Re: [PATCH rdma-next 2/9] RDMA: Promote field_avail() macro to be general code

[Leon Romanovsky <leon@kernel.org>]

On Thu, Mar 05, 2020 at 11:18:50AM -0400, Jason Gunthorpe wrote:
> On Thu, Mar 05, 2020 at 05:00:58PM +0200, Leon Romanovsky wrote:
> >
> > +/**
> > + * FIELD_SIZEOF - get the size of a struct's field
> > + * @t: the target struct
> > + * @f: the target struct's field
> > + * Return: the size of @f in the struct definition without having a
> > + * declared instance of @t.
> > + */
> > +#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
>
> This is already sizeof_field

Ohh, thanks

>
> > +/**
> > + * field_avail - check if specific field exists in provided data
> > + * @x: the source data, usually struct received from the user
> > + * @fld: field name
> > + * @sz: size of the data
> > + */
> > +#define field_avail(x, fld, sz) \
> > +	(offsetof(typeof(x), fld) + FIELD_SIZEOF(typeof(x), fld) <= (sz))
>
> This is just offsetofend, I'm not sure there is such a reason to even
> have this field_avail macro really..

Even better.

Thanks

>
> Jason