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    CWG Issue 2068</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="2068"></A><H4>2068.
  
When can/must a defaulted virtual destructor be defined?
</H4>
<B>Section: </B>11.4.7&#160; [<A href="https://wg21.link/class.dtor">class.dtor</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2015-01-12<BR>


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



<P>The rules in 6.3 [<A href="https://wg21.link/basic.def.odr">basic.def.odr</A>] and 11.4.7 [<A href="https://wg21.link/class.dtor">class.dtor</A>]
do not specify when the destructor for <TT>B</TT> can/must be defined:</P>

<PRE>
   struct A { virtual ~A(); };
   struct B : A {};
   int main() {
     A *p = new B;
     delete p;
   }
</PRE>

<P>An implementation should be allowed, but not required, to
implicitly define a virtual special member function at any point
where it has been desclared, as well as being required to define
it as described in 11.4.7 [<A href="https://wg21.link/class.dtor#6">class.dtor</A>] paragraph 6, etc.</P>

<P><B>Proposed resolution (September, 2015):</B></P>

<P>Change 11.4.7 [<A href="https://wg21.link/class.dtor#6">class.dtor</A>] paragraph 6 as follows:</P>

<BLOCKQUOTE>

A destructor that is defaulted and not defined as deleted is implicitly
defined when it is odr-used (6.3 [<A href="https://wg21.link/basic.def.odr">basic.def.odr</A>]) <DEL>to destroy an
object of its class type (6.8.6 [<A href="https://wg21.link/basic.stc">basic.stc</A>])</DEL> or when it is
explicitly defaulted after its first declaration.

</BLOCKQUOTE>

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