hurd: compliance fixes for getlogin_r

* do not make `login' static, as it would make getlogin_r no more reentrant
* fail with ERANGE if the `name' buffer has not enough space for the actual
login string
* make sure to copy with strncpy only the chars of the string

2012-04-27  Pino Toscano  <toscano.pino@tiscali.it>

	* sysdeps/mach/hurd/getlogin_r.c (getlogin_r): Do not make `login'
	static.  Return -1 and set ERANGE if `name' is not big enough.
--- a/sysdeps/mach/hurd/getlogin_r.c
+++ b/sysdeps/mach/hurd/getlogin_r.c
@@ -29,13 +29,22 @@ getlogin_r (name, name_len)
      char *name;
      size_t name_len;
 {
-  static char login[1024];	/* XXX */
+  char login[1024];	/* XXX */
   error_t err;
+  size_t len;
 
+  login[0] = '\0';
   if (err = __USEPORT (PROC, __proc_getlogin (port, login)))
     return errno = err;
 
-  strncpy (name, login, name_len);
+  len = strlen (login) + 1;
+  if (len > name_len)
+    {
+      errno = ERANGE;
+      return errno;
+    }
+
+  strncpy (name, login, len);
   return 0;
 }
 libc_hidden_def (getlogin_r)