CODEWITHSUNDEEP
cpointers
Amad27
Amad27

Reputation: 149

Not getting a NULL pointer error in C

I was purposely trying to get a NULL pointer in C but I failed to do this. Here is what I was coding:

int main(void) {
  int x; //UNINITIALIZED so that it will represent "nothing"
  int *null_test = &x;
  printf("This should be null   %p \n", null_test);
}

But it gave me an address: 0x7fd96c300020 which doesnt seem to be NULL as I was hoping.

Why? I didn't even initializex but still not null?

Upvotes: 0

Views: 217

Answers (2)

Jabberwocky
Jabberwocky

Reputation: 50774

After

int *null_test = &x;

null_test contains the address of x. This address is independent of the content of x even if x has never been initialized.

Upvotes: 9

tdao
tdao

Reputation: 17668

Why? I didn't even initializex but still not null?

You need to differentiate between 1) definition and 2) initialisation. A variable is defined when the memory is allocated to it. A variable is initialised when that memory location is filled in with some value.

Here x is uninitialised but already defined - that means being allocated - that means x has a specific location in memory. And so &x is not NULL and so null_test:

int *null_test = &x;

If you want null_test to be NULL, just assign it explicitly

int *null_test = NULL;

Upvotes: 5

Related Questions