Error: incompatible integer to pointer conversion initializing 'int *' with an expression of type 'int'; take the address with &

Question

To get a better grasp of pointers for this problem set, I watched a non-cs50 video on pointers, which showed the following basic code:

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

int main ()
{
int p = 10;
int *pointer = p;
printf("the addres of the pointer p is %u", &pointer);

return 0;
}

In the Youtube, this code compiled and printed out the memory address. Nonetheless, I am getting an error:

"incompatible integer to pointer conversion initializing 'int *' with an expression of type 'int'; take the address with &
      [-Werror,-Wint-conversion]"

Why is this not working in my system?

Answer 1

I'm a little suspicious of whether it worked, or maybe they are using a different, more forgiving, compiler or compile settings, or maybe c++. There are a couple issues. First, int *pointer = p; tries to assign the contents of p to an address pointer. Instead it should assign the address of p, using the & modifier.

Second, there's a type mismatch in the print statement. You need to use a pointer type formatter to print an address.

Try the following instead:

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

int main ()
{
    int p = 10;
    int *pointer = &p;
    printf("the addres of the pointer p is %p \n", pointer);
    return 0;
}

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