[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 6d35c51830795c204d86d6b0d358666869a1a711..2e1b23380cfa1ab27d6cd7849a36885a9d8cf93b 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1200,6 +1200,32 @@ 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, 2017/02/08 23:32:47]

Please just make this a struct, forward declare it, and put it in the isolate.cc
file.

[titzer, 2017/02/08 23:32:48]

ManagedObjectList?

[Mircea Trofin, 2017/02/08 23:52:35]

Maybe - although the fact it's a list is an implementation detail to its
consumer. The consumer sees it as something that it can get a value from and can
be deleted. It's a handle, rather, but that term is something else in V8 :)

[Mircea Trofin, 2017/02/08 23:52:36]

The user of this needs to call the value() API (see managed.h, get()). 

+   public:
+    typedef void (*Deleter)(void*);
+    ~ManagedLifeline();
+    void* value() const { return value_; }
+
+   private:
+    friend class Isolate;
+
+    ManagedLifeline()
+        : prev_(nullptr), next_(nullptr), deleter_(nullptr), value_(nullptr) {}

[titzer, 2017/02/08 23:32:47]

I think you can use the inline initializer for these fields now.

[Mircea Trofin, 2017/02/08 23:52:36]

Acknowledged.

+    void Clear();
+    void CallDeleter();
+
+    ManagedLifeline* prev_;
+    ManagedLifeline* next_;
+    Deleter deleter_;
+    void* value_;
+  };
+
+  ManagedLifeline* AddManagedObject(void* value,
+                                    ManagedLifeline::Deleter deleter);
+
  protected:
   explicit Isolate(bool enable_serializer);
   bool IsArrayOrObjectPrototype(Object* object);
@@ -1481,6 +1507,8 @@ class Isolate {
 
   bool allow_atomics_wait_;
 
+  ManagedLifeline managed_lifelines_root_;
+
   friend class ExecutionAccess;
   friend class HandleScopeImplementer;
   friend class HeapTester;