http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49171
--- Comment #2 from Daniel Krügler <daniel.kruegler at googlemail dot com>
2011-08-30 09:39:43 UTC ---
I believe I found a conforming usage of reinterpret_cast in constant
expressions useable in C++03:
//----------------
struct X {
X* operator&();
};
X x[2];
const bool p = (reinterpret_cast<X*>(&reinterpret_cast<char&>(x[1]))
- reinterpret_cast<X*>(&reinterpret_cast<char&>(x[0]))) == sizeof(X);
enum E { e = p }; // e should have a value equal to 1
//----------------
Basically this program demonstrates the technique, the C++11 library function
addressof is based on and thus excluding reinterpret_cast *unconditionally*
from constant expressions in the core language would render this useful program
invalid and would make it impossible to declare addressof as a constexpr
function.
