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From: Jeff King <peff@peff.net>
To: Alejandro Sanchez <asanchez1987@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: Abort (core dumped)
Date: Mon, 20 May 2019 06:02:11 -0400
Message-ID: <20190520100211.GA26426@sigill.intra.peff.net> (raw)
In-Reply-To: <CAA4phoGrA=AsBFHkqZ54=6ev5BH+F7rLd0Hcr-t2kF_YFNrs2g@mail.gmail.com>

On Mon, May 20, 2019 at 10:35:53AM +0200, Alejandro Sanchez wrote:

> alex@polaris:~/slurm/source$ git add -u
> alex@polaris:~/slurm/source$ git am -i --continue
> Applying: Handle duplicate archive file names.
> error: object 861d3c6f689a3ca5eb5fb5c409d46de0ad5555e1 is a commit, not a tree
> BUG: diff-lib.c:526: run_diff_index must be passed exactly one tree
> Aborted (core dumped)

Hmm. So I think the interesting error is probably that first line: some
code expects to look up a tree but sees a commit, and then as a result
it probably feeds too few items to run_diff_index(), triggering the
assertion failure.

Just grepping around, this looks quite suspicious:

  $ git grep -hW get_oid_tree builtin/am.c
  static void write_index_patch(const struct am_state *state)
  ...
  if (!get_oid_tree("HEAD", &head))
	tree = lookup_tree(the_repository, &head);
  else
	tree = lookup_tree(the_repository,
			   the_repository->hash_algo->empty_tree);

Using get_oid_tree() does not actually return a tree; it just
prioritizes trees when disambiguating names (which is pointless here,
since we're not feeding an ambiguous oid). HEAD will always be a commit,
and then lookup_tree() similarly does not peel that down to an actual
tree. And this whole function is called only in interactive-mode, so
it's possible that it's simply not used much and nobody noticed.

I haven't tried to reproduce yet. Is the repository (and patch) that you
used to demonstrate this publicly available? Or alternatively, is it
possible to show a backtrace from the coredump?

If my blind guess is right, then something like this probably fixes it:

diff --git a/builtin/am.c b/builtin/am.c
index bdd1bbc35d..93305560c1 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1339,9 +1339,17 @@ static void write_index_patch(const struct am_state *state)
 	struct rev_info rev_info;
 	FILE *fp;
 
-	if (!get_oid_tree("HEAD", &head))
-		tree = lookup_tree(the_repository, &head);
-	else
+	if (!get_oid("HEAD", &head)) {
+		struct object *obj;
+		struct commit *commit;
+
+		obj = parse_object_or_die(&head, NULL);
+		commit = object_as_type(the_repository, obj, OBJ_COMMIT, 0);
+		if (!commit)
+			die("unable to parse HEAD as a commit");
+
+		tree = get_commit_tree(commit);
+	} else
 		tree = lookup_tree(the_repository,
 				   the_repository->hash_algo->empty_tree);
 

-Peff

  reply	other threads:[~2019-05-20 10:02 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20  8:35 Alejandro Sanchez
2019-05-20 10:02 ` Jeff King [this message]
2019-05-20 12:06   ` [PATCH 0/4] fix BUG() with "git am -i --resolved" Jeff King
2019-05-20 12:07     ` [PATCH 1/4] am: simplify prompt response handling Jeff King
2019-05-20 12:09     ` [PATCH 2/4] am: read interactive input from stdin Jeff King
2019-05-20 12:11     ` [PATCH 3/4] am: drop tty requirement for --interactive Jeff King
2019-05-20 12:50       ` Jeff King
2019-05-23  6:44         ` Johannes Schindelin
2019-05-24  6:27           ` Jeff King
2019-05-20 12:13     ` [PATCH 4/4] am: fix --interactive HEAD tree resolution Jeff King
2019-05-23  7:12       ` Johannes Schindelin
2019-05-24  6:39         ` Jeff King
2019-05-24  6:46           ` [PATCH v2 " Jeff King
2019-05-28 11:06           ` [PATCH " Johannes Schindelin
2019-05-28 21:35             ` Jeff King
2019-05-29 11:56               ` Johannes Schindelin
2019-09-26 14:20                 ` Alejandro Sanchez
2019-09-26 21:11                   ` Jeff King

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