From: Jonathan Wakely Date: Fri, 22 Mar 2024 13:20:21 +0000 (+0000) Subject: libstdc++: Add std::reference_wrapper comparison operators for C++26 X-Git-Tag: basepoints/gcc-15~159 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d58450659ade002666c1c3604c94cd8e0cc6b50;p=thirdparty%2Fgcc.git libstdc++: Add std::reference_wrapper comparison operators for C++26 This C++26 change was just approved in Tokyo, in P2944R3. It adds operator== and operator<=> overloads to std::reference_wrapper. The operator<=> overloads in the paper cause compilation errors for any type without <=> so they're implemented here with deduced return types and constrained by a requires clause. libstdc++-v3/ChangeLog: * include/bits/refwrap.h (reference_wrapper): Add comparison operators as proposed by P2944R3. * include/bits/version.def (reference_wrapper): Define. * include/bits/version.h: Regenerate. * include/std/functional: Enable feature test macro. * testsuite/20_util/reference_wrapper/compare.cc: New test. --- diff --git a/libstdc++-v3/include/bits/refwrap.h b/libstdc++-v3/include/bits/refwrap.h index 2d4338b718fc..fd1cc2b63e67 100644 --- a/libstdc++-v3/include/bits/refwrap.h +++ b/libstdc++-v3/include/bits/refwrap.h @@ -38,6 +38,10 @@ #include #include // for unary_function and binary_function +#if __glibcxx_reference_wrapper >= 202403L // >= C++26 +# include +#endif + namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION @@ -358,6 +362,47 @@ _GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type) #endif return std::__invoke(get(), std::forward<_Args>(__args)...); } + +#if __glibcxx_reference_wrapper >= 202403L // >= C++26 + // [refwrap.comparisons], comparisons + [[nodiscard]] + friend constexpr bool + operator==(reference_wrapper __x, reference_wrapper __y) + requires requires { { __x.get() == __y.get() } -> convertible_to; } + { return __x.get() == __y.get(); } + + [[nodiscard]] + friend constexpr bool + operator==(reference_wrapper __x, const _Tp& __y) + requires requires { { __x.get() == __y } -> convertible_to; } + { return __x.get() == __y; } + + [[nodiscard]] + friend constexpr bool + operator==(reference_wrapper __x, reference_wrapper __y) + requires (!is_const_v<_Tp>) + && requires { { __x.get() == __y.get() } -> convertible_to; } + { return __x.get() == __y.get(); } + + [[nodiscard]] + friend constexpr auto + operator<=>(reference_wrapper __x, reference_wrapper<_Tp> __y) + requires requires { __detail::__synth3way(__x.get(), __y.get()); } + { return __detail::__synth3way(__x.get(), __y.get()); } + + [[nodiscard]] + friend constexpr auto + operator<=>(reference_wrapper __x, const _Tp& __y) + requires requires { __detail::__synth3way(__x.get(), __y); } + { return __detail::__synth3way(__x.get(), __y); } + + [[nodiscard]] + friend constexpr auto + operator<=>(reference_wrapper __x, reference_wrapper __y) + requires (!is_const_v<_Tp>) + && requires { __detail::__synth3way(__x.get(), __y.get()); } + { return __detail::__synth3way(__x.get(), __y.get()); } +#endif }; #if __cpp_deduction_guides diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def index 5ad44941bff0..5c0477fb61e7 100644 --- a/libstdc++-v3/include/bits/version.def +++ b/libstdc++-v3/include/bits/version.def @@ -1760,6 +1760,14 @@ ftms = { }; }; +ftms = { + name = reference_wrapper; + values = { + v = 202403; + cxxmin = 26; + }; +}; + ftms = { name = saturation_arithmetic; values = { diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h index 460a3e0116af..65e708c73fb3 100644 --- a/libstdc++-v3/include/bits/version.h +++ b/libstdc++-v3/include/bits/version.h @@ -1963,6 +1963,16 @@ #endif /* !defined(__cpp_lib_ratio) && defined(__glibcxx_want_ratio) */ #undef __glibcxx_want_ratio +#if !defined(__cpp_lib_reference_wrapper) +# if (__cplusplus > 202302L) +# define __glibcxx_reference_wrapper 202403L +# if defined(__glibcxx_want_all) || defined(__glibcxx_want_reference_wrapper) +# define __cpp_lib_reference_wrapper 202403L +# endif +# endif +#endif /* !defined(__cpp_lib_reference_wrapper) && defined(__glibcxx_want_reference_wrapper) */ +#undef __glibcxx_want_reference_wrapper + #if !defined(__cpp_lib_saturation_arithmetic) # if (__cplusplus > 202302L) # define __glibcxx_saturation_arithmetic 202311L diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional index 766558b3ce0e..99364286a72e 100644 --- a/libstdc++-v3/include/std/functional +++ b/libstdc++-v3/include/std/functional @@ -83,6 +83,7 @@ #define __glibcxx_want_move_only_function #define __glibcxx_want_not_fn #define __glibcxx_want_ranges +#define __glibcxx_want_reference_wrapper #define __glibcxx_want_transparent_operators #include diff --git a/libstdc++-v3/testsuite/20_util/reference_wrapper/compare.cc b/libstdc++-v3/testsuite/20_util/reference_wrapper/compare.cc new file mode 100644 index 000000000000..039c9d264964 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/reference_wrapper/compare.cc @@ -0,0 +1,95 @@ +// { dg-do compile { target c++26 } } + + +#include + +#ifndef __cpp_lib_reference_wrapper +# error "Feature-test macro for reference_wrapper missing" +#elif __cpp_lib_reference_wrapper != 202403 +# error "Feature-test macro for reference_wrapper has wrong value" +#endif + +// P2944R3 Comparisons for reference_wrapper + +auto check(int i, std::reference_wrapper r) -> bool { + return i == r; +} + +template using Ref = std::reference_wrapper; + +template +concept ref_equality_comparable += requires (T a, T const ca, Ref r, Ref cr) { + // the usual T is equality-comparable with itself + a == a; + a == ca; + ca == ca; + + // Ref is equality-comparable with itself + r == r; + r == cr; + cr == cr; + + // T and Ref are equality-comparable + a == r; + a == cr; + ca == r; + ca == cr; +}; + +static_assert( ref_equality_comparable ); + +struct A { + auto operator==(A const&) const -> bool { return true; } +}; + +struct B { + friend auto operator==(B const&, B const&) -> bool { return true; } +}; + +template +struct C { + friend auto operator==(C const&, C const&) -> bool { return true; } +}; + +template +struct D { }; +template +auto operator==(D const&, D const&) -> bool { return true; } + +static_assert(ref_equality_comparable); +static_assert(ref_equality_comparable); +static_assert(ref_equality_comparable); +static_assert(ref_equality_comparable>); +static_assert(ref_equality_comparable>); +#include +static_assert(ref_equality_comparable); + +template +struct ValArray { + friend auto operator==(ValArray const&, ValArray const&) -> ValArray { + return {}; + } +}; + +void f(ValArray v) { + // this is valid and has type ValArray + v == v; + + // this is also valid today and has the same type + std::ref(v) == std::ref(v); +} + +struct ComparesAsInt { + friend auto operator==(ComparesAsInt, ComparesAsInt) -> int; +}; + +auto f(std::reference_wrapper a, + std::reference_wrapper b) { + // today: compiles and returns int + // proposed: compiles and returns bool + return a == b; +} + +ComparesAsInt& c(); +static_assert( std::is_same_v );