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    CWG Issue 1806</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="1806"></A><H4>1806.
  
Virtual bases and move-assignment
</H4>
<B>Section: </B>11.4.6&#160; [<A href="https://wg21.link/class.copy.assign">class.copy.assign</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2013-11-04<BR>


<P>[Moved to DR at the November, 2014 meeting.]</P>



<P>The proposed resolution for <A HREF="1402.html">issue 1402</A>
overlooked some needed changes in 11.4.5.3 [<A href="https://wg21.link/class.copy.ctor">class.copy.ctor</A>] paragraph
28.</P>

<P><B>Proposed resolution (February, 2014):</B></P>

<P>Change 11.4.5.3 [<A href="https://wg21.link/class.copy.ctor#28">class.copy.ctor</A>] paragraph 28 as follows:</P>

<BLOCKQUOTE>

<P>...It is unspecified whether subobjects representing virtual
base classes are assigned more than once by the
implicitly-defined copy<INS>/move</INS> assignment
operator. [<I>Example:</I>
</P>

<PRE>
  struct V { };
  struct A : virtual V { };
  struct B : virtual V { };
  struct C : B, A { };
</PRE>

<P>It is unspecified whether the virtual base class
subobject <TT>V</TT> is assigned twice by the
implicitly-defined copy<INS>/move</INS> assignment operator
for <TT>C</TT>. &#8212;<I>end example</I>] <DEL>[<I>Note:</I>
This does not apply to move assignment, as a defaulted move
assignment operator is deleted if the class has virtual
bases. &#8212;<I>end note</I>]</DEL>
</P>

</BLOCKQUOTE>

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