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

[Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>]

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.
>
> Jan
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.
     Configure ECLAIR to treat 'noreturn' attributes as safe.

Dmytro.