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<title>Issue 2849: Why does !is_regular_file(from) cause copy_file to report a "file already exists" error?</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++20">C++20</a> status.</em></p>
<h3 id="2849"><a href="lwg-defects.html#2849">2849</a>. Why does <code>!is_regular_file(from)</code> cause <code>copy_file</code> to report a "file already exists" error?</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++20">C++20</a>
 <b>Submitter:</b> Tim Song <b>Opened:</b> 2016-12-17 <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++20">C++20</a> status.</p>
<p><b>Discussion:</b></p>
<p>
 [fs.op.copy_file]/4 says that <code>copy_file</code> reports "a file already exists error as specified in
[fs.err.report] if" any of several error conditions exist.
<p/>
It's not clear how some of those error conditions, such as <code>!is_regular_file(from)</code>, can be sensibly described
as "file already exists". Pretty much everywhere else in the filesystem specification just says "an error" without
further elaboration.
</p>

<p><i>[2017-01-27 Telecon]</i></p>

<p>Priority 2; Jonathan to provide updated wording.</p>

<p><i>[2018-01-16, Jonathan comments]</i></p>

<p>
I said I'd provide updated wording because I wanted to preserve the requirement that the reported error is
"file already exists" for some of the error cases. I no longer think that's necessary, so I think the
current P/R is fine. Please note that I don't think new wording is needed.
</p>

<p><i>[
2018-01-23 Moved to Tentatively Ready after 6 positive votes on c++std-lib.
]</i></p>

<p><i>[2018-3-17 Adopted in Jacksonville]</i></p>



<p id="res-2849"><b>Proposed resolution:</b></p>
<p>This wording is relative to <a href="https://wg21.link/n4713">N4713</a>.</p>

<ol>
<li><p>Edit  [fs.op.copy_file]/4 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>
-4- <i>Effects:</i> As follows:
</p>
<ol style="list-style-type: none">
<li><p>(4.1) &mdash; Report <del>a file already exists</del><ins>an</ins> error as specified in 31.12.5 <a href="https://wg21.link/fs.err.report">[fs.err.report]</a> if:</p></li>
<li>
<ol style="list-style-type: none">
<li><p>(4.1.1) &mdash;[&hellip;]</p></li>
</ol>
</li>
<li><p>(4.2) &mdash;[&hellip;]</p></li>
</ol>
</blockquote>
</blockquote>
</li>
</ol>





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