CODEWITHSUNDEEP
cpointersnull
Mooncrater
Mooncrater

Reputation: 4861

Why is a Null Pointer in C equal to another Null Pointer in C?

Like consider I declare two pointers NULL. Then if I compare them, the result is true. But if we consider NULL to be "nothing" then how can we say that two "nothings" are equal? Is that for some specific reason? Any help appreciated. :)

Upvotes: 0

Views: 209

Answers (2)

Akshay Patole
Akshay Patole

Reputation: 474

When you point pointer to NULL then it means that it is pointing to the memory address 0x0.

Consider following example,

#include <stdio.h>

int main()
{
        char *p = NULL;
..
..

Here, *p is pointing to NULL. If we check in gdb then we will get following,

(gdb) p p
$1 = 0x0

0x0 is the address of NULL value i.e. 0. You cannot access 0x0 memory address.

(gdb) p *p
Cannot access memory at address 0x0

If you try to access memory address 0x0 then program will be crashed by saying segmentation fault

Now if you compare two pointers which are pointing to memory address 0x0 i.e. NULL then it will be same only as the NULL value is 0 by default

Upvotes: 2

rishit_s
rishit_s

Reputation: 350

In C, two null pointers of any type are guaranteed to compare equal. The macro NULL is defined as an implementation-defined null pointer constant, which in C99 can be portably expressed as the integer value 0 converted implicitly or explicitly to the type void * .

Upvotes: 7

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