[libc++] Avoid type-punning between __Value_type and pair

Author: philnik777

libcxx/include/__fwd/pair.h

@@ -22,6 +22,12 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <class, class>
 struct _LIBCPP_TEMPLATE_VIS pair;
 
+template <class _Type>
+inline const bool __is_pair_v = false;
+
+template <class _Type1, class _Type2>
+inline const bool __is_pair_v<pair<_Type1, _Type2> > = true;
+
 template <size_t _Ip, class _T1, class _T2>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(pair<_T1, _T2>&) _NOEXCEPT;

libcxx/include/__memory/uses_allocator_construction.h

@@ -14,7 +14,6 @@
 #include <__memory/uses_allocator.h>
 #include <__tuple/tuple_like_no_subrange.h>
 #include <__type_traits/enable_if.h>
-#include <__type_traits/is_same.h>
 #include <__type_traits/remove_cv.h>
 #include <__utility/declval.h>
 #include <__utility/pair.h>
@@ -31,14 +30,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 17
 
-template <class _Type>
-inline constexpr bool __is_std_pair = false;
-
-template <class _Type1, class _Type2>
-inline constexpr bool __is_std_pair<pair<_Type1, _Type2>> = true;
-
 template <class _Tp>
-inline constexpr bool __is_cv_std_pair = __is_std_pair<remove_cv_t<_Tp>>;
+inline constexpr bool __is_cv_std_pair = __is_pair_v<remove_cv_t<_Tp>>;
 
 template <class _Tp, class = void>
 struct __uses_allocator_construction_args;

libcxx/include/__node_handle

@@ -175,15 +175,15 @@ struct __set_node_handle_specifics {
 
 template <class _NodeType, class _Derived>
 struct __map_node_handle_specifics {
-  typedef typename _NodeType::__node_value_type::key_type key_type;
-  typedef typename _NodeType::__node_value_type::mapped_type mapped_type;
+  typedef __remove_const_t<typename _NodeType::__node_value_type::first_type> key_type;
+  typedef typename _NodeType::__node_value_type::second_type mapped_type;
 
   _LIBCPP_HIDE_FROM_ABI key_type& key() const {
-    return static_cast<_Derived const*>(this)->__ptr_->__get_value().__ref().first;
+    return const_cast<key_type&>(static_cast<_Derived const*>(this)->__ptr_->__get_value().first);
   }
 
   _LIBCPP_HIDE_FROM_ABI mapped_type& mapped() const {
-    return static_cast<_Derived const*>(this)->__ptr_->__get_value().__ref().second;
+    return static_cast<_Derived const*>(this)->__ptr_->__get_value().second;
   }
 };
 

libcxx/include/__tree

@@ -505,48 +505,24 @@ struct __is_tree_value_type<_One> : __is_tree_value_type_imp<__remove_cvref_t<_O
 template <class _Tp>
 struct __tree_key_value_types {
   typedef _Tp key_type;
-  typedef _Tp __node_value_type;
   typedef _Tp __container_value_type;
   static const bool __is_map = false;
 
   _LIBCPP_HIDE_FROM_ABI static key_type const& __get_key(_Tp const& __v) { return __v; }
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type const& __get_value(__node_value_type const& __v) { return __v; }
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type* __get_ptr(__node_value_type& __n) { return std::addressof(__n); }
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type&& __move(__node_value_type& __v) { return std::move(__v); }
 };
 
 template <class _Key, class _Tp>
 struct __tree_key_value_types<__value_type<_Key, _Tp> > {
   typedef _Key key_type;
   typedef _Tp mapped_type;
-  typedef __value_type<_Key, _Tp> __node_value_type;
   typedef pair<const _Key, _Tp> __container_value_type;
   typedef __container_value_type __map_value_type;
   static const bool __is_map = true;
 
-  _LIBCPP_HIDE_FROM_ABI static key_type const& __get_key(__node_value_type const& __t) {
-    return __t.__get_value().first;
-  }
-
   template <class _Up, __enable_if_t<__is_same_uncvref<_Up, __container_value_type>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI static key_type const& __get_key(_Up& __t) {
     return __t.first;
   }
-
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type const& __get_value(__node_value_type const& __t) {
-    return __t.__get_value();
-  }
-
-  template <class _Up, __enable_if_t<__is_same_uncvref<_Up, __container_value_type>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type const& __get_value(_Up& __t) {
-    return __t;
-  }
-
-  _LIBCPP_HIDE_FROM_ABI static __container_value_type* __get_ptr(__node_value_type& __n) {
-    return std::addressof(__n.__get_value());
-  }
-
-  _LIBCPP_HIDE_FROM_ABI static pair<key_type&&, mapped_type&&> __move(__node_value_type& __v) { return __v.__move(); }
 };
 
 template <class _VoidPtr>
@@ -587,6 +563,19 @@ struct __tree_map_pointer_types<_Tp, _AllocPtr, _KVTypes, true> {
   typedef __rebind_pointer_t<_AllocPtr, const _Mv> __const_map_value_type_pointer;
 };
 
+template <class _Tp>
+struct __get_node_value_type {
+  using type _LIBCPP_NODEBUG = _Tp;
+};
+
+template <class _Key, class _ValueT>
+struct __get_node_value_type<__value_type<_Key, _ValueT> > {
+  using type _LIBCPP_NODEBUG = pair<const _Key, _ValueT>;
+};
+
+template <class _Tp>
+using __get_node_value_type_t = typename __get_node_value_type<_Tp>::type;
+
 template <class _NodePtr, class _NodeT = typename pointer_traits<_NodePtr>::element_type>
 struct __tree_node_types;
 
@@ -601,7 +590,7 @@ public:
   typedef typename pointer_traits<_NodePtr>::element_type __node_type;
   typedef _NodePtr __node_pointer;
 
-  typedef _Tp __node_value_type;
+  using __node_value_type = __get_node_value_type_t<_Tp>;
   typedef __rebind_pointer_t<_VoidPtr, __node_value_type> __node_value_type_pointer;
   typedef __rebind_pointer_t<_VoidPtr, const __node_value_type> __const_node_value_type_pointer;
   typedef typename __base::__end_node_pointer __iter_pointer;
@@ -653,11 +642,11 @@ public:
 template <class _Tp, class _VoidPtr>
 class _LIBCPP_STANDALONE_DEBUG __tree_node : public __tree_node_base<_VoidPtr> {
 public:
-  typedef _Tp __node_value_type;
+  using __node_value_type = __get_node_value_type_t<_Tp>;
 
   __node_value_type __value_;
 
-  _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return __value_; }
+  _LIBCPP_HIDE_FROM_ABI __node_value_type& __get_value() { return __value_; }
 
   ~__tree_node()                             = delete;
   __tree_node(__tree_node const&)            = delete;
@@ -688,7 +677,7 @@ public:
 
   _LIBCPP_HIDE_FROM_ABI void operator()(pointer __p) _NOEXCEPT {
     if (__value_constructed)
-      __alloc_traits::destroy(__na_, _NodeTypes::__get_ptr(__p->__value_));
+      __alloc_traits::destroy(__na_, std::addressof(__p->__value_));
     if (__p)
       __alloc_traits::deallocate(__na_, __p, 1);
   }
@@ -719,7 +708,7 @@ class _LIBCPP_TEMPLATE_VIS __tree_iterator {
 
 public:
   typedef bidirectional_iterator_tag iterator_category;
-  typedef _Tp value_type;
+  using value_type = __get_node_value_type_t<_Tp>;
   typedef _DiffType difference_type;
   typedef value_type& reference;
   typedef typename _NodeTypes::__node_value_type_pointer pointer;
@@ -796,7 +785,7 @@ class _LIBCPP_TEMPLATE_VIS __tree_const_iterator {
 
 public:
   typedef bidirectional_iterator_tag iterator_category;
-  typedef _Tp value_type;
+  using value_type = __get_node_value_type_t<_Tp>;
   typedef _DiffType difference_type;
   typedef const value_type& reference;
   typedef typename _NodeTypes::__const_node_value_type_pointer pointer;
@@ -809,7 +798,7 @@ public:
   }
 
 private:
-  typedef __tree_iterator<value_type, __node_pointer, difference_type> __non_const_iterator;
+  typedef __tree_iterator<_Tp, __node_pointer, difference_type> __non_const_iterator;
 
 public:
   _LIBCPP_HIDE_FROM_ABI __tree_const_iterator(__non_const_iterator __p) _NOEXCEPT : __ptr_(__p.__ptr_) {}
@@ -1276,6 +1265,32 @@ private:
   }
   _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__tree&, false_type) _NOEXCEPT {}
 
+  template <class _From, __enable_if_t<__is_pair_v<__remove_cvref_t<_From> >, int> = 0>
+  _LIBCPP_HIDE_FROM_ABI static void __assign_value(__get_node_value_type_t<value_type>& __lhs, _From&& __rhs) {
+    using __punned_type = pair<typename _NodeTypes::key_type, typename _NodeTypes::mapped_type>;
+
+    reinterpret_cast<__punned_type&>(__lhs) = reinterpret_cast<__copy_cvref_t<_From, __punned_type>&&>(__rhs);
+  }
+
+  template <class _To,
+            class _From,
+            class _ValueT                                                                                      = _Tp,
+            __enable_if_t<__is_tree_value_type<_ValueT>::value && !__is_pair_v<__remove_cvref_t<_From> >, int> = 0>
+  _LIBCPP_HIDE_FROM_ABI static void __assign_value(_To& __lhs, _From&& __rhs) {
+    static_assert(__is_pair_v<__remove_cvref_t<_From> >);
+    using __punned_type = pair<typename _NodeTypes::key_type, typename _NodeTypes::mapped_type>;
+
+    reinterpret_cast<__punned_type&>(__lhs) = __rhs;
+  }
+
+  template <class _To,
+            class _From,
+            class _ValueT                                                                                       = _Tp,
+            __enable_if_t<!__is_tree_value_type<_ValueT>::value && !__is_pair_v<__remove_cvref_t<_From> >, int> = 0>
+  _LIBCPP_HIDE_FROM_ABI static void __assign_value(_To& __lhs, _From&& __rhs) {
+    __lhs = std::forward<_From>(__rhs);
+  }
+
   struct _DetachedTreeCache {
     _LIBCPP_HIDE_FROM_ABI explicit _DetachedTreeCache(__tree* __t) _NOEXCEPT
         : __t_(__t),
@@ -1416,13 +1431,13 @@ void __tree<_Tp, _Compare, _Allocator>::__assign_multi(_InputIterator __first, _
   if (size() != 0) {
     _DetachedTreeCache __cache(this);
     for (; __cache.__get() && __first != __last; ++__first) {
-      __cache.__get()->__value_ = *__first;
+      __assign_value(__cache.__get()->__value_, *__first);
       __node_insert_multi(__cache.__get());
       __cache.__advance();
     }
   }
   for (; __first != __last; ++__first)
-    __insert_multi(_NodeTypes::__get_value(*__first));
+    __insert_multi(*__first);
 }
 
 template <class _Tp, class _Compare, class _Allocator>
@@ -1501,13 +1516,19 @@ void __tree<_Tp, _Compare, _Allocator>::__move_assign(__tree& __t, false_type) {
     if (size() != 0) {
       _DetachedTreeCache __cache(this);
       while (__cache.__get() != nullptr && __t.size() != 0) {
-        __cache.__get()->__value_ = std::move(__t.remove(__t.begin())->__value_);
+        __assign_value(__cache.__get()->__value_, std::move(__t.remove(__t.begin())->__value_));
         __node_insert_multi(__cache.__get());
         __cache.__advance();
       }
     }
-    while (__t.size() != 0)
-      __insert_multi(__e, _NodeTypes::__move(__t.remove(__t.begin())->__value_));
+    while (__t.size() != 0) {
+      if constexpr (__is_tree_value_type<_Tp>::value) {
+        using __punned_type = pair<typename _NodeTypes::key_type, typename _NodeTypes::mapped_type>;
+        __insert_multi(__e, reinterpret_cast<__punned_type&&>(__t.remove(__t.begin())->__value_));
+      } else {
+        __insert_multi(__e, std::move(__t.remove(__t.begin())->__value_));
+      }
+    }
   }
 }
 
@@ -1533,7 +1554,7 @@ void __tree<_Tp, _Compare, _Allocator>::destroy(__node_pointer __nd) _NOEXCEPT {
     destroy(static_cast<__node_pointer>(__nd->__left_));
     destroy(static_cast<__node_pointer>(__nd->__right_));
     __node_allocator& __na = __node_alloc();
-    __node_traits::destroy(__na, _NodeTypes::__get_ptr(__nd->__value_));
+    __node_traits::destroy(__na, std::addressof(__nd->__value_));
     __node_traits::deallocate(__na, __nd, 1);
   }
 }
@@ -1803,10 +1824,9 @@ template <class _Tp, class _Compare, class _Allocator>
 template <class... _Args>
 typename __tree<_Tp, _Compare, _Allocator>::__node_holder
 __tree<_Tp, _Compare, _Allocator>::__construct_node(_Args&&... __args) {
-  static_assert(!__is_tree_value_type<_Args...>::value, "Cannot construct from __value_type");
   __node_allocator& __na = __node_alloc();
   __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
-  __node_traits::construct(__na, _NodeTypes::__get_ptr(__h->__value_), std::forward<_Args>(__args)...);
+  __node_traits::construct(__na, std::addressof(__h->__value_), std::forward<_Args>(__args)...);
   __h.get_deleter().__value_constructed = true;
   return __h;
 }
@@ -1874,7 +1894,7 @@ __tree<_Tp, _Compare, _Allocator>::__node_assign_unique(const __container_value_
   __node_pointer __r           = static_cast<__node_pointer>(__child);
   bool __inserted              = false;
   if (__child == nullptr) {
-    __nd->__value_ = __v;
+    __assign_value(__nd->__value_, __v);
     __insert_node_at(__parent, __child, static_cast<__node_base_pointer>(__nd));
     __r        = __nd;
     __inserted = true;
@@ -2036,7 +2056,7 @@ typename __tree<_Tp, _Compare, _Allocator>::iterator __tree<_Tp, _Compare, _Allo
   __node_pointer __np    = __p.__get_np();
   iterator __r           = __remove_node_pointer(__np);
   __node_allocator& __na = __node_alloc();
-  __node_traits::destroy(__na, _NodeTypes::__get_ptr(const_cast<__node_value_type&>(*__p)));
+  __node_traits::destroy(__na, std::addressof(const_cast<__node_value_type&>(*__p)));
   __node_traits::deallocate(__na, __np, 1);
   return __r;
 }