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
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).
> >
>
