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<title>Issue 4049: C &lt;foo.h&gt; headers not in freestanding</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#New">New</a> status.</em></p>
<h3 id="4049"><a href="lwg-active.html#4049">4049</a>. C <code>&lt;<i>foo</i>.h&gt;</code> headers not in freestanding</h3>
<p><b>Section:</b> 16.4.2 <a href="https://wg21.link/organization">[organization]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Ben Craig <b>Opened:</b> 2024-01-26 <b>Last modified:</b> 2024-08-21</p>
<p><b>Priority: </b>3
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
There are many C-ish <code>&lt;c<i>foo</i>&gt;</code> headers in freestanding. There isn't anything that 
requires the matching C <code>&lt;<i>foo</i>.h&gt;</code> headers to be in freestanding.
</p>

<p><i>[2024-08-21; Reflector poll]</i></p>

<p>
Set priority to 3 after reflector poll.
Some discomfort requiring <code class='backtick'>errno.h</code> and <code class='backtick'>wchar.h</code> to be freestanding in C++
when they are not in C23. <code class='backtick'>string.h</code> is not freestanding in C17, but is in C23
(but C++ is still based on C17).
<code class='backtick'>stdlib.h</code> is "conditionally partially freestanding" in C23, but not in C17.
Suggestion to incorporate this into <a href="https://wg21.link/P3348" title=" C++26 should refer to C23 not C17">P3348</a>.
</p>



<p id="res-4049"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4971" title=" Working Draft, Programming Languages — C++">N4971</a>.
</p>

<ol>
<li><p>Modify 16.4.2.3 <a href="https://wg21.link/headers">[headers]</a> as indicated:</p>

<blockquote>
<p>
-9- 17.15 <a href="https://wg21.link/support.c.headers">[support.c.headers]</a>, C standard library headers, describes the effects of using the 
<code><i>name</i>.h</code> (C header) form in a C++ program. <ins>The <code><i>name</i>.h</code> form is the 
<i>corresponding C header form</i>.</ins>
</p>
</blockquote>
</li>

<li><p>Modify 16.4.2.5 <a href="https://wg21.link/compliance">[compliance]</a> as indicated:</p>

<blockquote>
<p>
-2- A freestanding implementation has an implementation-defined set of headers. This set shall include at least
the headers shown in Table 27 <ins>and the corresponding C header form (16.4.2.3 <a href="https://wg21.link/headers">[headers]</a>) of each of the 
C++ headers for C library facilities (Table 25) included in Table 27</ins>.
</p>
</blockquote>
</li>
</ol>





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