Tested x86_64-linux. Pushed to trunk. -- >8 --
libstdc++-v3/ChangeLog: * include/bits/move.h (forward_list): Define for C++23. * include/bits/version.def (forward_like): Define. * include/bits/version.h: Regenerate. * include/std/utility (__glibcxx_want_forward_like): Define. * testsuite/20_util/forward_like/1.cc: New test. * testsuite/20_util/forward_like/2_neg.cc: New test. * testsuite/20_util/forward_like/version.cc: New test. --- libstdc++-v3/include/bits/move.h | 26 ++++++++ libstdc++-v3/include/bits/version.def | 8 +++ libstdc++-v3/include/bits/version.h | 27 ++++++--- libstdc++-v3/include/std/utility | 5 +- .../testsuite/20_util/forward_like/1.cc | 59 +++++++++++++++++++ .../testsuite/20_util/forward_like/2_neg.cc | 10 ++++ .../testsuite/20_util/forward_like/version.cc | 10 ++++ 7 files changed, 135 insertions(+), 10 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/forward_like/1.cc create mode 100644 libstdc++-v3/testsuite/20_util/forward_like/2_neg.cc create mode 100644 libstdc++-v3/testsuite/20_util/forward_like/version.cc diff --git a/libstdc++-v3/include/bits/move.h b/libstdc++-v3/include/bits/move.h index 00997d6f1fb..0151d78aff9 100644 --- a/libstdc++-v3/include/bits/move.h +++ b/libstdc++-v3/include/bits/move.h @@ -89,6 +89,32 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return static_cast<_Tp&&>(__t); } +#if __glibcxx_forward_like // C++ >= 23 + template<typename _Tp, typename _Up> + [[nodiscard]] + constexpr decltype(auto) + forward_like(_Up&& __x) noexcept + { + constexpr bool __as_rval = is_rvalue_reference_v<_Tp&&>; + + if constexpr (is_const_v<remove_reference_t<_Tp>>) + { + using _Up2 = remove_reference_t<_Up>; + if constexpr (__as_rval) + return static_cast<const _Up2&&>(__x); + else + return static_cast<const _Up2&>(__x); + } + else + { + if constexpr (__as_rval) + return static_cast<remove_reference_t<_Up>&&>(__x); + else + return static_cast<_Up&>(__x); + } + } +#endif + /** * @brief Convert a value to an rvalue. * @param __t A thing of arbitrary type. diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def index 6252f5478e0..8f008f9048f 100644 --- a/libstdc++-v3/include/bits/version.def +++ b/libstdc++-v3/include/bits/version.def @@ -1542,6 +1542,14 @@ ftms = { }; }; +ftms = { + name = forward_like; + values = { + v = 202207; + cxxmin = 23; + }; +}; + ftms = { name = ios_noreplace; values = { diff --git a/libstdc++-v3/include/std/utility b/libstdc++-v3/include/std/utility index f30e802a88d..bdaf5d4c31b 100644 --- a/libstdc++-v3/include/std/utility +++ b/libstdc++-v3/include/std/utility @@ -68,9 +68,10 @@ #include <bits/stl_relops.h> #include <bits/stl_pair.h> -#define __glibcxx_want_exchange_function -#define __glibcxx_want_constexpr_algorithms #define __glibcxx_want_as_const +#define __glibcxx_want_constexpr_algorithms +#define __glibcxx_want_exchange_function +#define __glibcxx_want_forward_like #define __glibcxx_want_integer_comparison_functions #define __glibcxx_want_to_underlying #define __glibcxx_want_unreachable diff --git a/libstdc++-v3/testsuite/20_util/forward_like/1.cc b/libstdc++-v3/testsuite/20_util/forward_like/1.cc new file mode 100644 index 00000000000..928e60094a3 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/forward_like/1.cc @@ -0,0 +1,59 @@ +// { dg-do compile { target c++23 } } +// { dg-add-options no_pch } + +#include <utility> + +#ifndef __cpp_lib_forward_like +# error "Feature-test macro for forward_like missing in <utility>" +#elif __cpp_lib_forward_like != 202207L +# error "Feature-test macro for forward_like has wrong value in <utility>" +#endif + +template<typename T, typename U> +using forward_like_t = decltype(std::forward_like<T>(std::declval<U>())); + +#if 0 +using std::is_same_v; +#else +#include <concepts> +template<class T, class U> concept is_same_v = std::same_as<T, U>; +#endif + +static_assert( is_same_v<forward_like_t<int, long>, long&&> ); +static_assert( is_same_v<forward_like_t<int&, long>, long&> ); +static_assert( is_same_v<forward_like_t<int&&, long>, long&&> ); + +static_assert( is_same_v<forward_like_t<const int, long>, const long&&> ); +static_assert( is_same_v<forward_like_t<const int&, long>, const long&> ); +static_assert( is_same_v<forward_like_t<const int&&, long>, const long&&> ); + +static_assert( is_same_v<forward_like_t<int, const long>, const long&&> ); +static_assert( is_same_v<forward_like_t<int&, const long>, const long&> ); +static_assert( is_same_v<forward_like_t<int&&, const long>, const long&&> ); + +static_assert( is_same_v<forward_like_t<const int, long&>, const long&&> ); +static_assert( is_same_v<forward_like_t<const int&, long&>, const long&> ); +static_assert( is_same_v<forward_like_t<const int&&, long&>, const long&&> ); + +static_assert( is_same_v<forward_like_t<int, const long&>, const long&&> ); +static_assert( is_same_v<forward_like_t<int&, const long&>, const long&> ); +static_assert( is_same_v<forward_like_t<int&&, const long&>, const long&&> ); + +static_assert( is_same_v<forward_like_t<const int, long&&>, const long&&> ); +static_assert( is_same_v<forward_like_t<const int&, long&&>, const long&> ); +static_assert( is_same_v<forward_like_t<const int&&, long&&>, const long&&> ); + +static_assert( is_same_v<forward_like_t<int, const long&&>, const long&&> ); +static_assert( is_same_v<forward_like_t<int&, const long&&>, const long&> ); +static_assert( is_same_v<forward_like_t<int&&, const long&&>, const long&&> ); + +static_assert( is_same_v<forward_like_t<volatile int, long>, long&&> ); +static_assert( is_same_v<forward_like_t<volatile int&, long>, long&> ); +static_assert( is_same_v<forward_like_t<volatile int&&, long>, long&&> ); + +static_assert( is_same_v<forward_like_t<const int, volatile long>, + const volatile long&&> ); +static_assert( is_same_v<forward_like_t<const int&, volatile long>, + const volatile long&> ); +static_assert( is_same_v<forward_like_t<const int&&, volatile long>, + const volatile long&&> ); diff --git a/libstdc++-v3/testsuite/20_util/forward_like/2_neg.cc b/libstdc++-v3/testsuite/20_util/forward_like/2_neg.cc new file mode 100644 index 00000000000..ff835af1915 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/forward_like/2_neg.cc @@ -0,0 +1,10 @@ +// { dg-do compile { target c++23 } } + +#include <utility> + +auto x1 = std::forward_like<void>(1); // { dg-error "here" } +// { dg-error "forming reference to void" "" { target *-*-* } 0 } +auto x2 = std::forward_like<void()const>(1); // { dg-error "here" } +// { dg-error "forming reference to qualified function" "" { target *-*-* } 0 } + +// { dg-prune-output "inconsistent deduction for auto return type" } // PR111484 diff --git a/libstdc++-v3/testsuite/20_util/forward_like/version.cc b/libstdc++-v3/testsuite/20_util/forward_like/version.cc new file mode 100644 index 00000000000..058dccfabe2 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/forward_like/version.cc @@ -0,0 +1,10 @@ +// { dg-do preprocess { target c++23 } } +// { dg-add-options no_pch } + +#include <version> + +#ifndef __cpp_lib_forward_like +# error "Feature-test macro for forward_like missing in <version>" +#elif __cpp_lib_forward_like != 202207L +# error "Feature-test macro for forward_like has wrong value in <version>" +#endif -- 2.41.0