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<title>Issue 2828: Clarify &lt;cstdalign&gt; (following adoption of P0063r3)</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#NAD_Editorial">NAD Editorial</a> status.</em></p>
<h3 id="2828"><a href="lwg-closed.html#2828">2828</a>. Clarify <code>&lt;cstdalign&gt;</code> (following adoption of P0063r3)</h3>
<p><b>Section:</b> 21.3.6.4 <a href="https://wg21.link/meta.unary.prop">[meta.unary.prop]</a> <b>Status:</b> <a href="lwg-active.html#NAD_Editorial">NAD Editorial</a>
 <b>Submitter:</b> Thomas Koeppe <b>Opened:</b> 2016-11-20 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>Not Prioritized
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<p><b>Discussion:</b></p>
<p>
In Oulu, we adopted <a href="https://wg21.link/p0063r3">P0063r3</a> to base C++ on C11. C11 is the first version 
of C that defines a header <code>&lt;stdalign.h&gt;</code>. However, C++11 (!) already seems to have defined headers 
<code>&lt;cstdalign&gt;</code> and <code>&lt;stdalign.h&gt;</code>, even though C99 does not have <code>&lt;stdalign.h&gt;</code>.
<p/>
This appears to be the consequence of the partial application of N3093 from 2010, which proposes both to add 
<code>&lt;cstdalign&gt;</code> and to rebase C++ onto C11. However, the latter part didn't happen, leaving the header 
dangling without a sensible specification.
<p/>
I suggest two actions:
</p>
<ol style="list-style-type: none">
<li>1) Recognize that C++11 and C++14 are defective in mentioning <code>&lt;cstdalign&gt;</code> and <code>&lt;stdalign.h&gt;</code>.</li>

<li>2a) Consequently, P0063r3 is <em>adding</em> <code>&lt;cstdalign&gt;</code> as a new feature; I would like to revert that 
decision and not add this header. Instead, P0063r3 should <em>only</em> add <code>&lt;stdalign.h&gt;</code> (which should 
be done in Annex D) for compatibility with C.</li>

<li>2b) If we do not want to un-add <code>&lt;cstdalign&gt;</code>, we should at least put the specification of <code>&lt;cstdalign&gt;</code> into Annex D.</li>
</ol>
<p>
Moreover, I would like to ask LWG for editorial dispensation to move the specifications of <code>&lt;ccomplex&gt;</code>, 
<code>&lt;ctgmath&gt;</code> and <code>&lt;cstdbool&gt;</code> wholly into Annex D, too, since these are now deprecated features that are not otherwise referred to or needed by the main text. An example change is available 
<a href="https://github.com/cplusplus/draft/pull/1054">on github</a>, which incorporates solution 2b. 
Wording for solution 2a can be produced on request.
</p>
<p><i>[2017-01-27 Telecon]</i></p>

<p>NAD Editorial; Thomas will make the editorial changes (option 2B)</p>


<p id="res-2828"><b>Proposed resolution:</b></p>





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