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

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Message-ID: <20260109111310-4b387d2e-1459-4701-9e58-dc02ad74c499@linutronix.de>
Date: Fri, 9 Jan 2026 11:20:21 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Arnd Bergmann <arnd@...db.de>
Cc: "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Andrew Lunn <andrew@...n.ch>, 
	Pablo Neira Ayuso <pablo@...filter.org>, Jozsef Kadlecsik <kadlec@...filter.org>, 
	Florian Westphal <fw@...len.de>, Phil Sutter <phil@....cc>, linux-kernel@...r.kernel.org, 
	Netdev <netdev@...r.kernel.org>, netfilter-devel@...r.kernel.org, coreteam@...filter.org
Subject: Re: [PATCH RFC net-next 3/3] netfilter: uapi: Use UAPI definition of
 INT_MAX and INT_MIN

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@...utronix.de>
> 
> 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