> On Apr 10, 2024, at 15:05, Martin Uecker <[email protected]> wrote:
>
> Am Mittwoch, dem 10.04.2024 um 20:25 +0200 schrieb Martin Uecker:
>> Am Mittwoch, dem 10.04.2024 um 17:35 +0000 schrieb Joseph Myers:
>>> On Fri, 29 Mar 2024, Qing Zhao wrote:
>>>
>>>> + /* Issue error when there is a counted_by attribute with a different
>>>> + field as the argument for the same flexible array member field. */
>>>
>>> There's another case of this to consider, though I'm not sure where best
>>> to check for it (Martin might have suggestions) - of course this case will
>>> need testcases as well.
>>>
>>> Suppose, as allowed in C23, a structure is defined twice in the same
>>> scope, but the two definitions of the structure use inconsistent
>>> counted_by attributes. I'd say that, when the declarations are in the
>>> same scope (thus required to be consistent), it should be an error for the
>>> two definitions of what is meant to be the same structure to use
>>> incompatible counted_by attributes (even though the member declarations
>>> are otherwise the same).
>>
>> I think the right place could be comp_types_attributes in
>> attributes.cc. It may be sufficient to set the
>> affects_type_identify flag.
>>
>> This should then give a redefinition error as it should do for
>> "packed".
>
> Thinking about this a bit more, this will not work here, because
> the counted_by attribute is not applied to the struct type but
> one of the members.
>
> So probably there should be a check added directly
> to tagged_types_tu_compatible_p
There are two cases we will check:
A. Both definitions are in the same scope;
Then if the 2nd definition has a counted-by attribute different from the
1st definition, the 2nd definition will be given a redefinition error;
B. These two definitions are in different scope;
When these two definitions are used in a way need to be compatible, an
incompatible error need to be issued at that
Point;
My question is, Will the routine “tagged_types_tu_compatible_p” can handle both
A and B?
Thanks.
Qing
>
> Martin
>
>>
>>>
>>> In C23 structures defined with the same tag in different scopes are
>>> compatible given requirements including compatible types for corresponding
>>> elements. It would seem most appropriate to me for such structures with
>>> incompatible counted_by attributes to be considered *not* compatible types
>>> (but it would be valid to define structures with the same tag, different
>>> scopes, and elements the same except for counted_by - just not to use them
>>> in any way requiring them to be compatible).
>>
>> Another option might be to warn about the case when those types
>> are then used together in a way where they are required to
>> be compatible. Then comp_types_attributes would have to return 2.
>>
>>
>> Martin
>>
>>>
>>>> +The @code{counted_by} attribute may be attached to the C99 flexible array
>>>> +member of a structure. It indicates that the number of the elements of
>>>> the
>>>> +array is given by the field "@var{count}" in the same structure as the
>>>
>>> As noted previously, the "" quotes should be removed there (or replaced by
>>> ``'' quotes).
>>>
>>
>
