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<!DOCTYPE html>
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<title>va_start</title>
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<h1 id="firstHeading" class="firstHeading">va_start</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-variadic.html">variadic</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-cstdarg.html">&lt;cstdarg&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> va_start<span class="br0">(</span> std<span class="sy4">::</span><span class="kw4">va_list</span> ap, parm_n <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p><code>va_start</code> &#23439;&#20801;&#35768;&#35775;&#38382;&#21518;&#38543;&#20855;&#21517;&#21442;&#25968; <code>parm_n</code> &#30340;&#21487;&#21464;&#21442;&#25968;&#12290;</p>
<p><code>va_start</code> &#24212;&#24403;&#22312;&#20219;&#20309;&#23545; <span class="t-lc"><a href="cpp-utility-variadic-va_arg.html">va_arg</a></span> &#30340;&#35843;&#29992;&#21069;&#65292;&#20197;&#21040;&#21512;&#27861; <span class="t-lc">std::va_list</span> &#23545;&#35937; <code>ap</code> &#30340;&#23454;&#20363;&#35843;&#29992;&#12290;</p>
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<p>&#33509; <code>parm_n</code> &#20026;<a href="cpp-language-parameter_pack.html#.E5.8C.85.E5.B1.95.E5.BC.80">&#21253;&#23637;&#24320;</a>&#25110;&#28304;&#33258; <a href="cpp-language-lambda.html#Lambda_.E6.8D.95.E8.8E.B7">lambda &#25429;&#33719;</a>&#30340;&#23454;&#20307;&#65292;&#21017;&#31243;&#24207;&#20026;&#38750;&#33391;&#26500;&#65292;&#19981;&#35201;&#27714;&#35786;&#26029;&#12290;</p>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#33509; <code>parm_n</code> &#20197;&#24341;&#29992;&#31867;&#22411;&#65292;&#25110;&#19982;&#26469;&#33258;<a href="cpp-language-variadic_arguments.html#.E9.BB.98.E8.AE.A4.E8.BD.AC.E6.8D.A2">&#40664;&#35748;&#21442;&#25968;&#25552;&#21319;</a>&#30340;&#32467;&#26524;&#19981;&#20860;&#23481;&#30340;&#31867;&#22411;&#22768;&#26126;&#65292;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
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<td>ap</td>
<td>-</td>
<td><span class="t-lc">std::va_list</span> &#31867;&#22411;&#30340;&#23454;&#20363;</td>
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<tr class="t-par">
<td>parm_n</td>
<td>-</td>
<td>&#39318;&#20010;&#21487;&#21464;&#21442;&#25968;&#21069;&#32039;&#25509;&#30340;&#20855;&#21517;&#21442;&#25968;</td>
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<h3><span class="mw-headline" id=".E5.B1.95.E5.BC.80.E5.80.BC">&#23637;&#24320;&#20540;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#35201;&#27714; <code>va_start</code> &#25903;&#25345;&#24102;&#37325;&#36733;&#30340; <code>operator&amp;</code> &#30340; <code>parm_n</code> &#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;cstdarg&gt;</span>
<span class="kw4">int</span> add_nums<span class="br0">(</span><span class="kw4">int</span> count, ...<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">int</span> result <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="kw4">va_list</span> args<span class="sy4">;</span>
va_start<span class="br0">(</span>args, count<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> i <span class="sy1">&lt;</span> count<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span> <span class="br0">{</span>
result <span class="sy2">+</span><span class="sy1">=</span> <a href="cpp-utility-variadic-va_arg.html"><span class="kw962">va_arg</span></a><span class="br0">(</span>args, <span class="kw4">int</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<a href="cpp-utility-variadic-va_end.html"><span class="kw963">va_end</span></a><span class="br0">(</span>args<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> result<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> add_nums<span class="br0">(</span><span class="nu0">4</span>, <span class="nu0">25</span>, <span class="nu0">25</span>, <span class="nu0">50</span>, <span class="nu0">50</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">150</pre></div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">&#32570;&#38519;&#25253;&#21578;</span></h3>
<p>&#19979;&#21015;&#26356;&#25913;&#34892;&#20026;&#30340;&#32570;&#38519;&#25253;&#21578;&#36861;&#28335;&#22320;&#24212;&#29992;&#20110;&#20197;&#21069;&#20986;&#29256;&#30340; C++ &#26631;&#20934;&#12290;</p>
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<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
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<tr>
<td><a rel="nofollow" class="external text" href="https://wg21.cmeerw.net/cwg/issue273">CWG 273</a></td>
<td>C++98</td>
<td>&#33509;&#37325;&#36733;&#20102;&#19968;&#20803; <code>operator&amp;</code> &#21017; <code>va_start</code> &#21487;&#33021;&#26080;&#27861;&#24037;&#20316;</td>
<td>&#21363;&#20351;&#37325;&#36733;&#20102; <code>operator&amp;</code> &#20063;&#35201;&#27714;&#23427;&#27491;&#30830;&#24037;&#20316;</td>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-variadic-va_arg.html"><span class="t-lines"><span>va_arg</span></span></a></div>
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</td>
<td>&#35775;&#38382;&#19979;&#19968;&#20010;&#21487;&#21464;&#20989;&#25968;&#23454;&#21442;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-variadic-va_end.html"><span class="t-lines"><span>va_end</span></span></a></div>
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<td>&#32467;&#26463;&#23545;&#21487;&#21464;&#20989;&#25968;&#23454;&#21442;&#30340;&#36941;&#21382;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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