[libcxx-commits] [libcxx] 59d246e - [libc++] Remove __deque_base

Nikolas Klauser via libcxx-commits libcxx-commits at lists.llvm.org
Fri Aug 26 12:59:42 PDT 2022


Author: Nikolas Klauser
Date: 2022-08-26T21:59:33+02:00
New Revision: 59d246e55f56799ef47dcaae9788c0c3e77a2244

URL: https://github.com/llvm/llvm-project/commit/59d246e55f56799ef47dcaae9788c0c3e77a2244
DIFF: https://github.com/llvm/llvm-project/commit/59d246e55f56799ef47dcaae9788c0c3e77a2244.diff

LOG: [libc++] Remove __deque_base

This patch simplifies the implementation of `deque` by removing the `__deque_base` class which results in a lot less indirections and removes the need for `__base::`.

Reviewed By: ldionne, #libc

Spies: AdvenamTacet, libcxx-commits

Differential Revision: https://reviews.llvm.org/D132081

Added: 
    libcxx/test/std/containers/sequences/deque/abi.compile.pass.cpp

Modified: 
    libcxx/include/deque
    libcxx/test/std/containers/container.adaptors/queue/queue.cons/ctor_iterators.pass.cpp
    libcxx/test/std/containers/container.adaptors/stack/stack.cons/ctor_iterators.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/deque b/libcxx/include/deque
index 2bb2643c2214f..c758327595405 100644
--- a/libcxx/include/deque
+++ b/libcxx/include/deque
@@ -214,7 +214,6 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp, class _Allocator> class __deque_base;
 template <class _Tp, class _Allocator = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS deque;
 
 template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
@@ -475,7 +474,6 @@ private:
     _LIBCPP_INLINE_VISIBILITY explicit __deque_iterator(__map_iterator __m, pointer __p) _NOEXCEPT
         : __m_iter_(__m), __ptr_(__p) {}
 
-    template <class _Tp, class _Ap> friend class __deque_base;
     template <class _Tp, class _Ap> friend class _LIBCPP_TEMPLATE_VIS deque;
     template <class _Vp, class _Pp, class _Rp, class _MP, class _Dp, _Dp>
         friend class _LIBCPP_TEMPLATE_VIS __deque_iterator;
@@ -939,381 +937,142 @@ move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
     return __r;
 }
 
-template <class _Tp, class _Allocator>
-class __deque_base
+template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
+class _LIBCPP_TEMPLATE_VIS deque
 {
-    __deque_base(const __deque_base& __c);
-    __deque_base& operator=(const __deque_base& __c);
 public:
-    typedef _Allocator                                allocator_type;
-    typedef allocator_traits<allocator_type>          __alloc_traits;
-    typedef typename __alloc_traits::size_type        size_type;
-
-    typedef _Tp                                       value_type;
-    typedef value_type&                               reference;
-    typedef const value_type&                         const_reference;
-    typedef typename __alloc_traits::
diff erence_type  
diff erence_type;
-    typedef typename __alloc_traits::pointer          pointer;
-    typedef typename __alloc_traits::const_pointer    const_pointer;
-
-    static const 
diff erence_type __block_size;
-
-    typedef typename __rebind_alloc_helper<__alloc_traits, pointer>::type __pointer_allocator;
-    typedef allocator_traits<__pointer_allocator>        __map_traits;
-    typedef typename __map_traits::pointer               __map_pointer;
-    typedef typename __rebind_alloc_helper<__alloc_traits, const_pointer>::type __const_pointer_allocator;
-    typedef typename allocator_traits<__const_pointer_allocator>::const_pointer __map_const_pointer;
-    typedef __split_buffer<pointer, __pointer_allocator> __map;
-
-    typedef __deque_iterator<value_type, pointer, reference, __map_pointer,
-                             
diff erence_type>    iterator;
-    typedef __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer,
-                             
diff erence_type>    const_iterator;
-
-    struct __deque_block_range {
-      explicit __deque_block_range(pointer __b, pointer __e) _NOEXCEPT : __begin_(__b), __end_(__e) {}
-      const pointer __begin_;
-      const pointer __end_;
-    };
-
-    struct __deque_range {
-      iterator __pos_;
-      const iterator __end_;
-
-      __deque_range(iterator __pos, iterator __e) _NOEXCEPT
-        : __pos_(__pos), __end_(__e) {}
-
-      explicit operator bool() const _NOEXCEPT {
-        return __pos_ != __end_;
-      }
-
-      __deque_range begin() const {
-        return *this;
-      }
-
-      __deque_range end() const {
-        return __deque_range(__end_, __end_);
-      }
-      __deque_block_range operator*() const _NOEXCEPT {
-         if (__pos_.__m_iter_ == __end_.__m_iter_) {
-          return __deque_block_range(__pos_.__ptr_, __end_.__ptr_);
-        }
-        return __deque_block_range(__pos_.__ptr_, *__pos_.__m_iter_ + __block_size);
-      }
-
-      __deque_range& operator++() _NOEXCEPT {
-        if (__pos_.__m_iter_ == __end_.__m_iter_) {
-          __pos_ = __end_;
-        } else {
-          ++__pos_.__m_iter_;
-          __pos_.__ptr_ = *__pos_.__m_iter_;
-        }
-        return *this;
-      }
+    // types:
 
+  using value_type = _Tp;
 
-      _LIBCPP_HIDE_FROM_ABI friend bool operator==(__deque_range const& __lhs, __deque_range const& __rhs) {
-        return __lhs.__pos_ == __rhs.__pos_;
-      }
-      _LIBCPP_HIDE_FROM_ABI friend bool operator!=(__deque_range const& __lhs, __deque_range const& __rhs) {
-        return !(__lhs == __rhs);
-      }
-    };
-
+  static_assert((is_same<typename _Allocator::value_type, value_type>::value),
+                "Allocator::value_type must be same type as value_type");
 
+  using allocator_type = _Allocator;
+  using __alloc_traits = allocator_traits<allocator_type>;
 
-    struct _ConstructTransaction {
-      _ConstructTransaction(__deque_base* __db, __deque_block_range& __r)
-        : __pos_(__r.__begin_), __end_(__r.__end_), __begin_(__r.__begin_), __base_(__db) {}
+  using size_type       = typename __alloc_traits::size_type;
+  using 
diff erence_type = typename __alloc_traits::
diff erence_type;
 
+  using pointer       = typename __alloc_traits::pointer;
+  using const_pointer = typename __alloc_traits::const_pointer;
 
-      ~_ConstructTransaction() {
-        __base_->size() += (__pos_ - __begin_);
-      }
+  using __pointer_allocator       = typename __rebind_alloc_helper<__alloc_traits, pointer>::type;
+  using __const_pointer_allocator = typename __rebind_alloc_helper<__alloc_traits, const_pointer>::type;
+  using __map                     = __split_buffer<pointer, __pointer_allocator>;
+  using __map_alloc_traits        = allocator_traits<__pointer_allocator>;
+  using __map_pointer             = typename __map_alloc_traits::pointer;
+  using __map_const_pointer       = typename allocator_traits<__const_pointer_allocator>::const_pointer;
 
-      pointer __pos_;
-      const pointer __end_;
-    private:
-      const pointer __begin_;
-      __deque_base * const __base_;
-    };
+  using reference       = value_type&;
+  using const_reference = const value_type&;
 
-protected:
-    __map __map_;
-    size_type __start_;
-    __compressed_pair<size_type, allocator_type> __size_;
+  using iterator = __deque_iterator<value_type, pointer, reference, __map_pointer, 
diff erence_type>;
+  using const_iterator =
+      __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer, 
diff erence_type>;
+  using reverse_iterator       = std::reverse_iterator<iterator>;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
-    iterator       begin() _NOEXCEPT;
-    const_iterator begin() const _NOEXCEPT;
-    iterator       end() _NOEXCEPT;
-    const_iterator end() const _NOEXCEPT;
+  static_assert(is_same<allocator_type, typename __rebind_alloc_helper<__alloc_traits, value_type>::type>::value,
+                "rebinding an allocator to value_type should result in the original allocator");
+  static_assert(is_nothrow_default_constructible<allocator_type>::value ==
+                    is_nothrow_default_constructible<__pointer_allocator>::value,
+                "rebinding an allocator should not change excpetion guarantees");
+  static_assert(is_nothrow_move_constructible<allocator_type>::value ==
+                    is_nothrow_move_constructible<typename __map::allocator_type>::value,
+                "rebinding an allocator should not change excpetion guarantees");
 
-    _LIBCPP_INLINE_VISIBILITY size_type&            size()          {return __size_.first();}
-    _LIBCPP_INLINE_VISIBILITY
-    const size_type& size() const _NOEXCEPT {return __size_.first();}
-    _LIBCPP_INLINE_VISIBILITY allocator_type&       __alloc()       {return __size_.second();}
-    _LIBCPP_INLINE_VISIBILITY
-    const allocator_type& __alloc() const _NOEXCEPT {return __size_.second();}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __deque_base()
-        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value);
-    _LIBCPP_INLINE_VISIBILITY
-    explicit __deque_base(const allocator_type& __a);
-public:
-    ~__deque_base();
-
-#ifndef _LIBCPP_CXX03_LANG
-    __deque_base(__deque_base&& __c)
-        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
-    __deque_base(__deque_base&& __c, const allocator_type& __a);
-#endif // _LIBCPP_CXX03_LANG
+private:
+  struct __deque_block_range {
+    explicit __deque_block_range(pointer __b, pointer __e) _NOEXCEPT : __begin_(__b), __end_(__e) {}
+    const pointer __begin_;
+    const pointer __end_;
+  };
 
-    void swap(__deque_base& __c)
-#if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT;
-#else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
-                    __is_nothrow_swappable<allocator_type>::value);
-#endif
-protected:
-    void clear() _NOEXCEPT;
+  struct __deque_range {
+    iterator __pos_;
+    const iterator __end_;
 
-    bool __invariants() const;
+    __deque_range(iterator __pos, iterator __e) _NOEXCEPT
+      : __pos_(__pos), __end_(__e) {}
 
-    _LIBCPP_INLINE_VISIBILITY
-    void __move_assign(__deque_base& __c)
-        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
-                   is_nothrow_move_assignable<allocator_type>::value)
-    {
-        __map_ = _VSTD::move(__c.__map_);
-        __start_ = __c.__start_;
-        size() = __c.size();
-        __move_assign_alloc(__c);
-        __c.__start_ = __c.size() = 0;
+    explicit operator bool() const _NOEXCEPT {
+      return __pos_ != __end_;
     }
 
-    _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__deque_base& __c)
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_move_assignment::value ||
-                   is_nothrow_move_assignable<allocator_type>::value)
-        {__move_assign_alloc(__c, integral_constant<bool,
-                      __alloc_traits::propagate_on_container_move_assignment::value>());}
-
-private:
-    _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__deque_base& __c, true_type)
-        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
-        {
-            __alloc() = _VSTD::move(__c.__alloc());
-        }
-
-    _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__deque_base&, false_type) _NOEXCEPT
-        {}
-};
-
-template <class _Tp, class _Allocator>
-const typename __deque_base<_Tp, _Allocator>::
diff erence_type
-    __deque_base<_Tp, _Allocator>::__block_size =
-        __deque_block_size<value_type, 
diff erence_type>::value;
+    __deque_range begin() const {
+      return *this;
+    }
 
-template <class _Tp, class _Allocator>
-bool
-__deque_base<_Tp, _Allocator>::__invariants() const
-{
-    if (!__map_.__invariants())
-        return false;
-    if (__map_.size() >= size_type(-1) / __block_size)
-        return false;
-    for (typename __map::const_iterator __i = __map_.begin(), __e = __map_.end();
-         __i != __e; ++__i)
-        if (*__i == nullptr)
-            return false;
-    if (__map_.size() != 0)
-    {
-        if (size() >= __map_.size() * __block_size)
-            return false;
-        if (__start_ >= __map_.size() * __block_size - size())
-            return false;
+    __deque_range end() const {
+      return __deque_range(__end_, __end_);
     }
-    else
-    {
-        if (size() != 0)
-            return false;
-        if (__start_ != 0)
-            return false;
+    __deque_block_range operator*() const _NOEXCEPT {
+        if (__pos_.__m_iter_ == __end_.__m_iter_) {
+        return __deque_block_range(__pos_.__ptr_, __end_.__ptr_);
+      }
+      return __deque_block_range(__pos_.__ptr_, *__pos_.__m_iter_ + __block_size);
     }
-    return true;
-}
-
-template <class _Tp, class _Allocator>
-typename __deque_base<_Tp, _Allocator>::iterator
-__deque_base<_Tp, _Allocator>::begin() _NOEXCEPT
-{
-    __map_pointer __mp = __map_.begin() + __start_ / __block_size;
-    return iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
-}
-
-template <class _Tp, class _Allocator>
-typename __deque_base<_Tp, _Allocator>::const_iterator
-__deque_base<_Tp, _Allocator>::begin() const _NOEXCEPT
-{
-    __map_const_pointer __mp = static_cast<__map_const_pointer>(__map_.begin() + __start_ / __block_size);
-    return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
-}
-
-template <class _Tp, class _Allocator>
-typename __deque_base<_Tp, _Allocator>::iterator
-__deque_base<_Tp, _Allocator>::end() _NOEXCEPT
-{
-    size_type __p = size() + __start_;
-    __map_pointer __mp = __map_.begin() + __p / __block_size;
-    return iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
-}
-
-template <class _Tp, class _Allocator>
-typename __deque_base<_Tp, _Allocator>::const_iterator
-__deque_base<_Tp, _Allocator>::end() const _NOEXCEPT
-{
-    size_type __p = size() + __start_;
-    __map_const_pointer __mp = static_cast<__map_const_pointer>(__map_.begin() + __p / __block_size);
-    return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
-}
-
-template <class _Tp, class _Allocator>
-inline
-__deque_base<_Tp, _Allocator>::__deque_base()
-    _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
-    : __start_(0), __size_(0, __default_init_tag()) {}
-
-template <class _Tp, class _Allocator>
-inline
-__deque_base<_Tp, _Allocator>::__deque_base(const allocator_type& __a)
-    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a) {}
 
-template <class _Tp, class _Allocator>
-__deque_base<_Tp, _Allocator>::~__deque_base()
-{
-    clear();
-    typename __map::iterator __i = __map_.begin();
-    typename __map::iterator __e = __map_.end();
-    for (; __i != __e; ++__i)
-        __alloc_traits::deallocate(__alloc(), *__i, __block_size);
-}
+    __deque_range& operator++() _NOEXCEPT {
+      if (__pos_.__m_iter_ == __end_.__m_iter_) {
+        __pos_ = __end_;
+      } else {
+        ++__pos_.__m_iter_;
+        __pos_.__ptr_ = *__pos_.__m_iter_;
+      }
+      return *this;
+    }
 
-#ifndef _LIBCPP_CXX03_LANG
 
-template <class _Tp, class _Allocator>
-__deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c)
-    _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
-    : __map_(_VSTD::move(__c.__map_)),
-      __start_(_VSTD::move(__c.__start_)),
-      __size_(_VSTD::move(__c.__size_))
-{
-    __c.__start_ = 0;
-    __c.size() = 0;
-}
-
-template <class _Tp, class _Allocator>
-__deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c, const allocator_type& __a)
-    : __map_(_VSTD::move(__c.__map_), __pointer_allocator(__a)),
-      __start_(_VSTD::move(__c.__start_)),
-      __size_(_VSTD::move(__c.size()), __a)
-{
-    if (__a == __c.__alloc())
-    {
-        __c.__start_ = 0;
-        __c.size() = 0;
+    _LIBCPP_HIDE_FROM_ABI friend bool operator==(__deque_range const& __lhs, __deque_range const& __rhs) {
+      return __lhs.__pos_ == __rhs.__pos_;
     }
-    else
-    {
-        __map_.clear();
-        __start_ = 0;
-        size() = 0;
+    _LIBCPP_HIDE_FROM_ABI friend bool operator!=(__deque_range const& __lhs, __deque_range const& __rhs) {
+      return !(__lhs == __rhs);
     }
-}
+  };
 
-#endif // _LIBCPP_CXX03_LANG
+  struct _ConstructTransaction {
+    _ConstructTransaction(deque* __db, __deque_block_range& __r)
+      : __pos_(__r.__begin_), __end_(__r.__end_), __begin_(__r.__begin_), __base_(__db) {}
 
-template <class _Tp, class _Allocator>
-void
-__deque_base<_Tp, _Allocator>::swap(__deque_base& __c)
-#if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT
-#else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
-                    __is_nothrow_swappable<allocator_type>::value)
-#endif
-{
-    __map_.swap(__c.__map_);
-    _VSTD::swap(__start_, __c.__start_);
-    _VSTD::swap(size(), __c.size());
-    _VSTD::__swap_allocator(__alloc(), __c.__alloc());
-}
 
-template <class _Tp, class _Allocator>
-void
-__deque_base<_Tp, _Allocator>::clear() _NOEXCEPT
-{
-    allocator_type& __a = __alloc();
-    for (iterator __i = begin(), __e = end(); __i != __e; ++__i)
-        __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
-    size() = 0;
-    while (__map_.size() > 2)
-    {
-        __alloc_traits::deallocate(__a, __map_.front(), __block_size);
-        __map_.pop_front();
-    }
-    switch (__map_.size())
-    {
-    case 1:
-        __start_ = __block_size / 2;
-        break;
-    case 2:
-        __start_ = __block_size;
-        break;
+    ~_ConstructTransaction() {
+      __base_->__size() += (__pos_ - __begin_);
     }
-}
 
-template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
-class _LIBCPP_TEMPLATE_VIS deque
-    : private __deque_base<_Tp, _Allocator>
-{
-public:
-    // types:
+    pointer __pos_;
+    const pointer __end_;
+  private:
+    const pointer __begin_;
+    deque* const __base_;
+  };
 
-    typedef _Tp value_type;
-    typedef _Allocator allocator_type;
+  static const 
diff erence_type __block_size;
 
-    static_assert((is_same<typename allocator_type::value_type, value_type>::value),
-                  "Allocator::value_type must be same type as value_type");
+  __map __map_;
+  size_type __start_;
+  __compressed_pair<size_type, allocator_type> __size_;
 
-    typedef __deque_base<value_type, allocator_type>      __base;
+public:
 
-    typedef typename __base::__alloc_traits               __alloc_traits;
-    typedef typename __base::reference                    reference;
-    typedef typename __base::const_reference              const_reference;
-    typedef typename __base::iterator                     iterator;
-    typedef typename __base::const_iterator               const_iterator;
-    typedef typename __base::size_type                    size_type;
-    typedef typename __base::
diff erence_type              
diff erence_type;
+    // construct/copy/destroy:
+    _LIBCPP_INLINE_VISIBILITY
+    deque() _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
+        : __start_(0), __size_(0, __default_init_tag()) {}
 
-    typedef typename __base::pointer                      pointer;
-    typedef typename __base::const_pointer                const_pointer;
-    typedef _VSTD::reverse_iterator<iterator>             reverse_iterator;
-    typedef _VSTD::reverse_iterator<const_iterator>       const_reverse_iterator;
+    _LIBCPP_HIDE_FROM_ABI ~deque() {
+      clear();
+      typename __map::iterator __i = __map_.begin();
+      typename __map::iterator __e = __map_.end();
+      for (; __i != __e; ++__i)
+          __alloc_traits::deallocate(__alloc(), *__i, __block_size);
+    }
 
-    using typename __base::__deque_range;
-    using typename __base::__deque_block_range;
-    using typename __base::_ConstructTransaction;
+    _LIBCPP_INLINE_VISIBILITY explicit deque(const allocator_type& __a)
+        : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a) {}
 
-    // construct/copy/destroy:
-    _LIBCPP_INLINE_VISIBILITY
-    deque()
-        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
-        {}
-    _LIBCPP_INLINE_VISIBILITY explicit deque(const allocator_type& __a) : __base(__a) {}
     explicit deque(size_type __n);
 #if _LIBCPP_STD_VER > 11
     explicit deque(size_type __n, const _Allocator& __a);
@@ -1321,7 +1080,8 @@ public:
     deque(size_type __n, const value_type& __v);
 
     template <class = __enable_if_t<__is_allocator<_Allocator>::value> >
-    deque(size_type __n, const value_type& __v, const allocator_type& __a) : __base(__a)
+    deque(size_type __n, const value_type& __v, const allocator_type& __a)
+        : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
     {
         if (__n > 0)
             __append(__n, __v);
@@ -1346,7 +1106,7 @@ public:
     deque& operator=(initializer_list<value_type> __il) {assign(__il); return *this;}
 
     _LIBCPP_INLINE_VISIBILITY
-    deque(deque&& __c) _NOEXCEPT_(is_nothrow_move_constructible<__base>::value);
+    deque(deque&& __c) _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
     _LIBCPP_INLINE_VISIBILITY
     deque(deque&& __c, const __type_identity_t<allocator_type>& __a);
     _LIBCPP_INLINE_VISIBILITY
@@ -1369,57 +1129,77 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT;
-
-    // iterators:
-
-    _LIBCPP_INLINE_VISIBILITY
-    iterator       begin() _NOEXCEPT       {return __base::begin();}
-    _LIBCPP_INLINE_VISIBILITY
-    const_iterator begin() const _NOEXCEPT {return __base::begin();}
-    _LIBCPP_INLINE_VISIBILITY
-    iterator       end() _NOEXCEPT         {return __base::end();}
-    _LIBCPP_INLINE_VISIBILITY
-    const_iterator end()   const _NOEXCEPT {return __base::end();}
+  _LIBCPP_HIDE_FROM_ABI allocator_type& __alloc() _NOEXCEPT { return __size_.second(); }
+  _LIBCPP_HIDE_FROM_ABI const allocator_type& __alloc() const _NOEXCEPT { return __size_.second(); }
+
+  // iterators:
+
+  _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT {
+      __map_pointer __mp = __map_.begin() + __start_ / __block_size;
+      return iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT {
+      __map_const_pointer __mp =
+          static_cast<__map_const_pointer>(__map_.begin() + __start_ / __block_size);
+      return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT {
+      size_type __p      = size() + __start_;
+      __map_pointer __mp = __map_.begin() + __p / __block_size;
+      return iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT {
+      size_type __p            = size() + __start_;
+      __map_const_pointer __mp = static_cast<__map_const_pointer>(__map_.begin() + __p / __block_size);
+      return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
+  }
 
     _LIBCPP_INLINE_VISIBILITY
     reverse_iterator       rbegin() _NOEXCEPT
-        {return       reverse_iterator(__base::end());}
+        {return       reverse_iterator(end());}
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator rbegin() const _NOEXCEPT
-        {return const_reverse_iterator(__base::end());}
+        {return const_reverse_iterator(end());}
     _LIBCPP_INLINE_VISIBILITY
     reverse_iterator       rend() _NOEXCEPT
-        {return       reverse_iterator(__base::begin());}
+        {return       reverse_iterator(begin());}
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator rend()   const _NOEXCEPT
-        {return const_reverse_iterator(__base::begin());}
+        {return const_reverse_iterator(begin());}
 
     _LIBCPP_INLINE_VISIBILITY
     const_iterator         cbegin()  const _NOEXCEPT
-        {return __base::begin();}
+        {return begin();}
     _LIBCPP_INLINE_VISIBILITY
     const_iterator         cend()    const _NOEXCEPT
-        {return __base::end();}
+        {return end();}
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crbegin() const _NOEXCEPT
-        {return const_reverse_iterator(__base::end());}
+        {return const_reverse_iterator(end());}
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crend()   const _NOEXCEPT
-        {return const_reverse_iterator(__base::begin());}
+        {return const_reverse_iterator(begin());}
 
     // capacity:
     _LIBCPP_INLINE_VISIBILITY
-    size_type size() const _NOEXCEPT {return __base::size();}
+    size_type size() const _NOEXCEPT {return __size();}
+
+  _LIBCPP_HIDE_FROM_ABI size_type& __size() _NOEXCEPT { return __size_.first(); }
+  _LIBCPP_HIDE_FROM_ABI const size_type& __size() const _NOEXCEPT { return __size_.first(); }
+
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
         {return _VSTD::min<size_type>(
-            __alloc_traits::max_size(__base::__alloc()),
+            __alloc_traits::max_size(__alloc()),
             numeric_limits<
diff erence_type>::max());}
     void resize(size_type __n);
     void resize(size_type __n, const value_type& __v);
     void shrink_to_fit() _NOEXCEPT;
     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
-    bool empty() const _NOEXCEPT {return __base::size() == 0;}
+    bool empty() const _NOEXCEPT {return size() == 0;}
 
     // element access:
     _LIBCPP_INLINE_VISIBILITY
@@ -1489,53 +1269,105 @@ public:
     void clear() _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
-    bool __invariants() const {return __base::__invariants();}
+    bool __invariants() const {
+        if (!__map_.__invariants())
+            return false;
+        if (__map_.size() >= size_type(-1) / __block_size)
+            return false;
+        for (typename __map::const_iterator __i = __map_.begin(), __e = __map_.end();
+            __i != __e; ++__i)
+            if (*__i == nullptr)
+                return false;
+        if (__map_.size() != 0)
+        {
+            if (size() >= __map_.size() * __block_size)
+                return false;
+            if (__start_ >= __map_.size() * __block_size - size())
+                return false;
+        }
+        else
+        {
+            if (size() != 0)
+                return false;
+            if (__start_ != 0)
+                return false;
+        }
+        return true;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __move_assign_alloc(deque& __c)
+        _NOEXCEPT_(!__alloc_traits::propagate_on_container_move_assignment::value ||
+                   is_nothrow_move_assignable<allocator_type>::value)
+        {__move_assign_alloc(__c, integral_constant<bool,
+                      __alloc_traits::propagate_on_container_move_assignment::value>());}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __move_assign_alloc(deque& __c, true_type)
+        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
+        {
+            __alloc() = _VSTD::move(__c.__alloc());
+        }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __move_assign_alloc(deque&, false_type) _NOEXCEPT
+        {}
 
-    typedef typename __base::__map_const_pointer __map_const_pointer;
+    _LIBCPP_INLINE_VISIBILITY
+    void __move_assign(deque& __c)
+        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
+                   is_nothrow_move_assignable<allocator_type>::value)
+    {
+        __map_ = _VSTD::move(__c.__map_);
+        __start_ = __c.__start_;
+        __size() = __c.size();
+        __move_assign_alloc(__c);
+        __c.__start_ = __c.__size() = 0;
+    }
 
     _LIBCPP_INLINE_VISIBILITY
     static size_type __recommend_blocks(size_type __n)
     {
-        return __n / __base::__block_size + (__n % __base::__block_size != 0);
+        return __n / __block_size + (__n % __block_size != 0);
     }
     _LIBCPP_INLINE_VISIBILITY
     size_type __capacity() const
     {
-        return __base::__map_.size() == 0 ? 0 : __base::__map_.size() * __base::__block_size - 1;
+        return __map_.size() == 0 ? 0 : __map_.size() * __block_size - 1;
     }
     _LIBCPP_INLINE_VISIBILITY
     size_type __block_count() const
     {
-        return __base::__map_.size();
+        return __map_.size();
     }
 
     _LIBCPP_INLINE_VISIBILITY
     size_type __front_spare() const
     {
-        return __base::__start_;
+        return __start_;
     }
     _LIBCPP_INLINE_VISIBILITY
     size_type __front_spare_blocks() const {
-      return __front_spare() / __base::__block_size;
+      return __front_spare() / __block_size;
     }
     _LIBCPP_INLINE_VISIBILITY
     size_type __back_spare() const
     {
-        return __capacity() - (__base::__start_ + __base::size());
+        return __capacity() - (__start_ + size());
     }
     _LIBCPP_INLINE_VISIBILITY
     size_type __back_spare_blocks() const {
-      return __back_spare() / __base::__block_size;
+      return __back_spare() / __block_size;
     }
 
  private:
     _LIBCPP_INLINE_VISIBILITY
     bool __maybe_remove_front_spare(bool __keep_one = true) {
       if (__front_spare_blocks() >= 2 || (!__keep_one && __front_spare_blocks())) {
-        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.front(),
-                                   __base::__block_size);
-        __base::__map_.pop_front();
-        __base::__start_ -= __base::__block_size;
+        __alloc_traits::deallocate(__alloc(), __map_.front(),
+                                   __block_size);
+        __map_.pop_front();
+        __start_ -= __block_size;
         return true;
       }
       return false;
@@ -1544,9 +1376,9 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     bool __maybe_remove_back_spare(bool __keep_one = true) {
       if (__back_spare_blocks() >= 2 || (!__keep_one && __back_spare_blocks())) {
-        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.back(),
-                                   __base::__block_size);
-        __base::__map_.pop_back();
+        __alloc_traits::deallocate(__alloc(), __map_.back(),
+                                   __block_size);
+        __map_.pop_back();
         return true;
       }
       return false;
@@ -1582,13 +1414,13 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void __copy_assign_alloc(const deque& __c, true_type)
         {
-            if (__base::__alloc() != __c.__alloc())
+            if (__alloc() != __c.__alloc())
             {
                 clear();
                 shrink_to_fit();
             }
-            __base::__alloc() = __c.__alloc();
-            __base::__map_.__alloc() = __c.__map_.__alloc();
+            __alloc() = __c.__alloc();
+            __map_.__alloc() = __c.__map_.__alloc();
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1600,6 +1432,10 @@ public:
     void __move_assign(deque& __c, false_type);
 };
 
+template <class _Tp, class _Alloc>
+_LIBCPP_CONSTEXPR const typename allocator_traits<_Alloc>::
diff erence_type deque<_Tp, _Alloc>::__block_size =
+    __deque_block_size<value_type, 
diff erence_type>::value;
+
 #if _LIBCPP_STD_VER >= 17
 template<class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
@@ -1620,6 +1456,7 @@ deque(_InputIterator, _InputIterator, _Alloc)
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n)
+    : __start_(0), __size_(0, __default_init_tag())
 {
     if (__n > 0)
         __append(__n);
@@ -1628,7 +1465,7 @@ deque<_Tp, _Allocator>::deque(size_type __n)
 #if _LIBCPP_STD_VER > 11
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n, const _Allocator& __a)
-    : __base(__a)
+    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
 {
     if (__n > 0)
         __append(__n);
@@ -1637,6 +1474,7 @@ deque<_Tp, _Allocator>::deque(size_type __n, const _Allocator& __a)
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v)
+    : __start_(0), __size_(0, __default_init_tag())
 {
     if (__n > 0)
         __append(__n, __v);
@@ -1646,6 +1484,7 @@ template <class _Tp, class _Allocator>
 template <class _InputIter>
 deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l,
               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
+    : __start_(0), __size_(0, __default_init_tag())
 {
     __append(__f, __l);
 }
@@ -1654,21 +1493,23 @@ template <class _Tp, class _Allocator>
 template <class _InputIter>
 deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
-    : __base(__a)
+    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
 {
     __append(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(const deque& __c)
-    : __base(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))
+    : __map_(__pointer_allocator(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))),
+      __start_(0),
+      __size_(0, __map_.__alloc())
 {
     __append(__c.begin(), __c.end());
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(const deque& __c, const __type_identity_t<allocator_type>& __a)
-    : __base(__a)
+    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
 {
     __append(__c.begin(), __c.end());
 }
@@ -1689,13 +1530,14 @@ deque<_Tp, _Allocator>::operator=(const deque& __c)
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il)
+    : __start_(0), __size_(0, __default_init_tag())
 {
     __append(__il.begin(), __il.end());
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator_type& __a)
-    : __base(__a)
+    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a)
 {
     __append(__il.begin(), __il.end());
 }
@@ -1703,18 +1545,30 @@ deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator
 template <class _Tp, class _Allocator>
 inline
 deque<_Tp, _Allocator>::deque(deque&& __c)
-    _NOEXCEPT_(is_nothrow_move_constructible<__base>::value)
-    : __base(_VSTD::move(__c))
+    _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
+    : __map_(std::move(__c.__map_)), __start_(std::move(__c.__start_)), __size_(std::move(__c.__size_))
 {
+  __c.__start_ = 0;
+  __c.__size() = 0;
 }
 
 template <class _Tp, class _Allocator>
 inline
 deque<_Tp, _Allocator>::deque(deque&& __c, const __type_identity_t<allocator_type>& __a)
-    : __base(_VSTD::move(__c), __a)
+    : __map_(std::move(__c.__map_), __pointer_allocator(__a)),
+      __start_(std::move(__c.__start_)),
+      __size_(std::move(__c.__size()), __a)
 {
-    if (__a != __c.__alloc())
+    if (__a == __c.__alloc())
+    {
+        __c.__start_ = 0;
+        __c.__size() = 0;
+    }
+    else
     {
+        __map_.clear();
+        __start_ = 0;
+        __size() = 0;
         typedef move_iterator<iterator> _Ip;
         assign(_Ip(__c.begin()), _Ip(__c.end()));
     }
@@ -1736,7 +1590,7 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__move_assign(deque& __c, false_type)
 {
-    if (__base::__alloc() != __c.__alloc())
+    if (__alloc() != __c.__alloc())
     {
         typedef move_iterator<iterator> _Ip;
         assign(_Ip(__c.begin()), _Ip(__c.end()));
@@ -1752,7 +1606,7 @@ deque<_Tp, _Allocator>::__move_assign(deque& __c, true_type)
 {
     clear();
     shrink_to_fit();
-    __base::__move_assign(__c);
+    __move_assign(__c);
 }
 
 #endif // _LIBCPP_CXX03_LANG
@@ -1764,8 +1618,8 @@ deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l,
                                typename enable_if<__is_cpp17_input_iterator<_InputIter>::value &&
                                                  !__is_cpp17_random_access_iterator<_InputIter>::value>::type*)
 {
-    iterator __i = __base::begin();
-    iterator __e = __base::end();
+    iterator __i = begin();
+    iterator __e = end();
     for (; __f != __l && __i != __e; ++__f, (void) ++__i)
         *__i = *__f;
     if (__f != __l)
@@ -1780,28 +1634,28 @@ void
 deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l,
                                typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
-    if (static_cast<size_type>(__l - __f) > __base::size())
+    if (static_cast<size_type>(__l - __f) > size())
     {
-        _RAIter __m = __f + __base::size();
-        _VSTD::copy(__f, __m, __base::begin());
+        _RAIter __m = __f + size();
+        _VSTD::copy(__f, __m, begin());
         __append(__m, __l);
     }
     else
-        __erase_to_end(_VSTD::copy(__f, __l, __base::begin()));
+        __erase_to_end(_VSTD::copy(__f, __l, begin()));
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::assign(size_type __n, const value_type& __v)
 {
-    if (__n > __base::size())
+    if (__n > size())
     {
-        _VSTD::fill_n(__base::begin(), __base::size(), __v);
-        __n -= __base::size();
+        _VSTD::fill_n(begin(), size(), __v);
+        __n -= size();
         __append(__n, __v);
     }
     else
-        __erase_to_end(_VSTD::fill_n(__base::begin(), __n, __v));
+        __erase_to_end(_VSTD::fill_n(begin(), __n, __v));
 }
 
 template <class _Tp, class _Allocator>
@@ -1809,49 +1663,49 @@ inline
 _Allocator
 deque<_Tp, _Allocator>::get_allocator() const _NOEXCEPT
 {
-    return __base::__alloc();
+    return __alloc();
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::resize(size_type __n)
 {
-    if (__n > __base::size())
-        __append(__n - __base::size());
-    else if (__n < __base::size())
-        __erase_to_end(__base::begin() + __n);
+    if (__n > size())
+        __append(__n - size());
+    else if (__n < size())
+        __erase_to_end(begin() + __n);
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::resize(size_type __n, const value_type& __v)
 {
-    if (__n > __base::size())
-        __append(__n - __base::size(), __v);
-    else if (__n < __base::size())
-        __erase_to_end(__base::begin() + __n);
+    if (__n > size())
+        __append(__n - size(), __v);
+    else if (__n < size())
+        __erase_to_end(begin() + __n);
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (empty())
     {
-        while (__base::__map_.size() > 0)
+        while (__map_.size() > 0)
         {
-            __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-            __base::__map_.pop_back();
+            __alloc_traits::deallocate(__a, __map_.back(), __block_size);
+            __map_.pop_back();
         }
-        __base::__start_ = 0;
+        __start_ = 0;
     }
     else
     {
       __maybe_remove_front_spare(/*__keep_one=*/false);
       __maybe_remove_back_spare(/*__keep_one=*/false);
     }
-    __base::__map_.shrink_to_fit();
+    __map_.shrink_to_fit();
 }
 
 template <class _Tp, class _Allocator>
@@ -1859,8 +1713,8 @@ inline
 typename deque<_Tp, _Allocator>::reference
 deque<_Tp, _Allocator>::operator[](size_type __i) _NOEXCEPT
 {
-    size_type __p = __base::__start_ + __i;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = __start_ + __i;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1868,8 +1722,8 @@ inline
 typename deque<_Tp, _Allocator>::const_reference
 deque<_Tp, _Allocator>::operator[](size_type __i) const _NOEXCEPT
 {
-    size_type __p = __base::__start_ + __i;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = __start_ + __i;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1877,10 +1731,10 @@ inline
 typename deque<_Tp, _Allocator>::reference
 deque<_Tp, _Allocator>::at(size_type __i)
 {
-    if (__i >= __base::size())
+    if (__i >= size())
         _VSTD::__throw_out_of_range("deque");
-    size_type __p = __base::__start_ + __i;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = __start_ + __i;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1888,10 +1742,10 @@ inline
 typename deque<_Tp, _Allocator>::const_reference
 deque<_Tp, _Allocator>::at(size_type __i) const
 {
-    if (__i >= __base::size())
+    if (__i >= size())
         _VSTD::__throw_out_of_range("deque");
-    size_type __p = __base::__start_ + __i;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = __start_ + __i;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1899,8 +1753,8 @@ inline
 typename deque<_Tp, _Allocator>::reference
 deque<_Tp, _Allocator>::front() _NOEXCEPT
 {
-    return *(*(__base::__map_.begin() + __base::__start_ / __base::__block_size)
-                                      + __base::__start_ % __base::__block_size);
+    return *(*(__map_.begin() + __start_ / __block_size)
+                                    + __start_ % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1908,8 +1762,8 @@ inline
 typename deque<_Tp, _Allocator>::const_reference
 deque<_Tp, _Allocator>::front() const _NOEXCEPT
 {
-    return *(*(__base::__map_.begin() + __base::__start_ / __base::__block_size)
-                                      + __base::__start_ % __base::__block_size);
+    return *(*(__map_.begin() + __start_ / __block_size)
+                                      + __start_ % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1917,8 +1771,8 @@ inline
 typename deque<_Tp, _Allocator>::reference
 deque<_Tp, _Allocator>::back() _NOEXCEPT
 {
-    size_type __p = __base::size() + __base::__start_ - 1;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = size() + __start_ - 1;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
@@ -1926,33 +1780,33 @@ inline
 typename deque<_Tp, _Allocator>::const_reference
 deque<_Tp, _Allocator>::back() const _NOEXCEPT
 {
-    size_type __p = __base::size() + __base::__start_ - 1;
-    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
+    size_type __p = size() + __start_ - 1;
+    return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_back(const value_type& __v)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__back_spare() == 0)
         __add_back_capacity();
     // __back_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
-    ++__base::size();
+    __alloc_traits::construct(__a, _VSTD::addressof(*end()), __v);
+    ++__size();
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_front(const value_type& __v)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__front_spare() == 0)
         __add_front_capacity();
     // __front_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
-    --__base::__start_;
-    ++__base::size();
+    __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), __v);
+    --__start_;
+    ++__size();
 }
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -1960,12 +1814,12 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_back(value_type&& __v)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__back_spare() == 0)
         __add_back_capacity();
     // __back_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
-    ++__base::size();
+    __alloc_traits::construct(__a, _VSTD::addressof(*end()), _VSTD::move(__v));
+    ++__size();
 }
 
 template <class _Tp, class _Allocator>
@@ -1977,15 +1831,15 @@ void
 #endif
 deque<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__back_spare() == 0)
         __add_back_capacity();
     // __back_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()),
+    __alloc_traits::construct(__a, _VSTD::addressof(*end()),
                               _VSTD::forward<_Args>(__args)...);
-    ++__base::size();
+    ++__size();
 #if _LIBCPP_STD_VER > 14
-    return *--__base::end();
+    return *--end();
 #endif
 }
 
@@ -1993,13 +1847,13 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_front(value_type&& __v)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__front_spare() == 0)
         __add_front_capacity();
     // __front_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
-    --__base::__start_;
-    ++__base::size();
+    __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), _VSTD::move(__v));
+    --__start_;
+    ++__size();
 }
 
 
@@ -2012,15 +1866,15 @@ void
 #endif
 deque<_Tp, _Allocator>::emplace_front(_Args&&... __args)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     if (__front_spare() == 0)
         __add_front_capacity();
     // __front_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
-    --__base::__start_;
-    ++__base::size();
+    __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), _VSTD::forward<_Args>(__args)...);
+    --__start_;
+    ++__size();
 #if _LIBCPP_STD_VER > 14
-    return *__base::begin();
+    return *begin();
 #endif
 }
 
@@ -2028,9 +1882,9 @@ template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
 {
-    size_type __pos = __p - __base::begin();
-    size_type __to_end = __base::size() - __pos;
-    allocator_type& __a = __base::__alloc();
+    size_type __pos = __p - begin();
+    size_type __to_end = size() - __pos;
+    allocator_type& __a = __alloc();
     if (__pos < __to_end)
     {   // insert by shifting things backward
         if (__front_spare() == 0)
@@ -2038,17 +1892,17 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
-            --__base::__start_;
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), _VSTD::move(__v));
+            --__start_;
+            ++__size();
         }
         else
         {
-            iterator __b = __base::begin();
+            iterator __b = begin();
             iterator __bm1 = _VSTD::prev(__b);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
-            --__base::__start_;
-            ++__base::size();
+            --__start_;
+            ++__size();
             if (__pos > 1)
                 __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
             *__b = _VSTD::move(__v);
@@ -2059,24 +1913,24 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
         if (__back_spare() == 0)
             __add_back_capacity();
         // __back_capacity >= 1
-        size_type __de = __base::size() - __pos;
+        size_type __de = size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*end()), _VSTD::move(__v));
+            ++__size();
         }
         else
         {
-            iterator __e = __base::end();
+            iterator __e = end();
             iterator __em1 = _VSTD::prev(__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
-            ++__base::size();
+            ++__size();
             if (__de > 1)
                 __e = _VSTD::move_backward(__e - __de, __em1, __e);
             *--__e = _VSTD::move(__v);
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
@@ -2084,9 +1938,9 @@ template <class... _Args>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
 {
-    size_type __pos = __p - __base::begin();
-    size_type __to_end = __base::size() - __pos;
-    allocator_type& __a = __base::__alloc();
+    size_type __pos = __p - begin();
+    size_type __to_end = size() - __pos;
+    allocator_type& __a = __alloc();
     if (__pos < __to_end)
     {   // insert by shifting things backward
         if (__front_spare() == 0)
@@ -2094,18 +1948,18 @@ deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
-            --__base::__start_;
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), _VSTD::forward<_Args>(__args)...);
+            --__start_;
+            ++__size();
         }
         else
         {
-            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
-            iterator __b = __base::begin();
+            __temp_value<value_type, _Allocator> __tmp(__alloc(), _VSTD::forward<_Args>(__args)...);
+            iterator __b = begin();
             iterator __bm1 = _VSTD::prev(__b);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
-            --__base::__start_;
-            ++__base::size();
+            --__start_;
+            ++__size();
             if (__pos > 1)
                 __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
             *__b = _VSTD::move(__tmp.get());
@@ -2116,25 +1970,25 @@ deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
         if (__back_spare() == 0)
             __add_back_capacity();
         // __back_capacity >= 1
-        size_type __de = __base::size() - __pos;
+        size_type __de = size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::forward<_Args>(__args)...);
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*end()), _VSTD::forward<_Args>(__args)...);
+            ++__size();
         }
         else
         {
-            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
-            iterator __e = __base::end();
+            __temp_value<value_type, _Allocator> __tmp(__alloc(), _VSTD::forward<_Args>(__args)...);
+            iterator __e = end();
             iterator __em1 = _VSTD::prev(__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
-            ++__base::size();
+            ++__size();
             if (__de > 1)
                 __e = _VSTD::move_backward(__e - __de, __em1, __e);
             *--__e = _VSTD::move(__tmp.get());
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 #endif // _LIBCPP_CXX03_LANG
@@ -2144,9 +1998,9 @@ template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
 {
-    size_type __pos = __p - __base::begin();
-    size_type __to_end = __base::size() - __pos;
-    allocator_type& __a = __base::__alloc();
+    size_type __pos = __p - begin();
+    size_type __to_end = size() - __pos;
+    allocator_type& __a = __alloc();
     if (__pos < __to_end)
     {   // insert by shifting things backward
         if (__front_spare() == 0)
@@ -2154,20 +2008,20 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
-            --__base::__start_;
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*--begin()), __v);
+            --__start_;
+            ++__size();
         }
         else
         {
             const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
-            iterator __b = __base::begin();
+            iterator __b = begin();
             iterator __bm1 = _VSTD::prev(__b);
             if (__vt == pointer_traits<const_pointer>::pointer_to(*__b))
                 __vt = pointer_traits<const_pointer>::pointer_to(*__bm1);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
-            --__base::__start_;
-            ++__base::size();
+            --__start_;
+            ++__size();
             if (__pos > 1)
                 __b = __move_and_check(_VSTD::next(__b), __b + __pos, __b, __vt);
             *__b = *__vt;
@@ -2178,46 +2032,46 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
         if (__back_spare() == 0)
             __add_back_capacity();
         // __back_capacity >= 1
-        size_type __de = __base::size() - __pos;
+        size_type __de = size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
-            ++__base::size();
+            __alloc_traits::construct(__a, _VSTD::addressof(*end()), __v);
+            ++__size();
         }
         else
         {
             const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
-            iterator __e = __base::end();
+            iterator __e = end();
             iterator __em1 = _VSTD::prev(__e);
             if (__vt == pointer_traits<const_pointer>::pointer_to(*__em1))
                 __vt = pointer_traits<const_pointer>::pointer_to(*__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
-            ++__base::size();
+            ++__size();
             if (__de > 1)
                 __e = __move_backward_and_check(__e - __de, __em1, __e, __vt);
             *--__e = *__vt;
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, size_type __n, const value_type& __v)
 {
-    size_type __pos = __p - __base::begin();
-    size_type __to_end = __base::size() - __pos;
-    allocator_type& __a = __base::__alloc();
+    size_type __pos = __p - begin();
+    size_type __to_end = __size() - __pos;
+    allocator_type& __a = __alloc();
     if (__pos < __to_end)
     {   // insert by shifting things backward
         if (__n > __front_spare())
             __add_front_capacity(__n - __front_spare());
         // __n <= __front_spare()
-        iterator __old_begin = __base::begin();
+        iterator __old_begin = begin();
         iterator __i = __old_begin;
         if (__n > __pos)
         {
-            for (size_type __m = __n - __pos; __m; --__m, --__base::__start_, ++__base::size())
+            for (size_type __m = __n - __pos; __m; --__m, --__start_, ++__size())
                 __alloc_traits::construct(__a, _VSTD::addressof(*--__i), __v);
             __n = __pos;
         }
@@ -2237,12 +2091,12 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, size_type __n, const value_ty
         if (__n > __back_capacity)
             __add_back_capacity(__n - __back_capacity);
         // __n <= __back_capacity
-        iterator __old_end = __base::end();
+        iterator __old_end = end();
         iterator __i = __old_end;
-        size_type __de = __base::size() - __pos;
+        size_type __de = size() - __pos;
         if (__n > __de)
         {
-            for (size_type __m = __n - __de; __m; --__m, (void) ++__i, ++__base::size())
+            for (size_type __m = __n - __de; __m; --__m, (void) ++__i, ++__size())
                 __alloc_traits::construct(__a, _VSTD::addressof(*__i), __v);
             __n = __de;
         }
@@ -2256,7 +2110,7 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, size_type __n, const value_ty
             _VSTD::fill_n(__old_end - __n, __n, *__vt);
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
@@ -2265,7 +2119,7 @@ typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l,
                                typename enable_if<__is_exactly_cpp17_input_iterator<_InputIter>::value>::type*)
 {
-    __split_buffer<value_type, allocator_type&> __buf(__base::__alloc());
+    __split_buffer<value_type, allocator_type&> __buf(__alloc());
     __buf.__construct_at_end(__f, __l);
     typedef typename __split_buffer<value_type, allocator_type&>::iterator __bi;
     return insert(__p, move_iterator<__bi>(__buf.begin()), move_iterator<__bi>(__buf.end()));
@@ -2278,7 +2132,7 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _Forwar
                                typename enable_if<__is_exactly_cpp17_forward_iterator<_ForwardIterator>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
-    __split_buffer<value_type, allocator_type&> __buf(__n, 0, __base::__alloc());
+    __split_buffer<value_type, allocator_type&> __buf(__n, 0, __alloc());
     __buf.__construct_at_end(__f, __l);
     typedef typename __split_buffer<value_type, allocator_type&>::iterator __fwd;
     return insert(__p, move_iterator<__fwd>(__buf.begin()), move_iterator<__fwd>(__buf.end()));
@@ -2291,21 +2145,21 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
                                typename enable_if<__is_cpp17_bidirectional_iterator<_BiIter>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
-    size_type __pos = __p - __base::begin();
-    size_type __to_end = __base::size() - __pos;
-    allocator_type& __a = __base::__alloc();
+    size_type __pos = __p - begin();
+    size_type __to_end = size() - __pos;
+    allocator_type& __a = __alloc();
     if (__pos < __to_end)
     {   // insert by shifting things backward
         if (__n > __front_spare())
             __add_front_capacity(__n - __front_spare());
         // __n <= __front_spare()
-        iterator __old_begin = __base::begin();
+        iterator __old_begin = begin();
         iterator __i = __old_begin;
         _BiIter __m = __f;
         if (__n > __pos)
         {
             __m = __pos < __n / 2 ? _VSTD::prev(__l, __pos) : _VSTD::next(__f, __n - __pos);
-            for (_BiIter __j = __m; __j != __f; --__base::__start_, ++__base::size())
+            for (_BiIter __j = __m; __j != __f; --__start_, ++__size())
                 __alloc_traits::construct(__a, _VSTD::addressof(*--__i), *--__j);
             __n = __pos;
         }
@@ -2315,8 +2169,8 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
             for (iterator __j = __obn; __j != __old_begin;)
             {
                 __alloc_traits::construct(__a, _VSTD::addressof(*--__i), _VSTD::move(*--__j));
-                --__base::__start_;
-                ++__base::size();
+                --__start_;
+                ++__size();
             }
             if (__n < __pos)
                 __old_begin = _VSTD::move(__obn, __old_begin + __pos, __old_begin);
@@ -2329,28 +2183,28 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
         if (__n > __back_capacity)
             __add_back_capacity(__n - __back_capacity);
         // __n <= __back_capacity
-        iterator __old_end = __base::end();
+        iterator __old_end = end();
         iterator __i = __old_end;
         _BiIter __m = __l;
-        size_type __de = __base::size() - __pos;
+        size_type __de = size() - __pos;
         if (__n > __de)
         {
             __m = __de < __n / 2 ? _VSTD::next(__f, __de) : _VSTD::prev(__l, __n - __de);
-            for (_BiIter __j = __m; __j != __l; ++__i, (void) ++__j, ++__base::size())
+            for (_BiIter __j = __m; __j != __l; ++__i, (void) ++__j, ++__size())
                 __alloc_traits::construct(__a, _VSTD::addressof(*__i), *__j);
             __n = __de;
         }
         if (__n > 0)
         {
             iterator __oen = __old_end - __n;
-            for (iterator __j = __oen; __j != __old_end; ++__i, (void) ++__j, ++__base::size())
+            for (iterator __j = __oen; __j != __old_end; ++__i, (void) ++__j, ++__size())
                 __alloc_traits::construct(__a, _VSTD::addressof(*__i), _VSTD::move(*__j));
             if (__n < __de)
                 __old_end = _VSTD::move_backward(__old_end - __de, __oen, __old_end);
             _VSTD::copy_backward(__f, __m, __old_end);
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
@@ -2374,12 +2228,12 @@ deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l,
                                  typename enable_if<__is_cpp17_forward_iterator<_ForIter>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     size_type __back_capacity = __back_spare();
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+    for (__deque_block_range __br : __deque_range(end(), end() + __n)) {
       _ConstructTransaction __tx(this, __br);
       for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_, (void)++__f) {
         __alloc_traits::construct(__a, _VSTD::__to_address(__tx.__pos_), *__f);
@@ -2391,12 +2245,12 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__append(size_type __n)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     size_type __back_capacity = __back_spare();
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+    for (__deque_block_range __br : __deque_range(end(), end() + __n)) {
       _ConstructTransaction __tx(this, __br);
       for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
         __alloc_traits::construct(__a, _VSTD::__to_address(__tx.__pos_));
@@ -2408,12 +2262,12 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__append(size_type __n, const value_type& __v)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     size_type __back_capacity = __back_spare();
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+    for (__deque_block_range __br : __deque_range(end(), end() + __n)) {
       _ConstructTransaction __tx(this, __br);
       for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
         __alloc_traits::construct(__a, _VSTD::__to_address(__tx.__pos_), __v);
@@ -2428,57 +2282,57 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__add_front_capacity()
 {
-    allocator_type& __a = __base::__alloc();
-    if (__back_spare() >= __base::__block_size)
+    allocator_type& __a = __alloc();
+    if (__back_spare() >= __block_size)
     {
-        __base::__start_ += __base::__block_size;
-        pointer __pt = __base::__map_.back();
-        __base::__map_.pop_back();
-        __base::__map_.push_front(__pt);
+        __start_ += __block_size;
+        pointer __pt = __map_.back();
+        __map_.pop_back();
+        __map_.push_front(__pt);
     }
-    // Else if __base::__map_.size() < __base::__map_.capacity() then we need to allocate 1 buffer
-    else if (__base::__map_.size() < __base::__map_.capacity())
+    // Else if __map_.size() < __map_.capacity() then we need to allocate 1 buffer
+    else if (__map_.size() < __map_.capacity())
     {   // we can put the new buffer into the map, but don't shift things around
         // until all buffers are allocated.  If we throw, we don't need to fix
         // anything up (any added buffers are undetectible)
-        if (__base::__map_.__front_spare() > 0)
-            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
+        if (__map_.__front_spare() > 0)
+            __map_.push_front(__alloc_traits::allocate(__a, __block_size));
         else
         {
-            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+            __map_.push_back(__alloc_traits::allocate(__a, __block_size));
             // Done allocating, reorder capacity
-            pointer __pt = __base::__map_.back();
-            __base::__map_.pop_back();
-            __base::__map_.push_front(__pt);
+            pointer __pt = __map_.back();
+            __map_.pop_back();
+            __map_.push_front(__pt);
         }
-        __base::__start_ = __base::__map_.size() == 1 ?
-                               __base::__block_size / 2 :
-                               __base::__start_ + __base::__block_size;
+        __start_ = __map_.size() == 1 ?
+                               __block_size / 2 :
+                               __start_ + __block_size;
     }
     // Else need to allocate 1 buffer, *and* we need to reallocate __map_.
     else
     {
-        __split_buffer<pointer, typename __base::__pointer_allocator&>
-            __buf(max<size_type>(2 * __base::__map_.capacity(), 1),
-                  0, __base::__map_.__alloc());
+        __split_buffer<pointer, __pointer_allocator&>
+            __buf(max<size_type>(2 * __map_.capacity(), 1),
+                  0, __map_.__alloc());
 
         typedef __allocator_destructor<_Allocator> _Dp;
         unique_ptr<pointer, _Dp> __hold(
-            __alloc_traits::allocate(__a, __base::__block_size),
-                _Dp(__a, __base::__block_size));
+            __alloc_traits::allocate(__a, __block_size),
+                _Dp(__a, __block_size));
         __buf.push_back(__hold.get());
         __hold.release();
 
-        for (typename __base::__map_pointer __i = __base::__map_.begin();
-                __i != __base::__map_.end(); ++__i)
+        for (__map_pointer __i = __map_.begin();
+                __i != __map_.end(); ++__i)
             __buf.push_back(*__i);
-        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
-        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
-        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
-        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
-        __base::__start_ = __base::__map_.size() == 1 ?
-                               __base::__block_size / 2 :
-                               __base::__start_ + __base::__block_size;
+        _VSTD::swap(__map_.__first_, __buf.__first_);
+        _VSTD::swap(__map_.__begin_, __buf.__begin_);
+        _VSTD::swap(__map_.__end_, __buf.__end_);
+        _VSTD::swap(__map_.__end_cap(), __buf.__end_cap());
+        __start_ = __map_.size() == 1 ?
+                               __block_size / 2 :
+                               __start_ + __block_size;
     }
 }
 
@@ -2488,82 +2342,82 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__add_front_capacity(size_type __n)
 {
-    allocator_type& __a = __base::__alloc();
-    size_type __nb = __recommend_blocks(__n + __base::__map_.empty());
+    allocator_type& __a = __alloc();
+    size_type __nb = __recommend_blocks(__n + __map_.empty());
     // Number of unused blocks at back:
-    size_type __back_capacity = __back_spare() / __base::__block_size;
+    size_type __back_capacity = __back_spare() / __block_size;
     __back_capacity = _VSTD::min(__back_capacity, __nb);  // don't take more than you need
     __nb -= __back_capacity;  // number of blocks need to allocate
     // If __nb == 0, then we have sufficient capacity.
     if (__nb == 0)
     {
-        __base::__start_ += __base::__block_size * __back_capacity;
+        __start_ += __block_size * __back_capacity;
         for (; __back_capacity > 0; --__back_capacity)
         {
-            pointer __pt = __base::__map_.back();
-            __base::__map_.pop_back();
-            __base::__map_.push_front(__pt);
+            pointer __pt = __map_.back();
+            __map_.pop_back();
+            __map_.push_front(__pt);
         }
     }
     // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
-    else if (__nb <= __base::__map_.capacity() - __base::__map_.size())
+    else if (__nb <= __map_.capacity() - __map_.size())
     {   // we can put the new buffers into the map, but don't shift things around
         // until all buffers are allocated.  If we throw, we don't need to fix
         // anything up (any added buffers are undetectible)
-        for (; __nb > 0; --__nb, __base::__start_ += __base::__block_size - (__base::__map_.size() == 1))
+        for (; __nb > 0; --__nb, __start_ += __block_size - (__map_.size() == 1))
         {
-            if (__base::__map_.__front_spare() == 0)
+            if (__map_.__front_spare() == 0)
                 break;
-            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
+            __map_.push_front(__alloc_traits::allocate(__a, __block_size));
         }
         for (; __nb > 0; --__nb, ++__back_capacity)
-            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+            __map_.push_back(__alloc_traits::allocate(__a, __block_size));
         // Done allocating, reorder capacity
-        __base::__start_ += __back_capacity * __base::__block_size;
+        __start_ += __back_capacity * __block_size;
         for (; __back_capacity > 0; --__back_capacity)
         {
-            pointer __pt = __base::__map_.back();
-            __base::__map_.pop_back();
-            __base::__map_.push_front(__pt);
+            pointer __pt = __map_.back();
+            __map_.pop_back();
+            __map_.push_front(__pt);
         }
     }
     // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
     else
     {
-        size_type __ds = (__nb + __back_capacity) * __base::__block_size - __base::__map_.empty();
-        __split_buffer<pointer, typename __base::__pointer_allocator&>
-            __buf(max<size_type>(2* __base::__map_.capacity(),
-                                 __nb + __base::__map_.size()),
-                  0, __base::__map_.__alloc());
+        size_type __ds = (__nb + __back_capacity) * __block_size - __map_.empty();
+        __split_buffer<pointer, __pointer_allocator&>
+            __buf(max<size_type>(2* __map_.capacity(),
+                                 __nb + __map_.size()),
+                  0, __map_.__alloc());
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif // _LIBCPP_NO_EXCEPTIONS
             for (; __nb > 0; --__nb)
-                __buf.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+                __buf.push_back(__alloc_traits::allocate(__a, __block_size));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
-            for (typename __base::__map_pointer __i = __buf.begin();
+            for (__map_pointer __i = __buf.begin();
                     __i != __buf.end(); ++__i)
-                __alloc_traits::deallocate(__a, *__i, __base::__block_size);
+                __alloc_traits::deallocate(__a, *__i, __block_size);
             throw;
         }
 #endif // _LIBCPP_NO_EXCEPTIONS
         for (; __back_capacity > 0; --__back_capacity)
         {
-            __buf.push_back(__base::__map_.back());
-            __base::__map_.pop_back();
+            __buf.push_back(__map_.back());
+            __map_.pop_back();
         }
-        for (typename __base::__map_pointer __i = __base::__map_.begin();
-                __i != __base::__map_.end(); ++__i)
+        for (__map_pointer __i = __map_.begin();
+                __i != __map_.end(); ++__i)
             __buf.push_back(*__i);
-        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
-        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
-        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
-        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
-        __base::__start_ += __ds;
+        _VSTD::swap(__map_.__first_, __buf.__first_);
+        _VSTD::swap(__map_.__begin_, __buf.__begin_);
+        _VSTD::swap(__map_.__end_, __buf.__end_);
+        _VSTD::swap(__map_.__end_cap(), __buf.__end_cap());
+        __start_ += __ds;
     }
 }
 
@@ -2573,52 +2427,52 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__add_back_capacity()
 {
-    allocator_type& __a = __base::__alloc();
-    if (__front_spare() >= __base::__block_size)
+    allocator_type& __a = __alloc();
+    if (__front_spare() >= __block_size)
     {
-        __base::__start_ -= __base::__block_size;
-        pointer __pt = __base::__map_.front();
-        __base::__map_.pop_front();
-        __base::__map_.push_back(__pt);
+        __start_ -= __block_size;
+        pointer __pt = __map_.front();
+        __map_.pop_front();
+        __map_.push_back(__pt);
     }
     // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
-    else if (__base::__map_.size() < __base::__map_.capacity())
+    else if (__map_.size() < __map_.capacity())
     {   // we can put the new buffer into the map, but don't shift things around
         // until it is allocated.  If we throw, we don't need to fix
         // anything up (any added buffers are undetectible)
-        if (__base::__map_.__back_spare() != 0)
-            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+        if (__map_.__back_spare() != 0)
+            __map_.push_back(__alloc_traits::allocate(__a, __block_size));
         else
         {
-            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
+            __map_.push_front(__alloc_traits::allocate(__a, __block_size));
             // Done allocating, reorder capacity
-            pointer __pt = __base::__map_.front();
-            __base::__map_.pop_front();
-            __base::__map_.push_back(__pt);
+            pointer __pt = __map_.front();
+            __map_.pop_front();
+            __map_.push_back(__pt);
         }
     }
     // Else need to allocate 1 buffer, *and* we need to reallocate __map_.
     else
     {
-        __split_buffer<pointer, typename __base::__pointer_allocator&>
-            __buf(max<size_type>(2* __base::__map_.capacity(), 1),
-                  __base::__map_.size(),
-                  __base::__map_.__alloc());
+        __split_buffer<pointer, __pointer_allocator&>
+            __buf(max<size_type>(2* __map_.capacity(), 1),
+                  __map_.size(),
+                  __map_.__alloc());
 
         typedef __allocator_destructor<_Allocator> _Dp;
         unique_ptr<pointer, _Dp> __hold(
-            __alloc_traits::allocate(__a, __base::__block_size),
-                _Dp(__a, __base::__block_size));
+            __alloc_traits::allocate(__a, __block_size),
+                _Dp(__a, __block_size));
         __buf.push_back(__hold.get());
         __hold.release();
 
-        for (typename __base::__map_pointer __i = __base::__map_.end();
-                __i != __base::__map_.begin();)
+        for (__map_pointer __i = __map_.end();
+                __i != __map_.begin();)
             __buf.push_front(*--__i);
-        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
-        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
-        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
-        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
+        _VSTD::swap(__map_.__first_, __buf.__first_);
+        _VSTD::swap(__map_.__begin_, __buf.__begin_);
+        _VSTD::swap(__map_.__end_, __buf.__end_);
+        _VSTD::swap(__map_.__end_cap(), __buf.__end_cap());
     }
 }
 
@@ -2628,84 +2482,84 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__add_back_capacity(size_type __n)
 {
-    allocator_type& __a = __base::__alloc();
-    size_type __nb = __recommend_blocks(__n + __base::__map_.empty());
+    allocator_type& __a = __alloc();
+    size_type __nb = __recommend_blocks(__n + __map_.empty());
     // Number of unused blocks at front:
-    size_type __front_capacity = __front_spare() / __base::__block_size;
+    size_type __front_capacity = __front_spare() / __block_size;
     __front_capacity = _VSTD::min(__front_capacity, __nb);  // don't take more than you need
     __nb -= __front_capacity;  // number of blocks need to allocate
     // If __nb == 0, then we have sufficient capacity.
     if (__nb == 0)
     {
-        __base::__start_ -= __base::__block_size * __front_capacity;
+        __start_ -= __block_size * __front_capacity;
         for (; __front_capacity > 0; --__front_capacity)
         {
-            pointer __pt = __base::__map_.front();
-            __base::__map_.pop_front();
-            __base::__map_.push_back(__pt);
+            pointer __pt = __map_.front();
+            __map_.pop_front();
+            __map_.push_back(__pt);
         }
     }
     // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
-    else if (__nb <= __base::__map_.capacity() - __base::__map_.size())
+    else if (__nb <= __map_.capacity() - __map_.size())
     {   // we can put the new buffers into the map, but don't shift things around
         // until all buffers are allocated.  If we throw, we don't need to fix
         // anything up (any added buffers are undetectible)
         for (; __nb > 0; --__nb)
         {
-            if (__base::__map_.__back_spare() == 0)
+            if (__map_.__back_spare() == 0)
                 break;
-            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+            __map_.push_back(__alloc_traits::allocate(__a, __block_size));
         }
-        for (; __nb > 0; --__nb, ++__front_capacity, __base::__start_ +=
-                                 __base::__block_size - (__base::__map_.size() == 1))
-            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
+        for (; __nb > 0; --__nb, ++__front_capacity, __start_ +=
+                                 __block_size - (__map_.size() == 1))
+            __map_.push_front(__alloc_traits::allocate(__a, __block_size));
         // Done allocating, reorder capacity
-        __base::__start_ -= __base::__block_size * __front_capacity;
+        __start_ -= __block_size * __front_capacity;
         for (; __front_capacity > 0; --__front_capacity)
         {
-            pointer __pt = __base::__map_.front();
-            __base::__map_.pop_front();
-            __base::__map_.push_back(__pt);
+            pointer __pt = __map_.front();
+            __map_.pop_front();
+            __map_.push_back(__pt);
         }
     }
     // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
     else
     {
-        size_type __ds = __front_capacity * __base::__block_size;
-        __split_buffer<pointer, typename __base::__pointer_allocator&>
-            __buf(max<size_type>(2* __base::__map_.capacity(),
-                                 __nb + __base::__map_.size()),
-                  __base::__map_.size() - __front_capacity,
-                  __base::__map_.__alloc());
+        size_type __ds = __front_capacity * __block_size;
+        __split_buffer<pointer, __pointer_allocator&>
+            __buf(max<size_type>(2* __map_.capacity(),
+                                 __nb + __map_.size()),
+                  __map_.size() - __front_capacity,
+                  __map_.__alloc());
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif // _LIBCPP_NO_EXCEPTIONS
             for (; __nb > 0; --__nb)
-                __buf.push_back(__alloc_traits::allocate(__a, __base::__block_size));
+                __buf.push_back(__alloc_traits::allocate(__a, __block_size));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
-            for (typename __base::__map_pointer __i = __buf.begin();
+            for (__map_pointer __i = __buf.begin();
                     __i != __buf.end(); ++__i)
-                __alloc_traits::deallocate(__a, *__i, __base::__block_size);
+                __alloc_traits::deallocate(__a, *__i, __block_size);
             throw;
         }
 #endif // _LIBCPP_NO_EXCEPTIONS
         for (; __front_capacity > 0; --__front_capacity)
         {
-            __buf.push_back(__base::__map_.front());
-            __base::__map_.pop_front();
+            __buf.push_back(__map_.front());
+            __map_.pop_front();
         }
-        for (typename __base::__map_pointer __i = __base::__map_.end();
-                __i != __base::__map_.begin();)
+        for (__map_pointer __i = __map_.end();
+                __i != __map_.begin();)
             __buf.push_front(*--__i);
-        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
-        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
-        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
-        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
-        __base::__start_ -= __ds;
+        _VSTD::swap(__map_.__first_, __buf.__first_);
+        _VSTD::swap(__map_.__begin_, __buf.__begin_);
+        _VSTD::swap(__map_.__end_, __buf.__end_);
+        _VSTD::swap(__map_.__end_cap(), __buf.__end_cap());
+        __start_ -= __ds;
     }
 }
 
@@ -2713,12 +2567,12 @@ template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::pop_front()
 {
-    allocator_type& __a = __base::__alloc();
-    __alloc_traits::destroy(__a, _VSTD::__to_address(*(__base::__map_.begin() +
-                                                    __base::__start_ / __base::__block_size) +
-                                                    __base::__start_ % __base::__block_size));
-    --__base::size();
-    ++__base::__start_;
+    allocator_type& __a = __alloc();
+    __alloc_traits::destroy(__a, _VSTD::__to_address(*(__map_.begin() +
+                                                    __start_ / __block_size) +
+                                                    __start_ % __block_size));
+    --__size();
+    ++__start_;
     __maybe_remove_front_spare();
 }
 
@@ -2727,12 +2581,12 @@ void
 deque<_Tp, _Allocator>::pop_back()
 {
     _LIBCPP_ASSERT(!empty(), "deque::pop_back called on an empty deque");
-    allocator_type& __a = __base::__alloc();
-    size_type __p = __base::size() + __base::__start_ - 1;
-    __alloc_traits::destroy(__a, _VSTD::__to_address(*(__base::__map_.begin() +
-                                                    __p / __base::__block_size) +
-                                                    __p % __base::__block_size));
-    --__base::size();
+    allocator_type& __a = __alloc();
+    size_type __p = size() + __start_ - 1;
+    __alloc_traits::destroy(__a, _VSTD::__to_address(*(__map_.begin() +
+                                                    __p / __block_size) +
+                                                    __p % __block_size));
+    --__size();
     __maybe_remove_back_spare();
 }
 
@@ -2750,7 +2604,7 @@ deque<_Tp, _Allocator>::__move_and_check(iterator __f, iterator __l, iterator __
     while (__n > 0)
     {
         pointer __fb = __f.__ptr_;
-        pointer __fe = *__f.__m_iter_ + __base::__block_size;
+        pointer __fe = *__f.__m_iter_ + __block_size;
         
diff erence_type __bs = __fe - __fb;
         if (__bs > __n)
         {
@@ -2804,15 +2658,15 @@ void
 deque<_Tp, _Allocator>::__move_construct_and_check(iterator __f, iterator __l,
                                                    iterator __r, const_pointer& __vt)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     // as if
-    //   for (; __f != __l; ++__r, ++__f, ++__base::size())
+    //   for (; __f != __l; ++__r, ++__f, ++__size())
     //       __alloc_traits::construct(__a, _VSTD::addressof(*__r), _VSTD::move(*__f));
     
diff erence_type __n = __l - __f;
     while (__n > 0)
     {
         pointer __fb = __f.__ptr_;
-        pointer __fe = *__f.__m_iter_ + __base::__block_size;
+        pointer __fe = *__f.__m_iter_ + __block_size;
         
diff erence_type __bs = __fe - __fb;
         if (__bs > __n)
         {
@@ -2821,7 +2675,7 @@ deque<_Tp, _Allocator>::__move_construct_and_check(iterator __f, iterator __l,
         }
         if (__fb <= __vt && __vt < __fe)
             __vt = (const_iterator(static_cast<__map_const_pointer>(__f.__m_iter_), __vt) += __r - __f).__ptr_;
-        for (; __fb != __fe; ++__fb, ++__r, ++__base::size())
+        for (; __fb != __fe; ++__fb, ++__r, ++__size())
             __alloc_traits::construct(__a, _VSTD::addressof(*__r), _VSTD::move(*__fb));
         __n -= __bs;
         __f += __bs;
@@ -2835,13 +2689,13 @@ void
 deque<_Tp, _Allocator>::__move_construct_backward_and_check(iterator __f, iterator __l,
                                                             iterator __r, const_pointer& __vt)
 {
-    allocator_type& __a = __base::__alloc();
+    allocator_type& __a = __alloc();
     // as if
     //   for (iterator __j = __l; __j != __f;)
     //   {
     //       __alloc_traitsconstruct(__a, _VSTD::addressof(*--__r), _VSTD::move(*--__j));
-    //       --__base::__start_;
-    //       ++__base::size();
+    //       --__start_;
+    //       ++__size();
     //   }
     
diff erence_type __n = __l - __f;
     while (__n > 0)
@@ -2860,8 +2714,8 @@ deque<_Tp, _Allocator>::__move_construct_backward_and_check(iterator __f, iterat
         while (__le != __lb)
         {
             __alloc_traits::construct(__a, _VSTD::addressof(*--__r), _VSTD::move(*--__le));
-            --__base::__start_;
-            ++__base::size();
+            --__start_;
+            ++__size();
         }
         __n -= __bs;
         __l -= __bs - 1;
@@ -2872,26 +2726,26 @@ template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::erase(const_iterator __f)
 {
-    iterator __b = __base::begin();
+    iterator __b = begin();
     
diff erence_type __pos = __f - __b;
     iterator __p = __b + __pos;
-    allocator_type& __a = __base::__alloc();
-    if (static_cast<size_t>(__pos) <= (__base::size() - 1) / 2)
+    allocator_type& __a = __alloc();
+    if (static_cast<size_t>(__pos) <= (size() - 1) / 2)
     {   // erase from front
         _VSTD::move_backward(__b, __p, _VSTD::next(__p));
         __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
-        --__base::size();
-        ++__base::__start_;
+        --__size();
+        ++__start_;
         __maybe_remove_front_spare();
     }
     else
     {   // erase from back
-        iterator __i = _VSTD::move(_VSTD::next(__p), __base::end(), __p);
+        iterator __i = _VSTD::move(_VSTD::next(__p), end(), __p);
         __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
-        --__base::size();
+        --__size();
         __maybe_remove_back_spare();
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
@@ -2899,49 +2753,49 @@ typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l)
 {
     
diff erence_type __n = __l - __f;
-    iterator __b = __base::begin();
+    iterator __b = begin();
     
diff erence_type __pos = __f - __b;
     iterator __p = __b + __pos;
     if (__n > 0)
     {
-        allocator_type& __a = __base::__alloc();
-        if (static_cast<size_t>(__pos) <= (__base::size() - __n) / 2)
+        allocator_type& __a = __alloc();
+        if (static_cast<size_t>(__pos) <= (size() - __n) / 2)
         {   // erase from front
             iterator __i = _VSTD::move_backward(__b, __p, __p + __n);
             for (; __b != __i; ++__b)
                 __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
-            __base::size() -= __n;
-            __base::__start_ += __n;
+            __size() -= __n;
+            __start_ += __n;
             while (__maybe_remove_front_spare()) {
             }
         }
         else
         {   // erase from back
-            iterator __i = _VSTD::move(__p + __n, __base::end(), __p);
-            for (iterator __e = __base::end(); __i != __e; ++__i)
+            iterator __i = _VSTD::move(__p + __n, end(), __p);
+            for (iterator __e = end(); __i != __e; ++__i)
                 __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
-            __base::size() -= __n;
+            __size() -= __n;
             while (__maybe_remove_back_spare()) {
             }
         }
     }
-    return __base::begin() + __pos;
+    return begin() + __pos;
 }
 
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::__erase_to_end(const_iterator __f)
 {
-    iterator __e = __base::end();
+    iterator __e = end();
     
diff erence_type __n = __e - __f;
     if (__n > 0)
     {
-        allocator_type& __a = __base::__alloc();
-        iterator __b = __base::begin();
+        allocator_type& __a = __alloc();
+        iterator __b = begin();
         
diff erence_type __pos = __f - __b;
         for (iterator __p = __b + __pos; __p != __e; ++__p)
             __alloc_traits::destroy(__a, _VSTD::addressof(*__p));
-        __base::size() -= __n;
+        __size() -= __n;
         while (__maybe_remove_back_spare()) {
         }
     }
@@ -2958,7 +2812,10 @@ deque<_Tp, _Allocator>::swap(deque& __c)
                     __is_nothrow_swappable<allocator_type>::value)
 #endif
 {
-    __base::swap(__c);
+    __map_.swap(__c.__map_);
+    _VSTD::swap(__start_, __c.__start_);
+    _VSTD::swap(__size(), __c.__size());
+    _VSTD::__swap_allocator(__alloc(), __c.__alloc());
 }
 
 template <class _Tp, class _Allocator>
@@ -2966,7 +2823,24 @@ inline
 void
 deque<_Tp, _Allocator>::clear() _NOEXCEPT
 {
-    __base::clear();
+    allocator_type& __a = __alloc();
+    for (iterator __i = begin(), __e = end(); __i != __e; ++__i)
+        __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
+    __size() = 0;
+    while (__map_.size() > 2)
+    {
+        __alloc_traits::deallocate(__a, __map_.front(), __block_size);
+        __map_.pop_front();
+    }
+    switch (__map_.size())
+    {
+    case 1:
+        __start_ = __block_size / 2;
+        break;
+    case 2:
+        __start_ = __block_size;
+        break;
+    }
 }
 
 template <class _Tp, class _Allocator>

diff  --git a/libcxx/test/std/containers/container.adaptors/queue/queue.cons/ctor_iterators.pass.cpp b/libcxx/test/std/containers/container.adaptors/queue/queue.cons/ctor_iterators.pass.cpp
index 26ac1b605e908..5b4a77e90754c 100644
--- a/libcxx/test/std/containers/container.adaptors/queue/queue.cons/ctor_iterators.pass.cpp
+++ b/libcxx/test/std/containers/container.adaptors/queue/queue.cons/ctor_iterators.pass.cpp
@@ -24,10 +24,17 @@ static_assert(!std::is_constructible_v<std::queue<int>, int*, int*, int>);
 static_assert( std::is_constructible_v<std::queue<int, std::deque<int, test_allocator<int>>>, int*, int*, test_allocator<int>>);
 static_assert(!std::is_constructible_v<std::queue<int, std::deque<int, test_allocator<int>>>, int*, int*, std::allocator<int>>);
 
-struct alloc : test_allocator<int> {
+template <class T>
+struct alloc : test_allocator<T> {
   alloc(test_allocator_statistics* a);
+
+  template <class U>
+  struct rebind {
+    using other = alloc<U>;
+  };
 };
-static_assert( std::is_constructible_v<std::queue<int, std::deque<int, alloc>>, int*, int*, test_allocator_statistics*>);
+static_assert(
+    std::is_constructible_v<std::queue<int, std::deque<int, alloc<int>>>, int*, int*, test_allocator_statistics*>);
 
 int main(int, char**) {
   const int a[] = {4, 3, 2, 1};

diff  --git a/libcxx/test/std/containers/container.adaptors/stack/stack.cons/ctor_iterators.pass.cpp b/libcxx/test/std/containers/container.adaptors/stack/stack.cons/ctor_iterators.pass.cpp
index a4c0d0bba2b4e..e458b139baaba 100644
--- a/libcxx/test/std/containers/container.adaptors/stack/stack.cons/ctor_iterators.pass.cpp
+++ b/libcxx/test/std/containers/container.adaptors/stack/stack.cons/ctor_iterators.pass.cpp
@@ -23,10 +23,16 @@ static_assert(!std::is_constructible_v<std::stack<int>, int*, int*, int>);
 static_assert( std::is_constructible_v<std::stack<int, std::deque<int, test_allocator<int>>>, int*, int*, test_allocator<int>>);
 static_assert(!std::is_constructible_v<std::stack<int, std::deque<int, test_allocator<int>>>, int*, int*, std::allocator<int>>);
 
-struct alloc : test_allocator<int> {
+template <class T>
+struct alloc : test_allocator<T> {
+  template <class U>
+  struct rebind {
+    using other = alloc<U>;
+  };
   alloc(test_allocator_statistics* a);
 };
-static_assert( std::is_constructible_v<std::stack<int, std::deque<int, alloc>>, int*, int*, test_allocator_statistics*>);
+static_assert(
+    std::is_constructible_v<std::stack<int, std::deque<int, alloc<int>>>, int*, int*, test_allocator_statistics*>);
 
 int main(int, char**) {
   const int a[] = {4, 3, 2, 1};

diff  --git a/libcxx/test/std/containers/sequences/deque/abi.compile.pass.cpp b/libcxx/test/std/containers/sequences/deque/abi.compile.pass.cpp
new file mode 100644
index 0000000000000..74cbfe3ffaec2
--- /dev/null
+++ b/libcxx/test/std/containers/sequences/deque/abi.compile.pass.cpp
@@ -0,0 +1,86 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <deque>
+
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_macros.h"
+
+template <class T>
+class small_pointer {
+  uint16_t offset;
+};
+
+template <class T>
+class small_iter_allocator {
+public:
+  using value_type      = T;
+  using pointer         = small_pointer<T>;
+  using size_type       = int16_t;
+  using 
diff erence_type = int16_t;
+
+  small_iter_allocator() TEST_NOEXCEPT {}
+
+  template <class U>
+  small_iter_allocator(small_iter_allocator<U>) TEST_NOEXCEPT {}
+
+  T* allocate(std::size_t n);
+  void deallocate(T* p, std::size_t);
+
+  friend bool operator==(small_iter_allocator, small_iter_allocator) { return true; }
+  friend bool operator!=(small_iter_allocator, small_iter_allocator) { return false; }
+};
+
+#if __SIZE_WIDTH__ == 64
+
+static_assert(sizeof(std::deque<int>) == 48, "");
+static_assert(sizeof(std::deque<int, min_allocator<int> >) == 48, "");
+static_assert(sizeof(std::deque<int, test_allocator<int> >) == 80, "");
+static_assert(sizeof(std::deque<int, small_iter_allocator<int> >) == 12, "");
+
+static_assert(sizeof(std::deque<char>) == 48, "");
+static_assert(sizeof(std::deque<char, min_allocator<char> >) == 48, "");
+static_assert(sizeof(std::deque<char, test_allocator<char> >) == 80, "");
+static_assert(sizeof(std::deque<char, small_iter_allocator<char> >) == 12, "");
+
+static_assert(TEST_ALIGNOF(std::deque<int>) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<int, min_allocator<int> >) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<int, test_allocator<int> >) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<int, small_iter_allocator<int> >) == 2, "");
+
+static_assert(TEST_ALIGNOF(std::deque<char>) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<char, min_allocator<char> >) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<char, test_allocator<char> >) == 8, "");
+static_assert(TEST_ALIGNOF(std::deque<char, small_iter_allocator<char> >) == 2, "");
+
+#elif __SIZE_WIDTH__ == 32
+
+static_assert(sizeof(std::deque<int>) == 24, "");
+static_assert(sizeof(std::deque<int, min_allocator<int> >) == 24, "");
+static_assert(sizeof(std::deque<int, test_allocator<int> >) == 48, "");
+static_assert(sizeof(std::deque<int, small_iter_allocator<int> >) == 12, "");
+
+static_assert(sizeof(std::deque<char>) == 24, "");
+static_assert(sizeof(std::deque<char, min_allocator<char> >) == 24, "");
+static_assert(sizeof(std::deque<char, test_allocator<char> >) == 48, "");
+static_assert(sizeof(std::deque<char, small_iter_allocator<char> >) == 12, "");
+
+static_assert(TEST_ALIGNOF(std::deque<int>) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<int, min_allocator<int> >) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<int, test_allocator<int> >) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<int, small_iter_allocator<int> >) == 2, "");
+
+static_assert(TEST_ALIGNOF(std::deque<char>) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<char, min_allocator<char> >) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<char, test_allocator<char> >) == 4, "");
+static_assert(TEST_ALIGNOF(std::deque<char, small_iter_allocator<char> >) == 2, "");
+
+#else
+#  error size_t has an unexpected size
+#endif


        


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