Resolution for issue #5092: Unit test handle checks consider dangling handles to be valid.

runtime/vm/dart_api_impl.h

Index: runtime/vm/dart_api_impl.h
diff --git a/runtime/vm/dart_api_impl.h b/runtime/vm/dart_api_impl.h
index f597ca29d4e782aec56cab3c99d5d6b0654985c4..a1b8ded132a8038969b0663283ab75f141fca62b 100644
--- a/runtime/vm/dart_api_impl.h
+++ b/runtime/vm/dart_api_impl.h
@@ -9,6 +9,7 @@
 #include "vm/native_arguments.h"
 #include "vm/object.h"
 #include "vm/safepoint.h"
+#include "vm/thread_registry.h"
 
 namespace dart {
 
@@ -18,6 +19,7 @@ class FinalizablePersistentHandle;
 class LocalHandle;
 class PersistentHandle;
 class ReusableObjectHandleScope;
+class ThreadRegistry;
 
 const char* CanonicalFunction(const char* func);
 
@@ -166,6 +168,18 @@ class Api : AllStatic {
     return (ClassId(handle) >= kInstanceCid);
   }
 
+  // Returns true if the handle is non-dangling.
+  static bool IsValid(Dart_Handle handle) {
+    Isolate* isolate = Isolate::Current();
+    CHECK_ISOLATE(isolate);
+
+    // Check against all of the handles in the current isolate as well as the
+    // read-only handles.
+    return isolate->thread_registry()->IsValidHandle(handle) ||

[bkonyi, 2017/01/18 00:44:47]

I'm not sure if I should be checking to see if any isolate contains this handle
or if I should only be looking at the current isolate. All tests currently pass
in the current state.

[Cutch, 2017/01/18 14:49:51]

In general our API always interacts with the current isolate. 

+           Dart::IsReadOnlyApiHandle(handle) ||
+           Dart::IsReadOnlyHandle(reinterpret_cast<uword>(handle));
+  }
+
   // Returns true if the handle holds an Error.
   static bool IsError(Dart_Handle handle) {
     return RawObject::IsErrorClassId(ClassId(handle));