diff --git a/regcomp.c b/regcomp.c
index 24d44dd1b8..de44cfe037 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -3021,7 +3021,7 @@ setup_tree(Node* node, regex_t* reg, int state, ScanEnv* env)
 	  NSTRING_SET_CASE_AMBIG(node);
 	  break;
 	}
-	p++;
+        p += enc_len(reg->enc, *p);
       }
     }
     break;
@@ -3950,22 +3950,17 @@ optimize_node_left(Node* node, NodeOptInfo* opt, OptEnv* env)
 	}
       }
 
-      if (IS_NULL(cc->mbuf)) {
-	if (cc->not) {
-	  for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
-	    add_char_opt_map_info(&opt->map, i);
-	  }
-	  mb_found = 1;
-	}
-      }
-      else {
-	for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
-	  z = ONIGENC_IS_MBC_HEAD(env->enc, i);
-	  if (z) {
-	    mb_found = 1;
-	    add_char_opt_map_info(&opt->map, i);
-	  }
-	}
+      if (! ONIGENC_IS_SINGLEBYTE(env->enc)) {
+        if (! IS_NULL(cc->mbuf) ||
+            (cc->not != 0 && found != 0)) {
+          for (i = 0; i < SINGLE_BYTE_SIZE; i++) {
+            z = ONIGENC_IS_MBC_HEAD(env->enc, i);
+            if (z) {
+              mb_found = 1;
+              add_char_opt_map_info(&opt->map, i);
+            }
+          }
+        }
       }
 
       if (mb_found) {
diff --git a/regexec.c b/regexec.c
index 870a6535bd..1bae0d9516 100644
--- a/regexec.c
+++ b/regexec.c
@@ -362,11 +362,26 @@ typedef struct {
   };\
 } while(0)
 
+static unsigned int MatchStackLimitSize = DEFAULT_MATCH_STACK_LIMIT_SIZE;
+
+extern unsigned int
+onig_get_match_stack_limit_size(void)
+{
+  return MatchStackLimitSize;
+}
+
+extern int
+onig_set_match_stack_limit_size(unsigned int size)
+{
+  MatchStackLimitSize = size;
+  return 0;
+}
+
 static int
 stack_double(StackType** arg_stk_base, StackType** arg_stk_end,
 	     StackType** arg_stk, StackType* stk_alloc, MatchArg* msa)
 {
-  int n;
+  unsigned int n;
   StackType *x, *stk_base, *stk_end, *stk;
 
   stk_base = *arg_stk_base;
@@ -385,7 +400,12 @@ stack_double(StackType** arg_stk_base, StackType** arg_stk_end,
   }
   else {
     n *= 2;
-    if (n > MATCH_STACK_LIMIT_SIZE) return ONIGERR_MATCH_STACK_LIMIT_OVER;
+    if (MatchStackLimitSize != 0 && n > MatchStackLimitSize) {
+      if ((unsigned int )(stk_end - stk_base) == MatchStackLimitSize)
+        return ONIGERR_MATCH_STACK_LIMIT_OVER;
+      else
+        n = MatchStackLimitSize;
+    }
     x = (StackType* )xrealloc(stk_base, sizeof(StackType) * n);
     if (IS_NULL(x)) {
       STACK_SAVE;
@@ -1171,10 +1191,9 @@ match_at(regex_t* reg, UChar* str, UChar* end, UChar* sstart,
 	  goto fail; /* for retry */
 	}
       }
-      else {
-	/* default behavior: return first-matching result. */
-	goto finish;
-      }
+
+      /* default behavior: return first-matching result. */
+      goto finish;
       break;
 
     case OP_EXACT1:  STAT_OP_IN(OP_EXACT1);
@@ -2574,11 +2593,13 @@ bm_search_notrev(regex_t* reg, UChar* target, UChar* target_end,
       if (t < target) return p + 1;
 
       skip = reg->map[*s];
-      p++;
+      p = s + 1;
+      if (p >= text_end) return (UChar* )NULL;
       t = p;
-      while ((p - t) < skip) {
+      do {
 	p += enc_len(reg->enc, *p);
-      }
+      } while ((p - t) < skip && p < text_end);
+
       s += (p - t);
     }
   }
@@ -2592,11 +2613,13 @@ bm_search_notrev(regex_t* reg, UChar* target, UChar* target_end,
       if (t < target) return p + 1;
 
       skip = reg->int_map[*s];
-      p++;
+      p = s + 1;
+      if (p >= text_end) return (UChar* )NULL;
       t = p;
-      while ((p - t) < skip) {
+      do {
 	p += enc_len(reg->enc, *p);
-      }
+      } while ((p - t) < skip && p < text_end);
+
       s += (p - t);
     }
   }
@@ -3288,13 +3311,3 @@ onig_get_syntax(regex_t* reg)
 {
   return reg->syntax;
 }
-
-extern const char*
-onig_version(void)
-{
-#define MSTR(a)  # a
-
-  return (MSTR(ONIGURUMA_VERSION_MAJOR) "."
-	  MSTR(ONIGURUMA_VERSION_MINOR) "."
-	  MSTR(ONIGURUMA_VERSION_TEENY));
-}
diff --git a/regint.h b/regint.h
index dacc0400be..bcc5fa5fc4 100644
--- a/regint.h
+++ b/regint.h
@@ -46,13 +46,12 @@
 #define USE_QUALIFIER_PEEK_NEXT
 
 #define INIT_MATCH_STACK_SIZE                     160
-#define MATCH_STACK_LIMIT_SIZE                 500000
+#define DEFAULT_MATCH_STACK_LIMIT_SIZE              0 /* unlimited */
 
 /* interface to external system */
 #ifdef NOT_RUBY      /* gived from Makefile */
 #include "config.h"
 #define USE_VARIABLE_META_CHARS
-#define USE_VARIABLE_SYNTAX
 #define USE_WORD_BEGIN_END          /* "\<": word-begin, "\>": word-end */
 #define USE_POSIX_REGION_OPTION     /* needed for POSIX API support */
 #define THREAD_ATOMIC_START         /* depend on thread system */
@@ -654,6 +653,31 @@ extern OnigMetaCharTableType OnigMetaCharTable;
 #define MC_ONE_OR_MORE_TIME  OnigMetaCharTable.one_or_more_time
 #define MC_ANYCHAR_ANYTIME   OnigMetaCharTable.anychar_anytime
 
+#define SYN_POSIX_COMMON_OP \
+ ( ONIG_SYN_OP_DOT_ANYCHAR | ONIG_SYN_OP_POSIX_BRACKET | \
+   ONIG_SYN_OP_DECIMAL_BACKREF | \
+   ONIG_SYN_OP_BRACKET_CC | ONIG_SYN_OP_ASTERISK_ZERO_INF | \
+   ONIG_SYN_OP_LINE_ANCHOR | \
+   ONIG_SYN_OP_ESC_CONTROL_CHARS )
+
+#define SYN_GNU_REGEX_OP \
+  ( ONIG_SYN_OP_DOT_ANYCHAR | ONIG_SYN_OP_BRACKET_CC | \
+    ONIG_SYN_OP_POSIX_BRACKET | ONIG_SYN_OP_DECIMAL_BACKREF | \
+    ONIG_SYN_OP_BRACE_INTERVAL | ONIG_SYN_OP_LPAREN_SUBEXP | \
+    ONIG_SYN_OP_VBAR_ALT | \
+    ONIG_SYN_OP_ASTERISK_ZERO_INF | ONIG_SYN_OP_PLUS_ONE_INF | \
+    ONIG_SYN_OP_QMARK_ZERO_ONE | \
+    ONIG_SYN_OP_ESC_AZ_BUF_ANCHOR | ONIG_SYN_OP_ESC_CAPITAL_G_BEGIN_ANCHOR | \
+    ONIG_SYN_OP_ESC_W_WORD | \
+    ONIG_SYN_OP_ESC_B_WORD_BOUND | ONIG_SYN_OP_ESC_LTGT_WORD_BEGIN_END | \
+    ONIG_SYN_OP_ESC_S_WHITE_SPACE | ONIG_SYN_OP_ESC_D_DIGIT | \
+    ONIG_SYN_OP_LINE_ANCHOR )
+
+#define SYN_GNU_REGEX_BV \
+  ( ONIG_SYN_CONTEXT_INDEP_ANCHORS | ONIG_SYN_CONTEXT_INDEP_REPEAT_OPS | \
+    ONIG_SYN_CONTEXT_INVALID_REPEAT_OPS | ONIG_SYN_ALLOW_INVALID_INTERVAL | \
+    ONIG_SYN_BACKSLASH_ESCAPE_IN_CC | ONIG_SYN_ALLOW_DOUBLE_RANGE_OP_IN_CC )
+
 
 #ifdef ONIG_DEBUG