From: Nicolas Pitre <nico@fluxnic.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Stefan Beller <stefanbeller@googlemail.com>
Subject: Re: [PATCH] create_delta_index: simplify condition always evaluating to true
Date: Thu, 15 Aug 2013 22:34:06 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.2.03.1308152231230.14472@syhkavp.arg> (raw)
In-Reply-To: <7vzjsipr3s.fsf@alter.siamese.dyndns.org>
On Thu, 15 Aug 2013, Junio C Hamano wrote:
> Forwarding to the area expert...
>
> Stefan Beller <stefanbeller@googlemail.com> writes:
>
> > 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>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
You probably could dispense with the comment. The code is obvious
enough and the commit log has the rationale already.
> > ---
> > 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 void *buf, unsigned long bufsize)
> > */
> > entries = 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 = entries / 4;
> > - for (i = 4; (1u << i) < hsize && i < 31; i++);
> > + for (i = 4; (1u << i) < hsize; i++);
> > hsize = 1 << i;
> > hmask = hsize - 1;
> --
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next prev parent reply other threads:[~2013-08-16 2:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-15 19:37 [PATCH] create_delta_index: simplify condition always evaluating to true Stefan Beller
2013-08-15 21:21 ` Eric Sunshine
2013-08-15 21:34 ` Stefan Beller
2013-08-15 21:46 ` Eric Sunshine
2013-08-16 2:38 ` Nicolas Pitre
2013-08-16 16:47 ` Philip Oakley
2013-08-16 21:22 ` Stefan Beller
2013-08-17 6:58 ` Philip Oakley
2013-08-15 22:14 ` Philip Oakley
2013-08-15 21:43 ` Junio C Hamano
2013-08-15 22:04 ` Stefan Beller
2013-08-16 2:34 ` Nicolas Pitre [this message]
2013-08-16 11:43 ` brian m. carlson
2013-08-16 12:40 ` Eric Sunshine
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