diff --git a/src/char_property.h b/src/char_property.h
index 35f4b05..7be47c5 100644
--- a/src/char_property.h
+++ b/src/char_property.h
@@ -37,7 +37,7 @@ class CharProperty {
   inline const char *seekToOtherType(const char *begin, const char *end,
                                      CharInfo c, CharInfo *fail,
                                      size_t *mblen, size_t *clen) const {
-    register const char *p =  begin;
+    const char *p =  begin;
     *clen = 0;
     while (p != end && c.isKindOf(*fail = getCharInfo(p, end, mblen))) {
       p += *mblen;
@@ -89,4 +89,4 @@ class CharProperty {
   whatlog                    what_;
 };
 }
-#endif   // MECAB_CHARACTER_CATEGORY_H_
+#endif   // MECAB_CHARACTER_CATEGORY_H_
\ No newline at end of file
diff --git a/src/darts.h b/src/darts.h
index 91b2eae..875b64f 100644
--- a/src/darts.h
+++ b/src/darts.h
@@ -404,10 +404,10 @@ class DoubleArrayImpl {
     T result;
     set_result(result, -1, 0);
 
-    register array_type_  b = array_[node_pos].base;
-    register array_u_type_ p;
+    array_type_  b = array_[node_pos].base;
+    array_u_type_ p;
 
-    for (register size_t i = 0; i < len; ++i) {
+    for (size_t i = 0; i < len; ++i) {
       p = b +(node_u_type_)(key[i]) + 1;
       if (static_cast<array_u_type_>(b) == array_[p].check)
         b = array_[p].base;
@@ -431,12 +431,12 @@ class DoubleArrayImpl {
                             size_t node_pos = 0) const {
     if (!len) len = length_func_()(key);
 
-    register array_type_  b   = array_[node_pos].base;
-    register size_t     num = 0;
-    register array_type_  n;
-    register array_u_type_ p;
+    array_type_  b   = array_[node_pos].base;
+    size_t     num = 0;
+    array_type_  n;
+    array_u_type_ p;
 
-    for (register size_t i = 0; i < len; ++i) {
+    for ( size_t i = 0; i < len; ++i) {
       p = b;  // + 0;
       n = array_[p].base;
       if ((array_u_type_) b == array_[p].check && n < 0) {
@@ -469,8 +469,8 @@ class DoubleArrayImpl {
                       size_t len = 0) const {
     if (!len) len = length_func_()(key);
 
-    register array_type_  b = array_[node_pos].base;
-    register array_u_type_ p;
+    array_type_  b = array_[node_pos].base;
+    array_u_type_ p;
 
     for (; key_pos < len; ++key_pos) {
       p = b +(node_u_type_)(key[key_pos]) + 1;
@@ -515,4 +515,4 @@ typedef Darts::DoubleArrayImpl<char, unsigned char, long long,
 #endif
 }
 }
-#endif
+#endif
\ No newline at end of file
diff --git a/src/viterbi.cpp b/src/viterbi.cpp
index a4b46dc..e2273b9 100644
--- a/src/viterbi.cpp
+++ b/src/viterbi.cpp
@@ -318,11 +318,11 @@ template <bool IsAllPath> bool connect(size_t pos, Node *rnode,
                                        const Connector *connector,
                                        Allocator<Node, Path> *allocator) {
   for (;rnode; rnode = rnode->bnext) {
-    register long best_cost = 2147483647;
+     long best_cost = 2147483647;
     Node* best_node = 0;
     for (Node *lnode = end_node_list[pos]; lnode; lnode = lnode->enext) {
-      register int lcost = connector->cost(lnode, rnode);  // local cost
-      register long cost = lnode->cost + lcost;
+       int lcost = connector->cost(lnode, rnode);  // local cost
+       long cost = lnode->cost + lcost;
 
       if (cost < best_cost) {
         best_node  = lnode;
@@ -410,4 +410,4 @@ bool Viterbi::viterbi(Lattice *lattice) const {
 
   return true;
 }
-}  // Mecab
+}  // Mecab
\ No newline at end of file
diff --git a/src/viterbi.h b/src/viterbi.h
index 54bfdf9..ae76030 100644
--- a/src/viterbi.h
+++ b/src/viterbi.h
@@ -9,6 +9,8 @@
 #include <vector>
 #include "mecab.h"
 #include "thread.h"
+#include "scoped_ptr.h"
+#include "common.h"
 
 namespace MeCab {
 
@@ -50,4 +52,4 @@ class Viterbi {
   whatlog               what_;
 };
 }
-#endif  // MECAB_VITERBI_H_
+#endif  // MECAB_VITERBI_H_
\ No newline at end of file