[libc++] Make forward_list constexpr as part of P3372R3 #129435
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@llvm/pr-subscribers-libcxx Author: Peng Liu (winner245) ChangesFixes #128658. Patch is 165.20 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/129435.diff 76 Files Affected:
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index dcf9838edd74b..5ac25a69ac52e 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -416,6 +416,8 @@ Status
---------------------------------------------------------- -----------------
``__cpp_lib_bitset`` ``202306L``
---------------------------------------------------------- -----------------
+ ``__cpp_lib_constexpr_forward_list`` ``202502L``
+ ---------------------------------------------------------- -----------------
``__cpp_lib_constexpr_new`` ``202406L``
---------------------------------------------------------- -----------------
``__cpp_lib_constrained_equality`` *unimplemented*
diff --git a/libcxx/include/__memory/allocation_guard.h b/libcxx/include/__memory/allocation_guard.h
index 66edcd92ed618..2fc485f4ed0ed 100644
--- a/libcxx/include/__memory/allocation_guard.h
+++ b/libcxx/include/__memory/allocation_guard.h
@@ -49,24 +49,26 @@ struct __allocation_guard {
using _Size _LIBCPP_NODEBUG = typename allocator_traits<_Alloc>::size_type;
template <class _AllocT> // we perform the allocator conversion inside the constructor
- _LIBCPP_HIDE_FROM_ABI explicit __allocation_guard(_AllocT __alloc, _Size __n)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __allocation_guard(_AllocT __alloc, _Size __n)
: __alloc_(std::move(__alloc)),
__n_(__n),
__ptr_(allocator_traits<_Alloc>::allocate(__alloc_, __n_)) // initialization order is important
{}
- _LIBCPP_HIDE_FROM_ABI ~__allocation_guard() _NOEXCEPT { __destroy(); }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI ~__allocation_guard() _NOEXCEPT { __destroy(); }
- _LIBCPP_HIDE_FROM_ABI __allocation_guard(const __allocation_guard&) = delete;
- _LIBCPP_HIDE_FROM_ABI __allocation_guard(__allocation_guard&& __other) _NOEXCEPT
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __allocation_guard(const __allocation_guard&) = delete;
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __allocation_guard(__allocation_guard&& __other) _NOEXCEPT
: __alloc_(std::move(__other.__alloc_)),
__n_(__other.__n_),
__ptr_(__other.__ptr_) {
__other.__ptr_ = nullptr;
}
- _LIBCPP_HIDE_FROM_ABI __allocation_guard& operator=(const __allocation_guard& __other) = delete;
- _LIBCPP_HIDE_FROM_ABI __allocation_guard& operator=(__allocation_guard&& __other) _NOEXCEPT {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __allocation_guard&
+ operator=(const __allocation_guard& __other) = delete;
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __allocation_guard&
+ operator=(__allocation_guard&& __other) _NOEXCEPT {
if (std::addressof(__other) != this) {
__destroy();
@@ -79,17 +81,17 @@ struct __allocation_guard {
return *this;
}
- _LIBCPP_HIDE_FROM_ABI _Pointer
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI _Pointer
__release_ptr() _NOEXCEPT { // not called __release() because it's a keyword in objective-c++
_Pointer __tmp = __ptr_;
__ptr_ = nullptr;
return __tmp;
}
- _LIBCPP_HIDE_FROM_ABI _Pointer __get() const _NOEXCEPT { return __ptr_; }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI _Pointer __get() const _NOEXCEPT { return __ptr_; }
private:
- _LIBCPP_HIDE_FROM_ABI void __destroy() _NOEXCEPT {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __destroy() _NOEXCEPT {
if (__ptr_ != nullptr) {
allocator_traits<_Alloc>::deallocate(__alloc_, __ptr_, __n_);
}
diff --git a/libcxx/include/forward_list b/libcxx/include/forward_list
index 8c688611d5ee2..aca31bc37dc1d 100644
--- a/libcxx/include/forward_list
+++ b/libcxx/include/forward_list
@@ -295,9 +295,14 @@ struct __forward_node_traits {
"the _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB macro to silence this diagnostic.");
# endif
- _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__begin_node_pointer __p) { return __p; }
- _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__node_pointer __p) {
- return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__p));
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer
+ __as_iter_node(__begin_node_pointer __p) {
+ return __p;
+ }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__node_pointer __p) {
+ // return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__p));
+ return __p ? pointer_traits<__begin_node_pointer>::pointer_to(*__p) // fancy pointer
+ : static_cast<__begin_node_pointer>(nullptr);
}
};
@@ -308,11 +313,13 @@ struct __forward_begin_node {
pointer __next_;
- _LIBCPP_HIDE_FROM_ABI __forward_begin_node() : __next_(nullptr) {}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_begin_node(pointer __n) : __next_(__n) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_begin_node() : __next_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_begin_node(pointer __n) : __next_(__n) {}
- _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __next_as_begin() const {
- return static_cast<__begin_node_pointer>(__next_);
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __next_as_begin() const {
+ // return static_cast<__begin_node_pointer>(__next_);
+ return __next_ ? pointer_traits<__begin_node_pointer>::pointer_to(*__next_) // fancy pointer
+ : static_cast<__begin_node_pointer>(nullptr);
}
};
@@ -336,18 +343,20 @@ private:
};
public:
- _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return __value_; }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return __value_; }
# else
private:
_ALIGNAS_TYPE(_Tp) char __buffer_[sizeof(_Tp)];
public:
- _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return *std::__launder(reinterpret_cast<_Tp*>(&__buffer_)); }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() {
+ return *std::__launder(reinterpret_cast<_Tp*>(&__buffer_));
+ }
# endif
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_node(_NodePtr __next) : _Base(__next) {}
- _LIBCPP_HIDE_FROM_ABI ~__forward_list_node() {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_node(_NodePtr __next) : _Base(__next) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI ~__forward_list_node() {}
};
template <class _Tp, class _Alloc = allocator<_Tp> >
@@ -358,25 +367,29 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
template <class _NodePtr>
class _LIBCPP_TEMPLATE_VIS __forward_list_iterator {
typedef __forward_node_traits<_NodePtr> __traits;
+ typedef typename __traits::__node_type __node_type;
typedef typename __traits::__node_pointer __node_pointer;
typedef typename __traits::__begin_node_pointer __begin_node_pointer;
typedef typename __traits::__void_pointer __void_pointer;
__begin_node_pointer __ptr_;
- _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
- return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
- }
- _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
- return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const { return __ptr_; }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
+ // return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
+ return __ptr_ ? pointer_traits<__node_pointer>::pointer_to(
+ const_cast<__node_type&>(static_cast<const __node_type&>(*__ptr_))) // fancy pointer
+ : static_cast<__node_pointer>(nullptr);
}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(nullptr_t) _NOEXCEPT
+ : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26
_LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__begin_node_pointer __p) _NOEXCEPT
: __ptr_(__traits::__as_iter_node(__p)) {}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
: __ptr_(__traits::__as_iter_node(__p)) {}
template <class, class>
@@ -391,27 +404,31 @@ public:
typedef typename pointer_traits<__node_pointer>::difference_type difference_type;
typedef __rebind_pointer_t<__node_pointer, value_type> pointer;
- _LIBCPP_HIDE_FROM_ABI __forward_list_iterator() _NOEXCEPT : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_iterator() _NOEXCEPT : __ptr_(nullptr) {}
- _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_unsafe_node_pointer()->__get_value(); }
- _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference operator*() const {
+ return __get_unsafe_node_pointer()->__get_value();
+ }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
return pointer_traits<pointer>::pointer_to(__get_unsafe_node_pointer()->__get_value());
}
- _LIBCPP_HIDE_FROM_ABI __forward_list_iterator& operator++() {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_iterator& operator++() {
__ptr_ = __traits::__as_iter_node(__ptr_->__next_);
return *this;
}
- _LIBCPP_HIDE_FROM_ABI __forward_list_iterator operator++(int) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_iterator operator++(int) {
__forward_list_iterator __t(*this);
++(*this);
return __t;
}
- friend _LIBCPP_HIDE_FROM_ABI bool operator==(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
+ friend _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool
+ operator==(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
return __x.__ptr_ == __y.__ptr_;
}
- friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
+ friend _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool
+ operator!=(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
return !(__x == __y);
}
};
@@ -429,18 +446,22 @@ class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator {
__begin_node_pointer __ptr_;
- _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
- return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
- }
- _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
- return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const { return __ptr_; }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
+ // return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
+ return __ptr_ ? pointer_traits<__node_pointer>::pointer_to(
+ const_cast<__node_type&>(static_cast<const __node_type&>(*__ptr_))) // fancy pointer
+ : static_cast<__node_pointer>(nullptr);
}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT
+ : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26
_LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__begin_node_pointer __p) _NOEXCEPT
: __ptr_(__traits::__as_iter_node(__p)) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26
_LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__node_pointer __p) _NOEXCEPT
: __ptr_(__traits::__as_iter_node(__p)) {}
@@ -454,30 +475,32 @@ public:
typedef typename pointer_traits<__node_pointer>::difference_type difference_type;
typedef __rebind_pointer_t<__node_pointer, const value_type> pointer;
- _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
- _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator(__forward_list_iterator<__node_pointer> __p) _NOEXCEPT
- : __ptr_(__p.__ptr_) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI
+ __forward_list_const_iterator(__forward_list_iterator<__node_pointer> __p) _NOEXCEPT : __ptr_(__p.__ptr_) {}
- _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_unsafe_node_pointer()->__get_value(); }
- _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI reference operator*() const {
+ return __get_unsafe_node_pointer()->__get_value();
+ }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
return pointer_traits<pointer>::pointer_to(__get_unsafe_node_pointer()->__get_value());
}
- _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator& operator++() {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator& operator++() {
__ptr_ = __traits::__as_iter_node(__ptr_->__next_);
return *this;
}
- _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator operator++(int) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator operator++(int) {
__forward_list_const_iterator __t(*this);
++(*this);
return __t;
}
- friend _LIBCPP_HIDE_FROM_ABI bool
+ friend _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool
operator==(const __forward_list_const_iterator& __x, const __forward_list_const_iterator& __y) {
return __x.__ptr_ == __y.__ptr_;
}
- friend _LIBCPP_HIDE_FROM_ABI bool
+ friend _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI bool
operator!=(const __forward_list_const_iterator& __x, const __forward_list_const_iterator& __y) {
return !(__x == __y);
}
@@ -501,48 +524,51 @@ protected:
_LIBCPP_COMPRESSED_PAIR(__begin_node, __before_begin_, __node_allocator, __alloc_);
- _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() _NOEXCEPT {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() _NOEXCEPT {
return pointer_traits<__begin_node_pointer>::pointer_to(__before_begin_);
}
- _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() const _NOEXCEPT {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() const _NOEXCEPT {
return pointer_traits<__begin_node_pointer>::pointer_to(const_cast<__begin_node&>(__before_begin_));
}
typedef __forward_list_iterator<__node_pointer> iterator;
typedef __forward_list_const_iterator<__node_pointer> const_iterator;
- _LIBCPP_HIDE_FROM_ABI __forward_list_base() _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __forward_list_base()
+ _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
: __before_begin_(__begin_node()) {}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const allocator_type& __a)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const allocator_type& __a)
: __before_begin_(__begin_node()), __alloc_(__node_allocator(__a)) {}
- _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const __node_allocator& __a)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const __node_allocator& __a)
: __before_begin_(__begin_node()), __alloc_(__a) {}
public:
# ifndef _LIBCPP_CXX03_LANG
- _LIBCPP_HIDE_FROM_ABI
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI
__forward_list_base(__forward_list_base&& __x) noexcept(is_nothrow_move_constructible<__node_allocator>::value);
- _LIBCPP_HIDE_FROM_ABI __forward_list_base(__forward_list_base&& __x, const allocator_type& __a);
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI
+ __forward_list_base(__forward_list_base&& __x, const allocator_type& __a);
# endif // _LIBCPP_CXX03_LANG
__forward_list_base(const __forward_list_base&) = delete;
__forward_list_base& operator=(const __forward_list_base&) = delete;
- _LIBCPP_HIDE_FROM_ABI ~__forward_list_base();
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI ~__forward_list_base();
protected:
- _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base& __x) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base& __x) {
__copy_assign_alloc(__x, integral_constant<bool, __node_traits::propagate_on_container_copy_assignment::value>());
}
- _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x)
_NOEXCEPT_(!__node_traits::propagate_on_container_move_assignment::value ||
is_nothrow_move_assignable<__node_allocator>::value) {
__move_assign_alloc(__x, integral_constant<bool, __node_traits::propagate_on_container_move_assignment::value>());
}
template <class... _Args>
- _LIBCPP_HIDE_FROM_ABI __node_pointer __create_node(__node_pointer __next, _Args&&... __args) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI __node_pointer
+ __create_node(__node_pointer __next, _Args&&... __args) {
__allocation_guard<__node_allocator> __guard(__alloc_, 1);
// Begin the lifetime of the node itself. Note that this doesn't begin the lifetime of the value
// held inside the node, since we need to use the allocator's construct() method for that.
@@ -557,7 +583,7 @@ protected:
return __guard.__release_ptr();
}
- _LIBCPP_HIDE_FROM_ABI void __delete_node(__node_pointer __node) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __delete_node(__node_pointer __node) {
// For the same reason as above, we use the allocator's destroy() method for the value_type,
// but not for the node itself.
__node_traits::destroy(__alloc_, std::addressof(__node->__get_value()));
@@ -566,7 +592,7 @@ protected:
}
public:
- _LIBCPP_HIDE_FROM_ABI void swap(__forward_list_base& __x)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void swap(__forward_list_base& __x)
# if _LIBCPP_STD_VER >= 14
_NOEXCEPT;
# else
@@ -574,18 +600,21 @@ public:
# endif
protected:
- _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT;
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT;
private:
- _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base&, false_type) {}
- _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base& __x, true_type) {
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base&, false_type) {
+ }
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void
+ __copy_assign_alloc(const __forward_list_base& __x, true_type) {
if (__alloc_ != __x.__alloc_)
clear();
__alloc_ = __x.__alloc_;
}
- _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base&, false_type) _NOEXCEPT {}
- _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x, true_type)
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void
+ __move_assign_alloc(__forward_list_base&, false_type) _NOEXCEPT {}
+ _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x, true_type)
_NOEXCEPT_(is_nothrow_move_assignable<__node_allocator>::value) {
__alloc_ = std::move(__x.__alloc_);
}
@@ -594,14 +623,15 @@ private:
# ifndef _LIBCPP_CXX03_LANG
template <class _Tp, class _Alloc>
-inline __forward_...
[truncated]
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winner245
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philnik777
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Mar 2, 2025
winner245
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I've just updated this patch mainly for GCC to correctly handle fancy pointers in constant evaluations. Before this update, the patch passed all stage 1 CIs except for GCC: stage1 (generic-gcc, gcc-14, g++-14). The reason for the failure is that the In Clang, To fix this, I take a somewhat tedious approach, which manually expands |
This is LWG3454 whose proposed resolution is speculatively implemented by libc++ and MSVC STL.
But how did this happen? libc++ is consistently marking that function |
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| _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__node_pointer __p) { | ||
| # ifdef _LIBCPP_CXX03_LANG | ||
| return static_cast<__begin_node_pointer>(__p); | ||
| # else | ||
| if constexpr (std::is_pointer<__begin_node_pointer>::value) { | ||
| return static_cast<__begin_node_pointer>(__p); | ||
| } else { | ||
| return __p ? __begin_node_pointer::pointer_to(*static_cast<__begin_node*>(std::addressof(*__p))) | ||
| : static_cast<__begin_node_pointer>(nullptr); | ||
| } | ||
| # endif |
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I think it would be helpful to introduce __static_fancy_pointer_cast function template (in <__memory/pointer_traits.h> or a new internal header). The current changes don't seem correct to me (as libc++ backports C++11 fancy pointer mechanisms to C++03 mode). Let's see whether putting it into free functions would help.
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Thank you for the suggestion! Adding a __static_fancy_pointer_cast function template indeed makes a lot of sense, especially since it could also be beneficial for making <list> constexpr. Following your suggestion, I have introduced a __static_fancy_pointer_cast function template in <__memory/pointer_traits.h>.
Thanks for your clarification! From what you said, I just realized that the problem I mentioned might not exist. I was debugging the GCC CI failure on my local platform using GCC, and I encountered an error with After a bit more investigation of c6a1c3d, I realized that the GCC CI failure might be most likely due to a missing cast in _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI
static __begin_node_pointer __as_iter_node(__node_pointer __p) {
return __p ? pointer_traits<__begin_node_pointer>::pointer_to(*__p)
: static_cast<__begin_node_pointer>(nullptr);
}For GCC constant evaluation, I need an extra _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI
static __begin_node_pointer __as_iter_node(__node_pointer __p) {
return __p ? pointer_traits<__begin_node_pointer>::pointer_to(*static_cast<__begin_node*>(std::addressof(*__p)))
: static_cast<__begin_node_pointer>(nullptr);
}My latest push already included this cast, which actually fixed my real issue with the GCC CI. So maybe I should switch back to |
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philnik777
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libcxx/include/forward_list
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| _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer | ||
| __as_iter_node(__begin_node_pointer __p) { | ||
| return __p; | ||
| } | ||
| _LIBCPP_CONSTEXPR_SINCE_CXX26 _LIBCPP_HIDE_FROM_ABI static __begin_node_pointer __as_iter_node(__node_pointer __p) { | ||
| return std::__static_fancy_pointer_cast<__begin_node_pointer>(__p); |
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Why did this change? What's incorrect about the old version?
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The old version was roughly equivalent to static_cast<Base*>(static_cast<void*>(ptr_to_derived)) (except that it works for fancy pointers), which didn't work in constant evaluation and possibly had UB (Godbolt link).
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I'm quite certain this didn't have UB. It's defined behaviour to reinterpret_cast<Base*>(derived) if Base is the first object after all. Anyways, I think we'd be better off if we don't try to do the round tripping through a void* if we can get away with it (which IMO is quite reasonable). That would allow us to collapse the entire __as_iter_node construct. Could we do that in a separate patch and rebase this on top to simplify this whole thing?
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The old version fails in constant evaluation. I fixed it without resorting to the void* pointer. Given that the redundant __as_iter_node identity cast has already been fixed for forward_list, is there anything else that needs to be addressed before this patch is landed? I've just rebased the patch to resolve conflicts due to the removal of __as_iter_node.
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@philnik777 I am not sure if I understood your comment correctly in the first place. Were you suggesting me clean up the unnecessary static_casts before this one? If so, I've submitted a separate patch #130310 for that.
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Fixes #128658.