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Author: brevzin

3074_consexpr_union_lifetime/Makefile

@@ -1,2 +1,2 @@
-p3074r5.html : constexpr-union-lifetime.md
+p3074r6.html : constexpr-union-lifetime.md
 include ../md/mpark-wg21.mk

3074_consexpr_union_lifetime/constexpr-union-lifetime.md

@@ -1,6 +1,6 @@
 ---
 title: "trivial `union`s (was `std::uninitialized<T>`)"
-document: P3074R5
+document: P3074R6
 date: today
 audience: EWG
 author:
@@ -531,15 +531,15 @@ I was able to compile Clang with this update successfully, which wasn't particul
 Change [class.default.ctor]{.sref}/2-3. [The third and fourth bullets can be removed because such cases become trivially default constructible too]{.ednote}
 
 ::: std
-[2]{.pnum} A defaulted default constructor for class `X` is defined as deleted if [`X` is a non-union class and]{.addu}:
+[2]{.pnum} A defaulted default constructor for class `X` is defined as deleted if [`X` is a non-union class and]{.addu}
 
 * [2.1]{.pnum} any non-static data member with no default member initializer ([class.mem]) is of reference type,
 * [2.2]{.pnum} any non-variant non-static data member of const-qualified type (or possibly multi-dimensional array thereof) with no brace-or-equal-initializer is not const-default-constructible ([dcl.init]),
 * [2.3]{.pnum} [`X` is a union and all of its variant members are of const-qualified type (or possibly multi-dimensional array thereof),]{.rm}
 * [2.4]{.pnum} [`X` is a non-union class and all members of any anonymous union member are of const-qualified type (or possibly multi-dimensional array thereof)]{.rm},
 * [2.5]{.pnum} any potentially constructed subobject, except for a non-static data member with a brace-or-equal-initializer [or a variant member of a union where another non-static data member has a brace-or-equal-initializer]{.rm}, has class type `M` (or possibly multi-dimensional array thereof) and overload resolution ([over.match]) as applied to find `M`'s corresponding constructor either does not result in a usable candidate ([over.match.general]) [or, in the case of a variant member, selects a non-trivial function,]{.rm} or
 
-[3]{.pnum} A default constructor [for a class `X`]{.addu} is *trivial* if it is not user-provided and if:
+[3]{.pnum} A default constructor [for a class `X`]{.addu} is *trivial* if it is not user-provided and if[:]{.rm}
 
 * [3.1]{.pnum} [its class]{.rm} [`X`]{.addu} has no virtual functions ([class.virtual]) and no virtual base classes ([class.mi]), and
 * [3.2]{.pnum} no non-static data member of [its class]{.rm} [`X`]{.addu} has a default member initializer ([class.mem]), and
@@ -554,20 +554,20 @@ Otherwise, the default constructor is *non-trivial*.
 Change [class.dtor]{.sref}/7-8:
 
 ::: std
-[7]{.pnum} A defaulted destructor for a class `X` is defined as deleted if:
+[7]{.pnum} A defaulted destructor for a class `X` is defined as deleted if[:]{.rm}
 
 * [7.1]{.pnum} [`X` is a non-union class and]{.addu} any potentially constructed subobject has class type `M` (or possibly multi-dimensional array thereof) [and]{.rm} [where]{.addu} `M` has a destructor that is deleted or is inaccessible from the defaulted destructor [or, in the case of a variant member, is non-trivial]{.rm},
 
 ::: addu
-* [7.x]{.pnum} `X` is a union and either:
+* [7.x]{.pnum} `X` is a union and either
 
-    * [#.x.#]{.pnum} `X` has a user-provided default constructor, or
-    * [#.x.#]{.pnum} `X` has a variant member `M` where `M` has a default member initializer and `M` has a destructor that is deleted, inaccessible from the defaulted destructor, or non-trivial,
+    * [#.x.#]{.pnum} `X` does not have a default constructor that is defaulted on its first declaration,
+    * [#.x.#]{.pnum} `X` has a variant member `V` of class type `M` (or possibly multi-dimensional array thereof) where `V` has a default member initializer and `M` has a destructor that is non-trivial, deleted, or inaccessible from the defaulted destructor,
 :::
 
 * [7.2]{.pnum} or, for a virtual destructor, lookup of the non-array deallocation function results in an ambiguity or in a function that is deleted or inaccessible from the defaulted destructor.
 
-[8]{.pnum} A destructor [for a class `X`]{.addu} is *trivial* if it is not user-provided and if:
+[8]{.pnum} A destructor [for a class `X`]{.addu} is *trivial* if it is not user-provided and if[:]{.rm}
 
 * [8.1]{.pnum} the destructor is not virtual,
 * [8.2]{.pnum} all of the direct base classes of [its class]{.rm} [`X`]{.addu} have trivial destructors, and
@@ -597,7 +597,7 @@ Add a new macro to [cpp.predefined]{.sref}:
 
 ::: {.std .ins}
 ```
-__cpp_trivial_union 2024XXL
+__cpp_trivial_union 2025XXL
 ```
 :::
 
@@ -606,6 +606,6 @@ And update the macro for `inplace_vector` in [version.syn]{.sref}:
 ::: std
 ```diff
 - #define __cpp_lib_inplace_vector 202406L // also in <inplace_vector>
-+ #define __cpp_lib_inplace_vector 2024XXL // also in <inplace_vector>
++ #define __cpp_lib_inplace_vector 2025XXL // also in <inplace_vector>
 ```
 :::

3074_consexpr_union_lifetime/p3074r5.html

@@ -4,7 +4,7 @@
   <meta charset="utf-8" />
   <meta name="generator" content="mpark/wg21" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
-  <meta name="dcterms.date" content="2024-12-16" />
+  <meta name="dcterms.date" content="2025-02-11" />
   <title>trivial unions (was std::uninitialized&lt;T&gt;)</title>
   <style>
       code{white-space: pre-wrap;}
@@ -448,6 +448,9 @@
 td > div.sourceCode {
 background-color: inherit;
 }
+td > div > div.sourceCode {
+background-color: inherit;
+}
 table {
 border-collapse: collapse;
 }
@@ -567,7 +570,7 @@ <h1 class="title" style="text-align:center">trivial
   </tr>
   <tr>
     <td>Date:</td>
-    <td>2024-12-16</td>
+    <td>2025-02-11</td>
   </tr>
   <tr>
     <td style="vertical-align:top">Project:</td>
@@ -632,10 +635,10 @@ <h1 id="toctitle">Contents</h1>
 </div>
 <h1 data-number="1" style="border-bottom:1px solid #cccccc" id="revision-history"><span class="header-section-number">1</span>
 Revision History<a href="#revision-history" class="self-link"></a></h1>
-<p>Since <span class="citation" data-cites="P3074R4">[<a href="https://wg21.link/p3074r4" role="doc-biblioref">P3074R4</a>]</span>, wording changes and adjusted
+<p>Since <span class="citation" data-cites="P3074R4"><a href="https://wg21.link/p3074r4" role="doc-biblioref">[P3074R4]</a></span>, wording changes and adjusted
 the rule for when a <a href="#constructordestructor-intention-matching">union’s destructor is
 deleted</a></p>
-<p>Since <span class="citation" data-cites="P3074R3">[<a href="https://wg21.link/p3074r3" role="doc-biblioref">P3074R3</a>]</span>, in <a href="https://github.com/cplusplus/papers/issues/1734#issuecomment-2195769496">St. Louis</a>,
+<p>Since <span class="citation" data-cites="P3074R3"><a href="https://wg21.link/p3074r3" role="doc-biblioref">[P3074R3]</a></span>, in <a href="https://github.com/cplusplus/papers/issues/1734#issuecomment-2195769496">St. Louis</a>,
 EWG had expressed a clear preference for “just make it work”:</p>
 <table>
 <thead>
@@ -699,15 +702,15 @@ <h1 data-number="1" style="border-bottom:1px solid #cccccc" id="revision-history
 </tbody>
 </table>
 <p>So proposing to make it work and adding <a href="#implementation-experience">implementation experience</a>.</p>
-<p>Since <span class="citation" data-cites="P3074R2">[<a href="https://wg21.link/p3074r2" role="doc-biblioref">P3074R2</a>]</span>, changed to instead propose a
+<p>Since <span class="citation" data-cites="P3074R2"><a href="https://wg21.link/p3074r2" role="doc-biblioref">[P3074R2]</a></span>, changed to instead propose a
 language change to unions (with two options) to solve the problems
 presented</p>
-<p>Since <span class="citation" data-cites="P3074R1">[<a href="https://wg21.link/p3074r1" role="doc-biblioref">P3074R1</a>]</span>, the <code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">&gt;</span></code>
+<p>Since <span class="citation" data-cites="P3074R1"><a href="https://wg21.link/p3074r1" role="doc-biblioref">[P3074R1]</a></span>, the <code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">&gt;</span></code>
 design was designed in an EWG telecon and the suggestion was made to
 make this a language feature. Added a section to argue against and
 re-spelled <code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">&gt;</span></code>
 to be a union instead of a class containing an anonymous union.</p>
-<p>Since <span class="citation" data-cites="P3074R0">[<a href="https://wg21.link/p3074r0" role="doc-biblioref">P3074R0</a>]</span>, originally proposed the
+<p>Since <span class="citation" data-cites="P3074R0"><a href="https://wg21.link/p3074r0" role="doc-biblioref">[P3074R0]</a></span>, originally proposed the
 function <code class="sourceCode cpp">std<span class="op">::</span>start_lifetime<span class="op">(</span>p<span class="op">)</span></code>.
 R1 adds a new section discussing the <a href="#the-uninitialized-storage-problem">uninitialized storage
 problem</a>, which motivates a change in design to instead propose <code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">&gt;</span></code>.</p>
@@ -750,10 +753,10 @@ <h1 data-number="2" style="border-bottom:1px solid #cccccc" id="introduction"><s
 MSVC and EDG accept it and GCC did accept it even up to 13.2, but GCC
 trunk and Clang reject).</p>
 <p>Getting this example to work would allow <code class="sourceCode cpp">std<span class="op">::</span>inplace_vector</code>
-(<span class="citation" data-cites="P0843R14">[<a href="https://wg21.link/p0843r14" role="doc-biblioref">P0843R14</a>]</span>) to simply work during
+(<span class="citation" data-cites="P0843R14"><a href="https://wg21.link/p0843r14" role="doc-biblioref">[P0843R14]</a></span>) to simply work during
 <code class="sourceCode cpp"><span class="kw">constexpr</span></code>
 time for all times (instead of just trivial ones), and was a problem
-briefly touched on in <span class="citation" data-cites="P2747R0">[<a href="https://wg21.link/p2747r0" role="doc-biblioref">P2747R0</a>]</span>.</p>
+briefly touched on in <span class="citation" data-cites="P2747R0"><a href="https://wg21.link/p2747r0" role="doc-biblioref">[P2747R0]</a></span>.</p>
 <h2 data-number="2.1" id="the-uninitialized-storage-problem"><span class="header-section-number">2.1</span> The uninitialized storage
 problem<a href="#the-uninitialized-storage-problem" class="self-link"></a></h2>
 <p>A closely related problem to the above is: how do you do
@@ -957,16 +960,16 @@ <h1 data-number="3" style="border-bottom:1px solid #cccccc" id="design-space"><s
 <li>provide an explicit function to start lifetime of a union
 alternative (<code class="sourceCode cpp">std<span class="op">::</span>start_lifetime</code>).</li>
 </ol>
-<p>The first revision of this paper (<span class="citation" data-cites="P3074R0">[<a href="https://wg21.link/p3074r0" role="doc-biblioref">P3074R0</a>]</span>) proposed that last option.
+<p>The first revision of this paper (<span class="citation" data-cites="P3074R0"><a href="https://wg21.link/p3074r0" role="doc-biblioref">[P3074R0]</a></span>) proposed that last option.
 However, with the addition of the overlapping subobjects problem and the
 realization that the union solution has overhead compared to the buffer
 storage solution, it would be more desirable to solve both problems in
 one go. That is, it’s not enough to just start the lifetime of the
 alternative, we also want a trivially constructible/destructible
 solution for uninitialized storage.</p>
-<p><span class="citation" data-cites="P3074R1">[<a href="https://wg21.link/p3074r1" role="doc-biblioref">P3074R1</a>]</span> and <span class="citation" data-cites="P3074R2">[<a href="https://wg21.link/p3074r2" role="doc-biblioref">P3074R2</a>]</span> proposed the first solution
+<p><span class="citation" data-cites="P3074R1"><a href="https://wg21.link/p3074r1" role="doc-biblioref">[P3074R1]</a></span> and <span class="citation" data-cites="P3074R2"><a href="https://wg21.link/p3074r2" role="doc-biblioref">[P3074R2]</a></span> proposed the first solution
 (<code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">&gt;</span></code>).
-<span class="citation" data-cites="P3074R3">[<a href="https://wg21.link/p3074r3" role="doc-biblioref">P3074R3</a>]</span> proposed either the third or
+<span class="citation" data-cites="P3074R3"><a href="https://wg21.link/p3074r3" role="doc-biblioref">[P3074R3]</a></span> proposed either the third or
 fourth. This revision (R4) proposes specifically the third (just make it
 work).</p>
 <p>Let’s go over some of the solutions.</p>
@@ -994,8 +997,9 @@ <h2 data-number="3.1" id="a-library-type-stduninitializedt"><span class="header-
 <p><code class="sourceCode cpp">std<span class="op">::</span>inplace_vector<span class="op">&lt;</span>T, N<span class="op">&gt;</span></code>
 would then have a <code class="sourceCode cpp">std<span class="op">::</span>uninitialized<span class="op">&lt;</span>T<span class="op">[</span>N<span class="op">]&gt;</span></code>
 and go ahead and <code class="sourceCode cpp">std<span class="op">::</span>construct_at</code>
-(or, with <span class="citation" data-cites="P2747R2">[<a href="https://wg21.link/p2747r2" role="doc-biblioref">P2747R2</a>]</span>, simply placement-new) into the
-appropriate elements of that array and everything would just work.</p>
+(or, with <span class="citation" data-cites="P2747R2"><a href="https://wg21.link/p2747r2" role="doc-biblioref">[P2747R2]</a></span>, simply placement-new) into
+the appropriate elements of that array and everything would just
+work.</p>
 <p>Because the language would recognize this type, this would also solve
 the overlapping objects problem.</p>
 <h2 data-number="3.2" id="a-language-annotation"><span class="header-section-number">3.2</span> A language annotation<a href="#a-language-annotation" class="self-link"></a></h2>
@@ -1272,7 +1276,7 @@ <h2 data-number="3.5" id="existing-practice"><span class="header-section-number"
 purpose.</p>
 <h2 data-number="3.6" id="st.-louis-meeting-2024"><span class="header-section-number">3.6</span> St. Louis Meeting, 2024<a href="#st.-louis-meeting-2024" class="self-link"></a></h2>
 <p>In <a href="https://github.com/cplusplus/papers/issues/1734#issuecomment-2195769496">St. Louis</a>,
-we discussed a previous revision of this paper (<span class="citation" data-cites="P3074R3">[<a href="https://wg21.link/p3074r3" role="doc-biblioref">P3074R3</a>]</span>), specifically the <a href="#trivial-unions">trivial union</a> and <a href="#just-make-it-work">just make it work</a> designs. There, EWG
+we discussed a previous revision of this paper (<span class="citation" data-cites="P3074R3"><a href="https://wg21.link/p3074r3" role="doc-biblioref">[P3074R3]</a></span>), specifically the <a href="#trivial-unions">trivial union</a> and <a href="#just-make-it-work">just make it work</a> designs. There, EWG
 expressed a clear preference for “just make it work”:</p>
 <table>
 <thead>
@@ -1627,11 +1631,11 @@ <h2 data-number="4.2" id="language-wording"><span class="header-section-number">
 </blockquote>
 </div>
 <h2 data-number="4.3" id="library-wording"><span class="header-section-number">4.3</span> Library Wording<a href="#library-wording" class="self-link"></a></h2>
-<p>While this paper was in flight, <span class="citation" data-cites="P0843R14">[<a href="https://wg21.link/p0843r14" role="doc-biblioref">P0843R14</a>]</span> was moved, which had to work
+<p>While this paper was in flight, <span class="citation" data-cites="P0843R14"><a href="https://wg21.link/p0843r14" role="doc-biblioref">[P0843R14]</a></span> was moved, which had to work
 around the lack of ability to actually support non-trivial types during
 constant evaluation. Since this paper now provides that, might as well
 fix the library to account for the new functionality.</p>
-<p>Strike <span>24.3.14.1 <a href="https://wg21.link/inplace.vector.overview">[inplace.vector.overview]</a></span>/4:</p>
+<p>Strike <span>23.3.14.1 <a href="https://wg21.link/inplace.vector.overview">[inplace.vector.overview]</a></span>/4:</p>
 <div class="std">
 <blockquote>
 <p><span class="marginalizedparent"><a class="marginalized" href="#pnum_23" id="pnum_23">3</a></span>