走进C++程序世界-----operator new delete 重载

 在C++ 的世界里，new 和delete 是keyword。而在C的世界里相相应的malloc和free是函数，关键C++的new和delete分析，详见前面的章节。这里就不在过多的介绍了。链接。

以下来研究下关于new 和delete的重载。

 1、对照使用重载和未使用重载

 未使用“

/*File : operator_new.cpp
 *Auth : sjin
 *Date : 2014-04-27
 *Mail : 413977243@qq.com
 */
 
#include <iostream>
 
using namespace std;
 
class test {
public:
	test(){cout << "*****构造test()*****"<< endl;};
	~test(){cout << "+++++析构test()+++++"<< endl;};
};
 
int main()
{
	test * x = new test;//运行分配空间，再运行析构函数
	delete x;//先运行析构函数，在释放空间
}

使用重载后，

/*File : operator_new.cpp
 *Auth : sjin
 *Date : 2014-04-27
 *Mail : 413977243@qq.com
 */
 
#include <iostream>
 
using namespace std;
 
char mem[10000] = {'\0'};
int pos = 0;
 
class test {
public:
	test(){cout << "*****构造test()*****"<< endl;};
	~test(){cout << "+++++析构test()+++++"<< endl;};
 
public:
	void * operator new(size_t bytes){
		cout << "------new test()------" << endl;
		int alloc = pos;
		pos += bytes;
		return (mem + alloc);
	};
 
	void operator delete(void *){
		cout << "------delete test()------" << endl;
 
	};
};
 
int main()
{
	test * x = new test;
 
	delete x;
}

/*File : operator_new.cpp
 *Auth : sjin
 *Date : 2014-04-27
 *Mail : 413977243@qq.com
 */
 
#include <iostream>
 
using namespace std;
 
char mem[10000] = {'\0'};
int pos = 0;
 
class test {
public:
	test(){cout << "*****构造test()*****"<< endl;};
	~test(){cout << "+++++析构test()+++++"<< endl;};
 
public:
	void * operator new(size_t bytes){
		cout << "------new test()------" << endl;
		int alloc = pos;
		pos += bytes;
		return (mem + alloc);
	};
 
	void operator delete(void *){
		cout << "------delete test()------" << endl;
 
	};
};
 
int main()
{
	test * x = new test;
 
	delete x;
 
	x = new test[3];
 
	delete [] x;//这里对数组释放，须要注意
}

#include <iostream>
 
using namespace std;
 
char mem[10000] = {'\0'};
int pos = 0;
 
class test {
public:
	test(){cout << "*****构造test()*****"<< endl;};
	~test(){cout << "+++++析构test()+++++"<< endl;};
 
public:
	void * operator new(size_t bytes){
		cout << "------new test()------" << endl;
		int alloc = pos;
		pos += bytes;
		return (mem + alloc);
	};
 
	void operator delete(void *){
		cout << "------delete test()------" << endl;
 
	};
 
	void * operator new[](size_t bytes){
		cout << "------new test()------" << endl;
		int alloc = pos;
		pos += bytes;
		return (mem + alloc);
	};
 
	void operator delete[](void *){
		cout << "------delete test()------" << endl;
 
	};
};
 
int main()
{
	test * x = new test;
 
	delete x;
 
	x = new test[3];
 
	delete [] x;
}

对new 和delete 函数的重载能够用来检測 内存泄露的情况。