--- old/src/hotspot/share/runtime/jniHandles.cpp	2017-11-02 08:30:10.000000000 +0100
+++ new/src/hotspot/share/runtime/jniHandles.cpp	2017-11-02 08:30:10.000000000 +0100
@@ -126,6 +126,11 @@
 template oop JNIHandles::resolve_jweak<true>(jweak);
 template oop JNIHandles::resolve_jweak<false>(jweak);
 
+bool JNIHandles::is_global_weak_cleared(jweak handle) {
+  assert(is_jweak(handle), "not a weak handle");
+  return guard_value<false>(jweak_ref(handle)) == NULL;
+}
+
 void JNIHandles::destroy_global(jobject handle) {
   if (handle != NULL) {
     assert(is_global_handle(handle), "Invalid delete of global JNI handle");