Re: [PATCH] misra: deviate MISRA C Rule 10.1 for boolean operands of arithmetic

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.10.2026 18:54, Dmytro Prokopchuk1 wrote:
> MISRA C Rule 10.1 states: "Operands shall not be of an inappropriate
> essential type".
> 
> The result of relational, equality and logical negation operators has
> type int and value 0 or 1 (C99 6.5.8p6, 6.5.9p3, 6.5.3.3p5), so using
> it as an operand of +, -, * and their assignment forms has well-defined
> semantics.
> 
> Update ECLAIR configuration to tag such uses as safe.
> 
> Update deviations.rst and rules.rst accordingly.
> 
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
> ---
> Current patch resolves all ARM Rule 10.1 violations (actually, there were 
> only two),
> and resolves around 55 x86 violations.
> 
> Test CI pipeline:
> https://gitlab.com/xen-project/people/dimaprkp4k/xen/-/pipelines/2963748389
> ---
>  automation/eclair_analysis/ECLAIR/deviations.ecl | 5 +++++
>  docs/misra/deviations.rst                        | 6 ++++++
>  docs/misra/rules.rst                             | 2 ++
>  3 files changed, 13 insertions(+)
> 
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 6cdb10a129..8bfb1a0f89 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -335,6 +335,11 @@ still non-negative."
>  -config=MC3A2.R10.1,etypes+={safe, 
> "stmt(operator(logical)||node(conditional_operator||binary_conditional_operator))",
>  "dst_type(ebool||boolean)"}
>  -doc_end
>  
> +-doc_begin="The result of relational, equality and logical negation 
> operators has type int and value 0 or 1 (C99 6.5.8p6, 6.5.9p3, 6.5.3.3p5),
> +so using it as an operand of an arithmetic operator is well defined and well 
> known to all Xen developers."
> +-config=MC3A2.R10.1,etypes+={safe, 
> "stmt(operator(add||sub||mul||add_assign||sub_assign))", 
> "src_type(ebool||boolean)"}
> +-doc_end

Why the restriction to add/sub/mul? The text ...

> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -347,6 +347,12 @@ Deviations related to MISRA C:2012 Rules:
>         well-known to all Xen developers to be a comparison with 0.
>       - Tagged as `safe` for ECLAIR.
>  
> +   * - R10.1
> +     - The result of relational, equality and logical negation operators has
> +       type int and value 0 or 1 (C99 6.5.8p6, 6.5.9p3, 6.5.3.3p5), so using
> +       it as an operand of an arithmetic operator has well-defined semantics.
> +     - Tagged as `safe` for ECLAIR.

... here is less strict, albeit ...

> --- a/docs/misra/rules.rst
> +++ b/docs/misra/rules.rst
> @@ -387,6 +387,8 @@ maintainers if you want to suggest a change.
>             compilers' extensions)
>           - Implicit conversions to boolean for conditionals (?: if while
>             for) and logical operators (! || &&)
> +         - Results of relational, equality and logical negation operators
> +           (0 or 1) used as operands of arithmetic operators (+ - *)

... it's again more strict here, yet at the same time somewhat ambiguous: Are
all arithmetic operators meant, or merely those named in parentheses?

Jan