[libcxx-commits] [libcxx] [libc++] Fix UB in <expected> related to "has value" flag (#68552) (PR #68733)
Jan Kokemüller via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Oct 17 18:23:05 PDT 2023
https://github.com/jiixyj updated https://github.com/llvm/llvm-project/pull/68733
>From 9832a97756cdb800947827ff881f0509159bcc12 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 10 Oct 2023 20:24:06 +0200
Subject: [PATCH 01/13] [libc++] Fix UB in <expected> related to "has value"
flag (#68552)
The calls to `std::construct_at` might overwrite the previously set
`__has_value_` flag, so reverse the order everywhere. Where possible,
avoid calling `std::construct_at` and construct the value/error
directly into the union.
---
libcxx/include/__expected/expected.h | 168 ++++++++----------
.../observers/has_value.pass.cpp | 39 ++++
2 files changed, 117 insertions(+), 90 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 045370a486fae6b..08f35b1111f6bf9 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -119,9 +119,7 @@ class expected {
_LIBCPP_HIDE_FROM_ABI constexpr expected()
noexcept(is_nothrow_default_constructible_v<_Tp>) // strengthened
requires is_default_constructible_v<_Tp>
- : __has_val_(true) {
- std::construct_at(std::addressof(__union_.__val_));
- }
+ : __union_(__construct_in_place_tag{}), __has_val_(true) {}
_LIBCPP_HIDE_FROM_ABI constexpr expected(const expected&) = delete;
@@ -136,14 +134,7 @@ class expected {
noexcept(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>))
- : __has_val_(__other.__has_val_) {
- if (__has_val_) {
- std::construct_at(std::addressof(__union_.__val_), __other.__union_.__val_);
- } else {
- std::construct_at(std::addressof(__union_.__unex_), __other.__union_.__unex_);
- }
- }
-
+ : __union_(__union_from_expected(__other)), __has_val_(__other.__has_val_) { }
_LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&)
requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err>
@@ -154,13 +145,7 @@ class expected {
noexcept(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>))
- : __has_val_(__other.__has_val_) {
- if (__has_val_) {
- std::construct_at(std::addressof(__union_.__val_), std::move(__other.__union_.__val_));
- } else {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__other.__union_.__unex_));
- }
- }
+ : __union_(__union_from_expected(std::move(__other))), __has_val_(__other.__has_val_) { }
private:
template <class _Up, class _OtherErr, class _UfQual, class _OtherErrQual>
@@ -200,26 +185,14 @@ class expected {
expected(const expected<_Up, _OtherErr>& __other)
noexcept(is_nothrow_constructible_v<_Tp, const _Up&> &&
is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened
- : __has_val_(__other.__has_val_) {
- if (__has_val_) {
- std::construct_at(std::addressof(__union_.__val_), __other.__union_.__val_);
- } else {
- std::construct_at(std::addressof(__union_.__unex_), __other.__union_.__unex_);
- }
- }
+ : __union_(__union_from_expected(__other)), __has_val_(__other.__has_val_) {}
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
- : __has_val_(__other.__has_val_) {
- if (__has_val_) {
- std::construct_at(std::addressof(__union_.__val_), std::move(__other.__union_.__val_));
- } else {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__other.__union_.__unex_));
- }
- }
+ : __union_(__union_from_expected(std::move(__other))), __has_val_(__other.__has_val_) {}
template <class _Up = _Tp>
requires(!is_same_v<remove_cvref_t<_Up>, in_place_t> && !is_same_v<expected, remove_cvref_t<_Up>> &&
@@ -227,61 +200,47 @@ class expected {
(!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
- : __has_val_(true) {
- std::construct_at(std::addressof(__union_.__val_), std::forward<_Up>(__u));
- }
+ : __union_(__construct_in_place_tag{}, std::forward<_Up>(__u)), __has_val_(true) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), __unex.error());
- }
+ : __union_(__construct_unexpected_tag{}, __unex.error()), __has_val_(false) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__unex.error()));
- }
+ : __union_(__construct_unexpected_tag{}, std::move(__unex.error())), __has_val_(false) {}
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
- : __has_val_(true) {
- std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...);
- }
+ : __union_(__construct_in_place_tag{}, std::forward<_Args>(__args)...), __has_val_(true) {}
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
- : __has_val_(true) {
- std::construct_at(std::addressof(__union_.__val_), __il, std::forward<_Args>(__args)...);
- }
+ : __union_(__construct_in_place_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(true) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), std::forward<_Args>(__args)...);
- }
+ noexcept(is_nothrow_constructible_v<_Err, _Args...>) // strengthened
+ : __union_(__construct_unexpected_tag{}, std::forward<_Args>(__args)...), __has_val_(false) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), __il, std::forward<_Args>(__args)...);
- }
+ : __union_(__construct_unexpected_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
// [expected.object.dtor], destructor
@@ -440,9 +399,10 @@ class expected {
std::destroy_at(std::addressof(__union_.__val_));
} else {
std::destroy_at(std::addressof(__union_.__unex_));
- __has_val_ = true;
}
- return *std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...);
+ std::construct_at(std::addressof(__union_.__val_), std::forward<_Args>(__args)...);
+ __has_val_ = true;
+ return *std::addressof(__union_.__val_);
}
template <class _Up, class... _Args>
@@ -452,9 +412,10 @@ class expected {
std::destroy_at(std::addressof(__union_.__val_));
} else {
std::destroy_at(std::addressof(__union_.__unex_));
- __has_val_ = true;
}
- return *std::construct_at(std::addressof(__union_.__val_), __il, std::forward<_Args>(__args)...);
+ std::construct_at(std::addressof(__union_.__val_), __il, std::forward<_Args>(__args)...);
+ __has_val_ = true;
+ return *std::addressof(__union_.__val_);
}
@@ -894,11 +855,21 @@ class expected {
private:
struct __empty_t {};
+ struct __construct_in_place_tag {};
+ struct __construct_unexpected_tag {};
template <class _ValueType, class _ErrorType>
union __union_t {
_LIBCPP_HIDE_FROM_ABI constexpr __union_t() {}
+ template <class... _Args>
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_in_place_tag, _Args&&... __args)
+ : __val_(std::forward<_Args>(__args)...) {}
+
+ template <class... _Args>
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_unexpected_tag, _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)
@@ -931,6 +902,14 @@ class expected {
_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(__construct_in_place_tag, _Args&&... __args)
+ : __val_(std::forward<_Args>(__args)...) {}
+
+ template <class... _Args>
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_unexpected_tag, _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)
@@ -955,6 +934,18 @@ class expected {
_LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
};
+ template <class _Up, class _OtherErr>
+ _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
+ return __other.__has_val_ ? __union_t<_Tp, _Err>(__construct_in_place_tag{}, __other.__union_.__val_)
+ : __union_t<_Tp, _Err>(__construct_unexpected_tag{}, __other.__union_.__unex_);
+ }
+
+ template <class _Up, class _OtherErr>
+ _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
+ return __other.__has_val_ ? __union_t<_Tp, _Err>(__construct_in_place_tag{}, std::move(__other.__union_.__val_))
+ : __union_t<_Tp, _Err>(__construct_unexpected_tag{}, std::move(__other.__union_.__unex_));
+ }
+
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Tp, _Err> __union_;
bool __has_val_;
};
@@ -998,11 +989,7 @@ class expected<_Tp, _Err> {
_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>)
- : __has_val_(__rhs.__has_val_) {
- if (!__rhs.__has_val_) {
- std::construct_at(std::addressof(__union_.__unex_), __rhs.__union_.__unex_);
- }
- }
+ : __union_(__union_from_expected(__rhs)), __has_val_(__rhs.__has_val_) {}
_LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&)
requires(is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Err>)
@@ -1011,51 +998,35 @@ class expected<_Tp, _Err> {
_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>)
- : __has_val_(__rhs.__has_val_) {
- if (!__rhs.__has_val_) {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__rhs.__union_.__unex_));
- }
- }
+ : __union_(__union_from_expected(std::move(__rhs))), __has_val_(__rhs.__has_val_) {}
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
- : __has_val_(__rhs.__has_val_) {
- if (!__rhs.__has_val_) {
- std::construct_at(std::addressof(__union_.__unex_), __rhs.__union_.__unex_);
- }
- }
+ : __union_(__union_from_expected(__rhs)), __has_val_(__rhs.__has_val_) {}
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
- : __has_val_(__rhs.__has_val_) {
- if (!__rhs.__has_val_) {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__rhs.__union_.__unex_));
- }
- }
+ : __union_(__union_from_expected(std::move(__rhs))), __has_val_(__rhs.__has_val_) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), __unex.error());
- }
+ : __union_(__construct_unexpected_tag{}, __unex.error()), __has_val_(false) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), std::move(__unex.error()));
- }
+ : __union_(__construct_unexpected_tag{}, std::move(__unex.error())), __has_val_(false) {}
_LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t) noexcept : __has_val_(true) {}
@@ -1063,17 +1034,13 @@ class expected<_Tp, _Err> {
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), std::forward<_Args>(__args)...);
- }
+ : __union_(__construct_unexpected_tag{}, std::forward<_Args>(__args)...), __has_val_(false) {}
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
- : __has_val_(false) {
- std::construct_at(std::addressof(__union_.__unex_), __il, std::forward<_Args>(__args)...);
- }
+ : __union_(__construct_unexpected_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
private:
template <class _Func>
@@ -1502,11 +1469,16 @@ class expected<_Tp, _Err> {
private:
struct __empty_t {};
+ struct __construct_unexpected_tag {};
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(__construct_unexpected_tag, _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)
@@ -1534,6 +1506,10 @@ class expected<_Tp, _Err> {
_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(__construct_unexpected_tag, _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)
@@ -1552,6 +1528,18 @@ class expected<_Tp, _Err> {
_LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
};
+ template <class _Up, class _OtherErr>
+ _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
+ return __other.__has_val_ ? __union_t<_Err>()
+ : __union_t<_Err>(__construct_unexpected_tag{}, __other.__union_.__unex_);
+ }
+
+ template <class _Up, class _OtherErr>
+ _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
+ return __other.__has_val_ ? __union_t<_Err>()
+ : __union_t<_Err>(__construct_unexpected_tag{}, std::move(__other.__union_.__unex_));
+ }
+
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Err> __union_;
bool __has_val_;
};
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index 27d657a065699ea..8979e0f45d44f50 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -12,6 +12,7 @@
#include <cassert>
#include <concepts>
#include <expected>
+#include <optional>
#include <type_traits>
#include <utility>
@@ -30,6 +31,22 @@ static_assert(!HasValueNoexcept<Foo>);
static_assert(HasValueNoexcept<std::expected<int, int>>);
static_assert(HasValueNoexcept<const std::expected<int, int>>);
+// This type has one byte of tail padding where `std::expected` will put its
+// "has value" flag. The constructor will clobber all bytes including the
+// tail padding. With this type we can check that `std::expected` will set
+// its "has value" flag _after_ the value/error object is constructed.
+template <int c>
+struct tail_clobberer {
+ constexpr tail_clobberer() {
+ if (!std::is_constant_evaluated()) {
+ // This `memset` might actually be UB (?) but suffices to reproduce bugs
+ // related to the "has value" flag.
+ std::memset(this, c, sizeof(*this));
+ }
+ }
+ alignas(2) bool b;
+};
+
constexpr bool test() {
// has_value
{
@@ -43,6 +60,28 @@ constexpr bool test() {
assert(!e.has_value());
}
+ // See https://github.com/llvm/llvm-project/issues/68552
+ {
+ static constexpr auto f1 = [] -> std::expected<std::optional<int>, long> { return 0; };
+
+ static constexpr auto f2 = [] -> std::expected<std::optional<int>, int> {
+ return f1().transform_error([](auto) { return 0; });
+ };
+
+ auto e = f2();
+ assert(e.has_value());
+ }
+ {
+ const std::expected<tail_clobberer<0>, bool> e = {};
+ static_assert(sizeof(tail_clobberer<0>) == sizeof(e));
+ assert(e.has_value());
+ }
+ {
+ const std::expected<void, tail_clobberer<1>> e(std::unexpect);
+ static_assert(sizeof(tail_clobberer<1>) == sizeof(e));
+ assert(!e.has_value());
+ }
+
return true;
}
>From 1f9028a0de836e8e30a58f4da4bcc1b4610c21fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Sun, 15 Oct 2023 13:32:14 +0200
Subject: [PATCH 02/13] replace home-grown constructor tags with standard ones
---
libcxx/include/__expected/expected.h | 51 +++++++++++++---------------
1 file changed, 24 insertions(+), 27 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 08f35b1111f6bf9..6440b31e7183201 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -119,7 +119,7 @@ class expected {
_LIBCPP_HIDE_FROM_ABI constexpr expected()
noexcept(is_nothrow_default_constructible_v<_Tp>) // strengthened
requires is_default_constructible_v<_Tp>
- : __union_(__construct_in_place_tag{}), __has_val_(true) {}
+ : __union_(std::in_place), __has_val_(true) {}
_LIBCPP_HIDE_FROM_ABI constexpr expected(const expected&) = delete;
@@ -200,47 +200,47 @@ class expected {
(!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_(__construct_in_place_tag{}, std::forward<_Up>(__u)), __has_val_(true) {}
+ : __union_(std::in_place, std::forward<_Up>(__u)), __has_val_(true) {}
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_(__construct_unexpected_tag{}, __unex.error()), __has_val_(false) {}
+ : __union_(std::unexpect, __unex.error()), __has_val_(false) {}
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_(__construct_unexpected_tag{}, std::move(__unex.error())), __has_val_(false) {}
+ : __union_(std::unexpect, std::move(__unex.error())), __has_val_(false) {}
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_(__construct_in_place_tag{}, std::forward<_Args>(__args)...), __has_val_(true) {}
+ : __union_(std::in_place, std::forward<_Args>(__args)...), __has_val_(true) {}
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_(__construct_in_place_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(true) {}
+ : __union_(std::in_place, __il, std::forward<_Args>(__args)...), __has_val_(true) {}
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_(__construct_unexpected_tag{}, std::forward<_Args>(__args)...), __has_val_(false) {}
+ : __union_(std::unexpect, std::forward<_Args>(__args)...), __has_val_(false) {}
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_(__construct_unexpected_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
+ : __union_(std::unexpect, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
// [expected.object.dtor], destructor
@@ -855,19 +855,17 @@ class expected {
private:
struct __empty_t {};
- struct __construct_in_place_tag {};
- struct __construct_unexpected_tag {};
template <class _ValueType, class _ErrorType>
union __union_t {
_LIBCPP_HIDE_FROM_ABI constexpr __union_t() {}
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_in_place_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::in_place_t, _Args&&... __args)
: __val_(std::forward<_Args>(__args)...) {}
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_unexpected_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args)
: __unex_(std::forward<_Args>(__args)...) {}
template <class _Func, class... _Args>
@@ -903,11 +901,11 @@ class expected {
_LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = default;
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_in_place_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::in_place_t, _Args&&... __args)
: __val_(std::forward<_Args>(__args)...) {}
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_unexpected_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args)
: __unex_(std::forward<_Args>(__args)...) {}
template <class _Func, class... _Args>
@@ -936,14 +934,14 @@ class expected {
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
- return __other.__has_val_ ? __union_t<_Tp, _Err>(__construct_in_place_tag{}, __other.__union_.__val_)
- : __union_t<_Tp, _Err>(__construct_unexpected_tag{}, __other.__union_.__unex_);
+ return __other.__has_val_ ? __union_t<_Tp, _Err>(std::in_place, __other.__union_.__val_)
+ : __union_t<_Tp, _Err>(std::unexpect, __other.__union_.__unex_);
}
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
- return __other.__has_val_ ? __union_t<_Tp, _Err>(__construct_in_place_tag{}, std::move(__other.__union_.__val_))
- : __union_t<_Tp, _Err>(__construct_unexpected_tag{}, std::move(__other.__union_.__unex_));
+ return __other.__has_val_ ? __union_t<_Tp, _Err>(std::in_place, std::move(__other.__union_.__val_))
+ : __union_t<_Tp, _Err>(std::unexpect, std::move(__other.__union_.__unex_));
}
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Tp, _Err> __union_;
@@ -1019,14 +1017,14 @@ class expected<_Tp, _Err> {
_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_(__construct_unexpected_tag{}, __unex.error()), __has_val_(false) {}
+ : __union_(std::unexpect, __unex.error()), __has_val_(false) {}
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_(__construct_unexpected_tag{}, std::move(__unex.error())), __has_val_(false) {}
+ : __union_(std::unexpect, std::move(__unex.error())), __has_val_(false) {}
_LIBCPP_HIDE_FROM_ABI constexpr explicit expected(in_place_t) noexcept : __has_val_(true) {}
@@ -1034,13 +1032,13 @@ class expected<_Tp, _Err> {
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_(__construct_unexpected_tag{}, std::forward<_Args>(__args)...), __has_val_(false) {}
+ : __union_(std::unexpect, std::forward<_Args>(__args)...), __has_val_(false) {}
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_(__construct_unexpected_tag{}, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
+ : __union_(std::unexpect, __il, std::forward<_Args>(__args)...), __has_val_(false) {}
private:
template <class _Func>
@@ -1469,14 +1467,13 @@ class expected<_Tp, _Err> {
private:
struct __empty_t {};
- struct __construct_unexpected_tag {};
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(__construct_unexpected_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args)
: __unex_(std::forward<_Args>(__args)...) {}
template <class _Func, class... _Args>
@@ -1507,7 +1504,7 @@ class expected<_Tp, _Err> {
_LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = default;
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(__construct_unexpected_tag, _Args&&... __args)
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::unexpect_t, _Args&&... __args)
: __unex_(std::forward<_Args>(__args)...) {}
template <class _Func, class... _Args>
@@ -1531,13 +1528,13 @@ class expected<_Tp, _Err> {
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
return __other.__has_val_ ? __union_t<_Err>()
- : __union_t<_Err>(__construct_unexpected_tag{}, __other.__union_.__unex_);
+ : __union_t<_Err>(std::unexpect, __other.__union_.__unex_);
}
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
return __other.__has_val_ ? __union_t<_Err>()
- : __union_t<_Err>(__construct_unexpected_tag{}, std::move(__other.__union_.__unex_));
+ : __union_t<_Err>(std::unexpect, std::move(__other.__union_.__unex_));
}
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Err> __union_;
>From ecac62ff16a0253c91c2ff261212085d0eadb615 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Sun, 15 Oct 2023 13:37:48 +0200
Subject: [PATCH 03/13] replace use of ternary operator by explicit if/else
---
libcxx/include/__expected/expected.h | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 6440b31e7183201..55036d3f55c2432 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -934,14 +934,18 @@ class expected {
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
- return __other.__has_val_ ? __union_t<_Tp, _Err>(std::in_place, __other.__union_.__val_)
- : __union_t<_Tp, _Err>(std::unexpect, __other.__union_.__unex_);
+ if (__other.__has_val_)
+ return __union_t<_Tp, _Err>(std::in_place, __other.__union_.__val_);
+ else
+ return __union_t<_Tp, _Err>(std::unexpect, __other.__union_.__unex_);
}
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
- return __other.__has_val_ ? __union_t<_Tp, _Err>(std::in_place, std::move(__other.__union_.__val_))
- : __union_t<_Tp, _Err>(std::unexpect, std::move(__other.__union_.__unex_));
+ if (__other.__has_val_)
+ return __union_t<_Tp, _Err>(std::in_place, std::move(__other.__union_.__val_));
+ else
+ return __union_t<_Tp, _Err>(std::unexpect, std::move(__other.__union_.__unex_));
}
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Tp, _Err> __union_;
@@ -1527,14 +1531,18 @@ class expected<_Tp, _Err> {
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
- return __other.__has_val_ ? __union_t<_Err>()
- : __union_t<_Err>(std::unexpect, __other.__union_.__unex_);
+ if (__other.__has_val_)
+ return __union_t<_Err>();
+ else
+ return __union_t<_Err>(std::unexpect, __other.__union_.__unex_);
}
template <class _Up, class _OtherErr>
_LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
- return __other.__has_val_ ? __union_t<_Err>()
- : __union_t<_Err>(std::unexpect, std::move(__other.__union_.__unex_));
+ if (__other.__has_val_)
+ return __union_t<_Err>();
+ else
+ return __union_t<_Err>(std::unexpect, std::move(__other.__union_.__unex_));
}
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Err> __union_;
>From 83488c8485cb206295995098d432ae82c31143c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Sun, 15 Oct 2023 13:47:06 +0200
Subject: [PATCH 04/13] add a short description to the tests
---
.../expected.expected/observers/has_value.pass.cpp | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index 8979e0f45d44f50..b203253e897795e 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -60,7 +60,17 @@ constexpr bool test() {
assert(!e.has_value());
}
- // See https://github.com/llvm/llvm-project/issues/68552
+ // The following tests check that the "has_value" flag is not overwritten
+ // by the constructor of the value. This could happen because the flag is
+ // stored in the tail padding of the value.
+ //
+ // The first test is a simplified version of the real code where this was
+ // first observed.
+ //
+ // The other tests use a synthetic struct that clobbers its tail padding
+ // on construction, making the issue easier to reproduce.
+ //
+ // See https://github.com/llvm/llvm-project/issues/68552 and the linked PR.
{
static constexpr auto f1 = [] -> std::expected<std::optional<int>, long> { return 0; };
>From 7b81fb560f60f9742f754e8f7adbffcdab8a7efb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Sun, 15 Oct 2023 13:50:57 +0200
Subject: [PATCH 05/13] remove comment about memset being UB here
---
.../expected/expected.expected/observers/has_value.pass.cpp | 2 --
1 file changed, 2 deletions(-)
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index b203253e897795e..d7591718ae784b6 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -39,8 +39,6 @@ template <int c>
struct tail_clobberer {
constexpr tail_clobberer() {
if (!std::is_constant_evaluated()) {
- // This `memset` might actually be UB (?) but suffices to reproduce bugs
- // related to the "has value" flag.
std::memset(this, c, sizeof(*this));
}
}
>From 238d1ca6560069d4d8e2558ee171782e14e50195 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 15:59:37 +0200
Subject: [PATCH 06/13] add constructors to __union_t from expected parts and
refactor
GCC 13 didn't like the previous approach.
---
libcxx/include/__expected/expected.h | 80 ++++++++++++++--------------
1 file changed, 40 insertions(+), 40 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 55036d3f55c2432..06c9a26c8e3a88f 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -134,7 +134,7 @@ class expected {
noexcept(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_(__union_from_expected(__other)), __has_val_(__other.__has_val_) { }
+ : __union_(__other.__has_val_, __other.__union_), __has_val_(__other.__has_val_) { }
_LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&)
requires(is_move_constructible_v<_Tp> && is_move_constructible_v<_Err>
@@ -145,7 +145,7 @@ class expected {
noexcept(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_(__union_from_expected(std::move(__other))), __has_val_(__other.__has_val_) { }
+ : __union_(__other.__has_val_, std::move(__other.__union_)), __has_val_(__other.__has_val_) { }
private:
template <class _Up, class _OtherErr, class _UfQual, class _OtherErrQual>
@@ -185,14 +185,14 @@ class expected {
expected(const expected<_Up, _OtherErr>& __other)
noexcept(is_nothrow_constructible_v<_Tp, const _Up&> &&
is_nothrow_constructible_v<_Err, const _OtherErr&>) // strengthened
- : __union_(__union_from_expected(__other)), __has_val_(__other.__has_val_) {}
+ : __union_(__other.__has_val_, __other.__union_), __has_val_(__other.__has_val_) {}
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_(__union_from_expected(std::move(__other))), __has_val_(__other.__has_val_) {}
+ : __union_(__other.__has_val_, std::move(__other.__union_)), __has_val_(__other.__has_val_) {}
template <class _Up = _Tp>
requires(!is_same_v<remove_cvref_t<_Up>, in_place_t> && !is_same_v<expected, remove_cvref_t<_Up>> &&
@@ -878,6 +878,14 @@ class expected {
std::__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(this, std::in_place, std::forward<_Union>(__other).__val_);
+ else
+ std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ }
+
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
requires(is_trivially_destructible_v<_ValueType> && is_trivially_destructible_v<_ErrorType>)
= default;
@@ -918,6 +926,14 @@ class expected {
std::__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(this, std::in_place, std::forward<_Union>(__other).__val_);
+ else
+ std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ }
+
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
requires(is_trivially_destructible_v<_ValueType> && is_trivially_destructible_v<_ErrorType>)
= default;
@@ -932,22 +948,6 @@ class expected {
_LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
};
- template <class _Up, class _OtherErr>
- _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
- if (__other.__has_val_)
- return __union_t<_Tp, _Err>(std::in_place, __other.__union_.__val_);
- else
- return __union_t<_Tp, _Err>(std::unexpect, __other.__union_.__unex_);
- }
-
- template <class _Up, class _OtherErr>
- _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Tp, _Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
- if (__other.__has_val_)
- return __union_t<_Tp, _Err>(std::in_place, std::move(__other.__union_.__val_));
- else
- return __union_t<_Tp, _Err>(std::unexpect, std::move(__other.__union_.__unex_));
- }
-
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Tp, _Err> __union_;
bool __has_val_;
};
@@ -991,7 +991,7 @@ class expected<_Tp, _Err> {
_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_(__union_from_expected(__rhs)), __has_val_(__rhs.__has_val_) {}
+ : __union_(__rhs.__has_val_, __rhs.__union_), __has_val_(__rhs.__has_val_) {}
_LIBCPP_HIDE_FROM_ABI constexpr expected(expected&&)
requires(is_move_constructible_v<_Err> && is_trivially_move_constructible_v<_Err>)
@@ -1000,21 +1000,21 @@ class expected<_Tp, _Err> {
_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_(__union_from_expected(std::move(__rhs))), __has_val_(__rhs.__has_val_) {}
+ : __union_(__rhs.__has_val_, std::move(__rhs.__union_)), __has_val_(__rhs.__has_val_) {}
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_(__union_from_expected(__rhs)), __has_val_(__rhs.__has_val_) {}
+ : __union_(__rhs.__has_val_, __rhs.__union_), __has_val_(__rhs.__has_val_) {}
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_(__union_from_expected(std::move(__rhs))), __has_val_(__rhs.__has_val_) {}
+ : __union_(__rhs.__has_val_, std::move(__rhs.__union_)), __has_val_(__rhs.__has_val_) {}
template <class _OtherErr>
requires is_constructible_v<_Err, const _OtherErr&>
@@ -1485,6 +1485,14 @@ class expected<_Tp, _Err> {
__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(this);
+ else
+ std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ }
+
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
requires(is_trivially_destructible_v<_ErrorType>)
= default;
@@ -1516,6 +1524,14 @@ class expected<_Tp, _Err> {
__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(this);
+ else
+ std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ }
+
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
requires(is_trivially_destructible_v<_ErrorType>)
= default;
@@ -1529,22 +1545,6 @@ class expected<_Tp, _Err> {
_LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
};
- template <class _Up, class _OtherErr>
- _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(const expected<_Up, _OtherErr>& __other) {
- if (__other.__has_val_)
- return __union_t<_Err>();
- else
- return __union_t<_Err>(std::unexpect, __other.__union_.__unex_);
- }
-
- template <class _Up, class _OtherErr>
- _LIBCPP_HIDE_FROM_ABI constexpr __union_t<_Err> __union_from_expected(expected<_Up, _OtherErr>&& __other) {
- if (__other.__has_val_)
- return __union_t<_Err>();
- else
- return __union_t<_Err>(std::unexpect, std::move(__other.__union_.__unex_));
- }
-
_LIBCPP_NO_UNIQUE_ADDRESS __union_t<_Err> __union_;
bool __has_val_;
};
>From dfa9b3cf6e5951b4935e3e310b3e338f721beada Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 16:06:19 +0200
Subject: [PATCH 07/13] put new expected<void> test into appropriate folder
---
.../observers/has_value.pass.cpp | 24 +++----------------
.../observers/has_value.pass.cpp | 8 +++++++
libcxx/test/std/utilities/expected/types.h | 16 +++++++++++++
3 files changed, 27 insertions(+), 21 deletions(-)
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index d7591718ae784b6..74569cfa2083e92 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -17,6 +17,7 @@
#include <utility>
#include "test_macros.h"
+#include "../../types.h"
// Test noexcept
template <class T>
@@ -31,20 +32,6 @@ static_assert(!HasValueNoexcept<Foo>);
static_assert(HasValueNoexcept<std::expected<int, int>>);
static_assert(HasValueNoexcept<const std::expected<int, int>>);
-// This type has one byte of tail padding where `std::expected` will put its
-// "has value" flag. The constructor will clobber all bytes including the
-// tail padding. With this type we can check that `std::expected` will set
-// its "has value" flag _after_ the value/error object is constructed.
-template <int c>
-struct tail_clobberer {
- constexpr tail_clobberer() {
- if (!std::is_constant_evaluated()) {
- std::memset(this, c, sizeof(*this));
- }
- }
- alignas(2) bool b;
-};
-
constexpr bool test() {
// has_value
{
@@ -80,15 +67,10 @@ constexpr bool test() {
assert(e.has_value());
}
{
- const std::expected<tail_clobberer<0>, bool> e = {};
- static_assert(sizeof(tail_clobberer<0>) == sizeof(e));
+ const std::expected<TailClobberer<0>, bool> e = {};
+ static_assert(sizeof(TailClobberer<0>) == sizeof(e));
assert(e.has_value());
}
- {
- const std::expected<void, tail_clobberer<1>> e(std::unexpect);
- static_assert(sizeof(tail_clobberer<1>) == sizeof(e));
- assert(!e.has_value());
- }
return true;
}
diff --git a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
index 42a173d60c898c6..89c79541f995526 100644
--- a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
@@ -16,6 +16,7 @@
#include <utility>
#include "test_macros.h"
+#include "../../types.h"
// Test noexcept
template <class T>
@@ -43,6 +44,13 @@ constexpr bool test() {
assert(!e.has_value());
}
+ // See comments of the corresponding test in "expected.expected".
+ {
+ const std::expected<void, TailClobberer<1>> e(std::unexpect);
+ static_assert(sizeof(TailClobberer<1>) == sizeof(e));
+ assert(!e.has_value());
+ }
+
return true;
}
diff --git a/libcxx/test/std/utilities/expected/types.h b/libcxx/test/std/utilities/expected/types.h
index 7c7e517785b4f78..874b72b64e8ae11 100644
--- a/libcxx/test/std/utilities/expected/types.h
+++ b/libcxx/test/std/utilities/expected/types.h
@@ -9,7 +9,9 @@
#ifndef TEST_STD_UTILITIES_EXPECTED_TYPES_H
#define TEST_STD_UTILITIES_EXPECTED_TYPES_H
+#include <cstring>
#include <utility>
+#include <type_traits>
#include "test_macros.h"
template <bool copyMoveNoexcept, bool convertNoexcept = true>
@@ -102,6 +104,20 @@ struct TrackedMove {
}
};
+// This type has one byte of tail padding where `std::expected` will put its
+// "has value" flag. The constructor will clobber all bytes including the
+// tail padding. With this type we can check that `std::expected` will set
+// its "has value" flag _after_ the value/error object is constructed.
+template <int c>
+struct TailClobberer {
+ constexpr TailClobberer() {
+ if (!std::is_constant_evaluated()) {
+ std::memset(this, c, sizeof(*this));
+ }
+ }
+ alignas(2) bool b;
+};
+
#ifndef TEST_HAS_NO_EXCEPTIONS
struct Except {};
>From 3028a7c37c3f7208fc55ca11029d86da2f06c0da Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 18:21:47 +0200
Subject: [PATCH 08/13] disable new tests on compilers that cannot build them
---
.../expected/expected.expected/observers/has_value.pass.cpp | 5 +++++
.../expected/expected.void/observers/has_value.pass.cpp | 3 +++
2 files changed, 8 insertions(+)
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index 74569cfa2083e92..3cb46bcf79abee3 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -57,6 +57,7 @@ constexpr bool test() {
//
// See https://github.com/llvm/llvm-project/issues/68552 and the linked PR.
{
+#if !defined(TEST_COMPILER_CLANG) || TEST_CLANG_VER >= 1600
static constexpr auto f1 = [] -> std::expected<std::optional<int>, long> { return 0; };
static constexpr auto f2 = [] -> std::expected<std::optional<int>, int> {
@@ -65,10 +66,14 @@ constexpr bool test() {
auto e = f2();
assert(e.has_value());
+#endif
}
{
const std::expected<TailClobberer<0>, bool> e = {};
+ // clang-cl does not support [[no_unique_address]] yet.
+#if !(defined(TEST_COMPILER_CLANG) && defined(_MSC_VER))
static_assert(sizeof(TailClobberer<0>) == sizeof(e));
+#endif
assert(e.has_value());
}
diff --git a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
index 89c79541f995526..50098d10977b702 100644
--- a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
@@ -47,7 +47,10 @@ constexpr bool test() {
// See comments of the corresponding test in "expected.expected".
{
const std::expected<void, TailClobberer<1>> e(std::unexpect);
+ // clang-cl does not support [[no_unique_address]] yet.
+#if !(defined(TEST_COMPILER_CLANG) && defined(_MSC_VER))
static_assert(sizeof(TailClobberer<1>) == sizeof(e));
+#endif
assert(!e.has_value());
}
>From 8df519aabf2c02931dafc6543165518c3033dfcd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 19:57:07 +0200
Subject: [PATCH 09/13] make comment in
libcxx/test/std/utilities/expected/types.h more general
Co-authored-by: Louis Dionne <ldionne.2 at gmail.com>
---
libcxx/test/std/utilities/expected/types.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/libcxx/test/std/utilities/expected/types.h b/libcxx/test/std/utilities/expected/types.h
index 874b72b64e8ae11..e6fd5ac479266ad 100644
--- a/libcxx/test/std/utilities/expected/types.h
+++ b/libcxx/test/std/utilities/expected/types.h
@@ -104,10 +104,12 @@ struct TrackedMove {
}
};
-// This type has one byte of tail padding where `std::expected` will put its
+// This type has one byte of tail padding where `std::expected` may put its
// "has value" flag. The constructor will clobber all bytes including the
-// tail padding. With this type we can check that `std::expected` will set
-// its "has value" flag _after_ the value/error object is constructed.
+// tail padding. With this type we can check that `std::expected` handles
+// the case where the "has value" flag is an overlapping subobject correctly.
+//
+// See https://github.com/llvm/llvm-project/issues/68552 for details.
template <int c>
struct TailClobberer {
constexpr TailClobberer() {
>From bea099d230a4fa5dfa32c88051bbdaf180f0ef3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 20:12:00 +0200
Subject: [PATCH 10/13] spell out full path to corresponding test file
---
.../expected/expected.void/observers/has_value.pass.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
index 50098d10977b702..06a45ed43018041 100644
--- a/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.void/observers/has_value.pass.cpp
@@ -44,7 +44,8 @@ constexpr bool test() {
assert(!e.has_value());
}
- // See comments of the corresponding test in "expected.expected".
+ // See comments of the corresponding test in
+ // "expected.expected/observers/has_value.pass.cpp".
{
const std::expected<void, TailClobberer<1>> e(std::unexpect);
// clang-cl does not support [[no_unique_address]] yet.
>From bf28eba0392a151d08d0b0b04761305afbd4930c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 20:14:28 +0200
Subject: [PATCH 11/13] directly construct into union member instead of trying
to delegate to another constructor
---
libcxx/include/__expected/expected.h | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 06c9a26c8e3a88f..9d09485d22ae4de 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -881,9 +881,9 @@ class expected {
template <class _Union>
_LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) {
if (__has_val)
- std::construct_at(this, std::in_place, std::forward<_Union>(__other).__val_);
+ std::construct_at(std::addressof(__val_), std::forward<_Union>(__other).__val_);
else
- std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_);
}
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
@@ -929,9 +929,9 @@ class expected {
template <class _Union>
_LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) {
if (__has_val)
- std::construct_at(this, std::in_place, std::forward<_Union>(__other).__val_);
+ std::construct_at(std::addressof(__val_), std::forward<_Union>(__other).__val_);
else
- std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_);
}
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
@@ -1488,9 +1488,9 @@ class expected<_Tp, _Err> {
template <class _Union>
_LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) {
if (__has_val)
- std::construct_at(this);
+ std::construct_at(std::addressof(__empty_));
else
- std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_);
}
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
@@ -1527,9 +1527,9 @@ class expected<_Tp, _Err> {
template <class _Union>
_LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(bool __has_val, _Union&& __other) {
if (__has_val)
- std::construct_at(this);
+ std::construct_at(std::addressof(__empty_));
else
- std::construct_at(this, std::unexpect, std::forward<_Union>(__other).__unex_);
+ std::construct_at(std::addressof(__unex_), std::forward<_Union>(__other).__unex_);
}
_LIBCPP_HIDE_FROM_ABI constexpr ~__union_t()
>From 5922253fbed8e3c161829860d461819741532b63 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Tue, 17 Oct 2023 20:24:03 +0200
Subject: [PATCH 12/13] remove unneeded '__empty_t' in union of non-void
expected
---
libcxx/include/__expected/expected.h | 6 ------
1 file changed, 6 deletions(-)
diff --git a/libcxx/include/__expected/expected.h b/libcxx/include/__expected/expected.h
index 9d09485d22ae4de..f874a3a126a58f3 100644
--- a/libcxx/include/__expected/expected.h
+++ b/libcxx/include/__expected/expected.h
@@ -854,12 +854,8 @@ class expected {
}
private:
- struct __empty_t {};
-
template <class _ValueType, class _ErrorType>
union __union_t {
- _LIBCPP_HIDE_FROM_ABI constexpr __union_t() {}
-
template <class... _Args>
_LIBCPP_HIDE_FROM_ABI constexpr explicit __union_t(std::in_place_t, _Args&&... __args)
: __val_(std::forward<_Args>(__args)...) {}
@@ -904,7 +900,6 @@ class expected {
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() : __empty_() {}
_LIBCPP_HIDE_FROM_ABI constexpr __union_t(const __union_t&) = default;
_LIBCPP_HIDE_FROM_ABI constexpr __union_t& operator=(const __union_t&) = default;
@@ -943,7 +938,6 @@ class expected {
requires(!is_trivially_destructible_v<_ValueType> || !is_trivially_destructible_v<_ErrorType>)
{}
- _LIBCPP_NO_UNIQUE_ADDRESS __empty_t __empty_;
_LIBCPP_NO_UNIQUE_ADDRESS _ValueType __val_;
_LIBCPP_NO_UNIQUE_ADDRESS _ErrorType __unex_;
};
>From 6167b0e718b741c2b8e0a9aece0e9999320967d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Kokem=C3=BCller?= <jan.kokemueller at gmail.com>
Date: Wed, 18 Oct 2023 03:22:39 +0200
Subject: [PATCH 13/13] make lambdas automatic variables
---
.../expected/expected.expected/observers/has_value.pass.cpp | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
index 3cb46bcf79abee3..0e19da065594644 100644
--- a/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
+++ b/libcxx/test/std/utilities/expected/expected.expected/observers/has_value.pass.cpp
@@ -57,16 +57,14 @@ constexpr bool test() {
//
// See https://github.com/llvm/llvm-project/issues/68552 and the linked PR.
{
-#if !defined(TEST_COMPILER_CLANG) || TEST_CLANG_VER >= 1600
- static constexpr auto f1 = [] -> std::expected<std::optional<int>, long> { return 0; };
+ auto f1 = [] -> std::expected<std::optional<int>, long> { return 0; };
- static constexpr auto f2 = [] -> std::expected<std::optional<int>, int> {
+ auto f2 = [&f1] -> std::expected<std::optional<int>, int> {
return f1().transform_error([](auto) { return 0; });
};
auto e = f2();
assert(e.has_value());
-#endif
}
{
const std::expected<TailClobberer<0>, bool> e = {};
More information about the libcxx-commits
mailing list