https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113551
--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Yuxuan Shui from comment #12)
> I think this is the MRE:
>
>
> void bug(struct obj *dso) {
> if (&dso->i) {
> if (dso == (void *)0)
> return;
>
> assert_not_null(dso);
> }
> }
Except that is undefined ...
Manually unswitching introduces the undefined behavior in the code.
So even though the code was unswitched before GCC 13 incorrectly, GCC didn't
take into that account before hand.
I am 99% sure what is happening is GCC is see `if (a+1)` and then assuming a
can't be a nullptr. Which is due to undefinedness there of adding 1 to an null
ptr ... (for C that is).
Basically the unswitch is the issue ... Or we maybe we should turn `if (a+1)`
into just `if (a)` ... Likewise for `if (&a->i)` into `if (a)`
