<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Issue 3901: Is uses-allocator construction of a cv-qualified object type still well-formed after LWG 3870?</title>
<meta property="og:title" content="Issue 3901: Is uses-allocator construction of a cv-qualified object type still well-formed after LWG 3870?">
<meta property="og:description" content="C++ library issue. Status: NAD">
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue3901.html">
<meta property="og:type" content="website">
<meta property="og:image" content="http://cplusplus.github.io/LWG/images/cpp_logo.png">
<meta property="og:image:alt" content="C++ logo">
<style>
  p {text-align:justify}
  li {text-align:justify}
  pre code.backtick::before { content: "`" }
  pre code.backtick::after { content: "`" }
  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}
  table.issues-index { border: 1px solid; border-collapse: collapse; }
  table.issues-index th { text-align: center; padding: 4px; border: 1px solid; }
  table.issues-index td { padding: 4px; border: 1px solid; }
  table.issues-index td:nth-child(1) { text-align: right; }
  table.issues-index td:nth-child(2) { text-align: left; }
  table.issues-index td:nth-child(3) { text-align: left; }
  table.issues-index td:nth-child(4) { text-align: left; }
  table.issues-index td:nth-child(5) { text-align: center; }
  table.issues-index td:nth-child(6) { text-align: center; }
  table.issues-index td:nth-child(7) { text-align: left; }
  table.issues-index td:nth-child(5) span.no-pr { color: red; }
  @media (prefers-color-scheme: dark) {
     html {
        color: #ddd;
        background-color: black;
     }
     ins {
        background-color: #225522
     }
     del {
        background-color: #662222
     }
     a {
        color: #6af
     }
     a:visited {
        color: #6af
     }
     blockquote.note
     {
        background-color: rgba(255, 255, 255, .10)
     }
  }
</style>
</head>
<body>
<hr>
<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#NAD">NAD</a> status.</em></p>
<h3 id="3901"><a href="lwg-closed.html#3901">3901</a>. Is uses-allocator construction of a <i>cv</i>-qualified object type still well-formed after LWG 3870?</h3>
<p><b>Section:</b> 20.2.8 <a href="https://wg21.link/allocator.uses">[allocator.uses]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Jiang An <b>Opened:</b> 2023-03-05 <b>Last modified:</b> 2024-06-24</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
LWG <a href="lwg-defects.html#3870" title="Remove voidify (Status: C++23)">3870</a><sup><a href="https://cplusplus.github.io/LWG/issue3870" title="Latest snapshot">(i)</a></sup> made <code>std::construct_at</code> unable to create an object of a <i>cv</i>-qualified type, 
which affects <code>std::uninitialized_construct_using_allocator</code>. However, uses-allocator construction is 
currently not required to be equivalent to some call to <code>std::uninitialized_construct_using_allocator</code>, 
which possibly implies that uses-allocator construction of a <i>cv</i>-qualified type may still be required to be 
well-formed.
<p/>
Should we make such construction ill-formed?
</p>

<p><i>[2023-03-22; Reflector poll]</i></p>

<p>Set status to Tentatively NAD.</p>
<p>Not all uses-allocator construction is done using <code>construct_at</code>.
<code>std::tuple&lt;const T&gt;(allocator_arg, alloc)</code> does
uses-allocator construction of a const type, so we can't make it ill-formed.
</p>

<p><i>[St. Louis 2024-06-24 Status changed: Tentatively NAD &rarr; NAD.]</i></p>



<p id="res-3901"><b>Proposed resolution:</b></p>





</body>
</html>
