This-pointer change

gistfile1.cpp

#include <iostream>
#include <cassert>

class MyClass {
public:
	MyClass() :
		magic_number_(MAGIC_NUMBER ^ (size_t)this)
	{
		// Do nothing
	}

	bool isValid() {
		return magic_number_ == (MAGIC_NUMBER ^ ((size_t) this));
	}

	void foo() {
		assert(isValid());

		std::cout << "Everything is ok!" << std::endl;
	}

	MyClass* getThis() {
		return this;
	}

private:
	enum { MAGIC_NUMBER = 0xcafed00d };

	const unsigned long magic_number_;
};

int main() {
	char* buffer = new char[sizeof(MyClass)];
	std::cout << "Buffer adress: " << (size_t)buffer << std::endl;

	MyClass* x = new MyClass;
	std::cout << "Class adress: " << (size_t)(x->getThis()) << std::endl;

	std::cout << "Moving class to buffer" << std::endl;

	memmove(buffer, x, sizeof(MyClass));

	std::cout << "Now class adress: " << (size_t)(reinterpret_cast<MyClass*>(buffer)->getThis()) << std::endl;
	
	reinterpret_cast<MyClass*>(buffer)->foo();

	return 0;
}

What is this about ?