[PATCH v2 1/2] builtin/merge-base: UNLEAK commit lists

[Martin Ågren <martin.agren@xxxxxxxxx>]

In several functions, we iterate through a commit list by assigning
`result = result->next`. As a consequence, we lose the original pointer
and eventually leak the list.

These are immediate helpers to `cmd_merge_base()` which is just about to
return, so we can use UNLEAK. For example, we could `UNLEAK(result)`
before we start iterating. That would be a one-liner change per
function. Instead, leave the lists alone and iterate using a dedicated
pointer. Then UNLEAK immediately before returning.

After this change, it is clearer that the leaks happen as we return, and
not as we process the list. That is, we could just as well have used
`free_commit_list()`. Also, leaving a "result" unchanged as we display
it feels (marginally) better.

In `handle_independent()` we can drop `result` while we're here and
reuse the `revs`-variable instead. That matches several other users of
`reduce_heads()`. The memory-leak that this hides will be addressed in
the next commit.

Signed-off-by: Martin Ågren <martin.agren@xxxxxxxxx>
---
 builtin/merge-base.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/builtin/merge-base.c b/builtin/merge-base.c
index 6dbd167d3..fd0eba14b 100644
--- a/builtin/merge-base.c
+++ b/builtin/merge-base.c
@@ -9,20 +9,20 @@
 
 static int show_merge_base(struct commit **rev, int rev_nr, int show_all)
 {
-	struct commit_list *result;
+	struct commit_list *result, *r;
 
 	result = get_merge_bases_many_dirty(rev[0], rev_nr - 1, rev + 1);
 
 	if (!result)
 		return 1;
 
-	while (result) {
-		printf("%s\n", oid_to_hex(&result->item->object.oid));
+	for (r = result; r; r = r->next) {
+		printf("%s\n", oid_to_hex(&r->item->object.oid));
 		if (!show_all)
-			return 0;
-		result = result->next;
+			break;
 	}
 
+	UNLEAK(result);
 	return 0;
 }
 
@@ -51,28 +51,28 @@ static struct commit *get_commit_reference(const char *arg)
 
 static int handle_independent(int count, const char **args)
 {
-	struct commit_list *revs = NULL;
-	struct commit_list *result;
+	struct commit_list *revs = NULL, *rev;
 	int i;
 
 	for (i = count - 1; i >= 0; i--)
 		commit_list_insert(get_commit_reference(args[i]), &revs);
 
-	result = reduce_heads(revs);
-	if (!result)
+	revs = reduce_heads(revs);
+
+	if (!revs)
 		return 1;
 
-	while (result) {
-		printf("%s\n", oid_to_hex(&result->item->object.oid));
-		result = result->next;
-	}
+	for (rev = revs; rev; rev = rev->next)
+		printf("%s\n", oid_to_hex(&rev->item->object.oid));
+
+	UNLEAK(revs);
 	return 0;
 }
 
 static int handle_octopus(int count, const char **args, int show_all)
 {
 	struct commit_list *revs = NULL;
-	struct commit_list *result;
+	struct commit_list *result, *rev;
 	int i;
 
 	for (i = count - 1; i >= 0; i--)
@@ -83,13 +83,13 @@ static int handle_octopus(int count, const char **args, int show_all)
 	if (!result)
 		return 1;
 
-	while (result) {
-		printf("%s\n", oid_to_hex(&result->item->object.oid));
+	for (rev = result; rev; rev = rev->next) {
+		printf("%s\n", oid_to_hex(&rev->item->object.oid));
 		if (!show_all)
-			return 0;
-		result = result->next;
+			break;
 	}
 
+	UNLEAK(result);
 	return 0;
 }
 
-- 
2.15.0.415.gac1375d7e