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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-2858] libstdc++: Define std::is_pointer_interconvertible_base_of for C++20 Date: Wed, 11 Aug 2021 16:00:11 +0000 (GMT) [thread overview] Message-ID: <20210811160011.28AB4383A81E@sourceware.org> (raw) https://gcc.gnu.org/g:4fa6c0ec350bb4a8dd52a7c6f9881ab427151588 commit r12-2858-g4fa6c0ec350bb4a8dd52a7c6f9881ab427151588 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Aug 10 15:37:23 2021 +0100 libstdc++: Define std::is_pointer_interconvertible_base_of for C++20 Implement these traits using the new built-ins that Jakub added recently. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> libstdc++-v3/ChangeLog: * include/std/type_traits (__cpp_lib_is_pointer_interconvertible) (is_pointer_interconvertible_base_of_v) (is_pointer_interconvertible_base_of): Define for C++20. * include/std/version (__cpp_lib_is_pointer_interconvertible): Define. * testsuite/23_containers/span/layout_compat.cc: Use correct feature test macro for std::is_layout_compatible_v. * testsuite/20_util/is_pointer_interconvertible/value.cc: New test. * testsuite/20_util/is_pointer_interconvertible/version.cc: New test. Diff: --- libstdc++-v3/include/std/type_traits | 27 ++++++++++++ libstdc++-v3/include/std/version | 4 ++ .../20_util/is_pointer_interconvertible/value.cc | 51 ++++++++++++++++++++++ .../20_util/is_pointer_interconvertible/version.cc | 10 +++++ .../testsuite/23_containers/span/layout_compat.cc | 2 +- 5 files changed, 93 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 46edde905f8..2be4944e2a6 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -3389,6 +3389,33 @@ template<typename _Ret, typename _Fn, typename... _Args> inline constexpr bool is_unbounded_array_v = is_unbounded_array<_Tp>::value; +#if __has_builtin(__is_pointer_interconvertible_base_of) + /// True if `_Derived` is standard-layout and has a base class of type `_Base` + /// @since C++20 + template<typename _Base, typename _Derived> + struct is_pointer_interconvertible_base_of + : bool_constant<__is_pointer_interconvertible_base_of(_Base, _Derived)> + { }; + + /// @ingroup variable_templates + /// @since C++20 + template<typename _Base, typename _Derived> + constexpr bool is_pointer_interconvertible_base_of_v + = __is_pointer_interconvertible_base_of(_Base, _Derived); + +#if __has_builtin(__builtin_is_pointer_interconvertible_with_class) +#define __cpp_lib_is_pointer_interconvertible 201907L + + /// True if `__mp` points to the first member of a standard-layout type + /// @returns true if `s.*__mp` is pointer-interconvertible with `s` + /// @since C++20 + template<typename _Tp, typename _Mem> + constexpr bool + is_pointer_interconvertible_with_class(_Mem _Tp::*__mp) noexcept + { return __builtin_is_pointer_interconvertible_with_class(__mp); } +#endif +#endif + #if __cplusplus > 202002L #define __cpp_lib_is_scoped_enum 202011L diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version index d5fa38d7786..925f27704c4 100644 --- a/libstdc++-v3/include/std/version +++ b/libstdc++-v3/include/std/version @@ -236,6 +236,10 @@ #ifdef _GLIBCXX_HAS_GTHREADS # define __cpp_lib_jthread 201911L #endif +#if __has_builtin(__is_pointer_interconvertible_base_of) \ + && __has_builtin(__builtin_is_pointer_interconvertible_with_class) +# define __cpp_lib_is_pointer_interconvertible 201907L +#endif #if __cpp_lib_atomic_wait # define __cpp_lib_latch 201907L #endif diff --git a/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/value.cc b/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/value.cc new file mode 100644 index 00000000000..471571cac58 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/value.cc @@ -0,0 +1,51 @@ +// { dg-options "-std=gnu++20" } +// { dg-do compile { target c++20 } } +#include <type_traits> + +#ifndef __cpp_lib_is_pointer_interconvertible +# error "Feature test macro for is_pointer_interconvertible is missing in <type_traits>" +#elif __cpp_lib_is_pointer_interconvertible < 201907L +# error "Feature test macro for is_pointer_interconvertible has wrong value in <type_traits>" +#endif + +static_assert( std::is_pointer_interconvertible_base_of<void, void>::value + == std::is_pointer_interconvertible_base_of_v<void, void> ); + +struct B { }; + +static_assert( std::is_pointer_interconvertible_base_of<B, B>::value + == std::is_pointer_interconvertible_base_of_v<B, B> ); + +static_assert( std::is_pointer_interconvertible_base_of_v<B, B> ); +static_assert( std::is_pointer_interconvertible_base_of_v<B, const B> ); +static_assert( std::is_pointer_interconvertible_base_of_v<const B, B> ); +static_assert( std::is_pointer_interconvertible_base_of_v<const B, const B> ); + +struct D : B { int i; }; + +static_assert( std::is_pointer_interconvertible_base_of_v<D, D> ); + +static_assert( std::is_pointer_interconvertible_base_of_v<B, D> ); +static_assert( std::is_pointer_interconvertible_base_of_v<const B, D> ); +static_assert( std::is_pointer_interconvertible_base_of_v<B, const D> ); +static_assert( std::is_pointer_interconvertible_base_of_v<const B, const D> ); + +static_assert( ! std::is_pointer_interconvertible_base_of_v<D, B> ); + +struct E : D { }; +// E is not standard-layout +static_assert( ! std::is_pointer_interconvertible_base_of_v<E, B> ); + +struct D1 : B { }; +struct D2 : B { }; +struct D3 : D1, D2 { }; +// B is ambiguously derived +static_assert( ! std::is_pointer_interconvertible_base_of_v<B, D3> ); + +union U; +static_assert( ! std::is_pointer_interconvertible_base_of_v<U, U> ); +static_assert( ! std::is_pointer_interconvertible_base_of_v<U, D> ); + +struct I; // incomplete +static_assert( std::is_pointer_interconvertible_base_of_v<I, I> ); +static_assert( std::is_pointer_interconvertible_base_of_v<I, const I> ); diff --git a/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/version.cc b/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/version.cc new file mode 100644 index 00000000000..138c4be9f93 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/is_pointer_interconvertible/version.cc @@ -0,0 +1,10 @@ +// { dg-options "-std=gnu++20" } +// { dg-do compile { target c++20 } } + +#include <version> + +#ifndef __cpp_lib_is_pointer_interconvertible +# error "Feature test macro for is_pointer_interconvertible is missing in <version>" +#elif __cpp_lib_is_pointer_interconvertible < 201907L +# error "Feature test macro for is_pointer_interconvertible has wrong value in <version>" +#endif diff --git a/libstdc++-v3/testsuite/23_containers/span/layout_compat.cc b/libstdc++-v3/testsuite/23_containers/span/layout_compat.cc index 7959aa76633..04947e93dbc 100644 --- a/libstdc++-v3/testsuite/23_containers/span/layout_compat.cc +++ b/libstdc++-v3/testsuite/23_containers/span/layout_compat.cc @@ -27,7 +27,7 @@ struct iovec { void* iov_base; std::size_t iov_len; }; #endif -#if __cpp_lib_is_pointer_interconvertible +#if __cpp_lib_is_layout_compatible using std::is_layout_compatible_v; #else // A poor substitute for is_layout_compatible_v
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