linux-kernel - Re: [PATCH] x86: fix CFI macro invocations to deal with shortcomings in gas

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Message-ID: <4CBE0A34.4060002@zytor.com>
Date:	Tue, 19 Oct 2010 14:14:28 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jan Beulich <JBeulich@...ell.com>
CC:	mingo@...e.hu, tglx@...utronix.de, akpm@...ux-foundation.org,
	heukelum@...tmail.fm, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: fix CFI macro invocations to deal with	 shortcomings
 in gas

On 10/19/2010 06:52 AM, Jan Beulich wrote:
> gas prior to (perhaps) 2.16.90 has problems with passing non-
> parenthesized expressions containing spaces to macros. Spaces, however,
> get inserted by cpp between any macro expanding to a number and a
> subsequent + or -. For the +, current x86 gas then removes the space
> again (future gas may not do so), but for the - the space gets retained
> and is then considered a separator between macro arguments.
> 
> Fix the respective definitions for both the - and + cases, so that they
> neither contain spaces nor make cpp insert any (the latter by adding
> seemingly redundant parentheses).
> 
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
> Cc: Alexander van Heukelum <heukelum@...tmail.fm>
> 

It's ugly -- very ugly -- and will almost certainly bitrot and break
again, but it's a lot less ugly than any other alternative I can think
of.  Unfortunately these versions of gas are not old enough that we can
just kill them off, I don't think.

	-hpa
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