> On Mar 12, 2025, at 12:58, Joseph Myers <josmy...@redhat.com> wrote:
>
> On Wed, 12 Mar 2025, Martin Uecker wrote:
>
>> For a designator
>>
>> struct foo { int n; } a = { .n = 1 };
>>
>> we also refer to a member 'n' of an instance 'a' of a structure type.
>> The instance is simply implied by the context.
>>
>> For
>>
>> struct foo { int n; char *x __counted_by(.n) };
>>
>> is also refers to a member of an instance of the struct. The
>> instance is the 'a' which is later used in an expression 'a.x'
>> So the instance would again be implied by the context.
>>
>> So for me this makes perfect sense in both cases (and
>> for both C and C++)
>
> The main concern with the designator syntax is if you try to embed it in
> arbitrary expressions (that is, say that __counted_by takes an expression,
> but with an additional kind of primary-expression .IDENTIFIER that can be
> used as a sub-expression therein). The above is fine, but
>
> struct foo { int n; char *x __counted_by((struct bar){.n = 1}.n };
>
> leaves an ambiguity of whether ".n = 1" is a designated initializer in the
> struct bar compound literal, or an assignment expression where .n refers
> to the member of the struct foo for which the number of elements of x is
> being counted. Note that N3188 definitely does not allow .IDENTIFIER as
> part of an expression, only as an alternative to an expression in an array
> declarator.
Is N3188 the following:
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3188.htm
What’s the status of this proposal?
Qing
>
> --
> Joseph S. Myers
> josmy...@redhat.com
>
