<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<TITLE>
    CWG Issue 2096</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="2096"></A><H4>2096.
  
Constraints on literal unions
</H4>
<B>Section: </B>6.9&#160; [<A href="https://wg21.link/basic.types">basic.types</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD4
 &#160;&#160;&#160;

 <B>Submitter: </B>Agust&#237;n K-ballo Berg&#233;
 &#160;&#160;&#160;

 <B>Date: </B>2015-03-11<BR>


<P>[Adopted at the February, 2016 meeting.]</P>



<P>According to 6.9 [<A href="https://wg21.link/basic.types#10.5.3">basic.types</A>] bullet 10.5.3, all the
members of a class type must be of non-volatile literal types.
This seems overly constraining for unions; it would seem to be
sufficient if at least one of its non-static members were of a
literal type.</P>

<P><B>Proposed resolution (September, 2015):</B></P>

<P>Change 6.9 [<A href="https://wg21.link/basic.types#10.5">basic.types</A>] bullet 10.5 as follows:</P>

<BLOCKQUOTE>

<P>A type is a <I>literal type</I> if it is:</P>

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

<LI>

<P>a possibly cv-qualified class type (Clause 11 [<A href="https://wg21.link/class">class</A>]) that has
all of the following properties:</P>
</LI>

<UL>
<LI><P>it has a trivial destructor,</P></LI>

<LI><P>it is an aggregate type (9.5.2 [<A href="https://wg21.link/dcl.init.aggr">dcl.init.aggr</A>]) or has at least
one constexpr constructor or constructor template that is not a copy or
move constructor, <DEL>and</DEL>
</P></LI>

<LI><P><INS>if it is a union, at least one of its non-static data members
is of non-volatile literal type, and</INS></P></LI>

<LI><P>
<INS>if it is not a union,</INS> all of its non-static data members
and base classes are of non-volatile literal types.</P></LI>

</UL>

</UL>

</BLOCKQUOTE>

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