[PATCH] nis: Fix stringop-truncation warning with -O3 in nis_local_host.

[Wilco Dijkstra]

Hi Stefan,

> We can just ignore this warning as the hostname + '.' + directory-name + '\0' always fits
> in __nishostname with length of (NIS_MAXNAMELEN + 1) as there is the runtime check above.
> Furthermore as we already know the length of the directory-name, we can also just use
> memcpy to copy the directory-name inclusive the NUL-termination.

Agreed, that is a much more natural way of doing it.

> Note: This werror was introduced with commit
> 32c7acd46401530fdbd4e98508c9baaa705f8b53
> "Replace rawmemchr (s, '\0') with strchr"

The compiler now uses strlen and so it can do more optimization, including
giving warnings.

LGTM

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco

@@ -161,15 +161,19 @@ nis_local_host (void)
 	  if (cp[-1] == '.')
 	    return __nishostname;
 
-	  if (len + strlen (nis_local_directory ()) + 1 > NIS_MAXNAMELEN)
+	  nis_name local_directory = nis_local_directory ();
+	  size_t local_directory_len = strlen (local_directory);
+	  if (len + 1 + local_directory_len > NIS_MAXNAMELEN)

OK
 	    {
 	      __nishostname[0] = '\0';
 	      return __nishostname;
 	    }
 
+	  /* We have enough space in __nishostname with length of
+	     (NIS_MAXNAMELEN + 1) for
+	     hostname + '.' + directory-name + '\0'.  */
 	  *cp++ = '.';
-	  strncpy (cp, nis_local_directory (), NIS_MAXNAMELEN - len -1);
-	  __nishostname[NIS_MAXNAMELEN] = '\0';
+	  memcpy (cp, local_directory, local_directory_len + 1);
 
OK