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JMazurkiewiczJMazurkiewicz
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[libc++] Implement std::not_fn<NTTP> (#86133)
Implement `std::not_fn<NTTP>` from "P2714R1 Bind front and back to NTTP callables".
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‎libcxx/docs/FeatureTestMacroTable.rst

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@@ -458,6 +458,8 @@ Status
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---------------------------------------------------------- -----------------
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``__cpp_lib_mdspan`` ``202406L``
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---------------------------------------------------------- -----------------
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``__cpp_lib_not_fn`` ``202306L``
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---------------------------------------------------------- -----------------
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``__cpp_lib_optional_range_support`` *unimplemented*
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---------------------------------------------------------- -----------------
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``__cpp_lib_out_ptr`` ``202311L``

‎libcxx/docs/Status/Cxx2cPapers.csv

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@@ -24,7 +24,7 @@
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"`P1383R2 <https://wg21.link/P1383R2>`__","More ``constexpr`` for ``<cmath>`` and ``<complex>``","2023-06 (Varna)","","",""
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"`P2734R0 <https://wg21.link/P2734R0>`__","Adding the new SI prefixes","2023-06 (Varna)","|Complete|","17",""
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"`P2548R6 <https://wg21.link/P2548R6>`__","``copyable_function``","2023-06 (Varna)","","",""
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"`P2714R1 <https://wg21.link/P2714R1>`__","Bind front and back to NTTP callables","2023-06 (Varna)","","",""
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"`P2714R1 <https://wg21.link/P2714R1>`__","Bind front and back to NTTP callables","2023-06 (Varna)","|Partial|","20","``not_fn`` only"
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"`P2630R4 <https://wg21.link/P2630R4>`__","``submdspan``","2023-06 (Varna)","","",""
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"","","","","",""
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"`P0543R3 <https://wg21.link/P0543R3>`__","Saturation arithmetic","2023-11 (Kona)","|Complete|","18",""

‎libcxx/include/__functional/not_fn.h

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#include <__type_traits/decay.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_constructible.h>
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#include <__type_traits/is_member_pointer.h>
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#include <__type_traits/is_pointer.h>
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#include <__utility/forward.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -48,6 +50,27 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto not_fn(_Fn&& __f) {
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#endif // _LIBCPP_STD_VER >= 17
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#if _LIBCPP_STD_VER >= 26
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template <auto _Fn>
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struct __nttp_not_fn_t {
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template <class... _Args>
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[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const
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noexcept(noexcept(!std::invoke(_Fn, std::forward<_Args>(__args)...)))
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-> decltype(!std::invoke(_Fn, std::forward<_Args>(__args)...)) {
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return !std::invoke(_Fn, std::forward<_Args>(__args)...);
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}
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};
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template <auto _Fn>
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[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI constexpr auto not_fn() noexcept {
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if constexpr (using _Ty = decltype(_Fn); is_pointer_v<_Ty> || is_member_pointer_v<_Ty>)
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static_assert(_Fn != nullptr, "f cannot be equal to nullptr");
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return __nttp_not_fn_t<_Fn>();
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}
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#endif // _LIBCPP_STD_VER >= 26
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___FUNCTIONAL_NOT_FN_H

‎libcxx/include/functional

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@@ -214,7 +214,9 @@ template <class Predicate> // deprecated in C++17, removed in C++20
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binary_negate<Predicate> not2(const Predicate& pred);
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template <class F>
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constexpr unspecified not_fn(F&& f); // C++17, constexpr in C++20
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constexpr unspecified not_fn(F&& f); // C++17, constexpr in C++20
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template <auto f>
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constexpr unspecified not_fn() noexcept; // C++26
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// [func.bind.partial], function templates bind_front and bind_back
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template<class F, class... Args>

‎libcxx/include/version

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@@ -171,7 +171,8 @@ __cpp_lib_nonmember_container_access 201411L <array> <deque>
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<iterator> <list> <map>
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<regex> <set> <string>
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<unordered_map> <unordered_set> <vector>
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__cpp_lib_not_fn 201603L <functional>
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__cpp_lib_not_fn 202306L <functional>
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201603L // C++17
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__cpp_lib_null_iterators 201304L <iterator>
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__cpp_lib_optional 202110L <optional>
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202106L // C++20
@@ -557,6 +558,8 @@ __cpp_lib_void_t 201411L <type_traits>
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// # define __cpp_lib_linalg 202311L
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# undef __cpp_lib_mdspan
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# define __cpp_lib_mdspan 202406L
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# undef __cpp_lib_not_fn
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# define __cpp_lib_not_fn 202306L
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// # define __cpp_lib_optional_range_support 202406L
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# undef __cpp_lib_out_ptr
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# define __cpp_lib_out_ptr 202311L

‎libcxx/test/libcxx/utilities/function.objects/func.not.fn/not_fn.nttp.compile.pass.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
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// <functional>
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// Type of `std::not_fn<NTTP>()` is always empty.
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#include <functional>
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#include <type_traits>
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struct NonEmptyFunctionObject {
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bool val = true;
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bool operator()() const;
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};
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bool func();
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struct SomeClass {
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bool member_object;
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bool member_function();
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};
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using ResultWithEmptyFuncObject = decltype(std::not_fn<std::false_type{}>());
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static_assert(std::is_empty_v<ResultWithEmptyFuncObject>);
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using ResultWithNotEmptyFuncObject = decltype(std::not_fn<NonEmptyFunctionObject{}>());
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static_assert(std::is_empty_v<ResultWithNotEmptyFuncObject>);
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using ResultWithFunctionPointer = decltype(std::not_fn<&func>());
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static_assert(std::is_empty_v<ResultWithFunctionPointer>);
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using ResultWithMemberObjectPointer = decltype(std::not_fn<&SomeClass::member_object>());
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static_assert(std::is_empty_v<ResultWithMemberObjectPointer>);
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using ResultWithMemberFunctionPointer = decltype(std::not_fn<&SomeClass::member_function>());
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static_assert(std::is_empty_v<ResultWithMemberFunctionPointer>);

‎libcxx/test/libcxx/utilities/function.objects/func.not.fn/not_fn.nttp.nodiscard.verify.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
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// <functional>
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// Test the libc++ extension that std::not_fn<NTTP> is marked as [[nodiscard]].
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#include <functional>
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#include <type_traits>
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void test() {
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using F = std::true_type;
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std::not_fn<F{}>(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
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auto negated = std::not_fn<F{}>();
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negated(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
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}

‎libcxx/test/std/language.support/support.limits/support.limits.general/functional.version.compile.pass.cpp

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__cpp_lib_invoke_r 202106L [C++23]
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__cpp_lib_move_only_function 202110L [C++23]
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__cpp_lib_not_fn 201603L [C++17]
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202306L [C++26]
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__cpp_lib_ranges 202110L [C++20]
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202406L [C++23]
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__cpp_lib_reference_wrapper 202403L [C++26]
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# ifndef __cpp_lib_not_fn
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# error "__cpp_lib_not_fn should be defined in c++26"
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# endif
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# if __cpp_lib_not_fn != 201603L
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# error "__cpp_lib_not_fn should have the value 201603L in c++26"
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# if __cpp_lib_not_fn != 202306L
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# error "__cpp_lib_not_fn should have the value 202306L in c++26"
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# endif
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# ifndef __cpp_lib_ranges

‎libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp

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__cpp_lib_node_extract 201606L [C++17]
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__cpp_lib_nonmember_container_access 201411L [C++17]
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__cpp_lib_not_fn 201603L [C++17]
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202306L [C++26]
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__cpp_lib_null_iterators 201304L [C++14]
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__cpp_lib_optional 201606L [C++17]
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202106L [C++20]
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# ifndef __cpp_lib_not_fn
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# error "__cpp_lib_not_fn should be defined in c++26"
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# endif
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# if __cpp_lib_not_fn != 201603L
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# error "__cpp_lib_not_fn should have the value 201603L in c++26"
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# if __cpp_lib_not_fn != 202306L
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# error "__cpp_lib_not_fn should have the value 202306L in c++26"
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# endif
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# ifndef __cpp_lib_null_iterators

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