linux-kernel - Re: [PATCH v3 2/2] bsearch: prevent overflow when computing middle comparison element

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Date:	Wed, 11 Nov 2009 10:48:46 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	André Goddard Rosa <andre.goddard@...il.com>
Cc:	tabbott@...lice.com, alan-jenkins@...fmail.co.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] bsearch: prevent overflow when computing middle comparison element

On Tue, 10 Nov 2009 02:12:31 am André Goddard Rosa wrote:
> It's really difficult to occur in practice because the sum of the lower
> and higher limits must overflow an int variable, but it can occur when
> working with large arrays. We'd better safe than sorry by avoiding this
> overflow situation when computing the middle element for comparison.

I always thought the obvious answer was:

	mid = start + (end - start)/2;

Your version does nothing for 32 bit platforms...
Rusty.
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