CAS原子操作

	void pop()
	{
		std::lock_guard<std::mutex>lock(mtx);
		if (base != NULL)
		{
			StackNode* q = base;
			base = q->next;
			&(q->data)->~T();
			Freenode(q);
			cursize -= 1;
		}
	}

&(q->data)->~T();//类似于定位new

new的三种构建方式：
Testp=new Test(10)//申请空间 构建对象 返回对象地址 (在多核CPU上二三步骤可能错位)
Tests=(Test*)::operator new(sizeof(Test));//和malloc的最大区别就是，malloc在空间不足时，会返回一个NULL，而operator new会抛出一个异常
new(s)Test(10)//定位new,不管是malloc申请的，还是operator new来的，定位new都可在申请的空间中构建对象

在释放节点空间之前，必须将节点里边的对象析构掉（楼房拆迁前，必须把人员全都撤离）

改为原子操作：

完整代码：

#include<iostream>
#include<thread>
#include<mutex>
#include<condition_variable>
#include <semaphore>
using namespace std;

template<class T>
class Stack
{
private:
	struct StackNode
	{
		T data;
		StackNode* next;
	};
	StackNode* Buynode()
	{
		StackNode* s = (StackNode*)malloc(sizeof(StackNode));
		if (NULL == s)exit(1);
		memset(s, 0, sizeof(StackNode));
		return s;
	}
	void Freenode(StackNode* s)
	{
		free(s);
	}
private:
	StackNode* base;
	size_t cursize;
	mutable std::atomic<StackNode*>pHead;
	Stack(const Stack&) = delete;
	Stack& operator=(const Stack&) = delete;
public:
	Stack() :base(NULL), cursize(0) {}
	~Stack() {}
	void Push(const T& val)
	{
		StackNode* newnode = Buynode();
		new(&(newnode->data))T(val);
		//newnode->next = pHead;
		newnode->next = pHead.load();
		while (!pHead.compare_exchange_weak(newnode->next, newnode));
		//pHead = newnode;
	}
};
void thread_funa(Stack<int>& s)
{
	for (int i = 0; i < 10; i += 2)
	{
		cout << i << endl;
		s.Push(i);
	}
}
void thread_funb(Stack<int>& s)
{
	for (int i = 1; i < 10; i += 2)
	{
		cout << i << endl;
		s.Push(i);
	}
}
int main()
{
	Stack<int>ist;
	thread tha(thread_funa, std::ref(ist));
	thread thb(thread_funb, std::ref(ist));
	tha.join();
	thb.join();
	return 0;
}

标签：CAS,原子,base,StackNode,new,操作,newnode,include,Stack
来源： https://blog.csdn.net/qq_54669536/article/details/123144988