Fix an issue that caused some guild channels not to be left when leaving allychat

- The issue was caused by an array compaction while iterating through the array members.
- A visible effect was that under certain conditions (depending on the
  alliance size), a character that left a guild could still see allychat
  messages from some of the allied guilds.

Signed-off-by: Haru <haru@dotalux.com>

2 files changed, 7 insertions, 8 deletions

diff --git a/src/map/atcommand.c b/src/map/atcommand.c
index adf617ccd..f46ce0362 100644
--- a/src/map/atcommand.c
+++ b/src/map/atcommand.c
@@ -9125,14 +9125,12 @@ ACMD(channel)
 			return false;
 		}
 		if (VECTOR_INDEX(sd->channels, k)->type == HCS_TYPE_ALLY) {
-			do {
-				for (k = 0; k < VECTOR_LENGTH(sd->channels); k++) {
-					if (VECTOR_INDEX(sd->channels, k)->type == HCS_TYPE_ALLY) {
-						channel->leave(VECTOR_INDEX(sd->channels, k), sd);
-						break;
-					}
+			for (k = VECTOR_LENGTH(sd->channels) - 1; k >= 0; k--) {
+				// Loop downward to avoid issues when channel->leave() compacts the array
+				if (VECTOR_INDEX(sd->channels, k)->type == HCS_TYPE_ALLY) {
+					channel->leave(VECTOR_INDEX(sd->channels, k), sd);
 				}
-			} while (k != VECTOR_LENGTH(sd->channels)); // FIXME
+			}
 		} else {
 			channel->leave(VECTOR_INDEX(sd->channels, k), sd);
 		}
diff --git a/src/map/channel.c b/src/map/channel.c
index 86ca44ea2..e27e9fb0b 100644
--- a/src/map/channel.c
+++ b/src/map/channel.c
@@ -565,7 +565,8 @@ static void channel_guild_leave_alliance(const struct guild *g_source, const str
 static void channel_quit_guild(struct map_session_data *sd)
 {
 	nullpo_retv(sd);
-	for (int i = 0; i < VECTOR_LENGTH(sd->channels); i++) { // FIXME
+	for (int i = VECTOR_LENGTH(sd->channels) - 1; i >= 0; i--) {
+		// Loop downward to avoid issues when channel->leave() compacts the array
 		struct channel_data *chan = VECTOR_INDEX(sd->channels, i);
 
 		if (chan->type != HCS_TYPE_ALLY)