regex implementation from musl.

6 files changed, 4794 insertions, 0 deletions

diff --git a/system/lib/libc/musl/src/regex/regcomp.c b/system/lib/libc/musl/src/regex/regcomp.c
new file mode 100644
index 00000000..5cedfd52
--- /dev/null
+++ b/system/lib/libc/musl/src/regex/regcomp.c
@@ -0,0 +1,3352 @@
+/*
+  regcomp.c - TRE POSIX compatible regex compilation functions.
+
+  Copyright (c) 2001-2009 Ville Laurikari <vl@iki.fi>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS
+  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <regex.h>
+#include <limits.h>
+#include <stdint.h>
+
+#include "tre.h"
+
+#include <assert.h>
+
+/***********************************************************************
+ from tre-compile.h
+***********************************************************************/
+
+typedef struct {
+  int position;
+  int code_min;
+  int code_max;
+  int *tags;
+  int assertions;
+  tre_ctype_t class;
+  tre_ctype_t *neg_classes;
+  int backref;
+} tre_pos_and_tags_t;
+
+
+/***********************************************************************
+ from tre-ast.c and tre-ast.h
+***********************************************************************/
+
+/* The different AST node types. */
+typedef enum {
+  LITERAL,
+  CATENATION,
+  ITERATION,
+  UNION
+} tre_ast_type_t;
+
+/* Special subtypes of TRE_LITERAL. */
+#define EMPTY	  -1   /* Empty leaf (denotes empty string). */
+#define ASSERTION -2   /* Assertion leaf. */
+#define TAG	  -3   /* Tag leaf. */
+#define BACKREF	  -4   /* Back reference leaf. */
+
+#define IS_SPECIAL(x)	((x)->code_min < 0)
+#define IS_EMPTY(x)	((x)->code_min == EMPTY)
+#define IS_ASSERTION(x) ((x)->code_min == ASSERTION)
+#define IS_TAG(x)	((x)->code_min == TAG)
+#define IS_BACKREF(x)	((x)->code_min == BACKREF)
+
+
+/* A generic AST node.  All AST nodes consist of this node on the top
+   level with `obj' pointing to the actual content. */
+typedef struct {
+  tre_ast_type_t type;   /* Type of the node. */
+  void *obj;             /* Pointer to actual node. */
+  int nullable;
+  int submatch_id;
+  int num_submatches;
+  int num_tags;
+  tre_pos_and_tags_t *firstpos;
+  tre_pos_and_tags_t *lastpos;
+} tre_ast_node_t;
+
+
+/* A "literal" node.  These are created for assertions, back references,
+   tags, matching parameter settings, and all expressions that match one
+   character. */
+typedef struct {
+  long code_min;
+  long code_max;
+  int position;
+  tre_ctype_t class;
+  tre_ctype_t *neg_classes;
+} tre_literal_t;
+
+/* A "catenation" node.	 These are created when two regexps are concatenated.
+   If there are more than one subexpressions in sequence, the `left' part
+   holds all but the last, and `right' part holds the last subexpression
+   (catenation is left associative). */
+typedef struct {
+  tre_ast_node_t *left;
+  tre_ast_node_t *right;
+} tre_catenation_t;
+
+/* An "iteration" node.	 These are created for the "*", "+", "?", and "{m,n}"
+   operators. */
+typedef struct {
+  /* Subexpression to match. */
+  tre_ast_node_t *arg;
+  /* Minimum number of consecutive matches. */
+  int min;
+  /* Maximum number of consecutive matches. */
+  int max;
+  /* If 0, match as many characters as possible, if 1 match as few as
+     possible.	Note that this does not always mean the same thing as
+     matching as many/few repetitions as possible. */
+  unsigned int minimal:1;
+} tre_iteration_t;
+
+/* An "union" node.  These are created for the "|" operator. */
+typedef struct {
+  tre_ast_node_t *left;
+  tre_ast_node_t *right;
+} tre_union_t;
+
+static tre_ast_node_t *
+tre_ast_new_node(tre_mem_t mem, tre_ast_type_t type, size_t size);
+
+static tre_ast_node_t *
+tre_ast_new_literal(tre_mem_t mem, int code_min, int code_max, int position);
+
+static tre_ast_node_t *
+tre_ast_new_iter(tre_mem_t mem, tre_ast_node_t *arg, int min, int max,
+		 int minimal);
+
+static tre_ast_node_t *
+tre_ast_new_union(tre_mem_t mem, tre_ast_node_t *left, tre_ast_node_t *right);
+
+static tre_ast_node_t *
+tre_ast_new_catenation(tre_mem_t mem, tre_ast_node_t *left,
+		       tre_ast_node_t *right);
+
+
+static tre_ast_node_t *
+tre_ast_new_node(tre_mem_t mem, tre_ast_type_t type, size_t size)
+{
+  tre_ast_node_t *node;
+
+  node = tre_mem_calloc(mem, sizeof(*node));
+  if (!node)
+    return NULL;
+  node->obj = tre_mem_calloc(mem, size);
+  if (!node->obj)
+    return NULL;
+  node->type = type;
+  node->nullable = -1;
+  node->submatch_id = -1;
+
+  return node;
+}
+
+static tre_ast_node_t *
+tre_ast_new_literal(tre_mem_t mem, int code_min, int code_max, int position)
+{
+  tre_ast_node_t *node;
+  tre_literal_t *lit;
+
+  node = tre_ast_new_node(mem, LITERAL, sizeof(tre_literal_t));
+  if (!node)
+    return NULL;
+  lit = node->obj;
+  lit->code_min = code_min;
+  lit->code_max = code_max;
+  lit->position = position;
+
+  return node;
+}
+
+static tre_ast_node_t *
+tre_ast_new_iter(tre_mem_t mem, tre_ast_node_t *arg, int min, int max,
+		 int minimal)
+{
+  tre_ast_node_t *node;
+  tre_iteration_t *iter;
+
+  node = tre_ast_new_node(mem, ITERATION, sizeof(tre_iteration_t));
+  if (!node)
+    return NULL;
+  iter = node->obj;
+  iter->arg = arg;
+  iter->min = min;
+  iter->max = max;
+  iter->minimal = minimal;
+  node->num_submatches = arg->num_submatches;
+
+  return node;
+}
+
+static tre_ast_node_t *
+tre_ast_new_union(tre_mem_t mem, tre_ast_node_t *left, tre_ast_node_t *right)
+{
+  tre_ast_node_t *node;
+
+  node = tre_ast_new_node(mem, UNION, sizeof(tre_union_t));
+  if (node == NULL)
+    return NULL;
+  ((tre_union_t *)node->obj)->left = left;
+  ((tre_union_t *)node->obj)->right = right;
+  node->num_submatches = left->num_submatches + right->num_submatches;
+
+  return node;
+}
+
+static tre_ast_node_t *
+tre_ast_new_catenation(tre_mem_t mem, tre_ast_node_t *left,
+		       tre_ast_node_t *right)
+{
+  tre_ast_node_t *node;
+
+  node = tre_ast_new_node(mem, CATENATION, sizeof(tre_catenation_t));
+  if (node == NULL)
+    return NULL;
+  ((tre_catenation_t *)node->obj)->left = left;
+  ((tre_catenation_t *)node->obj)->right = right;
+  node->num_submatches = left->num_submatches + right->num_submatches;
+
+  return node;
+}
+
+
+/***********************************************************************
+ from tre-stack.c and tre-stack.h
+***********************************************************************/
+
+typedef struct tre_stack_rec tre_stack_t;
+
+/* Creates a new stack object.	`size' is initial size in bytes, `max_size'
+   is maximum size, and `increment' specifies how much more space will be
+   allocated with realloc() if all space gets used up.	Returns the stack
+   object or NULL if out of memory. */
+static tre_stack_t *
+tre_stack_new(int size, int max_size, int increment);
+
+/* Frees the stack object. */
+static void
+tre_stack_destroy(tre_stack_t *s);
+
+/* Returns the current number of objects in the stack. */
+static int
+tre_stack_num_objects(tre_stack_t *s);
+
+/* Each tre_stack_push_*(tre_stack_t *s, <type> value) function pushes
+   `value' on top of stack `s'.  Returns REG_ESPACE if out of memory.
+   This tries to realloc() more space before failing if maximum size
+   has not yet been reached.  Returns REG_OK if successful. */
+#define declare_pushf(typetag, type)					      \
+  static reg_errcode_t tre_stack_push_ ## typetag(tre_stack_t *s, type value)
+
+declare_pushf(voidptr, void *);
+declare_pushf(int, int);
+
+/* Each tre_stack_pop_*(tre_stack_t *s) function pops the topmost
+   element off of stack `s' and returns it.  The stack must not be
+   empty. */
+#define declare_popf(typetag, type)		  \
+  static type tre_stack_pop_ ## typetag(tre_stack_t *s)
+
+declare_popf(voidptr, void *);
+declare_popf(int, int);
+
+/* Just to save some typing. */
+#define STACK_PUSH(s, typetag, value)					      \
+  do									      \
+    {									      \
+      status = tre_stack_push_ ## typetag(s, value);			      \
+    }									      \
+  while (/*CONSTCOND*/0)
+
+#define STACK_PUSHX(s, typetag, value)					      \
+  {									      \
+    status = tre_stack_push_ ## typetag(s, value);			      \
+    if (status != REG_OK)						      \
+      break;								      \
+  }
+
+#define STACK_PUSHR(s, typetag, value)					      \
+  {									      \
+    reg_errcode_t _status;						      \
+    _status = tre_stack_push_ ## typetag(s, value);			      \
+    if (_status != REG_OK)						      \
+      return _status;							      \
+  }
+
+union tre_stack_item {
+  void *voidptr_value;
+  int int_value;
+};
+
+struct tre_stack_rec {
+  int size;
+  int max_size;
+  int increment;
+  int ptr;
+  union tre_stack_item *stack;
+};
+
+
+static tre_stack_t *
+tre_stack_new(int size, int max_size, int increment)
+{
+  tre_stack_t *s;
+
+  s = xmalloc(sizeof(*s));
+  if (s != NULL)
+    {
+      s->stack = xmalloc(sizeof(*s->stack) * size);
+      if (s->stack == NULL)
+	{
+	  xfree(s);
+	  return NULL;
+	}
+      s->size = size;
+      s->max_size = max_size;
+      s->increment = increment;
+      s->ptr = 0;
+    }
+  return s;
+}
+
+static void
+tre_stack_destroy(tre_stack_t *s)
+{
+  xfree(s->stack);
+  xfree(s);
+}
+
+static int
+tre_stack_num_objects(tre_stack_t *s)
+{
+  return s->ptr;
+}
+
+static reg_errcode_t
+tre_stack_push(tre_stack_t *s, union tre_stack_item value)
+{
+  if (s->ptr < s->size)
+    {
+      s->stack[s->ptr] = value;
+      s->ptr++;
+    }
+  else
+    {
+      if (s->size >= s->max_size)
+	{
+	  return REG_ESPACE;
+	}
+      else
+	{
+	  union tre_stack_item *new_buffer;
+	  int new_size;
+	  new_size = s->size + s->increment;
+	  if (new_size > s->max_size)
+	    new_size = s->max_size;
+	  new_buffer = xrealloc(s->stack, sizeof(*new_buffer) * new_size);
+	  if (new_buffer == NULL)
+	    {
+	      return REG_ESPACE;
+	    }
+	  assert(new_size > s->size);
+	  s->size = new_size;
+	  s->stack = new_buffer;
+	  tre_stack_push(s, value);
+	}
+    }
+  return REG_OK;
+}
+
+#define define_pushf(typetag, type)  \
+  declare_pushf(typetag, type) {     \
+    union tre_stack_item item;	     \
+    item.typetag ## _value = value;  \
+    return tre_stack_push(s, item);  \
+}
+
+define_pushf(int, int)
+define_pushf(voidptr, void *)
+
+#define define_popf(typetag, type)		    \
+  declare_popf(typetag, type) {			    \
+    return s->stack[--s->ptr].typetag ## _value;    \
+  }
+
+define_popf(int, int)
+define_popf(voidptr, void *)
+
+
+/***********************************************************************
+ from tre-parse.c and tre-parse.h
+***********************************************************************/
+
+/* Parse context. */
+typedef struct {
+  /* Memory allocator.	The AST is allocated using this. */
+  tre_mem_t mem;
+  /* Stack used for keeping track of regexp syntax. */
+  tre_stack_t *stack;
+  /* The parse result. */
+  tre_ast_node_t *result;
+  /* The regexp to parse and its length. */
+  const char *re;
+  /* The first character of the entire regexp. */
+  const char *re_start;
+  /* Current submatch ID. */
+  int submatch_id;
+  /* Current position (number of literal). */
+  int position;
+  /* The highest back reference or -1 if none seen so far. */
+  int max_backref;
+  /* This flag is set if the regexp uses approximate matching. */
+  int have_approx;
+  /* Compilation flags. */
+  int cflags;
+  /* If this flag is set the top-level submatch is not captured. */
+  int nofirstsub;
+} tre_parse_ctx_t;
+
+/* Parses a wide character regexp pattern into a syntax tree.  This parser
+   handles both syntaxes (BRE and ERE), including the TRE extensions. */
+static reg_errcode_t
+tre_parse(tre_parse_ctx_t *ctx);
+
+
+/*
+  This parser is just a simple recursive descent parser for POSIX.2
+  regexps.  The parser supports both the obsolete default syntax and
+  the "extended" syntax, and some nonstandard extensions.
+*/
+
+/* Characters with special meanings in regexp syntax. */
+#define CHAR_PIPE	   '|'
+#define CHAR_LPAREN	   '('
+#define CHAR_RPAREN	   ')'
+#define CHAR_LBRACE	   '{'
+#define CHAR_RBRACE	   '}'
+#define CHAR_LBRACKET	   '['
+#define CHAR_RBRACKET	   ']'
+#define CHAR_MINUS	   '-'
+#define CHAR_STAR	   '*'
+#define CHAR_QUESTIONMARK  '?'
+#define CHAR_PLUS	   '+'
+#define CHAR_PERIOD	   '.'
+#define CHAR_COLON	   ':'
+#define CHAR_EQUAL	   '='
+#define CHAR_COMMA	   ','
+#define CHAR_CARET	   '^'
+#define CHAR_DOLLAR	   '$'
+#define CHAR_BACKSLASH	   '\\'
+#define CHAR_HASH	   '#'
+#define CHAR_TILDE	   '~'
+
+
+/* Some macros for expanding \w, \s, etc. */
+static const struct tre_macro_struct {
+  const char c;
+  const char *expansion;
+} tre_macros[] =
+  { {'t', "\t"},	   {'n', "\n"},		   {'r', "\r"},
+    {'f', "\f"},	   {'a', "\a"},		   {'e', "\033"},
+    {'w', "[[:alnum:]_]"}, {'W', "[^[:alnum:]_]"}, {'s', "[[:space:]]"},
+    {'S', "[^[:space:]]"}, {'d', "[[:digit:]]"},   {'D', "[^[:digit:]]"},
+    { 0, NULL }
+  };
+
+
+/* Expands a macro delimited by `regex' and `regex_end' to `buf', which
+   must have at least `len' items.  Sets buf[0] to zero if the there
+   is no match in `tre_macros'. */
+static const char *
+tre_expand_macro(const char *regex)
+{
+  int i;
+
+  if (!*regex)
+    return 0;
+
+  for (i = 0; tre_macros[i].expansion && tre_macros[i].c != *regex; i++);
+  return tre_macros[i].expansion;
+}
+
+static reg_errcode_t
+tre_new_item(tre_mem_t mem, int min, int max, int *i, int *max_i,
+	 tre_ast_node_t ***items)
+{
+  reg_errcode_t status;
+  tre_ast_node_t **array = *items;
+  /* Allocate more space if necessary. */
+  if (*i >= *max_i)
+    {
+      tre_ast_node_t **new_items;
+      /* If the array is already 1024 items large, give up -- there's
+	 probably an error in the regexp (e.g. not a '\0' terminated
+	 string and missing ']') */
+      if (*max_i > 1024)
+	return REG_ESPACE;
+      *max_i *= 2;
+      new_items = xrealloc(array, sizeof(*items) * *max_i);
+      if (new_items == NULL)
+	return REG_ESPACE;
+      *items = array = new_items;
+    }
+  array[*i] = tre_ast_new_literal(mem, min, max, -1);
+  status = array[*i] == NULL ? REG_ESPACE : REG_OK;
+  (*i)++;
+  return status;
+}
+
+
+static int
+tre_compare_items(const void *a, const void *b)
+{
+  const tre_ast_node_t *node_a = *(tre_ast_node_t * const *)a;
+  const tre_ast_node_t *node_b = *(tre_ast_node_t * const *)b;
+  tre_literal_t *l_a = node_a->obj, *l_b = node_b->obj;
+  int a_min = l_a->code_min, b_min = l_b->code_min;
+
+  if (a_min < b_min)
+    return -1;
+  else if (a_min > b_min)
+    return 1;
+  else
+    return 0;
+}
+
+/* Maximum number of character classes that can occur in a negated bracket
+   expression.	*/
+#define MAX_NEG_CLASSES 64
+
+/* Maximum length of character class names. */
+#define MAX_CLASS_NAME
+
+static reg_errcode_t
+tre_parse_bracket_items(tre_parse_ctx_t *ctx, int negate,
+			tre_ctype_t neg_classes[], int *num_neg_classes,
+			tre_ast_node_t ***items, int *num_items,
+			int *items_size)
+{
+  const char *re = ctx->re;
+  reg_errcode_t status = REG_OK;
+  tre_ctype_t class = (tre_ctype_t)0;
+  int i = *num_items;
+  int max_i = *items_size;
+  int skip;
+
+  /* Build an array of the items in the bracket expression. */
+  while (status == REG_OK)
+    {
+      skip = 0;
+      if (!*re)
+	{
+	  status = REG_EBRACK;
+	}
+      else if (*re == CHAR_RBRACKET && re > ctx->re)
+	{
+	  re++;
+	  break;
+	}
+      else
+	{
+	  tre_cint_t min = 0, max = 0;
+	  wchar_t wc;
+	  int clen = mbtowc(&wc, re, -1);
+
+	  if (clen<0) clen=1, wc=WEOF;
+
+	  class = (tre_ctype_t)0;
+	  if (*(re + clen) == CHAR_MINUS && *(re + clen + 1) != CHAR_RBRACKET)
+	    {
+	      min = wc;
+	      re += clen+1;
+	      clen = mbtowc(&wc, re, -1);
+	      if (clen<0) clen=1, wc=WEOF;
+	      max = wc;
+	      re += clen;
+	      /* XXX - Should use collation order instead of encoding values
+		 in character ranges. */
+	      if (min > max)
+		status = REG_ERANGE;
+	    }
+	  else if (*re == CHAR_LBRACKET && *(re + 1) == CHAR_PERIOD)
+	    status = REG_ECOLLATE;
+	  else if (*re == CHAR_LBRACKET && *(re + 1) == CHAR_EQUAL)
+	    status = REG_ECOLLATE;
+	  else if (*re == CHAR_LBRACKET && *(re + 1) == CHAR_COLON)
+	    {
+	      char tmp_str[64];
+	      const char *endptr = re + 2;
+	      int len;
+	      while (*endptr && *endptr != CHAR_COLON)
+		endptr++;
+	      if (*endptr)
+		{
+		  len = MIN(endptr - re - 2, 63);
+		  strncpy(tmp_str, re + 2, len);
+		  tmp_str[len] = '\0';
+		  class = tre_ctype(tmp_str);
+		  if (!class)
+		    status = REG_ECTYPE;
+		  re = endptr + 2;
+		}
+	      else
+		status = REG_ECTYPE;
+	      min = 0;
+	      max = TRE_CHAR_MAX;
+	    }
+	  else
+	    {
+	      if (*re == CHAR_MINUS && *(re + 1) != CHAR_RBRACKET
+		  && ctx->re != re)
+		/* Two ranges are not allowed to share and endpoint. */
+		status = REG_ERANGE;
+	      min = max = wc;
+	      re += clen;
+	    }
+
+	  if (status != REG_OK)
+	    break;
+
+	  if (class && negate)
+	    if (*num_neg_classes >= MAX_NEG_CLASSES)
+	      status = REG_ESPACE;
+	    else
+	      neg_classes[(*num_neg_classes)++] = class;
+	  else if (!skip)
+	    {
+	      status = tre_new_item(ctx->mem, min, max, &i, &max_i, items);
+	      if (status != REG_OK)
+		break;
+	      ((tre_literal_t*)((*items)[i-1])->obj)->class = class;
+	    }
+
+	  /* Add opposite-case counterpoints if REG_ICASE is present.
+	     This is broken if there are more than two "same" characters. */
+	  if (ctx->cflags & REG_ICASE && !class && status == REG_OK && !skip)
+	    {
+	      tre_cint_t cmin, ccurr;
+
+	      while (min <= max)
+		{
+		  if (tre_islower(min))
+		    {
+		      cmin = ccurr = tre_toupper(min++);
+		      while (tre_islower(min) && tre_toupper(min) == ccurr + 1
+			     && min <= max)
+			ccurr = tre_toupper(min++);
+		      status = tre_new_item(ctx->mem, cmin, ccurr,
+					    &i, &max_i, items);
+		    }
+		  else if (tre_isupper(min))
+		    {
+		      cmin = ccurr = tre_tolower(min++);
+		      while (tre_isupper(min) && tre_tolower(min) == ccurr + 1
+			     && min <= max)
+			ccurr = tre_tolower(min++);
+		      status = tre_new_item(ctx->mem, cmin, ccurr,
+					    &i, &max_i, items);
+		    }
+		  else min++;
+		  if (status != REG_OK)
+		    break;
+		}
+	      if (status != REG_OK)
+		break;
+	    }
+	}
+    }
+  *num_items = i;
+  *items_size = max_i;
+  ctx->re = re;
+  return status;
+}
+
+static reg_errcode_t
+tre_parse_bracket(tre_parse_ctx_t *ctx, tre_ast_node_t **result)
+{
+  tre_ast_node_t *node = NULL;
+  int negate = 0;
+  reg_errcode_t status = REG_OK;
+  tre_ast_node_t **items, *u, *n;
+  int i = 0, j, max_i = 32, curr_max, curr_min;
+  tre_ctype_t neg_classes[MAX_NEG_CLASSES];
+  int num_neg_classes = 0;
+
+  /* Start off with an array of `max_i' elements. */
+  items = xmalloc(sizeof(*items) * max_i);
+  if (items == NULL)
+    return REG_ESPACE;
+
+  if (*ctx->re == CHAR_CARET)
+    {
+      negate = 1;
+      ctx->re++;
+    }
+
+  status = tre_parse_bracket_items(ctx, negate, neg_classes, &num_neg_classes,
+				   &items, &i, &max_i);
+
+  if (status != REG_OK)
+    goto parse_bracket_done;
+
+  /* Sort the array if we need to negate it. */
+  if (negate)
+    qsort(items, (unsigned)i, sizeof(*items), tre_compare_items);
+
+  curr_max = curr_min = 0;
+  /* Build a union of the items in the array, negated if necessary. */
+  for (j = 0; j < i && status == REG_OK; j++)
+    {
+      int min, max;
+      tre_literal_t *l = items[j]->obj;
+      min = l->code_min;
+      max = l->code_max;
+
+      if (negate)
+	{
+	  if (min < curr_max)
+	    {
+	      /* Overlap. */
+	      curr_max = MAX(max + 1, curr_max);
+	      l = NULL;
+	    }
+	  else
+	    {
+	      /* No overlap. */
+	      curr_max = min - 1;
+	      if (curr_max >= curr_min)
+		{
+		  l->code_min = curr_min;
+		  l->code_max = curr_max;
+		}
+	      else
+		{
+		  l = NULL;
+		}
+	      curr_min = curr_max = max + 1;
+	    }
+	}
+
+      if (l != NULL)
+	{
+	  int k;
+	  l->position = ctx->position;
+	  if (num_neg_classes > 0)
+	    {
+	      l->neg_classes = tre_mem_alloc(ctx->mem,
+					     (sizeof(l->neg_classes)
+					      * (num_neg_classes + 1)));
+	      if (l->neg_classes == NULL)
+		{
+		  status = REG_ESPACE;
+		  break;
+		}
+	      for (k = 0; k < num_neg_classes; k++)
+		l->neg_classes[k] = neg_classes[k];
+	      l->neg_classes[k] = (tre_ctype_t)0;
+	    }
+	  else
+	    l->neg_classes = NULL;
+	  if (node == NULL)
+	    node = items[j];
+	  else
+	    {
+	      u = tre_ast_new_union(ctx->mem, node, items[j]);
+	      if (u == NULL)
+		status = REG_ESPACE;
+	      node = u;
+	    }
+	}
+    }
+
+  if (status != REG_OK)
+    goto parse_bracket_done;
+
+  if (negate)
+    {
+      int k;
+      n = tre_ast_new_literal(ctx->mem, curr_min, TRE_CHAR_MAX, ctx->position);
+      if (n == NULL)
+	status = REG_ESPACE;
+      else
+	{
+	  tre_literal_t *l = n->obj;
+	  if (num_neg_classes > 0)
+	    {
+	      l->neg_classes = tre_mem_alloc(ctx->mem,
+					     (sizeof(l->neg_classes)
+					      * (num_neg_classes + 1)));
+	      if (l->neg_classes == NULL)
+		{
+		  status = REG_ESPACE;
+		  goto parse_bracket_done;
+		}
+	      for (k = 0; k < num_neg_classes; k++)
+		l->neg_classes[k] = neg_classes[k];
+	      l->neg_classes[k] = (tre_ctype_t)0;
+	    }
+	  else
+	    l->neg_classes = NULL;
+	  if (node == NULL)
+	    node = n;
+	  else
+	    {
+	      u = tre_ast_new_union(ctx->mem, node, n);
+	      if (u == NULL)
+		status = REG_ESPACE;
+	      node = u;
+	    }
+	}
+    }
+
+  if (status != REG_OK)
+    goto parse_bracket_done;
+
+#ifdef TRE_DEBUG
+  tre_ast_print(node);
+#endif /* TRE_DEBUG */
+
+ parse_bracket_done:
+  xfree(items);
+  ctx->position++;
+  *result = node;
+  return status;
+}
+
+
+/* Parses a positive decimal integer.  Returns -1 if the string does not
+   contain a valid number. */
+static int
+tre_parse_int(const char **regex)
+{
+  int num = -1;
+  const char *r = *regex;
+  while (*r-'0'<10U)
+    {
+      if (num < 0)
+	num = 0;
+      num = num * 10 + *r - '0';
+      r++;
+    }
+  *regex = r;
+  return num;
+}
+
+
+static reg_errcode_t
+tre_parse_bound(tre_parse_ctx_t *ctx, tre_ast_node_t **result)
+{
+  int min, max;
+  const char *r = ctx->re;
+  int minimal = 0;
+
+  /* Parse number (minimum repetition count). */
+  min = -1;
+  if (*r >= '0' && *r <= '9') {
+    min = tre_parse_int(&r);
+  }
+
+  /* Parse comma and second number (maximum repetition count). */
+  max = min;
+  if (*r == CHAR_COMMA)
+    {
+      r++;
+      max = tre_parse_int(&r);
+    }
+
+  /* Check that the repeat counts are sane. */
+  if ((max >= 0 && min > max) || max > RE_DUP_MAX)
+    return REG_BADBR;
+
+  /* Missing }. */
+  if (!*r)
+    return REG_EBRACE;
+
+  /* Empty contents of {}. */
+  if (r == ctx->re)
+    return REG_BADBR;
+
+  /* Parse the ending '}' or '\}'.*/
+  if (ctx->cflags & REG_EXTENDED)
+    {
+      if (*r != CHAR_RBRACE)
+	return REG_BADBR;
+      r++;
+    }
+  else
+    {
+      if (*r != CHAR_BACKSLASH || *(r + 1) != CHAR_RBRACE)
+	return REG_BADBR;
+      r += 2;
+    }
+
+  /* Create the AST node(s). */
+  if (min == 0 && max == 0)
+    {
+      *result = tre_ast_new_literal(ctx->mem, EMPTY, -1, -1);
+      if (*result == NULL)
+	return REG_ESPACE;
+    }
+  else
+    {
+      if (min < 0 && max < 0)
+	/* Only approximate parameters set, no repetitions. */
+	min = max = 1;
+
+      *result = tre_ast_new_iter(ctx->mem, *result, min, max, minimal);
+      if (!*result)
+	return REG_ESPACE;
+    }
+
+  ctx->re = r;
+  return REG_OK;
+}
+
+typedef enum {
+  PARSE_RE = 0,
+  PARSE_ATOM,
+  PARSE_MARK_FOR_SUBMATCH,
+  PARSE_BRANCH,
+  PARSE_PIECE,
+  PARSE_CATENATION,
+  PARSE_POST_CATENATION,
+  PARSE_UNION,
+  PARSE_POST_UNION,
+  PARSE_POSTFIX,
+  PARSE_RESTORE_CFLAGS
+} tre_parse_re_stack_symbol_t;
+
+
+static reg_errcode_t
+tre_parse(tre_parse_ctx_t *ctx)
+{
+  tre_ast_node_t *result = NULL;
+  tre_parse_re_stack_symbol_t symbol;
+  reg_errcode_t status = REG_OK;
+  tre_stack_t *stack = ctx->stack;
+  int bottom = tre_stack_num_objects(stack);
+  int depth = 0;
+  wchar_t wc;
+  int clen;
+
+  if (!ctx->nofirstsub)
+    {
+      STACK_PUSH(stack, int, ctx->submatch_id);
+      STACK_PUSH(stack, int, PARSE_MARK_FOR_SUBMATCH);
+      ctx->submatch_id++;
+    }
+  STACK_PUSH(stack, int, PARSE_RE);
+  ctx->re_start = ctx->re;
+
+
+  /* The following is basically just a recursive descent parser.  I use
+     an explicit stack instead of recursive functions mostly because of
+     two reasons: compatibility with systems which have an overflowable
+     call stack, and efficiency (both in lines of code and speed).  */
+  while (tre_stack_num_objects(stack) > bottom && status == REG_OK)
+    {
+      if (status != REG_OK)
+	break;
+      symbol = tre_stack_pop_int(stack);
+      switch (symbol)
+	{
+	case PARSE_RE:
+	  /* Parse a full regexp.  A regexp is one or more branches,
+	     separated by the union operator `|'. */
+	  if (ctx->cflags & REG_EXTENDED)
+	    STACK_PUSHX(stack, int, PARSE_UNION);
+	  STACK_PUSHX(stack, int, PARSE_BRANCH);
+	  break;
+
+	case PARSE_BRANCH:
+	  /* Parse a branch.  A branch is one or more pieces, concatenated.
+	     A piece is an atom possibly followed by a postfix operator. */
+	  STACK_PUSHX(stack, int, PARSE_CATENATION);
+	  STACK_PUSHX(stack, int, PARSE_PIECE);
+	  break;
+
+	case PARSE_PIECE:
+	  /* Parse a piece.  A piece is an atom possibly followed by one
+	     or more postfix operators. */
+	    STACK_PUSHX(stack, int, PARSE_POSTFIX);
+	  STACK_PUSHX(stack, int, PARSE_ATOM);
+	  break;
+
+	case PARSE_CATENATION:
+	  /* If the expression has not ended, parse another piece. */
+	  {
+	    tre_char_t c;
+	    if (!*ctx->re)
+	      break;
+	    c = *ctx->re;
+		if (ctx->cflags & REG_EXTENDED && c == CHAR_PIPE)
+		  break;
+		if ((ctx->cflags & REG_EXTENDED
+		     && c == CHAR_RPAREN && depth > 0)
+		    || (!(ctx->cflags & REG_EXTENDED)
+			&& (c == CHAR_BACKSLASH
+			    && *(ctx->re + 1) == CHAR_RPAREN)))
+		  {
+		    if (!(ctx->cflags & REG_EXTENDED) && depth == 0)
+		      status = REG_EPAREN;
+		    depth--;
+		    if (!(ctx->cflags & REG_EXTENDED))
+		      ctx->re += 2;
+		    break;
+		  }
+
+	      {
+		/* Default case, left associative concatenation. */
+		STACK_PUSHX(stack, int, PARSE_CATENATION);
+		STACK_PUSHX(stack, voidptr, result);
+		STACK_PUSHX(stack, int, PARSE_POST_CATENATION);
+		STACK_PUSHX(stack, int, PARSE_PIECE);
+	      }
+	    break;
+	  }
+
+	case PARSE_POST_CATENATION:
+	  {
+	    tre_ast_node_t *tree = tre_stack_pop_voidptr(stack);
+	    tre_ast_node_t *tmp_node;
+	    tmp_node = tre_ast_new_catenation(ctx->mem, tree, result);
+	    if (!tmp_node)
+	      return REG_ESPACE;
+	    result = tmp_node;
+	    break;
+	  }
+
+	case PARSE_UNION:
+	  switch (*ctx->re)
+	    {
+	    case CHAR_PIPE:
+	      STACK_PUSHX(stack, int, PARSE_UNION);
+	      STACK_PUSHX(stack, voidptr, result);
+	      STACK_PUSHX(stack, int, PARSE_POST_UNION);
+	      STACK_PUSHX(stack, int, PARSE_BRANCH);
+	      ctx->re++;
+	      break;
+
+	    case CHAR_RPAREN:
+	      ctx->re++;
+	      break;
+
+	    default:
+	      break;
+	    }
+	  break;
+
+	case PARSE_POST_UNION:
+	  {
+	    tre_ast_node_t *tmp_node;
+	    tre_ast_node_t *tree = tre_stack_pop_voidptr(stack);
+	    tmp_node = tre_ast_new_union(ctx->mem, tree, result);
+	    if (!tmp_node)
+	      return REG_ESPACE;
+	    result = tmp_node;
+	    break;
+	  }
+
+	case PARSE_POSTFIX:
+	  /* Parse postfix operators. */
+	  switch (*ctx->re)
+	    {
+	    case CHAR_PLUS:
+	    case CHAR_QUESTIONMARK:
+	      if (!(ctx->cflags & REG_EXTENDED))
+		break;
+		/*FALLTHROUGH*/
+	    case CHAR_STAR:
+	      {
+		tre_ast_node_t *tmp_node;
+		int minimal = 0;
+		int rep_min = 0;
+		int rep_max = -1;
+
+		if (*ctx->re == CHAR_PLUS)
+		  rep_min = 1;
+		if (*ctx->re == CHAR_QUESTIONMARK)
+		  rep_max = 1;
+
+		ctx->re++;
+		tmp_node = tre_ast_new_iter(ctx->mem, result, rep_min, rep_max,
+					    minimal);
+		if (tmp_node == NULL)
+		  return REG_ESPACE;
+		result = tmp_node;
+		STACK_PUSHX(stack, int, PARSE_POSTFIX);
+	      }
+	      break;
+
+	    case CHAR_BACKSLASH:
+	      /* "\{" is special without REG_EXTENDED */
+	      if (!(ctx->cflags & REG_EXTENDED)
+		  && *(ctx->re + 1) == CHAR_LBRACE)
+		{
+		  ctx->re++;
+		  goto parse_brace;
+		}
+	      else
+		break;
+
+	    case CHAR_LBRACE:
+	      /* "{" is literal without REG_EXTENDED */
+	      if (!(ctx->cflags & REG_EXTENDED))
+		break;
+
+	    parse_brace:
+	      ctx->re++;
+
+	      status = tre_parse_bound(ctx, &result);
+	      if (status != REG_OK)
+		return status;
+	      STACK_PUSHX(stack, int, PARSE_POSTFIX);
+	      break;
+	    }
+	  break;
+
+	case PARSE_ATOM:
+	  /* Parse an atom.  An atom is a regular expression enclosed in `()',
+	     an empty set of `()', a bracket expression, `.', `^', `$',
+	     a `\' followed by a character, or a single character. */
+
+	  switch (*ctx->re)
+	    {
+	    case CHAR_LPAREN:  /* parenthesized subexpression */
+
+	      if (ctx->cflags & REG_EXTENDED)
+		{
+		lparen:
+		  depth++;
+		    {
+		      ctx->re++;
+		      /* First parse a whole RE, then mark the resulting tree
+			 for submatching. */
+		      STACK_PUSHX(stack, int, ctx->submatch_id);
+		      STACK_PUSHX(stack, int, PARSE_MARK_FOR_SUBMATCH);
+		      STACK_PUSHX(stack, int, PARSE_RE);
+		      ctx->submatch_id++;
+		    }
+		}
+	      else
+		goto parse_literal;
+	      break;
+
+	    case CHAR_LBRACKET: /* bracket expression */
+	      ctx->re++;
+	      status = tre_parse_bracket(ctx, &result);
+	      if (status != REG_OK)
+		return status;
+	      break;
+
+	    case CHAR_BACKSLASH:
+	      /* If this is "\(" or "\)" chew off the backslash and
+		 try again. */
+	      if (!(ctx->cflags & REG_EXTENDED) && *(ctx->re + 1) == CHAR_LPAREN)
+		{
+		  ctx->re++;
+		  goto lparen;
+		}
+	      if (!(ctx->cflags & REG_EXTENDED) && *(ctx->re + 1) == CHAR_RPAREN)
+		{
+		  goto empty_atom;
+		}
+
+	      /* If a macro is used, parse the expanded macro recursively. */
+	      {
+		const char *buf = tre_expand_macro(ctx->re + 1);
+		if (buf)
+		  {
+		    tre_parse_ctx_t subctx;
+		    memcpy(&subctx, ctx, sizeof(subctx));
+		    subctx.re = buf;
+		    subctx.nofirstsub = 1;
+		    status = tre_parse(&subctx);
+		    if (status != REG_OK)
+		      return status;
+		    ctx->re += 2;
+		    ctx->position = subctx.position;
+		    result = subctx.result;
+		    break;
+		  }
+	      }
+
+	      if (!ctx->re[1])
+		/* Trailing backslash. */
+		return REG_EESCAPE;
+
+	      ctx->re++;
+	      switch (*ctx->re)
+		{
+		case 'b':
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_WB, -1);
+		  ctx->re++;
+		  break;
+		case 'B':
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_WB_NEG, -1);
+		  ctx->re++;
+		  break;
+		case '<':
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_BOW, -1);
+		  ctx->re++;
+		  break;
+		case '>':
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_EOW, -1);
+		  ctx->re++;
+		  break;
+		case 'x':
+		  ctx->re++;
+		  if (ctx->re[0] != CHAR_LBRACE)
+		    {
+		      /* 8 bit hex char. */
+		      char tmp[3] = {0, 0, 0};
+		      long val;
+
+		      if (tre_isxdigit(ctx->re[0]))
+			{
+			  tmp[0] = (char)ctx->re[0];
+			  ctx->re++;
+			}
+		      if (tre_isxdigit(ctx->re[0]))
+			{
+			  tmp[1] = (char)ctx->re[0];
+			  ctx->re++;
+			}
+		      val = strtol(tmp, NULL, 16);
+		      result = tre_ast_new_literal(ctx->mem, (int)val,
+						   (int)val, ctx->position);
+		      ctx->position++;
+		      break;
+		    }
+		  else if (*ctx->re)
+		    {
+		      /* Wide char. */
+		      char tmp[32];
+		      long val;
+		      int i = 0;
+		      ctx->re++;
+		      while (*ctx->re && i < sizeof tmp)
+			{
+			  if (ctx->re[0] == CHAR_RBRACE)
+			    break;
+			  if (tre_isxdigit(ctx->re[0]))
+			    {
+			      tmp[i] = (char)ctx->re[0];
+			      i++;
+			      ctx->re++;
+			      continue;
+			    }
+			  return REG_EBRACE;
+			}
+		      ctx->re++;
+		      tmp[i] = 0;
+		      val = strtol(tmp, NULL, 16);
+		      result = tre_ast_new_literal(ctx->mem, (int)val, (int)val,
+						   ctx->position);
+		      ctx->position++;
+		      break;
+		    }
+		  /*FALLTHROUGH*/
+
+		default:
+		  if (tre_isdigit(*ctx->re))
+		    {
+		      /* Back reference. */
+		      int val = *ctx->re - '0';
+		      result = tre_ast_new_literal(ctx->mem, BACKREF, val,
+						   ctx->position);
+		      if (result == NULL)
+			return REG_ESPACE;
+		      ctx->position++;
+		      ctx->max_backref = MAX(val, ctx->max_backref);
+		      ctx->re++;
+		    }
+		  else
+		    {
+		      /* Escaped character. */
+		      result = tre_ast_new_literal(ctx->mem, *ctx->re, *ctx->re,
+						   ctx->position);
+		      ctx->position++;
+		      ctx->re++;
+		    }
+		  break;
+		}
+	      if (result == NULL)
+		return REG_ESPACE;
+	      break;
+
+	    case CHAR_PERIOD:	 /* the any-symbol */
+	      if (ctx->cflags & REG_NEWLINE)
+		{
+		  tre_ast_node_t *tmp1;
+		  tre_ast_node_t *tmp2;
+		  tmp1 = tre_ast_new_literal(ctx->mem, 0, '\n' - 1,
+					     ctx->position);
+		  if (!tmp1)
+		    return REG_ESPACE;
+		  tmp2 = tre_ast_new_literal(ctx->mem, '\n' + 1, TRE_CHAR_MAX,
+					     ctx->position + 1);
+		  if (!tmp2)
+		    return REG_ESPACE;
+		  result = tre_ast_new_union(ctx->mem, tmp1, tmp2);
+		  if (!result)
+		    return REG_ESPACE;
+		  ctx->position += 2;
+		}
+	      else
+		{
+		  result = tre_ast_new_literal(ctx->mem, 0, TRE_CHAR_MAX,
+					       ctx->position);
+		  if (!result)
+		    return REG_ESPACE;
+		  ctx->position++;
+		}
+	      ctx->re++;
+	      break;
+
+	    case CHAR_CARET:	 /* beginning of line assertion */
+	      /* '^' has a special meaning everywhere in EREs, and at
+		 beginning of BRE. */
+	      if (ctx->cflags & REG_EXTENDED
+		  || ctx->re == ctx->re_start)
+		{
+		  if (!(ctx->cflags & REG_EXTENDED))
+		    STACK_PUSHX(stack, int, PARSE_CATENATION);
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_BOL, -1);
+		  if (result == NULL)
+		    return REG_ESPACE;
+		  ctx->re++;
+		}
+	      else
+		goto parse_literal;
+	      break;
+
+	    case CHAR_DOLLAR:	 /* end of line assertion. */
+	      /* '$' is special everywhere in EREs, and in the end of the
+		 string in BREs. */
+	      if (ctx->cflags & REG_EXTENDED
+		  || !*(ctx->re + 1))
+		{
+		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
+					       ASSERT_AT_EOL, -1);
+		  if (result == NULL)
+		    return REG_ESPACE;
+		  ctx->re++;
+		}
+	      else
+		goto parse_literal;
+	      break;
+
+	    case CHAR_RPAREN:
+	      if (!depth)
+	        goto parse_literal;
+	    case CHAR_STAR:
+	    case CHAR_PIPE:
+	    case CHAR_LBRACE:
+	    case CHAR_PLUS:
+	    case CHAR_QUESTIONMARK:
+	      if (!(ctx->cflags & REG_EXTENDED))
+	        goto parse_literal;
+
+	    case 0:
+	    empty_atom:
+	      result = tre_ast_new_literal(ctx->mem, EMPTY, -1, -1);
+	      if (!result)
+		return REG_ESPACE;
+	      break;
+
+	    default:
+	    parse_literal:
+
+	      clen = mbtowc(&wc, ctx->re, -1);
+	      if (clen<0) clen=1, wc=WEOF;
+
+	      /* Note that we can't use an tre_isalpha() test here, since there
+		 may be characters which are alphabetic but neither upper or
+		 lower case. */
+	      if (ctx->cflags & REG_ICASE
+		  && (tre_isupper(wc) || tre_islower(wc)))
+		{
+		  tre_ast_node_t *tmp1;
+		  tre_ast_node_t *tmp2;
+
+		  /* XXX - Can there be more than one opposite-case
+		     counterpoints for some character in some locale?  Or
+		     more than two characters which all should be regarded
+		     the same character if case is ignored?  If yes, there
+		     does not seem to be a portable way to detect it.  I guess
+		     that at least for multi-character collating elements there
+		     could be several opposite-case counterpoints, but they
+		     cannot be supported portably anyway. */
+		  tmp1 = tre_ast_new_literal(ctx->mem, tre_toupper(wc),
+					     tre_toupper(wc),
+					     ctx->position);
+		  if (!tmp1)
+		    return REG_ESPACE;
+		  tmp2 = tre_ast_new_literal(ctx->mem, tre_tolower(wc),
+					     tre_tolower(wc),
+					     ctx->position);
+		  if (!tmp2)
+		    return REG_ESPACE;
+		  result = tre_ast_new_union(ctx->mem, tmp1, tmp2);
+		  if (!result)
+		    return REG_ESPACE;
+		}
+	      else
+		{
+		  result = tre_ast_new_literal(ctx->mem, wc, wc,
+					       ctx->position);
+		  if (!result)
+		    return REG_ESPACE;
+		}
+	      ctx->position++;
+	      ctx->re += clen;
+	      break;
+	    }
+	  break;
+
+	case PARSE_MARK_FOR_SUBMATCH:
+	  {
+	    int submatch_id = tre_stack_pop_int(stack);
+
+	    if (result->submatch_id >= 0)
+	      {
+		tre_ast_node_t *n, *tmp_node;
+		n = tre_ast_new_literal(ctx->mem, EMPTY, -1, -1);
+		if (n == NULL)
+		  return REG_ESPACE;
+		tmp_node = tre_ast_new_catenation(ctx->mem, n, result);
+		if (tmp_node == NULL)
+		  return REG_ESPACE;
+		tmp_node->num_submatches = result->num_submatches;
+		result = tmp_node;
+	      }
+	    result->submatch_id = submatch_id;
+	    result->num_submatches++;
+	    break;
+	  }
+
+	case PARSE_RESTORE_CFLAGS:
+	  ctx->cflags = tre_stack_pop_int(stack);
+	  break;
+
+	default:
+	  assert(0);
+	  break;
+	}
+    }
+
+  /* Check for missing closing parentheses. */
+  if (depth > 0)
+    return REG_EPAREN;
+
+  if (status == REG_OK)
+    ctx->result = result;
+
+  return status;
+}
+
+
+
+/***********************************************************************
+ from tre-compile.c
+***********************************************************************/
+
+
+/*
+  TODO:
+   - Fix tre_ast_to_tnfa() to recurse using a stack instead of recursive
+     function calls.
+*/
+
+/*
+  Algorithms to setup tags so that submatch addressing can be done.
+*/
+
+
+/* Inserts a catenation node to the root of the tree given in `node'.
+   As the left child a new tag with number `tag_id' to `node' is added,
+   and the right child is the old root. */
+static reg_errcode_t
+tre_add_tag_left(tre_mem_t mem, tre_ast_node_t *node, int tag_id)
+{
+  tre_catenation_t *c;
+
+  c = tre_mem_alloc(mem, sizeof(*c));
+  if (c == NULL)
+    return REG_ESPACE;
+  c->left = tre_ast_new_literal(mem, TAG, tag_id, -1);
+  if (c->left == NULL)
+    return REG_ESPACE;
+  c->right = tre_mem_alloc(mem, sizeof(tre_ast_node_t));
+  if (c->right == NULL)
+    return REG_ESPACE;
+
+  c->right->obj = node->obj;
+  c->right->type = node->type;
+  c->right->nullable = -1;
+  c->right->submatch_id = -1;
+  c->right->firstpos = NULL;
+  c->right->lastpos = NULL;
+  c->right->num_tags = 0;
+  node->obj = c;
+  node->type = CATENATION;
+  return REG_OK;
+}
+
+/* Inserts a catenation node to the root of the tree given in `node'.
+   As the right child a new tag with number `tag_id' to `node' is added,
+   and the left child is the old root. */
+static reg_errcode_t
+tre_add_tag_right(tre_mem_t mem, tre_ast_node_t *node, int tag_id)
+{
+  tre_catenation_t *c;
+
+  c = tre_mem_alloc(mem, sizeof(*c));
+  if (c == NULL)
+    return REG_ESPACE;
+  c->right = tre_ast_new_literal(mem, TAG, tag_id, -1);
+  if (c->right == NULL)
+    return REG_ESPACE;
+  c->left = tre_mem_alloc(mem, sizeof(tre_ast_node_t));
+  if (c->left == NULL)
+    return REG_ESPACE;
+
+  c->left->obj = node->obj;
+  c->left->type = node->type;
+  c->left->nullable = -1;
+  c->left->submatch_id = -1;
+  c->left->firstpos = NULL;
+  c->left->lastpos = NULL;
+  c->left->num_tags = 0;
+  node->obj = c;
+  node->type = CATENATION;
+  return REG_OK;
+}
+
+typedef enum {
+  ADDTAGS_RECURSE,
+  ADDTAGS_AFTER_ITERATION,
+  ADDTAGS_AFTER_UNION_LEFT,
+  ADDTAGS_AFTER_UNION_RIGHT,
+  ADDTAGS_AFTER_CAT_LEFT,
+  ADDTAGS_AFTER_CAT_RIGHT,
+  ADDTAGS_SET_SUBMATCH_END
+} tre_addtags_symbol_t;
+
+
+typedef struct {
+  int tag;
+  int next_tag;
+} tre_tag_states_t;
+
+
+/* Go through `regset' and set submatch data for submatches that are
+   using this tag. */
+static void
+tre_purge_regset(int *regset, tre_tnfa_t *tnfa, int tag)
+{
+  int i;
+
+  for (i = 0; regset[i] >= 0; i++)
+    {
+      int id = regset[i] / 2;
+      int start = !(regset[i] % 2);
+      if (start)
+	tnfa->submatch_data[id].so_tag = tag;
+      else
+	tnfa->submatch_data[id].eo_tag = tag;
+    }
+  regset[0] = -1;
+}
+
+
+/* Adds tags to appropriate locations in the parse tree in `tree', so that
+   subexpressions marked for submatch addressing can be traced. */
+static reg_errcode_t
+tre_add_tags(tre_mem_t mem, tre_stack_t *stack, tre_ast_node_t *tree,
+	     tre_tnfa_t *tnfa)
+{
+  reg_errcode_t status = REG_OK;
+  tre_addtags_symbol_t symbol;
+  tre_ast_node_t *node = tree; /* Tree node we are currently looking at. */
+  int bottom = tre_stack_num_objects(stack);
+  /* True for first pass (counting number of needed tags) */
+  int first_pass = (mem == NULL || tnfa == NULL);
+  int *regset, *orig_regset;
+  int num_tags = 0; /* Total number of tags. */
+  int num_minimals = 0;	 /* Number of special minimal tags. */
+  int tag = 0;	    /* The tag that is to be added next. */
+  int next_tag = 1; /* Next tag to use after this one. */
+  int *parents;	    /* Stack of submatches the current submatch is
+		       contained in. */
+  int minimal_tag = -1; /* Tag that marks the beginning of a minimal match. */
+  tre_tag_states_t *saved_states;
+
+  tre_tag_direction_t direction = TRE_TAG_MINIMIZE;
+  if (!first_pass)
+    {
+      tnfa->end_tag = 0;
+      tnfa->minimal_tags[0] = -1;
+    }
+
+  regset = xmalloc(sizeof(*regset) * ((tnfa->num_submatches + 1) * 2));
+  if (regset == NULL)
+    return REG_ESPACE;
+  regset[0] = -1;
+  orig_regset = regset;
+
+  parents = xmalloc(sizeof(*parents) * (tnfa->num_submatches + 1));
+  if (parents == NULL)
+    {
+      xfree(regset);
+      return REG_ESPACE;
+    }
+  parents[0] = -1;
+
+  saved_states = xmalloc(sizeof(*saved_states) * (tnfa->num_submatches + 1));
+  if (saved_states == NULL)
+    {
+      xfree(regset);
+      xfree(parents);
+      return REG_ESPACE;
+    }
+  else
+    {
+      unsigned int i;
+      for (i = 0; i <= tnfa->num_submatches; i++)
+	saved_states[i].tag = -1;
+    }
+
+  STACK_PUSH(stack, voidptr, node);
+  STACK_PUSH(stack, int, ADDTAGS_RECURSE);
+
+  while (tre_stack_num_objects(stack) > bottom)
+    {
+      if (status != REG_OK)
+	break;
+
+      symbol = (tre_addtags_symbol_t)tre_stack_pop_int(stack);
+      switch (symbol)
+	{
+
+	case ADDTAGS_SET_SUBMATCH_END:
+	  {
+	    int id = tre_stack_pop_int(stack);
+	    int i;
+
+	    /* Add end of this submatch to regset. */
+	    for (i = 0; regset[i] >= 0; i++);
+	    regset[i] = id * 2 + 1;
+	    regset[i + 1] = -1;
+
+	    /* Pop this submatch from the parents stack. */
+	    for (i = 0; parents[i] >= 0; i++);
+	    parents[i - 1] = -1;
+	    break;
+	  }
+
+	case ADDTAGS_RECURSE:
+	  node = tre_stack_pop_voidptr(stack);
+
+	  if (node->submatch_id >= 0)
+	    {
+	      int id = node->submatch_id;
+	      int i;
+
+
+	      /* Add start of this submatch to regset. */
+	      for (i = 0; regset[i] >= 0; i++);
+	      regset[i] = id * 2;
+	      regset[i + 1] = -1;
+
+	      if (!first_pass)
+		{
+		  for (i = 0; parents[i] >= 0; i++);
+		  tnfa->submatch_data[id].parents = NULL;
+		  if (i > 0)
+		    {
+		      int *p = xmalloc(sizeof(*p) * (i + 1));
+		      if (p == NULL)
+			{
+			  status = REG_ESPACE;
+			  break;
+			}
+		      assert(tnfa->submatch_data[id].parents == NULL);
+		      tnfa->submatch_data[id].parents = p;
+		      for (i = 0; parents[i] >= 0; i++)
+			p[i] = parents[i];
+		      p[i] = -1;
+		    }
+		}
+
+	      /* Add end of this submatch to regset after processing this
+		 node. */
+	      STACK_PUSHX(stack, int, node->submatch_id);
+	      STACK_PUSHX(stack, int, ADDTAGS_SET_SUBMATCH_END);
+	    }
+
+	  switch (node->type)
+	    {
+	    case LITERAL:
+	      {
+		tre_literal_t *lit = node->obj;
+
+		if (!IS_SPECIAL(lit) || IS_BACKREF(lit))
+		  {
+		    int i;
+		    if (regset[0] >= 0)
+		      {
+			/* Regset is not empty, so add a tag before the
+			   literal or backref. */
+			if (!first_pass)
+			  {
+			    status = tre_add_tag_left(mem, node, tag);
+			    tnfa->tag_directions[tag] = direction;
+			    if (minimal_tag >= 0)
+			      {
+				for (i = 0; tnfa->minimal_tags[i] >= 0; i++);
+				tnfa->minimal_tags[i] = tag;
+				tnfa->minimal_tags[i + 1] = minimal_tag;
+				tnfa->minimal_tags[i + 2] = -1;
+				minimal_tag = -1;
+				num_minimals++;
+			      }
+			    tre_purge_regset(regset, tnfa, tag);
+			  }
+			else
+			  {
+			    node->num_tags = 1;
+			  }
+
+			regset[0] = -1;
+			tag = next_tag;
+			num_tags++;
+			next_tag++;
+		      }
+		  }
+		else
+		  {
+		    assert(!IS_TAG(lit));
+		  }
+		break;
+	      }
+	    case CATENATION:
+	      {
+		tre_catenation_t *cat = node->obj;
+		tre_ast_node_t *left = cat->left;
+		tre_ast_node_t *right = cat->right;
+		int reserved_tag = -1;
+
+
+		/* After processing right child. */
+		STACK_PUSHX(stack, voidptr, node);
+		STACK_PUSHX(stack, int, ADDTAGS_AFTER_CAT_RIGHT);
+
+		/* Process right child. */
+		STACK_PUSHX(stack, voidptr, right);
+		STACK_PUSHX(stack, int, ADDTAGS_RECURSE);
+
+		/* After processing left child. */
+		STACK_PUSHX(stack, int, next_tag + left->num_tags);
+		if (left->num_tags > 0 && right->num_tags > 0)
+		  {
+		    /* Reserve the next tag to the right child. */
+		    reserved_tag = next_tag;
+		    next_tag++;
+		  }
+		STACK_PUSHX(stack, int, reserved_tag);
+		STACK_PUSHX(stack, int, ADDTAGS_AFTER_CAT_LEFT);
+
+		/* Process left child. */
+		STACK_PUSHX(stack, voidptr, left);
+		STACK_PUSHX(stack, int, ADDTAGS_RECURSE);
+
+		}
+	      break;
+	    case ITERATION:
+	      {
+		tre_iteration_t *iter = node->obj;
+
+		if (first_pass)
+		  {
+		    STACK_PUSHX(stack, int, regset[0] >= 0 || iter->minimal);
+		  }
+		else
+		  {
+		    STACK_PUSHX(stack, int, tag);
+		    STACK_PUSHX(stack, int, iter->minimal);
+		  }
+		STACK_PUSHX(stack, voidptr, node);
+		STACK_PUSHX(stack, int, ADDTAGS_AFTER_ITERATION);
+
+		STACK_PUSHX(stack, voidptr, iter->arg);
+		STACK_PUSHX(stack, int, ADDTAGS_RECURSE);
+
+		/* Regset is not empty, so add a tag here. */
+		if (regset[0] >= 0 || iter->minimal)
+		  {
+		    if (!first_pass)
+		      {
+			int i;
+			status = tre_add_tag_left(mem, node, tag);
+			if (iter->minimal)
+			  tnfa->tag_directions[tag] = TRE_TAG_MAXIMIZE;
+			else
+			  tnfa->tag_directions[tag] = direction;
+			if (minimal_tag >= 0)
+			  {
+			    for (i = 0; tnfa->minimal_tags[i] >= 0; i++);
+			    tnfa->minimal_tags[i] = tag;
+			    tnfa->minimal_tags[i + 1] = minimal_tag;
+			    tnfa->minimal_tags[i + 2] = -1;
+			    minimal_tag = -1;
+			    num_minimals++;
+			  }
+			tre_purge_regset(regset, tnfa, tag);
+		      }
+
+		    regset[0] = -1;
+		    tag = next_tag;
+		    num_tags++;
+		    next_tag++;
+		  }
+		direction = TRE_TAG_MINIMIZE;
+	      }
+	      break;
+	    case UNION:
+	      {
+		tre_union_t *uni = node->obj;
+		tre_ast_node_t *left = uni->left;
+		tre_ast_node_t *right = uni->right;
+		int left_tag;
+		int right_tag;
+
+		if (regset[0] >= 0)
+		  {
+		    left_tag = next_tag;
+		    right_tag = next_tag + 1;
+		  }
+		else
+		  {
+		    left_tag = tag;
+		    right_tag = next_tag;
+		  }
+
+		/* After processing right child. */
+		STACK_PUSHX(stack, int, right_tag);
+		STACK_PUSHX(stack, int, left_tag);
+		STACK_PUSHX(stack, voidptr, regset);
+		STACK_PUSHX(stack, int, regset[0] >= 0);
+		STACK_PUSHX(stack, voidptr, node);
+		STACK_PUSHX(stack, voidptr, right);
+		STACK_PUSHX(stack, voidptr, left);
+		STACK_PUSHX(stack, int, ADDTAGS_AFTER_UNION_RIGHT);
+
+		/* Process right child. */
+		STACK_PUSHX(stack, voidptr, right);
+		STACK_PUSHX(stack, int, ADDTAGS_RECURSE);
+
+		/* After processing left child. */
+		STACK_PUSHX(stack, int, ADDTAGS_AFTER_UNION_LEFT);
+
+		/* Process left child. */
+		STACK_PUSHX(stack, voidptr, left);
+		STACK_PUSHX(stack, int, ADDTAGS_RECURSE);
+
+		/* Regset is not empty, so add a tag here. */
+		if (regset[0] >= 0)
+		  {
+		    if (!first_pass)
+		      {
+			int i;
+			status = tre_add_tag_left(mem, node, tag);
+			tnfa->tag_directions[tag] = direction;
+			if (minimal_tag >= 0)
+			  {
+			    for (i = 0; tnfa->minimal_tags[i] >= 0; i++);
+			    tnfa->minimal_tags[i] = tag;
+			    tnfa->minimal_tags[i + 1] = minimal_tag;
+			    tnfa->minimal_tags[i + 2] = -1;
+			    minimal_tag = -1;
+			    num_minimals++;
+			  }
+			tre_purge_regset(regset, tnfa, tag);
+		      }
+
+		    regset[0] = -1;
+		    tag = next_tag;
+		    num_tags++;
+		    next_tag++;
+		  }
+
+		if (node->num_submatches > 0)
+		  {
+		    /* The next two tags are reserved for markers. */
+		    next_tag++;
+		    tag = next_tag;
+		    next_tag++;
+		  }
+
+		break;
+	      }
+	    }
+
+	  if (node->submatch_id >= 0)
+	    {
+	      int i;
+	      /* Push this submatch on the parents stack. */
+	      for (i = 0; parents[i] >= 0; i++);
+	      parents[i] = node->submatch_id;
+	      parents[i + 1] = -1;
+	    }
+
+	  break; /* end case: ADDTAGS_RECURSE */
+
+	case ADDTAGS_AFTER_ITERATION:
+	  {
+	    int minimal = 0;
+	    int enter_tag;
+	    node = tre_stack_pop_voidptr(stack);
+	    if (first_pass)
+	      {
+		node->num_tags = ((tre_iteration_t *)node->obj)->arg->num_tags
+		  + tre_stack_pop_int(stack);
+		minimal_tag = -1;
+	      }
+	    else
+	      {
+		minimal = tre_stack_pop_int(stack);
+		enter_tag = tre_stack_pop_int(stack);
+		if (minimal)
+		  minimal_tag = enter_tag;
+	      }
+
+	    if (!first_pass)
+	      {
+		if (minimal)
+		  direction = TRE_TAG_MINIMIZE;
+		else
+		  direction = TRE_TAG_MAXIMIZE;
+	      }
+	    break;
+	  }
+
+	case ADDTAGS_AFTER_CAT_LEFT:
+	  {
+	    int new_tag = tre_stack_pop_int(stack);
+	    next_tag = tre_stack_pop_int(stack);
+	    if (new_tag >= 0)
+	      {
+		tag = new_tag;
+	      }
+	    break;
+	  }
+
+	case ADDTAGS_AFTER_CAT_RIGHT:
+	  node = tre_stack_pop_voidptr(stack);
+	  if (first_pass)
+	    node->num_tags = ((tre_catenation_t *)node->obj)->left->num_tags
+	      + ((tre_catenation_t *)node->obj)->right->num_tags;
+	  break;
+
+	case ADDTAGS_AFTER_UNION_LEFT:
+	  /* Lift the bottom of the `regset' array so that when processing
+	     the right operand the items currently in the array are
+	     invisible.	 The original bottom was saved at ADDTAGS_UNION and
+	     will be restored at ADDTAGS_AFTER_UNION_RIGHT below. */
+	  while (*regset >= 0)
+	    regset++;
+	  break;
+
+	case ADDTAGS_AFTER_UNION_RIGHT:
+	  {
+	    int added_tags, tag_left, tag_right;
+	    tre_ast_node_t *left = tre_stack_pop_voidptr(stack);
+	    tre_ast_node_t *right = tre_stack_pop_voidptr(stack);
+	    node = tre_stack_pop_voidptr(stack);
+	    added_tags = tre_stack_pop_int(stack);
+	    if (first_pass)
+	      {
+		node->num_tags = ((tre_union_t *)node->obj)->left->num_tags
+		  + ((tre_union_t *)node->obj)->right->num_tags + added_tags
+		  + ((node->num_submatches > 0) ? 2 : 0);
+	      }
+	    regset = tre_stack_pop_voidptr(stack);
+	    tag_left = tre_stack_pop_int(stack);
+	    tag_right = tre_stack_pop_int(stack);
+
+	    /* Add tags after both children, the left child gets a smaller
+	       tag than the right child.  This guarantees that we prefer
+	       the left child over the right child. */
+	    /* XXX - This is not always necessary (if the children have
+	       tags which must be seen for every match of that child). */
+	    /* XXX - Check if this is the only place where tre_add_tag_right
+	       is used.	 If so, use tre_add_tag_left (putting the tag before
+	       the child as opposed after the child) and throw away
+	       tre_add_tag_right. */
+	    if (node->num_submatches > 0)
+	      {
+		if (!first_pass)
+		  {
+		    status = tre_add_tag_right(mem, left, tag_left);
+		    tnfa->tag_directions[tag_left] = TRE_TAG_MAXIMIZE;
+		    status = tre_add_tag_right(mem, right, tag_right);
+		    tnfa->tag_directions[tag_right] = TRE_TAG_MAXIMIZE;
+		  }
+		num_tags += 2;
+	      }
+	    direction = TRE_TAG_MAXIMIZE;
+	    break;
+	  }
+
+	default:
+	  assert(0);
+	  break;
+
+	} /* end switch(symbol) */
+    } /* end while(tre_stack_num_objects(stack) > bottom) */
+
+  if (!first_pass)
+    tre_purge_regset(regset, tnfa, tag);
+
+  if (!first_pass && minimal_tag >= 0)
+    {
+      int i;
+      for (i = 0; tnfa->minimal_tags[i] >= 0; i++);
+      tnfa->minimal_tags[i] = tag;
+      tnfa->minimal_tags[i + 1] = minimal_tag;
+      tnfa->minimal_tags[i + 2] = -1;
+      minimal_tag = -1;
+      num_minimals++;
+    }
+
+  assert(tree->num_tags == num_tags);
+  tnfa->end_tag = num_tags;
+  tnfa->num_tags = num_tags;
+  tnfa->num_minimals = num_minimals;
+  xfree(orig_regset);
+  xfree(parents);
+  xfree(saved_states);
+  return status;
+}
+
+
+
+/*
+  AST to TNFA compilation routines.
+*/
+
+typedef enum {
+  COPY_RECURSE,
+  COPY_SET_RESULT_PTR
+} tre_copyast_symbol_t;
+
+/* Flags for tre_copy_ast(). */
+#define COPY_REMOVE_TAGS	 1
+#define COPY_MAXIMIZE_FIRST_TAG	 2
+
+static reg_errcode_t
+tre_copy_ast(tre_mem_t mem, tre_stack_t *stack, tre_ast_node_t *ast,
+	     int flags, int *pos_add, tre_tag_direction_t *tag_directions,
+	     tre_ast_node_t **copy, int *max_pos)
+{
+  reg_errcode_t status = REG_OK;
+  int bottom = tre_stack_num_objects(stack);
+  int num_copied = 0;
+  int first_tag = 1;
+  tre_ast_node_t **result = copy;
+  tre_copyast_symbol_t symbol;
+
+  STACK_PUSH(stack, voidptr, ast);
+  STACK_PUSH(stack, int, COPY_RECURSE);
+
+  while (status == REG_OK && tre_stack_num_objects(stack) > bottom)
+    {
+      tre_ast_node_t *node;
+      if (status != REG_OK)
+	break;
+
+      symbol = (tre_copyast_symbol_t)tre_stack_pop_int(stack);
+      switch (symbol)
+	{
+	case COPY_SET_RESULT_PTR:
+	  result = tre_stack_pop_voidptr(stack);
+	  break;
+	case COPY_RECURSE:
+	  node = tre_stack_pop_voidptr(stack);
+	  switch (node->type)
+	    {
+	    case LITERAL:
+	      {
+		tre_literal_t *lit = node->obj;
+		int pos = lit->position;
+		int min = lit->code_min;
+		int max = lit->code_max;
+		if (!IS_SPECIAL(lit) || IS_BACKREF(lit))
+		  {
+		    /* XXX - e.g. [ab] has only one position but two
+		       nodes, so we are creating holes in the state space
+		       here.  Not fatal, just wastes memory. */
+		    pos += *pos_add;
+		    num_copied++;
+		  }
+		else if (IS_TAG(lit) && (flags & COPY_REMOVE_TAGS))
+		  {
+		    /* Change this tag to empty. */
+		    min = EMPTY;
+		    max = pos = -1;
+		  }
+		else if (IS_TAG(lit) && (flags & COPY_MAXIMIZE_FIRST_TAG)
+			 && first_tag)
+		  {
+		    /* Maximize the first tag. */
+		    tag_directions[max] = TRE_TAG_MAXIMIZE;
+		    first_tag = 0;
+		  }
+		*result = tre_ast_new_literal(mem, min, max, pos);
+		if (*result == NULL)
+		  status = REG_ESPACE;
+
+		if (pos > *max_pos)
+		  *max_pos = pos;
+		break;
+	      }
+	    case UNION:
+	      {
+		tre_union_t *uni = node->obj;
+		tre_union_t *tmp;
+		*result = tre_ast_new_union(mem, uni->left, uni->right);
+		if (*result == NULL)
+		  {
+		    status = REG_ESPACE;
+		    break;
+		  }
+		tmp = (*result)->obj;
+		result = &tmp->left;
+		STACK_PUSHX(stack, voidptr, uni->right);
+		STACK_PUSHX(stack, int, COPY_RECURSE);
+		STACK_PUSHX(stack, voidptr, &tmp->right);
+		STACK_PUSHX(stack, int, COPY_SET_RESULT_PTR);
+		STACK_PUSHX(stack, voidptr, uni->left);
+		STACK_PUSHX(stack, int, COPY_RECURSE);
+		break;
+	      }
+	    case CATENATION:
+	      {
+		tre_catenation_t *cat = node->obj;
+		tre_catenation_t *tmp;
+		*result = tre_ast_new_catenation(mem, cat->left, cat->right);
+		if (*result == NULL)
+		  {
+		    status = REG_ESPACE;
+		    break;
+		  }
+		tmp = (*result)->obj;
+		tmp->left = NULL;
+		tmp->right = NULL;
+		result = &tmp->left;
+
+		STACK_PUSHX(stack, voidptr, cat->right);
+		STACK_PUSHX(stack, int, COPY_RECURSE);
+		STACK_PUSHX(stack, voidptr, &tmp->right);
+		STACK_PUSHX(stack, int, COPY_SET_RESULT_PTR);
+		STACK_PUSHX(stack, voidptr, cat->left);
+		STACK_PUSHX(stack, int, COPY_RECURSE);
+		break;
+	      }
+	    case ITERATION:
+	      {
+		tre_iteration_t *iter = node->obj;
+		STACK_PUSHX(stack, voidptr, iter->arg);
+		STACK_PUSHX(stack, int, COPY_RECURSE);
+		*result = tre_ast_new_iter(mem, iter->arg, iter->min,
+					   iter->max, iter->minimal);
+		if (*result == NULL)
+		  {
+		    status = REG_ESPACE;
+		    break;
+		  }
+		iter = (*result)->obj;
+		result = &iter->arg;
+		break;
+	      }
+	    default:
+	      assert(0);
+	      break;
+	    }
+	  break;
+	}
+    }
+  *pos_add += num_copied;
+  return status;
+}
+
+typedef enum {
+  EXPAND_RECURSE,
+  EXPAND_AFTER_ITER
+} tre_expand_ast_symbol_t;
+
+/* Expands each iteration node that has a finite nonzero minimum or maximum
+   iteration count to a catenated sequence of copies of the node. */
+static reg_errcode_t
+tre_expand_ast(tre_mem_t mem, tre_stack_t *stack, tre_ast_node_t *ast,
+	       int *position, tre_tag_direction_t *tag_directions)
+{
+  reg_errcode_t status = REG_OK;
+  int bottom = tre_stack_num_objects(stack);
+  int pos_add = 0;
+  int pos_add_total = 0;
+  int max_pos = 0;
+  int iter_depth = 0;
+
+  STACK_PUSHR(stack, voidptr, ast);
+  STACK_PUSHR(stack, int, EXPAND_RECURSE);
+  while (status == REG_OK && tre_stack_num_objects(stack) > bottom)
+    {
+      tre_ast_node_t *node;
+      tre_expand_ast_symbol_t symbol;
+
+      if (status != REG_OK)
+	break;
+
+      symbol = (tre_expand_ast_symbol_t)tre_stack_pop_int(stack);
+      node = tre_stack_pop_voidptr(stack);
+      switch (symbol)
+	{
+	case EXPAND_RECURSE:
+	  switch (node->type)
+	    {
+	    case LITERAL:
+	      {
+		tre_literal_t *lit= node->obj;
+		if (!IS_SPECIAL(lit) || IS_BACKREF(lit))
+		  {
+		    lit->position += pos_add;
+		    if (lit->position > max_pos)
+		      max_pos = lit->position;
+		  }
+		break;
+	      }
+	    case UNION:
+	      {
+		tre_union_t *uni = node->obj;
+		STACK_PUSHX(stack, voidptr, uni->right);
+		STACK_PUSHX(stack, int, EXPAND_RECURSE);
+		STACK_PUSHX(stack, voidptr, uni->left);
+		STACK_PUSHX(stack, int, EXPAND_RECURSE);
+		break;
+	      }
+	    case CATENATION:
+	      {
+		tre_catenation_t *cat = node->obj;
+		STACK_PUSHX(stack, voidptr, cat->right);
+		STACK_PUSHX(stack, int, EXPAND_RECURSE);
+		STACK_PUSHX(stack, voidptr, cat->left);
+		STACK_PUSHX(stack, int, EXPAND_RECURSE);
+		break;
+	      }
+	    case ITERATION:
+	      {
+		tre_iteration_t *iter = node->obj;
+		STACK_PUSHX(stack, int, pos_add);
+		STACK_PUSHX(stack, voidptr, node);
+		STACK_PUSHX(stack, int, EXPAND_AFTER_ITER);
+		STACK_PUSHX(stack, voidptr, iter->arg);
+		STACK_PUSHX(stack, int, EXPAND_RECURSE);
+		/* If we are going to expand this node at EXPAND_AFTER_ITER
+		   then don't increase the `pos' fields of the nodes now, it
+		   will get done when expanding. */
+		if (iter->min > 1 || iter->max > 1)
+		  pos_add = 0;
+		iter_depth++;
+		break;
+	      }
+	    default:
+	      assert(0);
+	      break;
+	    }
+	  break;
+	case EXPAND_AFTER_ITER:
+	  {
+	    tre_iteration_t *iter = node->obj;
+	    int pos_add_last;
+	    pos_add = tre_stack_pop_int(stack);
+	    pos_add_last = pos_add;
+	    if (iter->min > 1 || iter->max > 1)
+	      {
+		tre_ast_node_t *seq1 = NULL, *seq2 = NULL;
+		int j;
+		int pos_add_save = pos_add;
+
+		/* Create a catenated sequence of copies of the node. */
+		for (j = 0; j < iter->min; j++)
+		  {
+		    tre_ast_node_t *copy;
+		    /* Remove tags from all but the last copy. */
+		    int flags = ((j + 1 < iter->min)
+				 ? COPY_REMOVE_TAGS
+				 : COPY_MAXIMIZE_FIRST_TAG);
+		    pos_add_save = pos_add;
+		    status = tre_copy_ast(mem, stack, iter->arg, flags,
+					  &pos_add, tag_directions, &copy,
+					  &max_pos);
+		    if (status != REG_OK)
+		      return status;
+		    if (seq1 != NULL)
+		      seq1 = tre_ast_new_catenation(mem, seq1, copy);
+		    else
+		      seq1 = copy;
+		    if (seq1 == NULL)
+		      return REG_ESPACE;
+		  }
+
+		if (iter->max == -1)
+		  {
+		    /* No upper limit. */
+		    pos_add_save = pos_add;
+		    status = tre_copy_ast(mem, stack, iter->arg, 0,
+					  &pos_add, NULL, &seq2, &max_pos);
+		    if (status != REG_OK)
+		      return status;
+		    seq2 = tre_ast_new_iter(mem, seq2, 0, -1, 0);
+		    if (seq2 == NULL)
+		      return REG_ESPACE;
+		  }
+		else
+		  {
+		    for (j = iter->min; j < iter->max; j++)
+		      {
+			tre_ast_node_t *tmp, *copy;
+			pos_add_save = pos_add;
+			status = tre_copy_ast(mem, stack, iter->arg, 0,
+					      &pos_add, NULL, &copy, &max_pos);
+			if (status != REG_OK)
+			  return status;
+			if (seq2 != NULL)
+			  seq2 = tre_ast_new_catenation(mem, copy, seq2);
+			else
+			  seq2 = copy;
+			if (seq2 == NULL)
+			  return REG_ESPACE;
+			tmp = tre_ast_new_literal(mem, EMPTY, -1, -1);
+			if (tmp == NULL)
+			  return REG_ESPACE;
+			seq2 = tre_ast_new_union(mem, tmp, seq2);
+			if (seq2 == NULL)
+			  return REG_ESPACE;
+		      }
+		  }
+
+		pos_add = pos_add_save;
+		if (seq1 == NULL)
+		  seq1 = seq2;
+		else if (seq2 != NULL)
+		  seq1 = tre_ast_new_catenation(mem, seq1, seq2);
+		if (seq1 == NULL)
+		  return REG_ESPACE;
+		node->obj = seq1->obj;
+		node->type = seq1->type;
+	      }
+
+	    iter_depth--;
+	    pos_add_total += pos_add - pos_add_last;
+	    if (iter_depth == 0)
+	      pos_add = pos_add_total;
+
+	    break;
+	  }
+	default:
+	  assert(0);
+	  break;
+	}
+    }
+
+  *position += pos_add_total;
+
+  /* `max_pos' should never be larger than `*position' if the above
+     code works, but just an extra safeguard let's make sure
+     `*position' is set large enough so enough memory will be
+     allocated for the transition table. */
+  if (max_pos > *position)
+    *position = max_pos;
+
+  return status;
+}
+
+static tre_pos_and_tags_t *
+tre_set_empty(tre_mem_t mem)
+{
+  tre_pos_and_tags_t *new_set;
+
+  new_set = tre_mem_calloc(mem, sizeof(*new_set));
+  if (new_set == NULL)
+    return NULL;
+
+  new_set[0].position = -1;
+  new_set[0].code_min = -1;
+  new_set[0].code_max = -1;
+
+  return new_set;
+}
+
+static tre_pos_and_tags_t *
+tre_set_one(tre_mem_t mem, int position, int code_min, int code_max,
+	    tre_ctype_t class, tre_ctype_t *neg_classes, int backref)
+{
+  tre_pos_and_tags_t *new_set;
+
+  new_set = tre_mem_calloc(mem, sizeof(*new_set) * 2);
+  if (new_set == NULL)
+    return NULL;
+
+  new_set[0].position = position;
+  new_set[0].code_min = code_min;
+  new_set[0].code_max = code_max;
+  new_set[0].class = class;
+  new_set[0].neg_classes = neg_classes;
+  new_set[0].backref = backref;
+  new_set[1].position = -1;
+  new_set[1].code_min = -1;
+  new_set[1].code_max = -1;
+
+  return new_set;
+}
+
+static tre_pos_and_tags_t *
+tre_set_union(tre_mem_t mem, tre_pos_and_tags_t *set1, tre_pos_and_tags_t *set2,
+	      int *tags, int assertions)
+{
+  int s1, s2, i, j;
+  tre_pos_and_tags_t *new_set;
+  int *new_tags;
+  int num_tags;
+
+  for (num_tags = 0; tags != NULL && tags[num_tags] >= 0; num_tags++);
+  for (s1 = 0; set1[s1].position >= 0; s1++);
+  for (s2 = 0; set2[s2].position >= 0; s2++);
+  new_set = tre_mem_calloc(mem, sizeof(*new_set) * (s1 + s2 + 1));
+  if (!new_set )
+    return NULL;
+
+  for (s1 = 0; set1[s1].position >= 0; s1++)
+    {
+      new_set[s1].position = set1[s1].position;
+      new_set[s1].code_min = set1[s1].code_min;
+      new_set[s1].code_max = set1[s1].code_max;
+      new_set[s1].assertions = set1[s1].assertions | assertions;
+      new_set[s1].class = set1[s1].class;
+      new_set[s1].neg_classes = set1[s1].neg_classes;
+      new_set[s1].backref = set1[s1].backref;
+      if (set1[s1].tags == NULL && tags == NULL)
+	new_set[s1].tags = NULL;
+      else
+	{
+	  for (i = 0; set1[s1].tags != NULL && set1[s1].tags[i] >= 0; i++);
+	  new_tags = tre_mem_alloc(mem, (sizeof(*new_tags)
+					 * (i + num_tags + 1)));
+	  if (new_tags == NULL)
+	    return NULL;
+	  for (j = 0; j < i; j++)
+	    new_tags[j] = set1[s1].tags[j];
+	  for (i = 0; i < num_tags; i++)
+	    new_tags[j + i] = tags[i];
+	  new_tags[j + i] = -1;
+	  new_set[s1].tags = new_tags;
+	}
+    }
+
+  for (s2 = 0; set2[s2].position >= 0; s2++)
+    {
+      new_set[s1 + s2].position = set2[s2].position;
+      new_set[s1 + s2].code_min = set2[s2].code_min;
+      new_set[s1 + s2].code_max = set2[s2].code_max;
+      /* XXX - why not | assertions here as well? */
+      new_set[s1 + s2].assertions = set2[s2].assertions;
+      new_set[s1 + s2].class = set2[s2].class;
+      new_set[s1 + s2].neg_classes = set2[s2].neg_classes;
+      new_set[s1 + s2].backref = set2[s2].backref;
+      if (set2[s2].tags == NULL)
+	new_set[s1 + s2].tags = NULL;
+      else
+	{
+	  for (i = 0; set2[s2].tags[i] >= 0; i++);
+	  new_tags = tre_mem_alloc(mem, sizeof(*new_tags) * (i + 1));
+	  if (new_tags == NULL)
+	    return NULL;
+	  for (j = 0; j < i; j++)
+	    new_tags[j] = set2[s2].tags[j];
+	  new_tags[j] = -1;
+	  new_set[s1 + s2].tags = new_tags;
+	}
+    }
+  new_set[s1 + s2].position = -1;
+  return new_set;
+}
+
+/* Finds the empty path through `node' which is the one that should be
+   taken according to POSIX.2 rules, and adds the tags on that path to
+   `tags'.   `tags' may be NULL.  If `num_tags_seen' is not NULL, it is
+   set to the number of tags seen on the path. */
+static reg_errcode_t
+tre_match_empty(tre_stack_t *stack, tre_ast_node_t *node, int *tags,
+		int *assertions, int *num_tags_seen)
+{
+  tre_literal_t *lit;
+  tre_union_t *uni;
+  tre_catenation_t *cat;
+  tre_iteration_t *iter;
+  int i;
+  int bottom = tre_stack_num_objects(stack);
+  reg_errcode_t status = REG_OK;
+  if (num_tags_seen)
+    *num_tags_seen = 0;
+
+  status = tre_stack_push_voidptr(stack, node);
+
+  /* Walk through the tree recursively. */
+  while (status == REG_OK && tre_stack_num_objects(stack) > bottom)
+    {
+      node = tre_stack_pop_voidptr(stack);
+
+      switch (node->type)
+	{
+	case LITERAL:
+	  lit = (tre_literal_t *)node->obj;
+	  switch (lit->code_min)
+	    {
+	    case TAG:
+	      if (lit->code_max >= 0)
+		{
+		  if (tags != NULL)
+		    {
+		      /* Add the tag to `tags'. */
+		      for (i = 0; tags[i] >= 0; i++)
+			if (tags[i] == lit->code_max)
+			  break;
+		      if (tags[i] < 0)
+			{
+			  tags[i] = lit->code_max;
+			  tags[i + 1] = -1;
+			}
+		    }
+		  if (num_tags_seen)
+		    (*num_tags_seen)++;
+		}
+	      break;
+	    case ASSERTION:
+	      assert(lit->code_max >= 1
+		     || lit->code_max <= ASSERT_LAST);
+	      if (assertions != NULL)
+		*assertions |= lit->code_max;
+	      break;
+	    case EMPTY:
+	      break;
+	    default:
+	      assert(0);
+	      break;
+	    }
+	  break;
+
+	case UNION:
+	  /* Subexpressions starting earlier take priority over ones
+	     starting later, so we prefer the left subexpression over the
+	     right subexpression. */
+	  uni = (tre_union_t *)node->obj;
+	  if (uni->left->nullable)
+	    STACK_PUSHX(stack, voidptr, uni->left)
+	  else if (uni->right->nullable)
+	    STACK_PUSHX(stack, voidptr, uni->right)
+	  else
+	    assert(0);
+	  break;
+
+	case CATENATION:
+	  /* The path must go through both children. */
+	  cat = (tre_catenation_t *)node->obj;
+	  assert(cat->left->nullable);
+	  assert(cat->right->nullable);
+	  STACK_PUSHX(stack, voidptr, cat->left);
+	  STACK_PUSHX(stack, voidptr, cat->right);
+	  break;
+
+	case ITERATION:
+	  /* A match with an empty string is preferred over no match at
+	     all, so we go through the argument if possible. */
+	  iter = (tre_iteration_t *)node->obj;
+	  if (iter->arg->nullable)
+	    STACK_PUSHX(stack, voidptr, iter->arg);
+	  break;
+
+	default:
+	  assert(0);
+	  break;
+	}
+    }
+
+  return status;
+}
+
+
+typedef enum {
+  NFL_RECURSE,
+  NFL_POST_UNION,
+  NFL_POST_CATENATION,
+  NFL_POST_ITERATION
+} tre_nfl_stack_symbol_t;
+
+
+/* Computes and fills in the fields `nullable', `firstpos', and `lastpos' for
+   the nodes of the AST `tree'. */
+static reg_errcode_t
+tre_compute_nfl(tre_mem_t mem, tre_stack_t *stack, tre_ast_node_t *tree)
+{
+  int bottom = tre_stack_num_objects(stack);
+
+  STACK_PUSHR(stack, voidptr, tree);
+  STACK_PUSHR(stack, int, NFL_RECURSE);
+
+  while (tre_stack_num_objects(stack) > bottom)
+    {
+      tre_nfl_stack_symbol_t symbol;
+      tre_ast_node_t *node;
+
+      symbol = (tre_nfl_stack_symbol_t)tre_stack_pop_int(stack);
+      node = tre_stack_pop_voidptr(stack);
+      switch (symbol)
+	{
+	case NFL_RECURSE:
+	  switch (node->type)
+	    {
+	    case LITERAL:
+	      {
+		tre_literal_t *lit = (tre_literal_t *)node->obj;
+		if (IS_BACKREF(lit))
+		  {
+		    /* Back references: nullable = false, firstpos = {i},
+		       lastpos = {i}. */
+		    node->nullable = 0;
+		    node->firstpos = tre_set_one(mem, lit->position, 0,
+					     TRE_CHAR_MAX, 0, NULL, -1);
+		    if (!node->firstpos)
+		      return REG_ESPACE;
+		    node->lastpos = tre_set_one(mem, lit->position, 0,
+						TRE_CHAR_MAX, 0, NULL,
+						(int)lit->code_max);
+		    if (!node->lastpos)
+		      return REG_ESPACE;
+		  }
+		else if (lit->code_min < 0)
+		  {
+		    /* Tags, empty strings, params, and zero width assertions:
+		       nullable = true, firstpos = {}, and lastpos = {}. */
+		    node->nullable = 1;
+		    node->firstpos = tre_set_empty(mem);
+		    if (!node->firstpos)
+		      return REG_ESPACE;
+		    node->lastpos = tre_set_empty(mem);
+		    if (!node->lastpos)
+		      return REG_ESPACE;
+		  }
+		else
+		  {
+		    /* Literal at position i: nullable = false, firstpos = {i},
+		       lastpos = {i}. */
+		    node->nullable = 0;
+		    node->firstpos =
+		      tre_set_one(mem, lit->position, (int)lit->code_min,
+				  (int)lit->code_max, 0, NULL, -1);
+		    if (!node->firstpos)
+		      return REG_ESPACE;
+		    node->lastpos = tre_set_one(mem, lit->position,
+						(int)lit->code_min,
+						(int)lit->code_max,
+						lit->class, lit->neg_classes,
+						-1);
+		    if (!node->lastpos)
+		      return REG_ESPACE;
+		  }
+		break;
+	      }
+
+	    case UNION:
+	      /* Compute the attributes for the two subtrees, and after that
+		 for this node. */
+	      STACK_PUSHR(stack, voidptr, node);
+	      STACK_PUSHR(stack, int, NFL_POST_UNION);
+	      STACK_PUSHR(stack, voidptr, ((tre_union_t *)node->obj)->right);
+	      STACK_PUSHR(stack, int, NFL_RECURSE);
+	      STACK_PUSHR(stack, voidptr, ((tre_union_t *)node->obj)->left);
+	      STACK_PUSHR(stack, int, NFL_RECURSE);
+	      break;
+
+	    case CATENATION:
+	      /* Compute the attributes for the two subtrees, and after that
+		 for this node. */
+	      STACK_PUSHR(stack, voidptr, node);
+	      STACK_PUSHR(stack, int, NFL_POST_CATENATION);
+	      STACK_PUSHR(stack, voidptr, ((tre_catenation_t *)node->obj)->right);
+	      STACK_PUSHR(stack, int, NFL_RECURSE);
+	      STACK_PUSHR(stack, voidptr, ((tre_catenation_t *)node->obj)->left);
+	      STACK_PUSHR(stack, int, NFL_RECURSE);
+	      break;
+
+	    case ITERATION:
+	      /* Compute the attributes for the subtree, and after that for
+		 this node. */
+	      STACK_PUSHR(stack, voidptr, node);
+	      STACK_PUSHR(stack, int, NFL_POST_ITERATION);
+	      STACK_PUSHR(stack, voidptr, ((tre_iteration_t *)node->obj)->arg);
+	      STACK_PUSHR(stack, int, NFL_RECURSE);
+	      break;
+	    }
+	  break; /* end case: NFL_RECURSE */
+
+	case NFL_POST_UNION:
+	  {
+	    tre_union_t *uni = (tre_union_t *)node->obj;
+	    node->nullable = uni->left->nullable || uni->right->nullable;
+	    node->firstpos = tre_set_union(mem, uni->left->firstpos,
+					   uni->right->firstpos, NULL, 0);
+	    if (!node->firstpos)
+	      return REG_ESPACE;
+	    node->lastpos = tre_set_union(mem, uni->left->lastpos,
+					  uni->right->lastpos, NULL, 0);
+	    if (!node->lastpos)
+	      return REG_ESPACE;
+	    break;
+	  }
+
+	case NFL_POST_ITERATION:
+	  {
+	    tre_iteration_t *iter = (tre_iteration_t *)node->obj;
+
+	    if (iter->min == 0 || iter->arg->nullable)
+	      node->nullable = 1;
+	    else
+	      node->nullable = 0;
+	    node->firstpos = iter->arg->firstpos;
+	    node->lastpos = iter->arg->lastpos;
+	    break;
+	  }
+
+	case NFL_POST_CATENATION:
+	  {
+	    int num_tags, *tags, assertions;
+	    reg_errcode_t status;
+	    tre_catenation_t *cat = node->obj;
+	    node->nullable = cat->left->nullable && cat->right->nullable;
+
+	    /* Compute firstpos. */
+	    if (cat->left->nullable)
+	      {
+		/* The left side matches the empty string.  Make a first pass
+		   with tre_match_empty() to get the number of tags and
+		   parameters. */
+		status = tre_match_empty(stack, cat->left,
+					 NULL, NULL, &num_tags);
+		if (status != REG_OK)
+		  return status;
+		/* Allocate arrays for the tags and parameters. */
+		tags = xmalloc(sizeof(*tags) * (num_tags + 1));
+		if (!tags)
+		  return REG_ESPACE;
+		tags[0] = -1;
+		assertions = 0;
+		/* Second pass with tre_mach_empty() to get the list of
+		   tags and parameters. */
+		status = tre_match_empty(stack, cat->left, tags,
+					 &assertions, NULL);
+		if (status != REG_OK)
+		  {
+		    xfree(tags);
+		    return status;
+		  }
+		node->firstpos =
+		  tre_set_union(mem, cat->right->firstpos, cat->left->firstpos,
+				tags, assertions);
+		xfree(tags);
+		if (!node->firstpos)
+		  return REG_ESPACE;
+	      }
+	    else
+	      {
+		node->firstpos = cat->left->firstpos;
+	      }
+
+	    /* Compute lastpos. */
+	    if (cat->right->nullable)
+	      {
+		/* The right side matches the empty string.  Make a first pass
+		   with tre_match_empty() to get the number of tags and
+		   parameters. */
+		status = tre_match_empty(stack, cat->right,
+					 NULL, NULL, &num_tags);
+		if (status != REG_OK)
+		  return status;
+		/* Allocate arrays for the tags and parameters. */
+		tags = xmalloc(sizeof(int) * (num_tags + 1));
+		if (!tags)
+		  return REG_ESPACE;
+		tags[0] = -1;
+		assertions = 0;
+		/* Second pass with tre_mach_empty() to get the list of
+		   tags and parameters. */
+		status = tre_match_empty(stack, cat->right, tags,
+					 &assertions, NULL);
+		if (status != REG_OK)
+		  {
+		    xfree(tags);
+		    return status;
+		  }
+		node->lastpos =
+		  tre_set_union(mem, cat->left->lastpos, cat->right->lastpos,
+				tags, assertions);
+		xfree(tags);
+		if (!node->lastpos)
+		  return REG_ESPACE;
+	      }
+	    else
+	      {
+		node->lastpos = cat->right->lastpos;
+	      }
+	    break;
+	  }
+
+	default:
+	  assert(0);
+	  break;
+	}
+    }
+
+  return REG_OK;
+}
+
+
+/* Adds a transition from each position in `p1' to each position in `p2'. */
+static reg_errcode_t
+tre_make_trans(tre_pos_and_tags_t *p1, tre_pos_and_tags_t *p2,
+	       tre_tnfa_transition_t *transitions,
+	       int *counts, int *offs)
+{
+  tre_pos_and_tags_t *orig_p2 = p2;
+  tre_tnfa_transition_t *trans;
+  int i, j, k, l, dup, prev_p2_pos;
+
+  if (transitions != NULL)
+    while (p1->position >= 0)
+      {
+	p2 = orig_p2;
+	prev_p2_pos = -1;
+	while (p2->position >= 0)
+	  {
+	    /* Optimization: if this position was already handled, skip it. */
+	    if (p2->position == prev_p2_pos)
+	      {
+		p2++;
+		continue;
+	      }
+	    prev_p2_pos = p2->position;
+	    /* Set `trans' to point to the next unused transition from
+	       position `p1->position'. */
+	    trans = transitions + offs[p1->position];
+	    while (trans->state != NULL)
+	      {
+#if 0
+		/* If we find a previous transition from `p1->position' to
+		   `p2->position', it is overwritten.  This can happen only
+		   if there are nested loops in the regexp, like in "((a)*)*".
+		   In POSIX.2 repetition using the outer loop is always
+		   preferred over using the inner loop.	 Therefore the
+		   transition for the inner loop is useless and can be thrown
+		   away. */
+		/* XXX - The same position is used for all nodes in a bracket
+		   expression, so this optimization cannot be used (it will
+		   break bracket expressions) unless I figure out a way to
+		   detect it here. */
+		if (trans->state_id == p2->position)
+		  {
+		    break;
+		  }
+#endif
+		trans++;
+	      }
+
+	    if (trans->state == NULL)
+	      (trans + 1)->state = NULL;
+	    /* Use the character ranges, assertions, etc. from `p1' for
+	       the transition from `p1' to `p2'. */
+	    trans->code_min = p1->code_min;
+	    trans->code_max = p1->code_max;
+	    trans->state = transitions + offs[p2->position];
+	    trans->state_id = p2->position;
+	    trans->assertions = p1->assertions | p2->assertions
+	      | (p1->class ? ASSERT_CHAR_CLASS : 0)
+	      | (p1->neg_classes != NULL ? ASSERT_CHAR_CLASS_NEG : 0);
+	    if (p1->backref >= 0)
+	      {
+		assert((trans->assertions & ASSERT_CHAR_CLASS) == 0);
+		assert(p2->backref < 0);
+		trans->u.backref = p1->backref;
+		trans->assertions |= ASSERT_BACKREF;
+	      }
+	    else
+	      trans->u.class = p1->class;
+	    if (p1->neg_classes != NULL)
+	      {
+		for (i = 0; p1->neg_classes[i] != (tre_ctype_t)0; i++);
+		trans->neg_classes =
+		  xmalloc(sizeof(*trans->neg_classes) * (i + 1));
+		if (trans->neg_classes == NULL)
+		  return REG_ESPACE;
+		for (i = 0; p1->neg_classes[i] != (tre_ctype_t)0; i++)
+		  trans->neg_classes[i] = p1->neg_classes[i];
+		trans->neg_classes[i] = (tre_ctype_t)0;
+	      }
+	    else
+	      trans->neg_classes = NULL;
+
+	    /* Find out how many tags this transition has. */
+	    i = 0;
+	    if (p1->tags != NULL)
+	      while(p1->tags[i] >= 0)
+		i++;
+	    j = 0;
+	    if (p2->tags != NULL)
+	      while(p2->tags[j] >= 0)
+		j++;
+
+	    /* If we are overwriting a transition, free the old tag array. */
+	    if (trans->tags != NULL)
+	      xfree(trans->tags);
+	    trans->tags = NULL;
+
+	    /* If there were any tags, allocate an array and fill it. */
+	    if (i + j > 0)
+	      {
+		trans->tags = xmalloc(sizeof(*trans->tags) * (i + j + 1));
+		if (!trans->tags)
+		  return REG_ESPACE;
+		i = 0;
+		if (p1->tags != NULL)
+		  while(p1->tags[i] >= 0)
+		    {
+		      trans->tags[i] = p1->tags[i];
+		      i++;
+		    }
+		l = i;
+		j = 0;
+		if (p2->tags != NULL)
+		  while (p2->tags[j] >= 0)
+		    {
+		      /* Don't add duplicates. */
+		      dup = 0;
+		      for (k = 0; k < i; k++)
+			if (trans->tags[k] == p2->tags[j])
+			  {
+			    dup = 1;
+			    break;
+			  }
+		      if (!dup)
+			trans->tags[l++] = p2->tags[j];
+		      j++;
+		    }
+		trans->tags[l] = -1;
+	      }
+
+	    p2++;
+	  }
+	p1++;
+      }
+  else
+    /* Compute a maximum limit for the number of transitions leaving
+       from each state. */
+    while (p1->position >= 0)
+      {
+	p2 = orig_p2;
+	while (p2->position >= 0)
+	  {
+	    counts[p1->position]++;
+	    p2++;
+	  }
+	p1++;
+      }
+  return REG_OK;
+}
+
+/* Converts the syntax tree to a TNFA.	All the transitions in the TNFA are
+   labelled with one character range (there are no transitions on empty
+   strings).  The TNFA takes O(n^2) space in the worst case, `n' is size of
+   the regexp. */
+static reg_errcode_t
+tre_ast_to_tnfa(tre_ast_node_t *node, tre_tnfa_transition_t *transitions,
+		int *counts, int *offs)
+{
+  tre_union_t *uni;
+  tre_catenation_t *cat;
+  tre_iteration_t *iter;
+  reg_errcode_t errcode = REG_OK;
+
+  /* XXX - recurse using a stack!. */
+  switch (node->type)
+    {
+    case LITERAL:
+      break;
+    case UNION:
+      uni = (tre_union_t *)node->obj;
+      errcode = tre_ast_to_tnfa(uni->left, transitions, counts, offs);
+      if (errcode != REG_OK)
+	return errcode;
+      errcode = tre_ast_to_tnfa(uni->right, transitions, counts, offs);
+      break;
+
+    case CATENATION:
+      cat = (tre_catenation_t *)node->obj;
+      /* Add a transition from each position in cat->left->lastpos
+	 to each position in cat->right->firstpos. */
+      errcode = tre_make_trans(cat->left->lastpos, cat->right->firstpos,
+			       transitions, counts, offs);
+      if (errcode != REG_OK)
+	return errcode;
+      errcode = tre_ast_to_tnfa(cat->left, transitions, counts, offs);
+      if (errcode != REG_OK)
+	return errcode;
+      errcode = tre_ast_to_tnfa(cat->right, transitions, counts, offs);
+      break;
+
+    case ITERATION:
+      iter = (tre_iteration_t *)node->obj;
+      assert(iter->max == -1 || iter->max == 1);
+
+      if (iter->max == -1)
+	{
+	  assert(iter->min == 0 || iter->min == 1);
+	  /* Add a transition from each last position in the iterated
+	     expression to each first position. */
+	  errcode = tre_make_trans(iter->arg->lastpos, iter->arg->firstpos,
+				   transitions, counts, offs);
+	  if (errcode != REG_OK)
+	    return errcode;
+	}
+      errcode = tre_ast_to_tnfa(iter->arg, transitions, counts, offs);
+      break;
+    }
+  return errcode;
+}
+
+
+#define ERROR_EXIT(err)		  \
+  do				  \
+    {				  \
+      errcode = err;		  \
+      if (/*CONSTCOND*/1)	  \
+      	goto error_exit;	  \
+    }				  \
+ while (/*CONSTCOND*/0)
+
+
+int
+regcomp(regex_t *restrict preg, const char *restrict regex, int cflags)
+{
+  tre_stack_t *stack;
+  tre_ast_node_t *tree, *tmp_ast_l, *tmp_ast_r;
+  tre_pos_and_tags_t *p;
+  int *counts = NULL, *offs = NULL;
+  int i, add = 0;
+  tre_tnfa_transition_t *transitions, *initial;
+  tre_tnfa_t *tnfa = NULL;
+  tre_submatch_data_t *submatch_data;
+  tre_tag_direction_t *tag_directions = NULL;
+  reg_errcode_t errcode;
+  tre_mem_t mem;
+
+  /* Parse context. */
+  tre_parse_ctx_t parse_ctx;
+
+  /* Allocate a stack used throughout the compilation process for various
+     purposes. */
+  stack = tre_stack_new(512, 10240, 128);
+  if (!stack)
+    return REG_ESPACE;
+  /* Allocate a fast memory allocator. */
+  mem = tre_mem_new();
+  if (!mem)
+    {
+      tre_stack_destroy(stack);
+      return REG_ESPACE;
+    }
+
+  /* Parse the regexp. */
+  memset(&parse_ctx, 0, sizeof(parse_ctx));
+  parse_ctx.mem = mem;
+  parse_ctx.stack = stack;
+  parse_ctx.re = regex;
+  parse_ctx.cflags = cflags;
+  parse_ctx.max_backref = -1;
+  errcode = tre_parse(&parse_ctx);
+  if (errcode != REG_OK)
+    ERROR_EXIT(errcode);
+  preg->re_nsub = parse_ctx.submatch_id - 1;
+  tree = parse_ctx.result;
+
+  /* Back references and approximate matching cannot currently be used
+     in the same regexp. */
+  if (parse_ctx.max_backref >= 0 && parse_ctx.have_approx)
+    ERROR_EXIT(REG_BADPAT);
+
+#ifdef TRE_DEBUG
+  tre_ast_print(tree);
+#endif /* TRE_DEBUG */
+
+  /* Referring to nonexistent subexpressions is illegal. */
+  if (parse_ctx.max_backref > (int)preg->re_nsub)
+    ERROR_EXIT(REG_ESUBREG);
+
+  /* Allocate the TNFA struct. */
+  tnfa = xcalloc(1, sizeof(tre_tnfa_t));
+  if (tnfa == NULL)
+    ERROR_EXIT(REG_ESPACE);
+  tnfa->have_backrefs = parse_ctx.max_backref >= 0;
+  tnfa->have_approx = parse_ctx.have_approx;
+  tnfa->num_submatches = parse_ctx.submatch_id;
+
+  /* Set up tags for submatch addressing.  If REG_NOSUB is set and the
+     regexp does not have back references, this can be skipped. */
+  if (tnfa->have_backrefs || !(cflags & REG_NOSUB))
+    {
+
+      /* Figure out how many tags we will need. */
+      errcode = tre_add_tags(NULL, stack, tree, tnfa);
+      if (errcode != REG_OK)
+	ERROR_EXIT(errcode);
+
+      if (tnfa->num_tags > 0)
+	{
+	  tag_directions = xmalloc(sizeof(*tag_directions)
+				   * (tnfa->num_tags + 1));
+	  if (tag_directions == NULL)
+	    ERROR_EXIT(REG_ESPACE);
+	  tnfa->tag_directions = tag_directions;
+	  memset(tag_directions, -1,
+		 sizeof(*tag_directions) * (tnfa->num_tags + 1));
+	}
+      tnfa->minimal_tags = xcalloc((unsigned)tnfa->num_tags * 2 + 1,
+				   sizeof(tnfa->minimal_tags));
+      if (tnfa->minimal_tags == NULL)
+	ERROR_EXIT(REG_ESPACE);
+
+      submatch_data = xcalloc((unsigned)parse_ctx.submatch_id,
+			      sizeof(*submatch_data));
+      if (submatch_data == NULL)
+	ERROR_EXIT(REG_ESPACE);
+      tnfa->submatch_data = submatch_data;
+
+      errcode = tre_add_tags(mem, stack, tree, tnfa);
+      if (errcode != REG_OK)
+	ERROR_EXIT(errcode);
+
+    }
+
+  /* Expand iteration nodes. */
+  errcode = tre_expand_ast(mem, stack, tree, &parse_ctx.position,
+			   tag_directions);
+  if (errcode != REG_OK)
+    ERROR_EXIT(errcode);
+
+  /* Add a dummy node for the final state.
+     XXX - For certain patterns this dummy node can be optimized away,
+	   for example "a*" or "ab*".	Figure out a simple way to detect
+	   this possibility. */
+  tmp_ast_l = tree;
+  tmp_ast_r = tre_ast_new_literal(mem, 0, 0, parse_ctx.position++);
+  if (tmp_ast_r == NULL)
+    ERROR_EXIT(REG_ESPACE);
+
+  tree = tre_ast_new_catenation(mem, tmp_ast_l, tmp_ast_r);
+  if (tree == NULL)
+    ERROR_EXIT(REG_ESPACE);
+
+  errcode = tre_compute_nfl(mem, stack, tree);
+  if (errcode != REG_OK)
+    ERROR_EXIT(errcode);
+
+  counts = xmalloc(sizeof(int) * parse_ctx.position);
+  if (counts == NULL)
+    ERROR_EXIT(REG_ESPACE);
+
+  offs = xmalloc(sizeof(int) * parse_ctx.position);
+  if (offs == NULL)
+    ERROR_EXIT(REG_ESPACE);
+
+  for (i = 0; i < parse_ctx.position; i++)
+    counts[i] = 0;
+  tre_ast_to_tnfa(tree, NULL, counts, NULL);
+
+  add = 0;
+  for (i = 0; i < parse_ctx.position; i++)
+    {
+      offs[i] = add;
+      add += counts[i] + 1;
+      counts[i] = 0;
+    }
+  transitions = xcalloc((unsigned)add + 1, sizeof(*transitions));
+  if (transitions == NULL)
+    ERROR_EXIT(REG_ESPACE);
+  tnfa->transitions = transitions;
+  tnfa->num_transitions = add;
+
+  errcode = tre_ast_to_tnfa(tree, transitions, counts, offs);
+  if (errcode != REG_OK)
+    ERROR_EXIT(errcode);
+
+  tnfa->firstpos_chars = NULL;
+
+  p = tree->firstpos;
+  i = 0;
+  while (p->position >= 0)
+    {
+      i++;
+      p++;
+    }
+
+  initial = xcalloc((unsigned)i + 1, sizeof(tre_tnfa_transition_t));
+  if (initial == NULL)
+    ERROR_EXIT(REG_ESPACE);
+  tnfa->initial = initial;
+
+  i = 0;
+  for (p = tree->firstpos; p->position >= 0; p++)
+    {
+      initial[i].state = transitions + offs[p->position];
+      initial[i].state_id = p->position;
+      initial[i].tags = NULL;
+      /* Copy the arrays p->tags, and p->params, they are allocated
+	 from a tre_mem object. */
+      if (p->tags)
+	{
+	  int j;
+	  for (j = 0; p->tags[j] >= 0; j++);
+	  initial[i].tags = xmalloc(sizeof(*p->tags) * (j + 1));
+	  if (!initial[i].tags)
+	    ERROR_EXIT(REG_ESPACE);
+	  memcpy(initial[i].tags, p->tags, sizeof(*p->tags) * (j + 1));
+	}
+      initial[i].assertions = p->assertions;
+      i++;
+    }
+  initial[i].state = NULL;
+
+  tnfa->num_transitions = add;
+  tnfa->final = transitions + offs[tree->lastpos[0].position];
+  tnfa->num_states = parse_ctx.position;
+  tnfa->cflags = cflags;
+
+  tre_mem_destroy(mem);
+  tre_stack_destroy(stack);
+  xfree(counts);
+  xfree(offs);
+
+  preg->TRE_REGEX_T_FIELD = (void *)tnfa;
+  return REG_OK;
+
+ error_exit:
+  /* Free everything that was allocated and return the error code. */
+  tre_mem_destroy(mem);
+  if (stack != NULL)
+    tre_stack_destroy(stack);
+  if (counts != NULL)
+    xfree(counts);
+  if (offs != NULL)
+    xfree(offs);
+  preg->TRE_REGEX_T_FIELD = (void *)tnfa;
+  regfree(preg);
+  return errcode;
+}
+
+
+
+
+void
+regfree(regex_t *preg)
+{
+  tre_tnfa_t *tnfa;
+  unsigned int i;
+  tre_tnfa_transition_t *trans;
+
+  tnfa = (void *)preg->TRE_REGEX_T_FIELD;
+  if (!tnfa)
+    return;
+
+  for (i = 0; i < tnfa->num_transitions; i++)
+    if (tnfa->transitions[i].state)
+      {
+	if (tnfa->transitions[i].tags)
+	  xfree(tnfa->transitions[i].tags);
+	if (tnfa->transitions[i].neg_classes)
+	  xfree(tnfa->transitions[i].neg_classes);
+      }
+  if (tnfa->transitions)
+    xfree(tnfa->transitions);
+
+  if (tnfa->initial)
+    {
+      for (trans = tnfa->initial; trans->state; trans++)
+	{
+	  if (trans->tags)
+	    xfree(trans->tags);
+	}
+      xfree(tnfa->initial);
+    }
+
+  if (tnfa->submatch_data)
+    {
+      for (i = 0; i < tnfa->num_submatches; i++)
+	if (tnfa->submatch_data[i].parents)
+	  xfree(tnfa->submatch_data[i].parents);
+      xfree(tnfa->submatch_data);
+    }
+
+  if (tnfa->tag_directions)
+    xfree(tnfa->tag_directions);
+  if (tnfa->firstpos_chars)
+    xfree(tnfa->firstpos_chars);
+  if (tnfa->minimal_tags)
+    xfree(tnfa->minimal_tags);
+  xfree(tnfa);
+}
diff --git a/system/lib/libc/musl/src/regex/regerror.c b/system/lib/libc/musl/src/regex/regerror.c
new file mode 100644
index 00000000..df4afa4f
--- /dev/null
+++ b/system/lib/libc/musl/src/regex/regerror.c
@@ -0,0 +1,35 @@
+#include <string.h>
+#include <regex.h>
+#include <stdio.h>
+
+/* Error message strings for error codes listed in `regex.h'.  This list
+   needs to be in sync with the codes listed there, naturally. */
+
+/* Converted to single string by Rich Felker to remove the need for
+ * data relocations at runtime, 27 Feb 2006. */
+
+static const char messages[] = {
+  "No error\0"
+  "No match\0"
+  "Invalid regexp\0"
+  "Unknown collating element\0"
+  "Unknown character class name\0"
+  "Trailing backslash\0"
+  "Invalid back reference\0"
+  "Missing ']'\0"
+  "Missing ')'\0"
+  "Missing '}'\0"
+  "Invalid contents of {}\0"
+  "Invalid character range\0"
+  "Out of memory\0"
+  "Repetition not preceded by valid expression\0"
+  "\0Unknown error"
+};
+
+size_t regerror(int e, const regex_t *restrict preg, char *restrict buf, size_t size)
+{
+	const char *s;
+	for (s=messages; e && *s; e--, s+=strlen(s)+1);
+	if (!*s) s++;
+	return 1+snprintf(buf, size, "%s", s);
+}
diff --git a/system/lib/libc/musl/src/regex/regexec.c b/system/lib/libc/musl/src/regex/regexec.c
new file mode 100644
index 00000000..855cef57
--- /dev/null
+++ b/system/lib/libc/musl/src/regex/regexec.c
@@ -0,0 +1,1011 @@
+/*
+  regexec.c - TRE POSIX compatible matching functions (and more).
+
+  Copyright (c) 2001-2009 Ville Laurikari <vl@iki.fi>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS
+  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+#include <wctype.h>
+#include <limits.h>
+
+#include <regex.h>
+
+#include "tre.h"
+
+#include <assert.h>
+
+static void
+tre_fill_pmatch(size_t nmatch, regmatch_t pmatch[], int cflags,
+		const tre_tnfa_t *tnfa, int *tags, int match_eo);
+
+/***********************************************************************
+ from tre-match-utils.h
+***********************************************************************/
+
+#define GET_NEXT_WCHAR() do {                                                 \
+    prev_c = next_c; pos += pos_add_next;                                     \
+    if ((pos_add_next = mbtowc(&next_c, str_byte, MB_LEN_MAX)) <= 0) {        \
+        if (pos_add_next < 0) return REG_NOMATCH;                             \
+        else pos_add_next++;                                                  \
+    }                                                                         \
+    str_byte += pos_add_next;                                                 \
+  } while (0)
+
+#define IS_WORD_CHAR(c)	 ((c) == L'_' || tre_isalnum(c))
+
+#define CHECK_ASSERTIONS(assertions)					      \
+  (((assertions & ASSERT_AT_BOL)					      \
+    && (pos > 0 || reg_notbol)						      \
+    && (prev_c != L'\n' || !reg_newline))				      \
+   || ((assertions & ASSERT_AT_EOL)					      \
+       && (next_c != L'\0' || reg_noteol)				      \
+       && (next_c != L'\n' || !reg_newline))				      \
+   || ((assertions & ASSERT_AT_BOW)					      \
+       && (IS_WORD_CHAR(prev_c) || !IS_WORD_CHAR(next_c)))	              \
+   || ((assertions & ASSERT_AT_EOW)					      \
+       && (!IS_WORD_CHAR(prev_c) || IS_WORD_CHAR(next_c)))		      \
+   || ((assertions & ASSERT_AT_WB)					      \
+       && (pos != 0 && next_c != L'\0'					      \
+	   && IS_WORD_CHAR(prev_c) == IS_WORD_CHAR(next_c)))		      \
+   || ((assertions & ASSERT_AT_WB_NEG)					      \
+       && (pos == 0 || next_c == L'\0'					      \
+	   || IS_WORD_CHAR(prev_c) != IS_WORD_CHAR(next_c))))
+
+#define CHECK_CHAR_CLASSES(trans_i, tnfa, eflags)                             \
+  (((trans_i->assertions & ASSERT_CHAR_CLASS)                                 \
+       && !(tnfa->cflags & REG_ICASE)                                         \
+       && !tre_isctype((tre_cint_t)prev_c, trans_i->u.class))                 \
+    || ((trans_i->assertions & ASSERT_CHAR_CLASS)                             \
+        && (tnfa->cflags & REG_ICASE)                                         \
+        && !tre_isctype(tre_tolower((tre_cint_t)prev_c),trans_i->u.class)     \
+	&& !tre_isctype(tre_toupper((tre_cint_t)prev_c),trans_i->u.class))    \
+    || ((trans_i->assertions & ASSERT_CHAR_CLASS_NEG)                         \
+        && tre_neg_char_classes_match(trans_i->neg_classes,(tre_cint_t)prev_c,\
+                                      tnfa->cflags & REG_ICASE)))
+
+
+
+
+/* Returns 1 if `t1' wins `t2', 0 otherwise. */
+static int
+tre_tag_order(int num_tags, tre_tag_direction_t *tag_directions,
+	      int *t1, int *t2)
+{
+  int i;
+  for (i = 0; i < num_tags; i++)
+    {
+      if (tag_directions[i] == TRE_TAG_MINIMIZE)
+	{
+	  if (t1[i] < t2[i])
+	    return 1;
+	  if (t1[i] > t2[i])
+	    return 0;
+	}
+      else
+	{
+	  if (t1[i] > t2[i])
+	    return 1;
+	  if (t1[i] < t2[i])
+	    return 0;
+	}
+    }
+  /*  assert(0);*/
+  return 0;
+}
+
+static int
+tre_neg_char_classes_match(tre_ctype_t *classes, tre_cint_t wc, int icase)
+{
+  while (*classes != (tre_ctype_t)0)
+    if ((!icase && tre_isctype(wc, *classes))
+	|| (icase && (tre_isctype(tre_toupper(wc), *classes)
+		      || tre_isctype(tre_tolower(wc), *classes))))
+      return 1; /* Match. */
+    else
+      classes++;
+  return 0; /* No match. */
+}
+
+
+/***********************************************************************
+ from tre-match-parallel.c
+***********************************************************************/
+
+/*
+  This algorithm searches for matches basically by reading characters
+  in the searched string one by one, starting at the beginning.	 All
+  matching paths in the TNFA are traversed in parallel.	 When two or
+  more paths reach the same state, exactly one is chosen according to
+  tag ordering rules; if returning submatches is not required it does
+  not matter which path is chosen.
+
+  The worst case time required for finding the leftmost and longest
+  match, or determining that there is no match, is always linearly
+  dependent on the length of the text being searched.
+
+  This algorithm cannot handle TNFAs with back referencing nodes.
+  See `tre-match-backtrack.c'.
+*/
+
+typedef struct {
+  tre_tnfa_transition_t *state;
+  int *tags;
+} tre_tnfa_reach_t;
+
+typedef struct {
+  int pos;
+  int **tags;
+} tre_reach_pos_t;
+
+
+static reg_errcode_t
+tre_tnfa_run_parallel(const tre_tnfa_t *tnfa, const void *string,
+		      int *match_tags, int eflags,
+		      int *match_end_ofs)
+{
+  /* State variables required by GET_NEXT_WCHAR. */
+  tre_char_t prev_c = 0, next_c = 0;
+  const char *str_byte = string;
+  int pos = -1;
+  int pos_add_next = 1;
+#ifdef TRE_MBSTATE
+  mbstate_t mbstate;
+#endif /* TRE_MBSTATE */
+  int reg_notbol = eflags & REG_NOTBOL;
+  int reg_noteol = eflags & REG_NOTEOL;
+  int reg_newline = tnfa->cflags & REG_NEWLINE;
+
+  char *buf;
+  tre_tnfa_transition_t *trans_i;
+  tre_tnfa_reach_t *reach, *reach_next, *reach_i, *reach_next_i;
+  tre_reach_pos_t *reach_pos;
+  int *tag_i;
+  int num_tags, i;
+
+  int match_eo = -1;	   /* end offset of match (-1 if no match found yet) */
+  int new_match = 0;
+  int *tmp_tags = NULL;
+  int *tmp_iptr;
+
+#ifdef TRE_MBSTATE
+  memset(&mbstate, '\0', sizeof(mbstate));
+#endif /* TRE_MBSTATE */
+
+  if (!match_tags)
+    num_tags = 0;
+  else
+    num_tags = tnfa->num_tags;
+
+  /* Allocate memory for temporary data required for matching.	This needs to
+     be done for every matching operation to be thread safe.  This allocates
+     everything in a single large block from the stack frame using alloca()
+     or with malloc() if alloca is unavailable. */
+  {
+    int tbytes, rbytes, pbytes, xbytes, total_bytes;
+    char *tmp_buf;
+    /* Compute the length of the block we need. */
+    tbytes = sizeof(*tmp_tags) * num_tags;
+    rbytes = sizeof(*reach_next) * (tnfa->num_states + 1);
+    pbytes = sizeof(*reach_pos) * tnfa->num_states;
+    xbytes = sizeof(int) * num_tags;
+    total_bytes =
+      (sizeof(long) - 1) * 4 /* for alignment paddings */
+      + (rbytes + xbytes * tnfa->num_states) * 2 + tbytes + pbytes;
+
+    /* Allocate the memory. */
+    buf = xmalloc((unsigned)total_bytes);
+    if (buf == NULL)
+      return REG_ESPACE;
+    memset(buf, 0, (size_t)total_bytes);
+
+    /* Get the various pointers within tmp_buf (properly aligned). */
+    tmp_tags = (void *)buf;
+    tmp_buf = buf + tbytes;
+    tmp_buf += ALIGN(tmp_buf, long);
+    reach_next = (void *)tmp_buf;
+    tmp_buf += rbytes;
+    tmp_buf += ALIGN(tmp_buf, long);
+    reach = (void *)tmp_buf;
+    tmp_buf += rbytes;
+    tmp_buf += ALIGN(tmp_buf, long);
+    reach_pos = (void *)tmp_buf;
+    tmp_buf += pbytes;
+    tmp_buf += ALIGN(tmp_buf, long);
+    for (i = 0; i < tnfa->num_states; i++)
+      {
+	reach[i].tags = (void *)tmp_buf;
+	tmp_buf += xbytes;
+	reach_next[i].tags = (void *)tmp_buf;
+	tmp_buf += xbytes;
+      }
+  }
+
+  for (i = 0; i < tnfa->num_states; i++)
+    reach_pos[i].pos = -1;
+
+  GET_NEXT_WCHAR();
+  pos = 0;
+
+  reach_next_i = reach_next;
+  while (1)
+    {
+      /* If no match found yet, add the initial states to `reach_next'. */
+      if (match_eo < 0)
+	{
+	  trans_i = tnfa->initial;
+	  while (trans_i->state != NULL)
+	    {
+	      if (reach_pos[trans_i->state_id].pos < pos)
+		{
+		  if (trans_i->assertions
+		      && CHECK_ASSERTIONS(trans_i->assertions))
+		    {
+		      trans_i++;
+		      continue;
+		    }
+
+		  reach_next_i->state = trans_i->state;
+		  for (i = 0; i < num_tags; i++)
+		    reach_next_i->tags[i] = -1;
+		  tag_i = trans_i->tags;
+		  if (tag_i)
+		    while (*tag_i >= 0)
+		      {
+			if (*tag_i < num_tags)
+			  reach_next_i->tags[*tag_i] = pos;
+			tag_i++;
+		      }
+		  if (reach_next_i->state == tnfa->final)
+		    {
+		      match_eo = pos;
+		      new_match = 1;
+		      for (i = 0; i < num_tags; i++)
+			match_tags[i] = reach_next_i->tags[i];
+		    }
+		  reach_pos[trans_i->state_id].pos = pos;
+		  reach_pos[trans_i->state_id].tags = &reach_next_i->tags;
+		  reach_next_i++;
+		}
+	      trans_i++;
+	    }
+	  reach_next_i->state = NULL;
+	}
+      else
+	{
+	  if (num_tags == 0 || reach_next_i == reach_next)
+	    /* We have found a match. */
+	    break;
+	}
+
+      /* Check for end of string. */
+      if (!next_c) break;
+
+      GET_NEXT_WCHAR();
+
+      /* Swap `reach' and `reach_next'. */
+      reach_i = reach;
+      reach = reach_next;
+      reach_next = reach_i;
+
+      /* For each state in `reach', weed out states that don't fulfill the
+	 minimal matching conditions. */
+      if (tnfa->num_minimals && new_match)
+	{
+	  new_match = 0;
+	  reach_next_i = reach_next;
+	  for (reach_i = reach; reach_i->state; reach_i++)
+	    {
+	      int skip = 0;
+	      for (i = 0; tnfa->minimal_tags[i] >= 0; i += 2)
+		{
+		  int end = tnfa->minimal_tags[i];
+		  int start = tnfa->minimal_tags[i + 1];
+		  if (end >= num_tags)
+		    {
+		      skip = 1;
+		      break;
+		    }
+		  else if (reach_i->tags[start] == match_tags[start]
+			   && reach_i->tags[end] < match_tags[end])
+		    {
+		      skip = 1;
+		      break;
+		    }
+		}
+	      if (!skip)
+		{
+		  reach_next_i->state = reach_i->state;
+		  tmp_iptr = reach_next_i->tags;
+		  reach_next_i->tags = reach_i->tags;
+		  reach_i->tags = tmp_iptr;
+		  reach_next_i++;
+		}
+	    }
+	  reach_next_i->state = NULL;
+
+	  /* Swap `reach' and `reach_next'. */
+	  reach_i = reach;
+	  reach = reach_next;
+	  reach_next = reach_i;
+	}
+
+      /* For each state in `reach' see if there is a transition leaving with
+	 the current input symbol to a state not yet in `reach_next', and
+	 add the destination states to `reach_next'. */
+      reach_next_i = reach_next;
+      for (reach_i = reach; reach_i->state; reach_i++)
+	{
+	  for (trans_i = reach_i->state; trans_i->state; trans_i++)
+	    {
+	      /* Does this transition match the input symbol? */
+	      if (trans_i->code_min <= (tre_cint_t)prev_c &&
+		  trans_i->code_max >= (tre_cint_t)prev_c)
+		{
+		  if (trans_i->assertions
+		      && (CHECK_ASSERTIONS(trans_i->assertions)
+			  || CHECK_CHAR_CLASSES(trans_i, tnfa, eflags)))
+		    {
+		      continue;
+		    }
+
+		  /* Compute the tags after this transition. */
+		  for (i = 0; i < num_tags; i++)
+		    tmp_tags[i] = reach_i->tags[i];
+		  tag_i = trans_i->tags;
+		  if (tag_i != NULL)
+		    while (*tag_i >= 0)
+		      {
+			if (*tag_i < num_tags)
+			  tmp_tags[*tag_i] = pos;
+			tag_i++;
+		      }
+
+		  if (reach_pos[trans_i->state_id].pos < pos)
+		    {
+		      /* Found an unvisited node. */
+		      reach_next_i->state = trans_i->state;
+		      tmp_iptr = reach_next_i->tags;
+		      reach_next_i->tags = tmp_tags;
+		      tmp_tags = tmp_iptr;
+		      reach_pos[trans_i->state_id].pos = pos;
+		      reach_pos[trans_i->state_id].tags = &reach_next_i->tags;
+
+		      if (reach_next_i->state == tnfa->final
+			  && (match_eo == -1
+			      || (num_tags > 0
+				  && reach_next_i->tags[0] <= match_tags[0])))
+			{
+			  match_eo = pos;
+			  new_match = 1;
+			  for (i = 0; i < num_tags; i++)
+			    match_tags[i] = reach_next_i->tags[i];
+			}
+		      reach_next_i++;
+
+		    }
+		  else
+		    {
+		      assert(reach_pos[trans_i->state_id].pos == pos);
+		      /* Another path has also reached this state.  We choose
+			 the winner by examining the tag values for both
+			 paths. */
+		      if (tre_tag_order(num_tags, tnfa->tag_directions,
+					tmp_tags,
+					*reach_pos[trans_i->state_id].tags))
+			{
+			  /* The new path wins. */
+			  tmp_iptr = *reach_pos[trans_i->state_id].tags;
+			  *reach_pos[trans_i->state_id].tags = tmp_tags;
+			  if (trans_i->state == tnfa->final)
+			    {
+			      match_eo = pos;
+			      new_match = 1;
+			      for (i = 0; i < num_tags; i++)
+				match_tags[i] = tmp_tags[i];
+			    }
+			  tmp_tags = tmp_iptr;
+			}
+		    }
+		}
+	    }
+	}
+      reach_next_i->state = NULL;
+    }
+
+  if (buf)
+    xfree(buf);
+
+  *match_end_ofs = match_eo;
+  return match_eo >= 0 ? REG_OK : REG_NOMATCH;
+}
+
+
+
+/***********************************************************************
+ from tre-match-backtrack.c
+***********************************************************************/
+
+/*
+  This matcher is for regexps that use back referencing.  Regexp matching
+  with back referencing is an NP-complete problem on the number of back
+  references.  The easiest way to match them is to use a backtracking
+  routine which basically goes through all possible paths in the TNFA
+  and chooses the one which results in the best (leftmost and longest)
+  match.  This can be spectacularly expensive and may run out of stack
+  space, but there really is no better known generic algorithm.	 Quoting
+  Henry Spencer from comp.compilers:
+  <URL: http://compilers.iecc.com/comparch/article/93-03-102>
+
+    POSIX.2 REs require longest match, which is really exciting to
+    implement since the obsolete ("basic") variant also includes
+    \<digit>.  I haven't found a better way of tackling this than doing
+    a preliminary match using a DFA (or simulation) on a modified RE
+    that just replicates subREs for \<digit>, and then doing a
+    backtracking match to determine whether the subRE matches were
+    right.  This can be rather slow, but I console myself with the
+    thought that people who use \<digit> deserve very slow execution.
+    (Pun unintentional but very appropriate.)
+
+*/
+
+typedef struct {
+  int pos;
+  const char *str_byte;
+  tre_tnfa_transition_t *state;
+  int state_id;
+  int next_c;
+  int *tags;
+#ifdef TRE_MBSTATE
+  mbstate_t mbstate;
+#endif /* TRE_MBSTATE */
+} tre_backtrack_item_t;
+
+typedef struct tre_backtrack_struct {
+  tre_backtrack_item_t item;
+  struct tre_backtrack_struct *prev;
+  struct tre_backtrack_struct *next;
+} *tre_backtrack_t;
+
+#ifdef TRE_MBSTATE
+#define BT_STACK_MBSTATE_IN  stack->item.mbstate = (mbstate)
+#define BT_STACK_MBSTATE_OUT (mbstate) = stack->item.mbstate
+#else /* !TRE_MBSTATE */
+#define BT_STACK_MBSTATE_IN
+#define BT_STACK_MBSTATE_OUT
+#endif /* !TRE_MBSTATE */
+
+#define tre_bt_mem_new		  tre_mem_new
+#define tre_bt_mem_alloc	  tre_mem_alloc
+#define tre_bt_mem_destroy	  tre_mem_destroy
+
+
+#define BT_STACK_PUSH(_pos, _str_byte, _str_wide, _state, _state_id, _next_c, _tags, _mbstate) \
+  do									      \
+    {									      \
+      int i;								      \
+      if (!stack->next)							      \
+	{								      \
+	  tre_backtrack_t s;						      \
+	  s = tre_bt_mem_alloc(mem, sizeof(*s));			      \
+	  if (!s)							      \
+	    {								      \
+	      tre_bt_mem_destroy(mem);					      \
+	      if (tags)							      \
+		xfree(tags);						      \
+	      if (pmatch)						      \
+		xfree(pmatch);						      \
+	      if (states_seen)						      \
+		xfree(states_seen);					      \
+	      return REG_ESPACE;					      \
+	    }								      \
+	  s->prev = stack;						      \
+	  s->next = NULL;						      \
+	  s->item.tags = tre_bt_mem_alloc(mem,				      \
+					  sizeof(*tags) * tnfa->num_tags);    \
+	  if (!s->item.tags)						      \
+	    {								      \
+	      tre_bt_mem_destroy(mem);					      \
+	      if (tags)							      \
+		xfree(tags);						      \
+	      if (pmatch)						      \
+		xfree(pmatch);						      \
+	      if (states_seen)						      \
+		xfree(states_seen);					      \
+	      return REG_ESPACE;					      \
+	    }								      \
+	  stack->next = s;						      \
+	  stack = s;							      \
+	}								      \
+      else								      \
+	stack = stack->next;						      \
+      stack->item.pos = (_pos);						      \
+      stack->item.str_byte = (_str_byte);				      \
+      stack->item.state = (_state);					      \
+      stack->item.state_id = (_state_id);				      \
+      stack->item.next_c = (_next_c);					      \
+      for (i = 0; i < tnfa->num_tags; i++)				      \
+	stack->item.tags[i] = (_tags)[i];				      \
+      BT_STACK_MBSTATE_IN;						      \
+    }									      \
+  while (0)
+
+#define BT_STACK_POP()							      \
+  do									      \
+    {									      \
+      int i;								      \
+      assert(stack->prev);						      \
+      pos = stack->item.pos;						      \
+      str_byte = stack->item.str_byte;					      \
+      state = stack->item.state;					      \
+      next_c = stack->item.next_c;					      \
+      for (i = 0; i < tnfa->num_tags; i++)				      \
+	tags[i] = stack->item.tags[i];					      \
+      BT_STACK_MBSTATE_OUT;						      \
+      stack = stack->prev;						      \
+    }									      \
+  while (0)
+
+#undef MIN
+#define MIN(a, b) ((a) <= (b) ? (a) : (b))
+
+static reg_errcode_t
+tre_tnfa_run_backtrack(const tre_tnfa_t *tnfa, const void *string,
+		       int *match_tags, int eflags, int *match_end_ofs)
+{
+  /* State variables required by GET_NEXT_WCHAR. */
+  tre_char_t prev_c = 0, next_c = 0;
+  const char *str_byte = string;
+  int pos = 0;
+  int pos_add_next = 1;
+#ifdef TRE_MBSTATE
+  mbstate_t mbstate;
+#endif /* TRE_MBSTATE */
+  int reg_notbol = eflags & REG_NOTBOL;
+  int reg_noteol = eflags & REG_NOTEOL;
+  int reg_newline = tnfa->cflags & REG_NEWLINE;
+
+  /* These are used to remember the necessary values of the above
+     variables to return to the position where the current search
+     started from. */
+  int next_c_start;
+  const char *str_byte_start;
+  int pos_start = -1;
+#ifdef TRE_MBSTATE
+  mbstate_t mbstate_start;
+#endif /* TRE_MBSTATE */
+
+  /* End offset of best match so far, or -1 if no match found yet. */
+  int match_eo = -1;
+  /* Tag arrays. */
+  int *next_tags, *tags = NULL;
+  /* Current TNFA state. */
+  tre_tnfa_transition_t *state;
+  int *states_seen = NULL;
+
+  /* Memory allocator to for allocating the backtracking stack. */
+  tre_mem_t mem = tre_bt_mem_new();
+
+  /* The backtracking stack. */
+  tre_backtrack_t stack;
+
+  tre_tnfa_transition_t *trans_i;
+  regmatch_t *pmatch = NULL;
+  int ret;
+
+#ifdef TRE_MBSTATE
+  memset(&mbstate, '\0', sizeof(mbstate));
+#endif /* TRE_MBSTATE */
+
+  if (!mem)
+    return REG_ESPACE;
+  stack = tre_bt_mem_alloc(mem, sizeof(*stack));
+  if (!stack)
+    {
+      ret = REG_ESPACE;
+      goto error_exit;
+    }
+  stack->prev = NULL;
+  stack->next = NULL;
+
+  if (tnfa->num_tags)
+    {
+      tags = xmalloc(sizeof(*tags) * tnfa->num_tags);
+      if (!tags)
+	{
+	  ret = REG_ESPACE;
+	  goto error_exit;
+	}
+    }
+  if (tnfa->num_submatches)
+    {
+      pmatch = xmalloc(sizeof(*pmatch) * tnfa->num_submatches);
+      if (!pmatch)
+	{
+	  ret = REG_ESPACE;
+	  goto error_exit;
+	}
+    }
+  if (tnfa->num_states)
+    {
+      states_seen = xmalloc(sizeof(*states_seen) * tnfa->num_states);
+      if (!states_seen)
+	{
+	  ret = REG_ESPACE;
+	  goto error_exit;
+	}
+    }
+
+ retry:
+  {
+    int i;
+    for (i = 0; i < tnfa->num_tags; i++)
+      {
+	tags[i] = -1;
+	if (match_tags)
+	  match_tags[i] = -1;
+      }
+    for (i = 0; i < tnfa->num_states; i++)
+      states_seen[i] = 0;
+  }
+
+  state = NULL;
+  pos = pos_start;
+  GET_NEXT_WCHAR();
+  pos_start = pos;
+  next_c_start = next_c;
+  str_byte_start = str_byte;
+#ifdef TRE_MBSTATE
+  mbstate_start = mbstate;
+#endif /* TRE_MBSTATE */
+
+  /* Handle initial states. */
+  next_tags = NULL;
+  for (trans_i = tnfa->initial; trans_i->state; trans_i++)
+    {
+      if (trans_i->assertions && CHECK_ASSERTIONS(trans_i->assertions))
+	{
+	  continue;
+	}
+      if (state == NULL)
+	{
+	  /* Start from this state. */
+	  state = trans_i->state;
+	  next_tags = trans_i->tags;
+	}
+      else
+	{
+	  /* Backtrack to this state. */
+	  BT_STACK_PUSH(pos, str_byte, 0, trans_i->state,
+			trans_i->state_id, next_c, tags, mbstate);
+	  {
+	    int *tmp = trans_i->tags;
+	    if (tmp)
+	      while (*tmp >= 0)
+		stack->item.tags[*tmp++] = pos;
+	  }
+	}
+    }
+
+  if (next_tags)
+    for (; *next_tags >= 0; next_tags++)
+      tags[*next_tags] = pos;
+
+
+  if (state == NULL)
+    goto backtrack;
+
+  while (1)
+    {
+      tre_tnfa_transition_t *next_state;
+      int empty_br_match;
+
+      if (state == tnfa->final)
+	{
+	  if (match_eo < pos
+	      || (match_eo == pos
+		  && match_tags
+		  && tre_tag_order(tnfa->num_tags, tnfa->tag_directions,
+				   tags, match_tags)))
+	    {
+	      int i;
+	      /* This match wins the previous match. */
+	      match_eo = pos;
+	      if (match_tags)
+		for (i = 0; i < tnfa->num_tags; i++)
+		  match_tags[i] = tags[i];
+	    }
+	  /* Our TNFAs never have transitions leaving from the final state,
+	     so we jump right to backtracking. */
+	  goto backtrack;
+	}
+
+      /* Go to the next character in the input string. */
+      empty_br_match = 0;
+      trans_i = state;
+      if (trans_i->state && trans_i->assertions & ASSERT_BACKREF)
+	{
+	  /* This is a back reference state.  All transitions leaving from
+	     this state have the same back reference "assertion".  Instead
+	     of reading the next character, we match the back reference. */
+	  int so, eo, bt = trans_i->u.backref;
+	  int bt_len;
+	  int result;
+
+	  /* Get the substring we need to match against.  Remember to
+	     turn off REG_NOSUB temporarily. */
+	  tre_fill_pmatch(bt + 1, pmatch, tnfa->cflags & ~REG_NOSUB,
+			  tnfa, tags, pos);
+	  so = pmatch[bt].rm_so;
+	  eo = pmatch[bt].rm_eo;
+	  bt_len = eo - so;
+
+	  result = strncmp((const char*)string + so, str_byte - 1,
+				 (size_t)bt_len);
+
+	  if (result == 0)
+	    {
+	      /* Back reference matched.  Check for infinite loop. */
+	      if (bt_len == 0)
+		empty_br_match = 1;
+	      if (empty_br_match && states_seen[trans_i->state_id])
+		{
+		  goto backtrack;
+		}
+
+	      states_seen[trans_i->state_id] = empty_br_match;
+
+	      /* Advance in input string and resync `prev_c', `next_c'
+		 and pos. */
+	      str_byte += bt_len - 1;
+	      pos += bt_len - 1;
+	      GET_NEXT_WCHAR();
+	    }
+	  else
+	    {
+	      goto backtrack;
+	    }
+	}
+      else
+	{
+	  /* Check for end of string. */
+	  if (next_c == L'\0')
+		goto backtrack;
+
+	  /* Read the next character. */
+	  GET_NEXT_WCHAR();
+	}
+
+      next_state = NULL;
+      for (trans_i = state; trans_i->state; trans_i++)
+	{
+	  if (trans_i->code_min <= (tre_cint_t)prev_c
+	      && trans_i->code_max >= (tre_cint_t)prev_c)
+	    {
+	      if (trans_i->assertions
+		  && (CHECK_ASSERTIONS(trans_i->assertions)
+		      || CHECK_CHAR_CLASSES(trans_i, tnfa, eflags)))
+		{
+		  continue;
+		}
+
+	      if (next_state == NULL)
+		{
+		  /* First matching transition. */
+		  next_state = trans_i->state;
+		  next_tags = trans_i->tags;
+		}
+	      else
+		{
+		  /* Second matching transition.  We may need to backtrack here
+		     to take this transition instead of the first one, so we
+		     push this transition in the backtracking stack so we can
+		     jump back here if needed. */
+		  BT_STACK_PUSH(pos, str_byte, 0, trans_i->state,
+				trans_i->state_id, next_c, tags, mbstate);
+		  {
+		    int *tmp;
+		    for (tmp = trans_i->tags; tmp && *tmp >= 0; tmp++)
+		      stack->item.tags[*tmp] = pos;
+		  }
+#if 0 /* XXX - it's important not to look at all transitions here to keep
+	 the stack small! */
+		  break;
+#endif
+		}
+	    }
+	}
+
+      if (next_state != NULL)
+	{
+	  /* Matching transitions were found.  Take the first one. */
+	  state = next_state;
+
+	  /* Update the tag values. */
+	  if (next_tags)
+	    while (*next_tags >= 0)
+	      tags[*next_tags++] = pos;
+	}
+      else
+	{
+	backtrack:
+	  /* A matching transition was not found.  Try to backtrack. */
+	  if (stack->prev)
+	    {
+	      if (stack->item.state->assertions & ASSERT_BACKREF)
+		{
+		  states_seen[stack->item.state_id] = 0;
+		}
+
+	      BT_STACK_POP();
+	    }
+	  else if (match_eo < 0)
+	    {
+	      /* Try starting from a later position in the input string. */
+	      /* Check for end of string. */
+	      if (next_c == L'\0')
+		    {
+		      break;
+		    }
+	      next_c = next_c_start;
+#ifdef TRE_MBSTATE
+	      mbstate = mbstate_start;
+#endif /* TRE_MBSTATE */
+	      str_byte = str_byte_start;
+	      goto retry;
+	    }
+	  else
+	    {
+	      break;
+	    }
+	}
+    }
+
+  ret = match_eo >= 0 ? REG_OK : REG_NOMATCH;
+  *match_end_ofs = match_eo;
+
+ error_exit:
+  tre_bt_mem_destroy(mem);
+#ifndef TRE_USE_ALLOCA
+  if (tags)
+    xfree(tags);
+  if (pmatch)
+    xfree(pmatch);
+  if (states_seen)
+    xfree(states_seen);
+#endif /* !TRE_USE_ALLOCA */
+
+  return ret;
+}
+
+/***********************************************************************
+ from regexec.c
+***********************************************************************/
+
+/* Fills the POSIX.2 regmatch_t array according to the TNFA tag and match
+   endpoint values. */
+static void
+tre_fill_pmatch(size_t nmatch, regmatch_t pmatch[], int cflags,
+		const tre_tnfa_t *tnfa, int *tags, int match_eo)
+{
+  tre_submatch_data_t *submatch_data;
+  unsigned int i, j;
+  int *parents;
+
+  i = 0;
+  if (match_eo >= 0 && !(cflags & REG_NOSUB))
+    {
+      /* Construct submatch offsets from the tags. */
+      submatch_data = tnfa->submatch_data;
+      while (i < tnfa->num_submatches && i < nmatch)
+	{
+	  if (submatch_data[i].so_tag == tnfa->end_tag)
+	    pmatch[i].rm_so = match_eo;
+	  else
+	    pmatch[i].rm_so = tags[submatch_data[i].so_tag];
+
+	  if (submatch_data[i].eo_tag == tnfa->end_tag)
+	    pmatch[i].rm_eo = match_eo;
+	  else
+	    pmatch[i].rm_eo = tags[submatch_data[i].eo_tag];
+
+	  /* If either of the endpoints were not used, this submatch
+	     was not part of the match. */
+	  if (pmatch[i].rm_so == -1 || pmatch[i].rm_eo == -1)
+	    pmatch[i].rm_so = pmatch[i].rm_eo = -1;
+
+	  i++;
+	}
+      /* Reset all submatches that are not within all of their parent
+	 submatches. */
+      i = 0;
+      while (i < tnfa->num_submatches && i < nmatch)
+	{
+	  if (pmatch[i].rm_eo == -1)
+	    assert(pmatch[i].rm_so == -1);
+	  assert(pmatch[i].rm_so <= pmatch[i].rm_eo);
+
+	  parents = submatch_data[i].parents;
+	  if (parents != NULL)
+	    for (j = 0; parents[j] >= 0; j++)
+	      {
+		if (pmatch[i].rm_so < pmatch[parents[j]].rm_so
+		    || pmatch[i].rm_eo > pmatch[parents[j]].rm_eo)
+		  pmatch[i].rm_so = pmatch[i].rm_eo = -1;
+	      }
+	  i++;
+	}
+    }
+
+  while (i < nmatch)
+    {
+      pmatch[i].rm_so = -1;
+      pmatch[i].rm_eo = -1;
+      i++;
+    }
+}
+
+
+/*
+  Wrapper functions for POSIX compatible regexp matching.
+*/
+
+int
+regexec(const regex_t *restrict preg, const char *restrict string,
+	  size_t nmatch, regmatch_t pmatch[restrict], int eflags)
+{
+  tre_tnfa_t *tnfa = (void *)preg->TRE_REGEX_T_FIELD;
+  reg_errcode_t status;
+  int *tags = NULL, eo;
+  if (tnfa->num_tags > 0 && nmatch > 0)
+    {
+      tags = xmalloc(sizeof(*tags) * tnfa->num_tags);
+      if (tags == NULL)
+	return REG_ESPACE;
+    }
+
+  /* Dispatch to the appropriate matcher. */
+  if (tnfa->have_backrefs)
+    {
+      /* The regex has back references, use the backtracking matcher. */
+      status = tre_tnfa_run_backtrack(tnfa, string, tags, eflags, &eo);
+    }
+  else
+    {
+      /* Exact matching, no back references, use the parallel matcher. */
+      status = tre_tnfa_run_parallel(tnfa, string, tags, eflags, &eo);
+    }
+
+  if (status == REG_OK)
+    /* A match was found, so fill the submatch registers. */
+    tre_fill_pmatch(nmatch, pmatch, tnfa->cflags, tnfa, tags, eo);
+  if (tags)
+    xfree(tags);
+  return status;
+}
diff --git a/system/lib/libc/musl/src/regex/tre-mem.c b/system/lib/libc/musl/src/regex/tre-mem.c
new file mode 100644
index 00000000..86f809d4
--- /dev/null
+++ b/system/lib/libc/musl/src/regex/tre-mem.c
@@ -0,0 +1,158 @@
+/*
+  tre-mem.c - TRE memory allocator
+
+  Copyright (c) 2001-2009 Ville Laurikari <vl@iki.fi>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS
+  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+/*
+  This memory allocator is for allocating small memory blocks efficiently
+  in terms of memory overhead and execution speed.  The allocated blocks
+  cannot be freed individually, only all at once.  There can be multiple
+  allocators, though.
+*/
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "tre.h"
+
+/*
+  This memory allocator is for allocating small memory blocks efficiently
+  in terms of memory overhead and execution speed.  The allocated blocks
+  cannot be freed individually, only all at once.  There can be multiple
+  allocators, though.
+*/
+
+/* Returns a new memory allocator or NULL if out of memory. */
+tre_mem_t
+tre_mem_new_impl(int provided, void *provided_block)
+{
+  tre_mem_t mem;
+  if (provided)
+    {
+      mem = provided_block;
+      memset(mem, 0, sizeof(*mem));
+    }
+  else
+    mem = xcalloc(1, sizeof(*mem));
+  if (mem == NULL)
+    return NULL;
+  return mem;
+}
+
+
+/* Frees the memory allocator and all memory allocated with it. */
+void
+tre_mem_destroy(tre_mem_t mem)
+{
+  tre_list_t *tmp, *l = mem->blocks;
+
+  while (l != NULL)
+    {
+      xfree(l->data);
+      tmp = l->next;
+      xfree(l);
+      l = tmp;
+    }
+  xfree(mem);
+}
+
+
+/* Allocates a block of `size' bytes from `mem'.  Returns a pointer to the
+   allocated block or NULL if an underlying malloc() failed. */
+void *
+tre_mem_alloc_impl(tre_mem_t mem, int provided, void *provided_block,
+		   int zero, size_t size)
+{
+  void *ptr;
+
+  if (mem->failed)
+    {
+      return NULL;
+    }
+
+  if (mem->n < size)
+    {
+      /* We need more memory than is available in the current block.
+	 Allocate a new block. */
+      tre_list_t *l;
+      if (provided)
+	{
+	  if (provided_block == NULL)
+	    {
+	      mem->failed = 1;
+	      return NULL;
+	    }
+	  mem->ptr = provided_block;
+	  mem->n = TRE_MEM_BLOCK_SIZE;
+	}
+      else
+	{
+	  int block_size;
+	  if (size * 8 > TRE_MEM_BLOCK_SIZE)
+	    block_size = size * 8;
+	  else
+	    block_size = TRE_MEM_BLOCK_SIZE;
+	  l = xmalloc(sizeof(*l));
+	  if (l == NULL)
+	    {
+	      mem->failed = 1;
+	      return NULL;
+	    }
+	  l->data = xmalloc(block_size);
+	  if (l->data == NULL)
+	    {
+	      xfree(l);
+	      mem->failed = 1;
+	      return NULL;
+	    }
+	  l->next = NULL;
+	  if (mem->current != NULL)
+	    mem->current->next = l;
+	  if (mem->blocks == NULL)
+	    mem->blocks = l;
+	  mem->current = l;
+	  mem->ptr = l->data;
+	  mem->n = block_size;
+	}
+    }
+
+  /* Make sure the next pointer will be aligned. */
+  size += ALIGN(mem->ptr + size, long);
+
+  /* Allocate from current block. */
+  ptr = mem->ptr;
+  mem->ptr += size;
+  mem->n -= size;
+
+  /* Set to zero if needed. */
+  if (zero)
+    memset(ptr, 0, size);
+
+  return ptr;
+}
diff --git a/system/lib/libc/musl/src/regex/tre.h b/system/lib/libc/musl/src/regex/tre.h
new file mode 100644
index 00000000..67cb9a84
--- /dev/null
+++ b/system/lib/libc/musl/src/regex/tre.h
@@ -0,0 +1,231 @@
+/*
+  tre-internal.h - TRE internal definitions
+
+  Copyright (c) 2001-2009 Ville Laurikari <vl@iki.fi>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS
+  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#include <regex.h>
+#include <wchar.h>
+#include <wctype.h>
+
+#undef  TRE_MBSTATE
+
+#define NDEBUG
+
+#define TRE_REGEX_T_FIELD __opaque
+typedef int reg_errcode_t;
+
+typedef wchar_t tre_char_t;
+
+#define DPRINT(msg) do { } while(0)
+
+#define elementsof(x)	( sizeof(x) / sizeof(x[0]) )
+
+#define tre_mbrtowc(pwc, s, n, ps) (mbtowc((pwc), (s), (n)))
+
+/* Wide characters. */
+typedef wint_t tre_cint_t;
+#define TRE_CHAR_MAX 0x10ffff
+
+#define tre_isalnum iswalnum
+#define tre_isalpha iswalpha
+#define tre_isblank iswblank
+#define tre_iscntrl iswcntrl
+#define tre_isdigit iswdigit
+#define tre_isgraph iswgraph
+#define tre_islower iswlower
+#define tre_isprint iswprint
+#define tre_ispunct iswpunct
+#define tre_isspace iswspace
+#define tre_isupper iswupper
+#define tre_isxdigit iswxdigit
+
+#define tre_tolower towlower
+#define tre_toupper towupper
+#define tre_strlen  wcslen
+
+/* Use system provided iswctype() and wctype(). */
+typedef wctype_t tre_ctype_t;
+#define tre_isctype iswctype
+#define tre_ctype   wctype
+
+/* Returns number of bytes to add to (char *)ptr to make it
+   properly aligned for the type. */
+#define ALIGN(ptr, type) \
+  ((((long)ptr) % sizeof(type)) \
+   ? (sizeof(type) - (((long)ptr) % sizeof(type))) \
+   : 0)
+
+#undef MAX
+#undef MIN
+#define MAX(a, b) (((a) >= (b)) ? (a) : (b))
+#define MIN(a, b) (((a) <= (b)) ? (a) : (b))
+
+/* TNFA transition type. A TNFA state is an array of transitions,
+   the terminator is a transition with NULL `state'. */
+typedef struct tnfa_transition tre_tnfa_transition_t;
+
+struct tnfa_transition {
+  /* Range of accepted characters. */
+  tre_cint_t code_min;
+  tre_cint_t code_max;
+  /* Pointer to the destination state. */
+  tre_tnfa_transition_t *state;
+  /* ID number of the destination state. */
+  int state_id;
+  /* -1 terminated array of tags (or NULL). */
+  int *tags;
+  /* Assertion bitmap. */
+  int assertions;
+  /* Assertion parameters. */
+  union {
+    /* Character class assertion. */
+    tre_ctype_t class;
+    /* Back reference assertion. */
+    int backref;
+  } u;
+  /* Negative character class assertions. */
+  tre_ctype_t *neg_classes;
+};
+
+
+/* Assertions. */
+#define ASSERT_AT_BOL		  1   /* Beginning of line. */
+#define ASSERT_AT_EOL		  2   /* End of line. */
+#define ASSERT_CHAR_CLASS	  4   /* Character class in `class'. */
+#define ASSERT_CHAR_CLASS_NEG	  8   /* Character classes in `neg_classes'. */
+#define ASSERT_AT_BOW		 16   /* Beginning of word. */
+#define ASSERT_AT_EOW		 32   /* End of word. */
+#define ASSERT_AT_WB		 64   /* Word boundary. */
+#define ASSERT_AT_WB_NEG	128   /* Not a word boundary. */
+#define ASSERT_BACKREF		256   /* A back reference in `backref'. */
+#define ASSERT_LAST		256
+
+/* Tag directions. */
+typedef enum {
+  TRE_TAG_MINIMIZE = 0,
+  TRE_TAG_MAXIMIZE = 1
+} tre_tag_direction_t;
+
+/* Instructions to compute submatch register values from tag values
+   after a successful match.  */
+struct tre_submatch_data {
+  /* Tag that gives the value for rm_so (submatch start offset). */
+  int so_tag;
+  /* Tag that gives the value for rm_eo (submatch end offset). */
+  int eo_tag;
+  /* List of submatches this submatch is contained in. */
+  int *parents;
+};
+
+typedef struct tre_submatch_data tre_submatch_data_t;
+
+
+/* TNFA definition. */
+typedef struct tnfa tre_tnfa_t;
+
+struct tnfa {
+  tre_tnfa_transition_t *transitions;
+  unsigned int num_transitions;
+  tre_tnfa_transition_t *initial;
+  tre_tnfa_transition_t *final;
+  tre_submatch_data_t *submatch_data;
+  char *firstpos_chars;
+  int first_char;
+  unsigned int num_submatches;
+  tre_tag_direction_t *tag_directions;
+  int *minimal_tags;
+  int num_tags;
+  int num_minimals;
+  int end_tag;
+  int num_states;
+  int cflags;
+  int have_backrefs;
+  int have_approx;
+};
+
+/* from tre-mem.h: */
+
+#define TRE_MEM_BLOCK_SIZE 1024
+
+typedef struct tre_list {
+  void *data;
+  struct tre_list *next;
+} tre_list_t;
+
+typedef struct tre_mem_struct {
+  tre_list_t *blocks;
+  tre_list_t *current;
+  char *ptr;
+  size_t n;
+  int failed;
+  void **provided;
+} *tre_mem_t;
+
+#define tre_mem_new_impl   __tre_mem_new_impl
+#define tre_mem_alloc_impl __tre_mem_alloc_impl
+#define tre_mem_destroy    __tre_mem_destroy
+
+tre_mem_t tre_mem_new_impl(int provided, void *provided_block);
+void *tre_mem_alloc_impl(tre_mem_t mem, int provided, void *provided_block,
+			 int zero, size_t size);
+
+/* Returns a new memory allocator or NULL if out of memory. */
+#define tre_mem_new()  tre_mem_new_impl(0, NULL)
+
+/* Allocates a block of `size' bytes from `mem'.  Returns a pointer to the
+   allocated block or NULL if an underlying malloc() failed. */
+#define tre_mem_alloc(mem, size) tre_mem_alloc_impl(mem, 0, NULL, 0, size)
+
+/* Allocates a block of `size' bytes from `mem'.  Returns a pointer to the
+   allocated block or NULL if an underlying malloc() failed.  The memory
+   is set to zero. */
+#define tre_mem_calloc(mem, size) tre_mem_alloc_impl(mem, 0, NULL, 1, size)
+
+#ifdef TRE_USE_ALLOCA
+/* alloca() versions.  Like above, but memory is allocated with alloca()
+   instead of malloc(). */
+
+#define tre_mem_newa() \
+  tre_mem_new_impl(1, alloca(sizeof(struct tre_mem_struct)))
+
+#define tre_mem_alloca(mem, size)					      \
+  ((mem)->n >= (size)							      \
+   ? tre_mem_alloc_impl((mem), 1, NULL, 0, (size))			      \
+   : tre_mem_alloc_impl((mem), 1, alloca(TRE_MEM_BLOCK_SIZE), 0, (size)))
+#endif /* TRE_USE_ALLOCA */
+
+
+/* Frees the memory allocator and all memory allocated with it. */
+void tre_mem_destroy(tre_mem_t mem);
+
+#define xmalloc malloc
+#define xcalloc calloc
+#define xfree free
+#define xrealloc realloc
+
diff --git a/system/lib/libcextra.symbols b/system/lib/libcextra.symbols
index 522137c6..d169ead6 100644
--- a/system/lib/libcextra.symbols
+++ b/system/lib/libcextra.symbols
@@ -2,6 +2,9 @@
          T __strxfrm_l
          W __towlower_l
          W __towupper_l
+         T __tre_mem_alloc_impl
+         T __tre_mem_destroy
+         T __tre_mem_new_impl
          T __wcscoll_l
          T __wcsxfrm_l
          W __wctype_l
@@ -47,6 +50,10 @@
          T mbsrtowcs
          T mbstowcs
          T mbtowc
+         T regcomp
+         T regerror
+         T regexec
+         T regfree
          T strfmon
          T strfmon_l
          T strxfrm