234 lines
13 KiB
HTML
234 lines
13 KiB
HTML
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<title>std::shared_lock</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_shared_lock skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>shared_lock</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-thread.html">thread</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<div>定义于头文件 <code><a href="cpp-header-shared_mutex.html"><shared_mutex></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Mutex <span class="sy1">></span><br />
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<span class="kw1">class</span> shared_lock<span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td>
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<p>类 <code>shared_lock</code> 是通用共享互斥所有权包装器，允许延迟锁定、定时锁定和锁所有权的转移。锁定 <code>shared_lock</code> ，会以共享模式锁定关联的共享互斥（ <span class="t-lc"><a href="cpp-thread-unique_lock.html">std::unique_lock</a></span> 可用于以排他性模式锁定）。</p>
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<p><code>shared_lock</code> 类可移动，但不可复制——它满足<a href="cpp-named_req-MoveConstructible.html"><span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span></a> 与<a href="cpp-named_req-MoveAssignable.html"><span style="font-style:italic">可移动赋值</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveAssignable)</span></a> 的要求，但不满足<a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">可复制构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyConstructible)</span></a> 或<a href="cpp-named_req-CopyAssignable.html"><span style="font-style:italic">可复制赋值</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyAssignable)</span></a> 。</p>
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<p><code>shared_lock</code> 符合<a href="cpp-named_req-Lockable.html"><span style="font-style:italic">可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Lockable)</span></a> 要求。若 <code>Mutex</code> 符合<a href="cpp-named_req-SharedTimedLockable.html"><span style="font-style:italic">可共享定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(SharedTimedLockable)</span></a> 要求，则 <code>shared_lock</code> 亦符合 <a href="cpp-named_req-TimedLockable.html"><span style="font-style:italic">可定时锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TimedLockable)</span></a> 要求。</p>
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<p>为以共享所有权模式等待于共享互斥，可使用 <span class="t-lc"><a href="cpp-thread-condition_variable_any.html">std::condition_variable_any</a></span> （ <span class="t-lc"><a href="cpp-thread-condition_variable.html">std::condition_variable</a></span> 要求 <span class="t-lc"><a href="cpp-thread-unique_lock.html">std::unique_lock</a></span> 故而只能以唯一所有权模式等待）。</p>
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<h3><span class="mw-headline" id=".E6.A8.A1.E6.9D.BF.E5.BD.A2.E5.8F.82">模板形参</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>Mutex</td>
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<td>-</td>
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<td>要锁定的共享互斥类型。类型必须符合<a href="cpp-named_req-SharedLockable.html"><span style="font-style:italic">可共享锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(SharedLockable)</span></a> 要求。</td>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<table class="t-dsc-begin">
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<td>类型</td>
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<td>定义</td>
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<tr class="t-dsc">
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<td><code>mutex_type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">Mutex</span></span></td>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<table class="t-dsc-begin">
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-thread-shared_lock-shared_lock.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造 <code>shared_lock</code> ，可选地锁定提供的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-thread-shared_lock-~shared_lock.html"><span class="t-lines"><span>(析构函数)</span></span></a></div>
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</div>
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</td>
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<td>解锁关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>若占有则解锁互斥，然后获得对方的所有权<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E5.85.B1.E4.BA.AB.E9.94.81.E5.AE.9A">共享锁定</span></h5>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-lock.html"><span class="t-lines"><span>lock</span></span></a></div>
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</div>
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</td>
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<td>锁定关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-try_lock.html"><span class="t-lines"><span>try_lock</span></span></a></div>
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</div>
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</td>
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<td>尝试锁定关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-try_lock_for.html"><span class="t-lines"><span>try_lock_for</span></span></a></div>
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</div>
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</td>
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<td>尝试锁定关联的互斥，以指定时长<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-try_lock_until.html"><span class="t-lines"><span>try_lock_until</span></span></a></div>
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</div>
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</td>
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<td>尝试锁定关联的互斥，直至指定的时间点<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-unlock.html"><span class="t-lines"><span>unlock</span></span></a></div>
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</div>
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</td>
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<td>解锁关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E4.BF.AE.E6.94.B9.E5.99.A8">修改器</span></h5>
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</td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-swap.html"><span class="t-lines"><span>swap</span></span></a></div>
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</div>
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</td>
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<td>与另一 shared_lock 交换数据成员<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-release.html"><span class="t-lines"><span>release</span></span></a></div>
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</div>
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</td>
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<td>解除关联 mutex 而不解锁<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h5><span class="mw-headline" id=".E8.A7.82.E5.AF.9F.E5.99.A8">观察器</span></h5>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-mutex.html"><span class="t-lines"><span>mutex</span></span></a></div>
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</div>
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</td>
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<td>返回指向关联的互斥的指针<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-owns_lock.html"><span class="t-lines"><span>owns_lock</span></span></a></div>
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</div>
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</td>
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<td>测试锁是否占有其关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-operator_bool.html"><span class="t-lines"><span>operator bool</span></span></a></div>
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</div>
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</td>
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<td>测试锁是否占有其关联的互斥<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E9.9D.9E.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">非成员函数</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-thread-shared_lock-swap2.html"><span class="t-lines"><span>std::swap<span class="t-dsc-small">(std::shared_lock)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
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</div>
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</td>
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<td><span class="t-lc"><a href="cpp-algorithm-swap.html">std::swap</a></span> 对 <code>shared_lock</code> 的特化<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
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<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
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<table class="dsctable" style="font-size:0.8em">
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<tr>
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<th>DR</th>
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<th>应用于</th>
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<th>出版时的行为</th>
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<th>正确行为</th>
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</tr>
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<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2981">LWG 2981</a></td>
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<td>C++17</td>
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<td>曾提供来自 <code>shared_lock<Mutex></code> 的冗余推导指引</td>
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<td>已移除</td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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