diff --git a/contrib/03.callcc/callcc.c b/contrib/03.callcc/callcc.c
index e366b8e0..eb519331 100644
--- a/contrib/03.callcc/callcc.c
+++ b/contrib/03.callcc/callcc.c
@@ -161,7 +161,7 @@ native_stack_extend(pic_state *pic, struct pic_cont *cont)
   restore_cont(pic, cont);
 }
 
-noreturn static void
+pic_noreturn static void
 restore_cont(pic_state *pic, struct pic_cont *cont)
 {
   char v;
@@ -203,7 +203,7 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
   longjmp(tmp->jmp, 1);
 }
 
-noreturn static pic_value
+pic_noreturn static pic_value
 cont_call(pic_state *pic)
 {
   struct pic_proc *proc;
diff --git a/extlib/benz/codegen.c b/extlib/benz/codegen.c
index f6183278..e43f19c0 100644
--- a/extlib/benz/codegen.c
+++ b/extlib/benz/codegen.c
@@ -492,7 +492,7 @@ analyze_if(analyze_state *state, pic_value obj, bool tailpos)
     pic_errorf(pic, "syntax error");
   case 4:
     if_false = pic_list_ref(pic, obj, 3);
-    FALLTHROUGH;
+    PIC_FALLTHROUGH;
   case 3:
     if_true = pic_list_ref(pic, obj, 2);
   }
diff --git a/extlib/benz/cont.c b/extlib/benz/cont.c
index 4e38e8c6..b1af6eca 100644
--- a/extlib/benz/cont.c
+++ b/extlib/benz/cont.c
@@ -93,7 +93,7 @@ pic_load_point(pic_state *pic, struct pic_escape *escape)
   escape->valid = false;
 }
 
-noreturn static pic_value
+static pic_value
 escape_call(pic_state *pic)
 {
   size_t argc;
diff --git a/extlib/benz/dict.c b/extlib/benz/dict.c
index 81bdea68..ca411551 100644
--- a/extlib/benz/dict.c
+++ b/extlib/benz/dict.c
@@ -14,7 +14,7 @@ xh_value_hash(const void *key, void *data)
   pic_value val = *(pic_value *)key;
   int hash, vtype;
 
-  UNUSED(data);
+  PIC_UNUSED(data);
 
   vtype = pic_vtype(val);
 
@@ -96,7 +96,7 @@ pic_dict_ref(pic_state *pic, struct pic_dict *dict, pic_value key)
 void
 pic_dict_set(pic_state *pic, struct pic_dict *dict, pic_value key, pic_value val)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   xh_put_value(&dict->hash, key, &val);
 }
@@ -104,7 +104,7 @@ pic_dict_set(pic_state *pic, struct pic_dict *dict, pic_value key, pic_value val
 size_t
 pic_dict_size(pic_state *pic, struct pic_dict *dict)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   return dict->hash.count;
 }
@@ -112,7 +112,7 @@ pic_dict_size(pic_state *pic, struct pic_dict *dict)
 bool
 pic_dict_has(pic_state *pic, struct pic_dict *dict, pic_value key)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   return xh_get_value(&dict->hash, key) != NULL;
 }
diff --git a/extlib/benz/error.c b/extlib/benz/error.c
index 3b462969..69c12206 100644
--- a/extlib/benz/error.c
+++ b/extlib/benz/error.c
@@ -17,7 +17,7 @@
 void
 pic_panic(pic_state *pic, const char *msg)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   fprintf(stderr, "abort: %s\n", msg);
   abort();
@@ -69,7 +69,7 @@ pic_errmsg(pic_state *pic)
   return pic_str_cstr(str);
 }
 
-noreturn static pic_value
+static pic_value
 native_exception_handler(pic_state *pic)
 {
   pic_value err;
@@ -83,7 +83,7 @@ native_exception_handler(pic_state *pic)
 
   pic_apply1(pic, cont, pic_false_value());
 
-  UNREACHABLE();
+  PIC_UNREACHABLE();
 }
 
 void
@@ -166,7 +166,7 @@ pic_raise_continuable(pic_state *pic, pic_value err)
   return v;
 }
 
-noreturn void
+void
 pic_raise(pic_state *pic, pic_value err)
 {
   pic_value val;
@@ -178,7 +178,7 @@ pic_raise(pic_state *pic, pic_value err)
   pic_errorf(pic, "error handler returned with ~s on error ~s", val, err);
 }
 
-noreturn void
+void
 pic_throw(pic_state *pic, pic_sym type, const char *msg, pic_value irrs)
 {
   struct pic_error *e;
@@ -188,7 +188,7 @@ pic_throw(pic_state *pic, pic_sym type, const char *msg, pic_value irrs)
   pic_raise(pic, pic_obj_value(e));
 }
 
-noreturn void
+void
 pic_error(pic_state *pic, const char *msg, pic_value irrs)
 {
   pic_throw(pic, pic_intern_cstr(pic, ""), msg, irrs);
@@ -221,7 +221,7 @@ pic_error_with_exception_handler(pic_state *pic)
   return val;
 }
 
-noreturn static pic_value
+static pic_value
 pic_error_raise(pic_state *pic)
 {
   pic_value v;
@@ -241,7 +241,7 @@ pic_error_raise_continuable(pic_state *pic)
   return pic_raise_continuable(pic, v);
 }
 
-noreturn static pic_value
+static pic_value
 pic_error_error(pic_state *pic)
 {
   const char *str;
diff --git a/extlib/benz/file.c b/extlib/benz/file.c
index 4a5f57d7..d438c23a 100644
--- a/extlib/benz/file.c
+++ b/extlib/benz/file.c
@@ -6,7 +6,7 @@
 #include "picrin/port.h"
 #include "picrin/error.h"
 
-static noreturn void
+pic_noreturn static void
 file_error(pic_state *pic, const char *msg)
 {
   pic_throw(pic, pic->sFILE, msg, pic_nil_value());
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index 7768f8b9..633445e8 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -170,7 +170,7 @@ pic_calloc(pic_state *pic, size_t count, size_t size)
 void
 pic_free(pic_state *pic, void *ptr)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   free(ptr);
 }
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 442e06a0..00c1cbe4 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -141,7 +141,7 @@ pic_value pic_gc_protect(pic_state *, pic_value);
 size_t pic_gc_arena_preserve(pic_state *);
 void pic_gc_arena_restore(pic_state *, size_t);
 #define pic_void(exec)                          \
-  pic_void_(GENSYM(ai), exec)
+  pic_void_(PIC_GENSYM(ai), exec)
 #define pic_void_(ai,exec) do {                 \
     size_t ai = pic_gc_arena_preserve(pic);     \
     exec;                                       \
@@ -202,7 +202,7 @@ struct pic_lib *pic_open_library(pic_state *, pic_value);
 struct pic_lib *pic_find_library(pic_state *, pic_value);
 
 #define pic_deflibrary(pic, spec)                                       \
-  pic_deflibrary_helper_(pic, GENSYM(i), GENSYM(prev_lib), spec)
+  pic_deflibrary_helper_(pic, PIC_GENSYM(i), PIC_GENSYM(prev_lib), spec)
 #define pic_deflibrary_helper_(pic, i, prev_lib, spec)                  \
   for (int i = 0; ! i; )                                                \
     for (struct pic_lib *prev_lib; ! i; )                               \
@@ -212,8 +212,8 @@ void pic_import(pic_state *, pic_value);
 void pic_import_library(pic_state *, struct pic_lib *);
 void pic_export(pic_state *, pic_sym);
 
-noreturn void pic_panic(pic_state *, const char *);
-noreturn void pic_errorf(pic_state *, const char *, ...);
+pic_noreturn void pic_panic(pic_state *, const char *);
+pic_noreturn void pic_errorf(pic_state *, const char *, ...);
 void pic_warnf(pic_state *, const char *, ...);
 const char *pic_errmsg(pic_state *);
 pic_str *pic_get_backtrace(pic_state *);
diff --git a/extlib/benz/include/picrin/error.h b/extlib/benz/include/picrin/error.h
index 784b95f8..e4cc630a 100644
--- a/extlib/benz/include/picrin/error.h
+++ b/extlib/benz/include/picrin/error.h
@@ -27,7 +27,7 @@ struct pic_error *pic_make_error(pic_state *, pic_sym, const char *, pic_list);
 /* do not return from try block! */
 
 #define pic_try                                 \
-  pic_try_(GENSYM(escape))
+  pic_try_(PIC_GENSYM(escape))
 #define pic_try_(escape)                                                \
   struct pic_escape *escape = pic_alloc(pic, sizeof(struct pic_escape)); \
   pic_save_point(pic, escape);                                          \
@@ -43,9 +43,9 @@ void pic_push_try(pic_state *, struct pic_escape *);
 void pic_pop_try(pic_state *);
 
 pic_value pic_raise_continuable(pic_state *, pic_value);
-noreturn void pic_raise(pic_state *, pic_value);
-noreturn void pic_throw(pic_state *, pic_sym, const char *, pic_list);
-noreturn void pic_error(pic_state *, const char *, pic_list);
+pic_noreturn void pic_raise(pic_state *, pic_value);
+pic_noreturn void pic_throw(pic_state *, pic_sym, const char *, pic_list);
+pic_noreturn void pic_error(pic_state *, const char *, pic_list);
 
 #if defined(__cplusplus)
 }
diff --git a/extlib/benz/include/picrin/pair.h b/extlib/benz/include/picrin/pair.h
index d489b765..11859482 100644
--- a/extlib/benz/include/picrin/pair.h
+++ b/extlib/benz/include/picrin/pair.h
@@ -59,9 +59,9 @@ pic_value pic_list7(pic_state *, pic_value, pic_value, pic_value, pic_value, pic
 pic_value pic_list_by_array(pic_state *, size_t, pic_value *);
 pic_value pic_make_list(pic_state *, size_t, pic_value);
 
-#define pic_for_each(var, list)                                 \
-  pic_for_each_helper_(var, GENSYM(tmp), list)
-#define pic_for_each_helper_(var, tmp, list)                           \
+#define pic_for_each(var, list)                         \
+  pic_for_each_helper_(var, PIC_GENSYM(tmp), list)
+#define pic_for_each_helper_(var, tmp, list)                            \
   for (pic_value tmp = (list);                                          \
        pic_nil_p(tmp) ? false : ((var = pic_car(pic, tmp)), true);      \
        tmp = pic_cdr(pic, tmp))
diff --git a/extlib/benz/include/picrin/util.h b/extlib/benz/include/picrin/util.h
index d56cd9f6..afa0e037 100644
--- a/extlib/benz/include/picrin/util.h
+++ b/extlib/benz/include/picrin/util.h
@@ -11,33 +11,34 @@ extern "C" {
 
 #if __STDC_VERSION__ >= 201112L
 # include <stdnoreturn.h>
+# define pic_noreturn noreturn
 #elif __GNUC__ || __clang__
-# define noreturn __attribute__((noreturn))
+# define pic_noreturn __attribute__((noreturn))
 #else
-# define noreturn
+# define pic_noreturn
 #endif
 
-#define FALLTHROUGH ((void)0)
-#define UNUSED(v) ((void)(v))
+#define PIC_FALLTHROUGH ((void)0)
+#define PIC_UNUSED(v) ((void)(v))
 
-#define GENSYM2_(x,y) G##x##_##y##__
-#define GENSYM1_(x,y) GENSYM2_(x,y)
+#define PIC_GENSYM2_(x,y) PIC_G##x##_##y##_
+#define PIC_GENSYM1_(x,y) PIC_GENSYM2_(x,y)
 #if defined(__COUNTER__)
-# define GENSYM(x) GENSYM1_(__COUNTER__,x)
+# define PIC_GENSYM(x) PIC_GENSYM1_(__COUNTER__,x)
 #else
-# define GENSYM(x) GENSYM1_(__LINE__,x)
+# define PIC_GENSYM(x) PIC_GENSYM1_(__LINE__,x)
 #endif
 
 #if GCC_VERSION >= 40500 || __clang__
-# define UNREACHABLE() (__builtin_unreachable())
+# define PIC_UNREACHABLE() (__builtin_unreachable())
 #else
 # include <assert.h>
-# define UNREACHABLE() (assert(false))
+# define PIC_UNREACHABLE() (assert(false))
 #endif
 
-#define SWAP(type,a,b)                          \
-  SWAP_HELPER_(type,GENSYM(tmp),a,b)
-#define SWAP_HELPER_(type,tmp,a,b)             \
+#define PIC_SWAP(type,a,b)                      \
+  PIC_SWAP_HELPER_(type, PIC_GENSYM(tmp), a, b)
+#define PIC_SWAP_HELPER_(type,tmp,a,b)          \
   do {                                          \
     type tmp = (a);                             \
     (a) = (b);                                  \
diff --git a/extlib/benz/include/picrin/value.h b/extlib/benz/include/picrin/value.h
index 709fcf77..d21a8418 100644
--- a/extlib/benz/include/picrin/value.h
+++ b/extlib/benz/include/picrin/value.h
@@ -225,7 +225,7 @@ pic_type(pic_value v)
     return ((struct pic_object *)pic_ptr(v))->tt;
   }
 
-  UNREACHABLE();
+  PIC_UNREACHABLE();
 }
 
 static inline const char *
@@ -279,7 +279,7 @@ pic_type_repr(enum pic_tt tt)
   case PIC_TT_RECORD:
     return "record";
   }
-  UNREACHABLE();
+  PIC_UNREACHABLE();
 }
 
 static inline bool
diff --git a/extlib/benz/macro.c b/extlib/benz/macro.c
index c7cd243f..eb811253 100644
--- a/extlib/benz/macro.c
+++ b/extlib/benz/macro.c
@@ -25,7 +25,7 @@ pic_add_rename(pic_state *pic, struct pic_senv *senv, pic_sym sym)
 void
 pic_put_rename(pic_state *pic, struct pic_senv *senv, pic_sym sym, pic_sym rename)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   xh_put_int(&senv->map, sym, &rename);
 }
@@ -35,7 +35,7 @@ pic_find_rename(pic_state *pic, struct pic_senv *senv, pic_sym sym, pic_sym *ren
 {
   xh_entry *e;
 
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   if ((e = xh_get_int(&senv->map, sym)) == NULL) {
     return false;
diff --git a/extlib/benz/proc.c b/extlib/benz/proc.c
index 210f157d..2b94201b 100644
--- a/extlib/benz/proc.c
+++ b/extlib/benz/proc.c
@@ -43,7 +43,7 @@ pic_proc_name(struct pic_proc *proc)
   case PIC_PROC_KIND_IREP:
     return proc->u.irep->name;
   }
-  UNREACHABLE();
+  PIC_UNREACHABLE();
 }
 
 static pic_value
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index be160c0d..46a056f8 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -18,7 +18,7 @@
 static pic_value read(pic_state *pic, struct pic_port *port, int c);
 static pic_value read_nullable(pic_state *pic, struct pic_port *port, int c);
 
-static noreturn void
+pic_noreturn static void
 read_error(pic_state *pic, const char *msg)
 {
   pic_throw(pic, pic->sREAD, msg, pic_nil_value());
@@ -86,8 +86,8 @@ read_comment(pic_state *pic, struct pic_port *port, const char *str)
 {
   int c;
 
-  UNUSED(pic);
-  UNUSED(str);
+  PIC_UNUSED(pic);
+  PIC_UNUSED(str);
 
   do {
     c = next(port);
@@ -102,8 +102,8 @@ read_block_comment(pic_state *pic, struct pic_port *port, const char *str)
   int x, y;
   int i = 1;
 
-  UNUSED(pic);
-  UNUSED(str);
+  PIC_UNUSED(pic);
+  PIC_UNUSED(str);
 
   y = next(port);
 
@@ -124,7 +124,7 @@ read_block_comment(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_datum_comment(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   read(pic, port, next(port));
 
@@ -157,7 +157,7 @@ read_eval(pic_state *pic, struct pic_port *port, const char *str)
 {
   pic_value form;
 
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   form = read(pic, port, next(port));
 
@@ -167,7 +167,7 @@ read_eval(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_quote(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   return pic_list2(pic, pic_sym_value(pic->sQUOTE), read(pic, port, next(port)));
 }
@@ -175,7 +175,7 @@ read_quote(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_quasiquote(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   return pic_list2(pic, pic_sym_value(pic->sQUASIQUOTE), read(pic, port, next(port)));
 }
@@ -183,7 +183,7 @@ read_quasiquote(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_unquote(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   return pic_list2(pic, pic_sym_value(pic->sUNQUOTE), read(pic, port, next(port)));
 }
@@ -191,7 +191,7 @@ read_unquote(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_unquote_splicing(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   return pic_list2(pic, pic_sym_value(pic->sUNQUOTE_SPLICING), read(pic, port, next(port)));
 }
@@ -354,9 +354,9 @@ read_plus(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_true(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(pic);
-  UNUSED(port);
-  UNUSED(str);
+  PIC_UNUSED(pic);
+  PIC_UNUSED(port);
+  PIC_UNUSED(str);
 
   return pic_true_value();
 }
@@ -364,9 +364,9 @@ read_true(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_false(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(pic);
-  UNUSED(port);
-  UNUSED(str);
+  PIC_UNUSED(pic);
+  PIC_UNUSED(port);
+  PIC_UNUSED(str);
 
   return pic_false_value();
 }
@@ -376,7 +376,7 @@ read_char(pic_state *pic, struct pic_port *port, const char *str)
 {
   int c;
 
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   c = next(port);
 
@@ -418,7 +418,7 @@ read_string(pic_state *pic, struct pic_port *port, const char *name)
   size_t size, cnt;
   pic_str *str;
 
-  UNUSED(name);
+  PIC_UNUSED(name);
 
   size = 256;
   buf = pic_alloc(pic, size);
@@ -459,7 +459,7 @@ read_pipe(pic_state *pic, struct pic_port *port, const char *str)
   size_t i = 0;
   int c;
 
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   size = 256;
   buf = pic_alloc(pic, size);
@@ -504,7 +504,7 @@ read_blob(pic_state *pic, struct pic_port *port, const char *str)
   unsigned char *dat;
   pic_blob *blob;
 
-  UNUSED(str);
+  PIC_UNUSED(str);
 
   nbits = 0;
 
@@ -631,13 +631,13 @@ read_label_set(pic_state *pic, struct pic_port *port, int i)
         xh_put_int(&pic->reader->labels, i, &val);
 
         tmp = pic_vec_ptr(read(pic, port, c));
-        SWAP(pic_value *, tmp->data, pic_vec_ptr(val)->data);
-        SWAP(size_t, tmp->len, pic_vec_ptr(val)->len);
+        PIC_SWAP(pic_value *, tmp->data, pic_vec_ptr(val)->data);
+        PIC_SWAP(size_t, tmp->len, pic_vec_ptr(val)->len);
 
         return val;
       }
 
-      FALLTHROUGH;
+      PIC_FALLTHROUGH;
     }
   default:
     {
@@ -655,7 +655,7 @@ read_label_ref(pic_state *pic, struct pic_port *port, int i)
 {
   xh_entry *e;
 
-  UNUSED(port);
+  PIC_UNUSED(port);
 
   e = xh_get_int(&pic->reader->labels, i);
   if (! e) {
@@ -687,8 +687,8 @@ read_label(pic_state *pic, struct pic_port *port, const char *str)
 static pic_value
 read_unmatch(pic_state *pic, struct pic_port *port, const char *str)
 {
-  UNUSED(port);
-  UNUSED(str);
+  PIC_UNUSED(port);
+  PIC_UNUSED(str);
 
   read_error(pic, "unmatched parenthesis");
 }
diff --git a/extlib/benz/record.c b/extlib/benz/record.c
index 52fbe050..7ba4be29 100644
--- a/extlib/benz/record.c
+++ b/extlib/benz/record.c
@@ -39,7 +39,7 @@ pic_record_ref(pic_state *pic, struct pic_record *rec, pic_sym slot)
 void
 pic_record_set(pic_state *pic, struct pic_record *rec, pic_sym slot, pic_value val)
 {
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   xh_put_int(&rec->hash, slot, &val);
 }
diff --git a/extlib/benz/var.c b/extlib/benz/var.c
index ea9cbff5..84ecda61 100644
--- a/extlib/benz/var.c
+++ b/extlib/benz/var.c
@@ -73,7 +73,7 @@ var_call(pic_state *pic)
       return val;
     }
   }
-  UNREACHABLE();
+  PIC_UNREACHABLE();
 }
 
 struct pic_proc *
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index fb01addc..dde4b3a7 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -164,7 +164,7 @@ write_str(pic_state *pic, struct pic_string *str, xFILE *file)
   size_t i;
   const char *cstr = pic_str_cstr(str);
 
-  UNUSED(pic);
+  PIC_UNUSED(pic);
 
   for (i = 0; i < pic_strlen(str); ++i) {
     if (cstr[i] == '"' || cstr[i] == '\\') {