Re: [XEN PATCH 3/4] xen/include: add pure and const attributes

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 18 Oct 2023, Simone Ballarin wrote:
> Add const and pure attributes to address reports
> of MISRA C:2012 Rule 13.1: Initializer lists shall
> not contain persistent side effects
> 
> Add pure attribute to function pdx_to_pfn.
> Add const attribute to functions generated by TYPE_SAFE.
> 
> These functions are used in initializer lists: adding
> the attributes ensures that no effect will be performed
> by them.
> 
> Signed-off-by: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

However one comment below...

> ---
> Function attributes pure and const do not need to be added as GCC
> attributes, they can be added using ECLAIR configurations.
> ---
>  xen/include/xen/pdx.h      | 2 +-
>  xen/include/xen/typesafe.h | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/include/xen/pdx.h b/xen/include/xen/pdx.h
> index f3fbc4273a..5d1050967a 100644
> --- a/xen/include/xen/pdx.h
> +++ b/xen/include/xen/pdx.h
> @@ -164,7 +164,7 @@ static inline unsigned long pfn_to_pdx(unsigned long pfn)
>   * @param pdx Page index
>   * @return Obtained pfn after decompressing the pdx
>   */
> -static inline unsigned long pdx_to_pfn(unsigned long pdx)
> +static inline __attribute_pure__ unsigned long pdx_to_pfn(unsigned long pdx)
>  {
>      return (pdx & pfn_pdx_bottom_mask) |
>             ((pdx << pfn_pdx_hole_shift) & pfn_top_mask);
> diff --git a/xen/include/xen/typesafe.h b/xen/include/xen/typesafe.h
> index 7ecd3b4a8d..615df6f944 100644
> --- a/xen/include/xen/typesafe.h
> +++ b/xen/include/xen/typesafe.h
> @@ -21,8 +21,8 @@
>  
>  #define TYPE_SAFE(_type, _name)                                         \
>      typedef struct { _type _name; } _name##_t;                          \
> -    static inline _name##_t _##_name(_type n) { return (_name##_t) { n }; } \
> -    static inline _type _name##_x(_name##_t n) { return n._name; }
> +    static inline __attribute_const__ _name##_t _##_name(_type n) { return 
> (_name##_t) { n }; } \
> +    static inline __attribute_const__ _type _name##_x(_name##_t n) { return 
> n._name; }
>  
>  #else

I think we should also add __attribute_const__ in the NDEBUG definitions
just below.