Re: Xen Coding style and clang-format

[Jan Beulich <jbeulich@suse.com>]

On 30.09.2020 11:18, Anastasiia Lukianenko wrote:
> I would like to know your opinion on the following coding style cases.
> Which option do you think is correct?
> 1) Function prototype when the string length is longer than the allowed
> one
> -static int __init
> -acpi_parse_gic_cpu_interface(struct acpi_subtable_header *header,
> -                             const unsigned long end)
> +static int __init acpi_parse_gic_cpu_interface(
> +    struct acpi_subtable_header *header, const unsigned long end)

Both variants are deemed valid style, I think (same also goes for
function calls with this same problem). In fact you mix two
different style aspects together (placement of parameter
declarations and placement of return type etc) - for each
individually both forms are deemed acceptable, I think.

> 2) Wrapping an operator to a new line when the length of the line is
> longer than the allowed one
> -    if ( table->revision > 6
> -         || (table->revision == 6 && fadt->minor_revision >= 0) )
> +    if ( table->revision > 6 ||
> +         (table->revision == 6 && fadt->minor_revision >= 0) )

Only the latter variant is correct.

> 3) define code style
> -#define ALLREGS \
> -    C(r0,r0_usr);   C(r1,r1_usr);   C(r2,r2_usr);   C(r3,r3_usr);   \
> -    C(cpsr,cpsr)
> +#define ALLREGS            \
> +    C(r0, r0_usr);         \
> +    C(r1, r1_usr);         \
> +    C(r2, r2_usr);         \

You're again mixing multiple style aspects together: There definitely
should be a blank after the comma, but I don't think we require
every item to be on its own line. But this latter aspect is a little
bogus here anyway - generally, macros better wouldn't contain
embedded semicolons, unless e.g. in a compound statement.

I also don't think we require backslashes (not) to be aligned; this
has typically been left to the author's taste so far, I guess.

> 4) Comment style
> -    /* PC should be always a multiple of 4, as Xen is using ARM
> instruction set */
> +    /* PC should be always a multiple of 4, as Xen is using ARM
> instruction set
> +     */

For a single line comment, only the former variant is correct.
In a multi-line comment neither would be. But comment style is
described well in ./CODING_STYLE, I think, so I'm not sure why
the question arose in the first place.

Jan