159 lines
10 KiB
HTML
159 lines
10 KiB
HTML
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<title>标准库头文件 <cstddef></title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_header_cstddef skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">标准库头文件</span> <cstddef></h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-header.html">header</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>此头文件原作为 <code><b><stddef.h></b></code> 存在于 C 标准库。</p>
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<p>此头文件是<a href="cpp-utility.html">工具</a>库的一部分。</p>
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<table class="t-dsc-begin">
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<tr>
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<td colspan="2">
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<h3><span class="mw-headline" id=".E5.AE.8F">宏</span></h3>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-NULL.html"><span class="t-lines"><span>NULL</span></span></a></div>
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</div>
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</td>
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<td>实现定义的空指针常量<br />
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<span class="t-mark">(宏常量)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-offsetof.html"><span class="t-lines"><span>offsetof</span></span></a></div>
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</div>
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</td>
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<td>从标准布局类型的起始到其指定成员的字节偏移量<br />
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<span class="t-mark">(宏函数)</span></td>
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</tr>
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<tr>
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<td colspan="2">
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<h3><span class="mw-headline" id=".E7.B1.BB.E5.9E.8B">类型</span></h3>
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</td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-size_t.html"><span class="t-lines"><span>size_t</span></span></a></div>
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</div>
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</td>
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<td><a href="cpp-language-sizeof.html"><tt>sizeof</tt></a> 运算符返回的无符号整数类型<br />
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<span class="t-mark">(typedef)</span></td>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-ptrdiff_t.html"><span class="t-lines"><span>ptrdiff_t</span></span></a></div>
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</div>
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</td>
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<td>在两个指针相减时返回的有符号整数类型<br />
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<span class="t-mark">(typedef)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-nullptr_t.html"><span class="t-lines"><span>nullptr_t</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>空指针字面量 <a href="cpp-language-nullptr.html"><tt>nullptr</tt></a> 的类型<br />
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<span class="t-mark">(typedef)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-max_align_t.html"><span class="t-lines"><span>max_align_t</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>具有不小于任何基础类型的内存对齐需求的平凡类型<br />
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<span class="t-mark">(typedef)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-byte.html"><span class="t-lines"><span>byte</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>字节类型<br />
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<span class="t-mark">(枚举)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.A6.82.E8.A6.81">概要</span></h3>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="kw1">namespace</span> std <span class="br0">{</span>
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<span class="kw1">using</span> ptrdiff_­t <span class="sy1">=</span> <span class="coMULTI">/* 见描述 */</span><span class="sy4">;</span>
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<span class="kw1">using</span> size_­t <span class="sy1">=</span> <span class="coMULTI">/* 见描述 */</span><span class="sy4">;</span>
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<span class="kw1">using</span> max_­align_­t <span class="sy1">=</span> <span class="coMULTI">/* 见描述 */</span><span class="sy4">;</span>
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<span class="kw1">using</span> nullptr_­t <span class="sy1">=</span> decltype<span class="br0">(</span>nullptr<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw2">enum</span> <span class="kw1">class</span> byte <span class="sy4">:</span> <span class="kw4">unsigned</span> <span class="kw4">char</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="co1">// 字节类型运算</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> IntType<span class="sy1">></span>
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<span class="kw4">constexpr</span> byte<span class="sy3">&</span> operator<span class="sy1"><<=</span><span class="br0">(</span>byte<span class="sy3">&</span> b, IntType shift<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> IntType<span class="sy1">></span>
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<span class="kw4">constexpr</span> byte operator<span class="sy1"><<</span><span class="br0">(</span>byte b, IntType shift<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> IntType<span class="sy1">></span>
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<span class="kw4">constexpr</span> byte<span class="sy3">&</span> operator<span class="sy1">>>=</span><span class="br0">(</span>byte<span class="sy3">&</span> b, IntType shift<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> IntType<span class="sy1">></span>
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<span class="kw4">constexpr</span> byte operator<span class="sy1">>></span><span class="br0">(</span>byte b, IntType shift<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte<span class="sy3">&</span> operator<span class="sy3">|</span><span class="sy1">=</span><span class="br0">(</span>byte<span class="sy3">&</span> l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte operator<span class="sy3">|</span><span class="br0">(</span>byte l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte<span class="sy3">&</span> operator<span class="sy3">&</span><span class="sy1">=</span><span class="br0">(</span>byte<span class="sy3">&</span> l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte operator<span class="sy3">&</span><span class="br0">(</span>byte l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte<span class="sy3">&</span> operator<span class="sy3">^</span><span class="sy1">=</span><span class="br0">(</span>byte<span class="sy3">&</span> l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte operator<span class="sy3">^</span><span class="br0">(</span>byte l, byte r<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw4">constexpr</span> byte operator~<span class="br0">(</span>byte b<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> IntType<span class="sy1">></span>
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<span class="kw4">constexpr</span> IntType to_integer<span class="br0">(</span>byte b<span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="co2">#define NULL /* 见描述 */</span>
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<span class="co2">#define offsetof(P, D) /* 见描述 */</span></pre></div>
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</div>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<ul>
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<li><span class="t-lc"><a href="cpp-types-NULL.html">NULL</a></span> 亦定义于下列头文件:
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<ul>
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<li><a href="cpp-header-clocale.html"><tt><clocale></tt></a></li>
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<li><a href="cpp-header-ctime.html"><tt><ctime></tt></a></li>
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<li><a href="cpp-header-cstring.html"><tt><cstring></tt></a></li>
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<li><a href="cpp-header-cstdio.html"><tt><cstdio></tt></a></li>
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<li><a href="cpp-header-cstdlib.html"><tt><cstdlib></tt></a></li>
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<li><a href="cpp-header-cwchar.html"><tt><cwchar></tt></a></li>
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</ul>
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</li>
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<li><span class="t-lc"><a href="cpp-types-size_t.html">std::size_t</a></span> 亦定义于下列头文件:
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<ul>
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<li><a href="cpp-header-ctime.html"><tt><ctime></tt></a></li>
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<li><a href="cpp-header-cstring.html"><tt><cstring></tt></a></li>
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<li><a href="cpp-header-cstdio.html"><tt><cstdio></tt></a></li>
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<li><a href="cpp-header-cwchar.html"><tt><cwchar></tt></a></li>
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<li><a href="cpp-header-cuchar.html"><tt><cuchar></tt></a> <span class="t-mark-rev t-since-cxx17">(C++17 起)</span></li>
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</ul>
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</li>
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</ul>
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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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