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Expand 4172 to include shared_lock::operator=(shared_lock&&) #449

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Merged
jwakely merged 1 commit into from
Nov 18, 2024
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Expand 4172 to include shared_lock::operator=(shared_lock&&) #449

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34 changes: 33 additions & 1 deletion xml/issue4172.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@

<issue num="4172" status="New">
<title>unique_lock self-move-assignment is broken</title>
<section><sref ref="[thread.lock.unique.cons]"/></section>
<section><sref ref="[thread.lock.unique.cons]"/> <sref ref="[thread.lock.shared.cons]"/></section>
<submitter>Casey Carter</submitter>
<date>13 Nov 2024</date>
<priority>99</priority>
Expand All @@ -28,6 +28,11 @@ from self-move-assignment as of LWG <iref ref="2839"/>.
<p>
Also, the move assignment operator doesn't specify what it returns.
</p>

<note>2024-11-18; Casey expands the PR to cover `shared_lock`</note>
<p>
`shared_lock` has the same problems, and can be fixed in the same way.
</p>
</discussion>

<resolution>
Expand Down Expand Up @@ -99,6 +104,33 @@ In this case, *this will own the mutex after the assignment and u will not.
</p>
</blockquote>
</li>

<li>
<p>
Modify <sref ref="[thread.lock.shared.cons]"/> as follows:
</p>

<blockquote>
<pre><code>
shared_lock&amp; operator=(shared_lock&amp;&amp; sl) noexcept;
</code></pre>
<p>
-17- <i>Effects</i>:
<del>If `owns` calls `pm->unlock_shared()`.</del>
<ins>Equivalent to: `shared_lock{std::move(sl)}.swap(*this)`.</ins>
</p>
<p>
<ins>-?- <i>Returns</i>: `*this`.</ins>
</p>
<p>
<del>-18- <i>Postconditions</i>:
`pm == sl_p.pm` and `owns == sl_p.owns`
(where `sl_p` is the state of `sl` just prior to this assignment),
`sl.pm == nullptr` and `sl.owns == false`.
</del>
</p>
</blockquote>
</li>
</ol>

</resolution>
Expand Down