1 files changed, 96 insertions, 13 deletions

diff --git a/core/extension/gdextension.cpp b/core/extension/gdextension.cpp
index 9b3282ecba..5d43dceece 100644
--- a/core/extension/gdextension.cpp
+++ b/core/extension/gdextension.cpp
@@ -205,6 +205,7 @@ public:
 	virtual Variant call(Object *p_object, const Variant **p_args, int p_arg_count, Callable::CallError &r_error) const override {
 #ifdef TOOLS_ENABLED
 		ERR_FAIL_COND_V_MSG(!valid, Variant(), vformat("Cannot call invalid GDExtension method bind '%s'. It's probably cached - you may need to restart Godot.", name));
+		ERR_FAIL_COND_V_MSG(p_object && p_object->is_extension_placeholder(), Variant(), vformat("Cannot call GDExtension method bind '%s' on placeholder instance.", name));
 #endif
 		Variant ret;
 		GDExtensionClassInstancePtr extension_instance = is_static() ? nullptr : p_object->_get_extension_instance();
@@ -218,6 +219,7 @@ public:
 	virtual void validated_call(Object *p_object, const Variant **p_args, Variant *r_ret) const override {
 #ifdef TOOLS_ENABLED
 		ERR_FAIL_COND_MSG(!valid, vformat("Cannot call invalid GDExtension method bind '%s'. It's probably cached - you may need to restart Godot.", name));
+		ERR_FAIL_COND_MSG(p_object && p_object->is_extension_placeholder(), vformat("Cannot call GDExtension method bind '%s' on placeholder instance.", name));
 #endif
 		ERR_FAIL_COND_MSG(vararg, "Vararg methods don't have validated call support. This is most likely an engine bug.");
 		GDExtensionClassInstancePtr extension_instance = is_static() ? nullptr : p_object->_get_extension_instance();
@@ -249,6 +251,7 @@ public:
 	virtual void ptrcall(Object *p_object, const void **p_args, void *r_ret) const override {
 #ifdef TOOLS_ENABLED
 		ERR_FAIL_COND_MSG(!valid, vformat("Cannot call invalid GDExtension method bind '%s'. It's probably cached - you may need to restart Godot.", name));
+		ERR_FAIL_COND_MSG(p_object && p_object->is_extension_placeholder(), vformat("Cannot call GDExtension method bind '%s' on placeholder instance.", name));
 #endif
 		ERR_FAIL_COND_MSG(vararg, "Vararg methods don't have ptrcall support. This is most likely an engine bug.");
 		GDExtensionClassInstancePtr extension_instance = p_object->_get_extension_instance();
@@ -341,10 +344,11 @@ public:
 
 #ifndef DISABLE_DEPRECATED
 void GDExtension::_register_extension_class(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo *p_extension_funcs) {
-	const GDExtensionClassCreationInfo2 class_info2 = {
+	const GDExtensionClassCreationInfo3 class_info3 = {
 		p_extension_funcs->is_virtual, // GDExtensionBool is_virtual;
 		p_extension_funcs->is_abstract, // GDExtensionBool is_abstract;
 		true, // GDExtensionBool is_exposed;
+		false, // GDExtensionBool is_runtime;
 		p_extension_funcs->set_func, // GDExtensionClassSet set_func;
 		p_extension_funcs->get_func, // GDExtensionClassGet get_func;
 		p_extension_funcs->get_property_list_func, // GDExtensionClassGetPropertyList get_property_list_func;
@@ -369,15 +373,45 @@ void GDExtension::_register_extension_class(GDExtensionClassLibraryPtr p_library
 	const ClassCreationDeprecatedInfo legacy = {
 		p_extension_funcs->notification_func,
 	};
-	_register_extension_class_internal(p_library, p_class_name, p_parent_class_name, &class_info2, &legacy);
+	_register_extension_class_internal(p_library, p_class_name, p_parent_class_name, &class_info3, &legacy);
 }
-#endif // DISABLE_DEPRECATED
 
 void GDExtension::_register_extension_class2(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo2 *p_extension_funcs) {
+	const GDExtensionClassCreationInfo3 class_info3 = {
+		p_extension_funcs->is_virtual, // GDExtensionBool is_virtual;
+		p_extension_funcs->is_abstract, // GDExtensionBool is_abstract;
+		p_extension_funcs->is_exposed, // GDExtensionBool is_exposed;
+		false, // GDExtensionBool is_runtime;
+		p_extension_funcs->set_func, // GDExtensionClassSet set_func;
+		p_extension_funcs->get_func, // GDExtensionClassGet get_func;
+		p_extension_funcs->get_property_list_func, // GDExtensionClassGetPropertyList get_property_list_func;
+		p_extension_funcs->free_property_list_func, // GDExtensionClassFreePropertyList free_property_list_func;
+		p_extension_funcs->property_can_revert_func, // GDExtensionClassPropertyCanRevert property_can_revert_func;
+		p_extension_funcs->property_get_revert_func, // GDExtensionClassPropertyGetRevert property_get_revert_func;
+		p_extension_funcs->validate_property_func, // GDExtensionClassValidateProperty validate_property_func;
+		p_extension_funcs->notification_func, // GDExtensionClassNotification2 notification_func;
+		p_extension_funcs->to_string_func, // GDExtensionClassToString to_string_func;
+		p_extension_funcs->reference_func, // GDExtensionClassReference reference_func;
+		p_extension_funcs->unreference_func, // GDExtensionClassUnreference unreference_func;
+		p_extension_funcs->create_instance_func, // GDExtensionClassCreateInstance create_instance_func; /* this one is mandatory */
+		p_extension_funcs->free_instance_func, // GDExtensionClassFreeInstance free_instance_func; /* this one is mandatory */
+		p_extension_funcs->recreate_instance_func, // GDExtensionClassRecreateInstance recreate_instance_func;
+		p_extension_funcs->get_virtual_func, // GDExtensionClassGetVirtual get_virtual_func;
+		p_extension_funcs->get_virtual_call_data_func, // GDExtensionClassGetVirtualCallData get_virtual_call_data_func;
+		p_extension_funcs->call_virtual_with_data_func, // GDExtensionClassCallVirtualWithData call_virtual_func;
+		p_extension_funcs->get_rid_func, // GDExtensionClassGetRID get_rid;
+		p_extension_funcs->class_userdata, // void *class_userdata;
+	};
+
+	_register_extension_class_internal(p_library, p_class_name, p_parent_class_name, &class_info3);
+}
+#endif // DISABLE_DEPRECATED
+
+void GDExtension::_register_extension_class3(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo3 *p_extension_funcs) {
 	_register_extension_class_internal(p_library, p_class_name, p_parent_class_name, p_extension_funcs);
 }
 
-void GDExtension::_register_extension_class_internal(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo2 *p_extension_funcs, const ClassCreationDeprecatedInfo *p_deprecated_funcs) {
+void GDExtension::_register_extension_class_internal(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo3 *p_extension_funcs, const ClassCreationDeprecatedInfo *p_deprecated_funcs) {
 	GDExtension *self = reinterpret_cast<GDExtension *>(p_library);
 
 	StringName class_name = *reinterpret_cast<const StringName *>(p_class_name);
@@ -397,15 +431,20 @@ void GDExtension::_register_extension_class_internal(GDExtensionClassLibraryPtr
 			//inheriting from engine class
 		}
 	} else {
-		ERR_FAIL_MSG("Attempt to register an extension class '" + String(class_name) + "' using non-existing parent class '" + String(parent_class_name) + "'");
+		ERR_FAIL_MSG("Attempt to register an extension class '" + String(class_name) + "' using non-existing parent class '" + String(parent_class_name) + "'.");
 	}
 
 #ifdef TOOLS_ENABLED
 	Extension *extension = nullptr;
+	bool is_runtime = (bool)p_extension_funcs->is_runtime;
 	if (self->is_reloading && self->extension_classes.has(class_name)) {
 		extension = &self->extension_classes[class_name];
 		if (!parent_extension && parent_class_name != extension->gdextension.parent_class_name) {
-			ERR_FAIL_MSG(vformat("GDExtension class '%s' attempt to change parent type from '%s' to '%s' on hot reload. Restart Godot for this change to take effect.", class_name, extension->gdextension.parent_class_name, parent_class_name));
+			ERR_FAIL_MSG(vformat("GDExtension class '%s' cannot change parent type from '%s' to '%s' on hot reload. Restart Godot for this change to take effect.", class_name, extension->gdextension.parent_class_name, parent_class_name));
+		}
+		if (extension->gdextension.is_runtime != is_runtime) {
+			ERR_PRINT(vformat("GDExtension class '%s' cannot change to/from runtime class on hot reload. Restart Godot for this change to take effect.", class_name));
+			is_runtime = extension->gdextension.is_runtime;
 		}
 		extension->is_reloading = false;
 	} else {
@@ -434,6 +473,9 @@ void GDExtension::_register_extension_class_internal(GDExtensionClassLibraryPtr
 	extension->gdextension.is_virtual = p_extension_funcs->is_virtual;
 	extension->gdextension.is_abstract = p_extension_funcs->is_abstract;
 	extension->gdextension.is_exposed = p_extension_funcs->is_exposed;
+#ifdef TOOLS_ENABLED
+	extension->gdextension.is_runtime = is_runtime;
+#endif
 	extension->gdextension.set = p_extension_funcs->set_func;
 	extension->gdextension.get = p_extension_funcs->get_func;
 	extension->gdextension.get_property_list = p_extension_funcs->get_property_list_func;
@@ -836,8 +878,9 @@ void GDExtension::initialize_gdextensions() {
 
 #ifndef DISABLE_DEPRECATED
 	register_interface_function("classdb_register_extension_class", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class);
-#endif // DISABLE_DEPRECATED
 	register_interface_function("classdb_register_extension_class2", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class2);
+#endif // DISABLE_DEPRECATED
+	register_interface_function("classdb_register_extension_class3", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class3);
 	register_interface_function("classdb_register_extension_class_method", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class_method);
 	register_interface_function("classdb_register_extension_class_virtual_method", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class_virtual_method);
 	register_interface_function("classdb_register_extension_class_integer_constant", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_extension_class_integer_constant);
@@ -910,6 +953,39 @@ Error GDExtensionResourceLoader::load_gdextension_resource(const String &p_path,
 		return ERR_INVALID_DATA;
 	}
 
+	// Optionally check maximum compatibility.
+	if (config->has_section_key("configuration", "compatibility_maximum")) {
+		uint32_t compatibility_maximum[3] = { 0, 0, 0 };
+		String compat_string = config->get_value("configuration", "compatibility_maximum");
+		Vector<int> parts = compat_string.split_ints(".");
+		for (int i = 0; i < 3; i++) {
+			if (i < parts.size() && parts[i] >= 0) {
+				compatibility_maximum[i] = parts[i];
+			} else {
+				// If a version part is missing, set the maximum to an arbitrary high value.
+				compatibility_maximum[i] = 9999;
+			}
+		}
+
+		compatible = true;
+		if (VERSION_MAJOR != compatibility_maximum[0]) {
+			compatible = VERSION_MAJOR < compatibility_maximum[0];
+		} else if (VERSION_MINOR != compatibility_maximum[1]) {
+			compatible = VERSION_MINOR < compatibility_maximum[1];
+		}
+#if VERSION_PATCH
+		// #if check to avoid -Wtype-limits warning when 0.
+		else {
+			compatible = VERSION_PATCH <= compatibility_maximum[2];
+		}
+#endif
+
+		if (!compatible) {
+			ERR_PRINT(vformat("GDExtension only compatible with Godot version %s or earlier: %s", compat_string, p_path));
+			return ERR_INVALID_DATA;
+		}
+	}
+
 	String library_path = GDExtension::find_extension_library(p_path, config, [](const String &p_feature) { return OS::get_singleton()->has_feature(p_feature); });
 
 	if (library_path.is_empty()) {
@@ -1056,7 +1132,10 @@ void GDExtension::prepare_reload() {
 
 				state.push_back(Pair<String, Variant>(P.name, value));
 			}
-			E.value.instance_state[obj_id] = state;
+			E.value.instance_state[obj_id] = {
+				state, // List<Pair<String, Variant>> properties;
+				obj->is_extension_placeholder(), // bool is_placeholder;
+			};
 		}
 	}
 }
@@ -1131,25 +1210,29 @@ void GDExtension::finish_reload() {
 	for (KeyValue<StringName, Extension> &E : extension_classes) {
 		// Loop over 'instance_state' rather than 'instance' because new instances
 		// may have been created when re-initializing the extension.
-		for (const KeyValue<ObjectID, List<Pair<String, Variant>>> &S : E.value.instance_state) {
+		for (const KeyValue<ObjectID, Extension::InstanceState> &S : E.value.instance_state) {
 			Object *obj = ObjectDB::get_instance(S.key);
 			if (!obj) {
 				continue;
 			}
 
-			obj->reset_internal_extension(&E.value.gdextension);
+			if (S.value.is_placeholder) {
+				obj->reset_internal_extension(ClassDB::get_placeholder_extension(E.value.gdextension.class_name));
+			} else {
+				obj->reset_internal_extension(&E.value.gdextension);
+			}
 		}
 	}
 
 	// Now that all the classes are back, restore the state.
 	for (KeyValue<StringName, Extension> &E : extension_classes) {
-		for (const KeyValue<ObjectID, List<Pair<String, Variant>>> &S : E.value.instance_state) {
+		for (const KeyValue<ObjectID, Extension::InstanceState> &S : E.value.instance_state) {
 			Object *obj = ObjectDB::get_instance(S.key);
 			if (!obj) {
 				continue;
 			}
 
-			for (const Pair<String, Variant> &state : S.value) {
+			for (const Pair<String, Variant> &state : S.value.properties) {
 				obj->set(state.first, state.second);
 			}
 		}
@@ -1157,7 +1240,7 @@ void GDExtension::finish_reload() {
 
 	// Finally, let the objects know that we are done reloading them.
 	for (KeyValue<StringName, Extension> &E : extension_classes) {
-		for (const KeyValue<ObjectID, List<Pair<String, Variant>>> &S : E.value.instance_state) {
+		for (const KeyValue<ObjectID, Extension::InstanceState> &S : E.value.instance_state) {
 			Object *obj = ObjectDB::get_instance(S.key);
 			if (!obj) {
 				continue;