diff --git a/contrib/20.r7rs/src/mutable-string.c b/contrib/20.r7rs/src/mutable-string.c
index 0f5817d7..9458ef15 100644
--- a/contrib/20.r7rs/src/mutable-string.c
+++ b/contrib/20.r7rs/src/mutable-string.c
@@ -1,9 +1,9 @@
 #include "picrin.h"
 
 void
-pic_str_set(pic_state *pic, pic_str *str, int i, char c)
+pic_str_set(pic_state *pic, struct pic_string *str, int i, char c)
 {
-  pic_str *x, *y, *z, *tmp;
+  struct pic_string *x, *y, *z, *tmp;
   char buf[1];
 
   if (pic_str_len(str) <= i) {
@@ -26,7 +26,7 @@ pic_str_set(pic_state *pic, pic_str *str, int i, char c)
 static pic_value
 pic_str_string_set(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   char c;
   int k;
 
@@ -39,7 +39,7 @@ pic_str_string_set(pic_state *pic)
 static pic_value
 pic_str_string_copy_ip(pic_state *pic)
 {
-  pic_str *to, *from;
+  struct pic_string *to, *from;
   int n, at, start, end;
 
   n = pic_get_args(pic, "sis|ii", &to, &at, &from, &start, &end);
@@ -63,7 +63,7 @@ pic_str_string_copy_ip(pic_state *pic)
 static pic_value
 pic_str_string_fill_ip(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   char c;
   int n, start, end;
 
diff --git a/contrib/20.r7rs/src/system.c b/contrib/20.r7rs/src/system.c
index 7cda6527..09ba6e76 100644
--- a/contrib/20.r7rs/src/system.c
+++ b/contrib/20.r7rs/src/system.c
@@ -105,7 +105,7 @@ pic_system_getenvs(pic_state *pic)
   }
 
   for (envp = picrin_envp; *envp; ++envp) {
-    pic_str *key, *val;
+    struct pic_string *key, *val;
     int i;
 
     for (i = 0; (*envp)[i] != '='; ++i)
diff --git a/contrib/30.regexp/src/regexp.c b/contrib/30.regexp/src/regexp.c
index 2af663dd..481a703d 100644
--- a/contrib/30.regexp/src/regexp.c
+++ b/contrib/30.regexp/src/regexp.c
@@ -82,7 +82,7 @@ pic_regexp_regexp_match(pic_state *pic)
   const char *input;
   regmatch_t match[100];
   pic_value matches, positions;
-  pic_str *str;
+  struct pic_string *str;
   int i, offset;
 
   pic_get_args(pic, "oz", &reg, &input);
@@ -157,7 +157,7 @@ pic_regexp_regexp_replace(pic_state *pic)
   pic_value reg;
   const char *input;
   regmatch_t match;
-  pic_str *txt, *output = pic_make_lit(pic, "");
+  struct pic_string *txt, *output = pic_make_lit(pic, "");
 
   pic_get_args(pic, "ozs", &reg, &input, &txt);
 
diff --git a/extlib/benz/blob.c b/extlib/benz/blob.c
index b4acfc67..c7cbff9f 100644
--- a/extlib/benz/blob.c
+++ b/extlib/benz/blob.c
@@ -30,7 +30,7 @@ pic_blob_bytevector(pic_state *pic)
 {
   pic_value *argv;
   int argc, i;
-  pic_blob *blob;
+  struct pic_blob *blob;
   unsigned char *data;
 
   pic_get_args(pic, "*", &argc, &argv);
@@ -55,7 +55,7 @@ pic_blob_bytevector(pic_state *pic)
 static pic_value
 pic_blob_make_bytevector(pic_state *pic)
 {
-  pic_blob *blob;
+  struct pic_blob *blob;
   int k, i, b = 0;
 
   pic_get_args(pic, "i|i", &k, &b);
@@ -110,7 +110,7 @@ pic_blob_bytevector_u8_set(pic_state *pic)
 static pic_value
 pic_blob_bytevector_copy_i(pic_state *pic)
 {
-  pic_blob *to, *from;
+  struct pic_blob *to, *from;
   int n, at, start, end;
 
   n = pic_get_args(pic, "bib|ii", &to, &at, &from, &start, &end);
@@ -141,7 +141,7 @@ pic_blob_bytevector_copy_i(pic_state *pic)
 static pic_value
 pic_blob_bytevector_copy(pic_state *pic)
 {
-  pic_blob *from, *to;
+  struct pic_blob *from, *to;
   int n, start, end, i = 0;
 
   n = pic_get_args(pic, "b|ii", &from, &start, &end);
@@ -170,7 +170,7 @@ pic_blob_bytevector_append(pic_state *pic)
 {
   int argc, i, j, len;
   pic_value *argv;
-  pic_blob *blob;
+  struct pic_blob *blob;
 
   pic_get_args(pic, "*", &argc, &argv);
 
@@ -196,7 +196,7 @@ pic_blob_bytevector_append(pic_state *pic)
 static pic_value
 pic_blob_list_to_bytevector(pic_state *pic)
 {
-  pic_blob *blob;
+  struct pic_blob *blob;
   unsigned char *data;
   pic_value list, e, it;
 
@@ -220,7 +220,7 @@ pic_blob_list_to_bytevector(pic_state *pic)
 static pic_value
 pic_blob_bytevector_to_list(pic_state *pic)
 {
-  pic_blob *blob;
+  struct pic_blob *blob;
   pic_value list;
   int n, start, end, i;
 
diff --git a/extlib/benz/bool.c b/extlib/benz/bool.c
index 6e5a39b7..e54a8988 100644
--- a/extlib/benz/bool.c
+++ b/extlib/benz/bool.c
@@ -54,7 +54,7 @@ internal_equal_p(pic_state *pic, pic_value x, pic_value y, int depth, khash_t(m)
     return pic_str_cmp(pic, pic_str_ptr(x), pic_str_ptr(y)) == 0;
   }
   case PIC_TT_BLOB: {
-    pic_blob *blob1, *blob2;
+    struct pic_blob *blob1, *blob2;
     int i;
 
     blob1 = pic_blob_ptr(x);
diff --git a/extlib/benz/debug.c b/extlib/benz/debug.c
index fb1cb197..106be269 100644
--- a/extlib/benz/debug.c
+++ b/extlib/benz/debug.c
@@ -4,12 +4,12 @@
 
 #include "picrin.h"
 
-pic_str *
+struct pic_string *
 pic_get_backtrace(pic_state *pic)
 {
   size_t ai = pic_gc_arena_preserve(pic);
   pic_callinfo *ci;
-  pic_str *trace;
+  struct pic_string *trace;
 
   trace = pic_make_lit(pic, "");
 
diff --git a/extlib/benz/error.c b/extlib/benz/error.c
index 2c68b5f1..3a3af27e 100644
--- a/extlib/benz/error.c
+++ b/extlib/benz/error.c
@@ -21,7 +21,7 @@ void
 pic_warnf(pic_state *pic, const char *fmt, ...)
 {
   va_list ap;
-  pic_str *err;
+  struct pic_string *err;
 
   va_start(ap, fmt);
   err = pic_vformat(pic, fmt, ap);
@@ -35,7 +35,7 @@ pic_errorf(pic_state *pic, const char *fmt, ...)
 {
   va_list ap;
   const char *msg;
-  pic_str *err;
+  struct pic_string *err;
 
   va_start(ap, fmt);
   err = pic_vformat(pic, fmt, ap);
@@ -94,7 +94,7 @@ struct pic_error *
 pic_make_error(pic_state *pic, pic_sym *type, const char *msg, pic_value irrs)
 {
   struct pic_error *e;
-  pic_str *stack;
+  struct pic_string *stack;
 
   stack = pic_get_backtrace(pic);
 
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 8d6f035c..39d9d0f0 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -47,7 +47,7 @@ typedef void *(*pic_allocf)(void *, void *, size_t);
 #include "picrin/read.h"
 #include "picrin/gc.h"
 
-KHASH_DECLARE(s, pic_str *, pic_sym *)
+KHASH_DECLARE(s, struct pic_string *, pic_sym *)
 
 typedef struct pic_checkpoint {
   PIC_OBJECT_HEADER
@@ -247,19 +247,19 @@ void pic_weak_del(pic_state *, struct pic_weak *, void *);
 bool pic_weak_has(pic_state *, struct pic_weak *, void *);
 
 /* symbol */
-pic_sym *pic_intern(pic_state *, pic_str *);
+pic_sym *pic_intern(pic_state *, struct pic_string *);
 #define pic_intern_str(pic,s,i) pic_intern(pic, pic_make_str(pic, (s), (i)))
 #define pic_intern_cstr(pic,s) pic_intern(pic, pic_make_cstr(pic, (s)))
 #define pic_intern_lit(pic,lit) pic_intern(pic, pic_make_lit(pic, lit))
 const char *pic_symbol_name(pic_state *, pic_sym *);
 
 /* string */
-int pic_str_len(pic_str *);
-char pic_str_ref(pic_state *, pic_str *, int);
-pic_str *pic_str_cat(pic_state *, pic_str *, pic_str *);
-pic_str *pic_str_sub(pic_state *, pic_str *, int, int);
-int pic_str_cmp(pic_state *, pic_str *, pic_str *);
-int pic_str_hash(pic_state *, pic_str *);
+int pic_str_len(struct pic_string *);
+char pic_str_ref(pic_state *, struct pic_string *, int);
+struct pic_string *pic_str_cat(pic_state *, struct pic_string *, struct pic_string *);
+struct pic_string *pic_str_sub(pic_state *, struct pic_string *, int, int);
+int pic_str_cmp(pic_state *, struct pic_string *, struct pic_string *);
+int pic_str_hash(pic_state *, struct pic_string *);
 
 #include "picrin/blob.h"
 #include "picrin/cont.h"
@@ -313,7 +313,7 @@ struct pic_proc *pic_make_var(pic_state *, pic_value, struct pic_proc *);
         (pic->prev_lib = NULL)))
 
 void pic_warnf(pic_state *, const char *, ...);
-pic_str *pic_get_backtrace(pic_state *);
+struct pic_string *pic_get_backtrace(pic_state *);
 void pic_print_backtrace(pic_state *, xFILE *);
 
 struct pic_port *pic_stdin(pic_state *);
diff --git a/extlib/benz/include/picrin/error.h b/extlib/benz/include/picrin/error.h
index 540cae65..36e35409 100644
--- a/extlib/benz/include/picrin/error.h
+++ b/extlib/benz/include/picrin/error.h
@@ -12,9 +12,9 @@ extern "C" {
 struct pic_error {
   PIC_OBJECT_HEADER
   pic_sym *type;
-  pic_str *msg;
+  struct pic_string *msg;
   pic_value irrs;
-  pic_str *stack;
+  struct pic_string *stack;
 };
 
 #define pic_error_p(v) (pic_type(v) == PIC_TT_ERROR)
diff --git a/extlib/benz/include/picrin/macro.h b/extlib/benz/include/picrin/macro.h
index 5076f367..e52196ff 100644
--- a/extlib/benz/include/picrin/macro.h
+++ b/extlib/benz/include/picrin/macro.h
@@ -15,13 +15,13 @@ struct pic_env {
   PIC_OBJECT_HEADER
   khash_t(env) map;
   struct pic_env *up;
-  pic_str *prefix;
+  struct pic_string *prefix;
 };
 
 #define pic_env_p(v) (pic_type(v) == PIC_TT_ENV)
 #define pic_env_ptr(v) ((struct pic_env *)pic_ptr(v))
 
-struct pic_env *pic_make_topenv(pic_state *, pic_str *);
+struct pic_env *pic_make_topenv(pic_state *, struct pic_string *);
 struct pic_env *pic_make_env(pic_state *, struct pic_env *);
 
 pic_sym *pic_add_identifier(pic_state *, pic_id *, struct pic_env *);
diff --git a/extlib/benz/include/picrin/string.h b/extlib/benz/include/picrin/string.h
index f5c32314..f9b44fbc 100644
--- a/extlib/benz/include/picrin/string.h
+++ b/extlib/benz/include/picrin/string.h
@@ -19,14 +19,14 @@ void pic_rope_decref(pic_state *, struct pic_rope *);
 
 #define pic_str_ptr(o) ((struct pic_string *)pic_ptr(o))
 
-pic_str *pic_make_str(pic_state *, const char *, int);
+struct pic_string *pic_make_str(pic_state *, const char *, int);
 #define pic_make_cstr(pic, cstr) pic_make_str(pic, (cstr), strlen(cstr))
 #define pic_make_lit(pic, lit) pic_make_str(pic, "" lit, -((int)sizeof lit - 1))
 
-const char *pic_str_cstr(pic_state *, pic_str *);
+const char *pic_str_cstr(pic_state *, struct pic_string *);
 
-pic_str *pic_format(pic_state *, const char *, ...);
-pic_str *pic_vformat(pic_state *, const char *, va_list);
+struct pic_string *pic_format(pic_state *, const char *, ...);
+struct pic_string *pic_vformat(pic_state *, const char *, va_list);
 
 #if defined(__cplusplus)
 }
diff --git a/extlib/benz/include/picrin/symbol.h b/extlib/benz/include/picrin/symbol.h
index b390a7cc..3c905cd9 100644
--- a/extlib/benz/include/picrin/symbol.h
+++ b/extlib/benz/include/picrin/symbol.h
@@ -13,7 +13,7 @@ struct pic_id {
   union {
     struct pic_symbol {
       PIC_OBJECT_HEADER
-      pic_str *str;
+      struct pic_string *str;
     } sym;
     struct {
       PIC_OBJECT_HEADER
diff --git a/extlib/benz/include/picrin/type.h b/extlib/benz/include/picrin/type.h
index a3e9ed78..f6cda486 100644
--- a/extlib/benz/include/picrin/type.h
+++ b/extlib/benz/include/picrin/type.h
@@ -202,9 +202,7 @@ struct pic_env;
 typedef struct pic_symbol pic_sym;
 typedef struct pic_id pic_id;
 typedef struct pic_pair pic_pair;
-typedef struct pic_string pic_str;
 typedef struct pic_vector pic_vec;
-typedef struct pic_blob pic_blob;
 
 #define pic_obj_p(v) (pic_vtype(v) == PIC_VTYPE_HEAP)
 #define pic_obj_ptr(v) ((struct pic_object *)pic_ptr(v))
diff --git a/extlib/benz/lib.c b/extlib/benz/lib.c
index 0faac96b..1bf6444b 100644
--- a/extlib/benz/lib.c
+++ b/extlib/benz/lib.c
@@ -9,7 +9,7 @@ make_library_env(pic_state *pic, pic_value name)
 {
   struct pic_env *env;
   pic_value dir, it;
-  pic_str *prefix = NULL;
+  struct pic_string *prefix = NULL;
 
   pic_for_each (dir, name, it) {
     if (prefix == NULL) {
diff --git a/extlib/benz/macro.c b/extlib/benz/macro.c
index 8646986d..27bd76e0 100644
--- a/extlib/benz/macro.c
+++ b/extlib/benz/macro.c
@@ -21,7 +21,7 @@ pic_make_env(pic_state *pic, struct pic_env *up)
 }
 
 struct pic_env *
-pic_make_topenv(pic_state *pic, pic_str *prefix)
+pic_make_topenv(pic_state *pic, struct pic_string *prefix)
 {
   struct pic_env *env;
 
@@ -37,7 +37,7 @@ pic_add_identifier(pic_state *pic, pic_id *id, struct pic_env *env)
 {
   const char *name;
   pic_sym *uid;
-  pic_str *str;
+  struct pic_string *str;
 
   name = pic_identifier_name(pic, id);
 
diff --git a/extlib/benz/number.c b/extlib/benz/number.c
index 035528b3..32f86608 100644
--- a/extlib/benz/number.c
+++ b/extlib/benz/number.c
@@ -218,7 +218,7 @@ pic_number_number_to_string(pic_state *pic)
   double f;
   bool e;
   int radix = 10;
-  pic_str *str;
+  struct pic_string *str;
 
   pic_get_args(pic, "F|i", &f, &e, &radix);
 
diff --git a/extlib/benz/port.c b/extlib/benz/port.c
index 504b48ad..1cad0ed8 100644
--- a/extlib/benz/port.c
+++ b/extlib/benz/port.c
@@ -546,7 +546,7 @@ static pic_value
 pic_port_get_output_bytevector(pic_state *pic)
 {
   struct pic_port *port = pic_stdout(pic);
-  pic_blob *blob;
+  struct pic_blob *blob;
   struct strfile *s;
 
   pic_get_args(pic, "|p", &port);
@@ -646,7 +646,7 @@ pic_port_char_ready_p(pic_state *pic)
 static pic_value
 pic_port_read_string(pic_state *pic){
   struct pic_port *port = pic_stdin(pic), *buf;
-  pic_str *str;
+  struct pic_string *str;
   int k, i;
   int c;
   pic_value res = pic_eof_object();
@@ -725,7 +725,7 @@ static pic_value
 pic_port_read_blob(pic_state *pic)
 {
   struct pic_port *port = pic_stdin(pic);
-  pic_blob *blob;
+  struct pic_blob *blob;
   int k, i;
 
   pic_get_args(pic, "i|p", &k, &port);
diff --git a/extlib/benz/proc.c b/extlib/benz/proc.c
index 8d209418..62dd9ba3 100644
--- a/extlib/benz/proc.c
+++ b/extlib/benz/proc.c
@@ -19,10 +19,10 @@
  *  F   double *, bool *        float with exactness
  *  c   char *                  char
  *  z   char **                 c string
- *  s   pic_str **              string object
  *  m   pic_sym **              symbol
  *  v   pic_vec **              vector object
- *  b   pic_blob **             bytevector object
+ *  s   struct pic_str **       string object
+ *  b   struct pic_blob **      bytevector object
  *  l   struct pic_proc **      lambda object
  *  p   struct pic_port **      port object
  *  d   struct pic_dict **      dictionary object
@@ -146,10 +146,10 @@ pic_get_args(pic_state *pic, const char *format, ...)
 #define PTR_CASE(c, type, ctype)                        \
       VAL_CASE(c, type, ctype, pic_## type ##_ptr(v))
 
-    PTR_CASE('s', str, pic_str *)
     PTR_CASE('m', sym, pic_sym *)
     PTR_CASE('v', vec, pic_vec *)
-    PTR_CASE('b', blob, pic_blob *)
+    PTR_CASE('s', str, struct pic_string *)
+    PTR_CASE('b', blob, struct pic_blob *)
     PTR_CASE('l', proc, struct pic_proc *)
     PTR_CASE('p', port, struct pic_port *)
     PTR_CASE('d', dict, struct pic_dict *)
diff --git a/extlib/benz/read.c b/extlib/benz/read.c
index 1fb6a713..84522faa 100644
--- a/extlib/benz/read.c
+++ b/extlib/benz/read.c
@@ -419,7 +419,7 @@ read_string(pic_state *pic, struct pic_port *port, int c)
 {
   char *buf;
   int size, cnt;
-  pic_str *str;
+  struct pic_string *str;
 
   size = 256;
   buf = pic_malloc(pic, size);
@@ -499,7 +499,7 @@ read_blob(pic_state *pic, struct pic_port *port, int c)
   int nbits, n;
   int len, i;
   unsigned char *dat;
-  pic_blob *blob;
+  struct pic_blob *blob;
 
   nbits = 0;
 
diff --git a/extlib/benz/string.c b/extlib/benz/string.c
index dc5dcb9e..c838fa6a 100644
--- a/extlib/benz/string.c
+++ b/extlib/benz/string.c
@@ -93,12 +93,12 @@ pic_make_rope(pic_state *pic, struct pic_chunk *c)
   return x;
 }
 
-static pic_str *
+static struct pic_string *
 pic_make_string(pic_state *pic, struct pic_rope *rope)
 {
-  pic_str *str;
+  struct pic_string *str;
 
-  str = (pic_str *)pic_obj_alloc(pic, sizeof(pic_str), PIC_TT_STRING);
+  str = (struct pic_string *)pic_obj_alloc(pic, sizeof(struct pic_string), PIC_TT_STRING);
   str->rope = rope;             /* delegate ownership */
   return str;
 }
@@ -236,7 +236,7 @@ rope_cstr(pic_state *pic, struct pic_rope *x)
   return c->str;
 }
 
-pic_str *
+struct pic_string *
 pic_make_str(pic_state *pic, const char *str, int len)
 {
   struct pic_chunk *c;
@@ -253,13 +253,13 @@ pic_make_str(pic_state *pic, const char *str, int len)
 }
 
 int
-pic_str_len(pic_str *str)
+pic_str_len(struct pic_string *str)
 {
   return rope_len(str->rope);
 }
 
 char
-pic_str_ref(pic_state *pic, pic_str *str, int i)
+pic_str_ref(pic_state *pic, struct pic_string *str, int i)
 {
   int c;
 
@@ -270,26 +270,26 @@ pic_str_ref(pic_state *pic, pic_str *str, int i)
   return (char)c;
 }
 
-pic_str *
-pic_str_cat(pic_state *pic, pic_str *a, pic_str *b)
+struct pic_string *
+pic_str_cat(pic_state *pic, struct pic_string *a, struct pic_string *b)
 {
   return pic_make_string(pic, rope_cat(pic, a->rope, b->rope));
 }
 
-pic_str *
-pic_str_sub(pic_state *pic, pic_str *str, int s, int e)
+struct pic_string *
+pic_str_sub(pic_state *pic, struct pic_string *str, int s, int e)
 {
   return pic_make_string(pic, rope_sub(pic, str->rope, s, e));
 }
 
 int
-pic_str_cmp(pic_state *pic, pic_str *str1, pic_str *str2)
+pic_str_cmp(pic_state *pic, struct pic_string *str1, struct pic_string *str2)
 {
   return strcmp(pic_str_cstr(pic, str1), pic_str_cstr(pic, str2));
 }
 
 int
-pic_str_hash(pic_state *pic, pic_str *str)
+pic_str_hash(pic_state *pic, struct pic_string *str)
 {
   const char *s;
   int h = 0;
@@ -302,7 +302,7 @@ pic_str_hash(pic_state *pic, pic_str *str)
 }
 
 const char *
-pic_str_cstr(pic_state *pic, pic_str *str)
+pic_str_cstr(pic_state *pic, struct pic_string *str)
 {
   return rope_cstr(pic, str->rope);
 }
@@ -373,11 +373,11 @@ pic_vfformat(pic_state *pic, xFILE *file, const char *fmt, va_list ap)
   return;
 }
 
-pic_str *
+struct pic_string *
 pic_vformat(pic_state *pic, const char *fmt, va_list ap)
 {
   struct pic_port *port;
-  pic_str *str;
+  struct pic_string *str;
 
   port = pic_open_output_string(pic);
 
@@ -388,11 +388,11 @@ pic_vformat(pic_state *pic, const char *fmt, va_list ap)
   return str;
 }
 
-pic_str *
+struct pic_string *
 pic_format(pic_state *pic, const char *fmt, ...)
 {
   va_list ap;
-  pic_str *str;
+  struct pic_string *str;
 
   va_start(ap, fmt);
   str = pic_vformat(pic, fmt, ap);
@@ -416,7 +416,7 @@ pic_str_string(pic_state *pic)
 {
   int argc, i;
   pic_value *argv;
-  pic_str *str;
+  struct pic_string *str;
   char *buf;
 
   pic_get_args(pic, "*", &argc, &argv);
@@ -456,7 +456,7 @@ pic_str_make_string(pic_state *pic)
 static pic_value
 pic_str_string_length(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
 
   pic_get_args(pic, "s", &str);
 
@@ -466,7 +466,7 @@ pic_str_string_length(pic_state *pic)
 static pic_value
 pic_str_string_ref(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   int k;
 
   pic_get_args(pic, "si", &str, &k);
@@ -507,7 +507,7 @@ DEFINE_STRING_CMP(ge, >=)
 static pic_value
 pic_str_string_copy(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   int n, start, end, len;
 
   n = pic_get_args(pic, "s|ii", &str, &start, &end);
@@ -532,7 +532,7 @@ pic_str_string_append(pic_state *pic)
 {
   int argc, i;
   pic_value *argv;
-  pic_str *str;
+  struct pic_string *str;
 
   pic_get_args(pic, "*", &argc, &argv);
 
@@ -552,7 +552,7 @@ pic_str_string_map(pic_state *pic)
   struct pic_proc *proc;
   pic_value *argv, vals, val;
   int argc, i, len, j;
-  pic_str *str;
+  struct pic_string *str;
   char *buf;
 
   pic_get_args(pic, "l*", &proc, &argc, &argv);
@@ -632,7 +632,7 @@ pic_str_string_for_each(pic_state *pic)
 static pic_value
 pic_str_list_to_string(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   pic_value list, e, it;
   int i;
   char *buf;
@@ -667,7 +667,7 @@ pic_str_list_to_string(pic_state *pic)
 static pic_value
 pic_str_string_to_list(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   pic_value list;
   int n, start, end, i;
 
diff --git a/extlib/benz/symbol.c b/extlib/benz/symbol.c
index 0c81ddfa..32d533d2 100644
--- a/extlib/benz/symbol.c
+++ b/extlib/benz/symbol.c
@@ -7,10 +7,10 @@
 #define kh_pic_str_hash(a) (pic_str_hash(pic, (a)))
 #define kh_pic_str_cmp(a, b) (pic_str_cmp(pic, (a), (b)) == 0)
 
-KHASH_DEFINE(s, pic_str *, pic_sym *, kh_pic_str_hash, kh_pic_str_cmp)
+KHASH_DEFINE(s, struct pic_string *, pic_sym *, kh_pic_str_hash, kh_pic_str_cmp)
 
 pic_sym *
-pic_intern(pic_state *pic, pic_str *str)
+pic_intern(pic_state *pic, struct pic_string *str)
 {
   khash_t(s) *h = &pic->oblist;
   pic_sym *sym;
@@ -102,7 +102,7 @@ pic_symbol_symbol_to_string(pic_state *pic)
 static pic_value
 pic_symbol_string_to_symbol(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
 
   pic_get_args(pic, "s", &str);
 
diff --git a/extlib/benz/vector.c b/extlib/benz/vector.c
index 09ed95fb..582c9d63 100644
--- a/extlib/benz/vector.c
+++ b/extlib/benz/vector.c
@@ -323,7 +323,7 @@ pic_vec_vector_to_string(pic_state *pic)
   pic_vec *vec;
   char *buf;
   int n, start, end, i;
-  pic_str *str;
+  struct pic_string *str;
 
   n = pic_get_args(pic, "v|ii", &vec, &start, &end);
 
@@ -355,7 +355,7 @@ pic_vec_vector_to_string(pic_state *pic)
 static pic_value
 pic_vec_string_to_vector(pic_state *pic)
 {
-  pic_str *str;
+  struct pic_string *str;
   int n, start, end, i;
   pic_vec *vec;
 
diff --git a/extlib/benz/write.c b/extlib/benz/write.c
index e36a8a0b..0c86fcb8 100644
--- a/extlib/benz/write.c
+++ b/extlib/benz/write.c
@@ -47,7 +47,7 @@ writer_control_destroy(struct writer_control *p)
 }
 
 static void
-write_blob(pic_state *pic, pic_blob *blob, xFILE *file)
+write_blob(pic_state *pic, struct pic_blob *blob, xFILE *file)
 {
   int i;
 
@@ -82,7 +82,7 @@ write_char(pic_state *pic, char c, xFILE *file, int mode)
 }
 
 static void
-write_str(pic_state *pic, pic_str *str, xFILE *file, int mode)
+write_str(pic_state *pic, struct pic_string *str, xFILE *file, int mode)
 {
   int i;
   const char *cstr = pic_str_cstr(pic, str);
@@ -433,7 +433,7 @@ pic_printf(pic_state *pic, const char *fmt, ...)
 {
   xFILE *file = pic_stdout(pic)->file;
   va_list ap;
-  pic_str *str;
+  struct pic_string *str;
 
   va_start(ap, fmt);