[NativeAOT] Add DefaultUncaughtExceptionHandler (#9994)

jonpryor · web-flow · commit 9ad492a42b38 · 2025-04-09T09:20:47.000-04:00
Context: dotnet/runtime#102730 Context: 1aa0ea7 What should happen when an exception is thrown and not caught? partial class MainActivity { protected override void OnCreate(Bundle? savedInstanceState) => throw new Exception("Uncaught exception"); } What *previously* happened is that the app would exit, with an `AndroidRuntime` tag containing the Java-side exception, which will contain *some* managed info courtesy of 1aa0ea7. I ActivityManager: Start proc 6911:net.dot.hellonativeaot/u0a205 for top-activity {net.dot.hellonativeaot/my.MainActivity} … D NativeAotRuntimeProvider: NativeAotRuntimeProvider() D NativeAotRuntimeProvider: NativeAotRuntimeProvider.attachInfo(): calling JavaInteropRuntime.init()… D JavaInteropRuntime: Loading NativeAOT.so... I JavaInteropRuntime: JNI_OnLoad() … D NativeAotRuntimeProvider: NativeAotRuntimeProvider.onCreate() D NativeAOT: Application..ctor(7fff01a958, DoNotTransfer) D NativeAOT: Application.OnCreate() … D NativeAOT: MainActivity.OnCreate() … D NativeAOT: MainActivity.OnCreate() ColorStateList: ColorStateList{mThemeAttrs=nullmChangingConfigurations=0mStateSpecs=[[0, 1]]mColors=[0, 1]mDefaultColor=0} D AndroidRuntime: Shutting down VM E AndroidRuntime: FATAL EXCEPTION: main E AndroidRuntime: Process: net.dot.hellonativeaot, PID: 6911 E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.InvalidOperationException: What happened? E AndroidRuntime: at NativeAOT.MainActivity.OnCreate(Bundle savedInstanceState) + 0x2f4 E AndroidRuntime: at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState) + 0xc8 E AndroidRuntime: at my.MainActivity.n_onCreate(Native Method) E AndroidRuntime: at my.MainActivity.onCreate(MainActivity.java:28) E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8595) E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8573) E AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1456) E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3805) E AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3963) E AndroidRuntime: at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:103) E AndroidRuntime: at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:139) E AndroidRuntime: at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:96) E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2484) E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:106) E AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:205) E AndroidRuntime: at android.os.Looper.loop(Looper.java:294) E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:8225) E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:573) E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1049) W ActivityTaskManager: Force finishing activity net.dot.hellonativeaot/my.MainActivity What *won't* happen is that the [`AppDomain.UnhandledException`][0] event will ***not*** be raised This is less than ideal, and will cause the `InstallAndRunTests.SubscribeToAppDomainUnhandledException()` test to fail, once that test is enabled for NativeAOT. *Begin* to address this by setting `Java.Lang.Thread.DefaultUncaughtExceptionHandler` to a `Thread.IUncaughtExceptionHandler` instance which at least prints the exception to `adb logcat`. Update `samples/NativeAOT` to demonstrate this, by using a new boolean `thrown` extra; if true, then `OnCreate()` throws: adb shell am start --ez throw 1 net.dot.hellonativeaot/my.MainActivity `adb logcat` continues to have the `FATAL EXCEPTION` message from `AndroidRuntime`, as shown above, and `adb logcat` now also contains: F DOTNET : FATAL UNHANDLED EXCEPTION: System.InvalidOperationException: What happened? F DOTNET : at NativeAOT.MainActivity.OnCreate(Bundle savedInstanceState) + 0x2f4 F DOTNET : at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState) + 0xc8 which prints out the managed exception that we would expect to be raised by `AppDomain.UnhandledException`, once that integration works. TODO: once dotnet/runtime#102730 is fixed, update `UncaughtExceptionMarshaler` to do whatever it needs to do to cause the `AppDomain.UnhandledException` event to be raised. Update `JavaInteropRuntime.init()` to marshal excpetions back to Java, so that the process appropriately terminates if `init()` fails. [0]: https://learn.microsoft.com/dotnet/api/system.appdomain.unhandledexception?view=net-9.0
diff --git a/samples/NativeAOT/MainActivity.cs b/samples/NativeAOT/MainActivity.cs
@@ -22,5 +22,10 @@ protected override void OnCreate(Bundle? savedInstanceState)
         // An example of an Android API that uses a Java array
         var list = new ColorStateList (new int[][] { [ 0, 1 ]}, [0, 1]);
         Log.Debug ("NativeAOT", "MainActivity.OnCreate() ColorStateList: " + list);
+
+        var t = Intent?.Extras?.GetBoolean ("throw") ?? false;
+        if (t) {
+            throw new InvalidOperationException ("What happened?");
+        }
     }
 }
diff --git a/src/Microsoft.Android.Runtime.NativeAOT/Android.Runtime.NativeAOT/JavaInteropRuntime.cs b/src/Microsoft.Android.Runtime.NativeAOT/Android.Runtime.NativeAOT/JavaInteropRuntime.cs
@@ -33,6 +33,7 @@ static void JNI_OnUnload (IntPtr vm, IntPtr reserved)
 	[UnmanagedCallersOnly (EntryPoint="Java_net_dot_jni_nativeaot_JavaInteropRuntime_init")]
 	static void init (IntPtr jnienv, IntPtr klass)
 	{
+		JniTransition   transition  = default;
 		try {
 			var settings    = new DiagnosticSettings ();
 			settings.AddDebugDotnetLog ();
@@ -50,9 +51,16 @@ static void init (IntPtr jnienv, IntPtr klass)
 
 			// Entry point into Mono.Android.dll
 			JNIEnvInit.InitializeJniRuntime (runtime);
+
+			transition  = new JniTransition (jnienv);
+
+			var handler = Java.Lang.Thread.DefaultUncaughtExceptionHandler;
+			Java.Lang.Thread.DefaultUncaughtExceptionHandler = new UncaughtExceptionMarshaler (handler);
 		}
 		catch (Exception e) {
 			AndroidLog.Print (AndroidLogLevel.Error, "JavaInteropRuntime", $"JavaInteropRuntime.init: error: {e}");
+			transition.SetPendingException (e);
 		}
+		transition.Dispose ();
 	}
 }
diff --git a/src/Microsoft.Android.Runtime.NativeAOT/UncaughtExceptionMarshaler.cs b/src/Microsoft.Android.Runtime.NativeAOT/UncaughtExceptionMarshaler.cs
@@ -0,0 +1,20 @@
+using Java.Interop;
+
+namespace Microsoft.Android.Runtime;
+
+class UncaughtExceptionMarshaler (Java.Lang.Thread.IUncaughtExceptionHandler? OriginalHandler)
+	: Java.Lang.Object, Java.Lang.Thread.IUncaughtExceptionHandler
+{
+	public void UncaughtException (Java.Lang.Thread thread, Java.Lang.Throwable exception)
+	{
+		var e = (JniEnvironment.Runtime.ValueManager.PeekValue (exception.PeerReference) as System.Exception)
+			?? exception;
+
+		AndroidLog.Print (AndroidLogLevel.Fatal, "DOTNET", $"FATAL UNHANDLED EXCEPTION: {e}");
+
+		// TODO: https://github.com/dotnet/runtime/issues/102730
+		// ExceptionHandling.RaiseUnhandledExceptionEvent(e);
+
+		OriginalHandler?.UncaughtException (thread, exception);
+	}
+}

Original file line number	Diff line number	Diff line change
`@@ -22,5 +22,10 @@ protected override void OnCreate(Bundle? savedInstanceState)`
`22`	`22`	`// An example of an Android API that uses a Java array`
`23`	`23`	`var list = new ColorStateList (new int[][] { [ 0, 1 ]}, [0, 1]);`
`24`	`24`	`Log.Debug ("NativeAOT", "MainActivity.OnCreate() ColorStateList: " + list);`
	`25`	`+`
	`26`	`+ var t = Intent?.Extras?.GetBoolean ("throw") ?? false;`
	`27`	`+ if (t) {`
	`28`	`+ throw new InvalidOperationException ("What happened?");`
	`29`	`+ }`
`25`	`30`	`}`
`26`	`31`	`}`
Original file line number	Diff line number	Diff line change
`@@ -33,6 +33,7 @@ static void JNI_OnUnload (IntPtr vm, IntPtr reserved)`
`33`	`33`	`[UnmanagedCallersOnly (EntryPoint="Java_net_dot_jni_nativeaot_JavaInteropRuntime_init")]`
`34`	`34`	`static void init (IntPtr jnienv, IntPtr klass)`
`35`	`35`	`{`
	`36`	`+ JniTransition transition = default;`
`36`	`37`	`try {`
`37`	`38`	`var settings = new DiagnosticSettings ();`
`38`	`39`	`settings.AddDebugDotnetLog ();`
`@@ -50,9 +51,16 @@ static void init (IntPtr jnienv, IntPtr klass)`
`50`	`51`
`51`	`52`	`// Entry point into Mono.Android.dll`
`52`	`53`	`JNIEnvInit.InitializeJniRuntime (runtime);`
	`54`	`+`
	`55`	`+ transition = new JniTransition (jnienv);`
	`56`	`+`
	`57`	`+ var handler = Java.Lang.Thread.DefaultUncaughtExceptionHandler;`
	`58`	`+ Java.Lang.Thread.DefaultUncaughtExceptionHandler = new UncaughtExceptionMarshaler (handler);`
`53`	`59`	`}`
`54`	`60`	`catch (Exception e) {`
`55`	`61`	`AndroidLog.Print (AndroidLogLevel.Error, "JavaInteropRuntime", $"JavaInteropRuntime.init: error: {e}");`
	`62`	`+ transition.SetPendingException (e);`
`56`	`63`	`}`
	`64`	`+ transition.Dispose ();`
`57`	`65`	`}`
`58`	`66`	`}`