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl t-since-libfund_ts">
<td> <div><span class="mw-geshi cpp source-cpp">weak_ptr<span class="br0">(</span> weak_ptr<span class="sy3">&&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (3) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl t-since-libfund_ts">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span> <br />
weak_ptr<span class="br0">(</span> weak_ptr<span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (3) </td>
<td> <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(library fundamentals TS)</span> </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<p>Constructs a new <code>weak_ptr</code> that potentially shares an object with <code>r</code>.
</p>
<div class="t-li1"><span class="t-li">1)</span> Default constructor. Constructs empty <code>weak_ptr</code>.</div>
<div class="t-li1"><span class="t-li">2)</span> Constructs new <code>weak_ptr</code> which shares an object managed by <code>r</code>. If <code>r</code> manages no object, <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> manages no object too. The templated overloads don't participate in overload resolution unless either <code>Y*</code> is implicitly convertible to <code>T*</code>, or <code>Y</code> is the type "array of <code>N</code> <code>U</code>" for some type <code>U</code> and some number <code>N</code>, and <code>T</code> is the type "array of unknown bound of (possibly cv-qualified) <code>U</code>". </div>
<div class="t-li1"><span class="t-li">3)</span> Move constructors. Moves a <code>weak_ptr</code> instance from <code>r</code> into <code>*this</code>. After this, <code>r</code> is empty and <span class="t-c"><span class="mw-geshi cpp source-cpp">r.<span class="me1">use_count</span><span class="br0">(</span><span class="br0">)</span><span class="sy1">==</span><span class="nu0">0</span></span></span>. The templated overload doesn't participate in overload resolution unless <code>Y*</code> is implicitly convertible to <code>T*</code>. </div>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="weak_ptr.html#Parameters"><span class="tocnumber">1</span> <span class="toctext">Parameters</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="weak_ptr.html#Exceptions"><span class="tocnumber">2</span> <span class="toctext">Exceptions</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="weak_ptr.html#Example"><span class="tocnumber">3</span> <span class="toctext">Example</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="weak_ptr.html#See_also"><span class="tocnumber">4</span> <span class="toctext">See also</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/experimental/weak_ptr/weak_ptr&action=edit&section=1" title="Edit section: Parameters">edit</a>]</span> <span class="mw-headline" id="Parameters">Parameters</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td> r
</td>
<td> -
</td>
<td> a <span class="t-lc">std::experimental::shared_ptr</span> or <span class="t-lc">std::experimental::weak_ptr</span> that will be viewed by this <span class="t-lc">std::experimental::weak_ptr</span>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/experimental/weak_ptr/weak_ptr&action=edit&section=2" title="Edit section: Exceptions">edit</a>]</span> <span class="mw-headline" id="Exceptions">Exceptions</span></h3>
<div class="t-noexcept-inline"><a href="../../language/noexcept_spec.html" title="cpp/language/noexcept spec"><tt>noexcept</tt></a> specification:  <div class="t-noexcept-box"><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span></span></span></div>  </div>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/experimental/weak_ptr/weak_ptr&action=edit&section=3" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span></h3>
<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: no example </td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/experimental/weak_ptr/weak_ptr&action=edit&section=4" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td> <div class="t-dsc-member-div t-dsc-member-nobold-div"><div><a href="../../memory/weak_ptr/weak_ptr.html" title="cpp/memory/weak ptr/weak ptr"> <span class="t-lines"><span>(constructor)</span></span></a></div></div>
</td>
<td> creates a new <code>weak_ptr</code> <br /> <span class="t-mark">(public member function of <code>std::weak_ptr</code>)</span> <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/memory/weak_ptr/dsc_constructor&action=edit">[edit]</a></span>
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<td> <div class="t-dsc-member-div"><div><a href="../../memory/weak_ptr/operator=.html" title="cpp/memory/weak ptr/operator="> <span class="t-lines"><span>operator=</span></span></a></div></div>
</td>
<td> assigns the <code>weak_ptr</code> <br /> <span class="t-mark">(public member function of <code>std::weak_ptr</code>)</span> <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/memory/weak_ptr/dsc_operator%3D&action=edit">[edit]</a></span>
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