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From: Jeff King <peff@peff.net>
To: Derrick Stolee <stolee@gmail.com>
Cc: git@vger.kernel.org, Yiyuan guo <yguoaz@gmail.com>
Subject: Re: [PATCH 3/5] pack-objects: clamp negative window size to 0
Date: Mon, 3 May 2021 10:55:09 -0400	[thread overview]
Message-ID: <YJAOzTIXkO2lhxSs@coredump.intra.peff.net> (raw)
In-Reply-To: <3d77d70b-2cc5-4ca9-8753-fa9af5111842@gmail.com>

On Mon, May 03, 2021 at 08:10:24AM -0400, Derrick Stolee wrote:

> On 5/1/2021 10:03 AM, Jeff King wrote:
> > A negative window size makes no sense, and the code in find_deltas() is
> > not prepared to handle it. If you pass "-1", for example, we end up
> > generate a 0-length array of "struct unpacked", but our loop assumes it
> > has at least one entry in it (and we end up reading garbage memory).
> > 
> > We could complain to the user about this, but it's more forgiving to
> > just clamp it to 0, which means "do not find any deltas at all". The
> > 0-case is already tested earlier in the script, so we'll make sure this
> > does the same thing.
> 
> This seems like a reasonable approach. It takes existing "undefined"
> behavior and turns it into well-understood, "defined" behavior.

I was on the fence on doing that, or just:

  if (window < 0)
	die("sorry dude, negative windows are nonsense");

So if anybody has a strong preference, I could be easily persuaded. Part
of what led me to being forgiving was that we similarly clamp too-large
depth values (with a warning; I didn't think it was really necessary
here, though).

-Peff

  reply	other threads:[~2021-05-03 14:55 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01 14:02 [PATCH 0/5] pack-objects: better handling of negative options Jeff King
2021-05-01 14:02 ` [PATCH 1/5] t5300: modernize basic tests Jeff King
2021-05-03  5:27   ` Junio C Hamano
2021-05-03 14:53     ` Jeff King
2021-05-01 14:03 ` [PATCH 2/5] t5300: check that we produced expected number of deltas Jeff King
2021-05-01 14:03 ` [PATCH 3/5] pack-objects: clamp negative window size to 0 Jeff King
2021-05-03 12:10   ` Derrick Stolee
2021-05-03 14:55     ` Jeff King [this message]
2021-05-04 18:47       ` René Scharfe
2021-05-04 21:38         ` Jeff King
2021-05-05 11:53         ` Ævar Arnfjörð Bjarmason
2021-05-05 16:19           ` René Scharfe
2021-05-01 14:04 ` [PATCH 4/5] t5316: check behavior of pack-objects --depth=0 Jeff King
2021-05-01 14:04 ` [PATCH 5/5] pack-objects: clamp negative depth to 0 Jeff King
2021-05-03 12:11   ` Derrick Stolee

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