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    CWG Issue 2171</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="2171"></A><H4>2171.
  
Triviality of copy constructor with less-qualified parameter
</H4>
<B>Section: </B>11.4.5.3&#160; [<A href="https://wg21.link/class.copy.ctor">class.copy.ctor</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2015-09-14<BR>


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



<P>
<A HREF="1333.html">Issue 1333</A> says that a defaulted
copy constructor with a less-const-qualified parameter type than
the implicit declaration is non-trivial.  This is inconsistent
with the usual pattern that whether a special member function
is callable is separate from whether it is trivial; the different
declaration only affects whether you can call it with a <TT>const</TT>
argument, it doesn't affect the operations involved.  Should this
outcome be reconsidered?</P>

<P><B>Proposed resolution (April, 2016):</B></P>

<OL>
<LI><P>Change 11.4.5.3 [<A href="https://wg21.link/class.copy.ctor#12">class.copy.ctor</A>] paragraph 12 as follows:</P></LI>

<BLOCKQUOTE>

A copy/move constructor for class <TT>X</TT> is trivial if it is not
user-provided<DEL>, its parameter-type-list is equivalent to the
parameter-type-list of an implicit declaration,</DEL> and if...

</BLOCKQUOTE>

<LI><P>Change 11.4.5.3 [<A href="https://wg21.link/class.copy.ctor#25">class.copy.ctor</A>] paragraph 25 as follows:</P></LI>

<BLOCKQUOTE>

A copy/move assignment operator for class <TT>X</TT> is trivial if it
is not user-provided<DEL>, its parameter-type-list is equivalent
to the parameter-type-list of an implicit declaration,</DEL> and
if...

</BLOCKQUOTE>

</OL>

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