On Mon, Jan 28, 2019 at 08:27:17AM -0800, Bart Van Assche wrote:
> On Mon, 2019-01-28 at 17:20 +0200, Leon Romanovsky wrote:
> > On Mon, Jan 28, 2019 at 07:01:41AM -0800, Bart Van Assche wrote:
> > > On 1/28/19 6:14 AM, Leon Romanovsky wrote:
> > > > -struct ib_device *ib_alloc_device(size_t size);
> > > > +void *_ib_alloc_device(size_t size);
> > > > +#define ib_alloc_device(drv_struct, member) \
> > > > + (BUILD_BUG_ON_ZERO(offsetof(struct drv_struct, member)) + \
> > > > + BUILD_BUG_ON_ZERO(!__builtin_types_compatible_p( \
> > > > + typeof(((struct drv_struct *)NULL)->member), \
> > > > + struct ib_device)) + \
> > > > + _ib_alloc_device(sizeof(struct drv_struct)))
> > > > +
> > >
> > > Hi Leon,
> > >
> > > Have you considered to use a comma expression and BUILD_BUG_ON() instead
> > > of adding the BUILD_BUG_ON_ZERO() results to the _ib_alloc_device()
> > > return value? I think that would result in slightly easier to read code
> > > and also in code that reflects the intent better.
> >
> > I wanted to make sure that macro is used as assignment and returns
> > value, in such case it should be art of expression, hence in success
> > it is evaluated to 0.
> >
> > I will very happy to receive code snippet for the same with BUILD_BUG_ON().
>
> Hi Leon,
>
> How about the following macro definition, which uses BUILD_BUG_ON() instead of
> BUILD_BUG_ON_ZERO() and which uses __same_type() instead of
> __builtin_types_compatible_p() (compile-tested only):
Strange, i tried __same_type() too and the second typeof didn't work for
me. But in your macro it works, maybe I missed some brackets.
>
> #define ib_alloc_device(drv_struct, member) \
> (({BUILD_BUG_ON(offsetof(struct drv_struct, member) != 0);}), \
> ({BUILD_BUG_ON(!__same_type(((struct drv_struct *)NULL)->member, \
> struct ib_device));}), \
> _ib_alloc_device(sizeof(struct drv_struct)))
>
> Thanks,
>
> Bart.
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