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). >