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    CWG Issue 1312</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="1312"></A><H4>1312.
  
Simulated <TT>reinterpret_cast</TT> in constant expressions
</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>Nikolay Ivchenkov
 &#160;&#160;&#160;

 <B>Date: </B>2011-05-06<BR>


<P>[Moved to DR at the October, 2012 meeting.]</P>



<P>Although a <TT>reinterpret_cast</TT> is prohibited in a constant
expression, casting to and from <TT>void*</TT> can achieve the same
effect.</P>

<P><B>Proposed resolution (August, 2011):</B></P>

<P>Change 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2 as follows:</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>

<LI><P><INS>an lvalue-to-rvalue conversion (7.3.2 [<A href="https://wg21.link/conv.lval">conv.lval</A>])
that is applied to a glvalue of type <I>cv1</I> <TT>T</TT> that refers
to an object of type <I>cv2</I> <TT>U</TT>, where <TT>T</TT> and
<TT>U</TT> are neither the same type nor similar types (7.3.6 [<A href="https://wg21.link/conv.qual">conv.qual</A>]);</INS></P></LI>

<LI><P>an lvalue-to-rvalue conversion (7.3.2 [<A href="https://wg21.link/conv.lval">conv.lval</A>]) that
is applied to a glvalue that refers to a non-active member...</P></LI>

</UL>

<P><B>Note, January, 2012:</B></P>

<P>Additional discussion  has occurred, so this issue has been returned to
"review" status to allow further consideration.</P>

<P><B>Proposed resolution (February, 2012):</B></P>

<P>Change 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2 as follows:</P>

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

<LI><P>an <I>id-expression</I> that refers to a variable or data
member of reference type unless...</P></LI>

<LI><P><INS>a conversion from type <I>cv</I> <TT>void *</TT> to a
pointer-to-object type;</INS></P></LI>

<LI><P>a dynamic cast (7.6.1.7 [<A href="https://wg21.link/expr.dynamic.cast">expr.dynamic.cast</A>]);</P></LI>

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

</UL>

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