[release/10.0] Implement UnhandledException hook for finalizer scenario in Mono. (#118878)

github-actions[bot] · VSadov · web-flow · commit 39349e82be75 · 2025-08-29T09:08:14.000-07:00
* Implement UnhandledException hook for finalizers in Mono. * Cache the finalize method on wasm * Precompile invoke helper for GuardedFinalize * only check for GuardedFinalize in corlib * make GuardedFinalize virtual * use mono_runtime_try_invoke, since we can wih instance methods * comment out unused * Move GuardedFinalize to a helper class * make it static * some cleanup * remove no longer relevant comment * Disable UnhandledExceptionHandler tests with foreign threads on `llvmfullaot` (#119039) These kind of tests are not compatible. --------- Co-authored-by: vsadov <8218165+VSadov@users.noreply.github.com> Co-authored-by: Vladimir Sadov <vsadov@microsoft.com>
diff --git a/src/mono/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.xml b/src/mono/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.xml
@@ -278,6 +278,12 @@
 			<method name="GetHashCode" />
 		</type>
 
+		<!-- domain.c: mono_defaults.gc_class -->
+		<type fullname="System.GC">
+			<!-- gc.c: mono_gc_run_finalize -->
+			<method name="GuardedFinalize" />
+		</type>
+
 		<!-- appdomain.c (create_domain_objects) domain->out_of_memory_ex -->
 		<type fullname="System.OutOfMemoryException">
 			<!-- mono_exception_from_name_two_strings (only one string in the signature since NULL is used as the 2nd parameter) -->
diff --git a/src/mono/System.Private.CoreLib/src/System/GC.Mono.cs b/src/mono/System.Private.CoreLib/src/System/GC.Mono.cs
@@ -4,6 +4,7 @@
 using System.Diagnostics.Tracing;
 using System.Runtime;
 using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
 
 namespace System
 {
@@ -149,6 +150,20 @@ public static void ReRegisterForFinalize(object obj)
             _ReRegisterForFinalize(obj);
         }
 
+        [UnsafeAccessor(UnsafeAccessorKind.Method, Name = nameof(Finalize))]
+        private static extern void CallFinalize(object o);
+        private static void GuardedFinalize(object o)
+        {
+            try
+            {
+                CallFinalize(o);
+            }
+            catch (Exception ex) when (ExceptionHandling.IsHandledByGlobalHandler(ex))
+            {
+                // the handler returned "true" means the exception is now "handled" and we should continue.
+            }
+        }
+
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         public static extern long GetTotalMemory(bool forceFullCollection);
 
diff --git a/src/mono/mono/metadata/class-internals.h b/src/mono/mono/metadata/class-internals.h
@@ -889,6 +889,7 @@ typedef struct {
 	MonoClass *threadabortexception_class;
 	MonoClass *thread_class;
 	MonoClass *internal_thread_class;
+	MonoClass *gc_class;
 	MonoClass *autoreleasepool_class;
 	MonoClass *mono_method_message_class;
 	MonoClass *field_info_class;
diff --git a/src/mono/mono/metadata/domain.c b/src/mono/mono/metadata/domain.c
@@ -238,6 +238,9 @@ mono_init_internal (const char *root_domain_name)
 	/* There is only one thread class */
 	mono_defaults.internal_thread_class = mono_defaults.thread_class;
 
+	mono_defaults.gc_class = mono_class_load_from_name (
+                mono_defaults.corlib, "System", "GC");
+
 #if defined(HOST_DARWIN)
 	mono_defaults.autoreleasepool_class = mono_class_try_load_from_name (
                 mono_defaults.corlib, "System.Threading", "AutoreleasePool");
diff --git a/src/mono/mono/metadata/gc.c b/src/mono/mono/metadata/gc.c
@@ -81,9 +81,8 @@ static gboolean finalizer_thread_exited;
 static MonoCoopCond exited_cond;
 
 static MonoInternalThread *gc_thread;
-#ifndef HOST_WASM
-static RuntimeInvokeFunction finalize_runtime_invoke;
-#endif
+
+static MonoMethod *finalize_helper;
 
 /*
  * This must be a GHashTable, since these objects can't be finalized
@@ -280,31 +279,14 @@ mono_gc_run_finalize (void *obj, void *data)
 		return;
 	}
 
-
-	/*
-	 * To avoid the locking plus the other overhead of mono_runtime_invoke_checked (),
-	 * create and precompile a wrapper which calls the finalize method using
-	 * a CALLVIRT.
-	 */
 	if (mono_log_finalizers)
 		g_log ("mono-gc-finalizers", G_LOG_LEVEL_MESSAGE, "<%s at %p> Compiling finalizer.", o_name, o);
 
-#ifndef HOST_WASM
-	if (!finalize_runtime_invoke) {
-		MonoMethod *finalize_method = mono_class_get_method_from_name_checked (mono_defaults.object_class, "Finalize", 0, 0, error);
+	if (!finalize_helper) {
+		finalize_helper = mono_class_get_method_from_name_checked (mono_defaults.gc_class, "GuardedFinalize", 1, 0, error);
 		mono_error_assert_ok (error);
-		MonoMethod *invoke = mono_marshal_get_runtime_invoke (finalize_method, TRUE);
-
-		finalize_runtime_invoke = (RuntimeInvokeFunction)mono_compile_method_checked (invoke, error);
-		mono_error_assert_ok (error); /* expect this not to fail */
 	}
 
-	RuntimeInvokeFunction runtime_invoke = finalize_runtime_invoke;
-#endif
-
-	mono_runtime_class_init_full (o->vtable, error);
-	goto_if_nok (error, unhandled_error);
-
 	if (G_UNLIKELY (MONO_GC_FINALIZE_INVOKE_ENABLED ())) {
 		MONO_GC_FINALIZE_INVOKE ((unsigned long)o, mono_object_get_size_internal (o),
 				o_ns, o_name);
@@ -315,23 +297,15 @@ mono_gc_run_finalize (void *obj, void *data)
 
 	MONO_PROFILER_RAISE (gc_finalizing_object, (o));
 
-#ifdef HOST_WASM
-	MonoMethod* finalizer = mono_class_get_finalizer (o->vtable->klass);
-	if (finalizer) { // null finalizers work fine when using the vcall invoke as Object has an empty one
-		gpointer params [1];
-		params [0] = NULL;
-		mono_runtime_try_invoke (finalizer, o, params, &exc, error);
-	}
-#else
-	runtime_invoke (o, NULL, &exc, NULL);
-#endif
+	gpointer params [1];
+	params [0] = o;
+	mono_runtime_try_invoke (finalize_helper, NULL, params, &exc, error);
 
 	MONO_PROFILER_RAISE (gc_finalized_object, (o));
 
 	if (mono_log_finalizers)
 		g_log ("mono-gc-finalizers", G_LOG_LEVEL_MESSAGE, "<%s at %p> Returned from finalizer.", o_name, o);
 
-unhandled_error:
 	if (!is_ok (error))
 		exc = (MonoObject*)mono_error_convert_to_exception (error);
 	if (exc)
diff --git a/src/mono/mono/mini/aot-compiler.c b/src/mono/mono/mini/aot-compiler.c
@@ -4977,7 +4977,7 @@ add_full_aot_wrappers (MonoAotCompile *acfg)
 		add_method (acfg, get_runtime_invoke_sig (csig));
 
 		/* runtime-invoke used by finalizers */
-		add_method (acfg, get_runtime_invoke (acfg, get_method_nofail (mono_defaults.object_class, "Finalize", 0, 0), TRUE));
+		add_method (acfg, get_runtime_invoke (acfg, get_method_nofail (mono_defaults.gc_class, "GuardedFinalize", 1, 0), FALSE));
 
 		/* This is used by mono_runtime_capture_context () */
 		method = mono_get_context_capture_method ();
diff --git a/src/mono/mono/mini/mini-runtime.c b/src/mono/mono/mini/mini-runtime.c
@@ -5363,7 +5363,7 @@ mono_precompile_assembly (MonoAssembly *ass, void *user_data)
 			mono_error_cleanup (error); /* FIXME don't swallow the error */
 			continue;
 		}
-		if (strcmp (method->name, "Finalize") == 0) {
+		if (strcmp (method->name, "GuardedFinalize") == 0) {
 			invoke = mono_marshal_get_runtime_invoke (method, FALSE);
 			mono_compile_method_checked (invoke, error);
 			mono_error_assert_ok (error);
diff --git a/src/tests/issues.targets b/src/tests/issues.targets
@@ -1707,8 +1707,11 @@
         <ExcludeList Include="$(XunitTestBinBase)/JIT/opt/Structs/MemsetMemcpyNullref/*">
             <Issue>https://github.com/dotnet/runtime/issues/98628</Issue>
         </ExcludeList>
-        <ExcludeList Include="$(XunitTestBinBase)/baseservices/exceptions/UnhandledExceptionHandler/**">
-          <Issue>NYI on Mono</Issue>
+        <ExcludeList Include="$(XunitTestBinBase)/baseservices/exceptions/UnhandledExceptionHandler/HandlerThrows/*">
+            <Issue>https://github.com/dotnet/runtime/issues/47624</Issue>
+        </ExcludeList>
+        <ExcludeList Include="$(XunitTestBinBase)/baseservices/exceptions/UnhandledExceptionHandler/NoEffectInMainThread/*">
+            <Issue>Test issue. The test relies on overriding the process return code.</Issue>
         </ExcludeList>
     </ItemGroup>
 
@@ -2186,6 +2189,12 @@
         <ExcludeList Include = "$(XunitTestBinBase)/Exceptions/ForeignThread/ForeignThreadExceptions/**">
             <Issue>llvmfullaot: EH problem</Issue>
         </ExcludeList>
+        <ExcludeList Include = "$(XunitTestBinBase)/baseservices/exceptions/UnhandledExceptionHandler/Foreign/**">
+            <Issue>llvmfullaot: EH problem</Issue>
+        </ExcludeList>
+        <ExcludeList Include = "$(XunitTestBinBase)/baseservices/exceptions/UnhandledExceptionHandler/PInvoke/**">
+            <Issue>llvmfullaot: EH problem</Issue>
+        </ExcludeList>
 
         <ExcludeList Include = "$(XunitTestBinBase)/JIT/Directed/nullabletypes/Desktop/boxunboxvaluetype_*/**">
             <Issue>https://github.com/dotnet/runtime/issues/57353</Issue>

Original file line number	Diff line number	Diff line change
`@@ -5363,7 +5363,7 @@ mono_precompile_assembly (MonoAssembly ass, void user_data)`
`5363`	`5363`	`mono_error_cleanup (error); /* FIXME don't swallow the error */`
`5364`	`5364`	`continue;`
`5365`	`5365`	`}`
`5366`		`- if (strcmp (method->name, "Finalize") == 0) {`
	`5366`	`+ if (strcmp (method->name, "GuardedFinalize") == 0) {`
`5367`	`5367`	`invoke = mono_marshal_get_runtime_invoke (method, FALSE);`
`5368`	`5368`	`mono_compile_method_checked (invoke, error);`
`5369`	`5369`	`mono_error_assert_ok (error);`