From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Nigel Roles" <nigel@9fs.org>
To: <9fans@cse.psu.edu>
Subject: RE: [9fans] struct problems
Message-ID: <HOEHIDJJJINMLFPOLFJCKEELCPAA.nigel@9fs.org>
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In-Reply-To: <20030507053411.GZ36080@cassie.foobarbaz.net>
Date: Wed,  7 May 2003 06:36:51 +0100
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structs and unions are aligned on 4 byte boundaries.
bit fields are never portable. are you sure they will
work on any Plan 9 platform (not just x86)?

> -----Original Message-----
> From: 9fans-admin@cse.psu.edu [mailto:9fans-admin@cse.psu.edu]On Behalf
> Of Christopher Nielsen
> Sent: 07 May 2003 06:34
> To: 9fans@cse.psu.edu
> Subject: Re: [9fans] struct problems
>
>
> I forgot to add that my guess as to what is happening
> is due to alignment issues.
>
> On Tue, May 06, 2003 at 09:36:33PM -0700, Christopher Nielsen wrote:
> > I've been working on 48-bit LBA support for ATA, and
> > I've run into something peculiar. I decided to rewrite
> > the identify array as a struct of bit fields for better
> > readability. As it turns out, the struct is 16 bytes
> > bigger than expected, which is causing all sorts of
> > trouble with accessing the fields properly. I am pretty
> > sure I copied all the fields correctly; the struct
> > should be 512 bytes, but it's 528 bytes. Below is the
> > struct definition for folks to look at. I am in the
> > process of rooting out where the extra bytes are
> > coming from, but if someone can provide some insight,
> > it would save me some time.
>
> --
> Christopher Nielsen
> "They who can give up essential liberty for temporary
> safety, deserve neither liberty nor safety." --Benjamin Franklin