The previous patch didn't resolve all the false positives
in the Linux kernel.  The attached is an update that fixes
the remaining one having to do with multidimensional array
members:

   struct S { char a[2][4]; };

   void f (struct S *p, int i)
   {
     strcpy (p->a[0], "012");
     strcpy (p->a[i] + 1, p->a[0]);   // false positive here
   }

In the process of fixing this I also made a couple of minor
restructuring changes to the builtin_memref constructor to
in order to make the code easier to follow: I broke it out
into a couple of helper functions and called those.

As with the first revision of the patch, this one is also
meant to be applied on top of

   https://gcc.gnu.org/ml/gcc-patches/2018-01/msg01488.html

Sorry about the late churn.  Even though I tested the original
implementation with the Linux kernel the bugs were only exposed
non-default configurations that I didn't build.

Jakub, you had concerns about the code in the constructor
and about interpreting the offsets in the diagnostics.
I tried to address those in the patch.  Please review
the changes and let me know if you have any further comments.

Thanks
Martin

On 01/30/2018 04:19 PM, Martin Sebor wrote:
> Testing GCC 8 with recent Linux kernel sources has uncovered
> a bug in the handling of arrays of arrays by the -Wrestrict
> checker where it fails to take references to different array
> elements into consideration, issuing false positives.
>
> The attached patch corrects this mistake.
>
> In addition, to make warnings involving excessive offset bounds
> more meaningful (less confusing), I've made a cosmetic change
> to constrain them to the bounds of the accessed object.  I've
> done this in response to multiple comments indicating that
> the warnings are hard to interpret.  This change is meant to
> be applied on top of the patch for bug 83698 (submitted mainly
> to improve the readability of the offsets):
>
>   https://gcc.gnu.org/ml/gcc-patches/2018-01/msg01488.html
>
> Martin