linux-kernel - Re: [RFC] Documentation about unaligned memory access

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Message-ID: <20071124182822.GB17654@bit.office.eurotux.com>
Date:	Sat, 24 Nov 2007 18:28:22 +0000
From:	Luciano Rocha <strange@....no-ip.org>
To:	Pierre Ossman <drzeus-list@...eus.cx>
Cc:	Daniel Drake <dsd@...too.org>, linux-kernel@...r.kernel.org,
	davem@...emloft.net, kune@...ne-taler.de, johannes@...solutions.net
Subject: Re: [RFC] Documentation about unaligned memory access

On Sat, Nov 24, 2007 at 06:35:25PM +0100, Pierre Ossman wrote:
> On Sat, 24 Nov 2007 17:22:36 +0000
> Luciano Rocha <strange@....no-ip.org> wrote:
> 
> > On Sat, Nov 24, 2007 at 05:19:31PM +0100, Pierre Ossman wrote:
> > > It most certainly does not. gcc will assume that an int* has int alignment. memcpy() is a builtin, which gcc can translate to pretty much anything. And C specifies that a pointer to foo, will point to a real object of type foo, so gcc can't be blamed for the unsafe typecasts. I have tested this the hard way, so this is not just speculation.
> > 
> > Yes, on *int and other assumed aligned pointers, gcc uses its internal
> > version.
> > 
> > However, my point is that those pointers, unless speaking of packed
> > structures, can safely be assumed aligned, while char*/void* can't.
> > 
> 
> I get the sensation we're violently in agreement here, just misunderstanding each other. :)

That's it. :)

Sorry for the noise,...

-- 
lfr
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