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New issue from Dietmar Kühl: Missing rvalue reference qualification f… #476

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jwakely merged 2 commits into from
Sep 1, 2025
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New issue from Dietmar Kühl: Missing rvalue reference qualification f… #476

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New issue from Dietmar Kühl: Missing rvalue reference qualification f…
dietmarkuehl Aug 31, 2025
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jwakely Sep 1, 2025
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55 changes: 55 additions & 0 deletions xml/issue4342.xml
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Original file line number Diff line number Diff line change
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<?xml version='1.0' encoding='utf-8' standalone='no'?>
<!DOCTYPE issue SYSTEM "lwg-issue.dtd">

<issue num="4342" status="New">
<title>Missing rvalue reference qualification for <code>task_scheduler::ts-sender::connect()</code></title>
<section><sref ref="[exec.task.scheduler]"/></section>
<submitter>Dietmar Kühl</submitter>
<date>01 Sep 2025</date>
<priority>99</priority>

<discussion>
<p>
The result of <code>schedule(sched)</code> for a scheduler
<code>sched</code> is only required to be movable. An object of
this type may need to be forwarded to an operation state constructor
by <code>task_scheduler::<i>ts-sender</i>::connect</code>. Thus,
this function should be qualified with an rvalue reference.
</p>
</discussion>

<resolution>
<p>
Add an rvalue qualifier to the declaration of <code>connect</code> in <a href="https://wg21.link/exec.task.scheduler#8">[exec.task.scheduler] paragraph 8</a>:
<blockquote>
<pre>
namespace std::execution {
class task_scheduler::ts-sender { // exposition only
public:
using sender_concept = sender_t;

template&lt;receiver Rcvr&gt;
<i>state</i>&lt;Rcvr&gt; connect(Rcvr&amp;&amp; rcvr)<ins> &amp;&amp;</ins>;
};
}
</pre>
</blockquote>
</p>
<p>
In the specification in <a href="https://wg21.link/exec.task.scheduler#10">[exec.task.scheduler] paragraph 10</a> add an rvalue qualifier to <code>connect</code>:
<blockquote>
<pre>
template&lt;receiver Rcvr&gt;
<i>state</i>&lt;Rcvr&gt; connect(Rcvr&amp;&amp; rcvr)<ins> &amp;&amp;</ins>;
</pre>
<p>-10- <i>Effects</i>: Let <i>r</i> be an object of a type that
models receiver and whose completion handlers result in invoking
the corresponding completion handlers of <code>rcvr</code> or copy thereof.
Returns an object of type <code><i>state</i>&lt;Rcvr&gt;</code> containing an operation state
object initialized with <code>connect(<i>SENDER</i>(*this), std::move(<i>r</i>))</code>.
</p>
</blockquote>
</p>
</resolution>

</issue>