n-api: free instance data as reference

Instance data associated with a `napi_env` is no longer stored on the
env itself but is instead rendered as a reference. Since
`v8impl::Reference` is tied to a JS object, this modification factors
out the `v8impl::Reference` refcounting and the deletion process into
a base class for `v8impl::Reference`, called `v8impl::RefBase`. The
instance data is then stored as a `v8impl::RefBase`, along with other
references, preventing a segfault that arises from the fact that, up
until now, upon `napi_env` destruction, the instance data was freed
after all references had already been forcefully freed. If the addon
freed a reference during the `napi_set_instance_data` finalizer
callback, such a reference had already been freed during environment
teardown, causing a double free.

Re: https://github.com/nodejs/node-addon-api/pull/663
PR-URL: https://github.com/nodejs/node/pull/31638
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>

1 files changed, 0 insertions, 39 deletions

diff --git a/src/js_native_api_v8_internals.h b/src/js_native_api_v8_internals.h
index 74afd1172e5..ddd219818cd 100644
--- a/src/js_native_api_v8_internals.h
+++ b/src/js_native_api_v8_internals.h
@@ -28,45 +28,6 @@
 
 namespace v8impl {
 
-class RefTracker {
- public:
-  RefTracker() {}
-  virtual ~RefTracker() {}
-  virtual void Finalize(bool isEnvTeardown) {}
-
-  typedef RefTracker RefList;
-
-  inline void Link(RefList* list) {
-    prev_ = list;
-    next_ = list->next_;
-    if (next_ != nullptr) {
-      next_->prev_ = this;
-    }
-    list->next_ = this;
-  }
-
-  inline void Unlink() {
-    if (prev_ != nullptr) {
-      prev_->next_ = next_;
-    }
-    if (next_ != nullptr) {
-      next_->prev_ = prev_;
-    }
-    prev_ = nullptr;
-    next_ = nullptr;
-  }
-
-  static void FinalizeAll(RefList* list) {
-    while (list->next_ != nullptr) {
-      list->next_->Finalize(true);
-    }
-  }
-
- private:
-  RefList* next_ = nullptr;
-  RefList* prev_ = nullptr;
-};
-
 template <typename T>
 using Persistent = v8::Global<T>;