diff options
Diffstat (limited to 'absl/functional')
| -rw-r--r-- | absl/functional/BUILD.bazel | 51 | ||||
| -rw-r--r-- | absl/functional/function_ref.h | 137 | ||||
| -rw-r--r-- | absl/functional/function_ref_benchmark.cc | 140 | ||||
| -rw-r--r-- | absl/functional/function_ref_test.cc | 255 | ||||
| -rw-r--r-- | absl/functional/internal/function_ref.h | 104 |
5 files changed, 687 insertions, 0 deletions
diff --git a/absl/functional/BUILD.bazel b/absl/functional/BUILD.bazel new file mode 100644 index 000000000000..e861b8a56010 --- /dev/null +++ b/absl/functional/BUILD.bazel @@ -0,0 +1,51 @@ +load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test") +load( + "//absl:copts/configure_copts.bzl", + "ABSL_DEFAULT_COPTS", + "ABSL_DEFAULT_LINKOPTS", + "ABSL_TEST_COPTS", +) + +package(default_visibility = ["//visibility:public"]) + +licenses(["notice"]) # Apache 2.0 + +cc_library( + name = "function_ref", + srcs = ["internal/function_ref.h"], + hdrs = ["function_ref.h"], + copts = ABSL_DEFAULT_COPTS, + linkopts = ABSL_DEFAULT_LINKOPTS, + deps = [ + "//absl/base:base_internal", + "//absl/meta:type_traits", + ], +) + +cc_test( + name = "function_ref_test", + size = "small", + srcs = ["function_ref_test.cc"], + copts = ABSL_TEST_COPTS, + deps = [ + ":function_ref", + "//absl/container:test_instance_tracker", + "//absl/memory", + "@com_google_googletest//:gtest_main", + ], +) + +cc_test( + name = "function_ref_benchmark", + srcs = [ + "function_ref_benchmark.cc", + ], + copts = ABSL_TEST_COPTS, + tags = ["benchmark"], + visibility = ["//visibility:private"], + deps = [ + ":function_ref", + "//absl/base:core_headers", + "@com_github_google_benchmark//:benchmark_main", + ], +) diff --git a/absl/functional/function_ref.h b/absl/functional/function_ref.h new file mode 100644 index 000000000000..42d9f16fca6b --- /dev/null +++ b/absl/functional/function_ref.h @@ -0,0 +1,137 @@ +// Copyright 2019 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// ----------------------------------------------------------------------------- +// File: function_ref.h +// ----------------------------------------------------------------------------- +// +// This header file defines the `absl::FunctionRef` type for holding a +// non-owning reference to an object of any invocable type. This function +// reference is typically most useful as a type-erased argument type for +// accepting function types that neither take ownership nor copy the type; using +// the reference type in this case avoids a copy and an allocation. Best +// practices of other non-owning reference-like objects (such as +// `absl::string_view`) apply here. +// +// An `absl::FunctionRef` is similar in usage to a `std::function` but has the +// following differences: +// +// * It doesn't own the underlying object. +// * It doesn't have a null or empty state. +// * It never performs deep copies or allocations. +// * It's much faster and cheaper to construct. +// * It's trivially copyable and destructable. +// +// Generally, `absl::FunctionRef` should not be used as a return value, data +// member, or to initialize a `std::function`. Such usages will often lead to +// problematic lifetime issues. Once you convert something to an +// `absl::FunctionRef` you cannot make a deep copy later. +// +// This class is suitable for use wherever a "const std::function<>&" +// would be used without making a copy. ForEach functions and other versions of +// the visitor pattern are a good example of when this class should be used. +// +// This class is trivial to copy and should be passed by value. +#ifndef ABSL_FUNCTIONAL_FUNCTION_REF_H_ +#define ABSL_FUNCTIONAL_FUNCTION_REF_H_ + +#include <cassert> +#include <functional> +#include <type_traits> + +#include "absl/functional/internal/function_ref.h" +#include "absl/meta/type_traits.h" + +namespace absl { + +// FunctionRef +// +// Dummy class declaration to allow the partial specialization based on function +// types below. +template <typename T> +class FunctionRef; + +// FunctionRef +// +// An `absl::FunctionRef` is a lightweight wrapper to any invokable object with +// a compatible signature. Generally, an `absl::FunctionRef` should only be used +// as an argument type and should be preferred as an argument over a const +// reference to a `std::function`. +// +// Example: +// +// // The following function takes a function callback by const reference +// bool Visitor(const std::function<void(my_proto&, +// absl::string_view)>& callback); +// +// // Assuming that the function is not stored or otherwise copied, it can be +// // replaced by an `absl::FunctionRef`: +// bool Visitor(absl::FunctionRef<void(my_proto&, absl::string_view)> +// callback); +// +// Note: the assignment operator within an `absl::FunctionRef` is intentionally +// deleted to prevent misuse; because the `absl::FunctionRef` does not own the +// underlying type, assignment likely indicates misuse. +template <typename R, typename... Args> +class FunctionRef<R(Args...)> { + private: + // Used to disable constructors for objects that are not compatible with the + // signature of this FunctionRef. + template <typename F, + typename FR = absl::base_internal::InvokeT<F, Args&&...>> + using EnableIfCompatible = + typename std::enable_if<std::is_void<R>::value || + std::is_convertible<FR, R>::value>::type; + + public: + // Constructs a FunctionRef from any invokable type. + template <typename F, typename = EnableIfCompatible<const F&>> + FunctionRef(const F& f) // NOLINT(runtime/explicit) + : invoker_(&absl::functional_internal::InvokeObject<F, R, Args...>) { + absl::functional_internal::AssertNonNull(f); + ptr_.obj = &f; + } + + // Overload for function pointers. This eliminates a level of indirection that + // would happen if the above overload was used (it lets us store the pointer + // instead of a pointer to a pointer). + // + // This overload is also used for references to functions, since references to + // functions can decay to function pointers implicitly. + template < + typename F, typename = EnableIfCompatible<F*>, + absl::functional_internal::EnableIf<absl::is_function<F>::value> = 0> + FunctionRef(F* f) // NOLINT(runtime/explicit) + : invoker_(&absl::functional_internal::InvokeFunction<F*, R, Args...>) { + assert(f != nullptr); + ptr_.fun = reinterpret_cast<decltype(ptr_.fun)>(f); + } + + // To help prevent subtle lifetime bugs, FunctionRef is not assignable. + // Typically, it should only be used as an argument type. + FunctionRef& operator=(const FunctionRef& rhs) = delete; + + // Call the underlying object. + R operator()(Args... args) const { + return invoker_(ptr_, std::forward<Args>(args)...); + } + + private: + absl::functional_internal::VoidPtr ptr_; + absl::functional_internal::Invoker<R, Args...> invoker_; +}; + +} // namespace absl + +#endif // ABSL_FUNCTIONAL_FUNCTION_REF_H_ diff --git a/absl/functional/function_ref_benchmark.cc b/absl/functional/function_ref_benchmark.cc new file mode 100644 index 000000000000..f6dfcabf1108 --- /dev/null +++ b/absl/functional/function_ref_benchmark.cc @@ -0,0 +1,140 @@ +// Copyright 2019 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/functional/function_ref.h" + +#include <memory> + +#include "benchmark/benchmark.h" +#include "absl/base/attributes.h" + +namespace absl { +namespace { + +int dummy = 0; + +void FreeFunction() { benchmark::DoNotOptimize(dummy); } + +struct TrivialFunctor { + void operator()() const { benchmark::DoNotOptimize(dummy); } +}; + +struct LargeFunctor { + void operator()() const { benchmark::DoNotOptimize(this); } + std::string a, b, c; +}; + +template <typename Function, typename... Args> +void ABSL_ATTRIBUTE_NOINLINE CallFunction(Function f, Args&&... args) { + f(std::forward<Args>(args)...); +} + +template <typename Function, typename Callable, typename... Args> +void ConstructAndCallFunctionBenchmark(benchmark::State& state, + const Callable& c, Args&&... args) { + for (auto _ : state) { + CallFunction<Function>(c, std::forward<Args>(args)...); + } +} + +void BM_TrivialStdFunction(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<std::function<void()>>(state, + TrivialFunctor{}); +} +BENCHMARK(BM_TrivialStdFunction); + +void BM_TrivialFunctionRef(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state, + TrivialFunctor{}); +} +BENCHMARK(BM_TrivialFunctionRef); + +void BM_LargeStdFunction(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<std::function<void()>>(state, + LargeFunctor{}); +} +BENCHMARK(BM_LargeStdFunction); + +void BM_LargeFunctionRef(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state, LargeFunctor{}); +} +BENCHMARK(BM_LargeFunctionRef); + +void BM_FunPtrStdFunction(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<std::function<void()>>(state, FreeFunction); +} +BENCHMARK(BM_FunPtrStdFunction); + +void BM_FunPtrFunctionRef(benchmark::State& state) { + ConstructAndCallFunctionBenchmark<FunctionRef<void()>>(state, FreeFunction); +} +BENCHMARK(BM_FunPtrFunctionRef); + +// Doesn't include construction or copy overhead in the loop. +template <typename Function, typename Callable, typename... Args> +void CallFunctionBenchmark(benchmark::State& state, const Callable& c, + Args... args) { + Function f = c; + for (auto _ : state) { + benchmark::DoNotOptimize(&f); + f(args...); + } +} + +struct FunctorWithTrivialArgs { + void operator()(int a, int b, int c) const { + benchmark::DoNotOptimize(a); + benchmark::DoNotOptimize(b); + benchmark::DoNotOptimize(c); + } +}; + +void BM_TrivialArgsStdFunction(benchmark::State& state) { + CallFunctionBenchmark<std::function<void(int, int, int)>>( + state, FunctorWithTrivialArgs{}, 1, 2, 3); +} +BENCHMARK(BM_TrivialArgsStdFunction); + +void BM_TrivialArgsFunctionRef(benchmark::State& state) { + CallFunctionBenchmark<FunctionRef<void(int, int, int)>>( + state, FunctorWithTrivialArgs{}, 1, 2, 3); +} +BENCHMARK(BM_TrivialArgsFunctionRef); + +struct FunctorWithNonTrivialArgs { + void operator()(std::string a, std::string b, std::string c) const { + benchmark::DoNotOptimize(&a); + benchmark::DoNotOptimize(&b); + benchmark::DoNotOptimize(&c); + } +}; + +void BM_NonTrivialArgsStdFunction(benchmark::State& state) { + std::string a, b, c; + CallFunctionBenchmark< + std::function<void(std::string, std::string, std::string)>>( + state, FunctorWithNonTrivialArgs{}, a, b, c); +} +BENCHMARK(BM_NonTrivialArgsStdFunction); + +void BM_NonTrivialArgsFunctionRef(benchmark::State& state) { + std::string a, b, c; + CallFunctionBenchmark< + FunctionRef<void(std::string, std::string, std::string)>>( + state, FunctorWithNonTrivialArgs{}, a, b, c); +} +BENCHMARK(BM_NonTrivialArgsFunctionRef); + +} // namespace +} // namespace absl diff --git a/absl/functional/function_ref_test.cc b/absl/functional/function_ref_test.cc new file mode 100644 index 000000000000..90829db09a4d --- /dev/null +++ b/absl/functional/function_ref_test.cc @@ -0,0 +1,255 @@ +// Copyright 2019 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/functional/function_ref.h" + +#include <memory> + +#include "gmock/gmock.h" +#include "gtest/gtest.h" +#include "absl/container/internal/test_instance_tracker.h" +#include "absl/memory/memory.h" + +namespace absl { +namespace { + +void RunFun(FunctionRef<void()> f) { f(); } + +TEST(FunctionRefTest, Lambda) { + bool ran = false; + RunFun([&] { ran = true; }); + EXPECT_TRUE(ran); +} + +int Function() { return 1337; } + +TEST(FunctionRefTest, Function1) { + FunctionRef<int()> ref(&Function); + EXPECT_EQ(1337, ref()); +} + +TEST(FunctionRefTest, Function2) { + FunctionRef<int()> ref(Function); + EXPECT_EQ(1337, ref()); +} + +int NoExceptFunction() noexcept { return 1337; } + +// TODO(jdennett): Add a test for noexcept member functions. +TEST(FunctionRefTest, NoExceptFunction) { + FunctionRef<int()> ref(NoExceptFunction); + EXPECT_EQ(1337, ref()); +} + +TEST(FunctionRefTest, ForwardsArgs) { + auto l = [](std::unique_ptr<int> i) { return *i; }; + FunctionRef<int(std::unique_ptr<int>)> ref(l); + EXPECT_EQ(42, ref(absl::make_unique<int>(42))); +} + +TEST(FunctionRef, ReturnMoveOnly) { + auto l = [] { return absl::make_unique<int>(29); }; + FunctionRef<std::unique_ptr<int>()> ref(l); + EXPECT_EQ(29, *ref()); +} + +TEST(FunctionRef, ManyArgs) { + auto l = [](int a, int b, int c) { return a + b + c; }; + FunctionRef<int(int, int, int)> ref(l); + EXPECT_EQ(6, ref(1, 2, 3)); +} + +TEST(FunctionRef, VoidResultFromNonVoidFunctor) { + bool ran = false; + auto l = [&]() -> int { + ran = true; + return 2; + }; + FunctionRef<void()> ref(l); + ref(); + EXPECT_TRUE(ran); +} + +TEST(FunctionRef, CastFromDerived) { + struct Base {}; + struct Derived : public Base {}; + + Derived d; + auto l1 = [&](Base* b) { EXPECT_EQ(&d, b); }; + FunctionRef<void(Derived*)> ref1(l1); + ref1(&d); + + auto l2 = [&]() -> Derived* { return &d; }; + FunctionRef<Base*()> ref2(l2); + EXPECT_EQ(&d, ref2()); +} + +TEST(FunctionRef, VoidResultFromNonVoidFuncton) { + FunctionRef<void()> ref(Function); + ref(); +} + +TEST(FunctionRef, MemberPtr) { + struct S { + int i; + }; + + S s{1100111}; + auto mem_ptr = &S::i; + FunctionRef<int(const S& s)> ref(mem_ptr); + EXPECT_EQ(1100111, ref(s)); +} + +TEST(FunctionRef, MemberFun) { + struct S { + int i; + int get_i() const { return i; } + }; + + S s{22}; + auto mem_fun_ptr = &S::get_i; + FunctionRef<int(const S& s)> ref(mem_fun_ptr); + EXPECT_EQ(22, ref(s)); +} + +TEST(FunctionRef, MemberFunRefqualified) { + struct S { + int i; + int get_i() && { return i; } + }; + auto mem_fun_ptr = &S::get_i; + S s{22}; + FunctionRef<int(S && s)> ref(mem_fun_ptr); + EXPECT_EQ(22, ref(std::move(s))); +} + +#if !defined(_WIN32) && defined(GTEST_HAS_DEATH_TEST) + +TEST(FunctionRef, MemberFunRefqualifiedNull) { + struct S { + int i; + int get_i() && { return i; } + }; + auto mem_fun_ptr = &S::get_i; + mem_fun_ptr = nullptr; + EXPECT_DEBUG_DEATH({ FunctionRef<int(S && s)> ref(mem_fun_ptr); }, ""); +} + +TEST(FunctionRef, NullMemberPtrAssertFails) { + struct S { + int i; + }; + using MemberPtr = int S::*; + MemberPtr mem_ptr = nullptr; + EXPECT_DEBUG_DEATH({ FunctionRef<int(const S& s)> ref(mem_ptr); }, ""); +} + +#endif // GTEST_HAS_DEATH_TEST + +TEST(FunctionRef, CopiesAndMovesPerPassByValue) { + absl::test_internal::InstanceTracker tracker; + absl::test_internal::CopyableMovableInstance instance(0); + auto l = [](absl::test_internal::CopyableMovableInstance) {}; + FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l); + ref(instance); + EXPECT_EQ(tracker.copies(), 1); + EXPECT_EQ(tracker.moves(), 1); +} + +TEST(FunctionRef, CopiesAndMovesPerPassByRef) { + absl::test_internal::InstanceTracker tracker; + absl::test_internal::CopyableMovableInstance instance(0); + auto l = [](const absl::test_internal::CopyableMovableInstance&) {}; + FunctionRef<void(const absl::test_internal::CopyableMovableInstance&)> ref(l); + ref(instance); + EXPECT_EQ(tracker.copies(), 0); + EXPECT_EQ(tracker.moves(), 0); +} + +TEST(FunctionRef, CopiesAndMovesPerPassByValueCallByMove) { + absl::test_internal::InstanceTracker tracker; + absl::test_internal::CopyableMovableInstance instance(0); + auto l = [](absl::test_internal::CopyableMovableInstance) {}; + FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l); + ref(std::move(instance)); + EXPECT_EQ(tracker.copies(), 0); + EXPECT_EQ(tracker.moves(), 2); +} + +TEST(FunctionRef, CopiesAndMovesPerPassByValueToRef) { + absl::test_internal::InstanceTracker tracker; + absl::test_internal::CopyableMovableInstance instance(0); + auto l = [](const absl::test_internal::CopyableMovableInstance&) {}; + FunctionRef<void(absl::test_internal::CopyableMovableInstance)> ref(l); + ref(std::move(instance)); + EXPECT_EQ(tracker.copies(), 0); + EXPECT_EQ(tracker.moves(), 1); +} + +TEST(FunctionRef, PassByValueTypes) { + using absl::functional_internal::Invoker; + using absl::functional_internal::VoidPtr; + using absl::test_internal::CopyableMovableInstance; + struct Trivial { + void* p[2]; + }; + struct LargeTrivial { + void* p[3]; + }; + + static_assert(std::is_same<Invoker<void, int>, void (*)(VoidPtr, int)>::value, + "Scalar types should be passed by value"); + static_assert( + std::is_same<Invoker<void, Trivial>, void (*)(VoidPtr, Trivial)>::value, + "Small trivial types should be passed by value"); + static_assert(std::is_same<Invoker<void, LargeTrivial>, + void (*)(VoidPtr, LargeTrivial &&)>::value, + "Large trivial types should be passed by rvalue reference"); + static_assert( + std::is_same<Invoker<void, CopyableMovableInstance>, + void (*)(VoidPtr, CopyableMovableInstance &&)>::value, + "Types with copy/move ctor should be passed by rvalue reference"); + + // References are passed as references. + static_assert( + std::is_same<Invoker<void, int&>, void (*)(VoidPtr, int&)>::value, + "Reference types should be preserved"); + static_assert( + std::is_same<Invoker<void, CopyableMovableInstance&>, + void (*)(VoidPtr, CopyableMovableInstance&)>::value, + "Reference types should be preserved"); + static_assert( + std::is_same<Invoker<void, CopyableMovableInstance&&>, + void (*)(VoidPtr, CopyableMovableInstance &&)>::value, + "Reference types should be preserved"); + + // Make sure the address of an object received by reference is the same as the + // addess of the object passed by the caller. + { + LargeTrivial obj; + auto test = [&obj](LargeTrivial& input) { ASSERT_EQ(&input, &obj); }; + absl::FunctionRef<void(LargeTrivial&)> ref(test); + ref(obj); + } + + { + Trivial obj; + auto test = [&obj](Trivial& input) { ASSERT_EQ(&input, &obj); }; + absl::FunctionRef<void(Trivial&)> ref(test); + ref(obj); + } +} + +} // namespace +} // namespace absl diff --git a/absl/functional/internal/function_ref.h b/absl/functional/internal/function_ref.h new file mode 100644 index 000000000000..fcb0496c2c06 --- /dev/null +++ b/absl/functional/internal/function_ref.h @@ -0,0 +1,104 @@ +// Copyright 2019 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_ +#define ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_ + +#include <cassert> +#include <functional> +#include <type_traits> + +#include "absl/base/internal/invoke.h" +#include "absl/meta/type_traits.h" + +namespace absl { +namespace functional_internal { + +// Like a void* that can handle function pointers as well. The standard does not +// allow function pointers to round-trip through void*, but void(*)() is fine. +// +// Note: It's important that this class remains trivial and is the same size as +// a pointer, since this allows the compiler to perform tail-call optimizations +// when the underlying function is a callable object with a matching signature. +union VoidPtr { + const void* obj; + void (*fun)(); +}; + +// Chooses the best type for passing T as an argument. +// Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are +// passed by value. +template <typename T> +constexpr bool PassByValue() { + return !std::is_lvalue_reference<T>::value && + absl::is_trivially_copy_constructible<T>::value && + absl::is_trivially_copy_assignable< + typename std::remove_cv<T>::type>::value && + std::is_trivially_destructible<T>::value && + sizeof(T) <= 2 * sizeof(void*); +} + +template <typename T> +struct ForwardT : std::conditional<PassByValue<T>(), T, T&&> {}; + +// An Invoker takes a pointer to the type-erased invokable object, followed by +// the arguments that the invokable object expects. +// +// Note: The order of arguments here is an optimization, since member functions +// have an implicit "this" pointer as their first argument, putting VoidPtr +// first allows the compiler to perform tail-call optimization in many cases. +template <typename R, typename... Args> +using Invoker = R (*)(VoidPtr, typename ForwardT<Args>::type...); + +// +// InvokeObject and InvokeFunction provide static "Invoke" functions that can be +// used as Invokers for objects or functions respectively. +// +// static_cast<R> handles the case the return type is void. +template <typename Obj, typename R, typename... Args> +R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) { + auto o = static_cast<const Obj*>(ptr.obj); + return static_cast<R>( + absl::base_internal::Invoke(*o, std::forward<Args>(args)...)); +} + +template <typename Fun, typename R, typename... Args> +R InvokeFunction(VoidPtr ptr, typename ForwardT<Args>::type... args) { + auto f = reinterpret_cast<Fun>(ptr.fun); + return static_cast<R>( + absl::base_internal::Invoke(f, std::forward<Args>(args)...)); +} + +template <typename Sig> +void AssertNonNull(const std::function<Sig>& f) { + assert(f != nullptr); + (void)f; +} + +template <typename F> +void AssertNonNull(const F&) {} + +template <typename F, typename C> +void AssertNonNull(F C::*f) { + assert(f != nullptr); + (void)f; +} + +template <bool C> +using EnableIf = typename ::std::enable_if<C, int>::type; + +} // namespace functional_internal +} // namespace absl + +#endif // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_ |