Re: [XEN PATCH v6] CODING_STYLE: Add a section on header guards naming conventions

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.09.2024 03:13, Stefano Stabellini wrote:
> Hi Jan, we have gone back and forth on this a few times, but neither
> Alessandro nor I fully understand your perspective. To help streamline
> the process and save time for everyone, I suggest you provide an example
> of the rules written in the style you believe is appropriate. Once you
> set the initial direction, Alessandro and I can continue and complete
> the rest in that preferred style.

Header inclusion guards
-----------------------

Unless otherwise specified, all header files should include proper
guards to prevent multiple inclusions. The following naming conventions
apply:

- Guard names are derived from directory path underneath xen/ and the
  actual file name.  Path components are separated by double underscores.
  Alphabetic characters are converted to upper case.  Non-alphanumeric
  characters are replaced by single underscores.
- Certain directory components are omitted, to keep identifier length
  bounded:
  - The top level include/,
  - Any architecture's arch/<arch>/include/asm/ collapses to
    ASM__<ARCH>__,
  - Architecture-specific private files' arch/.

For example:

- Xen headers: XEN__<filename>_H
  - include/xen/something.h -> XEN__SOMETHING_H

- asm-generic headers: ASM_GENERIC__<filename>_H
  - include/asm-generic/something.h -> ASM_GENERIC__SOMETHING_H

- arch-specific headers: ASM__<architecture>__<subdir>__<filename>_H
  - arch/x86/include/asm/something.h -> ASM__X86__SOMETHING_H

- Private headers: <dir>__<filename>_H
  - arch/arm/arm64/lib/something.h -> ARM__ARM64__LIB__SOMETHING_H
  - arch/x86/lib/something.h -> X86__LIB__SOMETHING_H
  - common/something.h -> COMMON__SOMETHING_H

Note that this requires some discipline on the naming of future new
sub-directories: There shouldn't be any random asm/ one anywhere, for
example.  Nor should any new ports be named the same as top-level (within
xen/) directories.  Which may in turn require some care if any new top-
level directories were to be added.  Rule of thumb: Whenever a new sub-
directory is added, check the rules for no collisions to result.

Jan