[wasm] Managed<T> ensures T's lifetime does not leak past Isolate's

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 142ff8eb1e08dbe253326c7276ccc0df1c394346..d78783c5759388e8695e140c22675960e716ab5e 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2025,6 +2025,44 @@ Isolate::ThreadDataTable::~ThreadDataTable() {
   // DCHECK_NULL(list_);
 }
 
+void Isolate::ReleaseManagedLifelines() {
+  for (Isolate::ManagedLifeline* current = managed_lifelines_root_.next_;
+       current != nullptr;) {
+    Isolate::ManagedLifeline* next = current->next_;
+    current->Dispose();
+    delete current;

[Eric Holk, 2017/02/11 02:19:29]

Out of curiosity, would it make sense to just rely on current's destructor
rather than having a separate Deleter?

[Mircea Trofin, 2017/02/11 02:29:32]

You mean, instead of a separate Dispose?

[Mircea Trofin, 2017/02/11 02:29:32]

You mean, instead of a separate Dispose?

[Eric Holk, 2017/02/13 21:55:35]

Sure, although I was referring to the Deleter in isolate.h, which seems to
include a Dispose method.

+    current = next;
+  }
+}
+
+Isolate::ManagedLifeline* Isolate::RegisterForReleaseAtTeardown(
+    void* value, Isolate::ManagedLifeline::Deleter deleter) {
+  DCHECK_NOT_NULL(value);
+  DCHECK_NOT_NULL(deleter);
+
+  Isolate::ManagedLifeline* ret = new Isolate::ManagedLifeline();
+  ret->value_ = value;
+  ret->deleter_ = deleter;
+  // Insert at head. We keep the head alive for the lifetime of the Isolate
+  // because otherwise we can't reset the head, should we delete it before
+  // the isolate expires
+  Isolate::ManagedLifeline* next = managed_lifelines_root_.next_;
+  managed_lifelines_root_.next_ = ret;
+  ret->prev_ = &managed_lifelines_root_;
+  ret->next_ = next;
+  if (next != nullptr) next->prev_ = ret;
+  return ret;
+}
+
+void Isolate::UnregisterFromReleaseAtTeardown(
+    Isolate::ManagedLifeline*& lifeline) {
+  DCHECK_NOT_NULL(lifeline->prev_);
+
+  lifeline->prev_->next_ = lifeline->next_;
+  if (lifeline->next_ != nullptr) lifeline->next_->prev_ = lifeline->prev_;
+  delete lifeline;
+  lifeline = nullptr;
+}
 
 Isolate::PerIsolateThreadData::~PerIsolateThreadData() {
 #if defined(USE_SIMULATOR)
@@ -2394,6 +2432,7 @@ void Isolate::Deinit() {
   root_index_map_ = NULL;
 
   ClearSerializerData();
+  ReleaseManagedLifelines();
 }