Re: [XEN PATCH] xen: Add SAF deviations for MISRA C:2012 Rule 7.1

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 11/10/2023 00:39, Stefano Stabellini wrote:
> On Tue, 10 Oct 2023, Julien Grall wrote:
> > Hi Stefano,
> >
> > On 09/10/2023 23:19, Stefano Stabellini wrote:
> > > > I am not sure this is better. This is a long line to read. But this is a
> > > > personal opinion.
> > > >
> > > > On the technical side, can we easily teach a tool to format this kind of
> > > > exception? If not, then this should not be an exception we should
> > > > implement.
> > > I am not sure I understand what you mean by "can we easily teach a tool
> > > to format this kind of exception". Do you mean whether we can teach a
> > > tool to interpret a multiline statement as a single statement?
> > Sorry for the wording was not clear. I was referring to tools formatting the
> > code (e.g. clang-format). Hopefully, at some point, we will finally have a way
> > to automatically format the code. So we need a coding style that can be easily
> > be checked.
> >
> > It is not clear to me whether your proposed exception would work. We may have
> > to allow longer lines (and this has drawback).
> Yes, that's a good point. It will probably be an issue with clang-format.
>
>
> > > /* cppcheck tag */
> > > line1
> > > /* cppcheck tag */
> > > line2
> > > /* cppcheck tag */
> > > line3
> > >
> > > and that would end up changing the line numbers in the source files so
> > > the cppcheck report wouldn't match with the original line numbers any
> > > longer
> > Would cppcheck accepts tag at the end of the line? If so, the following would
> > not modify the line count:
> >
> > /* cppcheck tag */
> > line1 /* added cppcheck tag */
> > line2 /* added cppcheck tag */
> > line3 /* added cppcheck tag */
> Luca answered to a similar, more generic, question a few days ago about
> Coverity: https://marc.info/?l=xen-devel&m=169657904027210
Interesting.

> So even if we get cppcheck to work like that, we would lose Coverity
> support.
I think my suggestion was probably misunderstood. So let me clarify it. 
To cover multi-line, we could write the following in Xen:
/* cppcheck tag next-3-lines */
line 1
line 2
line 3

AFAIU Eclair supports multi-line, so the tag would be transformed to 
there internal solution. For CPPCheck, this could be transformed to:
/* cppcheck tag next-3 lines */
line 1 /* generated cppcheck tag */
line 2 /* generated cppcheck tag */
line 3 /* generated cppcheck tag */

Now, I understand that coverity doesn't support any of the two format. 
So the only solution would be to add the comment before each line which 
would impact the line numbers. This is not great, but I think this is 
acceptable as the context would likely help to find where this is coming 
from.
Cheers,

--
Julien Grall