Re: [XEN PATCH 3/5] xen/sort: address violations of MISRA C:2012 Rule 8.2

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 21 Nov 2023, Jan Beulich wrote:
> On 21.11.2023 01:04, Stefano Stabellini wrote:
> > On Mon, 20 Nov 2023, Jan Beulich wrote:
> >> On 20.11.2023 14:13, Federico Serafini wrote:
> >>> On 20/11/23 10:02, Jan Beulich wrote:
> >>>> On 17.11.2023 09:40, Federico Serafini wrote:
> >>>>> --- a/xen/include/xen/sort.h
> >>>>> +++ b/xen/include/xen/sort.h
> >>>>> @@ -23,8 +23,8 @@
> >>>>>   extern gnu_inline
> >>>>>   #endif
> >>>>>   void sort(void *base, size_t num, size_t size,
> >>>>> -          int (*cmp)(const void *, const void *),
> >>>>> -          void (*swap)(void *, void *, size_t))
> >>>>> +          int (*cmp)(const void *key, const void *elem),
> >>>>
> >>>> Why "key" and "elem" here, but ...
> >>>>
> >>>>> +          void (*swap)(void *a, void *b, size_t size))
> >>>>
> >>>> ... "a" and "b" here? The first example of users of sort() that I'm
> >>>> looking at right now (x86/extable.c) is consistent in its naming.
> >>>>
> >>>
> >>> On the Arm side there are {cmp,swap}_memory_node() and
> >>> {cmp,swap}_mmio_handler(): "key"/"elem" are used for the comparison
> >>> and "_a"/"_b" for the swap.
> >>
> >> So - re-raising a question Stefano did raise - is Misra concerned about
> >> such discrepancies? If yes, _all_ instances need harmonizing. If not, I
> >> see no reason to go with misleading names here.
> > 
> > Federico confirmed that the answer is "no".
> > 
> > I think we can use "key" and "elem" in this patch as they are more
> > informative than "a" and "b"
> 
> Except that "key" and "elem" are (imo) inapplicable to sort() callbacks
> (and inconsistent with the naming in the 2nd callback here); they _may_
> be applicable in bsearch() ones. Note also how in the C99 spec these
> parameters of callback functions don't have names either.

Yes, reading the example in extable.c I think you are right. Maybe it is
better to use "a" and "b" in both cmp and swap if you agree.