--- Libc/Libc-1725.40.4/secure/strncat_chk.c
+++ Libc/Libc-583/secure/strncat_chk.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007-2013 Apple Inc. All rights reserved.
+ * Copyright (c) 2007 Apple Inc. All rights reserved.
  *
  * @APPLE_LICENSE_HEADER_START@
  *
@@ -23,24 +23,36 @@
 
 #include <stdlib.h>
 #include <string.h>
-#include "secure.h"
+
+extern void __chk_fail (void) __attribute__((__noreturn__));
 
 char *
-__strncat_chk (char *restrict dest, const char *restrict append,
-               size_t len, size_t dstlen)
+__strncat_chk (char *restrict dest, const char *restrict src,
+	      size_t len, size_t dstlen)
 {
-  size_t len1 = strlen(dest);
-  size_t len2 = strnlen(append, len);
+  char *s1 = dest;
+  const char *s2 = src;
 
-  if (__builtin_expect (dstlen < len1 + len2 + 1, 0))
-    __chk_fail_overflow ();
+  /* Advance to the end. */
+  while (*s1 != 0)
+    {
+      if (__builtin_expect (dstlen-- == 0, 0))
+	__chk_fail ();
+      s1++;
+    }
 
-  if (__builtin_expect (__chk_assert_no_overlap != 0, 1))
-    __chk_overlap(dest, len1 + len2 + 1, append, len2 + 1);
-
-  /* memmove() all but the NUL, since it might not actually be NUL */
-  memcpy(dest + len1, append, len2);
-  dest[len1 + len2] = '\0';
+  /* Append the string. */
+  while (len > 0)
+    {
+      if (__builtin_expect (dstlen-- == 0, 0))
+	__chk_fail ();
+      if ((*s1 = *s2++) == 0)
+	break;
+      s1++;
+      len--;
+    }
+    *s1 = 0;
 
   return dest;
+
 }