Re: [XEN PATCH] xen/bitmap: remove comment-based deviations

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 28 Aug 2024, Federico Serafini wrote:
> Update ECLAIR configuration of MISRA C:2012 Rule 20.7 ("Expressions
> resulting from the expansion of macro parameters shall be enclosed in
> parentheses") to tag as 'safe' the expansions of arguments surrounded
> by the following tokens: '{', '}' and ';'.
> 
> Remove redundant comment-based deviations.
> 
> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>

I am missing some context: is this done to cover other cases similar to
the one below (bitmap_allocate_region) or is this done only to get rid
of the three SAF-7-safe in-code comments?


> ---
>  automation/eclair_analysis/ECLAIR/deviations.ecl | 4 ++++
>  docs/misra/deviations.rst                        | 5 +++++
>  xen/include/xen/bitmap.h                         | 3 ---
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 1aa8277066..f37329973f 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -565,6 +565,10 @@ of this macro do not lead to developer confusion, and 
> can thus be deviated."
>  -config=MC3R1.R20.7,reports+={safe, 
> "any_area(any_loc(any_exp(macro(^count_args_$))))"}
>  -doc_end
>  
> +-doc_begin="The expansion of an argument surrounded by tokens '{', '}' and 
> ';' is safe."
> +-config=MC3R1.R20.7,expansion_context+={safe, 
> "left_right(^[\\{;]$,^[;\\}]$)"}
> +-doc_end
> +
>  -doc_begin="Uses of variadic macros that have one of their arguments defined 
> as
>  a macro and used within the body for both ordinary parameter expansion and 
> as an
>  operand to the # or ## operators have a behavior that is well-understood and
> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> index d51aa422b5..d529726464 100644
> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -512,6 +512,11 @@ Deviations related to MISRA C:2012 Rules:
>         refactoring it to add parentheses breaks its functionality.
>       - Tagged as `safe` for ECLAIR.
>  
> +   * - R20.7
> +     - The expansion of an argument surrounded by tokens '{', '}' and ';' is
> +       safe.
> +     - Tagged as `safe` for ECLAIR.
> +
>     * - R20.12
>       - Variadic macros that use token pasting often employ the gcc extension
>         `ext_paste_comma`, as detailed in `C-language-toolchain.rst`, which is
> diff --git a/xen/include/xen/bitmap.h b/xen/include/xen/bitmap.h
> index 5d668053b0..4b642cd420 100644
> --- a/xen/include/xen/bitmap.h
> +++ b/xen/include/xen/bitmap.h
> @@ -103,13 +103,10 @@ extern int bitmap_allocate_region(unsigned long 
> *bitmap, int pos, int order);
>  #define bitmap_switch(nbits, zero, small, large)                       \
>       unsigned int n__ = (nbits);                                       \
>       if (__builtin_constant_p(nbits) && !n__) {                        \
> -             /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
>               zero;                                                     \
>       } else if (__builtin_constant_p(nbits) && n__ <= BITS_PER_LONG) { \
> -             /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
>               small;                                                    \
>       } else {                                                          \
> -             /* SAF-7-safe Rule 20.7 non-parenthesized macro argument */ \
>               large;                                                    \
>       }
>  
> -- 
> 2.34.1
>