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

[Roberto Bagnara <roberto.bagnara@xxxxxxxxxxx>]

On 09/06/23 10:46, 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.
Typedefs being used this way can be deviated with tool configuration.
Here is a list of candidates for that treatment:

guest_intpte_t
guest_l1e_t
guest_l2e_t
ret_

I am not sure about the latter.  Please let me know if this is what
you would prefer and possible additions to/removals from the above list.
Kind regards,

   Roberto