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<title>Issue 1285: allocator_traits call to new</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#C++11">C++11</a> status.</em></p>
<h3 id="1285"><a href="lwg-defects.html#1285">1285</a>. <code>allocator_traits</code> call to <code>new</code></h3>
<p><b>Section:</b> 20.2.9.3 <a href="https://wg21.link/allocator.traits.members">[allocator.traits.members]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Howard Hinnant <b>Opened:</b> 2009-12-10 <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#allocator.traits.members">issues</a> in [allocator.traits.members].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p>
LWG issue <a href="lwg-defects.html#402" title="wrong new expression in [some_]allocator::construct (Status: CD1)">402</a><sup><a href="https://cplusplus.github.io/LWG/issue402" title="Latest snapshot">(i)</a></sup> added "<code>::</code>" to the call to <code>new</code>
within <code>allocator::construct</code>.  I suspect we want to retain that fix.
</p>

<p><i>[
2009-12-13 Moved to Tentatively Ready after 7 positive votes on c++std-lib.
]</i></p>



<p id="res-1285"><b>Proposed resolution:</b></p>
<p>
Change 16.4.4.6 <a href="https://wg21.link/allocator.requirements">[allocator.requirements]</a>, table 40 "Allocator requirements":
</p>

<blockquote>
<table border="1">
<caption>Table 40 &mdash; Allocator requirements</caption>
<tr>
<th>Expression</th>
<th>Return type</th>
<th>Assertion/note<br/>pre-/post-condition</th>
<th>Default</th>
</tr>
<tr>
<td>
<code>a.construct(c,args)</code>
</td>
<td>
(not used)
</td>
<td>
Effect: Constructs an object of type <code>C</code> at <code>c</code>
</td>
<td>
<code><ins>::</ins>new ((void*)c) C(forward&lt;Args&gt;(args)...)</code>
</td>
</tr>
</table>
</blockquote>

<p>
Change 20.2.9.3 <a href="https://wg21.link/allocator.traits.members">[allocator.traits.members]</a>, p4:
</p>

<blockquote><pre>
template &lt;class T, class... Args&gt;
  static void construct(Alloc&amp; a, T* p, Args&amp;&amp;... args);
</pre>
<blockquote><p>
4 <i>Effects:</i> calls <code>a.construct(p,
std::forward&lt;Args&gt;(args)...)</code> if that call is well-formed; otherwise,
invokes <code><ins>::</ins>new (static_cast&lt;void*&gt;(p))
T(std::forward&lt;Args&gt;(args)...)</code>.
</p></blockquote>
</blockquote>





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