linux-kernel - Re: [PATCH v2] ext3, ext4: do_split() fix loop, with obvious unsigned wrap

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Message-ID: <4935C219.3070006@tmr.com>
Date:	Tue, 02 Dec 2008 18:17:45 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Theodore Tso <tytso@....edu>, Bill Davidsen <davidsen@....com>,
	roel kluin <roel.kluin@...il.com>, adilger@....com,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ext3, ext4: do_split() fix loop, with obvious	unsigned
 wrap

Theodore Tso wrote:
> On Tue, Dec 02, 2008 at 12:08:38PM -0500, Bill Davidsen wrote:
>   
>> Sorry, you are reading it wrong, the i values inside the loop are  
>> identical to those in the original. The value of i starts at count, and  
>> the test comes *before* the value is used inside the loop. The values of  
>> i inside the loop start at count-1 and go to zero, just as it did in the  
>> original. That's why the "i--" is there, the test is on the  
>> unincremented value range count to one, but the value inside the loop is  
>> correct (or at least is the same as the original patch).
>>     
>
> You're right; my bad.  But with something like this:
>
>   
>>>> +	for (i = count; i--; ) {
>>>>         
>
> ...where there is no third part of the for loop, and a decrement in
> the second part of the loop, just for clarity's sake, it's much better
> to write it as a while loop.
>   

I seriously disagree on that, writing it as a for makes it totally clear 
that the index initialization is part of the loop.
I know, looks funny, not the way we have always done it, not invented 
here...

-- 
Bill Davidsen <davidsen@....com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 


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