diff options
Diffstat (limited to 'libcxx/include/__expected/expected.h')
| -rw-r--r-- | libcxx/include/__expected/expected.h | 1140 |
1 files changed, 750 insertions, 390 deletions
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h index 9f36c41..443d925 100644 --- a/libcxx/include/__expected/expected.h +++ b/libcxx/include/__expected/expected.h @@ -88,8 +88,372 @@ _LIBCPP_HIDE_FROM_ABI void __throw_bad_expected_access(_Arg&& __arg) { # endif } +// If parameter type `_Tp` of `__conditional_no_unique_address` is neither +// copyable nor movable, a constructor with this tag is provided. For that +// constructor, the user has to provide a function and arguments. The function +// must return an object of type `_Tp`. When the function is invoked by the +// constructor, guaranteed copy elision kicks in and the `_Tp` is constructed +// in place. +struct __conditional_no_unique_address_invoke_tag {}; + +// This class implements an object with `[[no_unique_address]]` conditionally applied to it, +// based on the value of `_NoUnique`. +// +// A member of this class must always have `[[no_unique_address]]` applied to +// it. Otherwise, the `[[no_unique_address]]` in the "`_NoUnique == true`" case +// would not have any effect. In the `false` case, the `__v` is not +// `[[no_unique_address]]`, so nullifies the effects of the "outer" +// `[[no_unique_address]]` regarding data layout. +// +// If we had a language feature, this class would basically be replaced by `[[no_unique_address(condition)]]`. +template <bool _NoUnique, class _Tp> +struct __conditional_no_unique_address; + +template <class _Tp> +struct __conditional_no_unique_address<true, _Tp> { + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __conditional_no_unique_address(in_place_t, _Args&&... __args) + : __v(std::forward<_Args>(__args)...) {} + + template <class _Func, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __conditional_no_unique_address( + __conditional_no_unique_address_invoke_tag, _Func&& __f, _Args&&... __args) + : __v(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + + _LIBCPP_NO_UNIQUE_ADDRESS _Tp __v; +}; + +template <class _Tp> +struct __conditional_no_unique_address<false, _Tp> { + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __conditional_no_unique_address(in_place_t, _Args&&... __args) + : __v(std::forward<_Args>(__args)...) {} + + template <class _Func, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __conditional_no_unique_address( + __conditional_no_unique_address_invoke_tag, _Func&& __f, _Args&&... __args) + : __v(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + + _Tp __v; +}; + +// This function returns whether the type `_Second` can be stuffed into the tail padding +// of the `_First` type if both of them are given `[[no_unique_address]]`. +template <class _First, class _Second> +inline constexpr bool __fits_in_tail_padding = []() { + struct __x { + _LIBCPP_NO_UNIQUE_ADDRESS _First __first; + _LIBCPP_NO_UNIQUE_ADDRESS _Second __second; + }; + return sizeof(__x) == sizeof(_First); +}(); + +// This class implements the storage used by `std::expected`. We have a few +// goals for this storage: +// 1. Whenever the underlying {_Tp | _Unex} combination has free bytes in its +// tail padding, we should reuse it to store the bool discriminator of the +// expected, so as to save space. +// 2. Whenever the `expected<_Tp, _Unex>` as a whole has free bytes in its tail +// padding, we should allow an object following the expected to be stored in +// its tail padding. +// 3. However, we never want a user object (say `X`) that would follow an +// `expected<_Tp, _Unex>` to be stored in the padding bytes of the +// underlying {_Tp | _Unex} union, if any. That is because we use +// `construct_at` on that union, which would end up overwriting the `X` +// member if it is stored in the tail padding of the union. +// +// To achieve this, `__expected_base`'s logic is implemented in an inner +// `__repr` class. `__expected_base` holds one `__repr` member which is +// conditionally `[[no_unique_address]]`. The `__repr` class holds the +// underlying {_Tp | _Unex} union and a boolean "has value" flag. +// +// Which one of the `__repr_`/`__union_` members is `[[no_unique_address]]` +// depends on whether the "has value" boolean fits into the tail padding of +// the underlying {_Tp | _Unex} union: +// +// - In case the "has value" bool fits into the tail padding of the union, the +// whole `__repr_` member is _not_ `[[no_unique_address]]` as it needs to be +// transparently replaced on `emplace()`/`swap()` etc. +// - In case the "has value" bool does not fit into the tail padding of the +// union, only the union member must be transparently replaced (therefore is +// _not_ `[[no_unique_address]]`) and the "has value" flag must be adjusted +// manually. +// +// This way, the member that is transparently replaced on mutating operations +// is never `[[no_unique_address]]`, satisfying the requirements from +// "[basic.life]" in the standard. +// +// Stripped away of all superfluous elements, the layout of `__expected_base` +// then looks like this: +// +// template <class Tp, class Err> +// class expected_base { +// union union_t { +// [[no_unique_address]] Tp val; +// [[no_unique_address]] Err unex; +// }; +// +// static constexpr bool put_flag_in_tail = fits_in_tail_padding<union_t, bool>; +// static constexpr bool allow_reusing_expected_tail_padding = !put_flag_in_tail; +// +// struct repr { +// private: +// // If "has value" fits into the tail, this should be +// // `[[no_unique_address]]`, otherwise not. +// [[no_unique_address]] conditional_no_unique_address< +// put_flag_in_tail, +// union_t>::type union_; +// [[no_unique_address]] bool has_val_; +// }; +// +// protected: +// // If "has value" fits into the tail, this must _not_ be +// // `[[no_unique_address]]` so that we fill out the +// // complete `expected` object. +// [[no_unique_address]] conditional_no_unique_address< +// allow_reusing_expected_tail_padding, +// repr>::type repr_; +// }; +// template <class _Tp, class _Err> -class expected { +class __expected_base { + // use named union because [[no_unique_address]] cannot be applied to an unnamed union, + // also guaranteed elision into a potentially-overlapping subobject is unsettled (and + // it's not clear that it's implementable, given that the function is allowed to clobber + // the tail padding) - see https://github.com/itanium-cxx-abi/cxx-abi/issues/107. + union __union_t { + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) + requires(is_copy_constructible_v<_Tp> && is_copy_constructible_v<_Err> && + is_trivially_copy_constructible_v<_Tp> && is_trivially_copy_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(__union_t&&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(__union_t&&) + requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err> && + is_trivially_move_constructible_v<_Tp> && is_trivially_move_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(__union_t&&) = delete; + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(in_place_t, _Args&&... __args) + : __val_(std::forward<_Args>(__args)...) {} + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(unexpect_t, _Args&&... __args) + : __unex_(std::forward<_Args>(__args)...) {} + + template <class _Func, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( + std::__expected_construct_in_place_from_invoke_tag, _Func&& __f, _Args&&... __args) + : __val_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + + template <class _Func, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( + std::__expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) + : __unex_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + + _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() + requires(is_trivially_destructible_v<_Tp> && is_trivially_destructible_v<_Err>) + = default; + + // __repr's destructor handles this + _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() {} + + _LIBCPP_NO_UNIQUE_ADDRESS _Tp __val_; + _LIBCPP_NO_UNIQUE_ADDRESS _Err __unex_; + }; + + static constexpr bool __put_flag_in_tail = __fits_in_tail_padding<__union_t, bool>; + static constexpr bool __allow_reusing_expected_tail_padding = !__put_flag_in_tail; + + struct __repr { + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr() = delete; + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(in_place_t __tag, _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(true) {} + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(unexpect_t __tag, _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(false) {} + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(std::__expected_construct_in_place_from_invoke_tag __tag, + _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(true) {} + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(std::__expected_construct_unexpected_from_invoke_tag __tag, + _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(false) {} + + // The return value of `__make_union` must be constructed in place in the + // `__v` member of `__union_`, relying on guaranteed copy elision. To do + // this, the `__conditional_no_unique_address_invoke_tag` constructor is + // called with a lambda that is immediately called inside + // `__conditional_no_unique_address`'s constructor. + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(bool __has_val, _OtherUnion&& __other) + requires(__allow_reusing_expected_tail_padding) + : __union_(__conditional_no_unique_address_invoke_tag{}, + [&] { return __make_union(__has_val, std::forward<_OtherUnion>(__other)); }), + __has_val_(__has_val) {} + + _LIBCPP_HIDE_FROM_ABI constexpr __repr(const __repr&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(const __repr&) + requires(is_copy_constructible_v<_Tp> && is_copy_constructible_v<_Err> && + is_trivially_copy_constructible_v<_Tp> && is_trivially_copy_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(__repr&&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(__repr&&) + requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err> && + is_trivially_move_constructible_v<_Tp> && is_trivially_move_constructible_v<_Err>) + = default; + + _LIBCPP_HIDE_FROM_ABI constexpr __repr& operator=(const __repr&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr& operator=(__repr&&) = delete; + + _LIBCPP_HIDE_FROM_ABI constexpr ~__repr() + requires(is_trivially_destructible_v<_Tp> && is_trivially_destructible_v<_Err>) + = default; + + _LIBCPP_HIDE_FROM_ABI constexpr ~__repr() + requires(!is_trivially_destructible_v<_Tp> || !is_trivially_destructible_v<_Err>) + { + __destroy_union_member(); + } + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union() + requires(__allow_reusing_expected_tail_padding && + (is_trivially_destructible_v<_Tp> && is_trivially_destructible_v<_Err>)) + { + // Note: Since the destructor of the union is trivial, this does nothing + // except to end the lifetime of the union. + std::destroy_at(&__union_.__v); + } + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union() + requires(__allow_reusing_expected_tail_padding && + (!is_trivially_destructible_v<_Tp> || !is_trivially_destructible_v<_Err>)) + { + __destroy_union_member(); + std::destroy_at(&__union_.__v); + } + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __construct_union(in_place_t, _Args&&... __args) + requires(__allow_reusing_expected_tail_padding) + { + std::construct_at(&__union_.__v, in_place, std::forward<_Args>(__args)...); + __has_val_ = true; + } + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __construct_union(unexpect_t, _Args&&... __args) + requires(__allow_reusing_expected_tail_padding) + { + std::construct_at(&__union_.__v, unexpect, std::forward<_Args>(__args)...); + __has_val_ = false; + } + + private: + template <class, class> + friend class __expected_base; + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union_member() + requires(!is_trivially_destructible_v<_Tp> || !is_trivially_destructible_v<_Err>) + { + if (__has_val_) { + std::destroy_at(std::addressof(__union_.__v.__val_)); + } else { + std::destroy_at(std::addressof(__union_.__v.__unex_)); + } + } + + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI static constexpr __union_t __make_union(bool __has_val, _OtherUnion&& __other) + requires(__allow_reusing_expected_tail_padding) + { + if (__has_val) + return __union_t(in_place, std::forward<_OtherUnion>(__other).__val_); + else + return __union_t(unexpect, std::forward<_OtherUnion>(__other).__unex_); + } + + _LIBCPP_NO_UNIQUE_ADDRESS __conditional_no_unique_address<__put_flag_in_tail, __union_t> __union_; + _LIBCPP_NO_UNIQUE_ADDRESS bool __has_val_; + }; + + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI static constexpr __repr __make_repr(bool __has_val, _OtherUnion&& __other) + requires(__put_flag_in_tail) + { + if (__has_val) + return __repr(in_place, std::forward<_OtherUnion>(__other).__val_); + else + return __repr(unexpect, std::forward<_OtherUnion>(__other).__unex_); + } + +protected: + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __expected_base(_Args&&... __args) + : __repr_(in_place, std::forward<_Args>(__args)...) {} + + // In case we copy/move construct from another `expected` we need to create + // our `expected` so that it either has a value or not, depending on the "has + // value" flag of the other `expected`. To do this without falling back on + // `std::construct_at` we rely on guaranteed copy elision using two helper + // functions `__make_repr` and `__make_union`. There have to be two since + // there are two data layouts with different members being + // `[[no_unique_address]]`. GCC (as of version 13) does not do guaranteed + // copy elision when initializing `[[no_unique_address]]` members. The two + // cases are: + // + // - `__make_repr`: This is used when the "has value" flag lives in the tail + // of the union. In this case, the `__repr` member is _not_ + // `[[no_unique_address]]`. + // - `__make_union`: When the "has value" flag does _not_ fit in the tail of + // the union, the `__repr` member is `[[no_unique_address]]` and the union + // is not. + // + // This constructor "catches" the first case and leaves the second case to + // `__union_t`, its constructors and `__make_union`. + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __expected_base(bool __has_val, _OtherUnion&& __other) + requires(__put_flag_in_tail) + : __repr_(__conditional_no_unique_address_invoke_tag{}, + [&] { return __make_repr(__has_val, std::forward<_OtherUnion>(__other)); }) {} + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy() { + if constexpr (__put_flag_in_tail) + std::destroy_at(&__repr_.__v); + else + __repr_.__v.__destroy_union(); + } + + template <class _Tag, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __construct(_Tag __tag, _Args&&... __args) { + if constexpr (__put_flag_in_tail) + std::construct_at(&__repr_.__v, __tag, std::forward<_Args>(__args)...); + else + __repr_.__v.__construct_union(__tag, std::forward<_Args>(__args)...); + } + + _LIBCPP_HIDE_FROM_ABI constexpr bool __has_val() const { return __repr_.__v.__has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& __union() { return __repr_.__v.__union_.__v; } + _LIBCPP_HIDE_FROM_ABI constexpr const __union_t& __union() const { return __repr_.__v.__union_.__v; } + _LIBCPP_HIDE_FROM_ABI constexpr _Tp& __val() { return __repr_.__v.__union_.__v.__val_; } + _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& __val() const { return __repr_.__v.__union_.__v.__val_; } + _LIBCPP_HIDE_FROM_ABI constexpr _Err& __unex() { return __repr_.__v.__union_.__v.__unex_; } + _LIBCPP_HIDE_FROM_ABI constexpr const _Err& __unex() const { return __repr_.__v.__union_.__v.__unex_; } + +private: + _LIBCPP_NO_UNIQUE_ADDRESS __conditional_no_unique_address<__allow_reusing_expected_tail_padding, __repr> __repr_; +}; + +template <class _Tp, class _Err> +class expected : private __expected_base<_Tp, _Err> { static_assert(!is_reference_v<_Tp> && !is_function_v<_Tp> && !is_same_v<remove_cv_t<_Tp>, in_place_t> && !is_same_v<remove_cv_t<_Tp>, unexpect_t> && !__is_std_unexpected<remove_cv_t<_Tp>>::value && __valid_std_unexpected<_Err>::value, @@ -102,6 +466,8 @@ class expected { template <class _Up, class _OtherErr> friend class expected; + using __base = __expected_base<_Tp, _Err>; + public: using value_type = _Tp; using error_type = _Err; @@ -113,7 +479,7 @@ public: // [expected.object.ctor], constructors _LIBCPP_HIDE_FROM_ABI constexpr expected() noexcept(is_nothrow_default_constructible_v<_Tp>) // strengthened requires is_default_constructible_v<_Tp> - : __union_(std::in_place), __has_val_(true) {} + : __base(in_place) {} _LIBCPP_HIDE_FROM_ABI constexpr expected(const expected&) = delete; @@ -126,7 +492,7 @@ public: is_nothrow_copy_constructible_v<_Tp> && is_nothrow_copy_constructible_v<_Err>) // strengthened requires(is_copy_constructible_v<_Tp> && is_copy_constructible_v<_Err> && !(is_trivially_copy_constructible_v<_Tp> && is_trivially_copy_constructible_v<_Err>)) - : __union_(__other.__has_val_, __other.__union_), __has_val_(__other.__has_val_) {} + : __base(__other.__has_val(), __other.__union()) {} _LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&) requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Tp> && @@ -137,7 +503,7 @@ public: is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_constructible_v<_Err>) requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err> && !(is_trivially_move_constructible_v<_Tp> && is_trivially_move_constructible_v<_Err>)) - : __union_(__other.__has_val_, std::move(__other.__union_)), __has_val_(__other.__has_val_) {} + : __base(__other.__has_val(), std::move(__other.__union())) {} private: template <class _Up, class _OtherErr, class _UfQual, class _OtherErrQual> @@ -162,12 +528,12 @@ private: template <class _Func, class... _Args> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected( std::__expected_construct_in_place_from_invoke_tag __tag, _Func&& __f, _Args&&... __args) - : __union_(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...), __has_val_(true) {} + : __base(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...) {} template <class _Func, class... _Args> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected( std::__expected_construct_unexpected_from_invoke_tag __tag, _Func&& __f, _Args&&... __args) - : __union_(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...) {} public: template <class _Up, class _OtherErr> @@ -177,14 +543,14 @@ public: expected(const expected<_Up, _OtherErr>& __other) noexcept( is_nothrow_constructible_v<_Tp, const _Up&> && is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened - : __union_(__other.__has_val_, __other.__union_), __has_val_(__other.__has_val_) {} + : __base(__other.__has_val(), __other.__union()) {} template <class _Up, class _OtherErr> requires __can_convert<_Up, _OtherErr, _Up, _OtherErr>::value _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_Up, _Tp> || !is_convertible_v<_OtherErr, _Err>) expected(expected<_Up, _OtherErr>&& __other) noexcept( is_nothrow_constructible_v<_Tp, _Up> && is_nothrow_constructible_v<_Err, _OtherErr>) // strengthened - : __union_(__other.__has_val_, std::move(__other.__union_)), __has_val_(__other.__has_val_) {} + : __base(__other.__has_val(), std::move(__other.__union())) {} template <class _Up = _Tp> requires(!is_same_v<remove_cvref_t<_Up>, in_place_t> && !is_same_v<expected, remove_cvref_t<_Up>> && @@ -192,80 +558,67 @@ public: (!is_same_v<remove_cv_t<_Tp>, bool> || !__is_std_expected<remove_cvref_t<_Up>>::value)) _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_Up, _Tp>) expected(_Up&& __u) noexcept(is_nothrow_constructible_v<_Tp, _Up>) // strengthened - : __union_(std::in_place, std::forward<_Up>(__u)), __has_val_(true) {} + : __base(in_place, std::forward<_Up>(__u)) {} template <class _OtherErr> requires is_constructible_v<_Err, const _OtherErr&> _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<const _OtherErr&, _Err>) expected( const unexpected<_OtherErr>& __unex) noexcept(is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened - : __union_(std::unexpect, __unex.error()), __has_val_(false) {} + : __base(unexpect, __unex.error()) {} template <class _OtherErr> requires is_constructible_v<_Err, _OtherErr> _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherErr, _Err>) expected(unexpected<_OtherErr>&& __unex) noexcept(is_nothrow_constructible_v<_Err, _OtherErr>) // strengthened - : __union_(std::unexpect, std::move(__unex.error())), __has_val_(false) {} + : __base(unexpect, std::move(__unex.error())) {} template <class... _Args> requires is_constructible_v<_Tp, _Args...> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Tp, _Args...>) // strengthened - : __union_(std::in_place, std::forward<_Args>(__args)...), __has_val_(true) {} + : __base(in_place, std::forward<_Args>(__args)...) {} template <class _Up, class... _Args> requires is_constructible_v< _Tp, initializer_list<_Up>&, _Args... > _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t, initializer_list<_Up> __il, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>) // strengthened - : __union_(std::in_place, __il, std::forward<_Args>(__args)...), __has_val_(true) {} + : __base(in_place, __il, std::forward<_Args>(__args)...) {} template <class... _Args> requires is_constructible_v<_Err, _Args...> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(unexpect_t, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Err, _Args...>) // strengthened - : __union_(std::unexpect, std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(unexpect, std::forward<_Args>(__args)...) {} template <class _Up, class... _Args> requires is_constructible_v< _Err, initializer_list<_Up>&, _Args... > _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(unexpect_t, initializer_list<_Up> __il, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Err, initializer_list<_Up>&, _Args...>) // strengthened - : __union_(std::unexpect, __il, std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(unexpect, __il, std::forward<_Args>(__args)...) {} // [expected.object.dtor], destructor - _LIBCPP_HIDE_FROM_ABI constexpr ~expected() - requires(is_trivially_destructible_v<_Tp> && is_trivially_destructible_v<_Err>) - = default; - - _LIBCPP_HIDE_FROM_ABI constexpr ~expected() - requires(!is_trivially_destructible_v<_Tp> || !is_trivially_destructible_v<_Err>) - { - if (__has_val_) { - std::destroy_at(std::addressof(__union_.__val_)); - } else { - std::destroy_at(std::addressof(__union_.__unex_)); - } - } + _LIBCPP_HIDE_FROM_ABI constexpr ~expected() = default; private: - template <class _T1, class _T2, class... _Args> - _LIBCPP_HIDE_FROM_ABI static constexpr void __reinit_expected(_T1& __newval, _T2& __oldval, _Args&&... __args) { + template <class _Tag, class _OtherTag, class _T1, class _T2, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __reinit_expected(_T2& __oldval, _Args&&... __args) { if constexpr (is_nothrow_constructible_v<_T1, _Args...>) { - std::destroy_at(std::addressof(__oldval)); - std::construct_at(std::addressof(__newval), std::forward<_Args>(__args)...); + this->__destroy(); + this->__construct(_Tag{}, std::forward<_Args>(__args)...); } else if constexpr (is_nothrow_move_constructible_v<_T1>) { _T1 __tmp(std::forward<_Args>(__args)...); - std::destroy_at(std::addressof(__oldval)); - std::construct_at(std::addressof(__newval), std::move(__tmp)); + this->__destroy(); + this->__construct(_Tag{}, std::move(__tmp)); } else { static_assert( is_nothrow_move_constructible_v<_T2>, "To provide strong exception guarantee, T2 has to satisfy `is_nothrow_move_constructible_v` so that it can " "be reverted to the previous state in case an exception is thrown during the assignment."); _T2 __tmp(std::move(__oldval)); - std::destroy_at(std::addressof(__oldval)); - auto __trans = - std::__make_exception_guard([&] { std::construct_at(std::addressof(__oldval), std::move(__tmp)); }); - std::construct_at(std::addressof(__newval), std::forward<_Args>(__args)...); + this->__destroy(); + auto __trans = std::__make_exception_guard([&] { this->__construct(_OtherTag{}, std::move(__tmp)); }); + this->__construct(_Tag{}, std::forward<_Args>(__args)...); __trans.__complete(); } } @@ -281,17 +634,15 @@ public: is_copy_constructible_v<_Err> && (is_nothrow_move_constructible_v<_Tp> || is_nothrow_move_constructible_v<_Err>)) { - if (__has_val_ && __rhs.__has_val_) { - __union_.__val_ = __rhs.__union_.__val_; - } else if (__has_val_) { - __reinit_expected(__union_.__unex_, __union_.__val_, __rhs.__union_.__unex_); - } else if (__rhs.__has_val_) { - __reinit_expected(__union_.__val_, __union_.__unex_, __rhs.__union_.__val_); + if (this->__has_val() && __rhs.__has_val()) { + this->__val() = __rhs.__val(); + } else if (this->__has_val()) { + __reinit_expected<unexpect_t, in_place_t, _Err, _Tp>(this->__val(), __rhs.__unex()); + } else if (__rhs.__has_val()) { + __reinit_expected<in_place_t, unexpect_t, _Tp, _Err>(this->__unex(), __rhs.__val()); } else { - __union_.__unex_ = __rhs.__union_.__unex_; + this->__unex() = __rhs.__unex(); } - // note: only reached if no exception+rollback was done inside __reinit_expected - __has_val_ = __rhs.__has_val_; return *this; } @@ -302,17 +653,15 @@ public: is_move_assignable_v<_Err> && (is_nothrow_move_constructible_v<_Tp> || is_nothrow_move_constructible_v<_Err>)) { - if (__has_val_ && __rhs.__has_val_) { - __union_.__val_ = std::move(__rhs.__union_.__val_); - } else if (__has_val_) { - __reinit_expected(__union_.__unex_, __union_.__val_, std::move(__rhs.__union_.__unex_)); - } else if (__rhs.__has_val_) { - __reinit_expected(__union_.__val_, __union_.__unex_, std::move(__rhs.__union_.__val_)); + if (this->__has_val() && __rhs.__has_val()) { + this->__val() = std::move(__rhs.__val()); + } else if (this->__has_val()) { + __reinit_expected<unexpect_t, in_place_t, _Err, _Tp>(this->__val(), std::move(__rhs.__unex())); + } else if (__rhs.__has_val()) { + __reinit_expected<in_place_t, unexpect_t, _Tp, _Err>(this->__unex(), std::move(__rhs.__val())); } else { - __union_.__unex_ = std::move(__rhs.__union_.__unex_); + this->__unex() = std::move(__rhs.__unex()); } - // note: only reached if no exception+rollback was done inside __reinit_expected - __has_val_ = __rhs.__has_val_; return *this; } @@ -323,11 +672,10 @@ public: (is_nothrow_constructible_v<_Tp, _Up> || is_nothrow_move_constructible_v<_Tp> || is_nothrow_move_constructible_v<_Err>)) { - if (__has_val_) { - __union_.__val_ = std::forward<_Up>(__v); + if (this->__has_val()) { + this->__val() = std::forward<_Up>(__v); } else { - __reinit_expected(__union_.__val_, __union_.__unex_, std::forward<_Up>(__v)); - __has_val_ = true; + __reinit_expected<in_place_t, unexpect_t, _Tp, _Err>(this->__unex(), std::forward<_Up>(__v)); } return *this; } @@ -346,11 +694,10 @@ public: template <class _OtherErr> requires(__can_assign_from_unexpected<const _OtherErr&>) _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(const unexpected<_OtherErr>& __un) { - if (__has_val_) { - __reinit_expected(__union_.__unex_, __union_.__val_, __un.error()); - __has_val_ = false; + if (this->__has_val()) { + __reinit_expected<unexpect_t, in_place_t, _Err, _Tp>(this->__val(), __un.error()); } else { - __union_.__unex_ = __un.error(); + this->__unex() = __un.error(); } return *this; } @@ -358,11 +705,10 @@ public: template <class _OtherErr> requires(__can_assign_from_unexpected<_OtherErr>) _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(unexpected<_OtherErr>&& __un) { - if (__has_val_) { - __reinit_expected(__union_.__unex_, __union_.__val_, std::move(__un.error())); - __has_val_ = false; + if (this->__has_val()) { + __reinit_expected<unexpect_t, in_place_t, _Err, _Tp>(this->__val(), std::move(__un.error())); } else { - __union_.__unex_ = std::move(__un.error()); + this->__unex() = std::move(__un.error()); } return *this; } @@ -370,27 +716,17 @@ public: template <class... _Args> requires is_nothrow_constructible_v<_Tp, _Args...> _LIBCPP_HIDE_FROM_ABI constexpr _Tp& emplace(_Args&&... __args) noexcept { - if (__has_val_) { - std::destroy_at(std::addressof(__union_.__val_)); - } else { - std::destroy_at(std::addressof(__union_.__unex_)); - } - std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...); - __has_val_ = true; - return __union_.__val_; + this->__destroy(); + this->__construct(in_place, std::forward<_Args>(__args)...); + return this->__val(); } template <class _Up, class... _Args> - requires is_nothrow_constructible_v< _Tp, initializer_list<_Up>&, _Args... > + requires is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...> _LIBCPP_HIDE_FROM_ABI constexpr _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) noexcept { - if (__has_val_) { - std::destroy_at(std::addressof(__union_.__val_)); - } else { - std::destroy_at(std::addressof(__union_.__unex_)); - } - std::construct_at(std::addressof(__union_.__val_), __il, std::forward<_Args>(__args)...); - __has_val_ = true; - return __union_.__val_; + this->__destroy(); + this->__construct(in_place, __il, std::forward<_Args>(__args)...); + return this->__val(); } public: @@ -402,48 +738,42 @@ public: is_move_constructible_v<_Err> && (is_nothrow_move_constructible_v<_Tp> || is_nothrow_move_constructible_v<_Err>)) { - auto __swap_val_unex_impl = [&](expected& __with_val, expected& __with_err) { + auto __swap_val_unex_impl = [](expected& __with_val, expected& __with_err) { if constexpr (is_nothrow_move_constructible_v<_Err>) { - _Err __tmp(std::move(__with_err.__union_.__unex_)); - std::destroy_at(std::addressof(__with_err.__union_.__unex_)); - auto __trans = std::__make_exception_guard([&] { - std::construct_at(std::addressof(__with_err.__union_.__unex_), std::move(__tmp)); - }); - std::construct_at(std::addressof(__with_err.__union_.__val_), std::move(__with_val.__union_.__val_)); + _Err __tmp(std::move(__with_err.__unex())); + __with_err.__destroy(); + auto __trans = std::__make_exception_guard([&] { __with_err.__construct(unexpect, std::move(__tmp)); }); + __with_err.__construct(in_place, std::move(__with_val.__val())); __trans.__complete(); - std::destroy_at(std::addressof(__with_val.__union_.__val_)); - std::construct_at(std::addressof(__with_val.__union_.__unex_), std::move(__tmp)); + __with_val.__destroy(); + __with_val.__construct(unexpect, std::move(__tmp)); } else { static_assert(is_nothrow_move_constructible_v<_Tp>, "To provide strong exception guarantee, Tp has to satisfy `is_nothrow_move_constructible_v` so " "that it can be reverted to the previous state in case an exception is thrown during swap."); - _Tp __tmp(std::move(__with_val.__union_.__val_)); - std::destroy_at(std::addressof(__with_val.__union_.__val_)); - auto __trans = std::__make_exception_guard([&] { - std::construct_at(std::addressof(__with_val.__union_.__val_), std::move(__tmp)); - }); - std::construct_at(std::addressof(__with_val.__union_.__unex_), std::move(__with_err.__union_.__unex_)); + _Tp __tmp(std::move(__with_val.__val())); + __with_val.__destroy(); + auto __trans = std::__make_exception_guard([&] { __with_val.__construct(in_place, std::move(__tmp)); }); + __with_val.__construct(unexpect, std::move(__with_err.__unex())); __trans.__complete(); - std::destroy_at(std::addressof(__with_err.__union_.__unex_)); - std::construct_at(std::addressof(__with_err.__union_.__val_), std::move(__tmp)); + __with_err.__destroy(); + __with_err.__construct(in_place, std::move(__tmp)); } - __with_val.__has_val_ = false; - __with_err.__has_val_ = true; }; - if (__has_val_) { - if (__rhs.__has_val_) { + if (this->__has_val()) { + if (__rhs.__has_val()) { using std::swap; - swap(__union_.__val_, __rhs.__union_.__val_); + swap(this->__val(), __rhs.__val()); } else { __swap_val_unex_impl(*this, __rhs); } } else { - if (__rhs.__has_val_) { + if (__rhs.__has_val()) { __swap_val_unex_impl(__rhs, *this); } else { using std::swap; - swap(__union_.__unex_, __rhs.__union_.__unex_); + swap(this->__unex(), __rhs.__unex()); } } } @@ -456,105 +786,115 @@ public: // [expected.object.obs], observers _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* operator->() const noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator-> requires the expected to contain a value"); - return std::addressof(__union_.__val_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator-> requires the expected to contain a value"); + return std::addressof(this->__val()); } _LIBCPP_HIDE_FROM_ABI constexpr _Tp* operator->() noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator-> requires the expected to contain a value"); - return std::addressof(__union_.__val_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator-> requires the expected to contain a value"); + return std::addressof(this->__val()); } _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& operator*() const& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator* requires the expected to contain a value"); - return __union_.__val_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator* requires the expected to contain a value"); + return this->__val(); } _LIBCPP_HIDE_FROM_ABI constexpr _Tp& operator*() & noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator* requires the expected to contain a value"); - return __union_.__val_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator* requires the expected to contain a value"); + return this->__val(); } _LIBCPP_HIDE_FROM_ABI constexpr const _Tp&& operator*() const&& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator* requires the expected to contain a value"); - return std::move(__union_.__val_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator* requires the expected to contain a value"); + return std::move(this->__val()); } _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& operator*() && noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator* requires the expected to contain a value"); - return std::move(__union_.__val_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator* requires the expected to contain a value"); + return std::move(this->__val()); } - _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return this->__has_val(); } - _LIBCPP_HIDE_FROM_ABI constexpr bool has_value() const noexcept { return __has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr bool has_value() const noexcept { return this->__has_val(); } _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& value() const& { static_assert(is_copy_constructible_v<_Err>, "error_type has to be copy constructible"); - if (!__has_val_) { + if (!this->__has_val()) { std::__throw_bad_expected_access<_Err>(std::as_const(error())); } - return __union_.__val_; + return this->__val(); } _LIBCPP_HIDE_FROM_ABI constexpr _Tp& value() & { static_assert(is_copy_constructible_v<_Err>, "error_type has to be copy constructible"); - if (!__has_val_) { + if (!this->__has_val()) { std::__throw_bad_expected_access<_Err>(std::as_const(error())); } - return __union_.__val_; + return this->__val(); } _LIBCPP_HIDE_FROM_ABI constexpr const _Tp&& value() const&& { static_assert(is_copy_constructible_v<_Err> && is_constructible_v<_Err, decltype(std::move(error()))>, "error_type has to be both copy constructible and constructible from decltype(std::move(error()))"); - if (!__has_val_) { + if (!this->__has_val()) { std::__throw_bad_expected_access<_Err>(std::move(error())); } - return std::move(__union_.__val_); + return std::move(this->__val()); } _LIBCPP_HIDE_FROM_ABI constexpr _Tp&& value() && { static_assert(is_copy_constructible_v<_Err> && is_constructible_v<_Err, decltype(std::move(error()))>, "error_type has to be both copy constructible and constructible from decltype(std::move(error()))"); - if (!__has_val_) { + if (!this->__has_val()) { std::__throw_bad_expected_access<_Err>(std::move(error())); } - return std::move(__union_.__val_); + return std::move(this->__val()); } _LIBCPP_HIDE_FROM_ABI constexpr const _Err& error() const& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return __union_.__unex_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return this->__unex(); } _LIBCPP_HIDE_FROM_ABI constexpr _Err& error() & noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return __union_.__unex_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return this->__unex(); } _LIBCPP_HIDE_FROM_ABI constexpr const _Err&& error() const&& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return std::move(__union_.__unex_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return std::move(this->__unex()); } _LIBCPP_HIDE_FROM_ABI constexpr _Err&& error() && noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return std::move(__union_.__unex_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return std::move(this->__unex()); } template <class _Up> _LIBCPP_HIDE_FROM_ABI constexpr _Tp value_or(_Up&& __v) const& { static_assert(is_copy_constructible_v<_Tp>, "value_type has to be copy constructible"); static_assert(is_convertible_v<_Up, _Tp>, "argument has to be convertible to value_type"); - return __has_val_ ? __union_.__val_ : static_cast<_Tp>(std::forward<_Up>(__v)); + return this->__has_val() ? this->__val() : static_cast<_Tp>(std::forward<_Up>(__v)); } template <class _Up> _LIBCPP_HIDE_FROM_ABI constexpr _Tp value_or(_Up&& __v) && { static_assert(is_move_constructible_v<_Tp>, "value_type has to be move constructible"); static_assert(is_convertible_v<_Up, _Tp>, "argument has to be convertible to value_type"); - return __has_val_ ? std::move(__union_.__val_) : static_cast<_Tp>(std::forward<_Up>(__v)); + return this->__has_val() ? std::move(this->__val()) : static_cast<_Tp>(std::forward<_Up>(__v)); } template <class _Up = _Err> @@ -584,7 +924,7 @@ public: static_assert(is_same_v<typename _Up::error_type, _Err>, "The result of f(**this) must have the same error_type as this expected"); if (has_value()) { - return std::invoke(std::forward<_Func>(__f), __union_.__val_); + return std::invoke(std::forward<_Func>(__f), this->__val()); } return _Up(unexpect, error()); } @@ -597,7 +937,7 @@ public: static_assert(is_same_v<typename _Up::error_type, _Err>, "The result of f(**this) must have the same error_type as this expected"); if (has_value()) { - return std::invoke(std::forward<_Func>(__f), __union_.__val_); + return std::invoke(std::forward<_Func>(__f), this->__val()); } return _Up(unexpect, error()); } @@ -611,7 +951,7 @@ public: static_assert(is_same_v<typename _Up::error_type, _Err>, "The result of f(std::move(**this)) must have the same error_type as this expected"); if (has_value()) { - return std::invoke(std::forward<_Func>(__f), std::move(__union_.__val_)); + return std::invoke(std::forward<_Func>(__f), std::move(this->__val())); } return _Up(unexpect, std::move(error())); } @@ -625,7 +965,7 @@ public: static_assert(is_same_v<typename _Up::error_type, _Err>, "The result of f(std::move(**this)) must have the same error_type as this expected"); if (has_value()) { - return std::invoke(std::forward<_Func>(__f), std::move(__union_.__val_)); + return std::invoke(std::forward<_Func>(__f), std::move(this->__val())); } return _Up(unexpect, std::move(error())); } @@ -638,7 +978,7 @@ public: static_assert(is_same_v<typename _Gp::value_type, _Tp>, "The result of f(error()) must have the same value_type as this expected"); if (has_value()) { - return _Gp(in_place, __union_.__val_); + return _Gp(in_place, this->__val()); } return std::invoke(std::forward<_Func>(__f), error()); } @@ -651,7 +991,7 @@ public: static_assert(is_same_v<typename _Gp::value_type, _Tp>, "The result of f(error()) must have the same value_type as this expected"); if (has_value()) { - return _Gp(in_place, __union_.__val_); + return _Gp(in_place, this->__val()); } return std::invoke(std::forward<_Func>(__f), error()); } @@ -665,7 +1005,7 @@ public: static_assert(is_same_v<typename _Gp::value_type, _Tp>, "The result of f(std::move(error())) must have the same value_type as this expected"); if (has_value()) { - return _Gp(in_place, std::move(__union_.__val_)); + return _Gp(in_place, std::move(this->__val())); } return std::invoke(std::forward<_Func>(__f), std::move(error())); } @@ -679,7 +1019,7 @@ public: static_assert(is_same_v<typename _Gp::value_type, _Tp>, "The result of f(std::move(error())) must have the same value_type as this expected"); if (has_value()) { - return _Gp(in_place, std::move(__union_.__val_)); + return _Gp(in_place, std::move(this->__val())); } return std::invoke(std::forward<_Func>(__f), std::move(error())); } @@ -693,9 +1033,9 @@ public: } if constexpr (!is_void_v<_Up>) { return expected<_Up, _Err>( - __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), __union_.__val_); + __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), this->__val()); } else { - std::invoke(std::forward<_Func>(__f), __union_.__val_); + std::invoke(std::forward<_Func>(__f), this->__val()); return expected<_Up, _Err>(); } } @@ -709,9 +1049,9 @@ public: } if constexpr (!is_void_v<_Up>) { return expected<_Up, _Err>( - __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), __union_.__val_); + __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), this->__val()); } else { - std::invoke(std::forward<_Func>(__f), __union_.__val_); + std::invoke(std::forward<_Func>(__f), this->__val()); return expected<_Up, _Err>(); } } @@ -725,9 +1065,9 @@ public: } if constexpr (!is_void_v<_Up>) { return expected<_Up, _Err>( - __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), std::move(__union_.__val_)); + __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), std::move(this->__val())); } else { - std::invoke(std::forward<_Func>(__f), std::move(__union_.__val_)); + std::invoke(std::forward<_Func>(__f), std::move(this->__val())); return expected<_Up, _Err>(); } } @@ -741,9 +1081,9 @@ public: } if constexpr (!is_void_v<_Up>) { return expected<_Up, _Err>( - __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), std::move(__union_.__val_)); + __expected_construct_in_place_from_invoke_tag{}, std::forward<_Func>(__f), std::move(this->__val())); } else { - std::invoke(std::forward<_Func>(__f), std::move(__union_.__val_)); + std::invoke(std::forward<_Func>(__f), std::move(this->__val())); return expected<_Up, _Err>(); } } @@ -755,7 +1095,7 @@ public: static_assert(__valid_std_unexpected<_Gp>::value, "The result of f(error()) must be a valid template argument for unexpected"); if (has_value()) { - return expected<_Tp, _Gp>(in_place, __union_.__val_); + return expected<_Tp, _Gp>(in_place, this->__val()); } return expected<_Tp, _Gp>(__expected_construct_unexpected_from_invoke_tag{}, std::forward<_Func>(__f), error()); } @@ -767,7 +1107,7 @@ public: static_assert(__valid_std_unexpected<_Gp>::value, "The result of f(error()) must be a valid template argument for unexpected"); if (has_value()) { - return expected<_Tp, _Gp>(in_place, __union_.__val_); + return expected<_Tp, _Gp>(in_place, this->__val()); } return expected<_Tp, _Gp>(__expected_construct_unexpected_from_invoke_tag{}, std::forward<_Func>(__f), error()); } @@ -779,7 +1119,7 @@ public: static_assert(__valid_std_unexpected<_Gp>::value, "The result of f(std::move(error())) must be a valid template argument for unexpected"); if (has_value()) { - return expected<_Tp, _Gp>(in_place, std::move(__union_.__val_)); + return expected<_Tp, _Gp>(in_place, std::move(this->__val())); } return expected<_Tp, _Gp>( __expected_construct_unexpected_from_invoke_tag{}, std::forward<_Func>(__f), std::move(error())); @@ -792,7 +1132,7 @@ public: static_assert(__valid_std_unexpected<_Gp>::value, "The result of f(std::move(error())) must be a valid template argument for unexpected"); if (has_value()) { - return expected<_Tp, _Gp>(in_place, std::move(__union_.__val_)); + return expected<_Tp, _Gp>(in_place, std::move(this->__val())); } return expected<_Tp, _Gp>( __expected_construct_unexpected_from_invoke_tag{}, std::forward<_Func>(__f), std::move(error())); @@ -802,123 +1142,220 @@ public: template <class _T2, class _E2> requires(!is_void_v<_T2>) _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const expected<_T2, _E2>& __y) { - if (__x.__has_val_ != __y.__has_val_) { + if (__x.__has_val() != __y.__has_val()) { return false; } else { - if (__x.__has_val_) { - return __x.__union_.__val_ == __y.__union_.__val_; + if (__x.__has_val()) { + return __x.__val() == __y.__val(); } else { - return __x.__union_.__unex_ == __y.__union_.__unex_; + return __x.__unex() == __y.__unex(); } } } template <class _T2> _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const _T2& __v) { - return __x.__has_val_ && static_cast<bool>(__x.__union_.__val_ == __v); + return __x.__has_val() && static_cast<bool>(__x.__val() == __v); } template <class _E2> _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const unexpected<_E2>& __e) { - return !__x.__has_val_ && static_cast<bool>(__x.__union_.__unex_ == __e.error()); + return !__x.__has_val() && static_cast<bool>(__x.__unex() == __e.error()); } +}; -private: - template <class _ValueType, class _ErrorType> +template <class _Err> +class __expected_void_base { + struct __empty_t {}; + // use named union because [[no_unique_address]] cannot be applied to an unnamed union, + // also guaranteed elision into a potentially-overlapping subobject is unsettled (and + // it's not clear that it's implementable, given that the function is allowed to clobber + // the tail padding) - see https://github.com/itanium-cxx-abi/cxx-abi/issues/107. union __union_t { - template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::in_place_t, _Args&&... __args) - : __val_(std::forward<_Args>(__args)...) {} + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) + requires(is_copy_constructible_v<_Err> && is_trivially_copy_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(__union_t&&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t(__union_t&&) + requires(is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(__union_t&&) = delete; + + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(in_place_t) : __empty_() {} template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args) + _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(unexpect_t, _Args&&... __args) : __unex_(std::forward<_Args>(__args)...) {} template <class _Func, class... _Args> _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - std::__expected_construct_in_place_from_invoke_tag, _Func&& __f, _Args&&... __args) - : __val_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} - - template <class _Func, class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - std::__expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) + __expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) : __unex_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} - template <class _Union> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) { - if (__has_val) - std::construct_at(std::addressof(__val_), std::forward<_Union>(__other).__val_); - else - std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_); - } - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(is_trivially_destructible_v<_ValueType> && is_trivially_destructible_v<_ErrorType>) + requires(is_trivially_destructible_v<_Err>) = default; - // the expected's destructor handles this - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() {} + // __repr's destructor handles this + _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() + requires(!is_trivially_destructible_v<_Err>) + {} - _ValueType __val_; - _ErrorType __unex_; + _LIBCPP_NO_UNIQUE_ADDRESS __empty_t __empty_; + _LIBCPP_NO_UNIQUE_ADDRESS _Err __unex_; }; - // use named union because [[no_unique_address]] cannot be applied to an unnamed union, - // also guaranteed elision into a potentially-overlapping subobject is unsettled (and - // it's not clear that it's implementable, given that the function is allowed to clobber - // the tail padding) - see https://github.com/itanium-cxx-abi/cxx-abi/issues/107. - template <class _ValueType, class _ErrorType> - requires(is_trivially_move_constructible_v<_ValueType> && is_trivially_move_constructible_v<_ErrorType>) - union __union_t<_ValueType, _ErrorType> { - _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) = default; - _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = default; + static constexpr bool __put_flag_in_tail = __fits_in_tail_padding<__union_t, bool>; + static constexpr bool __allow_reusing_expected_tail_padding = !__put_flag_in_tail; + + struct __repr { + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr() = delete; template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::in_place_t, _Args&&... __args) - : __val_(std::forward<_Args>(__args)...) {} + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(in_place_t __tag) : __union_(in_place, __tag), __has_val_(true) {} template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args) - : __unex_(std::forward<_Args>(__args)...) {} + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(unexpect_t __tag, _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(false) {} - template <class _Func, class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - std::__expected_construct_in_place_from_invoke_tag, _Func&& __f, _Args&&... __args) - : __val_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(std::__expected_construct_unexpected_from_invoke_tag __tag, + _Args&&... __args) + : __union_(in_place, __tag, std::forward<_Args>(__args)...), __has_val_(false) {} + + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __repr(bool __has_val, _OtherUnion&& __other) + requires(__allow_reusing_expected_tail_padding) + : __union_(__conditional_no_unique_address_invoke_tag{}, + [&] { return __make_union(__has_val, std::forward<_OtherUnion>(__other)); }), + __has_val_(__has_val) {} + + _LIBCPP_HIDE_FROM_ABI constexpr __repr(const __repr&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(const __repr&) + requires(is_copy_constructible_v<_Err> && is_trivially_copy_constructible_v<_Err>) + = default; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(__repr&&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr(__repr&&) + requires(is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Err>) + = default; - template <class _Func, class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - std::__expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) - : __unex_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} + _LIBCPP_HIDE_FROM_ABI constexpr __repr& operator=(const __repr&) = delete; + _LIBCPP_HIDE_FROM_ABI constexpr __repr& operator=(__repr&&) = delete; + + _LIBCPP_HIDE_FROM_ABI constexpr ~__repr() + requires(is_trivially_destructible_v<_Err>) + = default; - template <class _Union> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) { + _LIBCPP_HIDE_FROM_ABI constexpr ~__repr() + requires(!is_trivially_destructible_v<_Err>) + { + __destroy_union_member(); + } + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union() + requires(__allow_reusing_expected_tail_padding && is_trivially_destructible_v<_Err>) + { + std::destroy_at(&__union_.__v); + } + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union() + requires(__allow_reusing_expected_tail_padding && !is_trivially_destructible_v<_Err>) + { + __destroy_union_member(); + std::destroy_at(&__union_.__v); + } + + _LIBCPP_HIDE_FROM_ABI constexpr void __construct_union(in_place_t) + requires(__allow_reusing_expected_tail_padding) + { + std::construct_at(&__union_.__v, in_place); + __has_val_ = true; + } + + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __construct_union(unexpect_t, _Args&&... __args) + requires(__allow_reusing_expected_tail_padding) + { + std::construct_at(&__union_.__v, unexpect, std::forward<_Args>(__args)...); + __has_val_ = false; + } + + private: + template <class> + friend class __expected_void_base; + + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy_union_member() + requires(!is_trivially_destructible_v<_Err>) + { + if (!__has_val_) + std::destroy_at(std::addressof(__union_.__v.__unex_)); + } + + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI static constexpr __union_t __make_union(bool __has_val, _OtherUnion&& __other) + requires(__allow_reusing_expected_tail_padding) + { if (__has_val) - std::construct_at(std::addressof(__val_), std::forward<_Union>(__other).__val_); + return __union_t(in_place); else - std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_); + return __union_t(unexpect, std::forward<_OtherUnion>(__other).__unex_); } - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(is_trivially_destructible_v<_ValueType> && is_trivially_destructible_v<_ErrorType>) - = default; + _LIBCPP_NO_UNIQUE_ADDRESS __conditional_no_unique_address<__put_flag_in_tail, __union_t> __union_; + _LIBCPP_NO_UNIQUE_ADDRESS bool __has_val_; + }; - // the expected's destructor handles this - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(!is_trivially_destructible_v<_ValueType> || !is_trivially_destructible_v<_ErrorType>) - {} + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI static constexpr __repr __make_repr(bool __has_val, _OtherUnion&& __other) + requires(__put_flag_in_tail) + { + if (__has_val) + return __repr(in_place); + else + return __repr(unexpect, std::forward<_OtherUnion>(__other).__unex_); + } - _LIBCPP_NO_UNIQUE_ADDRESS _ValueType __val_; - _LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_; - }; +protected: + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __expected_void_base(_Args&&... __args) + : __repr_(in_place, std::forward<_Args>(__args)...) {} + + template <class _OtherUnion> + _LIBCPP_HIDE_FROM_ABI constexpr explicit __expected_void_base(bool __has_val, _OtherUnion&& __other) + requires(__put_flag_in_tail) + : __repr_(__conditional_no_unique_address_invoke_tag{}, + [&] { return __make_repr(__has_val, std::forward<_OtherUnion>(__other)); }) {} - _LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Tp, _Err> __union_; - bool __has_val_; + _LIBCPP_HIDE_FROM_ABI constexpr void __destroy() { + if constexpr (__put_flag_in_tail) + std::destroy_at(&__repr_.__v); + else + __repr_.__v.__destroy_union(); + } + + template <class _Tag, class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __construct(_Tag __tag, _Args&&... __args) { + if constexpr (__put_flag_in_tail) + std::construct_at(&__repr_.__v, __tag, std::forward<_Args>(__args)...); + else + __repr_.__v.__construct_union(__tag, std::forward<_Args>(__args)...); + } + + _LIBCPP_HIDE_FROM_ABI constexpr bool __has_val() const { return __repr_.__v.__has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr __union_t& __union() { return __repr_.__v.__union_.__v; } + _LIBCPP_HIDE_FROM_ABI constexpr const __union_t& __union() const { return __repr_.__v.__union_.__v; } + _LIBCPP_HIDE_FROM_ABI constexpr _Err& __unex() { return __repr_.__v.__union_.__v.__unex_; } + _LIBCPP_HIDE_FROM_ABI constexpr const _Err& __unex() const { return __repr_.__v.__union_.__v.__unex_; } + +private: + _LIBCPP_NO_UNIQUE_ADDRESS __conditional_no_unique_address<__allow_reusing_expected_tail_padding, __repr> __repr_; }; template <class _Tp, class _Err> requires is_void_v<_Tp> -class expected<_Tp, _Err> { +class expected<_Tp, _Err> : private __expected_void_base<_Err> { static_assert(__valid_std_unexpected<_Err>::value, "[expected.void.general] A program that instantiates expected<T, E> with a E that is not a " "valid argument for unexpected<E> is ill-formed"); @@ -935,6 +1372,8 @@ class expected<_Tp, _Err> { _Not<is_constructible<unexpected<_Err>, const expected<_Up, _OtherErr>&>>, _Not<is_constructible<unexpected<_Err>, const expected<_Up, _OtherErr>>>>; + using __base = __expected_void_base<_Err>; + public: using value_type = _Tp; using error_type = _Err; @@ -944,7 +1383,7 @@ public: using rebind = expected<_Up, error_type>; // [expected.void.ctor], constructors - _LIBCPP_HIDE_FROM_ABI constexpr expected() noexcept : __has_val_(true) {} + _LIBCPP_HIDE_FROM_ABI constexpr expected() noexcept : __base(in_place) {} _LIBCPP_HIDE_FROM_ABI constexpr expected(const expected&) = delete; @@ -955,7 +1394,7 @@ public: _LIBCPP_HIDE_FROM_ABI constexpr expected(const expected& __rhs) noexcept( is_nothrow_copy_constructible_v<_Err>) // strengthened requires(is_copy_constructible_v<_Err> && !is_trivially_copy_constructible_v<_Err>) - : __union_(__rhs.__has_val_, __rhs.__union_), __has_val_(__rhs.__has_val_) {} + : __base(__rhs.__has_val(), __rhs.__union()) {} _LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&) requires(is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Err>) @@ -963,93 +1402,93 @@ public: _LIBCPP_HIDE_FROM_ABI constexpr expected(expected&& __rhs) noexcept(is_nothrow_move_constructible_v<_Err>) requires(is_move_constructible_v<_Err> && !is_trivially_move_constructible_v<_Err>) - : __union_(__rhs.__has_val_, std::move(__rhs.__union_)), __has_val_(__rhs.__has_val_) {} + : __base(__rhs.__has_val(), std::move(__rhs.__union())) {} template <class _Up, class _OtherErr> requires __can_convert<_Up, _OtherErr, const _OtherErr&>::value _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<const _OtherErr&, _Err>) expected(const expected<_Up, _OtherErr>& __rhs) noexcept( is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened - : __union_(__rhs.__has_val_, __rhs.__union_), __has_val_(__rhs.__has_val_) {} + : __base(__rhs.__has_val(), __rhs.__union()) {} template <class _Up, class _OtherErr> requires __can_convert<_Up, _OtherErr, _OtherErr>::value _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherErr, _Err>) expected(expected<_Up, _OtherErr>&& __rhs) noexcept(is_nothrow_constructible_v<_Err, _OtherErr>) // strengthened - : __union_(__rhs.__has_val_, std::move(__rhs.__union_)), __has_val_(__rhs.__has_val_) {} + : __base(__rhs.__has_val(), std::move(__rhs.__union())) {} template <class _OtherErr> requires is_constructible_v<_Err, const _OtherErr&> _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<const _OtherErr&, _Err>) expected( const unexpected<_OtherErr>& __unex) noexcept(is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened - : __union_(std::unexpect, __unex.error()), __has_val_(false) {} + : __base(unexpect, __unex.error()) {} template <class _OtherErr> requires is_constructible_v<_Err, _OtherErr> _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherErr, _Err>) expected(unexpected<_OtherErr>&& __unex) noexcept(is_nothrow_constructible_v<_Err, _OtherErr>) // strengthened - : __union_(std::unexpect, std::move(__unex.error())), __has_val_(false) {} + : __base(unexpect, std::move(__unex.error())) {} - _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t) noexcept : __has_val_(true) {} + _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t) noexcept : __base(in_place) {} template <class... _Args> requires is_constructible_v<_Err, _Args...> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(unexpect_t, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Err, _Args...>) // strengthened - : __union_(std::unexpect, std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(unexpect, std::forward<_Args>(__args)...) {} template <class _Up, class... _Args> requires is_constructible_v< _Err, initializer_list<_Up>&, _Args... > _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(unexpect_t, initializer_list<_Up> __il, _Args&&... __args) noexcept( is_nothrow_constructible_v<_Err, initializer_list<_Up>&, _Args...>) // strengthened - : __union_(std::unexpect, __il, std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(unexpect, __il, std::forward<_Args>(__args)...) {} private: - template <class _Func> - _LIBCPP_HIDE_FROM_ABI constexpr explicit expected(__expected_construct_in_place_from_invoke_tag, _Func&& __f) - : __has_val_(true) { - std::invoke(std::forward<_Func>(__f)); - } - template <class _Func, class... _Args> _LIBCPP_HIDE_FROM_ABI constexpr explicit expected( __expected_construct_unexpected_from_invoke_tag __tag, _Func&& __f, _Args&&... __args) - : __union_(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...), __has_val_(false) {} + : __base(__tag, std::forward<_Func>(__f), std::forward<_Args>(__args)...) {} public: // [expected.void.dtor], destructor - _LIBCPP_HIDE_FROM_ABI constexpr ~expected() - requires is_trivially_destructible_v<_Err> - = default; + _LIBCPP_HIDE_FROM_ABI constexpr ~expected() = default; - _LIBCPP_HIDE_FROM_ABI constexpr ~expected() - requires(!is_trivially_destructible_v<_Err>) - { - if (!__has_val_) { - std::destroy_at(std::addressof(__union_.__unex_)); - } +private: + template <class... _Args> + _LIBCPP_HIDE_FROM_ABI constexpr void __reinit_expected(unexpect_t, _Args&&... __args) { + _LIBCPP_ASSERT_INTERNAL(this->__has_val(), "__reinit_expected(unexpect_t, ...) needs value to be set"); + + this->__destroy(); + auto __trans = std::__make_exception_guard([&] { this->__construct(in_place); }); + this->__construct(unexpect, std::forward<_Args>(__args)...); + __trans.__complete(); } - // [expected.void.assign], assignment + _LIBCPP_HIDE_FROM_ABI constexpr void __reinit_expected(in_place_t) { + _LIBCPP_ASSERT_INTERNAL(!this->__has_val(), "__reinit_expected(in_place_t, ...) needs value to be unset"); + this->__destroy(); + this->__construct(in_place); + } + +public: + // [expected.void.assign], assignment _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(const expected&) = delete; _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(const expected& __rhs) noexcept( is_nothrow_copy_assignable_v<_Err> && is_nothrow_copy_constructible_v<_Err>) // strengthened requires(is_copy_assignable_v<_Err> && is_copy_constructible_v<_Err>) { - if (__has_val_) { - if (!__rhs.__has_val_) { - std::construct_at(std::addressof(__union_.__unex_), __rhs.__union_.__unex_); - __has_val_ = false; + if (this->__has_val()) { + if (!__rhs.__has_val()) { + __reinit_expected(unexpect, __rhs.__unex()); } } else { - if (__rhs.__has_val_) { - std::destroy_at(std::addressof(__union_.__unex_)); - __has_val_ = true; + if (__rhs.__has_val()) { + __reinit_expected(in_place); } else { - __union_.__unex_ = __rhs.__union_.__unex_; + this->__unex() = __rhs.__unex(); } } return *this; @@ -1061,17 +1500,15 @@ public: operator=(expected&& __rhs) noexcept(is_nothrow_move_assignable_v<_Err> && is_nothrow_move_constructible_v<_Err>) requires(is_move_assignable_v<_Err> && is_move_constructible_v<_Err>) { - if (__has_val_) { - if (!__rhs.__has_val_) { - std::construct_at(std::addressof(__union_.__unex_), std::move(__rhs.__union_.__unex_)); - __has_val_ = false; + if (this->__has_val()) { + if (!__rhs.__has_val()) { + __reinit_expected(unexpect, std::move(__rhs.__unex())); } } else { - if (__rhs.__has_val_) { - std::destroy_at(std::addressof(__union_.__unex_)); - __has_val_ = true; + if (__rhs.__has_val()) { + __reinit_expected(in_place); } else { - __union_.__unex_ = std::move(__rhs.__union_.__unex_); + this->__unex() = std::move(__rhs.__unex()); } } return *this; @@ -1080,11 +1517,10 @@ public: template <class _OtherErr> requires(is_constructible_v<_Err, const _OtherErr&> && is_assignable_v<_Err&, const _OtherErr&>) _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(const unexpected<_OtherErr>& __un) { - if (__has_val_) { - std::construct_at(std::addressof(__union_.__unex_), __un.error()); - __has_val_ = false; + if (this->__has_val()) { + __reinit_expected(unexpect, __un.error()); } else { - __union_.__unex_ = __un.error(); + this->__unex() = __un.error(); } return *this; } @@ -1092,19 +1528,17 @@ public: template <class _OtherErr> requires(is_constructible_v<_Err, _OtherErr> && is_assignable_v<_Err&, _OtherErr>) _LIBCPP_HIDE_FROM_ABI constexpr expected& operator=(unexpected<_OtherErr>&& __un) { - if (__has_val_) { - std::construct_at(std::addressof(__union_.__unex_), std::move(__un.error())); - __has_val_ = false; + if (this->__has_val()) { + __reinit_expected(unexpect, std::move(__un.error())); } else { - __union_.__unex_ = std::move(__un.error()); + this->__unex() = std::move(__un.error()); } return *this; } _LIBCPP_HIDE_FROM_ABI constexpr void emplace() noexcept { - if (!__has_val_) { - std::destroy_at(std::addressof(__union_.__unex_)); - __has_val_ = true; + if (!this->__has_val()) { + __reinit_expected(in_place); } } @@ -1113,23 +1547,23 @@ public: swap(expected& __rhs) noexcept(is_nothrow_move_constructible_v<_Err> && is_nothrow_swappable_v<_Err>) requires(is_swappable_v<_Err> && is_move_constructible_v<_Err>) { - auto __swap_val_unex_impl = [&](expected& __with_val, expected& __with_err) { - std::construct_at(std::addressof(__with_val.__union_.__unex_), std::move(__with_err.__union_.__unex_)); - std::destroy_at(std::addressof(__with_err.__union_.__unex_)); - __with_val.__has_val_ = false; - __with_err.__has_val_ = true; + auto __swap_val_unex_impl = [](expected& __with_val, expected& __with_err) { + // May throw, but will re-engage `__with_val` in that case. + __with_val.__reinit_expected(unexpect, std::move(__with_err.__unex())); + // Will not throw. + __with_err.__reinit_expected(in_place); }; - if (__has_val_) { - if (!__rhs.__has_val_) { + if (this->__has_val()) { + if (!__rhs.__has_val()) { __swap_val_unex_impl(*this, __rhs); } } else { - if (__rhs.__has_val_) { + if (__rhs.__has_val()) { __swap_val_unex_impl(__rhs, *this); } else { using std::swap; - swap(__union_.__unex_, __rhs.__union_.__unex_); + swap(this->__unex(), __rhs.__unex()); } } } @@ -1141,46 +1575,51 @@ public: } // [expected.void.obs], observers - _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return this->__has_val(); } - _LIBCPP_HIDE_FROM_ABI constexpr bool has_value() const noexcept { return __has_val_; } + _LIBCPP_HIDE_FROM_ABI constexpr bool has_value() const noexcept { return this->__has_val(); } _LIBCPP_HIDE_FROM_ABI constexpr void operator*() const noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__has_val_, "expected::operator* requires the expected to contain a value"); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + this->__has_val(), "expected::operator* requires the expected to contain a value"); } _LIBCPP_HIDE_FROM_ABI constexpr void value() const& { static_assert(is_copy_constructible_v<_Err>); - if (!__has_val_) { - std::__throw_bad_expected_access<_Err>(__union_.__unex_); + if (!this->__has_val()) { + std::__throw_bad_expected_access<_Err>(this->__unex()); } } _LIBCPP_HIDE_FROM_ABI constexpr void value() && { static_assert(is_copy_constructible_v<_Err> && is_move_constructible_v<_Err>); - if (!__has_val_) { - std::__throw_bad_expected_access<_Err>(std::move(__union_.__unex_)); + if (!this->__has_val()) { + std::__throw_bad_expected_access<_Err>(std::move(this->__unex())); } } _LIBCPP_HIDE_FROM_ABI constexpr const _Err& error() const& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return __union_.__unex_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return this->__unex(); } _LIBCPP_HIDE_FROM_ABI constexpr _Err& error() & noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return __union_.__unex_; + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return this->__unex(); } _LIBCPP_HIDE_FROM_ABI constexpr const _Err&& error() const&& noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return std::move(__union_.__unex_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return std::move(this->__unex()); } _LIBCPP_HIDE_FROM_ABI constexpr _Err&& error() && noexcept { - _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!__has_val_, "expected::error requires the expected to contain an error"); - return std::move(__union_.__unex_); + _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( + !this->__has_val(), "expected::error requires the expected to contain an error"); + return std::move(this->__unex()); } template <class _Up = _Err> @@ -1416,96 +1855,17 @@ public: template <class _T2, class _E2> requires is_void_v<_T2> _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const expected<_T2, _E2>& __y) { - if (__x.__has_val_ != __y.__has_val_) { + if (__x.__has_val() != __y.__has_val()) { return false; } else { - return __x.__has_val_ || static_cast<bool>(__x.__union_.__unex_ == __y.__union_.__unex_); + return __x.__has_val() || static_cast<bool>(__x.__unex() == __y.__unex()); } } template <class _E2> _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const expected& __x, const unexpected<_E2>& __y) { - return !__x.__has_val_ && static_cast<bool>(__x.__union_.__unex_ == __y.error()); + return !__x.__has_val() && static_cast<bool>(__x.__unex() == __y.error()); } - -private: - struct __empty_t {}; - - template <class _ErrorType> - union __union_t { - _LIBCPP_HIDE_FROM_ABI constexpr __union_t() : __empty_() {} - - template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args) - : __unex_(std::forward<_Args>(__args)...) {} - - template <class _Func, class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - __expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) - : __unex_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} - - template <class _Union> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) { - if (__has_val) - std::construct_at(std::addressof(__empty_)); - else - std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_); - } - - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(is_trivially_destructible_v<_ErrorType>) - = default; - - // the expected's destructor handles this - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() {} - - __empty_t __empty_; - _ErrorType __unex_; - }; - - // use named union because [[no_unique_address]] cannot be applied to an unnamed union, - // also guaranteed elision into a potentially-overlapping subobject is unsettled (and - // it's not clear that it's implementable, given that the function is allowed to clobber - // the tail padding) - see https://github.com/itanium-cxx-abi/cxx-abi/issues/107. - template <class _ErrorType> - requires is_trivially_move_constructible_v<_ErrorType> - union __union_t<_ErrorType> { - _LIBCPP_HIDE_FROM_ABI constexpr __union_t() : __empty_() {} - _LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) = default; - _LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = default; - - template <class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args) - : __unex_(std::forward<_Args>(__args)...) {} - - template <class _Func, class... _Args> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t( - __expected_construct_unexpected_from_invoke_tag, _Func&& __f, _Args&&... __args) - : __unex_(std::invoke(std::forward<_Func>(__f), std::forward<_Args>(__args)...)) {} - - template <class _Union> - _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) { - if (__has_val) - std::construct_at(std::addressof(__empty_)); - else - std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_); - } - - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(is_trivially_destructible_v<_ErrorType>) - = default; - - // the expected's destructor handles this - _LIBCPP_HIDE_FROM_ABI constexpr ~__union_t() - requires(!is_trivially_destructible_v<_ErrorType>) - {} - - _LIBCPP_NO_UNIQUE_ADDRESS __empty_t __empty_; - _LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_; - }; - - _LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Err> __union_; - bool __has_val_; }; _LIBCPP_END_NAMESPACE_STD |