What is dangling Pointer in c ?

webmaster — Thu, 06 Oct 2022 10:38:33 +0000

The most common bugs related to pointer & memory management is called dangling or wild pointers.
Sometimes programmer fails to assign the pointer with a valid address, then this type of assigned or initialized pointer is known as dangling pointer.
Dangling pointer usually occurs during object destruction when the object is deleted or deallocated from memory without changing the values or address of the pointer.
Dangling pointer points to the memory which contains either the program code or code of the operating system.
If a value or address is assigned to this type of pointer, it overwrites the program’s value or operating system instructions.
During this time, the program may show the undesirable results or may crash.
If the memory is re allocated to some other process, then we will dereference the dangling pointer.
This dereferencing of the dangling pointer may cause segmentation faults.

Dangling Pointer ?

Editor — Mon, 12 Jul 2021 23:36:28 +0000

A dangling pointer is pointing to a memory location that has been deleted (or freed). The dangling pointer act as a different ways there are,
- De-allocation of memory
- Function Call
- Variable goes out of scope

#include
void main()
{
    char *ptr = malloc(Constant_Value);
    free (ptr); //ptr now becomes a dangling pointer
}

First we have declared in the character pointer. After execution of some statements we have de-allocated memory which is allocated previously for the pointer.
Immediately memory is de-allocated for pointer, pointer becomes dangling pointer.

int * func ( void )
{
    int num = 14;
    return #
}

The pointer may be return the correct value (1234) for a while after calling func, but any functions called thereafter will overwrite the stack storage allocated for num with other values and the pointer would no longer work correctly.
If a pointer to num must be returned, num must have scope beyond the function it might be declared as static.

#include
void main()
{
    char *ptr = NULL;
    {
        char ch;
        ptr = &ch;
    }//dp is now a dangling pointer
}

First we have declared in the Character Pointer.
Next the Pointer Variable ‘ptr’ is pointing to Character Variable ‘ch’ declared in the inner block .
As character variable is non-visible in Outer Block , then Pointer is still pointing to Same Invalid memory location in Outer block , then Pointer becomes “Dangling”.