util/Error: new error passing library

Replaces GLib's GError.

test/dump_playlist.cxx

@@ -30,6 +30,7 @@
 #include "PlaylistRegistry.hxx"
 #include "PlaylistPlugin.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -84,7 +85,8 @@ decoder_read(gcc_unused struct decoder *decoder,
 	     struct input_stream *is,
 	     void *buffer, size_t length)
 {
-	return input_stream_lock_read(is, buffer, length, NULL);
+	Error error;
+	return input_stream_lock_read(is, buffer, length, error);
 }
 
 void
@@ -139,7 +141,6 @@ int main(int argc, char **argv)
 {
 	const char *uri;
 	struct input_stream *is = NULL;
-	GError *error = NULL;
 	struct playlist_provider *playlist;
 	Song *song;
 
@@ -162,18 +163,18 @@ int main(int argc, char **argv)
 	/* initialize MPD */
 
 	config_global_init();
-	if (!ReadConfigFile(config_path, &error)) {
-		g_printerr("%s\n", error->message);
-		g_error_free(error);
+
+	Error error;
+	if (!ReadConfigFile(config_path, error)) {
+		g_printerr("%s\n", error.GetMessage());
 		return 1;
 	}
 
 	io_thread_init();
 	io_thread_start();
 
-	if (!input_stream_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_global_init(error)) {
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
@@ -189,12 +190,11 @@ int main(int argc, char **argv)
 	if (playlist == NULL) {
 		/* open the stream and wait until it becomes ready */
 
-		is = input_stream_open(uri, mutex, cond, &error);
+		is = input_stream_open(uri, mutex, cond, error);
 		if (is == NULL) {
-			if (error != NULL) {
-				g_warning("%s", error->message);
-				g_error_free(error);
-			} else
+			if (error.IsDefined())
+				g_warning("%s", error.GetMessage());
+			else
 				g_printerr("input_stream_open() failed\n");
 			return 2;
 		}