113 lines
7.4 KiB
HTML
113 lines
7.4 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>文件名和行信息</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_preprocessor_line 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">文件名和行信息</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-preprocessor.html">preprocessor</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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<p>在预处理器中更改当前行号和文件名。</p>
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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>#line</b></code> <span class="t-spar">行号</span></td>
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<td>(1)</td>
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<td class="t-sdsc-nopad"></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>#line</b></code> <span class="t-spar">行号</span> <code><b>"</b></code><span class="t-spar">文件名</span><code><b>"</b></code></td>
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<td>(2)</td>
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<td class="t-sdsc-nopad"></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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<h3><span class="mw-headline" id=".E8.A7.A3.E9.87.8A">解释</span></h3>
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<div class="t-li1"><span class="t-li">1)</span> 更改当前预处理器行号为 <span class="t-spar">行号</span> 。从此点开始，宏 <span class="t-c"><span class="mw-geshi c source-c">__LINE__</span></span> 的出现会展开成 <span class="t-spar">行号</span> 加上自此遇到的实际代码行数。</div>
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<div class="t-li1"><span class="t-li">2)</span> 亦将当前预处理器文件名更改为 <span class="t-spar">文件名</span> 。此点后宏 <span class="t-c"><span class="mw-geshi c source-c">__FILE__</span></span> 的每次出现将生成 <span class="t-spar">文件名</span> 。</div>
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<p>任何预处理器记号（宏常量及表达式）都允许出现为 <code>#line</code> 的参数，只要它们展开成合法的十进制整数，可以后随一个合法的字符串。</p>
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<p><span class="t-spar">行号</span> 必须是至少有一个十进制位的序列（否则程序为病式），并且始终按十进制转译（即使它以 <code>0</code> 开始）。</p>
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<p>若 <span class="t-spar">行号</span> 为 0 或大于 <span class="t-rev-inl t-until-c99"><span>32767</span> <span><span class="t-mark-rev t-until-c99">(C99 前)</span></span></span><span class="t-rev-inl t-since-c99"><span>2147483647</span> <span><span class="t-mark-rev t-since-c99">(C99 起)</span></span></span> ，则行为未定义。</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>一些自动代码生成工具从以其他语言书写的文件产生 C 源文件，它们会使用此指令。该情况下，它们可能插入引用原始（人类可读）源文件的行号和文件名的 <code>#line</code> 指令到生成的 C 文件中。</p>
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<p>后随指令 <span class="t-c"><span class="mw-geshi c source-c"><span class="co2">#line __LINE__</span></span></span> 的行号是实现定义的（该情况下 <span class="t-c"><span class="mw-geshi c source-c">__LINE__</span></span> 能展开成二个可选值：迄今为止所见的换行符数，或迄今为止所见的换行符数加上结束 <code>#line</code> 指令的换行符）</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="co2">#define FNAME "test.c"</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="co2">#line 777 FNAME</span>
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<a href="c-error-assert.html"><span class="kw407">assert</span></a><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">5</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">test: test.c:777: int main(): Assertion `2+2 == 5' failed.</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>6.10.4 Line control (p: 173)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</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>6.10.4 Line control (p: 158)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</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>3.8.4 Line control</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"></table>
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</div>
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</div>
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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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