[Bug c++/107798] optimizing -O3, "for" loop condition not checked anymore

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107798

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
With -fsanitize=undefined we do detect the original undefined behavior at
runtime:

/app/example.cpp:21:50: runtime error: index 3 out of bounds for type 'A [3]'