Re: deque: unneccessary copy constructor in _M_push_front_aux

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

Thanks - I oversaw this sort of self-referencing...

Maybe the function should just be 

template <class _Tp, class _Alloc>
void
deque<_Tp,_Alloc>::_M_push_front_aux(const value_type __t)

without the '&'... -- optimizer kills that anyway..

\Christoph


On Fri, 2003-02-07 at 10:37, Gabriel Dos Reis wrote:
> Christoph Schlenker <Christoph.Schlenker@schlund.de> writes:
> 
> | 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
> 
> How would you handle this
> 
>   d.push_front(d.back())
> 
> ?
> 
> -- Gaby
-- 
Christoph Schlenker
Schlund + Partner AG
Erbprinzenstr. 4-12                      Tel.0721/91374-388
76133 Karlsruhe                          Fax.0721/91374-212
http://www.schlund.de                    Christoph.Schlenker@schlund.de

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