[api] Prototype WeakRef implementation

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 3319 matching lines @@
       call_completed_callbacks_.Remove(i);
     }
   }
 }
 
 
 void Isolate::FireCallCompletedCallback() {
   if (!handle_scope_implementer()->CallDepthIsZero()) return;
 
   bool run_microtasks =
-      pending_microtask_count() &&
+      (heap()->weak_refs()->length() ||
+      pending_microtask_count()) &&
       !handle_scope_implementer()->HasMicrotasksSuppressions() &&
       handle_scope_implementer()->microtasks_policy() ==
           v8::MicrotasksPolicy::kAuto;
 
   if (run_microtasks) RunMicrotasks();
 
   if (call_completed_callbacks_.is_empty()) return;
   // Fire callbacks.  Increase call depth to prevent recursive callbacks.
   v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(this);
   v8::Isolate::SuppressMicrotaskExecutionScope suppress(isolate);
@@ skipping 144 matching lines @@
 
 
 void Isolate::RunMicrotasks() {
   // Increase call depth to prevent recursive callbacks.
   v8::Isolate::SuppressMicrotaskExecutionScope suppress(
       reinterpret_cast<v8::Isolate*>(this));
   is_running_microtasks_ = true;
   RunMicrotasksInternal();
   is_running_microtasks_ = false;
   FireMicrotasksCompletedCallback();
+  int left = 0;
+  for (int i = 0; i < heap()->weak_refs()->length(); i++) {
+    JSWeakRef* weak_ref = reinterpret_cast<JSWeakRef*>(
+        heap()->weak_refs()->get(i));
+    if (weak_ref->queued()) {
+      JSFunction* executor = weak_ref->executor();
+      if (executor == nullptr) continue;
+      MaybeHandle<Object> maybe_exception;
+      Handle<Object> argv[] = {
+        Handle<Object>(weak_ref->holdings(), this),
+        Handle<Object>(weak_ref, this)
+      };
+      int argc = 2;
+      Execution::TryCall(this,
+                        Handle<Object>(executor, this),
+                        factory()->undefined_value(),
+                        argc, argv,
+                        Execution::MessageHandling::kReport, &maybe_exception);
+      weak_ref->set_executor(nullptr);
+      weak_ref->set_holdings(nullptr);
+      weak_ref->set_held(false);
+      heap()->weak_refs()->set(left, weak_ref);
+    } else {
+      left++;
+    }
+    weak_ref->set_held(false);
+  }
+  heap()->weak_refs()->Shrink(left);
 }
 
 
 void Isolate::RunMicrotasksInternal() {
   if (!pending_microtask_count()) return;
   TRACE_EVENT0("v8.execute", "RunMicrotasks");
   TRACE_EVENT_CALL_STATS_SCOPED(this, "v8", "V8.RunMicrotasks");
   while (pending_microtask_count() > 0) {
     HandleScope scope(this);
     int num_tasks = pending_microtask_count();
@@ skipping 80 matching lines @@
   }
 }
 
 
 void Isolate::FireMicrotasksCompletedCallback() {
   for (int i = 0; i < microtasks_completed_callbacks_.length(); i++) {
     microtasks_completed_callbacks_.at(i)(reinterpret_cast<v8::Isolate*>(this));
   }
 }
 
-
 void Isolate::SetUseCounterCallback(v8::Isolate::UseCounterCallback callback) {
   DCHECK(!use_counter_callback_);
   use_counter_callback_ = callback;
 }
 
 
 void Isolate::CountUsage(v8::Isolate::UseCounterFeature feature) {
   // The counter callback may cause the embedder to call into V8, which is not
   // generally possible during GC.
   if (heap_.gc_state() == Heap::NOT_IN_GC) {
@@ skipping 162 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8