dereferencing C pointer at scheme level

[Andy Tai]

Hi, a question on access to C pointer in scheme:

if a C function returning a pointer is wrapped and accessed from scheme code,

int64_t * func() {
    int64_t *p = make_new_pointer();
   *p = // something

   return p;
}

in scheme (GNU guile)
(set! p (func))

it is possible to see that p is now a pointer.  How to dereference the
pointer to get the value it points to, in guile, on the scheme side?
Thanks