Re: [PATCH] docs/misra: new rules addition

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 9 Jun 2023, Jan Beulich wrote:
> On 08.06.2023 13:02, Roberto Bagnara wrote:
> > On 07/06/23 23:53, Stefano Stabellini wrote:
> >> On Wed, 7 Jun 2023, Jan Beulich wrote:
> >>>> +   * - `Rule 5.6 
> >>>> <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_05_06.c>`_
> >>>> +     - Required
> >>>> +     - A typedef name shall be a unique identifier
> >>>> +     -
> >>>
> >>> Considering that the rule requires uniqueness across the entire code
> >>> base (and hence precludes e.g. two functions having identically named
> >>> local typedefs), I'm a little puzzled this was adopted. I for one
> >>> question that a use like the one mentioned is really at risk of being
> >>> confusing. Instead I think that the need to change at least one of
> >>> the names is at risk of making the code less readable then, even if
> >>> ever so slightly. (All of this said - I don't know if we have any
> >>> violations of this rule.)
> >>
> >> I don't think we have many local typedefs and I think we have only few
> >> violations if I remember right. I'll let Roberto confirm how many. This
> >> rule was considered not a difficult rule (some difficult rules were
> >> found, namely 2.1, 5.5 and 7.4.)
> > 
> > There currently are 30 violations for ARM64:
> > 
> > - some involve a typedef module_name (in the call it was said this should
> >    be renamed module_name_t, which will solve the issue);
> > - most concern repeated typedefs (UINT64 and similar) which are repeated
> >    in xen/arch/arm/include/asm/arm64/efibind.h
> >    and xen/include/acpi/actypes.h
> > - ret_t and phys_addr_t are also redefined in a couple of places.
> > 
> > There are 90 violations for X86_64, for the same reasons, plus
> > 
> > - another set of typedefs for basic types (such as u8);
> > - repeated typedefs for things like guest_l1e_t in the same header file:
> > 
> > xen/arch/x86/include/asm/guest_pt.h:60.39-60.49:
> > for program `xen/.xen-syms.0', the identifier for typedef `guest_l1e_t' is 
> > reused
> > xen/arch/x86/include/asm/guest_pt.h:128.22-128.32:
> > for program `xen/.xen-syms.0', the identifier for typedef `guest_l1e_t' is 
> > reused
> > 
> > The indicated lines read as follows:
> > 
> > typedef struct { guest_intpte_t l1; } guest_l1e_t;
> > typedef l1_pgentry_t guest_l1e_t;
> 
> So this is an example where I don't think we can sensibly do away with the
> re-use of the same typedef name: We use it so we can build the same source
> files multiple ways, dealing with different paging modes guests may be in.

Maybe we can have a quick discussion on Rule 5.6 during the next
meeting.

In the meantime, I'll resend the patch without Rule 5.6 and additing the
extra types in the notes for 6.1.