mapper: allocate the result of map_directory_child_fs(), map_song_fs()

Don't use fixed stack buffers.

src/mapper.c

@@ -108,11 +108,11 @@ map_directory_fs(const struct directory *directory)
 	return map_uri_fs(dirname);
 }
 
-const char *
-map_directory_child_fs(const struct directory *directory, const char *name,
-		       char *buffer)
+char *
+map_directory_child_fs(const struct directory *directory, const char *name)
 {
-	char *parent_fs;
+	char buffer[MPD_PATH_MAX];
+	char *parent_fs, *path;
 
 	/* check for invalid or unauthorized base names */
 	if (*name == 0 || strchr(name, '/') != NULL ||
@@ -124,21 +124,22 @@ map_directory_child_fs(const struct directory *directory, const char *name,
 		return NULL;
 
 	name = utf8_to_fs_charset(buffer, name);
-	pfx_dir(buffer, name, strlen(name),
-		parent_fs, strlen(parent_fs));
+	path = g_build_filename(parent_fs, name, NULL);
 	g_free(parent_fs);
-	return buffer;
+	return path;
 }
 
-const char *
-map_song_fs(const struct song *song, char *buffer)
+char *
+map_song_fs(const struct song *song)
 {
+	char buffer[MPD_PATH_MAX];
+
 	assert(song_is_file(song));
 
 	if (song_in_database(song))
-		return map_directory_child_fs(song->parent, song->url, buffer);
+		return map_directory_child_fs(song->parent, song->url);
 	else
-		return utf8_to_fs_charset(buffer, song->url);
+		return g_strdup(utf8_to_fs_charset(buffer, song->url));
 }
 
 const char *