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<title>Issue 4024: Underspecified destruction of objects created in std::make_shared_for_overwrite/std::allocate_shared_for_overwrite</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#WP">WP</a> status.</em></p>
<h3 id="4024"><a href="lwg-defects.html#4024">4024</a>. Underspecified destruction of objects created in <code>std::make_shared_for_overwrite/std::allocate_shared_for_overwrite</code></h3>
<p><b>Section:</b> 20.3.2.2.7 <a href="https://wg21.link/util.smartptr.shared.create">[util.smartptr.shared.create]</a> <b>Status:</b> <a href="lwg-active.html#WP">WP</a>
 <b>Submitter:</b> Jiang An <b>Opened:</b> 2023-12-16 <b>Last modified:</b> 2024-11-28</p>
<p><b>Priority: </b>2
</p>
<p><b>View all other</b> <a href="lwg-index.html#util.smartptr.shared.create">issues</a> in [util.smartptr.shared.create].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#WP">WP</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Currently, only destructions of non-array (sub)objects created in <code>std::make_shared</code> and <code>std::allocate_shared</code> 
are specified in 20.3.2.2.7 <a href="https://wg21.link/util.smartptr.shared.create">[util.smartptr.shared.create]</a>. Presumably, objects created in 
<code>std::make_shared_for_overwrite</code> and <code>std::allocate_shared_for_overwrite</code> should be destroyed by plain 
destructor calls.
</p>

<p><i>[2024-03-11; Reflector poll]</i></p>

<p>
Set priority to 2 after reflector poll in December 2023.
</p>
<p>
This was the <a href="https://wg21.link/P1020R1" title=" Smart pointer creation with default initialization">P1020R1</a> author's intent (see LWG reflector mail
in November 2018) but it was never clarified in the wording. This fixes that.
</p>

<p><i>[2024-08-21; Move to Ready at LWG telecon]</i></p>


<p><i>[Wrocław 2024-11-23; Status changed: Voting &rarr; WP.]</i></p>



<p id="res-4024"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4964" title=" Working Draft, Programming Languages — C++">N4964</a>.
</p>

<ol>

<li><p>Modify 20.3.2.2.7 <a href="https://wg21.link/util.smartptr.shared.create">[util.smartptr.shared.create]</a> as indicated:</p>

<blockquote>
<pre>
template&lt;class T, ...&gt;
  shared_ptr&lt;T&gt; make_shared(<i>args</i>);
template&lt;class T, class A, ...&gt;
  shared_ptr&lt;T&gt; allocate_shared(const A&amp; a, <i>args</i>);
template&lt;class T, ...&gt;
  shared_ptr&lt;T&gt; make_shared_for_overwrite(<i>args</i>);
template&lt;class T, class A, ...&gt;
  shared_ptr&lt;T&gt; allocate_shared_for_overwrite(const A&amp; a, <i>args</i>);
</pre>
<blockquote>
<p>
[&hellip;]
<p/>
-7- <i>Remarks:</i>
</p>
<ol style="list-style-type: none">
<li><p>[&hellip;]</p></li>
<li><p>(7.11) &mdash; When a (sub)object of non-array type <code>U</code> that was initialized by 
<code>make_shared</code><ins>, <code>make_shared_for_overwrite</code>, or <code>allocate_shared_for_overwrite</code></ins> 
is to be destroyed, it is destroyed via the expression <code>pv-&gt;~U()</code> where <code>pv</code> points to that 
object of type <code>U</code>.</p></li>
<li><p>[&hellip;]</p></li>
</ol>
</blockquote>
</blockquote>
</li>

</ol>







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