Re: [PATCH] generic/altp2m: address violations of MISRA C Rule 2.1

[Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>]

On 6/22/26 13:29, Dmytro Prokopchuk wrote:
> Hello, Jan
> 
> On 4/10/26 09:04, Jan Beulich wrote:
>> On 09.04.2026 19:37, Dmytro Prokopchuk1 wrote:
>>> MISRA C Rule 2.1 states: "A project shall not contain unreachable code".
>>>
>>> In certain build configurations,
>>
>> Can you give an example where ...
> If CONFIG_VM_EVENT is enabled on ARM.
>>
>>> the function 'altp2m_vcpu_idx()' is defined
>>> as an inline function that contains the 'BUG()' macro. This resulted 
>>> in a
>>> violation because the 'BUG()' macro makes the function non-returning.
>>>
>>> To ensure compliance with MISRA C Rule 2.1, this patch removes the 
>>> inline
>>> function implementation and its BUG()-based unreachable code. It is 
>>> replaced
>>> with an unconditional function declaration for 'altp2m_vcpu_idx()'.
>>
>> ... a declaration is needed? The sole non-x86 reference I see is from
> Yes, declaration is needed. The file 'common/monitor.c' contains a usage 
> of the 'altp2m_vcpu_idx()' and compiler must see it to avoid "error: 
> implicit declaration of function ‘altp2m_vcpu_idx’".
>> common/monitor.c, and the sole relevant Kconfig option I can spot is
>> VM_EVENT. When that's off, the file won't be built at all.
> But when 'CONFIG_VM_EVENT=y' this file is compiled on ARM.
>>
>> Further, BUG() and a few more constructs have a dedicated deviation
>> already in place. I don't mind a useless function to be shrunk (or, as
>> per above, perhaps even dropped), but the justification then needs to
>> be different.
> Well, with Stefano's comment regarding return type, the commit subject 
> and message could be rewritten like:
> 
> generic/altp2m: align and simplify altp2m_vcpu_idx()
> 
> The return type of 'altp2m_vcpu_idx()' in the generic altp2m.h header is
> currently 'unsigned int', which is inconsistent with its 'uint16_t'
> return type on x86 and the 'altp2m_idx' member of the monitor structures.
> 
> To fix this type inconsistency and simplify the header, this patch
> replaces the static inline implementation of 
> 'altp2m_vcpu_idx()' (contained a BUG() stub) with a simple function 
> declaration returning
> uint16_t.
> 
> For architectures using the generic altp2m.h header (such as ARM when
> CONFIG_VM_EVENT is enabled), common code calls to 'altp2m_vcpu_idx()' in 
> common/monitor.c are guarded by 'altp2m_active()', which
> statically returns 'false'. The compiler's DCE will optimize out these 
> calls, avoiding any linker issues for the missing definition.
> 
>>
>> Jan
> 
> BR, Dmytro.

Hello Jan,

kind reminder. Please, take a look.