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<title>Issue 3437: __cpp_lib_polymorphic_allocator is in the wrong header</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++23">C++23</a> status.</em></p>
<h3 id="3437"><a href="lwg-defects.html#3437">3437</a>. <code>__cpp_lib_polymorphic_allocator</code> is in the wrong header</h3>
<p><b>Section:</b> 17.3.2 <a href="https://wg21.link/version.syn">[version.syn]</a> <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> Jonathan Wakely <b>Opened:</b> 2020-04-29 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>0
</p>
<p><b>View other</b> <a href="lwg-index-open.html#version.syn">active issues</a> in [version.syn].</p>
<p><b>View all other</b> <a href="lwg-index.html#version.syn">issues</a> in [version.syn].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++23">C++23</a> status.</p>
<p><b>Discussion:</b></p>
<p>
17.3.2 <a href="https://wg21.link/version.syn">[version.syn]</a> says that <code>__cpp_lib_polymorphic_allocator</code> is also defined in <code>&lt;memory&gt;</code>, 
but <code>std::polymorphic_allocator</code> is defined in <code>&lt;memory_resource&gt;</code>. This seems like an error in 
<a href="https://wg21.link/p1902r1">P1902R1</a>. The macro should be in the same header as the feature it relates to.
</p>

<p><i>[2020-05-09; Reflector prioritization]</i></p>

<p>
Set status to Tentatively Ready after six votes in favour during reflector discussions.
</p>
<p><i>[2020-11-09 Approved In November virtual meeting. Status changed: Tentatively Ready &rarr; WP.]</i></p>



<p id="res-3437"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4861">N4861</a>.
</p>

<ol>
<li><p>Modify 17.3.2 <a href="https://wg21.link/version.syn">[version.syn]</a> as indicated:</p>

<blockquote>
<pre>
[&hellip;]
#define __cpp_lib_parallel_algorithm    201603L <i>// also in &lt;algorithm&gt;, &lt;numeric&gt;</i>
#define __cpp_lib_polymorphic_allocator 201902L <i>// also in &lt;<del>memory</del><ins>memory_resource</ins>&gt;</i>
#define __cpp_lib_quoted_string_io      201304L <i>// also in &lt;iomanip&gt;</i>
[&hellip;]
</pre>
</blockquote>
</li>
</ol>




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