c++ - 为什么添加静态数据成员会导致链接器失败？

Question

<分区>

Answer 1

您需要定义/初始化在类中声明的静态变量

static inline Node* lastAdded {nullptr};

在c++17中你可以使用inline来定义静态变量

#include <iostream>
#include <string>

using namespace std;

struct Node {
    static inline Node* lastAdded {nullptr};

    Node(const int data);   // General data node constructor
    Node(); // head constructor
    static void push(Node* previousNode);

    int data;
    Node* previous;
    Node* next;
};

Node::Node(const int data) {
    this->data = data;
}

Node::Node() {
    // Note that data is left uninitalized for head node
    previous = nullptr;
    next = nullptr;
    lastAdded = this;
}

static void push(Node* currentNode, Node* previousNode) {
    previousNode->next = currentNode;
    currentNode->previous = previousNode;
    currentNode->next = nullptr;
    Node::lastAdded = currentNode;
}

int main()
{
    Node* head = new Node();
    push(new Node(1), Node::lastAdded);
    push(new Node(12), Node::lastAdded);

    for (Node* temp = head->next; temp != nullptr; temp=temp->next) {
        cout << temp->data << endl;
    }
}

输出

1
12
Program ended with exit code: 0