From 33efb3e950b88cbefa9554ce1e4f2f194d388a76 Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Tue, 16 Sep 2014 23:43:15 +0900
Subject: [PATCH 1/6] remove pic_error

---
 blob.c           |  8 ++++----
 char.c           |  2 +-
 codegen.c        | 24 ++++++++++++------------
 include/picrin.h |  4 ----
 macro.c          | 14 +++++++-------
 number.c         |  6 +++---
 pair.c           |  8 ++++----
 port.c           | 18 +++++++++---------
 proc.c           |  2 +-
 string.c         |  2 +-
 symbol.c         |  4 ++--
 vector.c         |  4 ++--
 vm.c             | 24 ++++++++++++------------
 13 files changed, 58 insertions(+), 62 deletions(-)

diff --git a/blob.c b/blob.c
index 337e3333..a8f28c9b 100644
--- a/blob.c
+++ b/blob.c
@@ -64,7 +64,7 @@ pic_blob_bytevector(pic_state *pic)
     pic_assert_type(pic, argv[i], int);
 
     if (pic_int(argv[i]) < 0 || pic_int(argv[i]) > 255) {
-      pic_error(pic, "byte out of range");
+      pic_errorf(pic, "byte out of range");
     }
 
     *data++ = pic_int(argv[i]);
@@ -82,7 +82,7 @@ pic_blob_make_bytevector(pic_state *pic)
   pic_get_args(pic, "i|i", &k, &b);
 
   if (b < 0 || b > 255)
-    pic_error(pic, "byte out of range");
+    pic_errorf(pic, "byte out of range");
 
   blob = pic_make_blob(pic, k);
   for (i = 0; i < k; ++i) {
@@ -122,7 +122,7 @@ pic_blob_bytevector_u8_set(pic_state *pic)
   pic_get_args(pic, "bii", &bv, &k, &v);
 
   if (v < 0 || v > 255)
-    pic_error(pic, "byte out of range");
+    pic_errorf(pic, "byte out of range");
 
   bv->data[k] = v;
   return pic_none_value();
@@ -227,7 +227,7 @@ pic_blob_list_to_bytevector(pic_state *pic)
     pic_assert_type(pic, e, int);
 
     if (pic_int(e) < 0 || pic_int(e) > 255)
-      pic_error(pic, "byte out of range");
+      pic_errorf(pic, "byte out of range");
 
     *data++ = pic_int(e);
   }
diff --git a/char.c b/char.c
index 0dca9f52..a460fb2b 100644
--- a/char.c
+++ b/char.c
@@ -53,7 +53,7 @@ pic_char_integer_to_char(pic_state *pic)
       if (pic_char_p(argv[i]))                          \
         d = pic_char(argv[i]);                          \
       else						\
-	pic_error(pic, #op ": char required");          \
+	pic_errorf(pic, #op ": char required");         \
       							\
       if (! (c op d))					\
 	return pic_false_value();			\
diff --git a/codegen.c b/codegen.c
index 34505723..55bb8587 100644
--- a/codegen.c
+++ b/codegen.c
@@ -425,7 +425,7 @@ analyze_lambda(analyze_state *state, pic_value obj)
   pic_value formals, body_exprs;
 
   if (pic_length(pic, obj) < 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   formals = pic_list_ref(pic, obj, 1);
@@ -450,12 +450,12 @@ analyze_define(analyze_state *state, pic_value obj)
   pic_sym sym;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_list_ref(pic, obj, 1);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   } else {
     sym = pic_sym(var);
   }
@@ -472,7 +472,7 @@ analyze_define(analyze_state *state, pic_value obj)
     val = analyze_defer(state, pic_sym_value(sym), formals, body_exprs);
   } else {
     if (pic_length(pic, obj) != 3) {
-      pic_error(pic, "syntax error");
+      pic_errorf(pic, "syntax error");
     }
     val = analyze(state, pic_list_ref(pic, obj, 2), false);
   }
@@ -489,7 +489,7 @@ analyze_if(analyze_state *state, pic_value obj, bool tailpos)
   if_false = pic_none_value();
   switch (pic_length(pic, obj)) {
   default:
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
     break;
   case 4:
     if_false = pic_list_ref(pic, obj, 3);
@@ -539,12 +539,12 @@ analyze_set(analyze_state *state, pic_value obj)
   pic_value var, val;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_list_ref(pic, obj, 1);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   val = pic_list_ref(pic, obj, 2);
@@ -561,14 +561,14 @@ analyze_quote(analyze_state *state, pic_value obj)
   pic_state *pic = state->pic;
 
   if (pic_length(pic, obj) != 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
   return pic_list2(pic, pic_sym_value(pic->sQUOTE), pic_list_ref(pic, obj, 1));
 }
 
 #define ARGC_ASSERT_GE(n) do {				\
 	if (pic_length(pic, obj) < (n) + 1) {		\
-	  pic_error(pic, "wrong number of arguments");	\
+	  pic_errorf(pic, "wrong number of arguments");	\
 	}						\
       } while (0)
 
@@ -699,7 +699,7 @@ analyze_call_with_values(analyze_state *state, pic_value obj, bool tailpos)
   pic_sym call;
 
   if (pic_length(pic, obj) != 3) {
-    pic_error(pic, "wrong number of arguments");
+    pic_errorf(pic, "wrong number of arguments");
   }
 
   if (! tailpos) {
@@ -714,7 +714,7 @@ analyze_call_with_values(analyze_state *state, pic_value obj, bool tailpos)
 
 #define ARGC_ASSERT(n) do {				\
 	if (pic_length(pic, obj) != (n) + 1) {		\
-	  pic_error(pic, "wrong number of arguments");	\
+	  pic_errorf(pic, "wrong number of arguments");	\
 	}						\
       } while (0)
 
@@ -1413,7 +1413,7 @@ codegen(codegen_state *state, pic_value obj)
     cxt->clen++;
     return;
   }
-  pic_error(pic, "codegen: unknown AST type");
+  pic_errorf(pic, "codegen: unknown AST type");
 }
 
 static struct pic_irep *
diff --git a/include/picrin.h b/include/picrin.h
index e726ee4c..e911ff04 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -209,10 +209,6 @@ pic_str *pic_get_backtrace(pic_state *);
 void pic_print_backtrace(pic_state *, struct pic_error *);
 
 /* obsoleted */
-noreturn static inline void pic_error(pic_state *pic, const char *msg)
-{
-  pic_errorf(pic, msg);
-}
 static inline void pic_warn(pic_state *pic, const char *msg)
 {
   pic_warnf(pic, msg);
diff --git a/macro.c b/macro.c
index 17f12cc6..c7cd243f 100644
--- a/macro.c
+++ b/macro.c
@@ -161,7 +161,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
   pic_value a;
 
   if (pic_length(pic, expr) < 2) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   in = pic_make_senv(pic, senv);
@@ -170,7 +170,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
     pic_value v = pic_car(pic, a);
 
     if (! pic_sym_p(v)) {
-      pic_error(pic, "syntax error");
+      pic_errorf(pic, "syntax error");
     }
     pic_add_rename(pic, in, pic_sym(v));
   }
@@ -178,7 +178,7 @@ macroexpand_lambda(pic_state *pic, pic_value expr, struct pic_senv *senv)
     pic_add_rename(pic, in, pic_sym(a));
   }
   else if (! pic_nil_p(a)) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   formal = macroexpand_list(pic, pic_cadr(pic, expr), in);
@@ -203,12 +203,12 @@ macroexpand_define(pic_state *pic, pic_value expr, struct pic_senv *senv)
   }
 
   if (pic_length(pic, expr) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_cadr(pic, expr);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "binding to non-symbol object");
+    pic_errorf(pic, "binding to non-symbol object");
   }
   sym = pic_sym(var);
   if (! pic_find_rename(pic, senv, sym, &rename)) {
@@ -226,12 +226,12 @@ macroexpand_defsyntax(pic_state *pic, pic_value expr, struct pic_senv *senv)
   pic_sym sym, rename;
 
   if (pic_length(pic, expr) != 3) {
-    pic_error(pic, "syntax error");
+    pic_errorf(pic, "syntax error");
   }
 
   var = pic_cadr(pic, expr);
   if (! pic_sym_p(var)) {
-    pic_error(pic, "binding to non-symbol object");
+    pic_errorf(pic, "binding to non-symbol object");
   }
   sym = pic_sym(var);
   if (! pic_find_rename(pic, senv, sym, &rename)) {
diff --git a/number.c b/number.c
index 10dc03aa..4c13df35 100644
--- a/number.c
+++ b/number.c
@@ -179,7 +179,7 @@ pic_number_nan_p(pic_state *pic)
       else if (pic_int_p(argv[i]))			\
 	g = pic_int(argv[i]);				\
       else						\
-	pic_error(pic, #op ": number required");	\
+	pic_errorf(pic, #op ": number required");	\
       							\
       if (! (f op g))					\
 	return pic_false_value();			\
@@ -216,7 +216,7 @@ DEFINE_ARITH_CMP(>=, ge)
         f op##= pic_float(argv[i]);                             \
       }                                                         \
       else {                                                    \
-        pic_error(pic, #op ": number required");                \
+        pic_errorf(pic, #op ": number required");               \
       }                                                         \
     }                                                           \
                                                                 \
@@ -252,7 +252,7 @@ DEFINE_ARITH_OP(*, mul, 1)
        f op##= pic_float(argv[i]);                                      \
      }                                                                  \
      else {                                                             \
-       pic_error(pic, #op ": number required");                         \
+       pic_errorf(pic, #op ": number required");                        \
      }                                                                  \
    }                                                                    \
                                                                         \
diff --git a/pair.c b/pair.c
index d9960347..0bb0d90e 100644
--- a/pair.c
+++ b/pair.c
@@ -51,7 +51,7 @@ pic_set_car(pic_state *pic, pic_value obj, pic_value val)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required");
   }
   pair = pic_pair_ptr(obj);
 
@@ -64,7 +64,7 @@ pic_set_cdr(pic_state *pic, pic_value obj, pic_value val)
   struct pic_pair *pair;
 
   if (! pic_pair_p(obj)) {
-    pic_error(pic, "pair required");
+    pic_errorf(pic, "pair required");
   }
   pair = pic_pair_ptr(obj);
 
@@ -520,7 +520,7 @@ pic_pair_set_car(pic_state *pic)
   pic_get_args(pic, "oo", &v, &w);
 
   if (! pic_pair_p(v))
-    pic_error(pic, "pair expected");
+    pic_errorf(pic, "pair expected");
 
   pic_pair_ptr(v)->car = w;
   return pic_none_value();
@@ -534,7 +534,7 @@ pic_pair_set_cdr(pic_state *pic)
   pic_get_args(pic, "oo", &v, &w);
 
   if (! pic_pair_p(v))
-    pic_error(pic, "pair expected");
+    pic_errorf(pic, "pair expected");
 
   pic_pair_ptr(v)->cdr = w;
   return pic_none_value();
diff --git a/port.c b/port.c
index 859df8a5..558a81b6 100644
--- a/port.c
+++ b/port.c
@@ -107,7 +107,7 @@ void
 pic_close_port(pic_state *pic, struct pic_port *port)
 {
   if (xfclose(port->file) == EOF) {
-    pic_error(pic, "close-port: failure");
+    pic_errorf(pic, "close-port: failure");
   }
   port->status = PIC_PORT_CLOSE;
 }
@@ -247,25 +247,25 @@ pic_port_close_port(pic_state *pic)
     if ((port->flags & (flgs)) != (flgs)) {                             \
       switch (flgs) {                                                   \
       case PIC_PORT_IN:                                                 \
-        pic_error(pic, caller ": expected output port");                \
+        pic_errorf(pic, caller ": expected output port");               \
       case PIC_PORT_OUT:                                                \
-        pic_error(pic, caller ": expected input port");                 \
+        pic_errorf(pic, caller ": expected input port");                \
       case PIC_PORT_IN | PIC_PORT_TEXT:                                 \
-        pic_error(pic, caller ": expected input/textual port");         \
+        pic_errorf(pic, caller ": expected input/textual port");        \
       case PIC_PORT_IN | PIC_PORT_BINARY:                               \
-        pic_error(pic, caller ": expected input/binary port");          \
+        pic_errorf(pic, caller ": expected input/binary port");         \
       case PIC_PORT_OUT | PIC_PORT_TEXT:                                \
-        pic_error(pic, caller ": expected output/textual port");        \
+        pic_errorf(pic, caller ": expected output/textual port");       \
       case PIC_PORT_OUT | PIC_PORT_BINARY:                              \
-        pic_error(pic, caller ": expected output/binary port");         \
+        pic_errorf(pic, caller ": expected output/binary port");        \
       }                                                                 \
     }                                                                   \
     if (port->status != stat) {                                         \
       switch (stat) {                                                   \
       case PIC_PORT_OPEN:                                               \
-        pic_error(pic, caller ": expected open port");                  \
+        pic_errorf(pic, caller ": expected open port");                 \
       case PIC_PORT_CLOSE:                                              \
-        pic_error(pic, caller ": expected close port");                 \
+        pic_errorf(pic, caller ": expected close port");                \
       }                                                                 \
     }                                                                   \
   } while (0)
diff --git a/proc.c b/proc.c
index 1dee4813..9702819c 100644
--- a/proc.c
+++ b/proc.c
@@ -91,7 +91,7 @@ pic_proc_apply(pic_state *pic)
   pic_get_args(pic, "l*", &proc, &argc, &args);
 
   if (argc == 0) {
-    pic_error(pic, "apply: wrong number of arguments");
+    pic_errorf(pic, "apply: wrong number of arguments");
   }
 
   arg_list = args[--argc];
diff --git a/string.c b/string.c
index fc2d2ab6..6876a969 100644
--- a/string.c
+++ b/string.c
@@ -404,7 +404,7 @@ pic_str_string_append(pic_state *pic)
   str = pic_make_str(pic, NULL, 0);
   for (i = 0; i < argc; ++i) {
     if (! pic_str_p(argv[i])) {
-      pic_error(pic, "type error");
+      pic_errorf(pic, "type error");
     }
     str = pic_strcat(pic, str, pic_str_ptr(argv[i]));
   }
diff --git a/symbol.c b/symbol.c
index 7c6479b4..6629abac 100644
--- a/symbol.c
+++ b/symbol.c
@@ -132,7 +132,7 @@ pic_symbol_symbol_to_string(pic_state *pic)
   pic_get_args(pic, "o", &v);
 
   if (! pic_sym_p(v)) {
-    pic_error(pic, "symbol->string: expected symbol");
+    pic_errorf(pic, "symbol->string: expected symbol");
   }
 
   return pic_obj_value(pic_make_str_cstr(pic, pic_symbol_name(pic, pic_sym(v))));
@@ -146,7 +146,7 @@ pic_symbol_string_to_symbol(pic_state *pic)
   pic_get_args(pic, "o", &v);
 
   if (! pic_str_p(v)) {
-    pic_error(pic, "string->symbol: expected string");
+    pic_errorf(pic, "string->symbol: expected string");
   }
 
   return pic_symbol_value(pic_intern_cstr(pic, pic_str_cstr(pic_str_ptr(v))));
diff --git a/vector.c b/vector.c
index 4a3e8194..57790b36 100644
--- a/vector.c
+++ b/vector.c
@@ -105,7 +105,7 @@ pic_vec_vector_ref(pic_state *pic)
   pic_get_args(pic, "vi", &v, &k);
 
   if (k < 0 || v->len <= (size_t)k) {
-    pic_error(pic, "vector-ref: index out of range");
+    pic_errorf(pic, "vector-ref: index out of range");
   }
   return v->data[k];
 }
@@ -120,7 +120,7 @@ pic_vec_vector_set(pic_state *pic)
   pic_get_args(pic, "vio", &v, &k, &o);
 
   if (k < 0 || v->len <= (size_t)k) {
-    pic_error(pic, "vector-set!: index out of range");
+    pic_errorf(pic, "vector-set!: index out of range");
   }
   v->data[k] = o;
   return pic_none_value();
diff --git a/vm.c b/vm.c
index b84bc96e..609c702f 100644
--- a/vm.c
+++ b/vm.c
@@ -29,7 +29,7 @@ pic_get_proc(pic_state *pic)
   pic_value v = GET_OPERAND(pic,0);
 
   if (! pic_proc_p(v)) {
-    pic_error(pic, "fatal error");
+    pic_errorf(pic, "fatal error");
   }
   return pic_proc_ptr(v);
 }
@@ -70,7 +70,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
     switch (c) {
     default:
       if (argc <= i && ! opt) {
-	pic_error(pic, "wrong number of arguments");
+	pic_errorf(pic, "wrong number of arguments");
       }
       break;
     case '|':
@@ -375,7 +375,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
           *e = pic_error_ptr(v);
         }
         else {
-          pic_error(pic, "pic_get_args, expected error");
+          pic_errorf(pic, "pic_get_args, expected error");
         }
         i++;
       }
@@ -398,7 +398,7 @@ pic_get_args(pic_state *pic, const char *format, ...)
     }
   }
   else if (argc > i) {
-    pic_error(pic, "wrong number of arguments");
+    pic_errorf(pic, "wrong number of arguments");
   }
   va_end(ap);
   return i - 1;
@@ -675,7 +675,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 #endif
 
   if (! pic_list_p(argv)) {
-    pic_error(pic, "argv must be a proper list");
+    pic_errorf(pic, "argv must be a proper list");
   }
 
   argc = pic_length(pic, argv) + 1;
@@ -728,11 +728,11 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 
       self = pic->ci->fp[0];
       if (! pic_proc_p(self)) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       irep = pic_proc_ptr(self)->u.irep;
       if (! pic_proc_irep_p(pic_proc_ptr(self))) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       PUSH(irep->pool[c.u.i]);
       NEXT;
@@ -950,11 +950,11 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 
       self = pic->ci->fp[0];
       if (! pic_proc_p(self)) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
       irep = pic_proc_ptr(self)->u.irep;
       if (! pic_proc_irep_p(pic_proc_ptr(self))) {
-        pic_error(pic, "logic flaw");
+        pic_errorf(pic, "logic flaw");
       }
 
       if (pic->ci->env == NULL) {
@@ -1017,7 +1017,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_float_value(pic_float(a) op pic_int(b)));	\
       }								\
       else {							\
-	pic_error(pic, #op " got non-number operands");		\
+	pic_errorf(pic, #op " got non-number operands");        \
       }								\
       NEXT;							\
     }
@@ -1037,7 +1037,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_float_value(-pic_float(n)));
       }
       else {
-	pic_error(pic, "unary - got a non-number operand");
+	pic_errorf(pic, "unary - got a non-number operand");
       }
       NEXT;
     }
@@ -1060,7 +1060,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
 	PUSH(pic_bool_value(pic_float(a) op pic_int(b)));	\
       }								\
       else {							\
-	pic_error(pic, #op " got non-number operands");		\
+	pic_errorf(pic, #op " got non-number operands");        \
       }								\
       NEXT;							\
     }

From 78a982fb4148d1c5dcd8ec24a8d3d0a36f5d3ccb Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 17 Sep 2014 00:28:55 +0900
Subject: [PATCH 2/6] refactor error object

---
 debug.c                | 41 +++++++++++++----------------
 error.c                | 60 +++++++++++++++++++++++++-----------------
 file.c                 |  2 +-
 gc.c                   |  4 +--
 include/picrin.h       |  5 ++--
 include/picrin/error.h | 14 ++++------
 include/picrin/value.h |  1 +
 lib.c                  |  2 +-
 read.c                 |  2 +-
 state.c                |  6 +++--
 10 files changed, 71 insertions(+), 66 deletions(-)

diff --git a/debug.c b/debug.c
index 09c70553..3d7b92c6 100644
--- a/debug.c
+++ b/debug.c
@@ -36,37 +36,32 @@ pic_get_backtrace(pic_state *pic)
 }
 
 void
-pic_print_backtrace(pic_state *pic, struct pic_error *e)
+pic_print_backtrace(pic_state *pic)
 {
   size_t ai = pic_gc_arena_preserve(pic);
   pic_str *trace;
 
-  assert(pic->err != NULL);
+  assert(! pic_undef_p(pic->err));
 
-  trace = pic_make_str(pic, NULL, 0);
+  if (! pic_error_p(pic->err)) {
+    trace = pic_format(pic, "raised: ~s", pic->err);
+  } else {
+    struct pic_error *e;
 
-  switch (e->type) {
-  case PIC_ERROR_OTHER:
-    trace = pic_strcat(pic, trace, pic_make_str_cstr(pic, "error: "));
-    break;
-  case PIC_ERROR_FILE:
-    trace = pic_strcat(pic, trace, pic_make_str_cstr(pic, "file error: "));
-    break;
-  case PIC_ERROR_READ:
-    trace = pic_strcat(pic, trace, pic_make_str_cstr(pic, "read error: "));
-    break;
-  case PIC_ERROR_RAISED:
-    trace = pic_strcat(pic, trace, pic_make_str_cstr(pic, "raised: "));
-    break;
+    e = pic_error_ptr(pic->err);
+    if (e->type != pic_intern_cstr(pic, "")) {
+      trace = pic_format(pic, "~s ", pic_sym_value(e->type));
+    } else {
+      trace = pic_make_str(pic, NULL, 0);
+    }
+    trace = pic_strcat(pic, trace, pic_format(pic, "error: ~s", pic_obj_value(e->msg)));
+
+    /* TODO: print error irritants */
+
+    trace = pic_strcat(pic, trace, pic_make_str(pic, "\n", 1));
+    trace = pic_strcat(pic, trace, e->stack);
   }
 
-  trace = pic_strcat(pic, trace, e->msg);
-
-  /* TODO: print error irritants */
-
-  trace = pic_strcat(pic, trace, pic_make_str(pic, "\n", 1));
-  trace = pic_strcat(pic, trace, e->stack);
-
   /* print! */
   printf("%s", pic_str_cstr(trace));
 
diff --git a/error.c b/error.c
index d5596a7b..dad4a604 100644
--- a/error.c
+++ b/error.c
@@ -89,37 +89,51 @@ make_error(pic_state *pic, short type, pic_str *msg, pic_value irrs)
 }
 
 noreturn void
-pic_throw_error(pic_state *pic, struct pic_error *e)
+pic_raise(pic_state *pic, pic_value err)
 {
   void pic_vm_tear_off(pic_state *);
 
   pic_vm_tear_off(pic);         /* tear off */
 
-  pic->err = e;
+  pic->err = err;
   if (! pic->jmp) {
     puts(pic_errmsg(pic));
-    abort();
+    pic_abort(pic, "no handler found on stack");
   }
 
   longjmp(*pic->jmp, 1);
 }
 
 noreturn void
-pic_throw(pic_state *pic, short type, const char *msg, pic_value irrs)
+pic_throw(pic_state *pic, pic_sym type, const char *msg, pic_value irrs)
 {
   struct pic_error *e;
 
   e = make_error(pic, type, pic_make_str_cstr(pic, msg), irrs);
 
-  pic_throw_error(pic, e);
+  pic_raise(pic, pic_obj_value(e));
+}
+
+noreturn void
+pic_error(pic_state *pic, const char *msg, pic_value irrs)
+{
+  pic_throw(pic, pic_intern_cstr(pic, ""), msg, irrs);
 }
 
 const char *
 pic_errmsg(pic_state *pic)
 {
-  assert(pic->err != NULL);
+  pic_str *str;
 
-  return pic_str_cstr(pic->err->msg);
+  assert(! pic_undef_p(pic->err));
+
+  if (! pic_error_p(pic->err)) {
+    str = pic_format(pic, "~s", pic->err);
+  } else {
+    str = pic_error_ptr(pic->err)->msg;
+  }
+
+  return pic_str_cstr(str);
 }
 
 void
@@ -136,34 +150,30 @@ pic_errorf(pic_state *pic, const char *fmt, ...)
   msg = pic_str_cstr(pic_str_ptr(pic_car(pic, err_line)));
   irrs = pic_cdr(pic, err_line);
 
-  pic_throw(pic, PIC_ERROR_OTHER, msg, irrs);
+  pic_error(pic, msg, irrs);
 }
 
 static pic_value
 pic_error_with_exception_handler(pic_state *pic)
 {
   struct pic_proc *handler, *thunk;
-  pic_value v;
+  pic_value val;
 
   pic_get_args(pic, "ll", &handler, &thunk);
 
   pic_try_with_handler(handler) {
-    v = pic_apply0(pic, thunk);
+    val = pic_apply0(pic, thunk);
   }
   pic_catch {
-    struct pic_error *e = pic->err;
+    pic_value e = pic->err;
 
-    pic->err = NULL;
+    pic->err = pic_undef_value();
 
-    if (e->type == PIC_ERROR_RAISED) {
-      v = pic_list_ref(pic, e->irrs, 0);
-    } else {
-      v = pic_obj_value(e);
-    }
-    v = pic_apply1(pic, handler, v);
-    pic_errorf(pic, "error handler returned ~s, by error ~s", v, pic_obj_value(e));
+    val = pic_apply1(pic, handler, e);
+
+    pic_errorf(pic, "error handler returned with ~s on error ~s", val, e);
   }
-  return v;
+  return val;
 }
 
 noreturn static pic_value
@@ -173,7 +183,7 @@ pic_error_raise(pic_state *pic)
 
   pic_get_args(pic, "o", &v);
 
-  pic_throw(pic, PIC_ERROR_RAISED, "object is raised", pic_list1(pic, v));
+  pic_raise(pic, v);
 }
 
 static pic_value
@@ -206,7 +216,7 @@ pic_error_error(pic_state *pic)
 
   pic_get_args(pic, "z*", &str, &argc, &argv);
 
-  pic_throw(pic, PIC_ERROR_OTHER, str, pic_list_by_array(pic, argc, argv));
+  pic_error(pic, str, pic_list_by_array(pic, argc, argv));
 }
 
 static pic_value
@@ -252,7 +262,8 @@ pic_error_read_error_p(pic_state *pic)
   }
 
   e = pic_error_ptr(v);
-  return pic_bool_value(e->type == PIC_ERROR_READ);
+
+  return pic_bool_value(e->type == pic->sREAD);
 }
 
 static pic_value
@@ -268,7 +279,8 @@ pic_error_file_error_p(pic_state *pic)
   }
 
   e = pic_error_ptr(v);
-  return pic_bool_value(e->type == PIC_ERROR_FILE);
+
+  return pic_bool_value(e->type == pic->sFILE);
 }
 
 void
diff --git a/file.c b/file.c
index cfc266b5..4a5f57d7 100644
--- a/file.c
+++ b/file.c
@@ -9,7 +9,7 @@
 static noreturn void
 file_error(pic_state *pic, const char *msg)
 {
-  pic_throw(pic, PIC_ERROR_FILE, msg, pic_nil_value());
+  pic_throw(pic, pic->sFILE, msg, pic_nil_value());
 }
 
 static pic_value
diff --git a/gc.c b/gc.c
index ba0e23d7..bb241a43 100644
--- a/gc.c
+++ b/gc.c
@@ -580,9 +580,7 @@ gc_mark_phase(pic_state *pic)
   }
 
   /* error object */
-  if (pic->err) {
-    gc_mark_object(pic, (struct pic_object *)pic->err);
-  }
+  gc_mark(pic, pic->err);
 
   /* arena */
   for (j = 0; j < pic->arena_idx; ++j) {
diff --git a/include/picrin.h b/include/picrin.h
index e911ff04..fe564822 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -81,6 +81,7 @@ typedef struct {
   pic_sym sCONS, sCAR, sCDR, sNILP;
   pic_sym sADD, sSUB, sMUL, sDIV, sMINUS;
   pic_sym sEQ, sLT, sLE, sGT, sGE, sNOT;
+  pic_sym sREAD, sFILE;
 
   pic_sym rDEFINE, rLAMBDA, rIF, rBEGIN, rQUOTE, rSETBANG;
   pic_sym rDEFINE_SYNTAX, rIMPORT, rEXPORT;
@@ -104,7 +105,7 @@ typedef struct {
   struct pic_reader *reader;
 
   jmp_buf *jmp;
-  struct pic_error *err;
+  pic_value err;
   struct pic_jmpbuf *try_jmps;
   size_t try_jmp_size, try_jmp_idx;
 
@@ -206,7 +207,7 @@ noreturn void pic_abort(pic_state *, const char *);
 noreturn void pic_errorf(pic_state *, const char *, ...);
 void pic_warnf(pic_state *, const char *, ...);
 pic_str *pic_get_backtrace(pic_state *);
-void pic_print_backtrace(pic_state *, struct pic_error *);
+void pic_print_backtrace(pic_state *);
 
 /* obsoleted */
 static inline void pic_warn(pic_state *pic, const char *msg)
diff --git a/include/picrin/error.h b/include/picrin/error.h
index 5005346a..f61f8082 100644
--- a/include/picrin/error.h
+++ b/include/picrin/error.h
@@ -34,18 +34,14 @@ struct pic_jmpbuf {
 void pic_push_try(pic_state *, struct pic_proc *);
 void pic_pop_try(pic_state *);
 
-noreturn void pic_throw(pic_state *, short, const char *, pic_value);
-noreturn void pic_throw_error(pic_state *, struct pic_error *);
+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);
 
 struct pic_error {
   PIC_OBJECT_HEADER
-  enum pic_error_kind {
-    PIC_ERROR_OTHER,
-    PIC_ERROR_FILE,
-    PIC_ERROR_READ,
-    PIC_ERROR_RAISED
-  } type;
-  struct pic_string *msg;
+  pic_sym type;
+  pic_str *msg;
   pic_value irrs;
   pic_str *stack;
 };
diff --git a/include/picrin/value.h b/include/picrin/value.h
index 0523c688..6a211dc1 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -142,6 +142,7 @@ struct pic_blob;
 
 struct pic_proc;
 struct pic_port;
+struct pic_error;
 
 /* set aliases to basic types */
 typedef pic_value pic_list;
diff --git a/lib.c b/lib.c
index b716d41e..cb1843d8 100644
--- a/lib.c
+++ b/lib.c
@@ -318,7 +318,7 @@ pic_lib_define_library(pic_state *pic)
   }
   pic_catch {
     pic_in_library(pic, prev->name); /* restores pic->lib even if an error occurs */
-    pic_throw_error(pic, pic->err);
+    pic_raise(pic, pic->err);
   }
 
   return pic_none_value();
diff --git a/read.c b/read.c
index ad23436f..7deb5eb2 100644
--- a/read.c
+++ b/read.c
@@ -21,7 +21,7 @@ static pic_value read_nullable(pic_state *pic, struct pic_port *port, int c);
 static noreturn void
 read_error(pic_state *pic, const char *msg)
 {
-  pic_throw(pic, PIC_ERROR_READ, msg, pic_nil_value());
+  pic_throw(pic, pic->sREAD, msg, pic_nil_value());
 }
 
 static int
diff --git a/state.c b/state.c
index e7300e9c..b88f40a1 100644
--- a/state.c
+++ b/state.c
@@ -72,7 +72,7 @@ pic_open(int argc, char *argv[], char **envp)
 
   /* error handling */
   pic->jmp = NULL;
-  pic->err = NULL;
+  pic->err = pic_undef_value();
   pic->try_jmps = calloc(PIC_RESCUE_SIZE, sizeof(struct pic_jmpbuf));
   pic->try_jmp_idx = 0;
   pic->try_jmp_size = PIC_RESCUE_SIZE;
@@ -131,6 +131,8 @@ pic_open(int argc, char *argv[], char **envp)
   S(sGT, ">");
   S(sGE, ">=");
   S(sNOT, "not");
+  S(sREAD, "read");
+  S(sFILE, "file");
   pic_gc_arena_restore(pic, ai);
 
 #define R(slot,name) pic->slot = pic_gensym(pic, pic_intern_cstr(pic, name));
@@ -191,7 +193,7 @@ pic_close(pic_state *pic)
   pic->sp = pic->stbase;
   pic->ci = pic->cibase;
   pic->arena_idx = 0;
-  pic->err = NULL;
+  pic->err = pic_undef_value();
   xh_clear(&pic->macros);
   pic->features = pic_nil_value();
   pic->libs = pic_nil_value();

From 486c99bf6fdebf453c3aa2199c4c48715e50828e Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 17 Sep 2014 00:32:52 +0900
Subject: [PATCH 3/6] [bugfix] 'type' field is now of pic_sym type

---
 error.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/error.c b/error.c
index dad4a604..82f7f968 100644
--- a/error.c
+++ b/error.c
@@ -72,7 +72,7 @@ pic_pop_try(pic_state *pic)
 }
 
 static struct pic_error *
-make_error(pic_state *pic, short type, pic_str *msg, pic_value irrs)
+make_error(pic_state *pic, pic_sym type, pic_str *msg, pic_value irrs)
 {
   struct pic_error *e;
   pic_str *stack;

From 061ddb58eed60a6c02dc0ed6ebb9874367865602 Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 17 Sep 2014 00:43:03 +0900
Subject: [PATCH 4/6] publish pic_make_error

---
 error.c                | 8 ++++----
 include/picrin/error.h | 2 ++
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/error.c b/error.c
index 82f7f968..468935c3 100644
--- a/error.c
+++ b/error.c
@@ -71,8 +71,8 @@ pic_pop_try(pic_state *pic)
   pic->jmp = try_jmp->prev_jmp;
 }
 
-static struct pic_error *
-make_error(pic_state *pic, pic_sym type, pic_str *msg, pic_value irrs)
+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;
@@ -81,7 +81,7 @@ make_error(pic_state *pic, pic_sym type, pic_str *msg, pic_value irrs)
 
   e = (struct pic_error *)pic_obj_alloc(pic, sizeof(struct pic_error), PIC_TT_ERROR);
   e->type = type;
-  e->msg = msg;
+  e->msg = pic_make_str_cstr(pic, msg);
   e->irrs = irrs;
   e->stack = stack;
 
@@ -109,7 +109,7 @@ pic_throw(pic_state *pic, pic_sym type, const char *msg, pic_value irrs)
 {
   struct pic_error *e;
 
-  e = make_error(pic, type, pic_make_str_cstr(pic, msg), irrs);
+  e = pic_make_error(pic, type, msg, irrs);
 
   pic_raise(pic, pic_obj_value(e));
 }
diff --git a/include/picrin/error.h b/include/picrin/error.h
index f61f8082..1b96f3ee 100644
--- a/include/picrin/error.h
+++ b/include/picrin/error.h
@@ -49,6 +49,8 @@ struct pic_error {
 #define pic_error_p(v) (pic_type(v) == PIC_TT_ERROR)
 #define pic_error_ptr(v) ((struct pic_error *)pic_ptr(v))
 
+struct pic_error *pic_make_error(pic_state *, pic_sym, const char *, pic_list);
+
 #if defined(__cplusplus)
 }
 #endif

From 854f83a247b6f980c9db9462c9f8d088fa58f9ef Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 17 Sep 2014 00:43:12 +0900
Subject: [PATCH 5/6] add make-error-object procedure

---
 error.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/error.c b/error.c
index 468935c3..276fc7d1 100644
--- a/error.c
+++ b/error.c
@@ -219,6 +219,22 @@ pic_error_error(pic_state *pic)
   pic_error(pic, str, pic_list_by_array(pic, argc, argv));
 }
 
+static pic_value
+pic_error_make_error_object(pic_state *pic)
+{
+  struct pic_error *e;
+  pic_sym type;
+  pic_str *msg;
+  size_t argc;
+  pic_value *argv;
+
+  pic_get_args(pic, "ms*", &type, &msg, &argc, &argv);
+
+  e = pic_make_error(pic, type, pic_str_cstr(msg), pic_list_by_array(pic, argc, argv));
+
+  return pic_obj_value(e);
+}
+
 static pic_value
 pic_error_error_object_p(pic_state *pic)
 {
@@ -290,6 +306,7 @@ pic_init_error(pic_state *pic)
   pic_defun(pic, "raise", pic_error_raise);
   pic_defun(pic, "raise-continuable", pic_error_raise_continuable);
   pic_defun(pic, "error", pic_error_error);
+  pic_defun(pic, "make-error-object", pic_error_make_error_object);
   pic_defun(pic, "error-object?", pic_error_error_object_p);
   pic_defun(pic, "error-object-message", pic_error_error_object_message);
   pic_defun(pic, "error-object-irritants", pic_error_error_object_irritants);

From 05e76c0467af886f2cd88d2f6ad3d008dc64e73d Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 17 Sep 2014 00:49:37 +0900
Subject: [PATCH 6/6] remove read-error? and file-error? and add
 error-object-type instead

---
 error.c | 33 ++++-----------------------------
 1 file changed, 4 insertions(+), 29 deletions(-)

diff --git a/error.c b/error.c
index 276fc7d1..054a780a 100644
--- a/error.c
+++ b/error.c
@@ -266,37 +266,13 @@ pic_error_error_object_irritants(pic_state *pic)
 }
 
 static pic_value
-pic_error_read_error_p(pic_state *pic)
+pic_error_error_object_type(pic_state *pic)
 {
-  pic_value v;
   struct pic_error *e;
 
-  pic_get_args(pic, "o", &v);
+  pic_get_args(pic, "e", &e);
 
-  if (! pic_error_p(v)) {
-    return pic_false_value();
-  }
-
-  e = pic_error_ptr(v);
-
-  return pic_bool_value(e->type == pic->sREAD);
-}
-
-static pic_value
-pic_error_file_error_p(pic_state *pic)
-{
-  pic_value v;
-  struct pic_error *e;
-
-  pic_get_args(pic, "o", &v);
-
-  if (! pic_error_p(v)) {
-    return pic_false_value();
-  }
-
-  e = pic_error_ptr(v);
-
-  return pic_bool_value(e->type == pic->sFILE);
+  return pic_sym_value(e->type);
 }
 
 void
@@ -310,6 +286,5 @@ pic_init_error(pic_state *pic)
   pic_defun(pic, "error-object?", pic_error_error_object_p);
   pic_defun(pic, "error-object-message", pic_error_error_object_message);
   pic_defun(pic, "error-object-irritants", pic_error_error_object_irritants);
-  pic_defun(pic, "read-error?", pic_error_read_error_p);
-  pic_defun(pic, "file-error?", pic_error_file_error_p);
+  pic_defun(pic, "error-object-type", pic_error_error_object_type);
 }