Mailbox: Address feedback

Common/Common.vcxproj

@@ -998,4 +998,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>

Common/Thread/Promise.h

@@ -4,12 +4,16 @@
 
 #include "Common/Thread/Channel.h"
 #include "Common/Thread/ThreadManager.h"
+#include "Common/Log.h"
 
 template<class T>
 class PromiseTask : public Task {
 public:
-	PromiseTask() {}
+	PromiseTask(std::function<T *()> fun, Mailbox<T> *tx) : fun_(fun), tx_(tx) {
+		tx_->AddRef();
+	}
 	~PromiseTask() {
+		tx_->Release();
 	}
 
 	void Run() override {
@@ -22,30 +26,27 @@ public:
 };
 
 // Represents pending or actual data.
-// Has ownership over the data.
-// Single use.
+// Has ownership over the data. Single use.
 // TODO: Split Mailbox (rx_ and tx_) up into separate proxy objects.
+// NOTE: Poll/BlockUntilReady should only be used from one thread.
 template<class T>
 class Promise {
 public:
 	static Promise<T> *Spawn(ThreadManager *threadman, std::function<T *()> fun, TaskType taskType) {
-		// std::pair<Rx<T>, Tx<T>> channel = CreateChannel<T>();
 		Mailbox<T> *mailbox = new Mailbox<T>();
 
-		PromiseTask<T> *task = new PromiseTask<T>();
-		task->fun_ = fun;
-		task->tx_ = mailbox;
-		threadman->EnqueueTask(task, taskType);
-
 		Promise<T> *promise = new Promise<T>();
 		promise->rx_ = mailbox;
+
+		PromiseTask<T> *task = new PromiseTask<T>(fun, mailbox);
+		threadman->EnqueueTask(task, taskType);
 		return promise;
 	}
 
 	~Promise() {
-		if (rx_) {
-			rx_->Release();
-		}
+		// A promise should have been fulfilled before it's destroyed.
+		_assert_(ready_);
+		_assert_(!rx_);
 		delete data_;
 	}
 
@@ -55,6 +56,8 @@ public:
 			return data_;
 		} else {
 			if (rx_->Poll(&data_)) {
+				rx_->Release();
+				rx_ = nullptr;
 				ready_ = true;
 				return data_;
 			} else {

unittest/TestThreadManager.cpp

@@ -57,10 +57,6 @@ bool TestParallelLoop(ThreadManager *threadMan) {
 }
 
 bool TestThreadManager() {
-	if (!TestMailbox()) {
-		return false;
-	}
-
 	ThreadManager manager;
 	manager.Init(8, 1);
 
@@ -73,11 +69,14 @@ bool TestThreadManager() {
 
 	ResultObject *result = object->BlockUntilReady();
 	if (result) {
-		// Note that the data is owned by the promise so we don't
-		// delete it here.
 		printf("Got result back!");
 	}
 
 	delete object;
+
+	if (!TestMailbox()) {
+		return false;
+	}
+
 	return true;
 }