Adding upstream version 1:2.39.2.upstream/1%2.39.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 11484 insertions, 0 deletions

diff --git a/compat/regex/regcomp.c b/compat/regex/regcomp.c
new file mode 100644
index 0000000..d1bc09e
--- /dev/null
+++ b/compat/regex/regcomp.c
@@ -0,0 +1,3891 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2007,2009,2010 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.
+
+   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/>.  */
+
+#if defined __TANDEM
+ /* This is currently duplicated from git-compat-utils.h */
+# ifdef NO_INTPTR_T
+ typedef long intptr_t;
+ typedef unsigned long uintptr_t;
+# endif
+#endif
+
+static reg_errcode_t re_compile_internal (regex_t *preg, const char * pattern,
+					  size_t length, reg_syntax_t syntax);
+static void re_compile_fastmap_iter (regex_t *bufp,
+				     const re_dfastate_t *init_state,
+				     char *fastmap);
+static reg_errcode_t init_dfa (re_dfa_t *dfa, size_t pat_len);
+#ifdef RE_ENABLE_I18N
+static void free_charset (re_charset_t *cset);
+#endif /* RE_ENABLE_I18N */
+static void free_workarea_compile (regex_t *preg);
+static reg_errcode_t create_initial_state (re_dfa_t *dfa);
+#ifdef RE_ENABLE_I18N
+static void optimize_utf8 (re_dfa_t *dfa);
+#endif
+static reg_errcode_t analyze (regex_t *preg);
+static reg_errcode_t preorder (bin_tree_t *root,
+			       reg_errcode_t (fn (void *, bin_tree_t *)),
+			       void *extra);
+static reg_errcode_t postorder (bin_tree_t *root,
+				reg_errcode_t (fn (void *, bin_tree_t *)),
+				void *extra);
+static reg_errcode_t optimize_subexps (void *extra, bin_tree_t *node);
+static reg_errcode_t lower_subexps (void *extra, bin_tree_t *node);
+static bin_tree_t *lower_subexp (reg_errcode_t *err, regex_t *preg,
+				 bin_tree_t *node);
+static reg_errcode_t calc_first (void *extra, bin_tree_t *node);
+static reg_errcode_t calc_next (void *extra, bin_tree_t *node);
+static reg_errcode_t link_nfa_nodes (void *extra, bin_tree_t *node);
+static int duplicate_node (re_dfa_t *dfa, int org_idx, unsigned int constraint);
+static int search_duplicated_node (const re_dfa_t *dfa, int org_node,
+				   unsigned int constraint);
+static reg_errcode_t calc_eclosure (re_dfa_t *dfa);
+static reg_errcode_t calc_eclosure_iter (re_node_set *new_set, re_dfa_t *dfa,
+					 int node, int root);
+static reg_errcode_t calc_inveclosure (re_dfa_t *dfa);
+static int fetch_number (re_string_t *input, re_token_t *token,
+			 reg_syntax_t syntax);
+static int peek_token (re_token_t *token, re_string_t *input,
+			reg_syntax_t syntax) internal_function;
+static bin_tree_t *parse (re_string_t *regexp, regex_t *preg,
+			  reg_syntax_t syntax, reg_errcode_t *err);
+static bin_tree_t *parse_reg_exp (re_string_t *regexp, regex_t *preg,
+				  re_token_t *token, reg_syntax_t syntax,
+				  int nest, reg_errcode_t *err);
+static bin_tree_t *parse_branch (re_string_t *regexp, regex_t *preg,
+				 re_token_t *token, reg_syntax_t syntax,
+				 int nest, reg_errcode_t *err);
+static bin_tree_t *parse_expression (re_string_t *regexp, regex_t *preg,
+				     re_token_t *token, reg_syntax_t syntax,
+				     int nest, reg_errcode_t *err);
+static bin_tree_t *parse_sub_exp (re_string_t *regexp, regex_t *preg,
+				  re_token_t *token, reg_syntax_t syntax,
+				  int nest, reg_errcode_t *err);
+static bin_tree_t *parse_dup_op (bin_tree_t *dup_elem, re_string_t *regexp,
+				 re_dfa_t *dfa, re_token_t *token,
+				 reg_syntax_t syntax, reg_errcode_t *err);
+static bin_tree_t *parse_bracket_exp (re_string_t *regexp, re_dfa_t *dfa,
+				      re_token_t *token, reg_syntax_t syntax,
+				      reg_errcode_t *err);
+static reg_errcode_t parse_bracket_element (bracket_elem_t *elem,
+					    re_string_t *regexp,
+					    re_token_t *token, int token_len,
+					    re_dfa_t *dfa,
+					    reg_syntax_t syntax,
+					    int accept_hyphen);
+static reg_errcode_t parse_bracket_symbol (bracket_elem_t *elem,
+					  re_string_t *regexp,
+					  re_token_t *token);
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t build_equiv_class (bitset_t sbcset,
+					re_charset_t *mbcset,
+					int *equiv_class_alloc,
+					const unsigned char *name);
+static reg_errcode_t build_charclass (RE_TRANSLATE_TYPE trans,
+				      bitset_t sbcset,
+				      re_charset_t *mbcset,
+				      int *char_class_alloc,
+				      const char *class_name,
+				      reg_syntax_t syntax);
+#else  /* not RE_ENABLE_I18N */
+static reg_errcode_t build_equiv_class (bitset_t sbcset,
+					const unsigned char *name);
+static reg_errcode_t build_charclass (RE_TRANSLATE_TYPE trans,
+				      bitset_t sbcset,
+				      const char *class_name,
+				      reg_syntax_t syntax);
+#endif /* not RE_ENABLE_I18N */
+static bin_tree_t *build_charclass_op (re_dfa_t *dfa,
+				       RE_TRANSLATE_TYPE trans,
+				       const char *class_name,
+				       const char *extra,
+				       int non_match, reg_errcode_t *err);
+static bin_tree_t *create_tree (re_dfa_t *dfa,
+				bin_tree_t *left, bin_tree_t *right,
+				re_token_type_t type);
+static bin_tree_t *create_token_tree (re_dfa_t *dfa,
+				      bin_tree_t *left, bin_tree_t *right,
+				      const re_token_t *token);
+static bin_tree_t *duplicate_tree (const bin_tree_t *src, re_dfa_t *dfa);
+static void free_token (re_token_t *node);
+static reg_errcode_t free_tree (void *extra, bin_tree_t *node);
+static reg_errcode_t mark_opt_subexp (void *extra, bin_tree_t *node);
+
+/* This table gives an error message for each of the error codes listed
+   in regex.h.  Obviously the order here has to be same as there.
+   POSIX doesn't require that we do anything for REG_NOERROR,
+   but why not be nice?  */
+
+const char __re_error_msgid[] attribute_hidden =
+  {
+#define REG_NOERROR_IDX	0
+    gettext_noop ("Success")	/* REG_NOERROR */
+    "\0"
+#define REG_NOMATCH_IDX (REG_NOERROR_IDX + sizeof "Success")
+    gettext_noop ("No match")	/* REG_NOMATCH */
+    "\0"
+#define REG_BADPAT_IDX	(REG_NOMATCH_IDX + sizeof "No match")
+    gettext_noop ("Invalid regular expression") /* REG_BADPAT */
+    "\0"
+#define REG_ECOLLATE_IDX (REG_BADPAT_IDX + sizeof "Invalid regular expression")
+    gettext_noop ("Invalid collation character") /* REG_ECOLLATE */
+    "\0"
+#define REG_ECTYPE_IDX	(REG_ECOLLATE_IDX + sizeof "Invalid collation character")
+    gettext_noop ("Invalid character class name") /* REG_ECTYPE */
+    "\0"
+#define REG_EESCAPE_IDX	(REG_ECTYPE_IDX + sizeof "Invalid character class name")
+    gettext_noop ("Trailing backslash") /* REG_EESCAPE */
+    "\0"
+#define REG_ESUBREG_IDX	(REG_EESCAPE_IDX + sizeof "Trailing backslash")
+    gettext_noop ("Invalid back reference") /* REG_ESUBREG */
+    "\0"
+#define REG_EBRACK_IDX	(REG_ESUBREG_IDX + sizeof "Invalid back reference")
+    gettext_noop ("Unmatched [ or [^")	/* REG_EBRACK */
+    "\0"
+#define REG_EPAREN_IDX	(REG_EBRACK_IDX + sizeof "Unmatched [ or [^")
+    gettext_noop ("Unmatched ( or \\(") /* REG_EPAREN */
+    "\0"
+#define REG_EBRACE_IDX	(REG_EPAREN_IDX + sizeof "Unmatched ( or \\(")
+    gettext_noop ("Unmatched \\{") /* REG_EBRACE */
+    "\0"
+#define REG_BADBR_IDX	(REG_EBRACE_IDX + sizeof "Unmatched \\{")
+    gettext_noop ("Invalid content of \\{\\}") /* REG_BADBR */
+    "\0"
+#define REG_ERANGE_IDX	(REG_BADBR_IDX + sizeof "Invalid content of \\{\\}")
+    gettext_noop ("Invalid range end")	/* REG_ERANGE */
+    "\0"
+#define REG_ESPACE_IDX	(REG_ERANGE_IDX + sizeof "Invalid range end")
+    gettext_noop ("Memory exhausted") /* REG_ESPACE */
+    "\0"
+#define REG_BADRPT_IDX	(REG_ESPACE_IDX + sizeof "Memory exhausted")
+    gettext_noop ("Invalid preceding regular expression") /* REG_BADRPT */
+    "\0"
+#define REG_EEND_IDX	(REG_BADRPT_IDX + sizeof "Invalid preceding regular expression")
+    gettext_noop ("Premature end of regular expression") /* REG_EEND */
+    "\0"
+#define REG_ESIZE_IDX	(REG_EEND_IDX + sizeof "Premature end of regular expression")
+    gettext_noop ("Regular expression too big") /* REG_ESIZE */
+    "\0"
+#define REG_ERPAREN_IDX	(REG_ESIZE_IDX + sizeof "Regular expression too big")
+    gettext_noop ("Unmatched ) or \\)") /* REG_ERPAREN */
+  };
+
+const size_t __re_error_msgid_idx[] attribute_hidden =
+  {
+    REG_NOERROR_IDX,
+    REG_NOMATCH_IDX,
+    REG_BADPAT_IDX,
+    REG_ECOLLATE_IDX,
+    REG_ECTYPE_IDX,
+    REG_EESCAPE_IDX,
+    REG_ESUBREG_IDX,
+    REG_EBRACK_IDX,
+    REG_EPAREN_IDX,
+    REG_EBRACE_IDX,
+    REG_BADBR_IDX,
+    REG_ERANGE_IDX,
+    REG_ESPACE_IDX,
+    REG_BADRPT_IDX,
+    REG_EEND_IDX,
+    REG_ESIZE_IDX,
+    REG_ERPAREN_IDX
+  };
+
+/* Entry points for GNU code.  */
+
+
+#ifdef ZOS_USS
+
+/* For ZOS USS we must define btowc */
+
+wchar_t 
+btowc (int c)
+{
+   wchar_t wtmp[2];
+   char tmp[2];
+
+   tmp[0] = c;
+   tmp[1] = 0;
+
+   mbtowc (wtmp, tmp, 1);
+   return wtmp[0];
+}
+#endif
+
+/* re_compile_pattern is the GNU regular expression compiler: it
+   compiles PATTERN (of length LENGTH) and puts the result in BUFP.
+   Returns 0 if the pattern was valid, otherwise an error string.
+
+   Assumes the `allocated' (and perhaps `buffer') and `translate' fields
+   are set in BUFP on entry.  */
+
+const char *
+re_compile_pattern (const char *pattern,
+		    size_t length,
+		    struct re_pattern_buffer *bufp)
+{
+  reg_errcode_t ret;
+
+  /* And GNU code determines whether or not to get register information
+     by passing null for the REGS argument to re_match, etc., not by
+     setting no_sub, unless RE_NO_SUB is set.  */
+  bufp->no_sub = !!(re_syntax_options & RE_NO_SUB);
+
+  /* Match anchors at newline.  */
+  bufp->newline_anchor = 1;
+
+  ret = re_compile_internal (bufp, pattern, length, re_syntax_options);
+
+  if (!ret)
+    return NULL;
+  return gettext (__re_error_msgid + __re_error_msgid_idx[(int) ret]);
+}
+#ifdef _LIBC
+weak_alias (__re_compile_pattern, re_compile_pattern)
+#endif
+
+/* Set by `re_set_syntax' to the current regexp syntax to recognize.  Can
+   also be assigned to arbitrarily: each pattern buffer stores its own
+   syntax, so it can be changed between regex compilations.  */
+/* This has no initializer because initialized variables in Emacs
+   become read-only after dumping.  */
+reg_syntax_t re_syntax_options;
+
+
+/* Specify the precise syntax of regexps for compilation.  This provides
+   for compatibility for various utilities which historically have
+   different, incompatible syntaxes.
+
+   The argument SYNTAX is a bit mask comprised of the various bits
+   defined in regex.h.  We return the old syntax.  */
+
+reg_syntax_t
+re_set_syntax (reg_syntax_t syntax)
+{
+  reg_syntax_t ret = re_syntax_options;
+
+  re_syntax_options = syntax;
+  return ret;
+}
+#ifdef _LIBC
+weak_alias (__re_set_syntax, re_set_syntax)
+#endif
+
+int
+re_compile_fastmap (struct re_pattern_buffer *bufp)
+{
+  re_dfa_t *dfa = (re_dfa_t *) bufp->buffer;
+  char *fastmap = bufp->fastmap;
+
+  memset (fastmap, '\0', sizeof (char) * SBC_MAX);
+  re_compile_fastmap_iter (bufp, dfa->init_state, fastmap);
+  if (dfa->init_state != dfa->init_state_word)
+    re_compile_fastmap_iter (bufp, dfa->init_state_word, fastmap);
+  if (dfa->init_state != dfa->init_state_nl)
+    re_compile_fastmap_iter (bufp, dfa->init_state_nl, fastmap);
+  if (dfa->init_state != dfa->init_state_begbuf)
+    re_compile_fastmap_iter (bufp, dfa->init_state_begbuf, fastmap);
+  bufp->fastmap_accurate = 1;
+  return 0;
+}
+#ifdef _LIBC
+weak_alias (__re_compile_fastmap, re_compile_fastmap)
+#endif
+
+static inline void
+__attribute ((always_inline))
+re_set_fastmap (char *fastmap, int icase, int ch)
+{
+  fastmap[ch] = 1;
+  if (icase)
+    fastmap[tolower (ch)] = 1;
+}
+
+/* Helper function for re_compile_fastmap.
+   Compile fastmap for the initial_state INIT_STATE.  */
+
+static void
+re_compile_fastmap_iter (regex_t *bufp, const re_dfastate_t *init_state,
+			 char *fastmap)
+{
+  volatile re_dfa_t *dfa = (re_dfa_t *) bufp->buffer;
+  int node_cnt;
+  int icase = (dfa->mb_cur_max == 1 && (bufp->syntax & RE_ICASE));
+  for (node_cnt = 0; node_cnt < init_state->nodes.nelem; ++node_cnt)
+    {
+      int node = init_state->nodes.elems[node_cnt];
+      re_token_type_t type = dfa->nodes[node].type;
+
+      if (type == CHARACTER)
+	{
+	  re_set_fastmap (fastmap, icase, dfa->nodes[node].opr.c);
+#ifdef RE_ENABLE_I18N
+	  if ((bufp->syntax & RE_ICASE) && dfa->mb_cur_max > 1)
+	    {
+	      unsigned char *buf = re_malloc (unsigned char, dfa->mb_cur_max), *p;
+	      wchar_t wc;
+	      mbstate_t state;
+
+	      p = buf;
+	      *p++ = dfa->nodes[node].opr.c;
+	      while (++node < dfa->nodes_len
+		     && dfa->nodes[node].type == CHARACTER
+		     && dfa->nodes[node].mb_partial)
+		*p++ = dfa->nodes[node].opr.c;
+	      memset (&state, '\0', sizeof (state));
+	      if (__mbrtowc (&wc, (const char *) buf, p - buf,
+			     &state) == p - buf
+		  && (__wcrtomb ((char *) buf, towlower (wc), &state)
+		      != (size_t) -1))
+		re_set_fastmap (fastmap, 0, buf[0]);
+	      re_free (buf);
+	    }
+#endif
+	}
+      else if (type == SIMPLE_BRACKET)
+	{
+	  int i, ch;
+	  for (i = 0, ch = 0; i < BITSET_WORDS; ++i)
+	    {
+	      int j;
+	      bitset_word_t w = dfa->nodes[node].opr.sbcset[i];
+	      for (j = 0; j < BITSET_WORD_BITS; ++j, ++ch)
+		if (w & ((bitset_word_t) 1 << j))
+		  re_set_fastmap (fastmap, icase, ch);
+	    }
+	}
+#ifdef RE_ENABLE_I18N
+      else if (type == COMPLEX_BRACKET)
+	{
+	  re_charset_t *cset = dfa->nodes[node].opr.mbcset;
+	  int i;
+
+# ifdef _LIBC
+	  /* See if we have to try all bytes which start multiple collation
+	     elements.
+	     e.g. In da_DK, we want to catch 'a' since "aa" is a valid
+		  collation element, and don't catch 'b' since 'b' is
+		  the only collation element which starts from 'b' (and
+		  it is caught by SIMPLE_BRACKET).  */
+	      if (_NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES) != 0
+		  && (cset->ncoll_syms || cset->nranges))
+		{
+		  const int32_t *table = (const int32_t *)
+		    _NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
+		  for (i = 0; i < SBC_MAX; ++i)
+		    if (table[i] < 0)
+		      re_set_fastmap (fastmap, icase, i);
+		}
+# endif /* _LIBC */
+
+	  /* See if we have to start the match at all multibyte characters,
+	     i.e. where we would not find an invalid sequence.  This only
+	     applies to multibyte character sets; for single byte character
+	     sets, the SIMPLE_BRACKET again suffices.  */
+	  if (dfa->mb_cur_max > 1
+	      && (cset->nchar_classes || cset->non_match || cset->nranges
+# ifdef _LIBC
+		  || cset->nequiv_classes
+# endif /* _LIBC */
+		 ))
+	    {
+	      unsigned char c = 0;
+	      do
+		{
+		  mbstate_t mbs;
+		  memset (&mbs, 0, sizeof (mbs));
+		  if (__mbrtowc (NULL, (char *) &c, 1, &mbs) == (size_t) -2)
+		    re_set_fastmap (fastmap, false, (int) c);
+		}
+	      while (++c != 0);
+	    }
+
+	  else
+	    {
+	      /* ... Else catch all bytes which can start the mbchars.  */
+	      for (i = 0; i < cset->nmbchars; ++i)
+		{
+		  char buf[256];
+		  mbstate_t state;
+		  memset (&state, '\0', sizeof (state));
+		  if (__wcrtomb (buf, cset->mbchars[i], &state) != (size_t) -1)
+		    re_set_fastmap (fastmap, icase, *(unsigned char *) buf);
+		  if ((bufp->syntax & RE_ICASE) && dfa->mb_cur_max > 1)
+		    {
+		      if (__wcrtomb (buf, towlower (cset->mbchars[i]), &state)
+			  != (size_t) -1)
+			re_set_fastmap (fastmap, false, *(unsigned char *) buf);
+		    }
+		}
+	    }
+	}
+#endif /* RE_ENABLE_I18N */
+      else if (type == OP_PERIOD
+#ifdef RE_ENABLE_I18N
+	       || type == OP_UTF8_PERIOD
+#endif /* RE_ENABLE_I18N */
+	       || type == END_OF_RE)
+	{
+	  memset (fastmap, '\1', sizeof (char) * SBC_MAX);
+	  if (type == END_OF_RE)
+	    bufp->can_be_null = 1;
+	  return;
+	}
+    }
+}
+
+/* Entry point for POSIX code.  */
+/* regcomp takes a regular expression as a string and compiles it.
+
+   PREG is a regex_t *.  We do not expect any fields to be initialized,
+   since POSIX says we shouldn't.  Thus, we set
+
+     `buffer' to the compiled pattern;
+     `used' to the length of the compiled pattern;
+     `syntax' to RE_SYNTAX_POSIX_EXTENDED if the
+       REG_EXTENDED bit in CFLAGS is set; otherwise, to
+       RE_SYNTAX_POSIX_BASIC;
+     `newline_anchor' to REG_NEWLINE being set in CFLAGS;
+     `fastmap' to an allocated space for the fastmap;
+     `fastmap_accurate' to zero;
+     `re_nsub' to the number of subexpressions in PATTERN.
+
+   PATTERN is the address of the pattern string.
+
+   CFLAGS is a series of bits which affect compilation.
+
+     If REG_EXTENDED is set, we use POSIX extended syntax; otherwise, we
+     use POSIX basic syntax.
+
+     If REG_NEWLINE is set, then . and [^...] don't match newline.
+     Also, regexec will try a match beginning after every newline.
+
+     If REG_ICASE is set, then we considers upper- and lowercase
+     versions of letters to be equivalent when matching.
+
+     If REG_NOSUB is set, then when PREG is passed to regexec, that
+     routine will report only success or failure, and nothing about the
+     registers.
+
+   It returns 0 if it succeeds, nonzero if it doesn't.  (See regex.h for
+   the return codes and their meanings.)  */
+
+int
+regcomp (regex_t *__restrict preg,
+	 const char *__restrict pattern,
+	 int cflags)
+{
+  reg_errcode_t ret;
+  reg_syntax_t syntax = ((cflags & REG_EXTENDED) ? RE_SYNTAX_POSIX_EXTENDED
+			 : RE_SYNTAX_POSIX_BASIC);
+
+  preg->buffer = NULL;
+  preg->allocated = 0;
+  preg->used = 0;
+
+  /* Try to allocate space for the fastmap.  */
+  preg->fastmap = re_malloc (char, SBC_MAX);
+  if (BE (preg->fastmap == NULL, 0))
+    return REG_ESPACE;
+
+  syntax |= (cflags & REG_ICASE) ? RE_ICASE : 0;
+
+  /* If REG_NEWLINE is set, newlines are treated differently.  */
+  if (cflags & REG_NEWLINE)
+    { /* REG_NEWLINE implies neither . nor [^...] match newline.  */
+      syntax &= ~RE_DOT_NEWLINE;
+      syntax |= RE_HAT_LISTS_NOT_NEWLINE;
+      /* It also changes the matching behavior.  */
+      preg->newline_anchor = 1;
+    }
+  else
+    preg->newline_anchor = 0;
+  preg->no_sub = !!(cflags & REG_NOSUB);
+  preg->translate = NULL;
+
+  ret = re_compile_internal (preg, pattern, strlen (pattern), syntax);
+
+  /* POSIX doesn't distinguish between an unmatched open-group and an
+     unmatched close-group: both are REG_EPAREN.  */
+  if (ret == REG_ERPAREN)
+    ret = REG_EPAREN;
+
+  /* We have already checked preg->fastmap != NULL.  */
+  if (BE (ret == REG_NOERROR, 1))
+    /* Compute the fastmap now, since regexec cannot modify the pattern
+       buffer.  This function never fails in this implementation.  */
+    (void) re_compile_fastmap (preg);
+  else
+    {
+      /* Some error occurred while compiling the expression.  */
+      re_free (preg->fastmap);
+      preg->fastmap = NULL;
+    }
+
+  return (int) ret;
+}
+#ifdef _LIBC
+weak_alias (__regcomp, regcomp)
+#endif
+
+/* Returns a message corresponding to an error code, ERRCODE, returned
+   from either regcomp or regexec.   We don't use PREG here.  */
+
+size_t
+regerror(int errcode, const regex_t *__restrict preg,
+	 char *__restrict errbuf, size_t errbuf_size)
+{
+  const char *msg;
+  size_t msg_size;
+
+  if (BE (errcode < 0
+	  || errcode >= (int) (sizeof (__re_error_msgid_idx)
+			       / sizeof (__re_error_msgid_idx[0])), 0))
+    /* Only error codes returned by the rest of the code should be passed
+       to this routine.  If we are given anything else, or if other regex
+       code generates an invalid error code, then the program has a bug.
+       Dump core so we can fix it.  */
+    abort ();
+
+  msg = gettext (__re_error_msgid + __re_error_msgid_idx[errcode]);
+
+  msg_size = strlen (msg) + 1; /* Includes the null.  */
+
+  if (BE (errbuf_size != 0, 1))
+    {
+      if (BE (msg_size > errbuf_size, 0))
+	{
+	  memcpy (errbuf, msg, errbuf_size - 1);
+	  errbuf[errbuf_size - 1] = 0;
+	}
+      else
+	memcpy (errbuf, msg, msg_size);
+    }
+
+  return msg_size;
+}
+#ifdef _LIBC
+weak_alias (__regerror, regerror)
+#endif
+
+
+#ifdef RE_ENABLE_I18N
+/* This static array is used for the map to single-byte characters when
+   UTF-8 is used.  Otherwise we would allocate memory just to initialize
+   it the same all the time.  UTF-8 is the preferred encoding so this is
+   a worthwhile optimization.  */
+#if __GNUC__ >= 3
+static const bitset_t utf8_sb_map = {
+  /* Set the first 128 bits.  */
+  [0 ... 0x80 / BITSET_WORD_BITS - 1] = BITSET_WORD_MAX
+};
+#else /* ! (__GNUC__ >= 3) */
+static bitset_t utf8_sb_map;
+#endif /* __GNUC__ >= 3 */
+#endif /* RE_ENABLE_I18N */
+
+
+static void
+free_dfa_content (re_dfa_t *dfa)
+{
+  int i, j;
+
+  if (dfa->nodes)
+    for (i = 0; i < dfa->nodes_len; ++i)
+      free_token (dfa->nodes + i);
+  re_free (dfa->nexts);
+  for (i = 0; i < dfa->nodes_len; ++i)
+    {
+      if (dfa->eclosures != NULL)
+	re_node_set_free (dfa->eclosures + i);
+      if (dfa->inveclosures != NULL)
+	re_node_set_free (dfa->inveclosures + i);
+      if (dfa->edests != NULL)
+	re_node_set_free (dfa->edests + i);
+    }
+  re_free (dfa->edests);
+  re_free (dfa->eclosures);
+  re_free (dfa->inveclosures);
+  re_free (dfa->nodes);
+
+  if (dfa->state_table)
+    for (i = 0; i <= dfa->state_hash_mask; ++i)
+      {
+	struct re_state_table_entry *entry = dfa->state_table + i;
+	for (j = 0; j < entry->num; ++j)
+	  {
+	    re_dfastate_t *state = entry->array[j];
+	    free_state (state);
+	  }
+	re_free (entry->array);
+      }
+  re_free (dfa->state_table);
+#ifdef RE_ENABLE_I18N
+  if (dfa->sb_char != utf8_sb_map)
+    re_free (dfa->sb_char);
+#endif
+  re_free (dfa->subexp_map);
+#ifdef DEBUG
+  re_free (dfa->re_str);
+#endif
+
+  re_free (dfa);
+}
+
+
+/* Free dynamically allocated space used by PREG.  */
+
+void
+regfree (regex_t *preg)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  if (BE (dfa != NULL, 1))
+    free_dfa_content (dfa);
+  preg->buffer = NULL;
+  preg->allocated = 0;
+
+  re_free (preg->fastmap);
+  preg->fastmap = NULL;
+
+  re_free (preg->translate);
+  preg->translate = NULL;
+}
+#ifdef _LIBC
+weak_alias (__regfree, regfree)
+#endif
+
+/* Entry points compatible with 4.2 BSD regex library.  We don't define
+   them unless specifically requested.  */
+
+#if defined _REGEX_RE_COMP || defined _LIBC
+
+/* BSD has one and only one pattern buffer.  */
+static struct re_pattern_buffer re_comp_buf;
+
+char *
+# ifdef _LIBC
+/* Make these definitions weak in libc, so POSIX programs can redefine
+   these names if they don't use our functions, and still use
+   regcomp/regexec above without link errors.  */
+weak_function
+# endif
+re_comp (s)
+     const char *s;
+{
+  reg_errcode_t ret;
+  char *fastmap;
+
+  if (!s)
+    {
+      if (!re_comp_buf.buffer)
+	return gettext ("No previous regular expression");
+      return 0;
+    }
+
+  if (re_comp_buf.buffer)
+    {
+      fastmap = re_comp_buf.fastmap;
+      re_comp_buf.fastmap = NULL;
+      __regfree (&re_comp_buf);
+      memset (&re_comp_buf, '\0', sizeof (re_comp_buf));
+      re_comp_buf.fastmap = fastmap;
+    }
+
+  if (re_comp_buf.fastmap == NULL)
+    {
+      re_comp_buf.fastmap = (char *) malloc (SBC_MAX);
+      if (re_comp_buf.fastmap == NULL)
+	return (char *) gettext (__re_error_msgid
+				 + __re_error_msgid_idx[(int) REG_ESPACE]);
+    }
+
+  /* Since `re_exec' always passes NULL for the `regs' argument, we
+     don't need to initialize the pattern buffer fields which affect it.  */
+
+  /* Match anchors at newlines.  */
+  re_comp_buf.newline_anchor = 1;
+
+  ret = re_compile_internal (&re_comp_buf, s, strlen (s), re_syntax_options);
+
+  if (!ret)
+    return NULL;
+
+  /* Yes, we're discarding `const' here if !HAVE_LIBINTL.  */
+  return (char *) gettext (__re_error_msgid + __re_error_msgid_idx[(int) ret]);
+}
+
+#ifdef _LIBC
+libc_freeres_fn (free_mem)
+{
+  __regfree (&re_comp_buf);
+}
+#endif
+
+#endif /* _REGEX_RE_COMP */
+
+/* Internal entry point.
+   Compile the regular expression PATTERN, whose length is LENGTH.
+   SYNTAX indicate regular expression's syntax.  */
+
+static reg_errcode_t
+re_compile_internal (regex_t *preg, const char * pattern, size_t length,
+		     reg_syntax_t syntax)
+{
+  reg_errcode_t err = REG_NOERROR;
+  re_dfa_t *dfa;
+  re_string_t regexp;
+
+  /* Initialize the pattern buffer.  */
+  preg->fastmap_accurate = 0;
+  preg->syntax = syntax;
+  preg->not_bol = preg->not_eol = 0;
+  preg->used = 0;
+  preg->re_nsub = 0;
+  preg->can_be_null = 0;
+  preg->regs_allocated = REGS_UNALLOCATED;
+
+  /* Initialize the dfa.  */
+  dfa = (re_dfa_t *) preg->buffer;
+  if (BE (preg->allocated < sizeof (re_dfa_t), 0))
+    {
+      /* If zero allocated, but buffer is non-null, try to realloc
+	 enough space.  This loses if buffer's address is bogus, but
+	 that is the user's responsibility.  If ->buffer is NULL this
+	 is a simple allocation.  */
+      dfa = re_realloc (preg->buffer, re_dfa_t, 1);
+      if (dfa == NULL)
+	return REG_ESPACE;
+      preg->allocated = sizeof (re_dfa_t);
+      preg->buffer = (unsigned char *) dfa;
+    }
+  preg->used = sizeof (re_dfa_t);
+
+  err = init_dfa (dfa, length);
+  if (BE (err != REG_NOERROR, 0))
+    {
+      free_dfa_content (dfa);
+      preg->buffer = NULL;
+      preg->allocated = 0;
+      return err;
+    }
+#ifdef DEBUG
+  /* Note: length+1 will not overflow since it is checked in init_dfa.  */
+  dfa->re_str = re_malloc (char, length + 1);
+  strncpy (dfa->re_str, pattern, length + 1);
+#endif
+
+  __libc_lock_init (dfa->lock);
+
+  err = re_string_construct (&regexp, pattern, length, preg->translate,
+			     syntax & RE_ICASE, dfa);
+  if (BE (err != REG_NOERROR, 0))
+    {
+    re_compile_internal_free_return:
+      free_workarea_compile (preg);
+      re_string_destruct (&regexp);
+      free_dfa_content (dfa);
+      preg->buffer = NULL;
+      preg->allocated = 0;
+      return err;
+    }
+
+  /* Parse the regular expression, and build a structure tree.  */
+  preg->re_nsub = 0;
+  dfa->str_tree = parse (&regexp, preg, syntax, &err);
+  if (BE (dfa->str_tree == NULL, 0))
+    goto re_compile_internal_free_return;
+
+  /* Analyze the tree and create the nfa.  */
+  err = analyze (preg);
+  if (BE (err != REG_NOERROR, 0))
+    goto re_compile_internal_free_return;
+
+#ifdef RE_ENABLE_I18N
+  /* If possible, do searching in single byte encoding to speed things up.  */
+  if (dfa->is_utf8 && !(syntax & RE_ICASE) && preg->translate == NULL)
+    optimize_utf8 (dfa);
+#endif
+
+  /* Then create the initial state of the dfa.  */
+  err = create_initial_state (dfa);
+
+  /* Release work areas.  */
+  free_workarea_compile (preg);
+  re_string_destruct (&regexp);
+
+  if (BE (err != REG_NOERROR, 0))
+    {
+      free_dfa_content (dfa);
+      preg->buffer = NULL;
+      preg->allocated = 0;
+    }
+
+  return err;
+}
+
+/* Initialize DFA.  We use the length of the regular expression PAT_LEN
+   as the initial length of some arrays.  */
+
+static reg_errcode_t
+init_dfa (re_dfa_t *dfa, size_t pat_len)
+{
+  unsigned int table_size;
+#ifndef _LIBC
+  char *codeset_name;
+#endif
+
+  memset (dfa, '\0', sizeof (re_dfa_t));
+
+  /* Force allocation of str_tree_storage the first time.  */
+  dfa->str_tree_storage_idx = BIN_TREE_STORAGE_SIZE;
+
+  /* Avoid overflows.  */
+  if (pat_len == SIZE_MAX)
+    return REG_ESPACE;
+
+  dfa->nodes_alloc = pat_len + 1;
+  dfa->nodes = re_malloc (re_token_t, dfa->nodes_alloc);
+
+  /*  table_size = 2 ^ ceil(log pat_len) */
+  for (table_size = 1; ; table_size <<= 1)
+    if (table_size > pat_len)
+      break;
+
+  dfa->state_table = calloc (sizeof (struct re_state_table_entry), table_size);
+  dfa->state_hash_mask = table_size - 1;
+
+  dfa->mb_cur_max = MB_CUR_MAX;
+#ifdef _LIBC
+  if (dfa->mb_cur_max == 6
+      && strcmp (_NL_CURRENT (LC_CTYPE, _NL_CTYPE_CODESET_NAME), "UTF-8") == 0)
+    dfa->is_utf8 = 1;
+  dfa->map_notascii = (_NL_CURRENT_WORD (LC_CTYPE, _NL_CTYPE_MAP_TO_NONASCII)
+		       != 0);
+#else
+# ifdef HAVE_LANGINFO_CODESET
+  codeset_name = nl_langinfo (CODESET);
+# else
+  codeset_name = getenv ("LC_ALL");
+  if (codeset_name == NULL || codeset_name[0] == '\0')
+    codeset_name = getenv ("LC_CTYPE");
+  if (codeset_name == NULL || codeset_name[0] == '\0')
+    codeset_name = getenv ("LANG");
+  if (codeset_name == NULL)
+    codeset_name = "";
+  else if (strchr (codeset_name, '.') !=  NULL)
+    codeset_name = strchr (codeset_name, '.') + 1;
+# endif
+
+  /* strcasecmp isn't a standard interface. brute force check */
+#if 0
+  if (strcasecmp (codeset_name, "UTF-8") == 0
+      || strcasecmp (codeset_name, "UTF8") == 0)
+    dfa->is_utf8 = 1;
+#else
+  if (   (codeset_name[0] == 'U' || codeset_name[0] == 'u')
+      && (codeset_name[1] == 'T' || codeset_name[1] == 't')
+      && (codeset_name[2] == 'F' || codeset_name[2] == 'f')
+      && (codeset_name[3] == '-'
+          ? codeset_name[4] == '8' && codeset_name[5] == '\0'
+          : codeset_name[3] == '8' && codeset_name[4] == '\0'))
+    dfa->is_utf8 = 1;
+#endif
+
+  /* We check exhaustively in the loop below if this charset is a
+     superset of ASCII.  */
+  dfa->map_notascii = 0;
+#endif
+
+#ifdef RE_ENABLE_I18N
+  if (dfa->mb_cur_max > 1)
+    {
+      if (dfa->is_utf8)
+        {
+#if !defined(__GNUC__) || __GNUC__ < 3
+	  static short utf8_sb_map_inited = 0;
+
+	  if (! utf8_sb_map_inited)
+	    {
+		int i;
+
+	  	utf8_sb_map_inited = 0;
+		for (i = 0; i <= 0x80 / BITSET_WORD_BITS - 1; i++)
+		  utf8_sb_map[i] = BITSET_WORD_MAX;
+	    }
+#endif
+	  dfa->sb_char = (re_bitset_ptr_t) utf8_sb_map;
+	}
+      else
+	{
+	  int i, j, ch;
+
+	  dfa->sb_char = (re_bitset_ptr_t) calloc (sizeof (bitset_t), 1);
+	  if (BE (dfa->sb_char == NULL, 0))
+	    return REG_ESPACE;
+
+	  /* Set the bits corresponding to single byte chars.  */
+	  for (i = 0, ch = 0; i < BITSET_WORDS; ++i)
+	    for (j = 0; j < BITSET_WORD_BITS; ++j, ++ch)
+	      {
+		wint_t wch = __btowc (ch);
+		if (wch != WEOF)
+		  dfa->sb_char[i] |= (bitset_word_t) 1 << j;
+# ifndef _LIBC
+		if (isascii (ch) && wch != ch)
+		  dfa->map_notascii = 1;
+# endif
+	      }
+	}
+    }
+#endif
+
+  if (BE (dfa->nodes == NULL || dfa->state_table == NULL, 0))
+    return REG_ESPACE;
+  return REG_NOERROR;
+}
+
+/* Initialize WORD_CHAR table, which indicate which character is
+   "word".  In this case "word" means that it is the word construction
+   character used by some operators like "\<", "\>", etc.  */
+
+static void
+internal_function
+init_word_char (re_dfa_t *dfa)
+{
+  int i, j, ch;
+  dfa->word_ops_used = 1;
+  for (i = 0, ch = 0; i < BITSET_WORDS; ++i)
+    for (j = 0; j < BITSET_WORD_BITS; ++j, ++ch)
+      if (isalnum (ch) || ch == '_')
+	dfa->word_char[i] |= (bitset_word_t) 1 << j;
+}
+
+/* Free the work area which are only used while compiling.  */
+
+static void
+free_workarea_compile (regex_t *preg)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_storage_t *storage, *next;
+  for (storage = dfa->str_tree_storage; storage; storage = next)
+    {
+      next = storage->next;
+      re_free (storage);
+    }
+  dfa->str_tree_storage = NULL;
+  dfa->str_tree_storage_idx = BIN_TREE_STORAGE_SIZE;
+  dfa->str_tree = NULL;
+  re_free (dfa->org_indices);
+  dfa->org_indices = NULL;
+}
+
+/* Create initial states for all contexts.  */
+
+static reg_errcode_t
+create_initial_state (re_dfa_t *dfa)
+{
+  int first, i;
+  reg_errcode_t err;
+  re_node_set init_nodes;
+
+  /* Initial states have the epsilon closure of the node which is
+     the first node of the regular expression.  */
+  first = dfa->str_tree->first->node_idx;
+  dfa->init_node = first;
+  err = re_node_set_init_copy (&init_nodes, dfa->eclosures + first);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  /* The back-references which are in initial states can epsilon transit,
+     since in this case all of the subexpressions can be null.
+     Then we add epsilon closures of the nodes which are the next nodes of
+     the back-references.  */
+  if (dfa->nbackref > 0)
+    for (i = 0; i < init_nodes.nelem; ++i)
+      {
+	int node_idx = init_nodes.elems[i];
+	re_token_type_t type = dfa->nodes[node_idx].type;
+
+	int clexp_idx;
+	if (type != OP_BACK_REF)
+	  continue;
+	for (clexp_idx = 0; clexp_idx < init_nodes.nelem; ++clexp_idx)
+	  {
+	    re_token_t *clexp_node;
+	    clexp_node = dfa->nodes + init_nodes.elems[clexp_idx];
+	    if (clexp_node->type == OP_CLOSE_SUBEXP
+		&& clexp_node->opr.idx == dfa->nodes[node_idx].opr.idx)
+	      break;
+	  }
+	if (clexp_idx == init_nodes.nelem)
+	  continue;
+
+	if (type == OP_BACK_REF)
+	  {
+	    int dest_idx = dfa->edests[node_idx].elems[0];
+	    if (!re_node_set_contains (&init_nodes, dest_idx))
+	      {
+		reg_errcode_t err = re_node_set_merge (&init_nodes,
+						       dfa->eclosures
+						       + dest_idx);
+		if (err != REG_NOERROR)
+		  return err;
+		i = 0;
+	      }
+	  }
+      }
+
+  /* It must be the first time to invoke acquire_state.  */
+  dfa->init_state = re_acquire_state_context (&err, dfa, &init_nodes, 0);
+  /* We don't check ERR here, since the initial state must not be NULL.  */
+  if (BE (dfa->init_state == NULL, 0))
+    return err;
+  if (dfa->init_state->has_constraint)
+    {
+      dfa->init_state_word = re_acquire_state_context (&err, dfa, &init_nodes,
+						       CONTEXT_WORD);
+      dfa->init_state_nl = re_acquire_state_context (&err, dfa, &init_nodes,
+						     CONTEXT_NEWLINE);
+      dfa->init_state_begbuf = re_acquire_state_context (&err, dfa,
+							 &init_nodes,
+							 CONTEXT_NEWLINE
+							 | CONTEXT_BEGBUF);
+      if (BE (dfa->init_state_word == NULL || dfa->init_state_nl == NULL
+	      || dfa->init_state_begbuf == NULL, 0))
+	return err;
+    }
+  else
+    dfa->init_state_word = dfa->init_state_nl
+      = dfa->init_state_begbuf = dfa->init_state;
+
+  re_node_set_free (&init_nodes);
+  return REG_NOERROR;
+}
+
+#ifdef RE_ENABLE_I18N
+/* If it is possible to do searching in single byte encoding instead of UTF-8
+   to speed things up, set dfa->mb_cur_max to 1, clear is_utf8 and change
+   DFA nodes where needed.  */
+
+static void
+optimize_utf8 (re_dfa_t *dfa)
+{
+  int node, i, mb_chars = 0, has_period = 0;
+
+  for (node = 0; node < dfa->nodes_len; ++node)
+    switch (dfa->nodes[node].type)
+      {
+      case CHARACTER:
+	if (dfa->nodes[node].opr.c >= 0x80)
+	  mb_chars = 1;
+	break;
+      case ANCHOR:
+	switch (dfa->nodes[node].opr.ctx_type)
+	  {
+	  case LINE_FIRST:
+	  case LINE_LAST:
+	  case BUF_FIRST:
+	  case BUF_LAST:
+	    break;
+	  default:
+	    /* Word anchors etc. cannot be handled.  It's okay to test
+	       opr.ctx_type since constraints (for all DFA nodes) are
+	       created by ORing one or more opr.ctx_type values.  */
+	    return;
+	  }
+	break;
+      case OP_PERIOD:
+	has_period = 1;
+	break;
+      case OP_BACK_REF:
+      case OP_ALT:
+      case END_OF_RE:
+      case OP_DUP_ASTERISK:
+      case OP_OPEN_SUBEXP:
+      case OP_CLOSE_SUBEXP:
+	break;
+      case COMPLEX_BRACKET:
+	return;
+      case SIMPLE_BRACKET:
+	/* Just double check.  The non-ASCII range starts at 0x80.  */
+	assert (0x80 % BITSET_WORD_BITS == 0);
+	for (i = 0x80 / BITSET_WORD_BITS; i < BITSET_WORDS; ++i)
+	  if (dfa->nodes[node].opr.sbcset[i])
+	    return;
+	break;
+      default:
+	abort ();
+      }
+
+  if (mb_chars || has_period)
+    for (node = 0; node < dfa->nodes_len; ++node)
+      {
+	if (dfa->nodes[node].type == CHARACTER
+	    && dfa->nodes[node].opr.c >= 0x80)
+	  dfa->nodes[node].mb_partial = 0;
+	else if (dfa->nodes[node].type == OP_PERIOD)
+	  dfa->nodes[node].type = OP_UTF8_PERIOD;
+      }
+
+  /* The search can be in single byte locale.  */
+  dfa->mb_cur_max = 1;
+  dfa->is_utf8 = 0;
+  dfa->has_mb_node = dfa->nbackref > 0 || has_period;
+}
+#endif
+
+/* Analyze the structure tree, and calculate "first", "next", "edest",
+   "eclosure", and "inveclosure".  */
+
+static reg_errcode_t
+analyze (regex_t *preg)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  reg_errcode_t ret;
+
+  /* Allocate arrays.  */
+  dfa->nexts = re_malloc (int, dfa->nodes_alloc);
+  dfa->org_indices = re_malloc (int, dfa->nodes_alloc);
+  dfa->edests = re_malloc (re_node_set, dfa->nodes_alloc);
+  dfa->eclosures = re_malloc (re_node_set, dfa->nodes_alloc);
+  if (BE (dfa->nexts == NULL || dfa->org_indices == NULL || dfa->edests == NULL
+	  || dfa->eclosures == NULL, 0))
+    return REG_ESPACE;
+
+  dfa->subexp_map = re_malloc (int, preg->re_nsub);
+  if (dfa->subexp_map != NULL)
+    {
+      int i;
+      for (i = 0; i < preg->re_nsub; i++)
+	dfa->subexp_map[i] = i;
+      preorder (dfa->str_tree, optimize_subexps, dfa);
+      for (i = 0; i < preg->re_nsub; i++)
+	if (dfa->subexp_map[i] != i)
+	  break;
+      if (i == preg->re_nsub)
+	{
+	  free (dfa->subexp_map);
+	  dfa->subexp_map = NULL;
+	}
+    }
+
+  ret = postorder (dfa->str_tree, lower_subexps, preg);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+  ret = postorder (dfa->str_tree, calc_first, dfa);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+  preorder (dfa->str_tree, calc_next, dfa);
+  ret = preorder (dfa->str_tree, link_nfa_nodes, dfa);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+  ret = calc_eclosure (dfa);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+
+  /* We only need this during the prune_impossible_nodes pass in regexec.c;
+     skip it if p_i_n will not run, as calc_inveclosure can be quadratic.  */
+  if ((!preg->no_sub && preg->re_nsub > 0 && dfa->has_plural_match)
+      || dfa->nbackref)
+    {
+      dfa->inveclosures = re_malloc (re_node_set, dfa->nodes_len);
+      if (BE (dfa->inveclosures == NULL, 0))
+	return REG_ESPACE;
+      ret = calc_inveclosure (dfa);
+    }
+
+  return ret;
+}
+
+/* Our parse trees are very unbalanced, so we cannot use a stack to
+   implement parse tree visits.  Instead, we use parent pointers and
+   some hairy code in these two functions.  */
+static reg_errcode_t
+postorder (bin_tree_t *root, reg_errcode_t (fn (void *, bin_tree_t *)),
+	   void *extra)
+{
+  bin_tree_t *node, *prev;
+
+  for (node = root; ; )
+    {
+      /* Descend down the tree, preferably to the left (or to the right
+	 if that's the only child).  */
+      while (node->left || node->right)
+	if (node->left)
+	  node = node->left;
+	else
+	  node = node->right;
+
+      do
+	{
+	  reg_errcode_t err = fn (extra, node);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	  if (node->parent == NULL)
+	    return REG_NOERROR;
+	  prev = node;
+	  node = node->parent;
+	}
+      /* Go up while we have a node that is reached from the right.  */
+      while (node->right == prev || node->right == NULL);
+      node = node->right;
+    }
+}
+
+static reg_errcode_t
+preorder (bin_tree_t *root, reg_errcode_t (fn (void *, bin_tree_t *)),
+	  void *extra)
+{
+  bin_tree_t *node;
+
+  for (node = root; ; )
+    {
+      reg_errcode_t err = fn (extra, node);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+
+      /* Go to the left node, or up and to the right.  */
+      if (node->left)
+	node = node->left;
+      else
+	{
+	  bin_tree_t *prev = NULL;
+	  while (node->right == prev || node->right == NULL)
+	    {
+	      prev = node;
+	      node = node->parent;
+	      if (!node)
+		return REG_NOERROR;
+	    }
+	  node = node->right;
+	}
+    }
+}
+
+/* Optimization pass: if a SUBEXP is entirely contained, strip it and tell
+   re_search_internal to map the inner one's opr.idx to this one's.  Adjust
+   backreferences as well.  Requires a preorder visit.  */
+static reg_errcode_t
+optimize_subexps (void *extra, bin_tree_t *node)
+{
+  re_dfa_t *dfa = (re_dfa_t *) extra;
+
+  if (node->token.type == OP_BACK_REF && dfa->subexp_map)
+    {
+      int idx = node->token.opr.idx;
+      node->token.opr.idx = dfa->subexp_map[idx];
+      dfa->used_bkref_map |= 1 << node->token.opr.idx;
+    }
+
+  else if (node->token.type == SUBEXP
+	   && node->left && node->left->token.type == SUBEXP)
+    {
+      int other_idx = node->left->token.opr.idx;
+
+      node->left = node->left->left;
+      if (node->left)
+	node->left->parent = node;
+
+      dfa->subexp_map[other_idx] = dfa->subexp_map[node->token.opr.idx];
+      if (other_idx < BITSET_WORD_BITS)
+	  dfa->used_bkref_map &= ~((bitset_word_t) 1 << other_idx);
+    }
+
+  return REG_NOERROR;
+}
+
+/* Lowering pass: Turn each SUBEXP node into the appropriate concatenation
+   of OP_OPEN_SUBEXP, the body of the SUBEXP (if any) and OP_CLOSE_SUBEXP.  */
+static reg_errcode_t
+lower_subexps (void *extra, bin_tree_t *node)
+{
+  regex_t *preg = (regex_t *) extra;
+  reg_errcode_t err = REG_NOERROR;
+
+  if (node->left && node->left->token.type == SUBEXP)
+    {
+      node->left = lower_subexp (&err, preg, node->left);
+      if (node->left)
+	node->left->parent = node;
+    }
+  if (node->right && node->right->token.type == SUBEXP)
+    {
+      node->right = lower_subexp (&err, preg, node->right);
+      if (node->right)
+	node->right->parent = node;
+    }
+
+  return err;
+}
+
+static bin_tree_t *
+lower_subexp (reg_errcode_t *err, regex_t *preg, bin_tree_t *node)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_t *body = node->left;
+  bin_tree_t *op, *cls, *tree1, *tree;
+
+  if (preg->no_sub
+      /* We do not optimize empty subexpressions, because otherwise we may
+	 have bad CONCAT nodes with NULL children.  This is obviously not
+	 very common, so we do not lose much.  An example that triggers
+	 this case is the sed "script" /\(\)/x.  */
+      && node->left != NULL
+      && (node->token.opr.idx >= BITSET_WORD_BITS
+	  || !(dfa->used_bkref_map
+	       & ((bitset_word_t) 1 << node->token.opr.idx))))
+    return node->left;
+
+  /* Convert the SUBEXP node to the concatenation of an
+     OP_OPEN_SUBEXP, the contents, and an OP_CLOSE_SUBEXP.  */
+  op = create_tree (dfa, NULL, NULL, OP_OPEN_SUBEXP);
+  cls = create_tree (dfa, NULL, NULL, OP_CLOSE_SUBEXP);
+  tree1 = body ? create_tree (dfa, body, cls, CONCAT) : cls;
+  tree = create_tree (dfa, op, tree1, CONCAT);
+  if (BE (tree == NULL || tree1 == NULL || op == NULL || cls == NULL, 0))
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+
+  op->token.opr.idx = cls->token.opr.idx = node->token.opr.idx;
+  op->token.opt_subexp = cls->token.opt_subexp = node->token.opt_subexp;
+  return tree;
+}
+
+/* Pass 1 in building the NFA: compute FIRST and create unlinked automaton
+   nodes.  Requires a postorder visit.  */
+static reg_errcode_t
+calc_first (void *extra, bin_tree_t *node)
+{
+  re_dfa_t *dfa = (re_dfa_t *) extra;
+  if (node->token.type == CONCAT)
+    {
+      node->first = node->left->first;
+      node->node_idx = node->left->node_idx;
+    }
+  else
+    {
+      node->first = node;
+      node->node_idx = re_dfa_add_node (dfa, node->token);
+      if (BE (node->node_idx == -1, 0))
+	return REG_ESPACE;
+      if (node->token.type == ANCHOR)
+	dfa->nodes[node->node_idx].constraint = node->token.opr.ctx_type;
+    }
+  return REG_NOERROR;
+}
+
+/* Pass 2: compute NEXT on the tree.  Preorder visit.  */
+static reg_errcode_t
+calc_next (void *extra, bin_tree_t *node)
+{
+  switch (node->token.type)
+    {
+    case OP_DUP_ASTERISK:
+      node->left->next = node;
+      break;
+    case CONCAT:
+      node->left->next = node->right->first;
+      node->right->next = node->next;
+      break;
+    default:
+      if (node->left)
+	node->left->next = node->next;
+      if (node->right)
+	node->right->next = node->next;
+      break;
+    }
+  return REG_NOERROR;
+}
+
+/* Pass 3: link all DFA nodes to their NEXT node (any order will do).  */
+static reg_errcode_t
+link_nfa_nodes (void *extra, bin_tree_t *node)
+{
+  re_dfa_t *dfa = (re_dfa_t *) extra;
+  int idx = node->node_idx;
+  reg_errcode_t err = REG_NOERROR;
+
+  switch (node->token.type)
+    {
+    case CONCAT:
+      break;
+
+    case END_OF_RE:
+      assert (node->next == NULL);
+      break;
+
+    case OP_DUP_ASTERISK:
+    case OP_ALT:
+      {
+	int left, right;
+	dfa->has_plural_match = 1;
+	if (node->left != NULL)
+	  left = node->left->first->node_idx;
+	else
+	  left = node->next->node_idx;
+	if (node->right != NULL)
+	  right = node->right->first->node_idx;
+	else
+	  right = node->next->node_idx;
+	assert (left > -1);
+	assert (right > -1);
+	err = re_node_set_init_2 (dfa->edests + idx, left, right);
+      }
+      break;
+
+    case ANCHOR:
+    case OP_OPEN_SUBEXP:
+    case OP_CLOSE_SUBEXP:
+      err = re_node_set_init_1 (dfa->edests + idx, node->next->node_idx);
+      break;
+
+    case OP_BACK_REF:
+      dfa->nexts[idx] = node->next->node_idx;
+      if (node->token.type == OP_BACK_REF)
+	err = re_node_set_init_1 (dfa->edests + idx, dfa->nexts[idx]);
+      break;
+
+    default:
+      assert (!IS_EPSILON_NODE (node->token.type));
+      dfa->nexts[idx] = node->next->node_idx;
+      break;
+    }
+
+  return err;
+}
+
+/* Duplicate the epsilon closure of the node ROOT_NODE.
+   Note that duplicated nodes have constraint INIT_CONSTRAINT in addition
+   to their own constraint.  */
+
+static reg_errcode_t
+internal_function
+duplicate_node_closure (re_dfa_t *dfa, int top_org_node, int top_clone_node,
+			int root_node, unsigned int init_constraint)
+{
+  int org_node, clone_node, ret;
+  unsigned int constraint = init_constraint;
+  for (org_node = top_org_node, clone_node = top_clone_node;;)
+    {
+      int org_dest, clone_dest;
+      if (dfa->nodes[org_node].type == OP_BACK_REF)
+	{
+	  /* If the back reference epsilon-transit, its destination must
+	     also have the constraint.  Then duplicate the epsilon closure
+	     of the destination of the back reference, and store it in
+	     edests of the back reference.  */
+	  org_dest = dfa->nexts[org_node];
+	  re_node_set_empty (dfa->edests + clone_node);
+	  clone_dest = duplicate_node (dfa, org_dest, constraint);
+	  if (BE (clone_dest == -1, 0))
+	    return REG_ESPACE;
+	  dfa->nexts[clone_node] = dfa->nexts[org_node];
+	  ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (ret < 0, 0))
+	    return REG_ESPACE;
+	}
+      else if (dfa->edests[org_node].nelem == 0)
+	{
+	  /* In case of the node can't epsilon-transit, don't duplicate the
+	     destination and store the original destination as the
+	     destination of the node.  */
+	  dfa->nexts[clone_node] = dfa->nexts[org_node];
+	  break;
+	}
+      else if (dfa->edests[org_node].nelem == 1)
+	{
+	  /* In case of the node can epsilon-transit, and it has only one
+	     destination.  */
+	  org_dest = dfa->edests[org_node].elems[0];
+	  re_node_set_empty (dfa->edests + clone_node);
+	  /* If the node is root_node itself, it means the epsilon clsoure
+	     has a loop.   Then tie it to the destination of the root_node.  */
+	  if (org_node == root_node && clone_node != org_node)
+	    {
+	      ret = re_node_set_insert (dfa->edests + clone_node, org_dest);
+	      if (BE (ret < 0, 0))
+		return REG_ESPACE;
+	      break;
+	    }
+	  /* In case of the node has another constraint, add it.  */
+	  constraint |= dfa->nodes[org_node].constraint;
+	  clone_dest = duplicate_node (dfa, org_dest, constraint);
+	  if (BE (clone_dest == -1, 0))
+	    return REG_ESPACE;
+	  ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (ret < 0, 0))
+	    return REG_ESPACE;
+	}
+      else /* dfa->edests[org_node].nelem == 2 */
+	{
+	  /* In case of the node can epsilon-transit, and it has two
+	     destinations. In the bin_tree_t and DFA, that's '|' and '*'.   */
+	  org_dest = dfa->edests[org_node].elems[0];
+	  re_node_set_empty (dfa->edests + clone_node);
+	  /* Search for a duplicated node which satisfies the constraint.  */
+	  clone_dest = search_duplicated_node (dfa, org_dest, constraint);
+	  if (clone_dest == -1)
+	    {
+	      /* There is no such duplicated node, create a new one.  */
+	      reg_errcode_t err;
+	      clone_dest = duplicate_node (dfa, org_dest, constraint);
+	      if (BE (clone_dest == -1, 0))
+		return REG_ESPACE;
+	      ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	      if (BE (ret < 0, 0))
+		return REG_ESPACE;
+	      err = duplicate_node_closure (dfa, org_dest, clone_dest,
+					    root_node, constraint);
+	      if (BE (err != REG_NOERROR, 0))
+		return err;
+	    }
+	  else
+	    {
+	      /* There is a duplicated node which satisfies the constraint,
+		 use it to avoid infinite loop.  */
+	      ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	      if (BE (ret < 0, 0))
+		return REG_ESPACE;
+	    }
+
+	  org_dest = dfa->edests[org_node].elems[1];
+	  clone_dest = duplicate_node (dfa, org_dest, constraint);
+	  if (BE (clone_dest == -1, 0))
+	    return REG_ESPACE;
+	  ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (ret < 0, 0))
+	    return REG_ESPACE;
+	}
+      org_node = org_dest;
+      clone_node = clone_dest;
+    }
+  return REG_NOERROR;
+}
+
+/* Search for a node which is duplicated from the node ORG_NODE, and
+   satisfies the constraint CONSTRAINT.  */
+
+static int
+search_duplicated_node (const re_dfa_t *dfa, int org_node,
+			unsigned int constraint)
+{
+  int idx;
+  for (idx = dfa->nodes_len - 1; dfa->nodes[idx].duplicated && idx > 0; --idx)
+    {
+      if (org_node == dfa->org_indices[idx]
+	  && constraint == dfa->nodes[idx].constraint)
+	return idx; /* Found.  */
+    }
+  return -1; /* Not found.  */
+}
+
+/* Duplicate the node whose index is ORG_IDX and set the constraint CONSTRAINT.
+   Return the index of the new node, or -1 if insufficient storage is
+   available.  */
+
+static int
+duplicate_node (re_dfa_t *dfa, int org_idx, unsigned int constraint)
+{
+  int dup_idx = re_dfa_add_node (dfa, dfa->nodes[org_idx]);
+  if (BE (dup_idx != -1, 1))
+    {
+      dfa->nodes[dup_idx].constraint = constraint;
+      dfa->nodes[dup_idx].constraint |= dfa->nodes[org_idx].constraint;
+      dfa->nodes[dup_idx].duplicated = 1;
+
+      /* Store the index of the original node.  */
+      dfa->org_indices[dup_idx] = org_idx;
+    }
+  return dup_idx;
+}
+
+static reg_errcode_t
+calc_inveclosure (re_dfa_t *dfa)
+{
+  int src, idx, ret;
+  for (idx = 0; idx < dfa->nodes_len; ++idx)
+    re_node_set_init_empty (dfa->inveclosures + idx);
+
+  for (src = 0; src < dfa->nodes_len; ++src)
+    {
+      int *elems = dfa->eclosures[src].elems;
+      for (idx = 0; idx < dfa->eclosures[src].nelem; ++idx)
+	{
+	  ret = re_node_set_insert_last (dfa->inveclosures + elems[idx], src);
+	  if (BE (ret == -1, 0))
+	    return REG_ESPACE;
+	}
+    }
+
+  return REG_NOERROR;
+}
+
+/* Calculate "eclosure" for all the node in DFA.  */
+
+static reg_errcode_t
+calc_eclosure (re_dfa_t *dfa)
+{
+  int node_idx, incomplete;
+#ifdef DEBUG
+  assert (dfa->nodes_len > 0);
+#endif
+  incomplete = 0;
+  /* For each nodes, calculate epsilon closure.  */
+  for (node_idx = 0; ; ++node_idx)
+    {
+      reg_errcode_t err;
+      re_node_set eclosure_elem;
+      if (node_idx == dfa->nodes_len)
+	{
+	  if (!incomplete)
+	    break;
+	  incomplete = 0;
+	  node_idx = 0;
+	}
+
+#ifdef DEBUG
+      assert (dfa->eclosures[node_idx].nelem != -1);
+#endif
+
+      /* If we have already calculated, skip it.  */
+      if (dfa->eclosures[node_idx].nelem != 0)
+	continue;
+      /* Calculate epsilon closure of `node_idx'.  */
+      err = calc_eclosure_iter (&eclosure_elem, dfa, node_idx, 1);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+
+      if (dfa->eclosures[node_idx].nelem == 0)
+	{
+	  incomplete = 1;
+	  re_node_set_free (&eclosure_elem);
+	}
+    }
+  return REG_NOERROR;
+}
+
+/* Calculate epsilon closure of NODE.  */
+
+static reg_errcode_t
+calc_eclosure_iter (re_node_set *new_set, re_dfa_t *dfa, int node, int root)
+{
+  reg_errcode_t err;
+  int i;
+  re_node_set eclosure;
+  int ret;
+  int incomplete = 0;
+  err = re_node_set_alloc (&eclosure, dfa->edests[node].nelem + 1);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  /* This indicates that we are calculating this node now.
+     We reference this value to avoid infinite loop.  */
+  dfa->eclosures[node].nelem = -1;
+
+  /* If the current node has constraints, duplicate all nodes
+     since they must inherit the constraints.  */
+  if (dfa->nodes[node].constraint
+      && dfa->edests[node].nelem
+      && !dfa->nodes[dfa->edests[node].elems[0]].duplicated)
+    {
+      err = duplicate_node_closure (dfa, node, node, node,
+				    dfa->nodes[node].constraint);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+    }
+
+  /* Expand each epsilon destination nodes.  */
+  if (IS_EPSILON_NODE(dfa->nodes[node].type))
+    for (i = 0; i < dfa->edests[node].nelem; ++i)
+      {
+	re_node_set eclosure_elem;
+	int edest = dfa->edests[node].elems[i];
+	/* If calculating the epsilon closure of `edest' is in progress,
+	   return intermediate result.  */
+	if (dfa->eclosures[edest].nelem == -1)
+	  {
+	    incomplete = 1;
+	    continue;
+	  }
+	/* If we haven't calculated the epsilon closure of `edest' yet,
+	   calculate now. Otherwise use calculated epsilon closure.  */
+	if (dfa->eclosures[edest].nelem == 0)
+	  {
+	    err = calc_eclosure_iter (&eclosure_elem, dfa, edest, 0);
+	    if (BE (err != REG_NOERROR, 0))
+	      return err;
+	  }
+	else
+	  eclosure_elem = dfa->eclosures[edest];
+	/* Merge the epsilon closure of `edest'.  */
+	err = re_node_set_merge (&eclosure, &eclosure_elem);
+	if (BE (err != REG_NOERROR, 0))
+	  return err;
+	/* If the epsilon closure of `edest' is incomplete,
+	   the epsilon closure of this node is also incomplete.  */
+	if (dfa->eclosures[edest].nelem == 0)
+	  {
+	    incomplete = 1;
+	    re_node_set_free (&eclosure_elem);
+	  }
+      }
+
+  /* An epsilon closure includes itself.  */
+  ret = re_node_set_insert (&eclosure, node);
+  if (BE (ret < 0, 0))
+    return REG_ESPACE;
+  if (incomplete && !root)
+    dfa->eclosures[node].nelem = 0;
+  else
+    dfa->eclosures[node] = eclosure;
+  *new_set = eclosure;
+  return REG_NOERROR;
+}
+
+/* Functions for token which are used in the parser.  */
+
+/* Fetch a token from INPUT.
+   We must not use this function inside bracket expressions.  */
+
+static void
+internal_function
+fetch_token (re_token_t *result, re_string_t *input, reg_syntax_t syntax)
+{
+  re_string_skip_bytes (input, peek_token (result, input, syntax));
+}
+
+/* Peek a token from INPUT, and return the length of the token.
+   We must not use this function inside bracket expressions.  */
+
+static int
+internal_function
+peek_token (re_token_t *token, re_string_t *input, reg_syntax_t syntax)
+{
+  unsigned char c;
+
+  if (re_string_eoi (input))
+    {
+      token->type = END_OF_RE;
+      return 0;
+    }
+
+  c = re_string_peek_byte (input, 0);
+  token->opr.c = c;
+
+  token->word_char = 0;
+#ifdef RE_ENABLE_I18N
+  token->mb_partial = 0;
+  if (input->mb_cur_max > 1 &&
+      !re_string_first_byte (input, re_string_cur_idx (input)))
+    {
+      token->type = CHARACTER;
+      token->mb_partial = 1;
+      return 1;
+    }
+#endif
+  if (c == '\\')
+    {
+      unsigned char c2;
+      if (re_string_cur_idx (input) + 1 >= re_string_length (input))
+	{
+	  token->type = BACK_SLASH;
+	  return 1;
+	}
+
+      c2 = re_string_peek_byte_case (input, 1);
+      token->opr.c = c2;
+      token->type = CHARACTER;
+#ifdef RE_ENABLE_I18N
+      if (input->mb_cur_max > 1)
+	{
+	  wint_t wc = re_string_wchar_at (input,
+					  re_string_cur_idx (input) + 1);
+	  token->word_char = IS_WIDE_WORD_CHAR (wc) != 0;
+	}
+      else
+#endif
+	token->word_char = IS_WORD_CHAR (c2) != 0;
+
+      switch (c2)
+	{
+	case '|':
+	  if (!(syntax & RE_LIMITED_OPS) && !(syntax & RE_NO_BK_VBAR))
+	    token->type = OP_ALT;
+	  break;
+	case '1': case '2': case '3': case '4': case '5':
+	case '6': case '7': case '8': case '9':
+	  if (!(syntax & RE_NO_BK_REFS))
+	    {
+	      token->type = OP_BACK_REF;
+	      token->opr.idx = c2 - '1';
+	    }
+	  break;
+	case '<':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = WORD_FIRST;
+	    }
+	  break;
+	case '>':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = WORD_LAST;
+	    }
+	  break;
+	case 'b':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = WORD_DELIM;
+	    }
+	  break;
+	case 'B':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = NOT_WORD_DELIM;
+	    }
+	  break;
+	case 'w':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    token->type = OP_WORD;
+	  break;
+	case 'W':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    token->type = OP_NOTWORD;
+	  break;
+	case 's':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    token->type = OP_SPACE;
+	  break;
+	case 'S':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    token->type = OP_NOTSPACE;
+	  break;
+	case '`':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = BUF_FIRST;
+	    }
+	  break;
+	case '\'':
+	  if (!(syntax & RE_NO_GNU_OPS))
+	    {
+	      token->type = ANCHOR;
+	      token->opr.ctx_type = BUF_LAST;
+	    }
+	  break;
+	case '(':
+	  if (!(syntax & RE_NO_BK_PARENS))
+	    token->type = OP_OPEN_SUBEXP;
+	  break;
+	case ')':
+	  if (!(syntax & RE_NO_BK_PARENS))
+	    token->type = OP_CLOSE_SUBEXP;
+	  break;
+	case '+':
+	  if (!(syntax & RE_LIMITED_OPS) && (syntax & RE_BK_PLUS_QM))
+	    token->type = OP_DUP_PLUS;
+	  break;
+	case '?':
+	  if (!(syntax & RE_LIMITED_OPS) && (syntax & RE_BK_PLUS_QM))
+	    token->type = OP_DUP_QUESTION;
+	  break;
+	case '{':
+	  if ((syntax & RE_INTERVALS) && (!(syntax & RE_NO_BK_BRACES)))
+	    token->type = OP_OPEN_DUP_NUM;
+	  break;
+	case '}':
+	  if ((syntax & RE_INTERVALS) && (!(syntax & RE_NO_BK_BRACES)))
+	    token->type = OP_CLOSE_DUP_NUM;
+	  break;
+	default:
+	  break;
+	}
+      return 2;
+    }
+
+  token->type = CHARACTER;
+#ifdef RE_ENABLE_I18N
+  if (input->mb_cur_max > 1)
+    {
+      wint_t wc = re_string_wchar_at (input, re_string_cur_idx (input));
+      token->word_char = IS_WIDE_WORD_CHAR (wc) != 0;
+    }
+  else
+#endif
+    token->word_char = IS_WORD_CHAR (token->opr.c);
+
+  switch (c)
+    {
+    case '\n':
+      if (syntax & RE_NEWLINE_ALT)
+	token->type = OP_ALT;
+      break;
+    case '|':
+      if (!(syntax & RE_LIMITED_OPS) && (syntax & RE_NO_BK_VBAR))
+	token->type = OP_ALT;
+      break;
+    case '*':
+      token->type = OP_DUP_ASTERISK;
+      break;
+    case '+':
+      if (!(syntax & RE_LIMITED_OPS) && !(syntax & RE_BK_PLUS_QM))
+	token->type = OP_DUP_PLUS;
+      break;
+    case '?':
+      if (!(syntax & RE_LIMITED_OPS) && !(syntax & RE_BK_PLUS_QM))
+	token->type = OP_DUP_QUESTION;
+      break;
+    case '{':
+      if ((syntax & RE_INTERVALS) && (syntax & RE_NO_BK_BRACES))
+	token->type = OP_OPEN_DUP_NUM;
+      break;
+    case '}':
+      if ((syntax & RE_INTERVALS) && (syntax & RE_NO_BK_BRACES))
+	token->type = OP_CLOSE_DUP_NUM;
+      break;
+    case '(':
+      if (syntax & RE_NO_BK_PARENS)
+	token->type = OP_OPEN_SUBEXP;
+      break;
+    case ')':
+      if (syntax & RE_NO_BK_PARENS)
+	token->type = OP_CLOSE_SUBEXP;
+      break;
+    case '[':
+      token->type = OP_OPEN_BRACKET;
+      break;
+    case '.':
+      token->type = OP_PERIOD;
+      break;
+    case '^':
+      if (!(syntax & (RE_CONTEXT_INDEP_ANCHORS | RE_CARET_ANCHORS_HERE)) &&
+	  re_string_cur_idx (input) != 0)
+	{
+	  char prev = re_string_peek_byte (input, -1);
+	  if (!(syntax & RE_NEWLINE_ALT) || prev != '\n')
+	    break;
+	}
+      token->type = ANCHOR;
+      token->opr.ctx_type = LINE_FIRST;
+      break;
+    case '$':
+      if (!(syntax & RE_CONTEXT_INDEP_ANCHORS) &&
+	  re_string_cur_idx (input) + 1 != re_string_length (input))
+	{
+	  re_token_t next;
+	  re_string_skip_bytes (input, 1);
+	  peek_token (&next, input, syntax);
+	  re_string_skip_bytes (input, -1);
+	  if (next.type != OP_ALT && next.type != OP_CLOSE_SUBEXP)
+	    break;
+	}
+      token->type = ANCHOR;
+      token->opr.ctx_type = LINE_LAST;
+      break;
+    default:
+      break;
+    }
+  return 1;
+}
+
+/* Peek a token from INPUT, and return the length of the token.
+   We must not use this function out of bracket expressions.  */
+
+static int
+internal_function
+peek_token_bracket (re_token_t *token, re_string_t *input, reg_syntax_t syntax)
+{
+  unsigned char c;
+  if (re_string_eoi (input))
+    {
+      token->type = END_OF_RE;
+      return 0;
+    }
+  c = re_string_peek_byte (input, 0);
+  token->opr.c = c;
+
+#ifdef RE_ENABLE_I18N
+  if (input->mb_cur_max > 1 &&
+      !re_string_first_byte (input, re_string_cur_idx (input)))
+    {
+      token->type = CHARACTER;
+      return 1;
+    }
+#endif /* RE_ENABLE_I18N */
+
+  if (c == '\\' && (syntax & RE_BACKSLASH_ESCAPE_IN_LISTS)
+      && re_string_cur_idx (input) + 1 < re_string_length (input))
+    {
+      /* In this case, '\' escape a character.  */
+      unsigned char c2;
+      re_string_skip_bytes (input, 1);
+      c2 = re_string_peek_byte (input, 0);
+      token->opr.c = c2;
+      token->type = CHARACTER;
+      return 1;
+    }
+  if (c == '[') /* '[' is a special char in a bracket exps.  */
+    {
+      unsigned char c2;
+      int token_len;
+      if (re_string_cur_idx (input) + 1 < re_string_length (input))
+	c2 = re_string_peek_byte (input, 1);
+      else
+	c2 = 0;
+      token->opr.c = c2;
+      token_len = 2;
+      switch (c2)
+	{
+	case '.':
+	  token->type = OP_OPEN_COLL_ELEM;
+	  break;
+	case '=':
+	  token->type = OP_OPEN_EQUIV_CLASS;
+	  break;
+	case ':':
+	  if (syntax & RE_CHAR_CLASSES)
+	    {
+	      token->type = OP_OPEN_CHAR_CLASS;
+	      break;
+	    }
+	  /* else fall through.  */
+	default:
+	  token->type = CHARACTER;
+	  token->opr.c = c;
+	  token_len = 1;
+	  break;
+	}
+      return token_len;
+    }
+  switch (c)
+    {
+    case '-':
+      token->type = OP_CHARSET_RANGE;
+      break;
+    case ']':
+      token->type = OP_CLOSE_BRACKET;
+      break;
+    case '^':
+      token->type = OP_NON_MATCH_LIST;
+      break;
+    default:
+      token->type = CHARACTER;
+    }
+  return 1;
+}
+
+/* Functions for parser.  */
+
+/* Entry point of the parser.
+   Parse the regular expression REGEXP and return the structure tree.
+   If an error has occurred, ERR is set by error code, and return NULL.
+   This function build the following tree, from regular expression <reg_exp>:
+	   CAT
+	   / \
+	  /   \
+   <reg_exp>  EOR
+
+   CAT means concatenation.
+   EOR means end of regular expression.  */
+
+static bin_tree_t *
+parse (re_string_t *regexp, regex_t *preg, reg_syntax_t syntax,
+       reg_errcode_t *err)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_t *tree, *eor, *root;
+  re_token_t current_token;
+  dfa->syntax = syntax;
+  fetch_token (&current_token, regexp, syntax | RE_CARET_ANCHORS_HERE);
+  tree = parse_reg_exp (regexp, preg, &current_token, syntax, 0, err);
+  if (BE (*err != REG_NOERROR && tree == NULL, 0))
+    return NULL;
+  eor = create_tree (dfa, NULL, NULL, END_OF_RE);
+  if (tree != NULL)
+    root = create_tree (dfa, tree, eor, CONCAT);
+  else
+    root = eor;
+  if (BE (eor == NULL || root == NULL, 0))
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+  return root;
+}
+
+/* This function build the following tree, from regular expression
+   <branch1>|<branch2>:
+	   ALT
+	   / \
+	  /   \
+   <branch1> <branch2>
+
+   ALT means alternative, which represents the operator `|'.  */
+
+static bin_tree_t *
+parse_reg_exp (re_string_t *regexp, regex_t *preg, re_token_t *token,
+	       reg_syntax_t syntax, int nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_t *tree, *branch = NULL;
+  tree = parse_branch (regexp, preg, token, syntax, nest, err);
+  if (BE (*err != REG_NOERROR && tree == NULL, 0))
+    return NULL;
+
+  while (token->type == OP_ALT)
+    {
+      fetch_token (token, regexp, syntax | RE_CARET_ANCHORS_HERE);
+      if (token->type != OP_ALT && token->type != END_OF_RE
+	  && (nest == 0 || token->type != OP_CLOSE_SUBEXP))
+	{
+	  branch = parse_branch (regexp, preg, token, syntax, nest, err);
+	  if (BE (*err != REG_NOERROR && branch == NULL, 0))
+	    return NULL;
+	}
+      else
+	branch = NULL;
+      tree = create_tree (dfa, tree, branch, OP_ALT);
+      if (BE (tree == NULL, 0))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+    }
+  return tree;
+}
+
+/* This function build the following tree, from regular expression
+   <exp1><exp2>:
+	CAT
+	/ \
+       /   \
+   <exp1> <exp2>
+
+   CAT means concatenation.  */
+
+static bin_tree_t *
+parse_branch (re_string_t *regexp, regex_t *preg, re_token_t *token,
+	      reg_syntax_t syntax, int nest, reg_errcode_t *err)
+{
+  bin_tree_t *tree, *exp;
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  tree = parse_expression (regexp, preg, token, syntax, nest, err);
+  if (BE (*err != REG_NOERROR && tree == NULL, 0))
+    return NULL;
+
+  while (token->type != OP_ALT && token->type != END_OF_RE
+	 && (nest == 0 || token->type != OP_CLOSE_SUBEXP))
+    {
+      exp = parse_expression (regexp, preg, token, syntax, nest, err);
+      if (BE (*err != REG_NOERROR && exp == NULL, 0))
+	{
+	  return NULL;
+	}
+      if (tree != NULL && exp != NULL)
+	{
+	  tree = create_tree (dfa, tree, exp, CONCAT);
+	  if (tree == NULL)
+	    {
+	      *err = REG_ESPACE;
+	      return NULL;
+	    }
+	}
+      else if (tree == NULL)
+	tree = exp;
+      /* Otherwise exp == NULL, we don't need to create new tree.  */
+    }
+  return tree;
+}
+
+/* This function build the following tree, from regular expression a*:
+	 *
+	 |
+	 a
+*/
+
+static bin_tree_t *
+parse_expression (re_string_t *regexp, regex_t *preg, re_token_t *token,
+		  reg_syntax_t syntax, int nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_t *tree;
+  switch (token->type)
+    {
+    case CHARACTER:
+      tree = create_token_tree (dfa, NULL, NULL, token);
+      if (BE (tree == NULL, 0))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+#ifdef RE_ENABLE_I18N
+      if (dfa->mb_cur_max > 1)
+	{
+	  while (!re_string_eoi (regexp)
+		 && !re_string_first_byte (regexp, re_string_cur_idx (regexp)))
+	    {
+	      bin_tree_t *mbc_remain;
+	      fetch_token (token, regexp, syntax);
+	      mbc_remain = create_token_tree (dfa, NULL, NULL, token);
+	      tree = create_tree (dfa, tree, mbc_remain, CONCAT);
+	      if (BE (mbc_remain == NULL || tree == NULL, 0))
+		{
+		  *err = REG_ESPACE;
+		  return NULL;
+		}
+	    }
+	}
+#endif
+      break;
+    case OP_OPEN_SUBEXP:
+      tree = parse_sub_exp (regexp, preg, token, syntax, nest + 1, err);
+      if (BE (*err != REG_NOERROR && tree == NULL, 0))
+	return NULL;
+      break;
+    case OP_OPEN_BRACKET:
+      tree = parse_bracket_exp (regexp, dfa, token, syntax, err);
+      if (BE (*err != REG_NOERROR && tree == NULL, 0))
+	return NULL;
+      break;
+    case OP_BACK_REF:
+      if (!BE (dfa->completed_bkref_map & (1 << token->opr.idx), 1))
+	{
+	  *err = REG_ESUBREG;
+	  return NULL;
+	}
+      dfa->used_bkref_map |= 1 << token->opr.idx;
+      tree = create_token_tree (dfa, NULL, NULL, token);
+      if (BE (tree == NULL, 0))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+      ++dfa->nbackref;
+      dfa->has_mb_node = 1;
+      break;
+    case OP_OPEN_DUP_NUM:
+      if (syntax & RE_CONTEXT_INVALID_DUP)
+	{
+	  *err = REG_BADRPT;
+	  return NULL;
+	}
+      /* FALLTHROUGH */
+    case OP_DUP_ASTERISK:
+    case OP_DUP_PLUS:
+    case OP_DUP_QUESTION:
+      if (syntax & RE_CONTEXT_INVALID_OPS)
+	{
+	  *err = REG_BADRPT;
+	  return NULL;
+	}
+      else if (syntax & RE_CONTEXT_INDEP_OPS)
+	{
+	  fetch_token (token, regexp, syntax);
+	  return parse_expression (regexp, preg, token, syntax, nest, err);
+	}
+      /* else fall through  */
+    case OP_CLOSE_SUBEXP:
+      if ((token->type == OP_CLOSE_SUBEXP) &&
+	  !(syntax & RE_UNMATCHED_RIGHT_PAREN_ORD))
+	{
+	  *err = REG_ERPAREN;
+	  return NULL;
+	}
+      /* else fall through  */
+    case OP_CLOSE_DUP_NUM:
+      /* We treat it as a normal character.  */
+
+      /* Then we can these characters as normal characters.  */
+      token->type = CHARACTER;
+      /* mb_partial and word_char bits should be initialized already
+	 by peek_token.  */
+      tree = create_token_tree (dfa, NULL, NULL, token);
+      if (BE (tree == NULL, 0))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+      break;
+    case ANCHOR:
+      if ((token->opr.ctx_type
+	   & (WORD_DELIM | NOT_WORD_DELIM | WORD_FIRST | WORD_LAST))
+	  && dfa->word_ops_used == 0)
+	init_word_char (dfa);
+      if (token->opr.ctx_type == WORD_DELIM
+	  || token->opr.ctx_type == NOT_WORD_DELIM)
+	{
+	  bin_tree_t *tree_first, *tree_last;
+	  if (token->opr.ctx_type == WORD_DELIM)
+	    {
+	      token->opr.ctx_type = WORD_FIRST;
+	      tree_first = create_token_tree (dfa, NULL, NULL, token);
+	      token->opr.ctx_type = WORD_LAST;
+	    }
+	  else
+	    {
+	      token->opr.ctx_type = INSIDE_WORD;
+	      tree_first = create_token_tree (dfa, NULL, NULL, token);
+	      token->opr.ctx_type = INSIDE_NOTWORD;
+	    }
+	  tree_last = create_token_tree (dfa, NULL, NULL, token);
+	  tree = create_tree (dfa, tree_first, tree_last, OP_ALT);
+	  if (BE (tree_first == NULL || tree_last == NULL || tree == NULL, 0))
+	    {
+	      *err = REG_ESPACE;
+	      return NULL;
+	    }
+	}
+      else
+	{
+	  tree = create_token_tree (dfa, NULL, NULL, token);
+	  if (BE (tree == NULL, 0))
+	    {
+	      *err = REG_ESPACE;
+	      return NULL;
+	    }
+	}
+      /* We must return here, since ANCHORs can't be followed
+	 by repetition operators.
+	 eg. RE"^*" is invalid or "<ANCHOR(^)><CHAR(*)>",
+	     it must not be "<ANCHOR(^)><REPEAT(*)>".  */
+      fetch_token (token, regexp, syntax);
+      return tree;
+    case OP_PERIOD:
+      tree = create_token_tree (dfa, NULL, NULL, token);
+      if (BE (tree == NULL, 0))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+      if (dfa->mb_cur_max > 1)
+	dfa->has_mb_node = 1;
+      break;
+    case OP_WORD:
+    case OP_NOTWORD:
+      tree = build_charclass_op (dfa, regexp->trans,
+				 "alnum",
+				 "_",
+				 token->type == OP_NOTWORD, err);
+      if (BE (*err != REG_NOERROR && tree == NULL, 0))
+	return NULL;
+      break;
+    case OP_SPACE:
+    case OP_NOTSPACE:
+      tree = build_charclass_op (dfa, regexp->trans,
+				 "space",
+				 "",
+				 token->type == OP_NOTSPACE, err);
+      if (BE (*err != REG_NOERROR && tree == NULL, 0))
+	return NULL;
+      break;
+    case OP_ALT:
+    case END_OF_RE:
+      return NULL;
+    case BACK_SLASH:
+      *err = REG_EESCAPE;
+      return NULL;
+    default:
+      /* Must not happen?  */
+#ifdef DEBUG
+      assert (0);
+#endif
+      return NULL;
+    }
+  fetch_token (token, regexp, syntax);
+
+  while (token->type == OP_DUP_ASTERISK || token->type == OP_DUP_PLUS
+	 || token->type == OP_DUP_QUESTION || token->type == OP_OPEN_DUP_NUM)
+    {
+      tree = parse_dup_op (tree, regexp, dfa, token, syntax, err);
+      if (BE (*err != REG_NOERROR && tree == NULL, 0))
+	return NULL;
+      /* In BRE consecutive duplications are not allowed.  */
+      if ((syntax & RE_CONTEXT_INVALID_DUP)
+	  && (token->type == OP_DUP_ASTERISK
+	      || token->type == OP_OPEN_DUP_NUM))
+	{
+	  *err = REG_BADRPT;
+	  return NULL;
+	}
+    }
+
+  return tree;
+}
+
+/* This function build the following tree, from regular expression
+   (<reg_exp>):
+	 SUBEXP
+	    |
+	<reg_exp>
+*/
+
+static bin_tree_t *
+parse_sub_exp (re_string_t *regexp, regex_t *preg, re_token_t *token,
+	       reg_syntax_t syntax, int nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
+  bin_tree_t *tree;
+  size_t cur_nsub;
+  cur_nsub = preg->re_nsub++;
+
+  fetch_token (token, regexp, syntax | RE_CARET_ANCHORS_HERE);
+
+  /* The subexpression may be a null string.  */
+  if (token->type == OP_CLOSE_SUBEXP)
+    tree = NULL;
+  else
+    {
+      tree = parse_reg_exp (regexp, preg, token, syntax, nest, err);
+      if (BE (*err == REG_NOERROR && token->type != OP_CLOSE_SUBEXP, 0))
+	*err = REG_EPAREN;
+      if (BE (*err != REG_NOERROR, 0))
+	return NULL;
+    }
+
+  if (cur_nsub <= '9' - '1')
+    dfa->completed_bkref_map |= 1 << cur_nsub;
+
+  tree = create_tree (dfa, tree, NULL, SUBEXP);
+  if (BE (tree == NULL, 0))
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+  tree->token.opr.idx = cur_nsub;
+  return tree;
+}
+
+/* This function parse repetition operators like "*", "+", "{1,3}" etc.  */
+
+static bin_tree_t *
+parse_dup_op (bin_tree_t *elem, re_string_t *regexp, re_dfa_t *dfa,
+	      re_token_t *token, reg_syntax_t syntax, reg_errcode_t *err)
+{
+  bin_tree_t *tree = NULL, *old_tree = NULL;
+  int i, start, end, start_idx = re_string_cur_idx (regexp);
+#ifndef RE_TOKEN_INIT_BUG
+  re_token_t start_token = *token;
+#else
+  re_token_t start_token;
+
+  memcpy ((void *) &start_token, (void *) token, sizeof start_token);
+#endif
+
+  if (token->type == OP_OPEN_DUP_NUM)
+    {
+      end = 0;
+      start = fetch_number (regexp, token, syntax);
+      if (start == -1)
+	{
+	  if (token->type == CHARACTER && token->opr.c == ',')
+	    start = 0; /* We treat "{,m}" as "{0,m}".  */
+	  else
+	    {
+	      *err = REG_BADBR; /* <re>{} is invalid.  */
+	      return NULL;
+	    }
+	}
+      if (BE (start != -2, 1))
+	{
+	  /* We treat "{n}" as "{n,n}".  */
+	  end = ((token->type == OP_CLOSE_DUP_NUM) ? start
+		 : ((token->type == CHARACTER && token->opr.c == ',')
+		    ? fetch_number (regexp, token, syntax) : -2));
+	}
+      if (BE (start == -2 || end == -2, 0))
+	{
+	  /* Invalid sequence.  */
+	  if (BE (!(syntax & RE_INVALID_INTERVAL_ORD), 0))
+	    {
+	      if (token->type == END_OF_RE)
+		*err = REG_EBRACE;
+	      else
+		*err = REG_BADBR;
+
+	      return NULL;
+	    }
+
+	  /* If the syntax bit is set, rollback.  */
+	  re_string_set_index (regexp, start_idx);
+	  *token = start_token;
+	  token->type = CHARACTER;
+	  /* mb_partial and word_char bits should be already initialized by
+	     peek_token.  */
+	  return elem;
+	}
+
+      if (BE ((end != -1 && start > end) || token->type != OP_CLOSE_DUP_NUM, 0))
+	{
+	  /* First number greater than second.  */
+	  *err = REG_BADBR;
+	  return NULL;
+	}
+    }
+  else
+    {
+      start = (token->type == OP_DUP_PLUS) ? 1 : 0;
+      end = (token->type == OP_DUP_QUESTION) ? 1 : -1;
+    }
+
+  fetch_token (token, regexp, syntax);
+
+  if (BE (elem == NULL, 0))
+    return NULL;
+  if (BE (start == 0 && end == 0, 0))
+    {
+      postorder (elem, free_tree, NULL);
+      return NULL;
+    }
+
+  /* Extract "<re>{n,m}" to "<re><re>...<re><re>{0,<m-n>}".  */
+  if (BE (start > 0, 0))
+    {
+      tree = elem;
+      for (i = 2; i <= start; ++i)
+	{
+	  elem = duplicate_tree (elem, dfa);
+	  tree = create_tree (dfa, tree, elem, CONCAT);
+	  if (BE (elem == NULL || tree == NULL, 0))
+	    goto parse_dup_op_espace;
+	}
+
+      if (start == end)
+	return tree;
+
+      /* Duplicate ELEM before it is marked optional.  */
+      elem = duplicate_tree (elem, dfa);
+      old_tree = tree;
+    }
+  else
+    old_tree = NULL;
+
+  if (elem->token.type == SUBEXP)
+    postorder (elem, mark_opt_subexp, (void *) (intptr_t) elem->token.opr.idx);
+
+  tree = create_tree (dfa, elem, NULL, (end == -1 ? OP_DUP_ASTERISK : OP_ALT));
+  if (BE (tree == NULL, 0))
+    goto parse_dup_op_espace;
+
+  /* This loop is actually executed only when end != -1,
+     to rewrite <re>{0,n} as (<re>(<re>...<re>?)?)?...  We have
+     already created the start+1-th copy.  */
+  for (i = start + 2; i <= end; ++i)
+    {
+      elem = duplicate_tree (elem, dfa);
+      tree = create_tree (dfa, tree, elem, CONCAT);
+      if (BE (elem == NULL || tree == NULL, 0))
+	goto parse_dup_op_espace;
+
+      tree = create_tree (dfa, tree, NULL, OP_ALT);
+      if (BE (tree == NULL, 0))
+	goto parse_dup_op_espace;
+    }
+
+  if (old_tree)
+    tree = create_tree (dfa, old_tree, tree, CONCAT);
+
+  return tree;
+
+ parse_dup_op_espace:
+  *err = REG_ESPACE;
+  return NULL;
+}
+
+/* Size of the names for collating symbol/equivalence_class/character_class.
+   I'm not sure, but maybe enough.  */
+#define BRACKET_NAME_BUF_SIZE 32
+
+#ifndef _LIBC
+  /* Local function for parse_bracket_exp only used in case of NOT _LIBC.
+     Build the range expression which starts from START_ELEM, and ends
+     at END_ELEM.  The result are written to MBCSET and SBCSET.
+     RANGE_ALLOC is the allocated size of mbcset->range_starts, and
+     mbcset->range_ends, is a pointer argument since we may
+     update it.  */
+
+static reg_errcode_t
+internal_function
+# ifdef RE_ENABLE_I18N
+build_range_exp (bitset_t sbcset, re_charset_t *mbcset, int *range_alloc,
+		 bracket_elem_t *start_elem, bracket_elem_t *end_elem)
+# else /* not RE_ENABLE_I18N */
+build_range_exp (bitset_t sbcset, bracket_elem_t *start_elem,
+		 bracket_elem_t *end_elem)
+# endif /* not RE_ENABLE_I18N */
+{
+  unsigned int start_ch, end_ch;
+  /* Equivalence Classes and Character Classes can't be a range start/end.  */
+  if (BE (start_elem->type == EQUIV_CLASS || start_elem->type == CHAR_CLASS
+	  || end_elem->type == EQUIV_CLASS || end_elem->type == CHAR_CLASS,
+	  0))
+    return REG_ERANGE;
+
+  /* We can handle no multi character collating elements without libc
+     support.  */
+  if (BE ((start_elem->type == COLL_SYM
+	   && strlen ((char *) start_elem->opr.name) > 1)
+	  || (end_elem->type == COLL_SYM
+	      && strlen ((char *) end_elem->opr.name) > 1), 0))
+    return REG_ECOLLATE;
+
+# ifdef RE_ENABLE_I18N
+  {
+    wchar_t wc;
+    wint_t start_wc;
+    wint_t end_wc;
+    wchar_t cmp_buf[6] = {L'\0', L'\0', L'\0', L'\0', L'\0', L'\0'};
+
+    start_ch = ((start_elem->type == SB_CHAR) ? start_elem->opr.ch
+		: ((start_elem->type == COLL_SYM) ? start_elem->opr.name[0]
+		   : 0));
+    end_ch = ((end_elem->type == SB_CHAR) ? end_elem->opr.ch
+	      : ((end_elem->type == COLL_SYM) ? end_elem->opr.name[0]
+		 : 0));
+#ifdef GAWK
+    /*
+     * Fedora Core 2, maybe others, have broken `btowc' that returns -1
+     * for any value > 127. Sigh. Note that `start_ch' and `end_ch' are
+     * unsigned, so we don't have sign extension problems.
+     */
+    start_wc = ((start_elem->type == SB_CHAR || start_elem->type == COLL_SYM)
+		? start_ch : start_elem->opr.wch);
+    end_wc = ((end_elem->type == SB_CHAR || end_elem->type == COLL_SYM)
+	      ? end_ch : end_elem->opr.wch);
+#else
+    start_wc = ((start_elem->type == SB_CHAR || start_elem->type == COLL_SYM)
+		? __btowc (start_ch) : start_elem->opr.wch);
+    end_wc = ((end_elem->type == SB_CHAR || end_elem->type == COLL_SYM)
+	      ? __btowc (end_ch) : end_elem->opr.wch);
+#endif
+    if (start_wc == WEOF || end_wc == WEOF)
+      return REG_ECOLLATE;
+    cmp_buf[0] = start_wc;
+    cmp_buf[4] = end_wc;
+    if (wcscoll (cmp_buf, cmp_buf + 4) > 0)
+      return REG_ERANGE;
+
+    /* Got valid collation sequence values, add them as a new entry.
+       However, for !_LIBC we have no collation elements: if the
+       character set is single byte, the single byte character set
+       that we build below suffices.  parse_bracket_exp passes
+       no MBCSET if dfa->mb_cur_max == 1.  */
+    if (mbcset)
+      {
+	/* Check the space of the arrays.  */
+	if (BE (*range_alloc == mbcset->nranges, 0))
+	  {
+	    /* There is not enough space, need realloc.  */
+	    wchar_t *new_array_start, *new_array_end;
+	    int new_nranges;
+
+	    /* +1 in case of mbcset->nranges is 0.  */
+	    new_nranges = 2 * mbcset->nranges + 1;
+	    /* Use realloc since mbcset->range_starts and mbcset->range_ends
+	       are NULL if *range_alloc == 0.  */
+	    new_array_start = re_realloc (mbcset->range_starts, wchar_t,
+					  new_nranges);
+	    new_array_end = re_realloc (mbcset->range_ends, wchar_t,
+					new_nranges);
+
+	    if (BE (new_array_start == NULL || new_array_end == NULL, 0))
+	      return REG_ESPACE;
+
+	    mbcset->range_starts = new_array_start;
+	    mbcset->range_ends = new_array_end;
+	    *range_alloc = new_nranges;
+	  }
+
+	mbcset->range_starts[mbcset->nranges] = start_wc;
+	mbcset->range_ends[mbcset->nranges++] = end_wc;
+      }
+
+    /* Build the table for single byte characters.  */
+    for (wc = 0; wc < SBC_MAX; ++wc)
+      {
+	cmp_buf[2] = wc;
+	if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
+	    && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
+	  bitset_set (sbcset, wc);
+      }
+  }
+# else /* not RE_ENABLE_I18N */
+  {
+    unsigned int ch;
+    start_ch = ((start_elem->type == SB_CHAR ) ? start_elem->opr.ch
+		: ((start_elem->type == COLL_SYM) ? start_elem->opr.name[0]
+		   : 0));
+    end_ch = ((end_elem->type == SB_CHAR ) ? end_elem->opr.ch
+	      : ((end_elem->type == COLL_SYM) ? end_elem->opr.name[0]
+		 : 0));
+    if (start_ch > end_ch)
+      return REG_ERANGE;
+    /* Build the table for single byte characters.  */
+    for (ch = 0; ch < SBC_MAX; ++ch)
+      if (start_ch <= ch  && ch <= end_ch)
+	bitset_set (sbcset, ch);
+  }
+# endif /* not RE_ENABLE_I18N */
+  return REG_NOERROR;
+}
+#endif /* not _LIBC */
+
+#ifndef _LIBC
+/* Helper function for parse_bracket_exp only used in case of NOT _LIBC..
+   Build the collating element which is represented by NAME.
+   The result are written to MBCSET and SBCSET.
+   COLL_SYM_ALLOC is the allocated size of mbcset->coll_sym, is a
+   pointer argument since we may update it.  */
+
+static reg_errcode_t
+internal_function
+# ifdef RE_ENABLE_I18N
+build_collating_symbol (bitset_t sbcset, re_charset_t *mbcset,
+			int *coll_sym_alloc, const unsigned char *name)
+# else /* not RE_ENABLE_I18N */
+build_collating_symbol (bitset_t sbcset, const unsigned char *name)
+# endif /* not RE_ENABLE_I18N */
+{
+  size_t name_len = strlen ((const char *) name);
+  if (BE (name_len != 1, 0))
+    return REG_ECOLLATE;
+  else
+    {
+      bitset_set (sbcset, name[0]);
+      return REG_NOERROR;
+    }
+}
+#endif /* not _LIBC */
+
+/* This function parse bracket expression like "[abc]", "[a-c]",
+   "[[.a-a.]]" etc.  */
+
+static bin_tree_t *
+parse_bracket_exp (re_string_t *regexp, re_dfa_t *dfa, re_token_t *token,
+		   reg_syntax_t syntax, reg_errcode_t *err)
+{
+#ifdef _LIBC
+  const unsigned char *collseqmb;
+  const char *collseqwc;
+  uint32_t nrules;
+  int32_t table_size;
+  const int32_t *symb_table;
+  const unsigned char *extra;
+
+  /* Local function for parse_bracket_exp used in _LIBC environment.
+     Seek the collating symbol entry correspondings to NAME.
+     Return the index of the symbol in the SYMB_TABLE.  */
+
+  auto inline int32_t
+  __attribute ((always_inline))
+  seek_collating_symbol_entry (name, name_len)
+	 const unsigned char *name;
+	 size_t name_len;
+    {
+      int32_t hash = elem_hash ((const char *) name, name_len);
+      int32_t elem = hash % table_size;
+      if (symb_table[2 * elem] != 0)
+	{
+	  int32_t second = hash % (table_size - 2) + 1;
+
+	  do
+	    {
+	      /* First compare the hashing value.  */
+	      if (symb_table[2 * elem] == hash
+		  /* Compare the length of the name.  */
+		  && name_len == extra[symb_table[2 * elem + 1]]
+		  /* Compare the name.  */
+		  && memcmp (name, &extra[symb_table[2 * elem + 1] + 1],
+			     name_len) == 0)
+		{
+		  /* Yep, this is the entry.  */
+		  break;
+		}
+
+	      /* Next entry.  */
+	      elem += second;
+	    }
+	  while (symb_table[2 * elem] != 0);
+	}
+      return elem;
+    }
+
+  /* Local function for parse_bracket_exp used in _LIBC environment.
+     Look up the collation sequence value of BR_ELEM.
+     Return the value if succeeded, UINT_MAX otherwise.  */
+
+  auto inline unsigned int
+  __attribute ((always_inline))
+  lookup_collation_sequence_value (br_elem)
+	 bracket_elem_t *br_elem;
+    {
+      if (br_elem->type == SB_CHAR)
+	{
+	  /*
+	  if (MB_CUR_MAX == 1)
+	  */
+	  if (nrules == 0)
+	    return collseqmb[br_elem->opr.ch];
+	  else
+	    {
+	      wint_t wc = __btowc (br_elem->opr.ch);
+	      return __collseq_table_lookup (collseqwc, wc);
+	    }
+	}
+      else if (br_elem->type == MB_CHAR)
+	{
+	  if (nrules != 0)
+	    return __collseq_table_lookup (collseqwc, br_elem->opr.wch);
+	}
+      else if (br_elem->type == COLL_SYM)
+	{
+	  size_t sym_name_len = strlen ((char *) br_elem->opr.name);
+	  if (nrules != 0)
+	    {
+	      int32_t elem, idx;
+	      elem = seek_collating_symbol_entry (br_elem->opr.name,
+						  sym_name_len);
+	      if (symb_table[2 * elem] != 0)
+		{
+		  /* We found the entry.  */
+		  idx = symb_table[2 * elem + 1];
+		  /* Skip the name of collating element name.  */
+		  idx += 1 + extra[idx];
+		  /* Skip the byte sequence of the collating element.  */
+		  idx += 1 + extra[idx];
+		  /* Adjust for the alignment.  */
+		  idx = (idx + 3) & ~3;
+		  /* Skip the multibyte collation sequence value.  */
+		  idx += sizeof (unsigned int);
+		  /* Skip the wide char sequence of the collating element.  */
+		  idx += sizeof (unsigned int) *
+		    (1 + *(unsigned int *) (extra + idx));
+		  /* Return the collation sequence value.  */
+		  return *(unsigned int *) (extra + idx);
+		}
+	      else if (symb_table[2 * elem] == 0 && sym_name_len == 1)
+		{
+		  /* No valid character.  Match it as a single byte
+		     character.  */
+		  return collseqmb[br_elem->opr.name[0]];
+		}
+	    }
+	  else if (sym_name_len == 1)
+	    return collseqmb[br_elem->opr.name[0]];
+	}
+      return UINT_MAX;
+    }
+
+  /* Local function for parse_bracket_exp used in _LIBC environment.
+     Build the range expression which starts from START_ELEM, and ends
+     at END_ELEM.  The result are written to MBCSET and SBCSET.
+     RANGE_ALLOC is the allocated size of mbcset->range_starts, and
+     mbcset->range_ends, is a pointer argument since we may
+     update it.  */
+
+  auto inline reg_errcode_t
+  __attribute ((always_inline))
+  build_range_exp (sbcset, mbcset, range_alloc, start_elem, end_elem)
+	 re_charset_t *mbcset;
+	 int *range_alloc;
+	 bitset_t sbcset;
+	 bracket_elem_t *start_elem, *end_elem;
+    {
+      unsigned int ch;
+      uint32_t start_collseq;
+      uint32_t end_collseq;
+
+      /* Equivalence Classes and Character Classes can't be a range
+	 start/end.  */
+      if (BE (start_elem->type == EQUIV_CLASS || start_elem->type == CHAR_CLASS
+	      || end_elem->type == EQUIV_CLASS || end_elem->type == CHAR_CLASS,
+	      0))
+	return REG_ERANGE;
+
+      start_collseq = lookup_collation_sequence_value (start_elem);
+      end_collseq = lookup_collation_sequence_value (end_elem);
+      /* Check start/end collation sequence values.  */
+      if (BE (start_collseq == UINT_MAX || end_collseq == UINT_MAX, 0))
+	return REG_ECOLLATE;
+      if (BE ((syntax & RE_NO_EMPTY_RANGES) && start_collseq > end_collseq, 0))
+	return REG_ERANGE;
+
+      /* Got valid collation sequence values, add them as a new entry.
+	 However, if we have no collation elements, and the character set
+	 is single byte, the single byte character set that we
+	 build below suffices. */
+      if (nrules > 0 || dfa->mb_cur_max > 1)
+	{
+	  /* Check the space of the arrays.  */
+	  if (BE (*range_alloc == mbcset->nranges, 0))
+	    {
+	      /* There is not enough space, need realloc.  */
+	      uint32_t *new_array_start;
+	      uint32_t *new_array_end;
+	      int new_nranges;
+
+	      /* +1 in case of mbcset->nranges is 0.  */
+	      new_nranges = 2 * mbcset->nranges + 1;
+	      new_array_start = re_realloc (mbcset->range_starts, uint32_t,
+					    new_nranges);
+	      new_array_end = re_realloc (mbcset->range_ends, uint32_t,
+					  new_nranges);
+
+	      if (BE (new_array_start == NULL || new_array_end == NULL, 0))
+		return REG_ESPACE;
+
+	      mbcset->range_starts = new_array_start;
+	      mbcset->range_ends = new_array_end;
+	      *range_alloc = new_nranges;
+	    }
+
+	  mbcset->range_starts[mbcset->nranges] = start_collseq;
+	  mbcset->range_ends[mbcset->nranges++] = end_collseq;
+	}
+
+      /* Build the table for single byte characters.  */
+      for (ch = 0; ch < SBC_MAX; ch++)
+	{
+	  uint32_t ch_collseq;
+	  /*
+	  if (MB_CUR_MAX == 1)
+	  */
+	  if (nrules == 0)
+	    ch_collseq = collseqmb[ch];
+	  else
+	    ch_collseq = __collseq_table_lookup (collseqwc, __btowc (ch));
+	  if (start_collseq <= ch_collseq && ch_collseq <= end_collseq)
+	    bitset_set (sbcset, ch);
+	}
+      return REG_NOERROR;
+    }
+
+  /* Local function for parse_bracket_exp used in _LIBC environment.
+     Build the collating element which is represented by NAME.
+     The result are written to MBCSET and SBCSET.
+     COLL_SYM_ALLOC is the allocated size of mbcset->coll_sym, is a
+     pointer argument since we may update it.  */
+
+  auto inline reg_errcode_t
+  __attribute ((always_inline))
+  build_collating_symbol (sbcset, mbcset, coll_sym_alloc, name)
+	 re_charset_t *mbcset;
+	 int *coll_sym_alloc;
+	 bitset_t sbcset;
+	 const unsigned char *name;
+    {
+      int32_t elem, idx;
+      size_t name_len = strlen ((const char *) name);
+      if (nrules != 0)
+	{
+	  elem = seek_collating_symbol_entry (name, name_len);
+	  if (symb_table[2 * elem] != 0)
+	    {
+	      /* We found the entry.  */
+	      idx = symb_table[2 * elem + 1];
+	      /* Skip the name of collating element name.  */
+	      idx += 1 + extra[idx];
+	    }
+	  else if (symb_table[2 * elem] == 0 && name_len == 1)
+	    {
+	      /* No valid character, treat it as a normal
+		 character.  */
+	      bitset_set (sbcset, name[0]);
+	      return REG_NOERROR;
+	    }
+	  else
+	    return REG_ECOLLATE;
+
+	  /* Got valid collation sequence, add it as a new entry.  */
+	  /* Check the space of the arrays.  */
+	  if (BE (*coll_sym_alloc == mbcset->ncoll_syms, 0))
+	    {
+	      /* Not enough, realloc it.  */
+	      /* +1 in case of mbcset->ncoll_syms is 0.  */
+	      int new_coll_sym_alloc = 2 * mbcset->ncoll_syms + 1;
+	      /* Use realloc since mbcset->coll_syms is NULL
+		 if *alloc == 0.  */
+	      int32_t *new_coll_syms = re_realloc (mbcset->coll_syms, int32_t,
+						   new_coll_sym_alloc);
+	      if (BE (new_coll_syms == NULL, 0))
+		return REG_ESPACE;
+	      mbcset->coll_syms = new_coll_syms;
+	      *coll_sym_alloc = new_coll_sym_alloc;
+	    }
+	  mbcset->coll_syms[mbcset->ncoll_syms++] = idx;
+	  return REG_NOERROR;
+	}
+      else
+	{
+	  if (BE (name_len != 1, 0))
+	    return REG_ECOLLATE;
+	  else
+	    {
+	      bitset_set (sbcset, name[0]);
+	      return REG_NOERROR;
+	    }
+	}
+    }
+#endif
+
+  re_token_t br_token;
+  re_bitset_ptr_t sbcset;
+#ifdef RE_ENABLE_I18N
+  re_charset_t *mbcset;
+  int coll_sym_alloc = 0, range_alloc = 0, mbchar_alloc = 0;
+  int equiv_class_alloc = 0, char_class_alloc = 0;
+#endif /* not RE_ENABLE_I18N */
+  int non_match = 0;
+  bin_tree_t *work_tree;
+  int token_len;
+  int first_round = 1;
+#ifdef _LIBC
+  collseqmb = (const unsigned char *)
+    _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQMB);
+  nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+  if (nrules)
+    {
+      /*
+      if (MB_CUR_MAX > 1)
+      */
+      collseqwc = _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQWC);
+      table_size = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_SYMB_HASH_SIZEMB);
+      symb_table = (const int32_t *) _NL_CURRENT (LC_COLLATE,
+						  _NL_COLLATE_SYMB_TABLEMB);
+      extra = (const unsigned char *) _NL_CURRENT (LC_COLLATE,
+						   _NL_COLLATE_SYMB_EXTRAMB);
+    }
+#endif
+  sbcset = (re_bitset_ptr_t) calloc (sizeof (bitset_t), 1);
+#ifdef RE_ENABLE_I18N
+  mbcset = (re_charset_t *) calloc (sizeof (re_charset_t), 1);
+#endif /* RE_ENABLE_I18N */
+#ifdef RE_ENABLE_I18N
+  if (BE (sbcset == NULL || mbcset == NULL, 0))
+#else
+  if (BE (sbcset == NULL, 0))
+#endif /* RE_ENABLE_I18N */
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+
+  token_len = peek_token_bracket (token, regexp, syntax);
+  if (BE (token->type == END_OF_RE, 0))
+    {
+      *err = REG_BADPAT;
+      goto parse_bracket_exp_free_return;
+    }
+  if (token->type == OP_NON_MATCH_LIST)
+    {
+#ifdef RE_ENABLE_I18N
+      mbcset->non_match = 1;
+#endif /* not RE_ENABLE_I18N */
+      non_match = 1;
+      if (syntax & RE_HAT_LISTS_NOT_NEWLINE)
+	bitset_set (sbcset, '\n');
+      re_string_skip_bytes (regexp, token_len); /* Skip a token.  */
+      token_len = peek_token_bracket (token, regexp, syntax);
+      if (BE (token->type == END_OF_RE, 0))
+	{
+	  *err = REG_BADPAT;
+	  goto parse_bracket_exp_free_return;
+	}
+    }
+
+  /* We treat the first ']' as a normal character.  */
+  if (token->type == OP_CLOSE_BRACKET)
+    token->type = CHARACTER;
+
+  while (1)
+    {
+      bracket_elem_t start_elem, end_elem;
+      unsigned char start_name_buf[BRACKET_NAME_BUF_SIZE];
+      unsigned char end_name_buf[BRACKET_NAME_BUF_SIZE];
+      reg_errcode_t ret;
+      int token_len2 = 0, is_range_exp = 0;
+      re_token_t token2;
+
+      start_elem.opr.name = start_name_buf;
+      ret = parse_bracket_element (&start_elem, regexp, token, token_len, dfa,
+				   syntax, first_round);
+      if (BE (ret != REG_NOERROR, 0))
+	{
+	  *err = ret;
+	  goto parse_bracket_exp_free_return;
+	}
+      first_round = 0;
+
+      /* Get information about the next token.  We need it in any case.  */
+      token_len = peek_token_bracket (token, regexp, syntax);
+
+      /* Do not check for ranges if we know they are not allowed.  */
+      if (start_elem.type != CHAR_CLASS && start_elem.type != EQUIV_CLASS)
+	{
+	  if (BE (token->type == END_OF_RE, 0))
+	    {
+	      *err = REG_EBRACK;
+	      goto parse_bracket_exp_free_return;
+	    }
+	  if (token->type == OP_CHARSET_RANGE)
+	    {
+	      re_string_skip_bytes (regexp, token_len); /* Skip '-'.  */
+	      token_len2 = peek_token_bracket (&token2, regexp, syntax);
+	      if (BE (token2.type == END_OF_RE, 0))
+		{
+		  *err = REG_EBRACK;
+		  goto parse_bracket_exp_free_return;
+		}
+	      if (token2.type == OP_CLOSE_BRACKET)
+		{
+		  /* We treat the last '-' as a normal character.  */
+		  re_string_skip_bytes (regexp, -token_len);
+		  token->type = CHARACTER;
+		}
+	      else
+		is_range_exp = 1;
+	    }
+	}
+
+      if (is_range_exp == 1)
+	{
+	  end_elem.opr.name = end_name_buf;
+	  ret = parse_bracket_element (&end_elem, regexp, &token2, token_len2,
+				       dfa, syntax, 1);
+	  if (BE (ret != REG_NOERROR, 0))
+	    {
+	      *err = ret;
+	      goto parse_bracket_exp_free_return;
+	    }
+
+	  token_len = peek_token_bracket (token, regexp, syntax);
+
+#ifdef _LIBC
+	  *err = build_range_exp (sbcset, mbcset, &range_alloc,
+				  &start_elem, &end_elem);
+#else
+# ifdef RE_ENABLE_I18N
+	  *err = build_range_exp (sbcset,
+				  dfa->mb_cur_max > 1 ? mbcset : NULL,
+				  &range_alloc, &start_elem, &end_elem);
+# else
+	  *err = build_range_exp (sbcset, &start_elem, &end_elem);
+# endif
+#endif /* RE_ENABLE_I18N */
+	  if (BE (*err != REG_NOERROR, 0))
+	    goto parse_bracket_exp_free_return;
+	}
+      else
+	{
+	  switch (start_elem.type)
+	    {
+	    case SB_CHAR:
+	      bitset_set (sbcset, start_elem.opr.ch);
+	      break;
+#ifdef RE_ENABLE_I18N
+	    case MB_CHAR:
+	      /* Check whether the array has enough space.  */
+	      if (BE (mbchar_alloc == mbcset->nmbchars, 0))
+		{
+		  wchar_t *new_mbchars;
+		  /* Not enough, realloc it.  */
+		  /* +1 in case of mbcset->nmbchars is 0.  */
+		  mbchar_alloc = 2 * mbcset->nmbchars + 1;
+		  /* Use realloc since array is NULL if *alloc == 0.  */
+		  new_mbchars = re_realloc (mbcset->mbchars, wchar_t,
+					    mbchar_alloc);
+		  if (BE (new_mbchars == NULL, 0))
+		    goto parse_bracket_exp_espace;
+		  mbcset->mbchars = new_mbchars;
+		}
+	      mbcset->mbchars[mbcset->nmbchars++] = start_elem.opr.wch;
+	      break;
+#endif /* RE_ENABLE_I18N */
+	    case EQUIV_CLASS:
+	      *err = build_equiv_class (sbcset,
+#ifdef RE_ENABLE_I18N
+					mbcset, &equiv_class_alloc,
+#endif /* RE_ENABLE_I18N */
+					start_elem.opr.name);
+	      if (BE (*err != REG_NOERROR, 0))
+		goto parse_bracket_exp_free_return;
+	      break;
+	    case COLL_SYM:
+	      *err = build_collating_symbol (sbcset,
+#ifdef RE_ENABLE_I18N
+					     mbcset, &coll_sym_alloc,
+#endif /* RE_ENABLE_I18N */
+					     start_elem.opr.name);
+	      if (BE (*err != REG_NOERROR, 0))
+		goto parse_bracket_exp_free_return;
+	      break;
+	    case CHAR_CLASS:
+	      *err = build_charclass (regexp->trans, sbcset,
+#ifdef RE_ENABLE_I18N
+				      mbcset, &char_class_alloc,
+#endif /* RE_ENABLE_I18N */
+				      (const char *) start_elem.opr.name, syntax);
+	      if (BE (*err != REG_NOERROR, 0))
+	       goto parse_bracket_exp_free_return;
+	      break;
+	    default:
+	      assert (0);
+	      break;
+	    }
+	}
+      if (BE (token->type == END_OF_RE, 0))
+	{
+	  *err = REG_EBRACK;
+	  goto parse_bracket_exp_free_return;
+	}
+      if (token->type == OP_CLOSE_BRACKET)
+	break;
+    }
+
+  re_string_skip_bytes (regexp, token_len); /* Skip a token.  */
+
+  /* If it is non-matching list.  */
+  if (non_match)
+    bitset_not (sbcset);
+
+#ifdef RE_ENABLE_I18N
+  /* Ensure only single byte characters are set.  */
+  if (dfa->mb_cur_max > 1)
+    bitset_mask (sbcset, dfa->sb_char);
+
+  if (mbcset->nmbchars || mbcset->ncoll_syms || mbcset->nequiv_classes
+      || mbcset->nranges || (dfa->mb_cur_max > 1 && (mbcset->nchar_classes
+						     || mbcset->non_match)))
+    {
+      bin_tree_t *mbc_tree;
+      int sbc_idx;
+      /* Build a tree for complex bracket.  */
+      dfa->has_mb_node = 1;
+      br_token.type = COMPLEX_BRACKET;
+      br_token.opr.mbcset = mbcset;
+      mbc_tree = create_token_tree (dfa, NULL, NULL, &br_token);
+      if (BE (mbc_tree == NULL, 0))
+	goto parse_bracket_exp_espace;
+      for (sbc_idx = 0; sbc_idx < BITSET_WORDS; ++sbc_idx)
+	if (sbcset[sbc_idx])
+	  break;
+      /* If there are no bits set in sbcset, there is no point
+	 of having both SIMPLE_BRACKET and COMPLEX_BRACKET.  */
+      if (sbc_idx < BITSET_WORDS)
+	{
+	  /* Build a tree for simple bracket.  */
+	  br_token.type = SIMPLE_BRACKET;
+	  br_token.opr.sbcset = sbcset;
+	  work_tree = create_token_tree (dfa, NULL, NULL, &br_token);
+	  if (BE (work_tree == NULL, 0))
+	    goto parse_bracket_exp_espace;
+
+	  /* Then join them by ALT node.  */
+	  work_tree = create_tree (dfa, work_tree, mbc_tree, OP_ALT);
+	  if (BE (work_tree == NULL, 0))
+	    goto parse_bracket_exp_espace;
+	}
+      else
+	{
+	  re_free (sbcset);
+	  work_tree = mbc_tree;
+	}
+    }
+  else
+#endif /* not RE_ENABLE_I18N */
+    {
+#ifdef RE_ENABLE_I18N
+      free_charset (mbcset);
+#endif
+      /* Build a tree for simple bracket.  */
+      br_token.type = SIMPLE_BRACKET;
+      br_token.opr.sbcset = sbcset;
+      work_tree = create_token_tree (dfa, NULL, NULL, &br_token);
+      if (BE (work_tree == NULL, 0))
+	goto parse_bracket_exp_espace;
+    }
+  return work_tree;
+
+ parse_bracket_exp_espace:
+  *err = REG_ESPACE;
+ parse_bracket_exp_free_return:
+  re_free (sbcset);
+#ifdef RE_ENABLE_I18N
+  free_charset (mbcset);
+#endif /* RE_ENABLE_I18N */
+  return NULL;
+}
+
+/* Parse an element in the bracket expression.  */
+
+static reg_errcode_t
+parse_bracket_element (bracket_elem_t *elem, re_string_t *regexp,
+		       re_token_t *token, int token_len, re_dfa_t *dfa,
+		       reg_syntax_t syntax, int accept_hyphen)
+{
+#ifdef RE_ENABLE_I18N
+  int cur_char_size;
+  cur_char_size = re_string_char_size_at (regexp, re_string_cur_idx (regexp));
+  if (cur_char_size > 1)
+    {
+      elem->type = MB_CHAR;
+      elem->opr.wch = re_string_wchar_at (regexp, re_string_cur_idx (regexp));
+      re_string_skip_bytes (regexp, cur_char_size);
+      return REG_NOERROR;
+    }
+#endif /* RE_ENABLE_I18N */
+  re_string_skip_bytes (regexp, token_len); /* Skip a token.  */
+  if (token->type == OP_OPEN_COLL_ELEM || token->type == OP_OPEN_CHAR_CLASS
+      || token->type == OP_OPEN_EQUIV_CLASS)
+    return parse_bracket_symbol (elem, regexp, token);
+  if (BE (token->type == OP_CHARSET_RANGE, 0) && !accept_hyphen)
+    {
+      /* A '-' must only appear as anything but a range indicator before
+	 the closing bracket.  Everything else is an error.  */
+      re_token_t token2;
+      (void) peek_token_bracket (&token2, regexp, syntax);
+      if (token2.type != OP_CLOSE_BRACKET)
+	/* The actual error value is not standardized since this whole
+	   case is undefined.  But ERANGE makes good sense.  */
+	return REG_ERANGE;
+    }
+  elem->type = SB_CHAR;
+  elem->opr.ch = token->opr.c;
+  return REG_NOERROR;
+}
+
+/* Parse a bracket symbol in the bracket expression.  Bracket symbols are
+   such as [:<character_class>:], [.<collating_element>.], and
+   [=<equivalent_class>=].  */
+
+static reg_errcode_t
+parse_bracket_symbol (bracket_elem_t *elem, re_string_t *regexp,
+		      re_token_t *token)
+{
+  unsigned char ch, delim = token->opr.c;
+  int i = 0;
+  if (re_string_eoi(regexp))
+    return REG_EBRACK;
+  for (;; ++i)
+    {
+      if (i >= BRACKET_NAME_BUF_SIZE)
+	return REG_EBRACK;
+      if (token->type == OP_OPEN_CHAR_CLASS)
+	ch = re_string_fetch_byte_case (regexp);
+      else
+	ch = re_string_fetch_byte (regexp);
+      if (re_string_eoi(regexp))
+	return REG_EBRACK;
+      if (ch == delim && re_string_peek_byte (regexp, 0) == ']')
+	break;
+      elem->opr.name[i] = ch;
+    }
+  re_string_skip_bytes (regexp, 1);
+  elem->opr.name[i] = '\0';
+  switch (token->type)
+    {
+    case OP_OPEN_COLL_ELEM:
+      elem->type = COLL_SYM;
+      break;
+    case OP_OPEN_EQUIV_CLASS:
+      elem->type = EQUIV_CLASS;
+      break;
+    case OP_OPEN_CHAR_CLASS:
+      elem->type = CHAR_CLASS;
+      break;
+    default:
+      break;
+    }
+  return REG_NOERROR;
+}
+
+  /* Helper function for parse_bracket_exp.
+     Build the equivalence class which is represented by NAME.
+     The result are written to MBCSET and SBCSET.
+     EQUIV_CLASS_ALLOC is the allocated size of mbcset->equiv_classes,
+     is a pointer argument since we may update it.  */
+
+static reg_errcode_t
+#ifdef RE_ENABLE_I18N
+build_equiv_class (bitset_t sbcset, re_charset_t *mbcset,
+		   int *equiv_class_alloc, const unsigned char *name)
+#else /* not RE_ENABLE_I18N */
+build_equiv_class (bitset_t sbcset, const unsigned char *name)
+#endif /* not RE_ENABLE_I18N */
+{
+#ifdef _LIBC
+  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+  if (nrules != 0)
+    {
+      const int32_t *table, *indirect;
+      const unsigned char *weights, *extra, *cp;
+      unsigned char char_buf[2];
+      int32_t idx1, idx2;
+      unsigned int ch;
+      size_t len;
+      /* This #include defines a local function!  */
+# include <locale/weight.h>
+      /* Calculate the index for equivalence class.  */
+      cp = name;
+      table = (const int32_t *) _NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
+      weights = (const unsigned char *) _NL_CURRENT (LC_COLLATE,
+					       _NL_COLLATE_WEIGHTMB);
+      extra = (const unsigned char *) _NL_CURRENT (LC_COLLATE,
+						   _NL_COLLATE_EXTRAMB);
+      indirect = (const int32_t *) _NL_CURRENT (LC_COLLATE,
+						_NL_COLLATE_INDIRECTMB);
+      idx1 = findidx (&cp);
+      if (BE (idx1 == 0 || cp < name + strlen ((const char *) name), 0))
+	/* This isn't a valid character.  */
+	return REG_ECOLLATE;
+
+      /* Build single byte matching table for this equivalence class.  */
+      char_buf[1] = (unsigned char) '\0';
+      len = weights[idx1 & 0xffffff];
+      for (ch = 0; ch < SBC_MAX; ++ch)
+	{
+	  char_buf[0] = ch;
+	  cp = char_buf;
+	  idx2 = findidx (&cp);
+/*
+	  idx2 = table[ch];
+*/
+	  if (idx2 == 0)
+	    /* This isn't a valid character.  */
+	    continue;
+	  /* Compare only if the length matches and the collation rule
+	     index is the same.  */
+	  if (len == weights[idx2 & 0xffffff] && (idx1 >> 24) == (idx2 >> 24))
+	    {
+	      int cnt = 0;
+
+	      while (cnt <= len &&
+		     weights[(idx1 & 0xffffff) + 1 + cnt]
+		     == weights[(idx2 & 0xffffff) + 1 + cnt])
+		++cnt;
+
+	      if (cnt > len)
+		bitset_set (sbcset, ch);
+	    }
+	}
+      /* Check whether the array has enough space.  */
+      if (BE (*equiv_class_alloc == mbcset->nequiv_classes, 0))
+	{
+	  /* Not enough, realloc it.  */
+	  /* +1 in case of mbcset->nequiv_classes is 0.  */
+	  int new_equiv_class_alloc = 2 * mbcset->nequiv_classes + 1;
+	  /* Use realloc since the array is NULL if *alloc == 0.  */
+	  int32_t *new_equiv_classes = re_realloc (mbcset->equiv_classes,
+						   int32_t,
+						   new_equiv_class_alloc);
+	  if (BE (new_equiv_classes == NULL, 0))
+	    return REG_ESPACE;
+	  mbcset->equiv_classes = new_equiv_classes;
+	  *equiv_class_alloc = new_equiv_class_alloc;
+	}
+      mbcset->equiv_classes[mbcset->nequiv_classes++] = idx1;
+    }
+  else
+#endif /* _LIBC */
+    {
+      if (BE (strlen ((const char *) name) != 1, 0))
+	return REG_ECOLLATE;
+      bitset_set (sbcset, *name);
+    }
+  return REG_NOERROR;
+}
+
+  /* Helper function for parse_bracket_exp.
+     Build the character class which is represented by NAME.
+     The result are written to MBCSET and SBCSET.
+     CHAR_CLASS_ALLOC is the allocated size of mbcset->char_classes,
+     is a pointer argument since we may update it.  */
+
+static reg_errcode_t
+#ifdef RE_ENABLE_I18N
+build_charclass (RE_TRANSLATE_TYPE trans, bitset_t sbcset,
+		 re_charset_t *mbcset, int *char_class_alloc,
+		 const char *class_name, reg_syntax_t syntax)
+#else /* not RE_ENABLE_I18N */
+build_charclass (RE_TRANSLATE_TYPE trans, bitset_t sbcset,
+		 const char *class_name, reg_syntax_t syntax)
+#endif /* not RE_ENABLE_I18N */
+{
+  int i;
+
+  /* In case of REG_ICASE "upper" and "lower" match the both of
+     upper and lower cases.  */
+  if ((syntax & RE_ICASE)
+      && (strcmp (class_name, "upper") == 0 || strcmp (class_name, "lower") == 0))
+    class_name = "alpha";
+
+#ifdef RE_ENABLE_I18N
+  /* Check the space of the arrays.  */
+  if (BE (*char_class_alloc == mbcset->nchar_classes, 0))
+    {
+      /* Not enough, realloc it.  */
+      /* +1 in case of mbcset->nchar_classes is 0.  */
+      int new_char_class_alloc = 2 * mbcset->nchar_classes + 1;
+      /* Use realloc since array is NULL if *alloc == 0.  */
+      wctype_t *new_char_classes = re_realloc (mbcset->char_classes, wctype_t,
+					       new_char_class_alloc);
+      if (BE (new_char_classes == NULL, 0))
+	return REG_ESPACE;
+      mbcset->char_classes = new_char_classes;
+      *char_class_alloc = new_char_class_alloc;
+    }
+  mbcset->char_classes[mbcset->nchar_classes++] = __wctype (class_name);
+#endif /* RE_ENABLE_I18N */
+
+#define BUILD_CHARCLASS_LOOP(ctype_func)	\
+  do {						\
+    if (BE (trans != NULL, 0))			\
+      {						\
+	for (i = 0; i < SBC_MAX; ++i)		\
+  	  if (ctype_func (i))			\
+	    bitset_set (sbcset, trans[i]);	\
+      }						\
+    else					\
+      {						\
+	for (i = 0; i < SBC_MAX; ++i)		\
+  	  if (ctype_func (i))			\
+	    bitset_set (sbcset, i);		\
+      }						\
+  } while (0)
+
+  if (strcmp (class_name, "alnum") == 0)
+    BUILD_CHARCLASS_LOOP (isalnum);
+  else if (strcmp (class_name, "cntrl") == 0)
+    BUILD_CHARCLASS_LOOP (iscntrl);
+  else if (strcmp (class_name, "lower") == 0)
+    BUILD_CHARCLASS_LOOP (islower);
+  else if (strcmp (class_name, "space") == 0)
+    BUILD_CHARCLASS_LOOP (isspace);
+  else if (strcmp (class_name, "alpha") == 0)
+    BUILD_CHARCLASS_LOOP (isalpha);
+  else if (strcmp (class_name, "digit") == 0)
+    BUILD_CHARCLASS_LOOP (isdigit);
+  else if (strcmp (class_name, "print") == 0)
+    BUILD_CHARCLASS_LOOP (isprint);
+  else if (strcmp (class_name, "upper") == 0)
+    BUILD_CHARCLASS_LOOP (isupper);
+  else if (strcmp (class_name, "blank") == 0)
+#ifndef GAWK
+    BUILD_CHARCLASS_LOOP (isblank);
+#else
+    /* see comments above */
+    BUILD_CHARCLASS_LOOP (is_blank);
+#endif
+  else if (strcmp (class_name, "graph") == 0)
+    BUILD_CHARCLASS_LOOP (isgraph);
+  else if (strcmp (class_name, "punct") == 0)
+    BUILD_CHARCLASS_LOOP (ispunct);
+  else if (strcmp (class_name, "xdigit") == 0)
+    BUILD_CHARCLASS_LOOP (isxdigit);
+  else
+    return REG_ECTYPE;
+
+  return REG_NOERROR;
+}
+
+static bin_tree_t *
+build_charclass_op (re_dfa_t *dfa, RE_TRANSLATE_TYPE trans,
+		    const char *class_name,
+		    const char *extra, int non_match,
+		    reg_errcode_t *err)
+{
+  re_bitset_ptr_t sbcset;
+#ifdef RE_ENABLE_I18N
+  re_charset_t *mbcset;
+  int alloc = 0;
+#endif /* not RE_ENABLE_I18N */
+  reg_errcode_t ret;
+  re_token_t br_token;
+  bin_tree_t *tree;
+
+  sbcset = (re_bitset_ptr_t) calloc (sizeof (bitset_t), 1);
+#ifdef RE_ENABLE_I18N
+  mbcset = (re_charset_t *) calloc (sizeof (re_charset_t), 1);
+#endif /* RE_ENABLE_I18N */
+
+#ifdef RE_ENABLE_I18N
+  if (BE (sbcset == NULL || mbcset == NULL, 0))
+#else /* not RE_ENABLE_I18N */
+  if (BE (sbcset == NULL, 0))
+#endif /* not RE_ENABLE_I18N */
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+
+  if (non_match)
+    {
+#ifdef RE_ENABLE_I18N
+      mbcset->non_match = 1;
+#endif /* not RE_ENABLE_I18N */
+    }
+
+  /* We don't care the syntax in this case.  */
+  ret = build_charclass (trans, sbcset,
+#ifdef RE_ENABLE_I18N
+			 mbcset, &alloc,
+#endif /* RE_ENABLE_I18N */
+			 class_name, 0);
+
+  if (BE (ret != REG_NOERROR, 0))
+    {
+      re_free (sbcset);
+#ifdef RE_ENABLE_I18N
+      free_charset (mbcset);
+#endif /* RE_ENABLE_I18N */
+      *err = ret;
+      return NULL;
+    }
+  /* \w match '_' also.  */
+  for (; *extra; extra++)
+    bitset_set (sbcset, *extra);
+
+  /* If it is non-matching list.  */
+  if (non_match)
+    bitset_not (sbcset);
+
+#ifdef RE_ENABLE_I18N
+  /* Ensure only single byte characters are set.  */
+  if (dfa->mb_cur_max > 1)
+    bitset_mask (sbcset, dfa->sb_char);
+#endif
+
+  /* Build a tree for simple bracket.  */
+  br_token.type = SIMPLE_BRACKET;
+  br_token.opr.sbcset = sbcset;
+  tree = create_token_tree (dfa, NULL, NULL, &br_token);
+  if (BE (tree == NULL, 0))
+    goto build_word_op_espace;
+
+#ifdef RE_ENABLE_I18N
+  if (dfa->mb_cur_max > 1)
+    {
+      bin_tree_t *mbc_tree;
+      /* Build a tree for complex bracket.  */
+      br_token.type = COMPLEX_BRACKET;
+      br_token.opr.mbcset = mbcset;
+      dfa->has_mb_node = 1;
+      mbc_tree = create_token_tree (dfa, NULL, NULL, &br_token);
+      if (BE (mbc_tree == NULL, 0))
+	goto build_word_op_espace;
+      /* Then join them by ALT node.  */
+      tree = create_tree (dfa, tree, mbc_tree, OP_ALT);
+      if (BE (mbc_tree != NULL, 1))
+	return tree;
+    }
+  else
+    {
+      free_charset (mbcset);
+      return tree;
+    }
+#else /* not RE_ENABLE_I18N */
+  return tree;
+#endif /* not RE_ENABLE_I18N */
+
+ build_word_op_espace:
+  re_free (sbcset);
+#ifdef RE_ENABLE_I18N
+  free_charset (mbcset);
+#endif /* RE_ENABLE_I18N */
+  *err = REG_ESPACE;
+  return NULL;
+}
+
+/* This is intended for the expressions like "a{1,3}".
+   Fetch a number from `input', and return the number.
+   Return -1, if the number field is empty like "{,1}".
+   Return -2, if an error has occurred.  */
+
+static int
+fetch_number (re_string_t *input, re_token_t *token, reg_syntax_t syntax)
+{
+  int num = -1;
+  unsigned char c;
+  while (1)
+    {
+      fetch_token (token, input, syntax);
+      c = token->opr.c;
+      if (BE (token->type == END_OF_RE, 0))
+	return -2;
+      if (token->type == OP_CLOSE_DUP_NUM || c == ',')
+	break;
+      num = ((token->type != CHARACTER || c < '0' || '9' < c || num == -2)
+	     ? -2 : ((num == -1) ? c - '0' : num * 10 + c - '0'));
+      num = (num > RE_DUP_MAX) ? -2 : num;
+    }
+  return num;
+}
+
+#ifdef RE_ENABLE_I18N
+static void
+free_charset (re_charset_t *cset)
+{
+  re_free (cset->mbchars);
+# ifdef _LIBC
+  re_free (cset->coll_syms);
+  re_free (cset->equiv_classes);
+  re_free (cset->range_starts);
+  re_free (cset->range_ends);
+# endif
+  re_free (cset->char_classes);
+  re_free (cset);
+}
+#endif /* RE_ENABLE_I18N */
+
+/* Functions for binary tree operation.  */
+
+/* Create a tree node.  */
+
+static bin_tree_t *
+create_tree (re_dfa_t *dfa, bin_tree_t *left, bin_tree_t *right,
+	     re_token_type_t type)
+{
+  re_token_t t;
+  t.type = type;
+  return create_token_tree (dfa, left, right, &t);
+}
+
+static bin_tree_t *
+create_token_tree (re_dfa_t *dfa, bin_tree_t *left, bin_tree_t *right,
+		   const re_token_t *token)
+{
+  bin_tree_t *tree;
+  if (BE (dfa->str_tree_storage_idx == BIN_TREE_STORAGE_SIZE, 0))
+    {
+      bin_tree_storage_t *storage = re_malloc (bin_tree_storage_t, 1);
+
+      if (storage == NULL)
+	return NULL;
+      storage->next = dfa->str_tree_storage;
+      dfa->str_tree_storage = storage;
+      dfa->str_tree_storage_idx = 0;
+    }
+  tree = &dfa->str_tree_storage->data[dfa->str_tree_storage_idx++];
+
+  tree->parent = NULL;
+  tree->left = left;
+  tree->right = right;
+  tree->token = *token;
+  tree->token.duplicated = 0;
+  tree->token.opt_subexp = 0;
+  tree->first = NULL;
+  tree->next = NULL;
+  tree->node_idx = -1;
+
+  if (left != NULL)
+    left->parent = tree;
+  if (right != NULL)
+    right->parent = tree;
+  return tree;
+}
+
+/* Mark the tree SRC as an optional subexpression.
+   To be called from preorder or postorder.  */
+
+static reg_errcode_t
+mark_opt_subexp (void *extra, bin_tree_t *node)
+{
+  int idx = (int) (intptr_t) extra;
+  if (node->token.type == SUBEXP && node->token.opr.idx == idx)
+    node->token.opt_subexp = 1;
+
+  return REG_NOERROR;
+}
+
+/* Free the allocated memory inside NODE. */
+
+static void
+free_token (re_token_t *node)
+{
+#ifdef RE_ENABLE_I18N
+  if (node->type == COMPLEX_BRACKET && node->duplicated == 0)
+    free_charset (node->opr.mbcset);
+  else
+#endif /* RE_ENABLE_I18N */
+    if (node->type == SIMPLE_BRACKET && node->duplicated == 0)
+      re_free (node->opr.sbcset);
+}
+
+/* Worker function for tree walking.  Free the allocated memory inside NODE
+   and its children. */
+
+static reg_errcode_t
+free_tree (void *extra, bin_tree_t *node)
+{
+  free_token (&node->token);
+  return REG_NOERROR;
+}
+
+
+/* Duplicate the node SRC, and return new node.  This is a preorder
+   visit similar to the one implemented by the generic visitor, but
+   we need more infrastructure to maintain two parallel trees --- so,
+   it's easier to duplicate.  */
+
+static bin_tree_t *
+duplicate_tree (const bin_tree_t *root, re_dfa_t *dfa)
+{
+  const bin_tree_t *node;
+  bin_tree_t *dup_root;
+  bin_tree_t **p_new = &dup_root, *dup_node = root->parent;
+
+  for (node = root; ; )
+    {
+      /* Create a new tree and link it back to the current parent.  */
+      *p_new = create_token_tree (dfa, NULL, NULL, &node->token);
+      if (*p_new == NULL)
+	return NULL;
+      (*p_new)->parent = dup_node;
+      (*p_new)->token.duplicated = 1;
+      dup_node = *p_new;
+
+      /* Go to the left node, or up and to the right.  */
+      if (node->left)
+	{
+	  node = node->left;
+	  p_new = &dup_node->left;
+	}
+      else
+	{
+	  const bin_tree_t *prev = NULL;
+	  while (node->right == prev || node->right == NULL)
+	    {
+	      prev = node;
+	      node = node->parent;
+	      dup_node = dup_node->parent;
+	      if (!node)
+		return dup_root;
+	    }
+	  node = node->right;
+	  p_new = &dup_node->right;
+	}
+    }
+}
diff --git a/compat/regex/regex.c b/compat/regex/regex.c
new file mode 100644
index 0000000..e6f4a5d
--- /dev/null
+++ b/compat/regex/regex.c
@@ -0,0 +1,88 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002, 2003, 2005 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.
+
+   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/>.  */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+/* Make sure no one compiles this code with a C++ compiler.  */
+#ifdef __cplusplus
+# error "This is C code, use a C compiler"
+#endif
+
+#ifdef _LIBC
+/* We have to keep the namespace clean.  */
+# define regfree(preg) __regfree (preg)
+# define regexec(pr, st, nm, pm, ef) __regexec (pr, st, nm, pm, ef)
+# define regcomp(preg, pattern, cflags) __regcomp (preg, pattern, cflags)
+# define regerror(errcode, preg, errbuf, errbuf_size) \
+	__regerror(errcode, preg, errbuf, errbuf_size)
+# define re_set_registers(bu, re, nu, st, en) \
+	__re_set_registers (bu, re, nu, st, en)
+# define re_match_2(bufp, string1, size1, string2, size2, pos, regs, stop) \
+	__re_match_2 (bufp, string1, size1, string2, size2, pos, regs, stop)
+# define re_match(bufp, string, size, pos, regs) \
+	__re_match (bufp, string, size, pos, regs)
+# define re_search(bufp, string, size, startpos, range, regs) \
+	__re_search (bufp, string, size, startpos, range, regs)
+# define re_compile_pattern(pattern, length, bufp) \
+	__re_compile_pattern (pattern, length, bufp)
+# define re_set_syntax(syntax) __re_set_syntax (syntax)
+# define re_search_2(bufp, st1, s1, st2, s2, startpos, range, regs, stop) \
+	__re_search_2 (bufp, st1, s1, st2, s2, startpos, range, regs, stop)
+# define re_compile_fastmap(bufp) __re_compile_fastmap (bufp)
+
+# include "../locale/localeinfo.h"
+#endif
+
+#if defined (_MSC_VER)
+#include <stdio.h> /* for size_t */
+#endif
+
+/* On some systems, limits.h sets RE_DUP_MAX to a lower value than
+   GNU regex allows.  Include it before <regex.h>, which correctly
+   #undefs RE_DUP_MAX and sets it to the right value.  */
+#include <limits.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#ifdef GAWK
+#undef alloca
+#define alloca alloca_is_bad_you_should_never_use_it
+#endif
+#include <regex.h>
+#include "regex_internal.h"
+
+#include "regex_internal.c"
+#ifdef GAWK
+#define bool int
+#define true (1)
+#define false (0)
+#endif
+#include "regcomp.c"
+#include "regexec.c"
+
+/* Binary backward compatibility.  */
+#if _LIBC
+# include <shlib-compat.h>
+# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_3)
+link_warning (re_max_failures, "the 're_max_failures' variable is obsolete and will go away.")
+int re_max_failures = 2000;
+# endif
+#endif
diff --git a/compat/regex/regex.h b/compat/regex/regex.h
new file mode 100644
index 0000000..2d34128
--- /dev/null
+++ b/compat/regex/regex.h
@@ -0,0 +1,586 @@
+#include <stdio.h>
+#include <stddef.h>
+
+/* Definitions for data structures and routines for the regular
+   expression library.
+   Copyright (C) 1985,1989-93,1995-98,2000,2001,2002,2003,2005,2006,2008
+   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/>.  */
+
+#ifndef _REGEX_H
+#define _REGEX_H 1
+
+#ifdef HAVE_STDDEF_H
+#include <stddef.h>
+#endif
+
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+#ifndef _LIBC
+#define __USE_GNU	1
+#endif
+
+/* Allow the use in C++ code.  */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define regcomp git_regcomp
+#define regexec git_regexec
+#define regerror git_regerror
+#define regfree git_regfree
+
+/* The following two types have to be signed and unsigned integer type
+   wide enough to hold a value of a pointer.  For most ANSI compilers
+   ptrdiff_t and size_t should be likely OK.  Still size of these two
+   types is 2 for Microsoft C.  Ugh... */
+typedef long int s_reg_t;
+typedef unsigned long int active_reg_t;
+
+/* The following bits are used to determine the regexp syntax we
+   recognize.  The set/not-set meanings are chosen so that Emacs syntax
+   remains the value 0.  The bits are given in alphabetical order, and
+   the definitions shifted by one from the previous bit; thus, when we
+   add or remove a bit, only one other definition need change.  */
+typedef unsigned long int reg_syntax_t;
+
+#ifdef __USE_GNU
+/* If this bit is not set, then \ inside a bracket expression is literal.
+   If set, then such a \ quotes the following character.  */
+# define RE_BACKSLASH_ESCAPE_IN_LISTS ((unsigned long int) 1)
+
+/* If this bit is not set, then + and ? are operators, and \+ and \? are
+     literals.
+   If set, then \+ and \? are operators and + and ? are literals.  */
+# define RE_BK_PLUS_QM (RE_BACKSLASH_ESCAPE_IN_LISTS << 1)
+
+/* If this bit is set, then character classes are supported.  They are:
+     [:alpha:], [:upper:], [:lower:],  [:digit:], [:alnum:], [:xdigit:],
+     [:space:], [:print:], [:punct:], [:graph:], and [:cntrl:].
+   If not set, then character classes are not supported.  */
+# define RE_CHAR_CLASSES (RE_BK_PLUS_QM << 1)
+
+/* If this bit is set, then ^ and $ are always anchors (outside bracket
+     expressions, of course).
+   If this bit is not set, then it depends:
+        ^  is an anchor if it is at the beginning of a regular
+           expression or after an open-group or an alternation operator;
+        $  is an anchor if it is at the end of a regular expression, or
+           before a close-group or an alternation operator.
+
+   This bit could be (re)combined with RE_CONTEXT_INDEP_OPS, because
+   POSIX draft 11.2 says that * etc. in leading positions is undefined.
+   We already implemented a previous draft which made those constructs
+   invalid, though, so we haven't changed the code back.  */
+# define RE_CONTEXT_INDEP_ANCHORS (RE_CHAR_CLASSES << 1)
+
+/* If this bit is set, then special characters are always special
+     regardless of where they are in the pattern.
+   If this bit is not set, then special characters are special only in
+     some contexts; otherwise they are ordinary.  Specifically,
+     * + ? and intervals are only special when not after the beginning,
+     open-group, or alternation operator.  */
+# define RE_CONTEXT_INDEP_OPS (RE_CONTEXT_INDEP_ANCHORS << 1)
+
+/* If this bit is set, then *, +, ?, and { cannot be first in an re or
+     immediately after an alternation or begin-group operator.  */
+# define RE_CONTEXT_INVALID_OPS (RE_CONTEXT_INDEP_OPS << 1)
+
+/* If this bit is set, then . matches newline.
+   If not set, then it doesn't.  */
+# define RE_DOT_NEWLINE (RE_CONTEXT_INVALID_OPS << 1)
+
+/* If this bit is set, then . doesn't match NUL.
+   If not set, then it does.  */
+# define RE_DOT_NOT_NULL (RE_DOT_NEWLINE << 1)
+
+/* If this bit is set, nonmatching lists [^...] do not match newline.
+   If not set, they do.  */
+# define RE_HAT_LISTS_NOT_NEWLINE (RE_DOT_NOT_NULL << 1)
+
+/* If this bit is set, either \{...\} or {...} defines an
+     interval, depending on RE_NO_BK_BRACES.
+   If not set, \{, \}, {, and } are literals.  */
+# define RE_INTERVALS (RE_HAT_LISTS_NOT_NEWLINE << 1)
+
+/* If this bit is set, +, ? and | aren't recognized as operators.
+   If not set, they are.  */
+# define RE_LIMITED_OPS (RE_INTERVALS << 1)
+
+/* If this bit is set, newline is an alternation operator.
+   If not set, newline is literal.  */
+# define RE_NEWLINE_ALT (RE_LIMITED_OPS << 1)
+
+/* If this bit is set, then `{...}' defines an interval, and \{ and \}
+     are literals.
+  If not set, then `\{...\}' defines an interval.  */
+# define RE_NO_BK_BRACES (RE_NEWLINE_ALT << 1)
+
+/* If this bit is set, (...) defines a group, and \( and \) are literals.
+   If not set, \(...\) defines a group, and ( and ) are literals.  */
+# define RE_NO_BK_PARENS (RE_NO_BK_BRACES << 1)
+
+/* If this bit is set, then \<digit> matches <digit>.
+   If not set, then \<digit> is a back-reference.  */
+# define RE_NO_BK_REFS (RE_NO_BK_PARENS << 1)
+
+/* If this bit is set, then | is an alternation operator, and \| is literal.
+   If not set, then \| is an alternation operator, and | is literal.  */
+# define RE_NO_BK_VBAR (RE_NO_BK_REFS << 1)
+
+/* If this bit is set, then an ending range point collating higher
+     than the starting range point, as in [z-a], is invalid.
+   If not set, then when ending range point collates higher than the
+     starting range point, the range is ignored.  */
+# define RE_NO_EMPTY_RANGES (RE_NO_BK_VBAR << 1)
+
+/* If this bit is set, then an unmatched ) is ordinary.
+   If not set, then an unmatched ) is invalid.  */
+# define RE_UNMATCHED_RIGHT_PAREN_ORD (RE_NO_EMPTY_RANGES << 1)
+
+/* If this bit is set, succeed as soon as we match the whole pattern,
+   without further backtracking.  */
+# define RE_NO_POSIX_BACKTRACKING (RE_UNMATCHED_RIGHT_PAREN_ORD << 1)
+
+/* If this bit is set, do not process the GNU regex operators.
+   If not set, then the GNU regex operators are recognized. */
+# define RE_NO_GNU_OPS (RE_NO_POSIX_BACKTRACKING << 1)
+
+/* If this bit is set, a syntactically invalid interval is treated as
+   a string of ordinary characters.  For example, the ERE 'a{1' is
+   treated as 'a\{1'.  */
+# define RE_INVALID_INTERVAL_ORD (RE_NO_GNU_OPS << 1)
+
+/* If this bit is set, then ignore case when matching.
+   If not set, then case is significant.  */
+# define RE_ICASE (RE_INVALID_INTERVAL_ORD << 1)
+
+/* This bit is used internally like RE_CONTEXT_INDEP_ANCHORS but only
+   for ^, because it is difficult to scan the regex backwards to find
+   whether ^ should be special.  */
+# define RE_CARET_ANCHORS_HERE (RE_ICASE << 1)
+
+/* If this bit is set, then \{ cannot be first in an bre or
+   immediately after an alternation or begin-group operator.  */
+# define RE_CONTEXT_INVALID_DUP (RE_CARET_ANCHORS_HERE << 1)
+
+/* If this bit is set, then no_sub will be set to 1 during
+   re_compile_pattern.  */
+#define RE_NO_SUB (RE_CONTEXT_INVALID_DUP << 1)
+#endif
+
+/* This global variable defines the particular regexp syntax to use (for
+   some interfaces).  When a regexp is compiled, the syntax used is
+   stored in the pattern buffer, so changing this does not affect
+   already-compiled regexps.  */
+extern reg_syntax_t re_syntax_options;
+
+#ifdef __USE_GNU
+/* Define combinations of the above bits for the standard possibilities.
+   (The [[[ comments delimit what gets put into the Texinfo file, so
+   don't delete them!)  */
+/* [[[begin syntaxes]]] */
+#define RE_SYNTAX_EMACS 0
+
+#define RE_SYNTAX_AWK							\
+  (RE_BACKSLASH_ESCAPE_IN_LISTS   | RE_DOT_NOT_NULL			\
+   | RE_NO_BK_PARENS              | RE_NO_BK_REFS			\
+   | RE_NO_BK_VBAR                | RE_NO_EMPTY_RANGES			\
+   | RE_DOT_NEWLINE		  | RE_CONTEXT_INDEP_ANCHORS		\
+   | RE_UNMATCHED_RIGHT_PAREN_ORD | RE_NO_GNU_OPS)
+
+#define RE_SYNTAX_GNU_AWK						\
+  ((RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS		\
+   | RE_INVALID_INTERVAL_ORD)						\
+   & ~(RE_DOT_NOT_NULL | RE_CONTEXT_INDEP_OPS				\
+       | RE_CONTEXT_INVALID_OPS ))
+
+#define RE_SYNTAX_POSIX_AWK						\
+  (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS		\
+   | RE_INTERVALS	    | RE_NO_GNU_OPS				\
+   | RE_INVALID_INTERVAL_ORD)
+
+#define RE_SYNTAX_GREP							\
+  (RE_BK_PLUS_QM              | RE_CHAR_CLASSES				\
+   | RE_HAT_LISTS_NOT_NEWLINE | RE_INTERVALS				\
+   | RE_NEWLINE_ALT)
+
+#define RE_SYNTAX_EGREP							\
+  (RE_CHAR_CLASSES        | RE_CONTEXT_INDEP_ANCHORS			\
+   | RE_CONTEXT_INDEP_OPS | RE_HAT_LISTS_NOT_NEWLINE			\
+   | RE_NEWLINE_ALT       | RE_NO_BK_PARENS				\
+   | RE_NO_BK_VBAR)
+
+#define RE_SYNTAX_POSIX_EGREP						\
+  (RE_SYNTAX_EGREP | RE_INTERVALS | RE_NO_BK_BRACES			\
+   | RE_INVALID_INTERVAL_ORD)
+
+/* P1003.2/D11.2, section 4.20.7.1, lines 5078ff.  */
+#define RE_SYNTAX_ED RE_SYNTAX_POSIX_BASIC
+
+#define RE_SYNTAX_SED RE_SYNTAX_POSIX_BASIC
+
+/* Syntax bits common to both basic and extended POSIX regex syntax.  */
+#define _RE_SYNTAX_POSIX_COMMON						\
+  (RE_CHAR_CLASSES | RE_DOT_NEWLINE      | RE_DOT_NOT_NULL		\
+   | RE_INTERVALS  | RE_NO_EMPTY_RANGES)
+
+#define RE_SYNTAX_POSIX_BASIC						\
+  (_RE_SYNTAX_POSIX_COMMON | RE_BK_PLUS_QM | RE_CONTEXT_INVALID_DUP)
+
+/* Differs from ..._POSIX_BASIC only in that RE_BK_PLUS_QM becomes
+   RE_LIMITED_OPS, i.e., \? \+ \| are not recognized.  Actually, this
+   isn't minimal, since other operators, such as \`, aren't disabled.  */
+#define RE_SYNTAX_POSIX_MINIMAL_BASIC					\
+  (_RE_SYNTAX_POSIX_COMMON | RE_LIMITED_OPS)
+
+#define RE_SYNTAX_POSIX_EXTENDED					\
+  (_RE_SYNTAX_POSIX_COMMON  | RE_CONTEXT_INDEP_ANCHORS			\
+   | RE_CONTEXT_INDEP_OPS   | RE_NO_BK_BRACES				\
+   | RE_NO_BK_PARENS        | RE_NO_BK_VBAR				\
+   | RE_CONTEXT_INVALID_OPS | RE_UNMATCHED_RIGHT_PAREN_ORD)
+
+/* Differs from ..._POSIX_EXTENDED in that RE_CONTEXT_INDEP_OPS is
+   removed and RE_NO_BK_REFS is added.  */
+#define RE_SYNTAX_POSIX_MINIMAL_EXTENDED				\
+  (_RE_SYNTAX_POSIX_COMMON  | RE_CONTEXT_INDEP_ANCHORS			\
+   | RE_CONTEXT_INVALID_OPS | RE_NO_BK_BRACES				\
+   | RE_NO_BK_PARENS        | RE_NO_BK_REFS				\
+   | RE_NO_BK_VBAR	    | RE_UNMATCHED_RIGHT_PAREN_ORD)
+/* [[[end syntaxes]]] */
+
+/* Maximum number of duplicates an interval can allow.  Some systems
+   (erroneously) define this in other header files, but we want our
+   value, so remove any previous define.  */
+# ifdef RE_DUP_MAX
+#  undef RE_DUP_MAX
+# endif
+/* If sizeof(int) == 2, then ((1 << 15) - 1) overflows.  */
+# define RE_DUP_MAX (0x7fff)
+#endif
+
+
+/* POSIX `cflags' bits (i.e., information for `regcomp').  */
+
+/* If this bit is set, then use extended regular expression syntax.
+   If not set, then use basic regular expression syntax.  */
+#define REG_EXTENDED 1
+
+/* If this bit is set, then ignore case when matching.
+   If not set, then case is significant.  */
+#define REG_ICASE (REG_EXTENDED << 1)
+
+/* If this bit is set, then anchors do not match at newline
+     characters in the string.
+   If not set, then anchors do match at newlines.  */
+#define REG_NEWLINE (REG_ICASE << 1)
+
+/* If this bit is set, then report only success or fail in regexec.
+   If not set, then returns differ between not matching and errors.  */
+#define REG_NOSUB (REG_NEWLINE << 1)
+
+
+/* POSIX `eflags' bits (i.e., information for regexec).  */
+
+/* If this bit is set, then the beginning-of-line operator doesn't match
+     the beginning of the string (presumably because it's not the
+     beginning of a line).
+   If not set, then the beginning-of-line operator does match the
+     beginning of the string.  */
+#define REG_NOTBOL 1
+
+/* Like REG_NOTBOL, except for the end-of-line.  */
+#define REG_NOTEOL (1 << 1)
+
+/* Use PMATCH[0] to delimit the start and end of the search in the
+   buffer.  */
+#define REG_STARTEND (1 << 2)
+
+
+/* If any error codes are removed, changed, or added, update the
+   `re_error_msg' table in regex.c.  */
+typedef enum
+{
+#if defined _XOPEN_SOURCE || defined __USE_XOPEN2K
+  REG_ENOSYS = -1,	/* This will never happen for this implementation.  */
+#endif
+
+  REG_NOERROR = 0,	/* Success.  */
+  REG_NOMATCH,		/* Didn't find a match (for regexec).  */
+
+  /* POSIX regcomp return error codes.  (In the order listed in the
+     standard.)  */
+  REG_BADPAT,		/* Invalid pattern.  */
+  REG_ECOLLATE,		/* Invalid collating element.  */
+  REG_ECTYPE,		/* Invalid character class name.  */
+  REG_EESCAPE,		/* Trailing backslash.  */
+  REG_ESUBREG,		/* Invalid back reference.  */
+  REG_EBRACK,		/* Unmatched left bracket.  */
+  REG_EPAREN,		/* Parenthesis imbalance.  */
+  REG_EBRACE,		/* Unmatched \{.  */
+  REG_BADBR,		/* Invalid contents of \{\}.  */
+  REG_ERANGE,		/* Invalid range end.  */
+  REG_ESPACE,		/* Ran out of memory.  */
+  REG_BADRPT,		/* No preceding re for repetition op.  */
+
+  /* Error codes we've added.  */
+  REG_EEND,		/* Premature end.  */
+  REG_ESIZE,		/* Compiled pattern bigger than 2^16 bytes.  */
+  REG_ERPAREN		/* Unmatched ) or \); not returned from regcomp.  */
+} reg_errcode_t;
+
+/* This data structure represents a compiled pattern.  Before calling
+   the pattern compiler, the fields `buffer', `allocated', `fastmap',
+   `translate', and `no_sub' can be set.  After the pattern has been
+   compiled, the `re_nsub' field is available.  All other fields are
+   private to the regex routines.  */
+
+#ifndef RE_TRANSLATE_TYPE
+# define __RE_TRANSLATE_TYPE unsigned char *
+# ifdef __USE_GNU
+#  define RE_TRANSLATE_TYPE __RE_TRANSLATE_TYPE
+# endif
+#endif
+
+#ifdef __USE_GNU
+# define __REPB_PREFIX(name) name
+#else
+# define __REPB_PREFIX(name) __##name
+#endif
+
+struct re_pattern_buffer
+{
+  /* Space that holds the compiled pattern.  It is declared as
+     `unsigned char *' because its elements are sometimes used as
+     array indexes.  */
+  unsigned char *__REPB_PREFIX(buffer);
+
+  /* Number of bytes to which `buffer' points.  */
+  unsigned long int __REPB_PREFIX(allocated);
+
+  /* Number of bytes actually used in `buffer'.  */
+  unsigned long int __REPB_PREFIX(used);
+
+  /* Syntax setting with which the pattern was compiled.  */
+  reg_syntax_t __REPB_PREFIX(syntax);
+
+  /* Pointer to a fastmap, if any, otherwise zero.  re_search uses the
+     fastmap, if there is one, to skip over impossible starting points
+     for matches.  */
+  char *__REPB_PREFIX(fastmap);
+
+  /* Either a translate table to apply to all characters before
+     comparing them, or zero for no translation.  The translation is
+     applied to a pattern when it is compiled and to a string when it
+     is matched.  */
+  __RE_TRANSLATE_TYPE __REPB_PREFIX(translate);
+
+  /* Number of subexpressions found by the compiler.  */
+  size_t re_nsub;
+
+  /* Zero if this pattern cannot match the empty string, one else.
+     Well, in truth it's used only in `re_search_2', to see whether or
+     not we should use the fastmap, so we don't set this absolutely
+     perfectly; see `re_compile_fastmap' (the `duplicate' case).  */
+  unsigned __REPB_PREFIX(can_be_null) : 1;
+
+  /* If REGS_UNALLOCATED, allocate space in the `regs' structure
+     for `max (RE_NREGS, re_nsub + 1)' groups.
+     If REGS_REALLOCATE, reallocate space if necessary.
+     If REGS_FIXED, use what's there.  */
+#ifdef __USE_GNU
+# define REGS_UNALLOCATED 0
+# define REGS_REALLOCATE 1
+# define REGS_FIXED 2
+#endif
+  unsigned __REPB_PREFIX(regs_allocated) : 2;
+
+  /* Set to zero when `regex_compile' compiles a pattern; set to one
+     by `re_compile_fastmap' if it updates the fastmap.  */
+  unsigned __REPB_PREFIX(fastmap_accurate) : 1;
+
+  /* If set, `re_match_2' does not return information about
+     subexpressions.  */
+  unsigned __REPB_PREFIX(no_sub) : 1;
+
+  /* If set, a beginning-of-line anchor doesn't match at the beginning
+     of the string.  */
+  unsigned __REPB_PREFIX(not_bol) : 1;
+
+  /* Similarly for an end-of-line anchor.  */
+  unsigned __REPB_PREFIX(not_eol) : 1;
+
+  /* If true, an anchor at a newline matches.  */
+  unsigned __REPB_PREFIX(newline_anchor) : 1;
+};
+
+typedef struct re_pattern_buffer regex_t;
+
+/* Type for byte offsets within the string.  POSIX mandates this.  */
+typedef int regoff_t;
+
+
+#ifdef __USE_GNU
+/* This is the structure we store register match data in.  See
+   regex.texinfo for a full description of what registers match.  */
+struct re_registers
+{
+  unsigned num_regs;
+  regoff_t *start;
+  regoff_t *end;
+};
+
+
+/* If `regs_allocated' is REGS_UNALLOCATED in the pattern buffer,
+   `re_match_2' returns information about at least this many registers
+   the first time a `regs' structure is passed.  */
+# ifndef RE_NREGS
+#  define RE_NREGS 30
+# endif
+#endif
+
+
+/* POSIX specification for registers.  Aside from the different names than
+   `re_registers', POSIX uses an array of structures, instead of a
+   structure of arrays.  */
+typedef struct
+{
+  regoff_t rm_so;  /* Byte offset from string's start to substring's start.  */
+  regoff_t rm_eo;  /* Byte offset from string's start to substring's end.  */
+} regmatch_t;
+
+/* Declarations for routines.  */
+
+#ifdef __USE_GNU
+/* Sets the current default syntax to SYNTAX, and return the old syntax.
+   You can also simply assign to the `re_syntax_options' variable.  */
+extern reg_syntax_t re_set_syntax (reg_syntax_t __syntax);
+
+/* Compile the regular expression PATTERN, with length LENGTH
+   and syntax given by the global `re_syntax_options', into the buffer
+   BUFFER.  Return NULL if successful, and an error string if not.  */
+extern const char *re_compile_pattern (const char *__pattern, size_t __length,
+				       struct re_pattern_buffer *__buffer);
+
+
+/* Compile a fastmap for the compiled pattern in BUFFER; used to
+   accelerate searches.  Return 0 if successful and -2 if was an
+   internal error.  */
+extern int re_compile_fastmap (struct re_pattern_buffer *__buffer);
+
+
+/* Search in the string STRING (with length LENGTH) for the pattern
+   compiled into BUFFER.  Start searching at position START, for RANGE
+   characters.  Return the starting position of the match, -1 for no
+   match, or -2 for an internal error.  Also return register
+   information in REGS (if REGS and BUFFER->no_sub are nonzero).  */
+extern int re_search (struct re_pattern_buffer *__buffer, const char *__cstring,
+		      int __length, int __start, int __range,
+		      struct re_registers *__regs);
+
+
+/* Like `re_search', but search in the concatenation of STRING1 and
+   STRING2.  Also, stop searching at index START + STOP.  */
+extern int re_search_2 (struct re_pattern_buffer *__buffer,
+			const char *__string1, int __length1,
+			const char *__string2, int __length2, int __start,
+			int __range, struct re_registers *__regs, int __stop);
+
+
+/* Like `re_search', but return how many characters in STRING the regexp
+   in BUFFER matched, starting at position START.  */
+extern int re_match (struct re_pattern_buffer *__buffer, const char *__cstring,
+		     int __length, int __start, struct re_registers *__regs);
+
+
+/* Relates to `re_match' as `re_search_2' relates to `re_search'.  */
+extern int re_match_2 (struct re_pattern_buffer *__buffer,
+		       const char *__string1, int __length1,
+		       const char *__string2, int __length2, int __start,
+		       struct re_registers *__regs, int __stop);
+
+
+/* Set REGS to hold NUM_REGS registers, storing them in STARTS and
+   ENDS.  Subsequent matches using BUFFER and REGS will use this memory
+   for recording register information.  STARTS and ENDS must be
+   allocated with malloc, and must each be at least `NUM_REGS * sizeof
+   (regoff_t)' bytes long.
+
+   If NUM_REGS == 0, then subsequent matches should allocate their own
+   register data.
+
+   Unless this function is called, the first search or match using
+   PATTERN_BUFFER will allocate its own register data, without
+   freeing the old data.  */
+extern void re_set_registers (struct re_pattern_buffer *__buffer,
+			      struct re_registers *__regs,
+			      unsigned int __num_regs,
+			      regoff_t *__starts, regoff_t *__ends);
+#endif	/* Use GNU */
+
+#if defined _REGEX_RE_COMP || (defined _LIBC && defined __USE_BSD)
+# ifndef _CRAY
+/* 4.2 bsd compatibility.  */
+extern char *re_comp (const char *);
+extern int re_exec (const char *);
+# endif
+#endif
+
+/* GCC 2.95 and later have "__restrict"; C99 compilers have
+   "restrict", and "configure" may have defined "restrict".  */
+#ifndef __restrict
+# if ! (2 < __GNUC__ || (2 == __GNUC__ && 95 <= __GNUC_MINOR__))
+#  if defined restrict || 199901L <= __STDC_VERSION__
+#   define __restrict restrict
+#  else
+#   define __restrict
+#  endif
+# endif
+#endif
+/* gcc 3.1 and up support the [restrict] syntax.  */
+#ifndef __restrict_arr
+# if (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1)) \
+     && !defined __GNUG__
+#  define __restrict_arr __restrict
+# else
+#  define __restrict_arr
+# endif
+#endif
+
+/* POSIX compatibility.  */
+extern int regcomp (regex_t *__restrict __preg,
+		    const char *__restrict __pattern,
+		    int __cflags);
+
+extern int regexec (const regex_t *__restrict __preg,
+		    const char *__restrict __cstring, size_t __nmatch,
+		    regmatch_t __pmatch[__restrict_arr],
+		    int __eflags);
+
+extern size_t regerror (int __errcode, const regex_t *__restrict __preg,
+			char *__restrict __errbuf, size_t __errbuf_size);
+
+extern void regfree (regex_t *__preg);
+
+
+#ifdef __cplusplus
+}
+#endif	/* C++ */
+
+#endif /* regex.h */
diff --git a/compat/regex/regex_internal.c b/compat/regex/regex_internal.c
new file mode 100644
index 0000000..ec51cf3
--- /dev/null
+++ b/compat/regex/regex_internal.c
@@ -0,0 +1,1743 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2006, 2010 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.
+
+   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/>.  */
+
+static void re_string_construct_common (const char *str, int len,
+					re_string_t *pstr,
+					RE_TRANSLATE_TYPE trans, int icase,
+					const re_dfa_t *dfa) internal_function;
+static re_dfastate_t *create_ci_newstate (const re_dfa_t *dfa,
+					  const re_node_set *nodes,
+					  unsigned int hash) internal_function;
+static re_dfastate_t *create_cd_newstate (const re_dfa_t *dfa,
+					  const re_node_set *nodes,
+					  unsigned int context,
+					  unsigned int hash) internal_function;
+
+#ifdef GAWK
+#undef MAX	/* safety */
+static int
+MAX(size_t a, size_t b)
+{
+	return (a > b ? a : b);
+}
+#endif
+
+/* Functions for string operation.  */
+
+/* This function allocate the buffers.  It is necessary to call
+   re_string_reconstruct before using the object.  */
+
+static reg_errcode_t
+internal_function
+re_string_allocate (re_string_t *pstr, const char *str, int len, int init_len,
+		    RE_TRANSLATE_TYPE trans, int icase, const re_dfa_t *dfa)
+{
+  reg_errcode_t ret;
+  int init_buf_len;
+
+  /* Ensure at least one character fits into the buffers.  */
+  if (init_len < dfa->mb_cur_max)
+    init_len = dfa->mb_cur_max;
+  init_buf_len = (len + 1 < init_len) ? len + 1: init_len;
+  re_string_construct_common (str, len, pstr, trans, icase, dfa);
+
+  ret = re_string_realloc_buffers (pstr, init_buf_len);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+
+  pstr->word_char = dfa->word_char;
+  pstr->word_ops_used = dfa->word_ops_used;
+  pstr->mbs = pstr->mbs_allocated ? pstr->mbs : (unsigned char *) str;
+  pstr->valid_len = (pstr->mbs_allocated || dfa->mb_cur_max > 1) ? 0 : len;
+  pstr->valid_raw_len = pstr->valid_len;
+  return REG_NOERROR;
+}
+
+/* This function allocate the buffers, and initialize them.  */
+
+static reg_errcode_t
+internal_function
+re_string_construct (re_string_t *pstr, const char *str, int len,
+		     RE_TRANSLATE_TYPE trans, int icase, const re_dfa_t *dfa)
+{
+  reg_errcode_t ret;
+  memset (pstr, '\0', sizeof (re_string_t));
+  re_string_construct_common (str, len, pstr, trans, icase, dfa);
+
+  if (len > 0)
+    {
+      ret = re_string_realloc_buffers (pstr, len + 1);
+      if (BE (ret != REG_NOERROR, 0))
+	return ret;
+    }
+  pstr->mbs = pstr->mbs_allocated ? pstr->mbs : (unsigned char *) str;
+
+  if (icase)
+    {
+#ifdef RE_ENABLE_I18N
+      if (dfa->mb_cur_max > 1)
+	{
+	  while (1)
+	    {
+	      ret = build_wcs_upper_buffer (pstr);
+	      if (BE (ret != REG_NOERROR, 0))
+		return ret;
+	      if (pstr->valid_raw_len >= len)
+		break;
+	      if (pstr->bufs_len > pstr->valid_len + dfa->mb_cur_max)
+		break;
+	      ret = re_string_realloc_buffers (pstr, pstr->bufs_len * 2);
+	      if (BE (ret != REG_NOERROR, 0))
+		return ret;
+	    }
+	}
+      else
+#endif /* RE_ENABLE_I18N  */
+	build_upper_buffer (pstr);
+    }
+  else
+    {
+#ifdef RE_ENABLE_I18N
+      if (dfa->mb_cur_max > 1)
+	build_wcs_buffer (pstr);
+      else
+#endif /* RE_ENABLE_I18N  */
+	{
+	  if (trans != NULL)
+	    re_string_translate_buffer (pstr);
+	  else
+	    {
+	      pstr->valid_len = pstr->bufs_len;
+	      pstr->valid_raw_len = pstr->bufs_len;
+	    }
+	}
+    }
+
+  return REG_NOERROR;
+}
+
+/* Helper functions for re_string_allocate, and re_string_construct.  */
+
+static reg_errcode_t
+internal_function
+re_string_realloc_buffers (re_string_t *pstr, int new_buf_len)
+{
+#ifdef RE_ENABLE_I18N
+  if (pstr->mb_cur_max > 1)
+    {
+      wint_t *new_wcs;
+
+      /* Avoid overflow in realloc.  */
+      const size_t max_object_size = MAX (sizeof (wint_t), sizeof (int));
+      if (BE (SIZE_MAX / max_object_size < new_buf_len, 0))
+	return REG_ESPACE;
+
+      new_wcs = re_realloc (pstr->wcs, wint_t, new_buf_len);
+      if (BE (new_wcs == NULL, 0))
+	return REG_ESPACE;
+      pstr->wcs = new_wcs;
+      if (pstr->offsets != NULL)
+	{
+	  int *new_offsets = re_realloc (pstr->offsets, int, new_buf_len);
+	  if (BE (new_offsets == NULL, 0))
+	    return REG_ESPACE;
+	  pstr->offsets = new_offsets;
+	}
+    }
+#endif /* RE_ENABLE_I18N  */
+  if (pstr->mbs_allocated)
+    {
+      unsigned char *new_mbs = re_realloc (pstr->mbs, unsigned char,
+					   new_buf_len);
+      if (BE (new_mbs == NULL, 0))
+	return REG_ESPACE;
+      pstr->mbs = new_mbs;
+    }
+  pstr->bufs_len = new_buf_len;
+  return REG_NOERROR;
+}
+
+
+static void
+internal_function
+re_string_construct_common (const char *str, int len, re_string_t *pstr,
+			    RE_TRANSLATE_TYPE trans, int icase,
+			    const re_dfa_t *dfa)
+{
+  pstr->raw_mbs = (const unsigned char *) str;
+  pstr->len = len;
+  pstr->raw_len = len;
+  pstr->trans = trans;
+  pstr->icase = icase ? 1 : 0;
+  pstr->mbs_allocated = (trans != NULL || icase);
+  pstr->mb_cur_max = dfa->mb_cur_max;
+  pstr->is_utf8 = dfa->is_utf8;
+  pstr->map_notascii = dfa->map_notascii;
+  pstr->stop = pstr->len;
+  pstr->raw_stop = pstr->stop;
+}
+
+#ifdef RE_ENABLE_I18N
+
+/* Build wide character buffer PSTR->WCS.
+   If the byte sequence of the string are:
+     <mb1>(0), <mb1>(1), <mb2>(0), <mb2>(1), <sb3>
+   Then wide character buffer will be:
+     <wc1>   , WEOF    , <wc2>   , WEOF    , <wc3>
+   We use WEOF for padding, they indicate that the position isn't
+   a first byte of a multibyte character.
+
+   Note that this function assumes PSTR->VALID_LEN elements are already
+   built and starts from PSTR->VALID_LEN.  */
+
+static void
+internal_function
+build_wcs_buffer (re_string_t *pstr)
+{
+#ifdef _LIBC
+  unsigned char buf[MB_LEN_MAX];
+  assert (MB_LEN_MAX >= pstr->mb_cur_max);
+#else
+  unsigned char buf[64];
+#endif
+  mbstate_t prev_st;
+  int byte_idx, end_idx, remain_len;
+  size_t mbclen;
+
+  /* Build the buffers from pstr->valid_len to either pstr->len or
+     pstr->bufs_len.  */
+  end_idx = (pstr->bufs_len > pstr->len) ? pstr->len : pstr->bufs_len;
+  for (byte_idx = pstr->valid_len; byte_idx < end_idx;)
+    {
+      wchar_t wc;
+      const char *p;
+
+      remain_len = end_idx - byte_idx;
+      prev_st = pstr->cur_state;
+      /* Apply the translation if we need.  */
+      if (BE (pstr->trans != NULL, 0))
+	{
+	  int i, ch;
+
+	  for (i = 0; i < pstr->mb_cur_max && i < remain_len; ++i)
+	    {
+	      ch = pstr->raw_mbs [pstr->raw_mbs_idx + byte_idx + i];
+	      buf[i] = pstr->mbs[byte_idx + i] = pstr->trans[ch];
+	    }
+	  p = (const char *) buf;
+	}
+      else
+	p = (const char *) pstr->raw_mbs + pstr->raw_mbs_idx + byte_idx;
+      mbclen = __mbrtowc (&wc, p, remain_len, &pstr->cur_state);
+      if (BE (mbclen == (size_t) -2, 0))
+	{
+	  /* The buffer doesn't have enough space, finish to build.  */
+	  pstr->cur_state = prev_st;
+	  break;
+	}
+      else if (BE (mbclen == (size_t) -1 || mbclen == 0, 0))
+	{
+	  /* We treat these cases as a singlebyte character.  */
+	  mbclen = 1;
+	  wc = (wchar_t) pstr->raw_mbs[pstr->raw_mbs_idx + byte_idx];
+	  if (BE (pstr->trans != NULL, 0))
+	    wc = pstr->trans[wc];
+	  pstr->cur_state = prev_st;
+	}
+
+      /* Write wide character and padding.  */
+      pstr->wcs[byte_idx++] = wc;
+      /* Write paddings.  */
+      for (remain_len = byte_idx + mbclen - 1; byte_idx < remain_len ;)
+	pstr->wcs[byte_idx++] = WEOF;
+    }
+  pstr->valid_len = byte_idx;
+  pstr->valid_raw_len = byte_idx;
+}
+
+/* Build wide character buffer PSTR->WCS like build_wcs_buffer,
+   but for REG_ICASE.  */
+
+static reg_errcode_t
+internal_function
+build_wcs_upper_buffer (re_string_t *pstr)
+{
+  mbstate_t prev_st;
+  int src_idx, byte_idx, end_idx, remain_len;
+  size_t mbclen;
+#ifdef _LIBC
+  char buf[MB_LEN_MAX];
+  assert (MB_LEN_MAX >= pstr->mb_cur_max);
+#else
+  char buf[64];
+#endif
+
+  byte_idx = pstr->valid_len;
+  end_idx = (pstr->bufs_len > pstr->len) ? pstr->len : pstr->bufs_len;
+
+  /* The following optimization assumes that ASCII characters can be
+     mapped to wide characters with a simple cast.  */
+  if (! pstr->map_notascii && pstr->trans == NULL && !pstr->offsets_needed)
+    {
+      while (byte_idx < end_idx)
+	{
+	  wchar_t wc;
+
+	  if (isascii (pstr->raw_mbs[pstr->raw_mbs_idx + byte_idx])
+	      && mbsinit (&pstr->cur_state))
+	    {
+	      /* In case of a singlebyte character.  */
+	      pstr->mbs[byte_idx]
+		= toupper (pstr->raw_mbs[pstr->raw_mbs_idx + byte_idx]);
+	      /* The next step uses the assumption that wchar_t is encoded
+		 ASCII-safe: all ASCII values can be converted like this.  */
+	      pstr->wcs[byte_idx] = (wchar_t) pstr->mbs[byte_idx];
+	      ++byte_idx;
+	      continue;
+	    }
+
+	  remain_len = end_idx - byte_idx;
+	  prev_st = pstr->cur_state;
+	  mbclen = __mbrtowc (&wc,
+			      ((const char *) pstr->raw_mbs + pstr->raw_mbs_idx
+			       + byte_idx), remain_len, &pstr->cur_state);
+	  if (BE (mbclen + 2 > 2, 1))
+	    {
+	      wchar_t wcu = wc;
+	      if (iswlower (wc))
+		{
+		  size_t mbcdlen;
+
+		  wcu = towupper (wc);
+		  mbcdlen = wcrtomb (buf, wcu, &prev_st);
+		  if (BE (mbclen == mbcdlen, 1))
+		    memcpy (pstr->mbs + byte_idx, buf, mbclen);
+		  else
+		    {
+		      src_idx = byte_idx;
+		      goto offsets_needed;
+		    }
+		}
+	      else
+		memcpy (pstr->mbs + byte_idx,
+			pstr->raw_mbs + pstr->raw_mbs_idx + byte_idx, mbclen);
+	      pstr->wcs[byte_idx++] = wcu;
+	      /* Write paddings.  */
+	      for (remain_len = byte_idx + mbclen - 1; byte_idx < remain_len ;)
+		pstr->wcs[byte_idx++] = WEOF;
+	    }
+	  else if (mbclen == (size_t) -1 || mbclen == 0)
+	    {
+	      /* It is an invalid character or '\0'.  Just use the byte.  */
+	      int ch = pstr->raw_mbs[pstr->raw_mbs_idx + byte_idx];
+	      pstr->mbs[byte_idx] = ch;
+	      /* And also cast it to wide char.  */
+	      pstr->wcs[byte_idx++] = (wchar_t) ch;
+	      if (BE (mbclen == (size_t) -1, 0))
+		pstr->cur_state = prev_st;
+	    }
+	  else
+	    {
+	      /* The buffer doesn't have enough space, finish to build.  */
+	      pstr->cur_state = prev_st;
+	      break;
+	    }
+	}
+      pstr->valid_len = byte_idx;
+      pstr->valid_raw_len = byte_idx;
+      return REG_NOERROR;
+    }
+  else
+    for (src_idx = pstr->valid_raw_len; byte_idx < end_idx;)
+      {
+	wchar_t wc;
+	const char *p;
+      offsets_needed:
+	remain_len = end_idx - byte_idx;
+	prev_st = pstr->cur_state;
+	if (BE (pstr->trans != NULL, 0))
+	  {
+	    int i, ch;
+
+	    for (i = 0; i < pstr->mb_cur_max && i < remain_len; ++i)
+	      {
+		ch = pstr->raw_mbs [pstr->raw_mbs_idx + src_idx + i];
+		buf[i] = pstr->trans[ch];
+	      }
+	    p = (const char *) buf;
+	  }
+	else
+	  p = (const char *) pstr->raw_mbs + pstr->raw_mbs_idx + src_idx;
+	mbclen = __mbrtowc (&wc, p, remain_len, &pstr->cur_state);
+	if (BE (mbclen + 2 > 2, 1))
+	  {
+	    wchar_t wcu = wc;
+	    if (iswlower (wc))
+	      {
+		size_t mbcdlen;
+
+		wcu = towupper (wc);
+		mbcdlen = wcrtomb ((char *) buf, wcu, &prev_st);
+		if (BE (mbclen == mbcdlen, 1))
+		  memcpy (pstr->mbs + byte_idx, buf, mbclen);
+		else if (mbcdlen != (size_t) -1)
+		  {
+		    size_t i;
+
+		    if (byte_idx + mbcdlen > pstr->bufs_len)
+		      {
+			pstr->cur_state = prev_st;
+			break;
+		      }
+
+		    if (pstr->offsets == NULL)
+		      {
+			pstr->offsets = re_malloc (int, pstr->bufs_len);
+
+			if (pstr->offsets == NULL)
+			  return REG_ESPACE;
+		      }
+		    if (!pstr->offsets_needed)
+		      {
+			for (i = 0; i < (size_t) byte_idx; ++i)
+			  pstr->offsets[i] = i;
+			pstr->offsets_needed = 1;
+		      }
+
+		    memcpy (pstr->mbs + byte_idx, buf, mbcdlen);
+		    pstr->wcs[byte_idx] = wcu;
+		    pstr->offsets[byte_idx] = src_idx;
+		    for (i = 1; i < mbcdlen; ++i)
+		      {
+			pstr->offsets[byte_idx + i]
+			  = src_idx + (i < mbclen ? i : mbclen - 1);
+			pstr->wcs[byte_idx + i] = WEOF;
+		      }
+		    pstr->len += mbcdlen - mbclen;
+		    if (pstr->raw_stop > src_idx)
+		      pstr->stop += mbcdlen - mbclen;
+		    end_idx = (pstr->bufs_len > pstr->len)
+			      ? pstr->len : pstr->bufs_len;
+		    byte_idx += mbcdlen;
+		    src_idx += mbclen;
+		    continue;
+		  }
+		else
+		  memcpy (pstr->mbs + byte_idx, p, mbclen);
+	      }
+	    else
+	      memcpy (pstr->mbs + byte_idx, p, mbclen);
+
+	    if (BE (pstr->offsets_needed != 0, 0))
+	      {
+		size_t i;
+		for (i = 0; i < mbclen; ++i)
+		  pstr->offsets[byte_idx + i] = src_idx + i;
+	      }
+	    src_idx += mbclen;
+
+	    pstr->wcs[byte_idx++] = wcu;
+	    /* Write paddings.  */
+	    for (remain_len = byte_idx + mbclen - 1; byte_idx < remain_len ;)
+	      pstr->wcs[byte_idx++] = WEOF;
+	  }
+	else if (mbclen == (size_t) -1 || mbclen == 0)
+	  {
+	    /* It is an invalid character or '\0'.  Just use the byte.  */
+	    int ch = pstr->raw_mbs[pstr->raw_mbs_idx + src_idx];
+
+	    if (BE (pstr->trans != NULL, 0))
+	      ch = pstr->trans [ch];
+	    pstr->mbs[byte_idx] = ch;
+
+	    if (BE (pstr->offsets_needed != 0, 0))
+	      pstr->offsets[byte_idx] = src_idx;
+	    ++src_idx;
+
+	    /* And also cast it to wide char.  */
+	    pstr->wcs[byte_idx++] = (wchar_t) ch;
+	    if (BE (mbclen == (size_t) -1, 0))
+	      pstr->cur_state = prev_st;
+	  }
+	else
+	  {
+	    /* The buffer doesn't have enough space, finish to build.  */
+	    pstr->cur_state = prev_st;
+	    break;
+	  }
+      }
+  pstr->valid_len = byte_idx;
+  pstr->valid_raw_len = src_idx;
+  return REG_NOERROR;
+}
+
+/* Skip characters until the index becomes greater than NEW_RAW_IDX.
+   Return the index.  */
+
+static int
+internal_function
+re_string_skip_chars (re_string_t *pstr, int new_raw_idx, wint_t *last_wc)
+{
+  mbstate_t prev_st;
+  int rawbuf_idx;
+  size_t mbclen;
+  wint_t wc = WEOF;
+
+  /* Skip the characters which are not necessary to check.  */
+  for (rawbuf_idx = pstr->raw_mbs_idx + pstr->valid_raw_len;
+       rawbuf_idx < new_raw_idx;)
+    {
+      wchar_t wc2;
+      int remain_len = pstr->len - rawbuf_idx;
+      prev_st = pstr->cur_state;
+      mbclen = __mbrtowc (&wc2, (const char *) pstr->raw_mbs + rawbuf_idx,
+			  remain_len, &pstr->cur_state);
+      if (BE (mbclen == (size_t) -2 || mbclen == (size_t) -1 || mbclen == 0, 0))
+	{
+	  /* We treat these cases as a single byte character.  */
+	  if (mbclen == 0 || remain_len == 0)
+	    wc = L'\0';
+	  else
+	    wc = *(unsigned char *) (pstr->raw_mbs + rawbuf_idx);
+	  mbclen = 1;
+	  pstr->cur_state = prev_st;
+	}
+      else
+	wc = (wint_t) wc2;
+      /* Then proceed the next character.  */
+      rawbuf_idx += mbclen;
+    }
+  *last_wc = (wint_t) wc;
+  return rawbuf_idx;
+}
+#endif /* RE_ENABLE_I18N  */
+
+/* Build the buffer PSTR->MBS, and apply the translation if we need.
+   This function is used in case of REG_ICASE.  */
+
+static void
+internal_function
+build_upper_buffer (re_string_t *pstr)
+{
+  int char_idx, end_idx;
+  end_idx = (pstr->bufs_len > pstr->len) ? pstr->len : pstr->bufs_len;
+
+  for (char_idx = pstr->valid_len; char_idx < end_idx; ++char_idx)
+    {
+      int ch = pstr->raw_mbs[pstr->raw_mbs_idx + char_idx];
+      if (BE (pstr->trans != NULL, 0))
+	ch = pstr->trans[ch];
+      if (islower (ch))
+	pstr->mbs[char_idx] = toupper (ch);
+      else
+	pstr->mbs[char_idx] = ch;
+    }
+  pstr->valid_len = char_idx;
+  pstr->valid_raw_len = char_idx;
+}
+
+/* Apply TRANS to the buffer in PSTR.  */
+
+static void
+internal_function
+re_string_translate_buffer (re_string_t *pstr)
+{
+  int buf_idx, end_idx;
+  end_idx = (pstr->bufs_len > pstr->len) ? pstr->len : pstr->bufs_len;
+
+  for (buf_idx = pstr->valid_len; buf_idx < end_idx; ++buf_idx)
+    {
+      int ch = pstr->raw_mbs[pstr->raw_mbs_idx + buf_idx];
+      pstr->mbs[buf_idx] = pstr->trans[ch];
+    }
+
+  pstr->valid_len = buf_idx;
+  pstr->valid_raw_len = buf_idx;
+}
+
+/* This function re-construct the buffers.
+   Concretely, convert to wide character in case of pstr->mb_cur_max > 1,
+   convert to upper case in case of REG_ICASE, apply translation.  */
+
+static reg_errcode_t
+internal_function
+re_string_reconstruct (re_string_t *pstr, int idx, int eflags)
+{
+  int offset = idx - pstr->raw_mbs_idx;
+  if (BE (offset < 0, 0))
+    {
+      /* Reset buffer.  */
+#ifdef RE_ENABLE_I18N
+      if (pstr->mb_cur_max > 1)
+	memset (&pstr->cur_state, '\0', sizeof (mbstate_t));
+#endif /* RE_ENABLE_I18N */
+      pstr->len = pstr->raw_len;
+      pstr->stop = pstr->raw_stop;
+      pstr->valid_len = 0;
+      pstr->raw_mbs_idx = 0;
+      pstr->valid_raw_len = 0;
+      pstr->offsets_needed = 0;
+      pstr->tip_context = ((eflags & REG_NOTBOL) ? CONTEXT_BEGBUF
+			   : CONTEXT_NEWLINE | CONTEXT_BEGBUF);
+      if (!pstr->mbs_allocated)
+	pstr->mbs = (unsigned char *) pstr->raw_mbs;
+      offset = idx;
+    }
+
+  if (BE (offset != 0, 1))
+    {
+      /* Should the already checked characters be kept?  */
+      if (BE (offset < pstr->valid_raw_len, 1))
+	{
+	  /* Yes, move them to the front of the buffer.  */
+#ifdef RE_ENABLE_I18N
+	  if (BE (pstr->offsets_needed, 0))
+	    {
+	      int low = 0, high = pstr->valid_len, mid;
+	      do
+		{
+		  mid = low + (high - low) / 2;
+		  if (pstr->offsets[mid] > offset)
+		    high = mid;
+		  else if (pstr->offsets[mid] < offset)
+		    low = mid + 1;
+		  else
+		    break;
+		}
+	      while (low < high);
+	      if (pstr->offsets[mid] < offset)
+		++mid;
+	      pstr->tip_context = re_string_context_at (pstr, mid - 1,
+							eflags);
+	      /* This can be quite complicated, so handle specially
+		 only the common and easy case where the character with
+		 different length representation of lower and upper
+		 case is present at or after offset.  */
+	      if (pstr->valid_len > offset
+		  && mid == offset && pstr->offsets[mid] == offset)
+		{
+		  memmove (pstr->wcs, pstr->wcs + offset,
+			   (pstr->valid_len - offset) * sizeof (wint_t));
+		  memmove (pstr->mbs, pstr->mbs + offset, pstr->valid_len - offset);
+		  pstr->valid_len -= offset;
+		  pstr->valid_raw_len -= offset;
+		  for (low = 0; low < pstr->valid_len; low++)
+		    pstr->offsets[low] = pstr->offsets[low + offset] - offset;
+		}
+	      else
+		{
+		  /* Otherwise, just find out how long the partial multibyte
+		     character at offset is and fill it with WEOF/255.  */
+		  pstr->len = pstr->raw_len - idx + offset;
+		  pstr->stop = pstr->raw_stop - idx + offset;
+		  pstr->offsets_needed = 0;
+		  while (mid > 0 && pstr->offsets[mid - 1] == offset)
+		    --mid;
+		  while (mid < pstr->valid_len)
+		    if (pstr->wcs[mid] != WEOF)
+		      break;
+		    else
+		      ++mid;
+		  if (mid == pstr->valid_len)
+		    pstr->valid_len = 0;
+		  else
+		    {
+		      pstr->valid_len = pstr->offsets[mid] - offset;
+		      if (pstr->valid_len)
+			{
+			  for (low = 0; low < pstr->valid_len; ++low)
+			    pstr->wcs[low] = WEOF;
+			  memset (pstr->mbs, 255, pstr->valid_len);
+			}
+		    }
+		  pstr->valid_raw_len = pstr->valid_len;
+		}
+	    }
+	  else
+#endif
+	    {
+	      pstr->tip_context = re_string_context_at (pstr, offset - 1,
+							eflags);
+#ifdef RE_ENABLE_I18N
+	      if (pstr->mb_cur_max > 1)
+		memmove (pstr->wcs, pstr->wcs + offset,
+			 (pstr->valid_len - offset) * sizeof (wint_t));
+#endif /* RE_ENABLE_I18N */
+	      if (BE (pstr->mbs_allocated, 0))
+		memmove (pstr->mbs, pstr->mbs + offset,
+			 pstr->valid_len - offset);
+	      pstr->valid_len -= offset;
+	      pstr->valid_raw_len -= offset;
+#if DEBUG
+	      assert (pstr->valid_len > 0);
+#endif
+	    }
+	}
+      else
+	{
+#ifdef RE_ENABLE_I18N
+	  /* No, skip all characters until IDX.  */
+	  int prev_valid_len = pstr->valid_len;
+
+	  if (BE (pstr->offsets_needed, 0))
+	    {
+	      pstr->len = pstr->raw_len - idx + offset;
+	      pstr->stop = pstr->raw_stop - idx + offset;
+	      pstr->offsets_needed = 0;
+	    }
+#endif
+	  pstr->valid_len = 0;
+#ifdef RE_ENABLE_I18N
+	  if (pstr->mb_cur_max > 1)
+	    {
+	      int wcs_idx;
+	      wint_t wc = WEOF;
+
+	      if (pstr->is_utf8)
+		{
+		  const unsigned char *raw, *p, *end;
+
+		  /* Special case UTF-8.  Multi-byte chars start with any
+		     byte other than 0x80 - 0xbf.  */
+		  raw = pstr->raw_mbs + pstr->raw_mbs_idx;
+		  end = raw + (offset - pstr->mb_cur_max);
+		  if (end < pstr->raw_mbs)
+		    end = pstr->raw_mbs;
+		  p = raw + offset - 1;
+#ifdef _LIBC
+		  /* We know the wchar_t encoding is UCS4, so for the simple
+		     case, ASCII characters, skip the conversion step.  */
+		  if (isascii (*p) && BE (pstr->trans == NULL, 1))
+		    {
+		      memset (&pstr->cur_state, '\0', sizeof (mbstate_t));
+		      /* pstr->valid_len = 0; */
+		      wc = (wchar_t) *p;
+		    }
+		  else
+#endif
+		    for (; p >= end; --p)
+		      if ((*p & 0xc0) != 0x80)
+			{
+			  mbstate_t cur_state;
+			  wchar_t wc2;
+			  int mlen = raw + pstr->len - p;
+			  unsigned char buf[6];
+			  size_t mbclen;
+
+			  if (BE (pstr->trans != NULL, 0))
+			    {
+			      int i = mlen < 6 ? mlen : 6;
+			      while (--i >= 0)
+				buf[i] = pstr->trans[p[i]];
+			    }
+			  /* XXX Don't use mbrtowc, we know which conversion
+			     to use (UTF-8 -> UCS4).  */
+			  memset (&cur_state, 0, sizeof (cur_state));
+			  mbclen = __mbrtowc (&wc2, (const char *) p, mlen,
+					      &cur_state);
+			  if (raw + offset - p <= mbclen
+			      && mbclen < (size_t) -2)
+			    {
+			      memset (&pstr->cur_state, '\0',
+				      sizeof (mbstate_t));
+			      pstr->valid_len = mbclen - (raw + offset - p);
+			      wc = wc2;
+			    }
+			  break;
+			}
+		}
+
+	      if (wc == WEOF)
+		pstr->valid_len = re_string_skip_chars (pstr, idx, &wc) - idx;
+	      if (wc == WEOF)
+		pstr->tip_context
+		  = re_string_context_at (pstr, prev_valid_len - 1, eflags);
+	      else
+		pstr->tip_context = ((BE (pstr->word_ops_used != 0, 0)
+				      && IS_WIDE_WORD_CHAR (wc))
+				     ? CONTEXT_WORD
+				     : ((IS_WIDE_NEWLINE (wc)
+					 && pstr->newline_anchor)
+					? CONTEXT_NEWLINE : 0));
+	      if (BE (pstr->valid_len, 0))
+		{
+		  for (wcs_idx = 0; wcs_idx < pstr->valid_len; ++wcs_idx)
+		    pstr->wcs[wcs_idx] = WEOF;
+		  if (pstr->mbs_allocated)
+		    memset (pstr->mbs, 255, pstr->valid_len);
+		}
+	      pstr->valid_raw_len = pstr->valid_len;
+	    }
+	  else
+#endif /* RE_ENABLE_I18N */
+	    {
+	      int c = pstr->raw_mbs[pstr->raw_mbs_idx + offset - 1];
+	      pstr->valid_raw_len = 0;
+	      if (pstr->trans)
+		c = pstr->trans[c];
+	      pstr->tip_context = (bitset_contain (pstr->word_char, c)
+				   ? CONTEXT_WORD
+				   : ((IS_NEWLINE (c) && pstr->newline_anchor)
+				      ? CONTEXT_NEWLINE : 0));
+	    }
+	}
+      if (!BE (pstr->mbs_allocated, 0))
+	pstr->mbs += offset;
+    }
+  pstr->raw_mbs_idx = idx;
+  pstr->len -= offset;
+  pstr->stop -= offset;
+
+  /* Then build the buffers.  */
+#ifdef RE_ENABLE_I18N
+  if (pstr->mb_cur_max > 1)
+    {
+      if (pstr->icase)
+	{
+	  reg_errcode_t ret = build_wcs_upper_buffer (pstr);
+	  if (BE (ret != REG_NOERROR, 0))
+	    return ret;
+	}
+      else
+	build_wcs_buffer (pstr);
+    }
+  else
+#endif /* RE_ENABLE_I18N */
+    if (BE (pstr->mbs_allocated, 0))
+      {
+	if (pstr->icase)
+	  build_upper_buffer (pstr);
+	else if (pstr->trans != NULL)
+	  re_string_translate_buffer (pstr);
+      }
+    else
+      pstr->valid_len = pstr->len;
+
+  pstr->cur_idx = 0;
+  return REG_NOERROR;
+}
+
+static unsigned char
+internal_function __attribute ((pure))
+re_string_peek_byte_case (const re_string_t *pstr, int idx)
+{
+  int ch, off;
+
+  /* Handle the common (easiest) cases first.  */
+  if (BE (!pstr->mbs_allocated, 1))
+    return re_string_peek_byte (pstr, idx);
+
+#ifdef RE_ENABLE_I18N
+  if (pstr->mb_cur_max > 1
+      && ! re_string_is_single_byte_char (pstr, pstr->cur_idx + idx))
+    return re_string_peek_byte (pstr, idx);
+#endif
+
+  off = pstr->cur_idx + idx;
+#ifdef RE_ENABLE_I18N
+  if (pstr->offsets_needed)
+    off = pstr->offsets[off];
+#endif
+
+  ch = pstr->raw_mbs[pstr->raw_mbs_idx + off];
+
+#ifdef RE_ENABLE_I18N
+  /* Ensure that e.g. for tr_TR.UTF-8 BACKSLASH DOTLESS SMALL LETTER I
+     this function returns CAPITAL LETTER I instead of first byte of
+     DOTLESS SMALL LETTER I.  The latter would confuse the parser,
+     since peek_byte_case doesn't advance cur_idx in any way.  */
+  if (pstr->offsets_needed && !isascii (ch))
+    return re_string_peek_byte (pstr, idx);
+#endif
+
+  return ch;
+}
+
+static unsigned char
+internal_function __attribute ((pure))
+re_string_fetch_byte_case (re_string_t *pstr)
+{
+  if (BE (!pstr->mbs_allocated, 1))
+    return re_string_fetch_byte (pstr);
+
+#ifdef RE_ENABLE_I18N
+  if (pstr->offsets_needed)
+    {
+      int off, ch;
+
+      /* For tr_TR.UTF-8 [[:islower:]] there is
+	 [[: CAPITAL LETTER I WITH DOT lower:]] in mbs.  Skip
+	 in that case the whole multi-byte character and return
+	 the original letter.  On the other side, with
+	 [[: DOTLESS SMALL LETTER I return [[:I, as doing
+	 anything else would complicate things too much.  */
+
+      if (!re_string_first_byte (pstr, pstr->cur_idx))
+	return re_string_fetch_byte (pstr);
+
+      off = pstr->offsets[pstr->cur_idx];
+      ch = pstr->raw_mbs[pstr->raw_mbs_idx + off];
+
+      if (! isascii (ch))
+	return re_string_fetch_byte (pstr);
+
+      re_string_skip_bytes (pstr,
+			    re_string_char_size_at (pstr, pstr->cur_idx));
+      return ch;
+    }
+#endif
+
+  return pstr->raw_mbs[pstr->raw_mbs_idx + pstr->cur_idx++];
+}
+
+static void
+internal_function
+re_string_destruct (re_string_t *pstr)
+{
+#ifdef RE_ENABLE_I18N
+  re_free (pstr->wcs);
+  re_free (pstr->offsets);
+#endif /* RE_ENABLE_I18N  */
+  if (pstr->mbs_allocated)
+    re_free (pstr->mbs);
+}
+
+/* Return the context at IDX in INPUT.  */
+
+static unsigned int
+internal_function
+re_string_context_at (const re_string_t *input, int idx, int eflags)
+{
+  int c;
+  if (BE (idx < 0, 0))
+    /* In this case, we use the value stored in input->tip_context,
+       since we can't know the character in input->mbs[-1] here.  */
+    return input->tip_context;
+  if (BE (idx == input->len, 0))
+    return ((eflags & REG_NOTEOL) ? CONTEXT_ENDBUF
+	    : CONTEXT_NEWLINE | CONTEXT_ENDBUF);
+#ifdef RE_ENABLE_I18N
+  if (input->mb_cur_max > 1)
+    {
+      wint_t wc;
+      int wc_idx = idx;
+      while(input->wcs[wc_idx] == WEOF)
+	{
+#ifdef DEBUG
+	  /* It must not happen.  */
+	  assert (wc_idx >= 0);
+#endif
+	  --wc_idx;
+	  if (wc_idx < 0)
+	    return input->tip_context;
+	}
+      wc = input->wcs[wc_idx];
+      if (BE (input->word_ops_used != 0, 0) && IS_WIDE_WORD_CHAR (wc))
+	return CONTEXT_WORD;
+      return (IS_WIDE_NEWLINE (wc) && input->newline_anchor
+	      ? CONTEXT_NEWLINE : 0);
+    }
+  else
+#endif
+    {
+      c = re_string_byte_at (input, idx);
+      if (bitset_contain (input->word_char, c))
+	return CONTEXT_WORD;
+      return IS_NEWLINE (c) && input->newline_anchor ? CONTEXT_NEWLINE : 0;
+    }
+}
+
+/* Functions for set operation.  */
+
+static reg_errcode_t
+internal_function
+re_node_set_alloc (re_node_set *set, int size)
+{
+  /*
+   * ADR: valgrind says size can be 0, which then doesn't
+   * free the block of size 0.  Harumph. This seems
+   * to work ok, though.
+   */
+  if (size == 0)
+    {
+       memset(set, 0, sizeof(*set));
+       return REG_NOERROR;
+    }
+  set->alloc = size;
+  set->nelem = 0;
+  set->elems = re_malloc (int, size);
+  if (BE (set->elems == NULL, 0))
+    return REG_ESPACE;
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+re_node_set_init_1 (re_node_set *set, int elem)
+{
+  set->alloc = 1;
+  set->nelem = 1;
+  set->elems = re_malloc (int, 1);
+  if (BE (set->elems == NULL, 0))
+    {
+      set->alloc = set->nelem = 0;
+      return REG_ESPACE;
+    }
+  set->elems[0] = elem;
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+re_node_set_init_2 (re_node_set *set, int elem1, int elem2)
+{
+  set->alloc = 2;
+  set->elems = re_malloc (int, 2);
+  if (BE (set->elems == NULL, 0))
+    return REG_ESPACE;
+  if (elem1 == elem2)
+    {
+      set->nelem = 1;
+      set->elems[0] = elem1;
+    }
+  else
+    {
+      set->nelem = 2;
+      if (elem1 < elem2)
+	{
+	  set->elems[0] = elem1;
+	  set->elems[1] = elem2;
+	}
+      else
+	{
+	  set->elems[0] = elem2;
+	  set->elems[1] = elem1;
+	}
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+re_node_set_init_copy (re_node_set *dest, const re_node_set *src)
+{
+  dest->nelem = src->nelem;
+  if (src->nelem > 0)
+    {
+      dest->alloc = dest->nelem;
+      dest->elems = re_malloc (int, dest->alloc);
+      if (BE (dest->elems == NULL, 0))
+	{
+	  dest->alloc = dest->nelem = 0;
+	  return REG_ESPACE;
+	}
+      memcpy (dest->elems, src->elems, src->nelem * sizeof (int));
+    }
+  else
+    re_node_set_init_empty (dest);
+  return REG_NOERROR;
+}
+
+/* Calculate the intersection of the sets SRC1 and SRC2. And merge it to
+   DEST. Return value indicate the error code or REG_NOERROR if succeeded.
+   Note: We assume dest->elems is NULL, when dest->alloc is 0.  */
+
+static reg_errcode_t
+internal_function
+re_node_set_add_intersect (re_node_set *dest, const re_node_set *src1,
+			   const re_node_set *src2)
+{
+  int i1, i2, is, id, delta, sbase;
+  if (src1->nelem == 0 || src2->nelem == 0)
+    return REG_NOERROR;
+
+  /* We need dest->nelem + 2 * elems_in_intersection; this is a
+     conservative estimate.  */
+  if (src1->nelem + src2->nelem + dest->nelem > dest->alloc)
+    {
+      int new_alloc = src1->nelem + src2->nelem + dest->alloc;
+      int *new_elems = re_realloc (dest->elems, int, new_alloc);
+      if (BE (new_elems == NULL, 0))
+	return REG_ESPACE;
+      dest->elems = new_elems;
+      dest->alloc = new_alloc;
+    }
+
+  /* Find the items in the intersection of SRC1 and SRC2, and copy
+     into the top of DEST those that are not already in DEST itself.  */
+  sbase = dest->nelem + src1->nelem + src2->nelem;
+  i1 = src1->nelem - 1;
+  i2 = src2->nelem - 1;
+  id = dest->nelem - 1;
+  for (;;)
+    {
+      if (src1->elems[i1] == src2->elems[i2])
+	{
+	  /* Try to find the item in DEST.  Maybe we could binary search?  */
+	  while (id >= 0 && dest->elems[id] > src1->elems[i1])
+	    --id;
+
+	  if (id < 0 || dest->elems[id] != src1->elems[i1])
+	    dest->elems[--sbase] = src1->elems[i1];
+
+	  if (--i1 < 0 || --i2 < 0)
+	    break;
+	}
+
+      /* Lower the highest of the two items.  */
+      else if (src1->elems[i1] < src2->elems[i2])
+	{
+	  if (--i2 < 0)
+	    break;
+	}
+      else
+	{
+	  if (--i1 < 0)
+	    break;
+	}
+    }
+
+  id = dest->nelem - 1;
+  is = dest->nelem + src1->nelem + src2->nelem - 1;
+  delta = is - sbase + 1;
+
+  /* Now copy.  When DELTA becomes zero, the remaining
+     DEST elements are already in place; this is more or
+     less the same loop that is in re_node_set_merge.  */
+  dest->nelem += delta;
+  if (delta > 0 && id >= 0)
+    for (;;)
+      {
+	if (dest->elems[is] > dest->elems[id])
+	  {
+	    /* Copy from the top.  */
+	    dest->elems[id + delta--] = dest->elems[is--];
+	    if (delta == 0)
+	      break;
+	  }
+	else
+	  {
+	    /* Slide from the bottom.  */
+	    dest->elems[id + delta] = dest->elems[id];
+	    if (--id < 0)
+	      break;
+	  }
+      }
+
+  /* Copy remaining SRC elements.  */
+  memcpy (dest->elems, dest->elems + sbase, delta * sizeof (int));
+
+  return REG_NOERROR;
+}
+
+/* Calculate the union set of the sets SRC1 and SRC2. And store it to
+   DEST. Return value indicate the error code or REG_NOERROR if succeeded.  */
+
+static reg_errcode_t
+internal_function
+re_node_set_init_union (re_node_set *dest, const re_node_set *src1,
+			const re_node_set *src2)
+{
+  int i1, i2, id;
+  if (src1 != NULL && src1->nelem > 0 && src2 != NULL && src2->nelem > 0)
+    {
+      dest->alloc = src1->nelem + src2->nelem;
+      dest->elems = re_malloc (int, dest->alloc);
+      if (BE (dest->elems == NULL, 0))
+	return REG_ESPACE;
+    }
+  else
+    {
+      if (src1 != NULL && src1->nelem > 0)
+	return re_node_set_init_copy (dest, src1);
+      else if (src2 != NULL && src2->nelem > 0)
+	return re_node_set_init_copy (dest, src2);
+      else
+	re_node_set_init_empty (dest);
+      return REG_NOERROR;
+    }
+  for (i1 = i2 = id = 0 ; i1 < src1->nelem && i2 < src2->nelem ;)
+    {
+      if (src1->elems[i1] > src2->elems[i2])
+	{
+	  dest->elems[id++] = src2->elems[i2++];
+	  continue;
+	}
+      if (src1->elems[i1] == src2->elems[i2])
+	++i2;
+      dest->elems[id++] = src1->elems[i1++];
+    }
+  if (i1 < src1->nelem)
+    {
+      memcpy (dest->elems + id, src1->elems + i1,
+	     (src1->nelem - i1) * sizeof (int));
+      id += src1->nelem - i1;
+    }
+  else if (i2 < src2->nelem)
+    {
+      memcpy (dest->elems + id, src2->elems + i2,
+	     (src2->nelem - i2) * sizeof (int));
+      id += src2->nelem - i2;
+    }
+  dest->nelem = id;
+  return REG_NOERROR;
+}
+
+/* Calculate the union set of the sets DEST and SRC. And store it to
+   DEST. Return value indicate the error code or REG_NOERROR if succeeded.  */
+
+static reg_errcode_t
+internal_function
+re_node_set_merge (re_node_set *dest, const re_node_set *src)
+{
+  int is, id, sbase, delta;
+  if (src == NULL || src->nelem == 0)
+    return REG_NOERROR;
+  if (dest->alloc < 2 * src->nelem + dest->nelem)
+    {
+      int new_alloc = 2 * (src->nelem + dest->alloc);
+      int *new_buffer = re_realloc (dest->elems, int, new_alloc);
+      if (BE (new_buffer == NULL, 0))
+	return REG_ESPACE;
+      dest->elems = new_buffer;
+      dest->alloc = new_alloc;
+    }
+
+  if (BE (dest->nelem == 0, 0))
+    {
+      dest->nelem = src->nelem;
+      memcpy (dest->elems, src->elems, src->nelem * sizeof (int));
+      return REG_NOERROR;
+    }
+
+  /* Copy into the top of DEST the items of SRC that are not
+     found in DEST.  Maybe we could binary search in DEST?  */
+  for (sbase = dest->nelem + 2 * src->nelem,
+       is = src->nelem - 1, id = dest->nelem - 1; is >= 0 && id >= 0; )
+    {
+      if (dest->elems[id] == src->elems[is])
+	is--, id--;
+      else if (dest->elems[id] < src->elems[is])
+	dest->elems[--sbase] = src->elems[is--];
+      else /* if (dest->elems[id] > src->elems[is]) */
+	--id;
+    }
+
+  if (is >= 0)
+    {
+      /* If DEST is exhausted, the remaining items of SRC must be unique.  */
+      sbase -= is + 1;
+      memcpy (dest->elems + sbase, src->elems, (is + 1) * sizeof (int));
+    }
+
+  id = dest->nelem - 1;
+  is = dest->nelem + 2 * src->nelem - 1;
+  delta = is - sbase + 1;
+  if (delta == 0)
+    return REG_NOERROR;
+
+  /* Now copy.  When DELTA becomes zero, the remaining
+     DEST elements are already in place.  */
+  dest->nelem += delta;
+  for (;;)
+    {
+      if (dest->elems[is] > dest->elems[id])
+	{
+	  /* Copy from the top.  */
+	  dest->elems[id + delta--] = dest->elems[is--];
+	  if (delta == 0)
+	    break;
+	}
+      else
+	{
+	  /* Slide from the bottom.  */
+	  dest->elems[id + delta] = dest->elems[id];
+	  if (--id < 0)
+	    {
+	      /* Copy remaining SRC elements.  */
+	      memcpy (dest->elems, dest->elems + sbase,
+		      delta * sizeof (int));
+	      break;
+	    }
+	}
+    }
+
+  return REG_NOERROR;
+}
+
+/* Insert the new element ELEM to the re_node_set* SET.
+   SET should not already have ELEM.
+   return -1 if an error has occurred, return 1 otherwise.  */
+
+static int
+internal_function
+re_node_set_insert (re_node_set *set, int elem)
+{
+  int idx;
+  /* In case the set is empty.  */
+  if (set->alloc == 0)
+    {
+      if (BE (re_node_set_init_1 (set, elem) == REG_NOERROR, 1))
+	return 1;
+      else
+	return -1;
+    }
+
+  if (BE (set->nelem, 0) == 0)
+    {
+      /* We already guaranteed above that set->alloc != 0.  */
+      set->elems[0] = elem;
+      ++set->nelem;
+      return 1;
+    }
+
+  /* Realloc if we need.  */
+  if (set->alloc == set->nelem)
+    {
+      int *new_elems;
+      set->alloc = set->alloc * 2;
+      new_elems = re_realloc (set->elems, int, set->alloc);
+      if (BE (new_elems == NULL, 0))
+	return -1;
+      set->elems = new_elems;
+    }
+
+  /* Move the elements which follows the new element.  Test the
+     first element separately to skip a check in the inner loop.  */
+  if (elem < set->elems[0])
+    {
+      idx = 0;
+      for (idx = set->nelem; idx > 0; idx--)
+	set->elems[idx] = set->elems[idx - 1];
+    }
+  else
+    {
+      for (idx = set->nelem; set->elems[idx - 1] > elem; idx--)
+	set->elems[idx] = set->elems[idx - 1];
+    }
+
+  /* Insert the new element.  */
+  set->elems[idx] = elem;
+  ++set->nelem;
+  return 1;
+}
+
+/* Insert the new element ELEM to the re_node_set* SET.
+   SET should not already have any element greater than or equal to ELEM.
+   Return -1 if an error has occurred, return 1 otherwise.  */
+
+static int
+internal_function
+re_node_set_insert_last (re_node_set *set, int elem)
+{
+  /* Realloc if we need.  */
+  if (set->alloc == set->nelem)
+    {
+      int *new_elems;
+      set->alloc = (set->alloc + 1) * 2;
+      new_elems = re_realloc (set->elems, int, set->alloc);
+      if (BE (new_elems == NULL, 0))
+	return -1;
+      set->elems = new_elems;
+    }
+
+  /* Insert the new element.  */
+  set->elems[set->nelem++] = elem;
+  return 1;
+}
+
+/* Compare two node sets SET1 and SET2.
+   return 1 if SET1 and SET2 are equivalent, return 0 otherwise.  */
+
+static int
+internal_function __attribute ((pure))
+re_node_set_compare (const re_node_set *set1, const re_node_set *set2)
+{
+  int i;
+  if (set1 == NULL || set2 == NULL || set1->nelem != set2->nelem)
+    return 0;
+  for (i = set1->nelem ; --i >= 0 ; )
+    if (set1->elems[i] != set2->elems[i])
+      return 0;
+  return 1;
+}
+
+/* Return (idx + 1) if SET contains the element ELEM, return 0 otherwise.  */
+
+static int
+internal_function __attribute ((pure))
+re_node_set_contains (const re_node_set *set, int elem)
+{
+  unsigned int idx, right, mid;
+  if (set->nelem <= 0)
+    return 0;
+
+  /* Binary search the element.  */
+  idx = 0;
+  right = set->nelem - 1;
+  while (idx < right)
+    {
+      mid = idx + (right - idx) / 2;
+      if (set->elems[mid] < elem)
+	idx = mid + 1;
+      else
+	right = mid;
+    }
+  return set->elems[idx] == elem ? idx + 1 : 0;
+}
+
+static void
+internal_function
+re_node_set_remove_at (re_node_set *set, int idx)
+{
+  if (idx < 0 || idx >= set->nelem)
+    return;
+  --set->nelem;
+  for (; idx < set->nelem; idx++)
+    set->elems[idx] = set->elems[idx + 1];
+}
+
+
+/* Add the token TOKEN to dfa->nodes, and return the index of the token.
+   Or return -1, if an error has occurred.  */
+
+static int
+internal_function
+re_dfa_add_node (re_dfa_t *dfa, re_token_t token)
+{
+  if (BE (dfa->nodes_len >= dfa->nodes_alloc, 0))
+    {
+      size_t new_nodes_alloc = dfa->nodes_alloc * 2;
+      int *new_nexts, *new_indices;
+      re_node_set *new_edests, *new_eclosures;
+      re_token_t *new_nodes;
+
+      /* Avoid overflows in realloc.  */
+      const size_t max_object_size = MAX (sizeof (re_token_t),
+					  MAX (sizeof (re_node_set),
+					       sizeof (int)));
+      if (BE (SIZE_MAX / max_object_size < new_nodes_alloc, 0))
+	return -1;
+
+      new_nodes = re_realloc (dfa->nodes, re_token_t, new_nodes_alloc);
+      if (BE (new_nodes == NULL, 0))
+	return -1;
+      dfa->nodes = new_nodes;
+      new_nexts = re_realloc (dfa->nexts, int, new_nodes_alloc);
+      new_indices = re_realloc (dfa->org_indices, int, new_nodes_alloc);
+      new_edests = re_realloc (dfa->edests, re_node_set, new_nodes_alloc);
+      new_eclosures = re_realloc (dfa->eclosures, re_node_set, new_nodes_alloc);
+      if (BE (new_nexts == NULL || new_indices == NULL
+	      || new_edests == NULL || new_eclosures == NULL, 0))
+	return -1;
+      dfa->nexts = new_nexts;
+      dfa->org_indices = new_indices;
+      dfa->edests = new_edests;
+      dfa->eclosures = new_eclosures;
+      dfa->nodes_alloc = new_nodes_alloc;
+    }
+  dfa->nodes[dfa->nodes_len] = token;
+  dfa->nodes[dfa->nodes_len].constraint = 0;
+#ifdef RE_ENABLE_I18N
+  dfa->nodes[dfa->nodes_len].accept_mb =
+    (token.type == OP_PERIOD && dfa->mb_cur_max > 1) || token.type == COMPLEX_BRACKET;
+#endif
+  dfa->nexts[dfa->nodes_len] = -1;
+  re_node_set_init_empty (dfa->edests + dfa->nodes_len);
+  re_node_set_init_empty (dfa->eclosures + dfa->nodes_len);
+  return dfa->nodes_len++;
+}
+
+static inline unsigned int
+internal_function
+calc_state_hash (const re_node_set *nodes, unsigned int context)
+{
+  unsigned int hash = nodes->nelem + context;
+  int i;
+  for (i = 0 ; i < nodes->nelem ; i++)
+    hash += nodes->elems[i];
+  return hash;
+}
+
+/* Search for the state whose node_set is equivalent to NODES.
+   Return the pointer to the state, if we found it in the DFA.
+   Otherwise create the new one and return it.  In case of an error
+   return NULL and set the error code in ERR.
+   Note: - We assume NULL as the invalid state, then it is possible that
+	   return value is NULL and ERR is REG_NOERROR.
+	 - We never return non-NULL value in case of any errors, it is for
+	   optimization.  */
+
+static re_dfastate_t *
+internal_function
+re_acquire_state (reg_errcode_t *err, const re_dfa_t *dfa,
+		  const re_node_set *nodes)
+{
+  unsigned int hash;
+  re_dfastate_t *new_state;
+  struct re_state_table_entry *spot;
+  int i;
+  if (BE (nodes->nelem == 0, 0))
+    {
+      *err = REG_NOERROR;
+      return NULL;
+    }
+  hash = calc_state_hash (nodes, 0);
+  spot = dfa->state_table + (hash & dfa->state_hash_mask);
+
+  for (i = 0 ; i < spot->num ; i++)
+    {
+      re_dfastate_t *state = spot->array[i];
+      if (hash != state->hash)
+	continue;
+      if (re_node_set_compare (&state->nodes, nodes))
+	return state;
+    }
+
+  /* There are no appropriate state in the dfa, create the new one.  */
+  new_state = create_ci_newstate (dfa, nodes, hash);
+  if (BE (new_state == NULL, 0))
+    *err = REG_ESPACE;
+
+  return new_state;
+}
+
+/* Search for the state whose node_set is equivalent to NODES and
+   whose context is equivalent to CONTEXT.
+   Return the pointer to the state, if we found it in the DFA.
+   Otherwise create the new one and return it.  In case of an error
+   return NULL and set the error code in ERR.
+   Note: - We assume NULL as the invalid state, then it is possible that
+	   return value is NULL and ERR is REG_NOERROR.
+	 - We never return non-NULL value in case of any errors, it is for
+	   optimization.  */
+
+static re_dfastate_t *
+internal_function
+re_acquire_state_context (reg_errcode_t *err, const re_dfa_t *dfa,
+			  const re_node_set *nodes, unsigned int context)
+{
+  unsigned int hash;
+  re_dfastate_t *new_state;
+  struct re_state_table_entry *spot;
+  int i;
+  if (nodes->nelem == 0)
+    {
+      *err = REG_NOERROR;
+      return NULL;
+    }
+  hash = calc_state_hash (nodes, context);
+  spot = dfa->state_table + (hash & dfa->state_hash_mask);
+
+  for (i = 0 ; i < spot->num ; i++)
+    {
+      re_dfastate_t *state = spot->array[i];
+      if (state->hash == hash
+	  && state->context == context
+	  && re_node_set_compare (state->entrance_nodes, nodes))
+	return state;
+    }
+  /* There are no appropriate state in `dfa', create the new one.  */
+  new_state = create_cd_newstate (dfa, nodes, context, hash);
+  if (BE (new_state == NULL, 0))
+    *err = REG_ESPACE;
+
+  return new_state;
+}
+
+/* Finish initialization of the new state NEWSTATE, and using its hash value
+   HASH put in the appropriate bucket of DFA's state table.  Return value
+   indicates the error code if failed.  */
+
+static reg_errcode_t
+register_state (const re_dfa_t *dfa, re_dfastate_t *newstate,
+		unsigned int hash)
+{
+  struct re_state_table_entry *spot;
+  reg_errcode_t err;
+  int i;
+
+  newstate->hash = hash;
+  err = re_node_set_alloc (&newstate->non_eps_nodes, newstate->nodes.nelem);
+  if (BE (err != REG_NOERROR, 0))
+    return REG_ESPACE;
+  for (i = 0; i < newstate->nodes.nelem; i++)
+    {
+      int elem = newstate->nodes.elems[i];
+      if (!IS_EPSILON_NODE (dfa->nodes[elem].type))
+	if (re_node_set_insert_last (&newstate->non_eps_nodes, elem) < 0)
+	  return REG_ESPACE;
+    }
+
+  spot = dfa->state_table + (hash & dfa->state_hash_mask);
+  if (BE (spot->alloc <= spot->num, 0))
+    {
+      int new_alloc = 2 * spot->num + 2;
+      re_dfastate_t **new_array = re_realloc (spot->array, re_dfastate_t *,
+					      new_alloc);
+      if (BE (new_array == NULL, 0))
+	return REG_ESPACE;
+      spot->array = new_array;
+      spot->alloc = new_alloc;
+    }
+  spot->array[spot->num++] = newstate;
+  return REG_NOERROR;
+}
+
+static void
+free_state (re_dfastate_t *state)
+{
+  re_node_set_free (&state->non_eps_nodes);
+  re_node_set_free (&state->inveclosure);
+  if (state->entrance_nodes != &state->nodes)
+    {
+      re_node_set_free (state->entrance_nodes);
+      re_free (state->entrance_nodes);
+    }
+  re_node_set_free (&state->nodes);
+  re_free (state->word_trtable);
+  re_free (state->trtable);
+  re_free (state);
+}
+
+/* Create the new state which is independent of contexts.
+   Return the new state if succeeded, otherwise return NULL.  */
+
+static re_dfastate_t *
+internal_function
+create_ci_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
+		    unsigned int hash)
+{
+  int i;
+  reg_errcode_t err;
+  re_dfastate_t *newstate;
+
+  newstate = (re_dfastate_t *) calloc (sizeof (re_dfastate_t), 1);
+  if (BE (newstate == NULL, 0))
+    return NULL;
+  err = re_node_set_init_copy (&newstate->nodes, nodes);
+  if (BE (err != REG_NOERROR, 0))
+    {
+      re_free (newstate);
+      return NULL;
+    }
+
+  newstate->entrance_nodes = &newstate->nodes;
+  for (i = 0 ; i < nodes->nelem ; i++)
+    {
+      re_token_t *node = dfa->nodes + nodes->elems[i];
+      re_token_type_t type = node->type;
+      if (type == CHARACTER && !node->constraint)
+	continue;
+#ifdef RE_ENABLE_I18N
+      newstate->accept_mb |= node->accept_mb;
+#endif /* RE_ENABLE_I18N */
+
+      /* If the state has the halt node, the state is a halt state.  */
+      if (type == END_OF_RE)
+	newstate->halt = 1;
+      else if (type == OP_BACK_REF)
+	newstate->has_backref = 1;
+      else if (type == ANCHOR || node->constraint)
+	newstate->has_constraint = 1;
+    }
+  err = register_state (dfa, newstate, hash);
+  if (BE (err != REG_NOERROR, 0))
+    {
+      free_state (newstate);
+      newstate = NULL;
+    }
+  return newstate;
+}
+
+/* Create the new state which is depend on the context CONTEXT.
+   Return the new state if succeeded, otherwise return NULL.  */
+
+static re_dfastate_t *
+internal_function
+create_cd_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
+		    unsigned int context, unsigned int hash)
+{
+  int i, nctx_nodes = 0;
+  reg_errcode_t err;
+  re_dfastate_t *newstate;
+
+  newstate = (re_dfastate_t *) calloc (sizeof (re_dfastate_t), 1);
+  if (BE (newstate == NULL, 0))
+    return NULL;
+  err = re_node_set_init_copy (&newstate->nodes, nodes);
+  if (BE (err != REG_NOERROR, 0))
+    {
+      re_free (newstate);
+      return NULL;
+    }
+
+  newstate->context = context;
+  newstate->entrance_nodes = &newstate->nodes;
+
+  for (i = 0 ; i < nodes->nelem ; i++)
+    {
+      re_token_t *node = dfa->nodes + nodes->elems[i];
+      re_token_type_t type = node->type;
+      unsigned int constraint = node->constraint;
+
+      if (type == CHARACTER && !constraint)
+	continue;
+#ifdef RE_ENABLE_I18N
+      newstate->accept_mb |= node->accept_mb;
+#endif /* RE_ENABLE_I18N */
+
+      /* If the state has the halt node, the state is a halt state.  */
+      if (type == END_OF_RE)
+	newstate->halt = 1;
+      else if (type == OP_BACK_REF)
+	newstate->has_backref = 1;
+
+      if (constraint)
+	{
+	  if (newstate->entrance_nodes == &newstate->nodes)
+	    {
+	      newstate->entrance_nodes = re_malloc (re_node_set, 1);
+	      if (BE (newstate->entrance_nodes == NULL, 0))
+		{
+		  free_state (newstate);
+		  return NULL;
+		}
+	      if (re_node_set_init_copy (newstate->entrance_nodes, nodes)
+		  != REG_NOERROR)
+		return NULL;
+	      nctx_nodes = 0;
+	      newstate->has_constraint = 1;
+	    }
+
+	  if (NOT_SATISFY_PREV_CONSTRAINT (constraint,context))
+	    {
+	      re_node_set_remove_at (&newstate->nodes, i - nctx_nodes);
+	      ++nctx_nodes;
+	    }
+	}
+    }
+  err = register_state (dfa, newstate, hash);
+  if (BE (err != REG_NOERROR, 0))
+    {
+      free_state (newstate);
+      newstate = NULL;
+    }
+  return  newstate;
+}
diff --git a/compat/regex/regex_internal.h b/compat/regex/regex_internal.h
new file mode 100644
index 0000000..0bad8b8
--- /dev/null
+++ b/compat/regex/regex_internal.h
@@ -0,0 +1,808 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2005, 2007, 2008, 2010 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.
+
+   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/>.  */
+
+#ifndef _REGEX_INTERNAL_H
+#define _REGEX_INTERNAL_H 1
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+#if defined HAVE_LANGINFO_H || defined HAVE_LANGINFO_CODESET || defined _LIBC
+# include <langinfo.h>
+#endif
+#if defined HAVE_LOCALE_H || defined _LIBC
+# include <locale.h>
+#endif
+#if defined HAVE_WCHAR_H || defined _LIBC
+# include <wchar.h>
+#endif /* HAVE_WCHAR_H || _LIBC */
+#if defined HAVE_WCTYPE_H || defined _LIBC
+# include <wctype.h>
+#endif /* HAVE_WCTYPE_H || _LIBC */
+#if defined HAVE_STDBOOL_H || defined _LIBC
+# include <stdbool.h>
+#endif /* HAVE_STDBOOL_H || _LIBC */
+#if !defined(ZOS_USS)
+#if defined HAVE_STDINT_H || defined _LIBC
+# include <stdint.h>
+#endif /* HAVE_STDINT_H || _LIBC */
+#endif /* !ZOS_USS */
+#if defined _LIBC
+# include <bits/libc-lock.h>
+#else
+# define __libc_lock_define(CLASS,NAME)
+# define __libc_lock_init(NAME) do { } while (0)
+# define __libc_lock_lock(NAME) do { } while (0)
+# define __libc_lock_unlock(NAME) do { } while (0)
+#endif
+
+#ifndef GAWK
+/* In case that the system doesn't have isblank().  */
+#if !defined _LIBC && !defined HAVE_ISBLANK && !defined isblank
+# define isblank(ch) ((ch) == ' ' || (ch) == '\t')
+#endif
+#else /* GAWK */
+/*
+ * This is a freaking mess. On glibc systems you have to define
+ * a magic constant to get isblank() out of <ctype.h>, since it's
+ * a C99 function.  To heck with all that and borrow a page from
+ * dfa.c's book.
+ */
+
+static int
+is_blank (int c)
+{
+   return (c == ' ' || c == '\t');
+}
+#endif /* GAWK */
+
+#ifdef _LIBC
+# ifndef _RE_DEFINE_LOCALE_FUNCTIONS
+#  define _RE_DEFINE_LOCALE_FUNCTIONS 1
+#   include <locale/localeinfo.h>
+#   include <locale/elem-hash.h>
+#   include <locale/coll-lookup.h>
+# endif
+#endif
+
+/* This is for other GNU distributions with internationalized messages.  */
+#if (HAVE_LIBINTL_H && ENABLE_NLS) || defined _LIBC
+# include <libintl.h>
+# ifdef _LIBC
+#  undef gettext
+#  define gettext(msgid) \
+  INTUSE(__dcgettext) (_libc_intl_domainname, msgid, LC_MESSAGES)
+# endif
+#else
+# define gettext(msgid) (msgid)
+#endif
+
+#ifndef gettext_noop
+/* This define is so xgettext can find the internationalizable
+   strings.  */
+# define gettext_noop(String) String
+#endif
+
+/* For loser systems without the definition.  */
+#ifndef SIZE_MAX
+# define SIZE_MAX ((size_t) -1)
+#endif
+
+#ifndef NO_MBSUPPORT
+#include "mbsupport.h" /* gawk */
+#endif
+#ifndef MB_CUR_MAX
+#define MB_CUR_MAX 1
+#endif
+
+#if (defined MBS_SUPPORT) || _LIBC
+# define RE_ENABLE_I18N
+#endif
+
+#if __GNUC__ >= 3
+# define BE(expr, val) __builtin_expect (expr, val)
+#else
+# define BE(expr, val) (expr)
+# ifdef inline
+# undef inline
+# endif
+# define inline
+#endif
+
+/* Number of single byte character.  */
+#define SBC_MAX 256
+
+#define COLL_ELEM_LEN_MAX 8
+
+/* The character which represents newline.  */
+#define NEWLINE_CHAR '\n'
+#define WIDE_NEWLINE_CHAR L'\n'
+
+/* Rename to standard API for using out of glibc.  */
+#ifndef _LIBC
+# ifdef __wctype
+# undef __wctype
+# endif
+# define __wctype wctype
+# ifdef __iswctype
+# undef __iswctype
+# endif
+# define __iswctype iswctype
+# define __btowc btowc
+# define __mbrtowc mbrtowc
+#undef __mempcpy	/* GAWK */
+# define __mempcpy mempcpy
+# define __wcrtomb wcrtomb
+# define __regfree regfree
+# define attribute_hidden
+#endif /* not _LIBC */
+
+#ifdef __GNUC__
+# define __attribute(arg) __attribute__ (arg)
+#else
+# define __attribute(arg)
+#endif
+
+extern const char __re_error_msgid[] attribute_hidden;
+extern const size_t __re_error_msgid_idx[] attribute_hidden;
+
+/* An integer used to represent a set of bits.  It must be unsigned,
+   and must be at least as wide as unsigned int.  */
+typedef unsigned long int bitset_word_t;
+/* All bits set in a bitset_word_t.  */
+#define BITSET_WORD_MAX ULONG_MAX
+/* Number of bits in a bitset_word_t.  */
+#define BITSET_WORD_BITS (sizeof (bitset_word_t) * CHAR_BIT)
+/* Number of bitset_word_t in a bit_set.  */
+#define BITSET_WORDS (SBC_MAX / BITSET_WORD_BITS)
+typedef bitset_word_t bitset_t[BITSET_WORDS];
+typedef bitset_word_t *re_bitset_ptr_t;
+typedef const bitset_word_t *re_const_bitset_ptr_t;
+
+#define bitset_set(set,i) \
+  (set[i / BITSET_WORD_BITS] |= (bitset_word_t) 1 << i % BITSET_WORD_BITS)
+#define bitset_clear(set,i) \
+  (set[i / BITSET_WORD_BITS] &= ~((bitset_word_t) 1 << i % BITSET_WORD_BITS))
+#define bitset_contain(set,i) \
+  (set[i / BITSET_WORD_BITS] & ((bitset_word_t) 1 << i % BITSET_WORD_BITS))
+#define bitset_empty(set) memset (set, '\0', sizeof (bitset_t))
+#define bitset_set_all(set) memset (set, '\xff', sizeof (bitset_t))
+#define bitset_copy(dest,src) memcpy (dest, src, sizeof (bitset_t))
+
+#define PREV_WORD_CONSTRAINT 0x0001
+#define PREV_NOTWORD_CONSTRAINT 0x0002
+#define NEXT_WORD_CONSTRAINT 0x0004
+#define NEXT_NOTWORD_CONSTRAINT 0x0008
+#define PREV_NEWLINE_CONSTRAINT 0x0010
+#define NEXT_NEWLINE_CONSTRAINT 0x0020
+#define PREV_BEGBUF_CONSTRAINT 0x0040
+#define NEXT_ENDBUF_CONSTRAINT 0x0080
+#define WORD_DELIM_CONSTRAINT 0x0100
+#define NOT_WORD_DELIM_CONSTRAINT 0x0200
+
+typedef enum
+{
+  INSIDE_WORD = PREV_WORD_CONSTRAINT | NEXT_WORD_CONSTRAINT,
+  WORD_FIRST = PREV_NOTWORD_CONSTRAINT | NEXT_WORD_CONSTRAINT,
+  WORD_LAST = PREV_WORD_CONSTRAINT | NEXT_NOTWORD_CONSTRAINT,
+  INSIDE_NOTWORD = PREV_NOTWORD_CONSTRAINT | NEXT_NOTWORD_CONSTRAINT,
+  LINE_FIRST = PREV_NEWLINE_CONSTRAINT,
+  LINE_LAST = NEXT_NEWLINE_CONSTRAINT,
+  BUF_FIRST = PREV_BEGBUF_CONSTRAINT,
+  BUF_LAST = NEXT_ENDBUF_CONSTRAINT,
+  WORD_DELIM = WORD_DELIM_CONSTRAINT,
+  NOT_WORD_DELIM = NOT_WORD_DELIM_CONSTRAINT
+} re_context_type;
+
+typedef struct
+{
+  int alloc;
+  int nelem;
+  int *elems;
+} re_node_set;
+
+typedef enum
+{
+  NON_TYPE = 0,
+
+  /* Node type, These are used by token, node, tree.  */
+  CHARACTER = 1,
+  END_OF_RE = 2,
+  SIMPLE_BRACKET = 3,
+  OP_BACK_REF = 4,
+  OP_PERIOD = 5,
+#ifdef RE_ENABLE_I18N
+  COMPLEX_BRACKET = 6,
+  OP_UTF8_PERIOD = 7,
+#endif /* RE_ENABLE_I18N */
+
+  /* We define EPSILON_BIT as a macro so that OP_OPEN_SUBEXP is used
+     when the debugger shows values of this enum type.  */
+#define EPSILON_BIT 8
+  OP_OPEN_SUBEXP = EPSILON_BIT | 0,
+  OP_CLOSE_SUBEXP = EPSILON_BIT | 1,
+  OP_ALT = EPSILON_BIT | 2,
+  OP_DUP_ASTERISK = EPSILON_BIT | 3,
+  ANCHOR = EPSILON_BIT | 4,
+
+  /* Tree type, these are used only by tree. */
+  CONCAT = 16,
+  SUBEXP = 17,
+
+  /* Token type, these are used only by token.  */
+  OP_DUP_PLUS = 18,
+  OP_DUP_QUESTION,
+  OP_OPEN_BRACKET,
+  OP_CLOSE_BRACKET,
+  OP_CHARSET_RANGE,
+  OP_OPEN_DUP_NUM,
+  OP_CLOSE_DUP_NUM,
+  OP_NON_MATCH_LIST,
+  OP_OPEN_COLL_ELEM,
+  OP_CLOSE_COLL_ELEM,
+  OP_OPEN_EQUIV_CLASS,
+  OP_CLOSE_EQUIV_CLASS,
+  OP_OPEN_CHAR_CLASS,
+  OP_CLOSE_CHAR_CLASS,
+  OP_WORD,
+  OP_NOTWORD,
+  OP_SPACE,
+  OP_NOTSPACE,
+  BACK_SLASH
+
+} re_token_type_t;
+
+#ifdef RE_ENABLE_I18N
+typedef struct
+{
+  /* Multibyte characters.  */
+  wchar_t *mbchars;
+
+  /* Collating symbols.  */
+# ifdef _LIBC
+  int32_t *coll_syms;
+# endif
+
+  /* Equivalence classes. */
+# ifdef _LIBC
+  int32_t *equiv_classes;
+# endif
+
+  /* Range expressions. */
+# ifdef _LIBC
+  uint32_t *range_starts;
+  uint32_t *range_ends;
+# else /* not _LIBC */
+  wchar_t *range_starts;
+  wchar_t *range_ends;
+# endif /* not _LIBC */
+
+  /* Character classes. */
+  wctype_t *char_classes;
+
+  /* If this character set is the non-matching list.  */
+  unsigned int non_match : 1;
+
+  /* # of multibyte characters.  */
+  int nmbchars;
+
+  /* # of collating symbols.  */
+  int ncoll_syms;
+
+  /* # of equivalence classes. */
+  int nequiv_classes;
+
+  /* # of range expressions. */
+  int nranges;
+
+  /* # of character classes. */
+  int nchar_classes;
+} re_charset_t;
+#endif /* RE_ENABLE_I18N */
+
+typedef struct
+{
+  union
+  {
+    unsigned char c;		/* for CHARACTER */
+    re_bitset_ptr_t sbcset;	/* for SIMPLE_BRACKET */
+#ifdef RE_ENABLE_I18N
+    re_charset_t *mbcset;	/* for COMPLEX_BRACKET */
+#endif /* RE_ENABLE_I18N */
+    int idx;			/* for BACK_REF */
+    re_context_type ctx_type;	/* for ANCHOR */
+  } opr;
+#if __GNUC__ >= 2
+  re_token_type_t type : 8;
+#else
+  re_token_type_t type;
+#endif
+  unsigned int constraint : 10;	/* context constraint */
+  unsigned int duplicated : 1;
+  unsigned int opt_subexp : 1;
+#ifdef RE_ENABLE_I18N
+  unsigned int accept_mb : 1;
+  /* These 2 bits can be moved into the union if needed (e.g. if running out
+     of bits; move opr.c to opr.c.c and move the flags to opr.c.flags).  */
+  unsigned int mb_partial : 1;
+#endif
+  unsigned int word_char : 1;
+} re_token_t;
+
+#define IS_EPSILON_NODE(type) ((type) & EPSILON_BIT)
+
+struct re_string_t
+{
+  /* Indicate the raw buffer which is the original string passed as an
+     argument of regexec(), re_search(), etc..  */
+  const unsigned char *raw_mbs;
+  /* Store the multibyte string.  In case of "case insensitive mode" like
+     REG_ICASE, upper cases of the string are stored, otherwise MBS points
+     the same address that RAW_MBS points.  */
+  unsigned char *mbs;
+#ifdef RE_ENABLE_I18N
+  /* Store the wide character string which is corresponding to MBS.  */
+  wint_t *wcs;
+  int *offsets;
+  mbstate_t cur_state;
+#endif
+  /* Index in RAW_MBS.  Each character mbs[i] corresponds to
+     raw_mbs[raw_mbs_idx + i].  */
+  int raw_mbs_idx;
+  /* The length of the valid characters in the buffers.  */
+  int valid_len;
+  /* The corresponding number of bytes in raw_mbs array.  */
+  int valid_raw_len;
+  /* The length of the buffers MBS and WCS.  */
+  int bufs_len;
+  /* The index in MBS, which is updated by re_string_fetch_byte.  */
+  int cur_idx;
+  /* length of RAW_MBS array.  */
+  int raw_len;
+  /* This is RAW_LEN - RAW_MBS_IDX + VALID_LEN - VALID_RAW_LEN.  */
+  int len;
+  /* End of the buffer may be shorter than its length in the cases such
+     as re_match_2, re_search_2.  Then, we use STOP for end of the buffer
+     instead of LEN.  */
+  int raw_stop;
+  /* This is RAW_STOP - RAW_MBS_IDX adjusted through OFFSETS.  */
+  int stop;
+
+  /* The context of mbs[0].  We store the context independently, since
+     the context of mbs[0] may be different from raw_mbs[0], which is
+     the beginning of the input string.  */
+  unsigned int tip_context;
+  /* The translation passed as a part of an argument of re_compile_pattern.  */
+  RE_TRANSLATE_TYPE trans;
+  /* Copy of re_dfa_t's word_char.  */
+  re_const_bitset_ptr_t word_char;
+  /* 1 if REG_ICASE.  */
+  unsigned char icase;
+  unsigned char is_utf8;
+  unsigned char map_notascii;
+  unsigned char mbs_allocated;
+  unsigned char offsets_needed;
+  unsigned char newline_anchor;
+  unsigned char word_ops_used;
+  int mb_cur_max;
+};
+typedef struct re_string_t re_string_t;
+
+
+struct re_dfa_t;
+typedef struct re_dfa_t re_dfa_t;
+
+#ifndef _LIBC
+# ifdef __i386__
+#  define internal_function   __attribute ((regparm (3), stdcall))
+# else
+#  define internal_function
+# endif
+#endif
+
+#ifndef NOT_IN_libc
+static reg_errcode_t re_string_realloc_buffers (re_string_t *pstr,
+						int new_buf_len)
+     internal_function;
+# ifdef RE_ENABLE_I18N
+static void build_wcs_buffer (re_string_t *pstr) internal_function;
+static reg_errcode_t build_wcs_upper_buffer (re_string_t *pstr)
+  internal_function;
+# endif /* RE_ENABLE_I18N */
+static void build_upper_buffer (re_string_t *pstr) internal_function;
+static void re_string_translate_buffer (re_string_t *pstr) internal_function;
+static unsigned int re_string_context_at (const re_string_t *input, int idx,
+					  int eflags)
+     internal_function __attribute ((pure));
+#endif
+#define re_string_peek_byte(pstr, offset) \
+  ((pstr)->mbs[(pstr)->cur_idx + offset])
+#define re_string_fetch_byte(pstr) \
+  ((pstr)->mbs[(pstr)->cur_idx++])
+#define re_string_first_byte(pstr, idx) \
+  ((idx) == (pstr)->valid_len || (pstr)->wcs[idx] != WEOF)
+#define re_string_is_single_byte_char(pstr, idx) \
+  ((pstr)->wcs[idx] != WEOF && ((pstr)->valid_len == (idx) + 1 \
+				|| (pstr)->wcs[(idx) + 1] != WEOF))
+#define re_string_eoi(pstr) ((pstr)->stop <= (pstr)->cur_idx)
+#define re_string_cur_idx(pstr) ((pstr)->cur_idx)
+#define re_string_get_buffer(pstr) ((pstr)->mbs)
+#define re_string_length(pstr) ((pstr)->len)
+#define re_string_byte_at(pstr,idx) ((pstr)->mbs[idx])
+#define re_string_skip_bytes(pstr,idx) ((pstr)->cur_idx += (idx))
+#define re_string_set_index(pstr,idx) ((pstr)->cur_idx = (idx))
+
+#ifndef _LIBC
+# if HAVE_ALLOCA
+#  if (_MSC_VER)
+#   include <malloc.h>
+#   define __libc_use_alloca(n) 0
+#  else
+#   include <alloca.h>
+/* The OS usually guarantees only one guard page at the bottom of the stack,
+   and a page size can be as small as 4096 bytes.  So we cannot safely
+   allocate anything larger than 4096 bytes.  Also care for the possibility
+   of a few compiler-allocated temporary stack slots.  */
+#  define __libc_use_alloca(n) ((n) < 4032)
+#  endif
+# else
+/* alloca is implemented with malloc, so just use malloc.  */
+#  define __libc_use_alloca(n) 0
+# endif
+#endif
+
+#define re_malloc(t,n) ((t *) malloc ((n) * sizeof (t)))
+/* SunOS 4.1.x realloc doesn't accept null pointers: pre-Standard C. Sigh. */
+#define re_realloc(p,t,n) ((p != NULL) ? (t *) realloc (p,(n)*sizeof(t)) : (t *) calloc(n,sizeof(t)))
+#define re_free(p) free (p)
+
+struct bin_tree_t
+{
+  struct bin_tree_t *parent;
+  struct bin_tree_t *left;
+  struct bin_tree_t *right;
+  struct bin_tree_t *first;
+  struct bin_tree_t *next;
+
+  re_token_t token;
+
+  /* `node_idx' is the index in dfa->nodes, if `type' == 0.
+     Otherwise `type' indicate the type of this node.  */
+  int node_idx;
+};
+typedef struct bin_tree_t bin_tree_t;
+
+#define BIN_TREE_STORAGE_SIZE \
+  ((1024 - sizeof (void *)) / sizeof (bin_tree_t))
+
+struct bin_tree_storage_t
+{
+  struct bin_tree_storage_t *next;
+  bin_tree_t data[BIN_TREE_STORAGE_SIZE];
+};
+typedef struct bin_tree_storage_t bin_tree_storage_t;
+
+#define CONTEXT_WORD 1
+#define CONTEXT_NEWLINE (CONTEXT_WORD << 1)
+#define CONTEXT_BEGBUF (CONTEXT_NEWLINE << 1)
+#define CONTEXT_ENDBUF (CONTEXT_BEGBUF << 1)
+
+#define IS_WORD_CONTEXT(c) ((c) & CONTEXT_WORD)
+#define IS_NEWLINE_CONTEXT(c) ((c) & CONTEXT_NEWLINE)
+#define IS_BEGBUF_CONTEXT(c) ((c) & CONTEXT_BEGBUF)
+#define IS_ENDBUF_CONTEXT(c) ((c) & CONTEXT_ENDBUF)
+#define IS_ORDINARY_CONTEXT(c) ((c) == 0)
+
+#define IS_WORD_CHAR(ch) (isalnum (ch) || (ch) == '_')
+#define IS_NEWLINE(ch) ((ch) == NEWLINE_CHAR)
+#define IS_WIDE_WORD_CHAR(ch) (iswalnum (ch) || (ch) == L'_')
+#define IS_WIDE_NEWLINE(ch) ((ch) == WIDE_NEWLINE_CHAR)
+
+#define NOT_SATISFY_PREV_CONSTRAINT(constraint,context) \
+ ((((constraint) & PREV_WORD_CONSTRAINT) && !IS_WORD_CONTEXT (context)) \
+  || ((constraint & PREV_NOTWORD_CONSTRAINT) && IS_WORD_CONTEXT (context)) \
+  || ((constraint & PREV_NEWLINE_CONSTRAINT) && !IS_NEWLINE_CONTEXT (context))\
+  || ((constraint & PREV_BEGBUF_CONSTRAINT) && !IS_BEGBUF_CONTEXT (context)))
+
+#define NOT_SATISFY_NEXT_CONSTRAINT(constraint,context) \
+ ((((constraint) & NEXT_WORD_CONSTRAINT) && !IS_WORD_CONTEXT (context)) \
+  || (((constraint) & NEXT_NOTWORD_CONSTRAINT) && IS_WORD_CONTEXT (context)) \
+  || (((constraint) & NEXT_NEWLINE_CONSTRAINT) && !IS_NEWLINE_CONTEXT (context)) \
+  || (((constraint) & NEXT_ENDBUF_CONSTRAINT) && !IS_ENDBUF_CONTEXT (context)))
+
+struct re_dfastate_t
+{
+  unsigned int hash;
+  re_node_set nodes;
+  re_node_set non_eps_nodes;
+  re_node_set inveclosure;
+  re_node_set *entrance_nodes;
+  struct re_dfastate_t **trtable, **word_trtable;
+  unsigned int context : 4;
+  unsigned int halt : 1;
+  /* If this state can accept `multi byte'.
+     Note that we refer to multibyte characters, and multi character
+     collating elements as `multi byte'.  */
+  unsigned int accept_mb : 1;
+  /* If this state has backreference node(s).  */
+  unsigned int has_backref : 1;
+  unsigned int has_constraint : 1;
+};
+typedef struct re_dfastate_t re_dfastate_t;
+
+struct re_state_table_entry
+{
+  int num;
+  int alloc;
+  re_dfastate_t **array;
+};
+
+/* Array type used in re_sub_match_last_t and re_sub_match_top_t.  */
+
+typedef struct
+{
+  int next_idx;
+  int alloc;
+  re_dfastate_t **array;
+} state_array_t;
+
+/* Store information about the node NODE whose type is OP_CLOSE_SUBEXP.  */
+
+typedef struct
+{
+  int node;
+  int str_idx; /* The position NODE match at.  */
+  state_array_t path;
+} re_sub_match_last_t;
+
+/* Store information about the node NODE whose type is OP_OPEN_SUBEXP.
+   And information about the node, whose type is OP_CLOSE_SUBEXP,
+   corresponding to NODE is stored in LASTS.  */
+
+typedef struct
+{
+  int str_idx;
+  int node;
+  state_array_t *path;
+  int alasts; /* Allocation size of LASTS.  */
+  int nlasts; /* The number of LASTS.  */
+  re_sub_match_last_t **lasts;
+} re_sub_match_top_t;
+
+struct re_backref_cache_entry
+{
+  int node;
+  int str_idx;
+  int subexp_from;
+  int subexp_to;
+  char more;
+  char unused;
+  unsigned short int eps_reachable_subexps_map;
+};
+
+typedef struct
+{
+  /* The string object corresponding to the input string.  */
+  re_string_t input;
+#if defined _LIBC || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L)
+  const re_dfa_t *const dfa;
+#else
+  const re_dfa_t *dfa;
+#endif
+  /* EFLAGS of the argument of regexec.  */
+  int eflags;
+  /* Where the matching ends.  */
+  int match_last;
+  int last_node;
+  /* The state log used by the matcher.  */
+  re_dfastate_t **state_log;
+  int state_log_top;
+  /* Back reference cache.  */
+  int nbkref_ents;
+  int abkref_ents;
+  struct re_backref_cache_entry *bkref_ents;
+  int max_mb_elem_len;
+  int nsub_tops;
+  int asub_tops;
+  re_sub_match_top_t **sub_tops;
+} re_match_context_t;
+
+typedef struct
+{
+  re_dfastate_t **sifted_states;
+  re_dfastate_t **limited_states;
+  int last_node;
+  int last_str_idx;
+  re_node_set limits;
+} re_sift_context_t;
+
+struct re_fail_stack_ent_t
+{
+  int idx;
+  int node;
+  regmatch_t *regs;
+  re_node_set eps_via_nodes;
+};
+
+struct re_fail_stack_t
+{
+  int num;
+  int alloc;
+  struct re_fail_stack_ent_t *stack;
+};
+
+struct re_dfa_t
+{
+  re_token_t *nodes;
+  size_t nodes_alloc;
+  size_t nodes_len;
+  int *nexts;
+  int *org_indices;
+  re_node_set *edests;
+  re_node_set *eclosures;
+  re_node_set *inveclosures;
+  struct re_state_table_entry *state_table;
+  re_dfastate_t *init_state;
+  re_dfastate_t *init_state_word;
+  re_dfastate_t *init_state_nl;
+  re_dfastate_t *init_state_begbuf;
+  bin_tree_t *str_tree;
+  bin_tree_storage_t *str_tree_storage;
+  re_bitset_ptr_t sb_char;
+  int str_tree_storage_idx;
+
+  /* number of subexpressions `re_nsub' is in regex_t.  */
+  unsigned int state_hash_mask;
+  int init_node;
+  int nbackref; /* The number of backreference in this dfa.  */
+
+  /* Bitmap expressing which backreference is used.  */
+  bitset_word_t used_bkref_map;
+  bitset_word_t completed_bkref_map;
+
+  unsigned int has_plural_match : 1;
+  /* If this dfa has "multibyte node", which is a backreference or
+     a node which can accept multibyte character or multi character
+     collating element.  */
+  unsigned int has_mb_node : 1;
+  unsigned int is_utf8 : 1;
+  unsigned int map_notascii : 1;
+  unsigned int word_ops_used : 1;
+  int mb_cur_max;
+  bitset_t word_char;
+  reg_syntax_t syntax;
+  int *subexp_map;
+#ifdef DEBUG
+  char* re_str;
+#endif
+#if defined _LIBC
+  __libc_lock_define (, lock)
+#endif
+};
+
+#define re_node_set_init_empty(set) memset (set, '\0', sizeof (re_node_set))
+#define re_node_set_remove(set,id) \
+  (re_node_set_remove_at (set, re_node_set_contains (set, id) - 1))
+#define re_node_set_empty(p) ((p)->nelem = 0)
+#define re_node_set_free(set) re_free ((set)->elems)
+
+
+typedef enum
+{
+  SB_CHAR,
+  MB_CHAR,
+  EQUIV_CLASS,
+  COLL_SYM,
+  CHAR_CLASS
+} bracket_elem_type;
+
+typedef struct
+{
+  bracket_elem_type type;
+  union
+  {
+    unsigned char ch;
+    unsigned char *name;
+    wchar_t wch;
+  } opr;
+} bracket_elem_t;
+
+
+/* Inline functions for bitset operation.  */
+static inline void
+bitset_not (bitset_t set)
+{
+  int bitset_i;
+  for (bitset_i = 0; bitset_i < BITSET_WORDS; ++bitset_i)
+    set[bitset_i] = ~set[bitset_i];
+}
+
+static inline void
+bitset_merge (bitset_t dest, const bitset_t src)
+{
+  int bitset_i;
+  for (bitset_i = 0; bitset_i < BITSET_WORDS; ++bitset_i)
+    dest[bitset_i] |= src[bitset_i];
+}
+
+static inline void
+bitset_mask (bitset_t dest, const bitset_t src)
+{
+  int bitset_i;
+  for (bitset_i = 0; bitset_i < BITSET_WORDS; ++bitset_i)
+    dest[bitset_i] &= src[bitset_i];
+}
+
+#ifdef RE_ENABLE_I18N
+/* Inline functions for re_string.  */
+static inline int
+internal_function __attribute ((pure))
+re_string_char_size_at (const re_string_t *pstr, int idx)
+{
+  int byte_idx;
+  if (pstr->mb_cur_max == 1)
+    return 1;
+  for (byte_idx = 1; idx + byte_idx < pstr->valid_len; ++byte_idx)
+    if (pstr->wcs[idx + byte_idx] != WEOF)
+      break;
+  return byte_idx;
+}
+
+static inline wint_t
+internal_function __attribute ((pure))
+re_string_wchar_at (const re_string_t *pstr, int idx)
+{
+  if (pstr->mb_cur_max == 1)
+    return (wint_t) pstr->mbs[idx];
+  return (wint_t) pstr->wcs[idx];
+}
+
+# ifndef NOT_IN_libc
+static int
+internal_function __attribute ((pure))
+re_string_elem_size_at (const re_string_t *pstr, int idx)
+{
+#  ifdef _LIBC
+  const unsigned char *p, *extra;
+  const int32_t *table, *indirect;
+  int32_t tmp;
+#   include <locale/weight.h>
+  uint_fast32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+
+  if (nrules != 0)
+    {
+      table = (const int32_t *) _NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
+      extra = (const unsigned char *)
+	_NL_CURRENT (LC_COLLATE, _NL_COLLATE_EXTRAMB);
+      indirect = (const int32_t *) _NL_CURRENT (LC_COLLATE,
+						_NL_COLLATE_INDIRECTMB);
+      p = pstr->mbs + idx;
+      tmp = findidx (&p);
+      return p - pstr->mbs - idx;
+    }
+  else
+#  endif /* _LIBC */
+    return 1;
+}
+# endif
+#endif /* RE_ENABLE_I18N */
+
+#endif /*  _REGEX_INTERNAL_H */
diff --git a/compat/regex/regexec.c b/compat/regex/regexec.c
new file mode 100644
index 0000000..49358ae
--- /dev/null
+++ b/compat/regex/regexec.c
@@ -0,0 +1,4368 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2005, 2007, 2009, 2010 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <isamu@yamato.ibm.com>.
+
+   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/>.  */
+
+static reg_errcode_t match_ctx_init (re_match_context_t *cache, int eflags,
+				     int n) internal_function;
+static void match_ctx_clean (re_match_context_t *mctx) internal_function;
+static void match_ctx_free (re_match_context_t *cache) internal_function;
+static reg_errcode_t match_ctx_add_entry (re_match_context_t *cache, int node,
+					  int str_idx, int from, int to)
+     internal_function;
+static int search_cur_bkref_entry (const re_match_context_t *mctx, int str_idx)
+     internal_function;
+static reg_errcode_t match_ctx_add_subtop (re_match_context_t *mctx, int node,
+					   int str_idx) internal_function;
+static re_sub_match_last_t * match_ctx_add_sublast (re_sub_match_top_t *subtop,
+						   int node, int str_idx)
+     internal_function;
+static void sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
+			   re_dfastate_t **limited_sts, int last_node,
+			   int last_str_idx)
+     internal_function;
+static reg_errcode_t re_search_internal (const regex_t *preg,
+					 const char *string, int length,
+					 int start, int range, int stop,
+					 size_t nmatch, regmatch_t pmatch[],
+					 int eflags);
+static int re_search_2_stub (struct re_pattern_buffer *bufp,
+			     const char *string1, int length1,
+			     const char *string2, int length2,
+			     int start, int range, struct re_registers *regs,
+			     int stop, int ret_len);
+static int re_search_stub (struct re_pattern_buffer *bufp,
+			   const char *string, int length, int start,
+			   int range, int stop, struct re_registers *regs,
+			   int ret_len);
+static unsigned re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
+			      int nregs, int regs_allocated);
+static reg_errcode_t prune_impossible_nodes (re_match_context_t *mctx);
+static int check_matching (re_match_context_t *mctx, int fl_longest_match,
+			   int *p_match_first) internal_function;
+static int check_halt_state_context (const re_match_context_t *mctx,
+				     const re_dfastate_t *state, int idx)
+     internal_function;
+static void update_regs (const re_dfa_t *dfa, regmatch_t *pmatch,
+			 regmatch_t *prev_idx_match, int cur_node,
+			 int cur_idx, int nmatch) internal_function;
+static reg_errcode_t push_fail_stack (struct re_fail_stack_t *fs,
+				      int str_idx, int dest_node, int nregs,
+				      regmatch_t *regs,
+				      re_node_set *eps_via_nodes)
+     internal_function;
+static reg_errcode_t set_regs (const regex_t *preg,
+			       const re_match_context_t *mctx,
+			       size_t nmatch, regmatch_t *pmatch,
+			       int fl_backtrack) internal_function;
+static reg_errcode_t free_fail_stack_return (struct re_fail_stack_t *fs)
+     internal_function;
+
+#ifdef RE_ENABLE_I18N
+static int sift_states_iter_mb (const re_match_context_t *mctx,
+				re_sift_context_t *sctx,
+				int node_idx, int str_idx, int max_str_idx)
+     internal_function;
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t sift_states_backward (const re_match_context_t *mctx,
+					   re_sift_context_t *sctx)
+     internal_function;
+static reg_errcode_t build_sifted_states (const re_match_context_t *mctx,
+					  re_sift_context_t *sctx, int str_idx,
+					  re_node_set *cur_dest)
+     internal_function;
+static reg_errcode_t update_cur_sifted_state (const re_match_context_t *mctx,
+					      re_sift_context_t *sctx,
+					      int str_idx,
+					      re_node_set *dest_nodes)
+     internal_function;
+static reg_errcode_t add_epsilon_src_nodes (const re_dfa_t *dfa,
+					    re_node_set *dest_nodes,
+					    const re_node_set *candidates)
+     internal_function;
+static int check_dst_limits (const re_match_context_t *mctx,
+			     re_node_set *limits,
+			     int dst_node, int dst_idx, int src_node,
+			     int src_idx) internal_function;
+static int check_dst_limits_calc_pos_1 (const re_match_context_t *mctx,
+					int boundaries, int subexp_idx,
+					int from_node, int bkref_idx)
+     internal_function;
+static int check_dst_limits_calc_pos (const re_match_context_t *mctx,
+				      int limit, int subexp_idx,
+				      int node, int str_idx,
+				      int bkref_idx) internal_function;
+static reg_errcode_t check_subexp_limits (const re_dfa_t *dfa,
+					  re_node_set *dest_nodes,
+					  const re_node_set *candidates,
+					  re_node_set *limits,
+					  struct re_backref_cache_entry *bkref_ents,
+					  int str_idx) internal_function;
+static reg_errcode_t sift_states_bkref (const re_match_context_t *mctx,
+					re_sift_context_t *sctx,
+					int str_idx, const re_node_set *candidates)
+     internal_function;
+static reg_errcode_t merge_state_array (const re_dfa_t *dfa,
+					re_dfastate_t **dst,
+					re_dfastate_t **src, int num)
+     internal_function;
+static re_dfastate_t *find_recover_state (reg_errcode_t *err,
+					 re_match_context_t *mctx) internal_function;
+static re_dfastate_t *transit_state (reg_errcode_t *err,
+				     re_match_context_t *mctx,
+				     re_dfastate_t *state) internal_function;
+static re_dfastate_t *merge_state_with_log (reg_errcode_t *err,
+					    re_match_context_t *mctx,
+					    re_dfastate_t *next_state)
+     internal_function;
+static reg_errcode_t check_subexp_matching_top (re_match_context_t *mctx,
+						re_node_set *cur_nodes,
+						int str_idx) internal_function;
+#if 0
+static re_dfastate_t *transit_state_sb (reg_errcode_t *err,
+					re_match_context_t *mctx,
+					re_dfastate_t *pstate)
+     internal_function;
+#endif
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t transit_state_mb (re_match_context_t *mctx,
+				       re_dfastate_t *pstate)
+     internal_function;
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t transit_state_bkref (re_match_context_t *mctx,
+					  const re_node_set *nodes)
+     internal_function;
+static reg_errcode_t get_subexp (re_match_context_t *mctx,
+				 int bkref_node, int bkref_str_idx)
+     internal_function;
+static reg_errcode_t get_subexp_sub (re_match_context_t *mctx,
+				     const re_sub_match_top_t *sub_top,
+				     re_sub_match_last_t *sub_last,
+				     int bkref_node, int bkref_str)
+     internal_function;
+static int find_subexp_node (const re_dfa_t *dfa, const re_node_set *nodes,
+			     int subexp_idx, int type) internal_function;
+static reg_errcode_t check_arrival (re_match_context_t *mctx,
+				    state_array_t *path, int top_node,
+				    int top_str, int last_node, int last_str,
+				    int type) internal_function;
+static reg_errcode_t check_arrival_add_next_nodes (re_match_context_t *mctx,
+						   int str_idx,
+						   re_node_set *cur_nodes,
+						   re_node_set *next_nodes)
+     internal_function;
+static reg_errcode_t check_arrival_expand_ecl (const re_dfa_t *dfa,
+					       re_node_set *cur_nodes,
+					       int ex_subexp, int type)
+     internal_function;
+static reg_errcode_t check_arrival_expand_ecl_sub (const re_dfa_t *dfa,
+						   re_node_set *dst_nodes,
+						   int target, int ex_subexp,
+						   int type) internal_function;
+static reg_errcode_t expand_bkref_cache (re_match_context_t *mctx,
+					 re_node_set *cur_nodes, int cur_str,
+					 int subexp_num, int type)
+     internal_function;
+static int build_trtable (const re_dfa_t *dfa,
+			  re_dfastate_t *state) internal_function;
+#ifdef RE_ENABLE_I18N
+static int check_node_accept_bytes (const re_dfa_t *dfa, int node_idx,
+				    const re_string_t *input, int idx)
+     internal_function;
+# ifdef _LIBC
+static unsigned int find_collation_sequence_value (const unsigned char *mbs,
+						   size_t name_len)
+     internal_function;
+# endif /* _LIBC */
+#endif /* RE_ENABLE_I18N */
+static int group_nodes_into_DFAstates (const re_dfa_t *dfa,
+				       const re_dfastate_t *state,
+				       re_node_set *states_node,
+				       bitset_t *states_ch) internal_function;
+static int check_node_accept (const re_match_context_t *mctx,
+			      const re_token_t *node, int idx)
+     internal_function;
+static reg_errcode_t extend_buffers (re_match_context_t *mctx)
+     internal_function;
+
+/* Entry point for POSIX code.  */
+
+/* regexec searches for a given pattern, specified by PREG, in the
+   string STRING.
+
+   If NMATCH is zero or REG_NOSUB was set in the cflags argument to
+   `regcomp', we ignore PMATCH.  Otherwise, we assume PMATCH has at
+   least NMATCH elements, and we set them to the offsets of the
+   corresponding matched substrings.
+
+   EFLAGS specifies `execution flags' which affect matching: if
+   REG_NOTBOL is set, then ^ does not match at the beginning of the
+   string; if REG_NOTEOL is set, then $ does not match at the end.
+
+   We return 0 if we find a match and REG_NOMATCH if not.  */
+
+int
+regexec (
+	const regex_t *__restrict preg,
+	const char *__restrict string,
+	size_t nmatch,
+	regmatch_t pmatch[],
+	int eflags)
+{
+  reg_errcode_t err;
+  int start, length;
+
+  if (eflags & ~(REG_NOTBOL | REG_NOTEOL | REG_STARTEND))
+    return REG_BADPAT;
+
+  if (eflags & REG_STARTEND)
+    {
+      start = pmatch[0].rm_so;
+      length = pmatch[0].rm_eo;
+    }
+  else
+    {
+      start = 0;
+      length = strlen (string);
+    }
+
+  __libc_lock_lock (dfa->lock);
+  if (preg->no_sub)
+    err = re_search_internal (preg, string, length, start, length - start,
+			      length, 0, NULL, eflags);
+  else
+    err = re_search_internal (preg, string, length, start, length - start,
+			      length, nmatch, pmatch, eflags);
+  __libc_lock_unlock (dfa->lock);
+  return err != REG_NOERROR;
+}
+
+#ifdef _LIBC
+# include <shlib-compat.h>
+versioned_symbol (libc, __regexec, regexec, GLIBC_2_3_4);
+
+# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_3_4)
+__typeof__ (__regexec) __compat_regexec;
+
+int
+attribute_compat_text_section
+__compat_regexec (const regex_t *__restrict preg,
+		  const char *__restrict string, size_t nmatch,
+		  regmatch_t pmatch[], int eflags)
+{
+  return regexec (preg, string, nmatch, pmatch,
+		  eflags & (REG_NOTBOL | REG_NOTEOL));
+}
+compat_symbol (libc, __compat_regexec, regexec, GLIBC_2_0);
+# endif
+#endif
+
+/* Entry points for GNU code.  */
+
+/* re_match, re_search, re_match_2, re_search_2
+
+   The former two functions operate on STRING with length LENGTH,
+   while the later two operate on concatenation of STRING1 and STRING2
+   with lengths LENGTH1 and LENGTH2, respectively.
+
+   re_match() matches the compiled pattern in BUFP against the string,
+   starting at index START.
+
+   re_search() first tries matching at index START, then it tries to match
+   starting from index START + 1, and so on.  The last start position tried
+   is START + RANGE.  (Thus RANGE = 0 forces re_search to operate the same
+   way as re_match().)
+
+   The parameter STOP of re_{match,search}_2 specifies that no match exceeding
+   the first STOP characters of the concatenation of the strings should be
+   concerned.
+
+   If REGS is not NULL, and BUFP->no_sub is not set, the offsets of the match
+   and all groups is stroed in REGS.  (For the "_2" variants, the offsets are
+   computed relative to the concatenation, not relative to the individual
+   strings.)
+
+   On success, re_match* functions return the length of the match, re_search*
+   return the position of the start of the match.  Return value -1 means no
+   match was found and -2 indicates an internal error.  */
+
+int
+re_match (struct re_pattern_buffer *bufp,
+	  const char *string,
+	  int length,
+	  int start,
+	  struct re_registers *regs)
+{
+  return re_search_stub (bufp, string, length, start, 0, length, regs, 1);
+}
+#ifdef _LIBC
+weak_alias (__re_match, re_match)
+#endif
+
+int
+re_search (struct re_pattern_buffer *bufp,
+	   const char *string,
+	   int length, int start, int range,
+	   struct re_registers *regs)
+{
+  return re_search_stub (bufp, string, length, start, range, length, regs, 0);
+}
+#ifdef _LIBC
+weak_alias (__re_search, re_search)
+#endif
+
+int
+re_match_2 (struct re_pattern_buffer *bufp,
+	    const char *string1, int length1,
+	    const char *string2, int length2, int start,
+	    struct re_registers *regs, int stop)
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+			   start, 0, regs, stop, 1);
+}
+#ifdef _LIBC
+weak_alias (__re_match_2, re_match_2)
+#endif
+
+int
+re_search_2 (struct re_pattern_buffer *bufp,
+	     const char *string1, int length1,
+	     const char *string2, int length2, int start,
+	     int range, struct re_registers *regs,  int stop)
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+			   start, range, regs, stop, 0);
+}
+#ifdef _LIBC
+weak_alias (__re_search_2, re_search_2)
+#endif
+
+static int
+re_search_2_stub (struct re_pattern_buffer *bufp,
+		  const char *string1, int length1,
+		  const char *string2, int length2, int start,
+		  int range, struct re_registers *regs,
+		  int stop, int ret_len)
+{
+  const char *str;
+  int rval;
+  int len = length1 + length2;
+  int free_str = 0;
+
+  if (BE (length1 < 0 || length2 < 0 || stop < 0, 0))
+    return -2;
+
+  /* Concatenate the strings.  */
+  if (length2 > 0)
+    if (length1 > 0)
+      {
+	char *s = re_malloc (char, len);
+
+	if (BE (s == NULL, 0))
+	  return -2;
+	memcpy (s, string1, length1);
+	memcpy (s + length1, string2, length2);
+	str = s;
+	free_str = 1;
+      }
+    else
+      str = string2;
+  else
+    str = string1;
+
+  rval = re_search_stub (bufp, str, len, start, range, stop, regs, ret_len);
+  if (free_str)
+    re_free ((char *) str);
+  return rval;
+}
+
+/* The parameters have the same meaning as those of re_search.
+   Additional parameters:
+   If RET_LEN is nonzero the length of the match is returned (re_match style);
+   otherwise the position of the match is returned.  */
+
+static int
+re_search_stub (struct re_pattern_buffer *bufp,
+		const char *string, int length, int start,
+		int range, int stop,
+		struct re_registers *regs, int ret_len)
+{
+  reg_errcode_t result;
+  regmatch_t *pmatch;
+  int nregs, rval;
+  int eflags = 0;
+
+  /* Check for out-of-range.  */
+  if (BE (start < 0 || start > length, 0))
+    return -1;
+  if (BE (start + range > length, 0))
+    range = length - start;
+  else if (BE (start + range < 0, 0))
+    range = -start;
+
+  __libc_lock_lock (dfa->lock);
+
+  eflags |= (bufp->not_bol) ? REG_NOTBOL : 0;
+  eflags |= (bufp->not_eol) ? REG_NOTEOL : 0;
+
+  /* Compile fastmap if we haven't yet.  */
+  if (range > 0 && bufp->fastmap != NULL && !bufp->fastmap_accurate)
+    re_compile_fastmap (bufp);
+
+  if (BE (bufp->no_sub, 0))
+    regs = NULL;
+
+  /* We need at least 1 register.  */
+  if (regs == NULL)
+    nregs = 1;
+  else if (BE (bufp->regs_allocated == REGS_FIXED &&
+	       regs->num_regs < bufp->re_nsub + 1, 0))
+    {
+      nregs = regs->num_regs;
+      if (BE (nregs < 1, 0))
+	{
+	  /* Nothing can be copied to regs.  */
+	  regs = NULL;
+	  nregs = 1;
+	}
+    }
+  else
+    nregs = bufp->re_nsub + 1;
+  pmatch = re_malloc (regmatch_t, nregs);
+  if (BE (pmatch == NULL, 0))
+    {
+      rval = -2;
+      goto out;
+    }
+
+  result = re_search_internal (bufp, string, length, start, range, stop,
+			       nregs, pmatch, eflags);
+
+  rval = 0;
+
+  /* I hope we needn't fill their regs with -1's when no match was found.  */
+  if (result != REG_NOERROR)
+    rval = -1;
+  else if (regs != NULL)
+    {
+      /* If caller wants register contents data back, copy them.  */
+      bufp->regs_allocated = re_copy_regs (regs, pmatch, nregs,
+					   bufp->regs_allocated);
+      if (BE (bufp->regs_allocated == REGS_UNALLOCATED, 0))
+	rval = -2;
+    }
+
+  if (BE (rval == 0, 1))
+    {
+      if (ret_len)
+	{
+	  assert (pmatch[0].rm_so == start);
+	  rval = pmatch[0].rm_eo - start;
+	}
+      else
+	rval = pmatch[0].rm_so;
+    }
+  re_free (pmatch);
+ out:
+  __libc_lock_unlock (dfa->lock);
+  return rval;
+}
+
+static unsigned
+re_copy_regs (struct re_registers *regs,
+	      regmatch_t *pmatch,
+	      int nregs, int regs_allocated)
+{
+  int rval = REGS_REALLOCATE;
+  int i;
+  int need_regs = nregs + 1;
+  /* We need one extra element beyond `num_regs' for the `-1' marker GNU code
+     uses.  */
+
+  /* Have the register data arrays been allocated?  */
+  if (regs_allocated == REGS_UNALLOCATED)
+    { /* No.  So allocate them with malloc.  */
+      regs->start = re_malloc (regoff_t, need_regs);
+      if (BE (regs->start == NULL, 0))
+	return REGS_UNALLOCATED;
+      regs->end = re_malloc (regoff_t, need_regs);
+      if (BE (regs->end == NULL, 0))
+	{
+	  re_free (regs->start);
+	  return REGS_UNALLOCATED;
+	}
+      regs->num_regs = need_regs;
+    }
+  else if (regs_allocated == REGS_REALLOCATE)
+    { /* Yes.  If we need more elements than were already
+	 allocated, reallocate them.  If we need fewer, just
+	 leave it alone.  */
+      if (BE (need_regs > regs->num_regs, 0))
+	{
+	  regoff_t *new_start = re_realloc (regs->start, regoff_t, need_regs);
+	  regoff_t *new_end;
+	  if (BE (new_start == NULL, 0))
+	    return REGS_UNALLOCATED;
+	  new_end = re_realloc (regs->end, regoff_t, need_regs);
+	  if (BE (new_end == NULL, 0))
+	    {
+	      re_free (new_start);
+	      return REGS_UNALLOCATED;
+	    }
+	  regs->start = new_start;
+	  regs->end = new_end;
+	  regs->num_regs = need_regs;
+	}
+    }
+  else
+    {
+      assert (regs_allocated == REGS_FIXED);
+      /* This function may not be called with REGS_FIXED and nregs too big.  */
+      assert (regs->num_regs >= nregs);
+      rval = REGS_FIXED;
+    }
+
+  /* Copy the regs.  */
+  for (i = 0; i < nregs; ++i)
+    {
+      regs->start[i] = pmatch[i].rm_so;
+      regs->end[i] = pmatch[i].rm_eo;
+    }
+  for ( ; i < regs->num_regs; ++i)
+    regs->start[i] = regs->end[i] = -1;
+
+  return rval;
+}
+
+/* Set REGS to hold NUM_REGS registers, storing them in STARTS and
+   ENDS.  Subsequent matches using PATTERN_BUFFER and REGS will use
+   this memory for recording register information.  STARTS and ENDS
+   must be allocated using the malloc library routine, and must each
+   be at least NUM_REGS * sizeof (regoff_t) bytes long.
+
+   If NUM_REGS == 0, then subsequent matches should allocate their own
+   register data.
+
+   Unless this function is called, the first search or match using
+   PATTERN_BUFFER will allocate its own register data, without
+   freeing the old data.  */
+
+void
+re_set_registers (struct re_pattern_buffer *bufp,
+		  struct re_registers *regs,
+		  unsigned num_regs,
+		  regoff_t *starts,
+		  regoff_t *ends)
+{
+  if (num_regs)
+    {
+      bufp->regs_allocated = REGS_REALLOCATE;
+      regs->num_regs = num_regs;
+      regs->start = starts;
+      regs->end = ends;
+    }
+  else
+    {
+      bufp->regs_allocated = REGS_UNALLOCATED;
+      regs->num_regs = 0;
+      regs->start = regs->end = (regoff_t *) 0;
+    }
+}
+#ifdef _LIBC
+weak_alias (__re_set_registers, re_set_registers)
+#endif
+
+/* Entry points compatible with 4.2 BSD regex library.  We don't define
+   them unless specifically requested.  */
+
+#if defined _REGEX_RE_COMP || defined _LIBC
+int
+# ifdef _LIBC
+weak_function
+# endif
+re_exec (s)
+     const char *s;
+{
+  return 0 == regexec (&re_comp_buf, s, 0, NULL, 0);
+}
+#endif /* _REGEX_RE_COMP */
+
+/* Internal entry point.  */
+
+/* Searches for a compiled pattern PREG in the string STRING, whose
+   length is LENGTH.  NMATCH, PMATCH, and EFLAGS have the same
+   mingings with regexec.  START, and RANGE have the same meanings
+   with re_search.
+   Return REG_NOERROR if we find a match, and REG_NOMATCH if not,
+   otherwise return the error code.
+   Note: We assume front end functions already check ranges.
+   (START + RANGE >= 0 && START + RANGE <= LENGTH)  */
+
+static reg_errcode_t
+re_search_internal (const regex_t *preg,
+		    const char *string,
+		    int length, int start, int range, int stop,
+		    size_t nmatch, regmatch_t pmatch[],
+		    int eflags)
+{
+  reg_errcode_t err;
+  const re_dfa_t *dfa = (const re_dfa_t *) preg->buffer;
+  int left_lim, right_lim, incr;
+  int fl_longest_match, match_first, match_kind, match_last = -1;
+  int extra_nmatch;
+  int sb, ch;
+#if defined _LIBC || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L)
+  re_match_context_t mctx = { .dfa = dfa };
+#else
+  re_match_context_t mctx;
+#endif
+  char *fastmap = (preg->fastmap != NULL && preg->fastmap_accurate
+		   && range && !preg->can_be_null) ? preg->fastmap : NULL;
+  RE_TRANSLATE_TYPE t = preg->translate;
+
+#if !(defined _LIBC || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
+  memset (&mctx, '\0', sizeof (re_match_context_t));
+  mctx.dfa = dfa;
+#endif
+
+  extra_nmatch = (nmatch > preg->re_nsub) ? nmatch - (preg->re_nsub + 1) : 0;
+  nmatch -= extra_nmatch;
+
+  /* Check if the DFA haven't been compiled.  */
+  if (BE (preg->used == 0 || dfa->init_state == NULL
+	  || dfa->init_state_word == NULL || dfa->init_state_nl == NULL
+	  || dfa->init_state_begbuf == NULL, 0))
+    return REG_NOMATCH;
+
+#ifdef DEBUG
+  /* We assume front-end functions already check them.  */
+  assert (start + range >= 0 && start + range <= length);
+#endif
+
+  /* If initial states with non-begbuf contexts have no elements,
+     the regex must be anchored.  If preg->newline_anchor is set,
+     we'll never use init_state_nl, so do not check it.  */
+  if (dfa->init_state->nodes.nelem == 0
+      && dfa->init_state_word->nodes.nelem == 0
+      && (dfa->init_state_nl->nodes.nelem == 0
+	  || !preg->newline_anchor))
+    {
+      if (start != 0 && start + range != 0)
+	return REG_NOMATCH;
+      start = range = 0;
+    }
+
+  /* We must check the longest matching, if nmatch > 0.  */
+  fl_longest_match = (nmatch != 0 || dfa->nbackref);
+
+  err = re_string_allocate (&mctx.input, string, length, dfa->nodes_len + 1,
+			    preg->translate, preg->syntax & RE_ICASE, dfa);
+  if (BE (err != REG_NOERROR, 0))
+    goto free_return;
+  mctx.input.stop = stop;
+  mctx.input.raw_stop = stop;
+  mctx.input.newline_anchor = preg->newline_anchor;
+
+  err = match_ctx_init (&mctx, eflags, dfa->nbackref * 2);
+  if (BE (err != REG_NOERROR, 0))
+    goto free_return;
+
+  /* We will log all the DFA states through which the dfa pass,
+     if nmatch > 1, or this dfa has "multibyte node", which is a
+     back-reference or a node which can accept multibyte character or
+     multi character collating element.  */
+  if (nmatch > 1 || dfa->has_mb_node)
+    {
+      /* Avoid overflow.  */
+      if (BE (SIZE_MAX / sizeof (re_dfastate_t *) <= mctx.input.bufs_len, 0))
+	{
+	  err = REG_ESPACE;
+	  goto free_return;
+	}
+
+      mctx.state_log = re_malloc (re_dfastate_t *, mctx.input.bufs_len + 1);
+      if (BE (mctx.state_log == NULL, 0))
+	{
+	  err = REG_ESPACE;
+	  goto free_return;
+	}
+    }
+  else
+    mctx.state_log = NULL;
+
+  match_first = start;
+  mctx.input.tip_context = (eflags & REG_NOTBOL) ? CONTEXT_BEGBUF
+			   : CONTEXT_NEWLINE | CONTEXT_BEGBUF;
+
+  /* Check incrementally whether of not the input string match.  */
+  incr = (range < 0) ? -1 : 1;
+  left_lim = (range < 0) ? start + range : start;
+  right_lim = (range < 0) ? start : start + range;
+  sb = dfa->mb_cur_max == 1;
+  match_kind =
+    (fastmap
+     ? ((sb || !(preg->syntax & RE_ICASE || t) ? 4 : 0)
+	| (range >= 0 ? 2 : 0)
+	| (t != NULL ? 1 : 0))
+     : 8);
+
+  for (;; match_first += incr)
+    {
+      err = REG_NOMATCH;
+      if (match_first < left_lim || right_lim < match_first)
+	goto free_return;
+
+      /* Advance as rapidly as possible through the string, until we
+	 find a plausible place to start matching.  This may be done
+	 with varying efficiency, so there are various possibilities:
+	 only the most common of them are specialized, in order to
+	 save on code size.  We use a switch statement for speed.  */
+      switch (match_kind)
+	{
+	case 8:
+	  /* No fastmap.  */
+	  break;
+
+	case 7:
+	  /* Fastmap with single-byte translation, match forward.  */
+	  while (BE (match_first < right_lim, 1)
+		 && !fastmap[t[(unsigned char) string[match_first]]])
+	    ++match_first;
+	  goto forward_match_found_start_or_reached_end;
+
+	case 6:
+	  /* Fastmap without translation, match forward.  */
+	  while (BE (match_first < right_lim, 1)
+		 && !fastmap[(unsigned char) string[match_first]])
+	    ++match_first;
+
+	forward_match_found_start_or_reached_end:
+	  if (BE (match_first == right_lim, 0))
+	    {
+	      ch = match_first >= length
+		       ? 0 : (unsigned char) string[match_first];
+	      if (!fastmap[t ? t[ch] : ch])
+		goto free_return;
+	    }
+	  break;
+
+	case 4:
+	case 5:
+	  /* Fastmap without multi-byte translation, match backwards.  */
+	  while (match_first >= left_lim)
+	    {
+	      ch = match_first >= length
+		       ? 0 : (unsigned char) string[match_first];
+	      if (fastmap[t ? t[ch] : ch])
+		break;
+	      --match_first;
+	    }
+	  if (match_first < left_lim)
+	    goto free_return;
+	  break;
+
+	default:
+	  /* In this case, we can't determine easily the current byte,
+	     since it might be a component byte of a multibyte
+	     character.  Then we use the constructed buffer instead.  */
+	  for (;;)
+	    {
+	      /* If MATCH_FIRST is out of the valid range, reconstruct the
+		 buffers.  */
+	      unsigned int offset = match_first - mctx.input.raw_mbs_idx;
+	      if (BE (offset >= (unsigned int) mctx.input.valid_raw_len, 0))
+		{
+		  err = re_string_reconstruct (&mctx.input, match_first,
+					       eflags);
+		  if (BE (err != REG_NOERROR, 0))
+		    goto free_return;
+
+		  offset = match_first - mctx.input.raw_mbs_idx;
+		}
+	      /* If MATCH_FIRST is out of the buffer, leave it as '\0'.
+		 Note that MATCH_FIRST must not be smaller than 0.  */
+	      ch = (match_first >= length
+		    ? 0 : re_string_byte_at (&mctx.input, offset));
+	      if (fastmap[ch])
+		break;
+	      match_first += incr;
+	      if (match_first < left_lim || match_first > right_lim)
+		{
+		  err = REG_NOMATCH;
+		  goto free_return;
+		}
+	    }
+	  break;
+	}
+
+      /* Reconstruct the buffers so that the matcher can assume that
+	 the matching starts from the beginning of the buffer.  */
+      err = re_string_reconstruct (&mctx.input, match_first, eflags);
+      if (BE (err != REG_NOERROR, 0))
+	goto free_return;
+
+#ifdef RE_ENABLE_I18N
+     /* Don't consider this char as a possible match start if it part,
+	yet isn't the head, of a multibyte character.  */
+      if (!sb && !re_string_first_byte (&mctx.input, 0))
+	continue;
+#endif
+
+      /* It seems to be appropriate one, then use the matcher.  */
+      /* We assume that the matching starts from 0.  */
+      mctx.state_log_top = mctx.nbkref_ents = mctx.max_mb_elem_len = 0;
+      match_last = check_matching (&mctx, fl_longest_match,
+				   range >= 0 ? &match_first : NULL);
+      if (match_last != -1)
+	{
+	  if (BE (match_last == -2, 0))
+	    {
+	      err = REG_ESPACE;
+	      goto free_return;
+	    }
+	  else
+	    {
+	      mctx.match_last = match_last;
+	      if ((!preg->no_sub && nmatch > 1) || dfa->nbackref)
+		{
+		  re_dfastate_t *pstate = mctx.state_log[match_last];
+		  mctx.last_node = check_halt_state_context (&mctx, pstate,
+							     match_last);
+		}
+	      if ((!preg->no_sub && nmatch > 1 && dfa->has_plural_match)
+		  || dfa->nbackref)
+		{
+		  err = prune_impossible_nodes (&mctx);
+		  if (err == REG_NOERROR)
+		    break;
+		  if (BE (err != REG_NOMATCH, 0))
+		    goto free_return;
+		  match_last = -1;
+		}
+	      else
+		break; /* We found a match.  */
+	    }
+	}
+
+      match_ctx_clean (&mctx);
+    }
+
+#ifdef DEBUG
+  assert (match_last != -1);
+  assert (err == REG_NOERROR);
+#endif
+
+  /* Set pmatch[] if we need.  */
+  if (nmatch > 0)
+    {
+      int reg_idx;
+
+      /* Initialize registers.  */
+      for (reg_idx = 1; reg_idx < nmatch; ++reg_idx)
+	pmatch[reg_idx].rm_so = pmatch[reg_idx].rm_eo = -1;
+
+      /* Set the points where matching start/end.  */
+      pmatch[0].rm_so = 0;
+      pmatch[0].rm_eo = mctx.match_last;
+
+      if (!preg->no_sub && nmatch > 1)
+	{
+	  err = set_regs (preg, &mctx, nmatch, pmatch,
+			  dfa->has_plural_match && dfa->nbackref > 0);
+	  if (BE (err != REG_NOERROR, 0))
+	    goto free_return;
+	}
+
+      /* At last, add the offset to the each registers, since we slided
+	 the buffers so that we could assume that the matching starts
+	 from 0.  */
+      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
+	if (pmatch[reg_idx].rm_so != -1)
+	  {
+#ifdef RE_ENABLE_I18N
+	    if (BE (mctx.input.offsets_needed != 0, 0))
+	      {
+		pmatch[reg_idx].rm_so =
+		  (pmatch[reg_idx].rm_so == mctx.input.valid_len
+		   ? mctx.input.valid_raw_len
+		   : mctx.input.offsets[pmatch[reg_idx].rm_so]);
+		pmatch[reg_idx].rm_eo =
+		  (pmatch[reg_idx].rm_eo == mctx.input.valid_len
+		   ? mctx.input.valid_raw_len
+		   : mctx.input.offsets[pmatch[reg_idx].rm_eo]);
+	      }
+#else
+	    assert (mctx.input.offsets_needed == 0);
+#endif
+	    pmatch[reg_idx].rm_so += match_first;
+	    pmatch[reg_idx].rm_eo += match_first;
+	  }
+      for (reg_idx = 0; reg_idx < extra_nmatch; ++reg_idx)
+	{
+	  pmatch[nmatch + reg_idx].rm_so = -1;
+	  pmatch[nmatch + reg_idx].rm_eo = -1;
+	}
+
+      if (dfa->subexp_map)
+	for (reg_idx = 0; reg_idx + 1 < nmatch; reg_idx++)
+	  if (dfa->subexp_map[reg_idx] != reg_idx)
+	    {
+	      pmatch[reg_idx + 1].rm_so
+		= pmatch[dfa->subexp_map[reg_idx] + 1].rm_so;
+	      pmatch[reg_idx + 1].rm_eo
+		= pmatch[dfa->subexp_map[reg_idx] + 1].rm_eo;
+	    }
+    }
+
+ free_return:
+  re_free (mctx.state_log);
+  if (dfa->nbackref)
+    match_ctx_free (&mctx);
+  re_string_destruct (&mctx.input);
+  return err;
+}
+
+static reg_errcode_t
+prune_impossible_nodes (re_match_context_t *mctx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int halt_node, match_last;
+  reg_errcode_t ret;
+  re_dfastate_t **sifted_states;
+  re_dfastate_t **lim_states = NULL;
+  re_sift_context_t sctx;
+#ifdef DEBUG
+  assert (mctx->state_log != NULL);
+#endif
+  match_last = mctx->match_last;
+  halt_node = mctx->last_node;
+
+  /* Avoid overflow.  */
+  if (BE (SIZE_MAX / sizeof (re_dfastate_t *) <= match_last, 0))
+    return REG_ESPACE;
+
+  sifted_states = re_malloc (re_dfastate_t *, match_last + 1);
+  if (BE (sifted_states == NULL, 0))
+    {
+      ret = REG_ESPACE;
+      goto free_return;
+    }
+  if (dfa->nbackref)
+    {
+      lim_states = re_malloc (re_dfastate_t *, match_last + 1);
+      if (BE (lim_states == NULL, 0))
+	{
+	  ret = REG_ESPACE;
+	  goto free_return;
+	}
+      while (1)
+	{
+	  memset (lim_states, '\0',
+		  sizeof (re_dfastate_t *) * (match_last + 1));
+	  sift_ctx_init (&sctx, sifted_states, lim_states, halt_node,
+			 match_last);
+	  ret = sift_states_backward (mctx, &sctx);
+	  re_node_set_free (&sctx.limits);
+	  if (BE (ret != REG_NOERROR, 0))
+	      goto free_return;
+	  if (sifted_states[0] != NULL || lim_states[0] != NULL)
+	    break;
+	  do
+	    {
+	      --match_last;
+	      if (match_last < 0)
+		{
+		  ret = REG_NOMATCH;
+		  goto free_return;
+		}
+	    } while (mctx->state_log[match_last] == NULL
+		     || !mctx->state_log[match_last]->halt);
+	  halt_node = check_halt_state_context (mctx,
+						mctx->state_log[match_last],
+						match_last);
+	}
+      ret = merge_state_array (dfa, sifted_states, lim_states,
+			       match_last + 1);
+      re_free (lim_states);
+      lim_states = NULL;
+      if (BE (ret != REG_NOERROR, 0))
+	goto free_return;
+    }
+  else
+    {
+      sift_ctx_init (&sctx, sifted_states, lim_states, halt_node, match_last);
+      ret = sift_states_backward (mctx, &sctx);
+      re_node_set_free (&sctx.limits);
+      if (BE (ret != REG_NOERROR, 0))
+	goto free_return;
+      if (sifted_states[0] == NULL)
+	{
+	  ret = REG_NOMATCH;
+	  goto free_return;
+	}
+    }
+  re_free (mctx->state_log);
+  mctx->state_log = sifted_states;
+  sifted_states = NULL;
+  mctx->last_node = halt_node;
+  mctx->match_last = match_last;
+  ret = REG_NOERROR;
+ free_return:
+  re_free (sifted_states);
+  re_free (lim_states);
+  return ret;
+}
+
+/* Acquire an initial state and return it.
+   We must select appropriate initial state depending on the context,
+   since initial states may have constraints like "\<", "^", etc..  */
+
+static inline re_dfastate_t *
+__attribute ((always_inline)) internal_function
+acquire_init_state_context (reg_errcode_t *err, const re_match_context_t *mctx,
+			    int idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  if (dfa->init_state->has_constraint)
+    {
+      unsigned int context;
+      context = re_string_context_at (&mctx->input, idx - 1, mctx->eflags);
+      if (IS_WORD_CONTEXT (context))
+	return dfa->init_state_word;
+      else if (IS_ORDINARY_CONTEXT (context))
+	return dfa->init_state;
+      else if (IS_BEGBUF_CONTEXT (context) && IS_NEWLINE_CONTEXT (context))
+	return dfa->init_state_begbuf;
+      else if (IS_NEWLINE_CONTEXT (context))
+	return dfa->init_state_nl;
+      else if (IS_BEGBUF_CONTEXT (context))
+	{
+	  /* It is relatively rare case, then calculate on demand.  */
+	  return re_acquire_state_context (err, dfa,
+					   dfa->init_state->entrance_nodes,
+					   context);
+	}
+      else
+	/* Must not happen?  */
+	return dfa->init_state;
+    }
+  else
+    return dfa->init_state;
+}
+
+/* Check whether the regular expression match input string INPUT or not,
+   and return the index where the matching end, return -1 if not match,
+   or return -2 in case of an error.
+   FL_LONGEST_MATCH means we want the POSIX longest matching.
+   If P_MATCH_FIRST is not NULL, and the match fails, it is set to the
+   next place where we may want to try matching.
+   Note that the matcher assume that the matching starts from the current
+   index of the buffer.  */
+
+static int
+internal_function
+check_matching (re_match_context_t *mctx, int fl_longest_match,
+		int *p_match_first)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  int match = 0;
+  int match_last = -1;
+  int cur_str_idx = re_string_cur_idx (&mctx->input);
+  re_dfastate_t *cur_state;
+  int at_init_state = p_match_first != NULL;
+  int next_start_idx = cur_str_idx;
+
+  err = REG_NOERROR;
+  cur_state = acquire_init_state_context (&err, mctx, cur_str_idx);
+  /* An initial state must not be NULL (invalid).  */
+  if (BE (cur_state == NULL, 0))
+    {
+      assert (err == REG_ESPACE);
+      return -2;
+    }
+
+  if (mctx->state_log != NULL)
+    {
+      mctx->state_log[cur_str_idx] = cur_state;
+
+      /* Check OP_OPEN_SUBEXP in the initial state in case that we use them
+	 later.  E.g. Processing back references.  */
+      if (BE (dfa->nbackref, 0))
+	{
+	  at_init_state = 0;
+	  err = check_subexp_matching_top (mctx, &cur_state->nodes, 0);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+
+	  if (cur_state->has_backref)
+	    {
+	      err = transit_state_bkref (mctx, &cur_state->nodes);
+	      if (BE (err != REG_NOERROR, 0))
+		return err;
+	    }
+	}
+    }
+
+  /* If the RE accepts NULL string.  */
+  if (BE (cur_state->halt, 0))
+    {
+      if (!cur_state->has_constraint
+	  || check_halt_state_context (mctx, cur_state, cur_str_idx))
+	{
+	  if (!fl_longest_match)
+	    return cur_str_idx;
+	  else
+	    {
+	      match_last = cur_str_idx;
+	      match = 1;
+	    }
+	}
+    }
+
+  while (!re_string_eoi (&mctx->input))
+    {
+      re_dfastate_t *old_state = cur_state;
+      int next_char_idx = re_string_cur_idx (&mctx->input) + 1;
+
+      if (BE (next_char_idx >= mctx->input.bufs_len, 0)
+	  || (BE (next_char_idx >= mctx->input.valid_len, 0)
+	      && mctx->input.valid_len < mctx->input.len))
+	{
+	  err = extend_buffers (mctx);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      assert (err == REG_ESPACE);
+	      return -2;
+	    }
+	}
+
+      cur_state = transit_state (&err, mctx, cur_state);
+      if (mctx->state_log != NULL)
+	cur_state = merge_state_with_log (&err, mctx, cur_state);
+
+      if (cur_state == NULL)
+	{
+	  /* Reached the invalid state or an error.  Try to recover a valid
+	     state using the state log, if available and if we have not
+	     already found a valid (even if not the longest) match.  */
+	  if (BE (err != REG_NOERROR, 0))
+	    return -2;
+
+	  if (mctx->state_log == NULL
+	      || (match && !fl_longest_match)
+	      || (cur_state = find_recover_state (&err, mctx)) == NULL)
+	    break;
+	}
+
+      if (BE (at_init_state, 0))
+	{
+	  if (old_state == cur_state)
+	    next_start_idx = next_char_idx;
+	  else
+	    at_init_state = 0;
+	}
+
+      if (cur_state->halt)
+	{
+	  /* Reached a halt state.
+	     Check the halt state can satisfy the current context.  */
+	  if (!cur_state->has_constraint
+	      || check_halt_state_context (mctx, cur_state,
+					   re_string_cur_idx (&mctx->input)))
+	    {
+	      /* We found an appropriate halt state.  */
+	      match_last = re_string_cur_idx (&mctx->input);
+	      match = 1;
+
+	      /* We found a match, do not modify match_first below.  */
+	      p_match_first = NULL;
+	      if (!fl_longest_match)
+		break;
+	    }
+	}
+    }
+
+  if (p_match_first)
+    *p_match_first += next_start_idx;
+
+  return match_last;
+}
+
+/* Check NODE match the current context.  */
+
+static int
+internal_function
+check_halt_node_context (const re_dfa_t *dfa, int node, unsigned int context)
+{
+  re_token_type_t type = dfa->nodes[node].type;
+  unsigned int constraint = dfa->nodes[node].constraint;
+  if (type != END_OF_RE)
+    return 0;
+  if (!constraint)
+    return 1;
+  if (NOT_SATISFY_NEXT_CONSTRAINT (constraint, context))
+    return 0;
+  return 1;
+}
+
+/* Check the halt state STATE match the current context.
+   Return 0 if not match, if the node, STATE has, is a halt node and
+   match the context, return the node.  */
+
+static int
+internal_function
+check_halt_state_context (const re_match_context_t *mctx,
+			  const re_dfastate_t *state, int idx)
+{
+  int i;
+  unsigned int context;
+#ifdef DEBUG
+  assert (state->halt);
+#endif
+  context = re_string_context_at (&mctx->input, idx, mctx->eflags);
+  for (i = 0; i < state->nodes.nelem; ++i)
+    if (check_halt_node_context (mctx->dfa, state->nodes.elems[i], context))
+      return state->nodes.elems[i];
+  return 0;
+}
+
+/* Compute the next node to which "NFA" transit from NODE("NFA" is a NFA
+   corresponding to the DFA).
+   Return the destination node, and update EPS_VIA_NODES, return -1 in case
+   of errors.  */
+
+static int
+internal_function
+proceed_next_node (const re_match_context_t *mctx, int nregs, regmatch_t *regs,
+		   int *pidx, int node, re_node_set *eps_via_nodes,
+		   struct re_fail_stack_t *fs)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int i, err;
+  if (IS_EPSILON_NODE (dfa->nodes[node].type))
+    {
+      re_node_set *cur_nodes = &mctx->state_log[*pidx]->nodes;
+      re_node_set *edests = &dfa->edests[node];
+      int dest_node;
+      err = re_node_set_insert (eps_via_nodes, node);
+      if (BE (err < 0, 0))
+	return -2;
+      /* Pick up a valid destination, or return -1 if none is found.  */
+      for (dest_node = -1, i = 0; i < edests->nelem; ++i)
+	{
+	  int candidate = edests->elems[i];
+	  if (!re_node_set_contains (cur_nodes, candidate))
+	    continue;
+	  if (dest_node == -1)
+	    dest_node = candidate;
+
+	  else
+	    {
+	      /* In order to avoid infinite loop like "(a*)*", return the second
+		 epsilon-transition if the first was already considered.  */
+	      if (re_node_set_contains (eps_via_nodes, dest_node))
+		return candidate;
+
+	      /* Otherwise, push the second epsilon-transition on the fail stack.  */
+	      else if (fs != NULL
+		       && push_fail_stack (fs, *pidx, candidate, nregs, regs,
+					   eps_via_nodes))
+		return -2;
+
+	      /* We know we are going to exit.  */
+	      break;
+	    }
+	}
+      return dest_node;
+    }
+  else
+    {
+      int naccepted = 0;
+      re_token_type_t type = dfa->nodes[node].type;
+
+#ifdef RE_ENABLE_I18N
+      if (dfa->nodes[node].accept_mb)
+	naccepted = check_node_accept_bytes (dfa, node, &mctx->input, *pidx);
+      else
+#endif /* RE_ENABLE_I18N */
+      if (type == OP_BACK_REF)
+	{
+	  int subexp_idx = dfa->nodes[node].opr.idx + 1;
+	  naccepted = regs[subexp_idx].rm_eo - regs[subexp_idx].rm_so;
+	  if (fs != NULL)
+	    {
+	      if (regs[subexp_idx].rm_so == -1 || regs[subexp_idx].rm_eo == -1)
+		return -1;
+	      else if (naccepted)
+		{
+		  char *buf = (char *) re_string_get_buffer (&mctx->input);
+		  if (memcmp (buf + regs[subexp_idx].rm_so, buf + *pidx,
+			      naccepted) != 0)
+		    return -1;
+		}
+	    }
+
+	  if (naccepted == 0)
+	    {
+	      int dest_node;
+	      err = re_node_set_insert (eps_via_nodes, node);
+	      if (BE (err < 0, 0))
+		return -2;
+	      dest_node = dfa->edests[node].elems[0];
+	      if (re_node_set_contains (&mctx->state_log[*pidx]->nodes,
+					dest_node))
+		return dest_node;
+	    }
+	}
+
+      if (naccepted != 0
+	  || check_node_accept (mctx, dfa->nodes + node, *pidx))
+	{
+	  int dest_node = dfa->nexts[node];
+	  *pidx = (naccepted == 0) ? *pidx + 1 : *pidx + naccepted;
+	  if (fs && (*pidx > mctx->match_last || mctx->state_log[*pidx] == NULL
+		     || !re_node_set_contains (&mctx->state_log[*pidx]->nodes,
+					       dest_node)))
+	    return -1;
+	  re_node_set_empty (eps_via_nodes);
+	  return dest_node;
+	}
+    }
+  return -1;
+}
+
+static reg_errcode_t
+internal_function
+push_fail_stack (struct re_fail_stack_t *fs, int str_idx, int dest_node,
+		 int nregs, regmatch_t *regs, re_node_set *eps_via_nodes)
+{
+  reg_errcode_t err;
+  int num = fs->num++;
+  if (fs->num == fs->alloc)
+    {
+      struct re_fail_stack_ent_t *new_array;
+      new_array = realloc (fs->stack, (sizeof (struct re_fail_stack_ent_t)
+				       * fs->alloc * 2));
+      if (new_array == NULL)
+	return REG_ESPACE;
+      fs->alloc *= 2;
+      fs->stack = new_array;
+    }
+  fs->stack[num].idx = str_idx;
+  fs->stack[num].node = dest_node;
+  fs->stack[num].regs = re_malloc (regmatch_t, nregs);
+  if (fs->stack[num].regs == NULL)
+    return REG_ESPACE;
+  memcpy (fs->stack[num].regs, regs, sizeof (regmatch_t) * nregs);
+  err = re_node_set_init_copy (&fs->stack[num].eps_via_nodes, eps_via_nodes);
+  return err;
+}
+
+static int
+internal_function
+pop_fail_stack (struct re_fail_stack_t *fs, int *pidx, int nregs,
+		regmatch_t *regs, re_node_set *eps_via_nodes)
+{
+  int num = --fs->num;
+  assert (num >= 0);
+  *pidx = fs->stack[num].idx;
+  memcpy (regs, fs->stack[num].regs, sizeof (regmatch_t) * nregs);
+  re_node_set_free (eps_via_nodes);
+  re_free (fs->stack[num].regs);
+  *eps_via_nodes = fs->stack[num].eps_via_nodes;
+  return fs->stack[num].node;
+}
+
+/* Set the positions where the subexpressions are starts/ends to registers
+   PMATCH.
+   Note: We assume that pmatch[0] is already set, and
+   pmatch[i].rm_so == pmatch[i].rm_eo == -1 for 0 < i < nmatch.  */
+
+static reg_errcode_t
+internal_function
+set_regs (const regex_t *preg, const re_match_context_t *mctx, size_t nmatch,
+	  regmatch_t *pmatch, int fl_backtrack)
+{
+  const re_dfa_t *dfa = (const re_dfa_t *) preg->buffer;
+  int idx, cur_node;
+  re_node_set eps_via_nodes;
+  struct re_fail_stack_t *fs;
+  struct re_fail_stack_t fs_body = { 0, 2, NULL };
+  regmatch_t *prev_idx_match;
+  int prev_idx_match_malloced = 0;
+
+#ifdef DEBUG
+  assert (nmatch > 1);
+  assert (mctx->state_log != NULL);
+#endif
+  if (fl_backtrack)
+    {
+      fs = &fs_body;
+      fs->stack = re_malloc (struct re_fail_stack_ent_t, fs->alloc);
+      if (fs->stack == NULL)
+	return REG_ESPACE;
+    }
+  else
+    fs = NULL;
+
+  cur_node = dfa->init_node;
+  re_node_set_init_empty (&eps_via_nodes);
+
+#ifdef HAVE_ALLOCA
+  if (__libc_use_alloca (nmatch * sizeof (regmatch_t)))
+    prev_idx_match = (regmatch_t *) alloca (nmatch * sizeof (regmatch_t));
+  else
+#endif
+    {
+      prev_idx_match = re_malloc (regmatch_t, nmatch);
+      if (prev_idx_match == NULL)
+	{
+	  free_fail_stack_return (fs);
+	  return REG_ESPACE;
+	}
+      prev_idx_match_malloced = 1;
+    }
+  memcpy (prev_idx_match, pmatch, sizeof (regmatch_t) * nmatch);
+
+  for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
+    {
+      update_regs (dfa, pmatch, prev_idx_match, cur_node, idx, nmatch);
+
+      if (idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
+	{
+	  int reg_idx;
+	  if (fs)
+	    {
+	      for (reg_idx = 0; reg_idx < nmatch; ++reg_idx)
+		if (pmatch[reg_idx].rm_so > -1 && pmatch[reg_idx].rm_eo == -1)
+		  break;
+	      if (reg_idx == nmatch)
+		{
+		  re_node_set_free (&eps_via_nodes);
+		  if (prev_idx_match_malloced)
+		    re_free (prev_idx_match);
+		  return free_fail_stack_return (fs);
+		}
+	      cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
+					 &eps_via_nodes);
+	    }
+	  else
+	    {
+	      re_node_set_free (&eps_via_nodes);
+	      if (prev_idx_match_malloced)
+		re_free (prev_idx_match);
+	      return REG_NOERROR;
+	    }
+	}
+
+      /* Proceed to next node.  */
+      cur_node = proceed_next_node (mctx, nmatch, pmatch, &idx, cur_node,
+				    &eps_via_nodes, fs);
+
+      if (BE (cur_node < 0, 0))
+	{
+	  if (BE (cur_node == -2, 0))
+	    {
+	      re_node_set_free (&eps_via_nodes);
+	      if (prev_idx_match_malloced)
+		re_free (prev_idx_match);
+	      free_fail_stack_return (fs);
+	      return REG_ESPACE;
+	    }
+	  if (fs)
+	    cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
+				       &eps_via_nodes);
+	  else
+	    {
+	      re_node_set_free (&eps_via_nodes);
+	      if (prev_idx_match_malloced)
+		re_free (prev_idx_match);
+	      return REG_NOMATCH;
+	    }
+	}
+    }
+  re_node_set_free (&eps_via_nodes);
+  if (prev_idx_match_malloced)
+    re_free (prev_idx_match);
+  return free_fail_stack_return (fs);
+}
+
+static reg_errcode_t
+internal_function
+free_fail_stack_return (struct re_fail_stack_t *fs)
+{
+  if (fs)
+    {
+      int fs_idx;
+      for (fs_idx = 0; fs_idx < fs->num; ++fs_idx)
+	{
+	  re_node_set_free (&fs->stack[fs_idx].eps_via_nodes);
+	  re_free (fs->stack[fs_idx].regs);
+	}
+      re_free (fs->stack);
+    }
+  return REG_NOERROR;
+}
+
+static void
+internal_function
+update_regs (const re_dfa_t *dfa, regmatch_t *pmatch,
+	     regmatch_t *prev_idx_match, int cur_node, int cur_idx, int nmatch)
+{
+  int type = dfa->nodes[cur_node].type;
+  if (type == OP_OPEN_SUBEXP)
+    {
+      int reg_num = dfa->nodes[cur_node].opr.idx + 1;
+
+      /* We are at the first node of this sub expression.  */
+      if (reg_num < nmatch)
+	{
+	  pmatch[reg_num].rm_so = cur_idx;
+	  pmatch[reg_num].rm_eo = -1;
+	}
+    }
+  else if (type == OP_CLOSE_SUBEXP)
+    {
+      int reg_num = dfa->nodes[cur_node].opr.idx + 1;
+      if (reg_num < nmatch)
+	{
+	  /* We are at the last node of this sub expression.  */
+	  if (pmatch[reg_num].rm_so < cur_idx)
+	    {
+	      pmatch[reg_num].rm_eo = cur_idx;
+	      /* This is a non-empty match or we are not inside an optional
+		 subexpression.  Accept this right away.  */
+	      memcpy (prev_idx_match, pmatch, sizeof (regmatch_t) * nmatch);
+	    }
+	  else
+	    {
+	      if (dfa->nodes[cur_node].opt_subexp
+		  && prev_idx_match[reg_num].rm_so != -1)
+		/* We transited through an empty match for an optional
+		   subexpression, like (a?)*, and this is not the subexp's
+		   first match.  Copy back the old content of the registers
+		   so that matches of an inner subexpression are undone as
+		   well, like in ((a?))*.  */
+		memcpy (pmatch, prev_idx_match, sizeof (regmatch_t) * nmatch);
+	      else
+		/* We completed a subexpression, but it may be part of
+		   an optional one, so do not update PREV_IDX_MATCH.  */
+		pmatch[reg_num].rm_eo = cur_idx;
+	    }
+	}
+    }
+}
+
+/* This function checks the STATE_LOG from the SCTX->last_str_idx to 0
+   and sift the nodes in each states according to the following rules.
+   Updated state_log will be wrote to STATE_LOG.
+
+   Rules: We throw away the Node `a' in the STATE_LOG[STR_IDX] if...
+     1. When STR_IDX == MATCH_LAST(the last index in the state_log):
+	If `a' isn't the LAST_NODE and `a' can't epsilon transit to
+	the LAST_NODE, we throw away the node `a'.
+     2. When 0 <= STR_IDX < MATCH_LAST and `a' accepts
+	string `s' and transit to `b':
+	i. If 'b' isn't in the STATE_LOG[STR_IDX+strlen('s')], we throw
+	   away the node `a'.
+	ii. If 'b' is in the STATE_LOG[STR_IDX+strlen('s')] but 'b' is
+	    thrown away, we throw away the node `a'.
+     3. When 0 <= STR_IDX < MATCH_LAST and 'a' epsilon transit to 'b':
+	i. If 'b' isn't in the STATE_LOG[STR_IDX], we throw away the
+	   node `a'.
+	ii. If 'b' is in the STATE_LOG[STR_IDX] but 'b' is thrown away,
+	    we throw away the node `a'.  */
+
+#define STATE_NODE_CONTAINS(state,node) \
+  ((state) != NULL && re_node_set_contains (&(state)->nodes, node))
+
+static reg_errcode_t
+internal_function
+sift_states_backward (const re_match_context_t *mctx, re_sift_context_t *sctx)
+{
+  reg_errcode_t err;
+  int null_cnt = 0;
+  int str_idx = sctx->last_str_idx;
+  re_node_set cur_dest;
+
+#ifdef DEBUG
+  assert (mctx->state_log != NULL && mctx->state_log[str_idx] != NULL);
+#endif
+
+  /* Build sifted state_log[str_idx].  It has the nodes which can epsilon
+     transit to the last_node and the last_node itself.  */
+  err = re_node_set_init_1 (&cur_dest, sctx->last_node);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  err = update_cur_sifted_state (mctx, sctx, str_idx, &cur_dest);
+  if (BE (err != REG_NOERROR, 0))
+    goto free_return;
+
+  /* Then check each states in the state_log.  */
+  while (str_idx > 0)
+    {
+      /* Update counters.  */
+      null_cnt = (sctx->sifted_states[str_idx] == NULL) ? null_cnt + 1 : 0;
+      if (null_cnt > mctx->max_mb_elem_len)
+	{
+	  memset (sctx->sifted_states, '\0',
+		  sizeof (re_dfastate_t *) * str_idx);
+	  re_node_set_free (&cur_dest);
+	  return REG_NOERROR;
+	}
+      re_node_set_empty (&cur_dest);
+      --str_idx;
+
+      if (mctx->state_log[str_idx])
+	{
+	  err = build_sifted_states (mctx, sctx, str_idx, &cur_dest);
+	  if (BE (err != REG_NOERROR, 0))
+	    goto free_return;
+	}
+
+      /* Add all the nodes which satisfy the following conditions:
+	 - It can epsilon transit to a node in CUR_DEST.
+	 - It is in CUR_SRC.
+	 And update state_log.  */
+      err = update_cur_sifted_state (mctx, sctx, str_idx, &cur_dest);
+      if (BE (err != REG_NOERROR, 0))
+	goto free_return;
+    }
+  err = REG_NOERROR;
+ free_return:
+  re_node_set_free (&cur_dest);
+  return err;
+}
+
+static reg_errcode_t
+internal_function
+build_sifted_states (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		     int str_idx, re_node_set *cur_dest)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  const re_node_set *cur_src = &mctx->state_log[str_idx]->non_eps_nodes;
+  int i;
+
+  /* Then build the next sifted state.
+     We build the next sifted state on `cur_dest', and update
+     `sifted_states[str_idx]' with `cur_dest'.
+     Note:
+     `cur_dest' is the sifted state from `state_log[str_idx + 1]'.
+     `cur_src' points the node_set of the old `state_log[str_idx]'
+     (with the epsilon nodes pre-filtered out).  */
+  for (i = 0; i < cur_src->nelem; i++)
+    {
+      int prev_node = cur_src->elems[i];
+      int naccepted = 0;
+      int ret;
+
+#ifdef DEBUG
+      re_token_type_t type = dfa->nodes[prev_node].type;
+      assert (!IS_EPSILON_NODE (type));
+#endif
+#ifdef RE_ENABLE_I18N
+      /* If the node may accept `multi byte'.  */
+      if (dfa->nodes[prev_node].accept_mb)
+	naccepted = sift_states_iter_mb (mctx, sctx, prev_node,
+					 str_idx, sctx->last_str_idx);
+#endif /* RE_ENABLE_I18N */
+
+      /* We don't check backreferences here.
+	 See update_cur_sifted_state().  */
+      if (!naccepted
+	  && check_node_accept (mctx, dfa->nodes + prev_node, str_idx)
+	  && STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + 1],
+				  dfa->nexts[prev_node]))
+	naccepted = 1;
+
+      if (naccepted == 0)
+	continue;
+
+      if (sctx->limits.nelem)
+	{
+	  int to_idx = str_idx + naccepted;
+	  if (check_dst_limits (mctx, &sctx->limits,
+				dfa->nexts[prev_node], to_idx,
+				prev_node, str_idx))
+	    continue;
+	}
+      ret = re_node_set_insert (cur_dest, prev_node);
+      if (BE (ret == -1, 0))
+	return REG_ESPACE;
+    }
+
+  return REG_NOERROR;
+}
+
+/* Helper functions.  */
+
+static reg_errcode_t
+internal_function
+clean_state_log_if_needed (re_match_context_t *mctx, int next_state_log_idx)
+{
+  int top = mctx->state_log_top;
+
+  if (next_state_log_idx >= mctx->input.bufs_len
+      || (next_state_log_idx >= mctx->input.valid_len
+	  && mctx->input.valid_len < mctx->input.len))
+    {
+      reg_errcode_t err;
+      err = extend_buffers (mctx);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+    }
+
+  if (top < next_state_log_idx)
+    {
+      memset (mctx->state_log + top + 1, '\0',
+	      sizeof (re_dfastate_t *) * (next_state_log_idx - top));
+      mctx->state_log_top = next_state_log_idx;
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+merge_state_array (const re_dfa_t *dfa, re_dfastate_t **dst,
+		   re_dfastate_t **src, int num)
+{
+  int st_idx;
+  reg_errcode_t err;
+  for (st_idx = 0; st_idx < num; ++st_idx)
+    {
+      if (dst[st_idx] == NULL)
+	dst[st_idx] = src[st_idx];
+      else if (src[st_idx] != NULL)
+	{
+	  re_node_set merged_set;
+	  err = re_node_set_init_union (&merged_set, &dst[st_idx]->nodes,
+					&src[st_idx]->nodes);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	  dst[st_idx] = re_acquire_state (&err, dfa, &merged_set);
+	  re_node_set_free (&merged_set);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+update_cur_sifted_state (const re_match_context_t *mctx,
+			 re_sift_context_t *sctx, int str_idx,
+			 re_node_set *dest_nodes)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err = REG_NOERROR;
+  const re_node_set *candidates;
+  candidates = ((mctx->state_log[str_idx] == NULL) ? NULL
+		: &mctx->state_log[str_idx]->nodes);
+
+  if (dest_nodes->nelem == 0)
+    sctx->sifted_states[str_idx] = NULL;
+  else
+    {
+      if (candidates)
+	{
+	  /* At first, add the nodes which can epsilon transit to a node in
+	     DEST_NODE.  */
+	  err = add_epsilon_src_nodes (dfa, dest_nodes, candidates);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+
+	  /* Then, check the limitations in the current sift_context.  */
+	  if (sctx->limits.nelem)
+	    {
+	      err = check_subexp_limits (dfa, dest_nodes, candidates, &sctx->limits,
+					 mctx->bkref_ents, str_idx);
+	      if (BE (err != REG_NOERROR, 0))
+		return err;
+	    }
+	}
+
+      sctx->sifted_states[str_idx] = re_acquire_state (&err, dfa, dest_nodes);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+    }
+
+  if (candidates && mctx->state_log[str_idx]->has_backref)
+    {
+      err = sift_states_bkref (mctx, sctx, str_idx, candidates);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+add_epsilon_src_nodes (const re_dfa_t *dfa, re_node_set *dest_nodes,
+		       const re_node_set *candidates)
+{
+  reg_errcode_t err = REG_NOERROR;
+  int i;
+
+  re_dfastate_t *state = re_acquire_state (&err, dfa, dest_nodes);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+
+  if (!state->inveclosure.alloc)
+    {
+      err = re_node_set_alloc (&state->inveclosure, dest_nodes->nelem);
+      if (BE (err != REG_NOERROR, 0))
+	return REG_ESPACE;
+      for (i = 0; i < dest_nodes->nelem; i++)
+	{
+	  err = re_node_set_merge (&state->inveclosure,
+				   dfa->inveclosures + dest_nodes->elems[i]);
+	  if (BE (err != REG_NOERROR, 0))
+	    return REG_ESPACE;
+	}
+    }
+  return re_node_set_add_intersect (dest_nodes, candidates,
+				    &state->inveclosure);
+}
+
+static reg_errcode_t
+internal_function
+sub_epsilon_src_nodes (const re_dfa_t *dfa, int node, re_node_set *dest_nodes,
+		       const re_node_set *candidates)
+{
+    int ecl_idx;
+    reg_errcode_t err;
+    re_node_set *inv_eclosure = dfa->inveclosures + node;
+    re_node_set except_nodes;
+    re_node_set_init_empty (&except_nodes);
+    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
+      {
+	int cur_node = inv_eclosure->elems[ecl_idx];
+	if (cur_node == node)
+	  continue;
+	if (IS_EPSILON_NODE (dfa->nodes[cur_node].type))
+	  {
+	    int edst1 = dfa->edests[cur_node].elems[0];
+	    int edst2 = ((dfa->edests[cur_node].nelem > 1)
+			 ? dfa->edests[cur_node].elems[1] : -1);
+	    if ((!re_node_set_contains (inv_eclosure, edst1)
+		 && re_node_set_contains (dest_nodes, edst1))
+		|| (edst2 > 0
+		    && !re_node_set_contains (inv_eclosure, edst2)
+		    && re_node_set_contains (dest_nodes, edst2)))
+	      {
+		err = re_node_set_add_intersect (&except_nodes, candidates,
+						 dfa->inveclosures + cur_node);
+		if (BE (err != REG_NOERROR, 0))
+		  {
+		    re_node_set_free (&except_nodes);
+		    return err;
+		  }
+	      }
+	  }
+      }
+    for (ecl_idx = 0; ecl_idx < inv_eclosure->nelem; ++ecl_idx)
+      {
+	int cur_node = inv_eclosure->elems[ecl_idx];
+	if (!re_node_set_contains (&except_nodes, cur_node))
+	  {
+	    int idx = re_node_set_contains (dest_nodes, cur_node) - 1;
+	    re_node_set_remove_at (dest_nodes, idx);
+	  }
+      }
+    re_node_set_free (&except_nodes);
+    return REG_NOERROR;
+}
+
+static int
+internal_function
+check_dst_limits (const re_match_context_t *mctx, re_node_set *limits,
+		  int dst_node, int dst_idx, int src_node, int src_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int lim_idx, src_pos, dst_pos;
+
+  int dst_bkref_idx = search_cur_bkref_entry (mctx, dst_idx);
+  int src_bkref_idx = search_cur_bkref_entry (mctx, src_idx);
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      int subexp_idx;
+      struct re_backref_cache_entry *ent;
+      ent = mctx->bkref_ents + limits->elems[lim_idx];
+      subexp_idx = dfa->nodes[ent->node].opr.idx;
+
+      dst_pos = check_dst_limits_calc_pos (mctx, limits->elems[lim_idx],
+					   subexp_idx, dst_node, dst_idx,
+					   dst_bkref_idx);
+      src_pos = check_dst_limits_calc_pos (mctx, limits->elems[lim_idx],
+					   subexp_idx, src_node, src_idx,
+					   src_bkref_idx);
+
+      /* In case of:
+	 <src> <dst> ( <subexp> )
+	 ( <subexp> ) <src> <dst>
+	 ( <subexp1> <src> <subexp2> <dst> <subexp3> )  */
+      if (src_pos == dst_pos)
+	continue; /* This is unrelated limitation.  */
+      else
+	return 1;
+    }
+  return 0;
+}
+
+static int
+internal_function
+check_dst_limits_calc_pos_1 (const re_match_context_t *mctx, int boundaries,
+			     int subexp_idx, int from_node, int bkref_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  const re_node_set *eclosures = dfa->eclosures + from_node;
+  int node_idx;
+
+  /* Else, we are on the boundary: examine the nodes on the epsilon
+     closure.  */
+  for (node_idx = 0; node_idx < eclosures->nelem; ++node_idx)
+    {
+      int node = eclosures->elems[node_idx];
+      switch (dfa->nodes[node].type)
+	{
+	case OP_BACK_REF:
+	  if (bkref_idx != -1)
+	    {
+	      struct re_backref_cache_entry *ent = mctx->bkref_ents + bkref_idx;
+	      do
+		{
+		  int dst, cpos;
+
+		  if (ent->node != node)
+		    continue;
+
+		  if (subexp_idx < BITSET_WORD_BITS
+		      && !(ent->eps_reachable_subexps_map
+			   & ((bitset_word_t) 1 << subexp_idx)))
+		    continue;
+
+		  /* Recurse trying to reach the OP_OPEN_SUBEXP and
+		     OP_CLOSE_SUBEXP cases below.  But, if the
+		     destination node is the same node as the source
+		     node, don't recurse because it would cause an
+		     infinite loop: a regex that exhibits this behavior
+		     is ()\1*\1*  */
+		  dst = dfa->edests[node].elems[0];
+		  if (dst == from_node)
+		    {
+		      if (boundaries & 1)
+			return -1;
+		      else /* if (boundaries & 2) */
+			return 0;
+		    }
+
+		  cpos =
+		    check_dst_limits_calc_pos_1 (mctx, boundaries, subexp_idx,
+						 dst, bkref_idx);
+		  if (cpos == -1 /* && (boundaries & 1) */)
+		    return -1;
+		  if (cpos == 0 && (boundaries & 2))
+		    return 0;
+
+		  if (subexp_idx < BITSET_WORD_BITS)
+		    ent->eps_reachable_subexps_map
+		      &= ~((bitset_word_t) 1 << subexp_idx);
+		}
+	      while (ent++->more);
+	    }
+	  break;
+
+	case OP_OPEN_SUBEXP:
+	  if ((boundaries & 1) && subexp_idx == dfa->nodes[node].opr.idx)
+	    return -1;
+	  break;
+
+	case OP_CLOSE_SUBEXP:
+	  if ((boundaries & 2) && subexp_idx == dfa->nodes[node].opr.idx)
+	    return 0;
+	  break;
+
+	default:
+	    break;
+	}
+    }
+
+  return (boundaries & 2) ? 1 : 0;
+}
+
+static int
+internal_function
+check_dst_limits_calc_pos (const re_match_context_t *mctx, int limit,
+			   int subexp_idx, int from_node, int str_idx,
+			   int bkref_idx)
+{
+  struct re_backref_cache_entry *lim = mctx->bkref_ents + limit;
+  int boundaries;
+
+  /* If we are outside the range of the subexpression, return -1 or 1.  */
+  if (str_idx < lim->subexp_from)
+    return -1;
+
+  if (lim->subexp_to < str_idx)
+    return 1;
+
+  /* If we are within the subexpression, return 0.  */
+  boundaries = (str_idx == lim->subexp_from);
+  boundaries |= (str_idx == lim->subexp_to) << 1;
+  if (boundaries == 0)
+    return 0;
+
+  /* Else, examine epsilon closure.  */
+  return check_dst_limits_calc_pos_1 (mctx, boundaries, subexp_idx,
+				      from_node, bkref_idx);
+}
+
+/* Check the limitations of sub expressions LIMITS, and remove the nodes
+   which are against limitations from DEST_NODES. */
+
+static reg_errcode_t
+internal_function
+check_subexp_limits (const re_dfa_t *dfa, re_node_set *dest_nodes,
+		     const re_node_set *candidates, re_node_set *limits,
+		     struct re_backref_cache_entry *bkref_ents, int str_idx)
+{
+  reg_errcode_t err;
+  int node_idx, lim_idx;
+
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      int subexp_idx;
+      struct re_backref_cache_entry *ent;
+      ent = bkref_ents + limits->elems[lim_idx];
+
+      if (str_idx <= ent->subexp_from || ent->str_idx < str_idx)
+	continue; /* This is unrelated limitation.  */
+
+      subexp_idx = dfa->nodes[ent->node].opr.idx;
+      if (ent->subexp_to == str_idx)
+	{
+	  int ops_node = -1;
+	  int cls_node = -1;
+	  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+	    {
+	      int node = dest_nodes->elems[node_idx];
+	      re_token_type_t type = dfa->nodes[node].type;
+	      if (type == OP_OPEN_SUBEXP
+		  && subexp_idx == dfa->nodes[node].opr.idx)
+		ops_node = node;
+	      else if (type == OP_CLOSE_SUBEXP
+		       && subexp_idx == dfa->nodes[node].opr.idx)
+		cls_node = node;
+	    }
+
+	  /* Check the limitation of the open subexpression.  */
+	  /* Note that (ent->subexp_to = str_idx != ent->subexp_from).  */
+	  if (ops_node >= 0)
+	    {
+	      err = sub_epsilon_src_nodes (dfa, ops_node, dest_nodes,
+					   candidates);
+	      if (BE (err != REG_NOERROR, 0))
+		return err;
+	    }
+
+	  /* Check the limitation of the close subexpression.  */
+	  if (cls_node >= 0)
+	    for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+	      {
+		int node = dest_nodes->elems[node_idx];
+		if (!re_node_set_contains (dfa->inveclosures + node,
+					   cls_node)
+		    && !re_node_set_contains (dfa->eclosures + node,
+					      cls_node))
+		  {
+		    /* It is against this limitation.
+		       Remove it form the current sifted state.  */
+		    err = sub_epsilon_src_nodes (dfa, node, dest_nodes,
+						 candidates);
+		    if (BE (err != REG_NOERROR, 0))
+		      return err;
+		    --node_idx;
+		  }
+	      }
+	}
+      else /* (ent->subexp_to != str_idx)  */
+	{
+	  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+	    {
+	      int node = dest_nodes->elems[node_idx];
+	      re_token_type_t type = dfa->nodes[node].type;
+	      if (type == OP_CLOSE_SUBEXP || type == OP_OPEN_SUBEXP)
+		{
+		  if (subexp_idx != dfa->nodes[node].opr.idx)
+		    continue;
+		  /* It is against this limitation.
+		     Remove it form the current sifted state.  */
+		  err = sub_epsilon_src_nodes (dfa, node, dest_nodes,
+					       candidates);
+		  if (BE (err != REG_NOERROR, 0))
+		    return err;
+		}
+	    }
+	}
+    }
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+internal_function
+sift_states_bkref (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		   int str_idx, const re_node_set *candidates)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  int node_idx, node;
+  re_sift_context_t local_sctx;
+  int first_idx = search_cur_bkref_entry (mctx, str_idx);
+
+  if (first_idx == -1)
+    return REG_NOERROR;
+
+  local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */
+
+  for (node_idx = 0; node_idx < candidates->nelem; ++node_idx)
+    {
+      int enabled_idx;
+      re_token_type_t type;
+      struct re_backref_cache_entry *entry;
+      node = candidates->elems[node_idx];
+      type = dfa->nodes[node].type;
+      /* Avoid infinite loop for the REs like "()\1+".  */
+      if (node == sctx->last_node && str_idx == sctx->last_str_idx)
+	continue;
+      if (type != OP_BACK_REF)
+	continue;
+
+      entry = mctx->bkref_ents + first_idx;
+      enabled_idx = first_idx;
+      do
+	{
+	  int subexp_len;
+	  int to_idx;
+	  int dst_node;
+	  int ret;
+	  re_dfastate_t *cur_state;
+
+	  if (entry->node != node)
+	    continue;
+	  subexp_len = entry->subexp_to - entry->subexp_from;
+	  to_idx = str_idx + subexp_len;
+	  dst_node = (subexp_len ? dfa->nexts[node]
+		      : dfa->edests[node].elems[0]);
+
+	  if (to_idx > sctx->last_str_idx
+	      || sctx->sifted_states[to_idx] == NULL
+	      || !STATE_NODE_CONTAINS (sctx->sifted_states[to_idx], dst_node)
+	      || check_dst_limits (mctx, &sctx->limits, node,
+				   str_idx, dst_node, to_idx))
+	    continue;
+
+	  if (local_sctx.sifted_states == NULL)
+	    {
+	      local_sctx = *sctx;
+	      err = re_node_set_init_copy (&local_sctx.limits, &sctx->limits);
+	      if (BE (err != REG_NOERROR, 0))
+		goto free_return;
+	    }
+	  local_sctx.last_node = node;
+	  local_sctx.last_str_idx = str_idx;
+	  ret = re_node_set_insert (&local_sctx.limits, enabled_idx);
+	  if (BE (ret < 0, 0))
+	    {
+	      err = REG_ESPACE;
+	      goto free_return;
+	    }
+	  cur_state = local_sctx.sifted_states[str_idx];
+	  err = sift_states_backward (mctx, &local_sctx);
+	  if (BE (err != REG_NOERROR, 0))
+	    goto free_return;
+	  if (sctx->limited_states != NULL)
+	    {
+	      err = merge_state_array (dfa, sctx->limited_states,
+				       local_sctx.sifted_states,
+				       str_idx + 1);
+	      if (BE (err != REG_NOERROR, 0))
+		goto free_return;
+	    }
+	  local_sctx.sifted_states[str_idx] = cur_state;
+	  re_node_set_remove (&local_sctx.limits, enabled_idx);
+
+	  /* mctx->bkref_ents may have changed, reload the pointer.  */
+	  entry = mctx->bkref_ents + enabled_idx;
+	}
+      while (enabled_idx++, entry++->more);
+    }
+  err = REG_NOERROR;
+ free_return:
+  if (local_sctx.sifted_states != NULL)
+    {
+      re_node_set_free (&local_sctx.limits);
+    }
+
+  return err;
+}
+
+
+#ifdef RE_ENABLE_I18N
+static int
+internal_function
+sift_states_iter_mb (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		     int node_idx, int str_idx, int max_str_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int naccepted;
+  /* Check the node can accept `multi byte'.  */
+  naccepted = check_node_accept_bytes (dfa, node_idx, &mctx->input, str_idx);
+  if (naccepted > 0 && str_idx + naccepted <= max_str_idx &&
+      !STATE_NODE_CONTAINS (sctx->sifted_states[str_idx + naccepted],
+			    dfa->nexts[node_idx]))
+    /* The node can't accept the `multi byte', or the
+       destination was already thrown away, then the node
+       couldn't accept the current input `multi byte'.   */
+    naccepted = 0;
+  /* Otherwise, it is sure that the node could accept
+     `naccepted' bytes input.  */
+  return naccepted;
+}
+#endif /* RE_ENABLE_I18N */
+
+
+/* Functions for state transition.  */
+
+/* Return the next state to which the current state STATE will transit by
+   accepting the current input byte, and update STATE_LOG if necessary.
+   If STATE can accept a multibyte char/collating element/back reference
+   update the destination of STATE_LOG.  */
+
+static re_dfastate_t *
+internal_function
+transit_state (reg_errcode_t *err, re_match_context_t *mctx,
+	       re_dfastate_t *state)
+{
+  re_dfastate_t **trtable;
+  unsigned char ch;
+
+#ifdef RE_ENABLE_I18N
+  /* If the current state can accept multibyte.  */
+  if (BE (state->accept_mb, 0))
+    {
+      *err = transit_state_mb (mctx, state);
+      if (BE (*err != REG_NOERROR, 0))
+	return NULL;
+    }
+#endif /* RE_ENABLE_I18N */
+
+  /* Then decide the next state with the single byte.  */
+#if 0
+  if (0)
+    /* don't use transition table  */
+    return transit_state_sb (err, mctx, state);
+#endif
+
+  /* Use transition table  */
+  ch = re_string_fetch_byte (&mctx->input);
+  for (;;)
+    {
+      trtable = state->trtable;
+      if (BE (trtable != NULL, 1))
+	return trtable[ch];
+
+      trtable = state->word_trtable;
+      if (BE (trtable != NULL, 1))
+	{
+	  unsigned int context;
+	  context
+	    = re_string_context_at (&mctx->input,
+				    re_string_cur_idx (&mctx->input) - 1,
+				    mctx->eflags);
+	  if (IS_WORD_CONTEXT (context))
+	    return trtable[ch + SBC_MAX];
+	  else
+	    return trtable[ch];
+	}
+
+      if (!build_trtable (mctx->dfa, state))
+	{
+	  *err = REG_ESPACE;
+	  return NULL;
+	}
+
+      /* Retry, we now have a transition table.  */
+    }
+}
+
+/* Update the state_log if we need */
+static re_dfastate_t *
+internal_function
+merge_state_with_log (reg_errcode_t *err, re_match_context_t *mctx,
+		      re_dfastate_t *next_state)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int cur_idx = re_string_cur_idx (&mctx->input);
+
+  if (cur_idx > mctx->state_log_top)
+    {
+      mctx->state_log[cur_idx] = next_state;
+      mctx->state_log_top = cur_idx;
+    }
+  else if (mctx->state_log[cur_idx] == NULL)
+    {
+      mctx->state_log[cur_idx] = next_state;
+    }
+  else
+    {
+      re_dfastate_t *pstate;
+      unsigned int context;
+      re_node_set next_nodes, *log_nodes, *table_nodes = NULL;
+      /* If (state_log[cur_idx] != 0), it implies that cur_idx is
+	 the destination of a multibyte char/collating element/
+	 back reference.  Then the next state is the union set of
+	 these destinations and the results of the transition table.  */
+      pstate = mctx->state_log[cur_idx];
+      log_nodes = pstate->entrance_nodes;
+      if (next_state != NULL)
+	{
+	  table_nodes = next_state->entrance_nodes;
+	  *err = re_node_set_init_union (&next_nodes, table_nodes,
+					     log_nodes);
+	  if (BE (*err != REG_NOERROR, 0))
+	    return NULL;
+	}
+      else
+	next_nodes = *log_nodes;
+      /* Note: We already add the nodes of the initial state,
+	 then we don't need to add them here.  */
+
+      context = re_string_context_at (&mctx->input,
+				      re_string_cur_idx (&mctx->input) - 1,
+				      mctx->eflags);
+      next_state = mctx->state_log[cur_idx]
+	= re_acquire_state_context (err, dfa, &next_nodes, context);
+      /* We don't need to check errors here, since the return value of
+	 this function is next_state and ERR is already set.  */
+
+      if (table_nodes != NULL)
+	re_node_set_free (&next_nodes);
+    }
+
+  if (BE (dfa->nbackref, 0) && next_state != NULL)
+    {
+      /* Check OP_OPEN_SUBEXP in the current state in case that we use them
+	 later.  We must check them here, since the back references in the
+	 next state might use them.  */
+      *err = check_subexp_matching_top (mctx, &next_state->nodes,
+					cur_idx);
+      if (BE (*err != REG_NOERROR, 0))
+	return NULL;
+
+      /* If the next state has back references.  */
+      if (next_state->has_backref)
+	{
+	  *err = transit_state_bkref (mctx, &next_state->nodes);
+	  if (BE (*err != REG_NOERROR, 0))
+	    return NULL;
+	  next_state = mctx->state_log[cur_idx];
+	}
+    }
+
+  return next_state;
+}
+
+/* Skip bytes in the input that correspond to part of a
+   multi-byte match, then look in the log for a state
+   from which to restart matching.  */
+static re_dfastate_t *
+internal_function
+find_recover_state (reg_errcode_t *err, re_match_context_t *mctx)
+{
+  re_dfastate_t *cur_state;
+  do
+    {
+      int max = mctx->state_log_top;
+      int cur_str_idx = re_string_cur_idx (&mctx->input);
+
+      do
+	{
+	  if (++cur_str_idx > max)
+	    return NULL;
+	  re_string_skip_bytes (&mctx->input, 1);
+	}
+      while (mctx->state_log[cur_str_idx] == NULL);
+
+      cur_state = merge_state_with_log (err, mctx, NULL);
+    }
+  while (*err == REG_NOERROR && cur_state == NULL);
+  return cur_state;
+}
+
+/* Helper functions for transit_state.  */
+
+/* From the node set CUR_NODES, pick up the nodes whose types are
+   OP_OPEN_SUBEXP and which have corresponding back references in the regular
+   expression. And register them to use them later for evaluating the
+   corresponding back references.  */
+
+static reg_errcode_t
+internal_function
+check_subexp_matching_top (re_match_context_t *mctx, re_node_set *cur_nodes,
+			   int str_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int node_idx;
+  reg_errcode_t err;
+
+  /* TODO: This isn't efficient.
+	   Because there might be more than one nodes whose types are
+	   OP_OPEN_SUBEXP and whose index is SUBEXP_IDX, we must check all
+	   nodes.
+	   E.g. RE: (a){2}  */
+  for (node_idx = 0; node_idx < cur_nodes->nelem; ++node_idx)
+    {
+      int node = cur_nodes->elems[node_idx];
+      if (dfa->nodes[node].type == OP_OPEN_SUBEXP
+	  && dfa->nodes[node].opr.idx < BITSET_WORD_BITS
+	  && (dfa->used_bkref_map
+	      & ((bitset_word_t) 1 << dfa->nodes[node].opr.idx)))
+	{
+	  err = match_ctx_add_subtop (mctx, node, str_idx);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+    }
+  return REG_NOERROR;
+}
+
+#if 0
+/* Return the next state to which the current state STATE will transit by
+   accepting the current input byte.  */
+
+static re_dfastate_t *
+transit_state_sb (reg_errcode_t *err, re_match_context_t *mctx,
+		  re_dfastate_t *state)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  re_node_set next_nodes;
+  re_dfastate_t *next_state;
+  int node_cnt, cur_str_idx = re_string_cur_idx (&mctx->input);
+  unsigned int context;
+
+  *err = re_node_set_alloc (&next_nodes, state->nodes.nelem + 1);
+  if (BE (*err != REG_NOERROR, 0))
+    return NULL;
+  for (node_cnt = 0; node_cnt < state->nodes.nelem; ++node_cnt)
+    {
+      int cur_node = state->nodes.elems[node_cnt];
+      if (check_node_accept (mctx, dfa->nodes + cur_node, cur_str_idx))
+	{
+	  *err = re_node_set_merge (&next_nodes,
+				    dfa->eclosures + dfa->nexts[cur_node]);
+	  if (BE (*err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return NULL;
+	    }
+	}
+    }
+  context = re_string_context_at (&mctx->input, cur_str_idx, mctx->eflags);
+  next_state = re_acquire_state_context (err, dfa, &next_nodes, context);
+  /* We don't need to check errors here, since the return value of
+     this function is next_state and ERR is already set.  */
+
+  re_node_set_free (&next_nodes);
+  re_string_skip_bytes (&mctx->input, 1);
+  return next_state;
+}
+#endif
+
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t
+internal_function
+transit_state_mb (re_match_context_t *mctx, re_dfastate_t *pstate)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  int i;
+
+  for (i = 0; i < pstate->nodes.nelem; ++i)
+    {
+      re_node_set dest_nodes, *new_nodes;
+      int cur_node_idx = pstate->nodes.elems[i];
+      int naccepted, dest_idx;
+      unsigned int context;
+      re_dfastate_t *dest_state;
+
+      if (!dfa->nodes[cur_node_idx].accept_mb)
+	continue;
+
+      if (dfa->nodes[cur_node_idx].constraint)
+	{
+	  context = re_string_context_at (&mctx->input,
+					  re_string_cur_idx (&mctx->input),
+					  mctx->eflags);
+	  if (NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[cur_node_idx].constraint,
+					   context))
+	    continue;
+	}
+
+      /* How many bytes the node can accept?  */
+      naccepted = check_node_accept_bytes (dfa, cur_node_idx, &mctx->input,
+					   re_string_cur_idx (&mctx->input));
+      if (naccepted == 0)
+	continue;
+
+      /* The node can accepts `naccepted' bytes.  */
+      dest_idx = re_string_cur_idx (&mctx->input) + naccepted;
+      mctx->max_mb_elem_len = ((mctx->max_mb_elem_len < naccepted) ? naccepted
+			       : mctx->max_mb_elem_len);
+      err = clean_state_log_if_needed (mctx, dest_idx);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+#ifdef DEBUG
+      assert (dfa->nexts[cur_node_idx] != -1);
+#endif
+      new_nodes = dfa->eclosures + dfa->nexts[cur_node_idx];
+
+      dest_state = mctx->state_log[dest_idx];
+      if (dest_state == NULL)
+	dest_nodes = *new_nodes;
+      else
+	{
+	  err = re_node_set_init_union (&dest_nodes,
+					dest_state->entrance_nodes, new_nodes);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+      context = re_string_context_at (&mctx->input, dest_idx - 1,
+				      mctx->eflags);
+      mctx->state_log[dest_idx]
+	= re_acquire_state_context (&err, dfa, &dest_nodes, context);
+      if (dest_state != NULL)
+	re_node_set_free (&dest_nodes);
+      if (BE (mctx->state_log[dest_idx] == NULL && err != REG_NOERROR, 0))
+	return err;
+    }
+  return REG_NOERROR;
+}
+#endif /* RE_ENABLE_I18N */
+
+static reg_errcode_t
+internal_function
+transit_state_bkref (re_match_context_t *mctx, const re_node_set *nodes)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  int i;
+  int cur_str_idx = re_string_cur_idx (&mctx->input);
+
+  for (i = 0; i < nodes->nelem; ++i)
+    {
+      int dest_str_idx, prev_nelem, bkc_idx;
+      int node_idx = nodes->elems[i];
+      unsigned int context;
+      const re_token_t *node = dfa->nodes + node_idx;
+      re_node_set *new_dest_nodes;
+
+      /* Check whether `node' is a backreference or not.  */
+      if (node->type != OP_BACK_REF)
+	continue;
+
+      if (node->constraint)
+	{
+	  context = re_string_context_at (&mctx->input, cur_str_idx,
+					  mctx->eflags);
+	  if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
+	    continue;
+	}
+
+      /* `node' is a backreference.
+	 Check the substring which the substring matched.  */
+      bkc_idx = mctx->nbkref_ents;
+      err = get_subexp (mctx, node_idx, cur_str_idx);
+      if (BE (err != REG_NOERROR, 0))
+	goto free_return;
+
+      /* And add the epsilon closures (which is `new_dest_nodes') of
+	 the backreference to appropriate state_log.  */
+#ifdef DEBUG
+      assert (dfa->nexts[node_idx] != -1);
+#endif
+      for (; bkc_idx < mctx->nbkref_ents; ++bkc_idx)
+	{
+	  int subexp_len;
+	  re_dfastate_t *dest_state;
+	  struct re_backref_cache_entry *bkref_ent;
+	  bkref_ent = mctx->bkref_ents + bkc_idx;
+	  if (bkref_ent->node != node_idx || bkref_ent->str_idx != cur_str_idx)
+	    continue;
+	  subexp_len = bkref_ent->subexp_to - bkref_ent->subexp_from;
+	  new_dest_nodes = (subexp_len == 0
+			    ? dfa->eclosures + dfa->edests[node_idx].elems[0]
+			    : dfa->eclosures + dfa->nexts[node_idx]);
+	  dest_str_idx = (cur_str_idx + bkref_ent->subexp_to
+			  - bkref_ent->subexp_from);
+	  context = re_string_context_at (&mctx->input, dest_str_idx - 1,
+					  mctx->eflags);
+	  dest_state = mctx->state_log[dest_str_idx];
+	  prev_nelem = ((mctx->state_log[cur_str_idx] == NULL) ? 0
+			: mctx->state_log[cur_str_idx]->nodes.nelem);
+	  /* Add `new_dest_node' to state_log.  */
+	  if (dest_state == NULL)
+	    {
+	      mctx->state_log[dest_str_idx]
+		= re_acquire_state_context (&err, dfa, new_dest_nodes,
+					    context);
+	      if (BE (mctx->state_log[dest_str_idx] == NULL
+		      && err != REG_NOERROR, 0))
+		goto free_return;
+	    }
+	  else
+	    {
+	      re_node_set dest_nodes;
+	      err = re_node_set_init_union (&dest_nodes,
+					    dest_state->entrance_nodes,
+					    new_dest_nodes);
+	      if (BE (err != REG_NOERROR, 0))
+		{
+		  re_node_set_free (&dest_nodes);
+		  goto free_return;
+		}
+	      mctx->state_log[dest_str_idx]
+		= re_acquire_state_context (&err, dfa, &dest_nodes, context);
+	      re_node_set_free (&dest_nodes);
+	      if (BE (mctx->state_log[dest_str_idx] == NULL
+		      && err != REG_NOERROR, 0))
+		goto free_return;
+	    }
+	  /* We need to check recursively if the backreference can epsilon
+	     transit.  */
+	  if (subexp_len == 0
+	      && mctx->state_log[cur_str_idx]->nodes.nelem > prev_nelem)
+	    {
+	      err = check_subexp_matching_top (mctx, new_dest_nodes,
+					       cur_str_idx);
+	      if (BE (err != REG_NOERROR, 0))
+		goto free_return;
+	      err = transit_state_bkref (mctx, new_dest_nodes);
+	      if (BE (err != REG_NOERROR, 0))
+		goto free_return;
+	    }
+	}
+    }
+  err = REG_NOERROR;
+ free_return:
+  return err;
+}
+
+/* Enumerate all the candidates which the backreference BKREF_NODE can match
+   at BKREF_STR_IDX, and register them by match_ctx_add_entry().
+   Note that we might collect inappropriate candidates here.
+   However, the cost of checking them strictly here is too high, then we
+   delay these checking for prune_impossible_nodes().  */
+
+static reg_errcode_t
+internal_function
+get_subexp (re_match_context_t *mctx, int bkref_node, int bkref_str_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int subexp_num, sub_top_idx;
+  const char *buf = (const char *) re_string_get_buffer (&mctx->input);
+  /* Return if we have already checked BKREF_NODE at BKREF_STR_IDX.  */
+  int cache_idx = search_cur_bkref_entry (mctx, bkref_str_idx);
+  if (cache_idx != -1)
+    {
+      const struct re_backref_cache_entry *entry
+	= mctx->bkref_ents + cache_idx;
+      do
+	if (entry->node == bkref_node)
+	  return REG_NOERROR; /* We already checked it.  */
+      while (entry++->more);
+    }
+
+  subexp_num = dfa->nodes[bkref_node].opr.idx;
+
+  /* For each sub expression  */
+  for (sub_top_idx = 0; sub_top_idx < mctx->nsub_tops; ++sub_top_idx)
+    {
+      reg_errcode_t err;
+      re_sub_match_top_t *sub_top = mctx->sub_tops[sub_top_idx];
+      re_sub_match_last_t *sub_last;
+      int sub_last_idx, sl_str, bkref_str_off;
+
+      if (dfa->nodes[sub_top->node].opr.idx != subexp_num)
+	continue; /* It isn't related.  */
+
+      sl_str = sub_top->str_idx;
+      bkref_str_off = bkref_str_idx;
+      /* At first, check the last node of sub expressions we already
+	 evaluated.  */
+      for (sub_last_idx = 0; sub_last_idx < sub_top->nlasts; ++sub_last_idx)
+	{
+	  int sl_str_diff;
+	  sub_last = sub_top->lasts[sub_last_idx];
+	  sl_str_diff = sub_last->str_idx - sl_str;
+	  /* The matched string by the sub expression match with the substring
+	     at the back reference?  */
+	  if (sl_str_diff > 0)
+	    {
+	      if (BE (bkref_str_off + sl_str_diff > mctx->input.valid_len, 0))
+		{
+		  /* Not enough chars for a successful match.  */
+		  if (bkref_str_off + sl_str_diff > mctx->input.len)
+		    break;
+
+		  err = clean_state_log_if_needed (mctx,
+						   bkref_str_off
+						   + sl_str_diff);
+		  if (BE (err != REG_NOERROR, 0))
+		    return err;
+		  buf = (const char *) re_string_get_buffer (&mctx->input);
+		}
+	      if (memcmp (buf + bkref_str_off, buf + sl_str, sl_str_diff) != 0)
+		/* We don't need to search this sub expression any more.  */
+		break;
+	    }
+	  bkref_str_off += sl_str_diff;
+	  sl_str += sl_str_diff;
+	  err = get_subexp_sub (mctx, sub_top, sub_last, bkref_node,
+				bkref_str_idx);
+
+	  /* Reload buf, since the preceding call might have reallocated
+	     the buffer.  */
+	  buf = (const char *) re_string_get_buffer (&mctx->input);
+
+	  if (err == REG_NOMATCH)
+	    continue;
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+
+      if (sub_last_idx < sub_top->nlasts)
+	continue;
+      if (sub_last_idx > 0)
+	++sl_str;
+      /* Then, search for the other last nodes of the sub expression.  */
+      for (; sl_str <= bkref_str_idx; ++sl_str)
+	{
+	  int cls_node, sl_str_off;
+	  const re_node_set *nodes;
+	  sl_str_off = sl_str - sub_top->str_idx;
+	  /* The matched string by the sub expression match with the substring
+	     at the back reference?  */
+	  if (sl_str_off > 0)
+	    {
+	      if (BE (bkref_str_off >= mctx->input.valid_len, 0))
+		{
+		  /* If we are at the end of the input, we cannot match.  */
+		  if (bkref_str_off >= mctx->input.len)
+		    break;
+
+		  err = extend_buffers (mctx);
+		  if (BE (err != REG_NOERROR, 0))
+		    return err;
+
+		  buf = (const char *) re_string_get_buffer (&mctx->input);
+		}
+	      if (buf [bkref_str_off++] != buf[sl_str - 1])
+		break; /* We don't need to search this sub expression
+			  any more.  */
+	    }
+	  if (mctx->state_log[sl_str] == NULL)
+	    continue;
+	  /* Does this state have a ')' of the sub expression?  */
+	  nodes = &mctx->state_log[sl_str]->nodes;
+	  cls_node = find_subexp_node (dfa, nodes, subexp_num,
+				       OP_CLOSE_SUBEXP);
+	  if (cls_node == -1)
+	    continue; /* No.  */
+	  if (sub_top->path == NULL)
+	    {
+	      sub_top->path = calloc (sizeof (state_array_t),
+				      sl_str - sub_top->str_idx + 1);
+	      if (sub_top->path == NULL)
+		return REG_ESPACE;
+	    }
+	  /* Can the OP_OPEN_SUBEXP node arrive the OP_CLOSE_SUBEXP node
+	     in the current context?  */
+	  err = check_arrival (mctx, sub_top->path, sub_top->node,
+			       sub_top->str_idx, cls_node, sl_str,
+			       OP_CLOSE_SUBEXP);
+	  if (err == REG_NOMATCH)
+	      continue;
+	  if (BE (err != REG_NOERROR, 0))
+	      return err;
+	  sub_last = match_ctx_add_sublast (sub_top, cls_node, sl_str);
+	  if (BE (sub_last == NULL, 0))
+	    return REG_ESPACE;
+	  err = get_subexp_sub (mctx, sub_top, sub_last, bkref_node,
+				bkref_str_idx);
+	  if (err == REG_NOMATCH)
+	    continue;
+	}
+    }
+  return REG_NOERROR;
+}
+
+/* Helper functions for get_subexp().  */
+
+/* Check SUB_LAST can arrive to the back reference BKREF_NODE at BKREF_STR.
+   If it can arrive, register the sub expression expressed with SUB_TOP
+   and SUB_LAST.  */
+
+static reg_errcode_t
+internal_function
+get_subexp_sub (re_match_context_t *mctx, const re_sub_match_top_t *sub_top,
+		re_sub_match_last_t *sub_last, int bkref_node, int bkref_str)
+{
+  reg_errcode_t err;
+  int to_idx;
+  /* Can the subexpression arrive the back reference?  */
+  err = check_arrival (mctx, &sub_last->path, sub_last->node,
+		       sub_last->str_idx, bkref_node, bkref_str,
+		       OP_OPEN_SUBEXP);
+  if (err != REG_NOERROR)
+    return err;
+  err = match_ctx_add_entry (mctx, bkref_node, bkref_str, sub_top->str_idx,
+			     sub_last->str_idx);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  to_idx = bkref_str + sub_last->str_idx - sub_top->str_idx;
+  return clean_state_log_if_needed (mctx, to_idx);
+}
+
+/* Find the first node which is '(' or ')' and whose index is SUBEXP_IDX.
+   Search '(' if FL_OPEN, or search ')' otherwise.
+   TODO: This function isn't efficient...
+	 Because there might be more than one nodes whose types are
+	 OP_OPEN_SUBEXP and whose index is SUBEXP_IDX, we must check all
+	 nodes.
+	 E.g. RE: (a){2}  */
+
+static int
+internal_function
+find_subexp_node (const re_dfa_t *dfa, const re_node_set *nodes,
+		  int subexp_idx, int type)
+{
+  int cls_idx;
+  for (cls_idx = 0; cls_idx < nodes->nelem; ++cls_idx)
+    {
+      int cls_node = nodes->elems[cls_idx];
+      const re_token_t *node = dfa->nodes + cls_node;
+      if (node->type == type
+	  && node->opr.idx == subexp_idx)
+	return cls_node;
+    }
+  return -1;
+}
+
+/* Check whether the node TOP_NODE at TOP_STR can arrive to the node
+   LAST_NODE at LAST_STR.  We record the path onto PATH since it will be
+   heavily reused.
+   Return REG_NOERROR if it can arrive, or REG_NOMATCH otherwise.  */
+
+static reg_errcode_t
+internal_function
+check_arrival (re_match_context_t *mctx, state_array_t *path, int top_node,
+	       int top_str, int last_node, int last_str, int type)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err = REG_NOERROR;
+  int subexp_num, backup_cur_idx, str_idx, null_cnt;
+  re_dfastate_t *cur_state = NULL;
+  re_node_set *cur_nodes, next_nodes;
+  re_dfastate_t **backup_state_log;
+  unsigned int context;
+
+  subexp_num = dfa->nodes[top_node].opr.idx;
+  /* Extend the buffer if we need.  */
+  if (BE (path->alloc < last_str + mctx->max_mb_elem_len + 1, 0))
+    {
+      re_dfastate_t **new_array;
+      int old_alloc = path->alloc;
+      path->alloc += last_str + mctx->max_mb_elem_len + 1;
+      new_array = re_realloc (path->array, re_dfastate_t *, path->alloc);
+      if (BE (new_array == NULL, 0))
+	{
+	  path->alloc = old_alloc;
+	  return REG_ESPACE;
+	}
+      path->array = new_array;
+      memset (new_array + old_alloc, '\0',
+	      sizeof (re_dfastate_t *) * (path->alloc - old_alloc));
+    }
+
+  str_idx = path->next_idx ? path->next_idx : top_str;
+
+  /* Temporary modify MCTX.  */
+  backup_state_log = mctx->state_log;
+  backup_cur_idx = mctx->input.cur_idx;
+  mctx->state_log = path->array;
+  mctx->input.cur_idx = str_idx;
+
+  /* Setup initial node set.  */
+  context = re_string_context_at (&mctx->input, str_idx - 1, mctx->eflags);
+  if (str_idx == top_str)
+    {
+      err = re_node_set_init_1 (&next_nodes, top_node);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+      err = check_arrival_expand_ecl (dfa, &next_nodes, subexp_num, type);
+      if (BE (err != REG_NOERROR, 0))
+	{
+	  re_node_set_free (&next_nodes);
+	  return err;
+	}
+    }
+  else
+    {
+      cur_state = mctx->state_log[str_idx];
+      if (cur_state && cur_state->has_backref)
+	{
+	  err = re_node_set_init_copy (&next_nodes, &cur_state->nodes);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+      else
+	re_node_set_init_empty (&next_nodes);
+    }
+  if (str_idx == top_str || (cur_state && cur_state->has_backref))
+    {
+      if (next_nodes.nelem)
+	{
+	  err = expand_bkref_cache (mctx, &next_nodes, str_idx,
+				    subexp_num, type);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return err;
+	    }
+	}
+      cur_state = re_acquire_state_context (&err, dfa, &next_nodes, context);
+      if (BE (cur_state == NULL && err != REG_NOERROR, 0))
+	{
+	  re_node_set_free (&next_nodes);
+	  return err;
+	}
+      mctx->state_log[str_idx] = cur_state;
+    }
+
+  for (null_cnt = 0; str_idx < last_str && null_cnt <= mctx->max_mb_elem_len;)
+    {
+      re_node_set_empty (&next_nodes);
+      if (mctx->state_log[str_idx + 1])
+	{
+	  err = re_node_set_merge (&next_nodes,
+				   &mctx->state_log[str_idx + 1]->nodes);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return err;
+	    }
+	}
+      if (cur_state)
+	{
+	  err = check_arrival_add_next_nodes (mctx, str_idx,
+					      &cur_state->non_eps_nodes,
+					      &next_nodes);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return err;
+	    }
+	}
+      ++str_idx;
+      if (next_nodes.nelem)
+	{
+	  err = check_arrival_expand_ecl (dfa, &next_nodes, subexp_num, type);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return err;
+	    }
+	  err = expand_bkref_cache (mctx, &next_nodes, str_idx,
+				    subexp_num, type);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&next_nodes);
+	      return err;
+	    }
+	}
+      context = re_string_context_at (&mctx->input, str_idx - 1, mctx->eflags);
+      cur_state = re_acquire_state_context (&err, dfa, &next_nodes, context);
+      if (BE (cur_state == NULL && err != REG_NOERROR, 0))
+	{
+	  re_node_set_free (&next_nodes);
+	  return err;
+	}
+      mctx->state_log[str_idx] = cur_state;
+      null_cnt = cur_state == NULL ? null_cnt + 1 : 0;
+    }
+  re_node_set_free (&next_nodes);
+  cur_nodes = (mctx->state_log[last_str] == NULL ? NULL
+	       : &mctx->state_log[last_str]->nodes);
+  path->next_idx = str_idx;
+
+  /* Fix MCTX.  */
+  mctx->state_log = backup_state_log;
+  mctx->input.cur_idx = backup_cur_idx;
+
+  /* Then check the current node set has the node LAST_NODE.  */
+  if (cur_nodes != NULL && re_node_set_contains (cur_nodes, last_node))
+    return REG_NOERROR;
+
+  return REG_NOMATCH;
+}
+
+/* Helper functions for check_arrival.  */
+
+/* Calculate the destination nodes of CUR_NODES at STR_IDX, and append them
+   to NEXT_NODES.
+   TODO: This function is similar to the functions transit_state*(),
+	 however this function has many additional works.
+	 Can't we unify them?  */
+
+static reg_errcode_t
+internal_function
+check_arrival_add_next_nodes (re_match_context_t *mctx, int str_idx,
+			      re_node_set *cur_nodes, re_node_set *next_nodes)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  int result;
+  int cur_idx;
+#ifdef RE_ENABLE_I18N
+  reg_errcode_t err = REG_NOERROR;
+#endif
+  re_node_set union_set;
+  re_node_set_init_empty (&union_set);
+  for (cur_idx = 0; cur_idx < cur_nodes->nelem; ++cur_idx)
+    {
+      int naccepted = 0;
+      int cur_node = cur_nodes->elems[cur_idx];
+#ifdef DEBUG
+      re_token_type_t type = dfa->nodes[cur_node].type;
+      assert (!IS_EPSILON_NODE (type));
+#endif
+#ifdef RE_ENABLE_I18N
+      /* If the node may accept `multi byte'.  */
+      if (dfa->nodes[cur_node].accept_mb)
+	{
+	  naccepted = check_node_accept_bytes (dfa, cur_node, &mctx->input,
+					       str_idx);
+	  if (naccepted > 1)
+	    {
+	      re_dfastate_t *dest_state;
+	      int next_node = dfa->nexts[cur_node];
+	      int next_idx = str_idx + naccepted;
+	      dest_state = mctx->state_log[next_idx];
+	      re_node_set_empty (&union_set);
+	      if (dest_state)
+		{
+		  err = re_node_set_merge (&union_set, &dest_state->nodes);
+		  if (BE (err != REG_NOERROR, 0))
+		    {
+		      re_node_set_free (&union_set);
+		      return err;
+		    }
+		}
+	      result = re_node_set_insert (&union_set, next_node);
+	      if (BE (result < 0, 0))
+		{
+		  re_node_set_free (&union_set);
+		  return REG_ESPACE;
+		}
+	      mctx->state_log[next_idx] = re_acquire_state (&err, dfa,
+							    &union_set);
+	      if (BE (mctx->state_log[next_idx] == NULL
+		      && err != REG_NOERROR, 0))
+		{
+		  re_node_set_free (&union_set);
+		  return err;
+		}
+	    }
+	}
+#endif /* RE_ENABLE_I18N */
+      if (naccepted
+	  || check_node_accept (mctx, dfa->nodes + cur_node, str_idx))
+	{
+	  result = re_node_set_insert (next_nodes, dfa->nexts[cur_node]);
+	  if (BE (result < 0, 0))
+	    {
+	      re_node_set_free (&union_set);
+	      return REG_ESPACE;
+	    }
+	}
+    }
+  re_node_set_free (&union_set);
+  return REG_NOERROR;
+}
+
+/* For all the nodes in CUR_NODES, add the epsilon closures of them to
+   CUR_NODES, however exclude the nodes which are:
+    - inside the sub expression whose number is EX_SUBEXP, if FL_OPEN.
+    - out of the sub expression whose number is EX_SUBEXP, if !FL_OPEN.
+*/
+
+static reg_errcode_t
+internal_function
+check_arrival_expand_ecl (const re_dfa_t *dfa, re_node_set *cur_nodes,
+			  int ex_subexp, int type)
+{
+  reg_errcode_t err;
+  int idx, outside_node;
+  re_node_set new_nodes;
+#ifdef DEBUG
+  assert (cur_nodes->nelem);
+#endif
+  err = re_node_set_alloc (&new_nodes, cur_nodes->nelem);
+  if (BE (err != REG_NOERROR, 0))
+    return err;
+  /* Create a new node set NEW_NODES with the nodes which are epsilon
+     closures of the node in CUR_NODES.  */
+
+  for (idx = 0; idx < cur_nodes->nelem; ++idx)
+    {
+      int cur_node = cur_nodes->elems[idx];
+      const re_node_set *eclosure = dfa->eclosures + cur_node;
+      outside_node = find_subexp_node (dfa, eclosure, ex_subexp, type);
+      if (outside_node == -1)
+	{
+	  /* There are no problematic nodes, just merge them.  */
+	  err = re_node_set_merge (&new_nodes, eclosure);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&new_nodes);
+	      return err;
+	    }
+	}
+      else
+	{
+	  /* There are problematic nodes, re-calculate incrementally.  */
+	  err = check_arrival_expand_ecl_sub (dfa, &new_nodes, cur_node,
+					      ex_subexp, type);
+	  if (BE (err != REG_NOERROR, 0))
+	    {
+	      re_node_set_free (&new_nodes);
+	      return err;
+	    }
+	}
+    }
+  re_node_set_free (cur_nodes);
+  *cur_nodes = new_nodes;
+  return REG_NOERROR;
+}
+
+/* Helper function for check_arrival_expand_ecl.
+   Check incrementally the epsilon closure of TARGET, and if it isn't
+   problematic append it to DST_NODES.  */
+
+static reg_errcode_t
+internal_function
+check_arrival_expand_ecl_sub (const re_dfa_t *dfa, re_node_set *dst_nodes,
+			      int target, int ex_subexp, int type)
+{
+  int cur_node;
+  for (cur_node = target; !re_node_set_contains (dst_nodes, cur_node);)
+    {
+      int err;
+
+      if (dfa->nodes[cur_node].type == type
+	  && dfa->nodes[cur_node].opr.idx == ex_subexp)
+	{
+	  if (type == OP_CLOSE_SUBEXP)
+	    {
+	      err = re_node_set_insert (dst_nodes, cur_node);
+	      if (BE (err == -1, 0))
+		return REG_ESPACE;
+	    }
+	  break;
+	}
+      err = re_node_set_insert (dst_nodes, cur_node);
+      if (BE (err == -1, 0))
+	return REG_ESPACE;
+      if (dfa->edests[cur_node].nelem == 0)
+	break;
+      if (dfa->edests[cur_node].nelem == 2)
+	{
+	  err = check_arrival_expand_ecl_sub (dfa, dst_nodes,
+					      dfa->edests[cur_node].elems[1],
+					      ex_subexp, type);
+	  if (BE (err != REG_NOERROR, 0))
+	    return err;
+	}
+      cur_node = dfa->edests[cur_node].elems[0];
+    }
+  return REG_NOERROR;
+}
+
+
+/* For all the back references in the current state, calculate the
+   destination of the back references by the appropriate entry
+   in MCTX->BKREF_ENTS.  */
+
+static reg_errcode_t
+internal_function
+expand_bkref_cache (re_match_context_t *mctx, re_node_set *cur_nodes,
+		    int cur_str, int subexp_num, int type)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  int cache_idx_start = search_cur_bkref_entry (mctx, cur_str);
+  struct re_backref_cache_entry *ent;
+
+  if (cache_idx_start == -1)
+    return REG_NOERROR;
+
+ restart:
+  ent = mctx->bkref_ents + cache_idx_start;
+  do
+    {
+      int to_idx, next_node;
+
+      /* Is this entry ENT is appropriate?  */
+      if (!re_node_set_contains (cur_nodes, ent->node))
+	continue; /* No.  */
+
+      to_idx = cur_str + ent->subexp_to - ent->subexp_from;
+      /* Calculate the destination of the back reference, and append it
+	 to MCTX->STATE_LOG.  */
+      if (to_idx == cur_str)
+	{
+	  /* The backreference did epsilon transit, we must re-check all the
+	     node in the current state.  */
+	  re_node_set new_dests;
+	  reg_errcode_t err2, err3;
+	  next_node = dfa->edests[ent->node].elems[0];
+	  if (re_node_set_contains (cur_nodes, next_node))
+	    continue;
+	  err = re_node_set_init_1 (&new_dests, next_node);
+	  err2 = check_arrival_expand_ecl (dfa, &new_dests, subexp_num, type);
+	  err3 = re_node_set_merge (cur_nodes, &new_dests);
+	  re_node_set_free (&new_dests);
+	  if (BE (err != REG_NOERROR || err2 != REG_NOERROR
+		  || err3 != REG_NOERROR, 0))
+	    {
+	      err = (err != REG_NOERROR ? err
+		     : (err2 != REG_NOERROR ? err2 : err3));
+	      return err;
+	    }
+	  /* TODO: It is still inefficient...  */
+	  goto restart;
+	}
+      else
+	{
+	  re_node_set union_set;
+	  next_node = dfa->nexts[ent->node];
+	  if (mctx->state_log[to_idx])
+	    {
+	      int ret;
+	      if (re_node_set_contains (&mctx->state_log[to_idx]->nodes,
+					next_node))
+		continue;
+	      err = re_node_set_init_copy (&union_set,
+					   &mctx->state_log[to_idx]->nodes);
+	      ret = re_node_set_insert (&union_set, next_node);
+	      if (BE (err != REG_NOERROR || ret < 0, 0))
+		{
+		  re_node_set_free (&union_set);
+		  err = err != REG_NOERROR ? err : REG_ESPACE;
+		  return err;
+		}
+	    }
+	  else
+	    {
+	      err = re_node_set_init_1 (&union_set, next_node);
+	      if (BE (err != REG_NOERROR, 0))
+		return err;
+	    }
+	  mctx->state_log[to_idx] = re_acquire_state (&err, dfa, &union_set);
+	  re_node_set_free (&union_set);
+	  if (BE (mctx->state_log[to_idx] == NULL
+		  && err != REG_NOERROR, 0))
+	    return err;
+	}
+    }
+  while (ent++->more);
+  return REG_NOERROR;
+}
+
+/* Build transition table for the state.
+   Return 1 if succeeded, otherwise return NULL.  */
+
+static int
+internal_function
+build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
+{
+  reg_errcode_t err;
+  int i, j, ch, need_word_trtable = 0;
+  bitset_word_t elem, mask;
+  bool dests_node_malloced = false;
+  bool dest_states_malloced = false;
+  int ndests; /* Number of the destination states from `state'.  */
+  re_dfastate_t **trtable;
+  re_dfastate_t **dest_states = NULL, **dest_states_word, **dest_states_nl;
+  re_node_set follows, *dests_node;
+  bitset_t *dests_ch;
+  bitset_t acceptable;
+
+  struct dests_alloc
+  {
+    re_node_set dests_node[SBC_MAX];
+    bitset_t dests_ch[SBC_MAX];
+  } *dests_alloc;
+
+  /* We build DFA states which corresponds to the destination nodes
+     from `state'.  `dests_node[i]' represents the nodes which i-th
+     destination state contains, and `dests_ch[i]' represents the
+     characters which i-th destination state accepts.  */
+#ifdef HAVE_ALLOCA
+  if (__libc_use_alloca (sizeof (struct dests_alloc)))
+    dests_alloc = (struct dests_alloc *) alloca (sizeof (struct dests_alloc));
+  else
+#endif
+    {
+      dests_alloc = re_malloc (struct dests_alloc, 1);
+      if (BE (dests_alloc == NULL, 0))
+	return 0;
+      dests_node_malloced = true;
+    }
+  dests_node = dests_alloc->dests_node;
+  dests_ch = dests_alloc->dests_ch;
+
+  /* Initialize transition table.  */
+  state->word_trtable = state->trtable = NULL;
+
+  /* At first, group all nodes belonging to `state' into several
+     destinations.  */
+  ndests = group_nodes_into_DFAstates (dfa, state, dests_node, dests_ch);
+  if (BE (ndests <= 0, 0))
+    {
+      if (dests_node_malloced)
+	free (dests_alloc);
+      /* Return 0 in case of an error, 1 otherwise.  */
+      if (ndests == 0)
+	{
+	  state->trtable = (re_dfastate_t **)
+	    calloc (sizeof (re_dfastate_t *), SBC_MAX);
+	  return 1;
+	}
+      return 0;
+    }
+
+  err = re_node_set_alloc (&follows, ndests + 1);
+  if (BE (err != REG_NOERROR, 0))
+    goto out_free;
+
+  /* Avoid arithmetic overflow in size calculation.  */
+  if (BE ((((SIZE_MAX - (sizeof (re_node_set) + sizeof (bitset_t)) * SBC_MAX)
+	    / (3 * sizeof (re_dfastate_t *)))
+	   < ndests),
+	  0))
+    goto out_free;
+
+#ifdef HAVE_ALLOCA
+  if (__libc_use_alloca ((sizeof (re_node_set) + sizeof (bitset_t)) * SBC_MAX
+			 + ndests * 3 * sizeof (re_dfastate_t *)))
+    dest_states = (re_dfastate_t **)
+      alloca (ndests * 3 * sizeof (re_dfastate_t *));
+  else
+#endif
+    {
+      dest_states = (re_dfastate_t **)
+	malloc (ndests * 3 * sizeof (re_dfastate_t *));
+      if (BE (dest_states == NULL, 0))
+	{
+out_free:
+	  if (dest_states_malloced)
+	    free (dest_states);
+	  re_node_set_free (&follows);
+	  for (i = 0; i < ndests; ++i)
+	    re_node_set_free (dests_node + i);
+	  if (dests_node_malloced)
+	    free (dests_alloc);
+	  return 0;
+	}
+      dest_states_malloced = true;
+    }
+  dest_states_word = dest_states + ndests;
+  dest_states_nl = dest_states_word + ndests;
+  bitset_empty (acceptable);
+
+  /* Then build the states for all destinations.  */
+  for (i = 0; i < ndests; ++i)
+    {
+      int next_node;
+      re_node_set_empty (&follows);
+      /* Merge the follows of this destination states.  */
+      for (j = 0; j < dests_node[i].nelem; ++j)
+	{
+	  next_node = dfa->nexts[dests_node[i].elems[j]];
+	  if (next_node != -1)
+	    {
+	      err = re_node_set_merge (&follows, dfa->eclosures + next_node);
+	      if (BE (err != REG_NOERROR, 0))
+		goto out_free;
+	    }
+	}
+      dest_states[i] = re_acquire_state_context (&err, dfa, &follows, 0);
+      if (BE (dest_states[i] == NULL && err != REG_NOERROR, 0))
+	goto out_free;
+      /* If the new state has context constraint,
+	 build appropriate states for these contexts.  */
+      if (dest_states[i]->has_constraint)
+	{
+	  dest_states_word[i] = re_acquire_state_context (&err, dfa, &follows,
+							  CONTEXT_WORD);
+	  if (BE (dest_states_word[i] == NULL && err != REG_NOERROR, 0))
+	    goto out_free;
+
+	  if (dest_states[i] != dest_states_word[i] && dfa->mb_cur_max > 1)
+	    need_word_trtable = 1;
+
+	  dest_states_nl[i] = re_acquire_state_context (&err, dfa, &follows,
+							CONTEXT_NEWLINE);
+	  if (BE (dest_states_nl[i] == NULL && err != REG_NOERROR, 0))
+	    goto out_free;
+ 	}
+      else
+	{
+	  dest_states_word[i] = dest_states[i];
+	  dest_states_nl[i] = dest_states[i];
+	}
+      bitset_merge (acceptable, dests_ch[i]);
+    }
+
+  if (!BE (need_word_trtable, 0))
+    {
+      /* We don't care about whether the following character is a word
+	 character, or we are in a single-byte character set so we can
+	 discern by looking at the character code: allocate a
+	 256-entry transition table.  */
+      trtable = state->trtable =
+	(re_dfastate_t **) calloc (sizeof (re_dfastate_t *), SBC_MAX);
+      if (BE (trtable == NULL, 0))
+	goto out_free;
+
+      /* For all characters ch...:  */
+      for (i = 0; i < BITSET_WORDS; ++i)
+	for (ch = i * BITSET_WORD_BITS, elem = acceptable[i], mask = 1;
+	     elem;
+	     mask <<= 1, elem >>= 1, ++ch)
+	  if (BE (elem & 1, 0))
+	    {
+	      /* There must be exactly one destination which accepts
+		 character ch.  See group_nodes_into_DFAstates.  */
+	      for (j = 0; (dests_ch[j][i] & mask) == 0; ++j)
+		;
+
+	      /* j-th destination accepts the word character ch.  */
+	      if (dfa->word_char[i] & mask)
+		trtable[ch] = dest_states_word[j];
+	      else
+		trtable[ch] = dest_states[j];
+	    }
+    }
+  else
+    {
+      /* We care about whether the following character is a word
+	 character, and we are in a multi-byte character set: discern
+	 by looking at the character code: build two 256-entry
+	 transition tables, one starting at trtable[0] and one
+	 starting at trtable[SBC_MAX].  */
+      trtable = state->word_trtable =
+	(re_dfastate_t **) calloc (sizeof (re_dfastate_t *), 2 * SBC_MAX);
+      if (BE (trtable == NULL, 0))
+	goto out_free;
+
+      /* For all characters ch...:  */
+      for (i = 0; i < BITSET_WORDS; ++i)
+	for (ch = i * BITSET_WORD_BITS, elem = acceptable[i], mask = 1;
+	     elem;
+	     mask <<= 1, elem >>= 1, ++ch)
+	  if (BE (elem & 1, 0))
+	    {
+	      /* There must be exactly one destination which accepts
+		 character ch.  See group_nodes_into_DFAstates.  */
+	      for (j = 0; (dests_ch[j][i] & mask) == 0; ++j)
+		;
+
+	      /* j-th destination accepts the word character ch.  */
+	      trtable[ch] = dest_states[j];
+	      trtable[ch + SBC_MAX] = dest_states_word[j];
+	    }
+    }
+
+  /* new line */
+  if (bitset_contain (acceptable, NEWLINE_CHAR))
+    {
+      /* The current state accepts newline character.  */
+      for (j = 0; j < ndests; ++j)
+	if (bitset_contain (dests_ch[j], NEWLINE_CHAR))
+	  {
+	    /* k-th destination accepts newline character.  */
+	    trtable[NEWLINE_CHAR] = dest_states_nl[j];
+	    if (need_word_trtable)
+	      trtable[NEWLINE_CHAR + SBC_MAX] = dest_states_nl[j];
+	    /* There must be only one destination which accepts
+	       newline.  See group_nodes_into_DFAstates.  */
+	    break;
+	  }
+    }
+
+  if (dest_states_malloced)
+    free (dest_states);
+
+  re_node_set_free (&follows);
+  for (i = 0; i < ndests; ++i)
+    re_node_set_free (dests_node + i);
+
+  if (dests_node_malloced)
+    free (dests_alloc);
+
+  return 1;
+}
+
+/* Group all nodes belonging to STATE into several destinations.
+   Then for all destinations, set the nodes belonging to the destination
+   to DESTS_NODE[i] and set the characters accepted by the destination
+   to DEST_CH[i].  This function return the number of destinations.  */
+
+static int
+internal_function
+group_nodes_into_DFAstates (const re_dfa_t *dfa, const re_dfastate_t *state,
+			    re_node_set *dests_node, bitset_t *dests_ch)
+{
+  reg_errcode_t err;
+  int result;
+  int i, j, k;
+  int ndests; /* Number of the destinations from `state'.  */
+  bitset_t accepts; /* Characters a node can accept.  */
+  const re_node_set *cur_nodes = &state->nodes;
+  bitset_empty (accepts);
+  ndests = 0;
+
+  /* For all the nodes belonging to `state',  */
+  for (i = 0; i < cur_nodes->nelem; ++i)
+    {
+      re_token_t *node = &dfa->nodes[cur_nodes->elems[i]];
+      re_token_type_t type = node->type;
+      unsigned int constraint = node->constraint;
+
+      /* Enumerate all single byte character this node can accept.  */
+      if (type == CHARACTER)
+	bitset_set (accepts, node->opr.c);
+      else if (type == SIMPLE_BRACKET)
+	{
+	  bitset_merge (accepts, node->opr.sbcset);
+	}
+      else if (type == OP_PERIOD)
+	{
+#ifdef RE_ENABLE_I18N
+	  if (dfa->mb_cur_max > 1)
+	    bitset_merge (accepts, dfa->sb_char);
+	  else
+#endif
+	    bitset_set_all (accepts);
+	  if (!(dfa->syntax & RE_DOT_NEWLINE))
+	    bitset_clear (accepts, '\n');
+	  if (dfa->syntax & RE_DOT_NOT_NULL)
+	    bitset_clear (accepts, '\0');
+	}
+#ifdef RE_ENABLE_I18N
+      else if (type == OP_UTF8_PERIOD)
+	{
+	  memset (accepts, '\xff', sizeof (bitset_t) / 2);
+	  if (!(dfa->syntax & RE_DOT_NEWLINE))
+	    bitset_clear (accepts, '\n');
+	  if (dfa->syntax & RE_DOT_NOT_NULL)
+	    bitset_clear (accepts, '\0');
+	}
+#endif
+      else
+	continue;
+
+      /* Check the `accepts' and sift the characters which are not
+	 match it the context.  */
+      if (constraint)
+	{
+	  if (constraint & NEXT_NEWLINE_CONSTRAINT)
+	    {
+	      bool accepts_newline = bitset_contain (accepts, NEWLINE_CHAR);
+	      bitset_empty (accepts);
+	      if (accepts_newline)
+		bitset_set (accepts, NEWLINE_CHAR);
+	      else
+		continue;
+	    }
+	  if (constraint & NEXT_ENDBUF_CONSTRAINT)
+	    {
+	      bitset_empty (accepts);
+	      continue;
+	    }
+
+	  if (constraint & NEXT_WORD_CONSTRAINT)
+	    {
+	      bitset_word_t any_set = 0;
+	      if (type == CHARACTER && !node->word_char)
+		{
+		  bitset_empty (accepts);
+		  continue;
+		}
+#ifdef RE_ENABLE_I18N
+	      if (dfa->mb_cur_max > 1)
+		for (j = 0; j < BITSET_WORDS; ++j)
+		  any_set |= (accepts[j] &= (dfa->word_char[j] | ~dfa->sb_char[j]));
+	      else
+#endif
+		for (j = 0; j < BITSET_WORDS; ++j)
+		  any_set |= (accepts[j] &= dfa->word_char[j]);
+	      if (!any_set)
+		continue;
+	    }
+	  if (constraint & NEXT_NOTWORD_CONSTRAINT)
+	    {
+	      bitset_word_t any_set = 0;
+	      if (type == CHARACTER && node->word_char)
+		{
+		  bitset_empty (accepts);
+		  continue;
+		}
+#ifdef RE_ENABLE_I18N
+	      if (dfa->mb_cur_max > 1)
+		for (j = 0; j < BITSET_WORDS; ++j)
+		  any_set |= (accepts[j] &= ~(dfa->word_char[j] & dfa->sb_char[j]));
+	      else
+#endif
+		for (j = 0; j < BITSET_WORDS; ++j)
+		  any_set |= (accepts[j] &= ~dfa->word_char[j]);
+	      if (!any_set)
+		continue;
+	    }
+	}
+
+      /* Then divide `accepts' into DFA states, or create a new
+	 state.  Above, we make sure that accepts is not empty.  */
+      for (j = 0; j < ndests; ++j)
+	{
+	  bitset_t intersec; /* Intersection sets, see below.  */
+	  bitset_t remains;
+	  /* Flags, see below.  */
+	  bitset_word_t has_intersec, not_subset, not_consumed;
+
+	  /* Optimization, skip if this state doesn't accept the character.  */
+	  if (type == CHARACTER && !bitset_contain (dests_ch[j], node->opr.c))
+	    continue;
+
+	  /* Enumerate the intersection set of this state and `accepts'.  */
+	  has_intersec = 0;
+	  for (k = 0; k < BITSET_WORDS; ++k)
+	    has_intersec |= intersec[k] = accepts[k] & dests_ch[j][k];
+	  /* And skip if the intersection set is empty.  */
+	  if (!has_intersec)
+	    continue;
+
+	  /* Then check if this state is a subset of `accepts'.  */
+	  not_subset = not_consumed = 0;
+	  for (k = 0; k < BITSET_WORDS; ++k)
+	    {
+	      not_subset |= remains[k] = ~accepts[k] & dests_ch[j][k];
+	      not_consumed |= accepts[k] = accepts[k] & ~dests_ch[j][k];
+	    }
+
+	  /* If this state isn't a subset of `accepts', create a
+	     new group state, which has the `remains'. */
+	  if (not_subset)
+	    {
+	      bitset_copy (dests_ch[ndests], remains);
+	      bitset_copy (dests_ch[j], intersec);
+	      err = re_node_set_init_copy (dests_node + ndests, &dests_node[j]);
+	      if (BE (err != REG_NOERROR, 0))
+		goto error_return;
+	      ++ndests;
+	    }
+
+	  /* Put the position in the current group. */
+	  result = re_node_set_insert (&dests_node[j], cur_nodes->elems[i]);
+	  if (BE (result < 0, 0))
+	    goto error_return;
+
+	  /* If all characters are consumed, go to next node. */
+	  if (!not_consumed)
+	    break;
+	}
+      /* Some characters remain, create a new group. */
+      if (j == ndests)
+	{
+	  bitset_copy (dests_ch[ndests], accepts);
+	  err = re_node_set_init_1 (dests_node + ndests, cur_nodes->elems[i]);
+	  if (BE (err != REG_NOERROR, 0))
+	    goto error_return;
+	  ++ndests;
+	  bitset_empty (accepts);
+	}
+    }
+  return ndests;
+ error_return:
+  for (j = 0; j < ndests; ++j)
+    re_node_set_free (dests_node + j);
+  return -1;
+}
+
+#ifdef RE_ENABLE_I18N
+/* Check how many bytes the node `dfa->nodes[node_idx]' accepts.
+   Return the number of the bytes the node accepts.
+   STR_IDX is the current index of the input string.
+
+   This function handles the nodes which can accept one character, or
+   one collating element like '.', '[a-z]', opposite to the other nodes
+   can only accept one byte.  */
+
+static int
+internal_function
+check_node_accept_bytes (const re_dfa_t *dfa, int node_idx,
+			 const re_string_t *input, int str_idx)
+{
+  const re_token_t *node = dfa->nodes + node_idx;
+  int char_len, elem_len;
+  int i;
+  wint_t wc;
+
+  if (BE (node->type == OP_UTF8_PERIOD, 0))
+    {
+      unsigned char c = re_string_byte_at (input, str_idx), d;
+      if (BE (c < 0xc2, 1))
+	return 0;
+
+      if (str_idx + 2 > input->len)
+	return 0;
+
+      d = re_string_byte_at (input, str_idx + 1);
+      if (c < 0xe0)
+	return (d < 0x80 || d > 0xbf) ? 0 : 2;
+      else if (c < 0xf0)
+	{
+	  char_len = 3;
+	  if (c == 0xe0 && d < 0xa0)
+	    return 0;
+	}
+      else if (c < 0xf8)
+	{
+	  char_len = 4;
+	  if (c == 0xf0 && d < 0x90)
+	    return 0;
+	}
+      else if (c < 0xfc)
+	{
+	  char_len = 5;
+	  if (c == 0xf8 && d < 0x88)
+	    return 0;
+	}
+      else if (c < 0xfe)
+	{
+	  char_len = 6;
+	  if (c == 0xfc && d < 0x84)
+	    return 0;
+	}
+      else
+	return 0;
+
+      if (str_idx + char_len > input->len)
+	return 0;
+
+      for (i = 1; i < char_len; ++i)
+	{
+	  d = re_string_byte_at (input, str_idx + i);
+	  if (d < 0x80 || d > 0xbf)
+	    return 0;
+	}
+      return char_len;
+    }
+
+  char_len = re_string_char_size_at (input, str_idx);
+  if (node->type == OP_PERIOD)
+    {
+      if (char_len <= 1)
+	return 0;
+      /* FIXME: I don't think this if is needed, as both '\n'
+	 and '\0' are char_len == 1.  */
+      /* '.' accepts any one character except the following two cases.  */
+      if ((!(dfa->syntax & RE_DOT_NEWLINE) &&
+	   re_string_byte_at (input, str_idx) == '\n') ||
+	  ((dfa->syntax & RE_DOT_NOT_NULL) &&
+	   re_string_byte_at (input, str_idx) == '\0'))
+	return 0;
+      return char_len;
+    }
+
+  elem_len = re_string_elem_size_at (input, str_idx);
+  wc = __btowc(*(input->mbs+str_idx));
+  if (((elem_len <= 1 && char_len <= 1) || char_len == 0) && (wc != WEOF && wc < SBC_MAX))
+    return 0;
+
+  if (node->type == COMPLEX_BRACKET)
+    {
+      const re_charset_t *cset = node->opr.mbcset;
+# ifdef _LIBC
+      const unsigned char *pin
+	= ((const unsigned char *) re_string_get_buffer (input) + str_idx);
+      int j;
+      uint32_t nrules;
+# endif /* _LIBC */
+      int match_len = 0;
+      wchar_t wc = ((cset->nranges || cset->nchar_classes || cset->nmbchars)
+		    ? re_string_wchar_at (input, str_idx) : 0);
+
+      /* match with multibyte character?  */
+      for (i = 0; i < cset->nmbchars; ++i)
+	if (wc == cset->mbchars[i])
+	  {
+	    match_len = char_len;
+	    goto check_node_accept_bytes_match;
+	  }
+      /* match with character_class?  */
+      for (i = 0; i < cset->nchar_classes; ++i)
+	{
+	  wctype_t wt = cset->char_classes[i];
+	  if (__iswctype (wc, wt))
+	    {
+	      match_len = char_len;
+	      goto check_node_accept_bytes_match;
+	    }
+	}
+
+# ifdef _LIBC
+      nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+      if (nrules != 0)
+	{
+	  unsigned int in_collseq = 0;
+	  const int32_t *table, *indirect;
+	  const unsigned char *weights, *extra;
+	  const char *collseqwc;
+	  /* This #include defines a local function!  */
+#  include <locale/weight.h>
+
+	  /* match with collating_symbol?  */
+	  if (cset->ncoll_syms)
+	    extra = (const unsigned char *)
+	      _NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
+	  for (i = 0; i < cset->ncoll_syms; ++i)
+	    {
+	      const unsigned char *coll_sym = extra + cset->coll_syms[i];
+	      /* Compare the length of input collating element and
+		 the length of current collating element.  */
+	      if (*coll_sym != elem_len)
+		continue;
+	      /* Compare each bytes.  */
+	      for (j = 0; j < *coll_sym; j++)
+		if (pin[j] != coll_sym[1 + j])
+		  break;
+	      if (j == *coll_sym)
+		{
+		  /* Match if every bytes is equal.  */
+		  match_len = j;
+		  goto check_node_accept_bytes_match;
+		}
+	    }
+
+	  if (cset->nranges)
+	    {
+	      if (elem_len <= char_len)
+		{
+		  collseqwc = _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQWC);
+		  in_collseq = __collseq_table_lookup (collseqwc, wc);
+		}
+	      else
+		in_collseq = find_collation_sequence_value (pin, elem_len);
+	    }
+	  /* match with range expression?  */
+	  for (i = 0; i < cset->nranges; ++i)
+	    if (cset->range_starts[i] <= in_collseq
+		&& in_collseq <= cset->range_ends[i])
+	      {
+		match_len = elem_len;
+		goto check_node_accept_bytes_match;
+	      }
+
+	  /* match with equivalence_class?  */
+	  if (cset->nequiv_classes)
+	    {
+	      const unsigned char *cp = pin;
+	      table = (const int32_t *)
+		_NL_CURRENT (LC_COLLATE, _NL_COLLATE_TABLEMB);
+	      weights = (const unsigned char *)
+		_NL_CURRENT (LC_COLLATE, _NL_COLLATE_WEIGHTMB);
+	      extra = (const unsigned char *)
+		_NL_CURRENT (LC_COLLATE, _NL_COLLATE_EXTRAMB);
+	      indirect = (const int32_t *)
+		_NL_CURRENT (LC_COLLATE, _NL_COLLATE_INDIRECTMB);
+	      int32_t idx = findidx (&cp);
+	      if (idx > 0)
+		for (i = 0; i < cset->nequiv_classes; ++i)
+		  {
+		    int32_t equiv_class_idx = cset->equiv_classes[i];
+		    size_t weight_len = weights[idx & 0xffffff];
+		    if (weight_len == weights[equiv_class_idx & 0xffffff]
+			&& (idx >> 24) == (equiv_class_idx >> 24))
+		      {
+			int cnt = 0;
+
+			idx &= 0xffffff;
+			equiv_class_idx &= 0xffffff;
+
+			while (cnt <= weight_len
+			       && (weights[equiv_class_idx + 1 + cnt]
+				   == weights[idx + 1 + cnt]))
+			  ++cnt;
+			if (cnt > weight_len)
+			  {
+			    match_len = elem_len;
+			    goto check_node_accept_bytes_match;
+			  }
+		      }
+		  }
+	    }
+	}
+      else
+# endif /* _LIBC */
+	{
+	  /* match with range expression?  */
+#if __GNUC__ >= 2
+	  wchar_t cmp_buf[] = {L'\0', L'\0', wc, L'\0', L'\0', L'\0'};
+#else
+	  wchar_t cmp_buf[] = {L'\0', L'\0', L'\0', L'\0', L'\0', L'\0'};
+	  cmp_buf[2] = wc;
+#endif
+	  for (i = 0; i < cset->nranges; ++i)
+	    {
+	      cmp_buf[0] = cset->range_starts[i];
+	      cmp_buf[4] = cset->range_ends[i];
+	      if (wcscoll (cmp_buf, cmp_buf + 2) <= 0
+		  && wcscoll (cmp_buf + 2, cmp_buf + 4) <= 0)
+		{
+		  match_len = char_len;
+		  goto check_node_accept_bytes_match;
+		}
+	    }
+	}
+    check_node_accept_bytes_match:
+      if (!cset->non_match)
+	return match_len;
+      else
+	{
+	  if (match_len > 0)
+	    return 0;
+	  else
+	    return (elem_len > char_len) ? elem_len : char_len;
+	}
+    }
+  return 0;
+}
+
+# ifdef _LIBC
+static unsigned int
+internal_function
+find_collation_sequence_value (const unsigned char *mbs, size_t mbs_len)
+{
+  uint32_t nrules = _NL_CURRENT_WORD (LC_COLLATE, _NL_COLLATE_NRULES);
+  if (nrules == 0)
+    {
+      if (mbs_len == 1)
+	{
+	  /* No valid character.  Match it as a single byte character.  */
+	  const unsigned char *collseq = (const unsigned char *)
+	    _NL_CURRENT (LC_COLLATE, _NL_COLLATE_COLLSEQMB);
+	  return collseq[mbs[0]];
+	}
+      return UINT_MAX;
+    }
+  else
+    {
+      int32_t idx;
+      const unsigned char *extra = (const unsigned char *)
+	_NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB);
+      int32_t extrasize = (const unsigned char *)
+	_NL_CURRENT (LC_COLLATE, _NL_COLLATE_SYMB_EXTRAMB + 1) - extra;
+
+      for (idx = 0; idx < extrasize;)
+	{
+	  int mbs_cnt, found = 0;
+	  int32_t elem_mbs_len;
+	  /* Skip the name of collating element name.  */
+	  idx = idx + extra[idx] + 1;
+	  elem_mbs_len = extra[idx++];
+	  if (mbs_len == elem_mbs_len)
+	    {
+	      for (mbs_cnt = 0; mbs_cnt < elem_mbs_len; ++mbs_cnt)
+		if (extra[idx + mbs_cnt] != mbs[mbs_cnt])
+		  break;
+	      if (mbs_cnt == elem_mbs_len)
+		/* Found the entry.  */
+		found = 1;
+	    }
+	  /* Skip the byte sequence of the collating element.  */
+	  idx += elem_mbs_len;
+	  /* Adjust for the alignment.  */
+	  idx = (idx + 3) & ~3;
+	  /* Skip the collation sequence value.  */
+	  idx += sizeof (uint32_t);
+	  /* Skip the wide char sequence of the collating element.  */
+	  idx = idx + sizeof (uint32_t) * (extra[idx] + 1);
+	  /* If we found the entry, return the sequence value.  */
+	  if (found)
+	    return *(uint32_t *) (extra + idx);
+	  /* Skip the collation sequence value.  */
+	  idx += sizeof (uint32_t);
+	}
+      return UINT_MAX;
+    }
+}
+# endif /* _LIBC */
+#endif /* RE_ENABLE_I18N */
+
+/* Check whether the node accepts the byte which is IDX-th
+   byte of the INPUT.  */
+
+static int
+internal_function
+check_node_accept (const re_match_context_t *mctx, const re_token_t *node,
+		   int idx)
+{
+  unsigned char ch;
+  ch = re_string_byte_at (&mctx->input, idx);
+  switch (node->type)
+    {
+    case CHARACTER:
+      if (node->opr.c != ch)
+	return 0;
+      break;
+
+    case SIMPLE_BRACKET:
+      if (!bitset_contain (node->opr.sbcset, ch))
+	return 0;
+      break;
+
+#ifdef RE_ENABLE_I18N
+    case OP_UTF8_PERIOD:
+      if (ch >= 0x80)
+	return 0;
+      /* FALLTHROUGH */
+#endif
+    case OP_PERIOD:
+      if ((ch == '\n' && !(mctx->dfa->syntax & RE_DOT_NEWLINE))
+	  || (ch == '\0' && (mctx->dfa->syntax & RE_DOT_NOT_NULL)))
+	return 0;
+      break;
+
+    default:
+      return 0;
+    }
+
+  if (node->constraint)
+    {
+      /* The node has constraints.  Check whether the current context
+	 satisfies the constraints.  */
+      unsigned int context = re_string_context_at (&mctx->input, idx,
+						   mctx->eflags);
+      if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
+	return 0;
+    }
+
+  return 1;
+}
+
+/* Extend the buffers, if the buffers have run out.  */
+
+static reg_errcode_t
+internal_function
+extend_buffers (re_match_context_t *mctx)
+{
+  reg_errcode_t ret;
+  re_string_t *pstr = &mctx->input;
+
+  /* Avoid overflow.  */
+  if (BE (INT_MAX / 2 / sizeof (re_dfastate_t *) <= pstr->bufs_len, 0))
+    return REG_ESPACE;
+
+  /* Double the lengths of the buffers.  */
+  ret = re_string_realloc_buffers (pstr, pstr->bufs_len * 2);
+  if (BE (ret != REG_NOERROR, 0))
+    return ret;
+
+  if (mctx->state_log != NULL)
+    {
+      /* And double the length of state_log.  */
+      /* XXX We have no indication of the size of this buffer.  If this
+	 allocation fail we have no indication that the state_log array
+	 does not have the right size.  */
+      re_dfastate_t **new_array = re_realloc (mctx->state_log, re_dfastate_t *,
+					      pstr->bufs_len + 1);
+      if (BE (new_array == NULL, 0))
+	return REG_ESPACE;
+      mctx->state_log = new_array;
+    }
+
+  /* Then reconstruct the buffers.  */
+  if (pstr->icase)
+    {
+#ifdef RE_ENABLE_I18N
+      if (pstr->mb_cur_max > 1)
+	{
+	  ret = build_wcs_upper_buffer (pstr);
+	  if (BE (ret != REG_NOERROR, 0))
+	    return ret;
+	}
+      else
+#endif /* RE_ENABLE_I18N  */
+	build_upper_buffer (pstr);
+    }
+  else
+    {
+#ifdef RE_ENABLE_I18N
+      if (pstr->mb_cur_max > 1)
+	build_wcs_buffer (pstr);
+      else
+#endif /* RE_ENABLE_I18N  */
+	{
+	  if (pstr->trans != NULL)
+	    re_string_translate_buffer (pstr);
+	}
+    }
+  return REG_NOERROR;
+}
+
+
+/* Functions for matching context.  */
+
+/* Initialize MCTX.  */
+
+static reg_errcode_t
+internal_function
+match_ctx_init (re_match_context_t *mctx, int eflags, int n)
+{
+  mctx->eflags = eflags;
+  mctx->match_last = -1;
+  if (n > 0)
+    {
+      mctx->bkref_ents = re_malloc (struct re_backref_cache_entry, n);
+      mctx->sub_tops = re_malloc (re_sub_match_top_t *, n);
+      if (BE (mctx->bkref_ents == NULL || mctx->sub_tops == NULL, 0))
+	return REG_ESPACE;
+    }
+  /* Already zero-ed by the caller.
+     else
+       mctx->bkref_ents = NULL;
+     mctx->nbkref_ents = 0;
+     mctx->nsub_tops = 0;  */
+  mctx->abkref_ents = n;
+  mctx->max_mb_elem_len = 1;
+  mctx->asub_tops = n;
+  return REG_NOERROR;
+}
+
+/* Clean the entries which depend on the current input in MCTX.
+   This function must be invoked when the matcher changes the start index
+   of the input, or changes the input string.  */
+
+static void
+internal_function
+match_ctx_clean (re_match_context_t *mctx)
+{
+  int st_idx;
+  for (st_idx = 0; st_idx < mctx->nsub_tops; ++st_idx)
+    {
+      int sl_idx;
+      re_sub_match_top_t *top = mctx->sub_tops[st_idx];
+      for (sl_idx = 0; sl_idx < top->nlasts; ++sl_idx)
+	{
+	  re_sub_match_last_t *last = top->lasts[sl_idx];
+	  re_free (last->path.array);
+	  re_free (last);
+	}
+      re_free (top->lasts);
+      if (top->path)
+	{
+	  re_free (top->path->array);
+	  re_free (top->path);
+	}
+      free (top);
+    }
+
+  mctx->nsub_tops = 0;
+  mctx->nbkref_ents = 0;
+}
+
+/* Free all the memory associated with MCTX.  */
+
+static void
+internal_function
+match_ctx_free (re_match_context_t *mctx)
+{
+  /* First, free all the memory associated with MCTX->SUB_TOPS.  */
+  match_ctx_clean (mctx);
+  re_free (mctx->sub_tops);
+  re_free (mctx->bkref_ents);
+}
+
+/* Add a new backreference entry to MCTX.
+   Note that we assume that caller never call this function with duplicate
+   entry, and call with STR_IDX which isn't smaller than any existing entry.
+*/
+
+static reg_errcode_t
+internal_function
+match_ctx_add_entry (re_match_context_t *mctx, int node, int str_idx, int from,
+		     int to)
+{
+  if (mctx->nbkref_ents >= mctx->abkref_ents)
+    {
+      struct re_backref_cache_entry* new_entry;
+      new_entry = re_realloc (mctx->bkref_ents, struct re_backref_cache_entry,
+			      mctx->abkref_ents * 2);
+      if (BE (new_entry == NULL, 0))
+	{
+	  re_free (mctx->bkref_ents);
+	  return REG_ESPACE;
+	}
+      mctx->bkref_ents = new_entry;
+      memset (mctx->bkref_ents + mctx->nbkref_ents, '\0',
+	      sizeof (struct re_backref_cache_entry) * mctx->abkref_ents);
+      mctx->abkref_ents *= 2;
+    }
+  if (mctx->nbkref_ents > 0
+      && mctx->bkref_ents[mctx->nbkref_ents - 1].str_idx == str_idx)
+    mctx->bkref_ents[mctx->nbkref_ents - 1].more = 1;
+
+  mctx->bkref_ents[mctx->nbkref_ents].node = node;
+  mctx->bkref_ents[mctx->nbkref_ents].str_idx = str_idx;
+  mctx->bkref_ents[mctx->nbkref_ents].subexp_from = from;
+  mctx->bkref_ents[mctx->nbkref_ents].subexp_to = to;
+
+  /* This is a cache that saves negative results of check_dst_limits_calc_pos.
+     If bit N is clear, means that this entry won't epsilon-transition to
+     an OP_OPEN_SUBEXP or OP_CLOSE_SUBEXP for the N+1-th subexpression.  If
+     it is set, check_dst_limits_calc_pos_1 will recurse and try to find one
+     such node.
+
+     A backreference does not epsilon-transition unless it is empty, so set
+     to all zeros if FROM != TO.  */
+  mctx->bkref_ents[mctx->nbkref_ents].eps_reachable_subexps_map
+    = (from == to ? ~0 : 0);
+
+  mctx->bkref_ents[mctx->nbkref_ents++].more = 0;
+  if (mctx->max_mb_elem_len < to - from)
+    mctx->max_mb_elem_len = to - from;
+  return REG_NOERROR;
+}
+
+/* Search for the first entry which has the same str_idx, or -1 if none is
+   found.  Note that MCTX->BKREF_ENTS is already sorted by MCTX->STR_IDX.  */
+
+static int
+internal_function
+search_cur_bkref_entry (const re_match_context_t *mctx, int str_idx)
+{
+  int left, right, mid, last;
+  last = right = mctx->nbkref_ents;
+  for (left = 0; left < right;)
+    {
+      mid = left + (right - left) / 2;
+      if (mctx->bkref_ents[mid].str_idx < str_idx)
+	left = mid + 1;
+      else
+	right = mid;
+    }
+  if (left < last && mctx->bkref_ents[left].str_idx == str_idx)
+    return left;
+  else
+    return -1;
+}
+
+/* Register the node NODE, whose type is OP_OPEN_SUBEXP, and which matches
+   at STR_IDX.  */
+
+static reg_errcode_t
+internal_function
+match_ctx_add_subtop (re_match_context_t *mctx, int node, int str_idx)
+{
+#ifdef DEBUG
+  assert (mctx->sub_tops != NULL);
+  assert (mctx->asub_tops > 0);
+#endif
+  if (BE (mctx->nsub_tops == mctx->asub_tops, 0))
+    {
+      int new_asub_tops = mctx->asub_tops * 2;
+      re_sub_match_top_t **new_array = re_realloc (mctx->sub_tops,
+						   re_sub_match_top_t *,
+						   new_asub_tops);
+      if (BE (new_array == NULL, 0))
+	return REG_ESPACE;
+      mctx->sub_tops = new_array;
+      mctx->asub_tops = new_asub_tops;
+    }
+  mctx->sub_tops[mctx->nsub_tops] = calloc (1, sizeof (re_sub_match_top_t));
+  if (BE (mctx->sub_tops[mctx->nsub_tops] == NULL, 0))
+    return REG_ESPACE;
+  mctx->sub_tops[mctx->nsub_tops]->node = node;
+  mctx->sub_tops[mctx->nsub_tops++]->str_idx = str_idx;
+  return REG_NOERROR;
+}
+
+/* Register the node NODE, whose type is OP_CLOSE_SUBEXP, and which matches
+   at STR_IDX, whose corresponding OP_OPEN_SUBEXP is SUB_TOP.  */
+
+static re_sub_match_last_t *
+internal_function
+match_ctx_add_sublast (re_sub_match_top_t *subtop, int node, int str_idx)
+{
+  re_sub_match_last_t *new_entry;
+  if (BE (subtop->nlasts == subtop->alasts, 0))
+    {
+      int new_alasts = 2 * subtop->alasts + 1;
+      re_sub_match_last_t **new_array = re_realloc (subtop->lasts,
+						    re_sub_match_last_t *,
+						    new_alasts);
+      if (BE (new_array == NULL, 0))
+	return NULL;
+      subtop->lasts = new_array;
+      subtop->alasts = new_alasts;
+    }
+  new_entry = calloc (1, sizeof (re_sub_match_last_t));
+  if (BE (new_entry != NULL, 1))
+    {
+      subtop->lasts[subtop->nlasts] = new_entry;
+      new_entry->node = node;
+      new_entry->str_idx = str_idx;
+      ++subtop->nlasts;
+    }
+  return new_entry;
+}
+
+static void
+internal_function
+sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
+	       re_dfastate_t **limited_sts, int last_node, int last_str_idx)
+{
+  sctx->sifted_states = sifted_sts;
+  sctx->limited_states = limited_sts;
+  sctx->last_node = last_node;
+  sctx->last_str_idx = last_str_idx;
+  re_node_set_init_empty (&sctx->limits);
+}