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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Martin Ågren <martin.agren@gmail.com>,
	Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 3/5] match-trees: use hashcpy to splice trees
Date: Thu, 10 Jan 2019 23:55:51 +0000
Message-ID: <20190110235551.GM423984@genre.crustytoothpaste.net> (raw)
In-Reply-To: <20190110064520.GC20497@sigill.intra.peff.net>

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On Thu, Jan 10, 2019 at 01:45:20AM -0500, Jeff King wrote:
> On Thu, Jan 10, 2019 at 04:25:49AM +0000, brian m. carlson wrote:
> > diff --git a/match-trees.c b/match-trees.c
> > index feca48a5fd..b1fbd022d1 100644
> > --- a/match-trees.c
> > +++ b/match-trees.c
> > @@ -224,7 +224,7 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
> >  	} else {
> >  		rewrite_with = oid2;
> >  	}
> > -	oidcpy(rewrite_here, rewrite_with);
> > +	hashcpy(rewrite_here->hash, rewrite_with->hash);
> 
> Hrm. Our coccinelle patches will want to convert this back to oidcpy(),
> though I see you drop them in the final patch.
> 
> However, I wonder if it points to another mismatch. Isn't the point that
> we _don't_ actually have "struct object_id"s here? I.e., rewrite_here
> and rewrite_with should actually be "const unsigned char *" that we
> happen to know are the_hash_algo->raw_sz?

Correct.

> I think the only reason they are "struct object_id" is because that's
> what tree_entry_extract() returns. Should we be providing another
> function to allow more byte-oriented access?

The reason is we recursively call splice_tree, passing rewrite_here as
the first argument. That argument is then used for read_object_file,
which requires a struct object_id * (because it is, logically, an object
ID).

I *think* we could fix this by copying an unsigned char *rewrite_here
into a temporary struct object_id before we recurse, but it's not
obvious to me if that's safe to do.
-- 
brian m. carlson: Houston, Texas, US
OpenPGP: https://keybase.io/bk2204

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  reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-07 23:34 What's cooking in git.git (Jan 2019, #01; Mon, 7) Junio C Hamano
2019-01-08  9:50 ` tg/checkout-no-overlay, was " Thomas Gummerer
2019-01-08 17:51   ` Junio C Hamano
2019-01-08 17:30 ` ag/sequencer-reduce-rewriting-todo " Alban Gruin
2019-01-08 21:20 ` sb/more-repo-in-api, was " Jonathan Tan
2019-01-08 21:35   ` Junio C Hamano
2019-01-09 21:28     ` Stefan Beller
2019-01-09  7:37 ` Martin Ågren
2019-01-09 21:06   ` Martin Ågren
2019-01-10  1:02     ` brian m. carlson
2019-01-10 18:55       ` Junio C Hamano
2019-01-10 19:03       ` Martin Ågren
2019-01-10  4:25     ` [PATCH 0/5] tree-walk object_id refactor brian m. carlson
2019-01-10  4:25       ` [PATCH 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-10  4:25       ` [PATCH 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-10  4:25       ` [PATCH 3/5] match-trees: use hashcpy to splice trees brian m. carlson
2019-01-10  6:45         ` Jeff King
2019-01-10 23:55           ` brian m. carlson [this message]
2019-01-11 14:51             ` Jeff King
2019-01-11 14:54               ` Jeff King
2019-01-14  1:30                 ` brian m. carlson
2019-01-14 15:40                   ` Jeff King
2019-01-10  4:25       ` [PATCH 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-10  6:49         ` Jeff King
2019-01-10 23:57           ` brian m. carlson
2019-01-10  4:25       ` [PATCH 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-10  6:50         ` Jeff King
2019-01-10  6:40       ` [PATCH 0/5] tree-walk object_id refactor Jeff King
2019-01-11  0:17         ` brian m. carlson
2019-01-11 14:17           ` Jeff King
2019-01-15  0:39     ` [PATCH v2 " brian m. carlson
2019-01-15  0:39       ` [PATCH v2 1/5] tree-walk: copy object ID before use brian m. carlson
2019-01-15  0:39       ` [PATCH v2 2/5] match-trees: compute buffer offset correctly when splicing brian m. carlson
2019-01-15  0:39       ` [PATCH v2 3/5] match-trees: use hashcpy to splice trees brian m. carlson
2019-01-15  0:39       ` [PATCH v2 4/5] tree-walk: store object_id in a separate member brian m. carlson
2019-01-15  0:39       ` [PATCH v2 5/5] cache: make oidcpy always copy GIT_MAX_RAWSZ bytes brian m. carlson
2019-01-15 17:51       ` [PATCH v2 0/5] tree-walk object_id refactor Junio C Hamano
2019-01-09 10:28 ` What's cooking in git.git (Jan 2019, #01; Mon, 7) Jeff King
2019-01-10 19:05   ` Junio C Hamano
2019-01-10 19:46   ` Junio C Hamano
2019-01-10 18:02 ` Stefan Beller

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