https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70143
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to rguent...@suse.de from comment #5)
> Though that will FAIL the gcc.dg/Wstrict-aliasing-struct-member.c
> I added.
>
> Note that we then also don't warn for
>
> struct a {
> int i;
> int k;
> };
> struct b {
> struct a a;
> int j;
> };
> int main(void) {
> static struct b b;
> struct a *ap=(struct a *)&b;
> return ((struct b *)&ap->k)->j;
> }
>
> then either. Doing this kind of warnings strictly based on alias
> sets only is going to be "broken" - though I consider our strict-aliasing
> warnings broken anyway (and I don't think we can ever implement something
> sensible :/).
The point of -Wstrict-aliasing=3 is to give very few false positives and still
catch lots of likely bugs. So, if there is INDIRECT_REF or *MEM_REF involved
and you can't analyze what it points to, we should err on the side that it
might be valid, people can still use -Wstrict-aliasing=2 that will warn even
about these.
