Installs additional safeguards against unsafe deconstruction.

Concurrency/AsyncTaskQueue.cpp

@@ -80,6 +80,10 @@ void AsyncTaskQueue::flush() {
 #endif
 }
 
+DeferringAsyncTaskQueue::~DeferringAsyncTaskQueue() {
+	perform();
+}
+
 void DeferringAsyncTaskQueue::defer(std::function<void(void)> function) {
 	if(!deferred_tasks_) {
 		deferred_tasks_.reset(new std::list<std::function<void(void)>>);

Concurrency/AsyncTaskQueue.hpp

@@ -30,7 +30,7 @@ namespace Concurrency {
 class AsyncTaskQueue {
 	public:
 		AsyncTaskQueue();
-		~AsyncTaskQueue();
+		virtual ~AsyncTaskQueue();
 
 		/*!
 			Adds @c function to the queue.
@@ -69,6 +69,8 @@ class AsyncTaskQueue {
 */
 class DeferringAsyncTaskQueue: public AsyncTaskQueue {
 	public:
+		~DeferringAsyncTaskQueue();
+
 		/*!
 			Adds a function to the deferral list.
 

Concurrency/BestEffortUpdater.cpp

@@ -17,6 +17,11 @@ BestEffortUpdater::BestEffortUpdater() {
 	update_is_ongoing_.clear();
 }
 
+BestEffortUpdater::~BestEffortUpdater() {
+	// Don't allow further deconstruction until the task queue is stopped.
+	flush();
+}
+
 void BestEffortUpdater::update() {
 	// Perform an update only if one is not currently ongoing.
 	if(!update_is_ongoing_.test_and_set()) {

Concurrency/BestEffortUpdater.hpp

@@ -26,6 +26,7 @@ namespace Concurrency {
 class BestEffortUpdater {
 	public:
 		BestEffortUpdater();
+		~BestEffortUpdater();
 
 		/// A delegate receives timing cues.
 		struct Delegate {

OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift

@@ -106,6 +106,7 @@ class MachineDocument:
 
 		bestEffortLock.lock()
 		bestEffortUpdater!.delegate = nil
+		bestEffortUpdater!.flush()
 		bestEffortUpdater = nil
 		bestEffortLock.unlock()