Re: [XEN PATCH] automaton/eclair: add deviations for MISRA C:2012 Rule 13.6

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.04.2024 16:21, Federico Serafini wrote:
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -333,6 +333,14 @@ of the short-circuit evaluation strategy of such logical 
> operators."
>  -config=MC3R1.R13.5,reports+={disapplied,"any()"}
>  -doc_end
>  
> +-doc_begin="Macros alternative_vcall[0-9] use sizeof to type-check \"func\" 
> and the func parameters without evaluating them."
> +-config=MC3R1.R13.6,reports+={deliberate,"any_area(any_loc(any_exp(macro(^alternative_vcall[0-9]$))))"}
> +-doc_end

alternative_vcall(), for now at least, is x86-only. Why blindly deviate it also
for Arm?

> +-doc_begin="Macro chk_fld is only used to introduce BUILD_BUG_ON checks in 
> very specific cases where by code inspection you can see that its usage is 
> correct. The BUILD_BUG_ON checks check that EFI_TIME and struct 
> xenpf_efi_time fields match."
> +-config=MC3R1.R13.6,reports+={deliberate,"any_area(any_loc(any_exp(macro(^chk_fld$))))"}
> +-doc_end

As indicated on earlier occasions - when a macro isn't global, its deviation
better wouldn't be global either. An identically named macro may be introduced
elsewhere, and may not need deviating there.

> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -279,6 +279,18 @@ Deviations related to MISRA C:2012 Rules:
>         the short-circuit evaluation strategy for logical operators.
>       - Project-wide deviation; tagged as `disapplied` for ECLAIR.
>  
> +   * - R13.6
> +     - Macros alternative_vcall[0-9] use sizeof to type-check \"func\" and 
> the
> +       func parameters without evaluating them.

Just to mention it: The return type of the function isn't really of interest
there. What's being checked is that the argument types match the corresponding
parameter ones, which otherwise would "naturally" be done by the compiler when
seeing function calls. Might be useful to state no more and no less than what
is really needed.

Further, according to the discussion on the matter: alternative_call() is
quite similar in this regard, just that it uses typeof(). Imo it should be
deviated here as well right away, no matter whether Eclair can actually be
configured to also check typeof() and alignof().

Jan