[Bug sanitizer/80536] [6/7/8 Regression] UBSAN: compile time segfault

["mpolacek at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80536

--- Comment #17 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #16)
> (In reply to Marek Polacek from comment #15)
> > In C I don't think so, because we mostly call c_save_expr and c_fully_fold
> > therein would fold that expression to 0.  And when we call save_expr, it's
> 
> Yeah, I know that, and I think it is a serious bug.  With the c_fully_fold
> in c_save_expr the C FE is not doing anything close to delayed folding, it
> folds immediately whenever we might need a save_expr, the old trees gone.
> So I think it would be nice to kill c_save_expr, just use save_expr, and let
> c_fully_fold fold SAVE_EXPR operand (just once, not many times).

I agree.  I'll try (guess we'll need the fold cache).  That can be a separate
project, though.