Re: [XEN PATCH][for-next][for-4.19 v2 1/8] xen/include: add macro LOWEST_BIT

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

On 20/10/2023 08:00, Jan Beulich wrote:
> On 19.10.2023 21:58, Stefano Stabellini wrote:
>>>>>>> --- a/xen/include/xen/macros.h
>>>>>>> +++ b/xen/include/xen/macros.h
>>>>>>> @@ -8,8 +8,10 @@
>>>>>>>  #define DIV_ROUND(n, d) (((n) + (d) / 2) / (d))
>>>>>>>  #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
>>>>>>> 
>>>>>>> -#define MASK_EXTR(v, m) (((v) & (m)) / ((m) & -(m)))
>>>>>>> -#define MASK_INSR(v, m) (((v) * ((m) & -(m))) & (m))
>>>>>> 
>>>>>> a SAF-<n>-safe comment here?
>>>>>> 
>>>>> 
>>>>> One reason is that now that violations only belonging to tool
>>>>> configurations
>>>>> and similar are documented in docs/misra/deviations.rst (committed 
>>>>> in
>>>>> Stefano's
>>>>> branch for-4.19 [1]).
>>>> 
>>>> But tool configuration means every analysis tool needs configuring
>>>> separately. That's why the comment tagging scheme was decided to be
>>>> preferred, iirc.
>>>> 
>>>>> Also, there were disagreements on the SAF naming
>>>>> scheme, and
>>>>> patches like those would not be accepted at the moment.
>>>> 
>>>> Well, that needs resolving. The naming there shouldn't lead to 
>>>> patches
>>>> being accepted that later may need redoing.
>>>> 
>>>> Jan
>>> 
>>> While this is true, in this case I'm not willing to deviate with a 
>>> SAF, given
>>> that
>>> some ECLAIR-specific configuration would be needed anyways, given 
>>> that I'm
>>> deviating a macro definition, rather than the line where it's 
>>> actually used
>>> (and maybe other tools would need
>>> that as well).
>> 
>> Did I get it right that the problem with using SAF in this case is 
>> that
>> it wouldn't be sufficient to add a SAF comment on top of the MACRO
>> definition, but we would need a SAF comment on top of every MACRO
>> invocation?
>> 
>> If so, then not just for this MACRO but in general basically we have 
>> to
>> use deviations.rst.
> 
> That would be pretty sad.
> 
> Jan
> 

Local deviation comments are for local deviations; deviating patterns is 
a tool configuration.

>> Luca, do you know what would be the behavior for cppcheck and/or
>> Coverity? I imagine it will be the same and they would also need a
>> deviation at every MACRO invocation, not just the definition?

-- 
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)