Fix possible race condition in EventListener

Author: asfernandes

src/fb-cpp/EventListener.cpp

@@ -111,6 +111,11 @@ EventListener::EventListener(Attachment& attachment, const std::vector<std::stri
 		&statusWrapper, &firebirdCallback, static_cast<unsigned>(eventBuffer.size()), eventBuffer.data()));
 
 	dispatcher = std::thread{&EventListener::dispatchLoop, this};
+
+	{  // scope
+		std::unique_lock mutexGuard{mutex};
+		condition.wait(mutexGuard, [this] { return initialized || !listening; });
+	}
 }
 
 bool EventListener::isListening() noexcept
@@ -186,6 +191,7 @@ void EventListener::handleEvent(unsigned length, const std::uint8_t* events)
 		unsigned copyLength = 0;
 		bool notify = false;
 		bool shouldRequeue = false;
+		bool notifyInitialized = false;
 
 		{  // scope
 			std::lock_guard mutexGuard{mutex};
@@ -243,6 +249,7 @@ void EventListener::handleEvent(unsigned length, const std::uint8_t* events)
 			if (listening)
 			{
 				listening = false;
+				initialized = true;
 				condition.notify_all();
 			}
 
@@ -267,6 +274,7 @@ void EventListener::handleEvent(unsigned length, const std::uint8_t* events)
 					return;
 
 				listening = false;
+				initialized = true;
 				condition.notify_all();
 			}
 
@@ -282,8 +290,17 @@ void EventListener::handleEvent(unsigned length, const std::uint8_t* events)
 			{
 				previousHandle = std::move(eventsHandle);
 				eventsHandle = std::move(newHandle);
+
+				if (!initialized)
+				{
+					initialized = true;
+					notifyInitialized = true;
+				}
 			}
 		}
+
+		if (notifyInitialized)
+			condition.notify_all();
 	}
 	catch (...)
 	{
@@ -296,6 +313,7 @@ void EventListener::handleEvent(unsigned length, const std::uint8_t* events)
 			if (listening)
 			{
 				listening = false;
+				initialized = true;
 				condition.notify_all();
 			}
 		}

src/fb-cpp/EventListener.h

@@ -168,6 +168,7 @@ namespace fbcpp
 		bool listening = false;
 		bool running = false;
 		bool first = false;
+		bool initialized = false;
 	};
 }  // namespace fbcpp