--- /dev/null
+++ Libc/Libc-583/secure/snprintf_chk.c
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2007 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <limits.h>
+
+extern void __chk_fail (void) __attribute__((__noreturn__));
+extern int __snprintf_chk (char * __restrict, size_t, int, size_t,
+                           const char * __restrict, ...)
+  __DARWIN_LDBL_COMPAT (__snprintf_chk);
+
+int
+__snprintf_chk (char *s, size_t maxlen, int flags, size_t len,
+		const char *format, ...)
+{
+  va_list arg;
+  int done;
+
+  if (__builtin_expect (maxlen > len, 0))
+    __chk_fail ();
+
+  va_start (arg, format);
+
+  done = vsnprintf (s, maxlen, format, arg);
+
+  va_end (arg);
+
+  return done;
+}