--- a/ChangeLog	Fri Feb 19 08:41:58 2016 -0800
+++ b/ChangeLog	Fri Feb 19 09:27:41 2016 -0800
@@ -1,5 +1,18 @@
 2016-02-19  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* lib/regex_internal.h (IDX_MAX) [_REGEX_LARGE_OFFSETS]: Now SSIZE_MAX.
+
+	regex: make it closer to libc
+	Make Idx a signed type, rather than possibly unsigned.
+	The unsignedness was not really buying us anything, since the code
+	overflows for other reasons before getting to PTRDIFF_MAX.  Making
+	it signed allows us to use -1 and -2 with abandon, like libc does,
+	thus lessening the number of differences between gnulib and libc.
+	Also, it should help avoid gratuitous warnings like the one
+	reported by Nelson H. F. Beebe in: http://bugs.gnu.org/22702
+	* lib/regex.h (__re_idx_t): Remove.  All uses changed to regoff_t.
+
+
 	regex: merge patches from libc
 
 	2015-10-21  Joseph Myers  <joseph@codesourcery.com>

--- a/lib/regcomp.c	Fri Feb 19 08:41:58 2016 -0800
+++ b/lib/regcomp.c	Fri Feb 19 09:27:41 2016 -0800
@@ -1397,7 +1397,7 @@
     {
       node->first = node;
       node->node_idx = re_dfa_add_node (dfa, node->token);
-      if (BE (node->node_idx == REG_MISSING, 0))
+      if (BE (node->node_idx == -1, 0))
 	return REG_ESPACE;
       if (node->token.type == ANCHOR)
 	dfa->nodes[node->node_idx].constraint = node->token.opr.ctx_type;
@@ -1458,8 +1458,8 @@
 	  right = node->right->first->node_idx;
 	else
 	  right = node->next->node_idx;
-	assert (REG_VALID_INDEX (left));
-	assert (REG_VALID_INDEX (right));
+	assert (left > -1);
+	assert (right > -1);
 	err = re_node_set_init_2 (dfa->edests + idx, left, right);
       }
       break;
@@ -1509,7 +1509,7 @@
 	  org_dest = dfa->nexts[org_node];
 	  re_node_set_empty (dfa->edests + clone_node);
 	  clone_dest = duplicate_node (dfa, org_dest, constraint);
-	  if (BE (clone_dest == REG_MISSING, 0))
+	  if (BE (clone_dest == -1, 0))
 	    return REG_ESPACE;
 	  dfa->nexts[clone_node] = dfa->nexts[org_node];
 	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
@@ -1542,7 +1542,7 @@
 	  /* In case the node has another constraint, append it.  */
 	  constraint |= dfa->nodes[org_node].constraint;
 	  clone_dest = duplicate_node (dfa, org_dest, constraint);
-	  if (BE (clone_dest == REG_MISSING, 0))
+	  if (BE (clone_dest == -1, 0))
 	    return REG_ESPACE;
 	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
 	  if (BE (! ok, 0))
@@ -1556,12 +1556,12 @@
 	  re_node_set_empty (dfa->edests + clone_node);
 	  /* Search for a duplicated node which satisfies the constraint.  */
 	  clone_dest = search_duplicated_node (dfa, org_dest, constraint);
-	  if (clone_dest == REG_MISSING)
+	  if (clone_dest == -1)
 	    {
 	      /* There is no such duplicated node, create a new one.  */
 	      reg_errcode_t err;
 	      clone_dest = duplicate_node (dfa, org_dest, constraint);
-	      if (BE (clone_dest == REG_MISSING, 0))
+	      if (BE (clone_dest == -1, 0))
 		return REG_ESPACE;
 	      ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
 	      if (BE (! ok, 0))
@@ -1582,7 +1582,7 @@
 
 	  org_dest = dfa->edests[org_node].elems[1];
 	  clone_dest = duplicate_node (dfa, org_dest, constraint);
-	  if (BE (clone_dest == REG_MISSING, 0))
+	  if (BE (clone_dest == -1, 0))
 	    return REG_ESPACE;
 	  ok = re_node_set_insert (dfa->edests + clone_node, clone_dest);
 	  if (BE (! ok, 0))
@@ -1608,18 +1608,18 @@
 	  && constraint == dfa->nodes[idx].constraint)
 	return idx; /* Found.  */
     }
-  return REG_MISSING; /* Not found.  */
+  return -1; /* Not found.  */
 }
 
 /* Duplicate the node whose index is ORG_IDX and set the constraint CONSTRAINT.
-   Return the index of the new node, or REG_MISSING if insufficient storage is
+   Return the index of the new node, or -1 if insufficient storage is
    available.  */
 
 static Idx
 duplicate_node (re_dfa_t *dfa, Idx org_idx, unsigned int constraint)
 {
   Idx dup_idx = re_dfa_add_node (dfa, dfa->nodes[org_idx]);
-  if (BE (dup_idx != REG_MISSING, 1))
+  if (BE (dup_idx != -1, 1))
     {
       dfa->nodes[dup_idx].constraint = constraint;
       dfa->nodes[dup_idx].constraint |= dfa->nodes[org_idx].constraint;
@@ -1678,7 +1678,7 @@
 	}
 
 #ifdef DEBUG
-      assert (dfa->eclosures[node_idx].nelem != REG_MISSING);
+      assert (dfa->eclosures[node_idx].nelem != -1);
 #endif
 
       /* If we have already calculated, skip it.  */
@@ -1714,7 +1714,7 @@
 
   /* This indicates that we are calculating this node now.
      We reference this value to avoid infinite loop.  */
-  dfa->eclosures[node].nelem = REG_MISSING;
+  dfa->eclosures[node].nelem = -1;
 
   /* If the current node has constraints, duplicate all nodes
      since they must inherit the constraints.  */
@@ -1736,7 +1736,7 @@
 	Idx edest = dfa->edests[node].elems[i];
 	/* If calculating the epsilon closure of 'edest' is in progress,
 	   return intermediate result.  */
-	if (dfa->eclosures[edest].nelem == REG_MISSING)
+	if (dfa->eclosures[edest].nelem == -1)
 	  {
 	    incomplete = true;
 	    continue;
@@ -2533,7 +2533,7 @@
     {
       end = 0;
       start = fetch_number (regexp, token, syntax);
-      if (start == REG_MISSING)
+      if (start == -1)
 	{
 	  if (token->type == CHARACTER && token->opr.c == ',')
 	    start = 0; /* We treat "{,m}" as "{0,m}".  */
@@ -2543,14 +2543,14 @@
 	      return NULL;
 	    }
 	}
-      if (BE (start != REG_ERROR, 1))
+      if (BE (start != -2, 1))
 	{
 	  /* We treat "{n}" as "{n,n}".  */
 	  end = ((token->type == OP_CLOSE_DUP_NUM) ? start
 		 : ((token->type == CHARACTER && token->opr.c == ',')
-		    ? fetch_number (regexp, token, syntax) : REG_ERROR));
+		    ? fetch_number (regexp, token, syntax) : -2));
 	}
-      if (BE (start == REG_ERROR || end == REG_ERROR, 0))
+      if (BE (start == -2 || end == -2, 0))
 	{
 	  /* Invalid sequence.  */
 	  if (BE (!(syntax & RE_INVALID_INTERVAL_ORD), 0))
@@ -2572,7 +2572,7 @@
 	  return elem;
 	}
 
-      if (BE ((end != REG_MISSING && start > end)
+      if (BE ((end != -1 && start > end)
 	      || token->type != OP_CLOSE_DUP_NUM, 0))
 	{
 	  /* First number greater than second.  */
@@ -2580,7 +2580,7 @@
 	  return NULL;
 	}
 
-      if (BE (RE_DUP_MAX < (end == REG_MISSING ? start : end), 0))
+      if (BE (RE_DUP_MAX < (end == -1 ? start : end), 0))
 	{
 	  *err = REG_ESIZE;
 	  return NULL;
@@ -2589,7 +2589,7 @@
   else
     {
       start = (token->type == OP_DUP_PLUS) ? 1 : 0;
-      end = (token->type == OP_DUP_QUESTION) ? 1 : REG_MISSING;
+      end = (token->type == OP_DUP_QUESTION) ? 1 : -1;
     }
 
   fetch_token (token, regexp, syntax);
@@ -2633,7 +2633,7 @@
     }
 
   tree = create_tree (dfa, elem, NULL,
-		      (end == REG_MISSING ? OP_DUP_ASTERISK : OP_ALT));
+		      (end == -1 ? OP_DUP_ASTERISK : OP_ALT));
   if (BE (tree == NULL, 0))
     goto parse_dup_op_espace;
 
@@ -2641,10 +2641,10 @@
    True if the arithmetic type T is signed.  */
 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
 
-  /* This loop is actually executed only when end != REG_MISSING,
+  /* This loop is actually executed only when end != -1,
      to rewrite <re>{0,n} as (<re>(<re>...<re>?)?)?...  We have
      already created the start+1-th copy.  */
-  if (TYPE_SIGNED (Idx) || end != REG_MISSING)
+  if (TYPE_SIGNED (Idx) || end != -1)
     for (i = start + 2; i <= end; ++i)
       {
 	elem = duplicate_tree (elem, dfa);
@@ -3761,27 +3761,26 @@
 
 /* This is intended for the expressions like "a{1,3}".
    Fetch a number from 'input', and return the number.
-   Return REG_MISSING if the number field is empty like "{,1}".
+   Return -1 if the number field is empty like "{,1}".
    Return RE_DUP_MAX + 1 if the number field is too large.
-   Return REG_ERROR if an error occurred.  */
+   Return -2 if an error occurred.  */
 
 static Idx
 fetch_number (re_string_t *input, re_token_t *token, reg_syntax_t syntax)
 {
-  Idx num = REG_MISSING;
+  Idx num = -1;
   unsigned char c;
   while (1)
     {
       fetch_token (token, input, syntax);
       c = token->opr.c;
       if (BE (token->type == END_OF_RE, 0))
-	return REG_ERROR;
+	return -2;
       if (token->type == OP_CLOSE_DUP_NUM || c == ',')
 	break;
-      num = ((token->type != CHARACTER || c < '0' || '9' < c
-	      || num == REG_ERROR)
-	     ? REG_ERROR
-	     : num == REG_MISSING
+      num = ((token->type != CHARACTER || c < '0' || '9' < c || num == -2)
+	     ? -2
+	     : num == -1
 	     ? c - '0'
 	     : MIN (RE_DUP_MAX + 1, num * 10 + c - '0'));
     }
@@ -3845,7 +3844,7 @@
   tree->token.opt_subexp = 0;
   tree->first = NULL;
   tree->next = NULL;
-  tree->node_idx = REG_MISSING;
+  tree->node_idx = -1;
 
   if (left != NULL)
     left->parent = tree;

--- a/lib/regex.h	Fri Feb 19 08:41:58 2016 -0800
+++ b/lib/regex.h	Fri Feb 19 09:27:41 2016 -0800
@@ -42,11 +42,6 @@
    supported within glibc itself, and glibc users should not define
    _REGEX_LARGE_OFFSETS.  */
 
-/* The type of nonnegative object indexes.  Traditionally, GNU regex
-   uses 'int' for these.  Code that uses __re_idx_t should work
-   regardless of whether the type is signed.  */
-typedef size_t __re_idx_t;
-
 /* The type of object sizes.  */
 typedef size_t __re_size_t;
 
@@ -58,7 +53,6 @@
 
 /* The traditional GNU regex implementation mishandles strings longer
    than INT_MAX.  */
-typedef int __re_idx_t;
 typedef unsigned int __re_size_t;
 typedef unsigned long int __re_long_size_t;
 
@@ -488,7 +482,8 @@
 #ifdef _REGEX_LARGE_OFFSETS
 /* POSIX 1003.1-2008 requires that regoff_t be at least as wide as
    ptrdiff_t and ssize_t.  We don't know of any hosts where ptrdiff_t
-   is wider than ssize_t, so ssize_t is safe.  */
+   is wider than ssize_t, so ssize_t is safe.  ptrdiff_t is not
+   visible here, so use ssize_t.  */
 typedef ssize_t regoff_t;
 #else
 /* The traditional GNU regex implementation mishandles strings longer
@@ -557,34 +552,34 @@
    match, or -2 for an internal error.  Also return register
    information in REGS (if REGS and BUFFER->no_sub are nonzero).  */
 extern regoff_t re_search (struct re_pattern_buffer *__buffer,
-			   const char *__string, __re_idx_t __length,
-			   __re_idx_t __start, regoff_t __range,
+			   const char *__string, regoff_t __length,
+			   regoff_t __start, regoff_t __range,
 			   struct re_registers *__regs);
 
 
 /* Like 're_search', but search in the concatenation of STRING1 and
    STRING2.  Also, stop searching at index START + STOP.  */
 extern regoff_t re_search_2 (struct re_pattern_buffer *__buffer,
-			     const char *__string1, __re_idx_t __length1,
-			     const char *__string2, __re_idx_t __length2,
-			     __re_idx_t __start, regoff_t __range,
+			     const char *__string1, regoff_t __length1,
+			     const char *__string2, regoff_t __length2,
+			     regoff_t __start, regoff_t __range,
 			     struct re_registers *__regs,
-			     __re_idx_t __stop);
+			     regoff_t __stop);
 
 
 /* Like 're_search', but return how many characters in STRING the regexp
    in BUFFER matched, starting at position START.  */
 extern regoff_t re_match (struct re_pattern_buffer *__buffer,
-			  const char *__string, __re_idx_t __length,
-			  __re_idx_t __start, struct re_registers *__regs);
+			  const char *__string, regoff_t __length,
+			  regoff_t __start, struct re_registers *__regs);
 
 
 /* Relates to 're_match' as 're_search_2' relates to 're_search'.  */
 extern regoff_t re_match_2 (struct re_pattern_buffer *__buffer,
-			    const char *__string1, __re_idx_t __length1,
-			    const char *__string2, __re_idx_t __length2,
-			    __re_idx_t __start, struct re_registers *__regs,
-			    __re_idx_t __stop);
+			    const char *__string1, regoff_t __length1,
+			    const char *__string2, regoff_t __length2,
+			    regoff_t __start, struct re_registers *__regs,
+			    regoff_t __stop);
 
 
 /* Set REGS to hold NUM_REGS registers, storing them in STARTS and

--- a/lib/regex_internal.c	Fri Feb 19 08:41:58 2016 -0800
+++ b/lib/regex_internal.c	Fri Feb 19 09:27:41 2016 -0800
@@ -922,7 +922,7 @@
 re_string_context_at (const re_string_t *input, Idx idx, int eflags)
 {
   int c;
-  if (BE (! REG_VALID_INDEX (idx), 0))
+  if (BE (idx < 0, 0))
     /* In this case, we use the value stored in input->tip_context,
        since we can't know the character in input->mbs[-1] here.  */
     return input->tip_context;
@@ -938,10 +938,10 @@
 	{
 #if defined DEBUG && DEBUG
 	  /* It must not happen.  */
-	  assert (REG_VALID_INDEX (wc_idx));
+	  assert (wc_idx >= 0);
 #endif
 	  --wc_idx;
-	  if (! REG_VALID_INDEX (wc_idx))
+	  if (wc_idx < 0)
 	    return input->tip_context;
 	}
       wc = input->wcs[wc_idx];
@@ -1077,25 +1077,25 @@
       if (src1->elems[i1] == src2->elems[i2])
 	{
 	  /* Try to find the item in DEST.  Maybe we could binary search?  */
-	  while (REG_VALID_INDEX (id) && dest->elems[id] > src1->elems[i1])
+	  while (id >= 0 && dest->elems[id] > src1->elems[i1])
 	    --id;
 
-          if (! REG_VALID_INDEX (id) || dest->elems[id] != src1->elems[i1])
+	  if (id < 0 || dest->elems[id] != src1->elems[i1])
             dest->elems[--sbase] = src1->elems[i1];
 
-	  if (! REG_VALID_INDEX (--i1) || ! REG_VALID_INDEX (--i2))
+	  if (--i1 < 0 || --i2 < 0)
 	    break;
 	}
 
       /* Lower the highest of the two items.  */
       else if (src1->elems[i1] < src2->elems[i2])
 	{
-	  if (! REG_VALID_INDEX (--i2))
+	  if (--i2 < 0)
 	    break;
 	}
       else
 	{
-	  if (! REG_VALID_INDEX (--i1))
+	  if (--i1 < 0)
 	    break;
 	}
     }
@@ -1108,7 +1108,7 @@
      DEST elements are already in place; this is more or
      less the same loop that is in re_node_set_merge.  */
   dest->nelem += delta;
-  if (delta > 0 && REG_VALID_INDEX (id))
+  if (delta > 0 && id >= 0)
     for (;;)
       {
 	if (dest->elems[is] > dest->elems[id])
@@ -1122,7 +1122,7 @@
 	  {
 	    /* Slide from the bottom.  */
 	    dest->elems[id + delta] = dest->elems[id];
-	    if (! REG_VALID_INDEX (--id))
+	    if (--id < 0)
 	      break;
 	  }
       }
@@ -1216,8 +1216,7 @@
   /* Copy into the top of DEST the items of SRC that are not
      found in DEST.  Maybe we could binary search in DEST?  */
   for (sbase = dest->nelem + 2 * src->nelem,
-       is = src->nelem - 1, id = dest->nelem - 1;
-       REG_VALID_INDEX (is) && REG_VALID_INDEX (id); )
+       is = src->nelem - 1, id = dest->nelem - 1; is >= 0 && id >= 0; )
     {
       if (dest->elems[id] == src->elems[is])
 	is--, id--;
@@ -1227,7 +1226,7 @@
 	--id;
     }
 
-  if (REG_VALID_INDEX (is))
+  if (is >= 0)
     {
       /* If DEST is exhausted, the remaining items of SRC must be unique.  */
       sbase -= is + 1;
@@ -1256,7 +1255,7 @@
 	{
 	  /* Slide from the bottom.  */
 	  dest->elems[id + delta] = dest->elems[id];
-	  if (! REG_VALID_INDEX (--id))
+	  if (--id < 0)
 	    {
 	      /* Copy remaining SRC elements.  */
 	      memcpy (dest->elems, dest->elems + sbase,
@@ -1355,7 +1354,7 @@
   Idx i;
   if (set1 == NULL || set2 == NULL || set1->nelem != set2->nelem)
     return false;
-  for (i = set1->nelem ; REG_VALID_INDEX (--i) ; )
+  for (i = set1->nelem ; --i >= 0 ; )
     if (set1->elems[i] != set2->elems[i])
       return false;
   return true;
@@ -1368,7 +1367,7 @@
 re_node_set_contains (const re_node_set *set, Idx elem)
 {
   __re_size_t idx, right, mid;
-  if (! REG_VALID_NONZERO_INDEX (set->nelem))
+  if (set->nelem <= 0)
     return 0;
 
   /* Binary search the element.  */
@@ -1398,7 +1397,7 @@
 
 
 /* Add the token TOKEN to dfa->nodes, and return the index of the token.
-   Or return REG_MISSING if an error occurred.  */
+   Or return -1 if an error occurred.  */
 
 static Idx
 internal_function
@@ -1416,11 +1415,11 @@
 					  MAX (sizeof (re_node_set),
 					       sizeof (Idx)));
       if (BE (MIN (IDX_MAX, SIZE_MAX / max_object_size) < new_nodes_alloc, 0))
-	return REG_MISSING;
+	return -1;
 
       new_nodes = re_realloc (dfa->nodes, re_token_t, new_nodes_alloc);
       if (BE (new_nodes == NULL, 0))
-	return REG_MISSING;
+	return -1;
       dfa->nodes = new_nodes;
       new_nexts = re_realloc (dfa->nexts, Idx, new_nodes_alloc);
       new_indices = re_realloc (dfa->org_indices, Idx, new_nodes_alloc);
@@ -1433,7 +1432,7 @@
 	   re_free (new_indices);
 	   re_free (new_edests);
 	   re_free (new_eclosures);
-	   return REG_MISSING;
+	   return -1;
 	}
       dfa->nexts = new_nexts;
       dfa->org_indices = new_indices;
@@ -1448,7 +1447,7 @@
     ((token.type == OP_PERIOD && dfa->mb_cur_max > 1)
      || token.type == COMPLEX_BRACKET);
 #endif
-  dfa->nexts[dfa->nodes_len] = REG_MISSING;
+  dfa->nexts[dfa->nodes_len] = -1;
   re_node_set_init_empty (dfa->edests + dfa->nodes_len);
   re_node_set_init_empty (dfa->eclosures + dfa->nodes_len);
   return dfa->nodes_len++;

--- a/lib/regex_internal.h	Fri Feb 19 08:41:58 2016 -0800
+++ b/lib/regex_internal.h	Fri Feb 19 09:27:41 2016 -0800
@@ -151,31 +151,22 @@
 # define __attribute__(arg)
 #endif
 
-typedef __re_idx_t Idx;
-#ifdef _REGEX_LARGE_OFFSETS
-# define IDX_MAX (SIZE_MAX - 2)
-#else
-# define IDX_MAX INT_MAX
+#ifndef SSIZE_MAX
+# define SSIZE_MAX ((ssize_t) (SIZE_MAX / 2))
 #endif
 
-/* Special return value for failure to match.  */
-#define REG_MISSING ((Idx) -1)
-
-/* Special return value for internal error.  */
-#define REG_ERROR ((Idx) -2)
-
-/* Test whether N is a valid index, and is not one of the above.  */
+/* The type of indexes into strings.  This is signed, not size_t,
+   since the API requires indexes to fit in regoff_t anyway, and using
+   signed integers makes the code a bit smaller and presumably faster.
+   The traditional GNU regex implementation uses int for indexes.
+   The POSIX-compatible implementation uses a possibly-wider type.
+   The name 'Idx' is three letters to minimize the hassle of
+   reindenting a lot of regex code that formerly used 'int'.  */
+typedef regoff_t Idx;
 #ifdef _REGEX_LARGE_OFFSETS
-# define REG_VALID_INDEX(n) ((Idx) (n) < REG_ERROR)
+# define IDX_MAX SSIZE_MAX
 #else
-# define REG_VALID_INDEX(n) (0 <= (n))
-#endif
-
-/* Test whether N is a valid nonzero index.  */
-#ifdef _REGEX_LARGE_OFFSETS
-# define REG_VALID_NONZERO_INDEX(n) ((Idx) ((n) - 1) < (Idx) (REG_ERROR - 1))
-#else
-# define REG_VALID_NONZERO_INDEX(n) (0 < (n))
+# define IDX_MAX INT_MAX
 #endif
 
 /* A hash value, suitable for computing hash tables.  */

--- a/lib/regexec.c	Fri Feb 19 08:41:58 2016 -0800
+++ b/lib/regexec.c	Fri Feb 19 09:27:41 2016 -0800
@@ -621,7 +621,7 @@
   bool fl_longest_match;
   int match_kind;
   Idx match_first;
-  Idx match_last = REG_MISSING;
+  Idx match_last = -1;
   Idx extra_nmatch;
   bool sb;
   int ch;
@@ -830,9 +830,9 @@
       mctx.state_log_top = mctx.nbkref_ents = mctx.max_mb_elem_len = 0;
       match_last = check_matching (&mctx, fl_longest_match,
 				   start <= last_start ? &match_first : NULL);
-      if (match_last != REG_MISSING)
+      if (match_last != -1)
 	{
-	  if (BE (match_last == REG_ERROR, 0))
+	  if (BE (match_last == -2, 0))
 	    {
 	      err = REG_ESPACE;
 	      goto free_return;
@@ -854,7 +854,7 @@
 		    break;
 		  if (BE (err != REG_NOMATCH, 0))
 		    goto free_return;
-		  match_last = REG_MISSING;
+		  match_last = -1;
 		}
 	      else
 		break; /* We found a match.  */
@@ -865,7 +865,7 @@
     }
 
 #ifdef DEBUG
-  assert (match_last != REG_MISSING);
+  assert (match_last != -1);
   assert (err == REG_NOERROR);
 #endif
 
@@ -991,7 +991,7 @@
 	  do
 	    {
 	      --match_last;
-	      if (! REG_VALID_INDEX (match_last))
+	      if (match_last < 0)
 		{
 		  ret = REG_NOMATCH;
 		  goto free_return;
@@ -1072,8 +1072,8 @@
 }
 
 /* Check whether the regular expression match input string INPUT or not,
-   and return the index where the matching end.  Return REG_MISSING if
-   there is no match, and return REG_ERROR in case of an error.
+   and return the index where the matching end.  Return -1 if
+   there is no match, and return -2 in case of an error.
    FL_LONGEST_MATCH means we want the POSIX longest matching.
    If P_MATCH_FIRST is not NULL, and the match fails, it is set to the
    next place where we may want to try matching.
@@ -1088,7 +1088,7 @@
   const re_dfa_t *const dfa = mctx->dfa;
   reg_errcode_t err;
   Idx match = 0;
-  Idx match_last = REG_MISSING;
+  Idx match_last = -1;
   Idx cur_str_idx = re_string_cur_idx (&mctx->input);
   re_dfastate_t *cur_state;
   bool at_init_state = p_match_first != NULL;
@@ -1100,7 +1100,7 @@
   if (BE (cur_state == NULL, 0))
     {
       assert (err == REG_ESPACE);
-      return REG_ERROR;
+      return -2;
     }
 
   if (mctx->state_log != NULL)
@@ -1155,7 +1155,7 @@
 	  if (BE (err != REG_NOERROR, 0))
 	    {
 	      assert (err == REG_ESPACE);
-	      return REG_ERROR;
+	      return -2;
 	    }
 	}
 
@@ -1169,7 +1169,7 @@
 	     state using the state log, if available and if we have not
 	     already found a valid (even if not the longest) match.  */
 	  if (BE (err != REG_NOERROR, 0))
-	    return REG_ERROR;
+	    return -2;
 
 	  if (mctx->state_log == NULL
 	      || (match && !fl_longest_match)
@@ -1252,7 +1252,7 @@
 /* Compute the next node to which "NFA" transit from NODE("NFA" is a NFA
    corresponding to the DFA).
    Return the destination node, and update EPS_VIA_NODES;
-   return REG_MISSING in case of errors.  */
+   return -1 in case of errors.  */
 
 static Idx
 internal_function
@@ -1270,15 +1270,15 @@
       Idx dest_node;
       ok = re_node_set_insert (eps_via_nodes, node);
       if (BE (! ok, 0))
-	return REG_ERROR;
-      /* Pick up a valid destination, or return REG_MISSING if none
+	return -2;
+      /* Pick up a valid destination, or return -1 if none
 	 is found.  */
-      for (dest_node = REG_MISSING, i = 0; i < edests->nelem; ++i)
+      for (dest_node = -1, i = 0; i < edests->nelem; ++i)
 	{
 	  Idx candidate = edests->elems[i];
 	  if (!re_node_set_contains (cur_nodes, candidate))
 	    continue;
-          if (dest_node == REG_MISSING)
+          if (dest_node == -1)
 	    dest_node = candidate;
 
 	  else
@@ -1292,7 +1292,7 @@
 	      else if (fs != NULL
 		       && push_fail_stack (fs, *pidx, candidate, nregs, regs,
 					   eps_via_nodes))
-		return REG_ERROR;
+		return -2;
 
 	      /* We know we are going to exit.  */
 	      break;
@@ -1317,13 +1317,13 @@
 	  if (fs != NULL)
 	    {
 	      if (regs[subexp_idx].rm_so == -1 || regs[subexp_idx].rm_eo == -1)
-		return REG_MISSING;
+		return -1;
 	      else if (naccepted)
 		{
 		  char *buf = (char *) re_string_get_buffer (&mctx->input);
 		  if (memcmp (buf + regs[subexp_idx].rm_so, buf + *pidx,
 			      naccepted) != 0)
-		    return REG_MISSING;
+		    return -1;
 		}
 	    }
 
@@ -1332,7 +1332,7 @@
 	      Idx dest_node;
 	      ok = re_node_set_insert (eps_via_nodes, node);
 	      if (BE (! ok, 0))
-		return REG_ERROR;
+		return -2;
 	      dest_node = dfa->edests[node].elems[0];
 	      if (re_node_set_contains (&mctx->state_log[*pidx]->nodes,
 					dest_node))
@@ -1348,12 +1348,12 @@
 	  if (fs && (*pidx > mctx->match_last || mctx->state_log[*pidx] == NULL
 		     || !re_node_set_contains (&mctx->state_log[*pidx]->nodes,
 					       dest_node)))
-	    return REG_MISSING;
+	    return -1;
 	  re_node_set_empty (eps_via_nodes);
 	  return dest_node;
 	}
     }
-  return REG_MISSING;
+  return -1;
 }
 
 static reg_errcode_t
@@ -1389,7 +1389,7 @@
 		regmatch_t *regs, re_node_set *eps_via_nodes)
 {
   Idx num = --fs->num;
-  assert (REG_VALID_INDEX (num));
+  assert (num >= 0);
   *pidx = fs->stack[num].idx;
   memcpy (regs, fs->stack[num].regs, sizeof (regmatch_t) * nregs);
   re_node_set_free (eps_via_nodes);
@@ -1482,9 +1482,9 @@
       cur_node = proceed_next_node (mctx, nmatch, pmatch, &idx, cur_node,
 				    &eps_via_nodes, fs);
 
-      if (BE (! REG_VALID_INDEX (cur_node), 0))
+      if (BE (cur_node < 0, 0))
 	{
-	  if (BE (cur_node == REG_ERROR, 0))
+	  if (BE (cur_node == -2, 0))
 	    {
 	      re_node_set_free (&eps_via_nodes);
 	      if (prev_idx_match_malloced)
@@ -1868,10 +1868,10 @@
 	  {
 	    Idx edst1 = dfa->edests[cur_node].elems[0];
 	    Idx edst2 = ((dfa->edests[cur_node].nelem > 1)
-			 ? dfa->edests[cur_node].elems[1] : REG_MISSING);
+			 ? dfa->edests[cur_node].elems[1] : -1);
 	    if ((!re_node_set_contains (inv_eclosure, edst1)
 		 && re_node_set_contains (dest_nodes, edst1))
-		|| (REG_VALID_NONZERO_INDEX (edst2)
+		|| (edst2 > 0
 		    && !re_node_set_contains (inv_eclosure, edst2)
 		    && re_node_set_contains (dest_nodes, edst2)))
 	      {
@@ -1951,7 +1951,7 @@
       switch (dfa->nodes[node].type)
 	{
 	case OP_BACK_REF:
-	  if (bkref_idx != REG_MISSING)
+	  if (bkref_idx != -1)
 	    {
 	      struct re_backref_cache_entry *ent = mctx->bkref_ents + bkref_idx;
 	      do
@@ -2067,8 +2067,8 @@
       subexp_idx = dfa->nodes[ent->node].opr.idx;
       if (ent->subexp_to == str_idx)
 	{
-	  Idx ops_node = REG_MISSING;
-	  Idx cls_node = REG_MISSING;
+	  Idx ops_node = -1;
+	  Idx cls_node = -1;
 	  for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
 	    {
 	      Idx node = dest_nodes->elems[node_idx];
@@ -2083,7 +2083,7 @@
 
 	  /* Check the limitation of the open subexpression.  */
 	  /* Note that (ent->subexp_to = str_idx != ent->subexp_from).  */
-	  if (REG_VALID_INDEX (ops_node))
+	  if (ops_node >= 0)
 	    {
 	      err = sub_epsilon_src_nodes (dfa, ops_node, dest_nodes,
 					   candidates);
@@ -2092,7 +2092,7 @@
 	    }
 
 	  /* Check the limitation of the close subexpression.  */
-	  if (REG_VALID_INDEX (cls_node))
+	  if (cls_node >= 0)
 	    for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
 	      {
 		Idx node = dest_nodes->elems[node_idx];
@@ -2145,7 +2145,7 @@
   re_sift_context_t local_sctx;
   Idx first_idx = search_cur_bkref_entry (mctx, str_idx);
 
-  if (first_idx == REG_MISSING)
+  if (first_idx == -1)
     return REG_NOERROR;
 
   local_sctx.sifted_states = NULL; /* Mark that it hasn't been initialized.  */
@@ -2549,7 +2549,7 @@
       if (BE (err != REG_NOERROR, 0))
 	return err;
 #ifdef DEBUG
-      assert (dfa->nexts[cur_node_idx] != REG_MISSING);
+      assert (dfa->nexts[cur_node_idx] != -1);
 #endif
       new_nodes = dfa->eclosures + dfa->nexts[cur_node_idx];
 
@@ -2615,7 +2615,7 @@
       /* And add the epsilon closures (which is 'new_dest_nodes') of
 	 the backreference to appropriate state_log.  */
 #ifdef DEBUG
-      assert (dfa->nexts[node_idx] != REG_MISSING);
+      assert (dfa->nexts[node_idx] != -1);
 #endif
       for (; bkc_idx < mctx->nbkref_ents; ++bkc_idx)
 	{
@@ -2699,7 +2699,7 @@
   const char *buf = (const char *) re_string_get_buffer (&mctx->input);
   /* Return if we have already checked BKREF_NODE at BKREF_STR_IDX.  */
   Idx cache_idx = search_cur_bkref_entry (mctx, bkref_str_idx);
-  if (cache_idx != REG_MISSING)
+  if (cache_idx != -1)
     {
       const struct re_backref_cache_entry *entry
 	= mctx->bkref_ents + cache_idx;
@@ -2804,7 +2804,7 @@
 	  nodes = &mctx->state_log[sl_str]->nodes;
 	  cls_node = find_subexp_node (dfa, nodes, subexp_num,
 				       OP_CLOSE_SUBEXP);
-	  if (cls_node == REG_MISSING)
+	  if (cls_node == -1)
 	    continue; /* No.  */
 	  if (sub_top->path == NULL)
 	    {
@@ -2883,7 +2883,7 @@
 	  && node->opr.idx == subexp_idx)
 	return cls_node;
     }
-  return REG_MISSING;
+  return -1;
 }
 
 /* Check whether the node TOP_NODE at TOP_STR can arrive to the node
@@ -3159,7 +3159,7 @@
       Idx cur_node = cur_nodes->elems[idx];
       const re_node_set *eclosure = dfa->eclosures + cur_node;
       outside_node = find_subexp_node (dfa, eclosure, ex_subexp, type);
-      if (outside_node == REG_MISSING)
+      if (outside_node == -1)
 	{
 	  /* There are no problematic nodes, just merge them.  */
 	  err = re_node_set_merge (&new_nodes, eclosure);
@@ -3245,7 +3245,7 @@
   Idx cache_idx_start = search_cur_bkref_entry (mctx, cur_str);
   struct re_backref_cache_entry *ent;
 
-  if (cache_idx_start == REG_MISSING)
+  if (cache_idx_start == -1)
     return REG_NOERROR;
 
  restart:
@@ -3370,7 +3370,7 @@
   /* At first, group all nodes belonging to 'state' into several
      destinations.  */
   ndests = group_nodes_into_DFAstates (dfa, state, dests_node, dests_ch);
-  if (BE (! REG_VALID_NONZERO_INDEX (ndests), 0))
+  if (BE (ndests <= 0, 0))
     {
       if (dests_node_malloced)
 	free (dests_alloc);
@@ -3432,7 +3432,7 @@
       for (j = 0; j < dests_node[i].nelem; ++j)
 	{
 	  next_node = dfa->nexts[dests_node[i].elems[j]];
-	  if (next_node != REG_MISSING)
+	  if (next_node != -1)
 	    {
 	      err = re_node_set_merge (&follows, dfa->eclosures + next_node);
 	      if (BE (err != REG_NOERROR, 0))
@@ -3743,7 +3743,7 @@
  error_return:
   for (j = 0; j < ndests; ++j)
     re_node_set_free (dests_node + j);
-  return REG_MISSING;
+  return -1;
 }
 
 #ifdef RE_ENABLE_I18N
@@ -4174,7 +4174,7 @@
 match_ctx_init (re_match_context_t *mctx, int eflags, Idx n)
 {
   mctx->eflags = eflags;
-  mctx->match_last = REG_MISSING;
+  mctx->match_last = -1;
   if (n > 0)
     {
       /* Avoid overflow.  */
@@ -4295,7 +4295,7 @@
   return REG_NOERROR;
 }
 
-/* Return the first entry with the same str_idx, or REG_MISSING if none is
+/* Return the first entry with the same str_idx, or -1 if none is
    found.  Note that MCTX->BKREF_ENTS is already sorted by MCTX->STR_IDX.  */
 
 static Idx
@@ -4315,7 +4315,7 @@
   if (left < last && mctx->bkref_ents[left].str_idx == str_idx)
     return left;
   else
-    return REG_MISSING;
+    return -1;
 }
 
 /* Register the node NODE, whose type is OP_OPEN_SUBEXP, and which matches