C++ operator new placement new

#include<iostream>  
  
#include <stdlib.h>  
  
usingnamespace std;  
class Test  
{  
public:  
   Test(int n) : n_(n)  
   {  
       cout<<"Test(int n) : n_(n)"<<endl;  
   }  
   Test(const Test& other)  
   {  
       cout<<"Test(const Test& other)"<<endl;  
   }  
   ~Test()  
   {  
       cout<<"~Test()"<<endl;  
   }  
   void *operator new(size_t size)//普通情况调用，标注为0  
   {  
       cout<<"void* operator new(size_t size)"<<endl;  
       void* p = malloc(size);  
       return p;  
   }  
   void operator delete(void* p)  
   {  
       cout<<"void operator delete(void* p)"<<endl;  
       free(p);  
   }  
   void operator delete(void* p, size_t size)//如果上面那个和这个delete都有，那么调用上面的。  
   {  
       cout<<"void operator delete(void* p, size_t size)"<<endl;  
       free(p);  
   }  
   void* operator new(size_t size, constchar* file, long line)//另一种情况调用，标注为1  
   {  
       cout<<file<<":"<<line<<endl;  
       void* p = malloc(size);  
       return p;  
   }  
   void operator delete(void* p, constchar* file, long line)  
   {  
       cout<<file<<":"<<line<<endl;  
       free(p);  
   }  
   void* operator new(size_t size, void* p)//另一种情况调用，标注为2  
   {  
       cout<<"run"<<endl;  
       return p;  
   }  
   void operator delete(void*, void*)  
   {  
       cout<<"destory"<<endl;  
   }  
   int n_;  
};  
void* operator new[](size_t size)//全局非Test类调用此方法，标注为3  
{  
   cout<<"global void* operator new[](size_t size)"<<endl;  
   void* p = malloc(size);  
   return p;  
}  
void operator delete[](void* p)  
{  
   cout<<"global void operator delete[](void* p)"<<endl;  
   free(p);  
}  
int main(void)  
{  
   Test* p1 =new Test(100);    // new operator = operator new + 构造函数的调用 调用标注0  
   delete p1;                  //delete = 析构函数的调用+operator delete  
   char* str =new char[100]; //调用标注3  
   delete[] str;  
   char chunk[10];  
  
   Test* p2 =new (chunk) Test(200);    //operator new(size_t, void *_Where)+构造函数的调用  
                                       // placement new，不分配内存+ 构造函数的调用  
                                       //调用标注2  
   cout<<p2->n_<<endl;  
   p2->~Test();                        // 显式调用析构函数，因为没有分配内存，所以直接调用析构函数  
   return0;  
}