Re: [PATCH] correct -Wrestrict handling of arrays of arrays (PR 84095)

[Martin Sebor <msebor@gmail.com>]

Ping: https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00076.html

On 02/01/2018 04:45 PM, Martin Sebor wrote:
> 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
>