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<title>Issue 1035: &lt;array&gt;::swap can invalidate references, pointers, and iterators</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">NAD</a> status.</em></p>
<h3 id="1035"><a href="lwg-closed.html#1035">1035</a>. <code>&lt;array&gt;::swap</code> can invalidate references, pointers, and iterators</h3>
<p><b>Section:</b> 23.2.2 <a href="https://wg21.link/container.requirements.general">[container.requirements.general]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Alisdair Meredith <b>Opened:</b> 2009-03-12 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#container.requirements.general">active issues</a> in [container.requirements.general].</p>
<p><b>View all other</b> <a href="lwg-index.html#container.requirements.general">issues</a> in [container.requirements.general].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>

<p><b>Addresses UK 226 [CD1]</b></p>

<p>
<code>&lt;array&gt;</code> must be added to this list. In particular it
doesn't satisfy: - no <code>swap()</code> function invalidates any
references, pointers, or iterators referring to the elements of the
containers being swapped. and probably doesn't satisfy: - no
<code>swap()</code> function throws an exception.
</p>
<p>
If <code>&lt;array&gt;</code> remains a container, this will have to also
reference <code>array</code>, which will then have to say which of these
points it satisfies.
</p>

<p><i>[
Summit:
]</i></p>


<blockquote><p>
Agree. The proposed resolution is incomplete. Further work required.
</p></blockquote>

<p><i>[
2009-05-01 Daniel adds:
]</i></p>


<blockquote><p>
Issue <a href="lwg-closed.html#1099" title="Various issues (Status: NAD)">1099</a><sup><a href="https://cplusplus.github.io/LWG/issue1099" title="Latest snapshot">(i)</a></sup> also suggests adding move constructor to this.
</p></blockquote>

<p><i>[
2009-07 post-Frankfurt:
]</i></p>


<blockquote><p>
Howard is to draft a note that explains what happens to references.
</p></blockquote>

<p><i>[
2009-10 Santa Cruz:
]</i></p>


<blockquote><p>
Mark as NAD.  No consensus for change.
</p></blockquote>



<p><i>[
2009-08-01 Howard provided wording.
]</i></p>


<p id="res-1035"><b>Proposed resolution:</b></p>
<p>
Add a paragraph to 23.3.3.4 <a href="https://wg21.link/array.special">[array.special]</a>:
</p>

<blockquote><pre>
template &lt;Swappable T, size_t N&gt; void swap(array&lt;T,N&gt;&amp; x, array&lt;T,N&gt;&amp; y);
</pre>
<blockquote>
<p>
<i>Effects:</i>
</p>
<blockquote><pre>
swap_ranges(x.begin(), x.end(), y.begin());
</pre></blockquote>

<p><ins>
[<i>Note:</i>
Outstanding iterators, references and pointers may be invalidated.
&mdash; <i>end note</i>]
</ins></p>
</blockquote>
</blockquote>





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