C++: Reference to member in sizeof expression of another member declaration

clang++ (trunk, both C++03 and C++11 modes) rejects the following program:

union u {
   int a;
   char b[sizeof(a)];

t.cpp:3:17: error: invalid use of non-static data member 'a'
   char b[sizeof(a)];

This seems valid C++, considering this language in [expr.prim.general]: "An id-expression that denotes a non-static data member […] can only be used […] if that id-expression […] appears in an unevaluated operand"

Could you please report a bug for this one too?

Trunk accepts this for me in C++11, and rejects in C++98, which IIRC is correct behavior.

You are right, I found the matching location in the C++98 standard and it does not contain the exception for unevaluated operands.