虚函数析构函数（内存泄漏）（12）

#ifndef
#define
#include <iostream>
using namespace std;
class A{
public:
   A();
   ~A();
};
#endif

#include "A.h"
 A::A() {
  cout << "A::A()" << endl;
}

 A::~A() {
  cout << "A::~A()" << endl;
}

#ifndef
#define
#include "A.h"
using namespace std;
class B:public A{
public:
   B();
   ~B();
};
#endif

#include "B.h"
 B::B() {
  cout << "B::B()" << endl;
}

 B::~B() {
  cout << "B::~B()" << endl;
}

#include "A.h"
#include "B.h"
#include <stdio.h>

void f() {
  //基类指针指向动态（new）创建的派生类对象,会发生内存泄漏
  A *p = new B;
  if (p != NULL) {
    delete p;
    p = NULL;
  }
}

int main() {

  f();
  return 0;
}