模拟operator new 和 operator delete实现内存泄漏追踪器和内存池

内存泄漏追踪器

operator new 和 operator delete是两个全局函数，new/delete底层调用它们，所以我们可以模拟实现这两个全局函数，起到追踪内存的创建和销毁。已知优先调用：类成员函数>全局函数>系统函数；

class Date
{
private:
	int _year;
	int _month;
	int _day;

public:
	Date(int year = 1990, int month = 1, int day = 1)
	{
		this->_year = year;
		_month = month;
		_day = day;
	}
	void *operator new(size_t size, const char* FileName, const char *FuncName, size_t LineNo)
	{
		cout << FileName << "-" << FuncName << "-" << LineNo << endl;
		void *p = ::operator new(size);
		return p;
	}
};
//返回值必须是void*，第一个参数必须是size
//这个函数主要处理内置类型
void *operator new(size_t size, const char* FileName, const char *FuncName, size_t LineNo)
{
	cout << FileName << "-" << FuncName << "-" << LineNo << endl;
	void *p = ::operator new(size);
	return p;
}
void operator delete(void *p, const char* FileName, const char *FuncName, size_t LineNo)
{
	cout << FileName << "-" << FuncName << "-" << LineNo << endl;
	::operator delete(p);
}
//放到后面
#define new new(__FILE__,__FUNCDNAME__,__LINE__)
#define delete(p) operator delete(p,__FILE__,__FUNCDNAME__,__LINE__)

int main()
{
	Date *p = new Date;
	delete(p);
	int *pp = new int;
	delete(pp);
	return 0;
}

 

内存池

如果我们实现一个双向链表，每申请一个链表节点，都需要malloc或者new，又因为他两会多申请36个字节，所以整个链表下来，会造成内存特别浪费，而且效率也不咋地，所以有了内存池。内存池就是我们申请一块特别大的空间，当我们需要的时候进行从内存池取出空间，一般内存池和定位new搭配使用。

struct ListNode
{
	ListNode* _next;
	ListNode* _prev;
	int _data;
	void* operator new(size_t n)
	{
		void* p = nullptr;
		p = allocator<ListNode>().allocate(1);
		cout << "memory pool allocate" << endl;
		return p;
	}
	void operator delete(void* p)
	{
		allocator<ListNode>().deallocate((ListNode*)p, 1);
		cout << "memory pool deallocate" << endl;
	}
};
class List
{
public:
	List()
	{
		_head = new ListNode;
		_head->_next = _head;
		_head->_prev = _head;
	}
	~List()
	{
		ListNode* cur = _head->_next;
		while (cur != _head)
		{
			ListNode* next = cur->_next;
			delete cur;
			cur = next;
		}
		delete _head;
		_head = nullptr;
	}
private:
	ListNode* _head;
};
int main()
{
	List l;
	return 0;
}