Re: [PATCH 4/5] CodingGuidelines: mention C99 features we can't use

> The C99 section of the CodingGuidelines is a good overview of what we
> can use, but is sorely lacking in what we can't use. Something that
> comes up occasionally is the portability of %z.
>
> Per [1] we couldn't use it for the longest time due to MSVC not
> supporting it, but nowadays by requiring C99 we rely on the MSVC
> version that does, but we can't use it yet because a C library that
> MinGW uses doesn't support it.
>
> 1. https://lore.kernel.org/git/a67e0fd8-4a14-16c9-9b57-3430440ef93c@gmail.com/
>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>  Documentation/CodingGuidelines | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
> index f9affc4050a..893f960231f 100644
> --- a/Documentation/CodingGuidelines
> +++ b/Documentation/CodingGuidelines
> @@ -235,6 +235,13 @@ For C programs:
>     . since late 2021 with 44ba10d6, we have had variables declared in
>       the for loop "for (int i = 0; i < 10; i++)".
>  
> +   New C99 features that we cannot use yet:
> +
> +   . %z and %zu as a printf() argument for a size_t (the %z being for
> +     the POSIX-specific ssize_t). Instead you should use
> +     printf("%"PRIuMAX, (uintmax_t)v); These days the MSVC version we
> +     rely on supports %z, but the C library used by MinGW does not.
> +