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<title>Issue 2712: copy_file(from, to, ...) has a number of unspecified error conditions</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="2712"><a href="lwg-defects.html#2712">2712</a>. <code>copy_file(from, to, ...)</code> has a number of unspecified error conditions</h3>
<p><b>Section:</b> 31.12.13.5 <a href="https://wg21.link/fs.op.copy.file">[fs.op.copy.file]</a> <b>Status:</b> <a href="lwg-active.html#C++17">C++17</a>
 <b>Submitter:</b> Eric Fiselier <b>Opened:</b> 2016-05-10 <b>Last modified:</b> 2021-06-06</p>
<p><b>Priority: </b>2
</p>
<p><b>View all other</b> <a href="lwg-index.html#fs.op.copy.file">issues</a> in [fs.op.copy.file].</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>
There are a number of error cases that <code>copy_file(from, to, ...)</code> does not take into account.
Specifically the cases where:
</p>
<ol style="list-style-type:upper-alpha">
<li><code>from</code> does not exist</li>
<li><code>from</code> is not a regular file</li>
<li><code>to</code> exists and is not a regular file</li>
</ol>
<p>
These error cases should be specified as such.
</p>

<p><i>[2016-05 Issues Telecon]</i></p>

<p>
Eric to provide wording.
</p>

<p><i>[2016-05-28, Eric Fiselier provides wording]</i></p>


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

<p>Wed AM: Move to Tentatively Ready</p>


<p id="res-2712"><b>Proposed resolution:</b></p>
<p>This wording is relative to N4582.</p>
<ol>
<li><p>Modify  [fs.op.copy_file] as indicated:</p>

<blockquote>
<pre>
bool copy_file(const path&amp; from, const path&amp; to, copy_options options);
bool copy_file(const path&amp; from, const path&amp; to, copy_options options,
               error_code&amp; ec) noexcept;
</pre>
<blockquote>
<p>
-3- <i>Requires:</i> At most one constant from each <code>copy_options</code> option group (27.10.10.2) is present in
<code>options</code>.
<p/>
-4- <i>Effects:</i> Report a file already exists error as specified in Error reporting (27.5.6.5) if:
</p>
<ul>
<li><ins><code>!is_regular_file(from)</code>, or</ins></li>
<li><ins><code>exists(to)</code> and <code>!is_regular_file(to)</code>, or</ins></li>
<li><code>exists(to)</code> and <code>equivalent(from, to)</code>, or</li>
<li><code>exists(to)</code> and <code>(options &amp; (copy_options::skip_existing | copy_options::overwrite_existing |
copy_options::update_existing)) == copy_options::none</code>.</li>
</ul>
</blockquote>
</blockquote>
</li>
</ol>





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