On 24.04.2025 23:45, Stefano Stabellini wrote:
> On Thu, 24 Apr 2025, Jan Beulich wrote:
>> On 23.04.2025 19:54, victorm.l...@amd.com wrote:
>>> From: Nicola Vetrini <nicola.vetr...@bugseng.com>
>>>
>>> MISRA C Rules 21.1 ("#define and #undef shall not be used on a
>>> reserved identifier or reserved macro name") and R21.2 ("A reserved
>>> identifier or reserved macro name shall not be declared") violations
>>> are not problematic for Xen, as it does not use the C or POSIX
>>> libraries.
>>>
>>> Xen uses -fno-builtin and -nostdinc to ensure this, but there are still
>>> __builtin_* functions from the compiler that are available so
>>> a deviation is formulated for all identifiers not starting with
>>> "__builtin_".
>>>
>>> The missing text of a deviation for Rule 21.2 is added to
>>> docs/misra/deviations.rst.
>>>
>>> To avoid regressions, tag both rules as clean and add them to the
>>> monitored set.
>>>
>>> Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com>
>>> Signed-off-by: Federico Serafini <federico.seraf...@bugseng.com>
>>> Signed-off-by: Victor Lira <victorm.l...@amd.com>
>>
>> While the rule is in the library section, ...
>>
>>> --- a/docs/misra/deviations.rst
>>> +++ b/docs/misra/deviations.rst
>>> @@ -587,7 +587,31 @@ Deviations related to MISRA C:2012 Rules:
>>> construct is deviated only in Translation Units that present a
>>> violation
>>> of the Rule due to uses of this macro.
>>> - Tagged as `deliberate` for ECLAIR.
>>> -
>>> +
>>> + * - R21.1
>>> + - Rule 21.1 reports identifiers reserved for the C and POSIX standard
>>> + libraries. Xen does not use such libraries and all translation units
>>> + are compiled with option '-nostdinc', therefore there is no reason
>>> to
>>> + avoid to use `#define` or `#undef` on such identifiers except for
>>> those
>>> + beginning with `__builtin_` for which compilers may perform (wrong)
>>> + optimizations.
>>> + - Tagged as `safe` for ECLAIR.
>>
>> ... I'd like to ask that it be explicitly clarified here that it's solely
>> the library (and not e.g. the compiler itself) that are of concern here.
>
> The language can be clarified:
>
> - Rule 21.1 reports identifiers reserved for the C and POSIX standard
> libraries. Xen does not use such libraries and all translation units
> are compiled with option '-nostdinc', therefore there is no reason to
> avoid to use `#define` or `#undef` on C and POSIX standard libraries
> identifiers except for those beginning with `__builtin_` for which
> compilers may perform (wrong) optimizations.
Which makes it more apparent that there is a gap: What about e.g. __x86_64__?
That falls within what the rules cover, is not a C or POSIX standard library
identifier, yet very clearly must not be fiddled with. Whereas the text
above deviates it.
Jan
