/gnu/usr.bin/grep/dfa.c

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/* dfa.c - deterministic extended regexp routines for GNU
   Copyright 1988, 1998, 2000 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA */

/* Written June, 1988 by Mike Haertel
   Modified July, 1988 by Arthur David Olson to assist BMG speedups  */

/* $FreeBSD$ */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <assert.h>
#include <ctype.h>
#include <stdio.h>

#include <sys/types.h>
#ifdef STDC_HEADERS
#include <stdlib.h>
#else
extern char *calloc(), *malloc(), *realloc();
extern void free();
#endif

#if defined(HAVE_STRING_H) || defined(STDC_HEADERS)
#include <string.h>
#else
#include <strings.h>
#endif

#if HAVE_SETLOCALE
# include <locale.h>
#endif

#if defined HAVE_WCTYPE_H && defined HAVE_WCHAR_H && defined HAVE_MBRTOWC
/* We can handle multibyte string.  */
# define MBS_SUPPORT
#endif

#ifdef MBS_SUPPORT
# include <wchar.h>
# include <wctype.h>
#endif

#ifndef DEBUG	/* use the same approach as regex.c */
#undef assert
#define assert(e)
#endif /* DEBUG */

#ifndef isgraph
#define isgraph(C) (isprint(C) && !isspace(C))
#endif

#if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII))
#define ISALPHA(C) isalpha(C)
#define ISUPPER(C) isupper(C)
#define ISLOWER(C) islower(C)
#define ISDIGIT(C) isdigit(C)
#define ISXDIGIT(C) isxdigit(C)
#define ISSPACE(C) isspace(C)
#define ISPUNCT(C) ispunct(C)
#define ISALNUM(C) isalnum(C)
#define ISPRINT(C) isprint(C)
#define ISGRAPH(C) isgraph(C)
#define ISCNTRL(C) iscntrl(C)
#else
#define ISALPHA(C) (isascii(C) && isalpha(C))
#define ISUPPER(C) (isascii(C) && isupper(C))
#define ISLOWER(C) (isascii(C) && islower(C))
#define ISDIGIT(C) (isascii(C) && isdigit(C))
#define ISXDIGIT(C) (isascii(C) && isxdigit(C))
#define ISSPACE(C) (isascii(C) && isspace(C))
#define ISPUNCT(C) (isascii(C) && ispunct(C))
#define ISALNUM(C) (isascii(C) && isalnum(C))
#define ISPRINT(C) (isascii(C) && isprint(C))
#define ISGRAPH(C) (isascii(C) && isgraph(C))
#define ISCNTRL(C) (isascii(C) && iscntrl(C))
#endif

/* ISASCIIDIGIT differs from ISDIGIT, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char.
   - It's guaranteed to evaluate its argument exactly once.
   - It's typically faster.
   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
   only '0' through '9' are digits.  Prefer ISASCIIDIGIT to ISDIGIT unless
   it's important to use the locale's definition of `digit' even when the
   host does not conform to Posix.  */
#define ISASCIIDIGIT(c) ((unsigned) (c) - '0' <= 9)

/* If we (don't) have I18N.  */
/* glibc defines _ */
#ifndef _
# ifdef HAVE_LIBINTL_H
#  include <libintl.h>
#  ifndef _
#   define _(Str) gettext (Str)
#  endif
# else
#  define _(Str) (Str)
# endif
#endif

#include "regex.h"
#include "dfa.h"
#include "hard-locale.h"

/* HPUX, define those as macros in sys/param.h */
#ifdef setbit
# undef setbit
#endif
#ifdef clrbit
# undef clrbit
#endif

static void dfamust PARAMS ((struct dfa *dfa));
static void regexp PARAMS ((int toplevel));

static ptr_t
xcalloc (size_t n, size_t s)
{
  ptr_t r = calloc(n, s);

  if (!r)
    dfaerror(_("Memory exhausted"));
  return r;
}

static ptr_t
xmalloc (size_t n)
{
  ptr_t r = malloc(n);

  assert(n != 0);
  if (!r)
    dfaerror(_("Memory exhausted"));
  return r;
}

static ptr_t
xrealloc (ptr_t p, size_t n)
{
  ptr_t r = realloc(p, n);

  assert(n != 0);
  if (!r)
    dfaerror(_("Memory exhausted"));
  return r;
}

#define CALLOC(p, t, n) ((p) = (t *) xcalloc((size_t)(n), sizeof (t)))
#define MALLOC(p, t, n) ((p) = (t *) xmalloc((n) * sizeof (t)))
#define REALLOC(p, t, n) ((p) = (t *) xrealloc((ptr_t) (p), (n) * sizeof (t)))

/* Reallocate an array of type t if nalloc is too small for index. */
#define REALLOC_IF_NECESSARY(p, t, nalloc, index) \
  if ((index) >= (nalloc))			  \
    {						  \
      do					  \
	(nalloc) *= 2;				  \
      while ((index) >= (nalloc));		  \
      REALLOC(p, t, nalloc);			  \
    }

#ifdef DEBUG

static void
prtok (token t)
{
  char const *s;

  if (t < 0)
    fprintf(stderr, "END");
  else if (t < NOTCHAR)
    fprintf(stderr, "%c", t);
  else
    {
      switch (t)
	{
	case EMPTY: s = "EMPTY"; break;
	case BACKREF: s = "BACKREF"; break;
	case BEGLINE: s = "BEGLINE"; break;
	case ENDLINE: s = "ENDLINE"; break;
	case BEGWORD: s = "BEGWORD"; break;
	case ENDWORD: s = "ENDWORD"; break;
	case LIMWORD: s = "LIMWORD"; break;
	case NOTLIMWORD: s = "NOTLIMWORD"; break;
	case QMARK: s = "QMARK"; break;
	case STAR: s = "STAR"; break;
	case PLUS: s = "PLUS"; break;
	case CAT: s = "CAT"; break;
	case OR: s = "OR"; break;
	case ORTOP: s = "ORTOP"; break;
	case LPAREN: s = "LPAREN"; break;
	case RPAREN: s = "RPAREN"; break;
	case CRANGE: s = "CRANGE"; break;
#ifdef MBS_SUPPORT
	case ANYCHAR: s = "ANYCHAR"; break;
	case MBCSET: s = "MBCSET"; break;
#endif /* MBS_SUPPORT */
	default: s = "CSET"; break;
	}
      fprintf(stderr, "%s", s);
    }
}
#endif /* DEBUG */

/* Stuff pertaining to charclasses. */

static int
tstbit (unsigned b, charclass c)
{
  return c[b / INTBITS] & 1 << b % INTBITS;
}

static void
setbit (unsigned b, charclass c)
{
  c[b / INTBITS] |= 1 << b % INTBITS;
}

static void
clrbit (unsigned b, charclass c)
{
  c[b / INTBITS] &= ~(1 << b % INTBITS);
}

static void
copyset (charclass src, charclass dst)
{
  memcpy (dst, src, sizeof (charclass));
}

static void
zeroset (charclass s)
{
  memset (s, 0, sizeof (charclass));
}

static void
notset (charclass s)
{
  int i;

  for (i = 0; i < CHARCLASS_INTS; ++i)
    s[i] = ~s[i];
}

static int
equal (charclass s1, charclass s2)
{
  return memcmp (s1, s2, sizeof (charclass)) == 0;
}

/* A pointer to the current dfa is kept here during parsing. */
static struct dfa *dfa;

/* Find the index of charclass s in dfa->charclasses, or allocate a new charclass. */
static int
charclass_index (charclass s)
{
  int i;

  for (i = 0; i < dfa->cindex; ++i)
    if (equal(s, dfa->charclasses[i]))
      return i;
  REALLOC_IF_NECESSARY(dfa->charclasses, charclass, dfa->calloc, dfa->cindex);
  ++dfa->cindex;
  copyset(s, dfa->charclasses[i]);
  return i;
}

/* Syntax bits controlling the behavior of the lexical analyzer. */
static reg_syntax_t syntax_bits, syntax_bits_set;

/* Flag for case-folding letters into sets. */
static int case_fold;

/* End-of-line byte in data.  */
static unsigned char eolbyte;

/* Entry point to set syntax options. */
void
dfasyntax (reg_syntax_t bits, int fold, unsigned char eol)
{
  syntax_bits_set = 1;
  syntax_bits = bits;
  case_fold = fold;
  eolbyte = eol;
}

/* Like setbit, but if case is folded, set both cases of a letter.  */
static void
setbit_case_fold (unsigned b, charclass c)
{
  setbit (b, c);
  if (case_fold)
    {
      if (ISUPPER (b))
	setbit (tolower (b), c);
      else if (ISLOWER (b))
	setbit (toupper (b), c);
    }
}

/* Lexical analyzer.  All the dross that deals with the obnoxious
   GNU Regex syntax bits is located here.  The poor, suffering
   reader is referred to the GNU Regex documentation for the
   meaning of the @#%!@#%^!@ syntax bits. */

static char const *lexstart;	/* Pointer to beginning of input string. */
static char const *lexptr;	/* Pointer to next input character. */
static int lexleft;		/* Number of characters remaining. */
static token lasttok;		/* Previous token returned; initially END. */
static int laststart;		/* True if we're separated from beginning or (, |
				   only by zero-width characters. */
static int parens;		/* Count of outstanding left parens. */
static int minrep, maxrep;	/* Repeat counts for {m,n}. */
static int hard_LC_COLLATE;	/* Nonzero if LC_COLLATE is hard.  */

#ifdef MBS_SUPPORT
/* These variables are used only if (MB_CUR_MAX > 1).  */
static mbstate_t mbs;		/* Mbstate for mbrlen().  */
static int cur_mb_len;		/* Byte length of the current scanning
				   multibyte character.  */
static int cur_mb_index;        /* Byte index of the current scanning multibyte
                                   character.

				   singlebyte character : cur_mb_index = 0
				   multibyte character
				       1st byte : cur_mb_index = 1
				       2nd byte : cur_mb_index = 2
				         ...
				       nth byte : cur_mb_index = n  */
static unsigned char *mblen_buf;/* Correspond to the input buffer in dfaexec().
                                  Each element store the amount of remain
                                  byte of corresponding multibyte character
                                  in the input string.  A element's value
                                  is 0 if corresponding character is a
                                  singlebyte chracter.
                                  e.g. input : 'a', <mb(0)>, <mb(1)>, <mb(2)>
                                   mblen_buf :   0,       3,       2,       1
                               */
static wchar_t *inputwcs;	/* Wide character representation of input
				   string in dfaexec().
				   The length of this array is same as
				   the length of input string(char array).
				   inputstring[i] is a single-byte char,
				   or 1st byte of a multibyte char.
				   And inputwcs[i] is the codepoint.  */
static unsigned char const *buf_begin;/* refference to begin in dfaexec().  */
static unsigned char const *buf_end;	/* refference to end in dfaexec().  */
#endif /* MBS_SUPPORT  */

#ifdef MBS_SUPPORT
/* This function update cur_mb_len, and cur_mb_index.
   p points current lexptr, len is the remaining buffer length.  */
static void
update_mb_len_index (unsigned char const *p, int len)
{
  /* If last character is a part of a multibyte character,
     we update cur_mb_index.  */
  if (cur_mb_index)
    cur_mb_index = (cur_mb_index >= cur_mb_len)? 0
			: cur_mb_index + 1;

  /* If last character is a single byte character, or the
     last portion of a multibyte character, we check whether
     next character is a multibyte character or not.  */
  if (! cur_mb_index)
    {
      cur_mb_len = mbrlen(p, len, &mbs);
      if (cur_mb_len > 1)
	/* It is a multibyte character.
	   cur_mb_len was already set by mbrlen().  */
	cur_mb_index = 1;
      else if (cur_mb_len < 1)
	/* Invalid sequence.  We treat it as a singlebyte character.
	   cur_mb_index is aleady 0.  */
	cur_mb_len = 1;
      /* Otherwise, cur_mb_len == 1, it is a singlebyte character.
	 cur_mb_index is aleady 0.  */
    }
}
#endif /* MBS_SUPPORT */

#ifdef MBS_SUPPORT
/* Note that characters become unsigned here. */
# define FETCH(c, eoferr)			\
  {						\
    if (! lexleft)				\
     {						\
	if (eoferr != 0)			\
	  dfaerror (eoferr);			\
	else					\
	  return lasttok = END;			\
      }						\
    if (MB_CUR_MAX > 1)				\
      update_mb_len_index(lexptr, lexleft);	\
    (c) = (unsigned char) *lexptr++;		\
    --lexleft;					\
  }

/* This function fetch a wide character, and update cur_mb_len,
   used only if the current locale is a multibyte environment.  */
static wint_t
fetch_wc (char const *eoferr)
{
  wchar_t wc;
  if (! lexleft)
    {
      if (eoferr != 0)
	dfaerror (eoferr);
      else
	return WEOF;
    }

  cur_mb_len = mbrtowc(&wc, lexptr, lexleft, &mbs);
  if (cur_mb_len <= 0)
   {
      cur_mb_len = 1;
      wc = *lexptr;
    }
  lexptr += cur_mb_len;
  lexleft -= cur_mb_len;
  return wc;
}
#else
/* Note that characters become unsigned here. */
# define FETCH(c, eoferr)   	      \
  {			   	      \
    if (! lexleft)	   	      \
      {				      \
	if (eoferr != 0)	      \
	  dfaerror (eoferr);	      \
	else		   	      \
	  return lasttok = END;	      \
      }				      \
    (c) = (unsigned char) *lexptr++;  \
    --lexleft;		   	      \
  }
#endif /* MBS_SUPPORT */

#ifdef MBS_SUPPORT
/* Multibyte character handling sub-routin for lex.
   This function  parse a bracket expression and build a struct
   mb_char_classes.  */
static void
parse_bracket_exp_mb ()
{
  wint_t wc, wc1, wc2;

  /* Work area to build a mb_char_classes.  */
  struct mb_char_classes *work_mbc;
  int chars_al, range_sts_al, range_ends_al, ch_classes_al,
    equivs_al, coll_elems_al;

  REALLOC_IF_NECESSARY(dfa->mbcsets, struct mb_char_classes,
		       dfa->mbcsets_alloc, dfa->nmbcsets + 1);
  /* dfa->multibyte_prop[] hold the index of dfa->mbcsets.
     We will update dfa->multibyte_prop in addtok(), because we can't
     decide the index in dfa->tokens[].  */

  /* Initialize work are */
  work_mbc = &(dfa->mbcsets[dfa->nmbcsets++]);

  chars_al = 1;
  range_sts_al = range_ends_al = 0;
  ch_classes_al = equivs_al = coll_elems_al = 0;
  MALLOC(work_mbc->chars, wchar_t, chars_al);

  work_mbc->nchars = work_mbc->nranges = work_mbc->nch_classes = 0;
  work_mbc->nequivs = work_mbc->ncoll_elems = 0;
  work_mbc->chars = work_mbc->ch_classes = NULL;
  work_mbc->range_sts = work_mbc->range_ends = NULL;
  work_mbc->equivs = work_mbc->coll_elems = NULL;

  wc = fetch_wc(_("Unbalanced ["));
  if (wc == L'^')
    {
      wc = fetch_wc(_("Unbalanced ["));
      work_mbc->invert = 1;
    }
  else
    work_mbc->invert = 0;
  do
    {
      wc1 = WEOF; /* mark wc1 is not initialized".  */

      /* Note that if we're looking at some other [:...:] construct,
	 we just treat it as a bunch of ordinary characters.  We can do
	 this because we assume regex has checked for syntax errors before
	 dfa is ever called. */
      if (wc == L'[' && (syntax_bits & RE_CHAR_CLASSES))
	{
#define BRACKET_BUFFER_SIZE 128
	  char str[BRACKET_BUFFER_SIZE];
	  wc1 = wc;
	  wc = fetch_wc(_("Unbalanced ["));

	  /* If pattern contains `[[:', `[[.', or `[[='.  */
	  if (cur_mb_len == 1 && (wc == L':' || wc == L'.' || wc == L'='))
	    {
	      unsigned char c;
	      unsigned char delim = (unsigned char)wc;
	      int len = 0;
	      for (;;)
		{
		  if (! lexleft)
		    dfaerror (_("Unbalanced ["));
		  c = (unsigned char) *lexptr++;
		  --lexleft;

		  if ((c == delim && *lexptr == ']') || lexleft == 0)
		    break;
		  if (len < BRACKET_BUFFER_SIZE)
		    str[len++] = c;
		  else
		    /* This is in any case an invalid class name.  */
		    str[0] = '\0';
		}
	      str[len] = '\0';

	      if (lexleft == 0)
		{
		  REALLOC_IF_NECESSARY(work_mbc->chars, wchar_t, chars_al,
				       work_mbc->nchars + 2);
		  work_mbc->chars[work_mbc->nchars++] = L'[';
		  work_mbc->chars[work_mbc->nchars++] = delim;
		  break; 
		}

	      if (--lexleft, *lexptr++ != ']')
		dfaerror (_("Unbalanced ["));
	      if (delim == ':')
		/* build character class.  */
		{
		  wctype_t wt;
		  /* Query the character class as wctype_t.  */
		  wt = wctype (str);

		  if (ch_classes_al == 0)
		    MALLOC(work_mbc->ch_classes, wchar_t, ++ch_classes_al);
		  REALLOC_IF_NECESSARY(work_mbc->ch_classes, wctype_t,
				       ch_classes_al,
				       work_mbc->nch_classes + 1);
		  work_mbc->ch_classes[work_mbc->nch_classes++] = wt;

 		}
	      else if (delim == '=' || delim == '.')
		{
		  char *elem;
		  MALLOC(elem, char, len + 1);
		  strncpy(elem, str, len + 1);

		  if (delim == '=')
		    /* build equivalent class.  */
		    {
		      if (equivs_al == 0)
			MALLOC(work_mbc->equivs, char*, ++equivs_al);
		      REALLOC_IF_NECESSARY(work_mbc->equivs, char*,
					   equivs_al,
					   work_mbc->nequivs + 1);
		      work_mbc->equivs[work_mbc->nequivs++] = elem;
		    }

		  if (delim == '.')
		    /* build collating element.  */
		    {
		      if (coll_elems_al == 0)
			MALLOC(work_mbc->coll_elems, char*, ++coll_elems_al);
		      REALLOC_IF_NECESSARY(work_mbc->coll_elems, char*,
					   coll_elems_al,
					   work_mbc->ncoll_elems + 1);
		      work_mbc->coll_elems[work_mbc->ncoll_elems++] = elem;
		    }
 		}
	      wc1 = wc = WEOF;
	    }
	  else
	    /* We treat '[' as a normal character here.  */
	    {
	      wc2 = wc1; wc1 = wc; wc = wc2; /* swap */
	    }
	}
      else
	{
	  if (wc == L'\\' && (syntax_bits & RE_BACKSLASH_ESCAPE_IN_LISTS))
	    wc = fetch_wc(("Unbalanced ["));
	}

      if (wc1 == WEOF)
	wc1 = fetch_wc(_("Unbalanced ["));

      if (wc1 == L'-')
	/* build range characters.  */
	{
	  wc2 = fetch_wc(_("Unbalanced ["));
	  if (wc2 == L']')
	    {
	      /* In the case [x-], the - is an ordinary hyphen,
		 which is left in c1, the lookahead character. */
	      lexptr -= cur_mb_len;
	      lexleft += cur_mb_len;
	      wc2 = wc;
	    }
	  else
	    {
	      if (wc2 == L'\\'
		  && (syntax_bits & RE_BACKSLASH_ESCAPE_IN_LISTS))
		wc2 = fetch_wc(_("Unbalanced ["));
	      wc1 = fetch_wc(_("Unbalanced ["));
	    }

	  if (range_sts_al == 0)
	    {
	      MALLOC(work_mbc->range_sts, wchar_t, ++range_sts_al);
	      MALLOC(work_mbc->range_ends, wchar_t, ++range_ends_al);
	    }
	  REALLOC_IF_NECESSARY(work_mbc->range_sts, wchar_t,
			       range_sts_al, work_mbc->nranges + 1);
	  work_mbc->range_sts[work_mbc->nranges] = (wchar_t)wc;
	  REALLOC_IF_NECESSARY(work_mbc->range_ends, wchar_t,
			       range_ends_al, work_mbc->nranges + 1);
	  work_mbc->range_ends[work_mbc->nranges++] = (wchar_t)wc2;
	}
      else if (wc != WEOF)
	/* build normal characters.  */
	{
	  REALLOC_IF_NECESSARY(work_mbc->chars, wchar_t, chars_al,
			       work_mbc->nchars + 1);
	  work_mbc->chars[work_mbc->nchars++] = (wchar_t)wc;
	}
    }
  while ((wc = wc1) != L']');
}
#endif /* MBS_SUPPORT */

#ifdef __STDC__
#define FUNC(F, P) static int F(int c) { return P(c); }
#else
#define FUNC(F, P) static int F(c) int c; { return P(c); }
#endif

FUNC(is_alpha, ISALPHA)
FUNC(is_upper, ISUPPER)
FUNC(is_lower, ISLOWER)
FUNC(is_digit, ISDIGIT)
FUNC(is_xdigit, ISXDIGIT)
FUNC(is_space, ISSPACE)
FUNC(is_punct, ISPUNCT)
FUNC(is_alnum, ISALNUM)
FUNC(is_print, ISPRINT)
FUNC(is_graph, ISGRAPH)
FUNC(is_cntrl, ISCNTRL)

static int
is_blank (int c)
{
   return (c == ' ' || c == '\t');
}

/* The following list maps the names of the Posix named character classes
   to predicate functions that determine whether a given character is in
   the class.  The leading [ has already been eaten by the lexical analyzer. */
static struct {
  const char *name;
  int (*pred) PARAMS ((int));
} const prednames[] = {
  { ":alpha:]", is_alpha },
  { ":upper:]", is_upper },
  { ":lower:]", is_lower },
  { ":digit:]", is_digit },
  { ":xdigit:]", is_xdigit },
  { ":space:]", is_space },
  { ":punct:]", is_punct },
  { ":alnum:]", is_alnum },
  { ":print:]", is_print },
  { ":graph:]", is_graph },
  { ":cntrl:]", is_cntrl },
  { ":blank:]", is_blank },
  { 0 }
};

/* Return non-zero if C is a `word-constituent' byte; zero otherwise.  */
#define IS_WORD_CONSTITUENT(C) (ISALNUM(C) || (C) == '_')

static int
looking_at (char const *s)
{
  size_t len;

  len = strlen(s);
  if (lexleft < len)
    return 0;
  return strncmp(s, lexptr, len) == 0;
}

static token
lex (void)
{
  unsigned c, c1, c2;
  int backslash = 0, invert;
  charclass ccl;
  int i;

  /* Basic plan: We fetch a character.  If it's a backslash,
     we set the backslash flag and go through the loop again.
     On the plus side, this avoids having a duplicate of the
     main switch inside the backslash case.  On the minus side,
     it means that just about every case begins with
     "if (backslash) ...".  */
  for (i = 0; i < 2; ++i)
    {
      FETCH(c, 0);
#ifdef MBS_SUPPORT
      if (MB_CUR_MAX > 1 && cur_mb_index)
	/* If this is a part of a multi-byte character, we must treat
	   this byte data as a normal character.
	   e.g. In case of SJIS encoding, some character contains '\',
	        but they must not be backslash.  */
	goto normal_char;
#endif /* MBS_SUPPORT  */
      switch (c)
	{
	case '\\':
	  if (backslash)
	    goto normal_char;
	  if (lexleft == 0)
	    dfaerror(_("Unfinished \\ escape"));
	  backslash = 1;
	  break;

	case '^':
	  if (backslash)
	    goto normal_char;
	  if (syntax_bits & RE_CONTEXT_INDEP_ANCHORS
	      || lasttok == END
	      || lasttok == LPAREN
	      || lasttok == OR)
	    return lasttok = BEGLINE;
	  goto normal_char;

	case '$':
	  if (backslash)
	    goto normal_char;
	  if (syntax_bits & RE_CONTEXT_INDEP_ANCHORS
	      || lexleft == 0
	      || (syntax_bits & RE_NO_BK_PARENS
		  ? lexleft > 0 && *lexptr == ')'
		  : lexleft > 1 && lexptr[0] == '\\' && lexptr[1] == ')')
	      || (syntax_bits & RE_NO_BK_VBAR
		  ? lexleft > 0 && *lexptr == '|'
		  : lexleft > 1 && lexptr[0] == '\\' && lexptr[1] == '|')
	      || ((syntax_bits & RE_NEWLINE_ALT)
	          && lexleft > 0 && *lexptr == '\n'))
	    return lasttok = ENDLINE;
	  goto normal_char;

	case '1':
	case '2':
	case '3':
	case '4':
	case '5':
	case '6':
	case '7':
	case '8':
	case '9':
	  if (backslash && !(syntax_bits & RE_NO_BK_REFS))
	    {
	      laststart = 0;
	      return lasttok = BACKREF;
	    }
	  goto normal_char;

	case '`':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = BEGLINE;	/* FIXME: should be beginning of string */
	  goto normal_char;

	case '\'':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = ENDLINE;	/* FIXME: should be end of string */
	  goto normal_char;

	case '<':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = BEGWORD;
	  goto normal_char;

	case '>':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = ENDWORD;
	  goto normal_char;

	case 'b':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = LIMWORD;
	  goto normal_char;

	case 'B':
	  if (backslash && !(syntax_bits & RE_NO_GNU_OPS))
	    return lasttok = NOTLIMWORD;
	  goto normal_char;

	case '?':
	  if (syntax_bits & RE_LIMITED_OPS)
	    goto normal_char;
	  if (backslash != ((syntax_bits & RE_BK_PLUS_QM) != 0))
	    goto normal_char;
	  if (!(syntax_bits & RE_CONTEXT_INDEP_OPS) && laststart)
	    goto normal_char;
	  return lasttok = QMARK;

	case '*':
	  if (backslash)
	    goto normal_char;
	  if (!(syntax_bits & RE_CONTEXT_INDEP_OPS) && laststart)
	    goto normal_char;
	  return lasttok = STAR;

	case '+':
	  if (syntax_bits & RE_LIMITED_OPS)
	    goto normal_char;
	  if (backslash != ((syntax_bits & RE_BK_PLUS_QM) != 0))
	    goto normal_char;
	  if (!(syntax_bits & RE_CONTEXT_INDEP_OPS) && laststart)
	    goto normal_char;
	  return lasttok = PLUS;

	case '{':
	  if (!(syntax_bits & RE_INTERVALS))
	    goto normal_char;
	  if (backslash != ((syntax_bits & RE_NO_BK_BRACES) == 0))
	    goto normal_char;
	  if (!(syntax_bits & RE_CONTEXT_INDEP_OPS) && laststart)
	    goto normal_char;

	  if (syntax_bits & RE_NO_BK_BRACES)
	    {
	      /* Scan ahead for a valid interval; if it's not valid,
		 treat it as a literal '{'.  */
	      int lo = -1, hi = -1;
	      char const *p = lexptr;
	      char const *lim = p + lexleft;
	      for (;  p != lim && ISASCIIDIGIT (*p);  p++)
		lo = (lo < 0 ? 0 : lo * 10) + *p - '0';
	      if (p != lim && *p == ',')
		while (++p != lim && ISASCIIDIGIT (*p))
		  hi = (hi < 0 ? 0 : hi * 10) + *p - '0';
	      else
		hi = lo;
	      if (p == lim || *p != '}'
		  || lo < 0 || RE_DUP_MAX < hi || (0 <= hi && hi < lo))
		goto normal_char;
	    }

	  minrep = 0;
	  /* Cases:
	     {M} - exact count
	     {M,} - minimum count, maximum is infinity
	     {M,N} - M through N */
	  FETCH(c, _("unfinished repeat count"));
	  if (ISASCIIDIGIT (c))
	    {
	      minrep = c - '0';
	      for (;;)
		{
		  FETCH(c, _("unfinished repeat count"));
		  if (! ISASCIIDIGIT (c))
		    break;
		  minrep = 10 * minrep + c - '0';
		}
	    }
	  else
	    dfaerror(_("malformed repeat count"));
	  if (c == ',')
	    {
	      FETCH (c, _("unfinished repeat count"));
	      if (! ISASCIIDIGIT (c))
		maxrep = -1;
	      else
		{
		  maxrep = c - '0';
		  for (;;)
		    {
		      FETCH (c, _("unfinished repeat count"));
		      if (! ISASCIIDIGIT (c))
			break;
		      maxrep = 10 * maxrep + c - '0';
		    }
		  if (0 <= maxrep && maxrep < minrep)
		    dfaerror (_("malformed repeat count"));
		}
	    }
	  else
	    maxrep = minrep;
	  if (!(syntax_bits & RE_NO_BK_BRACES))
	    {
	      if (c != '\\')
		dfaerror(_("malformed repeat count"));
	      FETCH(c, _("unfinished repeat count"));
	    }
	  if (c != '}')
	    dfaerror(_("malformed repeat count"));
	  laststart = 0;
	  return lasttok = REPMN;

	case '|':
	  if (syntax_bits & RE_LIMITED_OPS)
	    goto normal_char;
	  if (backslash != ((syntax_bits & RE_NO_BK_VBAR) == 0))
	    goto normal_char;
	  laststart = 1;
	  return lasttok = OR;

	case '\n':
	  if (syntax_bits & RE_LIMITED_OPS
	      || backslash
	      || !(syntax_bits & RE_NEWLINE_ALT))
	    goto normal_char;
	  laststart = 1;
	  return lasttok = OR;

	case '(':
	  if (backslash != ((syntax_bits & RE_NO_BK_PARENS) == 0))
	    goto normal_char;
	  ++parens;
	  laststart = 1;
	  return lasttok = LPAREN;

	case ')':
	  if (backslash != ((syntax_bits & RE_NO_BK_PARENS) == 0))
	    goto normal_char;
	  if (parens == 0 && syntax_bits & RE_UNMATCHED_RIGHT_PAREN_ORD)
	    goto normal_char;
	  --parens;
	  laststart = 0;
	  return lasttok = RPAREN;

	case '.':
	  if (backslash)
	    goto normal_char;
#ifdef MBS_SUPPORT
	  if (MB_CUR_MAX > 1)
	    {
	      /* In multibyte environment period must match with a single
		 character not a byte.  So we use ANYCHAR.  */
	      laststart = 0;
	      return lasttok = ANYCHAR;
	    }
#endif /* MBS_SUPPORT */
	  zeroset(ccl);
	  notset(ccl);
	  if (!(syntax_bits & RE_DOT_NEWLINE))
	    clrbit(eolbyte, ccl);
	  if (syntax_bits & RE_DOT_NOT_NULL)
	    clrbit('\0', ccl);
	  laststart = 0;
	  return lasttok = CSET + charclass_index(ccl);

	case 'w':
	case 'W':
	  if (!backslash || (syntax_bits & RE_NO_GNU_OPS))
	    goto normal_char;
	  zeroset(ccl);
	  for (c2 = 0; c2 < NOTCHAR; ++c2)
	    if (IS_WORD_CONSTITUENT(c2))
	      setbit(c2, ccl);
	  if (c == 'W')
	    notset(ccl);
	  laststart = 0;
	  return lasttok = CSET + charclass_index(ccl);

	case '[':
	  if (backslash)
	    goto normal_char;
	  laststart = 0;
#ifdef MBS_SUPPORT
	  if (MB_CUR_MAX > 1)
	    {
	      /* In multibyte environment a bracket expression may contain
		 multibyte characters, which must be treated as characters
		 (not bytes).  So we parse it by parse_bracket_exp_mb().  */
	      parse_bracket_exp_mb();
	      return lasttok = MBCSET;
	    }
#endif
	  zeroset(ccl);
	  FETCH(c, _("Unbalanced ["));
	  if (c == '^')
	    {
	      FETCH(c, _("Unbalanced ["));
	      invert = 1;
	    }
	  else
	    invert = 0;
	  do
	    {
	      /* Nobody ever said this had to be fast. :-)
		 Note that if we're looking at some other [:...:]
		 construct, we just treat it as a bunch of ordinary
		 characters.  We can do this because we assume
		 regex has checked for syntax errors before
		 dfa is ever called. */
	      if (c == '[' && (syntax_bits & RE_CHAR_CLASSES))
		for (c1 = 0; prednames[c1].name; ++c1)
		  if (looking_at(prednames[c1].name))
		    {
		      int (*pred) PARAMS ((int)) = prednames[c1].pred;

		      for (c2 = 0; c2 < NOTCHAR; ++c2)
			if ((*pred)(c2))
			  setbit_case_fold (c2, ccl);
		      lexptr += strlen(prednames[c1].name);
		      lexleft -= strlen(prednames[c1].name);
		      FETCH(c1, _("Unbalanced ["));
		      goto skip;
		    }
	      if (c == '\\' && (syntax_bits & RE_BACKSLASH_ESCAPE_IN_LISTS))
		FETCH(c, _("Unbalanced ["));
	      FETCH(c1, _("Unbalanced ["));
	      if (c1 == '-')
		{
		  FETCH(c2, _("Unbalanced ["));
		  if (c2 == ']')
		    {
		      /* In the case [x-], the - is an ordinary hyphen,
			 which is left in c1, the lookahead character. */
		      --lexptr;
		      ++lexleft;
		    }
		  else
		    {
		      if (c2 == '\\'
			  && (syntax_bits & RE_BACKSLASH_ESCAPE_IN_LISTS))
			FETCH(c2, _("Unbalanced ["));
		      FETCH(c1, _("Unbalanced ["));
		      if (!hard_LC_COLLATE) {
		        for (; c <= c2; c++)
			  setbit_case_fold (c, ccl);
		      } else {
			/* POSIX locales are painful - leave the decision to libc */
			char expr[6] = { '[', c, '-', c2, ']', '\0' };
			regex_t re;
			if (regcomp (&re, expr, case_fold ? REG_ICASE : 0) == REG_NOERROR) {
			  for (c = 0; c < NOTCHAR; ++c) {
			    char buf[2] = { c, '\0' };
			    regmatch_t mat;
			    if (regexec (&re, buf, 1, &mat, 0) == REG_NOERROR
                               && mat.rm_so == 0 && mat.rm_eo == 1)
                              setbit_case_fold (c, ccl);
			  }
			  regfree (&re);
			}
		      }
		      continue;
		    }
		}

	      setbit_case_fold (c, ccl);

	    skip:
	      ;
	    }
	  while ((c = c1) != ']');
	  if (invert)
	    {
	      notset(ccl);
	      if (syntax_bits & RE_HAT_LISTS_NOT_NEWLINE)
		clrbit(eolbyte, ccl);
	    }
	  return lasttok = CSET + charclass_index(ccl);

	default:
	normal_char:
	  laststart = 0;
	  if (case_fold && ISALPHA(c))
	    {
	      zeroset(ccl);
	      setbit_case_fold (c, ccl);
	      return lasttok = CSET + charclass_index(ccl);
	    }
	  return c;
	}
    }

  /* The above loop should consume at most a backslash
     and some other character. */
  abort();
  return END;	/* keeps pedantic compilers happy. */
}

/* Recursive descent parser for regular expressions. */

static token tok;		/* Lookahead token. */
static int depth;		/* Current depth of a hypothetical stack
				   holding deferred productions.  This is
				   used to determine the depth that will be
				   required of the real stack later on in
				   dfaanalyze(). */

/* Add the given token to the parse tree, maintaining the depth count and
   updating the maximum depth if necessary. */
static void
addtok (token t)
{
#ifdef MBS_SUPPORT
  if (MB_CUR_MAX > 1)
    {
      REALLOC_IF_NECESSARY(dfa->multibyte_prop, int, dfa->nmultibyte_prop,
			   dfa->tindex);
      /* Set dfa->multibyte_prop.  See struct dfa in dfa.h.  */
      if (t == MBCSET)
	dfa->multibyte_prop[dfa->tindex] = ((dfa->nmbcsets - 1) << 2) + 3;
      else if (t < NOTCHAR)
	dfa->multibyte_prop[dfa->tindex]
	  = (cur_mb_len == 1)? 3 /* single-byte char */
	  : (((cur_mb_index == 1)? 1 : 0) /* 1st-byte of multibyte char */
	     + ((cur_mb_index == cur_mb_len)? 2 : 0)); /* last-byte */
      else
	/* It may be unnecesssary, but it is safer to treat other
	   symbols as singlebyte characters.  */
	dfa->multibyte_prop[dfa->tindex] = 3;
    }
#endif

  REALLOC_IF_NECESSARY(dfa->tokens, token, dfa->talloc, dfa->tindex);
  dfa->tokens[dfa->tindex++] = t;

  switch (t)
    {
    case QMARK:
    case STAR:
    case PLUS:
      break;

    case CAT:
    case OR:
    case ORTOP:
      --depth;
      break;

    default:
      ++dfa->nleaves;
    case EMPTY:
      ++depth;
      break;
    }
  if (depth > dfa->depth)
    dfa->depth = depth;
}

/* The grammar understood by the parser is as follows.

   regexp:
     regexp OR branch
     branch

   branch:
     branch closure
     closure

   closure:
     closure QMARK
     closure STAR
     closure PLUS
     closure REPMN
     atom

   atom:
     <normal character>
     <multibyte character>
     ANYCHAR
     MBCSET
     CSET
     BACKREF
     BEGLINE
     ENDLINE
     BEGWORD
     ENDWORD
     LIMWORD
     NOTLIMWORD
     CRANGE
     LPAREN regexp RPAREN
     <empty>

   The parser builds a parse tree in postfix form in an array of tokens. */

static void
atom (void)
{
  if ((tok >= 0 && tok < NOTCHAR) || tok >= CSET || tok == BACKREF
      || tok == BEGLINE || tok == ENDLINE || tok == BEGWORD
#ifdef MBS_SUPPORT
      || tok == ANYCHAR || tok == MBCSET /* MB_CUR_MAX > 1 */
#endif /* MBS_SUPPORT */
      || tok == ENDWORD || tok == LIMWORD || tok == NOTLIMWORD)
    {
      addtok(tok);
      tok = lex();
#ifdef MBS_SUPPORT
      /* We treat a multibyte character as a single atom, so that DFA
	 can treat a multibyte character as a single expression.

         e.g. We construct following tree from "<mb1><mb2>".
              <mb1(1st-byte)><mb1(2nd-byte)><CAT><mb1(3rd-byte)><CAT>
              <mb2(1st-byte)><mb2(2nd-byte)><CAT><mb2(3rd-byte)><CAT><CAT>
      */
      if (MB_CUR_MAX > 1)
	{
	  while (cur_mb_index > 1 && tok >= 0 && tok < NOTCHAR)
	    {
	      addtok(tok);
	      addtok(CAT);
	      tok = lex();
	    }
	}
#endif /* MBS_SUPPORT  */
    }
  else if (tok == CRANGE)
    {
      /* A character range like "[a-z]" in a locale other than "C" or
	 "POSIX".  This range might any sequence of one or more
	 characters.  Unfortunately the POSIX locale primitives give
	 us no practical way to find what character sequences might be
	 matched.  Treat this approximately like "(.\1)" -- i.e. match
	 one character, and then punt to the full matcher.  */
      charclass ccl;
      zeroset (ccl);
      notset (ccl);
      addtok (CSET + charclass_index (ccl));
      addtok (BACKREF);
      addtok (CAT);
      tok = lex ();
    }
  else if (tok == LPAREN)
    {
      tok = lex();
      regexp(0);
      if (tok != RPAREN)
	dfaerror(_("Unbalanced ("));
      tok = lex();
    }
  else
    addtok(EMPTY);
}

/* Return the number of tokens in the given subexpression. */
static int
nsubtoks (int tindex)
{
  int ntoks1;

  switch (dfa->tokens[tindex - 1])
    {
    default:
      return 1;
    case QMARK:
    case STAR:
    case PLUS:
      return 1 + nsubtoks(tindex - 1);
    case CAT:
    case OR:
    case ORTOP:
      ntoks1 = nsubtoks(tindex - 1);
      return 1 + ntoks1 + nsubtoks(tindex - 1 - ntoks1);
    }
}

/* Copy the given subexpression to the top of the tree. */
static void
copytoks (int tindex, int ntokens)
{
  int i;

  for (i = 0; i < ntokens; ++i)
    addtok(dfa->tokens[tindex + i]);
}

static void
closure (void)
{
  int tindex, ntokens, i;

  atom();
  while (tok == QMARK || tok == STAR || tok == PLUS || tok == REPMN)
    if (tok == REPMN)
      {
	ntokens = nsubtoks(dfa->tindex);
	tindex = dfa->tindex - ntokens;
	if (maxrep < 0)
	  addtok(PLUS);
	if (minrep == 0)
	  addtok(QMARK);
	for (i = 1; i < minrep; ++i)
	  {
	    copytoks(tindex, ntokens);
	    addtok(CAT);
	  }
	for (; i < maxrep; ++i)
	  {
	    copytoks(tindex, ntokens);
	    addtok(QMARK);
	    addtok(CAT);
	  }
	tok = lex();
      }
    else
      {
	addtok(tok);
	tok = lex();
      }
}

static void
branch (void)
{
  closure();
  while (tok != RPAREN && tok != OR && tok >= 0)
    {
      closure();
      addtok(CAT);
    }
}

static void
regexp (int toplevel)
{
  branch();
  while (tok == OR)
    {
      tok = lex();
      branch();
      if (toplevel)
	addtok(ORTOP);
      else
	addtok(OR);
    }
}

/* Main entry point for the parser.  S is a string to be parsed, len is the
   length of the string, so s can include NUL characters.  D is a pointer to
   the struct dfa to parse into. */
void
dfaparse (char const *s, size_t len, struct dfa *d)
{
  dfa = d;
  lexstart = lexptr = s;
  lexleft = len;
  lasttok = END;
  laststart = 1;
  parens = 0;
  hard_LC_COLLATE = hard_locale (LC_COLLATE);
#ifdef MBS_SUPPORT
  if (MB_CUR_MAX > 1)
    {
      cur_mb_index = 0;
      cur_mb_len = 0;
      memset(&mbs, 0, sizeof(mbstate_t));
    }
#endif /* MBS_SUPPORT  */

  if (! syntax_bits_set)
    dfaerror(_("No syntax specified"));

  tok = lex();
  depth = d->depth;

  regexp(1);

  if (tok != END)
    dfaerror(_("Unbalanced )"));

  addtok(END - d->nregexps);
  addtok(CAT);

  if (d->nregexps)
    addtok(ORTOP);

  ++d->nregexps;
}

/* Some primitives for operating on sets of positions. */

/* Copy one set to another; the destination must be large enough. */
static void
copy (position_set const *src, position_set *dst)
{
  int i;

  for (i = 0; i < src->nelem; ++i)
    dst->elems[i] = src->elems[i];
  dst->nelem = src->nelem;
}

/* Insert a position in a set.  Position sets are maintained in sorted
   order according to index.  If position already exists in the set with
   the same index then their constraints are logically or'd together.
   S->elems must point to an array large enough to hold the resulting set. */
static void
insert (position p, position_set *s)
{
  int i;
  position t1, t2;

  for (i = 0; i < s->nelem && p.index < s->elems[i].index; ++i)
    continue;
  if (i < s->nelem && p.index == s->elems[i].index)
    s->elems[i].constraint |= p.constraint;
  else
    {
      t1 = p;
      ++s->nelem;
      while (i < s->nelem)
	{
	  t2 = s->elems[i];
	  s->elems[i++] = t1;
	  t1 = t2;
	}
    }
}

/* Merge two sets of positions into a third.  The result is exactly as if
   the positions of both sets were inserted into an initially empty set. */
static void
merge (position_set const *s1, position_set const *s2, position_set *m)
{
  int i = 0, j = 0;

  m->nelem = 0;
  while (i < s1->nelem && j < s2->nelem)
    if (s1->elems[i].index > s2->elems[j].index)
      m->elems[m->nelem++] = s1->elems[i++];
    else if (s1->elems[i].index < s2->elems[j].index)
      m->elems[m->nelem++] = s2->elems[j++];
    else
      {
	m->elems[m->nelem] = s1->elems[i++];
	m->elems[m->nelem++].constraint |= s2->elems[j++].constraint;
      }
  while (i < s1->nelem)
    m->elems[m->nelem++] = s1->elems[i++];
  while (j < s2->nelem)
    m->elems[m->nelem++] = s2->elems[j++];
}

/* Delete a position from a set. */
static void
delete (position p, position_set *s)
{
  int i;

  for (i = 0; i < s->nelem; ++i)
    if (p.index == s->elems[i].index)
      break;
  if (i < s->nelem)
    for (--s->nelem; i < s->nelem; ++i)
      s->elems[i] = s->elems[i + 1];
}

/* Find the index of the state corresponding to the given position set with
   the given preceding context, or create a new state if there is no such
   state.  Newline and letter tell whether we got here on a newline or
   letter, respectively. */
static int
state_index (struct dfa *d, position_set const *s, int newline, int letter)
{
  int hash = 0;
  int constraint;
  int i, j;

  newline = newline ? 1 : 0;
  letter = letter ? 1 : 0;

  for (i = 0; i < s->nelem; ++i)
    hash ^= s->elems[i].index + s->elems[i].constraint;

  /* Try to find a state that exactly matches the proposed one. */
  for (i = 0; i < d->sindex; ++i)
    {
      if (hash != d->states[i].hash || s->nelem != d->states[i].elems.nelem
	  || newline != d->states[i].newline || letter != d->states[i].letter)
	continue;
      for (j = 0; j < s->nelem; ++j)
	if (s->elems[j].constraint
	    != d->states[i].elems.elems[j].constraint
	    || s->elems[j].index != d->states[i].elems.elems[j].index)
	  break;
      if (j == s->nelem)
	return i;
    }

  /* We'll have to create a new state. */
  REALLOC_IF_NECESSARY(d->states, dfa_state, d->salloc, d->sindex);
  d->states[i].hash = hash;
  MALLOC(d->states[i].elems.elems, position, s->nelem);
  copy(s, &d->states[i].elems);
  d->states[i].newline = newline;
  d->states[i].letter = letter;
  d->states[i].backref = 0;
  d->states[i].constraint = 0;
  d->states[i].first_end = 0;
#ifdef MBS_SUPPORT
  if (MB_CUR_MAX > 1)
    d->states[i].mbps.nelem = 0;
#endif
  for (j = 0; j < s->nelem; ++j)
    if (d->tokens[s->elems[j].index] < 0)
      {
	constraint = s->elems[j].constraint;
	if (SUCCEEDS_IN_CONTEXT(constraint, newline, 0, letter, 0)
	    || SUCCEEDS_IN_CONTEXT(constraint, newline, 0, letter, 1)
	    || SUCCEEDS_IN_CONTEXT(constraint, newline, 1, letter, 0)
	    || SUCCEEDS_IN_CONTEXT(constraint, newline, 1, letter, 1))
	  d->states[i].constraint |= constraint;
	if (! d->states[i].first_end)
	  d->states[i].first_end = d->tokens[s->elems[j].index];
      }
    else if (d->tokens[s->elems[j].index] == BACKREF)
      {
	d->states[i].constraint = NO_CONSTRAINT;
	d->states[i].backref = 1;
      }

  ++d->sindex;

  return i;
}

/* Find the epsilon closure of a set of positions.  If any position of the set
   contains a symbol that matches the empty string in some context, replace
   that position with the elements of its follow labeled with an appropriate
   constraint.  Repeat exhaustively until no funny positions are left.
   S->elems must be large enough to hold the result. */
static void
epsclosure (position_set *s, struct dfa const *d)
{
  int i, j;
  int *visited;
  position p, old;

  MALLOC(visited, int, d->tindex);
  for (i = 0; i < d->tindex; ++i)
    visited[i] = 0;

  for (i = 0; i < s->nelem; ++i)
    if (d->tokens[s->elems[i].index] >= NOTCHAR
	&& d->tokens[s->elems[i].index] != BACKREF
#ifdef MBS_SUPPORT
	&& d->tokens[s->elems[i].index] != ANYCHAR
	&& d->tokens[s->elems[i].index] != MBCSET
#endif
	&& d->tokens[s->elems[i].index] < CSET)
      {
	old = s->elems[i];
	p.constraint = old.constraint;
	delete(s->elems[i], s);
	if (visited[old.index])
	  {
	    --i;
	    continue;
	  }
	visited[old.index] = 1;
	switch (d->tokens[old.index])
	  {
	  case BEGLINE:
	    p.constraint &= BEGLINE_CONSTRAINT;
	    break;
	  case ENDLINE:
	    p.constraint &= ENDLINE_CONSTRAINT;
	    break;
	  case BEGWORD:
	    p.constraint &= BEGWORD_CONSTRAINT;
	    break;
	  case ENDWORD:
	    p.constraint &= ENDWORD_CONSTRAINT;
	    break;
	  case LIMWORD:
	    p.constraint &= LIMWORD_CONSTRAINT;
	    break;
	  case NOTLIMWORD:
	    p.constraint &= NOTLIMWORD_CONSTRAINT;
	    break;
	  default:
	    break;
	  }
	for (j = 0; j < d->follows[old.index].nelem; ++j)
	  {
	    p.index = d->follows[old.index].elems[j].index;
	    insert(p, s);
	  }
	/* Force rescan to start at the beginning. */
	i = -1;
      }

  free(visited);
}

/* Perform bottom-up analysis on the parse tree, computing various functions.
   Note that at this point, we're pretending constructs like \< are real
   characters rather than constraints on what can follow them.

   Nullable:  A node is nullable if it is at the root of a regexp that can
   match the empty string.
   *  EMPTY leaves are nullable.
   * No other leaf is nullable.
   * A QMARK or STAR node is nullable.
   * A PLUS node is nullable if its argument is nullable.
   * A CAT node is nullable if both its arguments are nullable.
   * An OR node is nullable if either argument is nullable.

   Firstpos:  The firstpos of a node is the set of positions (nonempty leaves)
   that could correspond to the first character of a string matching the
   regexp rooted at the given node.
   * EMPTY leaves have empty firstpos.
   * The firstpos of a nonempty leaf is that leaf itself.
   * The firstpos of a QMARK, STAR, or PLUS node is the firstpos of its
     argument.
   * The firstpos of a CAT node is the firstpos of the left argument, union
     the firstpos of the right if the left argument is nullable.
   * The firstpos of an OR node is the union of firstpos of each argument.

   Lastpos:  The lastpos of a node is the set of positions that could
   correspond to the last character of a string matching the regexp at
   the given node.
   * EMPTY leaves have empty lastpos.
   * The lastpos of a nonempty leaf is that leaf itself.
   * The lastpos of a QMARK, STAR, or PLUS node is the lastpos of its
     argument.
   * The lastpos of a CAT node is the lastpos of its right argument, union
     the lastpos of the left if the right argument is nullable.
   * The lastpos of an OR node is the union of the lastpos of each argument.

   Follow:  The follow of a position is the set of positions that could
   correspond to the character following a character matching the node in
   a string matching the regexp.  At this point we consider special symbols
   that match the empty string in some context to be just normal characters.
   Later, if we find that a special symbol is in a follow set, we will
   replace it with the elements of its follow, labeled with an appropriate
   constraint.
   * Every node in the firstpos of the argument of a STAR or PLUS node is in
     the follow of every node in the lastpos.
   * Every node in the firstpos of the second argument of a CAT node is in
     the follow of every node in the lastpos of the first argument.

   Because of the postfix representation of the parse tree, the depth-first
   analysis is conveniently done by a linear scan with the aid of a stack.
   Sets are stored as arrays of the elements, obeying a stack-like allocation
   scheme; the number of elements in each set deeper in the stack can be
   used to determine the address of a particular set's array. */
void
dfaanalyze (struct dfa *d, int searchflag)
{
  int *nullable;		/* Nullable stack. */
  int *nfirstpos;		/* Element count stack for firstpos sets. */
  position *firstpos;		/* Array where firstpos elements are stored. */
  int *nlastpos;		/* Element count stack for lastpos sets. */
  position *lastpos;		/* Array where lastpos elements are stored. */
  int *nalloc;			/* Sizes of arrays allocated to follow sets. */
  position_set tmp;		/* Temporary set for merging sets. */
  position_set merged;		/* Result of merging sets. */
  int wants_newline;		/* True if some position wants newline info. */
  int *o_nullable;
  int *o_nfirst, *o_nlast;
  position *o_firstpos, *o_lastpos;
  int i, j;
  position *pos;

#ifdef DEBUG
  fprintf(stderr, "dfaanalyze:\n");
  for (i = 0; i < d->tindex; ++i)
    {
      fprintf(stderr, " %d:", i);
      prtok(d->tokens[i]);
    }
  putc('\n', stderr);
#endif

  d->searchflag = searchflag;

  MALLOC(nullable, int, d->depth);
  o_nullable = nullable;
  MALLOC(nfirstpos, int, d->depth);
  o_nfirst = nfirstpos;
  MALLOC(firstpos, position, d->nleaves);
  o_firstpos = firstpos, firstpos += d->nleaves;
  MALLOC(nlastpos, int, d->depth);
  o_nlast = nlastpos;
  MALLOC(lastpos, position, d->nleaves);
  o_lastpos = lastpos, lastpos += d->nleaves;
  MALLOC(nalloc, int, d->tindex);
  for (i = 0; i < d->tindex; ++i)
    nalloc[i] = 0;
  MALLOC(merged.elems, position, d->nleaves);

  CALLOC(d->follows, position_set, d->tindex);

  for (i = 0; i < d->tindex; ++i)
#ifdef DEBUG
    {				/* Nonsyntactic #ifdef goo... */
#endif
    switch (d->tokens[i])
      {
      case EMPTY:
	/* The empty set is nullable. */
	*nullable++ = 1;

	/* The firstpos and lastpos of the empty leaf are both empty. */
	*nfirstpos++ = *nlastpos++ = 0;
	break;

      case STAR:
      case PLUS:
	/* Every element in the firstpos of the argument is in the follow
	   of every element in the lastpos. */
	tmp.nelem = nfirstpos[-1];
	tmp.elems = firstpos;
	pos = lastpos;
	for (j = 0; j < nlastpos[-1]; ++j)
	  {
	    merge(&tmp, &d->follows[pos[j].index], &merged);
	    REALLOC_IF_NECESSARY(d->follows[pos[j].index].elems, position,
				 nalloc[pos[j].index], merged.nelem - 1);
	    copy(&merged, &d->follows[pos[j].index]);
	  }

      case QMARK:
	/* A QMARK or STAR node is automatically nullable. */
	if (d->tokens[i] != PLUS)
	  nullable[-1] = 1;
	break;

      case CAT:
	/* Every element in the firstpos of the second argument is in the
	   follow of every element in the lastpos of the first argument. */
	tmp.nelem = nfirstpos[-1];
	tmp.elems = firstpos;
	pos = lastpos + nlastpos[-1];
	for (j = 0; j < nlastpos[-2]; ++j)
	  {
	    merge(&tmp, &d->follows[pos[j].index], &merged);
	    REALLOC_IF_NECESSARY(d->follows[pos[j].index].elems, position,
				 nalloc[pos[j].index], merged.nelem - 1);
	    copy(&merged, &d->follows[pos[j].index]);
	  }

	/* The firstpos of a CAT node is the firstpos of the first argument,
	   union that of the second argument if the first is nullable. */
	if (nullable[-2])
	  nfirstpos[-2] += nfirstpos[-1];
	else
	  firstpos += nfirstpos[-1];
	--nfirstpos;

	/* The lastpos of a CAT node is the lastpos of the second argument,
	   union that of the first argument if the second is nullable. */
	if (nullable[-1])
	  nlastpos[-2] += nlastpos[-1];
	else
	  {
	    pos = lastpos + nlastpos[-2];
	    for (j = nlastpos[-1] - 1; j >= 0; --j)
	      pos[j] = lastpos[j];
	    lastpos += nlastpos[-2];
	    nlastpos[-2] = nlastpos[-1];
	  }
	--nlastpos;

	/* A CAT node is nullable if both arguments are nullable. */
	nullable[-2] = nullable[-1] && nullable[-2];
	--nullable;
	break;

      case OR:
      case ORTOP:
	/* The firstpos is the union of the firstpos of each argument. */
	nfirstpos[-2] += nfirstpos[-1];
	--nfirstpos;

	/* The lastpos is the union of the lastpos of each argument. */
	nlastpos[-2] += nlastpos[-1];
	--nlastpos;

	/* An OR node is nullable if either argument is nullable. */
	nullable[-2] = nullable[-1] || nullable[-2];
	--nullable;
	break;

      default:
	/* Anything else is a nonempty position.  (Note that special
	   constructs like \< are treated as nonempty strings here;
	   an "epsilon closure" effectively makes them nullable later.
	   Backreferences have to get a real position so we can detect
	   transitions on them later.  But they are nullable. */
	*nullable++ = d->tokens[i] == BACKREF;

	/* This position is in its own firstpos and lastpos. */
	*nfirstpos++ = *nlastpos++ = 1;
	--firstpos, --lastpos;
	firstpos->index = lastpos->index = i;
	firstpos->constraint = lastpos->constraint = NO_CONSTRAINT;

	/* Allocate the follow set for this position. */
	nalloc[i] = 1;
	MALLOC(d->follows[i].elems, position, nalloc[i]);
	break;
      }
#ifdef DEBUG
    /* ... balance the above nonsyntactic #ifdef goo... */
      fprintf(stderr, "node %d:", i);
      prtok(d->tokens[i]);
      putc('\n', stderr);
      fprintf(stderr, nullable[-1] ? " nullable: yes\n" : " nullable: no\n");
      fprintf(stderr, " firstpos:");
      for (j = nfirstpos[-1] - 1; j >= 0; --j)
	{
	  fprintf(stderr, " %d:", firstpos[j].index);
	  prtok(d->tokens[firstpos[j].index]);
	}
      fprintf(stderr, "\n lastpos:");
      for (j = nlastpos[-1] - 1; j >= 0; --j)
	{
	  fprintf(stderr, " %d:", lastpos[j].index);
	  prtok(d->tokens[lastpos[j].index]);
	}
      putc('\n', stderr);
    }
#endif

  /* For each follow set that is the follow set of a real position, replace
     it with its epsilon closure. */
  for (i = 0; i < d->tindex; ++i)
    if (d->tokens[i] < NOTCHAR || d->tokens[i] == BACKREF
#ifdef MBS_SUPPORT
        || d->tokens[i] == ANYCHAR
        || d->tokens[i] == MBCSE…