// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_DEQUE
#define _LIBCPP_DEQUE

/*
    deque synopsis

namespace std
{

template <class T, class Allocator = allocator<T> >
class deque
{
public:
    // types:
    typedef T value_type;
    typedef Allocator allocator_type;

    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   iterator;
    typedef implementation-defined                   const_iterator;
    typedef typename allocator_type::size_type       size_type;
    typedef typename allocator_type::difference_type difference_type;

    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef std::reverse_iterator<iterator>          reverse_iterator;
    typedef std::reverse_iterator<const_iterator>    const_reverse_iterator;

    // construct/copy/destroy:
    deque() noexcept(is_nothrow_default_constructible<allocator_type>::value);
    explicit deque(const allocator_type& a);
    explicit deque(size_type n);
    explicit deque(size_type n, const allocator_type& a); // C++14
    deque(size_type n, const value_type& v);
    deque(size_type n, const value_type& v, const allocator_type& a);
    template <class InputIterator>
        deque(InputIterator f, InputIterator l);
    template <class InputIterator>
        deque(InputIterator f, InputIterator l, const allocator_type& a);
    template<container-compatible-range<T> R>
        deque(from_range_t, R&& rg, const Allocator& = Allocator()); // C++23
    deque(const deque& c);
    deque(deque&& c)
        noexcept(is_nothrow_move_constructible<allocator_type>::value);
    deque(initializer_list<value_type> il, const Allocator& a = allocator_type());
    deque(const deque& c, const allocator_type& a);
    deque(deque&& c, const allocator_type& a);
    ~deque();

    deque& operator=(const deque& c);
    deque& operator=(deque&& c)
        noexcept((__alloc_traits::propagate_on_container_move_assignment::value &&
                  is_nothrow_move_assignable<allocator_type>::value) ||
                 allocator_traits<allocator_type>::is_always_equal::value);
    deque& operator=(initializer_list<value_type> il);

    template <class InputIterator>
        void assign(InputIterator f, InputIterator l);
    template<container-compatible-range<T> R>
      void assign_range(R&& rg); // C++23
    void assign(size_type n, const value_type& v);
    void assign(initializer_list<value_type> il);

    allocator_type get_allocator() const noexcept;

    // iterators:

    iterator       begin() noexcept;
    const_iterator begin() const noexcept;
    iterator       end() noexcept;
    const_iterator end() const noexcept;

    reverse_iterator       rbegin() noexcept;
    const_reverse_iterator rbegin() const noexcept;
    reverse_iterator       rend() noexcept;
    const_reverse_iterator rend() const noexcept;

    const_iterator         cbegin() const noexcept;
    const_iterator         cend() const noexcept;
    const_reverse_iterator crbegin() const noexcept;
    const_reverse_iterator crend() const noexcept;

    // capacity:
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    void resize(size_type n);
    void resize(size_type n, const value_type& v);
    void shrink_to_fit();
    bool empty() const noexcept;

    // element access:
    reference operator[](size_type i);
    const_reference operator[](size_type i) const;
    reference at(size_type i);
    const_reference at(size_type i) const;
    reference front();
    const_reference front() const;
    reference back();
    const_reference back() const;

    // modifiers:
    void push_front(const value_type& v);
    void push_front(value_type&& v);
    template<container-compatible-range<T> R>
      void prepend_range(R&& rg); // C++23
    void push_back(const value_type& v);
    void push_back(value_type&& v);
    template<container-compatible-range<T> R>
      void append_range(R&& rg); // C++23
    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
    template <class... Args> reference emplace_back(Args&&... args);   // reference in C++17
    template <class... Args> iterator emplace(const_iterator p, Args&&... args);
    iterator insert(const_iterator p, const value_type& v);
    iterator insert(const_iterator p, value_type&& v);
    iterator insert(const_iterator p, size_type n, const value_type& v);
    template <class InputIterator>
        iterator insert(const_iterator p, InputIterator f, InputIterator l);
    template<container-compatible-range<T> R>
      iterator insert_range(const_iterator position, R&& rg); // C++23
    iterator insert(const_iterator p, initializer_list<value_type> il);
    void pop_front();
    void pop_back();
    iterator erase(const_iterator p);
    iterator erase(const_iterator f, const_iterator l);
    void swap(deque& c)
        noexcept(allocator_traits<allocator_type>::is_always_equal::value);  // C++17
    void clear() noexcept;
};

template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
   deque(InputIterator, InputIterator, Allocator = Allocator())
   -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>; // C++17

template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>>
  deque(from_range_t, R&&, Allocator = Allocator())
    -> deque<ranges::range_value_t<R>, Allocator>; // C++23

template <class T, class Allocator>
    bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
template <class T, class Allocator>
    bool operator< (const deque<T,Allocator>& x, const deque<T,Allocator>& y); // removed in C++20
template <class T, class Allocator>
    bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y); // removed in C++20
template <class T, class Allocator>
    bool operator> (const deque<T,Allocator>& x, const deque<T,Allocator>& y); // removed in C++20
template <class T, class Allocator>
    bool operator>=(const deque<T,Allocator>& x, const deque<T,Allocator>& y); // removed in C++20
template <class T, class Allocator>
    bool operator<=(const deque<T,Allocator>& x, const deque<T,Allocator>& y); // removed in C++20
template<class T, class Allocator>
    synth-three-way-result<T> operator<=>(const deque<T, Allocator>& x,
                                          const deque<T, Allocator>& y);       // since C++20

// specialized algorithms:
template <class T, class Allocator>
    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y)
         noexcept(noexcept(x.swap(y)));

template <class T, class Allocator, class U>
    typename deque<T, Allocator>::size_type
    erase(deque<T, Allocator>& c, const U& value);       // C++20
template <class T, class Allocator, class Predicate>
    typename deque<T, Allocator>::size_type
    erase_if(deque<T, Allocator>& c, Predicate pred);    // C++20

}  // std

*/

#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
#  include <__cxx03/deque>
#else
#  include <__algorithm/copy.h>
#  include <__algorithm/copy_backward.h>
#  include <__algorithm/copy_n.h>
#  include <__algorithm/equal.h>
#  include <__algorithm/fill_n.h>
#  include <__algorithm/lexicographical_compare.h>
#  include <__algorithm/lexicographical_compare_three_way.h>
#  include <__algorithm/max.h>
#  include <__algorithm/min.h>
#  include <__algorithm/move.h>
#  include <__algorithm/move_backward.h>
#  include <__algorithm/remove.h>
#  include <__algorithm/remove_if.h>
#  include <__algorithm/unwrap_iter.h>
#  include <__assert>
#  include <__config>
#  include <__debug_utils/sanitizers.h>
#  include <__format/enable_insertable.h>
#  include <__fwd/deque.h>
#  include <__iterator/distance.h>
#  include <__iterator/iterator_traits.h>
#  include <__iterator/move_iterator.h>
#  include <__iterator/next.h>
#  include <__iterator/prev.h>
#  include <__iterator/reverse_iterator.h>
#  include <__iterator/segmented_iterator.h>
#  include <__memory/addressof.h>
#  include <__memory/allocator.h>
#  include <__memory/allocator_destructor.h>
#  include <__memory/allocator_traits.h>
#  include <__memory/compressed_pair.h>
#  include <__memory/pointer_traits.h>
#  include <__memory/swap_allocator.h>
#  include <__memory/temp_value.h>
#  include <__memory/unique_ptr.h>
#  include <__memory_resource/polymorphic_allocator.h>
#  include <__ranges/access.h>
#  include <__ranges/concepts.h>
#  include <__ranges/container_compatible_range.h>
#  include <__ranges/from_range.h>
#  include <__ranges/size.h>
#  include <__split_buffer>
#  include <__type_traits/conditional.h>
#  include <__type_traits/container_traits.h>
#  include <__type_traits/disjunction.h>
#  include <__type_traits/enable_if.h>
#  include <__type_traits/is_allocator.h>
#  include <__type_traits/is_convertible.h>
#  include <__type_traits/is_nothrow_assignable.h>
#  include <__type_traits/is_nothrow_constructible.h>
#  include <__type_traits/is_same.h>
#  include <__type_traits/is_swappable.h>
#  include <__type_traits/is_trivially_relocatable.h>
#  include <__type_traits/type_identity.h>
#  include <__utility/forward.h>
#  include <__utility/move.h>
#  include <__utility/pair.h>
#  include <__utility/swap.h>
#  include <limits>
#  include <stdexcept>
#  include <version>

// standard-mandated includes

// [iterator.range]
#  include <__iterator/access.h>
#  include <__iterator/data.h>
#  include <__iterator/empty.h>
#  include <__iterator/reverse_access.h>
#  include <__iterator/size.h>

// [deque.syn]
#  include <compare>
#  include <initializer_list>

#  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#    pragma GCC system_header
#  endif

_LIBCPP_PUSH_MACROS
#  include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _ValueType, class _DiffType>
struct __deque_block_size {
  static const _DiffType value = sizeof(_ValueType) < 256 ? 4096 / sizeof(_ValueType) : 16;
};

template <class _ValueType,
          class _Pointer,
          class _Reference,
          class _MapPointer,
          class _DiffType,
          _DiffType _BS =
#  ifdef _LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
              // Keep template parameter to avoid changing all template declarations thoughout
              // this file.
          0
#  else
              __deque_block_size<_ValueType, _DiffType>::value
#  endif
          >
class _LIBCPP_TEMPLATE_VIS __deque_iterator {
  typedef _MapPointer __map_iterator;

public:
  typedef _Pointer pointer;
  typedef _DiffType difference_type;

private:
  __map_iterator __m_iter_;
  pointer __ptr_;

  static const difference_type __block_size;

public:
  typedef _ValueType value_type;
  typedef random_access_iterator_tag iterator_category;
  typedef _Reference reference;

  _LIBCPP_HIDE_FROM_ABI __deque_iterator() _NOEXCEPT
#  if _LIBCPP_STD_VER >= 14
      : __m_iter_(nullptr),
        __ptr_(nullptr)
#  endif
  {
  }

  template <class _Pp, class _Rp, class _MP, __enable_if_t<is_convertible<_Pp, pointer>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI
  __deque_iterator(const __deque_iterator<value_type, _Pp, _Rp, _MP, difference_type, _BS>& __it) _NOEXCEPT
      : __m_iter_(__it.__m_iter_),
        __ptr_(__it.__ptr_) {}

  _LIBCPP_HIDE_FROM_ABI reference operator*() const { return *__ptr_; }
  _LIBCPP_HIDE_FROM_ABI pointer operator->() const { return __ptr_; }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator& operator++() {
    if (++__ptr_ - *__m_iter_ == __block_size) {
      ++__m_iter_;
      __ptr_ = *__m_iter_;
    }
    return *this;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator operator++(int) {
    __deque_iterator __tmp = *this;
    ++(*this);
    return __tmp;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator& operator--() {
    if (__ptr_ == *__m_iter_) {
      --__m_iter_;
      __ptr_ = *__m_iter_ + __block_size;
    }
    --__ptr_;
    return *this;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator operator--(int) {
    __deque_iterator __tmp = *this;
    --(*this);
    return __tmp;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator& operator+=(difference_type __n) {
    if (__n != 0) {
      __n += __ptr_ - *__m_iter_;
      if (__n > 0) {
        __m_iter_ += __n / __block_size;
        __ptr_ = *__m_iter_ + __n % __block_size;
      } else // (__n < 0)
      {
        difference_type __z = __block_size - 1 - __n;
        __m_iter_ -= __z / __block_size;
        __ptr_ = *__m_iter_ + (__block_size - 1 - __z % __block_size);
      }
    }
    return *this;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator& operator-=(difference_type __n) { return *this += -__n; }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator operator+(difference_type __n) const {
    __deque_iterator __t(*this);
    __t += __n;
    return __t;
  }

  _LIBCPP_HIDE_FROM_ABI __deque_iterator operator-(difference_type __n) const {
    __deque_iterator __t(*this);
    __t -= __n;
    return __t;
  }

  _LIBCPP_HIDE_FROM_ABI friend __deque_iterator operator+(difference_type __n, const __deque_iterator& __it) {
    return __it + __n;
  }

  _LIBCPP_HIDE_FROM_ABI friend difference_type operator-(const __deque_iterator& __x, const __deque_iterator& __y) {
    if (__x != __y)
      return (__x.__m_iter_ - __y.__m_iter_) * __block_size + (__x.__ptr_ - *__x.__m_iter_) -
             (__y.__ptr_ - *__y.__m_iter_);
    return 0;
  }

  _LIBCPP_HIDE_FROM_ABI reference operator[](difference_type __n) const { return *(*this + __n); }

  _LIBCPP_HIDE_FROM_ABI friend bool operator==(const __deque_iterator& __x, const __deque_iterator& __y) {
    return __x.__ptr_ == __y.__ptr_;
  }

#  if _LIBCPP_STD_VER <= 17
  _LIBCPP_HIDE_FROM_ABI friend bool operator!=(const __deque_iterator& __x, const __deque_iterator& __y) {
    return !(__x == __y);
  }
  _LIBCPP_HIDE_FROM_ABI friend bool operator<(const __deque_iterator& __x, const __deque_iterator& __y) {
    return __x.__m_iter_ < __y.__m_iter_ || (__x.__m_iter_ == __y.__m_iter_ && __x.__ptr_ < __y.__ptr_);
  }

  _LIBCPP_HIDE_FROM_ABI friend bool operator>(const __deque_iterator& __x, const __deque_iterator& __y) {
    return __y < __x;
  }

  _LIBCPP_HIDE_FROM_ABI friend bool operator<=(const __deque_iterator& __x, const __deque_iterator& __y) {
    return !(__y < __x);
  }

  _LIBCPP_HIDE_FROM_ABI friend bool operator>=(const __deque_iterator& __x, const __deque_iterator& __y) {
    return !(__x < __y);
  }

#  else

  _LIBCPP_HIDE_FROM_ABI friend strong_ordering operator<=>(const __deque_iterator& __x, const __deque_iterator& __y) {
    if (__x.__m_iter_ < __y.__m_iter_)
      return strong_ordering::less;

    if (__x.__m_iter_ == __y.__m_iter_) {
      if constexpr (three_way_comparable<pointer, strong_ordering>) {
        return __x.__ptr_ <=> __y.__ptr_;
      } else {
        if (__x.__ptr_ < __y.__ptr_)
          return strong_ordering::less;

        if (__x.__ptr_ == __y.__ptr_)
          return strong_ordering::equal;

        return strong_ordering::greater;
      }
    }

    return strong_ordering::greater;
  }
#  endif // _LIBCPP_STD_VER >= 20

private:
  _LIBCPP_HIDE_FROM_ABI explicit __deque_iterator(__map_iterator __m, pointer __p) _NOEXCEPT
      : __m_iter_(__m),
        __ptr_(__p) {}

  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;

  template <class>
  friend struct __segmented_iterator_traits;
};

template <class _ValueType, class _Pointer, class _Reference, class _MapPointer, class _DiffType, _DiffType _BlockSize>
struct __segmented_iterator_traits<
    __deque_iterator<_ValueType, _Pointer, _Reference, _MapPointer, _DiffType, _BlockSize> > {
private:
  using _Iterator _LIBCPP_NODEBUG =
      __deque_iterator<_ValueType, _Pointer, _Reference, _MapPointer, _DiffType, _BlockSize>;

public:
  using __is_segmented_iterator _LIBCPP_NODEBUG = true_type;
  using __segment_iterator _LIBCPP_NODEBUG      = _MapPointer;
  using __local_iterator _LIBCPP_NODEBUG        = _Pointer;

  static _LIBCPP_HIDE_FROM_ABI __segment_iterator __segment(_Iterator __iter) { return __iter.__m_iter_; }
  static _LIBCPP_HIDE_FROM_ABI __local_iterator __local(_Iterator __iter) { return __iter.__ptr_; }
  static _LIBCPP_HIDE_FROM_ABI __local_iterator __begin(__segment_iterator __iter) { return *__iter; }

  static _LIBCPP_HIDE_FROM_ABI __local_iterator __end(__segment_iterator __iter) {
    return *__iter + _Iterator::__block_size;
  }

  static _LIBCPP_HIDE_FROM_ABI _Iterator __compose(__segment_iterator __segment, __local_iterator __local) {
    if (__segment && __local == __end(__segment)) {
      ++__segment;
      return _Iterator(__segment, *__segment);
    }
    return _Iterator(__segment, __local);
  }
};

template <class _ValueType, class _Pointer, class _Reference, class _MapPointer, class _DiffType, _DiffType _BlockSize>
const _DiffType __deque_iterator<_ValueType, _Pointer, _Reference, _MapPointer, _DiffType, _BlockSize>::__block_size =
    __deque_block_size<_ValueType, _DiffType>::value;

template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
class _LIBCPP_TEMPLATE_VIS deque {
public:
  // types:

  using value_type = _Tp;

  using allocator_type                 = _Allocator;
  using __alloc_traits _LIBCPP_NODEBUG = allocator_traits<allocator_type>;
  static_assert(__check_valid_allocator<allocator_type>::value, "");
  static_assert(is_same<typename allocator_type::value_type, value_type>::value,
                "Allocator::value_type must be same type as value_type");

  using size_type       = typename __alloc_traits::size_type;
  using difference_type = typename __alloc_traits::difference_type;

  using pointer       = typename __alloc_traits::pointer;
  using const_pointer = typename __alloc_traits::const_pointer;

  using __pointer_allocator _LIBCPP_NODEBUG       = __rebind_alloc<__alloc_traits, pointer>;
  using __const_pointer_allocator _LIBCPP_NODEBUG = __rebind_alloc<__alloc_traits, const_pointer>;
  using __map _LIBCPP_NODEBUG                     = __split_buffer<pointer, __pointer_allocator>;
  using __map_alloc_traits _LIBCPP_NODEBUG        = allocator_traits<__pointer_allocator>;
  using __map_pointer _LIBCPP_NODEBUG             = typename __map_alloc_traits::pointer;
  using __map_const_pointer _LIBCPP_NODEBUG       = typename allocator_traits<__const_pointer_allocator>::const_pointer;
  using __map_const_iterator _LIBCPP_NODEBUG      = typename __map::const_iterator;

  using reference       = value_type&;
  using const_reference = const value_type&;

  using iterator = __deque_iterator<value_type, pointer, reference, __map_pointer, difference_type>;
  using const_iterator =
      __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer, difference_type>;
  using reverse_iterator       = std::reverse_iterator<iterator>;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;

  // A deque contains the following members which may be trivially relocatable:
  // - __map: is a `__split_buffer`, see `__split_buffer` for more information on when it is trivially relocatable
  // - size_type: is always trivially relocatable, since it is required to be an integral type
  // - allocator_type: may not be trivially relocatable, so it's checked
  // None of these are referencing the `deque` itself, so if all of them are trivially relocatable, `deque` is too.
  using __trivially_relocatable _LIBCPP_NODEBUG = __conditional_t<
      __libcpp_is_trivially_relocatable<__map>::value && __libcpp_is_trivially_relocatable<allocator_type>::value,
      deque,
      void>;

  static_assert(is_nothrow_default_constructible<allocator_type>::value ==
                    is_nothrow_default_constructible<__pointer_allocator>::value,
                "rebinding an allocator should not change exception 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 exception guarantees");

private:
  struct __deque_block_range {
    explicit _LIBCPP_HIDE_FROM_ABI __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_;

    _LIBCPP_HIDE_FROM_ABI __deque_range(iterator __pos, iterator __e) _NOEXCEPT : __pos_(__pos), __end_(__e) {}

    explicit _LIBCPP_HIDE_FROM_ABI operator bool() const _NOEXCEPT { return __pos_ != __end_; }

    _LIBCPP_HIDE_FROM_ABI __deque_range begin() const { return *this; }

    _LIBCPP_HIDE_FROM_ABI __deque_range end() const { return __deque_range(__end_, __end_); }
    _LIBCPP_HIDE_FROM_ABI __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);
    }

    _LIBCPP_HIDE_FROM_ABI __deque_range& operator++() _NOEXCEPT {
      if (__pos_.__m_iter_ == __end_.__m_iter_) {
        __pos_ = __end_;
      } else {
        ++__pos_.__m_iter_;
        __pos_.__ptr_ = *__pos_.__m_iter_;
      }
      return *this;
    }

    _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);
    }
  };

  struct _ConstructTransaction {
    _LIBCPP_HIDE_FROM_ABI _ConstructTransaction(deque* __db, __deque_block_range& __r)
        : __pos_(__r.__begin_), __end_(__r.__end_), __begin_(__r.__begin_), __base_(__db) {}

    _LIBCPP_HIDE_FROM_ABI ~_ConstructTransaction() { __base_->__size() += (__pos_ - __begin_); }

    pointer __pos_;
    const pointer __end_;

  private:
    const pointer __begin_;
    deque* const __base_;
  };

  static const difference_type __block_size;

  __map __map_;
  size_type __start_;
  _LIBCPP_COMPRESSED_PAIR(size_type, __size_, allocator_type, __alloc_);

public:
  // construct/copy/destroy:
  _LIBCPP_HIDE_FROM_ABI deque() _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
      : __start_(0), __size_(0) {
    __annotate_new(0);
  }

  _LIBCPP_HIDE_FROM_ABI ~deque() {
    clear();
    __annotate_delete();
    typename __map::iterator __i = __map_.begin();
    typename __map::iterator __e = __map_.end();
    for (; __i != __e; ++__i)
      __alloc_traits::deallocate(__alloc(), *__i, __block_size);
  }

  _LIBCPP_HIDE_FROM_ABI explicit deque(const allocator_type& __a)
      : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
    __annotate_new(0);
  }

  explicit _LIBCPP_HIDE_FROM_ABI deque(size_type __n);
#  if _LIBCPP_STD_VER >= 14
  explicit _LIBCPP_HIDE_FROM_ABI deque(size_type __n, const _Allocator& __a);
#  endif
  _LIBCPP_HIDE_FROM_ABI deque(size_type __n, const value_type& __v);

  template <__enable_if_t<__is_allocator<_Allocator>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI deque(size_type __n, const value_type& __v, const allocator_type& __a)
      : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
    __annotate_new(0);
    if (__n > 0)
      __append(__n, __v);
  }

  template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l);
  template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI deque(_InputIter __f, _InputIter __l, const allocator_type& __a);

#  if _LIBCPP_STD_VER >= 23
  template <_ContainerCompatibleRange<_Tp> _Range>
  _LIBCPP_HIDE_FROM_ABI deque(from_range_t, _Range&& __range, const allocator_type& __a = allocator_type())
      : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
    if constexpr (ranges::forward_range<_Range> || ranges::sized_range<_Range>) {
      __append_with_size(ranges::begin(__range), ranges::distance(__range));

    } else {
      for (auto&& __e : __range) {
        emplace_back(std::forward<decltype(__e)>(__e));
      }
    }
  }
#  endif

  _LIBCPP_HIDE_FROM_ABI deque(const deque& __c);
  _LIBCPP_HIDE_FROM_ABI deque(const deque& __c, const __type_identity_t<allocator_type>& __a);

  _LIBCPP_HIDE_FROM_ABI deque& operator=(const deque& __c);

#  ifndef _LIBCPP_CXX03_LANG
  _LIBCPP_HIDE_FROM_ABI deque(initializer_list<value_type> __il);
  _LIBCPP_HIDE_FROM_ABI deque(initializer_list<value_type> __il, const allocator_type& __a);

  _LIBCPP_HIDE_FROM_ABI deque& operator=(initializer_list<value_type> __il) {
    assign(__il);
    return *this;
  }

  _LIBCPP_HIDE_FROM_ABI deque(deque&& __c) noexcept(is_nothrow_move_constructible<allocator_type>::value);
  _LIBCPP_HIDE_FROM_ABI deque(deque&& __c, const __type_identity_t<allocator_type>& __a);
  _LIBCPP_HIDE_FROM_ABI deque& operator=(deque&& __c) noexcept(
      (__alloc_traits::propagate_on_container_move_assignment::value &&
       is_nothrow_move_assignable<allocator_type>::value) ||
      allocator_traits<allocator_type>::is_always_equal::value);

  _LIBCPP_HIDE_FROM_ABI void assign(initializer_list<value_type> __il) { assign(__il.begin(), __il.end()); }
#  endif // _LIBCPP_CXX03_LANG

  template <class _InputIter,
            __enable_if_t<__has_input_iterator_category<_InputIter>::value &&
                              !__has_random_access_iterator_category<_InputIter>::value,
                          int> = 0>
  _LIBCPP_HIDE_FROM_ABI void assign(_InputIter __f, _InputIter __l);
  template <class _RAIter, __enable_if_t<__has_random_access_iterator_category<_RAIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI void assign(_RAIter __f, _RAIter __l);

#  if _LIBCPP_STD_VER >= 23
  template <_ContainerCompatibleRange<_Tp> _Range>
  _LIBCPP_HIDE_FROM_ABI void assign_range(_Range&& __range) {
    if constexpr (ranges::random_access_range<_Range>) {
      auto __n = static_cast<size_type>(ranges::distance(__range));
      __assign_with_size_random_access(ranges::begin(__range), __n);

    } else if constexpr (ranges::forward_range<_Range> || ranges::sized_range<_Range>) {
      auto __n = static_cast<size_type>(ranges::distance(__range));
      __assign_with_size(ranges::begin(__range), __n);

    } else {
      __assign_with_sentinel(ranges::begin(__range), ranges::end(__range));
    }
  }
#  endif

  _LIBCPP_HIDE_FROM_ABI void assign(size_type __n, const value_type& __v);

  _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI allocator_type& __alloc() _NOEXCEPT { return __alloc_; }
  _LIBCPP_HIDE_FROM_ABI const allocator_type& __alloc() const _NOEXCEPT { return __alloc_; }

  // 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_HIDE_FROM_ABI reverse_iterator rbegin() _NOEXCEPT { return reverse_iterator(end()); }
  _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const _NOEXCEPT { return const_reverse_iterator(end()); }
  _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() _NOEXCEPT { return reverse_iterator(begin()); }
  _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT { return const_reverse_iterator(begin()); }

  _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { return begin(); }
  _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return end(); }
  _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const _NOEXCEPT { return const_reverse_iterator(end()); }
  _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT { return const_reverse_iterator(begin()); }

  // capacity:
  _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __size(); }

  _LIBCPP_HIDE_FROM_ABI size_type& __size() _NOEXCEPT { return __size_; }
  _LIBCPP_HIDE_FROM_ABI const size_type& __size() const _NOEXCEPT { return __size_; }

  _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
    return std::min<size_type>(__alloc_traits::max_size(__alloc()), numeric_limits<difference_type>::max());
  }
  _LIBCPP_HIDE_FROM_ABI void resize(size_type __n);
  _LIBCPP_HIDE_FROM_ABI void resize(size_type __n, const value_type& __v);
  _LIBCPP_HIDE_FROM_ABI void shrink_to_fit() _NOEXCEPT;
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT { return size() == 0; }

  // element access:
  _LIBCPP_HIDE_FROM_ABI reference operator[](size_type __i) _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI const_reference operator[](size_type __i) const _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI reference at(size_type __i);
  _LIBCPP_HIDE_FROM_ABI const_reference at(size_type __i) const;
  _LIBCPP_HIDE_FROM_ABI reference front() _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI const_reference front() const _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI reference back() _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI const_reference back() const _NOEXCEPT;

  // 23.2.2.3 modifiers:
  _LIBCPP_HIDE_FROM_ABI void push_front(const value_type& __v);
  _LIBCPP_HIDE_FROM_ABI void push_back(const value_type& __v);
#  ifndef _LIBCPP_CXX03_LANG
#    if _LIBCPP_STD_VER >= 17
  template <class... _Args>
  _LIBCPP_HIDE_FROM_ABI reference emplace_front(_Args&&... __args);
  template <class... _Args>
  _LIBCPP_HIDE_FROM_ABI reference emplace_back(_Args&&... __args);
#    else
  template <class... _Args>
  _LIBCPP_HIDE_FROM_ABI void emplace_front(_Args&&... __args);
  template <class... _Args>
  _LIBCPP_HIDE_FROM_ABI void emplace_back(_Args&&... __args);
#    endif
  template <class... _Args>
  _LIBCPP_HIDE_FROM_ABI iterator emplace(const_iterator __p, _Args&&... __args);

  _LIBCPP_HIDE_FROM_ABI void push_front(value_type&& __v);
  _LIBCPP_HIDE_FROM_ABI void push_back(value_type&& __v);

#    if _LIBCPP_STD_VER >= 23
  template <_ContainerCompatibleRange<_Tp> _Range>
  _LIBCPP_HIDE_FROM_ABI void prepend_range(_Range&& __range) {
    insert_range(begin(), std::forward<_Range>(__range));
  }

  template <_ContainerCompatibleRange<_Tp> _Range>
  _LIBCPP_HIDE_FROM_ABI void append_range(_Range&& __range) {
    insert_range(end(), std::forward<_Range>(__range));
  }
#    endif

  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, value_type&& __v);

  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, initializer_list<value_type> __il) {
    return insert(__p, __il.begin(), __il.end());
  }
#  endif // _LIBCPP_CXX03_LANG
  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, const value_type& __v);
  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, size_type __n, const value_type& __v);
  template <class _InputIter, __enable_if_t<__has_exactly_input_iterator_category<_InputIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _InputIter __f, _InputIter __l);
  template <class _ForwardIterator,
            __enable_if_t<__has_exactly_forward_iterator_category<_ForwardIterator>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l);
  template <class _BiIter, __enable_if_t<__has_bidirectional_iterator_category<_BiIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, _BiIter __f, _BiIter __l);

#  if _LIBCPP_STD_VER >= 23
  template <_ContainerCompatibleRange<_Tp> _Range>
  _LIBCPP_HIDE_FROM_ABI iterator insert_range(const_iterator __position, _Range&& __range) {
    if constexpr (ranges::bidirectional_range<_Range>) {
      auto __n = static_cast<size_type>(ranges::distance(__range));
      return __insert_bidirectional(__position, ranges::begin(__range), ranges::end(__range), __n);

    } else if constexpr (ranges::forward_range<_Range> || ranges::sized_range<_Range>) {
      auto __n = static_cast<size_type>(ranges::distance(__range));
      return __insert_with_size(__position, ranges::begin(__range), __n);

    } else {
      return __insert_with_sentinel(__position, ranges::begin(__range), ranges::end(__range));
    }
  }
#  endif

  _LIBCPP_HIDE_FROM_ABI void pop_front();
  _LIBCPP_HIDE_FROM_ABI void pop_back();
  _LIBCPP_HIDE_FROM_ABI iterator erase(const_iterator __p);
  _LIBCPP_HIDE_FROM_ABI iterator erase(const_iterator __f, const_iterator __l);

  _LIBCPP_HIDE_FROM_ABI void swap(deque& __c)
#  if _LIBCPP_STD_VER >= 14
      _NOEXCEPT;
#  else
      _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || __is_nothrow_swappable_v<allocator_type>);
#  endif
  _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT;

  _LIBCPP_HIDE_FROM_ABI bool __invariants() const {
    if (!__map_.__invariants())
      return false;
    if (__map_.size() >= size_type(-1) / __block_size)
      return false;
    for (__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_HIDE_FROM_ABI 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_HIDE_FROM_ABI void __move_assign_alloc(deque& __c, true_type)
      _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value) {
    __alloc() = std::move(__c.__alloc());
  }

  _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(deque&, false_type) _NOEXCEPT {}

  _LIBCPP_HIDE_FROM_ABI void __move_assign(deque& __c)
      _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value&&
                     is_nothrow_move_assignable<allocator_type>::value) {
    __map_   = std::move(__c.__map_);
    __start_ = __c.__start_;
    __size() = __c.size();
    __move_assign_alloc(__c);
    __c.__start_ = __c.__size() = 0;
  }

  _LIBCPP_HIDE_FROM_ABI static size_type __recommend_blocks(size_type __n) {
    return __n / __block_size + (__n % __block_size != 0);
  }
  _LIBCPP_HIDE_FROM_ABI size_type __capacity() const {
    return __map_.size() == 0 ? 0 : __map_.size() * __block_size - 1;
  }
  _LIBCPP_HIDE_FROM_ABI size_type __block_count() const { return __map_.size(); }

  _LIBCPP_HIDE_FROM_ABI size_type __front_spare() const { return __start_; }
  _LIBCPP_HIDE_FROM_ABI size_type __front_spare_blocks() const { return __front_spare() / __block_size; }
  _LIBCPP_HIDE_FROM_ABI size_type __back_spare() const { return __capacity() - (__start_ + size()); }
  _LIBCPP_HIDE_FROM_ABI size_type __back_spare_blocks() const { return __back_spare() / __block_size; }

private:
  enum __asan_annotation_type { __asan_unposion, __asan_poison };

  enum __asan_annotation_place {
    __asan_front_moved,
    __asan_back_moved,
  };

  _LIBCPP_HIDE_FROM_ABI void __annotate_from_to(
      size_type __beg,
      size_type __end,
      __asan_annotation_type __annotation_type,
      __asan_annotation_place __place) const _NOEXCEPT {
    (void)__beg;
    (void)__end;
    (void)__annotation_type;
    (void)__place;
#  if _LIBCPP_HAS_ASAN
    // __beg - index of the first item to annotate
    // __end - index behind the last item to annotate (so last item + 1)
    // __annotation_type - __asan_unposion or __asan_poison
    // __place - __asan_front_moved or __asan_back_moved
    // Note: All indexes in __map_
    if (__beg == __end)
      return;
    // __annotations_beg_map - first chunk which annotations we want to modify
    // __annotations_end_map - last chunk which annotations we want to modify
    // NOTE: if __end % __block_size == 0, __annotations_end_map points at the next block, which may not exist
    __map_const_iterator __annotations_beg_map = __map_.begin() + __beg / __block_size;
    __map_const_iterator __annotations_end_map = __map_.begin() + __end / __block_size;

    bool const __poisoning = __annotation_type == __asan_poison;
    // __old_c_beg_index - index of the first element in old container
    // __old_c_end_index - index of the end of old container (last + 1)
    // Note: may be outside the area we are annotating
    size_t __old_c_beg_index = (__poisoning && __place == __asan_front_moved) ? __beg : __start_;
    size_t __old_c_end_index = (__poisoning && __place == __asan_back_moved) ? __end : __start_ + size();
    bool const __front       = __place == __asan_front_moved;

    if (__poisoning && empty()) {
      // Special case: we shouldn't trust __start_
      __old_c_beg_index = __beg;
      __old_c_end_index = __end;
    }
    // __old_c_beg_map - memory block (chunk) with first element
    // __old_c_end_map - memory block (chunk) with end of old container
    // Note: if __old_c_end_index % __block_size == 0, __old_c_end_map points at the next block,
    // which may not exist
    __map_const_iterator __old_c_beg_map = __map_.begin() + __old_c_beg_index / __block_size;
    __map_const_iterator __old_c_end_map = __map_.begin() + __old_c_end_index / __block_size;

    // One edge (front/end) of the container was moved and one was not modified.
    // __new_edge_index - index of new edge
    // __new_edge_map    - memory block (chunk) with new edge, it always equals to
    //                    __annotations_beg_map or __annotations_end_map
    // __old_edge_map    - memory block (chunk) with old edge, it always equals to
    //                    __old_c_beg_map or __old_c_end_map
    size_t __new_edge_index             = (__poisoning ^ __front) ? __beg : __end;
    __map_const_iterator __new_edge_map = __map_.begin() + __new_edge_index / __block_size;
    __map_const_iterator __old_edge_map = __front ? __old_c_end_map : __old_c_beg_map;

    // We iterate over map pointers (chunks) and fully poison all memory blocks between the first and the last.
    // First and last chunk may be partially poisoned.
    // __annotate_end_map may point at not existing chunk, therefore we have to have a check for it.
    for (__map_const_iterator __map_it = __annotations_beg_map; __map_it <= __annotations_end_map; ++__map_it) {
      if (__map_it == __annotations_end_map && __end % __block_size == 0)
        // Chunk may not exist, but nothing to do here anyway
        break;

      // The beginning and the end of the current memory block
      const void* __mem_beg = std::__to_address(*__map_it);
      const void* __mem_end = std::__to_address(*__map_it + __block_size);

      // The beginning of memory-in-use in the memory block before container modification
      const void* __old_beg =
          (__map_it == __old_c_beg_map) ? std::__to_address(*__map_it + (__old_c_beg_index % __block_size)) : __mem_beg;

      // The end of memory-in-use in the memory block before container modification
      const void* __old_end;
      if (__map_it < __old_c_beg_map || __map_it > __old_c_end_map || (!__poisoning && empty()))
        __old_end = __old_beg;
      else
        __old_end = (__map_it == __old_c_end_map)
                      ? std::__to_address(*__map_it + (__old_c_end_index % __block_size))
                      : __mem_end;

      // New edge of the container in current memory block
      // If the edge is in a different chunk it points on corresponding end of the memory block
      const void* __new_edge;
      if (__map_it == __new_edge_map)
        __new_edge = std::__to_address(*__map_it + (__new_edge_index % __block_size));
      else
        __new_edge = (__poisoning ^ __front) ? __mem_beg : __mem_end;

      // Not modified edge of the container
      // If the edge is in a different chunk it points on corresponding end of the memory block
      const void* __old_edge;
      if (__map_it == __old_edge_map)
        __old_edge = __front ? __old_end : __old_beg;
      else
        __old_edge = __front ? __mem_end : __mem_beg;

      // __new_beg - the beginning of memory-in-use in the memory block after container modification
      // __new_end - the end of memory-in-use in the memory block after container modification
      const void* __new_beg = __front ? __new_edge : __old_edge;
      const void* __new_end = __front ? __old_edge : __new_edge;

      std::__annotate_double_ended_contiguous_container<_Allocator>(
          __mem_beg, __mem_end, __old_beg, __old_end, __new_beg, __new_end);
    }
#  endif // _LIBCPP_HAS_ASAN
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_new(size_type __current_size) const _NOEXCEPT {
    (void)__current_size;
#  if _LIBCPP_HAS_ASAN
    if (__current_size == 0)
      __annotate_from_to(0, __map_.size() * __block_size, __asan_poison, __asan_back_moved);
    else {
      __annotate_from_to(0, __start_, __asan_poison, __asan_front_moved);
      __annotate_from_to(__start_ + __current_size, __map_.size() * __block_size, __asan_poison, __asan_back_moved);
    }
#  endif // _LIBCPP_HAS_ASAN
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_delete() const _NOEXCEPT {
#  if _LIBCPP_HAS_ASAN
    if (empty()) {
      for (size_t __i = 0; __i < __map_.size(); ++__i) {
        __annotate_whole_block(__i, __asan_unposion);
      }
    } else {
      __annotate_from_to(0, __start_, __asan_unposion, __asan_front_moved);
      __annotate_from_to(__start_ + size(), __map_.size() * __block_size, __asan_unposion, __asan_back_moved);
    }
#  endif // _LIBCPP_HAS_ASAN
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_increase_front(size_type __n) const _NOEXCEPT {
    (void)__n;
#  if _LIBCPP_HAS_ASAN
    __annotate_from_to(__start_ - __n, __start_, __asan_unposion, __asan_front_moved);
#  endif
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_increase_back(size_type __n) const _NOEXCEPT {
    (void)__n;
#  if _LIBCPP_HAS_ASAN
    __annotate_from_to(__start_ + size(), __start_ + size() + __n, __asan_unposion, __asan_back_moved);
#  endif
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_shrink_front(size_type __old_size, size_type __old_start) const _NOEXCEPT {
    (void)__old_size;
    (void)__old_start;
#  if _LIBCPP_HAS_ASAN
    __annotate_from_to(__old_start, __old_start + (__old_size - size()), __asan_poison, __asan_front_moved);
#  endif
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_shrink_back(size_type __old_size, size_type __old_start) const _NOEXCEPT {
    (void)__old_size;
    (void)__old_start;
#  if _LIBCPP_HAS_ASAN
    __annotate_from_to(__old_start + size(), __old_start + __old_size, __asan_poison, __asan_back_moved);
#  endif
  }

  _LIBCPP_HIDE_FROM_ABI void __annotate_poison_block(const void* __beginning, const void* __end) const _NOEXCEPT {
    std::__annotate_double_ended_contiguous_container<_Allocator>(__beginning, __end, __beginning, __end, __end, __end);
  }

  _LIBCPP_HIDE_FROM_ABI void
  __annotate_whole_block(size_t __block_index, __asan_annotation_type __annotation_type) const _NOEXCEPT {
    (void)__block_index;
    (void)__annotation_type;
#  if _LIBCPP_HAS_ASAN
    __map_const_iterator __block_it = __map_.begin() + __block_index;
    const void* __block_start       = std::__to_address(*__block_it);
    const void* __block_end         = std::__to_address(*__block_it + __block_size);

    if (__annotation_type == __asan_poison)
      __annotate_poison_block(__block_start, __block_end);
    else {
      std::__annotate_double_ended_contiguous_container<_Allocator>(
          __block_start, __block_end, __block_start, __block_start, __block_start, __block_end);
    }
#  endif
  }
#  if _LIBCPP_HAS_ASAN

public:
  _LIBCPP_HIDE_FROM_ABI bool __verify_asan_annotations() const _NOEXCEPT {
    // This function tests deque object annotations.
    if (empty()) {
      for (__map_const_iterator __it = __map_.begin(); __it != __map_.end(); ++__it) {
        if (!__sanitizer_verify_double_ended_contiguous_container(
                std::__to_address(*__it),
                std::__to_address(*__it),
                std::__to_address(*__it),
                std::__to_address(*__it + __block_size)))
          return false;
      }

      return true;
    }

    size_type __end                 = __start_ + size();
    __map_const_iterator __first_mp = __map_.begin() + __start_ / __block_size;
    __map_const_iterator __last_mp  = __map_.begin() + (__end - 1) / __block_size;

    // Pointers to first and after last elements
    // Those can be in different deque blocks
    const void* __p_beg = std::__to_address(*__first_mp + (__start_ % __block_size));
    const void* __p_end =
        std::__to_address(*__last_mp + ((__end % __block_size == 0) ? __block_size : __end % __block_size));

    for (__map_const_iterator __it = __map_.begin(); __it != __map_.end(); ++__it) {
      // Go over all blocks, find the place we are in and verify its annotations
      // Note that __p_end points *behind* the last item.

      // - blocks before the first block with container elements
      // - first block with items
      // - last block with items
      // - blocks after last block with ciontainer elements

      // Is the block before or after deque blocks that contain elements?
      if (__it < __first_mp || __it > __last_mp) {
        if (!__sanitizer_verify_double_ended_contiguous_container(
                std::__to_address(*__it),
                std::__to_address(*__it),
                std::__to_address(*__it),
                std::__to_address(*__it + __block_size)))
          return false;
      } else {
        const void* __containers_buffer_beg = (__it == __first_mp) ? __p_beg : (const void*)std::__to_address(*__it);
        const void* __containers_buffer_end =
            (__it == __last_mp) ? __p_end : (const void*)std::__to_address(*__it + __block_size);
        if (!__sanitizer_verify_double_ended_contiguous_container(
                std::__to_address(*__it),
                __containers_buffer_beg,
                __containers_buffer_end,
                std::__to_address(*__it + __block_size))) {
          return false;
        }
      }
    }
    return true;
  }

private:
#  endif // _LIBCPP_HAS_ASAN
  _LIBCPP_HIDE_FROM_ABI bool __maybe_remove_front_spare(bool __keep_one = true) {
    if (__front_spare_blocks() >= 2 || (!__keep_one && __front_spare_blocks())) {
      __annotate_whole_block(0, __asan_unposion);
      __alloc_traits::deallocate(__alloc(), __map_.front(), __block_size);
      __map_.pop_front();
      __start_ -= __block_size;
      return true;
    }
    return false;
  }

  _LIBCPP_HIDE_FROM_ABI bool __maybe_remove_back_spare(bool __keep_one = true) {
    if (__back_spare_blocks() >= 2 || (!__keep_one && __back_spare_blocks())) {
      __annotate_whole_block(__map_.size() - 1, __asan_unposion);
      __alloc_traits::deallocate(__alloc(), __map_.back(), __block_size);
      __map_.pop_back();
      return true;
    }
    return false;
  }

  template <class _Iterator, class _Sentinel>
  _LIBCPP_HIDE_FROM_ABI void __assign_with_sentinel(_Iterator __f, _Sentinel __l);

  template <class _RandomAccessIterator>
  _LIBCPP_HIDE_FROM_ABI void __assign_with_size_random_access(_RandomAccessIterator __f, difference_type __n);
  template <class _Iterator>
  _LIBCPP_HIDE_FROM_ABI void __assign_with_size(_Iterator __f, difference_type __n);

  template <class _Iterator, class _Sentinel>
  _LIBCPP_HIDE_FROM_ABI iterator __insert_with_sentinel(const_iterator __p, _Iterator __f, _Sentinel __l);

  template <class _Iterator>
  _LIBCPP_HIDE_FROM_ABI iterator __insert_with_size(const_iterator __p, _Iterator __f, size_type __n);

  template <class _BiIter, class _Sentinel>
  _LIBCPP_HIDE_FROM_ABI iterator
  __insert_bidirectional(const_iterator __p, _BiIter __f, _Sentinel __sent, size_type __n);
  template <class _BiIter>
  _LIBCPP_HIDE_FROM_ABI iterator __insert_bidirectional(const_iterator __p, _BiIter __f, _BiIter __l, size_type __n);

  template <class _InpIter, __enable_if_t<__has_exactly_input_iterator_category<_InpIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI void __append(_InpIter __f, _InpIter __l);
  template <class _ForIter, __enable_if_t<__has_forward_iterator_category<_ForIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI void __append(_ForIter __f, _ForIter __l);

  template <class _InputIterator>
  _LIBCPP_HIDE_FROM_ABI void __append_with_size(_InputIterator __from, size_type __n);
  template <class _InputIterator, class _Sentinel>
  _LIBCPP_HIDE_FROM_ABI void __append_with_sentinel(_InputIterator __f, _Sentinel __l);

  _LIBCPP_HIDE_FROM_ABI void __append(size_type __n);
  _LIBCPP_HIDE_FROM_ABI void __append(size_type __n, const value_type& __v);
  _LIBCPP_HIDE_FROM_ABI void __erase_to_end(const_iterator __f);
  _LIBCPP_HIDE_FROM_ABI void __add_front_capacity();
  _LIBCPP_HIDE_FROM_ABI void __add_front_capacity(size_type __n);
  _LIBCPP_HIDE_FROM_ABI void __add_back_capacity();
  _LIBCPP_HIDE_FROM_ABI void __add_back_capacity(size_type __n);
  _LIBCPP_HIDE_FROM_ABI iterator __move_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt);
  _LIBCPP_HIDE_FROM_ABI iterator
  __move_backward_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt);
  _LIBCPP_HIDE_FROM_ABI void __move_construct_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt);
  _LIBCPP_HIDE_FROM_ABI void
  __move_construct_backward_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt);

  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const deque& __c) {
    __copy_assign_alloc(__c, integral_constant<bool, __alloc_traits::propagate_on_container_copy_assignment::value>());
  }

  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const deque& __c, true_type) {
    if (__alloc() != __c.__alloc()) {
      clear();
      shrink_to_fit();
    }
    __alloc()       = __c.__alloc();
    __map_.__alloc_ = __c.__map_.__alloc_;
  }

  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const deque&, false_type) {}

  _LIBCPP_HIDE_FROM_ABI void __move_assign(deque& __c, true_type)
      _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
  _LIBCPP_HIDE_FROM_ABI void __move_assign(deque& __c, false_type);
};

template <class _Tp, class _Alloc>
_LIBCPP_CONSTEXPR const typename allocator_traits<_Alloc>::difference_type deque<_Tp, _Alloc>::__block_size =
    __deque_block_size<value_type, difference_type>::value;

#  if _LIBCPP_STD_VER >= 17
template <class _InputIterator,
          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
          class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
          class        = enable_if_t<__is_allocator<_Alloc>::value> >
deque(_InputIterator, _InputIterator) -> deque<__iter_value_type<_InputIterator>, _Alloc>;

template <class _InputIterator,
          class _Alloc,
          class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
          class = enable_if_t<__is_allocator<_Alloc>::value> >
deque(_InputIterator, _InputIterator, _Alloc) -> deque<__iter_value_type<_InputIterator>, _Alloc>;
#  endif

#  if _LIBCPP_STD_VER >= 23
template <ranges::input_range _Range,
          class _Alloc = allocator<ranges::range_value_t<_Range>>,
          class        = enable_if_t<__is_allocator<_Alloc>::value> >
deque(from_range_t, _Range&&, _Alloc = _Alloc()) -> deque<ranges::range_value_t<_Range>, _Alloc>;
#  endif

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(size_type __n) : __start_(0), __size_(0) {
  __annotate_new(0);
  if (__n > 0)
    __append(__n);
}

#  if _LIBCPP_STD_VER >= 14
template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(size_type __n, const _Allocator& __a)
    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
  __annotate_new(0);
  if (__n > 0)
    __append(__n);
}
#  endif

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v) : __start_(0), __size_(0) {
  __annotate_new(0);
  if (__n > 0)
    __append(__n, __v);
}

template <class _Tp, class _Allocator>
template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> >
deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l) : __start_(0), __size_(0) {
  __annotate_new(0);
  __append(__f, __l);
}

template <class _Tp, class _Allocator>
template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> >
deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a)
    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
  __annotate_new(0);
  __append(__f, __l);
}

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(const deque& __c)
    : __map_(__pointer_allocator(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))),
      __start_(0),
      __size_(0),
      __alloc_(__map_.__alloc_) {
  __annotate_new(0);
  __append(__c.begin(), __c.end());
}

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(const deque& __c, const __type_identity_t<allocator_type>& __a)
    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
  __annotate_new(0);
  __append(__c.begin(), __c.end());
}

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>& deque<_Tp, _Allocator>::operator=(const deque& __c) {
  if (this != std::addressof(__c)) {
    __copy_assign_alloc(__c);
    assign(__c.begin(), __c.end());
  }
  return *this;
}

#  ifndef _LIBCPP_CXX03_LANG

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il) : __start_(0), __size_(0) {
  __annotate_new(0);
  __append(__il.begin(), __il.end());
}

template <class _Tp, class _Allocator>
deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator_type& __a)
    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0), __alloc_(__a) {
  __annotate_new(0);
  __append(__il.begin(), __il.end());
}

template <class _Tp, class _Allocator>
inline deque<_Tp, _Allocator>::deque(deque&& __c) noexcept(is_nothrow_move_constructible<allocator_type>::value)
    : __map_(std::move(__c.__map_)),
      __start_(std::move(__c.__start_)),
      __size_(std::move(__c.__size_)),
      __alloc_(std::move(__c.__alloc_)) {
  __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)
    : __map_(std::move(__c.__map_), __pointer_allocator(__a)),
      __start_(std::move(__c.__start_)),
      __size_(std::move(__c.__size_)),
      __alloc_(__a) {
  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()));
  }
}

template <class _Tp, class _Allocator>
inline deque<_Tp, _Allocator>& deque<_Tp, _Allocator>::operator=(deque&& __c) noexcept(
    (__alloc_traits::propagate_on_container_move_assignment::value &&
     is_nothrow_move_assignable<allocator_type>::value) ||
    allocator_traits<allocator_type>::is_always_equal::value) {
  __move_assign(__c, integral_constant<bool, __alloc_traits::propagate_on_container_move_assignment::value>());
  return *this;
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__move_assign(deque& __c, false_type) {
  if (__alloc() != __c.__alloc()) {
    typedef move_iterator<iterator> _Ip;
    assign(_Ip(__c.begin()), _Ip(__c.end()));
  } else
    __move_assign(__c, true_type());
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__move_assign(deque& __c,
                                           true_type) noexcept(is_nothrow_move_assignable<allocator_type>::value) {
  clear();
  shrink_to_fit();
  __move_assign(__c);
}

#  endif // _LIBCPP_CXX03_LANG

template <class _Tp, class _Allocator>
template <class _InputIter,
          __enable_if_t<__has_input_iterator_category<_InputIter>::value &&
                            !__has_random_access_iterator_category<_InputIter>::value,
                        int> >
void deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l) {
  __assign_with_sentinel(__f, __l);
}

template <class _Tp, class _Allocator>
template <class _Iterator, class _Sentinel>
_LIBCPP_HIDE_FROM_ABI void deque<_Tp, _Allocator>::__assign_with_sentinel(_Iterator __f, _Sentinel __l) {
  iterator __i = begin();
  iterator __e = end();
  for (; __f != __l && __i != __e; ++__f, (void)++__i)
    *__i = *__f;
  if (__f != __l)
    __append_with_sentinel(std::move(__f), std::move(__l));
  else
    __erase_to_end(__i);
}

template <class _Tp, class _Allocator>
template <class _RAIter, __enable_if_t<__has_random_access_iterator_category<_RAIter>::value, int> >
void deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l) {
  __assign_with_size_random_access(__f, __l - __f);
}

template <class _Tp, class _Allocator>
template <class _RandomAccessIterator>
_LIBCPP_HIDE_FROM_ABI void
deque<_Tp, _Allocator>::__assign_with_size_random_access(_RandomAccessIterator __f, difference_type __n) {
  if (static_cast<size_type>(__n) > size()) {
    auto __l = __f + size();
    std::copy(__f, __l, begin());
    __append_with_size(__l, __n - size());
  } else
    __erase_to_end(std::copy_n(__f, __n, begin()));
}

template <class _Tp, class _Allocator>
template <class _Iterator>
_LIBCPP_HIDE_FROM_ABI void deque<_Tp, _Allocator>::__assign_with_size(_Iterator __f, difference_type __n) {
  if (static_cast<size_type>(__n) > size()) {
    auto __added_size = __n - size();

    auto __i = begin();
    for (auto __count = size(); __count != 0; --__count) {
      *__i++ = *__f++;
    }

    __append_with_size(__f, __added_size);

  } else {
    __erase_to_end(std::copy_n(__f, __n, begin()));
  }
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::assign(size_type __n, const value_type& __v) {
  if (__n > size()) {
    std::fill_n(begin(), size(), __v);
    __n -= size();
    __append(__n, __v);
  } else
    __erase_to_end(std::fill_n(begin(), __n, __v));
}

template <class _Tp, class _Allocator>
inline _Allocator deque<_Tp, _Allocator>::get_allocator() const _NOEXCEPT {
  return __alloc();
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::resize(size_type __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 > 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 = __alloc();
  if (empty()) {
    __annotate_delete();
    while (__map_.size() > 0) {
      __alloc_traits::deallocate(__a, __map_.back(), __block_size);
      __map_.pop_back();
    }
    __start_ = 0;
  } else {
    __maybe_remove_front_spare(/*__keep_one=*/false);
    __maybe_remove_back_spare(/*__keep_one=*/false);
  }
  __map_.shrink_to_fit();
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::reference deque<_Tp, _Allocator>::operator[](size_type __i) _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__i < size(), "deque::operator[] index out of bounds");
  size_type __p = __start_ + __i;
  return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::const_reference
deque<_Tp, _Allocator>::operator[](size_type __i) const _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__i < size(), "deque::operator[] index out of bounds");
  size_type __p = __start_ + __i;
  return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::reference deque<_Tp, _Allocator>::at(size_type __i) {
  if (__i >= size())
    std::__throw_out_of_range("deque");
  size_type __p = __start_ + __i;
  return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::const_reference deque<_Tp, _Allocator>::at(size_type __i) const {
  if (__i >= size())
    std::__throw_out_of_range("deque");
  size_type __p = __start_ + __i;
  return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::reference deque<_Tp, _Allocator>::front() _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::front called on an empty deque");
  return *(*(__map_.begin() + __start_ / __block_size) + __start_ % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::const_reference deque<_Tp, _Allocator>::front() const _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::front called on an empty deque");
  return *(*(__map_.begin() + __start_ / __block_size) + __start_ % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::reference deque<_Tp, _Allocator>::back() _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::back called on an empty deque");
  size_type __p = size() + __start_ - 1;
  return *(*(__map_.begin() + __p / __block_size) + __p % __block_size);
}

template <class _Tp, class _Allocator>
inline typename deque<_Tp, _Allocator>::const_reference deque<_Tp, _Allocator>::back() const _NOEXCEPT {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::back called on an empty deque");
  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 = __alloc();
  if (__back_spare() == 0)
    __add_back_capacity();
  // __back_spare() >= 1
  __annotate_increase_back(1);
  __alloc_traits::construct(__a, std::addressof(*end()), __v);
  ++__size();
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::push_front(const value_type& __v) {
  allocator_type& __a = __alloc();
  if (__front_spare() == 0)
    __add_front_capacity();
  // __front_spare() >= 1
  __annotate_increase_front(1);
  __alloc_traits::construct(__a, std::addressof(*--begin()), __v);
  --__start_;
  ++__size();
}

#  ifndef _LIBCPP_CXX03_LANG
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::push_back(value_type&& __v) {
  allocator_type& __a = __alloc();
  if (__back_spare() == 0)
    __add_back_capacity();
  // __back_spare() >= 1
  __annotate_increase_back(1);
  __alloc_traits::construct(__a, std::addressof(*end()), std::move(__v));
  ++__size();
}

template <class _Tp, class _Allocator>
template <class... _Args>
#    if _LIBCPP_STD_VER >= 17
typename deque<_Tp, _Allocator>::reference
#    else
void
#    endif
deque<_Tp, _Allocator>::emplace_back(_Args&&... __args) {
  allocator_type& __a = __alloc();
  if (__back_spare() == 0)
    __add_back_capacity();
  // __back_spare() >= 1
  __annotate_increase_back(1);
  __alloc_traits::construct(__a, std::addressof(*end()), std::forward<_Args>(__args)...);
  ++__size();
#    if _LIBCPP_STD_VER >= 17
  return *--end();
#    endif
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::push_front(value_type&& __v) {
  allocator_type& __a = __alloc();
  if (__front_spare() == 0)
    __add_front_capacity();
  // __front_spare() >= 1
  __annotate_increase_front(1);
  __alloc_traits::construct(__a, std::addressof(*--begin()), std::move(__v));
  --__start_;
  ++__size();
}

template <class _Tp, class _Allocator>
template <class... _Args>
#    if _LIBCPP_STD_VER >= 17
typename deque<_Tp, _Allocator>::reference
#    else
void
#    endif
deque<_Tp, _Allocator>::emplace_front(_Args&&... __args) {
  allocator_type& __a = __alloc();
  if (__front_spare() == 0)
    __add_front_capacity();
  // __front_spare() >= 1
  __annotate_increase_front(1);
  __alloc_traits::construct(__a, std::addressof(*--begin()), std::forward<_Args>(__args)...);
  --__start_;
  ++__size();
#    if _LIBCPP_STD_VER >= 17
  return *begin();
#    endif
}

template <class _Tp, class _Allocator>
typename deque<_Tp, _Allocator>::iterator deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v) {
  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)
      __add_front_capacity();
    // __front_spare() >= 1
    __annotate_increase_front(1);
    if (__pos == 0) {
      __alloc_traits::construct(__a, std::addressof(*--begin()), std::move(__v));
      --__start_;
      ++__size();
    } else {
      iterator __b   = begin();
      iterator __bm1 = std::prev(__b);
      __alloc_traits::construct(__a, std::addressof(*__bm1), std::move(*__b));
      --__start_;
      ++__size();
      if (__pos > 1)
        __b = std::move(std::next(__b), __b + __pos, __b);
      *__b = std::move(__v);
    }
  } else { // insert by shifting things forward
    if (__back_spare() == 0)
      __add_back_capacity();
    // __back_capacity >= 1
    __annotate_increase_back(1);
    size_type __de = size() - __pos;
    if (__de == 0) {
      __alloc_traits::construct(__a, std::addressof(*end()), std::move(__v));
      ++__size();
    } else {
      iterator __e   = end();
      iterator __em1 = std::prev(__e);
      __alloc_traits::construct(__a, std::addressof(*__e), std::move(*__em1));
      ++__size();
      if (__de > 1)
        __e = std::move_backward(__e - __de, __em1, __e);
      *--__e = std::move(__v);
    }
  }
  return begin() + __pos;
}

template <class _Tp, class _Allocator>
template <class... _Args>
typename deque<_Tp, _Allocator>::iterator deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args) {
  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)
      __add_front_capacity();
    // __front_spare() >= 1
    __annotate_increase_front(1);
    if (__pos == 0) {
      __alloc_traits::construct(__a, std::addressof(*--begin()), std::forward<_Args>(__args)...);
      --__start_;
      ++__size();
    } else {
      __temp_value<value_type, _Allocator> __tmp(__alloc(), std::forward<_Args>(__args)...);
      iterator __b   = begin();
      iterator __bm1 = std::prev(__b);
      __alloc_traits::construct(__a, std::addressof(*__bm1), std::move(*__b));
      --__start_;
      ++__size();
      if (__pos > 1)
        __b = std::move(std::next(__b), __b + __pos, __b);
      *__b = std::move(__tmp.get());
    }
  } else { // insert by shifting things forward
    if (__back_spare() == 0)
      __add_back_capacity();
    // __back_capacity >= 1
    __annotate_increase_back(1);
    size_type __de = size() - __pos;
    if (__de == 0) {
      __alloc_traits::construct(__a, std::addressof(*end()), std::forward<_Args>(__args)...);
      ++__size();
    } else {
      __temp_value<value_type, _Allocator> __tmp(__alloc(), std::forward<_Args>(__args)...);
      iterator __e   = end();
      iterator __em1 = std::prev(__e);
      __alloc_traits::construct(__a, std::addressof(*__e), std::move(*__em1));
      ++__size();
      if (__de > 1)
        __e = std::move_backward(__e - __de, __em1, __e);
      *--__e = std::move(__tmp.get());
    }
  }
  return begin() + __pos;
}

#  endif // _LIBCPP_CXX03_LANG

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 - begin();
  size_type __to_end  = size() - __pos;
  allocator_type& __a = __alloc();
  if (__pos < __to_end) { // insert by shifting things backward
    if (__front_spare() == 0)
      __add_front_capacity();
    // __front_spare() >= 1
    __annotate_increase_front(1);
    if (__pos == 0) {
      __alloc_traits::construct(__a, std::addressof(*--begin()), __v);
      --__start_;
      ++__size();
    } else {
      const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
      iterator __b       = begin();
      iterator __bm1     = std::prev(__b);
      if (__vt == pointer_traits<const_pointer>::pointer_to(*__b))
        __vt = pointer_traits<const_pointer>::pointer_to(*__bm1);
      __alloc_traits::construct(__a, std::addressof(*__bm1), std::move(*__b));
      --__start_;
      ++__size();
      if (__pos > 1)
        __b = __move_and_check(std::next(__b), __b + __pos, __b, __vt);
      *__b = *__vt;
    }
  } else { // insert by shifting things forward
    if (__back_spare() == 0)
      __add_back_capacity();
    // __back_capacity >= 1
    __annotate_increase_back(1);
    size_type __de = size() - __pos;
    if (__de == 0) {
      __alloc_traits::construct(__a, std::addressof(*end()), __v);
      ++__size();
    } else {
      const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
      iterator __e       = end();
      iterator __em1     = std::prev(__e);
      if (__vt == pointer_traits<const_pointer>::pointer_to(*__em1))
        __vt = pointer_traits<const_pointer>::pointer_to(*__e);
      __alloc_traits::construct(__a, std::addressof(*__e), std::move(*__em1));
      ++__size();
      if (__de > 1)
        __e = __move_backward_and_check(__e - __de, __em1, __e, __vt);
      *--__e = *__vt;
    }
  }
  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 - 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()
    __annotate_increase_front(__n);
    iterator __old_begin = begin();
    iterator __i         = __old_begin;
    if (__n > __pos) {
      for (size_type __m = __n - __pos; __m; --__m, --__start_, ++__size())
        __alloc_traits::construct(__a, std::addressof(*--__i), __v);
      __n = __pos;
    }
    if (__n > 0) {
      const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
      iterator __obn     = __old_begin + __n;
      __move_construct_backward_and_check(__old_begin, __obn, __i, __vt);
      if (__n < __pos)
        __old_begin = __move_and_check(__obn, __old_begin + __pos, __old_begin, __vt);
      std::fill_n(__old_begin, __n, *__vt);
    }
  } else { // insert by shifting things forward
    size_type __back_capacity = __back_spare();
    if (__n > __back_capacity)
      __add_back_capacity(__n - __back_capacity);
    // __n <= __back_capacity
    __annotate_increase_back(__n);
    iterator __old_end = end();
    iterator __i       = __old_end;
    size_type __de     = size() - __pos;
    if (__n > __de) {
      for (size_type __m = __n - __de; __m; --__m, (void)++__i, ++__size())
        __alloc_traits::construct(__a, std::addressof(*__i), __v);
      __n = __de;
    }
    if (__n > 0) {
      const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
      iterator __oen     = __old_end - __n;
      __move_construct_and_check(__oen, __old_end, __i, __vt);
      if (__n < __de)
        __old_end = __move_backward_and_check(__old_end - __de, __oen, __old_end, __vt);
      std::fill_n(__old_end - __n, __n, *__vt);
    }
  }
  return begin() + __pos;
}

template <class _Tp, class _Allocator>
template <class _InputIter, __enable_if_t<__has_exactly_input_iterator_category<_InputIter>::value, int> >
typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l) {
  return __insert_with_sentinel(__p, __f, __l);
}

template <class _Tp, class _Allocator>
template <class _Iterator, class _Sentinel>
_LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__insert_with_sentinel(const_iterator __p, _Iterator __f, _Sentinel __l) {
  __split_buffer<value_type, allocator_type&> __buf(__alloc());
  __buf.__construct_at_end_with_sentinel(std::move(__f), std::move(__l));
  typedef typename __split_buffer<value_type, allocator_type&>::iterator __bi;
  return insert(__p, move_iterator<__bi>(__buf.begin()), move_iterator<__bi>(__buf.end()));
}

template <class _Tp, class _Allocator>
template <class _ForwardIterator, __enable_if_t<__has_exactly_forward_iterator_category<_ForwardIterator>::value, int> >
typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l) {
  return __insert_with_size(__p, __f, std::distance(__f, __l));
}

template <class _Tp, class _Allocator>
template <class _Iterator>
_LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__insert_with_size(const_iterator __p, _Iterator __f, size_type __n) {
  __split_buffer<value_type, allocator_type&> __buf(__n, 0, __alloc());
  __buf.__construct_at_end_with_size(__f, __n);
  typedef typename __split_buffer<value_type, allocator_type&>::iterator __fwd;
  return insert(__p, move_iterator<__fwd>(__buf.begin()), move_iterator<__fwd>(__buf.end()));
}

template <class _Tp, class _Allocator>
template <class _BiIter, __enable_if_t<__has_bidirectional_iterator_category<_BiIter>::value, int> >
typename deque<_Tp, _Allocator>::iterator deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l) {
  return __insert_bidirectional(__p, __f, __l, std::distance(__f, __l));
}

template <class _Tp, class _Allocator>
template <class _BiIter, class _Sentinel>
_LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__insert_bidirectional(const_iterator __p, _BiIter __f, _Sentinel, size_type __n) {
  return __insert_bidirectional(__p, __f, std::next(__f, __n), __n);
}

template <class _Tp, class _Allocator>
template <class _BiIter>
_LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__insert_bidirectional(const_iterator __p, _BiIter __f, _BiIter __l, size_type __n) {
  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()
    __annotate_increase_front(__n);
    iterator __old_begin = begin();
    iterator __i         = __old_begin;
    _BiIter __m          = __f;
    if (__n > __pos) {
      __m = __pos < __n / 2 ? std::prev(__l, __pos) : std::next(__f, __n - __pos);
      for (_BiIter __j = __m; __j != __f; --__start_, ++__size())
        __alloc_traits::construct(__a, std::addressof(*--__i), *--__j);
      __n = __pos;
    }
    if (__n > 0) {
      iterator __obn = __old_begin + __n;
      for (iterator __j = __obn; __j != __old_begin;) {
        __alloc_traits::construct(__a, std::addressof(*--__i), std::move(*--__j));
        --__start_;
        ++__size();
      }
      if (__n < __pos)
        __old_begin = std::move(__obn, __old_begin + __pos, __old_begin);
      std::copy(__m, __l, __old_begin);
    }
  } else { // insert by shifting things forward
    size_type __back_capacity = __back_spare();
    if (__n > __back_capacity)
      __add_back_capacity(__n - __back_capacity);
    // __n <= __back_capacity
    __annotate_increase_back(__n);
    iterator __old_end = end();
    iterator __i       = __old_end;
    _BiIter __m        = __l;
    size_type __de     = size() - __pos;
    if (__n > __de) {
      __m = __de < __n / 2 ? std::next(__f, __de) : std::prev(__l, __n - __de);
      for (_BiIter __j = __m; __j != __l; ++__i, (void)++__j, ++__size())
        __alloc_traits::construct(__a, std::addressof(*__i), *__j);
      __n = __de;
    }
    if (__n > 0) {
      iterator __oen = __old_end - __n;
      for (iterator __j = __oen; __j != __old_end; ++__i, (void)++__j, ++__size())
        __alloc_traits::construct(__a, std::addressof(*__i), std::move(*__j));
      if (__n < __de)
        __old_end = std::move_backward(__old_end - __de, __oen, __old_end);
      std::copy_backward(__f, __m, __old_end);
    }
  }
  return begin() + __pos;
}

template <class _Tp, class _Allocator>
template <class _InpIter, __enable_if_t<__has_exactly_input_iterator_category<_InpIter>::value, int> >
void deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l) {
  __append_with_sentinel(__f, __l);
}

template <class _Tp, class _Allocator>
template <class _InputIterator, class _Sentinel>
_LIBCPP_HIDE_FROM_ABI void deque<_Tp, _Allocator>::__append_with_sentinel(_InputIterator __f, _Sentinel __l) {
  for (; __f != __l; ++__f)
#  ifdef _LIBCPP_CXX03_LANG
    push_back(*__f);
#  else
    emplace_back(*__f);
#  endif
}

template <class _Tp, class _Allocator>
template <class _ForIter, __enable_if_t<__has_forward_iterator_category<_ForIter>::value, int> >
void deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l) {
  __append_with_size(__f, std::distance(__f, __l));
}

template <class _Tp, class _Allocator>
template <class _InputIterator>
_LIBCPP_HIDE_FROM_ABI void deque<_Tp, _Allocator>::__append_with_size(_InputIterator __f, size_type __n) {
  allocator_type& __a       = __alloc();
  size_type __back_capacity = __back_spare();
  if (__n > __back_capacity)
    __add_back_capacity(__n - __back_capacity);

  // __n <= __back_capacity
  __annotate_increase_back(__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, std::__to_address(__tx.__pos_), *__f);
    }
  }
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__append(size_type __n) {
  allocator_type& __a       = __alloc();
  size_type __back_capacity = __back_spare();
  if (__n > __back_capacity)
    __add_back_capacity(__n - __back_capacity);
  // __n <= __back_capacity
  __annotate_increase_back(__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, std::__to_address(__tx.__pos_));
    }
  }
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__append(size_type __n, const value_type& __v) {
  allocator_type& __a       = __alloc();
  size_type __back_capacity = __back_spare();
  if (__n > __back_capacity)
    __add_back_capacity(__n - __back_capacity);
  // __n <= __back_capacity
  __annotate_increase_back(__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, std::__to_address(__tx.__pos_), __v);
    }
  }
}

// Create front capacity for one block of elements.
// Strong guarantee.  Either do it or don't touch anything.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__add_front_capacity() {
  allocator_type& __a = __alloc();
  if (__back_spare() >= __block_size) {
    __start_ += __block_size;
    pointer __pt = __map_.back();
    __map_.pop_back();
    __map_.emplace_front(__pt);
  }
  // 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 (__map_.__front_spare() > 0)
      __map_.emplace_front(__alloc_traits::allocate(__a, __block_size));
    else {
      __map_.emplace_back(__alloc_traits::allocate(__a, __block_size));
      // Done allocating, reorder capacity
      pointer __pt = __map_.back();
      __map_.pop_back();
      __map_.emplace_front(__pt);
    }
    __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, __pointer_allocator&> __buf(
        std::max<size_type>(2 * __map_.capacity(), 1), 0, __map_.__alloc_);

    typedef __allocator_destructor<_Allocator> _Dp;
    unique_ptr<pointer, _Dp> __hold(__alloc_traits::allocate(__a, __block_size), _Dp(__a, __block_size));
    __buf.emplace_back(__hold.get());
    __hold.release();

    for (__map_pointer __i = __map_.begin(); __i != __map_.end(); ++__i)
      __buf.emplace_back(*__i);
    std::swap(__map_.__first_, __buf.__first_);
    std::swap(__map_.__begin_, __buf.__begin_);
    std::swap(__map_.__end_, __buf.__end_);
    std::swap(__map_.__cap_, __buf.__cap_);
    __start_ = __map_.size() == 1 ? __block_size / 2 : __start_ + __block_size;
  }
  __annotate_whole_block(0, __asan_poison);
}

// Create front capacity for __n elements.
// Strong guarantee.  Either do it or don't touch anything.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__add_front_capacity(size_type __n) {
  allocator_type& __a = __alloc();
  size_type __nb      = __recommend_blocks(__n + __map_.empty());
  // Number of unused blocks at back:
  size_type __back_capacity = __back_spare() / __block_size;
  __back_capacity           = std::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) {
    __start_ += __block_size * __back_capacity;
    for (; __back_capacity > 0; --__back_capacity) {
      pointer __pt = __map_.back();
      __map_.pop_back();
      __map_.emplace_front(__pt);
    }
  }
  // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
  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, __start_ += __block_size - (__map_.size() == 1)) {
      if (__map_.__front_spare() == 0)
        break;
      __map_.emplace_front(__alloc_traits::allocate(__a, __block_size));
      __annotate_whole_block(0, __asan_poison);
    }
    for (; __nb > 0; --__nb, ++__back_capacity)
      __map_.emplace_back(__alloc_traits::allocate(__a, __block_size));
    // Done allocating, reorder capacity
    __start_ += __back_capacity * __block_size;
    for (; __back_capacity > 0; --__back_capacity) {
      pointer __pt = __map_.back();
      __map_.pop_back();
      __map_.emplace_front(__pt);
      __annotate_whole_block(0, __asan_poison);
    }
  }
  // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
  else {
    size_type __ds = (__nb + __back_capacity) * __block_size - __map_.empty();
    __split_buffer<pointer, __pointer_allocator&> __buf(
        std::max<size_type>(2 * __map_.capacity(), __nb + __map_.size()), 0, __map_.__alloc_);
#  if _LIBCPP_HAS_EXCEPTIONS
    try {
#  endif // _LIBCPP_HAS_EXCEPTIONS
      for (; __nb > 0; --__nb) {
        __buf.emplace_back(__alloc_traits::allocate(__a, __block_size));
        // ASan: this is empty container, we have to poison whole block
        __annotate_poison_block(std::__to_address(__buf.back()), std::__to_address(__buf.back() + __block_size));
      }
#  if _LIBCPP_HAS_EXCEPTIONS
    } catch (...) {
      __annotate_delete();
      for (__map_pointer __i = __buf.begin(); __i != __buf.end(); ++__i)
        __alloc_traits::deallocate(__a, *__i, __block_size);
      throw;
    }
#  endif // _LIBCPP_HAS_EXCEPTIONS
    for (; __back_capacity > 0; --__back_capacity) {
      __buf.emplace_back(__map_.back());
      __map_.pop_back();
    }
    for (__map_pointer __i = __map_.begin(); __i != __map_.end(); ++__i)
      __buf.emplace_back(*__i);
    std::swap(__map_.__first_, __buf.__first_);
    std::swap(__map_.__begin_, __buf.__begin_);
    std::swap(__map_.__end_, __buf.__end_);
    std::swap(__map_.__cap_, __buf.__cap_);
    __start_ += __ds;
  }
}

// Create back capacity for one block of elements.
// Strong guarantee.  Either do it or don't touch anything.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__add_back_capacity() {
  allocator_type& __a = __alloc();
  if (__front_spare() >= __block_size) {
    __start_ -= __block_size;
    pointer __pt = __map_.front();
    __map_.pop_front();
    __map_.emplace_back(__pt);
  }
  // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
  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 (__map_.__back_spare() != 0)
      __map_.emplace_back(__alloc_traits::allocate(__a, __block_size));
    else {
      __map_.emplace_front(__alloc_traits::allocate(__a, __block_size));
      // Done allocating, reorder capacity
      pointer __pt = __map_.front();
      __map_.pop_front();
      __map_.emplace_back(__pt);
    }
    __annotate_whole_block(__map_.size() - 1, __asan_poison);
  }
  // Else need to allocate 1 buffer, *and* we need to reallocate __map_.
  else {
    __split_buffer<pointer, __pointer_allocator&> __buf(
        std::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, __block_size), _Dp(__a, __block_size));
    __buf.emplace_back(__hold.get());
    __hold.release();

    for (__map_pointer __i = __map_.end(); __i != __map_.begin();)
      __buf.emplace_front(*--__i);
    std::swap(__map_.__first_, __buf.__first_);
    std::swap(__map_.__begin_, __buf.__begin_);
    std::swap(__map_.__end_, __buf.__end_);
    std::swap(__map_.__cap_, __buf.__cap_);
    __annotate_whole_block(__map_.size() - 1, __asan_poison);
  }
}

// Create back capacity for __n elements.
// Strong guarantee.  Either do it or don't touch anything.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__add_back_capacity(size_type __n) {
  allocator_type& __a = __alloc();
  size_type __nb      = __recommend_blocks(__n + __map_.empty());
  // Number of unused blocks at front:
  size_type __front_capacity = __front_spare() / __block_size;
  __front_capacity           = std::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) {
    __start_ -= __block_size * __front_capacity;
    for (; __front_capacity > 0; --__front_capacity) {
      pointer __pt = __map_.front();
      __map_.pop_front();
      __map_.emplace_back(__pt);
    }
  }
  // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
  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 (__map_.__back_spare() == 0)
        break;
      __map_.emplace_back(__alloc_traits::allocate(__a, __block_size));
      __annotate_whole_block(__map_.size() - 1, __asan_poison);
    }
    for (; __nb > 0; --__nb, ++__front_capacity, __start_ += __block_size - (__map_.size() == 1)) {
      __map_.emplace_front(__alloc_traits::allocate(__a, __block_size));
      __annotate_whole_block(0, __asan_poison);
    }
    // Done allocating, reorder capacity
    __start_ -= __block_size * __front_capacity;
    for (; __front_capacity > 0; --__front_capacity) {
      pointer __pt = __map_.front();
      __map_.pop_front();
      __map_.emplace_back(__pt);
    }
  }
  // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
  else {
    size_type __ds = __front_capacity * __block_size;
    __split_buffer<pointer, __pointer_allocator&> __buf(
        std::max<size_type>(2 * __map_.capacity(), __nb + __map_.size()),
        __map_.size() - __front_capacity,
        __map_.__alloc_);
#  if _LIBCPP_HAS_EXCEPTIONS
    try {
#  endif // _LIBCPP_HAS_EXCEPTIONS
      for (; __nb > 0; --__nb) {
        __buf.emplace_back(__alloc_traits::allocate(__a, __block_size));
        // ASan: this is an empty container, we have to poison the whole block
        __annotate_poison_block(std::__to_address(__buf.back()), std::__to_address(__buf.back() + __block_size));
      }
#  if _LIBCPP_HAS_EXCEPTIONS
    } catch (...) {
      __annotate_delete();
      for (__map_pointer __i = __buf.begin(); __i != __buf.end(); ++__i)
        __alloc_traits::deallocate(__a, *__i, __block_size);
      throw;
    }
#  endif // _LIBCPP_HAS_EXCEPTIONS
    for (; __front_capacity > 0; --__front_capacity) {
      __buf.emplace_back(__map_.front());
      __map_.pop_front();
    }
    for (__map_pointer __i = __map_.end(); __i != __map_.begin();)
      __buf.emplace_front(*--__i);
    std::swap(__map_.__first_, __buf.__first_);
    std::swap(__map_.__begin_, __buf.__begin_);
    std::swap(__map_.__end_, __buf.__end_);
    std::swap(__map_.__cap_, __buf.__cap_);
    __start_ -= __ds;
  }
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::pop_front() {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::pop_front called on an empty deque");
  size_type __old_sz    = size();
  size_type __old_start = __start_;
  allocator_type& __a   = __alloc();
  __alloc_traits::destroy(
      __a, std::__to_address(*(__map_.begin() + __start_ / __block_size) + __start_ % __block_size));
  --__size();
  ++__start_;
  __annotate_shrink_front(__old_sz, __old_start);
  __maybe_remove_front_spare();
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::pop_back() {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "deque::pop_back called on an empty deque");
  size_type __old_sz    = size();
  size_type __old_start = __start_;
  allocator_type& __a   = __alloc();
  size_type __p         = size() + __start_ - 1;
  __alloc_traits::destroy(__a, std::__to_address(*(__map_.begin() + __p / __block_size) + __p % __block_size));
  --__size();
  __annotate_shrink_back(__old_sz, __old_start);
  __maybe_remove_back_spare();
}

// move assign [__f, __l) to [__r, __r + (__l-__f)).
// If __vt points into [__f, __l), then subtract (__f - __r) from __vt.
template <class _Tp, class _Allocator>
typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__move_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt) {
  // as if
  //   for (; __f != __l; ++__f, ++__r)
  //       *__r = std::move(*__f);
  difference_type __n = __l - __f;
  while (__n > 0) {
    pointer __fb         = __f.__ptr_;
    pointer __fe         = *__f.__m_iter_ + __block_size;
    difference_type __bs = __fe - __fb;
    if (__bs > __n) {
      __bs = __n;
      __fe = __fb + __bs;
    }
    if (__fb <= __vt && __vt < __fe)
      __vt = (const_iterator(static_cast<__map_const_pointer>(__f.__m_iter_), __vt) -= __f - __r).__ptr_;
    __r = std::move(__fb, __fe, __r);
    __n -= __bs;
    __f += __bs;
  }
  return __r;
}

// move assign [__f, __l) to [__r - (__l-__f), __r) backwards.
// If __vt points into [__f, __l), then add (__r - __l) to __vt.
template <class _Tp, class _Allocator>
typename deque<_Tp, _Allocator>::iterator
deque<_Tp, _Allocator>::__move_backward_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt) {
  // as if
  //   while (__f != __l)
  //       *--__r = std::move(*--__l);
  difference_type __n = __l - __f;
  while (__n > 0) {
    --__l;
    pointer __lb         = *__l.__m_iter_;
    pointer __le         = __l.__ptr_ + 1;
    difference_type __bs = __le - __lb;
    if (__bs > __n) {
      __bs = __n;
      __lb = __le - __bs;
    }
    if (__lb <= __vt && __vt < __le)
      __vt = (const_iterator(static_cast<__map_const_pointer>(__l.__m_iter_), __vt) += __r - __l - 1).__ptr_;
    __r = std::move_backward(__lb, __le, __r);
    __n -= __bs;
    __l -= __bs - 1;
  }
  return __r;
}

// move construct [__f, __l) to [__r, __r + (__l-__f)).
// If __vt points into [__f, __l), then add (__r - __f) to __vt.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__move_construct_and_check(iterator __f, iterator __l, iterator __r, const_pointer& __vt) {
  allocator_type& __a = __alloc();
  // as if
  //   for (; __f != __l; ++__r, ++__f, ++__size())
  //       __alloc_traits::construct(__a, std::addressof(*__r), std::move(*__f));
  difference_type __n = __l - __f;
  while (__n > 0) {
    pointer __fb         = __f.__ptr_;
    pointer __fe         = *__f.__m_iter_ + __block_size;
    difference_type __bs = __fe - __fb;
    if (__bs > __n) {
      __bs = __n;
      __fe = __fb + __bs;
    }
    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, ++__size())
      __alloc_traits::construct(__a, std::addressof(*__r), std::move(*__fb));
    __n -= __bs;
    __f += __bs;
  }
}

// move construct [__f, __l) to [__r - (__l-__f), __r) backwards.
// If __vt points into [__f, __l), then subtract (__l - __r) from __vt.
template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__move_construct_backward_and_check(
    iterator __f, iterator __l, iterator __r, const_pointer& __vt) {
  allocator_type& __a = __alloc();
  // as if
  //   for (iterator __j = __l; __j != __f;)
  //   {
  //       __alloc_traitsconstruct(__a, std::addressof(*--__r), std::move(*--__j));
  //       --__start_;
  //       ++__size();
  //   }
  difference_type __n = __l - __f;
  while (__n > 0) {
    --__l;
    pointer __lb         = *__l.__m_iter_;
    pointer __le         = __l.__ptr_ + 1;
    difference_type __bs = __le - __lb;
    if (__bs > __n) {
      __bs = __n;
      __lb = __le - __bs;
    }
    if (__lb <= __vt && __vt < __le)
      __vt = (const_iterator(static_cast<__map_const_pointer>(__l.__m_iter_), __vt) -= __l - __r + 1).__ptr_;
    while (__le != __lb) {
      __alloc_traits::construct(__a, std::addressof(*--__r), std::move(*--__le));
      --__start_;
      ++__size();
    }
    __n -= __bs;
    __l -= __bs - 1;
  }
}

template <class _Tp, class _Allocator>
typename deque<_Tp, _Allocator>::iterator deque<_Tp, _Allocator>::erase(const_iterator __f) {
  _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
      __f != end(), "deque::erase(iterator) called with a non-dereferenceable iterator");
  size_type __old_sz    = size();
  size_type __old_start = __start_;
  iterator __b          = begin();
  difference_type __pos = __f - __b;
  iterator __p          = __b + __pos;
  allocator_type& __a   = __alloc();
  if (static_cast<size_type>(__pos) <= (size() - 1) / 2) { // erase from front
    std::move_backward(__b, __p, std::next(__p));
    __alloc_traits::destroy(__a, std::addressof(*__b));
    --__size();
    ++__start_;
    __annotate_shrink_front(__old_sz, __old_start);
    __maybe_remove_front_spare();
  } else { // erase from back
    iterator __i = std::move(std::next(__p), end(), __p);
    __alloc_traits::destroy(__a, std::addressof(*__i));
    --__size();
    __annotate_shrink_back(__old_sz, __old_start);
    __maybe_remove_back_spare();
  }
  return begin() + __pos;
}

template <class _Tp, class _Allocator>
typename deque<_Tp, _Allocator>::iterator deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l) {
  _LIBCPP_ASSERT_VALID_INPUT_RANGE(__f <= __l, "deque::erase(first, last) called with an invalid range");
  size_type __old_sz    = size();
  size_type __old_start = __start_;
  difference_type __n   = __l - __f;
  iterator __b          = begin();
  difference_type __pos = __f - __b;
  iterator __p          = __b + __pos;
  if (__n > 0) {
    allocator_type& __a = __alloc();
    if (static_cast<size_type>(__pos) <= (size() - __n) / 2) { // erase from front
      iterator __i = std::move_backward(__b, __p, __p + __n);
      for (; __b != __i; ++__b)
        __alloc_traits::destroy(__a, std::addressof(*__b));
      __size() -= __n;
      __start_ += __n;
      __annotate_shrink_front(__old_sz, __old_start);
      while (__maybe_remove_front_spare()) {
      }
    } else { // erase from back
      iterator __i = std::move(__p + __n, end(), __p);
      for (iterator __e = end(); __i != __e; ++__i)
        __alloc_traits::destroy(__a, std::addressof(*__i));
      __size() -= __n;
      __annotate_shrink_back(__old_sz, __old_start);
      while (__maybe_remove_back_spare()) {
      }
    }
  }
  return begin() + __pos;
}

template <class _Tp, class _Allocator>
void deque<_Tp, _Allocator>::__erase_to_end(const_iterator __f) {
  size_type __old_sz    = size();
  size_type __old_start = __start_;
  iterator __e          = end();
  difference_type __n   = __e - __f;
  if (__n > 0) {
    allocator_type& __a   = __alloc();
    iterator __b          = begin();
    difference_type __pos = __f - __b;
    for (iterator __p = __b + __pos; __p != __e; ++__p)
      __alloc_traits::destroy(__a, std::addressof(*__p));
    __size() -= __n;
    __annotate_shrink_back(__old_sz, __old_start);
    while (__maybe_remove_back_spare()) {
    }
  }
}

template <class _Tp, class _Allocator>
inline void deque<_Tp, _Allocator>::swap(deque& __c)
#  if _LIBCPP_STD_VER >= 14
    _NOEXCEPT
#  else
    _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || __is_nothrow_swappable_v<allocator_type>)
#  endif
{
  __map_.swap(__c.__map_);
  std::swap(__start_, __c.__start_);
  std::swap(__size(), __c.__size());
  std::__swap_allocator(__alloc(), __c.__alloc());
}

template <class _Tp, class _Allocator>
inline void deque<_Tp, _Allocator>::clear() _NOEXCEPT {
  __annotate_delete();
  allocator_type& __a = __alloc();
  for (iterator __i = begin(), __e = end(); __i != __e; ++__i)
    __alloc_traits::destroy(__a, std::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;
  }
  __annotate_new(0);
}

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator==(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  const typename deque<_Tp, _Allocator>::size_type __sz = __x.size();
  return __sz == __y.size() && std::equal(__x.begin(), __x.end(), __y.begin());
}

#  if _LIBCPP_STD_VER <= 17

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return !(__x == __y);
}

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator<(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return std::lexicographical_compare(__x.begin(), __x.end(), __y.begin(), __y.end());
}

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator>(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return __y < __x;
}

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator>=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return !(__x < __y);
}

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI bool operator<=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return !(__y < __x);
}

#  else // _LIBCPP_STD_VER <= 17

template <class _Tp, class _Allocator>
_LIBCPP_HIDE_FROM_ABI __synth_three_way_result<_Tp>
operator<=>(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y) {
  return std::lexicographical_compare_three_way(__x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way);
}

#  endif // _LIBCPP_STD_VER <= 17

template <class _Tp, class _Allocator>
inline _LIBCPP_HIDE_FROM_ABI void swap(deque<_Tp, _Allocator>& __x, deque<_Tp, _Allocator>& __y)
    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
  __x.swap(__y);
}

#  if _LIBCPP_STD_VER >= 20
template <class _Tp, class _Allocator, class _Up>
inline _LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::size_type
erase(deque<_Tp, _Allocator>& __c, const _Up& __v) {
  auto __old_size = __c.size();
  __c.erase(std::remove(__c.begin(), __c.end(), __v), __c.end());
  return __old_size - __c.size();
}

template <class _Tp, class _Allocator, class _Predicate>
inline _LIBCPP_HIDE_FROM_ABI typename deque<_Tp, _Allocator>::size_type
erase_if(deque<_Tp, _Allocator>& __c, _Predicate __pred) {
  auto __old_size = __c.size();
  __c.erase(std::remove_if(__c.begin(), __c.end(), __pred), __c.end());
  return __old_size - __c.size();
}

template <>
inline constexpr bool __format::__enable_insertable<std::deque<char>> = true;
#    if _LIBCPP_HAS_WIDE_CHARACTERS
template <>
inline constexpr bool __format::__enable_insertable<std::deque<wchar_t>> = true;
#    endif

#  endif // _LIBCPP_STD_VER >= 20

template <class _Tp, class _Allocator>
struct __container_traits<deque<_Tp, _Allocator> > {
  // http://eel.is/c++draft/deque.modifiers#3
  //  If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move
  //  assignment operator of T, there are no effects. If an exception is thrown while inserting a single element at
  //  either end, there are no effects. Otherwise, if an exception is thrown by the move constructor of a
  //  non-Cpp17CopyInsertable T, the effects are unspecified.
  static _LIBCPP_CONSTEXPR const bool __emplacement_has_strong_exception_safety_guarantee =
      _Or<is_nothrow_move_constructible<_Tp>, __is_cpp17_copy_insertable<_Allocator> >::value;
};

_LIBCPP_END_NAMESPACE_STD

#  if _LIBCPP_STD_VER >= 17
_LIBCPP_BEGIN_NAMESPACE_STD
namespace pmr {
template <class _ValueT>
using deque _LIBCPP_AVAILABILITY_PMR = std::deque<_ValueT, polymorphic_allocator<_ValueT>>;
} // namespace pmr
_LIBCPP_END_NAMESPACE_STD
#  endif

_LIBCPP_POP_MACROS

#  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
#    include <algorithm>
#    include <atomic>
#    include <concepts>
#    include <cstdlib>
#    include <functional>
#    include <iosfwd>
#    include <iterator>
#    include <type_traits>
#    include <typeinfo>
#  endif
#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)

#endif // _LIBCPP_DEQUE
