Update.

2003-12-23  Paolo Bonzini  <bonzini@gnu.org>

	* posix/regex_internal.c (re_dfa_add_node): Initialize opt_subexp.
	* posix/regex_internal.h (re_token_type_t): Put OP_DUP_PLUS
	among the tokens, rather than among the epsilon-transiting nodes.
	(re_token_t): Add the opt_subexp flag.
	* posix/regcomp.c (optimize_utf8, calc_first,
	calc_next, calc_epsdest): Don't consider OP_DUP_PLUS.
	(mark_opt_subexp, mark_opt_subexp_iter): New functions.
	(parse_dup_op): Mostly rewritten, lowering OP_DUP_PLUS to
	OP_DUP_ASTERISK and marking optional subexpressions
	as such using mark_opt_subexp.
	* posix/regexec.c (set_regs): Initialize PREV_INDEX_MATCH
	and pass it to update_regs.
	(update_regs): Use the PREV_INDEX_MATCH parameter, together
	with the opt_subexp flag, in order to discard a final empty
	match of a repeated subexpression.
	* posix/BOOST.tests: Adjust test vectors.
	* posix/PCRE.tests: Likewise.
	* posix/rxspencer/tests: Likewise.

2003-12-17  Paolo Bonzini  <bonzini@gnu.org>
2003-12-16  Paolo Bonzini  <bonzini@gnu.org>
2003-12-17  Paolo Bonzini  <bonzini@gnu.org>
2003-12-16  Jakub Jelinek  <jakub@redhat.com>
2003-04-06  Kaz Kojima  <kkojima@rr.iij4u.or.jp>
2003-02-20  Paolo Bonzini  <bonzini@gnu.org>
2003-01-12  Franz Sirl  <Franz.Sirl-kernel@lauterbach.com>
2003-01-09  Richard Henderson  <rth@redhat.com>
2003-01-09  Richard Henderson  <rth@redhat.com>
2003-01-03  Paul Eggert  <eggert@twinsun.com>

7 files changed, 214 insertions, 172 deletions

diff --git a/posix/BOOST.tests b/posix/BOOST.tests
index 32b6c921ad..98fd3b6abf 100644
--- a/posix/BOOST.tests
+++ b/posix/BOOST.tests
@@ -432,27 +432,22 @@ a(b|c){2,4}d abcbd 0 5 3 4
 a(b|c){2,4}d abcbcd 0 6 4 5
 a(b|c){2,}d abcd 0 4 2 3
 a(b|c){2,}d abcbd 0 5 3 4
-; perl only:
-a(b|c?)+d abcd 0 4 3 3
-a(b+|((c)*))+d abd 0 3 2 2 2 2 -1 -1
-a(b+|((c)*))+d abcd 0 4 3 3 3 3 2 3
+; perl only: these conflict with the POSIX test below
+;a(b|c?)+d abcd 0 4 3 3
+;a(b+|((c)*))+d abd 0 3 2 2 2 2 -1 -1
+;a(b+|((c)*))+d abcd 0 4 3 3 3 3 2 3
 
 ; posix only:
 - match_default extended REG_EXTENDED REG_STARTEND
 
-; XXX FIXME the following 4 tests fail ATM
-;a(b|c?)+d abcd 0 4 2 3
-;a(b|((c)*))+d abcd 0 4 2 3 2 3 2 3
-;a(b+|((c)*))+d abd 0 3 1 2 -1 -1 -1 -1
-;a(b+|((c)*))+d abcd 0 4 2 3 2 3 2 3
-
+a(b|c?)+d abcd 0 4 2 3
+a(b|((c)*))+d abcd 0 4 2 3 2 3 2 3
+a(b+|((c)*))+d abd 0 3 1 2 -1 -1 -1 -1
+a(b+|((c)*))+d abcd 0 4 2 3 2 3 2 3
 a(b|((c)*))+d ad 0 2 1 1 1 1 -1 -1
-
-; XXX FIXME the following 3 tests fail ATM
-;a(b|((c)*))*d abcd 0 4 2 3 2 3 2 3
-;a(b+|((c)*))*d abd 0 3 1 2 -1 -1 -1 -1
-;a(b+|((c)*))*d abcd 0 4 2 3 2 3 2 3
-
+a(b|((c)*))*d abcd 0 4 2 3 2 3 2 3
+a(b+|((c)*))*d abd 0 3 1 2 -1 -1 -1 -1
+a(b+|((c)*))*d abcd 0 4 2 3 2 3 2 3
 a(b|((c)*))*d ad 0 2 1 1 1 1 -1 -1
 
 - match_default normal REG_PERL
diff --git a/posix/PCRE.tests b/posix/PCRE.tests
index 182f29f7a1..7ea5b9e70c 100644
--- a/posix/PCRE.tests
+++ b/posix/PCRE.tests
@@ -1151,13 +1151,13 @@ No match
 /(abc|)+/
     abc
  0: abc
- 1: 
+ 1: abc
     abcabc
  0: abcabc
- 1: 
+ 1: abc
     abcabcabc
  0: abcabcabc
- 1: 
+ 1: abc
     xyz      
  0: 
  1: 
@@ -1165,46 +1165,44 @@ No match
 /([a]*)*/
     a
  0: a
- 1: 
+ 1: a
     aaaaa 
  0: aaaaa
- 1: 
+ 1: aaaaa
 
 /([ab]*)*/
     a
  0: a
- 1: 
+ 1: a
     b
  0: b
- 1: 
+ 1: b
     ababab
  0: ababab
- 1: 
+ 1: ababab
     aaaabcde
  0: aaaab
- 1: 
+ 1: aaaab
     bbbb    
  0: bbbb
- 1: 
+ 1: bbbb
 
 /([^a]*)*/
     b
  0: b
- 1: 
+ 1: b
     bbbb
  0: bbbb
- 1: 
+ 1: bbbb
     aaa   
  0: 
- 1: 
 
 /([^ab]*)*/
     cccc
  0: cccc
- 1: 
+ 1: cccc
     abab  
  0: 
- 1: 
 
 /abc/
     abc
diff --git a/posix/regcomp.c b/posix/regcomp.c
index 1a7e5192cf..38b1b9c604 100644
--- a/posix/regcomp.c
+++ b/posix/regcomp.c
@@ -135,6 +135,8 @@ static bin_tree_t *re_dfa_add_tree_node (re_dfa_t *dfa,
 					 const re_token_t *token)
   __attribute ((noinline));
 static bin_tree_t *duplicate_tree (const bin_tree_t *src, re_dfa_t *dfa);
+static void mark_opt_subexp (const bin_tree_t *src, re_dfa_t *dfa);
+static void mark_opt_subexp_iter (const bin_tree_t *src, re_dfa_t *dfa, int idx);
 
 /* This table gives an error message for each of the error codes listed
    in regex.h.  Obviously the order here has to be same as there.
@@ -1031,7 +1033,6 @@ optimize_utf8 (dfa)
       case END_OF_RE:
       case OP_DUP_ASTERISK:
       case OP_DUP_QUESTION:
-      case OP_DUP_PLUS:
       case OP_OPEN_SUBEXP:
       case OP_CLOSE_SUBEXP:
 	break;
@@ -1150,6 +1151,7 @@ calc_first (dfa, node)
     case OP_CLOSE_BRACKET:
     case OP_OPEN_DUP_NUM:
     case OP_CLOSE_DUP_NUM:
+    case OP_DUP_PLUS:
     case OP_NON_MATCH_LIST:
     case OP_OPEN_COLL_ELEM:
     case OP_CLOSE_COLL_ELEM:
@@ -1176,14 +1178,6 @@ calc_first (dfa, node)
     case OP_CLOSE_SUBEXP:
       node->first = idx;
       break;
-    case OP_DUP_PLUS:
-#ifdef DEBUG
-      assert (node->left != NULL);
-#endif
-      if (node->left->first == -1)
-	calc_first (dfa, node->left);
-      node->first = node->left->first;
-      break;
     case OP_ALT:
       node->first = idx;
       break;
@@ -1223,7 +1217,6 @@ calc_next (dfa, node)
   switch (type)
     {
     case OP_DUP_ASTERISK:
-    case OP_DUP_PLUS:
       node->next = idx;
       break;
     case CONCAT:
@@ -1258,7 +1251,6 @@ calc_epsdest (dfa, node)
   if (node->type == 0)
     {
       if (dfa->nodes[idx].type == OP_DUP_ASTERISK
-	  || dfa->nodes[idx].type == OP_DUP_PLUS
 	  || dfa->nodes[idx].type == OP_DUP_QUESTION)
 	{
 	  if (node->left->first == -1)
@@ -2377,8 +2369,8 @@ parse_sub_exp (regexp, preg, token, syntax, nest, err)
 /* This function parse repetition operators like "*", "+", "{1,3}" etc.  */
 
 static bin_tree_t *
-parse_dup_op (dup_elem, regexp, dfa, token, syntax, err)
-     bin_tree_t *dup_elem;
+parse_dup_op (elem, regexp, dfa, token, syntax, err)
+     bin_tree_t *elem;
      re_string_t *regexp;
      re_dfa_t *dfa;
      re_token_t *token;
@@ -2386,15 +2378,14 @@ parse_dup_op (dup_elem, regexp, dfa, token, syntax, err)
      reg_errcode_t *err;
 {
   re_token_t dup_token;
-  bin_tree_t *tree = dup_elem, *work_tree;
-  int start_idx = re_string_cur_idx (regexp);
+  bin_tree_t *tree = NULL;
+  int i, start, end, start_idx = re_string_cur_idx (regexp);
   re_token_t start_token = *token;
+
   if (token->type == OP_OPEN_DUP_NUM)
     {
-      int i;
-      int end = 0;
-      int start = fetch_number (regexp, token, syntax);
-      bin_tree_t *elem;
+      end = 0;
+      start = fetch_number (regexp, token, syntax);
       if (start == -1)
 	{
 	  if (token->type == CHARACTER && token->opr.c == ',')
@@ -2415,123 +2406,104 @@ parse_dup_op (dup_elem, regexp, dfa, token, syntax, err)
       if (BE (start == -2 || end == -2, 0))
 	{
 	  /* Invalid sequence.  */
-	  if (token->type == OP_CLOSE_DUP_NUM)
-	    goto parse_dup_op_invalid_interval;
-	  else
-	    goto parse_dup_op_ebrace;
+	  if (BE (!(syntax & RE_INVALID_INTERVAL_ORD), 0))
+	    {
+	      if (token->type == END_OF_RE)
+		*err = REG_EBRACE;
+	      else
+		*err = REG_BADBR;
+
+	      return NULL;
+	    }
+
+	  /* If the syntax bit is set, rollback.  */
+	  re_string_set_index (regexp, start_idx);
+	  *token = start_token;
+	  token->type = CHARACTER;
+	  /* mb_partial and word_char bits should be already initialized by
+	     peek_token.  */
+	  return elem;
 	}
-      if (BE ((start == 0 && end == 0) || tree == NULL, 0))
+
+      if (BE (end != -1 && start > end, 0))
 	{
-	  /* We treat "<re>{0}" and "<re>{0,0}" as null string.
-	     Similarly "<re>{0}{m,n}".  */
-	  fetch_token (token, regexp, syntax);
+	  /* First number greater than second.  */
+	  *err = REG_BADBR;
 	  return NULL;
 	}
+    }
+  else
+    {
+      start = (token->type == OP_DUP_PLUS) ? 1 : 0;
+      end = (token->type == OP_DUP_QUESTION) ? 1 : -1;
+    }
+
+  /* Treat "<re>{0}*" etc. as "<re>{0}".  */
+  if (BE (elem == NULL, 0))
+    start = end = 0;
 
-      /* Extract "<re>{n,m}" to "<re><re>...<re><re>{0,<m-n>}".  */
-      elem = tree;
-      for (i = 1; i < start; ++i)
+  /* Extract "<re>{n,m}" to "<re><re>...<re><re>{0,<m-n>}".  */
+  else if (BE (start > 0, 0))
+    {
+      tree = elem;
+      for (i = 2; i <= start; ++i)
 	{
-	  work_tree = duplicate_tree (elem, dfa);
-	  tree = create_tree (dfa, tree, work_tree, CONCAT, 0);
-	  if (BE (work_tree == NULL || tree == NULL, 0))
+	  elem = duplicate_tree (elem, dfa);
+	  tree = create_tree (dfa, tree, elem, CONCAT, 0);
+	  if (BE (elem == NULL || tree == NULL, 0))
 	    goto parse_dup_op_espace;
 	}
+    }
 
-      if (end == -1)
-	{
-	  /* We treat "<re>{0,}" as "<re>*".  */
-	  dup_token.type = OP_DUP_ASTERISK;
-	  if (start > 0)
-	    {
-	      elem = duplicate_tree (elem, dfa);
-	      work_tree = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
-	      tree = create_tree (dfa, tree, work_tree, CONCAT, 0);
-	      if (BE (elem == NULL || work_tree == NULL || tree == NULL, 0))
-		goto parse_dup_op_espace;
-	    }
-	  else
-	    {
-	      tree = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
-	      if (BE (tree == NULL, 0))
-		goto parse_dup_op_espace;
-	    }
-	}
-      else if (BE (start > end, 0))
+  if (BE (end != start, 1))
+    {
+      dup_token.type = (end == -1 ? OP_DUP_ASTERISK : OP_DUP_QUESTION);
+      if (BE (start > 0, 0))
 	{
-	  /* First  number greater than first.  */
-	  *err = REG_BADBR;
-	  return NULL;
+          elem = duplicate_tree (elem, dfa);
+          if (BE (elem == NULL, 0))
+	    goto parse_dup_op_espace;
+
+          /* This subexpression will be marked as optional, so that
+             empty matches do not touch the registers.  */
+          mark_opt_subexp (elem, dfa);
+
+          /* Prepare the tree with the modifier.  */
+          elem = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
+          tree = create_tree (dfa, tree, elem, CONCAT, 0);
 	}
-      else if (end - start > 0)
+      else
 	{
-	  /* Then extract "<re>{0,m}" to "<re>?<re>?...<re>?".  */
-	  dup_token.type = OP_DUP_QUESTION;
-	  if (start > 0)
-	    {
-	      elem = duplicate_tree (elem, dfa);
-	      elem = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
-	      tree = create_tree (dfa, tree, elem, CONCAT, 0);
-	      if (BE (elem == NULL || tree == NULL, 0))
-		goto parse_dup_op_espace;
-	    }
-	  else
-	    {
-	      tree = elem = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
-	      if (BE (tree == NULL, 0))
-		goto parse_dup_op_espace;
-	    }
-	  for (i = 1; i < end - start; ++i)
+	  /* We do not need to duplicate the tree because we have not
+	     created it yet.  */
+          mark_opt_subexp (elem, dfa);
+          tree = elem = re_dfa_add_tree_node (dfa, elem, NULL, &dup_token);
+	}
+      
+      if (BE (elem == NULL || tree == NULL, 0))
+        goto parse_dup_op_espace;
+
+      /* This loop is actually executed only when end != -1,
+         to rewrite <re>{0,n} as <re>?<re>?<re>?...  We have
+         already created the start+1-th copy.  */
+      for (i = start + 2; i <= end; ++i)
+        {
+          elem = duplicate_tree (elem, dfa);
+          tree = create_tree (dfa, tree, elem, CONCAT, 0);
+          if (BE (elem == NULL || tree == NULL, 0))
 	    {
-	      work_tree = duplicate_tree (elem, dfa);
-	      tree = create_tree (dfa, tree, work_tree, CONCAT, 0);
-	      if (BE (work_tree == NULL || tree == NULL, 0))
-		{
-		  *err = REG_ESPACE;
-		  return NULL;
-		}
+	      *err = REG_ESPACE;
+	      return NULL;
 	    }
-	}
-    }
-  /* Treat "<re>{0}*" etc. as "<re>{0}".  */
-  else if (tree == NULL)
-    ;
-  else
-    {
-      tree = re_dfa_add_tree_node (dfa, tree, NULL, token);
-      if (BE (tree == NULL, 0))
-	{
-	  *err = REG_ESPACE;
-	  return NULL;
-	}
+        }
     }
+
   fetch_token (token, regexp, syntax);
   return tree;
 
  parse_dup_op_espace:
   *err = REG_ESPACE;
   return NULL;
-
- parse_dup_op_ebrace:
-  if (BE (!(syntax & RE_INVALID_INTERVAL_ORD), 0))
-    {
-      *err = REG_EBRACE;
-      return NULL;
-    }
-  goto parse_dup_op_rollback;
- parse_dup_op_invalid_interval:
-  if (BE (!(syntax & RE_INVALID_INTERVAL_ORD), 0))
-    {
-      *err = REG_BADBR;
-      return NULL;
-    }
- parse_dup_op_rollback:
-  re_string_set_index (regexp, start_idx);
-  *token = start_token;
-  token->type = CHARACTER;
-  /* mb_partial and word_char bits should be already initialized by
-     peek_token.  */
-  return dup_elem;
 }
 
 /* Size of the names for collating symbol/equivalence_class/character_class.
@@ -3737,6 +3709,47 @@ re_dfa_add_tree_node (dfa, left, right, token)
   return create_tree (dfa, left, right, 0, new_idx);
 }
 
+/* Mark the tree SRC as an optional subexpression.  */
+
+static void
+mark_opt_subexp (src, dfa)
+     const bin_tree_t *src;
+     re_dfa_t *dfa;
+{
+  /* Pass an OPT_SUBEXP_IDX which is != 1 if the duplicated tree is
+     a subexpression.  */
+  if (src->type == CONCAT
+      && src->left->type == NON_TYPE
+      && dfa->nodes[src->left->node_idx].type == OP_OPEN_SUBEXP)
+    mark_opt_subexp_iter (src, dfa, dfa->nodes[src->left->node_idx].opr.idx);
+}
+
+
+/* Recursive tree walker for mark_opt_subexp.  */
+
+static void
+mark_opt_subexp_iter (src, dfa, idx)
+     const bin_tree_t *src;
+     re_dfa_t *dfa;
+{
+  int node_idx;
+
+  if (src->type == NON_TYPE)
+    {
+      node_idx = src->node_idx;
+      if ((dfa->nodes[node_idx].type == OP_OPEN_SUBEXP
+	   || dfa->nodes[node_idx].type == OP_CLOSE_SUBEXP)
+	  && dfa->nodes[node_idx].opr.idx == idx)
+	dfa->nodes[node_idx].opt_subexp = 1;
+     }
+
+  if (src->left != NULL)
+    mark_opt_subexp_iter (src->left, dfa, idx);
+
+  if (src->right != NULL)
+    mark_opt_subexp_iter (src->right, dfa, idx);
+}
+
 
 /* Duplicate the node SRC, and return new node.  */
 
diff --git a/posix/regex_internal.c b/posix/regex_internal.c
index 45b45aaaf0..4cff96f6d6 100644
--- a/posix/regex_internal.c
+++ b/posix/regex_internal.c
@@ -1306,6 +1306,7 @@ re_dfa_add_node (dfa, token, mode)
       dfa->nodes_alloc = new_nodes_alloc;
     }
   dfa->nodes[dfa->nodes_len] = token;
+  dfa->nodes[dfa->nodes_len].opt_subexp = 0;
   dfa->nodes[dfa->nodes_len].duplicated = 0;
   dfa->nodes[dfa->nodes_len].constraint = 0;
   return dfa->nodes_len++;
diff --git a/posix/regex_internal.h b/posix/regex_internal.h
index 8f11ba7a44..18414a58cc 100644
--- a/posix/regex_internal.h
+++ b/posix/regex_internal.h
@@ -281,6 +281,7 @@ typedef struct
 #endif
   unsigned int constraint : 10;	/* context constraint */
   unsigned int duplicated : 1;
+  unsigned int opt_subexp : 1;
 #ifdef RE_ENABLE_I18N
   /* These 2 bits can be moved into the union if needed (e.g. if running out
      of bits; move opr.c to opr.c.c and move the flags to opr.c.flags).  */
diff --git a/posix/regexec.c b/posix/regexec.c
index b0f9a53cfb..973d1c788f 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -62,7 +62,8 @@ static int check_halt_node_context (const re_dfa_t *dfa, int node,
 static int check_halt_state_context (const regex_t *preg,
 				     const re_dfastate_t *state,
 				     const re_match_context_t *mctx, int idx) internal_function;
-static void update_regs (re_dfa_t *dfa, regmatch_t *pmatch, int cur_node,
+static void update_regs (re_dfa_t *dfa, regmatch_t *pmatch,
+			 regmatch_t *prev_idx_match, int cur_node,
 			 int cur_idx, int nmatch) internal_function;
 static int proceed_next_node (const regex_t *preg, int nregs, regmatch_t *regs,
 			      const re_match_context_t *mctx,
@@ -1277,11 +1278,13 @@ set_regs (preg, mctx, nmatch, pmatch, fl_backtrack)
      regmatch_t *pmatch;
      int fl_backtrack;
 {
-  re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
+  re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
   int idx, cur_node, real_nmatch;
   re_node_set eps_via_nodes;
   struct re_fail_stack_t *fs;
-  struct re_fail_stack_t fs_body = {0, 2, NULL};
+  struct re_fail_stack_t fs_body = { 0, 2, NULL };
+  regmatch_t *prev_idx_match;
+
 #ifdef DEBUG
   assert (nmatch > 1);
   assert (mctx->state_log != NULL);
@@ -1290,15 +1293,23 @@ set_regs (preg, mctx, nmatch, pmatch, fl_backtrack)
     {
       fs = &fs_body;
       fs->stack = re_malloc (struct re_fail_stack_ent_t, fs->alloc);
+      if (fs->stack == NULL)
+	return REG_ESPACE;
     }
   else
     fs = NULL;
+
   cur_node = dfa->init_node;
   real_nmatch = (nmatch <= preg->re_nsub) ? nmatch : preg->re_nsub + 1;
   re_node_set_init_empty (&eps_via_nodes);
+
+  prev_idx_match = (regmatch_t *) alloca (sizeof (regmatch_t) * real_nmatch);
+  memcpy (prev_idx_match, pmatch, sizeof (regmatch_t) * real_nmatch);
+
   for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
     {
-      update_regs (dfa, pmatch, cur_node, idx, real_nmatch);
+      update_regs (dfa, pmatch, prev_idx_match, cur_node, idx, real_nmatch);
+
       if (idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
 	{
 	  int reg_idx;
@@ -1362,31 +1373,55 @@ free_fail_stack_return (fs)
 }
 
 static void
-update_regs (dfa, pmatch, cur_node, cur_idx, nmatch)
+update_regs (dfa, pmatch, prev_idx_match, cur_node, cur_idx, nmatch)
      re_dfa_t *dfa;
-     regmatch_t *pmatch;
+     regmatch_t *pmatch, *prev_idx_match;
      int cur_node, cur_idx, nmatch;
 {
   int type = dfa->nodes[cur_node].type;
-  int reg_num;
-  if (type != OP_OPEN_SUBEXP && type != OP_CLOSE_SUBEXP)
-    return;
-  reg_num = dfa->nodes[cur_node].opr.idx + 1;
-  if (reg_num >= nmatch)
-    return;
   if (type == OP_OPEN_SUBEXP)
     {
+      int reg_num = dfa->nodes[cur_node].opr.idx + 1;
+
       /* We are at the first node of this sub expression.  */
-      pmatch[reg_num].rm_so = cur_idx;
-      pmatch[reg_num].rm_eo = -1;
+      if (reg_num < nmatch)
+	{
+	  pmatch[reg_num].rm_so = cur_idx;
+	  pmatch[reg_num].rm_eo = -1;
+	}
     }
   else if (type == OP_CLOSE_SUBEXP)
-    /* We are at the first node of this sub expression.  */
-    pmatch[reg_num].rm_eo = cur_idx;
+    {
+      int reg_num = dfa->nodes[cur_node].opr.idx + 1;
+      if (reg_num < nmatch)
+	{
+	  /* We are at the last node of this sub expression.  */
+	  if (pmatch[reg_num].rm_so < cur_idx)
+	    {
+	      pmatch[reg_num].rm_eo = cur_idx;
+	      /* This is a non-empty match or we are not inside an optional
+		 subexpression.  Accept this right away.  */
+	      memcpy (prev_idx_match, pmatch, sizeof (regmatch_t) * nmatch);
+	    }
+	  else
+	    {
+	      if (dfa->nodes[cur_node].opt_subexp
+		  && prev_idx_match[reg_num].rm_so != -1)
+		/* We transited through an empty match for an optional
+		   subexpression, like (a?)*, and this is not the subexp's
+		   first match.  Copy back the old content of the registers
+		   so that matches of an inner subexpression are undone as
+		   well, like in ((a?))*.  */
+		memcpy (pmatch, prev_idx_match, sizeof (regmatch_t) * nmatch);
+	      else
+		/* We completed a subexpression, but it may be part of
+		   an optional one, so do not update PREV_IDX_MATCH.  */
+		pmatch[reg_num].rm_eo = cur_idx;
+	    }
+	}
+    }
 }
 
-#define NUMBER_OF_STATE 1
-
 /* This function checks the STATE_LOG from the SCTX->last_str_idx to 0
    and sift the nodes in each states according to the following rules.
    Updated state_log will be wrote to STATE_LOG.
@@ -3279,7 +3314,7 @@ out_free:
 		 character ch.  See group_nodes_into_DFAstates.  */
 	      for (j = 0; (dests_ch[j][i] & mask) == 0; ++j)
 		;
-	      
+
 	      /* j-th destination accepts the word character ch.  */
 	      if (IS_WORD_CHAR (ch))
 		trtable[ch] = dest_states_word[j];
@@ -3298,7 +3333,7 @@ out_free:
 					   2 * SBC_MAX);
       if (BE (trtable == NULL, 0))
 	goto out_free;
-      
+
       /* For all characters ch...:  */
       for (i = 0; i < BITSET_UINTS; ++i)
 	for (ch = i * UINT_BITS, elem = acceptable[i], mask = 1;
@@ -3310,13 +3345,13 @@ out_free:
 		 character ch.  See group_nodes_into_DFAstates.  */
 	      for (j = 0; (dests_ch[j][i] & mask) == 0; ++j)
 		;
-	      
+
 	      /* j-th destination accepts the word character ch.  */
 	      trtable[ch] = dest_states[j];
 	      trtable[ch + SBC_MAX] = dest_states_word[j];
 	    }
     }
-  
+
   /* new line */
   if (bitset_contain (acceptable, NEWLINE_CHAR))
     {
diff --git a/posix/rxspencer/tests b/posix/rxspencer/tests
index 8e93133d24..f4a3fb3df5 100644
--- a/posix/rxspencer/tests
+++ b/posix/rxspencer/tests
@@ -431,7 +431,7 @@ a(b|c)*d	-	abcd	abcd	c
 a(b|c)+d	-	abd	abd	b
 a(b|c)+d	-	abcd	abcd	c
 a(b|c?)+d	-	ad	ad	@d
-a(b|c?)+d	-	abcd	abcd	@d
+a(b|c?)+d	-	abcd	abcd	c
 a(b|c){0,0}d	-	ad	ad	-
 a(b|c){0,1}d	-	ad	ad	-
 a(b|c){0,1}d	-	abd	abd	b
@@ -452,9 +452,8 @@ a(b|c){2,4}d	-	abcbd	abcbd	b
 a(b|c){2,4}d	-	abcbcd	abcbcd	c
 a(b|c){2,}d	-	abcd	abcd	c
 a(b|c){2,}d	-	abcbd	abcbd	b
-a(b+|((c)*))+d	-	abd	abd	@d,@d,-
-# XXX Needs to be checked.
-#a(b+|((c)*))+d	-	abcd	abcd	@d,@d,-
+a(b+|((c)*))+d	-	abd	abd	b,-,-
+a(b+|((c)*))+d	-	abcd	abcd	c,c,c
 
 # check out the STARTEND option
 [abc]		&#	a(b)c	b