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    CWG Issue 753</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="753"></A><H4>753.
  
Array names in lambda capture sets
</H4>
<B>Section: </B>7.5.6.3&#160; [<A href="https://wg21.link/expr.prim.lambda.capture">expr.prim.lambda.capture</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>10 December, 2008<BR>


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



<P>The current specification does not adequately describe what happens
when an array name is part of the effective capture set of a lambda
expression.  7.5.6 [<A href="https://wg21.link/expr.prim.lambda#13">expr.prim.lambda</A>] paragraph 13 says that the
array member of the closure object is direct-initialized by the local
array; however, 9.5 [<A href="https://wg21.link/dcl.init#16">dcl.init</A>] paragraph 16 says that such
an initialization is ill-formed.  There are several possibilities for
handling this problem:</P>

<OL>
<LI><P>This results in an array member of the closure object,
which is initialized by copying each element, along the lines of
11.4.5.3 [<A href="https://wg21.link/class.copy.ctor#8">class.copy.ctor</A>] paragraph 8.</P></LI>

<LI><P>This results in a pointer member of the closure object,
initialized to point to the first element of the array (i.e., the
array lvalue decays to a pointer rvalue).</P></LI>

<LI><P>This is ill-formed.</P></LI>

<LI><P>This results in a reference-to-array member of the closure
object, initialized to refer to the array, regardless of whether
<TT>&amp;</TT> was used or not.</P></LI>

<LI><P>This is ill-formed unless the capture is &#8220;by
reference.&#8221;</P></LI>

</OL>

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

<P>See document PL22.16/09-0117 = WG21 N2927.</P>

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