Re: [XEN PATCH] xen/compiler: deviate the inline macro for MISRA C Rule 20.4

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.03.2024 09:10, Nicola Vetrini wrote:
> Rule 20.4 states: "A macro shall not be defined with the same name
> as a keyword".
> 
> Defining this macro with the same name as the inline keyword
> allows for additionally checking that out-of-lined static inline
> functions end up in the correct section while minimizing churn and
> has a positive impact on the overall safety. See [1] for additional
> context on the motivation of this deviation.
> 
> No functional change.
> 
> [1] 
> https://lore.kernel.org/xen-devel/adaa6d55-266d-4df8-8967-9340080d17e4@xxxxxxxxxx/
> 
> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> ---
>  docs/misra/safe.json       | 8 ++++++++
>  xen/include/xen/compiler.h | 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/docs/misra/safe.json b/docs/misra/safe.json
> index 952324f85cf9..a2bbacddf06a 100644
> --- a/docs/misra/safe.json
> +++ b/docs/misra/safe.json
> @@ -28,6 +28,14 @@
>          },
>          {
>              "id": "SAF-3-safe",
> +            "analyser": {
> +                "eclair": "MC3R1.R20.4"
> +            },
> +            "name": "MC3R1.R20.4: allow the augmentation of the inline 
> keyword in some build configurations",
> +            "text": "The definition of this macro named inline allows 
> further checking in some build configurations that certain symbols end up in 
> the right sections."
> +        },

With this wording the ID isn't going to be re-usable anywhere else. Even
if the exact same reasoning would apply.

> +        {
> +            "id": "SAF-4-safe",
>              "analyser": {},
>              "name": "Sentinel",
>              "text": "Next ID to be used"
> diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
> index 16d554f2a593..e3d9f9fb8e4b 100644
> --- a/xen/include/xen/compiler.h
> +++ b/xen/include/xen/compiler.h
> @@ -82,6 +82,7 @@
>   * inline functions not expanded inline get placed in .init.text.
>   */
>  #include <xen/init.h>
> +/* SAF-3-safe MISRA C Rule 20.4: define the inline macro to perform checks */
>  #define inline inline __init
>  #endif

I don't think the definition is "to perform checks"; it's rather to make
sure checking elsewhere wouldn't (seemingly) randomly fail. 'Override
"inline" for section contents checks to pass when the compiler chooses
not to inline a particular function' perhaps? Albeit that's getting
long-ish, I fear.

Jan