[libcxx-commits] [libcxx] [libc++] Simplify the implementation of std::invoke (PR #213623)
Nikolas Klauser via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Aug 3 01:52:19 PDT 2026
https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/213623
Since we've dropped support for Clang 20, we can assume `__builtin_invoke` is available on Clang. This allows us to make use of GCC-specific extensions in the fallback, making it possible to significantly simplify the implementation.
>From 3d70bf1edc04234b84378e67741836479cfd6180 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Mon, 3 Aug 2026 10:50:57 +0200
Subject: [PATCH] [libc++] Simplify the implementation of std::invoke
---
libcxx/include/__configuration/namespace.h | 1 +
libcxx/include/__type_traits/invoke.h | 264 ++++++---------------
2 files changed, 70 insertions(+), 195 deletions(-)
diff --git a/libcxx/include/__configuration/namespace.h b/libcxx/include/__configuration/namespace.h
index 1f4b8ce247b13..9368c45d79ae4 100644
--- a/libcxx/include/__configuration/namespace.h
+++ b/libcxx/include/__configuration/namespace.h
@@ -34,6 +34,7 @@
_LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++17-extensions") \
_LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions") \
_LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++23-extensions")
+ _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++26-extensions")
# define _LIBCPP_POP_EXTENSION_DIAGNOSTICS _LIBCPP_DIAGNOSTIC_POP
# define _LIBCPP_PUSH_ABI_PRAGMA_DIAGNOSTICS \
_LIBCPP_DIAGNOSTIC_PUSH _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wpragma-clang-attribute") \
diff --git a/libcxx/include/__type_traits/invoke.h b/libcxx/include/__type_traits/invoke.h
index ba8202576593e..26da53d2d89af 100644
--- a/libcxx/include/__type_traits/invoke.h
+++ b/libcxx/include/__type_traits/invoke.h
@@ -22,6 +22,7 @@
#include <__type_traits/is_same.h>
#include <__type_traits/is_void.h>
#include <__type_traits/nat.h>
+#include <__type_traits/remove_cvref.h>
#include <__type_traits/void_t.h>
#include <__utility/declval.h>
#include <__utility/forward.h>
@@ -102,16 +103,6 @@ inline const bool __is_invocable_v = __is_invocable_impl<void, _Args...>;
template <class... _Args>
struct __is_invocable : integral_constant<bool, __is_invocable_v<_Args...> > {};
-template <class _Ret, bool, class... _Args>
-inline const bool __is_invocable_r_impl = false;
-
-template <class _Ret, class... _Args>
-inline const bool __is_invocable_r_impl<_Ret, true, _Args...> =
- __is_core_convertible<__invoke_result_t<_Args...>, _Ret>::value || is_void<_Ret>::value;
-
-template <class _Ret, class... _Args>
-inline const bool __is_invocable_r_v = __is_invocable_r_impl<_Ret, __is_invocable_v<_Args...>, _Args...>;
-
template <bool __is_invocable, class... _Args>
inline const bool __is_nothrow_invocable_impl = false;
@@ -123,17 +114,6 @@ inline const bool __is_nothrow_invocable_impl<true, _Args...> = noexcept(__built
template <class... _Args>
inline const bool __is_nothrow_invocable_v = __is_nothrow_invocable_impl<__is_invocable_v<_Args...>, _Args...>;
-template <bool __is_invocable, class _Ret, class... _Args>
-inline const bool __is_nothrow_invocable_r_impl = false;
-
-template <class _Ret, class... _Args>
-inline const bool __is_nothrow_invocable_r_impl<true, _Ret, _Args...> =
- __is_nothrow_core_convertible_v<__invoke_result_t<_Args...>, _Ret> || is_void<_Ret>::value;
-
-template <class _Ret, class... _Args>
-inline const bool __is_nothrow_invocable_r_v =
- __is_nothrow_invocable_r_impl<__is_nothrow_invocable_v<_Args...>, _Ret, _Args...>;
-
#else // __has_builtin(__builtin_invoke)
template <class _DecayedFp>
@@ -144,193 +124,87 @@ struct __member_pointer_class_type<_Ret _ClassType::*> {
typedef _ClassType type;
};
-template <class _Fp,
- class _A0,
- class _DecayFp = __decay_t<_Fp>,
- class _DecayA0 = __decay_t<_A0>,
- class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
-using __enable_if_bullet1 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_function_pointer<_DecayFp>::value &&
- (is_same<_ClassT, _DecayA0>::value || is_base_of<_ClassT, _DecayA0>::value)>;
-
-template <class _Fp, class _A0, class _DecayFp = __decay_t<_Fp>, class _DecayA0 = __decay_t<_A0> >
-using __enable_if_bullet2 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_function_pointer<_DecayFp>::value && __is_reference_wrapper<_DecayA0>::value>;
-
-template <class _Fp,
- class _A0,
- class _DecayFp = __decay_t<_Fp>,
- class _DecayA0 = __decay_t<_A0>,
- class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
-using __enable_if_bullet3 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_function_pointer<_DecayFp>::value &&
- !(is_same<_ClassT, _DecayA0>::value || is_base_of<_ClassT, _DecayA0>::value) &&
- !__is_reference_wrapper<_DecayA0>::value>;
-
-template <class _Fp,
- class _A0,
- class _DecayFp = __decay_t<_Fp>,
- class _DecayA0 = __decay_t<_A0>,
- class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
-using __enable_if_bullet4 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_object_pointer<_DecayFp>::value &&
- (is_same<_ClassT, _DecayA0>::value || is_base_of<_ClassT, _DecayA0>::value)>;
-
-template <class _Fp, class _A0, class _DecayFp = __decay_t<_Fp>, class _DecayA0 = __decay_t<_A0> >
-using __enable_if_bullet5 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_object_pointer<_DecayFp>::value && __is_reference_wrapper<_DecayA0>::value>;
-
-template <class _Fp,
- class _A0,
- class _DecayFp = __decay_t<_Fp>,
- class _DecayA0 = __decay_t<_A0>,
- class _ClassT = typename __member_pointer_class_type<_DecayFp>::type>
-using __enable_if_bullet6 _LIBCPP_NODEBUG =
- __enable_if_t<is_member_object_pointer<_DecayFp>::value &&
- !(is_same<_ClassT, _DecayA0>::value || is_base_of<_ClassT, _DecayA0>::value) &&
- !__is_reference_wrapper<_DecayA0>::value>;
-
-// __invoke forward declarations
-
-// fall back - none of the bullets
-
-template <class... _Args>
-__nat __invoke(_Args&&... __args);
-
-// bullets 1, 2 and 3
-
-// clang-format off
-template <class _Fp, class _A0, class... _Args, class = __enable_if_bullet1<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype((std::declval<_A0>().*std::declval<_Fp>())(std::declval<_Args>()...))
-__invoke(_Fp&& __f, _A0&& __a0, _Args&&... __args)
- _NOEXCEPT_(noexcept((static_cast<_A0&&>(__a0).*__f)(static_cast<_Args&&>(__args)...)))
- { return (static_cast<_A0&&>(__a0).*__f)(static_cast<_Args&&>(__args)...); }
-
-template <class _Fp, class _A0, class... _Args, class = __enable_if_bullet2<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype((std::declval<_A0>().get().*std::declval<_Fp>())(std::declval<_Args>()...))
-__invoke(_Fp&& __f, _A0&& __a0, _Args&&... __args)
- _NOEXCEPT_(noexcept((__a0.get().*__f)(static_cast<_Args&&>(__args)...)))
- { return (__a0.get().*__f)(static_cast<_Args&&>(__args)...); }
-
-template <class _Fp, class _A0, class... _Args, class = __enable_if_bullet3<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype(((*std::declval<_A0>()).*std::declval<_Fp>())(std::declval<_Args>()...))
-__invoke(_Fp&& __f, _A0&& __a0, _Args&&... __args)
- _NOEXCEPT_(noexcept(((*static_cast<_A0&&>(__a0)).*__f)(static_cast<_Args&&>(__args)...)))
- { return ((*static_cast<_A0&&>(__a0)).*__f)(static_cast<_Args&&>(__args)...); }
-
-// bullets 4, 5 and 6
-
-template <class _Fp, class _A0, class = __enable_if_bullet4<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype(std::declval<_A0>().*std::declval<_Fp>())
-__invoke(_Fp&& __f, _A0&& __a0)
- _NOEXCEPT_(noexcept(static_cast<_A0&&>(__a0).*__f))
- { return static_cast<_A0&&>(__a0).*__f; }
-
-template <class _Fp, class _A0, class = __enable_if_bullet5<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype(std::declval<_A0>().get().*std::declval<_Fp>())
-__invoke(_Fp&& __f, _A0&& __a0)
- _NOEXCEPT_(noexcept(__a0.get().*__f))
- { return __a0.get().*__f; }
-
-template <class _Fp, class _A0, class = __enable_if_bullet6<_Fp, _A0> >
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype((*std::declval<_A0>()).*std::declval<_Fp>())
-__invoke(_Fp&& __f, _A0&& __a0)
- _NOEXCEPT_(noexcept((*static_cast<_A0&&>(__a0)).*__f))
- { return (*static_cast<_A0&&>(__a0)).*__f; }
-
-// bullet 7
-
-template <class _Fp, class... _Args>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
-decltype(std::declval<_Fp>()(std::declval<_Args>()...))
-__invoke(_Fp&& __f, _Args&&... __args)
- _NOEXCEPT_(noexcept(static_cast<_Fp&&>(__f)(static_cast<_Args&&>(__args)...)))
- { return static_cast<_Fp&&>(__f)(static_cast<_Args&&>(__args)...); }
-// clang-format on
-
-// __invokable
-template <class _Ret, class _Fp, class... _Args>
-struct __invokable_r {
- template <class _XFp, class... _XArgs>
- static decltype(std::__invoke(std::declval<_XFp>(), std::declval<_XArgs>()...)) __try_call(int);
- template <class _XFp, class... _XArgs>
- static __nat __try_call(...);
-
- // FIXME: Check that _Ret, _Fp, and _Args... are all complete types, cv void,
- // or incomplete array types as required by the standard.
- using _Result _LIBCPP_NODEBUG = decltype(__try_call<_Fp, _Args...>(0));
-
- using type = __conditional_t<_IsNotSame<_Result, __nat>::value,
- __conditional_t<is_void<_Ret>::value, true_type, __is_core_convertible<_Result, _Ret> >,
- false_type>;
- static const bool value = type::value;
-};
-template <class _Fp, class... _Args>
-using __is_invocable _LIBCPP_NODEBUG = __invokable_r<void, _Fp, _Args...>;
-
-template <bool _IsInvokable, bool _IsCVVoid, class _Ret, class _Fp, class... _Args>
-struct __nothrow_invokable_r_imp {
- static const bool value = false;
-};
+template <class _Func, class... _Args>
+inline const bool __is_invocable_v = __is_invocable(_Func, _Args...);
-template <class _Ret, class _Fp, class... _Args>
-struct __nothrow_invokable_r_imp<true, false, _Ret, _Fp, _Args...> {
- typedef __nothrow_invokable_r_imp _ThisT;
+template <class _Func, class... _Args>
+inline const bool __is_nothrow_invocable_v = __is_nothrow_invocable(_Func, _Args...);
+
+template <class _Func, class... _Args, class = __enable_if_t<__is_invocable_v<_Func, _Args...>>>
+constexpr decltype(auto)
+__invoke(_Func&& __func, _Args&&... __args) noexcept(__is_nothrow_invocable_v<_Func, _Args...>) {
+ using _RawFunc = __remove_cvref_t<_Func>;
+ if constexpr (is_member_pointer<_RawFunc>::value) {
+ using _Tp = typename __member_pointer_class_type<_RawFunc>::type;
+ using _T1 = _Args...[0];
+ using _RawT1 = __remove_cvref_t<_T1>;
+ if constexpr (is_member_function_pointer<_RawFunc>::value) {
+ if constexpr (is_same<_Tp, __remove_cvref_t<_T1>>::value || is_base_of<_Tp, __remove_cvref_t<_T1>>::value) {
+ return []<class _Func2, class _Arg0, class... _Args2>(
+ _Func2&& __func2, _Arg0&& __arg0, _Args2&&... __args2) -> decltype(auto) {
+ return (std::forward<_Arg0>(__arg0).*__func2)(std::forward<_Args2>(__args2)...);
+ }(std::forward<_Func>(__func), std::forward<_Args>(__args)...);
+ } else if constexpr (__is_reference_wrapper<_RawT1>::value) {
+ return []<class _Func2, class _Arg0, class... _Args2>(
+ _Func2&& __func2, _Arg0&& __arg0, _Args2&&... __args2) -> decltype(auto) {
+ return ((std::forward<_Arg0>(__arg0).get()).*__func2)(std::forward<_Args2>(__args2)...);
+ }(std::forward<_Func>(__func), std::forward<_Args>(__args)...);
+ } else {
+ return []<class _Func2, class _Arg0, class... _Args2>(
+ _Func2&& __func2, _Arg0&& __arg0, _Args2&&... __args2) -> decltype(auto) {
+ return ((*std::forward<_Arg0>(__arg0)).*__func2)(std::forward<_Args2>(__args2)...);
+ }(std::forward<_Func>(__func), std::forward<_Args>(__args)...);
+ }
+ } else {
+ if constexpr (is_same<_Tp, __remove_cvref_t<_T1>>::value || is_base_of<_Tp, __remove_cvref_t<_T1>>::value) {
+ return std::forward<_Args...[0]>(__args...[0]).*__func;
+ } else if constexpr (__is_reference_wrapper<_RawT1>::value) {
+ return std::forward<_Args...[0]>(__args...[0]).get().*__func;
+ } else {
+ return (*std::forward<_Args...[0]>(__args...[0])).*__func;
+ }
+ }
+ } else {
+ return std::forward<_Func>(__func)(std::forward<_Args>(__args)...);
+ }
+}
- template <class _Tp>
- static void __test_noexcept(_Tp) _NOEXCEPT;
+template <class... _Args>
+using __invoke_result_t = decltype(std::__invoke(std::declval<_Args>()...));
-# ifdef _LIBCPP_CXX03_LANG
- static const bool value = false;
-# else
- static const bool value =
- noexcept(_ThisT::__test_noexcept<_Ret>(std::__invoke(std::declval<_Fp>(), std::declval<_Args>()...)));
-# endif
-};
+template <bool _Invocable, class _Func, class... _Args>
+struct __invoke_result_impl {};
-template <class _Ret, class _Fp, class... _Args>
-struct __nothrow_invokable_r_imp<true, true, _Ret, _Fp, _Args...> {
-# ifdef _LIBCPP_CXX03_LANG
- static const bool value = false;
-# else
- static const bool value = noexcept(std::__invoke(std::declval<_Fp>(), std::declval<_Args>()...));
-# endif
+template <class _Func, class... _Args>
+struct __invoke_result_impl<true, _Func, _Args...> {
+ using type = __invoke_result_t<_Func, _Args...>;
};
-template <class _Ret, class _Fp, class... _Args>
-using __nothrow_invokable_r _LIBCPP_NODEBUG =
- __nothrow_invokable_r_imp<__invokable_r<_Ret, _Fp, _Args...>::value, is_void<_Ret>::value, _Ret, _Fp, _Args...>;
-
-template <class _Fp, class... _Args>
-using __nothrow_invokable _LIBCPP_NODEBUG =
- __nothrow_invokable_r_imp<__is_invocable<_Fp, _Args...>::value, true, void, _Fp, _Args...>;
-
template <class _Func, class... _Args>
-inline const bool __is_invocable_v = __is_invocable<_Func, _Args...>::value;
+using __invoke_result = __invoke_result_impl<__is_invocable_v<_Func, _Args...>, _Func, _Args...>;
-template <class _Ret, class _Func, class... _Args>
-inline const bool __is_invocable_r_v = __invokable_r<_Ret, _Func, _Args...>::value;
+#endif // __has_builtin(__builtin_invoke_r)
-template <class _Func, class... _Args>
-inline const bool __is_nothrow_invocable_v = __nothrow_invokable<_Func, _Args...>::value;
+template <class _Ret, bool, class... _Args>
+inline const bool __is_invocable_r_impl = false;
-template <class _Ret, class _Func, class... _Args>
-inline const bool __is_nothrow_invocable_r_v = __nothrow_invokable_r<_Ret, _Func, _Args...>::value;
+template <class _Ret, class... _Args>
+inline const bool __is_invocable_r_impl<_Ret, true, _Args...> =
+ __is_core_convertible_v<__invoke_result_t<_Args...>, _Ret> || is_void<_Ret>::value;
-template <class _Func, class... _Args>
-struct __invoke_result
- : enable_if<__is_invocable_v<_Func, _Args...>, typename __invokable_r<void, _Func, _Args...>::_Result> {};
+template <class _Ret, class... _Args>
+inline const bool __is_invocable_r_v = __is_invocable_r_impl<_Ret, __is_invocable_v<_Args...>, _Args...>;
-template <class _Func, class... _Args>
-using __invoke_result_t _LIBCPP_NODEBUG = typename __invoke_result<_Func, _Args...>::type;
+template <bool __is_invocable, class _Ret, class... _Args>
+inline const bool __is_nothrow_invocable_r_impl = false;
-#endif // __has_builtin(__builtin_invoke_r)
+template <class _Ret, class... _Args>
+inline const bool __is_nothrow_invocable_r_impl<true, _Ret, _Args...> =
+ __is_nothrow_core_convertible_v<__invoke_result_t<_Args...>, _Ret> || is_void<_Ret>::value;
+
+template <class _Ret, class... _Args>
+inline const bool __is_nothrow_invocable_r_v =
+ __is_nothrow_invocable_r_impl<__is_nothrow_invocable_v<_Args...>, _Ret, _Args...>;
template <class _Ret, class _Func, class... _Args>
struct __is_invocable_r : integral_constant<bool, __is_invocable_r_v<_Ret, _Func, _Args...> > {};
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