c++ - 间接实例化一个指针

Question

我有这样的东西:

int* a = NULL;
int* b = *a;

b = new int(5);
std::cout << *a;
std::cout << *b;

我想从 b 实例化 a 所以 a 的值为 5。这可能吗？

编辑:

实际代码是这样的-

int* a = null; //Global variable
int* b = null; //Global variable

int* returnInt(int position)
{
    switch(position)
    {
      case 0:
         return a;
      case 1:
         return b;
     }
}

some other function -

int* c = returnInt(0); // Get Global a

if (c == null)
    c = new int(5);

---

如果可能，我想以这种方式实例化全局变量。

Answer 1

int* a = NULL;
int* b = *a; //here you dereference a NULL pointer, undefined behavior.

你需要

int* b = new int(5);
int*& a = b; //a is a reference to pointer to int, it is a synonym of b
std::cout << *a;
std::cout << *b;

或者，a 可以是对 int 的引用，并且是 *b 的同义词

int* b = new int(5);
int& a = *b; //a is a reference to int, it is a synonym of `*b`
std::cout << a;  //prints 5
std::cout << *b; //prints 5
a = 4;
std::cout << a;  //prints 4
std::cout << *b; //prints 4

Please consult a good C++ book for details.