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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>rethrow_if_nested</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-error.html">error</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-exception.html">&lt;exception&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> E <span class="sy1">&gt;</span><br />
<span class="kw4">void</span> rethrow_if_nested<span class="br0">(</span> <span class="kw4">const</span> E<span class="sy3">&amp;</span> e <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#33509; <code>E</code> &#19981;&#26159;&#22810;&#24577;&#31867;&#31867;&#22411;&#65292;&#25110;&#33509; <span class="t-lc"><a href="cpp-error-nested_exception.html">std::nested_exception</a></span> &#26159; <code>E</code> &#30340;&#19981;&#21487;&#35775;&#38382;&#25110;&#26377;&#27495;&#20041;&#22522;&#31867;&#65292;&#21017;&#26080;&#25928;&#26524;&#12290;</p>
<p>&#21542;&#21017;&#65292;&#36827;&#34892;</p>
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<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">if</span> <span class="br0">(</span><span class="kw4">auto</span> p <span class="sy1">=</span> <span class="kw1">dynamic_cast</span><span class="sy1">&lt;</span><span class="kw4">const</span> <a href="cpp-error-nested_exception.html"><span class="kw780">std::<span class="me2">nested_exception</span></span></a><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><a href="cpp-memory-addressof.html"><span class="kw757">std::<span class="me2">addressof</span></span></a><span class="br0">(</span>e<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
p<span class="sy2">-</span><span class="sy1">&gt;</span>rethrow_nested<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>e</td>
<td>-</td>
<td>&#35201;&#37325;&#25243;&#30340;&#24322;&#24120;&#23545;&#35937;</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>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">&#21487;&#33021;&#30340;&#23454;&#29616;</span></h3>
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<div class="cpp source-cpp">
<pre class="de1"><span class="kw1">namespace</span> details <span class="br0">{</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> E<span class="sy1">&gt;</span>
<span class="kw1">struct</span> can_dynamic_cast
<span class="sy4">:</span> <a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1">&lt;</span><span class="kw4">bool</span>,
<a href="cpp-types-is_polymorphic.html"><span class="kw510">std::<span class="me2">is_polymorphic</span></span></a><span class="sy1">&lt;</span>E<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span> <span class="sy3">&amp;&amp;</span>
<span class="br0">(</span><span class="sy3">!</span><a href="cpp-types-is_base_of.html"><span class="kw590">std::<span class="me2">is_base_of</span></span></a><span class="sy1">&lt;</span><a href="cpp-error-nested_exception.html"><span class="kw780">std::<span class="me2">nested_exception</span></span></a>, E<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span> <span class="sy3">||</span>
<a href="cpp-types-is_convertible.html"><span class="kw592">std::<span class="me2">is_convertible</span></span></a><span class="sy1">&lt;</span>E<span class="sy2">*</span>, <a href="cpp-error-nested_exception.html"><span class="kw780">std::<span class="me2">nested_exception</span></span></a><span class="sy2">*</span><span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">value</span><span class="br0">)</span>
<span class="sy1">&gt;</span> <span class="br0">{</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span>
<span class="kw4">void</span> rethrow_if_nested_impl<span class="br0">(</span><span class="kw4">const</span> T<span class="sy3">&amp;</span> e, <a href="cpp-types-integral_constant.html"><span class="kw649">std::<span class="me2">true_type</span></span></a><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">if</span><span class="br0">(</span><span class="kw4">auto</span> nep <span class="sy1">=</span> <span class="kw1">dynamic_cast</span><span class="sy1">&lt;</span><span class="kw4">const</span> <a href="cpp-error-nested_exception.html"><span class="kw780">std::<span class="me2">nested_exception</span></span></a><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><a href="cpp-memory-addressof.html"><span class="kw757">std::<span class="me2">addressof</span></span></a><span class="br0">(</span>e<span class="br0">)</span><span class="br0">)</span><span class="br0">)</span>
nep<span class="sy2">-</span><span class="sy1">&gt;</span>rethrow_nested<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">template</span> <span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span>
<span class="kw4">void</span> rethrow_if_nested_impl<span class="br0">(</span><span class="kw4">const</span> T<span class="sy3">&amp;</span>, <a href="cpp-types-integral_constant.html"><span class="kw650">std::<span class="me2">false_type</span></span></a><span class="br0">)</span> <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">class</span> T<span class="sy1">&gt;</span>
<span class="kw4">void</span> rethrow_if_nested<span class="br0">(</span><span class="kw4">const</span> T<span class="sy3">&amp;</span> t<span class="br0">)</span><span class="br0">{</span>
details<span class="sy4">::</span><span class="me2">rethrow_if_nested_impl</span><span class="br0">(</span>t, details<span class="sy4">::</span><span class="me2">can_dynamic_cast</span><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-template-editlink" style=""></div>
<div class="t-example">
<p>&#28436;&#31034;&#26500;&#36896;&#24182;&#36890;&#36807; nested_exception &#23545;&#35937;&#36882;&#24402;</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;stdexcept&gt;</span>
<span class="co2">#include &lt;exception&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="co2">#include &lt;fstream&gt;</span>
<span class="co1">// &#25171;&#21360;&#24322;&#24120;&#30340;&#35299;&#37322;&#24615;&#23383;&#31526;&#20018;&#12290;&#33509;&#24322;&#24120;&#20869;&#23884;&#65292;&#21017;&#36882;&#24402;&#25171;&#21360;&#20854;&#20445;&#26377;&#30340;&#24322;&#24120;&#30340;&#35299;&#37322;</span>
<span class="kw4">void</span> print_exception<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">&amp;</span> e, <span class="kw4">int</span> level <span class="sy1">=</span> <span class="nu0">0</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-io-cerr.html"><span class="kw1759">std::<span class="me2">cerr</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="br0">(</span>level, <span class="st0">&#39; &#39;</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;exception: &quot;</span> <span class="sy1">&lt;&lt;</span> e.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="kw1">try</span> <span class="br0">{</span>
std<span class="sy4">::</span><span class="me2">rethrow_if_nested</span><span class="br0">(</span>e<span class="br0">)</span><span class="sy4">;</span>
<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">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
print_exception<span class="br0">(</span>e, level<span class="sy2">+</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
<span class="br0">}</span>
<span class="co1">// &#31034;&#20363;&#20989;&#25968;&#65292;&#25429;&#25417;&#24322;&#24120;&#24182;&#23558;&#20854;&#21253;&#35013;&#20110; nested_exception</span>
<span class="kw4">void</span> open_file<span class="br0">(</span><span class="kw4">const</span> <a href="cpp-string-basic_string.html"><span class="kw1229">std::<span class="me2">string</span></span></a><span class="sy3">&amp;</span> s<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">try</span> <span class="br0">{</span>
<a href="cpp-io-basic_ifstream.html"><span class="kw1731">std::<span class="me2">ifstream</span></span></a> file<span class="br0">(</span>s<span class="br0">)</span><span class="sy4">;</span>
file.<span class="me1">exceptions</span><span class="br0">(</span><a href="cpp-io-ios_base-iostate.html"><span class="kw1699">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">failbit</span></span></a><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-error-throw_with_nested.html"><span class="kw781">std::<span class="me2">throw_with_nested</span></span></a><span class="br0">(</span> <a href="cpp-error-runtime_error.html"><span class="kw770">std::<span class="me2">runtime_error</span></span></a><span class="br0">(</span><span class="st0">&quot;Couldn&#39;t open &quot;</span> <span class="sy2">+</span> s<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="co1">// &#31034;&#20363;&#20989;&#25968;&#65292;&#25429;&#25417;&#24322;&#24120;&#24182;&#23558;&#20854;&#21253;&#35013;&#20110; nested_exception</span>
<span class="kw4">void</span> run<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">try</span> <span class="br0">{</span>
open_file<span class="br0">(</span><span class="st0">&quot;nonexistent.file&quot;</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-error-throw_with_nested.html"><span class="kw781">std::<span class="me2">throw_with_nested</span></span></a><span class="br0">(</span> <a href="cpp-error-runtime_error.html"><span class="kw770">std::<span class="me2">runtime_error</span></span></a><span class="br0">(</span><span class="st0">&quot;run() failed&quot;</span><span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="co1">// &#36816;&#34892;&#19978;&#36848;&#23454;&#20363;&#20989;&#25968;&#24182;&#25171;&#21360;&#25429;&#25417;&#30340;&#24322;&#24120;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">try</span> <span class="br0">{</span>
run<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<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">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
print_exception<span class="br0">(</span>e<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">exception: run() failed
exception: Couldn&#39;t open nonexistent.file
exception: basic_ios::clear</pre></div>
</div>
</div>
<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>
<div class="t-dsc-member-div">
<div><a href="cpp-error-nested_exception.html"><span class="t-lines"><span>nested_exception</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>&#29992;&#20110;&#25429;&#33719;&#24182;&#23384;&#20648;&#24403;&#21069;&#24322;&#24120;&#30340;&#28151;&#20837;&#31867;&#22411;<br />
<span class="t-mark">(&#31867;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-error-throw_with_nested.html"><span class="t-lines"><span>throw_with_nested</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>&#25243;&#20986;&#23454;&#21442;&#65292;&#24102;&#19978;&#28151;&#20837;&#30340; <span class="t-lc"><a href="cpp-error-nested_exception.html">std::nested_exception</a></span><br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
</tr>
</table>
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