112 lines
8.0 KiB
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112 lines
8.0 KiB
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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<title>atomic_is_lock_free</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_atomic_atomic_is_lock_free 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_is_lock_free</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-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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<div>定义于头文件 <code><stdatomic.h></code></div>
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<td></td>
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<div><span class="mw-geshi c source-c">_Bool atomic_is_lock_free<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">volatile</span> A<span class="sy2">*</span> obj <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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<p>确定所有 <code>A</code> 类型对象（<code>obj</code>所指向对象的类型）上的原子操作是否为免锁。在任何给定的程序执行中，调用 <code>atomic_is_lock_free</code> 的结果对于所有同一类型的指针相同。</p>
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<p>这是为所有<a href="c-language-atomic.html">原子对象类型</a> <code>A</code> 定义的<a href="c-language-generic.html">泛型函数</a>。参数为指向 volatile 原子对象的指针，以接受非 volatile 与 <a href="c-language-volatile.html">volatile</a> （例如内存映射 I/O ）的原子对象，而 volatile 语义在应用此操作时保留。</p>
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<p>泛型函数名是宏或是声明有外部链接的标识符是未指定的。若为访问实际函数压制宏定义（例如像 <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">(</span>atomic_is_lock_free<span class="br0">)</span><span class="br0">(</span>...<span class="br0">)</span></span></span> 这样加括号），或程序定义拥有泛型函数名的外部标识符，则行为未定义。</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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<td>obj</td>
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<td>-</td>
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<td>指向要调查的原子对象的指针</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>若所有 <code>A</code> 类型对象的原子操作为免锁，则为 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw2">true</span></span></span> ，否则为 <code>false</code> 。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>C11 在出版时指名此函数针对每个对象，而非每个类型。这已为 DR 465 所订正。</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 dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <stdatomic.h></span>
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_Atomic <span class="kw1">struct</span> A <span class="br0">{</span> <span class="kw4">int</span> a<span class="br0">[</span><span class="nu0">100</span><span class="br0">]</span><span class="sy4">;</span> <span class="br0">}</span> a<span class="sy4">;</span>
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_Atomic <span class="kw1">struct</span> B <span class="br0">{</span> <span class="kw4">int</span> x, y<span class="sy4">;</span> <span class="br0">}</span> b<span class="sy4">;</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">"_Atomic struct A is lock free? %s<span class="es1">\n</span>"</span>,
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atomic_is_lock_free<span class="br0">(</span><span class="sy3">&</span>a<span class="br0">)</span> <span class="sy4">?</span> <span class="st0">"true"</span> <span class="sy4">:</span> <span class="st0">"false"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">"_Atomic struct B is lock free? %s<span class="es1">\n</span>"</span>,
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atomic_is_lock_free<span class="br0">(</span><span class="sy3">&</span>b<span class="br0">)</span> <span class="sy4">?</span> <span class="st0">"true"</span> <span class="sy4">:</span> <span class="st0">"false"</span><span class="br0">)</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>可能的输出：</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">_Atomic struct A is lock free? false
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_Atomic struct B is lock free? true</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.17.5.1 The atomic_is_lock_free generic function (p: 280)</li>
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</ul>
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</dd>
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</dl>
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</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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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="c-atomic-ATOMIC_LOCK_FREE_consts.html"><span class="t-lines"><span>ATOMIC_BOOL_LOCK_FREE</span><span>ATOMIC_CHAR_LOCK_FREE</span><span>ATOMIC_CHAR16_T_LOCK_FREE</span><span>ATOMIC_CHAR32_T_LOCK_FREE</span><span>ATOMIC_WCHAR_T_LOCK_FREE</span><span>ATOMIC_SHORT_LOCK_FREE</span><span>ATOMIC_INT_LOCK_FREE</span><span>ATOMIC_LONG_LOCK_FREE</span><span>ATOMIC_LLONG_LOCK_FREE</span><span>ATOMIC_POINTER_LOCK_FREE</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>指示给定的原子类型为免锁<br />
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<span class="t-mark">(宏常量)</span></td>
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