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From: Robert Watson <rwatson@FreeBSD.org>
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To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no>
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Cc: hackers@freebsd.org, Pascal Hofstee <caelian@gmail.com>
Subject: Re: a question regarding <sys/shm.h>
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On Wed, 31 Jan 2007, Dag-Erling Sm=F8rgrav wrote:

> Pascal Hofstee <caelian@gmail.com> writes:
>> Any additional sugestions/objections are always greatly appreciated.
>
> On 32-bit platforms (i386, powerpc), int is a 32-bit signed integer while=
=20
> size_t is a 32-bit unsigned integer.
>
> On 64-bit platforms (amd64, sparc64 etc), int is a 32-bit signed integer=
=20
> while size_t is a 64-bit unsigned integer.
>
> In both cases, changing this structure member from int to size_t will bre=
ak=20
> the ABI.
>
> This doesn't mean you shouldn't do it, just that it should be done with=
=20
> care.

If we do decide to go ahead with the ABI change, there are a number of othe=
r=20
things that should be done simultaneously, such as changing the uid and gid=
=20
fields to uid_t and gid_t.  I would very much like to see the ABI change=20
happen, and the first step (breaking out kernel from user structures) has b=
een=20
done already as part of the MAC work.  The next step is to add routines tha=
t=20
translate internal/external formats, which isn't hard, but requires a moder=
ate=20
pile of code to do (as well as great care :-).

Robert N M Watson
Computer Laboratory
University of Cambridge
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