linux-kernel - Re: [PATCH] perf: fix wrong DEBUG configuration

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Date:	Fri, 22 May 2015 15:50:27 +0200
From:	Martin Liška <mliska@...e.cz>
To:	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] perf: fix wrong DEBUG configuration

On 05/22/2015 09:02 AM, Ingo Molnar wrote:
>
> * Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>
>> Em Wed, May 20, 2015 at 06:16:51PM +0200, Martin Liška escreveu:
>>> On 05/20/2015 04:55 PM, Ingo Molnar wrote:
>>>> * Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>>>>> So the rule has been: What are the kernel requirements for the
>>>>> toolchain? tools/perf/ should build with that.
>>>>
>>>> So we could use -Og if it works, like Kbuild does it:
>>>>
>>>>          KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
>>>>
>>>> the 'cc-option' Make function does some magic of silently calling GCC
>>>> with that option and observing the result.
>>
>>>> See:
>>
>>>>    scripts/Kbuild.include:cc-option = $(call try-run,\
>>
>>> I am sorry, I did mistake in understanding of DEBUG variable.
>>> Following patch should be fixed, except missing auto-detection
>>> of -Og option.
>>>
>>> Unfortunately, following hunk does not work, no -Ox is added to CFLAGS?
>>>
>>> --  CFLAGS += -Og
>>> ++  CFLAGS += $(call cc-option,-Og,-O0)
>>
>> I don't know if we have this cc-option, perhaps Ingo is suggesting
>> we get it in tools/build/? Or include scripts/Kbuild.include and
>> then use it?
>>
>> I.e. we have checks to see if we can use, for instance
>> -fstack-protector-all, see tools/build/feature/Makefile, using this
>> cc-option thing, importing it from Kbuild would solve the issue at
>> hand in a definitive way and in line with what we have been
>> pursuing: to make the tools/ build system be based on Kbuild.
>
> So I'd suggest copying any necessary functions instead of outright
> including all of Kbuild in the tooling build system which creates
> non-trivial dependencies that is not necessarily tested as thoroughly
> on the kbuild side as on the tooling side.
>
> Thanks,
>
> 	Ingo
>

May I ask you Ingo for helping with that? It would be easy to test if you
grab my patch and add necessary bash functions.

Thank you,
Martin
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