http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25466
--- Comment #10 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-11-01 09:10:56 UTC --- (In reply to comment #9) I don't think that the standard says (or intends to say) that an implementation has to defer all evaluations here. For example, assume you provide polymorphic& operator+(polymorphic a, polymorphic b); with some definition this is still UB when the expression *(T*)0 + *(T*)0 occurs as operand of typeid (Note the arguments are by value). An implementation is only required to detect whether an (immediate) runtime glvalue of a polymorphic class as argument of typeid refers to an "empty glvalue". Anything beyond that would fall under http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#232 I think.
