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From: Junio C Hamano <>
Cc: "Érico Rolim" <>,
	"Nguyễn Thái Ngọc Duy" <>
Subject: Re: [BUG] segmentation fault in git-diff
Date: Thu, 09 Apr 2020 16:37:15 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Junio C. Hamano's message of "Thu, 09 Apr 2020 15:57:00 -0700")

The problem bisects down to c931ba4e (sha1-name.c: remove the_repo
from handle_one_ref(), 2019-04-16), which did this:

-			for_each_ref(handle_one_ref, &list);
-			head_ref(handle_one_ref, &list);
+			cb.repo = repo;
+			cb.list = &list;
+			refs_for_each_ref(repo->refs, handle_one_ref, &cb);
+			refs_head_ref(repo->refs, handle_one_ref, &cb);

The old code used the helper for_each_ref().  This is a thin wrapper
around refs_for_each_ref() and allows the default repository object
to be used implicitly by the caller.  It is understandable that the
code wanted to work on arbitrary repository object, and replaced the
for_each_ref() helper with refs_for_each_ref() helper that takes any
ref store object.

But there is a small mistake.  for_each_ref() makes sure that the
ref store is initialized; the new code blindly assumes it has
already been initialized.

    int for_each_ref(each_ref_fn fn, void *cb_data)
            return refs_for_each_ref(get_main_ref_store(the_repository), fn, cb_data);

So, I think the fix is simple.  With the attached one liner on top
of c931ba4e (sha1-name.c: remove the_repo from handle_one_ref(),

	$ git rev-parse :/any/path/

no longer segfaults.  I think it would also work just fine when
merged to more modern codebase, but I haven't tried it (yet).

 sha1-name.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sha1-name.c b/sha1-name.c
index d9050776dd..3aba62938f 100644
--- a/sha1-name.c
+++ b/sha1-name.c
@@ -1771,7 +1771,7 @@ static enum get_oid_result get_oid_with_context_1(struct repository *repo,
 			cb.repo = repo;
 			cb.list = &list;
-			refs_for_each_ref(repo->refs, handle_one_ref, &cb);
+			refs_for_each_ref(get_main_ref_store(repo), handle_one_ref, &cb);
 			refs_head_ref(repo->refs, handle_one_ref, &cb);
 			return get_oid_oneline(repo, name + 2, oid, list);

  reply	other threads:[~2020-04-09 23:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-09 22:22 [BUG] segmentation fault in git-diff Érico Rolim
2020-04-09 22:45 ` Junio C Hamano
2020-04-09 22:47   ` Junio C Hamano
2020-04-09 22:57     ` Junio C Hamano
2020-04-09 23:37       ` Junio C Hamano [this message]
2020-04-09 23:41       ` Jeff King
2020-04-10  0:03         ` Re* " Junio C Hamano
2020-04-10  1:42           ` Érico Rolim
2020-04-10  3:04           ` Jeff King
2020-04-10  5:39             ` Junio C Hamano

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