queue/PlaylistEdit: fix crash in SetSongIdRange() while playing

An assertion failure in UpdateQueuedSong() could trigger because the `prev` parameter is always `nullptr`, but `queued` may be set. And in fact, calling UpdateQueuedSong() is only necessary when the queued song was edited, to re-queue it with the new range. Closes https://github.com/MusicPlayerDaemon/MPD/issues/901

queue/PlaylistEdit: fix crash in SetSongIdRange() while playing
5716cde1 · Max Kellermann · b7a99b4a · 5716cde1 · 5716cde1
Commit 5716cde1 authored Jun 11, 2020 by Max Kellermann
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Showing with 10 additions and 1 deletion

NEWS NEWS +2 -0

PlaylistEdit.cxx src/queue/PlaylistEdit.cxx +8 -1

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--- a/NEWS
+++ b/NEWS
 ver 0.21.25 (not yet released)
+* protocol:
+  - fix crash when using "rangeid" while playing

 ver 0.21.24 (2020/06/10)
 * protocol

--- a/src/queue/PlaylistEdit.cxx
+++ b/src/queue/PlaylistEdit.cxx
@@ -431,6 +431,8 @@ playlist::SetSongIdRange(PlayerControl &pc, unsigned id,
 	if (position < 0)
 		throw PlaylistError::NoSuchSong();

+	bool was_queued = false;
+
 	if (playing) {
 		if (position == current)
 			throw PlaylistError(PlaylistResult::DENIED,
@@ -442,6 +444,10 @@ playlist::SetSongIdRange(PlayerControl &pc, unsigned id,
 			   already; cancel that */
 			pc.LockCancel();
 			queued = -1;
+
+			/* schedule a call to UpdateQueuedSong() to
+			   re-queue the song with its new range */
+			was_queued = true;
 		}
 	}

@@ -464,7 +470,8 @@ playlist::SetSongIdRange(PlayerControl &pc, unsigned id,
 	song.SetEndTime(end);

 	/* announce the change to all interested subsystems */
-	UpdateQueuedSong(pc, nullptr);
+	if (was_queued)
+		UpdateQueuedSong(pc, nullptr);
 	queue.ModifyAtPosition(position);
 	OnModified();
 }