linux-kernel - Re: Subtleties of __attribute_

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Message-ID: <20061206140138.GA16350@slug>
Date:	Wed, 6 Dec 2006 14:01:38 +0000
From:	Frederik Deweerdt <deweerdt@...e.fr>
To:	Phil Endecott <phil_arcwk_endecott@...zphil.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Subtleties of __attribute__((packed))

On Wed, Dec 06, 2006 at 01:20:41PM +0000, Phil Endecott wrote:
> Dear All,
> 
> I used to think that this:
> 
> struct foo {
>   int a  __attribute__((packed));
>   char b __attribute__((packed));
>   ... more fields, all packed ...
> };
> 
> was exactly the same as this:
> 
> struct foo {
>   int a;
>   char b;
>   ... more fields ...
> } __attribute__((packed));
> 
> but it is not, in a subtle way.
> 
This is likely a gcc bug isn't it? The gcc info page states:
  Specifying this attribute for `struct' and `union' types is
  equivalent to specifying the `packed' attribute on each of the
  structure or union members.

Regards,
Frederik
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