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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>noop_coroutine</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-coroutine.html">coroutine</a></span></div>
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<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-coroutine.html">&lt;coroutine&gt;</a></code></div>
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<div><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">noop_coroutine_handle</span> noop_coroutine<span class="br0">(</span><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-cxx20">(C++20 &#36215;)</span></td>
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<p>&#36820;&#22238;&#25351;&#20195;&#26080;&#25805;&#20316;&#21327;&#31243;&#30340;&#21327;&#31243;&#26564;&#12290;</p>
<p>&#33509;&#24050;&#26377;&#26080;&#25805;&#20316;&#21327;&#31243;&#30340;&#21327;&#31243;&#29366;&#24577;&#65292;&#21017;&#19981;&#25351;&#23450; <code>noop_coroutine</code> &#30340;&#21518;&#32493;&#35843;&#29992;&#26159;&#36820;&#22238;&#20808;&#21069;&#33719;&#24471;&#30340;&#21327;&#31243;&#26564;&#65292;&#36824;&#26159;&#25351;&#20195;&#26032;&#30340;&#26080;&#25805;&#20316;&#21327;&#31243;&#30340;&#21327;&#31243;&#29366;&#24577;&#30340;&#21327;&#31243;&#26564;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#25351;&#20195;&#26080;&#25805;&#20316;&#21327;&#31243;&#30340; <span class="t-lc">std::noop_coroutine_handle</span> &#12290;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#19981;&#21516;&#30340; <code>noop_coroutine</code> &#35843;&#29992;&#30340;&#36820;&#22238;&#20540;&#21487;&#33021;&#20063;&#21487;&#33021;&#19981;&#27604;&#36739;&#30456;&#31561;&#12290;</p>
<p><code>noop_coroutine</code> &#21487;&#20197;&#20165;&#36820;&#22238;&#25351;&#20195;&#21327;&#31243;&#29366;&#24577;&#23545;&#35937;&#30340; <code>noop_coroutine_handle</code> &#32780;&#26080;&#38656;&#24320;&#22987;&#21327;&#31243;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
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<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;coroutine&gt;</span>
<span class="co2">#include &lt;utility&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> T<span class="sy1">&gt;</span>
<span class="kw1">struct</span> task <span class="br0">{</span>
<span class="kw1">struct</span> promise_type <span class="br0">{</span>
<span class="kw4">auto</span> get_return_object<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">return</span> task<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>promise_type<span class="sy1">&gt;</span><span class="sy4">::</span><span class="me2">from_promise</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
std<span class="sy4">::</span><span class="me2">suspend_always</span> initial_suspend<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw1">struct</span> final_awaiter <span class="br0">{</span>
<span class="kw4">bool</span> await_ready<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">void</span> await_resume<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;&gt;</span> await_suspend<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>promise_type<span class="sy1">&gt;</span> h<span class="br0">)</span> <span class="br0">{</span>
<span class="co1">// &#22312;&#24403;&#21069;&#21327;&#31243;&#65288;&#20197; &#39;h&#39; &#25351;&#20195;&#65289;&#25191;&#34892;&#21363;&#23558;&#32467;&#26463;&#26102;&#35843;&#29992; final_awaiter::await_suspend &#12290;</span>
<span class="co1">// &#33509;&#24403;&#21069;&#21327;&#31243;&#34987;&#21478;&#19968;&#21327;&#31243;&#32463;&#30001; co_await get_task() &#24674;&#22797;&#65292;&#21017;&#23384;&#20648;&#21040;&#35813;&#21327;&#31243;&#30340;&#26564;</span>
<span class="co1">// &#20026; h.promise().previous &#12290;&#35813;&#24773;&#20917;&#19979;&#65292;&#36820;&#22238;&#26564;&#20197;&#24674;&#22797;&#20808;&#21069;&#30340;&#21327;&#31243;&#12290;</span>
<span class="co1">// &#21542;&#21017;&#36820;&#22238; noop_coroutine() &#65292;&#20854;&#24674;&#22797;&#19981;&#20570;&#20219;&#20309;&#20107;&#12290;</span>
<span class="kw4">auto</span> previous <span class="sy1">=</span> h.<span class="me1">promise</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">previous</span><span class="sy4">;</span>
<span class="kw1">if</span> <span class="br0">(</span>previous<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">return</span> previous<span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">else</span> <span class="br0">{</span>
<span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">noop_coroutine</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
final_awaiter final_suspend<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">void</span> unhandled_exception<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">throw</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">void</span> return_value<span class="br0">(</span>T value<span class="br0">)</span> <span class="br0">{</span> result <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>value<span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span>
T result<span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;&gt;</span> previous<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
task<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>promise_type<span class="sy1">&gt;</span> h<span class="br0">)</span> <span class="sy4">:</span> coro<span class="br0">(</span>h<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
task<span class="br0">(</span>task<span class="sy3">&amp;&amp;</span> t<span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span>
~task<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> coro.<span class="me1">destroy</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw1">struct</span> awaiter <span class="br0">{</span>
<span class="kw4">bool</span> await_ready<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="kw2">false</span><span class="sy4">;</span> <span class="br0">}</span>
T await_resume<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>coro.<span class="me1">promise</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">result</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">auto</span> await_suspend<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;&gt;</span> h<span class="br0">)</span> <span class="br0">{</span>
coro.<span class="me1">promise</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">previous</span> <span class="sy1">=</span> h<span class="sy4">;</span>
<span class="kw1">return</span> coro<span class="sy4">;</span>
<span class="br0">}</span>
std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>promise_type<span class="sy1">&gt;</span> coro<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
awaiter operator co_await<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> awaiter<span class="br0">{</span>coro<span class="br0">}</span><span class="sy4">;</span> <span class="br0">}</span>
T operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
coro.<span class="me1">resume</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw1">return</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>coro.<span class="me1">promise</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">result</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">private</span><span class="sy4">:</span>
std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>promise_type<span class="sy1">&gt;</span> coro<span class="sy4">;</span>
<span class="br0">}</span><span class="sy4">;</span>
task<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> get_random<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;in get_random()<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
co_return <span class="nu0">4</span><span class="sy4">;</span>
<span class="br0">}</span>
task<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> test<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
task<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v <span class="sy1">=</span> get_random<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
task<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> u <span class="sy1">=</span> get_random<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;in test()<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="kw4">int</span> x <span class="sy1">=</span> <span class="br0">(</span>co_await v <span class="sy2">+</span> co_await u<span class="br0">)</span><span class="sy4">;</span>
co_return x<span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span>
task<span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> t <span class="sy1">=</span> test<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="kw4">int</span> result <span class="sy1">=</span> t<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> result <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<div class="text source-text">
<pre class="de1">in test()
in get_random()
in get_random()
8</pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div><a href="cpp-coroutine-noop_coroutine_promise.html"><span class="t-lines"><span>noop_coroutine_promise</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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<td>&#29992;&#20110;&#26080;&#21487;&#35266;&#23519;&#20316;&#29992;&#30340;&#21327;&#31243;<br />
<span class="t-mark">(&#31867;)</span></td>
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<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-coroutine-coroutine_handle.html"><span class="t-lines"><span>noop_coroutine_handle</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">coroutine_handle</span><span class="sy1">&lt;</span>std<span class="sy4">::</span><span class="me2">noop_coroutine_promise</span><span class="sy1">&gt;</span></span></span> &#65292;&#26377;&#24847;&#29992;&#20110;&#25351;&#20195;&#26080;&#25805;&#20316;&#21327;&#31243;<br />
<span class="t-mark">(typedef)</span></td>
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