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    CWG Issue 2526</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="2526"></A><H4>2526.
  
Relational comparison of <TT>void*</TT> pointers
</H4>
<B>Section: </B>7.6.9&#160; [<A href="https://wg21.link/expr.rel">expr.rel</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Paul Keir
 &#160;&#160;&#160;

 <B>Date: </B>2020-06-15<BR>


<P>[Accepted as a DR at the February, 2023 meeting.]</P>



<P>Prior to the adoption of paper N3624 (resolving
<A HREF="1512.html">issue 1512</A>), comparison of
<TT>void*</TT> pointers was explicitly unspecified. The
current wording of 7.6.9 [<A href="https://wg21.link/expr.rel">expr.rel</A>], however,
describes only comparison of &#8220;pointers to
objects&#8221; (paragraphs 4 and 5), but a pointer
to <TT>void</TT> is not a pointer to an object, only an
object pointer type (as opposed to a function pointer type).
Formally, that means that comparing <TT>void*</TT> pointers
is undefined behavior, which seems undesirable.</P>

<P>As a related note, there is implementation divergence
over whether relational comparisons of <TT>void*</TT> pointers
are accepted in constant expressions (when the <TT>void*</TT>
values are converted from pointers that would otherwise be
comparable in constant expressions).</P>

<P><B>CWG 2022-11-11</B></P>

<P>Paper N3624 erroneously removed support for <TT>void*</TT> and
function pointer relational comparisons.  That ought to be restored.</P>

<P><B>Proposed resolution (approved by CWG 2023-02-09):</B></P>

<P>Change in 7.6.9 [<A href="https://wg21.link/expr.rel#5">expr.rel</A>] paragraph 5 as follows:</P>

<BLOCKQUOTE>

... Otherwise, the result of each of the operators is unspecified.
<INS>[ Note: A relational operator applied to unequal function
pointers or to unequal pointers to <TT>void</TT> yields an unspecified
result. -- end note ]</INS>

</BLOCKQUOTE>

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