From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stefan Beller <stefanbeller@googlemail.com>
Subject: Re: [PATCH] create_delta_index: simplify condition always evaluating
 to true
Date: Fri, 16 Aug 2013 00:04:25 +0200
Message-ID: <520D5069.5090905@googlemail.com>
References: <1376595460-6546-1-git-send-email-stefanbeller@googlemail.com> <7vzjsipr3s.fsf@alter.siamese.dyndns.org>
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Cc: Nicolas Pitre <nico@fluxnic.net>, git@vger.kernel.org
To: Junio C Hamano <gitster@pobox.com>
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Nicolas,

I am sorry for not including you in the first mail.
Just before Junio included you, there were these 2 mails
http://www.mail-archive.com/git@vger.kernel.org/msg34101.html
http://www.mail-archive.com/git@vger.kernel.org/msg34103.html

Stefan

On 08/15/2013 11:43 PM, Junio C Hamano wrote:
> Forwarding to the area expert...
>=20
> Stefan Beller <stefanbeller@googlemail.com> writes:
>=20
>> When checking the previous lines in that function, we can deduct that
>> hsize must always be smaller than (1u<<31), since 506049c7df2c6
>> (fix >4GiB source delta assertion failure), because the entries is
>> capped at an upper bound of 0xfffffffeU, so hsize contains a maximum
>> value of 0x3fffffff, which is smaller than (1u<<31), so i will never
>> be larger than 31.
>>
>> Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
>> ---
>>  diff-delta.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/diff-delta.c b/diff-delta.c
>> index 93385e1..54da95b 100644
>> --- a/diff-delta.c
>> +++ b/diff-delta.c
>> @@ -154,8 +154,15 @@ struct delta_index * create_delta_index(const voi=
d *buf, unsigned long bufsize)
>>  		 */
>>  		entries =3D 0xfffffffeU / RABIN_WINDOW;
>>  	}
>> +
>> +	/*
>> +	 * Do not check i < 31 in the loop, because the assignement
>> +	 * previous to the loop makes sure, hsize is definitely
>> +	 * smaller than 1<<31, hence the loop will always stop
>> +	 * before i exceeds 31 resulting in an infinite loop.
>> +	 */
>>  	hsize =3D entries / 4;
>> -	for (i =3D 4; (1u << i) < hsize && i < 31; i++);
>> +	for (i =3D 4; (1u << i) < hsize; i++);
>>  	hsize =3D 1 << i;
>>  	hmask =3D hsize - 1;



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