858 lines
37 KiB
C++
858 lines
37 KiB
C++
// Copyright 2022 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Implementation details for `absl::AnyInvocable`
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#ifndef ABSL_FUNCTIONAL_INTERNAL_ANY_INVOCABLE_H_
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#define ABSL_FUNCTIONAL_INTERNAL_ANY_INVOCABLE_H_
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////////////////////////////////////////////////////////////////////////////////
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// //
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// This implementation of the proposed `any_invocable` uses an approach that //
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// chooses between local storage and remote storage for the contained target //
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// object based on the target object's size, alignment requirements, and //
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// whether or not it has a nothrow move constructor. Additional optimizations //
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// are performed when the object is a trivially copyable type [basic.types]. //
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// //
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// There are three datamembers per `AnyInvocable` instance //
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// //
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// 1) A union containing either //
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// - A pointer to the target object referred to via a void*, or //
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// - the target object, emplaced into a raw char buffer //
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// //
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// 2) A function pointer to a "manager" function operation that takes a //
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// discriminator and logically branches to either perform a move operation //
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// or destroy operation based on that discriminator. //
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// //
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// 3) A function pointer to an "invoker" function operation that invokes the //
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// target object, directly returning the result. //
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// //
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// When in the logically empty state, the manager function is an empty //
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// function and the invoker function is one that would be undefined-behavior //
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// to call. //
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// //
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// An additional optimization is performed when converting from one //
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// AnyInvocable to another where only the noexcept specification and/or the //
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// cv/ref qualifiers of the function type differ. In these cases, the //
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// conversion works by "moving the guts", similar to if they were the same //
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// exact type, as opposed to having to perform an additional layer of //
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// wrapping through remote storage. //
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// //
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////////////////////////////////////////////////////////////////////////////////
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// IWYU pragma: private, include "absl/functional/any_invocable.h"
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#include <cassert>
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#include <cstddef>
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#include <cstring>
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#include <functional>
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#include <initializer_list>
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#include <memory>
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#include <new>
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#include <type_traits>
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#include <utility>
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#include "absl/base/config.h"
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#include "absl/base/internal/invoke.h"
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#include "absl/base/macros.h"
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#include "absl/meta/type_traits.h"
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#include "absl/utility/utility.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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// Helper macro used to prevent spelling `noexcept` in language versions older
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// than C++17, where it is not part of the type system, in order to avoid
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// compilation failures and internal compiler errors.
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#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
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#define ABSL_INTERNAL_NOEXCEPT_SPEC(noex) noexcept(noex)
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#else
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#define ABSL_INTERNAL_NOEXCEPT_SPEC(noex)
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#endif
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// Defined in functional/any_invocable.h
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template <class Sig>
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class AnyInvocable;
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namespace internal_any_invocable {
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// Constants relating to the small-object-storage for AnyInvocable
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enum StorageProperty : std::size_t {
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kAlignment = alignof(std::max_align_t), // The alignment of the storage
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kStorageSize = sizeof(void*) * 2 // The size of the storage
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};
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////////////////////////////////////////////////////////////////////////////////
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//
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// A metafunction for checking if a type is an AnyInvocable instantiation.
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// This is used during conversion operations.
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template <class T>
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struct IsAnyInvocable : std::false_type {};
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template <class Sig>
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struct IsAnyInvocable<AnyInvocable<Sig>> : std::true_type {};
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//
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////////////////////////////////////////////////////////////////////////////////
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// A type trait that tells us whether or not a target function type should be
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// stored locally in the small object optimization storage
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template <class T>
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using IsStoredLocally = std::integral_constant<
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bool, sizeof(T) <= kStorageSize && alignof(T) <= kAlignment &&
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kAlignment % alignof(T) == 0 &&
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std::is_nothrow_move_constructible<T>::value>;
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// An implementation of std::remove_cvref_t of C++20.
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template <class T>
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using RemoveCVRef =
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typename std::remove_cv<typename std::remove_reference<T>::type>::type;
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////////////////////////////////////////////////////////////////////////////////
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//
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// An implementation of the C++ standard INVOKE<R> pseudo-macro, operation is
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// equivalent to std::invoke except that it forces an implicit conversion to the
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// specified return type. If "R" is void, the function is executed and the
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// return value is simply ignored.
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template <class ReturnType, class F, class... P,
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typename = absl::enable_if_t<std::is_void<ReturnType>::value>>
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void InvokeR(F&& f, P&&... args) {
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absl::base_internal::invoke(std::forward<F>(f), std::forward<P>(args)...);
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}
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template <class ReturnType, class F, class... P,
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absl::enable_if_t<!std::is_void<ReturnType>::value, int> = 0>
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ReturnType InvokeR(F&& f, P&&... args) {
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return absl::base_internal::invoke(std::forward<F>(f),
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std::forward<P>(args)...);
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}
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//
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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///
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// A metafunction that takes a "T" corresponding to a parameter type of the
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// user's specified function type, and yields the parameter type to use for the
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// type-erased invoker. In order to prevent observable moves, this must be
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// either a reference or, if the type is trivial, the original parameter type
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// itself. Since the parameter type may be incomplete at the point that this
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// metafunction is used, we can only do this optimization for scalar types
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// rather than for any trivial type.
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template <typename T>
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T ForwardImpl(std::true_type);
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template <typename T>
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T&& ForwardImpl(std::false_type);
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// NOTE: We deliberately use an intermediate struct instead of a direct alias,
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// as a workaround for b/206991861 on MSVC versions < 1924.
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template <class T>
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struct ForwardedParameter {
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using type = decltype((
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ForwardImpl<T>)(std::integral_constant<bool,
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std::is_scalar<T>::value>()));
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};
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template <class T>
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using ForwardedParameterType = typename ForwardedParameter<T>::type;
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//
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////////////////////////////////////////////////////////////////////////////////
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// A discriminator when calling the "manager" function that describes operation
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// type-erased operation should be invoked.
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//
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// "relocate_from_to" specifies that the manager should perform a move.
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//
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// "dispose" specifies that the manager should perform a destroy.
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enum class FunctionToCall : bool { relocate_from_to, dispose };
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// The portion of `AnyInvocable` state that contains either a pointer to the
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// target object or the object itself in local storage
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union TypeErasedState {
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struct {
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// A pointer to the type-erased object when remotely stored
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void* target;
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// The size of the object for `RemoteManagerTrivial`
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std::size_t size;
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} remote;
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// Local-storage for the type-erased object when small and trivial enough
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alignas(kAlignment) char storage[kStorageSize];
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};
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// A typed accessor for the object in `TypeErasedState` storage
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template <class T>
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T& ObjectInLocalStorage(TypeErasedState* const state) {
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// We launder here because the storage may be reused with the same type.
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#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
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return *std::launder(reinterpret_cast<T*>(&state->storage));
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#elif ABSL_HAVE_BUILTIN(__builtin_launder)
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return *__builtin_launder(reinterpret_cast<T*>(&state->storage));
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#else
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// When `std::launder` or equivalent are not available, we rely on undefined
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// behavior, which works as intended on Abseil's officially supported
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// platforms as of Q2 2022.
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#if !defined(__clang__) && defined(__GNUC__)
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#pragma GCC diagnostic ignored "-Wstrict-aliasing"
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#pragma GCC diagnostic push
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#endif
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return *reinterpret_cast<T*>(&state->storage);
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#if !defined(__clang__) && defined(__GNUC__)
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#pragma GCC diagnostic pop
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#endif
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#endif
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}
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// The type for functions issuing lifetime-related operations: move and dispose
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// A pointer to such a function is contained in each `AnyInvocable` instance.
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// NOTE: When specifying `FunctionToCall::`dispose, the same state must be
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// passed as both "from" and "to".
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using ManagerType = void(FunctionToCall /*operation*/,
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TypeErasedState* /*from*/, TypeErasedState* /*to*/)
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ABSL_INTERNAL_NOEXCEPT_SPEC(true);
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// The type for functions issuing the actual invocation of the object
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// A pointer to such a function is contained in each AnyInvocable instance.
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template <bool SigIsNoexcept, class ReturnType, class... P>
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using InvokerType = ReturnType(TypeErasedState*, ForwardedParameterType<P>...)
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ABSL_INTERNAL_NOEXCEPT_SPEC(SigIsNoexcept);
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// The manager that is used when AnyInvocable is empty
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inline void EmptyManager(FunctionToCall /*operation*/,
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TypeErasedState* /*from*/,
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TypeErasedState* /*to*/) noexcept {}
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// The manager that is used when a target function is in local storage and is
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// a trivially copyable type.
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inline void LocalManagerTrivial(FunctionToCall /*operation*/,
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TypeErasedState* const from,
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TypeErasedState* const to) noexcept {
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// This single statement without branching handles both possible operations.
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//
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// For FunctionToCall::dispose, "from" and "to" point to the same state, and
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// so this assignment logically would do nothing.
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//
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// Note: Correctness here relies on http://wg21.link/p0593, which has only
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// become standard in C++20, though implementations do not break it in
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// practice for earlier versions of C++.
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//
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// The correct way to do this without that paper is to first placement-new a
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// default-constructed T in "to->storage" prior to the memmove, but doing so
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// requires a different function to be created for each T that is stored
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// locally, which can cause unnecessary bloat and be less cache friendly.
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*to = *from;
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// Note: Because the type is trivially copyable, the destructor does not need
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// to be called ("trivially copyable" requires a trivial destructor).
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}
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// The manager that is used when a target function is in local storage and is
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// not a trivially copyable type.
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template <class T>
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void LocalManagerNontrivial(FunctionToCall operation,
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TypeErasedState* const from,
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TypeErasedState* const to) noexcept {
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static_assert(IsStoredLocally<T>::value,
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"Local storage must only be used for supported types.");
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static_assert(!std::is_trivially_copyable<T>::value,
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"Locally stored types must be trivially copyable.");
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T& from_object = (ObjectInLocalStorage<T>)(from);
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switch (operation) {
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case FunctionToCall::relocate_from_to:
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// NOTE: Requires that the left-hand operand is already empty.
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::new (static_cast<void*>(&to->storage)) T(std::move(from_object));
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ABSL_FALLTHROUGH_INTENDED;
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case FunctionToCall::dispose:
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from_object.~T(); // Must not throw. // NOLINT
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return;
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}
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ABSL_INTERNAL_UNREACHABLE;
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}
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// The invoker that is used when a target function is in local storage
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// Note: QualTRef here is the target function type along with cv and reference
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// qualifiers that must be used when calling the function.
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template <bool SigIsNoexcept, class ReturnType, class QualTRef, class... P>
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ReturnType LocalInvoker(
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TypeErasedState* const state,
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ForwardedParameterType<P>... args) noexcept(SigIsNoexcept) {
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using RawT = RemoveCVRef<QualTRef>;
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static_assert(
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IsStoredLocally<RawT>::value,
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"Target object must be in local storage in order to be invoked from it.");
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auto& f = (ObjectInLocalStorage<RawT>)(state);
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return (InvokeR<ReturnType>)(static_cast<QualTRef>(f),
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static_cast<ForwardedParameterType<P>>(args)...);
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}
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// The manager that is used when a target function is in remote storage and it
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// has a trivial destructor
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inline void RemoteManagerTrivial(FunctionToCall operation,
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TypeErasedState* const from,
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TypeErasedState* const to) noexcept {
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switch (operation) {
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case FunctionToCall::relocate_from_to:
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// NOTE: Requires that the left-hand operand is already empty.
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to->remote = from->remote;
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return;
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case FunctionToCall::dispose:
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#if defined(__cpp_sized_deallocation)
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::operator delete(from->remote.target, from->remote.size);
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#else // __cpp_sized_deallocation
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::operator delete(from->remote.target);
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#endif // __cpp_sized_deallocation
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return;
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}
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ABSL_INTERNAL_UNREACHABLE;
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}
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// The manager that is used when a target function is in remote storage and the
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// destructor of the type is not trivial
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template <class T>
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void RemoteManagerNontrivial(FunctionToCall operation,
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TypeErasedState* const from,
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TypeErasedState* const to) noexcept {
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static_assert(!IsStoredLocally<T>::value,
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"Remote storage must only be used for types that do not "
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"qualify for local storage.");
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switch (operation) {
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case FunctionToCall::relocate_from_to:
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// NOTE: Requires that the left-hand operand is already empty.
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to->remote.target = from->remote.target;
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return;
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case FunctionToCall::dispose:
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::delete static_cast<T*>(from->remote.target); // Must not throw.
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return;
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}
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ABSL_INTERNAL_UNREACHABLE;
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}
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// The invoker that is used when a target function is in remote storage
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template <bool SigIsNoexcept, class ReturnType, class QualTRef, class... P>
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ReturnType RemoteInvoker(
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TypeErasedState* const state,
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ForwardedParameterType<P>... args) noexcept(SigIsNoexcept) {
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using RawT = RemoveCVRef<QualTRef>;
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static_assert(!IsStoredLocally<RawT>::value,
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"Target object must be in remote storage in order to be "
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"invoked from it.");
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auto& f = *static_cast<RawT*>(state->remote.target);
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return (InvokeR<ReturnType>)(static_cast<QualTRef>(f),
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static_cast<ForwardedParameterType<P>>(args)...);
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}
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////////////////////////////////////////////////////////////////////////////////
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//
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// A metafunction that checks if a type T is an instantiation of
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// absl::in_place_type_t (needed for constructor constraints of AnyInvocable).
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template <class T>
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struct IsInPlaceType : std::false_type {};
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template <class T>
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struct IsInPlaceType<absl::in_place_type_t<T>> : std::true_type {};
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//
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////////////////////////////////////////////////////////////////////////////////
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// A constructor name-tag used with CoreImpl (below) to request the
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// conversion-constructor. QualDecayedTRef is the decayed-type of the object to
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// wrap, along with the cv and reference qualifiers that must be applied when
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// performing an invocation of the wrapped object.
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template <class QualDecayedTRef>
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struct TypedConversionConstruct {};
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// A helper base class for all core operations of AnyInvocable. Most notably,
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// this class creates the function call operator and constraint-checkers so that
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// the top-level class does not have to be a series of partial specializations.
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//
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// Note: This definition exists (as opposed to being a declaration) so that if
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// the user of the top-level template accidentally passes a template argument
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// that is not a function type, they will get a static_assert in AnyInvocable's
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// class body rather than an error stating that Impl is not defined.
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template <class Sig>
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class Impl {}; // Note: This is partially-specialized later.
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// A std::unique_ptr deleter that deletes memory allocated via ::operator new.
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#if defined(__cpp_sized_deallocation)
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class TrivialDeleter {
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public:
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explicit TrivialDeleter(std::size_t size) : size_(size) {}
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void operator()(void* target) const {
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::operator delete(target, size_);
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}
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private:
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std::size_t size_;
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};
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#else // __cpp_sized_deallocation
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class TrivialDeleter {
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public:
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explicit TrivialDeleter(std::size_t) {}
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void operator()(void* target) const { ::operator delete(target); }
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};
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#endif // __cpp_sized_deallocation
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template <bool SigIsNoexcept, class ReturnType, class... P>
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class CoreImpl;
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constexpr bool IsCompatibleConversion(void*, void*) { return false; }
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template <bool NoExceptSrc, bool NoExceptDest, class... T>
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constexpr bool IsCompatibleConversion(CoreImpl<NoExceptSrc, T...>*,
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CoreImpl<NoExceptDest, T...>*) {
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return !NoExceptDest || NoExceptSrc;
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}
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// A helper base class for all core operations of AnyInvocable that do not
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// depend on the cv/ref qualifiers of the function type.
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template <bool SigIsNoexcept, class ReturnType, class... P>
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class CoreImpl {
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public:
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using result_type = ReturnType;
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CoreImpl() noexcept : manager_(EmptyManager), invoker_(nullptr) {}
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enum class TargetType : int {
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kPointer = 0,
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kCompatibleAnyInvocable = 1,
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kIncompatibleAnyInvocable = 2,
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kOther = 3,
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};
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// Note: QualDecayedTRef here includes the cv-ref qualifiers associated with
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// the invocation of the Invocable. The unqualified type is the target object
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// type to be stored.
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template <class QualDecayedTRef, class F>
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explicit CoreImpl(TypedConversionConstruct<QualDecayedTRef>, F&& f) {
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using DecayedT = RemoveCVRef<QualDecayedTRef>;
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constexpr TargetType kTargetType =
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(std::is_pointer<DecayedT>::value ||
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std::is_member_pointer<DecayedT>::value)
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? TargetType::kPointer
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: IsCompatibleAnyInvocable<DecayedT>::value
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? TargetType::kCompatibleAnyInvocable
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: IsAnyInvocable<DecayedT>::value
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? TargetType::kIncompatibleAnyInvocable
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: TargetType::kOther;
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// NOTE: We only use integers instead of enums as template parameters in
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// order to work around a bug on C++14 under MSVC 2017.
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// See b/236131881.
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Initialize<static_cast<int>(kTargetType), QualDecayedTRef>(
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std::forward<F>(f));
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}
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// Note: QualTRef here includes the cv-ref qualifiers associated with the
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// invocation of the Invocable. The unqualified type is the target object
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// type to be stored.
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template <class QualTRef, class... Args>
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explicit CoreImpl(absl::in_place_type_t<QualTRef>, Args&&... args) {
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InitializeStorage<QualTRef>(std::forward<Args>(args)...);
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}
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CoreImpl(CoreImpl&& other) noexcept {
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other.manager_(FunctionToCall::relocate_from_to, &other.state_, &state_);
|
|
manager_ = other.manager_;
|
|
invoker_ = other.invoker_;
|
|
other.manager_ = EmptyManager;
|
|
other.invoker_ = nullptr;
|
|
}
|
|
|
|
CoreImpl& operator=(CoreImpl&& other) noexcept {
|
|
// Put the left-hand operand in an empty state.
|
|
//
|
|
// Note: A full reset that leaves us with an object that has its invariants
|
|
// intact is necessary in order to handle self-move. This is required by
|
|
// types that are used with certain operations of the standard library, such
|
|
// as the default definition of std::swap when both operands target the same
|
|
// object.
|
|
Clear();
|
|
|
|
// Perform the actual move/destory operation on the target function.
|
|
other.manager_(FunctionToCall::relocate_from_to, &other.state_, &state_);
|
|
manager_ = other.manager_;
|
|
invoker_ = other.invoker_;
|
|
other.manager_ = EmptyManager;
|
|
other.invoker_ = nullptr;
|
|
|
|
return *this;
|
|
}
|
|
|
|
~CoreImpl() { manager_(FunctionToCall::dispose, &state_, &state_); }
|
|
|
|
// Check whether or not the AnyInvocable is in the empty state.
|
|
bool HasValue() const { return invoker_ != nullptr; }
|
|
|
|
// Effects: Puts the object into its empty state.
|
|
void Clear() {
|
|
manager_(FunctionToCall::dispose, &state_, &state_);
|
|
manager_ = EmptyManager;
|
|
invoker_ = nullptr;
|
|
}
|
|
|
|
template <int target_type, class QualDecayedTRef, class F,
|
|
absl::enable_if_t<target_type == 0, int> = 0>
|
|
void Initialize(F&& f) {
|
|
// This condition handles types that decay into pointers, which includes
|
|
// function references. Since function references cannot be null, GCC warns
|
|
// against comparing their decayed form with nullptr.
|
|
// Since this is template-heavy code, we prefer to disable these warnings
|
|
// locally instead of adding yet another overload of this function.
|
|
#if !defined(__clang__) && defined(__GNUC__)
|
|
#pragma GCC diagnostic ignored "-Wpragmas"
|
|
#pragma GCC diagnostic ignored "-Waddress"
|
|
#pragma GCC diagnostic ignored "-Wnonnull-compare"
|
|
#pragma GCC diagnostic push
|
|
#endif
|
|
if (static_cast<RemoveCVRef<QualDecayedTRef>>(f) == nullptr) {
|
|
#if !defined(__clang__) && defined(__GNUC__)
|
|
#pragma GCC diagnostic pop
|
|
#endif
|
|
manager_ = EmptyManager;
|
|
invoker_ = nullptr;
|
|
return;
|
|
}
|
|
InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
|
|
}
|
|
|
|
template <int target_type, class QualDecayedTRef, class F,
|
|
absl::enable_if_t<target_type == 1, int> = 0>
|
|
void Initialize(F&& f) {
|
|
// In this case we can "steal the guts" of the other AnyInvocable.
|
|
f.manager_(FunctionToCall::relocate_from_to, &f.state_, &state_);
|
|
manager_ = f.manager_;
|
|
invoker_ = f.invoker_;
|
|
|
|
f.manager_ = EmptyManager;
|
|
f.invoker_ = nullptr;
|
|
}
|
|
|
|
template <int target_type, class QualDecayedTRef, class F,
|
|
absl::enable_if_t<target_type == 2, int> = 0>
|
|
void Initialize(F&& f) {
|
|
if (f.HasValue()) {
|
|
InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
|
|
} else {
|
|
manager_ = EmptyManager;
|
|
invoker_ = nullptr;
|
|
}
|
|
}
|
|
|
|
template <int target_type, class QualDecayedTRef, class F,
|
|
typename = absl::enable_if_t<target_type == 3>>
|
|
void Initialize(F&& f) {
|
|
InitializeStorage<QualDecayedTRef>(std::forward<F>(f));
|
|
}
|
|
|
|
// Use local (inline) storage for applicable target object types.
|
|
template <class QualTRef, class... Args,
|
|
typename = absl::enable_if_t<
|
|
IsStoredLocally<RemoveCVRef<QualTRef>>::value>>
|
|
void InitializeStorage(Args&&... args) {
|
|
using RawT = RemoveCVRef<QualTRef>;
|
|
::new (static_cast<void*>(&state_.storage))
|
|
RawT(std::forward<Args>(args)...);
|
|
|
|
invoker_ = LocalInvoker<SigIsNoexcept, ReturnType, QualTRef, P...>;
|
|
// We can simplify our manager if we know the type is trivially copyable.
|
|
InitializeLocalManager<RawT>();
|
|
}
|
|
|
|
// Use remote storage for target objects that cannot be stored locally.
|
|
template <class QualTRef, class... Args,
|
|
absl::enable_if_t<!IsStoredLocally<RemoveCVRef<QualTRef>>::value,
|
|
int> = 0>
|
|
void InitializeStorage(Args&&... args) {
|
|
InitializeRemoteManager<RemoveCVRef<QualTRef>>(std::forward<Args>(args)...);
|
|
// This is set after everything else in case an exception is thrown in an
|
|
// earlier step of the initialization.
|
|
invoker_ = RemoteInvoker<SigIsNoexcept, ReturnType, QualTRef, P...>;
|
|
}
|
|
|
|
template <class T,
|
|
typename = absl::enable_if_t<std::is_trivially_copyable<T>::value>>
|
|
void InitializeLocalManager() {
|
|
manager_ = LocalManagerTrivial;
|
|
}
|
|
|
|
template <class T,
|
|
absl::enable_if_t<!std::is_trivially_copyable<T>::value, int> = 0>
|
|
void InitializeLocalManager() {
|
|
manager_ = LocalManagerNontrivial<T>;
|
|
}
|
|
|
|
template <class T>
|
|
using HasTrivialRemoteStorage =
|
|
std::integral_constant<bool, std::is_trivially_destructible<T>::value &&
|
|
alignof(T) <=
|
|
ABSL_INTERNAL_DEFAULT_NEW_ALIGNMENT>;
|
|
|
|
template <class T, class... Args,
|
|
typename = absl::enable_if_t<HasTrivialRemoteStorage<T>::value>>
|
|
void InitializeRemoteManager(Args&&... args) {
|
|
// unique_ptr is used for exception-safety in case construction throws.
|
|
std::unique_ptr<void, TrivialDeleter> uninitialized_target(
|
|
::operator new(sizeof(T)), TrivialDeleter(sizeof(T)));
|
|
::new (uninitialized_target.get()) T(std::forward<Args>(args)...);
|
|
state_.remote.target = uninitialized_target.release();
|
|
state_.remote.size = sizeof(T);
|
|
manager_ = RemoteManagerTrivial;
|
|
}
|
|
|
|
template <class T, class... Args,
|
|
absl::enable_if_t<!HasTrivialRemoteStorage<T>::value, int> = 0>
|
|
void InitializeRemoteManager(Args&&... args) {
|
|
state_.remote.target = ::new T(std::forward<Args>(args)...);
|
|
manager_ = RemoteManagerNontrivial<T>;
|
|
}
|
|
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// Type trait to determine if the template argument is an AnyInvocable whose
|
|
// function type is compatible enough with ours such that we can
|
|
// "move the guts" out of it when moving, rather than having to place a new
|
|
// object into remote storage.
|
|
|
|
template <typename Other>
|
|
struct IsCompatibleAnyInvocable {
|
|
static constexpr bool value = false;
|
|
};
|
|
|
|
template <typename Sig>
|
|
struct IsCompatibleAnyInvocable<AnyInvocable<Sig>> {
|
|
static constexpr bool value =
|
|
(IsCompatibleConversion)(static_cast<
|
|
typename AnyInvocable<Sig>::CoreImpl*>(
|
|
nullptr),
|
|
static_cast<CoreImpl*>(nullptr));
|
|
};
|
|
|
|
//
|
|
//////////////////////////////////////////////////////////////////////////////
|
|
|
|
TypeErasedState state_;
|
|
ManagerType* manager_;
|
|
InvokerType<SigIsNoexcept, ReturnType, P...>* invoker_;
|
|
};
|
|
|
|
// A constructor name-tag used with Impl to request the
|
|
// conversion-constructor
|
|
struct ConversionConstruct {};
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// A metafunction that is normally an identity metafunction except that when
|
|
// given a std::reference_wrapper<T>, it yields T&. This is necessary because
|
|
// currently std::reference_wrapper's operator() is not conditionally noexcept,
|
|
// so when checking if such an Invocable is nothrow-invocable, we must pull out
|
|
// the underlying type.
|
|
template <class T>
|
|
struct UnwrapStdReferenceWrapperImpl {
|
|
using type = T;
|
|
};
|
|
|
|
template <class T>
|
|
struct UnwrapStdReferenceWrapperImpl<std::reference_wrapper<T>> {
|
|
using type = T&;
|
|
};
|
|
|
|
template <class T>
|
|
using UnwrapStdReferenceWrapper =
|
|
typename UnwrapStdReferenceWrapperImpl<T>::type;
|
|
//
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
// An alias that always yields std::true_type (used with constraints) where
|
|
// substitution failures happen when forming the template arguments.
|
|
template <class... T>
|
|
using True =
|
|
std::integral_constant<bool, sizeof(absl::void_t<T...>*) != 0>;
|
|
|
|
/*SFINAE constraints for the conversion-constructor.*/
|
|
template <class Sig, class F,
|
|
class = absl::enable_if_t<
|
|
!std::is_same<RemoveCVRef<F>, AnyInvocable<Sig>>::value>>
|
|
using CanConvert =
|
|
True<absl::enable_if_t<!IsInPlaceType<RemoveCVRef<F>>::value>,
|
|
absl::enable_if_t<Impl<Sig>::template CallIsValid<F>::value>,
|
|
absl::enable_if_t<
|
|
Impl<Sig>::template CallIsNoexceptIfSigIsNoexcept<F>::value>,
|
|
absl::enable_if_t<std::is_constructible<absl::decay_t<F>, F>::value>>;
|
|
|
|
/*SFINAE constraints for the std::in_place constructors.*/
|
|
template <class Sig, class F, class... Args>
|
|
using CanEmplace = True<
|
|
absl::enable_if_t<Impl<Sig>::template CallIsValid<F>::value>,
|
|
absl::enable_if_t<
|
|
Impl<Sig>::template CallIsNoexceptIfSigIsNoexcept<F>::value>,
|
|
absl::enable_if_t<std::is_constructible<absl::decay_t<F>, Args...>::value>>;
|
|
|
|
/*SFINAE constraints for the conversion-assign operator.*/
|
|
template <class Sig, class F,
|
|
class = absl::enable_if_t<
|
|
!std::is_same<RemoveCVRef<F>, AnyInvocable<Sig>>::value>>
|
|
using CanAssign =
|
|
True<absl::enable_if_t<Impl<Sig>::template CallIsValid<F>::value>,
|
|
absl::enable_if_t<
|
|
Impl<Sig>::template CallIsNoexceptIfSigIsNoexcept<F>::value>,
|
|
absl::enable_if_t<std::is_constructible<absl::decay_t<F>, F>::value>>;
|
|
|
|
/*SFINAE constraints for the reference-wrapper conversion-assign operator.*/
|
|
template <class Sig, class F>
|
|
using CanAssignReferenceWrapper =
|
|
True<absl::enable_if_t<
|
|
Impl<Sig>::template CallIsValid<std::reference_wrapper<F>>::value>,
|
|
absl::enable_if_t<Impl<Sig>::template CallIsNoexceptIfSigIsNoexcept<
|
|
std::reference_wrapper<F>>::value>>;
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// The constraint for checking whether or not a call meets the noexcept
|
|
// callability requirements. This is a preprocessor macro because specifying it
|
|
// this way as opposed to a disjunction/branch can improve the user-side error
|
|
// messages and avoids an instantiation of std::is_nothrow_invocable_r in the
|
|
// cases where the user did not specify a noexcept function type.
|
|
//
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT(inv_quals, noex) \
|
|
ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT_##noex(inv_quals)
|
|
|
|
// The disjunction below is because we can't rely on std::is_nothrow_invocable_r
|
|
// to give the right result when ReturnType is non-moveable in toolchains that
|
|
// don't treat non-moveable result types correctly. For example this was the
|
|
// case in libc++ before commit c3a24882 (2022-05).
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT_true(inv_quals) \
|
|
absl::enable_if_t<absl::disjunction< \
|
|
std::is_nothrow_invocable_r< \
|
|
ReturnType, UnwrapStdReferenceWrapper<absl::decay_t<F>> inv_quals, \
|
|
P...>, \
|
|
std::conjunction< \
|
|
std::is_nothrow_invocable< \
|
|
UnwrapStdReferenceWrapper<absl::decay_t<F>> inv_quals, P...>, \
|
|
std::is_same< \
|
|
ReturnType, \
|
|
absl::base_internal::invoke_result_t< \
|
|
UnwrapStdReferenceWrapper<absl::decay_t<F>> inv_quals, \
|
|
P...>>>>::value>
|
|
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT_false(inv_quals)
|
|
//
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
// A macro to generate partial specializations of Impl with the different
|
|
// combinations of supported cv/reference qualifiers and noexcept specifier.
|
|
//
|
|
// Here, `cv` are the cv-qualifiers if any, `ref` is the ref-qualifier if any,
|
|
// inv_quals is the reference type to be used when invoking the target, and
|
|
// noex is "true" if the function type is noexcept, or false if it is not.
|
|
//
|
|
// The CallIsValid condition is more complicated than simply using
|
|
// absl::base_internal::is_invocable_r because we can't rely on it to give the
|
|
// right result when ReturnType is non-moveable in toolchains that don't treat
|
|
// non-moveable result types correctly. For example this was the case in libc++
|
|
// before commit c3a24882 (2022-05).
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_IMPL_(cv, ref, inv_quals, noex) \
|
|
template <class ReturnType, class... P> \
|
|
class Impl<ReturnType(P...) cv ref ABSL_INTERNAL_NOEXCEPT_SPEC(noex)> \
|
|
: public CoreImpl<noex, ReturnType, P...> { \
|
|
public: \
|
|
/*The base class, which contains the datamembers and core operations*/ \
|
|
using Core = CoreImpl<noex, ReturnType, P...>; \
|
|
\
|
|
/*SFINAE constraint to check if F is invocable with the proper signature*/ \
|
|
template <class F> \
|
|
using CallIsValid = True<absl::enable_if_t<absl::disjunction< \
|
|
absl::base_internal::is_invocable_r<ReturnType, \
|
|
absl::decay_t<F> inv_quals, P...>, \
|
|
std::is_same<ReturnType, \
|
|
absl::base_internal::invoke_result_t< \
|
|
absl::decay_t<F> inv_quals, P...>>>::value>>; \
|
|
\
|
|
/*SFINAE constraint to check if F is nothrow-invocable when necessary*/ \
|
|
template <class F> \
|
|
using CallIsNoexceptIfSigIsNoexcept = \
|
|
True<ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT(inv_quals, \
|
|
noex)>; \
|
|
\
|
|
/*Put the AnyInvocable into an empty state.*/ \
|
|
Impl() = default; \
|
|
\
|
|
/*The implementation of a conversion-constructor from "f*/ \
|
|
/*This forwards to Core, attaching inv_quals so that the base class*/ \
|
|
/*knows how to properly type-erase the invocation.*/ \
|
|
template <class F> \
|
|
explicit Impl(ConversionConstruct, F&& f) \
|
|
: Core(TypedConversionConstruct< \
|
|
typename std::decay<F>::type inv_quals>(), \
|
|
std::forward<F>(f)) {} \
|
|
\
|
|
/*Forward along the in-place construction parameters.*/ \
|
|
template <class T, class... Args> \
|
|
explicit Impl(absl::in_place_type_t<T>, Args&&... args) \
|
|
: Core(absl::in_place_type<absl::decay_t<T> inv_quals>, \
|
|
std::forward<Args>(args)...) {} \
|
|
\
|
|
/*The actual invocation operation with the proper signature*/ \
|
|
ReturnType operator()(P... args) cv ref noexcept(noex) { \
|
|
assert(this->invoker_ != nullptr); \
|
|
return this->invoker_(const_cast<TypeErasedState*>(&this->state_), \
|
|
static_cast<ForwardedParameterType<P>>(args)...); \
|
|
} \
|
|
}
|
|
|
|
// Define the `noexcept(true)` specialization only for C++17 and beyond, when
|
|
// `noexcept` is part of the type system.
|
|
#if ABSL_INTERNAL_CPLUSPLUS_LANG >= 201703L
|
|
// A convenience macro that defines specializations for the noexcept(true) and
|
|
// noexcept(false) forms, given the other properties.
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_IMPL(cv, ref, inv_quals) \
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL_(cv, ref, inv_quals, false); \
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL_(cv, ref, inv_quals, true)
|
|
#else
|
|
#define ABSL_INTERNAL_ANY_INVOCABLE_IMPL(cv, ref, inv_quals) \
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL_(cv, ref, inv_quals, false)
|
|
#endif
|
|
|
|
// Non-ref-qualified partial specializations
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(, , &);
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(const, , const&);
|
|
|
|
// Lvalue-ref-qualified partial specializations
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(, &, &);
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(const, &, const&);
|
|
|
|
// Rvalue-ref-qualified partial specializations
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(, &&, &&);
|
|
ABSL_INTERNAL_ANY_INVOCABLE_IMPL(const, &&, const&&);
|
|
|
|
// Undef the detail-only macros.
|
|
#undef ABSL_INTERNAL_ANY_INVOCABLE_IMPL
|
|
#undef ABSL_INTERNAL_ANY_INVOCABLE_IMPL_
|
|
#undef ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT_false
|
|
#undef ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT_true
|
|
#undef ABSL_INTERNAL_ANY_INVOCABLE_NOEXCEPT_CONSTRAINT
|
|
#undef ABSL_INTERNAL_NOEXCEPT_SPEC
|
|
|
|
} // namespace internal_any_invocable
|
|
ABSL_NAMESPACE_END
|
|
} // namespace absl
|
|
|
|
#endif // ABSL_FUNCTIONAL_INTERNAL_ANY_INVOCABLE_H_
|