New issue from Jiang An: "Some feature-test macros for fully freestanding features are not yet marked freestanding"

Author: Dani-Hub

xml/issue4126.xml

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+<?xml version='1.0' encoding='utf-8' standalone='no'?>
+<!DOCTYPE issue SYSTEM "lwg-issue.dtd">
+
+<issue num="4126" status="New">
+<title>Some feature-test macros for fully freestanding features are not yet marked freestanding</title>
+<section><sref ref="[version.syn]"/></section>
+<submitter>Jiang An</submitter>
+<date>24 Jul 2024</date>
+<priority>99</priority>
+
+<discussion>
+<p>
+Currently (<paper num="N4986"/>), it's a bit weird in <sref ref="[version.syn]"/> that some feature-test
+macros are not marked freestanding, despite the indicated features being fully freestanding. The 
+freestanding status seems sometimes implicitly covered by "also in" headers that are mostly or all 
+freestanding, but sometimes not.
+<p/>
+I think it's more consistent to ensure feature-test macros for fully freestanding features are also freestanding.
+</p>
+</discussion>
+
+<resolution>
+<p>
+This wording is relative to <paper num="N4986"/>.
+</p>
+
+<ol>
+<li><p>Modify <sref ref="[version.syn]"/> as indicated:</p>
+
+<blockquote class="note">
+<p>
+[<i>Drafting note</i>:  <tt>&lt;charconv&gt;</tt> is not fully freestanding, but all functions made <tt>constexpr</tt> 
+by <paper num="P2291R3"/> are furtherly made freestanding by <paper num="P2338R4"/>. ]
+</p>
+</blockquote>
+
+<blockquote>
+<pre>
+[&hellip;]
+#define __cpp_lib_common_reference                  202302L // <i><ins>freestanding,</ins> also in</i> &lt;type_traits&gt;
+#define __cpp_lib_common_reference_wrapper          202302L // <i><ins>freestanding,</ins> also in</i> &lt;functional&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_constexpr_charconv                202207L // <i><ins>freestanding,</ins> also in</i> &lt;charconv&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_coroutine                         201902L // <i><ins>freestanding,</ins> also in</i> &lt;coroutine&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_is_implicit_lifetime              202302L // <i><ins>freestanding,</ins> also in</i> &lt;type_traits&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_is_virtual_base_of                202406L // <i><ins>freestanding,</ins> also in</i> &lt;type_traits&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_is_within_lifetime                202306L // <i><ins>freestanding,</ins> also in</i> &lt;type_traits&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_mdspan                            202406L // <i><ins>freestanding,</ins> also in</i> &lt;mdspan&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_ratio                             202306L // <i><ins>freestanding,</ins> also in</i> &lt;ratio&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_span_initializer_list             202311L // <i><ins>freestanding,</ins> also in</i> &lt;span&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_submdspan                         202403L // <i><ins>freestanding,</ins> also in</i> &lt;mdspan&gt;
+[&hellip;]                                                                              
+#define __cpp_lib_to_array                          201907L // <i><ins>freestanding,</ins> also in</i> &lt;array&gt;
+[&hellip;]
+</pre>
+</blockquote>
+
+</li>
+
+</ol>
+</resolution>
+
+</issue>