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<title>Issue 3078: directory_entry, directory_iterator and recursive_directory_iterator perform needless path copies</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#New">New</a> status.</em></p>
<h3 id="3078"><a href="lwg-active.html#3078">3078</a>. <code>directory_entry</code>, <code>directory_iterator</code> and <code>recursive_directory_iterator</code> perform needless path copies</h3>
<p><b>Section:</b> 31.12.10 <a href="https://wg21.link/fs.class.directory.entry">[fs.class.directory.entry]</a>, 31.12.11 <a href="https://wg21.link/fs.class.directory.iterator">[fs.class.directory.iterator]</a>, 31.12.12 <a href="https://wg21.link/fs.class.rec.dir.itr">[fs.class.rec.dir.itr]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Gor Nishanov <b>Opened:</b> 2018-03-05 <b>Last modified:</b> 2019-04-02</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#fs.class.directory.entry">issues</a> in [fs.class.directory.entry].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
An implementation of <code>directory_entry</code> class is likely to store a <code>filesystem::path</code> as a member.
Constructors and assign member functions take <code>filesystem::path</code> by <code>const&amp;</code> thus forcing 
creation of a copy.
<p/>
An implementation of <code>directory_iterator</code> class is likely to store a <code>directory_entry</code> or a 
<code>path</code> as a part of its state. Constructors take <code>filesystem::path</code> by <code>const&amp;</code> 
thus forcing creation of a copy.
<p/>
An implementation of <code>recursive_directory_iterator</code> class is likely to store a <code>directory_entry</code> 
or a <code>path</code> as a part of its state. Constructors take <code>filesystem::path</code> by <code>const&amp;</code> 
thus forcing creation of a copy. 
<p/>
Suggested resolution:
<p/>
Add overloads to <code>directory_entry</code>, <code>directory_iterator</code>, and <code>recursive_directory_iterator</code>
that take <code>filesystem::path</code> by <code>&amp;&amp;</code>.
<p/>
Make it unspecified in case an exception is thrown from those new members where an argument was moved from or not.
</p>
<blockquote><pre>
explicit directory_entry(const filesystem::path&amp; p);
<ins>explicit directory_entry(filesystem::path&amp;&amp; p);</ins>
directory_entry(const filesystem::path&amp; p, error_code&amp; ec);
<ins>directory_entry(filesystem::path&amp;&amp; p, error_code&amp; ec);</ins>

void directory_entry::assign(const filesystem::path&amp; p);
<ins>void directory_entry::assign(filesystem::path&amp;&amp; p);</ins>
void directory_entry::assign(const filesystem::path&amp; p, error_code&amp; ec);
<ins>void directory_entry::assign(filesystem::path&amp;&amp; p, error_code&amp; ec);</ins>

explicit directory_iterator(const path&amp; p);
<ins>explicit directory_iterator(path&amp;&amp; p);</ins>
directory_iterator(const path&amp; p, directory_options options);
<ins>directory_iterator(path&amp;&amp; p, directory_options options);</ins>
directory_iterator(const path&amp; p, error_code&amp; ec) noexcept;
<ins>directory_iterator(path&amp;&amp; p, error_code&amp; ec) noexcept;</ins>
directory_iterator(const path&amp; p, directory_options options, error_code&amp; ec) noexcept;
<ins>directory_iterator(path&amp;&amp; p, directory_options options, error_code&amp; ec) noexcept;</ins>

explicit recursive_directory_iterator(const path&amp; p);
<ins>explicit recursive_directory_iterator(path&amp;&amp; p);</ins>
recursive_directory_iterator(const path&amp; p, directory_options options);
<ins>recursive_directory_iterator(path&amp;&amp; p, directory_options options);</ins>
recursive_directory_iterator(const path&amp; p, directory_options options, error_code&amp; ec) noexcept;
<ins>recursive_directory_iterator(path&amp;&amp; p, directory_options options, error_code&amp; ec) noexcept;</ins>
recursive_directory_iterator(const path&amp; p, error_code&amp; ec) noexcept;
<ins>recursive_directory_iterator(path&amp;&amp; p, error_code&amp; ec) noexcept;</ins>
</pre></blockquote>

<p><i>[2018-03-20 Priority set to 3 after discussion on the reflector.]</i></p>



<p id="res-3078"><b>Proposed resolution:</b></p>





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