Fix/workaround for issue #21667

When a Reference managed instance is garbage collected and its finalizer is called, it could happen that the native instance is referenced once again before the finalizer can unreference and memdelete it. The workaround is to create a new managed instance when this happens (at least for now).

1 files changed, 64 insertions, 6 deletions

diff --git a/modules/mono/glue/base_object_glue.cpp b/modules/mono/glue/base_object_glue.cpp
index 8ee2fae475..d718c3cc61 100644
--- a/modules/mono/glue/base_object_glue.cpp
+++ b/modules/mono/glue/base_object_glue.cpp
@@ -35,21 +35,78 @@
 #include "core/reference.h"
 #include "core/string_db.h"
 
+#include "../csharp_script.h"
 #include "../mono_gd/gd_mono_internals.h"
 #include "../mono_gd/gd_mono_utils.h"
 #include "../signal_awaiter_utils.h"
 
-Object *godot_icall_Object_Ctor(MonoObject *obj) {
+Object *godot_icall_Object_Ctor(MonoObject *p_obj) {
 	Object *instance = memnew(Object);
-	GDMonoInternals::tie_managed_to_unmanaged(obj, instance);
+	GDMonoInternals::tie_managed_to_unmanaged(p_obj, instance);
 	return instance;
 }
 
-void godot_icall_Object_Dtor(MonoObject *obj, Object *ptr) {
+void godot_icall_Object_Disposed(MonoObject *p_obj, Object *p_ptr) {
 #ifdef DEBUG_ENABLED
-	CRASH_COND(ptr == NULL);
+	CRASH_COND(p_ptr == NULL);
 #endif
-	_GodotSharp::get_singleton()->queue_dispose(obj, ptr);
+
+	if (p_ptr->get_script_instance()) {
+		CSharpInstance *cs_instance = CAST_CSHARP_INSTANCE(p_ptr->get_script_instance());
+		if (cs_instance) {
+			cs_instance->mono_object_disposed(p_obj);
+			p_ptr->set_script_instance(NULL);
+			return;
+		}
+	}
+
+	void *data = p_ptr->get_script_instance_binding(CSharpLanguage::get_singleton()->get_language_index());
+
+	if (data) {
+		Ref<MonoGCHandle> &gchandle = ((Map<Object *, CSharpScriptBinding>::Element *)data)->get().gchandle;
+		if (gchandle.is_valid()) {
+			CSharpLanguage::release_script_gchandle(p_obj, gchandle);
+		}
+	}
+}
+
+void godot_icall_Reference_Disposed(MonoObject *p_obj, Object *p_ptr, bool p_is_finalizer) {
+#ifdef DEBUG_ENABLED
+	CRASH_COND(p_ptr == NULL);
+	// This is only called with Reference derived classes
+	CRASH_COND(!Object::cast_to<Reference>(p_ptr));
+#endif
+
+	Reference *ref = static_cast<Reference *>(p_ptr);
+
+	if (ref->get_script_instance()) {
+		CSharpInstance *cs_instance = CAST_CSHARP_INSTANCE(ref->get_script_instance());
+		if (cs_instance) {
+			bool r_owner_deleted;
+			cs_instance->mono_object_disposed_baseref(p_obj, p_is_finalizer, r_owner_deleted);
+			if (!r_owner_deleted && !p_is_finalizer) {
+				// If the native instance is still alive and Dispose() was called
+				// (instead of the finalizer), then we remove the script instance.
+				ref->set_script_instance(NULL);
+			}
+			return;
+		}
+	}
+
+	// Unsafe refcount decrement. The managed instance also counts as a reference.
+	// See: CSharpLanguage::alloc_instance_binding_data(Object *p_object)
+	if (ref->unreference()) {
+		memdelete(ref);
+	} else {
+		void *data = ref->get_script_instance_binding(CSharpLanguage::get_singleton()->get_language_index());
+
+		if (data) {
+			Ref<MonoGCHandle> &gchandle = ((Map<Object *, CSharpScriptBinding>::Element *)data)->get().gchandle;
+			if (gchandle.is_valid()) {
+				CSharpLanguage::release_script_gchandle(p_obj, gchandle);
+			}
+		}
+	}
 }
 
 MethodBind *godot_icall_Object_ClassDB_get_method(MonoString *p_type, MonoString *p_method) {
@@ -87,7 +144,8 @@ Error godot_icall_SignalAwaiter_connect(Object *p_source, MonoString *p_signal,
 
 void godot_register_object_icalls() {
 	mono_add_internal_call("Godot.Object::godot_icall_Object_Ctor", (void *)godot_icall_Object_Ctor);
-	mono_add_internal_call("Godot.Object::godot_icall_Object_Dtor", (void *)godot_icall_Object_Dtor);
+	mono_add_internal_call("Godot.Object::godot_icall_Object_Disposed", (void *)godot_icall_Object_Disposed);
+	mono_add_internal_call("Godot.Object::godot_icall_Reference_Disposed", (void *)godot_icall_Reference_Disposed);
 	mono_add_internal_call("Godot.Object::godot_icall_Object_ClassDB_get_method", (void *)godot_icall_Object_ClassDB_get_method);
 	mono_add_internal_call("Godot.Object::godot_icall_Object_weakref", (void *)godot_icall_Object_weakref);
 	mono_add_internal_call("Godot.SignalAwaiter::godot_icall_SignalAwaiter_connect", (void *)godot_icall_SignalAwaiter_connect);