linux-kernel - Re: [PATCH 08/11] x86: use asm .macro instead of cpp #define in entry

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Message-ID: <4990D4E3.1010109@kernel.org>
Date:	Tue, 10 Feb 2009 10:14:11 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	hpa@...or.com, tglx@...utronix.de, mingo@...e.hu,
	linux-kernel@...r.kernel.org, x86@...nel.org, rusty@...tcorp.com.au
Subject: Re: [PATCH 08/11] x86: use asm .macro instead of cpp #define in entry_32.S

Jeremy Fitzhardinge wrote:
> Tejun Heo wrote:
>> Impact: cleanup
>>
>> Use .macro instead of cpp #define where approriate.  This cleans up
>> code and will ease future changes.
>>   
> 
> I agree with this in principle - cpp macros are indeed very ugly - but
> in practise I've found asm macros to be very hard to work with.  When
> things go wrong, the gas error messages are completely useless (it only
> reports the error on the line where the macro was used, without any
> detail about where in the macro the problem lies), and as far as I know,
> there's no way to see the source with macros expanded.

Hmm... I originally did the conversion because I had some .if trick in
SAVE_ALL which got removed later.  Even after the removal, it
generally looked like a good idea as x86_64 asm was primarily using
.macro too.  I do like being able to see the post-processing output of
cpp too but for assembler disassembling the output often seem to give
enough clue, so I don't think it's a deal breaker.  So, lacking
decisive technical merit either way, I was aiming for consistency with
x86_64 (and I already had the patch in queue so...).

Ingo, what do you think?

Thanks.

-- 
tejun
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