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    CWG Issue 772</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="772"></A><H4>772.
  
<I>capture-default</I> in lambdas in local default arguments
</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>Steve Adamczyk
 &#160;&#160;&#160;

 <B>Date: </B>10 February, 2009<BR>


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

<P>Assuming that it is permitted to use a lambda as a default argument
in a block-scope function declaration (see
<A HREF="754.html">issue 754</A>), it is presumably ill-formed for
such a lambda expression to refer to a local automatic variable
(9.3.4.7 [<A href="https://wg21.link/dcl.fct.default#7">dcl.fct.default</A>] paragraph 7).  What does this mean for
<I>capture-default</I>s?  For example,</P>

<PRE>
    void f() {
      int i = 1;
      void f(int = ([i]() { return i; })());  // Definitely an error
      void g(int = ([i]() { return 0; })());  // Probably an error
      void h(int = ([=]() { return i; })());  // Definitely an error
      void o(int = ([=]() { return 0; })());  // Okay?
      void p(int = ([]() { return sizeof i; })());  // Presumably okay
    }
</PRE>

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

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

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