Re: [PATCH 1/3] libstdc++: Fix zip_view's operator- for integer-class difference type [PR106766]

[Jonathan Wakely <jwakely.gcc@gmail.com>]

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On Fri, 9 Sep 2022, 18:25 Patrick Palka via Libstdc++, <
libstdc++@gcc.gnu.org> wrote:

> make_unsigned_t can't give us the unsigned version of an integer-class
> difference type, so use __make_unsigned_like_t / __to_unsigned_like
> instead.
>

OK, thanks



>         PR libstdc++/106766
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ranges (zip_view::_Iterator::operator-): Use
>         __to_unsigned_like instead of make_unsigned_t.
>         (zip_view::_Sentinel::operator-): Likewise.
>         * testsuite/std/ranges/zip/1.cc (test04): New test.
> ---
>  libstdc++-v3/include/std/ranges            |  8 ++++----
>  libstdc++-v3/testsuite/std/ranges/zip/1.cc | 14 ++++++++++++++
>  2 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges
> b/libstdc++-v3/include/std/ranges
> index 2b5cb0531f0..2b8fec3c386 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -4657,8 +4657,8 @@ namespace views::__adaptor
>         return ranges::min({difference_type(std::get<_Is>(__x._M_current)
>                                             -
> std::get<_Is>(__y._M_current))...},
>                            ranges::less{},
> -                          [](difference_type __i) ->
> make_unsigned_t<difference_type> {
> -                            return __i < 0 ? -__i : __i;
> +                          [](difference_type __i) {
> +                            return __detail::__to_unsigned_like(__i < 0 ?
> -__i : __i);
>                            });
>        }(make_index_sequence<sizeof...(_Vs)>{});
>      }
> @@ -4726,8 +4726,8 @@ namespace views::__adaptor
>        return [&]<size_t... _Is>(index_sequence<_Is...>) {
>         return ranges::min({_Ret(std::get<_Is>(__x._M_current) -
> std::get<_Is>(__y._M_end))...},
>                            ranges::less{},
> -                          [](_Ret __i) -> make_unsigned_t<_Ret> {
> -                            return __i < 0 ? -__i : __i;
> +                          [](_Ret __i) {
> +                            return __detail::__to_unsigned_like(__i < 0 ?
> -__i : __i);
>                            });
>        }(make_index_sequence<sizeof...(_Vs)>{});
>      }
> diff --git a/libstdc++-v3/testsuite/std/ranges/zip/1.cc
> b/libstdc++-v3/testsuite/std/ranges/zip/1.cc
> index 0113efdb537..f868c97cb69 100644
> --- a/libstdc++-v3/testsuite/std/ranges/zip/1.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/zip/1.cc
> @@ -102,10 +102,24 @@ test03()
>    return true;
>  }
>
> +constexpr bool
> +test04()
> +{
> +  // PR libstdc++/106766
> +  auto r = views::zip(views::iota(__int128(0), __int128(1)));
> +  auto i = r.begin();
> +  auto s = r.end();
> +  VERIFY( s - i == 1 );
> +  VERIFY( i + 1 - i == 1 );
> +
> +  return true;
> +}
> +
>  int
>  main()
>  {
>    static_assert(test01());
>    static_assert(test02());
>    static_assert(test03());
> +  static_assert(test04());
>  }
> --
> 2.37.3.518.g79f2338b37
>
>