99 lines
5.8 KiB
HTML
99 lines
5.8 KiB
HTML
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<title>std::atomic_ref<T>::fetch_sub</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_atomic_atomic_ref_fetch_sub skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::atomic_ref<T>::</span>fetch_sub</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>‎ | <a href="cpp-atomic-atomic_ref.html">atomic ref</a></span></div>
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<div>仅为 <code>atomic_ref<<i>Integral</i>></code> 与 <code>atomic_ref<<i>Floating</i>></code> 模板特化的成员</div>
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<div><span class="mw-geshi cpp source-cpp">T fetch_sub<span class="br0">(</span> T arg,<br />
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<a href="cpp-atomic-memory_order.html"><span class="kw2092">std::<span class="me2">memory_order</span></span></a> order <span class="sy1">=</span> <a href="cpp-atomic-memory_order.html"><span class="kw2098">std::<span class="me2">memory_order_seq_cst</span></span></a> <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td></td>
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<div>仅为 <code>atomic_ref<T*></code> 模板特化的成员</div>
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</td>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp">T<span class="sy2">*</span> fetch_sub<span class="br0">(</span> <a href="cpp-types-ptrdiff_t.html"><span class="kw101">std::<span class="me2">ptrdiff_t</span></span></a> arg,<br />
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<a href="cpp-atomic-memory_order.html"><span class="kw2092">std::<span class="me2">memory_order</span></span></a> order <span class="sy1">=</span> <a href="cpp-atomic-memory_order.html"><span class="kw2098">std::<span class="me2">memory_order_seq_cst</span></span></a> <span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td></td>
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<p>原子地以值和 <code>arg</code> 的算术减法结果替换当前被引用对象的值。此操作为读修改写操作。按照 <code>order</code> 的值影响内存。</p>
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<p>对于有符号整数类型，定义算术为使用补码。无未定义结果。</p>
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<p>对于浮点类型，有效的<a href="cpp-numeric-fenv.html">浮点环境</a>可能异于调用方线程的浮点环境。不需要操作服从对应的 <span class="t-lc"><a href="cpp-types-numeric_limits.html">std::numeric_limits</a></span> 特性，但鼓励这么做。若结果不是其类型的可表示值，则结果未指定，但操作不会另有未定义行为。</p>
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<p>对于 <code>T*</code> 类型，结果可以为未定义的地址，但操作不会另有未定义行为。若 <code>T</code> 不是对象类型则程序为谬构。</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>arg</td>
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<td>-</td>
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<td>算术减法的另一参数</td>
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</tr>
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<tr class="t-par">
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<td>order</td>
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<td>-</td>
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<td>施加的内存顺序制约</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>被引用对象立即于此函数效果前的值。</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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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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