修改指向函数中数组的指针

Question

I have a problem with passing an array to a function and then modifying it. For example:

void foo(int ** a) {
  int * b = new int[3]
  //Initialize b, i.e b = {3, 2, 1}
  a = &b;
  //*a = {3, 2, 1}
}

int * c = new int[3]
//Initialize c; c = {1, 2, 3}
foo(&c);
// c is still {1, 2, 3}. Why?

I'm not really sure why c doesn't point to the same array as b .

Answer 1

a has type int** and it's passed by value, so modifying it does not modify c .

To modify it, you have to do this:

  *a = b;

By doing this, you assign the address of b to the variable pointed by *a (which corresponds to c ), so they will point to the same array.