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-rw-r--r--absl/types/optional.h454
1 files changed, 42 insertions, 412 deletions
diff --git a/absl/types/optional.h b/absl/types/optional.h
index 1ca8dec6..6614d7bd 100644
--- a/absl/types/optional.h
+++ b/absl/types/optional.h
@@ -4,7 +4,7 @@
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
-// http://www.apache.org/licenses/LICENSE-2.0
+// 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,
@@ -35,21 +35,21 @@
#ifndef ABSL_TYPES_OPTIONAL_H_
#define ABSL_TYPES_OPTIONAL_H_
-#include "absl/base/config.h"
+#include "absl/base/config.h" // TODO(calabrese) IWYU removal?
#include "absl/utility/utility.h"
#ifdef ABSL_HAVE_STD_OPTIONAL
-#include <optional>
+#include <optional> // IWYU pragma: export
namespace absl {
-inline namespace lts_2018_12_18 {
+inline namespace lts_2019_08_08 {
using std::bad_optional_access;
using std::optional;
using std::make_optional;
using std::nullopt_t;
using std::nullopt;
-} // inline namespace lts_2018_12_18
+} // inline namespace lts_2019_08_08
} // namespace absl
#else // ABSL_HAVE_STD_OPTIONAL
@@ -57,45 +57,33 @@ using std::nullopt;
#include <cassert>
#include <functional>
#include <initializer_list>
-#include <new>
#include <type_traits>
#include <utility>
#include "absl/base/attributes.h"
-#include "absl/memory/memory.h"
+#include "absl/base/internal/inline_variable.h"
#include "absl/meta/type_traits.h"
#include "absl/types/bad_optional_access.h"
+#include "absl/types/internal/optional.h"
-// ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
+namespace absl {
+inline namespace lts_2019_08_08 {
+
+// nullopt_t
//
-// Inheriting constructors is supported in GCC 4.8+, Clang 3.3+ and MSVC 2015.
-// __cpp_inheriting_constructors is a predefined macro and a recommended way to
-// check for this language feature, but GCC doesn't support it until 5.0 and
-// Clang doesn't support it until 3.6.
-// Also, MSVC 2015 has a bug: it doesn't inherit the constexpr template
-// constructor. For example, the following code won't work on MSVC 2015 Update3:
-// struct Base {
-// int t;
-// template <typename T>
-// constexpr Base(T t_) : t(t_) {}
-// };
-// struct Foo : Base {
-// using Base::Base;
-// }
-// constexpr Foo foo(0); // doesn't work on MSVC 2015
-#if defined(__clang__)
-#if __has_feature(cxx_inheriting_constructors)
-#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
-#endif
-#elif (defined(__GNUC__) && \
- (__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 8)) || \
- (__cpp_inheriting_constructors >= 200802) || \
- (defined(_MSC_VER) && _MSC_VER >= 1910)
-#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
-#endif
+// Class type for `absl::nullopt` used to indicate an `absl::optional<T>` type
+// that does not contain a value.
+struct nullopt_t {
+ // It must not be default-constructible to avoid ambiguity for opt = {}.
+ explicit constexpr nullopt_t(optional_internal::init_t) noexcept {}
+};
-namespace absl {
-inline namespace lts_2018_12_18 {
+// nullopt
+//
+// A tag constant of type `absl::nullopt_t` used to indicate an empty
+// `absl::optional` in certain functions, such as construction or assignment.
+ABSL_INTERNAL_INLINE_CONSTEXPR(nullopt_t, nullopt,
+ nullopt_t(optional_internal::init_t()));
// -----------------------------------------------------------------------------
// absl::optional
@@ -117,10 +105,6 @@ inline namespace lts_2018_12_18 {
// need the inline variable support in C++17 for external linkage.
// * Throws `absl::bad_optional_access` instead of
// `std::bad_optional_access`.
-// * `optional::swap()` and `absl::swap()` relies on
-// `std::is_(nothrow_)swappable()`, which has been introduced in C++17.
-// As a workaround, we assume `is_swappable()` is always `true`
-// and `is_nothrow_swappable()` is the same as `std::is_trivial()`.
// * `make_optional()` cannot be declared `constexpr` due to the absence of
// guaranteed copy elision.
// * The move constructor's `noexcept` specification is stronger, i.e. if the
@@ -130,366 +114,13 @@ inline namespace lts_2018_12_18 {
// a) move constructors should only throw due to allocation failure and
// b) if T's move constructor allocates, it uses the same allocation
// function as the default allocator.
-template <typename T>
-class optional;
-
-// nullopt_t
-//
-// Class type for `absl::nullopt` used to indicate an `absl::optional<T>` type
-// that does not contain a value.
-struct nullopt_t {
- struct init_t {};
- static init_t init;
-
- // It must not be default-constructible to avoid ambiguity for opt = {}.
- // Note the non-const reference, which is to eliminate ambiguity for code
- // like:
- //
- // struct S { int value; };
- //
- // void Test() {
- // optional<S> opt;
- // opt = {{}};
- // }
- explicit constexpr nullopt_t(init_t& /*unused*/) {}
-};
-
-// nullopt
//
-// A tag constant of type `absl::nullopt_t` used to indicate an empty
-// `absl::optional` in certain functions, such as construction or assignment.
-extern const nullopt_t nullopt;
-
-namespace optional_internal {
-
-struct empty_struct {};
-// This class stores the data in optional<T>.
-// It is specialized based on whether T is trivially destructible.
-// This is the specialization for non trivially destructible type.
-template <typename T, bool unused = std::is_trivially_destructible<T>::value>
-class optional_data_dtor_base {
- struct dummy_type {
- static_assert(sizeof(T) % sizeof(empty_struct) == 0, "");
- // Use an array to avoid GCC 6 placement-new warning.
- empty_struct data[sizeof(T) / sizeof(empty_struct)];
- };
-
- protected:
- // Whether there is data or not.
- bool engaged_;
- // Data storage
- union {
- dummy_type dummy_;
- T data_;
- };
-
- void destruct() noexcept {
- if (engaged_) {
- data_.~T();
- engaged_ = false;
- }
- }
-
- // dummy_ must be initialized for constexpr constructor.
- constexpr optional_data_dtor_base() noexcept : engaged_(false), dummy_{{}} {}
-
- template <typename... Args>
- constexpr explicit optional_data_dtor_base(in_place_t, Args&&... args)
- : engaged_(true), data_(absl::forward<Args>(args)...) {}
-
- ~optional_data_dtor_base() { destruct(); }
-};
-
-// Specialization for trivially destructible type.
-template <typename T>
-class optional_data_dtor_base<T, true> {
- struct dummy_type {
- static_assert(sizeof(T) % sizeof(empty_struct) == 0, "");
- // Use array to avoid GCC 6 placement-new warning.
- empty_struct data[sizeof(T) / sizeof(empty_struct)];
- };
-
- protected:
- // Whether there is data or not.
- bool engaged_;
- // Data storage
- union {
- dummy_type dummy_;
- T data_;
- };
- void destruct() noexcept { engaged_ = false; }
-
- // dummy_ must be initialized for constexpr constructor.
- constexpr optional_data_dtor_base() noexcept : engaged_(false), dummy_{{}} {}
-
- template <typename... Args>
- constexpr explicit optional_data_dtor_base(in_place_t, Args&&... args)
- : engaged_(true), data_(absl::forward<Args>(args)...) {}
-};
-
-template <typename T>
-class optional_data_base : public optional_data_dtor_base<T> {
- protected:
- using base = optional_data_dtor_base<T>;
-#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
- using base::base;
-#else
- optional_data_base() = default;
-
- template <typename... Args>
- constexpr explicit optional_data_base(in_place_t t, Args&&... args)
- : base(t, absl::forward<Args>(args)...) {}
-#endif
-
- template <typename... Args>
- void construct(Args&&... args) {
- // Use dummy_'s address to work around casting cv-qualified T* to void*.
- ::new (static_cast<void*>(&this->dummy_)) T(std::forward<Args>(args)...);
- this->engaged_ = true;
- }
-
- template <typename U>
- void assign(U&& u) {
- if (this->engaged_) {
- this->data_ = std::forward<U>(u);
- } else {
- construct(std::forward<U>(u));
- }
- }
-};
-
-// TODO(absl-team): Add another class using
-// std::is_trivially_move_constructible trait when available to match
-// http://cplusplus.github.io/LWG/lwg-defects.html#2900, for types that
-// have trivial move but nontrivial copy.
-// Also, we should be checking is_trivially_copyable here, which is not
-// supported now, so we use is_trivially_* traits instead.
-template <typename T,
- bool unused = 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>
-class optional_data;
-
-// Trivially copyable types
-template <typename T>
-class optional_data<T, true> : public optional_data_base<T> {
- protected:
-#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
- using optional_data_base<T>::optional_data_base;
-#else
- optional_data() = default;
-
- template <typename... Args>
- constexpr explicit optional_data(in_place_t t, Args&&... args)
- : optional_data_base<T>(t, absl::forward<Args>(args)...) {}
-#endif
-};
-
-template <typename T>
-class optional_data<T, false> : public optional_data_base<T> {
- protected:
-#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
- using optional_data_base<T>::optional_data_base;
-#else
- template <typename... Args>
- constexpr explicit optional_data(in_place_t t, Args&&... args)
- : optional_data_base<T>(t, absl::forward<Args>(args)...) {}
-#endif
-
- optional_data() = default;
-
- optional_data(const optional_data& rhs) {
- if (rhs.engaged_) {
- this->construct(rhs.data_);
- }
- }
-
- optional_data(optional_data&& rhs) noexcept(
- absl::default_allocator_is_nothrow::value ||
- std::is_nothrow_move_constructible<T>::value) {
- if (rhs.engaged_) {
- this->construct(std::move(rhs.data_));
- }
- }
-
- optional_data& operator=(const optional_data& rhs) {
- if (rhs.engaged_) {
- this->assign(rhs.data_);
- } else {
- this->destruct();
- }
- return *this;
- }
-
- optional_data& operator=(optional_data&& rhs) noexcept(
- std::is_nothrow_move_assignable<T>::value&&
- std::is_nothrow_move_constructible<T>::value) {
- if (rhs.engaged_) {
- this->assign(std::move(rhs.data_));
- } else {
- this->destruct();
- }
- return *this;
- }
-};
-
-// Ordered by level of restriction, from low to high.
-// Copyable implies movable.
-enum class copy_traits { copyable = 0, movable = 1, non_movable = 2 };
-
-// Base class for enabling/disabling copy/move constructor.
-template <copy_traits>
-class optional_ctor_base;
-
-template <>
-class optional_ctor_base<copy_traits::copyable> {
- public:
- constexpr optional_ctor_base() = default;
- optional_ctor_base(const optional_ctor_base&) = default;
- optional_ctor_base(optional_ctor_base&&) = default;
- optional_ctor_base& operator=(const optional_ctor_base&) = default;
- optional_ctor_base& operator=(optional_ctor_base&&) = default;
-};
-
-template <>
-class optional_ctor_base<copy_traits::movable> {
- public:
- constexpr optional_ctor_base() = default;
- optional_ctor_base(const optional_ctor_base&) = delete;
- optional_ctor_base(optional_ctor_base&&) = default;
- optional_ctor_base& operator=(const optional_ctor_base&) = default;
- optional_ctor_base& operator=(optional_ctor_base&&) = default;
-};
-
-template <>
-class optional_ctor_base<copy_traits::non_movable> {
- public:
- constexpr optional_ctor_base() = default;
- optional_ctor_base(const optional_ctor_base&) = delete;
- optional_ctor_base(optional_ctor_base&&) = delete;
- optional_ctor_base& operator=(const optional_ctor_base&) = default;
- optional_ctor_base& operator=(optional_ctor_base&&) = default;
-};
-
-// Base class for enabling/disabling copy/move assignment.
-template <copy_traits>
-class optional_assign_base;
-
-template <>
-class optional_assign_base<copy_traits::copyable> {
- public:
- constexpr optional_assign_base() = default;
- optional_assign_base(const optional_assign_base&) = default;
- optional_assign_base(optional_assign_base&&) = default;
- optional_assign_base& operator=(const optional_assign_base&) = default;
- optional_assign_base& operator=(optional_assign_base&&) = default;
-};
-
-template <>
-class optional_assign_base<copy_traits::movable> {
- public:
- constexpr optional_assign_base() = default;
- optional_assign_base(const optional_assign_base&) = default;
- optional_assign_base(optional_assign_base&&) = default;
- optional_assign_base& operator=(const optional_assign_base&) = delete;
- optional_assign_base& operator=(optional_assign_base&&) = default;
-};
-
-template <>
-class optional_assign_base<copy_traits::non_movable> {
- public:
- constexpr optional_assign_base() = default;
- optional_assign_base(const optional_assign_base&) = default;
- optional_assign_base(optional_assign_base&&) = default;
- optional_assign_base& operator=(const optional_assign_base&) = delete;
- optional_assign_base& operator=(optional_assign_base&&) = delete;
-};
-
-template <typename T>
-constexpr copy_traits get_ctor_copy_traits() {
- return std::is_copy_constructible<T>::value
- ? copy_traits::copyable
- : std::is_move_constructible<T>::value ? copy_traits::movable
- : copy_traits::non_movable;
-}
-
-template <typename T>
-constexpr copy_traits get_assign_copy_traits() {
- return absl::is_copy_assignable<T>::value &&
- std::is_copy_constructible<T>::value
- ? copy_traits::copyable
- : absl::is_move_assignable<T>::value &&
- std::is_move_constructible<T>::value
- ? copy_traits::movable
- : copy_traits::non_movable;
-}
-
-// Whether T is constructible or convertible from optional<U>.
-template <typename T, typename U>
-struct is_constructible_convertible_from_optional
- : std::integral_constant<
- bool, std::is_constructible<T, optional<U>&>::value ||
- std::is_constructible<T, optional<U>&&>::value ||
- std::is_constructible<T, const optional<U>&>::value ||
- std::is_constructible<T, const optional<U>&&>::value ||
- std::is_convertible<optional<U>&, T>::value ||
- std::is_convertible<optional<U>&&, T>::value ||
- std::is_convertible<const optional<U>&, T>::value ||
- std::is_convertible<const optional<U>&&, T>::value> {};
-
-// Whether T is constructible or convertible or assignable from optional<U>.
-template <typename T, typename U>
-struct is_constructible_convertible_assignable_from_optional
- : std::integral_constant<
- bool, is_constructible_convertible_from_optional<T, U>::value ||
- std::is_assignable<T&, optional<U>&>::value ||
- std::is_assignable<T&, optional<U>&&>::value ||
- std::is_assignable<T&, const optional<U>&>::value ||
- std::is_assignable<T&, const optional<U>&&>::value> {};
-
-// Helper function used by [optional.relops], [optional.comp_with_t],
-// for checking whether an expression is convertible to bool.
-bool convertible_to_bool(bool);
-
-// Base class for std::hash<absl::optional<T>>:
-// If std::hash<std::remove_const_t<T>> is enabled, it provides operator() to
-// compute the hash; Otherwise, it is disabled.
-// Reference N4659 23.14.15 [unord.hash].
-template <typename T, typename = size_t>
-struct optional_hash_base {
- optional_hash_base() = delete;
- optional_hash_base(const optional_hash_base&) = delete;
- optional_hash_base(optional_hash_base&&) = delete;
- optional_hash_base& operator=(const optional_hash_base&) = delete;
- optional_hash_base& operator=(optional_hash_base&&) = delete;
-};
-
-template <typename T>
-struct optional_hash_base<T, decltype(std::hash<absl::remove_const_t<T> >()(
- std::declval<absl::remove_const_t<T> >()))> {
- using argument_type = absl::optional<T>;
- using result_type = size_t;
- size_t operator()(const absl::optional<T>& opt) const {
- if (opt) {
- return std::hash<absl::remove_const_t<T> >()(*opt);
- } else {
- return static_cast<size_t>(0x297814aaad196e6dULL);
- }
- }
-};
-
-} // namespace optional_internal
-
-// -----------------------------------------------------------------------------
-// absl::optional class definition
-// -----------------------------------------------------------------------------
-
template <typename T>
class optional : private optional_internal::optional_data<T>,
private optional_internal::optional_ctor_base<
- optional_internal::get_ctor_copy_traits<T>()>,
+ optional_internal::ctor_copy_traits<T>::traits>,
private optional_internal::optional_assign_base<
- optional_internal::get_assign_copy_traits<T>()> {
+ optional_internal::assign_copy_traits<T>::traits> {
using data_base = optional_internal::optional_data<T>;
public:
@@ -514,10 +145,11 @@ class optional : private optional_internal::optional_data<T>,
// the arguments `std::forward<Args>(args)...` within the `optional`.
// (The `in_place_t` is a tag used to indicate that the contained object
// should be constructed in-place.)
- //
- // TODO(absl-team): Add std::is_constructible<T, Args&&...> SFINAE.
- template <typename... Args>
- constexpr explicit optional(in_place_t, Args&&... args)
+ template <typename InPlaceT, typename... Args,
+ absl::enable_if_t<absl::conjunction<
+ std::is_same<InPlaceT, in_place_t>,
+ std::is_constructible<T, Args&&...> >::value>* = nullptr>
+ constexpr explicit optional(InPlaceT, Args&&... args)
: data_base(in_place_t(), absl::forward<Args>(args)...) {}
// Constructs a non-empty `optional` direct-initialized value of type `T` from
@@ -753,11 +385,10 @@ class optional : private optional_internal::optional_data<T>,
// Swap, standard semantics
void swap(optional& rhs) noexcept(
std::is_nothrow_move_constructible<T>::value&&
- std::is_trivial<T>::value) {
+ type_traits_internal::IsNothrowSwappable<T>::value) {
if (*this) {
if (rhs) {
- using std::swap;
- swap(**this, *rhs);
+ type_traits_internal::Swap(**this, *rhs);
} else {
rhs.construct(std::move(**this));
this->destruct();
@@ -793,7 +424,9 @@ class optional : private optional_internal::optional_data<T>,
//
// Accesses the underlying `T` value of an `optional`. If the `optional` is
// empty, behavior is undefined.
- constexpr const T& operator*() const & { return reference(); }
+ constexpr const T& operator*() const& {
+ return ABSL_ASSERT(this->engaged_), reference();
+ }
T& operator*() & {
assert(this->engaged_);
return reference();
@@ -869,7 +502,7 @@ class optional : private optional_internal::optional_data<T>,
template <typename U>
constexpr T value_or(U&& v) const& {
static_assert(std::is_copy_constructible<value_type>::value,
- "optional<T>::value_or: T must by copy constructible");
+ "optional<T>::value_or: T must be copy constructible");
static_assert(std::is_convertible<U&&, value_type>::value,
"optional<T>::value_or: U must be convertible to T");
return static_cast<bool>(*this)
@@ -879,7 +512,7 @@ class optional : private optional_internal::optional_data<T>,
template <typename U>
T value_or(U&& v) && { // NOLINT(build/c++11)
static_assert(std::is_move_constructible<value_type>::value,
- "optional<T>::value_or: T must by copy constructible");
+ "optional<T>::value_or: T must be move constructible");
static_assert(std::is_convertible<U&&, value_type>::value,
"optional<T>::value_or: U must be convertible to T");
return static_cast<bool>(*this) ? std::move(**this)
@@ -909,12 +542,10 @@ class optional : private optional_internal::optional_data<T>,
//
// Performs a swap between two `absl::optional` objects, using standard
// semantics.
-//
-// NOTE: we assume `is_swappable()` is always `true`. A compile error will
-// result if this is not the case.
-template <typename T,
- typename std::enable_if<std::is_move_constructible<T>::value,
- bool>::type = false>
+template <typename T, typename std::enable_if<
+ std::is_move_constructible<T>::value &&
+ type_traits_internal::IsSwappable<T>::value,
+ bool>::type = false>
void swap(optional<T>& a, optional<T>& b) noexcept(noexcept(a.swap(b))) {
a.swap(b);
}
@@ -1126,7 +757,7 @@ constexpr auto operator>=(const U& v, const optional<T>& x)
return static_cast<bool>(x) ? static_cast<bool>(v >= *x) : true;
}
-} // inline namespace lts_2018_12_18
+} // inline namespace lts_2019_08_08
} // namespace absl
namespace std {
@@ -1138,7 +769,6 @@ struct hash<absl::optional<T> >
} // namespace std
-#undef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#undef ABSL_MSVC_CONSTEXPR_BUG_IN_UNION_LIKE_CLASS
#endif // ABSL_HAVE_STD_OPTIONAL
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-02 20:11:24 +0000