linux-kernel - Re: [2.6 patch] re-add -ffreestanding

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Date:	Wed, 30 Aug 2006 19:39:05 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Andi Kleen <ak@...e.de>
Cc:	Adrian Bunk <bunk@...sta.de>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org, Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: [2.6 patch] re-add -ffreestanding

On Wed, Aug 30, 2006 at 08:13:58PM +0200, Andi Kleen wrote:
> On Wednesday 30 August 2006 19:57, Adrian Bunk wrote:
> > I got the following compile error with gcc 4.1.1 when trying to compile 
> > kernel 2.6.18-rc4-mm2 for m68k:
> 
> If anything then -ffreestanding needs to be added to arch/m68k/Makefile
> (assuming it doesn't compile at all right now)

Looking at the effect of -ffreestanding on ARM, it appears that on one
hand, the overall image size is reduced by 0.016% but we end up with worse
code - eg, strlen() of the same string in the same function evaluated
multiple times vs once without -ffreestanding.

The difference probably comes down to the lack of __attribute__((pure))
on our string functions in linux/string.h.

If we are going to go for -ffreestanding, we need to fix linux/string.h
in that respect _first_.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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