builtin/merge-recursive: fix leaking object ID bases

In `cmd_merge_recursive()` we have a static array of object ID bases
that we pass to `merge_recursive_generic()`. This interface is somewhat
weird though because the latter function accepts a pointer to a pointer
of object IDs, which requires us to allocate the object IDs on the heap.
And as we never free those object IDs, the end result is a leak.

While we can easily solve this leak by just freeing the respective
object IDs, the whole calling convention is somewhat weird. Instead,
refactor `merge_recursive_generic()` to accept a plain pointer to object
IDs so that we can avoid allocating them altogether.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

builtin/am.c

@@ -1573,8 +1573,8 @@ static int build_fake_ancestor(const struct am_state *state, const char *index_f
  */
 static int fall_back_threeway(const struct am_state *state, const char *index_path)
 {
-	struct object_id orig_tree, their_tree, our_tree;
-	const struct object_id *bases[1] = { &orig_tree };
+	struct object_id their_tree, our_tree;
+	struct object_id bases[1] = { 0 };
 	struct merge_options o;
 	struct commit *result;
 	char *their_tree_name;
@@ -1588,7 +1588,7 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 	discard_index(the_repository->index);
 	read_index_from(the_repository->index, index_path, get_git_dir());
 
-	if (write_index_as_tree(&orig_tree, the_repository->index, index_path, 0, NULL))
+	if (write_index_as_tree(&bases[0], the_repository->index, index_path, 0, NULL))
 		return error(_("Repository lacks necessary blobs to fall back on 3-way merge."));
 
 	say(state, stdout, _("Using index info to reconstruct a base tree..."));

builtin/merge-recursive.c

@@ -23,7 +23,7 @@ static char *better_branch_name(const char *branch)
 
 int cmd_merge_recursive(int argc, const char **argv, const char *prefix UNUSED)
 {
-	const struct object_id *bases[21];
+	struct object_id bases[21];
 	unsigned bases_count = 0;
 	int i, failed;
 	struct object_id h1, h2;
@@ -49,10 +49,8 @@ int cmd_merge_recursive(int argc, const char **argv, const char *prefix UNUSED)
 			continue;
 		}
 		if (bases_count < ARRAY_SIZE(bases)-1) {
-			struct object_id *oid = xmalloc(sizeof(struct object_id));
-			if (repo_get_oid(the_repository, argv[i], oid))
+			if (repo_get_oid(the_repository, argv[i], &bases[bases_count++]))
 				die(_("could not parse object '%s'"), argv[i]);
-			bases[bases_count++] = oid;
 		}
 		else
 			warning(Q_("cannot handle more than %d base. "

merge-recursive.c

@@ -3866,7 +3866,7 @@ int merge_recursive_generic(struct merge_options *opt,
 			    const struct object_id *head,
 			    const struct object_id *merge,
 			    int num_merge_bases,
-			    const struct object_id **merge_bases,
+			    const struct object_id *merge_bases,
 			    struct commit **result)
 {
 	int clean;
@@ -3879,10 +3879,10 @@ int merge_recursive_generic(struct merge_options *opt,
 		int i;
 		for (i = 0; i < num_merge_bases; ++i) {
 			struct commit *base;
-			if (!(base = get_ref(opt->repo, merge_bases[i],
-					     oid_to_hex(merge_bases[i]))))
+			if (!(base = get_ref(opt->repo, &merge_bases[i],
+					     oid_to_hex(&merge_bases[i]))))
 				return err(opt, _("Could not parse object '%s'"),
-					   oid_to_hex(merge_bases[i]));
+					   oid_to_hex(&merge_bases[i]));
 			commit_list_insert(base, &ca);
 		}
 		if (num_merge_bases == 1)

merge-recursive.h

@@ -123,7 +123,7 @@ int merge_recursive_generic(struct merge_options *opt,
 			    const struct object_id *head,
 			    const struct object_id *merge,
 			    int num_merge_bases,
-			    const struct object_id **merge_bases,
+			    const struct object_id *merge_bases,
 			    struct commit **result);
 
 #endif

t/t6432-merge-recursive-space-options.sh

@@ -14,6 +14,7 @@ test_description='merge-recursive space options
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_have_prereq SED_STRIPS_CR && SED_OPTIONS=-b

t/t6434-merge-recursive-rename-options.sh

@@ -29,6 +29,7 @@ mentions this in a different context).
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 get_expected_stages () {