T t(2), T t = 2, T t = T(2)三者完全等价

[cpp]
#include <iostream>
#include <ostream>
#include <string>
using namespace std;
class T{
    public:
        T(){};
        T(int t)
        {
            cout << "复制" << endl;
            a = t;
        };
        T& operator = (const T& t)
        {
            cout << "赋值" << endl;
            a = t.a;
            return *this;
        }
        int a;
};
int main()
{
    T t(2);
    cout << "------------------"<< endl;
    T t1 = 2;
    cout << "------------------"<< endl;
    T t2 = T(2);
    cout << "------------------"<< endl;
    T t3;
    t3 = t2;
    return 0;
}

#include <iostream>
#include <ostream>
#include <string>
using namespace std;
class T{
    public:
        T(){};
        T(int t)
        {
            cout << "复制" << endl;
            a = t;
        };
        T& operator = (const T& t)
        {
            cout << "赋值" << endl;
            a = t.a;
            return *this;
        }
        int a;
};
int main()
{
    T t(2);
    cout << "------------------"<< endl;
    T t1 = 2;
    cout << "------------------"<< endl;
    T t2 = T(2);
    cout << "------------------"<< endl;
    T t3;
    t3 = t2;
    return 0;
}

输出结果为：

复制
------------------
复制
------------------
复制
------------------
赋值

补充：软件开发 , C++ ,