CPP基础遗忘

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    int (*pArr)[5] = &arr;
    std::cout << arr << std::endl;  // 输出数组第一个元素的地址
    std::cout << &arr[0] << std::endl;  // 输出数组第一个元素的地址
    std::cout << pArr << std::endl;  // 输出整个数组的地址
    std::cout << ((void*)arr==(void*)pArr) << std::endl;  // 1
    std::cout << ((void*)arr==(void*)&arr) << std::endl;  // 1
    std::cout << (arr==&arr[0]) << std::endl;  // 1
}

#include <iostream>
#include <vector>
#include <algorithm>

class MyClass {
public:
    MyClass(int v1, int v2) : m_val1(v1), m_val2(v2) {}

    bool compare1(MyClass& other) {
        return m_val1 > other.m_val1;
    }

    bool compare2(MyClass& other) {
        return m_val2 > other.m_val2;
    }

    void my_sort(std::vector<MyClass>& vec) {
        ::my_sort(vec, compare1);  
        // 错误示范：直接传递成员函数指针会出现成员函数没有指定调用者的问题
    }

private:
    int m_val1, m_val2;
};

void my_sort(std::vector<MyClass>& vec, bool (*func_ptr)(MyClass&, MyClass&)) {
    for (auto i = vec.begin(); i != vec.end(); ++i) {
        for (auto j = i + 1; j != vec.end(); ++j) {
            if (func_ptr(*j, *i)) {
                std::swap(*i, *j);
            }
        }
    }
}

int main() {
    MyClass obj(4, 2);
    std::vector<MyClass> vec = {MyClass(3, 5), MyClass(1, 8), MyClass(2, 4)};
    obj.my_sort(vec);
    for (const auto& item : vec) {
        std::cout << "(" << item.compare1(obj) << ", " << item.compare2(obj) << ") ";
    }
    std::cout << std::endl;

    return 0;
}

class MyClass {
public:
    MyClass(int v) : m_val(v) {}

    int get_val() const {
        return m_val;
    }

private:
    int m_val;
};

int main() {
    MyClass obj(42);

    int (MyClass::*get_val_ptr)() const = &MyClass::get_val;
    int val = (obj.*get_val_ptr)();

    return 0;
}

MyClass obj(42);
    mov     DWORD PTR [rbp-4], 42   ; 创建对象 obj，并将其成员变量 m_val 的值设置为 42

    int (MyClass::*get_val_ptr)() const = &MyClass::get_val;
    lea     rax, [rip+get_val_ptr]  ; 将成员函数指针的地址存储到 rax 寄存器中

    int val = (obj.*get_val_ptr)();
    lea     rcx, [rbp-4]            ; 将对象 obj 的地址存储到 rcx 寄存器中，作为调用者的指针
    mov     rax, QWORD PTR [rax]    ; 将成员函数指针的值（即成员函数的地址）存储到 rax 寄存器中
    call    rax                     ; 调用成员函数，并将返回值存储到 eax 寄存器中

#include <iostream>
#include <bits/stdc++.h>
using namespace std;

class Base{
    protected:
    int m_data;
    
public:
    Base(int data = 0)
    {    m_data = data;}
    
    int GetData()
    {    return DoGetData();}
    
    virtual int DoGetData(){
        return m_data;
    }

};

class Derive : public Base
{
public:
    Derive(int data = 1)
    {
        m_data = data;
    }
    int DoGetData() override
    {
        return m_data;
    }
protected:
    int m_data;
};

int main()
{
    Derive d;
    std::cout << d.GetData() << std::endl;
    std::cout << d.DoGetData() << std::endl;
    std::cout << d.Base::GetData() << std::endl;
    std::cout << d.Base::DoGetData() << std::endl;
    return 0;
}

#include <iostream>
#include <cstring>

class MyClass {
private:
char* str;
int n;

public:
// 构造函数
MyClass(int n) {
    std::cout << "constructor "  << std::endl;
}

// 拷贝构造函数
MyClass(const MyClass& other) {
    std::cout << "Copy constructor called" << std::endl;
}

// 移动构造函数
MyClass(MyClass&& other)  {
    str = other.str;
    other.str = nullptr;
    std::cout << "Move constructor called" << std::endl;
}

// 析构函数
~MyClass() {
    std::cout<<"destructor()"<<std::endl;
    //delete str;
}

};
MyClass func(){
    // auto cs = (MyClass(1));
    // return std::move(cs);
    return MyClass(0);
}
int main() {

    MyClass obj = func();
    //MyClass obj2 = obj;
    return 0;
}