<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang xml:lang>
<head>
  <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="2021-02-12" />
  <title>Add a `pmr` alias for `std::stacktrace`</title>
  <style>
      code{white-space: pre-wrap;}
      span.smallcaps{font-variant: small-caps;}
      span.underline{text-decoration: underline;}
      div.column{display: inline-block; vertical-align: top; width: 50%;}
      div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;}
      ul.task-list{list-style: none;}
      pre > code.sourceCode { white-space: pre; position: relative; }
      pre > code.sourceCode > span { display: inline-block; line-height: 1.25; }
      pre > code.sourceCode > span:empty { height: 1.2em; }
      code.sourceCode > span { color: inherit; text-decoration: inherit; }
      div.sourceCode { margin: 1em 0; }
      pre.sourceCode { margin: 0; }
      @media screen {
      div.sourceCode { overflow: auto; }
      }
      @media print {
      pre > code.sourceCode { white-space: pre-wrap; }
      pre > code.sourceCode > span { text-indent: -5em; padding-left: 5em; }
      }
      pre.numberSource code
        { counter-reset: source-line 0; }
      pre.numberSource code > span
        { position: relative; left: -4em; counter-increment: source-line; }
      pre.numberSource code > span > a:first-child::before
        { content: counter(source-line);
          position: relative; left: -1em; text-align: right; vertical-align: baseline;
          border: none; display: inline-block;
          -webkit-touch-callout: none; -webkit-user-select: none;
          -khtml-user-select: none; -moz-user-select: none;
          -ms-user-select: none; user-select: none;
          padding: 0 4px; width: 4em;
          color: #aaaaaa;
        }
      pre.numberSource { margin-left: 3em; border-left: 1px solid #aaaaaa;  padding-left: 4px; }
      div.sourceCode
        {  background-color: #f6f8fa; }
      @media screen {
      pre > code.sourceCode > span > a:first-child::before { text-decoration: underline; }
      }
      code span. { } /* Normal */
      code span.al { color: #ff0000; } /* Alert */
      code span.an { } /* Annotation */
      code span.at { } /* Attribute */
      code span.bn { color: #9f6807; } /* BaseN */
      code span.bu { color: #9f6807; } /* BuiltIn */
      code span.cf { color: #00607c; } /* ControlFlow */
      code span.ch { color: #9f6807; } /* Char */
      code span.cn { } /* Constant */
      code span.co { color: #008000; font-style: italic; } /* Comment */
      code span.cv { color: #008000; font-style: italic; } /* CommentVar */
      code span.do { color: #008000; } /* Documentation */
      code span.dt { color: #00607c; } /* DataType */
      code span.dv { color: #9f6807; } /* DecVal */
      code span.er { color: #ff0000; font-weight: bold; } /* Error */
      code span.ex { } /* Extension */
      code span.fl { color: #9f6807; } /* Float */
      code span.fu { } /* Function */
      code span.im { } /* Import */
      code span.in { color: #008000; } /* Information */
      code span.kw { color: #00607c; } /* Keyword */
      code span.op { color: #af1915; } /* Operator */
      code span.ot { } /* Other */
      code span.pp { color: #6f4e37; } /* Preprocessor */
      code span.re { } /* RegionMarker */
      code span.sc { color: #9f6807; } /* SpecialChar */
      code span.ss { color: #9f6807; } /* SpecialString */
      code span.st { color: #9f6807; } /* String */
      code span.va { } /* Variable */
      code span.vs { color: #9f6807; } /* VerbatimString */
      code span.wa { color: #008000; font-weight: bold; } /* Warning */
      code.diff {color: #898887}
      code.diff span.va {color: #006e28}
      code.diff span.st {color: #bf0303}
  </style>
  <style type="text/css">
body {
margin: 5em;
font-family: serif;

hyphens: auto;
line-height: 1.35;
}
div.wrapper {
max-width: 60em;
margin: auto;
}
ul {
list-style-type: none;
padding-left: 2em;
margin-top: -0.2em;
margin-bottom: -0.2em;
}
a {
text-decoration: none;
color: #4183C4;
}
a.hidden_link {
text-decoration: none;
color: inherit;
}
li {
margin-top: 0.6em;
margin-bottom: 0.6em;
}
h1, h2, h3, h4 {
position: relative;
line-height: 1;
}
a.self-link {
position: absolute;
top: 0;
left: calc(-1 * (3.5rem - 26px));
width: calc(3.5rem - 26px);
height: 2em;
text-align: center;
border: none;
transition: opacity .2s;
opacity: .5;
font-family: sans-serif;
font-weight: normal;
font-size: 83%;
}
a.self-link:hover { opacity: 1; }
a.self-link::before { content: "§"; }
ul > li:before {
content: "\2014";
position: absolute;
margin-left: -1.5em;
}
:target { background-color: #C9FBC9; }
:target .codeblock { background-color: #C9FBC9; }
:target ul { background-color: #C9FBC9; }
.abbr_ref { float: right; }
.folded_abbr_ref { float: right; }
:target .folded_abbr_ref { display: none; }
:target .unfolded_abbr_ref { float: right; display: inherit; }
.unfolded_abbr_ref { display: none; }
.secnum { display: inline-block; min-width: 35pt; }
.header-section-number { display: inline-block; min-width: 35pt; }
.annexnum { display: block; }
div.sourceLinkParent {
float: right;
}
a.sourceLink {
position: absolute;
opacity: 0;
margin-left: 10pt;
}
a.sourceLink:hover {
opacity: 1;
}
a.itemDeclLink {
position: absolute;
font-size: 75%;
text-align: right;
width: 5em;
opacity: 0;
}
a.itemDeclLink:hover { opacity: 1; }
span.marginalizedparent {
position: relative;
left: -5em;
}
li span.marginalizedparent { left: -7em; }
li ul > li span.marginalizedparent { left: -9em; }
li ul > li ul > li span.marginalizedparent { left: -11em; }
li ul > li ul > li ul > li span.marginalizedparent { left: -13em; }
div.footnoteNumberParent {
position: relative;
left: -4.7em;
}
a.marginalized {
position: absolute;
font-size: 75%;
text-align: right;
width: 5em;
}
a.enumerated_item_num {
position: relative;
left: -3.5em;
display: inline-block;
margin-right: -3em;
text-align: right;
width: 3em;
}
div.para { margin-bottom: 0.6em; margin-top: 0.6em; text-align: justify; }
div.section { text-align: justify; }
div.sentence { display: inline; }
span.indexparent {
display: inline;
position: relative;
float: right;
right: -1em;
}
a.index {
position: absolute;
display: none;
}
a.index:before { content: "⟵"; }

a.index:target {
display: inline;
}
.indexitems {
margin-left: 2em;
text-indent: -2em;
}
div.itemdescr {
margin-left: 3em;
}
.bnf {
font-family: serif;
margin-left: 40pt;
margin-top: 0.5em;
margin-bottom: 0.5em;
}
.ncbnf {
font-family: serif;
margin-top: 0.5em;
margin-bottom: 0.5em;
margin-left: 40pt;
}
.ncsimplebnf {
font-family: serif;
font-style: italic;
margin-top: 0.5em;
margin-bottom: 0.5em;
margin-left: 40pt;
background: inherit; 
}
span.textnormal {
font-style: normal;
font-family: serif;
white-space: normal;
display: inline-block;
}
span.rlap {
display: inline-block;
width: 0px;
}
span.descr { font-style: normal; font-family: serif; }
span.grammarterm { font-style: italic; }
span.term { font-style: italic; }
span.terminal { font-family: monospace; font-style: normal; }
span.nonterminal { font-style: italic; }
span.tcode { font-family: monospace; font-style: normal; }
span.textbf { font-weight: bold; }
span.textsc { font-variant: small-caps; }
a.nontermdef { font-style: italic; font-family: serif; }
span.emph { font-style: italic; }
span.techterm { font-style: italic; }
span.mathit { font-style: italic; }
span.mathsf { font-family: sans-serif; }
span.mathrm { font-family: serif; font-style: normal; }
span.textrm { font-family: serif; }
span.textsl { font-style: italic; }
span.mathtt { font-family: monospace; font-style: normal; }
span.mbox { font-family: serif; font-style: normal; }
span.ungap { display: inline-block; width: 2pt; }
span.textit { font-style: italic; }
span.texttt { font-family: monospace; }
span.tcode_in_codeblock { font-family: monospace; font-style: normal; }
span.phantom { color: white; }

span.math { font-style: normal; }
span.mathblock {
display: block;
margin-left: auto;
margin-right: auto;
margin-top: 1.2em;
margin-bottom: 1.2em;
text-align: center;
}
span.mathalpha {
font-style: italic;
}
span.synopsis {
font-weight: bold;
margin-top: 0.5em;
display: block;
}
span.definition {
font-weight: bold;
display: block;
}
.codeblock {
margin-left: 1.2em;
line-height: 127%;
}
.outputblock {
margin-left: 1.2em;
line-height: 127%;
}
div.itemdecl {
margin-top: 2ex;
}
code.itemdeclcode {
white-space: pre;
display: block;
}
span.textsuperscript {
vertical-align: super;
font-size: smaller;
line-height: 0;
}
.footnotenum { vertical-align: super; font-size: smaller; line-height: 0; }
.footnote {
font-size: small;
margin-left: 2em;
margin-right: 2em;
margin-top: 0.6em;
margin-bottom: 0.6em;
}
div.minipage {
display: inline-block;
margin-right: 3em;
}
div.numberedTable {
text-align: center;
margin: 2em;
}
div.figure {
text-align: center;
margin: 2em;
}
table {
border: 1px solid black;
border-collapse: collapse;
margin-left: auto;
margin-right: auto;
margin-top: 0.8em;
text-align: left;
hyphens: none; 
}
td, th {
padding-left: 1em;
padding-right: 1em;
vertical-align: top;
}
td.empty {
padding: 0px;
padding-left: 1px;
}
td.left {
text-align: left;
}
td.right {
text-align: right;
}
td.center {
text-align: center;
}
td.justify {
text-align: justify;
}
td.border {
border-left: 1px solid black;
}
tr.rowsep, td.cline {
border-top: 1px solid black;
}
tr.even, tr.odd {
border-bottom: 1px solid black;
}
tr.capsep {
border-top: 3px solid black;
border-top-style: double;
}
tr.header {
border-bottom: 3px solid black;
border-bottom-style: double;
}
th {
border-bottom: 1px solid black;
}
span.centry {
font-weight: bold;
}
div.table {
display: block;
margin-left: auto;
margin-right: auto;
text-align: center;
width: 90%;
}
span.indented {
display: block;
margin-left: 2em;
margin-bottom: 1em;
margin-top: 1em;
}
ol.enumeratea { list-style-type: none; background: inherit; }
ol.enumerate { list-style-type: none; background: inherit; }

code.sourceCode > span { display: inline; }
</style>
  <link href="data:image/x-icon;base64,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" rel="icon" />
  <!--[if lt IE 9]>
    <script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.3/html5shiv-printshiv.min.js"></script>
  <![endif]-->
  
</head>
<body>
<div class="wrapper">
<header id="title-block-header">
<h1 class="title" style="text-align:center">Add a <code class="sourceCode default">pmr</code> alias for <code class="sourceCode default">std::stacktrace</code></h1>

<table style="border:none;float:right">
  <tr>
    <td>Document #:</td>
    <td>P2301R0</td>
  </tr>
  <tr>
    <td>Date:</td>
    <td>2021-02-12</td>
  </tr>
  <tr>
    <td style="vertical-align:top">Project:</td>
    <td>Programming Language C++</td>
  </tr>
  <tr>
    <td style="vertical-align:top">Audience:</td>
    <td>
      LEWG, LWG<br>
    </td>
  </tr>
  <tr>
    <td style="vertical-align:top">Reply-to:</td>
    <td>
      Steve Downey<br>&lt;<a href="mailto:sdowney2@bloomberg.net" class="email">sdowney2@bloomberg.net</a>, <a href="mailto:sdowney@gmail.com" class="email">sdowney@gmail.com</a>&gt;<br>
    </td>
  </tr>
</table>

</header>
<div style="clear:both">
<p>Abstract: This paper proposes to add an alias in the <code class="sourceCode default">pmr</code> namespace defaulting the allocator used by the <code class="sourceCode default">std::basic_stacktrace</code> template to <code class="sourceCode default">pmr::allocator</code>. No changes to the api of <code class="sourceCode default">std::stacktrace</code> are necessary.</p>
<h1 data-number="1" id="before-after-table"><span class="header-section-number">1</span> Before / After Table<a href="#before-after-table" class="self-link"></a></h1>
<table>
<thead>
<tr class="header">
<th><div style="text-align:center">
<strong>Before</strong>
</div></th>
<th><div style="text-align:center">
<strong>After</strong>
</div></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td><div class="sourceCode" id="cb1"><pre class="sourceCode c++"><code class="sourceCode cpp"><span id="cb1-1"><a href="#cb1-1"></a><span class="dt">char</span> buffer[<span class="dv">1024</span>];</span>
<span id="cb1-2"><a href="#cb1-2"></a></span>
<span id="cb1-3"><a href="#cb1-3"></a><span class="bu">std::</span>pmr<span class="bu">::</span>monotonic_buffer_resource pool{</span>
<span id="cb1-4"><a href="#cb1-4"></a>    <span class="bu">std::</span>data(buffer), <span class="bu">std::</span>size(buffer)};</span>
<span id="cb1-5"><a href="#cb1-5"></a></span>
<span id="cb1-6"><a href="#cb1-6"></a><span class="bu">std::</span>basic_stacktrace&lt;</span>
<span id="cb1-7"><a href="#cb1-7"></a>    <span class="bu">std::</span>pmr<span class="bu">::</span>polymorphic_allocator&lt;<span class="bu">std::</span>stacktrace_entry&gt;&gt;</span>
<span id="cb1-8"><a href="#cb1-8"></a>    trace{&amp;pool};</span></code></pre></div></td>
<td><div class="sourceCode" id="cb2"><pre class="sourceCode c++"><code class="sourceCode cpp"><span id="cb2-1"><a href="#cb2-1"></a><span class="dt">char</span> buffer[<span class="dv">1024</span>];</span>
<span id="cb2-2"><a href="#cb2-2"></a></span>
<span id="cb2-3"><a href="#cb2-3"></a><span class="bu">std::</span>pmr<span class="bu">::</span>monotonic_buffer_resource pool{</span>
<span id="cb2-4"><a href="#cb2-4"></a>    <span class="bu">std::</span>data(buffer), <span class="bu">std::</span>size(buffer)};</span>
<span id="cb2-5"><a href="#cb2-5"></a></span>
<span id="cb2-6"><a href="#cb2-6"></a><span class="bu">std::</span>pmr<span class="bu">::</span>stacktrace trace{&amp;pool};</span></code></pre></div></td>
</tr>
</tbody>
</table>
<h1 data-number="2" id="motivation"><span class="header-section-number">2</span> Motivation<a href="#motivation" class="self-link"></a></h1>
<p>The type <code class="sourceCode default">std::basic_stacktrace</code> is a class template with an allocator type parameter, the allocator is fixed to be <code class="sourceCode default">std::allocator</code> in the <code class="sourceCode default">std::stacktrace</code> alias, and it models <em>AllocatorAwareContainer</em>. All of the work to enable a pmr using type has been done, except for actually specifying the existence of the template alias std::pmr::stacktrace with a polymorphic_allocator.</p>
<p>In general a template should have an alias in the <code class="sourceCode default">pmr</code> namespace when the primary template supports the allocator model and the allocator template parameter is defaulted to be <code class="sourceCode default">std::allocator</code>. Providing the <code class="sourceCode default">pmr</code> alias is a convenience for changing the default.</p>
<h1 data-number="3" id="proposed-wording"><span class="header-section-number">3</span> Proposed Wording<a href="#proposed-wording" class="self-link"></a></h1>
<p>Modify <strong><span>20.21.2
 <a href="https://wg21.link/stacktrace.syn">[stacktrace.syn]</a></span></strong> as indicated</p>
<div class="sourceCode" id="cb1"><pre class="sourceCode default"><code class="sourceCode default"><span id="cb1-1"><a href="#cb1-1"></a>namespace std {</span>
<span id="cb1-2"><a href="#cb1-2"></a>  // [stacktrace.entry], class stacktrace_­entry</span>
<span id="cb1-3"><a href="#cb1-3"></a>  class stacktrace_entry;</span>
<span id="cb1-4"><a href="#cb1-4"></a></span>
<span id="cb1-5"><a href="#cb1-5"></a>  // [stacktrace.basic], class template basic_­stacktrace</span>
<span id="cb1-6"><a href="#cb1-6"></a>  template&lt;class Allocator&gt;</span>
<span id="cb1-7"><a href="#cb1-7"></a>    class basic_stacktrace;</span>
<span id="cb1-8"><a href="#cb1-8"></a></span>
<span id="cb1-9"><a href="#cb1-9"></a>  // basic_­stacktrace typedef names</span>
<span id="cb1-10"><a href="#cb1-10"></a>  using stacktrace = basic_stacktrace&lt;allocator&lt;stacktrace_entry&gt;&gt;;</span>
<span id="cb1-11"><a href="#cb1-11"></a></span>
<span id="cb1-12"><a href="#cb1-12"></a>  // [stacktrace.basic.nonmem], non-member functions</span>
<span id="cb1-13"><a href="#cb1-13"></a>  template&lt;class Allocator&gt;</span>
<span id="cb1-14"><a href="#cb1-14"></a>    void swap(basic_stacktrace&lt;Allocator&gt;&amp; a, basic_stacktrace&lt;Allocator&gt;&amp; b)</span>
<span id="cb1-15"><a href="#cb1-15"></a>      noexcept(noexcept(a.swap(b)));</span>
<span id="cb1-16"><a href="#cb1-16"></a></span>
<span id="cb1-17"><a href="#cb1-17"></a>  string to_string(const stacktrace_entry&amp; f);</span>
<span id="cb1-18"><a href="#cb1-18"></a></span>
<span id="cb1-19"><a href="#cb1-19"></a>  template&lt;class Allocator&gt;</span>
<span id="cb1-20"><a href="#cb1-20"></a>    string to_string(const basic_stacktrace&lt;Allocator&gt;&amp; st);</span>
<span id="cb1-21"><a href="#cb1-21"></a></span>
<span id="cb1-22"><a href="#cb1-22"></a>  template&lt;class charT, class traits&gt;</span>
<span id="cb1-23"><a href="#cb1-23"></a>    basic_ostream&lt;charT, traits&gt;&amp;</span>
<span id="cb1-24"><a href="#cb1-24"></a>      operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os, const stacktrace_entry&amp; f);</span>
<span id="cb1-25"><a href="#cb1-25"></a></span>
<span id="cb1-26"><a href="#cb1-26"></a>  template&lt;class charT, class traits, class Allocator&gt;</span>
<span id="cb1-27"><a href="#cb1-27"></a>    basic_ostream&lt;charT, traits&gt;&amp;</span>
<span id="cb1-28"><a href="#cb1-28"></a>      operator&lt;&lt;(basic_ostream&lt;charT, traits&gt;&amp; os, const basic_stacktrace&lt;Allocator&gt;&amp; st);</span>
<span id="cb1-29"><a href="#cb1-29"></a></span>
<span id="cb1-30"><a href="#cb1-30"></a>  <span class="add" style="color: #006e28"><ins><span><code class="sourceCode default">namespace pmr {</code></span></ins></span></span>
<span id="cb1-31"><a href="#cb1-31"></a>    <span class="add" style="color: #006e28"><ins><span><code class="sourceCode default">using stacktrace = std::basic_stacktrace&lt;polymorphic_allocator&lt;stacktrace_entry&gt;&gt;;</code></span></ins></span></span>
<span id="cb1-32"><a href="#cb1-32"></a>  <span class="add" style="color: #006e28"><ins><span><code class="sourceCode default">}</code></span></ins></span></span>
<span id="cb1-33"><a href="#cb1-33"></a></span>
<span id="cb1-34"><a href="#cb1-34"></a>  // [stacktrace.basic.hash], hash support</span>
<span id="cb1-35"><a href="#cb1-35"></a>  template&lt;class T&gt; struct hash;</span>
<span id="cb1-36"><a href="#cb1-36"></a>  template&lt;&gt; struct hash&lt;stacktrace_entry&gt;;</span>
<span id="cb1-37"><a href="#cb1-37"></a>  template&lt;class Allocator&gt; struct hash&lt;basic_stacktrace&lt;Allocator&gt;&gt;;</span>
<span id="cb1-38"><a href="#cb1-38"></a>}</span></code></pre></div>
<p><a href="https://godbolt.org/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAM1QDsCBlZAQwBtMQBGAFlICsupVs1qhkAUgBMAISnTSAZ0ztkBPHUqZa6AMKpWAVwC2tQVvQAZPLUwA5YwCNMxEAFYAbKQAOqBYXW0eoYmgj5%2BanRWNvZGTi4eisqYqgEMBMzEBEHGppyJKhG0aRkEUXaOzm6eCumZ2SF5NSVlMXFVAJSKqAbEyBwA5FIAzNbIhlgA1OJDOkaYRiQAntPY4gAMAILDo%2BOYUzNzC8SLAPrEmArdvZgr61ubd7TMcwpezH0TNehTAOyymxMJgB6IFTVzSJrIADWBGI70wADotLDlq4ACKkCZjZgKBSfdLQ2Hwk7iHSScQbNHI453QHY3H494wuF9E7U5ZDf73DaAkFgiEE5nwhEOHF4CTozH0vEEeZeYSyiaivzIElkiloyFCvq0iayozy5iy6Y6aUTDasVioFhEYi3AGArHCBnK8UnLVEnWcu66vmu1Wk8mUj0svYERZeTBYKgTJ4vXUGPyiRmE0P7NFKsWqkPwk1sK02kgmnOs9m3Iarb0PB188TgkuI/0I2h0Q51jGxugAWkOcQmVAMtBSdAUuv1huNMzNFoLRqLFd1gIAbqg8N8FAB3ZheCD%2B92Cz03GYz61zu0LyTuCbMTF7hsmk%2BF8%2BrS9K9qLx0tzAADz6XgIEBfr%2BmD/hAzAIpu267u0MHTFyuo1MQ1jAHqqD7khogQGgtA1Cm2qYGy9A0q%2BVDvlW3KAuOCpHqazp4o%2BZ72jyjqIchqHochWEjgQmYqvuTKHg%2BlqnratyvjUZHwQ6VFGjRZrIAgGQACpSnRepwoQo4Lg6gJ7r4sKYM8JoKcpmJEppYnuB%2BgKoJGcKiTMJq7lmJz6ecRlTopxAqepzAWReV6%2BFK3F4YehEolIV6kXBPrSXK1HGWpJneapOIyhpBAKKlDIMQ5qw6bxbpuYZRjGV5PnmZllnWRMtnOIxjkzM5fHFR5prlWZGVaS%2BgVZViIV3geoZCbOeWRfikmxcxcYXG8HxeEYxC/FyjoTImbENum%2BLoCAICDQJw0zD4rCLEcXgIG6%2BYifOOgNuFNILo9K2/GiU2%2BqCdYCgdwpNopCgIO2mJ/QgnwGF4PiZGO8WyYlaUTEpKz4sQBiqBMwMxXFBoJY12BIyjPHozMd1lk9UNYzDU5qbl8644h%2BNoziAMzPtqa5sewlPuWlbwT8r3Vhs1g8U4NDnBA7TLXcyVKgYVBUM4n2cGskjcO2GPcl8u0LS4IALC2RC0G6Dgy3LxBnBcVzzag%2BjiH8H4ayA6BGswu7G84nTbbtfgAF6YC7stuzbr3kXc9ss/hJp2wQO0gFrmv6KdJDnZdHMNbdUee0NxIk5W%2BXMZRw225ePjW7zauB1NgvXlQsrEGLEubFLRv%2B3a4KK8rqvB5s9uxzrdCoPrhuu6b5yXD0lsl89gL2476R%2Byb7v297vtN/P5edxs3eLRn30fIJhfuMXrBrzzaL9J0rAgP0rj9KQpj9GsN%2BoJfOhyHInwW3swycDfBCXw/MGkChCAIYQwEQgPARAyBngL79G4DfO%2BD9SBP36DfBQIA1ikF/vfM%2BpA4CwCQGgA0eB2BkAoFxIhJCUDCFECcWEg4oSkCoMQmuaDdx/xvg4awGRFiX2/qQQhcx6AAHlaAnXYaQLARgRDAHYOI/A5wUhLguOIn8yQDCyl4TfQWyhxGsDwA4OExw9BYE0ZgpCRhNGdBoPQJgbAOA8H4IIahYhX4yCEPotBkBOi2UKGg/oXYuxfGmGiCQMg5CSEQUoAoARNDaHqLkUg5gWgVBcHkMI/g6DxNCL4DJtBkmxEqI0JIw4ii1CyPoHIggonJEKMUTI%2BS2iNDKVkppzRrDlAKakzoo9rhcHPpfa%2Bt9xHIO/AADncF2dw3AnTSImBAOhtAoTiwgLgQgJApiSCGHkCYegKHOA2Vs8WL8wkyB/uwgBQCQFgMgTckB0DL5wKGdgpBl9UHoMwec3BMBEAgG6AQLw6jyCUEIV4YhhTEn4FtIIaxjAWCyIcRuOEXhLFCAGfA4Zl8v4TA3IQEGYyJlTJmcmeZyNFntDOdgi5wDQG3Nuai2B6LnnILeRgrB/9%2Bn9EkIyxBzKPmUs6Eo4gfgNDcCAA">Compiler Explorer Link</a></p>
</div>
</div>
</body>
</html>
