diff --git a/extlib/benz/file.c b/extlib/benz/file.c
index d5dc60b9..5032b480 100644
--- a/extlib/benz/file.c
+++ b/extlib/benz/file.c
@@ -35,6 +35,18 @@ int xfclose(pic_state *pic, xFILE *fp) {
   return fp->vtable.close(pic, fp->vtable.cookie);
 }
 
+void xclearerr(pic_state PIC_UNUSED(*pic), xFILE *fp) {
+  fp->flag &= ~(X_EOF | X_ERR);
+}
+
+int xfeof(pic_state PIC_UNUSED(*pic), xFILE *fp) {
+  return (fp->flag & X_EOF) != 0;
+}
+
+int xferror(pic_state PIC_UNUSED(*pic), xFILE *fp) {
+  return (fp->flag & X_ERR) != 0;
+}
+
 int x_fillbuf(pic_state *pic, xFILE *fp) {
   int bufsize;
 
@@ -187,7 +199,7 @@ char *xfgets(pic_state *pic, char *s, int size, xFILE *stream) {
   return (c == EOF && buf == s) ? NULL : s;
 }
 
-int xungetc(int c, xFILE *fp) {
+int xungetc(pic_state PIC_UNUSED(*pic), int c, xFILE *fp) {
   unsigned char uc = c;
 
   if (c == EOF || fp->base == fp->ptr) {
@@ -211,7 +223,7 @@ size_t xfread(pic_state *pic, void *ptr, size_t size, size_t count, xFILE *fp) {
     if ((c = x_fillbuf(pic, fp)) == EOF) {
       return (size * count - nbytes) / size;
     } else {
-      xungetc(c, fp);
+      xungetc(pic, c, fp);
     }
   }
   memcpy(bptr, fp->ptr, nbytes);
@@ -240,6 +252,10 @@ size_t xfwrite(pic_state *pic, const void *ptr, size_t size, size_t count, xFILE
   return count;
 }
 
+#define XSEEK_CUR 0
+#define XSEEK_END 1
+#define XSEEK_SET 2
+
 long xfseek(pic_state *pic, xFILE *fp, long offset, int whence) {
   long s;
 
@@ -535,17 +551,3 @@ xFILE *xfopen_null(pic_state PIC_UNUSED(*pic), const char *mode) {
     return xfunopen(pic, 0, 0, null_write, null_seek, null_close);
   }
 }
-
-#if 0
-int main()
-{
-  char buf[256];
-
-  xgets(buf);
-
-  xprintf("%s\n", buf);
-  xprintf("hello\n");
-  xprintf("hello\n");
-  //  xfflush(0);
-}
-#endif
diff --git a/extlib/benz/include/picrin/file.h b/extlib/benz/include/picrin/file.h
index 2118934c..657fa2e6 100644
--- a/extlib/benz/include/picrin/file.h
+++ b/extlib/benz/include/picrin/file.h
@@ -25,10 +25,6 @@ typedef struct {
   int flag;                     /* mode of the file access */
 } xFILE;
 
-#define xstdin  (&pic->files[0])
-#define xstdout (&pic->files[1])
-#define xstderr (&pic->files[2])
-
 enum {
   X_READ  = 01,
   X_WRITE = 02,
@@ -38,31 +34,28 @@ enum {
   X_LNBUF = 040
 };
 
-#define xclearerr(p) ((p)->flag &= ~(X_EOF | X_ERR))
-#define xfeof(p)     (((p)->flag & X_EOF) != 0)
-#define xferror(p)   (((p)->flag & X_ERR) != 0)
+#define xstdin  (&pic->files[0])
+#define xstdout (&pic->files[1])
+#define xstderr (&pic->files[2])
 
 xFILE *xfunopen(pic_state *, void *cookie, int (*read)(pic_state *, void *, char *, int), int (*write)(pic_state *, void *, const char *, int), long (*seek)(pic_state *, void *, long, int), int (*close)(pic_state *, void *));
+size_t xfread(pic_state *, void *ptr, size_t size, size_t count, xFILE *fp);
+size_t xfwrite(pic_state *, const void *ptr, size_t size, size_t count, xFILE *fp);
+long xfseek(pic_state *, xFILE *fp, long offset, int whence); /* 0:cur, 1:end, 2:set */
+int xfclose(pic_state *, xFILE *fp);
 
-enum {
-  XSEEK_CUR,
-  XSEEK_END,
-  XSEEK_SET
-};
+void xclearerr(pic_state *, xFILE *fp);
+int xfeof(pic_state *, xFILE *fp);
+int xferror(pic_state *, xFILE *fp);
 
-size_t xfread(pic_state *, void *, size_t, size_t, xFILE *);
-size_t xfwrite(pic_state *, const void *, size_t, size_t, xFILE *);
-long xfseek(pic_state *, xFILE *, long, int);
-int xfflush(pic_state *, xFILE *);
-int xfclose(pic_state *, xFILE *);
-
-int xfputc(pic_state *, int, xFILE *);
-int xfgetc(pic_state *, xFILE *);
-int xfputs(pic_state *, const char *, xFILE *);
-char *xfgets(pic_state *, char *, int, xFILE *);
-int xungetc(int, xFILE *);
-int xfprintf(pic_state *, xFILE *, const char *, ...);
-int xvfprintf(pic_state *, xFILE *, const char *, va_list);
+int xfputc(pic_state *, int c, xFILE *fp);
+int xfgetc(pic_state *, xFILE *fp);
+int xfputs(pic_state *, const char *s, xFILE *fp);
+char *xfgets(pic_state *, char *s, int size, xFILE *fp);
+int xungetc(pic_state *, int c, xFILE *fp);
+int xfflush(pic_state *, xFILE *fp);
+int xfprintf(pic_state *, xFILE *fp, const char *fmt, ...);
+int xvfprintf(pic_state *, xFILE *fp, const char *fmt, va_list);
 
 #if PIC_ENABLE_STDIO
 xFILE *xfopen_file(pic_state *, FILE *, const char *mode);
diff --git a/extlib/benz/port.c b/extlib/benz/port.c
index f89abe56..69a564ff 100644
--- a/extlib/benz/port.c
+++ b/extlib/benz/port.c
@@ -199,7 +199,7 @@ pic_port_peek_u8(pic_state *pic)
     return pic_eof_object(pic);
   }
   else {
-    xungetc(c, pic_fileno(pic, port));
+    xungetc(pic, c, pic_fileno(pic, port));
     return pic_int_value(pic, c);
   }
 }
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index ac3deb9f..6d3803fa 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -39,7 +39,7 @@ peek(pic_state *pic, xFILE *file)
 {
   int c;
 
-  xungetc((c = xfgetc(pic, file)), file);
+  xungetc(pic, (c = xfgetc(pic, file)), file);
 
   return c;
 }