util/Error: new error passing library

Replaces GLib's GError.

256 files changed, 3271 insertions, 3373 deletions

diff --git a/Makefile.am b/Makefile.am
index 2c9ff41ec..2ad19c3c8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -91,7 +91,7 @@ src_mpd_SOURCES = \
 	src/CheckAudioFormat.cxx src/CheckAudioFormat.hxx \
 	src/AudioFormat.cxx src/AudioFormat.hxx \
 	src/AudioParser.cxx src/AudioParser.hxx \
-	src/protocol/Ack.hxx \
+	src/protocol/Ack.cxx src/protocol/Ack.hxx \
 	src/protocol/ArgParser.cxx src/protocol/ArgParser.hxx \
 	src/protocol/Result.cxx src/protocol/Result.hxx \
 	src/CommandError.cxx src/CommandError.hxx \
@@ -107,7 +107,7 @@ src_mpd_SOURCES = \
 	src/CommandLine.cxx src/CommandLine.hxx \
 	src/CrossFade.cxx src/CrossFade.hxx \
 	src/cue/CueParser.cxx src/cue/CueParser.hxx \
-	src/DecoderError.hxx \
+	src/DecoderError.cxx src/DecoderError.hxx \
 	src/DecoderThread.cxx src/DecoderThread.hxx \
 	src/DecoderCommand.hxx \
 	src/DecoderControl.cxx src/DecoderControl.hxx \
@@ -122,7 +122,7 @@ src_mpd_SOURCES = \
 	src/DatabasePrint.cxx src/DatabasePrint.hxx \
 	src/DatabaseQueue.cxx src/DatabaseQueue.hxx \
 	src/DatabasePlaylist.cxx src/DatabasePlaylist.hxx \
-	src/DatabaseError.hxx \
+	src/DatabaseError.cxx src/DatabaseError.hxx \
 	src/DatabaseLock.cxx src/DatabaseLock.hxx \
 	src/DatabaseSave.cxx src/DatabaseSave.hxx \
 	src/DatabasePlugin.hxx \
@@ -160,7 +160,6 @@ src_mpd_SOURCES = \
 	src/Listen.cxx src/Listen.hxx \
 	src/Log.cxx src/Log.hxx \
 	src/ls.cxx src/ls.hxx \
-	src/io_error.h \
 	src/IOThread.cxx src/IOThread.hxx \
 	src/Main.cxx src/Main.hxx \
 	src/Instance.cxx src/Instance.hxx \
@@ -178,7 +177,7 @@ src_mpd_SOURCES = \
 	src/PlayerThread.cxx src/PlayerThread.hxx \
 	src/PlayerControl.cxx src/PlayerControl.hxx \
 	src/Playlist.cxx \
-	src/PlaylistError.hxx \
+	src/PlaylistError.cxx src/PlaylistError.hxx \
 	src/PlaylistGlobal.cxx src/PlaylistGlobal.hxx \
 	src/PlaylistControl.cxx \
 	src/PlaylistEdit.cxx \
@@ -261,6 +260,7 @@ endif
 # Generic utility library
 
 libutil_a_SOURCES = \
+	src/util/Error.cxx src/util/Error.hxx \
 	src/util/ReusableArray.hxx \
 	src/util/StringUtil.cxx src/util/StringUtil.hxx \
 	src/util/Tokenizer.cxx src/util/Tokenizer.hxx \
@@ -284,7 +284,7 @@ libsystem_a_SOURCES = \
 	src/system/FatalError.cxx src/system/FatalError.hxx \
 	src/system/fd_util.c src/system/fd_util.h \
 	src/system/SocketUtil.cxx src/system/SocketUtil.hxx \
-	src/system/SocketError.hxx \
+	src/system/SocketError.cxx src/system/SocketError.hxx \
 	src/system/Resolver.cxx src/system/Resolver.hxx \
 	src/system/EventPipe.cxx src/system/EventPipe.hxx \
 	src/system/EventFD.cxx src/system/EventFD.hxx \
@@ -420,7 +420,7 @@ libconf_a_SOURCES = \
 	src/ConfigGlobal.cxx src/ConfigGlobal.hxx \
 	src/ConfigFile.cxx src/ConfigFile.hxx \
 	src/ConfigTemplates.cxx src/ConfigTemplates.hxx \
-	src/ConfigQuark.hxx \
+	src/ConfigError.cxx src/ConfigError.hxx \
 	src/ConfigOption.hxx
 
 # tag plugins
@@ -793,7 +793,7 @@ OUTPUT_API_SRC = \
 	src/OutputList.cxx src/OutputList.hxx \
 	src/OutputAll.cxx src/OutputAll.hxx \
 	src/OutputThread.cxx src/OutputThread.hxx \
-	src/OutputError.hxx \
+	src/OutputError.cxx src/OutputError.hxx \
 	src/OutputControl.cxx src/OutputControl.hxx \
 	src/OutputState.cxx src/OutputState.hxx \
 	src/OutputPrint.cxx src/OutputPrint.hxx \
@@ -1071,6 +1071,7 @@ test_read_conf_SOURCES = test/read_conf.cxx
 
 test_run_resolver_LDADD = \
 	libsystem.a \
+	libutil.a \
 	$(GLIB_LIBS)
 test_run_resolver_SOURCES = test/run_resolver.cxx
 
@@ -1082,6 +1083,7 @@ test_DumpDatabase_LDADD = \
 	libfs.a \
 	$(GLIB_LIBS)
 test_DumpDatabase_SOURCES = test/DumpDatabase.cxx \
+	src/DatabaseError.cxx \
 	src/DatabaseRegistry.cxx \
 	src/DatabaseSelection.cxx \
 	src/Directory.cxx src/DirectorySave.cxx \
@@ -1217,6 +1219,7 @@ test_read_tags_SOURCES = test/read_tags.cxx \
 if HAVE_ID3TAG
 test_dump_rva2_LDADD = \
 	$(ID3TAG_LIBS) \
+	libutil.a \
 	$(GLIB_LIBS)
 test_dump_rva2_SOURCES = test/dump_rva2.cxx \
 	src/riff.c src/aiff.c \
@@ -1296,6 +1299,7 @@ test_software_volume_SOURCES = test/software_volume.cxx \
 	src/AudioParser.cxx
 test_software_volume_LDADD = \
 	$(PCM_LIBS) \
+	libutil.a \
 	$(GLIB_LIBS)
 
 test_run_normalize_SOURCES = test/run_normalize.cxx \
@@ -1304,6 +1308,7 @@ test_run_normalize_SOURCES = test/run_normalize.cxx \
 	src/AudioParser.cxx \
 	src/AudioCompress/compress.c
 test_run_normalize_LDADD = \
+	libutil.a \
 	$(GLIB_LIBS)
 
 test_run_convert_SOURCES = test/run_convert.cxx \
@@ -1337,6 +1342,7 @@ test_run_output_SOURCES = test/run_output.cxx \
 	src/Timer.cxx \
 	src/Tag.cxx src/TagNames.c src/TagPool.cxx \
 	src/Page.cxx \
+	src/OutputError.cxx \
 	src/OutputInit.cxx src/OutputFinish.cxx src/OutputList.cxx \
 	src/OutputPlugin.cxx \
 	src/MixerControl.cxx \
diff --git a/src/AllCommands.cxx b/src/AllCommands.cxx
index 88eee150e..acd7d263e 100644
--- a/src/AllCommands.cxx
+++ b/src/AllCommands.cxx
@@ -32,6 +32,7 @@
 #include "protocol/Result.hxx"
 #include "Client.hxx"
 #include "util/Tokenizer.hxx"
+#include "util/Error.hxx"
 
 #ifdef ENABLE_SQLITE
 #include "StickerCommands.hxx"
@@ -315,7 +316,7 @@ command_checked_lookup(Client *client, unsigned permission,
 enum command_return
 command_process(Client *client, unsigned num, char *line)
 {
-	GError *error = NULL;
+	Error error;
 	char *argv[COMMAND_ARGV_MAX] = { NULL };
 	const struct command *cmd;
 	enum command_return ret = COMMAND_RETURN_ERROR;
@@ -325,17 +326,16 @@ command_process(Client *client, unsigned num, char *line)
 	/* get the command name (first word on the line) */
 
 	Tokenizer tokenizer(line);
-	argv[0] = tokenizer.NextWord(&error);
+	argv[0] = tokenizer.NextWord(error);
 	if (argv[0] == NULL) {
 		current_command = "";
 		if (tokenizer.IsEnd())
 			command_error(client, ACK_ERROR_UNKNOWN,
 				      "No command given");
-		else {
+		else
 			command_error(client, ACK_ERROR_UNKNOWN,
-				      "%s", error->message);
-			g_error_free(error);
-		}
+				      "%s", error.GetMessage());
+
 		current_command = NULL;
 
 		return COMMAND_RETURN_ERROR;
@@ -347,7 +347,7 @@ command_process(Client *client, unsigned num, char *line)
 
 	while (argc < COMMAND_ARGV_MAX &&
 	       (argv[argc] =
-		tokenizer.NextParam(&error)) != NULL)
+		tokenizer.NextParam(error)) != NULL)
 		++argc;
 
 	/* some error checks; we have to set current_command because
@@ -362,10 +362,8 @@ command_process(Client *client, unsigned num, char *line)
 	}
 
 	if (!tokenizer.IsEnd()) {
-		command_error(client, ACK_ERROR_ARG,
-			      "%s", error->message);
+		command_error(client, ACK_ERROR_ARG, "%s", error.GetMessage());
 		current_command = NULL;
-		g_error_free(error);
 		return COMMAND_RETURN_ERROR;
 	}
 
diff --git a/src/ArchiveFile.hxx b/src/ArchiveFile.hxx
index c7933ebd1..de0ecc1e8 100644
--- a/src/ArchiveFile.hxx
+++ b/src/ArchiveFile.hxx
@@ -20,6 +20,8 @@
 #ifndef MPD_ARCHIVE_FILE_HXX
 #define MPD_ARCHIVE_FILE_HXX
 
+class Error;
+
 class ArchiveFile {
 public:
 	const struct archive_plugin &plugin;
@@ -50,7 +52,7 @@ public:
 	 */
 	virtual input_stream *OpenStream(const char *path,
 					 Mutex &mutex, Cond &cond,
-					 GError **error_r) = 0;
+					 Error &error) = 0;
 };
 
 #endif
diff --git a/src/ArchivePlugin.cxx b/src/ArchivePlugin.cxx
index 7c5164220..dd2059c0f 100644
--- a/src/ArchivePlugin.cxx
+++ b/src/ArchivePlugin.cxx
@@ -17,27 +17,23 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "config.h"
 #include "ArchivePlugin.hxx"
 #include "ArchiveFile.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 
 ArchiveFile *
 archive_file_open(const struct archive_plugin *plugin, const char *path,
-		  GError **error_r)
+		  Error &error)
 {
 	assert(plugin != NULL);
 	assert(plugin->open != NULL);
 	assert(path != NULL);
-	assert(error_r == NULL || *error_r == NULL);
 
-	ArchiveFile *file = plugin->open(path, error_r);
-
-	if (file != NULL) {
-		assert(error_r == NULL || *error_r == NULL);
-	} else {
-		assert(error_r == NULL || *error_r != NULL);
-	}
+	ArchiveFile *file = plugin->open(path, error);
+	assert((file == nullptr) == error.IsDefined());
 
 	return file;
 }
diff --git a/src/ArchivePlugin.hxx b/src/ArchivePlugin.hxx
index 13952940f..ac8c1c8e3 100644
--- a/src/ArchivePlugin.hxx
+++ b/src/ArchivePlugin.hxx
@@ -22,11 +22,11 @@
 
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
-#include "gerror.h"
 
 struct input_stream;
 class ArchiveFile;
 class ArchiveVisitor;
+class Error;
 
 struct archive_plugin {
 	const char *name;
@@ -49,7 +49,7 @@ struct archive_plugin {
 	 * returns pointer to handle used is all operations with this archive
 	 * or NULL when opening fails
 	 */
-	ArchiveFile *(*open)(const char *path_fs, GError **error_r);
+	ArchiveFile *(*open)(const char *path_fs, Error &error);
 
 	/**
 	 * suffixes handled by this plugin.
@@ -60,6 +60,6 @@ struct archive_plugin {
 
 ArchiveFile *
 archive_file_open(const struct archive_plugin *plugin, const char *path,
-		  GError **error_r);
+		  Error &error);
 
 #endif
diff --git a/src/AudioConfig.cxx b/src/AudioConfig.cxx
index 9ead61afe..64c9d76d5 100644
--- a/src/AudioConfig.cxx
+++ b/src/AudioConfig.cxx
@@ -23,6 +23,7 @@
 #include "AudioParser.hxx"
 #include "conf.h"
 #include "mpd_error.h"
+#include "util/Error.hxx"
 
 static AudioFormat configured_audio_format;
 
@@ -37,15 +38,13 @@ getOutputAudioFormat(AudioFormat inAudioFormat)
 void initAudioConfig(void)
 {
 	const struct config_param *param = config_get_param(CONF_AUDIO_OUTPUT_FORMAT);
-	GError *error = NULL;
-	bool ret;
 
 	if (param == NULL)
 		return;
 
-	ret = audio_format_parse(configured_audio_format, param->value,
-				 true, &error);
-	if (!ret)
+	Error error;
+	if (!audio_format_parse(configured_audio_format, param->value,
+				true, error))
 		MPD_ERROR("error parsing line %i: %s",
-			  param->line, error->message);
+			  param->line, error.GetMessage());
 }
diff --git a/src/AudioParser.cxx b/src/AudioParser.cxx
index 4c345ca33..db6d1d8e8 100644
--- a/src/AudioParser.cxx
+++ b/src/AudioParser.cxx
@@ -26,24 +26,16 @@
 #include "AudioParser.hxx"
 #include "AudioFormat.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 #include "gcc.h"
 
 #include <assert.h>
 #include <string.h>
 #include <stdlib.h>
 
-/**
- * The GLib quark used for errors reported by this library.
- */
-static inline GQuark
-audio_parser_quark(void)
-{
-	return g_quark_from_static_string("audio_parser");
-}
-
 static bool
 parse_sample_rate(const char *src, bool mask, uint32_t *sample_rate_r,
-		  const char **endptr_r, GError **error_r)
+		  const char **endptr_r, Error &error)
 {
 	unsigned long value;
 	char *endptr;
@@ -56,10 +48,10 @@ parse_sample_rate(const char *src, bool mask, uint32_t *sample_rate_r,
 
 	value = strtoul(src, &endptr, 10);
 	if (endptr == src) {
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Failed to parse the sample rate");
+		error.Set(audio_format_domain,
+			  "Failed to parse the sample rate");
 		return false;
-	} else if (!audio_check_sample_rate(value, error_r))
+	} else if (!audio_check_sample_rate(value, error))
 		return false;
 
 	*sample_rate_r = value;
@@ -70,7 +62,7 @@ parse_sample_rate(const char *src, bool mask, uint32_t *sample_rate_r,
 static bool
 parse_sample_format(const char *src, bool mask,
 		    SampleFormat *sample_format_r,
-		    const char **endptr_r, GError **error_r)
+		    const char **endptr_r, Error &error)
 {
 	unsigned long value;
 	char *endptr;
@@ -96,8 +88,8 @@ parse_sample_format(const char *src, bool mask,
 
 	value = strtoul(src, &endptr, 10);
 	if (endptr == src) {
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Failed to parse the sample format");
+		error.Set(audio_format_domain,
+			  "Failed to parse the sample format");
 		return false;
 	}
 
@@ -123,8 +115,8 @@ parse_sample_format(const char *src, bool mask,
 		break;
 
 	default:
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Invalid sample format: %lu", value);
+		error.Format(audio_format_domain,
+			     "Invalid sample format: %lu", value);
 		return false;
 	}
 
@@ -137,7 +129,7 @@ parse_sample_format(const char *src, bool mask,
 
 static bool
 parse_channel_count(const char *src, bool mask, uint8_t *channels_r,
-		    const char **endptr_r, GError **error_r)
+		    const char **endptr_r, Error &error)
 {
 	unsigned long value;
 	char *endptr;
@@ -150,10 +142,10 @@ parse_channel_count(const char *src, bool mask, uint8_t *channels_r,
 
 	value = strtoul(src, &endptr, 10);
 	if (endptr == src) {
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Failed to parse the channel count");
+		error.Set(audio_format_domain,
+			  "Failed to parse the channel count");
 		return false;
-	} else if (!audio_check_channel_count(value, error_r))
+	} else if (!audio_check_channel_count(value, error))
 		return false;
 
 	*channels_r = value;
@@ -163,7 +155,7 @@ parse_channel_count(const char *src, bool mask, uint8_t *channels_r,
 
 bool
 audio_format_parse(AudioFormat &dest, const char *src,
-		   bool mask, GError **error_r)
+		   bool mask, Error &error)
 {
 	uint32_t rate;
 	SampleFormat sample_format;
@@ -178,12 +170,11 @@ audio_format_parse(AudioFormat &dest, const char *src,
 	rate = 0;
 #endif
 
-	if (!parse_sample_rate(src, mask, &rate, &src, error_r))
+	if (!parse_sample_rate(src, mask, &rate, &src, error))
 		return false;
 
 	if (*src++ != ':') {
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Sample format missing");
+		error.Set(audio_format_domain, "Sample format missing");
 		return false;
 	}
 
@@ -194,22 +185,21 @@ audio_format_parse(AudioFormat &dest, const char *src,
 	sample_format = SampleFormat::UNDEFINED;
 #endif
 
-	if (!parse_sample_format(src, mask, &sample_format, &src, error_r))
+	if (!parse_sample_format(src, mask, &sample_format, &src, error))
 		return false;
 
 	if (*src++ != ':') {
-		g_set_error(error_r, audio_parser_quark(), 0,
-			    "Channel count missing");
+		error.Set(audio_format_domain, "Channel count missing");
 		return false;
 	}
 
 	/* parse channel count */
 
-	if (!parse_channel_count(src, mask, &channels, &src, error_r))
+	if (!parse_channel_count(src, mask, &channels, &src, error))
 		return false;
 
 	if (*src != 0) {
-		g_set_error(error_r, audio_parser_quark(), 0,
+		error.Format(audio_format_domain,
 			    "Extra data after channel count: %s", src);
 		return false;
 	}
diff --git a/src/AudioParser.hxx b/src/AudioParser.hxx
index 14c26392c..cb6eb3ca0 100644
--- a/src/AudioParser.hxx
+++ b/src/AudioParser.hxx
@@ -25,9 +25,8 @@
 #ifndef MPD_AUDIO_PARSER_HXX
 #define MPD_AUDIO_PARSER_HXX
 
-#include "gerror.h"
-
 struct AudioFormat;
+class Error;
 
 /**
  * Parses a string in the form "SAMPLE_RATE:BITS:CHANNELS" into an
@@ -42,6 +41,6 @@ struct AudioFormat;
  */
 bool
 audio_format_parse(AudioFormat &dest, const char *src,
-		   bool mask, GError **error_r);
+		   bool mask, Error &error);
 
 #endif
diff --git a/src/CheckAudioFormat.cxx b/src/CheckAudioFormat.cxx
index fabffd56c..1f3ef4925 100644
--- a/src/CheckAudioFormat.cxx
+++ b/src/CheckAudioFormat.cxx
@@ -17,17 +17,22 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "config.h"
 #include "CheckAudioFormat.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 
+const Domain audio_format_domain("audio_format");
+
 bool
-audio_check_sample_rate(unsigned long sample_rate, GError **error_r)
+audio_check_sample_rate(unsigned long sample_rate, Error &error)
 {
 	if (!audio_valid_sample_rate(sample_rate)) {
-		g_set_error(error_r, audio_format_quark(), 0,
-			    "Invalid sample rate: %lu", sample_rate);
+		error.Format(audio_format_domain,
+			     "Invalid sample rate: %lu", sample_rate);
 		return false;
 	}
 
@@ -35,12 +40,12 @@ audio_check_sample_rate(unsigned long sample_rate, GError **error_r)
 }
 
 bool
-audio_check_sample_format(SampleFormat sample_format, GError **error_r)
+audio_check_sample_format(SampleFormat sample_format, Error &error)
 {
 	if (!audio_valid_sample_format(sample_format)) {
-		g_set_error(error_r, audio_format_quark(), 0,
-			    "Invalid sample format: %u",
-			    unsigned(sample_format));
+		error.Format(audio_format_domain,
+			     "Invalid sample format: %u",
+			     unsigned(sample_format));
 		return false;
 	}
 
@@ -48,11 +53,11 @@ audio_check_sample_format(SampleFormat sample_format, GError **error_r)
 }
 
 bool
-audio_check_channel_count(unsigned channels, GError **error_r)
+audio_check_channel_count(unsigned channels, Error &error)
 {
 	if (!audio_valid_channel_count(channels)) {
-		g_set_error(error_r, audio_format_quark(), 0,
-			    "Invalid channel count: %u", channels);
+		error.Format(audio_format_domain,
+			     "Invalid channel count: %u", channels);
 		return false;
 	}
 
@@ -62,11 +67,11 @@ audio_check_channel_count(unsigned channels, GError **error_r)
 bool
 audio_format_init_checked(AudioFormat &af, unsigned long sample_rate,
 			  SampleFormat sample_format, unsigned channels,
-			  GError **error_r)
+			  Error &error)
 {
-	if (audio_check_sample_rate(sample_rate, error_r) &&
-	    audio_check_sample_format(sample_format, error_r) &&
-	    audio_check_channel_count(channels, error_r)) {
+	if (audio_check_sample_rate(sample_rate, error) &&
+	    audio_check_sample_format(sample_format, error) &&
+	    audio_check_channel_count(channels, error)) {
 		af = AudioFormat(sample_rate, sample_format, channels);
 		assert(af.IsValid());
 		return true;
diff --git a/src/CheckAudioFormat.hxx b/src/CheckAudioFormat.hxx
index 7fbce7f98..df952adc7 100644
--- a/src/CheckAudioFormat.hxx
+++ b/src/CheckAudioFormat.hxx
@@ -22,26 +22,18 @@
 
 #include "AudioFormat.hxx"
 
-#include <glib.h>
+class Error;
 
-/**
- * The GLib quark used for errors reported by this library.
- */
-gcc_const
-static inline GQuark
-audio_format_quark(void)
-{
-	return g_quark_from_static_string("audio_format");
-}
+extern const class Domain audio_format_domain;
 
 bool
-audio_check_sample_rate(unsigned long sample_rate, GError **error_r);
+audio_check_sample_rate(unsigned long sample_rate, Error &error);
 
 bool
-audio_check_sample_format(SampleFormat sample_format, GError **error_r);
+audio_check_sample_format(SampleFormat sample_format, Error &error);
 
 bool
-audio_check_channel_count(unsigned sample_format, GError **error_r);
+audio_check_channel_count(unsigned sample_format, Error &error);
 
 /**
  * Wrapper for audio_format_init(), which checks all attributes.
@@ -49,6 +41,6 @@ audio_check_channel_count(unsigned sample_format, GError **error_r);
 bool
 audio_format_init_checked(AudioFormat &af, unsigned long sample_rate,
 			  SampleFormat sample_format, unsigned channels,
-			  GError **error_r);
+			  Error &error);
 
 #endif
diff --git a/src/ClientEvent.cxx b/src/ClientEvent.cxx
index fe0f079b6..90b4a7499 100644
--- a/src/ClientEvent.cxx
+++ b/src/ClientEvent.cxx
@@ -19,14 +19,14 @@
 
 #include "config.h"
 #include "ClientInternal.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
 void
-Client::OnSocketError(GError *error)
+Client::OnSocketError(Error &&error)
 {
-	g_warning("error on client %d: %s", num, error->message);
-	g_error_free(error);
+	g_warning("error on client %d: %s", num, error.GetMessage());
 
 	SetExpired();
 }
diff --git a/src/ClientFile.cxx b/src/ClientFile.cxx
index 69bc465b4..a460310be 100644
--- a/src/ClientFile.cxx
+++ b/src/ClientFile.cxx
@@ -21,9 +21,10 @@
 #include "ClientFile.hxx"
 #include "Client.hxx"
 #include "protocol/Ack.hxx"
-#include "io_error.h"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -32,14 +33,13 @@
 
 bool
 client_allow_file(const Client *client, const Path &path_fs,
-		  GError **error_r)
+		  Error &error)
 {
 #ifdef WIN32
 	(void)client;
 	(void)path_fs;
 
-	g_set_error(error_r, ack_quark(), ACK_ERROR_PERMISSION,
-		    "Access denied");
+	error.Set(ack_domain, ACK_ERROR_PERMISSION, "Access denied");
 	return false;
 #else
 	const int uid = client_get_uid(client);
@@ -50,21 +50,19 @@ client_allow_file(const Client *client, const Path &path_fs,
 
 	if (uid <= 0) {
 		/* unauthenticated client */
-		g_set_error(error_r, ack_quark(), ACK_ERROR_PERMISSION,
-			    "Access denied");
+		error.Set(ack_domain, ACK_ERROR_PERMISSION, "Access denied");
 		return false;
 	}
 
 	struct stat st;
 	if (!StatFile(path_fs, st)) {
-		set_error_errno(error_r);
+		error.SetErrno();
 		return false;
 	}
 
 	if (st.st_uid != (uid_t)uid && (st.st_mode & 0444) != 0444) {
 		/* client is not owner */
-		g_set_error(error_r, ack_quark(), ACK_ERROR_PERMISSION,
-			    "Access denied");
+		error.Set(ack_domain, ACK_ERROR_PERMISSION, "Access denied");
 		return false;
 	}
 
diff --git a/src/ClientFile.hxx b/src/ClientFile.hxx
index 21db4d3ad..68d79ca08 100644
--- a/src/ClientFile.hxx
+++ b/src/ClientFile.hxx
@@ -20,10 +20,9 @@
 #ifndef MPD_CLIENT_FILE_HXX
 #define MPD_CLIENT_FILE_HXX
 
-#include "gerror.h"
-
 class Client;
 class Path;
+class Error;
 
 /**
  * Is this client allowed to use the specified local file?
@@ -37,6 +36,6 @@ class Path;
  */
 bool
 client_allow_file(const Client *client, const Path &path_fs,
-		  GError **error_r);
+		  Error &error);
 
 #endif
diff --git a/src/ClientInternal.hxx b/src/ClientInternal.hxx
index 8dd839cc2..ca2669db0 100644
--- a/src/ClientInternal.hxx
+++ b/src/ClientInternal.hxx
@@ -116,7 +116,7 @@ private:
 	/* virtual methods from class BufferedSocket */
 	virtual InputResult OnSocketInput(const void *data,
 					  size_t length) override;
-	virtual void OnSocketError(GError *error) override;
+	virtual void OnSocketError(Error &&error) override;
 	virtual void OnSocketClosed() override;
 
 	/* virtual methods from class TimeoutMonitor */
diff --git a/src/ClientNew.cxx b/src/ClientNew.cxx
index dd5aba318..bc12bbf6a 100644
--- a/src/ClientNew.cxx
+++ b/src/ClientNew.cxx
@@ -25,6 +25,7 @@
 #include "system/fd_util.h"
 #include "system/Resolver.hxx"
 #include "Permission.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <sys/types.h>
@@ -70,7 +71,8 @@ client_new(EventLoop &loop, Partition &partition,
 
 #ifdef HAVE_LIBWRAP
 	if (sa->sa_family != AF_UNIX) {
-		char *hostaddr = sockaddr_to_string(sa, sa_length, NULL);
+		char *hostaddr = sockaddr_to_string(sa, sa_length,
+						    IgnoreError());
 		const char *progname = g_get_prgname();
 
 		struct request_info req;
@@ -107,7 +109,7 @@ client_new(EventLoop &loop, Partition &partition,
 
 	client_list.Add(*client);
 
-	remote = sockaddr_to_string(sa, sa_length, NULL);
+	remote = sockaddr_to_string(sa, sa_length, IgnoreError());
 	g_log(G_LOG_DOMAIN, LOG_LEVEL_SECURE,
 	      "[%u] opened from %s", client->num, remote);
 	g_free(remote);
diff --git a/src/ClientProcess.cxx b/src/ClientProcess.cxx
index bcd20d1b7..caaef487b 100644
--- a/src/ClientProcess.cxx
+++ b/src/ClientProcess.cxx
@@ -22,6 +22,8 @@
 #include "protocol/Result.hxx"
 #include "AllCommands.hxx"
 
+#include <glib.h>
+
 #include <string.h>
 
 #define CLIENT_LIST_MODE_BEGIN "command_list_begin"
diff --git a/src/CommandError.cxx b/src/CommandError.cxx
index 7a33761ae..c9b6c2deb 100644
--- a/src/CommandError.cxx
+++ b/src/CommandError.cxx
@@ -20,8 +20,10 @@
 #include "config.h"
 #include "CommandError.hxx"
 #include "DatabaseError.hxx"
-#include "io_error.h"
 #include "protocol/Result.hxx"
+#include "util/Error.hxx"
+
+#include <glib.h>
 
 #include <assert.h>
 #include <errno.h>
@@ -85,50 +87,38 @@ print_playlist_result(Client *client, enum playlist_result result)
 	return COMMAND_RETURN_ERROR;
 }
 
-/**
- * Send the GError to the client and free the GError.
- */
 enum command_return
-print_error(Client *client, GError *error)
+print_error(Client *client, const Error &error)
 {
 	assert(client != NULL);
-	assert(error != NULL);
+	assert(error.IsDefined());
 
-	g_warning("%s", error->message);
+	g_warning("%s", error.GetMessage());
 
-	if (error->domain == playlist_quark()) {
-		enum playlist_result result = (playlist_result)error->code;
-		g_error_free(error);
-		return print_playlist_result(client, result);
-	} else if (error->domain == ack_quark()) {
-		command_error(client, (ack)error->code, "%s", error->message);
-		g_error_free(error);
+	if (error.IsDomain(playlist_domain)) {
+		return print_playlist_result(client,
+					     playlist_result(error.GetCode()));
+	} else if (error.IsDomain(ack_domain)) {
+		command_error(client, (ack)error.GetCode(),
+			      "%s", error.GetMessage());
 		return COMMAND_RETURN_ERROR;
-	} else if (error->domain == db_quark()) {
-		switch ((enum db_error)error->code) {
+	} else if (error.IsDomain(db_domain)) {
+		switch ((enum db_error)error.GetCode()) {
 		case DB_DISABLED:
 			command_error(client, ACK_ERROR_NO_EXIST, "%s",
-				      error->message);
-			g_error_free(error);
+				      error.GetMessage());
 			return COMMAND_RETURN_ERROR;
 
 		case DB_NOT_FOUND:
-			g_error_free(error);
 			command_error(client, ACK_ERROR_NO_EXIST, "Not found");
 			return COMMAND_RETURN_ERROR;
 		}
-	} else if (error->domain == errno_quark()) {
+	} else if (error.IsDomain(errno_domain)) {
 		command_error(client, ACK_ERROR_SYSTEM, "%s",
-			      g_strerror(error->code));
-		g_error_free(error);
-		return COMMAND_RETURN_ERROR;
-	} else if (error->domain == g_file_error_quark()) {
-		command_error(client, ACK_ERROR_SYSTEM, "%s", error->message);
-		g_error_free(error);
+			      g_strerror(error.GetCode()));
 		return COMMAND_RETURN_ERROR;
 	}
 
-	g_error_free(error);
 	command_error(client, ACK_ERROR_UNKNOWN, "error");
 	return COMMAND_RETURN_ERROR;
 }
diff --git a/src/CommandError.hxx b/src/CommandError.hxx
index 04d0aeb21..06f76390a 100644
--- a/src/CommandError.hxx
+++ b/src/CommandError.hxx
@@ -22,17 +22,17 @@
 
 #include "command.h"
 #include "PlaylistError.hxx"
-#include "gerror.h"
 
 class Client;
+class Error;
 
 enum command_return
 print_playlist_result(Client *client, enum playlist_result result);
 
 /**
- * Send the GError to the client and free the GError.
+ * Send the #Error to the client.
  */
 enum command_return
-print_error(Client *client, GError *error);
+print_error(Client *client, const Error &error);
 
 #endif
diff --git a/src/CommandLine.cxx b/src/CommandLine.cxx
index 89575a13f..71395fd0c 100644
--- a/src/CommandLine.cxx
+++ b/src/CommandLine.cxx
@@ -33,6 +33,8 @@
 #include "mpd_error.h"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #ifdef ENABLE_ENCODER
 #include "EncoderList.hxx"
@@ -57,11 +59,7 @@
 #define USER_CONFIG_FILE_LOCATION_XDG	"mpd/mpd.conf"
 #endif
 
-static GQuark
-cmdline_quark(void)
-{
-	return g_quark_from_static_string("cmdline");
-}
+static constexpr Domain cmdline_domain("cmdline");
 
 gcc_noreturn
 static void version(void)
@@ -147,9 +145,8 @@ PathBuildChecked(const Path &a, Path::const_pointer b)
 
 bool
 parse_cmdline(int argc, char **argv, struct options *options,
-	      GError **error_r)
+	      Error &error)
 {
-	GError *error = NULL;
 	GOptionContext *context;
 	bool ret;
 	static gboolean option_version,
@@ -183,11 +180,12 @@ parse_cmdline(int argc, char **argv, struct options *options,
 
 	g_option_context_set_summary(context, summary);
 
-	ret = g_option_context_parse(context, &argc, &argv, &error);
+	GError *gerror = nullptr;
+	ret = g_option_context_parse(context, &argc, &argv, &gerror);
 	g_option_context_free(context);
 
 	if (!ret)
-		MPD_ERROR("option parsing failed: %s\n", error->message);
+		MPD_ERROR("option parsing failed: %s\n", gerror->message);
 
 	if (option_version)
 		version();
@@ -208,7 +206,7 @@ parse_cmdline(int argc, char **argv, struct options *options,
 		Path path = PathBuildChecked(Path::FromUTF8(g_get_user_config_dir()),
 					     CONFIG_FILE_LOCATION);
 		if (!path.IsNull() && FileExists(path))
-			return ReadConfigFile(path, error_r);
+			return ReadConfigFile(path, error);
 
 		const char *const*system_config_dirs =
 			g_get_system_config_dirs();
@@ -217,38 +215,36 @@ parse_cmdline(int argc, char **argv, struct options *options,
 			path = PathBuildChecked(Path::FromUTF8(system_config_dirs[i]),
 						CONFIG_FILE_LOCATION);
 			if (!path.IsNull() && FileExists(path))
-				return ReadConfigFile(path, error_r);
+				return ReadConfigFile(path, error);
 		}
 #else /* G_OS_WIN32 */
 		Path path = PathBuildChecked(Path::FromUTF8(g_get_user_config_dir()),
 					     USER_CONFIG_FILE_LOCATION_XDG);
 		if (!path.IsNull() && FileExists(path))
-			return ReadConfigFile(path, error_r);
+			return ReadConfigFile(path, error);
 
 		path = PathBuildChecked(Path::FromUTF8(g_get_home_dir()),
 					     USER_CONFIG_FILE_LOCATION1);
 		if (!path.IsNull() && FileExists(path))
-			return ReadConfigFile(path, error_r);
+			return ReadConfigFile(path, error);
 
 		path = PathBuildChecked(Path::FromUTF8(g_get_home_dir()),
 					USER_CONFIG_FILE_LOCATION2);
 		if (!path.IsNull() && FileExists(path))
-			return ReadConfigFile(path, error_r);
+			return ReadConfigFile(path, error);
 
 		path = Path::FromUTF8(SYSTEM_CONFIG_FILE_LOCATION);
 		if (!path.IsNull() && FileExists(path))
-			return ReadConfigFile(path, error_r);
+			return ReadConfigFile(path, error);
 #endif
 
-		g_set_error(error_r, cmdline_quark(), 0,
-			    "No configuration file found");
+		error.Set(cmdline_domain, "No configuration file found");
 		return false;
 	} else if (argc == 2) {
 		/* specified configuration file */
-		return ReadConfigFile(Path::FromFS(argv[1]), error_r);
+		return ReadConfigFile(Path::FromFS(argv[1]), error);
 	} else {
-		g_set_error(error_r, cmdline_quark(), 0,
-			    "too many arguments");
+		error.Set(cmdline_domain, "too many arguments");
 		return false;
 	}
 }
diff --git a/src/CommandLine.hxx b/src/CommandLine.hxx
index 7a8731f82..214150eae 100644
--- a/src/CommandLine.hxx
+++ b/src/CommandLine.hxx
@@ -22,6 +22,8 @@
 
 #include <glib.h>
 
+class Error;
+
 struct options {
 	gboolean kill;
 	gboolean daemon;
@@ -31,6 +33,6 @@ struct options {
 
 bool
 parse_cmdline(int argc, char **argv, struct options *options,
-	      GError **error_r);
+	      Error &error);
 
 #endif
diff --git a/src/ConfigData.cxx b/src/ConfigData.cxx
index 2ed8e2f3b..84a726799 100644
--- a/src/ConfigData.cxx
+++ b/src/ConfigData.cxx
@@ -21,6 +21,7 @@
 #include "ConfigData.hxx"
 #include "ConfigParser.hxx"
 #include "ConfigPath.hxx"
+#include "util/Error.hxx"
 #include "fs/Path.hxx"
 #include "system/FatalError.hxx"
 #include "mpd_error.h"
@@ -97,10 +98,9 @@ config_param::DupBlockString(const char *name, const char *default_value) const
 
 Path
 config_param::GetBlockPath(const char *name, const char *default_value,
-			   GError **error_r) const
+			   Error &error) const
 {
-	assert(error_r != nullptr);
-	assert(*error_r == nullptr);
+	assert(!error.IsDefined());
 
 	int line2 = line;
 	const char *s;
@@ -112,19 +112,18 @@ config_param::GetBlockPath(const char *name, const char *default_value,
 	} else
 		s = default_value;
 
-	Path path = ParsePath(s, error_r);
+	Path path = ParsePath(s, error);
 	if (gcc_unlikely(path.IsNull()))
-		g_prefix_error(error_r,
-			       "Invalid path in \"%s\" at line %i: ",
-			       name, line2);
+		error.FormatPrefix("Invalid path in \"%s\" at line %i: ",
+				   name, line2);
 
 	return path;
 }
 
 Path
-config_param::GetBlockPath(const char *name, GError **error_r) const
+config_param::GetBlockPath(const char *name, Error &error) const
 {
-	return GetBlockPath(name, nullptr, error_r);
+	return GetBlockPath(name, nullptr, error);
 }
 
 unsigned
diff --git a/src/ConfigData.hxx b/src/ConfigData.hxx
index a7a733e4d..19613c610 100644
--- a/src/ConfigData.hxx
+++ b/src/ConfigData.hxx
@@ -21,7 +21,6 @@
 #define MPD_CONFIG_DATA_HXX
 
 #include "ConfigOption.hxx"
-#include "gerror.h"
 #include "gcc.h"
 
 #include <string>
@@ -29,6 +28,7 @@
 #include <vector>
 
 class Path;
+class Error;
 
 struct block_param {
 	std::string name;
@@ -113,9 +113,9 @@ struct config_param {
 	 * specified block.
 	 */
 	Path GetBlockPath(const char *name, const char *default_value,
-			  GError **error_r) const;
+			  Error &error) const;
 
-	Path GetBlockPath(const char *name, GError **error_r) const;
+	Path GetBlockPath(const char *name, Error &error) const;
 
 	gcc_pure
 	unsigned GetBlockValue(const char *name, unsigned default_value) const;
diff --git a/src/ConfigError.cxx b/src/ConfigError.cxx
new file mode 100644
index 000000000..bd529e670
--- /dev/null
+++ b/src/ConfigError.cxx
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2003-2013 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 "ConfigError.hxx"
+#include "util/Domain.hxx"
+
+const Domain config_domain("config");
diff --git a/src/ConfigQuark.hxx b/src/ConfigError.hxx
index 4d9be33b1..a8917d7d1 100644
--- a/src/ConfigQuark.hxx
+++ b/src/ConfigError.hxx
@@ -17,22 +17,9 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef MPD_CONFIG_QUARK_HXX
-#define MPD_CONFIG_QUARK_HXX
+#ifndef MPD_CONFIG_ERROR_HXX
+#define MPD_CONFIG_ERROR_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
-
-/**
- * A GQuark for GError instances, resulting from malformed
- * configuration.
- */
-gcc_const
-static inline GQuark
-config_quark(void)
-{
-	return g_quark_from_static_string("config");
-}
+extern const class Domain config_domain;
 
 #endif
diff --git a/src/ConfigFile.cxx b/src/ConfigFile.cxx
index 2573f66e5..595d6a1bf 100644
--- a/src/ConfigFile.cxx
+++ b/src/ConfigFile.cxx
@@ -19,12 +19,14 @@
 
 #include "config.h"
 #include "ConfigFile.hxx"
-#include "ConfigQuark.hxx"
+#include "ConfigError.hxx"
 #include "ConfigData.hxx"
 #include "ConfigTemplates.hxx"
 #include "conf.h"
 #include "util/Tokenizer.hxx"
 #include "util/StringUtil.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
 
@@ -42,42 +44,41 @@
 
 #define CONF_COMMENT		'#'
 
+static constexpr Domain config_file_domain("config_file");
+
 static bool
 config_read_name_value(struct config_param *param, char *input, unsigned line,
-		       GError **error_r)
+		       Error &error)
 {
 	Tokenizer tokenizer(input);
 
-	const char *name = tokenizer.NextWord(error_r);
+	const char *name = tokenizer.NextWord(error);
 	if (name == NULL) {
 		assert(!tokenizer.IsEnd());
 		return false;
 	}
 
-	const char *value = tokenizer.NextString(error_r);
+	const char *value = tokenizer.NextString(error);
 	if (value == NULL) {
 		if (tokenizer.IsEnd()) {
-			assert(error_r == NULL || *error_r == NULL);
-			g_set_error(error_r, config_quark(), 0,
-				    "Value missing");
+			error.Set(config_file_domain, "Value missing");
 		} else {
-			assert(error_r == NULL || *error_r != NULL);
+			assert(error.IsDefined());
 		}
 
 		return false;
 	}
 
 	if (!tokenizer.IsEnd() && tokenizer.CurrentChar() != CONF_COMMENT) {
-		g_set_error(error_r, config_quark(), 0,
-			    "Unknown tokens after value");
+		error.Set(config_file_domain, "Unknown tokens after value");
 		return false;
 	}
 
 	const struct block_param *bp = param->GetBlockParam(name);
 	if (bp != NULL) {
-		g_set_error(error_r, config_quark(), 0,
-			    "\"%s\" is duplicate, first defined on line %i",
-			    name, bp->line);
+		error.Format(config_file_domain,
+			     "\"%s\" is duplicate, first defined on line %i",
+			     name, bp->line);
 		return false;
 	}
 
@@ -86,10 +87,9 @@ config_read_name_value(struct config_param *param, char *input, unsigned line,
 }
 
 static struct config_param *
-config_read_block(FILE *fp, int *count, char *string, GError **error_r)
+config_read_block(FILE *fp, int *count, char *string, Error &error)
 {
 	struct config_param *ret = new config_param(*count);
-	GError *error = NULL;
 
 	while (true) {
 		char *line;
@@ -97,8 +97,8 @@ config_read_block(FILE *fp, int *count, char *string, GError **error_r)
 		line = fgets(string, MAX_STRING_SIZE, fp);
 		if (line == NULL) {
 			delete ret;
-			g_set_error(error_r, config_quark(), 0,
-				    "Expected '}' before end-of-file");
+			error.Set(config_file_domain,
+				  "Expected '}' before end-of-file");
 			return NULL;
 		}
 
@@ -114,9 +114,9 @@ config_read_block(FILE *fp, int *count, char *string, GError **error_r)
 			line = strchug_fast(line + 1);
 			if (*line != 0 && *line != CONF_COMMENT) {
 				delete ret;
-				g_set_error(error_r, config_quark(), 0,
-					    "line %i: Unknown tokens after '}'",
-					    *count);
+				error.Format(config_file_domain,
+					     "line %i: Unknown tokens after '}'",
+					     *count);
 				return nullptr;
 			}
 
@@ -125,11 +125,10 @@ config_read_block(FILE *fp, int *count, char *string, GError **error_r)
 
 		/* parse name and value */
 
-		if (!config_read_name_value(ret, line, *count, &error)) {
+		if (!config_read_name_value(ret, line, *count, error)) {
 			assert(*line != 0);
 			delete ret;
-			g_propagate_prefixed_error(error_r, error,
-						   "line %i: ", *count);
+			error.FormatPrefix("line %i: ", *count);
 			return NULL;
 		}
 	}
@@ -149,7 +148,7 @@ Append(config_param *&head, config_param *p)
 }
 
 static bool
-ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
+ReadConfigFile(ConfigData &config_data, FILE *fp, Error &error)
 {
 	assert(fp != nullptr);
 
@@ -160,7 +159,6 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 	while (fgets(string, MAX_STRING_SIZE, fp)) {
 		char *line;
 		const char *name, *value;
-		GError *error = NULL;
 
 		count++;
 
@@ -172,11 +170,10 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 		   by either the value or '{' */
 
 		Tokenizer tokenizer(line);
-		name = tokenizer.NextWord(&error);
+		name = tokenizer.NextWord(error);
 		if (name == NULL) {
 			assert(!tokenizer.IsEnd());
-			g_propagate_prefixed_error(error_r, error,
-						   "line %i: ", count);
+			error.FormatPrefix("line %i: ", count);
 			return false;
 		}
 
@@ -185,9 +182,9 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 
 		const ConfigOption o = ParseConfigOptionName(name);
 		if (o == CONF_MAX) {
-			g_set_error(error_r, config_quark(), 0,
-				    "unrecognized parameter in config file at "
-				    "line %i: %s\n", count, name);
+			error.Format(config_file_domain,
+				     "unrecognized parameter in config file at "
+				     "line %i: %s\n", count, name);
 			return false;
 		}
 
@@ -197,10 +194,10 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 
 		if (head != nullptr && !option.repeatable) {
 			param = head;
-			g_set_error(error_r, config_quark(), 0,
-				    "config parameter \"%s\" is first defined "
-				    "on line %i and redefined on line %i\n",
-				    name, param->line, count);
+			error.Format(config_file_domain,
+				     "config parameter \"%s\" is first defined "
+				     "on line %i and redefined on line %i\n",
+				     name, param->line, count);
 			return false;
 		}
 
@@ -210,47 +207,43 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 			/* it's a block, call config_read_block() */
 
 			if (tokenizer.CurrentChar() != '{') {
-				g_set_error(error_r, config_quark(), 0,
-					    "line %i: '{' expected", count);
+				error.Format(config_file_domain,
+					     "line %i: '{' expected", count);
 				return false;
 			}
 
 			line = strchug_fast(tokenizer.Rest() + 1);
 			if (*line != 0 && *line != CONF_COMMENT) {
-				g_set_error(error_r, config_quark(), 0,
-					    "line %i: Unknown tokens after '{'",
-					    count);
+				error.Format(config_file_domain,
+					     "line %i: Unknown tokens after '{'",
+					     count);
 				return false;
 			}
 
-			param = config_read_block(fp, &count, string, error_r);
+			param = config_read_block(fp, &count, string, error);
 			if (param == NULL) {
 				return false;
 			}
 		} else {
 			/* a string value */
 
-			value = tokenizer.NextString(&error);
+			value = tokenizer.NextString(error);
 			if (value == NULL) {
 				if (tokenizer.IsEnd())
-					g_set_error(error_r, config_quark(), 0,
-						    "line %i: Value missing",
-						    count);
-				else {
-					g_set_error(error_r, config_quark(), 0,
-						    "line %i: %s", count,
-						    error->message);
-					g_error_free(error);
-				}
+					error.Format(config_file_domain,
+						     "line %i: Value missing",
+						     count);
+				else
+					error.FormatPrefix("line %i: ", count);
 
 				return false;
 			}
 
 			if (!tokenizer.IsEnd() &&
 			    tokenizer.CurrentChar() != CONF_COMMENT) {
-				g_set_error(error_r, config_quark(), 0,
-					    "line %i: Unknown tokens after value",
-					    count);
+				error.Format(config_file_domain,
+					     "line %i: Unknown tokens after value",
+					     count);
 				return false;
 			}
 
@@ -264,7 +257,7 @@ ReadConfigFile(ConfigData &config_data, FILE *fp, GError **error_r)
 }
 
 bool
-ReadConfigFile(ConfigData &config_data, const Path &path, GError **error_r)
+ReadConfigFile(ConfigData &config_data, const Path &path, Error &error)
 {
 	assert(!path.IsNull());
 	const std::string path_utf8 = path.ToUTF8();
@@ -273,13 +266,11 @@ ReadConfigFile(ConfigData &config_data, const Path &path, GError **error_r)
 
 	FILE *fp = FOpen(path, FOpenMode::ReadText);
 	if (fp == nullptr) {
-		g_set_error(error_r, config_quark(), errno,
-			    "Failed to open %s: %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Failed to open %s", path_utf8.c_str());
 		return false;
 	}
 
-	bool result = ReadConfigFile(config_data, fp, error_r);
+	bool result = ReadConfigFile(config_data, fp, error);
 	fclose(fp);
 	return result;
 }
diff --git a/src/ConfigFile.hxx b/src/ConfigFile.hxx
index 49c0d31ec..0dca65567 100644
--- a/src/ConfigFile.hxx
+++ b/src/ConfigFile.hxx
@@ -20,12 +20,11 @@
 #ifndef MPD_CONFIG_FILE_HXX
 #define MPD_CONFIG_FILE_HXX
 
-#include "gerror.h"
-
+class Error;
 class Path;
 struct ConfigData;
 
 bool
-ReadConfigFile(ConfigData &data, const Path &path, GError **error_r);
+ReadConfigFile(ConfigData &data, const Path &path, Error &error);
 
 #endif
diff --git a/src/ConfigGlobal.cxx b/src/ConfigGlobal.cxx
index 1f89a1283..0bf2b4433 100644
--- a/src/ConfigGlobal.cxx
+++ b/src/ConfigGlobal.cxx
@@ -24,6 +24,7 @@
 #include "ConfigFile.hxx"
 #include "ConfigPath.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 #include "mpd_error.h"
 
 #include <glib.h>
@@ -47,9 +48,9 @@ void config_global_init(void)
 }
 
 bool
-ReadConfigFile(const Path &path, GError **error_r)
+ReadConfigFile(const Path &path, Error &error)
 {
-	return ReadConfigFile(config_data, path, error_r);
+	return ReadConfigFile(config_data, path, error);
 }
 
 static void
@@ -98,20 +99,16 @@ config_get_string(ConfigOption option, const char *default_value)
 }
 
 Path
-config_get_path(ConfigOption option, GError **error_r)
+config_get_path(ConfigOption option, Error &error)
 {
-	assert(error_r != NULL);
-	assert(*error_r == NULL);
-
 	const struct config_param *param = config_get_param(option);
 	if (param == NULL)
 		return Path::Null();
 
-	Path path = ParsePath(param->value, error_r);
+	Path path = ParsePath(param->value, error);
 	if (gcc_unlikely(path.IsNull()))
-		g_prefix_error(error_r,
-			       "Invalid path at line %i: ",
-			       param->line);
+		error.FormatPrefix("Invalid path at line %i: ",
+				   param->line);
 
 	return path;
 }
diff --git a/src/ConfigGlobal.hxx b/src/ConfigGlobal.hxx
index aaae82bd1..efa5e0604 100644
--- a/src/ConfigGlobal.hxx
+++ b/src/ConfigGlobal.hxx
@@ -21,7 +21,6 @@
 #define MPD_CONFIG_GLOBAL_HXX
 
 #include "ConfigOption.hxx"
-#include "gerror.h"
 #include "gcc.h"
 
 #include <stdbool.h>
@@ -30,6 +29,7 @@
 #define DEFAULT_PLAYLIST_MAX_LENGTH (1024*16)
 #define DEFAULT_PLAYLIST_SAVE_ABSOLUTE_PATHS false
 
+class Error;
 class Path;
 
 void config_global_init(void);
@@ -42,7 +42,7 @@ void config_global_finish(void);
 void config_global_check(void);
 
 bool
-ReadConfigFile(const Path &path, GError **error_r);
+ReadConfigFile(const Path &path, Error &error);
 
 /* don't free the returned value
    set _last_ to NULL to get first entry */
@@ -76,7 +76,7 @@ config_get_string(enum ConfigOption option, const char *default_value);
  * could not be parsed, returns Path::Null() and sets the error.
  */
 Path
-config_get_path(enum ConfigOption option, GError **error_r);
+config_get_path(enum ConfigOption option, Error &error);
 
 gcc_pure
 unsigned
diff --git a/src/ConfigPath.cxx b/src/ConfigPath.cxx
index b90956a2a..9c5945a32 100644
--- a/src/ConfigPath.cxx
+++ b/src/ConfigPath.cxx
@@ -20,6 +20,8 @@
 #include "config.h"
 #include "ConfigPath.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "conf.h"
 
 #include <glib.h>
@@ -46,31 +48,25 @@
 #include <windows.h>
 #endif
 
-gcc_const
-static inline GQuark
-parse_path_quark(void)
-{
-	return g_quark_from_static_string("path");
-}
+static constexpr Domain path_domain("path");
 
 Path
-ParsePath(const char *path, GError **error_r)
+ParsePath(const char *path, Error &error)
 {
 	assert(path != nullptr);
-	assert(error_r == nullptr || *error_r == nullptr);
 
 	Path path2 = Path::FromUTF8(path);
 	if (path2.IsNull()) {
-		g_set_error(error_r, parse_path_quark(), 0,
-			    "Failed to convert path to file system charset: %s",
-			    path);
+		error.Format(path_domain,
+			     "Failed to convert path to file system charset: %s",
+			     path);
 		return Path::Null();
 	}
 
 #ifndef WIN32
 	if (!g_path_is_absolute(path) && path[0] != '~') {
-		g_set_error(error_r, parse_path_quark(), 0,
-			    "not an absolute path: %s", path);
+		error.Format(path_domain,
+			     "not an absolute path: %s", path);
 		return Path::Null();
 	} else if (path[0] == '~') {
 		const char *home;
@@ -80,8 +76,8 @@ ParsePath(const char *path, GError **error_r)
 			if (user != nullptr) {
 				struct passwd *passwd = getpwnam(user);
 				if (!passwd) {
-					g_set_error(error_r, parse_path_quark(), 0,
-						    "no such user: %s", user);
+					error.Format(path_domain,
+						     "no such user: %s", user);
 					return Path::Null();
 				}
 
@@ -89,9 +85,9 @@ ParsePath(const char *path, GError **error_r)
 			} else {
 				home = g_get_home_dir();
 				if (home == nullptr) {
-					g_set_error_literal(error_r, parse_path_quark(), 0,
-							    "problems getting home "
-							    "for current user");
+					error.Set(path_domain,
+						  "problems getting home "
+						  "for current user");
 					return Path::Null();
 				}
 			}
@@ -107,8 +103,8 @@ ParsePath(const char *path, GError **error_r)
 
 			struct passwd *passwd = getpwnam(user);
 			if (!passwd) {
-				g_set_error(error_r, parse_path_quark(), 0,
-					    "no such user: %s", user);
+				error.Format(path_domain,
+					     "no such user: %s", user);
 				g_free(user);
 				return Path::Null();
 			}
diff --git a/src/ConfigPath.hxx b/src/ConfigPath.hxx
index 79da04bb1..7bc1d732c 100644
--- a/src/ConfigPath.hxx
+++ b/src/ConfigPath.hxx
@@ -20,11 +20,10 @@
 #ifndef MPD_CONFIG_PATH_HXX
 #define MPD_CONFIG_PATH_HXX
 
-#include "gerror.h"
-
 class Path;
+class Error;
 
 Path
-ParsePath(const char *path, GError **error_r);
+ParsePath(const char *path, Error &error);
 
 #endif
diff --git a/src/DatabaseCommands.cxx b/src/DatabaseCommands.cxx
index f179713d4..abed30564 100644
--- a/src/DatabaseCommands.cxx
+++ b/src/DatabaseCommands.cxx
@@ -27,6 +27,7 @@
 #include "ClientInternal.hxx"
 #include "Tag.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "SongFilter.hxx"
 #include "protocol/Result.hxx"
 
@@ -46,8 +47,8 @@ handle_lsinfo2(Client *client, int argc, char *argv[])
 
 	const DatabaseSelection selection(uri, false);
 
-	GError *error = NULL;
-	if (!db_selection_print(client, selection, true, &error))
+	Error error;
+	if (!db_selection_print(client, selection, true, error))
 		return print_error(client, error);
 
 	return COMMAND_RETURN_OK;
@@ -64,8 +65,8 @@ handle_match(Client *client, int argc, char *argv[], bool fold_case)
 
 	const DatabaseSelection selection("", true, &filter);
 
-	GError *error = NULL;
-	return db_selection_print(client, selection, true, &error)
+	Error error;
+	return db_selection_print(client, selection, true, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -92,8 +93,8 @@ handle_match_add(Client *client, int argc, char *argv[], bool fold_case)
 	}
 
 	const DatabaseSelection selection("", true, &filter);
-	GError *error = NULL;
-	return AddFromDatabase(client->partition, selection, &error)
+	Error error;
+	return AddFromDatabase(client->partition, selection, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -121,8 +122,8 @@ handle_searchaddpl(Client *client, int argc, char *argv[])
 		return COMMAND_RETURN_ERROR;
 	}
 
-	GError *error = NULL;
-	return search_add_to_playlist("", playlist, &filter, &error)
+	Error error;
+	return search_add_to_playlist("", playlist, &filter, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -136,8 +137,8 @@ handle_count(Client *client, int argc, char *argv[])
 		return COMMAND_RETURN_ERROR;
 	}
 
-	GError *error = NULL;
-	return  searchStatsForSongsIn(client, "", &filter, &error)
+	Error error;
+	return  searchStatsForSongsIn(client, "", &filter, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -150,8 +151,8 @@ handle_listall(Client *client, gcc_unused int argc, char *argv[])
 	if (argc == 2)
 		directory = argv[1];
 
-	GError *error = NULL;
-	return printAllIn(client, directory, &error)
+	Error error;
+	return printAllIn(client, directory, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -194,9 +195,9 @@ handle_list(Client *client, int argc, char *argv[])
 	} else
 		filter = nullptr;
 
-	GError *error = NULL;
+	Error error;
 	enum command_return ret =
-		listAllUniqueTags(client, tagType, filter, &error)
+		listAllUniqueTags(client, tagType, filter, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 
@@ -213,8 +214,8 @@ handle_listallinfo(Client *client, gcc_unused int argc, char *argv[])
 	if (argc == 2)
 		directory = argv[1];
 
-	GError *error = NULL;
-	return printInfoForAllIn(client, directory, &error)
+	Error error;
+	return printInfoForAllIn(client, directory, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
diff --git a/src/DatabaseError.cxx b/src/DatabaseError.cxx
new file mode 100644
index 000000000..800442b9f
--- /dev/null
+++ b/src/DatabaseError.cxx
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2003-2013 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 "DatabaseError.hxx"
+#include "util/Domain.hxx"
+
+const Domain db_domain("db");
diff --git a/src/DatabaseError.hxx b/src/DatabaseError.hxx
index 3827daff0..c133ee357 100644
--- a/src/DatabaseError.hxx
+++ b/src/DatabaseError.hxx
@@ -20,9 +20,7 @@
 #ifndef MPD_DB_ERROR_HXX
 #define MPD_DB_ERROR_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
+class Domain;
 
 enum db_error {
 	/**
@@ -34,14 +32,6 @@ enum db_error {
 	DB_NOT_FOUND,
 };
 
-/**
- * Quark for GError.domain; the code is an enum #db_error.
- */
-gcc_const
-static inline GQuark
-db_quark(void)
-{
-	return g_quark_from_static_string("db");
-}
+extern const Domain db_domain;
 
 #endif
diff --git a/src/DatabaseGlue.cxx b/src/DatabaseGlue.cxx
index 70b7acc9e..fb944dacc 100644
--- a/src/DatabaseGlue.cxx
+++ b/src/DatabaseGlue.cxx
@@ -24,6 +24,7 @@
 #include "DatabaseSave.hxx"
 #include "DatabaseError.hxx"
 #include "Directory.hxx"
+#include "util/Error.hxx"
 #include "conf.h"
 
 extern "C" {
@@ -50,7 +51,7 @@ static bool db_is_open;
 static bool is_simple;
 
 bool
-DatabaseGlobalInit(const config_param &param, GError **error_r)
+DatabaseGlobalInit(const config_param &param, Error &error)
 {
 	assert(db == NULL);
 	assert(!db_is_open);
@@ -61,12 +62,12 @@ DatabaseGlobalInit(const config_param &param, GError **error_r)
 
 	const DatabasePlugin *plugin = GetDatabasePluginByName(plugin_name);
 	if (plugin == NULL) {
-		g_set_error(error_r, db_quark(), 0,
-			    "No such database plugin: %s", plugin_name);
+		error.Format(db_domain,
+			     "No such database plugin: %s", plugin_name);
 		return false;
 	}
 
-	db = plugin->create(param, error_r);
+	db = plugin->create(param, error);
 	return db != NULL;
 }
 
@@ -89,13 +90,12 @@ GetDatabase()
 }
 
 const Database *
-GetDatabase(GError **error_r)
+GetDatabase(Error &error)
 {
 	assert(db == nullptr || db_is_open);
 
 	if (db == nullptr)
-		g_set_error_literal(error_r, db_quark(), DB_DISABLED,
-				    "No database");
+		error.Set(db_domain, DB_DISABLED, "No database");
 
 	return db;
 }
@@ -131,17 +131,17 @@ db_get_directory(const char *name)
 }
 
 bool
-db_save(GError **error_r)
+db_save(Error &error)
 {
 	assert(db != NULL);
 	assert(db_is_open);
 	assert(db_is_simple());
 
-	return ((SimpleDatabase *)db)->Save(error_r);
+	return ((SimpleDatabase *)db)->Save(error);
 }
 
 bool
-DatabaseGlobalOpen(GError **error)
+DatabaseGlobalOpen(Error &error)
 {
 	assert(db != NULL);
 	assert(!db_is_open);
diff --git a/src/DatabaseGlue.hxx b/src/DatabaseGlue.hxx
index e321e0ba8..5e23a8c35 100644
--- a/src/DatabaseGlue.hxx
+++ b/src/DatabaseGlue.hxx
@@ -21,10 +21,10 @@
 #define MPD_DATABASE_GLUE_HXX
 
 #include "gcc.h"
-#include "gerror.h"
 
 struct config_param;
 class Database;
+class Error;
 
 /**
  * Initialize the database library.
@@ -32,13 +32,13 @@ class Database;
  * @param param the database configuration block
  */
 bool
-DatabaseGlobalInit(const config_param &param, GError **error_r);
+DatabaseGlobalInit(const config_param &param, Error &error);
 
 void
 DatabaseGlobalDeinit(void);
 
 bool
-DatabaseGlobalOpen(GError **error);
+DatabaseGlobalOpen(Error &error);
 
 /**
  * Returns the global #Database instance.  May return NULL if this MPD
@@ -54,6 +54,6 @@ GetDatabase();
  */
 gcc_pure
 const Database *
-GetDatabase(GError **error_r);
+GetDatabase(Error &error);
 
 #endif
diff --git a/src/DatabaseHelpers.cxx b/src/DatabaseHelpers.cxx
index ecaf44915..f2086e5d2 100644
--- a/src/DatabaseHelpers.cxx
+++ b/src/DatabaseHelpers.cxx
@@ -61,17 +61,17 @@ bool
 VisitUniqueTags(const Database &db, const DatabaseSelection &selection,
 		enum tag_type tag_type,
 		VisitString visit_string,
-		GError **error_r)
+		Error &error)
 {
 	StringSet set;
 
 	using namespace std::placeholders;
 	const auto f = std::bind(CollectTags, std::ref(set), tag_type, _1);
-	if (!db.Visit(selection, f, error_r))
+	if (!db.Visit(selection, f, error))
 		return false;
 
 	for (auto value : set)
-		if (!visit_string(value, error_r))
+		if (!visit_string(value, error))
 			return false;
 
 	return true;
@@ -116,7 +116,7 @@ StatsVisitSong(DatabaseStats &stats, StringSet &artists, StringSet &albums,
 
 bool
 GetStats(const Database &db, const DatabaseSelection &selection,
-	 DatabaseStats &stats, GError **error_r)
+	 DatabaseStats &stats, Error &error)
 {
 	stats.Clear();
 
@@ -125,7 +125,7 @@ GetStats(const Database &db, const DatabaseSelection &selection,
 	const auto f = std::bind(StatsVisitSong,
 				 std::ref(stats), std::ref(artists),
 				 std::ref(albums), _1);
-	if (!db.Visit(selection, f, error_r))
+	if (!db.Visit(selection, f, error))
 		return false;
 
 	stats.artist_count = artists.size();
diff --git a/src/DatabaseHelpers.hxx b/src/DatabaseHelpers.hxx
index 5b71fd2fb..479cc37c1 100644
--- a/src/DatabaseHelpers.hxx
+++ b/src/DatabaseHelpers.hxx
@@ -24,6 +24,7 @@
 #include "TagType.h"
 #include "gcc.h"
 
+class Error;
 class Database;
 struct DatabaseSelection;
 struct DatabaseStats;
@@ -32,10 +33,10 @@ bool
 VisitUniqueTags(const Database &db, const DatabaseSelection &selection,
 		enum tag_type tag_type,
 		VisitString visit_string,
-		GError **error_r);
+		Error &error);
 
 bool
 GetStats(const Database &db, const DatabaseSelection &selection,
-	 DatabaseStats &stats, GError **error_r);
+	 DatabaseStats &stats, Error &error);
 
 #endif
diff --git a/src/DatabasePlaylist.cxx b/src/DatabasePlaylist.cxx
index 04d1a490d..8404a39c9 100644
--- a/src/DatabasePlaylist.cxx
+++ b/src/DatabasePlaylist.cxx
@@ -28,17 +28,17 @@
 
 static bool
 AddSong(const char *playlist_path_utf8,
-	Song &song, GError **error_r)
+	Song &song, Error &error)
 {
-	return spl_append_song(playlist_path_utf8, &song, error_r);
+	return spl_append_song(playlist_path_utf8, &song, error);
 }
 
 bool
 search_add_to_playlist(const char *uri, const char *playlist_path_utf8,
 		       const SongFilter *filter,
-		       GError **error_r)
+		       Error &error)
 {
-	const Database *db = GetDatabase(error_r);
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return false;
 
@@ -46,5 +46,5 @@ search_add_to_playlist(const char *uri, const char *playlist_path_utf8,
 
 	using namespace std::placeholders;
 	const auto f = std::bind(AddSong, playlist_path_utf8, _1, _2);
-	return db->Visit(selection, f, error_r);
+	return db->Visit(selection, f, error);
 }
diff --git a/src/DatabasePlaylist.hxx b/src/DatabasePlaylist.hxx
index 7c6952ffa..d91fe13be 100644
--- a/src/DatabasePlaylist.hxx
+++ b/src/DatabasePlaylist.hxx
@@ -21,14 +21,14 @@
 #define MPD_DATABASE_PLAYLIST_HXX
 
 #include "gcc.h"
-#include "gerror.h"
 
 class SongFilter;
+class Error;
 
 gcc_nonnull(1,2)
 bool
 search_add_to_playlist(const char *uri, const char *path_utf8,
 		       const SongFilter *filter,
-		       GError **error_r);
+		       Error &error);
 
 #endif
diff --git a/src/DatabasePlugin.hxx b/src/DatabasePlugin.hxx
index 835244020..c17bff63c 100644
--- a/src/DatabasePlugin.hxx
+++ b/src/DatabasePlugin.hxx
@@ -34,6 +34,7 @@ struct config_param;
 struct DatabaseSelection;
 struct db_visitor;
 struct Song;
+class Error;
 
 struct DatabaseStats {
 	/**
@@ -73,7 +74,7 @@ public:
 	/**
          * Open the database.  Read it into memory if applicable.
 	 */
-	virtual bool Open(gcc_unused GError **error_r) {
+	virtual bool Open(gcc_unused Error &error) {
 		return true;
 	}
 
@@ -90,7 +91,7 @@ public:
 	 * directory (UTF-8)
 	 */
 	virtual Song *GetSong(const char *uri_utf8,
-			      GError **error_r) const = 0;
+			      Error &error) const = 0;
 
 	/**
 	 * Mark the song object as "unused".  Call this on objects
@@ -105,19 +106,19 @@ public:
 			   VisitDirectory visit_directory,
 			   VisitSong visit_song,
 			   VisitPlaylist visit_playlist,
-			   GError **error_r) const = 0;
+			   Error &error) const = 0;
 
 	bool Visit(const DatabaseSelection &selection,
 		   VisitDirectory visit_directory,
 		   VisitSong visit_song,
-		   GError **error_r) const {
+		   Error &error) const {
 		return Visit(selection, visit_directory, visit_song,
-			     VisitPlaylist(), error_r);
+			     VisitPlaylist(), error);
 	}
 
 	bool Visit(const DatabaseSelection &selection, VisitSong visit_song,
-		   GError **error_r) const {
-		return Visit(selection, VisitDirectory(), visit_song, error_r);
+		   Error &error) const {
+		return Visit(selection, VisitDirectory(), visit_song, error);
 	}
 
 	/**
@@ -126,11 +127,11 @@ public:
 	virtual bool VisitUniqueTags(const DatabaseSelection &selection,
 				     enum tag_type tag_type,
 				     VisitString visit_string,
-				     GError **error_r) const = 0;
+				     Error &error) const = 0;
 
 	virtual bool GetStats(const DatabaseSelection &selection,
 			      DatabaseStats &stats,
-			      GError **error_r) const = 0;
+			      Error &error) const = 0;
 };
 
 struct DatabasePlugin {
@@ -140,7 +141,7 @@ struct DatabasePlugin {
 	 * Allocates and configures a database.
 	 */
 	Database *(*create)(const config_param &param,
-			    GError **error_r);
+			    Error &error);
 };
 
 #endif
diff --git a/src/DatabasePrint.cxx b/src/DatabasePrint.cxx
index 1f8999dc3..cc7bee9e2 100644
--- a/src/DatabasePrint.cxx
+++ b/src/DatabasePrint.cxx
@@ -118,9 +118,9 @@ PrintPlaylistFull(Client *client,
 
 bool
 db_selection_print(Client *client, const DatabaseSelection &selection,
-		   bool full, GError **error_r)
+		   bool full, Error &error)
 {
-	const Database *db = GetDatabase(error_r);
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return false;
 
@@ -136,7 +136,7 @@ db_selection_print(Client *client, const DatabaseSelection &selection,
 			    client, _1, _2)
 		: VisitPlaylist();
 
-	return db->Visit(selection, d, s, p, error_r);
+	return db->Visit(selection, d, s, p, error);
 }
 
 struct SearchStats {
@@ -162,9 +162,9 @@ stats_visitor_song(SearchStats &stats, Song &song)
 bool
 searchStatsForSongsIn(Client *client, const char *name,
 		      const SongFilter *filter,
-		      GError **error_r)
+		      Error &error)
 {
-	const Database *db = GetDatabase(error_r);
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return false;
 
@@ -177,7 +177,7 @@ searchStatsForSongsIn(Client *client, const char *name,
 	using namespace std::placeholders;
 	const auto f = std::bind(stats_visitor_song, std::ref(stats),
 				 _1);
-	if (!db->Visit(selection, f, error_r))
+	if (!db->Visit(selection, f, error))
 		return false;
 
 	printSearchStats(client, &stats);
@@ -185,18 +185,18 @@ searchStatsForSongsIn(Client *client, const char *name,
 }
 
 bool
-printAllIn(Client *client, const char *uri_utf8, GError **error_r)
+printAllIn(Client *client, const char *uri_utf8, Error &error)
 {
 	const DatabaseSelection selection(uri_utf8, true);
-	return db_selection_print(client, selection, false, error_r);
+	return db_selection_print(client, selection, false, error);
 }
 
 bool
 printInfoForAllIn(Client *client, const char *uri_utf8,
-		  GError **error_r)
+		  Error &error)
 {
 	const DatabaseSelection selection(uri_utf8, true);
-	return db_selection_print(client, selection, true, error_r);
+	return db_selection_print(client, selection, true, error);
 }
 
 static bool
@@ -218,9 +218,9 @@ PrintUniqueTag(Client *client, enum tag_type tag_type,
 bool
 listAllUniqueTags(Client *client, int type,
 		  const SongFilter *filter,
-		  GError **error_r)
+		  Error &error)
 {
-	const Database *db = GetDatabase(error_r);
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return false;
 
@@ -229,12 +229,12 @@ listAllUniqueTags(Client *client, int type,
 	if (type == LOCATE_TAG_FILE_TYPE) {
 		using namespace std::placeholders;
 		const auto f = std::bind(PrintSongURIVisitor, client, _1);
-		return db->Visit(selection, f, error_r);
+		return db->Visit(selection, f, error);
 	} else {
 		using namespace std::placeholders;
 		const auto f = std::bind(PrintUniqueTag, client,
 					 (enum tag_type)type, _1);
 		return db->VisitUniqueTags(selection, (enum tag_type)type,
-					   f, error_r);
+					   f, error);
 	}
 }
diff --git a/src/DatabasePrint.hxx b/src/DatabasePrint.hxx
index 68551b63c..042d0458e 100644
--- a/src/DatabasePrint.hxx
+++ b/src/DatabasePrint.hxx
@@ -21,37 +21,37 @@
 #define MPD_DB_PRINT_H
 
 #include "gcc.h"
-#include "gerror.h"
 
 class SongFilter;
 struct DatabaseSelection;
 struct db_visitor;
 class Client;
+class Error;
 
 gcc_nonnull(1)
 bool
 db_selection_print(Client *client, const DatabaseSelection &selection,
-		   bool full, GError **error_r);
+		   bool full, Error &error);
 
 gcc_nonnull(1,2)
 bool
-printAllIn(Client *client, const char *uri_utf8, GError **error_r);
+printAllIn(Client *client, const char *uri_utf8, Error &error);
 
 gcc_nonnull(1,2)
 bool
 printInfoForAllIn(Client *client, const char *uri_utf8,
-		  GError **error_r);
+		  Error &error);
 
 gcc_nonnull(1,2)
 bool
 searchStatsForSongsIn(Client *client, const char *name,
 		      const SongFilter *filter,
-		      GError **error_r);
+		      Error &error);
 
 gcc_nonnull(1)
 bool
 listAllUniqueTags(Client *client, int type,
 		  const SongFilter *filter,
-		  GError **error_r);
+		  Error &error);
 
 #endif
diff --git a/src/DatabaseQueue.cxx b/src/DatabaseQueue.cxx
index 67031b730..79ff004a7 100644
--- a/src/DatabaseQueue.cxx
+++ b/src/DatabaseQueue.cxx
@@ -23,17 +23,17 @@
 #include "DatabaseGlue.hxx"
 #include "DatabasePlugin.hxx"
 #include "Partition.hxx"
+#include "util/Error.hxx"
 
 #include <functional>
 
 static bool
-AddToQueue(Partition &partition, Song &song, GError **error_r)
+AddToQueue(Partition &partition, Song &song, Error &error)
 {
 	enum playlist_result result =
 		partition.playlist.AppendSong(partition.pc, &song, NULL);
 	if (result != PLAYLIST_RESULT_SUCCESS) {
-		g_set_error(error_r, playlist_quark(), result,
-			    "Playlist error");
+		error.Set(playlist_domain, result, "Playlist error");
 		return false;
 	}
 
@@ -42,13 +42,13 @@ AddToQueue(Partition &partition, Song &song, GError **error_r)
 
 bool
 AddFromDatabase(Partition &partition, const DatabaseSelection &selection,
-		GError **error_r)
+		Error &error)
 {
-	const Database *db = GetDatabase(error_r);
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return false;
 
 	using namespace std::placeholders;
 	const auto f = std::bind(AddToQueue, std::ref(partition), _1, _2);
-	return db->Visit(selection, f, error_r);
+	return db->Visit(selection, f, error);
 }
diff --git a/src/DatabaseQueue.hxx b/src/DatabaseQueue.hxx
index bae5b1f05..86e75a39b 100644
--- a/src/DatabaseQueue.hxx
+++ b/src/DatabaseQueue.hxx
@@ -20,13 +20,12 @@
 #ifndef MPD_DATABASE_QUEUE_HXX
 #define MPD_DATABASE_QUEUE_HXX
 
-#include "gerror.h"
-
 struct Partition;
 struct DatabaseSelection;
+class Error;
 
 bool
 AddFromDatabase(Partition &partition, const DatabaseSelection &selection,
-		GError **error_r);
+		Error &error);
 
 #endif
diff --git a/src/DatabaseSave.cxx b/src/DatabaseSave.cxx
index ff95cf788..4213fb9a0 100644
--- a/src/DatabaseSave.cxx
+++ b/src/DatabaseSave.cxx
@@ -28,6 +28,7 @@
 #include "TagInternal.hxx"
 #include "Tag.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -69,7 +70,7 @@ db_save_internal(FILE *fp, const Directory *music_root)
 }
 
 bool
-db_load_internal(TextFile &file, Directory *music_root, GError **error)
+db_load_internal(TextFile &file, Directory *music_root, Error &error)
 {
 	char *line;
 	int format = 0;
@@ -82,7 +83,7 @@ db_load_internal(TextFile &file, Directory *music_root, GError **error)
 	/* get initial info */
 	line = file.ReadLine();
 	if (line == NULL || strcmp(DIRECTORY_INFO_BEGIN, line) != 0) {
-		g_set_error(error, db_quark(), 0, "Database corrupted");
+		error.Set(db_domain, "Database corrupted");
 		return false;
 	}
 
@@ -94,8 +95,7 @@ db_load_internal(TextFile &file, Directory *music_root, GError **error)
 			format = atoi(line + sizeof(DB_FORMAT_PREFIX) - 1);
 		} else if (g_str_has_prefix(line, DIRECTORY_MPD_VERSION)) {
 			if (found_version) {
-				g_set_error(error, db_quark(), 0,
-					    "Duplicate version line");
+				error.Set(db_domain, "Duplicate version line");
 				return false;
 			}
 
@@ -104,8 +104,7 @@ db_load_internal(TextFile &file, Directory *music_root, GError **error)
 			const char *new_charset;
 
 			if (found_charset) {
-				g_set_error(error, db_quark(), 0,
-					    "Duplicate charset line");
+				error.Set(db_domain, "Duplicate charset line");
 				return false;
 			}
 
@@ -115,44 +114,43 @@ db_load_internal(TextFile &file, Directory *music_root, GError **error)
 			const std::string &old_charset = Path::GetFSCharset();
 			if (!old_charset.empty()
 			    && strcmp(new_charset, old_charset.c_str())) {
-				g_set_error(error, db_quark(), 0,
-					    "Existing database has charset "
-					    "\"%s\" instead of \"%s\"; "
-					    "discarding database file",
-					    new_charset, old_charset.c_str());
+				error.Format(db_domain,
+					     "Existing database has charset "
+					     "\"%s\" instead of \"%s\"; "
+					     "discarding database file",
+					     new_charset, old_charset.c_str());
 				return false;
 			}
 		} else if (g_str_has_prefix(line, DB_TAG_PREFIX)) {
 			const char *name = line + sizeof(DB_TAG_PREFIX) - 1;
 			enum tag_type tag = tag_name_parse(name);
 			if (tag == TAG_NUM_OF_ITEM_TYPES) {
-				g_set_error(error, db_quark(), 0,
-					    "Unrecognized tag '%s', "
-					    "discarding database file",
-					    name);
+				error.Format(db_domain,
+					     "Unrecognized tag '%s', "
+					     "discarding database file",
+					     name);
 				return false;
 			}
 
 			tags[tag] = true;
 		} else {
-			g_set_error(error, db_quark(), 0,
-				    "Malformed line: %s", line);
+			error.Format(db_domain, "Malformed line: %s", line);
 			return false;
 		}
 	}
 
 	if (format != DB_FORMAT) {
-		g_set_error(error, db_quark(), 0,
-			    "Database format mismatch, "
-			    "discarding database file");
+		error.Set(db_domain,
+			  "Database format mismatch, "
+			  "discarding database file");
 		return false;
 	}
 
 	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; ++i) {
 		if (!ignore_tag_items[i] && !tags[i]) {
-			g_set_error(error, db_quark(), 0,
-				    "Tag list mismatch, "
-				    "discarding database file");
+			error.Set(db_domain,
+				  "Tag list mismatch, "
+				  "discarding database file");
 			return false;
 		}
 	}
diff --git a/src/DatabaseSave.hxx b/src/DatabaseSave.hxx
index 40048f261..2410b0a71 100644
--- a/src/DatabaseSave.hxx
+++ b/src/DatabaseSave.hxx
@@ -20,17 +20,16 @@
 #ifndef MPD_DATABASE_SAVE_HXX
 #define MPD_DATABASE_SAVE_HXX
 
-#include "gerror.h"
-
 #include <stdio.h>
 
 struct Directory;
 class TextFile;
+class Error;
 
 void
 db_save_internal(FILE *file, const Directory *root);
 
 bool
-db_load_internal(TextFile &file, Directory *root, GError **error);
+db_load_internal(TextFile &file, Directory *root, Error &error);
 
 #endif
diff --git a/src/DatabaseSimple.hxx b/src/DatabaseSimple.hxx
index c387a64f9..f0223bce2 100644
--- a/src/DatabaseSimple.hxx
+++ b/src/DatabaseSimple.hxx
@@ -21,7 +21,6 @@
 #define MPD_DATABASE_SIMPLE_HXX
 
 #include "gcc.h"
-#include "gerror.h"
 
 #include <sys/time.h>
 
@@ -29,6 +28,7 @@ struct config_param;
 struct Directory;
 struct db_selection;
 struct db_visitor;
+class Error;
 
 /**
  * Check whether the default #SimpleDatabasePlugin is used.  This
@@ -60,7 +60,7 @@ db_get_directory(const char *name);
  * May only be used if db_is_simple() returns true.
  */
 bool
-db_save(GError **error_r);
+db_save(Error &error);
 
 /**
  * May only be used if db_is_simple() returns true.
diff --git a/src/DatabaseVisitor.hxx b/src/DatabaseVisitor.hxx
index e36933d7a..cd6a7c94d 100644
--- a/src/DatabaseVisitor.hxx
+++ b/src/DatabaseVisitor.hxx
@@ -20,19 +20,18 @@
 #ifndef MPD_DATABASE_VISITOR_HXX
 #define MPD_DATABASE_VISITOR_HXX
 
-#include "gerror.h"
-
 #include <functional>
 
 struct Directory;
 struct Song;
 struct PlaylistInfo;
+class Error;
 
-typedef std::function<bool(const Directory &, GError **)> VisitDirectory;
-typedef std::function<bool(struct Song &, GError **)> VisitSong;
+typedef std::function<bool(const Directory &, Error &)> VisitDirectory;
+typedef std::function<bool(struct Song &, Error &)> VisitSong;
 typedef std::function<bool(const PlaylistInfo &, const Directory &,
-			   GError **)> VisitPlaylist;
+			   Error &)> VisitPlaylist;
 
-typedef std::function<bool(const char *, GError **)> VisitString;
+typedef std::function<bool(const char *, Error &)> VisitString;
 
 #endif
diff --git a/src/DecoderAPI.cxx b/src/DecoderAPI.cxx
index 7286bb52f..d364a3aaa 100644
--- a/src/DecoderAPI.cxx
+++ b/src/DecoderAPI.cxx
@@ -28,6 +28,7 @@
 #include "DecoderInternal.hxx"
 #include "Song.hxx"
 #include "InputStream.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -257,8 +258,6 @@ size_t decoder_read(struct decoder *decoder,
 		    void *buffer, size_t length)
 {
 	/* XXX don't allow decoder==NULL */
-	GError *error = NULL;
-	size_t nbytes;
 
 	assert(decoder == NULL ||
 	       decoder->dc->state == DECODE_STATE_START ||
@@ -283,14 +282,13 @@ size_t decoder_read(struct decoder *decoder,
 		is->cond.wait(is->mutex);
 	}
 
-	nbytes = input_stream_read(is, buffer, length, &error);
-	assert(nbytes == 0 || error == NULL);
-	assert(nbytes > 0 || error != NULL || input_stream_eof(is));
+	Error error;
+	size_t nbytes = input_stream_read(is, buffer, length, error);
+	assert(nbytes == 0 || !error.IsDefined());
+	assert(nbytes > 0 || error.IsDefined() || input_stream_eof(is));
 
-	if (gcc_unlikely(nbytes == 0 && error != nullptr)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
-	}
+	if (gcc_unlikely(nbytes == 0 && error.IsDefined()))
+		g_warning("%s", error.GetMessage());
 
 	input_stream_unlock(is);
 
@@ -364,7 +362,6 @@ decoder_data(struct decoder *decoder,
 	     uint16_t kbit_rate)
 {
 	struct decoder_control *dc = decoder->dc;
-	GError *error = NULL;
 	enum decoder_command cmd;
 
 	assert(dc->state == DECODE_STATE_DECODE);
@@ -397,16 +394,17 @@ decoder_data(struct decoder *decoder,
 	}
 
 	if (dc->in_audio_format != dc->out_audio_format) {
+		Error error;
 		data = decoder->conv_state.Convert(dc->in_audio_format,
 						   data, length,
 						   dc->out_audio_format,
 						   &length,
-						   &error);
+						   error);
 		if (data == NULL) {
 			/* the PCM conversion has failed - stop
 			   playback, since we have no better way to
 			   bail out */
-			g_warning("%s", error->message);
+			g_warning("%s", error.GetMessage());
 			return DECODE_COMMAND_STOP;
 		}
 	}
diff --git a/src/DecoderControl.hxx b/src/DecoderControl.hxx
index 31c72657b..98492c450 100644
--- a/src/DecoderControl.hxx
+++ b/src/DecoderControl.hxx
@@ -24,6 +24,7 @@
 #include "AudioFormat.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -77,7 +78,7 @@ struct decoder_control {
 	 * The object must be freed when this object transitions to
 	 * any other state (usually #DECODE_STATE_START).
 	 */
-	GError *error;
+	Error error;
 
 	bool quit;
 	bool seek_error;
@@ -218,38 +219,41 @@ struct decoder_control {
 	}
 
 	/**
-	 * Checks whether an error has occurred, and if so, returns a newly
-	 * allocated copy of the #GError object.
+	 * Checks whether an error has occurred, and if so, returns a
+	 * copy of the #Error object.
 	 *
 	 * Caller must lock the object.
 	 */
-	GError *GetError() const {
+	gcc_pure
+	Error GetError() const {
 		assert(command == DECODE_COMMAND_NONE);
-		assert(state != DECODE_STATE_ERROR || error != nullptr);
+		assert(state != DECODE_STATE_ERROR || error.IsDefined());
 
-		return state == DECODE_STATE_ERROR
-			? g_error_copy(error)
-			: nullptr;
+		Error result;
+		if (state == DECODE_STATE_ERROR)
+			result.Set(error);
+		return result;
 	}
 
 	/**
 	 * Like dc_get_error(), but locks and unlocks the object.
 	 */
-	GError *LockGetError() const {
+	gcc_pure
+	Error LockGetError() const {
 		Lock();
-		GError *result = GetError();
+		Error result = GetError();
 		Unlock();
 		return result;
 	}
 
 	/**
-	 * Clear the error condition and free the #GError object (if any).
+	 * Clear the error condition and free the #Error object (if any).
 	 *
 	 * Caller must lock the object.
 	 */
 	void ClearError() {
 		if (state == DECODE_STATE_ERROR) {
-			g_error_free(error);
+			error.Clear();
 			state = DECODE_STATE_STOP;
 		}
 	}
diff --git a/src/DecoderError.cxx b/src/DecoderError.cxx
new file mode 100644
index 000000000..a8d3f548d
--- /dev/null
+++ b/src/DecoderError.cxx
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2003-2013 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 "DecoderError.hxx"
+#include "util/Domain.hxx"
+
+const Domain decoder_domain("decoder");
diff --git a/src/DecoderError.hxx b/src/DecoderError.hxx
index 94b5a964b..9ea74167f 100644
--- a/src/DecoderError.hxx
+++ b/src/DecoderError.hxx
@@ -20,18 +20,6 @@
 #ifndef MPD_DECODER_ERROR_HXX
 #define MPD_DECODER_ERROR_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
-
-/**
- * Quark for GError.domain.
- */
-gcc_pure
-static inline GQuark
-decoder_quark(void)
-{
-	return g_quark_from_static_string("decoder");
-}
+extern const class Domain decoder_domain;
 
 #endif
diff --git a/src/DecoderThread.cxx b/src/DecoderThread.cxx
index 8c196cdae..5a44f0453 100644
--- a/src/DecoderThread.cxx
+++ b/src/DecoderThread.cxx
@@ -32,6 +32,7 @@
 #include "InputStream.hxx"
 #include "DecoderList.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "ApeReplayGain.hxx"
 
 #include <glib.h>
@@ -72,15 +73,12 @@ decoder_command_finished_locked(struct decoder_control *dc)
 static struct input_stream *
 decoder_input_stream_open(struct decoder_control *dc, const char *uri)
 {
-	GError *error = NULL;
-	struct input_stream *is;
+	Error error;
 
-	is = input_stream_open(uri, dc->mutex, dc->cond, &error);
+	input_stream *is = input_stream_open(uri, dc->mutex, dc->cond, error);
 	if (is == NULL) {
-		if (error != NULL) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
+		if (error.IsDefined())
+			g_warning("%s", error.GetMessage());
 
 		return NULL;
 	}
@@ -98,12 +96,10 @@ decoder_input_stream_open(struct decoder_control *dc, const char *uri)
 		input_stream_update(is);
 	}
 
-	if (!input_stream_check(is, &error)) {
+	if (!input_stream_check(is, error)) {
 		dc->Unlock();
 
-		g_warning("%s", error->message);
-		g_error_free(error);
-
+		g_warning("%s", error.GetMessage());
 		return NULL;
 	}
 
@@ -132,7 +128,10 @@ decoder_stream_decode(const struct decoder_plugin *plugin,
 		return true;
 
 	/* rewind the stream, so each plugin gets a fresh start */
-	input_stream_seek(input_stream, 0, SEEK_SET, NULL);
+	{
+		Error error;
+		input_stream_seek(input_stream, 0, SEEK_SET, error);
+	}
 
 	decoder->dc->Unlock();
 
@@ -411,8 +410,8 @@ decoder_run_song(struct decoder_control *dc,
 		if (allocated != NULL)
 			error_uri = allocated;
 
-		dc->error = g_error_new(decoder_quark(), 0,
-					"Failed to decode %s", error_uri);
+		dc->error.Format(decoder_domain,
+				 "Failed to decode %s", error_uri);
 		g_free(allocated);
 	}
 
@@ -436,8 +435,7 @@ decoder_run(struct decoder_control *dc)
 
 	if (uri == NULL) {
 		dc->state = DECODE_STATE_ERROR;
-		dc->error = g_error_new(decoder_quark(), 0,
-					"Failed to map song");
+		dc->error.Set(decoder_domain, "Failed to map song");
 
 		decoder_command_finished_locked(dc);
 		return;
diff --git a/src/Directory.cxx b/src/Directory.cxx
index 6a0da2597..261d16385 100644
--- a/src/Directory.cxx
+++ b/src/Directory.cxx
@@ -24,6 +24,7 @@
 #include "DatabaseLock.hxx"
 #include "SongSort.hxx"
 #include "Song.hxx"
+#include "util/Error.hxx"
 
 extern "C" {
 #include "util/list_sort.h"
@@ -300,34 +301,34 @@ bool
 Directory::Walk(bool recursive, const SongFilter *filter,
 		VisitDirectory visit_directory, VisitSong visit_song,
 		VisitPlaylist visit_playlist,
-		GError **error_r) const
+		Error &error) const
 {
-	assert(error_r == NULL || *error_r == NULL);
+	assert(!error.IsDefined());
 
 	if (visit_song) {
 		Song *song;
 		directory_for_each_song(song, this)
 			if ((filter == nullptr || filter->Match(*song)) &&
-			    !visit_song(*song, error_r))
+			    !visit_song(*song, error))
 				return false;
 	}
 
 	if (visit_playlist) {
 		for (const PlaylistInfo &p : playlists)
-			if (!visit_playlist(p, *this, error_r))
+			if (!visit_playlist(p, *this, error))
 				return false;
 	}
 
 	Directory *child;
 	directory_for_each_child(child, this) {
 		if (visit_directory &&
-		    !visit_directory(*child, error_r))
+		    !visit_directory(*child, error))
 			return false;
 
 		if (recursive &&
 		    !child->Walk(recursive, filter,
 				 visit_directory, visit_song, visit_playlist,
-				 error_r))
+				 error))
 			return false;
 	}
 
diff --git a/src/Directory.hxx b/src/Directory.hxx
index 97a16f085..928f04163 100644
--- a/src/Directory.hxx
+++ b/src/Directory.hxx
@@ -25,7 +25,6 @@
 #include "gcc.h"
 #include "DatabaseVisitor.hxx"
 #include "PlaylistVector.hxx"
-#include "gerror.h"
 
 #include <sys/types.h>
 
@@ -47,6 +46,7 @@
 struct Song;
 struct db_visitor;
 class SongFilter;
+class Error;
 
 struct Directory {
 	/**
@@ -251,7 +251,7 @@ public:
 	bool Walk(bool recursive, const SongFilter *match,
 		  VisitDirectory visit_directory, VisitSong visit_song,
 		  VisitPlaylist visit_playlist,
-		  GError **error_r) const;
+		  Error &error) const;
 };
 
 static inline bool
diff --git a/src/DirectorySave.cxx b/src/DirectorySave.cxx
index 1dcc36dbf..c00338182 100644
--- a/src/DirectorySave.cxx
+++ b/src/DirectorySave.cxx
@@ -24,6 +24,8 @@
 #include "SongSave.hxx"
 #include "PlaylistDatabase.hxx"
 #include "TextFile.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 #include <string.h>
@@ -33,14 +35,7 @@
 #define DIRECTORY_BEGIN "begin: "
 #define DIRECTORY_END "end: "
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-directory_quark(void)
-{
-	return g_quark_from_static_string("directory");
-}
+static constexpr Domain directory_domain("directory");
 
 void
 directory_save(FILE *fp, const Directory *directory)
@@ -77,13 +72,13 @@ directory_save(FILE *fp, const Directory *directory)
 
 static Directory *
 directory_load_subdir(TextFile &file, Directory *parent, const char *name,
-		      GError **error_r)
+		      Error &error)
 {
 	bool success;
 
 	if (parent->FindChild(name) != nullptr) {
-		g_set_error(error_r, directory_quark(), 0,
-			    "Duplicate subdirectory '%s'", name);
+		error.Format(directory_domain,
+			     "Duplicate subdirectory '%s'", name);
 		return NULL;
 	}
 
@@ -91,8 +86,7 @@ directory_load_subdir(TextFile &file, Directory *parent, const char *name,
 
 	const char *line = file.ReadLine();
 	if (line == NULL) {
-		g_set_error(error_r, directory_quark(), 0,
-			    "Unexpected end of file");
+		error.Set(directory_domain, "Unexpected end of file");
 		directory->Delete();
 		return NULL;
 	}
@@ -104,21 +98,19 @@ directory_load_subdir(TextFile &file, Directory *parent, const char *name,
 
 		line = file.ReadLine();
 		if (line == NULL) {
-			g_set_error(error_r, directory_quark(), 0,
-				    "Unexpected end of file");
+			error.Set(directory_domain, "Unexpected end of file");
 			directory->Delete();
 			return NULL;
 		}
 	}
 
 	if (!g_str_has_prefix(line, DIRECTORY_BEGIN)) {
-		g_set_error(error_r, directory_quark(), 0,
-			    "Malformed line: %s", line);
+		error.Format(directory_domain, "Malformed line: %s", line);
 		directory->Delete();
 		return NULL;
 	}
 
-	success = directory_load(file, directory, error_r);
+	success = directory_load(file, directory, error);
 	if (!success) {
 		directory->Delete();
 		return NULL;
@@ -128,7 +120,7 @@ directory_load_subdir(TextFile &file, Directory *parent, const char *name,
 }
 
 bool
-directory_load(TextFile &file, Directory *directory, GError **error)
+directory_load(TextFile &file, Directory *directory, Error &error)
 {
 	const char *line;
 
@@ -146,8 +138,8 @@ directory_load(TextFile &file, Directory *directory, GError **error)
 			Song *song;
 
 			if (directory->FindSong(name) != nullptr) {
-				g_set_error(error, directory_quark(), 0,
-					    "Duplicate song '%s'", name);
+				error.Format(directory_domain,
+					     "Duplicate song '%s'", name);
 				return false;
 			}
 
@@ -170,8 +162,8 @@ directory_load(TextFile &file, Directory *directory, GError **error)
 
 			g_free(name);
 		} else {
-			g_set_error(error, directory_quark(), 0,
-				    "Malformed line: %s", line);
+			error.Format(directory_domain,
+				     "Malformed line: %s", line);
 			return false;
 		}
 	}
diff --git a/src/DirectorySave.hxx b/src/DirectorySave.hxx
index f4b4816f7..46a3b4462 100644
--- a/src/DirectorySave.hxx
+++ b/src/DirectorySave.hxx
@@ -20,17 +20,16 @@
 #ifndef MPD_DIRECTORY_SAVE_HXX
 #define MPD_DIRECTORY_SAVE_HXX
 
-#include "gerror.h"
-
 #include <stdio.h>
 
 struct Directory;
 class TextFile;
+class Error;
 
 void
 directory_save(FILE *fp, const Directory *directory);
 
 bool
-directory_load(TextFile &file, Directory *directory, GError **error);
+directory_load(TextFile &file, Directory *directory, Error &error);
 
 #endif
diff --git a/src/EncoderPlugin.hxx b/src/EncoderPlugin.hxx
index 6bb2e1583..1bca66e0a 100644
--- a/src/EncoderPlugin.hxx
+++ b/src/EncoderPlugin.hxx
@@ -20,8 +20,6 @@
 #ifndef MPD_ENCODER_PLUGIN_HXX
 #define MPD_ENCODER_PLUGIN_HXX
 
-#include "gerror.h"
-
 #include <assert.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -30,6 +28,7 @@ struct EncoderPlugin;
 struct AudioFormat;
 struct config_param;
 struct Tag;
+class Error;
 
 struct Encoder {
 	const EncoderPlugin &plugin;
@@ -50,28 +49,28 @@ struct EncoderPlugin {
 	const char *name;
 
 	Encoder *(*init)(const config_param &param,
-			 GError **error);
+			 Error &error);
 
 	void (*finish)(Encoder *encoder);
 
 	bool (*open)(Encoder *encoder,
 		     AudioFormat &audio_format,
-		     GError **error);
+		     Error &error);
 
 	void (*close)(Encoder *encoder);
 
-	bool (*end)(Encoder *encoder, GError **error);
+	bool (*end)(Encoder *encoder, Error &error);
 
-	bool (*flush)(Encoder *encoder, GError **error);
+	bool (*flush)(Encoder *encoder, Error &error);
 
-	bool (*pre_tag)(Encoder *encoder, GError **error);
+	bool (*pre_tag)(Encoder *encoder, Error &error);
 
 	bool (*tag)(Encoder *encoder, const Tag *tag,
-		    GError **error);
+		    Error &error);
 
 	bool (*write)(Encoder *encoder,
 		      const void *data, size_t length,
-		      GError **error);
+		      Error &error);
 
 	size_t (*read)(Encoder *encoder, void *dest, size_t length);
 
@@ -88,7 +87,7 @@ struct EncoderPlugin {
  */
 static inline Encoder *
 encoder_init(const EncoderPlugin &plugin, const config_param &param,
-	     GError **error_r)
+	     Error &error_r)
 {
 	return plugin.init(param, error_r);
 }
@@ -123,7 +122,7 @@ encoder_finish(Encoder *encoder)
  */
 static inline bool
 encoder_open(Encoder *encoder, AudioFormat &audio_format,
-	     GError **error)
+	     Error &error)
 {
 	assert(!encoder->open);
 
@@ -168,7 +167,7 @@ encoder_close(Encoder *encoder)
  * @return true on success
  */
 static inline bool
-encoder_end(Encoder *encoder, GError **error)
+encoder_end(Encoder *encoder, Error &error)
 {
 	assert(encoder->open);
 	assert(!encoder->end);
@@ -192,7 +191,7 @@ encoder_end(Encoder *encoder, GError **error)
  * @return true on success
  */
 static inline bool
-encoder_flush(Encoder *encoder, GError **error)
+encoder_flush(Encoder *encoder, Error &error)
 {
 	assert(encoder->open);
 	assert(!encoder->pre_tag);
@@ -216,7 +215,7 @@ encoder_flush(Encoder *encoder, GError **error)
  * @return true on success
  */
 static inline bool
-encoder_pre_tag(Encoder *encoder, GError **error)
+encoder_pre_tag(Encoder *encoder, Error &error)
 {
 	assert(encoder->open);
 	assert(!encoder->pre_tag);
@@ -246,7 +245,7 @@ encoder_pre_tag(Encoder *encoder, GError **error)
  * @return true on success
  */
 static inline bool
-encoder_tag(Encoder *encoder, const Tag *tag, GError **error)
+encoder_tag(Encoder *encoder, const Tag *tag, Error &error)
 {
 	assert(encoder->open);
 	assert(!encoder->pre_tag);
@@ -274,7 +273,7 @@ encoder_tag(Encoder *encoder, const Tag *tag, GError **error)
  */
 static inline bool
 encoder_write(Encoder *encoder, const void *data, size_t length,
-	      GError **error)
+	      Error &error)
 {
 	assert(encoder->open);
 	assert(!encoder->pre_tag);
diff --git a/src/FilterConfig.cxx b/src/FilterConfig.cxx
index 389afa99d..8a3377c7d 100644
--- a/src/FilterConfig.cxx
+++ b/src/FilterConfig.cxx
@@ -24,35 +24,31 @@
 #include "FilterPlugin.hxx"
 #include "FilterInternal.hxx"
 #include "FilterRegistry.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
 #include <string.h>
 
-static GQuark
-filter_quark(void)
-{
-	return g_quark_from_static_string("filter");
-}
-
 /**
  * Find the "filter" configuration block for the specified name.
  *
  * @param filter_template_name the name of the filter template
- * @param error_r space to return an error description
+ * @param error space to return an error description
  * @return the configuration block, or NULL if none was configured
  */
 static const struct config_param *
-filter_plugin_config(const char *filter_template_name, GError **error_r)
+filter_plugin_config(const char *filter_template_name, Error &error)
 {
 	const struct config_param *param = NULL;
 
 	while ((param = config_get_next_param(CONF_AUDIO_FILTER, param)) != NULL) {
 		const char *name = param->GetBlockValue("name");
 		if (name == NULL) {
-			g_set_error(error_r, filter_quark(), 1,
-				    "filter configuration without 'name' name in line %d",
-				    param->line);
+			error.Format(config_domain,
+				     "filter configuration without 'name' name in line %d",
+				     param->line);
 			return NULL;
 		}
 
@@ -60,10 +56,9 @@ filter_plugin_config(const char *filter_template_name, GError **error_r)
 			return param;
 	}
 
-	g_set_error(error_r, filter_quark(), 1,
-		    "filter template not found: %s",
-		    filter_template_name);
-
+	error.Format(config_domain,
+		     "filter template not found: %s",
+		     filter_template_name);
 	return NULL;
 }
 
@@ -73,11 +68,11 @@ filter_plugin_config(const char *filter_template_name, GError **error_r)
  * configured filter sections.
  * @param chain the chain to append filters on
  * @param spec the filter chain specification
- * @param error_r space to return an error description
+ * @param error space to return an error description
  * @return the number of filters which were successfully added
  */
 unsigned int
-filter_chain_parse(Filter &chain, const char *spec, GError **error_r)
+filter_chain_parse(Filter &chain, const char *spec, Error &error)
 {
 
 	// Split on comma
@@ -92,14 +87,14 @@ filter_chain_parse(Filter &chain, const char *spec, GError **error_r)
 		g_strstrip(*template_names);
 
 		const struct config_param *cfg =
-			filter_plugin_config(*template_names, error_r);
+			filter_plugin_config(*template_names, error);
 		if (cfg == NULL) {
 			// The error has already been set, just stop.
 			break;
 		}
 
 		// Instantiate one of those filter plugins with the template name as a hint
-		Filter *f = filter_configured_new(*cfg, error_r);
+		Filter *f = filter_configured_new(*cfg, error);
 		if (f == NULL) {
 			// The error has already been set, just stop.
 			break;
diff --git a/src/FilterConfig.hxx b/src/FilterConfig.hxx
index bad186354..3e6553b8d 100644
--- a/src/FilterConfig.hxx
+++ b/src/FilterConfig.hxx
@@ -25,9 +25,8 @@
 #ifndef MPD_FILTER_CONFIG_HXX
 #define MPD_FILTER_CONFIG_HXX
 
-#include "gerror.h"
-
 class Filter;
+class Error;
 
 /**
  * Builds a filter chain from a configuration string on the form
@@ -39,6 +38,6 @@ class Filter;
  * @return the number of filters which were successfully added
  */
 unsigned int
-filter_chain_parse(Filter &chain, const char *spec, GError **error_r);
+filter_chain_parse(Filter &chain, const char *spec, Error &error);
 
 #endif
diff --git a/src/FilterInternal.hxx b/src/FilterInternal.hxx
index 103687b61..ab648af1e 100644
--- a/src/FilterInternal.hxx
+++ b/src/FilterInternal.hxx
@@ -25,7 +25,10 @@
 #ifndef MPD_FILTER_INTERNAL_HXX
 #define MPD_FILTER_INTERNAL_HXX
 
+#include <stddef.h>
+
 struct AudioFormat;
+class Error;
 
 class Filter {
 public:
@@ -43,7 +46,7 @@ public:
 	 * @return the format of outgoing data or
 	 * AudioFormat::Undefined() on error
 	 */
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) = 0;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) = 0;
 
 	/**
 	 * Closes the filter.  After that, you may call Open() again.
@@ -65,7 +68,7 @@ public:
 	 */
 	virtual const void *FilterPCM(const void *src, size_t src_size,
 				      size_t *dest_size_r,
-				      GError **error_r) = 0;
+				      Error &error) = 0;
 };
 
 #endif
diff --git a/src/FilterPlugin.cxx b/src/FilterPlugin.cxx
index 076056fbe..e9f256090 100644
--- a/src/FilterPlugin.cxx
+++ b/src/FilterPlugin.cxx
@@ -22,40 +22,38 @@
 #include "FilterInternal.hxx"
 #include "FilterRegistry.hxx"
 #include "conf.h"
-#include "ConfigQuark.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 
 Filter *
 filter_new(const struct filter_plugin *plugin,
-	   const config_param &param, GError **error_r)
+	   const config_param &param, Error &error)
 {
 	assert(plugin != NULL);
-	assert(error_r == NULL || *error_r == NULL);
+	assert(!error.IsDefined());
 
-	return plugin->init(param, error_r);
+	return plugin->init(param, error);
 }
 
 Filter *
-filter_configured_new(const config_param &param, GError **error_r)
+filter_configured_new(const config_param &param, Error &error)
 {
-	const struct filter_plugin *plugin;
-
-	assert(error_r == NULL || *error_r == NULL);
+	assert(!error.IsDefined());
 
 	const char *plugin_name = param.GetBlockValue("plugin");
 	if (plugin_name == NULL) {
-		g_set_error(error_r, config_quark(), 0,
-			    "No filter plugin specified");
+		error.Set(config_domain, "No filter plugin specified");
 		return NULL;
 	}
 
-	plugin = filter_plugin_by_name(plugin_name);
+	const filter_plugin *plugin = filter_plugin_by_name(plugin_name);
 	if (plugin == NULL) {
-		g_set_error(error_r, config_quark(), 0,
-			    "No such filter plugin: %s", plugin_name);
+		error.Format(config_domain,
+			     "No such filter plugin: %s", plugin_name);
 		return NULL;
 	}
 
-	return filter_new(plugin, param, error_r);
+	return filter_new(plugin, param, error);
 }
diff --git a/src/FilterPlugin.hxx b/src/FilterPlugin.hxx
index af1e2f699..88c786120 100644
--- a/src/FilterPlugin.hxx
+++ b/src/FilterPlugin.hxx
@@ -26,12 +26,9 @@
 #ifndef MPD_FILTER_PLUGIN_HXX
 #define MPD_FILTER_PLUGIN_HXX
 
-#include "gerror.h"
-
-#include <stddef.h>
-
 struct config_param;
 class Filter;
+class Error;
 
 struct filter_plugin {
 	const char *name;
@@ -39,7 +36,7 @@ struct filter_plugin {
 	/**
          * Allocates and configures a filter.
 	 */
-	Filter *(*init)(const config_param &param, GError **error_r);
+	Filter *(*init)(const config_param &param, Error &error);
 };
 
 /**
@@ -53,7 +50,7 @@ struct filter_plugin {
  */
 Filter *
 filter_new(const struct filter_plugin *plugin,
-	   const config_param &param, GError **error_r);
+	   const config_param &param, Error &error);
 
 /**
  * Creates a new filter, loads configuration and the plugin name from
@@ -65,6 +62,6 @@ filter_new(const struct filter_plugin *plugin,
  * @return a new filter object, or NULL on error
  */
 Filter *
-filter_configured_new(const config_param &param, GError **error_r);
+filter_configured_new(const config_param &param, Error &error);
 
 #endif
diff --git a/src/InotifySource.cxx b/src/InotifySource.cxx
index 9a2d4d46d..c6f0ae4db 100644
--- a/src/InotifySource.cxx
+++ b/src/InotifySource.cxx
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "InotifySource.hxx"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
 #include "system/fd_util.h"
 #include "system/FatalError.hxx"
 
@@ -32,15 +33,6 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "inotify"
 
-/**
- * A GQuark for GError instances.
- */
-static inline GQuark
-mpd_inotify_quark(void)
-{
-	return g_quark_from_static_string("inotify");
-}
-
 bool
 InotifySource::OnSocketReady(gcc_unused unsigned flags)
 {
@@ -97,13 +89,11 @@ InotifySource::InotifySource(EventLoop &_loop,
 InotifySource *
 InotifySource::Create(EventLoop &loop,
 		      mpd_inotify_callback_t callback, void *callback_ctx,
-		      GError **error_r)
+		      Error &error)
 {
 	int fd = inotify_init_cloexec();
 	if (fd < 0) {
-		g_set_error(error_r, mpd_inotify_quark(), errno,
-			    "inotify_init() has failed: %s",
-			    g_strerror(errno));
+		error.SetErrno("inotify_init() has failed");
 		return NULL;
 	}
 
@@ -116,13 +106,11 @@ InotifySource::~InotifySource()
 }
 
 int
-InotifySource::Add(const char *path_fs, unsigned mask, GError **error_r)
+InotifySource::Add(const char *path_fs, unsigned mask, Error &error)
 {
 	int wd = inotify_add_watch(Get(), path_fs, mask);
 	if (wd < 0)
-		g_set_error(error_r, mpd_inotify_quark(), errno,
-			    "inotify_add_watch() has failed: %s",
-			    g_strerror(errno));
+		error.SetErrno("inotify_add_watch() has failed");
 
 	return wd;
 }
diff --git a/src/InotifySource.hxx b/src/InotifySource.hxx
index e8f9ff03c..2f686d3b1 100644
--- a/src/InotifySource.hxx
+++ b/src/InotifySource.hxx
@@ -21,9 +21,10 @@
 #define MPD_INOTIFY_SOURCE_HXX
 
 #include "event/SocketMonitor.hxx"
-#include "gerror.h"
 #include "gcc.h"
 
+class Error;
+
 typedef void (*mpd_inotify_callback_t)(int wd, unsigned mask,
 				       const char *name, void *ctx);
 
@@ -46,7 +47,7 @@ public:
 	static InotifySource *Create(EventLoop &_loop,
 				     mpd_inotify_callback_t callback,
 				     void *ctx,
-				     GError **error_r);
+				     Error &error);
 
 	~InotifySource();
 
@@ -56,7 +57,7 @@ public:
 	 *
 	 * @return a watch descriptor or -1 on error
 	 */
-	int Add(const char *path_fs, unsigned mask, GError **error_r);
+	int Add(const char *path_fs, unsigned mask, Error &error);
 
 	/**
 	 * Removes a path from the notify list.
diff --git a/src/InotifyUpdate.cxx b/src/InotifyUpdate.cxx
index 95c8317c8..cccb9650c 100644
--- a/src/InotifyUpdate.cxx
+++ b/src/InotifyUpdate.cxx
@@ -24,6 +24,7 @@
 #include "Mapper.hxx"
 #include "Main.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -162,7 +163,7 @@ static void
 recursive_watch_subdirectories(WatchDirectory *directory,
 			       const char *path_fs, unsigned depth)
 {
-	GError *error = NULL;
+	Error error;
 	DIR *dir;
 	struct dirent *ent;
 
@@ -204,12 +205,11 @@ recursive_watch_subdirectories(WatchDirectory *directory,
 			continue;
 		}
 
-		ret = inotify_source->Add(child_path_fs, IN_MASK, &error);
+		ret = inotify_source->Add(child_path_fs, IN_MASK, error);
 		if (ret < 0) {
 			g_warning("Failed to register %s: %s",
-				  child_path_fs, error->message);
-			g_error_free(error);
-			error = NULL;
+				  child_path_fs, error.GetMessage());
+			error.Clear();
 			g_free(child_path_fs);
 			continue;
 		}
@@ -309,8 +309,6 @@ mpd_inotify_callback(int wd, unsigned mask,
 void
 mpd_inotify_init(unsigned max_depth)
 {
-	GError *error = NULL;
-
 	g_debug("initializing inotify");
 
 	const Path &path = mapper_get_music_directory_fs();
@@ -319,21 +317,20 @@ mpd_inotify_init(unsigned max_depth)
 		return;
 	}
 
+	Error error;
 	inotify_source = InotifySource::Create(*main_loop,
 					       mpd_inotify_callback, nullptr,
-					       &error);
+					       error);
 	if (inotify_source == NULL) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
 	inotify_max_depth = max_depth;
 
-	int descriptor = inotify_source->Add(path.c_str(), IN_MASK, &error);
+	int descriptor = inotify_source->Add(path.c_str(), IN_MASK, error);
 	if (descriptor < 0) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		delete inotify_source;
 		inotify_source = NULL;
 		return;
diff --git a/src/InputInit.cxx b/src/InputInit.cxx
index f6e40a6f9..01ed57d5a 100644
--- a/src/InputInit.cxx
+++ b/src/InputInit.cxx
@@ -21,16 +21,14 @@
 #include "InputInit.hxx"
 #include "InputRegistry.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "conf.h"
 
 #include <assert.h>
 #include <string.h>
 
-static inline GQuark
-input_quark(void)
-{
-	return g_quark_from_static_string("input");
-}
+extern constexpr Domain input_domain("input");
 
 /**
  * Find the "input" configuration block for the specified plugin.
@@ -39,16 +37,16 @@ input_quark(void)
  * @return the configuration block, or NULL if none was configured
  */
 static const struct config_param *
-input_plugin_config(const char *plugin_name, GError **error_r)
+input_plugin_config(const char *plugin_name, Error &error)
 {
 	const struct config_param *param = NULL;
 
 	while ((param = config_get_next_param(CONF_INPUT, param)) != NULL) {
 		const char *name = param->GetBlockValue("plugin");
 		if (name == NULL) {
-			g_set_error(error_r, input_quark(), 0,
-				    "input configuration without 'plugin' name in line %d",
-				    param->line);
+			error.Format(input_domain,
+				     "input configuration without 'plugin' name in line %d",
+				     param->line);
 			return NULL;
 		}
 
@@ -60,12 +58,10 @@ input_plugin_config(const char *plugin_name, GError **error_r)
 }
 
 bool
-input_stream_global_init(GError **error_r)
+input_stream_global_init(Error &error)
 {
 	const config_param empty;
 
-	GError *error = NULL;
-
 	for (unsigned i = 0; input_plugins[i] != NULL; ++i) {
 		const struct input_plugin *plugin = input_plugins[i];
 
@@ -74,24 +70,21 @@ input_stream_global_init(GError **error_r)
 		assert(plugin->open != NULL);
 
 		const struct config_param *param =
-			input_plugin_config(plugin->name, &error);
+			input_plugin_config(plugin->name, error);
 		if (param == nullptr) {
-			if (error != nullptr) {
-				g_propagate_error(error_r, error);
+			if (error.IsDefined())
 				return false;
-			}
 
 			param = &empty;
 		} else if (!param->GetBlockValue("enabled", true))
 			/* the plugin is disabled in mpd.conf */
 			continue;
 
-		if (plugin->init == NULL || plugin->init(*param, &error))
+		if (plugin->init == NULL || plugin->init(*param, error))
 			input_plugins_enabled[i] = true;
 		else {
-			g_propagate_prefixed_error(error_r, error,
-						   "Failed to initialize input plugin '%s': ",
-						   plugin->name);
+			error.FormatPrefix("Failed to initialize input plugin '%s': ",
+					   plugin->name);
 			return false;
 		}
 	}
diff --git a/src/InputInit.hxx b/src/InputInit.hxx
index 9d503e5a8..9aa2de41a 100644
--- a/src/InputInit.hxx
+++ b/src/InputInit.hxx
@@ -20,7 +20,7 @@
 #ifndef MPD_INPUT_INIT_HXX
 #define MPD_INPUT_INIT_HXX
 
-#include "gerror.h"
+class Error;
 
 /**
  * Initializes this library and all input_stream implementations.
@@ -29,7 +29,7 @@
  * ignore errors
  */
 bool
-input_stream_global_init(GError **error_r);
+input_stream_global_init(Error &error);
 
 /**
  * Deinitializes this library and all input_stream implementations.
diff --git a/src/InputLegacy.hxx b/src/InputLegacy.hxx
index 53fab3aae..79cb1527a 100644
--- a/src/InputLegacy.hxx
+++ b/src/InputLegacy.hxx
@@ -31,6 +31,7 @@
 
 struct Tag;
 struct input_stream;
+class Error;
 
 /**
  * Opens a new input stream.  You may not access it until the "ready"
@@ -48,7 +49,7 @@ gcc_malloc
 struct input_stream *
 input_stream_open(const char *uri,
 		  Mutex &mutex, Cond &cond,
-		  GError **error_r);
+		  Error &error);
 
 /**
  * Close the input stream and free resources.
@@ -66,7 +67,7 @@ input_stream_close(struct input_stream *is);
  */
 gcc_nonnull(1)
 bool
-input_stream_check(struct input_stream *is, GError **error_r);
+input_stream_check(struct input_stream *is, Error &error);
 
 /**
  * Update the public attributes.  Call before accessing attributes
@@ -133,7 +134,7 @@ input_stream_cheap_seeking(const struct input_stream *is);
 gcc_nonnull(1)
 bool
 input_stream_seek(struct input_stream *is, goffset offset, int whence,
-		  GError **error_r);
+		  Error &error);
 
 /**
  * Wrapper for input_stream_seek() which locks and unlocks the
@@ -142,7 +143,7 @@ input_stream_seek(struct input_stream *is, goffset offset, int whence,
 gcc_nonnull(1)
 bool
 input_stream_lock_seek(struct input_stream *is, goffset offset, int whence,
-		       GError **error_r);
+		       Error &error);
 
 /**
  * Returns true if the stream has reached end-of-file.
@@ -210,7 +211,7 @@ input_stream_available(struct input_stream *is);
 gcc_nonnull(1, 2)
 size_t
 input_stream_read(struct input_stream *is, void *ptr, size_t size,
-		  GError **error_r);
+		  Error &error);
 
 /**
  * Wrapper for input_stream_tag() which locks and unlocks the
@@ -219,6 +220,6 @@ input_stream_read(struct input_stream *is, void *ptr, size_t size,
 gcc_nonnull(1, 2)
 size_t
 input_stream_lock_read(struct input_stream *is, void *ptr, size_t size,
-		       GError **error_r);
+		       Error &error);
 
 #endif
diff --git a/src/InputPlugin.hxx b/src/InputPlugin.hxx
index 0b3207c17..df6196f85 100644
--- a/src/InputPlugin.hxx
+++ b/src/InputPlugin.hxx
@@ -23,10 +23,10 @@
 #include "InputLegacy.hxx"
 
 #include <stddef.h>
-#include <sys/types.h>
 
 struct config_param;
 struct input_stream;
+class Error;
 
 struct input_plugin {
 	const char *name;
@@ -39,7 +39,7 @@ struct input_plugin {
 	 * @return true on success, false if the plugin should be
 	 * disabled
 	 */
-	bool (*init)(const config_param &param, GError **error_r);
+	bool (*init)(const config_param &param, Error &error);
 
 	/**
 	 * Global deinitialization.  Called once before MPD shuts
@@ -49,7 +49,7 @@ struct input_plugin {
 
 	struct input_stream *(*open)(const char *uri,
 				     Mutex &mutex, Cond &cond,
-				     GError **error_r);
+				     Error &error);
 	void (*close)(struct input_stream *is);
 
 	/**
@@ -58,7 +58,7 @@ struct input_plugin {
 	 *
 	 * @return false on error
 	 */
-	bool (*check)(struct input_stream *is, GError **error_r);
+	bool (*check)(struct input_stream *is, Error &error);
 
 	/**
 	 * Update the public attributes.  Call before access.  Can be
@@ -79,10 +79,10 @@ struct input_plugin {
 	bool (*available)(struct input_stream *is);
 
 	size_t (*read)(struct input_stream *is, void *ptr, size_t size,
-		       GError **error_r);
+		       Error &error);
 	bool (*eof)(struct input_stream *is);
 	bool (*seek)(struct input_stream *is, goffset offset, int whence,
-		     GError **error_r);
+		     Error &error);
 };
 
 #endif
diff --git a/src/InputStream.cxx b/src/InputStream.cxx
index 872d54fb7..c98797c89 100644
--- a/src/InputStream.cxx
+++ b/src/InputStream.cxx
@@ -23,29 +23,22 @@
 #include "InputPlugin.hxx"
 #include "input/RewindInputPlugin.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
-#include <glib.h>
 #include <assert.h>
 
-static inline GQuark
-input_quark(void)
-{
-	return g_quark_from_static_string("input");
-}
+static constexpr Domain input_domain("input");
 
 struct input_stream *
 input_stream_open(const char *url,
 		  Mutex &mutex, Cond &cond,
-		  GError **error_r)
+		  Error &error)
 {
-	GError *error = NULL;
-
-	assert(error_r == NULL || *error_r == NULL);
-
 	input_plugins_for_each_enabled(plugin) {
 		struct input_stream *is;
 
-		is = plugin->open(url, mutex, cond, &error);
+		is = plugin->open(url, mutex, cond, error);
 		if (is != NULL) {
 			assert(is->plugin.close != NULL);
 			assert(is->plugin.read != NULL);
@@ -55,23 +48,21 @@ input_stream_open(const char *url,
 			is = input_rewind_open(is);
 
 			return is;
-		} else if (error != NULL) {
-			g_propagate_error(error_r, error);
+		} else if (error.IsDefined())
 			return NULL;
-		}
 	}
 
-	g_set_error(error_r, input_quark(), 0, "Unrecognized URI");
+	error.Set(input_domain, "Unrecognized URI");
 	return NULL;
 }
 
 bool
-input_stream_check(struct input_stream *is, GError **error_r)
+input_stream_check(struct input_stream *is, Error &error)
 {
 	assert(is != NULL);
 
 	return is->plugin.check == NULL ||
-		is->plugin.check(is, error_r);
+		is->plugin.check(is, error);
 }
 
 void
@@ -159,19 +150,19 @@ input_stream_cheap_seeking(const struct input_stream *is)
 
 bool
 input_stream_seek(struct input_stream *is, goffset offset, int whence,
-		  GError **error_r)
+		  Error &error)
 {
 	assert(is != NULL);
 
 	if (is->plugin.seek == NULL)
 		return false;
 
-	return is->plugin.seek(is, offset, whence, error_r);
+	return is->plugin.seek(is, offset, whence, error);
 }
 
 bool
 input_stream_lock_seek(struct input_stream *is, goffset offset, int whence,
-		       GError **error_r)
+		       Error &error)
 {
 	assert(is != NULL);
 
@@ -179,7 +170,7 @@ input_stream_lock_seek(struct input_stream *is, goffset offset, int whence,
 		return false;
 
 	const ScopeLock protect(is->mutex);
-	return input_stream_seek(is, offset, whence, error_r);
+	return input_stream_seek(is, offset, whence, error);
 }
 
 Tag *
@@ -216,23 +207,23 @@ input_stream_available(struct input_stream *is)
 
 size_t
 input_stream_read(struct input_stream *is, void *ptr, size_t size,
-		  GError **error_r)
+		  Error &error)
 {
 	assert(ptr != NULL);
 	assert(size > 0);
 
-	return is->plugin.read(is, ptr, size, error_r);
+	return is->plugin.read(is, ptr, size, error);
 }
 
 size_t
 input_stream_lock_read(struct input_stream *is, void *ptr, size_t size,
-		       GError **error_r)
+		       Error &error)
 {
 	assert(ptr != NULL);
 	assert(size > 0);
 
 	const ScopeLock protect(is->mutex);
-	return input_stream_read(is, ptr, size, error_r);
+	return input_stream_read(is, ptr, size, error);
 }
 
 void input_stream_close(struct input_stream *is)
diff --git a/src/Listen.cxx b/src/Listen.cxx
index 659ed6bdf..6f6ff3f33 100644
--- a/src/Listen.cxx
+++ b/src/Listen.cxx
@@ -24,6 +24,7 @@
 #include "Client.hxx"
 #include "conf.h"
 #include "event/ServerSocket.hxx"
+#include "util/Error.hxx"
 
 #include <string.h>
 #include <assert.h>
@@ -55,7 +56,7 @@ int listen_port;
 static bool
 listen_add_config_param(unsigned int port,
 			const struct config_param *param,
-			GError **error_r)
+			Error &error_r)
 {
 	assert(param != NULL);
 
@@ -69,7 +70,7 @@ listen_add_config_param(unsigned int port,
 }
 
 static bool
-listen_systemd_activation(GError **error_r)
+listen_systemd_activation(Error &error_r)
 {
 #ifdef ENABLE_SYSTEMD_DAEMON
 	int n = sd_listen_fds(true);
@@ -93,7 +94,7 @@ listen_systemd_activation(GError **error_r)
 }
 
 bool
-listen_global_init(GError **error_r)
+listen_global_init(Error &error)
 {
 	assert(main_loop != nullptr);
 
@@ -101,29 +102,24 @@ listen_global_init(GError **error_r)
 	const struct config_param *param =
 		config_get_next_param(CONF_BIND_TO_ADDRESS, NULL);
 	bool success;
-	GError *error = NULL;
 
 	listen_socket = new ClientListener();
 
-	if (listen_systemd_activation(&error))
+	if (listen_systemd_activation(error))
 		return true;
 
-	if (error != NULL) {
-		g_propagate_error(error_r, error);
+	if (error.IsDefined())
 		return false;
-	}
 
 	if (param != NULL) {
 		/* "bind_to_address" is configured, create listeners
 		   for all values */
 
 		do {
-			success = listen_add_config_param(port, param, &error);
-			if (!success) {
+			if (!listen_add_config_param(port, param, error)) {
 				delete listen_socket;
-				g_propagate_prefixed_error(error_r, error,
-							   "Failed to listen on %s (line %i): ",
-							   param->value, param->line);
+				error.FormatPrefix("Failed to listen on %s (line %i): ",
+						   param->value, param->line);
 				return false;
 			}
 
@@ -134,17 +130,15 @@ listen_global_init(GError **error_r)
 		/* no "bind_to_address" configured, bind the
 		   configured port on all interfaces */
 
-		success = listen_socket->AddPort(port, error_r);
+		success = listen_socket->AddPort(port, error);
 		if (!success) {
 			delete listen_socket;
-			g_propagate_prefixed_error(error_r, error,
-						   "Failed to listen on *:%d: ",
-						   port);
+			error.FormatPrefix("Failed to listen on *:%d: ", port);
 			return false;
 		}
 	}
 
-	if (!listen_socket->Open(error_r)) {
+	if (!listen_socket->Open(error)) {
 		delete listen_socket;
 		return false;
 	}
diff --git a/src/Listen.hxx b/src/Listen.hxx
index 3e2be9e63..a6fdb2f1c 100644
--- a/src/Listen.hxx
+++ b/src/Listen.hxx
@@ -20,12 +20,12 @@
 #ifndef MPD_LISTEN_HXX
 #define MPD_LISTEN_HXX
 
-#include "gerror.h"
+class Error;
 
 extern int listen_port;
 
 bool
-listen_global_init(GError **error_r);
+listen_global_init(Error &error);
 
 void listen_global_finish(void);
 
diff --git a/src/Log.cxx b/src/Log.cxx
index fac5d95f1..667480ce2 100644
--- a/src/Log.cxx
+++ b/src/Log.cxx
@@ -25,6 +25,8 @@
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
 #include "mpd_error.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 #include <sys/types.h>
@@ -51,6 +53,8 @@
 #define LOG_DATE_BUF_SIZE 16
 #define LOG_DATE_LEN (LOG_DATE_BUF_SIZE - 1)
 
+static constexpr Domain log_domain("log");
+
 static GLogLevelFlags log_threshold = G_LOG_LEVEL_MESSAGE;
 
 static const char *log_charset;
@@ -92,7 +96,7 @@ chomp_length(const char *p)
 }
 
 static void
-file_log_func(const gchar *log_domain,
+file_log_func(const gchar *domain,
 	      GLogLevelFlags log_level,
 	      const gchar *message, gcc_unused gpointer user_data)
 {
@@ -110,12 +114,12 @@ file_log_func(const gchar *log_domain,
 	} else
 		converted = NULL;
 
-	if (log_domain == NULL)
-		log_domain = "";
+	if (domain == nullptr)
+		domain = "";
 
 	fprintf(stderr, "%s%s%s%.*s\n",
 		stdout_mode ? "" : log_date(),
-		log_domain, *log_domain == 0 ? "" : ": ",
+		domain, *domain == 0 ? "" : ": ",
 		chomp_length(message), message);
 
 	g_free(converted);
@@ -136,16 +140,15 @@ open_log_file(void)
 }
 
 static bool
-log_init_file(unsigned line, GError **error_r)
+log_init_file(unsigned line, Error &error)
 {
 	assert(!out_path.IsNull());
 
 	out_fd = open_log_file();
 	if (out_fd < 0) {
 		const std::string out_path_utf8 = out_path.ToUTF8();
-		g_set_error(error_r, log_quark(), errno,
-			    "failed to open log file \"%s\" (config line %u): %s",
-			    out_path_utf8.c_str(), line, g_strerror(errno));
+		error.FormatErrno("failed to open log file \"%s\" (config line %u)",
+				  out_path_utf8.c_str(), line);
 		return false;
 	}
 
@@ -181,14 +184,14 @@ glib_to_syslog_level(GLogLevelFlags log_level)
 }
 
 static void
-syslog_log_func(const gchar *log_domain,
+syslog_log_func(const gchar *domain,
 		GLogLevelFlags log_level, const gchar *message,
 		gcc_unused gpointer user_data)
 {
 	if (stdout_mode) {
 		/* fall back to the file log function during
 		   startup */
-		file_log_func(log_domain, log_level,
+		file_log_func(domain, log_level,
 			      message, user_data);
 		return;
 	}
@@ -196,11 +199,11 @@ syslog_log_func(const gchar *log_domain,
 	if (log_level > log_threshold)
 		return;
 
-	if (log_domain == NULL)
-		log_domain = "";
+	if (domain == nullptr)
+		domain = "";
 
 	syslog(glib_to_syslog_level(log_level), "%s%s%.*s",
-	       log_domain, *log_domain == 0 ? "" : ": ",
+	       domain, *domain == 0 ? "" : ": ",
 	       chomp_length(message), message);
 }
 
@@ -241,7 +244,7 @@ log_early_init(bool verbose)
 }
 
 bool
-log_init(bool verbose, bool use_stdout, GError **error_r)
+log_init(bool verbose, bool use_stdout, Error &error)
 {
 	const struct config_param *param;
 
@@ -264,8 +267,8 @@ log_init(bool verbose, bool use_stdout, GError **error_r)
 			log_init_syslog();
 			return true;
 #else
-			g_set_error(error_r, log_quark(), 0,
-				    "config parameter 'log_file' not found");
+			error.Set(log_domain,
+				  "config parameter 'log_file' not found");
 			return false;
 #endif
 #ifdef HAVE_SYSLOG
@@ -274,9 +277,9 @@ log_init(bool verbose, bool use_stdout, GError **error_r)
 			return true;
 #endif
 		} else {
-			out_path = config_get_path(CONF_LOG_FILE, error_r);
+			out_path = config_get_path(CONF_LOG_FILE, error);
 			return !out_path.IsNull() &&
-				log_init_file(param->line, error_r);
+				log_init_file(param->line, error);
 		}
 	}
 }
diff --git a/src/Log.hxx b/src/Log.hxx
index 55a6a7a31..24cbe5c8d 100644
--- a/src/Log.hxx
+++ b/src/Log.hxx
@@ -20,16 +20,7 @@
 #ifndef MPD_LOG_HXX
 #define MPD_LOG_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
-
-gcc_const
-static inline GQuark
-log_quark(void)
-{
-	return g_quark_from_static_string("log");
-}
+class Error;
 
 /**
  * Configure a logging destination for daemon startup, before the
@@ -43,7 +34,7 @@ void
 log_early_init(bool verbose);
 
 bool
-log_init(bool verbose, bool use_stdout, GError **error_r);
+log_init(bool verbose, bool use_stdout, Error &error);
 
 void
 log_deinit(void);
diff --git a/src/Main.cxx b/src/Main.cxx
index e724ebdb5..df06fd45a 100644
--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -56,6 +56,7 @@
 #include "pcm/PcmResample.hxx"
 #include "Daemon.hxx"
 #include "system/FatalError.hxx"
+#include "util/Error.hxx"
 
 extern "C" {
 #include "stats.h"
@@ -107,15 +108,11 @@ static inline GQuark main_quark()
 }
 
 static bool
-glue_daemonize_init(const struct options *options, GError **error_r)
+glue_daemonize_init(const struct options *options, Error &error)
 {
-	GError *error = NULL;
-
-	Path pid_file = config_get_path(CONF_PID_FILE, &error);
-	if (pid_file.IsNull() && error != NULL) {
-		g_propagate_error(error_r, error);
+	Path pid_file = config_get_path(CONF_PID_FILE, error);
+	if (pid_file.IsNull() && error.IsDefined())
 		return false;
-	}
 
 	daemonize_init(config_get_string(CONF_USER, NULL),
 		       config_get_string(CONF_GROUP, NULL),
@@ -128,20 +125,15 @@ glue_daemonize_init(const struct options *options, GError **error_r)
 }
 
 static bool
-glue_mapper_init(GError **error_r)
+glue_mapper_init(Error &error)
 {
-	GError *error = NULL;
-	Path music_dir = config_get_path(CONF_MUSIC_DIR, &error);
-	if (music_dir.IsNull() && error != NULL) {
-		g_propagate_error(error_r, error);
+	Path music_dir = config_get_path(CONF_MUSIC_DIR, error);
+	if (music_dir.IsNull() && error.IsDefined())
 		return false;
-	}
 
-	Path playlist_dir = config_get_path(CONF_PLAYLIST_DIR, &error);
-	if (playlist_dir.IsNull() && error != NULL) {
-		g_propagate_error(error_r, error);
+	Path playlist_dir = config_get_path(CONF_PLAYLIST_DIR, error);
+	if (playlist_dir.IsNull() && error.IsDefined())
 		return false;
-	}
 
 	if (music_dir.IsNull())
 		music_dir = Path::FromUTF8(g_get_user_special_dir(G_USER_DIRECTORY_MUSIC));
@@ -164,9 +156,6 @@ glue_db_init_and_load(void)
 	if (param != NULL && path != NULL)
 		g_message("Found both 'database' and 'db_file' setting - ignoring the latter");
 
-	GError *error = NULL;
-	bool ret;
-
 	if (!mapper_has_music_directory()) {
 		if (param != NULL)
 			g_message("Found database setting without "
@@ -185,13 +174,13 @@ glue_db_init_and_load(void)
 		param = allocated;
 	}
 
-	if (!DatabaseGlobalInit(*param, &error))
+	Error error;
+	if (!DatabaseGlobalInit(*param, error))
 		FatalError(error);
 
 	delete allocated;
 
-	ret = DatabaseGlobalOpen(&error);
-	if (!ret)
+	if (!DatabaseGlobalOpen(error))
 		FatalError(error);
 
 	/* run database update after daemonization? */
@@ -205,36 +194,22 @@ static void
 glue_sticker_init(void)
 {
 #ifdef ENABLE_SQLITE
-	GError *error = NULL;
-	Path sticker_file = config_get_path(CONF_STICKER_FILE, &error);
-	if (sticker_file.IsNull() && error != NULL)
+	Error error;
+	Path sticker_file = config_get_path(CONF_STICKER_FILE, error);
+	if (sticker_file.IsNull() && error.IsDefined())
 		FatalError(error);
 
-	if (!sticker_global_init(std::move(sticker_file), &error))
+	if (!sticker_global_init(std::move(sticker_file), error))
 		FatalError(error);
 #endif
 }
 
 static bool
-glue_state_file_init(GError **error_r)
+glue_state_file_init(Error &error)
 {
-	GError *error = NULL;
-
-	Path path_fs = config_get_path(CONF_STATE_FILE, &error);
-	if (path_fs.IsNull()) {
-		if (error != nullptr) {
-			g_propagate_error(error_r, error);
-			return false;
-		}
-
-		return true;
-	}
-
-	if (path_fs.IsNull()) {
-		g_set_error(error_r, main_quark(), 0,
-			    "Failed to convert state file path to FS encoding");
-		return false;
-	}
+	Path path_fs = config_get_path(CONF_STATE_FILE, error);
+	if (path_fs.IsNull())
+		return !error.IsDefined();
 
 	state_file = new StateFile(std::move(path_fs),
 				   *instance->partition, *main_loop);
@@ -364,7 +339,7 @@ int mpd_main(int argc, char *argv[])
 	struct options options;
 	clock_t start;
 	bool create_db;
-	GError *error = NULL;
+	Error error;
 	bool success;
 
 	daemonize_close_stdin();
@@ -385,25 +360,22 @@ int mpd_main(int argc, char *argv[])
 	winsock_init();
 	config_global_init();
 
-	success = parse_cmdline(argc, argv, &options, &error);
+	success = parse_cmdline(argc, argv, &options, error);
 	if (!success) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
-	if (!glue_daemonize_init(&options, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!glue_daemonize_init(&options, error)) {
+		g_printerr("%s\n", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
 	stats_global_init();
 	tag_lib_init();
 
-	if (!log_init(options.verbose, options.log_stderr, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!log_init(options.verbose, options.log_stderr, error)) {
+		g_warning("%s", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
@@ -415,10 +387,9 @@ int mpd_main(int argc, char *argv[])
 	const unsigned max_clients = config_get_positive(CONF_MAX_CONN, 10);
 	instance->client_list = new ClientList(max_clients);
 
-	success = listen_global_init(&error);
+	success = listen_global_init(error);
 	if (!success) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
@@ -432,9 +403,8 @@ int mpd_main(int argc, char *argv[])
 
 	Path::GlobalInit();
 
-	if (!glue_mapper_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!glue_mapper_init(error)) {
+		g_printerr("%s\n", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
@@ -445,9 +415,8 @@ int mpd_main(int argc, char *argv[])
 	archive_plugin_init_all();
 #endif
 
-	if (!pcm_resample_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!pcm_resample_global_init(error)) {
+		g_warning("%s", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
@@ -466,9 +435,8 @@ int mpd_main(int argc, char *argv[])
 	client_manager_init();
 	replay_gain_global_init();
 
-	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 EXIT_FAILURE;
 	}
 
@@ -494,9 +462,8 @@ int mpd_main(int argc, char *argv[])
 			FatalError("directory update failed");
 	}
 
-	if (!glue_state_file_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!glue_state_file_init(error)) {
+		g_printerr("%s\n", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
diff --git a/src/Mapper.hxx b/src/Mapper.hxx
index 1d3da3c00..a224b8051 100644
--- a/src/Mapper.hxx
+++ b/src/Mapper.hxx
@@ -25,7 +25,6 @@
 #define MPD_MAPPER_HXX
 
 #include "gcc.h"
-#include "gerror.h"
 
 #define PLAYLIST_FILE_SUFFIX ".m3u"
 
diff --git a/src/MixerAll.cxx b/src/MixerAll.cxx
index 5a6235de4..8005655e5 100644
--- a/src/MixerAll.cxx
+++ b/src/MixerAll.cxx
@@ -25,6 +25,7 @@
 #include "OutputAll.hxx"
 #include "pcm/PcmVolume.hxx"
 #include "OutputInternal.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -38,7 +39,6 @@ output_mixer_get_volume(unsigned i)
 {
 	struct audio_output *output;
 	int volume;
-	GError *error = NULL;
 
 	assert(i < audio_output_count());
 
@@ -50,12 +50,11 @@ output_mixer_get_volume(unsigned i)
 	if (mixer == NULL)
 		return -1;
 
-	volume = mixer_get_volume(mixer, &error);
-	if (volume < 0 && error != NULL) {
+	Error error;
+	volume = mixer_get_volume(mixer, error);
+	if (volume < 0 && error.IsDefined())
 		g_warning("Failed to read mixer for '%s': %s",
-			  output->name, error->message);
-		g_error_free(error);
-	}
+			  output->name, error.GetMessage());
 
 	return volume;
 }
@@ -85,7 +84,6 @@ output_mixer_set_volume(unsigned i, unsigned volume)
 {
 	struct audio_output *output;
 	bool success;
-	GError *error = NULL;
 
 	assert(i < audio_output_count());
 	assert(volume <= 100);
@@ -98,12 +96,11 @@ output_mixer_set_volume(unsigned i, unsigned volume)
 	if (mixer == NULL)
 		return false;
 
-	success = mixer_set_volume(mixer, volume, &error);
-	if (!success && error != NULL) {
+	Error error;
+	success = mixer_set_volume(mixer, volume, error);
+	if (!success && error.IsDefined())
 		g_warning("Failed to set mixer for '%s': %s",
-			  output->name, error->message);
-		g_error_free(error);
-	}
+			  output->name, error.GetMessage());
 
 	return success;
 }
@@ -138,7 +135,7 @@ output_mixer_get_software_volume(unsigned i)
 	if (mixer == NULL || !mixer->IsPlugin(software_mixer_plugin))
 		return -1;
 
-	return mixer_get_volume(mixer, NULL);
+	return mixer_get_volume(mixer, IgnoreError());
 }
 
 int
@@ -172,6 +169,6 @@ mixer_all_set_software_volume(unsigned volume)
 		struct audio_output *output = audio_output_get(i);
 		if (output->mixer != NULL &&
 		    output->mixer->plugin == &software_mixer_plugin)
-			mixer_set_volume(output->mixer, volume, NULL);
+			mixer_set_volume(output->mixer, volume, IgnoreError());
 	}
 }
diff --git a/src/MixerControl.cxx b/src/MixerControl.cxx
index bbb3ede2c..86db5dde4 100644
--- a/src/MixerControl.cxx
+++ b/src/MixerControl.cxx
@@ -20,8 +20,7 @@
 #include "config.h"
 #include "MixerControl.hxx"
 #include "MixerInternal.hxx"
-
-#include <glib.h>
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <stddef.h>
@@ -32,13 +31,13 @@
 Mixer *
 mixer_new(const struct mixer_plugin *plugin, void *ao,
 	  const config_param &param,
-	  GError **error_r)
+	  Error &error)
 {
 	Mixer *mixer;
 
 	assert(plugin != NULL);
 
-	mixer = plugin->init(ao, param, error_r);
+	mixer = plugin->init(ao, param, error);
 
 	assert(mixer == NULL || mixer->IsPlugin(*plugin));
 
@@ -59,7 +58,7 @@ mixer_free(Mixer *mixer)
 }
 
 bool
-mixer_open(Mixer *mixer, GError **error_r)
+mixer_open(Mixer *mixer, Error &error)
 {
 	bool success;
 
@@ -73,7 +72,7 @@ mixer_open(Mixer *mixer, GError **error_r)
 	else if (mixer->plugin->open == NULL)
 		success = mixer->open = true;
 	else
-		success = mixer->open = mixer->plugin->open(mixer, error_r);
+		success = mixer->open = mixer->plugin->open(mixer, error);
 
 	mixer->failed = !success;
 
@@ -127,26 +126,22 @@ mixer_failed(Mixer *mixer)
 }
 
 int
-mixer_get_volume(Mixer *mixer, GError **error_r)
+mixer_get_volume(Mixer *mixer, Error &error)
 {
 	int volume;
 
 	assert(mixer != NULL);
 
 	if (mixer->plugin->global && !mixer->failed &&
-	    !mixer_open(mixer, error_r))
+	    !mixer_open(mixer, error))
 		return -1;
 
 	const ScopeLock protect(mixer->mutex);
 
 	if (mixer->open) {
-		GError *error = NULL;
-
-		volume = mixer->plugin->get_volume(mixer, &error);
-		if (volume < 0 && error != NULL) {
-			g_propagate_error(error_r, error);
+		volume = mixer->plugin->get_volume(mixer, error);
+		if (volume < 0 && error.IsDefined())
 			mixer_failed(mixer);
-		}
 	} else
 		volume = -1;
 
@@ -154,17 +149,17 @@ mixer_get_volume(Mixer *mixer, GError **error_r)
 }
 
 bool
-mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
+mixer_set_volume(Mixer *mixer, unsigned volume, Error &error)
 {
 	assert(mixer != NULL);
 	assert(volume <= 100);
 
 	if (mixer->plugin->global && !mixer->failed &&
-	    !mixer_open(mixer, error_r))
+	    !mixer_open(mixer, error))
 		return false;
 
 	const ScopeLock protect(mixer->mutex);
 
 	return mixer->open &&
-		mixer->plugin->set_volume(mixer, volume, error_r);
+		mixer->plugin->set_volume(mixer, volume, error);
 }
diff --git a/src/MixerControl.hxx b/src/MixerControl.hxx
index cf609e817..c1ee01eec 100644
--- a/src/MixerControl.hxx
+++ b/src/MixerControl.hxx
@@ -25,8 +25,7 @@
 #ifndef MPD_MIXER_CONTROL_HXX
 #define MPD_MIXER_CONTROL_HXX
 
-#include "gerror.h"
-
+class Error;
 class Mixer;
 struct mixer_plugin;
 struct config_param;
@@ -34,13 +33,13 @@ struct config_param;
 Mixer *
 mixer_new(const struct mixer_plugin *plugin, void *ao,
 	  const config_param &param,
-	  GError **error_r);
+	  Error &error);
 
 void
 mixer_free(Mixer *mixer);
 
 bool
-mixer_open(Mixer *mixer, GError **error_r);
+mixer_open(Mixer *mixer, Error &error);
 
 void
 mixer_close(Mixer *mixer);
@@ -53,9 +52,9 @@ void
 mixer_auto_close(Mixer *mixer);
 
 int
-mixer_get_volume(Mixer *mixer, GError **error_r);
+mixer_get_volume(Mixer *mixer, Error &error);
 
 bool
-mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r);
+mixer_set_volume(Mixer *mixer, unsigned volume, Error &error);
 
 #endif
diff --git a/src/MixerPlugin.hxx b/src/MixerPlugin.hxx
index e80ae094e..4dd8969b9 100644
--- a/src/MixerPlugin.hxx
+++ b/src/MixerPlugin.hxx
@@ -27,10 +27,9 @@
 #ifndef MPD_MIXER_PLUGIN_HXX
 #define MPD_MIXER_PLUGIN_HXX
 
-#include "gerror.h"
-
 struct config_param;
 class Mixer;
+class Error;
 
 struct mixer_plugin {
 	/**
@@ -43,7 +42,7 @@ struct mixer_plugin {
 	 * @return a mixer object, or NULL on error
 	 */
 	Mixer *(*init)(void *ao, const config_param &param,
-		       GError **error_r);
+		       Error &error);
 
 	/**
 	 * Finish and free mixer data
@@ -57,7 +56,7 @@ struct mixer_plugin {
 	 * NULL to ignore errors
 	 * @return true on success, false on error
 	 */
-	bool (*open)(Mixer *data, GError **error_r);
+	bool (*open)(Mixer *data, Error &error);
 
 	/**
 	 * Close mixer device
@@ -70,9 +69,9 @@ struct mixer_plugin {
 	 * @param error_r location to store the error occurring, or
 	 * NULL to ignore errors
 	 * @return the current volume (0..100 including) or -1 if
-	 * unavailable or on error (error_r set, mixer will be closed)
+	 * unavailable or on error (error set, mixer will be closed)
 	 */
-	int (*get_volume)(Mixer *mixer, GError **error_r);
+	int (*get_volume)(Mixer *mixer, Error &error);
 
 	/**
 	 * Sets the volume.
@@ -83,7 +82,7 @@ struct mixer_plugin {
 	 * @return true on success, false on error
 	 */
 	bool (*set_volume)(Mixer *mixer, unsigned volume,
-			   GError **error_r);
+			   Error &error);
 
 	/**
 	 * If true, then the mixer is automatically opened, even if
diff --git a/src/OtherCommands.cxx b/src/OtherCommands.cxx
index 547946e3e..04ccf6d54 100644
--- a/src/OtherCommands.cxx
+++ b/src/OtherCommands.cxx
@@ -34,6 +34,7 @@
 #include "ls.hxx"
 #include "Volume.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "fs/Path.hxx"
 
 extern "C" {
@@ -126,8 +127,8 @@ handle_lsinfo(Client *client, int argc, char *argv[])
 			return COMMAND_RETURN_ERROR;
 		}
 
-		GError *error = NULL;
-		if (!client_allow_file(client, path_fs, &error))
+		Error error;
+		if (!client_allow_file(client, path_fs, error))
 			return print_error(client, error);
 
 		Song *song = Song::LoadFile(path_utf8, nullptr);
@@ -147,7 +148,8 @@ handle_lsinfo(Client *client, int argc, char *argv[])
 		return result;
 
 	if (isRootDirectory(uri)) {
-		const auto &list = ListPlaylistFiles(NULL);
+		Error error;
+		const auto &list = ListPlaylistFiles(error);
 		print_spl_list(client, list);
 	}
 
diff --git a/src/OutputAll.cxx b/src/OutputAll.cxx
index 575eb0c70..27a4e42f5 100644
--- a/src/OutputAll.cxx
+++ b/src/OutputAll.cxx
@@ -27,6 +27,7 @@
 #include "MusicPipe.hxx"
 #include "MusicChunk.hxx"
 #include "system/FatalError.hxx"
+#include "util/Error.hxx"
 #include "conf.h"
 #include "notify.hxx"
 
@@ -104,7 +105,7 @@ audio_output_all_init(struct player_control *pc)
 {
 	const struct config_param *param = NULL;
 	unsigned int i;
-	GError *error = NULL;
+	Error error;
 
 	num_audio_outputs = audio_output_config_count();
 	audio_outputs = g_new(struct audio_output *, num_audio_outputs);
@@ -125,11 +126,12 @@ audio_output_all_init(struct player_control *pc)
 			param = &empty;
 		}
 
-		struct audio_output *output = audio_output_new(*param, pc, &error);
+		audio_output *output = audio_output_new(*param, pc, error);
 		if (output == NULL) {
 			if (param != NULL)
 				FormatFatalError("line %i: %s",
-						 param->line, error->message);
+						 param->line,
+						 error.GetMessage());
 			else
 				FatalError(error);
 		}
@@ -271,7 +273,7 @@ audio_output_all_set_replay_gain_mode(enum replay_gain_mode mode)
 }
 
 bool
-audio_output_all_play(struct music_chunk *chunk, GError **error_r)
+audio_output_all_play(struct music_chunk *chunk, Error &error)
 {
 	bool ret;
 	unsigned int i;
@@ -284,8 +286,7 @@ audio_output_all_play(struct music_chunk *chunk, GError **error_r)
 	ret = audio_output_all_update();
 	if (!ret) {
 		/* TODO: obtain real error */
-		g_set_error(error_r, output_quark(), 0,
-			    "Failed to open audio output");
+		error.Set(output_domain, "Failed to open audio output");
 		return false;
 	}
 
@@ -300,7 +301,7 @@ audio_output_all_play(struct music_chunk *chunk, GError **error_r)
 bool
 audio_output_all_open(const AudioFormat audio_format,
 		      struct music_buffer *buffer,
-		      GError **error_r)
+		      Error &error)
 {
 	bool ret = false, enabled = false;
 	unsigned int i;
@@ -338,12 +339,10 @@ audio_output_all_open(const AudioFormat audio_format,
 	}
 
 	if (!enabled)
-		g_set_error(error_r, output_quark(), 0,
-			    "All audio outputs are disabled");
+		error.Set(output_domain, "All audio outputs are disabled");
 	else if (!ret)
 		/* TODO: obtain real error */
-		g_set_error(error_r, output_quark(), 0,
-			    "Failed to open audio output");
+		error.Set(output_domain, "Failed to open audio output");
 
 	if (!ret)
 		/* close all devices if there was an error */
diff --git a/src/OutputAll.hxx b/src/OutputAll.hxx
index 10f8196aa..fc27a4c6e 100644
--- a/src/OutputAll.hxx
+++ b/src/OutputAll.hxx
@@ -27,12 +27,12 @@
 #define OUTPUT_ALL_H
 
 #include "replay_gain_info.h"
-#include "gerror.h"
 
 struct AudioFormat;
 struct music_buffer;
 struct music_chunk;
 struct player_control;
+class Error;
 
 /**
  * Global initialization: load audio outputs from the configuration
@@ -84,7 +84,7 @@ audio_output_all_enable_disable(void);
 bool
 audio_output_all_open(AudioFormat audio_format,
 		      struct music_buffer *buffer,
-		      GError **error_r);
+		      Error &error);
 
 /**
  * Closes all audio outputs.
@@ -111,7 +111,7 @@ audio_output_all_set_replay_gain_mode(enum replay_gain_mode mode);
  * (all closed then)
  */
 bool
-audio_output_all_play(struct music_chunk *chunk, GError **error_r);
+audio_output_all_play(struct music_chunk *chunk, Error &error);
 
 /**
  * Checks if the output devices have drained their music pipe, and
diff --git a/src/OutputControl.cxx b/src/OutputControl.cxx
index b8f3a3ea4..820713593 100644
--- a/src/OutputControl.cxx
+++ b/src/OutputControl.cxx
@@ -27,6 +27,7 @@
 #include "notify.hxx"
 #include "filter/ReplayGainFilterPlugin.hxx"
 #include "FilterPlugin.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <stdlib.h>
@@ -187,13 +188,10 @@ audio_output_open(struct audio_output *ao,
 	open = ao->open;
 
 	if (open && ao->mixer != NULL) {
-		GError *error = NULL;
-
-		if (!mixer_open(ao->mixer, &error)) {
+		Error error;
+		if (!mixer_open(ao->mixer, error))
 			g_warning("Failed to open mixer for '%s': %s",
-				  ao->name, error->message);
-			g_error_free(error);
-		}
+				  ao->name, error.GetMessage());
 	}
 
 	return open;
diff --git a/src/OutputError.cxx b/src/OutputError.cxx
new file mode 100644
index 000000000..a18bfff23
--- /dev/null
+++ b/src/OutputError.cxx
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2003-2013 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 "OutputError.hxx"
+#include "util/Domain.hxx"
+
+const Domain output_domain("output");
diff --git a/src/OutputError.hxx b/src/OutputError.hxx
index e1f91e196..22a11fdbd 100644
--- a/src/OutputError.hxx
+++ b/src/OutputError.hxx
@@ -20,18 +20,6 @@
 #ifndef MPD_OUTPUT_ERROR_HXX
 #define MPD_OUTPUT_ERROR_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
-
-/**
- * Quark for GError.domain.
- */
-gcc_const
-static inline GQuark
-output_quark(void)
-{
-	return g_quark_from_static_string("output");
-}
+extern const class Domain output_domain;
 
 #endif
diff --git a/src/OutputInit.cxx b/src/OutputInit.cxx
index 2e50515c8..17fff933a 100644
--- a/src/OutputInit.cxx
+++ b/src/OutputInit.cxx
@@ -34,6 +34,8 @@
 #include "filter/AutoConvertFilterPlugin.hxx"
 #include "filter/ReplayGainFilterPlugin.hxx"
 #include "filter/ChainFilterPlugin.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -49,7 +51,7 @@
 #define AUDIO_FILTERS		"filters"
 
 static const struct audio_output_plugin *
-audio_output_detect(GError **error)
+audio_output_detect(Error &error)
 {
 	g_warning("Attempt to detect audio output device");
 
@@ -63,8 +65,7 @@ audio_output_detect(GError **error)
 			return plugin;
 	}
 
-	g_set_error(error, output_quark(), 0,
-		    "Unable to detect an audio device");
+	error.Set(output_domain, "Unable to detect an audio device");
 	return NULL;
 }
 
@@ -99,7 +100,7 @@ audio_output_load_mixer(struct audio_output *ao,
 			const config_param &param,
 			const struct mixer_plugin *plugin,
 			Filter &filter_chain,
-			GError **error_r)
+			Error &error)
 {
 	Mixer *mixer;
 
@@ -112,12 +113,12 @@ audio_output_load_mixer(struct audio_output *ao,
 		if (plugin == NULL)
 			return NULL;
 
-		return mixer_new(plugin, ao, param, error_r);
+		return mixer_new(plugin, ao, param, error);
 
 	case MIXER_TYPE_SOFTWARE:
 		mixer = mixer_new(&software_mixer_plugin, nullptr,
 				  config_param(),
-				  nullptr);
+				  IgnoreError());
 		assert(mixer != NULL);
 
 		filter_chain_append(filter_chain, "software_mixer",
@@ -132,7 +133,7 @@ audio_output_load_mixer(struct audio_output *ao,
 bool
 ao_base_init(struct audio_output *ao,
 	     const struct audio_output_plugin *plugin,
-	     const config_param &param, GError **error_r)
+	     const config_param &param, Error &error)
 {
 	assert(ao != NULL);
 	assert(plugin != NULL);
@@ -141,13 +142,11 @@ ao_base_init(struct audio_output *ao,
 	assert(plugin->close != NULL);
 	assert(plugin->play != NULL);
 
-	GError *error = NULL;
-
 	if (!param.IsNull()) {
 		ao->name = param.GetBlockValue(AUDIO_OUTPUT_NAME);
 		if (ao->name == NULL) {
-			g_set_error(error_r, output_quark(), 0,
-				    "Missing \"name\" configuration");
+			error.Set(config_domain,
+				  "Missing \"name\" configuration");
 			return false;
 		}
 
@@ -155,7 +154,7 @@ ao_base_init(struct audio_output *ao,
 		if (p != NULL) {
 			bool success =
 				audio_format_parse(ao->config_audio_format,
-						   p, true, error_r);
+						   p, true, error);
 			if (!success)
 				return false;
 		} else
@@ -186,25 +185,23 @@ ao_base_init(struct audio_output *ao,
 	if (config_get_bool(CONF_VOLUME_NORMALIZATION, false)) {
 		Filter *normalize_filter =
 			filter_new(&normalize_filter_plugin, config_param(),
-				   nullptr);
+				   IgnoreError());
 		assert(normalize_filter != NULL);
 
 		filter_chain_append(*ao->filter, "normalize",
 				    autoconvert_filter_new(normalize_filter));
 	}
 
+	Error filter_error;
 	filter_chain_parse(*ao->filter,
 			   param.GetBlockValue(AUDIO_FILTERS, ""),
-	                   &error
-	);
+			   filter_error);
 
 	// It's not really fatal - Part of the filter chain has been set up already
 	// and even an empty one will work (if only with unexpected behaviour)
-	if (error != NULL) {
+	if (filter_error.IsDefined())
 		g_warning("Failed to initialize filter chain for '%s': %s",
-			  ao->name, error->message);
-		g_error_free(error);
-	}
+			  ao->name, filter_error.GetMessage());
 
 	ao->thread = NULL;
 	ao->command = AO_COMMAND_NONE;
@@ -220,7 +217,7 @@ ao_base_init(struct audio_output *ao,
 
 static bool
 audio_output_setup(struct audio_output *ao, const config_param &param,
-		   GError **error_r)
+		   Error &error)
 {
 
 	/* create the replay_gain filter */
@@ -230,13 +227,14 @@ audio_output_setup(struct audio_output *ao, const config_param &param,
 
 	if (strcmp(replay_gain_handler, "none") != 0) {
 		ao->replay_gain_filter = filter_new(&replay_gain_filter_plugin,
-						    param, NULL);
+						    param, IgnoreError());
 		assert(ao->replay_gain_filter != NULL);
 
 		ao->replay_gain_serial = 0;
 
 		ao->other_replay_gain_filter = filter_new(&replay_gain_filter_plugin,
-							  param, NULL);
+							  param,
+							  IgnoreError());
 		assert(ao->other_replay_gain_filter != NULL);
 
 		ao->other_replay_gain_serial = 0;
@@ -247,15 +245,13 @@ audio_output_setup(struct audio_output *ao, const config_param &param,
 
 	/* set up the mixer */
 
-	GError *error = NULL;
+	Error mixer_error;
 	ao->mixer = audio_output_load_mixer(ao, param,
 					    ao->plugin->mixer_plugin,
-					    *ao->filter, &error);
-	if (ao->mixer == NULL && error != NULL) {
+					    *ao->filter, mixer_error);
+	if (ao->mixer == NULL && mixer_error.IsDefined())
 		g_warning("Failed to initialize hardware mixer for '%s': %s",
-			  ao->name, error->message);
-		g_error_free(error);
-	}
+			  ao->name, mixer_error.GetMessage());
 
 	/* use the hardware mixer for replay gain? */
 
@@ -267,15 +263,15 @@ audio_output_setup(struct audio_output *ao, const config_param &param,
 			g_warning("No such mixer for output '%s'", ao->name);
 	} else if (strcmp(replay_gain_handler, "software") != 0 &&
 		   ao->replay_gain_filter != NULL) {
-		g_set_error(error_r, output_quark(), 0,
-			    "Invalid \"replay_gain_handler\" value");
+		error.Set(config_domain,
+			  "Invalid \"replay_gain_handler\" value");
 		return false;
 	}
 
 	/* the "convert" filter must be the last one in the chain */
 
 	ao->convert_filter = filter_new(&convert_filter_plugin, config_param(),
-					nullptr);
+					IgnoreError());
 	assert(ao->convert_filter != NULL);
 
 	filter_chain_append(*ao->filter, "convert", ao->convert_filter);
@@ -286,7 +282,7 @@ audio_output_setup(struct audio_output *ao, const config_param &param,
 struct audio_output *
 audio_output_new(const config_param &param,
 		 struct player_control *pc,
-		 GError **error_r)
+		 Error &error)
 {
 	const struct audio_output_plugin *plugin;
 
@@ -295,21 +291,21 @@ audio_output_new(const config_param &param,
 
 		p = param.GetBlockValue(AUDIO_OUTPUT_TYPE);
 		if (p == NULL) {
-			g_set_error(error_r, output_quark(), 0,
-				    "Missing \"type\" configuration");
+			error.Set(config_domain,
+				  "Missing \"type\" configuration");
 			return nullptr;
 		}
 
 		plugin = audio_output_plugin_get(p);
 		if (plugin == NULL) {
-			g_set_error(error_r, output_quark(), 0,
-				    "No such audio output plugin: %s", p);
+			error.Format(config_domain,
+				     "No such audio output plugin: %s", p);
 			return nullptr;
 		}
 	} else {
 		g_warning("No 'audio_output' defined in config file\n");
 
-		plugin = audio_output_detect(error_r);
+		plugin = audio_output_detect(error);
 		if (plugin == NULL)
 			return nullptr;
 
@@ -317,11 +313,11 @@ audio_output_new(const config_param &param,
 			  plugin->name);
 	}
 
-	struct audio_output *ao = ao_plugin_init(plugin, param, error_r);
+	struct audio_output *ao = ao_plugin_init(plugin, param, error);
 	if (ao == NULL)
 		return NULL;
 
-	if (!audio_output_setup(ao, param, error_r)) {
+	if (!audio_output_setup(ao, param, error)) {
 		ao_plugin_finish(ao);
 		return NULL;
 	}
diff --git a/src/OutputInternal.hxx b/src/OutputInternal.hxx
index 20e48279f..188a56723 100644
--- a/src/OutputInternal.hxx
+++ b/src/OutputInternal.hxx
@@ -29,6 +29,7 @@
 
 #include <time.h>
 
+class Error;
 class Filter;
 struct config_param;
 
@@ -263,12 +264,12 @@ audio_output_command_is_finished(const struct audio_output *ao)
 struct audio_output *
 audio_output_new(const config_param &param,
 		 struct player_control *pc,
-		 GError **error_r);
+		 Error &error);
 
 bool
 ao_base_init(struct audio_output *ao,
 	     const struct audio_output_plugin *plugin,
-	     const config_param &param, GError **error_r);
+	     const config_param &param, Error &error);
 
 void
 ao_base_finish(struct audio_output *ao);
diff --git a/src/OutputPlugin.cxx b/src/OutputPlugin.cxx
index 7ac97cab9..038523ad9 100644
--- a/src/OutputPlugin.cxx
+++ b/src/OutputPlugin.cxx
@@ -24,7 +24,7 @@
 struct audio_output *
 ao_plugin_init(const struct audio_output_plugin *plugin,
 	       const config_param &param,
-	       GError **error)
+	       Error &error)
 {
 	assert(plugin != NULL);
 	assert(plugin->init != NULL);
@@ -39,7 +39,7 @@ ao_plugin_finish(struct audio_output *ao)
 }
 
 bool
-ao_plugin_enable(struct audio_output *ao, GError **error_r)
+ao_plugin_enable(struct audio_output *ao, Error &error_r)
 {
 	return ao->plugin->enable != NULL
 		? ao->plugin->enable(ao, error_r)
@@ -55,7 +55,7 @@ ao_plugin_disable(struct audio_output *ao)
 
 bool
 ao_plugin_open(struct audio_output *ao, AudioFormat &audio_format,
-	       GError **error)
+	       Error &error)
 {
 	return ao->plugin->open(ao, audio_format, error);
 }
@@ -83,7 +83,7 @@ ao_plugin_send_tag(struct audio_output *ao, const Tag *tag)
 
 size_t
 ao_plugin_play(struct audio_output *ao, const void *chunk, size_t size,
-	       GError **error)
+	       Error &error)
 {
 	return ao->plugin->play(ao, chunk, size, error);
 }
diff --git a/src/OutputPlugin.hxx b/src/OutputPlugin.hxx
index 5be476b68..20fd74453 100644
--- a/src/OutputPlugin.hxx
+++ b/src/OutputPlugin.hxx
@@ -21,13 +21,13 @@
 #define MPD_OUTPUT_PLUGIN_HXX
 
 #include "gcc.h"
-#include "gerror.h"
 
 #include <stddef.h>
 
 struct config_param;
 struct AudioFormat;
 struct Tag;
+class Error;
 
 /**
  * A plugin which controls an audio output device.
@@ -56,7 +56,7 @@ struct audio_output_plugin {
 	 * data
 	 */
 	struct audio_output *(*init)(const config_param &param,
-				     GError **error);
+				     Error &error);
 
 	/**
 	 * Free resources allocated by this device.
@@ -73,7 +73,7 @@ struct audio_output_plugin {
 	 * NULL to ignore errors
 	 * @return true on success, false on error
 	 */
-	bool (*enable)(struct audio_output *data, GError **error_r);
+	bool (*enable)(struct audio_output *data, Error &error);
 
 	/**
 	 * Disables the device.  It is closed before this method is
@@ -90,7 +90,7 @@ struct audio_output_plugin {
 	 * to ignore errors
 	 */
 	bool (*open)(struct audio_output *data, AudioFormat &audio_format,
-		     GError **error);
+		     Error &error);
 
 	/**
 	 * Close the device.
@@ -122,7 +122,7 @@ struct audio_output_plugin {
 	 */
 	size_t (*play)(struct audio_output *data,
 		       const void *chunk, size_t size,
-		       GError **error);
+		       Error &error);
 
 	/**
 	 * Wait until the device has finished playing.
@@ -169,20 +169,20 @@ gcc_malloc
 struct audio_output *
 ao_plugin_init(const struct audio_output_plugin *plugin,
 	       const config_param &param,
-	       GError **error);
+	       Error &error);
 
 void
 ao_plugin_finish(struct audio_output *ao);
 
 bool
-ao_plugin_enable(struct audio_output *ao, GError **error_r);
+ao_plugin_enable(struct audio_output *ao, Error &error);
 
 void
 ao_plugin_disable(struct audio_output *ao);
 
 bool
 ao_plugin_open(struct audio_output *ao, AudioFormat &audio_format,
-	       GError **error);
+	       Error &error);
 
 void
 ao_plugin_close(struct audio_output *ao);
@@ -196,7 +196,7 @@ ao_plugin_send_tag(struct audio_output *ao, const Tag *tag);
 
 size_t
 ao_plugin_play(struct audio_output *ao, const void *chunk, size_t size,
-	       GError **error);
+	       Error &error);
 
 void
 ao_plugin_drain(struct audio_output *ao);
diff --git a/src/OutputThread.cxx b/src/OutputThread.cxx
index 68c5c2c7b..fb73e158d 100644
--- a/src/OutputThread.cxx
+++ b/src/OutputThread.cxx
@@ -30,6 +30,7 @@
 #include "MusicPipe.hxx"
 #include "MusicChunk.hxx"
 #include "system/FatalError.hxx"
+#include "util/Error.hxx"
 #include "gcc.h"
 
 #include <glib.h>
@@ -55,19 +56,18 @@ static void ao_command_finished(struct audio_output *ao)
 static bool
 ao_enable(struct audio_output *ao)
 {
-	GError *error = NULL;
+	Error error;
 	bool success;
 
 	if (ao->really_enabled)
 		return true;
 
 	ao->mutex.unlock();
-	success = ao_plugin_enable(ao, &error);
+	success = ao_plugin_enable(ao, error);
 	ao->mutex.lock();
 	if (!success) {
 		g_warning("Failed to enable \"%s\" [%s]: %s\n",
-			  ao->name, ao->plugin->name, error->message);
-		g_error_free(error);
+			  ao->name, ao->plugin->name, error.GetMessage());
 		return false;
 	}
 
@@ -95,7 +95,7 @@ ao_disable(struct audio_output *ao)
 
 static AudioFormat
 ao_filter_open(struct audio_output *ao, AudioFormat &format,
-	       GError **error_r)
+	       Error &error_r)
 {
 	assert(format.IsValid());
 
@@ -131,7 +131,7 @@ static void
 ao_open(struct audio_output *ao)
 {
 	bool success;
-	GError *error = NULL;
+	Error error;
 	struct audio_format_string af_string;
 
 	assert(!ao->open);
@@ -157,11 +157,10 @@ ao_open(struct audio_output *ao)
 	/* open the filter */
 
 	const AudioFormat filter_audio_format =
-		ao_filter_open(ao, ao->in_audio_format, &error);
+		ao_filter_open(ao, ao->in_audio_format, error);
 	if (!filter_audio_format.IsDefined()) {
 		g_warning("Failed to open filter for \"%s\" [%s]: %s",
-			  ao->name, ao->plugin->name, error->message);
-		g_error_free(error);
+			  ao->name, ao->plugin->name, error.GetMessage());
 
 		ao->fail_timer = g_timer_new();
 		return;
@@ -173,15 +172,14 @@ ao_open(struct audio_output *ao)
 	ao->out_audio_format.ApplyMask(ao->config_audio_format);
 
 	ao->mutex.unlock();
-	success = ao_plugin_open(ao, ao->out_audio_format, &error);
+	success = ao_plugin_open(ao, ao->out_audio_format, error);
 	ao->mutex.lock();
 
 	assert(!ao->open);
 
 	if (!success) {
 		g_warning("Failed to open \"%s\" [%s]: %s",
-			  ao->name, ao->plugin->name, error->message);
-		g_error_free(error);
+			  ao->name, ao->plugin->name, error.GetMessage());
 
 		ao_filter_close(ao);
 		ao->fail_timer = g_timer_new();
@@ -231,15 +229,14 @@ ao_close(struct audio_output *ao, bool drain)
 static void
 ao_reopen_filter(struct audio_output *ao)
 {
-	GError *error = NULL;
+	Error error;
 
 	ao_filter_close(ao);
 	const AudioFormat filter_audio_format =
-		ao_filter_open(ao, ao->in_audio_format, &error);
+		ao_filter_open(ao, ao->in_audio_format, error);
 	if (!filter_audio_format.IsDefined()) {
 		g_warning("Failed to open filter for \"%s\" [%s]: %s",
-			  ao->name, ao->plugin->name, error->message);
-		g_error_free(error);
+			  ao->name, ao->plugin->name, error.GetMessage());
 
 		/* this is a little code duplication fro ao_close(),
 		   but we cannot call this function because we must
@@ -333,13 +330,12 @@ ao_chunk_data(struct audio_output *ao, const struct music_chunk *chunk,
 			*replay_gain_serial_p = chunk->replay_gain_serial;
 		}
 
-		GError *error = NULL;
+		Error error;
 		data = replay_gain_filter->FilterPCM(data, length,
-						     &length, &error);
+						     &length, error);
 		if (data == NULL) {
 			g_warning("\"%s\" [%s] failed to filter: %s",
-				  ao->name, ao->plugin->name, error->message);
-			g_error_free(error);
+				  ao->name, ao->plugin->name, error.GetMessage());
 			return NULL;
 		}
 	}
@@ -352,8 +348,6 @@ static const void *
 ao_filter_chunk(struct audio_output *ao, const struct music_chunk *chunk,
 		size_t *length_r)
 {
-	GError *error = NULL;
-
 	size_t length;
 	const void *data = ao_chunk_data(ao, chunk, ao->replay_gain_filter,
 					 &ao->replay_gain_serial, &length);
@@ -407,11 +401,11 @@ ao_filter_chunk(struct audio_output *ao, const struct music_chunk *chunk,
 
 	/* apply filter chain */
 
-	data = ao->filter->FilterPCM(data, length, &length, &error);
+	Error error;
+	data = ao->filter->FilterPCM(data, length, &length, error);
 	if (data == NULL) {
 		g_warning("\"%s\" [%s] failed to filter: %s",
-			  ao->name, ao->plugin->name, error->message);
-		g_error_free(error);
+			  ao->name, ao->plugin->name, error.GetMessage());
 		return NULL;
 	}
 
@@ -422,8 +416,6 @@ ao_filter_chunk(struct audio_output *ao, const struct music_chunk *chunk,
 static bool
 ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 {
-	GError *error = NULL;
-
 	assert(ao != NULL);
 	assert(ao->filter != NULL);
 
@@ -448,6 +440,8 @@ ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 		return false;
 	}
 
+	Error error;
+
 	while (size > 0 && ao->command == AO_COMMAND_NONE) {
 		size_t nbytes;
 
@@ -455,13 +449,13 @@ ao_play_chunk(struct audio_output *ao, const struct music_chunk *chunk)
 			break;
 
 		ao->mutex.unlock();
-		nbytes = ao_plugin_play(ao, data, size, &error);
+		nbytes = ao_plugin_play(ao, data, size, error);
 		ao->mutex.lock();
 		if (nbytes == 0) {
 			/* play()==0 means failure */
 			g_warning("\"%s\" [%s] failed to play: %s",
-				  ao->name, ao->plugin->name, error->message);
-			g_error_free(error);
+				  ao->name, ao->plugin->name,
+				  error.GetMessage());
 
 			ao_close(ao, false);
 
diff --git a/src/PlayerControl.cxx b/src/PlayerControl.cxx
index 357cdfc17..3fd09a8d1 100644
--- a/src/PlayerControl.cxx
+++ b/src/PlayerControl.cxx
@@ -40,7 +40,6 @@ player_control::player_control(unsigned _buffer_chunks,
 	 command(PLAYER_COMMAND_NONE),
 	 state(PLAYER_STATE_STOP),
 	 error_type(PLAYER_ERROR_NONE),
-	 error(nullptr),
 	 next_song(nullptr),
 	 cross_fade_seconds(0),
 	 mixramp_db(0),
@@ -216,16 +215,13 @@ player_control::GetStatus()
 }
 
 void
-player_control::SetError(player_error type, GError *_error)
+player_control::SetError(player_error type, Error &&_error)
 {
 	assert(type != PLAYER_ERROR_NONE);
-	assert(_error != NULL);
-
-	if (error_type != PLAYER_ERROR_NONE)
-	    g_error_free(error);
+	assert(_error.IsDefined());
 
 	error_type = type;
-	error = _error;
+	error = std::move(_error);
 }
 
 void
@@ -235,7 +231,7 @@ player_control::ClearError()
 
 	if (error_type != PLAYER_ERROR_NONE) {
 	    error_type = PLAYER_ERROR_NONE;
-	    g_error_free(error);
+	    error.Clear();
 	}
 
 	Unlock();
@@ -246,7 +242,7 @@ player_control::GetErrorMessage() const
 {
 	Lock();
 	char *message = error_type != PLAYER_ERROR_NONE
-		? g_strdup(error->message)
+		? g_strdup(error.GetMessage())
 		: NULL;
 	Unlock();
 	return message;
diff --git a/src/PlayerControl.hxx b/src/PlayerControl.hxx
index bea2e05eb..498f91143 100644
--- a/src/PlayerControl.hxx
+++ b/src/PlayerControl.hxx
@@ -23,6 +23,7 @@
 #include "AudioFormat.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -127,7 +128,7 @@ struct player_control {
 	 * #PLAYER_ERROR_NONE.  The object must be freed when this
 	 * object transitions back to #PLAYER_ERROR_NONE.
 	 */
-	GError *error;
+	Error error;
 
 	uint16_t bit_rate;
 	AudioFormat audio_format;
@@ -262,10 +263,9 @@ struct player_control {
 	 * Caller must lock the object.
 	 *
 	 * @param type the error type; must not be #PLAYER_ERROR_NONE
-	 * @param error detailed error information; must not be NULL; the
-	 * #player_control takes over ownership of this #GError instance
+	 * @param error detailed error information; must be defined.
 	 */
-	void SetError(player_error type, GError *error);
+	void SetError(player_error type, Error &&error);
 
 	void ClearError();
 
diff --git a/src/PlayerThread.cxx b/src/PlayerThread.cxx
index 87b173245..7d8c2b563 100644
--- a/src/PlayerThread.cxx
+++ b/src/PlayerThread.cxx
@@ -251,10 +251,10 @@ player_wait_for_decoder(struct player *player)
 
 	player->queued = false;
 
-	GError *error = dc->LockGetError();
-	if (error != NULL) {
+	Error error = dc->LockGetError();
+	if (error.IsDefined()) {
 		pc->Lock();
-		pc->SetError(PLAYER_ERROR_DECODER, error);
+		pc->SetError(PLAYER_ERROR_DECODER, std::move(error));
 
 		pc->next_song->Free();
 		pc->next_song = NULL;
@@ -327,9 +327,9 @@ player_open_output(struct player *player)
 	assert(pc->state == PLAYER_STATE_PLAY ||
 	       pc->state == PLAYER_STATE_PAUSE);
 
-	GError *error = NULL;
+	Error error;
 	if (audio_output_all_open(player->play_audio_format, player_buffer,
-				  &error)) {
+				  error)) {
 		player->output_open = true;
 		player->paused = false;
 
@@ -341,7 +341,7 @@ player_open_output(struct player *player)
 
 		return true;
 	} else {
-		g_warning("%s", error->message);
+		g_warning("%s", error.GetMessage());
 
 		player->output_open = false;
 
@@ -350,7 +350,7 @@ player_open_output(struct player *player)
 		player->paused = true;
 
 		pc->Lock();
-		pc->SetError(PLAYER_ERROR_OUTPUT, error);
+		pc->SetError(PLAYER_ERROR_OUTPUT, std::move(error));
 		pc->state = PLAYER_STATE_PAUSE;
 		pc->Unlock();
 
@@ -377,13 +377,13 @@ player_check_decoder_startup(struct player *player)
 
 	dc->Lock();
 
-	GError *error = dc->GetError();
-	if (error != NULL) {
+	Error error = dc->GetError();
+	if (error.IsDefined()) {
 		/* the decoder failed */
 		dc->Unlock();
 
 		pc->Lock();
-		pc->SetError(PLAYER_ERROR_DECODER, error);
+		pc->SetError(PLAYER_ERROR_DECODER, std::move(error));
 		pc->Unlock();
 
 		return false;
@@ -460,11 +460,9 @@ player_send_silence(struct player *player)
 	chunk->length = num_frames * frame_size;
 	memset(chunk->data, 0, chunk->length);
 
-	GError *error = NULL;
-	if (!audio_output_all_play(chunk, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
-
+	Error error;
+	if (!audio_output_all_play(chunk, error)) {
+		g_warning("%s", error.GetMessage());
 		music_buffer_return(player_buffer, chunk);
 		return false;
 	}
@@ -689,7 +687,7 @@ static bool
 play_chunk(struct player_control *pc,
 	   Song *song, struct music_chunk *chunk,
 	   const AudioFormat format,
-	   GError **error_r)
+	   Error &error)
 {
 	assert(chunk->CheckFormat(format));
 
@@ -707,7 +705,7 @@ play_chunk(struct player_control *pc,
 
 	/* send the chunk to the audio outputs */
 
-	if (!audio_output_all_play(chunk, error_r))
+	if (!audio_output_all_play(chunk, error))
 		return false;
 
 	pc->total_play_time += (double)chunk->length /
@@ -822,16 +820,16 @@ play_next_chunk(struct player *player)
 
 	/* play the current chunk */
 
-	GError *error = NULL;
+	Error error;
 	if (!play_chunk(player->pc, player->song, chunk,
-			player->play_audio_format, &error)) {
-		g_warning("%s", error->message);
+			player->play_audio_format, error)) {
+		g_warning("%s", error.GetMessage());
 
 		music_buffer_return(player_buffer, chunk);
 
 		pc->Lock();
 
-		pc->SetError(PLAYER_ERROR_OUTPUT, error);
+		pc->SetError(PLAYER_ERROR_OUTPUT, std::move(error));
 
 		/* pause: the user may resume playback as soon as an
 		   audio output becomes available */
diff --git a/src/PlaylistAny.cxx b/src/PlaylistAny.cxx
index e77b01467..9070f12a6 100644
--- a/src/PlaylistAny.cxx
+++ b/src/PlaylistAny.cxx
@@ -22,6 +22,7 @@
 #include "PlaylistMapper.hxx"
 #include "PlaylistRegistry.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "InputLegacy.hxx"
 
 #include <assert.h>
@@ -39,14 +40,12 @@ playlist_open_remote(const char *uri, Mutex &mutex, Cond &cond,
 		return playlist;
 	}
 
-	GError *error = NULL;
-	struct input_stream *is = input_stream_open(uri, mutex, cond, &error);
+	Error error;
+	input_stream *is = input_stream_open(uri, mutex, cond, error);
 	if (is == NULL) {
-		if (error != NULL) {
+		if (error.IsDefined())
 			g_warning("Failed to open %s: %s",
-				  uri, error->message);
-			g_error_free(error);
-		}
+				  uri, error.GetMessage());
 
 		return NULL;
 	}
diff --git a/src/PlaylistCommands.cxx b/src/PlaylistCommands.cxx
index faa8b72bb..785267c1d 100644
--- a/src/PlaylistCommands.cxx
+++ b/src/PlaylistCommands.cxx
@@ -33,6 +33,7 @@
 #include "ls.hxx"
 #include "Playlist.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <stdlib.h>
@@ -64,7 +65,7 @@ handle_load(Client *client, int argc, char *argv[])
 
 	if (argc < 3) {
 		start_index = 0;
-		end_index = G_MAXUINT;
+		end_index = unsigned(-1);
 	} else if (!check_range(client, &start_index, &end_index, argv[2]))
 		return COMMAND_RETURN_ERROR;
 
@@ -77,19 +78,22 @@ handle_load(Client *client, int argc, char *argv[])
 	if (result != PLAYLIST_RESULT_NO_SUCH_LIST)
 		return print_playlist_result(client, result);
 
-	GError *error = NULL;
+	Error error;
 	if (playlist_load_spl(&client->playlist, client->player_control,
 			      argv[1], start_index, end_index,
-			      &error))
+			      error))
 		return COMMAND_RETURN_OK;
 
-	if (error->domain == playlist_quark() &&
-	    error->code == PLAYLIST_RESULT_BAD_NAME)
+	if (error.IsDomain(playlist_domain) &&
+	    error.GetCode() == PLAYLIST_RESULT_BAD_NAME) {
 		/* the message for BAD_NAME is confusing when the
 		   client wants to load a playlist file from the music
-		   directory; patch the GError object to show "no such
+		   directory; patch the Error object to show "no such
 		   playlist" instead */
-		error->code = PLAYLIST_RESULT_NO_SUCH_LIST;
+		Error error2(playlist_domain, PLAYLIST_RESULT_NO_SUCH_LIST,
+			     error.GetMessage());
+		error = std::move(error2);
+	}
 
 	return print_error(client, error);
 }
@@ -100,8 +104,8 @@ handle_listplaylist(Client *client, gcc_unused int argc, char *argv[])
 	if (playlist_file_print(client, argv[1], false))
 		return COMMAND_RETURN_OK;
 
-	GError *error = NULL;
-	return spl_print(client, argv[1], false, &error)
+	Error error;
+	return spl_print(client, argv[1], false, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -113,8 +117,8 @@ handle_listplaylistinfo(Client *client,
 	if (playlist_file_print(client, argv[1], true))
 		return COMMAND_RETURN_OK;
 
-	GError *error = NULL;
-	return spl_print(client, argv[1], true, &error)
+	Error error;
+	return spl_print(client, argv[1], true, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -122,8 +126,8 @@ handle_listplaylistinfo(Client *client,
 enum command_return
 handle_rm(Client *client, gcc_unused int argc, char *argv[])
 {
-	GError *error = NULL;
-	return spl_delete(argv[1], &error)
+	Error error;
+	return spl_delete(argv[1], error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -131,8 +135,8 @@ handle_rm(Client *client, gcc_unused int argc, char *argv[])
 enum command_return
 handle_rename(Client *client, gcc_unused int argc, char *argv[])
 {
-	GError *error = NULL;
-	return spl_rename(argv[1], argv[2], &error)
+	Error error;
+	return spl_rename(argv[1], argv[2], error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -146,8 +150,8 @@ handle_playlistdelete(Client *client,
 	if (!check_unsigned(client, &from, argv[2]))
 		return COMMAND_RETURN_ERROR;
 
-	GError *error = NULL;
-	return spl_remove_index(playlist, from, &error)
+	Error error;
+	return spl_remove_index(playlist, from, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -163,8 +167,8 @@ handle_playlistmove(Client *client, gcc_unused int argc, char *argv[])
 	if (!check_unsigned(client, &to, argv[3]))
 		return COMMAND_RETURN_ERROR;
 
-	GError *error = NULL;
-	return spl_move_index(playlist, from, to, &error)
+	Error error;
+	return spl_move_index(playlist, from, to, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -172,8 +176,8 @@ handle_playlistmove(Client *client, gcc_unused int argc, char *argv[])
 enum command_return
 handle_playlistclear(Client *client, gcc_unused int argc, char *argv[])
 {
-	GError *error = NULL;
-	return spl_clear(argv[1], &error)
+	Error error;
+	return spl_clear(argv[1], error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -185,7 +189,7 @@ handle_playlistadd(Client *client, gcc_unused int argc, char *argv[])
 	char *uri = argv[2];
 
 	bool success;
-	GError *error = NULL;
+	Error error;
 	if (uri_has_scheme(uri)) {
 		if (!uri_supported_scheme(uri)) {
 			command_error(client, ACK_ERROR_NO_EXIST,
@@ -193,12 +197,12 @@ handle_playlistadd(Client *client, gcc_unused int argc, char *argv[])
 			return COMMAND_RETURN_ERROR;
 		}
 
-		success = spl_append_uri(uri, playlist, &error);
+		success = spl_append_uri(uri, playlist, error);
 	} else
 		success = search_add_to_playlist(uri, playlist, nullptr,
-						 &error);
+						 error);
 
-	if (!success && error == NULL) {
+	if (!success && !error.IsDefined()) {
 		command_error(client, ACK_ERROR_NO_EXIST,
 			      "directory or file not found");
 		return COMMAND_RETURN_ERROR;
@@ -211,9 +215,9 @@ enum command_return
 handle_listplaylists(Client *client,
 		     gcc_unused int argc, gcc_unused char *argv[])
 {
-	GError *error = NULL;
-	const auto list = ListPlaylistFiles(&error);
-	if (list.empty() && error != NULL)
+	Error error;
+	const auto list = ListPlaylistFiles(error);
+	if (list.empty() && error.IsDefined())
 		return print_error(client, error);
 
 	print_spl_list(client, list);
diff --git a/src/PlaylistDatabase.cxx b/src/PlaylistDatabase.cxx
index c5cfc8397..690845a68 100644
--- a/src/PlaylistDatabase.cxx
+++ b/src/PlaylistDatabase.cxx
@@ -22,15 +22,13 @@
 #include "PlaylistVector.hxx"
 #include "TextFile.hxx"
 #include "util/StringUtil.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <string.h>
 #include <stdlib.h>
 
-static GQuark
-playlist_database_quark(void)
-{
-	return g_quark_from_static_string("playlist_database");
-}
+static constexpr Domain playlist_database_domain("playlist_database");
 
 void
 playlist_vector_save(FILE *fp, const PlaylistVector &pv)
@@ -44,7 +42,7 @@ playlist_vector_save(FILE *fp, const PlaylistVector &pv)
 
 bool
 playlist_metadata_load(TextFile &file, PlaylistVector &pv, const char *name,
-		       GError **error_r)
+		       Error &error)
 {
 	PlaylistInfo pm(name, 0);
 
@@ -55,8 +53,8 @@ playlist_metadata_load(TextFile &file, PlaylistVector &pv, const char *name,
 	       strcmp(line, "playlist_end") != 0) {
 		colon = strchr(line, ':');
 		if (colon == NULL || colon == line) {
-			g_set_error(error_r, playlist_database_quark(), 0,
-				    "unknown line in db: %s", line);
+			error.Format(playlist_database_domain,
+				     "unknown line in db: %s", line);
 			return false;
 		}
 
@@ -66,8 +64,8 @@ playlist_metadata_load(TextFile &file, PlaylistVector &pv, const char *name,
 		if (strcmp(line, "mtime") == 0)
 			pm.mtime = strtol(value, NULL, 10);
 		else {
-			g_set_error(error_r, playlist_database_quark(), 0,
-				    "unknown line in db: %s", line);
+			error.Format(playlist_database_domain,
+				     "unknown line in db: %s", line);
 			return false;
 		}
 	}
diff --git a/src/PlaylistDatabase.hxx b/src/PlaylistDatabase.hxx
index a08d623fb..1481f621f 100644
--- a/src/PlaylistDatabase.hxx
+++ b/src/PlaylistDatabase.hxx
@@ -21,7 +21,6 @@
 #define MPD_PLAYLIST_DATABASE_HXX
 
 #include "check.h"
-#include "gerror.h"
 
 #include <stdio.h>
 
@@ -29,12 +28,13 @@
 
 class PlaylistVector;
 class TextFile;
+class Error;
 
 void
 playlist_vector_save(FILE *fp, const PlaylistVector &pv);
 
 bool
 playlist_metadata_load(TextFile &file, PlaylistVector &pv, const char *name,
-		       GError **error_r);
+		       Error &error);
 
 #endif
diff --git a/src/PlaylistEdit.cxx b/src/PlaylistEdit.cxx
index 0d46f66aa..4cb6e4bf3 100644
--- a/src/PlaylistEdit.cxx
+++ b/src/PlaylistEdit.cxx
@@ -27,6 +27,7 @@
 #include "Playlist.hxx"
 #include "PlayerControl.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "Song.hxx"
 #include "Idle.hxx"
 #include "DatabaseGlue.hxx"
@@ -110,11 +111,11 @@ playlist::AppendURI(struct player_control &pc,
 	if (uri_has_scheme(uri)) {
 		song = Song::NewRemote(uri);
 	} else {
-		db = GetDatabase(nullptr);
+		db = GetDatabase(IgnoreError());
 		if (db == nullptr)
 			return PLAYLIST_RESULT_NO_SUCH_SONG;
 
-		song = db->GetSong(uri, nullptr);
+		song = db->GetSong(uri, IgnoreError());
 		if (song == nullptr)
 			return PLAYLIST_RESULT_NO_SUCH_SONG;
 	}
diff --git a/src/PlaylistError.cxx b/src/PlaylistError.cxx
new file mode 100644
index 000000000..91291f551
--- /dev/null
+++ b/src/PlaylistError.cxx
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2003-2013 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 "PlaylistError.hxx"
+#include "util/Domain.hxx"
+
+const Domain playlist_domain("playlist");
diff --git a/src/PlaylistError.hxx b/src/PlaylistError.hxx
index 2750b82ba..7a3dad749 100644
--- a/src/PlaylistError.hxx
+++ b/src/PlaylistError.hxx
@@ -20,9 +20,7 @@
 #ifndef MPD_PLAYLIST_ERROR_HXX
 #define MPD_PLAYLIST_ERROR_HXX
 
-#include "gcc.h"
-
-#include <glib.h>
+class Domain;
 
 enum playlist_result {
 	PLAYLIST_RESULT_SUCCESS,
@@ -38,14 +36,6 @@ enum playlist_result {
 	PLAYLIST_RESULT_DISABLED,
 };
 
-/**
- * Quark for GError.domain; the code is an enum #playlist_result.
- */
-gcc_const
-static inline GQuark
-playlist_quark(void)
-{
-	return g_quark_from_static_string("playlist");
-}
+extern const Domain playlist_domain;
 
 #endif
diff --git a/src/PlaylistFile.cxx b/src/PlaylistFile.cxx
index 6541e6598..c05558fe3 100644
--- a/src/PlaylistFile.cxx
+++ b/src/PlaylistFile.cxx
@@ -25,7 +25,6 @@
 #include "DatabasePlugin.hxx"
 #include "DatabaseGlue.hxx"
 #include "Song.hxx"
-#include "io_error.h"
 #include "Mapper.hxx"
 #include "TextFile.hxx"
 #include "conf.h"
@@ -34,6 +33,7 @@
 #include "fs/FileSystem.hxx"
 #include "fs/DirectoryReader.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <sys/types.h>
@@ -79,22 +79,20 @@ spl_valid_name(const char *name_utf8)
 }
 
 static const Path &
-spl_map(GError **error_r)
+spl_map(Error &error)
 {
 	const Path &path_fs = map_spl_path();
 	if (path_fs.IsNull())
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_DISABLED,
-				    "Stored playlists are disabled");
+		error.Set(playlist_domain, PLAYLIST_RESULT_DISABLED,
+			  "Stored playlists are disabled");
 	return path_fs;
 }
 
 static bool
-spl_check_name(const char *name_utf8, GError **error_r)
+spl_check_name(const char *name_utf8, Error &error)
 {
 	if (!spl_valid_name(name_utf8)) {
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_BAD_NAME,
+		error.Set(playlist_domain, PLAYLIST_RESULT_BAD_NAME,
 				    "Bad playlist name");
 		return false;
 	}
@@ -103,35 +101,33 @@ spl_check_name(const char *name_utf8, GError **error_r)
 }
 
 static Path
-spl_map_to_fs(const char *name_utf8, GError **error_r)
+spl_map_to_fs(const char *name_utf8, Error &error)
 {
-	if (spl_map(error_r).IsNull() || !spl_check_name(name_utf8, error_r))
+	if (spl_map(error).IsNull() || !spl_check_name(name_utf8, error))
 		return Path::Null();
 
 	Path path_fs = map_spl_utf8_to_fs(name_utf8);
 	if (path_fs.IsNull())
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_BAD_NAME,
-				    "Bad playlist name");
+		error.Set(playlist_domain, PLAYLIST_RESULT_BAD_NAME,
+			  "Bad playlist name");
 
 	return path_fs;
 }
 
 /**
- * Create a GError for the current errno.
+ * Create an #Error for the current errno.
  */
 static void
-playlist_errno(GError **error_r)
+playlist_errno(Error &error)
 {
 	switch (errno) {
 	case ENOENT:
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_NO_SUCH_LIST,
-				    "No such playlist");
+		error.Set(playlist_domain, PLAYLIST_RESULT_NO_SUCH_LIST,
+			  "No such playlist");
 		break;
 
 	default:
-		set_error_errno(error_r);
+		error.SetErrno();
 		break;
 	}
 }
@@ -168,17 +164,17 @@ LoadPlaylistFileInfo(PlaylistInfo &info,
 }
 
 PlaylistVector
-ListPlaylistFiles(GError **error_r)
+ListPlaylistFiles(Error &error)
 {
 	PlaylistVector list;
 
-	const Path &parent_path_fs = spl_map(error_r);
+	const Path &parent_path_fs = spl_map(error);
 	if (parent_path_fs.IsNull())
 		return list;
 
 	DirectoryReader reader(parent_path_fs);
 	if (reader.HasFailed()) {
-		set_error_errno(error_r);
+		error.SetErrno();
 		return list;
 	}
 
@@ -194,20 +190,20 @@ ListPlaylistFiles(GError **error_r)
 
 static bool
 SavePlaylistFile(const PlaylistFileContents &contents, const char *utf8path,
-		 GError **error_r)
+		 Error &error)
 {
 	assert(utf8path != NULL);
 
-	if (spl_map(error_r).IsNull())
+	if (spl_map(error).IsNull())
 		return false;
 
-	const Path path_fs = spl_map_to_fs(utf8path, error_r);
+	const Path path_fs = spl_map_to_fs(utf8path, error);
 	if (path_fs.IsNull())
 		return false;
 
 	FILE *file = FOpen(path_fs, FOpenMode::WriteText);
 	if (file == NULL) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return false;
 	}
 
@@ -219,20 +215,20 @@ SavePlaylistFile(const PlaylistFileContents &contents, const char *utf8path,
 }
 
 PlaylistFileContents
-LoadPlaylistFile(const char *utf8path, GError **error_r)
+LoadPlaylistFile(const char *utf8path, Error &error)
 {
 	PlaylistFileContents contents;
 
-	if (spl_map(error_r).IsNull())
+	if (spl_map(error).IsNull())
 		return contents;
 
-	const Path path_fs = spl_map_to_fs(utf8path, error_r);
+	const Path path_fs = spl_map_to_fs(utf8path, error);
 	if (path_fs.IsNull())
 		return contents;
 
 	TextFile file(path_fs);
 	if (file.HasFailed()) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return contents;
 	}
 
@@ -262,24 +258,20 @@ LoadPlaylistFile(const char *utf8path, GError **error_r)
 
 bool
 spl_move_index(const char *utf8path, unsigned src, unsigned dest,
-	       GError **error_r)
+	       Error &error)
 {
 	if (src == dest)
 		/* this doesn't check whether the playlist exists, but
 		   what the hell.. */
 		return true;
 
-	GError *error = nullptr;
-	auto contents = LoadPlaylistFile(utf8path, &error);
-	if (contents.empty() && error != nullptr) {
-		g_propagate_error(error_r, error);
+	auto contents = LoadPlaylistFile(utf8path, error);
+	if (contents.empty() && error.IsDefined())
 		return false;
-	}
 
 	if (src >= contents.size() || dest >= contents.size()) {
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_BAD_RANGE,
-				    "Bad range");
+		error.Set(playlist_domain, PLAYLIST_RESULT_BAD_RANGE,
+			  "Bad range");
 		return false;
 	}
 
@@ -290,25 +282,25 @@ spl_move_index(const char *utf8path, unsigned src, unsigned dest,
 	const auto dest_i = std::next(contents.begin(), dest);
 	contents.insert(dest_i, std::move(value));
 
-	bool result = SavePlaylistFile(contents, utf8path, error_r);
+	bool result = SavePlaylistFile(contents, utf8path, error);
 
 	idle_add(IDLE_STORED_PLAYLIST);
 	return result;
 }
 
 bool
-spl_clear(const char *utf8path, GError **error_r)
+spl_clear(const char *utf8path, Error &error)
 {
-	if (spl_map(error_r).IsNull())
+	if (spl_map(error).IsNull())
 		return false;
 
-	const Path path_fs = spl_map_to_fs(utf8path, error_r);
+	const Path path_fs = spl_map_to_fs(utf8path, error);
 	if (path_fs.IsNull())
 		return false;
 
 	FILE *file = FOpen(path_fs, FOpenMode::WriteText);
 	if (file == NULL) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return false;
 	}
 
@@ -319,14 +311,14 @@ spl_clear(const char *utf8path, GError **error_r)
 }
 
 bool
-spl_delete(const char *name_utf8, GError **error_r)
+spl_delete(const char *name_utf8, Error &error)
 {
-	const Path path_fs = spl_map_to_fs(name_utf8, error_r);
+	const Path path_fs = spl_map_to_fs(name_utf8, error);
 	if (path_fs.IsNull())
 		return false;
 
 	if (!RemoveFile(path_fs)) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return false;
 	}
 
@@ -335,58 +327,53 @@ spl_delete(const char *name_utf8, GError **error_r)
 }
 
 bool
-spl_remove_index(const char *utf8path, unsigned pos, GError **error_r)
+spl_remove_index(const char *utf8path, unsigned pos, Error &error)
 {
-	GError *error = nullptr;
-	auto contents = LoadPlaylistFile(utf8path, &error);
-	if (contents.empty() && error != nullptr) {
-		g_propagate_error(error_r, error);
+	auto contents = LoadPlaylistFile(utf8path, error);
+	if (contents.empty() && error.IsDefined())
 		return false;
-	}
 
 	if (pos >= contents.size()) {
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_BAD_RANGE,
-				    "Bad range");
+		error.Set(playlist_domain, PLAYLIST_RESULT_BAD_RANGE,
+			  "Bad range");
 		return false;
 	}
 
 	contents.erase(std::next(contents.begin(), pos));
 
-	bool result = SavePlaylistFile(contents, utf8path, error_r);
+	bool result = SavePlaylistFile(contents, utf8path, error);
 
 	idle_add(IDLE_STORED_PLAYLIST);
 	return result;
 }
 
 bool
-spl_append_song(const char *utf8path, Song *song, GError **error_r)
+spl_append_song(const char *utf8path, Song *song, Error &error)
 {
-	if (spl_map(error_r).IsNull())
+	if (spl_map(error).IsNull())
 		return false;
 
-	const Path path_fs = spl_map_to_fs(utf8path, error_r);
+	const Path path_fs = spl_map_to_fs(utf8path, error);
 	if (path_fs.IsNull())
 		return false;
 
 	FILE *file = FOpen(path_fs, FOpenMode::AppendText);
 	if (file == NULL) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return false;
 	}
 
 	struct stat st;
 	if (fstat(fileno(file), &st) < 0) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		fclose(file);
 		return false;
 	}
 
 	if (st.st_size / (MPD_PATH_MAX + 1) >= (off_t)playlist_max_length) {
 		fclose(file);
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_TOO_LARGE,
-				    "Stored playlist is too large");
+		error.Set(playlist_domain, PLAYLIST_RESULT_TOO_LARGE,
+			  "Stored playlist is too large");
 		return false;
 	}
 
@@ -399,23 +386,23 @@ spl_append_song(const char *utf8path, Song *song, GError **error_r)
 }
 
 bool
-spl_append_uri(const char *url, const char *utf8file, GError **error_r)
+spl_append_uri(const char *url, const char *utf8file, Error &error)
 {
 	if (uri_has_scheme(url)) {
 		Song *song = Song::NewRemote(url);
-		bool success = spl_append_song(utf8file, song, error_r);
+		bool success = spl_append_song(utf8file, song, error);
 		song->Free();
 		return success;
 	} else {
-		const Database *db = GetDatabase(error_r);
+		const Database *db = GetDatabase(error);
 		if (db == nullptr)
 			return false;
 
-		Song *song = db->GetSong(url, error_r);
+		Song *song = db->GetSong(url, error);
 		if (song == nullptr)
 			return false;
 
-		bool success = spl_append_song(utf8file, song, error_r);
+		bool success = spl_append_song(utf8file, song, error);
 		db->ReturnSong(song);
 		return success;
 	}
@@ -423,24 +410,22 @@ spl_append_uri(const char *url, const char *utf8file, GError **error_r)
 
 static bool
 spl_rename_internal(const Path &from_path_fs, const Path &to_path_fs,
-		    GError **error_r)
+		    Error &error)
 {
 	if (!FileExists(from_path_fs)) {
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_NO_SUCH_LIST,
-				    "No such playlist");
+		error.Set(playlist_domain, PLAYLIST_RESULT_NO_SUCH_LIST,
+			  "No such playlist");
 		return false;
 	}
 
 	if (FileExists(to_path_fs)) {
-		g_set_error_literal(error_r, playlist_quark(),
-				    PLAYLIST_RESULT_LIST_EXISTS,
-				    "Playlist exists already");
+		error.Set(playlist_domain, PLAYLIST_RESULT_LIST_EXISTS,
+			  "Playlist exists already");
 		return false;
 	}
 
 	if (!RenameFile(from_path_fs, to_path_fs)) {
-		playlist_errno(error_r);
+		playlist_errno(error);
 		return false;
 	}
 
@@ -449,18 +434,18 @@ spl_rename_internal(const Path &from_path_fs, const Path &to_path_fs,
 }
 
 bool
-spl_rename(const char *utf8from, const char *utf8to, GError **error_r)
+spl_rename(const char *utf8from, const char *utf8to, Error &error)
 {
-	if (spl_map(error_r).IsNull())
+	if (spl_map(error).IsNull())
 		return false;
 
-	Path from_path_fs = spl_map_to_fs(utf8from, error_r);
+	Path from_path_fs = spl_map_to_fs(utf8from, error);
 	if (from_path_fs.IsNull())
 		return false;
 
-	Path to_path_fs = spl_map_to_fs(utf8to, error_r);
+	Path to_path_fs = spl_map_to_fs(utf8to, error);
 	if (to_path_fs.IsNull())
 		return false;
 
-	return spl_rename_internal(from_path_fs, to_path_fs, error_r);
+	return spl_rename_internal(from_path_fs, to_path_fs, error);
 }
diff --git a/src/PlaylistFile.hxx b/src/PlaylistFile.hxx
index 15dfd480d..5040d7406 100644
--- a/src/PlaylistFile.hxx
+++ b/src/PlaylistFile.hxx
@@ -20,14 +20,13 @@
 #ifndef MPD_PLAYLIST_FILE_HXX
 #define MPD_PLAYLIST_FILE_HXX
 
-#include "gerror.h"
-
 #include <vector>
 #include <string>
 
 struct Song;
 struct PlaylistInfo;
 class PlaylistVector;
+class Error;
 
 typedef std::vector<std::string> PlaylistFileContents;
 
@@ -51,31 +50,31 @@ spl_valid_name(const char *name_utf8);
  * NULL if an error occurred.
  */
 PlaylistVector
-ListPlaylistFiles(GError **error_r);
+ListPlaylistFiles(Error &error);
 
 PlaylistFileContents
-LoadPlaylistFile(const char *utf8path, GError **error_r);
+LoadPlaylistFile(const char *utf8path, Error &error);
 
 bool
 spl_move_index(const char *utf8path, unsigned src, unsigned dest,
-	       GError **error_r);
+	       Error &error);
 
 bool
-spl_clear(const char *utf8path, GError **error_r);
+spl_clear(const char *utf8path, Error &error);
 
 bool
-spl_delete(const char *name_utf8, GError **error_r);
+spl_delete(const char *name_utf8, Error &error);
 
 bool
-spl_remove_index(const char *utf8path, unsigned pos, GError **error_r);
+spl_remove_index(const char *utf8path, unsigned pos, Error &error);
 
 bool
-spl_append_song(const char *utf8path, Song *song, GError **error_r);
+spl_append_song(const char *utf8path, Song *song, Error &error);
 
 bool
-spl_append_uri(const char *file, const char *utf8file, GError **error_r);
+spl_append_uri(const char *file, const char *utf8file, Error &error);
 
 bool
-spl_rename(const char *utf8from, const char *utf8to, GError **error_r);
+spl_rename(const char *utf8from, const char *utf8to, Error &error);
 
 #endif
diff --git a/src/PlaylistPrint.cxx b/src/PlaylistPrint.cxx
index 6eb6bf76e..99f882f91 100644
--- a/src/PlaylistPrint.cxx
+++ b/src/PlaylistPrint.cxx
@@ -32,6 +32,7 @@
 #include "Client.hxx"
 #include "InputLegacy.hxx"
 #include "Song.hxx"
+#include "util/Error.hxx"
 
 void
 playlist_print_uris(Client *client, const struct playlist *playlist)
@@ -112,11 +113,11 @@ playlist_print_changes_position(Client *client,
 static bool
 PrintSongDetails(Client *client, const char *uri_utf8)
 {
-	const Database *db = GetDatabase(nullptr);
+	const Database *db = GetDatabase(IgnoreError());
 	if (db == nullptr)
 		return false;
 
-	Song *song = db->GetSong(uri_utf8, nullptr);
+	Song *song = db->GetSong(uri_utf8, IgnoreError());
 	if (song == nullptr)
 		return false;
 
@@ -127,14 +128,11 @@ PrintSongDetails(Client *client, const char *uri_utf8)
 
 bool
 spl_print(Client *client, const char *name_utf8, bool detail,
-	  GError **error_r)
+	  Error &error)
 {
-	GError *error = NULL;
-	PlaylistFileContents contents = LoadPlaylistFile(name_utf8, &error);
-	if (contents.empty() && error != nullptr) {
-		g_propagate_error(error_r, error);
+	PlaylistFileContents contents = LoadPlaylistFile(name_utf8, error);
+	if (contents.empty() && error.IsDefined())
 		return false;
-	}
 
 	for (const auto &uri_utf8 : contents) {
 		if (!detail || !PrintSongDetails(client, uri_utf8.c_str()))
diff --git a/src/PlaylistPrint.hxx b/src/PlaylistPrint.hxx
index 16bee9b85..c8c353d0c 100644
--- a/src/PlaylistPrint.hxx
+++ b/src/PlaylistPrint.hxx
@@ -20,13 +20,12 @@
 #ifndef MPD_PLAYLIST_PRINT_HXX
 #define MPD_PLAYLIST_PRINT_HXX
 
-#include "gerror.h"
-
 #include <stdint.h>
 
 struct playlist;
 class SongFilter;
 class Client;
+class Error;
 
 /**
  * Sends the whole playlist to the client, song URIs only.
@@ -94,7 +93,7 @@ playlist_print_changes_position(Client *client,
  */
 bool
 spl_print(Client *client, const char *name_utf8, bool detail,
-	  GError **error_r);
+	  Error &error);
 
 /**
  * Send the playlist file to the client.
diff --git a/src/PlaylistRegistry.cxx b/src/PlaylistRegistry.cxx
index 79fec4bd9..6f3c9aded 100644
--- a/src/PlaylistRegistry.cxx
+++ b/src/PlaylistRegistry.cxx
@@ -34,6 +34,7 @@
 #include "InputLegacy.hxx"
 #include "util/UriUtil.hxx"
 #include "util/StringUtil.hxx"
+#include "util/Error.hxx"
 #include "conf.h"
 #include "mpd_error.h"
 
@@ -219,7 +220,8 @@ playlist_list_open_stream_mime2(struct input_stream *is, const char *mime)
 		    string_array_contains(plugin->mime_types, mime)) {
 			/* rewind the stream, so each plugin gets a
 			   fresh start */
-			input_stream_seek(is, 0, SEEK_SET, NULL);
+			Error error;
+			input_stream_seek(is, 0, SEEK_SET, error);
 
 			playlist = playlist_plugin_open_stream(plugin, is);
 			if (playlist != NULL)
@@ -264,7 +266,8 @@ playlist_list_open_stream_suffix(struct input_stream *is, const char *suffix)
 		    string_array_contains(plugin->suffixes, suffix)) {
 			/* rewind the stream, so each plugin gets a
 			   fresh start */
-			input_stream_seek(is, 0, SEEK_SET, NULL);
+			Error error;
+			input_stream_seek(is, 0, SEEK_SET, error);
 
 			playlist = playlist_plugin_open_stream(plugin, is);
 			if (playlist != NULL)
@@ -318,9 +321,7 @@ struct playlist_provider *
 playlist_list_open_path(const char *path_fs, Mutex &mutex, Cond &cond,
 			struct input_stream **is_r)
 {
-	GError *error = NULL;
 	const char *suffix;
-	struct input_stream *is;
 	struct playlist_provider *playlist;
 
 	assert(path_fs != NULL);
@@ -329,12 +330,11 @@ playlist_list_open_path(const char *path_fs, Mutex &mutex, Cond &cond,
 	if (suffix == NULL || !playlist_suffix_supported(suffix))
 		return NULL;
 
-	is = input_stream_open(path_fs, mutex, cond, &error);
+	Error error;
+	input_stream *is = input_stream_open(path_fs, mutex, cond, error);
 	if (is == NULL) {
-		if (error != NULL) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
+		if (error.IsDefined())
+			g_warning("%s", error.GetMessage());
 
 		return NULL;
 	}
diff --git a/src/PlaylistSave.cxx b/src/PlaylistSave.cxx
index b259b1f3d..efcf03402 100644
--- a/src/PlaylistSave.cxx
+++ b/src/PlaylistSave.cxx
@@ -27,6 +27,7 @@
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -99,14 +100,11 @@ bool
 playlist_load_spl(struct playlist *playlist, struct player_control *pc,
 		  const char *name_utf8,
 		  unsigned start_index, unsigned end_index,
-		  GError **error_r)
+		  Error &error)
 {
-	GError *error = NULL;
-	PlaylistFileContents contents = LoadPlaylistFile(name_utf8, &error);
-	if (contents.empty() && error != nullptr) {
-		g_propagate_error(error_r, error);
+	PlaylistFileContents contents = LoadPlaylistFile(name_utf8, error);
+	if (contents.empty() && error.IsDefined())
 		return false;
-	}
 
 	if (end_index > contents.size())
 		end_index = contents.size();
diff --git a/src/PlaylistSave.hxx b/src/PlaylistSave.hxx
index 075ef2ea1..f85558755 100644
--- a/src/PlaylistSave.hxx
+++ b/src/PlaylistSave.hxx
@@ -28,6 +28,7 @@ struct Song;
 struct queue;
 struct playlist;
 struct player_control;
+class Error;
 
 void
 playlist_print_song(FILE *fp, const Song *song);
@@ -55,6 +56,6 @@ bool
 playlist_load_spl(struct playlist *playlist, struct player_control *pc,
 		  const char *name_utf8,
 		  unsigned start_index, unsigned end_index,
-		  GError **error_r);
+		  Error &error);
 
 #endif
diff --git a/src/PlaylistSong.cxx b/src/PlaylistSong.cxx
index 5de1f5c8c..f4c5b7478 100644
--- a/src/PlaylistSong.cxx
+++ b/src/PlaylistSong.cxx
@@ -26,6 +26,7 @@
 #include "Tag.hxx"
 #include "fs/Path.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "Song.hxx"
 
 #include <glib.h>
@@ -102,11 +103,11 @@ playlist_check_load_song(const Song *song, const char *uri, bool secure)
 		if (dest == NULL)
 			return NULL;
 	} else {
-		const Database *db = GetDatabase(nullptr);
+		const Database *db = GetDatabase(IgnoreError());
 		if (db == nullptr)
 			return nullptr;
 
-		Song *tmp = db->GetSong(uri, nullptr);
+		Song *tmp = db->GetSong(uri, IgnoreError());
 		if (tmp == NULL)
 			/* not found in database */
 			return NULL;
diff --git a/src/QueueCommands.cxx b/src/QueueCommands.cxx
index 683a88e50..a70a5f250 100644
--- a/src/QueueCommands.cxx
+++ b/src/QueueCommands.cxx
@@ -32,6 +32,7 @@
 #include "protocol/Result.hxx"
 #include "ls.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "fs/Path.hxx"
 
 #include <string.h>
@@ -52,8 +53,8 @@ handle_add(Client *client, gcc_unused int argc, char *argv[])
 			return COMMAND_RETURN_ERROR;
 		}
 
-		GError *error = NULL;
-		if (!client_allow_file(client, path_fs, &error))
+		Error error;
+		if (!client_allow_file(client, path_fs, error))
 			return print_error(client, error);
 
 		result = client->partition.AppendFile(path_utf8);
@@ -72,8 +73,8 @@ handle_add(Client *client, gcc_unused int argc, char *argv[])
 	}
 
 	const DatabaseSelection selection(uri, true);
-	GError *error = NULL;
-	return AddFromDatabase(client->partition, selection, &error)
+	Error error;
+	return AddFromDatabase(client->partition, selection, error)
 		? COMMAND_RETURN_OK
 		: print_error(client, error);
 }
@@ -95,8 +96,8 @@ handle_addid(Client *client, int argc, char *argv[])
 			return COMMAND_RETURN_ERROR;
 		}
 
-		GError *error = NULL;
-		if (!client_allow_file(client, path_fs, &error))
+		Error error;
+		if (!client_allow_file(client, path_fs, error))
 			return print_error(client, error);
 
 		result = client->partition.AppendFile(path_utf8, &added_id);
diff --git a/src/QueueSave.cxx b/src/QueueSave.cxx
index fd00009b1..a9c4b4cff 100644
--- a/src/QueueSave.cxx
+++ b/src/QueueSave.cxx
@@ -26,6 +26,7 @@
 #include "DatabaseGlue.hxx"
 #include "TextFile.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 
 #include <stdlib.h>
 
@@ -90,11 +91,10 @@ queue_load_song(TextFile &file, const char *line, queue *queue)
 		if (!uri_has_scheme(uri) && !g_path_is_absolute(uri))
 			return;
 
-		GError *error = NULL;
-		song = song_load(file, NULL, uri, &error);
+		Error error;
+		song = song_load(file, NULL, uri, error);
 		if (song == NULL) {
-			g_warning("%s", error->message);
-			g_error_free(error);
+			g_warning("%s", error.GetMessage());
 			return;
 		}
 	} else {
@@ -110,11 +110,11 @@ queue_load_song(TextFile &file, const char *line, queue *queue)
 		if (uri_has_scheme(uri)) {
 			song = Song::NewRemote(uri);
 		} else {
-			db = GetDatabase(nullptr);
+			db = GetDatabase(IgnoreError());
 			if (db == nullptr)
 				return;
 
-			song = db->GetSong(uri, nullptr);
+			song = db->GetSong(uri, IgnoreError());
 			if (song == nullptr)
 				return;
 		}
diff --git a/src/SongSave.cxx b/src/SongSave.cxx
index fcad320df..7b89eccf4 100644
--- a/src/SongSave.cxx
+++ b/src/SongSave.cxx
@@ -25,6 +25,8 @@
 #include "TextFile.hxx"
 #include "Tag.hxx"
 #include "util/StringUtil.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -36,11 +38,7 @@
 #define SONG_MTIME "mtime"
 #define SONG_END "song_end"
 
-static GQuark
-song_save_quark(void)
-{
-	return g_quark_from_static_string("song_save");
-}
+static constexpr Domain song_save_domain("song_save");
 
 void
 song_save(FILE *fp, const Song *song)
@@ -61,7 +59,7 @@ song_save(FILE *fp, const Song *song)
 
 Song *
 song_load(TextFile &file, Directory *parent, const char *uri,
-	  GError **error_r)
+	  Error &error)
 {
 	Song *song = parent != NULL
 		? Song::NewFile(uri, parent)
@@ -78,8 +76,8 @@ song_load(TextFile &file, Directory *parent, const char *uri,
 				song->tag->EndAdd();
 			song->Free();
 
-			g_set_error(error_r, song_save_quark(), 0,
-				    "unknown line in db: %s", line);
+			error.Format(song_save_domain,
+				     "unknown line in db: %s", line);
 			return NULL;
 		}
 
@@ -120,8 +118,8 @@ song_load(TextFile &file, Directory *parent, const char *uri,
 				song->tag->EndAdd();
 			song->Free();
 
-			g_set_error(error_r, song_save_quark(), 0,
-				    "unknown line in db: %s", line);
+			error.Format(song_save_domain,
+				     "unknown line in db: %s", line);
 			return NULL;
 		}
 	}
diff --git a/src/SongSave.hxx b/src/SongSave.hxx
index 9fd6ba86c..f18aa9660 100644
--- a/src/SongSave.hxx
+++ b/src/SongSave.hxx
@@ -20,8 +20,6 @@
 #ifndef MPD_SONG_SAVE_HXX
 #define MPD_SONG_SAVE_HXX
 
-#include "gerror.h"
-
 #include <stdio.h>
 
 #define SONG_BEGIN "song_begin: "
@@ -29,6 +27,7 @@
 struct Song;
 struct Directory;
 class TextFile;
+class Error;
 
 void
 song_save(FILE *fp, const Song *song);
@@ -37,12 +36,11 @@ song_save(FILE *fp, const Song *song);
  * Loads a song from the input file.  Reading stops after the
  * "song_end" line.
  *
- * @param error_r location to store the error occurring, or NULL to
- * ignore errors
+ * @param error location to store the error occurring
  * @return true on success, false on error
  */
 Song *
 song_load(TextFile &file, Directory *parent, const char *uri,
-	  GError **error_r);
+	  Error &error);
 
 #endif
diff --git a/src/SongSticker.hxx b/src/SongSticker.hxx
index 385aa59dc..0f3e0bf41 100644
--- a/src/SongSticker.hxx
+++ b/src/SongSticker.hxx
@@ -20,8 +20,6 @@
 #ifndef MPD_SONG_STICKER_HXX
 #define MPD_SONG_STICKER_HXX
 
-#include "gerror.h"
-
 struct Song;
 struct Directory;
 struct sticker;
diff --git a/src/SongUpdate.cxx b/src/SongUpdate.cxx
index b0d60b85a..d6f60c5cb 100644
--- a/src/SongUpdate.cxx
+++ b/src/SongUpdate.cxx
@@ -20,6 +20,7 @@
 #include "config.h" /* must be first for large file support */
 #include "Song.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "Directory.hxx"
 #include "Mapper.hxx"
 #include "fs/Path.hxx"
@@ -127,9 +128,10 @@ Song::UpdateFile()
 			/* open the input_stream (if not already
 			   open) */
 			if (is == NULL) {
+				Error error;
 				is = input_stream_open(path_fs.c_str(),
 						       mutex, cond,
-						       NULL);
+						       error);
 			}
 
 			/* now try the stream_tag() method */
@@ -143,7 +145,8 @@ Song::UpdateFile()
 				delete tag;
 				tag = nullptr;
 
-				input_stream_lock_seek(is, 0, SEEK_SET, NULL);
+				Error error;
+				input_stream_lock_seek(is, 0, SEEK_SET, error);
 			}
 		}
 
diff --git a/src/Stats.cxx b/src/Stats.cxx
index 354d26c59..0f9703674 100644
--- a/src/Stats.cxx
+++ b/src/Stats.cxx
@@ -29,6 +29,7 @@ extern "C" {
 #include "DatabaseGlue.hxx"
 #include "DatabasePlugin.hxx"
 #include "DatabaseSimple.hxx"
+#include "util/Error.hxx"
 
 struct stats stats;
 
@@ -44,19 +45,18 @@ void stats_global_finish(void)
 
 void stats_update(void)
 {
-	GError *error = nullptr;
+	Error error;
 
 	DatabaseStats stats2;
 
 	const DatabaseSelection selection("", true);
-	if (GetDatabase()->GetStats(selection, stats2, &error)) {
+	if (GetDatabase()->GetStats(selection, stats2, error)) {
 		stats.song_count = stats2.song_count;
 		stats.song_duration = stats2.total_duration;
 		stats.artist_count = stats2.artist_count;
 		stats.album_count = stats2.album_count;
 	} else {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 
 		stats.song_count = 0;
 		stats.song_duration = 0;
diff --git a/src/StickerCommands.cxx b/src/StickerCommands.cxx
index 5cbb7e984..5fdc0ba15 100644
--- a/src/StickerCommands.cxx
+++ b/src/StickerCommands.cxx
@@ -29,6 +29,9 @@
 #include "StickerDatabase.hxx"
 #include "CommandError.hxx"
 #include "protocol/Result.hxx"
+#include "util/Error.hxx"
+
+#include <glib.h>
 
 #include <string.h>
 
@@ -39,7 +42,7 @@ struct sticker_song_find_data {
 
 static void
 sticker_song_find_print_cb(Song *song, const char *value,
-			   gpointer user_data)
+			   void *user_data)
 {
 	struct sticker_song_find_data *data =
 		(struct sticker_song_find_data *)user_data;
@@ -51,14 +54,14 @@ sticker_song_find_print_cb(Song *song, const char *value,
 static enum command_return
 handle_sticker_song(Client *client, int argc, char *argv[])
 {
-	GError *error = nullptr;
-	const Database *db = GetDatabase(&error);
+	Error error;
+	const Database *db = GetDatabase(error);
 	if (db == nullptr)
 		return print_error(client, error);
 
 	/* get song song_id key */
 	if (argc == 5 && strcmp(argv[1], "get") == 0) {
-		Song *song = db->GetSong(argv[3], &error);
+		Song *song = db->GetSong(argv[3], error);
 		if (song == nullptr)
 			return print_error(client, error);
 
@@ -76,7 +79,7 @@ handle_sticker_song(Client *client, int argc, char *argv[])
 		return COMMAND_RETURN_OK;
 	/* list song song_id */
 	} else if (argc == 4 && strcmp(argv[1], "list") == 0) {
-		Song *song = db->GetSong(argv[3], &error);
+		Song *song = db->GetSong(argv[3], error);
 		if (song == nullptr)
 			return print_error(client, error);
 
@@ -90,7 +93,7 @@ handle_sticker_song(Client *client, int argc, char *argv[])
 		return COMMAND_RETURN_OK;
 	/* set song song_id id key */
 	} else if (argc == 6 && strcmp(argv[1], "set") == 0) {
-		Song *song = db->GetSong(argv[3], &error);
+		Song *song = db->GetSong(argv[3], error);
 		if (song == nullptr)
 			return print_error(client, error);
 
@@ -106,7 +109,7 @@ handle_sticker_song(Client *client, int argc, char *argv[])
 	/* delete song song_id [key] */
 	} else if ((argc == 4 || argc == 5) &&
 		   strcmp(argv[1], "delete") == 0) {
-		Song *song = db->GetSong(argv[3], &error);
+		Song *song = db->GetSong(argv[3], error);
 		if (song == nullptr)
 			return print_error(client, error);
 
diff --git a/src/StickerDatabase.cxx b/src/StickerDatabase.cxx
index f153231de..8ed82c770 100644
--- a/src/StickerDatabase.cxx
+++ b/src/StickerDatabase.cxx
@@ -21,6 +21,8 @@
 #include "StickerDatabase.hxx"
 #include "fs/Path.hxx"
 #include "Idle.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <string>
 #include <map>
@@ -81,23 +83,19 @@ static const char sticker_sql_create[] =
 static sqlite3 *sticker_db;
 static sqlite3_stmt *sticker_stmt[G_N_ELEMENTS(sticker_sql)];
 
-static GQuark
-sticker_quark(void)
-{
-	return g_quark_from_static_string("sticker");
-}
+static constexpr Domain sticker_domain("sticker");
 
 static sqlite3_stmt *
-sticker_prepare(const char *sql, GError **error_r)
+sticker_prepare(const char *sql, Error &error)
 {
 	int ret;
 	sqlite3_stmt *stmt;
 
 	ret = sqlite3_prepare_v2(sticker_db, sql, -1, &stmt, NULL);
 	if (ret != SQLITE_OK) {
-		g_set_error(error_r, sticker_quark(), ret,
-			    "sqlite3_prepare_v2() failed: %s",
-			    sqlite3_errmsg(sticker_db));
+		error.Format(sticker_domain, ret,
+			     "sqlite3_prepare_v2() failed: %s",
+			     sqlite3_errmsg(sticker_db));
 		return NULL;
 	}
 
@@ -105,7 +103,7 @@ sticker_prepare(const char *sql, GError **error_r)
 }
 
 bool
-sticker_global_init(Path &&path, GError **error_r)
+sticker_global_init(Path &&path, Error &error)
 {
 	int ret;
 
@@ -118,7 +116,7 @@ sticker_global_init(Path &&path, GError **error_r)
 	ret = sqlite3_open(path.c_str(), &sticker_db);
 	if (ret != SQLITE_OK) {
 		const std::string utf8 = path.ToUTF8();
-		g_set_error(error_r, sticker_quark(), ret,
+		error.Format(sticker_domain, ret,
 			    "Failed to open sqlite database '%s': %s",
 			    utf8.c_str(), sqlite3_errmsg(sticker_db));
 		return false;
@@ -128,9 +126,9 @@ sticker_global_init(Path &&path, GError **error_r)
 
 	ret = sqlite3_exec(sticker_db, sticker_sql_create, NULL, NULL, NULL);
 	if (ret != SQLITE_OK) {
-		g_set_error(error_r, sticker_quark(), ret,
-			    "Failed to create sticker table: %s",
-			    sqlite3_errmsg(sticker_db));
+		error.Format(sticker_domain, ret,
+			     "Failed to create sticker table: %s",
+			     sqlite3_errmsg(sticker_db));
 		return false;
 	}
 
@@ -139,7 +137,7 @@ sticker_global_init(Path &&path, GError **error_r)
 	for (unsigned i = 0; i < G_N_ELEMENTS(sticker_sql); ++i) {
 		assert(sticker_sql[i] != NULL);
 
-		sticker_stmt[i] = sticker_prepare(sticker_sql[i], error_r);
+		sticker_stmt[i] = sticker_prepare(sticker_sql[i], error);
 		if (sticker_stmt[i] == NULL)
 			return false;
 	}
diff --git a/src/StickerDatabase.hxx b/src/StickerDatabase.hxx
index 9034c8bb8..b3f4c63b8 100644
--- a/src/StickerDatabase.hxx
+++ b/src/StickerDatabase.hxx
@@ -42,8 +42,7 @@
 #ifndef MPD_STICKER_DATABASE_HXX
 #define MPD_STICKER_DATABASE_HXX
 
-#include "gerror.h"
-
+class Error;
 class Path;
 struct sticker;
 
@@ -55,7 +54,7 @@ struct sticker;
  * @return true on success, false on error
  */
 bool
-sticker_global_init(Path &&path, GError **error_r);
+sticker_global_init(Path &&path, Error &error);
 
 /**
  * Close the sticker database.
diff --git a/src/TagFile.cxx b/src/TagFile.cxx
index bd124e20d..cfb62b58e 100644
--- a/src/TagFile.cxx
+++ b/src/TagFile.cxx
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "TagFile.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 #include "DecoderList.hxx"
 #include "DecoderPlugin.hxx"
 #include "InputLegacy.hxx"
@@ -59,9 +60,11 @@ tag_file_scan(const char *path_fs,
 		if (plugin->scan_stream != NULL) {
 			/* open the input_stream (if not already
 			   open) */
-			if (is == nullptr)
+			if (is == nullptr) {
+				Error error;
 				is = input_stream_open(path_fs, mutex, cond,
-						       NULL);
+						       error);
+			}
 
 			/* now try the stream_tag() method */
 			if (is != NULL) {
@@ -70,7 +73,8 @@ tag_file_scan(const char *path_fs,
 							       handler_ctx))
 					break;
 
-				input_stream_lock_seek(is, 0, SEEK_SET, NULL);
+				Error error;
+				input_stream_lock_seek(is, 0, SEEK_SET, error);
 			}
 		}
 
diff --git a/src/TagId3.cxx b/src/TagId3.cxx
index 6b2174fe5..3f7605f5e 100644
--- a/src/TagId3.cxx
+++ b/src/TagId3.cxx
@@ -22,6 +22,7 @@
 #include "TagHandler.hxx"
 #include "TagTable.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 extern "C" {
 #include "riff.h"
@@ -29,7 +30,6 @@ extern "C" {
 }
 
 #include "conf.h"
-#include "io_error.h"
 
 #include <glib.h>
 #include <id3tag.h>
@@ -545,13 +545,11 @@ tag_id3_riff_aiff_load(FILE *file)
 }
 
 struct id3_tag *
-tag_id3_load(const char *path_fs, GError **error_r)
+tag_id3_load(const char *path_fs, Error &error)
 {
 	FILE *file = fopen(path_fs, "rb");
 	if (file == nullptr) {
-		g_set_error(error_r, errno_quark(), errno,
-			    "Failed to open file %s: %s",
-			    path_fs, g_strerror(errno));
+		error.FormatErrno("Failed to open file %s", path_fs);
 		return nullptr;
 	}
 
@@ -570,13 +568,11 @@ bool
 tag_id3_scan(const char *path_fs,
 	     const struct tag_handler *handler, void *handler_ctx)
 {
-	GError *error = nullptr;
-	struct id3_tag *tag = tag_id3_load(path_fs, &error);
+	Error error;
+	struct id3_tag *tag = tag_id3_load(path_fs, error);
 	if (tag == nullptr) {
-		if (error != nullptr) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
+		if (error.IsDefined())
+			g_warning("%s", error.GetMessage());
 
 		return false;
 	}
diff --git a/src/TagId3.hxx b/src/TagId3.hxx
index d359306e9..ca288754b 100644
--- a/src/TagId3.hxx
+++ b/src/TagId3.hxx
@@ -22,11 +22,11 @@
 
 #include "check.h"
 #include "gcc.h"
-#include "gerror.h"
 
 struct tag_handler;
 struct Tag;
 struct id3_tag;
+class Error;
 
 #ifdef HAVE_ID3TAG
 
@@ -42,10 +42,10 @@ tag_id3_import(struct id3_tag *);
  * return value must be freed with id3_tag_delete().
  *
  * @return NULL on error or if no ID3 tag was found in the file (no
- * GError will be set)
+ * Error will be set)
  */
 struct id3_tag *
-tag_id3_load(const char *path_fs, GError **error_r);
+tag_id3_load(const char *path_fs, Error &error);
 
 /**
  * Import all tags from the provided id3_tag *tag
diff --git a/src/TextInputStream.cxx b/src/TextInputStream.cxx
index bb4c8b868..486400f96 100644
--- a/src/TextInputStream.cxx
+++ b/src/TextInputStream.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -21,6 +21,7 @@
 #include "TextInputStream.hxx"
 #include "InputLegacy.hxx"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -40,7 +41,6 @@ TextInputStream::~TextInputStream()
 
 bool TextInputStream::ReadLine(std::string &line)
 {
-	GError *error = nullptr;
 	void *dest;
 	const char *src, *p;
 	size_t length, nbytes;
@@ -53,13 +53,13 @@ bool TextInputStream::ReadLine(std::string &line)
 			   newline character */
 			--length;
 
+			Error error;
 			nbytes = input_stream_lock_read(is, dest, length,
-							&error);
+							error);
 			if (nbytes > 0)
 				fifo_buffer_append(buffer, nbytes);
-			else if (error != nullptr) {
-				g_warning("%s", error->message);
-				g_error_free(error);
+			else if (error.IsDefined()) {
+				g_warning("%s", error.GetMessage());
 				return false;
 			}
 		} else
diff --git a/src/UpdateArchive.cxx b/src/UpdateArchive.cxx
index ab174fa53..2e0755244 100644
--- a/src/UpdateArchive.cxx
+++ b/src/UpdateArchive.cxx
@@ -29,6 +29,7 @@
 #include "ArchivePlugin.hxx"
 #include "ArchiveFile.hxx"
 #include "ArchiveVisitor.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -101,11 +102,10 @@ update_archive_file2(Directory *parent, const char *name,
 	const Path path_fs = map_directory_child_fs(parent, name);
 
 	/* open archive */
-	GError *error = NULL;
-	ArchiveFile *file = archive_file_open(plugin, path_fs.c_str(), &error);
+	Error error;
+	ArchiveFile *file = archive_file_open(plugin, path_fs.c_str(), error);
 	if (file == NULL) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
diff --git a/src/UpdateGlue.cxx b/src/UpdateGlue.cxx
index da8f92739..972842bb1 100644
--- a/src/UpdateGlue.cxx
+++ b/src/UpdateGlue.cxx
@@ -26,6 +26,7 @@
 #include "DatabaseSimple.hxx"
 #include "Idle.hxx"
 #include "GlobalEvents.hxx"
+#include "util/Error.hxx"
 
 extern "C" {
 #include "stats.h"
@@ -77,12 +78,10 @@ static void * update_task(void *_path)
 	modified = update_walk(path, discard);
 
 	if (modified || !db_exists()) {
-		GError *error = NULL;
-		if (!db_save(&error)) {
+		Error error;
+		if (!db_save(error))
 			g_warning("Failed to save database: %s",
-				  error->message);
-			g_error_free(error);
-		}
+				  error.GetMessage());
 	}
 
 	if (path != NULL && *path != 0)
diff --git a/src/archive/Bzip2ArchivePlugin.cxx b/src/archive/Bzip2ArchivePlugin.cxx
index 182b9ccd1..d997158a0 100644
--- a/src/archive/Bzip2ArchivePlugin.cxx
+++ b/src/archive/Bzip2ArchivePlugin.cxx
@@ -30,6 +30,8 @@
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
 #include "util/RefCount.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <stdint.h>
 #include <stddef.h>
@@ -85,7 +87,7 @@ public:
 
 	virtual input_stream *OpenStream(const char *path,
 					 Mutex &mutex, Cond &cond,
-					 GError **error_r) override;
+					 Error &error) override;
 };
 
 struct Bzip2InputStream {
@@ -103,12 +105,14 @@ struct Bzip2InputStream {
 			 Mutex &mutex, Cond &cond);
 	~Bzip2InputStream();
 
-	bool Open(GError **error_r);
+	bool Open(Error &error);
 	void Close();
 };
 
 extern const struct input_plugin bz2_inputplugin;
 
+static constexpr Domain bz2_domain("bz2");
+
 static inline GQuark
 bz2_quark(void)
 {
@@ -118,7 +122,7 @@ bz2_quark(void)
 /* single archive handling allocation helpers */
 
 inline bool
-Bzip2InputStream::Open(GError **error_r)
+Bzip2InputStream::Open(Error &error)
 {
 	bzstream.bzalloc = nullptr;
 	bzstream.bzfree = nullptr;
@@ -129,8 +133,8 @@ Bzip2InputStream::Open(GError **error_r)
 
 	int ret = BZ2_bzDecompressInit(&bzstream, 0, 0);
 	if (ret != BZ_OK) {
-		g_set_error(error_r, bz2_quark(), ret,
-			    "BZ2_bzDecompressInit() has failed");
+		error.Set(bz2_domain, ret,
+			  "BZ2_bzDecompressInit() has failed");
 		return false;
 	}
 
@@ -147,11 +151,11 @@ Bzip2InputStream::Close()
 /* archive open && listing routine */
 
 static ArchiveFile *
-bz2_open(const char *pathname, GError **error_r)
+bz2_open(const char *pathname, Error &error)
 {
 	static Mutex mutex;
 	static Cond cond;
-	input_stream *is = input_stream_open(pathname, mutex, cond, error_r);
+	input_stream *is = input_stream_open(pathname, mutex, cond, error);
 	if (is == nullptr)
 		return nullptr;
 
@@ -176,10 +180,10 @@ Bzip2InputStream::~Bzip2InputStream()
 input_stream *
 Bzip2ArchiveFile::OpenStream(const char *path,
 			     Mutex &mutex, Cond &cond,
-			     GError **error_r)
+			     Error &error)
 {
 	Bzip2InputStream *bis = new Bzip2InputStream(*this, path, mutex, cond);
-	if (!bis->Open(error_r)) {
+	if (!bis->Open(error)) {
 		delete bis;
 		return NULL;
 	}
@@ -197,7 +201,7 @@ bz2_is_close(struct input_stream *is)
 }
 
 static bool
-bz2_fillbuffer(Bzip2InputStream *bis, GError **error_r)
+bz2_fillbuffer(Bzip2InputStream *bis, Error &error)
 {
 	size_t count;
 	bz_stream *bzstream;
@@ -209,7 +213,7 @@ bz2_fillbuffer(Bzip2InputStream *bis, GError **error_r)
 
 	count = input_stream_read(bis->archive->istream,
 				  bis->buffer, sizeof(bis->buffer),
-				  error_r);
+				  error);
 	if (count == 0)
 		return false;
 
@@ -220,7 +224,7 @@ bz2_fillbuffer(Bzip2InputStream *bis, GError **error_r)
 
 static size_t
 bz2_is_read(struct input_stream *is, void *ptr, size_t length,
-	    GError **error_r)
+	    Error &error)
 {
 	Bzip2InputStream *bis = (Bzip2InputStream *)is;
 	bz_stream *bzstream;
@@ -235,7 +239,7 @@ bz2_is_read(struct input_stream *is, void *ptr, size_t length,
 	bzstream->avail_out = length;
 
 	do {
-		if (!bz2_fillbuffer(bis, error_r))
+		if (!bz2_fillbuffer(bis, error))
 			return 0;
 
 		bz_result = BZ2_bzDecompress(bzstream);
@@ -246,8 +250,8 @@ bz2_is_read(struct input_stream *is, void *ptr, size_t length,
 		}
 
 		if (bz_result != BZ_OK) {
-			g_set_error(error_r, bz2_quark(), bz_result,
-				    "BZ2_bzDecompress() has failed");
+			error.Set(bz2_domain, bz_result,
+				  "BZ2_bzDecompress() has failed");
 			return 0;
 		}
 	} while (bzstream->avail_out == length);
diff --git a/src/archive/Iso9660ArchivePlugin.cxx b/src/archive/Iso9660ArchivePlugin.cxx
index 97fd8bd52..2fee25311 100644
--- a/src/archive/Iso9660ArchivePlugin.cxx
+++ b/src/archive/Iso9660ArchivePlugin.cxx
@@ -30,6 +30,8 @@
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
 #include "util/RefCount.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <cdio/cdio.h>
 #include <cdio/iso9660.h>
@@ -69,16 +71,12 @@ public:
 
 	virtual input_stream *OpenStream(const char *path,
 					 Mutex &mutex, Cond &cond,
-					 GError **error_r) override;
+					 Error &error) override;
 };
 
 extern const struct input_plugin iso9660_input_plugin;
 
-static inline GQuark
-iso9660_quark(void)
-{
-	return g_quark_from_static_string("iso9660");
-}
+static constexpr Domain iso9660_domain("iso9660");
 
 /* archive open && listing routine */
 
@@ -115,13 +113,13 @@ Iso9660ArchiveFile::Visit(const char *psz_path, ArchiveVisitor &visitor)
 }
 
 static ArchiveFile *
-iso9660_archive_open(const char *pathname, GError **error_r)
+iso9660_archive_open(const char *pathname, Error &error)
 {
 	/* open archive */
 	auto iso = iso9660_open(pathname);
 	if (iso == nullptr) {
-		g_set_error(error_r, iso9660_quark(), 0,
-			    "Failed to open ISO9660 file %s", pathname);
+		error.Format(iso9660_domain,
+			     "Failed to open ISO9660 file %s", pathname);
 		return NULL;
 	}
 
@@ -166,12 +164,12 @@ struct Iso9660InputStream {
 input_stream *
 Iso9660ArchiveFile::OpenStream(const char *pathname,
 			       Mutex &mutex, Cond &cond,
-			       GError **error_r)
+			       Error &error)
 {
 	auto statbuf = iso9660_ifs_stat_translate(iso, pathname);
 	if (statbuf == nullptr) {
-		g_set_error(error_r, iso9660_quark(), 0,
-			    "not found in the ISO file: %s", pathname);
+		error.Format(iso9660_domain,
+			     "not found in the ISO file: %s", pathname);
 		return NULL;
 	}
 
@@ -191,7 +189,8 @@ iso9660_input_close(struct input_stream *is)
 
 
 static size_t
-iso9660_input_read(struct input_stream *is, void *ptr, size_t size, GError **error_r)
+iso9660_input_read(struct input_stream *is, void *ptr, size_t size,
+		   Error &error)
 {
 	Iso9660InputStream *iis = (Iso9660InputStream *)is;
 	int toread, readed = 0;
@@ -215,9 +214,9 @@ iso9660_input_read(struct input_stream *is, void *ptr, size_t size, GError **err
 			iis->statbuf->lsn + cur_block, no_blocks);
 
 		if (readed != no_blocks * ISO_BLOCKSIZE) {
-			g_set_error(error_r, iso9660_quark(), 0,
-				    "error reading ISO file at lsn %lu",
-				    (long unsigned int) cur_block);
+			error.Format(iso9660_domain,
+				     "error reading ISO file at lsn %lu",
+				     (unsigned long)cur_block);
 			return 0;
 		}
 		if (left_bytes < size) {
diff --git a/src/archive/ZzipArchivePlugin.cxx b/src/archive/ZzipArchivePlugin.cxx
index d0db7aa37..de2c62b5b 100644
--- a/src/archive/ZzipArchivePlugin.cxx
+++ b/src/archive/ZzipArchivePlugin.cxx
@@ -30,9 +30,11 @@
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
 #include "util/RefCount.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <zzip/zzip.h>
-#include <glib.h>
+
 #include <string.h>
 
 class ZzipArchiveFile final : public ArchiveFile {
@@ -61,26 +63,22 @@ public:
 
 	virtual input_stream *OpenStream(const char *path,
 					 Mutex &mutex, Cond &cond,
-					 GError **error_r) override;
+					 Error &error) override;
 };
 
 extern const struct input_plugin zzip_input_plugin;
 
-static inline GQuark
-zzip_quark(void)
-{
-	return g_quark_from_static_string("zzip");
-}
+static constexpr Domain zzip_domain("zzip");
 
 /* archive open && listing routine */
 
 static ArchiveFile *
-zzip_archive_open(const char *pathname, GError **error_r)
+zzip_archive_open(const char *pathname, Error &error)
 {
 	ZZIP_DIR *dir = zzip_dir_open(pathname, NULL);
 	if (dir == nullptr) {
-		g_set_error(error_r, zzip_quark(), 0,
-			    "Failed to open ZIP file %s", pathname);
+		error.Format(zzip_domain, "Failed to open ZIP file %s",
+			     pathname);
 		return NULL;
 	}
 
@@ -133,12 +131,12 @@ struct ZzipInputStream {
 input_stream *
 ZzipArchiveFile::OpenStream(const char *pathname,
 			    Mutex &mutex, Cond &cond,
-			    GError **error_r)
+			    Error &error)
 {
 	ZZIP_FILE *_file = zzip_file_open(dir, pathname, 0);
 	if (_file == nullptr) {
-		g_set_error(error_r, zzip_quark(), 0,
-			    "not found in the ZIP file: %s", pathname);
+		error.Format(zzip_domain, "not found in the ZIP file: %s",
+			     pathname);
 		return NULL;
 	}
 
@@ -159,15 +157,14 @@ zzip_input_close(struct input_stream *is)
 
 static size_t
 zzip_input_read(struct input_stream *is, void *ptr, size_t size,
-		GError **error_r)
+		Error &error)
 {
 	ZzipInputStream *zis = (ZzipInputStream *)is;
 	int ret;
 
 	ret = zzip_file_read(zis->file, ptr, size);
 	if (ret < 0) {
-		g_set_error(error_r, zzip_quark(), ret,
-			    "zzip_file_read() has failed");
+		error.Set(zzip_domain, "zzip_file_read() has failed");
 		return 0;
 	}
 
@@ -186,13 +183,12 @@ zzip_input_eof(struct input_stream *is)
 
 static bool
 zzip_input_seek(struct input_stream *is,
-		goffset offset, int whence, GError **error_r)
+		goffset offset, int whence, Error &error)
 {
 	ZzipInputStream *zis = (ZzipInputStream *)is;
 	zzip_off_t ofs = zzip_seek(zis->file, offset, whence);
 	if (ofs != -1) {
-		g_set_error(error_r, zzip_quark(), ofs,
-			    "zzip_seek() has failed");
+		error.Set(zzip_domain, "zzip_seek() has failed");
 		is->offset = ofs;
 		return true;
 	}
diff --git a/src/db/ProxyDatabasePlugin.cxx b/src/db/ProxyDatabasePlugin.cxx
index 81aad0a4c..e0af53cee 100644
--- a/src/db/ProxyDatabasePlugin.cxx
+++ b/src/db/ProxyDatabasePlugin.cxx
@@ -28,6 +28,8 @@
 #include "gcc.h"
 #include "conf.h"
 #include "Tag.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #undef MPD_DIRECTORY_H
 #undef MPD_SONG_H
@@ -46,39 +48,34 @@ class ProxyDatabase : public Database {
 
 public:
 	static Database *Create(const config_param &param,
-				GError **error_r);
+				Error &error);
 
-	virtual bool Open(GError **error_r) override;
+	virtual bool Open(Error &error) override;
 	virtual void Close() override;
 	virtual Song *GetSong(const char *uri_utf8,
-				     GError **error_r) const override;
+				     Error &error) const override;
 	virtual void ReturnSong(Song *song) const;
 
 	virtual bool Visit(const DatabaseSelection &selection,
 			   VisitDirectory visit_directory,
 			   VisitSong visit_song,
 			   VisitPlaylist visit_playlist,
-			   GError **error_r) const override;
+			   Error &error) const override;
 
 	virtual bool VisitUniqueTags(const DatabaseSelection &selection,
 				     enum tag_type tag_type,
 				     VisitString visit_string,
-				     GError **error_r) const override;
+				     Error &error) const override;
 
 	virtual bool GetStats(const DatabaseSelection &selection,
 			      DatabaseStats &stats,
-			      GError **error_r) const override;
+			      Error &error) const override;
 
 protected:
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 };
 
-gcc_pure
-static inline GQuark
-libmpdclient_quark(void)
-{
-	return g_quark_from_static_string("libmpdclient");
-}
+static constexpr Domain libmpdclient_domain("libmpdclient");
 
 static constexpr struct {
 	enum tag_type d;
@@ -116,23 +113,23 @@ Convert(enum tag_type tag_type)
 }
 
 static bool
-CheckError(struct mpd_connection *connection, GError **error_r)
+CheckError(struct mpd_connection *connection, Error &error)
 {
-	const auto error = mpd_connection_get_error(connection);
-	if (error == MPD_ERROR_SUCCESS)
+	const auto code = mpd_connection_get_error(connection);
+	if (code == MPD_ERROR_SUCCESS)
 		return true;
 
-	g_set_error_literal(error_r, libmpdclient_quark(), (int)error,
-			    mpd_connection_get_error_message(connection));
+	error.Set(libmpdclient_domain, (int)code,
+		  mpd_connection_get_error_message(connection));
 	mpd_connection_clear_error(connection);
 	return false;
 }
 
 Database *
-ProxyDatabase::Create(const config_param &param, GError **error_r)
+ProxyDatabase::Create(const config_param &param, Error &error)
 {
 	ProxyDatabase *db = new ProxyDatabase();
-	if (!db->Configure(param, error_r)) {
+	if (!db->Configure(param, error)) {
 		delete db;
 		db = NULL;
 	}
@@ -141,7 +138,7 @@ ProxyDatabase::Create(const config_param &param, GError **error_r)
 }
 
 bool
-ProxyDatabase::Configure(const config_param &param, GError **)
+ProxyDatabase::Configure(const config_param &param, gcc_unused Error &error)
 {
 	host = param.GetBlockValue("host", "");
 	port = param.GetBlockValue("port", 0u);
@@ -150,17 +147,16 @@ ProxyDatabase::Configure(const config_param &param, GError **)
 }
 
 bool
-ProxyDatabase::Open(GError **error_r)
+ProxyDatabase::Open(Error &error)
 {
 	connection = mpd_connection_new(host.empty() ? NULL : host.c_str(),
 					port, 0);
 	if (connection == NULL) {
-		g_set_error_literal(error_r, libmpdclient_quark(),
-				    (int)MPD_ERROR_OOM, "Out of memory");
+		error.Set(libmpdclient_domain, (int)MPD_ERROR_OOM, "Out of memory");
 		return false;
 	}
 
-	if (!CheckError(connection, error_r)) {
+	if (!CheckError(connection, error)) {
 		mpd_connection_free(connection);
 		return false;
 	}
@@ -183,13 +179,13 @@ static Song *
 Convert(const struct mpd_song *song);
 
 Song *
-ProxyDatabase::GetSong(const char *uri, GError **error_r) const
+ProxyDatabase::GetSong(const char *uri, Error &error) const
 {
 	// TODO: implement
 	// TODO: auto-reconnect
 
 	if (!mpd_send_list_meta(connection, uri)) {
-		CheckError(connection, error_r);
+		CheckError(connection, error);
 		return nullptr;
 	}
 
@@ -202,13 +198,12 @@ ProxyDatabase::GetSong(const char *uri, GError **error_r) const
 		if (song2 != nullptr)
 			song2->Free();
 
-		CheckError(connection, error_r);
+		CheckError(connection, error);
 		return nullptr;
 	}
 
 	if (song2 == nullptr)
-		g_set_error(error_r, db_quark(), DB_NOT_FOUND,
-			    "No such song: %s", uri);
+		error.Format(db_domain, DB_NOT_FOUND, "No such song: %s", uri);
 
 	return song2;
 }
@@ -226,19 +221,19 @@ ProxyDatabase::ReturnSong(Song *song) const
 static bool
 Visit(struct mpd_connection *connection, const char *uri,
       bool recursive, VisitDirectory visit_directory, VisitSong visit_song,
-      VisitPlaylist visit_playlist, GError **error_r);
+      VisitPlaylist visit_playlist, Error &error);
 
 static bool
 Visit(struct mpd_connection *connection,
       bool recursive, const struct mpd_directory *directory,
       VisitDirectory visit_directory, VisitSong visit_song,
-      VisitPlaylist visit_playlist, GError **error_r)
+      VisitPlaylist visit_playlist, Error &error)
 {
 	const char *path = mpd_directory_get_path(directory);
 
 	if (visit_directory) {
 		Directory *d = Directory::NewGeneric(path, &detached_root);
-		bool success = visit_directory(*d, error_r);
+		bool success = visit_directory(*d, error);
 		d->Free();
 		if (!success)
 			return false;
@@ -246,7 +241,7 @@ Visit(struct mpd_connection *connection,
 
 	if (recursive &&
 	    !Visit(connection, path, recursive,
-		   visit_directory, visit_song, visit_playlist, error_r))
+		   visit_directory, visit_song, visit_playlist, error))
 		return false;
 
 	return true;
@@ -290,13 +285,13 @@ Convert(const struct mpd_song *song)
 
 static bool
 Visit(const struct mpd_song *song,
-      VisitSong visit_song, GError **error_r)
+      VisitSong visit_song, Error &error)
 {
 	if (!visit_song)
 		return true;
 
 	Song *s = Convert(song);
-	bool success = visit_song(*s, error_r);
+	bool success = visit_song(*s, error);
 	s->Free();
 
 	return success;
@@ -304,7 +299,7 @@ Visit(const struct mpd_song *song,
 
 static bool
 Visit(const struct mpd_playlist *playlist,
-      VisitPlaylist visit_playlist, GError **error_r)
+      VisitPlaylist visit_playlist, Error &error)
 {
 	if (!visit_playlist)
 		return true;
@@ -312,7 +307,7 @@ Visit(const struct mpd_playlist *playlist,
 	PlaylistInfo p(mpd_playlist_get_path(playlist),
 		       mpd_playlist_get_last_modified(playlist));
 
-	return visit_playlist(p, detached_root, error_r);
+	return visit_playlist(p, detached_root, error);
 }
 
 class ProxyEntity {
@@ -356,13 +351,13 @@ ReceiveEntities(struct mpd_connection *connection)
 static bool
 Visit(struct mpd_connection *connection, const char *uri,
       bool recursive, VisitDirectory visit_directory, VisitSong visit_song,
-      VisitPlaylist visit_playlist, GError **error_r)
+      VisitPlaylist visit_playlist, Error &error)
 {
 	if (!mpd_send_list_meta(connection, uri))
-		return CheckError(connection, error_r);
+		return CheckError(connection, error);
 
 	std::list<ProxyEntity> entities(ReceiveEntities(connection));
-	if (!CheckError(connection, error_r))
+	if (!CheckError(connection, error))
 		return false;
 
 	for (const auto &entity : entities) {
@@ -374,25 +369,25 @@ Visit(struct mpd_connection *connection, const char *uri,
 			if (!Visit(connection, recursive,
 				   mpd_entity_get_directory(entity),
 				   visit_directory, visit_song, visit_playlist,
-				   error_r))
+				   error))
 				return false;
 			break;
 
 		case MPD_ENTITY_TYPE_SONG:
 			if (!Visit(mpd_entity_get_song(entity), visit_song,
-				   error_r))
+				   error))
 				return false;
 			break;
 
 		case MPD_ENTITY_TYPE_PLAYLIST:
 			if (!Visit(mpd_entity_get_playlist(entity),
-				   visit_playlist, error_r))
+				   visit_playlist, error))
 				return false;
 			break;
 		}
 	}
 
-	return CheckError(connection, error_r);
+	return CheckError(connection, error);
 }
 
 bool
@@ -400,55 +395,54 @@ ProxyDatabase::Visit(const DatabaseSelection &selection,
 		     VisitDirectory visit_directory,
 		     VisitSong visit_song,
 		     VisitPlaylist visit_playlist,
-		     GError **error_r) const
+		     Error &error) const
 {
 	// TODO: match
 	// TODO: auto-reconnect
 
 	return ::Visit(connection, selection.uri, selection.recursive,
 		       visit_directory, visit_song, visit_playlist,
-		       error_r);
+		       error);
 }
 
 bool
 ProxyDatabase::VisitUniqueTags(const DatabaseSelection &selection,
 			       enum tag_type tag_type,
 			       VisitString visit_string,
-			       GError **error_r) const
+			       Error &error) const
 {
 	enum mpd_tag_type tag_type2 = Convert(tag_type);
 	if (tag_type2 == MPD_TAG_COUNT) {
-		g_set_error_literal(error_r, libmpdclient_quark(), 0,
-				    "Unsupported tag");
+		error.Set(libmpdclient_domain, "Unsupported tag");
 		return false;
 	}
 
 	if (!mpd_search_db_tags(connection, tag_type2))
-		return CheckError(connection, error_r);
+		return CheckError(connection, error);
 
 	// TODO: match
 	(void)selection;
 
 	if (!mpd_search_commit(connection))
-		return CheckError(connection, error_r);
+		return CheckError(connection, error);
 
 	bool result = true;
 
 	struct mpd_pair *pair;
 	while (result &&
 	       (pair = mpd_recv_pair_tag(connection, tag_type2)) != nullptr) {
-		result = visit_string(pair->value, error_r);
+		result = visit_string(pair->value, error);
 		mpd_return_pair(connection, pair);
 	}
 
 	return mpd_response_finish(connection) &&
-		CheckError(connection, error_r) &&
+		CheckError(connection, error) &&
 		result;
 }
 
 bool
 ProxyDatabase::GetStats(const DatabaseSelection &selection,
-			DatabaseStats &stats, GError **error_r) const
+			DatabaseStats &stats, Error &error) const
 {
 	// TODO: match
 	(void)selection;
@@ -456,7 +450,7 @@ ProxyDatabase::GetStats(const DatabaseSelection &selection,
 	struct mpd_stats *stats2 =
 		mpd_run_stats(connection);
 	if (stats2 == nullptr)
-		return CheckError(connection, error_r);
+		return CheckError(connection, error);
 
 	stats.song_count = mpd_stats_get_number_of_songs(stats2);
 	stats.total_duration = mpd_stats_get_db_play_time(stats2);
diff --git a/src/db/SimpleDatabasePlugin.cxx b/src/db/SimpleDatabasePlugin.cxx
index 21eb8752d..56bdc2cb7 100644
--- a/src/db/SimpleDatabasePlugin.cxx
+++ b/src/db/SimpleDatabasePlugin.cxx
@@ -29,22 +29,19 @@
 #include "TextFile.hxx"
 #include "conf.h"
 #include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <sys/types.h>
 #include <errno.h>
 
-gcc_const
-static inline GQuark
-simple_db_quark(void)
-{
-	return g_quark_from_static_string("simple_db");
-}
+static constexpr Domain simple_db_domain("simple_db");
 
 Database *
-SimpleDatabase::Create(const config_param &param, GError **error_r)
+SimpleDatabase::Create(const config_param &param, Error &error)
 {
 	SimpleDatabase *db = new SimpleDatabase();
-	if (!db->Configure(param, error_r)) {
+	if (!db->Configure(param, error)) {
 		delete db;
 		db = NULL;
 	}
@@ -53,17 +50,13 @@ SimpleDatabase::Create(const config_param &param, GError **error_r)
 }
 
 bool
-SimpleDatabase::Configure(const config_param &param, GError **error_r)
+SimpleDatabase::Configure(const config_param &param, Error &error)
 {
-	GError *error = NULL;
-
-	path = param.GetBlockPath("path", &error);
+	path = param.GetBlockPath("path", error);
 	if (path.IsNull()) {
-		if (error != NULL)
-			g_propagate_error(error_r, error);
-		else
-			g_set_error(error_r, simple_db_quark(), 0,
-				    "No \"path\" parameter specified");
+		if (!error.IsDefined())
+			error.Set(simple_db_domain,
+				  "No \"path\" parameter specified");
 		return false;
 	}
 
@@ -73,7 +66,7 @@ SimpleDatabase::Configure(const config_param &param, GError **error_r)
 }
 
 bool
-SimpleDatabase::Check(GError **error_r) const
+SimpleDatabase::Check(Error &error) const
 {
 	assert(!path.IsNull());
 	assert(!path.empty());
@@ -88,28 +81,26 @@ SimpleDatabase::Check(GError **error_r) const
 		/* Check that the parent part of the path is a directory */
 		struct stat st;
 		if (!StatFile(dirPath, st)) {
-			g_set_error(error_r, simple_db_quark(), errno,
-				    "Couldn't stat parent directory of db file "
-				    "\"%s\": %s",
-				    path_utf8.c_str(), g_strerror(errno));
+			error.FormatErrno("Couldn't stat parent directory of db file "
+					  "\"%s\"",
+					  path_utf8.c_str());
 			return false;
 		}
 
 		if (!S_ISDIR(st.st_mode)) {
-			g_set_error(error_r, simple_db_quark(), 0,
-				    "Couldn't create db file \"%s\" because the "
-				    "parent path is not a directory",
-				    path_utf8.c_str());
+			error.Format(simple_db_domain,
+				     "Couldn't create db file \"%s\" because the "
+				     "parent path is not a directory",
+				     path_utf8.c_str());
 			return false;
 		}
 
 		/* Check if we can write to the directory */
 		if (!CheckAccess(dirPath, X_OK | W_OK)) {
-			int error = errno;
+			const int e = errno;
 			const std::string dirPath_utf8 = dirPath.ToUTF8();
-			g_set_error(error_r, simple_db_quark(), error,
-				    "Can't create db file in \"%s\": %s",
-				    dirPath_utf8.c_str(), g_strerror(error));
+			error.FormatErrno(e, "Can't create db file in \"%s\"",
+					  dirPath_utf8.c_str());
 			return false;
 		}
 
@@ -119,24 +110,22 @@ SimpleDatabase::Check(GError **error_r) const
 	/* Path exists, now check if it's a regular file */
 	struct stat st;
 	if (!StatFile(path, st)) {
-		g_set_error(error_r, simple_db_quark(), errno,
-			    "Couldn't stat db file \"%s\": %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Couldn't stat db file \"%s\"",
+				  path_utf8.c_str());
 		return false;
 	}
 
 	if (!S_ISREG(st.st_mode)) {
-		g_set_error(error_r, simple_db_quark(), 0,
-			    "db file \"%s\" is not a regular file",
-			    path_utf8.c_str());
+		error.Format(simple_db_domain,
+			     "db file \"%s\" is not a regular file",
+			     path_utf8.c_str());
 		return false;
 	}
 
 	/* And check that we can write to it */
 	if (!CheckAccess(path, R_OK | W_OK)) {
-		g_set_error(error_r, simple_db_quark(), errno,
-			    "Can't open db file \"%s\" for reading/writing: %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Can't open db file \"%s\" for reading/writing",
+				  path_utf8.c_str());
 		return false;
 	}
 
@@ -144,20 +133,19 @@ SimpleDatabase::Check(GError **error_r) const
 }
 
 bool
-SimpleDatabase::Load(GError **error_r)
+SimpleDatabase::Load(Error &error)
 {
 	assert(!path.empty());
 	assert(root != NULL);
 
 	TextFile file(path);
 	if (file.HasFailed()) {
-		g_set_error(error_r, simple_db_quark(), errno,
-			    "Failed to open database file \"%s\": %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Failed to open database file \"%s\"",
+				  path_utf8.c_str());
 		return false;
 	}
 
-	if (!db_load_internal(file, root, error_r))
+	if (!db_load_internal(file, root, error))
 		return false;
 
 	struct stat st;
@@ -168,7 +156,7 @@ SimpleDatabase::Load(GError **error_r)
 }
 
 bool
-SimpleDatabase::Open(GError **error_r)
+SimpleDatabase::Open(Error &error)
 {
 	root = Directory::NewRoot();
 	mtime = 0;
@@ -177,14 +165,13 @@ SimpleDatabase::Open(GError **error_r)
 	borrowed_song_count = 0;
 #endif
 
-	GError *error = NULL;
-	if (!Load(&error)) {
+	if (!Load(error)) {
 		root->Free();
 
-		g_warning("Failed to load database: %s", error->message);
-		g_error_free(error);
+		g_warning("Failed to load database: %s", error.GetMessage());
+		error.Clear();
 
-		if (!Check(error_r))
+		if (!Check(error))
 			return false;
 
 		root = Directory::NewRoot();
@@ -203,7 +190,7 @@ SimpleDatabase::Close()
 }
 
 Song *
-SimpleDatabase::GetSong(const char *uri, GError **error_r) const
+SimpleDatabase::GetSong(const char *uri, Error &error) const
 {
 	assert(root != NULL);
 
@@ -211,8 +198,8 @@ SimpleDatabase::GetSong(const char *uri, GError **error_r) const
 	Song *song = root->LookupSong(uri);
 	db_unlock();
 	if (song == NULL)
-		g_set_error(error_r, db_quark(), DB_NOT_FOUND,
-			    "No such song: %s", uri);
+		error.Format(db_domain, DB_NOT_FOUND,
+			     "No such song: %s", uri);
 #ifndef NDEBUG
 	else
 		++const_cast<unsigned &>(borrowed_song_count);
@@ -248,7 +235,7 @@ SimpleDatabase::Visit(const DatabaseSelection &selection,
 		      VisitDirectory visit_directory,
 		      VisitSong visit_song,
 		      VisitPlaylist visit_playlist,
-		      GError **error_r) const
+		      Error &error) const
 {
 	ScopeDatabaseLock protect;
 
@@ -258,42 +245,41 @@ SimpleDatabase::Visit(const DatabaseSelection &selection,
 			Song *song = root->LookupSong(selection.uri);
 			if (song != nullptr)
 				return !selection.Match(*song) ||
-					visit_song(*song, error_r);
+					visit_song(*song, error);
 		}
 
-		g_set_error(error_r, db_quark(), DB_NOT_FOUND,
-			    "No such directory");
+		error.Set(db_domain, DB_NOT_FOUND, "No such directory");
 		return false;
 	}
 
 	if (selection.recursive && visit_directory &&
-	    !visit_directory(*directory, error_r))
+	    !visit_directory(*directory, error))
 		return false;
 
 	return directory->Walk(selection.recursive, selection.filter,
 			       visit_directory, visit_song, visit_playlist,
-			       error_r);
+			       error);
 }
 
 bool
 SimpleDatabase::VisitUniqueTags(const DatabaseSelection &selection,
 				enum tag_type tag_type,
 				VisitString visit_string,
-				GError **error_r) const
+				Error &error) const
 {
 	return ::VisitUniqueTags(*this, selection, tag_type, visit_string,
-				 error_r);
+				 error);
 }
 
 bool
 SimpleDatabase::GetStats(const DatabaseSelection &selection,
-			 DatabaseStats &stats, GError **error_r) const
+			 DatabaseStats &stats, Error &error) const
 {
-	return ::GetStats(*this, selection, stats, error_r);
+	return ::GetStats(*this, selection, stats, error);
 }
 
 bool
-SimpleDatabase::Save(GError **error_r)
+SimpleDatabase::Save(Error &error)
 {
 	db_lock();
 
@@ -309,18 +295,15 @@ SimpleDatabase::Save(GError **error_r)
 
 	FILE *fp = FOpen(path, FOpenMode::WriteText);
 	if (!fp) {
-		g_set_error(error_r, simple_db_quark(), errno,
-			    "unable to write to db file \"%s\": %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("unable to write to db file \"%s\"",
+				  path_utf8.c_str());
 		return false;
 	}
 
 	db_save_internal(fp, root);
 
 	if (ferror(fp)) {
-		g_set_error(error_r, simple_db_quark(), errno,
-			    "Failed to write to database file: %s",
-			    g_strerror(errno));
+		error.SetErrno("Failed to write to database file");
 		fclose(fp);
 		return false;
 	}
diff --git a/src/db/SimpleDatabasePlugin.hxx b/src/db/SimpleDatabasePlugin.hxx
index 7250ea063..5de52cdeb 100644
--- a/src/db/SimpleDatabasePlugin.hxx
+++ b/src/db/SimpleDatabasePlugin.hxx
@@ -53,7 +53,7 @@ public:
 		return root;
 	}
 
-	bool Save(GError **error_r);
+	bool Save(Error &error);
 
 	gcc_pure
 	time_t GetLastModified() const {
@@ -61,37 +61,37 @@ public:
 	}
 
 	static Database *Create(const config_param &param,
-				GError **error_r);
+				Error &error);
 
-	virtual bool Open(GError **error_r) override;
+	virtual bool Open(Error &error) override;
 	virtual void Close() override;
 
 	virtual Song *GetSong(const char *uri_utf8,
-				     GError **error_r) const override;
+			      Error &error) const override;
 	virtual void ReturnSong(Song *song) const;
 
 	virtual bool Visit(const DatabaseSelection &selection,
 			   VisitDirectory visit_directory,
 			   VisitSong visit_song,
 			   VisitPlaylist visit_playlist,
-			   GError **error_r) const override;
+			   Error &error) const override;
 
 	virtual bool VisitUniqueTags(const DatabaseSelection &selection,
 				     enum tag_type tag_type,
 				     VisitString visit_string,
-				     GError **error_r) const override;
+				     Error &error) const override;
 
 	virtual bool GetStats(const DatabaseSelection &selection,
 			      DatabaseStats &stats,
-			      GError **error_r) const override;
+			      Error &error) const override;
 
 protected:
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 
 	gcc_pure
-	bool Check(GError **error_r) const;
+	bool Check(Error &error) const;
 
-	bool Load(GError **error_r);
+	bool Load(Error &error);
 
 	gcc_pure
 	const Directory *LookupDirectory(const char *uri) const;
diff --git a/src/decoder/AdPlugDecoderPlugin.cxx b/src/decoder/AdPlugDecoderPlugin.cxx
index 47ab1a7f3..f3b986fc8 100644
--- a/src/decoder/AdPlugDecoderPlugin.cxx
+++ b/src/decoder/AdPlugDecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "TagHandler.hxx"
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 
 #include <adplug/adplug.h>
 #include <adplug/emuopl.h>
@@ -38,12 +39,11 @@ static unsigned sample_rate;
 static bool
 adplug_init(const config_param &param)
 {
-	GError *error = NULL;
+	Error error;
 
 	sample_rate = param.GetBlockValue("sample_rate", 48000u);
-	if (!audio_check_sample_rate(sample_rate, &error)) {
-		g_warning("%s\n", error->message);
-		g_error_free(error);
+	if (!audio_check_sample_rate(sample_rate, error)) {
+		g_warning("%s", error.GetMessage());
 		return false;
 	}
 
diff --git a/src/decoder/AudiofileDecoderPlugin.cxx b/src/decoder/AudiofileDecoderPlugin.cxx
index 9c00b20ce..c146466cb 100644
--- a/src/decoder/AudiofileDecoderPlugin.cxx
+++ b/src/decoder/AudiofileDecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
 
 #include <audiofile.h>
 #include <af_vfs.h>
@@ -53,13 +54,11 @@ static ssize_t
 audiofile_file_read(AFvirtualfile *vfile, void *data, size_t length)
 {
 	struct input_stream *is = (struct input_stream *) vfile->closure;
-	GError *error = nullptr;
-	size_t nbytes;
 
-	nbytes = input_stream_lock_read(is, data, length, &error);
-	if (nbytes == 0 && error != nullptr) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	Error error;
+	size_t nbytes = input_stream_lock_read(is, data, length, error);
+	if (nbytes == 0 && error.IsDefined()) {
+		g_warning("%s", error.GetMessage());
 		return -1;
 	}
 
@@ -93,7 +92,9 @@ audiofile_file_seek(AFvirtualfile *vfile, AFfileoffset offset, int is_relative)
 {
 	struct input_stream *is = (struct input_stream *) vfile->closure;
 	int whence = (is_relative ? SEEK_CUR : SEEK_SET);
-	if (input_stream_lock_seek(is, offset, whence, nullptr)) {
+
+	Error error;
+	if (input_stream_lock_seek(is, offset, whence, error)) {
 		return input_stream_get_offset(is);
 	} else {
 		return -1;
@@ -156,7 +157,6 @@ audiofile_setup_sample_format(AFfilehandle af_fp)
 static void
 audiofile_stream_decode(struct decoder *decoder, struct input_stream *is)
 {
-	GError *error = nullptr;
 	AFvirtualfile *vf;
 	int fs, frame_count;
 	AFfilehandle af_fp;
@@ -180,13 +180,13 @@ audiofile_stream_decode(struct decoder *decoder, struct input_stream *is)
 		return;
 	}
 
+	Error error;
 	if (!audio_format_init_checked(audio_format,
 				       afGetRate(af_fp, AF_DEFAULT_TRACK),
 				       audiofile_setup_sample_format(af_fp),
 				       afGetVirtualChannels(af_fp, AF_DEFAULT_TRACK),
-				       &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       error)) {
+		g_warning("%s", error.GetMessage());
 		afCloseFile(af_fp);
 		return;
 	}
diff --git a/src/decoder/DsdLib.cxx b/src/decoder/DsdLib.cxx
index d18131184..a9cfc9147 100644
--- a/src/decoder/DsdLib.cxx
+++ b/src/decoder/DsdLib.cxx
@@ -29,6 +29,7 @@
 #include "util/bit_reverse.h"
 #include "TagHandler.hxx"
 #include "TagId3.hxx"
+#include "util/Error.hxx"
 
 #include <unistd.h>
 #include <string.h>
@@ -64,7 +65,7 @@ dsdlib_skip_to(struct decoder *decoder, struct input_stream *is,
 	       goffset offset)
 {
 	if (input_stream_is_seekable(is))
-		return input_stream_seek(is, offset, SEEK_SET, nullptr);
+		return input_stream_seek(is, offset, SEEK_SET, IgnoreError());
 
 	if (input_stream_get_offset(is) > offset)
 		return false;
@@ -97,7 +98,7 @@ dsdlib_skip(struct decoder *decoder, struct input_stream *is,
 		return true;
 
 	if (input_stream_is_seekable(is))
-		return input_stream_seek(is, delta, SEEK_CUR, nullptr);
+		return input_stream_seek(is, delta, SEEK_CUR, IgnoreError());
 
 	char buffer[8192];
 	while (delta > 0) {
diff --git a/src/decoder/DsdiffDecoderPlugin.cxx b/src/decoder/DsdiffDecoderPlugin.cxx
index b6d7f65cc..7c461f9c3 100644
--- a/src/decoder/DsdiffDecoderPlugin.cxx
+++ b/src/decoder/DsdiffDecoderPlugin.cxx
@@ -31,6 +31,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "util/bit_reverse.h"
+#include "util/Error.hxx"
 #include "TagHandler.hxx"
 #include "DsdLib.hxx"
 #include "TagHandler.hxx"
@@ -432,13 +433,12 @@ dsdiff_stream_decode(struct decoder *decoder, struct input_stream *is)
 	if (!dsdiff_read_metadata(decoder, is, &metadata, &chunk_header))
 		return;
 
-	GError *error = nullptr;
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, metadata.sample_rate / 8,
 				       SampleFormat::DSD,
-				       metadata.channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       metadata.channels, error)) {
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
@@ -490,7 +490,7 @@ dsdiff_scan_stream(struct input_stream *is,
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, metadata.sample_rate / 8,
 				       SampleFormat::DSD,
-				       metadata.channels, nullptr))
+				       metadata.channels, IgnoreError()))
 		/* refuse to parse files which we cannot play anyway */
 		return false;
 
diff --git a/src/decoder/DsfDecoderPlugin.cxx b/src/decoder/DsfDecoderPlugin.cxx
index e487879cb..26ba0e2d6 100644
--- a/src/decoder/DsfDecoderPlugin.cxx
+++ b/src/decoder/DsfDecoderPlugin.cxx
@@ -32,6 +32,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "util/bit_reverse.h"
+#include "util/Error.hxx"
 #include "DsdLib.hxx"
 #include "TagHandler.hxx"
 
@@ -284,13 +285,12 @@ dsf_stream_decode(struct decoder *decoder, struct input_stream *is)
 	if (!dsf_read_metadata(decoder, is, &metadata))
 		return;
 
-	GError *error = NULL;
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, metadata.sample_rate / 8,
 				       SampleFormat::DSD,
-				       metadata.channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       metadata.channels, error)) {
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 	/* Calculate song time from DSD chunk size and sample frequency */
@@ -320,7 +320,7 @@ dsf_scan_stream(struct input_stream *is,
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, metadata.sample_rate / 8,
 				       SampleFormat::DSD,
-				       metadata.channels, NULL))
+				       metadata.channels, IgnoreError()))
 		/* refuse to parse files which we cannot play anyway */
 		return false;
 
diff --git a/src/decoder/FaadDecoderPlugin.cxx b/src/decoder/FaadDecoderPlugin.cxx
index 547ba24e0..1387dc45c 100644
--- a/src/decoder/FaadDecoderPlugin.cxx
+++ b/src/decoder/FaadDecoderPlugin.cxx
@@ -23,6 +23,8 @@
 #include "DecoderBuffer.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <neaacdec.h>
 
@@ -42,14 +44,7 @@ static const unsigned adts_sample_rates[] =
 	16000, 12000, 11025, 8000, 7350, 0, 0, 0
 };
 
-/**
- * The GLib quark used for errors reported by this plugin.
- */
-static inline GQuark
-faad_decoder_quark(void)
-{
-	return g_quark_from_static_string("faad");
-}
+static constexpr Domain faad_decoder_domain("faad_decoder");
 
 /**
  * Check whether the buffer head is an AAC frame, and return the frame
@@ -211,7 +206,7 @@ faad_song_duration(DecoderBuffer *buffer, struct input_stream *is)
 		/* obtain the duration from the ADTS header */
 		float song_length = adts_song_duration(buffer);
 
-		input_stream_lock_seek(is, tagsize, SEEK_SET, nullptr);
+		input_stream_lock_seek(is, tagsize, SEEK_SET, IgnoreError());
 
 		data = (const uint8_t *)decoder_buffer_read(buffer, &length);
 		if (data != nullptr)
@@ -248,7 +243,7 @@ faad_song_duration(DecoderBuffer *buffer, struct input_stream *is)
  */
 static bool
 faad_decoder_init(NeAACDecHandle decoder, DecoderBuffer *buffer,
-		  AudioFormat &audio_format, GError **error_r)
+		  AudioFormat &audio_format, Error &error)
 {
 	int32_t nbytes;
 	uint32_t sample_rate;
@@ -266,8 +261,7 @@ faad_decoder_init(NeAACDecHandle decoder, DecoderBuffer *buffer,
 	const unsigned char *data = (const unsigned char *)
 		decoder_buffer_read(buffer, &length);
 	if (data == nullptr) {
-		g_set_error(error_r, faad_decoder_quark(), 0,
-			    "Empty file");
+		error.Set(faad_decoder_domain, "Empty file");
 		return false;
 	}
 
@@ -277,15 +271,14 @@ faad_decoder_init(NeAACDecHandle decoder, DecoderBuffer *buffer,
 			     length,
 			     sample_rate_p, &channels);
 	if (nbytes < 0) {
-		g_set_error(error_r, faad_decoder_quark(), 0,
-			    "Not an AAC stream");
+		error.Set(faad_decoder_domain, "Not an AAC stream");
 		return false;
 	}
 
 	decoder_buffer_consume(buffer, nbytes);
 
 	return audio_format_init_checked(audio_format, sample_rate,
-					 SampleFormat::S16, channels, error_r);
+					 SampleFormat::S16, channels, error);
 }
 
 /**
@@ -336,7 +329,8 @@ faad_get_file_time_float(struct input_stream *is)
 
 		decoder_buffer_fill(buffer);
 
-		ret = faad_decoder_init(decoder, buffer, audio_format, nullptr);
+		ret = faad_decoder_init(decoder, buffer, audio_format,
+					IgnoreError());
 		if (ret)
 			length = 0;
 
@@ -368,7 +362,6 @@ faad_get_file_time(struct input_stream *is)
 static void
 faad_stream_decode(struct decoder *mpd_decoder, struct input_stream *is)
 {
-	GError *error = nullptr;
 	float total_time = 0;
 	AudioFormat audio_format;
 	bool ret;
@@ -400,10 +393,10 @@ faad_stream_decode(struct decoder *mpd_decoder, struct input_stream *is)
 
 	/* initialize it */
 
-	ret = faad_decoder_init(decoder, buffer, audio_format, &error);
+	Error error;
+	ret = faad_decoder_init(decoder, buffer, audio_format, error);
 	if (!ret) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		NeAACDecClose(decoder);
 		return;
 	}
diff --git a/src/decoder/FfmpegDecoderPlugin.cxx b/src/decoder/FfmpegDecoderPlugin.cxx
index cf162b918..305662e6c 100644
--- a/src/decoder/FfmpegDecoderPlugin.cxx
+++ b/src/decoder/FfmpegDecoderPlugin.cxx
@@ -27,6 +27,7 @@
 #include "TagHandler.hxx"
 #include "InputStream.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -124,7 +125,8 @@ mpd_ffmpeg_stream_seek(void *opaque, int64_t pos, int whence)
 	if (whence == AVSEEK_SIZE)
 		return stream->input->size;
 
-	if (!input_stream_lock_seek(stream->input, pos, whence, NULL))
+	Error error;
+	if (!input_stream_lock_seek(stream->input, pos, whence, error))
 		return -1;
 
 	return stream->input->offset;
@@ -343,10 +345,12 @@ ffmpeg_probe(struct decoder *decoder, struct input_stream *is)
 		PADDING = 16,
 	};
 
+	Error error;
+
 	unsigned char *buffer = (unsigned char *)g_malloc(BUFFER_SIZE);
 	size_t nbytes = decoder_read(decoder, is, buffer, BUFFER_SIZE);
 	if (nbytes <= PADDING ||
-	    !input_stream_lock_seek(is, 0, SEEK_SET, NULL)) {
+	    !input_stream_lock_seek(is, 0, SEEK_SET, error)) {
 		g_free(buffer);
 		return NULL;
 	}
@@ -427,14 +431,13 @@ ffmpeg_decode(struct decoder *decoder, struct input_stream *input)
 	if (sample_format == SampleFormat::UNDEFINED)
 		return;
 
-	GError *error = NULL;
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format,
 				       codec_context->sample_rate,
 				       sample_format,
-				       codec_context->channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       codec_context->channels, error)) {
+		g_warning("%s", error.GetMessage());
 		avformat_close_input(&format_context);
 		return;
 	}
diff --git a/src/decoder/FlacCommon.cxx b/src/decoder/FlacCommon.cxx
index 5bcc20b97..62409d3cc 100644
--- a/src/decoder/FlacCommon.cxx
+++ b/src/decoder/FlacCommon.cxx
@@ -26,6 +26,7 @@
 #include "FlacMetadata.hxx"
 #include "FlacPcm.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -68,13 +69,12 @@ flac_got_stream_info(struct flac_data *data,
 	if (data->initialized || data->unsupported)
 		return;
 
-	GError *error = nullptr;
+	Error error;
 	if (!audio_format_init_checked(data->audio_format,
 				       stream_info->sample_rate,
 				       flac_sample_format(stream_info->bits_per_sample),
-				       stream_info->channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       stream_info->channels, error)) {
+		g_warning("%s", error.GetMessage());
 		data->unsupported = true;
 		return;
 	}
@@ -131,13 +131,12 @@ flac_got_first_frame(struct flac_data *data, const FLAC__FrameHeader *header)
 	if (data->unsupported)
 		return false;
 
-	GError *error = nullptr;
+	Error error;
 	if (!audio_format_init_checked(data->audio_format,
 				       header->sample_rate,
 				       flac_sample_format(header->bits_per_sample),
-				       header->channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       header->channels, error)) {
+		g_warning("%s", error.GetMessage());
 		data->unsupported = true;
 		return false;
 	}
diff --git a/src/decoder/FlacDecoderPlugin.cxx b/src/decoder/FlacDecoderPlugin.cxx
index 5b02c1f9e..1693e109b 100644
--- a/src/decoder/FlacDecoderPlugin.cxx
+++ b/src/decoder/FlacDecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "FlacCommon.hxx"
 #include "FlacMetadata.hxx"
 #include "OggCodec.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -330,7 +331,7 @@ oggflac_decode(struct decoder *decoder, struct input_stream *input_stream)
 
 	/* rewind the stream, because ogg_codec_detect() has
 	   moved it */
-	input_stream_lock_seek(input_stream, 0, SEEK_SET, nullptr);
+	input_stream_lock_seek(input_stream, 0, SEEK_SET, IgnoreError());
 
 	flac_decode_internal(decoder, input_stream, true);
 }
diff --git a/src/decoder/FlacIOHandle.cxx b/src/decoder/FlacIOHandle.cxx
index 16a07a9d1..cf877414b 100644
--- a/src/decoder/FlacIOHandle.cxx
+++ b/src/decoder/FlacIOHandle.cxx
@@ -19,7 +19,7 @@
 
 #include "config.h"
 #include "FlacIOHandle.hxx"
-#include "io_error.h"
+#include "util/Error.hxx"
 #include "gcc.h"
 
 #include <errno.h>
@@ -35,21 +35,20 @@ FlacIORead(void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle)
 	/* libFLAC is very picky about short reads, and expects the IO
 	   callback to fill the whole buffer (undocumented!) */
 
-	GError *error = nullptr;
+	Error error;
 	while (p < end) {
-		size_t nbytes = input_stream_lock_read(is, p, end - p, &error);
+		size_t nbytes = input_stream_lock_read(is, p, end - p, error);
 		if (nbytes == 0) {
-			if (error == nullptr)
+			if (!error.IsDefined())
 				/* end of file */
 				break;
 
-			if (error->domain == errno_quark())
-				errno = error->code;
+			if (error.IsDomain(errno_domain))
+				errno = error.GetCode();
 			else
 				/* just some random non-zero
 				   errno value */
 				errno = EINVAL;
-			g_error_free(error);
 			return 0;
 		}
 
@@ -67,7 +66,8 @@ FlacIOSeek(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
 {
 	input_stream *is = (input_stream *)handle;
 
-	return input_stream_lock_seek(is, offset, whence, nullptr) ? 0 : -1;
+	Error error;
+	return input_stream_lock_seek(is, offset, whence, error) ? 0 : -1;
 }
 
 static FLAC__int64
diff --git a/src/decoder/FlacInput.cxx b/src/decoder/FlacInput.cxx
index 0bb5ec7d7..46f213787 100644
--- a/src/decoder/FlacInput.cxx
+++ b/src/decoder/FlacInput.cxx
@@ -20,8 +20,9 @@
 #include "config.h"
 #include "FlacInput.hxx"
 #include "DecoderAPI.hxx"
-#include "gcc.h"
 #include "InputStream.hxx"
+#include "util/Error.hxx"
+#include "gcc.h"
 
 FLAC__StreamDecoderReadStatus
 FlacInput::Read(FLAC__byte buffer[], size_t *bytes)
@@ -47,9 +48,10 @@ FlacInput::Seek(FLAC__uint64 absolute_byte_offset)
 	if (!input_stream->seekable)
 		return FLAC__STREAM_DECODER_SEEK_STATUS_UNSUPPORTED;
 
+	::Error error;
 	if (!input_stream_lock_seek(input_stream,
 				    absolute_byte_offset, SEEK_SET,
-				    nullptr))
+				    error))
 		return FLAC__STREAM_DECODER_SEEK_STATUS_ERROR;
 
 	return FLAC__STREAM_DECODER_SEEK_STATUS_OK;
diff --git a/src/decoder/FluidsynthDecoderPlugin.cxx b/src/decoder/FluidsynthDecoderPlugin.cxx
index 9e9c9b2ce..66345e293 100644
--- a/src/decoder/FluidsynthDecoderPlugin.cxx
+++ b/src/decoder/FluidsynthDecoderPlugin.cxx
@@ -21,6 +21,7 @@
 #include "FluidsynthDecoderPlugin.hxx"
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 #include "conf.h"
 
 #include <glib.h>
@@ -73,12 +74,11 @@ fluidsynth_mpd_log_function(int level, char *message, gcc_unused void *data)
 static bool
 fluidsynth_init(const config_param &param)
 {
-	GError *error = nullptr;
+	Error error;
 
 	sample_rate = param.GetBlockValue("sample_rate", 48000u);
-	if (!audio_check_sample_rate(sample_rate, &error)) {
-		g_warning("%s\n", error->message);
-		g_error_free(error);
+	if (!audio_check_sample_rate(sample_rate, error)) {
+		g_warning("%s", error.GetMessage());
 		return false;
 	}
 
diff --git a/src/decoder/GmeDecoderPlugin.cxx b/src/decoder/GmeDecoderPlugin.cxx
index d8edbe4cb..006161c78 100644
--- a/src/decoder/GmeDecoderPlugin.cxx
+++ b/src/decoder/GmeDecoderPlugin.cxx
@@ -23,6 +23,7 @@
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
 #include "util/UriUtil.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 #include <assert.h>
@@ -152,13 +153,12 @@ gme_file_decode(struct decoder *decoder, const char *path_fs)
 
 	/* initialize the MPD decoder */
 
-	GError *error = nullptr;
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, GME_SAMPLE_RATE,
 				       SampleFormat::S16, GME_CHANNELS,
-				       &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       error)) {
+		g_warning("%s", error.GetMessage());
 		gme_free_info(ti);
 		gme_delete(emu);
 		return;
diff --git a/src/decoder/MadDecoderPlugin.cxx b/src/decoder/MadDecoderPlugin.cxx
index 29abfafbd..f77563fb2 100644
--- a/src/decoder/MadDecoderPlugin.cxx
+++ b/src/decoder/MadDecoderPlugin.cxx
@@ -25,6 +25,7 @@
 #include "TagRva2.hxx"
 #include "TagHandler.hxx"
 #include "CheckAudioFormat.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <unistd.h>
@@ -203,8 +204,9 @@ MadDecoder::MadDecoder(struct decoder *_decoder,
 inline bool
 MadDecoder::Seek(long offset)
 {
+	Error error;
 	if (!input_stream_lock_seek(input_stream, offset, SEEK_SET,
-				    nullptr))
+				    error))
 		return false;
 
 	mad_stream_buffer(&stream, input_buffer, 0);
@@ -1124,16 +1126,14 @@ mp3_decode(struct decoder *decoder, struct input_stream *input_stream)
 		return;
 	}
 
+	Error error;
 	AudioFormat audio_format;
-	GError *error = nullptr;
 	if (!audio_format_init_checked(audio_format,
 				       data.frame.header.samplerate,
 				       SampleFormat::S24_P32,
 				       MAD_NCHANNELS(&data.frame.header),
-				       &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
-
+				       error)) {
+		g_warning("%s", error.GetMessage());
 		delete tag;
 		return;
 	}
diff --git a/src/decoder/MpcdecDecoderPlugin.cxx b/src/decoder/MpcdecDecoderPlugin.cxx
index cfb9c034b..35d5ce0df 100644
--- a/src/decoder/MpcdecDecoderPlugin.cxx
+++ b/src/decoder/MpcdecDecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
 
 #include <mpc/mpcdec.h>
 
@@ -53,7 +54,8 @@ mpc_seek_cb(mpc_reader *reader, mpc_int32_t offset)
 	struct mpc_decoder_data *data =
 		(struct mpc_decoder_data *)reader->data;
 
-	return input_stream_lock_seek(data->is, offset, SEEK_SET, nullptr);
+	return input_stream_lock_seek(data->is, offset, SEEK_SET,
+				      IgnoreError());
 }
 
 static mpc_int32_t
@@ -153,13 +155,12 @@ mpcdec_decode(struct decoder *mpd_decoder, struct input_stream *is)
 	mpc_streaminfo info;
 	mpc_demux_get_info(demux, &info);
 
-	GError *error = nullptr;
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, info.sample_freq,
 				       SampleFormat::S24_P32,
-				       info.channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       info.channels, error)) {
+		g_warning("%s", error.GetMessage());
 		mpc_demux_exit(demux);
 		return;
 	}
diff --git a/src/decoder/Mpg123DecoderPlugin.cxx b/src/decoder/Mpg123DecoderPlugin.cxx
index 05fe4717c..c30455121 100644
--- a/src/decoder/Mpg123DecoderPlugin.cxx
+++ b/src/decoder/Mpg123DecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -58,7 +59,6 @@ static bool
 mpd_mpg123_open(mpg123_handle *handle, const char *path_fs,
 		AudioFormat &audio_format)
 {
-	GError *gerror = nullptr;
 	char *path_dup;
 	int error;
 	int channels, encoding;
@@ -90,10 +90,10 @@ mpd_mpg123_open(mpg123_handle *handle, const char *path_fs,
 		return false;
 	}
 
+	Error error2;
 	if (!audio_format_init_checked(audio_format, rate, SampleFormat::S16,
-				       channels, &gerror)) {
-		g_warning("%s", gerror->message);
-		g_error_free(gerror);
+				       channels, error2)) {
+		g_warning("%s", error2.GetMessage());
 		return false;
 	}
 
diff --git a/src/decoder/OpusDecoderPlugin.cxx b/src/decoder/OpusDecoderPlugin.cxx
index b6835f760..18da812ab 100644
--- a/src/decoder/OpusDecoderPlugin.cxx
+++ b/src/decoder/OpusDecoderPlugin.cxx
@@ -29,6 +29,7 @@
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
 #include "InputStream.hxx"
+#include "util/Error.hxx"
 
 #include <opus.h>
 #include <ogg/ogg.h>
@@ -271,7 +272,7 @@ mpd_opus_stream_decode(struct decoder *decoder,
 
 	/* rewind the stream, because ogg_codec_detect() has
 	   moved it */
-	input_stream_lock_seek(input_stream, 0, SEEK_SET, nullptr);
+	input_stream_lock_seek(input_stream, 0, SEEK_SET, IgnoreError());
 
 	MPDOpusDecoder d(decoder, input_stream);
 	OggSyncState oy(*input_stream, decoder);
@@ -302,7 +303,8 @@ SeekFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet,
 
 	oy.Reset();
 
-	return input_stream_lock_seek(is, -65536, SEEK_END, nullptr) &&
+	Error error;
+	return input_stream_lock_seek(is, -65536, SEEK_END, error) &&
 		oy.ExpectPageSeekIn(os) &&
 		OggFindEOS(oy, os, packet);
 }
diff --git a/src/decoder/PcmDecoderPlugin.cxx b/src/decoder/PcmDecoderPlugin.cxx
index 8976f511f..f47b54d03 100644
--- a/src/decoder/PcmDecoderPlugin.cxx
+++ b/src/decoder/PcmDecoderPlugin.cxx
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "decoder/PcmDecoderPlugin.hxx"
 #include "DecoderAPI.hxx"
+#include "util/Error.hxx"
 
 extern "C" {
 #include "util/byte_reverse.h"
@@ -46,7 +47,6 @@ pcm_stream_decode(struct decoder *decoder, struct input_stream *is)
 	const bool reverse_endian = mime != nullptr &&
 		strcmp(mime, "audio/x-mpd-cdda-pcm-reverse") == 0;
 
-	GError *error = nullptr;
 	enum decoder_command cmd;
 
 	const double time_to_size = audio_format.GetTimeToSize();
@@ -81,12 +81,13 @@ pcm_stream_decode(struct decoder *decoder, struct input_stream *is)
 		if (cmd == DECODE_COMMAND_SEEK) {
 			goffset offset = (goffset)(time_to_size *
 						   decoder_seek_where(decoder));
+
+			Error error;
 			if (input_stream_lock_seek(is, offset, SEEK_SET,
-						   &error)) {
+						   error)) {
 				decoder_command_finished(decoder);
 			} else {
-				g_warning("seeking failed: %s", error->message);
-				g_error_free(error);
+				g_warning("seeking failed: %s", error.GetMessage());
 				decoder_seek_error(decoder);
 			}
 
diff --git a/src/decoder/SndfileDecoderPlugin.cxx b/src/decoder/SndfileDecoderPlugin.cxx
index 29911a04e..0b83c142a 100644
--- a/src/decoder/SndfileDecoderPlugin.cxx
+++ b/src/decoder/SndfileDecoderPlugin.cxx
@@ -22,6 +22,7 @@
 #include "DecoderAPI.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
 
 #include <sndfile.h>
 
@@ -40,10 +41,8 @@ static sf_count_t
 sndfile_vio_seek(sf_count_t offset, int whence, void *user_data)
 {
 	struct input_stream *is = (struct input_stream *)user_data;
-	bool success;
 
-	success = input_stream_lock_seek(is, offset, whence, nullptr);
-	if (!success)
+	if (!input_stream_lock_seek(is, offset, whence, IgnoreError()))
 		return -1;
 
 	return input_stream_get_offset(is);
@@ -53,13 +52,11 @@ static sf_count_t
 sndfile_vio_read(void *ptr, sf_count_t count, void *user_data)
 {
 	struct input_stream *is = (struct input_stream *)user_data;
-	GError *error = nullptr;
-	size_t nbytes;
 
-	nbytes = input_stream_lock_read(is, ptr, count, &error);
-	if (nbytes == 0 && error != nullptr) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	Error error;
+	size_t nbytes = input_stream_lock_read(is, ptr, count, error);
+	if (nbytes == 0 && error.IsDefined()) {
+		g_warning("%s", error.GetMessage());
 		return -1;
 	}
 
@@ -116,7 +113,6 @@ time_to_frame(float t, const AudioFormat *audio_format)
 static void
 sndfile_stream_decode(struct decoder *decoder, struct input_stream *is)
 {
-	GError *error = nullptr;
 	SNDFILE *sf;
 	SF_INFO info;
 	size_t frame_size;
@@ -135,12 +131,12 @@ sndfile_stream_decode(struct decoder *decoder, struct input_stream *is)
 	/* for now, always read 32 bit samples.  Later, we could lower
 	   MPD's CPU usage by reading 16 bit samples with
 	   sf_readf_short() on low-quality source files. */
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, info.samplerate,
 				       SampleFormat::S32,
-				       info.channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       info.channels, error)) {
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
diff --git a/src/decoder/VorbisDecoderPlugin.cxx b/src/decoder/VorbisDecoderPlugin.cxx
index b9181ef75..3626fe162 100644
--- a/src/decoder/VorbisDecoderPlugin.cxx
+++ b/src/decoder/VorbisDecoderPlugin.cxx
@@ -23,6 +23,7 @@
 #include "DecoderAPI.hxx"
 #include "InputStream.hxx"
 #include "OggCodec.hxx"
+#include "util/Error.hxx"
 #include "util/UriUtil.hxx"
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
@@ -80,9 +81,10 @@ static int ogg_seek_cb(void *data, ogg_int64_t offset, int whence)
 {
 	struct vorbis_input_stream *vis = (struct vorbis_input_stream *)data;
 
+	Error error;
 	return vis->seekable &&
 		(!vis->decoder || decoder_get_command(vis->decoder) != DECODE_COMMAND_STOP) &&
-		input_stream_lock_seek(vis->input_stream, offset, whence, NULL)
+		input_stream_lock_seek(vis->input_stream, offset, whence, error)
 		? 0 : -1;
 }
 
@@ -182,14 +184,12 @@ static void
 vorbis_stream_decode(struct decoder *decoder,
 		     struct input_stream *input_stream)
 {
-	GError *error = NULL;
-
 	if (ogg_codec_detect(decoder, input_stream) != OGG_CODEC_VORBIS)
 		return;
 
 	/* rewind the stream, because ogg_codec_detect() has
 	   moved it */
-	input_stream_lock_seek(input_stream, 0, SEEK_SET, NULL);
+	input_stream_lock_seek(input_stream, 0, SEEK_SET, IgnoreError());
 
 	struct vorbis_input_stream vis;
 	OggVorbis_File vf;
@@ -202,6 +202,7 @@ vorbis_stream_decode(struct decoder *decoder,
 		return;
 	}
 
+	Error error;
 	AudioFormat audio_format;
 	if (!audio_format_init_checked(audio_format, vi->rate,
 #ifdef HAVE_TREMOR
@@ -209,9 +210,8 @@ vorbis_stream_decode(struct decoder *decoder,
 #else
 				       SampleFormat::FLOAT,
 #endif
-				       vi->channels, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       vi->channels, error)) {
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
diff --git a/src/decoder/WavpackDecoderPlugin.cxx b/src/decoder/WavpackDecoderPlugin.cxx
index 6b6c7f2ea..528ecdc3c 100644
--- a/src/decoder/WavpackDecoderPlugin.cxx
+++ b/src/decoder/WavpackDecoderPlugin.cxx
@@ -24,6 +24,7 @@
 #include "CheckAudioFormat.hxx"
 #include "TagHandler.hxx"
 #include "ApeTag.hxx"
+#include "util/Error.hxx"
 
 #include <wavpack/wavpack.h>
 #include <glib.h>
@@ -137,7 +138,6 @@ wavpack_bits_to_sample_format(bool is_float, int bytes_per_sample)
 static void
 wavpack_decode(struct decoder *decoder, WavpackContext *wpc, bool can_seek)
 {
-	GError *error = NULL;
 	bool is_float;
 	SampleFormat sample_format;
 	AudioFormat audio_format;
@@ -150,12 +150,12 @@ wavpack_decode(struct decoder *decoder, WavpackContext *wpc, bool can_seek)
 		wavpack_bits_to_sample_format(is_float,
 					      WavpackGetBytesPerSample(wpc));
 
+	Error error;
 	if (!audio_format_init_checked(audio_format,
 				       WavpackGetSampleRate(wpc),
 				       sample_format,
-				       WavpackGetNumChannels(wpc), &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+				       WavpackGetNumChannels(wpc), error)) {
+		g_warning("%s", error.GetMessage());
 		return;
 	}
 
@@ -401,14 +401,16 @@ wavpack_input_get_pos(void *id)
 static int
 wavpack_input_set_pos_abs(void *id, uint32_t pos)
 {
-	return input_stream_lock_seek(wpin(id)->is, pos, SEEK_SET, NULL)
+	Error error;
+	return input_stream_lock_seek(wpin(id)->is, pos, SEEK_SET, error)
 		? 0 : -1;
 }
 
 static int
 wavpack_input_set_pos_rel(void *id, int32_t delta, int mode)
 {
-	return input_stream_lock_seek(wpin(id)->is, delta, mode, NULL)
+	Error error;
+	return input_stream_lock_seek(wpin(id)->is, delta, mode, error)
 		? 0 : -1;
 }
 
@@ -476,7 +478,9 @@ wavpack_open_wvc(struct decoder *decoder, const char *uri,
 		return nullptr;
 
 	wvc_url = g_strconcat(uri, "c", NULL);
-	is_wvc = input_stream_open(wvc_url, mutex, cond, NULL);
+
+	Error error;
+	is_wvc = input_stream_open(wvc_url, mutex, cond, error);
 	g_free(wvc_url);
 
 	if (is_wvc == NULL)
diff --git a/src/decoder/WildmidiDecoderPlugin.cxx b/src/decoder/WildmidiDecoderPlugin.cxx
index c7bd3985e..738073d52 100644
--- a/src/decoder/WildmidiDecoderPlugin.cxx
+++ b/src/decoder/WildmidiDecoderPlugin.cxx
@@ -21,6 +21,7 @@
 #include "WildmidiDecoderPlugin.hxx"
 #include "DecoderAPI.hxx"
 #include "TagHandler.hxx"
+#include "util/Error.hxx"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
 #include "system/FatalError.hxx"
@@ -39,10 +40,10 @@ static constexpr unsigned WILDMIDI_SAMPLE_RATE = 48000;
 static bool
 wildmidi_init(const config_param &param)
 {
-	GError *error = nullptr;
+	Error error;
 	const Path path = param.GetBlockPath("config_file",
 					     "/etc/timidity/timidity.cfg",
-					     &error);
+					     error);
 	if (path.IsNull())
 		FatalError(error);
 
diff --git a/src/encoder/FlacEncoderPlugin.cxx b/src/encoder/FlacEncoderPlugin.cxx
index 509d9bfdd..5a77e24a7 100644
--- a/src/encoder/FlacEncoderPlugin.cxx
+++ b/src/encoder/FlacEncoderPlugin.cxx
@@ -22,6 +22,9 @@
 #include "EncoderAPI.hxx"
 #include "AudioFormat.hxx"
 #include "pcm/PcmBuffer.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "util/fifo_buffer.h"
 
 extern "C" {
@@ -58,15 +61,11 @@ struct flac_encoder {
 	flac_encoder():encoder(flac_encoder_plugin) {}
 };
 
-static inline GQuark
-flac_encoder_quark(void)
-{
-	return g_quark_from_static_string("flac_encoder");
-}
+static constexpr Domain flac_encoder_domain("vorbis_encoder");
 
 static bool
 flac_encoder_configure(struct flac_encoder *encoder, const config_param &param,
-		       gcc_unused GError **error)
+		       gcc_unused Error &error)
 {
 	encoder->compression = param.GetBlockValue("compression", 5u);
 
@@ -74,7 +73,7 @@ flac_encoder_configure(struct flac_encoder *encoder, const config_param &param,
 }
 
 static Encoder *
-flac_encoder_init(const config_param &param, GError **error)
+flac_encoder_init(const config_param &param, Error &error)
 {
 	flac_encoder *encoder = new flac_encoder();
 
@@ -100,35 +99,35 @@ flac_encoder_finish(Encoder *_encoder)
 
 static bool
 flac_encoder_setup(struct flac_encoder *encoder, unsigned bits_per_sample,
-		   GError **error)
+		   Error &error)
 {
 	if ( !FLAC__stream_encoder_set_compression_level(encoder->fse,
 					encoder->compression)) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "error setting flac compression to %d",
-			    encoder->compression);
+		error.Format(config_domain,
+			     "error setting flac compression to %d",
+			     encoder->compression);
 		return false;
 	}
 
 	if ( !FLAC__stream_encoder_set_channels(encoder->fse,
 					encoder->audio_format.channels)) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "error setting flac channels num to %d",
-			    encoder->audio_format.channels);
+		error.Format(config_domain,
+			     "error setting flac channels num to %d",
+			     encoder->audio_format.channels);
 		return false;
 	}
 	if ( !FLAC__stream_encoder_set_bits_per_sample(encoder->fse,
 							bits_per_sample)) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "error setting flac bit format to %d",
-			    bits_per_sample);
+		error.Format(config_domain,
+			     "error setting flac bit format to %d",
+			     bits_per_sample);
 		return false;
 	}
 	if ( !FLAC__stream_encoder_set_sample_rate(encoder->fse,
 					encoder->audio_format.sample_rate)) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "error setting flac sample rate to %d",
-			    encoder->audio_format.sample_rate);
+		error.Format(config_domain,
+			     "error setting flac sample rate to %d",
+			     encoder->audio_format.sample_rate);
 		return false;
 	}
 	return true;
@@ -161,8 +160,7 @@ flac_encoder_close(Encoder *_encoder)
 }
 
 static bool
-flac_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
-		     GError **error)
+flac_encoder_open(Encoder *_encoder, AudioFormat &audio_format, Error &error)
 {
 	struct flac_encoder *encoder = (struct flac_encoder *)_encoder;
 	unsigned bits_per_sample;
@@ -191,8 +189,7 @@ flac_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
 	/* allocate the encoder */
 	encoder->fse = FLAC__stream_encoder_new();
 	if (encoder->fse == nullptr) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "flac_new() failed");
+		error.Set(flac_encoder_domain, "flac_new() failed");
 		return false;
 	}
 
@@ -213,9 +210,9 @@ flac_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
 			    nullptr, nullptr, nullptr, encoder);
 
 		if(init_status != FLAC__STREAM_ENCODER_INIT_STATUS_OK) {
-			g_set_error(error, flac_encoder_quark(), 0,
-			    "failed to initialize encoder: %s\n",
-			    FLAC__StreamEncoderInitStatusString[init_status]);
+			error.Format(flac_encoder_domain,
+				     "failed to initialize encoder: %s\n",
+				     FLAC__StreamEncoderInitStatusString[init_status]);
 			flac_encoder_close(_encoder);
 			return false;
 		}
@@ -226,7 +223,7 @@ flac_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
 
 
 static bool
-flac_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
+flac_encoder_flush(Encoder *_encoder, gcc_unused Error &error)
 {
 	struct flac_encoder *encoder = (struct flac_encoder *)_encoder;
 
@@ -255,7 +252,7 @@ pcm16_to_flac(int32_t *out, const int16_t *in, unsigned num_samples)
 static bool
 flac_encoder_write(Encoder *_encoder,
 		   const void *data, size_t length,
-		   gcc_unused GError **error)
+		   gcc_unused Error &error)
 {
 	struct flac_encoder *encoder = (struct flac_encoder *)_encoder;
 	unsigned num_frames, num_samples;
@@ -298,8 +295,7 @@ flac_encoder_write(Encoder *_encoder,
 	if (!FLAC__stream_encoder_process_interleaved(encoder->fse,
 						      (const FLAC__int32 *)buffer,
 						      num_frames)) {
-		g_set_error(error, flac_encoder_quark(), 0,
-			    "flac encoder process failed");
+		error.Set(flac_encoder_domain, "flac encoder process failed");
 		return false;
 	}
 
diff --git a/src/encoder/LameEncoderPlugin.cxx b/src/encoder/LameEncoderPlugin.cxx
index 36e60dc4d..d3ed49a31 100644
--- a/src/encoder/LameEncoderPlugin.cxx
+++ b/src/encoder/LameEncoderPlugin.cxx
@@ -21,8 +21,11 @@
 #include "LameEncoderPlugin.hxx"
 #include "EncoderAPI.hxx"
 #include "AudioFormat.hxx"
+#include "ConfigError.hxx"
 #include "util/ReusableArray.hxx"
 #include "util/Manual.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <lame/lame.h>
 
@@ -45,17 +48,13 @@ struct LameEncoder final {
 
 	LameEncoder():encoder(lame_encoder_plugin) {}
 
-	bool Configure(const config_param &param, GError **error);
+	bool Configure(const config_param &param, Error &error);
 };
 
-static inline GQuark
-lame_encoder_quark(void)
-{
-	return g_quark_from_static_string("lame_encoder");
-}
+static constexpr Domain lame_encoder_domain("lame_encoder");
 
 bool
-LameEncoder::Configure(const config_param &param, GError **error)
+LameEncoder::Configure(const config_param &param, Error &error)
 {
 	const char *value;
 	char *endptr;
@@ -67,18 +66,18 @@ LameEncoder::Configure(const config_param &param, GError **error)
 		quality = g_ascii_strtod(value, &endptr);
 
 		if (*endptr != '\0' || quality < -1.0 || quality > 10.0) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "quality \"%s\" is not a number in the "
-				    "range -1 to 10, line %i",
-				    value, param.line);
+			error.Format(config_domain,
+				     "quality \"%s\" is not a number in the "
+				     "range -1 to 10, line %i",
+				     value, param.line);
 			return false;
 		}
 
 		if (param.GetBlockValue("bitrate") != nullptr) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "quality and bitrate are "
-				    "both defined (line %i)",
-				    param.line);
+			error.Format(config_domain,
+				     "quality and bitrate are "
+				     "both defined (line %i)",
+				     param.line);
 			return false;
 		}
 	} else {
@@ -86,10 +85,10 @@ LameEncoder::Configure(const config_param &param, GError **error)
 
 		value = param.GetBlockValue("bitrate");
 		if (value == nullptr) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "neither bitrate nor quality defined "
-				    "at line %i",
-				    param.line);
+			error.Format(config_domain,
+				     "neither bitrate nor quality defined "
+				     "at line %i",
+				     param.line);
 			return false;
 		}
 
@@ -97,9 +96,9 @@ LameEncoder::Configure(const config_param &param, GError **error)
 		bitrate = g_ascii_strtoll(value, &endptr, 10);
 
 		if (*endptr != '\0' || bitrate <= 0) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "bitrate at line %i should be a positive integer",
-				    param.line);
+			error.Format(config_domain,
+				     "bitrate at line %i should be a positive integer",
+				     param.line);
 			return false;
 		}
 	}
@@ -108,12 +107,12 @@ LameEncoder::Configure(const config_param &param, GError **error)
 }
 
 static Encoder *
-lame_encoder_init(const config_param &param, GError **error_r)
+lame_encoder_init(const config_param &param, Error &error)
 {
 	LameEncoder *encoder = new LameEncoder();
 
 	/* load configuration from "param" */
-	if (!encoder->Configure(param, error_r)) {
+	if (!encoder->Configure(param, error)) {
 		/* configuration has failed, roll back and return error */
 		delete encoder;
 		return nullptr;
@@ -133,55 +132,55 @@ lame_encoder_finish(Encoder *_encoder)
 }
 
 static bool
-lame_encoder_setup(LameEncoder *encoder, GError **error)
+lame_encoder_setup(LameEncoder *encoder, Error &error)
 {
 	if (encoder->quality >= -1.0) {
 		/* a quality was configured (VBR) */
 
 		if (0 != lame_set_VBR(encoder->gfp, vbr_rh)) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "error setting lame VBR mode");
+			error.Set(lame_encoder_domain,
+				  "error setting lame VBR mode");
 			return false;
 		}
 		if (0 != lame_set_VBR_q(encoder->gfp, encoder->quality)) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "error setting lame VBR quality");
+			error.Set(lame_encoder_domain,
+				  "error setting lame VBR quality");
 			return false;
 		}
 	} else {
 		/* a bit rate was configured */
 
 		if (0 != lame_set_brate(encoder->gfp, encoder->bitrate)) {
-			g_set_error(error, lame_encoder_quark(), 0,
-				    "error setting lame bitrate");
+			error.Set(lame_encoder_domain,
+				  "error setting lame bitrate");
 			return false;
 		}
 	}
 
 	if (0 != lame_set_num_channels(encoder->gfp,
 				       encoder->audio_format.channels)) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "error setting lame num channels");
+		error.Set(lame_encoder_domain,
+			  "error setting lame num channels");
 		return false;
 	}
 
 	if (0 != lame_set_in_samplerate(encoder->gfp,
 					encoder->audio_format.sample_rate)) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "error setting lame sample rate");
+		error.Set(lame_encoder_domain,
+			  "error setting lame sample rate");
 		return false;
 	}
 
 	if (0 != lame_set_out_samplerate(encoder->gfp,
 					 encoder->audio_format.sample_rate)) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "error setting lame out sample rate");
+		error.Set(lame_encoder_domain,
+			  "error setting lame out sample rate");
 		return false;
 	}
 
 	if (0 > lame_init_params(encoder->gfp)) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "error initializing lame params");
+		error.Set(lame_encoder_domain,
+			  "error initializing lame params");
 		return false;
 	}
 
@@ -189,8 +188,7 @@ lame_encoder_setup(LameEncoder *encoder, GError **error)
 }
 
 static bool
-lame_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
-		  GError **error)
+lame_encoder_open(Encoder *_encoder, AudioFormat &audio_format, Error &error)
 {
 	LameEncoder *encoder = (LameEncoder *)_encoder;
 
@@ -201,8 +199,7 @@ lame_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
 
 	encoder->gfp = lame_init();
 	if (encoder->gfp == nullptr) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "lame_init() failed");
+		error.Set(lame_encoder_domain, "lame_init() failed");
 		return false;
 	}
 
@@ -229,7 +226,7 @@ lame_encoder_close(Encoder *_encoder)
 static bool
 lame_encoder_write(Encoder *_encoder,
 		   const void *data, size_t length,
-		   gcc_unused GError **error)
+		   gcc_unused Error &error)
 {
 	LameEncoder *encoder = (LameEncoder *)_encoder;
 	const int16_t *src = (const int16_t*)data;
@@ -254,8 +251,7 @@ lame_encoder_write(Encoder *_encoder,
 						       output_buffer_size);
 
 	if (bytes_out < 0) {
-		g_set_error(error, lame_encoder_quark(), 0,
-			    "lame encoder failed");
+		error.Set(lame_encoder_domain, "lame encoder failed");
 		return false;
 	}
 
diff --git a/src/encoder/NullEncoderPlugin.cxx b/src/encoder/NullEncoderPlugin.cxx
index 5c01fbd98..38bc5cbe3 100644
--- a/src/encoder/NullEncoderPlugin.cxx
+++ b/src/encoder/NullEncoderPlugin.cxx
@@ -26,8 +26,6 @@ extern "C" {
 }
 #include "gcc.h"
 
-#include <glib.h>
-
 #include <assert.h>
 #include <string.h>
 
@@ -41,7 +39,7 @@ struct NullEncoder final {
 
 static Encoder *
 null_encoder_init(gcc_unused const config_param &param,
-		  gcc_unused GError **error)
+		  gcc_unused Error &error)
 {
 	NullEncoder *encoder = new NullEncoder();
 	return &encoder->encoder;
@@ -67,7 +65,7 @@ null_encoder_close(Encoder *_encoder)
 static bool
 null_encoder_open(Encoder *_encoder,
 		  gcc_unused AudioFormat &audio_format,
-		  gcc_unused GError **error)
+		  gcc_unused Error &error)
 {
 	NullEncoder *encoder = (NullEncoder *)_encoder;
 	encoder->buffer = growing_fifo_new();
@@ -77,7 +75,7 @@ null_encoder_open(Encoder *_encoder,
 static bool
 null_encoder_write(Encoder *_encoder,
 		   const void *data, size_t length,
-		   gcc_unused GError **error)
+		   gcc_unused Error &error)
 {
 	NullEncoder *encoder = (NullEncoder *)_encoder;
 
diff --git a/src/encoder/OpusEncoderPlugin.cxx b/src/encoder/OpusEncoderPlugin.cxx
index 9bb339312..c6e523ec4 100644
--- a/src/encoder/OpusEncoderPlugin.cxx
+++ b/src/encoder/OpusEncoderPlugin.cxx
@@ -22,11 +22,15 @@
 #include "OggStream.hxx"
 #include "EncoderAPI.hxx"
 #include "AudioFormat.hxx"
-#include "mpd_error.h"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <opus.h>
 #include <ogg/ogg.h>
 
+#include <glib.h>
+
 #include <assert.h>
 
 #undef G_LOG_DOMAIN
@@ -66,16 +70,11 @@ struct opus_encoder {
 	opus_encoder():encoder(opus_encoder_plugin) {}
 };
 
-gcc_const
-static inline GQuark
-opus_encoder_quark(void)
-{
-	return g_quark_from_static_string("opus_encoder");
-}
+static constexpr Domain opus_encoder_domain("opus_encoder");
 
 static bool
 opus_encoder_configure(struct opus_encoder *encoder,
-		       const config_param &param, GError **error_r)
+		       const config_param &param, Error &error)
 {
 	const char *value = param.GetBlockValue("bitrate", "auto");
 	if (strcmp(value, "auto") == 0)
@@ -87,16 +86,14 @@ opus_encoder_configure(struct opus_encoder *encoder,
 		encoder->bitrate = strtoul(value, &endptr, 10);
 		if (endptr == value || *endptr != 0 ||
 		    encoder->bitrate < 500 || encoder->bitrate > 512000) {
-			g_set_error(error_r, opus_encoder_quark(), 0,
-				    "Invalid bit rate");
+			error.Set(config_domain, "Invalid bit rate");
 			return false;
 		}
 	}
 
 	encoder->complexity = param.GetBlockValue("complexity", 10u);
 	if (encoder->complexity > 10) {
-		g_set_error(error_r, opus_encoder_quark(), 0,
-			    "Invalid complexity");
+		error.Format(config_domain, "Invalid complexity");
 		return false;
 	}
 
@@ -108,8 +105,7 @@ opus_encoder_configure(struct opus_encoder *encoder,
 	else if (strcmp(value, "music") == 0)
 		encoder->signal = OPUS_SIGNAL_MUSIC;
 	else {
-		g_set_error(error_r, opus_encoder_quark(), 0,
-			    "Invalid signal");
+		error.Format(config_domain, "Invalid signal");
 		return false;
 	}
 
@@ -117,7 +113,7 @@ opus_encoder_configure(struct opus_encoder *encoder,
 }
 
 static Encoder *
-opus_encoder_init(const config_param &param, GError **error)
+opus_encoder_init(const config_param &param, Error &error)
 {
 	opus_encoder *encoder = new opus_encoder();
 
@@ -144,7 +140,7 @@ opus_encoder_finish(Encoder *_encoder)
 static bool
 opus_encoder_open(Encoder *_encoder,
 		  AudioFormat &audio_format,
-		  GError **error_r)
+		  Error &error)
 {
 	struct opus_encoder *encoder = (struct opus_encoder *)_encoder;
 
@@ -171,14 +167,14 @@ opus_encoder_open(Encoder *_encoder,
 	encoder->audio_format = audio_format;
 	encoder->frame_size = audio_format.GetFrameSize();
 
-	int error;
+	int error_code;
 	encoder->enc = opus_encoder_create(audio_format.sample_rate,
 					   audio_format.channels,
 					   OPUS_APPLICATION_AUDIO,
-					   &error);
+					   &error_code);
 	if (encoder->enc == nullptr) {
-		g_set_error_literal(error_r, opus_encoder_quark(), error,
-				    opus_strerror(error));
+		error.Set(opus_encoder_domain, error_code,
+			  opus_strerror(error_code));
 		return false;
 	}
 
@@ -212,7 +208,7 @@ opus_encoder_close(Encoder *_encoder)
 
 static bool
 opus_encoder_do_encode(struct opus_encoder *encoder, bool eos,
-		       GError **error_r)
+		       Error &error)
 {
 	assert(encoder->buffer_position == encoder->buffer_size);
 
@@ -229,8 +225,7 @@ opus_encoder_do_encode(struct opus_encoder *encoder, bool eos,
 				    encoder->buffer2,
 				    sizeof(encoder->buffer2));
 	if (result < 0) {
-		g_set_error_literal(error_r, opus_encoder_quark(), 0,
-				    "Opus encoder error");
+		error.Set(opus_encoder_domain, "Opus encoder error");
 		return false;
 	}
 
@@ -251,7 +246,7 @@ opus_encoder_do_encode(struct opus_encoder *encoder, bool eos,
 }
 
 static bool
-opus_encoder_end(Encoder *_encoder, GError **error_r)
+opus_encoder_end(Encoder *_encoder, Error &error)
 {
 	struct opus_encoder *encoder = (struct opus_encoder *)_encoder;
 
@@ -261,11 +256,11 @@ opus_encoder_end(Encoder *_encoder, GError **error_r)
 	       encoder->buffer_size - encoder->buffer_position);
 	encoder->buffer_position = encoder->buffer_size;
 
-	return opus_encoder_do_encode(encoder, true, error_r);
+	return opus_encoder_do_encode(encoder, true, error);
 }
 
 static bool
-opus_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
+opus_encoder_flush(Encoder *_encoder, gcc_unused Error &error)
 {
 	struct opus_encoder *encoder = (struct opus_encoder *)_encoder;
 
@@ -275,7 +270,7 @@ opus_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
 
 static bool
 opus_encoder_write_silence(struct opus_encoder *encoder, unsigned fill_frames,
-			   GError **error_r)
+			   Error &error)
 {
 	size_t fill_bytes = fill_frames * encoder->frame_size;
 
@@ -291,7 +286,7 @@ opus_encoder_write_silence(struct opus_encoder *encoder, unsigned fill_frames,
 		fill_bytes -= nbytes;
 
 		if (encoder->buffer_position == encoder->buffer_size &&
-		    !opus_encoder_do_encode(encoder, false, error_r))
+		    !opus_encoder_do_encode(encoder, false, error))
 			return false;
 	}
 
@@ -301,7 +296,7 @@ opus_encoder_write_silence(struct opus_encoder *encoder, unsigned fill_frames,
 static bool
 opus_encoder_write(Encoder *_encoder,
 		   const void *_data, size_t length,
-		   GError **error_r)
+		   Error &error)
 {
 	struct opus_encoder *encoder = (struct opus_encoder *)_encoder;
 	const uint8_t *data = (const uint8_t *)_data;
@@ -313,7 +308,7 @@ opus_encoder_write(Encoder *_encoder,
 		assert(encoder->buffer_position == 0);
 
 		if (!opus_encoder_write_silence(encoder, encoder->lookahead,
-						error_r))
+						error))
 			return false;
 
 		encoder->lookahead = 0;
@@ -332,7 +327,7 @@ opus_encoder_write(Encoder *_encoder,
 		encoder->buffer_position += nbytes;
 
 		if (encoder->buffer_position == encoder->buffer_size &&
-		    !opus_encoder_do_encode(encoder, false, error_r))
+		    !opus_encoder_do_encode(encoder, false, error))
 			return false;
 	}
 
diff --git a/src/encoder/TwolameEncoderPlugin.cxx b/src/encoder/TwolameEncoderPlugin.cxx
index 4243a579b..a04c2afe2 100644
--- a/src/encoder/TwolameEncoderPlugin.cxx
+++ b/src/encoder/TwolameEncoderPlugin.cxx
@@ -21,6 +21,9 @@
 #include "TwolameEncoderPlugin.hxx"
 #include "EncoderAPI.hxx"
 #include "AudioFormat.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <twolame.h>
 
@@ -50,17 +53,13 @@ struct TwolameEncoder final {
 
 	TwolameEncoder():encoder(twolame_encoder_plugin) {}
 
-	bool Configure(const config_param &param, GError **error);
+	bool Configure(const config_param &param, Error &error);
 };
 
-static inline GQuark
-twolame_encoder_quark(void)
-{
-	return g_quark_from_static_string("twolame_encoder");
-}
+static constexpr Domain twolame_encoder_domain("twolame_encoder");
 
 bool
-TwolameEncoder::Configure(const config_param &param, GError **error)
+TwolameEncoder::Configure(const config_param &param, Error &error)
 {
 	const char *value;
 	char *endptr;
@@ -72,18 +71,18 @@ TwolameEncoder::Configure(const config_param &param, GError **error)
 		quality = g_ascii_strtod(value, &endptr);
 
 		if (*endptr != '\0' || quality < -1.0 || quality > 10.0) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "quality \"%s\" is not a number in the "
-				    "range -1 to 10, line %i",
-				    value, param.line);
+			error.Format(config_domain,
+				     "quality \"%s\" is not a number in the "
+				     "range -1 to 10, line %i",
+				     value, param.line);
 			return false;
 		}
 
 		if (param.GetBlockValue("bitrate") != nullptr) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "quality and bitrate are "
-				    "both defined (line %i)",
-				    param.line);
+			error.Format(config_domain,
+				     "quality and bitrate are "
+				     "both defined (line %i)",
+				     param.line);
 			return false;
 		}
 	} else {
@@ -91,10 +90,10 @@ TwolameEncoder::Configure(const config_param &param, GError **error)
 
 		value = param.GetBlockValue("bitrate");
 		if (value == nullptr) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "neither bitrate nor quality defined "
-				    "at line %i",
-				    param.line);
+			error.Format(config_domain,
+				     "neither bitrate nor quality defined "
+				     "at line %i",
+				     param.line);
 			return false;
 		}
 
@@ -102,9 +101,9 @@ TwolameEncoder::Configure(const config_param &param, GError **error)
 		bitrate = g_ascii_strtoll(value, &endptr, 10);
 
 		if (*endptr != '\0' || bitrate <= 0) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "bitrate at line %i should be a positive integer",
-				    param.line);
+			error.Format(config_domain,
+				     "bitrate at line %i should be a positive integer",
+				     param.line);
 			return false;
 		}
 	}
@@ -113,7 +112,7 @@ TwolameEncoder::Configure(const config_param &param, GError **error)
 }
 
 static Encoder *
-twolame_encoder_init(const config_param &param, GError **error_r)
+twolame_encoder_init(const config_param &param, Error &error_r)
 {
 	g_debug("libtwolame version %s", get_twolame_version());
 
@@ -140,48 +139,48 @@ twolame_encoder_finish(Encoder *_encoder)
 }
 
 static bool
-twolame_encoder_setup(TwolameEncoder *encoder, GError **error)
+twolame_encoder_setup(TwolameEncoder *encoder, Error &error)
 {
 	if (encoder->quality >= -1.0) {
 		/* a quality was configured (VBR) */
 
 		if (0 != twolame_set_VBR(encoder->options, true)) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "error setting twolame VBR mode");
+			error.Set(twolame_encoder_domain,
+				  "error setting twolame VBR mode");
 			return false;
 		}
 		if (0 != twolame_set_VBR_q(encoder->options, encoder->quality)) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "error setting twolame VBR quality");
+			error.Set(twolame_encoder_domain,
+				  "error setting twolame VBR quality");
 			return false;
 		}
 	} else {
 		/* a bit rate was configured */
 
 		if (0 != twolame_set_brate(encoder->options, encoder->bitrate)) {
-			g_set_error(error, twolame_encoder_quark(), 0,
-				    "error setting twolame bitrate");
+			error.Set(twolame_encoder_domain,
+				  "error setting twolame bitrate");
 			return false;
 		}
 	}
 
 	if (0 != twolame_set_num_channels(encoder->options,
 					  encoder->audio_format.channels)) {
-		g_set_error(error, twolame_encoder_quark(), 0,
-			    "error setting twolame num channels");
+		error.Set(twolame_encoder_domain,
+			  "error setting twolame num channels");
 		return false;
 	}
 
 	if (0 != twolame_set_in_samplerate(encoder->options,
 					   encoder->audio_format.sample_rate)) {
-		g_set_error(error, twolame_encoder_quark(), 0,
-			    "error setting twolame sample rate");
+		error.Set(twolame_encoder_domain,
+			  "error setting twolame sample rate");
 		return false;
 	}
 
 	if (0 > twolame_init_params(encoder->options)) {
-		g_set_error(error, twolame_encoder_quark(), 0,
-			    "error initializing twolame params");
+		error.Set(twolame_encoder_domain,
+			  "error initializing twolame params");
 		return false;
 	}
 
@@ -190,7 +189,7 @@ twolame_encoder_setup(TwolameEncoder *encoder, GError **error)
 
 static bool
 twolame_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
-		     GError **error)
+		     Error &error)
 {
 	TwolameEncoder *encoder = (TwolameEncoder *)_encoder;
 
@@ -201,8 +200,7 @@ twolame_encoder_open(Encoder *_encoder, AudioFormat &audio_format,
 
 	encoder->options = twolame_init();
 	if (encoder->options == nullptr) {
-		g_set_error(error, twolame_encoder_quark(), 0,
-			    "twolame_init() failed");
+		error.Set(twolame_encoder_domain, "twolame_init() failed");
 		return false;
 	}
 
@@ -227,7 +225,7 @@ twolame_encoder_close(Encoder *_encoder)
 }
 
 static bool
-twolame_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
+twolame_encoder_flush(Encoder *_encoder, gcc_unused Error &error)
 {
 	TwolameEncoder *encoder = (TwolameEncoder *)_encoder;
 
@@ -238,7 +236,7 @@ twolame_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
 static bool
 twolame_encoder_write(Encoder *_encoder,
 		      const void *data, size_t length,
-		      gcc_unused GError **error)
+		      gcc_unused Error &error)
 {
 	TwolameEncoder *encoder = (TwolameEncoder *)_encoder;
 	const int16_t *src = (const int16_t*)data;
@@ -254,8 +252,7 @@ twolame_encoder_write(Encoder *_encoder,
 							  encoder->output_buffer,
 							  sizeof(encoder->output_buffer));
 	if (bytes_out < 0) {
-		g_set_error(error, twolame_encoder_quark(), 0,
-			    "twolame encoder failed");
+		error.Set(twolame_encoder_domain, "twolame encoder failed");
 		return false;
 	}
 
diff --git a/src/encoder/VorbisEncoderPlugin.cxx b/src/encoder/VorbisEncoderPlugin.cxx
index 4fb6bb661..27a368766 100644
--- a/src/encoder/VorbisEncoderPlugin.cxx
+++ b/src/encoder/VorbisEncoderPlugin.cxx
@@ -23,10 +23,14 @@
 #include "EncoderAPI.hxx"
 #include "Tag.hxx"
 #include "AudioFormat.hxx"
-#include "mpd_error.h"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <vorbis/vorbisenc.h>
 
+#include <glib.h>
+
 #include <assert.h>
 
 #undef G_LOG_DOMAIN
@@ -54,15 +58,11 @@ struct vorbis_encoder {
 	vorbis_encoder():encoder(vorbis_encoder_plugin) {}
 };
 
-static inline GQuark
-vorbis_encoder_quark(void)
-{
-	return g_quark_from_static_string("vorbis_encoder");
-}
+static constexpr Domain vorbis_encoder_domain("vorbis_encoder");
 
 static bool
 vorbis_encoder_configure(struct vorbis_encoder *encoder,
-			 const config_param &param, GError **error)
+			 const config_param &param, Error &error)
 {
 	const char *value = param.GetBlockValue("quality");
 	if (value != nullptr) {
@@ -73,18 +73,18 @@ vorbis_encoder_configure(struct vorbis_encoder *encoder,
 
 		if (*endptr != '\0' || encoder->quality < -1.0 ||
 		    encoder->quality > 10.0) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "quality \"%s\" is not a number in the "
-				    "range -1 to 10, line %i",
-				    value, param.line);
+			error.Format(config_domain,
+				     "quality \"%s\" is not a number in the "
+				     "range -1 to 10, line %i",
+				     value, param.line);
 			return false;
 		}
 
 		if (param.GetBlockValue("bitrate") != nullptr) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "quality and bitrate are "
-				    "both defined (line %i)",
-				    param.line);
+			error.Format(config_domain,
+				     "quality and bitrate are "
+				     "both defined (line %i)",
+				     param.line);
 			return false;
 		}
 	} else {
@@ -92,10 +92,10 @@ vorbis_encoder_configure(struct vorbis_encoder *encoder,
 
 		value = param.GetBlockValue("bitrate");
 		if (value == nullptr) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "neither bitrate nor quality defined "
-				    "at line %i",
-				    param.line);
+			error.Format(config_domain,
+				     "neither bitrate nor quality defined "
+				     "at line %i",
+				     param.line);
 			return false;
 		}
 
@@ -104,9 +104,9 @@ vorbis_encoder_configure(struct vorbis_encoder *encoder,
 		char *endptr;
 		encoder->bitrate = g_ascii_strtoll(value, &endptr, 10);
 		if (*endptr != '\0' || encoder->bitrate <= 0) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "bitrate at line %i should be a positive integer",
-				    param.line);
+			error.Format(config_domain,
+				     "bitrate at line %i should be a positive integer",
+				     param.line);
 			return false;
 		}
 	}
@@ -115,7 +115,7 @@ vorbis_encoder_configure(struct vorbis_encoder *encoder,
 }
 
 static Encoder *
-vorbis_encoder_init(const config_param &param, GError **error)
+vorbis_encoder_init(const config_param &param, Error &error)
 {
 	vorbis_encoder *encoder = new vorbis_encoder();
 
@@ -140,7 +140,7 @@ vorbis_encoder_finish(Encoder *_encoder)
 }
 
 static bool
-vorbis_encoder_reinit(struct vorbis_encoder *encoder, GError **error)
+vorbis_encoder_reinit(struct vorbis_encoder *encoder, Error &error)
 {
 	vorbis_info_init(&encoder->vi);
 
@@ -151,8 +151,8 @@ vorbis_encoder_reinit(struct vorbis_encoder *encoder, GError **error)
 						encoder->audio_format.channels,
 						encoder->audio_format.sample_rate,
 						encoder->quality * 0.1)) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "error initializing vorbis vbr");
+			error.Set(vorbis_encoder_domain,
+				  "error initializing vorbis vbr");
 			vorbis_info_clear(&encoder->vi);
 			return false;
 		}
@@ -163,8 +163,8 @@ vorbis_encoder_reinit(struct vorbis_encoder *encoder, GError **error)
 					    encoder->audio_format.channels,
 					    encoder->audio_format.sample_rate, -1.0,
 					    encoder->bitrate * 1000, -1.0)) {
-			g_set_error(error, vorbis_encoder_quark(), 0,
-				    "error initializing vorbis encoder");
+			error.Set(vorbis_encoder_domain,
+				  "error initializing vorbis encoder");
 			vorbis_info_clear(&encoder->vi);
 			return false;
 		}
@@ -203,7 +203,7 @@ vorbis_encoder_send_header(struct vorbis_encoder *encoder)
 static bool
 vorbis_encoder_open(Encoder *_encoder,
 		    AudioFormat &audio_format,
-		    GError **error)
+		    Error &error)
 {
 	struct vorbis_encoder *encoder = (struct vorbis_encoder *)_encoder;
 
@@ -250,7 +250,7 @@ vorbis_encoder_blockout(struct vorbis_encoder *encoder)
 }
 
 static bool
-vorbis_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
+vorbis_encoder_flush(Encoder *_encoder, gcc_unused Error &error)
 {
 	struct vorbis_encoder *encoder = (struct vorbis_encoder *)_encoder;
 
@@ -259,7 +259,7 @@ vorbis_encoder_flush(Encoder *_encoder, gcc_unused GError **error)
 }
 
 static bool
-vorbis_encoder_pre_tag(Encoder *_encoder, gcc_unused GError **error)
+vorbis_encoder_pre_tag(Encoder *_encoder, gcc_unused Error &error)
 {
 	struct vorbis_encoder *encoder = (struct vorbis_encoder *)_encoder;
 
@@ -290,7 +290,7 @@ copy_tag_to_vorbis_comment(vorbis_comment *vc, const Tag *tag)
 
 static bool
 vorbis_encoder_tag(Encoder *_encoder, const Tag *tag,
-		   gcc_unused GError **error)
+		   gcc_unused Error &error)
 {
 	struct vorbis_encoder *encoder = (struct vorbis_encoder *)_encoder;
 	vorbis_comment comment;
@@ -324,7 +324,7 @@ interleaved_to_vorbis_buffer(float **dest, const float *src,
 static bool
 vorbis_encoder_write(Encoder *_encoder,
 		     const void *data, size_t length,
-		     gcc_unused GError **error)
+		     gcc_unused Error &error)
 {
 	struct vorbis_encoder *encoder = (struct vorbis_encoder *)_encoder;
 
diff --git a/src/encoder/WaveEncoderPlugin.cxx b/src/encoder/WaveEncoderPlugin.cxx
index 17560dfea..493b07b61 100644
--- a/src/encoder/WaveEncoderPlugin.cxx
+++ b/src/encoder/WaveEncoderPlugin.cxx
@@ -84,7 +84,7 @@ fill_wave_header(struct wave_header *header, int channels, int bits,
 
 static Encoder *
 wave_encoder_init(gcc_unused const config_param &param,
-		  gcc_unused GError **error)
+		  gcc_unused Error &error)
 {
 	WaveEncoder *encoder = new WaveEncoder();
 	return &encoder->encoder;
@@ -101,7 +101,7 @@ wave_encoder_finish(Encoder *_encoder)
 static bool
 wave_encoder_open(Encoder *_encoder,
 		  AudioFormat &audio_format,
-		  gcc_unused GError **error)
+		  gcc_unused Error &error)
 {
 	WaveEncoder *encoder = (WaveEncoder *)_encoder;
 
@@ -196,7 +196,7 @@ pcm24_to_wave(uint8_t *dst8, const uint32_t *src32, size_t length)
 static bool
 wave_encoder_write(Encoder *_encoder,
 		   const void *src, size_t length,
-		   gcc_unused GError **error)
+		   gcc_unused Error &error)
 {
 	WaveEncoder *encoder = (WaveEncoder *)_encoder;
 
diff --git a/src/event/BufferedSocket.cxx b/src/event/BufferedSocket.cxx
index ac3d2cf0e..f333a5987 100644
--- a/src/event/BufferedSocket.cxx
+++ b/src/event/BufferedSocket.cxx
@@ -21,6 +21,8 @@
 #include "BufferedSocket.hxx"
 #include "system/SocketError.hxx"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 #include <stdint.h>
@@ -97,8 +99,11 @@ BufferedSocket::ResumeInput()
 		case InputResult::MORE:
 			if (fifo_buffer_is_full(input)) {
 				// TODO
-				OnSocketError(g_error_new_literal(g_quark_from_static_string("buffered_socket"),
-								  0, "Input buffer is full"));
+				static constexpr Domain buffered_socket_domain("buffered_socket");
+				Error error;
+				error.Set(buffered_socket_domain,
+					  "Input buffer is full");
+				OnSocketError(std::move(error));
 				return false;
 			}
 
diff --git a/src/event/BufferedSocket.hxx b/src/event/BufferedSocket.hxx
index 07b0b903b..cc763c164 100644
--- a/src/event/BufferedSocket.hxx
+++ b/src/event/BufferedSocket.hxx
@@ -22,10 +22,10 @@
 
 #include "check.h"
 #include "SocketMonitor.hxx"
-#include "gerror.h"
 #include "gcc.h"
 
 struct fifo_buffer;
+class Error;
 
 /**
  * A #SocketMonitor specialization that adds an input buffer.
@@ -96,7 +96,7 @@ protected:
 	};
 
 	virtual InputResult OnSocketInput(const void *data, size_t length) = 0;
-	virtual void OnSocketError(GError *error) = 0;
+	virtual void OnSocketError(Error &&error) = 0;
 	virtual void OnSocketClosed() = 0;
 
 	virtual bool OnSocketReady(unsigned flags) override;
diff --git a/src/event/FullyBufferedSocket.cxx b/src/event/FullyBufferedSocket.cxx
index f8b149500..3ffd9f416 100644
--- a/src/event/FullyBufferedSocket.cxx
+++ b/src/event/FullyBufferedSocket.cxx
@@ -21,6 +21,8 @@
 #include "FullyBufferedSocket.hxx"
 #include "system/SocketError.hxx"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 #include <stdint.h>
@@ -98,8 +100,10 @@ FullyBufferedSocket::Write(const void *data, size_t length)
 
 	if (!output.Append(data, length)) {
 		// TODO
-		OnSocketError(g_error_new_literal(g_quark_from_static_string("buffered_socket"),
-						  0, "Output buffer is full"));
+		static constexpr Domain buffered_socket_domain("buffered_socket");
+		Error error;
+		error.Set(buffered_socket_domain, "Output buffer is full");
+		OnSocketError(std::move(error));
 		return false;
 	}
 
diff --git a/src/event/ServerSocket.cxx b/src/event/ServerSocket.cxx
index d22790de5..f0b02e34c 100644
--- a/src/event/ServerSocket.cxx
+++ b/src/event/ServerSocket.cxx
@@ -29,6 +29,8 @@
 #include "event/SocketMonitor.hxx"
 #include "system/Resolver.hxx"
 #include "system/fd_util.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -96,7 +98,7 @@ public:
 		path = g_strdup(_path);
 	}
 
-	bool Open(GError **error_r);
+	bool Open(Error &error);
 
 	using SocketMonitor::IsDefined;
 	using SocketMonitor::Close;
@@ -114,11 +116,7 @@ private:
 	virtual bool OnSocketReady(unsigned flags) override;
 };
 
-static GQuark
-server_socket_quark(void)
-{
-	return g_quark_from_static_string("server_socket");
-}
+static constexpr Domain server_socket_domain("server_socket");
 
 /**
  * Wraper for sockaddr_to_string() which never fails.
@@ -126,7 +124,7 @@ server_socket_quark(void)
 char *
 OneServerSocket::ToString() const
 {
-	char *p = sockaddr_to_string(address, address_length, nullptr);
+	char *p = sockaddr_to_string(address, address_length, IgnoreError());
 	if (p == nullptr)
 		p = g_strdup("[unknown]");
 	return p;
@@ -190,14 +188,14 @@ OneServerSocket::OnSocketReady(gcc_unused unsigned flags)
 }
 
 inline bool
-OneServerSocket::Open(GError **error_r)
+OneServerSocket::Open(Error &error)
 {
 	assert(!IsDefined());
 
 	int _fd = socket_bind_listen(address->sa_family,
 				     SOCK_STREAM, 0,
 				     address, address_length, 5,
-				     error_r);
+				     error);
 	if (_fd < 0)
 		return false;
 
@@ -221,10 +219,10 @@ ServerSocket::ServerSocket(EventLoop &_loop)
 ServerSocket::~ServerSocket() {}
 
 bool
-ServerSocket::Open(GError **error_r)
+ServerSocket::Open(Error &error)
 {
 	OneServerSocket *good = nullptr, *bad = nullptr;
-	GError *last_error = nullptr;
+	Error last_error;
 
 	for (auto &i : sockets) {
 		assert(i.GetSerial() > 0);
@@ -232,33 +230,33 @@ ServerSocket::Open(GError **error_r)
 
 		if (bad != nullptr && i.GetSerial() != bad->GetSerial()) {
 			Close();
-			g_propagate_error(error_r, last_error);
+			error = std::move(last_error);
 			return false;
 		}
 
-		GError *error = nullptr;
-		if (!i.Open(&error)) {
+		Error error2;
+		if (!i.Open(error2)) {
 			if (good != nullptr && good->GetSerial() == i.GetSerial()) {
 				char *address_string = i.ToString();
 				char *good_string = good->ToString();
 				g_warning("bind to '%s' failed: %s "
 					  "(continuing anyway, because "
 					  "binding to '%s' succeeded)",
-					  address_string, error->message,
+					  address_string, error2.GetMessage(),
 					  good_string);
 				g_free(address_string);
 				g_free(good_string);
-				g_error_free(error);
 			} else if (bad == nullptr) {
 				bad = &i;
 
 				char *address_string = i.ToString();
-				g_propagate_prefixed_error(&last_error, error,
-							   "Failed to bind to '%s': ",
-							   address_string);
+				error2.FormatPrefix("Failed to bind to '%s': ",
+						    address_string);
 				g_free(address_string);
-			} else
-				g_error_free(error);
+
+				last_error = std::move(error2);
+			}
+
 			continue;
 		}
 
@@ -269,14 +267,13 @@ ServerSocket::Open(GError **error_r)
 
 		if (bad != nullptr) {
 			bad = nullptr;
-			g_error_free(last_error);
-			last_error = nullptr;
+			last_error.Clear();
 		}
 	}
 
 	if (bad != nullptr) {
 		Close();
-		g_propagate_error(error_r, last_error);
+		error = std::move(last_error);
 		return false;
 	}
 
@@ -301,7 +298,7 @@ ServerSocket::AddAddress(const sockaddr &address, size_t address_length)
 }
 
 bool
-ServerSocket::AddFD(int fd, GError **error_r)
+ServerSocket::AddFD(int fd, Error &error)
 {
 	assert(fd >= 0);
 
@@ -309,8 +306,8 @@ ServerSocket::AddFD(int fd, GError **error_r)
 	socklen_t address_length = sizeof(address);
 	if (getsockname(fd, (struct sockaddr *)&address,
 			&address_length) < 0) {
-		SetSocketError(error_r);
-		g_prefix_error(error_r, "Failed to get socket address");
+		SetSocketError(error);
+		error.AddPrefix("Failed to get socket address: ");
 		return false;
 	}
 
@@ -351,12 +348,11 @@ ServerSocket::AddPortIPv6(unsigned port)
 #endif /* HAVE_TCP */
 
 bool
-ServerSocket::AddPort(unsigned port, GError **error_r)
+ServerSocket::AddPort(unsigned port, Error &error)
 {
 #ifdef HAVE_TCP
 	if (port == 0 || port > 0xffff) {
-		g_set_error(error_r, server_socket_quark(), 0,
-			    "Invalid TCP port");
+		error.Set(server_socket_domain, "Invalid TCP port");
 		return false;
 	}
 
@@ -371,19 +367,18 @@ ServerSocket::AddPort(unsigned port, GError **error_r)
 #else /* HAVE_TCP */
 	(void)port;
 
-	g_set_error(error_r, server_socket_quark(), 0,
-		    "TCP support is disabled");
+	error.Set(server_socket_domain, "TCP support is disabled");
 	return false;
 #endif /* HAVE_TCP */
 }
 
 bool
-ServerSocket::AddHost(const char *hostname, unsigned port, GError **error_r)
+ServerSocket::AddHost(const char *hostname, unsigned port, Error &error)
 {
 #ifdef HAVE_TCP
 	struct addrinfo *ai = resolve_host_port(hostname, port,
 						AI_PASSIVE, SOCK_STREAM,
-						error_r);
+						error);
 	if (ai == nullptr)
 		return false;
 
@@ -399,22 +394,21 @@ ServerSocket::AddHost(const char *hostname, unsigned port, GError **error_r)
 	(void)hostname;
 	(void)port;
 
-	g_set_error(error_r, server_socket_quark(), 0,
-		    "TCP support is disabled");
+	error.Set(server_socket_domain, "TCP support is disabled");
 	return false;
 #endif /* HAVE_TCP */
 }
 
 bool
-ServerSocket::AddPath(const char *path, GError **error_r)
+ServerSocket::AddPath(const char *path, Error &error)
 {
 #ifdef HAVE_UN
 	struct sockaddr_un s_un;
 
 	size_t path_length = strlen(path);
 	if (path_length >= sizeof(s_un.sun_path)) {
-		g_set_error(error_r, server_socket_quark(), 0,
-			    "UNIX socket path is too long");
+		error.Set(server_socket_domain,
+			  "UNIX socket path is too long");
 		return false;
 	}
 
@@ -430,8 +424,8 @@ ServerSocket::AddPath(const char *path, GError **error_r)
 #else /* !HAVE_UN */
 	(void)path;
 
-	g_set_error(error_r, server_socket_quark(), 0,
-		    "UNIX domain socket support is disabled");
+	error.Set(server_socket_domain,
+		  "UNIX domain socket support is disabled");
 	return false;
 #endif /* !HAVE_UN */
 }
diff --git a/src/event/ServerSocket.hxx b/src/event/ServerSocket.hxx
index 600cdf8a7..9f0745708 100644
--- a/src/event/ServerSocket.hxx
+++ b/src/event/ServerSocket.hxx
@@ -20,14 +20,13 @@
 #ifndef MPD_SERVER_SOCKET_HXX
 #define MPD_SERVER_SOCKET_HXX
 
-#include "gerror.h"
-
 #include <forward_list>
 
 #include <stddef.h>
 
 struct sockaddr;
 class EventLoop;
+class Error;
 
 typedef void (*server_socket_callback_t)(int fd,
 					 const struct sockaddr *address,
@@ -79,7 +78,7 @@ public:
 	 * ignore errors
 	 * @return true on success
 	 */
-	bool AddPort(unsigned port, GError **error_r);
+	bool AddPort(unsigned port, Error &error);
 
 	/**
 	 * Resolves a host name, and adds listeners on all addresses in the
@@ -91,7 +90,7 @@ public:
 	 * ignore errors
 	 * @return true on success
 	 */
-	bool AddHost(const char *hostname, unsigned port, GError **error_r);
+	bool AddHost(const char *hostname, unsigned port, Error &error);
 
 	/**
 	 * Add a listener on a Unix domain socket.
@@ -101,16 +100,16 @@ public:
 	 * ignore errors
 	 * @return true on success
 	 */
-	bool AddPath(const char *path, GError **error_r);
+	bool AddPath(const char *path, Error &error);
 
 	/**
 	 * Add a socket descriptor that is accepting connections.  After this
 	 * has been called, don't call server_socket_open(), because the
 	 * socket is already open.
 	 */
-	bool AddFD(int fd, GError **error_r);
+	bool AddFD(int fd, Error &error);
 
-	bool Open(GError **error_r);
+	bool Open(Error &error);
 	void Close();
 
 protected:
diff --git a/src/filter/AutoConvertFilterPlugin.cxx b/src/filter/AutoConvertFilterPlugin.cxx
index 19495acbc..4b5ebff4d 100644
--- a/src/filter/AutoConvertFilterPlugin.cxx
+++ b/src/filter/AutoConvertFilterPlugin.cxx
@@ -46,21 +46,22 @@ public:
 		delete filter;
 	}
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r);
-	virtual void Close();
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
+	virtual void Close() override;
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r,
+				      Error &error) override;
 };
 
 AudioFormat
-AutoConvertFilter::Open(AudioFormat &in_audio_format, GError **error_r)
+AutoConvertFilter::Open(AudioFormat &in_audio_format, Error &error)
 {
 	assert(in_audio_format.IsValid());
 
 	/* open the "real" filter */
 
 	const AudioFormat child_audio_format = in_audio_format;
-	AudioFormat out_audio_format = filter->Open(in_audio_format, error_r);
+	AudioFormat out_audio_format = filter->Open(in_audio_format, error);
 	if (!out_audio_format.IsDefined())
 		return out_audio_format;
 
@@ -70,7 +71,7 @@ AutoConvertFilter::Open(AudioFormat &in_audio_format, GError **error_r)
 		/* yes - create a convert_filter */
 
 		const config_param empty;
-		convert = filter_new(&convert_filter_plugin, empty, error_r);
+		convert = filter_new(&convert_filter_plugin, empty, error);
 		if (convert == nullptr) {
 			filter->Close();
 			return AudioFormat::Undefined();
@@ -78,7 +79,7 @@ AutoConvertFilter::Open(AudioFormat &in_audio_format, GError **error_r)
 
 		AudioFormat audio_format2 = in_audio_format;
 		AudioFormat audio_format3 =
-			convert->Open(audio_format2, error_r);
+			convert->Open(audio_format2, error);
 		if (!audio_format3.IsDefined()) {
 			delete convert;
 			filter->Close();
@@ -108,15 +109,15 @@ AutoConvertFilter::Close()
 
 const void *
 AutoConvertFilter::FilterPCM(const void *src, size_t src_size,
-			     size_t *dest_size_r, GError **error_r)
+			     size_t *dest_size_r, Error &error)
 {
 	if (convert != nullptr) {
-		src = convert->FilterPCM(src, src_size, &src_size, error_r);
+		src = convert->FilterPCM(src, src_size, &src_size, error);
 		if (src == nullptr)
 			return nullptr;
 	}
 
-	return filter->FilterPCM(src, src_size, dest_size_r, error_r);
+	return filter->FilterPCM(src, src_size, dest_size_r, error);
 }
 
 Filter *
diff --git a/src/filter/ChainFilterPlugin.cxx b/src/filter/ChainFilterPlugin.cxx
index fbb91795d..a24f533b1 100644
--- a/src/filter/ChainFilterPlugin.cxx
+++ b/src/filter/ChainFilterPlugin.cxx
@@ -24,6 +24,8 @@
 #include "FilterInternal.hxx"
 #include "FilterRegistry.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -53,10 +55,10 @@ public:
 		children.emplace_back(name, filter);
 	}
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
 	virtual void Close();
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r, Error &error);
 
 private:
 	/**
@@ -66,15 +68,11 @@ private:
 	void CloseUntil(const Filter *until);
 };
 
-static inline GQuark
-filter_quark(void)
-{
-	return g_quark_from_static_string("filter");
-}
+static constexpr Domain chain_filter_domain("chain_filter");
 
 static Filter *
 chain_filter_init(gcc_unused const config_param &param,
-		  gcc_unused GError **error_r)
+		  gcc_unused Error &error)
 {
 	return new ChainFilter();
 }
@@ -99,11 +97,11 @@ ChainFilter::CloseUntil(const Filter *until)
 static AudioFormat
 chain_open_child(const char *name, Filter *filter,
 		 const AudioFormat &prev_audio_format,
-		 GError **error_r)
+		 Error &error)
 {
 	AudioFormat conv_audio_format = prev_audio_format;
 	const AudioFormat next_audio_format =
-		filter->Open(conv_audio_format, error_r);
+		filter->Open(conv_audio_format, error);
 	if (!next_audio_format.IsDefined())
 		return next_audio_format;
 
@@ -111,10 +109,11 @@ chain_open_child(const char *name, Filter *filter,
 		struct audio_format_string s;
 
 		filter->Close();
-		g_set_error(error_r, filter_quark(), 0,
-			    "Audio format not supported by filter '%s': %s",
-			    name,
-			    audio_format_to_string(prev_audio_format, &s));
+
+		error.Format(chain_filter_domain,
+			     "Audio format not supported by filter '%s': %s",
+			     name,
+			     audio_format_to_string(prev_audio_format, &s));
 		return AudioFormat::Undefined();
 	}
 
@@ -122,13 +121,13 @@ chain_open_child(const char *name, Filter *filter,
 }
 
 AudioFormat
-ChainFilter::Open(AudioFormat &in_audio_format, GError **error_r)
+ChainFilter::Open(AudioFormat &in_audio_format, Error &error)
 {
 	AudioFormat audio_format = in_audio_format;
 
 	for (auto &child : children) {
 		audio_format = chain_open_child(child.name, child.filter,
-						audio_format, error_r);
+						audio_format, error);
 		if (!audio_format.IsDefined()) {
 			/* rollback, close all children */
 			CloseUntil(child.filter);
@@ -149,13 +148,13 @@ ChainFilter::Close()
 
 const void *
 ChainFilter::FilterPCM(const void *src, size_t src_size,
-		       size_t *dest_size_r, GError **error_r)
+		       size_t *dest_size_r, Error &error)
 {
 	for (auto &child : children) {
 		/* feed the output of the previous filter as input
 		   into the current one */
 		src = child.filter->FilterPCM(src, src_size, &src_size,
-					      error_r);
+					      error);
 		if (src == NULL)
 			return NULL;
 	}
diff --git a/src/filter/ConvertFilterPlugin.cxx b/src/filter/ConvertFilterPlugin.cxx
index 4dc0d0333..3ef2be719 100644
--- a/src/filter/ConvertFilterPlugin.cxx
+++ b/src/filter/ConvertFilterPlugin.cxx
@@ -56,21 +56,22 @@ public:
 		out_audio_format = _out_audio_format;
 	}
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
-	virtual void Close();
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
+	virtual void Close() override;
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r,
+				      Error &error) override;
 };
 
 static Filter *
 convert_filter_init(gcc_unused const config_param &param,
-		    gcc_unused GError **error_r)
+		    gcc_unused Error &error)
 {
 	return new ConvertFilter();
 }
 
 AudioFormat
-ConvertFilter::Open(AudioFormat &audio_format, gcc_unused GError **error_r)
+ConvertFilter::Open(AudioFormat &audio_format, gcc_unused Error &error)
 {
 	assert(audio_format.IsValid());
 
@@ -91,7 +92,7 @@ ConvertFilter::Close()
 
 const void *
 ConvertFilter::FilterPCM(const void *src, size_t src_size,
-			 size_t *dest_size_r, GError **error_r)
+			 size_t *dest_size_r, Error &error)
 {
 	if (in_audio_format == out_audio_format) {
 		/* optimized special case: no-op */
@@ -102,7 +103,7 @@ ConvertFilter::FilterPCM(const void *src, size_t src_size,
 	return state->Convert(in_audio_format,
 			      src, src_size,
 			      out_audio_format, dest_size_r,
-			      error_r);
+			      error);
 }
 
 const struct filter_plugin convert_filter_plugin = {
diff --git a/src/filter/NormalizeFilterPlugin.cxx b/src/filter/NormalizeFilterPlugin.cxx
index 63b562fa0..6c4f6b0e5 100644
--- a/src/filter/NormalizeFilterPlugin.cxx
+++ b/src/filter/NormalizeFilterPlugin.cxx
@@ -34,21 +34,21 @@ class NormalizeFilter final : public Filter {
 	PcmBuffer buffer;
 
 public:
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
 	virtual void Close();
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r, Error &error);
 };
 
 static Filter *
 normalize_filter_init(gcc_unused const config_param &param,
-		      gcc_unused GError **error_r)
+		      gcc_unused Error &error)
 {
 	return new NormalizeFilter();
 }
 
 AudioFormat
-NormalizeFilter::Open(AudioFormat &audio_format, gcc_unused GError **error_r)
+NormalizeFilter::Open(AudioFormat &audio_format, gcc_unused Error &error)
 {
 	audio_format.format = SampleFormat::S16;
 
@@ -66,7 +66,7 @@ NormalizeFilter::Close()
 
 const void *
 NormalizeFilter::FilterPCM(const void *src, size_t src_size,
-			   size_t *dest_size_r, gcc_unused GError **error_r)
+			   size_t *dest_size_r, gcc_unused Error &error)
 {
 	int16_t *dest = (int16_t *)buffer.Get(src_size);
 	memcpy(dest, src, src_size);
diff --git a/src/filter/NullFilterPlugin.cxx b/src/filter/NullFilterPlugin.cxx
index f76c05d3f..ad585d4b6 100644
--- a/src/filter/NullFilterPlugin.cxx
+++ b/src/filter/NullFilterPlugin.cxx
@@ -34,15 +34,15 @@
 class NullFilter final : public Filter {
 public:
 	virtual AudioFormat Open(AudioFormat &af,
-				 gcc_unused GError **error_r) {
+				 gcc_unused Error &error) override {
 		return af;
 	}
 
-	virtual void Close() {}
+	virtual void Close() override {}
 
 	virtual const void *FilterPCM(const void *src, size_t src_size,
 				      size_t *dest_size_r,
-				      gcc_unused GError **error_r) {
+				      gcc_unused Error &error) override {
 		*dest_size_r = src_size;
 		return src;
 	}
@@ -50,7 +50,7 @@ public:
 
 static Filter *
 null_filter_init(gcc_unused const config_param &param,
-		 gcc_unused GError **error_r)
+		 gcc_unused Error &error)
 {
 	return new NullFilter();
 }
diff --git a/src/filter/ReplayGainFilterPlugin.cxx b/src/filter/ReplayGainFilterPlugin.cxx
index 446264c6e..0dd8905cb 100644
--- a/src/filter/ReplayGainFilterPlugin.cxx
+++ b/src/filter/ReplayGainFilterPlugin.cxx
@@ -28,6 +28,8 @@
 #include "MixerControl.hxx"
 #include "pcm/PcmVolume.hxx"
 #include "pcm/PcmBuffer.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -114,17 +116,13 @@ public:
 	 */
 	void Update();
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
 	virtual void Close();
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r, Error &error);
 };
 
-static inline GQuark
-replay_gain_quark(void)
-{
-	return g_quark_from_static_string("replay_gain");
-}
+static constexpr Domain replay_gain_domain("replay_gain");
 
 void
 ReplayGainFilter::Update()
@@ -145,24 +143,22 @@ ReplayGainFilter::Update()
 		if (_volume > 100)
 			_volume = 100;
 
-		GError *error = NULL;
-		if (!mixer_set_volume(mixer, _volume, &error)) {
+		Error error;
+		if (!mixer_set_volume(mixer, _volume, error))
 			g_warning("Failed to update hardware mixer: %s",
-				  error->message);
-			g_error_free(error);
-		}
+				  error.GetMessage());
 	}
 }
 
 static Filter *
 replay_gain_filter_init(gcc_unused const config_param &param,
-			gcc_unused GError **error_r)
+			gcc_unused Error &error)
 {
 	return new ReplayGainFilter();
 }
 
 AudioFormat
-ReplayGainFilter::Open(AudioFormat &af, gcc_unused GError **error_r)
+ReplayGainFilter::Open(AudioFormat &af, gcc_unused Error &error)
 {
 	format = af;
 
@@ -177,7 +173,7 @@ ReplayGainFilter::Close()
 
 const void *
 ReplayGainFilter::FilterPCM(const void *src, size_t src_size,
-			    size_t *dest_size_r, GError **error_r)
+			    size_t *dest_size_r, Error &error)
 {
 
 	*dest_size_r = src_size;
@@ -201,8 +197,7 @@ ReplayGainFilter::FilterPCM(const void *src, size_t src_size,
 				  format.format,
 				  volume);
 	if (!success) {
-		g_set_error(error_r, replay_gain_quark(), 0,
-			    "pcm_volume() has failed");
+		error.Set(replay_gain_domain, "pcm_volume() has failed");
 		return NULL;
 	}
 
diff --git a/src/filter/RouteFilterPlugin.cxx b/src/filter/RouteFilterPlugin.cxx
index 2c0d60cbe..20ef5e963 100644
--- a/src/filter/RouteFilterPlugin.cxx
+++ b/src/filter/RouteFilterPlugin.cxx
@@ -41,13 +41,16 @@
 
 #include "config.h"
 #include "conf.h"
-#include "ConfigQuark.hxx"
+#include "ConfigError.hxx"
 #include "AudioFormat.hxx"
 #include "CheckAudioFormat.hxx"
 #include "FilterPlugin.hxx"
 #include "FilterInternal.hxx"
 #include "FilterRegistry.hxx"
 #include "pcm/PcmBuffer.hxx"
+#include "util/Error.hxx"
+
+#include <glib.h>
 
 #include <assert.h>
 #include <string.h>
@@ -118,16 +121,16 @@ public:
 	 * @param filter a route_filter whose min_channels and sources[] to set
 	 * @return true on success, false on error
 	 */
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
 	virtual void Close();
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r, Error &error);
 };
 
 bool
-RouteFilter::Configure(const config_param &param, GError **error_r) {
+RouteFilter::Configure(const config_param &param, Error &error) {
 
 	/* TODO:
 	 * With a more clever way of marking "don't copy to output N",
@@ -160,9 +163,9 @@ RouteFilter::Configure(const config_param &param, GError **error_r) {
 		// Split the a>b string into source and destination
 		sd = g_strsplit(tokens[c], ">", 2);
 		if (g_strv_length(sd) != 2) {
-			g_set_error(error_r, config_quark(), 1,
-				"Invalid copy around %d in routes spec: %s",
-				param.line, tokens[c]);
+			error.Format(config_domain,
+				     "Invalid copy around %d in routes spec: %s",
+				     param.line, tokens[c]);
 			g_strfreev(sd);
 			g_strfreev(tokens);
 			return false;
@@ -183,9 +186,9 @@ RouteFilter::Configure(const config_param &param, GError **error_r) {
 
 	if (!audio_valid_channel_count(min_output_channels)) {
 		g_strfreev(tokens);
-		g_set_error(error_r, audio_format_quark(), 0,
-			    "Invalid number of output channels requested: %d",
-			    min_output_channels);
+		error.Format(config_domain,
+			     "Invalid number of output channels requested: %d",
+			     min_output_channels);
 		return false;
 	}
 
@@ -207,9 +210,9 @@ RouteFilter::Configure(const config_param &param, GError **error_r) {
 		// Split the a>b string into source and destination
 		sd = g_strsplit(tokens[c], ">", 2);
 		if (g_strv_length(sd) != 2) {
-			g_set_error(error_r, config_quark(), 1,
-				"Invalid copy around %d in routes spec: %s",
-				param.line, tokens[c]);
+			error.Format(config_domain,
+				     "Invalid copy around %d in routes spec: %s",
+				     param.line, tokens[c]);
 			g_strfreev(sd);
 			g_strfreev(tokens);
 			return false;
@@ -229,10 +232,10 @@ RouteFilter::Configure(const config_param &param, GError **error_r) {
 }
 
 static Filter *
-route_filter_init(const config_param &param, GError **error_r)
+route_filter_init(const config_param &param, Error &error)
 {
 	RouteFilter *filter = new RouteFilter();
-	if (!filter->Configure(param, error_r)) {
+	if (!filter->Configure(param, error)) {
 		delete filter;
 		return nullptr;
 	}
@@ -241,7 +244,7 @@ route_filter_init(const config_param &param, GError **error_r)
 }
 
 AudioFormat
-RouteFilter::Open(AudioFormat &audio_format, gcc_unused GError **error_r)
+RouteFilter::Open(AudioFormat &audio_format, gcc_unused Error &error)
 {
 	// Copy the input format for later reference
 	input_format = audio_format;
@@ -266,7 +269,7 @@ RouteFilter::Close()
 
 const void *
 RouteFilter::FilterPCM(const void *src, size_t src_size,
-		       size_t *dest_size_r, gcc_unused GError **error_r)
+		       size_t *dest_size_r, gcc_unused Error &error)
 {
 	size_t number_of_frames = src_size / input_frame_size;
 
diff --git a/src/filter/VolumeFilterPlugin.cxx b/src/filter/VolumeFilterPlugin.cxx
index 239f0b899..4c51ac599 100644
--- a/src/filter/VolumeFilterPlugin.cxx
+++ b/src/filter/VolumeFilterPlugin.cxx
@@ -26,6 +26,8 @@
 #include "pcm/PcmVolume.hxx"
 #include "pcm/PcmBuffer.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -58,27 +60,23 @@ public:
 		volume = _volume;
 	}
 
-	virtual AudioFormat Open(AudioFormat &af, GError **error_r) override;
+	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
 	virtual void Close();
 	virtual const void *FilterPCM(const void *src, size_t src_size,
-				      size_t *dest_size_r, GError **error_r);
+				      size_t *dest_size_r, Error &error);
 };
 
-static inline GQuark
-volume_quark(void)
-{
-	return g_quark_from_static_string("pcm_volume");
-}
+static constexpr Domain volume_domain("pcm_volume");
 
 static Filter *
 volume_filter_init(gcc_unused const config_param &param,
-		   gcc_unused GError **error_r)
+		   gcc_unused Error &error)
 {
 	return new VolumeFilter();
 }
 
 AudioFormat
-VolumeFilter::Open(AudioFormat &audio_format, gcc_unused GError **error_r)
+VolumeFilter::Open(AudioFormat &audio_format, gcc_unused Error &error)
 {
 	format = audio_format;
 
@@ -93,7 +91,7 @@ VolumeFilter::Close()
 
 const void *
 VolumeFilter::FilterPCM(const void *src, size_t src_size,
-			size_t *dest_size_r, GError **error_r)
+			size_t *dest_size_r, Error &error)
 {
 	*dest_size_r = src_size;
 
@@ -117,8 +115,7 @@ VolumeFilter::FilterPCM(const void *src, size_t src_size,
 				  format.format,
 				  volume);
 	if (!success) {
-		g_set_error(error_r, volume_quark(), 0,
-			    "pcm_volume() has failed");
+		error.Set(volume_domain, "pcm_volume() has failed");
 		return NULL;
 	}
 
diff --git a/src/input/ArchiveInputPlugin.cxx b/src/input/ArchiveInputPlugin.cxx
index 0d856527f..025b25fef 100644
--- a/src/input/ArchiveInputPlugin.cxx
+++ b/src/input/ArchiveInputPlugin.cxx
@@ -24,6 +24,7 @@
 #include "ArchivePlugin.hxx"
 #include "ArchiveFile.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -38,7 +39,7 @@
 static struct input_stream *
 input_archive_open(const char *pathname,
 		   Mutex &mutex, Cond &cond,
-		   GError **error_r)
+		   Error &error)
 {
 	const struct archive_plugin *arplug;
 	char *archive, *filename, *suffix, *pname;
@@ -63,14 +64,14 @@ input_archive_open(const char *pathname,
 		return NULL;
 	}
 
-	auto file = archive_file_open(arplug, archive, error_r);
+	auto file = archive_file_open(arplug, archive, error);
 	if (file == NULL) {
 		g_free(pname);
 		return NULL;
 	}
 
 	//setup fileops
-	is = file->OpenStream(filename, mutex, cond, error_r);
+	is = file->OpenStream(filename, mutex, cond, error);
 	g_free(pname);
 	file->Close();
 
diff --git a/src/input/CdioParanoiaInputPlugin.cxx b/src/input/CdioParanoiaInputPlugin.cxx
index f0fa835b3..660c157e8 100644
--- a/src/input/CdioParanoiaInputPlugin.cxx
+++ b/src/input/CdioParanoiaInputPlugin.cxx
@@ -26,6 +26,8 @@
 #include "InputInternal.hxx"
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <stdio.h>
 #include <stdint.h>
@@ -71,11 +73,7 @@ struct CdioParanoiaInputStream {
 	}
 };
 
-static inline GQuark
-cdio_quark(void)
-{
-	return g_quark_from_static_string("cdio");
-}
+static constexpr Domain cdio_domain("cdio");
 
 static void
 input_cdio_close(struct input_stream *is)
@@ -91,7 +89,7 @@ struct cdio_uri {
 };
 
 static bool
-parse_cdio_uri(struct cdio_uri *dest, const char *src, GError **error_r)
+parse_cdio_uri(struct cdio_uri *dest, const char *src, Error &error)
 {
 	if (!g_str_has_prefix(src, "cdda://"))
 		return false;
@@ -125,8 +123,7 @@ parse_cdio_uri(struct cdio_uri *dest, const char *src, GError **error_r)
 	char *endptr;
 	dest->track = strtoul(track, &endptr, 10);
 	if (*endptr != 0) {
-		g_set_error(error_r, cdio_quark(), 0,
-			    "Malformed track number");
+		error.Set(cdio_domain, "Malformed track number");
 		return false;
 	}
 
@@ -154,10 +151,10 @@ cdio_detect_device(void)
 static struct input_stream *
 input_cdio_open(const char *uri,
 		Mutex &mutex, Cond &cond,
-		GError **error_r)
+		Error &error)
 {
 	struct cdio_uri parsed_uri;
-	if (!parse_cdio_uri(&parsed_uri, uri, error_r))
+	if (!parse_cdio_uri(&parsed_uri, uri, error))
 		return nullptr;
 
 	CdioParanoiaInputStream *i =
@@ -169,8 +166,8 @@ input_cdio_open(const char *uri,
 		? g_strdup(parsed_uri.device)
 		: cdio_detect_device();
 	if (device == nullptr) {
-		g_set_error(error_r, cdio_quark(), 0,
-			    "Unable find or access a CD-ROM drive with an audio CD in it.");
+		error.Set(cdio_domain,
+			  "Unable find or access a CD-ROM drive with an audio CD in it.");
 		delete i;
 		return nullptr;
 	}
@@ -182,8 +179,7 @@ input_cdio_open(const char *uri,
 	i->drv = cdio_cddap_identify_cdio(i->cdio, 1, nullptr);
 
 	if ( !i->drv ) {
-		g_set_error(error_r, cdio_quark(), 0,
-			    "Unable to identify audio CD disc.");
+		error.Set(cdio_domain, "Unable to identify audio CD disc.");
 		delete i;
 		return nullptr;
 	}
@@ -191,7 +187,7 @@ input_cdio_open(const char *uri,
 	cdda_verbose_set(i->drv, CDDA_MESSAGE_FORGETIT, CDDA_MESSAGE_FORGETIT);
 
 	if ( 0 != cdio_cddap_open(i->drv) ) {
-		g_set_error(error_r, cdio_quark(), 0, "Unable to open disc.");
+		error.Set(cdio_domain, "Unable to open disc.");
 		delete i;
 		return nullptr;
 	}
@@ -211,9 +207,8 @@ input_cdio_open(const char *uri,
 		reverse_endian = G_BYTE_ORDER == G_LITTLE_ENDIAN;
 		break;
 	default:
-		g_set_error(error_r, cdio_quark(), 0,
-			    "Drive returns unknown data type %d",
-			    data_bigendianp(i->drv));
+		error.Format(cdio_domain, "Drive returns unknown data type %d",
+			     data_bigendianp(i->drv));
 		delete i;
 		return nullptr;
 	}
@@ -250,7 +245,7 @@ input_cdio_open(const char *uri,
 
 static bool
 input_cdio_seek(struct input_stream *is,
-		goffset offset, int whence, GError **error_r)
+		goffset offset, int whence, Error &error)
 {
 	CdioParanoiaInputStream *cis = (CdioParanoiaInputStream *)is;
 
@@ -267,9 +262,8 @@ input_cdio_seek(struct input_stream *is,
 	}
 
 	if (offset < 0 || offset > cis->base.size) {
-		g_set_error(error_r, cdio_quark(), 0,
-			    "Invalid offset to seek %ld (%ld)",
-			    (long int)offset, (long int)cis->base.size);
+		error.Format(cdio_domain, "Invalid offset to seek %ld (%ld)",
+			     (long int)offset, (long int)cis->base.size);
 		return false;
 	}
 
@@ -288,7 +282,7 @@ input_cdio_seek(struct input_stream *is,
 
 static size_t
 input_cdio_read(struct input_stream *is, void *ptr, size_t length,
-		GError **error_r)
+		Error &error)
 {
 	CdioParanoiaInputStream *cis = (CdioParanoiaInputStream *)is;
 	size_t nbytes = 0;
@@ -319,8 +313,8 @@ input_cdio_read(struct input_stream *is, void *ptr, size_t length,
 				free(s_mess);
 			}
 			if (!rbuf) {
-				g_set_error(error_r, cdio_quark(), 0,
-					"paranoia read error. Stopping.");
+				error.Set(cdio_domain,
+					  "paranoia read error. Stopping.");
 				return 0;
 			}
 			//store current buffer
diff --git a/src/input/CurlInputPlugin.cxx b/src/input/CurlInputPlugin.cxx
index c5f524bc0..cbf5c6b83 100644
--- a/src/input/CurlInputPlugin.cxx
+++ b/src/input/CurlInputPlugin.cxx
@@ -28,6 +28,8 @@
 #include "event/MultiSocketMonitor.hxx"
 #include "event/Call.hxx"
 #include "IOThread.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 
@@ -162,16 +164,14 @@ struct input_curl {
 	    input_stream_tag() */
 	Tag *tag;
 
-	GError *postponed_error;
+	Error postponed_error;
 
 	input_curl(const char *url, Mutex &mutex, Cond &cond)
 		:base(input_plugin_curl, url, mutex, cond),
 		 range(nullptr), request_headers(nullptr),
 		 paused(false),
 		 meta_name(nullptr),
-		 tag(nullptr),
-		 postponed_error(nullptr) {
-	}
+		 tag(nullptr) {}
 
 	~input_curl();
 
@@ -215,12 +215,9 @@ static struct {
 	CurlSockets *sockets;
 } curl;
 
-gcc_const
-static inline GQuark
-curl_quark(void)
-{
-	return g_quark_from_static_string("curl");
-}
+static constexpr Domain http_domain("http");
+static constexpr Domain curl_domain("curl");
+static constexpr Domain curlm_domain("curlm");
 
 /**
  * Find a request by its CURL "easy" handle.
@@ -319,7 +316,7 @@ CurlSockets::UpdateSockets()
  * Runs in the I/O thread.  No lock needed.
  */
 static bool
-input_curl_easy_add(struct input_curl *c, GError **error_r)
+input_curl_easy_add(struct input_curl *c, Error &error)
 {
 	assert(io_thread_inside());
 	assert(c != NULL);
@@ -330,9 +327,9 @@ input_curl_easy_add(struct input_curl *c, GError **error_r)
 
 	CURLMcode mcode = curl_multi_add_handle(curl.multi, c->easy);
 	if (mcode != CURLM_OK) {
-		g_set_error(error_r, curl_quark(), mcode,
-			    "curl_multi_add_handle() failed: %s",
-			    curl_multi_strerror(mcode));
+		error.Format(curlm_domain, mcode,
+			     "curl_multi_add_handle() failed: %s",
+			     curl_multi_strerror(mcode));
 		return false;
 	}
 
@@ -346,14 +343,14 @@ input_curl_easy_add(struct input_curl *c, GError **error_r)
  * any thread.  Caller must not hold a mutex.
  */
 static bool
-input_curl_easy_add_indirect(struct input_curl *c, GError **error_r)
+input_curl_easy_add_indirect(struct input_curl *c, Error &error)
 {
 	assert(c != NULL);
 	assert(c->easy != NULL);
 
 	bool result;
-	BlockingCall(io_thread_get(), [c, error_r, &result](){
-			result = input_curl_easy_add(c, error_r);
+	BlockingCall(io_thread_get(), [c, &error, &result](){
+			result = input_curl_easy_add(c, error);
 		});
 	return result;
 }
@@ -409,27 +406,25 @@ input_curl_easy_free_indirect(struct input_curl *c)
  * Runs in the I/O thread.  The caller must not hold locks.
  */
 static void
-input_curl_abort_all_requests(GError *error)
+input_curl_abort_all_requests(const Error &error)
 {
 	assert(io_thread_inside());
-	assert(error != NULL);
+	assert(error.IsDefined());
 
 	while (!curl.requests.empty()) {
 		struct input_curl *c = curl.requests.front();
-		assert(c->postponed_error == NULL);
+		assert(!c->postponed_error.IsDefined());
 
 		input_curl_easy_free(c);
 
 		const ScopeLock protect(c->base.mutex);
 
-		c->postponed_error = g_error_copy(error);
+		c->postponed_error.Set(error);
 		c->base.ready = true;
 
 		c->base.cond.broadcast();
 	}
 
-	g_error_free(error);
-
 }
 
 /**
@@ -443,18 +438,17 @@ input_curl_request_done(struct input_curl *c, CURLcode result, long status)
 	assert(io_thread_inside());
 	assert(c != NULL);
 	assert(c->easy == NULL);
-	assert(c->postponed_error == NULL);
+	assert(!c->postponed_error.IsDefined());
 
 	const ScopeLock protect(c->base.mutex);
 
 	if (result != CURLE_OK) {
-		c->postponed_error = g_error_new(curl_quark(), result,
-						 "curl failed: %s",
-						 c->error);
+		c->postponed_error.Format(curl_domain, result,
+					  "curl failed: %s", c->error);
 	} else if (status < 200 || status >= 300) {
-		c->postponed_error = g_error_new(curl_quark(), 0,
-						 "got HTTP status %ld",
-						 status);
+		c->postponed_error.Format(http_domain, status,
+					  "got HTTP status %ld",
+					  status);
 	}
 
 	c->base.ready = true;
@@ -513,9 +507,10 @@ input_curl_perform(void)
 	} while (mcode == CURLM_CALL_MULTI_PERFORM);
 
 	if (mcode != CURLM_OK && mcode != CURLM_CALL_MULTI_PERFORM) {
-		GError *error = g_error_new(curl_quark(), mcode,
-					    "curl_multi_perform() failed: %s",
-					    curl_multi_strerror(mcode));
+		Error error;
+		error.Format(curlm_domain, mcode,
+			     "curl_multi_perform() failed: %s",
+			     curl_multi_strerror(mcode));
 		input_curl_abort_all_requests(error);
 		return false;
 	}
@@ -559,14 +554,13 @@ CurlSockets::DispatchSockets()
  */
 
 static bool
-input_curl_init(const config_param &param,
-		gcc_unused GError **error_r)
+input_curl_init(const config_param &param, Error &error)
 {
 	CURLcode code = curl_global_init(CURL_GLOBAL_ALL);
 	if (code != CURLE_OK) {
-		g_set_error(error_r, curl_quark(), code,
-			    "curl_global_init() failed: %s\n",
-			    curl_easy_strerror(code));
+		error.Format(curl_domain, code,
+			     "curl_global_init() failed: %s",
+			     curl_easy_strerror(code));
 		return false;
 	}
 
@@ -588,8 +582,7 @@ input_curl_init(const config_param &param,
 
 	curl.multi = curl_multi_init();
 	if (curl.multi == NULL) {
-		g_set_error(error_r, curl_quark(), 0,
-			    "curl_multi_init() failed");
+		error.Set(curl_domain, 0, "curl_multi_init() failed");
 		return false;
 	}
 
@@ -639,20 +632,17 @@ input_curl::~input_curl()
 	g_free(meta_name);
 
 	input_curl_easy_free_indirect(this);
-
-	if (postponed_error != NULL)
-		g_error_free(postponed_error);
 }
 
 static bool
-input_curl_check(struct input_stream *is, GError **error_r)
+input_curl_check(struct input_stream *is, Error &error)
 {
 	struct input_curl *c = (struct input_curl *)is;
 
-	bool success = c->postponed_error == NULL;
+	bool success = !c->postponed_error.IsDefined();
 	if (!success) {
-		g_propagate_error(error_r, c->postponed_error);
-		c->postponed_error = NULL;
+		error = std::move(c->postponed_error);
+		c->postponed_error.Clear();
 	}
 
 	return success;
@@ -669,14 +659,14 @@ input_curl_tag(struct input_stream *is)
 }
 
 static bool
-fill_buffer(struct input_curl *c, GError **error_r)
+fill_buffer(struct input_curl *c, Error &error)
 {
 	while (c->easy != NULL && c->buffers.empty())
 		c->base.cond.wait(c->base.mutex);
 
-	if (c->postponed_error != NULL) {
-		g_propagate_error(error_r, c->postponed_error);
-		c->postponed_error = NULL;
+	if (c->postponed_error.IsDefined()) {
+		error = std::move(c->postponed_error);
+		c->postponed_error.Clear();
 		return false;
 	}
 
@@ -754,13 +744,13 @@ input_curl_available(struct input_stream *is)
 {
 	struct input_curl *c = (struct input_curl *)is;
 
-	return c->postponed_error != NULL || c->easy == NULL ||
+	return c->postponed_error.IsDefined() || c->easy == NULL ||
 		!c->buffers.empty();
 }
 
 static size_t
 input_curl_read(struct input_stream *is, void *ptr, size_t size,
-		GError **error_r)
+		Error &error)
 {
 	struct input_curl *c = (struct input_curl *)is;
 	bool success;
@@ -770,7 +760,7 @@ input_curl_read(struct input_stream *is, void *ptr, size_t size,
 	do {
 		/* fill the buffer */
 
-		success = fill_buffer(c, error_r);
+		success = fill_buffer(c, error);
 		if (!success)
 			return 0;
 
@@ -927,14 +917,13 @@ input_curl_writefunction(void *ptr, size_t size, size_t nmemb, void *stream)
 }
 
 static bool
-input_curl_easy_init(struct input_curl *c, GError **error_r)
+input_curl_easy_init(struct input_curl *c, Error &error)
 {
 	CURLcode code;
 
 	c->easy = curl_easy_init();
 	if (c->easy == NULL) {
-		g_set_error(error_r, curl_quark(), 0,
-			    "curl_easy_init() failed");
+		error.Set(curl_domain, "curl_easy_init() failed");
 		return false;
 	}
 
@@ -971,9 +960,9 @@ input_curl_easy_init(struct input_curl *c, GError **error_r)
 
 	code = curl_easy_setopt(c->easy, CURLOPT_URL, c->base.uri.c_str());
 	if (code != CURLE_OK) {
-		g_set_error(error_r, curl_quark(), code,
-			    "curl_easy_setopt() failed: %s",
-			    curl_easy_strerror(code));
+		error.Format(curl_domain, code,
+			     "curl_easy_setopt() failed: %s",
+			     curl_easy_strerror(code));
 		return false;
 	}
 
@@ -987,7 +976,7 @@ input_curl_easy_init(struct input_curl *c, GError **error_r)
 
 static bool
 input_curl_seek(struct input_stream *is, goffset offset, int whence,
-		GError **error_r)
+		Error &error)
 {
 	struct input_curl *c = (struct input_curl *)is;
 	bool ret;
@@ -1059,7 +1048,7 @@ input_curl_seek(struct input_stream *is, goffset offset, int whence,
 		return true;
 	}
 
-	ret = input_curl_easy_init(c, error_r);
+	ret = input_curl_easy_init(c, error);
 	if (!ret)
 		return false;
 
@@ -1072,7 +1061,7 @@ input_curl_seek(struct input_stream *is, goffset offset, int whence,
 
 	c->base.ready = false;
 
-	if (!input_curl_easy_add_indirect(c, error_r))
+	if (!input_curl_easy_add_indirect(c, error))
 		return false;
 
 	c->base.mutex.lock();
@@ -1080,9 +1069,9 @@ input_curl_seek(struct input_stream *is, goffset offset, int whence,
 	while (!c->base.ready)
 		c->base.cond.wait(c->base.mutex);
 
-	if (c->postponed_error != NULL) {
-		g_propagate_error(error_r, c->postponed_error);
-		c->postponed_error = NULL;
+	if (c->postponed_error.IsDefined()) {
+		error = std::move(c->postponed_error);
+		c->postponed_error.Clear();
 		return false;
 	}
 
@@ -1091,19 +1080,19 @@ input_curl_seek(struct input_stream *is, goffset offset, int whence,
 
 static struct input_stream *
 input_curl_open(const char *url, Mutex &mutex, Cond &cond,
-		GError **error_r)
+		Error &error)
 {
 	if (strncmp(url, "http://", 7) != 0)
 		return NULL;
 
 	struct input_curl *c = new input_curl(url, mutex, cond);
 
-	if (!input_curl_easy_init(c, error_r)) {
+	if (!input_curl_easy_init(c, error)) {
 		delete c;
 		return NULL;
 	}
 
-	if (!input_curl_easy_add_indirect(c, error_r)) {
+	if (!input_curl_easy_add_indirect(c, error)) {
 		delete c;
 		return NULL;
 	}
diff --git a/src/input/DespotifyInputPlugin.cxx b/src/input/DespotifyInputPlugin.cxx
index 30ecceed7..f2b87dbcc 100644
--- a/src/input/DespotifyInputPlugin.cxx
+++ b/src/input/DespotifyInputPlugin.cxx
@@ -124,7 +124,7 @@ static void callback(gcc_unused struct despotify_session* ds,
 static struct input_stream *
 input_despotify_open(const char *url,
 		     Mutex &mutex, Cond &cond,
-		     gcc_unused GError **error_r)
+		     gcc_unused Error &error)
 {
 	struct despotify_session *session;
 	struct ds_link *ds_link;
@@ -172,7 +172,7 @@ input_despotify_open(const char *url,
 
 static size_t
 input_despotify_read(struct input_stream *is, void *ptr, size_t size,
-		     gcc_unused GError **error_r)
+		     gcc_unused Error &error)
 {
 	DespotifyInputStream *ctx = (DespotifyInputStream *)is;
 	size_t to_cpy = size;
diff --git a/src/input/FfmpegInputPlugin.cxx b/src/input/FfmpegInputPlugin.cxx
index f27348b27..1837303bb 100644
--- a/src/input/FfmpegInputPlugin.cxx
+++ b/src/input/FfmpegInputPlugin.cxx
@@ -25,6 +25,8 @@
 #include "InputInternal.hxx"
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 extern "C" {
 #include <libavutil/avutil.h>
@@ -62,11 +64,7 @@ struct FfmpegInputStream {
 	}
 };
 
-static inline GQuark
-ffmpeg_quark(void)
-{
-	return g_quark_from_static_string("ffmpeg");
-}
+static constexpr Domain ffmpeg_domain("ffmpeg");
 
 static inline bool
 input_ffmpeg_supported(void)
@@ -77,14 +75,13 @@ input_ffmpeg_supported(void)
 
 static bool
 input_ffmpeg_init(gcc_unused const config_param &param,
-		  gcc_unused GError **error_r)
+		  Error &error)
 {
 	av_register_all();
 
 	/* disable this plugin if there's no registered protocol */
 	if (!input_ffmpeg_supported()) {
-		g_set_error(error_r, ffmpeg_quark(), 0,
-			    "No protocol");
+		error.Set(ffmpeg_domain, "No protocol");
 		return false;
 	}
 
@@ -94,7 +91,7 @@ input_ffmpeg_init(gcc_unused const config_param &param,
 static struct input_stream *
 input_ffmpeg_open(const char *uri,
 		  Mutex &mutex, Cond &cond,
-		  GError **error_r)
+		  Error &error)
 {
 	if (!g_str_has_prefix(uri, "gopher://") &&
 	    !g_str_has_prefix(uri, "rtp://") &&
@@ -107,8 +104,8 @@ input_ffmpeg_open(const char *uri,
 	AVIOContext *h;
 	int ret = avio_open(&h, uri, AVIO_FLAG_READ);
 	if (ret != 0) {
-		g_set_error(error_r, ffmpeg_quark(), ret,
-			    "libavformat failed to open the URI");
+		error.Set(ffmpeg_domain, ret,
+			  "libavformat failed to open the URI");
 		return nullptr;
 	}
 
@@ -118,15 +115,14 @@ input_ffmpeg_open(const char *uri,
 
 static size_t
 input_ffmpeg_read(struct input_stream *is, void *ptr, size_t size,
-		  GError **error_r)
+		  Error &error)
 {
 	FfmpegInputStream *i = (FfmpegInputStream *)is;
 
 	int ret = avio_read(i->h, (unsigned char *)ptr, size);
 	if (ret <= 0) {
 		if (ret < 0)
-			g_set_error(error_r, ffmpeg_quark(), 0,
-				    "url_read() failed");
+			error.Set(ffmpeg_domain, "avio_read() failed");
 
 		i->eof = true;
 		return false;
@@ -154,7 +150,7 @@ input_ffmpeg_eof(struct input_stream *is)
 
 static bool
 input_ffmpeg_seek(struct input_stream *is, goffset offset, int whence,
-		  gcc_unused GError **error_r)
+		  Error &error)
 {
 	FfmpegInputStream *i = (FfmpegInputStream *)is;
 	int64_t ret = avio_seek(i->h, offset, whence);
@@ -163,7 +159,7 @@ input_ffmpeg_seek(struct input_stream *is, goffset offset, int whence,
 		i->eof = false;
 		return true;
 	} else {
-		g_set_error(error_r, ffmpeg_quark(), 0, "url_seek() failed");
+		error.Set(ffmpeg_domain, "avio_seek() failed");
 		return false;
 	}
 }
diff --git a/src/input/FileInputPlugin.cxx b/src/input/FileInputPlugin.cxx
index 6fd743179..7d1fc0a7f 100644
--- a/src/input/FileInputPlugin.cxx
+++ b/src/input/FileInputPlugin.cxx
@@ -22,9 +22,10 @@
 #include "InputInternal.hxx"
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "system/fd_util.h"
 #include "open.h"
-#include "io_error.h"
 
 #include <sys/stat.h>
 #include <unistd.h>
@@ -35,6 +36,8 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "input_file"
 
+static constexpr Domain file_domain("file");
+
 struct FileInputStream {
 	struct input_stream base;
 
@@ -57,7 +60,7 @@ struct FileInputStream {
 static struct input_stream *
 input_file_open(const char *filename,
 		Mutex &mutex, Cond &cond,
-		GError **error_r)
+		Error &error)
 {
 	int fd, ret;
 	struct stat st;
@@ -68,24 +71,20 @@ input_file_open(const char *filename,
 	fd = open_cloexec(filename, O_RDONLY|O_BINARY, 0);
 	if (fd < 0) {
 		if (errno != ENOENT && errno != ENOTDIR)
-			g_set_error(error_r, errno_quark(), errno,
-				    "Failed to open \"%s\": %s",
-				    filename, g_strerror(errno));
+			error.FormatErrno("Failed to open \"%s\"",
+					  filename);
 		return nullptr;
 	}
 
 	ret = fstat(fd, &st);
 	if (ret < 0) {
-		g_set_error(error_r, errno_quark(), errno,
-			    "Failed to stat \"%s\": %s",
-			    filename, g_strerror(errno));
+		error.FormatErrno("Failed to stat \"%s\"", filename);
 		close(fd);
 		return nullptr;
 	}
 
 	if (!S_ISREG(st.st_mode)) {
-		g_set_error(error_r, errno_quark(), 0,
-			    "Not a regular file: %s", filename);
+		error.Format(file_domain, "Not a regular file: %s", filename);
 		close(fd);
 		return nullptr;
 	}
@@ -101,14 +100,13 @@ input_file_open(const char *filename,
 
 static bool
 input_file_seek(struct input_stream *is, goffset offset, int whence,
-		GError **error_r)
+		Error &error)
 {
 	FileInputStream *fis = (FileInputStream *)is;
 
 	offset = (goffset)lseek(fis->fd, (off_t)offset, whence);
 	if (offset < 0) {
-		g_set_error(error_r, errno_quark(), errno,
-			    "Failed to seek: %s", g_strerror(errno));
+		error.SetErrno("Failed to seek");
 		return false;
 	}
 
@@ -118,15 +116,14 @@ input_file_seek(struct input_stream *is, goffset offset, int whence,
 
 static size_t
 input_file_read(struct input_stream *is, void *ptr, size_t size,
-		GError **error_r)
+		Error &error)
 {
 	FileInputStream *fis = (FileInputStream *)is;
 	ssize_t nbytes;
 
 	nbytes = read(fis->fd, ptr, size);
 	if (nbytes < 0) {
-		g_set_error(error_r, errno_quark(), errno,
-			    "Failed to read: %s", g_strerror(errno));
+		error.SetErrno("Failed to read");
 		return 0;
 	}
 
diff --git a/src/input/MmsInputPlugin.cxx b/src/input/MmsInputPlugin.cxx
index 80d479613..02810bb22 100644
--- a/src/input/MmsInputPlugin.cxx
+++ b/src/input/MmsInputPlugin.cxx
@@ -22,6 +22,8 @@
 #include "InputInternal.hxx"
 #include "InputStream.hxx"
 #include "InputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 #include <libmms/mmsx.h>
@@ -56,16 +58,12 @@ struct MmsInputStream {
 	}
 };
 
-static inline GQuark
-mms_quark(void)
-{
-	return g_quark_from_static_string("mms");
-}
+static constexpr Domain mms_domain("mms");
 
 static struct input_stream *
 input_mms_open(const char *url,
 	       Mutex &mutex, Cond &cond,
-	       GError **error_r)
+	       Error &error)
 {
 	if (!g_str_has_prefix(url, "mms://") &&
 	    !g_str_has_prefix(url, "mmsh://") &&
@@ -75,7 +73,7 @@ input_mms_open(const char *url,
 
 	const auto mms = mmsx_connect(nullptr, nullptr, url, 128 * 1024);
 	if (mms == nullptr) {
-		g_set_error(error_r, mms_quark(), 0, "mmsx_connect() failed");
+		error.Set(mms_domain, "mmsx_connect() failed");
 		return nullptr;
 	}
 
@@ -85,18 +83,15 @@ input_mms_open(const char *url,
 
 static size_t
 input_mms_read(struct input_stream *is, void *ptr, size_t size,
-	       GError **error_r)
+	       Error &error)
 {
 	MmsInputStream *m = (MmsInputStream *)is;
 	int ret;
 
 	ret = mmsx_read(nullptr, m->mms, (char *)ptr, size);
 	if (ret <= 0) {
-		if (ret < 0) {
-			g_set_error(error_r, mms_quark(), errno,
-				    "mmsx_read() failed: %s",
-				    g_strerror(errno));
-		}
+		if (ret < 0)
+			error.SetErrno("mmsx_read() failed");
 
 		m->eof = true;
 		return false;
diff --git a/src/input/RewindInputPlugin.cxx b/src/input/RewindInputPlugin.cxx
index d68fd3d73..7a88d4f52 100644
--- a/src/input/RewindInputPlugin.cxx
+++ b/src/input/RewindInputPlugin.cxx
@@ -24,8 +24,6 @@
 #include "InputPlugin.hxx"
 #include "Tag.hxx"
 
-#include <glib.h>
-
 #include <assert.h>
 #include <string.h>
 #include <stdio.h>
@@ -112,11 +110,11 @@ input_rewind_close(struct input_stream *is)
 }
 
 static bool
-input_rewind_check(struct input_stream *is, GError **error_r)
+input_rewind_check(struct input_stream *is, Error &error)
 {
 	RewindInputStream *r = (RewindInputStream *)is;
 
-	return input_stream_check(r->input, error_r);
+	return input_stream_check(r->input, error);
 }
 
 static void
@@ -146,7 +144,7 @@ input_rewind_available(struct input_stream *is)
 
 static size_t
 input_rewind_read(struct input_stream *is, void *ptr, size_t size,
-		  GError **error_r)
+		  Error &error)
 {
 	RewindInputStream *r = (RewindInputStream *)is;
 
@@ -167,7 +165,7 @@ input_rewind_read(struct input_stream *is, void *ptr, size_t size,
 	} else {
 		/* pass method call to underlying stream */
 
-		size_t nbytes = input_stream_read(r->input, ptr, size, error_r);
+		size_t nbytes = input_stream_read(r->input, ptr, size, error);
 
 		if (r->input->offset > (goffset)sizeof(r->buffer))
 			/* disable buffering */
@@ -197,7 +195,7 @@ input_rewind_eof(struct input_stream *is)
 
 static bool
 input_rewind_seek(struct input_stream *is, goffset offset, int whence,
-		  GError **error_r)
+		  Error &error)
 {
 	RewindInputStream *r = (RewindInputStream *)is;
 
@@ -216,7 +214,7 @@ input_rewind_seek(struct input_stream *is, goffset offset, int whence,
 		return true;
 	} else {
 		bool success = input_stream_seek(r->input, offset, whence,
-						 error_r);
+						 error);
 		r->CopyAttributes();
 
 		/* disable the buffer, because r->input has left the
diff --git a/src/mixer/AlsaMixerPlugin.cxx b/src/mixer/AlsaMixerPlugin.cxx
index 587ec699e..1ea26d0c1 100644
--- a/src/mixer/AlsaMixerPlugin.cxx
+++ b/src/mixer/AlsaMixerPlugin.cxx
@@ -25,6 +25,8 @@
 #include "event/MultiSocketMonitor.hxx"
 #include "event/Loop.hxx"
 #include "util/ReusableArray.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <algorithm>
 
@@ -68,23 +70,15 @@ public:
 	AlsaMixer():Mixer(alsa_mixer_plugin) {}
 
 	void Configure(const config_param &param);
-	bool Setup(GError **error_r);
-	bool Open(GError **error_r);
+	bool Setup(Error &error);
+	bool Open(Error &error);
 	void Close();
 
-	int GetVolume(GError **error_r);
-	bool SetVolume(unsigned volume, GError **error_r);
+	int GetVolume(Error &error);
+	bool SetVolume(unsigned volume, Error &error);
 };
 
-/**
- * The quark used for GError.domain.
- */
-gcc_const
-static inline GQuark
-alsa_mixer_quark(void)
-{
-	return g_quark_from_static_string("alsa_mixer");
-}
+static constexpr Domain alsa_mixer_domain("alsa_mixer");
 
 int
 AlsaMixerMonitor::PrepareSockets()
@@ -158,7 +152,7 @@ AlsaMixer::Configure(const config_param &param)
 
 static Mixer *
 alsa_mixer_init(gcc_unused void *ao, const config_param &param,
-		gcc_unused GError **error_r)
+		gcc_unused Error &error)
 {
 	AlsaMixer *am = new AlsaMixer();
 	am->Configure(param);
@@ -194,35 +188,35 @@ alsa_mixer_lookup_elem(snd_mixer_t *handle, const char *name, unsigned idx)
 }
 
 inline bool
-AlsaMixer::Setup(GError **error_r)
+AlsaMixer::Setup(Error &error)
 {
 	int err;
 
 	if ((err = snd_mixer_attach(handle, device)) < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "failed to attach to %s: %s",
-			    device, snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "failed to attach to %s: %s",
+			     device, snd_strerror(err));
 		return false;
 	}
 
 	if ((err = snd_mixer_selem_register(handle, NULL,
 		    NULL)) < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "snd_mixer_selem_register() failed: %s",
-			    snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "snd_mixer_selem_register() failed: %s",
+			     snd_strerror(err));
 		return false;
 	}
 
 	if ((err = snd_mixer_load(handle)) < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "snd_mixer_load() failed: %s\n",
-			    snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "snd_mixer_load() failed: %s\n",
+			     snd_strerror(err));
 		return false;
 	}
 
 	elem = alsa_mixer_lookup_elem(handle, control, index);
 	if (elem == NULL) {
-		g_set_error(error_r, alsa_mixer_quark(), 0,
+		error.Format(alsa_mixer_domain, 0,
 			    "no such mixer control: %s", control);
 		return false;
 	}
@@ -238,7 +232,7 @@ AlsaMixer::Setup(GError **error_r)
 }
 
 inline bool
-AlsaMixer::Open(GError **error_r)
+AlsaMixer::Open(Error &error)
 {
 	int err;
 
@@ -246,12 +240,12 @@ AlsaMixer::Open(GError **error_r)
 
 	err = snd_mixer_open(&handle, 0);
 	if (err < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "snd_mixer_open() failed: %s", snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "snd_mixer_open() failed: %s", snd_strerror(err));
 		return false;
 	}
 
-	if (!Setup(error_r)) {
+	if (!Setup(error)) {
 		snd_mixer_close(handle);
 		return false;
 	}
@@ -260,11 +254,11 @@ AlsaMixer::Open(GError **error_r)
 }
 
 static bool
-alsa_mixer_open(Mixer *data, GError **error_r)
+alsa_mixer_open(Mixer *data, Error &error)
 {
 	AlsaMixer *am = (AlsaMixer *)data;
 
-	return am->Open(error_r);
+	return am->Open(error);
 }
 
 inline void
@@ -286,7 +280,7 @@ alsa_mixer_close(Mixer *data)
 }
 
 inline int
-AlsaMixer::GetVolume(GError **error_r)
+AlsaMixer::GetVolume(Error &error)
 {
 	int err;
 	int ret;
@@ -296,9 +290,9 @@ AlsaMixer::GetVolume(GError **error_r)
 
 	err = snd_mixer_handle_events(handle);
 	if (err < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "snd_mixer_handle_events() failed: %s",
-			    snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "snd_mixer_handle_events() failed: %s",
+			     snd_strerror(err));
 		return false;
 	}
 
@@ -306,9 +300,9 @@ AlsaMixer::GetVolume(GError **error_r)
 						  SND_MIXER_SCHN_FRONT_LEFT,
 						  &level);
 	if (err < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "failed to read ALSA volume: %s",
-			    snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "failed to read ALSA volume: %s",
+			     snd_strerror(err));
 		return false;
 	}
 
@@ -325,14 +319,14 @@ AlsaMixer::GetVolume(GError **error_r)
 }
 
 static int
-alsa_mixer_get_volume(Mixer *mixer, GError **error_r)
+alsa_mixer_get_volume(Mixer *mixer, Error &error)
 {
 	AlsaMixer *am = (AlsaMixer *)mixer;
-	return am->GetVolume(error_r);
+	return am->GetVolume(error);
 }
 
 inline bool
-AlsaMixer::SetVolume(unsigned volume, GError **error_r)
+AlsaMixer::SetVolume(unsigned volume, Error &error)
 {
 	float vol;
 	long level;
@@ -351,9 +345,9 @@ AlsaMixer::SetVolume(unsigned volume, GError **error_r)
 
 	err = snd_mixer_selem_set_playback_volume_all(elem, level);
 	if (err < 0) {
-		g_set_error(error_r, alsa_mixer_quark(), err,
-			    "failed to set ALSA volume: %s",
-			    snd_strerror(err));
+		error.Format(alsa_mixer_domain, err,
+			     "failed to set ALSA volume: %s",
+			     snd_strerror(err));
 		return false;
 	}
 
@@ -361,10 +355,10 @@ AlsaMixer::SetVolume(unsigned volume, GError **error_r)
 }
 
 static bool
-alsa_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
+alsa_mixer_set_volume(Mixer *mixer, unsigned volume, Error &error)
 {
 	AlsaMixer *am = (AlsaMixer *)mixer;
-	return am->SetVolume(volume, error_r);
+	return am->SetVolume(volume, error);
 }
 
 const struct mixer_plugin alsa_mixer_plugin = {
diff --git a/src/mixer/OssMixerPlugin.cxx b/src/mixer/OssMixerPlugin.cxx
index 231f38432..84cd223e6 100644
--- a/src/mixer/OssMixerPlugin.cxx
+++ b/src/mixer/OssMixerPlugin.cxx
@@ -21,6 +21,8 @@
 #include "MixerInternal.hxx"
 #include "OutputAPI.hxx"
 #include "system/fd_util.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -51,22 +53,15 @@ class OssMixer : public Mixer {
 public:
 	OssMixer():Mixer(oss_mixer_plugin) {}
 
-	bool Configure(const config_param &param, GError **error_r);
-	bool Open(GError **error_r);
+	bool Configure(const config_param &param, Error &error);
+	bool Open(Error &error);
 	void Close();
 
-	int GetVolume(GError **error_r);
-	bool SetVolume(unsigned volume, GError **error_r);
+	int GetVolume(Error &error);
+	bool SetVolume(unsigned volume, Error &error);
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-oss_mixer_quark(void)
-{
-	return g_quark_from_static_string("oss_mixer");
-}
+static constexpr Domain oss_mixer_domain("oss_mixer");
 
 static int
 oss_find_mixer(const char *name)
@@ -84,17 +79,16 @@ oss_find_mixer(const char *name)
 }
 
 inline bool
-OssMixer::Configure(const config_param &param, GError **error_r)
+OssMixer::Configure(const config_param &param, Error &error)
 {
-	device = param.GetBlockValue("mixer_device",
-					     VOLUME_MIXER_OSS_DEFAULT);
+	device = param.GetBlockValue("mixer_device", VOLUME_MIXER_OSS_DEFAULT);
 	control = param.GetBlockValue("mixer_control");
 
 	if (control != NULL) {
 		volume_control = oss_find_mixer(control);
 		if (volume_control < 0) {
-			g_set_error(error_r, oss_mixer_quark(), 0,
-				    "no such mixer control: %s", control);
+			error.Format(oss_mixer_domain, 0,
+				     "no such mixer control: %s", control);
 			return false;
 		}
 	} else
@@ -105,11 +99,11 @@ OssMixer::Configure(const config_param &param, GError **error_r)
 
 static Mixer *
 oss_mixer_init(gcc_unused void *ao, const config_param &param,
-	       GError **error_r)
+	       Error &error)
 {
 	OssMixer *om = new OssMixer();
 
-	if (!om->Configure(param, error_r)) {
+	if (!om->Configure(param, error)) {
 		delete om;
 		return nullptr;
 	}
@@ -141,13 +135,11 @@ oss_mixer_close(Mixer *data)
 }
 
 inline bool
-OssMixer::Open(GError **error_r)
+OssMixer::Open(Error &error)
 {
 	device_fd = open_cloexec(device, O_RDONLY, 0);
 	if (device_fd < 0) {
-		g_set_error(error_r, oss_mixer_quark(), errno,
-			    "failed to open %s: %s",
-			    device, g_strerror(errno));
+		error.FormatErrno("failed to open %s", device);
 		return false;
 	}
 
@@ -155,17 +147,15 @@ OssMixer::Open(GError **error_r)
 		int devmask = 0;
 
 		if (ioctl(device_fd, SOUND_MIXER_READ_DEVMASK, &devmask) < 0) {
-			g_set_error(error_r, oss_mixer_quark(), errno,
-				    "READ_DEVMASK failed: %s",
-				    g_strerror(errno));
+			error.SetErrno("READ_DEVMASK failed");
 			Close();
 			return false;
 		}
 
 		if (((1 << volume_control) & devmask) == 0) {
-			g_set_error(error_r, oss_mixer_quark(), 0,
-				    "mixer control \"%s\" not usable",
-				    control);
+			error.Format(oss_mixer_domain, 0,
+				     "mixer control \"%s\" not usable",
+				     control);
 			Close();
 			return false;
 		}
@@ -175,15 +165,15 @@ OssMixer::Open(GError **error_r)
 }
 
 static bool
-oss_mixer_open(Mixer *data, GError **error_r)
+oss_mixer_open(Mixer *data, Error &error)
 {
 	OssMixer *om = (OssMixer *) data;
 
-	return om->Open(error_r);
+	return om->Open(error);
 }
 
 inline int
-OssMixer::GetVolume(GError **error_r)
+OssMixer::GetVolume(Error &error)
 {
 	int left, right, level;
 	int ret;
@@ -192,9 +182,7 @@ OssMixer::GetVolume(GError **error_r)
 
 	ret = ioctl(device_fd, MIXER_READ(volume_control), &level);
 	if (ret < 0) {
-		g_set_error(error_r, oss_mixer_quark(), errno,
-			    "failed to read OSS volume: %s",
-			    g_strerror(errno));
+		error.SetErrno("failed to read OSS volume");
 		return false;
 	}
 
@@ -210,14 +198,14 @@ OssMixer::GetVolume(GError **error_r)
 }
 
 static int
-oss_mixer_get_volume(Mixer *mixer, GError **error_r)
+oss_mixer_get_volume(Mixer *mixer, Error &error)
 {
 	OssMixer *om = (OssMixer *)mixer;
-	return om->GetVolume(error_r);
+	return om->GetVolume(error);
 }
 
 inline bool
-OssMixer::SetVolume(unsigned volume, GError **error_r)
+OssMixer::SetVolume(unsigned volume, Error &error)
 {
 	int level;
 	int ret;
@@ -229,9 +217,7 @@ OssMixer::SetVolume(unsigned volume, GError **error_r)
 
 	ret = ioctl(device_fd, MIXER_WRITE(volume_control), &level);
 	if (ret < 0) {
-		g_set_error(error_r, oss_mixer_quark(), errno,
-			    "failed to set OSS volume: %s",
-			    g_strerror(errno));
+		error.SetErrno("failed to set OSS volume");
 		return false;
 	}
 
@@ -239,10 +225,10 @@ OssMixer::SetVolume(unsigned volume, GError **error_r)
 }
 
 static bool
-oss_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
+oss_mixer_set_volume(Mixer *mixer, unsigned volume, Error &error)
 {
 	OssMixer *om = (OssMixer *)mixer;
-	return om->SetVolume(volume, error_r);
+	return om->SetVolume(volume, error);
 }
 
 const struct mixer_plugin oss_mixer_plugin = {
diff --git a/src/mixer/PulseMixerPlugin.cxx b/src/mixer/PulseMixerPlugin.cxx
index 1c99b2469..069f4e36f 100644
--- a/src/mixer/PulseMixerPlugin.cxx
+++ b/src/mixer/PulseMixerPlugin.cxx
@@ -23,6 +23,8 @@
 #include "output/PulseOutputPlugin.hxx"
 #include "conf.h"
 #include "GlobalEvents.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -52,14 +54,7 @@ struct PulseMixer final : public Mixer {
 	}
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-pulse_mixer_quark(void)
-{
-	return g_quark_from_static_string("pulse_mixer");
-}
+static constexpr Domain pulse_mixer_domain("pulse_mixer");
 
 static void
 pulse_mixer_offline(PulseMixer *pm)
@@ -154,13 +149,13 @@ pulse_mixer_on_change(PulseMixer *pm,
 
 static Mixer *
 pulse_mixer_init(void *ao, gcc_unused const config_param &param,
-		 GError **error_r)
+		 Error &error)
 {
 	PulseOutput *po = (PulseOutput *)ao;
 
 	if (ao == NULL) {
-		g_set_error(error_r, pulse_mixer_quark(), 0,
-			    "The pulse mixer cannot work without the audio output");
+		error.Set(pulse_mixer_domain,
+			  "The pulse mixer cannot work without the audio output");
 		return nullptr;
 	}
 
@@ -182,7 +177,7 @@ pulse_mixer_finish(Mixer *data)
 }
 
 static int
-pulse_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
+pulse_mixer_get_volume(Mixer *mixer, gcc_unused Error &error)
 {
 	PulseMixer *pm = (PulseMixer *) mixer;
 	int ret;
@@ -199,7 +194,7 @@ pulse_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
 }
 
 static bool
-pulse_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
+pulse_mixer_set_volume(Mixer *mixer, unsigned volume, Error &error)
 {
 	PulseMixer *pm = (PulseMixer *) mixer;
 	struct pa_cvolume cvolume;
@@ -209,13 +204,13 @@ pulse_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
 
 	if (!pm->online) {
 		pulse_output_unlock(pm->output);
-		g_set_error(error_r, pulse_mixer_quark(), 0, "disconnected");
+		error.Set(pulse_mixer_domain, "disconnected");
 		return false;
 	}
 
 	pa_cvolume_set(&cvolume, pm->volume.channels,
 		       (pa_volume_t)volume * PA_VOLUME_NORM / 100 + 0.5);
-	success = pulse_output_set_volume(pm->output, &cvolume, error_r);
+	success = pulse_output_set_volume(pm->output, &cvolume, error);
 	if (success)
 		pm->volume = cvolume;
 
diff --git a/src/mixer/RoarMixerPlugin.cxx b/src/mixer/RoarMixerPlugin.cxx
index 90d54ddaa..6bd700551 100644
--- a/src/mixer/RoarMixerPlugin.cxx
+++ b/src/mixer/RoarMixerPlugin.cxx
@@ -35,7 +35,7 @@ struct RoarMixer final : public Mixer {
 
 static Mixer *
 roar_mixer_init(void *ao, gcc_unused const config_param &param,
-		gcc_unused GError **error_r)
+		gcc_unused Error &error)
 {
 	return new RoarMixer((RoarOutput *)ao);
 }
@@ -49,7 +49,7 @@ roar_mixer_finish(Mixer *data)
 }
 
 static int
-roar_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
+roar_mixer_get_volume(Mixer *mixer, gcc_unused Error &error)
 {
 	RoarMixer *self = (RoarMixer *)mixer;
 	return roar_output_get_volume(self->self);
@@ -57,7 +57,7 @@ roar_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
 
 static bool
 roar_mixer_set_volume(Mixer *mixer, unsigned volume,
-		      gcc_unused GError **error_r)
+		      gcc_unused Error &error)
 {
 	RoarMixer *self = (RoarMixer *)mixer;
 	return roar_output_set_volume(self->self, volume);
diff --git a/src/mixer/SoftwareMixerPlugin.cxx b/src/mixer/SoftwareMixerPlugin.cxx
index 8a268aaf1..b7eb8ff0f 100644
--- a/src/mixer/SoftwareMixerPlugin.cxx
+++ b/src/mixer/SoftwareMixerPlugin.cxx
@@ -26,10 +26,18 @@
 #include "filter/VolumeFilterPlugin.hxx"
 #include "pcm/PcmVolume.hxx"
 #include "ConfigData.hxx"
+#include "util/Error.hxx"
 
 #include <assert.h>
 #include <math.h>
 
+static Filter *
+CreateVolumeFilter()
+{
+	Error error;
+	return filter_new(&volume_filter_plugin, config_param(), error);
+}
+
 struct SoftwareMixer final : public Mixer {
 	Filter *filter;
 
@@ -37,8 +45,7 @@ struct SoftwareMixer final : public Mixer {
 
 	SoftwareMixer()
 		:Mixer(software_mixer_plugin),
-		filter(filter_new(&volume_filter_plugin, config_param(),
-				  nullptr)),
+		filter(CreateVolumeFilter()),
 		volume(100)
 	{
 		assert(filter != nullptr);
@@ -52,7 +59,7 @@ struct SoftwareMixer final : public Mixer {
 static Mixer *
 software_mixer_init(gcc_unused void *ao,
 		    gcc_unused const config_param &param,
-		    gcc_unused GError **error_r)
+		    gcc_unused Error &error)
 {
 	return new SoftwareMixer();
 }
@@ -66,7 +73,7 @@ software_mixer_finish(Mixer *data)
 }
 
 static int
-software_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
+software_mixer_get_volume(Mixer *mixer, gcc_unused Error &error)
 {
 	SoftwareMixer *sm = (SoftwareMixer *)mixer;
 
@@ -75,7 +82,7 @@ software_mixer_get_volume(Mixer *mixer, gcc_unused GError **error_r)
 
 static bool
 software_mixer_set_volume(Mixer *mixer, unsigned volume,
-			  gcc_unused GError **error_r)
+			  gcc_unused Error &error)
 {
 	SoftwareMixer *sm = (SoftwareMixer *)mixer;
 
diff --git a/src/mixer/WinmmMixerPlugin.cxx b/src/mixer/WinmmMixerPlugin.cxx
index cbfb8f6cb..ae25b532c 100644
--- a/src/mixer/WinmmMixerPlugin.cxx
+++ b/src/mixer/WinmmMixerPlugin.cxx
@@ -21,6 +21,8 @@
 #include "MixerInternal.hxx"
 #include "OutputAPI.hxx"
 #include "output/WinmmOutputPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <mmsystem.h>
 
@@ -40,11 +42,7 @@ struct WinmmMixer final : public Mixer {
 	}
 };
 
-static inline GQuark
-winmm_mixer_quark(void)
-{
-	return g_quark_from_static_string("winmm_mixer");
-}
+static constexpr Domain winmm_mixer_domain("winmm_mixer");
 
 static inline int
 winmm_volume_decode(DWORD volume)
@@ -61,7 +59,7 @@ winmm_volume_encode(int volume)
 
 static Mixer *
 winmm_mixer_init(void *ao, gcc_unused const config_param &param,
-		 gcc_unused GError **error_r)
+		 gcc_unused Error &error)
 {
 	assert(ao != nullptr);
 
@@ -77,7 +75,7 @@ winmm_mixer_finish(Mixer *data)
 }
 
 static int
-winmm_mixer_get_volume(Mixer *mixer, GError **error_r)
+winmm_mixer_get_volume(Mixer *mixer, Error &error)
 {
 	WinmmMixer *wm = (WinmmMixer *) mixer;
 	DWORD volume;
@@ -85,8 +83,7 @@ winmm_mixer_get_volume(Mixer *mixer, GError **error_r)
 	MMRESULT result = waveOutGetVolume(handle, &volume);
 
 	if (result != MMSYSERR_NOERROR) {
-		g_set_error(error_r, 0, winmm_mixer_quark(),
-			    "Failed to get winmm volume");
+		error.Set(winmm_mixer_domain, "Failed to get winmm volume");
 		return -1;
 	}
 
@@ -94,7 +91,7 @@ winmm_mixer_get_volume(Mixer *mixer, GError **error_r)
 }
 
 static bool
-winmm_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
+winmm_mixer_set_volume(Mixer *mixer, unsigned volume, Error &error)
 {
 	WinmmMixer *wm = (WinmmMixer *) mixer;
 	DWORD value = winmm_volume_encode(volume);
@@ -102,8 +99,7 @@ winmm_mixer_set_volume(Mixer *mixer, unsigned volume, GError **error_r)
 	MMRESULT result = waveOutSetVolume(handle, value);
 
 	if (result != MMSYSERR_NOERROR) {
-		g_set_error(error_r, 0, winmm_mixer_quark(),
-			    "Failed to set winmm volume");
+		error.Set(winmm_mixer_domain, "Failed to set winmm volume");
 		return false;
 	}
 
diff --git a/src/mpd_error.h b/src/mpd_error.h
index e0b7d29a4..f7af84656 100644
--- a/src/mpd_error.h
+++ b/src/mpd_error.h
@@ -24,7 +24,7 @@
 #include <stdlib.h>
 
 /* This macro is used as an intermediate step to a proper error handling
- * using GError in mpd. It is used for unrecoverable error conditions
+ * using #Error in mpd. It is used for unrecoverable error conditions
  * and exits immediately. The long-term goal is to replace this macro by
  * proper error handling. */
 
diff --git a/src/output/AlsaOutputPlugin.cxx b/src/output/AlsaOutputPlugin.cxx
index d707166c5..c9bf01909 100644
--- a/src/output/AlsaOutputPlugin.cxx
+++ b/src/output/AlsaOutputPlugin.cxx
@@ -23,6 +23,8 @@
 #include "MixerList.hxx"
 #include "pcm/PcmExport.hxx"
 #include "util/Manual.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 #include <alsa/asoundlib.h>
@@ -115,9 +117,9 @@ struct AlsaOutput {
 	AlsaOutput():mode(0), writei(snd_pcm_writei) {
 	}
 
-	bool Init(const config_param &param, GError **error_r) {
+	bool Init(const config_param &param, Error &error) {
 		return ao_base_init(&base, &alsa_output_plugin,
-				    param, error_r);
+				    param, error);
 	}
 
 	void Deinit() {
@@ -125,14 +127,7 @@ struct AlsaOutput {
 	}
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-alsa_output_quark(void)
-{
-	return g_quark_from_static_string("alsa_output");
-}
+static constexpr Domain alsa_output_domain("alsa_output");
 
 static const char *
 alsa_device(const AlsaOutput *ad)
@@ -170,11 +165,11 @@ alsa_configure(AlsaOutput *ad, const config_param &param)
 }
 
 static struct audio_output *
-alsa_init(const config_param &param, GError **error_r)
+alsa_init(const config_param &param, Error &error)
 {
 	AlsaOutput *ad = new AlsaOutput();
 
-	if (!ad->Init(param, error_r)) {
+	if (!ad->Init(param, error)) {
 		delete ad;
 		return NULL;
 	}
@@ -197,7 +192,7 @@ alsa_finish(struct audio_output *ao)
 }
 
 static bool
-alsa_output_enable(struct audio_output *ao, gcc_unused GError **error_r)
+alsa_output_enable(struct audio_output *ao, gcc_unused Error &error)
 {
 	AlsaOutput *ad = (AlsaOutput *)ao;
 
@@ -394,7 +389,7 @@ alsa_output_setup_format(snd_pcm_t *pcm, snd_pcm_hw_params_t *hwparams,
  */
 static bool
 alsa_setup(AlsaOutput *ad, AudioFormat &audio_format,
-	   bool *packed_r, bool *reverse_endian_r, GError **error)
+	   bool *packed_r, bool *reverse_endian_r, Error &error)
 {
 	unsigned int sample_rate = audio_format.sample_rate;
 	unsigned int channels = audio_format.channels;
@@ -438,11 +433,11 @@ configure_hw:
 	err = alsa_output_setup_format(ad->pcm, hwparams, audio_format,
 				       packed_r, reverse_endian_r);
 	if (err < 0) {
-		g_set_error(error, alsa_output_quark(), err,
-			    "ALSA device \"%s\" does not support format %s: %s",
-			    alsa_device(ad),
-			    sample_format_to_string(audio_format.format),
-			    snd_strerror(-err));
+		error.Format(alsa_output_domain, err,
+			     "ALSA device \"%s\" does not support format %s: %s",
+			     alsa_device(ad),
+			     sample_format_to_string(audio_format.format),
+			     snd_strerror(-err));
 		return false;
 	}
 
@@ -454,10 +449,10 @@ configure_hw:
 	err = snd_pcm_hw_params_set_channels_near(ad->pcm, hwparams,
 						  &channels);
 	if (err < 0) {
-		g_set_error(error, alsa_output_quark(), err,
-			    "ALSA device \"%s\" does not support %i channels: %s",
-			    alsa_device(ad), (int)audio_format.channels,
-			    snd_strerror(-err));
+		error.Format(alsa_output_domain, err,
+			     "ALSA device \"%s\" does not support %i channels: %s",
+			     alsa_device(ad), (int)audio_format.channels,
+			     snd_strerror(-err));
 		return false;
 	}
 	audio_format.channels = (int8_t)channels;
@@ -465,9 +460,9 @@ configure_hw:
 	err = snd_pcm_hw_params_set_rate_near(ad->pcm, hwparams,
 					      &sample_rate, NULL);
 	if (err < 0 || sample_rate == 0) {
-		g_set_error(error, alsa_output_quark(), err,
-			    "ALSA device \"%s\" does not support %u Hz audio",
-			    alsa_device(ad), audio_format.sample_rate);
+		error.Format(alsa_output_domain, err,
+			     "ALSA device \"%s\" does not support %u Hz audio",
+			     alsa_device(ad), audio_format.sample_rate);
 		return false;
 	}
 	audio_format.sample_rate = sample_rate;
@@ -594,16 +589,16 @@ configure_hw:
 	return true;
 
 error:
-	g_set_error(error, alsa_output_quark(), err,
-		    "Error opening ALSA device \"%s\" (%s): %s",
-		    alsa_device(ad), cmd, snd_strerror(-err));
+	error.Format(alsa_output_domain, err,
+		     "Error opening ALSA device \"%s\" (%s): %s",
+		     alsa_device(ad), cmd, snd_strerror(-err));
 	return false;
 }
 
 static bool
 alsa_setup_dsd(AlsaOutput *ad, const AudioFormat audio_format,
 	       bool *shift8_r, bool *packed_r, bool *reverse_endian_r,
-	       GError **error_r)
+	       Error &error)
 {
 	assert(ad->dsd_usb);
 	assert(audio_format.format == SampleFormat::DSD);
@@ -616,7 +611,7 @@ alsa_setup_dsd(AlsaOutput *ad, const AudioFormat audio_format,
 
 	const AudioFormat check = usb_format;
 
-	if (!alsa_setup(ad, usb_format, packed_r, reverse_endian_r, error_r))
+	if (!alsa_setup(ad, usb_format, packed_r, reverse_endian_r, error))
 		return false;
 
 	/* if the device allows only 32 bit, shift all DSD-over-USB
@@ -631,9 +626,9 @@ alsa_setup_dsd(AlsaOutput *ad, const AudioFormat audio_format,
 	if (usb_format != check) {
 		/* no bit-perfect playback, which is required
 		   for DSD over USB */
-		g_set_error(error_r, alsa_output_quark(), 0,
-			    "Failed to configure DSD-over-USB on ALSA device \"%s\"",
-			    alsa_device(ad));
+		error.Format(alsa_output_domain,
+			     "Failed to configure DSD-over-USB on ALSA device \"%s\"",
+			     alsa_device(ad));
 		g_free(ad->silence);
 		return false;
 	}
@@ -643,7 +638,7 @@ alsa_setup_dsd(AlsaOutput *ad, const AudioFormat audio_format,
 
 static bool
 alsa_setup_or_dsd(AlsaOutput *ad, AudioFormat &audio_format,
-		  GError **error_r)
+		  Error &error)
 {
 	bool shift8 = false, packed, reverse_endian;
 
@@ -652,9 +647,9 @@ alsa_setup_or_dsd(AlsaOutput *ad, AudioFormat &audio_format,
 	const bool success = dsd_usb
 		? alsa_setup_dsd(ad, audio_format,
 				 &shift8, &packed, &reverse_endian,
-				 error_r)
+				 error)
 		: alsa_setup(ad, audio_format, &packed, &reverse_endian,
-			     error_r);
+			     error);
 	if (!success)
 		return false;
 
@@ -665,14 +660,14 @@ alsa_setup_or_dsd(AlsaOutput *ad, AudioFormat &audio_format,
 }
 
 static bool
-alsa_open(struct audio_output *ao, AudioFormat &audio_format, GError **error)
+alsa_open(struct audio_output *ao, AudioFormat &audio_format, Error &error)
 {
 	AlsaOutput *ad = (AlsaOutput *)ao;
 
 	int err = snd_pcm_open(&ad->pcm, alsa_device(ad),
 			       SND_PCM_STREAM_PLAYBACK, ad->mode);
 	if (err < 0) {
-		g_set_error(error, alsa_output_quark(), err,
+		error.Format(alsa_output_domain, err,
 			    "Failed to open ALSA device \"%s\": %s",
 			    alsa_device(ad), snd_strerror(err));
 		return false;
@@ -800,7 +795,7 @@ alsa_close(struct audio_output *ao)
 
 static size_t
 alsa_play(struct audio_output *ao, const void *chunk, size_t size,
-	  GError **error)
+	  Error &error)
 {
 	AlsaOutput *ad = (AlsaOutput *)ao;
 
@@ -824,8 +819,7 @@ alsa_play(struct audio_output *ao, const void *chunk, size_t size,
 
 		if (ret < 0 && ret != -EAGAIN && ret != -EINTR &&
 		    alsa_recover(ad, ret) < 0) {
-			g_set_error(error, alsa_output_quark(), errno,
-				    "%s", snd_strerror(-errno));
+			error.Set(alsa_output_domain, ret, snd_strerror(-ret));
 			return 0;
 		}
 	}
diff --git a/src/output/AoOutputPlugin.cxx b/src/output/AoOutputPlugin.cxx
index db7b9a360..a54611511 100644
--- a/src/output/AoOutputPlugin.cxx
+++ b/src/output/AoOutputPlugin.cxx
@@ -20,6 +20,8 @@
 #include "config.h"
 #include "AoOutputPlugin.hxx"
 #include "OutputAPI.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <ao/ao.h>
 #include <glib.h>
@@ -42,26 +44,22 @@ struct AoOutput {
 	ao_option *options;
 	ao_device *device;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error) {
 		return ao_base_init(&base, &ao_output_plugin, param,
-				    error_r);
+				    error);
 	}
 
 	void Deinitialize() {
 		ao_base_finish(&base);
 	}
 
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 };
 
-static inline GQuark
-ao_output_quark(void)
-{
-	return g_quark_from_static_string("ao_output");
-}
+static constexpr Domain ao_output_domain("ao_output");
 
 static void
-ao_output_error(GError **error_r)
+ao_output_error(Error &error_r)
 {
 	const char *error;
 
@@ -87,15 +85,15 @@ ao_output_error(GError **error_r)
 		break;
 
 	default:
-		error = g_strerror(errno);
+		error_r.SetErrno();
+		return;
 	}
 
-	g_set_error(error_r, ao_output_quark(), errno,
-		    "%s", error);
+	error_r.Set(ao_output_domain, errno, error);
 }
 
 inline bool
-AoOutput::Configure(const config_param &param, GError **error_r)
+AoOutput::Configure(const config_param &param, Error &error)
 {
 	const char *value;
 
@@ -115,16 +113,15 @@ AoOutput::Configure(const config_param &param, GError **error_r)
 		driver = ao_driver_id(value);
 
 	if (driver < 0) {
-		g_set_error(error_r, ao_output_quark(), 0,
-			    "\"%s\" is not a valid ao driver",
-			    value);
+		error.Format(ao_output_domain,
+			     "\"%s\" is not a valid ao driver",
+			     value);
 		return false;
 	}
 
 	ao_info *ai = ao_driver_info(driver);
 	if (ai == nullptr) {
-		g_set_error(error_r, ao_output_quark(), 0,
-			    "problems getting driver info");
+		error.Set(ao_output_domain, "problems getting driver info");
 		return false;
 	}
 
@@ -139,9 +136,9 @@ AoOutput::Configure(const config_param &param, GError **error_r)
 			gchar **key_value = g_strsplit(_options[i], "=", 2);
 
 			if (key_value[0] == nullptr || key_value[1] == nullptr) {
-				g_set_error(error_r, ao_output_quark(), 0,
-					    "problems parsing options \"%s\"",
-					    _options[i]);
+				error.Format(ao_output_domain,
+					     "problems parsing options \"%s\"",
+					     _options[i]);
 				return false;
 			}
 
@@ -158,16 +155,16 @@ AoOutput::Configure(const config_param &param, GError **error_r)
 }
 
 static struct audio_output *
-ao_output_init(const config_param &param, GError **error_r)
+ao_output_init(const config_param &param, Error &error)
 {
 	AoOutput *ad = new AoOutput();
 
-	if (!ad->Initialize(param, error_r)) {
+	if (!ad->Initialize(param, error)) {
 		delete ad;
 		return nullptr;
 	}
 
-	if (!ad->Configure(param, error_r)) {
+	if (!ad->Configure(param, error)) {
 		ad->Deinitialize();
 		delete ad;
 		return nullptr;
@@ -201,7 +198,7 @@ ao_output_close(struct audio_output *ao)
 
 static bool
 ao_output_open(struct audio_output *ao, AudioFormat &audio_format,
-	       GError **error)
+	       Error &error)
 {
 	ao_sample_format format = OUR_AO_FORMAT_INITIALIZER;
 	AoOutput *ad = (AoOutput *)ao;
@@ -257,7 +254,7 @@ static int ao_play_deconst(ao_device *device, const void *output_samples,
 
 static size_t
 ao_output_play(struct audio_output *ao, const void *chunk, size_t size,
-	       GError **error)
+	       Error &error)
 {
 	AoOutput *ad = (AoOutput *)ao;
 
diff --git a/src/output/FifoOutputPlugin.cxx b/src/output/FifoOutputPlugin.cxx
index 29dd50cb1..34199bff9 100644
--- a/src/output/FifoOutputPlugin.cxx
+++ b/src/output/FifoOutputPlugin.cxx
@@ -19,11 +19,14 @@
 
 #include "config.h"
 #include "FifoOutputPlugin.hxx"
+#include "ConfigError.hxx"
 #include "OutputAPI.hxx"
 #include "Timer.hxx"
 #include "system/fd_util.h"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "open.h"
 
 #include <glib.h>
@@ -53,31 +56,24 @@ struct FifoOutput {
 	FifoOutput()
 		:path(Path::Null()), input(-1), output(-1), created(false) {}
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error) {
 		return ao_base_init(&base, &fifo_output_plugin, param,
-				    error_r);
+				    error);
 	}
 
 	void Deinitialize() {
 		ao_base_finish(&base);
 	}
 
-	bool Create(GError **error_r);
-	bool Check(GError **error_r);
+	bool Create(Error &error);
+	bool Check(Error &error);
 	void Delete();
 
-	bool Open(GError **error_r);
+	bool Open(Error &error);
 	void Close();
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-fifo_output_quark(void)
-{
-	return g_quark_from_static_string("fifo_output");
-}
+static constexpr Domain fifo_output_domain("fifo_output");
 
 inline void
 FifoOutput::Delete()
@@ -112,12 +108,11 @@ FifoOutput::Close()
 }
 
 inline bool
-FifoOutput::Create(GError **error_r)
+FifoOutput::Create(Error &error)
 {
 	if (!MakeFifo(path, 0666)) {
-		g_set_error(error_r, fifo_output_quark(), errno,
-			    "Couldn't create FIFO \"%s\": %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Couldn't create FIFO \"%s\"",
+				  path_utf8.c_str());
 		return false;
 	}
 
@@ -126,25 +121,24 @@ FifoOutput::Create(GError **error_r)
 }
 
 inline bool
-FifoOutput::Check(GError **error_r)
+FifoOutput::Check(Error &error)
 {
 	struct stat st;
 	if (!StatFile(path, st)) {
 		if (errno == ENOENT) {
 			/* Path doesn't exist */
-			return Create(error_r);
+			return Create(error);
 		}
 
-		g_set_error(error_r, fifo_output_quark(), errno,
-			    "Failed to stat FIFO \"%s\": %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Failed to stat FIFO \"%s\"",
+				  path_utf8.c_str());
 		return false;
 	}
 
 	if (!S_ISFIFO(st.st_mode)) {
-		g_set_error(error_r, fifo_output_quark(), 0,
-			    "\"%s\" already exists, but is not a FIFO",
-			    path_utf8.c_str());
+		error.Format(fifo_output_domain,
+			     "\"%s\" already exists, but is not a FIFO",
+			     path_utf8.c_str());
 		return false;
 	}
 
@@ -152,25 +146,23 @@ FifoOutput::Check(GError **error_r)
 }
 
 inline bool
-FifoOutput::Open(GError **error_r)
+FifoOutput::Open(Error &error)
 {
-	if (!Check(error_r))
+	if (!Check(error))
 		return false;
 
 	input = OpenFile(path, O_RDONLY|O_NONBLOCK|O_BINARY, 0);
 	if (input < 0) {
-		g_set_error(error_r, fifo_output_quark(), errno,
-			    "Could not open FIFO \"%s\" for reading: %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Could not open FIFO \"%s\" for reading",
+				  path_utf8.c_str());
 		Close();
 		return false;
 	}
 
 	output = OpenFile(path, O_WRONLY|O_NONBLOCK|O_BINARY, 0);
 	if (output < 0) {
-		g_set_error(error_r, fifo_output_quark(), errno,
-			    "Could not open FIFO \"%s\" for writing: %s",
-			    path_utf8.c_str(), g_strerror(errno));
+		error.FormatErrno("Could not open FIFO \"%s\" for writing",
+				  path_utf8.c_str());
 		Close();
 		return false;
 	}
@@ -179,37 +171,34 @@ FifoOutput::Open(GError **error_r)
 }
 
 static bool
-fifo_open(FifoOutput *fd, GError **error_r)
+fifo_open(FifoOutput *fd, Error &error)
 {
-	return fd->Open(error_r);
+	return fd->Open(error);
 }
 
 static struct audio_output *
-fifo_output_init(const config_param &param, GError **error_r)
+fifo_output_init(const config_param &param, Error &error)
 {
-	GError *error = nullptr;
-
 	FifoOutput *fd = new FifoOutput();
 
-	fd->path = param.GetBlockPath("path", &error);
+	fd->path = param.GetBlockPath("path", error);
 	if (fd->path.IsNull()) {
 		delete fd;
-		if (error != nullptr)
-			g_propagate_error(error_r, error);
-		else
-			g_set_error(error_r, fifo_output_quark(), 0,
-				    "No \"path\" parameter specified");
+
+		if (!error.IsDefined())
+			error.Set(config_domain,
+				  "No \"path\" parameter specified");
 		return nullptr;
 	}
 
 	fd->path_utf8 = fd->path.ToUTF8();
 
-	if (!fd->Initialize(param, error_r)) {
+	if (!fd->Initialize(param, error)) {
 		delete fd;
 		return nullptr;
 	}
 
-	if (!fifo_open(fd, error_r)) {
+	if (!fifo_open(fd, error)) {
 		fd->Deinitialize();
 		delete fd;
 		return nullptr;
@@ -230,7 +219,7 @@ fifo_output_finish(struct audio_output *ao)
 
 static bool
 fifo_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		 gcc_unused GError **error)
+		 gcc_unused Error &error)
 {
 	FifoOutput *fd = (FifoOutput *)ao;
 
@@ -277,7 +266,7 @@ fifo_output_delay(struct audio_output *ao)
 
 static size_t
 fifo_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		 GError **error)
+		 Error &error)
 {
 	FifoOutput *fd = (FifoOutput *)ao;
 	ssize_t bytes;
@@ -301,9 +290,8 @@ fifo_output_play(struct audio_output *ao, const void *chunk, size_t size,
 				continue;
 			}
 
-			g_set_error(error, fifo_output_quark(), errno,
-				    "Failed to write to FIFO %s: %s",
-				    fd->path_utf8.c_str(), g_strerror(errno));
+			error.FormatErrno("Failed to write to FIFO %s",
+					  fd->path_utf8.c_str());
 			return 0;
 		}
 	}
diff --git a/src/output/HttpdClient.cxx b/src/output/HttpdClient.cxx
index c097e48f1..9ed7805dc 100644
--- a/src/output/HttpdClient.cxx
+++ b/src/output/HttpdClient.cxx
@@ -431,10 +431,9 @@ HttpdClient::OnSocketInput(const void *data, size_t length)
 }
 
 void
-HttpdClient::OnSocketError(GError *error)
+HttpdClient::OnSocketError(Error &&error)
 {
-	g_warning("error on HTTP client: %s", error->message);
-	g_error_free(error);
+	g_warning("error on HTTP client: %s", error.GetMessage());
 }
 
 void
diff --git a/src/output/HttpdClient.hxx b/src/output/HttpdClient.hxx
index 38e4ea96d..a596814ee 100644
--- a/src/output/HttpdClient.hxx
+++ b/src/output/HttpdClient.hxx
@@ -179,7 +179,7 @@ protected:
 	virtual bool OnSocketReady(unsigned flags) override;
 	virtual InputResult OnSocketInput(const void *data,
 					  size_t length) override;
-	virtual void OnSocketError(GError *error) override;
+	virtual void OnSocketError(Error &&error) override;
 	virtual void OnSocketClosed() override;
 };
 
diff --git a/src/output/HttpdInternal.hxx b/src/output/HttpdInternal.hxx
index e8a37e033..39fc700a3 100644
--- a/src/output/HttpdInternal.hxx
+++ b/src/output/HttpdInternal.hxx
@@ -33,6 +33,7 @@
 #include <forward_list>
 
 struct config_param;
+class Error;
 class EventLoop;
 class ServerSocket;
 class HttpdClient;
@@ -123,21 +124,20 @@ struct HttpdOutput final : private ServerSocket {
 	HttpdOutput(EventLoop &_loop);
 	~HttpdOutput();
 
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 
-	bool Bind(GError **error_r);
+	bool Bind(Error &error);
 	void Unbind();
 
 	/**
 	 * Caller must lock the mutex.
 	 */
-	bool OpenEncoder(AudioFormat &audio_format,
-			 GError **error_r);
+	bool OpenEncoder(AudioFormat &audio_format, Error &error);
 
 	/**
 	 * Caller must lock the mutex.
 	 */
-	bool Open(AudioFormat &audio_format, GError **error_r);
+	bool Open(AudioFormat &audio_format, Error &error);
 
 	/**
 	 * Caller must lock the mutex.
@@ -194,7 +194,7 @@ struct HttpdOutput final : private ServerSocket {
 	 */
 	void BroadcastFromEncoder();
 
-	bool EncodeAndPlay(const void *chunk, size_t size, GError **error_r);
+	bool EncodeAndPlay(const void *chunk, size_t size, Error &error);
 
 	void SendTag(const Tag *tag);
 
diff --git a/src/output/HttpdOutputPlugin.cxx b/src/output/HttpdOutputPlugin.cxx
index 745ed26a2..db395069e 100644
--- a/src/output/HttpdOutputPlugin.cxx
+++ b/src/output/HttpdOutputPlugin.cxx
@@ -29,6 +29,8 @@
 #include "IcyMetaDataServer.hxx"
 #include "system/fd_util.h"
 #include "Main.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 
@@ -45,14 +47,7 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "httpd_output"
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-httpd_output_quark(void)
-{
-	return g_quark_from_static_string("httpd_output");
-}
+static constexpr Domain httpd_output_domain("httpd_output");
 
 inline
 HttpdOutput::HttpdOutput(EventLoop &_loop)
@@ -73,12 +68,12 @@ HttpdOutput::~HttpdOutput()
 }
 
 inline bool
-HttpdOutput::Bind(GError **error_r)
+HttpdOutput::Bind(Error &error)
 {
 	open = false;
 
 	const ScopeLock protect(mutex);
-	return ServerSocket::Open(error_r);
+	return ServerSocket::Open(error);
 }
 
 inline void
@@ -91,7 +86,7 @@ HttpdOutput::Unbind()
 }
 
 inline bool
-HttpdOutput::Configure(const config_param &param, GError **error_r)
+HttpdOutput::Configure(const config_param &param, Error &error)
 {
 	/* read configuration */
 	name = param.GetBlockValue("name", "Set name in config");
@@ -104,8 +99,8 @@ HttpdOutput::Configure(const config_param &param, GError **error_r)
 		param.GetBlockValue("encoder", "vorbis");
 	const auto encoder_plugin = encoder_plugin_get(encoder_name);
 	if (encoder_plugin == NULL) {
-		g_set_error(error_r, httpd_output_quark(), 0,
-			    "No such encoder: %s", encoder_name);
+		error.Format(httpd_output_domain,
+			     "No such encoder: %s", encoder_name);
 		return false;
 	}
 
@@ -116,14 +111,14 @@ HttpdOutput::Configure(const config_param &param, GError **error_r)
 	const char *bind_to_address = param.GetBlockValue("bind_to_address");
 	bool success = bind_to_address != NULL &&
 		strcmp(bind_to_address, "any") != 0
-		? AddHost(bind_to_address, port, error_r)
-		: AddPort(port, error_r);
+		? AddHost(bind_to_address, port, error)
+		: AddPort(port, error);
 	if (!success)
 		return false;
 
 	/* initialize encoder */
 
-	encoder = encoder_init(*encoder_plugin, param, error_r);
+	encoder = encoder_init(*encoder_plugin, param, error);
 	if (encoder == nullptr)
 		return false;
 
@@ -136,18 +131,17 @@ HttpdOutput::Configure(const config_param &param, GError **error_r)
 }
 
 static struct audio_output *
-httpd_output_init(const struct config_param &param,
-		  GError **error_r)
+httpd_output_init(const config_param &param, Error &error)
 {
 	HttpdOutput *httpd = new HttpdOutput(*main_loop);
 
 	if (!ao_base_init(&httpd->base, &httpd_output_plugin, param,
-			  error_r)) {
+			  error)) {
 		delete httpd;
 		return nullptr;
 	}
 
-	if (!httpd->Configure(param, error_r)) {
+	if (!httpd->Configure(param, error)) {
 		ao_base_finish(&httpd->base);
 		delete httpd;
 		return nullptr;
@@ -205,7 +199,8 @@ HttpdOutput::OnAccept(int fd, const sockaddr &address,
 
 #ifdef HAVE_LIBWRAP
 	if (address.sa_family != AF_UNIX) {
-		char *hostaddr = sockaddr_to_string(&address, address_length, NULL);
+		char *hostaddr = sockaddr_to_string(&address, address_length,
+						    IgnoreError());
 		const char *progname = g_get_prgname();
 
 		struct request_info req;
@@ -249,7 +244,7 @@ HttpdOutput::ReadPage()
 		/* we have fed a lot of input into the encoder, but it
 		   didn't give anything back yet - flush now to avoid
 		   buffer underruns */
-		encoder_flush(encoder, NULL);
+		encoder_flush(encoder, IgnoreError());
 		unflushed_input = 0;
 	}
 
@@ -273,11 +268,11 @@ HttpdOutput::ReadPage()
 }
 
 static bool
-httpd_output_enable(struct audio_output *ao, GError **error_r)
+httpd_output_enable(struct audio_output *ao, Error &error)
 {
 	HttpdOutput *httpd = Cast(ao);
 
-	return httpd->Bind(error_r);
+	return httpd->Bind(error);
 }
 
 static void
@@ -289,7 +284,7 @@ httpd_output_disable(struct audio_output *ao)
 }
 
 inline bool
-HttpdOutput::OpenEncoder(AudioFormat &audio_format, GError **error)
+HttpdOutput::OpenEncoder(AudioFormat &audio_format, Error &error)
 {
 	if (!encoder_open(encoder, audio_format, error))
 		return false;
@@ -305,14 +300,14 @@ HttpdOutput::OpenEncoder(AudioFormat &audio_format, GError **error)
 }
 
 inline bool
-HttpdOutput::Open(AudioFormat &audio_format, GError **error_r)
+HttpdOutput::Open(AudioFormat &audio_format, Error &error)
 {
 	assert(!open);
 	assert(clients.empty());
 
 	/* open the encoder */
 
-	if (!OpenEncoder(audio_format, error_r))
+	if (!OpenEncoder(audio_format, error))
 		return false;
 
 	/* initialize other attributes */
@@ -327,7 +322,7 @@ HttpdOutput::Open(AudioFormat &audio_format, GError **error_r)
 
 static bool
 httpd_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		  GError **error)
+		  Error &error)
 {
 	HttpdOutput *httpd = Cast(ao);
 
@@ -439,9 +434,9 @@ HttpdOutput::BroadcastFromEncoder()
 }
 
 inline bool
-HttpdOutput::EncodeAndPlay(const void *chunk, size_t size, GError **error_r)
+HttpdOutput::EncodeAndPlay(const void *chunk, size_t size, Error &error)
 {
-	if (!encoder_write(encoder, chunk, size, error_r))
+	if (!encoder_write(encoder, chunk, size, error))
 		return false;
 
 	unflushed_input += size;
@@ -452,12 +447,12 @@ HttpdOutput::EncodeAndPlay(const void *chunk, size_t size, GError **error_r)
 
 static size_t
 httpd_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		  GError **error_r)
+		  Error &error)
 {
 	HttpdOutput *httpd = Cast(ao);
 
 	if (httpd->LockHasClients()) {
-		if (!httpd->EncodeAndPlay(chunk, size, error_r))
+		if (!httpd->EncodeAndPlay(chunk, size, error))
 			return 0;
 	}
 
@@ -476,7 +471,7 @@ httpd_output_pause(struct audio_output *ao)
 	if (httpd->LockHasClients()) {
 		static const char silence[1020] = { 0 };
 		return httpd_output_play(ao, silence, sizeof(silence),
-					 NULL) > 0;
+					 IgnoreError()) > 0;
 	} else {
 		return true;
 	}
@@ -492,13 +487,13 @@ HttpdOutput::SendTag(const Tag *tag)
 
 		/* flush the current stream, and end it */
 
-		encoder_pre_tag(encoder, NULL);
+		encoder_pre_tag(encoder, IgnoreError());
 		BroadcastFromEncoder();
 
 		/* send the tag to the encoder - which starts a new
 		   stream now */
 
-		encoder_tag(encoder, tag, NULL);
+		encoder_tag(encoder, tag, IgnoreError());
 
 		/* the first page generated by the encoder will now be
 		   used as the new "header" page, which is sent to all
diff --git a/src/output/JackOutputPlugin.cxx b/src/output/JackOutputPlugin.cxx
index bca57cfc1..63e46ef5a 100644
--- a/src/output/JackOutputPlugin.cxx
+++ b/src/output/JackOutputPlugin.cxx
@@ -20,6 +20,9 @@
 #include "config.h"
 #include "JackOutputPlugin.hxx"
 #include "OutputAPI.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <assert.h>
 
@@ -82,7 +85,7 @@ struct JackOutput {
 	 */
 	bool pause;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error_r) {
 		return ao_base_init(&base, &jack_output_plugin, param,
 				    error_r);
 	}
@@ -92,14 +95,7 @@ struct JackOutput {
 	}
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-jack_output_quark(void)
-{
-	return g_quark_from_static_string("jack_output");
-}
+static constexpr Domain jack_output_domain("jack_output");
 
 /**
  * Determine the number of frames guaranteed to be available on all
@@ -250,7 +246,7 @@ mpd_jack_disconnect(JackOutput *jd)
  * (e.g. register callbacks).
  */
 static bool
-mpd_jack_connect(JackOutput *jd, GError **error_r)
+mpd_jack_connect(JackOutput *jd, Error &error)
 {
 	jack_status_t status;
 
@@ -261,9 +257,9 @@ mpd_jack_connect(JackOutput *jd, GError **error_r)
 	jd->client = jack_client_open(jd->name, jd->options, &status,
 				      jd->server_name);
 	if (jd->client == nullptr) {
-		g_set_error(error_r, jack_output_quark(), 0,
-			    "Failed to connect to JACK server, status=%d",
-			    status);
+		error.Format(jack_output_domain, status,
+			     "Failed to connect to JACK server, status=%d",
+			     status);
 		return false;
 	}
 
@@ -276,9 +272,9 @@ mpd_jack_connect(JackOutput *jd, GError **error_r)
 						  JACK_DEFAULT_AUDIO_TYPE,
 						  JackPortIsOutput, 0);
 		if (jd->ports[i] == nullptr) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "Cannot register output port \"%s\"",
-				    jd->source_ports[i]);
+			error.Format(jack_output_domain,
+				     "Cannot register output port \"%s\"",
+				     jd->source_ports[i]);
 			mpd_jack_disconnect(jd);
 			return false;
 		}
@@ -294,16 +290,16 @@ mpd_jack_test_default_device(void)
 }
 
 static unsigned
-parse_port_list(int line, const char *source, char **dest, GError **error_r)
+parse_port_list(int line, const char *source, char **dest, Error &error)
 {
 	char **list = g_strsplit(source, ",", 0);
 	unsigned n = 0;
 
 	for (n = 0; list[n] != nullptr; ++n) {
 		if (n >= MAX_PORTS) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "too many port names in line %d",
-				    line);
+			error.Format(config_domain,
+				     "too many port names in line %d",
+				     line);
 			return 0;
 		}
 
@@ -313,9 +309,9 @@ parse_port_list(int line, const char *source, char **dest, GError **error_r)
 	g_free(list);
 
 	if (n == 0) {
-		g_set_error(error_r, jack_output_quark(), 0,
-			    "at least one port name expected in line %d",
-			    line);
+		error.Format(config_domain,
+			     "at least one port name expected in line %d",
+			     line);
 		return 0;
 	}
 
@@ -323,11 +319,11 @@ parse_port_list(int line, const char *source, char **dest, GError **error_r)
 }
 
 static struct audio_output *
-mpd_jack_init(const config_param &param, GError **error_r)
+mpd_jack_init(const config_param &param, Error &error)
 {
 	JackOutput *jd = new JackOutput();
 
-	if (!jd->Initialize(param, error_r)) {
+	if (!jd->Initialize(param, error)) {
 		delete jd;
 		return nullptr;
 	}
@@ -355,7 +351,7 @@ mpd_jack_init(const config_param &param, GError **error_r)
 
 	value = param.GetBlockValue("source_ports", "left,right");
 	jd->num_source_ports = parse_port_list(param.line, value,
-					       jd->source_ports, error_r);
+					       jd->source_ports, error);
 	if (jd->num_source_ports == 0)
 		return nullptr;
 
@@ -373,7 +369,7 @@ mpd_jack_init(const config_param &param, GError **error_r)
 	if (value != nullptr) {
 		jd->num_destination_ports =
 			parse_port_list(param.line, value,
-					jd->destination_ports, error_r);
+					jd->destination_ports, error);
 		if (jd->num_destination_ports == 0)
 			return nullptr;
 	} else {
@@ -414,14 +410,14 @@ mpd_jack_finish(struct audio_output *ao)
 }
 
 static bool
-mpd_jack_enable(struct audio_output *ao, GError **error_r)
+mpd_jack_enable(struct audio_output *ao, Error &error)
 {
 	JackOutput *jd = (JackOutput *)ao;
 
 	for (unsigned i = 0; i < jd->num_source_ports; ++i)
 		jd->ringbuffer[i] = nullptr;
 
-	return mpd_jack_connect(jd, error_r);
+	return mpd_jack_connect(jd, error);
 }
 
 static void
@@ -460,7 +456,7 @@ mpd_jack_stop(JackOutput *jd)
 }
 
 static bool
-mpd_jack_start(JackOutput *jd, GError **error_r)
+mpd_jack_start(JackOutput *jd, Error &error)
 {
 	const char *destination_ports[MAX_PORTS], **jports;
 	const char *duplicate_port = nullptr;
@@ -484,8 +480,7 @@ mpd_jack_start(JackOutput *jd, GError **error_r)
 	}
 
 	if ( jack_activate(jd->client) ) {
-		g_set_error(error_r, jack_output_quark(), 0,
-			    "cannot activate client");
+		error.Set(jack_output_domain, "cannot activate client");
 		mpd_jack_stop(jd);
 		return false;
 	}
@@ -496,8 +491,7 @@ mpd_jack_start(JackOutput *jd, GError **error_r)
 		jports = jack_get_ports(jd->client, nullptr, nullptr,
 					JackPortIsPhysical | JackPortIsInput);
 		if (jports == nullptr) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "no ports found");
+			error.Set(jack_output_domain, "no ports found");
 			mpd_jack_stop(jd);
 			return false;
 		}
@@ -551,9 +545,9 @@ mpd_jack_start(JackOutput *jd, GError **error_r)
 		ret = jack_connect(jd->client, jack_port_name(jd->ports[i]),
 				   destination_ports[i]);
 		if (ret != 0) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "Not a valid JACK port: %s",
-				    destination_ports[i]);
+			error.Format(jack_output_domain,
+				     "Not a valid JACK port: %s",
+				     destination_ports[i]);
 
 			if (jports != nullptr)
 				free(jports);
@@ -571,9 +565,9 @@ mpd_jack_start(JackOutput *jd, GError **error_r)
 		ret = jack_connect(jd->client, jack_port_name(jd->ports[0]),
 				   duplicate_port);
 		if (ret != 0) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "Not a valid JACK port: %s",
-				    duplicate_port);
+			error.Format(jack_output_domain,
+				     "Not a valid JACK port: %s",
+				     duplicate_port);
 
 			if (jports != nullptr)
 				free(jports);
@@ -591,7 +585,7 @@ mpd_jack_start(JackOutput *jd, GError **error_r)
 
 static bool
 mpd_jack_open(struct audio_output *ao, AudioFormat &audio_format,
-	      GError **error_r)
+	      Error &error)
 {
 	JackOutput *jd = (JackOutput *)ao;
 
@@ -602,13 +596,13 @@ mpd_jack_open(struct audio_output *ao, AudioFormat &audio_format,
 	if (jd->client != nullptr && jd->shutdown)
 		mpd_jack_disconnect(jd);
 
-	if (jd->client == nullptr && !mpd_jack_connect(jd, error_r))
+	if (jd->client == nullptr && !mpd_jack_connect(jd, error))
 		return false;
 
 	set_audioformat(jd, audio_format);
 	jd->audio_format = audio_format;
 
-	if (!mpd_jack_start(jd, error_r))
+	if (!mpd_jack_start(jd, error))
 		return false;
 
 	return true;
@@ -701,7 +695,7 @@ mpd_jack_write_samples(JackOutput *jd, const void *src,
 
 static size_t
 mpd_jack_play(struct audio_output *ao, const void *chunk, size_t size,
-	      GError **error_r)
+	      Error &error)
 {
 	JackOutput *jd = (JackOutput *)ao;
 	const size_t frame_size = jd->audio_format.GetFrameSize();
@@ -714,9 +708,9 @@ mpd_jack_play(struct audio_output *ao, const void *chunk, size_t size,
 
 	while (true) {
 		if (jd->shutdown) {
-			g_set_error(error_r, jack_output_quark(), 0,
-				    "Refusing to play, because "
-				    "there is no client thread");
+			error.Set(jack_output_domain,
+				  "Refusing to play, because "
+				  "there is no client thread");
 			return 0;
 		}
 
diff --git a/src/output/NullOutputPlugin.cxx b/src/output/NullOutputPlugin.cxx
index 0ce32fbda..e2eec9dbc 100644
--- a/src/output/NullOutputPlugin.cxx
+++ b/src/output/NullOutputPlugin.cxx
@@ -31,9 +31,9 @@ struct NullOutput {
 
 	Timer *timer;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error) {
 		return ao_base_init(&base, &null_output_plugin, param,
-				    error_r);
+				    error);
 	}
 
 	void Deinitialize() {
@@ -42,11 +42,11 @@ struct NullOutput {
 };
 
 static struct audio_output *
-null_init(const config_param &param, GError **error_r)
+null_init(const config_param &param, Error &error)
 {
 	NullOutput *nd = new NullOutput();
 
-	if (!nd->Initialize(param, error_r)) {
+	if (!nd->Initialize(param, error)) {
 		delete nd;
 		return nullptr;
 	}
@@ -67,7 +67,7 @@ null_finish(struct audio_output *ao)
 
 static bool
 null_open(struct audio_output *ao, AudioFormat &audio_format,
-	  gcc_unused GError **error)
+	  gcc_unused Error &error)
 {
 	NullOutput *nd = (NullOutput *)ao;
 
@@ -98,7 +98,7 @@ null_delay(struct audio_output *ao)
 
 static size_t
 null_play(struct audio_output *ao, gcc_unused const void *chunk, size_t size,
-	  gcc_unused GError **error)
+	  gcc_unused Error &error)
 {
 	NullOutput *nd = (NullOutput *)ao;
 	Timer *timer = nd->timer;
diff --git a/src/output/OSXOutputPlugin.cxx b/src/output/OSXOutputPlugin.cxx
index 09f5581d5..8445a8028 100644
--- a/src/output/OSXOutputPlugin.cxx
+++ b/src/output/OSXOutputPlugin.cxx
@@ -21,6 +21,8 @@
 #include "OSXOutputPlugin.hxx"
 #include "OutputAPI.hxx"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
 
@@ -47,14 +49,7 @@ struct OSXOutput {
 	struct fifo_buffer *buffer;
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-osx_output_quark(void)
-{
-	return g_quark_from_static_string("osx_output");
-}
+static constexpr Domain osx_output_domain("osx_output");
 
 static bool
 osx_output_test_default_device(void)
@@ -85,10 +80,10 @@ osx_output_configure(OSXOutput *oo, const config_param &param)
 }
 
 static struct audio_output *
-osx_output_init(const config_param &param, GError **error_r)
+osx_output_init(const config_param &param, Error &error)
 {
 	OSXOutput *oo = new OSXOutput();
-	if (!ao_base_init(&oo->base, &osx_output_plugin, param, error_r)) {
+	if (!ao_base_init(&oo->base, &osx_output_plugin, param, error)) {
 		delete oo;
 		return NULL;
 	}
@@ -107,7 +102,7 @@ osx_output_finish(struct audio_output *ao)
 }
 
 static bool
-osx_output_set_device(OSXOutput *oo, GError **error)
+osx_output_set_device(OSXOutput *oo, Error &error)
 {
 	bool ret = true;
 	OSStatus status;
@@ -124,9 +119,9 @@ osx_output_set_device(OSXOutput *oo, GError **error)
 					      &size,
 					      NULL);
 	if (status != noErr) {
-		g_set_error(error, osx_output_quark(), status,
-			    "Unable to determine number of OS X audio devices: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Format(osx_output_domain, status,
+			     "Unable to determine number of OS X audio devices: %s",
+			     GetMacOSStatusCommentString(status));
 		ret = false;
 		goto done;
 	}
@@ -138,9 +133,9 @@ osx_output_set_device(OSXOutput *oo, GError **error)
 					  &size,
 					  deviceids);
 	if (status != noErr) {
-		g_set_error(error, osx_output_quark(), status,
-			    "Unable to determine OS X audio device IDs: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Format(osx_output_domain, status,
+			     "Unable to determine OS X audio device IDs: %s",
+			     GetMacOSStatusCommentString(status));
 		ret = false;
 		goto done;
 	}
@@ -152,11 +147,11 @@ osx_output_set_device(OSXOutput *oo, GError **error)
 						kAudioDevicePropertyDeviceName,
 						&size, name);
 		if (status != noErr) {
-			g_set_error(error, osx_output_quark(), status,
-				    "Unable to determine OS X device name "
-				    "(device %u): %s",
-				    (unsigned int) deviceids[i],
-				    GetMacOSStatusCommentString(status));
+			error.Format(osx_output_domain, status,
+				     "Unable to determine OS X device name "
+				     "(device %u): %s",
+				     (unsigned int) deviceids[i],
+				     GetMacOSStatusCommentString(status));
 			ret = false;
 			goto done;
 		}
@@ -180,9 +175,9 @@ osx_output_set_device(OSXOutput *oo, GError **error)
 				      &(deviceids[i]),
 				      sizeof(AudioDeviceID));
 	if (status != noErr) {
-		g_set_error(error, osx_output_quark(), status,
-			    "Unable to set OS X audio output device: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Format(osx_output_domain, status,
+			     "Unable to set OS X audio output device: %s",
+			     GetMacOSStatusCommentString(status));
 		ret = false;
 		goto done;
 	}
@@ -237,7 +232,7 @@ osx_render(void *vdata,
 }
 
 static bool
-osx_output_enable(struct audio_output *ao, GError **error_r)
+osx_output_enable(struct audio_output *ao, Error &error)
 {
 	OSXOutput *oo = (OSXOutput *)ao;
 
@@ -250,20 +245,20 @@ osx_output_enable(struct audio_output *ao, GError **error_r)
 
 	Component comp = FindNextComponent(NULL, &desc);
 	if (comp == 0) {
-		g_set_error(error_r, osx_output_quark(), 0,
-			    "Error finding OS X component");
+		error.Set(osx_output_domain,
+			  "Error finding OS X component");
 		return false;
 	}
 
 	OSStatus status = OpenAComponent(comp, &oo->au);
 	if (status != noErr) {
-		g_set_error(error_r, osx_output_quark(), status,
-			    "Unable to open OS X component: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Format(osx_output_domain, status,
+			     "Unable to open OS X component: %s",
+			     GetMacOSStatusCommentString(status));
 		return false;
 	}
 
-	if (!osx_output_set_device(oo, error_r)) {
+	if (!osx_output_set_device(oo, error)) {
 		CloseComponent(oo->au);
 		return false;
 	}
@@ -279,8 +274,8 @@ osx_output_enable(struct audio_output *ao, GError **error_r)
 				     &callback, sizeof(callback));
 	if (result != noErr) {
 		CloseComponent(oo->au);
-		g_set_error(error_r, osx_output_quark(), result,
-			    "unable to set callback for OS X audio unit");
+		error.Set(osx_output_domain, result,
+			  "unable to set callback for OS X audio unit");
 		return false;
 	}
 
@@ -316,7 +311,8 @@ osx_output_close(struct audio_output *ao)
 }
 
 static bool
-osx_output_open(struct audio_output *ao, AudioFormat &audio_format, GError **error)
+osx_output_open(struct audio_output *ao, AudioFormat &audio_format,
+		Error &error)
 {
 	OSXOutput *od = (OSXOutput *)ao;
 
@@ -359,16 +355,16 @@ osx_output_open(struct audio_output *ao, AudioFormat &audio_format, GError **err
 				     &stream_description,
 				     sizeof(stream_description));
 	if (result != noErr) {
-		g_set_error(error, osx_output_quark(), result,
-			    "Unable to set format on OS X device");
+		error.Set(osx_output_domain, result,
+			  "Unable to set format on OS X device");
 		return false;
 	}
 
 	OSStatus status = AudioUnitInitialize(od->au);
 	if (status != noErr) {
-		g_set_error(error, osx_output_quark(), status,
-			    "Unable to initialize OS X audio unit: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Set(osx_output_domain, status,
+			  "Unable to initialize OS X audio unit: %s",
+			  GetMacOSStatusCommentString(status));
 		return false;
 	}
 
@@ -379,9 +375,9 @@ osx_output_open(struct audio_output *ao, AudioFormat &audio_format, GError **err
 	status = AudioOutputUnitStart(od->au);
 	if (status != 0) {
 		AudioUnitUninitialize(od->au);
-		g_set_error(error, osx_output_quark(), status,
-			    "unable to start audio output: %s",
-			    GetMacOSStatusCommentString(status));
+		error.Format(osx_output_domain, status,
+			     "unable to start audio output: %s",
+			     GetMacOSStatusCommentString(status));
 		return false;
 	}
 
@@ -390,7 +386,7 @@ osx_output_open(struct audio_output *ao, AudioFormat &audio_format, GError **err
 
 static size_t
 osx_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		gcc_unused GError **error)
+		gcc_unused Error &error)
 {
 	OSXOutput *od = (OSXOutput *)ao;
 
diff --git a/src/output/OpenALOutputPlugin.cxx b/src/output/OpenALOutputPlugin.cxx
index bf4f58aa7..f8b1f5417 100644
--- a/src/output/OpenALOutputPlugin.cxx
+++ b/src/output/OpenALOutputPlugin.cxx
@@ -20,6 +20,8 @@
 #include "config.h"
 #include "OpenALOutputPlugin.hxx"
 #include "OutputAPI.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -49,7 +51,7 @@ struct OpenALOutput {
 	ALenum format;
 	ALuint frequency;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error_r) {
 		return ao_base_init(&base, &openal_output_plugin, param,
 				    error_r);
 	}
@@ -59,12 +61,7 @@ struct OpenALOutput {
 	}
 };
 
-gcc_const
-static inline GQuark
-openal_output_quark(void)
-{
-	return g_quark_from_static_string("openal_output");
-}
+static constexpr Domain openal_output_domain("openal_output");
 
 static ALenum
 openal_audio_format(AudioFormat &audio_format)
@@ -115,24 +112,23 @@ openal_is_playing(const OpenALOutput *od)
 }
 
 static bool
-openal_setup_context(OpenALOutput *od,
-		     GError **error)
+openal_setup_context(OpenALOutput *od, Error &error)
 {
 	od->device = alcOpenDevice(od->device_name);
 
 	if (od->device == nullptr) {
-		g_set_error(error, openal_output_quark(), 0,
-			    "Error opening OpenAL device \"%s\"\n",
-			    od->device_name);
+		error.Format(openal_output_domain,
+			     "Error opening OpenAL device \"%s\"",
+			     od->device_name);
 		return false;
 	}
 
 	od->context = alcCreateContext(od->device, nullptr);
 
 	if (od->context == nullptr) {
-		g_set_error(error, openal_output_quark(), 0,
-			    "Error creating context for \"%s\"\n",
-			    od->device_name);
+		error.Format(openal_output_domain,
+			     "Error creating context for \"%s\"",
+			     od->device_name);
 		alcCloseDevice(od->device);
 		return false;
 	}
@@ -141,7 +137,7 @@ openal_setup_context(OpenALOutput *od,
 }
 
 static struct audio_output *
-openal_init(const config_param &param, GError **error_r)
+openal_init(const config_param &param, Error &error)
 {
 	const char *device_name = param.GetBlockValue("device");
 	if (device_name == nullptr) {
@@ -149,7 +145,7 @@ openal_init(const config_param &param, GError **error_r)
 	}
 
 	OpenALOutput *od = new OpenALOutput();
-	if (!od->Initialize(param, error_r)) {
+	if (!od->Initialize(param, error)) {
 		delete od;
 		return nullptr;
 	}
@@ -170,7 +166,7 @@ openal_finish(struct audio_output *ao)
 
 static bool
 openal_open(struct audio_output *ao, AudioFormat &audio_format,
-	    GError **error)
+	    Error &error)
 {
 	OpenALOutput *od = (OpenALOutput *)ao;
 
@@ -184,16 +180,14 @@ openal_open(struct audio_output *ao, AudioFormat &audio_format,
 	alGenBuffers(NUM_BUFFERS, od->buffers);
 
 	if (alGetError() != AL_NO_ERROR) {
-		g_set_error(error, openal_output_quark(), 0,
-			    "Failed to generate buffers");
+		error.Set(openal_output_domain, "Failed to generate buffers");
 		return false;
 	}
 
 	alGenSources(1, &od->source);
 
 	if (alGetError() != AL_NO_ERROR) {
-		g_set_error(error, openal_output_quark(), 0,
-			    "Failed to generate source");
+		error.Set(openal_output_domain, "Failed to generate source");
 		alDeleteBuffers(NUM_BUFFERS, od->buffers);
 		return false;
 	}
@@ -231,7 +225,7 @@ openal_delay(struct audio_output *ao)
 
 static size_t
 openal_play(struct audio_output *ao, const void *chunk, size_t size,
-	    gcc_unused GError **error)
+	    gcc_unused Error &error)
 {
 	OpenALOutput *od = (OpenALOutput *)ao;
 	ALuint buffer;
diff --git a/src/output/OssOutputPlugin.cxx b/src/output/OssOutputPlugin.cxx
index b31db6c43..7bf741397 100644
--- a/src/output/OssOutputPlugin.cxx
+++ b/src/output/OssOutputPlugin.cxx
@@ -22,6 +22,8 @@
 #include "OutputAPI.hxx"
 #include "MixerList.hxx"
 #include "system/fd_util.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -80,7 +82,7 @@ struct OssOutput {
 
 	OssOutput():fd(-1), device(nullptr) {}
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error_r) {
 		return ao_base_init(&base, &oss_output_plugin, param,
 				    error_r);
 	}
@@ -90,14 +92,7 @@ struct OssOutput {
 	}
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-oss_output_quark(void)
-{
-	return g_quark_from_static_string("oss_output");
-}
+static constexpr Domain oss_output_domain("oss_output");
 
 enum oss_stat {
 	OSS_STAT_NO_ERROR = 0,
@@ -155,7 +150,7 @@ oss_output_test_default_device(void)
 }
 
 static struct audio_output *
-oss_open_default(GError **error)
+oss_open_default(Error &error)
 {
 	int err[G_N_ELEMENTS(default_devices)];
 	enum oss_stat ret[G_N_ELEMENTS(default_devices)];
@@ -196,18 +191,18 @@ oss_open_default(GError **error)
 		}
 	}
 
-	g_set_error(error, oss_output_quark(), 0,
-		    "error trying to open default OSS device");
+	error.Set(oss_output_domain,
+		  "error trying to open default OSS device");
 	return NULL;
 }
 
 static struct audio_output *
-oss_output_init(const config_param &param, GError **error_r)
+oss_output_init(const config_param &param, Error &error)
 {
 	const char *device = param.GetBlockValue("device");
 	if (device != NULL) {
 		OssOutput *od = new OssOutput();
-		if (!od->Initialize(param, error_r)) {
+		if (!od->Initialize(param, error)) {
 			delete od;
 			return NULL;
 		}
@@ -216,7 +211,7 @@ oss_output_init(const config_param &param, GError **error_r)
 		return &od->base;
 	}
 
-	return oss_open_default(error_r);
+	return oss_open_default(error);
 }
 
 static void
@@ -231,7 +226,7 @@ oss_output_finish(struct audio_output *ao)
 #ifdef AFMT_S24_PACKED
 
 static bool
-oss_output_enable(struct audio_output *ao, gcc_unused GError **error_r)
+oss_output_enable(struct audio_output *ao, gcc_unused Error &error)
 {
 	OssOutput *od = (OssOutput *)ao;
 
@@ -269,16 +264,16 @@ enum oss_setup_result {
 /**
  * Invoke an ioctl on the OSS file descriptor.  On success, SUCCESS is
  * returned.  If the parameter is not supported, UNSUPPORTED is
- * returned.  Any other failure returns ERROR and allocates a GError.
+ * returned.  Any other failure returns ERROR and allocates an #Error.
  */
 static enum oss_setup_result
 oss_try_ioctl_r(int fd, unsigned long request, int *value_r,
-		const char *msg, GError **error_r)
+		const char *msg, Error &error)
 {
 	assert(fd >= 0);
 	assert(value_r != NULL);
 	assert(msg != NULL);
-	assert(error_r == NULL || *error_r == NULL);
+	assert(!error.IsDefined());
 
 	int ret = ioctl(fd, request, value_r);
 	if (ret >= 0)
@@ -287,19 +282,18 @@ oss_try_ioctl_r(int fd, unsigned long request, int *value_r,
 	if (errno == EINVAL)
 		return UNSUPPORTED;
 
-	g_set_error(error_r, oss_output_quark(), errno,
-		    "%s: %s", msg, g_strerror(errno));
+	error.SetErrno(msg);
 	return ERROR;
 }
 
 /**
  * Invoke an ioctl on the OSS file descriptor.  On success, SUCCESS is
  * returned.  If the parameter is not supported, UNSUPPORTED is
- * returned.  Any other failure returns ERROR and allocates a GError.
+ * returned.  Any other failure returns ERROR and allocates an #Error.
  */
 static enum oss_setup_result
 oss_try_ioctl(int fd, unsigned long request, int value,
-	      const char *msg, GError **error_r)
+	      const char *msg, Error &error_r)
 {
 	return oss_try_ioctl_r(fd, request, &value, msg, error_r);
 }
@@ -309,12 +303,12 @@ oss_try_ioctl(int fd, unsigned long request, int value,
  * specified number is not supported.
  */
 static bool
-oss_setup_channels(int fd, AudioFormat &audio_format, GError **error_r)
+oss_setup_channels(int fd, AudioFormat &audio_format, Error &error)
 {
 	const char *const msg = "Failed to set channel count";
 	int channels = audio_format.channels;
 	enum oss_setup_result result =
-		oss_try_ioctl_r(fd, SNDCTL_DSP_CHANNELS, &channels, msg, error_r);
+		oss_try_ioctl_r(fd, SNDCTL_DSP_CHANNELS, &channels, msg, error);
 	switch (result) {
 	case SUCCESS:
 		if (!audio_valid_channel_count(channels))
@@ -337,7 +331,7 @@ oss_setup_channels(int fd, AudioFormat &audio_format, GError **error_r)
 
 		channels = i;
 		result = oss_try_ioctl_r(fd, SNDCTL_DSP_CHANNELS, &channels,
-					 msg, error_r);
+					 msg, error);
 		switch (result) {
 		case SUCCESS:
 			if (!audio_valid_channel_count(channels))
@@ -354,7 +348,7 @@ oss_setup_channels(int fd, AudioFormat &audio_format, GError **error_r)
 		}
 	}
 
-	g_set_error(error_r, oss_output_quark(), EINVAL, "%s", msg);
+	error.Set(oss_output_domain, msg);
 	return false;
 }
 
@@ -364,13 +358,13 @@ oss_setup_channels(int fd, AudioFormat &audio_format, GError **error_r)
  */
 static bool
 oss_setup_sample_rate(int fd, AudioFormat &audio_format,
-		      GError **error_r)
+		      Error &error)
 {
 	const char *const msg = "Failed to set sample rate";
 	int sample_rate = audio_format.sample_rate;
 	enum oss_setup_result result =
 		oss_try_ioctl_r(fd, SNDCTL_DSP_SPEED, &sample_rate,
-				msg, error_r);
+				msg, error);
 	switch (result) {
 	case SUCCESS:
 		if (!audio_valid_sample_rate(sample_rate))
@@ -393,7 +387,7 @@ oss_setup_sample_rate(int fd, AudioFormat &audio_format,
 			continue;
 
 		result = oss_try_ioctl_r(fd, SNDCTL_DSP_SPEED, &sample_rate,
-					 msg, error_r);
+					 msg, error);
 		switch (result) {
 		case SUCCESS:
 			if (!audio_valid_sample_rate(sample_rate))
@@ -410,7 +404,7 @@ oss_setup_sample_rate(int fd, AudioFormat &audio_format,
 		}
 	}
 
-	g_set_error(error_r, oss_output_quark(), EINVAL, "%s", msg);
+	error.Set(oss_output_domain, msg);
 	return false;
 }
 
@@ -498,7 +492,7 @@ oss_probe_sample_format(int fd, SampleFormat sample_format,
 #ifdef AFMT_S24_PACKED
 			PcmExport &pcm_export,
 #endif
-			GError **error_r)
+			Error &error)
 {
 	int oss_format = sample_format_to_oss(sample_format);
 	if (oss_format == AFMT_QUERY)
@@ -507,7 +501,7 @@ oss_probe_sample_format(int fd, SampleFormat sample_format,
 	enum oss_setup_result result =
 		oss_try_ioctl_r(fd, SNDCTL_DSP_SAMPLESIZE,
 				&oss_format,
-				"Failed to set sample format", error_r);
+				"Failed to set sample format", error);
 
 #ifdef AFMT_S24_PACKED
 	if (result == UNSUPPORTED && sample_format == SampleFormat::S24_P32) {
@@ -516,7 +510,7 @@ oss_probe_sample_format(int fd, SampleFormat sample_format,
 		oss_format = AFMT_S24_PACKED;
 		result = oss_try_ioctl_r(fd, SNDCTL_DSP_SAMPLESIZE,
 					 &oss_format,
-					 "Failed to set sample format", error_r);
+					 "Failed to set sample format", error);
 	}
 #endif
 
@@ -550,7 +544,7 @@ oss_setup_sample_format(int fd, AudioFormat &audio_format,
 #ifdef AFMT_S24_PACKED
 			PcmExport &pcm_export,
 #endif
-			GError **error_r)
+			Error &error)
 {
 	SampleFormat mpd_format;
 	enum oss_setup_result result =
@@ -559,7 +553,7 @@ oss_setup_sample_format(int fd, AudioFormat &audio_format,
 #ifdef AFMT_S24_PACKED
 					pcm_export,
 #endif
-					error_r);
+					error);
 	switch (result) {
 	case SUCCESS:
 		audio_format.format = mpd_format;
@@ -597,7 +591,7 @@ oss_setup_sample_format(int fd, AudioFormat &audio_format,
 #ifdef AFMT_S24_PACKED
 						 pcm_export,
 #endif
-						 error_r);
+						 error);
 		switch (result) {
 		case SUCCESS:
 			audio_format.format = mpd_format;
@@ -611,8 +605,7 @@ oss_setup_sample_format(int fd, AudioFormat &audio_format,
 		}
 	}
 
-	g_set_error_literal(error_r, oss_output_quark(), EINVAL,
-			    "Failed to set sample format");
+	error.Set(oss_output_domain, "Failed to set sample format");
 	return false;
 }
 
@@ -621,30 +614,29 @@ oss_setup_sample_format(int fd, AudioFormat &audio_format,
  */
 static bool
 oss_setup(OssOutput *od, AudioFormat &audio_format,
-	  GError **error_r)
+	  Error &error)
 {
-	return oss_setup_channels(od->fd, audio_format, error_r) &&
-		oss_setup_sample_rate(od->fd, audio_format, error_r) &&
+	return oss_setup_channels(od->fd, audio_format, error) &&
+		oss_setup_sample_rate(od->fd, audio_format, error) &&
 		oss_setup_sample_format(od->fd, audio_format, &od->oss_format,
 #ifdef AFMT_S24_PACKED
 					od->pcm_export,
 #endif
-					error_r);
+					error);
 }
 
 /**
  * Reopen the device with the saved audio_format, without any probing.
  */
 static bool
-oss_reopen(OssOutput *od, GError **error_r)
+oss_reopen(OssOutput *od, Error &error)
 {
 	assert(od->fd < 0);
 
 	od->fd = open_cloexec(od->device, O_WRONLY, 0);
 	if (od->fd < 0) {
-		g_set_error(error_r, oss_output_quark(), errno,
-			    "Error opening OSS device \"%s\": %s",
-			    od->device, g_strerror(errno));
+		error.FormatErrno("Error opening OSS device \"%s\"",
+				  od->device);
 		return false;
 	}
 
@@ -652,35 +644,32 @@ oss_reopen(OssOutput *od, GError **error_r)
 
 	const char *const msg1 = "Failed to set channel count";
 	result = oss_try_ioctl(od->fd, SNDCTL_DSP_CHANNELS,
-			       od->audio_format.channels, msg1, error_r);
+			       od->audio_format.channels, msg1, error);
 	if (result != SUCCESS) {
 		oss_close(od);
 		if (result == UNSUPPORTED)
-			g_set_error(error_r, oss_output_quark(), EINVAL,
-				    "%s", msg1);
+			error.Set(oss_output_domain, msg1);
 		return false;
 	}
 
 	const char *const msg2 = "Failed to set sample rate";
 	result = oss_try_ioctl(od->fd, SNDCTL_DSP_SPEED,
-			       od->audio_format.sample_rate, msg2, error_r);
+			       od->audio_format.sample_rate, msg2, error);
 	if (result != SUCCESS) {
 		oss_close(od);
 		if (result == UNSUPPORTED)
-			g_set_error(error_r, oss_output_quark(), EINVAL,
-				    "%s", msg2);
+			error.Set(oss_output_domain, msg2);
 		return false;
 	}
 
 	const char *const msg3 = "Failed to set sample format";
 	result = oss_try_ioctl(od->fd, SNDCTL_DSP_SAMPLESIZE,
 			       od->oss_format,
-			       msg3, error_r);
+			       msg3, error);
 	if (result != SUCCESS) {
 		oss_close(od);
 		if (result == UNSUPPORTED)
-			g_set_error(error_r, oss_output_quark(), EINVAL,
-				    "%s", msg3);
+			error.Set(oss_output_domain, msg3);
 		return false;
 	}
 
@@ -689,15 +678,14 @@ oss_reopen(OssOutput *od, GError **error_r)
 
 static bool
 oss_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		GError **error)
+		Error &error)
 {
 	OssOutput *od = (OssOutput *)ao;
 
 	od->fd = open_cloexec(od->device, O_WRONLY, 0);
 	if (od->fd < 0) {
-		g_set_error(error, oss_output_quark(), errno,
-			    "Error opening OSS device \"%s\": %s",
-			    od->device, g_strerror(errno));
+		error.FormatErrno("Error opening OSS device \"%s\"",
+				  od->device);
 		return false;
 	}
 
@@ -731,7 +719,7 @@ oss_output_cancel(struct audio_output *ao)
 
 static size_t
 oss_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		GError **error)
+		Error &error)
 {
 	OssOutput *od = (OssOutput *)ao;
 	ssize_t ret;
@@ -754,9 +742,7 @@ oss_output_play(struct audio_output *ao, const void *chunk, size_t size,
 		}
 
 		if (ret < 0 && errno != EINTR) {
-			g_set_error(error, oss_output_quark(), errno,
-				    "Write error on %s: %s",
-				    od->device, g_strerror(errno));
+			error.FormatErrno("Write error on %s", od->device);
 			return 0;
 		}
 	}
diff --git a/src/output/PipeOutputPlugin.cxx b/src/output/PipeOutputPlugin.cxx
index 9ff3bb120..ca8f398da 100644
--- a/src/output/PipeOutputPlugin.cxx
+++ b/src/output/PipeOutputPlugin.cxx
@@ -20,6 +20,9 @@
 #include "config.h"
 #include "PipeOutputPlugin.hxx"
 #include "OutputAPI.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <stdio.h>
 #include <errno.h>
@@ -30,34 +33,27 @@ struct PipeOutput {
 	char *cmd;
 	FILE *fh;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error) {
 		return ao_base_init(&base, &pipe_output_plugin, param,
-				    error_r);
+				    error);
 	}
 
 	void Deinitialize() {
 		ao_base_finish(&base);
 	}
 
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-pipe_output_quark(void)
-{
-	return g_quark_from_static_string("pipe_output");
-}
+static constexpr Domain pipe_output_domain("pipe_output");
 
 inline bool
-PipeOutput::Configure(const config_param &param, GError **error_r)
+PipeOutput::Configure(const config_param &param, Error &error)
 {
 	cmd = param.DupBlockString("command");
 	if (cmd == nullptr) {
-		g_set_error(error_r, pipe_output_quark(), 0,
-			    "No \"command\" parameter specified");
+		error.Set(config_domain,
+			  "No \"command\" parameter specified");
 		return false;
 	}
 
@@ -65,16 +61,16 @@ PipeOutput::Configure(const config_param &param, GError **error_r)
 }
 
 static struct audio_output *
-pipe_output_init(const config_param &param, GError **error_r)
+pipe_output_init(const config_param &param, Error &error)
 {
 	PipeOutput *pd = new PipeOutput();
 
-	if (!pd->Initialize(param, error_r)) {
+	if (!pd->Initialize(param, error)) {
 		delete pd;
 		return nullptr;
 	}
 
-	if (!pd->Configure(param, error_r)) {
+	if (!pd->Configure(param, error)) {
 		pd->Deinitialize();
 		delete pd;
 		return nullptr;
@@ -96,15 +92,14 @@ pipe_output_finish(struct audio_output *ao)
 static bool
 pipe_output_open(struct audio_output *ao,
 		 gcc_unused AudioFormat &audio_format,
-		 gcc_unused GError **error)
+		 Error &error)
 {
 	PipeOutput *pd = (PipeOutput *)ao;
 
 	pd->fh = popen(pd->cmd, "w");
 	if (pd->fh == nullptr) {
-		g_set_error(error, pipe_output_quark(), errno,
-			    "Error opening pipe \"%s\": %s",
-			    pd->cmd, g_strerror(errno));
+		error.FormatErrno("Error opening pipe \"%s\"",
+				  pd->cmd);
 		return false;
 	}
 
@@ -120,15 +115,15 @@ pipe_output_close(struct audio_output *ao)
 }
 
 static size_t
-pipe_output_play(struct audio_output *ao, const void *chunk, size_t size, GError **error)
+pipe_output_play(struct audio_output *ao, const void *chunk, size_t size,
+		 Error &error)
 {
 	PipeOutput *pd = (PipeOutput *)ao;
 	size_t ret;
 
 	ret = fwrite(chunk, 1, size, pd->fh);
 	if (ret == 0)
-		g_set_error(error, pipe_output_quark(), errno,
-			    "Write error on pipe: %s", g_strerror(errno));
+		error.SetErrno("Write error on pipe");
 
 	return ret;
 }
diff --git a/src/output/PulseOutputPlugin.cxx b/src/output/PulseOutputPlugin.cxx
index 5394edfac..d64e0af16 100644
--- a/src/output/PulseOutputPlugin.cxx
+++ b/src/output/PulseOutputPlugin.cxx
@@ -22,6 +22,8 @@
 #include "OutputAPI.hxx"
 #include "MixerList.hxx"
 #include "mixer/PulseMixerPlugin.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -54,13 +56,13 @@ struct PulseOutput {
 	size_t writable;
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-pulse_output_quark(void)
+static constexpr Domain pulse_output_domain("pulse_output");
+
+static void
+SetError(Error &error, pa_context *context, const char *msg)
 {
-	return g_quark_from_static_string("pulse_output");
+	const int e = pa_context_errno(context);
+	error.Format(pulse_output_domain, e, "%s: %s", msg, pa_strerror(e));
 }
 
 void
@@ -112,14 +114,14 @@ pulse_output_clear_mixer(PulseOutput *po, gcc_unused PulseMixer *pm)
 }
 
 bool
-pulse_output_set_volume(PulseOutput *po,
-			const struct pa_cvolume *volume, GError **error_r)
+pulse_output_set_volume(PulseOutput *po, const pa_cvolume *volume,
+			Error &error)
 {
 	pa_operation *o;
 
 	if (po->context == nullptr || po->stream == nullptr ||
 	    pa_stream_get_state(po->stream) != PA_STREAM_READY) {
-		g_set_error(error_r, pulse_output_quark(), 0, "disconnected");
+		error.Set(pulse_output_domain, "disconnected");
 		return false;
 	}
 
@@ -127,9 +129,8 @@ pulse_output_set_volume(PulseOutput *po,
 					     pa_stream_get_index(po->stream),
 					     volume, nullptr, nullptr);
 	if (o == nullptr) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "failed to set PulseAudio volume: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+		SetError(error, po->context,
+			 "failed to set PulseAudio volume");
 		return false;
 	}
 
@@ -235,19 +236,15 @@ pulse_output_subscribe_cb(pa_context *context,
  * @return true on success, false on error
  */
 static bool
-pulse_output_connect(PulseOutput *po, GError **error_r)
+pulse_output_connect(PulseOutput *po, Error &error)
 {
 	assert(po != nullptr);
 	assert(po->context != nullptr);
 
-	int error;
-
-	error = pa_context_connect(po->context, po->server,
-				   (pa_context_flags_t)0, nullptr);
-	if (error < 0) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_context_connect() has failed: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+	if (pa_context_connect(po->context, po->server,
+			       (pa_context_flags_t)0, nullptr) < 0) {
+		SetError(error, po->context,
+			 "pa_context_connect() has failed");
 		return false;
 	}
 
@@ -300,7 +297,7 @@ pulse_output_delete_context(PulseOutput *po)
  * @return true on success, false on error
  */
 static bool
-pulse_output_setup_context(PulseOutput *po, GError **error_r)
+pulse_output_setup_context(PulseOutput *po, Error &error)
 {
 	assert(po != nullptr);
 	assert(po->mainloop != nullptr);
@@ -308,8 +305,7 @@ pulse_output_setup_context(PulseOutput *po, GError **error_r)
 	po->context = pa_context_new(pa_threaded_mainloop_get_api(po->mainloop),
 				     MPD_PULSE_NAME);
 	if (po->context == nullptr) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_context_new() has failed");
+		error.Set(pulse_output_domain, "pa_context_new() has failed");
 		return false;
 	}
 
@@ -318,7 +314,7 @@ pulse_output_setup_context(PulseOutput *po, GError **error_r)
 	pa_context_set_subscribe_callback(po->context,
 					  pulse_output_subscribe_cb, po);
 
-	if (!pulse_output_connect(po, error_r)) {
+	if (!pulse_output_connect(po, error)) {
 		pulse_output_delete_context(po);
 		return false;
 	}
@@ -327,14 +323,14 @@ pulse_output_setup_context(PulseOutput *po, GError **error_r)
 }
 
 static struct audio_output *
-pulse_output_init(const config_param &param, GError **error_r)
+pulse_output_init(const config_param &param, Error &error)
 {
 	PulseOutput *po;
 
 	g_setenv("PULSE_PROP_media.role", "music", true);
 
 	po = new PulseOutput();
-	if (!ao_base_init(&po->base, &pulse_output_plugin, param, error_r)) {
+	if (!ao_base_init(&po->base, &pulse_output_plugin, param, error)) {
 		delete po;
 		return nullptr;
 	}
@@ -361,7 +357,7 @@ pulse_output_finish(struct audio_output *ao)
 }
 
 static bool
-pulse_output_enable(struct audio_output *ao, GError **error_r)
+pulse_output_enable(struct audio_output *ao, Error &error)
 {
 	PulseOutput *po = (PulseOutput *)ao;
 
@@ -374,8 +370,8 @@ pulse_output_enable(struct audio_output *ao, GError **error_r)
 	if (po->mainloop == nullptr) {
 		g_free(po);
 
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_threaded_mainloop_new() has failed");
+		error.Set(pulse_output_domain,
+			  "pa_threaded_mainloop_new() has failed");
 		return false;
 	}
 
@@ -386,14 +382,14 @@ pulse_output_enable(struct audio_output *ao, GError **error_r)
 		pa_threaded_mainloop_free(po->mainloop);
 		po->mainloop = nullptr;
 
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_threaded_mainloop_start() has failed");
+		error.Set(pulse_output_domain,
+			  "pa_threaded_mainloop_start() has failed");
 		return false;
 	}
 
 	/* create the libpulse context and connect it */
 
-	if (!pulse_output_setup_context(po, error_r)) {
+	if (!pulse_output_setup_context(po, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
 		pa_threaded_mainloop_stop(po->mainloop);
 		pa_threaded_mainloop_free(po->mainloop);
@@ -429,13 +425,13 @@ pulse_output_disable(struct audio_output *ao)
  * @return true on success, false on error
  */
 static bool
-pulse_output_wait_connection(PulseOutput *po, GError **error_r)
+pulse_output_wait_connection(PulseOutput *po, Error &error)
 {
 	assert(po->mainloop != nullptr);
 
 	pa_context_state_t state;
 
-	if (po->context == nullptr && !pulse_output_setup_context(po, error_r))
+	if (po->context == nullptr && !pulse_output_setup_context(po, error))
 		return false;
 
 	while (true) {
@@ -449,9 +445,7 @@ pulse_output_wait_connection(PulseOutput *po, GError **error_r)
 		case PA_CONTEXT_TERMINATED:
 		case PA_CONTEXT_FAILED:
 			/* failure */
-			g_set_error(error_r, pulse_output_quark(), 0,
-				    "failed to connect: %s",
-				    pa_strerror(pa_context_errno(po->context)));
+			SetError(error, po->context, "failed to connect");
 			pulse_output_delete_context(po);
 			return false;
 
@@ -530,16 +524,14 @@ pulse_output_stream_write_cb(gcc_unused pa_stream *stream, size_t nbytes,
  */
 static bool
 pulse_output_setup_stream(PulseOutput *po, const pa_sample_spec *ss,
-			  GError **error_r)
+			  Error &error)
 {
 	assert(po != nullptr);
 	assert(po->context != nullptr);
 
 	po->stream = pa_stream_new(po->context, po->name, ss, nullptr);
 	if (po->stream == nullptr) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_stream_new() has failed: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+		SetError(error, po->context, "pa_stream_new() has failed");
 		return false;
 	}
 
@@ -556,11 +548,10 @@ pulse_output_setup_stream(PulseOutput *po, const pa_sample_spec *ss,
 
 static bool
 pulse_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		  GError **error_r)
+		  Error &error)
 {
 	PulseOutput *po = (PulseOutput *)ao;
 	pa_sample_spec ss;
-	int error;
 
 	assert(po->mainloop != nullptr);
 
@@ -585,7 +576,7 @@ pulse_output_open(struct audio_output *ao, AudioFormat &audio_format,
 		}
 	}
 
-	if (!pulse_output_wait_connection(po, error_r)) {
+	if (!pulse_output_wait_connection(po, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
 		return false;
 	}
@@ -600,22 +591,20 @@ pulse_output_open(struct audio_output *ao, AudioFormat &audio_format,
 
 	/* create a stream .. */
 
-	if (!pulse_output_setup_stream(po, &ss, error_r)) {
+	if (!pulse_output_setup_stream(po, &ss, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
 		return false;
 	}
 
 	/* .. and connect it (asynchronously) */
 
-	error = pa_stream_connect_playback(po->stream, po->sink,
-					   nullptr, pa_stream_flags_t(0),
-					   nullptr, nullptr);
-	if (error < 0) {
+	if (pa_stream_connect_playback(po->stream, po->sink,
+				       nullptr, pa_stream_flags_t(0),
+				       nullptr, nullptr) < 0) {
 		pulse_output_delete_stream(po);
 
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_stream_connect_playback() has failed: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+		SetError(error, po->context,
+			 "pa_stream_connect_playback() has failed");
 		pa_threaded_mainloop_unlock(po->mainloop);
 		return false;
 	}
@@ -661,7 +650,7 @@ pulse_output_close(struct audio_output *ao)
  * @return true on success, false on error
  */
 static bool
-pulse_output_wait_stream(PulseOutput *po, GError **error_r)
+pulse_output_wait_stream(PulseOutput *po, Error &error)
 {
 	while (true) {
 		switch (pa_stream_get_state(po->stream)) {
@@ -671,10 +660,8 @@ pulse_output_wait_stream(PulseOutput *po, GError **error_r)
 		case PA_STREAM_FAILED:
 		case PA_STREAM_TERMINATED:
 		case PA_STREAM_UNCONNECTED:
-			g_set_error(error_r, pulse_output_quark(),
-				    pa_context_errno(po->context),
-				    "failed to connect the stream: %s",
-				    pa_strerror(pa_context_errno(po->context)));
+			SetError(error, po->context,
+				 "failed to connect the stream");
 			return false;
 
 		case PA_STREAM_CREATING:
@@ -689,7 +676,7 @@ pulse_output_wait_stream(PulseOutput *po, GError **error_r)
  */
 static bool
 pulse_output_stream_pause(PulseOutput *po, bool pause,
-			  GError **error_r)
+			  Error &error)
 {
 	pa_operation *o;
 
@@ -700,16 +687,12 @@ pulse_output_stream_pause(PulseOutput *po, bool pause,
 	o = pa_stream_cork(po->stream, pause,
 			   pulse_output_stream_success_cb, po);
 	if (o == nullptr) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_stream_cork() has failed: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+		SetError(error, po->context, "pa_stream_cork() has failed");
 		return false;
 	}
 
 	if (!pulse_wait_for_operation(po->mainloop, o)) {
-		g_set_error(error_r, pulse_output_quark(), 0,
-			    "pa_stream_cork() has failed: %s",
-			    pa_strerror(pa_context_errno(po->context)));
+		SetError(error, po->context, "pa_stream_cork() has failed");
 		return false;
 	}
 
@@ -736,10 +719,9 @@ pulse_output_delay(struct audio_output *ao)
 
 static size_t
 pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		  GError **error_r)
+		  Error &error)
 {
 	PulseOutput *po = (PulseOutput *)ao;
-	int error;
 
 	assert(po->mainloop != nullptr);
 	assert(po->stream != nullptr);
@@ -748,7 +730,7 @@ pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
 
 	/* check if the stream is (already) connected */
 
-	if (!pulse_output_wait_stream(po, error_r)) {
+	if (!pulse_output_wait_stream(po, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
 		return 0;
 	}
@@ -758,7 +740,7 @@ pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
 	/* unpause if previously paused */
 
 	if (pa_stream_is_corked(po->stream) &&
-	    !pulse_output_stream_pause(po, false, error_r)) {
+	    !pulse_output_stream_pause(po, false, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
 		return 0;
 	}
@@ -768,8 +750,7 @@ pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
 	while (po->writable == 0) {
 		if (pa_stream_is_suspended(po->stream)) {
 			pa_threaded_mainloop_unlock(po->mainloop);
-			g_set_error(error_r, pulse_output_quark(), 0,
-				    "suspended");
+			error.Set(pulse_output_domain, "suspended");
 			return 0;
 		}
 
@@ -777,8 +758,7 @@ pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
 
 		if (pa_stream_get_state(po->stream) != PA_STREAM_READY) {
 			pa_threaded_mainloop_unlock(po->mainloop);
-			g_set_error(error_r, pulse_output_quark(), 0,
-				    "disconnected");
+			error.Set(pulse_output_domain, "disconnected");
 			return 0;
 		}
 	}
@@ -791,12 +771,11 @@ pulse_output_play(struct audio_output *ao, const void *chunk, size_t size,
 
 	po->writable -= size;
 
-	error = pa_stream_write(po->stream, chunk, size, nullptr,
-				0, PA_SEEK_RELATIVE);
+	int result = pa_stream_write(po->stream, chunk, size, nullptr,
+				     0, PA_SEEK_RELATIVE);
 	pa_threaded_mainloop_unlock(po->mainloop);
-	if (error < 0) {
-		g_set_error(error_r, pulse_output_quark(), error,
-			    "%s", pa_strerror(error));
+	if (result < 0) {
+		SetError(error, po->context, "pa_stream_write() failed");
 		return 0;
 	}
 
@@ -839,7 +818,6 @@ static bool
 pulse_output_pause(struct audio_output *ao)
 {
 	PulseOutput *po = (PulseOutput *)ao;
-	GError *error = nullptr;
 
 	assert(po->mainloop != nullptr);
 	assert(po->stream != nullptr);
@@ -848,10 +826,10 @@ pulse_output_pause(struct audio_output *ao)
 
 	/* check if the stream is (already/still) connected */
 
-	if (!pulse_output_wait_stream(po, &error)) {
+	Error error;
+	if (!pulse_output_wait_stream(po, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return false;
 	}
 
@@ -860,10 +838,9 @@ pulse_output_pause(struct audio_output *ao)
 	/* cork the stream */
 
 	if (!pa_stream_is_corked(po->stream) &&
-	    !pulse_output_stream_pause(po, true, &error)) {
+	    !pulse_output_stream_pause(po, true, error)) {
 		pa_threaded_mainloop_unlock(po->mainloop);
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return false;
 	}
 
@@ -878,11 +855,12 @@ pulse_output_test_default_device(void)
 	bool success;
 
 	const config_param empty;
-	PulseOutput *po = (PulseOutput *)pulse_output_init(empty, nullptr);
+	PulseOutput *po = (PulseOutput *)
+		pulse_output_init(empty, IgnoreError());
 	if (po == nullptr)
 		return false;
 
-	success = pulse_output_wait_connection(po, nullptr);
+	success = pulse_output_wait_connection(po, IgnoreError());
 	pulse_output_finish(&po->base);
 
 	return success;
diff --git a/src/output/PulseOutputPlugin.hxx b/src/output/PulseOutputPlugin.hxx
index 278969f8d..0ed8404bc 100644
--- a/src/output/PulseOutputPlugin.hxx
+++ b/src/output/PulseOutputPlugin.hxx
@@ -20,11 +20,10 @@
 #ifndef MPD_PULSE_OUTPUT_PLUGIN_HXX
 #define MPD_PULSE_OUTPUT_PLUGIN_HXX
 
-#include "gerror.h"
-
 struct PulseOutput;
 struct PulseMixer;
 struct pa_cvolume;
+class Error;
 
 extern const struct audio_output_plugin pulse_output_plugin;
 
@@ -42,6 +41,6 @@ pulse_output_clear_mixer(PulseOutput *po, PulseMixer *pm);
 
 bool
 pulse_output_set_volume(PulseOutput *po,
-			const struct pa_cvolume *volume, GError **error_r);
+			const struct pa_cvolume *volume, Error &error);
 
 #endif
diff --git a/src/output/RecorderOutputPlugin.cxx b/src/output/RecorderOutputPlugin.cxx
index 9374e4c20..31c378c56 100644
--- a/src/output/RecorderOutputPlugin.cxx
+++ b/src/output/RecorderOutputPlugin.cxx
@@ -22,6 +22,9 @@
 #include "OutputAPI.hxx"
 #include "EncoderPlugin.hxx"
 #include "EncoderList.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "system/fd_util.h"
 #include "open.h"
 
@@ -57,7 +60,7 @@ struct RecorderOutput {
 	 */
 	char buffer[32768];
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error_r) {
 		return ao_base_init(&base, &recorder_output_plugin, param,
 				    error_r);
 	}
@@ -66,27 +69,20 @@ struct RecorderOutput {
 		ao_base_finish(&base);
 	}
 
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 
-	bool WriteToFile(const void *data, size_t length, GError **error_r);
+	bool WriteToFile(const void *data, size_t length, Error &error);
 
 	/**
 	 * Writes pending data from the encoder to the output file.
 	 */
-	bool EncoderToFile(GError **error_r);
+	bool EncoderToFile(Error &error);
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-recorder_output_quark(void)
-{
-	return g_quark_from_static_string("recorder_output");
-}
+static constexpr Domain recorder_output_domain("recorder_output");
 
 inline bool
-RecorderOutput::Configure(const config_param &param, GError **error_r)
+RecorderOutput::Configure(const config_param &param, Error &error)
 {
 	/* read configuration */
 
@@ -94,21 +90,20 @@ RecorderOutput::Configure(const config_param &param, GError **error_r)
 		param.GetBlockValue("encoder", "vorbis");
 	const auto encoder_plugin = encoder_plugin_get(encoder_name);
 	if (encoder_plugin == nullptr) {
-		g_set_error(error_r, recorder_output_quark(), 0,
-			    "No such encoder: %s", encoder_name);
+		error.Format(config_domain,
+			     "No such encoder: %s", encoder_name);
 		return false;
 	}
 
 	path = param.GetBlockValue("path");
 	if (path == nullptr) {
-		g_set_error(error_r, recorder_output_quark(), 0,
-			    "'path' not configured");
+		error.Set(config_domain, "'path' not configured");
 		return false;
 	}
 
 	/* initialize encoder */
 
-	encoder = encoder_init(*encoder_plugin, param, error_r);
+	encoder = encoder_init(*encoder_plugin, param, error);
 	if (encoder == nullptr)
 		return false;
 
@@ -116,16 +111,16 @@ RecorderOutput::Configure(const config_param &param, GError **error_r)
 }
 
 static audio_output *
-recorder_output_init(const config_param &param, GError **error_r)
+recorder_output_init(const config_param &param, Error &error)
 {
 	RecorderOutput *recorder = new RecorderOutput();
 
-	if (!recorder->Initialize(param, error_r)) {
+	if (!recorder->Initialize(param, error)) {
 		delete recorder;
 		return nullptr;
 	}
 
-	if (!recorder->Configure(param, error_r)) {
+	if (!recorder->Configure(param, error)) {
 		recorder->Deinitialize();
 		delete recorder;
 		return nullptr;
@@ -145,7 +140,7 @@ recorder_output_finish(struct audio_output *ao)
 }
 
 inline bool
-RecorderOutput::WriteToFile(const void *_data, size_t length, GError **error_r)
+RecorderOutput::WriteToFile(const void *_data, size_t length, Error &error)
 {
 	assert(length > 0);
 
@@ -159,20 +154,18 @@ RecorderOutput::WriteToFile(const void *_data, size_t length, GError **error_r)
 				return true;
 		} else if (nbytes == 0) {
 			/* shouldn't happen for files */
-			g_set_error(error_r, recorder_output_quark(), 0,
-				    "write() returned 0");
+			error.Set(recorder_output_domain,
+				  "write() returned 0");
 			return false;
 		} else if (errno != EINTR) {
-			g_set_error(error_r, recorder_output_quark(), 0,
-				    "Failed to write to '%s': %s",
-				    path, g_strerror(errno));
+			error.FormatErrno("Failed to write to '%s'", path);
 			return false;
 		}
 	}
 }
 
 inline bool
-RecorderOutput::EncoderToFile(GError **error_r)
+RecorderOutput::EncoderToFile(Error &error)
 {
 	assert(fd >= 0);
 
@@ -185,7 +178,7 @@ RecorderOutput::EncoderToFile(GError **error_r)
 
 		/* write everything into the file */
 
-		if (!WriteToFile(buffer, size, error_r))
+		if (!WriteToFile(buffer, size, error))
 			return false;
 	}
 }
@@ -193,7 +186,7 @@ RecorderOutput::EncoderToFile(GError **error_r)
 static bool
 recorder_output_open(struct audio_output *ao,
 		     AudioFormat &audio_format,
-		     GError **error_r)
+		     Error &error)
 {
 	RecorderOutput *recorder = (RecorderOutput *)ao;
 
@@ -203,21 +196,19 @@ recorder_output_open(struct audio_output *ao,
 				    O_CREAT|O_WRONLY|O_TRUNC|O_BINARY,
 				    0666);
 	if (recorder->fd < 0) {
-		g_set_error(error_r, recorder_output_quark(), 0,
-			    "Failed to create '%s': %s",
-			    recorder->path, g_strerror(errno));
+		error.FormatErrno("Failed to create '%s'", recorder->path);
 		return false;
 	}
 
 	/* open the encoder */
 
-	if (!encoder_open(recorder->encoder, audio_format, error_r)) {
+	if (!encoder_open(recorder->encoder, audio_format, error)) {
 		close(recorder->fd);
 		unlink(recorder->path);
 		return false;
 	}
 
-	if (!recorder->EncoderToFile(error_r)) {
+	if (!recorder->EncoderToFile(error)) {
 		encoder_close(recorder->encoder);
 		close(recorder->fd);
 		unlink(recorder->path);
@@ -234,8 +225,8 @@ recorder_output_close(struct audio_output *ao)
 
 	/* flush the encoder and write the rest to the file */
 
-	if (encoder_end(recorder->encoder, nullptr))
-		recorder->EncoderToFile(nullptr);
+	if (encoder_end(recorder->encoder, IgnoreError()))
+		recorder->EncoderToFile(IgnoreError());
 
 	/* now really close everything */
 
@@ -246,12 +237,12 @@ recorder_output_close(struct audio_output *ao)
 
 static size_t
 recorder_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		     GError **error_r)
+		     Error &error)
 {
 	RecorderOutput *recorder = (RecorderOutput *)ao;
 
-	return encoder_write(recorder->encoder, chunk, size, error_r) &&
-		recorder->EncoderToFile(error_r)
+	return encoder_write(recorder->encoder, chunk, size, error) &&
+		recorder->EncoderToFile(error)
 		? size : 0;
 }
 
diff --git a/src/output/RoarOutputPlugin.cxx b/src/output/RoarOutputPlugin.cxx
index 36f7c395b..f6d261372 100644
--- a/src/output/RoarOutputPlugin.cxx
+++ b/src/output/RoarOutputPlugin.cxx
@@ -23,6 +23,8 @@
 #include "OutputAPI.hxx"
 #include "MixerList.hxx"
 #include "thread/Mutex.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -58,11 +60,7 @@ struct RoarOutput {
 	}
 };
 
-static inline GQuark
-roar_output_quark(void)
-{
-	return g_quark_from_static_string("roar_output");
-}
+static constexpr Domain roar_output_domain("roar_output");
 
 static int
 roar_output_get_volume_locked(RoarOutput *roar)
@@ -120,11 +118,11 @@ roar_configure(RoarOutput *self, const config_param &param)
 }
 
 static struct audio_output *
-roar_init(const config_param &param, GError **error_r)
+roar_init(const config_param &param, Error &error)
 {
 	RoarOutput *self = new RoarOutput();
 
-	if (!ao_base_init(&self->base, &roar_output_plugin, param, error_r)) {
+	if (!ao_base_init(&self->base, &roar_output_plugin, param, error)) {
 		delete self;
 		return nullptr;
 	}
@@ -178,15 +176,15 @@ roar_use_audio_format(struct roar_audio_info *info,
 }
 
 static bool
-roar_open(struct audio_output *ao, AudioFormat &audio_format, GError **error)
+roar_open(struct audio_output *ao, AudioFormat &audio_format, Error &error)
 {
 	RoarOutput *self = (RoarOutput *)ao;
 	const ScopeLock protect(self->mutex);
 
 	if (roar_simple_connect(&(self->con), self->host, self->name) < 0)
 	{
-		g_set_error(error, roar_output_quark(), 0,
-				"Failed to connect to Roar server");
+		error.Set(roar_output_domain,
+			  "Failed to connect to Roar server");
 		return false;
 	}
 
@@ -194,8 +192,7 @@ roar_open(struct audio_output *ao, AudioFormat &audio_format, GError **error)
 
 	if (self->vss == nullptr || self->err != ROAR_ERROR_NONE)
 	{
-		g_set_error(error, roar_output_quark(), 0,
-				"Failed to connect to server");
+		error.Set(roar_output_domain, "Failed to connect to server");
 		return false;
 	}
 
@@ -204,7 +201,7 @@ roar_open(struct audio_output *ao, AudioFormat &audio_format, GError **error)
 	if (roar_vs_stream(self->vss, &(self->info), ROAR_DIR_PLAY,
 				&(self->err)) < 0)
 	{
-		g_set_error(error, roar_output_quark(), 0, "Failed to start stream");
+		error.Set(roar_output_domain, "Failed to start stream");
 		return false;
 	}
 	roar_vs_role(self->vss, self->role, &(self->err));
@@ -264,21 +261,22 @@ roar_cancel(struct audio_output *ao)
 }
 
 static size_t
-roar_play(struct audio_output *ao, const void *chunk, size_t size, GError **error)
+roar_play(struct audio_output *ao, const void *chunk, size_t size,
+	  Error &error)
 {
 	RoarOutput *self = (RoarOutput *)ao;
 	ssize_t rc;
 
 	if (self->vss == nullptr)
 	{
-		g_set_error(error, roar_output_quark(), 0, "Connection is invalid");
+		error.Set(roar_output_domain, "Connection is invalid");
 		return 0;
 	}
 
 	rc = roar_vs_write(self->vss, chunk, size, &(self->err));
 	if ( rc <= 0 )
 	{
-		g_set_error(error, roar_output_quark(), 0, "Failed to play data");
+		error.Set(roar_output_domain, "Failed to play data");
 		return 0;
 	}
 
diff --git a/src/output/ShoutOutputPlugin.cxx b/src/output/ShoutOutputPlugin.cxx
index 40f468031..82b61f7c8 100644
--- a/src/output/ShoutOutputPlugin.cxx
+++ b/src/output/ShoutOutputPlugin.cxx
@@ -22,6 +22,9 @@
 #include "OutputAPI.hxx"
 #include "EncoderPlugin.hxx"
 #include "EncoderList.hxx"
+#include "ConfigError.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 #include "mpd_error.h"
 
 #include <shout/shout.h>
@@ -66,28 +69,21 @@ struct ShoutOutput final {
 			shout_free(shout_conn);
 	}
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error) {
 		return ao_base_init(&base, &shout_output_plugin, param,
-				    error_r);
+				    error);
 	}
 
 	void Deinitialize() {
 		ao_base_finish(&base);
 	}
 
-	bool Configure(const config_param &param, GError **error_r);
+	bool Configure(const config_param &param, Error &error);
 };
 
 static int shout_init_count;
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-shout_output_quark(void)
-{
-	return g_quark_from_static_string("shout_output");
-}
+static constexpr Domain shout_output_domain("shout_output");
 
 static const EncoderPlugin *
 shout_encoder_plugin_get(const char *name)
@@ -113,13 +109,13 @@ require_block_string(const config_param &param, const char *name)
 }
 
 inline bool
-ShoutOutput::Configure(const config_param &param, GError **error_r)
+ShoutOutput::Configure(const config_param &param, Error &error)
 {
 
 	const AudioFormat audio_format = base.config_audio_format;
 	if (!audio_format.IsFullyDefined()) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "Need full audio format specification");
+		error.Set(config_domain,
+			  "Need full audio format specification");
 		return nullptr;
 	}
 
@@ -127,8 +123,7 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 	const char *mount = require_block_string(param, "mount");
 	unsigned port = param.GetBlockValue("port", 0u);
 	if (port == 0) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "shout port must be configured");
+		error.Set(config_domain, "shout port must be configured");
 		return false;
 	}
 
@@ -145,24 +140,24 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 		quality = strtod(value, &test);
 
 		if (*test != '\0' || quality < -1.0 || quality > 10.0) {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "shout quality \"%s\" is not a number in the "
-				    "range -1 to 10, line %i",
-				    value, param.line);
+			error.Format(config_domain,
+				     "shout quality \"%s\" is not a number in the "
+				     "range -1 to 10, line %i",
+				     value, param.line);
 			return false;
 		}
 
 		if (param.GetBlockValue("bitrate") != nullptr) {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "quality and bitrate are "
-				    "both defined");
+			error.Set(config_domain,
+				  "quality and bitrate are "
+				  "both defined");
 			return false;
 		}
 	} else {
 		value = param.GetBlockValue("bitrate");
 		if (value == nullptr) {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "neither bitrate nor quality defined");
+			error.Set(config_domain,
+				  "neither bitrate nor quality defined");
 			return false;
 		}
 
@@ -170,8 +165,8 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 		bitrate = strtol(value, &test, 10);
 
 		if (*test != '\0' || bitrate <= 0) {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "bitrate must be a positive integer");
+			error.Set(config_domain,
+				  "bitrate must be a positive integer");
 			return false;
 		}
 	}
@@ -179,13 +174,13 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 	const char *encoding = param.GetBlockValue("encoding", "ogg");
 	const auto encoder_plugin = shout_encoder_plugin_get(encoding);
 	if (encoder_plugin == nullptr) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "couldn't find shout encoder plugin \"%s\"",
-			    encoding);
+		error.Format(config_domain,
+			     "couldn't find shout encoder plugin \"%s\"",
+			     encoding);
 		return false;
 	}
 
-	encoder = encoder_init(*encoder_plugin, param, error_r);
+	encoder = encoder_init(*encoder_plugin, param, error);
 	if (encoder == nullptr)
 		return false;
 
@@ -200,9 +195,9 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 	if (value != nullptr) {
 		if (0 == strcmp(value, "shoutcast") &&
 		    0 != strcmp(encoding, "mp3")) {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "you cannot stream \"%s\" to shoutcast, use mp3",
-				    encoding);
+			error.Format(config_domain,
+				     "you cannot stream \"%s\" to shoutcast, use mp3",
+				     encoding);
 			return false;
 		} else if (0 == strcmp(value, "shoutcast"))
 			protocol = SHOUT_PROTOCOL_ICY;
@@ -211,10 +206,10 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 		else if (0 == strcmp(value, "icecast2"))
 			protocol = SHOUT_PROTOCOL_HTTP;
 		else {
-			g_set_error(error_r, shout_output_quark(), 0,
-				    "shout protocol \"%s\" is not \"shoutcast\" or "
-				    "\"icecast1\"or \"icecast2\"",
-				    value);
+			error.Format(config_domain,
+				     "shout protocol \"%s\" is not \"shoutcast\" or "
+				     "\"icecast1\"or \"icecast2\"",
+				     value);
 			return false;
 		}
 	} else {
@@ -232,8 +227,7 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 	    != SHOUTERR_SUCCESS ||
 	    shout_set_protocol(shout_conn, protocol) != SHOUTERR_SUCCESS ||
 	    shout_set_agent(shout_conn, "MPD") != SHOUTERR_SUCCESS) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "%s", shout_get_error(shout_conn));
+		error.Set(shout_output_domain, shout_get_error(shout_conn));
 		return false;
 	}
 
@@ -242,22 +236,19 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 
 	value = param.GetBlockValue("genre");
 	if (value != nullptr && shout_set_genre(shout_conn, value)) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "%s", shout_get_error(shout_conn));
+		error.Set(shout_output_domain, shout_get_error(shout_conn));
 		return false;
 	}
 
 	value = param.GetBlockValue("description");
 	if (value != nullptr && shout_set_description(shout_conn, value)) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "%s", shout_get_error(shout_conn));
+		error.Set(shout_output_domain, shout_get_error(shout_conn));
 		return false;
 	}
 
 	value = param.GetBlockValue("url");
 	if (value != nullptr && shout_set_url(shout_conn, value)) {
-		g_set_error(error_r, shout_output_quark(), 0,
-			    "%s", shout_get_error(shout_conn));
+		error.Set(shout_output_domain, shout_get_error(shout_conn));
 		return false;
 	}
 
@@ -287,15 +278,15 @@ ShoutOutput::Configure(const config_param &param, GError **error_r)
 }
 
 static struct audio_output *
-my_shout_init_driver(const config_param &param, GError **error_r)
+my_shout_init_driver(const config_param &param, Error &error)
 {
 	ShoutOutput *sd = new ShoutOutput();
-	if (!sd->Initialize(param, error_r)) {
+	if (!sd->Initialize(param, error)) {
 		delete sd;
 		return nullptr;
 	}
 
-	if (!sd->Configure(param, error_r)) {
+	if (!sd->Configure(param, error)) {
 		sd->Deinitialize();
 		delete sd;
 		return nullptr;
@@ -310,7 +301,7 @@ my_shout_init_driver(const config_param &param, GError **error_r)
 }
 
 static bool
-handle_shout_error(ShoutOutput *sd, int err, GError **error)
+handle_shout_error(ShoutOutput *sd, int err, Error &error)
 {
 	switch (err) {
 	case SHOUTERR_SUCCESS:
@@ -318,19 +309,19 @@ handle_shout_error(ShoutOutput *sd, int err, GError **error)
 
 	case SHOUTERR_UNCONNECTED:
 	case SHOUTERR_SOCKET:
-		g_set_error(error, shout_output_quark(), err,
-			    "Lost shout connection to %s:%i: %s",
-			    shout_get_host(sd->shout_conn),
-			    shout_get_port(sd->shout_conn),
-			    shout_get_error(sd->shout_conn));
+		error.Format(shout_output_domain, err,
+			     "Lost shout connection to %s:%i: %s",
+			     shout_get_host(sd->shout_conn),
+			     shout_get_port(sd->shout_conn),
+			     shout_get_error(sd->shout_conn));
 		return false;
 
 	default:
-		g_set_error(error, shout_output_quark(), err,
-			    "connection to %s:%i error: %s",
-			    shout_get_host(sd->shout_conn),
-			    shout_get_port(sd->shout_conn),
-			    shout_get_error(sd->shout_conn));
+		error.Format(shout_output_domain, err,
+			     "connection to %s:%i error: %s",
+			     shout_get_host(sd->shout_conn),
+			     shout_get_port(sd->shout_conn),
+			     shout_get_error(sd->shout_conn));
 		return false;
 	}
 
@@ -338,7 +329,7 @@ handle_shout_error(ShoutOutput *sd, int err, GError **error)
 }
 
 static bool
-write_page(ShoutOutput *sd, GError **error)
+write_page(ShoutOutput *sd, Error &error)
 {
 	assert(sd->encoder != nullptr);
 
@@ -359,8 +350,8 @@ write_page(ShoutOutput *sd, GError **error)
 static void close_shout_conn(ShoutOutput * sd)
 {
 	if (sd->encoder != nullptr) {
-		if (encoder_end(sd->encoder, nullptr))
-			write_page(sd, nullptr);
+		if (encoder_end(sd->encoder, IgnoreError()))
+			write_page(sd, IgnoreError());
 
 		encoder_close(sd->encoder);
 	}
@@ -406,7 +397,7 @@ my_shout_close_device(struct audio_output *ao)
 }
 
 static bool
-shout_connect(ShoutOutput *sd, GError **error)
+shout_connect(ShoutOutput *sd, Error &error)
 {
 	switch (shout_open(sd->shout_conn)) {
 	case SHOUTERR_SUCCESS:
@@ -414,18 +405,18 @@ shout_connect(ShoutOutput *sd, GError **error)
 		return true;
 
 	default:
-		g_set_error(error, shout_output_quark(), 0,
-			    "problem opening connection to shout server %s:%i: %s",
-			    shout_get_host(sd->shout_conn),
-			    shout_get_port(sd->shout_conn),
-			    shout_get_error(sd->shout_conn));
+		error.Format(shout_output_domain,
+			     "problem opening connection to shout server %s:%i: %s",
+			     shout_get_host(sd->shout_conn),
+			     shout_get_port(sd->shout_conn),
+			     shout_get_error(sd->shout_conn));
 		return false;
 	}
 }
 
 static bool
 my_shout_open_device(struct audio_output *ao, AudioFormat &audio_format,
-		     GError **error)
+		     Error &error)
 {
 	ShoutOutput *sd = (ShoutOutput *)ao;
 
@@ -460,7 +451,7 @@ my_shout_delay(struct audio_output *ao)
 
 static size_t
 my_shout_play(struct audio_output *ao, const void *chunk, size_t size,
-	      GError **error)
+	      Error &error)
 {
 	ShoutOutput *sd = (ShoutOutput *)ao;
 
@@ -475,7 +466,7 @@ my_shout_pause(struct audio_output *ao)
 {
 	static char silence[1020];
 
-	return my_shout_play(ao, silence, sizeof(silence), nullptr);
+	return my_shout_play(ao, silence, sizeof(silence), IgnoreError());
 }
 
 static void
@@ -508,24 +499,17 @@ static void my_shout_set_tag(struct audio_output *ao,
 			     const Tag *tag)
 {
 	ShoutOutput *sd = (ShoutOutput *)ao;
-	GError *error = nullptr;
 
 	if (sd->encoder->plugin.tag != nullptr) {
 		/* encoder plugin supports stream tags */
 
-		if (!encoder_pre_tag(sd->encoder, &error)) {
-			g_warning("%s", error->message);
-			g_error_free(error);
+		Error error;
+		if (!encoder_pre_tag(sd->encoder, error) ||
+		    !write_page(sd, error) ||
+		    !encoder_tag(sd->encoder, tag, error)) {
+			g_warning("%s", error.GetMessage());
 			return;
 		}
-
-		if (!write_page(sd, nullptr))
-			return;
-
-		if (!encoder_tag(sd->encoder, tag, &error)) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
 	} else {
 		/* no stream tag support: fall back to icy-metadata */
 		char song[1024];
@@ -538,7 +522,7 @@ static void my_shout_set_tag(struct audio_output *ao,
 		}
 	}
 
-	write_page(sd, nullptr);
+	write_page(sd, IgnoreError());
 }
 
 const struct audio_output_plugin shout_output_plugin = {
diff --git a/src/output/SolarisOutputPlugin.cxx b/src/output/SolarisOutputPlugin.cxx
index aa2f853e6..e3428cbc2 100644
--- a/src/output/SolarisOutputPlugin.cxx
+++ b/src/output/SolarisOutputPlugin.cxx
@@ -21,8 +21,7 @@
 #include "SolarisOutputPlugin.hxx"
 #include "OutputAPI.hxx"
 #include "system/fd_util.h"
-
-#include <glib.h>
+#include "util/Error.hxx"
 
 #include <sys/stropts.h>
 #include <sys/types.h>
@@ -61,7 +60,7 @@ struct SolarisOutput {
 
 	int fd;
 
-	bool Initialize(const config_param &param, GError **error_r) {
+	bool Initialize(const config_param &param, Error &error_r) {
 		return ao_base_init(&base, &solaris_output_plugin, param,
 				    error_r);
 	}
@@ -71,15 +70,6 @@ struct SolarisOutput {
 	}
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-solaris_output_quark(void)
-{
-	return g_quark_from_static_string("solaris_output");
-}
-
 static bool
 solaris_output_test_default_device(void)
 {
@@ -90,7 +80,7 @@ solaris_output_test_default_device(void)
 }
 
 static struct audio_output *
-solaris_output_init(const config_param &param, GError **error_r)
+solaris_output_init(const config_param &param, Error &error_r)
 {
 	SolarisOutput *so = new SolarisOutput();
 	if (!so->Initialize(param, error_r)) {
@@ -114,7 +104,7 @@ solaris_output_finish(struct audio_output *ao)
 
 static bool
 solaris_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		    GError **error)
+		    Error &error)
 {
 	SolarisOutput *so = (SolarisOutput *)ao;
 	struct audio_info info;
@@ -128,9 +118,8 @@ solaris_output_open(struct audio_output *ao, AudioFormat &audio_format,
 
 	so->fd = open_cloexec(so->device, O_WRONLY|O_NONBLOCK, 0);
 	if (so->fd < 0) {
-		g_set_error(error, solaris_output_quark(), errno,
-			    "Failed to open %s: %s",
-			    so->device, g_strerror(errno));
+		error.FormatErrno("Failed to open %s",
+				  so->device);
 		return false;
 	}
 
@@ -144,8 +133,7 @@ solaris_output_open(struct audio_output *ao, AudioFormat &audio_format,
 
 	ret = ioctl(so->fd, AUDIO_GETINFO, &info);
 	if (ret < 0) {
-		g_set_error(error, solaris_output_quark(), errno,
-			    "AUDIO_GETINFO failed: %s", g_strerror(errno));
+		error.SetErrno("AUDIO_GETINFO failed");
 		close(so->fd);
 		return false;
 	}
@@ -157,8 +145,7 @@ solaris_output_open(struct audio_output *ao, AudioFormat &audio_format,
 
 	ret = ioctl(so->fd, AUDIO_SETINFO, &info);
 	if (ret < 0) {
-		g_set_error(error, solaris_output_quark(), errno,
-			    "AUDIO_SETINFO failed: %s", g_strerror(errno));
+		error.SetErrno("AUDIO_SETINFO failed");
 		close(so->fd);
 		return false;
 	}
@@ -176,15 +163,14 @@ solaris_output_close(struct audio_output *ao)
 
 static size_t
 solaris_output_play(struct audio_output *ao, const void *chunk, size_t size,
-		    GError **error)
+		    Error &error)
 {
 	SolarisOutput *so = (SolarisOutput *)ao;
 	ssize_t nbytes;
 
 	nbytes = write(so->fd, chunk, size);
 	if (nbytes <= 0) {
-		g_set_error(error, solaris_output_quark(), errno,
-			    "Write failed: %s", g_strerror(errno));
+		error.SetErrno("Write failed");
 		return 0;
 	}
 
diff --git a/src/output/WinmmOutputPlugin.cxx b/src/output/WinmmOutputPlugin.cxx
index d02b52c58..7d81576e8 100644
--- a/src/output/WinmmOutputPlugin.cxx
+++ b/src/output/WinmmOutputPlugin.cxx
@@ -22,6 +22,8 @@
 #include "OutputAPI.hxx"
 #include "pcm/PcmBuffer.hxx"
 #include "MixerList.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <stdlib.h>
 #include <string.h>
@@ -51,14 +53,7 @@ struct WinmmOutput {
 	unsigned next_buffer;
 };
 
-/**
- * The quark used for GError.domain.
- */
-static inline GQuark
-winmm_output_quark(void)
-{
-	return g_quark_from_static_string("winmm_output");
-}
+static constexpr Domain winmm_output_domain("winmm_output");
 
 HWAVEOUT
 winmm_output_get_handle(WinmmOutput *output)
@@ -73,7 +68,7 @@ winmm_output_test_default_device(void)
 }
 
 static bool
-get_device_id(const char *device_name, UINT *device_id, GError **error_r)
+get_device_id(const char *device_name, UINT *device_id, Error &error)
 {
 	/* if device is not specified use wave mapper */
 	if (device_name == nullptr) {
@@ -108,22 +103,22 @@ get_device_id(const char *device_name, UINT *device_id, GError **error_r)
 	}
 
 fail:
-	g_set_error(error_r, winmm_output_quark(), 0,
-		    "device \"%s\" is not found", device_name);
+	error.Format(winmm_output_domain,
+		     "device \"%s\" is not found", device_name);
 	return false;
 }
 
 static struct audio_output *
-winmm_output_init(const config_param &param, GError **error_r)
+winmm_output_init(const config_param &param, Error &error)
 {
 	WinmmOutput *wo = new WinmmOutput();
-	if (!ao_base_init(&wo->base, &winmm_output_plugin, param, error_r)) {
+	if (!ao_base_init(&wo->base, &winmm_output_plugin, param, error)) {
 		g_free(wo);
 		return nullptr;
 	}
 
 	const char *device = param.GetBlockValue("device");
-	if (!get_device_id(device, &wo->device_id, error_r)) {
+	if (!get_device_id(device, &wo->device_id, error)) {
 		ao_base_finish(&wo->base);
 		g_free(wo);
 		return nullptr;
@@ -143,14 +138,13 @@ winmm_output_finish(struct audio_output *ao)
 
 static bool
 winmm_output_open(struct audio_output *ao, AudioFormat &audio_format,
-		  GError **error_r)
+		  Error &error)
 {
 	WinmmOutput *wo = (WinmmOutput *)ao;
 
 	wo->event = CreateEvent(nullptr, false, false, nullptr);
 	if (wo->event == nullptr) {
-		g_set_error(error_r, winmm_output_quark(), 0,
-			    "CreateEvent() failed");
+		error.Set(winmm_output_domain, "CreateEvent() failed");
 		return false;
 	}
 
@@ -186,8 +180,7 @@ winmm_output_open(struct audio_output *ao, AudioFormat &audio_format,
 				      (DWORD_PTR)wo->event, 0, CALLBACK_EVENT);
 	if (result != MMSYSERR_NOERROR) {
 		CloseHandle(wo->event);
-		g_set_error(error_r, winmm_output_quark(), result,
-			    "waveOutOpen() failed");
+		error.Set(winmm_output_domain, "waveOutOpen() failed");
 		return false;
 	}
 
@@ -219,7 +212,7 @@ winmm_output_close(struct audio_output *ao)
 static bool
 winmm_set_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
 		 const void *data, size_t size,
-		 GError **error_r)
+		 Error &error)
 {
 	void *dest = buffer->buffer.Get(size);
 	assert(dest != nullptr);
@@ -233,8 +226,8 @@ winmm_set_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
 	MMRESULT result = waveOutPrepareHeader(wo->handle, &buffer->hdr,
 					       sizeof(buffer->hdr));
 	if (result != MMSYSERR_NOERROR) {
-		g_set_error(error_r, winmm_output_quark(), result,
-			    "waveOutPrepareHeader() failed");
+		error.Set(winmm_output_domain, result,
+			  "waveOutPrepareHeader() failed");
 		return false;
 	}
 
@@ -246,7 +239,7 @@ winmm_set_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
  */
 static bool
 winmm_drain_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
-		   GError **error_r)
+		   Error &error)
 {
 	if ((buffer->hdr.dwFlags & WHDR_DONE) == WHDR_DONE)
 		/* already finished */
@@ -259,8 +252,8 @@ winmm_drain_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
 		if (result == MMSYSERR_NOERROR)
 			return true;
 		else if (result != WAVERR_STILLPLAYING) {
-			g_set_error(error_r, winmm_output_quark(), result,
-				    "waveOutUnprepareHeader() failed");
+			error.Set(winmm_output_domain, result,
+				  "waveOutUnprepareHeader() failed");
 			return false;
 		}
 
@@ -270,14 +263,14 @@ winmm_drain_buffer(WinmmOutput *wo, WinmmBuffer *buffer,
 }
 
 static size_t
-winmm_output_play(struct audio_output *ao, const void *chunk, size_t size, GError **error_r)
+winmm_output_play(struct audio_output *ao, const void *chunk, size_t size, Error &error)
 {
 	WinmmOutput *wo = (WinmmOutput *)ao;
 
 	/* get the next buffer from the ring and prepare it */
 	WinmmBuffer *buffer = &wo->buffers[wo->next_buffer];
-	if (!winmm_drain_buffer(wo, buffer, error_r) ||
-	    !winmm_set_buffer(wo, buffer, chunk, size, error_r))
+	if (!winmm_drain_buffer(wo, buffer, error) ||
+	    !winmm_set_buffer(wo, buffer, chunk, size, error))
 		return 0;
 
 	/* enqueue the buffer */
@@ -286,8 +279,8 @@ winmm_output_play(struct audio_output *ao, const void *chunk, size_t size, GErro
 	if (result != MMSYSERR_NOERROR) {
 		waveOutUnprepareHeader(wo->handle, &buffer->hdr,
 				       sizeof(buffer->hdr));
-		g_set_error(error_r, winmm_output_quark(), result,
-			    "waveOutWrite() failed");
+		error.Set(winmm_output_domain, result,
+			  "waveOutWrite() failed");
 		return 0;
 	}
 
@@ -299,14 +292,14 @@ winmm_output_play(struct audio_output *ao, const void *chunk, size_t size, GErro
 }
 
 static bool
-winmm_drain_all_buffers(WinmmOutput *wo, GError **error_r)
+winmm_drain_all_buffers(WinmmOutput *wo, Error &error)
 {
 	for (unsigned i = wo->next_buffer; i < G_N_ELEMENTS(wo->buffers); ++i)
-		if (!winmm_drain_buffer(wo, &wo->buffers[i], error_r))
+		if (!winmm_drain_buffer(wo, &wo->buffers[i], error))
 			return false;
 
 	for (unsigned i = 0; i < wo->next_buffer; ++i)
-		if (!winmm_drain_buffer(wo, &wo->buffers[i], error_r))
+		if (!winmm_drain_buffer(wo, &wo->buffers[i], error))
 			return false;
 
 	return true;
@@ -329,7 +322,7 @@ winmm_output_drain(struct audio_output *ao)
 {
 	WinmmOutput *wo = (WinmmOutput *)ao;
 
-	if (!winmm_drain_all_buffers(wo, nullptr))
+	if (!winmm_drain_all_buffers(wo, IgnoreError()))
 		winmm_stop(wo);
 }
 
diff --git a/src/pcm/PcmConvert.cxx b/src/pcm/PcmConvert.cxx
index 7e71da283..38672810e 100644
--- a/src/pcm/PcmConvert.cxx
+++ b/src/pcm/PcmConvert.cxx
@@ -23,6 +23,8 @@
 #include "PcmFormat.hxx"
 #include "pcm_pack.h"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -32,6 +34,8 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "pcm"
 
+const Domain pcm_convert_domain("pcm_convert");
+
 PcmConvert::PcmConvert()
 {
 }
@@ -51,7 +55,7 @@ inline const int16_t *
 PcmConvert::Convert16(const AudioFormat src_format,
 		      const void *src_buffer, size_t src_size,
 		      const AudioFormat dest_format, size_t *dest_size_r,
-		      GError **error_r)
+		      Error &error)
 {
 	const int16_t *buf;
 	size_t len;
@@ -63,9 +67,9 @@ PcmConvert::Convert16(const AudioFormat src_format,
 				src_buffer, src_size,
 				&len);
 	if (buf == NULL) {
-		g_set_error(error_r, pcm_convert_quark(), 0,
-			    "Conversion from %s to 16 bit is not implemented",
-			    sample_format_to_string(src_format.format));
+		error.Format(pcm_convert_domain,
+			     "Conversion from %s to 16 bit is not implemented",
+			     sample_format_to_string(src_format.format));
 		return NULL;
 	}
 
@@ -75,11 +79,11 @@ PcmConvert::Convert16(const AudioFormat src_format,
 					      src_format.channels,
 					      buf, len, &len);
 		if (buf == NULL) {
-			g_set_error(error_r, pcm_convert_quark(), 0,
-				    "Conversion from %u to %u channels "
-				    "is not implemented",
-				    src_format.channels,
-				    dest_format.channels);
+			error.Format(pcm_convert_domain,
+				     "Conversion from %u to %u channels "
+				     "is not implemented",
+				     src_format.channels,
+				     dest_format.channels);
 			return NULL;
 		}
 	}
@@ -88,7 +92,7 @@ PcmConvert::Convert16(const AudioFormat src_format,
 		buf = resampler.Resample16(dest_format.channels,
 					   src_format.sample_rate, buf, len,
 					   dest_format.sample_rate, &len,
-					   error_r);
+					   error);
 		if (buf == NULL)
 			return NULL;
 	}
@@ -101,7 +105,7 @@ inline const int32_t *
 PcmConvert::Convert24(const AudioFormat src_format,
 		      const void *src_buffer, size_t src_size,
 		      const AudioFormat dest_format, size_t *dest_size_r,
-		      GError **error_r)
+		      Error &error)
 {
 	const int32_t *buf;
 	size_t len;
@@ -112,9 +116,9 @@ PcmConvert::Convert24(const AudioFormat src_format,
 				src_format.format,
 				src_buffer, src_size, &len);
 	if (buf == NULL) {
-		g_set_error(error_r, pcm_convert_quark(), 0,
-			    "Conversion from %s to 24 bit is not implemented",
-			    sample_format_to_string(src_format.format));
+		error.Format(pcm_convert_domain,
+			     "Conversion from %s to 24 bit is not implemented",
+			     sample_format_to_string(src_format.format));
 		return NULL;
 	}
 
@@ -124,11 +128,11 @@ PcmConvert::Convert24(const AudioFormat src_format,
 					      src_format.channels,
 					      buf, len, &len);
 		if (buf == NULL) {
-			g_set_error(error_r, pcm_convert_quark(), 0,
-				    "Conversion from %u to %u channels "
-				    "is not implemented",
-				    src_format.channels,
-				    dest_format.channels);
+			error.Format(pcm_convert_domain,
+				     "Conversion from %u to %u channels "
+				     "is not implemented",
+				     src_format.channels,
+				     dest_format.channels);
 			return NULL;
 		}
 	}
@@ -137,7 +141,7 @@ PcmConvert::Convert24(const AudioFormat src_format,
 		buf = resampler.Resample24(dest_format.channels,
 					   src_format.sample_rate, buf, len,
 					   dest_format.sample_rate, &len,
-					   error_r);
+					   error);
 		if (buf == NULL)
 			return NULL;
 	}
@@ -150,7 +154,7 @@ inline const int32_t *
 PcmConvert::Convert32(const AudioFormat src_format,
 		      const void *src_buffer, size_t src_size,
 		      const AudioFormat dest_format, size_t *dest_size_r,
-		      GError **error_r)
+		      Error &error)
 {
 	const int32_t *buf;
 	size_t len;
@@ -161,9 +165,9 @@ PcmConvert::Convert32(const AudioFormat src_format,
 				src_format.format,
 				src_buffer, src_size, &len);
 	if (buf == NULL) {
-		g_set_error(error_r, pcm_convert_quark(), 0,
-			    "Conversion from %s to 32 bit is not implemented",
-			    sample_format_to_string(src_format.format));
+		error.Format(pcm_convert_domain,
+			     "Conversion from %s to 32 bit is not implemented",
+			     sample_format_to_string(src_format.format));
 		return NULL;
 	}
 
@@ -173,11 +177,11 @@ PcmConvert::Convert32(const AudioFormat src_format,
 					      src_format.channels,
 					      buf, len, &len);
 		if (buf == NULL) {
-			g_set_error(error_r, pcm_convert_quark(), 0,
-				    "Conversion from %u to %u channels "
-				    "is not implemented",
-				    src_format.channels,
-				    dest_format.channels);
+			error.Format(pcm_convert_domain,
+				     "Conversion from %u to %u channels "
+				     "is not implemented",
+				     src_format.channels,
+				     dest_format.channels);
 			return NULL;
 		}
 	}
@@ -186,7 +190,7 @@ PcmConvert::Convert32(const AudioFormat src_format,
 		buf = resampler.Resample32(dest_format.channels,
 					   src_format.sample_rate, buf, len,
 					   dest_format.sample_rate, &len,
-					   error_r);
+					   error);
 		if (buf == NULL)
 			return buf;
 	}
@@ -199,7 +203,7 @@ inline const float *
 PcmConvert::ConvertFloat(const AudioFormat src_format,
 			 const void *src_buffer, size_t src_size,
 			 const AudioFormat dest_format, size_t *dest_size_r,
-			 GError **error_r)
+			 Error &error)
 {
 	const float *buffer = (const float *)src_buffer;
 	size_t size = src_size;
@@ -212,9 +216,9 @@ PcmConvert::ConvertFloat(const AudioFormat src_format,
 				      src_format.format,
 				      buffer, size, &size);
 	if (buffer == NULL) {
-		g_set_error(error_r, pcm_convert_quark(), 0,
-			    "Conversion from %s to float is not implemented",
-			    sample_format_to_string(src_format.format));
+		error.Format(pcm_convert_domain,
+			     "Conversion from %s to float is not implemented",
+			     sample_format_to_string(src_format.format));
 		return NULL;
 	}
 
@@ -226,11 +230,11 @@ PcmConvert::ConvertFloat(const AudioFormat src_format,
 						    src_format.channels,
 						    buffer, size, &size);
 		if (buffer == NULL) {
-			g_set_error(error_r, pcm_convert_quark(), 0,
-				    "Conversion from %u to %u channels "
-				    "is not implemented",
-				    src_format.channels,
-				    dest_format.channels);
+			error.Format(pcm_convert_domain,
+				     "Conversion from %u to %u channels "
+				     "is not implemented",
+				     src_format.channels,
+				     dest_format.channels);
 			return NULL;
 		}
 	}
@@ -243,7 +247,7 @@ PcmConvert::ConvertFloat(const AudioFormat src_format,
 						 src_format.sample_rate,
 						 buffer, size,
 						 dest_format.sample_rate,
-						 &size, error_r);
+						 &size, error);
 		if (buffer == NULL)
 			return NULL;
 	}
@@ -257,7 +261,7 @@ PcmConvert::Convert(AudioFormat src_format,
 		    const void *src, size_t src_size,
 		    const AudioFormat dest_format,
 		    size_t *dest_size_r,
-		    GError **error_r)
+		    Error &error)
 {
 	AudioFormat float_format;
 	if (src_format.format == SampleFormat::DSD) {
@@ -266,8 +270,8 @@ PcmConvert::Convert(AudioFormat src_format,
 					     false, (const uint8_t *)src,
 					     src_size, &f_size);
 		if (f == NULL) {
-			g_set_error_literal(error_r, pcm_convert_quark(), 0,
-					    "DSD to PCM conversion failed");
+			error.Set(pcm_convert_domain,
+				  "DSD to PCM conversion failed");
 			return NULL;
 		}
 
@@ -283,27 +287,27 @@ PcmConvert::Convert(AudioFormat src_format,
 	case SampleFormat::S16:
 		return Convert16(src_format, src, src_size,
 				 dest_format, dest_size_r,
-				 error_r);
+				 error);
 
 	case SampleFormat::S24_P32:
 		return Convert24(src_format, src, src_size,
 				 dest_format, dest_size_r,
-				 error_r);
+				 error);
 
 	case SampleFormat::S32:
 		return Convert32(src_format, src, src_size,
 				 dest_format, dest_size_r,
-				 error_r);
+				 error);
 
 	case SampleFormat::FLOAT:
 		return ConvertFloat(src_format, src, src_size,
 				    dest_format, dest_size_r,
-				    error_r);
+				    error);
 
 	default:
-		g_set_error(error_r, pcm_convert_quark(), 0,
-			    "PCM conversion to %s is not implemented",
-			    sample_format_to_string(dest_format.format));
+		error.Format(pcm_convert_domain,
+			     "PCM conversion to %s is not implemented",
+			     sample_format_to_string(dest_format.format));
 		return NULL;
 	}
 }
diff --git a/src/pcm/PcmConvert.hxx b/src/pcm/PcmConvert.hxx
index 42b59e407..40f785179 100644
--- a/src/pcm/PcmConvert.hxx
+++ b/src/pcm/PcmConvert.hxx
@@ -25,9 +25,10 @@
 #include "PcmResample.hxx"
 #include "PcmBuffer.hxx"
 
-#include <glib.h>
+#include <stddef.h>
 
 struct AudioFormat;
+class Error;
 
 /**
  * This object is statically allocated (within another struct), and
@@ -75,38 +76,34 @@ public:
 			    const void *src, size_t src_size,
 			    AudioFormat dest_format,
 			    size_t *dest_size_r,
-			    GError **error_r);
+			    Error &error);
 
 private:
 	const int16_t *Convert16(AudioFormat src_format,
 				 const void *src_buffer, size_t src_size,
 				 AudioFormat dest_format,
 				 size_t *dest_size_r,
-				 GError **error_r);
+				 Error &error);
 
 	const int32_t *Convert24(AudioFormat src_format,
 				 const void *src_buffer, size_t src_size,
 				 AudioFormat dest_format,
 				 size_t *dest_size_r,
-				 GError **error_r);
+				 Error &error);
 
 	const int32_t *Convert32(AudioFormat src_format,
 				 const void *src_buffer, size_t src_size,
 				 AudioFormat dest_format,
 				 size_t *dest_size_r,
-				 GError **error_r);
+				 Error &error);
 
 	const float *ConvertFloat(AudioFormat src_format,
 				  const void *src_buffer, size_t src_size,
 				  AudioFormat dest_format,
 				  size_t *dest_size_r,
-				  GError **error_r);
+				  Error &error);
 };
 
-static inline GQuark
-pcm_convert_quark(void)
-{
-	return g_quark_from_static_string("pcm_convert");
-}
+extern const class Domain pcm_convert_domain;
 
 #endif
diff --git a/src/pcm/PcmResample.cxx b/src/pcm/PcmResample.cxx
index 423e3d442..9ade8cf5b 100644
--- a/src/pcm/PcmResample.cxx
+++ b/src/pcm/PcmResample.cxx
@@ -39,7 +39,7 @@ pcm_resample_lsr_enabled(void)
 #endif
 
 bool
-pcm_resample_global_init(GError **error_r)
+pcm_resample_global_init(Error &error)
 {
 #ifdef HAVE_LIBSAMPLERATE
 	const char *converter =
@@ -47,11 +47,11 @@ pcm_resample_global_init(GError **error_r)
 
 	lsr_enabled = strcmp(converter, "internal") != 0;
 	if (lsr_enabled)
-		return pcm_resample_lsr_global_init(converter, error_r);
+		return pcm_resample_lsr_global_init(converter, error);
 	else
 		return true;
 #else
-	(void)error_r;
+	(void)error;
 	return true;
 #endif
 }
@@ -84,7 +84,7 @@ const float *
 PcmResampler::ResampleFloat(unsigned channels, unsigned src_rate,
 			    const float *src_buffer, size_t src_size,
 			    unsigned dest_rate, size_t *dest_size_r,
-			    GError **error_r)
+			    Error &error_r)
 {
 #ifdef HAVE_LIBSAMPLERATE
 	if (pcm_resample_lsr_enabled())
@@ -110,7 +110,7 @@ const int16_t *
 PcmResampler::Resample16(unsigned channels,
 			 unsigned src_rate, const int16_t *src_buffer, size_t src_size,
 			 unsigned dest_rate, size_t *dest_size_r,
-			 GError **error_r)
+			 Error &error_r)
 {
 #ifdef HAVE_LIBSAMPLERATE
 	if (pcm_resample_lsr_enabled())
@@ -131,7 +131,7 @@ const int32_t *
 PcmResampler::Resample32(unsigned channels, unsigned src_rate,
 			 const int32_t *src_buffer, size_t src_size,
 			 unsigned dest_rate, size_t *dest_size_r,
-			 GError **error_r)
+			 Error &error_r)
 {
 #ifdef HAVE_LIBSAMPLERATE
 	if (pcm_resample_lsr_enabled())
diff --git a/src/pcm/PcmResample.hxx b/src/pcm/PcmResample.hxx
index db0bbff8d..8a740744a 100644
--- a/src/pcm/PcmResample.hxx
+++ b/src/pcm/PcmResample.hxx
@@ -22,7 +22,6 @@
 
 #include "check.h"
 #include "PcmBuffer.hxx"
-#include "gerror.h"
 
 #include <stdint.h>
 #include <stddef.h>
@@ -31,6 +30,8 @@
 #include <samplerate.h>
 #endif
 
+class Error;
+
 /**
  * This object is statically allocated (within another struct), and
  * holds buffer allocations and the state for the resampler.
@@ -75,7 +76,7 @@ struct PcmResampler {
 	const float *ResampleFloat(unsigned channels, unsigned src_rate,
 				   const float *src_buffer, size_t src_size,
 				   unsigned dest_rate, size_t *dest_size_r,
-				   GError **error_r);
+				   Error &error_r);
 
 	/**
 	 * Resamples 16 bit PCM data.
@@ -91,7 +92,7 @@ struct PcmResampler {
 	const int16_t *Resample16(unsigned channels, unsigned src_rate,
 				  const int16_t *src_buffer, size_t src_size,
 				  unsigned dest_rate, size_t *dest_size_r,
-				  GError **error_r);
+				  Error &error_r);
 
 	/**
 	 * Resamples 32 bit PCM data.
@@ -107,7 +108,7 @@ struct PcmResampler {
 	const int32_t *Resample32(unsigned channels, unsigned src_rate,
 				  const int32_t *src_buffer, size_t src_size,
 				  unsigned dest_rate, size_t *dest_size_r,
-				  GError **error_r);
+				  Error &error_r);
 
 	/**
 	 * Resamples 24 bit PCM data.
@@ -123,7 +124,7 @@ struct PcmResampler {
 	const int32_t *Resample24(unsigned channels, unsigned src_rate,
 				  const int32_t *src_buffer, size_t src_size,
 				  unsigned dest_rate, size_t *dest_size_r,
-				  GError **error_r)
+				  Error &error_r)
 	{
 		/* reuse the 32 bit code - the resampler code doesn't care if
 		   the upper 8 bits are actually used */
@@ -133,6 +134,6 @@ struct PcmResampler {
 };
 
 bool
-pcm_resample_global_init(GError **error_r);
+pcm_resample_global_init(Error &error);
 
 #endif
diff --git a/src/pcm/PcmResampleInternal.hxx b/src/pcm/PcmResampleInternal.hxx
index 5275c090a..59bb2f5df 100644
--- a/src/pcm/PcmResampleInternal.hxx
+++ b/src/pcm/PcmResampleInternal.hxx
@@ -33,7 +33,7 @@
 #ifdef HAVE_LIBSAMPLERATE
 
 bool
-pcm_resample_lsr_global_init(const char *converter, GError **error_r);
+pcm_resample_lsr_global_init(const char *converter, Error &error);
 
 void
 pcm_resample_lsr_init(PcmResampler *state);
@@ -50,7 +50,7 @@ pcm_resample_lsr_float(PcmResampler *state,
 		       unsigned src_rate,
 		       const float *src_buffer, size_t src_size,
 		       unsigned dest_rate, size_t *dest_size_r,
-		       GError **error_r);
+		       Error &error);
 
 const int16_t *
 pcm_resample_lsr_16(PcmResampler *state,
@@ -58,7 +58,7 @@ pcm_resample_lsr_16(PcmResampler *state,
 		    unsigned src_rate,
 		    const int16_t *src_buffer, size_t src_size,
 		    unsigned dest_rate, size_t *dest_size_r,
-		    GError **error_r);
+		    Error &error);
 
 const int32_t *
 pcm_resample_lsr_32(PcmResampler *state,
@@ -67,7 +67,7 @@ pcm_resample_lsr_32(PcmResampler *state,
 		    const int32_t *src_buffer,
 		    size_t src_size,
 		    unsigned dest_rate, size_t *dest_size_r,
-		    GError **error_r);
+		    Error &error);
 
 #endif
 
diff --git a/src/pcm/PcmResampleLibsamplerate.cxx b/src/pcm/PcmResampleLibsamplerate.cxx
index d8dde62e9..6710c2070 100644
--- a/src/pcm/PcmResampleLibsamplerate.cxx
+++ b/src/pcm/PcmResampleLibsamplerate.cxx
@@ -20,6 +20,8 @@
 #include "config.h"
 #include "PcmResampleInternal.hxx"
 #include "conf.h"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
 
 #include <glib.h>
 
@@ -32,11 +34,7 @@
 
 static int lsr_converter = SRC_SINC_FASTEST;
 
-static inline GQuark
-libsamplerate_quark(void)
-{
-	return g_quark_from_static_string("libsamplerate");
-}
+static constexpr Domain libsamplerate_domain("libsamplerate");
 
 static bool
 lsr_parse_converter(const char *s)
@@ -69,11 +67,11 @@ lsr_parse_converter(const char *s)
 }
 
 bool
-pcm_resample_lsr_global_init(const char *converter, GError **error_r)
+pcm_resample_lsr_global_init(const char *converter, Error &error)
 {
 	if (!lsr_parse_converter(converter)) {
-		g_set_error(error_r, libsamplerate_quark(), 0,
-			    "unknown samplerate converter '%s'", converter);
+		error.Format(libsamplerate_domain,
+			     "unknown samplerate converter '%s'", converter);
 		return false;
 	}
 
@@ -109,7 +107,7 @@ pcm_resample_lsr_reset(PcmResampler *state)
 static bool
 pcm_resample_set(PcmResampler *state,
 		 unsigned channels, unsigned src_rate, unsigned dest_rate,
-		 GError **error_r)
+		 Error &error_r)
 {
 	/* (re)set the state/ratio if the in or out format changed */
 	if (channels == state->prev.channels &&
@@ -128,9 +126,9 @@ pcm_resample_set(PcmResampler *state,
 	int error;
 	state->state = src_new(lsr_converter, channels, &error);
 	if (!state->state) {
-		g_set_error(error_r, libsamplerate_quark(), state->error,
-			    "libsamplerate initialization has failed: %s",
-			    src_strerror(error));
+		error_r.Format(libsamplerate_domain, error,
+			       "libsamplerate initialization has failed: %s",
+			       src_strerror(error));
 		return false;
 	}
 
@@ -144,14 +142,14 @@ pcm_resample_set(PcmResampler *state,
 }
 
 static bool
-lsr_process(PcmResampler *state, GError **error_r)
+lsr_process(PcmResampler *state, Error &error)
 {
 	if (state->error == 0)
 		state->error = src_process(state->state, &state->data);
 	if (state->error) {
-		g_set_error(error_r, libsamplerate_quark(), state->error,
-			    "libsamplerate has failed: %s",
-			    src_strerror(state->error));
+		error.Format(libsamplerate_domain, state->error,
+			     "libsamplerate has failed: %s",
+			     src_strerror(state->error));
 		return false;
 	}
 
@@ -164,16 +162,15 @@ pcm_resample_lsr_float(PcmResampler *state,
 		       unsigned src_rate,
 		       const float *src_buffer, size_t src_size,
 		       unsigned dest_rate, size_t *dest_size_r,
-		       GError **error_r)
+		       Error &error)
 {
 	SRC_DATA *data = &state->data;
 
 	assert((src_size % (sizeof(*src_buffer) * channels)) == 0);
 
-	if (!pcm_resample_set(state, channels, src_rate, dest_rate, error_r))
+	if (!pcm_resample_set(state, channels, src_rate, dest_rate, error))
 		return nullptr;
 
-
 	data->input_frames = src_size / sizeof(*src_buffer) / channels;
 	data->data_in = const_cast<float *>(src_buffer);
 
@@ -181,7 +178,7 @@ pcm_resample_lsr_float(PcmResampler *state,
 	size_t data_out_size = data->output_frames * sizeof(float) * channels;
 	data->data_out = (float *)state->out.Get(data_out_size);
 
-	if (!lsr_process(state, error_r))
+	if (!lsr_process(state, error))
 		return nullptr;
 
 	*dest_size_r = data->output_frames_gen *
@@ -195,14 +192,14 @@ pcm_resample_lsr_16(PcmResampler *state,
 		    unsigned src_rate,
 		    const int16_t *src_buffer, size_t src_size,
 		    unsigned dest_rate, size_t *dest_size_r,
-		    GError **error_r)
+		    Error &error)
 {
 	SRC_DATA *data = &state->data;
 
 	assert((src_size % (sizeof(*src_buffer) * channels)) == 0);
 
 	if (!pcm_resample_set(state, channels, src_rate, dest_rate,
-			      error_r))
+			      error))
 		return nullptr;
 
 	data->input_frames = src_size / sizeof(*src_buffer) / channels;
@@ -216,7 +213,7 @@ pcm_resample_lsr_16(PcmResampler *state,
 	src_short_to_float_array(src_buffer, data->data_in,
 				 data->input_frames * channels);
 
-	if (!lsr_process(state, error_r))
+	if (!lsr_process(state, error))
 		return nullptr;
 
 	int16_t *dest_buffer;
@@ -255,14 +252,14 @@ pcm_resample_lsr_32(PcmResampler *state,
 		    unsigned src_rate,
 		    const int32_t *src_buffer, size_t src_size,
 		    unsigned dest_rate, size_t *dest_size_r,
-		    GError **error_r)
+		    Error &error)
 {
 	SRC_DATA *data = &state->data;
 
 	assert((src_size % (sizeof(*src_buffer) * channels)) == 0);
 
 	if (!pcm_resample_set(state, channels, src_rate, dest_rate,
-			      error_r))
+			      error))
 		return nullptr;
 
 	data->input_frames = src_size / sizeof(*src_buffer) / channels;
@@ -276,7 +273,7 @@ pcm_resample_lsr_32(PcmResampler *state,
 	src_int_to_float_array(src_buffer, data->data_in,
 			       data->input_frames * channels);
 
-	if (!lsr_process(state, error_r))
+	if (!lsr_process(state, error))
 		return nullptr;
 
 	int32_t *dest_buffer;
diff --git a/src/playlist/AsxPlaylistPlugin.cxx b/src/playlist/AsxPlaylistPlugin.cxx
index c0a47b8e3..16b187402 100644
--- a/src/playlist/AsxPlaylistPlugin.cxx
+++ b/src/playlist/AsxPlaylistPlugin.cxx
@@ -23,6 +23,7 @@
 #include "InputLegacy.hxx"
 #include "Song.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -208,6 +209,7 @@ asx_open_stream(struct input_stream *is)
 	char buffer[1024];
 	size_t nbytes;
 	bool success;
+	Error error2;
 	GError *error = NULL;
 
 	/* parse the ASX XML file */
@@ -218,12 +220,11 @@ asx_open_stream(struct input_stream *is)
 
 	while (true) {
 		nbytes = input_stream_lock_read(is, buffer, sizeof(buffer),
-						&error);
+						error2);
 		if (nbytes == 0) {
-			if (error != NULL) {
+			if (error2.IsDefined()) {
 				g_markup_parse_context_free(context);
-				g_warning("%s", error->message);
-				g_error_free(error);
+				g_warning("%s", error2.GetMessage());
 				return NULL;
 			}
 
diff --git a/src/playlist/LastFMPlaylistPlugin.cxx b/src/playlist/LastFMPlaylistPlugin.cxx
index a6071e092..5b168ee83 100644
--- a/src/playlist/LastFMPlaylistPlugin.cxx
+++ b/src/playlist/LastFMPlaylistPlugin.cxx
@@ -24,6 +24,7 @@
 #include "conf.h"
 #include "Song.hxx"
 #include "InputLegacy.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -92,16 +93,14 @@ static char *
 lastfm_get(const char *url, Mutex &mutex, Cond &cond)
 {
 	struct input_stream *input_stream;
-	GError *error = NULL;
+	Error error;
 	char buffer[4096];
-	size_t length = 0, nbytes;
+	size_t length = 0;
 
-	input_stream = input_stream_open(url, mutex, cond, &error);
+	input_stream = input_stream_open(url, mutex, cond, error);
 	if (input_stream == NULL) {
-		if (error != NULL) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
+		if (error.IsDefined())
+			g_warning("%s", error.GetMessage());
 
 		return NULL;
 	}
@@ -111,13 +110,12 @@ lastfm_get(const char *url, Mutex &mutex, Cond &cond)
 	input_stream_wait_ready(input_stream);
 
 	do {
-		nbytes = input_stream_read(input_stream, buffer + length,
-					   sizeof(buffer) - length, &error);
+		size_t nbytes =
+			input_stream_read(input_stream, buffer + length,
+					  sizeof(buffer) - length, error);
 		if (nbytes == 0) {
-			if (error != NULL) {
-				g_warning("%s", error->message);
-				g_error_free(error);
-			}
+			if (error.IsDefined())
+				g_warning("%s", error.GetMessage());
 
 			if (input_stream_eof(input_stream))
 				break;
@@ -166,7 +164,6 @@ lastfm_find(const char *response, const char *name)
 static struct playlist_provider *
 lastfm_open_uri(const char *uri, Mutex &mutex, Cond &cond)
 {
-	GError *error = NULL;
 	char *p, *q, *response, *session;
 
 	/* handshake */
@@ -225,15 +222,15 @@ lastfm_open_uri(const char *uri, Mutex &mutex, Cond &cond)
 			NULL);
 	g_free(session);
 
-	const auto is = input_stream_open(p, mutex, cond, &error);
+	Error error;
+	const auto is = input_stream_open(p, mutex, cond, error);
 	g_free(p);
 
 	if (is == nullptr) {
-		if (error != NULL) {
+		if (error.IsDefined())
 			g_warning("Failed to load XSPF playlist: %s",
-				  error->message);
-			g_error_free(error);
-		} else
+				  error.GetMessage());
+		else
 			g_warning("Failed to load XSPF playlist");
 		return NULL;
 	}
diff --git a/src/playlist/PlsPlaylistPlugin.cxx b/src/playlist/PlsPlaylistPlugin.cxx
index 9ef302388..ab8f93bef 100644
--- a/src/playlist/PlsPlaylistPlugin.cxx
+++ b/src/playlist/PlsPlaylistPlugin.cxx
@@ -23,6 +23,7 @@
 #include "InputLegacy.hxx"
 #include "Song.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -104,6 +105,7 @@ static struct playlist_provider *
 pls_open_stream(struct input_stream *is)
 {
 	GError *error = NULL;
+	Error error2;
 	size_t nbytes;
 	char buffer[1024];
 	bool success;
@@ -113,11 +115,10 @@ pls_open_stream(struct input_stream *is)
 
 	do {
 		nbytes = input_stream_lock_read(is, buffer, sizeof(buffer),
-						&error);
+						error2);
 		if (nbytes == 0) {
-			if (error != NULL) {
-				g_warning("%s", error->message);
-				g_error_free(error);
+			if (error2.IsDefined()) {
+				g_warning("%s", error2.GetMessage());
 				return NULL;
 			}
 
diff --git a/src/playlist/RssPlaylistPlugin.cxx b/src/playlist/RssPlaylistPlugin.cxx
index 16dcd5fe5..98f323e66 100644
--- a/src/playlist/RssPlaylistPlugin.cxx
+++ b/src/playlist/RssPlaylistPlugin.cxx
@@ -23,6 +23,7 @@
 #include "InputLegacy.hxx"
 #include "Song.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -205,6 +206,7 @@ rss_open_stream(struct input_stream *is)
 	char buffer[1024];
 	size_t nbytes;
 	bool success;
+	Error error2;
 	GError *error = NULL;
 
 	/* parse the RSS XML file */
@@ -215,12 +217,11 @@ rss_open_stream(struct input_stream *is)
 
 	while (true) {
 		nbytes = input_stream_lock_read(is, buffer, sizeof(buffer),
-						&error);
+						error2);
 		if (nbytes == 0) {
-			if (error != NULL) {
+			if (error2.IsDefined()) {
 				g_markup_parse_context_free(context);
-				g_warning("%s", error->message);
-				g_error_free(error);
+				g_warning("%s", error2.GetMessage());
 				return NULL;
 			}
 
diff --git a/src/playlist/SoundCloudPlaylistPlugin.cxx b/src/playlist/SoundCloudPlaylistPlugin.cxx
index b60635049..b6be4fd30 100644
--- a/src/playlist/SoundCloudPlaylistPlugin.cxx
+++ b/src/playlist/SoundCloudPlaylistPlugin.cxx
@@ -24,6 +24,7 @@
 #include "InputLegacy.hxx"
 #include "Song.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 #include <yajl/yajl_parse.h>
@@ -244,18 +245,15 @@ static int
 soundcloud_parse_json(const char *url, yajl_handle hand,
 		      Mutex &mutex, Cond &cond)
 {
-	struct input_stream *input_stream;
-	GError *error = NULL;
 	char buffer[4096];
 	unsigned char *ubuffer = (unsigned char *)buffer;
-	size_t nbytes;
 
-	input_stream = input_stream_open(url, mutex, cond, &error);
+	Error error;
+	input_stream *input_stream = input_stream_open(url, mutex, cond,
+						       error);
 	if (input_stream == NULL) {
-		if (error != NULL) {
-			g_warning("%s", error->message);
-			g_error_free(error);
-		}
+		if (error.IsDefined())
+			g_warning("%s", error.GetMessage());
 		return -1;
 	}
 
@@ -266,12 +264,13 @@ soundcloud_parse_json(const char *url, yajl_handle hand,
 	int done = 0;
 
 	while (!done) {
-		nbytes = input_stream_read(input_stream, buffer, sizeof(buffer), &error);
+		const size_t nbytes =
+			input_stream_read(input_stream, buffer, sizeof(buffer),
+					  error);
 		if (nbytes == 0) {
-			if (error != NULL) {
-				g_warning("%s", error->message);
-				g_error_free(error);
-			}
+			if (error.IsDefined())
+				g_warning("%s", error.GetMessage());
+
 			if (input_stream_eof(input_stream)) {
 				done = true;
 			} else {
diff --git a/src/playlist/XspfPlaylistPlugin.cxx b/src/playlist/XspfPlaylistPlugin.cxx
index c8a067da4..f2412897b 100644
--- a/src/playlist/XspfPlaylistPlugin.cxx
+++ b/src/playlist/XspfPlaylistPlugin.cxx
@@ -22,6 +22,7 @@
 #include "MemoryPlaylistProvider.hxx"
 #include "InputLegacy.hxx"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -224,6 +225,7 @@ xspf_open_stream(struct input_stream *is)
 	char buffer[1024];
 	size_t nbytes;
 	bool success;
+	Error error2;
 	GError *error = NULL;
 
 	/* parse the XSPF XML file */
@@ -234,12 +236,11 @@ xspf_open_stream(struct input_stream *is)
 
 	while (true) {
 		nbytes = input_stream_lock_read(is, buffer, sizeof(buffer),
-						&error);
+						error2);
 		if (nbytes == 0) {
-			if (error != NULL) {
+			if (error2.IsDefined()) {
 				g_markup_parse_context_free(context);
-				g_warning("%s", error->message);
-				g_error_free(error);
+				g_warning("%s", error2.GetMessage());
 				return NULL;
 			}
 
diff --git a/src/protocol/Ack.cxx b/src/protocol/Ack.cxx
new file mode 100644
index 000000000..3c8185afd
--- /dev/null
+++ b/src/protocol/Ack.cxx
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2003-2011 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 "Ack.hxx"
+#include "util/Domain.hxx"
+
+const Domain ack_domain("ack");
diff --git a/src/protocol/Ack.hxx b/src/protocol/Ack.hxx
index b76fae17d..a7f8e5e53 100644
--- a/src/protocol/Ack.hxx
+++ b/src/protocol/Ack.hxx
@@ -20,9 +20,7 @@
 #ifndef MPD_ACK_H
 #define MPD_ACK_H
 
-#include "gcc.h"
-
-#include <glib.h>
+class Domain;
 
 enum ack {
 	ACK_ERROR_NOT_LIST = 1,
@@ -40,14 +38,6 @@ enum ack {
 	ACK_ERROR_EXIST = 56,
 };
 
-/**
- * Quark for GError.domain; the code is an enum #ack.
- */
-gcc_const
-static inline GQuark
-ack_quark(void)
-{
-	return g_quark_from_static_string("ack");
-}
+extern const Domain ack_domain;
 
 #endif
diff --git a/src/protocol/Result.hxx b/src/protocol/Result.hxx
index 6766da3d5..0f953c62b 100644
--- a/src/protocol/Result.hxx
+++ b/src/protocol/Result.hxx
@@ -24,6 +24,8 @@
 #include "gcc.h"
 #include "Ack.hxx"
 
+#include <stdarg.h>
+
 class Client;
 
 extern const char *current_command;
diff --git a/src/system/FatalError.cxx b/src/system/FatalError.cxx
index 30ddc50ea..65cb9aa26 100644
--- a/src/system/FatalError.cxx
+++ b/src/system/FatalError.cxx
@@ -17,7 +17,9 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "config.h"
 #include "FatalError.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -53,6 +55,12 @@ FormatFatalError(const char *fmt, ...)
 }
 
 void
+FatalError(const Error &error)
+{
+	FatalError(error.GetMessage());
+}
+
+void
 FatalError(GError *error)
 {
 	FatalError(error->message);
diff --git a/src/system/FatalError.hxx b/src/system/FatalError.hxx
index 3918e5fc1..be67aabbd 100644
--- a/src/system/FatalError.hxx
+++ b/src/system/FatalError.hxx
@@ -20,9 +20,12 @@
 #ifndef MPD_FATAL_ERROR_HXX
 #define MPD_FATAL_ERROR_HXX
 
+#include "check.h"
 #include "gerror.h"
 #include "gcc.h"
 
+class Error;
+
 /**
  * Log the specified message and abort the process.
  */
@@ -36,6 +39,10 @@ FormatFatalError(const char *fmt, ...);
 
 gcc_noreturn
 void
+FatalError(const Error &error);
+
+gcc_noreturn
+void
 FatalError(GError *error);
 
 gcc_noreturn
diff --git a/src/system/Resolver.cxx b/src/system/Resolver.cxx
index a574e82c1..b7fa80c38 100644
--- a/src/system/Resolver.cxx
+++ b/src/system/Resolver.cxx
@@ -19,6 +19,10 @@
 
 #include "config.h"
 #include "Resolver.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
+
+#include <glib.h>
 
 #ifndef G_OS_WIN32
 #include <sys/socket.h>
@@ -30,8 +34,10 @@
 
 #include <string.h>
 
+const Domain resolver_domain("resolver");
+
 char *
-sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error)
+sockaddr_to_string(const struct sockaddr *sa, size_t length, Error &error)
 {
 #if defined(HAVE_IPV6) && defined(IN6_IS_ADDR_V4MAPPED)
 	const struct sockaddr_in6 *a6 = (const struct sockaddr_in6 *)sa;
@@ -59,8 +65,7 @@ sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error)
 	ret = getnameinfo(sa, length, host, sizeof(host), serv, sizeof(serv),
 			  NI_NUMERICHOST|NI_NUMERICSERV);
 	if (ret != 0) {
-		g_set_error(error, g_quark_from_static_string("netdb"), ret,
-			    "%s", gai_strerror(ret));
+		error.Set(resolver_domain, ret, gai_strerror(ret));
 		return NULL;
 	}
 
@@ -82,7 +87,7 @@ sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error)
 struct addrinfo *
 resolve_host_port(const char *host_port, unsigned default_port,
 		  int flags, int socktype,
-		  GError **error_r)
+		  Error &error)
 {
 	char *p = g_strdup(host_port);
 	const char *host = p, *port = NULL;
@@ -130,9 +135,9 @@ resolve_host_port(const char *host_port, unsigned default_port,
 	int ret = getaddrinfo(host, port, &hints, &ai);
 	g_free(p);
 	if (ret != 0) {
-		g_set_error(error_r, resolver_quark(), ret,
-			    "Failed to look up '%s': %s",
-			    host_port, gai_strerror(ret));
+		error.Format(resolver_domain, ret,
+			     "Failed to look up '%s': %s",
+			     host_port, gai_strerror(ret));
 		return NULL;
 	}
 
diff --git a/src/system/Resolver.hxx b/src/system/Resolver.hxx
index a1cd00329..38803dcd1 100644
--- a/src/system/Resolver.hxx
+++ b/src/system/Resolver.hxx
@@ -22,17 +22,13 @@
 
 #include "gcc.h"
 
-#include <glib.h>
+#include <stddef.h>
 
 struct sockaddr;
 struct addrinfo;
+class Error;
 
-gcc_const
-static inline GQuark
-resolver_quark(void)
-{
-	return g_quark_from_static_string("resolver");
-}
+extern const class Domain resolver_domain;
 
 /**
  * Converts the specified socket address into a string in the form
@@ -46,7 +42,7 @@ resolver_quark(void)
  */
 gcc_malloc
 char *
-sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error);
+sockaddr_to_string(const struct sockaddr *sa, size_t length, Error &error);
 
 /**
  * Resolve a specification in the form "host", "host:port",
@@ -61,6 +57,6 @@ sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error);
 struct addrinfo *
 resolve_host_port(const char *host_port, unsigned default_port,
 		  int flags, int socktype,
-		  GError **error_r);
+		  Error &error);
 
 #endif
diff --git a/src/system/SocketError.cxx b/src/system/SocketError.cxx
new file mode 100644
index 000000000..d3569c6f1
--- /dev/null
+++ b/src/system/SocketError.cxx
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2003-2013 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 "SocketError.hxx"
+#include "util/Domain.hxx"
+
+const Domain socket_domain("socket");
diff --git a/src/system/SocketError.hxx b/src/system/SocketError.hxx
index 53a0c1d8f..c42e267dd 100644
--- a/src/system/SocketError.hxx
+++ b/src/system/SocketError.hxx
@@ -21,6 +21,7 @@
 #define MPD_SOCKET_ERROR_HXX
 
 #include "gcc.h"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -33,15 +34,10 @@ typedef int socket_error_t;
 #endif
 
 /**
- * A GQuark for GError for socket I/O errors.  The code is an errno
+ * A #Domain for #Error for socket I/O errors.  The code is an errno
  * value (or WSAGetLastError() on Windows).
  */
-gcc_const
-static inline GQuark
-SocketErrorQuark(void)
-{
-	return g_quark_from_static_string("socket");
-}
+extern const class Domain socket_domain;
 
 gcc_pure
 static inline socket_error_t
@@ -121,33 +117,29 @@ public:
 };
 
 static inline void
-SetSocketError(GError **error_r, socket_error_t code)
+SetSocketError(Error &error, socket_error_t code)
 {
-#ifdef WIN32
-	if (error_r == NULL)
-		return;
-#endif
-
 	const SocketErrorMessage msg(code);
-	g_set_error_literal(error_r, SocketErrorQuark(), code, msg);
+	error.Set(socket_domain, code, msg);
 }
 
 static inline void
-SetSocketError(GError **error_r)
+SetSocketError(Error &error)
 {
-	SetSocketError(error_r, GetSocketError());
+	SetSocketError(error, GetSocketError());
 }
 
-gcc_malloc
-static inline GError *
+gcc_const
+static inline Error
 NewSocketError(socket_error_t code)
 {
-	const SocketErrorMessage msg(code);
-	return g_error_new_literal(SocketErrorQuark(), code, msg);
+	Error error;
+	SetSocketError(error, code);
+	return error;
 }
 
-gcc_malloc
-static inline GError *
+gcc_pure
+static inline Error
 NewSocketError()
 {
 	return NewSocketError(GetSocketError());
diff --git a/src/system/SocketUtil.cxx b/src/system/SocketUtil.cxx
index dd7eb7dd2..abaedb8e7 100644
--- a/src/system/SocketUtil.cxx
+++ b/src/system/SocketUtil.cxx
@@ -41,38 +41,38 @@ int
 socket_bind_listen(int domain, int type, int protocol,
 		   const struct sockaddr *address, size_t address_length,
 		   int backlog,
-		   GError **error_r)
+		   Error &error)
 {
 	int fd, ret;
 	const int reuse = 1;
 
 	fd = socket_cloexec_nonblock(domain, type, protocol);
 	if (fd < 0) {
-		SetSocketError(error_r);
-		g_prefix_error(error_r, "Failed to create socket: ");
+		SetSocketError(error);
+		error.AddPrefix("Failed to create socket: ");
 		return -1;
 	}
 
 	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
 			 (const char *) &reuse, sizeof(reuse));
 	if (ret < 0) {
-		SetSocketError(error_r);
-		g_prefix_error(error_r, "setsockopt() failed: ");
+		SetSocketError(error);
+		error.AddPrefix("setsockopt() failed: ");
 		close_socket(fd);
 		return -1;
 	}
 
 	ret = bind(fd, address, address_length);
 	if (ret < 0) {
-		SetSocketError(error_r);
+		SetSocketError(error);
 		close_socket(fd);
 		return -1;
 	}
 
 	ret = listen(fd, backlog);
 	if (ret < 0) {
-		SetSocketError(error_r);
-		g_prefix_error(error_r, "listen() failed: ");
+		SetSocketError(error);
+		error.AddPrefix("listen() failed: ");
 		close_socket(fd);
 		return -1;
 	}
diff --git a/src/system/SocketUtil.hxx b/src/system/SocketUtil.hxx
index 3d0be78c4..5e582ec0d 100644
--- a/src/system/SocketUtil.hxx
+++ b/src/system/SocketUtil.hxx
@@ -26,11 +26,10 @@
 #ifndef MPD_SOCKET_UTIL_HXX
 #define MPD_SOCKET_UTIL_HXX
 
-#include "gerror.h"
-
 #include <stddef.h>
 
 struct sockaddr;
+class Error;
 
 /**
  * Creates a socket listening on the specified address.  This is a
@@ -50,7 +49,7 @@ int
 socket_bind_listen(int domain, int type, int protocol,
 		   const struct sockaddr *address, size_t address_length,
 		   int backlog,
-		   GError **error);
+		   Error &error);
 
 int
 socket_keepalive(int fd);
diff --git a/src/io_error.h b/src/util/Domain.hxx
index 1442a08aa..bbdbf8371 100644
--- a/src/io_error.h
+++ b/src/util/Domain.hxx
@@ -17,35 +17,30 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef MPD_IO_ERROR_H
-#define MPD_IO_ERROR_H
+#ifndef MPD_DOMAIN_HXX
+#define MPD_DOMAIN_HXX
 
-#include <glib.h>
+class Domain {
+	const char *const name;
 
-#include <errno.h>
+public:
+	constexpr explicit Domain(const char *_name)
+		:name(_name) {}
 
-/**
- * A GQuark for GError for I/O errors.  The code is an errno value.
- */
-gcc_const
-static inline GQuark
-errno_quark(void)
-{
-	return g_quark_from_static_string("errno");
-}
-
-static inline void
-set_error_errno(GError **error_r)
-{
-	g_set_error_literal(error_r, errno_quark(), errno,
-			    g_strerror(errno));
-}
-
-static inline GError *
-new_error_errno(void)
-{
-	return g_error_new_literal(errno_quark(), errno,
-				   g_strerror(errno));
-}
+	Domain(const Domain &) = delete;
+	Domain &operator=(const Domain &) = delete;
+
+	constexpr const char *GetName() const {
+		return name;
+	}
+
+	bool operator==(const Domain &other) const {
+		return this == &other;
+	}
+
+	bool operator!=(const Domain &other) const {
+		return !(*this == other);
+	}
+};
 
 #endif
diff --git a/src/util/Error.cxx b/src/util/Error.cxx
new file mode 100644
index 000000000..1e6bd9cff
--- /dev/null
+++ b/src/util/Error.cxx
@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2003-2013 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 "Error.hxx"
+#include "Domain.hxx"
+
+#include <glib.h>
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+const Domain errno_domain("errno");
+
+Error::~Error() {}
+
+void
+Error::Set(const Domain &_domain, int _code, const char *_message)
+{
+	domain = &_domain;
+	code = _code;
+	message.assign(_message);
+}
+
+void
+Error::Format2(const Domain &_domain, int _code, const char *fmt, ...)
+{
+	char buffer[1024];
+	va_list ap;
+	va_start(ap, fmt);
+	vsnprintf(buffer, sizeof(buffer), fmt, ap);
+	va_end(ap);
+
+	Set(_domain, _code, buffer);
+}
+
+void
+Error::FormatPrefix(const char *fmt, ...)
+{
+	char buffer[1024];
+	va_list ap;
+	va_start(ap, fmt);
+	vsnprintf(buffer, sizeof(buffer), fmt, ap);
+	va_end(ap);
+
+	AddPrefix(buffer);
+}
+
+void
+Error::SetErrno(int e)
+{
+	Set(errno_domain, e, g_strerror(e));
+}
+
+void
+Error::SetErrno()
+{
+	SetErrno(errno);
+}
+
+void
+Error::SetErrno(int e, const char *prefix)
+{
+	Format(errno_domain, e, "%s: %s", prefix, g_strerror(e));
+}
+
+void
+Error::SetErrno(const char *prefix)
+{
+	SetErrno(errno, prefix);
+}
+
+void
+Error::FormatErrno(int e, const char *fmt, ...)
+{
+	char buffer[1024];
+	va_list ap;
+	va_start(ap, fmt);
+	vsnprintf(buffer, sizeof(buffer), fmt, ap);
+	va_end(ap);
+
+	SetErrno(e, buffer);
+}
+
+void
+Error::FormatErrno(const char *fmt, ...)
+{
+	const int e = errno;
+
+	char buffer[1024];
+	va_list ap;
+	va_start(ap, fmt);
+	vsnprintf(buffer, sizeof(buffer), fmt, ap);
+	va_end(ap);
+
+	SetErrno(e, buffer);
+}
diff --git a/src/util/Error.hxx b/src/util/Error.hxx
new file mode 100644
index 000000000..1fcf46061
--- /dev/null
+++ b/src/util/Error.hxx
@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2003-2013 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.
+ */
+
+#ifndef MPD_ERROR_HXX
+#define MPD_ERROR_HXX
+
+#include "check.h"
+#include "gcc.h"
+
+#include <string>
+
+#include <assert.h>
+
+class Domain;
+
+extern const Domain errno_domain;
+
+#ifdef WIN32
+/* fuck WIN32! */
+#include <windows.h>
+#define IgnoreError MPDIgnoreError
+#undef GetMessage
+#endif
+
+/**
+ * This class contains information about a runtime error.
+ */
+class Error {
+	const Domain *domain;
+	int code;
+	std::string message;
+
+public:
+	Error():domain(nullptr), code(0) {}
+
+	Error(const Domain &_domain, int _code, const char *_message)
+		:domain(&_domain), code(_code), message(_message) {}
+
+	Error(const Domain &_domain, const char *_message)
+		:domain(&_domain), code(0), message(_message) {}
+
+	Error(Error &&other)
+		:domain(other.domain), code(other.code),
+		 message(std::move(other.message)) {}
+
+	~Error();
+
+	Error(const Error &) = delete;
+	Error &operator=(const Error &) = delete;
+
+	Error &operator=(Error &&other) {
+		domain = other.domain;
+		code = other.code;
+		std::swap(message, other.message);
+		return *this;
+	}
+
+	bool IsDefined() const {
+		return domain != nullptr;
+	}
+
+	void Clear() {
+		domain = nullptr;
+	}
+
+	const Domain &GetDomain() const {
+		assert(IsDefined());
+
+		return *domain;
+	}
+
+	bool IsDomain(const Domain &other) const {
+		return domain == &other;
+	}
+
+	int GetCode() const {
+		assert(IsDefined());
+
+		return code;
+	}
+
+	const char *GetMessage() const {
+		assert(IsDefined());
+
+		return message.c_str();
+	}
+
+	void Set(const Error &other) {
+		assert(!IsDefined());
+		assert(other.IsDefined());
+
+		domain = other.domain;
+		code = other.code;
+		message = other.message;
+	}
+
+	void Set(const Domain &_domain, int _code, const char *_message);
+
+	void Set(const Domain &_domain, const char *_message) {
+		Set(_domain, 0, _message);
+	}
+
+private:
+	void Format2(const Domain &_domain, int _code, const char *fmt, ...);
+
+public:
+	template<typename... Args>
+	void Format(const Domain &_domain, int _code,
+		    const char *fmt, Args&&... args) {
+		Format2(_domain, _code, fmt, std::forward<Args>(args)...);
+	}
+
+	template<typename... Args>
+	void Format(const Domain &_domain, const char *fmt, Args&&... args) {
+		Format2(_domain, 0, fmt, std::forward<Args>(args)...);
+	}
+
+	void AddPrefix(const char *prefix) {
+		message.insert(0, prefix);
+	}
+
+	void FormatPrefix(const char *fmt, ...);
+
+	void SetErrno(int e);
+	void SetErrno();
+	void SetErrno(int e, const char *prefix);
+	void SetErrno(const char *prefix);
+	void FormatErrno(const char *prefix, ...);
+	void FormatErrno(int e, const char *prefix, ...);
+};
+
+/**
+ * Pass a temporary instance of this class to ignore errors.
+ */
+class IgnoreError final {
+	Error error;
+
+public:
+	operator Error &() {
+		assert(!error.IsDefined());
+
+		return error;
+	}
+};
+
+#endif
diff --git a/src/util/Tokenizer.cxx b/src/util/Tokenizer.cxx
index 0bb6edd71..726da0dd6 100644
--- a/src/util/Tokenizer.cxx
+++ b/src/util/Tokenizer.cxx
@@ -20,18 +20,15 @@
 #include "config.h"
 #include "Tokenizer.hxx"
 #include "StringUtil.hxx"
+#include "Error.hxx"
+#include "Domain.hxx"
 
 #include <glib.h>
 
 #include <assert.h>
 #include <string.h>
 
-gcc_const
-static GQuark
-tokenizer_quark(void)
-{
-	return g_quark_from_static_string("tokenizer");
-}
+static constexpr Domain tokenizer_domain("tokenizer");
 
 static inline bool
 valid_word_first_char(char ch)
@@ -46,7 +43,7 @@ valid_word_char(char ch)
 }
 
 char *
-Tokenizer::NextWord(GError **error_r)
+Tokenizer::NextWord(Error &error)
 {
 	char *const word = input;
 
@@ -56,8 +53,7 @@ Tokenizer::NextWord(GError **error_r)
 	/* check the first character */
 
 	if (!valid_word_first_char(*input)) {
-		g_set_error(error_r, tokenizer_quark(), 0,
-			    "Letter expected");
+		error.Set(tokenizer_domain, "Letter expected");
 		return nullptr;
 	}
 
@@ -74,8 +70,7 @@ Tokenizer::NextWord(GError **error_r)
 		}
 
 		if (!valid_word_char(*input)) {
-			g_set_error(error_r, tokenizer_quark(), 0,
-				    "Invalid word character");
+			error.Set(tokenizer_domain, "Invalid word character");
 			return nullptr;
 		}
 	}
@@ -93,7 +88,7 @@ valid_unquoted_char(char ch)
 }
 
 char *
-Tokenizer::NextUnquoted(GError **error_r)
+Tokenizer::NextUnquoted(Error &error)
 {
 	char *const word = input;
 
@@ -103,8 +98,7 @@ Tokenizer::NextUnquoted(GError **error_r)
 	/* check the first character */
 
 	if (!valid_unquoted_char(*input)) {
-		g_set_error(error_r, tokenizer_quark(), 0,
-			    "Invalid unquoted character");
+		error.Set(tokenizer_domain, "Invalid unquoted character");
 		return nullptr;
 	}
 
@@ -121,8 +115,8 @@ Tokenizer::NextUnquoted(GError **error_r)
 		}
 
 		if (!valid_unquoted_char(*input)) {
-			g_set_error(error_r, tokenizer_quark(), 0,
-				    "Invalid unquoted character");
+			error.Set(tokenizer_domain,
+				  "Invalid unquoted character");
 			return nullptr;
 		}
 	}
@@ -134,7 +128,7 @@ Tokenizer::NextUnquoted(GError **error_r)
 }
 
 char *
-Tokenizer::NextString(GError **error_r)
+Tokenizer::NextString(Error &error)
 {
 	char *const word = input, *dest = input;
 
@@ -145,8 +139,7 @@ Tokenizer::NextString(GError **error_r)
 	/* check for the opening " */
 
 	if (*input != '"') {
-		g_set_error(error_r, tokenizer_quark(), 0,
-			    "'\"' expected");
+		error.Set(tokenizer_domain, "'\"' expected");
 		return nullptr;
 	}
 
@@ -165,8 +158,7 @@ Tokenizer::NextString(GError **error_r)
 			   difference between "end of line" and
 			   "error" */
 			--input;
-			g_set_error(error_r, tokenizer_quark(), 0,
-				    "Missing closing '\"'");
+			error.Set(tokenizer_domain, "Missing closing '\"'");
 			return nullptr;
 		}
 
@@ -179,8 +171,8 @@ Tokenizer::NextString(GError **error_r)
 
 	++input;
 	if (*input != 0 && !g_ascii_isspace(*input)) {
-		g_set_error(error_r, tokenizer_quark(), 0,
-			    "Space expected after closing '\"'");
+		error.Set(tokenizer_domain,
+			  "Space expected after closing '\"'");
 		return nullptr;
 	}
 
@@ -192,10 +184,10 @@ Tokenizer::NextString(GError **error_r)
 }
 
 char *
-Tokenizer::NextParam(GError **error_r)
+Tokenizer::NextParam(Error &error)
 {
 	if (*input == '"')
-		return NextString(error_r);
+		return NextString(error);
 	else
-		return NextUnquoted(error_r);
+		return NextUnquoted(error);
 }
diff --git a/src/util/Tokenizer.hxx b/src/util/Tokenizer.hxx
index da45348d4..a689dc31d 100644
--- a/src/util/Tokenizer.hxx
+++ b/src/util/Tokenizer.hxx
@@ -20,7 +20,7 @@
 #ifndef MPD_TOKENIZER_HXX
 #define MPD_TOKENIZER_HXX
 
-#include "gerror.h"
+class Error;
 
 class Tokenizer {
 	char *input;
@@ -50,23 +50,23 @@ public:
 	/**
 	 * Reads the next word.
 	 *
-	 * @param error_r if this function returns nullptr and
-	 * **input_p!=0, it optionally provides a GError object in
+	 * @param error if this function returns nullptr and
+	 * **input_p!=0, it provides an #Error object in
 	 * this argument
 	 * @return a pointer to the null-terminated word, or nullptr
 	 * on error or end of line
 	 */
-	char *NextWord(GError **error_r);
+	char *NextWord(Error &error);
 
 	/**
 	 * Reads the next unquoted word from the input string.
 	 *
 	 * @param error_r if this function returns nullptr and **input_p!=0, it
-	 * optionally provides a GError object in this argument
+	 * provides an #Error object in this argument
 	 * @return a pointer to the null-terminated word, or nullptr
 	 * on error or end of line
 	 */
-	char *NextUnquoted(GError **error_r);
+	char *NextUnquoted(Error &error);
 
 	/**
 	 * Reads the next quoted string from the input string.  A backslash
@@ -76,11 +76,11 @@ public:
 	 * @param input_p the input string; this function returns a pointer to
 	 * the first non-whitespace character of the following token
 	 * @param error_r if this function returns nullptr and **input_p!=0, it
-	 * optionally provides a GError object in this argument
+	 * provides an #Error object in this argument
 	 * @return a pointer to the null-terminated string, or nullptr on error
 	 * or end of line
 	 */
-	char *NextString(GError **error_r);
+	char *NextString(Error &error);
 
 	/**
 	 * Reads the next unquoted word or quoted string from the
@@ -88,12 +88,12 @@ public:
 	 * NextString().
 	 *
 	 * @param error_r if this function returns nullptr and
-	 * **input_p!=0, it optionally provides a GError object in
+	 * **input_p!=0, it provides an #Error object in
 	 * this argument
 	 * @return a pointer to the null-terminated string, or nullptr
 	 * on error or end of line
 	 */
-	char *NextParam(GError **error_r);
+	char *NextParam(Error &error);
 };
 
 #endif
diff --git a/test/DumpDatabase.cxx b/test/DumpDatabase.cxx
index e788d625a..cf86d91ff 100644
--- a/test/DumpDatabase.cxx
+++ b/test/DumpDatabase.cxx
@@ -27,6 +27,7 @@
 #include "conf.h"
 #include "Tag.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <iostream>
 using std::cout;
@@ -46,14 +47,14 @@ my_log_func(const gchar *log_domain, gcc_unused GLogLevelFlags log_level,
 }
 
 static bool
-DumpDirectory(const Directory &directory, GError **)
+DumpDirectory(const Directory &directory, Error &)
 {
 	cout << "D " << directory.path << endl;
 	return true;
 }
 
 static bool
-DumpSong(Song &song, GError **)
+DumpSong(Song &song, Error &)
 {
 	cout << "S " << song.parent->path << "/" << song.uri << endl;
 	return true;
@@ -61,7 +62,7 @@ DumpSong(Song &song, GError **)
 
 static bool
 DumpPlaylist(const PlaylistInfo &playlist,
-	     const Directory &directory, GError **)
+	     const Directory &directory, Error &)
 {
 	cout << "P " << directory.path << "/" << playlist.name.c_str() << endl;
 	return true;
@@ -70,8 +71,6 @@ DumpPlaylist(const PlaylistInfo &playlist,
 int
 main(int argc, char **argv)
 {
-	GError *error = nullptr;
-
 	if (argc != 3) {
 		cerr << "Usage: DumpDatabase CONFIG PLUGIN" << endl;
 		return 1;
@@ -98,9 +97,9 @@ main(int argc, char **argv)
 
 	config_global_init();
 
-	if (!ReadConfigFile(config_path, &error)) {
-		cerr << error->message << endl;
-		g_error_free(error);
+	Error error;
+	if (!ReadConfigFile(config_path, error)) {
+		cerr << error.GetMessage() << endl;
 		return EXIT_FAILURE;
 	}
 
@@ -113,29 +112,26 @@ main(int argc, char **argv)
 	if (path != nullptr)
 		param.AddBlockParam("path", path->value, path->line);
 
-	Database *db = plugin->create(param, &error);
+	Database *db = plugin->create(param, error);
 
 	if (db == nullptr) {
-		cerr << error->message << endl;
-		g_error_free(error);
+		cerr << error.GetMessage() << endl;
 		return EXIT_FAILURE;
 	}
 
-	if (!db->Open(&error)) {
+	if (!db->Open(error)) {
 		delete db;
-		cerr << error->message << endl;
-		g_error_free(error);
+		cerr << error.GetMessage() << endl;
 		return EXIT_FAILURE;
 	}
 
 	const DatabaseSelection selection("", true);
 
 	if (!db->Visit(selection, DumpDirectory, DumpSong, DumpPlaylist,
-		       &error)) {
+		       error)) {
 		db->Close();
 		delete db;
-		cerr << error->message << endl;
-		g_error_free(error);
+		cerr << error.GetMessage() << endl;
 		return EXIT_FAILURE;
 	}
 
diff --git a/test/dump_playlist.cxx b/test/dump_playlist.cxx
index 768eee367..c3cdf638f 100644
--- a/test/dump_playlist.cxx
+++ b/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;
 		}
diff --git a/test/dump_rva2.cxx b/test/dump_rva2.cxx
index 9dbb018d6..95a55eb43 100644
--- a/test/dump_rva2.cxx
+++ b/test/dump_rva2.cxx
@@ -23,6 +23,7 @@
 #include "replay_gain_info.h"
 #include "conf.h"
 #include "Tag.hxx"
+#include "util/Error.hxx"
 
 #include <id3tag.h>
 
@@ -51,8 +52,6 @@ Tag::~Tag() {}
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
-
 #ifdef HAVE_LOCALE_H
 	/* initialize locale */
 	setlocale(LC_CTYPE,"");
@@ -65,12 +64,12 @@ int main(int argc, char **argv)
 
 	const char *path = argv[1];
 
-	struct id3_tag *tag = tag_id3_load(path, &error);
+	Error error;
+	struct id3_tag *tag = tag_id3_load(path, error);
 	if (tag == NULL) {
-		if (error != NULL) {
-			g_printerr("%s\n", error->message);
-			g_error_free(error);
-		} else
+		if (error.IsDefined())
+			g_printerr("%s\n", error.GetMessage());
+		else
 			g_printerr("No ID3 tag found\n");
 
 		return EXIT_FAILURE;
diff --git a/test/dump_text_file.cxx b/test/dump_text_file.cxx
index 165a6493c..a9f8c95a2 100644
--- a/test/dump_text_file.cxx
+++ b/test/dump_text_file.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -24,6 +24,7 @@
 #include "conf.h"
 #include "stdbin.h"
 #include "TextInputStream.hxx"
+#include "util/Error.hxx"
 
 #ifdef ENABLE_ARCHIVE
 #include "ArchiveList.hxx"
@@ -56,7 +57,7 @@ dump_text_file(TextInputStream &is)
 static int
 dump_input_stream(struct input_stream *is)
 {
-	GError *error = NULL;
+	Error error;
 
 	input_stream_lock(is);
 
@@ -64,9 +65,8 @@ dump_input_stream(struct input_stream *is)
 
 	input_stream_wait_ready(is);
 
-	if (!input_stream_check(is, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_check(is, error)) {
+		g_warning("%s", error.GetMessage());
 		input_stream_unlock(is);
 		return EXIT_FAILURE;
 	}
@@ -80,9 +80,8 @@ dump_input_stream(struct input_stream *is)
 	}
 	input_stream_lock(is);
 
-	if (!input_stream_check(is, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_check(is, error)) {
+		g_warning("%s", error.GetMessage());
 		input_stream_unlock(is);
 		return EXIT_FAILURE;
 	}
@@ -94,7 +93,6 @@ dump_input_stream(struct input_stream *is)
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
 	struct input_stream *is;
 	int ret;
 
@@ -122,9 +120,9 @@ int main(int argc, char **argv)
 	archive_plugin_init_all();
 #endif
 
-	if (!input_stream_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	Error error;
+	if (!input_stream_global_init(error)) {
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
@@ -133,15 +131,14 @@ int main(int argc, char **argv)
 	Mutex mutex;
 	Cond cond;
 
-	is = input_stream_open(argv[1], mutex, cond, &error);
+	is = input_stream_open(argv[1], mutex, cond, error);
 	if (is != NULL) {
 		ret = dump_input_stream(is);
 		input_stream_close(is);
 	} else {
-		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");
 		ret = 2;
 	}
diff --git a/test/read_conf.cxx b/test/read_conf.cxx
index 79f3eca54..55ff8c068 100644
--- a/test/read_conf.cxx
+++ b/test/read_conf.cxx
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "conf.h"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -50,10 +51,9 @@ int main(int argc, char **argv)
 
 	config_global_init();
 
-	GError *error = NULL;
-	if (!ReadConfigFile(config_path, &error)) {
-		g_printerr("%s:", error->message);
-		g_error_free(error);
+	Error error;
+	if (!ReadConfigFile(config_path, error)) {
+		g_printerr("%s:", error.GetMessage());
 		return 1;
 	}
 
diff --git a/test/read_mixer.cxx b/test/read_mixer.cxx
index 0cc84c9b9..8426443ae 100644
--- a/test/read_mixer.cxx
+++ b/test/read_mixer.cxx
@@ -26,6 +26,7 @@
 #include "Main.hxx"
 #include "event/Loop.hxx"
 #include "ConfigData.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -63,7 +64,7 @@ pulse_output_clear_mixer(gcc_unused PulseOutput *po,
 bool
 pulse_output_set_volume(gcc_unused PulseOutput *po,
 			gcc_unused const struct pa_cvolume *volume,
-			gcc_unused GError **error_r)
+			gcc_unused Error &error)
 {
 	return false;
 }
@@ -111,8 +112,6 @@ pcm_volume(gcc_unused void *buffer, gcc_unused size_t length,
 
 int main(int argc, gcc_unused char **argv)
 {
-	GError *error = NULL;
-	bool success;
 	int volume;
 
 	if (argc != 2) {
@@ -126,23 +125,21 @@ int main(int argc, gcc_unused char **argv)
 
 	main_loop = new EventLoop(EventLoop::Default());
 
+	Error error;
 	Mixer *mixer = mixer_new(&alsa_mixer_plugin, nullptr,
-				 config_param(), &error);
+				 config_param(), error);
 	if (mixer == NULL) {
-		g_printerr("mixer_new() failed: %s\n", error->message);
-		g_error_free(error);
+		g_printerr("mixer_new() failed: %s\n", error.GetMessage());
 		return 2;
 	}
 
-	success = mixer_open(mixer, &error);
-	if (!success) {
+	if (!mixer_open(mixer, error)) {
 		mixer_free(mixer);
-		g_printerr("failed to open the mixer: %s\n", error->message);
-		g_error_free(error);
+		g_printerr("failed to open the mixer: %s\n", error.GetMessage());
 		return 2;
 	}
 
-	volume = mixer_get_volume(mixer, &error);
+	volume = mixer_get_volume(mixer, error);
 	mixer_close(mixer);
 	mixer_free(mixer);
 
@@ -151,10 +148,9 @@ int main(int argc, gcc_unused char **argv)
 	assert(volume >= -1 && volume <= 100);
 
 	if (volume < 0) {
-		if (error != NULL) {
+		if (error.IsDefined()) {
 			g_printerr("failed to read volume: %s\n",
-				   error->message);
-			g_error_free(error);
+				   error.GetMessage());
 		} else
 			g_printerr("failed to read volume\n");
 		return 2;
diff --git a/test/read_tags.cxx b/test/read_tags.cxx
index d72721324..8e45be930 100644
--- a/test/read_tags.cxx
+++ b/test/read_tags.cxx
@@ -27,6 +27,7 @@
 #include "TagHandler.hxx"
 #include "TagId3.hxx"
 #include "ApeTag.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -70,7 +71,8 @@ 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
@@ -140,7 +142,6 @@ static const struct tag_handler print_handler = {
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
 	const char *decoder_name, *path;
 	const struct decoder_plugin *plugin;
 
@@ -164,9 +165,9 @@ int main(int argc, char **argv)
 	io_thread_init();
 	io_thread_start();
 
-	if (!input_stream_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	Error error;
+	if (!input_stream_global_init(error)) {
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
@@ -185,12 +186,11 @@ int main(int argc, char **argv)
 		Cond cond;
 
 		struct input_stream *is =
-			input_stream_open(path, mutex, cond, &error);
+			input_stream_open(path, mutex, cond, error);
 
 		if (is == NULL) {
 			g_printerr("Failed to open %s: %s\n",
-				   path, error->message);
-			g_error_free(error);
+				   path, error.GetMessage());
 			return 1;
 		}
 
@@ -201,13 +201,11 @@ int main(int argc, char **argv)
 			input_stream_update(is);
 		}
 
-		if (!input_stream_check(is, &error)) {
+		if (!input_stream_check(is, error)) {
 			mutex.unlock();
 
 			g_printerr("Failed to read %s: %s\n",
-				   path, error->message);
-			g_error_free(error);
-
+				   path, error.GetMessage());
 			return EXIT_FAILURE;
 		}
 
diff --git a/test/run_convert.cxx b/test/run_convert.cxx
index 37e2c8734..72e457338 100644
--- a/test/run_convert.cxx
+++ b/test/run_convert.cxx
@@ -29,6 +29,7 @@
 #include "pcm/PcmConvert.hxx"
 #include "conf.h"
 #include "util/fifo_buffer.h"
+#include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
@@ -56,7 +57,6 @@ config_get_string(gcc_unused enum ConfigOption option,
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
 	AudioFormat in_audio_format, out_audio_format;
 	const void *output;
 	ssize_t nbytes;
@@ -69,18 +69,19 @@ int main(int argc, char **argv)
 
 	g_log_set_default_handler(my_log_func, NULL);
 
+	Error error;
 	if (!audio_format_parse(in_audio_format, argv[1],
-				false, &error)) {
+				false, error)) {
 		g_printerr("Failed to parse audio format: %s\n",
-			   error->message);
+			   error.GetMessage());
 		return 1;
 	}
 
 	AudioFormat out_audio_format_mask;
 	if (!audio_format_parse(out_audio_format_mask, argv[2],
-				true, &error)) {
+				true, error)) {
 		g_printerr("Failed to parse audio format: %s\n",
-			   error->message);
+			   error.GetMessage());
 		return 1;
 	}
 
@@ -113,9 +114,9 @@ int main(int argc, char **argv)
 		fifo_buffer_consume(buffer, length);
 
 		output = state.Convert(in_audio_format, src, length,
-				       out_audio_format, &length, &error);
+				       out_audio_format, &length, error);
 		if (output == NULL) {
-			g_printerr("Failed to convert: %s\n", error->message);
+			g_printerr("Failed to convert: %s\n", error.GetMessage());
 			return 2;
 		}
 
diff --git a/test/run_decoder.cxx b/test/run_decoder.cxx
index c7ef92cf8..fb06c637a 100644
--- a/test/run_decoder.cxx
+++ b/test/run_decoder.cxx
@@ -24,6 +24,7 @@
 #include "InputInit.hxx"
 #include "InputLegacy.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
@@ -91,7 +92,8 @@ 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
@@ -144,7 +146,6 @@ decoder_mixramp(gcc_unused struct decoder *decoder,
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
 	const char *decoder_name;
 	struct decoder decoder;
 
@@ -165,9 +166,9 @@ int main(int argc, char **argv)
 	io_thread_init();
 	io_thread_start();
 
-	if (!input_stream_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	Error error;
+	if (!input_stream_global_init(error)) {
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
@@ -189,12 +190,11 @@ int main(int argc, char **argv)
 		Cond cond;
 
 		struct input_stream *is =
-			input_stream_open(decoder.uri, mutex, cond, &error);
+			input_stream_open(decoder.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 1;
diff --git a/test/run_encoder.cxx b/test/run_encoder.cxx
index b7d64e40a..46edc9618 100644
--- a/test/run_encoder.cxx
+++ b/test/run_encoder.cxx
@@ -23,6 +23,7 @@
 #include "AudioFormat.hxx"
 #include "AudioParser.hxx"
 #include "conf.h"
+#include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
@@ -43,8 +44,6 @@ encoder_to_stdout(Encoder &encoder)
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
-	bool ret;
 	const char *encoder_name;
 	static char buffer[32768];
 
@@ -71,11 +70,11 @@ int main(int argc, char **argv)
 	config_param param;
 	param.AddBlockParam("quality", "5.0", -1);
 
-	const auto encoder = encoder_init(*plugin, param, &error);
+	Error error;
+	const auto encoder = encoder_init(*plugin, param, error);
 	if (encoder == NULL) {
 		g_printerr("Failed to initialize encoder: %s\n",
-			   error->message);
-		g_error_free(error);
+			   error.GetMessage());
 		return 1;
 	}
 
@@ -83,20 +82,16 @@ int main(int argc, char **argv)
 
 	AudioFormat audio_format(44100, SampleFormat::S16, 2);
 	if (argc > 2) {
-		ret = audio_format_parse(audio_format, argv[2],
-					 false, &error);
-		if (!ret) {
+		if (!audio_format_parse(audio_format, argv[2], false, error)) {
 			g_printerr("Failed to parse audio format: %s\n",
-				   error->message);
-			g_error_free(error);
+				   error.GetMessage());
 			return 1;
 		}
 	}
 
-	if (!encoder_open(encoder, audio_format, &error)) {
+	if (!encoder_open(encoder, audio_format, error)) {
 		g_printerr("Failed to open encoder: %s\n",
-			   error->message);
-		g_error_free(error);
+			   error.GetMessage());
 		return 1;
 	}
 
@@ -106,22 +101,18 @@ int main(int argc, char **argv)
 
 	ssize_t nbytes;
 	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
-		ret = encoder_write(encoder, buffer, nbytes, &error);
-		if (!ret) {
+		if (!encoder_write(encoder, buffer, nbytes, error)) {
 			g_printerr("encoder_write() failed: %s\n",
-				   error->message);
-			g_error_free(error);
+				   error.GetMessage());
 			return 1;
 		}
 
 		encoder_to_stdout(*encoder);
 	}
 
-	ret = encoder_end(encoder, &error);
-	if (!ret) {
+	if (!encoder_end(encoder, error)) {
 		g_printerr("encoder_flush() failed: %s\n",
-			   error->message);
-		g_error_free(error);
+			   error.GetMessage());
 		return 1;
 	}
 
diff --git a/test/run_filter.cxx b/test/run_filter.cxx
index e39626ea5..62f8dde31 100644
--- a/test/run_filter.cxx
+++ b/test/run_filter.cxx
@@ -27,6 +27,8 @@
 #include "pcm/PcmVolume.hxx"
 #include "MixerControl.hxx"
 #include "stdbin.h"
+#include "util/Error.hxx"
+#include "system/FatalError.hxx"
 
 #include <glib.h>
 
@@ -37,7 +39,7 @@
 
 bool
 mixer_set_volume(gcc_unused Mixer *mixer,
-		 gcc_unused unsigned volume, gcc_unused GError **error_r)
+		 gcc_unused unsigned volume, gcc_unused Error &error)
 {
 	return true;
 }
@@ -70,7 +72,6 @@ static Filter *
 load_filter(const char *name)
 {
 	const struct config_param *param;
-	GError *error = NULL;
 
 	param = find_named_config_block(CONF_AUDIO_FILTER, name);
 	if (param == NULL) {
@@ -78,10 +79,10 @@ load_filter(const char *name)
 		return nullptr;
 	}
 
-	Filter *filter = filter_configured_new(*param, &error);
+	Error error;
+	Filter *filter = filter_configured_new(*param, error);
 	if (filter == NULL) {
-		g_printerr("Failed to load filter: %s\n", error->message);
-		g_error_free(error);
+		g_printerr("Failed to load filter: %s\n", error.GetMessage());
 		return NULL;
 	}
 
@@ -91,8 +92,7 @@ load_filter(const char *name)
 int main(int argc, char **argv)
 {
 	struct audio_format_string af_string;
-	bool success;
-	GError *error = NULL;
+	Error error2;
 	char buffer[4096];
 
 	if (argc < 3 || argc > 4) {
@@ -115,21 +115,16 @@ int main(int argc, char **argv)
 	/* read configuration file (mpd.conf) */
 
 	config_global_init();
-	if (!ReadConfigFile(config_path, &error)) {
-		g_printerr("%s:", error->message);
-		g_error_free(error);
-		return 1;
-	}
+	if (!ReadConfigFile(config_path, error2))
+		FatalError(error2);
 
 	/* parse the audio format */
 
 	if (argc > 3) {
-		success = audio_format_parse(audio_format, argv[3],
-					     false, &error);
-		if (!success) {
+		Error error;
+		if (!audio_format_parse(audio_format, argv[3], false, error)) {
 			g_printerr("Failed to parse audio format: %s\n",
-				   error->message);
-			g_error_free(error);
+				   error.GetMessage());
 			return 1;
 		}
 	}
@@ -142,11 +137,10 @@ int main(int argc, char **argv)
 
 	/* open the filter */
 
-	const AudioFormat out_audio_format =
-		filter->Open(audio_format, &error);
+	Error error;
+	const AudioFormat out_audio_format = filter->Open(audio_format, error);
 	if (!out_audio_format.IsDefined()) {
-		g_printerr("Failed to open filter: %s\n", error->message);
-		g_error_free(error);
+		g_printerr("Failed to open filter: %s\n", error.GetMessage());
 		delete filter;
 		return 1;
 	}
@@ -166,9 +160,9 @@ int main(int argc, char **argv)
 			break;
 
 		dest = filter->FilterPCM(buffer, (size_t)nbytes,
-					 &length, &error);
+					 &length, error);
 		if (dest == NULL) {
-			g_printerr("Filter failed: %s\n", error->message);
+			g_printerr("Filter failed: %s\n", error.GetMessage());
 			filter->Close();
 			delete filter;
 			return 1;
diff --git a/test/run_inotify.cxx b/test/run_inotify.cxx
index e8ca4c8bd..459d0c504 100644
--- a/test/run_inotify.cxx
+++ b/test/run_inotify.cxx
@@ -20,6 +20,7 @@
 #include "config.h"
 #include "InotifySource.hxx"
 #include "event/Loop.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -51,7 +52,6 @@ my_inotify_callback(gcc_unused int wd, unsigned mask,
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
 	const char *path;
 
 	if (argc != 2) {
@@ -63,20 +63,19 @@ int main(int argc, char **argv)
 
 	event_loop = new EventLoop(EventLoop::Default());
 
+	Error error;
 	InotifySource *source = InotifySource::Create(*event_loop,
 						      my_inotify_callback,
-						      nullptr, &error);
+						      nullptr, error);
 	if (source == NULL) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
-	int descriptor = source->Add(path, IN_MASK, &error);
+	int descriptor = source->Add(path, IN_MASK, error);
 	if (descriptor < 0) {
 		delete source;
-		g_warning("%s", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return 2;
 	}
 
diff --git a/test/run_input.cxx b/test/run_input.cxx
index 494bcd823..3c74ab509 100644
--- a/test/run_input.cxx
+++ b/test/run_input.cxx
@@ -26,6 +26,7 @@
 #include "InputStream.hxx"
 #include "InputInit.hxx"
 #include "IOThread.hxx"
+#include "util/Error.hxx"
 
 #ifdef ENABLE_ARCHIVE
 #include "ArchiveList.hxx"
@@ -49,7 +50,7 @@ my_log_func(const gchar *log_domain, gcc_unused GLogLevelFlags log_level,
 static int
 dump_input_stream(struct input_stream *is)
 {
-	GError *error = NULL;
+	Error error;
 	char buffer[4096];
 	size_t num_read;
 	ssize_t num_written;
@@ -60,9 +61,8 @@ dump_input_stream(struct input_stream *is)
 
 	input_stream_wait_ready(is);
 
-	if (!input_stream_check(is, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_check(is, error)) {
+		g_warning("%s", error.GetMessage());
 		input_stream_unlock(is);
 		return EXIT_FAILURE;
 	}
@@ -83,12 +83,10 @@ dump_input_stream(struct input_stream *is)
 		}
 
 		num_read = input_stream_read(is, buffer, sizeof(buffer),
-					     &error);
+					     error);
 		if (num_read == 0) {
-			if (error != NULL) {
-				g_warning("%s", error->message);
-				g_error_free(error);
-			}
+			if (error.IsDefined())
+				g_warning("%s", error.GetMessage());
 
 			break;
 		}
@@ -98,9 +96,8 @@ dump_input_stream(struct input_stream *is)
 			break;
 	}
 
-	if (!input_stream_check(is, &error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_check(is, error)) {
+		g_warning("%s", error.GetMessage());
 		input_stream_unlock(is);
 		return EXIT_FAILURE;
 	}
@@ -112,7 +109,7 @@ dump_input_stream(struct input_stream *is)
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
+	Error error;
 	struct input_stream *is;
 	int ret;
 
@@ -140,9 +137,8 @@ int main(int argc, char **argv)
 	archive_plugin_init_all();
 #endif
 
-	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;
 	}
 
@@ -151,15 +147,14 @@ int main(int argc, char **argv)
 	Mutex mutex;
 	Cond cond;
 
-	is = input_stream_open(argv[1], mutex, cond, &error);
+	is = input_stream_open(argv[1], mutex, cond, error);
 	if (is != NULL) {
 		ret = dump_input_stream(is);
 		input_stream_close(is);
 	} else {
-		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");
 		ret = 2;
 	}
diff --git a/test/run_normalize.cxx b/test/run_normalize.cxx
index 5b51f4631..3193fefd2 100644
--- a/test/run_normalize.cxx
+++ b/test/run_normalize.cxx
@@ -27,6 +27,7 @@
 #include "AudioCompress/compress.h"
 #include "AudioParser.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
@@ -37,8 +38,6 @@
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
-	bool ret;
 	struct Compressor *compressor;
 	static char buffer[4096];
 	ssize_t nbytes;
@@ -50,11 +49,10 @@ int main(int argc, char **argv)
 
 	AudioFormat audio_format(48000, SampleFormat::S16, 2);
 	if (argc > 1) {
-		ret = audio_format_parse(audio_format, argv[1],
-					 false, &error);
-		if (!ret) {
+		Error error;
+		if (!audio_format_parse(audio_format, argv[1], false, error)) {
 			g_printerr("Failed to parse audio format: %s\n",
-				   error->message);
+				   error.GetMessage());
 			return 1;
 		}
 	}
diff --git a/test/run_output.cxx b/test/run_output.cxx
index 6bf4ebced..59c1a543e 100644
--- a/test/run_output.cxx
+++ b/test/run_output.cxx
@@ -33,6 +33,7 @@
 #include "FilterRegistry.hxx"
 #include "PlayerControl.hxx"
 #include "stdbin.h"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -48,21 +49,6 @@ GlobalEvents::Emit(gcc_unused Event event)
 {
 }
 
-PcmConvert::PcmConvert() {}
-PcmConvert::~PcmConvert() {}
-
-const void *
-PcmConvert::Convert(gcc_unused const AudioFormat src_format,
-		    gcc_unused const void *src, gcc_unused size_t src_size,
-		    gcc_unused const AudioFormat dest_format,
-		    gcc_unused size_t *dest_size_r,
-		    gcc_unused GError **error_r)
-{
-	g_set_error(error_r, pcm_convert_quark(), 0,
-		    "Not implemented");
-	return NULL;
-}
-
 const struct filter_plugin *
 filter_plugin_by_name(gcc_unused const char *name)
 {
@@ -92,7 +78,6 @@ static struct audio_output *
 load_audio_output(const char *name)
 {
 	const struct config_param *param;
-	GError *error = NULL;
 
 	param = find_named_config_block(CONF_AUDIO_OUTPUT, name);
 	if (param == NULL) {
@@ -102,12 +87,11 @@ load_audio_output(const char *name)
 
 	static struct player_control dummy_player_control(32, 4);
 
+	Error error;
 	struct audio_output *ao =
-		audio_output_new(*param, &dummy_player_control, &error);
-	if (ao == NULL) {
-		g_printerr("%s\n", error->message);
-		g_error_free(error);
-	}
+		audio_output_new(*param, &dummy_player_control, error);
+	if (ao == nullptr)
+		g_printerr("%s\n", error.GetMessage());
 
 	return ao;
 }
@@ -117,19 +101,17 @@ run_output(struct audio_output *ao, AudioFormat audio_format)
 {
 	/* open the audio output */
 
-	GError *error = NULL;
-	if (!ao_plugin_enable(ao, &error)) {
+	Error error;
+	if (!ao_plugin_enable(ao, error)) {
 		g_printerr("Failed to enable audio output: %s\n",
-			   error->message);
-		g_error_free(error);
+			   error.GetMessage());
 		return false;
 	}
 
-	if (!ao_plugin_open(ao, audio_format, &error)) {
+	if (!ao_plugin_open(ao, audio_format, error)) {
 		ao_plugin_disable(ao);
 		g_printerr("Failed to open audio output: %s\n",
-			   error->message);
-		g_error_free(error);
+			   error.GetMessage());
 		return false;
 	}
 
@@ -157,13 +139,12 @@ run_output(struct audio_output *ao, AudioFormat audio_format)
 		if (play_length > 0) {
 			size_t consumed = ao_plugin_play(ao,
 							 buffer, play_length,
-							 &error);
+							 error);
 			if (consumed == 0) {
 				ao_plugin_close(ao);
 				ao_plugin_disable(ao);
 				g_printerr("Failed to play: %s\n",
-					   error->message);
-				g_error_free(error);
+					   error.GetMessage());
 				return false;
 			}
 
@@ -182,8 +163,7 @@ run_output(struct audio_output *ao, AudioFormat audio_format)
 
 int main(int argc, char **argv)
 {
-	bool success;
-	GError *error = NULL;
+	Error error;
 
 	if (argc < 3 || argc > 4) {
 		g_printerr("Usage: run_output CONFIG NAME [FORMAT] <IN\n");
@@ -201,9 +181,8 @@ int main(int argc, char **argv)
 	/* read configuration file (mpd.conf) */
 
 	config_global_init();
-	if (!ReadConfigFile(config_path, &error)) {
-		g_printerr("%s:", error->message);
-		g_error_free(error);
+	if (!ReadConfigFile(config_path, error)) {
+		g_printerr("%s\n", error.GetMessage());
 		return 1;
 	}
 
@@ -221,19 +200,16 @@ int main(int argc, char **argv)
 	/* parse the audio format */
 
 	if (argc > 3) {
-		success = audio_format_parse(audio_format, argv[3],
-					     false, &error);
-		if (!success) {
+		if (!audio_format_parse(audio_format, argv[3], false, error)) {
 			g_printerr("Failed to parse audio format: %s\n",
-				   error->message);
-			g_error_free(error);
+				   error.GetMessage());
 			return 1;
 		}
 	}
 
 	/* do it */
 
-	success = run_output(ao, audio_format);
+	bool success = run_output(ao, audio_format);
 
 	/* cleanup and exit */
 
diff --git a/test/run_resolver.cxx b/test/run_resolver.cxx
index bb7f6deaa..559e12934 100644
--- a/test/run_resolver.cxx
+++ b/test/run_resolver.cxx
@@ -19,6 +19,9 @@
 
 #include "config.h"
 #include "system/Resolver.hxx"
+#include "util/Error.hxx"
+
+#include <glib.h>
 
 #ifdef WIN32
 #include <ws2tcpip.h>
@@ -37,23 +40,21 @@ int main(int argc, char **argv)
 		return EXIT_FAILURE;
 	}
 
-	GError *error = NULL;
+	Error error;
 	struct addrinfo *ai =
 		resolve_host_port(argv[1], 80, AI_PASSIVE, SOCK_STREAM,
-				  &error);
+				  error);
 	if (ai == NULL) {
-		g_printerr("%s\n", error->message);
-		g_error_free(error);
+		g_warning("%s", error.GetMessage());
 		return EXIT_FAILURE;
 	}
 
 	for (const struct addrinfo *i = ai; i != NULL; i = i->ai_next) {
 		char *p = sockaddr_to_string(i->ai_addr, i->ai_addrlen,
-					     &error);
+					     error);
 		if (p == NULL) {
 			freeaddrinfo(ai);
-			g_printerr("%s\n", error->message);
-			g_error_free(error);
+			g_warning("%s", error.GetMessage());
 			return EXIT_FAILURE;
 		}
 
diff --git a/test/software_volume.cxx b/test/software_volume.cxx
index d3b47d74a..19a0be88c 100644
--- a/test/software_volume.cxx
+++ b/test/software_volume.cxx
@@ -27,6 +27,7 @@
 #include "pcm/PcmVolume.hxx"
 #include "AudioParser.hxx"
 #include "AudioFormat.hxx"
+#include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
@@ -36,8 +37,6 @@
 
 int main(int argc, char **argv)
 {
-	GError *error = NULL;
-	bool ret;
 	static char buffer[4096];
 	ssize_t nbytes;
 
@@ -46,13 +45,12 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
+	Error error;
 	AudioFormat audio_format(48000, SampleFormat::S16, 2);
 	if (argc > 1) {
-		ret = audio_format_parse(audio_format, argv[1],
-					 false, &error);
-		if (!ret) {
+		if (!audio_format_parse(audio_format, argv[1], false, error)) {
 			g_printerr("Failed to parse audio format: %s\n",
-				   error->message);
+				   error.GetMessage());
 			return 1;
 		}
 	}
diff --git a/test/test_vorbis_encoder.cxx b/test/test_vorbis_encoder.cxx
index 12e17a785..3d1ac535b 100644
--- a/test/test_vorbis_encoder.cxx
+++ b/test/test_vorbis_encoder.cxx
@@ -24,8 +24,7 @@
 #include "conf.h"
 #include "stdbin.h"
 #include "Tag.hxx"
-
-#include <glib.h>
+#include "util/Error.hxx"
 
 #include <stddef.h>
 #include <unistd.h>
@@ -56,27 +55,27 @@ main(gcc_unused int argc, gcc_unused char **argv)
 	config_param param;
 	param.AddBlockParam("quality", "5.0", -1);
 
-	const auto encoder = encoder_init(*plugin, param, NULL);
+	const auto encoder = encoder_init(*plugin, param, IgnoreError());
 	assert(encoder != NULL);
 
 	/* open the encoder */
 
 	AudioFormat audio_format(44100, SampleFormat::S16, 2);
-	success = encoder_open(encoder, audio_format, NULL);
+	success = encoder_open(encoder, audio_format, IgnoreError());
 	assert(success);
 
 	encoder_to_stdout(*encoder);
 
 	/* write a block of data */
 
-	success = encoder_write(encoder, zero, sizeof(zero), NULL);
+	success = encoder_write(encoder, zero, sizeof(zero), IgnoreError());
 	assert(success);
 
 	encoder_to_stdout(*encoder);
 
 	/* write a tag */
 
-	success = encoder_pre_tag(encoder, NULL);
+	success = encoder_pre_tag(encoder, IgnoreError());
 	assert(success);
 
 	encoder_to_stdout(*encoder);
@@ -85,19 +84,19 @@ main(gcc_unused int argc, gcc_unused char **argv)
 	tag.AddItem(TAG_ARTIST, "Foo");
 	tag.AddItem(TAG_TITLE, "Bar");
 
-	success = encoder_tag(encoder, &tag, NULL);
+	success = encoder_tag(encoder, &tag, IgnoreError());
 	assert(success);
 
 	encoder_to_stdout(*encoder);
 
 	/* write another block of data */
 
-	success = encoder_write(encoder, zero, sizeof(zero), NULL);
+	success = encoder_write(encoder, zero, sizeof(zero), IgnoreError());
 	assert(success);
 
 	/* finish */
 
-	success = encoder_end(encoder, NULL);
+	success = encoder_end(encoder, IgnoreError());
 	assert(success);
 
 	encoder_to_stdout(*encoder);
diff --git a/test/visit_archive.cxx b/test/visit_archive.cxx
index 047ef4d6d..b059f16f9 100644
--- a/test/visit_archive.cxx
+++ b/test/visit_archive.cxx
@@ -28,6 +28,7 @@
 #include "ArchiveFile.hxx"
 #include "ArchiveVisitor.hxx"
 #include "fs/Path.hxx"
+#include "util/Error.hxx"
 
 #include <glib.h>
 
@@ -54,7 +55,7 @@ class MyArchiveVisitor final : public ArchiveVisitor {
 int
 main(int argc, char **argv)
 {
-	GError *error = nullptr;
+	Error error;
 
 	if (argc != 3) {
 		fprintf(stderr, "Usage: visit_archive PLUGIN PATH\n");
@@ -81,9 +82,8 @@ main(int argc, char **argv)
 
 	archive_plugin_init_all();
 
-	if (!input_stream_global_init(&error)) {
-		g_warning("%s", error->message);
-		g_error_free(error);
+	if (!input_stream_global_init(error)) {
+		fprintf(stderr, "%s", error.GetMessage());
 		return 2;
 	}
 
@@ -97,14 +97,13 @@ main(int argc, char **argv)
 
 	int result = EXIT_SUCCESS;
 
-	ArchiveFile *file = archive_file_open(plugin, path.c_str(), &error);
+	ArchiveFile *file = archive_file_open(plugin, path.c_str(), error);
 	if (file != nullptr) {
 		MyArchiveVisitor visitor;
 		file->Visit(visitor);
 		file->Close();
 	} else {
-		fprintf(stderr, "%s\n", error->message);
-		g_error_free(error);
+		fprintf(stderr, "%s", error.GetMessage());
 		result = EXIT_FAILURE;
 	}