diff options
Diffstat (limited to 'absl/meta')
| -rw-r--r-- | absl/meta/BUILD.bazel | 17 | ||||
| -rw-r--r-- | absl/meta/type_traits.h | 65 | ||||
| -rw-r--r-- | absl/meta/type_traits_test.cc | 43 |
3 files changed, 93 insertions, 32 deletions
diff --git a/absl/meta/BUILD.bazel b/absl/meta/BUILD.bazel index e004b509..c06d2d97 100644 --- a/absl/meta/BUILD.bazel +++ b/absl/meta/BUILD.bazel @@ -1,3 +1,20 @@ +# +# 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. +# + +load("@rules_cc//cc:defs.bzl", "cc_library", "cc_test") load( "//absl:copts/configure_copts.bzl", "ABSL_DEFAULT_COPTS", diff --git a/absl/meta/type_traits.h b/absl/meta/type_traits.h index ae7130dd..ba87d2f0 100644 --- a/absl/meta/type_traits.h +++ b/absl/meta/type_traits.h @@ -41,8 +41,18 @@ #include "absl/base/config.h" +// MSVC constructibility traits do not detect destructor properties and so our +// implementations should not use them as a source-of-truth. +#if defined(_MSC_VER) && !defined(__clang__) && !defined(__GNUC__) +#define ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION 1 +#endif + namespace absl { -inline namespace lts_2019_08_08 { +ABSL_NAMESPACE_BEGIN + +// Defined and documented later on in this file. +template <typename T> +struct is_trivially_destructible; // Defined and documented later on in this file. template <typename T> @@ -67,6 +77,20 @@ union SingleMemberUnion { #endif // defined(_MSC_VER) && !defined(__GNUC__) template <class T> +struct IsTriviallyMoveConstructibleObject + : std::integral_constant< + bool, std::is_move_constructible< + type_traits_internal::SingleMemberUnion<T>>::value && + absl::is_trivially_destructible<T>::value> {}; + +template <class T> +struct IsTriviallyCopyConstructibleObject + : std::integral_constant< + bool, std::is_copy_constructible< + type_traits_internal::SingleMemberUnion<T>>::value && + absl::is_trivially_destructible<T>::value> {}; + +template <class T> struct IsTriviallyMoveAssignableReference : std::false_type {}; template <class T> @@ -146,6 +170,18 @@ using IsMoveAssignableImpl = decltype(std::declval<T&>() = std::declval<T&&>()); } // namespace type_traits_internal +// MSVC 19.20 has a regression that causes our workarounds to fail, but their +// std forms now appear to be compliant. +#if defined(_MSC_VER) && !defined(__clang__) && (_MSC_VER >= 1920) + +template <typename T> +using is_copy_assignable = std::is_copy_assignable<T>; + +template <typename T> +using is_move_assignable = std::is_move_assignable<T>; + +#else + template <typename T> struct is_copy_assignable : type_traits_internal::is_detected< type_traits_internal::IsCopyAssignableImpl, T> { @@ -156,6 +192,8 @@ struct is_move_assignable : type_traits_internal::is_detected< type_traits_internal::IsMoveAssignableImpl, T> { }; +#endif + // void_t() // // Ignores the type of any its arguments and returns `void`. In general, this @@ -244,7 +282,7 @@ struct is_function // is_trivially_destructible() // -// Determines whether the passed type `T` is trivially destructable. +// Determines whether the passed type `T` is trivially destructible. // // This metafunction is designed to be a drop-in replacement for the C++11 // `std::is_trivially_destructible()` metafunction for platforms that have @@ -310,7 +348,9 @@ struct is_trivially_default_constructible : std::integral_constant<bool, __has_trivial_constructor(T) && std::is_default_constructible<T>::value && is_trivially_destructible<T>::value> { -#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE +#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \ + !defined( \ + ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION) private: static constexpr bool compliant = std::is_trivially_default_constructible<T>::value == @@ -341,10 +381,11 @@ template <typename T> struct is_trivially_move_constructible : std::conditional< std::is_object<T>::value && !std::is_array<T>::value, - std::is_move_constructible< - type_traits_internal::SingleMemberUnion<T>>, + type_traits_internal::IsTriviallyMoveConstructibleObject<T>, std::is_reference<T>>::type::type { -#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE +#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \ + !defined( \ + ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION) private: static constexpr bool compliant = std::is_trivially_move_constructible<T>::value == @@ -375,10 +416,11 @@ template <typename T> struct is_trivially_copy_constructible : std::conditional< std::is_object<T>::value && !std::is_array<T>::value, - std::is_copy_constructible< - type_traits_internal::SingleMemberUnion<T>>, + type_traits_internal::IsTriviallyCopyConstructibleObject<T>, std::is_lvalue_reference<T>>::type::type { -#ifdef ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE +#if defined(ABSL_HAVE_STD_IS_TRIVIALLY_CONSTRUCTIBLE) && \ + !defined( \ + ABSL_META_INTERNAL_STD_CONSTRUCTION_TRAITS_DONT_CHECK_DESTRUCTION) private: static constexpr bool compliant = std::is_trivially_copy_constructible<T>::value == @@ -410,7 +452,8 @@ struct is_trivially_copy_constructible template <typename T> struct is_trivially_move_assignable : std::conditional< - std::is_object<T>::value && !std::is_array<T>::value, + std::is_object<T>::value && !std::is_array<T>::value && + std::is_move_assignable<T>::value, std::is_move_assignable<type_traits_internal::SingleMemberUnion<T>>, type_traits_internal::IsTriviallyMoveAssignableReference<T>>::type:: type { @@ -710,7 +753,7 @@ using swap_internal::Swap; using swap_internal::StdSwapIsUnconstrained; } // namespace type_traits_internal -} // inline namespace lts_2019_08_08 +ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_META_TYPE_TRAITS_H_ diff --git a/absl/meta/type_traits_test.cc b/absl/meta/type_traits_test.cc index a7a9c5c9..1aafd0d4 100644 --- a/absl/meta/type_traits_test.cc +++ b/absl/meta/type_traits_test.cc @@ -347,21 +347,6 @@ class Base { virtual ~Base() {} }; -// In GCC/Clang, std::is_trivially_constructible requires that the destructor is -// trivial. However, MSVC doesn't require that. This results in different -// behavior when checking is_trivially_constructible on any type with -// nontrivial destructor. Since absl::is_trivially_default_constructible and -// absl::is_trivially_copy_constructible both follows Clang/GCC's interpretation -// and check is_trivially_destructible, it results in inconsistency with -// std::is_trivially_xxx_constructible on MSVC. This macro is used to work -// around this issue in test. In practice, a trivially constructible type -// should also be trivially destructible. -// GCC bug 51452: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51452 -// LWG issue 2116: http://cplusplus.github.io/LWG/lwg-active.html#2116 -#ifndef _MSC_VER -#define ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE 1 -#endif - // Old versions of libc++, around Clang 3.5 to 3.6, consider deleted destructors // as also being trivial. With the resolution of CWG 1928 and CWG 1734, this // is no longer considered true and has thus been amended. @@ -499,11 +484,9 @@ TEST(TypeTraitsTest, TestTrivialDefaultCtor) { EXPECT_FALSE( absl::is_trivially_default_constructible<DeletedDefaultCtor>::value); -#ifdef ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE // types with nontrivial destructor are nontrivial EXPECT_FALSE( absl::is_trivially_default_constructible<NontrivialDestructor>::value); -#endif // types with vtables EXPECT_FALSE(absl::is_trivially_default_constructible<Base>::value); @@ -546,6 +529,28 @@ TEST(TypeTraitsTest, TestTrivialDefaultCtor) { #endif } +// GCC prior to 7.4 had a bug in its trivially-constructible traits +// (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654). +// This test makes sure that we do not depend on the trait in these cases when +// implementing absl triviality traits. + +template <class T> +struct BadConstructors { + BadConstructors() { static_assert(T::value, ""); } + + BadConstructors(BadConstructors&&) { static_assert(T::value, ""); } + + BadConstructors(const BadConstructors&) { static_assert(T::value, ""); } +}; + +TEST(TypeTraitsTest, TestTrivialityBadConstructors) { + using BadType = BadConstructors<int>; + + EXPECT_FALSE(absl::is_trivially_default_constructible<BadType>::value); + EXPECT_FALSE(absl::is_trivially_move_constructible<BadType>::value); + EXPECT_FALSE(absl::is_trivially_copy_constructible<BadType>::value); +} + TEST(TypeTraitsTest, TestTrivialMoveCtor) { // Verify that arithmetic types and pointers have trivial move // constructors. @@ -585,11 +590,9 @@ TEST(TypeTraitsTest, TestTrivialMoveCtor) { EXPECT_FALSE( absl::is_trivially_move_constructible<NonCopyableOrMovable>::value); -#ifdef ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE // type with nontrivial destructor are nontrivial move construbtible EXPECT_FALSE( absl::is_trivially_move_constructible<NontrivialDestructor>::value); -#endif // types with vtables EXPECT_FALSE(absl::is_trivially_move_constructible<Base>::value); @@ -660,11 +663,9 @@ TEST(TypeTraitsTest, TestTrivialCopyCtor) { EXPECT_FALSE( absl::is_trivially_copy_constructible<NonCopyableOrMovable>::value); -#ifdef ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE // type with nontrivial destructor are nontrivial copy construbtible EXPECT_FALSE( absl::is_trivially_copy_constructible<NontrivialDestructor>::value); -#endif // types with vtables EXPECT_FALSE(absl::is_trivially_copy_constructible<Base>::value); |