Re: [RFC PATCH 17/17] CODING_STYLE: Add a section on header guards naming conventions

[Alessandro Zucchelli <alessandro.zucchelli@bugseng.com>]

On 2024-07-19 17:21, Stefano Stabellini wrote:
> On Fri, 19 Jul 2024, Jan Beulich wrote:
>> On 19.07.2024 00:01, Stefano Stabellini wrote:
>> > On Thu, 18 Jul 2024, Jan Beulich wrote:
>> >> On 18.07.2024 01:02, Stefano Stabellini wrote:
>> >>> On Wed, 17 Jul 2024, Jan Beulich wrote:
>> >>>> On 17.07.2024 02:20, Stefano Stabellini wrote:
>> >>>>> On Tue, 16 Jul 2024, Jan Beulich wrote:
>> >>>>>> On 16.07.2024 02:43, Stefano Stabellini wrote:
>> >>>>>>> On Mon, 15 Jul 2024, Jan Beulich wrote:
>> >>>>>>>> On 13.07.2024 00:38, Stefano Stabellini wrote:
>> >>>>>>>>> On Wed, 3 Jul 2024, Jan Beulich wrote:
>> >>>>>>>>>> I further have to note that, as indicated during the earlier discussion,
>> >>>>>>>>>> I still cannot see how occasional ambiguity is going to be dealt with.
>> >>>>>>>>>> IOW from the rules above two different headers could still end up with
>> >>>>>>>>>> the same guard identifier.
>> >>>>>>>>>
>> >>>>>>>>> Maybe something like this?
>> >>>>>>>>>
>> >>>>>>>>> "In the event of naming collisions, exceptions to the coding style may
>> >>>>>>>>> be made at the discretion of the contributor and maintainers."
>> >>>>>>>>
>> >>>>>>>> Hmm, maybe I wasn't clear enough then. My take is that the scheme should
>> >>>>>>>> simply not allow for possible collisions. Neither the contributor nor the
>> >>>>>>>> reviewer may spot such a collision, and it may therefore take until the
>> >>>>>>>> first full scan that one is actually noticed. Which I consider too late
>> >>>>>>>> in the process, even if we already were at the point where commits were
>> >>>>>>>> checked pre-push.
>> >>>>>>>
>> >>>>>>> Looking at the proposal, copy/pasted here for convenience:
>> >>>>>>>
>> >>>>>>> - private headers -> <dir>_<filename>_H
>> >>>>>>> - asm-generic headers -> ASM_GENERIC_<filename>_H
>> >>>>>>>     - #ifndef ASM_GENERIC_X86_PERCPU_H
>> >>>>>>>       #define ASM_GENERIC_X86_PERCPU_H
>> >>>>>>>       //...
>> >>>>>>>       #endif /* ASM_GENERIC_X86_PERCPU_H */
>> >>>>>>> - arch/<architecture>/include/asm/<subdir>/<filename>.h -> ASM_<architecture>_<subdir>_<filename>_H
>> >>>>>>>     - #ifndef ASM_X86_DOMAIN_H
>> >>>>>>>       #define ASM_X86_DOMAIN_H
>> >>>>>>>       //...
>> >>>>>>>       #endif /* ASM_X86_DOMAIN_H */
>> >>>>>>> - xen/include/xen/<filename>.h -> XEN_<filename>_H
>> >>>>>>> - xen/include/xen/<subdir>/<filename>.h -> XEN_<subdir>_<filename>_H
>> >>>>>>>
>> >>>>>>>
>> >>>>>>> The only possibility for collision that I can see is from the first
>> >>>>>>> point:
>> >>>>>>>
>> >>>>>>> - private headers -> <dir>_<filename>_H
>> >>>>>>
>> >>>>>> I don't think this is the only possibility of collisions. The <subdir>_<filename>
>> >>>>>> parts can similarly cause problems if either of the two involved names contains
>> >>>>>> e.g. a dash (which would need converting to an underscore) or an underscore. To
>> >>>>>> avoid this, the name separators (slashes in the actual file names) there may need
>> >>>>>> representing by double underscores.
>> >>>>>
>> >>>>> I am OK with you two underscores as name separator (slashes in the
>> >>>>> actual file names). Would you do it for all levels like this?
>> >>>>>
>> >>>>> - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
>> >>>>> - arch/arm/arm32/lib/something.h -> ARM__ARM32__LIB__SOMETHING_H
>> >>>>> - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
>> >>>>>
>> >>>>>
>> >>>>> I think it is better than the below:
>> >>>>>
>> >>>>> - arch/arm/arm64/lib/something.h -> ARM_ARM64__LIB__SOMETHING_H
>> >>>>> - arch/arm/arm32/lib/something.h -> ARM_ARM32__LIB__SOMETHING_H
>> >>>>> - arch/x86/lib/something.h -> X86_LIB__SOMETHING_H
>> >>>>
>> >>>> Hmm, maybe it's indeed better to do it entirely uniformly then.
>> >>>
>> >>>
>> >>> Do we have agreement on the naming convention then?
>> >>>
>> >>>
>> >>> - private headers -> <dir>__<filename>__H
>> >>>     - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
>> >>>     - arch/arm/arm32/lib/something.h -> ARM__ARM32__LIB__SOMETHING_H
>> >>>     - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
>> >>>
>> >>> - asm-generic headers -> ASM_GENERIC_<filename>_H
>> >>>     - include/asm-generic/percpu.h -> ASM_GENERIC_X86_PERCPU_H
>> >>>
>> >>> - arch/<architecture>/include/asm/<subdir>/<filename>.h -> ASM_<architecture>_<subdir>_<filename>_H
>> >>>     - arch/x86/include/asm/domain.h -> ASM_X86_DOMAIN_H
>> >>>
>> >>> - include/xen -> XEN_<filename>_H
>> >>>     - include/xen/percpu.h -> XEN_PERCPU_H
>> >>>
>> >>>
>> >>> Or do you prefer the double underscore __  in all cases?
>> >>
>> >> It's not so much prefer, but a requirement if we want to be future proof.
>> >> Even for ASM_GENERIC_* that'll be needed, as your outline above simply
>> >> doesn't mention the (future) case of there being subdir-s there (see how
>> >> Linux already has some). Imo the question doesn't even arise for XEN_*,
>> >> as xen/ has subdir-s already.
>> >
>> > OK. So it becomes:
>> >
>> > - private headers -> <dir>__<filename>_H
>> >     - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
>> >     - arch/arm/arm32/lib/something.h -> ARM__ARM32__LIB__SOMETHING_H
>> >     - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
>> >
>> > - asm-generic headers -> ASM_GENERIC__<filename>_H
>> >     - include/asm-generic/percpu.h -> ASM_GENERIC__X86__PERCPU_H
>> 
>> Nit: There's still a stray _X86_ in here.
> 
> yes, good point.
> 
> Alessandro, let us know if we are good to go ahead or if we are missing
> anything.

I think we are good right now, I will provide the patch series v5 with 
all the
fixes and inclusion guards renamings soon.

>> > - arch/<architecture>/include/asm/<subdir>/<filename>.h -> ASM__<architecture>__<subdir>__<filename>_H
>> >     - arch/x86/include/asm/domain.h -> ASM__X86__DOMAIN_H
>> >
>> > - include/xen -> XEN__<filename>_H
>> >     - include/xen/percpu.h -> XEN__PERCPU_H
>> >
>> > If we have found agreement then Alessandro could send an update
>> 

-- 
Alessandro Zucchelli, B.Sc.

Software Engineer, BUGSENG (https://bugseng.com)