linux-kernel - Re: 2.6.24-rc1-82798a1 compile failure (x86

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Date:	Sun, 04 Nov 2007 19:33:41 +0100
From:	Giacomo Catenazzi <cate@...eee.net>
To:	Adrian Bunk <bunk@...nel.org>
CC:	David Miller <davem@...emloft.net>, mingo@...e.hu,
	sam@...nborg.org, thomas@...hlinux.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: 2.6.24-rc1-82798a1 compile failure (x86_64)

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@...e.hu>
>>>> Date: Sun, 4 Nov 2007 11:04:29 +0100
>>>>
>>>>> * Adrian Bunk <bunk@...nel.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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