Re: [PATCH: 1/1] sh4: avoid spurious gcc warning

[Michael Karcher]

Am 23.01.2023 um 17:11 schrieb Jakub Jelinek:

> On Mon, Jan 23, 2023 at 04:06:27PM +0000, David Laight wrote:
> > From: Michael.Karcher
> > > -#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
> > FWIW it is (currently) enough to add 0 to the top or bottom
> > of the division.
> If you don't want the warning at all, sure.  But if you want the compiler
> to warn if you use the macro on a (non-void *) pointer rather than array,
> what has been posted is needed.

Exactly. I actually had sizeof(a)/(sizeof(*a) + 0) at first, but a test showed
that it would silently generate invalid code on

  struct intc_mask_reg singleton = {...};
  _INTC_ARRAY(&singleton)

If it would expand to "&singleton, 1", it would be fine, but it will
expand to "&singleton, 0", as sizeof(intc_mask_reg*) is smaller than
sizeof(intc_mask_reg). The version I posted generates the intended warning
(upgraded to an error with -Werror) in that case. The old version also
generated the intended warning in this case, and not generating a warning
here is a regression I didn't want to be responsible for.

Kind regards,
  Michael Karcher