diff --git a/src/big5.c b/src/big5.c
index 79ae1e34..faff845a 100644
--- a/src/big5.c
+++ b/src/big5.c
@@ -2,7 +2,7 @@
   big5.c -  Oniguruma (regular expression library)
 **********************************************************************/
 /*-
- * Copyright (c) 2002-2019  K.Kosako
+ * Copyright (c) 2002-2020  K.Kosako
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -58,8 +58,15 @@ static int
 big5_code_to_mbclen(OnigCodePoint code)
 {
   if ((code & (~0xffff)) != 0) return ONIGERR_INVALID_CODE_POINT_VALUE;
-  if ((code &    0xff00) != 0) return 2;
-  if (EncLen_BIG5[(int )(code & 0xff)] == 1) return 1;
+
+  if ((code & 0xff00) != 0) {
+    if (EncLen_BIG5[(int )(code >> 8) & 0xff] == 2)
+      return 2;
+  }
+  else {
+    if (EncLen_BIG5[(int )(code & 0xff)] == 1)
+      return 1;
+  }
 
   return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
diff --git a/src/euc_jp.c b/src/euc_jp.c
index 640b3e3c..6ddd91c7 100644
--- a/src/euc_jp.c
+++ b/src/euc_jp.c
@@ -2,7 +2,7 @@
   euc_jp.c -  Oniguruma (regular expression library)
 **********************************************************************/
 /*-
- * Copyright (c) 2002-2019  K.Kosako
+ * Copyright (c) 2002-2020  K.Kosako
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -114,10 +114,20 @@ static int
 code_to_mbclen(OnigCodePoint code)
 {
   if (ONIGENC_IS_CODE_ASCII(code)) return 1;
-  else if ((code & 0xff0000) != 0) return 3;
-  else if ((code &   0xff00) != 0) return 2;
-  else
-    return ONIGERR_INVALID_CODE_POINT_VALUE;
+  else if ((code & 0xff0000) != 0) {
+    if (EncLen_EUCJP[(int )(code >> 16) & 0xff] == 3)
+      return 3;
+  }
+  else if ((code & 0xff00) != 0) {
+    if (EncLen_EUCJP[(int )(code >> 8) & 0xff] == 2)
+      return 2;
+  }
+  else if (code < 256) {
+    if (EncLen_EUCJP[(int )(code & 0xff)] == 1)
+      return 1;
+  }
+
+  return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
 
 static int
diff --git a/src/euc_kr.c b/src/euc_kr.c
index 7fa50afb..b0e9fbff 100644
--- a/src/euc_kr.c
+++ b/src/euc_kr.c
@@ -2,7 +2,7 @@
   euc_kr.c -  Oniguruma (regular expression library)
 **********************************************************************/
 /*-
- * Copyright (c) 2002-2019  K.Kosako
+ * Copyright (c) 2002-2020  K.Kosako
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -58,8 +58,15 @@ static int
 euckr_code_to_mbclen(OnigCodePoint code)
 {
   if ((code & (~0xffff)) != 0) return ONIGERR_INVALID_CODE_POINT_VALUE;
-  if ((code &    0xff00) != 0) return 2;
-  if (EncLen_EUCKR[(int )(code & 0xff)] == 1) return 1;
+
+  if ((code & 0xff00) != 0) {
+    if (EncLen_EUCKR[(int )(code >> 8) & 0xff] == 2)
+      return 2;
+  }
+  else {
+    if (EncLen_EUCKR[(int )(code & 0xff)] == 1)
+      return 1;
+  }
 
   return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
diff --git a/src/euc_tw.c b/src/euc_tw.c
index 8e72b970..99dc5eca 100644
--- a/src/euc_tw.c
+++ b/src/euc_tw.c
@@ -2,7 +2,7 @@
   euc_tw.c -  Oniguruma (regular expression library)
 **********************************************************************/
 /*-
- * Copyright (c) 2002-2019  K.Kosako
+ * Copyright (c) 2002-2020  K.Kosako
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -57,15 +57,22 @@ euctw_mbc_enc_len(const UChar* p)
 static int
 euctw_code_to_mbclen(OnigCodePoint code)
 {
-       if ((code & 0xff000000) != 0) return 4;
-  else if ((code &   0xff0000) != 0) return ONIGERR_INVALID_CODE_POINT_VALUE;
-  else if ((code &     0xff00) != 0) return 2;
+  if ((code & 0xff000000) != 0) {
+    if (EncLen_EUCTW[(int )(code >> 24) & 0xff] == 4)
+      return 4;
+  }
+  else if ((code & 0xff0000) != 0)
+    return ONIGERR_INVALID_CODE_POINT_VALUE;
+  else if ((code & 0xff00) != 0) {
+    if (EncLen_EUCTW[(int )(code >> 8) & 0xff] == 2)
+      return 2;
+  }
   else {
     if (EncLen_EUCTW[(int )(code & 0xff)] == 1)
       return 1;
-
-    return ONIGERR_INVALID_CODE_POINT_VALUE;
   }
+
+  return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
 
 static int
diff --git a/src/gb18030.c b/src/gb18030.c
index 1385a7fa..7409d3e0 100644
--- a/src/gb18030.c
+++ b/src/gb18030.c
@@ -89,15 +89,25 @@ gb18030_mbc_enc_len(const UChar* p)
 static int
 gb18030_code_to_mbclen(OnigCodePoint code)
 {
-       if ((code & 0xff000000) != 0) return 4;
-  else if ((code &   0xff0000) != 0) return ONIGERR_INVALID_CODE_POINT_VALUE;
-  else if ((code &     0xff00) != 0) return 2;
+  if ((code & 0xff000000) != 0) {
+    if (GB18030_MAP[(int )(code >> 24) & 0xff] == CM)
+      if (GB18030_MAP[(int )(code >> 16) & 0xff] == C4)
+        return 4;
+  }
+  else if ((code & 0xff0000) != 0) return ONIGERR_INVALID_CODE_POINT_VALUE;
+  else if ((code & 0xff00) != 0) {
+    if (GB18030_MAP[(int )(code >> 8) & 0xff] == CM) {
+      char c = GB18030_MAP[(int )code & 0xff];
+      if (c == CM || c == C2)
+        return 2;
+    }
+  }
   else {
-    if (GB18030_MAP[(int )(code & 0xff)] == CM)
-      return ONIGERR_INVALID_CODE_POINT_VALUE;
-
-    return 1;
+    if (GB18030_MAP[(int )(code & 0xff)] != CM)
+      return 1;
   }
+
+  return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
 
 static int
diff --git a/src/regexec.c b/src/regexec.c
index 1b6895d6..cd4c1c19 100644
--- a/src/regexec.c
+++ b/src/regexec.c
@@ -2362,6 +2362,10 @@ static int string_cmp_ic(OnigEncoding enc, int case_fold_flag,
       p1++;
       p2++;
     }
+    if (s2 >= end2) {
+      if (s1 < end1) return 0;
+      else           break;
+    }
   }
 
   *ps2 = s2;
diff --git a/src/regparse.c b/src/regparse.c
index cc015a76..e815b941 100644
--- a/src/regparse.c
+++ b/src/regparse.c
@@ -4564,7 +4564,7 @@ fetch_interval(UChar** src, UChar* end, PToken* tok, ScanEnv* env)
 
 /* \M-, \C-, \c, or \... */
 static int
-fetch_escaped_value(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
+fetch_escaped_value_raw(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
 {
   int v;
   OnigCodePoint c;
@@ -4583,7 +4583,7 @@ fetch_escaped_value(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
       if (PEND) return ONIGERR_END_PATTERN_AT_META;
       PFETCH_S(c);
       if (c == MC_ESC(env->syntax)) {
-        v = fetch_escaped_value(&p, end, env, &c);
+        v = fetch_escaped_value_raw(&p, end, env, &c);
         if (v < 0) return v;
       }
       c = ((c & 0xff) | 0x80);
@@ -4612,7 +4612,7 @@ fetch_escaped_value(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
       }
       else {
         if (c == MC_ESC(env->syntax)) {
-          v = fetch_escaped_value(&p, end, env, &c);
+          v = fetch_escaped_value_raw(&p, end, env, &c);
           if (v < 0) return v;
         }
         c &= 0x9f;
@@ -4634,6 +4634,21 @@ fetch_escaped_value(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
   return 0;
 }
 
+static int
+fetch_escaped_value(UChar** src, UChar* end, ScanEnv* env, OnigCodePoint* val)
+{
+  int r;
+  int len;
+
+  r = fetch_escaped_value_raw(src, end, env, val);
+  if (r != 0) return r;
+
+  len = ONIGENC_CODE_TO_MBCLEN(env->enc, *val);
+  if (len < 0) return len;
+
+  return 0;
+}
+
 static int fetch_token(PToken* tok, UChar** src, UChar* end, ScanEnv* env);
 
 static OnigCodePoint
@@ -5192,7 +5207,7 @@ fetch_token_cc(PToken* tok, UChar** src, UChar* end, ScanEnv* env, int state)
           else {
             int curr_state;
 
-	    curr_state = (state == CS_RANGE) ? CPS_EMPTY : CPS_START;
+            curr_state = (state == CS_RANGE) ? CPS_EMPTY : CPS_START;
             r = check_code_point_sequence_cc(p, end, tok->base_num, enc,
                                              curr_state);
             if (r < 0) return r;
@@ -8419,8 +8434,9 @@ parse_exp(Node** np, PToken* tok, int term, UChar** src, UChar* end,
   case TK_CODE_POINT:
     {
       UChar buf[ONIGENC_CODE_TO_MBC_MAXLEN];
-      len = ONIGENC_CODE_TO_MBC(env->enc, tok->u.code, buf);
+      len = ONIGENC_CODE_TO_MBCLEN(env->enc, tok->u.code);
       if (len < 0) return len;
+      len = ONIGENC_CODE_TO_MBC(env->enc, tok->u.code, buf);
 #ifdef NUMBERED_CHAR_IS_NOT_CASE_AMBIG
       *np = node_new_str_crude(buf, buf + len, env->options);
 #else
diff --git a/src/sjis.c b/src/sjis.c
index 1fd92d93..10afd9d3 100644
--- a/src/sjis.c
+++ b/src/sjis.c
@@ -2,7 +2,7 @@
   sjis.c -  Oniguruma (regular expression library)
 **********************************************************************/
 /*-
- * Copyright (c) 2002-2019  K.Kosako
+ * Copyright (c) 2002-2020  K.Kosako
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -113,13 +113,15 @@ static int
 code_to_mbclen(OnigCodePoint code)
 {
   if (code < 256) {
-    return EncLen_SJIS[(int )code] == 1;
+    if (EncLen_SJIS[(int )code] == 1)
+      return 1;
   }
-  else if (code <= 0xffff) {
-    return 2;
+  else if (code < 0x10000) {
+    if (EncLen_SJIS[(int )(code >>  8) & 0xff] == 2)
+      return 2;
   }
-  else
-    return ONIGERR_INVALID_CODE_POINT_VALUE;
+
+  return ONIGERR_INVALID_CODE_POINT_VALUE;
 }
 
 static OnigCodePoint