bool Threads::destroy_vm() {
... // no return statements
  return true;
}

This should be cleaned up, so the callsite doesn't try to handle the false case:

jni.cpp:

  if (Threads::destroy_vm()) {
    // Should not change thread state, VM is gone
    vm_created = 0;
    res = JNI_OK;
    return res;
  } else {
    ThreadStateTransition::transition(thread, _thread_in_vm, _thread_in_native);
    res = JNI_ERR;
    return res;
  }