[Bug rtl-optimization/14863] [3.4 regression] unit-at-a-time causes miscompilation

["rguenth at tat dot physik dot uni-tuebingen dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From rguenth at tat dot physik dot uni-tuebingen dot de  2004-06-02 12:05 -------
Subject: Re:  [3.4 regression] unit-at-a-time
 causes miscompilation

So we have:

void Engine<(int)1, int, Dynamic>::performDestroy<IntervalIterator>
	(IntervalIterator const&, IntervalIterator const&, BackFill const&, bool)
{
  int koffset = (offsetFlag ? 0 : first_m);

  int killed =
    Pooma::Algorithms::delete_backfill(data_m.begin(), data_m.end(),
                                       killBegin, killEnd, koffset);

  Interval<1> newdom;

  if (killed < domain().size())
    newdom = Interval<1>(domain().first(), domain().last() - killed);

  domain_m = newdom;

  data_m.resize(domain().size(), typename DataBlockPtr<T>::NoInitTag());
}

and inlined, with segfault at the marked place (note I already changed
IntervalIterator::operator*() to return by value, not by reference):

template <class DataIterator, class KillIterator>
inline
typename std::iterator_traits<DataIterator>::difference_type
delete_backfill(DataIterator data_begin, DataIterator data_end,
	        const KillIterator kill_begin, const KillIterator kill_end,
		typename std::iterator_traits<DataIterator>::difference_type offset = 0)
{
  PAssert(data_end >= data_begin);
  PAssert(kill_end >= kill_begin);

  std::reverse_iterator<KillIterator>            rk_pos(kill_end);
  std::reverse_iterator<KillIterator>            rk_end(kill_begin);

  typedef std::iterator_traits<DataIterator>     DataTraits_t;
  typedef typename DataTraits_t::difference_type Diff_t;
  Diff_t last = data_end - data_begin - 1;

  while (!(rk_pos == rk_end))
    {
      if ((*rk_pos - offset) != last) break;
           ^^^^^^^

      --last;
      ++rk_pos;
    }

  DataIterator last_pos = data_begin + last;

  while (!(rk_pos == rk_end))
    {
      *(data_begin + (*rk_pos++ - offset)) = *last_pos--;
    }

  return kill_end - kill_begin;
}



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14863