Go - Pointer to pointer

Go Pointer to Pointer (Double Pointer)

A pointer to a pointer is a form of chain of pointers. Normally, a pointer contains the address of a variable. When we define a pointer to a pointer, the first pointer contains the address of the second pointer, which points to the location that contains the actual value as shown below.

Declaration of Pointer to Pointer

A variable that is a pointer to a pointer must be declared as such. This is done by placing an additional asterisk in front of its name.

Syntax

For example, the following statement declares a pointer to a pointer of type int −

var ptr **int;

Example of Pointer to Pointer

When a target value is indirectly pointed to by a pointer to a pointer, accessing that value requires that the asterisk operator be applied twice, as is shown in the following example −

package main

import "fmt"

func main() {
   var a int
   var ptr *int
   var pptr **int

   a = 3000

   /* take the address of var */
   ptr = &a

   /* take the address of ptr using address of operator & */
   pptr = &ptr

   /* take the value using pptr */
   fmt.Printf("Value of a = %d\n", a )
   fmt.Printf("Value available at *ptr = %d\n", *ptr )
   fmt.Printf("Value available at **pptr = %d\n", **pptr)
}

Output

When the above code is compiled and executed, it produces the following result −

Value of var = 3000
Value available at *ptr = 3000
Value available at **pptr = 3000