src: revamp internal field count tracking

src/async_wrap.cc

@@ -176,6 +176,10 @@ void AsyncWrap::EmitAfter(Environment* env, double async_id) {
 
 class PromiseWrap : public AsyncWrap {
  public:
+  enum InternalFields {
+    kIsChainedPromiseField = AsyncWrap::kInternalFieldCount,
+    kInternalFieldCount
+  };
   PromiseWrap(Environment* env, Local<Object> object, bool silent)
       : AsyncWrap(env, object, PROVIDER_PROMISE, kInvalidAsyncId, silent) {
     MakeWeak();
@@ -185,9 +189,6 @@ class PromiseWrap : public AsyncWrap {
   SET_MEMORY_INFO_NAME(PromiseWrap)
   SET_SELF_SIZE(PromiseWrap)
 
-  static constexpr int kIsChainedPromiseField = 1;
-  static constexpr int kInternalFieldCount = 2;
-
   static PromiseWrap* New(Environment* env,
                           Local<Promise> promise,
                           PromiseWrap* parent_wrap,
@@ -214,15 +215,16 @@ PromiseWrap* PromiseWrap::New(Environment* env,
 void PromiseWrap::getIsChainedPromise(Local<String> property,
                                       const PropertyCallbackInfo<Value>& info) {
   info.GetReturnValue().Set(
-    info.Holder()->GetInternalField(kIsChainedPromiseField));
+      info.Holder()->GetInternalField(PromiseWrap::kIsChainedPromiseField));
 }
 
 static PromiseWrap* extractPromiseWrap(Local<Promise> promise) {
-  Local<Value> resource_object_value = promise->GetInternalField(0);
-  if (resource_object_value->IsObject()) {
-    return Unwrap<PromiseWrap>(resource_object_value.As<Object>());
-  }
-  return nullptr;
+  // This check is imperfect. If the internal field is set, it should
+  // be an object. If it's not, we just ignore it. Ideally v8 would
+  // have had GetInternalField returning a MaybeLocal but this works
+  // for now.
+  Local<Value> obj = promise->GetInternalField(0);
+  return obj->IsObject() ? Unwrap<PromiseWrap>(obj.As<Object>()) : nullptr;
 }
 
 static void PromiseHook(PromiseHookType type, Local<Promise> promise,
@@ -560,7 +562,7 @@ void AsyncWrap::Initialize(Local<Object> target,
     function_template->SetClassName(class_name);
     function_template->Inherit(AsyncWrap::GetConstructorTemplate(env));
     auto instance_template = function_template->InstanceTemplate();
-    instance_template->SetInternalFieldCount(1);
+    instance_template->SetInternalFieldCount(AsyncWrap::kInternalFieldCount);
     auto function =
         function_template->GetFunction(env->context()).ToLocalChecked();
     target->Set(env->context(), class_name, function).Check();

src/base_object-inl.h

@@ -43,7 +43,9 @@ BaseObject::BaseObject(Environment* env, v8::Local<v8::Object> object)
     : persistent_handle_(env->isolate(), object), env_(env) {
   CHECK_EQ(false, object.IsEmpty());
   CHECK_GT(object->InternalFieldCount(), 0);
-  object->SetAlignedPointerInInternalField(0, static_cast<void*>(this));
+  object->SetAlignedPointerInInternalField(
+      BaseObject::kSlot,
+      static_cast<void*>(this));
   env->AddCleanupHook(DeleteMe, static_cast<void*>(this));
   env->modify_base_object_count(1);
 }
@@ -67,7 +69,7 @@ BaseObject::~BaseObject() {
 
   {
     v8::HandleScope handle_scope(env()->isolate());
-    object()->SetAlignedPointerInInternalField(0, nullptr);
+    object()->SetAlignedPointerInInternalField(BaseObject::kSlot, nullptr);
   }
 }
 
@@ -100,7 +102,8 @@ Environment* BaseObject::env() const {
 
 BaseObject* BaseObject::FromJSObject(v8::Local<v8::Object> obj) {
   CHECK_GT(obj->InternalFieldCount(), 0);
-  return static_cast<BaseObject*>(obj->GetAlignedPointerFromInternalField(0));
+  return static_cast<BaseObject*>(
+      obj->GetAlignedPointerFromInternalField(BaseObject::kSlot));
 }
 
 
@@ -148,11 +151,12 @@ BaseObject::MakeLazilyInitializedJSTemplate(Environment* env) {
   auto constructor = [](const v8::FunctionCallbackInfo<v8::Value>& args) {
     DCHECK(args.IsConstructCall());
     DCHECK_GT(args.This()->InternalFieldCount(), 0);
-    args.This()->SetAlignedPointerInInternalField(0, nullptr);
+    args.This()->SetAlignedPointerInInternalField(BaseObject::kSlot, nullptr);
   };
 
   v8::Local<v8::FunctionTemplate> t = env->NewFunctionTemplate(constructor);
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      BaseObject::kInternalFieldCount);
   return t;
 }
 

src/base_object.h

@@ -36,6 +36,8 @@ class BaseObjectPtrImpl;
 
 class BaseObject : public MemoryRetainer {
  public:
+  enum InternalFields { kSlot, kInternalFieldCount };
+
   // Associates this object with `object`. It uses the 0th internal field for
   // that, and in particular aborts if there is no such field.
   inline BaseObject(Environment* env, v8::Local<v8::Object> object);

src/cares_wrap.cc

@@ -2223,7 +2223,8 @@ void Initialize(Local<Object> target,
 
   Local<FunctionTemplate> channel_wrap =
       env->NewFunctionTemplate(ChannelWrap::New);
-  channel_wrap->InstanceTemplate()->SetInternalFieldCount(1);
+  channel_wrap->InstanceTemplate()->SetInternalFieldCount(
+      ChannelWrap::kInternalFieldCount);
   channel_wrap->Inherit(AsyncWrap::GetConstructorTemplate(env));
 
   env->SetProtoMethod(channel_wrap, "queryAny", Query<QueryAnyWrap>);

src/fs_event_wrap.cc

@@ -97,7 +97,8 @@ void FSEventWrap::Initialize(Local<Object> target,
 
   auto fsevent_string = FIXED_ONE_BYTE_STRING(env->isolate(), "FSEvent");
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      FSEventWrap::kInternalFieldCount);
   t->SetClassName(fsevent_string);
 
   t->Inherit(AsyncWrap::GetConstructorTemplate(env));

src/heap_utils.cc

@@ -341,7 +341,7 @@ BaseObjectPtr<AsyncWrap> CreateHeapSnapshotStream(
     Local<FunctionTemplate> os = FunctionTemplate::New(env->isolate());
     os->Inherit(AsyncWrap::GetConstructorTemplate(env));
     Local<ObjectTemplate> ost = os->InstanceTemplate();
-    ost->SetInternalFieldCount(StreamBase::kStreamBaseFieldCount);
+    ost->SetInternalFieldCount(StreamBase::kInternalFieldCount);
     os->SetClassName(
         FIXED_ONE_BYTE_STRING(env->isolate(), "HeapSnapshotStream"));
     StreamBase::AddMethods(env, os);

src/inspector_js_api.cc

@@ -105,7 +105,8 @@ class JSBindingsConnection : public AsyncWrap {
     Local<String> class_name = ConnectionType::GetClassName(env);
     Local<FunctionTemplate> tmpl =
         env->NewFunctionTemplate(JSBindingsConnection::New);
-    tmpl->InstanceTemplate()->SetInternalFieldCount(1);
+    tmpl->InstanceTemplate()->SetInternalFieldCount(
+        JSBindingsConnection::kInternalFieldCount);
     tmpl->SetClassName(class_name);
     tmpl->Inherit(AsyncWrap::GetConstructorTemplate(env));
     env->SetProtoMethod(tmpl, "dispatch", JSBindingsConnection::Dispatch);

src/js_stream.cc

@@ -204,7 +204,7 @@ void JSStream::Initialize(Local<Object> target,
       FIXED_ONE_BYTE_STRING(env->isolate(), "JSStream");
   t->SetClassName(jsStreamString);
   t->InstanceTemplate()
-    ->SetInternalFieldCount(StreamBase::kStreamBaseFieldCount);
+    ->SetInternalFieldCount(StreamBase::kInternalFieldCount);
   t->Inherit(AsyncWrap::GetConstructorTemplate(env));
 
   env->SetProtoMethod(t, "finishWrite", Finish<WriteWrap>);

src/module_wrap.cc

@@ -1639,7 +1639,8 @@ void ModuleWrap::Initialize(Local<Object> target,
 
   Local<FunctionTemplate> tpl = env->NewFunctionTemplate(New);
   tpl->SetClassName(FIXED_ONE_BYTE_STRING(isolate, "ModuleWrap"));
-  tpl->InstanceTemplate()->SetInternalFieldCount(1);
+  tpl->InstanceTemplate()->SetInternalFieldCount(
+      ModuleWrap::kInternalFieldCount);
 
   env->SetProtoMethod(tpl, "link", Link);
   env->SetProtoMethod(tpl, "instantiate", Instantiate);

src/node_contextify.cc

@@ -142,7 +142,7 @@ MaybeLocal<Object> ContextifyContext::CreateDataWrapper(Environment* env) {
     return MaybeLocal<Object>();
   }
 
-  wrapper->SetAlignedPointerInInternalField(0, this);
+  wrapper->SetAlignedPointerInInternalField(ContextifyContext::kSlot, this);
   return wrapper;
 }
 
@@ -229,7 +229,8 @@ MaybeLocal<Context> ContextifyContext::CreateV8Context(
 void ContextifyContext::Init(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> function_template =
       FunctionTemplate::New(env->isolate());
-  function_template->InstanceTemplate()->SetInternalFieldCount(1);
+  function_template->InstanceTemplate()->SetInternalFieldCount(
+      ContextifyContext::kInternalFieldCount);
   env->set_script_data_constructor_function(
       function_template->GetFunction(env->context()).ToLocalChecked());
 
@@ -328,7 +329,8 @@ template <typename T>
 ContextifyContext* ContextifyContext::Get(const PropertyCallbackInfo<T>& args) {
   Local<Value> data = args.Data();
   return static_cast<ContextifyContext*>(
-      data.As<Object>()->GetAlignedPointerFromInternalField(0));
+      data.As<Object>()->GetAlignedPointerFromInternalField(
+          ContextifyContext::kSlot));
 }
 
 // static
@@ -625,7 +627,8 @@ void ContextifyScript::Init(Environment* env, Local<Object> target) {
       FIXED_ONE_BYTE_STRING(env->isolate(), "ContextifyScript");
 
   Local<FunctionTemplate> script_tmpl = env->NewFunctionTemplate(New);
-  script_tmpl->InstanceTemplate()->SetInternalFieldCount(1);
+  script_tmpl->InstanceTemplate()->SetInternalFieldCount(
+      ContextifyScript::kInternalFieldCount);
   script_tmpl->SetClassName(class_name);
   env->SetProtoMethod(script_tmpl, "createCachedData", CreateCachedData);
   env->SetProtoMethod(script_tmpl, "runInContext", RunInContext);
@@ -1220,7 +1223,8 @@ void Initialize(Local<Object> target,
   {
     Local<FunctionTemplate> tpl = FunctionTemplate::New(env->isolate());
     tpl->SetClassName(FIXED_ONE_BYTE_STRING(env->isolate(), "CompiledFnEntry"));
-    tpl->InstanceTemplate()->SetInternalFieldCount(1);
+    tpl->InstanceTemplate()->SetInternalFieldCount(
+        CompiledFnEntry::kInternalFieldCount);
 
     env->set_compiled_fn_entry_template(tpl->InstanceTemplate());
   }

src/node_contextify.h

@@ -19,6 +19,7 @@ struct ContextOptions {
 
 class ContextifyContext {
  public:
+  enum InternalFields { kSlot, kInternalFieldCount };
   ContextifyContext(Environment* env,
                     v8::Local<v8::Object> sandbox_obj,
                     const ContextOptions& options);

src/node_crypto.cc

@@ -464,7 +464,8 @@ static T* MallocOpenSSL(size_t count) {
 
 void SecureContext::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      SecureContext::kInternalFieldCount);
   Local<String> secureContextString =
       FIXED_ONE_BYTE_STRING(env->isolate(), "SecureContext");
   t->SetClassName(secureContextString);
@@ -3807,7 +3808,8 @@ EVP_PKEY* ManagedEVPPKey::get() const {
 
 Local<Function> KeyObject::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      KeyObject::kInternalFieldCount);
 
   env->SetProtoMethod(t, "init", Init);
   env->SetProtoMethodNoSideEffect(t, "getSymmetricKeySize",
@@ -4040,7 +4042,8 @@ CipherBase::CipherBase(Environment* env,
 void CipherBase::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      CipherBase::kInternalFieldCount);
 
   env->SetProtoMethod(t, "init", Init);
   env->SetProtoMethod(t, "initiv", InitIv);
@@ -4667,7 +4670,8 @@ Hmac::Hmac(Environment* env, v8::Local<v8::Object> wrap)
 void Hmac::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      Hmac::kInternalFieldCount);
 
   env->SetProtoMethod(t, "init", HmacInit);
   env->SetProtoMethod(t, "update", HmacUpdate);
@@ -4793,7 +4797,8 @@ Hash::Hash(Environment* env, v8::Local<v8::Object> wrap)
 void Hash::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      Hash::kInternalFieldCount);
 
   env->SetProtoMethod(t, "update", HashUpdate);
   env->SetProtoMethod(t, "digest", HashDigest);
@@ -5065,7 +5070,8 @@ Sign::Sign(Environment* env, v8::Local<v8::Object> wrap) : SignBase(env, wrap) {
 void Sign::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      SignBase::kInternalFieldCount);
 
   env->SetProtoMethod(t, "init", SignInit);
   env->SetProtoMethod(t, "update", SignUpdate);
@@ -5389,7 +5395,8 @@ Verify::Verify(Environment* env, v8::Local<v8::Object> wrap) :
 void Verify::Initialize(Environment* env, Local<Object> target) {
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(
+      SignBase::kInternalFieldCount);
 
   env->SetProtoMethod(t, "init", VerifyInit);
   env->SetProtoMethod(t, "update", VerifyUpdate);
@@ -5701,7 +5708,8 @@ void DiffieHellman::Initialize(Environment* env, Local<Object> target) {
     const PropertyAttribute attributes =
         static_cast<PropertyAttribute>(ReadOnly | DontDelete);
 
-    t->InstanceTemplate()->SetInternalFieldCount(1);
+    t->InstanceTemplate()->SetInternalFieldCount(
+        DiffieHellman::kInternalFieldCount);
 
     env->SetProtoMethod(t, "generateKeys", GenerateKeys);
     env->SetProtoMethod(t, "computeSecret", ComputeSecret);
@@ -6048,7 +6056,7 @@ void ECDH::Initialize(Environment* env, Local<Object> target) {
 
   Local<FunctionTemplate> t = env->NewFunctionTemplate(New);
 
-  t->InstanceTemplate()->SetInternalFieldCount(1);
+  t->InstanceTemplate()->SetInternalFieldCount(ECDH::kInternalFieldCount);
 
   env->SetProtoMethod(t, "generateKeys", GenerateKeys);
   env->SetProtoMethod(t, "computeSecret", ComputeSecret);

src/node_dir.cc

@@ -358,7 +358,7 @@ void Initialize(Local<Object> target,
   env->SetProtoMethod(dir, "read", DirHandle::Read);
   env->SetProtoMethod(dir, "close", DirHandle::Close);
   Local<ObjectTemplate> dirt = dir->InstanceTemplate();
-  dirt->SetInternalFieldCount(DirHandle::kDirHandleFieldCount);
+  dirt->SetInternalFieldCount(DirHandle::kInternalFieldCount);
   Local<String> handleString =
        FIXED_ONE_BYTE_STRING(isolate, "DirHandle");
   dir->SetClassName(handleString);

src/node_dir.h

@@ -12,8 +12,6 @@ namespace fs_dir {
 // Needed to propagate `uv_dir_t`.
 class DirHandle : public AsyncWrap {
  public:
-  static constexpr int kDirHandleFieldCount = 1;
-
   static DirHandle* New(Environment* env, uv_dir_t* dir);
   ~DirHandle() override;
 

src/node_file.cc

@@ -2290,7 +2290,8 @@ void Initialize(Local<Object> target,
 
   // Create FunctionTemplate for FSReqCallback
   Local<FunctionTemplate> fst = env->NewFunctionTemplate(NewFSReqCallback);
-  fst->InstanceTemplate()->SetInternalFieldCount(1);
+  fst->InstanceTemplate()->SetInternalFieldCount(
+      FSReqBase::kInternalFieldCount);
   fst->Inherit(AsyncWrap::GetConstructorTemplate(env));
   Local<String> wrapString =
       FIXED_ONE_BYTE_STRING(isolate, "FSReqCallback");
@@ -2303,7 +2304,8 @@ void Initialize(Local<Object> target,
   // Create FunctionTemplate for FileHandleReadWrap. There’s no need
   // to do anything in the constructor, so we only store the instance template.
   Local<FunctionTemplate> fh_rw = FunctionTemplate::New(isolate);
-  fh_rw->InstanceTemplate()->SetInternalFieldCount(1);
+  fh_rw->InstanceTemplate()->SetInternalFieldCount(
+      FSReqBase::kInternalFieldCount);
   fh_rw->Inherit(AsyncWrap::GetConstructorTemplate(env));
   Local<String> fhWrapString =
       FIXED_ONE_BYTE_STRING(isolate, "FileHandleReqWrap");
@@ -2318,7 +2320,7 @@ void Initialize(Local<Object> target,
       FIXED_ONE_BYTE_STRING(isolate, "FSReqPromise");
   fpt->SetClassName(promiseString);
   Local<ObjectTemplate> fpo = fpt->InstanceTemplate();
-  fpo->SetInternalFieldCount(1);
+  fpo->SetInternalFieldCount(FSReqBase::kInternalFieldCount);
   env->set_fsreqpromise_constructor_template(fpo);
 
   // Create FunctionTemplate for FileHandle
@@ -2327,7 +2329,7 @@ void Initialize(Local<Object> target,
   env->SetProtoMethod(fd, "close", FileHandle::Close);
   env->SetProtoMethod(fd, "releaseFD", FileHandle::ReleaseFD);
   Local<ObjectTemplate> fdt = fd->InstanceTemplate();
-  fdt->SetInternalFieldCount(StreamBase::kStreamBaseFieldCount);
+  fdt->SetInternalFieldCount(StreamBase::kInternalFieldCount);
   Local<String> handleString =
        FIXED_ONE_BYTE_STRING(isolate, "FileHandle");
   fd->SetClassName(handleString);
@@ -2344,7 +2346,7 @@ void Initialize(Local<Object> target,
                         "FileHandleCloseReq"));
   fdclose->Inherit(AsyncWrap::GetConstructorTemplate(env));
   Local<ObjectTemplate> fdcloset = fdclose->InstanceTemplate();
-  fdcloset->SetInternalFieldCount(1);
+  fdcloset->SetInternalFieldCount(FSReqBase::kInternalFieldCount);
   env->set_fdclose_constructor_template(fdcloset);
 
   Local<Symbol> use_promises_symbol =