重载operator new delete函数

可以重载global的operator new delete 函数，细节如下：

MyNewDelete.h

 #pragma once
 #include <stdlib.h>
 #include <string>
 #include <iostream>
 using namespace std;

 class Foo
 {
 public:
     int id;
     string str;

     Foo() : id() { cout << "default ctor.this=" << this << "id=" << id << endl; }
     Foo(int i) : id(i) { cout << "ctor.this=" << this << "id=" << id << endl; }

     //若构造函数为virtual 则Fool对象会多一个指针大小的内存用来存虚指针vptr
     ~Foo() { cout << "dtor.this=" << this << "id=" << id << endl; };

     static void *operator new(size_t size);                  //重载全局operator new 函数;
     static void operator delete(void *pdead, size_t size);   //重载全局operator delete函数;
     static void *operator new[](size_t size);                //重载全局operator new[]函数;
     static void operator delete[](void *pdead, size_t size); //重载全局operator delete[]函数;
 };

NewDelete.cpp

 #include <iostream>
 #include <ostream>
 #include "MyNewDelete.h"

 void *Foo::operator new(size_t size)
 {
     Foo *p = (Foo *)malloc(size);
     cout << "Foo::operator new. size=" << size << " return " << p << endl;
     return p;
 }

 void Foo::operator delete(void *pdead, size_t size)
 {
     cout << "Foo::operator delete. size=" << size << " pdead= " << pdead << endl;
     free(pdead);
 }

 void *Foo::operator new[](size_t size)
 {
     Foo *p = (Foo *)malloc(size * sizeof(Foo));
     cout << "Foo::operator new[]. size=" << size * sizeof(Foo) << " return " << p << endl;
     return p;
 }

 void Foo::operator delete[](void *pdead, size_t size)
 {
     cout << "Foo::operator delete[]. size=" << size * sizeof(Foo) << " pdead= " << pdead << endl;
     free(pdead);
 }

 int main()
 {
     cout << sizeof(Foo) << endl;
     //若无members 才调用globals
     //调用members
     Foo *pf = new Foo;
     delete pf;
     cout << "--------------------------------------------------" << endl;
     //调用globals
     //Foo *pf = ::new Foo;
     //::delete pf;

     Foo *p = new Foo();
     delete p;
     cout << "--------------------------------------------------" << endl;
     Foo *pArray = new Foo[];
     delete[] pArray;

     return ;
 }