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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Derrick Stolee <stolee@gmail.com>,
	Derrick Stolee <dstolee@microsoft.com>,
	git@vger.kernel.org, ramsay@ramsayjones.plus.com,
	sbeller@google.com
Subject: Re: [PATCH v4 4/4] sha1_name: minimize OID comparisons during disambiguation
Date: Tue, 10 Oct 2017 09:09:19 -0400
Message-ID: <20171010130919.r4b5v4k7mdyuxllu@sigill.intra.peff.net> (raw)
In-Reply-To: <xmqqbmlfp3eh.fsf@gitster.mtv.corp.google.com>

On Tue, Oct 10, 2017 at 09:56:38PM +0900, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > OK, I think that makes more sense. But note the p->num_objects thing I
> > mentioned. If I do:
> >
> >   git pack-objects .git/objects/pack/pack </dev/null
> >
> > then I have a pack with zero objects, which I think we'd similarly want
> > to return early from. I.e., I think we need:
> >
> >   if (p->num_objects)
> > 	return;
> >
> > Technically that also covers open_pack_index() failure, too, but that's
> > a subtlety I don't think we should rely on.
> 
> True.  I notice that the early part of the two functions look almost
> identical.  Do we need error condition handling for the other one,
> too?

I'm not sure which two you mean. Do you mean find_pack_entry_one() in
packfile.c as the other one? If so, I think it is fine in the
zero-object case, because it does not do the "this is the sha1 at the
position where it _would_ be found" trick, which is what causes us to
potentially dereference nonsense.

-Peff

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-08 18:49 [PATCH v4 0/4] Improve abbreviation disambiguation Derrick Stolee
2017-10-08 18:49 ` [PATCH v4 3/4] sha1_name: parse less while finding common prefix Derrick Stolee
2017-10-09 13:42   ` Jeff King
2017-10-08 18:49 ` [PATCH v4 4/4] sha1_name: minimize OID comparisons during disambiguation Derrick Stolee
2017-10-09 13:49   ` Jeff King
2017-10-10 12:16     ` Derrick Stolee
2017-10-10 12:36       ` Jeff King
2017-10-10 12:56         ` Junio C Hamano
2017-10-10 13:09           ` Jeff King [this message]
2017-10-10 13:11           ` Derrick Stolee
2017-10-10 13:30             ` Jeff King
2017-10-11 13:58               ` Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 0/4] Improve abbreviation disambiguation Derrick Stolee
2017-10-12 12:04                   ` Derrick Stolee
2017-10-12 12:21                     ` Junio C Hamano
2017-10-12 14:22                       ` Jeff King
2017-10-12 12:02                 ` [PATCH v5 1/4] p4211-line-log.sh: add log --online --raw --parents perf test Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 2/4] sha1_name: unroll len loop in find_unique_abbrev_r Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 3/4] sha1_name: parse less while finding common prefix Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 4/4] sha1_name: minimize OID comparisons during disambiguation Derrick Stolee

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