https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86376
--- Comment #3 from David Binderman <dcb314 at hotmail dot com> ---
This configure line seems to work:
../trunk/configure --prefix=/home/dcb/gcc/results.262304.ubsan \
--with-build-config=bootstrap-ubsan \
--disable-multilib \
--disable-werror \
--enable-checking=df,extra,fold \
--enable-languages=fortran
So it's looking like the rtl or yes flags are the problem.
