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<div id="contentSub"><span class="subpages">&lt; <a href="c.html">c</a>&lrm; | <a href="c-variadic.html">variadic</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code>&lt;stdarg.h&gt;</code></div>
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<div><span class="mw-geshi c source-c"><span class="kw4">void</span> va_copy<span class="br0">(</span> va_list dest, va_list src <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-c99">(C99 &#36215;)</span></td>
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<p><code>va_copy</code> &#23439;&#25226; <code>src</code> &#22797;&#21046;&#21040; <code>dest</code> &#12290;</p>
<p>&#22312;&#20989;&#25968;&#36820;&#22238;&#65292;&#25110; <code>dest</code> &#30340;&#20219;&#20309;&#20877;&#21021;&#22987;&#21270;&#65288;&#36890;&#36807;&#35843;&#29992; <span class="t-lc">va_start</span> &#25110; <span class="t-lc">va_copy</span> &#65289;&#21069;&#65292;&#24212;&#35813;&#23545; <code>dest</code> &#35843;&#29992; <span class="t-lc">va_end</span> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>dest</td>
<td>-</td>
<td>&#24453;&#21021;&#22987;&#21270;&#30340; <span class="t-lc">va_list</span>&#31867;&#22411;&#23545;&#35937;</td>
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<td>src</td>
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<td>&#23558;&#29992;&#20197;&#21021;&#22987;&#21270; <code>dest</code> &#30340;&#28304; <span class="t-lc">va_list</span></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=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;stdio.h&gt;</span>
<span class="co2">#include &lt;stdarg.h&gt;</span>
<span class="co2">#include &lt;math.h&gt;</span>
<span class="kw4">double</span> sample_stddev<span class="br0">(</span><span class="kw4">int</span> count, ...<span class="br0">)</span>
<span class="br0">{</span>
<span class="coMULTI">/* &#20197; args1 &#35745;&#31639;&#24179;&#22343;&#25968;&#12290; */</span>
<span class="kw4">double</span> sum <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
va_list args1<span class="sy4">;</span>
va_start<span class="br0">(</span>args1, count<span class="br0">)</span><span class="sy4">;</span>
va_list args2<span class="sy4">;</span>
va_copy<span class="br0">(</span>args2, args1<span class="br0">)</span><span class="sy4">;</span> <span class="coMULTI">/* &#22797;&#21046; va_list &#23545;&#35937; */</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>
<span class="kw4">double</span> num <span class="sy1">=</span> va_arg<span class="br0">(</span>args1, <span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span>
sum <span class="sy2">+</span><span class="sy1">=</span> num<span class="sy4">;</span>
<span class="br0">}</span>
va_end<span class="br0">(</span>args1<span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">double</span> mean <span class="sy1">=</span> sum <span class="sy2">/</span> count<span class="sy4">;</span>
<span class="coMULTI">/* &#20197;args2&#21644;&#24179;&#22343;&#25968;&#35745;&#31639;&#26631;&#20934;&#24046;&#12290; */</span>
<span class="kw4">double</span> sum_sq_diff <span class="sy1">=</span> <span class="nu0">0</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>
<span class="kw4">double</span> num <span class="sy1">=</span> va_arg<span class="br0">(</span>args2, <span class="kw4">double</span><span class="br0">)</span><span class="sy4">;</span>
sum_sq_diff <span class="sy2">+</span><span class="sy1">=</span> <span class="br0">(</span>num<span class="sy2">-</span>mean<span class="br0">)</span> <span class="sy2">*</span> <span class="br0">(</span>num<span class="sy2">-</span>mean<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
va_end<span class="br0">(</span>args2<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> <a href="c-numeric-math-sqrt.html"><span class="kw665">sqrt</span></a><span class="br0">(</span>sum_sq_diff <span class="sy2">/</span> count<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">&quot;%f<span class="es1">\n</span>&quot;</span>, sample_stddev<span class="br0">(</span><span class="nu0">4</span>, <span class="nu16">25.0</span>, <span class="nu16">27.3</span>, <span class="nu16">26.9</span>, <span class="nu16">25.7</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<pre class="de1">0.920258</pre></div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">&#24341;&#29992;</span></h3>
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<li>C11 &#26631;&#20934;&#65288;ISO/IEC 9899:2011&#65289;&#65306;</li>
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<li>7.16.1.2 The va_copy macro (p: 270)</li>
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<li>C99 &#26631;&#20934;&#65288;ISO/IEC 9899:1999&#65289;&#65306;</li>
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<li>7.15.1.2 The va_copy macro (p: 250)</li>
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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><a href="c-variadic-va_start.html"><span class="t-lines"><span>va_start</span></span></a></div>
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<td>&#20196;&#20989;&#25968;&#24471;&#20197;&#35775;&#38382;&#21487;&#21464;&#21442;&#25968;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div><a href="c-variadic-va_arg.html"><span class="t-lines"><span>va_arg</span></span></a></div>
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<td>&#35775;&#38382;&#19979;&#19968;&#20010;&#20989;&#25968;&#21487;&#21464;&#21442;&#25968;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div><a href="c-variadic-va_end.html"><span class="t-lines"><span>va_end</span></span></a></div>
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<td>&#32467;&#26463;&#20989;&#25968;&#21487;&#21464;&#21442;&#25968;&#30340;&#34892;&#31243;<br />
<span class="t-mark">(&#23439;&#20989;&#25968;)</span></td>
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<div><a href="c-variadic-va_list.html"><span class="t-lines"><span>va_list</span></span></a></div>
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<td>&#20445;&#26377; va_start &#12289; va_arg &#12289; va_end &#21450; va_copy &#25152;&#38656;&#20449;&#24687;<br />
<span class="t-mark">(typedef)</span></td>
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