Re: git 2.16.0 segfaults on clone of specific repo

["brian m. carlson" <sandals@crustytoothpaste.net>]

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On Thu, Jan 18, 2018 at 07:15:56PM -0500, Eric Sunshine wrote:
> [+cc:brian]
> 
> On Thu, Jan 18, 2018 at 3:55 PM, Александр Булаев
> <aleks.bulaev@gmail.com> wrote:
> > I found that git 2.16.0 segfaults on clone of vim-colorschemes repo.
> >
> > (lldb) run
> > Process 25643 launched: '/usr/local/bin/git' (x86_64)
> > Cloning into 'vim-colorschemes'...
> > remote: Counting objects: 1457, done.
> > remote: Total 1457 (delta 0), reused 0 (delta 0), pack-reused 1457
> > Receiving objects: 100% (1457/1457), 1.43 MiB | 289.00 KiB/s, done.
> > Resolving deltas: 100% (424/424), done.
> > Process 25643 stopped
> > * thread #1, queue = 'com.apple.main-thread', stop reason =
> > EXC_BAD_ACCESS (code=1, address=0x48)
> 
> I can confirm that this crashes on MacOS; it does not crash on Linux or BSD.
> 
> git-bisect places blame on eb0ccfd7f5 (Switch empty tree and blob
> lookups to use hash abstraction, 2017-11-12).

I unfortunately don't have a macOS system to test with, and I've
compiled with both gcc and clang on my Debian system and, as you
mentioned, it doesn't fail there.

I have a guess about what the problem might be.  Can you try this patch
and see if it fixes things?

-- >8 --
From 10b690241619a452634b31fbc5ccd054a4f6e5ec Mon Sep 17 00:00:00 2001
From: "brian m. carlson" <sandals@crustytoothpaste.net>
Date: Sun, 14 Jan 2018 18:26:29 +0000
Subject: [PATCH] repository: pre-initialize hash algo pointer

There are various git subcommands (among them, clone) which don't set up
the repository but end up needing to have information about the hash
algorithm in use.  In the future, we can add a command line option for
this or read it from the configuration, but until we're ready to expose
that functionality to the user, simply initialize the repository
structure to use the current hash algorithm, SHA-1.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 repository.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/repository.c b/repository.c
index 998413b8bb..f66fcb1342 100644
--- a/repository.c
+++ b/repository.c
@@ -5,7 +5,7 @@
 
 /* The main repository */
 static struct repository the_repo = {
-	NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &the_index, NULL, 0, 0
+	NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, &the_index, &hash_algos[GIT_HASH_SHA1], 0, 0
 };
 struct repository *the_repository = &the_repo;
 
-- 
2.16.0.rc2.280.g09355b536d
-- >8 --
-- 
brian m. carlson / brian with sandals: Houston, Texas, US
https://www.crustytoothpaste.net/~bmc | My opinion only
OpenPGP: https://keybase.io/bk2204

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