[Bug c++/85091] Compiler generates different code depending on whether -Wnonnull -Woverloaded-virtual given or not

[mathieu.malaterre at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85091

--- Comment #17 from Mathieu Malaterre <mathieu.malaterre at gmail dot com> ---
Here is what I did over here:

# debootstrap --arch amd64 sid /srv/chroot/sid-amd64
http://httpredir.debian.org/debian
# mount -t proc proc /srv/chroot/sid-amd64/proc
# chroot /srv/chroot/sid-amd64 apt install g++-mingw-w64-i686

Then (https://wiki.debian.org/AutomaticDebugPackages):

# apt install g++-mingw-w64-i686-dbgsym

And eventually ran valgrind on both:

# valgrind --trace-children=yes i686-w64-mingw32-g++ -c -std=c++17 -O2
-Wnonnull -Woverloaded-virtual -v tmp1/16795.cpp -o warn.o >& /tmp/ok
# valgrind --trace-children=yes i686-w64-mingw32-g++ -c -std=c++17 -O2
-Wnonnull -Woverloaded-virtual -v 16795.cpp -o warn.o >& /tmp/notok

The valgrind output seems rather different, so I suspect the issue is indeed an
invalid read/write which should be somewhere in the diff of ok vs notok.