linux-kernel - Re: Building Kernel with -O0

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Message-ID: <48C07203.1090706@shaw.ca>
Date:	Thu, 04 Sep 2008 17:40:51 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	"Keith A. Prickett" <keithp@...vell.com>
CC:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: Building Kernel with -O0

Keith A. Prickett wrote:
> I was looking at some changes to the 2.6.26.y kernel in "compiler-gcc.h"
> and had some questions.
> ( http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.26.y.git;a=commitdiff;h=ae3a0064e6d69068b1c9fd075095da062430bda9 )
> 
> I was attempting to cross-compile Linux for a Marvell core with
> Optimizations turned off and ran across an error due to the
> __attribute__((always_inline)) attribute.
> 
> It looks like the default behavior used to always have this feature on,
> but Ingo committed some changes that allows this behavior to be turned
> off (With the correct Kconfig file changes).
> 
> I'm VERY new to Linux but was wondering if there was a way (config
> option) to turn this inline attribute off in previous versions of the
> kernel besides these new macros.  It seems building with optimization
> level 0 should be a natural thing for kernel driver developers to do for
> debugging purposes.
> 
> In summary: I want to compile with optimizations off and the compile is
> failing now when I try this.  How can this be resolved?

I don't think this has ever been supported. Even in current kernels 
where the compiler is not always forced to inline all functions, I 
believe there are some functions that need to be inlined and still use 
forced inlining, and if no optimizations are enabled, no inlining can be 
done.
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