Trying to use stack memory after it's gone

stack.c

#include <stdio.h>

// void * return type means that it returns a naked pointer, which is just an address.
void *foo(void) {
  long bar = 5;
  printf("bar's address is: %p, holds %ld bytes\n", &bar, sizeof(long));
  long *ret = &bar;
  return (void *) ret; // ret is a pointer to a long, but we just turn it into a regular address
  // note that the previous line doesn't *do* anything, it just gets the compiler off our back
}

int main(void) {
  void *ptr = foo();
  printf("about to print what's at %p\n", ptr);
  long *l_ptr = (long *) ptr;
  printf("%ld\n", *l_ptr);
}