remove gcc_unused

[[maybe_unused]] (introduced in C++17) is standard C++.

https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
says that this is equivalent to the GNU unused attribute.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

test/DumpDecoderClient.cxx

@@ -86,26 +86,26 @@ DumpDecoderClient::Read(InputStream &is, void *buffer, size_t length) noexcept
 }
 
 void
-DumpDecoderClient::SubmitTimestamp(gcc_unused FloatDuration t) noexcept
+DumpDecoderClient::SubmitTimestamp([[maybe_unused]] FloatDuration t) noexcept
 {
 }
 
 DecoderCommand
-DumpDecoderClient::SubmitData(gcc_unused InputStream *is,
+DumpDecoderClient::SubmitData([[maybe_unused]] InputStream *is,
 			      const void *data, size_t datalen,
-			      gcc_unused uint16_t kbit_rate) noexcept
+			      [[maybe_unused]] uint16_t kbit_rate) noexcept
 {
 	if (kbit_rate != prev_kbit_rate) {
 		prev_kbit_rate = kbit_rate;
 		fprintf(stderr, "%u kbit/s\n", kbit_rate);
 	}
 
-	gcc_unused ssize_t nbytes = write(STDOUT_FILENO, data, datalen);
+	[[maybe_unused]] ssize_t nbytes = write(STDOUT_FILENO, data, datalen);
 	return GetCommand();
 }
 
 DecoderCommand
-DumpDecoderClient::SubmitTag(gcc_unused InputStream *is,
+DumpDecoderClient::SubmitTag([[maybe_unused]] InputStream *is,
 			     Tag &&tag) noexcept
 {
 	fprintf(stderr, "TAG: duration=%f\n", tag.duration.ToDoubleS());
@@ -139,7 +139,7 @@ DumpDecoderClient::SubmitReplayGain(const ReplayGainInfo *rgi) noexcept
 }
 
 void
-DumpDecoderClient::SubmitMixRamp(gcc_unused MixRampInfo &&mix_ramp) noexcept
+DumpDecoderClient::SubmitMixRamp([[maybe_unused]] MixRampInfo &&mix_ramp) noexcept
 {
 	fprintf(stderr, "MixRamp: start='%s' end='%s'\n",
 		mix_ramp.GetStart(), mix_ramp.GetEnd());

test/MakeTag.hxx

@@ -22,7 +22,7 @@
 #include "util/Compiler.h"
 
 inline void
-BuildTag(gcc_unused TagBuilder &tag) noexcept
+BuildTag([[maybe_unused]] TagBuilder &tag) noexcept
 {
 }
 

test/ReadApeTags.cxx

@@ -34,7 +34,7 @@
 #endif
 
 static bool
-MyApeTagCallback(gcc_unused unsigned long flags,
+MyApeTagCallback([[maybe_unused]] unsigned long flags,
 		 const char *key, StringView value)
 {
 	if ((flags & (0x3 << 1)) == 0)

test/read_mixer.cxx

@@ -30,13 +30,13 @@
 #include <stdlib.h>
 
 const FilterPlugin *
-filter_plugin_by_name(gcc_unused const char *name) noexcept
+filter_plugin_by_name([[maybe_unused]] const char *name) noexcept
 {
 	assert(false);
 	return nullptr;
 }
 
-int main(int argc, gcc_unused char **argv)
+int main(int argc, [[maybe_unused]] char **argv)
 try {
 	int volume;
 

test/run_avahi.cxx

@@ -26,7 +26,7 @@
 unsigned listen_port = 1234;
 
 int
-main(gcc_unused int argc, gcc_unused char **argv)
+main([[maybe_unused]] int argc, [[maybe_unused]] char **argv)
 {
 	EventLoop event_loop;
 	const ShutdownHandler shutdown_handler(event_loop);

test/run_convert.cxx

@@ -137,7 +137,7 @@ try {
 
 		auto output = state.Convert({src.data, src.size});
 
-		gcc_unused ssize_t ignored = write(1, output.data,
+		[[maybe_unused]] ssize_t ignored = write(1, output.data,
 						   output.size);
 	}
 
@@ -146,7 +146,7 @@ try {
 		if (output.IsNull())
 			break;
 
-		gcc_unused ssize_t ignored = write(1, output.data,
+		[[maybe_unused]] ssize_t ignored = write(1, output.data,
 						   output.size);
 	}
 

test/run_filter.cxx

@@ -42,8 +42,8 @@
 #include <stdio.h>
 
 void
-mixer_set_volume(gcc_unused Mixer *mixer,
-		 gcc_unused unsigned volume)
+mixer_set_volume([[maybe_unused]] Mixer *mixer,
+		 [[maybe_unused]] unsigned volume)
 {
 }
 

test/run_gunzip.cxx

@@ -55,7 +55,7 @@ CopyGunzip(FILE *_dest, Path src_path)
 }
 
 int
-main(int argc, gcc_unused char **argv)
+main(int argc, [[maybe_unused]] char **argv)
 try {
 	if (argc != 2) {
 		fprintf(stderr, "Usage: run_gunzip PATH\n");

test/run_gzip.cxx

@@ -59,7 +59,7 @@ CopyGzip(FILE *_dest, int src)
 }
 
 int
-main(int argc, gcc_unused char **argv)
+main(int argc, [[maybe_unused]] char **argv)
 try {
 	if (argc != 1) {
 		fprintf(stderr, "Usage: run_gzip\n");

test/run_inotify.cxx

@@ -34,8 +34,8 @@ static constexpr unsigned IN_MASK =
 	|IN_MOVE|IN_MOVE_SELF;
 
 static void
-my_inotify_callback(gcc_unused int wd, unsigned mask,
-		    const char *name, gcc_unused void *ctx)
+my_inotify_callback([[maybe_unused]] int wd, unsigned mask,
+		    const char *name, [[maybe_unused]] void *ctx)
 {
 	printf("mask=0x%x name='%s'\n", mask, name);
 }

test/run_normalize.cxx

@@ -57,7 +57,7 @@ try {
 		Compressor_Process_int16(compressor,
 					 (int16_t *)buffer, nbytes / 2);
 
-		gcc_unused ssize_t ignored = write(1, buffer, nbytes);
+		[[maybe_unused]] ssize_t ignored = write(1, buffer, nbytes);
 	}
 
 	Compressor_delete(compressor);

test/software_volume.cxx

@@ -58,7 +58,7 @@ try {
 
 	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
 		auto dest = pv.Apply({buffer, size_t(nbytes)});
-		gcc_unused ssize_t ignored = write(1, dest.data, dest.size);
+		[[maybe_unused]] ssize_t ignored = write(1, dest.data, dest.size);
 	}
 
 	pv.Close();

test/test_translate_song.cxx

@@ -85,8 +85,8 @@ static const char *uri1 = "/foo/bar.ogg";
 static const char *uri2 = "foo/bar.ogg";
 
 DetachedSong
-DatabaseDetachSong(gcc_unused const Database &db,
-		   gcc_unused const Storage *_storage,
+DatabaseDetachSong([[maybe_unused]] const Database &db,
+		   [[maybe_unused]] const Storage *_storage,
 		   const char *uri)
 {
 	if (strcmp(uri, uri2) == 0)
@@ -119,7 +119,7 @@ Client::GetStorage() const noexcept
 }
 
 void
-Client::AllowFile(gcc_unused Path path_fs) const
+Client::AllowFile([[maybe_unused]] Path path_fs) const
 {
 	/* always fail, so a SongLoader with a non-nullptr
 	   Client pointer will be regarded "insecure", while one with

test/test_vorbis_encoder.cxx

@@ -36,7 +36,7 @@
 static uint8_t zero[256];
 
 int
-main(gcc_unused int argc, gcc_unused char **argv)
+main([[maybe_unused]] int argc, [[maybe_unused]] char **argv)
 try {
 	/* create the encoder */