124 lines
9.3 KiB
HTML
124 lines
9.3 KiB
HTML
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<title>std::exception_ptr</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_error_exception_ptr 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>exception_ptr</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-error.html">error</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-exception.html"><exception></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">typedef</span> <span class="coMULTI">/*unspecified*/</span> exception_ptr<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><code>std::exception_ptr</code> 是一个类可空指针的类型，管理已抛出并为 <span class="t-lc"><a href="cpp-error-current_exception.html">std::current_exception</a></span> 所捕捉的异常对象。 <code>std::exception_ptr</code> 的实例可传递给另一函数，可以在另一线程，在那里异常可能重抛并为 catch 子句所处理。</p>
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<p>默认构造的 <code>std::exception_ptr</code> 是空指针；它不指向异常对象。</p>
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<p>二个 <code>std::exception_ptr</code> 实例比较相等，仅若它们均为空或都指向同一异常对象。</p>
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<p><code>std::exception_ptr</code> 不可隐式转换为任何算术、枚举或指针类型。它可以按语境转换成 <code>bool</code> ，且若它为空则求值为 false ，否则为 true 。</p>
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<p>一个 <code>std::exception_ptr</code> 所引用的异常对象只要为至少一个 <code>std::exception_ptr</code> 所引用就保持合法： <code>std::exception_ptr</code> 是共享所有权的智能指针（注意：这附加于<a href="cpp-language-throw.html#.E5.BC.82.E5.B8.B8.E5.AF.B9.E8.B1.A1">异常对象生存期规则</a>）</p>
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<p><code>std::exception_ptr</code> 满足<a href="cpp-named_req-NullablePointer.html"><span style="font-style:italic">可空指针</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(NullablePointer)</span></a> 的要求。</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-template-editlink" style=""></div>
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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 <string></span>
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<span class="co2">#include <exception></span>
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<span class="co2">#include <stdexcept></span>
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<span class="kw4">void</span> handle_eptr<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">exception_ptr</span> eptr<span class="br0">)</span> <span class="co1">// 按值传递 ok</span>
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<span class="br0">{</span>
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<span class="kw1">try</span> <span class="br0">{</span>
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<span class="kw1">if</span> <span class="br0">(</span>eptr<span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-error-rethrow_exception.html"><span class="kw778">std::<span class="me2">rethrow_exception</span></span></a><span class="br0">(</span>eptr<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-error-exception.html"><span class="kw764">std::<span class="me2">exception</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> <span class="st0">"Caught exception <span class="es1">\"</span>"</span> <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">\"</span><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>
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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">exception_ptr</span> eptr<span class="sy4">;</span>
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<span class="kw1">try</span> <span class="br0">{</span>
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<a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="br0">(</span><span class="br0">)</span>.<span class="me1">at</span><span class="br0">(</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 这生成一个 std::out_of_range</span>
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<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>
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eptr <span class="sy1">=</span> <a href="cpp-error-current_exception.html"><span class="kw777">std::<span class="me2">current_exception</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 捕获</span>
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<span class="br0">}</span>
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handle_eptr<span class="br0">(</span>eptr<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="co1">// std::out_of_range 的析构函数调用于此，在 ept 析构时</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">Caught exception "basic_string::at"</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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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="cpp-error-make_exception_ptr.html"><span class="t-lines"><span>make_exception_ptr</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>从异常对象创建一个<span class="t-lc"><strong class="selflink">std::exception_ptr</strong></span><br />
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<span class="t-mark">(函数模板)</span></td>
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<div><a href="cpp-error-current_exception.html"><span class="t-lines"><span>current_exception</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>捕获当前异常到 <span class="t-lc"><strong class="selflink">std::exception_ptr</strong></span> 之中<br />
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<span class="t-mark">(函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-error-rethrow_exception.html"><span class="t-lines"><span>rethrow_exception</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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</td>
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<td>从一个 <span class="t-lc"><strong class="selflink">std::exception_ptr</strong></span> 抛出异常<br />
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<span class="t-mark">(函数)</span></td>
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