From: Alexandre <thekyz@gmail.com>
To: "Paul D. DeRocco" <pderocco@ix.netcom.com>
Cc: ecos-discuss@ecos.sourceware.org
Subject: Re: [ECOS] Re: pragma pack
Date: Thu, 10 Jan 2008 09:43:00 -0000 [thread overview]
Message-ID: <d5aafeec0801100142o4c4c25e9r97c5dd5f6a78d332@mail.gmail.com> (raw)
In-Reply-To: <015801c85322$bf2055e0$887ba8c0@PAULD>
Actually i had some problems accessing my packed structures without
flows, I think that may help resolve things a bit.
Eg with things like that:
cyg_uint8 i = 0;
struct s_pelco_pattern_array a;
a.command2_byte = i++;
a.data3 = i++;
a.data4 = i++;
a.timestamp = i;
I finish having a structure which looks like this in memory:
cm2: 0x00
data3: 0x01
data4: 0x02
ts: 0x0300
Which is really not what i want to have eventually.
On Jan 10, 2008 1:50 AM, Paul D. DeRocco <pderocco@ix.netcom.com> wrote:
> > From: Grant Edwards
> >
> > The trap snaps shut when you take the address of a field in a
> > packed struct and pass that to somebody who's expecting a
> > pointer to a normally aligned value.
>
> True. I could imagine ways in which the type system could be designed to
> prevent that, using a pointer modifier like "int __packed*", but it's not.
>
> Anyway, for normal accesses, it works fine, so you can do things like
> operate on the fields in a DOS boot sector without problems. That's the only
> situation I've ever needed the feature.
>
> --
>
> Ciao, Paul D. DeRocco
> Paul mailto:pderocco@ix.netcom.com
>
>
> --
>
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>
>
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
next prev parent reply other threads:[~2008-01-10 9:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-09 14:19 [ECOS] " Alexandre
2008-01-09 14:40 ` Andrew Lunn
2008-01-09 14:51 ` Bernard Fouché
2008-01-09 14:56 ` Alexandre
2008-01-09 21:55 ` Bronislav Gabrhelik
2008-01-09 22:22 ` Paul D. DeRocco
2008-01-09 23:50 ` [ECOS] " Grant Edwards
2008-01-10 0:50 ` Paul D. DeRocco
2008-01-10 9:43 ` Alexandre [this message]
2008-01-10 10:07 ` EXTERNAL Gladis Olaf (Praktikant; CR/AEM)
2008-01-10 10:29 ` Alexandre
2008-01-09 15:02 ` [ECOS] " EXTERNAL Gladis Olaf (Praktikant; CR/AEM)
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