<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Issue 2429: std::basic_ostringstream is missing an allocator-extended constructor</title>
<meta property="og:title" content="Issue 2429: std::basic_ostringstream is missing an allocator-extended constructor">
<meta property="og:description" content="C++ library issue. Status: NAD">
<meta property="og:url" content="https://cplusplus.github.io/LWG/issue2429.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="2429"><a href="lwg-closed.html#2429">2429</a>. <code>std::basic_ostringstream</code> is missing an allocator-extended constructor</h3>
<p><b>Section:</b> 31.8.4 <a href="https://wg21.link/ostringstream">[ostringstream]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Markus Kemp <b>Opened:</b> 2014-09-03 <b>Last modified:</b> 2017-03-21</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#ostringstream">issues</a> in [ostringstream].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
I initially brought this issue up on <a href="http://stackoverflow.com/questions/23955828/how-to-use-basic-ostringstream-with-stateful-custom-allocator-c11">Stack Overflow</a>, 
where I was then told to make a topic about this problem on <a href="https://groups.google.com/a/isocpp.org/d/msg/std-discussion/kAQFOWz47m0/cOXSHa5Iwg4J">std-discussion</a>, 
where I was then in turn asked to report the issue.
<p/>
The problem: The <code>std::basic_ostringstream</code> class template can be instantiated with an allocator type, but none of the 
constructors provided accept an allocator argument, which means it's impossible to use <code>std::basic_ostringstream</code> with 
stateful allocators. The C++ Standard Library Defect Report List seems to already mention a similar issue (<a href="lwg-defects.html#2210" title="Missing allocator-extended constructor for allocator-aware containers (Status: C++14)">2210</a><sup><a href="https://cplusplus.github.io/LWG/issue2210" title="Latest snapshot">(i)</a></sup>).
</p>

<p><i>[2014-11 Urbana]</i></p>

<p>Closed as NAD</p>
<p>
This is not a rejection of the suggestion, but an observation that simply adding an allocator-aware
constructor is only part of the problem.  <code>stringstream</code> returns the <code>string</code> assembled
in its buffer by value, as the result of a call to <code>str</code>, and typically this will not use the
same allocator as would be supplied at construction.
</p>
<p>
The appropriate way to make progress on this issue, if motivated, is to submit a paper to LEWG
addressing the larger design concerns in addition to 'just' adding an (optional) allocator to
the constructors.
</p>


<p id="res-2429"><b>Proposed resolution:</b></p>





</body>
</html>
