实验一之4

#include <iostream>
class X{
public:
X();
~X() ;
X(int m);
X(const X& obj);
X(X&& obj) noexcept;
void show() const;
private: int data; };
X::X(): data{42} {
std::cout << "default constructor called.\n";
}
X::~X()
{ std::cout << "destructor called.\n"; }
X::X(int m): data{m}
{ std::cout << "constructor called.\n"; }
X::X(const X& obj): data{obj.data}
{ std::cout << "copy constructor called.\n"; }
X::X(X&& obj) noexcept: data{obj.data}
{ std::cout << "move constructor called.\n"; }
void X::show() const
{std::cout << data << std::endl; }int main() {
X x1;
x1.show();
X x2{2049};
x2.show();
X x3{x1};
x3.show();
X x4{ std::move(x2) };
x4.show();
}

对象被创建后即调用构造函数，对象被销毁前时即调用析构函数