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    CWG Issue 2394</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="2394"></A><H4>2394.
  
Const-default-constructible for members
</H4>
<B>Section: </B>11.4.5.2&#160; [<A href="https://wg21.link/class.default.ctor">class.default.ctor</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD5
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2018-07-10<BR>


<P>[Accepted as a DR at the February, 2019 meeting.]</P>



<P>After the changes for comment RU 1 in
<A HREF="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0490r0.html">P0490R0</A>,
a defaulted default constructor is acceptable for default
initialization of a <TT>const</TT> object under certain
circumstances; for example,</P>

<PRE>
   struct A {};
   const A a;
</PRE>

<P>is well-formed. However, default-initialization of such a
class member still requires a user-provided constructor:</P>

<PRE>
   struct B { const A a; };
   B b;   //<SPAN CLASS="cmnt">error</SPAN>
</PRE>

<P><B>Proposed resolution (November, 2018):</B></P>

<P>Change 11.4.5.2 [<A href="https://wg21.link/class.default.ctor#2.4">class.default.ctor</A>] bullet 2.4 as follows:</P>

<BLOCKQUOTE>

<P>A defaulted default constructor for class <TT>X</TT> is
defined as deleted if:</P>

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

<LI><P>any non-variant non-static data member of
const-qualified type (or array thereof) with
no <I>brace-or-equal-initializer</I> <DEL>does not have a
user-provided default constructor</DEL>
<INS>is not const-default-constructible
(9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>])</INS> ,</P></LI>

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

</UL>

</BLOCKQUOTE>

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