[dart:io] Adds a finalizer to _NativeSocket to avoid socket leaks

runtime/bin/reference_counting.h

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_BIN_REFERENCE_COUNTING_H_
 #define RUNTIME_BIN_REFERENCE_COUNTING_H_
 
 #include "vm/atomic.h"
 
 namespace dart {
@@ skipping 15 matching lines @@
 //
 // void DoStuffWithAFoo() {
 //   Foo* foo = new Foo();  // Reference count starts at 1, so no explicit
 //                          // call to Retain is needed after allocation.
 //   ...
 //   foo->Release();
 // }
 template <class Derived>
 class ReferenceCounted {
  public:
-  ReferenceCounted() : ref_count_(1) {}
+  ReferenceCounted() : ref_count_(1) {
+#if defined(DEBUG)
+    AtomicOperations::FetchAndIncrement(&instances_);
+#endif  // defined(DEBUG)
+  }
 
-  ~ReferenceCounted() { ASSERT(ref_count_ == 0); }
+  virtual ~ReferenceCounted() {
+    ASSERT(ref_count_ == 0);
+#if defined(DEBUG)
+    AtomicOperations::FetchAndDecrement(&instances_);
+#endif  // defined(DEBUG)
+  }
 
   void Retain() {
-    uintptr_t old = AtomicOperations::FetchAndIncrement(&ref_count_);
+    intptr_t old = AtomicOperations::FetchAndIncrement(&ref_count_);
     ASSERT(old > 0);
   }
 
   void Release() {
-    uintptr_t old = AtomicOperations::FetchAndDecrement(&ref_count_);
+    intptr_t old = AtomicOperations::FetchAndDecrement(&ref_count_);
     ASSERT(old > 0);
     if (old == 1) {
       delete static_cast<Derived*>(this);
     }
   }
 
+#if defined(DEBUG)
+  static intptr_t instances() { return instances_; }
+#endif  // defined(DEBUG)
+
  private:
-  uintptr_t ref_count_;
+#if defined(DEBUG)
+  static intptr_t instances_;
+#endif  // defined(DEBUG)
+
+  intptr_t ref_count_;
 
   // These are used only in the ASSERT below in RefCntReleaseScope.
-  uintptr_t ref_count() const { return ref_count_; }
+  intptr_t ref_count() const { return ref_count_; }
   friend class RefCntReleaseScope<Derived>;
   DISALLOW_COPY_AND_ASSIGN(ReferenceCounted);
 };
 
+#if defined(DEBUG)
+template <class Derived>
+intptr_t ReferenceCounted<Derived>::instances_ = 0;
+#endif
+
 // Creates a scope at the end of which a reference counted object is
 // Released. This is useful for reference counted objects recieved by the IO
 // Service, which have already been Retained E.g.:
 //
 // CObject* Foo::FooRequest(const CObjectArray& request) {
 //   Foo* foo = CObjectToFoo(request[0]);
 //   RefCntReleaseScope<Foo> rs(foo);
 //   ...
 // }
 template <class Target>
@@ skipping 71 matching lines @@
   ReferenceCounted<Target>* target_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(RetainedPointer);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // RUNTIME_BIN_REFERENCE_COUNTING_H_