156 lines
11 KiB
HTML
156 lines
11 KiB
HTML
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<title>std::set_new_handler</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_memory_new_set_new_handler skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>set_new_handler</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-memory.html">memory</a>‎ | <a href="cpp-memory-new.html">new</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-new.html"><new></a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-memory-new-new_handler.html"><span class="kw697">std::<span class="me2">new_handler</span></span></a> set_new_handler<span class="br0">(</span> <a href="cpp-memory-new-new_handler.html"><span class="kw697">std::<span class="me2">new_handler</span></span></a> new_p <span class="br0">)</span> <span class="kw1">throw</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-until-cxx11">(C++11 前)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-memory-new-new_handler.html"><span class="kw697">std::<span class="me2">new_handler</span></span></a> set_new_handler<span class="br0">(</span> <a href="cpp-memory-new-new_handler.html"><span class="kw697">std::<span class="me2">new_handler</span></span></a> new_p <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>令 <code>new_p</code> 成为新的全局 new 处理函数并返回先前安装的 new 处理函数。</p>
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<p><i>new 处理函数</i>是为<a href="cpp-memory-new-operator_new.html">分配函数</a>在凡是内存分配尝试失败时调用的函数。其目的是三件事之一：</p>
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<div class="t-li1"><span class="t-li">1)</span> 令更多内存可用</div>
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<div class="t-li1"><span class="t-li">2)</span> 终止程序（例如通过调用 <span class="t-lc"><a href="cpp-error-terminate.html">std::terminate</a></span></div>
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<div class="t-li1"><span class="t-li">3)</span> 抛出 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 或自 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 导出的类型的异常。</div>
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<p>默认实现抛 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 。用户可以安装自己的 <i>new 处理函数</i>，并可以提供异于默认者的行为。</p>
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<p>若 <i>new 处理函数</i>返回，则分配函数重复先前失败的分配，并若分配再次失败则调用 <i>new 处理函数</i>。为终止循环， <i>new 处理函数</i>可调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">set_new_handler</span><span class="br0">(</span>nullptr<span class="br0">)</span></span></span> ：若在失败的分配尝试后，分配函数发现 <span class="t-lc"><a href="cpp-memory-new-get_new_handler.html">std::get_new_handler</a></span> 返回空指针值，则它会试图抛出 <span class="t-lc"><a href="cpp-memory-new-bad_alloc.html">std::bad_alloc</a></span> 。</p>
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<p>在程序启动时， <i>new 处理函数</i>是空指针。</p>
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<p>此函数是线程安全的。每个对 <code>std::set_new_handler</code> 的调用<i>同步于</i>（见 <span class="t-lc"><a href="cpp-atomic-memory_order.html">std::memory_order</a></span> ）后继的 <code>std::set_new_handler</code> 和 <span class="t-lc"><a href="cpp-memory-new-get_new_handler.html">std::get_new_handler</a></span> 调用。</p>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>new_p</td>
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<td>-</td>
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<td><span class="t-lc"><a href="cpp-memory-new-new_handler.html">std::new_handler</a></span> 类型的指向函数指针，或空指针</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>先前安装的 new 处理函数，或若无安装者则返回空指针。</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="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <new></span>
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<span class="kw4">void</span> handler<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Memory allocation failed, terminating<span class="es1">\n</span>"</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">set_new_handler</span><span class="br0">(</span>nullptr<span class="br0">)</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="br0">)</span>
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<span class="br0">{</span>
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std<span class="sy4">::</span><span class="me2">set_new_handler</span><span class="br0">(</span>handler<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">try</span> <span class="br0">{</span>
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<span class="kw1">while</span> <span class="br0">(</span><span class="kw2">true</span><span class="br0">)</span> <span class="br0">{</span>
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new <span class="kw4">int</span><span class="br0">[</span>100000000ul<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="kw1">catch</span> <span class="br0">(</span><span class="kw4">const</span> <a href="cpp-memory-new-bad_alloc.html"><span class="kw692">std::<span class="me2">bad_alloc</span></span></a><span class="sy3">&</span> e<span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> e.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span></pre></div>
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<p>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">Memory allocation failed, terminating
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std::bad_alloc</pre></div>
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</div>
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</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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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-new-operator_new.html"><span class="t-lines"><span>operator new</span><span>operator new[]</span></span></a></div>
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</div>
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</td>
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<td>分配函数<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-new-get_new_handler.html"><span class="t-lines"><span>get_new_handler</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>获得当前的 new 处理函数<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-new-new_handler.html"><span class="t-lines"><span>new_handler</span></span></a></div>
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</div>
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</td>
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<td>new 处理函数的函数指针类型<br />
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<span class="t-mark">(typedef)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-memory-new-bad_alloc.html"><span class="t-lines"><span>bad_alloc</span></span></a></div>
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</div>
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</td>
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<td>内存分配失败时抛出的异常<br />
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<span class="t-mark">(类)</span></td>
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</div>
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<div class="visualClear"></div>
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</div>
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