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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta charset="utf-8">
<title>File System Immediate Issues</title>
<style type="text/css">
p {text-align:justify}
li {text-align:justify}
blockquote.note
{
background-color:#E0E0E0;
padding-left: 15px;
padding-right: 15px;
padding-top: 1px;
padding-bottom: 1px;
}
ins {background-color:#A0FFA0}
del {background-color:#FFA0A0}
</style>
</head>
<body>
<table>
<tr>
<td align="left">Doc. no.</td>
<td align="left">N4080</td>
</tr>
<tr>
<td align="left">Date:</td>
<td align="left">2014-06-20</td>
</tr>
<tr>
<td align="left">Project:</td>
<td align="left">File System TS</td>
</tr>
<tr>
<td align="left">Reply to:</td>
<td align="left">Beman Dawes <<a href="mailto:bdawes at acm dot org">bdawes at acm dot org</a>></td>
</tr>
</table>
<h1>File System TS Immediate Issues for Rapperswil</h1>
<p><p>Revised 2014-06-20 at 09:06:18 UTC</p>
</p>
<p>Reference ISO/IEC TS 18822</p>
<hr>
<h3><a name="5"></a>5. [PDTS] Parent of root directory unspecified</h3>
<p><b>Section:</b> X 8.1 [path.generic] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> CH-4 <b>Opened:</b> 2014-01-20 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>8.1 [path.generic] says:
"The filename dot-dot is treated as a reference to the parent directory." So it must be
specified what "/.." and "/../.." refer to.</p>
<p>Add a statement what the parent directory of the root directory is.</p>
<p><i>[2014-02-07, Beman Dawes suggests wording]</i></p>
<p><i>[
2014-02-11 Issaquah: Implementation defined. See wiki notes for rationale.
Beman to provide wording for review next meeting.
]</i></p>
<p><i>[
22 May 2014 Beman provides wording, taken directly from POSIX.
See pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap04.html#tag_21_04_12
]</i></p>
<p><b>Proposed resolution:</b></p>
<ol>
<li>
<p>Change 8.1 [path.generic]:</p>
<blockquote><p>
The filename <i>dot</i> is treated as a reference to the current directory.
The filename <i>dot-dot</i> is treated as a reference to the parent directory.
<ins>What the filename <i>dot-dot</i> refers to relative to <i>root-directory</i> is implementation-defined.</ins>
Specific filenames may have special meanings for a particular operating system.
</p></blockquote>
</li>
</ol>
<hr>
<h3><a name="22"></a>22. [PDTS] <tt>directory_iterator</tt> underspecified</h3>
<p><b>Section:</b> X 13.1 [directory_iterator.members] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> CH-13 <b>Opened:</b> 2014-01-20 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>The behaviour of increment is underspecified: What happens if the implementation
detects an endless loop (e.g. caused by links)? What happens with automounting and
possible race conditions?</p>
<p>More information on this can be found <a href="http://man7.org/linux/manpages/man3/fts.3.html">here</a>.
<p>Suggested action:</p>
<p>Specify the required behaviour in these cases.</p>
</p>
<p><i>[2014-02-13 LWG/SG-3 Issaquah: STL will provide wording for next meeting for
the endless loop case. The other cases are covered by existing wording in the front matter.]</i></p>
<p><i>[17 Jun 2014 At the request of the LWG, Beman provides wording for a note.]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>In 14 Class recursive_directory_iterator [class.rec.dir.itr], add:</i>
</p>
<blockquote>
<p>
<ins>
[<i>Note: </i>If the directory structure being iterated over contains
cycles then
the end iterator may be unreachable. <i>--end note</i>]
</ins>
</p>
</blockquote>
<hr>
<h3><a name="25"></a>25. [PDTS] Copying equivalent paths effects not specified</h3>
<p><b>Section:</b> X 15.4 [fs.op.copy_file] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> CH-15 <b>Opened:</b> 2014-01-20 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>Even if <tt>to</tt> and <tt>from</tt> are different paths, they may be equivalent.</p>
<p>Specify what happens if <tt>(options & copy_options::overwrite_existing)</tt> but <tt>from</tt> and <tt>to</tt>
resolve to the same file.</p>
<p><i>[2014-02-09, Beman Dawes: Need advice on this issue:]</i></p>
<p/>What do existing implentations do?
<p/>Possible resolutions:
<ol>
<li>Treat it as an error.</li>
<li>Once equivalence is determined, take no further action and return true? false?</li>
<li>Don't bother to detect a file overwriting itself. This will likely result in an error, anyhow.</li>
</ol>
<p><i>[2014-02-13 LWG/SG-3 Issaquah: LWG/SG-3 decided to treat equivalence in this case as an error.
Beman to provide wording.]</i></p>
<p><i>[2014-04-09 Beman provided wording as requested. The Effects were rewritten to increase
clarity. Behavior remains unchanged except for treating equivalence as an error.]</i></p>
<p><i>[17 Jun 2014 Rapperswil LWG moves to Immediate. Jonathan Wakely will provide editorial
changes to improve the presentation of bitmask values.]</i></p>
<p><b>Proposed resolution:</b></p>
<p/>
<i>Change 15.4 [fs.op.copy_file]:</i>
<blockquote>
<p>
<i>Precondition:</i> At most one constant from each <code>copy_options</code>
option group ([<a href="#enum.copy_options">enum.copy_options</a>]) is present
in <code>options</code>.
</p>
<p>
<i>Effects:</i>
</p>
<blockquote>
<p><del>
If <code>exists(to) &&</code> <code>
!(options & (copy_options::skip_existing
| copy_options::overwrite_existing | copy_options::update_existing))
</code> report a
file already exists error as specified in <a href="#Error-reporting">Error reporting (7)</a>.
</del></p>
<p><del>
If <code>
!exists(to) || (options & copy_options::overwrite_existing) || ((options & copy_options::update_existing)
&& last_write_time(from) > last_write_time(to)) || !(options & (copy_options::skip_existing
| copy_options::overwrite_existing | copy_options::update_existing))
</code> copy the contents and attributes of the file <code>from</code>
resolves to the file <code>to</code> resolves to.
</del></p>
</blockquote>
<blockquote>
<p>
<ins>
Report a file already exists error as specified in
<a href="file:///C:/dot16/filesystem-ts/working-draft.html#Error-reporting">
Error reporting (7)
</a> if:
</ins>
</p>
<ul>
<li><ins>
<ins><code>exists(to)</code> and <code>equivalent(from, to)</code>,
or</ins>
</ins></li>
<li><ins>
<code>exists(to)</code> and <code>
(options & (copy_options::skip_existing
| copy_options::overwrite_existing | copy_options::update_existing)) == copy_options::none.
</code>
</ins></li>
</ul>
<p><ins>
Otherwise copy the contents and attributes of the file <code>from</code>
resolves to to the file <code>to</code> resolves to if:
</ins></p>
<ul>
<li><ins>
<code>!exists(to)</code>, or
</ins></li>
<li><ins>
<code>exists(to)</code> and <code>
(options &
copy_options::overwrite_existing) != copy_options::none
</code>, or
</ins></li>
<li><ins>
<code>exists(to)</code> and <code>
(options &
copy_options::update_existing) != copy_options::none
</code> and <code>from</code> is more
recent than <code>to</code>, determined as if by use of the <code>
last_write_time
</code> function.
</ins></li>
</ul>
<p><ins>Otherwise no effects.</ins></p>
</blockquote>
<p>
<i>Returns</i>: <code>true</code> if the <code>from</code> file
was copied, otherwise <code>false</code>. The signature with argument <code>ec</code> return
<code>false</code> if an error occurs.
</p>
<p>
<i>Throws:</i> As specified in <a href="#Error-reporting">Error reporting (7)</a>.
</p>
<p>
<i>Complexity:</i> At most one direct or indirect invocation of <code>
status(to)</code>.
</p>
</blockquote>
<hr>
<h3><a name="27"></a>27. [PDTS] Return value of <tt>uintmax_t</tt> on error?</h3>
<p><b>Section:</b> X 15.14 [fs.op.file_size] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> FI-9 <b>Opened:</b> 2014-01-20 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>"The signature with argument <tt>ec</tt> returns <tt>static_cast<uintmax_t>(-1)</tt> if an error
occurs.", one would expect that <b>both</b> signatures return that if an error occurs?</p>
<p>Clarify the Returns clause, and apply the same for every function that returns an
<tt>uintmax_t</tt> where applicable.</p>
<p><i>[2014-02-13 LWG/SG-3 Issaquah:]</i></p>
<p/>Discussion when around in circles for a while, until someone suggested the reference to 15.15 was wrong,
and that the issue applied to the previous function in the WP, 15.14 File size [fs.op.file_size].
<p/>The NB Comment makes much more sense if it applies to file_size(), so the chair was directed
to change the reference from 15.15 [fs.op.hard_lk_ct] to 15.14 [fs.op.file_size].
<p/>The intent that file_size() is only meaningful for regular_files. Beman to strike the
the static_cast, changing it to "Otherwise an error is reported.".
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 15.14 [fs.op.file_size]:</i>
</p>
<pre>uintmax_t file_size(const path& p);
uintmax_t file_size(const path& p, error_code& ec) noexcept;</pre>
<blockquote>
<p><i>Returns:</i> If <code>
<ins>!</ins>exists(p) <del>&&</del> <ins>|| !</ins>is_regular_file(p)</code><ins>
an error is reported (7). Otherwise</ins>, the size in bytes
of the file <code>p</code> resolves to, determined as if by the value of the
POSIX <code>stat</code> structure member <code>st_size</code>
obtained as if by POSIX <code>stat()</code>.
<del>Otherwise, <code>static_cast<uintmax_t>(-1)</code>.</del> The signature with
argument <code>ec</code>
returns <code>static_cast<uintmax_t>(-1)</code> if an error occurs.</p>
<p><i>Throws:</i> As specified in <a href="#Error-reporting">Error reporting <ins>(7)</ins></a>.</p>
</blockquote>
<hr>
<h3><a name="34"></a>34.
[PDTS] <tt>enum class directory_options</tt> has no summary
</h3>
<p><b>Section:</b> X 6 [fs.filesystem.synopsis] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View other</b> <a href="open-index.html# [fs.filesystem.synopsis">active issues</a> in 6 [fs.filesystem.synopsis].</p>
<p><b>View all other</b> <a href="section-index.html# [fs.filesystem.synopsis">issues</a> in 6 [fs.filesystem.synopsis].</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p><tt>enum class directory_options</tt> has no summary.</p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 6 [fs.filesystem.synopsis]:</i>
</p>
<blockquote>
<pre> enum class directory_options<ins>;</ins>
<del>{</del>
<del>none,</del>
<del>follow_directory_symlink,</del>
<del>skip_permission_denied</del>
<del>};</del></pre>
</blockquote>
<p>
<i>Add the following sub-section:</i>
</p>
<blockquote>
<h3>
10.4 Enum class <code>directory_options</code> [<a name="enum.directory_options">enum.directory_options</a>]
</h3>
<p>
The <tt>enum class</tt> type <code>directory_options</code>
is a bitmask type (C++11 §17.5.2.1.3) that specifies bitmask constants used to identify
directory traversal options.
</p>
<table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111">
<tr>
<td>
<b>Name</b>
</td>
<td align="center">
<b>Value</b>
</td>
<td>
<b>Meaning</b>
</td>
</tr>
<tr>
<td>
<code>none</code>
</td>
<td align="center">
<code>0</code>
</td>
<td>(Default) Skip directory symlinks, permission denied is error.</td>
</tr>
<tr>
<td>
<code>follow_directory_symlink</code>
</td>
<td align="center">
<code>1</code>
</td>
<td> Follow rather than skip directory symlinks.</td>
</tr>
<tr>
<td>
<code>skip_permission_denied</code>
</td>
<td align="center">
<code>2</code>
</td>
<td> Skip directories that would otherwise result in permission denied errors.</td>
</tr>
</table>
</blockquote>
<hr>
<h3><a name="35"></a>35. [PDTS] <tt>directory_options::skip_permission_denied</tt> is not used</h3>
<p><b>Section:</b> X 6 [fs.filesystem.synopsis] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View other</b> <a href="open-index.html# [fs.filesystem.synopsis">active issues</a> in 6 [fs.filesystem.synopsis].</p>
<p><b>View all other</b> <a href="section-index.html# [fs.filesystem.synopsis">issues</a> in 6 [fs.filesystem.synopsis].</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>directory_options::skip_permission_denied</tt> is not used.
</p>
<p><i>[2014-04-13 Beman: <tt>skip_permissions_denied</tt> not being used is a
symptom of a more serious problem; two <tt>directory_itorator</tt> constructors
are missing <tt>directory_options</tt> arguments and a description of how they
are used. Proposed wording provided.]</i></p>
<p><i>[17 Jun 2014 LWG requests two signatures rather than one with default argument. Beman updates wording.]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 13 [class.directory_iterator]:</i>
</p>
<blockquote>
<pre> directory_iterator() noexcept;
explicit directory_iterator(const path& p);
<ins>directory_iterator(const path& p, directory_options options</ins>);
directory_iterator(const path& p, error_code& ec) noexcept;
<ins>directory_iterator(const path& p,</ins>
<ins>directory_options options, error_code& ec) noexcept;</ins>
directory_iterator(const directory_iterator&) = default;
directory_iterator(directory_iterator&&) = default;
~directory_iterator();
</pre>
</blockquote>
<p>
<i>Change 13.1 directory_iterator members [directory_iterator.members]:</i>
</p>
<blockquote>
<pre> explicit directory_iterator(const path& p);
<ins>directory_iterator(const path& p, directory_options options</ins>);
directory_iterator(const path& p, error_code& ec) noexcept;
<ins>directory_iterator(const path& p,</ins>
<ins>directory_options options, error_code& ec) noexcept;</ins>
</pre>
<p>
<i>Effects:</i> For the directory that <code>p</code> resolves to,
constructs an iterator for the first element in a sequence of <code>
directory_entry
</code> elements representing the files in the directory, if
any; otherwise the end iterator.
</p>
<p>
<ins>
However, if <code>options & directory_options::skip_permissions_denied != directory_options::none</code>
and construction encounters an error indicating that permission to access
<code>p</code> is denied, constructs the end iterator and does not report an
error.
</ins>
</p>
</blockquote>
<p>
<i>
Change 14 <a name="Class-recursive_directory_iterator">
Class <code>recursive_directory_iterator</code>
[class.rec.dir.itr]
</a>:
</i>
</p>
<blockquote>
<pre> explicit recursive_directory_iterator(const path& p<del>,</del>
<del>directory_options options = directory_options::none</del>);
<ins>recursive_directory_iterator(const path& p, directory_options options);</ins>
recursive_directory_iterator(const path& p,
directory_options options, error_code& ec) noexcept;
recursive_directory_iterator(const path& p, error_code& ec) noexcept;
</pre>
</blockquote>
<p>
<i>Change 14.1 recursive_directory_iterator members [rec.dir.itr.members]:</i>
</p>
<blockquote>
<pre> explicit recursive_directory_iterator(const path& p<del>,</del>
<del>directory_options options = directory_options::none</del>);
<ins>recursive_directory_iterator(const path& p, directory_options options);</ins>
recursive_directory_iterator(const path& p,
directory_options options, error_code& ec) noexcept;
recursive_directory_iterator(const path& p, error_code& ec) noexcept;
</pre>
<p>
<i>Effects:</i> Constructs a iterator representing the first entry in the
directory <code>p</code> resolves to, if any; otherwise, the end iterator.
</p>
<p>
<ins>
However, if <code>options & directory_options::skip_permissions_denied != directory_options::none</code>
and construction encounters an error indicating that permission to access
<code>p</code> is denied, constructs the end iterator and does not report an
error.
</ins>
</p>
</blockquote>
<p>
<i>Change 14.1 recursive_directory_iterator members [rec.dir.itr.members]:</i>
</p>
<blockquote>
<pre> recursive_directory_iterator& operator++();
recursive_directory_iterator& increment(error_code& ec);
</pre>
<p>
<i>Requires:</i> <code>*this != recursive_directory_iterator()</code>.
</p>
<p>
<i>Effects:</i> As specified by C++11 § 24.1.1 Input iterators, except
that:
</p>
<ul>
<li>
If there are no more entries at this depth, then if <code>depth()!= 0</code>
iteration over the parent directory resumes; otherwise <code>
*this =
recursive_directory_iterator()
</code>.
</li>
<li>
Otherwise if <code>
recursion_pending() && is_directory(this->status())
&& (!is_symlink(this->symlink_status()) || (options() &
directory_options::follow_directory_symlink) != <del>0</del> <ins>directory_options::none</ins>)
</code> then <ins>either</ins> directory
<code>(*this)->path()</code> is recursively iterated into
<ins>
or, if <code>
options() & directory_options::skip_permissions_denied != directory_options::none
</code>
and an error occurs indicating that permission to access directory
<code>(*this)->path()</code> is denied, then directory <code>(*this)->path()</code> is
treated as an empty directory and no error is reported
</ins>.
</li>
</ul>
</blockquote>
<hr>
<h3><a name="36"></a>36. [PDTS] <tt>copy_options::copy_symlinks</tt> is not used</h3>
<p><b>Section:</b> X 10.2 [enum.copy_options] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all other</b> <a href="section-index.html#0.2 [enum.copy_options">issues</a> in 10.2 [enum.copy_options].</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>copy_options::copy_symlinks</tt> is not used (should test it before calling <tt>copy_symlinks</tt> in <tt>copy</tt>).
</p>
<p><i>[20 May 2014 Beman Dawes provides proposed wording.]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 15.3 Copy [fs.op.copy]:</i>
</p>
<blockquote>
<blockquote>
<p>
If <code>is_symlink(f)</code>, then:
</p>
<ul>
<li>
If <code>options & copy_options::skip_symlinks</code>, then return.
<span style="font-style: italic; background-color: #C0C0C0">Missing != copy_options::none fixed by issue 59</span>
</li>
<li>
Otherwise if <code>
!exists(t) <ins>
&& (options & copy_options::copy_symlinks)
!= copy_options::none
</ins>
</code>, then <code>
copy_symlink(from,
to, options)
</code>.
</li>
<li>
Otherwise report an error as specified in
<a href="file:///C:/dot16/filesystem-ts/issues/mailing/active.html#Error-reporting"
style="color: #2020FF; text-decoration: none">
Error reporting (7)
</a>.
</li>
</ul>
</blockquote>
</blockquote>
<hr>
<h3><a name="37"></a>37. [PDTS] All functions with <tt>error_code</tt> arguments should be <tt>noexcept</tt></h3>
<p><b>Section:</b> X 15.2 [fs.op.canonical], X 15.11 [fs.op.current_path], X 15.27 [fs.op.read_symlink], X 15.36 [fs.op.system_complete], X 15.37 [fs.op.temp_dir_path], X 15.38 [fs.op.unique_path], X 8.4 [path.member] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
all functions with <tt>error_code</tt> arguments should be <tt>noexcept</tt>
(see <tt>canonical</tt>, <tt>current_path</tt>, <tt>read_symlink</tt>, <tt>system_complete</tt>,
<tt>temp_directory_path</tt>, <tt>unique_path</tt>, plus member functions).
</p>
<p><i>[2014-02-03: Stephan T. Lavavej comments:]</i></p>
<p>The declaration and definition of
"<tt>recursive_directory_iterator& increment(error_code& ec);</tt>" should almost certainly
be marked noexcept.</p>
<p><i>[2014-02-08: Daniel comments]</i></p>
<p>
All functions that return a <tt>path</tt> value such as <tt>canonical</tt>, <tt>current_path</tt>,
<tt>read_symlink</tt>, <tt>system_complete</tt>, <tt>temp_directory_path</tt>, <tt>unique_path</tt>,
or any member function returning a <tt>path</tt> value or <tt>basic_string</tt> value might legally
throw an exception, if the allocator of the underlying string complains about insufficient
memory. This is an anti-pattern for <tt>noexcept</tt>, because the exception-specification includes
the return statement of a function and given the fact that the language currently does declare RVO
as an optional action, we cannot rely on it.
<p/>
The Standard is currently very careful <em>not</em> to specify functions as <tt>noexcept</tt>,
if this case can happen, see e.g. <tt>std::locale::name()</tt>. To the contrary, enforcing them to be
<tt>noexcept</tt>, would cause a similar problem as the unconditional <tt>noexcept</tt> specifier of
the value-returning <tt>kill_dependency</tt> as denoted by LWG 2236.
<p/>
Basically this requirement conflicts with the section "Adopted Guidelines", second bullet of
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3279.pdf">N3279</a>.
</p>
<p><i>[Beman Dawes 2014-02-27]</i></p>
<p/>Issues <a href="active.html#37">37</a>,
<a href="active.html#38">38</a>,
<a href="active.html#41">41</a>,
and <a href="active.html#49">49</a> are concerned with signatures which should or should not
be <tt>noexcept</tt>. I will provide unified proposed wording for these issues, possibly in a separate paper.
<p><i>[21 May 2014 Beman Dawes reviewed all functions with <code>error_code&</code> arguments,
and provided proposed wording for the one case found where the above guidelines were not met.
This was the case previously identified by Stephan T. Lavavej.
]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 14 Class recursive_directory_iterator [class.rec.dir.itr]:</i>
</p>
<blockquote>
<pre>recursive_directory_iterator& increment(error_code& ec) <ins>noexcept</ins>;</pre>
</blockquote>
<p>
<i>Change 14.1 recursive_directory_iterator members [rec.dir.itr.members]:</i>
</p>
<blockquote>
<pre>recursive_directory_iterator& increment(error_code& ec) <ins>noexcept</ins>;</pre>
</blockquote>
<hr>
<h3><a name="40"></a>40. [PDTS] <tt>class directory_entry</tt> should retain <tt>operator const path&()</tt> from V2</h3>
<p><b>Section:</b> X 12 [class.directory_entry] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-17</p>
<p><b>View other</b> <a href="open-index.html#2 [class.directory_entry">active issues</a> in 12 [class.directory_entry].</p>
<p><b>View all other</b> <a href="section-index.html#2 [class.directory_entry">issues</a> in 12 [class.directory_entry].</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>class directory_entry</tt> should retain <tt>operator const path&()</tt> from V2.
</p>
<p><i>[2014-05-19 Beman Dawes supplied proposed wording.]</i></p>
<p><i>[2014-06-02 Beman Dawes provides rationale:]</i></p>
<blockquote>
This conversion operator was removed when <code>status()</code> and <code>symlink_status()</code>
were added during the transition from V2 to V3 as it seemed a bit unusual to have a conversion
operator for one of the several values held. Users complained as they had found the
automatic conversion convenient in the most common <code>directory_entry</code> use case.
</blockquote>
<p><i>[17 Jun 2014 Rapperswil LWG discusses in depth, accepts proposed wording.]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 12 Class directory_entry [class.directory_entry]:</i>
</p>
<blockquote>
<pre>// observers
const path& path() const noexcept;
<ins>operator const path&() const noexcept;</ins>
file_status status() const;
file_status status(error_code& ec) const noexcept;
file_status symlink_status() const;
file_status symlink_status(error_code& ec) const noexcept;</pre>
</blockquote>
<p>
<i>Change 12.3 directory_entry observers [directory_entry.obs]:</i>
</p>
<blockquote>
<pre>const path& path() const noexcept;
<ins>operator const path&() const noexcept;</ins></pre>
<blockquote>
<p>
<i>Returns:</i>
<code>m_path</code>
</p>
</blockquote>
</blockquote>
<hr>
<h3><a name="41"></a>41. [PDTS] <tt>directory_iterator</tt>, <tt>recursive_directory_iterator</tt>, move construct/assign should be <tt>noexcept</tt></h3>
<p><b>Section:</b> X 13 [class.directory_iterator], X 14 [class.rec.dir.itr] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all other</b> <a href="section-index.html#3 [class.directory_iterator">issues</a> in 13 [class.directory_iterator].</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>class directory_iterator</tt> move construct/assign should be <tt>noexcept</tt>.<br/>
<tt>class recursive_directory_iterator</tt> move construct/assign should be <tt>noexcept</tt>.
</p>
<p><i>[Beman Dawes 2014-02-27]</i></p>
<p/>Issues <a href="active.html#37">37</a>,
<a href="active.html#38">38</a>,
<a href="active.html#41">41</a>,
and <a href="active.html#49">49</a> are concerned with signatures which should or should not
be <tt>noexcept</tt>. I will provide unified proposed wording for these issues, possibly in a separate paper.
<p><i>[Daniel Krügler 2014-02-28]</i></p>
<pre>directory_iterator begin(directory_iterator iter) noexcept;
directory_iterator end(const directory_iterator&) noexcept;</pre>
<p/>are noexcept, but we have no guarantee that at least the
move-constructor is noexcept:
<pre>directory_iterator(const directory_iterator&) = default;
directory_iterator(directory_iterator&&) = default;</pre>
<p/>This means that either the above noexcept specifications are not
warranted or that at least the move-constructor of <tt>directory_iterator</tt>
is required to be noexcept.
<p/>The same applies to <tt>recursive_directory_iterator</tt>.
<p><i>[21 May 2014 Beman Dawes provided proposed resolution wording.]</i></p>
<p><i>[18 Jun 2014 "= default" removed per LWG discussion]</i></p>
<p><b>Proposed resolution:</b></p>
<p>
<i>Change 13 Class directory_iterator [class.directory_iterator]:</i></p>
<blockquote>
<pre>directory_iterator(const directory_iterator& <ins>rhs</ins>) <del>= default</del>;
directory_iterator(directory_iterator&& <ins>rhs</ins>) <ins>noexcept</ins> <del>= default</del>;
...
directory_iterator& operator=(const directory_iterator& <ins>rhs</ins>) <del>= default</del>;
directory_iterator& operator=(directory_iterator&& <ins>rhs</ins>) <ins>noexcept</ins> <del>= default</del>;</pre>
</blockquote>
<p/><i>To 13.1 directory_iterator members [directory_iterator.members] add:</i>
<blockquote>
<pre>directory_iterator(const directory_iterator& rhs);
directory_iterator(directory_iterator&& rhs) noexcept;</pre>
<blockquote>
<p>
<i>Effects:</i> Constructs an object of class <code>directory_iterator</code>.
</p>
<p>
<i>Postconditions:</i> <code>*this</code> has the original value of <code>rhs</code>.
</p>
</blockquote>
<pre>directory_iterator& operator=(const directory_iterator& rhs);
directory_iterator& operator=(directory_iterator&& rhs) noexcept;</pre>
<blockquote>
<p>
<i>Effects:</i>
If <code>*this</code> and <code>rhs</code> are the same object, the member has no effect.
</p>
<p>
<i>Postconditions:</i> <code>*this</code> has the original value of <code>rhs</code>.
</p>
<p/><i>Returns:</i>
<code>*this</code>.
</blockquote>
</blockquote>
<p>
<i>Change 14 Class recursive_directory_iterator [class.rec.dir.itr]:</i>
</p>
<blockquote>
<pre>recursive_directory_iterator(const recursive_directory_iterator& <ins>rhs</ins>) <del>= default</del>;
recursive_directory_iterator(recursive_directory_iterator&& <ins>rhs</ins>) <ins>noexcept</ins> <del>= default</del>;
...
recursive_directory_iterator& operator=(const recursive_directory_iterator& <ins>rhs</ins>) <del>= default</del>;
recursive_directory_iterator& operator=(recursive_directory_iterator&& <ins>rhs</ins>) <ins>noexcept</ins> <del>= default</del>;</pre>
</blockquote>
<p/>
<i>To 14.1 recursive_directory_iterator members [rec.dir.itr.members] add:</i>
<blockquote>
<pre>recursive_directory_iterator(const recursive_directory_iterator& rhs);</pre>
<blockquote>
<p>
<i>Effects:</i> Constructs an object of class <code>recursive_directory_iterator</code>.
</p>
<p>
<i>Postconditions:</i> <code>this->options() == rhs.options() && this->depth() ==
rhs.depth() && this->recursion_pending() ==
rhs.recursion_pending()</code>.
</p>
</blockquote>
<pre>recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;</pre>
<blockquote>
<p>
<i>Effects:</i> Constructs an object of class <code>recursive_directory_iterator</code>.
</p>
<p>
<i>Postconditions:</i> <code>this->options()</code>, <code>this->depth()</code>, and
<code>this->recursion_pending()</code> return the values that
<code>rhs.options()</code>, <code>rhs.depth()</code>, and <code>rhs.recursion_pending()</code>,
respectively, had before the function call.
</p>
</blockquote>
<pre>recursive_directory_iterator& operator=(const recursive_directory_iterator& rhs);</pre>
<blockquote>
<p>
<i>Effects:</i>
If <code>*this</code> and <code>rhs</code> are the same object, the member has no effect.
</p>
<p>
<i>Postconditions:</i> <code>
this->options() == rhs.options() && this->depth() ==
rhs.depth() && this->recursion_pending() ==
rhs.recursion_pending()
</code>.
</p>
<p/><i>Returns:</i>
<code>*this</code>.
</blockquote>
<pre>recursive_directory_iterator& operator=(recursive_directory_iterator&& rhs) noexcept;</pre>
<blockquote>
<p>
<i>Effects:</i>
If <code>*this</code> and <code>rhs</code> are the same object, the member has no effect.
</p>
<p>
<i>Postconditions:</i>
<code>this->options()</code>, <code>this->depth()</code>, and
<code>this->recursion_pending()</code> return the values that
<code>rhs.options()</code>, <code>rhs.depth()</code>, and <code>rhs.recursion_pending()</code>,
respectively, had before the function call.
</p>
<p/><i>Returns:</i> <code>*this</code>.
</blockquote>
</blockquote>
<hr>
<h3><a name="45"></a>45.
[PDTS] <tt>create_directory</tt> should refer to <tt>perms::all</tt> instead of Posix
<tt>S_IRWXU|S_IRWXG|S_IRWXO</tt>
</h3>
<p><b>Section:</b> X 15.7 [fs.op.create_directory] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>create_directory</tt> should refer to <tt>perms::all</tt> instead of the Posix
<tt>S_IRWXU|S_IRWXG|S_IRWXO</tt>.
</p>
<p><i>[2014-02-28 Beman provided proposed wording.]</i></p>
<p><b>Proposed resolution:</b></p>
<p><i>Effects:</i> Establishes the postcondition by attempting to create the
directory <code>p</code> resolves to, as if by POSIX <code>
mkdir()</code> with a second argument of <del>S_IRWXU|S_IRWXG|S_IRWXO</del> <ins><code>static_cast<int>(perms::all)</code></ins>. Creation
failure because <code>p</code> resolves to an existing directory shall not be
treated as an error. </p>
<hr>
<h3><a name="48"></a>48. [PDTS] <tt>path::template<class charT>string()</tt> conversion rules</h3>
<p><b>Section:</b> X 8.4.6 [path.native.obs] <b>Status:</b> <a href="active.html#Immediate">Immediate</a>
<b>Submitter:</b> P.J. Plauger <b>Opened:</b> 2014-01-30 <b>Last modified:</b> 2014-06-19</p>
<p><b>View all issues with</b> <a href="status-index.html#Immediate">Immediate</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<tt>path::template<class charT>string()</tt> should promise to convert by the same
rules as <tt>u16string</tt> for <tt>string<char16_t></tt>, etc. and one-for-one otherwise.
<p/>
What if <tt>charT</tt> is <tt>signed char</tt> (or even <tt>float</tt>)? I don't see where that choice
is disallowed, so we should either disallow it or make it be something that is quasi-sensible.
</p>
<p><i>[2014-02-08 Daniel comments]</i></p>
<p>
There are two relevant places in the wording that seem to clarify what is required here:
</p>
<ol>
<li><p>
Most importantly, 5 [fs.req] says:
</p>
<blockquote><p>
Throughout this Technical Specification, <tt>char</tt>, <tt>wchar_t</tt>, <tt>char16_t</tt>, and <tt>char32_t</tt>
are collectively called <em>encoded character types</em>.
<p/>
Template parameters named <tt>charT</tt> shall be one of the encoded character types.
<p/>
[…]
[<i>Note</i>: Use of an encoded character type implies an associated encoding. Since <tt>signed char</tt> and <tt>unsigned char</tt>
have no implied encoding, they are not included as permitted types. — <i>end note</i>]
</p></blockquote>
</li>
<li><p>
For both the mentioned <tt>string</tt> function template and the specific non-template functions (such as <tt>u16string()</tt>)
the same <tt>Remarks</tt> element exists, that refers to character conversion:
</p>
<blockquote><p>
Conversion, if any, is performed as specified by 8.2 [path.cvt].
</p></blockquote>
</li>
</ol>
<p>
The first quote excludes arbitrary types such as <tt>signed char</tt> or <tt>float</tt> as feasible template arguments.
The second quote makes clear that both the function template and the non-template functions do normatively refer to the same
wording in 8.2 [path.cvt].
<p/>
Based on this interpretation of the issue discussion I recommend resolving it as NAD.
<p/>
In addition to that recommendation I recommend to rename the current usage of the symbol <tt>charT</tt> in this technical
specification, because 5 [fs.req] assigns a very special meaning to the constraints on <tt>charT</tt> types that does not
exist to this extend in the rest of the standard library. A similar approach is used in Clause 22, where a special symbol <tt>C</tt>
is used for constrained character types (C++11 §22.3.1.1.1 [locale.category]):
</p>
<blockquote><p>
A template formal parameter with name <tt>C</tt> represents the set of types containing <tt>char</tt>, <tt>wchar_t</tt>,
and any other implementation-defined character types that satisfy the requirements for a character on which any of the