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<title>Issue 2024: Inconsistent implementation requirements for atomic&lt;integral&gt; and atomic&lt;T*&gt;</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#Resolved">Resolved</a> status.</em></p>
<h3 id="2024"><a href="lwg-defects.html#2024">2024</a>. Inconsistent implementation requirements for <code>atomic&lt;<i>integral</i>&gt;</code> and <code>atomic&lt;T*&gt;</code></h3>
<p><b>Section:</b> 32.5.8 <a href="https://wg21.link/atomics.types.generic">[atomics.types.generic]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Daniel Kr&uuml;gler <b>Opened:</b> 2010-12-08 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#atomics.types.generic">issues</a> in [atomics.types.generic].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Paragraph 5 and 6 of 32.5.8 <a href="https://wg21.link/atomics.types.generic">[atomics.types.generic]</a> impose different requirements on implementations for
specializations of the <code>atomic</code> class template for integral types and for pointer types:
</p>
<blockquote><p>
5 The atomic integral specializations and the specialization <code>atomic&lt;bool&gt;</code> shall have standard layout. 
They shall each have a trivial default constructor and a trivial destructor. They shall each support aggregate
initialization syntax.
</p></blockquote>

<blockquote><p>
6 There are pointer partial specializations on the <code>atomic</code> class template. These specializations shall have 
trivial default constructors and trivial destructors.
</p></blockquote>

<p>
It looks like an oversight to me, that for pointer specializations the requirements for standard layout and
support for aggregate initialization syntax are omitted. In fact, this been confirmed by the 
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3193.htm">N3193</a> proposal author. I suggest
to impose the same implementation requirements for pointer types as for integral types, this should not impose 
unrealistic requirements on implementations.
</p>

<p><i>[2011-02-10 Reflector discussion]</i></p>

<p>
Moved to Tentatively Ready after 5 votes.
</p>

<blockquote class="note">
<p>Proposed Resolution</p>
<p>
The suggested wording changes are against the working draft N3242.
</p>

<ol>
<li>
<p>Change 32.5.8 <a href="https://wg21.link/atomics.types.generic">[atomics.types.generic]</a> p. 6 as indicated:</p>

<blockquote><p>
6 There are pointer partial specializations on the <code>atomic</code> class template. These specializations shall have 
<ins>standard layout,</ins> trivial default constructors<ins>,</ins> and trivial destructors. <ins> They shall each 
support aggregate initialization syntax.</ins>
</p></blockquote>

</li>
</ol>
</blockquote>


<p id="res-2024"><b>Proposed resolution:</b></p><p>
Resolved 2011-03 Madrid meeting by paper <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3278">N3278</a>
</p>




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