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<title>Issue 2394: locale::name specification unclear &mdash; what is implementation-defined?</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++17">C++17</a> status.</em></p>
<h3 id="2394"><a href="lwg-defects.html#2394">2394</a>. <code>locale::name</code> specification unclear &mdash; what is implementation-defined?</h3>
<p><b>Section:</b> 28.3.3.1.4 <a href="https://wg21.link/locale.members">[locale.members]</a> <b>Status:</b> <a href="lwg-active.html#C++17">C++17</a>
 <b>Submitter:</b> Richard Smith <b>Opened:</b> 2014-06-09 <b>Last modified:</b> 2017-07-30</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#locale.members">issues</a> in [locale.members].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++17">C++17</a> status.</p>
<p><b>Discussion:</b></p>
<p>
28.3.3.1.4 <a href="https://wg21.link/locale.members">[locale.members]</a> p5 says:
</p>
<blockquote><p>
<i>Returns</i>: The name of <code>*this</code>, if it has one; otherwise, the string <code>"*"</code>. If <code>*this</code> has a name, then
<code>locale(name().c_str())</code> is equivalent to <code>*this</code>. Details of the contents of the resulting string are
otherwise implementation-defined.
</p></blockquote>
<p>
So&hellip; what is implementation-defined here, exactly? The first sentence <em>completely</em> defines the behavior of this function 
in all cases.
<p/>
Also, the second sentence says (effectively) that all locales with the same name are equivalent: given <code>L1</code> and <code>L2</code> 
that have the same name <code>N</code>, they are both equivalent to <code>locale(N)</code>, and since there is no definition of 
"equivalent" specific to <code>locale</code>, I assume it's the normal transitive equivalence property, which would imply that 
<code>L1</code> is equivalent to <code>L2</code>. I'm not sure why this central fact is in the description of <code>locale::name</code>, nor 
why it's written in this roundabout way.
</p>

<p><i>[2016-08-03 Chicago LWG]</i></p>

<p>
Walter, Nevin, and Jason provide initial Proposed Resolution.
</p>
<p><i>[2016-08 - Chicago]</i></p>

<p>Thurs PM: Moved to Tentatively Ready</p>


<p id="res-2394"><b>Proposed resolution:</b></p>
<p>This wording is relative to N4606.</p>

<ol>
<li><p>Change 28.3.3.1.4 <a href="https://wg21.link/locale.members">[locale.members]</a> as indicated:</p>

<blockquote>
<pre>
basic_string&lt;char&gt; name() const;
</pre>
<blockquote>
<p>
-5- <i>Returns:</i> The name of <code>*this</code>, if it has one; otherwise, the string <code>"*"</code>. 
<del>If <code>*this</code> has a name, then <code>locale(name().c_str())</code> is equivalent to <code>*this</code>. 
Details of the contents of the resulting string are
otherwise implementation-defined.</del>
</p>
</blockquote>
</blockquote>
</li>
</ol>





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