[Bug c++/49171] [C++0x][constexpr] Constant expressions support reinterpret_cast

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49171

--- Comment #23 from Jonathan Wakely <redi at gcc dot gnu.org> ---
What you want (and what everybody I've seen asking for similar things) is to
give a compile-time constant value to a pointer. All that's needed for that is
an extension to provide a compile-time constant value to a pointer, not to
allow arbitrary reinterpret_casts in constexpr.

A more limited extension that solves the problem is a lot more reasonable.