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From: Arnd Bergmann <arnd@arndb.de>
To: Lubos Lunak <l.lunak@suse.cz>
Subject: Re: [PATCH][RESEND] do not redefine userspace's NULL #define
Date: Sat, 14 Apr 2012 08:28:48 +0000
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
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On Friday 13 April 2012, Lubos Lunak wrote:
>  If that were the case, one of the earlier versions of the patch would have 
> been correct then, but as Arnd has pointed out, user applications do include 
> the header. It's even as simple as:
> 
> #include <signal.h>
> 
> ( -> bits/sigcontext.h -> asm/sigcontext.h -> linux/types.h -> 
> linux/posix_types.h -> linux/stddef.h ).
> 

I knew there must have been something wrong with my thinking and I
clearly missed the posix_types.h reference. I accidentally did
'git grep linux/stddef.h obj/usr/include', instead of 'grep -r'.

I've tried to be more thorough this time, and I think that nothing
stops us from removing the linux/stddef.h include from the exported
version of posix_types.h, but we should probably make sure that we
still include linux/compiler.h, because a lot of stuff that includes
linux/posix_types.h expects that. Alternatively, we can just move the
NULL definition inside of #ifdef __KERNEL__.

	Arnd