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

[Jonathan Wakely]

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.