Can i return address of a variable in a function of return type pointer?

I am trying to understand how pointer to a variable and address of a variable works.

When I am writing the following code :

#include<stdio.h>
int* g(void){
    int x = 10;
    int *p = &x;
    printf("%p,%p",p,&x);
    return (p);
}
void main(){
    int * p = g();
    printf("\n%d",*p);
}

Output:

0060FED8,0060FED8
10
Process returned 3 (0x3)   execution time : 0.031 s

---

Both the address and pointer to x gives the same value, but when i am returning address &x instead of pointer p the code doesn't print the value of x anymore:

#include<stdio.h>
int* g(void){
    int x = 10;
    int *p = &x;
    printf("%p,%p",p,&x);
    return (&x);
}
void main(){
    int * p = g();
    printf("\n%d",*p);
}

Warning:

warning: function returns address of local variable [-Wreturn-local-addr]

Output:

0060FED8,0060FED8
Process returned -1073741819 (0xC0000005)   execution time : 8.332 s

---

Can anyone tell me what am I doing wrong?

What you have been observing is an Undefined Behaviour. There is something called Storage Class in C programming language. The variables inside your function int *g(void) has automatic storage class. They have a lifetime and scope of your function. Whenever you get out of your function, the location allocated for your variables (x and *p) will be destroyed.

So, it doesn't make sense to use address of variables with automatic storage class outside their scope, i.e., outside your function (int *g(void)) as the pointer returned will be a dangling pointer.

You can make use of heap dynamic memory to allocate the space if you want to learn or use memory location outside the function scope.

You can also make use of global variable and return memory address of that global variable from your function.

#include <stdio.h>
#include <stdlib.h>

int x = 10;

int *g(void)
{
    int *p = &x;
    printf("%p,%p\r\n", p, &x);
    return (&x);
}

int *heap(void)
{
    int *p = malloc(sizeof(int));
    *p = 100;
    printf("%p\r\n", p);
    return p;
}


int main(void)
{
    int *p = g();

    printf("%d\r\n", *p);

    int *p1 = heap();
    printf("%d\r\n", *p1);

    return 0;
}