C++移动语义如何影响内存管理 资源所有权转移机制解析

#include <iostream>
#include <string>

class MyString {
private:
    char* data;
    size_t length;

public:
    // 构造函数
    MyString(const char* str) : length(std::strlen(str)) {
        data = new char[length + 1];
        std::strcpy(data, str);
        std::cout << "Constructor called for: " << data << std::endl;
    }

    // 拷贝构造函数
    MyString(const MyString& other) : length(other.length) {
        data = new char[length + 1];
        std::strcpy(data, other.data);
        std::cout << "Copy constructor called for: " << data << std::endl;
    }

    // 移动构造函数
    MyString(MyString&& other) : data(other.data), length(other.length) {
        other.data = nullptr;
        other.length = 0;
        std::cout << "Move constructor called, moving ownership" << std::endl;
    }

    // 析构函数
    ~MyString() {
        if (data != nullptr) {
            std::cout << "Destructor called for: " << data << std::endl;
            delete[] data;
        } else {
            std::cout << "Destructor called for empty MyString" << std::endl;
        }
    }

    // 赋值运算符
    MyString& operator=(const MyString& other) {
        if (this != &other) {
            delete[] data; // 释放现有资源
            length = other.length;
            data = new char[length + 1];
            std::strcpy(data, other.data);
            std::cout << "Assignment operator called for: " << other.data << std::endl;
        }
        return *this;
    }

    // 移动赋值运算符
    MyString& operator=(MyString&& other) {
        if (this != &other) {
            delete[] data; // 释放现有资源
            data = other.data;
            length = other.length;
            other.data = nullptr;
            other.length = 0;
            std::cout << "Move assignment operator called, moving ownership" << std::endl;
        }
        return *this;
    }

    void print() const {
        if (data) {
            std::cout << "String: " << data << std::endl;
        } else {
            std::cout << "String: Empty" << std::endl;
        }
    }
};

MyString createString(const char* str) {
    MyString temp(str);
    return temp; // 返回时会触发移动构造
}

int main() {
    MyString str1 = createString("Hello"); // 移动构造
    str1.print();

    MyString str2 = std::move(str1); // 显式移动构造
    str2.print();
    str1.print(); // str1现在为空

    str2 = createString("World"); // 移动赋值
    str2.print();

    return 0;
}