From: torvalds@transmeta.com (Linus Torvalds)
To: linux-kernel@vger.kernel.org
Subject: Re: PATCH: type safe(r) list_entry repacement: generic_out_cast
Date: Wed, 24 Jul 2002 01:04:53 +0000 (UTC) [thread overview]
Message-ID: <ahkufl$25v$1@penguin.transmeta.com> (raw)
In-Reply-To: 200207240051.CAA16434@harpo.it.uu.se
In article <200207240051.CAA16434@harpo.it.uu.se>,
Mikael Pettersson <mikpe@csd.uu.se> wrote:
>On Tue, 23 Jul 2002 18:58:52 -0400, Kevin O'Connor wrote:
>>#define BackPtr(ptr, type, member) ({ \
>> typeof( ((type *)0)->member ) *__mptr = (ptr); \
>> ((type *)( (char *)__mptr - (unsigned long)(&((type *)0)->member) ));})
>
>I've seen this sort of code several times now in the Linux kernel,
>and I've never liked it. Is there some reason why you guys avoid
>offsetof() like the plague?
Trivial answer: offsetof() does not exist when you don't have system
header files.
So it's not that it's getting avoided, it _has_ to be re-implemented
anyway. And once you do that, you might as well do it right (ie what
the kernel wants is not offsetof, but a new pointer.
Linus
next prev parent reply other threads:[~2002-07-24 1:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-24 0:51 PATCH: type safe(r) list_entry repacement: generic_out_cast Mikael Pettersson
2002-07-24 1:04 ` Linus Torvalds [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-07-23 11:28 Neil Brown
2002-07-23 11:47 ` Jakob Oestergaard
2002-07-23 12:42 ` Brian Gerst
2002-07-23 16:29 ` Linus Torvalds
2002-07-24 5:25 ` Thunder from the hill
2002-07-23 16:36 ` Christoph Hellwig
2002-07-23 22:58 ` Kevin O'Connor
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