Re: regression in 92392b4

[Pierre Habouzit <madcoder@debian.org>]

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On Tue, Jul 22, 2008 at 11:17:45PM +0000, Pierre Habouzit wrote:
>   Hi, here is a manual painful down-secting (opposed to a bisect ;P) I
> did, since git in next cannot fetch on a regular basis for me. The
> culprit seems to be commit  92392b4:
> 
>     ┌─(1:11)──<~/dev/scm/git 92392b4...>──
>     └[artemis] git fetch
>     remote: Counting objects: 461, done.
>     remote: Compressing objects: 100% (141/141), done.
>     remote: Total 263 (delta 227), reused 155 (delta 121)
>     Receiving objects: 100% (263/263), 95.55 KiB, done.
>     fatal: Out of memory, malloc failed
>     fatal: index-pack failed
>     [2]    16674 abort (core dumped)  git fetch
> 
>     ┌─(1:12)──<~/dev/scm/git 92392b4...>──
>     └[artemis] git checkout -m HEAD~1; make git-index-pack
>     Previous HEAD position was 92392b4... index-pack: Honor core.deltaBaseCacheLimit when resolving deltas
>     HEAD is now at 03993e1... index-pack: Track the object_entry that creates each base_data
>     GIT_VERSION = 1.5.6.3.3.g03993
> 	CC index-pack.o
> 	LINK git-index-pack
> 
>     ┌─(1:12)──<~/dev/scm/git 03993e1...>──
>     └[artemis] git fetch
>     remote: Counting objects: 461, done.
>     remote: Compressing objects: 100% (141/141), done.
>     remote: Total 263 (delta 227), reused 155 (delta 121)
>     Receiving objects: 100% (263/263), 95.55 KiB, done.
>     Resolving deltas: 100% (227/227), completed with 153 local objects.
>     From git://git.kernel.org/pub/scm/git/git
>        5ba2c22..0868a30  html       -> origin/html
>        2857e17..abeeabe  man        -> origin/man
>        93310a4..95f8ebb  master     -> origin/master
>        559998f..e8bf351  next       -> origin/next
> 
> You can see the commit sha's in the prompt. 03993e1 is fine, 92392b4 is
> broken, I've absolutely no clue about what happens.
> 
> All I can say is that at some point in get_data_from_pack, obj[1].idx
> points to something that is *not* a sha so it's probably corrupted.
> (from index-pack.c).

  Though reading the code, we trust c->data NULL-iness to mean we have
no data, and there is one code path that fails to reset it. The problem
is I'm not able to reproduce the bug, because I foolishly didn't
backuped the git repository that exhibited the failure, so I cannot know
if that can be the problem:

--- snip ---
From c3749f7bc50c642c5d437b2746d4ba589b7d9739 Mon Sep 17 00:00:00 2001
From: Pierre Habouzit <madcoder@debian.org>
Date: Wed, 23 Jul 2008 01:35:11 +0200
Subject: [PATCH] index-pack: missing pointer reset to NULL.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
---
 index-pack.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/index-pack.c b/index-pack.c
index ac20a46..19c39e5 100644
--- a/index-pack.c
+++ b/index-pack.c
@@ -257,6 +257,7 @@ static void unlink_base_data(struct base_data *c)
 		base_cache = NULL;
 	if (c->data) {
 		free(c->data);
+		c->data = NULL;
 		base_cache_used -= c->size;
 	}
 }
-- 
1.6.0.rc0.153.ge8bf3.dirty


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