> On Jun 15, 2023, at 6:48 PM, Joseph Myers <jos...@codesourcery.com> wrote:
>
> On Thu, 15 Jun 2023, Qing Zhao via Gcc-patches wrote:
>
>> B. The argument of the new attribute “counted_by” is an identifier that can
>> be
>> accepted by “c_parser_attribute_arguments”:
>>
>> struct trailing_array_B {
>> Int count;
>> int array_B[] __attribute ((counted_by (count)));
>> };
>>
>>
>> From my current very limited understanding of the C FE source code, it’s
>> not easy to extend the argument to an expression later for the above. Is
>> this understanding right?
>
> It wouldn't be entirely compatible: if you change to interpreting the
> argument as an expression, then the above would suggest a global variable
> count is used (as opposed to some other syntax for referring to an element
> of the containing structure).
Yeah, that’s the reason I tried to introduce the new “.count” syntax for the
argument
of the new attribute in the very beginning in order to avoid such incompatible
issue later. -:)
>
> So an attribute that takes an element name might best be a *different*
> attribute from any potential future one taking an expression (with some
> new syntax to refer to an element).
So, if we add this “counted_by (identifier)” attribute now, and later we need
to add another
new attribute “new_counted_by (expression)” at that time if needed?
Kees, what’s your opinion on this?
thanks.
Qing
>
> --
> Joseph S. Myers
> jos...@codesourcery.com
