fix crash when closing wesnoth during loadingscreen

http://gna.org/bugs/?25290

src/gui/dialogs/loading_screen.cpp

@@ -86,6 +86,7 @@ loading_screen::loading_screen(std::function<void()> f)
 	, visible_stages_()
 	, animation_stages_()
 	, current_visible_stage_()
+	, is_worker_running_(false)
 {
 	for (const auto& pair : stages) {
 		visible_stages_[pair.first] = t_string(pair.second, "wesnoth-lib") + "...";
@@ -117,12 +118,14 @@ void loading_screen::pre_show(window& window)
 {
 	if (work_) {
 		worker_.reset(new boost::thread([this]() {
+			is_worker_running_ = true;
 			try {
 				work_();
 			} catch(...) {
 				//TODO: guard this with a mutex.
 				exception_ = std::current_exception();
 			}
+			is_worker_running_ = false;
 		}));
 	}
 	timer_id_ = add_timer(100, std::bind(&loading_screen::timer_callback, this, std::ref(window)), true);
@@ -194,6 +197,16 @@ void loading_screen::timer_callback(window& window)
 
 loading_screen::~loading_screen()
 {
+	if (is_worker_running_) {
+		// The worker thread is running, exit the application to prevent memory corruption.
+		// TODO: this is still not optimal, the main problem is that this code here assumes
+		// that this happened becasue the window was closed which is not necessarily the case
+		// (other possibilities migth be a 'dialog doesn't fit on screen' exception casued by resizing the window)
+
+		// Another approach migth be to add exit points ( boost::this_thread::interruption_point() ) to the worker
+		// functions (filesystem.cpp config parsing code etc. ) and then use that to end the thread faster.
+		std::exit(0);
+	}
 	clear_timer();
 	close();
 	current_load = nullptr;

src/gui/dialogs/loading_screen.hpp

@@ -94,6 +94,8 @@ private:
 	std::map<std::string, t_string> visible_stages_;
 	std::vector<t_string> animation_stages_;
 	std::map<std::string, t_string>::const_iterator current_visible_stage_;
+
+	bool is_worker_running_;
 };
 
 } // namespace dialogs