void doit() {

  {- -------------------------------------------
  (1) JvmtiEnvBase::get_stack_trace() を呼び出すだけ.
      ---------------------------------------- -}

        _result = ((JvmtiEnvBase *)_env)->get_stack_trace(_java_thread,
                                                          _start_depth, _max_count,
                                                          _frame_buffer, _count_ptr);
      }