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

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index ec52183cdf9c6ce009782ca847edafc218da96da..6e125f97c45cbcb49799115438283bc0ba8bbad1 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -533,6 +533,8 @@ class Isolate {
   // for legacy API reasons.
   void TearDown();
 
+  void ReleaseManagedLifelines();
+
   static void GlobalTearDown();
 
   void ClearSerializerData();
@@ -1208,6 +1210,39 @@ class Isolate {
   void set_allow_atomics_wait(bool set) { allow_atomics_wait_ = set; }
   bool allow_atomics_wait() { return allow_atomics_wait_; }
 
+  // List of native heap values allocated by the runtime as part of its
+  // implementation that must be freed at isolate deinit.
+  class ManagedLifeline final {

[titzer, 2017/02/21 09:30:08]

Maybe a better name here? "Lifeline" feels like it is introducing a technical
term, when it really shouldn't.

[Mircea Trofin, 2017/02/21 15:52:28]

How about "NativeObjectLifetime{Manager|Handler}"

or 

"NativeObjectFinalizer"

+   public:
+    typedef void (*Deleter)(void*);
+    void Dispose() { deleter_(value_); }
+
+   private:
+    friend class Isolate;
+
+    ManagedLifeline() {
+      DCHECK_EQ(reinterpret_cast<void*>(this),
+                reinterpret_cast<void*>(&value_));
+    }
+
+    // value_ must be the first member
+    void* value_ = nullptr;
+    Deleter deleter_ = nullptr;
+    ManagedLifeline* prev_ = nullptr;
+    ManagedLifeline* next_ = nullptr;
+  };
+
+  // Register a native value for destruction at isolate teardown.
+  ManagedLifeline* RegisterForReleaseAtTeardown(
+      void* value, ManagedLifeline::Deleter deleter);
+
+  // Unregister a previously registered value from release at
+  // isolate teardown, deleting the ManagedLifeline.
+  // This transfers the responsibility of the previously managed value's
+  // deletion to the caller. Pass by pointer, because *lifeline_ptr gets
+  // reset to nullptr.
+  void UnregisterFromReleaseAtTeardown(ManagedLifeline** lifeline_ptr);
+
  protected:
   explicit Isolate(bool enable_serializer);
   bool IsArrayOrObjectPrototype(Object* object);
@@ -1489,6 +1524,8 @@ class Isolate {
 
   bool allow_atomics_wait_;
 
+  ManagedLifeline managed_lifelines_root_;
+
   size_t total_regexp_code_generated_;
 
   friend class ExecutionAccess;