[Bug c/61240] [6/7/8 Regression] Incorrect warning "integer overflow in expression" on pointer-pointer subtraction

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61240

--- Comment #15 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I've been meaning to address this PR (for too long, apparently), but it seems
it's too late for GCC 8 now.  If you want, you can take it.  If not, hopefully
I'll get to it for GCC 9.