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<title>Issue 821: Minor cleanup : unique_ptr</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="821"><a href="lwg-defects.html#821">821</a>. Minor cleanup : <code>unique_ptr</code></h3>
<p><b>Section:</b> 20.3.1.4.5 <a href="https://wg21.link/unique.ptr.runtime.modifiers">[unique.ptr.runtime.modifiers]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Alisdair Meredith <b>Opened:</b> 2008-03-30 <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#unique.ptr.runtime.modifiers">issues</a> in [unique.ptr.runtime.modifiers].</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>
Reading resolution of LWG issue <a href="lwg-defects.html#673" title="unique_ptr update (Status: CD1)">673</a><sup><a href="https://cplusplus.github.io/LWG/issue673" title="Latest snapshot">(i)</a></sup> I noticed the following:
</p>

<blockquote>
<pre>
void reset(<del>T*</del> <ins>pointer</ins> p = <del>0</del> <ins>pointer()</ins>);
</pre>

<p>
-1- <i>Requires:</i> Does not accept pointer types which are convertible
to <del><code>T*</code></del> <ins><code>pointer</code></ins> (diagnostic
required). [<i>Note:</i> One implementation technique is to create a private
templated overload. <i>-- end note</i>]
</p>
</blockquote>

<p>
This could be cleaned up by mandating the overload as a public deleted
function.  In addition, we should probably overload <code>reset</code> on <code>nullptr_t</code>
to be a stronger match than the deleted overload. Words...
</p>


<p id="res-821"><b>Proposed resolution:</b></p>
<p>
Add to class template definition in 20.3.1.4 <a href="https://wg21.link/unique.ptr.runtime">[unique.ptr.runtime]</a>
</p>

<blockquote>
<pre>
// modifiers 
pointer release(); 
void reset(pointer p = pointer()); 
<ins>void reset( nullptr_t );</ins>
<ins>template&lt; typename U &gt; void reset( U ) = delete;</ins>
void swap(unique_ptr&amp;&amp; u);
</pre>
</blockquote>

<p>
Update 20.3.1.4.5 <a href="https://wg21.link/unique.ptr.runtime.modifiers">[unique.ptr.runtime.modifiers]</a>
</p>

<blockquote>
<pre>
void reset(pointer p = pointer());
<ins>void reset(nullptr_t);</ins>
</pre>

<p>
<del>-1- <i>Requires:</i> Does not accept pointer types which are convertible
to <code>pointer</code> (diagnostic
required). [<i>Note:</i> One implementation technique is to create a private
templated overload. <i>-- end note</i>]</del>
</p>
<p>
<i>Effects:</i> If <code>get() == nullptr</code> there are no effects. Otherwise <code>get_deleter()(get())</code>. 
</p>
<p>...</p>
</blockquote>

<p><i>[
Note this wording incorporates resolutions for <a href="lwg-defects.html#806" title="unique_ptr::reset effects incorrect, too permissive (Status: CD1)">806</a><sup><a href="https://cplusplus.github.io/LWG/issue806" title="Latest snapshot">(i)</a></sup> (New) and <a href="lwg-defects.html#673" title="unique_ptr update (Status: CD1)">673</a><sup><a href="https://cplusplus.github.io/LWG/issue673" title="Latest snapshot">(i)</a></sup> (Ready).
]</i></p>






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