Skip to content

Commit 946253f

Browse files
author
github-actions
committed
Automatic update from GitHub Actions workflow
1 parent 0fa9a62 commit 946253f

22 files changed

+235
-128
lines changed

‎issue4252.html‎

Lines changed: 107 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,107 @@
1+
<!DOCTYPE html>
2+
<html lang="en">
3+
<head>
4+
<meta charset="utf-8">
5+
<title>Issue 4252: Are exposition-only classes considered specified for the purpose of final?</title>
6+
<meta property="og:title" content="Issue 4252: Are exposition-only classes considered specified for the purpose of final?">
7+
<meta property="og:description" content="C++ library issue. Status: New">
8+
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue4252.html">
9+
<meta property="og:type" content="website">
10+
<meta property="og:image" content="http://cplusplus.github.io/LWG/images/cpp_logo.png">
11+
<meta property="og:image:alt" content="C++ logo">
12+
<style>
13+
p {text-align:justify}
14+
li {text-align:justify}
15+
pre code.backtick::before { content: "`" }
16+
pre code.backtick::after { content: "`" }
17+
blockquote.note
18+
{
19+
background-color:#E0E0E0;
20+
padding-left: 15px;
21+
padding-right: 15px;
22+
padding-top: 1px;
23+
padding-bottom: 1px;
24+
}
25+
ins {background-color:#A0FFA0}
26+
del {background-color:#FFA0A0}
27+
table.issues-index { border: 1px solid; border-collapse: collapse; }
28+
table.issues-index th { text-align: center; padding: 4px; border: 1px solid; }
29+
table.issues-index td { padding: 4px; border: 1px solid; }
30+
table.issues-index td:nth-child(1) { text-align: right; }
31+
table.issues-index td:nth-child(2) { text-align: left; }
32+
table.issues-index td:nth-child(3) { text-align: left; }
33+
table.issues-index td:nth-child(4) { text-align: left; }
34+
table.issues-index td:nth-child(5) { text-align: center; }
35+
table.issues-index td:nth-child(6) { text-align: center; }
36+
table.issues-index td:nth-child(7) { text-align: left; }
37+
table.issues-index td:nth-child(5) span.no-pr { color: red; }
38+
@media (prefers-color-scheme: dark) {
39+
html {
40+
color: #ddd;
41+
background-color: black;
42+
}
43+
ins {
44+
background-color: #225522
45+
}
46+
del {
47+
background-color: #662222
48+
}
49+
a {
50+
color: #6af
51+
}
52+
a:visited {
53+
color: #6af
54+
}
55+
blockquote.note
56+
{
57+
background-color: rgba(255, 255, 255, .10)
58+
}
59+
}
60+
</style>
61+
</head>
62+
<body>
63+
<hr>
64+
<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>
65+
<h3 id="4252"><a href="lwg-active.html#4252">4252</a>. Are exposition-only classes considered specified for the purpose of <code class='backtick'>final</code>?</h3>
66+
<p><b>Section:</b> 16.4.6.13 <a href="https://wg21.link/derivation">[derivation]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
67+
<b>Submitter:</b> Jiang An <b>Opened:</b> 2025-04-28 <b>Last modified:</b> 2025-05-04</p>
68+
<p><b>Priority: </b>Not Prioritized
69+
</p>
70+
<p><b>View all other</b> <a href="lwg-index.html#derivation">issues</a> in [derivation].</p>
71+
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
72+
<p><b>Discussion:</b></p>
73+
<p>
74+
Currently, iterator and sentinel types of several views are exposition-only in the standard wording,
75+
and none of them is specified to be <code class='backtick'>final</code>. These types are arguably required to be non-final due to
76+
16.4.6.13 <a href="https://wg21.link/derivation">[derivation]</a> p4 because it's possible to say they are specified except for names.
77+
<p/>
78+
However, libc++ marks <code class='backtick'>join_view</code>'s iterator <code class='backtick'>final</code> for some reasons
79+
(<a href="https://reviews.llvm.org/D142811#inline-1383022">https://reviews.llvm.org/D142811#inline-1383022</a>).
80+
Perhaps we should clarify that the <code class='backtick'>final</code>-ity of exposition-only class is unspecified.
81+
</p>
82+
83+
84+
<p id="res-4252"><b>Proposed resolution:</b></p>
85+
<p>
86+
This wording is relative to <a href="https://wg21.link/N5008">N5008</a>.
87+
</p>
88+
<ol>
89+
90+
<li><p>Modify 16.4.6.13 <a href="https://wg21.link/derivation">[derivation]</a> as indicated:</p>
91+
92+
<blockquote>
93+
<p>
94+
-4- All types specified in the C++ standard library shall be non-<code class='backtick'>final</code> types unless otherwise specified.
95+
<ins>Exposition-only classes (16.3.3.2 <a href="https://wg21.link/expos.only.entity">[expos.only.entity]</a>) are not considered specified for the purpose
96+
of <code class='backtick'>final</code>.</ins>
97+
</p>
98+
</blockquote>
99+
</li>
100+
</ol>
101+
102+
103+
104+
105+
106+
</body>
107+
</html>

‎lwg-active.html‎

Lines changed: 44 additions & 44 deletions
Large diffs are not rendered by default.

‎lwg-closed.html‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -79,7 +79,7 @@
7979
</tr>
8080
</table>
8181
<h1>C++ Standard Library Closed Issues List (Revision D125)</h1>
82-
<p>Revised 2025-05-04 at 10:53:50 UTC
82+
<p>Revised 2025-05-04 at 10:55:39 UTC
8383
</p>
8484
<p>Reference ISO/IEC IS 14882:2020(E)</p>
8585
<p>Also see:</p>
@@ -120,7 +120,7 @@ <h2 id='History'>Revision History</h2>
120120
always provide iterator_category (Status: New)">4116</a>, <a href="lwg-active.html#4117" title="generator::iterator should provide iterator_concept (Status: New)">4117</a>, <a href="lwg-active.html#4118" title="How should duration formatters format custom rep types? (Status: New)">4118</a>, <a href="lwg-active.html#4120" title="move_iterator should provide iterator_category only when it models
121121
forward_iterator (Status: New)">4120</a>, <a href="lwg-active.html#4121" title="ranges::to constructs associative containers via c.emplace(c.end(), *it) (Status: New)">4121</a>, <a href="lwg-active.html#4122" title="Ill-formed operator&lt;=&gt; can cause hard error when instantiating std::inplace_vector (Status: New)">4122</a>, <a href="lwg-active.html#4123" title="Container effects use &quot;the assignment operator or move assignment operator&quot; (Status: New)">4123</a>, <a href="lwg-active.html#4125" title="move_iterator's default constructor should be constrained (Status: New)">4125</a>, <a href="lwg-active.html#4127" title="The Standard Library should not use predicates of the form pred(*i) != false (Status: New)">4127</a>, <a href="lwg-active.html#4128" title="Allocator requirements should not allow rebinding conversions to be explicit (Status: New)">4128</a>, <a href="lwg-active.html#4129" title="Possibly incorrect wording for data race avoidance (Status: New)">4129</a>, <a href="lwg-active.html#4131" title="Including &lt;optional&gt; doesn't provide std::begin/end (Status: New)">4131</a>, <a href="lwg-active.html#4132" title="Throws specifications need to include boolean-testable operations (Status: New)">4132</a>, <a href="lwg-active.html#4133" title="awaitable-receiver's members are potentially throwing (Status: New)">4133</a>, <a href="lwg-active.html#4136" title="Specify behavior of [linalg] Hermitian algorithms on diagonal with nonzero imaginary part (Status: New)">4136</a>, <a href="lwg-active.html#4137" title="Fix Mandates, Preconditions, and Complexity elements of [linalg] algorithms (Status: New)">4137</a>, <a href="lwg-active.html#4138" title="is_within_lifetime should mandate is_object (Status: New)">4138</a>, <a href="lwg-active.html#4139" title="&sect;[time.zone.leap] recursive constraint in &lt;=&gt; (Status: New)">4139</a>, <a href="lwg-active.html#4143" title="execution::set_value/set_error/set_stopped/start should always return void (Status: New)">4143</a>, <a href="lwg-active.html#4145" title="Unclear how [res.on.data.races] apply to templated functions (Status: New)">4145</a>, <a href="lwg-active.html#4146" title="&sect;[format.formatter.spec]/3 unconditionally enables nonlocking for container adaptors (Status: New)">4146</a>, <a href="lwg-active.html#4149" title="User defined macros without standard headers (294 redux) (Status: New)">4149</a>, <a href="lwg-active.html#4151" title="Precondition of inplace_vector::swap (Status: New)">4151</a>, <a href="lwg-active.html#4152" title="The primary template of std::char_traits is totally underspecified (Status: New)">4152</a>, <a href="lwg-active.html#4155" title="Cpp17NullablePointer should require that some expression can be contextually converted to bool (Status: New)">4155</a>, <a href="lwg-active.html#4158" title="packaged_task::operator= should abandon its shared state (Status: New)">4158</a>, <a href="lwg-active.html#4159" title="Uses-allocator construction mechanisms should be opted out for node handles (Status: New)">4159</a>, <a href="lwg-active.html#4160" title="packaged_task should reject rvalue reference return types (Status: New)">4160</a>, <a href="lwg-active.html#4161" title="Some free functions don't automatically work for program-defined std::complex&lt;NonFloatingPoint&gt; (Status: New)">4161</a>, <a href="lwg-active.html#4162" title="Worst time complexity of non-parallel versions of nth_element is underspecified (Status: New)">4162</a>, <a href="lwg-active.html#4165" title="Should swapping a built-in array or std::array with itself result in UB? (Status: New)">4165</a>, <a href="lwg-active.html#4166" title="concat_view::end() should be more constrained in order to support noncopyable iterators (Status: New)">4166</a>, <a href="lwg-active.html#4167" title="Use of &quot;smaller&quot; and &quot;larger&quot; in min,
122122
max, and minmax is unclear (Status: New)">4167</a>, <a href="lwg-active.html#4168" title="std::start_lifetime_as inadvertently has undefined behavior due to use of std::bit_cast (Status: New)">4168</a>, <a href="lwg-active.html#4171" title="P2609R3 breaks code that uses views::zip and get&lt;T&gt; (Status: New)">4171</a>, <a href="lwg-active.html#4173" title="Better term for &quot;references, pointers and iterators to elements&quot; (Status: New)">4173</a>, <a href="lwg-active.html#4176" title="Refer back to container requirements when extending them (Status: New)">4176</a>, <a href="lwg-active.html#4180" title="Inconsistent constraints on flat_foo::emplace (Status: New)">4180</a>, <a href="lwg-active.html#4181" title="Some ranges have negative ssize (Status: New)">4181</a>, <a href="lwg-active.html#4182" title="Definition of NULL is too broad (Status: New)">4182</a>, <a href="lwg-active.html#4183" title="subrange should provide data() (Status: New)">4183</a>, <a href="lwg-active.html#4185" title="Ill-formed, no diagnostic required on runtime behavior (Status: New)">4185</a>, <a href="lwg-active.html#4187" title="bitset::reference should be const-assignable (Status: New)">4187</a>, <a href="lwg-active.html#4190" title="Specification of completion-signatures-for in [exec.snd.expos]/p39 is recursive (Status: New)">4190</a>, <a href="lwg-active.html#4192" title="&sect;[ios.base.cons] ios_base members may not have indeterminate values after construction (Status: New)">4192</a>, <a href="lwg-active.html#4193" title="&sect;[time.zone.db] the specification uses the undefined term &quot;thread-safe&quot; (Status: New)">4193</a>, <a href="lwg-active.html#4195" title="expected&lt;int, int&gt; isn't specified to be trivially assignable (Status: New)">4195</a>, <a href="lwg-active.html#4197" title="Complexity of std::visit with immediate functions (Status: New)">4197</a>, <a href="lwg-active.html#4199" title="constraints on user customizations of standard sender algorithms are incorrectly specified (Status: New)">4199</a>, <a href="lwg-active.html#4206" title="Alias template connect_result_t should be constrained with sender_to (Status: New)">4206</a>, <a href="lwg-active.html#4207" title="Point of reference for source_location is not specified when used in an default template argument (Status: New)">4207</a>, <a href="lwg-active.html#4210" title="Issue with cache_latest_view::iterator's reference type (Status: New)">4210</a>, <a href="lwg-active.html#4211" title="IANA time zone database allows links to refer to links (Status: New)">4211</a>, <a href="lwg-active.html#4212" title="Make the round states in [rand.eng.philox] explicit (Status: New)">4212</a>, <a href="lwg-active.html#4213" title="Sender spec depends on unspecified order of evaluation (Status: New)">4213</a>, <a href="lwg-active.html#4214" title="Missing Preconditions for take/drop adaptor (Status: New)">4214</a>, <a href="lwg-active.html#4215" title="run_loop::finish should be noexcept (Status: New)">4215</a>, <a href="lwg-active.html#4216" title="num_put::do_put and void pointers (Status: New)">4216</a>, <a href="lwg-active.html#4217" title="Clarify mdspan layout mapping requirements for rank == 0 (Status: New)">4217</a>, <a href="lwg-active.html#4218" title="Constraint recursion in basic_const_iterator's relational operators due to ADL + CWG 2369 (Status: New)">4218</a>, <a href="lwg-active.html#4219" title="std::vector::erase[_if] should be based on ranges remove (Status: New)">4219</a>, <a href="lwg-active.html#4220" title="join_view incorrectly stores inner range (Status: New)">4220</a>, <a href="lwg-active.html#4221" title="Cannot format const-iterable only ranges (Status: New)">4221</a>, <a href="lwg-active.html#4222" title="expected constructor from a single value missing a constraint (Status: New)">4222</a>, <a href="lwg-active.html#4223" title="Deduction guides for maps are mishandling tuples and references (Status: New)">4223</a>, <a href="lwg-active.html#4224" title="Philox engines should be freestanding (Status: New)">4224</a>, <a href="lwg-active.html#4225" title="What should happen when an exception is thrown on resizing std::deque, std::forward_list, or std::list? (Status: New)">4225</a>, <a href="lwg-active.html#4226" title="to_input_view::iterator cannot be compared to its const sentinel (Status: New)">4226</a>, <a href="lwg-active.html#4227" title="Missing noexcept operator in [exec.when.all] (Status: New)">4227</a>, <a href="lwg-active.html#4228" title="Does vector&lt;bool, Allocator&gt; mandate that Allocator::value_type is bool? (Status: New)">4228</a>, <a href="lwg-active.html#4229" title="std::ranges::to with union return type (Status: New)">4229</a>, <a href="lwg-active.html#4230" title="simd&lt;complex&gt;::real/imag is overconstrained (Status: New)">4230</a>, <a href="lwg-active.html#4231" title="datapar::chunk&lt;N&gt; should use simd-size-type instead of size_t (Status: New)">4231</a>, <a href="lwg-active.html#4232" title="datapar::resize does not resize (Status: New)">4232</a>, <a href="lwg-active.html#4233" title="The helper lambda of std::erase for hive should specify return type as
123-
bool (Status: New)">4233</a>, <a href="lwg-active.html#4234" title="Including &lt;hive&gt; doesn't provide std::begin/end (Status: New)">4234</a>, <a href="lwg-active.html#4235" title="cache_latest_view and to_input_view miss reserve_hint (Status: New)">4235</a>, <a href="lwg-active.html#4236" title="chunk_view::outer-iterator::value_type should provide reserve_hint (Status: New)">4236</a>, <a href="lwg-active.html#4237" title="The standard library iterator adaptor does not handle iterator_category correctly (Status: New)">4237</a>, <a href="lwg-active.html#4238" title="simd_mask&lt;complex&lt;double&gt;&gt;::operator+/-/~ return a disabled simd specialization (Status: New)">4238</a>, <a href="lwg-active.html#4239" title="flat_map's transparent comparator no longer works for string literals (Status: New)">4239</a>, <a href="lwg-active.html#4240" title="The formattable type is not a formattable type (Status: New)">4240</a>, <a href="lwg-active.html#4241" title="ranges::for_each(_n) should be less constrained (Status: New)">4241</a>, <a href="lwg-active.html#4242" title="ranges::distance does not work with volatile iterators (Status: New)">4242</a>, <a href="lwg-active.html#4243" title="as_bytes/as_writable_bytes is broken with span&lt;volatile T&gt; (Status: New)">4243</a>, <a href="lwg-active.html#4244" title="Whether the spuriously failed comparison applies to compare_exchange_strong is unclear (Status: New)">4244</a>, <a href="lwg-active.html#4245" title="Operators that interact with counted_iterator and default_sentinel_t should be noexcept (Status: New)">4245</a>, <a href="lwg-active.html#4246" title="Redundant constraint in range_formatter::format (Status: New)">4246</a>, <a href="lwg-active.html#4247" title="Header &lt;stdbit.h&gt; is not yet freestanding (Status: New)">4247</a>, <a href="lwg-active.html#4248" title="Late domain-based dispatching of schedule_from and continues_on are flipped (Status: New)">4248</a>, <a href="lwg-active.html#4249" title="The past end issue for lazy_split_view (Status: New)">4249</a>, <a href="lwg-active.html#4250" title="swap overloads for indirect and polymorphic only found by ADL (Status: New)">4250</a>, <a href="lwg-active.html#4251" title="Are exposition-only classes considered specified for the purpose of final? (Status: New)">4251</a>, <a href="lwg-active.html#4251" title="Are exposition-only classes considered specified for the purpose of final? (Status: New)">4251</a>.</li>
123+
bool (Status: New)">4233</a>, <a href="lwg-active.html#4234" title="Including &lt;hive&gt; doesn't provide std::begin/end (Status: New)">4234</a>, <a href="lwg-active.html#4235" title="cache_latest_view and to_input_view miss reserve_hint (Status: New)">4235</a>, <a href="lwg-active.html#4236" title="chunk_view::outer-iterator::value_type should provide reserve_hint (Status: New)">4236</a>, <a href="lwg-active.html#4237" title="The standard library iterator adaptor does not handle iterator_category correctly (Status: New)">4237</a>, <a href="lwg-active.html#4238" title="simd_mask&lt;complex&lt;double&gt;&gt;::operator+/-/~ return a disabled simd specialization (Status: New)">4238</a>, <a href="lwg-active.html#4239" title="flat_map's transparent comparator no longer works for string literals (Status: New)">4239</a>, <a href="lwg-active.html#4240" title="The formattable type is not a formattable type (Status: New)">4240</a>, <a href="lwg-active.html#4241" title="ranges::for_each(_n) should be less constrained (Status: New)">4241</a>, <a href="lwg-active.html#4242" title="ranges::distance does not work with volatile iterators (Status: New)">4242</a>, <a href="lwg-active.html#4243" title="as_bytes/as_writable_bytes is broken with span&lt;volatile T&gt; (Status: New)">4243</a>, <a href="lwg-active.html#4244" title="Whether the spuriously failed comparison applies to compare_exchange_strong is unclear (Status: New)">4244</a>, <a href="lwg-active.html#4245" title="Operators that interact with counted_iterator and default_sentinel_t should be noexcept (Status: New)">4245</a>, <a href="lwg-active.html#4246" title="Redundant constraint in range_formatter::format (Status: New)">4246</a>, <a href="lwg-active.html#4247" title="Header &lt;stdbit.h&gt; is not yet freestanding (Status: New)">4247</a>, <a href="lwg-active.html#4248" title="Late domain-based dispatching of schedule_from and continues_on are flipped (Status: New)">4248</a>, <a href="lwg-active.html#4249" title="The past end issue for lazy_split_view (Status: New)">4249</a>, <a href="lwg-active.html#4250" title="swap overloads for indirect and polymorphic only found by ADL (Status: New)">4250</a>, <a href="lwg-active.html#4251" title="Move assignment for indirect unnecessarily requires copy construction (Status: New)">4251</a>, <a href="lwg-active.html#4252" title="Are exposition-only classes considered specified for the purpose of final? (Status: New)">4252</a>.</li>
124124
<li>Added the following 3 Open issues: <a href="lwg-active.html#3988" title="Should as_const_view and basic_const_iterator provide base()? (Status: Open)">3988</a>, <a href="lwg-active.html#4015" title="LWG 3973 broke const overloads of std::optional monadic operations (Status: Open)">4015</a>, <a href="lwg-active.html#4130" title="Preconditions for std::launder might be overly strict (Status: Open)">4130</a>.</li>
125125
<li>Added the following LEWG issue: <a href="lwg-active.html#4097" title="views::reverse should be specialized for some view types (Status: LEWG)">4097</a>.</li>
126126
<li>Added the following 4 SG1 issues: <a href="lwg-active.html#4004" title="The load and store operation in &sect;[atomics.order] p1 is ambiguous (Status: SG1)">4004</a>, <a href="lwg-active.html#4075" title="Thread stability requirement on constructors and destructors (Status: SG1)">4075</a>, <a href="lwg-active.html#4174" title="How does [atomics.order] p3 apply when then modification is an initialization? (Status: SG1)">4174</a>, <a href="lwg-active.html#4177" title="&sect;[atomics.order] p8 &quot;circularly depend on their own computation&quot; is unclear for loop (Status: SG1)">4177</a>.</li>

0 commit comments

Comments
 (0)