https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84046
--- Comment #3 from Martin Uecker <uecker at eecs dot berkeley.edu> ---
(In reply to Richard Biener from comment #1)
> Confirmed. I think the C language doesn't specify this since zero-sized
> arrays are a GNU extension and thus in C no zero-sized types/decls exist?
>
> So not sure if there's anything to fix - Joseph?
>
> Note that for global unique addresses you can use global objects of size 1,
> like a char object. Not sure why you think using a GNU extension is
> superior?
It makes it clear in a nice way that these variables are not used to store
information.
(In reply to Jakub Jelinek from comment #2)
> Zero sized objects of course can have the same address and always had.
> Just in your testcase the comparison used to be optimized away before
> r218462.
> If you hide it from the optimizers, like with:
> int *p = a;
> int *q = b;
> asm ("" : "+r" (p), "+r" (q));
> if(p == q) __builtin_abort ();
> you'll get aborts all the way to r104500 (oldest revision I have around).
Oh well, so this was simply an incorrect optimization.
