131 lines
6.5 KiB
HTML
131 lines
6.5 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>静态断言</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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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_language_Static_assert 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">静态断言</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-language.html">language</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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<h3><span class="mw-headline" id=".E8.AF.AD.E6.B3.95">语法</span></h3>
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<table class="t-sdsc-begin">
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<tr>
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<td colspan="10" class="t-sdsc-sep"></td>
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</tr>
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<tr class="t-sdsc">
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<td><code><b>_Static_assert</b></code> <code><b>(</b></code> <span class="t-spar">表达式</span> <code><b>,</b></code> <span class="t-spar">消息</span> <code><b>)</b></code></td>
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<td class="t-sdsc-nopad"></td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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</tr>
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<tr>
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<td colspan="10" class="t-sdsc-sep"></td>
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</tr>
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<tr class="t-sdsc">
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<td><code><b>_Static_assert</b></code> <code><b>(</b></code> <span class="t-spar">表达式</span> <code><b>)</b></code></td>
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<td class="t-sdsc-nopad"></td>
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<td><span class="t-mark-rev t-since-c23">(C23 起)</span></td>
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</tr>
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<tr>
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<td colspan="10" class="t-sdsc-sep"></td>
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</tr>
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</table>
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<table class="t-par-begin">
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<tr class="t-par">
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<td><span class="t-spar">表达式</span></td>
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<td>-</td>
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<td>任何<a href="c-language-constant_expression.html">整数常量表达式</a></td>
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</tr>
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<tr class="t-par">
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<td><span class="t-spar">消息</span></td>
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<td>-</td>
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<td>任何<a href="c-language-string_literal.html">字符串字面量</a></td>
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</tr>
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</table>
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<p>此关键词亦可用作便利宏 <a href="c-error-static_assert.html"><tt>static_assert</tt></a> ，宏于头文件 <code><assert.h></code> 可用。</p>
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<h3><span class="mw-headline" id=".E8.A7.A3.E9.87.8A">解释</span></h3>
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<p>在编译时求值该常量表达式并将它与零比较。若它比较等于零，则发生编译错误，而若提供 <span class="t-spar">消息</span> ，则编译器必须将它作为错误消息的一部分显示（除了不要求显示<a href="c-language-translation_phases.html">基本源码字符集</a>以外的字符）。</p>
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<p>否则，若 <span class="t-spar">表达式</span> 不等于零，则什么都不发生；不生成代码。</p>
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<h3><span class="mw-headline" id=".E5.85.B3.E9.94.AE.E8.AF.8D">关键词</span></h3>
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<p><a href="c-keyword-_Static_assert.html"><tt>_Static_assert</tt></a></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="c source-c">
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<pre class="de1"><span class="co2">#include <assert.h></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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<span class="co1">// 测试数学是否正常工作</span>
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static_assert<span class="br0">(</span><span class="nu0">2</span> <span class="sy2">+</span> <span class="nu0">2</span> <span class="sy1">==</span> <span class="nu0">4</span>, <span class="st0">"Whoa dude!"</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 或 _Static_assert(...</span>
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<span class="co1">// 这会在编译时产生错误。</span>
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static_assert<span class="br0">(</span><span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">int</span><span class="br0">)</span> <span class="sy1"><</span> <span class="kw4">sizeof</span><span class="br0">(</span><span class="kw4">char</span><span class="br0">)</span>,
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<span class="st0">"this program requires that int is less than char"</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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</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-17">
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<ul>
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<li>C17 标准（ISO/IEC 9899:2018）：</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>6.7.10 Static assertions (p: 105)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>7.2 Diagnostics <assert.h> (p: 135)</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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<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>6.7.10 Static assertions (p: 145)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>7.2 Diagnostics <assert.h> (p: 186-187)</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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<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="c-error-assert.html"><span class="t-lines"><span>assert</span></span></a></div>
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</div>
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</td>
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<td>若用户指定的条件非<span class="t-c"><span class="mw-geshi c source-c"><span class="kw2">true</span></span></span>，则异常终止程序。可以在发行版本禁用。<br />
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<span class="t-mark">(宏函数)</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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</div>
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</div>
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</div>
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</body>
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</html>
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