new和delete在高级内存管理中的应用

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#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new
		return 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new
		return 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 call



void 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 call

void 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();
}

new和delete在高级内存管理中的应用

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原文地址：http://blog.csdn.net/varygod/article/details/45649447