[Bug sanitizer/65610] Compare debug failure with -g3 -fsanitize=undefined -fno-sanitize=vptr -O3

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65610

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Note that the "-fno-sanitize=vptr" is crucial: without it doesn't give an ICE.