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Re: [PATCH] Fix v9/64-bit strcmp when string ends in multiple zero bytes.

On 05/01/2014 12:54 PM, Richard Earnshaw wrote:
> On 01/05/14 17:27, Carlos O'Donell wrote:
>> On 05/01/2014 12:05 PM, David Miller wrote:
>>> From: "Carlos O'Donell" <>
>>> Date: Thu, 01 May 2014 01:34:01 -0400
>>>> On 04/30/2014 04:00 PM, David Miller wrote:
>>>>> +    {
>>>>> +      int exp_result;
>>>>> +
>>>>> +      for (CHAR val = 0x01; val < 0x10; val++)
>>>> Permute over all char values e.g. [0x1,0xff] or val < 0x100;
>>> I tried that already, just making this change alone causes the test to
>>> take minutes rather then just a few seconds.
>>> I'll see if I can mitigate the cost and still add the extra coverage.
>> Perhaps not all values, but just values with interesting patterns then?
>> for (CHAR val = 0x01; val < 0x100; val << 1) ?
>> Cheers,
>> Carlos.
> I would expect the values that are likely to cause problems will lie
> somewhere in the set {0x00, 0x01, 0x7e, 0x7f, 0x80, 0x81, 0xfe, 0xff},
> given the way zero detection tends to work, plus the fact that standard
> arithmetic is often done with potential for overflow from one byte to
> another.

David's final patch goes through all values from [0x01,0xff], so it
covers all of these cases. Thanks for the review!


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