From: Al Viro <viro@ftp.linux.org.uk>
To: Ben Collins <ben.collins@ubuntu.com>
Cc: Linus Torvalds <torvalds@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.20-rc1] ib_verbs: Use explicit if-else statements to avoid errors with do-while macros
Date: Thu, 14 Dec 2006 06:56:24 +0000 [thread overview]
Message-ID: <20061214065624.GN4587@ftp.linux.org.uk> (raw)
In-Reply-To: <20061214064430.GM4587@ftp.linux.org.uk>
On Thu, Dec 14, 2006 at 06:44:30AM +0000, Al Viro wrote:
> On Wed, Dec 13, 2006 at 10:10:05PM -0500, Ben Collins wrote:
> > At least on PPC, the "op ? op : dma" construct causes a compile failure
> > because the dma_* is a do{}while(0) macro.
> >
> > This turns all of them into proper if/else to avoid this problem.
>
> NAK.
>
> Proper fix is to kill stupid do { } while (0) mess. It's supposed
> to behave like a function returning void, so it should be ((void)0).
BTW, even though the original patch is already merged, I think that
we ought to get rid of do-while in such stubs, exactly to avoid such
problems in the future. Probably even add to CodingStyle - it's not
the first time such crap happens.
IOW, do ; while(0) / do { } while (0) is not a proper way to do a macro
that imitates a function returning void.
Objections?
next prev parent reply other threads:[~2006-12-14 6:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-14 3:10 [PATCH 2.6.20-rc1] ib_verbs: Use explicit if-else statements to avoid errors with do-while macros Ben Collins
2006-12-14 6:16 ` Roland Dreier
2006-12-14 6:44 ` Al Viro
2006-12-14 6:56 ` Al Viro [this message]
2006-12-14 7:45 ` Roland Dreier
2006-12-14 14:24 ` Ben Collins
2006-12-14 9:08 ` Andrew Morton
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