[Bug libstdc++/63345] Multiple undefined behaviors (static_cast<>) in libstdc++-v3/include/bits

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63345

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Why does your patch need to touch operator* or operator-> for any of the
iterators? For any dereferenceable iterator the cast should be valid, so if
you're seeing invalid casts it suggests that you are dereferencing invalid
iterators.