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<title>Issue 3834: Missing constexpr for std::intmax_t math functions in &lt;cinttypes&gt;</title>
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<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++23">C++23</a> status.</em></p>
<h3 id="3834"><a href="lwg-defects.html#3834">3834</a>. Missing <code>constexpr</code> for <code>std::intmax_t</code> math functions in <code>&lt;cinttypes&gt;</code></h3>
<p><b>Section:</b> 31.13.2 <a href="https://wg21.link/cinttypes.syn">[cinttypes.syn]</a> <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> George Tokmaji <b>Opened:</b> 2022-11-27 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++23">C++23</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<a href="https://wg21.link/P0533R9" title=" constexpr for cmath and cstdlib">P0533R9</a> adds <code>constexpr</code> to math functions in <code>&lt;cmath&gt;</code> 
and <code>&lt;cstdlib&gt;</code>, which includes <code>std::abs</code> and <code>std::div</code>. This 
misses the overloads for <code>std::intmax_t</code> in <code>&lt;cinttypes&gt;</code>, as well as 
<code>std::imaxabs</code> and <code>std::imaxdiv</code>, which seems like an oversight.
</p>

<p><i>[2023-01-06; Reflector poll]</i></p>

<p>
Set status to Tentatively Ready after six votes in favour during reflector poll.
</p>

<p><i>[2023-02-13 Approved at February 2023 meeting in Issaquah. Status changed: Voting &rarr; WP.]</i></p>



<p id="res-3834"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4917" title=" Working Draft, Standard for Programming Language C++">N4917</a>.
</p>

<ol>
<li><p>Modify 31.13.2 <a href="https://wg21.link/cinttypes.syn">[cinttypes.syn]</a>, header <code>&lt;cinttypes&gt;</code> synopsis, as indicated:</p>

<blockquote>
<blockquote><pre>
[&hellip;]
namespace std {
  using imaxdiv_t = <i>see below</i>;
  
  <ins>constexpr</ins> intmax_t imaxabs(intmax_t j);
  <ins>constexpr</ins> imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
  intmax_t strtoimax(const char* nptr, char** endptr, int base);
  uintmax_t strtoumax(const char* nptr, char** endptr, int base);
  intmax_t wcstoimax(const wchar_t* nptr, wchar_t** endptr, int base);
  uintmax_t wcstoumax(const wchar_t* nptr, wchar_t** endptr, int base);

  <ins>constexpr</ins> intmax_t abs(intmax_t);            // <i>optional, see below</i>
  <ins>constexpr</ins> imaxdiv_t div(intmax_t, intmax_t); // <i>optional, see below</i>
  [&hellip;]
}
[&hellip;]
</pre></blockquote>
<p>
-1- The contents and meaning of the header <code>&lt;cinttypes&gt;</code> are the same as the C standard library header
<code>&lt;inttypes.h&gt;</code>, with the following changes:
</p>
<ol style="list-style-type: none">
<li><p>(1.1) &mdash; The header <code>&lt;cinttypes&gt;</code> includes the header <code>&lt;cstdint&gt;</code> 
(17.4.1 <a href="https://wg21.link/cstdint.syn">[cstdint.syn]</a>) instead of <code>&lt;stdint.h&gt;</code>, and</p></li>
<li><p>(1.2) &mdash; if and only if the type <code>intmax_t</code> designates an extended integer type 
(6.9.2 <a href="https://wg21.link/basic.fundamental">[basic.fundamental]</a>), the following function signatures are added:</p>
<blockquote><pre>
<ins>constexpr</ins> intmax_t abs(intmax_t);
<ins>constexpr</ins> imaxdiv_t div(intmax_t, intmax_t);
</pre></blockquote>
<p>which shall have the same semantics as the function signatures 
<code><ins>constexpr</ins> intmax_t imaxabs(intmax_t)</code> and
<code><ins>constexpr</ins> imaxdiv_t imaxdiv(intmax_t, intmax_t)</code>, respectively.</p></li>
</ol>

</blockquote>
</li>
</ol>






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