Mapper: map_fs_to_utf8() returns std::string

Avoid the conversion to an allocated char*, let the caller decide.

src/Mapper.cxx

@@ -248,7 +248,7 @@ map_song_fs(const Song *song)
 		return Path::FromUTF8(song->uri);
 }
 
-char *
+std::string
 map_fs_to_utf8(const char *path_fs)
 {
 	if (!music_dir_fs.IsNull() &&
@@ -263,11 +263,7 @@ map_fs_to_utf8(const char *path_fs)
 	while (path_fs[0] == G_DIR_SEPARATOR)
 		++path_fs;
 
-	const std::string path_utf8 = Path::ToUTF8(path_fs);
-	if (path_utf8.empty())
-		return nullptr;
-
-	return g_strdup(path_utf8.c_str());
+	return Path::ToUTF8(path_fs);
 }
 
 const Path &

src/Mapper.hxx

@@ -24,6 +24,8 @@
 #ifndef MPD_MAPPER_HXX
 #define MPD_MAPPER_HXX
 
+#include <string>
+
 #include "gcc.h"
 
 #define PLAYLIST_FILE_SUFFIX ".m3u"
@@ -118,10 +120,11 @@ map_song_fs(const Song *song);
  * absolute) to a relative path in UTF-8 encoding.
  *
  * @param path_fs a path in file system encoding
- * @return the relative path in UTF-8, or nullptr if mapping failed
+ * @return the relative path in UTF-8, or an empty string if mapping
+ * failed
  */
-gcc_malloc
-char *
+gcc_pure
+std::string
 map_fs_to_utf8(const char *path_fs);
 
 /**

src/PlaylistFile.cxx

@@ -248,13 +248,11 @@ LoadPlaylistFile(const char *utf8path, Error &error)
 
 			s = g_strconcat("file://", path.c_str(), NULL);
 		} else if (!uri_has_scheme(s)) {
-			char *path_utf8;
-
-			path_utf8 = map_fs_to_utf8(s);
-			if (path_utf8 == nullptr)
+			const auto path = map_fs_to_utf8(s);
+			if (path.empty())
 				continue;
 
-			s = path_utf8;
+			s = g_strdup(path.c_str());
 		} else {
 			const auto path = Path::ToUTF8(s);
 			if (path.empty())