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Date: Sun, 01 Apr 2012 09:49:53 -0700
From: Randy Dunlap <rdunlap@xenotime.net>
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To: Zhihua Che <zhihua.che@gmail.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: How can I turn off/disable -O2/-Os optimization?
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On 04/01/2012 09:31 AM, Zhihua Che wrote:

> Hi, everyone
> 
>     I'm debugging linux kernel using kgdb/qemu， but I find that the
> execution order didn't math the program order usually.  I guess it was
> because the compiling optimization. So I decided to remove -O options
> in Makefiles.
>     First I removed -Ox in variables HOSTCFLAGS/HOSTCXXFLAGS in
> <src_root_dir>/Makefile around line 248 and -Ox in variable
> KBUILD_CFLAGS in <src_root_dir>/arch/x86/boot/Makefile around line 55.
> But it didn't work, the step execution still didn't follow the program
> order. Then I found I missed -Ox in KBUILD_CFLAGS in
> <src_root_dir>/Makefile around line 562, so I removed them, but this
> time, the compiling failed, complaining
>     rcupdate.h:917:2: error: size of unnamed array is negative
>    And finally, after grep, I find there are a load of -O2 option are
> assigned in a load of Makefiles. So, How could I disable -O
> optimization for debugging?
> 
>    Thanks for any tips
> --


You could try the new CONFIG_READABLE_ASM patch:
  http://marc.info/?l=linux-kernel&m=133296079716268&w=2


-- 
~Randy