On Fri, Jul 21, 2023 at 08:22:35PM +0300, Andy Shevchenko wrote:
> On Fri, Jul 21, 2023 at 08:00:15PM +0300, Andy Shevchenko wrote:
> > Introduce opaque_struct_size() helper, which may be moved
> > to overflow.h in the future, and use it in the IIO core.
...
> > +#define opaque_struct_size(p, a, s) ({ \
> > + size_t _psize = sizeof(*(p)); \
> > + size_t _asize = ALIGN(_psize, (a)); \
> > + size_t _ssize = s; \
> > + _ssize ? size_add(_asize, _ssize) : _psize; \
> > +})
> > +
> > +#define opaque_struct_data(p, a) \
> > + ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
>
> Hmm... This can potentially evaluate p twice.
>
> Perhaps this variant is better:
>
> #define opaque_struct_data(p, a) ALIGN((p) + 1, (a)))
>
> Besides, I don't think we should worry about @s evaluation in the main macro
> which may be simplified to
>
> #define opaque_struct_size(p, a, s) \
> ((s) ? size_add(ALIGN(sizeof(*(p)), (a)), (s)) : sizeof(*(p)))
>
> Thoughts?
Also we may leave the struct always be aligned which makes the above even
simpler (but might waste bytes if @s = 0).
#define opaque_struct_size(p, a, s) size_add(ALIGN(sizeof(*(p)), (a)), (s))
(with the respective documentation update).
--
With Best Regards,
Andy Shevchenko
