diff --git a/hawk/lib/tre-compile.c b/hawk/lib/tre-compile.c
index 83647d12..7758bc71 100644
--- a/hawk/lib/tre-compile.c
+++ b/hawk/lib/tre-compile.c
@@ -58,13 +58,6 @@ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-/*
-  TODO:
-   - Fix tre_ast_to_tnfa() to recurse using a stack instead of recursive
-     function calls.
-*/
-
-
 #include <hawk-tre.h>
 #include "tre-stack.h"
 #include "tre-ast.h"
@@ -758,6 +751,9 @@ tre_copy_ast(tre_mem_t mem, tre_stack_t *stack, tre_ast_node_t *ast,
 				*result = tre_ast_new_literal(mem, min, max, pos);
 				if (*result == NULL) status = REG_ESPACE;
 
+				/* HAWK */
+				((tre_literal_t*)(*result)->obj)->u.class = lit->u.class;
+				/* END HAWK */
 				if (pos > *max_pos)
 					*max_pos = pos;
 				break;
@@ -1812,6 +1808,8 @@ tre_make_trans(hawk_gem_t* gem, tre_pos_and_tags_t *p1, tre_pos_and_tags_t *p2,
    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. */
+/* HAWK */
+#if 0
 static reg_errcode_t
 tre_ast_to_tnfa(hawk_gem_t* gem, tre_ast_node_t *node, tre_tnfa_transition_t *transitions,
                 int *counts, int *offs)
@@ -1867,7 +1865,75 @@ tre_ast_to_tnfa(hawk_gem_t* gem, tre_ast_node_t *node, tre_tnfa_transition_t *tr
 	}
 	return errcode;
 }
+#endif
+static reg_errcode_t
+__tre_ast_to_tnfa(hawk_gem_t *gem, tre_stack_t* stack, 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;
 
+	STACK_PUSHR(stack, voidptr, node);
+
+	while (tre_stack_num_objects(stack)) 
+	{
+		node = (tre_ast_node_t*)tre_stack_pop_voidptr(stack);
+
+		switch (node->type)
+		{
+			case LITERAL:
+				break;
+
+			case UNION:
+				uni = (tre_union_t *)node->obj;
+				STACK_PUSHR(stack, voidptr, uni->right);
+				STACK_PUSHR(stack, voidptr, uni->left);
+				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(gem, cat->left->lastpos, cat->right->firstpos, transitions, counts, offs);
+				if (errcode != REG_OK) return errcode;
+
+				STACK_PUSHR(stack, voidptr, cat->right);
+				STACK_PUSHR(stack, voidptr, cat->left);
+				break;
+
+			case ITERATION:
+				iter = (tre_iteration_t *)node->obj;
+				if(!(iter->max == -1 || iter->max == 1)) return REG_BADBR;
+
+				if (iter->max == -1)
+				{
+					if(!(iter->min == 0 || iter->min == 1)) return REG_BADBR;
+					/* Add a transition from each last position in the iterated expression to each first position. */
+					errcode = tre_make_trans(gem, iter->arg->lastpos, iter->arg->firstpos, transitions, counts, offs);
+					if (errcode != REG_OK) return errcode;	  
+				}
+				STACK_PUSHR(stack, voidptr, iter->arg);
+				break;
+		 }
+	}
+	return REG_OK;
+}
+
+static reg_errcode_t
+tre_ast_to_tnfa(hawk_gem_t* gem, tre_ast_node_t *node, tre_tnfa_transition_t *transitions, int *counts, int *offs)
+{
+	reg_errcode_t x;
+	tre_stack_t* stack;
+
+	stack = tre_stack_new(gem, 1024, -1, 4096);
+	if (HAWK_UNLIKELY(!stack)) return REG_ESPACE;
+
+	x = __tre_ast_to_tnfa(gem, stack, node, transitions, counts, offs);
+
+	tre_stack_destroy(stack);
+	return x;
+}
+/* END HAWK */
 
 #define ERROR_EXIT(err) \
 	do \
diff --git a/hawk/lib/tre-mem.c b/hawk/lib/tre-mem.c
index f1dc43d8..25ceb86f 100644
--- a/hawk/lib/tre-mem.c
+++ b/hawk/lib/tre-mem.c
@@ -114,13 +114,15 @@ hawk_tre_mem_alloc_impl(hawk_tre_mem_t mem, int provided, void *provided_block,
 	}
       else
 	{
-	  int block_size;
+	/* HAWK */	
+	/*  int block_size;*/
+	  hawk_oow_t block_size;
+	/* END HAWK */
 	  if (size * 8 > TRE_MEM_BLOCK_SIZE)
 	    block_size = size * 8;
 	  else
 	    block_size = TRE_MEM_BLOCK_SIZE;
-	  DPRINT(("tre_mem_alloc: allocating new %d byte block\n",
-		  block_size));
+	  DPRINT(("tre_mem_alloc: allocating new %lu byte block\n", (unsigned long int)block_size));
 
 	  l = xmalloc(mem->gem, sizeof(*l));
 	  if (l == NULL)
diff --git a/hawk/lib/tre-parse.c b/hawk/lib/tre-parse.c
index d39095dd..d670aa46 100644
--- a/hawk/lib/tre-parse.c
+++ b/hawk/lib/tre-parse.c
@@ -134,8 +134,11 @@ tre_expand_macro(const tre_char_t *regex, const tre_char_t *regex_end,
 			unsigned int j;
 			DPRINT(("Expanding macro '%c' => '%s'\n",
 			        tre_macros[i].c, tre_macros[i].expansion));
-			for (j = 0; tre_macros[i].expansion[j] && j < buf_len; j++)
+			/* HAWK */
+			/*for (j = 0; tre_macros[i].expansion[j] && j < buf_len; j++)*/
+			for (j = 0; tre_macros[i].expansion[j] && j < buf_len - 1; j++)
 				buf[j] = tre_macros[i].expansion[j];
+			/* END HAWK */
 			buf[j] = 0;
 			break;
 		}
@@ -214,7 +217,10 @@ tre_compare_items(const void *a, const void *b, void* ctx)
 	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;
+	/* HAWK: changed int to long */
+	/*int a_min = l_a->code_min, b_min = l_b->code_min;*/
+	long a_min = l_a->code_min, b_min = l_b->code_min;
+	/* END HAWK */
 
 	if (a_min < b_min)
 		return -1;
@@ -295,7 +301,10 @@ tre_parse_bracket_items(tre_parse_ctx_t *ctx, int negate,
 			         && *re == CHAR_LBRACKET && *(re + 1) == CHAR_COLON)
 			{
 				const tre_char_t *endptr = re + 2;
-				int len;
+				/* HAWK: changed int to hawk_oow_t */
+				/*int len;*/
+				hawk_oow_t len;
+				/* END HAWK */
 				DPRINT(("tre_parse_bracket:  class: '%.*" STRF "'\n", REST(re)));
 				while (endptr < ctx->re_end && *endptr != CHAR_COLON) endptr++;
 				if (endptr != ctx->re_end)
@@ -557,14 +566,24 @@ parse_bracket_done:
 static int
 tre_parse_int(const tre_char_t **regex, const tre_char_t *regex_end)
 {
+	/* HAWK : added overflow check with other code optimizations */
 	int num = -1;
 	const tre_char_t *r = *regex;
-	while (r < regex_end && *r >= HAWK_T('0') && *r <= HAWK_T('9'))
+
+	if (r < regex_end && *r >= HAWK_T('0') && *r <= HAWK_T('9'))
 	{
-		if (num < 0)
-			num = 0;
-		num = num * 10 + *r - HAWK_T('0');
-		r++;
+		int ever_overflowed = 0;
+
+		num = 0;
+		do
+		{
+			if (num > (HAWK_TYPE_MAX(int) - 9) / 10) ever_overflowed = 1;
+			num = num * 10 + *r - HAWK_T('0');
+			r++;
+		}
+		while (r < regex_end && *r >= HAWK_T('0') && *r <= HAWK_T('9'));
+
+		if (ever_overflowed) num = -1;
 	}
 	*regex = r;
 	return num;
@@ -1355,9 +1374,13 @@ reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
 				break;
 	
 			case CHAR_RPAREN:  /* end of current subexpression */
-				if ((ctx->cflags & REG_EXTENDED && depth > 0)
+				/* HAWK: fixed the condition */
+				/* if ((ctx->cflags & REG_EXTENDED && depth > 0)
 				        || (ctx->re > ctx->re_start
-				            && *(ctx->re - 1) == CHAR_BACKSLASH))
+				            && *(ctx->re - 1) == CHAR_BACKSLASH)) */
+				if (((ctx->cflags & REG_EXTENDED) && depth > 0) ||
+				    (!(ctx->cflags & REG_EXTENDED) && ctx->re > ctx->re_start && *(ctx->re - 1) == CHAR_BACKSLASH))
+				/* END HAWK */
 				{
 					DPRINT(("tre_parse:	    empty: '%.*" STRF "'\n", REST(ctx->re)));
 					/* We were expecting an atom, but instead the current
@@ -1649,7 +1672,7 @@ reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
 	
 	
 				/* We are expecting an atom.  If the subexpression (or the whole
-				 regexp ends here, we interpret it as an empty expression
+				 regexp) ends here, we interpret it as an empty expression
 				 (which matches an empty string).  */
 				if (
 	#ifdef REG_LITERAL
diff --git a/hawk/lib/tre-parse.h b/hawk/lib/tre-parse.h
index c55ef33a..c84dfe41 100644
--- a/hawk/lib/tre-parse.h
+++ b/hawk/lib/tre-parse.h
@@ -76,7 +76,10 @@ typedef struct
 	const tre_char_t *re_start;
 	/* The first character after the end of the regexp. */
 	const tre_char_t *re_end;
-	int len;
+	/* HAWK: changed int to hawk_oow_t */
+	/*int len;*/
+	hawk_oow_t len;
+	/* END HAWK */
 	/* Current submatch ID. */
 	int submatch_id;
 	/* Current position (number of literal). */