Re: [PATCH v4] docs/misra: new rules addition

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 15 Jun 2023, Michal Orzel wrote:
> Hi Stefano,
> 
> On 15/06/2023 00:55, Stefano Stabellini wrote:
> > 
> > 
> > From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> > 
> > For Dir 1.1, a document describing all implementation-defined behaviour
> > (i.e. gcc-specific behavior) will be added to docs/misra, also including
> > implementation-specific (gcc-specific) appropriate types for bit-field
> > relevant to Rule 6.1.
> > 
> > Rule 21.21 is lacking an example on gitlab but the rule is
> > straightforward: we don't use stdlib at all in Xen.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> > ---
> > Changes in v4:
> > - improve wording of the note in 6.1
> > 
> > Changes in v3:
> > - add all signed integer types to the Notes of 6.1
> > - clarify 7.2 in the Notes
> > - not added: marking "inapplicable" rules, to be a separate patch
> > 
> > Changes in v2:
> > - drop 5.6
> > - specify additional appropriate types for 6.1
> > ---
> >  docs/misra/rules.rst | 50 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 50 insertions(+)
> > 
> > diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
> > index d5a6ee8cb6..41a727ca98 100644
> > --- a/docs/misra/rules.rst
> > +++ b/docs/misra/rules.rst
> > @@ -40,6 +40,12 @@ existing codebase are work-in-progress.
> >       - Summary
> >       - Notes
> > 
> > +   * - `Dir 1.1 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_01_01.c>`_
> > +     - Required
> > +     - Any implementation-defined behaviour on which the output of the
> > +       program depends shall be documented and understood
> > +     -
> > +
> >     * - `Dir 2.1 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_02_01.c>`_
> >       - Required
> >       - All source files shall compile without any compilation errors
> > @@ -57,6 +63,13 @@ existing codebase are work-in-progress.
> >         header file being included more than once
> >       -
> > 
> > +   * - `Dir 4.11 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_11.c>`_
> > +     - Required
> > +     - The validity of values passed to library functions shall be checked
> > +     - We do not have libraries in Xen (libfdt and others are not
> > +       considered libraries from MISRA C point of view as they are
> > +       imported in source form)
> > +
> >     * - `Dir 4.14 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_14.c>`_
> >       - Required
> >       - The validity of values received from external sources shall be
> > @@ -133,6 +146,12 @@ existing codebase are work-in-progress.
> >         headers (xen/include/public/) are allowed to retain longer
> >         identifiers for backward compatibility.
> > 
> > +   * - `Rule 6.1 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_06_01.c>`_
> > +     - Required
> > +     - Bit-fields shall only be declared with an appropriate type
> > +     - In addition to the C99 types, we also consider appropriate types
> > +       enum and all explicitly signed / unsigned integer types.
> > +
> >     * - `Rule 6.2 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_06_02.c>`_
> >       - Required
> >       - Single-bit named bit fields shall not be of a signed type
> > @@ -143,6 +162,32 @@ existing codebase are work-in-progress.
> >       - Octal constants shall not be used
> >       -
> > 
> > +   * - `Rule 7.2 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_07_02.c>`_
> > +     - Required
> > +     - A "u" or "U" suffix shall be applied to all integer constants
> > +       that are represented in an unsigned type
> > +     - The rule asks that any integer literal that is implicitly
> > +       unsigned is made explicitly unsigned by using one of the
> > +       indicated suffixes.  As an example, on a machine where the int
> > +       type is 32-bit wide, 0x77777777 is signed whereas 0x80000000 is
> > +       (implicitly) unsigned. In order to comply with the rule, the
> > +       latter should be rewritten as either 0x80000000u or 0x80000000U.
> > +       Consistency considerations may suggest using the same suffix even
> > +       when not required by the rule. For instance, if one has:
> > +
> > +       Original: f(0x77777777); f(0x80000000);
> > +
> > +       one might prefer
> Shouldn't this be "one should do" in reference to Jan remark?

Yes OK


> > +
> > +       Solution 1: f(0x77777777U); f(0x80000000U);
> > +
> > +       over
> > +
> > +       Solution 2: f(0x77777777); f(0x80000000U);
> > +
> > +       after having ascertained that "Solution 1" is compatible with the
> > +       intended semantics.
> > +
> >     * - `Rule 7.3 
> > <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_07_03.c>`_
> >       - Required
> >       - The lowercase character l shall not be used in a literal suffix
> > @@ -314,6 +359,11 @@ existing codebase are work-in-progress.
> >         used following a subsequent call to the same function
> >       -
> > 
> > +   * - Rule 21.21
> This is incorrect as it should be surrounded by `` similar to other lines.
> Otherwise it will not be taken into account by convert_misra_doc.py which 
> converts this document into cppcheck rule list.

As there is no example for 21.21 yet, I'll link the base directory with
all the examples:
https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/


> With that fixed (i.e. on commit):
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

Thanks, I'll add