revision: note the lack of free() in simplify_merges()

Among the three similar-looking loops that walk singly linked
commit_list, the first one is only peeking and the same list is
later used for real work.  Leave a comment not to mistakenly
free its elements there.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/revision.c b/revision.c
index 00aaefe88580e618ffe4d8630dc70ca3e711547d..814b96ff53dd9f03cb1356bb9b0ab8683952d334 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -2015,23 +2015,31 @@ static struct commit_list **simplify_one(struct rev_info *revs, struct commit *c
 
 static void simplify_merges(struct rev_info *revs)
 {
-       struct commit_list *list;
+       struct commit_list *list, *next;
        struct commit_list *yet_to_do, **tail;
+       struct commit *commit;
 
        if (!revs->prune)
                return;
 
        /* feed the list reversed */
        yet_to_do = NULL;
-       for (list = revs->commits; list; list = list->next)
-               commit_list_insert(list->item, &yet_to_do);
+       for (list = revs->commits; list; list = next) {
+               commit = list->item;
+               next = list->next;
+               /*
+                * Do not free(list) here yet; the original list
+                * is used later in this function.
+                */
+               commit_list_insert(commit, &yet_to_do);
+       }
        while (yet_to_do) {
                list = yet_to_do;
                yet_to_do = NULL;
                tail = &yet_to_do;
                while (list) {
-                       struct commit *commit = list->item;
-                       struct commit_list *next = list->next;
+                       commit = list->item;
+                       next = list->next;
                        free(list);
                        list = next;
                        tail = simplify_one(revs, commit, tail);
@@ -2043,9 +2051,10 @@ static void simplify_merges(struct rev_info *revs)
        revs->commits = NULL;
        tail = &revs->commits;
        while (list) {
-               struct commit *commit = list->item;
-               struct commit_list *next = list->next;
                struct merge_simplify_state *st;
+
+               commit = list->item;
+               next = list->next;
                free(list);
                list = next;
                st = locate_simplify_state(revs, commit);