diff --git a/ap/libc/glibc/glibc-2.23/string/test-ffs.c b/ap/libc/glibc/glibc-2.23/string/test-ffs.c
new file mode 100644
index 0000000..035b63d
--- /dev/null
+++ b/ap/libc/glibc/glibc-2.23/string/test-ffs.c
@@ -0,0 +1,66 @@
+/* Copyright (C) 1994-2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Joel Sherrill (jsherril@redstone-emh2.army.mil),
+     On-Line Applications Research Corporation.
+
+   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 <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+static int
+do_test (void)
+{
+  int failures = 0;
+  int i;
+
+  auto void try (const char *name, long long int param, int value,
+		 int expected);
+
+  void try (const char *name, long long int param, int value, int expected)
+    {
+      if (value != expected)
+	{
+	  printf ("%s(%#llx) expected %d got %d\n",
+		  name, param, expected, value);
+	  ++failures;
+	}
+      else
+	printf ("%s(%#llx) as expected %d\n", name, param, value);
+    }
+
+#define TEST(fct, type) \
+  try (#fct, 0, fct ((type) 0), 0);					      \
+  for (i=0 ; i < 8 * sizeof (type); i++)				      \
+    try (#fct, 1ll << i, fct (((type) 1) << i), i + 1);			      \
+  for (i=0 ; i < 8 * sizeof (type) ; i++)				      \
+    try (#fct, (~((type) 0) >> i) << i, fct ((~((type) 0) >> i) << i), i + 1);\
+  try (#fct, 0x80008000, fct ((type) 0x80008000), 16)
+
+  TEST (ffs, int);
+  TEST (ffsl, long int);
+  TEST (ffsll, long long int);
+
+  if (failures)
+    printf ("Test FAILED!  %d failure%s.\n", failures, &"s"[failures == 1]);
+  else
+    puts ("Test succeeded.");
+
+  return failures;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"