Re: [PATCH] misra: add deviation for MISRA C Rule 11.3

[Jan Beulich <jbeulich@xxxxxxxx>]

On 20.08.2025 09:17, Dmytro Prokopchuk1 wrote:
> MISRA C Rule 11.3 states: "A cast shall not be performed between a pointer
> to object type and a pointer to a different object type."
> 
> Violations of this rule arise due to the 'container_of' macro, which casts
> a member of a structure to its containing structure:
>     container_of(ptr, type, member) ({                             \
>            typeof_field(type, member) *__mptr = (ptr);             \
>            (type *)( (char *)__mptr - offsetof(type,member) );})
> 
> The 'container_of' macro is safe because it relies on the standardized and
> well-defined 'offsetof' macro to calculate the memory address of the
> containing structure, while assuming proper alignment and ensuring no
> undefined behavior, provided that the input pointer is valid and points to
> the specified member.
> 
> Configure Eclair to suppress violation reports related to 'container_of
> macro. Update 'deviations.rst' file accordingly. Add Rule 11.3 to the
> monitored list.
> No functional changes.
> 
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>

Looks largely okay; just one nit and a question:

> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -403,6 +403,14 @@ because the semantics of the 'noreturn' attribute do not 
> alter the calling conve
>  }
>  -doc_end
>  
> +-doc_begin="Convesions in the 'container_of' macro are safe because it 
> relies on

"Conversions" (also in deviations.rst)

> --- a/automation/eclair_analysis/ECLAIR/monitored.ecl
> +++ b/automation/eclair_analysis/ECLAIR/monitored.ecl
> @@ -45,6 +45,7 @@
>  -enable=MC3A2.R10.2
>  -enable=MC3A2.R11.1
>  -enable=MC3A2.R11.2
> +-enable=MC3A2.R11.3

While the description mentions this change, it doesn't say why (e.g. "no
violations left" or "only this and that violation left" or some such).

> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -393,6 +393,14 @@ Deviations related to MISRA C:2012 Rules:
>         (i.e., less strict) alignment requirement are safe.
>       - Tagged as `safe` for ECLAIR.
>  
> +   * - R11.3
> +     - Convesions in the 'container_of' macro are safe because it relies on
> +       the standardized and well-defined 'offsetof' macro to calculate the 
> memory

Actually another nit: Here as well as in the description, it would be nice
to add parentheses, so indicate the function-ness of both macros (i.e.
container_of() and offsetof()).

Jan