new和delete在高级内存管理中的应用

#include <iostream>using namespace std;//new 的本质还是malloc  delete 的本质是free//delete new 最底层就是free  malloc//delete new 提供了重载的机制(官方说法)，通俗的理解就是劫持//delete new 全局重载，只要分配内存都劫持//内存防泄漏系统，内存反复释放，进制创建，禁止销毁//delete new 局部重载，只影响本类型，只要分配内存就劫持//内存防泄漏系统，内存反复释放，进制创建，禁止销毁int num = 0;void *operator new(size_t size)//全局重载，{num += 1;//计数if (size == 0){return nullptr;}void *p = malloc(size);cout << "全局new call" << endl;return p;}void *operator new[](size_t size)//[]数组{cout << "全局 new[] call " << endl;return operator new(size);}void operator delete(void *p)//监测内存释放的过程{num -= 1;cout << "全局delete call" << endl;free(p);}void operator delete[](void *p)//批量释放{cout << "全局 delete[] call" << endl;operator delete(p);}class myclass{public:int data;void *operator new(size_t size)//局部重载{cout << "mycalss new call" << endl;myclass *p = ::new myclass;//::使用全局的newreturn p;}void operator delete(void *p){cout << "myclass delete call" << endl;::delete p;free(p);}protected:private:};void main1(){int *p1 = new int;int *p2 = new int;int *p3 = new int;int *p4 = new int;myclass *p = new myclass;cout << num << endl;delete p1;delete p2;cout << num << endl;system("pause");//全局new call//全局new call//全局new call//全局new call//mycalss new call//全局new call//5//全局delete call//全局delete call//3}class newclass{public:newclass(){cout << "new class Create" << endl;}~newclass(){cout << "newclass Delete" << endl;}int data;void *operator new(size_t size){cout << "newclass new call" << endl;newclass *p = ::new newclass;//::使用全局的newreturn p;}void operator delete(void *p){cout << "newclass delete call" << endl;::delete p;free(p);}protected:private:};void main2(){newclass *p = new newclass;delete p;cin.get();system("pause");}//newclass new call//全局new call//new class Create//new class Create//newclass Delete//newclass delete call//全局delete callvoid main(){int *p = new int[10];//delete p;//对于基本数据类型，有无[]都没关系，但是建议写上[]delete [] p;system("pause");}//全局 new[] call//全局new call//全局delete callvoid main4(){newclass *p = new newclass;delete[]p;//delete必须加[]  必须批量释放数组，调用每一个元素析构函数  cin.get();}