Re: [PATCH v1] misra: add deviation for rules 21.1 and 21.2

[Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>]

On 4/23/25 20:54, 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.
> 
> 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.
> 
> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> ---
> 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..88328eaa8a 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

Hello All!

I tried to play with Rule 21.1 deviations.

After applying the following configurations:

-config=MC3A2.R21.1,macros+={safe, "^offsetof$ || ^(is|to)[a-z]+$ || 
name(NULL) || name(bool) || name(true) || name(false)"}
-config=MC3A2.R21.1,macros+={safe, 
"loc(file(^xen/include/xen/inttypes\\.h$))"}
-config=MC3A2.R21.1,macros+={safe, "loc(file(^xen/include/xen/types\\.h$))"}
-config=MC3A2.R21.1,macros+={safe, "^str[a-z]+$ || ^(v)?sprintf$ || 
^va_[a-z]+$"}

Eclair showed 699 remaining violations.
All of them were related to names beginning with an underscore (_).

It's possible to resolve the rest of them with help of (all, except for 
those beginning with '__builtin_' and '__x86_64__'):

-config=MC3A2.R21.1,macros+={safe, "^_.*$ && !^__builtin_.*$ && 
!^__x86_64__$"}

Probably, the exception list can be extended.

Jan,
I know you don't want to disallow "_all_" such reserved identifiers.
But how to deal with that?

Try to cover all macros? Like this, for example (I assume that there are 
no such reserved macros):
-config=MC3A2.R21.1,macros+={safe, "^.*XEN.*$ || ^.*HYPERVISOR.*$"}


Nicola,
Looks like it's possible to match macros (from ECLAIR User’s Manual)
"guard(): the macro is used as a guard".
I tried to use:
-config=MC3A2.R21.1,macros+={safe, "guard()"}
but it didn't work.
Did I miss something?

Thanks, Dmytro.