diff --git a/ap/libc/glibc/glibc-2.23/string/strcspn.c b/ap/libc/glibc/glibc-2.23/string/strcspn.c
new file mode 100644
index 0000000..8888919
--- /dev/null
+++ b/ap/libc/glibc/glibc-2.23/string/strcspn.c
@@ -0,0 +1,41 @@
+/* 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>
+
+#undef strcspn
+
+#ifndef STRCSPN
+# define STRCSPN strcspn
+#endif
+
+/* Return the length of the maximum initial segment of S
+   which contains no characters from REJECT.  */
+size_t
+STRCSPN (const char *s, const char *reject)
+{
+  size_t count = 0;
+
+  while (*s != '\0')
+    if (strchr (reject, *s++) == NULL)
+      ++count;
+    else
+      return count;
+
+  return count;
+}
+libc_hidden_builtin_def (strcspn)