Message-ID: <472E1085.8040801@cateee.net>
Date: Sun, 04 Nov 2007 19:33:41 +0100
From: Giacomo Catenazzi <cate@cateee.net>
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To: Adrian Bunk <bunk@kernel.org>
CC: David Miller <davem@davemloft.net>, mingo@elte.hu, sam@ravnborg.org,
       thomas@archlinux.org, tglx@linutronix.de, linux-kernel@vger.kernel.org,
       linux-kbuild@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: 2.6.24-rc1-82798a1 compile failure (x86_64)
References: <20071103121149.GA22149@uranus.ravnborg.org> <20071104020217.GJ12045@stusta.de> <20071104100429.GA12311@elte.hu> <20071104.023133.241080055.davem@davemloft.net> <20071104152930.GL12045@stusta.de> <472DF121.8000509@cateee.net> <20071104163439.GM12045@stusta.de>
In-Reply-To: <20071104163439.GM12045@stusta.de>
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Adrian Bunk wrote:
> On Sun, Nov 04, 2007 at 05:19:45PM +0100, Giacomo Catenazzi wrote:
>> Adrian Bunk wrote:
>>> On Sun, Nov 04, 2007 at 02:31:33AM -0800, David Miller wrote:
>>>> From: Ingo Molnar <mingo@elte.hu>
>>>> Date: Sun, 4 Nov 2007 11:04:29 +0100
>>>>
>>>>> * Adrian Bunk <bunk@kernel.org> wrote:
>>>>>
>>>>>> I also have CFLAGS set on some computers in my environments since for 
>>>>>> packages using GNU autoconf that's the correct way to set the compiler 
>>>>>> flags.
>>>>>>
>>>>>> The kernel already sets all flags correctly, and a user wanting to 
>>>>>> change the flags for the kernel is an exception with very special needs 
>>>>>> (I'd even claim so special that he could simply edit the Makefile...).
>>>>  ...
>>>>> At minimum the extra CFLAGS needs to be put into the .config - but 
>>>>> that's not a too nice solution either. How about just adding an 
>>>>> extra-CFLAGS option to .config and perhaps a 'make configpickupCFLAGS' 
>>>>> pass for anyone who wants to propagate the environment CFLAGS into the 
>>>>> kernel build.
>>>> I totally disagree.
>>>>
>>>> People can't have it both ways.  CFLAGS has global meaning in every
>>>> Makefile based build tree, it's not an "autoconf" thing.  This is well
>>>> established practice, and I think it's a good thing the kernel does it
>>>> now too.
>>> Makefiles do normally not pick such variables from the environment.
>> ????
>>
>> Are you sure???
>>
>> From http://www.gnu.org/software/make/manual/make.html#Environment
>>
>> : Variables in make can come from the environment in which make
>> : is run. Every environment variable that make sees when it starts
>> : up is transformed into a make variable with the same name and
>> : value.
>>
>> and most important:
>>
>> : Thus, by setting the variable CFLAGS in your environment, you
>> : can cause all C compilations in most makefiles to use the
>> : compiler switches you prefer. This is safe for variables with
>> : standard or conventional meanings because you know that no
>> : makefile will use them for other things. (Note this is not
>> : totally reliable; some makefiles set CFLAGS explicitly and
>> : therefore are not affected by the value in the environment.)
> 
> 
> Thanks for the correction, I had forgotten about the case where a 
> Makefile does not set CFLAGS at all.
> 
> But the main point that stuff like e.g. -I/usr/local/dist/include that 
> might in some environments be correct for all and required for most 
> userspace software should not leak into the kernel still stands.

Yes, you are right.
Kernel uses the gcc in "freestanding" mode, so I think we should
eventually share the compiler options and environment only with
other freestanding programs (aka: none).

ciao
	cate
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