linux-kernel - Re: [PATCH RFC net-next 1/3] uapi: add INT_MAX and INT

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Message-ID: <20260105154705-2301e4f2-948f-422d-bfed-81725ac82bc8@linutronix.de>
Date: Mon, 5 Jan 2026 15:48:38 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Andrew Lunn <andrew@...n.ch>
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>, 
	Pablo Neira Ayuso <pablo@...filter.org>, Jozsef Kadlecsik <kadlec@...filter.org>, 
	Florian Westphal <fw@...len.de>, Phil Sutter <phil@....cc>, Arnd Bergmann <arnd@...db.de>, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, 
	coreteam@...filter.org
Subject: Re: [PATCH RFC net-next 1/3] uapi: add INT_MAX and INT_MIN constants

On Mon, Jan 05, 2026 at 03:37:14PM +0100, Andrew Lunn wrote:
> On Mon, Jan 05, 2026 at 09:26:47AM +0100, Thomas Weißschuh wrote:
> > Some UAPI headers use INT_MAX and INT_MIN. Currently they include
> > <limits.h> for their definitions, which introduces a problematic
> > dependency on libc.
> > 
> > Add custom, namespaced definitions of INT_MAX and INT_MIN using the
> > same values as the regular kernel code.
> 
> Maybe a dumb question.
> 
> > +#define __KERNEL_INT_MAX ((int)(~0U >> 1))
> > +#define __KERNEL_INT_MIN (-__KERNEL_INT_MAX - 1)
> 
> How does this work for a 32 bit userspace on top of a 64 bit kernel?
>
> And do we need to be careful with KERNEL in the name, in that for a 32
> bit userspace, this is going to be 32bit max int, when in fact the
> kernel is using 64 bit max int?

'int' is always 32 bit on Linux.


Thomas