86 lines
3.9 KiB
HTML
86 lines
3.9 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>std::once_flag</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_once_flag skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>once_flag</h1>
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<div id="bodyContent">
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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-mutex.html"><mutex></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> once_flag<span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>类 <code>std::once_flag</code> 是 <span class="t-lc"><a href="cpp-thread-call_once.html">std::call_once</a></span> 的辅助类。</p>
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<p>传递给多个 <span class="t-lc"><a href="cpp-thread-call_once.html">std::call_once</a></span> 调用的 <code>std::once_flag</code> 对象允许那些调用彼此协调，从而只令调用之一实际运行完成。</p>
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<p><code>std::once_flag</code> 既不可复制亦不可移动。</p>
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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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<h2><span class="mw-headline" id="std::once_flag::once_flag"><span style="font-size:0.7em; line-height:130%">std::once_flag::</span>once_flag</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> once_flag<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<p>构造 <code>once_flag</code> 对象。设置内部状态为指示尚未调用函数。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<p>（无）</p>
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<p><br /></p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div><a href="cpp-thread-call_once.html"><span class="t-lines"><span>call_once</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>仅调用函数一次，即使从多个线程调用<br />
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<span class="t-mark">(函数模板)</span></td>
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