--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2011-02-06  Bruno Haible  <bruno@clisp.org>
+
+	New module 'wcsstr'.
+	* modules/wcsstr: New file.
+	* lib/wchar.in.h (wcsstr): New declaration.
+	* lib/wcsstr.c: New file.
+	* lib/wcsstr-impl.h: New file, from libutf8 with modifications.
+	* m4/wcsstr.m4: New file.
+	* m4/wchar_h.m4 (gl_WCHAR_H): Test whether wcsstr is declared.
+	(gl_WCHAR_H_DEFAULTS): Initialize GNULIB_WCSSTR, HAVE_WCSSTR.
+	* modules/wchar (Makefile.am): Substitute GNULIB_WCSSTR, HAVE_WCSSTR.
+	* tests/test-wchar-c++.cc: Test the declaration of wcsstr.
+	* doc/posix-functions/wcsstr.texi: Mention the new module.
+
 2011-02-06  Bruno Haible  <bruno@clisp.org>
 
 	New module 'wcspbrk'.

--- a/doc/posix-functions/wcsstr.texi
+++ b/doc/posix-functions/wcsstr.texi
@@ -4,18 +4,18 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/wcsstr.html}
 
-Gnulib module: ---
+Gnulib module: wcsstr
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+This function is missing on some platforms:
+HP-UX 11.00, IRIX 5.3, Solaris 2.6.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
 @item
-This function is missing on some platforms:
-HP-UX 11.00, IRIX 5.3, Solaris 2.6.
-@item
 On AIX and Windows platforms, @code{wchar_t} is a 16-bit type and therefore cannot
 accommodate all Unicode characters.
 @end itemize

--- a/lib/wchar.in.h
+++ b/lib/wchar.in.h
@@ -855,6 +855,24 @@
 #endif
 
 
+/* Find the first occurrence of NEEDLE in HAYSTACK.  */
+#if @GNULIB_WCSSTR@
+# if !@HAVE_WCSSTR@
+_GL_FUNCDECL_SYS (wcsstr, wchar_t *,
+                  (const wchar_t *haystack, const wchar_t *needle));
+# endif
+_GL_CXXALIAS_SYS (wcsstr, wchar_t *,
+                  (const wchar_t *haystack, const wchar_t *needle));
+_GL_CXXALIASWARN (wcsstr);
+#elif defined GNULIB_POSIXCHECK
+# undef wcsstr
+# if HAVE_RAW_DECL_WCSSTR
+_GL_WARN_ON_USE (wcsstr, "wcsstr is unportable - "
+                 "use gnulib module wcsstr for portability");
+# endif
+#endif
+
+
 #endif /* _GL_WCHAR_H */
 #endif /* _GL_WCHAR_H */
 #endif

new file mode 100644
--- /dev/null
+++ b/lib/wcsstr-impl.h
@@ -0,0 +1,51 @@
+/* Locate a substring in a wide string.
+   Copyright (C) 1999, 2011 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 1999.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+wchar_t *
+wcsstr (const wchar_t *haystack, const wchar_t *needle)
+{
+  wchar_t n = needle[0];
+
+  /* Is needle empty?  */
+  if (n == (wchar_t)'\0')
+    return (wchar_t *) haystack;
+
+  /* Is needle nearly empty?  */
+  if (needle[1] == (wchar_t)'\0')
+    return wcschr (haystack, n);
+
+  /* Search for needle's first character.  */
+  for (; *haystack != (wchar_t)'\0'; haystack++)
+    {
+      if (*haystack == n)
+        {
+          /* Compare with needle's remaining characters.  */
+          const wchar_t *hptr = haystack + 1;
+          const wchar_t *nptr = needle + 1;
+          for (;;)
+            {
+              if (*hptr != *nptr)
+                break;
+              hptr++; nptr++;
+              if (*nptr == (wchar_t)'\0')
+                return (wchar_t *) haystack;
+            }
+        }
+    }
+
+  return NULL;
+}

new file mode 100644
--- /dev/null
+++ b/lib/wcsstr.c
@@ -0,0 +1,23 @@
+/* Locate a substring in a wide string.
+   Copyright (C) 2011 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2011.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <wchar.h>
+
+#include "wcsstr-impl.h"

--- a/m4/wchar_h.m4
+++ b/m4/wchar_h.m4
@@ -53,7 +53,7 @@
      wcsrtombs wcsnrtombs wcwidth wmemchr wmemcmp wmemcpy wmemmove wmemset
      wcslen wcsnlen wcscpy wcpcpy wcsncpy wcpncpy wcscat wcsncat wcscmp
      wcsncmp wcscasecmp wcsncasecmp wcscoll wcsxfrm wcsdup wcschr wcsrchr
-     wcscspn wcsspn wcspbrk
+     wcscspn wcsspn wcspbrk wcsstr
     ])
 ])
 
@@ -173,6 +173,7 @@
   GNULIB_WCSCSPN=0;     AC_SUBST([GNULIB_WCSCSPN])
   GNULIB_WCSSPN=0;      AC_SUBST([GNULIB_WCSSPN])
   GNULIB_WCSPBRK=0;     AC_SUBST([GNULIB_WCSPBRK])
+  GNULIB_WCSSTR=0;      AC_SUBST([GNULIB_WCSSTR])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_BTOWC=1;         AC_SUBST([HAVE_BTOWC])
   HAVE_MBSINIT=1;       AC_SUBST([HAVE_MBSINIT])
@@ -208,6 +209,7 @@
   HAVE_WCSCSPN=1;       AC_SUBST([HAVE_WCSCSPN])
   HAVE_WCSSPN=1;        AC_SUBST([HAVE_WCSSPN])
   HAVE_WCSPBRK=1;       AC_SUBST([HAVE_WCSPBRK])
+  HAVE_WCSSTR=1;        AC_SUBST([HAVE_WCSSTR])
   HAVE_DECL_WCTOB=1;    AC_SUBST([HAVE_DECL_WCTOB])
   HAVE_DECL_WCWIDTH=1;  AC_SUBST([HAVE_DECL_WCWIDTH])
   REPLACE_MBSTATE_T=0;  AC_SUBST([REPLACE_MBSTATE_T])

new file mode 100644
--- /dev/null
+++ b/m4/wcsstr.m4
@@ -0,0 +1,15 @@
+# wcsstr.m4 serial 1
+dnl Copyright (C) 2011 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_WCSSTR],
+[
+  AC_REQUIRE([gl_WCHAR_H_DEFAULTS])
+  AC_CHECK_FUNCS_ONCE([wcsstr])
+  if test $ac_cv_func_wcsstr = no; then
+    HAVE_WCSSTR=0
+    AC_LIBOBJ([wcsstr])
+  fi
+])

--- a/modules/wchar
+++ b/modules/wchar
@@ -66,6 +66,7 @@
 	      -e 's|@''GNULIB_WCSCSPN''@|$(GNULIB_WCSCSPN)|g' \
 	      -e 's|@''GNULIB_WCSSPN''@|$(GNULIB_WCSSPN)|g' \
 	      -e 's|@''GNULIB_WCSPBRK''@|$(GNULIB_WCSPBRK)|g' \
+	      -e 's|@''GNULIB_WCSSTR''@|$(GNULIB_WCSSTR)|g' \
 	      -e 's|@''HAVE_WINT_T''@|$(HAVE_WINT_T)|g' \
 	      -e 's|@''HAVE_BTOWC''@|$(HAVE_BTOWC)|g' \
 	      -e 's|@''HAVE_MBSINIT''@|$(HAVE_MBSINIT)|g' \
@@ -101,6 +102,7 @@
 	      -e 's|@''HAVE_WCSCSPN''@|$(HAVE_WCSCSPN)|g' \
 	      -e 's|@''HAVE_WCSSPN''@|$(HAVE_WCSSPN)|g' \
 	      -e 's|@''HAVE_WCSPBRK''@|$(HAVE_WCSPBRK)|g' \
+	      -e 's|@''HAVE_WCSSTR''@|$(HAVE_WCSSTR)|g' \
 	      -e 's|@''HAVE_DECL_WCTOB''@|$(HAVE_DECL_WCTOB)|g' \
 	      -e 's|@''HAVE_DECL_WCWIDTH''@|$(HAVE_DECL_WCWIDTH)|g' \
 	      -e 's|@''REPLACE_MBSTATE_T''@|$(REPLACE_MBSTATE_T)|g' \

new file mode 100644
--- /dev/null
+++ b/modules/wcsstr
@@ -0,0 +1,26 @@
+Description:
+wcsstr() function: locate a substring in a wide string.
+
+Files:
+lib/wcsstr.c
+lib/wcsstr-impl.h
+m4/wcsstr.m4
+
+Depends-on:
+wchar
+wcschr
+
+configure.ac:
+gl_FUNC_WCSSTR
+gl_WCHAR_MODULE_INDICATOR([wcsstr])
+
+Makefile.am:
+
+Include:
+<wchar.h>
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible

--- a/tests/test-wchar-c++.cc
+++ b/tests/test-wchar-c++.cc
@@ -197,6 +197,11 @@
                  (const wchar_t *, const wchar_t *));
 #endif
 
+#if GNULIB_TEST_WCSSTR
+SIGNATURE_CHECK (GNULIB_NAMESPACE::wcsstr, wchar_t *,
+                 (const wchar_t *, const wchar_t *));
+#endif
+
 
 int
 main ()