What is Dangling pointer in c++?

A dangling pointer is a pointer that points to the unavailable memory location or data which is not valid,
for eg:

#include<iostream.h>
void main(){
int *ptr1;
int *ptr2 = new int;
ptr1=ptr2;
delete ptr2;
}

In the above example, ptr1 and ptr2 are pointing to the same location in memory.
but after deletion of ptr2. Ptr1 can not able to point any memory.
This is called as dangling pointer.

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

// ptr is a dangling pointer now and operations like following are invalid
*ptr = 10;  // or printf("%d", *ptr);
// EXAMPLE 2
int *ptr = NULL
{
   int x  = 10;
   ptr = &x;
}
// x goes out of scope and memory allocated to x is free now.
// So ptr is a dangling pointer now.

Dangling pointers and wild pointers in computer programming are pointers that do not point to a valid object of the appropriate type. These are special cases of memory safety violations. More generally, dangling references and wild references are references that do not resolve to a valid destination, and include such phenomena as link rot on the internet.