Re: [XEN PATCH][for-next][for-4.19 v2 1/8] xen/include: add macro LOWEST_BIT

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 20/10/2023 08:00, Jan Beulich wrote:
> On 19.10.2023 21:58, Stefano Stabellini wrote:
> > > > > > > --- a/xen/include/xen/macros.h
> > > > > > > +++ b/xen/include/xen/macros.h
> > > > > > > @@ -8,8 +8,10 @@
> > > > > > >  #define DIV_ROUND(n, d) (((n) + (d) / 2) / (d))
> > > > > > >  #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
> > > > > > >
> > > > > > > -#define MASK_EXTR(v, m) (((v) & (m)) / ((m) & -(m)))
> > > > > > > -#define MASK_INSR(v, m) (((v) * ((m) & -(m))) & (m))
> > > > > > a SAF-<n>-safe comment here?
> > > > > One reason is that now that violations only belonging to tool
> > > > > configurations
> > > > > and similar are documented in docs/misra/deviations.rst (committed 
> > > > > in
> > > > > Stefano's
> > > > > branch for-4.19 [1]).
> > > > But tool configuration means every analysis tool needs configuring
> > > > separately. That's why the comment tagging scheme was decided to be
> > > > preferred, iirc.
> > > >
> > > > > Also, there were disagreements on the SAF naming
> > > > > scheme, and
> > > > > patches like those would not be accepted at the moment.
> > > > Well, that needs resolving. The naming there shouldn't lead to 
> > > > patches
> > > > being accepted that later may need redoing.
> > > >
> > > > Jan
> > > While this is true, in this case I'm not willing to deviate with a 
> > > SAF, given
> > > that
> > > some ECLAIR-specific configuration would be needed anyways, given 
> > > that I'm
> > > deviating a macro definition, rather than the line where it's 
> > > actually used
> > > (and maybe other tools would need
> > > that as well).
> > Did I get it right that the problem with using SAF in this case is 
> > that
> > it wouldn't be sufficient to add a SAF comment on top of the MACRO
> > definition, but we would need a SAF comment on top of every MACRO
> > invocation?
> >
> > If so, then not just for this MACRO but in general basically we have 
> > to
> > use deviations.rst.
> That would be pretty sad.
>
> Jan
Local deviation comments are for local deviations; deviating patterns is 
a tool configuration.
> > Luca, do you know what would be the behavior for cppcheck and/or
> > Coverity? I imagine it will be the same and they would also need a
> > deviation at every MACRO invocation, not just the definition?
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)