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From: hpa@zytor.com (H. Peter Anvin)
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.6] bootmem.c cleanup
Date: Mon, 17 May 2004 00:43:16 +0000 (UTC)	[thread overview]
Message-ID: <c891r4$5i3$1@terminus.zytor.com> (raw)
In-Reply-To: <20040514133353.236acf3a.akpm@osdl.org>

Followup to:  <20040514133353.236acf3a.akpm@osdl.org>
By author:    Andrew Morton <akpm@osdl.org>
In newsgroup: linux.dev.kernel
>
> Michael Buesch <mbuesch@freenet.de> wrote:
> >
> >  -		if (!test_and_clear_bit(i, bdata->node_bootmem_map))
> >  -			BUG();
> >  +		BUG_ON(!test_and_clear_bit(i, bdata->node_bootmem_map));
> 
> Please don't put expressions whihc actually change state inside BUG_ON(). 
> Someone may decide to make BUG_ON() a no-op to save space.
> 
> I'm not aware of anyone actually trying that, but it's a good objective.
> 

If so they should make it:

#define	BUG_ON(x)	((void)(x))

.. which preserves side effects while generating no object code for a
side-effect-free expression.

The only reason for the cast to (void) at all is to keep gcc from
complaining about an ignored expression.

	-hpa

  parent reply	other threads:[~2004-05-17  0:43 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-14 20:05 Michael Buesch
2004-05-14 20:33 ` Andrew Morton
2004-05-14 20:43   ` Michael Buesch
2004-05-17  0:43   ` H. Peter Anvin [this message]
2004-05-18 19:50   ` Matt Mackall

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