Add the wcslcpy, wcslcat functions

These functions are about to be added to POSIX, under Austin Group
issue 986.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

debug/wcslcpy_chk.c

@@ -0,0 +1,31 @@
+/* Fortified version of wcslcpy.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <wchar.h>
+
+/* Check that the user-supplied size does not exceed the
+   compiler-determined size, and then forward to wcslcpy.  */
+size_t
+__wcslcpy_chk (wchar_t *__restrict s1, const wchar_t *__restrict s2,
+	       size_t n, size_t s1len)
+{
+  if (__glibc_unlikely (s1len < n))
+    __chk_fail ();
+
+  return __wcslcpy (s1, s2, n);
+}