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<title>Issue 1252: wbuffer_convert::state_type inconsistency</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="1252"><a href="lwg-defects.html#1252">1252</a>. <code>wbuffer_convert::state_type</code> inconsistency</h3>
<p><b>Section:</b> 99 [depr.conversions.buffer] <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Bo Persson  <b>Opened:</b> 2009-10-21 <b>Last modified:</b> 2017-04-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#depr.conversions.buffer">active issues</a> in [depr.conversions.buffer].</p>
<p><b>View all other</b> <a href="lwg-index.html#depr.conversions.buffer">issues</a> in [depr.conversions.buffer].</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>
The synopsis for <code>wbuffer_convert</code>  [conversions.buffer]/2 contains
</p>

<blockquote><pre>
typedef typename Tr::state_type   state_type; 
</pre></blockquote>

<p>
making <code>state_type</code> a synonym for (possibly) some
<code>char_traits&lt;x&gt;::state_type</code>. 
</p>

<p>
However, in paragraph 9 of the same section, we have 
</p>

<blockquote><pre>
typedef typename Codecvt::state_type state_type;
</pre>

<blockquote><p>
The type shall be a synonym for <code>Codecvt::state_type</code>.
</p></blockquote>
</blockquote>

<p>
From what I can see, it might be hard to implement <code>wbuffer_convert</code> if 
the types were not both <code>std::mbstate_t</code>, but I cannot find a requirement 
that they must be the same type.
</p>

<p><i>[
Batavia 2010:
]</i></p>


<p>
Howard to draft wording, move to Review. Run it by Bill. Need to move this in Madrid.
</p>

<p><i>[2011-03-06: Howard drafts wording]</i></p>


<p><i>[2011-03-24 Madrid meeting]</i></p>


<p>Moved to Immediate</p>


<p id="res-1252"><b>Proposed resolution:</b></p>
<p>Modify the <code>state_type</code> typedef in the synopsis of  [conversions.buffer] p.2 as shown
[This makes the synopsis consistent with  [conversions.buffer] p.9]:</p>

<blockquote><pre>
namespace std {
template&lt;class Codecvt,
  class Elem = wchar_t,
  class Tr = std::char_traits&lt;Elem&gt; &gt;
class wbuffer_convert
  : public std::basic_streambuf&lt;Elem, Tr&gt; {
public:
  typedef typename <del>Tr</del><ins>Codecvt</ins>::state_type state_type;
  [&hellip;]
};
}
</pre></blockquote>





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