why trying to deference void pointer does not work?

Question

int main()
{
    int b = 12;
    void *ptr = &b;
    printf("%d", *ptr);
    return 0;
}

I expected for this code to print 12, but it does not. if instead of void pointer, we define int pointer it would work. I wanted to know how can we use void pointer and print the address allocated to it and the amount saved in it?

Answer 1

Dereferencing a void * doesn't make sense because it has no way of knowing the type of the memory it points to.

You would need to cast to pointer to a int * and then dereference it.

printf("%d", *((int *)ptr));

Answer 2

void pointers cannot be dereferenced.it will give this warning

Compiler Error: 'void' is not a pointer-to-object type*

so, you have to do it like this.

#include<stdio.h>
int main()
{
    int b = 12;
    void *ptr = &b;
    printf("%d", *(int *)ptr);
    return 0;
}