Re: [XEN PATCH v2] x86: p2m-pod: address violation of MISRA C Rule 2.1

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2024-09-10 12:03, Jan Beulich wrote:
> On 10.09.2024 11:53, Nicola Vetrini wrote:
> > On 2024-09-10 11:08, Jan Beulich wrote:
> > > On 10.09.2024 10:56, Nicola Vetrini wrote:
> > > > On 2024-07-01 10:36, Jan Beulich wrote:
> > > > > On 28.06.2024 08:30, Nicola Vetrini wrote:
> > > > > This being about unreachable code, why are the domain_crash() not 
> > > > > the
> > > > > crucial points of "unreachability"? And even if they weren't there,
> > > > > why
> > > > > wouldn't it be the goto or ...
> > > > >
> > > > > > --- a/xen/arch/x86/mm/p2m-pod.c
> > > > > > +++ b/xen/arch/x86/mm/p2m-pod.c
> > > > > > @@ -1040,6 +1040,7 @@ out_unmap:
> > > > > >       * Something went wrong, probably crashing the domain.  Unmap
> > > > > >       * everything and return.
> > > > > >       */
> > > > > > +    /* SAF-8-safe Rule 2.1: defensive programming */
> > > > > >      for ( i = 0; i < count; i++ )
> > > > > >          if ( map[i] )
> > > > > >              unmap_domain_page(map[i]);
> > > > > ... the label (just out of context) where the comment needs to go?
> > > > Because of the way this rule's configuration work, deviations are
> > > > placed
> > > > on the construct that ends up being the target of the 
> > > > unreachability,
> > > What's "target" here? What if this loop was removed from the 
> > > function?
> > > Then both the label and the domain_crash() invocations would still be
> > > unreachable in debug builds. Are you telling me that this then 
> > > wouldn't
> > > be diagnosed by Eclair? Or that it would then consider the closing
> > > figure brace of the function "the target of the unreachability"?
> > Exactly, the end brace is a target to which the "function end" 
> > construct
> > is associated.
> > It would be kind of strange, though: why not just doing 
> > "domain_crash();
> > return;" in that case?
> Sure, the question was theoretical. Now if "return" was used directly
> there, what would then be the "target"? IOW - the more abstract 
> question
> of my earlier reply still wasn't answered.
The return statement in

...
domain_crash();
return;
<~~~~~>

Whichever statement is found to be unreachable in the current 
preprocessed code.
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)