diff --git a/Makefile b/Makefile
index 6c80d105..e498d0fd 100644
--- a/Makefile
+++ b/Makefile
@@ -71,7 +71,7 @@ test: test-contribs test-nostdlib test-issue
 test-contribs: bin/picrin $(CONTRIB_TESTS)
 
 test-nostdlib:
-	$(CC) -I extlib/benz/include -D'PIC_ENABLE_LIBC=0' -D'PIC_ENABLE_STDIO=0' -ffreestanding -nostdlib -Os -fPIC -shared -std=c89 -pedantic -Wall -Wextra -Werror -o lib/libbenz-tiny.so $(BENZ_SRCS) etc/libc_polyfill.c -fno-stack-protector
+	$(CC) -I extlib/benz/include -D'PIC_USE_LIBC=0' -D'PIC_USE_STDIO=0' -D'PIC_USE_WRITE=0' -ffreestanding -nostdlib -Os -fPIC -shared -std=c89 -pedantic -Wall -Wextra -Werror -o lib/libbenz-tiny.so $(BENZ_SRCS) etc/libc_polyfill.c -fno-stack-protector
 	strip lib/libbenz-tiny.so
 	ls -lh lib/libbenz-tiny.so
 	rm -f lib/libbenz-tiny.so
diff --git a/extlib/benz/debug.c b/extlib/benz/debug.c
index 043571b9..0a0efa0a 100644
--- a/extlib/benz/debug.c
+++ b/extlib/benz/debug.c
@@ -35,6 +35,8 @@ pic_get_backtrace(pic_state *pic)
   return trace;
 }
 
+#if PIC_USE_WRITE
+
 void
 pic_print_error(pic_state *pic, xFILE *file)
 {
@@ -65,3 +67,5 @@ pic_print_error(pic_state *pic, xFILE *file)
     xfputs(pic, pic_str(pic, pic_obj_value(e->stack)), file);
   }
 }
+
+#endif
diff --git a/extlib/benz/error.c b/extlib/benz/error.c
index 3012fc58..0105215f 100644
--- a/extlib/benz/error.c
+++ b/extlib/benz/error.c
@@ -14,7 +14,7 @@ pic_panic(pic_state *pic, const char *msg)
     pic->panicf(pic, msg);
   }
 
-#if PIC_ENABLE_STDIO
+#if PIC_USE_STDIO
   fprintf(stderr, "picrin panic!: %s\n", msg);
 #endif
 
@@ -26,6 +26,7 @@ pic_panic(pic_state *pic, const char *msg)
 void
 pic_warnf(pic_state *pic, const char *fmt, ...)
 {
+  xFILE *file = pic_fileno(pic, pic_stderr(pic));
   va_list ap;
   pic_value err;
 
@@ -33,7 +34,7 @@ pic_warnf(pic_state *pic, const char *fmt, ...)
   err = pic_vstrf_value(pic, fmt, ap);
   va_end(ap);
 
-  pic_fprintf(pic, pic_stderr(pic), "warn: %s\n", pic_str(pic, err));
+  xfprintf(pic, file, "warn: %s\n", pic_str(pic, err));
 }
 
 void
diff --git a/extlib/benz/file.c b/extlib/benz/file.c
index 9a844acd..7b846b00 100644
--- a/extlib/benz/file.c
+++ b/extlib/benz/file.c
@@ -364,7 +364,7 @@ xFILE *xfile_xstdin(pic_state *pic) { return &pic->files[0]; }
 xFILE *xfile_xstdout(pic_state *pic) { return &pic->files[1]; }
 xFILE *xfile_xstderr(pic_state *pic) { return &pic->files[2]; }
 
-#if PIC_ENABLE_STDIO
+#if PIC_USE_STDIO
 
 static int
 file_read(pic_state *PIC_UNUSED(pic), void *cookie, char *ptr, int size) {
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index f5ecd292..23ddd5e0 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -82,7 +82,7 @@ pic_heap_close(pic_state *pic, struct heap *heap)
   pic_free(pic, heap);
 }
 
-#if PIC_ENABLE_LIBC
+#if PIC_USE_LIBC
 void *
 pic_default_allocf(void *PIC_UNUSED(userdata), void *ptr, size_t size)
 {
diff --git a/extlib/benz/include/picrin/config.h b/extlib/benz/include/picrin/config.h
index e928f95f..eb1c3643 100644
--- a/extlib/benz/include/picrin/config.h
+++ b/extlib/benz/include/picrin/config.h
@@ -2,11 +2,14 @@
  * See Copyright Notice in picrin.h
  */
 
-/** no dependency on libc */
-/* #define PIC_ENABLE_LIBC 1 */
+/** no dependency on libc? */
+/* #define PIC_USE_LIBC 1 */
 
 /** use stdio or not */
-/* #define PIC_ENABLE_STDIO 1 */
+/* #define PIC_USE_STDIO 1 */
+
+/** enable some specific features? */
+/* #define PIC_USE_WRITE 1 */
 
 /** essential external functions */
 /* #define PIC_JMPBUF jmp_buf */
diff --git a/extlib/benz/include/picrin/extra.h b/extlib/benz/include/picrin/extra.h
index 955be4b1..e574e24c 100644
--- a/extlib/benz/include/picrin/extra.h
+++ b/extlib/benz/include/picrin/extra.h
@@ -10,7 +10,7 @@ extern "C" {
 #endif
 
 
-#if PIC_ENABLE_LIBC
+#if PIC_USE_LIBC
 void *pic_default_allocf(void *, void *, size_t);
 #endif
 
@@ -23,9 +23,11 @@ pic_value pic_eval(pic_state *, pic_value program, const char *lib);
 void pic_load(pic_state *, pic_value port);
 void pic_load_cstr(pic_state *, const char *);
 
+#if PIC_USE_WRITE
 void pic_printf(pic_state *, const char *fmt, ...);
 void pic_fprintf(pic_state *, pic_value port, const char *fmt, ...);
 void pic_vfprintf(pic_state *, pic_value port, const char *fmt, va_list ap);
+#endif
 
 /* extra xfile methods */
 
@@ -35,7 +37,7 @@ xFILE *xfile_xstderr(pic_state *);
 #define xstdin  (xfile_xstdin(pic))
 #define xstdout (xfile_xstdout(pic))
 #define xstderr (xfile_xstderr(pic))
-#if PIC_ENABLE_STDIO
+#if PIC_USE_STDIO
 xFILE *xfopen_file(pic_state *, FILE *, const char *mode);
 #endif
 xFILE *xfopen_buf(pic_state *, const char *buf, int len, const char *mode);
@@ -109,7 +111,9 @@ pic_value pic_err(pic_state *);
 
 void pic_warnf(pic_state *, const char *, ...);
 pic_value pic_get_backtrace(pic_state *);
+#if PIC_USE_WRITE
 void pic_print_error(pic_state *, xFILE *);
+#endif
 
 pic_value pic_library_environment(pic_state *, const char *);
 
diff --git a/extlib/benz/include/picrin/setup.h b/extlib/benz/include/picrin/setup.h
index 999a6f96..4fb9e36c 100644
--- a/extlib/benz/include/picrin/setup.h
+++ b/extlib/benz/include/picrin/setup.h
@@ -4,12 +4,16 @@
 
 #include "picrin/config.h"
 
-#ifndef PIC_ENABLE_LIBC
-# define PIC_ENABLE_LIBC 1
+#ifndef PIC_USE_LIBC
+# define PIC_USE_LIBC 1
 #endif
 
-#ifndef PIC_ENABLE_STDIO
-# define PIC_ENABLE_STDIO 1
+#ifndef PIC_USE_STDIO
+# define PIC_USE_STDIO 1
+#endif
+
+#ifndef PIC_USE_WRITE
+# define PIC_USE_WRITE 1
 #endif
 
 #ifndef PIC_JMPBUF
@@ -156,7 +160,7 @@ typedef unsigned long uint32_t;
   } while (0)
 
 
-#if PIC_ENABLE_LIBC
+#if PIC_USE_LIBC
 
 #include <string.h>
 #include <ctype.h>
@@ -375,7 +379,7 @@ atof(const char *nptr)
 
 #endif
 
-#if PIC_ENABLE_STDIO
+#if PIC_USE_STDIO
 # include <stdio.h>
 
 PIC_INLINE void
diff --git a/extlib/benz/lib.c b/extlib/benz/lib.c
index b200b4cb..b65fa3b0 100644
--- a/extlib/benz/lib.c
+++ b/extlib/benz/lib.c
@@ -175,7 +175,7 @@ pic_make_library(pic_state *pic, const char *lib)
 
   it = kh_put(ltable, h, pic_str(pic, name), &ret);
   if (ret == 0) {               /* if exists */
-    pic_error(pic, "library name already in use", pic_cstr_value(pic, lib));
+    pic_error(pic, "library name already in use", 1, pic_cstr_value(pic, lib));
   }
 
   kh_val(h, it).name = pic_str_ptr(pic, name);
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index 373412b8..bbbc28d7 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -168,7 +168,6 @@ pic_init_core(pic_state *pic)
   pic_init_error(pic); DONE;
   pic_init_str(pic); DONE;
   pic_init_var(pic); DONE;
-  pic_init_write(pic); DONE;
   pic_init_read(pic); DONE;
   pic_init_dict(pic); DONE;
   pic_init_record(pic); DONE;
@@ -176,6 +175,10 @@ pic_init_core(pic_state *pic)
   pic_init_lib(pic); DONE;
   pic_init_weak(pic); DONE;
 
+#if PIC_USE_WRITE
+  pic_init_write(pic); DONE;
+#endif
+
   pic_defun(pic, "features", pic_features);
 
   pic_load_cstr(pic, &pic_boot[0][0]);
@@ -275,7 +278,7 @@ pic_open(pic_allocf allocf, void *userdata)
 
   /* file pool */
   memset(pic->files, 0, sizeof pic->files);
-#if PIC_ENABLE_STDIO
+#if PIC_USE_STDIO
   xfopen_file(pic, stdin, "r");
   xfopen_file(pic, stdout, "w");
   xfopen_file(pic, stderr, "w");
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index 78cccb02..b76914d0 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -6,6 +6,8 @@
 #include "picrin/extra.h"
 #include "picrin/private/object.h"
 
+#if PIC_USE_WRITE
+
 struct writer_control {
   int mode;
   int op;
@@ -501,3 +503,5 @@ pic_init_write(pic_state *pic)
   pic_defun(pic, "write-shared", pic_write_write_shared);
   pic_defun(pic, "display", pic_write_display);
 }
+
+#endif