On Wed, 8 Mar 2023 at 15:53, Patrick Palka via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
OK. I think this would make sense for 12 too.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/ranges_util.h (view_interface::empty): Add
> preferred overloads that use ranges::size when the range is
> sized as per LWG 3715.
> * testsuite/std/ranges/adaptors/lwg3715.cc: New test.
> ---
> libstdc++-v3/include/bits/ranges_util.h | 16 +++++++--
> .../testsuite/std/ranges/adaptors/lwg3715.cc | 33 +++++++++++++++++++
> 2 files changed, 47 insertions(+), 2 deletions(-)
> create mode 100644 libstdc++-v3/testsuite/std/ranges/adaptors/lwg3715.cc
>
> diff --git a/libstdc++-v3/include/bits/ranges_util.h
> b/libstdc++-v3/include/bits/ranges_util.h
> index e4643e31a20..880a0ce0143 100644
> --- a/libstdc++-v3/include/bits/ranges_util.h
> +++ b/libstdc++-v3/include/bits/ranges_util.h
> @@ -97,15 +97,27 @@ namespace ranges
> constexpr bool
> empty()
> noexcept(noexcept(_S_empty(_M_derived())))
> - requires forward_range<_Derived>
> + requires forward_range<_Derived> && (!sized_range<_Derived>)
> { return _S_empty(_M_derived()); }
>
> + constexpr bool
> + empty()
> + noexcept(noexcept(ranges::size(_M_derived()) == 0))
> + requires sized_range<_Derived>
> + { return ranges::size(_M_derived()) == 0; }
> +
> constexpr bool
> empty() const
> noexcept(noexcept(_S_empty(_M_derived())))
> - requires forward_range<const _Derived>
> + requires forward_range<const _Derived> && (!sized_range<const
> _Derived>)
> { return _S_empty(_M_derived()); }
>
> + constexpr bool
> + empty() const
> + noexcept(noexcept(ranges::size(_M_derived()) == 0))
> + requires sized_range<const _Derived>
> + { return ranges::size(_M_derived()) == 0; }
> +
> constexpr explicit
> operator bool() noexcept(noexcept(ranges::empty(_M_derived())))
> requires requires { ranges::empty(_M_derived()); }
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/lwg3715.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/lwg3715.cc
> new file mode 100644
> index 00000000000..96ee7087be0
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/lwg3715.cc
> @@ -0,0 +1,33 @@
> +// { dg-options "-std=gnu++23" }
> +// { dg-do run { target c++23 } }
> +
> +// Verify LWG 3715 changes.
> +
> +#include <ranges>
> +#include <sstream>
> +#include <testsuite_hooks.h>
> +
> +void
> +test01()
> +{
> + std::istringstream ints("0 1 2 3 4");
> + auto i = std::views::istream<int>(ints);
> + auto r4 = std::views::counted(i.begin(), 4) | std::views::chunk(2);
> + VERIFY( !r4.empty() );
> +}
> +
> +void
> +test02()
> +{
> + std::istringstream ints("0 1 2 3 4");
> + auto i = std::views::istream<int>(ints);
> + auto r0 = std::views::counted(i.begin(), 0) | std::views::chunk(2);
> + VERIFY( r0.empty() );
> +}
> +
> +int
> +main()
> +{
> + test01();
> + test02();
> +}
> --
> 2.40.0.rc0.57.g454dfcbddf
>
