Re: [PATCH v3] libstdc++: Mark <queue>, <deque> constexpr

Yuao Ma <[email protected]> Thu, 6 Aug 2026 19:51:27 +0800
Newsgroups gmane.comp.gcc.patches,gmane.comp.gcc.libstdc++.devel
Message-ID <CA+m0iR8KMOPV-8zcDk9apRifG4yxbCWv7FjrivogqE81jfHCKQ@mail.gmail.com>
On Thu, Aug 6, 2026 at 7:16 PM Tomasz Kaminski <[email protected]> wrote:
>
>
>
> On Thu, Aug 6, 2026 at 12:28 PM Tomasz Kamiński <[email protected]> wrote:
>>
>> This patch makes partial progress towards P3372 by marking deque, queue,
>> and relevant internal helpers to be constexpr when using C++26
>> (priority_queue was made constexr by r17-1233-g5a6ae2b286a730).
>>
>> For debug version we use similar approach as is used for vector in
>> r14-6553-g7d00a59229ee17, and disable safe iterator instrumentation
>> and checking during constant evaluation, because of mutex locks
>> and call to non-inline functions.
>>
>> The __uninitialized_default_a overloads that do not depend on
>> _Deque_iterator, are marked as _GLIBCXX20_CONSTEXPR for that reason.
>>
>> libstdc++-v3/ChangeLog:
>>
>>         * include/bits/deque.tcc (deque): Declare out of line member
>>         defintions as _GLIBCXX26_CONSTEXPR.
>>         (std::__fill_a1, std::__copy_move_dit, std::__copy_move_a1)
>>         (std::__copy_move_a2, std::__copy_n_a)
>>         (std::__copy_move_backward_dit, std::__copy_move_backward_a1)
>>         (std::__equal_dit, std::__equal_aux1, std::__lex_cmp_dit)
>>         (std::__lexicographical_compare_aux1, std::__uninitialized_copy_a)
>>         (std::__uninitialized_move_a): Declare as _GLIBCXX26_CONSTEXPR.
>>         * include/bits/stl_algobase.h (std::__fill_a1, std::__copy_n_a)
>>         (std::__copy_move_a1, std::__copy_move_backward_a1)
>>         (std::__equal_aux1, __lexicographical_compare_aux1): Declare
>>         overloads accepting _Deque_iterator as _GLIBCXX26_CONSTEXPR.
>>         * include/bits/stl_deque.h (std::_Deque_iterator, std::_Deque_base)
>>         (std::deque): Declare members as _GLIBCXX26_CONSTEXPR.
>>         (std::operator==, std::operator<=>, std::swap): Declare as
>>         _GLIBCXX26_CONSTEXPR.
>>         * include/bits/stl_queue.h (std::queue): Declare members as
>>         _GLIBCXX26_CONSTEXPR.
>>         (std::priority_queue): Make _GLIBCXX26_CONSTEXPR placement
>>         consistient.
>>         (std::operator==, std::operator!=, std::operator<, std::operator>)
>>         (std::operator<=, std::operator>=, std::operator<=>, std::swap):
>>         Declare as _GLIBCXX26_CONSTEXPR.
>>         * include/bits/stl_uninitialized.h (std::__uninitialized_copy_a):
>>         Declare overloads accepting _Deque_iterator as _GLIBCXX26_CONSTEXPR.
>>         (std::__uninitialized_default_a): Declare as _GLIBCXX20_CONSTEXPR.
>>         * include/bits/version.def (constexpr_deque, constexpr_queue):
>>         Define.
>>         * include/bits/version.h: Regenerate.
>>         * include/debug/deque (__debug::deque): Declare members as
>>         _GLIBCXX26_CONSTEXPR.
>>         (__debug::operator==, __debug::operator<=>, __debug::swap)
>>         (__debug::erase, __debug::__erase_if): Declare as
>>         _GLIBCXX26_CONSTEXPR.
>>         * include/std/deque (__cpp_lib_constexpr_deque): Define.
>>         (std::erase, std::erase_if): Declare as _GLIBCXX26_CONSTEXPR.
>>         * include/std/queue (__cpp_lib_constexpr_queue): Define.
>>         (_GLIBCXX_CONSTEXPR_FORMAT): Define locally.
>>         (std::formatter<priority_queue<...>, _CharT>::format)
>>         (std::formatter<queue<...>, _CharT>::format): Declare as
>>         _GLIBCXX_CONSTEXPR_FORMAT.
>>         * testsuite/23_containers/deque/constexpr.cc: New test.
>>         * testsuite/23_containers/headers/deque/synopsis.cc: Updated
>>         declarations.
>
> Forgotten to squash equivalent changes to testsuite/23_containers/headers/queue/synopsis.c.
> Added them locally.
>>
>>         * testsuite/23_containers/queue/constexpr.cc: New test.
>>         * testsuite/23_containers/priority_queue/constexpr.cc: Replace
>>         existing test with expanded suite.
>>         * testsuite/std/format/ranges/adaptors.cc: Test at compile
>>         time.
>>
>> Co-authored-by: Thor Preimesberger <[email protected]>
>> Signed-off-by: Thor Preimesberger <[email protected]>
>> Signed-off-by: Tomasz Kamiński <[email protected]>
>> ---
>> v3 is recreation of previous patch, as (most likely due mailing
>> client) all tabs were removed, making it impossible to apply.
>> I was able to reuse the additional tests.
>>
>> v3:
>> - rebases the priority_queue changes, as it was merged
>> - provides proper support for debug::deque in constexpr,
>>   by disabling the checks (as for vector)
>> - expand the patch to cover cosntexpr formatting of the
>>   containers, as it was merged.
>> - updates test a bit, to use separate static_assert,
>>   and have more consistient formatting.
>>
>> Tested on x86_64-linx and testing on powerpc64-le.
>> All 23_containers/*ue* and format/ranges/adaptors.cc test
>> passed in all standard modes, -m32, debug and assertions.
>> OK for trunk when all test passes?
>>
>>  libstdc++-v3/include/bits/deque.tcc           |  97 +++--
>>  libstdc++-v3/include/bits/stl_algobase.h      |  22 +-
>>  libstdc++-v3/include/bits/stl_deque.h         | 363 ++++++++++--------
>>  libstdc++-v3/include/bits/stl_queue.h         | 107 +++---
>>  libstdc++-v3/include/bits/stl_uninitialized.h |   7 +-
>>  libstdc++-v3/include/bits/version.def         |  18 +
>>  libstdc++-v3/include/bits/version.h           |  20 +
>>  libstdc++-v3/include/debug/deque              | 210 ++++++----
>>  libstdc++-v3/include/std/deque                |   7 +-
>>  libstdc++-v3/include/std/queue                |  11 +
>>  .../23_containers/deque/constexpr.cc          | 334 ++++++++++++++++
>>  .../23_containers/headers/deque/synopsis.cc   |  26 +-
>>  .../23_containers/priority_queue/constexpr.cc | 253 ++++++++++--
>>  .../23_containers/queue/constexpr.cc          | 242 ++++++++++++
>>  .../testsuite/std/format/ranges/adaptors.cc   |  34 +-
>>  15 files changed, 1370 insertions(+), 381 deletions(-)
>>  create mode 100644 libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
>>  create mode 100644 libstdc++-v3/testsuite/23_containers/queue/constexpr.cc
>>
>> diff --git a/libstdc++-v3/include/bits/deque.tcc b/libstdc++-v3/include/bits/deque.tcc
>> index df4be080212..cf260a5269c 100644
>> --- a/libstdc++-v3/include/bits/deque.tcc
>> +++ b/libstdc++-v3/include/bits/deque.tcc
>> @@ -65,7 +65,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>  #if __cplusplus >= 201103L
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_default_initialize()
>>      {
>> @@ -91,6 +91,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #endif
>>
>>    template <typename _Tp, typename _Alloc>
>> +    _GLIBCXX26_CONSTEXPR
>>      deque<_Tp, _Alloc>&
>>      deque<_Tp, _Alloc>::
>>      operator=(const deque& __x)
>> @@ -133,6 +134,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    template<typename _Tp, typename _Alloc>
>>      template<typename... _Args>
>>  #if __cplusplus > 201402L
>> +      _GLIBCXX26_CONSTEXPR
>>        typename deque<_Tp, _Alloc>::reference
>>  #else
>>        void
>> @@ -157,6 +159,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    template<typename _Tp, typename _Alloc>
>>      template<typename... _Args>
>>  #if __cplusplus > 201402L
>> +      _GLIBCXX26_CONSTEXPR
>>        typename deque<_Tp, _Alloc>::reference
>>  #else
>>        void
>> @@ -183,6 +186,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #if __cplusplus >= 201103L
>>    template<typename _Tp, typename _Alloc>
>>      template<typename... _Args>
>> +      _GLIBCXX26_CONSTEXPR
>>        typename deque<_Tp, _Alloc>::iterator
>>        deque<_Tp, _Alloc>::
>>        emplace(const_iterator __position, _Args&&... __args)
>> @@ -206,6 +210,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #endif
>>
>>    template <typename _Tp, typename _Alloc>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename deque<_Tp, _Alloc>::iterator
>>      deque<_Tp, _Alloc>::
>>  #if __cplusplus >= 201103L
>> @@ -231,6 +236,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>     }
>>
>>    template <typename _Tp, typename _Alloc>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename deque<_Tp, _Alloc>::iterator
>>      deque<_Tp, _Alloc>::
>>      _M_erase(iterator __position)
>> @@ -254,6 +260,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template <typename _Tp, typename _Alloc>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename deque<_Tp, _Alloc>::iterator
>>      deque<_Tp, _Alloc>::
>>      _M_erase(iterator __first, iterator __last)
>> @@ -287,7 +294,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, class _Alloc>
>>      template <typename _InputIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_assign_aux(_InputIterator __first, _InputIterator __last,
>>                     std::input_iterator_tag)
>> @@ -303,7 +310,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_fill_insert(iterator __pos, size_type __n, const value_type& __x)
>>      {
>> @@ -346,7 +353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>  #if __cplusplus >= 201103L
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_default_append(size_type __n)
>>      {
>> @@ -370,7 +377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      deque<_Tp, _Alloc>::
>>      _M_shrink_to_fit()
>>      {
>> @@ -389,7 +396,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #endif
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_fill_initialize(const value_type& __value)
>>      {
>> @@ -415,7 +422,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _InputIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_initialize(_InputIterator __first, _InputIterator __last,
>>                           std::input_iterator_tag)
>> @@ -439,7 +446,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _ForwardIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
>>                           std::forward_iterator_tag)
>> @@ -480,7 +487,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    template<typename _Tp, typename _Alloc>
>>  #if __cplusplus >= 201103L
>>      template<typename... _Args>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_push_back_aux(_Args&&... __args)
>>  #else
>> @@ -519,7 +526,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    template<typename _Tp, typename _Alloc>
>>  #if __cplusplus >= 201103L
>>      template<typename... _Args>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_push_front_aux(_Args&&... __args)
>>  #else
>> @@ -557,7 +564,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    // Called only if _M_impl._M_finish._M_cur == _M_impl._M_finish._M_first.
>>    template <typename _Tp, typename _Alloc>
>> -    void deque<_Tp, _Alloc>::
>> +    _GLIBCXX26_CONSTEXPR void
>> +    deque<_Tp, _Alloc>::
>>      _M_pop_back_aux()
>>      {
>>        _M_deallocate_node(this->_M_impl._M_finish._M_first);
>> @@ -573,7 +581,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    //   _M_impl._M_start._M_cur == _M_impl._M_start._M_last,
>>    // then the deque must have at least two nodes.
>>    template <typename _Tp, typename _Alloc>
>> -    void deque<_Tp, _Alloc>::
>> +    _GLIBCXX26_CONSTEXPR void
>> +    deque<_Tp, _Alloc>::
>>      _M_pop_front_aux()
>>      {
>>        _Alloc_traits::destroy(_M_get_Tp_allocator(),
>> @@ -585,7 +594,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _InputIterator, typename _Sentinel>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_prepend(_InputIterator __first, _Sentinel __last,
>>                       size_type __n)
>> @@ -607,7 +616,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _InputIterator, typename _Sentinel>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_append(_InputIterator __first, _Sentinel __last,
>>                       size_type __n)
>> @@ -630,7 +639,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _InputIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_insert_aux(iterator __pos,
>>                           _InputIterator __first, _InputIterator __last,
>> @@ -639,7 +648,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _ForwardIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_range_insert_aux(iterator __pos,
>>                           _ForwardIterator __first, _ForwardIterator __last,
>> @@ -660,6 +669,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    template<typename _Tp, typename _Alloc>
>>  #if __cplusplus >= 201103L
>>      template<typename... _Args>
>> +      _GLIBCXX26_CONSTEXPR
>>        typename deque<_Tp, _Alloc>::iterator
>>        deque<_Tp, _Alloc>::
>>        _M_emplace_aux(iterator __pos, _Args&&... __args)
>> @@ -707,7 +717,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_insert_aux(iterator __pos, size_type __n, const value_type& __x)
>>      {
>> @@ -793,7 +803,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template <typename _Tp, typename _Alloc>
>>      template <typename _ForwardIterator>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        deque<_Tp, _Alloc>::
>>        _M_insert_aux(iterator __pos,
>>                     _ForwardIterator __first, _ForwardIterator __last,
>> @@ -882,7 +892,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>    template<ranges::forward_range _Rg>
>> -    auto __advance_dist(_Rg& __rg)
>> +    _GLIBCXX26_CONSTEXPR auto
>> +    __advance_dist(_Rg& __rg)
>>      {
>>        struct _Res
>>         {
>> @@ -914,7 +925,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp, typename _Alloc>
>>      template<__detail::__container_compatible_range<_Tp> _Rg>
>> -      auto
>> +      _GLIBCXX26_CONSTEXPR auto
>>        deque<_Tp, _Alloc>::
>>        insert_range(const_iterator __pos, _Rg&& __rg)
>>        -> iterator
>> @@ -954,7 +965,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>     template<typename _Tp, typename _Alloc>
>>       template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         deque<_Tp, _Alloc>::
>>         prepend_range(_Rg&& __rg)
>>         {
>> @@ -996,7 +1007,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>     template<typename _Tp, typename _Alloc>
>>       template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         deque<_Tp, _Alloc>::
>>         append_range(_Rg&& __rg)
>>         {
>> @@ -1013,6 +1024,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>                  deque& __self;
>>                  size_type __n = __self.size();
>>
>> +                _GLIBCXX26_CONSTEXPR
>>                  ~_Guard_elts_back()
>>                    {
>>                      if (__n < __self.size())
>> @@ -1032,7 +1044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #endif // containers_ranges
>>
>>     template<typename _Tp, typename _Alloc>
>> -     void
>> +     _GLIBCXX26_CONSTEXPR void
>>       deque<_Tp, _Alloc>::
>>       _M_destroy_data_aux(iterator __first, iterator __last)
>>       {
>> @@ -1054,7 +1066,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>       }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_new_elements_at_front(size_type __new_elems)
>>      {
>> @@ -1079,7 +1091,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_new_elements_at_back(size_type __new_elems)
>>      {
>> @@ -1104,7 +1116,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template <typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      deque<_Tp, _Alloc>::
>>      _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front)
>>      {
>> @@ -1158,7 +1170,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>    // Overload for deque::iterators, exploiting the "segmented-iterator
>>    // optimization".
>>    template<typename _Tp, typename _VTp>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      __fill_a1(const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>& __first,
>>               const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>& __last,
>>               const _VTp& __value)
>> @@ -1180,7 +1192,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_dit(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
>>                     _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
>>                     _OI __result)
>> @@ -1209,7 +1221,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
>>                    _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
>>                    _OI __result)
>> @@ -1217,6 +1229,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>>                    _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __last,
>> @@ -1224,6 +1237,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      { return __copy_move_dit<_IsMove>(__first, __last, __result); }
>>
>>    template<bool _IsMove, typename _II, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
>> @@ -1250,6 +1264,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<bool _IsMove, typename _CharT>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_char<_CharT>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
>> @@ -1277,6 +1292,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _CharT, typename _Size>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_char<_CharT>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
>> @@ -1302,7 +1318,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_backward_dit(
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
>> @@ -1329,7 +1345,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_backward_a1(
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
>> @@ -1338,6 +1354,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __copy_move_backward_a1(
>>                 _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>> @@ -1346,6 +1363,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      { return __copy_move_backward_dit<_IsMove>(__first, __last, __result); }
>>
>>    template<bool _IsMove, typename _II, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
>> @@ -1378,7 +1396,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __equal_dit(
>>         const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>& __first1,
>>         const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>& __last1,
>> @@ -1405,6 +1423,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value, bool>::__type
>>      __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first1,
>> @@ -1414,13 +1433,14 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
>>                  _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
>>                  _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2)
>>      { return std::__equal_dit(__first1, __last1, __first2); }
>>
>>    template<typename _II, typename _Tp, typename _Ref, typename _Ptr>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value, bool>::__type
>>      __equal_aux1(_II __first1, _II __last1,
>> @@ -1446,7 +1466,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Tp1, typename _Ref, typename _Ptr, typename _Tp2>
>> -    int
>> +    _GLIBCXX26_CONSTEXPR int
>>      __lex_cmp_dit(
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __first1,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __last1,
>> @@ -1487,7 +1507,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2>
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
>> @@ -1496,7 +1516,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    inline  bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(_Tp1* __first1, _Tp1* __last1,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __last2)
>> @@ -1504,7 +1524,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
>>                 _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
>> @@ -1554,6 +1574,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>  #pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
>>    template<typename _ITp, typename _IRef, typename _IPtr, typename _OTp,
>>            typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __uninitialized_copy_a(
>>        _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>> @@ -1583,6 +1604,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Iter, typename _OTp, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      __enable_if_t<__is_random_access_iter<_Iter>::value,
>>                   _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>>
>>      __uninitialized_copy_a(_Iter __first, _Iter __last,
>> @@ -1607,6 +1629,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _ITp, typename _IRef, typename _IPtr, typename _OTp,
>>            typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __uninitialized_move_a(
>>        _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>> diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
>> index 33b1177810a..1df48418c42 100644
>> --- a/libstdc++-v3/include/bits/stl_algobase.h
>> +++ b/libstdc++-v3/include/bits/stl_algobase.h
>> @@ -347,6 +347,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>                    istreambuf_iterator<_CharT, char_traits<_CharT> >, _CharT*);
>>
>>    template<bool _IsMove, typename _CharT>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_char<_CharT>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
>> @@ -464,19 +465,21 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>>                    _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>>                    _OI);
>>
>>    template<bool _IsMove,
>>            typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr>,
>>                    _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr>,
>>                    _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>);
>>
>>    template<bool _IsMove, typename _II, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
>> @@ -600,6 +603,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>                _Size, _CharT*, bool);
>>
>>    template<typename _CharT, typename _Size>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_char<_CharT>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
>> @@ -752,13 +756,14 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<bool _IsMove,
>>            typename _Tp, typename _Ref, typename _Ptr, typename _OI>
>> -    _OI
>> +    _GLIBCXX26_CONSTEXPR _OI
>>      __copy_move_backward_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>>                             _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>>                             _OI);
>>
>>    template<bool _IsMove,
>>            typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __copy_move_backward_a1(
>>                         _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr>,
>> @@ -766,6 +771,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>                         _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>);
>>
>>    template<bool _IsMove, typename _II, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value,
>>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
>> @@ -959,7 +965,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      { std::__fill_a1(__first.base(), __last.base(), __value); }
>>
>>    template<typename _Tp, typename _VTp>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      __fill_a1(const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&,
>>               const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&,
>>               const _VTp&);
>> @@ -1215,6 +1221,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>      };
>>
>>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value, bool>::__type
>>      __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>> @@ -1223,12 +1230,13 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>>                  _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>>                  _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2>);
>>
>>    template<typename _II, typename _Tp, typename _Ref, typename _Ptr>
>> +    _GLIBCXX26_CONSTEXPR
>>      typename __gnu_cxx::__enable_if<
>>        __is_any_random_access_iter<_II>::__value, bool>::__type
>>      __equal_aux1(_II, _II,
>> @@ -1434,7 +1442,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>> @@ -1442,14 +1450,14 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>>
>>    template<typename _Tp1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(_Tp1*, _Tp1*,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2>,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2>);
>>
>>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>>            typename _Tp2, typename _Ref2, typename _Ptr2>
>> -    bool
>> +    _GLIBCXX26_CONSTEXPR bool
>>      __lexicographical_compare_aux1(
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>>         _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
>> diff --git a/libstdc++-v3/include/bits/stl_deque.h b/libstdc++-v3/include/bits/stl_deque.h
>> index b51342e1751..9834787214a 100644
>> --- a/libstdc++-v3/include/bits/stl_deque.h
>> +++ b/libstdc++-v3/include/bits/stl_deque.h
>> @@ -131,6 +131,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        typedef __ptr_rebind<_Ptr, _Elt_pointer>            _Map_pointer;
>>  #endif
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
>>        { return __deque_buf_size(sizeof(_Tp)); }
>>
>> @@ -147,10 +148,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        _Elt_pointer _M_last;
>>        _Map_pointer _M_node;
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_iterator(_Elt_pointer __x, _Map_pointer __y) _GLIBCXX_NOEXCEPT
>>        : _M_cur(__x), _M_first(*__y),
>>         _M_last(*__y + _S_buffer_size()), _M_node(__y) { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_iterator() _GLIBCXX_NOEXCEPT
>>        : _M_cur(), _M_first(), _M_last(), _M_node() { }
>>
>> @@ -164,10 +167,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        template<typename _Iter,
>>                typename = _Require<is_same<_Self, const_iterator>,
>>                                    is_same<_Iter, iterator>>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_iterator(const _Iter& __x) noexcept
>>         : _M_cur(__x._M_cur), _M_first(__x._M_first),
>>          _M_last(__x._M_last), _M_node(__x._M_node) { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_iterator(const _Deque_iterator& __x) noexcept
>>         : _M_cur(__x._M_cur), _M_first(__x._M_first),
>>          _M_last(__x._M_last), _M_node(__x._M_node) { }
>> @@ -175,21 +180,21 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        _Deque_iterator& operator=(const _Deque_iterator&) = default;
>>  #endif
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_const_cast() const _GLIBCXX_NOEXCEPT
>>        { return iterator(_M_cur, _M_node); }
>>
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        operator*() const _GLIBCXX_NOEXCEPT
>>        { return *_M_cur; }
>>
>>        _GLIBCXX_NODISCARD
>> -      pointer
>> +      _GLIBCXX26_CONSTEXPR pointer
>>        operator->() const _GLIBCXX_NOEXCEPT
>>        { return _M_cur; }
>>
>> -      _Self&
>> +      _GLIBCXX26_CONSTEXPR _Self&
>>        operator++() _GLIBCXX_NOEXCEPT
>>        {
>>         ++_M_cur;
>> @@ -201,7 +206,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return *this;
>>        }
>>
>> -      _Self
>> +      _GLIBCXX26_CONSTEXPR _Self
>>        operator++(int) _GLIBCXX_NOEXCEPT
>>        {
>>         _Self __tmp = *this;
>> @@ -209,7 +214,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return __tmp;
>>        }
>>
>> -      _Self&
>> +      _GLIBCXX26_CONSTEXPR _Self&
>>        operator--() _GLIBCXX_NOEXCEPT
>>        {
>>         if (_M_cur == _M_first)
>> @@ -221,7 +226,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return *this;
>>        }
>>
>> -      _Self
>> +      _GLIBCXX26_CONSTEXPR _Self
>>        operator--(int) _GLIBCXX_NOEXCEPT
>>        {
>>         _Self __tmp = *this;
>> @@ -229,7 +234,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return __tmp;
>>        }
>>
>> -      _Self&
>> +      _GLIBCXX26_CONSTEXPR _Self&
>>        operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
>>        {
>>         const difference_type __offset = __n + (_M_cur - _M_first);
>> @@ -248,12 +253,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return *this;
>>        }
>>
>> -      _Self&
>> +      _GLIBCXX26_CONSTEXPR _Self&
>>        operator-=(difference_type __n) _GLIBCXX_NOEXCEPT
>>        { return *this += -__n; }
>>
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        operator[](difference_type __n) const _GLIBCXX_NOEXCEPT
>>        { return *(*this + __n); }
>>
>> @@ -262,7 +267,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  _M_cur, which should therefore be set by the caller
>>         *  immediately afterwards, based on _M_first and _M_last.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_set_node(_Map_pointer __new_node) _GLIBCXX_NOEXCEPT
>>        {
>>         _M_node = __new_node;
>> @@ -271,7 +276,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator==(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        { return __x._M_cur == __y._M_cur; }
>>
>> @@ -280,7 +285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // operators are in scope (for additional details, see libstdc++/3628)
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator==(const _Self& __x,
>>                    const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>> @@ -288,7 +293,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>  #if __cpp_lib_three_way_comparison
>>        [[nodiscard]]
>> -      friend strong_ordering
>> +      friend _GLIBCXX26_CONSTEXPR strong_ordering
>>        operator<=>(const _Self& __x, const _Self& __y) noexcept
>>        {
>>         if (const auto __cmp = __x._M_node <=> __y._M_node; __cmp != 0)
>> @@ -297,20 +302,20 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>  #else
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator!=(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        { return !(__x == __y); }
>>
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator!=(const _Self& __x,
>>                    const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>>         { return !(__x == __y); }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator<(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        {
>>         return (__x._M_node == __y._M_node)
>> @@ -319,7 +324,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator<(const _Self& __x,
>>                   const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>> @@ -329,39 +334,39 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator>(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        { return __y < __x; }
>>
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator>(const _Self& __x,
>>                   const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>>         { return __y < __x; }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator<=(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        { return !(__y < __x); }
>>
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator<=(const _Self& __x,
>>                    const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>>         { return !(__y < __x); }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend bool
>> +      friend _GLIBCXX26_CONSTEXPR bool
>>        operator>=(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        { return !(__x < __y); }
>>
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator>=(const _Self& __x,
>>                    const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>> @@ -369,7 +374,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #endif // three-way comparison
>>
>>        _GLIBCXX_NODISCARD
>> -      friend difference_type
>> +      friend _GLIBCXX26_CONSTEXPR difference_type
>>        operator-(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>>        {
>>         return difference_type(_S_buffer_size())
>> @@ -384,7 +389,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // parameters.
>>        template<typename _RefR, typename _PtrR>
>>         _GLIBCXX_NODISCARD
>> -       friend difference_type
>> +       friend _GLIBCXX26_CONSTEXPR difference_type
>>         operator-(const _Self& __x,
>>                   const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
>>         _GLIBCXX_NOEXCEPT
>> @@ -396,7 +401,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend _Self
>> +      friend _GLIBCXX26_CONSTEXPR _Self
>>        operator+(const _Self& __x, difference_type __n) _GLIBCXX_NOEXCEPT
>>        {
>>         _Self __tmp = __x;
>> @@ -405,7 +410,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend _Self
>> +      friend _GLIBCXX26_CONSTEXPR _Self
>>        operator-(const _Self& __x, difference_type __n) _GLIBCXX_NOEXCEPT
>>        {
>>         _Self __tmp = __x;
>> @@ -414,7 +419,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      friend _Self
>> +      friend _GLIBCXX26_CONSTEXPR _Self
>>        operator+(difference_type __n, const _Self& __x) _GLIBCXX_NOEXCEPT
>>        { return __x + __n; }
>>
>> @@ -488,30 +493,35 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        typedef _Alloc             allocator_type;
>>
>> -      allocator_type
>> +      _GLIBCXX26_CONSTEXPR allocator_type
>>        get_allocator() const _GLIBCXX_NOEXCEPT
>>        { return allocator_type(_M_get_Tp_allocator()); }
>>
>>        typedef _Deque_iterator<_Tp, _Tp&, _Ptr>   iterator;
>>        typedef _Deque_iterator<_Tp, const _Tp&, _Ptr_const>   const_iterator;
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base()
>>        : _M_impl()
>>        { _M_initialize_map(0); }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(size_t __num_elements)
>>        : _M_impl()
>>        { _M_initialize_map(__num_elements); }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(const allocator_type& __a, size_t __num_elements)
>>        : _M_impl(__a)
>>        { _M_initialize_map(__num_elements); }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(const allocator_type& __a)
>>        : _M_impl(__a)
>>        { /* Caller must initialize map. */ }
>>
>>  #if __cplusplus >= 201103L
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(_Deque_base&& __x)
>>        : _M_impl(std::move(__x._M_get_Tp_allocator()))
>>        {
>> @@ -520,10 +530,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>           this->_M_impl._M_swap_data(__x._M_impl);
>>        }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(_Deque_base&& __x, const allocator_type& __a)
>>        : _M_impl(std::move(__x._M_impl), _Tp_alloc_type(__a))
>>        { __x._M_initialize_map(0); }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        _Deque_base(_Deque_base&& __x, const allocator_type& __a, size_t __n)
>>        : _M_impl(__a)
>>        {
>> @@ -542,6 +554,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>  #endif
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        ~_Deque_base() _GLIBCXX_NOEXCEPT;
>>
>>        typedef typename iterator::_Map_pointer _Map_pointer;
>> @@ -553,6 +566,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         iterator _M_start;
>>         iterator _M_finish;
>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl_data() _GLIBCXX_NOEXCEPT
>>         : _M_map(), _M_map_size(), _M_start(), _M_finish()
>>         { }
>> @@ -562,12 +576,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         _Deque_impl_data&
>>         operator=(const _Deque_impl_data&) = default;
>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl_data(_Deque_impl_data&& __x) noexcept
>>         : _Deque_impl_data(__x)
>>         { __x = _Deque_impl_data(); }
>>  #endif
>>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_swap_data(_Deque_impl_data& __x) _GLIBCXX_NOEXCEPT
>>         {
>>           // Do not use std::swap(_M_start, __x._M_start), etc as it loses
>> @@ -582,11 +597,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        struct _Deque_impl
>>        : public _Tp_alloc_type, public _Deque_impl_data
>>        {
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl() _GLIBCXX_NOEXCEPT_IF(
>>           is_nothrow_default_constructible<_Tp_alloc_type>::value)
>>         : _Tp_alloc_type()
>>         { }
>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
>>         : _Tp_alloc_type(__a)
>>         { }
>> @@ -594,66 +611,74 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #if __cplusplus >= 201103L
>>         _Deque_impl(_Deque_impl&&) = default;
>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl(_Tp_alloc_type&& __a) noexcept
>>         : _Tp_alloc_type(std::move(__a))
>>         { }
>>
>> +       _GLIBCXX26_CONSTEXPR
>>         _Deque_impl(_Deque_impl&& __d, _Tp_alloc_type&& __a)
>>         : _Tp_alloc_type(std::move(__a)), _Deque_impl_data(std::move(__d))
>>         { }
>>  #endif
>>        };
>>
>> -      _Tp_alloc_type&
>> +      _GLIBCXX26_CONSTEXPR _Tp_alloc_type&
>>        _M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl; }
>>
>> -      const _Tp_alloc_type&
>> +      _GLIBCXX26_CONSTEXPR const _Tp_alloc_type&
>>        _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl; }
>>
>> -      _Map_alloc_type
>> +      _GLIBCXX26_CONSTEXPR _Map_alloc_type
>>        _M_get_map_allocator() const _GLIBCXX_NOEXCEPT
>>        { return _Map_alloc_type(_M_get_Tp_allocator()); }
>>
>> -      _Ptr
>> +      _GLIBCXX26_CONSTEXPR _Ptr
>>        _M_allocate_node()
>>        {
>>         typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Traits;
>>         return _Traits::allocate(_M_impl, __deque_buf_size(sizeof(_Tp)));
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_deallocate_node(_Ptr __p) _GLIBCXX_NOEXCEPT
>>        {
>>         typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Traits;
>>         _Traits::deallocate(_M_impl, __p, __deque_buf_size(sizeof(_Tp)));
>>        }
>>
>> -      _Map_pointer
>> +      _GLIBCXX26_CONSTEXPR _Map_pointer
>>        _M_allocate_map(size_t __n)
>>        {
>>         _Map_alloc_type __map_alloc = _M_get_map_allocator();
>>         return _Map_alloc_traits::allocate(__map_alloc, __n);
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_deallocate_map(_Map_pointer __p, size_t __n) _GLIBCXX_NOEXCEPT
>>        {
>>         _Map_alloc_type __map_alloc = _M_get_map_allocator();
>>         _Map_alloc_traits::deallocate(__map_alloc, __p, __n);
>>        }
>>
>> -      void _M_initialize_map(size_t);
>> -      void _M_create_nodes(_Map_pointer __nstart, _Map_pointer __nfinish);
>> -      void _M_destroy_nodes(_Map_pointer __nstart,
>> -                           _Map_pointer __nfinish) _GLIBCXX_NOEXCEPT;
>> +      _GLIBCXX26_CONSTEXPR void
>> +      _M_initialize_map(size_t);
>> +
>> +      _GLIBCXX26_CONSTEXPR void
>> +      _M_create_nodes(_Map_pointer __nstart, _Map_pointer __nfinish);
>> +
>> +      _GLIBCXX26_CONSTEXPR void
>> +      _M_destroy_nodes(_Map_pointer __nstart, _Map_pointer __nfinish) _GLIBCXX_NOEXCEPT;
>> +
>>        enum { _S_initial_map_size = 8 };
>>
>>        _Deque_impl _M_impl;
>>      };
>>
>>    template<typename _Tp, typename _Alloc>
>> +    _GLIBCXX26_CONSTEXPR
>>      _Deque_base<_Tp, _Alloc>::
>>      ~_Deque_base() _GLIBCXX_NOEXCEPT
>>      {
>> @@ -673,7 +698,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>     *  The initial underlying memory layout is a bit complicated...
>>    */
>>    template<typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      _Deque_base<_Tp, _Alloc>::
>>      _M_initialize_map(size_t __num_elements)
>>      {
>> @@ -712,7 +737,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      _Deque_base<_Tp, _Alloc>::
>>      _M_create_nodes(_Map_pointer __nstart, _Map_pointer __nfinish)
>>      {
>> @@ -730,7 +755,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>      }
>>
>>    template<typename _Tp, typename _Alloc>
>> -    void
>> +    _GLIBCXX26_CONSTEXPR void
>>      _Deque_base<_Tp, _Alloc>::
>>      _M_destroy_nodes(_Map_pointer __nstart,
>>                      _Map_pointer __nfinish) _GLIBCXX_NOEXCEPT
>> @@ -864,7 +889,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        typedef _Alloc                                   allocator_type;
>>
>>      private:
>> -      static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
>> +      static _GLIBCXX26_CONSTEXPR size_t
>> +      _S_buffer_size() _GLIBCXX_NOEXCEPT
>>        { return __deque_buf_size(sizeof(_Tp)); }
>>
>>        // Functions controlling memory layout, and nothing else.
>> @@ -900,7 +926,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  @brief  Creates a %deque with no elements.
>>         *  @param  __a  An allocator object.
>>         */
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        deque(const allocator_type& __a)
>>        : _Base(__a, 0) { }
>>
>> @@ -913,7 +939,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This constructor fills the %deque with @a n default
>>         *  constructed elements.
>>         */
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        deque(size_type __n, const allocator_type& __a = allocator_type())
>>        : _Base(__a, _S_check_init_len(__n, __a))
>>        { _M_default_initialize(); }
>> @@ -926,6 +952,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *
>>         *  This constructor fills the %deque with @a __n copies of @a __value.
>>         */
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(size_type __n, const value_type& __value,
>>             const allocator_type& __a = allocator_type())
>>        : _Base(__a, _S_check_init_len(__n, __a))
>> @@ -953,6 +980,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  The newly-created %deque uses a copy of the allocator object used
>>         *  by @a __x (unless the allocator traits dictate a different object).
>>         */
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(const deque& __x)
>>        : _Base(_Alloc_traits::_S_select_on_copy(__x._M_get_Tp_allocator()),
>>               __x.size())
>> @@ -972,6 +1000,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        deque(deque&&) = default;
>>
>>        /// Copy constructor with alternative allocator
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(const deque& __x, const __type_identity_t<allocator_type>& __a)
>>        : _Base(__a, __x.size())
>>        { std::__uninitialized_copy_a(__x.begin(), __x.end(),
>> @@ -979,15 +1008,18 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>                                     _M_get_Tp_allocator()); }
>>
>>        /// Move constructor with alternative allocator
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(deque&& __x, const __type_identity_t<allocator_type>& __a)
>>        : deque(std::move(__x), __a, typename _Alloc_traits::is_always_equal{})
>>        { }
>>
>>      private:
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(deque&& __x, const allocator_type& __a, true_type)
>>        : _Base(std::move(__x), __a)
>>        { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(deque&& __x, const allocator_type& __a, false_type)
>>        : _Base(std::move(__x), __a, __x.size())
>>        {
>> @@ -1012,6 +1044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This will call the element type's copy constructor N times
>>         *  (where N is __l.size()) and do no memory reallocation.
>>         */
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(initializer_list<value_type> __l,
>>             const allocator_type& __a = allocator_type())
>>        : _Base(__a)
>> @@ -1039,6 +1072,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #if __cplusplus >= 201103L
>>        template<typename _InputIterator,
>>                typename = std::_RequireInputIter<_InputIterator>>
>> +       _GLIBCXX26_CONSTEXPR
>>         deque(_InputIterator __first, _InputIterator __last,
>>               const allocator_type& __a = allocator_type())
>>         : _Base(__a)
>> @@ -1065,6 +1099,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         * @since C++23
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> +       _GLIBCXX26_CONSTEXPR
>>         deque(from_range_t, _Rg&& __rg, const allocator_type& __a = _Alloc())
>>         : deque(__a)
>>         { append_range(std::forward<_Rg>(__rg)); }
>> @@ -1075,6 +1110,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  themselves are pointers, the pointed-to memory is not touched in any
>>         *  way.  Managing the pointer is the user's responsibility.
>>         */
>> +      _GLIBCXX26_CONSTEXPR
>>        ~deque()
>>        { _M_destroy_data(begin(), end(), _M_get_Tp_allocator()); }
>>
>> @@ -1087,7 +1123,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  The newly-created %deque uses a copy of the allocator object used
>>         *  by @a __x (unless the allocator traits dictate a different object).
>>         */
>> -      deque&
>> +      _GLIBCXX26_CONSTEXPR deque&
>>        operator=(const deque& __x);
>>
>>  #if __cplusplus >= 201103L
>> @@ -1099,7 +1135,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  if the allocators permit it).
>>         *  @a __x is a valid, but unspecified %deque.
>>         */
>> -      deque&
>> +      _GLIBCXX26_CONSTEXPR deque&
>>        operator=(deque&& __x) noexcept(_Alloc_traits::_S_always_equal())
>>        {
>>         using __always_equal = typename _Alloc_traits::is_always_equal;
>> @@ -1118,7 +1154,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  resulting %deque's size is the same as the number of elements
>>         *  assigned.
>>         */
>> -      deque&
>> +      _GLIBCXX26_CONSTEXPR deque&
>>        operator=(initializer_list<value_type> __l)
>>        {
>>         _M_assign_aux(__l.begin(), __l.end(),
>> @@ -1137,7 +1173,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  %deque and that the resulting %deque's size is the same as
>>         *  the number of elements assigned.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        assign(size_type __n, const value_type& __val)
>>        { _M_fill_assign(__n, __val); }
>>
>> @@ -1156,7 +1192,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>  #if __cplusplus >= 201103L
>>        template<typename _InputIterator,
>>                typename = std::_RequireInputIter<_InputIterator>>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         assign(_InputIterator __first, _InputIterator __last)
>>         { _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
>>  #else
>> @@ -1181,7 +1217,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  resulting %deque's size is the same as the number of elements
>>         *  assigned.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        assign(initializer_list<value_type> __l)
>>        { _M_assign_aux(__l.begin(), __l.end(), random_access_iterator_tag()); }
>>  #endif
>> @@ -1235,7 +1271,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        /// Get a copy of the memory allocation object.
>>        _GLIBCXX_NODISCARD
>> -      allocator_type
>> +      _GLIBCXX26_CONSTEXPR allocator_type
>>        get_allocator() const _GLIBCXX_NOEXCEPT
>>        { return _Base::get_allocator(); }
>>
>> @@ -1245,7 +1281,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  %deque.  Iteration is done in ordinary element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        begin() _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl._M_start; }
>>
>> @@ -1254,7 +1290,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element in the %deque.  Iteration is done in ordinary element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        begin() const _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl._M_start; }
>>
>> @@ -1264,7 +1300,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        end() _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl._M_finish; }
>>
>> @@ -1274,7 +1310,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  ordinary element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        end() const _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl._M_finish; }
>>
>> @@ -1284,7 +1320,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR reverse_iterator
>>        rbegin() _GLIBCXX_NOEXCEPT
>>        { return reverse_iterator(this->_M_impl._M_finish); }
>>
>> @@ -1294,7 +1330,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  reverse element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        rbegin() const _GLIBCXX_NOEXCEPT
>>        { return const_reverse_iterator(this->_M_impl._M_finish); }
>>
>> @@ -1304,7 +1340,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  in reverse element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR reverse_iterator
>>        rend() _GLIBCXX_NOEXCEPT
>>        { return reverse_iterator(this->_M_impl._M_start); }
>>
>> @@ -1314,7 +1350,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  done in reverse element order.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        rend() const _GLIBCXX_NOEXCEPT
>>        { return const_reverse_iterator(this->_M_impl._M_start); }
>>
>> @@ -1324,7 +1360,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element in the %deque.  Iteration is done in ordinary element order.
>>         */
>>        [[__nodiscard__]]
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        cbegin() const noexcept
>>        { return this->_M_impl._M_start; }
>>
>> @@ -1334,7 +1370,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  ordinary element order.
>>         */
>>        [[__nodiscard__]]
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        cend() const noexcept
>>        { return this->_M_impl._M_finish; }
>>
>> @@ -1344,7 +1380,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  reverse element order.
>>         */
>>        [[__nodiscard__]]
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        crbegin() const noexcept
>>        { return const_reverse_iterator(this->_M_impl._M_finish); }
>>
>> @@ -1354,7 +1390,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  done in reverse element order.
>>         */
>>        [[__nodiscard__]]
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        crend() const noexcept
>>        { return const_reverse_iterator(this->_M_impl._M_start); }
>>  #endif
>> @@ -1362,7 +1398,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // [23.2.1.2] capacity
>>        /**  Returns the number of elements in the %deque.  */
>>        _GLIBCXX_NODISCARD
>> -      size_type
>> +      _GLIBCXX26_CONSTEXPR size_type
>>        size() const _GLIBCXX_NOEXCEPT
>>        {
>>         size_type __sz = this->_M_impl._M_finish - this->_M_impl._M_start;
>> @@ -1373,7 +1409,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        /**  Returns the size() of the largest possible %deque.  */
>>        _GLIBCXX_NODISCARD
>> -      size_type
>> +      _GLIBCXX26_CONSTEXPR size_type
>>        max_size() const _GLIBCXX_NOEXCEPT
>>        { return _S_max_size(_M_get_Tp_allocator()); }
>>
>> @@ -1387,7 +1423,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  %deque's current size the %deque is truncated, otherwise
>>         *  default constructed elements are appended.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        resize(size_type __new_size)
>>        {
>>         const size_type __len = size();
>> @@ -1409,7 +1445,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  %deque is extended and new elements are populated with given
>>         *  data.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        resize(size_type __new_size, const value_type& __x)
>>  #else
>>        /**
>> @@ -1437,7 +1473,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>  #if __cplusplus >= 201103L
>>        /**  A non-binding request to reduce memory use.  */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        shrink_to_fit() noexcept
>>        { _M_shrink_to_fit(); }
>>  #endif
>> @@ -1446,7 +1482,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  Returns true if the %deque is empty.  (Thus begin() would
>>         *  equal end().)
>>         */
>> -      _GLIBCXX_NODISCARD bool
>> +      _GLIBCXX_NODISCARD
>> +      _GLIBCXX26_CONSTEXPR bool
>>        empty() const _GLIBCXX_NOEXCEPT
>>        { return this->_M_impl._M_finish == this->_M_impl._M_start; }
>>
>> @@ -1463,7 +1500,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  see at().)
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        operator[](size_type __n) _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_subscript(__n);
>> @@ -1482,7 +1519,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  see at().)
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        operator[](size_type __n) const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_subscript(__n);
>> @@ -1491,7 +1528,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>      protected:
>>        /// Safety check used only from at().
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_range_check(size_type __n) const
>>        {
>>         if (__n >= this->size())
>> @@ -1513,7 +1550,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  is first checked that it is in the range of the deque.  The
>>         *  function throws out_of_range if the check fails.
>>         */
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        at(size_type __n)
>>        {
>>         _M_range_check(__n);
>> @@ -1531,7 +1568,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  checked that it is in the range of the deque.  The function throws
>>         *  out_of_range if the check fails.
>>         */
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        at(size_type __n) const
>>        {
>>         _M_range_check(__n);
>> @@ -1543,7 +1580,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element of the %deque.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        front() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1555,7 +1592,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element of the %deque.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        front() const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1567,7 +1604,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  %deque.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        back() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1581,7 +1618,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  element of the %deque.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        back() const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1600,7 +1637,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  data to it.  Due to the nature of a %deque this operation
>>         *  can be done in constant time.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_front(const value_type& __x)
>>        {
>>         if (this->_M_impl._M_start._M_cur != this->_M_impl._M_start._M_first)
>> @@ -1615,13 +1652,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_front(value_type&& __x)
>>        { emplace_front(std::move(__x)); }
>>
>>        template<typename... _Args>
>>  #if __cplusplus > 201402L
>> -       reference
>> +       _GLIBCXX26_CONSTEXPR reference
>>  #else
>>         void
>>  #endif
>> @@ -1637,7 +1674,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  to it.  Due to the nature of a %deque this operation can be
>>         *  done in constant time.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_back(const value_type& __x)
>>        {
>>         if (this->_M_impl._M_finish._M_cur
>> @@ -1652,13 +1689,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_back(value_type&& __x)
>>        { emplace_back(std::move(__x)); }
>>
>>        template<typename... _Args>
>>  #if __cplusplus > 201402L
>> -       reference
>> +       _GLIBCXX26_CONSTEXPR reference
>>  #else
>>         void
>>  #endif
>> @@ -1673,7 +1710,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  Note that no data is returned, and if the first element's data is
>>         *  needed, it should be retrieved before pop_front() is called.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop_front() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1696,7 +1733,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  Note that no data is returned, and if the last element's data is
>>         *  needed, it should be retrieved before pop_back() is called.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop_back() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -1722,7 +1759,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  with T(std::forward<Args>(args)...) before the specified location.
>>         */
>>        template<typename... _Args>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         emplace(const_iterator __position, _Args&&... __args);
>>
>>        /**
>> @@ -1734,7 +1771,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function will insert a copy of the given value before the
>>         *  specified location.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, const value_type& __x);
>>  #else
>>        /**
>> @@ -1746,7 +1783,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function will insert a copy of the given value before the
>>         *  specified location.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(iterator __position, const value_type& __x);
>>  #endif
>>
>> @@ -1760,7 +1797,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function will insert a copy of the given rvalue before the
>>         *  specified location.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, value_type&& __x)
>>        { return emplace(__position, std::move(__x)); }
>>
>> @@ -1774,7 +1811,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  initializer_list @a __l into the %deque before the location
>>         *  specified by @a __p.  This is known as <em>list insert</em>.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __p, initializer_list<value_type> __l)
>>        {
>>         auto __offset = __p - cbegin();
>> @@ -1793,7 +1830,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function will insert a specified number of copies of the given
>>         *  data before the location specified by @a __position.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, size_type __n, const value_type& __x)
>>        {
>>         difference_type __offset = __position - cbegin();
>> @@ -1810,7 +1847,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function will insert a specified number of copies of the given
>>         *  data before the location specified by @a __position.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        insert(iterator __position, size_type __n, const value_type& __x)
>>        { _M_fill_insert(__position, __n, __x); }
>>  #endif
>> @@ -1829,7 +1866,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         */
>>        template<typename _InputIterator,
>>                typename = std::_RequireInputIter<_InputIterator>>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         insert(const_iterator __position, _InputIterator __first,
>>                _InputIterator __last)
>>         {
>> @@ -1850,7 +1887,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  by @a __position.  This is known as <em>range insert</em>.
>>         */
>>        template<typename _InputIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         insert(iterator __position, _InputIterator __first,
>>                _InputIterator __last)
>>         {
>> @@ -1870,7 +1907,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         * @since C++23
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         insert_range(const_iterator __pos, _Rg&& __rg);
>>
>>        /**
>> @@ -1879,7 +1916,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         * @since C++23
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         prepend_range(_Rg&& __rg);
>>
>>        /**
>> @@ -1888,7 +1925,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         * @since C++23
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         append_range(_Rg&& __rg);
>>  #endif // containers_ranges
>>
>> @@ -1905,7 +1942,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  itself a pointer, the pointed-to memory is not touched in any way.
>>         *  Managing the pointer is the user's responsibility.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>  #if __cplusplus >= 201103L
>>        erase(const_iterator __position)
>>  #else
>> @@ -1929,7 +1966,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  themselves are pointers, the pointed-to memory is not touched in any
>>         *  way.  Managing the pointer is the user's responsibility.
>>         */
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>  #if __cplusplus >= 201103L
>>        erase(const_iterator __first, const_iterator __last)
>>  #else
>> @@ -1948,7 +1985,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *
>>         *  Whether the allocators are swapped depends on the allocator traits.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        swap(deque& __x) _GLIBCXX_NOEXCEPT
>>        {
>>  #if __cplusplus >= 201103L
>> @@ -1966,7 +2003,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  pointed-to memory is not touched in any way.  Managing the pointer is
>>         *  the user's responsibility.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        clear() _GLIBCXX_NOEXCEPT
>>        { _M_erase_at_end(begin()); }
>>
>> @@ -1998,7 +2035,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         }
>>  #endif
>>
>> -      static size_t
>> +      static _GLIBCXX26_CONSTEXPR size_t
>>        _S_check_init_len(size_t __n, const allocator_type& __a)
>>        {
>>         if (__n > _S_max_size(__a))
>> @@ -2007,7 +2044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return __n;
>>        }
>>
>> -      static size_type
>> +      static _GLIBCXX26_CONSTEXPR size_type
>>        _S_max_size(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
>>        {
>>         const size_t __diffmax = __gnu_cxx::__numeric_traits<ptrdiff_t>::__max;
>> @@ -2027,13 +2064,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  push_back on each value from the iterator.
>>         */
>>        template<typename _InputIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_range_initialize(_InputIterator __first, _InputIterator __last,
>>                             std::input_iterator_tag);
>>
>>        // called by the second initialize_dispatch above
>>        template<typename _ForwardIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
>>                             std::forward_iterator_tag);
>>        ///@}
>> @@ -2047,12 +2084,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  This function is called only when the user provides an explicit size
>>         *  (with or without an explicit exemplar value).
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_fill_initialize(const value_type& __value);
>>
>>  #if __cplusplus >= 201103L
>>        // called by deque(n).
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_default_initialize();
>>  #endif
>>
>> @@ -2079,13 +2116,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // called by the second assign_dispatch above
>>        template<typename _InputIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_assign_aux(_InputIterator __first, _InputIterator __last,
>>                       std::input_iterator_tag);
>>
>>        // called by the second assign_dispatch above
>>        template<typename _ForwardIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
>>                       std::forward_iterator_tag)
>>         {
>> @@ -2104,7 +2141,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // Called by assign(n,t), and the range assign when it turns out
>>        // to be the same thing.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_fill_assign(size_type __n, const value_type& __val)
>>        {
>>         if (__n > size())
>> @@ -2127,15 +2164,19 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        void _M_push_front_aux(const value_type&);
>>  #else
>>        template<typename... _Args>
>> -       void _M_push_back_aux(_Args&&... __args);
>> +       _GLIBCXX26_CONSTEXPR void
>> +       _M_push_back_aux(_Args&&... __args);
>>
>>        template<typename... _Args>
>> -       void _M_push_front_aux(_Args&&... __args);
>> +       _GLIBCXX26_CONSTEXPR void
>> +       _M_push_front_aux(_Args&&... __args);
>>  #endif
>>
>> -      void _M_pop_back_aux();
>> +      _GLIBCXX26_CONSTEXPR void
>> +      _M_pop_back_aux();
>>
>> -      void _M_pop_front_aux();
>> +      _GLIBCXX26_CONSTEXPR void
>> +      _M_pop_front_aux();
>>        ///@}
>>
>>        // Internal insert functions follow.  The *_aux functions do the actual
>> @@ -2147,14 +2188,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // _GLIBCXX_RESOLVE_LIB_DEFECTS
>>        // 438. Ambiguity in the "do the right thing" clause
>>        template<typename _Integer>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_insert_dispatch(iterator __pos,
>>                            _Integer __n, _Integer __x, __true_type)
>>         { _M_fill_insert(__pos, __n, __x); }
>>
>>        // called by the range insert to implement [23.1.1]/9
>>        template<typename _InputIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_insert_dispatch(iterator __pos,
>>                            _InputIterator __first, _InputIterator __last,
>>                            __false_type)
>> @@ -2166,30 +2207,32 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // insert [__first, __last) at the front, assumes distance(__first, __last) is n
>>        template<typename _InputIterator, typename _Sentinel>
>> -      void _M_range_prepend(_InputIterator __first, _Sentinel __last,
>> -                           size_type __n);
>> +       _GLIBCXX26_CONSTEXPR void
>> +       _M_range_prepend(_InputIterator __first, _Sentinel __last,
>> +                        size_type __n);
>>
>>        // insert [__first, __last) at the back, assumes distance(__first, __last) is n
>>        template<typename _InputIterator, typename _Sentinel>
>> -      void _M_range_append(_InputIterator __first, _Sentinel __last,
>> -                          size_type __n);
>> +       _GLIBCXX26_CONSTEXPR void
>> +       _M_range_append(_InputIterator __first, _Sentinel __last,
>> +                       size_type __n);
>>
>>        // called by the second insert_dispatch above
>>        template<typename _InputIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_range_insert_aux(iterator __pos, _InputIterator __first,
>>                             _InputIterator __last, std::input_iterator_tag);
>>
>>        // called by the second insert_dispatch above
>>        template<typename _ForwardIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_range_insert_aux(iterator __pos, _ForwardIterator __first,
>>                             _ForwardIterator __last, std::forward_iterator_tag);
>>
>>        // Called by insert(p,n,x), and the range insert when it turns out to be
>>        // the same thing.  Can use fill functions in optimal situations,
>>        // otherwise passes off to insert_aux(p,n,x).
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_fill_insert(iterator __pos, size_type __n, const value_type& __x);
>>
>>        // called by insert(p,x)
>> @@ -2200,22 +2243,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        struct _Temporary_value
>>        {
>>         template<typename... _Args>
>> -         _GLIBCXX20_CONSTEXPR explicit
>> +         explicit _GLIBCXX26_CONSTEXPR
>>           _Temporary_value(deque* __deque, _Args&&... __args) : _M_this(__deque)
>>           {
>>             _Alloc_traits::construct(_M_this->_M_impl, _M_ptr(),
>>                                      std::forward<_Args>(__args)...);
>>           }
>>
>> -       _GLIBCXX20_CONSTEXPR
>> +       _GLIBCXX26_CONSTEXPR
>>         ~_Temporary_value()
>>         { _Alloc_traits::destroy(_M_this->_M_impl, _M_ptr()); }
>>
>> -       _GLIBCXX20_CONSTEXPR value_type&
>> +       _GLIBCXX26_CONSTEXPR value_type&
>>         _M_val() noexcept { return __tmp_val; }
>>
>>        private:
>> -       _GLIBCXX20_CONSTEXPR _Tp*
>> +       _GLIBCXX26_CONSTEXPR _Tp*
>>         _M_ptr() noexcept { return std::__addressof(__tmp_val); }
>>
>>         union
>> @@ -2226,22 +2269,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         deque* _M_this;
>>        };
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_insert_aux(iterator __pos, const value_type& __x)
>>        { return _M_emplace_aux(__pos, __x); }
>>
>>        template<typename... _Args>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         _M_emplace_aux(iterator __pos, _Args&&... __args);
>>  #endif
>>
>>        // called by insert(p,n,x) via fill_insert
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_insert_aux(iterator __pos, size_type __n, const value_type& __x);
>>
>>        // called by range_insert_aux for forward iterators
>>        template<typename _ForwardIterator>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_insert_aux(iterator __pos,
>>                       _ForwardIterator __first, _ForwardIterator __last,
>>                       size_type __n);
>> @@ -2249,17 +2292,17 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // Internal erase functions follow.
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_destroy_data_aux(iterator __first, iterator __last);
>>
>>        // Called by ~deque().
>>        // NB: Doesn't deallocate the nodes.
>>        template<typename _Alloc1>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         _M_destroy_data(iterator __first, iterator __last, const _Alloc1&)
>>         { _M_destroy_data_aux(__first, __last); }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_destroy_data(iterator __first, iterator __last,
>>                       const std::allocator<_Tp>&)
>>        {
>> @@ -2268,7 +2311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>        // Called by erase(q1, q2).
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_erase_at_begin(iterator __pos)
>>        {
>>         _M_destroy_data(begin(), __pos, _M_get_Tp_allocator());
>> @@ -2278,7 +2321,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // Called by erase(q1, q2), resize(), clear(), _M_assign_aux,
>>        // _M_fill_assign, operator=.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_erase_at_end(iterator __pos)
>>        {
>>         _M_destroy_data(__pos, end(), _M_get_Tp_allocator());
>> @@ -2287,24 +2330,24 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         this->_M_impl._M_finish = __pos;
>>        }
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_erase(iterator __pos);
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_erase(iterator __first, iterator __last);
>>
>>  #if __cplusplus >= 201103L
>>        // Called by resize(sz).
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_default_append(size_type __n);
>>
>> -      bool
>> +      _GLIBCXX26_CONSTEXPR bool
>>        _M_shrink_to_fit();
>>  #endif
>>
>>        ///@{
>>        /// Memory-handling helpers for the previous internal insert functions.
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_reserve_elements_at_front(size_type __n)
>>        {
>>         const size_type __vacancies = this->_M_impl._M_start._M_cur
>> @@ -2314,7 +2357,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return this->_M_impl._M_start - difference_type(__n);
>>        }
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        _M_reserve_elements_at_back(size_type __n)
>>        {
>>         const size_type __vacancies = (this->_M_impl._M_finish._M_last
>> @@ -2324,10 +2367,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         return this->_M_impl._M_finish + difference_type(__n);
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_new_elements_at_front(size_type __new_elements);
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_new_elements_at_back(size_type __new_elements);
>>        ///@}
>>
>> @@ -2340,7 +2383,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>         *  actually add the nodes.  Can invalidate _M_map pointers.
>>         *  (And consequently, %deque iterators.)
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_reserve_map_at_back(size_type __nodes_to_add = 1)
>>        {
>>         if (__nodes_to_add + 1 > this->_M_impl._M_map_size
>> @@ -2348,7 +2391,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>           _M_reallocate_map(__nodes_to_add, false);
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_reserve_map_at_front(size_type __nodes_to_add = 1)
>>        {
>>         if (__nodes_to_add > size_type(this->_M_impl._M_start._M_node
>> @@ -2356,14 +2399,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>           _M_reallocate_map(__nodes_to_add, true);
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front);
>>        ///@}
>>
>>  #if __cplusplus >= 201103L
>>        // Constant-time, nothrow move assignment when source object's memory
>>        // can be moved because the allocators are equal.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_move_assign1(deque&& __x, /* always equal: */ true_type) noexcept
>>        {
>>         this->_M_impl._M_swap_data(__x._M_impl);
>> @@ -2374,7 +2417,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // When the allocators are not equal the operation could throw, because
>>        // we might need to allocate a new map for __x after moving from it
>>        // or we might need to allocate new elements for *this.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_move_assign1(deque&& __x, /* always equal: */ false_type)
>>        {
>>         if (_M_get_Tp_allocator() == __x._M_get_Tp_allocator())
>> @@ -2388,7 +2431,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        // Destroy all elements and deallocate all memory, then replace
>>        // with elements created from __args.
>>        template<typename... _Args>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_replace_map(_Args&&... __args)
>>        {
>>         // Create new data first, so if allocation fails there are no effects.
>> @@ -2404,7 +2447,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>        }
>>
>>        // Do move assignment when the allocator propagates.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_move_assign2(deque&& __x, /* propagate: */ true_type)
>>        {
>>         // Make a copy of the original allocator state.
>> @@ -2418,7 +2461,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>        // Do move assignment when it may not be possible to move source
>>        // object's memory, resulting in a linear-time operation.
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_move_assign2(deque&& __x, /* propagate: */ false_type)
>>        {
>>         if (__x._M_get_Tp_allocator() == this->_M_get_Tp_allocator())
>> @@ -2469,7 +2512,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    */
>>    template<typename _Tp, typename _Alloc>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator==(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>& __y)
>>      { return __x.size() == __y.size()
>>              && std::equal(__x.begin(), __x.end(), __y.begin()); }
>> @@ -2488,7 +2531,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>    */
>>    template<typename _Tp, typename _Alloc>
>>      [[nodiscard]]
>> -    inline __detail::__synth3way_t<_Tp>
>> +    inline _GLIBCXX26_CONSTEXPR __detail::__synth3way_t<_Tp>
>>      operator<=>(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>& __y)
>>      {
>>        return std::lexicographical_compare_three_way(__x.begin(), __x.end(),
>> @@ -2545,7 +2588,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>>
>>    /// See std::deque::swap().
>>    template<typename _Tp, typename _Alloc>
>> -    inline void
>> +    inline _GLIBCXX26_CONSTEXPR void
>>      swap(deque<_Tp,_Alloc>& __x, deque<_Tp,_Alloc>& __y)
>>      _GLIBCXX_NOEXCEPT_IF(noexcept(__x.swap(__y)))
>>      { __x.swap(__y); }
>> diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h
>> index d9edc4c838d..ced5660bc97 100644
>> --- a/libstdc++-v3/include/bits/stl_queue.h
>> +++ b/libstdc++-v3/include/bits/stl_queue.h
>> @@ -115,16 +115,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>  #endif
>>
>>        template<typename _Tp1, typename _Seq1>
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator==(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>>
>>        template<typename _Tp1, typename _Seq1>
>> -       friend bool
>> +       friend _GLIBCXX26_CONSTEXPR bool
>>         operator<(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>>
>>  #if __cpp_lib_three_way_comparison
>>        template<typename _Tp1, three_way_comparable _Seq1>
>> -       friend compare_three_way_result_t<_Seq1>
>> +       friend _GLIBCXX26_CONSTEXPR compare_three_way_result_t<_Seq1>
>>         operator<=>(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>>  #endif
>>
>> @@ -171,35 +171,40 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>  #else
>>        template<typename _Seq = _Sequence, typename _Requires = typename
>>                enable_if<is_default_constructible<_Seq>::value>::type>
>> +        _GLIBCXX26_CONSTEXPR
>>         queue()
>>         : c() { }
>>
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        queue(const _Sequence& __c)
>>        : c(__c) { }
>>
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        queue(_Sequence&& __c)
>>        : c(std::move(__c)) { }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> -       explicit
>> +       explicit _GLIBCXX26_CONSTEXPR
>>         queue(const _Alloc& __a)
>>         : c(__a) { }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> +        _GLIBCXX26_CONSTEXPR
>>         queue(const _Sequence& __c, const _Alloc& __a)
>>         : c(__c, __a) { }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(_Sequence&& __c, const _Alloc& __a)
>>         : c(std::move(__c), __a) { }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(const queue& __q, const _Alloc& __a)
>>         : c(__q.c, __a) { }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(queue&& __q, const _Alloc& __a)
>>         : c(std::move(__q.c), __a) { }
>>  #endif
>> @@ -207,12 +212,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>  #ifdef __glibcxx_adaptor_iterator_pair_constructor // C++ >= 23 && HOSTED
>>        template<typename _InputIterator,
>>                typename = _RequireInputIter<_InputIterator>>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(_InputIterator __first, _InputIterator __last)
>>         : c(__first, __last) { }
>>
>>        template<typename _InputIterator, typename _Alloc,
>>                typename = _RequireInputIter<_InputIterator>,
>>                typename = _Uses<_Alloc>>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(_InputIterator __first, _InputIterator __last, const _Alloc& __a)
>>         : c(__first, __last, __a) { }
>>  #endif
>> @@ -223,6 +230,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         * @since C++23
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(from_range_t, _Rg&& __rg)
>>         : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg)))
>>         { }
>> @@ -233,6 +241,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         */
>>        template<__detail::__container_compatible_range<_Tp> _Rg,
>>                typename _Alloc>
>> +       _GLIBCXX26_CONSTEXPR
>>         queue(from_range_t, _Rg&& __rg, const _Alloc& __a)
>>         : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a))
>>         { }
>> @@ -241,13 +250,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        /**
>>         *  Returns true if the %queue is empty.
>>         */
>> -      _GLIBCXX_NODISCARD bool
>> +      _GLIBCXX_NODISCARD
>> +      _GLIBCXX26_CONSTEXPR bool
>>        empty() const
>>        { return c.empty(); }
>>
>>        /**  Returns the number of elements in the %queue.  */
>>        _GLIBCXX_NODISCARD
>> -      size_type
>> +      _GLIBCXX26_CONSTEXPR size_type
>>        size() const
>>        { return c.size(); }
>>
>> @@ -256,7 +266,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  element of the %queue.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        front()
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -268,7 +278,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  element of the %queue.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        front() const
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -280,7 +290,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  element of the %queue.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        back()
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -292,7 +302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  element of the %queue.
>>         */
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        back() const
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -308,18 +318,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  to it.  The time complexity of the operation depends on the
>>         *  underlying sequence.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push(const value_type& __x)
>>        { c.push_back(__x); }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push(value_type&& __x)
>>        { c.push_back(std::move(__x)); }
>>
>>  #if __cplusplus > 201402L
>>        template<typename... _Args>
>> -       decltype(auto)
>> +       _GLIBCXX26_CONSTEXPR decltype(auto)
>>         emplace(_Args&&... __args)
>>         { return c.emplace_back(std::forward<_Args>(__args)...); }
>>  #else
>> @@ -332,7 +342,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         push_range(_Rg&& __rg)
>>         {
>>           if constexpr (requires { c.append_range(std::forward<_Rg>(__rg)); })
>> @@ -353,7 +363,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  data is needed, it should be retrieved before pop() is
>>         *  called.
>>         */
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop()
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -361,7 +371,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        swap(queue& __q)
>>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>>        noexcept(__is_nothrow_swappable<_Sequence>::value)
>> @@ -430,7 +440,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>    */
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator==(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return __x.c == __y.c; }
>>
>> @@ -449,49 +459,49 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>    */
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return __x.c < __y.c; }
>>
>>    /// Based on operator==
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator!=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return !(__x == __y); }
>>
>>    /// Based on operator<
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return __y < __x; }
>>
>>    /// Based on operator<
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator<=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return !(__y < __x); }
>>
>>    /// Based on operator<
>>    template<typename _Tp, typename _Seq>
>>      _GLIBCXX_NODISCARD
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator>=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return !(__x < __y); }
>>
>>  #if __cpp_lib_three_way_comparison
>>    template<typename _Tp, three_way_comparable _Seq>
>>      [[nodiscard]]
>> -    inline compare_three_way_result_t<_Seq>
>> +    inline _GLIBCXX26_CONSTEXPR compare_three_way_result_t<_Seq>
>>      operator<=>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>>      { return __x.c <=> __y.c; }
>>  #endif
>>
>>  #if __cplusplus >= 201103L
>>    template<typename _Tp, typename _Seq>
>> -    inline
>> +    inline _GLIBCXX26_CONSTEXPR
>>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>>      // Constrained free swap overload, see p0185r1
>>      typename enable_if<__is_swappable<_Seq>::value>::type
>> @@ -611,14 +621,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         priority_queue()
>>         : c(), comp() { }
>>
>> -      _GLIBCXX26_CONSTEXPR
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        priority_queue(const _Compare& __x, const _Sequence& __s)
>>        : c(__s), comp(__x)
>>        { std::make_heap(c.begin(), c.end(), comp); }
>>
>> -      _GLIBCXX26_CONSTEXPR
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        priority_queue(const _Compare& __x, _Sequence&& __s = _Sequence())
>>        : c(std::move(__s)), comp(__x)
>>        { std::make_heap(c.begin(), c.end(), comp); }
>> @@ -633,8 +641,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        : c(std::move(__q.c)), comp(std::move(__q.comp))
>>        { __q.c.clear(); }
>>
>> -      _GLIBCXX26_CONSTEXPR
>> -      priority_queue&
>> +      _GLIBCXX26_CONSTEXPR priority_queue&
>>        operator=(priority_queue&& __q)
>>        noexcept(__and_<is_nothrow_move_assignable<_Sequence>,
>>                       is_nothrow_move_assignable<_Compare>>::value)
>> @@ -646,8 +653,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        }
>>
>>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
>> -       _GLIBCXX26_CONSTEXPR
>> -       explicit
>> +       explicit _GLIBCXX26_CONSTEXPR
>>         priority_queue(const _Alloc& __a)
>>         : c(__a), comp() { }
>>
>> @@ -830,14 +836,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        /**
>>         *  Returns true if the %queue is empty.
>>         */
>> -      _GLIBCXX_NODISCARD _GLIBCXX26_CONSTEXPR
>> -      bool
>> +      _GLIBCXX_NODISCARD
>> +      _GLIBCXX26_CONSTEXPR bool
>>        empty() const
>>        { return c.empty(); }
>>
>>        /**  Returns the number of elements in the %queue.  */
>> -      _GLIBCXX_NODISCARD _GLIBCXX26_CONSTEXPR
>> -      size_type
>> +      _GLIBCXX_NODISCARD
>> +      _GLIBCXX26_CONSTEXPR size_type
>>        size() const
>>        { return c.size(); }
>>
>> @@ -845,8 +851,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  Returns a read-only (constant) reference to the data at the first
>>         *  element of the %queue.
>>         */
>> -      _GLIBCXX_NODISCARD _GLIBCXX26_CONSTEXPR
>> -      const_reference
>> +      _GLIBCXX_NODISCARD
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        top() const
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -861,8 +867,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  The time complexity of the operation depends on the underlying
>>         *  sequence.
>>         */
>> -      _GLIBCXX26_CONSTEXPR
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push(const value_type& __x)
>>        {
>>         c.push_back(__x);
>> @@ -870,8 +875,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      _GLIBCXX26_CONSTEXPR
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push(value_type&& __x)
>>        {
>>         c.push_back(std::move(__x));
>> @@ -879,8 +883,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        }
>>
>>        template<typename... _Args>
>> -       _GLIBCXX26_CONSTEXPR
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         emplace(_Args&&... __args)
>>         {
>>           c.emplace_back(std::forward<_Args>(__args)...);
>> @@ -890,8 +893,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       _GLIBCXX26_CONSTEXPR
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         push_range(_Rg&& __rg)
>>         {
>>           if constexpr (requires { c.append_range(std::forward<_Rg>(__rg)); })
>> @@ -913,8 +915,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>         *  data is needed, it should be retrieved before pop() is
>>         *  called.
>>         */
>> -      _GLIBCXX26_CONSTEXPR
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop()
>>        {
>>         __glibcxx_requires_nonempty();
>> @@ -923,8 +924,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      _GLIBCXX26_CONSTEXPR
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        swap(priority_queue& __pq)
>>        noexcept(__and_<
>>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>> @@ -992,8 +992,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>  #if __cplusplus >= 201103L
>>    template<typename _Tp, typename _Sequence, typename _Compare>
>> -    _GLIBCXX26_CONSTEXPR
>> -    inline
>> +    inline _GLIBCXX26_CONSTEXPR
>>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>>      // Constrained free swap overload, see p0185r1
>>      typename enable_if<__and_<__is_swappable<_Sequence>,
>> diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h b/libstdc++-v3/include/bits/stl_uninitialized.h
>> index a8791a66ae8..a418c079d2a 100644
>> --- a/libstdc++-v3/include/bits/stl_uninitialized.h
>> +++ b/libstdc++-v3/include/bits/stl_uninitialized.h
>> @@ -666,6 +666,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>  #if __cplusplus >= 201103L
>>    template<typename _ITp, typename _IRef, typename _IPtr, typename _OTp,
>>            typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __uninitialized_copy_a(
>>        _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>> @@ -674,6 +675,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        allocator<_Tp>&);
>>
>>    template<typename _Iter, typename _OTp, typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      __enable_if_t<__is_random_access_iter<_Iter>::value,
>>                   _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>>
>>      __uninitialized_copy_a(_Iter __first, _Iter __last,
>> @@ -682,6 +684,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>    template<typename _ITp, typename _IRef, typename _IPtr, typename _OTp,
>>            typename _Tp>
>> +    _GLIBCXX26_CONSTEXPR
>>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>>      __uninitialized_move_a(
>>        _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
>> @@ -1003,7 +1006,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>    // Fills [first, last) with value_types constructed by the allocator
>>    // alloc, with no arguments passed to the construct call.
>>    template<typename _ForwardIterator, typename _Allocator>
>> -    void
>> +    _GLIBCXX20_CONSTEXPR void
>>      __uninitialized_default_a(_ForwardIterator __first,
>>                               _ForwardIterator __last,
>>                               _Allocator& __alloc)
>> @@ -1018,7 +1021,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>  #if _GLIBCXX_HOSTED
>>    template<typename _ForwardIterator, typename _Tp>
>> -    inline void
>> +    inline _GLIBCXX20_CONSTEXPR void
>>      __uninitialized_default_a(_ForwardIterator __first,
>>                               _ForwardIterator __last,
>>                               allocator<_Tp>&)
>> diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
>> index d14d4f4ef25..b7349fdef63 100644
>> --- a/libstdc++-v3/include/bits/version.def
>> +++ b/libstdc++-v3/include/bits/version.def
>> @@ -1463,6 +1463,24 @@ ftms = {
>>    };
>>  };
>>
>> +ftms = {
>> +  name = constexpr_deque;
>> +  values = {
>> +    v = 202502;
>> +    cxxmin = 26;
>> +    hosted = yes;
>> +  };
>> +};
>> +
>> +ftms = {
>> +  name = constexpr_queue;
>> +  values = {
>> +    v = 202502;
>> +    cxxmin = 26;
>> +    hosted = yes;
>> +  };
>> +};
>> +
>>  ftms = {
>>    name = constrained_equality;
>>    values = {
>> diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
>> index 9a73f771e72..142d550279f 100644
>> --- a/libstdc++-v3/include/bits/version.h
>> +++ b/libstdc++-v3/include/bits/version.h
>> @@ -1596,6 +1596,26 @@
>>  #endif /* !defined(__cpp_lib_constexpr_vector) */
>>  #undef __glibcxx_want_constexpr_vector
>>
>> +#if !defined(__cpp_lib_constexpr_deque)
>> +# if (__cplusplus >  202302L) && _GLIBCXX_HOSTED
>> +#  define __glibcxx_constexpr_deque 202502L
>> +#  if defined(__glibcxx_want_all) || defined(__glibcxx_want_constexpr_deque)
>> +#   define __cpp_lib_constexpr_deque 202502L
>> +#  endif
>> +# endif
>> +#endif /* !defined(__cpp_lib_constexpr_deque) */
>> +#undef __glibcxx_want_constexpr_deque
>> +
>> +#if !defined(__cpp_lib_constexpr_queue)
>> +# if (__cplusplus >  202302L) && _GLIBCXX_HOSTED
>> +#  define __glibcxx_constexpr_queue 202502L
>> +#  if defined(__glibcxx_want_all) || defined(__glibcxx_want_constexpr_queue)
>> +#   define __cpp_lib_constexpr_queue 202502L
>> +#  endif
>> +# endif
>> +#endif /* !defined(__cpp_lib_constexpr_queue) */
>> +#undef __glibcxx_want_constexpr_queue
>> +
>>  #if !defined(__cpp_lib_constrained_equality)
>>  # if (__cplusplus >  202002L) && (__glibcxx_three_way_comparison)
>>  #  define __glibcxx_constrained_equality 202411L
>> diff --git a/libstdc++-v3/include/debug/deque b/libstdc++-v3/include/debug/deque
>> index 00b4220051e..9a1f493e494 100644
>> --- a/libstdc++-v3/include/debug/deque
>> +++ b/libstdc++-v3/include/debug/deque
>> @@ -110,12 +110,15 @@ namespace __debug
>>        deque(const deque&) = default;
>>        deque(deque&&) = default;
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(const deque& __d, const __type_identity_t<_Allocator>& __a)
>>        : _Base(__d, __a) { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(deque&& __d, const __type_identity_t<_Allocator>& __a)
>>        : _Safe(std::move(__d)), _Base(std::move(__d), __a) { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(initializer_list<value_type> __l,
>>             const allocator_type& __a = allocator_type())
>>        : _Base(__l, __a) { }
>> @@ -123,15 +126,16 @@ namespace __debug
>>        ~deque() = default;
>>  #endif
>>
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        deque(const _Allocator& __a)
>>        : _Base(__a) { }
>>
>>  #if __cplusplus >= 201103L
>> -      explicit
>> +      explicit _GLIBCXX26_CONSTEXPR
>>        deque(size_type __n, const _Allocator& __a = _Allocator())
>>        : _Base(__n, __a) { }
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(size_type __n, const __type_identity_t<_Tp>& __value,
>>             const _Allocator& __a = _Allocator())
>>        : _Base(__n, __value, __a) { }
>> @@ -145,23 +149,26 @@ namespace __debug
>>  #if __cplusplus >= 201103L
>>        template<class _InputIterator,
>>                typename = std::_RequireInputIter<_InputIterator>>
>> +       _GLIBCXX26_CONSTEXPR
>>  #else
>>        template<class _InputIterator>
>>  #endif
>>         deque(_InputIterator __first, _InputIterator __last,
>>               const _Allocator& __a = _Allocator())
>> -       : _Base(__gnu_debug::__base(
>> -                 __glibcxx_check_valid_constructor_range(__first, __last)),
>> +       : _Base(__gnu_debug::__base(std::__is_constant_evaluated() ? __first
>> +                 : __glibcxx_check_valid_constructor_range(__first, __last)),
>>                 __gnu_debug::__base(__last), __a)
>>         { }
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> +       _GLIBCXX26_CONSTEXPR
>>         deque(from_range_t, _Rg&& __rg, const _Allocator& __a = _Allocator())
>>         : _Base(from_range, std::forward<_Rg>(__rg), __a)
>>         { }
>>  #endif
>>
>> +      _GLIBCXX26_CONSTEXPR
>>        deque(_Base_ref __x)
>>        : _Base(__x._M_ref) { }
>>
>> @@ -172,11 +179,12 @@ namespace __debug
>>        deque&
>>        operator=(deque&&) = default;
>>
>> -      deque&
>> +      _GLIBCXX26_CONSTEXPR deque&
>>        operator=(initializer_list<value_type> __l)
>>        {
>>         _Base::operator=(__l);
>> -       this->_M_invalidate_all();
>> +       if (!std::__is_constant_evaluated())
>> +         this->_M_invalidate_all();
>>         return *this;
>>        }
>>  #endif
>> @@ -187,9 +195,13 @@ namespace __debug
>>  #else
>>        template<class _InputIterator>
>>  #endif
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         assign(_InputIterator __first, _InputIterator __last)
>>         {
>> +         if (std::__is_constant_evaluated())
>> +           return _Base::assign(__gnu_debug::__unsafe(__first),
>> +                                __gnu_debug::__unsafe(__last));
>> +
>>           typename __gnu_debug::_Distance_traits<_InputIterator>::__type __dist;
>>           __glibcxx_check_valid_range2(__first, __last, __dist);
>>           if (__dist.second >= __gnu_debug::__dp_sign)
>> @@ -201,29 +213,32 @@ namespace __debug
>>           this->_M_invalidate_all();
>>         }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        assign(size_type __n, const _Tp& __t)
>>        {
>>         _Base::assign(__n, __t);
>> -       this->_M_invalidate_all();
>> +       if (!std::__is_constant_evaluated())
>> +         this->_M_invalidate_all();
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        assign(initializer_list<value_type> __l)
>>        {
>>         _Base::assign(__l);
>> -       this->_M_invalidate_all();
>> +       if (!std::__is_constant_evaluated())
>> +         this->_M_invalidate_all();
>>        }
>>  #endif
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         assign_range(_Rg&& __rg)
>>         {
>>           _Base::assign_range(std::forward<_Rg>(__rg));
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>         }
>>  #endif
>>
>> @@ -231,69 +246,69 @@ namespace __debug
>>
>>        // iterators:
>>        _GLIBCXX_NODISCARD
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        begin() _GLIBCXX_NOEXCEPT
>>        { return iterator(_Base::begin(), this); }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        begin() const _GLIBCXX_NOEXCEPT
>>        { return const_iterator(_Base::begin(), this); }
>>
>>        _GLIBCXX_NODISCARD
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        end() _GLIBCXX_NOEXCEPT
>>        { return iterator(_Base::end(), this); }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        end() const _GLIBCXX_NOEXCEPT
>>        { return const_iterator(_Base::end(), this); }
>>
>>        _GLIBCXX_NODISCARD
>> -      reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR reverse_iterator
>>        rbegin() _GLIBCXX_NOEXCEPT
>>        { return reverse_iterator(end()); }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        rbegin() const _GLIBCXX_NOEXCEPT
>>        { return const_reverse_iterator(end()); }
>>
>>        _GLIBCXX_NODISCARD
>> -      reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR reverse_iterator
>>        rend() _GLIBCXX_NOEXCEPT
>>        { return reverse_iterator(begin()); }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        rend() const _GLIBCXX_NOEXCEPT
>>        { return const_reverse_iterator(begin()); }
>>
>>  #if __cplusplus >= 201103L
>>        [[__nodiscard__]]
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        cbegin() const noexcept
>>        { return const_iterator(_Base::begin(), this); }
>>
>>        [[__nodiscard__]]
>> -      const_iterator
>> +      _GLIBCXX26_CONSTEXPR const_iterator
>>        cend() const noexcept
>>        { return const_iterator(_Base::end(), this); }
>>
>>        [[__nodiscard__]]
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        crbegin() const noexcept
>>        { return const_reverse_iterator(end()); }
>>
>>        [[__nodiscard__]]
>> -      const_reverse_iterator
>> +      _GLIBCXX26_CONSTEXPR const_reverse_iterator
>>        crend() const noexcept
>>        { return const_reverse_iterator(begin()); }
>>  #endif
>>
>>      private:
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        _M_invalidate_after_nth(difference_type __n)
>>        {
>>         typedef __gnu_debug::_After_nth_from<_Base_const_iterator> _After_nth;
>> @@ -306,9 +321,12 @@ namespace __debug
>>        using _Base::max_size;
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        resize(size_type __sz)
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return _Base::resize(__sz);
>> +
>>         bool __invalidate_all = __sz > this->size();
>>         if (__sz < this->size())
>>           this->_M_invalidate_after_nth(__sz);
>> @@ -319,9 +337,12 @@ namespace __debug
>>           this->_M_invalidate_all();
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        resize(size_type __sz, const _Tp& __c)
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return _Base::resize(__sz, __c);
>> +
>>         bool __invalidate_all = __sz > this->size();
>>         if (__sz < this->size())
>>           this->_M_invalidate_after_nth(__sz);
>> @@ -347,11 +368,12 @@ namespace __debug
>>  #endif
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        shrink_to_fit() noexcept
>>        {
>>         if (_Base::_M_shrink_to_fit())
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>        }
>>  #endif
>>
>> @@ -359,7 +381,7 @@ namespace __debug
>>
>>        // element access:
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        operator[](size_type __n) _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_subscript(__n);
>> @@ -367,7 +389,7 @@ namespace __debug
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        operator[](size_type __n) const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_subscript(__n);
>> @@ -377,7 +399,7 @@ namespace __debug
>>        using _Base::at;
>>
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        front() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_nonempty();
>> @@ -385,7 +407,7 @@ namespace __debug
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        front() const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_nonempty();
>> @@ -393,7 +415,7 @@ namespace __debug
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      reference
>> +      _GLIBCXX26_CONSTEXPR reference
>>        back() _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_nonempty();
>> @@ -401,7 +423,7 @@ namespace __debug
>>        }
>>
>>        _GLIBCXX_NODISCARD
>> -      const_reference
>> +      _GLIBCXX26_CONSTEXPR const_reference
>>        back() const _GLIBCXX_NOEXCEPT
>>        {
>>         __glibcxx_check_nonempty();
>> @@ -409,14 +431,14 @@ namespace __debug
>>        }
>>
>>        // 23.2.1.3 modifiers:
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_front(const _Tp& __x)
>>        {
>>         _Base::push_front(__x);
>>         this->_M_invalidate_all();
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_back(const _Tp& __x)
>>        {
>>         _Base::push_back(__x);
>> @@ -424,24 +446,25 @@ namespace __debug
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_front(_Tp&& __x)
>>        { emplace_front(std::move(__x)); }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        push_back(_Tp&& __x)
>>        { emplace_back(std::move(__x)); }
>>
>>        template<typename... _Args>
>>  #if __cplusplus > 201402L
>> -       reference
>> +       _GLIBCXX26_CONSTEXPR reference
>>  #else
>>         void
>>  #endif
>>         emplace_front(_Args&&... __args)
>>         {
>>           _Base::emplace_front(std::forward<_Args>(__args)...);
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>  #if __cplusplus > 201402L
>>           return front();
>>  #endif
>> @@ -449,23 +472,29 @@ namespace __debug
>>
>>        template<typename... _Args>
>>  #if __cplusplus > 201402L
>> -       reference
>> +       _GLIBCXX26_CONSTEXPR reference
>>  #else
>>         void
>>  #endif
>>         emplace_back(_Args&&... __args)
>>         {
>>           _Base::emplace_back(std::forward<_Args>(__args)...);
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>  #if __cplusplus > 201402L
>>           return back();
>>  #endif
>>         }
>>
>>        template<typename... _Args>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         emplace(const_iterator __position, _Args&&... __args)
>>         {
>> +         if (std::__is_constant_evaluated())
>> +           return iterator(_Base::emplace(__position.base(),
>> +                                          std::forward<_Args>(__args)...),
>> +                           this);
>> +
>>           __glibcxx_check_insert(__position);
>>           _Base_iterator __res = _Base::emplace(__position.base(),
>>                                                 std::forward<_Args>(__args)...);
>> @@ -474,13 +503,16 @@ namespace __debug
>>         }
>>  #endif
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>  #if __cplusplus >= 201103L
>>        insert(const_iterator __position, const _Tp& __x)
>>  #else
>>        insert(iterator __position, const _Tp& __x)
>>  #endif
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return iterator(_Base::insert(__position.base(), __x), this);
>> +
>>         __glibcxx_check_insert(__position);
>>         _Base_iterator __res = _Base::insert(__position.base(), __x);
>>         this->_M_invalidate_all();
>> @@ -488,13 +520,16 @@ namespace __debug
>>        }
>>
>>  #if __cplusplus >= 201103L
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, _Tp&& __x)
>>        { return emplace(__position, std::move(__x)); }
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, initializer_list<value_type> __l)
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return iterator(_Base::insert(__position.base(), __l), this);
>> +
>>         __glibcxx_check_insert(__position);
>>         _Base_iterator __res = _Base::insert(__position.base(), __l);
>>         this->_M_invalidate_all();
>> @@ -503,9 +538,12 @@ namespace __debug
>>  #endif
>>
>>  #if __cplusplus >= 201103L
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>        insert(const_iterator __position, size_type __n, const _Tp& __x)
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return iterator(_Base::insert(__position.base(), __n, __x), this);
>> +
>>         __glibcxx_check_insert(__position);
>>         _Base_iterator __res = _Base::insert(__position.base(), __n, __x);
>>         this->_M_invalidate_all();
>> @@ -524,10 +562,15 @@ namespace __debug
>>  #if __cplusplus >= 201103L
>>        template<class _InputIterator,
>>                typename = std::_RequireInputIter<_InputIterator>>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         insert(const_iterator __position,
>>                _InputIterator __first, _InputIterator __last)
>>         {
>> +         if (std::__is_constant_evaluated())
>> +           return iterator(_Base::insert(__position.base(),
>> +                                         __gnu_debug::__unsafe(__first),
>> +                                         __gnu_debug::__unsafe(__last)), this);
>> +
>>           typename __gnu_debug::_Distance_traits<_InputIterator>::__type __dist;
>>           __glibcxx_check_insert_range(__position, __first, __last, __dist);
>>           _Base_iterator __res;
>> @@ -563,54 +606,66 @@ namespace __debug
>>
>>  #if __glibcxx_containers_ranges // C++ >= 23
>>        template<__detail::__container_compatible_range<_Tp> _Rg>
>> -       iterator
>> +       _GLIBCXX26_CONSTEXPR iterator
>>         insert_range(const_iterator __pos, _Rg&& __rg)
>>         {
>>           auto __res = _Base::insert_range(__pos.base(), std::forward<_Rg>(__rg));
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>           return iterator(__res, this);
>>         }
>>
>>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         prepend_range(_Rg&& __rg)
>>         {
>>           _Base::prepend_range(std::forward<_Rg>(__rg));
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>         }
>>
>>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
>> -       void
>> +       _GLIBCXX26_CONSTEXPR void
>>         append_range(_Rg&& __rg)
>>         {
>>           _Base::append_range(std::forward<_Rg>(__rg));
>> -         this->_M_invalidate_all();
>> +         if (!std::__is_constant_evaluated())
>> +           this->_M_invalidate_all();
>>         }
>>  #endif
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop_front() _GLIBCXX_NOEXCEPT
>>        {
>> -       __glibcxx_check_nonempty();
>> -       this->_M_invalidate_if(_Equal(_Base::begin()));
>> +       if (!std::__is_constant_evaluated())
>> +         {
>> +           __glibcxx_check_nonempty();
>> +           this->_M_invalidate_if(_Equal(_Base::begin()));
>> +         }
>>         _Base::pop_front();
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        pop_back() _GLIBCXX_NOEXCEPT
>>        {
>> -       __glibcxx_check_nonempty();
>> -       this->_M_invalidate_if(_Equal(--_Base::end()));
>> +       if (!std::__is_constant_evaluated())
>> +         {
>> +           __glibcxx_check_nonempty();
>> +           this->_M_invalidate_if(_Equal(_Base::begin()));
>> +         }
>>         _Base::pop_back();
>>        }
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>  #if __cplusplus >= 201103L
>>        erase(const_iterator __position)
>>  #else
>> -      erase(iterator __position)
>> +      erase(iterator __position)
>>  #endif
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return iterator(_Base::erase(__position.base()), this);
>> +
>>         __glibcxx_check_erase(__position);
>>  #if __cplusplus >= 201103L
>>         _Base_const_iterator __victim = __position.base();
>> @@ -630,13 +685,16 @@ namespace __debug
>>           }
>>        }
>>
>> -      iterator
>> +      _GLIBCXX26_CONSTEXPR iterator
>>  #if __cplusplus >= 201103L
>>        erase(const_iterator __first, const_iterator __last)
>>  #else
>>        erase(iterator __first, iterator __last)
>>  #endif
>>        {
>> +       if (std::__is_constant_evaluated())
>> +         return iterator(_Base::erase(__first.base(), __last.base()), this);
>> +
>>         // _GLIBCXX_RESOLVE_LIB_DEFECTS
>>         // 151. can't currently clear() empty container
>>         __glibcxx_check_erase_range(__first, __last);
>> @@ -677,25 +735,27 @@ namespace __debug
>>           }
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        swap(deque& __x)
>>        _GLIBCXX_NOEXCEPT_IF( noexcept(declval<_Base&>().swap(__x)) )
>>        {
>> -       _Safe::_M_swap(__x);
>> +       if (!std::__is_constant_evaluated())
>> +         _Safe::_M_swap(__x);
>>         _Base::swap(__x);
>>        }
>>
>> -      void
>> +      _GLIBCXX26_CONSTEXPR void
>>        clear() _GLIBCXX_NOEXCEPT
>>        {
>>         _Base::clear();
>> -       this->_M_invalidate_all();
>> +       if (!std::__is_constant_evaluated())
>> +         this->_M_invalidate_all();
>>        }
>>
>> -      _Base&
>> +      _GLIBCXX26_CONSTEXPR _Base&
>>        _M_base() _GLIBCXX_NOEXCEPT      { return *this; }
>>
>> -      const _Base&
>> +      _GLIBCXX26_CONSTEXPR const _Base&
>>        _M_base() const _GLIBCXX_NOEXCEPT        { return *this; }
>>      };
>>
>> @@ -722,7 +782,7 @@ namespace __debug
>>  #endif
>>
>>    template<typename _Tp, typename _Alloc>
>> -    inline bool
>> +    inline _GLIBCXX26_CONSTEXPR bool
>>      operator==(const deque<_Tp, _Alloc>& __lhs,
>>                const deque<_Tp, _Alloc>& __rhs)
>>      { return __lhs._M_base() == __rhs._M_base(); }
>> @@ -765,7 +825,7 @@ namespace __debug
>>  #endif // three-way comparison
>>
>>    template<typename _Tp, typename _Alloc>
>> -    inline void
>> +    inline _GLIBCXX26_CONSTEXPR void
>>      swap(deque<_Tp, _Alloc>& __lhs, deque<_Tp, _Alloc>& __rhs)
>>      _GLIBCXX_NOEXCEPT_IF(noexcept(__lhs.swap(__rhs)))
>>      { __lhs.swap(__rhs); }
>> @@ -775,14 +835,14 @@ namespace __debug
>>  #ifdef __glibcxx_erase_if // C++ >= 20 && HOSTED
>>  _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>    template<typename _Tp, typename _Alloc, typename _Predicate>
>> -    inline typename __debug::deque<_Tp, _Alloc>::size_type
>> +    inline _GLIBCXX26_CONSTEXPR typename __debug::deque<_Tp, _Alloc>::size_type
>>      erase_if(__debug::deque<_Tp, _Alloc>& __cont, _Predicate __pred)
>>      {
>>        return __detail::__erase_if(__cont, __cont._M_base(), std::move(__pred));
>>      }
>>
>>    template<typename _Tp, typename _Alloc, typename _Up = _Tp>
>> -    inline typename __debug::deque<_Tp, _Alloc>::size_type
>> +    inline _GLIBCXX26_CONSTEXPR typename __debug::deque<_Tp, _Alloc>::size_type
>>      erase(__debug::deque<_Tp, _Alloc>& __cont, const _Up& __value)
>>      { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
>>  _GLIBCXX_END_NAMESPACE_VERSION
>> diff --git a/libstdc++-v3/include/std/deque b/libstdc++-v3/include/std/deque
>> index 3b2f34fc707..f889c2cf4c7 100644
>> --- a/libstdc++-v3/include/std/deque
>> +++ b/libstdc++-v3/include/std/deque
>> @@ -73,6 +73,7 @@
>>
>>  #define __glibcxx_want_algorithm_default_value_type
>>  #define __glibcxx_want_allocator_traits_is_always_equal
>> +#define __glibcxx_want_constexpr_deque
>>  #define __glibcxx_want_containers_ranges
>>  #define __glibcxx_want_erase_if
>>  #define __glibcxx_want_hardened_deque
>> @@ -103,13 +104,15 @@ namespace std _GLIBCXX_VISIBILITY(default)
>>  _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>
>>    template<typename _Tp, typename _Alloc, typename _Predicate>
>> -    inline typename _GLIBCXX_STD_C::deque<_Tp, _Alloc>::size_type
>> +    inline _GLIBCXX26_CONSTEXPR
>> +    typename _GLIBCXX_STD_C::deque<_Tp, _Alloc>::size_type
>>      erase_if(_GLIBCXX_STD_C::deque<_Tp, _Alloc>& __cont, _Predicate __pred)
>>      { return __detail::__erase_if(__cont, __cont, std::move(__pred)); }
>>
>>    template<typename _Tp, typename _Alloc,
>>            typename _Up _GLIBCXX26_DEF_VAL_T(_Tp)>
>> -    inline typename _GLIBCXX_STD_C::deque<_Tp, _Alloc>::size_type
>> +    inline _GLIBCXX26_CONSTEXPR
>> +    typename _GLIBCXX_STD_C::deque<_Tp, _Alloc>::size_type
>>      erase(_GLIBCXX_STD_C::deque<_Tp, _Alloc>& __cont, const _Up& __value)
>>      { return std::erase_if(__cont, __gnu_cxx::__ops::__equal_to(__value)); }
>>
>> diff --git a/libstdc++-v3/include/std/queue b/libstdc++-v3/include/std/queue
>> index 13e25482125..061e7cae5d3 100644
>> --- a/libstdc++-v3/include/std/queue
>> +++ b/libstdc++-v3/include/std/queue
>> @@ -63,6 +63,7 @@
>>
>>  #define __glibcxx_want_adaptor_iterator_pair_constructor
>>  #define __glibcxx_want_containers_ranges
>> +#define __glibcxx_want_constexpr_queue
>>  #include <bits/version.h>
>>
>>  #include <deque>
>> @@ -74,6 +75,12 @@
>>  #ifdef __glibcxx_format_ranges // C++ >= 23 && HOSTED
>>  #include <bits/formatfwd.h>
>>
>> +#ifdef __glibcxx_constexpr_format // C++ >= 26 && HOSTED && CXX11 strings
>> +# define _GLIBCXX_CONSTEXPR_FORMAT constexpr
>> +#else
>> +# define _GLIBCXX_CONSTEXPR_FORMAT
>> +#endif
>> +
>>  namespace std _GLIBCXX_VISIBILITY(default)
>>  {
>>  _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> @@ -99,6 +106,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        // Standard declares this as template accepting unconstrained
>>        // FormatContext type.
>>        template<typename _Out>
>> +       _GLIBCXX_CONSTEXPR_FORMAT
>>         typename basic_format_context<_Out, _CharT>::iterator
>>         format(__maybe_const_adaptor& __a,
>>                basic_format_context<_Out, _CharT>& __fc) const
>> @@ -141,6 +149,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        // Standard declares this as template accepting unconstrained
>>        // FormatContext type.
>>        template<typename _Out>
>> +       _GLIBCXX_CONSTEXPR_FORMAT
>>         typename basic_format_context<_Out, _CharT>::iterator
>>         format(__maybe_const_adaptor& __a,
>>                basic_format_context<_Out, _CharT>& __fc) const
>> @@ -163,6 +172,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>        priority_queue<_Tp, _Container, _Comparator>> = false;
>>  #endif
>>
>> +#undef _GLIBCXX_CONSTEXPR_FORMAT
>> +
>>  _GLIBCXX_END_NAMESPACE_VERSION
>>  } // namespace std
>>  #endif // __glibcxx_format_ranges
>> diff --git a/libstdc++-v3/testsuite/23_containers/deque/constexpr.cc b/libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
>> new file mode 100644
>> index 00000000000..50e45a639ab
>> --- /dev/null
>> +++ b/libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
>> @@ -0,0 +1,334 @@
>> +// { dg-do compile { target c++26 } }
>> +
>> +#include <deque>
>> +
>> +#ifndef __cpp_lib_constexpr_deque
>> +#error "Feature test macro for constexpr deque is missing in <deque>"
>> +#elif __cpp_lib_constexpr_deque != 202502L
>> +# error "Feature test macro for constexpr deque has wrong value in <deque>"
>> +#endif
>> +
>> +#include <ranges>
>> +#include <numeric>
>> +#include <testsuite_hooks.h>
>> +#include <testsuite_iterators.h>
>> +#include <testsuite_allocator.h>
>> +
>> +using namespace __gnu_test;
>> +
>> +template<typename Alloc>
>> +constexpr bool
>> +ctor_tests()
>> +{
>> +  Alloc alloc;
>> +
>> +  std::deque<int, Alloc> dq2(alloc);
>> +  std::deque<int, Alloc> dq3(4, alloc);
>> +  VERIFY( dq3.front() == 0 );
>> +  VERIFY( dq3.size() == 4 );
>> +  std::deque<int, Alloc> dq4(4, 5, alloc);
>> +  VERIFY( dq4.front() == 5 );
>> +  VERIFY( dq4.size() == 4 );
>> +
>> +  auto rg = {2, 3, 5, 7};
>> +  std::deque<int> dq5(rg.begin(), rg.end());
>> +  VERIFY( dq5.front() == 2 );
>> +  VERIFY( dq5.back() == 7 );
>> +  VERIFY( dq5.size() == 4 );
>> +
>> +  std::deque<int> dq6(std::from_range, rg);
>> +  VERIFY( dq6 == dq5 );
>> +
>> +  std::deque<int> dq1{1, 2, 3};
>> +  std::deque<int> dq7(dq1);
>> +  VERIFY( dq7 == dq1 );
>> +  std::deque<int>dq8(std::move(dq1));
>> +  VERIFY( dq8 == dq7 );
>> +
>> +  dq2.insert_range(dq2.begin(), rg);
>> +  std::deque<int, Alloc> dq9(dq2, alloc);
>> +  std::deque<int, Alloc> dq10(std::move(dq2), alloc);
>> +  VERIFY( dq9 == dq10 );
>> +  std::deque<int, Alloc> dq11(rg, alloc);
>> +  VERIFY( dq11 == dq10 );
>> +
>> +  return true;
>> +}
>> +static_assert( ctor_tests<std::allocator<int>>() );
>> +static_assert( ctor_tests<SimpleAllocator<int>>() );
>> +
>> +constexpr bool
>> +insert_tests()
>> +{
>> +  std::deque<int> dq1 {};
>> +
>> +  auto rg = {1, 2, 3, 4, 5};
>> +
>> +  dq1.insert(dq1.begin() , 1);
>> +  dq1.insert(dq1.end(), 2);
>> +  VERIFY( dq1.size() == 2 );
>> +  VERIFY( dq1.front() == 1 );
>> +  VERIFY( dq1.back() == 2 );
>> +
>> +  dq1.insert(dq1.end(), 1, 3);
>> +
>> +  dq1.insert(dq1.end(), rg.begin() + 3, rg.end());
>> +
>> +  VERIFY( dq1[0] == 1 );
>> +  VERIFY( dq1[1] == 2 );
>> +  VERIFY( dq1[2] == 3 );
>> +  VERIFY( dq1[3] == 4 );
>> +  VERIFY( dq1[4] == 5 );
>> +  dq1.clear();
>> +
>> +  dq1.insert(dq1.begin(), rg.begin(), rg.end());
>> +  VERIFY( dq1[0] == 1 );
>> +  VERIFY( dq1[1] == 2 );
>> +  VERIFY( dq1[2] == 3 );
>> +  VERIFY( dq1[3] == 4 );
>> +  VERIFY( dq1[4] == 5 );
>> +
>> +  dq1.insert_range(dq1.end(), rg);
>> +  VERIFY( dq1[5] == 1 );
>> +  VERIFY( dq1[6] == 2 );
>> +  VERIFY( dq1[7] == 3 );
>> +  VERIFY( dq1[8] == 4 );
>> +  VERIFY( dq1[9] == 5 );
>> +
>> +  std::deque<int>dq2 {2, 3, 5, 7};
>> +  dq2.erase(dq2.begin());
>> +  VERIFY( dq2.size() == 3 );
>> +  dq2.clear();
>> +  VERIFY( dq2.size() == 0);
>> +  VERIFY( dq2.empty() );
>> +
>> +  std::deque<int> dq3, dq4;
>> +  dq3.insert_range(dq3.begin(), rg);
>> +  dq4.append_range(rg);
>> +  VERIFY( dq3 == dq4 );
>> +  dq3.erase(dq3.begin(), dq3.end());
>> +  dq3.prepend_range(rg);
>> +  VERIFY( dq3 == dq4 );
>> +
>> +  struct S {
>> +    int foo;
>> +    constexpr S (int i, int j) : foo{i + j} {}
>> +  };
>> +  std::deque<S> dq5 {};
>> +  dq5.emplace(dq5.end(), 0, 1);
>> +  const S& s1 = dq5.emplace_back(1, 1);
>> +  const S& s2 = dq5.emplace_front(2, 1);
>> +  VERIFY( dq5.front().foo == 3 );
>> +  VERIFY( dq5.back().foo == 2 );
>> +  VERIFY( dq5[1].foo == 1 );
>> +
>> +  std::deque<int> dq6 {2, 3};
>> +  dq6.push_front(1);
>> +  dq6.push_back(4);
>> +  VERIFY( dq6.front() == 1);
>> +  VERIFY( dq6.back() == 4 );
>> +  dq6.pop_front();
>> +  dq6.pop_back();
>> +
>> +  std::deque<int> dq7 {1, 2};
>> +  dq7.resize(4);
>> +  VERIFY( dq7.back() == 0 );
>> +  dq7.resize(2);
>> +  VERIFY( dq7.front() == 1 );
>> +  VERIFY( dq7.back() == 2 );
>> +  dq7.clear();
>> +  dq7.resize(2);
>> +  VERIFY( dq7.front() == 0 );
>> +  VERIFY( dq7.back() == 0 );
>> +
>> +  std::deque<int> dq8 {1, 4};
>> +  dq8.swap(dq6);
>> +  VERIFY( dq6.front() == 1 );
>> +  VERIFY( dq6.back() == 4 );
>> +  VERIFY( dq8.front() == 2 );
>> +  VERIFY( dq8.back() == 3 );
>> +
>> +  return true;
>> +}
>> +
>> +static_assert( insert_tests() );
>> +
>> +constexpr bool
>> +iterators_tests()
>> +{
>> +  std::deque<int> dq0 {};
>> +  VERIFY( dq0.begin() == dq0.end() );
>> +  dq0.resize(1);
>> +  VERIFY( dq0.begin() != dq0.end() );
>> +  dq0.resize(2);
>> +  VERIFY( dq0.begin() != dq0.end() );
>> +  VERIFY( dq0.cbegin() == dq0.begin() );
>> +  VERIFY( dq0.crbegin() == dq0.rbegin() );
>> +  VERIFY( dq0.cend() == dq0.end() );
>> +  VERIFY( dq0.crend() == dq0.rend() );
>> +
>> +  auto it = dq0.begin();
>> +  VERIFY( it[0] == 0 );
>> +  VERIFY( &*it == &dq0.front() );
>> +  VERIFY( &it[1] == &dq0[1] );
>> +  VERIFY( it++ == dq0.begin() );
>> +  VERIFY( ++it == dq0.end() );
>> +  VERIFY( (it - 2) == dq0.begin() );
>> +  VERIFY( (it - dq0.begin()) == 2 );
>> +  it -= 2;
>> +  it += 1;
>> +  VERIFY( (it + 1) == dq0.end() );
>> +  VERIFY( (1 + it) == dq0.end() );
>> +  it = it + 1;
>> +  auto it2 = dq0.begin();
>> +  std::swap(it, it2);
>> +  VERIFY( it == dq0.begin() );
>> +  VERIFY( it2 == dq0.end() );
>> +
>> +  auto rit = dq0.rbegin();
>> +  VERIFY( rit[0] == 0 );
>> +  VERIFY( &*rit == &dq0.back() );
>> +  VERIFY( &rit[1] == &dq0[0] );
>> +  VERIFY( rit++ == dq0.rbegin() );
>> +  VERIFY( ++rit == dq0.rend() );
>> +  VERIFY( (rit - 2) == dq0.rbegin() );
>> +  VERIFY( (rit - dq0.rbegin()) == 2 );
>> +  rit -= 2;
>> +  rit += 1;
>> +  VERIFY( (rit + 1) == dq0.rend() );
>> +  VERIFY( (1 + rit) == dq0.rend() );
>> +  rit = rit + 1;
>> +  auto rit2 = dq0.rbegin();
>> +  std::swap(rit, rit2);
>> +  VERIFY( rit == dq0.rbegin() );
>> +  VERIFY( rit2 == dq0.rend() );
>> +
>> +  return true;
>> +}
>> +static_assert( iterators_tests() );
>> +
>> +constexpr bool
>> +capacity_tests()
>> +{
>> +  std::deque<int> dq0 {};
>> +  VERIFY( dq0.empty() );
>> +  VERIFY( dq0.max_size() );
>> +  dq0.push_front(0);
>> +  VERIFY( dq0.size() == 1 );
>> +  dq0.erase(dq0.begin());
>> +  dq0.shrink_to_fit();
>> +
>> +  return true;
>> +}
>> +static_assert( capacity_tests() );
>> +
>> +constexpr bool
>> +nonmember_tests()
>> +{
>> +  std::deque<int> dq0 {0, 1};
>> +  std::deque<int> dq1 {0, 1};
>> +
>> +  VERIFY( (dq0 == dq1) == true );
>> +  VERIFY( (dq0 != dq1) == false );
>> +  VERIFY( (dq0 <= dq1) == true );
>> +  VERIFY( (dq0 >= dq1) == true );
>> +  VERIFY( (dq0  < dq1) == false );
>> +  VERIFY( (dq0  > dq1) == false );
>> +  VERIFY( (dq0 <=> dq1) == 0 );
>> +  VERIFY( (dq0 <=> dq1) <= 0 );
>> +  VERIFY( (dq0 <=> dq1) >= 0 );
>> +
>> +  std::deque<int> dq2 {2, 4};
>> +  std::swap(dq1, dq2);
>> +
>> +  VERIFY( (dq0 == dq1) == false );
>> +  VERIFY( (dq0 != dq1) == true );
>> +  VERIFY( (dq0 <= dq1) == true );
>> +  VERIFY( (dq0 >= dq1) == false );
>> +  VERIFY( (dq0  < dq1) == true );
>> +  VERIFY( (dq0  > dq1) == false );
>> +  VERIFY( (dq0 <=> dq1) != 0 );
>> +  VERIFY( (dq0 <=> dq1) <= 0 );
>> +  VERIFY( (dq0 <=> dq1)  < 0 );
>> +
>> +  std::erase(dq0, 0);
>> +  VERIFY( dq0.front() == 1 );
>> +
>> +  std::erase_if(dq1, [](int x) { return x % 2 == 0; });
>> +  VERIFY( dq1.empty() );
>> +  return true;
>> +}
>> +static_assert( nonmember_tests() );
>> +
>> +template<typename Range>
>> +constexpr bool
>> +ranges_test()
>> +{
>> +  using Tp = std::ranges::range_value_t<Range>;
>> +  Tp a[] {0, 1, 2, 3, 4,
>> +   5, 6, 7, 8, 9};
>> +
>> +  // Constructor tests
>> +  auto dq1 = std::deque<Tp>(std::from_range, Range(a, a+5));
>> +  VERIFY( dq1[0] == 0 );
>> +  VERIFY( dq1[1] == 1 );
>> +  VERIFY( dq1[2] == 2 );
>> +  VERIFY( dq1[3] == 3 );
>> +  VERIFY( dq1[4] == 4 );
>> +
>> +  // Insert tests
>> +  std::deque<Tp> dq2;
>> +  dq2.insert_range(dq2.begin(), Range(a, a+5));
>> +  VERIFY( dq2[0] == 0 );
>> +  VERIFY( dq2[1] == 1 );
>> +  VERIFY( dq2[2] == 2 );
>> +  VERIFY( dq2[3] == 3 );
>> +  VERIFY( dq2[4] == 4 );
>> +
>> +  std::deque<Tp> dq3;
>> +  dq3.assign_range(Range(a, a+5));
>> +  VERIFY( dq2 == dq3 );
>> +
>> +  dq2.insert_range(dq2.end(), Range(a+5, a+10));
>> +  VERIFY( dq2[5] == 5 );
>> +  VERIFY( dq2[6] == 6 );
>> +  VERIFY( dq2[7] == 7 );
>> +  VERIFY( dq2[8] == 8 );
>> +  VERIFY( dq2[9] == 9 );
>> +
>> +  std::deque<Tp> dq4;
>> +  dq4.prepend_range(Range(a, a+5));
>> +  dq4.append_range(Range(a+5, a+10));
>> +  VERIFY( dq2 == dq4 );
>> +
>> +  return true;
>> +}
>> +
>> +static_assert( ranges_test<test_forward_range<int>>() );
>> +static_assert( ranges_test<test_forward_sized_range<int>>() );
>> +static_assert( ranges_test<test_sized_range_sized_sent<int, forward_iterator_wrapper>>() );
>> +
>> +static_assert( ranges_test<test_input_range<int>>() );
>> +static_assert( ranges_test<test_input_sized_range<int>>() );
>> +static_assert( ranges_test<test_sized_range_sized_sent<int, input_iterator_wrapper>>() );
>> +
>> +static_assert( ranges_test<test_range<int, input_iterator_wrapper_nocopy>>() );
>> +static_assert( ranges_test<test_sized_range<int, input_iterator_wrapper_nocopy>>() );
>> +static_assert( ranges_test<test_sized_range_sized_sent<int, input_iterator_wrapper_nocopy>>() );
>> +
>> +static_assert( ranges_test<test_forward_range<short>>() );
>> +static_assert( ranges_test<test_input_range<short>>() );
>> +
>> +// Not lvalue-convertible to int
>> +struct C {
>> +  constexpr C(int v) : val(v) { }
>> +  constexpr operator int() && { return val; }
>> +
>> +  friend bool operator==(C c, C b) = default;
>> +  friend constexpr bool operator==(C c, int b)
>> +  { return b == c.val; }
>> +
>> +  int val;
>> +};
>> +using rvalue_input_range = test_range<C, input_iterator_wrapper_rval>;
>> +static_assert( ranges_test<rvalue_input_range>() );
>> diff --git a/libstdc++-v3/testsuite/23_containers/headers/deque/synopsis.cc b/libstdc++-v3/testsuite/23_containers/headers/deque/synopsis.cc
>> index 48e89592059..447eefd6319 100644
>> --- a/libstdc++-v3/testsuite/23_containers/headers/deque/synopsis.cc
>> +++ b/libstdc++-v3/testsuite/23_containers/headers/deque/synopsis.cc
>> @@ -21,6 +21,12 @@
>>
>>  #include <deque>
>>
>> +#if __cplusplus > 202302L
>> +# define CONSTEXPR constexpr
>> +#else
>> +# define CONSTEXPR
>> +#endif
>> +
>>  #if __cplusplus >= 201103L
>>  # define NOTHROW(X) noexcept(X)
>>  #else
>> @@ -31,24 +37,30 @@ namespace std {
>>    template <class T, class Allocator> class deque;
>>
>>    template <class T, class Allocator>
>> -    bool operator== (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
>> +    CONSTEXPR 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);
>> +    CONSTEXPR 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);
>> +    CONSTEXPR 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);
>> +    CONSTEXPR 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);
>> +    CONSTEXPR 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);
>> +    CONSTEXPR bool
>> +    operator<= (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
>>
>>    template <class T, class Allocator>
>> -    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y)
>> +    CONSTEXPR void swap(deque<T,Allocator>& x, deque<T,Allocator>& y)
>>        NOTHROW(noexcept(x.swap(y)));
>>  }
>> diff --git a/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc b/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
>> index fe85617416d..9cc6f932adb 100644
>> --- a/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
>> +++ b/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
>> @@ -1,43 +1,238 @@
>>  // { dg-do compile { target c++26 } }
>> +
>>  #include <queue>
>>
>> -constexpr bool test_constexpr_priority_queue() {
>> -  std::priority_queue<int> pq;
>> -  if (!pq.empty()) return false;
>> -  if (pq.size() != 0) return false;
>> +#ifndef __cpp_lib_constexpr_queue
>> +# error "Feature test macro for __cpp_lib_constexpr_queue is missing in <queue>"
>> +#elif __cpp_lib_constexpr_queue != 202502L
>> +# error "Feature test macro for __cpp_lib_constexpr_queue has wrong value in <queue>"
>> +#endif
>> +
>> +#include <algorithm>
>> +#include <ranges>
>> +#include <functional>
>> +#include <vector>
>> +#include <numeric>
>> +#include <testsuite_hooks.h>
>> +#include <testsuite_iterators.h>
>> +#include <testsuite_allocator.h>
>> +
>> +using namespace __gnu_test;
>> +
>> +template<typename Cont, typename Cmp = std::less<int>>
>> +constexpr bool
>> +ctor_tests(Cmp cmp = Cmp())
>> +{
>> +  using V = typename Cont::value_type;
>> +  using Alloc = Cont::allocator_type;
>> +
>> +  V rg[] {2, 3, 5, 7};
>> +  Cont v0{std::from_range, rg};
>> +  Cont v1 = v0;
>> +  Cont v2 = v0;
>> +  Alloc alloc;
>> +  auto top_range = * std::ranges::max_element(v0, cmp);
>> +
>> +  auto eq = [&] (std::priority_queue<V, Cont, Cmp>& l, std::span<V> r) {
>> +    if (l.size() != r.size())
>> +      return false;
>> +
>> +    std::vector<V> s(r.begin(), r.end());
>> +    std::ranges::sort(s, cmp);
>> +    for (auto const& v : s | std::views::reverse) {
>> +      if (v != l.top())
>> +       return false;
>> +      l.pop();
>> +    }
>> +    return true;
>> +  };
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq1;
>> +  VERIFY( pq1.size() == 0 && pq1.empty() );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq2(cmp);
>> +  VERIFY( pq2.size() == 0 && pq2.empty() );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq3(cmp, v0);
>> +  VERIFY( pq3.size() == 4 && pq3.top() == top_range );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq4(cmp, std::move(v0));
>> +  VERIFY( pq4.size() == 4 && pq4.top() == top_range );
>>
>> -  pq.push(10);
>> -  if (pq.empty()) return false;
>> -  if (pq.size() != 1) return false;
>> -  if (pq.top() != 10) return false;
>> +  std::priority_queue<V, Cont, Cmp> pq5(pq3);
>> +  VERIFY( pq5.top() == pq3.top() );
>> +  VERIFY( pq5.size() == pq3.size() );
>>
>> -  pq.emplace(30);
>> -  pq.emplace(20);
>> -  if (pq.size() != 3) return false;
>> -  if (pq.top() != 30) return false;
>> +  std::priority_queue<V, Cont, Cmp> pq6(std::move(pq3));
>> +  VERIFY( pq6.top() == pq5.top() );
>> +  VERIFY( pq6.size() == pq5.size() );
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq10(std::begin(rg), std::end(rg),  cmp);
>> +  VERIFY( pq4.size() == 4 && pq4.top() == top_range );
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq11(std::begin(rg), std::end(rg), cmp, v0);
>> +  VERIFY( pq4.size() == 4 && pq4.top() == top_range );
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq12(std::begin(rg), std::end(rg), cmp, std::move(v0));
>> +  VERIFY( pq4.size() == 4 && pq4.top() == top_range );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq14(alloc);
>> +  VERIFY( pq14.empty() );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq15(cmp, alloc);
>> +  VERIFY( pq15.empty() );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq16(cmp, v2, alloc);
>> +  VERIFY( eq(pq16, {rg, 4}) );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq17(cmp, std::move(v2), alloc);
>> +  VERIFY( eq(pq17, {rg, 4}) );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq18(pq12, alloc);
>> +  VERIFY( pq18.size() == pq12.size());
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq19(std::move(pq12), alloc);
>> +  VERIFY( pq19.size() == pq18.size() );
>> +  return true;
>> +}
>>
>> +static_assert( ctor_tests<std::vector<int>>() );
>> +static_assert( ctor_tests<std::vector<int>, std::greater<int>>() );
>> +static_assert( ctor_tests<std::vector<int, SimpleAllocator<int>>>() );
>> +static_assert( ctor_tests<std::deque<int>>() );
>> +static_assert( ctor_tests<std::deque<int>, std::greater<int>>() );
>> +static_assert( ctor_tests<std::deque<int, SimpleAllocator<int>>>() );
>> +
>> +constexpr bool
>> +push_and_pop_test()
>> +{
>> +  std::priority_queue<int> a;
>> +  a.push(2);
>> +  a.push(4);
>> +  VERIFY( a.top() == 4 );
>> +  a.pop();
>> +  VERIFY( a.top() == 2 );
>> +  a.pop();
>> +  VERIFY( a.empty() );
>> +  return true;
>> +}
>> +static_assert( push_and_pop_test() );
>> +
>> +constexpr int swap_test()
>> +{
>> +  std::priority_queue<int> a,b;
>> +  a.push(2);
>> +  b.push(4);
>> +  std::swap(a, b);
>> +  VERIFY( a.top() == 4 );
>> +  VERIFY( b.top() == 2 );
>> +  return true;
>> +}
>> +static_assert (swap_test());
>> +
>> +constexpr bool
>> +emplace_test()
>> +{
>> +  struct S
>> +  {
>> +    int foo;
>> +    constexpr S(int i, int j) : foo{i + j} {}
>> +    std::strong_ordering operator<=>(const S&) const = default;
>> +  };
>> +
>> +  std::priority_queue<S> pq;
>> +  pq.emplace(0, 0);
>> +  pq.emplace(1, 0);
>> +  VERIFY( pq.size() == 2 );
>> +  VERIFY( pq.top().foo == 1 );
>>    pq.pop();
>> -  if (pq.size() != 2) return false;
>> -  if (pq.top() != 20) return false;
>> +  VERIFY ( pq.top().foo == 0 );
>> +  return true;
>> +}
>> +static_assert( emplace_test() );
>> +
>> +template<typename Range, typename Cont, typename Cmp>
>> +constexpr void
>> +do_range_tests(Cmp cmp = Cmp())
>> +{
>> +  using V = typename Cont::value_type;
>> +  using Alloc = typename Cont::allocator_type;
>> +  using T = std::ranges::range_value_t<Range>;
>>
>> -  std::priority_queue<int> pq2;
>> -  pq2 = pq;
>> -  if (pq2.size() != 2) return false;
>> -  if (pq2.top() != 20) return false;
>> +  Alloc alloc;
>> +  T rg[] {2, 3, 5, 7, 11, 13};
>> +
>> +  auto top_range = std::ranges::max_element(rg, cmp);
>> +
>> +  auto eq = [&](std::priority_queue<V, Cont, Cmp>& l, std::span<T> r) {
>> +    if (l.size() != r.size())
>> +      return false;
>> +
>> +    std::vector<T> s(r.begin(), r.end());
>> +    std::ranges::sort(s, cmp);
>> +    for (auto const& v : s | std::views::reverse) {
>> +      if (v != l.top())
>> +       return false;
>> +      l.pop();
>> +    }
>> +    return true;
>> +  };
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq1(std::from_range, Range(rg, rg+4), cmp);
>> +  VERIFY( eq(pq1, {rg, 4}) );
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq2(std::from_range, Range(rg, rg+5), alloc);
>> +  VERIFY( eq(pq2, {rg, 5}) );
>> +
>> +  std::priority_queue<V, Cont, Cmp>
>> +    pq3(std::from_range, Range(rg, rg+6), cmp, alloc);
>> +  VERIFY( eq(pq3, {rg, 6}) );
>> +
>> +  std::priority_queue<V, Cont, Cmp> pq4;
>> +  pq4.push_range(Range(rg, rg+6));
>> +  VERIFY( eq(pq4, {rg, 6}) );
>> +}
>> +
>> +template<typename Range, typename Cont>
>> +constexpr void
>> +do_ranges_tests_b()
>> +{
>> +  do_range_tests<Range, Cont, std::less<>>();
>> +  do_range_tests<Range, Cont, std::greater<>>();
>> +}
>>
>> -  std::priority_queue<int> pq3;
>> -  pq3.push(100);
>> -  pq.swap(pq3);
>> -  if (pq.size() != 1 || pq.top() != 100) return false;
>> -  if (pq3.size() != 2 || pq3.top() != 20) return false;
>> +template<typename Cont>
>> +constexpr bool
>> +ranges_tests() {
>> +  using T = typename Cont::value_type;
>> +  do_ranges_tests_b<
>> +    test_forward_range<T>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_forward_sized_range<T>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_sized_range_sized_sent<T, forward_iterator_wrapper>, Cont>();
>>
>> -  int arr[] = {50, 200, 10};
>> -  pq.push_range(arr);
>> -  if (pq.size() != 4) return false;
>> -  if (pq.top() != 200) return false;
>> +  do_ranges_tests_b<
>> +    test_input_range<T>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_input_sized_range<T>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_sized_range_sized_sent<T, forward_iterator_wrapper>, Cont>();
>>
>> +  do_ranges_tests_b<
>> +    test_range<T, input_iterator_wrapper_nocopy>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_sized_range<T, input_iterator_wrapper_nocopy>, Cont>();
>> +  do_ranges_tests_b<
>> +    test_sized_range_sized_sent<T, input_iterator_wrapper_nocopy>, Cont>();
>>    return true;
>>  }
>>
>> -static_assert(test_constexpr_priority_queue(),
>> -              "constexpr priority_queue test failed!");
>> +static_assert( ranges_tests<std::vector<int>>() );
>> +static_assert( ranges_tests<std::vector<int, SimpleAllocator<int>>>() );
>> +static_assert( ranges_tests<std::deque<int, SimpleAllocator<int>>>() );
>> diff --git a/libstdc++-v3/testsuite/23_containers/queue/constexpr.cc b/libstdc++-v3/testsuite/23_containers/queue/constexpr.cc
>> new file mode 100644
>> index 00000000000..01dbc53b4ff
>> --- /dev/null
>> +++ b/libstdc++-v3/testsuite/23_containers/queue/constexpr.cc
>> @@ -0,0 +1,242 @@
>> +// { dg-do compile { target c++26 } }
>> +
>> +#include <queue>
>> +
>> +#ifndef __cpp_lib_constexpr_queue
>> +# error "Feature test macro for __cpp_lib_constexpr_queue is missing in <queue>"
>> +#elif __cpp_lib_constexpr_queue != 202502L
>> +# error "Feature test macro for __cpp_lib_constexpr_queue has wrong value in <queue>"
>> +#endif
>> +
>> +#include <ranges>
>> +#include <functional>
>> +#include <vector>
>> +#include <numeric>
>> +#include <testsuite_hooks.h>
>> +#include <testsuite_iterators.h>
>> +#include <testsuite_allocator.h>
>> +
>> +using namespace __gnu_test;
>> +
>> +template<typename Cont>
>> +constexpr bool
>> +ctor_tests()
>> +{
>> +  using Tp = typename Cont::value_type;
>> +  using Alloc = typename Cont::allocator_type;
>> +
>> +  auto eq = [] (std::queue<Tp, Cont> l, std::span<Tp> r) {
>> +    if (l.size() != r.size())
>> +      return false;
>> +
>> +    std::vector<Tp> s(r.begin(), r.end());
>> +    for (auto v : s) {
>> +      if (v != l.front())
>> +       return false;
>> +      l.pop();
>> +    }
>> +    return true;
>> +  };
>> +
>> +  Cont c0;
>> +  Alloc alloc0;
>> +
>> +  std::queue<Tp, Cont> q1(c0);
>> +  VERIFY( q1.size() == 0 && q1.empty() );
>> +  q1.push(1);
>> +  q1.push(2);
>> +  VERIFY( q1.size() == 2) ;
>> +
>> +  Cont c1{1, 2};
>> +  std::queue<Tp, Cont> q2(c1);
>> +  VERIFY ( q2 == q1 );
>> +  std::queue<Tp, Cont> q3(std::move(c1));
>> +  VERIFY ( q3 == q1 );
>> +
>> +  std::queue<Tp, Cont> q4(q1);
>> +  std::queue<Tp, Cont> q5(std::move(q1));
>> +  VERIFY ( q4 == q5 );
>> +
>> +  Tp rg[4] = {2, 3, 5, 7};
>> +  std::queue<Tp, Cont> q6(std::begin(rg), std::end(rg));
>> +  VERIFY ( eq(q6, rg) );
>> +
>> +  VERIFY( q6.size() == std::size(rg));
>> +  VERIFY( q6.front() == 2 );
>> +  q6.pop();
>> +  VERIFY( q6.front() == 3 );
>> +  q6.pop();
>> +  VERIFY( q6.front() == 5 );
>> +  q6.pop();
>> +  VERIFY( q6.front() == 7 );
>> +  q6.pop();
>> +
>> +  std::queue<Tp, Cont> q7(alloc0);
>> +  q7.push(1);
>> +  q7.push(2);
>> +  VERIFY( q7.size() == 2 );
>> +
>> +  Cont c2{1, 2};
>> +  std::queue<Tp, Cont> q8(c2, alloc0);
>> +  VERIFY( q8 == q7 );
>> +  std::queue<Tp, Cont> q9(std::move(c2), alloc0);
>> +  VERIFY( q9 == q7 );
>> +  VERIFY( c2.empty() );
>> +
>> +  std::queue<Tp, Cont> q10(q7, alloc0);
>> +  VERIFY( q10 == q7 );
>> +  VERIFY( q10.size() == q7.size() );
>> +  VERIFY( q10.front() == q7.front() );
>> +  VERIFY( q10.back() == q7.back() );
>> +
>> +  std::queue<Tp, Cont> q11(std::move(q7), alloc0);
>> +  VERIFY( q11 == q10 );
>> +  VERIFY( q11.size() == q10.size() );
>> +  VERIFY( q7.empty() );
>> +
>> +  std::queue<Tp, Cont> q12(std::begin(rg), std::end(rg), alloc0);
>> +  VERIFY ( eq(q12, rg) );
>> +  VERIFY( q12.size() == std::size(rg));
>> +  VERIFY( q12.front() == 2 );
>> +  q12.pop();
>> +  VERIFY( q12.front() == 3 );
>> +  q12.pop();
>> +  VERIFY( q12.front() == 5 );
>> +  q12.pop();
>> +  VERIFY( q12.front() == 7 );
>> +  q12.pop();
>> +
>> +  std::queue<Tp, Cont> q13(std::from_range, rg);
>> +  VERIFY( eq(q13, rg) );
>> +  std::queue<Tp, Cont> q14(std::from_range, rg, alloc0);
>> +  VERIFY( eq(q14, rg) );
>> +
>> +  return true;
>> +}
>> +// TODO check list when avaialble
>> +static_assert( ctor_tests<std::deque<int>>() );
>> +static_assert( ctor_tests<std::deque<int, SimpleAllocator<int>>>() );
>> +
>> +template<typename Range, typename Cont>
>> +constexpr void
>> +do_ranges_tests_a()
>> +{
>> +  using Tp = typename Cont::value_type;
>> +  typename Cont::allocator_type alloc;
>> +  Tp a[] {2, 3, 5, 7};
>> +
>> +  auto eq = [&] (auto l, auto r) {
>> +    if (l.size() != r.size())
>> +      return false;
>> +
>> +    while (!l.empty()) {
>> +      if (l.front() != r.front())
>> +       return false;
>> +      l.pop();
>> +      r.pop();
>> +    }
>> +    return true;
>> +  };
>> +
>> +  std::queue<Tp, Cont> q1(std::from_range, Range(a, a+4));
>> +  std::queue<Tp> q2;
>> +  q2.push_range(Range(a, a+4));
>> +  VERIFY( eq(q1, q2) );
>> +
>> +  std::queue<Tp, Cont> q3(std::from_range, Range(a, a+4), alloc);
>> +  std::queue<Tp, Cont> q4(std::from_range, Range(a, a+4));
>> +  VERIFY( eq(q3, q4) );
>> +}
>> +
>> +template<typename Cont>
>> +constexpr bool
>> +ranges_tests()
>> +{
>> +  using Tp = typename Cont::value_type;
>> +
>> +  do_ranges_tests_a<test_forward_range<Tp>,  Cont>();
>> +  do_ranges_tests_a<test_forward_sized_range<Tp>, Cont>();
>> +  do_ranges_tests_a<
>> +    test_sized_range_sized_sent<Tp, forward_iterator_wrapper>, Cont>();
>> +
>> +  do_ranges_tests_a<test_input_range<Tp>, Cont>();
>> +  do_ranges_tests_a<test_input_sized_range<Tp>, Cont>();
>> +  do_ranges_tests_a<
>> +    test_sized_range_sized_sent<Tp, forward_iterator_wrapper>, Cont>();
>> +
>> +  do_ranges_tests_a<
>> +    test_range<Tp, input_iterator_wrapper_nocopy>, Cont>();
>> +  do_ranges_tests_a<
>> +    test_sized_range<Tp, input_iterator_wrapper_nocopy>, Cont>();
>> +  do_ranges_tests_a<
>> +    test_sized_range_sized_sent<Tp, input_iterator_wrapper_nocopy>, Cont>();
>> +  return true;
>> +}
>> +// TODO check list when avaialble
>> +static_assert( ranges_tests<std::deque<int>>() );
>> +static_assert( ranges_tests<std::deque<int, SimpleAllocator<int>>>() );
>> +
>> +constexpr bool
>> +push_and_pop_test()
>> +{
>> +  std::queue<int> a;
>> +  a.push(2);
>> +  a.push(4);
>> +  VERIFY( a.front() == 2 && a.back() == 4);
>> +  a.pop();
>> +  VERIFY( a.front() == 4 && a.back() == 4);
>> +  a.pop();
>> +  VERIFY( a.empty() );
>> +  return true;
>> +}
>> +static_assert( push_and_pop_test() );
>> +
>> +constexpr bool
>> +swap_test()
>> +{
>> +  std::queue<int> a,b;
>> +  a.push(1);
>> +  b.push(2);
>> +  std::swap(a, b);
>> +  VERIFY( a.front() == 2 );
>> +  VERIFY( b.front() == 1 );
>> +  return true;
>> +}
>> +static_assert( swap_test() );
>> +
>> +constexpr bool
>> +emplace_test()
>> +{
>> +  struct S
>> +  {
>> +    int foo;
>> +    constexpr S(int i, int j) : foo{i + j} {}
>> +  };
>> +
>> +  std::queue<S> a;
>> +  const S& s = a.emplace(196883, 1);
>> +  VERIFY( a.size() == 1 );
>> +  VERIFY( a.front().foo == 196884 );
>> +  return true;
>> +}
>> +static_assert( emplace_test() );
>> +
>> +constexpr bool
>> +operator_test()
>> +{
>> +  std::queue<int> a, b;
>> +  a.push(1);
>> +  b.push(1);
>> +  VERIFY( a == b );
>> +  VERIFY( a <= b );
>> +  VERIFY( a >= b );
>> +  b.pop();
>> +  b.push(2);
>> +  VERIFY( a < b );
>> +  VERIFY( !(a > b) );
>> +  VERIFY( a <= b );
>> +  VERIFY( !(a >= b) );
>> +  VERIFY( a != b );
>> +  return true;
>> +}
>> +static_assert( operator_test() );
>> diff --git a/libstdc++-v3/testsuite/std/format/ranges/adaptors.cc b/libstdc++-v3/testsuite/std/format/ranges/adaptors.cc
>> index 649eea47f16..968ac00b63e 100644
>> --- a/libstdc++-v3/testsuite/std/format/ranges/adaptors.cc
>> +++ b/libstdc++-v3/testsuite/std/format/ranges/adaptors.cc
>> @@ -6,8 +6,14 @@
>>  #include <stack>
>>  #include <testsuite_hooks.h>
>>
>> +#ifdef __glibcxx_constexpr_format
>> +# define CONSTEXPR constexpr
>> +#else
>> +# define CONSTEXPR
>> +#endif
>> +
>>  template<typename... Args>
>> -bool
>> +CONSTEXPR bool
>>  is_format_string_for(const char* str, Args&&... args)
>>  {
>>    try {
>> @@ -22,7 +28,7 @@ is_format_string_for(const char* str, Args&&... args)
>>  #define WIDEN(S) WIDEN_(CharT, S)
>>
>>  template<template<typename Tp> class Adaptor>
>> -void
>> +CONSTEXPR void
>>  test_format_string()
>>  {
>>    Adaptor<int> q;
>> @@ -41,7 +47,7 @@ struct NoFormat
>>  struct MutFormat
>>  {
>>    MutFormat() = default;
>> -  MutFormat(int p) : x(p) {}
>> +  CONSTEXPR MutFormat(int p) : x(p) {}
>>
>>    int x;
>>    friend auto operator<=>(MutFormat, MutFormat) = default;
>> @@ -52,7 +58,8 @@ struct std::formatter<MutFormat, CharT>
>>    : std::formatter<int, CharT>
>>  {
>>     template<typename Out>
>> -   Out format(MutFormat& mf, basic_format_context<Out, CharT>& ctx) const
>> +   CONSTEXPR Out
>> +   format(MutFormat& mf, basic_format_context<Out, CharT>& ctx) const
>>     { return std::formatter<int, CharT>::format(mf.x, ctx); }
>>  };
>>
>> @@ -68,7 +75,7 @@ constexpr auto std::format_kind<NotFormattableCont<T>>
>>
>>  template<typename CharT,
>>          template<typename Tp, typename Cont = std::vector<Tp>> class Adaptor>
>> -void
>> +CONSTEXPR void
>>  test_output()
>>  {
>>    const std::vector<int> v{3, 2, 1};
>> @@ -133,7 +140,7 @@ test_output()
>>  }
>>
>>  template<template<typename Tp, typename Cont = std::vector<Tp>> class Adaptor>
>> -void
>> +CONSTEXPR void
>>  test_adaptor()
>>  {
>>    test_format_string<Adaptor>();
>> @@ -145,7 +152,7 @@ test_adaptor()
>>  }
>>
>>  template<typename CharT>
>> -void
>> +CONSTEXPR void
>>  test_compare()
>>  {
>>    const std::vector<int> v{3, 2, 1};
>> @@ -157,9 +164,20 @@ test_compare()
>>    VERIFY( res == WIDEN("[1, 2, 3]") );
>>  }
>>
>> -int main()
>> +CONSTEXPR bool
>> +test_all()
>>  {
>>    test_adaptor<std::queue>();
>>    test_adaptor<std::priority_queue>();
>>    test_compare<char>();
>> +  return true;
>> +}
>> +
>> +#ifdef __glibcxx_constexpr_format
>> +  static_assert(test_all());
>> +#endif
>> +
>> +int main()
>> +{
>> +  test_all();
>>  }
>> --
>> 2.55.0
>>

Looking forward to this! Just a quick question, does this patch
resolve the error in https://compiler-explorer.com/z/39MsxKxTT ?