treewide: replace lock_guard with scoped_lock

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).

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

src/output/plugins/AlsaOutputPlugin.cxx

@@ -311,13 +311,13 @@ private:
 
 	gcc_pure
 	bool LockIsActive() const noexcept {
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		return active;
 	}
 
 	gcc_pure
 	bool LockIsActiveAndNotWaiting() const noexcept {
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		return active && !waiting;
 	}
 
@@ -383,7 +383,7 @@ private:
 	void LockCaughtError() noexcept {
 		period_buffer.Clear();
 
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		error = std::current_exception();
 		active = false;
 		waiting = false;
@@ -398,7 +398,7 @@ private:
 	 */
 	void OnSilenceTimer() noexcept {
 		{
-			const std::lock_guard<Mutex> lock(mutex);
+			const std::scoped_lock<Mutex> lock(mutex);
 			assert(active);
 			waiting = false;
 		}
@@ -464,7 +464,7 @@ AlsaOutput::AlsaOutput(EventLoop &_loop, const ConfigBlock &block)
 std::map<std::string, std::string>
 AlsaOutput::GetAttributes() const noexcept
 {
-	const std::lock_guard<Mutex> lock(attributes_mutex);
+	const std::scoped_lock<Mutex> lock(attributes_mutex);
 
 	return {
 		{"allowed_formats", Alsa::ToString(allowed_formats)},
@@ -478,11 +478,11 @@ void
 AlsaOutput::SetAttribute(std::string &&name, std::string &&value)
 {
 	if (name == "allowed_formats") {
-		const std::lock_guard<Mutex> lock(attributes_mutex);
+		const std::scoped_lock<Mutex> lock(attributes_mutex);
 		allowed_formats = Alsa::AllowedFormat::ParseList(value);
 #ifdef ENABLE_DSD
 	} else if (name == "dop") {
-		const std::lock_guard<Mutex> lock(attributes_mutex);
+		const std::scoped_lock<Mutex> lock(attributes_mutex);
 		if (value == "0")
 			dop_setting = false;
 		else if (value == "1")
@@ -790,7 +790,7 @@ AlsaOutput::Open(AudioFormat &audio_format)
 #endif
 
 	{
-		const std::lock_guard<Mutex> lock(attributes_mutex);
+		const std::scoped_lock<Mutex> lock(attributes_mutex);
 #ifdef ENABLE_DSD
 		dop = dop_setting;
 #endif
@@ -966,7 +966,7 @@ AlsaOutput::CopyRingToPeriodBuffer() noexcept
 
 	period_buffer.AppendBytes(nbytes);
 
-	const std::lock_guard<Mutex> lock(mutex);
+	const std::scoped_lock<Mutex> lock(mutex);
 	/* notify the OutputThread that there is now
 	   room in ring_buffer */
 	cond.notify_one();
@@ -1276,7 +1276,7 @@ try {
 	}
 
 	{
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 
 		assert(active);
 
@@ -1316,7 +1316,7 @@ try {
 			   smaller than the ALSA-PCM buffer */
 
 			{
-				const std::lock_guard<Mutex> lock(mutex);
+				const std::scoped_lock<Mutex> lock(mutex);
 				waiting = true;
 				cond.notify_one();
 			}

src/output/plugins/JackOutputPlugin.cxx

@@ -121,7 +121,7 @@ private:
 	void Disconnect() noexcept;
 
 	void Shutdown(const char *reason) noexcept {
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		error = std::make_exception_ptr(FormatRuntimeError("JACK connection shutdown: %s",
 								   reason));
 	}
@@ -185,7 +185,7 @@ public:
 
 private:
 	bool LockWasShutdown() const noexcept {
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		return !!error;
 	}
 };
@@ -700,7 +700,7 @@ JackOutput::Play(const void *chunk, size_t size)
 
 	while (true) {
 		{
-			const std::lock_guard<Mutex> lock(mutex);
+			const std::scoped_lock<Mutex> lock(mutex);
 			if (error)
 				std::rethrow_exception(error);
 
@@ -730,7 +730,7 @@ inline bool
 JackOutput::Pause()
 {
 	{
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		interrupted = false;
 		if (error)
 			std::rethrow_exception(error);

src/output/plugins/httpd/HttpdClient.cxx

@@ -47,7 +47,7 @@ HttpdClient::Close() noexcept
 void
 HttpdClient::LockClose() noexcept
 {
-	const std::lock_guard<Mutex> protect(httpd.mutex);
+	const std::scoped_lock<Mutex> protect(httpd.mutex);
 	Close();
 }
 
@@ -251,7 +251,7 @@ HttpdClient::GetBytesTillMetaData() const noexcept
 inline bool
 HttpdClient::TryWrite() noexcept
 {
-	const std::lock_guard<Mutex> protect(httpd.mutex);
+	const std::scoped_lock<Mutex> protect(httpd.mutex);
 
 	assert(state == State::RESPONSE);
 

src/output/plugins/httpd/HttpdInternal.hxx

@@ -202,7 +202,7 @@ public:
 	 */
 	gcc_pure
 	bool LockHasClients() const noexcept {
-		const std::lock_guard<Mutex> protect(mutex);
+		const std::scoped_lock<Mutex> protect(mutex);
 		return HasClients();
 	}
 

src/output/plugins/httpd/HttpdOutputPlugin.cxx

@@ -104,7 +104,7 @@ HttpdOutput::OnDeferredBroadcast() noexcept
 	/* this method runs in the IOThread; it broadcasts pages from
 	   our own queue to all clients */
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	while (!pages.empty()) {
 		PagePtr page = std::move(pages.front());
@@ -126,7 +126,7 @@ HttpdOutput::OnAccept(UniqueSocketDescriptor fd,
 	/* the listener socket has become readable - a client has
 	   connected */
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	/* can we allow additional client */
 	if (open && (clients_max == 0 || clients.size() < clients_max))
@@ -186,7 +186,7 @@ HttpdOutput::Open(AudioFormat &audio_format)
 	assert(!open);
 	assert(clients.empty());
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	OpenEncoder(audio_format);
 
@@ -208,7 +208,7 @@ HttpdOutput::Close() noexcept
 	BlockingCall(GetEventLoop(), [this](){
 			defer_broadcast.Cancel();
 
-			const std::lock_guard<Mutex> protect(mutex);
+			const std::scoped_lock<Mutex> protect(mutex);
 			open = false;
 			clients.clear_and_dispose(DeleteDisposer());
 		});
@@ -261,7 +261,7 @@ HttpdOutput::BroadcastPage(PagePtr page) noexcept
 	assert(page != nullptr);
 
 	{
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		pages.emplace(std::move(page));
 	}
 
@@ -281,7 +281,7 @@ HttpdOutput::BroadcastFromEncoder()
 
 	PagePtr page;
 	while ((page = ReadPage()) != nullptr) {
-		const std::lock_guard<Mutex> lock(mutex);
+		const std::scoped_lock<Mutex> lock(mutex);
 		pages.emplace(std::move(page));
 		empty = false;
 	}
@@ -373,7 +373,7 @@ HttpdOutput::SendTag(const Tag &tag)
 
 		metadata = icy_server_metadata_page(tag, &types[0]);
 		if (metadata != nullptr) {
-			const std::lock_guard<Mutex> protect(mutex);
+			const std::scoped_lock<Mutex> protect(mutex);
 			for (auto &client : clients)
 				client.PushMetaData(metadata);
 		}
@@ -383,7 +383,7 @@ HttpdOutput::SendTag(const Tag &tag)
 inline void
 HttpdOutput::CancelAllClients() noexcept
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	while (!pages.empty()) {
 		PagePtr page = std::move(pages.front());

src/output/plugins/sles/SlesOutputPlugin.cxx

@@ -398,7 +398,7 @@ SlesOutput::Cancel() noexcept
 		LogWarning(sles_domain,
 			   "AndroidSimpleBufferQueue.Clear() failed");
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 	n_queued = 0;
 	filled = 0;
 }
@@ -423,7 +423,7 @@ SlesOutput::Pause()
 inline void
 SlesOutput::PlayedCallback()
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 	assert(n_queued > 0);
 	--n_queued;
 	cond.notify_one();

src/output/plugins/snapcast/Client.cxx

@@ -53,7 +53,7 @@ SnapcastClient::Close() noexcept
 void
 SnapcastClient::LockClose() noexcept
 {
-	const std::lock_guard<Mutex> protect(output.mutex);
+	const std::scoped_lock<Mutex> protect(output.mutex);
 	Close();
 }
 
@@ -70,7 +70,7 @@ SnapcastClient::Push(SnapcastChunkPtr chunk) noexcept
 SnapcastChunkPtr
 SnapcastClient::LockPopQueue() noexcept
 {
-	const std::lock_guard<Mutex> protect(output.mutex);
+	const std::scoped_lock<Mutex> protect(output.mutex);
 	if (chunks.empty())
 		return nullptr;
 

src/output/plugins/snapcast/Internal.hxx

@@ -134,7 +134,7 @@ public:
 	 */
 	[[gnu::pure]]
 	bool LockHasClients() const noexcept {
-		const std::lock_guard<Mutex> protect(mutex);
+		const std::scoped_lock<Mutex> protect(mutex);
 		return HasClients();
 	}
 

src/output/plugins/snapcast/SnapcastOutputPlugin.cxx

@@ -114,7 +114,7 @@ SnapcastOutput::OnAccept(UniqueSocketDescriptor fd,
 	/* the listener socket has become readable - a client has
 	   connected */
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	/* can we allow additional client */
 	if (open)
@@ -152,7 +152,7 @@ SnapcastOutput::Open(AudioFormat &audio_format)
 	assert(!open);
 	assert(clients.empty());
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	OpenEncoder(audio_format);
 
@@ -174,7 +174,7 @@ SnapcastOutput::Close() noexcept
 	BlockingCall(GetEventLoop(), [this](){
 		inject_event.Cancel();
 
-		const std::lock_guard<Mutex> protect(mutex);
+		const std::scoped_lock<Mutex> protect(mutex);
 		open = false;
 		clients.clear_and_dispose(DeleteDisposer{});
 	});
@@ -188,7 +188,7 @@ SnapcastOutput::Close() noexcept
 void
 SnapcastOutput::OnInject() noexcept
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	while (!chunks.empty()) {
 		const auto chunk = std::move(chunks.front());
@@ -296,7 +296,7 @@ SnapcastOutput::SendTag(const Tag &tag)
 
 	const ConstBuffer payload(json.data(), json.size());
 
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 	// TODO: enqueue StreamTags, don't send directly
 	for (auto &client : clients)
 		client.SendStreamTags(payload.ToVoid());
@@ -344,7 +344,7 @@ SnapcastOutput::Play(const void *chunk, size_t size)
 
 		unflushed_input = 0;
 
-		const std::lock_guard<Mutex> protect(mutex);
+		const std::scoped_lock<Mutex> protect(mutex);
 		if (chunks.empty())
 			inject_event.Schedule();
 
@@ -382,7 +382,7 @@ SnapcastOutput::Drain()
 void
 SnapcastOutput::Cancel() noexcept
 {
-	const std::lock_guard<Mutex> protect(mutex);
+	const std::scoped_lock<Mutex> protect(mutex);
 
 	ClearQueue(chunks);