Re: [PATCH v2 2/3] docs/misra/rules.rst: add rule 5.5

[Federico Serafini <federico.serafini@xxxxxxxxxxx>]

On 14/02/24 09:28, Jan Beulich wrote:
> On 13.02.2024 23:33, Stefano Stabellini wrote:
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> > ---
> >   docs/misra/rules.rst | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
> > index c185366966..931158b354 100644
> > --- a/docs/misra/rules.rst
> > +++ b/docs/misra/rules.rst
> > @@ -181,6 +181,12 @@ maintainers if you want to suggest a change.
> >          headers (xen/include/public/) are allowed to retain longer
> >          identifiers for backward compatibility.
> >   
> > +   * - `Rule 5.5 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_05_05.c>`_
> > +     - Required
> > +     - Identifiers shall be distinct from macro names
> > +     - Clashes between function-like macros and non-callable entities
> > +       are allowed. The pattern #define x x is also allowed.
> Just for me to know what exactly is covered (hence also a question
> to Roberto as to [to be] implemented Eclair behavior): Even when
> the above would be sufficient (and imo better) people frequently
> write
>
> #define a(x, y) b(x, y)
>
> which, transformed to the specific case here, would then be
>
> #define a(x, y) a(x, y)
>
> I'd assume such ought to also be covered, but that's not clear
> from the spelling above.
I list what happens in some different situations,
then we can find the right words for the documentation and/or
refine the configuration:

If you
#define x x
and then use `x' as identifier,
the resulting violation is deviated (allowed pattern).

If you
#define a(x, y) a(x, y)
and then use `a' as identifier for a non-callable entity,
the resulting violation is deviated (no clash with non-callable
entities).
If you use identifier `a' for a callable entity, the resulting violation
is reported: the allowed pattern covers only macros expanding to their
own name, in this case the macro name is considered to be
`a' only, not a(x, y).

If you
#define a(x, y) b(x, y)
and then use `a' as identifier for a non-callable entity,
the resulting violation is deviated (no clash with non-callable
entities).
If you use `a' as identifier for a callable entity,
this is not a violation because after the preprocessing phase,
identifier `a' no longer exists.

As far as I know, this is what was agreed upon in one of the recent
MISRA meetings.

--
Federico Serafini, M.Sc.

Software Engineer, BUGSENG (http://bugseng.com)