#include<iostream>

#include<string>

using namespace std;

const int BUF = ;

class JustTesting

{

private:

    string words;

    int number;

public:

    JustTesting(const string& s = "Just Testing", int n = )

    {

        words = s;

        number = n;

        cout << words << " constructed" << endl;

    }

    ~JustTesting()

    {

        cout << words << " destroyed" << endl;

    }

    void show() const

    {

        cout << words << " ," << number << endl;

    }

};

int main()

{

    char* buffer = new char[BUF];

    JustTesting *pc1, *pc2;

    pc1 = new(buffer)JustTesting;

    pc2 = new JustTesting("Heap1", );

    cout << "Memory block address" << endl << "buffer: " << (void*)buffer << "     heap: " << pc2 << endl;

    cout << pc1 << ": ";

    pc1->show();

    cout << pc2 << ": ";

    pc2->show();

    JustTesting *pc3, *pc4;

    //pc3 = new (buffer)JustTesting("Bad Idea", 6); //pc3直接占用了pc1的内存区域，这样一来如果pc1中有new分配的成员变量，将造成内存泄漏，

    //因此更好的方式是

    pc3 = new (buffer+sizeof(JustTesting)) JustTesting("Better Idea",);

    pc4 = new JustTesting("Heap2", );

    cout << "Memory Contents" << endl;

    cout << pc3 << ": ";

    pc3->show();

    cout << pc4 << ": ";

    pc4->show();

    delete pc2;

    delete pc4;

    //由于delete buffer并不会出发buffer内对象的析构函数，所以只能手动调用其析构函数

    //需要注意调用析构函数的顺序，由于晚创建的对象可能依赖早创建的对象，因此析构的顺序应该与创建顺序相反，另外，仅当析构了所有对象之后，才能释放用于存储这些对象的缓冲区

    pc3->~JustTesting();

    pc1->~JustTesting();

    delete[] buffer;

    //delete pc1; 因为buffer和pc1实际上指向同一个地址，因此如果注释掉上面一行，打开这里，也可以正常运行，但逻辑上却是没有道理的

    cout << "done" << endl;

    cin.get();

    return ;

}