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

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Date:	Tue, 05 Oct 2010 09:48:43 +0200
From:	Avi Kivity <avi@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.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 08:23 PM, H. Peter Anvin wrote:
> 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.

I see.

I suppose it isn't possible to refuse to build with the broken version?

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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