Subject: Re: bug#32194: [PATCH] Use Gnulib regex for lib-src

From: Paul Eggert <[email-masked]>
Date: Wed, 1 Aug 2018 20:19:03 -0700

Eli Zaretskii wrote:
>> From: Noam Postavsky <[email-masked]>
>> Date: Wed, 01 Aug 2018 20:58:22 -0400
>>
>> I think it might make sense to hold onto it, but I don't feel very
>> strongly about it.
> 
> If it's useful, I think it should stay.

OK, revised patchset attached. This keeps the debugging code in question. I took 
the liberty of renaming DEBUG (which clashes with other DEBUGs) to 
EMACS_REGEX_DEBUG.
>From 5121b21b26e4204a9d2249849b6108f6425da654 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Wed, 1 Aug 2018 19:13:07 -0700
Subject: [PATCH 1/4] Use Gnulib regex for lib-src
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Emacs regular expressions forked from everyone else long ago.
This makes it official and should allow simplification later.
etags.c now uses the glibc regex API, falling back on a
Gnulib-supplied substitute lib/regex.c if necessary.
Emacs proper now uses its own regular expression module.
Although this patch may look dauntingly large, most of it
was generated automatically by admin/merge-gnulib
and contains an exact copy of the glibc regex source,
and the by-hand changes do not grow the Emacs source code.
* admin/merge-gnulib (GNULIB_MODULES): Add regex.
(AVOIDED_MODULES): Add btowc, langinfo, lock, mbrtowc, mbsinit,
nl_langinfo, wchar, wcrtomb, wctype-h.
* lib-src/Makefile.in (regex.o): Remove; Gnulib does this for us now.
(etags_deps, etags_libs): Remove regex.o.
* lib-src/etags.c (add_regex): Use unsigned char translation array,
since glibc regex requires that.
* lib/Makefile.in (not_emacs_OBJECTS, for_emacs_OBJECTS): New macros.
(libegnu_a_OBJECTS): Use them, to avoid building e-regex.o.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/regcomp.c, lib/regex.c, lib/regex.h, lib/regex_internal.c:
* lib/regex_internal.h, lib/regexec.c, m4/builtin-expect.m4:
* m4/eealloc.m4, m4/glibc21.m4, m4/mbstate_t.m4, m4/regex.m4:
New files, copied from Gnulib.
* src/regex-emacs.c, src/regex-emacs.h:
Rename from src/regex.c and src/regex.h, to avoid confusion
with lib/regex.c.  All references changed.
* src/regex-emacs.h, src/conf_post.h:
(RE_TRANSLATE_TYPE, RE_TRANSLATE, RE_TRANSLATE_P):
Move from src/conf_post.h to src/regex-emacs.h,
so that they don’t interfere with compiling lib/regex.c.
* test/src/regex-emacs-tests.el:
Rename from test/src/regex-tests.el, for consistency.
---
 admin/MAINTAINERS                             |    2 +-
 admin/find-gc.el                              |    2 +-
 admin/merge-gnulib                            |    7 +-
 etc/NEWS                                      |    7 +
 lib-src/Makefile.in                           |    8 +-
 lib-src/etags.c                               |    2 +-
 lib/Makefile.in                               |    8 +-
 lib/gnulib.mk.in                              |   23 +
 lib/regcomp.c                                 | 3944 +++++++++++++++
 lib/regex.c                                   |   81 +
 lib/regex.h                                   |  658 +++
 lib/regex_internal.c                          | 1740 +++++++
 lib/regex_internal.h                          |  911 ++++
 lib/regexec.c                                 | 4324 +++++++++++++++++
 lisp/char-fold.el                             |    2 +-
 m4/builtin-expect.m4                          |   49 +
 m4/eealloc.m4                                 |   31 +
 m4/glibc21.m4                                 |   34 +
 m4/gnulib-comp.m4                             |   30 +
 m4/mbstate_t.m4                               |   41 +
 m4/regex.m4                                   |  300 ++
 src/Makefile.in                               |    2 +-
 src/casetab.c                                 |    2 +-
 src/conf_post.h                               |    7 -
 src/deps.mk                                   |   10 +-
 src/emacs.c                                   |    8 +-
 src/{regex.c => regex-emacs.c}                |   54 +-
 src/{regex.h => regex-emacs.h}                |   15 +-
 src/search.c                                  |    8 +-
 src/syntax.c                                  |    6 +-
 src/thread.h                                  |    2 +-
 .../{regex-tests.el => regex-emacs-tests.el}  |    6 +-
 32 files changed, 12249 insertions(+), 75 deletions(-)
 create mode 100644 lib/regcomp.c
 create mode 100644 lib/regex.c
 create mode 100644 lib/regex.h
 create mode 100644 lib/regex_internal.c
 create mode 100644 lib/regex_internal.h
 create mode 100644 lib/regexec.c
 create mode 100644 m4/builtin-expect.m4
 create mode 100644 m4/eealloc.m4
 create mode 100644 m4/glibc21.m4
 create mode 100644 m4/mbstate_t.m4
 create mode 100644 m4/regex.m4
 rename src/{regex.c => regex-emacs.c} (99%)
 rename src/{regex.h => regex-emacs.h} (98%)
 rename test/src/{regex-tests.el => regex-emacs-tests.el} (99%)

diff --git a/admin/MAINTAINERS b/admin/MAINTAINERS
index 1a4157ac53..10633a8e0e 100644
--- a/admin/MAINTAINERS
+++ b/admin/MAINTAINERS
@@ -37,7 +37,7 @@ Kenichi Handa
 	Mule
 
 Stefan Monnier
-	src/regex.c
+	src/regex-emacs.c
 	src/syntax.c
 	src/keymap.c
 	font-lock/jit-lock/syntax
diff --git a/admin/find-gc.el b/admin/find-gc.el
index fb564039c7..e8cc113650 100644
--- a/admin/find-gc.el
+++ b/admin/find-gc.el
@@ -57,7 +57,7 @@ find-gc-source-files
     "keymap.c" "sysdep.c" "buffer.c" "filelock.c"
     "insdel.c" "marker.c" "minibuf.c" "fileio.c"
     "dired.c" "cmds.c" "casefiddle.c"
-    "indent.c" "search.c" "regex.c" "undo.c"
+    "indent.c" "search.c" "regex-emacs.c" "undo.c"
     "alloc.c" "data.c" "doc.c" "editfns.c"
     "callint.c" "eval.c" "fns.c" "print.c" "lread.c"
     "syntax.c" "unexcoff.c"
diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index 1397ecfb9f..abb192911d 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -37,7 +37,7 @@ GNULIB_MODULES=
   getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog
   ieee754-h ignore-value intprops largefile lstat
   manywarnings memrchr minmax mkostemp mktime nstrftime
-  pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat
+  pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat regex
   sig2str socklen stat-time std-gnu11 stdalign stddef stdio
   stpcpy strtoimax symlink sys_stat sys_time
   tempname time time_r time_rz timegm timer-time timespec-add timespec-sub
@@ -46,11 +46,12 @@ GNULIB_MODULES=
 '
 
 AVOIDED_MODULES='
-  close dup fchdir fstat
-  malloc-posix msvc-inval msvc-nothrow
+  btowc close dup fchdir fstat langinfo lock
+  malloc-posix mbrtowc mbsinit msvc-inval msvc-nothrow nl_langinfo
   openat-die opendir raise
   save-cwd select setenv sigprocmask stat stdarg stdbool
   threadlib tzset unsetenv utime utime-h
+  wchar wcrtomb wctype-h
 '
 
 GNULIB_TOOL_FLAGS='
diff --git a/etc/NEWS b/etc/NEWS
index 6c79a46f24..a9b9eb2001 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -31,6 +31,13 @@ functions 'json-serialize', 'json-insert', 'json-parse-string', and
 'json-parse-buffer' are typically much faster than their Lisp
 counterparts from json.el.
 
+** The etags program now uses the C library's regular expression matcher
+when possible, and a compatible regex substitute otherwise.  This will
+let developers maintain Emacs's own regex code without having to also
+support other programs.  The new configure option '--without-included-regex'
+forces etags to use the C library's regex matcher even if the regex
+substitute ordinarily would be used to work around compatibility problems.
+
 ** Emacs has been ported to the -fcheck-pointer-bounds option of GCC.
 This causes Emacs to check bounds of some arrays addressed by its
 internal pointers, which can be helpful when debugging the Emacs
diff --git a/lib-src/Makefile.in b/lib-src/Makefile.in
index fa37d8ed85..b2b901788a 100644
--- a/lib-src/Makefile.in
+++ b/lib-src/Makefile.in
@@ -361,13 +361,9 @@ TAGS:
 ../lib/libgnu.a: $(config_h)
 	$(MAKE) -C ../lib all
 
-regex.o: $(srcdir)/../src/regex.c $(srcdir)/../src/regex.h $(config_h)
-	$(AM_V_CC)$(CC) -c $(CPP_CFLAGS) $<
-
-
-etags_deps = ${srcdir}/etags.c regex.o $(NTLIB) $(config_h)
+etags_deps = ${srcdir}/etags.c $(NTLIB) $(config_h)
 etags_cflags = -DEMACS_NAME="\"GNU Emacs\"" -DVERSION="\"${version}\"" -o $@
-etags_libs = regex.o $(NTLIB) $(LOADLIBES)
+etags_libs = $(NTLIB) $(LOADLIBES)
 
 etags${EXEEXT}: ${etags_deps}
 	$(AM_V_CCLD)$(CC) ${ALL_CFLAGS} $(etags_cflags) $< $(etags_libs)
diff --git a/lib-src/etags.c b/lib-src/etags.c
index b3b4575e0a..ee50670343 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -6401,7 +6401,7 @@ add_regex (char *regexp_pattern, language *lang)
   *patbuf = zeropattern;
   if (ignore_case)
     {
-      static char lc_trans[UCHAR_MAX + 1];
+      static unsigned char lc_trans[UCHAR_MAX + 1];
       int i;
       for (i = 0; i < UCHAR_MAX + 1; i++)
 	lc_trans[i] = c_tolower (i);
diff --git a/lib/Makefile.in b/lib/Makefile.in
index 201f4b5383..b26db27423 100644
--- a/lib/Makefile.in
+++ b/lib/Makefile.in
@@ -79,9 +79,15 @@ ../config.status:
 Makefile: ../config.status $(srcdir)/Makefile.in
 	$(MAKE) -C .. src/$@
 
+# Object modules that need not be built for Emacs.
+# Emacs does not need e-regex.o (it has its own regex-emacs.c),
+# and building it would just waste time.
+not_emacs_OBJECTS = regex.o
+
 libgnu_a_OBJECTS = $(gl_LIBOBJS) \
   $(patsubst %.c,%.o,$(filter %.c,$(libgnu_a_SOURCES)))
-libegnu_a_OBJECTS = $(patsubst %.o,e-%.o,$(libgnu_a_OBJECTS))
+for_emacs_OBJECTS = $(filter-out $(not_emacs_OBJECTS),$(libgnu_a_OBJECTS))
+libegnu_a_OBJECTS = $(patsubst %.o,e-%.o,$(for_emacs_OBJECTS))
 
 $(libegnu_a_OBJECTS) $(libgnu_a_OBJECTS): $(BUILT_SOURCES)
 
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 7d28dcc62b..7ad390875b 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -34,13 +34,19 @@
 #  --no-libtool \
 #  --macro-prefix=gl \
 #  --no-vc-files \
+#  --avoid=btowc \
 #  --avoid=close \
 #  --avoid=dup \
 #  --avoid=fchdir \
 #  --avoid=fstat \
+#  --avoid=langinfo \
+#  --avoid=lock \
 #  --avoid=malloc-posix \
+#  --avoid=mbrtowc \
+#  --avoid=mbsinit \
 #  --avoid=msvc-inval \
 #  --avoid=msvc-nothrow \
+#  --avoid=nl_langinfo \
 #  --avoid=openat-die \
 #  --avoid=opendir \
 #  --avoid=raise \
@@ -56,6 +62,9 @@
 #  --avoid=unsetenv \
 #  --avoid=utime \
 #  --avoid=utime-h \
+#  --avoid=wchar \
+#  --avoid=wcrtomb \
+#  --avoid=wctype-h \
 #  alloca-opt \
 #  binary-io \
 #  byteswap \
@@ -113,6 +122,7 @@
 #  qcopy-acl \
 #  readlink \
 #  readlinkat \
+#  regex \
 #  sig2str \
 #  socklen \
 #  stat-time \
@@ -216,6 +226,7 @@ GETOPT_CDEFS_H = @GETOPT_CDEFS_H@
 GETOPT_H = @GETOPT_H@
 GFILENOTIFY_CFLAGS = @GFILENOTIFY_CFLAGS@
 GFILENOTIFY_LIBS = @GFILENOTIFY_LIBS@
+GLIBC21 = @GLIBC21@
 GL_COND_LIBTOOL = @GL_COND_LIBTOOL@
 GL_GENERATE_ALLOCA_H = @GL_GENERATE_ALLOCA_H@
 GL_GENERATE_BYTESWAP_H = @GL_GENERATE_BYTESWAP_H@
@@ -1024,6 +1035,7 @@ gameuser = @gameuser@
 gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7 = @gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7@
 gl_GNULIB_ENABLED_2049e887c7e5308faad27b3f894bb8c9 = @gl_GNULIB_ENABLED_2049e887c7e5308faad27b3f894bb8c9@
 gl_GNULIB_ENABLED_260941c0e5dc67ec9e87d1fb321c300b = @gl_GNULIB_ENABLED_260941c0e5dc67ec9e87d1fb321c300b@
+gl_GNULIB_ENABLED_37f71b604aa9c54446783d80f42fe547 = @gl_GNULIB_ENABLED_37f71b604aa9c54446783d80f42fe547@
 gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31 = @gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31@
 gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c = @gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c@
 gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec = @gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec@
@@ -2095,6 +2107,17 @@ EXTRA_libgnu_a_SOURCES += at-func.c readlinkat.c
 endif
 ## end   gnulib module readlinkat
 
+## begin gnulib module regex
+ifeq (,$(OMIT_GNULIB_MODULE_regex))
+
+
+EXTRA_DIST += regcomp.c regex.c regex.h regex_internal.c regex_internal.h regexec.c
+
+EXTRA_libgnu_a_SOURCES += regcomp.c regex.c regex_internal.c regexec.c
+
+endif
+## end   gnulib module regex
+
 ## begin gnulib module root-uid
 ifeq (,$(OMIT_GNULIB_MODULE_root-uid))
 
diff --git a/lib/regcomp.c b/lib/regcomp.c
new file mode 100644
index 0000000000..53eb226374
--- /dev/null
+++ b/lib/regcomp.c
@@ -0,0 +1,3944 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email-masked]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifdef _LIBC
+# include <locale/weight.h>
+#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 Idx duplicate_node (re_dfa_t *dfa, Idx org_idx, unsigned int constraint);
+static Idx search_duplicated_node (const re_dfa_t *dfa, Idx 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,
+					 Idx node, bool root);
+static reg_errcode_t calc_inveclosure (re_dfa_t *dfa);
+static Idx 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);
+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,
+				  Idx 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,
+				 Idx 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,
+				     Idx 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,
+				  Idx 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,
+					    bool 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,
+					Idx *equiv_class_alloc,
+					const unsigned char *name);
+static reg_errcode_t build_charclass (RE_TRANSLATE_TYPE trans,
+				      bitset_t sbcset,
+				      re_charset_t *mbcset,
+				      Idx *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,
+				       bool 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?  */
+
+static const char __re_error_msgid[] =
+  {
+#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 */
+  };
+
+static const size_t __re_error_msgid_idx[] =
+  {
+    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.  */
+
+/* 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 = 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, bool 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)
+{
+  re_dfa_t *dfa = bufp->buffer;
+  Idx node_cnt;
+  bool icase = (dfa->mb_cur_max == 1 && (bufp->syntax & RE_ICASE));
+  for (node_cnt = 0; node_cnt < init_state->nodes.nelem; ++node_cnt)
+    {
+      Idx 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[MB_LEN_MAX];
+	      unsigned char *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, false, buf[0]);
+	    }
+#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;
+	  Idx 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
+libc_hidden_def (__regcomp)
+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))
+    {
+      size_t cpy_size = msg_size;
+      if (BE (msg_size > errbuf_size, 0))
+	{
+	  cpy_size = errbuf_size - 1;
+	  errbuf[cpy_size] = '\0';
+	}
+      memcpy (errbuf, msg, cpy_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.  */
+static const bitset_t utf8_sb_map =
+{
+  /* Set the first 128 bits.  */
+# if defined __GNUC__ && !defined __STRICT_ANSI__
+  [0 ... 0x80 / BITSET_WORD_BITS - 1] = BITSET_WORD_MAX
+# else
+#  if 4 * BITSET_WORD_BITS < ASCII_CHARS
+#   error "bitset_word_t is narrower than 32 bits"
+#  elif 3 * BITSET_WORD_BITS < ASCII_CHARS
+  BITSET_WORD_MAX, BITSET_WORD_MAX, BITSET_WORD_MAX,
+#  elif 2 * BITSET_WORD_BITS < ASCII_CHARS
+  BITSET_WORD_MAX, BITSET_WORD_MAX,
+#  elif 1 * BITSET_WORD_BITS < ASCII_CHARS
+  BITSET_WORD_MAX,
+#  endif
+  (BITSET_WORD_MAX
+   >> (SBC_MAX % BITSET_WORD_BITS == 0
+       ? 0
+       : BITSET_WORD_BITS - SBC_MAX % BITSET_WORD_BITS))
+# endif
+};
+#endif
+
+
+static void
+free_dfa_content (re_dfa_t *dfa)
+{
+  Idx 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 = preg->buffer;
+  if (BE (dfa != NULL, 1))
+    {
+      lock_fini (dfa->lock);
+      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
+libc_hidden_def (__regfree)
+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 (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 = re_malloc (char, 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 = 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 = dfa;
+    }
+  preg->used = sizeof (re_dfa_t);
+
+  err = init_dfa (dfa, length);
+  if (BE (err == REG_NOERROR && lock_init (dfa->lock) != 0, 0))
+    err = REG_ESPACE;
+  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
+
+  err = re_string_construct (&regexp, pattern, length, preg->translate,
+			     (syntax & RE_ICASE) != 0, dfa);
+  if (BE (err != REG_NOERROR, 0))
+    {
+    re_compile_internal_free_return:
+      free_workarea_compile (preg);
+      re_string_destruct (&regexp);
+      lock_fini (dfa->lock);
+      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))
+    {
+      lock_fini (dfa->lock);
+      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)
+{
+  __re_size_t table_size;
+#ifndef _LIBC
+  const char *codeset_name;
+#endif
+#ifdef RE_ENABLE_I18N
+  size_t max_i18n_object_size = MAX (sizeof (wchar_t), sizeof (wctype_t));
+#else
+  size_t max_i18n_object_size = 0;
+#endif
+  size_t max_object_size =
+    MAX (sizeof (struct re_state_table_entry),
+	 MAX (sizeof (re_token_t),
+	      MAX (sizeof (re_node_set),
+		   MAX (sizeof (regmatch_t),
+			max_i18n_object_size))));
+
+  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.  The extra "/ 2" is for the table_size doubling
+     calculation below, and for similar doubling calculations
+     elsewhere.  And it's <= rather than <, because some of the
+     doubling calculations add 1 afterwards.  */
+  if (BE (MIN (IDX_MAX, SIZE_MAX / max_object_size) / 2 <= pat_len, 0))
+    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
+  codeset_name = nl_langinfo (CODESET);
+  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')
+      && strcmp (codeset_name + 3 + (codeset_name[3] == '-'), "8") == 0)
+    dfa->is_utf8 = 1;
+
+  /* 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)
+	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
+init_word_char (re_dfa_t *dfa)
+{
+  int i = 0;
+  int j;
+  int ch = 0;
+  dfa->word_ops_used = 1;
+  if (BE (dfa->map_notascii == 0, 1))
+    {
+      /* Avoid uint32_t and uint64_t as some non-GCC platforms lack
+	 them, an issue when this code is used in Gnulib.  */
+      bitset_word_t bits0 = 0x00000000;
+      bitset_word_t bits1 = 0x03ff0000;
+      bitset_word_t bits2 = 0x87fffffe;
+      bitset_word_t bits3 = 0x07fffffe;
+      if (BITSET_WORD_BITS == 64)
+	{
+	  /* Pacify gcc -Woverflow on 32-bit platformns.  */
+	  dfa->word_char[0] = bits1 << 31 << 1 | bits0;
+	  dfa->word_char[1] = bits3 << 31 << 1 | bits2;
+	  i = 2;
+	}
+      else if (BITSET_WORD_BITS == 32)
+	{
+	  dfa->word_char[0] = bits0;
+	  dfa->word_char[1] = bits1;
+	  dfa->word_char[2] = bits2;
+	  dfa->word_char[3] = bits3;
+	  i = 4;
+	}
+      else
+        goto general_case;
+      ch = 128;
+
+      if (BE (dfa->is_utf8, 1))
+	{
+	  memset (&dfa->word_char[i], '\0', (SBC_MAX - ch) / 8);
+	  return;
+	}
+    }
+
+ general_case:
+  for (; 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 = 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)
+{
+  Idx 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)
+      {
+	Idx node_idx = init_nodes.elems[i];
+	re_token_type_t type = dfa->nodes[node_idx].type;
+
+	Idx 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)
+	  {
+	    Idx dest_idx = dfa->edests[node_idx].elems[0];
+	    if (!re_node_set_contains (&init_nodes, dest_idx))
+	      {
+		reg_errcode_t merge_err
+                  = re_node_set_merge (&init_nodes, dfa->eclosures + dest_idx);
+		if (merge_err != REG_NOERROR)
+		  return merge_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)
+{
+  Idx node;
+  int i;
+  bool mb_chars = false;
+  bool has_period = false;
+
+  for (node = 0; node < dfa->nodes_len; ++node)
+    switch (dfa->nodes[node].type)
+      {
+      case CHARACTER:
+	if (dfa->nodes[node].opr.c >= ASCII_CHARS)
+	  mb_chars = true;
+	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 = true;
+	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.  */
+	{
+	  int rshift = (ASCII_CHARS % BITSET_WORD_BITS == 0
+			? 0
+			: BITSET_WORD_BITS - ASCII_CHARS % BITSET_WORD_BITS);
+	  for (i = ASCII_CHARS / BITSET_WORD_BITS; i < BITSET_WORDS; ++i)
+	    {
+	      if (dfa->nodes[node].opr.sbcset[i] >> rshift != 0)
+		return;
+	      rshift = 0;
+	    }
+	}
+	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 >= ASCII_CHARS)
+	  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 = preg->buffer;
+  reg_errcode_t ret;
+
+  /* Allocate arrays.  */
+  dfa->nexts = re_malloc (Idx, dfa->nodes_alloc);
+  dfa->org_indices = re_malloc (Idx, 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 (Idx, preg->re_nsub);
+  if (dfa->subexp_map != NULL)
+    {
+      Idx 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)
+	{
+	  re_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)
+    {
+      Idx 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 = 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;
+  Idx 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:
+      {
+	Idx 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
+duplicate_node_closure (re_dfa_t *dfa, Idx top_org_node, Idx top_clone_node,
+			Idx root_node, unsigned int init_constraint)
+{
+  Idx org_node, clone_node;
+  bool ok;
+  unsigned int constraint = init_constraint;
+  for (org_node = top_org_node, clone_node = top_clone_node;;)
+    {
+      Idx 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];
+	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (! ok, 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 closure
+	     has a loop.  Then tie it to the destination of the root_node.  */
+	  if (org_node == root_node && clone_node != org_node)
+	    {
+	      ok = re_node_set_insert (dfa->edests + clone_node, org_dest);
+	      if (BE (! ok, 0))
+	        return REG_ESPACE;
+	      break;
+	    }
+	  /* In case the node has another constraint, append it.  */
+	  constraint |= dfa->nodes[org_node].constraint;
+	  clone_dest = duplicate_node (dfa, org_dest, constraint);
+	  if (BE (clone_dest == -1, 0))
+	    return REG_ESPACE;
+	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (! ok, 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;
+	      ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	      if (BE (! ok, 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.  */
+	      ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	      if (BE (! ok, 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;
+	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+	  if (BE (! ok, 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 Idx
+search_duplicated_node (const re_dfa_t *dfa, Idx org_node,
+			unsigned int constraint)
+{
+  Idx 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 Idx
+duplicate_node (re_dfa_t *dfa, Idx org_idx, unsigned int constraint)
+{
+  Idx 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)
+{
+  Idx src, idx;
+  bool ok;
+  for (idx = 0; idx < dfa->nodes_len; ++idx)
+    re_node_set_init_empty (dfa->inveclosures + idx);
+
+  for (src = 0; src < dfa->nodes_len; ++src)
+    {
+      Idx *elems = dfa->eclosures[src].elems;
+      for (idx = 0; idx < dfa->eclosures[src].nelem; ++idx)
+	{
+	  ok = re_node_set_insert_last (dfa->inveclosures + elems[idx], src);
+	  if (BE (! ok, 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)
+{
+  Idx node_idx;
+  bool incomplete;
+#ifdef DEBUG
+  assert (dfa->nodes_len > 0);
+#endif
+  incomplete = false;
+  /* 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 = false;
+	  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, true);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+
+      if (dfa->eclosures[node_idx].nelem == 0)
+	{
+	  incomplete = true;
+	  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, Idx node, bool root)
+{
+  reg_errcode_t err;
+  Idx i;
+  re_node_set eclosure;
+  bool ok;
+  bool incomplete = false;
+  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;
+	Idx 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 = true;
+	    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, false);
+	    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 = true;
+	    re_node_set_free (&eclosure_elem);
+	  }
+      }
+
+  /* An epsilon closure includes itself.  */
+  ok = re_node_set_insert (&eclosure, node);
+  if (BE (! ok, 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
+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
+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
+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;
+	    }
+	  FALLTHROUGH;
+	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 occurs, 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 = 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, Idx nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = preg->buffer;
+  bin_tree_t *tree, *branch = NULL;
+  bitset_word_t initial_bkref_map = dfa->completed_bkref_map;
+  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))
+	{
+	  bitset_word_t accumulated_bkref_map = dfa->completed_bkref_map;
+	  dfa->completed_bkref_map = initial_bkref_map;
+	  branch = parse_branch (regexp, preg, token, syntax, nest, err);
+	  if (BE (*err != REG_NOERROR && branch == NULL, 0))
+	    {
+	      if (tree != NULL)
+		postorder (tree, free_tree, NULL);
+	      return NULL;
+	    }
+	  dfa->completed_bkref_map |= accumulated_bkref_map;
+	}
+      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, Idx nest, reg_errcode_t *err)
+{
+  bin_tree_t *tree, *expr;
+  re_dfa_t *dfa = 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))
+    {
+      expr = parse_expression (regexp, preg, token, syntax, nest, err);
+      if (BE (*err != REG_NOERROR && expr == NULL, 0))
+	{
+	  if (tree != NULL)
+	    postorder (tree, free_tree, NULL);
+	  return NULL;
+	}
+      if (tree != NULL && expr != NULL)
+	{
+	  bin_tree_t *newtree = create_tree (dfa, tree, expr, CONCAT);
+	  if (newtree == NULL)
+	    {
+	      postorder (expr, free_tree, NULL);
+	      postorder (tree, free_tree, NULL);
+	      *err = REG_ESPACE;
+	      return NULL;
+	    }
+	  tree = newtree;
+	}
+      else if (tree == NULL)
+	tree = expr;
+      /* Otherwise expr == 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, Idx nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = 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);
+	}
+      FALLTHROUGH;
+    case OP_CLOSE_SUBEXP:
+      if ((token->type == OP_CLOSE_SUBEXP) &&
+	  !(syntax & RE_UNMATCHED_RIGHT_PAREN_ORD))
+	{
+	  *err = REG_ERPAREN;
+	  return NULL;
+	}
+      FALLTHROUGH;
+    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)
+    {
+      bin_tree_t *dup_tree = parse_dup_op (tree, regexp, dfa, token,
+					   syntax, err);
+      if (BE (*err != REG_NOERROR && dup_tree == NULL, 0))
+	{
+	  if (tree != NULL)
+	    postorder (tree, free_tree, NULL);
+	  return NULL;
+	}
+      tree = dup_tree;
+      /* In BRE consecutive duplications are not allowed.  */
+      if ((syntax & RE_CONTEXT_INVALID_DUP)
+	  && (token->type == OP_DUP_ASTERISK
+	      || token->type == OP_OPEN_DUP_NUM))
+	{
+	  if (tree != NULL)
+	    postorder (tree, free_tree, NULL);
+	  *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, Idx nest, reg_errcode_t *err)
+{
+  re_dfa_t *dfa = 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))
+	{
+	  if (tree != NULL)
+	    postorder (tree, free_tree, NULL);
+	  *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;
+  Idx i, start, end, start_idx = re_string_cur_idx (regexp);
+  re_token_t start_token = *token;
+
+  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;
+	}
+
+      if (BE (RE_DUP_MAX < (end == -1 ? start : end), 0))
+	{
+	  *err = REG_ESIZE;
+	  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);
+      if (BE (elem == NULL, 0))
+        goto parse_dup_op_espace;
+      old_tree = tree;
+    }
+  else
+    old_tree = NULL;
+
+  if (elem->token.type == SUBEXP)
+    {
+      uintptr_t subidx = elem->token.opr.idx;
+      postorder (elem, mark_opt_subexp, (void *) subidx);
+    }
+
+  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.  */
+  if (TYPE_SIGNED (Idx) || end != -1)
+    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
+
+# ifdef RE_ENABLE_I18N
+/* Convert the byte B to the corresponding wide character.  In a
+   unibyte locale, treat B as itself if it is an encoding error.
+   In a multibyte locale, return WEOF if B is an encoding error.  */
+static wint_t
+parse_byte (unsigned char b, re_charset_t *mbcset)
+{
+  wint_t wc = __btowc (b);
+  return wc == WEOF && !mbcset ? b : wc;
+}
+#endif
+
+  /* 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
+# ifdef RE_ENABLE_I18N
+build_range_exp (const reg_syntax_t syntax,
+                 bitset_t sbcset,
+                 re_charset_t *mbcset,
+                 Idx *range_alloc,
+                 const bracket_elem_t *start_elem,
+                 const bracket_elem_t *end_elem)
+# else /* not RE_ENABLE_I18N */
+build_range_exp (const reg_syntax_t syntax,
+                 bitset_t sbcset,
+                 const bracket_elem_t *start_elem,
+                 const 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;
+
+    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));
+    start_wc = ((start_elem->type == SB_CHAR || start_elem->type == COLL_SYM)
+		? parse_byte (start_ch, mbcset) : start_elem->opr.wch);
+    end_wc = ((end_elem->type == SB_CHAR || end_elem->type == COLL_SYM)
+	      ? parse_byte (end_ch, mbcset) : end_elem->opr.wch);
+    if (start_wc == WEOF || end_wc == WEOF)
+      return REG_ECOLLATE;
+    else if (BE ((syntax & RE_NO_EMPTY_RANGES) && start_wc > end_wc, 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;
+	    Idx 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))
+	      {
+		re_free (new_array_start);
+		re_free (new_array_end);
+		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)
+      {
+	if (start_wc <= wc && wc <= end_wc)
+	  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
+# ifdef RE_ENABLE_I18N
+build_collating_symbol (bitset_t sbcset, re_charset_t *mbcset,
+			Idx *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 corresponding to NAME.
+     Return the index of the symbol in the SYMB_TABLE,
+     or -1 if not found.  */
+
+  auto inline int32_t
+  __attribute__ ((always_inline))
+  seek_collating_symbol_entry (const unsigned char *name, size_t name_len)
+    {
+      int32_t elem;
+
+      for (elem = 0; elem < table_size; elem++)
+	if (symb_table[2 * elem] != 0)
+	  {
+	    int32_t idx = symb_table[2 * elem + 1];
+	    /* Skip the name of collating element name.  */
+	    idx += 1 + extra[idx];
+	    if (/* Compare the length of the name.  */
+		name_len == extra[idx]
+		/* Compare the name.  */
+		&& memcmp (name, &extra[idx + 1], name_len) == 0)
+	      /* Yep, this is the entry.  */
+	      return elem;
+	  }
+      return -1;
+    }
+
+  /* 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 (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 (elem != -1)
+		{
+		  /* 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 (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 (bitset_t sbcset, re_charset_t *mbcset, int *range_alloc,
+		   bracket_elem_t *start_elem, bracket_elem_t *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;
+
+      /* FIXME: Implement rational ranges here, too.  */
+      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;
+	      Idx 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 (bitset_t sbcset, re_charset_t *mbcset,
+			  Idx *coll_sym_alloc, 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 (elem != -1)
+	    {
+	      /* We found the entry.  */
+	      idx = symb_table[2 * elem + 1];
+	      /* Skip the name of collating element name.  */
+	      idx += 1 + extra[idx];
+	    }
+	  else if (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.  */
+	      Idx 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;
+  Idx coll_sym_alloc = 0, range_alloc = 0, mbchar_alloc = 0;
+  Idx equiv_class_alloc = 0, char_class_alloc = 0;
+#endif /* not RE_ENABLE_I18N */
+  bool non_match = false;
+  bin_tree_t *work_tree;
+  int token_len;
+  bool first_round = true;
+#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 */
+    {
+      re_free (sbcset);
+#ifdef RE_ENABLE_I18N
+      re_free (mbcset);
+#endif
+      *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 = true;
+      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;
+      bool is_range_exp = false;
+      re_token_t token2;
+
+      start_elem.opr.name = start_name_buf;
+      start_elem.type = COLL_SYM;
+      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 = false;
+
+      /* 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 = true;
+	    }
+	}
+
+      if (is_range_exp == true)
+	{
+	  end_elem.opr.name = end_name_buf;
+	  end_elem.type = COLL_SYM;
+	  ret = parse_bracket_element (&end_elem, regexp, &token2, token_len2,
+				       dfa, syntax, true);
+	  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 (syntax, sbcset,
+				  dfa->mb_cur_max > 1 ? mbcset : NULL,
+				  &range_alloc, &start_elem, &end_elem);
+# else
+	  *err = build_range_exp (syntax, 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, bool 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,
+		   Idx *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;
+      /* 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 (table, indirect, extra, &cp, -1);
+      if (BE (idx1 == 0 || *cp != '\0', 0))
+	/* This isn't a valid character.  */
+	return REG_ECOLLATE;
+
+      /* Build single byte matching table for this equivalence class.  */
+      len = weights[idx1 & 0xffffff];
+      for (ch = 0; ch < SBC_MAX; ++ch)
+	{
+	  char_buf[0] = ch;
+	  cp = char_buf;
+	  idx2 = findidx (table, indirect, extra, &cp, 1);
+/*
+	  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.  */
+	  Idx 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, Idx *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;
+  const char *name = class_name;
+
+  /* In case of REG_ICASE "upper" and "lower" match the both of
+     upper and lower cases.  */
+  if ((syntax & RE_ICASE)
+      && (strcmp (name, "upper") == 0 || strcmp (name, "lower") == 0))
+    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.  */
+      Idx 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 (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 (name, "alnum") == 0)
+    BUILD_CHARCLASS_LOOP (isalnum);
+  else if (strcmp (name, "cntrl") == 0)
+    BUILD_CHARCLASS_LOOP (iscntrl);
+  else if (strcmp (name, "lower") == 0)
+    BUILD_CHARCLASS_LOOP (islower);
+  else if (strcmp (name, "space") == 0)
+    BUILD_CHARCLASS_LOOP (isspace);
+  else if (strcmp (name, "alpha") == 0)
+    BUILD_CHARCLASS_LOOP (isalpha);
+  else if (strcmp (name, "digit") == 0)
+    BUILD_CHARCLASS_LOOP (isdigit);
+  else if (strcmp (name, "print") == 0)
+    BUILD_CHARCLASS_LOOP (isprint);
+  else if (strcmp (name, "upper") == 0)
+    BUILD_CHARCLASS_LOOP (isupper);
+  else if (strcmp (name, "blank") == 0)
+    BUILD_CHARCLASS_LOOP (isblank);
+  else if (strcmp (name, "graph") == 0)
+    BUILD_CHARCLASS_LOOP (isgraph);
+  else if (strcmp (name, "punct") == 0)
+    BUILD_CHARCLASS_LOOP (ispunct);
+  else if (strcmp (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, bool non_match,
+		    reg_errcode_t *err)
+{
+  re_bitset_ptr_t sbcset;
+#ifdef RE_ENABLE_I18N
+  re_charset_t *mbcset;
+  Idx 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);
+  if (BE (sbcset == NULL, 0))
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
+#ifdef RE_ENABLE_I18N
+  mbcset = (re_charset_t *) calloc (sizeof (re_charset_t), 1);
+  if (BE (mbcset == NULL, 0))
+    {
+      re_free (sbcset);
+      *err = REG_ESPACE;
+      return NULL;
+    }
+  mbcset->non_match = non_match;
+#endif /* 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.  */
+#if defined GCC_LINT || defined lint
+  memset (&br_token, 0, sizeof br_token);
+#endif
+  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 RE_DUP_MAX + 1 if the number field is too large.
+   Return -2 if an error occurred.  */
+
+static Idx
+fetch_number (re_string_t *input, re_token_t *token, reg_syntax_t syntax)
+{
+  Idx 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'
+	     : MIN (RE_DUP_MAX + 1, num * 10 + c - '0'));
+    }
+  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;
+#if defined GCC_LINT || defined lint
+  memset (&t, 0, sizeof t);
+#endif
+  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)
+{
+  Idx idx = (uintptr_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/lib/regex.c b/lib/regex.c
new file mode 100644
index 0000000000..499e1f0e03
--- /dev/null
+++ b/lib/regex.c
@@ -0,0 +1,81 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email-masked]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC
+# include <config.h>
+
+# if (__GNUC__ == 4 && 6 <= __GNUC_MINOR__) || 4 < __GNUC__
+#  pragma GCC diagnostic ignored "-Wsuggest-attribute=pure"
+# endif
+# if (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) || 4 < __GNUC__
+#  pragma GCC diagnostic ignored "-Wold-style-definition"
+#  pragma GCC diagnostic ignored "-Wtype-limits"
+# endif
+#endif
+
+/* Make sure no one compiles this code with a C++ compiler.  */
+#if defined __cplusplus && defined _LIBC
+# 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
+
+/* 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 <regex.h>
+#include "regex_internal.h"
+
+#include "regex_internal.c"
+#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/lib/regex.h b/lib/regex.h
new file mode 100644
index 0000000000..f2ac9507ad
--- /dev/null
+++ b/lib/regex.h
@@ -0,0 +1,658 @@
+/* Definitions for data structures and routines for the regular
+   expression library.
+   Copyright (C) 1985, 1989-2018 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 General Public
+   License as published by the Free Software Foundation; either
+   version 3 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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _REGEX_H
+#define _REGEX_H 1
+
+#include <sys/types.h>
+
+/* Allow the use in C++ code.  */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Define __USE_GNU to declare GNU extensions that violate the
+   POSIX name space rules.  */
+#ifdef _GNU_SOURCE
+# define __USE_GNU 1
+#endif
+
+#ifdef _REGEX_LARGE_OFFSETS
+
+/* Use types and values that are wide enough to represent signed and
+   unsigned byte offsets in memory.  This currently works only when
+   the regex code is used outside of the GNU C library; it is not yet
+   supported within glibc itself, and glibc users should not define
+   _REGEX_LARGE_OFFSETS.  */
+
+/* The type of object sizes.  */
+typedef size_t __re_size_t;
+
+/* The type of object sizes, in places where the traditional code
+   uses unsigned long int.  */
+typedef size_t __re_long_size_t;
+
+#else
+
+/* The traditional GNU regex implementation mishandles strings longer
+   than INT_MAX.  */
+typedef unsigned int __re_size_t;
+typedef unsigned long int __re_long_size_t;
+
+#endif
+
+/* 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, turn on internal regex debugging.
+   If not set, and debugging was on, turn it off.
+   This only works if regex.c is compiled -DDEBUG.
+   We define this bit always, so that all that's needed to turn on
+   debugging is to recompile regex.c; the calling code can always have
+   this bit set, and it won't affect anything in the normal case. */
+# define RE_DEBUG (RE_NO_GNU_OPS << 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_DEBUG << 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 a regex or
+   immediately after an alternation, open-group or \} 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_CHAR_CLASSES							\
+   | 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_SYNTAX_POSIX_BASIC | RE_NEWLINE_ALT)				\
+   & ~(RE_CONTEXT_INVALID_DUP | RE_DOT_NOT_NULL))
+
+# define RE_SYNTAX_EGREP						\
+  ((RE_SYNTAX_POSIX_EXTENDED | RE_INVALID_INTERVAL_ORD | RE_NEWLINE_ALT) \
+   & ~(RE_CONTEXT_INVALID_OPS | RE_DOT_NOT_NULL))
+
+/* POSIX grep -E behavior is no longer incompatible with GNU.  */
+# define RE_SYNTAX_POSIX_EGREP						\
+  RE_SYNTAX_EGREP
+
+/* 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.  POSIX-conforming
+   systems might define this in <limits.h>, but we want our
+   value, so remove any previous define.  */
+# ifdef _REGEX_INCLUDE_LIMITS_H
+#  include <limits.h>
+# endif
+# ifdef RE_DUP_MAX
+#  undef RE_DUP_MAX
+# endif
+
+/* RE_DUP_MAX is 2**15 - 1 because an earlier implementation stored
+   the counter as a 2-byte signed integer.  This is no longer true, so
+   RE_DUP_MAX could be increased to (INT_MAX / 10 - 1), or to
+   ((SIZE_MAX - 9) / 10) if _REGEX_LARGE_OFFSETS is defined.
+   However, there would be a huge performance problem if someone
+   actually used a pattern like a\{214748363\}, so RE_DUP_MAX retains
+   its historical value.  */
+# 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 (1 << 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 (1 << 2)
+
+/* 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 (1 << 3)
+
+
+/* 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_msgid' table in regcomp.c.  */
+
+typedef enum
+{
+  _REG_ENOSYS = -1,	/* This will never happen for this implementation.  */
+  _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,		/* Too large (e.g., repeat count too large).  */
+  _REG_ERPAREN		/* Unmatched ) or \); not returned from regcomp.  */
+} reg_errcode_t;
+
+#if defined _XOPEN_SOURCE || defined __USE_XOPEN2K
+# define REG_ENOSYS	_REG_ENOSYS
+#endif
+#define REG_NOERROR	_REG_NOERROR
+#define REG_NOMATCH	_REG_NOMATCH
+#define REG_BADPAT	_REG_BADPAT
+#define REG_ECOLLATE	_REG_ECOLLATE
+#define REG_ECTYPE	_REG_ECTYPE
+#define REG_EESCAPE	_REG_EESCAPE
+#define REG_ESUBREG	_REG_ESUBREG
+#define REG_EBRACK	_REG_EBRACK
+#define REG_EPAREN	_REG_EPAREN
+#define REG_EBRACE	_REG_EBRACE
+#define REG_BADBR	_REG_BADBR
+#define REG_ERANGE	_REG_ERANGE
+#define REG_ESPACE	_REG_ESPACE
+#define REG_BADRPT	_REG_BADRPT
+#define REG_EEND	_REG_EEND
+#define REG_ESIZE	_REG_ESIZE
+#define REG_ERPAREN	_REG_ERPAREN
+
+/* This data structure represents a compiled pattern.  Before calling
+   the pattern compiler, the fields 'buffer', 'allocated', 'fastmap',
+   and 'translate' can be set.  After the pattern has been compiled,
+   the fields 're_nsub', 'not_bol' and 'not_eol' are 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.  The type
+     'struct re_dfa_t' is private and is not declared here.  */
+  struct re_dfa_t *__REPB_PREFIX(buffer);
+
+  /* Number of bytes to which 'buffer' points.  */
+  __re_long_size_t __REPB_PREFIX(allocated);
+
+  /* Number of bytes actually used in 'buffer'.  */
+  __re_long_size_t __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 're_compile_pattern' 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.  */
+#ifdef _REGEX_LARGE_OFFSETS
+/* POSIX 1003.1-2008 requires that regoff_t be at least as wide as
+   ptrdiff_t and ssize_t.  We don't know of any hosts where ptrdiff_t
+   is wider than ssize_t, so ssize_t is safe.  ptrdiff_t is not
+   visible here, so use ssize_t.  */
+typedef ssize_t regoff_t;
+#else
+/* The traditional GNU regex implementation mishandles strings longer
+   than INT_MAX.  */
+typedef int regoff_t;
+#endif
+
+
+#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
+{
+  __re_size_t 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.
+
+   To free the allocated storage, you must call 'regfree' on BUFFER.
+   Note that the translate table must either have been initialized by
+   'regcomp', with a malloc'ed value, or set to NULL before calling
+   'regfree'.  */
+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 regoff_t re_search (struct re_pattern_buffer *__buffer,
+			   const char *__String, regoff_t __length,
+			   regoff_t __start, regoff_t __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 regoff_t re_search_2 (struct re_pattern_buffer *__buffer,
+			     const char *__string1, regoff_t __length1,
+			     const char *__string2, regoff_t __length2,
+			     regoff_t __start, regoff_t __range,
+			     struct re_registers *__regs,
+			     regoff_t __stop);
+
+
+/* Like 're_search', but return how many characters in STRING the regexp
+   in BUFFER matched, starting at position START.  */
+extern regoff_t re_match (struct re_pattern_buffer *__buffer,
+			  const char *__String, regoff_t __length,
+			  regoff_t __start, struct re_registers *__regs);
+
+
+/* Relates to 're_match' as 're_search_2' relates to 're_search'.  */
+extern regoff_t re_match_2 (struct re_pattern_buffer *__buffer,
+			    const char *__string1, regoff_t __length1,
+			    const char *__string2, regoff_t __length2,
+			    regoff_t __start, struct re_registers *__regs,
+			    regoff_t __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
+   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,
+			      __re_size_t __num_regs,
+			      regoff_t *__starts, regoff_t *__ends);
+#endif	/* Use GNU */
+
+#if defined _REGEX_RE_COMP || (defined _LIBC && defined __USE_MISC)
+# ifndef _CRAY
+/* 4.2 bsd compatibility.  */
+extern char *re_comp (const char *);
+extern int re_exec (const char *);
+# endif
+#endif
+
+/* For plain 'restrict', use glibc's __restrict if defined.
+   Otherwise, GCC 2.95 and later have "__restrict"; C99 compilers have
+   "restrict", and "configure" may have defined "restrict".
+   Other compilers use __restrict, __restrict__, and _Restrict, and
+   'configure' might #define 'restrict' to those words, so pick a
+   different name.  */
+#ifndef _Restrict_
+# if defined __restrict || 2 < __GNUC__ + (95 <= __GNUC_MINOR__)
+#  define _Restrict_ __restrict
+# elif 199901L <= __STDC_VERSION__ || defined restrict
+#  define _Restrict_ restrict
+# else
+#  define _Restrict_
+# endif
+#endif
+/* For [restrict], use glibc's __restrict_arr if available.
+   Otherwise, GCC 3.1 (not in C++ mode) and C99 support [restrict].  */
+#ifndef _Restrict_arr_
+# ifdef __restrict_arr
+#  define _Restrict_arr_ __restrict_arr
+# elif ((199901L <= __STDC_VERSION__ || 3 < __GNUC__ + (1 <= __GNUC_MINOR__)) \
+        && !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_ __String, 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/lib/regex_internal.c b/lib/regex_internal.c
new file mode 100644
index 0000000000..32373565e6
--- /dev/null
+++ b/lib/regex_internal.c
@@ -0,0 +1,1740 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email-masked]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+static void re_string_construct_common (const char *str, Idx len,
+					re_string_t *pstr,
+					RE_TRANSLATE_TYPE trans, bool icase,
+					const re_dfa_t *dfa);
+static re_dfastate_t *create_ci_newstate (const re_dfa_t *dfa,
+					  const re_node_set *nodes,
+					  re_hashval_t hash);
+static re_dfastate_t *create_cd_newstate (const re_dfa_t *dfa,
+					  const re_node_set *nodes,
+					  unsigned int context,
+					  re_hashval_t hash);
+static reg_errcode_t re_string_realloc_buffers (re_string_t *pstr,
+						Idx new_buf_len);
+#ifdef RE_ENABLE_I18N
+static void build_wcs_buffer (re_string_t *pstr);
+static reg_errcode_t build_wcs_upper_buffer (re_string_t *pstr);
+#endif /* RE_ENABLE_I18N */
+static void build_upper_buffer (re_string_t *pstr);
+static void re_string_translate_buffer (re_string_t *pstr);
+static unsigned int re_string_context_at (const re_string_t *input, Idx idx,
+					  int eflags) __attribute__ ((pure));
+
+/* 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
+__attribute_warn_unused_result__
+re_string_allocate (re_string_t *pstr, const char *str, Idx len, Idx init_len,
+		    RE_TRANSLATE_TYPE trans, bool icase, const re_dfa_t *dfa)
+{
+  reg_errcode_t ret;
+  Idx 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
+__attribute_warn_unused_result__
+re_string_construct (re_string_t *pstr, const char *str, Idx len,
+		     RE_TRANSLATE_TYPE trans, bool 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
+__attribute_warn_unused_result__
+re_string_realloc_buffers (re_string_t *pstr, Idx 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 (Idx));
+      if (BE (MIN (IDX_MAX, 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)
+	{
+	  Idx *new_offsets = re_realloc (pstr->offsets, Idx, 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
+re_string_construct_common (const char *str, Idx len, re_string_t *pstr,
+			    RE_TRANSLATE_TYPE trans, bool 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;
+  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
+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;
+  Idx 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) -1 || mbclen == 0
+	      || (mbclen == (size_t) -2 && pstr->bufs_len >= pstr->len), 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;
+	}
+      else if (BE (mbclen == (size_t) -2, 0))
+	{
+	  /* The buffer doesn't have enough space, finish to build.  */
+	  pstr->cur_state = prev_st;
+	  break;
+	}
+
+      /* 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
+__attribute_warn_unused_result__
+build_wcs_upper_buffer (re_string_t *pstr)
+{
+  mbstate_t prev_st;
+  Idx 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 < (size_t) -2, 1))
+	    {
+	      wchar_t wcu = __towupper (wc);
+	      if (wcu != wc)
+		{
+		  size_t mbcdlen;
+
+		  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
+		   || (mbclen == (size_t) -2 && pstr->bufs_len >= pstr->len))
+	    {
+	      /* It is an invalid character, an incomplete character
+		 at the end of the string, 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 < (size_t) -2, 1))
+	  {
+	    wchar_t wcu = __towupper (wc);
+	    if (wcu != wc)
+	      {
+		size_t mbcdlen;
+
+		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 (Idx, 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
+		 || (mbclen == (size_t) -2 && pstr->bufs_len >= pstr->len))
+	  {
+	    /* 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 Idx
+re_string_skip_chars (re_string_t *pstr, Idx new_raw_idx, wint_t *last_wc)
+{
+  mbstate_t prev_st;
+  Idx 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;
+      Idx remain_len = pstr->raw_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 = wc2;
+      /* Then proceed the next character.  */
+      rawbuf_idx += mbclen;
+    }
+  *last_wc = 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
+build_upper_buffer (re_string_t *pstr)
+{
+  Idx 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];
+      pstr->mbs[char_idx] = toupper (ch);
+    }
+  pstr->valid_len = char_idx;
+  pstr->valid_raw_len = char_idx;
+}
+
+/* Apply TRANS to the buffer in PSTR.  */
+
+static void
+re_string_translate_buffer (re_string_t *pstr)
+{
+  Idx 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
+__attribute_warn_unused_result__
+re_string_reconstruct (re_string_t *pstr, Idx idx, int eflags)
+{
+  Idx offset;
+
+  if (BE (pstr->raw_mbs_idx <= idx, 0))
+    offset = idx - pstr->raw_mbs_idx;
+  else
+    {
+      /* 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))
+	    {
+	      Idx low = 0, high = pstr->valid_len, mid;
+	      do
+		{
+		  mid = (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 defined DEBUG && DEBUG
+	      assert (pstr->valid_len > 0);
+#endif
+	    }
+	}
+      else
+	{
+#ifdef RE_ENABLE_I18N
+	  /* No, skip all characters until IDX.  */
+	  Idx 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)
+	    {
+	      Idx 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;
+			  Idx mlen = raw + pstr->len - p;
+			  unsigned char buf[6];
+			  size_t mbclen;
+
+			  const unsigned char *pp = p;
+			  if (BE (pstr->trans != NULL, 0))
+			    {
+			      int i = mlen < 6 ? mlen : 6;
+			      while (--i >= 0)
+				buf[i] = pstr->trans[p[i]];
+			      pp = buf;
+			    }
+			  /* 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 *) pp, 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
+__attribute__ ((pure))
+re_string_peek_byte_case (const re_string_t *pstr, Idx idx)
+{
+  int ch;
+  Idx 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
+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)
+    {
+      Idx off;
+      int 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
+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
+re_string_context_at (const re_string_t *input, Idx 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;
+      Idx wc_idx = idx;
+      while(input->wcs[wc_idx] == WEOF)
+	{
+#if defined DEBUG && 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
+__attribute_warn_unused_result__
+re_node_set_alloc (re_node_set *set, Idx size)
+{
+  set->alloc = size;
+  set->nelem = 0;
+  set->elems = re_malloc (Idx, size);
+  if (BE (set->elems == NULL, 0) && (MALLOC_0_IS_NONNULL || size != 0))
+    return REG_ESPACE;
+  return REG_NOERROR;
+}
+
+static reg_errcode_t
+__attribute_warn_unused_result__
+re_node_set_init_1 (re_node_set *set, Idx elem)
+{
+  set->alloc = 1;
+  set->nelem = 1;
+  set->elems = re_malloc (Idx, 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
+__attribute_warn_unused_result__
+re_node_set_init_2 (re_node_set *set, Idx elem1, Idx elem2)
+{
+  set->alloc = 2;
+  set->elems = re_malloc (Idx, 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
+__attribute_warn_unused_result__
+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 (Idx, dest->alloc);
+      if (BE (dest->elems == NULL, 0))
+	{
+	  dest->alloc = dest->nelem = 0;
+	  return REG_ESPACE;
+	}
+      memcpy (dest->elems, src->elems, src->nelem * sizeof (Idx));
+    }
+  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
+__attribute_warn_unused_result__
+re_node_set_add_intersect (re_node_set *dest, const re_node_set *src1,
+			   const re_node_set *src2)
+{
+  Idx 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)
+    {
+      Idx new_alloc = src1->nelem + src2->nelem + dest->alloc;
+      Idx *new_elems = re_realloc (dest->elems, Idx, 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 (Idx));
+
+  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
+__attribute_warn_unused_result__
+re_node_set_init_union (re_node_set *dest, const re_node_set *src1,
+			const re_node_set *src2)
+{
+  Idx i1, i2, id;
+  if (src1 != NULL && src1->nelem > 0 && src2 != NULL && src2->nelem > 0)
+    {
+      dest->alloc = src1->nelem + src2->nelem;
+      dest->elems = re_malloc (Idx, 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 (Idx));
+      id += src1->nelem - i1;
+    }
+  else if (i2 < src2->nelem)
+    {
+      memcpy (dest->elems + id, src2->elems + i2,
+	     (src2->nelem - i2) * sizeof (Idx));
+      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
+__attribute_warn_unused_result__
+re_node_set_merge (re_node_set *dest, const re_node_set *src)
+{
+  Idx is, id, sbase, delta;
+  if (src == NULL || src->nelem == 0)
+    return REG_NOERROR;
+  if (dest->alloc < 2 * src->nelem + dest->nelem)
+    {
+      Idx new_alloc = 2 * (src->nelem + dest->alloc);
+      Idx *new_buffer = re_realloc (dest->elems, Idx, 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 (Idx));
+      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 (Idx));
+    }
+
+  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 (Idx));
+	      break;
+	    }
+	}
+    }
+
+  return REG_NOERROR;
+}
+
+/* Insert the new element ELEM to the re_node_set* SET.
+   SET should not already have ELEM.
+   Return true if successful.  */
+
+static bool
+__attribute_warn_unused_result__
+re_node_set_insert (re_node_set *set, Idx elem)
+{
+  Idx idx;
+  /* In case the set is empty.  */
+  if (set->alloc == 0)
+    return BE (re_node_set_init_1 (set, elem) == REG_NOERROR, 1);
+
+  if (BE (set->nelem, 0) == 0)
+    {
+      /* We already guaranteed above that set->alloc != 0.  */
+      set->elems[0] = elem;
+      ++set->nelem;
+      return true;
+    }
+
+  /* Realloc if we need.  */
+  if (set->alloc == set->nelem)
+    {
+      Idx *new_elems;
+      set->alloc = set->alloc * 2;
+      new_elems = re_realloc (set->elems, Idx, set->alloc);
+      if (BE (new_elems == NULL, 0))
+	return false;
+      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 true;
+}
+
+/* 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 true if successful.  */
+
+static bool
+__attribute_warn_unused_result__
+re_node_set_insert_last (re_node_set *set, Idx elem)
+{
+  /* Realloc if we need.  */
+  if (set->alloc == set->nelem)
+    {
+      Idx *new_elems;
+      set->alloc = (set->alloc + 1) * 2;
+      new_elems = re_realloc (set->elems, Idx, set->alloc);
+      if (BE (new_elems == NULL, 0))
+	return false;
+      set->elems = new_elems;
+    }
+
+  /* Insert the new element.  */
+  set->elems[set->nelem++] = elem;
+  return true;
+}
+
+/* Compare two node sets SET1 and SET2.
+   Return true if SET1 and SET2 are equivalent.  */
+
+static bool
+__attribute__ ((pure))
+re_node_set_compare (const re_node_set *set1, const re_node_set *set2)
+{
+  Idx i;
+  if (set1 == NULL || set2 == NULL || set1->nelem != set2->nelem)
+    return false;
+  for (i = set1->nelem ; --i >= 0 ; )
+    if (set1->elems[i] != set2->elems[i])
+      return false;
+  return true;
+}
+
+/* Return (idx + 1) if SET contains the element ELEM, return 0 otherwise.  */
+
+static Idx
+__attribute__ ((pure))
+re_node_set_contains (const re_node_set *set, Idx elem)
+{
+  __re_size_t 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) / 2;
+      if (set->elems[mid] < elem)
+	idx = mid + 1;
+      else
+	right = mid;
+    }
+  return set->elems[idx] == elem ? idx + 1 : 0;
+}
+
+static void
+re_node_set_remove_at (re_node_set *set, Idx 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 occurred.  */
+
+static Idx
+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;
+      Idx *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 (Idx)));
+      if (BE (MIN (IDX_MAX, 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, Idx, new_nodes_alloc);
+      new_indices = re_realloc (dfa->org_indices, Idx, 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))
+	{
+	   re_free (new_nexts);
+	   re_free (new_indices);
+	   re_free (new_edests);
+	   re_free (new_eclosures);
+	   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 re_hashval_t
+calc_state_hash (const re_node_set *nodes, unsigned int context)
+{
+  re_hashval_t hash = nodes->nelem + context;
+  Idx 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 *
+__attribute_warn_unused_result__
+re_acquire_state (reg_errcode_t *err, const re_dfa_t *dfa,
+		  const re_node_set *nodes)
+{
+  re_hashval_t hash;
+  re_dfastate_t *new_state;
+  struct re_state_table_entry *spot;
+  Idx i;
+#if defined GCC_LINT || defined lint
+  /* Suppress bogus uninitialized-variable warnings.  */
+  *err = REG_NOERROR;
+#endif
+  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 *
+__attribute_warn_unused_result__
+re_acquire_state_context (reg_errcode_t *err, const re_dfa_t *dfa,
+			  const re_node_set *nodes, unsigned int context)
+{
+  re_hashval_t hash;
+  re_dfastate_t *new_state;
+  struct re_state_table_entry *spot;
+  Idx i;
+#if defined GCC_LINT || defined lint
+  /* Suppress bogus uninitialized-variable warnings.  */
+  *err = REG_NOERROR;
+#endif
+  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
+__attribute_warn_unused_result__
+register_state (const re_dfa_t *dfa, re_dfastate_t *newstate,
+		re_hashval_t hash)
+{
+  struct re_state_table_entry *spot;
+  reg_errcode_t err;
+  Idx 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++)
+    {
+      Idx elem = newstate->nodes.elems[i];
+      if (!IS_EPSILON_NODE (dfa->nodes[elem].type))
+	if (! re_node_set_insert_last (&newstate->non_eps_nodes, elem))
+	  return REG_ESPACE;
+    }
+
+  spot = dfa->state_table + (hash & dfa->state_hash_mask);
+  if (BE (spot->alloc <= spot->num, 0))
+    {
+      Idx 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 *
+__attribute_warn_unused_result__
+create_ci_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
+		    re_hashval_t hash)
+{
+  Idx 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 *
+__attribute_warn_unused_result__
+create_cd_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
+		    unsigned int context, re_hashval_t hash)
+{
+  Idx 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/lib/regex_internal.h b/lib/regex_internal.h
new file mode 100644
index 0000000000..7bbe802bc5
--- /dev/null
+++ b/lib/regex_internal.h
@@ -0,0 +1,911 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email-masked]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _REGEX_INTERNAL_H
+#define _REGEX_INTERNAL_H 1
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <langinfo.h>
+#include <locale.h>
+#include <wchar.h>
+#include <wctype.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+/* Properties of integers.  Although Gnulib has intprops.h, glibc does
+   without for now.  */
+#ifndef _LIBC
+# include "intprops.h"
+#else
+/* True if the real type T is signed.  */
+# define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
+
+/* True if adding the nonnegative Idx values A and B would overflow.
+   If false, set *R to A + B.  A, B, and R may be evaluated more than
+   once, or zero times.  Although this is not a full implementation of
+   Gnulib INT_ADD_WRAPV, it is good enough for glibc regex code.
+   FIXME: This implementation is a fragile stopgap, and this file would
+   be simpler and more robust if intprops.h were migrated into glibc.  */
+# define INT_ADD_WRAPV(a, b, r) \
+   (IDX_MAX - (a) < (b) ? true : (*(r) = (a) + (b), false))
+#endif
+
+#ifdef _LIBC
+# include <libc-lock.h>
+# define lock_define(name) __libc_lock_define (, name)
+# define lock_init(lock) (__libc_lock_init (lock), 0)
+# define lock_fini(lock) ((void) 0)
+# define lock_lock(lock) __libc_lock_lock (lock)
+# define lock_unlock(lock) __libc_lock_unlock (lock)
+#elif defined GNULIB_LOCK && !defined USE_UNLOCKED_IO
+# include "glthread/lock.h"
+  /* Use gl_lock_define if empty macro arguments are known to work.
+     Otherwise, fall back on less-portable substitutes.  */
+# if ((defined __GNUC__ && !defined __STRICT_ANSI__) \
+      || (defined __STDC_VERSION__ && 199901L <= __STDC_VERSION__))
+#  define lock_define(name) gl_lock_define (, name)
+# elif USE_POSIX_THREADS
+#  define lock_define(name) pthread_mutex_t name;
+# elif USE_PTH_THREADS
+#  define lock_define(name) pth_mutex_t name;
+# elif USE_SOLARIS_THREADS
+#  define lock_define(name) mutex_t name;
+# elif USE_WINDOWS_THREADS
+#  define lock_define(name) gl_lock_t name;
+# else
+#  define lock_define(name)
+# endif
+# define lock_init(lock) glthread_lock_init (&(lock))
+# define lock_fini(lock) glthread_lock_destroy (&(lock))
+# define lock_lock(lock) glthread_lock_lock (&(lock))
+# define lock_unlock(lock) glthread_lock_unlock (&(lock))
+#elif defined GNULIB_PTHREAD && !defined USE_UNLOCKED_IO
+# include <pthread.h>
+# define lock_define(name) pthread_mutex_t name;
+# define lock_init(lock) pthread_mutex_init (&(lock), 0)
+# define lock_fini(lock) pthread_mutex_destroy (&(lock))
+# define lock_lock(lock) pthread_mutex_lock (&(lock))
+# define lock_unlock(lock) pthread_mutex_unlock (&(lock))
+#else
+# define lock_define(name)
+# define lock_init(lock) 0
+# define lock_fini(lock) ((void) 0)
+  /* The 'dfa' avoids an "unused variable 'dfa'" warning from GCC.  */
+# define lock_lock(lock) ((void) dfa)
+# define lock_unlock(lock) ((void) 0)
+#endif
+
+/* In case that the system doesn't have isblank().  */
+#if !defined _LIBC && ! (defined isblank || (HAVE_ISBLANK && HAVE_DECL_ISBLANK))
+# define isblank(ch) ((ch) == ' ' || (ch) == '\t')
+#endif
+
+#ifdef _LIBC
+# ifndef _RE_DEFINE_LOCALE_FUNCTIONS
+#  define _RE_DEFINE_LOCALE_FUNCTIONS 1
+#   include <locale/localeinfo.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) \
+  __dcgettext (_libc_intl_domainname, msgid, LC_MESSAGES)
+# endif
+#else
+# undef gettext
+# define gettext(msgid) (msgid)
+#endif
+
+#ifndef gettext_noop
+/* This define is so xgettext can find the internationalizable
+   strings.  */
+# define gettext_noop(String) String
+#endif
+
+#if (defined MB_CUR_MAX && HAVE_WCTYPE_H && HAVE_ISWCTYPE) || _LIBC
+# define RE_ENABLE_I18N
+#endif
+
+#define BE(expr, val) __builtin_expect (expr, val)
+
+/* Number of ASCII characters.  */
+#define ASCII_CHARS 0x80
+
+/* Number of single byte characters.  */
+#define SBC_MAX (UCHAR_MAX + 1)
+
+#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
+# undef __wctype
+# undef __iswctype
+# define __wctype wctype
+# define __iswalnum iswalnum
+# define __iswctype iswctype
+# define __towlower towlower
+# define __towupper towupper
+# define __btowc btowc
+# define __mbrtowc mbrtowc
+# define __wcrtomb wcrtomb
+# define __regfree regfree
+# define attribute_hidden
+#endif /* not _LIBC */
+
+#if __GNUC__ < 3 + (__GNUC_MINOR__ < 1)
+# define __attribute__(arg)
+#endif
+
+#ifndef SSIZE_MAX
+# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
+#endif
+
+/* The type of indexes into strings.  This is signed, not size_t,
+   since the API requires indexes to fit in regoff_t anyway, and using
+   signed integers makes the code a bit smaller and presumably faster.
+   The traditional GNU regex implementation uses int for indexes.
+   The POSIX-compatible implementation uses a possibly-wider type.
+   The name 'Idx' is three letters to minimize the hassle of
+   reindenting a lot of regex code that formerly used 'int'.  */
+typedef regoff_t Idx;
+#ifdef _REGEX_LARGE_OFFSETS
+# define IDX_MAX SSIZE_MAX
+#else
+# define IDX_MAX INT_MAX
+#endif
+
+/* A hash value, suitable for computing hash tables.  */
+typedef __re_size_t re_hashval_t;
+
+/* 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.  For portability to hosts with
+   padding bits, do not use '(sizeof (bitset_word_t) * CHAR_BIT)';
+   instead, deduce it directly from BITSET_WORD_MAX.  Avoid
+   greater-than-32-bit integers and unconditional shifts by more than
+   31 bits, as they're not portable.  */
+#if BITSET_WORD_MAX == 0xffffffffUL
+# define BITSET_WORD_BITS 32
+#elif BITSET_WORD_MAX >> 31 >> 4 == 1
+# define BITSET_WORD_BITS 36
+#elif BITSET_WORD_MAX >> 31 >> 16 == 1
+# define BITSET_WORD_BITS 48
+#elif BITSET_WORD_MAX >> 31 >> 28 == 1
+# define BITSET_WORD_BITS 60
+#elif BITSET_WORD_MAX >> 31 >> 31 >> 1 == 1
+# define BITSET_WORD_BITS 64
+#elif BITSET_WORD_MAX >> 31 >> 31 >> 9 == 1
+# define BITSET_WORD_BITS 72
+#elif BITSET_WORD_MAX >> 31 >> 31 >> 31 >> 31 >> 3 == 1
+# define BITSET_WORD_BITS 128
+#elif BITSET_WORD_MAX >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 7 == 1
+# define BITSET_WORD_BITS 256
+#elif BITSET_WORD_MAX >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 31 >> 7 > 1
+# define BITSET_WORD_BITS 257 /* any value > SBC_MAX will do here */
+# if BITSET_WORD_BITS <= SBC_MAX
+#  error "Invalid SBC_MAX"
+# endif
+#else
+# error "Add case for new bitset_word_t size"
+#endif
+
+/* Number of bitset_word_t values in a bitset_t.  */
+#define BITSET_WORDS ((SBC_MAX + BITSET_WORD_BITS - 1) / 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 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
+{
+  Idx alloc;
+  Idx nelem;
+  Idx *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.  */
+  Idx nmbchars;
+
+  /* # of collating symbols.  */
+  Idx ncoll_syms;
+
+  /* # of equivalence classes. */
+  Idx nequiv_classes;
+
+  /* # of range expressions. */
+  Idx nranges;
+
+  /* # of character classes. */
+  Idx 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 */
+    Idx idx;			/* for BACK_REF */
+    re_context_type ctx_type;	/* for ANCHOR */
+  } opr;
+#if __GNUC__ >= 2 && !defined __STRICT_ANSI__
+  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;
+  Idx *offsets;
+  mbstate_t cur_state;
+#endif
+  /* Index in RAW_MBS.  Each character mbs[i] corresponds to
+     raw_mbs[raw_mbs_idx + i].  */
+  Idx raw_mbs_idx;
+  /* The length of the valid characters in the buffers.  */
+  Idx valid_len;
+  /* The corresponding number of bytes in raw_mbs array.  */
+  Idx valid_raw_len;
+  /* The length of the buffers MBS and WCS.  */
+  Idx bufs_len;
+  /* The index in MBS, which is updated by re_string_fetch_byte.  */
+  Idx cur_idx;
+  /* length of RAW_MBS array.  */
+  Idx raw_len;
+  /* This is RAW_LEN - RAW_MBS_IDX + VALID_LEN - VALID_RAW_LEN.  */
+  Idx 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.  */
+  Idx raw_stop;
+  /* This is RAW_STOP - RAW_MBS_IDX adjusted through OFFSETS.  */
+  Idx 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;
+  /* true 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
+# define IS_IN(libc) false
+#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))
+
+#if defined _LIBC || HAVE_ALLOCA
+# include <alloca.h>
+#endif
+
+#ifndef _LIBC
+# if HAVE_ALLOCA
+/* 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)
+# else
+/* alloca is implemented with malloc, so just use malloc.  */
+#  define __libc_use_alloca(n) 0
+#  undef alloca
+#  define alloca(n) malloc (n)
+# endif
+#endif
+
+#ifdef _LIBC
+# define MALLOC_0_IS_NONNULL 1
+#elif !defined MALLOC_0_IS_NONNULL
+# define MALLOC_0_IS_NONNULL 0
+#endif
+
+#ifndef MAX
+# define MAX(a,b) ((a) < (b) ? (b) : (a))
+#endif
+#ifndef MIN
+# define MIN(a,b) ((a) < (b) ? (a) : (b))
+#endif
+
+#define re_malloc(t,n) ((t *) malloc ((n) * sizeof (t)))
+#define re_realloc(p,t,n) ((t *) realloc (p, (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.  */
+  Idx 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
+{
+  re_hashval_t 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
+{
+  Idx num;
+  Idx alloc;
+  re_dfastate_t **array;
+};
+
+/* Array type used in re_sub_match_last_t and re_sub_match_top_t.  */
+
+typedef struct
+{
+  Idx next_idx;
+  Idx alloc;
+  re_dfastate_t **array;
+} state_array_t;
+
+/* Store information about the node NODE whose type is OP_CLOSE_SUBEXP.  */
+
+typedef struct
+{
+  Idx node;
+  Idx 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
+{
+  Idx str_idx;
+  Idx node;
+  state_array_t *path;
+  Idx alasts; /* Allocation size of LASTS.  */
+  Idx nlasts; /* The number of LASTS.  */
+  re_sub_match_last_t **lasts;
+} re_sub_match_top_t;
+
+struct re_backref_cache_entry
+{
+  Idx node;
+  Idx str_idx;
+  Idx subexp_from;
+  Idx 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.  */
+  Idx match_last;
+  Idx last_node;
+  /* The state log used by the matcher.  */
+  re_dfastate_t **state_log;
+  Idx state_log_top;
+  /* Back reference cache.  */
+  Idx nbkref_ents;
+  Idx abkref_ents;
+  struct re_backref_cache_entry *bkref_ents;
+  int max_mb_elem_len;
+  Idx nsub_tops;
+  Idx 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;
+  Idx last_node;
+  Idx last_str_idx;
+  re_node_set limits;
+} re_sift_context_t;
+
+struct re_fail_stack_ent_t
+{
+  Idx idx;
+  Idx node;
+  regmatch_t *regs;
+  re_node_set eps_via_nodes;
+};
+
+struct re_fail_stack_t
+{
+  Idx num;
+  Idx alloc;
+  struct re_fail_stack_ent_t *stack;
+};
+
+struct re_dfa_t
+{
+  re_token_t *nodes;
+  size_t nodes_alloc;
+  size_t nodes_len;
+  Idx *nexts;
+  Idx *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.  */
+  re_hashval_t state_hash_mask;
+  Idx init_node;
+  Idx 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;
+  Idx *subexp_map;
+#ifdef DEBUG
+  char* re_str;
+#endif
+  lock_define (lock)
+};
+
+#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;
+
+
+/* Functions for bitset_t operation.  */
+
+static inline void
+bitset_set (bitset_t set, Idx i)
+{
+  set[i / BITSET_WORD_BITS] |= (bitset_word_t) 1 << i % BITSET_WORD_BITS;
+}
+
+static inline void
+bitset_clear (bitset_t set, Idx i)
+{
+  set[i / BITSET_WORD_BITS] &= ~ ((bitset_word_t) 1 << i % BITSET_WORD_BITS);
+}
+
+static inline bool
+bitset_contain (const bitset_t set, Idx i)
+{
+  return (set[i / BITSET_WORD_BITS] >> i % BITSET_WORD_BITS) & 1;
+}
+
+static inline void
+bitset_empty (bitset_t set)
+{
+  memset (set, '\0', sizeof (bitset_t));
+}
+
+static inline void
+bitset_set_all (bitset_t set)
+{
+  memset (set, -1, sizeof (bitset_word_t) * (SBC_MAX / BITSET_WORD_BITS));
+  if (SBC_MAX % BITSET_WORD_BITS != 0)
+    set[BITSET_WORDS - 1] =
+      ((bitset_word_t) 1 << SBC_MAX % BITSET_WORD_BITS) - 1;
+}
+
+static inline void
+bitset_copy (bitset_t dest, const bitset_t src)
+{
+  memcpy (dest, src, sizeof (bitset_t));
+}
+
+static inline void
+bitset_not (bitset_t set)
+{
+  int bitset_i;
+  for (bitset_i = 0; bitset_i < SBC_MAX / BITSET_WORD_BITS; ++bitset_i)
+    set[bitset_i] = ~set[bitset_i];
+  if (SBC_MAX % BITSET_WORD_BITS != 0)
+    set[BITSET_WORDS - 1] =
+      ((((bitset_word_t) 1 << SBC_MAX % BITSET_WORD_BITS) - 1)
+       & ~set[BITSET_WORDS - 1]);
+}
+
+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
+/* Functions for re_string.  */
+static int
+__attribute__ ((pure, unused))
+re_string_char_size_at (const re_string_t *pstr, Idx 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 wint_t
+__attribute__ ((pure, unused))
+re_string_wchar_at (const re_string_t *pstr, Idx idx)
+{
+  if (pstr->mb_cur_max == 1)
+    return (wint_t) pstr->mbs[idx];
+  return (wint_t) pstr->wcs[idx];
+}
+
+# ifdef _LIBC
+#  include <locale/weight.h>
+# endif
+
+static int
+__attribute__ ((pure, unused))
+re_string_elem_size_at (const re_string_t *pstr, Idx idx)
+{
+# ifdef _LIBC
+  const unsigned char *p, *extra;
+  const int32_t *table, *indirect;
+  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;
+      findidx (table, indirect, extra, &p, pstr->len - idx);
+      return p - pstr->mbs - idx;
+    }
+  else
+# endif /* _LIBC */
+    return 1;
+}
+#endif /* RE_ENABLE_I18N */
+
+#ifndef __GNUC_PREREQ
+# if defined __GNUC__ && defined __GNUC_MINOR__
+#  define __GNUC_PREREQ(maj, min) \
+         ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
+# else
+#  define __GNUC_PREREQ(maj, min) 0
+# endif
+#endif
+
+#if __GNUC_PREREQ (3,4)
+# undef __attribute_warn_unused_result__
+# define __attribute_warn_unused_result__ \
+   __attribute__ ((__warn_unused_result__))
+#else
+# define __attribute_warn_unused_result__ /* empty */
+#endif
+
+#ifndef FALLTHROUGH
+# if __GNUC__ < 7
+#  define FALLTHROUGH ((void) 0)
+# else
+#  define FALLTHROUGH __attribute__ ((__fallthrough__))
+# endif
+#endif
+
+#endif /*  _REGEX_INTERNAL_H */
diff --git a/lib/regexec.c b/lib/regexec.c
new file mode 100644
index 0000000000..6591311164
--- /dev/null
+++ b/lib/regexec.c
@@ -0,0 +1,4324 @@
+/* Extended regular expression matching and search library.
+   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Isamu Hasegawa <[email-masked]>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+static reg_errcode_t match_ctx_init (re_match_context_t *cache, int eflags,
+				     Idx n);
+static void match_ctx_clean (re_match_context_t *mctx);
+static void match_ctx_free (re_match_context_t *cache);
+static reg_errcode_t match_ctx_add_entry (re_match_context_t *cache, Idx node,
+					  Idx str_idx, Idx from, Idx to);
+static Idx search_cur_bkref_entry (const re_match_context_t *mctx, Idx str_idx);
+static reg_errcode_t match_ctx_add_subtop (re_match_context_t *mctx, Idx node,
+					   Idx str_idx);
+static re_sub_match_last_t * match_ctx_add_sublast (re_sub_match_top_t *subtop,
+						    Idx node, Idx str_idx);
+static void sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
+			   re_dfastate_t **limited_sts, Idx last_node,
+			   Idx last_str_idx);
+static reg_errcode_t re_search_internal (const regex_t *preg,
+					 const char *string, Idx length,
+					 Idx start, Idx last_start, Idx stop,
+					 size_t nmatch, regmatch_t pmatch[],
+					 int eflags);
+static regoff_t re_search_2_stub (struct re_pattern_buffer *bufp,
+				  const char *string1, Idx length1,
+				  const char *string2, Idx length2,
+				  Idx start, regoff_t range,
+				  struct re_registers *regs,
+				  Idx stop, bool ret_len);
+static regoff_t re_search_stub (struct re_pattern_buffer *bufp,
+				const char *string, Idx length, Idx start,
+				regoff_t range, Idx stop,
+				struct re_registers *regs,
+				bool ret_len);
+static unsigned re_copy_regs (struct re_registers *regs, regmatch_t *pmatch,
+                              Idx nregs, int regs_allocated);
+static reg_errcode_t prune_impossible_nodes (re_match_context_t *mctx);
+static Idx check_matching (re_match_context_t *mctx, bool fl_longest_match,
+			   Idx *p_match_first);
+static Idx check_halt_state_context (const re_match_context_t *mctx,
+				     const re_dfastate_t *state, Idx idx);
+static void update_regs (const re_dfa_t *dfa, regmatch_t *pmatch,
+			 regmatch_t *prev_idx_match, Idx cur_node,
+			 Idx cur_idx, Idx nmatch);
+static reg_errcode_t push_fail_stack (struct re_fail_stack_t *fs,
+				      Idx str_idx, Idx dest_node, Idx nregs,
+				      regmatch_t *regs,
+				      re_node_set *eps_via_nodes);
+static reg_errcode_t set_regs (const regex_t *preg,
+			       const re_match_context_t *mctx,
+			       size_t nmatch, regmatch_t *pmatch,
+			       bool fl_backtrack);
+static reg_errcode_t free_fail_stack_return (struct re_fail_stack_t *fs);
+
+#ifdef RE_ENABLE_I18N
+static int sift_states_iter_mb (const re_match_context_t *mctx,
+				re_sift_context_t *sctx,
+				Idx node_idx, Idx str_idx, Idx max_str_idx);
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t sift_states_backward (const re_match_context_t *mctx,
+					   re_sift_context_t *sctx);
+static reg_errcode_t build_sifted_states (const re_match_context_t *mctx,
+					  re_sift_context_t *sctx, Idx str_idx,
+					  re_node_set *cur_dest);
+static reg_errcode_t update_cur_sifted_state (const re_match_context_t *mctx,
+					      re_sift_context_t *sctx,
+					      Idx str_idx,
+					      re_node_set *dest_nodes);
+static reg_errcode_t add_epsilon_src_nodes (const re_dfa_t *dfa,
+					    re_node_set *dest_nodes,
+					    const re_node_set *candidates);
+static bool check_dst_limits (const re_match_context_t *mctx,
+			      const re_node_set *limits,
+			      Idx dst_node, Idx dst_idx, Idx src_node,
+			      Idx src_idx);
+static int check_dst_limits_calc_pos_1 (const re_match_context_t *mctx,
+					int boundaries, Idx subexp_idx,
+					Idx from_node, Idx bkref_idx);
+static int check_dst_limits_calc_pos (const re_match_context_t *mctx,
+				      Idx limit, Idx subexp_idx,
+				      Idx node, Idx str_idx,
+				      Idx bkref_idx);
+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,
+					  Idx str_idx);
+static reg_errcode_t sift_states_bkref (const re_match_context_t *mctx,
+					re_sift_context_t *sctx,
+					Idx str_idx, const re_node_set *candidates);
+static reg_errcode_t merge_state_array (const re_dfa_t *dfa,
+					re_dfastate_t **dst,
+					re_dfastate_t **src, Idx num);
+static re_dfastate_t *find_recover_state (reg_errcode_t *err,
+					 re_match_context_t *mctx);
+static re_dfastate_t *transit_state (reg_errcode_t *err,
+				     re_match_context_t *mctx,
+				     re_dfastate_t *state);
+static re_dfastate_t *merge_state_with_log (reg_errcode_t *err,
+					    re_match_context_t *mctx,
+					    re_dfastate_t *next_state);
+static reg_errcode_t check_subexp_matching_top (re_match_context_t *mctx,
+						re_node_set *cur_nodes,
+						Idx str_idx);
+#if 0
+static re_dfastate_t *transit_state_sb (reg_errcode_t *err,
+					re_match_context_t *mctx,
+					re_dfastate_t *pstate);
+#endif
+#ifdef RE_ENABLE_I18N
+static reg_errcode_t transit_state_mb (re_match_context_t *mctx,
+				       re_dfastate_t *pstate);
+#endif /* RE_ENABLE_I18N */
+static reg_errcode_t transit_state_bkref (re_match_context_t *mctx,
+					  const re_node_set *nodes);
+static reg_errcode_t get_subexp (re_match_context_t *mctx,
+				 Idx bkref_node, Idx bkref_str_idx);
+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,
+				     Idx bkref_node, Idx bkref_str);
+static Idx find_subexp_node (const re_dfa_t *dfa, const re_node_set *nodes,
+			     Idx subexp_idx, int type);
+static reg_errcode_t check_arrival (re_match_context_t *mctx,
+				    state_array_t *path, Idx top_node,
+				    Idx top_str, Idx last_node, Idx last_str,
+				    int type);
+static reg_errcode_t check_arrival_add_next_nodes (re_match_context_t *mctx,
+						   Idx str_idx,
+						   re_node_set *cur_nodes,
+						   re_node_set *next_nodes);
+static reg_errcode_t check_arrival_expand_ecl (const re_dfa_t *dfa,
+					       re_node_set *cur_nodes,
+					       Idx ex_subexp, int type);
+static reg_errcode_t check_arrival_expand_ecl_sub (const re_dfa_t *dfa,
+						   re_node_set *dst_nodes,
+						   Idx target, Idx ex_subexp,
+						   int type);
+static reg_errcode_t expand_bkref_cache (re_match_context_t *mctx,
+					 re_node_set *cur_nodes, Idx cur_str,
+					 Idx subexp_num, int type);
+static bool build_trtable (const re_dfa_t *dfa, re_dfastate_t *state);
+#ifdef RE_ENABLE_I18N
+static int check_node_accept_bytes (const re_dfa_t *dfa, Idx node_idx,
+				    const re_string_t *input, Idx idx);
+# ifdef _LIBC
+static unsigned int find_collation_sequence_value (const unsigned char *mbs,
+						   size_t name_len);
+# endif /* _LIBC */
+#endif /* RE_ENABLE_I18N */
+static Idx group_nodes_into_DFAstates (const re_dfa_t *dfa,
+				       const re_dfastate_t *state,
+				       re_node_set *states_node,
+				       bitset_t *states_ch);
+static bool check_node_accept (const re_match_context_t *mctx,
+			       const re_token_t *node, Idx idx);
+static reg_errcode_t extend_buffers (re_match_context_t *mctx, int min_len);
+
+/* 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;
+  Idx start, length;
+  re_dfa_t *dfa = preg->buffer;
+
+  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);
+    }
+
+  lock_lock (dfa->lock);
+  if (preg->no_sub)
+    err = re_search_internal (preg, string, length, start, length,
+			      length, 0, NULL, eflags);
+  else
+    err = re_search_internal (preg, string, length, start, length,
+			      length, nmatch, pmatch, eflags);
+  lock_unlock (dfa->lock);
+  return err != REG_NOERROR;
+}
+
+#ifdef _LIBC
+libc_hidden_def (__regexec)
+
+# 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 stored 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.  */
+
+regoff_t
+re_match (struct re_pattern_buffer *bufp, const char *string, Idx length,
+	  Idx start, struct re_registers *regs)
+{
+  return re_search_stub (bufp, string, length, start, 0, length, regs, true);
+}
+#ifdef _LIBC
+weak_alias (__re_match, re_match)
+#endif
+
+regoff_t
+re_search (struct re_pattern_buffer *bufp, const char *string, Idx length,
+	   Idx start, regoff_t range, struct re_registers *regs)
+{
+  return re_search_stub (bufp, string, length, start, range, length, regs,
+			 false);
+}
+#ifdef _LIBC
+weak_alias (__re_search, re_search)
+#endif
+
+regoff_t
+re_match_2 (struct re_pattern_buffer *bufp, const char *string1, Idx length1,
+	    const char *string2, Idx length2, Idx start,
+	    struct re_registers *regs, Idx stop)
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+			   start, 0, regs, stop, true);
+}
+#ifdef _LIBC
+weak_alias (__re_match_2, re_match_2)
+#endif
+
+regoff_t
+re_search_2 (struct re_pattern_buffer *bufp, const char *string1, Idx length1,
+	     const char *string2, Idx length2, Idx start, regoff_t range,
+	     struct re_registers *regs, Idx stop)
+{
+  return re_search_2_stub (bufp, string1, length1, string2, length2,
+			   start, range, regs, stop, false);
+}
+#ifdef _LIBC
+weak_alias (__re_search_2, re_search_2)
+#endif
+
+static regoff_t
+re_search_2_stub (struct re_pattern_buffer *bufp, const char *string1,
+		  Idx length1, const char *string2, Idx length2, Idx start,
+		  regoff_t range, struct re_registers *regs,
+		  Idx stop, bool ret_len)
+{
+  const char *str;
+  regoff_t rval;
+  Idx len;
+  char *s = NULL;
+
+  if (BE ((length1 < 0 || length2 < 0 || stop < 0
+           || INT_ADD_WRAPV (length1, length2, &len)),
+          0))
+    return -2;
+
+  /* Concatenate the strings.  */
+  if (length2 > 0)
+    if (length1 > 0)
+      {
+	s = re_malloc (char, len);
+
+	if (BE (s == NULL, 0))
+	  return -2;
+#ifdef _LIBC
+	memcpy (__mempcpy (s, string1, length1), string2, length2);
+#else
+	memcpy (s, string1, length1);
+	memcpy (s + length1, string2, length2);
+#endif
+	str = s;
+      }
+    else
+      str = string2;
+  else
+    str = string1;
+
+  rval = re_search_stub (bufp, str, len, start, range, stop, regs,
+			 ret_len);
+  re_free (s);
+  return rval;
+}
+
+/* The parameters have the same meaning as those of re_search.
+   Additional parameters:
+   If RET_LEN is true the length of the match is returned (re_match style);
+   otherwise the position of the match is returned.  */
+
+static regoff_t
+re_search_stub (struct re_pattern_buffer *bufp, const char *string, Idx length,
+		Idx start, regoff_t range, Idx stop, struct re_registers *regs,
+		bool ret_len)
+{
+  reg_errcode_t result;
+  regmatch_t *pmatch;
+  Idx nregs;
+  regoff_t rval;
+  int eflags = 0;
+  re_dfa_t *dfa = bufp->buffer;
+  Idx last_start = start + range;
+
+  /* Check for out-of-range.  */
+  if (BE (start < 0 || start > length, 0))
+    return -1;
+  if (BE (length < last_start || (0 <= range && last_start < start), 0))
+    last_start = length;
+  else if (BE (last_start < 0 || (range < 0 && start <= last_start), 0))
+    last_start = 0;
+
+  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 (start < last_start && 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, 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, last_start, 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 = result == REG_NOMATCH ? -1 : -2;
+  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:
+  lock_unlock (dfa->lock);
+  return rval;
+}
+
+static unsigned
+re_copy_regs (struct re_registers *regs, regmatch_t *pmatch, Idx nregs,
+	      int regs_allocated)
+{
+  int rval = REGS_REALLOCATE;
+  Idx i;
+  Idx 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,
+		  __re_size_t 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 = NULL;
+    }
+}
+#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 (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
+   meaning as with regexec.  LAST_START is START + RANGE, where
+   START and RANGE have the same meaning as 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.
+   (0 <= LAST_START && LAST_START <= LENGTH)  */
+
+static reg_errcode_t
+__attribute_warn_unused_result__
+re_search_internal (const regex_t *preg, const char *string, Idx length,
+		    Idx start, Idx last_start, Idx stop, size_t nmatch,
+		    regmatch_t pmatch[], int eflags)
+{
+  reg_errcode_t err;
+  const re_dfa_t *dfa = preg->buffer;
+  Idx left_lim, right_lim;
+  int incr;
+  bool fl_longest_match;
+  int match_kind;
+  Idx match_first;
+  Idx match_last = -1;
+  Idx extra_nmatch;
+  bool sb;
+  int 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
+		    && start != last_start && !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 (0 <= last_start && last_start <= 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 && last_start != 0)
+        return REG_NOMATCH;
+      start = last_start = 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) != 0,
+			    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 ((MIN (IDX_MAX, 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 the input string matches.  */
+  incr = (last_start < start) ? -1 : 1;
+  left_lim = (last_start < start) ? last_start : start;
+  right_lim = (last_start < start) ? start : last_start;
+  sb = dfa->mb_cur_max == 1;
+  match_kind =
+    (fastmap
+     ? ((sb || !(preg->syntax & RE_ICASE || t) ? 4 : 0)
+	| (start <= last_start ? 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.  */
+	      __re_size_t offset = match_first - mctx.input.raw_mbs_idx;
+	      if (BE (offset >= (__re_size_t) 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,
+				   start <= last_start ? &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)
+    {
+      Idx 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;
+      /* FIXME: This function should fail if mctx.match_last exceeds
+	 the maximum possible regoff_t value.  We need a new error
+	 code REG_OVERFLOW.  */
+
+      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 each register, since we slid
+	 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
+__attribute_warn_unused_result__
+prune_impossible_nodes (re_match_context_t *mctx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  Idx 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 (MIN (IDX_MAX, 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))
+acquire_init_state_context (reg_errcode_t *err, const re_match_context_t *mctx,
+			    Idx 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
+   there is no match, and 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 assumes that the matching starts from the current
+   index of the buffer.  */
+
+static Idx
+__attribute_warn_unused_result__
+check_matching (re_match_context_t *mctx, bool fl_longest_match,
+		Idx *p_match_first)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  Idx match = 0;
+  Idx match_last = -1;
+  Idx cur_str_idx = re_string_cur_idx (&mctx->input);
+  re_dfastate_t *cur_state;
+  bool at_init_state = p_match_first != NULL;
+  Idx 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 = false;
+	  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;
+      Idx next_char_idx = re_string_cur_idx (&mctx->input) + 1;
+
+      if ((BE (next_char_idx >= mctx->input.bufs_len, 0)
+	   && mctx->input.bufs_len < mctx->input.len)
+	  || (BE (next_char_idx >= mctx->input.valid_len, 0)
+	      && mctx->input.valid_len < mctx->input.len))
+	{
+	  err = extend_buffers (mctx, next_char_idx + 1);
+	  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 = false;
+	}
+
+      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 bool
+check_halt_node_context (const re_dfa_t *dfa, Idx 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 false;
+  if (!constraint)
+    return true;
+  if (NOT_SATISFY_NEXT_CONSTRAINT (constraint, context))
+    return false;
+  return true;
+}
+
+/* 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 Idx
+check_halt_state_context (const re_match_context_t *mctx,
+			  const re_dfastate_t *state, Idx idx)
+{
+  Idx 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 Idx
+proceed_next_node (const re_match_context_t *mctx, Idx nregs, regmatch_t *regs,
+		   Idx *pidx, Idx node, re_node_set *eps_via_nodes,
+		   struct re_fail_stack_t *fs)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  Idx i;
+  bool ok;
+  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];
+      Idx dest_node;
+      ok = re_node_set_insert (eps_via_nodes, node);
+      if (BE (! ok, 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)
+	{
+	  Idx 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
+    {
+      Idx 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)
+	{
+	  Idx 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)
+	    {
+	      Idx dest_node;
+	      ok = re_node_set_insert (eps_via_nodes, node);
+	      if (BE (! ok, 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))
+	{
+	  Idx 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
+__attribute_warn_unused_result__
+push_fail_stack (struct re_fail_stack_t *fs, Idx str_idx, Idx dest_node,
+		 Idx nregs, regmatch_t *regs, re_node_set *eps_via_nodes)
+{
+  reg_errcode_t err;
+  Idx num = fs->num++;
+  if (fs->num == fs->alloc)
+    {
+      struct re_fail_stack_ent_t *new_array;
+      new_array = re_realloc (fs->stack, 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 Idx
+pop_fail_stack (struct re_fail_stack_t *fs, Idx *pidx, Idx nregs,
+		regmatch_t *regs, re_node_set *eps_via_nodes)
+{
+  Idx 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
+__attribute_warn_unused_result__
+set_regs (const regex_t *preg, const re_match_context_t *mctx, size_t nmatch,
+	  regmatch_t *pmatch, bool fl_backtrack)
+{
+  const re_dfa_t *dfa = preg->buffer;
+  Idx 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;
+  bool prev_idx_match_malloced = false;
+
+#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);
+
+  if (__libc_use_alloca (nmatch * sizeof (regmatch_t)))
+    prev_idx_match = (regmatch_t *) alloca (nmatch * sizeof (regmatch_t));
+  else
+    {
+      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 = true;
+    }
+  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)
+	{
+	  Idx 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
+free_fail_stack_return (struct re_fail_stack_t *fs)
+{
+  if (fs)
+    {
+      Idx 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
+update_regs (const re_dfa_t *dfa, regmatch_t *pmatch,
+	     regmatch_t *prev_idx_match, Idx cur_node, Idx cur_idx, Idx nmatch)
+{
+  int type = dfa->nodes[cur_node].type;
+  if (type == OP_OPEN_SUBEXP)
+    {
+      Idx 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)
+    {
+      Idx 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
+sift_states_backward (const re_match_context_t *mctx, re_sift_context_t *sctx)
+{
+  reg_errcode_t err;
+  int null_cnt = 0;
+  Idx 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
+__attribute_warn_unused_result__
+build_sifted_states (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		     Idx 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;
+  Idx 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++)
+    {
+      Idx prev_node = cur_src->elems[i];
+      int naccepted = 0;
+      bool ok;
+
+#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)
+	{
+	  Idx to_idx = str_idx + naccepted;
+	  if (check_dst_limits (mctx, &sctx->limits,
+				dfa->nexts[prev_node], to_idx,
+				prev_node, str_idx))
+	    continue;
+	}
+      ok = re_node_set_insert (cur_dest, prev_node);
+      if (BE (! ok, 0))
+	return REG_ESPACE;
+    }
+
+  return REG_NOERROR;
+}
+
+/* Helper functions.  */
+
+static reg_errcode_t
+clean_state_log_if_needed (re_match_context_t *mctx, Idx next_state_log_idx)
+{
+  Idx top = mctx->state_log_top;
+
+  if ((next_state_log_idx >= mctx->input.bufs_len
+       && mctx->input.bufs_len < mctx->input.len)
+      || (next_state_log_idx >= mctx->input.valid_len
+	  && mctx->input.valid_len < mctx->input.len))
+    {
+      reg_errcode_t err;
+      err = extend_buffers (mctx, next_state_log_idx + 1);
+      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
+merge_state_array (const re_dfa_t *dfa, re_dfastate_t **dst,
+		   re_dfastate_t **src, Idx num)
+{
+  Idx 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
+update_cur_sifted_state (const re_match_context_t *mctx,
+			 re_sift_context_t *sctx, Idx 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
+__attribute_warn_unused_result__
+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;
+  Idx 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
+sub_epsilon_src_nodes (const re_dfa_t *dfa, Idx node, re_node_set *dest_nodes,
+		       const re_node_set *candidates)
+{
+    Idx 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)
+      {
+	Idx cur_node = inv_eclosure->elems[ecl_idx];
+	if (cur_node == node)
+	  continue;
+	if (IS_EPSILON_NODE (dfa->nodes[cur_node].type))
+	  {
+	    Idx edst1 = dfa->edests[cur_node].elems[0];
+	    Idx 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)
+      {
+	Idx cur_node = inv_eclosure->elems[ecl_idx];
+	if (!re_node_set_contains (&except_nodes, cur_node))
+	  {
+	    Idx 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 bool
+check_dst_limits (const re_match_context_t *mctx, const re_node_set *limits,
+		  Idx dst_node, Idx dst_idx, Idx src_node, Idx src_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  Idx lim_idx, src_pos, dst_pos;
+
+  Idx dst_bkref_idx = search_cur_bkref_entry (mctx, dst_idx);
+  Idx src_bkref_idx = search_cur_bkref_entry (mctx, src_idx);
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      Idx 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 true;
+    }
+  return false;
+}
+
+static int
+check_dst_limits_calc_pos_1 (const re_match_context_t *mctx, int boundaries,
+			     Idx subexp_idx, Idx from_node, Idx bkref_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  const re_node_set *eclosures = dfa->eclosures + from_node;
+  Idx 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)
+    {
+      Idx 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
+		{
+		  Idx dst;
+		  int 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
+check_dst_limits_calc_pos (const re_match_context_t *mctx, Idx limit,
+			   Idx subexp_idx, Idx from_node, Idx str_idx,
+			   Idx 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
+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, Idx str_idx)
+{
+  reg_errcode_t err;
+  Idx node_idx, lim_idx;
+
+  for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
+    {
+      Idx 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)
+	{
+	  Idx ops_node = -1;
+	  Idx cls_node = -1;
+	  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
+	    {
+	      Idx 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)
+	      {
+		Idx 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)
+	    {
+	      Idx 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
+__attribute_warn_unused_result__
+sift_states_bkref (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		   Idx str_idx, const re_node_set *candidates)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  Idx node_idx, node;
+  re_sift_context_t local_sctx;
+  Idx 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)
+    {
+      Idx 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
+	{
+	  Idx subexp_len;
+	  Idx to_idx;
+	  Idx dst_node;
+	  bool ok;
+	  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;
+	  ok = re_node_set_insert (&local_sctx.limits, enabled_idx);
+	  if (BE (! ok, 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
+sift_states_iter_mb (const re_match_context_t *mctx, re_sift_context_t *sctx,
+		     Idx node_idx, Idx str_idx, Idx 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
+       could'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 *
+__attribute_warn_unused_result__
+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 *
+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;
+  Idx 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] == 0)
+    {
+      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 *
+find_recover_state (reg_errcode_t *err, re_match_context_t *mctx)
+{
+  re_dfastate_t *cur_state;
+  do
+    {
+      Idx max = mctx->state_log_top;
+      Idx 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
+check_subexp_matching_top (re_match_context_t *mctx, re_node_set *cur_nodes,
+			   Idx str_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  Idx 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)
+    {
+      Idx 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;
+  Idx 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)
+    {
+      Idx 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
+transit_state_mb (re_match_context_t *mctx, re_dfastate_t *pstate)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  Idx i;
+
+  for (i = 0; i < pstate->nodes.nelem; ++i)
+    {
+      re_node_set dest_nodes, *new_nodes;
+      Idx cur_node_idx = pstate->nodes.elems[i];
+      int naccepted;
+      Idx 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
+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;
+  Idx i;
+  Idx cur_str_idx = re_string_cur_idx (&mctx->input);
+
+  for (i = 0; i < nodes->nelem; ++i)
+    {
+      Idx dest_str_idx, prev_nelem, bkc_idx;
+      Idx 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)
+	{
+	  Idx 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
+__attribute_warn_unused_result__
+get_subexp (re_match_context_t *mctx, Idx bkref_node, Idx bkref_str_idx)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  Idx 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.  */
+  Idx 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;
+      Idx 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)
+	{
+	  regoff_t 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)
+	{
+	  Idx cls_node;
+	  regoff_t 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, bkref_str_off + 1);
+		  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
+get_subexp_sub (re_match_context_t *mctx, const re_sub_match_top_t *sub_top,
+		re_sub_match_last_t *sub_last, Idx bkref_node, Idx bkref_str)
+{
+  reg_errcode_t err;
+  Idx 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 Idx
+find_subexp_node (const re_dfa_t *dfa, const re_node_set *nodes,
+		  Idx subexp_idx, int type)
+{
+  Idx cls_idx;
+  for (cls_idx = 0; cls_idx < nodes->nelem; ++cls_idx)
+    {
+      Idx 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
+__attribute_warn_unused_result__
+check_arrival (re_match_context_t *mctx, state_array_t *path, Idx top_node,
+	       Idx top_str, Idx last_node, Idx last_str, int type)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err = REG_NOERROR;
+  Idx 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;
+      Idx old_alloc = path->alloc;
+      Idx incr_alloc = last_str + mctx->max_mb_elem_len + 1;
+      Idx new_alloc;
+      if (BE (IDX_MAX - old_alloc < incr_alloc, 0))
+	return REG_ESPACE;
+      new_alloc = old_alloc + incr_alloc;
+      if (BE (SIZE_MAX / sizeof (re_dfastate_t *) < new_alloc, 0))
+	return REG_ESPACE;
+      new_array = re_realloc (path->array, re_dfastate_t *, new_alloc);
+      if (BE (new_array == NULL, 0))
+	return REG_ESPACE;
+      path->array = new_array;
+      path->alloc = new_alloc;
+      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
+__attribute_warn_unused_result__
+check_arrival_add_next_nodes (re_match_context_t *mctx, Idx str_idx,
+			      re_node_set *cur_nodes, re_node_set *next_nodes)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  bool ok;
+  Idx 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;
+      Idx 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;
+	      Idx next_node = dfa->nexts[cur_node];
+	      Idx 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;
+		    }
+		}
+	      ok = re_node_set_insert (&union_set, next_node);
+	      if (BE (! ok, 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))
+	{
+	  ok = re_node_set_insert (next_nodes, dfa->nexts[cur_node]);
+	  if (BE (! ok, 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
+check_arrival_expand_ecl (const re_dfa_t *dfa, re_node_set *cur_nodes,
+			  Idx ex_subexp, int type)
+{
+  reg_errcode_t err;
+  Idx 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)
+    {
+      Idx 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
+__attribute_warn_unused_result__
+check_arrival_expand_ecl_sub (const re_dfa_t *dfa, re_node_set *dst_nodes,
+			      Idx target, Idx ex_subexp, int type)
+{
+  Idx cur_node;
+  for (cur_node = target; !re_node_set_contains (dst_nodes, cur_node);)
+    {
+      bool ok;
+
+      if (dfa->nodes[cur_node].type == type
+	  && dfa->nodes[cur_node].opr.idx == ex_subexp)
+	{
+	  if (type == OP_CLOSE_SUBEXP)
+	    {
+	      ok = re_node_set_insert (dst_nodes, cur_node);
+	      if (BE (! ok, 0))
+		return REG_ESPACE;
+	    }
+	  break;
+	}
+      ok = re_node_set_insert (dst_nodes, cur_node);
+      if (BE (! ok, 0))
+	return REG_ESPACE;
+      if (dfa->edests[cur_node].nelem == 0)
+	break;
+      if (dfa->edests[cur_node].nelem == 2)
+	{
+	  reg_errcode_t err;
+	  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
+__attribute_warn_unused_result__
+expand_bkref_cache (re_match_context_t *mctx, re_node_set *cur_nodes,
+		    Idx cur_str, Idx subexp_num, int type)
+{
+  const re_dfa_t *const dfa = mctx->dfa;
+  reg_errcode_t err;
+  Idx 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
+    {
+      Idx 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])
+	    {
+	      bool ok;
+	      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);
+	      ok = re_node_set_insert (&union_set, next_node);
+	      if (BE (err != REG_NOERROR || ! ok, 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 true if successful.  */
+
+static bool
+build_trtable (const re_dfa_t *dfa, re_dfastate_t *state)
+{
+  reg_errcode_t err;
+  Idx i, j;
+  int ch;
+  bool need_word_trtable = false;
+  bitset_word_t elem, mask;
+  bool dests_node_malloced = false;
+  bool dest_states_malloced = false;
+  Idx 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.  */
+  if (__libc_use_alloca (sizeof (struct dests_alloc)))
+    dests_alloc = (struct dests_alloc *) alloca (sizeof (struct dests_alloc));
+  else
+    {
+      dests_alloc = re_malloc (struct dests_alloc, 1);
+      if (BE (dests_alloc == NULL, 0))
+	return false;
+      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)
+	re_free (dests_alloc);
+      /* Return false in case of an error, true otherwise.  */
+      if (ndests == 0)
+	{
+	  state->trtable = (re_dfastate_t **)
+	    calloc (sizeof (re_dfastate_t *), SBC_MAX);
+          if (BE (state->trtable == NULL, 0))
+            return false;
+	  return true;
+	}
+      return false;
+    }
+
+  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;
+
+  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
+    {
+      dest_states = re_malloc (re_dfastate_t *, ndests * 3);
+      if (BE (dest_states == NULL, 0))
+	{
+out_free:
+	  if (dest_states_malloced)
+	    re_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)
+	    re_free (dests_alloc);
+	  return false;
+	}
+      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)
+    {
+      Idx 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 = true;
+
+	  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)
+    re_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)
+    re_free (dests_alloc);
+
+  return true;
+}
+
+/* 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 Idx
+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;
+  bool ok;
+  Idx i, j, k;
+  Idx 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)
+	{
+	  if (ASCII_CHARS % BITSET_WORD_BITS == 0)
+	    memset (accepts, -1, ASCII_CHARS / CHAR_BIT);
+	  else
+	    bitset_merge (accepts, utf8_sb_map);
+	  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. */
+	  ok = re_node_set_insert (&dests_node[j], cur_nodes->elems[i]);
+	  if (BE (! ok, 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.  */
+
+# ifdef _LIBC
+#  include <locale/weight.h>
+# endif
+
+static int
+check_node_accept_bytes (const re_dfa_t *dfa, Idx node_idx,
+			 const re_string_t *input, Idx str_idx)
+{
+  const re_token_t *node = dfa->nodes + node_idx;
+  int char_len, elem_len;
+  Idx i;
+
+  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);
+  if ((elem_len <= 1 && char_len <= 1) || char_len == 0)
+    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);
+      Idx 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;
+
+	  /* 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?  */
+	  /* FIXME: Implement rational ranges here, too.  */
+	  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 (table, indirect, extra, &cp, elem_len);
+	      int32_t rule = idx >> 24;
+	      idx &= 0xffffff;
+	      if (idx > 0)
+		{
+		  size_t weight_len = weights[idx];
+		  for (i = 0; i < cset->nequiv_classes; ++i)
+		    {
+		      int32_t equiv_class_idx = cset->equiv_classes[i];
+		      int32_t equiv_class_rule = equiv_class_idx >> 24;
+		      equiv_class_idx &= 0xffffff;
+		      if (weights[equiv_class_idx] == weight_len
+			  && equiv_class_rule == rule
+			  && memcmp (weights + idx + 1,
+				     weights + equiv_class_idx + 1,
+				     weight_len) == 0)
+			{
+			  match_len = elem_len;
+			  goto check_node_accept_bytes_match;
+			}
+		    }
+		}
+	    }
+	}
+      else
+# endif /* _LIBC */
+	{
+	  /* match with range expression?  */
+	  for (i = 0; i < cset->nranges; ++i)
+	    {
+	      if (cset->range_starts[i] <= wc && wc <= cset->range_ends[i])
+		{
+		  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
+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;
+	  bool found = false;
+	  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 = true;
+	    }
+	  /* 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) * (*(int32_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 bool
+check_node_accept (const re_match_context_t *mctx, const re_token_t *node,
+		   Idx idx)
+{
+  unsigned char ch;
+  ch = re_string_byte_at (&mctx->input, idx);
+  switch (node->type)
+    {
+    case CHARACTER:
+      if (node->opr.c != ch)
+        return false;
+      break;
+
+    case SIMPLE_BRACKET:
+      if (!bitset_contain (node->opr.sbcset, ch))
+        return false;
+      break;
+
+#ifdef RE_ENABLE_I18N
+    case OP_UTF8_PERIOD:
+      if (ch >= ASCII_CHARS)
+        return false;
+      FALLTHROUGH;
+#endif
+    case OP_PERIOD:
+      if ((ch == '\n' && !(mctx->dfa->syntax & RE_DOT_NEWLINE))
+	  || (ch == '\0' && (mctx->dfa->syntax & RE_DOT_NOT_NULL)))
+	return false;
+      break;
+
+    default:
+      return false;
+    }
+
+  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 false;
+    }
+
+  return true;
+}
+
+/* Extend the buffers, if the buffers have run out.  */
+
+static reg_errcode_t
+__attribute_warn_unused_result__
+extend_buffers (re_match_context_t *mctx, int min_len)
+{
+  reg_errcode_t ret;
+  re_string_t *pstr = &mctx->input;
+
+  /* Avoid overflow.  */
+  if (BE (MIN (IDX_MAX, SIZE_MAX / sizeof (re_dfastate_t *)) / 2
+          <= pstr->bufs_len, 0))
+    return REG_ESPACE;
+
+  /* Double the lengths of the buffers, but allocate at least MIN_LEN.  */
+  ret = re_string_realloc_buffers (pstr,
+				   MAX (min_len,
+					MIN (pstr->len, 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
+__attribute_warn_unused_result__
+match_ctx_init (re_match_context_t *mctx, int eflags, Idx n)
+{
+  mctx->eflags = eflags;
+  mctx->match_last = -1;
+  if (n > 0)
+    {
+      /* Avoid overflow.  */
+      size_t max_object_size =
+	MAX (sizeof (struct re_backref_cache_entry),
+	     sizeof (re_sub_match_top_t *));
+      if (BE (MIN (IDX_MAX, SIZE_MAX / max_object_size) < n, 0))
+	return REG_ESPACE;
+
+      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
+match_ctx_clean (re_match_context_t *mctx)
+{
+  Idx st_idx;
+  for (st_idx = 0; st_idx < mctx->nsub_tops; ++st_idx)
+    {
+      Idx 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);
+	}
+      re_free (top);
+    }
+
+  mctx->nsub_tops = 0;
+  mctx->nbkref_ents = 0;
+}
+
+/* Free all the memory associated with MCTX.  */
+
+static void
+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
+__attribute_warn_unused_result__
+match_ctx_add_entry (re_match_context_t *mctx, Idx node, Idx str_idx, Idx from,
+		     Idx 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 ? -1 : 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;
+}
+
+/* Return the first entry with the same str_idx, or -1 if none is
+   found.  Note that MCTX->BKREF_ENTS is already sorted by MCTX->STR_IDX.  */
+
+static Idx
+search_cur_bkref_entry (const re_match_context_t *mctx, Idx str_idx)
+{
+  Idx left, right, mid, last;
+  last = right = mctx->nbkref_ents;
+  for (left = 0; left < right;)
+    {
+      mid = (left + right) / 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
+__attribute_warn_unused_result__
+match_ctx_add_subtop (re_match_context_t *mctx, Idx node, Idx str_idx)
+{
+#ifdef DEBUG
+  assert (mctx->sub_tops != NULL);
+  assert (mctx->asub_tops > 0);
+#endif
+  if (BE (mctx->nsub_tops == mctx->asub_tops, 0))
+    {
+      Idx 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 *
+match_ctx_add_sublast (re_sub_match_top_t *subtop, Idx node, Idx str_idx)
+{
+  re_sub_match_last_t *new_entry;
+  if (BE (subtop->nlasts == subtop->alasts, 0))
+    {
+      Idx 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
+sift_ctx_init (re_sift_context_t *sctx, re_dfastate_t **sifted_sts,
+	       re_dfastate_t **limited_sts, Idx last_node, Idx 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);
+}
diff --git a/lisp/char-fold.el b/lisp/char-fold.el
index 9c05e364df..311fe885a9 100644
--- a/lisp/char-fold.el
+++ b/lisp/char-fold.el
@@ -214,7 +214,7 @@ char-fold-to-regexp
     (when (> spaces 0)
       (push (char-fold--make-space-string spaces) out))
     (let ((regexp (apply #'concat (nreverse out))))
-      ;; Limited by `MAX_BUF_SIZE' in `regex.c'.
+      ;; Limited by MAX_BUF_SIZE in regex-emacs.c.
       (if (> (length regexp) 5000)
           (regexp-quote string)
         regexp))))
diff --git a/m4/builtin-expect.m4 b/m4/builtin-expect.m4
new file mode 100644
index 0000000000..a1eaf965b4
--- /dev/null
+++ b/m4/builtin-expect.m4
@@ -0,0 +1,49 @@
+dnl Check for __builtin_expect.
+
+dnl Copyright 2016-2018 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl Written by Paul Eggert.
+
+AC_DEFUN([gl___BUILTIN_EXPECT],
+[
+  AC_CACHE_CHECK([for __builtin_expect],
+    [gl_cv___builtin_expect],
+    [AC_LINK_IFELSE(
+       [AC_LANG_SOURCE([[
+         int
+         main (int argc, char **argv)
+         {
+           argc = __builtin_expect (argc, 100);
+           return argv[argc != 100][0];
+         }]])],
+       [gl_cv___builtin_expect=yes],
+       [AC_LINK_IFELSE(
+          [AC_LANG_SOURCE([[
+             #include <builtins.h>
+             int
+             main (int argc, char **argv)
+             {
+               argc = __builtin_expect (argc, 100);
+               return argv[argc != 100][0];
+             }]])],
+          [gl_cv___builtin_expect="in <builtins.h>"],
+          [gl_cv___builtin_expect=no])])])
+  if test "$gl_cv___builtin_expect" = yes; then
+    AC_DEFINE([HAVE___BUILTIN_EXPECT], [1])
+  elif test "$gl_cv___builtin_expect" = "in <builtins.h>"; then
+    AC_DEFINE([HAVE___BUILTIN_EXPECT], [2])
+  fi
+  AH_VERBATIM([HAVE___BUILTIN_EXPECT],
+    [/* Define to 1 if the compiler supports __builtin_expect,
+   and to 2 if <builtins.h> does.  */
+#undef HAVE___BUILTIN_EXPECT
+#ifndef HAVE___BUILTIN_EXPECT
+# define __builtin_expect(e, c) (e)
+#elif HAVE___BUILTIN_EXPECT == 2
+# include <builtins.h>
+#endif
+    ])
+])
diff --git a/m4/eealloc.m4 b/m4/eealloc.m4
new file mode 100644
index 0000000000..a5a4e267d8
--- /dev/null
+++ b/m4/eealloc.m4
@@ -0,0 +1,31 @@
+# eealloc.m4 serial 3
+dnl Copyright (C) 2003, 2009-2018 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_EEALLOC],
+[
+  AC_REQUIRE([gl_EEMALLOC])
+  AC_REQUIRE([gl_EEREALLOC])
+])
+
+AC_DEFUN([gl_EEMALLOC],
+[
+  _AC_FUNC_MALLOC_IF(
+    [gl_cv_func_malloc_0_nonnull=1],
+    [gl_cv_func_malloc_0_nonnull=0])
+  AC_DEFINE_UNQUOTED([MALLOC_0_IS_NONNULL], [$gl_cv_func_malloc_0_nonnull],
+    [If malloc(0) is != NULL, define this to 1.  Otherwise define this
+     to 0.])
+])
+
+AC_DEFUN([gl_EEREALLOC],
+[
+  _AC_FUNC_REALLOC_IF(
+    [gl_cv_func_realloc_0_nonnull=1],
+    [gl_cv_func_realloc_0_nonnull=0])
+  AC_DEFINE_UNQUOTED([REALLOC_0_IS_NONNULL], [$gl_cv_func_realloc_0_nonnull],
+    [If realloc(NULL,0) is != NULL, define this to 1.  Otherwise define this
+     to 0.])
+])
diff --git a/m4/glibc21.m4 b/m4/glibc21.m4
new file mode 100644
index 0000000000..126aa1a959
--- /dev/null
+++ b/m4/glibc21.m4
@@ -0,0 +1,34 @@
+# glibc21.m4 serial 5
+dnl Copyright (C) 2000-2002, 2004, 2008, 2010-2018 Free Software Foundation,
+dnl Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# Test for the GNU C Library, version 2.1 or newer, or uClibc.
+# From Bruno Haible.
+
+AC_DEFUN([gl_GLIBC21],
+  [
+    AC_CACHE_CHECK([whether we are using the GNU C Library >= 2.1 or uClibc],
+      [ac_cv_gnu_library_2_1],
+      [AC_EGREP_CPP([Lucky],
+        [
+#include <features.h>
+#ifdef __GNU_LIBRARY__
+ #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1) || (__GLIBC__ > 2)
+  Lucky GNU user
+ #endif
+#endif
+#ifdef __UCLIBC__
+ Lucky user
+#endif
+        ],
+        [ac_cv_gnu_library_2_1=yes],
+        [ac_cv_gnu_library_2_1=no])
+      ]
+    )
+    AC_SUBST([GLIBC21])
+    GLIBC21="$ac_cv_gnu_library_2_1"
+  ]
+)
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 494c77c7c4..61aabaa342 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -48,6 +48,7 @@ AC_DEFUN
   # Code from module allocator:
   # Code from module at-internal:
   # Code from module binary-io:
+  # Code from module builtin-expect:
   # Code from module byteswap:
   # Code from module c-ctype:
   # Code from module c-strcase:
@@ -129,6 +130,7 @@ AC_DEFUN
   # Code from module qcopy-acl:
   # Code from module readlink:
   # Code from module readlinkat:
+  # Code from module regex:
   # Code from module root-uid:
   # Code from module sig2str:
   # Code from module signal-h:
@@ -358,6 +360,11 @@ AC_DEFUN
     AC_LIBOBJ([readlinkat])
   fi
   gl_UNISTD_MODULE_INDICATOR([readlinkat])
+  gl_REGEX
+  if test $ac_use_included_regex = yes; then
+    AC_LIBOBJ([regex])
+    gl_PREREQ_REGEX
+  fi
   gl_FUNC_SIG2STR
   if test $ac_cv_func_sig2str = no; then
     AC_LIBOBJ([sig2str])
@@ -425,6 +432,7 @@ AC_DEFUN
   gl_UTIMENS
   AC_C_VARARRAYS
   gl_gnulib_enabled_260941c0e5dc67ec9e87d1fb321c300b=false
+  gl_gnulib_enabled_37f71b604aa9c54446783d80f42fe547=false
   gl_gnulib_enabled_cloexec=false
   gl_gnulib_enabled_dirfd=false
   gl_gnulib_enabled_dosname=false
@@ -448,6 +456,13 @@ AC_DEFUN
       func_gl_gnulib_m4code_open
     fi
   }
+  func_gl_gnulib_m4code_37f71b604aa9c54446783d80f42fe547 ()
+  {
+    if ! $gl_gnulib_enabled_37f71b604aa9c54446783d80f42fe547; then
+      gl___BUILTIN_EXPECT
+      gl_gnulib_enabled_37f71b604aa9c54446783d80f42fe547=true
+    fi
+  }
   func_gl_gnulib_m4code_cloexec ()
   {
     if ! $gl_gnulib_enabled_cloexec; then
@@ -651,6 +666,9 @@ AC_DEFUN
   if test $HAVE_READLINKAT = 0; then
     func_gl_gnulib_m4code_03e0aaad4cb89ca757653bd367a6ccb7
   fi
+  if test $ac_use_included_regex = yes; then
+    func_gl_gnulib_m4code_37f71b604aa9c54446783d80f42fe547
+  fi
   if { test $HAVE_DECL_STRTOIMAX = 0 || test $REPLACE_STRTOIMAX = 1; } && test $ac_cv_type_long_long_int = yes; then
     func_gl_gnulib_m4code_strtoll
   fi
@@ -659,6 +677,7 @@ AC_DEFUN
   fi
   m4_pattern_allow([^gl_GNULIB_ENABLED_])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_260941c0e5dc67ec9e87d1fb321c300b], [$gl_gnulib_enabled_260941c0e5dc67ec9e87d1fb321c300b])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_37f71b604aa9c54446783d80f42fe547], [$gl_gnulib_enabled_37f71b604aa9c54446783d80f42fe547])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_cloexec], [$gl_gnulib_enabled_cloexec])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_dirfd], [$gl_gnulib_enabled_dirfd])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_dosname], [$gl_gnulib_enabled_dosname])
@@ -924,6 +943,12 @@ AC_DEFUN
   lib/qcopy-acl.c
   lib/readlink.c
   lib/readlinkat.c
+  lib/regcomp.c
+  lib/regex.c
+  lib/regex.h
+  lib/regex_internal.c
+  lib/regex_internal.h
+  lib/regexec.c
   lib/root-uid.h
   lib/set-permissions.c
   lib/sha1.c
@@ -980,6 +1005,7 @@ AC_DEFUN
   m4/absolute-header.m4
   m4/acl.m4
   m4/alloca.m4
+  m4/builtin-expect.m4
   m4/byteswap.m4
   m4/c-strtod.m4
   m4/clock_time.m4
@@ -991,6 +1017,7 @@ AC_DEFUN
   m4/dirent_h.m4
   m4/dirfd.m4
   m4/dup2.m4
+  m4/eealloc.m4
   m4/environ.m4
   m4/errno_h.m4
   m4/euidaccess.m4
@@ -1018,6 +1045,7 @@ AC_DEFUN
   m4/gettime.m4
   m4/gettimeofday.m4
   m4/gl-openssl.m4
+  m4/glibc21.m4
   m4/gnulib-common.m4
   m4/group-member.m4
   m4/ieee754-h.m4
@@ -1030,6 +1058,7 @@ AC_DEFUN
   m4/lstat.m4
   m4/manywarnings-c++.m4
   m4/manywarnings.m4
+  m4/mbstate_t.m4
   m4/md5.m4
   m4/memrchr.m4
   m4/minmax.m4
@@ -1048,6 +1077,7 @@ AC_DEFUN
   m4/putenv.m4
   m4/readlink.m4
   m4/readlinkat.m4
+  m4/regex.m4
   m4/sha1.m4
   m4/sha256.m4
   m4/sha512.m4
diff --git a/m4/mbstate_t.m4 b/m4/mbstate_t.m4
new file mode 100644
index 0000000000..004aa0d17c
--- /dev/null
+++ b/m4/mbstate_t.m4
@@ -0,0 +1,41 @@
+# mbstate_t.m4 serial 13
+dnl Copyright (C) 2000-2002, 2008-2018 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# From Paul Eggert.
+
+# BeOS 5 has <wchar.h> but does not define mbstate_t,
+# so you can't declare an object of that type.
+# Check for this incompatibility with Standard C.
+
+# AC_TYPE_MBSTATE_T
+# -----------------
+AC_DEFUN([AC_TYPE_MBSTATE_T],
+[
+   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) dnl for HP-UX 11.11
+
+   AC_CACHE_CHECK([for mbstate_t], [ac_cv_type_mbstate_t],
+     [AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM(
+           [AC_INCLUDES_DEFAULT[
+/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
+   <wchar.h>.
+   BSD/OS 4.0.1 has a bug: <stddef.h>, <stdio.h> and <time.h> must be
+   included before <wchar.h>.  */
+#include <stddef.h>
+#include <stdio.h>
+#include <time.h>
+#include <wchar.h>]],
+           [[mbstate_t x; return sizeof x;]])],
+        [ac_cv_type_mbstate_t=yes],
+        [ac_cv_type_mbstate_t=no])])
+   if test $ac_cv_type_mbstate_t = yes; then
+     AC_DEFINE([HAVE_MBSTATE_T], [1],
+               [Define to 1 if <wchar.h> declares mbstate_t.])
+   else
+     AC_DEFINE([mbstate_t], [int],
+               [Define to a type if <wchar.h> does not define.])
+   fi
+])
diff --git a/m4/regex.m4 b/m4/regex.m4
new file mode 100644
index 0000000000..055d71b5aa
--- /dev/null
+++ b/m4/regex.m4
@@ -0,0 +1,300 @@
+# serial 67
+
+# Copyright (C) 1996-2001, 2003-2018 Free Software Foundation, Inc.
+#
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+dnl Initially derived from code in GNU grep.
+dnl Mostly written by Jim Meyering.
+
+AC_PREREQ([2.50])
+
+AC_DEFUN([gl_REGEX],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_ARG_WITH([included-regex],
+    [AS_HELP_STRING([--without-included-regex],
+                    [don't compile regex; this is the default on systems
+                     with recent-enough versions of the GNU C Library
+                     (use with caution on other systems).])])
+
+  case $with_included_regex in #(
+  yes|no) ac_use_included_regex=$with_included_regex
+        ;;
+  '')
+    # If the system regex support is good enough that it passes the
+    # following run test, then default to *not* using the included regex.c.
+    # If cross compiling, assume the test would fail and use the included
+    # regex.c.
+    AC_CHECK_DECLS_ONCE([alarm])
+    AC_CHECK_HEADERS_ONCE([malloc.h])
+    AC_CACHE_CHECK([for working re_compile_pattern],
+                   [gl_cv_func_re_compile_pattern_working],
+      [AC_RUN_IFELSE(
+        [AC_LANG_PROGRAM(
+          [[#include <regex.h>
+
+            #include <locale.h>
+            #include <limits.h>
+            #include <string.h>
+
+            #if defined M_CHECK_ACTION || HAVE_DECL_ALARM
+            # include <signal.h>
+            # include <unistd.h>
+            #endif
+
+            #if HAVE_MALLOC_H
+            # include <malloc.h>
+            #endif
+
+            #ifdef M_CHECK_ACTION
+            /* Exit with distinguishable exit code.  */
+            static void sigabrt_no_core (int sig) { raise (SIGTERM); }
+            #endif
+          ]],
+          [[int result = 0;
+            static struct re_pattern_buffer regex;
+            unsigned char folded_chars[UCHAR_MAX + 1];
+            int i;
+            const char *s;
+            struct re_registers regs;
+
+            /* Some builds of glibc go into an infinite loop on this
+               test.  Use alarm to force death, and mallopt to avoid
+               malloc recursion in diagnosing the corrupted heap. */
+#if HAVE_DECL_ALARM
+            signal (SIGALRM, SIG_DFL);
+            alarm (2);
+#endif
+#ifdef M_CHECK_ACTION
+            signal (SIGABRT, sigabrt_no_core);
+            mallopt (M_CHECK_ACTION, 2);
+#endif
+
+            if (setlocale (LC_ALL, "en_US.UTF-8"))
+              {
+                {
+                  /* https://sourceware.org/ml/libc-hacker/2006-09/msg00008.html
+                     This test needs valgrind to catch the bug on Debian
+                     GNU/Linux 3.1 x86, but it might catch the bug better
+                     on other platforms and it shouldn't hurt to try the
+                     test here.  */
+                  static char const pat[] = "insert into";
+                  static char const data[] =
+                    "\xFF\0\x12\xA2\xAA\xC4\xB1,K\x12\xC4\xB1*\xACK";
+                  re_set_syntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE
+                                 | RE_ICASE);
+                  memset (&regex, 0, sizeof regex);
+                  s = re_compile_pattern (pat, sizeof pat - 1, &regex);
+                  if (s)
+                    result |= 1;
+                  else if (re_search (&regex, data, sizeof data - 1,
+                                      0, sizeof data - 1, &regs)
+                           != -1)
+                    result |= 1;
+                  regfree (&regex);
+                }
+
+                {
+                  /* This test is from glibc bug 15078.
+                     The test case is from Andreas Schwab in
+                     <https://sourceware.org/ml/libc-alpha/2013-01/msg00967.html>.
+                     */
+                  static char const pat[] = "[^x]x";
+                  static char const data[] =
+                    /* <U1000><U103B><U103D><U1014><U103A><U102F><U1015><U103A> */
+                    "\xe1\x80\x80"
+                    "\xe1\x80\xbb"
+                    "\xe1\x80\xbd"
+                    "\xe1\x80\x94"
+                    "\xe1\x80\xba"
+                    "\xe1\x80\xaf"
+                    "\xe1\x80\x95"
+                    "\xe1\x80\xba"
+                    "x";
+                  re_set_syntax (0);
+                  memset (&regex, 0, sizeof regex);
+                  s = re_compile_pattern (pat, sizeof pat - 1, &regex);
+                  if (s)
+                    result |= 1;
+                  else
+                    {
+                      i = re_search (&regex, data, sizeof data - 1,
+                                     0, sizeof data - 1, 0);
+                      if (i != 0 && i != 21)
+                        result |= 1;
+                    }
+                  regfree (&regex);
+                }
+
+                if (! setlocale (LC_ALL, "C"))
+                  return 1;
+              }
+
+            /* This test is from glibc bug 3957, reported by Andrew Mackey.  */
+            re_set_syntax (RE_SYNTAX_EGREP | RE_HAT_LISTS_NOT_NEWLINE);
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("a[^x]b", 6, &regex);
+            if (s)
+              result |= 2;
+            /* This should fail, but succeeds for glibc-2.5.  */
+            else if (re_search (&regex, "a\nb", 3, 0, 3, &regs) != -1)
+              result |= 2;
+
+            /* This regular expression is from Spencer ere test number 75
+               in grep-2.3.  */
+            re_set_syntax (RE_SYNTAX_POSIX_EGREP);
+            memset (&regex, 0, sizeof regex);
+            for (i = 0; i <= UCHAR_MAX; i++)
+              folded_chars[i] = i;
+            regex.translate = folded_chars;
+            s = re_compile_pattern ("a[[:@:>@:]]b\n", 11, &regex);
+            /* This should fail with _Invalid character class name_ error.  */
+            if (!s)
+              result |= 4;
+
+            /* Ensure that [b-a] is diagnosed as invalid, when
+               using RE_NO_EMPTY_RANGES. */
+            re_set_syntax (RE_SYNTAX_POSIX_EGREP | RE_NO_EMPTY_RANGES);
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("a[b-a]", 6, &regex);
+            if (s == 0)
+              result |= 8;
+
+            /* This should succeed, but does not for glibc-2.1.3.  */
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("{1", 2, &regex);
+            if (s)
+              result |= 8;
+
+            /* The following example is derived from a problem report
+               against gawk from Jorge Stolfi <[email-masked]>.  */
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("[an\371]*n", 7, &regex);
+            if (s)
+              result |= 8;
+            /* This should match, but does not for glibc-2.2.1.  */
+            else if (re_match (&regex, "an", 2, 0, &regs) != 2)
+              result |= 8;
+
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("x", 1, &regex);
+            if (s)
+              result |= 8;
+            /* glibc-2.2.93 does not work with a negative RANGE argument.  */
+            else if (re_search (&regex, "wxy", 3, 2, -2, &regs) != 1)
+              result |= 8;
+
+            /* The version of regex.c in older versions of gnulib
+               ignored RE_ICASE.  Detect that problem too.  */
+            re_set_syntax (RE_SYNTAX_EMACS | RE_ICASE);
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("x", 1, &regex);
+            if (s)
+              result |= 16;
+            else if (re_search (&regex, "WXY", 3, 0, 3, &regs) < 0)
+              result |= 16;
+
+            /* Catch a bug reported by Vin Shelton in
+               https://lists.gnu.org/r/bug-coreutils/2007-06/msg00089.html
+               */
+            re_set_syntax (RE_SYNTAX_POSIX_BASIC
+                           & ~RE_CONTEXT_INVALID_DUP
+                           & ~RE_NO_EMPTY_RANGES);
+            memset (&regex, 0, sizeof regex);
+            s = re_compile_pattern ("[[:alnum:]_-]\\\\+$", 16, &regex);
+            if (s)
+              result |= 32;
+
+            /* REG_STARTEND was added to glibc on 2004-01-15.
+               Reject older versions.  */
+            if (! REG_STARTEND)
+              result |= 64;
+
+#if 0
+            /* It would be nice to reject hosts whose regoff_t values are too
+               narrow (including glibc on hosts with 64-bit ptrdiff_t and
+               32-bit int), but we should wait until glibc implements this
+               feature.  Otherwise, support for equivalence classes and
+               multibyte collation symbols would always be broken except
+               when compiling --without-included-regex.   */
+            if (sizeof (regoff_t) < sizeof (ptrdiff_t)
+                || sizeof (regoff_t) < sizeof (ssize_t))
+              result |= 64;
+#endif
+
+            return result;
+          ]])],
+        [gl_cv_func_re_compile_pattern_working=yes],
+        [gl_cv_func_re_compile_pattern_working=no],
+        [case "$host_os" in
+                   # Guess no on native Windows.
+           mingw*) gl_cv_func_re_compile_pattern_working="guessing no" ;;
+                   # Otherwise, assume it is not working.
+           *)      gl_cv_func_re_compile_pattern_working="guessing no" ;;
+         esac
+        ])
+      ])
+    case "$gl_cv_func_re_compile_pattern_working" in #(
+      *yes) ac_use_included_regex=no;; #(
+      *no) ac_use_included_regex=yes;;
+    esac
+    ;;
+  *) AC_MSG_ERROR([Invalid value for --with-included-regex: $with_included_regex])
+    ;;
+  esac
+
+  if test $ac_use_included_regex = yes; then
+    AC_DEFINE([_REGEX_INCLUDE_LIMITS_H], [1],
+      [Define if you want <regex.h> to include <limits.h>, so that it
+       consistently overrides <limits.h>'s RE_DUP_MAX.])
+    AC_DEFINE([_REGEX_LARGE_OFFSETS], [1],
+      [Define if you want regoff_t to be at least as wide POSIX requires.])
+    AC_DEFINE([re_syntax_options], [rpl_re_syntax_options],
+      [Define to rpl_re_syntax_options if the replacement should be used.])
+    AC_DEFINE([re_set_syntax], [rpl_re_set_syntax],
+      [Define to rpl_re_set_syntax if the replacement should be used.])
+    AC_DEFINE([re_compile_pattern], [rpl_re_compile_pattern],
+      [Define to rpl_re_compile_pattern if the replacement should be used.])
+    AC_DEFINE([re_compile_fastmap], [rpl_re_compile_fastmap],
+      [Define to rpl_re_compile_fastmap if the replacement should be used.])
+    AC_DEFINE([re_search], [rpl_re_search],
+      [Define to rpl_re_search if the replacement should be used.])
+    AC_DEFINE([re_search_2], [rpl_re_search_2],
+      [Define to rpl_re_search_2 if the replacement should be used.])
+    AC_DEFINE([re_match], [rpl_re_match],
+      [Define to rpl_re_match if the replacement should be used.])
+    AC_DEFINE([re_match_2], [rpl_re_match_2],
+      [Define to rpl_re_match_2 if the replacement should be used.])
+    AC_DEFINE([re_set_registers], [rpl_re_set_registers],
+      [Define to rpl_re_set_registers if the replacement should be used.])
+    AC_DEFINE([re_comp], [rpl_re_comp],
+      [Define to rpl_re_comp if the replacement should be used.])
+    AC_DEFINE([re_exec], [rpl_re_exec],
+      [Define to rpl_re_exec if the replacement should be used.])
+    AC_DEFINE([regcomp], [rpl_regcomp],
+      [Define to rpl_regcomp if the replacement should be used.])
+    AC_DEFINE([regexec], [rpl_regexec],
+      [Define to rpl_regexec if the replacement should be used.])
+    AC_DEFINE([regerror], [rpl_regerror],
+      [Define to rpl_regerror if the replacement should be used.])
+    AC_DEFINE([regfree], [rpl_regfree],
+      [Define to rpl_regfree if the replacement should be used.])
+  fi
+])
+
+# Prerequisites of lib/regex.c and lib/regex_internal.c.
+AC_DEFUN([gl_PREREQ_REGEX],
+[
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+  AC_REQUIRE([AC_C_INLINE])
+  AC_REQUIRE([AC_C_RESTRICT])
+  AC_REQUIRE([AC_TYPE_MBSTATE_T])
+  AC_REQUIRE([gl_EEMALLOC])
+  AC_REQUIRE([gl_GLIBC21])
+  AC_CHECK_HEADERS([libintl.h])
+  AC_CHECK_FUNCS_ONCE([isblank iswctype])
+  AC_CHECK_DECLS([isblank], [], [], [[#include <ctype.h>]])
+])
diff --git a/src/Makefile.in b/src/Makefile.in
index c3bcc50349..1aae27b2f9 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -391,7 +391,7 @@ base_obj =
 	emacs.o keyboard.o macros.o keymap.o sysdep.o \
 	buffer.o filelock.o insdel.o marker.o \
 	minibuf.o fileio.o dired.o \
-	cmds.o casetab.o casefiddle.o indent.o search.o regex.o undo.o \
+	cmds.o casetab.o casefiddle.o indent.o search.o regex-emacs.o undo.o \
 	alloc.o data.o doc.o editfns.o callint.o \
 	eval.o floatfns.o fns.o font.o print.o lread.o $(MODULES_OBJ) \
 	syntax.o $(UNEXEC_OBJ) bytecode.o \
diff --git a/src/casetab.c b/src/casetab.c
index 8f806a0647..289dc65b85 100644
--- a/src/casetab.c
+++ b/src/casetab.c
@@ -144,7 +144,7 @@ set_case_table (Lisp_Object table, bool standard)
       set_char_table_extras (table, 2, eqv);
     }
 
-  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
+  /* This lets set_image_of_range_1 in regex-emacs.c find the EQV table.  */
   set_char_table_extras (canon, 2, eqv);
 
   if (standard)
diff --git a/src/conf_post.h b/src/conf_post.h
index 080d7b7e68..9758298437 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -202,13 +202,6 @@ extern void _DebPrint (const char *fmt, ...);
 #endif
 #endif
 
-#ifdef emacs /* Don't do this for lib-src.  */
-/* Tell regex.c to use a type compatible with Emacs.  */
-#define RE_TRANSLATE_TYPE Lisp_Object
-#define RE_TRANSLATE(TBL, C) char_table_translate (TBL, C)
-#define RE_TRANSLATE_P(TBL) (!EQ (TBL, make_number (0)))
-#endif
-
 /* Tell time_rz.c to use Emacs's getter and setter for TZ.
    Only Emacs uses time_rz so this is OK.  */
 #define getenv_TZ emacs_getenv_TZ
diff --git a/src/deps.mk b/src/deps.mk
index 7b6ae9cd8e..a12321d544 100644
--- a/src/deps.mk
+++ b/src/deps.mk
@@ -71,7 +71,7 @@ cmds.o:
 pre-crt0.o: pre-crt0.c
 dbusbind.o: dbusbind.c termhooks.h frame.h keyboard.h lisp.h $(config_h)
 dired.o: dired.c commands.h buffer.h lisp.h $(config_h) character.h charset.h \
-   coding.h regex.h systime.h blockinput.h atimer.h composite.h \
+   coding.h regex-emacs.h systime.h blockinput.h atimer.h composite.h \
    ../lib/filemode.h ../lib/unistd.h globals.h
 dispnew.o: dispnew.c systime.h commands.h process.h frame.h coding.h \
    window.h buffer.h termchar.h termopts.h termhooks.h cm.h \
@@ -169,20 +169,20 @@ process.o:
    blockinput.h atimer.h coding.h msdos.h nsterm.h composite.h \
    keyboard.h lisp.h globals.h $(config_h) character.h xgselect.h sysselect.h \
    ../lib/unistd.h gnutls.h
-regex.o: regex.c syntax.h buffer.h lisp.h globals.h $(config_h) regex.h \
-   category.h character.h
+regex-emacs.o: regex-emacs.c syntax.h buffer.h lisp.h globals.h $(config_h) \
+   regex-emacs.h category.h character.h
 region-cache.o: region-cache.c buffer.h region-cache.h \
    lisp.h globals.h $(config_h)
 scroll.o: scroll.c termchar.h dispextern.h frame.h msdos.h keyboard.h \
    termhooks.h lisp.h globals.h $(config_h) systime.h coding.h composite.h \
    window.h
-search.o: search.c regex.h commands.h buffer.h region-cache.h syntax.h \
+search.o: search.c regex-emacs.h commands.h buffer.h region-cache.h syntax.h \
    blockinput.h atimer.h systime.h category.h character.h charset.h \
    $(INTERVALS_H) lisp.h globals.h $(config_h)
 sound.o: sound.c dispextern.h syssignal.h lisp.h globals.h $(config_h) \
    atimer.h systime.h ../lib/unistd.h msdos.h
 syntax.o: syntax.c syntax.h buffer.h commands.h category.h character.h \
-   keymap.h regex.h $(INTERVALS_H) lisp.h globals.h $(config_h)
+   keymap.h regex-emacs.h $(INTERVALS_H) lisp.h globals.h $(config_h)
 sysdep.o: sysdep.c syssignal.h systty.h systime.h syswait.h blockinput.h \
    process.h dispextern.h termhooks.h termchar.h termopts.h coding.h \
    frame.h atimer.h window.h msdos.h dosfns.h keyboard.h cm.h lisp.h \
diff --git a/src/emacs.c b/src/emacs.c
index 130a9f8fc8..75febd372f 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -84,7 +84,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "composite.h"
 #include "dispextern.h"
 #include "ptr-bounds.h"
-#include "regex.h"
+#include "regex-emacs.h"
 #include "sheap.h"
 #include "syntax.h"
 #include "sysselect.h"
@@ -846,9 +846,9 @@ main (int argc, char **argv)
     {
       rlim_t lim = rlim.rlim_cur;
 
-      /* Approximate the amount regex.c needs per unit of
+      /* Approximate the amount regex-emacs.c needs per unit of
 	 emacs_re_max_failures, then add 33% to cover the size of the
-	 smaller stacks that regex.c successively allocates and
+	 smaller stacks that regex-emacs.c successively allocates and
 	 discards on its way to the maximum.  */
       int min_ratio = 20 * sizeof (char *);
       int ratio = min_ratio + min_ratio / 3;
@@ -887,7 +887,7 @@ main (int argc, char **argv)
 		lim = newlim;
 	    }
 	}
-      /* If the stack is big enough, let regex.c more of it before
+      /* If the stack is big enough, give regex-emacs.c more of it before
          falling back to heap allocation.  */
       emacs_re_safe_alloca = max
         (min (lim - extra, SIZE_MAX) * (min_ratio / ratio),
diff --git a/src/regex.c b/src/regex-emacs.c
similarity index 99%
rename from src/regex.c
rename to src/regex-emacs.c
index 6ee13c4c99..968a25dc79 100644
--- a/src/regex.c
+++ b/src/regex-emacs.c
@@ -53,7 +53,7 @@
 #include <stdlib.h>
 
 #ifdef emacs
-/* We need this for `regex.h', and perhaps for the Emacs include files.  */
+/* We need this for regex-emacs.h, and perhaps for the Emacs include files.  */
 # include <sys/types.h>
 #endif
 
@@ -289,7 +289,7 @@ enum syntaxcode { Swhitespace = 0, Sword = 1, Ssymbol = 2 };
 #endif
 
 /* Get the interface, including the syntax bits.  */
-#include "regex.h"
+#include "regex-emacs.h"
 
 /* isalpha etc. are used for the character classes.  */
 #include <ctype.h>
@@ -1157,7 +1157,7 @@ reg_syntax_t re_syntax_options;
    different, incompatible syntaxes.
 
    The argument SYNTAX is a bit mask comprised of the various bits
-   defined in regex.h.  We return the old syntax.  */
+   defined in regex-emacs.h.  We return the old syntax.  */
 
 reg_syntax_t
 re_set_syntax (reg_syntax_t syntax)
@@ -1172,7 +1172,7 @@ WEAK_ALIAS (__re_set_syntax, re_set_syntax)
 #endif
 
 /* 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.
+   in regex-emacs.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?  */
 
@@ -1474,28 +1474,28 @@ do {									\
   char *destination;							\
   /* Must be int, so when we don't save any registers, the arithmetic	\
      of 0 + -1 isn't done as unsigned.  */				\
-  									\
+									\
   DEBUG_STATEMENT (nfailure_points_pushed++);				\
   DEBUG_PRINT ("\nPUSH_FAILURE_POINT:\n");				\
   DEBUG_PRINT ("  Before push, next avail: %zd\n", (fail_stack).avail);	\
   DEBUG_PRINT ("			size: %zd\n", (fail_stack).size);\
-  									\
+									\
   ENSURE_FAIL_STACK (NUM_NONREG_ITEMS);					\
-  									\
+									\
   DEBUG_PRINT ("\n");							\
-  									\
+									\
   DEBUG_PRINT ("  Push frame index: %zd\n", fail_stack.frame);		\
   PUSH_FAILURE_INT (fail_stack.frame);					\
-  									\
+									\
   DEBUG_PRINT ("  Push string %p: \"", string_place);			\
   DEBUG_PRINT_DOUBLE_STRING (string_place, string1, size1, string2, size2);\
   DEBUG_PRINT ("\"\n");							\
   PUSH_FAILURE_POINTER (string_place);					\
-  									\
+									\
   DEBUG_PRINT ("  Push pattern %p: ", pattern);				\
   DEBUG_PRINT_COMPILED_PATTERN (bufp, pattern, pend);			\
   PUSH_FAILURE_POINTER (pattern);					\
-  									\
+									\
   /* Close the frame by moving the frame pointer past it.  */		\
   fail_stack.frame = fail_stack.avail;					\
 } while (0)
@@ -1822,7 +1822,7 @@ struct range_table_work_area
 #define SETUP_ASCII_RANGE(work_area, FROM, TO)			\
   do {								\
     int C0, C1;							\
-    								\
+								\
     for (C0 = (FROM); C0 <= (TO); C0++)				\
       {								\
 	C1 = TRANSLATE (C0);					\
@@ -1843,7 +1843,7 @@ struct range_table_work_area
   do {									       \
     int C0, C1, C2, I;							       \
     int USED = RANGE_TABLE_WORK_USED (work_area);			       \
-    									       \
+									       \
     for (C0 = (FROM); C0 <= (TO); C0++)					       \
       {									       \
 	C1 = RE_CHAR_TO_MULTIBYTE (C0);					       \
@@ -1882,7 +1882,7 @@ struct range_table_work_area
 #define SETUP_MULTIBYTE_RANGE(work_area, FROM, TO)			   \
   do {									   \
     int C0, C1, C2, I, USED = RANGE_TABLE_WORK_USED (work_area);	   \
-    									   \
+									   \
     SET_RANGE_TABLE_WORK_AREA ((work_area), (FROM), (TO));		   \
     for (C0 = (FROM); C0 <= (TO); C0++)					   \
       {									   \
@@ -1896,7 +1896,7 @@ struct range_table_work_area
 	  {								   \
 	    int from = RANGE_TABLE_WORK_ELT (work_area, I);		   \
 	    int to = RANGE_TABLE_WORK_ELT (work_area, I + 1);		   \
-	    								   \
+									   \
 	    if (C1 >= from - 1 && C1 <= to + 1)				   \
 	      {								   \
 		if (C1 == from - 1)					   \
@@ -2371,7 +2371,7 @@ static boolean group_in_compile_stack (compile_stack_type compile_stack,
 				       regnum_t regnum);
 
 /* `regex_compile' compiles PATTERN (of length SIZE) according to SYNTAX.
-   Returns one of error codes defined in `regex.h', or zero for success.
+   Returns one of error codes defined in regex-emacs.h, or zero for success.
 
    If WHITESPACE_REGEXP is given (only #ifdef emacs), it is used instead of
    a space character in PATTERN.
@@ -2714,15 +2714,15 @@ regex_compile (re_char *pattern, size_t size,
 
 		    if (!zero_times_ok && simple)
 		      { /* Since simple * loops can be made faster by using
-		    	   on_failure_keep_string_jump, we turn simple P+
-		    	   into PP* if P is simple.  */
-		    	unsigned char *p1, *p2;
-		    	startoffset = b - laststart;
-		    	GET_BUFFER_SPACE (startoffset);
-		    	p1 = b; p2 = laststart;
-		    	while (p2 < p1)
-		    	  *b++ = *p2++;
-		    	zero_times_ok = 1;
+			   on_failure_keep_string_jump, we turn simple P+
+			   into PP* if P is simple.  */
+			unsigned char *p1, *p2;
+			startoffset = b - laststart;
+			GET_BUFFER_SPACE (startoffset);
+			p1 = b; p2 = laststart;
+			while (p2 < p1)
+			  *b++ = *p2++;
+			zero_times_ok = 1;
 		      }
 
 		    GET_BUFFER_SPACE (6);
@@ -6217,7 +6217,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
   FREE_VARIABLES ();
 
-  return -1;         			/* Failure to match.  */
+  return -1;	/* Failure to match.  */
 }
 
 /* Subroutine definitions for re_match_2.  */
@@ -6400,7 +6400,7 @@ re_exec (const char *s)
      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
+   It returns 0 if it succeeds, nonzero if it doesn't.  (See regex-emacs.h for
    the return codes and their meanings.)  */
 
 reg_errcode_t
diff --git a/src/regex.h b/src/regex-emacs.h
similarity index 98%
rename from src/regex.h
rename to src/regex-emacs.h
index 3a2d74d86a..8a15e5793f 100644
--- a/src/regex.h
+++ b/src/regex-emacs.h
@@ -160,9 +160,9 @@ typedef unsigned long reg_syntax_t;
 
 /* If this bit is set, turn on internal regex debugging.
    If not set, and debugging was on, turn it off.
-   This only works if regex.c is compiled -DDEBUG.
+   This only works if regex-emacs.c is compiled -DDEBUG.
    We define this bit always, so that all that's needed to turn on
-   debugging is to recompile regex.c; the calling code can always have
+   debugging is to recompile regex-emacs.c; the calling code can always have
    this bit set, and it won't affect anything in the normal case. */
 #define RE_DEBUG (RE_NO_NEWLINE_ANCHOR << 1)
 
@@ -219,7 +219,7 @@ extern ptrdiff_t emacs_re_safe_alloca;
   ((RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS | RE_DEBUG)	\
    & ~(RE_DOT_NOT_NULL | RE_INTERVALS | RE_CONTEXT_INDEP_OPS))
 
-#define RE_SYNTAX_POSIX_AWK 						\
+#define RE_SYNTAX_POSIX_AWK						\
   (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS		\
    | RE_INTERVALS	    | RE_NO_GNU_OPS)
 
@@ -317,7 +317,7 @@ extern ptrdiff_t emacs_re_safe_alloca;

 /* If any error codes are removed, changed, or added, update the
-   `re_error_msg' table in regex.c.  */
+   re_error_msg table in regex-emacs.c.  */
 typedef enum
 {
 #ifdef _XOPEN_SOURCE
@@ -350,6 +350,11 @@ typedef enum
   REG_ESIZEBR           /* n or m too big in \{n,m\} */
 } reg_errcode_t;
 
+/* Use a type compatible with Emacs.  */
+#define RE_TRANSLATE_TYPE Lisp_Object
+#define RE_TRANSLATE(TBL, C) char_table_translate (TBL, C)
+#define RE_TRANSLATE_P(TBL) (!EQ (TBL, make_number (0)))
+
 /* 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
@@ -650,5 +655,5 @@ typedef int re_wchar_t;
 
 #endif /* not WIDE_CHAR_SUPPORT */
 
-#endif /* regex.h */
+#endif /* regex-emacs.h */
 
diff --git a/src/search.c b/src/search.c
index ccdb659776..4ee70144fc 100644
--- a/src/search.c
+++ b/src/search.c
@@ -30,7 +30,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "blockinput.h"
 #include "intervals.h"
 
-#include "regex.h"
+#include "regex-emacs.h"
 
 #define REGEXP_CACHE_SIZE 20
 
@@ -290,7 +290,7 @@ looking_at_1 (Lisp_Object string, bool posix)
   if (running_asynch_code)
     save_search_regs ();
 
-  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
+  /* This lets set_image_of_range_1 in regex-emacs.c find the EQV table.  */
   set_char_table_extras (BVAR (current_buffer, case_canon_table), 2,
 			 BVAR (current_buffer, case_eqv_table));
 
@@ -410,7 +410,7 @@ string_match_1 (Lisp_Object regexp, Lisp_Object string, Lisp_Object start,
       pos_byte = string_char_to_byte (string, pos);
     }
 
-  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
+  /* This lets set_image_of_range_1 in regex-emacs.c find the EQV table.  */
   set_char_table_extras (BVAR (current_buffer, case_canon_table), 2,
 			 BVAR (current_buffer, case_eqv_table));
 
@@ -1062,7 +1062,7 @@ search_command (Lisp_Object string, Lisp_Object bound, Lisp_Object noerror,
 	lim_byte = CHAR_TO_BYTE (lim);
     }
 
-  /* This is so set_image_of_range_1 in regex.c can find the EQV table.  */
+  /* This lets set_image_of_range_1 in regex-emacs.c find the EQV table.  */
   set_char_table_extras (BVAR (current_buffer, case_canon_table), 2,
 			 BVAR (current_buffer, case_eqv_table));
 
diff --git a/src/syntax.c b/src/syntax.c
index c5a4b03955..5b875ad296 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -23,7 +23,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "lisp.h"
 #include "character.h"
 #include "buffer.h"
-#include "regex.h"
+#include "regex-emacs.h"
 #include "syntax.h"
 #include "intervals.h"
 #include "category.h"
@@ -267,7 +267,7 @@ SETUP_SYNTAX_TABLE (ptrdiff_t from, ptrdiff_t count)
    If it is t (which is only used in fast_c_string_match_ignore_case),
    ignore properties altogether.
 
-   This is meant for regex.c to use.  For buffers, regex.c passes arguments
+   This is meant so that for buffers, regex-emacs.c passes arguments
    to the UPDATE_SYNTAX_TABLE functions which are relative to BEGV.
    So if it is a buffer, we set the offset field to BEGV.  */
 
@@ -3729,7 +3729,7 @@ syms_of_syntax (void)
   staticpro (&gl_state.current_syntax_table);
   staticpro (&gl_state.old_prop);
 
-  /* Defined in regex.c.  */
+  /* Defined in regex-emacs.c.  */
   staticpro (&re_match_object);
 
   DEFSYM (Qscan_error, "scan-error");
diff --git a/src/thread.h b/src/thread.h
index 922eea6217..e1eb40921b 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -19,7 +19,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #ifndef THREAD_H
 #define THREAD_H
 
-#include "regex.h"
+#include "regex-emacs.h"
 
 #ifdef WINDOWSNT
 #include <sys/socket.h>
diff --git a/test/src/regex-tests.el b/test/src/regex-emacs-tests.el
similarity index 99%
rename from test/src/regex-tests.el
rename to test/src/regex-emacs-tests.el
index 083ed5c4c8..7a075908a6 100644
--- a/test/src/regex-tests.el
+++ b/test/src/regex-emacs-tests.el
@@ -1,4 +1,4 @@
-;;; regex-tests.el --- tests for regex.c functions -*- lexical-binding: t -*-
+;;; regex-emacs-tests.el --- tests for regex-emacs.c -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2015-2018 Free Software Foundation, Inc.
 
@@ -24,7 +24,7 @@
 (defvar regex-tests--resources-dir
   (concat (concat (file-name-directory (or load-file-name buffer-file-name))
                   "/regex-resources/"))
-  "Path to regex-resources directory next to the \"regex-tests.el\" file.")
+  "Path to regex-resources directory next to the \"regex-emacs-tests.el\" file.")
 
 (ert-deftest regex-word-cc-fallback-test ()
   "Test that \"[[:cc:]]*x\" matches \"x\" (bug#24020).
@@ -683,4 +683,4 @@ regex-tests-TESTS
   (should-not (string-match "\\`x\\{65535\\}" (make-string 65534 ?x)))
   (should-error (string-match "\\`x\\{65536\\}" "X") :type 'invalid-regexp))
 
-;;; regex-tests.el ends here
+;;; regex-emacs-tests.el ends here
-- 
2.17.1

>From 5f2c74fd9504fe9a2e8fb5a9d3d045c682a4b786 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Wed, 1 Aug 2018 19:13:08 -0700
Subject: [PATCH 2/4] Simplify regex-emacs code by assuming Emacs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* src/regex-emacs.c: Omit no-longer-needed AIX code.
Don’t ignore GCC warnings.
Include regex-emacs.h immediately after config.h,
to test that it’s independent.
Omit the "#ifndef emacs" and "#ifdef REGEX_MALLOC" and
"#if WIDE_CHAR_SUPPORT" or "#ifdef _REGEX_RE_COMP",
code, as we are no longer interested in compiling outside
Emacs (with or without debugging or native wide char support)
or in avoiding alloca.
(REGEX_EMACS_DEBUG, regex_emacs_debug): Rename from DEBUG and debug,
to avoid collision with other DEBUGS.  All uses changed.
In debugging output, change %ld and %zd to %zu when appropriate.
No need to include stddef.h, stdlib.h, sys/types.h, wchar.h,
wctype.h, locale/localeinfo.h, locale/elem-hash.h, langinfo.h,
libintl.h, unistd.h, stdbool.h, string.h, stdio.h, assert.h.
All uses of assert changed to eassert.
(RE_DUP_MAX, reg_syntax_t, RE_BACKSLASH_ESCAPE_IN_LISTS)
(RE_BK_PLUS_QM, RE_CHAR_CLASSES, RE_CONTEXT_INDEP_ANCHORS)
(RE_CONTEXT_INDEP_OPS, RE_CONTEXT_INVALID_OPS, RE_DOT_NEWLINE)
(RE_DOT_NOT_NULL, RE_HAT_LISTS_NOT_NEWLINE, RE_INTERVALS)
(RE_LIMITED_OPS, RE_NEWLINE_ALT, RE_NO_BK_BRACES)
(RE_NO_BK_PARENS, RE_NO_BK_REFS, RE_NO_BK_VBAR)
(RE_NO_EMPTY_RANGES, RE_UNMATCHED_RIGHT_PAREN_ORD)
(RE_NO_POSIX_BACKTRACKING, RE_NO_GNU_OPS, RE_FRUGAL)
(RE_SHY_GROUPS, RE_NO_NEWLINE_ANCHOR, RE_SYNTAX_EMACS)
(REG_NOERROR, REG_NOMATCH, REG_BADPAT, REG_ECOLLATE)
(REG_ECTYPE, REG_EESCAPE, REG_ESUBREG, REG_EBRACK, REG_EPAREN)
(REG_EBRACE, REG_BADBR, REG_ERANGE, REG_ESPACE, REG_BADRPT)
(REG_EEND, REG_ESIZE, REG_ERPAREN, REG_ERANGEX, REG_ESIZEBR)
(reg_errcode_t, REGS_UNALLOCATED, REGS_REALLOCATE, REGS_FIXED)
(RE_NREGS, RE_TRANSLATE, RE_TRANSLATE_P):
Move here from regex-emacs.h.
(RE_NREGS): Define unconditionally.
(boolean): Remove.  All uses replaced by bool.
(WIDE_CHAR_SUPPORT, regfree, regexec, regcomp, regerror):
(re_set_syntax, re_syntax_options, WEAK_ALIAS, gettext, gettext_noop):
Remove. All uses removed.
(malloc, realloc, free): Do not redefine.  Adjust all callers
to use xmalloc, xrealloc, xfree instead.
(re_error_msgid): Use C99 to avoid need to keep in same order
as reg_error_t.
(REGEX_USE_SAFE_ALLOCA): Simplify by using USE_SAFE_ALLOCA.
(REGEX_ALLOCATE, REGEX_REALLOCATE, REGEX_FREE, REGEX_ALLOCATE_STACK)
(REGEX_REALLOCATE_STACK, REGEX_FREE_STACK): Remove.
All callers changed to use the non-REGEX_MALLOC version.
(REGEX_TALLOC): Remove.  All callers changed to use SAFE_ALLOCA.
(re_set_syntax): Remove; unused.
(MATCH_MAY_ALLOCATE): Remove; now always true.  All uses simplified.
(INIT_FAILURE_ALLOC): Define unconditionally.
(re_compile_fastmap): Now static.
(re_compile_pattern): Avoid unnecessary cast.
* src/regex-emacs.h (EMACS_REGEX_H): Renamed from _REGEX_H to
avoid possible collision with glibc.
Don’t include sys/types.h.  All uses of ssize_t changed to ptrdiff_t.
Don’t worry about C++ or VMS.
Assume emacs is defined and that _REGEX_RE_COMP and WIDE_CHAR_SUPPORT
are not.
Define struct re_registers before including lisp.h.
(REG_ENOSYS, RE_TRANSLATE_TYPE): Remove; all uses replaced by
Lisp_Object.
(regoff_t): Remove.  All uses replaced with ptrdiff_t.
(re_match, regcomp, regexec, regerror, regfree):
Remove decl of nonexistent functions.
(RE_DEBUG, RE_SYNTAX_AWK, RE_SYNTAX_GNU_AWK)
(RE_SYNTAX_POSIX_AWK, RE_SYNTAX_GREP, RE_SYNTAX_EGREP)
(RE_SYNTAX_POSIX_EGREP, RE_SYNTAX_ED, RE_SYNTAX_SED)
(_RE_SYNTAX_POSIX_COMMON, RE_SYNTAX_POSIX_BASIC)
(RE_SYNTAX_POSIX_MINIMAL_BASIC, RE_SYNTAX_POSIX_EXTENDED)
(RE_SYNTAX_POSIX_MINIMAL_EXTENDED, REG_EXTENDED, REG_ICASE)
(REG_NEWLINE, REG_NOSUB, REG_NOTBOL, REG_NOTEOL, regmatch_t):
Remove; unused.
* src/search.c (Fset_match_data): Simplify range test now that
we know it’s ptrdiff_t.
---
 src/regex-emacs.c | 2009 ++++++++++-----------------------------------
 src/regex-emacs.h |  542 ++----------
 src/search.c      |   21 +-
 src/thread.h      |    4 +-
 4 files changed, 498 insertions(+), 2078 deletions(-)

diff --git a/src/regex-emacs.c b/src/regex-emacs.c
index 968a25dc79..fd335de094 100644
--- a/src/regex-emacs.c
+++ b/src/regex-emacs.c
@@ -21,158 +21,187 @@
    - structure the opcode space into opcode+flag.
    - merge with glibc's regex.[ch].
    - replace (succeed_n + jump_n + set_number_at) with something that doesn't
-     need to modify the compiled regexp so that re_match can be reentrant.
+     need to modify the compiled regexp so that re_search can be reentrant.
    - get rid of on_failure_jump_smart by doing the optimization in re_comp
-     rather than at run-time, so that re_match can be reentrant.
+     rather than at run-time, so that re_search can be reentrant.
 */
 
-/* AIX requires this to be the first thing in the file.  */
-#if defined _AIX && !defined REGEX_MALLOC
-  #pragma alloca
-#endif
-
-/* Ignore some GCC warnings for now.  This section should go away
-   once the Emacs and Gnulib regex code is merged.  */
-#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__) || defined __clang__
-# pragma GCC diagnostic ignored "-Wstrict-overflow"
-# ifndef emacs
-#  pragma GCC diagnostic ignored "-Wunused-function"
-#  pragma GCC diagnostic ignored "-Wunused-macros"
-#  pragma GCC diagnostic ignored "-Wunused-result"
-#  pragma GCC diagnostic ignored "-Wunused-variable"
-# endif
-#endif
-
-#if 4 < __GNUC__ + (6 <= __GNUC_MINOR__) && ! defined __clang__
-# pragma GCC diagnostic ignored "-Wunused-but-set-variable"
-#endif
-
 #include <config.h>
 
-#include <stddef.h>
-#include <stdlib.h>
-
-#ifdef emacs
-/* We need this for regex-emacs.h, and perhaps for the Emacs include files.  */
-# include <sys/types.h>
-#endif
-
-/* Whether to use ISO C Amendment 1 wide char functions.
-   Those should not be used for Emacs since it uses its own.  */
-#if defined _LIBC
-#define WIDE_CHAR_SUPPORT 1
-#else
-#define WIDE_CHAR_SUPPORT \
-	(HAVE_WCTYPE_H && HAVE_WCHAR_H && HAVE_BTOWC && !emacs)
-#endif
+/* Get the interface, including the syntax bits.  */
+#include "regex-emacs.h"
 
-/* For platform which support the ISO C amendment 1 functionality we
-   support user defined character classes.  */
-#if WIDE_CHAR_SUPPORT
-/* Solaris 2.5 has a bug: <wchar.h> must be included before <wctype.h>.  */
-# include <wchar.h>
-# include <wctype.h>
-#endif
+#include <stdlib.h>
 
-#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(err_code, preg, errbuf, errbuf_size) \
-	__regerror (err_code, 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)
-
-/* Make sure we call libc's function even if the user overrides them.  */
-# define btowc __btowc
-# define iswctype __iswctype
-# define wctype __wctype
-
-# define WEAK_ALIAS(a,b) weak_alias (a, b)
-
-/* We are also using some library internals.  */
-# include <locale/localeinfo.h>
-# include <locale/elem-hash.h>
-# include <langinfo.h>
-#else
-# define WEAK_ALIAS(a,b)
-#endif
+#include "character.h"
+#include "buffer.h"
 
-/* This is for other GNU distributions with internationalized messages.  */
-#if HAVE_LIBINTL_H || defined _LIBC
-# include <libintl.h>
-#else
-# define gettext(msgid) (msgid)
-#endif
+#include "syntax.h"
+#include "category.h"
 
-#ifndef gettext_noop
-/* This define is so xgettext can find the internationalizable
-   strings.  */
-# define gettext_noop(String) String
+/* Maximum number of duplicates an interval can allow.  Some systems
+   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
-
-/* The `emacs' switch turns on certain matching commands
-   that make sense only in Emacs. */
-#ifdef emacs
-
-# include "lisp.h"
-# include "character.h"
-# include "buffer.h"
-
-# include "syntax.h"
-# include "category.h"
+/* Repeat counts are stored in opcodes as 2 byte integers.  This was
+   previously limited to 7fff because the parsing code uses signed
+   ints.  But Emacs only runs on 32 bit platforms anyway.  */
+#define RE_DUP_MAX (0xffff)
+
+/* The following bits are used to determine the regexp syntax we
+   recognize.  The set/not-set meanings where historically chosen so
+   that Emacs syntax had 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 reg_syntax_t;
+
+/* 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, then *?, +? and ?? match non greedily. */
+#define RE_FRUGAL (RE_NO_GNU_OPS << 1)
+
+/* If this bit is set, then (?:...) is treated as a shy group.  */
+#define RE_SHY_GROUPS (RE_FRUGAL << 1)
+
+/* If this bit is set, ^ and $ only match at beg/end of buffer.  */
+#define RE_NO_NEWLINE_ANCHOR (RE_SHY_GROUPS << 1)
+
+/* 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; */
+/* Define combinations of the above bits for the standard possibilities.  */
+#define RE_SYNTAX_EMACS							\
+  (RE_CHAR_CLASSES | RE_INTERVALS | RE_SHY_GROUPS | RE_FRUGAL)
 
 /* Make syntax table lookup grant data in gl_state.  */
-# define SYNTAX(c) syntax_property (c, 1)
-
-# ifdef malloc
-#  undef malloc
-# endif
-# define malloc xmalloc
-# ifdef realloc
-#  undef realloc
-# endif
-# define realloc xrealloc
-# ifdef free
-#  undef free
-# endif
-# define free xfree
+#define SYNTAX(c) syntax_property (c, 1)
 
 /* Converts the pointer to the char to BEG-based offset from the start.  */
-# define PTR_TO_OFFSET(d) POS_AS_IN_BUFFER (POINTER_TO_OFFSET (d))
+#define PTR_TO_OFFSET(d) POS_AS_IN_BUFFER (POINTER_TO_OFFSET (d))
 /* Strings are 0-indexed, buffers are 1-indexed; we pun on the boolean
    result to get the right base index.  */
-# define POS_AS_IN_BUFFER(p)                                    \
+#define POS_AS_IN_BUFFER(p)                                    \
   ((p) + (NILP (gl_state.object) || BUFFERP (gl_state.object)))
 
-# define RE_MULTIBYTE_P(bufp) ((bufp)->multibyte)
-# define RE_TARGET_MULTIBYTE_P(bufp) ((bufp)->target_multibyte)
-# define RE_STRING_CHAR(p, multibyte) \
+#define RE_MULTIBYTE_P(bufp) ((bufp)->multibyte)
+#define RE_TARGET_MULTIBYTE_P(bufp) ((bufp)->target_multibyte)
+#define RE_STRING_CHAR(p, multibyte) \
   (multibyte ? (STRING_CHAR (p)) : (*(p)))
-# define RE_STRING_CHAR_AND_LENGTH(p, len, multibyte) \
+#define RE_STRING_CHAR_AND_LENGTH(p, len, multibyte) \
   (multibyte ? (STRING_CHAR_AND_LENGTH (p, len)) : ((len) = 1, *(p)))
 
-# define RE_CHAR_TO_MULTIBYTE(c) UNIBYTE_TO_CHAR (c)
+#define RE_CHAR_TO_MULTIBYTE(c) UNIBYTE_TO_CHAR (c)
 
-# define RE_CHAR_TO_UNIBYTE(c) CHAR_TO_BYTE_SAFE (c)
+#define RE_CHAR_TO_UNIBYTE(c) CHAR_TO_BYTE_SAFE (c)
 
 /* Set C a (possibly converted to multibyte) character before P.  P
    points into a string which is the virtual concatenation of STR1
    (which ends at END1) or STR2 (which ends at END2).  */
-# define GET_CHAR_BEFORE_2(c, p, str1, end1, str2, end2)		     \
+#define GET_CHAR_BEFORE_2(c, p, str1, end1, str2, end2)			     \
   do {									     \
     if (target_multibyte)						     \
       {									     \
@@ -190,7 +219,7 @@
 
 /* Set C a (possibly converted to multibyte) character at P, and set
    LEN to the byte length of that character.  */
-# define GET_CHAR_AFTER(c, p, len)		\
+#define GET_CHAR_AFTER(c, p, len)		\
   do {						\
     if (target_multibyte)			\
       (c) = STRING_CHAR_AND_LENGTH (p, len);	\
@@ -201,235 +230,66 @@
 	(c) = RE_CHAR_TO_MULTIBYTE (c);		\
       }						\
    } while (0)
-
-#else  /* not emacs */
-
-/* If we are not linking with Emacs proper,
-   we can't use the relocating allocator
-   even if config.h says that we can.  */
-# undef REL_ALLOC
-
-# include <unistd.h>
-
-/* When used in Emacs's lib-src, we need xmalloc and xrealloc. */
-
-static ATTRIBUTE_MALLOC void *
-xmalloc (size_t size)
-{
-  void *val = malloc (size);
-  if (!val && size)
-    {
-      write (STDERR_FILENO, "virtual memory exhausted\n", 25);
-      exit (1);
-    }
-  return val;
-}
-
-static void *
-xrealloc (void *block, size_t size)
-{
-  void *val;
-  /* We must call malloc explicitly when BLOCK is 0, since some
-     reallocs don't do this.  */
-  if (! block)
-    val = malloc (size);
-  else
-    val = realloc (block, size);
-  if (!val && size)
-    {
-      write (STDERR_FILENO, "virtual memory exhausted\n", 25);
-      exit (1);
-    }
-  return val;
-}
-
-# ifdef malloc
-#  undef malloc
-# endif
-# define malloc xmalloc
-# ifdef realloc
-#  undef realloc
-# endif
-# define realloc xrealloc
-
-# include <stdbool.h>
-# include <string.h>
-
-/* Define the syntax stuff for \<, \>, etc.  */
-
-/* Sword must be nonzero for the wordchar pattern commands in re_match_2.  */
-enum syntaxcode { Swhitespace = 0, Sword = 1, Ssymbol = 2 };
-
-/* Dummy macros for non-Emacs environments.  */
-# define MAX_MULTIBYTE_LENGTH 1
-# define RE_MULTIBYTE_P(x) 0
-# define RE_TARGET_MULTIBYTE_P(x) 0
-# define WORD_BOUNDARY_P(c1, c2) (0)
-# define BYTES_BY_CHAR_HEAD(p) (1)
-# define PREV_CHAR_BOUNDARY(p, limit) ((p)--)
-# define STRING_CHAR(p) (*(p))
-# define RE_STRING_CHAR(p, multibyte) STRING_CHAR (p)
-# define CHAR_STRING(c, s) (*(s) = (c), 1)
-# define STRING_CHAR_AND_LENGTH(p, actual_len) ((actual_len) = 1, *(p))
-# define RE_STRING_CHAR_AND_LENGTH(p, len, multibyte) STRING_CHAR_AND_LENGTH (p, len)
-# define RE_CHAR_TO_MULTIBYTE(c) (c)
-# define RE_CHAR_TO_UNIBYTE(c) (c)
-# define GET_CHAR_BEFORE_2(c, p, str1, end1, str2, end2) \
-  (c = ((p) == (str2) ? *((end1) - 1) : *((p) - 1)))
-# define GET_CHAR_AFTER(c, p, len)	\
-  (c = *p, len = 1)
-# define CHAR_BYTE8_P(c) (0)
-# define CHAR_LEADING_CODE(c) (c)
-
-#endif /* not emacs */
-
-#ifndef RE_TRANSLATE
-# define RE_TRANSLATE(TBL, C) ((unsigned char)(TBL)[C])
-# define RE_TRANSLATE_P(TBL) (TBL)
-#endif
 
-/* Get the interface, including the syntax bits.  */
-#include "regex-emacs.h"
-
 /* isalpha etc. are used for the character classes.  */
 #include <ctype.h>
 
-#ifdef emacs
-
 /* 1 if C is an ASCII character.  */
-# define IS_REAL_ASCII(c) ((c) < 0200)
+#define IS_REAL_ASCII(c) ((c) < 0200)
 
 /* 1 if C is a unibyte character.  */
-# define ISUNIBYTE(c) (SINGLE_BYTE_CHAR_P ((c)))
+#define ISUNIBYTE(c) (SINGLE_BYTE_CHAR_P ((c)))
 
 /* The Emacs definitions should not be directly affected by locales.  */
 
 /* In Emacs, these are only used for single-byte characters.  */
-# define ISDIGIT(c) ((c) >= '0' && (c) <= '9')
-# define ISCNTRL(c) ((c) < ' ')
-# define ISXDIGIT(c) (0 <= char_hexdigit (c))
+#define ISDIGIT(c) ((c) >= '0' && (c) <= '9')
+#define ISCNTRL(c) ((c) < ' ')
+#define ISXDIGIT(c) (0 <= char_hexdigit (c))
 
 /* The rest must handle multibyte characters.  */
 
-# define ISBLANK(c) (IS_REAL_ASCII (c)                  \
+#define ISBLANK(c) (IS_REAL_ASCII (c)			\
                      ? ((c) == ' ' || (c) == '\t')      \
                      : blankp (c))
 
-# define ISGRAPH(c) (SINGLE_BYTE_CHAR_P (c)				\
+#define ISGRAPH(c) (SINGLE_BYTE_CHAR_P (c)				\
 		     ? (c) > ' ' && !((c) >= 0177 && (c) <= 0240)	\
 		     : graphicp (c))
 
-# define ISPRINT(c) (SINGLE_BYTE_CHAR_P (c)				\
+#define ISPRINT(c) (SINGLE_BYTE_CHAR_P (c)				\
 		    ? (c) >= ' ' && !((c) >= 0177 && (c) <= 0237)	\
 		     : printablep (c))
 
-# define ISALNUM(c) (IS_REAL_ASCII (c)			\
+#define ISALNUM(c) (IS_REAL_ASCII (c)			\
 		    ? (((c) >= 'a' && (c) <= 'z')	\
 		       || ((c) >= 'A' && (c) <= 'Z')	\
 		       || ((c) >= '0' && (c) <= '9'))	\
 		    : alphanumericp (c))
 
-# define ISALPHA(c) (IS_REAL_ASCII (c)			\
+#define ISALPHA(c) (IS_REAL_ASCII (c)			\
 		    ? (((c) >= 'a' && (c) <= 'z')	\
 		       || ((c) >= 'A' && (c) <= 'Z'))	\
 		    : alphabeticp (c))
 
-# define ISLOWER(c) lowercasep (c)
+#define ISLOWER(c) lowercasep (c)
 
-# define ISPUNCT(c) (IS_REAL_ASCII (c)				\
+#define ISPUNCT(c) (IS_REAL_ASCII (c)				\
 		    ? ((c) > ' ' && (c) < 0177			\
 		       && !(((c) >= 'a' && (c) <= 'z')		\
 		            || ((c) >= 'A' && (c) <= 'Z')	\
 		            || ((c) >= '0' && (c) <= '9')))	\
 		    : SYNTAX (c) != Sword)
 
-# define ISSPACE(c) (SYNTAX (c) == Swhitespace)
+#define ISSPACE(c) (SYNTAX (c) == Swhitespace)
 
-# define ISUPPER(c) uppercasep (c)
-
-# define ISWORD(c) (SYNTAX (c) == Sword)
-
-#else /* not emacs */
-
-/* 1 if C is an ASCII character.  */
-# define IS_REAL_ASCII(c) ((c) < 0200)
-
-/* This distinction is not meaningful, except in Emacs.  */
-# define ISUNIBYTE(c) 1
-
-# ifdef isblank
-#  define ISBLANK(c) isblank (c)
-# else
-#  define ISBLANK(c) ((c) == ' ' || (c) == '\t')
-# endif
-# ifdef isgraph
-#  define ISGRAPH(c) isgraph (c)
-# else
-#  define ISGRAPH(c) (isprint (c) && !isspace (c))
-# endif
-
-/* Solaris defines ISPRINT so we must undefine it first.  */
-# undef ISPRINT
-# define ISPRINT(c) isprint (c)
-# define ISDIGIT(c) isdigit (c)
-# define ISALNUM(c) isalnum (c)
-# define ISALPHA(c) isalpha (c)
-# define ISCNTRL(c) iscntrl (c)
-# define ISLOWER(c) islower (c)
-# define ISPUNCT(c) ispunct (c)
-# define ISSPACE(c) isspace (c)
-# define ISUPPER(c) isupper (c)
-# define ISXDIGIT(c) isxdigit (c)
-
-# define ISWORD(c) ISALPHA (c)
-
-# ifdef _tolower
-#  define TOLOWER(c) _tolower (c)
-# else
-#  define TOLOWER(c) tolower (c)
-# endif
-
-/* How many characters in the character set.  */
-# define CHAR_SET_SIZE 256
-
-# ifdef SYNTAX_TABLE
-
-extern char *re_syntax_table;
-
-# else /* not SYNTAX_TABLE */
-
-static char re_syntax_table[CHAR_SET_SIZE];
-
-static void
-init_syntax_once (void)
-{
-   register int c;
-   static int done = 0;
-
-   if (done)
-     return;
-
-   memset (re_syntax_table, 0, sizeof re_syntax_table);
-
-   for (c = 0; c < CHAR_SET_SIZE; ++c)
-     if (ISALNUM (c))
-	re_syntax_table[c] = Sword;
-
-   re_syntax_table['_'] = Ssymbol;
-
-   done = 1;
-}
+#define ISUPPER(c) uppercasep (c)
 
-# endif /* not SYNTAX_TABLE */
-
-# define SYNTAX(c) re_syntax_table[(c)]
-
-#endif /* not emacs */
+#define ISWORD(c) (SYNTAX (c) == Sword)
 
 #define SIGN_EXTEND_CHAR(c) ((signed char) (c))
 
-/* Should we use malloc or alloca?  If REGEX_MALLOC is not defined, we
-   use `alloca' instead of `malloc'.  This is because using malloc in
+/* Use alloca instead of malloc.  This is because using malloc in
    re_search* or re_match* could cause memory leaks when C-g is used
    in Emacs (note that SAFE_ALLOCA could also call malloc, but does so
    via `record_xmalloc' which uses `unwind_protect' to ensure the
@@ -441,64 +301,17 @@ init_syntax_once (void)
    not functions -- `alloca'-allocated space disappears at the end of the
    function it is called in.  */
 
-#ifdef REGEX_MALLOC
-
-# define REGEX_ALLOCATE malloc
-# define REGEX_REALLOCATE(source, osize, nsize) realloc (source, nsize)
-# define REGEX_FREE free
-
-#else /* not REGEX_MALLOC  */
-
-# ifdef emacs
 /* This may be adjusted in main(), if the stack is successfully grown.  */
 ptrdiff_t emacs_re_safe_alloca = MAX_ALLOCA;
 /* Like USE_SAFE_ALLOCA, but use emacs_re_safe_alloca.  */
-#  define REGEX_USE_SAFE_ALLOCA                                        \
-  ptrdiff_t sa_avail = emacs_re_safe_alloca;                           \
-  ptrdiff_t sa_count = SPECPDL_INDEX ()
-
-#  define REGEX_SAFE_FREE() SAFE_FREE ()
-#  define REGEX_ALLOCATE SAFE_ALLOCA
-# else
-#  include <alloca.h>
-#  define REGEX_ALLOCATE alloca
-# endif
+#define REGEX_USE_SAFE_ALLOCA					       \
+  USE_SAFE_ALLOCA; sa_avail = emacs_re_safe_alloca
 
 /* Assumes a `char *destination' variable.  */
-# define REGEX_REALLOCATE(source, osize, nsize)				\
-  (destination = REGEX_ALLOCATE (nsize),				\
+#define REGEX_REALLOCATE(source, osize, nsize)				\
+  (destination = SAFE_ALLOCA (nsize),					\
    memcpy (destination, source, osize))
 
-/* No need to do anything to free, after alloca.  */
-# define REGEX_FREE(arg) ((void)0) /* Do nothing!  But inhibit gcc warning.  */
-
-#endif /* not REGEX_MALLOC */
-
-#ifndef REGEX_USE_SAFE_ALLOCA
-# define REGEX_USE_SAFE_ALLOCA ((void) 0)
-# define REGEX_SAFE_FREE() ((void) 0)
-#endif
-
-/* Define how to allocate the failure stack.  */
-
-#if defined REL_ALLOC && defined REGEX_MALLOC
-
-# define REGEX_ALLOCATE_STACK(size)				\
-  r_alloc (&failure_stack_ptr, (size))
-# define REGEX_REALLOCATE_STACK(source, osize, nsize)		\
-  r_re_alloc (&failure_stack_ptr, (nsize))
-# define REGEX_FREE_STACK(ptr)					\
-  r_alloc_free (&failure_stack_ptr)
-
-#else /* not using relocating allocator */
-
-# define REGEX_ALLOCATE_STACK(size) REGEX_ALLOCATE (size)
-# define REGEX_REALLOCATE_STACK(source, o, n) REGEX_REALLOCATE (source, o, n)
-# define REGEX_FREE_STACK(ptr) REGEX_FREE (ptr)
-
-#endif /* not using relocating allocator */
-
-
 /* True if `size1' is non-NULL and PTR is pointing anywhere inside
    `string1' or just past its end.  This works if PTR is NULL, which is
    a good thing.  */
@@ -506,30 +319,21 @@ ptrdiff_t emacs_re_safe_alloca = MAX_ALLOCA;
   (size1 && string1 <= (ptr) && (ptr) <= string1 + size1)
 
 /* (Re)Allocate N items of type T using malloc, or fail.  */
-#define TALLOC(n, t) ((t *) malloc ((n) * sizeof (t)))
-#define RETALLOC(addr, n, t) ((addr) = (t *) realloc (addr, (n) * sizeof (t)))
-#define REGEX_TALLOC(n, t) ((t *) REGEX_ALLOCATE ((n) * sizeof (t)))
+#define TALLOC(n, t) ((t *) xmalloc ((n) * sizeof (t)))
+#define RETALLOC(addr, n, t) ((addr) = (t *) xrealloc (addr, (n) * sizeof (t)))
 
 #define BYTEWIDTH 8 /* In bits.  */
 
-#ifndef emacs
-# undef max
-# undef min
-# define max(a, b) ((a) > (b) ? (a) : (b))
-# define min(a, b) ((a) < (b) ? (a) : (b))
-#endif
-
 /* Type of source-pattern and string chars.  */
 typedef const unsigned char re_char;
 
-typedef char boolean;
-
-static regoff_t re_match_2_internal (struct re_pattern_buffer *bufp,
+static void re_compile_fastmap (struct re_pattern_buffer *);
+static ptrdiff_t re_match_2_internal (struct re_pattern_buffer *bufp,
 				     re_char *string1, size_t size1,
 				     re_char *string2, size_t size2,
-				     ssize_t pos,
+				     ptrdiff_t pos,
 				     struct re_registers *regs,
-				     ssize_t stop);
+				     ptrdiff_t stop);
 
 /* These are the command codes that appear in compiled regular
    expressions.  Some opcodes are followed by argument bytes.  A
@@ -591,8 +395,7 @@ typedef enum
 	/* Fail unless at end of line.  */
   endline,
 
-	/* Succeeds if at beginning of buffer (if emacs) or at beginning
-	   of string to be matched (if not).  */
+	/* Succeeds if at beginning of buffer.  */
   begbuf,
 
 	/* Analogously, for end of buffer/string.  */
@@ -657,10 +460,9 @@ typedef enum
   syntaxspec,
 
 	/* Matches any character whose syntax is not that specified.  */
-  notsyntaxspec
+  notsyntaxspec,
 
-#ifdef emacs
-  , at_dot,	/* Succeeds if at point.  */
+  at_dot,	/* Succeeds if at point.  */
 
   /* Matches any character whose category-set contains the specified
      category.  The operator is followed by a byte which contains a
@@ -671,7 +473,6 @@ typedef enum
      specified category.  The operator is followed by a byte which
      contains the category code (mnemonic ASCII character).  */
   notcategoryspec
-#endif /* emacs */
 } re_opcode_t;
 
 /* Common operations on the compiled pattern.  */
@@ -759,12 +560,10 @@ extract_number_and_incr (re_char **source)
    and the 2 bytes of flags at the start of the range table.  */
 #define CHARSET_RANGE_TABLE(p) (&(p)[4 + CHARSET_BITMAP_SIZE (p)])
 
-#ifdef emacs
 /* Extract the bit flags that start a range table.  */
 #define CHARSET_RANGE_TABLE_BITS(p)		\
   ((p)[2 + CHARSET_BITMAP_SIZE (p)]		\
    + (p)[3 + CHARSET_BITMAP_SIZE (p)] * 0x100)
-#endif
 
 /* Return the address of end of RANGE_TABLE.  COUNT is number of
    ranges (which is a pair of (start, end)) in the RANGE_TABLE.  `* 2'
@@ -773,29 +572,23 @@ extract_number_and_incr (re_char **source)
 #define CHARSET_RANGE_TABLE_END(range_table, count)	\
   ((range_table) + (count) * 2 * 3)
 
-/* If DEBUG is defined, Regex prints many voluminous messages about what
-   it is doing (if the variable `debug' is nonzero).  If linked with the
-   main program in `iregex.c', you can enter patterns and strings
-   interactively.  And if linked with the main program in `main.c' and
-   the other test files, you can run the already-written tests.  */
+/* If REGEX_EMACS_DEBUG is defined, print many voluminous messages
+   (if the variable regex_emacs_debug is positive).  */
 
-#ifdef DEBUG
+#ifdef REGEX_EMACS_DEBUG
 
 /* We use standard I/O for debugging.  */
 # include <stdio.h>
 
-/* It is useful to test things that ``must'' be true when debugging.  */
-# include <assert.h>
-
-static int debug = -100000;
+static int regex_emacs_debug = -100000;
 
 # define DEBUG_STATEMENT(e) e
-# define DEBUG_PRINT(...) if (debug > 0) printf (__VA_ARGS__)
+# define DEBUG_PRINT(...) if (regex_emacs_debug > 0) printf (__VA_ARGS__)
 # define DEBUG_COMPILES_ARGUMENTS
 # define DEBUG_PRINT_COMPILED_PATTERN(p, s, e)				\
-  if (debug > 0) print_partial_compiled_pattern (s, e)
+  if (regex_emacs_debug > 0) print_partial_compiled_pattern (s, e)
 # define DEBUG_PRINT_DOUBLE_STRING(w, s1, sz1, s2, sz2)			\
-  if (debug > 0) print_double_string (w, s1, sz1, s2, sz2)
+  if (regex_emacs_debug > 0) print_double_string (w, s1, sz1, s2, sz2)

 /* Print the fastmap in human-readable form.  */
@@ -1084,7 +877,7 @@ print_compiled_pattern (struct re_pattern_buffer *bufp)
   re_char *buffer = bufp->buffer;
 
   print_partial_compiled_pattern (buffer, buffer + bufp->used);
-  printf ("%ld bytes used/%ld bytes allocated.\n",
+  printf ("%zu bytes used/%zu bytes allocated.\n",
 	  bufp->used, bufp->allocated);
 
   if (bufp->fastmap_accurate && bufp->fastmap)
@@ -1130,146 +923,99 @@ print_double_string (re_char *where, re_char *string1, ssize_t size1,
     }
 }
 
-#else /* not DEBUG */
-
-# undef assert
-# define assert(e)
+#else /* not REGEX_EMACS_DEBUG */
 
 # define DEBUG_STATEMENT(e)
 # define DEBUG_PRINT(...)
 # define DEBUG_PRINT_COMPILED_PATTERN(p, s, e)
 # define DEBUG_PRINT_DOUBLE_STRING(w, s1, sz1, s2, sz2)
 
-#endif /* not DEBUG */
+#endif /* not REGEX_EMACS_DEBUG */
 
-#ifndef emacs
-
-/* 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-emacs.h.  We return the old syntax.  */
-
-reg_syntax_t
-re_set_syntax (reg_syntax_t syntax)
+typedef enum
 {
-  reg_syntax_t ret = re_syntax_options;
-
-  re_syntax_options = syntax;
-  return ret;
-}
-WEAK_ALIAS (__re_set_syntax, re_set_syntax)
-
-#endif
-
-/* This table gives an error message for each of the error codes listed
-   in regex-emacs.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?  */
+  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,		/* Not implemented.  */
+  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_ERANGEX,		/* Range striding over charsets.  */
+  REG_ESIZEBR           /* n or m too big in \{n,m\} */
+} reg_errcode_t;
 
 static const char *re_error_msgid[] =
   {
-    gettext_noop ("Success"),	/* REG_NOERROR */
-    gettext_noop ("No match"),	/* REG_NOMATCH */
-    gettext_noop ("Invalid regular expression"), /* REG_BADPAT */
-    gettext_noop ("Invalid collation character"), /* REG_ECOLLATE */
-    gettext_noop ("Invalid character class name"), /* REG_ECTYPE */
-    gettext_noop ("Trailing backslash"), /* REG_EESCAPE */
-    gettext_noop ("Invalid back reference"), /* REG_ESUBREG */
-    gettext_noop ("Unmatched [ or [^"),	/* REG_EBRACK */
-    gettext_noop ("Unmatched ( or \\("), /* REG_EPAREN */
-    gettext_noop ("Unmatched \\{"), /* REG_EBRACE */
-    gettext_noop ("Invalid content of \\{\\}"), /* REG_BADBR */
-    gettext_noop ("Invalid range end"),	/* REG_ERANGE */
-    gettext_noop ("Memory exhausted"), /* REG_ESPACE */
-    gettext_noop ("Invalid preceding regular expression"), /* REG_BADRPT */
-    gettext_noop ("Premature end of regular expression"), /* REG_EEND */
-    gettext_noop ("Regular expression too big"), /* REG_ESIZE */
-    gettext_noop ("Unmatched ) or \\)"), /* REG_ERPAREN */
-    gettext_noop ("Range striding over charsets"), /* REG_ERANGEX  */
-    gettext_noop ("Invalid content of \\{\\}, repetitions too big") /* REG_ESIZEBR  */
+   [REG_NOERROR] = "Success",
+   [REG_NOMATCH] = "No match",
+   [REG_BADPAT] = "Invalid regular expression",
+   [REG_ECOLLATE] = "Invalid collation character",
+   [REG_ECTYPE] = "Invalid character class name",
+   [REG_EESCAPE] = "Trailing backslash",
+   [REG_ESUBREG] = "Invalid back reference",
+   [REG_EBRACK] = "Unmatched [ or [^",
+   [REG_EPAREN] = "Unmatched ( or \\(",
+   [REG_EBRACE] = "Unmatched \\{",
+   [REG_BADBR] = "Invalid content of \\{\\}",
+   [REG_ERANGE] = "Invalid range end",
+   [REG_ESPACE] = "Memory exhausted",
+   [REG_BADRPT] = "Invalid preceding regular expression",
+   [REG_EEND] = "Premature end of regular expression",
+   [REG_ESIZE] = "Regular expression too big",
+   [REG_ERPAREN] = "Unmatched ) or \\)",
+   [REG_ERANGEX ] = "Range striding over charsets",
+   [REG_ESIZEBR ] = "Invalid content of \\{\\}",
   };
-
-/* Whether to allocate memory during matching.  */
-
-/* Define MATCH_MAY_ALLOCATE to allow the searching and matching
-   functions allocate memory for the failure stack and registers.
-   Normally should be defined, because otherwise searching and
-   matching routines will have much smaller memory resources at their
-   disposal, and therefore might fail to handle complex regexps.
-   Therefore undefine MATCH_MAY_ALLOCATE only in the following
-   exceptional situations:
-
-   . When running on a system where memory is at premium.
-   . When alloca cannot be used at all, perhaps due to bugs in
-     its implementation, or its being unavailable, or due to a
-     very small stack size.  This requires to define REGEX_MALLOC
-     to use malloc instead, which in turn could lead to memory
-     leaks if search is interrupted by a signal.  (For these
-     reasons, defining REGEX_MALLOC when building Emacs
-     automatically undefines MATCH_MAY_ALLOCATE, but outside
-     Emacs you may not care about memory leaks.)  If you want to
-     prevent the memory leaks, undefine MATCH_MAY_ALLOCATE.
-   . When code that calls the searching and matching functions
-     cannot allow memory allocation, for whatever reasons.  */
-
-/* Normally, this is fine.  */
-#define MATCH_MAY_ALLOCATE
-
-/* The match routines may not allocate if (1) they would do it with malloc
-   and (2) it's not safe for them to use malloc.
-   Note that if REL_ALLOC is defined, matching would not use malloc for the
-   failure stack, but we would still use it for the register vectors;
-   so REL_ALLOC should not affect this.  */
-#if defined REGEX_MALLOC && defined emacs
-# undef MATCH_MAY_ALLOCATE
-#endif
 
-/* While regex matching of a single compiled pattern isn't reentrant
-   (because we compile regexes to bytecode programs, and the bytecode
-   programs are self-modifying), the regex machinery must nevertheless
-   be reentrant with respect to _different_ patterns, and we do that
-   by avoiding global variables and using MATCH_MAY_ALLOCATE.  */
-#if !defined MATCH_MAY_ALLOCATE && defined emacs
-# error "Emacs requires MATCH_MAY_ALLOCATE"
-#endif
+/* For 'regs_allocated'.  */
+enum { REGS_UNALLOCATED, REGS_REALLOCATE, REGS_FIXED };
 
+/* 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.  */
+enum { RE_NREGS = 30 };
 
+/* The searching and matching functions allocate memory for the
+   failure stack and registers.  Otherwise searching and matching
+   routines would have much smaller memory resources at their
+   disposal, and therefore might fail to handle complex regexps.  */
+
 /* Failure stack declarations and macros; both re_compile_fastmap and
    re_match_2 use a failure stack.  These have to be macros because of
-   REGEX_ALLOCATE_STACK.  */
+   SAFE_ALLOCA.  */

 /* Approximate number of failure points for which to initially allocate space
    when matching.  If this number is exceeded, we allocate more
    space, so it is not a hard limit.  */
-#ifndef INIT_FAILURE_ALLOC
-# define INIT_FAILURE_ALLOC 20
-#endif
+#define INIT_FAILURE_ALLOC 20
 
 /* Roughly the maximum number of failure points on the stack.  Would be
    exactly that if always used TYPICAL_FAILURE_SIZE items each time we failed.
    This is a variable only so users of regex can assign to it; we never
    change it ourselves.  We always multiply it by TYPICAL_FAILURE_SIZE
    before using it, so it should probably be a byte-count instead.  */
-# if defined MATCH_MAY_ALLOCATE
 /* Note that 4400 was enough to cause a crash on Alpha OSF/1,
    whose default stack limit is 2mb.  In order for a larger
    value to work reliably, you have to try to make it accord
    with the process stack limit.  */
 size_t emacs_re_max_failures = 40000;
-# else
-size_t emacs_re_max_failures = 4000;
-# endif
 
 union fail_stack_elt
 {
@@ -1291,33 +1037,17 @@ typedef struct
 #define FAIL_STACK_EMPTY()     (fail_stack.frame == 0)

-/* Define macros to initialize and free the failure stack.
-   Do `return -2' if the alloc fails.  */
+/* Define macros to initialize and free the failure stack.  */
 
-#ifdef MATCH_MAY_ALLOCATE
-# define INIT_FAIL_STACK()						\
+#define INIT_FAIL_STACK()						\
   do {									\
     fail_stack.stack =							\
-      REGEX_ALLOCATE_STACK (INIT_FAILURE_ALLOC * TYPICAL_FAILURE_SIZE	\
-			    * sizeof (fail_stack_elt_t));		\
-									\
-    if (fail_stack.stack == NULL)					\
-      return -2;							\
-									\
+      SAFE_ALLOCA (INIT_FAILURE_ALLOC * TYPICAL_FAILURE_SIZE		\
+		   * sizeof (fail_stack_elt_t));			\
     fail_stack.size = INIT_FAILURE_ALLOC;				\
     fail_stack.avail = 0;						\
     fail_stack.frame = 0;						\
   } while (0)
-#else
-# define INIT_FAIL_STACK()						\
-  do {									\
-    fail_stack.avail = 0;						\
-    fail_stack.frame = 0;						\
-  } while (0)
-
-# define RETALLOC_IF(addr, n, t) \
-  if (addr) RETALLOC((addr), (n), t); else (addr) = TALLOC ((n), t)
-#endif

 /* Double the size of FAIL_STACK, up to a limit
@@ -1326,7 +1056,7 @@ typedef struct
    Return 1 if succeeds, and 0 if either ran out of memory
    allocating space for it or it was already too large.
 
-   REGEX_REALLOCATE_STACK requires `destination' be declared.   */
+   REGEX_REALLOCATE requires `destination' be declared.   */
 
 /* Factor to increase the failure stack size by
    when we increase it.
@@ -1339,18 +1069,15 @@ typedef struct
   (((fail_stack).size >= emacs_re_max_failures * TYPICAL_FAILURE_SIZE)        \
    ? 0									\
    : ((fail_stack).stack						\
-      = REGEX_REALLOCATE_STACK ((fail_stack).stack,			\
+      = REGEX_REALLOCATE ((fail_stack).stack,				\
 	  (fail_stack).size * sizeof (fail_stack_elt_t),		\
           min (emacs_re_max_failures * TYPICAL_FAILURE_SIZE,                  \
                ((fail_stack).size * FAIL_STACK_GROWTH_FACTOR))          \
           * sizeof (fail_stack_elt_t)),                                 \
-									\
-      (fail_stack).stack == NULL					\
-      ? 0								\
-      : ((fail_stack).size						\
-         = (min (emacs_re_max_failures * TYPICAL_FAILURE_SIZE,                \
-                 ((fail_stack).size * FAIL_STACK_GROWTH_FACTOR))),      \
-	 1)))
+      ((fail_stack).size						\
+       = (min (emacs_re_max_failures * TYPICAL_FAILURE_SIZE,		\
+	       ((fail_stack).size * FAIL_STACK_GROWTH_FACTOR)))),	\
+      1))

 /* Push a pointer value onto the failure stack.
@@ -1384,8 +1111,8 @@ typedef struct
 while (REMAINING_AVAIL_SLOTS <= space) {				\
   if (!GROW_FAIL_STACK (fail_stack))					\
     return -2;								\
-  DEBUG_PRINT ("\n  Doubled stack; size now: %zd\n", (fail_stack).size);\
-  DEBUG_PRINT ("	 slots available: %zd\n", REMAINING_AVAIL_SLOTS);\
+  DEBUG_PRINT ("\n  Doubled stack; size now: %zu\n", (fail_stack).size);\
+  DEBUG_PRINT ("	 slots available: %zu\n", REMAINING_AVAIL_SLOTS);\
 }
 
 /* Push register NUM onto the stack.  */
@@ -1423,7 +1150,7 @@ do {									\
   if (pfreg == -1)							\
     {									\
       /* It's a counter.  */						\
-      /* Here, we discard `const', making re_match non-reentrant.  */	\
+      /* Discard 'const', making re_search non-reentrant.  */		\
       unsigned char *ptr = (unsigned char *) POP_FAILURE_POINTER ();	\
       pfreg = POP_FAILURE_INT ();					\
       STORE_NUMBER (ptr, pfreg);					\
@@ -1441,14 +1168,14 @@ do {									\
 /* Check that we are not stuck in an infinite loop.  */
 #define CHECK_INFINITE_LOOP(pat_cur, string_place)			\
 do {									\
-  ssize_t failure = TOP_FAILURE_HANDLE ();				\
+  ptrdiff_t failure = TOP_FAILURE_HANDLE ();				\
   /* Check for infinite matching loops */				\
   while (failure > 0							\
 	 && (FAILURE_STR (failure) == string_place			\
 	     || FAILURE_STR (failure) == NULL))				\
     {									\
-      assert (FAILURE_PAT (failure) >= bufp->buffer			\
-	      && FAILURE_PAT (failure) <= bufp->buffer + bufp->used);	\
+      eassert (FAILURE_PAT (failure) >= bufp->buffer			\
+	       && FAILURE_PAT (failure) <= bufp->buffer + bufp->used);	\
       if (FAILURE_PAT (failure) == pat_cur)				\
 	{								\
 	  cycle = 1;							\
@@ -1477,14 +1204,14 @@ do {									\
 									\
   DEBUG_STATEMENT (nfailure_points_pushed++);				\
   DEBUG_PRINT ("\nPUSH_FAILURE_POINT:\n");				\
-  DEBUG_PRINT ("  Before push, next avail: %zd\n", (fail_stack).avail);	\
-  DEBUG_PRINT ("			size: %zd\n", (fail_stack).size);\
+  DEBUG_PRINT ("  Before push, next avail: %zu\n", (fail_stack).avail);	\
+  DEBUG_PRINT ("			size: %zu\n", (fail_stack).size);\
 									\
   ENSURE_FAIL_STACK (NUM_NONREG_ITEMS);					\
 									\
   DEBUG_PRINT ("\n");							\
 									\
-  DEBUG_PRINT ("  Push frame index: %zd\n", fail_stack.frame);		\
+  DEBUG_PRINT ("  Push frame index: %zu\n", fail_stack.frame);		\
   PUSH_FAILURE_INT (fail_stack.frame);					\
 									\
   DEBUG_PRINT ("  Push string %p: \"", string_place);			\
@@ -1522,12 +1249,12 @@ do {									\
 
 #define POP_FAILURE_POINT(str, pat)                                     \
 do {									\
-  assert (!FAIL_STACK_EMPTY ());					\
+  eassert (!FAIL_STACK_EMPTY ());					\
 									\
   /* Remove failure points and point to how many regs pushed.  */	\
   DEBUG_PRINT ("POP_FAILURE_POINT:\n");					\
-  DEBUG_PRINT ("  Before pop, next avail: %zd\n", fail_stack.avail);	\
-  DEBUG_PRINT ("		     size: %zd\n", fail_stack.size);	\
+  DEBUG_PRINT ("  Before pop, next avail: %zu\n", fail_stack.avail);	\
+  DEBUG_PRINT ("		     size: %zu\n", fail_stack.size);	\
 									\
   /* Pop the saved registers.  */					\
   while (fail_stack.frame < fail_stack.avail)				\
@@ -1546,10 +1273,10 @@ do {									\
   DEBUG_PRINT ("\"\n");							\
 									\
   fail_stack.frame = POP_FAILURE_INT ();				\
-  DEBUG_PRINT ("  Popping  frame index: %zd\n", fail_stack.frame);	\
+  DEBUG_PRINT ("  Popping  frame index: %zu\n", fail_stack.frame);	\
 									\
-  assert (fail_stack.avail >= 0);					\
-  assert (fail_stack.frame <= fail_stack.avail);			\
+  eassert (fail_stack.avail >= 0);					\
+  eassert (fail_stack.frame <= fail_stack.avail);			\
 									\
   DEBUG_STATEMENT (nfailure_points_popped++);				\
 } while (0) /* POP_FAILURE_POINT */
@@ -1562,12 +1289,8 @@ do {									\
 /* Subroutine declarations and macros for regex_compile.  */
 
 static reg_errcode_t regex_compile (re_char *pattern, size_t size,
-#ifdef emacs
 				    bool posix_backtracking,
 				    const char *whitespace_regexp,
-#else
-				    reg_syntax_t syntax,
-#endif
 				    struct re_pattern_buffer *bufp);
 static void store_op1 (re_opcode_t op, unsigned char *loc, int arg);
 static void store_op2 (re_opcode_t op, unsigned char *loc, int arg1, int arg2);
@@ -1575,10 +1298,10 @@ static void insert_op1 (re_opcode_t op, unsigned char *loc,
 			int arg, unsigned char *end);
 static void insert_op2 (re_opcode_t op, unsigned char *loc,
 			int arg1, int arg2, unsigned char *end);
-static boolean at_begline_loc_p (re_char *pattern, re_char *p,
-				 reg_syntax_t syntax);
-static boolean at_endline_loc_p (re_char *p, re_char *pend,
-				 reg_syntax_t syntax);
+static bool at_begline_loc_p (re_char *pattern, re_char *p,
+			      reg_syntax_t syntax);
+static bool at_endline_loc_p (re_char *p, re_char *pend,
+			      reg_syntax_t syntax);
 static re_char *skip_one_char (re_char *p);
 static int analyze_first (re_char *p, re_char *pend,
 			  char *fastmap, const int multibyte);
@@ -1594,14 +1317,15 @@ static int analyze_first (re_char *p, re_char *pend,
   } while (0)

-/* If `translate' is non-null, return translate[D], else just D.  We
+#define RE_TRANSLATE(TBL, C) char_table_translate (TBL, C)
+#define RE_TRANSLATE_P(TBL) (!EQ (TBL, make_number (0)))
+
+/* If `translate' is non-zero, return translate[D], else just D.  We
    cast the subscript to translate because some data is declared as
    `char *', to avoid warnings when a string constant is passed.  But
    when we use a character as a subscript we must make it unsigned.  */
-#ifndef TRANSLATE
-# define TRANSLATE(d) \
+#define TRANSLATE(d) \
   (RE_TRANSLATE_P (translate) ? RE_TRANSLATE (translate, (d)) : (d))
-#endif

 /* Macros for outputting the compiled pattern into `buffer'.  */
@@ -1676,8 +1400,6 @@ static int analyze_first (re_char *p, re_char *pend,
     if (laststart_set) laststart_off = laststart - old_buffer;		\
     if (pending_exact_set) pending_exact_off = pending_exact - old_buffer; \
     RETALLOC (bufp->buffer, bufp->allocated, unsigned char);		\
-    if (bufp->buffer == NULL)						\
-      return REG_ESPACE;						\
     unsigned char *new_buffer = bufp->buffer;				\
     b = new_buffer + b_off;						\
     begalt = new_buffer + begalt_off;					\
@@ -1728,12 +1450,6 @@ typedef struct
 
 /* The next available element.  */
 #define COMPILE_STACK_TOP (compile_stack.stack[compile_stack.avail])
-
-/* Explicit quit checking is needed for Emacs, which uses polling to
-   process input events.  */
-#ifndef emacs
-static void maybe_quit (void) {}
-#endif
 
 /* Structure to manage work area for range table.  */
 struct range_table_work_area
@@ -1744,8 +1460,6 @@ struct range_table_work_area
   int bits;			/* flag to record character classes */
 };
 
-#ifdef emacs
-
 /* Make sure that WORK_AREA can hold more N multibyte characters.
    This is used only in set_image_of_range and set_image_of_range_1.
    It expects WORK_AREA to be a pointer.
@@ -1772,13 +1486,11 @@ struct range_table_work_area
     (work_area).table[(work_area).used++] = (range_end);		\
   } while (0)
 
-#endif /* emacs */
-
 /* Free allocated memory for WORK_AREA.  */
 #define FREE_RANGE_TABLE_WORK_AREA(work_area)	\
   do {						\
     if ((work_area).table)			\
-      free ((work_area).table);			\
+      xfree ((work_area).table);			\
   } while (0)
 
 #define CLEAR_RANGE_TABLE_WORK_USED(work_area) ((work_area).used = 0, (work_area).bits = 0)
@@ -1806,8 +1518,6 @@ struct range_table_work_area
 #define SET_LIST_BIT(c) (b[((c)) / BYTEWIDTH] |= 1 << ((c) % BYTEWIDTH))

-#ifdef emacs
-
 /* Store characters in the range FROM to TO in the bitmap at B (for
    ASCII and unibyte characters) and WORK_AREA (for multibyte
    characters) while translating them and paying attention to the
@@ -1911,8 +1621,6 @@ struct range_table_work_area
       }									   \
   } while (0)
 
-#endif /* emacs */
-
 /* Get the next unsigned number in the uncompiled pattern.  */
 #define GET_INTERVAL_COUNT(num)					\
   do {									\
@@ -1935,8 +1643,6 @@ struct range_table_work_area
       }									\
   } while (0)
 
-#if ! WIDE_CHAR_SUPPORT
-
 /* Parse a character class, i.e. string such as "[:name:]".  *strp
    points to the string to be parsed and limit is length, in bytes, of
    that string.
@@ -2030,7 +1736,7 @@ re_wctype_parse (const unsigned char **strp, unsigned limit)
 }
 
 /* True if CH is in the char class CC.  */
-boolean
+bool
 re_iswctype (int ch, re_wctype_t cc)
 {
   switch (cc)
@@ -2083,7 +1789,6 @@ re_wctype_to_bit (re_wctype_t cc)
       abort ();
     }
 }
-#endif
 
 /* Filling in the work area of a range.  */
 
@@ -2093,287 +1798,15 @@ static void
 extend_range_table_work_area (struct range_table_work_area *work_area)
 {
   work_area->allocated += 16 * sizeof (int);
-  work_area->table = realloc (work_area->table, work_area->allocated);
+  work_area->table = xrealloc (work_area->table, work_area->allocated);
 }
-
-#if 0
-#ifdef emacs
-
-/* Carefully find the ranges of codes that are equivalent
-   under case conversion to the range start..end when passed through
-   TRANSLATE.  Handle the case where non-letters can come in between
-   two upper-case letters (which happens in Latin-1).
-   Also handle the case of groups of more than 2 case-equivalent chars.
-
-   The basic method is to look at consecutive characters and see
-   if they can form a run that can be handled as one.
-
-   Returns -1 if successful, REG_ESPACE if ran out of space.  */
-
-static int
-set_image_of_range_1 (struct range_table_work_area *work_area,
-		      re_wchar_t start, re_wchar_t end,
-		      RE_TRANSLATE_TYPE translate)
-{
-  /* `one_case' indicates a character, or a run of characters,
-     each of which is an isolate (no case-equivalents).
-     This includes all ASCII non-letters.
-
-     `two_case' indicates a character, or a run of characters,
-     each of which has two case-equivalent forms.
-     This includes all ASCII letters.
-
-     `strange' indicates a character that has more than one
-     case-equivalent.  */
-
-  enum case_type {one_case, two_case, strange};
-
-  /* Describe the run that is in progress,
-     which the next character can try to extend.
-     If run_type is strange, that means there really is no run.
-     If run_type is one_case, then run_start...run_end is the run.
-     If run_type is two_case, then the run is run_start...run_end,
-     and the case-equivalents end at run_eqv_end.  */
-
-  enum case_type run_type = strange;
-  int run_start, run_end, run_eqv_end;
-
-  Lisp_Object eqv_table;
-
-  if (!RE_TRANSLATE_P (translate))
-    {
-      EXTEND_RANGE_TABLE (work_area, 2);
-      work_area->table[work_area->used++] = (start);
-      work_area->table[work_area->used++] = (end);
-      return -1;
-    }
-
-  eqv_table = XCHAR_TABLE (translate)->extras[2];
-
-  for (; start <= end; start++)
-    {
-      enum case_type this_type;
-      int eqv = RE_TRANSLATE (eqv_table, start);
-      int minchar, maxchar;
-
-      /* Classify this character */
-      if (eqv == start)
-	this_type = one_case;
-      else if (RE_TRANSLATE (eqv_table, eqv) == start)
-	this_type = two_case;
-      else
-	this_type = strange;
-
-      if (start < eqv)
-	minchar = start, maxchar = eqv;
-      else
-	minchar = eqv, maxchar = start;
-
-      /* Can this character extend the run in progress?  */
-      if (this_type == strange || this_type != run_type
-	  || !(minchar == run_end + 1
-	       && (run_type == two_case
-		   ? maxchar == run_eqv_end + 1 : 1)))
-	{
-	  /* No, end the run.
-	     Record each of its equivalent ranges.  */
-	  if (run_type == one_case)
-	    {
-	      EXTEND_RANGE_TABLE (work_area, 2);
-	      work_area->table[work_area->used++] = run_start;
-	      work_area->table[work_area->used++] = run_end;
-	    }
-	  else if (run_type == two_case)
-	    {
-	      EXTEND_RANGE_TABLE (work_area, 4);
-	      work_area->table[work_area->used++] = run_start;
-	      work_area->table[work_area->used++] = run_end;
-	      work_area->table[work_area->used++]
-		= RE_TRANSLATE (eqv_table, run_start);
-	      work_area->table[work_area->used++]
-		= RE_TRANSLATE (eqv_table, run_end);
-	    }
-	  run_type = strange;
-	}
-
-      if (this_type == strange)
-	{
-	  /* For a strange character, add each of its equivalents, one
-	     by one.  Don't start a range.  */
-	  do
-	    {
-	      EXTEND_RANGE_TABLE (work_area, 2);
-	      work_area->table[work_area->used++] = eqv;
-	      work_area->table[work_area->used++] = eqv;
-	      eqv = RE_TRANSLATE (eqv_table, eqv);
-	    }
-	  while (eqv != start);
-	}
-
-      /* Add this char to the run, or start a new run.  */
-      else if (run_type == strange)
-	{
-	  /* Initialize a new range.  */
-	  run_type = this_type;
-	  run_start = start;
-	  run_end = start;
-	  run_eqv_end = RE_TRANSLATE (eqv_table, run_end);
-	}
-      else
-	{
-	  /* Extend a running range.  */
-	  run_end = minchar;
-	  run_eqv_end = RE_TRANSLATE (eqv_table, run_end);
-	}
-    }
-
-  /* If a run is still in progress at the end, finish it now
-     by recording its equivalent ranges.  */
-  if (run_type == one_case)
-    {
-      EXTEND_RANGE_TABLE (work_area, 2);
-      work_area->table[work_area->used++] = run_start;
-      work_area->table[work_area->used++] = run_end;
-    }
-  else if (run_type == two_case)
-    {
-      EXTEND_RANGE_TABLE (work_area, 4);
-      work_area->table[work_area->used++] = run_start;
-      work_area->table[work_area->used++] = run_end;
-      work_area->table[work_area->used++]
-	= RE_TRANSLATE (eqv_table, run_start);
-      work_area->table[work_area->used++]
-	= RE_TRANSLATE (eqv_table, run_end);
-    }
-
-  return -1;
-}
-
-#endif /* emacs */
-
-/* Record the image of the range start..end when passed through
-   TRANSLATE.  This is not necessarily TRANSLATE(start)..TRANSLATE(end)
-   and is not even necessarily contiguous.
-   Normally we approximate it with the smallest contiguous range that contains
-   all the chars we need.  However, for Latin-1 we go to extra effort
-   to do a better job.
-
-   This function is not called for ASCII ranges.
-
-   Returns -1 if successful, REG_ESPACE if ran out of space.  */
-
-static int
-set_image_of_range (struct range_table_work_area *work_area,
-		    re_wchar_t start, re_wchar_t end,
-		    RE_TRANSLATE_TYPE translate)
-{
-  re_wchar_t cmin, cmax;
-
-#ifdef emacs
-  /* For Latin-1 ranges, use set_image_of_range_1
-     to get proper handling of ranges that include letters and nonletters.
-     For a range that includes the whole of Latin-1, this is not necessary.
-     For other character sets, we don't bother to get this right.  */
-  if (RE_TRANSLATE_P (translate) && start < 04400
-      && !(start < 04200 && end >= 04377))
-    {
-      int newend;
-      int tem;
-      newend = end;
-      if (newend > 04377)
-	newend = 04377;
-      tem = set_image_of_range_1 (work_area, start, newend, translate);
-      if (tem > 0)
-	return tem;
-
-      start = 04400;
-      if (end < 04400)
-	return -1;
-    }
-#endif
-
-  EXTEND_RANGE_TABLE (work_area, 2);
-  work_area->table[work_area->used++] = (start);
-  work_area->table[work_area->used++] = (end);
-
-  cmin = -1, cmax = -1;
-
-  if (RE_TRANSLATE_P (translate))
-    {
-      int ch;
-
-      for (ch = start; ch <= end; ch++)
-	{
-	  re_wchar_t c = TRANSLATE (ch);
-	  if (! (start <= c && c <= end))
-	    {
-	      if (cmin == -1)
-		cmin = c, cmax = c;
-	      else
-		{
-		  cmin = min (cmin, c);
-		  cmax = max (cmax, c);
-		}
-	    }
-	}
-
-      if (cmin != -1)
-	{
-	  EXTEND_RANGE_TABLE (work_area, 2);
-	  work_area->table[work_area->used++] = (cmin);
-	  work_area->table[work_area->used++] = (cmax);
-	}
-    }
-
-  return -1;
-}
-#endif	/* 0 */
-
-#ifndef MATCH_MAY_ALLOCATE
-
-/* If we cannot allocate large objects within re_match_2_internal,
-   we make the fail stack and register vectors global.
-   The fail stack, we grow to the maximum size when a regexp
-   is compiled.
-   The register vectors, we adjust in size each time we
-   compile a regexp, according to the number of registers it needs.  */
-
-static fail_stack_type fail_stack;
-
-/* Size with which the following vectors are currently allocated.
-   That is so we can make them bigger as needed,
-   but never make them smaller.  */
-static int regs_allocated_size;
-
-static re_char **     regstart, **     regend;
-static re_char **best_regstart, **best_regend;
-
-/* Make the register vectors big enough for NUM_REGS registers,
-   but don't make them smaller.  */
-
-static
-regex_grow_registers (int num_regs)
-{
-  if (num_regs > regs_allocated_size)
-    {
-      RETALLOC_IF (regstart,	 num_regs, re_char *);
-      RETALLOC_IF (regend,	 num_regs, re_char *);
-      RETALLOC_IF (best_regstart, num_regs, re_char *);
-      RETALLOC_IF (best_regend,	 num_regs, re_char *);
-
-      regs_allocated_size = num_regs;
-    }
-}
-
-#endif /* not MATCH_MAY_ALLOCATE */
 
-static boolean group_in_compile_stack (compile_stack_type compile_stack,
-				       regnum_t regnum);
+static bool group_in_compile_stack (compile_stack_type, regnum_t);
 
 /* `regex_compile' compiles PATTERN (of length SIZE) according to SYNTAX.
    Returns one of error codes defined in regex-emacs.h, or zero for success.
 
-   If WHITESPACE_REGEXP is given (only #ifdef emacs), it is used instead of
+   If WHITESPACE_REGEXP is given, it is used instead of
    a space character in PATTERN.
 
    Assumes the `allocated' (and perhaps `buffer') and `translate'
@@ -2403,42 +1836,33 @@ do {									\
 #define FREE_STACK_RETURN(value)		\
   do {							\
     FREE_RANGE_TABLE_WORK_AREA (range_table_work);	\
-    free (compile_stack.stack);				\
+    xfree (compile_stack.stack);			\
     return value;					\
   } while (0)
 
 static reg_errcode_t
 regex_compile (re_char *pattern, size_t size,
-#ifdef emacs
-# define syntax RE_SYNTAX_EMACS
 	       bool posix_backtracking,
 	       const char *whitespace_regexp,
-#else
-	       reg_syntax_t syntax,
-# define posix_backtracking (!(syntax & RE_NO_POSIX_BACKTRACKING))
-#endif
 	       struct re_pattern_buffer *bufp)
 {
+  reg_syntax_t syntax = RE_SYNTAX_EMACS;
+
   /* We fetch characters from PATTERN here.  */
-  register re_wchar_t c, c1;
+  int c, c1;
 
   /* Points to the end of the buffer, where we should append.  */
-  register unsigned char *b;
+  unsigned char *b;
 
   /* Keeps track of unclosed groups.  */
   compile_stack_type compile_stack;
 
   /* Points to the current (ending) position in the pattern.  */
-#ifdef AIX
-  /* `const' makes AIX compiler fail.  */
-  unsigned char *p = pattern;
-#else
   re_char *p = pattern;
-#endif
   re_char *pend = pattern + size;
 
   /* How to translate the characters in the pattern.  */
-  RE_TRANSLATE_TYPE translate = bufp->translate;
+  Lisp_Object translate = bufp->translate;
 
   /* Address of the count-byte of the most recently inserted `exactn'
      command.  This makes it possible to tell if a new exact-match
@@ -2467,9 +1891,8 @@ regex_compile (re_char *pattern, size_t size,
   struct range_table_work_area range_table_work;
 
   /* If the object matched can contain multibyte characters.  */
-  const boolean multibyte = RE_MULTIBYTE_P (bufp);
+  bool multibyte = RE_MULTIBYTE_P (bufp);
 
-#ifdef emacs
   /* Nonzero if we have pushed down into a subpattern.  */
   int in_subpattern = 0;
 
@@ -2478,26 +1901,22 @@ regex_compile (re_char *pattern, size_t size,
   re_char *main_p;
   re_char *main_pattern;
   re_char *main_pend;
-#endif
 
-#ifdef DEBUG
-  debug++;
+#ifdef REGEX_EMACS_DEBUG
+  regex_emacs_debug++;
   DEBUG_PRINT ("\nCompiling pattern: ");
-  if (debug > 0)
+  if (regex_emacs_debug > 0)
     {
-      unsigned debug_count;
+      size_t debug_count;
 
       for (debug_count = 0; debug_count < size; debug_count++)
 	putchar (pattern[debug_count]);
       putchar ('\n');
     }
-#endif /* DEBUG */
+#endif
 
   /* Initialize the compile stack.  */
   compile_stack.stack = TALLOC (INIT_COMPILE_STACK_SIZE, compile_stack_elt_t);
-  if (compile_stack.stack == NULL)
-    return REG_ESPACE;
-
   compile_stack.size = INIT_COMPILE_STACK_SIZE;
   compile_stack.avail = 0;
 
@@ -2505,9 +1924,6 @@ regex_compile (re_char *pattern, size_t size,
   range_table_work.allocated = 0;
 
   /* Initialize the pattern buffer.  */
-#ifndef emacs
-  bufp->syntax = syntax;
-#endif
   bufp->fastmap_accurate = 0;
   bufp->not_bol = bufp->not_eol = 0;
   bufp->used_syntax = 0;
@@ -2520,11 +1936,6 @@ regex_compile (re_char *pattern, size_t size,
   /* Always count groups, whether or not bufp->no_sub is set.  */
   bufp->re_nsub = 0;
 
-#if !defined emacs && !defined SYNTAX_TABLE
-  /* Initialize the syntax table.  */
-   init_syntax_once ();
-#endif
-
   if (bufp->allocated == 0)
     {
       if (bufp->buffer)
@@ -2537,8 +1948,6 @@ regex_compile (re_char *pattern, size_t size,
 	{ /* Caller did not allocate a buffer.  Do it for them.  */
 	  bufp->buffer = TALLOC (INIT_BUF_SIZE, unsigned char);
 	}
-      if (!bufp->buffer) FREE_STACK_RETURN (REG_ESPACE);
-
       bufp->allocated = INIT_BUF_SIZE;
     }
 
@@ -2549,7 +1958,6 @@ regex_compile (re_char *pattern, size_t size,
     {
       if (p == pend)
 	{
-#ifdef emacs
 	  /* If this is the end of an included regexp,
 	     pop back to the main regexp and try again.  */
 	  if (in_subpattern)
@@ -2560,7 +1968,6 @@ regex_compile (re_char *pattern, size_t size,
 	      pend = main_pend;
 	      continue;
 	    }
-#endif
 	  /* If this is the end of the main regexp, we are done.  */
 	  break;
 	}
@@ -2569,7 +1976,6 @@ regex_compile (re_char *pattern, size_t size,
 
       switch (c)
 	{
-#ifdef emacs
 	case ' ':
 	  {
 	    re_char *p1 = p;
@@ -2602,7 +2008,6 @@ regex_compile (re_char *pattern, size_t size,
 	    pend = p + strlen (whitespace_regexp);
 	    break;
 	  }
-#endif
 
 	case '^':
 	  {
@@ -2653,8 +2058,8 @@ regex_compile (re_char *pattern, size_t size,
 
 	  {
 	    /* 1 means zero (many) matches is allowed.  */
-	    boolean zero_times_ok = 0, many_times_ok = 0;
-	    boolean greedy = 1;
+	    bool zero_times_ok = false, many_times_ok = false;
+	    bool greedy = true;
 
 	    /* If there is a sequence of repetition chars, collapse it
 	       down to just one (the right one).  We can't combine
@@ -2665,7 +2070,7 @@ regex_compile (re_char *pattern, size_t size,
 	      {
 		if ((syntax & RE_FRUGAL)
 		    && c == '?' && (zero_times_ok || many_times_ok))
-		  greedy = 0;
+		  greedy = false;
 		else
 		  {
 		    zero_times_ok |= c != '+';
@@ -2704,13 +2109,13 @@ regex_compile (re_char *pattern, size_t size,
 	      {
 		if (many_times_ok)
 		  {
-		    boolean simple = skip_one_char (laststart) == b;
+		    bool simple = skip_one_char (laststart) == b;
 		    size_t startoffset = 0;
 		    re_opcode_t ofj =
 		      /* Check if the loop can match the empty string.  */
 		      (simple || !analyze_first (laststart, b, NULL, 0))
 		      ? on_failure_jump : on_failure_jump_loop;
-		    assert (skip_one_char (laststart) <= b);
+		    eassert (skip_one_char (laststart) <= b);
 
 		    if (!zero_times_ok && simple)
 		      { /* Since simple * loops can be made faster by using
@@ -2743,7 +2148,7 @@ regex_compile (re_char *pattern, size_t size,
 		else
 		  {
 		    /* A simple ? pattern.  */
-		    assert (zero_times_ok);
+		    eassert (zero_times_ok);
 		    GET_BUFFER_SPACE (3);
 		    INSERT_JUMP (on_failure_jump, laststart, b + 3);
 		    b += 3;
@@ -2755,7 +2160,7 @@ regex_compile (re_char *pattern, size_t size,
 		GET_BUFFER_SPACE (7); /* We might use less.  */
 		if (many_times_ok)
 		  {
-		    boolean emptyp = analyze_first (laststart, b, NULL, 0);
+		    bool emptyp = analyze_first (laststart, b, NULL, 0);
 
 		    /* The non-greedy multiple match looks like
 		       a repeat..until: we only need a conditional jump
@@ -2830,10 +2235,9 @@ regex_compile (re_char *pattern, size_t size,
 	    /* Read in characters and ranges, setting map bits.  */
 	    for (;;)
 	      {
-		boolean escaped_char = false;
 		const unsigned char *p2 = p;
 		re_wctype_t cc;
-		re_wchar_t ch;
+		int ch;
 
 		if (p == pend) FREE_STACK_RETURN (REG_EBRACK);
 
@@ -2848,15 +2252,6 @@ regex_compile (re_char *pattern, size_t size,
 		    if (p == pend)
 		      FREE_STACK_RETURN (REG_EBRACK);
 
-#ifndef emacs
-		    for (ch = 0; ch < (1 << BYTEWIDTH); ++ch)
-		      if (re_iswctype (btowc (ch), cc))
-			{
-			  c = TRANSLATE (ch);
-			  if (c < (1 << BYTEWIDTH))
-			    SET_LIST_BIT (c);
-			}
-#else  /* emacs */
 		    /* Most character classes in a multibyte match just set
 		       a flag.  Exceptions are is_blank, is_digit, is_cntrl, and
 		       is_xdigit, since they can only match ASCII characters.
@@ -2883,7 +2278,7 @@ regex_compile (re_char *pattern, size_t size,
 			}
 		    SET_RANGE_TABLE_WORK_AREA_BIT
 		      (range_table_work, re_wctype_to_bit (cc));
-#endif	/* emacs */
+
 		    /* In most cases the matching rule for char classes only
 		       uses the syntax table for multibyte chars, so that the
 		       content of the syntax-table is not hardcoded in the
@@ -2907,7 +2302,6 @@ regex_compile (re_char *pattern, size_t size,
 		    if (p == pend) FREE_STACK_RETURN (REG_EESCAPE);
 
 		    PATFETCH (c);
-		    escaped_char = true;
 		  }
 		else
 		  {
@@ -2926,13 +2320,12 @@ regex_compile (re_char *pattern, size_t size,
 
 		    /* Fetch the character which ends the range. */
 		    PATFETCH (c1);
-#ifdef emacs
+
 		    if (CHAR_BYTE8_P (c1)
 			&& ! ASCII_CHAR_P (c) && ! CHAR_BYTE8_P (c))
 		      /* Treat the range from a multibyte character to
 			 raw-byte character as empty.  */
 		      c = c1 + 1;
-#endif	/* emacs */
 		  }
 		else
 		  /* Range from C to C. */
@@ -2946,15 +2339,6 @@ regex_compile (re_char *pattern, size_t size,
 		  }
 		else
 		  {
-#ifndef emacs
-		    /* Set the range into bitmap */
-		    for (; c <= c1; c++)
-		      {
-			ch = TRANSLATE (c);
-			if (ch < (1 << BYTEWIDTH))
-			  SET_LIST_BIT (ch);
-		      }
-#else  /* emacs */
 		    if (c < 128)
 		      {
 			ch = min (127, c1);
@@ -2981,7 +2365,6 @@ regex_compile (re_char *pattern, size_t size,
 			    SETUP_UNIBYTE_RANGE (range_table_work, c, c1);
 			  }
 		      }
-#endif /* emacs */
 		  }
 	      }
 
@@ -3006,8 +2389,7 @@ regex_compile (re_char *pattern, size_t size,
 		/* Indicate the existence of range table.  */
 		laststart[1] |= 0x80;
 
-		/* Store the character class flag bits into the range table.
-		   If not in emacs, these flag bits are always 0.  */
+		/* Store the character class flag bits into the range table.  */
 		*b++ = RANGE_TABLE_WORK_BITS (range_table_work) & 0xff;
 		*b++ = RANGE_TABLE_WORK_BITS (range_table_work) >> 8;
 
@@ -3126,8 +2508,6 @@ regex_compile (re_char *pattern, size_t size,
 		  {
 		    RETALLOC (compile_stack.stack, compile_stack.size << 1,
 			      compile_stack_elt_t);
-		    if (compile_stack.stack == NULL) return REG_ESPACE;
-
 		    compile_stack.size <<= 1;
 		  }
 
@@ -3183,7 +2563,7 @@ regex_compile (re_char *pattern, size_t size,
 
 	      /* Since we just checked for an empty stack above, this
 		 ``can't happen''.  */
-	      assert (compile_stack.avail != 0);
+	      eassert (compile_stack.avail != 0);
 	      {
 		/* We don't just want to restore into `regnum', because
 		   later groups should continue to be numbered higher,
@@ -3409,7 +2789,7 @@ regex_compile (re_char *pattern, size_t size,
 
 	    unfetch_interval:
 	      /* If an invalid interval, match the characters as literals.  */
-	       assert (beg_interval);
+	       eassert (beg_interval);
 	       p = beg_interval;
 	       beg_interval = NULL;
 
@@ -3418,13 +2798,12 @@ regex_compile (re_char *pattern, size_t size,
 
 	       if (!(syntax & RE_NO_BK_BRACES))
 		 {
-		   assert (p > pattern && p[-1] == '\\');
+		   eassert (p > pattern && p[-1] == '\\');
 		   goto normal_backslash;
 		 }
 	       else
 		 goto normal_char;
 
-#ifdef emacs
 	    case '=':
 	      laststart = b;
 	      BUF_PUSH (at_dot);
@@ -3453,8 +2832,6 @@ regex_compile (re_char *pattern, size_t size,
 	      PATFETCH (c);
 	      BUF_PUSH_2 (notcategoryspec, c);
 	      break;
-#endif /* emacs */
-
 
 	    case 'w':
 	      if (syntax & RE_NO_GNU_OPS)
@@ -3606,7 +2983,7 @@ regex_compile (re_char *pattern, size_t size,
 		c1 = RE_CHAR_TO_MULTIBYTE (c);
 		if (! CHAR_BYTE8_P (c1))
 		  {
-		    re_wchar_t c2 = TRANSLATE (c1);
+		    int c2 = TRANSLATE (c1);
 
 		    if (c1 != c2 && (c1 = RE_CHAR_TO_UNIBYTE (c2)) >= 0)
 		      c = c1;
@@ -3637,41 +3014,18 @@ regex_compile (re_char *pattern, size_t size,
   /* We have succeeded; set the length of the buffer.  */
   bufp->used = b - bufp->buffer;
 
-#ifdef DEBUG
-  if (debug > 0)
+#ifdef REGEX_EMACS_DEBUG
+  if (regex_emacs_debug > 0)
     {
       re_compile_fastmap (bufp);
       DEBUG_PRINT ("\nCompiled pattern: \n");
       print_compiled_pattern (bufp);
     }
-  debug--;
-#endif /* DEBUG */
-
-#ifndef MATCH_MAY_ALLOCATE
-  /* Initialize the failure stack to the largest possible stack.  This
-     isn't necessary unless we're trying to avoid calling alloca in
-     the search and match routines.  */
-  {
-    int num_regs = bufp->re_nsub + 1;
-
-    if (fail_stack.size < emacs_re_max_failures * TYPICAL_FAILURE_SIZE)
-      {
-	fail_stack.size = emacs_re_max_failures * TYPICAL_FAILURE_SIZE;
-	falk_stack.stack = realloc (fail_stack.stack,
-				    fail_stack.size * sizeof *falk_stack.stack);
-      }
-
-    regex_grow_registers (num_regs);
-  }
-#endif /* not MATCH_MAY_ALLOCATE */
+  regex_emacs_debug--;
+#endif
 
   FREE_STACK_RETURN (REG_NOERROR);
 
-#ifdef emacs
-# undef syntax
-#else
-# undef posix_backtracking
-#endif
 } /* regex_compile */
 
 /* Subroutines for `regex_compile'.  */
@@ -3732,11 +3086,11 @@ insert_op2 (re_opcode_t op, unsigned char *loc, int arg1, int arg2, unsigned cha
    after an alternative or a begin-subexpression.  We assume there is at
    least one character before the ^.  */
 
-static boolean
+static bool
 at_begline_loc_p (re_char *pattern, re_char *p, reg_syntax_t syntax)
 {
   re_char *prev = p - 2;
-  boolean odd_backslashes;
+  bool odd_backslashes;
 
   /* After a subexpression?  */
   if (*prev == '(')
@@ -3773,11 +3127,11 @@ at_begline_loc_p (re_char *pattern, re_char *p, reg_syntax_t syntax)
 /* The dual of at_begline_loc_p.  This one is for $.  We assume there is
    at least one character after the $, i.e., `P < PEND'.  */
 
-static boolean
+static bool
 at_endline_loc_p (re_char *p, re_char *pend, reg_syntax_t syntax)
 {
   re_char *next = p;
-  boolean next_backslash = *next == '\\';
+  bool next_backslash = *next == '\\';
   re_char *next_next = p + 1 < pend ? p + 1 : 0;
 
   return
@@ -3793,10 +3147,10 @@ at_endline_loc_p (re_char *p, re_char *pend, reg_syntax_t syntax)
 /* Returns true if REGNUM is in one of COMPILE_STACK's elements and
    false if it's not.  */
 
-static boolean
+static bool
 group_in_compile_stack (compile_stack_type compile_stack, regnum_t regnum)
 {
-  ssize_t this_element;
+  ptrdiff_t this_element;
 
   for (this_element = compile_stack.avail - 1;
        this_element >= 0;
@@ -3822,13 +3176,13 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 	       const int multibyte)
 {
   int j, k;
-  boolean not;
+  bool not;
 
   /* If all elements for base leading-codes in fastmap is set, this
      flag is set true.  */
-  boolean match_any_multibyte_characters = false;
+  bool match_any_multibyte_characters = false;
 
-  assert (p);
+  eassert (p);
 
   /* The loop below works as follows:
      - It has a working-list kept in the PATTERN_STACK and which basically
@@ -3919,7 +3273,6 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 	    if (!!(p[j / BYTEWIDTH] & (1 << (j % BYTEWIDTH))) ^ not)
 	      fastmap[j] = 1;
 
-#ifdef emacs
 	  if (/* Any leading code can possibly start a character
 		 which doesn't match the specified set of characters.  */
 	      not
@@ -3965,20 +3318,11 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 		    fastmap[j] = 1;
 		}
 	    }
-#endif
 	  break;
 
 	case syntaxspec:
 	case notsyntaxspec:
 	  if (!fastmap) break;
-#ifndef emacs
-	  not = (re_opcode_t)p[-1] == notsyntaxspec;
-	  k = *p++;
-	  for (j = 0; j < (1 << BYTEWIDTH); j++)
-	    if ((SYNTAX (j) == (enum syntaxcode) k) ^ not)
-	      fastmap[j] = 1;
-	  break;
-#else  /* emacs */
 	  /* This match depends on text properties.  These end with
 	     aborting optimizations.  */
 	  return -1;
@@ -4007,7 +3351,6 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 	 `continue'.  */
 
 	case at_dot:
-#endif /* !emacs */
 	case no_op:
 	case begline:
 	case endline:
@@ -4065,7 +3408,7 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 
 	case jump_n:
 	  /* This code simply does not properly handle forward jump_n.  */
-	  DEBUG_STATEMENT (EXTRACT_NUMBER (j, p); assert (j < 0));
+	  DEBUG_STATEMENT (EXTRACT_NUMBER (j, p); eassert (j < 0));
 	  p += 4;
 	  /* jump_n can either jump or fall through.  The (backward) jump
 	     case has already been handled, so we only need to look at the
@@ -4074,7 +3417,7 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 
 	case succeed_n:
 	  /* If N == 0, it should be an on_failure_jump_loop instead.  */
-	  DEBUG_STATEMENT (EXTRACT_NUMBER (j, p + 2); assert (j > 0));
+	  DEBUG_STATEMENT (EXTRACT_NUMBER (j, p + 2); eassert (j > 0));
 	  p += 4;
 	  /* We only care about one iteration of the loop, so we don't
 	     need to consider the case where this behaves like an
@@ -4125,13 +3468,13 @@ analyze_first (re_char *p, re_char *pend, char *fastmap,
 
    Returns 0 if we succeed, -2 if an internal error.   */
 
-int
+static void
 re_compile_fastmap (struct re_pattern_buffer *bufp)
 {
   char *fastmap = bufp->fastmap;
   int analysis;
 
-  assert (fastmap && bufp->buffer);
+  eassert (fastmap && bufp->buffer);
 
   memset (fastmap, 0, 1 << BYTEWIDTH);  /* Assume nothing's valid.  */
   bufp->fastmap_accurate = 1;	    /* It will be when we're done.  */
@@ -4139,14 +3482,13 @@ re_compile_fastmap (struct re_pattern_buffer *bufp)
   analysis = analyze_first (bufp->buffer, bufp->buffer + bufp->used,
 			    fastmap, RE_MULTIBYTE_P (bufp));
   bufp->can_be_null = (analysis != 0);
-  return 0;
 } /* re_compile_fastmap */
 
 /* 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.
+   be at least NUM_REGS * sizeof (ptrdiff_t) bytes long.
 
    If NUM_REGS == 0, then subsequent matches should allocate their own
    register data.
@@ -4156,7 +3498,8 @@ re_compile_fastmap (struct re_pattern_buffer *bufp)
    freeing the old data.  */
 
 void
-re_set_registers (struct re_pattern_buffer *bufp, struct re_registers *regs, unsigned int num_regs, regoff_t *starts, regoff_t *ends)
+re_set_registers (struct re_pattern_buffer *bufp, struct re_registers *regs,
+		  unsigned int num_regs, ptrdiff_t *starts, ptrdiff_t *ends)
 {
   if (num_regs)
     {
@@ -4172,21 +3515,19 @@ re_set_registers (struct re_pattern_buffer *bufp, struct re_registers *regs, uns
       regs->start = regs->end = 0;
     }
 }
-WEAK_ALIAS (__re_set_registers, re_set_registers)
 
 /* Searching routines.  */
 
 /* Like re_search_2, below, but only one string is specified, and
    doesn't let you say where to stop matching. */
 
-regoff_t
+ptrdiff_t
 re_search (struct re_pattern_buffer *bufp, const char *string, size_t size,
-	   ssize_t startpos, ssize_t range, struct re_registers *regs)
+	   ptrdiff_t startpos, ptrdiff_t range, struct re_registers *regs)
 {
   return re_search_2 (bufp, NULL, 0, string, size, startpos, range,
 		      regs, size);
 }
-WEAK_ALIAS (__re_search, re_search)
 
 /* Head address of virtual concatenation of string.  */
 #define HEAD_ADDR_VSTRING(P)		\
@@ -4217,21 +3558,21 @@ WEAK_ALIAS (__re_search, re_search)
    found, -1 if no match, or -2 if error (such as failure
    stack overflow).  */
 
-regoff_t
+ptrdiff_t
 re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
-	     const char *str2, size_t size2, ssize_t startpos, ssize_t range,
-	     struct re_registers *regs, ssize_t stop)
+	     const char *str2, size_t size2, ptrdiff_t startpos, ptrdiff_t range,
+	     struct re_registers *regs, ptrdiff_t stop)
 {
-  regoff_t val;
+  ptrdiff_t val;
   re_char *string1 = (re_char *) str1;
   re_char *string2 = (re_char *) str2;
-  register char *fastmap = bufp->fastmap;
-  register RE_TRANSLATE_TYPE translate = bufp->translate;
+  char *fastmap = bufp->fastmap;
+  Lisp_Object translate = bufp->translate;
   size_t total_size = size1 + size2;
-  ssize_t endpos = startpos + range;
-  boolean anchored_start;
+  ptrdiff_t endpos = startpos + range;
+  bool anchored_start;
   /* Nonzero if we are searching multibyte string.  */
-  const boolean multibyte = RE_TARGET_MULTIBYTE_P (bufp);
+  bool multibyte = RE_TARGET_MULTIBYTE_P (bufp);
 
   /* Check for out-of-range STARTPOS.  */
   if (startpos < 0 || startpos > total_size)
@@ -4255,7 +3596,6 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
 	range = 0;
     }
 
-#ifdef emacs
   /* In a forward search for something that starts with \=.
      don't keep searching past point.  */
   if (bufp->used > 0 && (re_opcode_t) bufp->buffer[0] == at_dot && range > 0)
@@ -4264,7 +3604,6 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
       if (range < 0)
 	return -1;
     }
-#endif /* emacs */
 
   /* Update the fastmap now if not correct already.  */
   if (fastmap && !bufp->fastmap_accurate)
@@ -4273,14 +3612,12 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
   /* See whether the pattern is anchored.  */
   anchored_start = (bufp->buffer[0] == begline);
 
-#ifdef emacs
   gl_state.object = re_match_object; /* Used by SYNTAX_TABLE_BYTE_TO_CHAR. */
   {
-    ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (POS_AS_IN_BUFFER (startpos));
+    ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (POS_AS_IN_BUFFER (startpos));
 
     SETUP_SYNTAX_TABLE_FOR_OBJECT (re_match_object, charpos, 1);
   }
-#endif
 
   /* Loop through the string, looking for a place to start matching.  */
   for (;;)
@@ -4303,14 +3640,14 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
 	 the first null string.  */
       if (fastmap && startpos < total_size && !bufp->can_be_null)
 	{
-	  register re_char *d;
-	  register re_wchar_t buf_ch;
+	  re_char *d;
+	  int buf_ch;
 
 	  d = POS_ADDR_VSTRING (startpos);
 
 	  if (range > 0)	/* Searching forwards.  */
 	    {
-	      ssize_t irange = range, lim = 0;
+	      ptrdiff_t irange = range, lim = 0;
 
 	      if (startpos < size1 && startpos + range >= size1)
 		lim = range - (size1 - startpos);
@@ -4335,11 +3672,9 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
 		  else
 		    while (range > lim)
 		      {
-			register re_wchar_t ch, translated;
-
 			buf_ch = *d;
-			ch = RE_CHAR_TO_MULTIBYTE (buf_ch);
-			translated = RE_TRANSLATE (translate, ch);
+			int ch = RE_CHAR_TO_MULTIBYTE (buf_ch);
+			int translated = RE_TRANSLATE (translate, ch);
 			if (translated != ch
 			    && (ch = RE_CHAR_TO_UNIBYTE (translated)) >= 0)
 			  buf_ch = ch;
@@ -4382,11 +3717,9 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
 		}
 	      else
 		{
-		  register re_wchar_t ch, translated;
-
 		  buf_ch = *d;
-		  ch = RE_CHAR_TO_MULTIBYTE (buf_ch);
-		  translated = TRANSLATE (ch);
+		  int ch = RE_CHAR_TO_MULTIBYTE (buf_ch);
+		  int translated = TRANSLATE (ch);
 		  if (translated != ch
 		      && (ch = RE_CHAR_TO_UNIBYTE (translated)) >= 0)
 		    buf_ch = ch;
@@ -4456,13 +3789,12 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
     }
   return -1;
 } /* re_search_2 */
-WEAK_ALIAS (__re_search_2, re_search_2)
 
 /* Declarations and macros for re_match_2.  */
 
 static int bcmp_translate (re_char *s1, re_char *s2,
-			   register ssize_t len,
-			   RE_TRANSLATE_TYPE translate,
+			   ptrdiff_t len,
+			   Lisp_Object translate,
 			   const int multibyte);
 
 /* This converts PTR, a pointer into one of the search strings `string1'
@@ -4530,29 +3862,6 @@ static int bcmp_translate (re_char *s1, re_char *s2,
    || WORDCHAR_P (d - 1) != WORDCHAR_P (d))
 #endif
 
-/* Free everything we malloc.  */
-#ifdef MATCH_MAY_ALLOCATE
-# define FREE_VAR(var)							\
-  do {									\
-    if (var)								\
-      {									\
-	REGEX_FREE (var);						\
-	var = NULL;							\
-      }									\
-  } while (0)
-# define FREE_VARIABLES()						\
-  do {									\
-    REGEX_FREE_STACK (fail_stack.stack);				\
-    FREE_VAR (regstart);						\
-    FREE_VAR (regend);							\
-    FREE_VAR (best_regstart);						\
-    FREE_VAR (best_regend);						\
-    REGEX_SAFE_FREE ();							\
-  } while (0)
-#else
-# define FREE_VARIABLES() ((void)0) /* Do nothing!  But inhibit gcc warning.  */
-#endif /* not MATCH_MAY_ALLOCATE */
-
 
 /* Optimization routines.  */
 
@@ -4585,10 +3894,8 @@ skip_one_char (re_char *p)
 
     case syntaxspec:
     case notsyntaxspec:
-#ifdef emacs
     case categoryspec:
     case notcategoryspec:
-#endif /* emacs */
       p++;
       break;
 
@@ -4622,7 +3929,7 @@ skip_noops (re_char *p, re_char *pend)
 	  return p;
 	}
     }
-  assert (p == pend);
+  eassert (p == pend);
   return p;
 }
 
@@ -4655,11 +3962,10 @@ execute_charset (re_char **pp, unsigned c, unsigned corig, bool unibyte)
 	  && p[2 + c / BYTEWIDTH] & (1 << (c % BYTEWIDTH)))
 	return !not;
     }
-#ifdef emacs
   else if (rtp)
     {
       int class_bits = CHARSET_RANGE_TABLE_BITS (p);
-      re_wchar_t range_start, range_end;
+      int range_start, range_end;
 
   /* Sort tests by the most commonly used classes with some adjustment to which
      tests are easiest to perform.  Take a look at comment in re_wctype_parse
@@ -4690,7 +3996,7 @@ execute_charset (re_char **pp, unsigned c, unsigned corig, bool unibyte)
 	    return !not;
 	}
     }
-#endif /* emacs */
+
   return not;
 }
 
@@ -4700,11 +4006,11 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
 		      re_char *p2)
 {
   re_opcode_t op2;
-  const boolean multibyte = RE_MULTIBYTE_P (bufp);
+  bool multibyte = RE_MULTIBYTE_P (bufp);
   unsigned char *pend = bufp->buffer + bufp->used;
 
-  assert (p1 >= bufp->buffer && p1 < pend
-	  && p2 >= bufp->buffer && p2 <= pend);
+  eassert (p1 >= bufp->buffer && p1 < pend
+	   && p2 >= bufp->buffer && p2 <= pend);
 
   /* Skip over open/close-group commands.
      If what follows this loop is a ...+ construct,
@@ -4715,8 +4021,8 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
      is only used in the case where p1 is a simple match operator.  */
   /* p1 = skip_noops (p1, pend); */
 
-  assert (p1 >= bufp->buffer && p1 < pend
-	  && p2 >= bufp->buffer && p2 <= pend);
+  eassert (p1 >= bufp->buffer && p1 < pend
+	   && p2 >= bufp->buffer && p2 <= pend);
 
   op2 = p2 == pend ? succeed : *p2;
 
@@ -4735,7 +4041,7 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
     case endline:
     case exactn:
       {
-	register re_wchar_t c
+	int c
 	  = (re_opcode_t) *p2 == endline ? '\n'
 	  : RE_STRING_CHAR (p2 + 2, multibyte);
 
@@ -4865,12 +4171,10 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
 	       || (re_opcode_t) *p1 == syntaxspec)
 	      && p1[1] == Sword);
 
-#ifdef emacs
     case categoryspec:
       return ((re_opcode_t) *p1 == notcategoryspec && p1[1] == p2[1]);
     case notcategoryspec:
       return ((re_opcode_t) *p1 == categoryspec && p1[1] == p2[1]);
-#endif /* emacs */
 
     default:
       ;
@@ -4883,20 +4187,6 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
 
 /* Matching routines.  */
 
-#ifndef emacs	/* Emacs never uses this.  */
-/* re_match is like re_match_2 except it takes only a single string.  */
-
-regoff_t
-re_match (struct re_pattern_buffer *bufp, const char *string,
-	  size_t size, ssize_t pos, struct re_registers *regs)
-{
-  regoff_t result = re_match_2_internal (bufp, NULL, 0, (re_char *) string,
-					 size, pos, regs, size);
-  return result;
-}
-WEAK_ALIAS (__re_match, re_match)
-#endif /* not emacs */
-
 /* re_match_2 matches the compiled pattern in BUFP against the
    the (virtual) concatenation of STRING1 and STRING2 (of length SIZE1
    and SIZE2, respectively).  We start matching at POS, and stop
@@ -4910,34 +4200,31 @@ WEAK_ALIAS (__re_match, re_match)
    failure stack overflowing).  Otherwise, we return the length of the
    matched substring.  */
 
-regoff_t
+ptrdiff_t
 re_match_2 (struct re_pattern_buffer *bufp, const char *string1,
-	    size_t size1, const char *string2, size_t size2, ssize_t pos,
-	    struct re_registers *regs, ssize_t stop)
+	    size_t size1, const char *string2, size_t size2, ptrdiff_t pos,
+	    struct re_registers *regs, ptrdiff_t stop)
 {
-  regoff_t result;
+  ptrdiff_t result;
 
-#ifdef emacs
-  ssize_t charpos;
+  ptrdiff_t charpos;
   gl_state.object = re_match_object; /* Used by SYNTAX_TABLE_BYTE_TO_CHAR. */
   charpos = SYNTAX_TABLE_BYTE_TO_CHAR (POS_AS_IN_BUFFER (pos));
   SETUP_SYNTAX_TABLE_FOR_OBJECT (re_match_object, charpos, 1);
-#endif
 
   result = re_match_2_internal (bufp, (re_char *) string1, size1,
 				(re_char *) string2, size2,
 				pos, regs, stop);
   return result;
 }
-WEAK_ALIAS (__re_match_2, re_match_2)

 /* This is a separate function so that we can force an alloca cleanup
    afterwards.  */
-static regoff_t
+static ptrdiff_t
 re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		     size_t size1, re_char *string2, size_t size2,
-		     ssize_t pos, struct re_registers *regs, ssize_t stop)
+		     ptrdiff_t pos, struct re_registers *regs, ptrdiff_t stop)
 {
   /* General temporaries.  */
   int mcnt;
@@ -4964,13 +4251,13 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
   re_char *pend = p + bufp->used;
 
   /* We use this to map every character in the string.	*/
-  RE_TRANSLATE_TYPE translate = bufp->translate;
+  Lisp_Object translate = bufp->translate;
 
-  /* Nonzero if BUFP is setup from a multibyte regex.  */
-  const boolean multibyte = RE_MULTIBYTE_P (bufp);
+  /* True if BUFP is setup from a multibyte regex.  */
+  bool multibyte = RE_MULTIBYTE_P (bufp);
 
-  /* Nonzero if STRING1/STRING2 are multibyte.  */
-  const boolean target_multibyte = RE_TARGET_MULTIBYTE_P (bufp);
+  /* True if STRING1/STRING2 are multibyte.  */
+  bool target_multibyte = RE_TARGET_MULTIBYTE_P (bufp);
 
   /* Failure point stack.  Each place that can handle a failure further
      down the line pushes a failure point on this stack.  It consists of
@@ -4979,19 +4266,11 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
      registers, and, finally, two char *'s.  The first char * is where
      to resume scanning the pattern; the second one is where to resume
      scanning the strings.  */
-#ifdef MATCH_MAY_ALLOCATE /* otherwise, this is global.  */
   fail_stack_type fail_stack;
-#endif
 #ifdef DEBUG_COMPILES_ARGUMENTS
   unsigned nfailure_points_pushed = 0, nfailure_points_popped = 0;
 #endif
 
-#if defined REL_ALLOC && defined REGEX_MALLOC
-  /* This holds the pointer to the failure stack, when
-     it is allocated relocatably.  */
-  fail_stack_elt_t *failure_stack_ptr;
-#endif
-
   /* We fill all the registers internally, independent of what we
      return, for use in backreferences.  The number here includes
      an element for register zero.  */
@@ -5004,18 +4283,14 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
      matching and the regnum-th regend points to right after where we
      stopped matching the regnum-th subexpression.  (The zeroth register
      keeps track of what the whole pattern matches.)  */
-#ifdef MATCH_MAY_ALLOCATE /* otherwise, these are global.  */
-  re_char **regstart, **regend;
-#endif
+  re_char **regstart UNINIT, **regend UNINIT;
 
   /* The following record the register info as found in the above
      variables when we find a match better than any we've seen before.
      This happens as we backtrack through the failure points, which in
      turn happens only if we have not yet matched the entire string. */
   unsigned best_regs_set = false;
-#ifdef MATCH_MAY_ALLOCATE /* otherwise, these are global.  */
-  re_char **best_regstart, **best_regend;
-#endif
+  re_char **best_regstart UNINIT, **best_regend UNINIT;
 
   /* Logically, this is `best_regend[0]'.  But we don't want to have to
      allocate space for that if we're not allocating space for anything
@@ -5038,7 +4313,6 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
   INIT_FAIL_STACK ();
 
-#ifdef MATCH_MAY_ALLOCATE
   /* Do not bother to initialize all the register variables if there are
      no groups in the pattern, as it takes a fair amount of time.  If
      there are groups, we include space for register 0 (the whole
@@ -5046,29 +4320,16 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
      array indexing.  We should fix this.  */
   if (bufp->re_nsub)
     {
-      regstart = REGEX_TALLOC (num_regs, re_char *);
-      regend = REGEX_TALLOC (num_regs, re_char *);
-      best_regstart = REGEX_TALLOC (num_regs, re_char *);
-      best_regend = REGEX_TALLOC (num_regs, re_char *);
-
-      if (!(regstart && regend && best_regstart && best_regend))
-	{
-	  FREE_VARIABLES ();
-	  return -2;
-	}
+      regstart = SAFE_ALLOCA (num_regs * 4 * sizeof *regstart);
+      regend = regstart + num_regs;
+      best_regstart = regend + num_regs;
+      best_regend = best_regstart + num_regs;
     }
-  else
-    {
-      /* We must initialize all our variables to NULL, so that
-	 `FREE_VARIABLES' doesn't try to free them.  */
-      regstart = regend = best_regstart = best_regend = NULL;
-    }
-#endif /* MATCH_MAY_ALLOCATE */
 
   /* The starting position is bogus.  */
   if (pos < 0 || pos > size1 + size2)
     {
-      FREE_VARIABLES ();
+      SAFE_FREE ();
       return -1;
     }
 
@@ -5228,13 +4489,8 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		     extra element beyond `num_regs' for the `-1' marker
 		     GNU code uses.  */
 		  regs->num_regs = max (RE_NREGS, num_regs + 1);
-		  regs->start = TALLOC (regs->num_regs, regoff_t);
-		  regs->end = TALLOC (regs->num_regs, regoff_t);
-		  if (regs->start == NULL || regs->end == NULL)
-		    {
-		      FREE_VARIABLES ();
-		      return -2;
-		    }
+		  regs->start = TALLOC (regs->num_regs, ptrdiff_t);
+		  regs->end = TALLOC (regs->num_regs, ptrdiff_t);
 		  bufp->regs_allocated = REGS_REALLOCATE;
 		}
 	      else if (bufp->regs_allocated == REGS_REALLOCATE)
@@ -5244,21 +4500,12 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		  if (regs->num_regs < num_regs + 1)
 		    {
 		      regs->num_regs = num_regs + 1;
-		      RETALLOC (regs->start, regs->num_regs, regoff_t);
-		      RETALLOC (regs->end, regs->num_regs, regoff_t);
-		      if (regs->start == NULL || regs->end == NULL)
-			{
-			  FREE_VARIABLES ();
-			  return -2;
-			}
+		      RETALLOC (regs->start, regs->num_regs, ptrdiff_t);
+		      RETALLOC (regs->end, regs->num_regs, ptrdiff_t);
 		    }
 		}
 	      else
-		{
-		  /* These braces fend off a "empty body in an else-statement"
-		     warning under GCC when assert expands to nothing.  */
-		  assert (bufp->regs_allocated == REGS_FIXED);
-		}
+		eassert (bufp->regs_allocated == REGS_FIXED);
 
 	      /* Convert the pointer data in `regstart' and `regend' to
 		 indices.  Register zero has to be set differently,
@@ -5300,7 +4547,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
 	  DEBUG_PRINT ("Returning %td from re_match_2.\n", dcnt);
 
-	  FREE_VARIABLES ();
+	  SAFE_FREE ();
 	  return dcnt;
 	}
 
@@ -5327,33 +4574,6 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  /* Remember the start point to rollback upon failure.  */
 	  dfail = d;
 
-#ifndef emacs
-	  /* This is written out as an if-else so we don't waste time
-	     testing `translate' inside the loop.  */
-	  if (RE_TRANSLATE_P (translate))
-	    do
-	      {
-		PREFETCH ();
-		if (RE_TRANSLATE (translate, *d) != *p++)
-		  {
-		    d = dfail;
-		    goto fail;
-		  }
-		d++;
-	      }
-	    while (--mcnt);
-	  else
-	    do
-	      {
-		PREFETCH ();
-		if (*d++ != *p++)
-		  {
-		    d = dfail;
-		    goto fail;
-		  }
-	      }
-	    while (--mcnt);
-#else  /* emacs */
 	  /* The cost of testing `translate' is comparatively small.  */
 	  if (target_multibyte)
 	    do
@@ -5418,7 +4638,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		d++;
 	      }
 	    while (--mcnt);
-#endif
+
 	  break;

@@ -5426,7 +4646,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	case anychar:
 	  {
 	    int buf_charlen;
-	    re_wchar_t buf_ch;
+	    int buf_ch;
 	    reg_syntax_t syntax;
 
 	    DEBUG_PRINT ("EXECUTING anychar.\n");
@@ -5436,11 +4656,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 						target_multibyte);
 	    buf_ch = TRANSLATE (buf_ch);
 
-#ifdef emacs
 	    syntax = RE_SYNTAX_EMACS;
-#else
-	    syntax = bufp->syntax;
-#endif
 
 	    if ((!(syntax & RE_DOT_NEWLINE) && buf_ch == '\n')
 		|| ((syntax & RE_DOT_NOT_NULL) && buf_ch == '\000'))
@@ -5459,7 +4675,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    int len;
 
 	    /* Whether matching against a unibyte character.  */
-	    boolean unibyte_char = false;
+	    bool unibyte_char = false;
 
 	    DEBUG_PRINT ("EXECUTING charset%s.\n",
 			 (re_opcode_t) *(p - 1) == charset_not ? "_not" : "");
@@ -5529,10 +4745,10 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	case stop_memory:
 	  DEBUG_PRINT ("EXECUTING stop_memory %d:\n", *p);
 
-	  assert (!REG_UNSET (regstart[*p]));
+	  eassert (!REG_UNSET (regstart[*p]));
 	  /* Strictly speaking, there should be code such as:
 
-		assert (REG_UNSET (regend[*p]));
+		eassert (REG_UNSET (regend[*p]));
 		PUSH_FAILURE_REGSTOP ((unsigned int)*p);
 
 	     But the only info to be pushed is regend[*p] and it is known to
@@ -5556,7 +4772,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	   followed by the numeric value of <digit> as the register number.  */
 	case duplicate:
 	  {
-	    register re_char *d2, *dend2;
+	    re_char *d2, *dend2;
 	    int regno = *p++;	/* Get which register to match against.  */
 	    DEBUG_PRINT ("EXECUTING duplicate %d.\n", regno);
 
@@ -5718,7 +4934,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  DEBUG_PRINT ("EXECUTING on_failure_jump_nastyloop %d (to %p):\n",
 		       mcnt, p + mcnt);
 
-	  assert ((re_opcode_t)p[-4] == no_op);
+	  eassert ((re_opcode_t)p[-4] == no_op);
 	  {
 	    int cycle = 0;
 	    CHECK_INFINITE_LOOP (p - 4, d);
@@ -5787,7 +5003,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		       mcnt, p + mcnt);
 	  {
 	    re_char *p1 = p; /* Next operation.  */
-	    /* Here, we discard `const', making re_match non-reentrant.  */
+	    /* Discard 'const', making re_search non-reentrant.  */
 	    unsigned char *p2 = (unsigned char *) p + mcnt; /* Jump dest.  */
 	    unsigned char *p3 = (unsigned char *) p - 3; /* opcode location.  */
 
@@ -5798,9 +5014,9 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
 	    /* Ensure this is indeed the trivial kind of loop
 	       we are expecting.  */
-	    assert (skip_one_char (p1) == p2 - 3);
-	    assert ((re_opcode_t) p2[-3] == jump && p2 + mcnt == p);
-	    DEBUG_STATEMENT (debug += 2);
+	    eassert (skip_one_char (p1) == p2 - 3);
+	    eassert ((re_opcode_t) p2[-3] == jump && p2 + mcnt == p);
+	    DEBUG_STATEMENT (regex_emacs_debug += 2);
 	    if (mutually_exclusive_p (bufp, p1, p2))
 	      {
 		/* Use a fast `on_failure_keep_string_jump' loop.  */
@@ -5814,7 +5030,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		DEBUG_PRINT ("  smart default => slow loop.\n");
 		*p3 = (unsigned char) on_failure_jump;
 	      }
-	    DEBUG_STATEMENT (debug -= 2);
+	    DEBUG_STATEMENT (regex_emacs_debug -= 2);
 	  }
 	  break;
 
@@ -5839,7 +5055,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  /* Originally, mcnt is how many times we HAVE to succeed.  */
 	  if (mcnt != 0)
 	    {
-	      /* Here, we discard `const', making re_match non-reentrant.  */
+	      /* Discard 'const', making re_search non-reentrant.  */
 	      unsigned char *p2 = (unsigned char *) p + 2; /* counter loc.  */
 	      mcnt--;
 	      p += 4;
@@ -5858,7 +5074,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  /* Originally, this is how many times we CAN jump.  */
 	  if (mcnt != 0)
 	    {
-	       /* Here, we discard `const', making re_match non-reentrant.  */
+	      /* Discard 'const', making re_search non-reentrant.  */
 	      unsigned char *p2 = (unsigned char *) p + 2; /* counter loc.  */
 	      mcnt--;
 	      PUSH_NUMBER (p2, mcnt);
@@ -5875,7 +5091,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    DEBUG_PRINT ("EXECUTING set_number_at.\n");
 
 	    EXTRACT_NUMBER_AND_INCR (mcnt, p);
-	    /* Here, we discard `const', making re_match non-reentrant.  */
+	    /* Discard 'const', making re_search non-reentrant.  */
 	    p2 = (unsigned char *) p + mcnt;
 	    /* Signedness doesn't matter since we only copy MCNT's bits.  */
 	    EXTRACT_NUMBER_AND_INCR (mcnt, p);
@@ -5887,7 +5103,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	case wordbound:
 	case notwordbound:
 	  {
-	    boolean not = (re_opcode_t) *(p - 1) == notwordbound;
+	    bool not = (re_opcode_t) *(p - 1) == notwordbound;
 	    DEBUG_PRINT ("EXECUTING %swordbound.\n", not ? "not" : "");
 
 	    /* We SUCCEED (or FAIL) in one of the following cases: */
@@ -5899,19 +5115,15 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	      {
 		/* C1 is the character before D, S1 is the syntax of C1, C2
 		   is the character at D, and S2 is the syntax of C2.  */
-		re_wchar_t c1, c2;
+		int c1, c2;
 		int s1, s2;
 		int dummy;
-#ifdef emacs
-		ssize_t offset = PTR_TO_OFFSET (d - 1);
-		ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+		ptrdiff_t offset = PTR_TO_OFFSET (d - 1);
+		ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 		UPDATE_SYNTAX_TABLE (charpos);
-#endif
 		GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
 		s1 = SYNTAX (c1);
-#ifdef emacs
 		UPDATE_SYNTAX_TABLE_FORWARD (charpos + 1);
-#endif
 		PREFETCH_NOLIMIT ();
 		GET_CHAR_AFTER (c2, d, dummy);
 		s2 = SYNTAX (c2);
@@ -5941,14 +5153,12 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    {
 	      /* C1 is the character before D, S1 is the syntax of C1, C2
 		 is the character at D, and S2 is the syntax of C2.  */
-	      re_wchar_t c1, c2;
+	      int c1, c2;
 	      int s1, s2;
 	      int dummy;
-#ifdef emacs
-	      ssize_t offset = PTR_TO_OFFSET (d);
-	      ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+	      ptrdiff_t offset = PTR_TO_OFFSET (d);
+	      ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 	      UPDATE_SYNTAX_TABLE (charpos);
-#endif
 	      PREFETCH ();
 	      GET_CHAR_AFTER (c2, d, dummy);
 	      s2 = SYNTAX (c2);
@@ -5961,9 +5171,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	      if (!AT_STRINGS_BEG (d))
 		{
 		  GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
-#ifdef emacs
 		  UPDATE_SYNTAX_TABLE_BACKWARD (charpos - 1);
-#endif
 		  s1 = SYNTAX (c1);
 
 		  /* ... and S1 is Sword, and WORD_BOUNDARY_P (C1, C2)
@@ -5986,14 +5194,12 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    {
 	      /* C1 is the character before D, S1 is the syntax of C1, C2
 		 is the character at D, and S2 is the syntax of C2.  */
-	      re_wchar_t c1, c2;
+	      int c1, c2;
 	      int s1, s2;
 	      int dummy;
-#ifdef emacs
-	      ssize_t offset = PTR_TO_OFFSET (d) - 1;
-	      ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+	      ptrdiff_t offset = PTR_TO_OFFSET (d) - 1;
+	      ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 	      UPDATE_SYNTAX_TABLE (charpos);
-#endif
 	      GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
 	      s1 = SYNTAX (c1);
 
@@ -6006,9 +5212,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		{
 		  PREFETCH_NOLIMIT ();
 		  GET_CHAR_AFTER (c2, d, dummy);
-#ifdef emacs
 		  UPDATE_SYNTAX_TABLE_FORWARD (charpos);
-#endif
 		  s2 = SYNTAX (c2);
 
 		  /* ... and S2 is Sword, and WORD_BOUNDARY_P (C1, C2)
@@ -6031,13 +5235,11 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    {
 	      /* C1 is the character before D, S1 is the syntax of C1, C2
 		 is the character at D, and S2 is the syntax of C2.  */
-	      re_wchar_t c1, c2;
+	      int c1, c2;
 	      int s1, s2;
-#ifdef emacs
-	      ssize_t offset = PTR_TO_OFFSET (d);
-	      ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+	      ptrdiff_t offset = PTR_TO_OFFSET (d);
+	      ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 	      UPDATE_SYNTAX_TABLE (charpos);
-#endif
 	      PREFETCH ();
 	      c2 = RE_STRING_CHAR (d, target_multibyte);
 	      s2 = SYNTAX (c2);
@@ -6050,9 +5252,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	      if (!AT_STRINGS_BEG (d))
 		{
 		  GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
-#ifdef emacs
 		  UPDATE_SYNTAX_TABLE_BACKWARD (charpos - 1);
-#endif
 		  s1 = SYNTAX (c1);
 
 		  /* ... and S1 is Sword or Ssymbol.  */
@@ -6074,13 +5274,11 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    {
 	      /* C1 is the character before D, S1 is the syntax of C1, C2
 		 is the character at D, and S2 is the syntax of C2.  */
-	      re_wchar_t c1, c2;
+	      int c1, c2;
 	      int s1, s2;
-#ifdef emacs
-	      ssize_t offset = PTR_TO_OFFSET (d) - 1;
-	      ssize_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+	      ptrdiff_t offset = PTR_TO_OFFSET (d) - 1;
+	      ptrdiff_t charpos = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 	      UPDATE_SYNTAX_TABLE (charpos);
-#endif
 	      GET_CHAR_BEFORE_2 (c1, d, string1, end1, string2, end2);
 	      s1 = SYNTAX (c1);
 
@@ -6093,9 +5291,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		{
 		  PREFETCH_NOLIMIT ();
 		  c2 = RE_STRING_CHAR (d, target_multibyte);
-#ifdef emacs
 		  UPDATE_SYNTAX_TABLE_FORWARD (charpos + 1);
-#endif
 		  s2 = SYNTAX (c2);
 
 		  /* ... and S2 is Sword or Ssymbol.  */
@@ -6108,21 +5304,19 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	case syntaxspec:
 	case notsyntaxspec:
 	  {
-	    boolean not = (re_opcode_t) *(p - 1) == notsyntaxspec;
+	    bool not = (re_opcode_t) *(p - 1) == notsyntaxspec;
 	    mcnt = *p++;
 	    DEBUG_PRINT ("EXECUTING %ssyntaxspec %d.\n", not ? "not" : "",
 			 mcnt);
 	    PREFETCH ();
-#ifdef emacs
 	    {
-	      ssize_t offset = PTR_TO_OFFSET (d);
-	      ssize_t pos1 = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
+	      ptrdiff_t offset = PTR_TO_OFFSET (d);
+	      ptrdiff_t pos1 = SYNTAX_TABLE_BYTE_TO_CHAR (offset);
 	      UPDATE_SYNTAX_TABLE (pos1);
 	    }
-#endif
 	    {
 	      int len;
-	      re_wchar_t c;
+	      int c;
 
 	      GET_CHAR_AFTER (c, d, len);
 	      if ((SYNTAX (c) != (enum syntaxcode) mcnt) ^ not)
@@ -6132,7 +5326,6 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  }
 	  break;
 
-#ifdef emacs
 	case at_dot:
 	  DEBUG_PRINT ("EXECUTING at_dot.\n");
 	  if (PTR_BYTE_POS (d) != PT_BYTE)
@@ -6142,7 +5335,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	case categoryspec:
 	case notcategoryspec:
 	  {
-	    boolean not = (re_opcode_t) *(p - 1) == notcategoryspec;
+	    bool not = (re_opcode_t) *(p - 1) == notcategoryspec;
 	    mcnt = *p++;
 	    DEBUG_PRINT ("EXECUTING %scategoryspec %d.\n",
 			 not ? "not" : "", mcnt);
@@ -6150,7 +5343,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
 	    {
 	      int len;
-	      re_wchar_t c;
+	      int c;
 	      GET_CHAR_AFTER (c, d, len);
 	      if ((!CHAR_HAS_CATEGORY (c, mcnt)) ^ not)
 		goto fail;
@@ -6159,8 +5352,6 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  }
 	  break;
 
-#endif /* emacs */
-
 	default:
 	  abort ();
 	}
@@ -6179,11 +5370,11 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  switch (*pat++)
 	    {
 	    case on_failure_keep_string_jump:
-	      assert (str == NULL);
+	      eassert (str == NULL);
 	      goto continue_failure_jump;
 
 	    case on_failure_jump_nastyloop:
-	      assert ((re_opcode_t)pat[-2] == no_op);
+	      eassert ((re_opcode_t)pat[-2] == no_op);
 	      PUSH_FAILURE_POINT (pat - 2, str);
 	      FALLTHROUGH;
 	    case on_failure_jump_loop:
@@ -6203,7 +5394,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	      abort ();
 	    }
 
-	  assert (p >= bufp->buffer && p <= pend);
+	  eassert (p >= bufp->buffer && p <= pend);
 
 	  if (d >= string1 && d <= end1)
 	    dend = end_match_1;
@@ -6215,7 +5406,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
   if (best_regs_set)
     goto restore_best_regs;
 
-  FREE_VARIABLES ();
+  SAFE_FREE ();
 
   return -1;	/* Failure to match.  */
 }
@@ -6226,8 +5417,8 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
    bytes; nonzero otherwise.  */
 
 static int
-bcmp_translate (re_char *s1, re_char *s2, ssize_t len,
-		RE_TRANSLATE_TYPE translate, const int target_multibyte)
+bcmp_translate (re_char *s1, re_char *s2, ptrdiff_t len,
+		Lisp_Object translate, int target_multibyte)
 {
   re_char *p1 = s1, *p2 = s2;
   re_char *p1_end = s1 + len;
@@ -6238,7 +5429,7 @@ bcmp_translate (re_char *s1, re_char *s2, ssize_t len,
   while (p1 < p1_end && p2 < p2_end)
     {
       int p1_charlen, p2_charlen;
-      re_wchar_t p1_ch, p2_ch;
+      int p1_ch, p2_ch;
 
       GET_CHAR_AFTER (p1_ch, p1, p1_charlen);
       GET_CHAR_AFTER (p2_ch, p2, p2_charlen);
@@ -6269,9 +5460,7 @@ bcmp_translate (re_char *s1, re_char *s2, ssize_t len,
 
 const char *
 re_compile_pattern (const char *pattern, size_t length,
-#ifdef emacs
 		    bool posix_backtracking, const char *whitespace_regexp,
-#endif
 		    struct re_pattern_buffer *bufp)
 {
   reg_errcode_t ret;
@@ -6281,334 +5470,16 @@ re_compile_pattern (const char *pattern, size_t length,
   bufp->regs_allocated = REGS_UNALLOCATED;
 
   /* And GNU code determines whether or not to get register information
-     by passing null for the REGS argument to re_match, etc., not by
+     by passing null for the REGS argument to re_search, etc., not by
      setting no_sub.  */
   bufp->no_sub = 0;
 
   ret = regex_compile ((re_char *) pattern, length,
-#ifdef emacs
 		       posix_backtracking,
 		       whitespace_regexp,
-#else
-		       re_syntax_options,
-#endif
 		       bufp);
 
   if (!ret)
     return NULL;
-  return gettext (re_error_msgid[(int) ret]);
-}
-WEAK_ALIAS (__re_compile_pattern, re_compile_pattern)
-
-/* 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 below without link errors.  */
-weak_function
-# endif
-re_comp (const char *s)
-{
-  reg_errcode_t ret;
-
-  if (!s)
-    {
-      if (!re_comp_buf.buffer)
-	/* Yes, we're discarding `const' here if !HAVE_LIBINTL.  */
-	return (char *) gettext ("No previous regular expression");
-      return 0;
-    }
-
-  if (!re_comp_buf.buffer)
-    {
-      re_comp_buf.buffer = malloc (200);
-      if (re_comp_buf.buffer == NULL)
-	/* Yes, we're discarding `const' here if !HAVE_LIBINTL.  */
-	return (char *) gettext (re_error_msgid[(int) REG_ESPACE]);
-      re_comp_buf.allocated = 200;
-
-      re_comp_buf.fastmap = malloc (1 << BYTEWIDTH);
-      if (re_comp_buf.fastmap == NULL)
-	/* Yes, we're discarding `const' here if !HAVE_LIBINTL.  */
-	return (char *) gettext (re_error_msgid[(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.  */
-
-  ret = regex_compile (s, strlen (s), re_syntax_options, &re_comp_buf);
-
-  if (!ret)
-    return NULL;
-
-  /* Yes, we're discarding `const' here if !HAVE_LIBINTL.  */
-  return (char *) gettext (re_error_msgid[(int) ret]);
-}
-
-
-int
-# ifdef _LIBC
-weak_function
-# endif
-re_exec (const char *s)
-{
-  const size_t len = strlen (s);
-  return re_search (&re_comp_buf, s, len, 0, len, 0) >= 0;
+  return re_error_msgid[ret];
 }
-#endif /* _REGEX_RE_COMP */
-
-/* POSIX.2 functions.  Don't define these for Emacs.  */
-
-#ifndef emacs
-
-/* 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;
-     `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-emacs.h for
-   the return codes and their meanings.)  */
-
-reg_errcode_t
-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;
-
-  /* regex_compile will allocate the space for the compiled pattern.  */
-  preg->buffer = 0;
-  preg->allocated = 0;
-  preg->used = 0;
-
-  /* Try to allocate space for the fastmap.  */
-  preg->fastmap = malloc (1 << BYTEWIDTH);
-
-  if (cflags & REG_ICASE)
-    {
-      unsigned i;
-
-      preg->translate = malloc (CHAR_SET_SIZE * sizeof *preg->translate);
-      if (preg->translate == NULL)
-	return (int) REG_ESPACE;
-
-      /* Map uppercase characters to corresponding lowercase ones.  */
-      for (i = 0; i < CHAR_SET_SIZE; i++)
-	preg->translate[i] = ISUPPER (i) ? TOLOWER (i) : i;
-    }
-  else
-    preg->translate = NULL;
-
-  /* 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;
-    }
-  else
-    syntax |= RE_NO_NEWLINE_ANCHOR;
-
-  preg->no_sub = !!(cflags & REG_NOSUB);
-
-  /* POSIX says a null character in the pattern terminates it, so we
-     can use strlen here in compiling the pattern.  */
-  ret = regex_compile ((re_char *) pattern, strlen (pattern), syntax, preg);
-
-  /* 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;
-
-  if (ret == REG_NOERROR && preg->fastmap)
-    { /* Compute the fastmap now, since regexec cannot modify the pattern
-	 buffer.  */
-      re_compile_fastmap (preg);
-      if (preg->can_be_null)
-	{ /* The fastmap can't be used anyway.  */
-	  free (preg->fastmap);
-	  preg->fastmap = NULL;
-	}
-    }
-  return ret;
-}
-WEAK_ALIAS (__regcomp, regcomp)
-
-
-/* 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.  */
-
-reg_errcode_t
-regexec (const regex_t *_Restrict_ preg, const char *_Restrict_ string,
-	 size_t nmatch, regmatch_t pmatch[_Restrict_arr_], int eflags)
-{
-  regoff_t ret;
-  struct re_registers regs;
-  regex_t private_preg;
-  size_t len = strlen (string);
-  boolean want_reg_info = !preg->no_sub && nmatch > 0 && pmatch;
-
-  private_preg = *preg;
-
-  private_preg.not_bol = !!(eflags & REG_NOTBOL);
-  private_preg.not_eol = !!(eflags & REG_NOTEOL);
-
-  /* The user has told us exactly how many registers to return
-     information about, via `nmatch'.  We have to pass that on to the
-     matching routines.  */
-  private_preg.regs_allocated = REGS_FIXED;
-
-  if (want_reg_info)
-    {
-      regs.num_regs = nmatch;
-      regs.start = TALLOC (nmatch * 2, regoff_t);
-      if (regs.start == NULL)
-	return REG_NOMATCH;
-      regs.end = regs.start + nmatch;
-    }
-
-  /* Instead of using not_eol to implement REG_NOTEOL, we could simply
-     pass (&private_preg, string, len + 1, 0, len, ...) pretending the string
-     was a little bit longer but still only matching the real part.
-     This works because the `endline' will check for a '\n' and will find a
-     '\0', correctly deciding that this is not the end of a line.
-     But it doesn't work out so nicely for REG_NOTBOL, since we don't have
-     a convenient '\0' there.  For all we know, the string could be preceded
-     by '\n' which would throw things off.  */
-
-  /* Perform the searching operation.  */
-  ret = re_search (&private_preg, string, len,
-		   /* start: */ 0, /* range: */ len,
-		   want_reg_info ? &regs : 0);
-
-  /* Copy the register information to the POSIX structure.  */
-  if (want_reg_info)
-    {
-      if (ret >= 0)
-	{
-	  unsigned r;
-
-	  for (r = 0; r < nmatch; r++)
-	    {
-	      pmatch[r].rm_so = regs.start[r];
-	      pmatch[r].rm_eo = regs.end[r];
-	    }
-	}
-
-      /* If we needed the temporary register info, free the space now.  */
-      free (regs.start);
-    }
-
-  /* We want zero return to mean success, unlike `re_search'.  */
-  return ret >= 0 ? REG_NOERROR : REG_NOMATCH;
-}
-WEAK_ALIAS (__regexec, regexec)
-
-
-/* Returns a message corresponding to an error code, ERR_CODE, returned
-   from either regcomp or regexec.   We don't use PREG here.
-
-   ERR_CODE was previously called ERRCODE, but that name causes an
-   error with msvc8 compiler.  */
-
-size_t
-regerror (int err_code, const regex_t *preg, char *errbuf, size_t errbuf_size)
-{
-  const char *msg;
-  size_t msg_size;
-
-  if (err_code < 0
-      || err_code >= (sizeof (re_error_msgid) / sizeof (re_error_msgid[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[err_code]);
-
-  msg_size = strlen (msg) + 1; /* Includes the null.  */
-
-  if (errbuf_size != 0)
-    {
-      if (msg_size > errbuf_size)
-	{
-	  memcpy (errbuf, msg, errbuf_size - 1);
-	  errbuf[errbuf_size - 1] = 0;
-	}
-      else
-	strcpy (errbuf, msg);
-    }
-
-  return msg_size;
-}
-WEAK_ALIAS (__regerror, regerror)
-
-
-/* Free dynamically allocated space used by PREG.  */
-
-void
-regfree (regex_t *preg)
-{
-  free (preg->buffer);
-  preg->buffer = NULL;
-
-  preg->allocated = 0;
-  preg->used = 0;
-
-  free (preg->fastmap);
-  preg->fastmap = NULL;
-  preg->fastmap_accurate = 0;
-
-  free (preg->translate);
-  preg->translate = NULL;
-}
-WEAK_ALIAS (__regfree, regfree)
-
-#endif /* not emacs  */
diff --git a/src/regex-emacs.h b/src/regex-emacs.h
index 8a15e5793f..898c0f2aea 100644
--- a/src/regex-emacs.h
+++ b/src/regex-emacs.h
@@ -17,163 +17,24 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
-#ifndef _REGEX_H
-#define _REGEX_H 1
-
-#if defined emacs && (defined _REGEX_RE_COMP || defined _LIBC)
-/* We're not defining re_set_syntax and using a different prototype of
-   re_compile_pattern when building Emacs so fail compilation early with
-   a (somewhat helpful) error message when conflict is detected. */
-# error "_REGEX_RE_COMP nor _LIBC can be defined if emacs is defined."
-#endif
-
-#include <sys/types.h>
-
-/* Allow the use in C++ code.  */
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#if !defined _POSIX_C_SOURCE && !defined _POSIX_SOURCE && defined VMS
-/* VMS doesn't have `size_t' in <sys/types.h>, even though POSIX says it
-   should be there.  */
-# include <stddef.h>
-#endif
-
-/* The following bits are used to determine the regexp syntax we
-   recognize.  The set/not-set meanings where historically chosen so
-   that Emacs syntax had 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 reg_syntax_t;
-
-/* 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, then *?, +? and ?? match non greedily. */
-#define RE_FRUGAL (RE_NO_GNU_OPS << 1)
-
-/* If this bit is set, then (?:...) is treated as a shy group.  */
-#define RE_SHY_GROUPS (RE_FRUGAL << 1)
-
-/* If this bit is set, ^ and $ only match at beg/end of buffer.  */
-#define RE_NO_NEWLINE_ANCHOR (RE_SHY_GROUPS << 1)
-
-/* If this bit is set, turn on internal regex debugging.
-   If not set, and debugging was on, turn it off.
-   This only works if regex-emacs.c is compiled -DDEBUG.
-   We define this bit always, so that all that's needed to turn on
-   debugging is to recompile regex-emacs.c; the calling code can always have
-   this bit set, and it won't affect anything in the normal case. */
-#define RE_DEBUG (RE_NO_NEWLINE_ANCHOR << 1)
-
-/* 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 emacs
-# include "lisp.h"
+#ifndef EMACS_REGEX_H
+#define EMACS_REGEX_H 1
+
+#include <stddef.h>
+
+/* This is the structure we store register match data in.  See
+   regex.texinfo for a full description of what registers match.
+   Declare this before including lisp.h, since lisp.h (via thread.h)
+   uses struct re_registers.  */
+struct re_registers
+{
+  unsigned num_regs;
+  ptrdiff_t *start;
+  ptrdiff_t *end;
+};
+
+#include "lisp.h"
+
 /* In Emacs, this is the string or buffer in which we are matching.
    It is used for looking up syntax properties.
 
@@ -187,187 +48,24 @@ typedef unsigned long reg_syntax_t;
    and match functions.  These functions capture the current value of
    re_match_object into gl_state on entry.
 
-   TODO: once we get rid of the !emacs case in this code, turn into an
-   actual function parameter.  */
+   TODO: turn into an actual function parameter.  */
 extern Lisp_Object re_match_object;
-#endif
 
 /* Roughly the maximum number of failure points on the stack.  */
 extern size_t emacs_re_max_failures;
 
-#ifdef emacs
 /* Amount of memory that we can safely stack allocate.  */
 extern ptrdiff_t emacs_re_safe_alloca;
-#endif
-
-
-/* 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							\
-  (RE_CHAR_CLASSES | RE_INTERVALS | RE_SHY_GROUPS | RE_FRUGAL)
-
-#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_DEBUG)	\
-   & ~(RE_DOT_NOT_NULL | RE_INTERVALS | RE_CONTEXT_INDEP_OPS))
-
-#define RE_SYNTAX_POSIX_AWK						\
-  (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS		\
-   | RE_INTERVALS	    | RE_NO_GNU_OPS)
-
-#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)
-
-/* 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)
-
-/* 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
-/* Repeat counts are stored in opcodes as 2 byte integers.  This was
-   previously limited to 7fff because the parsing code uses signed
-   ints.  But Emacs only runs on 32 bit platforms anyway.  */
-#define RE_DUP_MAX (0xffff)
-
 
-/* 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)
-
-
-/* If any error codes are removed, changed, or added, update the
-   re_error_msg table in regex-emacs.c.  */
-typedef enum
-{
-#ifdef _XOPEN_SOURCE
-  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,		/* Not implemented.  */
-  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_ERANGEX,		/* Range striding over charsets.  */
-  REG_ESIZEBR           /* n or m too big in \{n,m\} */
-} reg_errcode_t;
 
-/* Use a type compatible with Emacs.  */
-#define RE_TRANSLATE_TYPE Lisp_Object
-#define RE_TRANSLATE(TBL, C) char_table_translate (TBL, C)
-#define RE_TRANSLATE_P(TBL) (!EQ (TBL, make_number (0)))
-
 /* 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 char *
-#endif
-
 struct re_pattern_buffer
 {
-/* [[[begin pattern_buffer]]] */
 	/* Space that holds the compiled pattern.  It is declared as
           `unsigned char *' because its elements are
            sometimes used as array indexes.  */
@@ -379,13 +77,9 @@ struct re_pattern_buffer
 	/* Number of bytes actually used in `buffer'.  */
   size_t used;
 
-#ifdef emacs
         /* Charset of unibyte characters at compiling time. */
   int charset_unibyte;
-#else
-        /* Syntax setting with which the pattern was compiled.  */
-  reg_syntax_t syntax;
-#endif
+
         /* 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.  */
@@ -395,7 +89,7 @@ struct re_pattern_buffer
            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 translate;
+  Lisp_Object translate;
 
 	/* Number of subexpressions found by the compiler.  */
   size_t re_nsub;
@@ -410,9 +104,6 @@ struct re_pattern_buffer
              for `max (RE_NREGS, re_nsub + 1)' groups.
            If REGS_REALLOCATE, reallocate space if necessary.
            If REGS_FIXED, use what's there.  */
-#define REGS_UNALLOCATED 0
-#define REGS_REALLOCATE 1
-#define REGS_FIXED 2
   unsigned regs_allocated : 2;
 
         /* Set to zero when `regex_compile' compiles a pattern; set to one
@@ -434,7 +125,6 @@ struct re_pattern_buffer
      so the compiled pattern is only valid for the current syntax table.  */
   unsigned used_syntax : 1;
 
-#ifdef emacs
   /* If true, multi-byte form in the regexp pattern should be
      recognized as a multibyte character.  */
   unsigned multibyte : 1;
@@ -442,72 +132,17 @@ struct re_pattern_buffer
   /* If true, multi-byte form in the target of match should be
      recognized as a multibyte character.  */
   unsigned target_multibyte : 1;
-#endif
-
-/* [[[end pattern_buffer]]] */
 };
-
-typedef struct re_pattern_buffer regex_t;
-
-/* POSIX 1003.1-2008 requires that regoff_t be at least as wide as
-   ptrdiff_t and ssize_t.  We don't know of any hosts where ptrdiff_t
-   is wider than ssize_t, so ssize_t is safe.  ptrdiff_t is not
-   necessarily visible here, so use ssize_t.  */
-typedef ssize_t regoff_t;
-
-
-/* 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
-
-
-/* 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.  */
 
-#ifndef emacs
-
-/* 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);
-
-#endif
-
 /* 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,
-#ifdef emacs
+extern const char *re_compile_pattern (const char *pattern, size_t length,
 				       bool posix_backtracking,
 				       const char *whitespace_regexp,
-#endif
-				       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);
+				       struct re_pattern_buffer *buffer);

 /* Search in the string STRING (with length LENGTH) for the pattern
@@ -515,42 +150,36 @@ extern int re_compile_fastmap (struct re_pattern_buffer *__buffer);
    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 regoff_t re_search (struct re_pattern_buffer *__buffer,
-			   const char *__string, size_t __length,
-			   ssize_t __start, ssize_t __range,
-			   struct re_registers *__regs);
+extern ptrdiff_t re_search (struct re_pattern_buffer *buffer,
+			   const char *string, size_t length,
+			   ptrdiff_t start, ptrdiff_t 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 regoff_t re_search_2 (struct re_pattern_buffer *__buffer,
-			     const char *__string1, size_t __length1,
-			     const char *__string2, size_t __length2,
-			     ssize_t __start, ssize_t __range,
-			     struct re_registers *__regs,
-			     ssize_t __stop);
+extern ptrdiff_t re_search_2 (struct re_pattern_buffer *buffer,
+			     const char *string1, size_t length1,
+			     const char *string2, size_t length2,
+			     ptrdiff_t start, ptrdiff_t range,
+			     struct re_registers *regs,
+			     ptrdiff_t stop);

-/* Like `re_search', but return how many characters in STRING the regexp
+/* Like 're_search_2', but return how many characters in STRING the regexp
    in BUFFER matched, starting at position START.  */
-extern regoff_t re_match (struct re_pattern_buffer *__buffer,
-			  const char *__string, size_t __length,
-			  ssize_t __start, struct re_registers *__regs);
-
-
-/* Relates to `re_match' as `re_search_2' relates to `re_search'.  */
-extern regoff_t re_match_2 (struct re_pattern_buffer *__buffer,
-			    const char *__string1, size_t __length1,
-			    const char *__string2, size_t __length2,
-			    ssize_t __start, struct re_registers *__regs,
-			    ssize_t __stop);
+extern ptrdiff_t re_match_2 (struct re_pattern_buffer *buffer,
+			    const char *string1, size_t length1,
+			    const char *string2, size_t length2,
+			    ptrdiff_t start, struct re_registers *regs,
+			    ptrdiff_t 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.
+   (ptrdiff_t)' bytes long.
 
    If NUM_REGS == 0, then subsequent matches should allocate their own
    register data.
@@ -558,83 +187,10 @@ extern regoff_t re_match_2 (struct re_pattern_buffer *__buffer,
    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 __num_regs,
-			      regoff_t *__starts, regoff_t *__ends);
-
-#if defined _REGEX_RE_COMP || defined _LIBC
-# 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".
-   Other compilers use __restrict, __restrict__, and _Restrict, and
-   'configure' might #define 'restrict' to those words, so pick a
-   different name.  */
-#ifndef _Restrict_
-# if 199901L <= __STDC_VERSION__
-#  define _Restrict_ restrict
-# elif 2 < __GNUC__ || (2 == __GNUC__ && 95 <= __GNUC_MINOR__)
-#  define _Restrict_ __restrict
-# else
-#  define _Restrict_
-# endif
-#endif
-/* gcc 3.1 and up support the [restrict] syntax.  Don't trust
-   sys/cdefs.h's definition of __restrict_arr, though, as it
-   mishandles gcc -ansi -pedantic.  */
-#ifndef _Restrict_arr_
-# if ((199901L <= __STDC_VERSION__					\
-       || ((3 < __GNUC__ || (3 == __GNUC__ && 1 <= __GNUC_MINOR__))	\
-	   && !defined __STRICT_ANSI__))					\
-      && !defined __GNUG__)
-#  define _Restrict_arr_ _Restrict_
-# else
-#  define _Restrict_arr_
-# endif
-#endif
-
-/* POSIX compatibility.  */
-extern reg_errcode_t regcomp (regex_t *_Restrict_ __preg,
-			      const char *_Restrict_ __pattern,
-			      int __cflags);
-
-extern reg_errcode_t regexec (const regex_t *_Restrict_ __preg,
-			      const char *_Restrict_ __string, size_t __nmatch,
-			      regmatch_t __pmatch[_Restrict_arr_],
-			      int __eflags);
-
-extern size_t regerror (int __errcode, const regex_t * __preg,
-			char *__errbuf, size_t __errbuf_size);
-
-extern void regfree (regex_t *__preg);
-
-
-#ifdef __cplusplus
-}
-#endif	/* C++ */
-
-/* For platform which support the ISO C amendment 1 functionality we
-   support user defined character classes.  */
-#if WIDE_CHAR_SUPPORT
-/* Solaris 2.5 has a bug: <wchar.h> must be included before <wctype.h>.  */
-# include <wchar.h>
-# include <wctype.h>
-
-typedef wctype_t re_wctype_t;
-typedef wchar_t re_wchar_t;
-# define re_wctype wctype
-# define re_iswctype iswctype
-# define re_wctype_to_bit(cc) 0
-#else
-# ifndef emacs
-#  define btowc(c) c
-# endif
+extern void re_set_registers (struct re_pattern_buffer *buffer,
+			      struct re_registers *regs,
+			      unsigned num_regs,
+			      ptrdiff_t *starts, ptrdiff_t *ends);
 
 /* Character classes.  */
 typedef enum { RECC_ERROR = 0,
@@ -648,12 +204,8 @@ typedef enum { RECC_ERROR = 0,
 	       RECC_ASCII, RECC_UNIBYTE
 } re_wctype_t;
 
-extern char re_iswctype (int ch,    re_wctype_t cc);
-extern re_wctype_t re_wctype_parse (const unsigned char **strp, unsigned limit);
-
-typedef int re_wchar_t;
-
-#endif /* not WIDE_CHAR_SUPPORT */
+extern bool re_iswctype (int ch, re_wctype_t cc);
+extern re_wctype_t re_wctype_parse (const unsigned char **strp,
+				    unsigned limit);
 
 #endif /* regex-emacs.h */
-
diff --git a/src/search.c b/src/search.c
index 4ee70144fc..2031bdc6d2 100644
--- a/src/search.c
+++ b/src/search.c
@@ -59,8 +59,8 @@ static struct regexp_cache searchbufs[REGEXP_CACHE_SIZE];
 static struct regexp_cache *searchbuf_head;

-/* Every call to re_match, etc., must pass &search_regs as the regs
-   argument unless you can show it is unnecessary (i.e., if re_match
+/* Every call to re_search, etc., must pass &search_regs as the regs
+   argument unless you can show it is unnecessary (i.e., if re_search
    is certainly going to be called again before region-around-match
    can be called).
 
@@ -2186,8 +2186,8 @@ set_search_regs (ptrdiff_t beg_byte, ptrdiff_t nbytes)
      the match position.  */
   if (search_regs.num_regs == 0)
     {
-      search_regs.start = xmalloc (2 * sizeof (regoff_t));
-      search_regs.end = xmalloc (2 * sizeof (regoff_t));
+      search_regs.start = xmalloc (2 * sizeof *search_regs.start);
+      search_regs.end = xmalloc (2 * sizeof *search_regs.end);
       search_regs.num_regs = 2;
     }
 
@@ -2998,9 +2998,9 @@ If optional arg RESEAT is non-nil, make markers on LIST point nowhere.  */)
 	  memory_full (SIZE_MAX);
 	search_regs.start =
 	  xpalloc (search_regs.start, &num_regs, length - num_regs,
-		   min (PTRDIFF_MAX, UINT_MAX), sizeof (regoff_t));
+		   min (PTRDIFF_MAX, UINT_MAX), sizeof *search_regs.start);
 	search_regs.end =
-	  xrealloc (search_regs.end, num_regs * sizeof (regoff_t));
+	  xrealloc (search_regs.end, num_regs * sizeof *search_regs.end);
 
 	for (i = search_regs.num_regs; i < num_regs; i++)
 	  search_regs.start[i] = -1;
@@ -3055,12 +3055,9 @@ If optional arg RESEAT is non-nil, make markers on LIST point nowhere.  */)
 	      XSETFASTINT (marker, 0);
 
 	    CHECK_NUMBER_COERCE_MARKER (marker);
-	    if ((XINT (from) < 0
-		 ? TYPE_MINIMUM (regoff_t) <= XINT (from)
-		 : XINT (from) <= TYPE_MAXIMUM (regoff_t))
-		&& (XINT (marker) < 0
-		    ? TYPE_MINIMUM (regoff_t) <= XINT (marker)
-		    : XINT (marker) <= TYPE_MAXIMUM (regoff_t)))
+	    if (PTRDIFF_MIN <= XINT (from) && XINT (from) <= PTRDIFF_MAX
+		&& PTRDIFF_MIN <= XINT (marker)
+		&& XINT (marker) <= PTRDIFF_MAX)
 	      {
 		search_regs.start[i] = XINT (from);
 		search_regs.end[i] = XINT (marker);
diff --git a/src/thread.h b/src/thread.h
index e1eb40921b..8ecb00824d 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -112,8 +112,8 @@ struct thread_state
   struct buffer *m_current_buffer;
 #define current_buffer (current_thread->m_current_buffer)
 
-  /* Every call to re_match, etc., must pass &search_regs as the regs
-     argument unless you can show it is unnecessary (i.e., if re_match
+  /* Every call to re_match_2, etc., must pass &search_regs as the regs
+     argument unless you can show it is unnecessary (i.e., if re_match_2
      is certainly going to be called again before region-around-match
      can be called).
 
-- 
2.17.1

>From a0c2b2e521e3523cc45a8a7e91fb5a42f4dd60d9 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Wed, 1 Aug 2018 19:13:08 -0700
Subject: [PATCH 3/4] Simplify regex-emacs by assuming Emacs syntax

* src/regex-emacs.c (reg_syntax_t)
(RE_BACKSLASH_ESCAPE_IN_LISTS, RE_BK_PLUS_QM)
(RE_CHAR_CLASSES, RE_CONTEXT_INDEP_ANCHORS)
(RE_CONTEXT_INDEP_OPS, RE_CONTEXT_INVALID_OPS)
(RE_DOT_NEWLINE, RE_DOT_NOT_NULL, RE_HAT_LISTS_NOT_NEWLINE)
(RE_INTERVALS, RE_LIMITED_OPS, RE_NEWLINE_ALT)
(RE_NO_BK_BRACES, RE_NO_BK_PARENS, RE_NO_BK_REFS)
(RE_NO_BK_VBAR, RE_NO_EMPTY_RANGES)
(RE_UNMATCHED_RIGHT_PAREN_ORD, RE_NO_POSIX_BACKTRACKING)
(RE_NO_GNU_OPS, RE_FRUGAL, RE_SHY_GROUPS)
(RE_NO_NEWLINE_ANCHOR, RE_SYNTAX_EMACS, RE_TRANSLATE_P):
Remove.  All uses removed and resulting code simplified.
(TRANSLATE): Treat nil as an absent translation table, not zero.
All uses changed.
---
 src/regex-emacs.c | 493 +++++++---------------------------------------
 src/search.c      |   4 +-
 2 files changed, 70 insertions(+), 427 deletions(-)

diff --git a/src/regex-emacs.c b/src/regex-emacs.c
index fd335de094..c2582281da 100644
--- a/src/regex-emacs.c
+++ b/src/regex-emacs.c
@@ -50,133 +50,6 @@
    ints.  But Emacs only runs on 32 bit platforms anyway.  */
 #define RE_DUP_MAX (0xffff)
 
-/* The following bits are used to determine the regexp syntax we
-   recognize.  The set/not-set meanings where historically chosen so
-   that Emacs syntax had 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 reg_syntax_t;
-
-/* 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, then *?, +? and ?? match non greedily. */
-#define RE_FRUGAL (RE_NO_GNU_OPS << 1)
-
-/* If this bit is set, then (?:...) is treated as a shy group.  */
-#define RE_SHY_GROUPS (RE_FRUGAL << 1)
-
-/* If this bit is set, ^ and $ only match at beg/end of buffer.  */
-#define RE_NO_NEWLINE_ANCHOR (RE_SHY_GROUPS << 1)
-
-/* 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; */
-/* Define combinations of the above bits for the standard possibilities.  */
-#define RE_SYNTAX_EMACS							\
-  (RE_CHAR_CLASSES | RE_INTERVALS | RE_SHY_GROUPS | RE_FRUGAL)
-
 /* Make syntax table lookup grant data in gl_state.  */
 #define SYNTAX(c) syntax_property (c, 1)
 
@@ -1298,10 +1171,8 @@ static void insert_op1 (re_opcode_t op, unsigned char *loc,
 			int arg, unsigned char *end);
 static void insert_op2 (re_opcode_t op, unsigned char *loc,
 			int arg1, int arg2, unsigned char *end);
-static bool at_begline_loc_p (re_char *pattern, re_char *p,
-			      reg_syntax_t syntax);
-static bool at_endline_loc_p (re_char *p, re_char *pend,
-			      reg_syntax_t syntax);
+static bool at_begline_loc_p (re_char *pattern, re_char *p);
+static bool at_endline_loc_p (re_char *p, re_char *pend);
 static re_char *skip_one_char (re_char *p);
 static int analyze_first (re_char *p, re_char *pend,
 			  char *fastmap, const int multibyte);
@@ -1318,15 +1189,7 @@ static int analyze_first (re_char *p, re_char *pend,

 #define RE_TRANSLATE(TBL, C) char_table_translate (TBL, C)
-#define RE_TRANSLATE_P(TBL) (!EQ (TBL, make_number (0)))
-
-/* If `translate' is non-zero, return translate[D], else just D.  We
-   cast the subscript to translate because some data is declared as
-   `char *', to avoid warnings when a string constant is passed.  But
-   when we use a character as a subscript we must make it unsigned.  */
-#define TRANSLATE(d) \
-  (RE_TRANSLATE_P (translate) ? RE_TRANSLATE (translate, (d)) : (d))
-
+#define TRANSLATE(d) (!NILP (translate) ? RE_TRANSLATE (translate, d) : (d))
 
 /* Macros for outputting the compiled pattern into `buffer'.  */
 
@@ -1846,8 +1709,6 @@ regex_compile (re_char *pattern, size_t size,
 	       const char *whitespace_regexp,
 	       struct re_pattern_buffer *bufp)
 {
-  reg_syntax_t syntax = RE_SYNTAX_EMACS;
-
   /* We fetch characters from PATTERN here.  */
   int c, c1;
 
@@ -2010,51 +1871,24 @@ regex_compile (re_char *pattern, size_t size,
 	  }
 
 	case '^':
-	  {
-	    if (   /* If at start of pattern, it's an operator.  */
-		   p == pattern + 1
-		   /* If context independent, it's an operator.  */
-		|| syntax & RE_CONTEXT_INDEP_ANCHORS
-		   /* Otherwise, depends on what's come before.  */
-		|| at_begline_loc_p (pattern, p, syntax))
-	      BUF_PUSH ((syntax & RE_NO_NEWLINE_ANCHOR) ? begbuf : begline);
-	    else
-	      goto normal_char;
-	  }
+	  if (! (p == pattern + 1 || at_begline_loc_p (pattern, p)))
+	    goto normal_char;
+	  BUF_PUSH (begline);
 	  break;
 
-
 	case '$':
-	  {
-	    if (   /* If at end of pattern, it's an operator.  */
-		   p == pend
-		   /* If context independent, it's an operator.  */
-		|| syntax & RE_CONTEXT_INDEP_ANCHORS
-		   /* Otherwise, depends on what's next.  */
-		|| at_endline_loc_p (p, pend, syntax))
-	       BUF_PUSH ((syntax & RE_NO_NEWLINE_ANCHOR) ? endbuf : endline);
-	     else
-	       goto normal_char;
-	   }
-	   break;
+	  if (! (p == pend || at_endline_loc_p (p, pend)))
+	    goto normal_char;
+	  BUF_PUSH (endline);
+	  break;

 	case '+':
 	case '?':
-	  if ((syntax & RE_BK_PLUS_QM)
-	      || (syntax & RE_LIMITED_OPS))
-	    goto normal_char;
-	  FALLTHROUGH;
 	case '*':
-	handle_plus:
 	  /* If there is no previous pattern...  */
 	  if (!laststart)
-	    {
-	      if (syntax & RE_CONTEXT_INVALID_OPS)
-		FREE_STACK_RETURN (REG_BADRPT);
-	      else if (!(syntax & RE_CONTEXT_INDEP_OPS))
-		goto normal_char;
-	    }
+	    goto normal_char;
 
 	  {
 	    /* 1 means zero (many) matches is allowed.  */
@@ -2068,8 +1902,7 @@ regex_compile (re_char *pattern, size_t size,
 
 	    for (;;)
 	      {
-		if ((syntax & RE_FRUGAL)
-		    && c == '?' && (zero_times_ok || many_times_ok))
+		if (c == '?' && (zero_times_ok || many_times_ok))
 		  greedy = false;
 		else
 		  {
@@ -2077,25 +1910,10 @@ regex_compile (re_char *pattern, size_t size,
 		    many_times_ok |= c != '?';
 		  }
 
-		if (p == pend)
-		  break;
-		else if (*p == '*'
-			 || (!(syntax & RE_BK_PLUS_QM)
-			     && (*p == '+' || *p == '?')))
-		  ;
-		else if (syntax & RE_BK_PLUS_QM	 && *p == '\\')
-		  {
-		    if (p+1 == pend)
-		      FREE_STACK_RETURN (REG_EESCAPE);
-		    if (p[1] == '+' || p[1] == '?')
-		      PATFETCH (c); /* Gobble up the backslash.  */
-		    else
-		      break;
-		  }
-		else
+		if (! (p < pend && (*p == '*' || *p == '+' || *p == '?')))
 		  break;
 		/* If we get here, we found another repeat character.  */
-		PATFETCH (c);
+		c = *p++;
 	       }
 
 	    /* Star, etc. applied to an empty pattern is equivalent
@@ -2227,24 +2045,18 @@ regex_compile (re_char *pattern, size_t size,
 	    /* Clear the whole map.  */
 	    memset (b, 0, (1 << BYTEWIDTH) / BYTEWIDTH);
 
-	    /* charset_not matches newline according to a syntax bit.  */
-	    if ((re_opcode_t) b[-2] == charset_not
-		&& (syntax & RE_HAT_LISTS_NOT_NEWLINE))
-	      SET_LIST_BIT ('\n');
-
 	    /* Read in characters and ranges, setting map bits.  */
 	    for (;;)
 	      {
 		const unsigned char *p2 = p;
-		re_wctype_t cc;
 		int ch;
 
 		if (p == pend) FREE_STACK_RETURN (REG_EBRACK);
 
 		/* See if we're at the beginning of a possible character
 		   class.  */
-		if (syntax & RE_CHAR_CLASSES &&
-		    (cc = re_wctype_parse(&p, pend - p)) != -1)
+		re_wctype_t cc = re_wctype_parse (&p, pend - p);
+		if (cc != -1)
 		  {
 		    if (cc == 0)
 		      FREE_STACK_RETURN (REG_ECTYPE);
@@ -2296,21 +2108,11 @@ regex_compile (re_char *pattern, size_t size,
 		   (let ((case-fold-search t)) (string-match "[A-_]" "A"))  */
 		PATFETCH (c);
 
-		/* \ might escape characters inside [...] and [^...].  */
-		if ((syntax & RE_BACKSLASH_ESCAPE_IN_LISTS) && c == '\\')
-		  {
-		    if (p == pend) FREE_STACK_RETURN (REG_EESCAPE);
-
-		    PATFETCH (c);
-		  }
-		else
-		  {
-		    /* Could be the end of the bracket expression.  If it's
-		       not (i.e., when the bracket expression is `[]' so
-		       far), the ']' character bit gets set way below.  */
-		    if (c == ']' && p2 != p1)
-		      break;
-		  }
+		/* Could be the end of the bracket expression.  If it's
+		   not (i.e., when the bracket expression is `[]' so
+		   far), the ']' character bit gets set way below.  */
+		if (c == ']' && p2 != p1)
+		  break;
 
 		if (p < pend && p[0] == '-' && p[1] != ']')
 		  {
@@ -2331,13 +2133,7 @@ regex_compile (re_char *pattern, size_t size,
 		  /* Range from C to C. */
 		  c1 = c;
 
-		if (c > c1)
-		  {
-		    if (syntax & RE_NO_EMPTY_RANGES)
-		      FREE_STACK_RETURN (REG_ERANGEX);
-		    /* Else, repeat the loop.  */
-		  }
-		else
+		if (c <= c1)
 		  {
 		    if (c < 128)
 		      {
@@ -2347,24 +2143,17 @@ regex_compile (re_char *pattern, size_t size,
 			if (CHAR_BYTE8_P (c1))
 			  c = BYTE8_TO_CHAR (128);
 		      }
-		    if (c <= c1)
+		    if (CHAR_BYTE8_P (c))
 		      {
-			if (CHAR_BYTE8_P (c))
-			  {
-			    c = CHAR_TO_BYTE8 (c);
-			    c1 = CHAR_TO_BYTE8 (c1);
-			    for (; c <= c1; c++)
-			      SET_LIST_BIT (c);
-			  }
-			else if (multibyte)
-			  {
-			    SETUP_MULTIBYTE_RANGE (range_table_work, c, c1);
-			  }
-			else
-			  {
-			    SETUP_UNIBYTE_RANGE (range_table_work, c, c1);
-			  }
+			c = CHAR_TO_BYTE8 (c);
+			c1 = CHAR_TO_BYTE8 (c1);
+			for (; c <= c1; c++)
+			  SET_LIST_BIT (c);
 		      }
+		    else if (multibyte)
+		      SETUP_MULTIBYTE_RANGE (range_table_work, c, c1);
+		    else
+		      SETUP_UNIBYTE_RANGE (range_table_work, c, c1);
 		  }
 	      }
 
@@ -2402,41 +2191,6 @@ regex_compile (re_char *pattern, size_t size,
 	  break;

-	case '(':
-	  if (syntax & RE_NO_BK_PARENS)
-	    goto handle_open;
-	  else
-	    goto normal_char;
-
-
-	case ')':
-	  if (syntax & RE_NO_BK_PARENS)
-	    goto handle_close;
-	  else
-	    goto normal_char;
-
-
-	case '\n':
-	  if (syntax & RE_NEWLINE_ALT)
-	    goto handle_alt;
-	  else
-	    goto normal_char;
-
-
-	case '|':
-	  if (syntax & RE_NO_BK_VBAR)
-	    goto handle_alt;
-	  else
-	    goto normal_char;
-
-
-	case '{':
-	   if (syntax & RE_INTERVALS && syntax & RE_NO_BK_BRACES)
-	     goto handle_interval;
-	   else
-	     goto normal_char;
-
-
 	case '\\':
 	  if (p == pend) FREE_STACK_RETURN (REG_EESCAPE);
 
@@ -2448,17 +2202,13 @@ regex_compile (re_char *pattern, size_t size,
 	  switch (c)
 	    {
 	    case '(':
-	      if (syntax & RE_NO_BK_PARENS)
-		goto normal_backslash;
-
-	    handle_open:
 	      {
 		int shy = 0;
 		regnum_t regnum = 0;
 		if (p+1 < pend)
 		  {
 		    /* Look for a special (?...) construct */
-		    if ((syntax & RE_SHY_GROUPS) && *p == '?')
+		    if (*p == '?')
 		      {
 			PATFETCH (c); /* Gobble up the '?'.  */
 			while (!shy)
@@ -2539,27 +2289,14 @@ regex_compile (re_char *pattern, size_t size,
 	      }
 
 	    case ')':
-	      if (syntax & RE_NO_BK_PARENS) goto normal_backslash;
-
 	      if (COMPILE_STACK_EMPTY)
-		{
-		  if (syntax & RE_UNMATCHED_RIGHT_PAREN_ORD)
-		    goto normal_backslash;
-		  else
-		    FREE_STACK_RETURN (REG_ERPAREN);
-		}
+		FREE_STACK_RETURN (REG_ERPAREN);
 
-	    handle_close:
 	      FIXUP_ALT_JUMP ();
 
 	      /* See similar code for backslashed left paren above.  */
 	      if (COMPILE_STACK_EMPTY)
-		{
-		  if (syntax & RE_UNMATCHED_RIGHT_PAREN_ORD)
-		    goto normal_char;
-		  else
-		    FREE_STACK_RETURN (REG_ERPAREN);
-		}
+		FREE_STACK_RETURN (REG_ERPAREN);
 
 	      /* Since we just checked for an empty stack above, this
 		 ``can't happen''.  */
@@ -2592,12 +2329,6 @@ regex_compile (re_char *pattern, size_t size,

 	    case '|':					/* `\|'.  */
-	      if (syntax & RE_LIMITED_OPS || syntax & RE_NO_BK_VBAR)
-		goto normal_backslash;
-	    handle_alt:
-	      if (syntax & RE_LIMITED_OPS)
-		goto normal_char;
-
 	      /* Insert before the previous alternative a jump which
 		 jumps to this alternative if the former fails.  */
 	      GET_BUFFER_SPACE (3);
@@ -2636,17 +2367,7 @@ regex_compile (re_char *pattern, size_t size,

 	    case '{':
-	      /* If \{ is a literal.  */
-	      if (!(syntax & RE_INTERVALS)
-		     /* If we're at `\{' and it's not the open-interval
-			operator.  */
-		  || (syntax & RE_NO_BK_BRACES))
-		goto normal_backslash;
-
-	    handle_interval:
 	      {
-		/* If got here, then the syntax allows intervals.  */
-
 		/* At least (most) this many matches must be made.  */
 		int lower_bound = 0, upper_bound = -1;
 
@@ -2661,33 +2382,19 @@ regex_compile (re_char *pattern, size_t size,
 		  upper_bound = lower_bound;
 
 		if (lower_bound < 0
-		    || (0 <= upper_bound && upper_bound < lower_bound))
+		    || (0 <= upper_bound && upper_bound < lower_bound)
+		    || c != '\\')
 		  FREE_STACK_RETURN (REG_BADBR);
-
-		if (!(syntax & RE_NO_BK_BRACES))
-		  {
-		    if (c != '\\')
-		      FREE_STACK_RETURN (REG_BADBR);
-		    if (p == pend)
-		      FREE_STACK_RETURN (REG_EESCAPE);
-		    PATFETCH (c);
-		  }
-
-		if (c != '}')
+		if (p == pend)
+		  FREE_STACK_RETURN (REG_EESCAPE);
+		if (*p++ != '}')
 		  FREE_STACK_RETURN (REG_BADBR);
 
 		/* We just parsed a valid interval.  */
 
 		/* If it's invalid to have no preceding re.  */
 		if (!laststart)
-		  {
-		    if (syntax & RE_CONTEXT_INVALID_OPS)
-		      FREE_STACK_RETURN (REG_BADRPT);
-		    else if (syntax & RE_CONTEXT_INDEP_OPS)
-		      laststart = b;
-		    else
-		      goto unfetch_interval;
-		  }
+		  goto unfetch_interval;
 
 		if (upper_bound == 0)
 		  /* If the upper bound is zero, just drop the sub pattern
@@ -2792,17 +2499,9 @@ regex_compile (re_char *pattern, size_t size,
 	       eassert (beg_interval);
 	       p = beg_interval;
 	       beg_interval = NULL;
-
-	       /* normal_char and normal_backslash need `c'.  */
+	       eassert (p > pattern && p[-1] == '\\');
 	       c = '{';
-
-	       if (!(syntax & RE_NO_BK_BRACES))
-		 {
-		   eassert (p > pattern && p[-1] == '\\');
-		   goto normal_backslash;
-		 }
-	       else
-		 goto normal_char;
+	       goto normal_char;
 
 	    case '=':
 	      laststart = b;
@@ -2834,38 +2533,28 @@ regex_compile (re_char *pattern, size_t size,
 	      break;
 
 	    case 'w':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      laststart = b;
 	      BUF_PUSH_2 (syntaxspec, Sword);
 	      break;

 	    case 'W':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      laststart = b;
 	      BUF_PUSH_2 (notsyntaxspec, Sword);
 	      break;

 	    case '<':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      laststart = b;
 	      BUF_PUSH (wordbeg);
 	      break;
 
 	    case '>':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      laststart = b;
 	      BUF_PUSH (wordend);
 	      break;
 
 	    case '_':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
               laststart = b;
               PATFETCH (c);
               if (c == '<')
@@ -2877,38 +2566,25 @@ regex_compile (re_char *pattern, size_t size,
               break;
 
 	    case 'b':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      BUF_PUSH (wordbound);
 	      break;
 
 	    case 'B':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      BUF_PUSH (notwordbound);
 	      break;
 
 	    case '`':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      BUF_PUSH (begbuf);
 	      break;
 
 	    case '\'':
-	      if (syntax & RE_NO_GNU_OPS)
-		goto normal_char;
 	      BUF_PUSH (endbuf);
 	      break;
 
 	    case '1': case '2': case '3': case '4': case '5':
 	    case '6': case '7': case '8': case '9':
 	      {
-		regnum_t reg;
-
-		if (syntax & RE_NO_BK_REFS)
-		  goto normal_backslash;
-
-		reg = c - '0';
+		regnum_t reg = c - '0';
 
 		if (reg > bufp->re_nsub || reg < 1
 		    /* Can't back reference to a subexp before its end.  */
@@ -2920,16 +2596,7 @@ regex_compile (re_char *pattern, size_t size,
 	      }
 	      break;
 
-
-	    case '+':
-	    case '?':
-	      if (syntax & RE_BK_PLUS_QM)
-		goto handle_plus;
-	      else
-		goto normal_backslash;
-
 	    default:
-	    normal_backslash:
 	      /* You might think it would be useful for \ to mean
 		 not to translate; but if we don't translate it
 		 it will never match anything.  */
@@ -2951,14 +2618,9 @@ regex_compile (re_char *pattern, size_t size,
 	      || *pending_exact >= (1 << BYTEWIDTH) - MAX_MULTIBYTE_LENGTH
 
 	      /* If followed by a repetition operator.  */
-	      || (p != pend && (*p == '*' || *p == '^'))
-	      || ((syntax & RE_BK_PLUS_QM)
-		  ? p + 1 < pend && *p == '\\' && (p[1] == '+' || p[1] == '?')
-		  : p != pend && (*p == '+' || *p == '?'))
-	      || ((syntax & RE_INTERVALS)
-		  && ((syntax & RE_NO_BK_BRACES)
-		      ? p != pend && *p == '{'
-		      : p + 1 < pend && p[0] == '\\' && p[1] == '{')))
+	      || (p != pend
+		  && (*p == '*' || *p == '+' || *p == '?' || *p == '^'))
+	      || (p + 1 < pend && p[0] == '\\' && p[1] == '{'))
 	    {
 	      /* Start building a new exactn.  */
 
@@ -3087,40 +2749,35 @@ insert_op2 (re_opcode_t op, unsigned char *loc, int arg1, int arg2, unsigned cha
    least one character before the ^.  */
 
 static bool
-at_begline_loc_p (re_char *pattern, re_char *p, reg_syntax_t syntax)
+at_begline_loc_p (re_char *pattern, re_char *p)
 {
   re_char *prev = p - 2;
-  bool odd_backslashes;
-
-  /* After a subexpression?  */
-  if (*prev == '(')
-    odd_backslashes = (syntax & RE_NO_BK_PARENS) == 0;
 
-  /* After an alternative?  */
-  else if (*prev == '|')
-    odd_backslashes = (syntax & RE_NO_BK_VBAR) == 0;
-
-  /* After a shy subexpression?  */
-  else if (*prev == ':' && (syntax & RE_SHY_GROUPS))
+  switch (*prev)
     {
+    case '(': /* After a subexpression.  */
+    case '|': /* After an alternative.  */
+      break;
+
+    case ':': /* After a shy subexpression.  */
       /* Skip over optional regnum.  */
-      while (prev - 1 >= pattern && prev[-1] >= '0' && prev[-1] <= '9')
+      while (prev > pattern && '0' <= prev[-1] && prev[-1] <= '9')
 	--prev;
 
-      if (!(prev - 2 >= pattern
-	    && prev[-1] == '?' && prev[-2] == '('))
+      if (! (prev > pattern + 1 && prev[-1] == '?' && prev[-2] == '('))
 	return false;
       prev -= 2;
-      odd_backslashes = (syntax & RE_NO_BK_PARENS) == 0;
+      break;
+
+    default:
+      return false;
     }
-  else
-    return false;
 
   /* Count the number of preceding backslashes.  */
   p = prev;
-  while (prev - 1 >= pattern && prev[-1] == '\\')
+  while (prev > pattern && prev[-1] == '\\')
     --prev;
-  return (p - prev) & odd_backslashes;
+  return (p - prev) & 1;
 }

@@ -3128,19 +2785,10 @@ at_begline_loc_p (re_char *pattern, re_char *p, reg_syntax_t syntax)
    at least one character after the $, i.e., `P < PEND'.  */
 
 static bool
-at_endline_loc_p (re_char *p, re_char *pend, reg_syntax_t syntax)
+at_endline_loc_p (re_char *p, re_char *pend)
 {
-  re_char *next = p;
-  bool next_backslash = *next == '\\';
-  re_char *next_next = p + 1 < pend ? p + 1 : 0;
-
-  return
-       /* Before a subexpression?  */
-       (syntax & RE_NO_BK_PARENS ? *next == ')'
-	: next_backslash && next_next && *next_next == ')')
-       /* Before an alternative?  */
-    || (syntax & RE_NO_BK_VBAR ? *next == '|'
-	: next_backslash && next_next && *next_next == '|');
+  /* Before a subexpression or an alternative?  */
+  return *p == '\\' && p + 1 < pend && (p[1] == ')' || p[1] == '|');
 }

@@ -3654,7 +3302,7 @@ re_search_2 (struct re_pattern_buffer *bufp, const char *str1, size_t size1,
 
 	      /* Written out as an if-else to avoid testing `translate'
 		 inside the loop.  */
-	      if (RE_TRANSLATE_P (translate))
+	      if (!NILP (translate))
 		{
 		  if (multibyte)
 		    while (range > lim)
@@ -4642,12 +4290,11 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  break;

-	/* Match any character except possibly a newline or a null.  */
+	/* Match any character except newline.  */
 	case anychar:
 	  {
 	    int buf_charlen;
 	    int buf_ch;
-	    reg_syntax_t syntax;
 
 	    DEBUG_PRINT ("EXECUTING anychar.\n");
 
@@ -4655,11 +4302,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	    buf_ch = RE_STRING_CHAR_AND_LENGTH (d, buf_charlen,
 						target_multibyte);
 	    buf_ch = TRANSLATE (buf_ch);
-
-	    syntax = RE_SYNTAX_EMACS;
-
-	    if ((!(syntax & RE_DOT_NEWLINE) && buf_ch == '\n')
-		|| ((syntax & RE_DOT_NOT_NULL) && buf_ch == '\000'))
+	    if (buf_ch == '\n')
 	      goto fail;
 
 	    DEBUG_PRINT ("  Matched \"%d\".\n", *d);
@@ -4825,7 +4468,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 
 		/* Compare that many; failure if mismatch, else move
 		   past them.  */
-		if (RE_TRANSLATE_P (translate)
+		if (!NILP (translate)
 		    ? bcmp_translate (d, d2, dcnt, translate, target_multibyte)
 		    : memcmp (d, d2, dcnt))
 		  {
diff --git a/src/search.c b/src/search.c
index 2031bdc6d2..95cbbd8c81 100644
--- a/src/search.c
+++ b/src/search.c
@@ -132,7 +132,7 @@ compile_pattern_1 (struct regexp_cache *cp, Lisp_Object pattern,
 
   eassert (!cp->busy);
   cp->regexp = Qnil;
-  cp->buf.translate = (! NILP (translate) ? translate : make_number (0));
+  cp->buf.translate = translate;
   cp->posix = posix;
   cp->buf.multibyte = STRING_MULTIBYTE (pattern);
   cp->buf.charset_unibyte = charset_unibyte;
@@ -238,7 +238,7 @@ compile_pattern (Lisp_Object pattern, struct re_registers *regp,
           && !cp->busy
 	  && STRING_MULTIBYTE (cp->regexp) == STRING_MULTIBYTE (pattern)
 	  && !NILP (Fstring_equal (cp->regexp, pattern))
-	  && EQ (cp->buf.translate, (! NILP (translate) ? translate : make_number (0)))
+	  && EQ (cp->buf.translate, translate)
 	  && cp->posix == posix
 	  && (EQ (cp->syntax_table, Qt)
 	      || EQ (cp->syntax_table, BVAR (current_buffer, syntax_table)))
-- 
2.17.1

>From 04435ddc85dd7b126571417a5daf09e28dd39f7c Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Wed, 1 Aug 2018 19:13:08 -0700
Subject: [PATCH 4/4] Remove always-0 struct re_pattern_buffer members

* src/regex-emacs.h (struct re_pattern_buffer):
Remove no_sub, not_bol, not_eol.  They are always zero.
All uses removed, and code simplified.
---
 src/regex-emacs.c | 42 +++++++++++-------------------------------
 src/regex-emacs.h | 15 ++-------------
 2 files changed, 13 insertions(+), 44 deletions(-)

diff --git a/src/regex-emacs.c b/src/regex-emacs.c
index c2582281da..747874b826 100644
--- a/src/regex-emacs.c
+++ b/src/regex-emacs.c
@@ -762,9 +762,6 @@ print_compiled_pattern (struct re_pattern_buffer *bufp)
   printf ("re_nsub: %zu\t", bufp->re_nsub);
   printf ("regs_alloc: %d\t", bufp->regs_allocated);
   printf ("can_be_null: %d\t", bufp->can_be_null);
-  printf ("no_sub: %d\t", bufp->no_sub);
-  printf ("not_bol: %d\t", bufp->not_bol);
-  printf ("not_eol: %d\t", bufp->not_eol);
 #ifndef emacs
   printf ("syntax: %lx\n", bufp->syntax);
 #endif
@@ -1682,7 +1679,6 @@ static bool group_in_compile_stack (compile_stack_type, regnum_t);
      `used' is set to the length of the compiled pattern;
      `fastmap_accurate' is zero;
      `re_nsub' is the number of subexpressions in PATTERN;
-     `not_bol' and `not_eol' are zero;
 
    The `fastmap' field is neither examined nor set.  */
 
@@ -1786,7 +1782,6 @@ regex_compile (re_char *pattern, size_t size,
 
   /* Initialize the pattern buffer.  */
   bufp->fastmap_accurate = 0;
-  bufp->not_bol = bufp->not_eol = 0;
   bufp->used_syntax = 0;
 
   /* Set `used' to zero, so that if we return an error, the pattern
@@ -1794,7 +1789,6 @@ regex_compile (re_char *pattern, size_t size,
      at the end.  */
   bufp->used = 0;
 
-  /* Always count groups, whether or not bufp->no_sub is set.  */
   bufp->re_nsub = 0;
 
   if (bufp->allocated == 0)
@@ -3840,9 +3834,8 @@ mutually_exclusive_p (struct re_pattern_buffer *bufp, re_char *p1,
    and SIZE2, respectively).  We start matching at POS, and stop
    matching at STOP.
 
-   If REGS is non-null and the `no_sub' field of BUFP is nonzero, we
-   store offsets for the substring each group matched in REGS.  See the
-   documentation for exactly how many groups we fill.
+   If REGS is non-null, store offsets for the substring each group
+   matched in REGS.
 
    We return -1 if no match, -2 if an internal error (such as the
    failure stack overflowing).  Otherwise, we return the length of the
@@ -4129,7 +4122,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  DEBUG_PRINT ("Accepting match.\n");
 
 	  /* If caller wants register contents data back, do it.  */
-	  if (regs && !bufp->no_sub)
+	  if (regs)
 	    {
 	      /* Have the register data arrays been allocated?	*/
 	      if (bufp->regs_allocated == REGS_UNALLOCATED)
@@ -4184,7 +4177,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 		 -1 at the end.  */
 	      for (reg = num_regs; reg < regs->num_regs; reg++)
 		regs->start[reg] = regs->end[reg] = -1;
-	    } /* regs && !bufp->no_sub */
+	    }
 
 	  DEBUG_PRINT ("%u failure points pushed, %u popped (%u remain).\n",
 		       nfailure_points_pushed, nfailure_points_popped,
@@ -4481,15 +4474,13 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  break;

-	/* begline matches the empty string at the beginning of the string
-	   (unless `not_bol' is set in `bufp'), and after newlines.  */
+	/* begline matches the empty string at the beginning of the string,
+	   and after newlines.  */
 	case begline:
 	  DEBUG_PRINT ("EXECUTING begline.\n");
 
 	  if (AT_STRINGS_BEG (d))
-	    {
-	      if (!bufp->not_bol) break;
-	    }
+	    break;
 	  else
 	    {
 	      unsigned c;
@@ -4497,7 +4488,6 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	      if (c == '\n')
 		break;
 	    }
-	  /* In all other cases, we fail.  */
 	  goto fail;

@@ -4506,15 +4496,10 @@ re_match_2_internal (struct re_pattern_buffer *bufp, re_char *string1,
 	  DEBUG_PRINT ("EXECUTING endline.\n");
 
 	  if (AT_STRINGS_END (d))
-	    {
-	      if (!bufp->not_eol) break;
-	    }
-	  else
-	    {
-	      PREFETCH_NOLIMIT ();
-	      if (*d == '\n')
-		break;
-	    }
+	    break;
+	  PREFETCH_NOLIMIT ();
+	  if (*d == '\n')
+	    break;
 	  goto fail;

@@ -5112,11 +5097,6 @@ re_compile_pattern (const char *pattern, size_t length,
      (and at least one extra will be -1).  */
   bufp->regs_allocated = REGS_UNALLOCATED;
 
-  /* And GNU code determines whether or not to get register information
-     by passing null for the REGS argument to re_search, etc., not by
-     setting no_sub.  */
-  bufp->no_sub = 0;
-
   ret = regex_compile ((re_char *) pattern, length,
 		       posix_backtracking,
 		       whitespace_regexp,
diff --git a/src/regex-emacs.h b/src/regex-emacs.h
index 898c0f2aea..4dabe680ef 100644
--- a/src/regex-emacs.h
+++ b/src/regex-emacs.h
@@ -60,7 +60,7 @@ extern ptrdiff_t emacs_re_safe_alloca;
 
 /* 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
+   and `translate' can be set.  After the pattern has been
    compiled, the `re_nsub' field is available.  All other fields are
    private to the regex routines.  */
 
@@ -110,17 +110,6 @@ struct re_pattern_buffer
            by `re_compile_fastmap' if it updates the fastmap.  */
   unsigned fastmap_accurate : 1;
 
-        /* If set, `re_match_2' does not return information about
-           subexpressions.  */
-  unsigned no_sub : 1;
-
-        /* If set, a beginning-of-line anchor doesn't match at the
-           beginning of the string.  */
-  unsigned not_bol : 1;
-
-        /* Similarly for an end-of-line anchor.  */
-  unsigned not_eol : 1;
-
   /* If true, the compilation of the pattern had to look up the syntax table,
      so the compiled pattern is only valid for the current syntax table.  */
   unsigned used_syntax : 1;
@@ -149,7 +138,7 @@ extern const char *re_compile_pattern (const char *pattern, size_t length,
    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).  */
+   information in REGS (if REGS is nonzero).  */
 extern ptrdiff_t re_search (struct re_pattern_buffer *buffer,
 			   const char *string, size_t length,
 			   ptrdiff_t start, ptrdiff_t range,
-- 
2.17.1