Hi,
Based on the discussion so far and further consideration, the following is my
plan for this new attribute:
1. The syntax of the new attribute will be:
__attribute__((counted_by (count_field_id)));
In the above, count_field_id is the identifier for the field that carries the
number
of elements info in the same structure of the FAM.
For example:
struct object {
..
size_t count: /* carries the number of elements info for the FAM flex. */
int flex[] __attribute__((counted_by (count)));
};
2. Later, if the argument of the this attribute need to be extended to an
expression, we might need to
extend the C FE to accept ".count” in the future.
Let me know if you have further comments and suggestions.
thanks.
Qing
> On Jun 20, 2023, at 3:40 PM, Qing Zhao via Gcc-patches
> <[email protected]> wrote:
>
>
>
>> On Jun 16, 2023, at 5:35 PM, Joseph Myers <[email protected]> wrote:
>>
>> On Fri, 16 Jun 2023, Qing Zhao via Gcc-patches wrote:
>>
>>>> So for
>>>>
>>>> struct foo { int c; int buf[(struct { int d; }){ .d = .c }]; };
>>>>
>>>> one knows during parsing that the .d is a designator
>>>> and that .c is not.
>>>
>>> Therefore, the above should be invalid based on this rule since .c is
>>> not a member in the current structure.
>>
>> What do you mean by "current structure"? I think two different concepts
>> are being conflated: the structure *being initialized* (what the C
>> standard calls the "current object" for a brace-enclosed initializer
>> list),
>
> I think the concept of “current structure” should be stick to this.
>
>> and the structure *being defined*.
> Not this.
>
> (Forgive me about my poor English -:)).
>
> Then it will be cleaner?
>
> What’s your opinion?
>
>
>> The former is what's relevant
>> for designators. The latter is what's relevant for the suggested new
>> syntax. And .c *is* a member of the structure being defined in this
>> example.
>>
>> Those two structure types are always different, except for corner cases
>> with C2x tag compatibility (where an object of structure type might be
>> initialized in the middle of a redefinition of that type).
>
> Can you give an example on this? Thanks.
>
> Qing
>>
>> --
>> Joseph S. Myers
>> [email protected]
