Exit after vm shutdown

On macos this was not exiting due to the vm running on a thread.

Also set exit status to be dependent upon if an exception was thrown out of the main thread, and print the exception.

src/main/native/packr/src/macos/packr_macos.cpp

@@ -42,7 +42,8 @@ void sourceCallBack(void* info) {
 */
 static LaunchJavaVMDelegate s_delegate = NULL;
 void* launchVM(void* param) {
-    return s_delegate(param);
+    s_delegate();
+    return nullptr;
 }
 
 int main(int argc, char** argv) {
@@ -61,7 +62,7 @@ int main(int argc, char** argv) {
                     cout << "Starting JVM on main thread (-XstartOnFirstThread found) ..." << endl;
                 }
 
-                delegate(nullptr);
+                delegate();
                 return;
             }
         }

src/main/native/packr/src/packr.cpp

@@ -532,7 +532,7 @@ void launchJavaVM(LaunchJavaVMCallback callback) {
 		Done as lambda to capture local variables, and remain in function scope.
 	*/
 
-	callback([&](void*) {
+	callback([&]() {
 
 		// create JVM
 
@@ -585,6 +585,21 @@ void launchJavaVM(LaunchJavaVMCallback callback) {
 
 		env->CallStaticVoidMethod(mainClass, mainMethod, appArgs);
 
+		// check if main thread threw an exception
+		jboolean exception = env->ExceptionCheck();
+		int status = EXIT_SUCCESS;
+		if (exception) {
+			env->ExceptionDescribe();
+			status = EXIT_FAILURE;
+		}
+
+		// blocks this thread until all non-daemon threads unload
+		jvm->DestroyJavaVM();
+
+		if (verbose) {
+			cout << "Destroyed Java VM ..." << endl;
+		}
+
 		// cleanup
 
 		for (size_t vmArg = 0; vmArg < vmArgc; vmArg++) {
@@ -599,14 +614,7 @@ void launchJavaVM(LaunchJavaVMCallback callback) {
 
 		delete[] cmdLineArgv;
 
-		// blocks this thread until the Java main() method exits
-
-		jvm->DestroyJavaVM();
-
-		if (verbose) {
-			cout << "Destroyed Java VM ..." << endl;
-		}
-
-		return nullptr;
+		// on macOS this is run in a thread, so use exit() to exit the process
+		exit(status);
 	}, args);
 }

src/main/native/packr/src/packr.h

@@ -27,11 +27,11 @@
 typedef jint(JNICALL *GetDefaultJavaVMInitArgs)(void*);
 typedef jint(JNICALL *CreateJavaVM)(JavaVM**, void**, void*);
 
-typedef std::function<void* (void*)> LaunchJavaVMDelegate;
+typedef std::function<void ()> LaunchJavaVMDelegate;
 typedef std::function<void (LaunchJavaVMDelegate delegate, const JavaVMInitArgs& args)> LaunchJavaVMCallback;
 
 #define defaultLaunchVMDelegate \
-	[](LaunchJavaVMDelegate delegate, const JavaVMInitArgs&) { delegate(nullptr); }
+	[](LaunchJavaVMDelegate delegate, const JavaVMInitArgs&) { delegate(); }
 
 extern "C" {