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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 2/3] docs/misra/rules.rst: add rule 5.5
On 04.03.2024 17:36, Jan Beulich wrote: > On 04.03.2024 16:39, Federico Serafini wrote: >> On 04/03/24 15:17, Jan Beulich wrote: >>> On 04.03.2024 14:31, Federico Serafini wrote: >>>> On 01/03/24 09:06, Jan Beulich wrote: >>>>> On 01.03.2024 00:28, Stefano Stabellini wrote: >>>>>> On Wed, 14 Feb 2024, Federico Serafini wrote: >>>>>>> On 14/02/24 14:15, Jan Beulich wrote: >>>>>>>> On 14.02.2024 12:27, Federico Serafini wrote: >>>>>>>>> On 14/02/24 09:28, Jan Beulich wrote: >>>>>>>>>> On 13.02.2024 23:33, Stefano Stabellini wrote: >>>>>>>>>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx> >>>>>>>>>>> --- >>>>>>>>>>> docs/misra/rules.rst | 6 ++++++ >>>>>>>>>>> 1 file changed, 6 insertions(+) >>>>>>>>>>> >>>>>>>>>>> diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst >>>>>>>>>>> index c185366966..931158b354 100644 >>>>>>>>>>> --- a/docs/misra/rules.rst >>>>>>>>>>> +++ b/docs/misra/rules.rst >>>>>>>>>>> @@ -181,6 +181,12 @@ maintainers if you want to suggest a change. >>>>>>>>>>> headers (xen/include/public/) are allowed to retain >>>>>>>>>>> longer >>>>>>>>>>> identifiers for backward compatibility. >>>>>>>>>>> + * - `Rule 5.5 >>>>>>>>>>> <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_05_05.c>`_ >>>>>>>>>>> + - Required >>>>>>>>>>> + - Identifiers shall be distinct from macro names >>>>>>>>>>> + - Clashes between function-like macros and non-callable >>>>>>>>>>> entities >>>>>>>>>>> + are allowed. The pattern #define x x is also allowed. >>>>>>>>>> >>>>>>>>>> Just for me to know what exactly is covered (hence also a question >>>>>>>>>> to Roberto as to [to be] implemented Eclair behavior): Even when >>>>>>>>>> the above would be sufficient (and imo better) people frequently >>>>>>>>>> write >>>>>>>>>> >>>>>>>>>> #define a(x, y) b(x, y) >>>>>>>>>> >>>>>>>>>> which, transformed to the specific case here, would then be >>>>>>>>>> >>>>>>>>>> #define a(x, y) a(x, y) >>>>>>>>>> >>>>>>>>>> I'd assume such ought to also be covered, but that's not clear >>>>>>>>>> from the spelling above. >>>>>>>>> >>>>>>>>> I list what happens in some different situations, >>>>>>>>> then we can find the right words for the documentation and/or >>>>>>>>> refine the configuration: >>>>>>>>> >>>>>>>>> If you >>>>>>>>> #define x x >>>>>>>>> and then use `x' as identifier, >>>>>>>>> the resulting violation is deviated (allowed pattern). >>>>>>>>> >>>>>>>>> If you >>>>>>>>> #define a(x, y) a(x, y) >>>>>>>>> and then use `a' as identifier for a non-callable entity, >>>>>>>>> the resulting violation is deviated (no clash with non-callable >>>>>>>>> entities). >>>>>>>>> If you use identifier `a' for a callable entity, the resulting >>>>>>>>> violation >>>>>>>>> is reported: the allowed pattern covers only macros expanding to their >>>>>>>>> own name, in this case the macro name is considered to be >>>>>>>>> `a' only, not a(x, y). >>>>>>>>> >>>>>>>>> If you >>>>>>>>> #define a(x, y) b(x, y) >>>>>>>>> and then use `a' as identifier for a non-callable entity, >>>>>>>>> the resulting violation is deviated (no clash with non-callable >>>>>>>>> entities). >>>>>>>> >>>>>>>> I'm afraid I don't see what violation there is in this case, to >>>>>>>> deviate. As a result I'm also not sure I correctly understand the >>>>>>>> rest of your reply. >>>>>>> >>>>>>> #define a(x, y) b(x, y) >>>>>>> >>>>>>> int a; // Violation of Rule 5.5. >>>>>>> >>>>>>> The macro name `a' that exist before the preprocessing phase, >>>>>>> still exists after the preprocessing phase as identifier for the integer >>>>>>> variable and this is a violation. >>>>>>> >>>>>>>>> If you use `a' as identifier for a callable entity, >>>>>>>>> this is not a violation because after the preprocessing phase, >>>>>>>>> identifier `a' no longer exists. >>>>>>> I correct myself: >>>>>>> if you use `a' as identifier for a *function*, >>>>>>> it is not a violation because after the preprocessing phase >>>>>>> the identifier `a' no longer exists, for example: >>>>>>> >>>>>>> #define a(x, y) b(x, y) >>>>>>> >>>>>>> void a(int x, int y); // Ok. >>>>>> >>>>>> Federico, do you have a better wording suggestion for this rule? >>>>>> >>>>>> Jan, any further requests here? What would you like to see as next step? >>>>> >>>>> A more concise wording proposal would probably help. >>>> >>>> What do you think about: >>>> >>>> diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst >>>> index 1e134ccebc..a975b9a85f 100644 >>>> --- a/docs/misra/rules.rst >>>> +++ b/docs/misra/rules.rst >>>> @@ -181,6 +181,13 @@ maintainers if you want to suggest a change. >>>> headers (xen/include/public/) are allowed to retain longer >>>> identifiers for backward compatibility. >>>> >>>> + * - `Rule 5.5 >>>> <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_05_05.c>`_ >>>> + - Required >>>> + - Identifiers shall be distinct from macro names >>>> + - Macros expanding to their own name are allowed (e.g., #define x x). >>>> + Clashes between names of function-like macros and identifiers of >>>> + non-callable entities are allowed. >>> >>> Imo that still leaves open e.g. the >>> >>> #define a(x, y) a(x, y) >>> >>> case: Permitted ("own name") or not permitted ("a" pretty clearly is >>> expected >>> to be a callable entity here, besides being a function-like macro)? >> >> I would not consider your example as a macro that expands to its own >> name, the macro name is considered to be `a' only. > > That's what I was assuming, and hence my asking back. I think the > above ought to be permitted just like "#define x x", and hence the > suggested text would need expanding, to ... > >> Rather, you example can be used to trigger the "callable-noncallable" >> part of the deviation, for example: >> >> #define a(x, y) a(x, y) >> >> void a(int x, int y); /* Not permitted (callable entity 'a'). */ > > ... prevent this ("not permitted") from happening. I'm pretty sure > you've already found instances of this pattern in our code base. And btw, see https://lists.xen.org/archives/html/xen-devel/2024-03/msg00159.html for yet another slightly different pattern that I'd rather not see becoming "forbidden". Jan
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