lw_shared_ptr & virtual dtor

#include <stdio.h>
#include <new>

template <typename T>
struct lw_shared_ptr {

	char *_mem;

	void destroy() {

		if (_mem != nullptr) {
			int *counter = reinterpret_cast<int *>(_mem);
			*counter -= 1;

			if (*counter == 0) {
				T *t = reinterpret_cast<T*>(_mem + alignof(int));
				t->~T();
				delete [] _mem;
			}
			_mem = nullptr;
		}
	}
	template <typename U> void
	init(lw_shared_ptr<U> &rhs) {

		_mem = rhs._mem;
		if (_mem != nullptr) {
			int *counter = reinterpret_cast<int *>(_mem);
			*counter += 1;
		}
	}

	lw_shared_ptr(const T& t)
		: _mem(new char[alignof(int) + sizeof(T)]) {

		int *counter = reinterpret_cast<int *>(_mem);
		*counter = 1;
		T *place = reinterpret_cast<T*>(_mem + alignof(int));
		new (place) T(t);
	}


	template <typename U>
	lw_shared_ptr(lw_shared_ptr<U> &rhs) {

		init(rhs);
	}

	template <typename U> lw_shared_ptr<T>& operator=(lw_shared_ptr<U> &rhs) {

		destroy();
		init(rhs);
		return *this;
	}

	~lw_shared_ptr() {
		destroy();
	}
};

struct Base {
	Base() {
		printf("%p::Base()\n", this);
	}
	Base(const Base &)
	{
		printf("%p::Base(Base&)\n", this);
	}
	virtual ~Base() {
		printf("%p::~Base()\n", this);
	}
};

struct Derived: public Base {
	Derived() {
		printf("%p::Dervied()\n", this);
	}
	Derived(const Derived &) {
		printf("%p::Dervied(Derived&)\n", this);
	}
	virtual ~Derived() {
		printf("%p::~Dervied()\n", this);
	}
};

int main() {
	auto foo = lw_shared_ptr<Base>(Base());

	auto bar = lw_shared_ptr<Derived>(Derived());
	printf("foo = bar;\n");

	foo = bar;

	printf("return 0;\n");
	return 0;
}

kostja@atlas ~ % g++ main2.cc; ./a.out
0x7ffe3a866800::Base()
0x55875c7a6284::Base(Base&)
0x7ffe3a866800::~Base()
0x7ffe3a866800::Base()
0x7ffe3a866800::Dervied()
0x55875c7a62a4::Base()
0x55875c7a62a4::Dervied(Derived&)
0x7ffe3a866800::~Dervied()
0x7ffe3a866800::~Base()
foo = bar;
0x55875c7a6284::~Base()
return 0;
0x55875c7a62a4::~Dervied()
0x55875c7a62a4::~Base()
kostja@atlas ~ %