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    CWG Issue 2353</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="2353"></A><H4>2353.
  
Potential results of a member access expression for a static data member
</H4>
<B>Section: </B>6.3&#160; [<A href="https://wg21.link/basic.def.odr">basic.def.odr</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD5
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2017-08-18<BR>


<P>[Accepted as a DR at the February, 2019 meeting.]</P>

<P>According to 6.3 [<A href="https://wg21.link/basic.def.odr#2.3">basic.def.odr</A>] bullet 2.3, the potential
results of a member access expression are simply the object expression.
This rule incorrectly handles an example like:</P>

<PRE>
  struct X {
    static const int n = 0;
  };
  X x = {};

  int b = x.n;
</PRE>

<P>Because <TT>X::n</TT> is not one of the potential results, the
expression <TT>x.n</TT> odr-uses <TT>X::n</TT>, requiring it to be
defined.</P>

<P><B>Notes from the April, 2018 teleconference:</B></P>

<P>CWG agreed with the suggested direction to make the member a
potential result in cases like the example.</P>

<P><B>Proposed resolution (February, 2019):</B></P>

<P>Change 6.3 [<A href="https://wg21.link/basic.def.odr#2">basic.def.odr</A>] paragraph 2 as follows:</P>

<BLOCKQUOTE>

<P>An expression is potentially evaluated unless it is an
unevaluated operand (7.2 [<A href="https://wg21.link/expr.prop">expr.prop</A>]) or a
subexpression thereof.  The set of potential results of an
expression <TT>e</TT> is defined as follows:</P>

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

<LI><P>If <TT>e</TT> is a class member access expression
(7.6.1.5 [<A href="https://wg21.link/expr.ref">expr.ref</A>]) <INS>of the form
<TT>e1 . template</TT><SUB><I>opt</I></SUB><TT> e2</TT>
naming a non-static data member</INS>, the set contains the
potential results of <DEL>the object expression</DEL>
<INS><TT>e1</TT></INS>.</P></LI>

<LI><P><INS>if <TT>e</TT> is a class member access expression
naming a static data member, the set contains the
<I>id-expression</I> designating the data member.</INS></P></LI>

<LI><P>If <TT>e</TT> is a pointer-to-member expression
(7.6.4 [<A href="https://wg21.link/expr.mptr.oper">expr.mptr.oper</A>]) <DEL>whose second operand is a
constant expression</DEL> <INS>of the form
<TT>e1 .* e2</TT></INS>, the set contains the potential results
of <DEL>the object expression</DEL>
<INS><TT>e1</TT></INS>.</P></LI>

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

</UL>

</BLOCKQUOTE>

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