On Thu, 27 Feb 2025, Jonathan Wakely wrote:
> The ranges::move and ranges::move_backward algorithms are supposed to
> use ranges::iter_move(iter) instead of std::move(*iter), which matters
> for an iterator type with an iter_move overload findable by ADL.
>
> Currently those algorithms use std::__assign_one which uses std::move,
> so define a new ranges::__detail::__assign_one helper function that uses
> ranges::iter_move.
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/105609
> * include/bits/ranges_algobase.h (__detail::__assign_one): New
> helper function.
> (__copy_or_move, __copy_or_move_backward): Use new function
> instead of std::__assign_one.
> * testsuite/25_algorithms/move/constrained.cc: Check that
> ADL iter_move is used in preference to std::move.
> * testsuite/25_algorithms/move_backward/constrained.cc:
> Likewise.
LGTM
> ---
>
> Tested x86_64-linux.
>
> libstdc++-v3/include/bits/ranges_algobase.h | 26 +++++++++++++----
> .../25_algorithms/move/constrained.cc | 29 +++++++++++++++++++
> .../move_backward/constrained.cc | 29 +++++++++++++++++++
> 3 files changed, 78 insertions(+), 6 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/ranges_algobase.h
> b/libstdc++-v3/include/bits/ranges_algobase.h
> index eceb859e88b..a08f659b3ae 100644
> --- a/libstdc++-v3/include/bits/ranges_algobase.h
> +++ b/libstdc++-v3/include/bits/ranges_algobase.h
> @@ -188,6 +188,20 @@ namespace ranges
>
> inline constexpr __equal_fn equal{};
>
> +namespace __detail
> +{
> + template<bool _IsMove, typename _OutIter, typename _InIter>
> + [[__gnu__::__always_inline__]]
> + constexpr void
> + __assign_one(_OutIter& __out, _InIter& __in)
> + {
> + if constexpr (_IsMove)
> + *__out = ranges::iter_move(__in);
> + else
> + *__out = *__in;
> + }
> +} // namespace __detail
> +
> template<typename _Iter, typename _Out>
> struct in_out_result
> {
> @@ -291,14 +305,14 @@ namespace ranges
> __builtin_memmove(__result, __first,
> sizeof(_ValueTypeI) * __num);
> else if (__num == 1)
> - std::__assign_one<_IsMove>(__result, __first);
> + __detail::__assign_one<_IsMove>(__result, __first);
> return {__first + __num, __result + __num};
> }
> }
>
> for (auto __n = __last - __first; __n > 0; --__n)
> {
> - std::__assign_one<_IsMove>(__result, __first);
> + __detail::__assign_one<_IsMove>(__result, __first);
> ++__first;
> ++__result;
> }
> @@ -308,7 +322,7 @@ namespace ranges
> {
> while (__first != __last)
> {
> - std::__assign_one<_IsMove>(__result, __first);
> + __detail::__assign_one<_IsMove>(__result, __first);
> ++__first;
> ++__result;
> }
> @@ -420,7 +434,7 @@ namespace ranges
> __builtin_memmove(__result, __first,
> sizeof(_ValueTypeI) * __num);
> else if (__num == 1)
> - std::__assign_one<_IsMove>(__result, __first);
> + __detail::__assign_one<_IsMove>(__result, __first);
> return {__first + __num, __result};
> }
> }
> @@ -432,7 +446,7 @@ namespace ranges
> {
> --__tail;
> --__result;
> - std::__assign_one<_IsMove>(__result, __tail);
> + __detail::__assign_one<_IsMove>(__result, __tail);
> }
> return {std::move(__lasti), std::move(__result)};
> }
> @@ -445,7 +459,7 @@ namespace ranges
> {
> --__tail;
> --__result;
> - std::__assign_one<_IsMove>(__result, __tail);
> + __detail::__assign_one<_IsMove>(__result, __tail);
> }
> return {std::move(__lasti), std::move(__result)};
> }
> diff --git a/libstdc++-v3/testsuite/25_algorithms/move/constrained.cc
> b/libstdc++-v3/testsuite/25_algorithms/move/constrained.cc
> index 587b2f3728b..e2b45b070ef 100644
> --- a/libstdc++-v3/testsuite/25_algorithms/move/constrained.cc
> +++ b/libstdc++-v3/testsuite/25_algorithms/move/constrained.cc
> @@ -204,6 +204,35 @@ test05()
> VERIFY( ranges::equal(v, (int[]){1,2,3,0}) );
> }
>
> +namespace pr105609
> +{
> + struct I {
> + using value_type = int;
> + using difference_type = std::ptrdiff_t;
> + int operator*() const;
> + I& operator++();
> + I operator++(int);
> + I& operator--();
> + I operator--(int);
> + bool operator==(I) const;
> + friend int& iter_move(const I&);
> + };
> +}
> +
> +void
> +test06(pr105609::I i)
> +{
> + // PR libstdc++/105609
> + // ranges::move should use ranges::iter_move instead of std::move
> + struct O {
> + O(int&) { }
> + O(int&&) = delete;
> + };
> +
> + O* o = nullptr;
> + std::ranges::move(i, i, o);
> +}
> +
> int
> main()
> {
> diff --git
> a/libstdc++-v3/testsuite/25_algorithms/move_backward/constrained.cc
> b/libstdc++-v3/testsuite/25_algorithms/move_backward/constrained.cc
> index 8f6fd455b4b..4d94d386dd0 100644
> --- a/libstdc++-v3/testsuite/25_algorithms/move_backward/constrained.cc
> +++ b/libstdc++-v3/testsuite/25_algorithms/move_backward/constrained.cc
> @@ -160,6 +160,35 @@ test03()
> return ok;
> }
>
> +namespace pr105609
> +{
> + struct I {
> + using value_type = int;
> + using difference_type = std::ptrdiff_t;
> + int operator*() const;
> + I& operator++();
> + I operator++(int);
> + I& operator--();
> + I operator--(int);
> + bool operator==(I) const;
> + friend int& iter_move(const I&);
> + };
> +}
> +
> +void
> +test04(pr105609::I i)
> +{
> + // PR libstdc++/105609
> + // ranges::move should use ranges::iter_move instead of std::move
> + struct O {
> + O(int&) { }
> + O(int&&) = delete;
> + };
> +
> + O* o = nullptr;
> + std::ranges::move_backward(i, i, o);
> +}
> +
> int
> main()
> {
> --
> 2.48.1
>
>
