This is the constructor:

  PreserveExceptionMark::PreserveExceptionMark(Thread*& thread) {
    thread = Thread::current();
    _thread = thread;
    _preserved_exception_oop = Handle(thread, _thread->pending_exception());
    _thread->clear_pending_exception(); // Needed to avoid infinite recursion
    _preserved_exception_line = _thread->exception_line();
    _preserved_exception_file = _thread->exception_file();
  }

File and line are saved after they have been cleared.

Also, thread, is reference parameter which set is both non-intuitive and not in the style of HotSpot. However, this is needed with the primary usage via this macro:

   #define PRESERVE_EXCEPTION_MARK Thread* THREAD; PreserveExceptionMark __em(THREAD);

Finally, the comment, on clear the pending exception appears to be incorrect.