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

[Thomas Weißschuh]

On Mon, Jan 05, 2026 at 02:02:17PM +0100, Arnd Bergmann wrote:
> 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

Ack.

> 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.

If we can rely on compiler built-ins I would prefer this option.

> 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>

...


Thomas