Re: [PATCH 2/2] libstdc++: Implement ranges [specialized.algorithms]

[Patrick Palka <ppalka@redhat.com>]

On Thu, 13 Feb 2020, Jonathan Wakely wrote:

> On 12/02/20 15:41 -0500, Patrick Palka wrote:
> > This implements all the ranges members defined in [specialized.algorithms]:
> > 
> >  ranges::uninitialized_default_construct
> >  ranges::uninitialized_value_construct
> >  ranges::uninitialized_copy
> >  ranges::uninitialized_copy_n
> >  ranges::uninitialized_move
> >  ranges::uninitialized_move_n
> >  ranges::uninitialized_fill
> >  ranges::uninitialized_fill_n
> >  ranges::construct_at
> >  ranges::destroy_at
> >  ranges::destroy
> > 
> > It also implements (hopefully correctly) the "obvious" optimizations for
> > these
> > algos, namely that if the output range has a trivial value type and if the
> > appropriate operation won't throw then we can dispatch to the standard
> > ranges
> > version of the algorithm which will then potentially enable further
> > optimizations.
> > 
> > libstdc++-v3/ChangeLog:
> > 
> > 	* include/Makefile.am: Add <bits/ranges_uninitialized.h>.
> > 	* include/Makefile.in: Regenerate.
> > 	* include/bits/ranges_uninitialized.h: New header.
> > 	* include/std/memory: Include it.
> > 	* testsuite/20_util/specialized_algorithms/destroy/constrained.cc: New
> > 	test.
> > 	* .../uninitialized_copy/constrained.cc: New test.
> > 	* .../uninitialized_default_construct/constrained.cc: New test.
> > 	* .../uninitialized_fill/constrained.cc: New test.
> > 	* .../uninitialized_move/constrained.cc: New test.
> > 	* .../uninitialized_value_construct/constrained.cc: New test.
> 
> 
> 
> > +  template<__detail::__nothrow_input_iterator _Iter,
> > +	   __detail::__nothrow_sentinel<_Iter> _Sent>
> > +    requires destructible<iter_value_t<_Iter>>
> > +    constexpr _Iter
> > +    destroy(_Iter __first, _Sent __last) noexcept
> > +    {
> > +      if constexpr (is_trivially_destructible_v<iter_value_t<_Iter>>)
> > +	return ranges::next(__first, __last);
> > +      else
> > +	{
> > +	  for (; __first != __last; ++__first)
> > +	    ranges::destroy_at(addressof(*__first));
> 
> This should be std::__addressof
> 
> > +	  return __first;
> > +	}
> > +    }
> > +
> > +  template<__detail::__nothrow_input_range _Range>
> > +    requires destructible<range_value_t<_Range>>
> > +    constexpr safe_iterator_t<_Range>
> > +    destroy(_Range&& __r) noexcept
> > +    { return ranges::destroy(ranges::begin(__r), ranges::end(__r)); }
> > +
> > +  template<__detail::__nothrow_input_iterator _Iter>
> > +    requires destructible<iter_value_t<_Iter>>
> > +    constexpr _Iter
> > +    destroy_n(_Iter __first, iter_difference_t<_Iter> __n) noexcept
> > +    {
> > +      if constexpr (is_trivially_destructible_v<iter_value_t<_Iter>>)
> > +	return ranges::next(__first, __n);
> > +      else
> > +	{
> > +	  for (; __n > 0; ++__first, (void)--__n)
> > +	    ranges::destroy_at(addressof(*__first));
> 
> Same here.
> 
> OK for master with those two adjustments.

Incorporated those two changes and committed both patches.  Thanks for
the review!