Calling C++ method using function pointer

thiscall_ptr.cpp

#include "stdafx.h"
#include <stdlib.h>

class MyClass {
private:
	int val = 0;

public:
	MyClass(int i) {
		val = i;
	}

	virtual int test(int a);
};

typedef int(__thiscall *myclass_test)(void* pThis, int a);

int MyClass::test(int a)
{
	return a * 2 + val;
}

uintptr_t get_myclass_test_addr() {
	char buffer[256];
	sprintf_s(buffer, "%d", &MyClass::test);
	return (uintptr_t) _atoi64(buffer);
}

int _tmain(int argc, _TCHAR* argv[])
{
	uintptr_t ptr_func = get_myclass_test_addr();

	MyClass *inst = new MyClass(5);		
	myclass_test test_method = (myclass_test)ptr_func;
	int result = test_method(inst, 10);
	printf_s("result = %d", result);
	getchar();
	return 0;
}