--- a/src/dfa.c

+++ b/src/dfa.c

@@ -1238,6 +1238,20 @@ parse_bracket_exp (void)

   return CSET + charclass_index (ccl);

 }

+#define PUSH_LEX_STATE(s)			\

+  do						\

+    {						\

+      char const *lexptr_saved = lexptr;	\

+      size_t lexleft_saved = lexleft;		\

+      lexptr = (s);				\

+      lexleft = strlen (lexptr)

+

+#define POP_LEX_STATE()				\

+      lexptr = lexptr_saved;			\

+      lexleft = lexleft_saved;			\

+    }						\

+  while (0)

+

 static token

 lex (void)

 {

@@ -1485,20 +1499,6 @@ lex (void)

               return lasttok = CSET + charclass_index (ccl);

             }

-#define PUSH_LEX_STATE(s)			\

-  do						\

-    {						\

-      char const *lexptr_saved = lexptr;	\

-      size_t lexleft_saved = lexleft;		\

-      lexptr = (s);				\

-      lexleft = strlen (lexptr)

-

-#define POP_LEX_STATE()				\

-      lexptr = lexptr_saved;			\

-      lexleft = lexleft_saved;			\

-    }						\

-  while (0)

-

           /* FIXME: see if optimizing this, as is done with ANYCHAR and

              add_utf8_anychar, makes sense.  */

@@ -1518,14 +1518,33 @@ lex (void)

         case 'W':

           if (!backslash || (syntax_bits & RE_NO_GNU_OPS))

             goto normal_char;

-          zeroset (ccl);

-          for (c2 = 0; c2 < NOTCHAR; ++c2)

-            if (IS_WORD_CONSTITUENT (c2))

-              setbit (c2, ccl);

-          if (c == 'W')

-            notset (ccl);

+

+          if (!dfa->multibyte)

+            {

+              zeroset (ccl);

+              for (c2 = 0; c2 < NOTCHAR; ++c2)

+                if (IS_WORD_CONSTITUENT (c2))

+                  setbit (c2, ccl);

+              if (c == 'W')

+                notset (ccl);

+              laststart = false;

+              return lasttok = CSET + charclass_index (ccl);

+            }

+

+          /* FIXME: see if optimizing this, as is done with ANYCHAR and

+             add_utf8_anychar, makes sense.  */

+

+          /* \w and \W are documented to be equivalent to [_[:alnum:]] and

+             [^_[:alnum:]] respectively, so tell the lexer to process those

+             strings, each minus its "already processed" '['.  */

+          PUSH_LEX_STATE (c == 'w' ? "_[:alnum:]]" : "^_[:alnum:]]");

+

+          lasttok = parse_bracket_exp ();

+

+          POP_LEX_STATE ();

+

           laststart = false;

-          return lasttok = CSET + charclass_index (ccl);

+          return lasttok;

         case '[':

           if (backslash)

--- a/tests/Makefile.am

+++ b/tests/Makefile.am

@@ -110,6 +110,7 @@ TESTS =						\

   warn-char-classes				\

   word-delim-multibyte				\

   word-multi-file				\

+  word-multibyte				\

   yesno

 EXTRA_DIST =					\

--- a/tests/Makefile.in

+++ b/tests/Makefile.in

@@ -1409,6 +1409,7 @@ TESTS = \

   warn-char-classes				\

   word-delim-multibyte				\

   word-multi-file				\

+  word-multibyte				\

   yesno

 EXTRA_DIST = \

@@ -2286,6 +2287,13 @@ word-multi-file.log: word-multi-file

 	--log-file $$b.log --trs-file $$b.trs \

 	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \

 	"$$tst" $(AM_TESTS_FD_REDIRECT)

+word-multibyte.log: word-multibyte

+	@p='word-multibyte'; \

+	b='word-multibyte'; \

+	$(am__check_pre) $(LOG_DRIVER) --test-name "$$f" \

+	--log-file $$b.log --trs-file $$b.trs \

+	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \

+	"$$tst" $(AM_TESTS_FD_REDIRECT)

 yesno.log: yesno

 	@p='yesno'; \

 	b='yesno'; \

--- a/dev/null

+++ a/tests/word-multibyte

@@ -0,0 +1,23 @@ 

+#!/bin/sh

+# This would fail for grep-2.20

+. "${srcdir=.}/init.sh"; path_prepend_ ../src

+

+require_en_utf8_locale_

+

+printf '\xc3\xa1\n' > in || framework_failure_

+LC_ALL=en_US.UTF-8

+export LC_ALL

+

+fail=0

+

+for LOC in en_US.UTF-8 zh_CN $LOCALE_FR_UTF8; do

+  out=out1-$LOC

+  LC_ALL=$LOC grep '\w' in >$out || fail=1

+  compare in $out || fail=1

+

+  out=out2-$LOC

+  LC_ALL=$LOC grep '\W' in >$out && fail=1

+  compare /dev/null $out || fail=1

+done

+

+Exit $fail