[CoreCLR] Propagate unhandled exceptions

src/Mono.Android/Android.Runtime/JNIEnv.cs

@@ -104,7 +104,7 @@ internal static void PropagateUncaughtException (IntPtr env, IntPtr javaThreadPt
 				if (RuntimeFeature.IsMonoRuntime) {
 					MonoDroidUnhandledException (innerException ?? javaException);
 				} else if (RuntimeFeature.IsCoreClrRuntime) {
-					// TODO: what to do here?
+					ExceptionHandling.RaiseAppDomainUnhandledExceptionEvent (innerException ?? javaException);
 				} else {
 					throw new NotSupportedException ("Internal error: unknown runtime not supported");
 				}

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -35,6 +35,7 @@ internal struct JnienvInitializeArgs {
 			public bool            marshalMethodsEnabled;
 			public IntPtr          grefGCUserPeerable;
 			public bool            managedMarshalMethodsLookupEnabled;
+			public IntPtr          propagateUncaughtExceptionFn;
 		}
 #pragma warning restore 0649
 
@@ -49,6 +50,12 @@ internal struct JnienvInitializeArgs {
 
 		internal static JniRuntime? androidRuntime;
 
+		[UnmanagedCallersOnly]
+		static void PropagateUncaughtException (IntPtr env, IntPtr javaThread, IntPtr javaException)
+		{
+			JNIEnv.PropagateUncaughtException (env, javaThread, javaException);
+		}
+
 		[UnmanagedCallersOnly]
 		static unsafe void RegisterJniNatives (IntPtr typeName_ptr, int typeName_len, IntPtr jniClass, IntPtr methods_ptr, int methods_len)
 		{
@@ -157,6 +164,8 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)
 				xamarin_app_init (args->env, getFunctionPointer);
 			}
 
+			args->propagateUncaughtExceptionFn = (IntPtr)(delegate* unmanaged<IntPtr, IntPtr, IntPtr, void>)&PropagateUncaughtException;
+
 			SetSynchronizationContext ();
 		}
 

src/native/clr/host/host-jni.cc

@@ -47,9 +47,9 @@ Java_mono_android_Runtime_initInternal (JNIEnv *env, jclass klass, jstring lang,
 }
 
 JNIEXPORT void
-JNICALL Java_mono_android_Runtime_propagateUncaughtException ([[maybe_unused]] JNIEnv *env, [[maybe_unused]] jclass klass, [[maybe_unused]] jobject javaThread, [[maybe_unused]] jthrowable javaException)
+JNICALL Java_mono_android_Runtime_propagateUncaughtException (JNIEnv *env, [[maybe_unused]] jclass klass, jobject javaThread, jthrowable javaException)
 {
-	// TODO: implement or remove
+	Host::propagate_uncaught_exception (env, javaThread, javaException);
 }
 
 JNIEXPORT void

src/native/clr/host/host.cc

@@ -560,6 +560,10 @@ void Host::Java_mono_android_Runtime_initInternal (
 	log_debug (LOG_DEFAULT, "Calling into managed runtime init"sv);
 	FastTiming::time_call ("JNIEnv.Initialize UCO"sv, initialize, &init);
 
+	// PropagateUncaughtException is returned from Initialize to avoid an extra create_delegate call
+	jnienv_propagate_uncaught_exception = init.propagateUncaughtExceptionFn;
+	abort_unless (jnienv_propagate_uncaught_exception != nullptr, "Failed to obtain unmanaged-callers-only function pointer to the PropagateUncaughtException method.");
+
 	if (FastTiming::enabled ()) [[unlikely]] {
 		internal_timing.end_event (); // native to managed
 		internal_timing.end_event (); // total init time
@@ -613,3 +617,13 @@ auto HostCommon::Java_JNI_OnLoad (JavaVM *vm, [[maybe_unused]] void *reserved) n
 	AndroidSystem::init_max_gref_count ();
 	return JNI_VERSION_1_6;
 }
+
+void Host::propagate_uncaught_exception (JNIEnv *env, jobject javaThread, jthrowable javaException) noexcept
+{
+	if (jnienv_propagate_uncaught_exception == nullptr) {
+		log_warn (LOG_DEFAULT, "propagate_uncaught_exception called before JNIEnvInit.PropagateUncaughtException was initialized"sv);
+		return;
+	}
+
+	jnienv_propagate_uncaught_exception (env, javaThread, javaException);
+}

src/native/clr/include/host/host.hh

@@ -20,6 +20,7 @@ namespace xamarin::android {
 			jstring runtimeNativeLibDir, jobjectArray appDirs, jint localDateTimeOffset, jobject loader,
 			jobjectArray assembliesJava, jboolean isEmulator, jboolean haveSplitApks) noexcept;
 		static void Java_mono_android_Runtime_register (JNIEnv *env, jstring managedType, jclass nativeClass, jstring methods) noexcept;
+		static void propagate_uncaught_exception (JNIEnv *env, jobject javaThread, jthrowable javaException) noexcept;
 
 		static auto get_timing () -> std::shared_ptr<Timing>
 		{
@@ -53,6 +54,7 @@ namespace xamarin::android {
 		static inline std::shared_ptr<Timing> _timing{};
 		static inline bool found_assembly_store = false;
 		static inline jnienv_register_jni_natives_fn jnienv_register_jni_natives = nullptr;
+		static inline jnienv_propagate_uncaught_exception_fn jnienv_propagate_uncaught_exception = nullptr;
 
 		static inline jclass java_TimeZone = nullptr;
 

src/native/common/include/managed-interface.hh

@@ -14,6 +14,8 @@ namespace xamarin::android {
 		Signals = 0x08,
 	};
 
+	using jnienv_propagate_uncaught_exception_fn = void (*)(JNIEnv *env, jobject javaThread, jthrowable javaException);
+
 	// NOTE: Keep this in sync with managed side in src/Mono.Android/Android.Runtime/JNIEnvInit.cs
 	struct JnienvInitializeArgs {
 		JavaVM         *javaVm;
@@ -33,6 +35,7 @@ namespace xamarin::android {
 		bool            marshalMethodsEnabled;
 		jobject         grefGCUserPeerable;
 		bool            managedMarshalMethodsLookupEnabled;
+		jnienv_propagate_uncaught_exception_fn propagateUncaughtExceptionFn;
 	};
 
 	// Keep the enum values in sync with those in src/Mono.Android/AndroidRuntime/BoundExceptionType.cs

tests/MSBuildDeviceIntegration/Tests/InstallAndRunTests.cs

@@ -213,15 +213,9 @@ void Button_ViewTreeObserver_GlobalLayout (object sender, EventArgs e)
 			}, Path.Combine (Root, builder.ProjectDirectory, "startup-logcat.log"), 60), $"Output did not contain {expectedLogcatOutput}!");
 		}
 
-		// TODO: check if AppDomain.CurrentDomain.UnhandledException even works in CoreCLR
 		[Test]
 		public void SubscribeToAppDomainUnhandledException ([Values (AndroidRuntime.MonoVM, AndroidRuntime.CoreCLR)] AndroidRuntime runtime)
 		{
-			if (runtime == AndroidRuntime.CoreCLR) {
-				Assert.Ignore ("AppDomain.CurrentDomain.UnhandledException doesn't work in CoreCLR");
-				return;
-			}
-
 			proj = new XamarinAndroidApplicationProject () {
 				IsRelease = true,
 			};
@@ -243,7 +237,13 @@ public void SubscribeToAppDomainUnhandledException ([Values (AndroidRuntime.Mono
 			Assert.IsTrue (builder.Install (proj), "Install should have succeeded.");
 			RunProjectAndAssert (proj, builder);
 
-			string expectedLogcatOutput = "# Unhandled Exception: sender=System.Object; e.IsTerminating=True; e.ExceptionObject=System.Exception: CRASH";
+			string? expectedSender = runtime switch
+			{
+				AndroidRuntime.MonoVM => "System.Object", // MonoVM passes the current domain as the sender
+				AndroidRuntime.CoreCLR => null, // CoreCLR explicitly passes a `null` sender
+				_ => throw new NotImplementedException($"Test does not support runtime {runtime}"),
+			};
+			string expectedLogcatOutput = $"# Unhandled Exception: sender={expectedSender}; e.IsTerminating=True; e.ExceptionObject=System.Exception: CRASH";
 			Assert.IsTrue (
 				MonitorAdbLogcat (CreateLineChecker (expectedLogcatOutput),
 					logcatFilePath: Path.Combine (Root, builder.ProjectDirectory, "startup-logcat.log"), timeout: 60),