Re: [PATCH] misra: add deviation for PrintErrMesg() function

[Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>]

On 8/19/25 16:25, Jan Beulich wrote:
> On 19.08.2025 15:12, Dmytro Prokopchuk1 wrote:
>> MISRA C Rule 2.1 states: "A project shall not contain unreachable code."
>>
>> The function 'PrintErrMesg()' is implemented to never return control to
>> its caller. At the end of its execution, it calls 'blexit()', which, in
>> turn, invokes '__builtin_unreachable()'. This makes the 'return false;'
>> statement in 'read_file()' function unreachable.
> 
> I'm disappointed. In earlier review comments I pointed out that there are
> two. Yet you say "the", without further disambiguation.
> 
>> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
>> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
>> @@ -41,6 +41,10 @@ not executable, and therefore it is safe for them to be 
>> unreachable."
>>   
>> -call_properties+={"name(__builtin_unreachable)&&stmt(begin(any_exp(macro(name(ASSERT_UNREACHABLE)))))",
>>  {"noreturn(false)"}}
>>   -doc_end
>>   
>> +-doc_begin="Unreachability caused by the call to the 'PrintErrMesg()' 
>> function is deliberate, as it terminates execution, ensuring no control flow 
>> continues past this point."
>> +-config=MC3A2.R2.1,reports+={deliberate, "any_area(^.*PrintErrMesg.*$ && 
>> any_loc(file(^xen/common/efi/boot\\.c$)))"}
>> +-doc_end
> 
> I don't understand the description here, nor ...
> 
>> --- a/docs/misra/deviations.rst
>> +++ b/docs/misra/deviations.rst
>> @@ -97,6 +97,13 @@ Deviations related to MISRA C:2012 Rules:
>>          Xen expects developers to ensure code remains safe and reliable in 
>> builds,
>>          even when debug-only assertions like `ASSERT_UNREACHABLE() are 
>> removed.
>>   
>> +   * - R2.1
>> +     - Function `PrintErrMesg()` terminates execution (at the end it calls
>> +       `blexit()`, which, in turn, invokes `__builtin_unreachable()`), 
>> ensuring
>> +       no code beyond this point is ever reached. This guarantees that 
>> execution
>> +       won't incorrectly proceed or introduce unwanted behavior.
>> +     - Tagged as `deliberate` for ECLAIR.
> 
> .. the text here. PrintErrMesg() is noreturn. Why would anything need saying 
> about
> it? Isn't the problem here solely with the tail of read_file(), while other 
> uses
> of PrintErrMesg() are okay?
> 
> Jan

I'm a little bit confused.

As I understood you proposed to insert the SAF comment before the 
'return' statement (with proper justification).

And current Eclair configuration & descriptions are not good at all.

Am I right?

Dmytro.