diff --git a/ap/libc/glibc/glibc-2.23/string/ffs.c b/ap/libc/glibc/glibc-2.23/string/ffs.c
new file mode 100644
index 0000000..9294750
--- /dev/null
+++ b/ap/libc/glibc/glibc-2.23/string/ffs.c
@@ -0,0 +1,54 @@
+/* Copyright (C) 1991-2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Torbjorn Granlund (tege@sics.se).
+
+   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 <limits.h>
+#define ffsl __something_else
+#include <string.h>
+
+#undef	ffs
+
+/* Find the first bit set in I.  */
+int
+__ffs (int i)
+{
+  static const unsigned char table[] =
+    {
+      0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+      6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+      7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+      7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+      8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
+      8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
+      8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
+      8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8
+    };
+  unsigned int a;
+  unsigned int x = i & -i;
+
+  a = x <= 0xffff ? (x <= 0xff ? 0 : 8) : (x <= 0xffffff ?  16 : 24);
+
+  return table[x >> a] + a;
+}
+weak_alias (__ffs, ffs)
+libc_hidden_def (__ffs)
+libc_hidden_builtin_def (ffs)
+
+#if ULONG_MAX == UINT_MAX
+#undef ffsl
+weak_alias (__ffs, ffsl)
+#endif