模板与继承之艺术——空基类优化

#include<iostream>
using namespace std;

template<typename CustomClass>
class Optimizable{
    private:
      CustomClass info;
      void* storage;
};
class Test{
};
int main()
{
    cout << sizeof(Optimizable<Test>) << endl;
 //结果为8
    return 0;
}

#include<iostream>
using namespace std;

template<typename Base, typename Member>
class BaseMemberPair : private Base{
    private:
         Member member;
public:
         BaseMemberPair(Base const &b, Member const &m):Base(b), member(m){}
//通过first来访问基类数据
Base const&  first() const{ return (Base const&)*this; }
 //提供给const对象调用
Base& first() { return (Base&)*this; }

//通过second()来访问成员变量
Member const& second() const { return this->member; }
Member& second() { return this->member; }
};

template <typename CustomClass>
class Optimizable {
    private:
       BaseMemberPair<CustomClass, void*> info_and_storage;
};

class Test{
};
int main()
{
    cout << sizeof(Optimizable<Test>) << endl;
//结果为4
    return 0;
}