--- card.cpp
+++ card.cpp
@@ -1,5 +1,6 @@
+#include <cstdlib>
 #include <cstdio>
-#include <math.h>
+#include <cmath>
 #ifdef SHAPE
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
--- freecell.cpp
+++ freecell.cpp
@@ -1,6 +1,7 @@
 #include <dirent.h>
 #include <fcntl.h>
-#include <stdlib.h>
+#include <cstdlib>
+#include <cstring>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
--- option.cpp
+++ option.cpp
@@ -3,7 +3,9 @@
 #include <fcntl.h>
 #include <dirent.h>
 #include <unistd.h>
-#include <stdio.h>
+#include <cstdlib>
+#include <cstdio>
+#include <cstring>
 
 #include "general.h"
 #include "option.h"
--- subwindows.cpp
+++ subwindows.cpp
@@ -3,7 +3,8 @@
 #include <fcntl.h>
 #include <dirent.h>
 #include <unistd.h>
-#include <stdio.h>
+#include <cstdlib>
+#include <cstdio>
 
 #include "general.h"
 #include "subwindows.h"
--- widget/widget.h
+++ widget/widget.h
@@ -4,7 +4,9 @@
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <X11/keysym.h>
-#include <stdio.h>
+#include <cstdlib>
+#include <cstdio>
+#include <cstring>
 #include <vector>
 #include <string>