<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Issue 2083: const-qualification on weak_ptr::owner_before</title>
<meta property="og:title" content="Issue 2083: const-qualification on weak_ptr::owner_before">
<meta property="og:description" content="C++ library issue. Status: C++14">
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue2083.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#C++14">C++14</a> status.</em></p>
<h3 id="2083"><a href="lwg-defects.html#2083">2083</a>. const-qualification on <code>weak_ptr::owner_before</code></h3>
<p><b>Section:</b> 20.3.2.3 <a href="https://wg21.link/util.smartptr.weak">[util.smartptr.weak]</a>, 20.3.2.3.6 <a href="https://wg21.link/util.smartptr.weak.obs">[util.smartptr.weak.obs]</a> <b>Status:</b> <a href="lwg-active.html#C++14">C++14</a>
 <b>Submitter:</b> Ai Azuma <b>Opened:</b> 2011-09-06 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#util.smartptr.weak">issues</a> in [util.smartptr.weak].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++14">C++14</a> status.</p>
<p><b>Discussion:</b></p>

<p>
Is there any reason why <code>weak_ptr::owner_before</code> member function templates are not const-qualified?
</p>

<p>
Daniel Kr&uuml;gler:
</p>
<blockquote><p>
I don't think so. To the contrary, without these to be const member function templates, the
semantics of the specializations <code>owner_less&lt;weak_ptr&lt;T&gt;&gt;</code>  and
<code>owner_less&lt;shared_ptr&lt;T&gt;&gt;</code> described in 20.3.2.4 <a href="https://wg21.link/util.smartptr.ownerless">[util.smartptr.ownerless]</a> 
is unclear.
<p/>
It is amusing to note that this miss has remain undetected from the accepted paper
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2637.pdf">n2637</a> 
on. For the suggested wording changes see below. 
</p></blockquote>


<p><i>[2012, Kona]</i></p>

<p>
Move to Ready.
</p>

<p><i>[2012, Portland: applied to WP]</i></p>




<p id="res-2083"><b>Proposed resolution:</b></p>
<p>This wording is relative to the FDIS.</p>

<ol>
<li><p>Change the class template <code>weak_ptr</code> synopsis in 20.3.2.3 <a href="https://wg21.link/util.smartptr.weak">[util.smartptr.weak]</a>
as indicated:</p>
<blockquote><pre>
namespace std {
  template&lt;class T&gt; class weak_ptr {
  public:
    typedef T element_type;
    [&hellip;]
    template&lt;class U&gt; bool owner_before(shared_ptr&lt;U&gt; const&amp; b) <ins>const</ins>;
    template&lt;class U&gt; bool owner_before(weak_ptr&lt;U&gt; const&amp; b) <ins>const</ins>;
  };
  [&hellip;]
}
</pre></blockquote>
</li>
<li><p>Change the prototypes in 20.3.2.3.6 <a href="https://wg21.link/util.smartptr.weak.obs">[util.smartptr.weak.obs]</a> before p6 as indicated:</p>
<blockquote><pre>
template&lt;class U&gt; bool owner_before(shared_ptr&lt;U&gt; const&amp; b) <ins>const</ins>;
template&lt;class U&gt; bool owner_before(weak_ptr&lt;U&gt; const&amp; b) <ins>const</ins>;
</pre></blockquote>
</li>
</ol>





</body>
</html>
