Try #1 at setting up a fully automatic memnew() macro.

core/containers/hash_map.h

@@ -641,7 +641,7 @@ private:
 				_resize_and_rehash(capacity_index + 1);
 			}
 
-			Element *elem = memnew(Element(p_key, p_value));
+			Element *elem = memnew_core(Element(p_key, p_value));
 
 			if (tail_element == nullptr) {
 				head_element = elem;

core/os/memory.h

@@ -32,8 +32,10 @@
 
 #include "core/defs.h"
 #include "core/os/safe_refcount.h"
+#include "core/wrapped.h"
 
 #include <stddef.h>
+#include <type_traits>
 
 #ifndef PAD_ALIGN
 #define PAD_ALIGN 16 // must always be greater than this at much
@@ -88,7 +90,17 @@ _ALWAYS_INLINE_ T *_post_initialize(T *p_obj) {
 	return p_obj;
 }
 
-#define memnew(m_class) _post_initialize(new ("") m_class)
+template <typename T>
+_ALWAYS_INLINE_ T *memnew_template() {
+	if (std::is_base_of<_Wrapped, T>::value) {
+		return T::_new();
+	}
+
+	return _post_initialize(new T);
+}
+
+#define memnew_core(m_class) _post_initialize(new ("") m_class)
+#define memnew(m_class) memnew_template<m_class>()
 
 _ALWAYS_INLINE_ void *operator new(size_t p_size, void *p_pointer, size_t check, const char *p_description) {
 	// void *failptr=0;
@@ -109,6 +121,12 @@ void memdelete(T *p_class) {
 	if (!predelete_handler(p_class)) {
 		return; // doesn't want to be deleted
 	}
+
+	if (std::is_base_of<_Wrapped, T>::value) {
+		reinterpret_cast<_Wrapped *>(p_class)->free();
+		return;
+	}
+
 	if (!HAS_TRIVIAL_DESTRUCTOR(T)) {
 		p_class->~T();
 	}
@@ -121,6 +139,12 @@ void memdelete_allocator(T *p_class) {
 	if (!predelete_handler(p_class)) {
 		return; // doesn't want to be deleted
 	}
+
+	if (std::is_base_of<_Wrapped, T>::value) {
+		reinterpret_cast<_Wrapped *>(p_class)->free();
+		return;
+	}
+
 	if (!HAS_TRIVIAL_DESTRUCTOR(T)) {
 		p_class->~T();
 	}

core/wrapped.h

@@ -38,6 +38,8 @@ class _Wrapped {
 public:
 	pandemonium_object *_owner;
 	size_t _type_tag;
+
+	virtual void free() {}
 };
 
 #endif // WRAPPED_H