object_array: use `object_array_clear()`, not `free()`

Instead of freeing `foo.objects` for an object array `foo` (sometimes
conditionally), call `object_array_clear(&foo)`. This means we don't
poke as much into the implementation, which is already a good thing, but
also that we release the individual entries as well, thereby fixing at
least one memory-leak (in diff-lib.c).

If someone is holding on to a pointer to an element's `name` or `path`,
that is now a dangling pointer, i.e., we'd be turning an unpleasant
situation into an outright bug. To the best of my understanding no such
long-term pointers are being taken.

The way we handle `study` in builting/reflog.c still looks like it might
leak. That will be addressed in the next commit.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 6 insertions, 7 deletions

diff --git a/builtin/reflog.c b/builtin/reflog.c
index e237d927a0..6b34f23e78 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -182,8 +182,8 @@ static int commit_is_complete(struct commit *commit)
 			found.objects[i].item->flags |= SEEN;
 	}
 	/* free object arrays */
-	free(study.objects);
-	free(found.objects);
+	object_array_clear(&study);
+	object_array_clear(&found);
 	return !is_incomplete;
 }
 
diff --git a/diff-lib.c b/diff-lib.c
index 2a52b07954..4e0980caa8 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -549,7 +549,6 @@ int index_differs_from(const char *def, int diff_flags,
 	rev.diffopt.flags |= diff_flags;
 	rev.diffopt.ita_invisible_in_index = ita_invisible_in_index;
 	run_diff_index(&rev, 1);
-	if (rev.pending.alloc)
-		free(rev.pending.objects);
+	object_array_clear(&rev.pending);
 	return (DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0);
 }
diff --git a/submodule.c b/submodule.c
index 36f45f5a5a..79fd01f7b0 100644
--- a/submodule.c
+++ b/submodule.c
@@ -1728,7 +1728,7 @@ static int find_first_merges(struct object_array *result, const char *path,
 			add_object_array(merges.objects[i].item, NULL, result);
 	}
 
-	free(merges.objects);
+	object_array_clear(&merges);
 	return result->nr;
 }
 
@@ -1833,7 +1833,7 @@ int merge_submodule(struct object_id *result, const char *path,
 			print_commit((struct commit *) merges.objects[i].item);
 	}
 
-	free(merges.objects);
+	object_array_clear(&merges);
 	return 0;
 }
 
diff --git a/upload-pack.c b/upload-pack.c
index 7efff2fbfd..ec0eee8fc4 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -888,7 +888,7 @@ static void receive_needs(void)
 		}
 
 	shallow_nr += shallows.nr;
-	free(shallows.objects);
+	object_array_clear(&shallows);
 }
 
 /* return non-zero if the ref is hidden, otherwise 0 */