Re: [PATCH] c/67882 - improve -Warray-bounds for invalid offsetof

[Bernd Schmidt <bschmidt@redhat.com>]

On 10/21/2015 12:10 AM, Joseph Myers wrote:
> On Tue, 20 Oct 2015, Bernd Schmidt wrote:
>>  How about
>>    &a.v[2].a
>> and
>>    &a.v[2].b
>
> I don't think either is valid.

>> typedef struct FA5_7 {
>>    int i;
>>    char a5_7 [5][7];
>> } FA5_7;
>>
>>      __builtin_offsetof (FA5_7, a5_7 [0][7]),         // { dg-warning "index" }
>>      __builtin_offsetof (FA5_7, a5_7 [1][7]),         // { dg-warning "index" }
>>      __builtin_offsetof (FA5_7, a5_7 [5][0]),         // { dg-warning "index" }
>>      __builtin_offsetof (FA5_7, a5_7 [5][7]),         // { dg-warning "index" }
>
> The last one is certainly invalid.  The one before is arguably invalid as
> well (in the unary '&' equivalent, &a5_7[5][0] which is equivalent to
> a5_7[5] + 0, the questionable operation is implicit conversion of a5_7[5]
> from array to pointer - an array expression gets converted to an
> expression "that points to the initial element of the array object", but
> there is no array object a5_7[5] here).

Martin, is this something you're working on, or should I have a go?


Bernd