Re: [PATCH RFC net-next 3/3] netfilter: uapi: Use UAPI definition of INT_MAX and INT_MIN

[Arnd Bergmann]

On Mon, Jan 5, 2026, at 09:26, Thomas Weißschuh wrote:
> Using <limits.h> to gain access to INT_MAX and INT_MIN introduces a
> dependency on a libc, which UAPI headers should not do.
>
> Use the equivalent UAPI constants.
>
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>

I agree with the idea of the patch series, but I think this
introduces a different problem:

>  #include <linux/in.h>
> +#include <linux/limits.h>

linux/limits.h is not always clean against limits.h. In glibc,
you can include both in any order, but in musl, you cannot:

gcc -xc /dev/null -nostdinc -I /usr/include/aarch64-linux-musl -include limits.h -include linux/limits.h  -o - -Wall  -c 
In file included from <command-line>:
/usr/include/aarch64-linux-musl/linux/limits.h:7: warning: "NGROUPS_MAX" redefined
    7 | #define NGROUPS_MAX    65536    /* supplemental group IDs are available */
      | 
In file included from <command-line>:
/usr/include/aarch64-linux-musl/limits.h:48: note: this is the location of the previous definition
   48 | #define NGROUPS_MAX 32

I can think of two alternative approaches here:

- put the __KERNEL_INT_MIN into a different header -- either a new one
  or maybe uapi/linux/types.h
- use the compiler's built-in __INT_MIN__ instead of INT_MIN in
  UAPI headers.

On the other hand, there are a few other uapi headers
that already include linux/limits.h:

include/uapi/linux/auto_fs.h:#include <linux/limits.h>
include/uapi/linux/fs.h:#include <linux/limits.h>
include/uapi/linux/netfilter/xt_bpf.h:#include <linux/limits.h>
include/uapi/linux/netfilter/xt_cgroup.h:#include <linux/limits.h>
include/uapi/linux/netfilter/xt_hashlimit.h:#include <linux/limits.h>

     Arnd