Re: [XEN PATCH 10/10] xen/keyhandler: address violations of MISRA C Rule 20.7

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 1 Mar 2024, Jan Beulich wrote:
> On 29.02.2024 23:57, Stefano Stabellini wrote:
> > On Thu, 29 Feb 2024, Nicola Vetrini wrote:
> >> MISRA C Rule 20.7 states: "Expressions resulting from the expansion
> >> of macro parameters shall be enclosed in parentheses". Therefore, some
> >> macro definitions should gain additional parentheses to ensure that all
> >> current and future users will be safe with respect to expansions that
> >> can possibly alter the semantics of the passed-in macro parameter.
> >>
> >> No functional change.
> >>
> >> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> > 
> > Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> 
> You did see the discussion on earlier patches, though? I don't think
> any of the parentheses here are needed or wanted.

We need to align on this. Currently if we go by what's written in
docs/misra/deviations.rst, then rhs should have parentheses.

Can we safely claim that rhs parentheses are never needed? If so, then
great, let's add it to deviations.rst and skip them here and other
places in this patch series (e.g. patch #8). When I say "never" I am
taking for granted that the caller is not doing something completely
unacceptably broken such as: 

     WRITE_SYSREG64(var +, TTBR0_EL1)

If we cannot generically claim that rhs parentheses are never needed,
then I don't think we should make any exceptions. We should add them here
and everywhere else. It should be easy to write a macro or review a
patch with a macro from someone else, and making special exception makes
it more difficult for everyone.