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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>align</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-memory.html">memory</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-memory.html">&lt;memory&gt;</a></code></div>
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<td></td>
<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><span class="sy2">*</span> align<span class="br0">(</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> alignment,<br /></span>
<p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> size,<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span class="kw4">void</span><span class="sy2">*</span><span class="sy3">&amp;</span> ptr,<br /></p>
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a><span class="sy3">&amp;</span> space <span class="br0">)</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#32473;&#23450;&#25351;&#38024; <code>ptr</code> &#25351;&#23450;&#22823;&#23567;&#20026; <code>space</code> &#30340;&#32531;&#20914;&#21306;&#65292;&#36820;&#22238;&#25353;&#25351;&#23450; <code>alignment</code> &#20026; <code>size</code> &#23383;&#33410;&#25968;&#23545;&#40784;&#30340;&#25351;&#38024;&#65292;&#24182;&#20943;&#23567; <code>space</code> &#21442;&#25968;&#23545;&#40784;&#25152;&#29992;&#30340;&#23383;&#33410;&#25968;&#12290;&#36820;&#22238;&#39318;&#20010;&#23545;&#40784;&#30340;&#22320;&#22336;&#12290;</p>
<p>&#20165;&#20197;&#32473;&#23450;&#23545;&#40784;&#37327;&#23545;&#40784;&#20837;&#32531;&#20914;&#21306;&#30340;&#25152;&#38656;&#23383;&#33410;&#25968;&#21512;&#36866;&#65292;&#20989;&#25968;&#25165;&#20250;&#20462;&#25913;&#25351;&#38024;&#12290;&#33509;&#32531;&#20914;&#21306;&#22826;&#23567;&#65292;&#21017;&#20989;&#25968;&#19981;&#20570;&#20219;&#20309;&#20107;&#24182;&#36820;&#22238; <span class="t-c"><span class="mw-geshi cpp source-cpp">nullptr</span></span> &#12290;</p>
<p>&#33509; <code>alignment</code> &#19981;&#26159;&#20108;&#30340;&#24130;&#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">
<tr class="t-par">
<td>alignment</td>
<td>-</td>
<td>&#27442;&#27714;&#30340;&#23545;&#40784;&#37327;</td>
</tr>
<tr class="t-par">
<td>size</td>
<td>-</td>
<td>&#35201;&#34987;&#23545;&#40784;&#30340;&#23384;&#20648;&#30340;&#22823;&#23567;</td>
</tr>
<tr class="t-par">
<td>ptr</td>
<td>-</td>
<td>&#25351;&#21521;&#33267;&#23569;&#26377; <code>space</code> &#23383;&#33410;&#30340;&#36830;&#32493;&#23384;&#20648;&#30340;&#25351;&#38024;</td>
</tr>
<tr class="t-par">
<td>space</td>
<td>-</td>
<td>&#35201;&#22312;&#20854;&#20013;&#25805;&#20316;&#30340;&#32531;&#20914;&#21306;&#30340;&#22823;&#23567;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p><code>ptr</code> &#30340;&#35843;&#25972;&#20540;&#65292;&#25110;&#33509;&#25552;&#20379;&#31354;&#38388;&#22826;&#23567;&#21017;&#20026;&#31354;&#25351;&#38024;&#20540;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<p>&#28436;&#31034;&#20351;&#29992; std::align &#22312;&#20869;&#23384;&#20013;&#25918;&#32622;&#19981;&#21516;&#31867;&#22411;&#30340;&#23545;&#35937;</p>
<div class="t-example-live-link"></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;memory&gt;</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> N<span class="sy1">&gt;</span>
<span class="kw1">struct</span> MyAllocator
<span class="br0">{</span>
<span class="kw4">char</span> data<span class="br0">[</span>N<span class="br0">]</span><span class="sy4">;</span>
<span class="kw4">void</span><span class="sy2">*</span> p<span class="sy4">;</span>
<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> sz<span class="sy4">;</span>
MyAllocator<span class="br0">(</span><span class="br0">)</span> <span class="sy4">:</span> p<span class="br0">(</span>data<span class="br0">)</span>, sz<span class="br0">(</span>N<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">typename</span> T<span class="sy1">&gt;</span>
T<span class="sy2">*</span> aligned_alloc<span class="br0">(</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> a <span class="sy1">=</span> alignof<span class="br0">(</span>T<span class="br0">)</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">if</span> <span class="br0">(</span>std<span class="sy4">::</span><span class="me2">align</span><span class="br0">(</span>a, sizeof<span class="br0">(</span>T<span class="br0">)</span>, p, sz<span class="br0">)</span><span class="br0">)</span>
<span class="br0">{</span>
T<span class="sy2">*</span> result <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span>T<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span>p<span class="br0">)</span><span class="sy4">;</span>
p <span class="sy1">=</span> <span class="br0">(</span><span class="kw4">char</span><span class="sy2">*</span><span class="br0">)</span>p <span class="sy2">+</span> sizeof<span class="br0">(</span>T<span class="br0">)</span><span class="sy4">;</span>
sz <span class="sy2">-</span><span class="sy1">=</span> sizeof<span class="br0">(</span>T<span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> result<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">return</span> nullptr<span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
MyAllocator<span class="sy1">&lt;</span><span class="nu0">64</span><span class="sy1">&gt;</span> a<span class="sy4">;</span>
<span class="co1">// &#20998;&#37197;&#19968;&#20010; char</span>
<span class="kw4">char</span><span class="sy2">*</span> p1 <span class="sy1">=</span> a.<span class="me1">aligned_alloc</span><span class="sy1">&lt;</span><span class="kw4">char</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>p1<span class="br0">)</span>
<span class="sy2">*</span>p1 <span class="sy1">=</span> <span class="st0">&#39;a&#39;</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;allocated a char at &quot;</span> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span><span class="kw4">void</span><span class="sy2">*</span><span class="br0">)</span>p1 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="co1">// &#20998;&#37197;&#19968;&#20010; int</span>
<span class="kw4">int</span><span class="sy2">*</span> p2 <span class="sy1">=</span> a.<span class="me1">aligned_alloc</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>p2<span class="br0">)</span>
<span class="sy2">*</span>p2 <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;allocated an int at &quot;</span> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span><span class="kw4">void</span><span class="sy2">*</span><span class="br0">)</span>p2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="co1">// &#20998;&#37197;&#19968;&#20010; int &#65292;&#23545;&#40784;&#20110; 32 &#23383;&#33410;&#36793;&#30028;</span>
<span class="kw4">int</span><span class="sy2">*</span> p3 <span class="sy1">=</span> a.<span class="me1">aligned_alloc</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="nu0">32</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>p3<span class="br0">)</span>
<span class="sy2">*</span>p3 <span class="sy1">=</span> <span class="nu0">2</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;allocated an int at &quot;</span> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span><span class="kw4">void</span><span class="sy2">*</span><span class="br0">)</span>p3 <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; (32 byte alignment)<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">allocated a char at 0x2ff21a08
allocated an int at 0x2ff21a0c
allocated an int at 0x2ff21a20 (32 byte alignment)</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>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
</tr>
<tr>
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2377">LWG 2377</a></td>
<td>C++11</td>
<td>&#35201;&#27714; <code>alignment</code> &#20026;&#22522;&#30784;&#25110;&#21463;&#25903;&#25345;&#30340;&#25193;&#23637;&#23545;&#40784;&#20540;</td>
<td>&#20165;&#38656;&#35201;&#20026;&#20108;&#30340;&#24130;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td><a href="cpp-language-alignof.html"><code>alignof</code> &#36816;&#31639;&#31526;</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td>
<td>&#26597;&#35810;&#31867;&#22411;&#30340;&#23545;&#40784;&#35201;&#27714;</td>
</tr>
<tr class="t-dsc">
<td><a href="cpp-language-alignas.html"><code>alignas</code> &#35828;&#26126;&#31526;</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td>
<td>&#25351;&#23450;&#35813;&#21464;&#37327;&#30340;&#23384;&#20648;&#24212;&#35813;&#25353;&#25351;&#23450;&#37327;&#23545;&#40784;</td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-types-aligned_storage.html"><span class="t-lines"><span>aligned_storage</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td>&#23450;&#20041;&#36866;&#20110;&#29992;&#20316;&#32473;&#23450;&#22823;&#23567;&#30340;&#31867;&#22411;&#30340;&#26410;&#21021;&#22987;&#21270;&#23384;&#20648;&#30340;&#31867;&#22411;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
</tr>
</table>
</div>
<div class="visualClear"></div>
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