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


  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 18 Jul 2024 10:59:26 +0200
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  • Cc: Alessandro Zucchelli <alessandro.zucchelli@xxxxxxxxxxx>, consulting@xxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 18 Jul 2024 08:59:56 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

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.

Jan



 


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