This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115d. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-10-26
[Voted into WP at October, 2009 meeting.]
The resolution of issue 613, as reflected in the sixth bullet of _N4567_.5.1.1 [expr.prim.general] paragraph 10, allows an id-expression designating a non-static data member to be used
- if... it is the sole constituent of an unevaluated operand, except for optional enclosing parentheses.
The requirement that the id-expression be the “sole constituent” of the unevaluated operand seems unnecessarily strict, forbidding such plausible use cases as
struct S { int ar[42]; }; int i = sizeof(S::ar[0]);
or the use of the member as a function argument in template metaprogramming. The more general version of the restriction seems not to be very difficult to implement and may actually represent a simplification in some implementations.
Proposed resolution (July, 2009):
Change _N4567_.5.1.1 [expr.prim.general] paragraph 10 as follows:
...
if that id-expression denotes a non-static data member
and it is the sole constituent of appears in an
unevaluated operand, except for optional enclosing
parentheses. [Example:
struct S { int m; }; int i = sizeof(S::m); // OK int j = sizeof(S::m + 42); //error: reference to non-static member in subexpressionOK
—end example]