C++深拷贝及重载赋值运算符出错，找不到问题点

Question

代码如下，写了一个类，然后构造函数用深拷贝的方法，重载赋值运算符，也用的深拷贝的方法。出错了

#ifndef _OPERATOR_H_
#define _OPERATOR_H_

#include <iostream>
using namespace std;

class Opeassignment
{
public:
    int m_age;
    int *m_score;
    Opeassignment();
    Opeassignment(int age, int score);
    Opeassignment(const Opeassignment& p);
    Opeassignment& operator=(const Opeassignment& p);
    ~Opeassignment();
};

void operatormain();
ostream& operator<< (ostream &cout, const Opeassignment &p);


#endif
#include "operator.h"

void operatormain() {
    cout << endl << __FILE__ << ":" << __func__ << " line: " << __LINE__ << endl;
    Opeassignment k1(18,99);
    cout << "k1.m_age :" << k1.m_age << "\tk1.m_score :" << *k1.m_score << endl;
    Opeassignment k2;
    k2.m_age = 20;
    *k2.m_score = 100;
    cout << "k2.m_age :" << k2.m_age << "\tk2.m_score :" << *k2.m_score << endl;
**##error : Segmentation fault (core dumped)!**
    Opeassignment k3(k2);
    cout << "k3.m_age :" << k3.m_age << "\tk3.m_score :" << *k3.m_score << endl;
    Opeassignment k4 = k2;
    cout << "k4.m_age :" << k4.m_age << "\tk4.m_score :" << *k4.m_score << endl;
}

ostream& operator<< (ostream &cout, const Opeassignment &p) {
    cout << __FILE__ << ": " << __func__ << ": " << __LINE__ << endl;
    cout << "Age : " << p.m_age << "\tScore : " << *p.m_score;
    return cout;
}

Opeassignment::Opeassignment() {
    m_score = new int();
}

Opeassignment::Opeassignment(int age, int score) {
    m_age = age;
    m_score = new int(score);
}

Opeassignment::Opeassignment(const Opeassignment& p) {
    m_age = p.m_age;
    if(m_score != NULL) {
        delete m_score;
    m_score = NULL;
    }
    m_score = new int(*p.m_score);
}

Opeassignment& Opeassignment::operator=(const Opeassignment& p){
    m_age = p.m_age;
    if(m_score != NULL) {
        delete m_score;
    m_score = NULL;
    }
    m_score = new int(*p.m_score);
    return *this;
}

Opeassignment::~Opeassignment() {
    if(m_score != NULL) {
        delete m_score;
    m_score = NULL;
    }
}

有大佬能帮忙看看为什么回报错呢，编译环境是G++，linux中编译的，报错内容是：##error : Segmentation fault (core dumped)!
具体是在进行类的拷贝时，以及用等号进行赋值时，会报错感觉是深拷贝有问题，现在正在学习深拷贝的知识，不知道为什么会报错，我用的深拷贝方法，看了好几遍我也没看出问题来。

Answer 1

晚上好🌙🌙🌙
本答案参考通义千问

你的代码中存在一些问题，导致在进行深拷贝时出现段错误（Segmentation Fault）。以下是一些可能的问题和解决方案：

1. 初始化 m_score

在默认构造函数中，m_score 没有被正确初始化。这会导致未定义行为。

Opeassignment::Opeassignment() {
    m_score = nullptr; // 初始化为 nullptr
}

2. 拷贝构造函数中的条件检查

在拷贝构造函数中，你不应该在复制之前检查 m_score 是否为空。这样会导致不必要的删除操作，并且可能导致未定义行为。

Opeassignment::Opeassignment(const Opeassignment& p) {
    m_age = p.m_age;
    m_score = new int(*p.m_score); // 直接分配新的内存
}

3. 赋值运算符中的条件检查

同样，在赋值运算符中，你不应该在复制之前检查 m_score 是否为空。这样会导致不必要的删除操作，并且可能导致未定义行为。

Opeassignment& Opeassignment::operator=(const Opeassignment& p){
    if (this != &p) { // 避免自赋值
        m_age = p.m_age;
        delete m_score; // 删除旧的内存
        m_score = new int(*p.m_score); // 分配新的内存
    }
    return *this;
}

4. 使用智能指针

为了简化内存管理，可以使用智能指针（如 std::unique_ptr 或 std::shared_ptr），这样可以避免手动管理内存带来的问题。

以下是修改后的代码：

#ifndef _OPERATOR_H_
#define _OPERATOR_H_

#include <iostream>
#include <memory> // 包含智能指针头文件

using namespace std;

class Opeassignment
{
public:
    int m_age;
    unique_ptr<int> m_score; // 使用智能指针
    Opeassignment();
    Opeassignment(int age, int score);
    Opeassignment(const Opeassignment& p);
    Opeassignment& operator=(const Opeassignment& p);
    ~Opeassignment();
};

void operatormain();
ostream& operator<< (ostream &cout, const Opeassignment &p);

#endif

#include "operator.h"

void operatormain() {
    cout << endl << __FILE__ << ":" << __func__ << " line: " << __LINE__ << endl;
    Opeassignment k1(18,99);
    cout << "k1.m_age :" << k1.m_age << "\tk1.m_score :" << *k1.m_score << endl;
    Opeassignment k2;
    k2.m_age = 20;
    *k2.m_score = 100;
    cout << "k2.m_age :" << k2.m_age << "\tk2.m_score :" << *k2.m_score << endl;
    Opeassignment k3(k2);
    cout << "k3.m_age :" << k3.m_age << "\tk3.m_score :" << *k3.m_score << endl;
    Opeassignment k4 = k2;
    cout << "k4.m_age :" << k4.m_age << "\tk4.m_score :" << *k4.m_score << endl;
}

ostream& operator<< (ostream &cout, const Opeassignment &p) {
    cout << __FILE__ << ": " << __func__ << ": " << __LINE__ << endl;
    cout << "Age : " << p.m_age << "\tScore : " << *p.m_score;
    return cout;
}

Opeassignment::Opeassignment() : m_score(make_unique<int>()) {}

Opeassignment::Opeassignment(int age, int score) : m_age(age), m_score(make_unique<int>(score)) {}

Opeassignment::Opeassignment(const Opeassignment& p) : m_age(p.m_age), m_score(make_unique<int>(*p.m_score)) {}

Opeassignment& Opeassignment::operator=(const Opeassignment& p){
    if (this != &p) {
        m_age = p.m_age;
        *m_score = *p.m_score; // 直接赋值
    }
    return *this;
}

Opeassignment::~Opeassignment() {}

通过这些修改，你可以避免手动管理内存带来的问题，并且代码会更加简洁和安全。