94 lines
5.6 KiB
HTML
94 lines
5.6 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>ATOMIC_VAR_INIT</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_atomic_ATOMIC_VAR_INIT 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">ATOMIC_VAR_INIT</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-atomic.html">atomic</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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<table class="t-dcl-begin">
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<td>
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<div>定义于头文件 <code><a href="cpp-header-atomic.html"><atomic></a></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="co2">#define ATOMIC_VAR_INIT(value) /* implementation-defined */</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark">(C++20 中弃用)</span></td>
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<p>展开成能用于初始化能从 <code>value</code> 初始化的 <span class="t-lc"><a href="cpp-atomic-atomic.html">std::atomic</a></span> 对象的表达式。若原子对象拥有静态存储期，则此初始化为<a href="cpp-language-constant_initialization.html">常量初始化</a>。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>从另一线程在初始化期间访问，即使通过原子操作，也是数据竞争（若立即传递地址给带 <span class="t-lc"><a href="cpp-atomic-memory_order.html">std::memory_order_relaxed</a></span> 操作的另一线程则可以发生）。</p>
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<p>此宏主要为与 C 的兼容性提供；它表现与 <span class="t-lc"><a href="cpp-atomic-atomic.html">std::atomic</a></span> 的构造函数相同。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <atomic></span>
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<span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-atomic-atomic.html"><span class="kw2066">std::<span class="me2">atomic</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> a <span class="sy1">=</span> ATOMIC_VAR_INIT<span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// std::atomic<int> a(1); // 仅 C++ 的替用品</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Initialized std::atomic<int> as: "</span> <span class="sy1"><<</span> a <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">Initialized std::atomic<int> as: 1</pre></div>
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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 class="t-dsc-member-div">
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<div><a href="cpp-atomic-atomic_init.html"><span class="t-lines"><span>atomic_init</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 class="t-mark-rev t-deprecated-cxx20">(C++20 中弃用)</span></span></span></div>
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</div>
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</td>
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<td>对默认构造的原子对象进行非原子初始化<br />
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<span class="t-mark">(函数模板)</span></td>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-atomic-atomic-atomic.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>构造原子对象<br />
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<span class="t-mark">(<code>std::atomic<T></code> 的公开成员函数)</span></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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