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    CWG Issue 1480</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="1480"></A><H4>1480.
  
Constant initialization via non-constant temporary
</H4>
<B>Section: </B>7.7&#160; [<A href="https://wg21.link/expr.const">expr.const</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2012-03-17<BR>




<P>The following initializations appear to be well-formed:</P>

<PRE>
  struct C {
   int m;
   constexpr C(int m ) : m{m} {};
   constexpr int get() { return m; };
  };

  C&amp;&amp; rr = C{1};
  constexpr int k1 = rr.get();

  const C&amp; cl = C{1};
  constexpr int k2 = cl.get();
</PRE>

<P>They appear to fall under the bullet of 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2,
</P>

<UL>
<LI>

<P>an lvalue-to-rvalue conversion (7.3.2 [<A href="https://wg21.link/conv.lval">conv.lval</A>]) unless it is
applied to
</P>
</LI>

<UL>

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

<LI>

<P>a non-volatile glvalue of literal type that refers to a non-volatile
temporary object whose lifetime has not ended, initialized with a
constant expression;
</P>
</LI>

</UL>

</UL>

<P>The problem in this example is that the referenced temporary object
is not a constant, so it would be well-defined for intervening code to
modify its value before it was used in the later initialization.</P>

<P><B>Additional note (February, 2013):</B></P>

<P>The intent is that non-const references to temporaries should be allowed
within constant expressions, e.g., across <TT>constexpr</TT> function
calls, but not as the result of a constant expression.</P>

<P><B>Proposed resolution (April, 2013):</B></P>

<P>This issue was rendered moot by paper N3652, adopted at
the April, 2013 meeting.</P>

<BR><BR>
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