queue: duplicate all song objects

Makefile.am

@@ -1351,6 +1351,7 @@ test_test_pcm_LDADD = \
 
 test_test_queue_priority_SOURCES = \
 	src/queue.c \
+	test/FakeSong.cxx \
 	test/test_queue_priority.c
 test_test_queue_priority_LDADD = \
 	$(GLIB_LIBS)

src/queue.c

@@ -103,7 +103,7 @@ queue_append(struct queue *queue, struct song *song)
 	assert(!queue_is_full(queue));
 
 	queue->items[queue->length] = (struct queue_item){
-		.song = song,
+		.song = song_dup_detached(song),
 		.id = id,
 		.version = queue->version,
 		.priority = 0,
@@ -256,8 +256,8 @@ queue_delete(struct queue *queue, unsigned position)
 	assert(position < queue->length);
 
 	song = queue_get(queue, position);
-	if (!song_in_database(song))
-		song_free(song);
+	assert(!song_in_database(song) || song_is_detached(song));
+	song_free(song);
 
 	id = queue_position_to_id(queue, position);
 	order = queue_position_to_order(queue, position);
@@ -291,8 +291,9 @@ queue_clear(struct queue *queue)
 	for (unsigned i = 0; i < queue->length; i++) {
 		struct queue_item *item = &queue->items[i];
 
-		if (!song_in_database(item->song))
-			song_free(item->song);
+		assert(!song_in_database(item->song) ||
+		       song_is_detached(item->song));
+		song_free(item->song);
 
 		queue->id_to_position[item->id] = -1;
 	}

test/FakeSong.cxx

+/*
+ * Copyright (C) 2003-2012 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "song.h"
+#include "directory.h"
+#include "gcc.h"
+
+#include <stdlib.h>
+
+struct directory detached_root;
+
+struct song *
+song_dup_detached(gcc_unused const struct song *src)
+{
+	abort();
+}