pack-redundant: fix crash when one packfile in repo

Commit Message

Jiang Xin Dec. 16, 2020, 10:09 a.m. UTC

From: Jiang Xin <[e-mail]>

Command `git pack-redundant --all` will crash if there is only one
packfile in the repository.  This is because, if there is only one
packfile in local_packs, `cmp_local_packs` will do nothing and will
leave `pl->unique_objects` as uninitialized.

Junio will add additional option for pack-redundant for preparing
its removal.  So replace `git pack-redundant` command with variable
`$git_pack_redundant` in t5323.

Reported-by: Daniel C. Klauer <[e-mail]>
Signed-off-by: Jiang Xin <[e-mail]>
---
 builtin/pack-redundant.c  |  6 ++++
 t/t5323-pack-redundant.sh | 65 +++++++++++++++++++++++++++++----------
 2 files changed, 54 insertions(+), 17 deletions(-)

Comments

Junio C Hamano Dec. 16, 2020, 5:32 p.m. UTC | #1

Jiang Xin <[e-mail]> writes:

> Junio will add additional option for pack-redundant for preparing
> its removal.  So replace `git pack-redundant` command with variable
> `$git_pack_redundant` in t5323.

Could you please revert the part about $git_pack_redundant,
pretending as if the other patch never existed, so that this fix can
be applied without having to wait until the discussion to deprecate
and remove comes to conclusion?

Thanks.

Jeff King Dec. 16, 2020, 6:46 p.m. UTC | #2

On Wed, Dec 16, 2020 at 05:09:52AM -0500, Jiang Xin wrote:

> Command `git pack-redundant --all` will crash if there is only one
> packfile in the repository.  This is because, if there is only one
> packfile in local_packs, `cmp_local_packs` will do nothing and will
> leave `pl->unique_objects` as uninitialized.

Thanks, that makes sense. And I'm glad I waited to get the opinion of
somebody much more clueful. Mine was a band-aid, but yours is hitting
the root cause and will help any other downstream code that assumes
unique_objects isn't NULL.

>  builtin/pack-redundant.c  |  6 ++++
>  t/t5323-pack-redundant.sh | 65 +++++++++++++++++++++++++++++----------

The new test coverage makes sense, I think, though as Junio noted, it
should be done independent of the $git_pack_redundant change (which will
also make the diff a lot easier to review).

-Peff

Patch

diff --git a/builtin/pack-redundant.c b/builtin/pack-redundant.c
index 178e3409b7..690775fa82 100644
--- a/builtin/pack-redundant.c
+++ b/builtin/pack-redundant.c
@@ -473,6 +473,12 @@  static void cmp_local_packs(void)
 {
 	struct pack_list *subset, *pl = local_packs;
 
+	/* only one packfile */
+	if (!pl->next) {
+		llist_init(&pl->unique_objects);
+		return;
+	}
+
 	while ((subset = pl)) {
 		while ((subset = subset->next))
 			cmp_two_packs(pl, subset);
diff --git a/t/t5323-pack-redundant.sh b/t/t5323-pack-redundant.sh
index 6b4d1ca353..45436bd6e1 100755
--- a/t/t5323-pack-redundant.sh
+++ b/t/t5323-pack-redundant.sh
@@ -39,6 +39,8 @@  relationship between packs and objects is as follows:
 master_repo=master.git
 shared_repo=shared.git
 
+git_pack_redundant='git pack-redundant'
+
 # Create commits in <repo> and assign each commit's oid to shell variables
 # given in the arguments (A, B, and C). E.g.:
 #
@@ -112,19 +114,28 @@  test_expect_success 'setup master repo' '
 	create_commits_in "$master_repo" A B C D E F G H I J K L M N O P Q R
 '
 
+test_expect_success 'master: pack-redundant works with no packfile' '
+	(
+		cd "$master_repo" &&
+		cat >expect <<-EOF &&
+			fatal: Zero packs found!
+			EOF
+		test_must_fail $git_pack_redundant --all >actual 2>&1 &&
+		test_cmp expect actual
+	)
+'
+
 #############################################################################
 # Chart of packs and objects for this test case
 #
 #         | T A B C D E F G H I J K L M N O P Q R
 #     ----+--------------------------------------
 #     P1  | x x x x x x x                       x
-#     P2  |     x x x x   x x x
-#     P3  |             x     x x x x x
 #     ----+--------------------------------------
-#     ALL | x x x x x x x x x x x x x x         x
+#     ALL | x x x x x x x                       x
 #
 #############################################################################
-test_expect_success 'master: no redundant for pack 1, 2, 3' '
+test_expect_success 'master: pack-redundant works with one packfile' '
 	create_pack_in "$master_repo" P1 <<-EOF &&
 		$T
 		$A
@@ -135,6 +146,26 @@  test_expect_success 'master: no redundant for pack 1, 2, 3' '
 		$F
 		$R
 		EOF
+	(
+		cd "$master_repo" &&
+		$git_pack_redundant --all >out &&
+		test_must_be_empty out
+	)
+'
+
+#############################################################################
+# Chart of packs and objects for this test case
+#
+#         | T A B C D E F G H I J K L M N O P Q R
+#     ----+--------------------------------------
+#     P1  | x x x x x x x                       x
+#     P2  |     x x x x   x x x
+#     P3  |             x     x x x x x
+#     ----+--------------------------------------
+#     ALL | x x x x x x x x x x x x x x         x
+#
+#############################################################################
+test_expect_success 'master: no redundant for pack 1, 2, 3' '
 	create_pack_in "$master_repo" P2 <<-EOF &&
 		$B
 		$C
@@ -154,7 +185,7 @@  test_expect_success 'master: no redundant for pack 1, 2, 3' '
 		EOF
 	(
 		cd "$master_repo" &&
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		test_must_be_empty out
 	)
 '
@@ -192,7 +223,7 @@  test_expect_success 'master: one of pack-2/pack-3 is redundant' '
 		cat >expect <<-EOF &&
 			P3:$P3
 			EOF
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		format_packfiles <out >actual &&
 		test_cmp expect actual
 	)
@@ -231,7 +262,7 @@  test_expect_success 'master: pack 2, 4, and 6 are redundant' '
 			P4:$P4
 			P6:$P6
 			EOF
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		format_packfiles <out >actual &&
 		test_cmp expect actual
 	)
@@ -266,7 +297,7 @@  test_expect_success 'master: pack-8 (subset of pack-1) is also redundant' '
 			P6:$P6
 			P8:$P8
 			EOF
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		format_packfiles <out >actual &&
 		test_cmp expect actual
 	)
@@ -284,9 +315,9 @@  test_expect_success 'master: clean loose objects' '
 test_expect_success 'master: remove redundant packs and pass fsck' '
 	(
 		cd "$master_repo" &&
-		git pack-redundant --all | xargs rm &&
+		$git_pack_redundant --all | xargs rm &&
 		git fsck &&
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		test_must_be_empty out
 	)
 '
@@ -304,7 +335,7 @@  test_expect_success 'setup shared.git' '
 test_expect_success 'shared: all packs are redundant, but no output without --alt-odb' '
 	(
 		cd "$shared_repo" &&
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		test_must_be_empty out
 	)
 '
@@ -343,7 +374,7 @@  test_expect_success 'shared: show redundant packs in stderr for verbose mode' '
 			P5:$P5
 			P7:$P7
 			EOF
-		git pack-redundant --all --verbose >out 2>out.err &&
+		$git_pack_redundant --all --verbose >out 2>out.err &&
 		test_must_be_empty out &&
 		grep "pack$" out.err | format_packfiles >actual &&
 		test_cmp expect actual
@@ -356,9 +387,9 @@  test_expect_success 'shared: remove redundant packs, no packs left' '
 		cat >expect <<-EOF &&
 			fatal: Zero packs found!
 			EOF
-		git pack-redundant --all --alt-odb | xargs rm &&
+		$git_pack_redundant --all --alt-odb | xargs rm &&
 		git fsck &&
-		test_must_fail git pack-redundant --all --alt-odb >actual 2>&1 &&
+		test_must_fail $git_pack_redundant --all --alt-odb >actual 2>&1 &&
 		test_cmp expect actual
 	)
 '
@@ -386,7 +417,7 @@  test_expect_success 'shared: create new objects and packs' '
 test_expect_success 'shared: no redundant without --alt-odb' '
 	(
 		cd "$shared_repo" &&
-		git pack-redundant --all >out &&
+		$git_pack_redundant --all >out &&
 		test_must_be_empty out
 	)
 '
@@ -417,7 +448,7 @@  test_expect_success 'shared: no redundant without --alt-odb' '
 test_expect_success 'shared: one pack is redundant with --alt-odb' '
 	(
 		cd "$shared_repo" &&
-		git pack-redundant --all --alt-odb >out &&
+		$git_pack_redundant --all --alt-odb >out &&
 		format_packfiles <out >actual &&
 		test_line_count = 1 actual
 	)
@@ -454,7 +485,7 @@  test_expect_success 'shared: ignore unique objects and all two packs are redunda
 			Px1:$Px1
 			Px2:$Px2
 			EOF
-		git pack-redundant --all --alt-odb >out <<-EOF &&
+		$git_pack_redundant --all --alt-odb >out <<-EOF &&
 			$X
 			$Y
 			$Z