Re: [PATCH] misra/eclair: set 'noreturn' attribute as safe during cast

[Jan Beulich <jbeulich@xxxxxxxx>]

On 29.07.2025 12:55, Nicola Vetrini wrote:
> On 2025-07-29 12:52, Jan Beulich wrote:
>> On 29.07.2025 12:04, Dmytro Prokopchuk1 wrote:
>>>
>>>
>>> On 7/29/25 11:04, Jan Beulich wrote:
>>>> On 29.07.2025 00:15, Dmytro Prokopchuk1 wrote:
>>>>> ECLAIR reports a non-compliant cast due to the presence
>>>>> of the 'noreturn' attribute in the callee function.
>>>>
>>>> Which callee function? Which cast? Please be concrete. You don't need
>>>> to enumerate all case, but one specific example wants pointing at.
>>>>
>>>>> The issue occurs when casting a function pointer with
>>>>> the 'noreturn' attribute (void noreturn (*)(void *))
>>>>> to a general function pointer type (void (*)(void *)).
>>>>
>>>> And again - why "casting"? As per ...
>>>>
>>>>> Configure ECLAIR to treat 'noreturn' attributes as safe
>>>>> in this conversion.
>>>>>
>>>>> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
>>>>> ---
>>>>> Previous discussion thread:
>>>>> https://patchew.org/Xen/181a03d5c7625d42c06cf9fa0cf48a9bc6825361.1753647875.git.dmytro._5Fprokopchuk1@xxxxxxxx/
>>>>
>>>> ... there was no cast involved, iirc. We specifically rejected your
>>>> attempt to add a cast there. It's a conversion the compiler does, 
>>>> aiui.
>>>>
>>> Yes, you are right.
>>> Word "cast" is not appropriate there.
>>>
>>> Below is updated text:
>>>
>>>      misra: allow 'noreturn' as safe for function pointer conversions
>>>
>>>      The conversion from a function pointer with the
>>>      'noreturn' attribute ('void noreturn (*)(void *)')
>>>      to a function pointer type ('void (*)(void *)'
>>>      causes type incompatibility according to
>>>      MISRA C Rule 11.1, which forbids conversions
>>>      between incompatible function pointer types.
>>>
>>>      The violation occurs at the call site
>>>          smp_call_function(halt_this_cpu, NULL, 0);
>>>      where 'halt_this_cpu' with type 'void noreturn (*)(void *)'
>>>      is passed to 'smp_call_function' expecting a function
>>>      pointer of type 'void (*)(void *)'.
>>>
>>>      The 'noreturn' attribute does not change the function
>>>      calling convention or parameter handling at runtime,
>>>      making the conversion safe.
>>
>> Up to here things read much better now, thanks. Just one more request:
>> Please make better use of the 72 (or maybe even 75) characters that are
>> permitted per line.
>>
>>>      Configure ECLAIR to treat 'noreturn' attributes as safe.
> 
> Configure ECLAIR to treat implicit casts that lose the "noreturn" 
> attribute on a function void (*fp)(void*) as safe. This is because the 
> deviation actually just deviates void noreturn (*fp)(void*) -> void 
> (*fp)(void*)

Thanks. Just one more nit: s/casts/conversions/.

Jan