linux-kernel - Re: [PATCH][RESEND] do not redefine userspace's NULL #define

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Message-ID: <20120416094355.53309edb@de.ibm.com>
Date:	Mon, 16 Apr 2012 09:43:55 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Lubos Lunak <l.lunak@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RESEND] do not redefine userspace's NULL #define

On Fri, 13 Apr 2012 21:02:14 +0000
Arnd Bergmann <arnd@...db.de> wrote:

> On Friday 13 April 2012, Linus Torvalds wrote:
> > There's no way user should ever include the linux internal stddef.h.
> > 
> > And quite frankly, kernel-external definitions of NULL have
> > traditionally been pure sh*t (ie plain "0" without the cast to a
> > pointer), so I'm not entirely convinced about this patch.
> > 
> > So what is the actual thing this helps with?
> 
> I think it used to get included implictly though other exported
> kernel headers, but I found only one instance where this is still
> true, in the s390 version of asm/ptrace.h.
> 
> Martin, does this work for you?
> 
> 8<-----
> headers: do not export linux/stddef.h
> 
> There is no reason to export linux/stddef.h and users should never
> include it because the header conflicts with the standard stddef.h.
> 
> The only other exported header file that actually includes linux/stddef.h
> is the s390 asm/ptrace.h, but there is no reason for it to do so, so
> we can remove both the export and the inclusion.
> When the file is no longer exported, we can also remove the extra lines
> that attempt to make it safe for inclusion
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Kernel compiles and boots. After protecting the stddef.h #include in
include/linux/posix_types.h with #ifdef __KERNEL__ gdb and strace
could be build as well.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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