Message-ID: <45433D3E.3070109@0Bits.COM>
Date: Sat, 28 Oct 2006 15:21:34 +0400
From: Mitch <Mitch@0Bits.COM>
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To: jdike@addtoit.com, linux-kernel@vger.kernel.org, blaisorblade@yahoo.it,
       penberg@cs.helsinki.fi
Subject: Re: More uml build failures on 2.16.19-rc3 and 2.6.18.1
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Hi Jeff, all,

Sorry for the dealy but i've been out of the country.

Anyhow i did some investigation and i've figured out the bug.

Essentially if you try to compile a UML kernel on a 2.6.18.1 or above 
*host* kernel it will fail with the error messages shown (essentially 
offsetof macro undefined) because between 2.6.18 and 2.6.18.1 that macro 
in /usr/include/linux/stddef.h is now wrapped in a #ifdef __KERNEL__ . 
However since UML doesn't build it's sources with that defined we get an 
undefined macro and a build failure.

So i'm partly right and partly wrong in my statement below. Yes i did 
compile a guest UML kernel 2.6.18 fine on host kernel of 2.6.18, and i 
believe i will be able to compile 2.6.18.1 and above also on a host 
kernel of 2.6.18 but if i change my host kernel to 2.6.18.1 or above all 
UML guest builds will fail.

Can someone confirm they can build guest UML kernels on a host kernel >= 
2.6.18.1 ??

Thanks
M

-------- Original Message --------
Subject: Re: More uml build failures on 2.16.19-rc3 and 2.6.18.1
Date: Wed, 25 Oct 2006 11:41:30 -0400
From: Jeff Dike <jdike@addtoit.com>
To: Mitch <Mitch@0Bits.COM>
CC: linux-kernel@vger.kernel.org
References: <453E7F07.9010804@0Bits.COM>

On Wed, Oct 25, 2006 at 01:00:55AM +0400, Mitch wrote:
> I've definetly not done any such change on my machine. Remember with the 
> same compile, same environment, if i go back to 2.6.18 i can build uml 
> fine. If i move to 2.6.18.1 or above it breaks...

You're sure about that?  I just looked through the 2.6.18.1 changelog and
I see nothing that would cause this.

> I do notice my gcc stddef does have this defined
> 
> % grep offsetof /usr/lib/gcc/i686-linux/4.0.3/include/stddef.h
> #define offsetof(TYPE, MEMBER) __builtin_offsetof (TYPE, MEMBER)

I would do a -E build and make sure that this header, or another one that
defines offsetof is getting pulled in.

				Jeff
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