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    CWG Issue 759</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="759"></A><H4>759.
  
Destruction of closure objects
</H4>
<B>Section: </B>7.5.6.2&#160; [<A href="https://wg21.link/expr.prim.lambda.closure">expr.prim.lambda.closure</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD2
 &#160;&#160;&#160;

 <B>Submitter: </B>Daveed Vandevoorde
 &#160;&#160;&#160;

 <B>Date: </B>22 January, 2009<BR><BR>


<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3086.html#UK39">N2800 comment
  UK&#160;39<BR></A>

<P>[Voted into the WP at the July, 2009 meeting as part of N2927.]</P>



<P>The specification of closure objects is missing a couple of important
points regarding their destruction.  First, although 7.5.6 [<A href="https://wg21.link/expr.prim.lambda#11">expr.prim.lambda</A>] paragraph 11
mentions other implicitly-declared special member functions,
it is silent on the destructor, leading to questions about whether the
closure class has one or not.</P>

<P>Second, nothing is said about the timing of the destruction of a
closure object: is it normally destroyed at the end of the full-expression
to which the lambda expression belongs, and is its lifetime extended if
the closure object is bound to a reference?  These questions would be
addressed if paragraph 2 defined the closure object as a temporary instead
of just as an rvalue.  (It should be noted that 7.6.1.4 [<A href="https://wg21.link/expr.type.conv">expr.type.conv</A>]
also does not define the conceptually-similar <TT>T()</TT> as a
temporary.)</P>

<P><B>Proposed resolution (July, 2009)</B></P>

<P>See document PL22.16/09-0117 = WG21 N2927.  (The question regarding
the failure of 7.6.1.4 [<A href="https://wg21.link/expr.type.conv">expr.type.conv</A>] failing to categorize
<TT>T()</TT> as a temporary was split off into a separate issue; see
<A HREF="943.html">issue 943</A>.)</P>

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