Update validate_user_pointer to be a void function

src/userprog/syscall.c

@@ -45,7 +45,7 @@ static unsigned syscall_tell (int fd);
 static void syscall_close (int fd);
 
 static struct open_file *fd_get_file (int fd);
-static void *validate_user_pointer (const void *ptr, size_t size);
+static void validate_user_pointer (const void *ptr, size_t size);
 
 /* A struct defining a syscall_function pointer along with its arity. */
 typedef struct
@@ -401,7 +401,7 @@ fd_get_file (int fd)
    fully contained within user virtual memory. Kills the thread (by calling
    thread_exit) if the memory is invalid. Otherwise, returns the PTR given.
    If the size is 0, the function does no checks and returns PTR.*/
-static void *
+static void
 validate_user_pointer (const void *ptr, size_t size)
 {
   if (size > 0 && (ptr == NULL ||
@@ -409,6 +409,4 @@ validate_user_pointer (const void *ptr, size_t size)
                    !is_user_vaddr (ptr + size - 1) ||
                    pagedir_get_page (thread_current()->pagedir, ptr) == NULL))
     thread_exit ();
-
-  return (void *) ptr;
 }