Re: [BUG] segmentation fault in git-diff

[Junio C Hamano <gitster@pobox.com>]

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(),
2019-04-16),

	$ 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);
 			commit_list_sort_by_date(&list);
 			return get_oid_oneline(repo, name + 2, oid, list);