122 lines
10 KiB
HTML
122 lines
10 KiB
HTML
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<title>C 属性： deprecated (C23 起)</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_language_attributes_deprecated skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">C 属性：</span> deprecated <span class="t-mark-rev t-since-c23">(C23 起)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-language.html">language</a>‎ | <a href="c-language-attributes.html">attributes</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>指示声明有此属性的名字或实体被<a href="https://en.wikipedia.org/wiki/Deprecation" class="extiw" title="enwiki:Deprecation">弃用</a>，即允许但因故不鼓励使用。</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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<td colspan="10" class="t-sdsc-sep"></td>
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<td><code><b>[[</b></code> <code><b>deprecated</b></code> <code><b>]]</b></code><br />
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<code><b>[[</b></code> <code><b>__deprecated__</b></code> <code><b>]]</b></code></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 class="t-sdsc">
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<td><code><b>[[</b></code> <code><b>deprecated</b></code> <code><b>(</b></code> <span class="t-spar">字符串字面量</span> <code><b>)</b></code> <code><b>]]</b></code><br />
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<code><b>[[</b></code> <code><b>__deprecated__</b></code> <code><b>(</b></code> <span class="t-spar">字符串字面量</span> <code><b>)</b></code> <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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</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">字符串字面量</span></td>
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<td>-</td>
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<td>能用于解释弃用的理由并/或提议代替用实体的文本</td>
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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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<p>指示允许使用声明带此属性的名字或实体，但因某原因不鼓励。编译器常对这些情况发出警告。若指定 <span class="t-spar">字符串字面量</span> ，则通常将它包含于警告中。</p>
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<p>下列名字或实体的声明中允许使用这个属性：</p>
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<ul>
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<li><a href="c-language-struct.html">结构体</a>/<a href="c-language-union.html">联合体</a>： <span class="t-c"><span class="mw-geshi c source-c"><span class="kw1">struct</span> <span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> S<span class="sy4">;</span></span></span> ，</li>
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<li><a href="c-language-typedef.html">typedef 名</a>： <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> <span class="kw1">typedef</span> S<span class="sy2">*</span> PS<span class="sy4">;</span></span></span> ，</li>
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<li>对象： <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> <span class="kw4">int</span> x<span class="sy4">;</span></span></span> ，</li>
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<li>结构体/联合体成员： <span class="t-c"><span class="mw-geshi c source-c"><span class="kw1">union</span> U <span class="br0">{</span> <span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> <span class="kw4">int</span> n<span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span></span></span> ，</li>
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<li><a href="c-language-function_definition.html">函数</a>： <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> <span class="kw4">void</span> f<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span><span class="sy4">;</span></span></span> ，</li>
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<li><a href="c-language-enum.html">枚举</a>： <span class="t-c"><span class="mw-geshi c source-c"><span class="kw2">enum</span> <span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> E <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span></span></span> ，</li>
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<li>枚举项： <span class="t-c"><span class="mw-geshi c source-c"><span class="kw2">enum</span> <span class="br0">{</span> A <span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span>, B <span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span> <span class="sy1">=</span> <span class="nu0">42</span> <span class="br0">}</span><span class="sy4">;</span></span></span> 。</li>
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</ul>
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<p>声明时未弃用的名字可被重声明为 <code>deprecated</code>。声明为 <code>deprecated</code> 的名字不能通过重声明它而不带此属性变为未弃用。</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 <stdio.h></span>
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<span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">]</span><span class="br0">]</span>
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<span class="kw4">void</span> TriassicPeriod<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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<a href="c-io-puts.html"><span class="kw836">puts</span></a><span class="br0">(</span><span class="st0">"Triassic Period: [251.9 - 208.5] million years ago."</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">(</span><span class="st0">"Use NeogenePeriod() instead."</span><span class="br0">)</span><span class="br0">]</span><span class="br0">]</span>
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<span class="kw4">void</span> JurassicPeriod<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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<a href="c-io-puts.html"><span class="kw836">puts</span></a><span class="br0">(</span><span class="st0">"Jurassic Period: [201.3 - 152.1] million years ago."</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">[</span><span class="br0">[</span>deprecated<span class="br0">(</span><span class="st0">"Use calcSomethingDifferently(int)."</span><span class="br0">)</span><span class="br0">]</span><span class="br0">]</span>
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<span class="kw4">int</span> calcSomething<span class="br0">(</span><span class="kw4">int</span> x<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> x <span class="sy2">*</span> <span class="nu0">2</span><span class="sy4">;</span>
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<span class="br0">}</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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TriassicPeriod<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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JurassicPeriod<span class="br0">(</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">Triassic Period: [251.9 - 208.5] million years ago.
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Jurassic Period: [201.3 - 152.1] million years ago.
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prog.c:23:5: warning: 'TriassicPeriod' is deprecated [-Wdeprecated-declarations]
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TriassicPeriod();
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^
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prog.c:3:3: note: 'TriassicPeriod' has been explicitly marked deprecated here
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[[deprecated]]
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^
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prog.c:24:5: warning: 'JurassicPeriod' is deprecated: Use NeogenePeriod() instead. [-Wdeprecated-declarations]
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JurassicPeriod();
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^
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prog.c:9:3: note: 'JurassicPeriod' has been explicitly marked deprecated here
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[[deprecated("Use NeogenePeriod() instead.")]]
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^
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2 warnings generated.</pre></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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