From b56cbdd23834a65682c0b46f367f8679e83bc894 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 18 Sep 2020 15:55:15 -0700 Subject: Abseil LTS 20200923 What's New: * `absl::StatusOr` has been released. See our [blog post](https://abseil.io/blog/2020-091021-status) for more information. * Abseil Flags reflection interfaces have been released. * Abseil Flags memory usage has been significantly optimized. * Abseil now supports a "hardened" build mode. This build mode enables runtime checks that guard against programming errors that may lead to security vulnerabilities. Notable Fixes: * Sanitizer dynamic annotations like `AnnotateRWLockCreate` that are also defined by the compiler sanitizer implementation are no longer also defined by Abseil. * Sanitizer macros are now prefixed with `ABSL_` to avoid naming collisions. * Sanitizer usage is now automatically detected and no longer requires macros like `ADDRESS_SANITIZER` to be defined on the command line. Breaking Changes: * Abseil no longer contains a `dynamic_annotations` library. Users using a supported build system (Bazel or CMake) are unaffected by this, but users manually specifying link libraries may get an error about a missing linker input. Baseline: 7680a5f8efe32de4753baadbd63e74e59d95bac1 Cherry picks: None --- absl/status/internal/statusor_internal.h | 399 +++++++++++++++++++++++++++++++ 1 file changed, 399 insertions(+) create mode 100644 absl/status/internal/statusor_internal.h (limited to 'absl/status/internal/statusor_internal.h') diff --git a/absl/status/internal/statusor_internal.h b/absl/status/internal/statusor_internal.h new file mode 100644 index 00000000..96e41da5 --- /dev/null +++ b/absl/status/internal/statusor_internal.h @@ -0,0 +1,399 @@ +// Copyright 2020 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_STATUS_INTERNAL_STATUSOR_INTERNAL_H_ +#define ABSL_STATUS_INTERNAL_STATUSOR_INTERNAL_H_ + +#include +#include + +#include "absl/meta/type_traits.h" +#include "absl/status/status.h" +#include "absl/utility/utility.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN + +template +class ABSL_MUST_USE_RESULT StatusOr; + +namespace internal_statusor { + +// Detects whether `U` has conversion operator to `StatusOr`, i.e. `operator +// StatusOr()`. +template +struct HasConversionOperatorToStatusOr : std::false_type {}; + +template +void test(char (*)[sizeof(std::declval().operator absl::StatusOr())]); + +template +struct HasConversionOperatorToStatusOr(0))> + : std::true_type {}; + +// Detects whether `T` is constructible or convertible from `StatusOr`. +template +using IsConstructibleOrConvertibleFromStatusOr = + absl::disjunction&>, + std::is_constructible&>, + std::is_constructible&&>, + std::is_constructible&&>, + std::is_convertible&, T>, + std::is_convertible&, T>, + std::is_convertible&&, T>, + std::is_convertible&&, T>>; + +// Detects whether `T` is constructible or convertible or assignable from +// `StatusOr`. +template +using IsConstructibleOrConvertibleOrAssignableFromStatusOr = + absl::disjunction, + std::is_assignable&>, + std::is_assignable&>, + std::is_assignable&&>, + std::is_assignable&&>>; + +// Detects whether direct initializing `StatusOr` from `U` is ambiguous, i.e. +// when `U` is `StatusOr` and `T` is constructible or convertible from `V`. +template +struct IsDirectInitializationAmbiguous + : public absl::conditional_t< + std::is_same>, + U>::value, + std::false_type, + IsDirectInitializationAmbiguous< + T, absl::remove_cv_t>>> {}; + +template +struct IsDirectInitializationAmbiguous> + : public IsConstructibleOrConvertibleFromStatusOr {}; + +// Checks against the constraints of the direction initialization, i.e. when +// `StatusOr::StatusOr(U&&)` should participate in overload resolution. +template +using IsDirectInitializationValid = absl::disjunction< + // Short circuits if T is basically U. + std::is_same>>, + absl::negation, + absl::remove_cv_t>>, + std::is_same>>, + std::is_same>>, + IsDirectInitializationAmbiguous>>>; + +// This trait detects whether `StatusOr::operator=(U&&)` is ambiguous, which +// is equivalent to whether all the following conditions are met: +// 1. `U` is `StatusOr`. +// 2. `T` is constructible and assignable from `V`. +// 3. `T` is constructible and assignable from `U` (i.e. `StatusOr`). +// For example, the following code is considered ambiguous: +// (`T` is `bool`, `U` is `StatusOr`, `V` is `bool`) +// StatusOr s1 = true; // s1.ok() && s1.ValueOrDie() == true +// StatusOr s2 = false; // s2.ok() && s2.ValueOrDie() == false +// s1 = s2; // ambiguous, `s1 = s2.ValueOrDie()` or `s1 = bool(s2)`? +template +struct IsForwardingAssignmentAmbiguous + : public absl::conditional_t< + std::is_same>, + U>::value, + std::false_type, + IsForwardingAssignmentAmbiguous< + T, absl::remove_cv_t>>> {}; + +template +struct IsForwardingAssignmentAmbiguous> + : public IsConstructibleOrConvertibleOrAssignableFromStatusOr {}; + +// Checks against the constraints of the forwarding assignment, i.e. whether +// `StatusOr::operator(U&&)` should participate in overload resolution. +template +using IsForwardingAssignmentValid = absl::disjunction< + // Short circuits if T is basically U. + std::is_same>>, + absl::negation, + absl::remove_cv_t>>, + std::is_same>>, + std::is_same>>, + IsForwardingAssignmentAmbiguous>>>; + +class Helper { + public: + // Move type-agnostic error handling to the .cc. + static void HandleInvalidStatusCtorArg(Status*); + static void Crash(const absl::Status& status); +}; + +// Construct an instance of T in `p` through placement new, passing Args... to +// the constructor. +// This abstraction is here mostly for the gcc performance fix. +template +void PlacementNew(void* p, Args&&... args) { +#if defined(__GNUC__) && !defined(__clang__) + // Teach gcc that 'p' cannot be null, fixing code size issues. + if (p == nullptr) __builtin_unreachable(); +#endif + new (p) T(std::forward(args)...); +} + +// Helper base class to hold the data and all operations. +// We move all this to a base class to allow mixing with the appropriate +// TraitsBase specialization. +template +class StatusOrData { + template + friend class StatusOrData; + + public: + StatusOrData() = delete; + + StatusOrData(const StatusOrData& other) { + if (other.ok()) { + MakeValue(other.data_); + MakeStatus(); + } else { + MakeStatus(other.status_); + } + } + + StatusOrData(StatusOrData&& other) noexcept { + if (other.ok()) { + MakeValue(std::move(other.data_)); + MakeStatus(); + } else { + MakeStatus(std::move(other.status_)); + } + } + + template + explicit StatusOrData(const StatusOrData& other) { + if (other.ok()) { + MakeValue(other.data_); + MakeStatus(); + } else { + MakeStatus(other.status_); + } + } + + template + explicit StatusOrData(StatusOrData&& other) { + if (other.ok()) { + MakeValue(std::move(other.data_)); + MakeStatus(); + } else { + MakeStatus(std::move(other.status_)); + } + } + + template + explicit StatusOrData(absl::in_place_t, Args&&... args) + : data_(std::forward(args)...) { + MakeStatus(); + } + + explicit StatusOrData(const T& value) : data_(value) { + MakeStatus(); + } + explicit StatusOrData(T&& value) : data_(std::move(value)) { + MakeStatus(); + } + + template ::value, + int> = 0> + explicit StatusOrData(U&& v) : status_(v) { + EnsureNotOk(); + } + + StatusOrData& operator=(const StatusOrData& other) { + if (this == &other) return *this; + if (other.ok()) + Assign(other.data_); + else + AssignStatus(other.status_); + return *this; + } + + StatusOrData& operator=(StatusOrData&& other) { + if (this == &other) return *this; + if (other.ok()) + Assign(std::move(other.data_)); + else + AssignStatus(std::move(other.status_)); + return *this; + } + + ~StatusOrData() { + if (ok()) { + status_.~Status(); + data_.~T(); + } else { + status_.~Status(); + } + } + + template + void Assign(U&& value) { + if (ok()) { + data_ = std::forward(value); + } else { + MakeValue(std::forward(value)); + status_ = OkStatus(); + } + } + + template + void AssignStatus(U&& v) { + Clear(); + status_ = static_cast(std::forward(v)); + EnsureNotOk(); + } + + bool ok() const { return status_.ok(); } + + protected: + // status_ will always be active after the constructor. + // We make it a union to be able to initialize exactly how we need without + // waste. + // Eg. in the copy constructor we use the default constructor of Status in + // the ok() path to avoid an extra Ref call. + union { + Status status_; + }; + + // data_ is active iff status_.ok()==true + struct Dummy {}; + union { + // When T is const, we need some non-const object we can cast to void* for + // the placement new. dummy_ is that object. + Dummy dummy_; + T data_; + }; + + void Clear() { + if (ok()) data_.~T(); + } + + void EnsureOk() const { + if (ABSL_PREDICT_FALSE(!ok())) Helper::Crash(status_); + } + + void EnsureNotOk() { + if (ABSL_PREDICT_FALSE(ok())) Helper::HandleInvalidStatusCtorArg(&status_); + } + + // Construct the value (ie. data_) through placement new with the passed + // argument. + template + void MakeValue(Arg&&... arg) { + internal_statusor::PlacementNew(&dummy_, std::forward(arg)...); + } + + // Construct the status (ie. status_) through placement new with the passed + // argument. + template + void MakeStatus(Args&&... args) { + internal_statusor::PlacementNew(&status_, + std::forward(args)...); + } +}; + +// Helper base classes to allow implicitly deleted constructors and assignment +// operators in `StatusOr`. For example, `CopyCtorBase` will explicitly delete +// the copy constructor when T is not copy constructible and `StatusOr` will +// inherit that behavior implicitly. +template ::value> +struct CopyCtorBase { + CopyCtorBase() = default; + CopyCtorBase(const CopyCtorBase&) = default; + CopyCtorBase(CopyCtorBase&&) = default; + CopyCtorBase& operator=(const CopyCtorBase&) = default; + CopyCtorBase& operator=(CopyCtorBase&&) = default; +}; + +template +struct CopyCtorBase { + CopyCtorBase() = default; + CopyCtorBase(const CopyCtorBase&) = delete; + CopyCtorBase(CopyCtorBase&&) = default; + CopyCtorBase& operator=(const CopyCtorBase&) = default; + CopyCtorBase& operator=(CopyCtorBase&&) = default; +}; + +template ::value> +struct MoveCtorBase { + MoveCtorBase() = default; + MoveCtorBase(const MoveCtorBase&) = default; + MoveCtorBase(MoveCtorBase&&) = default; + MoveCtorBase& operator=(const MoveCtorBase&) = default; + MoveCtorBase& operator=(MoveCtorBase&&) = default; +}; + +template +struct MoveCtorBase { + MoveCtorBase() = default; + MoveCtorBase(const MoveCtorBase&) = default; + MoveCtorBase(MoveCtorBase&&) = delete; + MoveCtorBase& operator=(const MoveCtorBase&) = default; + MoveCtorBase& operator=(MoveCtorBase&&) = default; +}; + +template ::value&& + std::is_copy_assignable::value> +struct CopyAssignBase { + CopyAssignBase() = default; + CopyAssignBase(const CopyAssignBase&) = default; + CopyAssignBase(CopyAssignBase&&) = default; + CopyAssignBase& operator=(const CopyAssignBase&) = default; + CopyAssignBase& operator=(CopyAssignBase&&) = default; +}; + +template +struct CopyAssignBase { + CopyAssignBase() = default; + CopyAssignBase(const CopyAssignBase&) = default; + CopyAssignBase(CopyAssignBase&&) = default; + CopyAssignBase& operator=(const CopyAssignBase&) = delete; + CopyAssignBase& operator=(CopyAssignBase&&) = default; +}; + +template ::value&& + std::is_move_assignable::value> +struct MoveAssignBase { + MoveAssignBase() = default; + MoveAssignBase(const MoveAssignBase&) = default; + MoveAssignBase(MoveAssignBase&&) = default; + MoveAssignBase& operator=(const MoveAssignBase&) = default; + MoveAssignBase& operator=(MoveAssignBase&&) = default; +}; + +template +struct MoveAssignBase { + MoveAssignBase() = default; + MoveAssignBase(const MoveAssignBase&) = default; + MoveAssignBase(MoveAssignBase&&) = default; + MoveAssignBase& operator=(const MoveAssignBase&) = default; + MoveAssignBase& operator=(MoveAssignBase&&) = delete; +}; + +ABSL_ATTRIBUTE_NORETURN void ThrowBadStatusOrAccess(absl::Status status); + +} // namespace internal_statusor +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STATUS_INTERNAL_STATUSOR_INTERNAL_H_ -- cgit v1.2.3