Ensures all audio queues are fully merged before machine destruction.

Thereby avoids a race condition.

Components/6560/6560.hpp

@@ -68,6 +68,10 @@ template <class T> class MOS6560 {
 			set_output_mode(OutputMode::NTSC);
 		}
 
+		~MOS6560() {
+			audio_queue_.flush();
+		}
+
 		void set_clock_rate(double clock_rate) {
 			speaker_.set_input_rate(static_cast<float>(clock_rate / 4.0));
 		}

Concurrency/AsyncTaskQueue.cpp

@@ -45,6 +45,7 @@ AsyncTaskQueue::AsyncTaskQueue()
 
 AsyncTaskQueue::~AsyncTaskQueue() {
 #ifdef __APPLE__
+	flush();
 	dispatch_release(serial_dispatch_queue_);
 	serial_dispatch_queue_ = nullptr;
 #else
@@ -82,6 +83,7 @@ void AsyncTaskQueue::flush() {
 
 DeferringAsyncTaskQueue::~DeferringAsyncTaskQueue() {
 	perform();
+	flush();
 }
 
 void DeferringAsyncTaskQueue::defer(std::function<void(void)> function) {

Machines/AmstradCPC/AmstradCPC.cpp

@@ -126,6 +126,10 @@ class AYDeferrer {
 			speaker_.set_input_rate(1000000);
 		}
 
+		~AYDeferrer() {
+			audio_queue_.flush();
+		}
+
 		/// Adds @c half_cycles half cycles to the amount of time that has passed.
 		inline void run_for(HalfCycles half_cycles) {
 			cycles_since_update_ += half_cycles;

Machines/Atari2600/Bus.hpp

@@ -26,6 +26,10 @@ class Bus {
 			tia_sound_(audio_queue_),
 			speaker_(tia_sound_) {}
 
+		virtual ~Bus() {
+			audio_queue_.flush();
+		}
+
 		virtual void run_for(const Cycles cycles) = 0;
 		virtual void apply_confidence(Analyser::Dynamic::ConfidenceCounter &confidence_counter) = 0;
 		virtual void set_reset_line(bool state) = 0;

Machines/ColecoVision/ColecoVision.cpp

@@ -125,6 +125,10 @@ class ConcreteMachine:
 			joysticks_.emplace_back(new Joystick);
 		}
 
+		~ConcreteMachine() {
+			audio_queue_.flush();
+		}
+
 		std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {
 			return joysticks_;
 		}

Machines/Electron/Electron.cpp

@@ -61,6 +61,10 @@ class ConcreteMachine:
 			speaker_.set_input_rate(2000000 / SoundGenerator::clock_rate_divider);
 		}
 
+		~ConcreteMachine() {
+			audio_queue_.flush();
+		}
+
 		void set_rom(ROMSlot slot, const std::vector<uint8_t> &data, bool is_writeable) override final {
 			uint8_t *target = nullptr;
 			switch(slot) {

Machines/MSX/MSX.cpp

@@ -144,6 +144,10 @@ class ConcreteMachine:
 			tape_player_.set_sleep_observer(this);
 		}
 
+		~ConcreteMachine() {
+			audio_queue_.flush();
+		}
+
 		void setup_output(float aspect_ratio) override {
 			vdp_.reset(new TI::TMS9918(TI::TMS9918::TMS9918A));
 		}

Machines/Oric/Oric.cpp

@@ -215,6 +215,10 @@ class ConcreteMachine:
 			Memory::Fuzz(ram_, sizeof(ram_));
 		}
 
+		~ConcreteMachine() {
+			audio_queue_.flush();
+		}
+
 		// Obtains the system ROMs.
 		bool set_rom_fetcher(const std::function<std::vector<std::unique_ptr<std::vector<uint8_t>>>(const std::string &machine, const std::vector<std::string> &names)> &roms_with_names) override {
 			auto roms = roms_with_names(

Machines/ZX8081/ZX8081.cpp

@@ -76,6 +76,10 @@ template<bool is_zx81> class ConcreteMachine:
 			clear_all_keys();
 		}
 
+		~ConcreteMachine() {
+			audio_queue_.flush();
+		}
+
 		forceinline HalfCycles perform_machine_cycle(const CPU::Z80::PartialMachineCycle &cycle) {
 			const HalfCycles previous_counter = horizontal_counter_;
 			horizontal_counter_ += cycle.length;