linux-kernel - Re: gas 2.16 and assembly macros -- entry

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Message-ID: <4CAA1BA3.1010306@zytor.com>
Date:	Mon, 04 Oct 2010 11:23:31 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Jan Beulich <JBeulich@...ell.com>, Ingo Molnar <mingo@...e.hu>,
	heukelum@...tmail.fm, tglx@...utronix.de,
	akpm@...ux-foundation.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: gas 2.16 and assembly macros -- entry_64.S build failure

On 10/04/2010 09:20 AM, Avi Kivity wrote:
>   On 10/04/2010 05:43 PM, H. Peter Anvin wrote:
>> On 10/04/2010 03:04 AM, Avi Kivity wrote:
>>>   On 10/01/2010 02:26 AM, H. Peter Anvin wrote:
>>>>  ... but that doesn't work with the macros like movq_cfi.  On those, we
>>>>  could argue that at least people won't put $ on them, but cpp will still
>>>>  split them apart with spaces; this apparently causes problems at least
>>>>  as soon as there is an expression more complicated than addition
>>>>  involved (apparently plus signs are okay, but minus signs aren't!)
>>>
>>>  Likely due to the fact that a minus sign can later join with a number
>>>  and become a new token, but a plug sign cannot.
>>>
>>
>> ... except the same thing applies to other operators, other than the
>> plus sign.  This kind of characterization is insanely frustrating, and
>> really doesn't seem to follow logical rules ... we had a previous one
>> where changing a macro name from upper case to lower case made gas 2.16
>> work...
>> 	
> 
> Well, / and * do join.  % doesn't.  In a way, + does.
> 
> cpp is not a pure text processing language.  It's specifically geared to 
> C, and is fairly creaky when applying it to something other than C (and 
> is only somewhat creaky when applying it to C).
> 

The problem isn't with cpp, though, it's with gas.  There are bugs in
the gas 2.16 macro features that don't apply to any other gas version,
before *or* after.

	-hpa
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