n-api: detach external ArrayBuffers on env exit

Make sure that `ArrayBuffer`s created using `napi_create_external_arraybuffer` are rendered unusable after its memory has been released. PR-URL: #30551 Reviewed-By: Gabriel Schulhof <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Denys Otrishko <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

Author: addaleax

src/js_native_api_v8.cc

@@ -186,8 +186,8 @@ inline static napi_status ConcludeDeferred(napi_env env,
 }
 
 // Wrapper around v8impl::Persistent that implements reference counting.
-classReference : privateFinalizer, RefTracker{
-private:
+classReference : protectedFinalizer, RefTracker{
+protected:
 Reference(napi_env env,
  v8::Local<v8::Value> value,
 uint32_t initial_refcount,
@@ -289,7 +289,7 @@ class Reference : private Finalizer, RefTracker{
  }
  }
 
-private:
+protected:
 voidFinalize(bool is_env_teardown = false) override{
 if (_finalize_callback != nullptr){
  _env->CallIntoModuleThrow([&](napi_env env){
@@ -310,6 +310,7 @@ class Reference : private Finalizer, RefTracker{
  }
  }
 
+private:
 // The N-API finalizer callback may make calls into the engine. V8's heap is
 // not in a consistent state during the weak callback, and therefore it does
 // not support calls back into it. However, it provides a mechanism for adding
@@ -335,6 +336,37 @@ class Reference : private Finalizer, RefTracker{
 bool _delete_self;
 };
 
+classArrayBufferReferencefinal : public Reference{
+public:
+// Same signatures for ctor and New() as Reference, except this only works
+// with ArrayBuffers:
+template <typename... Args>
+explicitArrayBufferReference(napi_env env,
+ v8::Local<v8::ArrayBuffer> value,
+ Args&&... args)
+ : Reference(env, value, std::forward<Args>(args)...){}
+
+template <typename... Args>
+static ArrayBufferReference* New(napi_env env,
+ v8::Local<v8::ArrayBuffer> value,
+ Args&&... args){
+returnnewArrayBufferReference(env, value, std::forward<Args>(args)...);
+ }
+
+private:
+voidFinalize(bool is_env_teardown) override{
+if (is_env_teardown){
+ v8::HandleScope handle_scope(_env->isolate);
+ v8::Local<v8::Value> ab = Get();
+CHECK(!ab.IsEmpty());
+CHECK(ab->IsArrayBuffer());
+ ab.As<v8::ArrayBuffer>()->Detach();
+ }
+
+Reference::Finalize(is_env_teardown);
+ }
+};
+
 enum UnwrapAction{
  KeepWrap,
  RemoveWrap
@@ -2587,8 +2619,9 @@ napi_status napi_create_external_arraybuffer(napi_env env,
 
 if (finalize_cb != nullptr){
 // Create a self-deleting weak reference that invokes the finalizer
-// callback.
-v8impl::Reference::New(env,
+// callback and detaches the ArrayBuffer if it still exists on Environment
+// teardown.
+v8impl::ArrayBufferReference::New(env,
  buffer,
 0,
 true,