protect access to embedded VALUEs in a struct that will clear be awar…

…e if the VALUE has become garbage collected.
evanphx · May 26, 2011 · a6c7757 · a6c7757
1 parent cfa2570
commit a6c7757
Showing 1 changed file with 40 additions and 10 deletions.
diff --git a/ext/v8/v8_external.cpp b/ext/v8/v8_external.cpp
@@ -9,29 +9,59 @@ namespace {
   VALUE ExternalClass;
   VALUE references;
 
+  struct Weaklink {
+    bool finalized_from_rb;
+    bool finalized_from_v8;
+    VALUE target;
+  };
+
+  VALUE Weaklink_finalized_from_ruby(VALUE object_id, VALUE data) {
+    Weaklink* link = 0;
+    Data_Get_Struct(data, struct Weaklink, link);
+    link->finalized_from_rb = true;
+    if (link->finalized_from_v8) {
+      delete link;
+    }
+    return Qnil;
+  }
+  void Weaklink_finalized_from_v8(Persistent<Value> value, void* data) {
+    Weaklink* link = (Weaklink*)data;
+    link->finalized_from_v8 = true;
+    if (link->finalized_from_rb) {
+      delete link;
+    }
+    value.Dispose();
+  }
+
   VALUE New(VALUE self, VALUE value) {
     HandleScope scope;
-    return rr_v8_handle_new(self, External::New((void*)value));
+    Weaklink* link = new Weaklink();
+    link->finalized_from_v8 = false;
+    link->finalized_from_rb = false;
+    link->target = value;
+    Persistent<External> external = Persistent<External>::New(External::New((void*)link));
+    external.MakeWeak(link,Weaklink_finalized_from_v8);
+    VALUE finalizer_data = Data_Wrap_Struct(rb_cObject, 0, 0, link);
+    rr_define_finalizer(value, (void*)Weaklink_finalized_from_ruby, finalizer_data);
+    return rr_v8_handle_new(self, external);
   }
-  VALUE Unwrap(VALUE self, VALUE value) {
+
+  VALUE _Value(VALUE self) {
     HandleScope scope;
-    if (rb_obj_is_kind_of(value, self)) {
-      return (VALUE)External::Unwrap(rr_v8_handle<External>(self));
-    } else {
-      rb_raise(rb_eArgError, "cannot unwrap %s. It is not a kind of %s", RSTRING_PTR(rb_class_name(rb_class_of(value))), RSTRING_PTR(rb_class_name(self)));
+    Weaklink* link = (Weaklink*)rr_v8_handle<External>(self)->Value();
+    if (link->finalized_from_rb) {
+      rb_warn("an active v8::External wraps a VALUE that has already been finalized! This is not good.\n");
       return Qnil;
+    } else {
+      return link->target;
     }
-  }
-  VALUE _Value(VALUE self) {
-    HandleScope scope;
     return (VALUE)rr_v8_handle<External>(self)->Value();
   }
 }
 
 void rr_init_v8_external() {
   ExternalClass = rr_define_class("External", rr_v8_value_class());
   rr_define_singleton_method(ExternalClass, "New", New, 1);
-  rr_define_singleton_method(ExternalClass, "Unwrap", Unwrap, 1);
   rr_define_method(ExternalClass, "Value", _Value, 0);
 }