* fix namespace issue on singleton class expressions. [Bug #10943]

* vm_core.h, method.h: remove rb_iseq_t::cref_stack. CREF is stored
  to rb_method_definition_t::body.iseq_body.cref.
* vm_insnhelper.c: modify SVAR usage.
  When calling ISEQ type method, push CREF information onto method
  frame, SVAR located place. Before this fix, SVAR is simply nil.
  After this patch, CREF (or NULL == Qfalse for not iseq methods)
  is stored at the method invocation.
  When SVAR is requierd, then put NODE_IF onto SVAR location,
  and NDOE_IF::nd_reserved points CREF itself.
* vm.c (vm_cref_new, vm_cref_dump, vm_cref_new_toplevel): added.
* vm_insnhelper.c (vm_push_frame): accept CREF.
* method.h, vm_method.c (rb_add_method_iseq): added. This function
  accepts iseq and CREF.
* class.c (clone_method): use rb_add_method_iseq().
* gc.c (mark_method_entry): mark method_entry::body.iseq_body.cref.
* iseq.c: remove CREF related codes.
* insns.def (getinlinecache/setinlinecache): CREF should be cache key
  because a different CREF has a different namespace.
* node.c (rb_gc_mark_node): mark NODE_IF::nd_reserved for SVAR.
* proc.c: catch up changes.
* struct.c: ditto.
* insns.def: ditto.
* vm_args.c (raise_argument_error): ditto.
* vm_eval.c: ditto.
* test/ruby/test_class.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49874 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

16 files changed, 378 insertions, 131 deletions

diff --git a/ChangeLog b/ChangeLog
index 737e6222d0..cfcf7a7a00 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,49 @@
+Fri Mar  6 20:18:38 2015  Koichi Sasada  <ko1@atdot.net>
+
+	* fix namespace issue on singleton class expressions. [Bug #10943]
+
+	* vm_core.h, method.h: remove rb_iseq_t::cref_stack. CREF is stored
+	  to rb_method_definition_t::body.iseq_body.cref.
+
+	* vm_insnhelper.c: modify SVAR usage.
+	  When calling ISEQ type method, push CREF information onto method
+	  frame, SVAR located place. Before this fix, SVAR is simply nil.
+	  After this patch, CREF (or NULL == Qfalse for not iseq methods)
+	  is stored at the method invocation.
+
+	  When SVAR is requierd, then put NODE_IF onto SVAR location,
+	  and NDOE_IF::nd_reserved points CREF itself.
+
+	* vm.c (vm_cref_new, vm_cref_dump, vm_cref_new_toplevel): added.
+
+	* vm_insnhelper.c (vm_push_frame): accept CREF.
+
+	* method.h, vm_method.c (rb_add_method_iseq): added. This function
+	  accepts iseq and CREF.
+
+	* class.c (clone_method): use rb_add_method_iseq().
+
+	* gc.c (mark_method_entry): mark method_entry::body.iseq_body.cref.
+
+	* iseq.c: remove CREF related codes.
+
+	* insns.def (getinlinecache/setinlinecache): CREF should be cache key
+	  because a different CREF has a different namespace.
+
+	* node.c (rb_gc_mark_node): mark NODE_IF::nd_reserved for SVAR.
+
+	* proc.c: catch up changes.
+
+	* struct.c: ditto.
+
+	* insns.def: ditto.
+
+	* vm_args.c (raise_argument_error): ditto.
+
+	* vm_eval.c: ditto.
+
+	* test/ruby/test_class.rb: add a test.
+
 Fri Mar  6 18:19:13 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* test/webrick/test_filehandler.rb: on vboxsf (on VirtualBox
diff --git a/class.c b/class.c
index 12bac24487..42c27b5f32 100644
--- a/class.c
+++ b/class.c
@@ -247,11 +247,10 @@ clone_method(VALUE klass, ID mid, const rb_method_entry_t *me)
     if (me->def && me->def->type == VM_METHOD_TYPE_ISEQ) {
 	rb_iseq_t *iseq;
 	NODE *new_cref;
-	newiseqval = rb_iseq_clone(me->def->body.iseq->self, klass);
+	newiseqval = rb_iseq_clone(me->def->body.iseq_body.iseq->self, klass);
 	GetISeqPtr(newiseqval, iseq);
-	rb_vm_rewrite_cref_stack(me->def->body.iseq->cref_stack, me->klass, klass, &new_cref);
-	RB_OBJ_WRITE(iseq->self, &iseq->cref_stack, new_cref);
-	rb_add_method(klass, mid, VM_METHOD_TYPE_ISEQ, iseq, me->flag);
+	rb_vm_rewrite_cref_stack(me->def->body.iseq_body.cref, me->klass, klass, &new_cref);
+	rb_add_method_iseq(klass, mid, iseq, new_cref, me->flag);
 	RB_GC_GUARD(newiseqval);
     }
     else {
diff --git a/gc.c b/gc.c
index d69276ee3e..10b74b0cae 100644
--- a/gc.c
+++ b/gc.c
@@ -3786,11 +3786,14 @@ mark_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
     const rb_method_definition_t *def = me->def;
 
     gc_mark(objspace, me->klass);
+
   again:
     if (!def) return;
+
     switch (def->type) {
       case VM_METHOD_TYPE_ISEQ:
-	gc_mark(objspace, def->body.iseq->self);
+	gc_mark(objspace, def->body.iseq_body.iseq->self);
+	gc_mark(objspace, (VALUE)def->body.iseq_body.cref);
 	break;
       case VM_METHOD_TYPE_BMETHOD:
 	gc_mark(objspace, def->body.proc);
diff --git a/insns.def b/insns.def
index 778999d7db..761d1fc5eb 100644
--- a/insns.def
+++ b/insns.def
@@ -159,7 +159,7 @@ getclassvariable
 ()
 (VALUE val)
 {
-    NODE *cref = rb_vm_get_cref(GET_ISEQ(), GET_EP());
+    NODE *cref = rb_vm_get_cref(GET_EP());
     val = rb_cvar_get(vm_get_cvar_base(cref, GET_CFP()), id);
 }
 
@@ -174,7 +174,7 @@ setclassvariable
 (VALUE val)
 ()
 {
-    NODE *cref = rb_vm_get_cref(GET_ISEQ(), GET_EP());
+    NODE *cref = rb_vm_get_cref(GET_EP());
     rb_cvar_set(vm_get_cvar_base(cref, GET_CFP()), id, val);
 }
 
@@ -196,7 +196,7 @@ getconstant
 (VALUE klass)
 (VALUE val)
 {
-    val = vm_get_ev_const(th, GET_ISEQ(), klass, id, 0);
+    val = vm_get_ev_const(th, klass, id, 0);
 }
 
 /**
@@ -318,10 +318,10 @@ putspecialobject
 	val = rb_mRubyVMFrozenCore;
 	break;
       case VM_SPECIAL_OBJECT_CBASE:
-	val = vm_get_cbase(GET_ISEQ(), GET_EP());
+	val = vm_get_cbase(GET_EP());
 	break;
       case VM_SPECIAL_OBJECT_CONST_BASE:
-	val = vm_get_const_base(GET_ISEQ(), GET_EP());
+	val = vm_get_const_base(GET_EP());
 	break;
       default:
 	rb_bug("putspecialobject insn: unknown value_type");
@@ -730,7 +730,7 @@ defined
 	}
 	break;
       case DEFINED_IVAR2:
-	klass = vm_get_cbase(GET_ISEQ(), GET_EP());
+	klass = vm_get_cbase(GET_EP());
 	break;
       case DEFINED_GVAR:
 	if (rb_gvar_defined(rb_global_entry(SYM2ID(obj)))) {
@@ -738,7 +738,7 @@ defined
 	}
 	break;
       case DEFINED_CVAR: {
-	NODE *cref = rb_vm_get_cref(GET_ISEQ(), GET_EP());
+	NODE *cref = rb_vm_get_cref(GET_EP());
 	klass = vm_get_cvar_base(cref, GET_CFP());
 	if (rb_cvar_defined(klass, SYM2ID(obj))) {
 	    expr_type = DEFINED_CVAR;
@@ -747,7 +747,7 @@ defined
       }
       case DEFINED_CONST:
 	klass = v;
-	if (vm_get_ev_const(th, GET_ISEQ(), klass, SYM2ID(obj), 1)) {
+	if (vm_get_ev_const(th, klass, SYM2ID(obj), 1)) {
 	    expr_type = DEFINED_CONST;
 	}
 	break;
@@ -1013,13 +1013,14 @@ defineclass
 	rb_bug("unknown defineclass type: %d", (int)type);
     }
 
-    COPY_CREF(class_iseq->cref_stack, vm_cref_push(th, klass, NOEX_PUBLIC, NULL));
-
     /* enter scope */
     vm_push_frame(th, class_iseq, VM_FRAME_MAGIC_CLASS,
-		  klass, 0, VM_ENVVAL_BLOCK_PTR(GET_BLOCK_PTR()),
+		  klass, 0,
+		  VM_ENVVAL_BLOCK_PTR(GET_BLOCK_PTR()),
+		  vm_cref_push(th, klass, NOEX_PUBLIC, NULL),
 		  class_iseq->iseq_encoded, GET_SP(),
 		  class_iseq->local_size, 0, class_iseq->stack_max);
+
     RESTORE_REGS();
     NEXT_INSN();
 }
@@ -1241,7 +1242,8 @@ getinlinecache
 ()
 (VALUE val)
 {
-    if (ic->ic_serial == GET_GLOBAL_CONSTANT_STATE()) {
+    if (ic->ic_serial == GET_GLOBAL_CONSTANT_STATE() &&
+	ic->ic_cref == rb_vm_get_cref(GET_EP())) {
 	val = ic->ic_value.value;
 	JUMP(dst);
     }
@@ -1267,6 +1269,7 @@ setinlinecache
     }
     ic->ic_value.value = val;
     ic->ic_serial = GET_GLOBAL_CONSTANT_STATE() - ruby_vm_const_missing_count;
+    ic->ic_cref = rb_vm_get_cref(GET_EP());
     ruby_vm_const_missing_count = 0;
 }
 
diff --git a/iseq.c b/iseq.c
index de65dcbf33..1eac9309f3 100644
--- a/iseq.c
+++ b/iseq.c
@@ -121,7 +121,6 @@ iseq_mark(void *ptr)
 	RUBY_MARK_UNLESS_NULL(iseq->location.path);
 	RUBY_MARK_UNLESS_NULL(iseq->location.absolute_path);
 
-	RUBY_MARK_UNLESS_NULL((VALUE)iseq->cref_stack);
 	RUBY_MARK_UNLESS_NULL(iseq->klass);
 	RUBY_MARK_UNLESS_NULL(iseq->coverage);
 	RUBY_MARK_UNLESS_NULL(iseq->orig);
@@ -213,38 +212,21 @@ iseq_location_setup(rb_iseq_t *iseq, VALUE path, VALUE absolute_path, VALUE name
     return loc;
 }
 
-#define ISEQ_SET_CREF(iseq, cref) RB_OBJ_WRITE((iseq)->self, &(iseq)->cref_stack, (cref))
-
 static void
 set_relation(rb_iseq_t *iseq, const VALUE parent)
 {
     const VALUE type = iseq->type;
-    rb_thread_t *th = GET_THREAD();
     rb_iseq_t *piseq;
 
     /* set class nest stack */
     if (type == ISEQ_TYPE_TOP) {
-	/* toplevel is private */
-	RB_OBJ_WRITE(iseq->self, &iseq->cref_stack, NEW_CREF(rb_cObject));
-	iseq->cref_stack->nd_refinements = Qnil;
-	iseq->cref_stack->nd_visi = NOEX_PRIVATE;
-	if (th->top_wrapper) {
-	    NODE *cref = NEW_CREF(th->top_wrapper);
-	    cref->nd_refinements = Qnil;
-	    cref->nd_visi = NOEX_PRIVATE;
-	    RB_OBJ_WRITE(cref, &cref->nd_next, iseq->cref_stack);
-	    ISEQ_SET_CREF(iseq, cref);
-	}
 	iseq->local_iseq = iseq;
     }
     else if (type == ISEQ_TYPE_METHOD || type == ISEQ_TYPE_CLASS) {
-	ISEQ_SET_CREF(iseq, NEW_CREF(0)); /* place holder */
-	iseq->cref_stack->nd_refinements = Qnil;
 	iseq->local_iseq = iseq;
     }
     else if (RTEST(parent)) {
 	GetISeqPtr(parent, piseq);
-	ISEQ_SET_CREF(iseq, piseq->cref_stack);
 	iseq->local_iseq = piseq->local_iseq;
     }
 
@@ -1973,13 +1955,8 @@ rb_iseq_clone(VALUE iseqval, VALUE newcbase)
     if (iseq0->local_iseq == iseq0) {
 	iseq1->local_iseq = iseq1;
     }
+
     if (newcbase) {
-	ISEQ_SET_CREF(iseq1, NEW_CREF(newcbase));
-	RB_OBJ_WRITE(iseq1->cref_stack, &iseq1->cref_stack->nd_refinements, iseq0->cref_stack->nd_refinements);
-	iseq1->cref_stack->nd_visi = iseq0->cref_stack->nd_visi;
-	if (iseq0->cref_stack->nd_next) {
-	    RB_OBJ_WRITE(iseq1->cref_stack, &iseq1->cref_stack->nd_next, iseq0->cref_stack->nd_next);
-	}
 	RB_OBJ_WRITE(iseq1->self, &iseq1->klass, newcbase);
     }
 
diff --git a/method.h b/method.h
index 65070532aa..9df9430946 100644
--- a/method.h
+++ b/method.h
@@ -12,6 +12,7 @@
 #define METHOD_H
 
 #include "internal.h"
+#include "node.h"
 
 #ifndef END_OF_ENUMERATION
 # if defined(__GNUC__) &&! defined(__STRICT_ANSI__)
@@ -79,8 +80,12 @@ typedef struct rb_method_definition_struct {
     rb_method_type_t type; /* method type */
     int alias_count;
     ID original_id;
+
     union {
-	rb_iseq_t * const iseq;            /* should be mark */
+	struct {
+	    rb_iseq_t *const iseq;            /* should be mark */
+	    NODE *cref;
+	} iseq_body;
 	rb_method_cfunc_t cfunc;
 	rb_method_attr_t attr;
 	const VALUE proc;                 /* should be mark */
@@ -113,6 +118,7 @@ struct unlinked_method_entry_list_entry {
      UNDEFINED_METHOD_ENTRY_P((def)->body.orig_me))
 
 void rb_add_method_cfunc(VALUE klass, ID mid, VALUE (*func)(ANYARGS), int argc, rb_method_flag_t noex);
+void rb_add_method_iseq(VALUE klass, ID mid, rb_iseq_t *iseq, NODE *cref, rb_method_flag_t noex);
 rb_method_entry_t *rb_add_method(VALUE klass, ID mid, rb_method_type_t type, void *option, rb_method_flag_t noex);
 rb_method_entry_t *rb_method_entry(VALUE klass, ID id, VALUE *define_class_ptr);
 rb_method_entry_t *rb_method_entry_at(VALUE obj, ID id);
diff --git a/node.c b/node.c
index 32518d3154..8e2dcdf8b7 100644
--- a/node.c
+++ b/node.c
@@ -947,6 +947,7 @@ rb_gc_mark_node(NODE *obj)
 {
     switch (nd_type(obj)) {
       case NODE_IF:		/* 1,2,3 */
+	rb_gc_mark(obj->nd_refinements); /* use as SVAR */
       case NODE_FOR:
       case NODE_ITER:
       case NODE_WHEN:
diff --git a/proc.c b/proc.c
index 224df0120f..6da2f547c5 100644
--- a/proc.c
+++ b/proc.c
@@ -1208,7 +1208,6 @@ mnew_internal(rb_method_entry_t *me, VALUE defined_class, VALUE klass,
 	def->type = VM_METHOD_TYPE_MISSING;
 	def->original_id = id;
 	def->alias_count = 0;
-
     }
     data->ume = ALLOC(struct unlinked_method_entry_list_entry);
     data->me->def->alias_count++;
@@ -2025,7 +2024,7 @@ rb_method_entry_min_max_arity(const rb_method_entry_t *me, int *max)
       case VM_METHOD_TYPE_BMETHOD:
 	return rb_proc_min_max_arity(def->body.proc, max);
       case VM_METHOD_TYPE_ISEQ: {
-	rb_iseq_t *iseq = def->body.iseq;
+	rb_iseq_t *iseq = def->body.iseq_body.iseq;
 	return rb_iseq_min_max_arity(iseq, max);
       }
       case VM_METHOD_TYPE_UNDEF:
@@ -2162,12 +2161,24 @@ method_get_iseq(rb_method_definition_t *def)
       case VM_METHOD_TYPE_BMETHOD:
 	return get_proc_iseq(def->body.proc, 0);
       case VM_METHOD_TYPE_ISEQ:
-	return def->body.iseq;
+	return def->body.iseq_body.iseq;
       default:
-	return 0;
+	return NULL;
+    }
+}
+
+static NODE *
+method_get_cref(rb_method_definition_t *def)
+{
+    switch (def->type) {
+      case VM_METHOD_TYPE_ISEQ:
+	return def->body.iseq_body.cref;
+      default:
+	return NULL;
     }
 }
 
+
 rb_iseq_t *
 rb_method_get_iseq(VALUE method)
 {
@@ -2376,6 +2387,7 @@ method_proc(VALUE method)
     env->block.self = meth->recv;
     env->block.klass = meth->defined_class;
     env->block.iseq = method_get_iseq(meth->me->def);
+    env->block.ep[-1] = (VALUE)method_get_cref(meth->me->def);
     return procval;
 }
 
diff --git a/struct.c b/struct.c
index c123318b81..cd427ffef5 100644
--- a/struct.c
+++ b/struct.c
@@ -179,7 +179,7 @@ define_aref_method(VALUE nstr, VALUE name, VALUE off)
     VALUE iseqval = rb_method_for_self_aref(name, off, rb_vm_opt_struct_aref);
     rb_iseq_t *iseq = DATA_PTR(iseqval);
 
-    rb_add_method(nstr, SYM2ID(name), VM_METHOD_TYPE_ISEQ, iseq, NOEX_PUBLIC);
+    rb_add_method_iseq(nstr, SYM2ID(name), iseq, NULL, NOEX_PUBLIC);
     RB_GC_GUARD(iseqval);
 }
 
@@ -190,7 +190,7 @@ define_aset_method(VALUE nstr, VALUE name, VALUE off)
     VALUE iseqval = rb_method_for_self_aset(name, off, rb_vm_opt_struct_aset);
     rb_iseq_t *iseq = DATA_PTR(iseqval);
 
-    rb_add_method(nstr, SYM2ID(name), VM_METHOD_TYPE_ISEQ, iseq, NOEX_PUBLIC);
+    rb_add_method_iseq(nstr, SYM2ID(name), iseq, NULL, NOEX_PUBLIC);
     RB_GC_GUARD(iseqval);
 }
 
diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb
index e17f56f913..36aeaf2bdf 100644
--- a/test/ruby/test_class.rb
+++ b/test/ruby/test_class.rb
@@ -399,4 +399,124 @@ class TestClass < Test::Unit::TestCase
       def c.f; end
     }
   end
+
+  def test_singleton_class_should_has_own_namespace
+    # CONST in singleton class
+    objs = []
+    $i = 0
+
+    2.times{
+      objs << obj = Object.new
+      class << obj
+        CONST = ($i += 1)
+        def foo
+          CONST
+        end
+      end
+    }
+    assert_equal(1, objs[0].foo, '[Bug #10943]')
+    assert_equal(2, objs[1].foo, '[Bug #10943]')
+
+    # CONST in block in singleton class
+    objs = []
+    $i = 0
+
+    2.times{
+      objs << obj = Object.new
+      class << obj
+        1.times{
+          CONST = ($i += 1)
+        }
+        def foo
+          [nil].map{
+            CONST
+          }
+        end
+      end
+    }
+    assert_equal([1], objs[0].foo, '[Bug #10943]')
+    assert_equal([2], objs[1].foo, '[Bug #10943]')
+
+    # class def in singleton class
+    objs = []
+    $xs = []
+    $i = 0
+
+    2.times{
+      objs << obj = Object.new
+      class << obj
+        CONST = ($i += 1)
+        class X
+          $xs << self
+          CONST = ($i += 1)
+          def foo
+            CONST
+          end
+        end
+
+        def x
+          X
+        end
+      end
+    }
+    assert_not_equal($xs[0], $xs[1], '[Bug #10943]')
+    assert_not_equal(objs[0].x, objs[1].x, '[Bug #10943]')
+    assert_equal(2, $xs[0]::CONST, '[Bug #10943]')
+    assert_equal(2, $xs[0].new.foo, '[Bug #10943]')
+    assert_equal(4, $xs[1]::CONST, '[Bug #10943]')
+    assert_equal(4, $xs[1].new.foo, '[Bug #10943]')
+
+    # class def in block in singleton class
+    objs = []
+    $xs = []
+    $i = 0
+
+    2.times{
+      objs << obj = Object.new
+      class << obj
+        1.times{
+          CONST = ($i += 1)
+        }
+        1.times{
+          class X
+            $xs << self
+            CONST = ($i += 1)
+            def foo
+              CONST
+            end
+          end
+
+          def x
+            X
+          end
+        }
+      end
+    }
+    assert_not_equal($xs[0], $xs[1], '[Bug #10943]')
+    assert_not_equal(objs[0].x, objs[1].x, '[Bug #10943]')
+    assert_equal(2, $xs[0]::CONST, '[Bug #10943]')
+    assert_equal(2, $xs[0].new.foo, '[Bug #10943]')
+    assert_equal(4, $xs[1]::CONST, '[Bug #10943]')
+    assert_equal(4, $xs[1].new.foo, '[Bug #10943]')
+
+    # method def in singleton class
+    ms = []
+    ps = $test_singleton_class_shared_cref_ps = []
+    2.times{
+      ms << Module.new do
+        class << self
+          $test_singleton_class_shared_cref_ps << Proc.new{
+            def xyzzy
+              self
+            end
+          }
+        end
+      end
+    }
+
+    ps.each{|p| p.call} # define xyzzy methods for each singleton classes
+    ms.each{|m|
+      assert_equal(m, m.xyzzy, "Bug #10871")
+    }
+  end
 end
diff --git a/vm.c b/vm.c
index b84ba788c2..cc9acbcb7d 100644
--- a/vm.c
+++ b/vm.c
@@ -79,6 +79,39 @@ rb_vm_control_frame_block_ptr(const rb_control_frame_t *cfp)
     return VM_CF_BLOCK_PTR(cfp);
 }
 
+static NODE *
+vm_cref_new(VALUE klass, long visi, NODE *prev_cref)
+{
+    NODE *cref = NEW_CREF(klass);
+    cref->nd_refinements = Qnil;
+    cref->nd_visi = visi;
+    cref->nd_next = prev_cref;
+    return cref;
+}
+
+static NODE *
+vm_cref_new_toplevel(rb_thread_t *th)
+{
+    NODE *cref = vm_cref_new(rb_cObject, NOEX_PRIVATE /* toplevel visibility is private */, NULL);
+
+    if (th->top_wrapper) {
+	cref = vm_cref_new(th->top_wrapper, NOEX_PRIVATE, cref);
+    }
+
+    return cref;
+}
+
+static void
+vm_cref_dump(const char *mesg, const NODE *cref)
+{
+    fprintf(stderr, "vm_cref_dump: %s (%p)\n", mesg, cref);
+
+    while (cref) {
+	fprintf(stderr, "= cref| klass: %s\n", RSTRING_PTR(rb_class_path(cref->nd_clss)));
+	cref = cref->nd_next;
+    }
+}
+
 #if VM_COLLECT_USAGE_DETAILS
 static void vm_collect_usage_operand(int insn, int n, VALUE op);
 static void vm_collect_usage_insn(int insn);
@@ -200,7 +233,7 @@ vm_stat(int argc, VALUE *argv, VALUE self)
 /* control stack frame */
 
 static void
-vm_set_top_stack(rb_thread_t * th, VALUE iseqval)
+vm_set_top_stack(rb_thread_t *th, VALUE iseqval)
 {
     rb_iseq_t *iseq;
     GetISeqPtr(iseqval, iseq);
@@ -211,7 +244,9 @@ vm_set_top_stack(rb_thread_t * th, VALUE iseqval)
 
     /* for return */
     vm_push_frame(th, iseq, VM_FRAME_MAGIC_TOP | VM_FRAME_FLAG_FINISH,
-		  th->top_self, rb_cObject, VM_ENVVAL_BLOCK_PTR(0),
+		  th->top_self, rb_cObject,
+		  VM_ENVVAL_BLOCK_PTR(0),
+		  vm_cref_new_toplevel(th),
 		  iseq->iseq_encoded, th->cfp->sp, iseq->local_size, 0, iseq->stack_max);
 }
 
@@ -223,12 +258,10 @@ vm_set_eval_stack(rb_thread_t * th, VALUE iseqval, const NODE *cref, rb_block_t
 
     vm_push_frame(th, iseq, VM_FRAME_MAGIC_EVAL | VM_FRAME_FLAG_FINISH,
 		  base_block->self, base_block->klass,
-		  VM_ENVVAL_PREV_EP_PTR(base_block->ep), iseq->iseq_encoded,
+		  VM_ENVVAL_PREV_EP_PTR(base_block->ep),
+		  cref,
+		  iseq->iseq_encoded,
 		  th->cfp->sp, iseq->local_size, 0, iseq->stack_max);
-
-    if (cref) {
-	th->cfp->ep[-1] = (VALUE)cref;
-    }
 }
 
 static void
@@ -790,6 +823,7 @@ invoke_block_from_c(rb_thread_t *th, const rb_block_t *block,
 	    vm_push_frame(th, iseq, type | VM_FRAME_FLAG_FINISH | VM_FRAME_FLAG_BMETHOD,
 			  self, defined_class,
 			  VM_ENVVAL_PREV_EP_PTR(block->ep),
+			  cref,
 			  iseq->iseq_encoded + opt_pc,
 			  cfp->sp + arg_size, iseq->local_size - arg_size,
 			  me, iseq->stack_max);
@@ -801,15 +835,12 @@ invoke_block_from_c(rb_thread_t *th, const rb_block_t *block,
 	    vm_push_frame(th, iseq, type | VM_FRAME_FLAG_FINISH,
 			  self, defined_class,
 			  VM_ENVVAL_PREV_EP_PTR(block->ep),
+			  cref,
 			  iseq->iseq_encoded + opt_pc,
 			  cfp->sp + arg_size, iseq->local_size - arg_size,
 			  0, iseq->stack_max);
 	}
 
-	if (cref) {
-	    th->cfp->ep[-1] = (VALUE)cref;
-	}
-
 	ret = vm_exec(th);
 
 	if (me) {
@@ -1017,7 +1048,8 @@ rb_vm_cref(void)
     if (cfp == 0) {
 	return NULL;
     }
-    return rb_vm_get_cref(cfp->iseq, cfp->ep);
+
+    return rb_vm_get_cref(cfp->ep);
 }
 
 const NODE *
@@ -1027,7 +1059,7 @@ rb_vm_cref_in_context(VALUE self, VALUE cbase)
     const rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);
     const NODE *cref;
     if (cfp->self != self) return NULL;
-    cref = rb_vm_get_cref(cfp->iseq, cfp->ep);
+    cref = rb_vm_get_cref(cfp->ep);
     if (cref->nd_clss != cbase) return NULL;
     return cref;
 }
@@ -1053,7 +1085,7 @@ rb_vm_cbase(void)
     if (cfp == 0) {
 	rb_raise(rb_eRuntimeError, "Can't call on top of Fiber or Thread");
     }
-    return vm_get_cbase(cfp->iseq, cfp->ep);
+    return vm_get_cbase(cfp->ep);
 }
 
 /* jump */
@@ -1594,6 +1626,7 @@ vm_exec(rb_thread_t *th)
 	    vm_push_frame(th, catch_iseq, VM_FRAME_MAGIC_RESCUE,
 			  cfp->self, cfp->klass,
 			  VM_ENVVAL_PREV_EP_PTR(cfp->ep),
+			  NULL,
 			  catch_iseq->iseq_encoded,
 			  cfp->sp + 1 /* push value */,
 			  catch_iseq->local_size - 1,
@@ -1745,7 +1778,8 @@ rb_vm_call_cfunc(VALUE recv, VALUE (*func)(VALUE), VALUE arg,
     VALUE val;
 
     vm_push_frame(th, DATA_PTR(iseqval), VM_FRAME_MAGIC_TOP | VM_FRAME_FLAG_FINISH,
-		  recv, CLASS_OF(recv), VM_ENVVAL_BLOCK_PTR(blockptr), 0, reg_cfp->sp, 1, 0, 0);
+		  recv, CLASS_OF(recv), VM_ENVVAL_BLOCK_PTR(blockptr), vm_cref_new_toplevel(th),
+		  0, reg_cfp->sp, 1, 0, 0);
 
     val = (*func)(arg);
 
@@ -2183,7 +2217,9 @@ th_init(rb_thread_t *th, VALUE self)
     th->cfp = (void *)(th->stack + th->stack_size);
 
     vm_push_frame(th, 0 /* dummy iseq */, VM_FRAME_MAGIC_TOP | VM_FRAME_FLAG_FINISH,
-		  Qnil /* dummy self */, Qnil /* dummy klass */, VM_ENVVAL_BLOCK_PTR(0), 0 /* dummy pc */, th->stack, 1, 0, 0);
+		  Qnil /* dummy self */, Qnil /* dummy klass */, VM_ENVVAL_BLOCK_PTR(0),
+		  NULL /* dummy cref */,
+		  0 /* dummy pc */, th->stack, 1, 0, 0);
 
     th->status = THREAD_RUNNABLE;
     th->errinfo = Qnil;
@@ -2250,15 +2286,13 @@ vm_define_method(rb_thread_t *th, VALUE obj, ID id, VALUE iseqval,
     }
 
     /* dup */
-    COPY_CREF(miseq->cref_stack, cref);
-    miseq->cref_stack->nd_visi = NOEX_PUBLIC;
     RB_OBJ_WRITE(miseq->self, &miseq->klass, klass);
     miseq->defined_method_id = id;
-    rb_add_method(klass, id, VM_METHOD_TYPE_ISEQ, miseq, noex);
+    rb_add_method_iseq(klass, id, miseq, cref, noex);
 
     if (!is_singleton && noex == NOEX_MODFUNC) {
 	klass = rb_singleton_class(klass);
-	rb_add_method(klass, id, VM_METHOD_TYPE_ISEQ, miseq, NOEX_PUBLIC);
+	rb_add_method_iseq(klass, id, miseq, cref, NOEX_PUBLIC);
     }
 }
 
@@ -2745,6 +2779,8 @@ Init_VM(void)
 	th->cfp->self = th->top_self;
 	th->cfp->klass = Qnil;
 
+	th->cfp->ep[-1] = (VALUE)vm_cref_new(rb_cObject, NOEX_PRIVATE, NULL);
+
 	/*
 	 * The Binding of the top level scope
 	 */
diff --git a/vm_args.c b/vm_args.c
index cf7256b2d7..e4ade6bb2f 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -675,7 +675,7 @@ raise_argument_error(rb_thread_t *th, const rb_iseq_t *iseq, const VALUE exc)
     VALUE at;
 
     if (iseq) {
-	vm_push_frame(th, iseq, VM_FRAME_MAGIC_METHOD, Qnil /* self */, Qnil /* klass */, Qnil /* specval*/,
+	vm_push_frame(th, iseq, VM_FRAME_MAGIC_METHOD, Qnil /* self */, Qnil /* klass */, Qnil /* specval*/, NULL /* cref */,
 		      iseq->iseq_encoded, th->cfp->sp, 0 /* local_size */, 0 /* me */, 0 /* stack_max */);
 	at = rb_vm_backtrace_object();
 	vm_pop_frame(th);
diff --git a/vm_core.h b/vm_core.h
index 1f17dfd56a..5b364129bb 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -117,6 +117,7 @@ typedef struct rb_compile_option_struct rb_compile_option_t;
 
 struct iseq_inline_cache_entry {
     rb_serial_t ic_serial;
+    NODE *ic_cref;
     union {
 	size_t index;
 	VALUE value;
@@ -322,17 +323,6 @@ struct rb_iseq_struct {
 
     VALUE self;
     const VALUE orig;			/* non-NULL if its data have origin */
-
-    /* block inlining */
-    /*
-     * NODE *node;
-     * void *special_block_builder;
-     * void *cached_special_block_builder;
-     * VALUE cached_special_block;
-     */
-
-    /* klass/module nest information stack (cref) */
-    NODE * const cref_stack;
     const VALUE klass;
 
     /* misc */
@@ -416,7 +406,6 @@ typedef struct rb_vm_struct {
 
     /* object management */
     VALUE mark_object_ary;
-
     const VALUE special_exceptions[ruby_special_error_count];
 
     /* load */
diff --git a/vm_eval.c b/vm_eval.c
index 4039b6c9f2..add2aaf50a 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -119,7 +119,8 @@ vm_call0_cfunc_with_frame(rb_thread_t* th, rb_call_info_t *ci, const VALUE *argv
 	rb_control_frame_t *reg_cfp = th->cfp;
 
 	vm_push_frame(th, 0, VM_FRAME_MAGIC_CFUNC, recv, defined_class,
-		      VM_ENVVAL_BLOCK_PTR(blockptr), 0, reg_cfp->sp, 1, me, 0);
+		      VM_ENVVAL_BLOCK_PTR(blockptr), NULL /* cref */,
+		      0, reg_cfp->sp, 1, me, 0);
 
 	if (len >= 0) rb_check_arity(argc, len, len);
 
@@ -1306,13 +1307,13 @@ eval_string_with_cref(VALUE self, VALUE src, VALUE scope, NODE *const cref_arg,
 
 	if (!cref && base_block->iseq) {
 	    if (NIL_P(scope)) {
-		orig_cref = rb_vm_get_cref(base_block->iseq, base_block->ep);
+		orig_cref = rb_vm_get_cref(base_block->ep);
 		cref = NEW_CREF(Qnil);
 		crefval = (VALUE) cref;
 		COPY_CREF(cref, orig_cref);
 	    }
 	    else {
-		cref = rb_vm_get_cref(base_block->iseq, base_block->ep);
+		cref = rb_vm_get_cref(base_block->ep);
 	    }
 	}
 	vm_set_eval_stack(th, iseqval, cref, base_block);
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 815cf4e30b..e4afbdb0fb 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -46,6 +46,7 @@ vm_push_frame(rb_thread_t *th,
 	      VALUE self,
 	      VALUE klass,
 	      VALUE specval,
+	      const NODE *cref,
 	      const VALUE *pc,
 	      VALUE *sp,
 	      int local_size,
@@ -68,7 +69,8 @@ vm_push_frame(rb_thread_t *th,
     }
 
     /* set special val */
-    *sp = specval;
+    sp[-1] = (VALUE)cref;
+    sp[ 0] = specval;
 
     /* setup vm control frame stack */
 
@@ -161,6 +163,7 @@ lep_svar_get(rb_thread_t *th, const VALUE *lep, rb_num_t key)
     const NODE * const svar = *svar_place;
 
     if (NIL_P((VALUE)svar)) return Qnil;
+    if (nd_type(svar) == NODE_CREF) return Qnil;
 
     switch (key) {
       case VM_SVAR_LASTLINE:
@@ -188,6 +191,12 @@ lep_svar_set(rb_thread_t *th, VALUE *lep, rb_num_t key, VALUE val)
 
     if (NIL_P((VALUE)svar)) {
 	svar = *svar_place = NEW_IF(Qnil, Qnil, Qnil);
+	svar->nd_reserved = Qfalse;
+    }
+    else if (nd_type(svar) == NODE_CREF) {
+	NODE *cref = svar;
+	svar = *svar_place = NEW_IF(Qnil, Qnil, Qnil);
+	svar->nd_reserved = (VALUE)cref;
     }
 
     switch (key) {
@@ -245,28 +254,42 @@ vm_getspecial(rb_thread_t *th, VALUE *lep, rb_num_t key, rb_num_t type)
 }
 
 static NODE *
-vm_get_cref0(const rb_iseq_t *iseq, const VALUE *ep)
+ep_cref(const VALUE *ep)
 {
-    while (1) {
-	if (VM_EP_LEP_P(ep)) {
-	    if (!RUBY_VM_NORMAL_ISEQ_P(iseq)) return NULL;
-	    return iseq->cref_stack;
-	}
-	else if (ep[-1] != Qnil) {
+    const VALUE svar = ep[-1];
+
+    if (!svar) {
+	return NULL;
+    }
+    else if (nd_type(svar) == NODE_CREF) {
+	return (NODE *)svar;
+    }
+    else {
+	return (NODE *)((NODE *)svar)->nd_reserved;
+    }
+}
+
+static NODE *
+vm_get_cref0(const VALUE *ep)
+{
+    while (!VM_EP_LEP_P(ep)) {
+	if (ep[-1]) {
 	    return (NODE *)ep[-1];
 	}
 	ep = VM_EP_PREV_EP(ep);
     }
+    return ep_cref(ep);
 }
 
 NODE *
-rb_vm_get_cref(const rb_iseq_t *iseq, const VALUE *ep)
+rb_vm_get_cref(const VALUE *ep)
 {
-    NODE *cref = vm_get_cref0(iseq, ep);
+    NODE *cref = vm_get_cref0(ep);
 
     if (cref == 0) {
 	rb_bug("rb_vm_get_cref: unreachable");
     }
+
     return cref;
 }
 
@@ -274,6 +297,7 @@ void
 rb_vm_rewrite_cref_stack(NODE *node, VALUE old_klass, VALUE new_klass, NODE **new_cref_ptr)
 {
     NODE *new_node;
+
     while (node) {
 	if (node->nd_clss == old_klass) {
 	    new_node = NEW_CREF(new_klass);
@@ -294,17 +318,21 @@ rb_vm_rewrite_cref_stack(NODE *node, VALUE old_klass, VALUE new_klass, NODE **ne
 static NODE *
 vm_cref_push(rb_thread_t *th, VALUE klass, int noex, rb_block_t *blockptr)
 {
-    rb_control_frame_t *cfp = vm_get_ruby_level_caller_cfp(th, th->cfp);
-    NODE *cref = NEW_CREF(klass);
-    cref->nd_refinements = Qnil;
-    cref->nd_visi = noex;
+    NODE *prev_cref = NULL;
+    NODE *cref = NULL;
 
     if (blockptr) {
-	RB_OBJ_WRITE(cref, &cref->nd_next, vm_get_cref0(blockptr->iseq, blockptr->ep));
+	prev_cref = vm_get_cref0(blockptr->ep);
     }
-    else if (cfp) {
-	RB_OBJ_WRITE(cref, &cref->nd_next, vm_get_cref0(cfp->iseq, cfp->ep));
+    else {
+	rb_control_frame_t *cfp = vm_get_ruby_level_caller_cfp(th, th->cfp);
+
+	if (cfp) {
+	    prev_cref = vm_get_cref0(cfp->ep);
+	}
     }
+    cref = vm_cref_new(klass, noex, prev_cref);
+
     /* TODO: why cref->nd_next is 1? */
     if (cref->nd_next && cref->nd_next != (void *) 1 &&
 	!NIL_P(cref->nd_next->nd_refinements)) {
@@ -315,9 +343,9 @@ vm_cref_push(rb_thread_t *th, VALUE klass, int noex, rb_block_t *blockptr)
 }
 
 static inline VALUE
-vm_get_cbase(const rb_iseq_t *iseq, const VALUE *ep)
+vm_get_cbase(const VALUE *ep)
 {
-    NODE *cref = rb_vm_get_cref(iseq, ep);
+    NODE *cref = rb_vm_get_cref(ep);
     VALUE klass = Qundef;
 
     while (cref) {
@@ -331,9 +359,9 @@ vm_get_cbase(const rb_iseq_t *iseq, const VALUE *ep)
 }
 
 static inline VALUE
-vm_get_const_base(const rb_iseq_t *iseq, const VALUE *ep)
+vm_get_const_base(const VALUE *ep)
 {
-    NODE *cref = rb_vm_get_cref(iseq, ep);
+    NODE *cref = rb_vm_get_cref(ep);
     VALUE klass = Qundef;
 
     while (cref) {
@@ -373,14 +401,13 @@ vm_get_iclass(rb_control_frame_t *cfp, VALUE klass)
 }
 
 static inline VALUE
-vm_get_ev_const(rb_thread_t *th, const rb_iseq_t *iseq,
-		VALUE orig_klass, ID id, int is_defined)
+vm_get_ev_const(rb_thread_t *th, VALUE orig_klass, ID id, int is_defined)
 {
     VALUE val;
 
     if (orig_klass == Qnil) {
 	/* in current lexical scope */
-	const NODE *root_cref = rb_vm_get_cref(iseq, th->cfp->ep);
+	const NODE *root_cref = rb_vm_get_cref(th->cfp->ep);
 	const NODE *cref;
 	VALUE klass = orig_klass;
 
@@ -1128,7 +1155,7 @@ vm_callee_setup_arg(rb_thread_t *th, rb_call_info_t *ci, const rb_iseq_t *iseq,
 static VALUE
 vm_call_iseq_setup(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_info_t *ci)
 {
-    vm_callee_setup_arg(th, ci, ci->me->def->body.iseq, cfp->sp - ci->argc);
+    vm_callee_setup_arg(th, ci, ci->me->def->body.iseq_body.iseq, cfp->sp - ci->argc);
     return vm_call_iseq_setup_2(th, cfp, ci);
 }
 
@@ -1148,7 +1175,7 @@ vm_call_iseq_setup_normal(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_info
 {
     int i, local_size;
     VALUE *argv = cfp->sp - ci->argc;
-    rb_iseq_t *iseq = ci->me->def->body.iseq;
+    rb_iseq_t *iseq = ci->me->def->body.iseq_body.iseq;
     VALUE *sp = argv + iseq->param.size;
 
     /* clear local variables (arg_size...local_size) */
@@ -1157,7 +1184,7 @@ vm_call_iseq_setup_normal(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_info
     }
 
     vm_push_frame(th, iseq, VM_FRAME_MAGIC_METHOD, ci->recv, ci->defined_class,
-		  VM_ENVVAL_BLOCK_PTR(ci->blockptr),
+		  VM_ENVVAL_BLOCK_PTR(ci->blockptr), ci->me->def->body.iseq_body.cref,
 		  iseq->iseq_encoded + ci->aux.opt_pc, sp, 0, ci->me, iseq->stack_max);
 
     cfp->sp = argv - 1 /* recv */;
@@ -1169,7 +1196,7 @@ vm_call_iseq_setup_tailcall(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_in
 {
     int i;
     VALUE *argv = cfp->sp - ci->argc;
-    rb_iseq_t *iseq = ci->me->def->body.iseq;
+    rb_iseq_t *iseq = ci->me->def->body.iseq_body.iseq;
     VALUE *src_argv = argv;
     VALUE *sp_orig, *sp;
     VALUE finish_flag = VM_FRAME_TYPE_FINISH_P(cfp) ? VM_FRAME_FLAG_FINISH : 0;
@@ -1195,7 +1222,8 @@ vm_call_iseq_setup_tailcall(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_in
     }
 
     vm_push_frame(th, iseq, VM_FRAME_MAGIC_METHOD | finish_flag,
-		  ci->recv, ci->defined_class, VM_ENVVAL_BLOCK_PTR(ci->blockptr),
+		  ci->recv, ci->defined_class,
+		  VM_ENVVAL_BLOCK_PTR(ci->blockptr), ci->me->def->body.iseq_body.cref,
 		  iseq->iseq_encoded + ci->aux.opt_pc, sp, 0, ci->me, iseq->stack_max);
 
     cfp->sp = sp_orig;
@@ -1377,7 +1405,8 @@ vm_call_cfunc_with_frame(rb_thread_t *th, rb_control_frame_t *reg_cfp, rb_call_i
     EXEC_EVENT_HOOK(th, RUBY_EVENT_C_CALL, recv, me->called_id, me->klass, Qundef);
 
     vm_push_frame(th, 0, VM_FRAME_MAGIC_CFUNC, recv, defined_class,
-		  VM_ENVVAL_BLOCK_PTR(blockptr), 0, th->cfp->sp, 1, me, 0);
+		  VM_ENVVAL_BLOCK_PTR(blockptr), NULL /* cref */,
+		  0, th->cfp->sp, 1, me, 0);
 
     if (len >= 0) rb_check_arity(argc, len, len);
 
@@ -1465,7 +1494,8 @@ vm_call_cfunc_push_frame(rb_thread_t *th)
     th->passed_ci = 0;
 
     vm_push_frame(th, 0, VM_FRAME_MAGIC_CFUNC, ci->recv, ci->defined_class,
-		  VM_ENVVAL_BLOCK_PTR(ci->blockptr), 0, th->cfp->sp + ci->aux.inc_sp, 1, me);
+		  VM_ENVVAL_BLOCK_PTR(ci->blockptr), NULL /* cref */,
+		  0, th->cfp->sp + ci->aux.inc_sp, 1, me);
 
     if (ci->call != vm_call_general) {
 	ci->call = vm_call_cfunc_with_frame;
@@ -1754,7 +1784,7 @@ vm_call_method(rb_thread_t *th, rb_control_frame_t *cfp, rb_call_info_t *ci)
 	      case VM_METHOD_TYPE_UNDEF:
 		break;
 	      case VM_METHOD_TYPE_REFINED:{
-		NODE *cref = rb_vm_get_cref(cfp->iseq, cfp->ep);
+		NODE *cref = rb_vm_get_cref(cfp->ep);
 		VALUE refinements = cref ? cref->nd_refinements : Qnil;
 		VALUE refinement, defined_class;
 		rb_method_entry_t *me;
@@ -1983,7 +2013,7 @@ vm_search_super_method(rb_thread_t *th, rb_control_frame_t *reg_cfp, rb_call_inf
 	iseq = iseq->parent_iseq;
     }
 
-    if (ci->me && ci->me->def->type == VM_METHOD_TYPE_ISEQ && ci->me->def->body.iseq == iseq) {
+    if (ci->me && ci->me->def->type == VM_METHOD_TYPE_ISEQ && ci->me->def->body.iseq_body.iseq == iseq) {
 	ci->klass = RCLASS_SUPER(ci->defined_class);
 	ci->me = rb_method_entry(ci->klass, ci->mid, &ci->defined_class);
     }
@@ -2039,8 +2069,8 @@ vm_yield_with_cfunc(rb_thread_t *th, const rb_block_t *block,
 
     vm_push_frame(th, (rb_iseq_t *)ifunc, VM_FRAME_MAGIC_IFUNC,
 		  self, defined_class,
-		  VM_ENVVAL_PREV_EP_PTR(block->ep), 0,
-		  th->cfp->sp, 1, th->passed_bmethod_me, 0);
+		  VM_ENVVAL_PREV_EP_PTR(block->ep), NULL /* cref */,
+		  0, th->cfp->sp, 1, th->passed_bmethod_me, 0);
 
     val = (*ifunc->nd_cfnc) (arg, ifunc->nd_tval, argc, argv, blockarg);
 
@@ -2095,7 +2125,7 @@ vm_invoke_block(rb_thread_t *th, rb_control_frame_t *reg_cfp, rb_call_info_t *ci
 		      is_lambda ? VM_FRAME_MAGIC_LAMBDA : VM_FRAME_MAGIC_BLOCK,
 		      block->self,
 		      block->klass,
-		      VM_ENVVAL_PREV_EP_PTR(block->ep),
+		      VM_ENVVAL_PREV_EP_PTR(block->ep), NULL /* cref */,
 		      iseq->iseq_encoded + opt_pc,
 		      rsp + arg_size,
 		      iseq->local_size - arg_size, 0, iseq->stack_max);
diff --git a/vm_method.c b/vm_method.c
index 7dd2f4bff7..d5fe52404a 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -245,8 +245,7 @@ rb_add_refined_method_entry(VALUE refined_class, ID mid)
 	rb_clear_method_cache_by_class(refined_class);
     }
     else {
-	rb_add_method(refined_class, mid, VM_METHOD_TYPE_REFINED, 0,
-		      NOEX_PUBLIC);
+	rb_add_method(refined_class, mid, VM_METHOD_TYPE_REFINED, 0, NOEX_PUBLIC);
     }
 }
 
@@ -325,7 +324,7 @@ rb_method_entry_make(VALUE klass, ID mid, rb_method_type_t type,
 	    rb_warning("method redefined; discarding old %"PRIsVALUE, rb_id2str(mid));
 	    switch (old_def->type) {
 	      case VM_METHOD_TYPE_ISEQ:
-		iseq = old_def->body.iseq;
+		iseq = old_def->body.iseq_body.iseq;
 		break;
 	      case VM_METHOD_TYPE_BMETHOD:
 		iseq = rb_proc_get_iseq(old_def->body.proc, 0);
@@ -359,7 +358,8 @@ rb_method_entry_make(VALUE klass, ID mid, rb_method_type_t type,
 
 	switch(def->type) {
 	  case VM_METHOD_TYPE_ISEQ:
-	    RB_OBJ_WRITTEN(klass, Qundef, def->body.iseq->self);
+	    RB_OBJ_WRITTEN(klass, Qundef, def->body.iseq_body.iseq->self);
+	    RB_OBJ_WRITTEN(klass, Qundef, def->body.iseq_body.cref);
 	    break;
 	  case VM_METHOD_TYPE_IVAR:
 	    RB_OBJ_WRITTEN(klass, Qundef, def->body.attr.location);
@@ -447,27 +447,40 @@ setup_method_cfunc_struct(rb_method_cfunc_t *cfunc, VALUE (*func)(), int argc)
 }
 
 rb_method_entry_t *
-rb_add_method(VALUE klass, ID mid, rb_method_type_t type, void *opts, rb_method_flag_t noex)
+rb_add_method0(VALUE klass, ID mid, rb_method_type_t type, void *opts, rb_method_flag_t noex, NODE *cref)
 {
     rb_thread_t *th;
     rb_control_frame_t *cfp;
     int line;
     rb_method_entry_t *me = rb_method_entry_make(klass, mid, type, 0, noex, klass);
     rb_method_definition_t *def = ALLOC(rb_method_definition_t);
+
     if (me->def && me->def->type == VM_METHOD_TYPE_REFINED) {
 	me->def->body.orig_me->def = def;
     }
     else {
 	me->def = def;
     }
+
+    if (0 && cref) vm_cref_dump("rb_add_method0", cref);
+
     def->type = type;
     def->original_id = mid;
     def->alias_count = 0;
+
     switch (type) {
       case VM_METHOD_TYPE_ISEQ: {
 	  rb_iseq_t *iseq = (rb_iseq_t *)opts;
-	  *(rb_iseq_t **)&def->body.iseq = iseq;
-	  RB_OBJ_WRITTEN(klass, Qundef, iseq->self);
+	  NODE *private_cref;
+
+	  *(rb_iseq_t **)&def->body.iseq_body.iseq = iseq;
+	  RB_OBJ_WRITTEN(klass, Qundef, iseq->self); /* should be set iseq before newobj */
+	  def->body.iseq_body.cref = NULL;
+
+	  private_cref = vm_cref_new_toplevel(GET_THREAD()); /* TODO: CREF should be shared with other methods */
+	  if (cref) COPY_CREF(private_cref, cref);
+	  private_cref->nd_visi = NOEX_PUBLIC;
+	  RB_OBJ_WRITE(klass, &def->body.iseq_body.cref, private_cref);
 	  break;
       }
       case VM_METHOD_TYPE_CFUNC:
@@ -511,13 +524,24 @@ rb_add_method(VALUE klass, ID mid, rb_method_type_t type, void *opts, rb_method_
     return me;
 }
 
+rb_method_entry_t *
+rb_add_method(VALUE klass, ID mid, rb_method_type_t type, void *opts, rb_method_flag_t noex)
+{
+    return rb_add_method0(klass, mid, type, opts, noex, NULL);
+}
+
+void
+rb_add_method_iseq(VALUE klass, ID mid, rb_iseq_t *iseq, NODE *cref, rb_method_flag_t noex)
+{
+    rb_add_method0(klass, mid, VM_METHOD_TYPE_ISEQ, iseq, noex, cref);
+}
+
 static rb_method_entry_t *
 method_entry_set(VALUE klass, ID mid, const rb_method_entry_t *me,
 		 rb_method_flag_t noex, VALUE defined_class)
 {
     rb_method_type_t type = me->def ? me->def->type : VM_METHOD_TYPE_UNDEF;
-    rb_method_entry_t *newme = rb_method_entry_make(klass, mid, type, me->def, noex,
-						    defined_class);
+    rb_method_entry_t *newme = rb_method_entry_make(klass, mid, type, me->def, noex, defined_class);
     method_added(klass, mid);
     return newme;
 }
@@ -1195,7 +1219,7 @@ rb_method_definition_eq(const rb_method_definition_t *d1, const rb_method_defini
     }
     switch (d1->type) {
       case VM_METHOD_TYPE_ISEQ:
-	return d1->body.iseq == d2->body.iseq;
+	return d1->body.iseq_body.iseq == d2->body.iseq_body.iseq;
       case VM_METHOD_TYPE_CFUNC:
 	return
 	  d1->body.cfunc.func == d2->body.cfunc.func &&
@@ -1226,7 +1250,7 @@ rb_hash_method_definition(st_index_t hash, const rb_method_definition_t *def)
     hash = rb_hash_uint(hash, def->type);
     switch (def->type) {
       case VM_METHOD_TYPE_ISEQ:
-	return rb_hash_uint(hash, (st_index_t)def->body.iseq);
+	return rb_hash_uint(hash, (st_index_t)def->body.iseq_body.iseq);
       case VM_METHOD_TYPE_CFUNC:
 	hash = rb_hash_uint(hash, (st_index_t)def->body.cfunc.func);
 	return rb_hash_uint(hash, def->body.cfunc.argc);