[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 38a26be1e29a70450d6d08460fbe0e7473b25244..7cd688a5ca436b8f1cf5730f24e16f565207d627 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2030,6 +2030,46 @@ Isolate::ThreadDataTable::~ThreadDataTable() {
   // DCHECK_NULL(list_);
 }
 
+void Isolate::ReleaseManagedLifelines() {
+  for (Isolate::ManagedLifeline* current = managed_lifelines_root_.next_;
+       current != nullptr;) {

[bradnelson, 2017/02/16 23:59:20]

The for loop vs while obscures this slightly, maybe a while?

+    Isolate::ManagedLifeline* next = current->next_;
+    current->Dispose();
+    delete current;
+    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_ptr) {
+  DCHECK_NOT_NULL(lifeline_ptr);
+  Isolate::ManagedLifeline* lifeline = *lifeline_ptr;
+  DCHECK_NOT_NULL(lifeline->prev_);
+
+  lifeline->prev_->next_ = lifeline->next_;
+  if (lifeline->next_ != nullptr) lifeline->next_->prev_ = lifeline->prev_;
+  delete lifeline;
+  *lifeline_ptr = nullptr;
+}
 
 Isolate::PerIsolateThreadData::~PerIsolateThreadData() {
 #if defined(USE_SIMULATOR)
@@ -2399,6 +2439,7 @@ void Isolate::Deinit() {
   root_index_map_ = NULL;
 
   ClearSerializerData();
+  ReleaseManagedLifelines();
 }