为什么指针 object 没有调用默认构造函数

Question

#include<iostream>
using namespace std;

class test
{
  public:
      test(){cout<<"Constructor called ";}
};

int main()
{
  test a,*b;
  return 0;
}

I expected the constructor to be called two times. Why does a pointer object did not call the default constructor

Answer 1

A pointer is just a pointer. It can point to an object but it does not necessarily do so. Declaring a pointer does not automagically create an instance. Your pointer is not initialized to point anywhere.

For a far-fetched analogy consider I give you a paper on which it is written: "My wallet". I didn't give you any money, I just gave you a "pointer" to where you can find money (not necessarily, only if there actually is money in my wallet). For your code the better analogy is: I give you an empty piece of paper. In any case, giving you a "pointer" to where you can find money, unfortunately does not create money in my wallet:(