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<title>Issue 830: Incomplete list of char_traits specializations</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="830"><a href="lwg-closed.html#830">830</a>. Incomplete list of char_traits specializations</h3>
<p><b>Section:</b> 27.2 <a href="https://wg21.link/char.traits">[char.traits]</a> <b>Status:</b> <a href="lwg-active.html#NAD_Editorial">NAD Editorial</a>
 <b>Submitter:</b> Dietmar K&#252;hl <b>Opened:</b> 2008-04-23 <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#char.traits">issues</a> in [char.traits].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD Editorial">NAD Editorial</a> status.</p>
<p><b>Discussion:</b></p>
<p>
  Paragraph 4 of 27.2 <a href="https://wg21.link/char.traits">[char.traits]</a> mentions that this
  section specifies two specializations (<code>char_traits&lt;char&gt;</code>
  and (<code>char_traits&lt;wchar_t&gt;</code>). However, there are actually
  four specializations provided, i.e. in addition to the two above also
  <code>char_traits&lt;char16_t&gt;</code> and <code>char_traits&lt;char32_t&gt;</code>).
  I guess this was just an oversight and there is nothing wrong with just
  fixing this.
</p>

<p><i>[
Alisdair adds:
]</i></p>

<blockquote><p>
<code>char_traits&lt; char16/32_t &gt;</code>
should also be added to <code>&lt;ios_fwd&gt;</code> in 31.3 <a href="https://wg21.link/iostream.forward">[iostream.forward]</a>, and all the specializations
taking a <code>char_traits</code> parameter in that header.
</p></blockquote>

<p><i>[
Sophia Antipolis:
]</i></p>


<blockquote>
<p>
Idea of the issue is ok.
</p>
<p>
Alisdair to provide wording, once that wording arrives, move to review.
</p>

</blockquote>

<p><i>[
2009-05-04 Alisdair adds:
]</i></p>


<blockquote>
<p>
The main point of the issue was resolved editorially in
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2723.pdf">N2723</a>,
so we are
close to NAD Editorial.
However, exploring the issue we found a second tweak was necessary for
<code>&lt;iosfwd&gt;</code> and that is still outstanding, so here are the words I am long
overdue delivering:
</p>

<p><i>[
Howard:  I've put Alisdair's words into the proposed wording section and
moved the issue to Review.
]</i></p>


</blockquote>

<p><i>[
Original proposed wording.
]</i></p>


<blockquote>

<p>
  Replace paragraph 4 of 27.2 <a href="https://wg21.link/char.traits">[char.traits]</a> by:
</p>
<blockquote>
<p>
  This subclause specifies a struct template, <code>char_traits&lt;charT&gt;</code>,
  and four explicit specializations of it, <code>char_traits&lt;char&gt;</code>,
  <code>char_traits&lt;char16_t&gt;</code>, <code>char_traits&lt;char32_t&gt;</code>, and
  <code>char_traits&lt;wchar_t&gt;</code>, all of which appear in the header
  &lt;string&gt; and satisfy the requirements below.
</p>
</blockquote>
</blockquote>

<p><i>[
Batavia (2009-05):
]</i></p>

<blockquote><p>
We agree.  Move to NAD Editorial.
</p></blockquote>


<p id="res-830"><b>Proposed resolution:</b></p>
<p>
Change Forward declarations 31.3 <a href="https://wg21.link/iostream.forward">[iostream.forward]</a>:
</p>

<blockquote>
<p>
<b>Header <code>&lt;iosfwd&gt;</code> synopsis</b>
</p>
<pre>
namespace std {
   template&lt;class charT&gt; class char_traits;
   template&lt;&gt; class char_traits&lt;char&gt;;
   <ins>template&lt;&gt; class char_traits&lt;char16_t&gt;;</ins>
   <ins>template&lt;&gt; class char_traits&lt;char32_t&gt;;</ins>
   template&lt;&gt; class char_traits&lt;wchar_t&gt;;
...
}
</pre>
</blockquote>





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