/src/abseil-cpp/absl/functional/internal/function_ref.h

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// 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/functional/any_invocable.h"
#include "absl/meta/type_traits.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
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,
          bool IsLValueReference = std::is_lvalue_reference<T>::value>
struct PassByValue : std::false_type {};

template <typename T>
struct PassByValue<T, /*IsLValueReference=*/false>
    : std::integral_constant<bool,
                             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>::value, 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>(std::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>(std::invoke(f, std::forward<Args>(args)...));
}

template <typename Sig>
void AssertNonNull(const std::function<Sig>& f) {
  assert(f != nullptr);
  (void)f;
}

template <typename Sig>
void AssertNonNull(const AnyInvocable<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
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

Line	Count	Source (jump to first uncovered line)
1		// Copyright 2019 The Abseil Authors.
2		//
3		// Licensed under the Apache License, Version 2.0 (the "License");
4		// you may not use this file except in compliance with the License.
5		// You may obtain a copy of the License at
6		//
7		// https://www.apache.org/licenses/LICENSE-2.0
8		//
9		// Unless required by applicable law or agreed to in writing, software
10		// distributed under the License is distributed on an "AS IS" BASIS,
11		// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12		// See the License for the specific language governing permissions and
13		// limitations under the License.
14
15		#ifndef ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
16		#define ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
17
18		#include <cassert>
19		#include <functional>
20		#include <type_traits>
21
22		#include "absl/functional/any_invocable.h"
23		#include "absl/meta/type_traits.h"
24
25		namespace absl {
26		ABSL_NAMESPACE_BEGIN
27		namespace functional_internal {
28
29		// Like a void* that can handle function pointers as well. The standard does not
30		// allow function pointers to round-trip through void, but void()() is fine.
31		//
32		// Note: It's important that this class remains trivial and is the same size as
33		// a pointer, since this allows the compiler to perform tail-call optimizations
34		// when the underlying function is a callable object with a matching signature.
35		union VoidPtr {
36		const void* obj;
37		void (*fun)();
38		};
39
40		// Chooses the best type for passing T as an argument.
41		// Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are
42		// passed by value.
43		template <typename T,
44		bool IsLValueReference = std::is_lvalue_reference<T>::value>
45		struct PassByValue : std::false_type {};
46
47		template <typename T>
48		struct PassByValue<T, /IsLValueReference=/false>
49		: std::integral_constant<bool,
50		absl::is_trivially_copy_constructible<T>::value &&
51		absl::is_trivially_copy_assignable<
52		typename std::remove_cv<T>::type>::value &&
53		std::is_trivially_destructible<T>::value &&
54		sizeof(T) <= 2 * sizeof(void*)> {};
55
56		template <typename T>
57		struct ForwardT : std::conditional<PassByValue<T>::value, T, T&&> {};
58
59		// An Invoker takes a pointer to the type-erased invokable object, followed by
60		// the arguments that the invokable object expects.
61		//
62		// Note: The order of arguments here is an optimization, since member functions
63		// have an implicit "this" pointer as their first argument, putting VoidPtr
64		// first allows the compiler to perform tail-call optimization in many cases.
65		template <typename R, typename... Args>
66		using Invoker = R (*)(VoidPtr, typename ForwardT<Args>::type...);
67
68		//
69		// InvokeObject and InvokeFunction provide static "Invoke" functions that can be
70		// used as Invokers for objects or functions respectively.
71		//
72		// static_cast<R> handles the case the return type is void.
73		template <typename Obj, typename R, typename... Args>
74	0	R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
75	0	auto o = static_cast<const Obj*>(ptr.obj);
76	0	return static_cast<R>(std::invoke(*o, std::forward<Args>(args)...));
77	0	} Unexecuted instantiation: void absl::functional_internal::InvokeObject<absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1}, void, std::__1::basic_string_view<char, std::__1::char_traits<char> > >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<std::__1::basic_string_view<char, std::__1::char_traits<char> > >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1}, void, absl::Span<unsigned int> >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::Span<unsigned int> >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0, void, absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1}, void, absl::Span<unsigned int> >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::Span<unsigned int> >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0, void, absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>::type)
78
79		template <typename Fun, typename R, typename... Args>
80		R InvokeFunction(VoidPtr ptr, typename ForwardT<Args>::type... args) {
81		auto f = reinterpret_cast<Fun>(ptr.fun);
82		return static_cast<R>(std::invoke(f, std::forward<Args>(args)...));
83		}
84
85		template <typename Sig>
86		void AssertNonNull(const std::function<Sig>& f) {
87		assert(f != nullptr);
88		(void)f;
89		}
90
91		template <typename Sig>
92		void AssertNonNull(const AnyInvocable<Sig>& f) {
93		assert(f != nullptr);
94		(void)f;
95		}
96
97		template <typename F>
98	0	void AssertNonNull(const F&) {} Unexecuted instantiation: void absl::functional_internal::AssertNonNull<absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1}>(absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1}>(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0 const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1}>(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&)::$_0 const&)
99
100		template <typename F, typename C>
101		void AssertNonNull(F C::*f) {
102		assert(f != nullptr);
103		(void)f;
104		}
105
106		template <bool C>
107		using EnableIf = typename ::std::enable_if<C, int>::type;
108
109		} // namespace functional_internal
110		ABSL_NAMESPACE_END
111		} // namespace absl
112
113		#endif // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

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Created: 2025-07-11 06:37