Re: [PATCH 1/3] misra: add deviation for rules 21.1 and 21.2

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.04.2025 01:43, victorm.lira@xxxxxxx wrote:
> From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> 
> MISRA C Rules 21.1 ("#define and #undef shall not be used on a
> reserved identifier or reserved macro name") and R21.2 ("A reserved
> identifier or reserved macro name shall not be declared") violations
> are not problematic for Xen, as it does not use the C or POSIX
> libraries.

In the course of all the Misra discussions it was pointed out more than
once that it's not just the titles which matter, but also the
"Amplification" text. While the latter two of the three bullet points
applying to both rules clearly are library-centric, the first one isn't.
In that light it's entirely unclear to me how ...

> Xen uses -fno-builtin and -nostdinc to ensure this, but there are still
> __builtin_* functions from the compiler that are available so
> a deviation is formulated for all identifiers not starting with
> "__builtin_".
> 
> The missing text of a deviation for Rule 21.2 is added to
> docs/misra/deviations.rst.
> 
> To avoid regressions, tag both rules as clean and add them to the
> monitored set.

... our code base could be anywhere near clean towards these two rules.

(Unlike I would normally do, I'm leaving the entire patch in context, so
on the list - lacking the submission - it'll be visible in its entirety.)

Jan

> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>
> ---
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Cc: Michal Orzel <michal.orzel@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Julien Grall <julien@xxxxxxx>
> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Cc: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
>  .../eclair_analysis/ECLAIR/deviations.ecl     |  9 ++++++-
>  .../eclair_analysis/ECLAIR/monitored.ecl      |  2 ++
>  automation/eclair_analysis/ECLAIR/tagging.ecl |  2 ++
>  docs/misra/deviations.rst                     | 26 ++++++++++++++++++-
>  4 files changed, 37 insertions(+), 2 deletions(-)
> 
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 2c8fb92713..ffa23b53b7 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -639,8 +639,15 @@ in the expansion."
>  # Series 21.
>  #
> 
> +-doc_begin="Xen does not use C and POSIX libraries:
> +identifiers reserved by these libraries can be used safely, except for those
> +beginning with '__builtin_'."
> +-config=MC3A2.R21.1,macros={safe, "!^__builtin_.*$"}
> +-config=MC3A2.R21.2,declarations={safe, "!^__builtin_.*$"}
> +-doc_end
> +
>  -doc_begin="or, and and xor are reserved identifiers because they constitute 
> alternate
> -spellings for the corresponding operators (they are defined as macros by 
> iso646.h).
> +spellings for the corresponding logical operators (as defined in header 
> 'iso646.h').
>  However, Xen doesn't use standard library headers, so there is no risk of 
> overlap."
>  -config=MC3A2.R21.2,reports+={safe, 
> "any_area(stmt(ref(kind(label)&&^(or|and|xor|not)$)))"}
>  -doc_end
> diff --git a/automation/eclair_analysis/ECLAIR/monitored.ecl 
> b/automation/eclair_analysis/ECLAIR/monitored.ecl
> index 8351996ec8..da229a0d84 100644
> --- a/automation/eclair_analysis/ECLAIR/monitored.ecl
> +++ b/automation/eclair_analysis/ECLAIR/monitored.ecl
> @@ -79,6 +79,8 @@
>  -enable=MC3A2.R20.12
>  -enable=MC3A2.R20.13
>  -enable=MC3A2.R20.14
> +-enable=MC3A2.R21.1
> +-enable=MC3A2.R21.2
>  -enable=MC3A2.R21.3
>  -enable=MC3A2.R21.4
>  -enable=MC3A2.R21.5
> diff --git a/automation/eclair_analysis/ECLAIR/tagging.ecl 
> b/automation/eclair_analysis/ECLAIR/tagging.ecl
> index 1d078d8905..3292bf751e 100644
> --- a/automation/eclair_analysis/ECLAIR/tagging.ecl
> +++ b/automation/eclair_analysis/ECLAIR/tagging.ecl
> @@ -88,6 +88,8 @@ MC3A2.R20.11||
>  MC3A2.R20.12||
>  MC3A2.R20.13||
>  MC3A2.R20.14||
> +MC3A2.R21.1||
> +MC3A2.R21.2||
>  MC3A2.R21.3||
>  MC3A2.R21.4||
>  MC3A2.R21.5||
> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> index fe0b1e10a2..d116aca7b9 100644
> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -587,7 +587,31 @@ Deviations related to MISRA C:2012 Rules:
>         construct is deviated only in Translation Units that present a 
> violation
>         of the Rule due to uses of this macro.
>       - Tagged as `deliberate` for ECLAIR.
> -
> +
> +   * - R21.1
> +     - Rule 21.1 reports identifiers reserved for the C and POSIX standard
> +       libraries. Xen does not use such libraries and all translation units
> +       are compiled with option `-nostdinc`, therefore there is no reason to
> +       avoid to use `#define` or `#undef` on such identifiers except for 
> those
> +       beginning with `__builtin_` for which compilers may perform (wrong)
> +       optimizations.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - R21.2
> +     - Rule 21.2 reports identifiers reserved for the C and POSIX standard
> +       libraries. Xen does not use such libraries and all translation units
> +       are compiled with option `-nostdinc`, therefore there is no reason to
> +       avoid declaring such identifiers except for those beginning with
> +       `__builtin_` for which compilers may perform (wrong) optimizations.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - R21.2
> +     - `or`, `and` and `xor` are reserved identifiers because they constitute
> +       alternate spellings for the corresponding logical operators
> +       (as defined in Standard Library header `\<iso646.h\>`). Xen does not 
> use
> +       Standard library headers, so there is no risk of overlap.
> +     - Tagged as `safe` for ECLAIR.
> +
>     * - R21.9
>       - Xen does not use the `bsearch` and `qsort` functions provided by the C
>         Standard Library, but provides in source form its own implementation,
> --
> 2.47.0