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<title>Issue 378: locale immutability and locale::operator=()</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#Dup">Dup</a> status.</em></p>
<h3 id="378"><a href="lwg-closed.html#378">378</a>. locale immutability and locale::operator=()</h3>
<p><b>Section:</b> 28.3.3.1 <a href="https://wg21.link/locale">[locale]</a> <b>Status:</b> <a href="lwg-active.html#Dup">Dup</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2002-09-06 <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#locale">issues</a> in [locale].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Dup">Dup</a> status.</p>
<p><b>Duplicate of:</b> <a href="lwg-defects.html#31" title="Immutable locale values (Status: TC1)">31</a></p>
<p><b>Discussion:</b></p>
<p>
I think there is a problem with 22.1.1, p6 which says that
</p>
<pre>
    -6- An instance of locale is immutable; once a facet reference
        is obtained from it, that reference remains usable as long
        as the locale value itself exists.
</pre>
<p>
and 22.1.1.2, p4:
</p>
<pre>
    const locale&amp; operator=(const locale&amp; other) throw();

    -4- Effects: Creates a copy of other, replacing the current value.
</pre>
<p>
How can a reference to a facet obtained from a locale object remain
valid after an assignment that clearly must replace all the facets
in the locale object? Imagine a program such as this
</p>
<pre>
    std::locale loc ("de_DE");
    const std::ctype&lt;char> &amp;r0 = std::use_facet&lt;std::ctype&lt;char> >(loc);
    loc = std::locale ("en_US");
    const std::ctype&lt;char> &amp;r1 = std::use_facet&lt;std::ctype&lt;char> >(loc);
</pre>
<p>
Is r0 really supposed to be preserved and destroyed only when loc goes
out of scope?
</p>


<p id="res-378"><b>Proposed resolution:</b></p>
<p><i>[Summer '04 mid-meeting mailing: Martin and Dietmar believe this
  is a duplicate of issue <a href="lwg-defects.html#31" title="Immutable locale values (Status: TC1)">31</a><sup><a href="https://cplusplus.github.io/LWG/issue31" title="Latest snapshot">(i)</a></sup> and recommend that it be
  closed.
]</i></p>






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