On Fri, 20 Oct 2023, Jan Beulich wrote: > On 19.10.2023 18:19, Stefano Stabellini wrote: > > On Thu, 19 Oct 2023, Jan Beulich wrote: > >> On 19.10.2023 02:44, Stefano Stabellini wrote: > >>> On Wed, 18 Oct 2023, Jan Beulich wrote: > >>>> On 18.10.2023 02:48, Stefano Stabellini wrote: > >>>>> On Mon, 16 Oct 2023, Jan Beulich wrote: > >>>>>> On 29.09.2023 00:24, Stefano Stabellini wrote: > >>>>>>> If it is not a MISRA requirement, then I think we should go for the > >>>>>>> path > >>>>>>> of least resistance and try to make the smallest amount of changes > >>>>>>> overall, which seems to be: > >>>>>> > >>>>>> ... "least resistance" won't gain us much, as hardly any guards don't > >>>>>> start with an underscore. > >>>>>> > >>>>>>> - for xen/include/blah.h, __BLAH_H__ > >>>>>>> - for xen/arch/arm/asm/include/blah.h, __ASM_ARM_BLAH_H__ > >>>>>>> - for xen/arch/x86/asm/include/blah.h, it is far less consistent, > >>>>>>> maybe __ASM_X86_BLAH_H__ ? > >>>>>> > >>>>>> There are no headers in xen/include/. For (e.g.) xen/include/xen/ we > >>>>>> may go with XEN_BLAH_H; whether ASM prefixes are needed I'm not sure; > >>>>>> we could go with just ARM_BLAH_H and X86_BLAH_H? > >>>>>> > >>>>>> The primary question though is (imo) how to deal with private headers, > >>>>>> such that the risk of name collisions is as small as possible. > >>>>> > >>>>> Looking at concrete examples under xen/include/xen: > >>>>> xen/include/xen/mm.h __XEN_MM_H__ > >>>>> xen/include/xen/dm.h __XEN_DM_H__ > >>>>> xen/include/xen/hypfs.h __XEN_HYPFS_H__ > >>>>> > >>>>> So I think we should do for consistency: > >>>>> xen/include/xen/blah.h __XEN_BLAH_H__ > >>>>> > >>>>> Even if we know the leading underscore are undesirable, in this case I > >>>>> would prefer consistency. > >>>> > >>>> I'm kind of okay with that. FTAOD - here and below you mean to make this > >>>> one explicit first exception from the "no new leading underscores" goal, > >>>> for newly added headers? > >>> > >>> Yes. The reason is for consistency with the existing header files. > >>> > >>> > >>>>> On the other hand looking at ARM examples: > >>>>> xen/arch/arm/include/asm/traps.h __ASM_ARM_TRAPS__ > >>>>> xen/arch/arm/include/asm/time.h __ARM_TIME_H__ > >>>>> xen/arch/arm/include/asm/sysregs.h __ASM_ARM_SYSREGS_H > >>>>> xen/arch/arm/include/asm/io.h _ASM_IO_H > >>>>> > >>>>> And also looking at x86 examples: > >>>>> xen/arch/x86/include/asm/paging.h _XEN_PAGING_H > >>>>> xen/arch/x86/include/asm/p2m.h _XEN_ASM_X86_P2M_H > >>>>> xen/arch/x86/include/asm/io.h _ASM_IO_H > >>>>> > >>>>> Thet are very inconsistent. > >>>>> > >>>>> > >>>>> So for ARM and X86 headers I think we are free to pick anything we want, > >>>>> including your suggested ARM_BLAH_H and X86_BLAH_H. Those are fine by > >>>>> me. > >>>> > >>>> To be honest, I'd prefer a global underlying pattern, i.e. if common > >>>> headers are "fine" to use leading underscores for guards, arch header > >>>> should, too. > >>> > >>> I am OK with that too. We could go with: > >>> __ASM_ARM_BLAH_H__ > >>> __ASM_X86_BLAH_H__ > >>> > >>> I used "ASM" to make it easier to differentiate with the private headers > >>> below. Also the version without "ASM" would work but it would only > >>> differ with the private headers in terms of leading underscores. I > >>> thought that also having "ASM" would help readability and help avoid > >>> confusion. > >>> > >>> > >>>>> For private headers such as: > >>>>> xen/arch/arm/vuart.h __ARCH_ARM_VUART_H__ > >>>>> xen/arch/arm/decode.h __ARCH_ARM_DECODE_H_ > >>>>> xen/arch/x86/mm/p2m.h __ARCH_MM_P2M_H__ > >>>>> xen/arch/x86/hvm/viridian/private.h X86_HVM_VIRIDIAN_PRIVATE_H > >>>>> > >>>>> More similar but still inconsistent. I would go with ARCH_ARM_BLAH_H and > >>>>> ARCH_X86_BLAH_H for new headers. > >>>> > >>>> I'm afraid I don't like this, as deeper paths would lead to unwieldy > >>>> guard names. If we continue to use double-underscore prefixed names > >>>> in common and arch headers, why don't we demand no leading underscores > >>>> and no path-derived prefixes in private headers? That'll avoid any > >>>> collisions between the two groups. > >>> > >>> OK, so for private headers: > >>> > >>> ARM_BLAH_H > >>> X86_BLAH_H > >>> > >>> What that work for you? > >> > >> What are the ARM_ and X86_ prefixes supposed to indicate here? Or to ask > >> differently, how would you see e.g. common/decompress.h's guard named? > > > > I meant that: > > > > xen/arch/arm/blah.h would use ARM_BLAH_H > > xen/arch/x86/blah.h would use X86_BLAH_H > > > > You have a good question on something like xen/common/decompress.h and > > xen/common/event_channel.h. What do you think about: > > > > COMMON_BLAH_H, so specifically COMMON_DECOMPRESS_H > > > > otherwise: > > > > XEN_BLAH_H, so specifically XEN_DECOMPRESS_H > > > > I prefer COMMON_BLAH_H but I think both versions are OK. > > IOW you disagree with my earlier "... and no path-derived prefixes", > and you prefer e.g. DRIVERS_PASSTHROUGH_VTD_DMAR_H as a consequence? > FTAOD my earlier suggestion was simply based on the observation that > the deeper the location of a header in the tree, the more unwieldy > its guard name would end up being if path prefixes were to be used.
I don't have a strong opinion on "path-derived prefixes". I prefer consistency and easy-to-figure-out guidelines over shortness. The advantage of a path-derived prefix is that it is trivial to figure out at first glance. If we can come up with another system that is also easy then fine. Do you have a suggestion? If so, sorry I missed it.
