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; }