diff --git a/ap/libc/glibc/glibc-2.23/string/strncat.c b/ap/libc/glibc/glibc-2.23/string/strncat.c
new file mode 100644
index 0000000..8b00a10
--- /dev/null
+++ b/ap/libc/glibc/glibc-2.23/string/strncat.c
@@ -0,0 +1,39 @@
+/* Copyright (C) 1991-2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+
+#ifndef STRNCAT
+# undef strncat
+# define STRNCAT  strncat
+#endif
+
+char *
+STRNCAT (char *s1, const char *s2, size_t n)
+{
+  char *s = s1;
+
+  /* Find the end of S1.  */
+  s1 += strlen (s1);
+
+  size_t ss = __strnlen (s2, n);
+
+  s1[ss] = '\0';
+  memcpy (s1, s2, ss);
+
+  return s;
+}