decoder_control: duplicate the song object

Make sure the decoder "owns" the song object, so nobody else can free
it.

src/decoder_control.c

@@ -41,6 +41,8 @@ dc_new(GCond *client_cond)
 	dc->state = DECODE_STATE_STOP;
 	dc->command = DECODE_COMMAND_NONE;
 
+	dc->song = NULL;
+
 	dc->replay_gain_db = 0;
 	dc->replay_gain_prev_db = 0;
 	dc->mixramp_start = NULL;
@@ -55,6 +57,9 @@ dc_free(struct decoder_control *dc)
 {
 	dc_clear_error(dc);
 
+	if (dc->song != NULL)
+		song_free(dc->song);
+
 	g_cond_free(dc->cond);
 	g_mutex_free(dc->mutex);
 	g_free(dc->mixramp_start);
@@ -129,6 +134,9 @@ dc_start(struct decoder_control *dc, struct song *song,
 	assert(pipe != NULL);
 	assert(music_pipe_empty(pipe));
 
+	if (dc->song != NULL)
+		song_free(dc->song);
+
 	dc->song = song;
 	dc->start_ms = start_ms;
 	dc->end_ms = end_ms;

src/decoder_control.h

@@ -90,8 +90,11 @@ struct decoder_control {
 	 * The song currently being decoded.  This attribute is set by
 	 * the player thread, when it sends the #DECODE_COMMAND_START
 	 * command.
+	 *
+	 * This is a duplicate, and must be freed when this attribute
+	 * is cleared.
 	 */
-	const struct song *song;
+	struct song *song;
 
 	/**
 	 * The initial seek position (in milliseconds), e.g. to the
@@ -303,7 +306,8 @@ decoder_lock_is_current_song(struct decoder_control *dc,
  * Start the decoder.
  *
  * @param the decoder
- * @param song the song to be decoded
+ * @param song the song to be decoded; the given instance will be
+ * owned and freed by the decoder
  * @param start_ms see #decoder_control
  * @param end_ms see #decoder_control
  * @param pipe the pipe which receives the decoded chunks (owned by

src/player_thread.c

@@ -162,7 +162,7 @@ player_dc_start(struct player *player, struct music_pipe *pipe)
 	if (pc->command == PLAYER_COMMAND_SEEK)
 		start_ms += (unsigned)(pc->seek_where * 1000);
 
-	dc_start(dc, pc->next_song,
+	dc_start(dc, song_dup_detached(pc->next_song),
 		 start_ms, pc->next_song->end_ms,
 		 player_buffer, pipe);
 }