src,tools: initialize cppgc

This patch:

- Initializes cppgc in InitializeOncePerProcess() when
  kNoInitializeCppgc is not set
- Create a CppHeap and attach it to the Isolate when
  there isn't one already during IsolateData initialization.
  The CppHeap is detached and terminated when IsolateData
  is freed.
- Publishes the cppgc headers in the tarball.

This allows C++ addons to start using cppgc to manage objects.

A helper node::SetCppgcReference() is also added to help addons
enable cppgc tracing in a user-defined object.

Co-authored-by: Joyee Cheung <joyeec9h3@gmail.com>
Refs: #40786
PR-URL: #45704
Refs: https://docs.google.com/document/d/1ny2Qz_EsUnXGKJRGxoA-FXIE2xpLgaMAN6jD7eAkqFQ/edit
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>

src/env-inl.h

@@ -34,6 +34,7 @@
 #include "node_realm-inl.h"
 #include "util-inl.h"
 #include "uv.h"
+#include "v8-cppgc.h"
 #include "v8.h"
 
 #include <cstddef>
@@ -61,6 +62,31 @@ inline uv_loop_t* IsolateData::event_loop() const {
   return event_loop_;
 }
 
+inline void IsolateData::SetCppgcReference(v8::Isolate* isolate,
+                                           v8::Local<v8::Object> object,
+                                           void* wrappable) {
+  v8::CppHeap* heap = isolate->GetCppHeap();
+  CHECK_NOT_NULL(heap);
+  v8::WrapperDescriptor descriptor = heap->wrapper_descriptor();
+  uint16_t required_size = std::max(descriptor.wrappable_instance_index,
+                                    descriptor.wrappable_type_index);
+  CHECK_GT(object->InternalFieldCount(), required_size);
+
+  uint16_t* id_ptr = nullptr;
+  {
+    Mutex::ScopedLock lock(isolate_data_mutex_);
+    auto it =
+        wrapper_data_map_.find(descriptor.embedder_id_for_garbage_collected);
+    CHECK_NE(it, wrapper_data_map_.end());
+    id_ptr = &(it->second->cppgc_id);
+  }
+
+  object->SetAlignedPointerInInternalField(descriptor.wrappable_type_index,
+                                           id_ptr);
+  object->SetAlignedPointerInInternalField(descriptor.wrappable_instance_index,
+                                           wrappable);
+}
+
 inline uint16_t* IsolateData::embedder_id_for_cppgc() const {
   return &(wrapper_data_->cppgc_id);
 }

src/env.cc

@@ -37,6 +37,8 @@ using errors::TryCatchScope;
 using v8::Array;
 using v8::Boolean;
 using v8::Context;
+using v8::CppHeap;
+using v8::CppHeapCreateParams;
 using v8::EmbedderGraph;
 using v8::EscapableHandleScope;
 using v8::Function;
@@ -61,6 +63,7 @@ using v8::TracingController;
 using v8::TryCatch;
 using v8::Undefined;
 using v8::Value;
+using v8::WrapperDescriptor;
 using worker::Worker;
 
 int const ContextEmbedderTag::kNodeContextTag = 0x6e6f64;
@@ -538,6 +541,14 @@ IsolateData::IsolateData(Isolate* isolate,
     // for embedder ID, V8 could accidentally enable cppgc on them. So
     // safe guard against this.
     DCHECK_NE(descriptor.wrappable_type_index, BaseObject::kSlot);
+  } else {
+    cpp_heap_ = CppHeap::Create(
+        platform,
+        CppHeapCreateParams{
+            {},
+            WrapperDescriptor(
+                BaseObject::kEmbedderType, BaseObject::kSlot, cppgc_id)});
+    isolate->AttachCppHeap(cpp_heap_.get());
   }
   // We do not care about overflow since we just want this to be different
   // from the cppgc id.
@@ -565,6 +576,21 @@ IsolateData::IsolateData(Isolate* isolate,
   }
 }
 
+IsolateData::~IsolateData() {
+  if (cpp_heap_ != nullptr) {
+    // The CppHeap must be detached before being terminated.
+    isolate_->DetachCppHeap();
+    cpp_heap_->Terminate();
+  }
+}
+
+// Public API
+void SetCppgcReference(Isolate* isolate,
+                       Local<Object> object,
+                       void* wrappable) {
+  IsolateData::SetCppgcReference(isolate, object, wrappable);
+}
+
 void IsolateData::MemoryInfo(MemoryTracker* tracker) const {
 #define V(PropertyName, StringValue)                                           \
   tracker->TrackField(#PropertyName, PropertyName());

src/env.h

@@ -62,6 +62,10 @@
 #include <unordered_set>
 #include <vector>
 
+namespace v8 {
+class CppHeap;
+}
+
 namespace node {
 
 namespace shadow_realm {
@@ -136,6 +140,7 @@ class NODE_EXTERN_PRIVATE IsolateData : public MemoryRetainer {
               MultiIsolatePlatform* platform = nullptr,
               ArrayBufferAllocator* node_allocator = nullptr,
               const SnapshotData* snapshot_data = nullptr);
+  ~IsolateData();
 
   SET_MEMORY_INFO_NAME(IsolateData)
   SET_SELF_SIZE(IsolateData)
@@ -148,6 +153,10 @@ class NODE_EXTERN_PRIVATE IsolateData : public MemoryRetainer {
   uint16_t* embedder_id_for_cppgc() const;
   uint16_t* embedder_id_for_non_cppgc() const;
 
+  static inline void SetCppgcReference(v8::Isolate* isolate,
+                                       v8::Local<v8::Object> object,
+                                       void* wrappable);
+
   inline uv_loop_t* event_loop() const;
   inline MultiIsolatePlatform* platform() const;
   inline const SnapshotData* snapshot_data() const;
@@ -229,6 +238,7 @@ class NODE_EXTERN_PRIVATE IsolateData : public MemoryRetainer {
   NodeArrayBufferAllocator* const node_allocator_;
   MultiIsolatePlatform* platform_;
   const SnapshotData* snapshot_data_;
+  std::unique_ptr<v8::CppHeap> cpp_heap_;
   std::shared_ptr<PerIsolateOptions> options_;
   worker::Worker* worker_context_ = nullptr;
   bool is_building_snapshot_ = false;

src/node.cc

@@ -62,6 +62,8 @@
 #endif  // NODE_USE_V8_PLATFORM
 #include "v8-profiler.h"
 
+#include "cppgc/platform.h"
+
 #if HAVE_INSPECTOR
 #include "inspector/worker_inspector.h"  // ParentInspectorHandle
 #endif
@@ -1096,6 +1098,14 @@ InitializeOncePerProcessInternal(const std::vector<std::string>& args,
     V8::Initialize();
   }
 
+  if (!(flags & ProcessInitializationFlags::kNoInitializeCppgc)) {
+    v8::PageAllocator* allocator = nullptr;
+    if (result->platform_ != nullptr) {
+      allocator = result->platform_->GetPageAllocator();
+    }
+    cppgc::InitializeProcess(allocator);
+  }
+
   performance::performance_v8_start = PERFORMANCE_NOW();
   per_process::v8_initialized = true;
 
@@ -1115,6 +1125,10 @@ void TearDownOncePerProcess() {
     ResetSignalHandlers();
   }
 
+  if (!(flags & ProcessInitializationFlags::kNoInitializeCppgc)) {
+    cppgc::ShutdownProcess();
+  }
+
   per_process::v8_initialized = false;
   if (!(flags & ProcessInitializationFlags::kNoInitializeV8)) {
     V8::Dispose();

src/node.h

@@ -261,6 +261,10 @@ enum Flags : uint32_t {
   kNoUseLargePages = 1 << 11,
   // Skip printing output for --help, --version, --v8-options.
   kNoPrintHelpOrVersionOutput = 1 << 12,
+  // Do not perform cppgc initialization. If set, the embedder must call
+  // cppgc::InitializeProcess() before creating a Node.js environment
+  // and call cppgc::ShutdownProcess() before process shutdown.
+  kNoInitializeCppgc = 1 << 13,
 
   // Emulate the behavior of InitializeNodeWithArgs() when passing
   // a flags argument to the InitializeOncePerProcess() replacement
@@ -269,7 +273,7 @@ enum Flags : uint32_t {
       kNoStdioInitialization | kNoDefaultSignalHandling | kNoInitializeV8 |
       kNoInitializeNodeV8Platform | kNoInitOpenSSL |
       kNoParseGlobalDebugVariables | kNoAdjustResourceLimits |
-      kNoUseLargePages | kNoPrintHelpOrVersionOutput,
+      kNoUseLargePages | kNoPrintHelpOrVersionOutput | kNoInitializeCppgc,
 };
 }  // namespace ProcessInitializationFlags
 namespace ProcessFlags = ProcessInitializationFlags;  // Legacy alias.
@@ -1486,6 +1490,25 @@ void RegisterSignalHandler(int signal,
                            bool reset_handler = false);
 #endif  // _WIN32
 
+// Configure the layout of the JavaScript object with a cppgc::GarbageCollected
+// instance so that when the JavaScript object is reachable, the garbage
+// collected instance would have its Trace() method invoked per the cppgc
+// contract. To make it work, the process must have called
+// cppgc::InitializeProcess() before, which is usually the case for addons
+// loaded by the stand-alone Node.js executable. Embedders of Node.js can use
+// either need to call it themselves or make sure that
+// ProcessInitializationFlags::kNoInitializeCppgc is *not* set for cppgc to
+// work.
+// If the CppHeap is owned by Node.js, which is usually the case for addon,
+// the object must be created with at least two internal fields available,
+// and the first two internal fields would be configured by Node.js.
+// This may be superseded by a V8 API in the future, see
+// https://bugs.chromium.org/p/v8/issues/detail?id=13960. Until then this
+// serves as a helper for Node.js isolates.
+NODE_EXTERN void SetCppgcReference(v8::Isolate* isolate,
+                                   v8::Local<v8::Object> object,
+                                   void* wrappable);
+
 }  // namespace node
 
 #endif  // SRC_NODE_H_

src/node_main_instance.cc

@@ -68,6 +68,8 @@ NodeMainInstance::~NodeMainInstance() {
     return;
   }
   // This should only be done on a main instance that owns its isolate.
+  // IsolateData must be freed before UnregisterIsolate() is called.
+  isolate_data_.reset();
   platform_->UnregisterIsolate(isolate_);
   isolate_->Dispose();
 }

src/node_worker.cc

@@ -11,6 +11,7 @@
 #include "node_snapshot_builder.h"
 #include "permission/permission.h"
 #include "util-inl.h"
+#include "v8-cppgc.h"
 
 #include <memory>
 #include <string>

test/addons/cppgc-object/binding.cc

@@ -0,0 +1,78 @@
+#include <cppgc/allocation.h>
+#include <cppgc/garbage-collected.h>
+#include <cppgc/heap.h>
+#include <node.h>
+#include <v8-cppgc.h>
+#include <v8.h>
+#include <algorithm>
+
+class CppGCed : public cppgc::GarbageCollected<CppGCed> {
+ public:
+  static uint16_t states[2];
+  static constexpr int kDestructCount = 0;
+  static constexpr int kTraceCount = 1;
+
+  static void New(const v8::FunctionCallbackInfo<v8::Value>& args) {
+    v8::Isolate* isolate = args.GetIsolate();
+    v8::Local<v8::Object> js_object = args.This();
+    CppGCed* gc_object = cppgc::MakeGarbageCollected<CppGCed>(
+        isolate->GetCppHeap()->GetAllocationHandle());
+    node::SetCppgcReference(isolate, js_object, gc_object);
+    args.GetReturnValue().Set(js_object);
+  }
+
+  static v8::Local<v8::Function> GetConstructor(
+      v8::Local<v8::Context> context) {
+    auto ft = v8::FunctionTemplate::New(context->GetIsolate(), New);
+    auto ot = ft->InstanceTemplate();
+    v8::WrapperDescriptor descriptor =
+        context->GetIsolate()->GetCppHeap()->wrapper_descriptor();
+    uint16_t required_size = std::max(descriptor.wrappable_instance_index,
+                                      descriptor.wrappable_type_index);
+    ot->SetInternalFieldCount(required_size + 1);
+    return ft->GetFunction(context).ToLocalChecked();
+  }
+
+  CppGCed() = default;
+
+  ~CppGCed() { states[kDestructCount]++; }
+
+  void Trace(cppgc::Visitor* visitor) const { states[kTraceCount]++; }
+};
+
+uint16_t CppGCed::states[] = {0, 0};
+
+void InitModule(v8::Local<v8::Object> exports) {
+  v8::Isolate* isolate = v8::Isolate::GetCurrent();
+  auto context = isolate->GetCurrentContext();
+
+  auto store = v8::ArrayBuffer::NewBackingStore(
+      CppGCed::states,
+      sizeof(uint16_t) * 2,
+      [](void*, size_t, void*) {},
+      nullptr);
+  auto ab = v8::ArrayBuffer::New(isolate, std::move(store));
+
+  exports
+      ->Set(context,
+            v8::String::NewFromUtf8(isolate, "CppGCed").ToLocalChecked(),
+            CppGCed::GetConstructor(context))
+      .FromJust();
+  exports
+      ->Set(context,
+            v8::String::NewFromUtf8(isolate, "states").ToLocalChecked(),
+            v8::Uint16Array::New(ab, 0, 2))
+      .FromJust();
+  exports
+      ->Set(context,
+            v8::String::NewFromUtf8(isolate, "kDestructCount").ToLocalChecked(),
+            v8::Integer::New(isolate, CppGCed::kDestructCount))
+      .FromJust();
+  exports
+      ->Set(context,
+            v8::String::NewFromUtf8(isolate, "kTraceCount").ToLocalChecked(),
+            v8::Integer::New(isolate, CppGCed::kTraceCount))
+      .FromJust();
+}
+
+NODE_MODULE(NODE_GYP_MODULE_NAME, InitModule)

test/addons/cppgc-object/binding.gyp

@@ -0,0 +1,9 @@
+{
+  'targets': [
+    {
+      'target_name': 'binding',
+      'sources': [ 'binding.cc' ],
+      'includes': ['../common.gypi'],
+    }
+  ]
+}

test/addons/cppgc-object/test.js

@@ -0,0 +1,51 @@
+'use strict';
+
+// Flags: --expose-gc
+
+const common = require('../../common');
+
+// Verify that addons can create GarbageCollected objects and
+// have them traced properly.
+
+const assert = require('assert');
+const {
+  CppGCed, states, kDestructCount, kTraceCount,
+} = require(`./build/${common.buildType}/binding`);
+
+assert.strictEqual(states[kDestructCount], 0);
+assert.strictEqual(states[kTraceCount], 0);
+
+let array = [];
+const count = 100;
+for (let i = 0; i < count; ++i) {
+  array.push(new CppGCed());
+}
+
+globalThis.gc();
+
+setTimeout(async function() {
+  // GC should have invoked Trace() on at least some of the CppGCed objects,
+  // but they should all be alive at this point.
+  assert.strictEqual(states[kDestructCount], 0);
+  assert.notStrictEqual(states[kTraceCount], 0);
+
+  // Replace the old CppGCed objects with new ones, after GC we should have
+  // destructed all the old ones and called Trace() on the
+  // new ones.
+  for (let i = 0; i < count; ++i) {
+    array[i] = new CppGCed();
+  }
+  await common.gcUntil(
+    'All old CppGCed are destroyed',
+    () => states[kDestructCount] === count,
+  );
+  // Release all the CppGCed objects, after GC we should have destructed
+  // all of them.
+  array = null;
+  globalThis.gc();
+
+  await common.gcUntil(
+    'All old CppGCed are destroyed',
+    () => states[kDestructCount] === count * 2,
+  );
+}, 1);