GDExtension: add support for abstract and virtual classes

core/extension/gdnative_interface.h

@@ -234,6 +234,8 @@ typedef void (*GDNativeExtensionClassFreeInstance)(void *p_userdata, GDExtension
 typedef GDNativeExtensionClassCallVirtual (*GDNativeExtensionClassGetVirtual)(void *p_userdata, const char *p_name);
 
 typedef struct {
+	GDNativeBool is_virtual;
+	GDNativeBool is_abstract;
 	GDNativeExtensionClassSet set_func;
 	GDNativeExtensionClassGet get_func;
 	GDNativeExtensionClassGetPropertyList get_property_list_func;

core/extension/native_extension.cpp

@@ -152,6 +152,8 @@ void NativeExtension::_register_extension_class(const GDNativeExtensionClassLibr
 	extension->native_extension.parent_class_name = parent_class_name;
 	extension->native_extension.class_name = class_name;
 	extension->native_extension.editor_class = self->level_initialized == INITIALIZATION_LEVEL_EDITOR;
+	extension->native_extension.is_virtual = p_extension_funcs->is_virtual;
+	extension->native_extension.is_abstract = p_extension_funcs->is_abstract;
 	extension->native_extension.set = p_extension_funcs->set_func;
 	extension->native_extension.get = p_extension_funcs->get_func;
 	extension->native_extension.get_property_list = p_extension_funcs->get_property_list_func;

core/object/class_db.cpp

@@ -1528,7 +1528,10 @@ void ClassDB::register_extension_class(ObjectNativeExtension *p_extension) {
 	c.api = p_extension->editor_class ? API_EDITOR_EXTENSION : API_EXTENSION;
 	c.native_extension = p_extension;
 	c.name = p_extension->class_name;
-	c.creation_func = parent->creation_func;
+	c.is_virtual = p_extension->is_virtual;
+	if (!p_extension->is_abstract) {
+		c.creation_func = parent->creation_func;
+	}
 	c.inherits = parent->name;
 	c.class_ptr = parent->class_ptr;
 	c.inherits_ptr = parent;

core/object/object.h

@@ -295,6 +295,8 @@ struct ObjectNativeExtension {
 	StringName parent_class_name;
 	StringName class_name;
 	bool editor_class = false;
+	bool is_virtual = false;
+	bool is_abstract = false;
 	GDNativeExtensionClassSet set;
 	GDNativeExtensionClassGet get;
 	GDNativeExtensionClassGetPropertyList get_property_list;