Re: [XEN PATCH 2/7] x86/mm: address MISRA C:2012 Rule 2.1

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2023-12-14 08:57, Jan Beulich wrote:
> On 13.12.2023 15:44, Nicola Vetrini wrote:
> > On 2023-12-12 10:53, Jan Beulich wrote:
> > > On 12.12.2023 10:12, Nicola Vetrini wrote:
> > > > On 2023-12-12 02:42, Stefano Stabellini wrote:
> > > > > On Mon, 11 Dec 2023, Nicola Vetrini wrote:
> > > > > > The "return 0" after the swich statement in 'xen/arch/x86/mm.c'
> > > > > > is unreachable because all switch clauses end with returns.
> > > > > > However, some of them can be substituted with "break"s to allow
> > > > > > the "return 0" outside the switch to be reachable.
> > > > > >
> > > > > > No functional changes.
> > > > > This is correct but makes the code inconsistent. I would either
> > > > > remove
> > > > > the return 0; at the end of arch_memory_op, or do the following:
> > > > >
> > > > > - initialize rc to 0 at the beginning: int rc = 0;
> > > > > - all switch clauses break instead of return;
> > > > > - at the end: return rc;
> > > > Given the feedback on the Arm side, the first solution is likely to 
> > > > be
> > > > preferred.
> > > I wouldn't mind either option, with
> > > - the former ensured to be okay with all compiler versions we (still)
> > >   support,
> > I tested a stripped-down version of the switch on godbolt.org (as far
> > back as gcc-4.8.5) and it doesn't complain. It should be tested on a
> > real Xen build, though.
> I didn't fear any issue when going back to just 4.8. Quoting ./README:
>
>       - For x86:
>         - GCC 4.1.2_20070115 or later
I found no issue in 4.1.2 (see https://godbolt.org/z/cxecnKseG)

> > > - the latter having the initialize rc to 0 part dropped; imo it's
> > > better
> > >   if every case block makes sure to set the intended value 
> > > explicitly.
> > This is a lot of churn, I'd rather avoid it.
> Rant (sorry): There's already excessive churn for entirely benign 
> issues
> that Misra claims need adjusting.
>
> Jan
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)