<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<TITLE>
    CWG Issue 2499</TITLE>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<STYLE TYPE="text/css">
  INS { text-decoration:none; font-weight:bold; background-color:#A0FFA0 }
  .INS { text-decoration:none; background-color:#D0FFD0 }
  DEL { text-decoration:line-through; background-color:#FFA0A0 }
  .DEL { text-decoration:line-through; background-color: #FFD0D0 }
  @media (prefers-color-scheme: dark) {
    HTML { background-color:#202020; color:#f0f0f0; }
    A { color:#5bc0ff; }
    A:visited { color:#c6a8ff; }
    A:hover, a:focus { color:#afd7ff; }
    INS { background-color:#033a16; color:#aff5b4; }
    .INS { background-color: #033a16; }
    DEL { background-color:#67060c; color:#ffdcd7; }
    .DEL { background-color:#67060c; }
  }
  SPAN.cmnt { font-family:Times; font-style:italic }
</STYLE>
</HEAD>
<BODY>
<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="2499"></A><H4>2499.
  
Inconsistency in definition of pointer-interconvertibility
</H4>
<B>Section: </B>6.9.4&#160; [<A href="https://wg21.link/basic.compound">basic.compound</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD6
 &#160;&#160;&#160;

 <B>Submitter: </B>Jason Merrill
 &#160;&#160;&#160;

 <B>Date: </B>2021-07-29<BR>


<P>[Accepted at the February, 2022 meeting.]</P>



<P>The changes for <A HREF="2254.html">issue 2254</A>
included the following:</P>

<P>Change 6.9.4 [<A href="https://wg21.link/basic.compound#4.3">basic.compound</A>] bullet 4.3 as follows:</P>

<BLOCKQUOTE>

<P>Two objects <I>a</I> and <I>b</I>
are <I>pointer-interconvertible</I> if:</P>

<UL>
<LI><P>...</P></LI>

<LI><P>one is a standard-layout class object and the other
is the first non-static data member of that object, or, if
the object has no non-static data members, <DEL>the
first</DEL> <INS>any</INS> base class subobject of that
object (11.4 [<A href="https://wg21.link/class.mem">class.mem</A>]), or</P></LI>
</UL>

</BLOCKQUOTE>

<P>This should also have removed the phrase,</P>

<BLOCKQUOTE>

or, if the object has no non-static data members,

</BLOCKQUOTE>

<P>since the change to 11.4 [<A href="https://wg21.link/class.mem#25">class.mem</A>] paragraph 25
specifies that all bases of a standard-layout
class have the same address, regardless of whether the
derived class has non-static data members.</P>

<P><B>Proposed resolution (November, 2021):</B></P>

<P>Change 6.9.4 [<A href="https://wg21.link/basic.compound#4.3">basic.compound</A>] bullet 4.3 as follows:</P>

<BLOCKQUOTE>

<P>Two objects <I>a</I> and <I>b</I>
are <I>pointer-interconvertible</I> if:</P>

<UL>
<LI><P>...</P></LI>

<LI><P>one is a standard-layout class object and the other
is the first non-static data member of that
object<DEL>,</DEL> or<DEL>, if the object has no non-static
data members,</DEL> any base class subobject of that object
(11.4 [<A href="https://wg21.link/class.mem">class.mem</A>]), or</P></LI>

<LI><P>...</P></LI>

</UL>

</BLOCKQUOTE>

<BR><BR>
</BODY>
</HTML>
