deque: unneccessary copy constructor in _M_push_front_aux

[Christoph Schlenker <Christoph dot Schlenker at schlund dot de>]

Hi all,

I'm a bit puzzeled about line 1 in the function _M_push_front_aux in 

template <class _Tp, class _Alloc>
void
deque<_Tp,_Alloc>::_M_push_front_aux(const value_type& __t)
{
1  value_type __t_copy = __t;   // *** who needs that copy? ***
2  _M_reserve_map_at_front();
3  *(_M_start._M_node - 1) = _M_allocate_node();
4  try {
5    _M_start._M_set_node(_M_start._M_node - 1);
6    _M_start._M_cur = _M_start._M_last - 1;
7    _Construct(_M_start._M_cur, __t_copy);
8  }
9  catch(...)
0    {
1      ++_M_start;
2      _M_deallocate_node(*(_M_start._M_node - 1));
3      __throw_exception_again;
4    }
}

Can anyone tell we there is a __t_copy needed? As far as I can see
neither _Construct nor the try...catch-block needs a copy and could use
__t directly.

Thanks,
\Christoph

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