From 83f73c3f02216266d6e33c426c6d17cfe464be50 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 28 Feb 2018 22:15:22 -0500
Subject: [PATCH] Installs additional safeguards against unsafe deconstruction.

---
 Concurrency/AsyncTaskQueue.cpp                              | 4 ++++
 Concurrency/AsyncTaskQueue.hpp                              | 4 +++-
 Concurrency/BestEffortUpdater.cpp                           | 5 +++++
 Concurrency/BestEffortUpdater.hpp                           | 1 +
 OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift | 1 +
 5 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Concurrency/AsyncTaskQueue.cpp b/Concurrency/AsyncTaskQueue.cpp
index 6b8fd90f8..8775c4309 100644
--- a/Concurrency/AsyncTaskQueue.cpp
+++ b/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)>>);
diff --git a/Concurrency/AsyncTaskQueue.hpp b/Concurrency/AsyncTaskQueue.hpp
index be8517454..577f97b1a 100644
--- a/Concurrency/AsyncTaskQueue.hpp
+++ b/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.
 
diff --git a/Concurrency/BestEffortUpdater.cpp b/Concurrency/BestEffortUpdater.cpp
index a3ea15067..96156b742 100644
--- a/Concurrency/BestEffortUpdater.cpp
+++ b/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()) {
diff --git a/Concurrency/BestEffortUpdater.hpp b/Concurrency/BestEffortUpdater.hpp
index 6fb21edc3..c75877dac 100644
--- a/Concurrency/BestEffortUpdater.hpp
+++ b/Concurrency/BestEffortUpdater.hpp
@@ -26,6 +26,7 @@ namespace Concurrency {
 class BestEffortUpdater {
 	public:
 		BestEffortUpdater();
+		~BestEffortUpdater();
 
 		/// A delegate receives timing cues.
 		struct Delegate {
diff --git a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift
index 0c24166bd..f94963372 100644
--- a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
@@ -106,6 +106,7 @@ class MachineDocument:
 
 		bestEffortLock.lock()
 		bestEffortUpdater!.delegate = nil
+		bestEffortUpdater!.flush()
 		bestEffortUpdater = nil
 		bestEffortLock.unlock()