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".
>
> 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).
>
