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    CWG Issue 1333</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="1333"></A><H4>1333.
  
Omission of <TT>const</TT> in a defaulted copy constructor
</H4>
<B>Section: </B>9.6.2&#160; [<A href="https://wg21.link/dcl.fct.def.default">dcl.fct.def.default</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD3
 &#160;&#160;&#160;

 <B>Submitter: </B>Daniel Kr&#252;gler
 &#160;&#160;&#160;

 <B>Date: </B>2011-06-21<BR>


<P>[Voted into the WP at the February, 2012 meeting;
moved to DR at the October, 2012 meeting.]</P>



<P>Paragraph 1 of 9.6.2 [<A href="https://wg21.link/dcl.fct.def.default">dcl.fct.def.default</A>] allows an explicitly-defaulted
copy constructor or copy assignment operator to have a parameter type
that is a reference to non-const, even if the corresponding
implicitly-declared function would have a reference to const.  However,
paragraph 2 says that a copy constructor or copy assignment operator that
is defaulted on its first declaration, the parameter type must be exactly
the same.  Is there a good reason for the stricter rule for a function
that is defaulted on its first declaration?</P>

<P><B>Proposed resolution (August, 2011):</B></P>

<OL>
<LI><P>Change 9.6.2 [<A href="https://wg21.link/dcl.fct.def.default#2">dcl.fct.def.default</A>] paragraph 2 as follows:</P></LI>

<BLOCKQUOTE>

<P>...If a function is explicitly defaulted on its first declaration,</P>

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

<LI><P><DEL>in the case of a copy constructor, move constructor, copy
assignment operator, or move assignment operator, it shall have the
same parameter type as if it had been implicitly
declared.</DEL></P></LI>

</UL>

</BLOCKQUOTE>

<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<INS>, its declared parameter type is the same as if it
had been implicitly declared,</INS> 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 X is trivial if it is not
user-provided<INS>, its declared parameter type is the same as if it
had been implicitly declared,</INS> and if...

</BLOCKQUOTE>

</OL>

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