linux-kernel - Re: __packed vs. __attribute_

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Date:	Thu, 23 Jun 2011 09:42:09 -0400
From:	Nick Bowler <nbowler@...iptictech.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mike Frysinger <vapier@...too.org>,
	Sam Ravnborg <sam@...nborg.org>,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Subject: Re: __packed vs. __attribute__((packed)) in kernel headers

On 2011-06-22 08:34 +0200, Markus Trippelsdorf wrote:
> One possible solution would be to let the "scripts/headers_install.pl"
> script automatically substitute __packed with __attribute__((packed)):
> 
> diff --git a/scripts/headers_install.pl b/scripts/headers_install.pl
> index efb3be1..e0dc065 100644
> --- a/scripts/headers_install.pl
> +++ b/scripts/headers_install.pl
> @@ -35,6 +35,7 @@ foreach my $file (@files) {
>  		$line =~ s/([\s(])__iomem\s/$1/g;
>  		$line =~ s/\s__attribute_const__\s/ /g;
>  		$line =~ s/\s__attribute_const__$//g;
> +		$line =~ s/\s__packed/__attribute__((packed))/g;
>  		$line =~ s/^#include <linux\/compiler.h>//;
>  		$line =~ s/(^|\s)(inline)\b/$1__$2__/g;
>  		$line =~ s/(^|\s)(asm)\b(\s|[(]|$)/$1__$2__$3/g;
> 
> Any thoughts?

Without any comment on the approach itself, the above change will eat a
space character before __packed, which may break the header by merging a
preceding token into the __attribute__.  It may also change instances of
__packed that occur as a prefix of a longer token.

Note that the __attribute_const__ lines above it take some care to avoid
both of these situations.

Cheers,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
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