Make mrb_top_self return a real instance.

src/gc.c

@@ -392,6 +392,7 @@ gc_mark_children(mrb_state *mrb, struct RBasic *obj)
     }
     /* fall through */
 
+  case MRB_TT_MAIN:
   case MRB_TT_OBJECT:
   case MRB_TT_DATA:
     mrb_gc_mark_iv(mrb, (struct RObject*)obj);
@@ -478,6 +479,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj)
     /* cannot happen */
     return;
 
+  case MRB_TT_MAIN:
   case MRB_TT_OBJECT:
     mrb_gc_free_iv(mrb, (struct RObject*)obj);
     break;
@@ -618,6 +620,7 @@ gc_gray_mark(mrb_state *mrb, struct RBasic *obj)
     }
     break;
 
+  case MRB_TT_MAIN:
   case MRB_TT_OBJECT:
   case MRB_TT_DATA:
     children += mrb_gc_mark_iv_size(mrb, (struct RObject*)obj);

src/kernel.c

@@ -306,6 +306,7 @@ init_copy(mrb_state *mrb, mrb_value dest, mrb_value obj)
       case MRB_TT_SCLASS:
       case MRB_TT_HASH:
       case MRB_TT_DATA:
+      case MRB_TT_MAIN:
         mrb_iv_copy(mrb, dest, obj);
         break;
 

src/state.c

@@ -7,6 +7,7 @@
 #include "mruby.h"
 #include "mruby/irep.h"
 #include "mruby/variable.h"
+#include "mruby/class.h"
 #include <stdlib.h>
 #include <string.h>
 
@@ -160,8 +161,11 @@ mrb_add_irep(mrb_state *mrb)
 mrb_value
 mrb_top_self(mrb_state *mrb)
 {
-  mrb_value v;
-
-  MRB_SET_VALUE(v, MRB_TT_MAIN, value.i, 0);
-  return v;
+  if(mrb->top_self == NULL)
+  {
+    mrb->top_self = (mrb_value *)mrb_calloc(mrb, 1, sizeof(mrb_value));
+    *(mrb->top_self) = mrb_class_new_instance(mrb, 0, NULL, mrb->object_class);
+    mrb->top_self->tt = MRB_TT_MAIN;
+  }
+  return *(mrb->top_self);
 }

src/variable.c

@@ -419,6 +419,7 @@ obj_iv_p(mrb_value obj)
     case MRB_TT_SCLASS:
     case MRB_TT_HASH:
     case MRB_TT_DATA:
+    case MRB_TT_MAIN:
       return TRUE;
     default:
       return FALSE;