Re: [XEN PATCH][for-4.19 v2 1/1] xen: introduce a deviation for Rule 11.9

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 16/10/2023 15:43, Jan Beulich wrote:
> On 11.10.2023 14:46, Nicola Vetrini wrote:
> > --- a/xen/include/xen/compiler.h
> > +++ b/xen/include/xen/compiler.h
> > @@ -109,13 +109,16 @@
> >
> >  #define offsetof(a,b) __builtin_offsetof(a,b)
> >
> > +/* Access the field of structure type, without defining a local 
> > variable */
> > +#define access_field(type, member) (((type *)NULL)->member)
> This is not a field access, so I consider the macro misnamed. Question 
> is
> whether such a helper macro is needed in the first place.
>
> > +#define typeof_field(type, member) typeof(access_field(type, member))
> If this needs adding, it wants to come ...
>
> >  /**
> >   * sizeof_field(TYPE, MEMBER)
> >   *
> >   * @TYPE: The structure containing the field of interest
> >   * @MEMBER: The field to return the size of
> >   */
> > -#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
> > +#define sizeof_field(TYPE, MEMBER) sizeof(access_field(TYPE, MEMBER))
> ... with a commend similar as this one has. (Or the commend could be
> slightly altered to cover both).
I added access_field since it's possibly useful on its own in the 
future,
but that may not be the case. Not a real field access, perhaps a 
fake_access_field?
Ok about the missing comment for typeof_field.

> Further, if fiddling with these: Wouldn't they better move to macros.h?
>
> Jan
That seems a good suggestion, as they are not compiler-specific.

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)