Experiments on the C ++ new

#include <iostream>

using namespace std;

class Anew
{
public:
    int a;
    Anew()
    {}
};

Built class
{
public:
    int a;
    Built (): a (100)
    {}
};

class Cnew
{
public:
    int a;
};


int main(int argc, char *argv[])
{
    Anew tmp1;
    Anew* tmp2 = new Anew;
    Anew* tmp3 = new Anew();
    cout << tmp1.a<<endl;
    cout << tmp2->a<<endl;
    cout << tmp3->a<<endl;

    Built tmp11;
    * = New built tmp22 built;
    * Built tmp33 = new built ()
    cout << tmp11.a<<endl;
    cout << tmp22->a<<endl;
    cout << tmp33->a<<endl;

    Cnew tmp111;
    Cnew* tmp222 = new Cnew;
    Cnew* tmp333 = new Cnew();
    cout << tmp111.a<<endl;
    cout << tmp222->a<<endl;
    cout << tmp333->a<<endl;

    return 0;
}

g++ 8.1.0

Output:

0

-1163005939

-1163005939

 

100

100

100

 

2046

-1163005939

0

 

Anew manually write a constructor

Bnew manually write a constructor to initialize and have a value

Cnew compiler that comes with the constructor