Dangling, Void , Null and Wild Pointers

• Difficulty Level : Easy
• Last Updated : 28 Jun, 2021

Dangling pointer

A pointer pointing to a memory location that has been deleted (or freed) is called dangling pointer. There are three different ways where Pointer acts as dangling pointer

1. De-allocation of memory

    

    

    

   // Deallocating a memory pointed by ptr causes

   // dangling pointer

   #include <stdlib.h>

   #include <stdio.h>

   int main()

   {

       int *ptr = (int *)malloc(sizeof(int));

     

       // After below free call, ptr becomes a 

       // dangling pointer

       free(ptr); 

         

       // No more a dangling pointer

       ptr = NULL;

   }

2. Function Call

    

    

    

   // The pointer pointing to local variable becomes

   // dangling when local variable is not static.

   #include<stdio.h>

     

   int *fun()

   {

       // x is local variable and goes out of

       // scope after an execution of fun() is

       // over.

       int x = 5;

     

       return &x;

   }

     

   // Driver Code

   int main()

   {

       int *p = fun();

       fflush(stdin);

     

       // p points to something which is not

       // valid anymore

       printf("%d", *p);

       return 0;

   }

   Output:

   A garbage Address