有关类对象的NEW布局操作符

#include <iostream>
#include <string>
#include <new>  //包含布局操作符原型
using namespace std;
const int BUF=512;

class JustTesting
{
private:
 string words;
 int number;
public:
 JustTesting (const string & s="just testing",int n=0)
 {words=s;number=n;cout<<words<<" constructed\n";}
 ~JustTesting(){cout<<words<<" destroyed\n";}
 void show()const {cout<<words<<","<<number<<endl;}
};

int main(void)
{
 char * buffer=new char[BUF];

    JustTesting *pc1,*pc2;
 pc1=new (buffer) JustTesting;
 pc2=new JustTesting("heap1",20);

 cout<<"mem block addr:\n"<<"buffer: "<<(void*)buffer<<"  heap: "<<pc2<<endl;
 cout<<"Mem contents:\n";
 cout<<pc1<<": ";
 pc1->show();
 cout<<pc2<<": ";
 pc2->show();

 JustTesting *pc3,*pc4;
    pc3=new (buffer+sizeof(JustTesting)) JustTesting("bad idea",6);
 pc4=new JustTesting("heap2",10);
    cout<<"Mem contents:\n";
 cout<<pc3<<": ";
 pc3->show();
 cout<<pc4<<": ";
 pc4->show();

    delete pc2;
 delete pc4;
 pc3->~JustTesting();//显式调用析构函数
 pc1->~JustTesting();//显式调用析构函数

 delete [] buffer;
 cout<<"done\n";

    return 0;
}