linux-kernel - Re: Subtleties of __attribute_

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Message-ID: <1165421636345@dmwebmail.belize.chezphil.org>
Date:	Wed, 06 Dec 2006 16:13:56 +0000
From:	"Phil Endecott" <phil_arcwk_endecott@...zphil.org>
To:	"Jan Blunck" <jblunck@...e.de>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: Subtleties of __attribute__((packed))

Jan Blunk wrote:
> Maybe the arm backend is somehow broken. AFAIK (and I verfied it on S390 and
> i386) the alignment shouldn't change.

To see a difference with your example structs you need to compare these two:

struct wibble1 {
   char c;
   struct bar1 b1;
};

struct wibble2 {
   char c;
   struct bar2 b2;
};

struct wibble1 w1 = { 1, { 2, {3,4,5} } };
struct wibble2 w2 = { 1, { 2, {3,4,5} } };

Can you try that with your compilers?  I get:

w1:
	.byte	1
	.space	3    <<<----
	.byte	2
	.4byte	3
	.byte	4
	.space	3
	.4byte	5
	.space	3
	.global	w2
	.align	2
	.type	w2, %object
	.size	w2, 16
w2:
	.byte	1
	.byte	2
	.4byte	3
	.byte	4
	.space	3
	.4byte	5
	.space	2


Phil.




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