<HTML>
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<TITLE>
    CWG Issue 644</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="644"></A><H4>644.
  
Should a trivial class type be a literal type?
</H4>
<B>Section: </B>6.9&#160; [<A href="https://wg21.link/basic.types">basic.types</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD1
 &#160;&#160;&#160;

 <B>Submitter: </B>Alisdair Meredith
 &#160;&#160;&#160;

 <B>Date: </B>8 Aug 2007<BR>


<P>[Voted into the WP at the June, 2008 meeting.]</P>



<P>The original proposed wording for 6.9 [<A href="https://wg21.link/basic.types#11">basic.types</A>] paragraph 11
required a constexpr constructor for a literal class
only &#8220;if the class has at least one user-declared
constructor.&#8221;  This wording was dropped during the
review by CWG out of a desire to ensure that literal types not
have any uninitialized members.  Thus, a class like</P>

<PRE>
    struct pixel {
        int x, y;
    };
</PRE>

<P>is not a literal type.  However, if an object of that type is
aggregate-initialized or value-initialized, there can be no
uninitialized members; the missing wording should be restored in
order to permit use of expressions like <TT>pixel().x</TT> as
constant expressions.</P>

<P><B>Proposed resolution (February, 2008):</B></P>

<P>Change 6.9 [<A href="https://wg21.link/basic.types#10">basic.types</A>] paragraph 10 as follows:</P>

<BLOCKQUOTE>

A type is a <I>literal type</I> if it is:
<UL>
<LI>a scalar type; or</LI>
<LI>a class type (Clause 11 [<A href="https://wg21.link/class">class</A>]) with</LI>
<UL>
<LI>a trivial copy constructor,</LI>
<LI>a trivial destructor,</LI>
<LI>
<INS>a trivial default constructor or</INS> at least one constexpr
constructor other than the copy constructor,</LI>
<DEL><LI>no virtual base classes, and</LI></DEL>
<LI>all non-static data members and base classes of literal types; or</LI>
</UL>
<LI>an array of literal type.</LI>
</UL>

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