Declaring a pointer without initializing

Question

I want to know whether is it okay to declare a pointer without initializing?

#include <stdio.h>

int main()
{
    int i, *ptr_i; // Is this okay to declare a pointer without initializing?
    int a, *ptr_a = 0;

    i = 1;
    a = 2;

    ptr_i = &i;
    ptr_a = &a;

    printf("The values of i and a are %d and %d", *ptr_i, *ptr_a);

    return 0;
}

In the above program, pointer ptr_i is not initialized but ptr_a is. But still the program runs without errors and warning. So is it necessary to initialize a pointer at the time of declaration?

Answer 1

Hi,Walkbitterwyrm Lightwarg

is it okay to declare a pointer without initializing?

You can declare a pointer without initializing it. But it is recommended using initializationint* ptr_i = NULL;
so that you can check if the variable has been initialized.

if (ptr_i != NULL)
 {
     //do something
 }

Best regards,

Minxin Yu

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

It may be worth noting that variables that aren't given an explicit initial value may be default initialized.

Global variables and static local variables are default initialized to zero.

Non-static local variables are not default initialized. However, some compilers such as Visual Studio may give them a specific initial value in Debug builds to assist in the debugging process.

#include <stdio.h>

int g1, *gp1; // default initialized to zero

int main()

#include <stdio.h>

int g1, *gp1; // default initialized to zero

int main()
{

    static int sn, *snp; // default initialized to zero
    int n1, *np1; // not default initialized, contents indeterminate

    printf("g1 = %d\tgp1 = %p\n", g1, gp1); // g1 = 0  gp1 = 00000000

    printf("sn = %d\tsnp = %p\n", sn, snp); // sn = 0  snp = 00000000

    //printf("n1 = %d\tnp1 = %p\n", n1, np1); // gives compiler errors

    return 0;

}