Change constructor/destructor management of extension classes

This makes sure custom constructors are always called on extension
classes. However, note that constructors should not take any parameters,
since Godot doesn't support that. Parameters are ignore in memnew macro.

Use memnew(MyClass()) instead of memnew(MyClass) since it now needs a
value instead of a class name. This macro calls MyClass::_new() (define
in GDCLASS macro) which ultimately calls Godot to create the object,
ensuring that both the Godot and the extension instances are created.

Non Godot classes (that don't derive godot::Object) are constructed as
usual an can have parameters.

memdelete is also changed for the same reason, as it needs to destroy
the Godot object as well, and that automatically frees the bound
extension instance.

4 files changed, 175 insertions, 114 deletions

diff --git a/include/godot_cpp/classes/ref.hpp b/include/godot_cpp/classes/ref.hpp
index 2140ef3..2ca5f83 100644
--- a/include/godot_cpp/classes/ref.hpp
+++ b/include/godot_cpp/classes/ref.hpp
@@ -199,7 +199,7 @@ public:
 	}
 
 	void instantiate() {
-		ref(memnew(T));
+		ref(memnew(T()));
 	}
 
 	Ref() {}
diff --git a/include/godot_cpp/classes/wrapped.hpp b/include/godot_cpp/classes/wrapped.hpp
index 8402e9c..2a0422a 100644
--- a/include/godot_cpp/classes/wrapped.hpp
+++ b/include/godot_cpp/classes/wrapped.hpp
@@ -33,10 +33,8 @@
 
 #include <godot_cpp/core/memory.hpp>
 
+#include <godot_cpp/godot.hpp>
 namespace godot {
-namespace internal {
-struct empty_constructor {};
-} // namespace internal
 
 typedef void GodotObject;
 
@@ -50,124 +48,169 @@ class Wrapped {
 
 protected:
 	Wrapped() = default;
-	Wrapped(internal::empty_constructor empty) {}
 
 public:
 	// Must be public but you should not touch this.
 	GodotObject *_owner = nullptr;
+
+	static Wrapped *_new() {
+		return nullptr;
+	}
+};
+
+namespace internal {
+
+template <class T, class Enable = void>
+struct Creator {
+	static T *_new() { return nullptr; }
 };
 
+template <class T>
+struct Creator<T, typename std::enable_if<std::is_base_of_v<godot::Wrapped, T>>::type> {
+	static T *_new() { return T::_new(); }
+};
+
+// template <class T>
+// struct Creator<T, std::false_type> {
+// };
+
+// template <class T>
+// struct Creator<T, std::enable_if_t<std::is_base_of_v<godot::Wrapped, T>, bool>> {
+// 	static T *_new() { return T::_new(); }
+// };
+
+}; // namespace internal
+
 } // namespace godot
 
-#define GDCLASS(m_class, m_inherits)                                                                               \
-private:                                                                                                           \
-	friend class ClassDB;                                                                                          \
-                                                                                                                   \
-	using SelfType = m_class;                                                                                      \
-                                                                                                                   \
-protected:                                                                                                         \
-	static void (*_get_bind_methods())() {                                                                         \
-		return &m_class::_bind_methods;                                                                            \
-	}                                                                                                              \
-                                                                                                                   \
-	m_class(godot::GodotObject *owner) : m_inherits(godot::internal::empty_constructor()) {                        \
-		_owner = owner;                                                                                            \
-	}                                                                                                              \
-                                                                                                                   \
-	m_class(godot::internal::empty_constructor empty) : m_inherits(empty) {}                                       \
-                                                                                                                   \
-	template <class T>                                                                                             \
-	static void register_virtuals() {                                                                              \
-		m_inherits::register_virtuals<T>();                                                                        \
-	}                                                                                                              \
-                                                                                                                   \
-public:                                                                                                            \
-	static void initialize_class() {                                                                               \
-		static bool initialized = false;                                                                           \
-		if (initialized) {                                                                                         \
-			return;                                                                                                \
-		}                                                                                                          \
-		m_inherits::initialize_class();                                                                            \
-		if (m_class::_get_bind_methods() != m_inherits::_get_bind_methods()) {                                     \
-			_bind_methods();                                                                                       \
-			m_inherits::register_virtuals<m_class>();                                                              \
-		}                                                                                                          \
-		initialized = true;                                                                                        \
-	}                                                                                                              \
-                                                                                                                   \
-	static const char *get_class_static() {                                                                        \
-		return #m_class;                                                                                           \
-	}                                                                                                              \
-                                                                                                                   \
-	static const char *get_parent_class_static() {                                                                 \
-		return #m_inherits;                                                                                        \
-	}                                                                                                              \
-                                                                                                                   \
-	static GDExtensionClassInstancePtr create(void *data) {                                                        \
-		return (GDExtensionClassInstancePtr)godot::Memory::alloc_static(sizeof(m_class));                          \
-	}                                                                                                              \
-                                                                                                                   \
-	static void free(void *data, GDExtensionClassInstancePtr ptr) {                                                \
-		godot::memdelete(reinterpret_cast<m_class *>(ptr));                                                        \
-	}                                                                                                              \
-                                                                                                                   \
-	static void set_object_instance(GDExtensionClassInstancePtr p_instance, GDNativeObjectPtr p_object_instance) { \
-		memnew_placement((void *)p_instance, m_class((godot::GodotObject *)p_object_instance));                    \
-	}                                                                                                              \
-                                                                                                                   \
-	static void *___binding_create_callback(void *p_token, void *p_instance) {                                     \
-		return memnew(m_class((godot::GodotObject *)p_instance));                                                  \
-	}                                                                                                              \
-	static void ___binding_free_callback(void *p_token, void *p_instance, void *p_binding) {                       \
-		memdelete((m_class *)p_binding);                                                                           \
-	}                                                                                                              \
-	static GDNativeBool ___binding_reference_callback(void *p_token, void *p_instance, GDNativeBool p_reference) { \
-		return true;                                                                                               \
-	}                                                                                                              \
-	static constexpr GDNativeInstanceBindingCallbacks ___binding_callbacks = {                                     \
-		___binding_create_callback,                                                                                \
-		___binding_free_callback,                                                                                  \
-		___binding_reference_callback,                                                                             \
-	};                                                                                                             \
-                                                                                                                   \
+#ifdef DEBUG_ENABLED
+#define CHECK_CLASS_CONSTRUCTOR(m_constructor, m_class)                                                      \
+	if (unlikely(!m_constructor)) {                                                                          \
+		ERR_PRINT_ONCE("Constructor for class " #m_class "not found. Likely wasn't registered in ClassDB."); \
+		return nullptr;                                                                                      \
+	} else                                                                                                   \
+		((void)0)
+#else
+#define CHECK_CLASS_CONSTRUCTOR(m_constructor, m_class)
+#endif
+
+#define GDCLASS(m_class, m_inherits)                                                                                                                              \
+private:                                                                                                                                                          \
+	friend class ClassDB;                                                                                                                                         \
+                                                                                                                                                                  \
+	using SelfType = m_class;                                                                                                                                     \
+                                                                                                                                                                  \
+protected:                                                                                                                                                        \
+	static void (*_get_bind_methods())() {                                                                                                                        \
+		return &m_class::_bind_methods;                                                                                                                           \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	template <class T>                                                                                                                                            \
+	static void register_virtuals() {                                                                                                                             \
+		m_inherits::register_virtuals<T>();                                                                                                                       \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+public:                                                                                                                                                           \
+	static void initialize_class() {                                                                                                                              \
+		static bool initialized = false;                                                                                                                          \
+		if (initialized) {                                                                                                                                        \
+			return;                                                                                                                                               \
+		}                                                                                                                                                         \
+		m_inherits::initialize_class();                                                                                                                           \
+		if (m_class::_get_bind_methods() != m_inherits::_get_bind_methods()) {                                                                                    \
+			_bind_methods();                                                                                                                                      \
+			m_inherits::register_virtuals<m_class>();                                                                                                             \
+		}                                                                                                                                                         \
+		initialized = true;                                                                                                                                       \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static const char *get_class_static() {                                                                                                                       \
+		return #m_class;                                                                                                                                          \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static const char *get_parent_class_static() {                                                                                                                \
+		return #m_inherits;                                                                                                                                       \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static GDExtensionClassInstancePtr create(void *data) {                                                                                                       \
+		return reinterpret_cast<GDExtensionClassInstancePtr>(new ("") m_class);                                                                                   \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static void free(void *data, GDExtensionClassInstancePtr ptr) {                                                                                               \
+		Memory::free_static(reinterpret_cast<m_class *>(ptr));                                                                                                    \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static void set_object_instance(GDExtensionClassInstancePtr p_instance, GDNativeObjectPtr p_object_instance) {                                                \
+		reinterpret_cast<m_class *>(p_instance)->_owner = reinterpret_cast<GodotObject *>(p_object_instance);                                                     \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static void *___binding_create_callback(void *p_token, void *p_instance) {                                                                                    \
+		m_class *result = new ("") m_class;                                                                                                                       \
+		result->_owner = reinterpret_cast<godot::GodotObject *>(p_instance);                                                                                      \
+		return result;                                                                                                                                            \
+	}                                                                                                                                                             \
+	static void ___binding_free_callback(void *p_token, void *p_instance, void *p_binding) {                                                                      \
+		Memory::free_static(reinterpret_cast<m_class *>(p_binding));                                                                                              \
+	}                                                                                                                                                             \
+	static GDNativeBool ___binding_reference_callback(void *p_token, void *p_instance, GDNativeBool p_reference) {                                                \
+		return true;                                                                                                                                              \
+	}                                                                                                                                                             \
+	static constexpr GDNativeInstanceBindingCallbacks ___binding_callbacks = {                                                                                    \
+		___binding_create_callback,                                                                                                                               \
+		___binding_free_callback,                                                                                                                                 \
+		___binding_reference_callback,                                                                                                                            \
+	};                                                                                                                                                            \
+                                                                                                                                                                  \
+	static m_class *_new() {                                                                                                                                      \
+		static GDNativeClassConstructor ___constructor = godot::internal::interface->classdb_get_constructor(#m_class);                                           \
+		CHECK_CLASS_CONSTRUCTOR(___constructor, m_class);                                                                                                         \
+		GDNativeObjectPtr obj = ___constructor();                                                                                                                 \
+		return reinterpret_cast<m_class *>(godot::internal::interface->object_get_instance_binding(obj, godot::internal::token, &m_class::___binding_callbacks)); \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
 private:
 
 // Don't use this for your classes, use GDCLASS() instead.
-#define GDNATIVE_CLASS(m_class, m_inherits)                                                                        \
-protected:                                                                                                         \
-	static void (*_get_bind_methods())() {                                                                         \
-		return nullptr;                                                                                            \
-	}                                                                                                              \
-	m_class(godot::internal::empty_constructor empty) : m_inherits(empty) {}                                       \
-                                                                                                                   \
-public:                                                                                                            \
-	static void initialize_class() {}                                                                              \
-                                                                                                                   \
-	static const char *get_class_static() {                                                                        \
-		return #m_class;                                                                                           \
-	}                                                                                                              \
-                                                                                                                   \
-	static const char *get_parent_class_static() {                                                                 \
-		return #m_inherits;                                                                                        \
-	}                                                                                                              \
-                                                                                                                   \
-	static void *___binding_create_callback(void *p_token, void *p_instance) {                                     \
-		m_class *obj = memnew(m_class(godot::internal::empty_constructor()));                                      \
-		obj->_owner = (godot::GodotObject *)p_instance;                                                            \
-		return obj;                                                                                                \
-	}                                                                                                              \
-	static void ___binding_free_callback(void *p_token, void *p_instance, void *p_binding) {                       \
-		memdelete((m_class *)p_binding);                                                                           \
-	}                                                                                                              \
-	static GDNativeBool ___binding_reference_callback(void *p_token, void *p_instance, GDNativeBool p_reference) { \
-		return true;                                                                                               \
-	}                                                                                                              \
-	static constexpr GDNativeInstanceBindingCallbacks ___binding_callbacks = {                                     \
-		___binding_create_callback,                                                                                \
-		___binding_free_callback,                                                                                  \
-		___binding_reference_callback,                                                                             \
-	};                                                                                                             \
-                                                                                                                   \
+#define GDNATIVE_CLASS(m_class, m_inherits)                                                                                                                       \
+protected:                                                                                                                                                        \
+	static void (*_get_bind_methods())() {                                                                                                                        \
+		return nullptr;                                                                                                                                           \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+public:                                                                                                                                                           \
+	static void initialize_class() {}                                                                                                                             \
+                                                                                                                                                                  \
+	static const char *get_class_static() {                                                                                                                       \
+		return #m_class;                                                                                                                                          \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static const char *get_parent_class_static() {                                                                                                                \
+		return #m_inherits;                                                                                                                                       \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
+	static void *___binding_create_callback(void *p_token, void *p_instance) {                                                                                    \
+		m_class *obj = new ("") m_class;                                                                                                                          \
+		obj->_owner = (godot::GodotObject *)p_instance;                                                                                                           \
+		return obj;                                                                                                                                               \
+	}                                                                                                                                                             \
+	static void ___binding_free_callback(void *p_token, void *p_instance, void *p_binding) {                                                                      \
+		Memory::free_static(reinterpret_cast<m_class *>(p_binding));                                                                                              \
+	}                                                                                                                                                             \
+	static GDNativeBool ___binding_reference_callback(void *p_token, void *p_instance, GDNativeBool p_reference) {                                                \
+		return true;                                                                                                                                              \
+	}                                                                                                                                                             \
+	static constexpr GDNativeInstanceBindingCallbacks ___binding_callbacks = {                                                                                    \
+		___binding_create_callback,                                                                                                                               \
+		___binding_free_callback,                                                                                                                                 \
+		___binding_reference_callback,                                                                                                                            \
+	};                                                                                                                                                            \
+	static m_class *_new() {                                                                                                                                      \
+		static GDNativeClassConstructor ___constructor = godot::internal::interface->classdb_get_constructor(#m_class);                                           \
+		CHECK_CLASS_CONSTRUCTOR(___constructor, m_class);                                                                                                         \
+		GDNativeObjectPtr obj = ___constructor();                                                                                                                 \
+		return reinterpret_cast<m_class *>(godot::internal::interface->object_get_instance_binding(obj, godot::internal::token, &m_class::___binding_callbacks)); \
+	}                                                                                                                                                             \
+                                                                                                                                                                  \
 private:
 
 #endif // ! GODOT_CPP_WRAPPED_HPP
diff --git a/include/godot_cpp/core/memory.hpp b/include/godot_cpp/core/memory.hpp
index d95ca40..c493e89 100644
--- a/include/godot_cpp/core/memory.hpp
+++ b/include/godot_cpp/core/memory.hpp
@@ -36,6 +36,9 @@
 
 #include <godot_cpp/core/defs.hpp>
 #include <godot_cpp/core/error_macros.hpp>
+#include <godot_cpp/godot.hpp>
+
+#include <type_traits>
 
 void *operator new(size_t p_size, const char *p_description); ///< operator new that takes a description and uses MemoryStaticPool
 void *operator new(size_t p_size, void *p_pointer, size_t check, const char *p_description); ///< operator new that takes a description and uses a pointer to the preallocated memory
@@ -54,6 +57,8 @@ void operator delete(void *p_mem, void *p_pointer, size_t check, const char *p_d
 
 namespace godot {
 
+class Wrapped;
+
 class Memory {
 	Memory();
 
@@ -63,11 +68,19 @@ public:
 	static void free_static(void *p_ptr);
 };
 
-#define memnew(m_v) (new ("") m_v)
+#define memnew(m_v)                                                           \
+	([&]() {                                                                  \
+		if constexpr (std::is_base_of<godot::Object, decltype(m_v)>::value) { \
+			return godot::internal::Creator<decltype(m_v)>::_new();           \
+		} else {                                                              \
+			return new ("") m_v;                                              \
+		}                                                                     \
+	}())
+
 #define memnew_placement(m_placement, m_class) (new (m_placement, sizeof(m_class), "") m_class)
 
 template <class T>
-void memdelete(T *p_class) {
+void memdelete(T *p_class, typename std::enable_if<!std::is_base_of_v<godot::Wrapped, T>>::type * = 0) {
 	if (!__has_trivial_destructor(T)) {
 		p_class->~T();
 	}
@@ -75,6 +88,11 @@ void memdelete(T *p_class) {
 	Memory::free_static(p_class);
 }
 
+template <class T, std::enable_if_t<std::is_base_of_v<godot::Wrapped, T>, bool> = true>
+void memdelete(T *p_class) {
+	godot::internal::interface->object_destroy(p_class->_owner);
+}
+
 #define memnew_arr(m_class, m_count) memnew_arr_template<m_class>(m_count)
 
 template <typename T>
diff --git a/include/godot_cpp/core/method_bind.hpp b/include/godot_cpp/core/method_bind.hpp
index 2c3e7b3..176a53c 100644
--- a/include/godot_cpp/core/method_bind.hpp
+++ b/include/godot_cpp/core/method_bind.hpp
@@ -194,7 +194,7 @@ public:
 
 template <class T>
 MethodBind *create_vararg_method_bind(Variant (T::*p_method)(const Variant **, GDNativeInt, GDNativeCallError &), const MethodInfo &p_info, bool p_return_nil_is_variant) {
-	MethodBindVarArg<T> *a = memnew((MethodBindVarArg<T>));
+	MethodBindVarArg<T> *a = memnew(MethodBindVarArg<T>());
 	a->set_method(p_method);
 	a->set_method_info(p_info, p_return_nil_is_variant);
 	a->set_instance_class(T::get_class_static());