[PATCHv2] libstdc++: Mark <queue>, <deque> constexpr

Tomasz Kaminski tkaminsk@redhat.com
Mon Jul 13 06:46:57 GMT 2026


On Fri, Mar 6, 2026 at 12:02 AM Thor Preimesberger <
tcpreimesberger@gmail.com> wrote:

> With Tomasz' comments from last time. I (at least tried to :P)
> implemented everything except for getting the tests to function
> properly with -D_GLIBCXX_DEBUG. I think we think we may want to hold
> off on marking all the debug stuff constexpr until all other
> containers are finished; I think it's technically do-able now, but it
> involves fussing with the test infrastructure in a way that should be
> more convenient to do later.
>
> I have some other patches bitrotting on my computer that make partial
> progress towards P3372. I'll eventually get around to sending them
> in, but feel free to email me if interested on taking them further ^^
>
> Testsuite works on my x86_64 machine.
> --- 8< ---
> This patch makes partial progress towards P3372 by marking
> std::{deque, priority_queue, queue} and relevant internal helpers to be
> constexpr when using C++26. Although the debug versions of deque are
> marked as constexpr, the rest of the debug functionality in libstdc++
> still needs to be marked constexpr as well. So our tests are xfail with
> -D_GLIBCXX_DEBUG for now.
>
> libstdc++-v3/ChangeLog:
>
> * include/Makefile.am: Have stdc++.h precompiled header build
> * with --std=gnu++2c due to symbol changes in stl_algobase.h
> * include/bits/deque.tcc: Mark constexpr; note that those
> * functions in stl_algobase.h are marked as CXX20 constexpr only.
> * include/bits/stl_algobase.h: Mark deque helper functions CXX20
> * constexpr.
> * include/bits/stl_deque.h: Mark CXX26 constexpr.
> * include/bits/stl_queue.h: Mark CXX26 constexpr.
> * include/bits/stl_uninitialized.h: Mark helper
> * __uninitialized_default_a CXX26 constexpr.
> * include/bits/version.def: Add feature test macros for
> * __cpp_lib_constexpr_{queue, dequeue}.
> * include/bits/version.h: Regenerate.
> * include/debug/deque: Mark member functions CXX26 constexpr.
> * include/std/deque: Mark nonmember functions CXX26 constexpr
> * and add macros.
> * include/std/queue: Mark nonmember functions CXX26 constexpr
> * and add macros.
> * testsuite/23_containers/deque/constexpr.cc: New test.
> * testsuite/23_containers/deque/debug/constexpr.cc: New test.
> * testsuite/23_containers/priority_queue/constexpr.cc: New test.
> * testsuite/23_containers/queue/constexpr.cc: New test.
>
> Signed-off-by: Thor Preimesberger <tcpreimesberger@gmail.com>
> ---
>  libstdc++-v3/include/Makefile.am              |   2 +-
>  libstdc++-v3/include/bits/deque.tcc           |  53 +++
>  libstdc++-v3/include/bits/stl_algobase.h      |  16 +-
>  libstdc++-v3/include/bits/stl_deque.h         | 168 +++++++-
>  libstdc++-v3/include/bits/stl_queue.h         |  73 +++-
>  libstdc++-v3/include/bits/stl_uninitialized.h |   2 +
>  libstdc++-v3/include/bits/version.def         |  16 +
>  libstdc++-v3/include/bits/version.h           |  20 +
>  libstdc++-v3/include/debug/deque              |  72 ++++
>  libstdc++-v3/include/std/deque                |   4 +-
>  libstdc++-v3/include/std/queue                |  12 +-
>  .../23_containers/deque/constexpr.cc          | 348 +++++++++++++++++
>  .../23_containers/deque/debug/constexpr.cc    | 361 ++++++++++++++++++
>  .../23_containers/priority_queue/constexpr.cc | 323 ++++++++++++++++
>  .../23_containers/queue/constexpr.cc          | 281 ++++++++++++++
>  15 files changed, 1737 insertions(+), 14 deletions(-)
>  create mode 100644 libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
>  create mode 100644
> libstdc++-v3/testsuite/23_containers/deque/debug/constexpr.cc
>  create mode 100644
> libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
>  create mode 100644 libstdc++-v3/testsuite/23_containers/queue/constexpr.cc
>
> diff --git a/libstdc++-v3/include/Makefile.am
> b/libstdc++-v3/include/Makefile.am
> index e6ac312ac7a..62f4b6862bc 100644
> --- a/libstdc++-v3/include/Makefile.am
> +++ b/libstdc++-v3/include/Makefile.am
> @@ -1481,7 +1481,7 @@ ${host_builddir}/gthr-default.h:
> ${toplevel_srcdir}/libgcc/${thread_header} \
>  # Build two precompiled C++ includes, stdc++.h.gch/*.gch
>  ${pch1a_output}: ${allstamped} ${host_builddir}/c++config.h ${pch1_source}
>   -mkdir -p ${pch1_output_builddir}
> - $(CXX) $(PCHFLAGS) $(AM_CPPFLAGS) -O2 -g -std=gnu++0x ${pch1_source} \
> + $(CXX) $(PCHFLAGS) $(AM_CPPFLAGS) -O2 -g -std=gnu++2c ${pch1_source} \
>   -o $@
>
Is this change necessary? It does not look correct, given the produced file
pch is named:
pch1a_output = ${pch1_output_builddir}/O2ggnu++0x.gch

The changelog message seem even more confusing, as I do not thrink that
adding/
removing constexpr changes the symbol name.
* include/Makefile.am: Have stdc++.h precompiled header build
* with --std=gnu++2c due to symbol changes in stl_algobase.h


>
>  ${pch1b_output}: ${allstamped} ${host_builddir}/c++config.h ${pch1_source}
> diff --git a/libstdc++-v3/include/bits/deque.tcc
> b/libstdc++-v3/include/bits/deque.tcc
> index 7a690466cd5..b9ef85073e4 100644
> --- a/libstdc++-v3/include/bits/deque.tcc
> +++ b/libstdc++-v3/include/bits/deque.tcc
> @@ -65,6 +65,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>  #if __cplusplus >= 201103L
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_default_initialize()
> @@ -91,6 +92,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  #endif
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      deque<_Tp, _Alloc>&
>      deque<_Tp, _Alloc>::
>      operator=(const deque& __x)
> @@ -133,6 +135,7 @@ _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 +160,7 @@ _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 +187,7 @@ _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 +211,7 @@ _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 +237,7 @@ _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 +261,7 @@ _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)
> @@ -303,6 +311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_fill_insert(iterator __pos, size_type __n, const value_type& __x)
> @@ -346,6 +355,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>  #if __cplusplus >= 201103L
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_default_append(size_type __n)
> @@ -370,6 +380,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      bool
>      deque<_Tp, _Alloc>::
>      _M_shrink_to_fit()
> @@ -389,6 +400,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  #endif
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_fill_initialize(const value_type& __value)
> @@ -415,6 +427,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _InputIterator>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_initialize(_InputIterator __first, _InputIterator __last,
> @@ -439,6 +452,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _ForwardIterator>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_initialize(_ForwardIterator __first, _ForwardIterator
> __last,
> @@ -480,6 +494,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>    template<typename _Tp, typename _Alloc>
>  #if __cplusplus >= 201103L
>      template<typename... _Args>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_push_back_aux(_Args&&... __args)
> @@ -519,6 +534,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>    template<typename _Tp, typename _Alloc>
>  #if __cplusplus >= 201103L
>      template<typename... _Args>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_push_front_aux(_Args&&... __args)
> @@ -557,6 +573,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    // Called only if _M_impl._M_finish._M_cur ==
> _M_impl._M_finish._M_first.
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void deque<_Tp, _Alloc>::
>      _M_pop_back_aux()
>      {
> @@ -573,6 +590,7 @@ _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>
> +    _GLIBCXX26_CONSTEXPR
>      void deque<_Tp, _Alloc>::
>      _M_pop_front_aux()
>      {
> @@ -585,6 +603,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _InputIterator, typename _Sentinel>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_prepend(_InputIterator __first, _Sentinel __last,
> @@ -607,6 +626,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _InputIterator, typename _Sentinel>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_append(_InputIterator __first, _Sentinel __last,
> @@ -630,6 +650,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _InputIterator>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_insert_aux(iterator __pos,
> @@ -639,6 +660,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _ForwardIterator>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_range_insert_aux(iterator __pos,
> @@ -660,6 +682,7 @@ _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)
> @@ -707,6 +730,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_insert_aux(iterator __pos, size_type __n, const value_type& __x)
> @@ -793,6 +817,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template <typename _Tp, typename _Alloc>
>      template <typename _ForwardIterator>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        deque<_Tp, _Alloc>::
>        _M_insert_aux(iterator __pos,
> @@ -882,6 +907,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>  #if __glibcxx_containers_ranges // C++ >= 23
>    template<ranges::forward_range _Rg>
> +    _GLIBCXX26_CONSTEXPR
>      auto __advance_dist(_Rg& __rg)
>      {
>        struct _Res
> @@ -914,6 +940,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    template<typename _Tp, typename _Alloc>
>      template<__detail::__container_compatible_range<_Tp> _Rg>
> +      _GLIBCXX26_CONSTEXPR
>        auto
>        deque<_Tp, _Alloc>::
>        insert_range(const_iterator __pos, _Rg&& __rg)
> @@ -954,6 +981,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>     template<typename _Tp, typename _Alloc>
>       template<__detail::__container_compatible_range<_Tp> _Rg>
> +      _GLIBCXX26_CONSTEXPR
>         void
>         deque<_Tp, _Alloc>::
>         prepend_range(_Rg&& __rg)
> @@ -996,6 +1024,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>     template<typename _Tp, typename _Alloc>
>       template<__detail::__container_compatible_range<_Tp> _Rg>
> +       _GLIBCXX26_CONSTEXPR
>         void
>         deque<_Tp, _Alloc>::
>         append_range(_Rg&& __rg)
> @@ -1013,6 +1042,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   deque& __self;
>   size_type __n = __self.size();
>
> + _GLIBCXX26_CONSTEXPR
>   ~_Guard_elts_back()
>      {
>        if (__n < __self.size())
> @@ -1032,6 +1062,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  #endif // containers_ranges
>
>     template<typename _Tp, typename _Alloc>
> +     _GLIBCXX26_CONSTEXPR
>       void
>       deque<_Tp, _Alloc>::
>       _M_destroy_data_aux(iterator __first, iterator __last)
> @@ -1054,6 +1085,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>       }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_new_elements_at_front(size_type __new_elems)
> @@ -1079,6 +1111,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_new_elements_at_back(size_type __new_elems)
> @@ -1104,6 +1137,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      }
>
>    template <typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      deque<_Tp, _Alloc>::
>      _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front)
> @@ -1158,6 +1192,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>    // Overload for deque::iterators, exploiting the "segmented-iterator
>    // optimization".
>    template<typename _Tp, typename _VTp>
> +    _GLIBCXX20_CONSTEXPR
>      void
>      __fill_a1(const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&
> __first,
>         const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>& __last,
> @@ -1180,6 +1215,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX20_CONSTEXPR
>      _OI
>      __copy_move_dit(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>
> __first,
>       _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
> @@ -1209,6 +1245,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX20_CONSTEXPR
>      _OI
>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>
> __first,
>      _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __last,
> @@ -1217,6 +1254,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
> +    _GLIBCXX20_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 +1262,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      { return __copy_move_dit<_IsMove>(__first, __last, __result); }
>
>    template<bool _IsMove, typename _II, typename _Tp>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
> @@ -1250,6 +1289,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      }
>
>    template<bool _IsMove, typename _CharT>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_char<_CharT>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
> @@ -1277,6 +1317,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      }
>
>    template<typename _CharT, typename _Size>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_char<_CharT>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
> @@ -1302,6 +1343,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX26_CONSTEXPR
>      _OI
>      __copy_move_backward_dit(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
> @@ -1329,6 +1371,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX20_CONSTEXPR
>      _OI
>      __copy_move_backward_a1(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr> __first,
> @@ -1338,6 +1381,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
> +    _GLIBCXX20_CONSTEXPR
>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>      __copy_move_backward_a1(
>   _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr> __first,
> @@ -1346,6 +1390,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      { return __copy_move_backward_dit<_IsMove>(__first, __last,
> __result); }
>
>    template<bool _IsMove, typename _II, typename _Tp>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
> @@ -1378,6 +1423,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      }
>
>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
> +    _GLIBCXX20_CONSTEXPR
>      bool
>      __equal_dit(
>   const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>& __first1,
> @@ -1405,6 +1451,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      }
>
>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
> +    _GLIBCXX20_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,
> @@ -1414,6 +1461,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_CONSTEXPR
>      bool
>      __equal_aux1(_GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>
> __first1,
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __last1,
> @@ -1421,6 +1469,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      { return std::__equal_dit(__first1, __last1, __first2); }
>
>    template<typename _II, typename _Tp, typename _Ref, typename _Ptr>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value, bool>::__type
>      __equal_aux1(_II __first1, _II __last1,
> @@ -1446,6 +1495,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      }
>
>    template<typename _Tp1, typename _Ref, typename _Ptr, typename _Tp2>
> +    _GLIBCXX26_CONSTEXPR
>      int
>      __lex_cmp_dit(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref, _Ptr> __first1,
> @@ -1487,6 +1537,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2>
> +    _GLIBCXX20_CONSTEXPR
>      inline bool
>      __lexicographical_compare_aux1(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
> @@ -1496,6 +1547,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_CONSTEXPR
>      inline  bool
>      __lexicographical_compare_aux1(_Tp1* __first1, _Tp1* __last1,
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2> __first2,
> @@ -1504,6 +1556,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_CONSTEXPR
>      inline bool
>      __lexicographical_compare_aux1(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1> __first1,
> diff --git a/libstdc++-v3/include/bits/stl_algobase.h
> b/libstdc++-v3/include/bits/stl_algobase.h
> index 3fdbff97353..a84a0705d53 100644
> --- a/libstdc++-v3/include/bits/stl_algobase.h
> +++ b/libstdc++-v3/include/bits/stl_algobase.h
> @@ -348,6 +348,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      istreambuf_iterator<_CharT, char_traits<_CharT> >, _CharT*);
>
>    template<bool _IsMove, typename _CharT>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_char<_CharT>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
> @@ -465,6 +466,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX20_CONSTEXPR
>      _OI
>      __copy_move_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
>      _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
> @@ -472,12 +474,14 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
> +    _GLIBCXX20_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>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
> @@ -529,7 +533,6 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>  #pragma GCC diagnostic push
>  #pragma GCC diagnostic ignored "-Wc++17-extensions" // for if-constexpr
>    template<typename _InputIterator, typename _Size, typename
> _OutputIterator>
> -    _GLIBCXX20_CONSTEXPR
>      _OutputIterator
>      __copy_n_a(_InputIterator __first, _Size __n, _OutputIterator
> __result,
>          bool)
> @@ -601,6 +604,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>          _Size, _CharT*, bool);
>
>    template<typename _CharT, typename _Size>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_char<_CharT>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_CharT, _CharT&, _CharT*> >::__type
> @@ -753,6 +757,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _Tp, typename _Ref, typename _Ptr, typename _OI>
> +    _GLIBCXX20_CONSTEXPR
>      _OI
>      __copy_move_backward_a1(_GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref,
> _Ptr>,
>       _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Ref, _Ptr>,
> @@ -760,6 +765,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<bool _IsMove,
>      typename _ITp, typename _IRef, typename _IPtr, typename _OTp>
> +    _GLIBCXX20_CONSTEXPR
>      _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>
>      __copy_move_backward_a1(
>   _GLIBCXX_STD_C::_Deque_iterator<_ITp, _IRef, _IPtr>,
> @@ -767,6 +773,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>   _GLIBCXX_STD_C::_Deque_iterator<_OTp, _OTp&, _OTp*>);
>
>    template<bool _IsMove, typename _II, typename _Tp>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value,
>        _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*> >::__type
> @@ -960,6 +967,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      { std::__fill_a1(__first.base(), __last.base(), __value); }
>
>    template<typename _Tp, typename _VTp>
> +    _GLIBCXX20_CONSTEXPR
>      void
>      __fill_a1(const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&,
>         const _GLIBCXX_STD_C::_Deque_iterator<_Tp, _Tp&, _Tp*>&,
> @@ -1217,6 +1225,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>      };
>
>    template<typename _Tp, typename _Ref, typename _Ptr, typename _II>
> +    _GLIBCXX20_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>,
> @@ -1225,12 +1234,14 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_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>
> +    _GLIBCXX20_CONSTEXPR
>      typename __gnu_cxx::__enable_if<
>        __is_any_random_access_iter<_II>::__value, bool>::__type
>      __equal_aux1(_II, _II,
> @@ -1436,6 +1447,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2>
> +    _GLIBCXX20_CONSTEXPR
>      bool
>      __lexicographical_compare_aux1(
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp1, _Ref1, _Ptr1>,
> @@ -1444,6 +1456,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_CONSTEXPR
>      bool
>      __lexicographical_compare_aux1(_Tp1*, _Tp1*,
>   _GLIBCXX_STD_C::_Deque_iterator<_Tp2, _Ref2, _Ptr2>,
> @@ -1451,6 +1464,7 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
>
>    template<typename _Tp1, typename _Ref1, typename _Ptr1,
>      typename _Tp2, typename _Ref2, typename _Ptr2>
> +    _GLIBCXX20_CONSTEXPR
>      bool
>      __lexicographical_compare_aux1(
>   _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 c08212861b6..ba50795d46b 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) { }
> @@ -175,20 +180,24 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        _Deque_iterator& operator=(const _Deque_iterator&) = default;
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_const_cast() const _GLIBCXX_NOEXCEPT
>        { return iterator(_M_cur, _M_node); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        operator*() const _GLIBCXX_NOEXCEPT
>        { return *_M_cur; }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        pointer
>        operator->() const _GLIBCXX_NOEXCEPT
>        { return _M_cur; }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self&
>        operator++() _GLIBCXX_NOEXCEPT
>        {
> @@ -201,6 +210,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return *this;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self
>        operator++(int) _GLIBCXX_NOEXCEPT
>        {
> @@ -209,6 +219,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return __tmp;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self&
>        operator--() _GLIBCXX_NOEXCEPT
>        {
> @@ -221,6 +232,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return *this;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self
>        operator--(int) _GLIBCXX_NOEXCEPT
>        {
> @@ -229,6 +241,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return __tmp;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self&
>        operator+=(difference_type __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -248,11 +261,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return *this;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Self&
>        operator-=(difference_type __n) _GLIBCXX_NOEXCEPT
>        { return *this += -__n; }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        operator[](difference_type __n) const _GLIBCXX_NOEXCEPT
>        { return *(*this + __n); }
> @@ -262,6 +277,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  _M_cur, which should therefore be set by the caller
>         *  immediately afterwards, based on _M_first and _M_last.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_set_node(_Map_pointer __new_node) _GLIBCXX_NOEXCEPT
>        {
> @@ -271,6 +287,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        friend bool
>        operator==(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>        { return __x._M_cur == __y._M_cur; }
> @@ -280,6 +297,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        // operators are in scope (for additional details, see
> libstdc++/3628)
>        template<typename _RefR, typename _PtrR>
>   _GLIBCXX_NODISCARD
> + _GLIBCXX26_CONSTEXPR
>   friend bool
>   operator==(const _Self& __x,
>      const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
> @@ -288,6 +306,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>  #if __cpp_lib_three_way_comparison
>        [[nodiscard]]
> +      _GLIBCXX26_CONSTEXPR
>        friend strong_ordering
>        operator<=>(const _Self& __x, const _Self& __y) noexcept
>        {
> @@ -369,6 +388,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  #endif // three-way comparison
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        friend difference_type
>        operator-(const _Self& __x, const _Self& __y) _GLIBCXX_NOEXCEPT
>        {
> @@ -384,6 +404,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        // parameters.
>        template<typename _RefR, typename _PtrR>
>   _GLIBCXX_NODISCARD
> + _GLIBCXX26_CONSTEXPR
>   friend difference_type
>   operator-(const _Self& __x,
>     const _Deque_iterator<_Tp, _RefR, _PtrR>& __y)
> @@ -396,6 +417,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        friend _Self
>        operator+(const _Self& __x, difference_type __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -405,6 +427,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        friend _Self
>        operator-(const _Self& __x, difference_type __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -414,6 +437,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        friend _Self
>        operator+(difference_type __n, const _Self& __x) _GLIBCXX_NOEXCEPT
>        { return __x + __n; }
> @@ -451,6 +475,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        typedef _Alloc   allocator_type;
>
> +      _GLIBCXX26_CONSTEXPR
>        allocator_type
>        get_allocator() const _GLIBCXX_NOEXCEPT
>        { return allocator_type(_M_get_Tp_allocator()); }
> @@ -458,23 +483,28 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        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()))
>        {
> @@ -483,10 +513,12 @@ _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)
>        {
> @@ -505,6 +537,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        ~_Deque_base() _GLIBCXX_NOEXCEPT;
>
>        typedef typename iterator::_Map_pointer _Map_pointer;
> @@ -516,20 +549,25 @@ _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()
>   { }
>
>  #if __cplusplus >= 201103L
> + _GLIBCXX26_CONSTEXPR
>   _Deque_impl_data(const _Deque_impl_data&) = default;
> + _GLIBCXX26_CONSTEXPR
>   _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
>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_swap_data(_Deque_impl_data& __x) _GLIBCXX_NOEXCEPT
>   {
> @@ -545,40 +583,49 @@ _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)
>   { }
>
>  #if __cplusplus >= 201103L
> + _GLIBCXX26_CONSTEXPR
>   _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
>        };
>
> +      _GLIBCXX26_CONSTEXPR
>        _Tp_alloc_type&
>        _M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
>        { return this->_M_impl; }
>
> +      _GLIBCXX26_CONSTEXPR
>        const _Tp_alloc_type&
>        _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
>        { return this->_M_impl; }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Map_alloc_type
>        _M_get_map_allocator() const _GLIBCXX_NOEXCEPT
>        { return _Map_alloc_type(_M_get_Tp_allocator()); }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Ptr
>        _M_allocate_node()
>        {
> @@ -586,6 +633,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return _Traits::allocate(_M_impl, __deque_buf_size(sizeof(_Tp)));
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_deallocate_node(_Ptr __p) _GLIBCXX_NOEXCEPT
>        {
> @@ -593,6 +641,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   _Traits::deallocate(_M_impl, __p, __deque_buf_size(sizeof(_Tp)));
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Map_pointer
>        _M_allocate_map(size_t __n)
>        {
> @@ -600,6 +649,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return _Map_alloc_traits::allocate(__map_alloc, __n);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_deallocate_map(_Map_pointer __p, size_t __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -607,8 +657,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   _Map_alloc_traits::deallocate(__map_alloc, __p, __n);
>        }
>
> +      _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 };
> @@ -617,6 +670,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      };
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      _Deque_base<_Tp, _Alloc>::
>      ~_Deque_base() _GLIBCXX_NOEXCEPT
>      {
> @@ -637,6 +691,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>     *  The initial underlying memory layout is a bit complicated...
>    */
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      _Deque_base<_Tp, _Alloc>::
>      _M_initialize_map(size_t __num_elements)
> @@ -676,6 +731,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      _Deque_base<_Tp, _Alloc>::
>      _M_create_nodes(_Map_pointer __nstart, _Map_pointer __nfinish)
> @@ -694,6 +750,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>      }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      _Deque_base<_Tp, _Alloc>::
>      _M_destroy_nodes(_Map_pointer __nstart,
> @@ -828,6 +885,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        typedef _Alloc allocator_type;
>
>      private:
> +      _GLIBCXX26_CONSTEXPR
>        static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
>        { return __deque_buf_size(sizeof(_Tp)); }
>
> @@ -854,6 +912,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        /**
>         *  @brief  Creates a %deque with no elements.
>         */
> +      _GLIBCXX26_CONSTEXPR
>  #if __cplusplus >= 201103L
>        deque() = default;
>  #else
> @@ -864,6 +923,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  @brief  Creates a %deque with no elements.
>         *  @param  __a  An allocator object.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        deque(const allocator_type& __a)
>        : _Base(__a, 0) { }
> @@ -877,6 +937,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  This constructor fills the %deque with @a n default
>         *  constructed elements.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        deque(size_type __n, const allocator_type& __a = allocator_type())
>        : _Base(__a, _S_check_init_len(__n, __a))
> @@ -890,6 +951,7 @@ _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))
> @@ -917,6 +979,7 @@ _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())
> @@ -933,9 +996,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  The contents of the moved instance are a valid, but unspecified
>         *  %deque.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        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(),
> @@ -943,15 +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())
>        {
> @@ -976,6 +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)
> @@ -1003,6 +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)
> @@ -1029,6 +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)); }
> @@ -1039,6 +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()); }
>
> @@ -1051,6 +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).
>         */
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(const deque& __x);
>
> @@ -1063,6 +1136,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  if the allocators permit it).
>         *  @a __x is a valid, but unspecified %deque.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(deque&& __x) noexcept(_Alloc_traits::_S_always_equal())
>        {
> @@ -1082,6 +1156,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  resulting %deque's size is the same as the number of elements
>         *  assigned.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(initializer_list<value_type> __l)
>        {
> @@ -1101,6 +1176,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  %deque and that the resulting %deque's size is the same as
>         *  the number of elements assigned.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        assign(size_type __n, const value_type& __val)
>        { _M_fill_assign(__n, __val); }
> @@ -1120,6 +1196,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  #if __cplusplus >= 201103L
>        template<typename _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   void
>   assign(_InputIterator __first, _InputIterator __last)
>   { _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
> @@ -1145,6 +1222,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  resulting %deque's size is the same as the number of elements
>         *  assigned.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        assign(initializer_list<value_type> __l)
>        { _M_assign_aux(__l.begin(), __l.end(),
> random_access_iterator_tag()); }
> @@ -1199,6 +1277,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        /// Get a copy of the memory allocation object.
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        allocator_type
>        get_allocator() const _GLIBCXX_NOEXCEPT
>        { return _Base::get_allocator(); }
> @@ -1209,6 +1288,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  %deque.  Iteration is done in ordinary element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        begin() _GLIBCXX_NOEXCEPT
>        { return this->_M_impl._M_start; }
> @@ -1218,6 +1298,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element in the %deque.  Iteration is done in ordinary element
> order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        begin() const _GLIBCXX_NOEXCEPT
>        { return this->_M_impl._M_start; }
> @@ -1228,6 +1309,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        end() _GLIBCXX_NOEXCEPT
>        { return this->_M_impl._M_finish; }
> @@ -1238,6 +1320,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  ordinary element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        end() const _GLIBCXX_NOEXCEPT
>        { return this->_M_impl._M_finish; }
> @@ -1248,6 +1331,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reverse_iterator
>        rbegin() _GLIBCXX_NOEXCEPT
>        { return reverse_iterator(this->_M_impl._M_finish); }
> @@ -1258,6 +1342,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  reverse element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        rbegin() const _GLIBCXX_NOEXCEPT
>        { return const_reverse_iterator(this->_M_impl._M_finish); }
> @@ -1268,6 +1353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  in reverse element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reverse_iterator
>        rend() _GLIBCXX_NOEXCEPT
>        { return reverse_iterator(this->_M_impl._M_start); }
> @@ -1278,6 +1364,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  done in reverse element order.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        rend() const _GLIBCXX_NOEXCEPT
>        { return const_reverse_iterator(this->_M_impl._M_start); }
> @@ -1288,6 +1375,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element in the %deque.  Iteration is done in ordinary element
> order.
>         */
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        cbegin() const noexcept
>        { return this->_M_impl._M_start; }
> @@ -1298,6 +1386,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  ordinary element order.
>         */
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        cend() const noexcept
>        { return this->_M_impl._M_finish; }
> @@ -1308,6 +1397,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  reverse element order.
>         */
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        crbegin() const noexcept
>        { return const_reverse_iterator(this->_M_impl._M_finish); }
> @@ -1318,6 +1408,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  done in reverse element order.
>         */
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        crend() const noexcept
>        { return const_reverse_iterator(this->_M_impl._M_start); }
> @@ -1326,6 +1417,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        // [23.2.1.2] capacity
>        /**  Returns the number of elements in the %deque.  */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        size_type
>        size() const _GLIBCXX_NOEXCEPT
>        {
> @@ -1337,6 +1429,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        /**  Returns the size() of the largest possible %deque.  */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        size_type
>        max_size() const _GLIBCXX_NOEXCEPT
>        { return _S_max_size(_M_get_Tp_allocator()); }
> @@ -1351,6 +1444,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  %deque's current size the %deque is truncated, otherwise
>         *  default constructed elements are appended.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        resize(size_type __new_size)
>        {
> @@ -1373,6 +1467,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  %deque is extended and new elements are populated with given
>         *  data.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        resize(size_type __new_size, const value_type& __x)
>  #else
> @@ -1401,6 +1496,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>  #if __cplusplus >= 201103L
>        /**  A non-binding request to reduce memory use.  */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        shrink_to_fit() noexcept
>        { _M_shrink_to_fit(); }
> @@ -1410,7 +1506,9 @@ _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; }
>
> @@ -1427,6 +1525,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  see at().)
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        operator[](size_type __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -1446,6 +1545,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  see at().)
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        operator[](size_type __n) const _GLIBCXX_NOEXCEPT
>        {
> @@ -1477,6 +1577,7 @@ _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.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        at(size_type __n)
>        {
> @@ -1495,6 +1596,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  checked that it is in the range of the deque.  The function
> throws
>         *  out_of_range if the check fails.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        at(size_type __n) const
>        {
> @@ -1507,6 +1609,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element of the %deque.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        front() _GLIBCXX_NOEXCEPT
>        {
> @@ -1519,6 +1622,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element of the %deque.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        front() const _GLIBCXX_NOEXCEPT
>        {
> @@ -1531,6 +1635,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  %deque.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        back() _GLIBCXX_NOEXCEPT
>        {
> @@ -1545,6 +1650,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  element of the %deque.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        back() const _GLIBCXX_NOEXCEPT
>        {
> @@ -1564,6 +1670,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  data to it.  Due to the nature of a %deque this operation
>         *  can be done in constant time.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_front(const value_type& __x)
>        {
> @@ -1579,12 +1686,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_front(value_type&& __x)
>        { emplace_front(std::move(__x)); }
>
>        template<typename... _Args>
>  #if __cplusplus > 201402L
> + _GLIBCXX26_CONSTEXPR
>   reference
>  #else
>   void
> @@ -1601,6 +1710,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  to it.  Due to the nature of a %deque this operation can be
>         *  done in constant time.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_back(const value_type& __x)
>        {
> @@ -1616,12 +1726,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_back(value_type&& __x)
>        { emplace_back(std::move(__x)); }
>
>        template<typename... _Args>
>  #if __cplusplus > 201402L
> + _GLIBCXX26_CONSTEXPR
>   reference
>  #else
>   void
> @@ -1637,6 +1749,7 @@ _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.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop_front() _GLIBCXX_NOEXCEPT
>        {
> @@ -1660,6 +1773,7 @@ _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.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop_back() _GLIBCXX_NOEXCEPT
>        {
> @@ -1686,6 +1800,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  with T(std::forward<Args>(args)...) before the specified
> location.
>         */
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   emplace(const_iterator __position, _Args&&... __args);
>
> @@ -1698,6 +1813,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  This function will insert a copy of the given value before the
>         *  specified location.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, const value_type& __x);
>  #else
> @@ -1724,6 +1840,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  This function will insert a copy of the given rvalue before the
>         *  specified location.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, value_type&& __x)
>        { return emplace(__position, std::move(__x)); }
> @@ -1738,6 +1855,7 @@ _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>.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __p, initializer_list<value_type> __l)
>        {
> @@ -1757,6 +1875,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  This function will insert a specified number of copies of the
> given
>         *  data before the location specified by @a __position.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, size_type __n, const value_type&
> __x)
>        {
> @@ -1793,6 +1912,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         */
>        template<typename _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   insert(const_iterator __position, _InputIterator __first,
>          _InputIterator __last)
> @@ -1834,6 +1954,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         * @since C++23
>         */
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   insert_range(const_iterator __pos, _Rg&& __rg);
>
> @@ -1843,6 +1964,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         * @since C++23
>         */
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   prepend_range(_Rg&& __rg);
>
> @@ -1852,6 +1974,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         * @since C++23
>         */
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   append_range(_Rg&& __rg);
>  #endif // containers_ranges
> @@ -1871,6 +1994,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         */
>        iterator
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        erase(const_iterator __position)
>  #else
>        erase(iterator __position)
> @@ -1895,6 +2019,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         */
>        iterator
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        erase(const_iterator __first, const_iterator __last)
>  #else
>        erase(iterator __first, iterator __last)
> @@ -1912,6 +2037,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *
>         *  Whether the allocators are swapped depends on the allocator
> traits.
>         */
> +      // TODO: I don't know if we should poke this.
> +      _GLIBCXX26_CONSTEXPR
>        void
>        swap(deque& __x) _GLIBCXX_NOEXCEPT
>        {
> @@ -1930,6 +2057,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  pointed-to memory is not touched in any way.  Managing the
> pointer is
>         *  the user's responsibility.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        clear() _GLIBCXX_NOEXCEPT
>        { _M_erase_at_end(begin()); }
> @@ -1962,6 +2090,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   }
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        static size_t
>        _S_check_init_len(size_t __n, const allocator_type& __a)
>        {
> @@ -1971,6 +2100,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return __n;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        static size_type
>        _S_max_size(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
>        {
> @@ -1992,12 +2122,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  push_back on each value from the iterator.
>         */
>        template<typename _InputIterator>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_range_initialize(_InputIterator __first, _InputIterator __last,
>       std::input_iterator_tag);
>
>        // called by the second initialize_dispatch above
>        template<typename _ForwardIterator>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
>       std::forward_iterator_tag);
> @@ -2013,11 +2145,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  This function is called only when the user provides an explicit
> size
>         *  (with or without an explicit exemplar value).
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_fill_initialize(const value_type& __value);
>
>  #if __cplusplus >= 201103L
>        // called by deque(n).
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_default_initialize();
>  #endif
> @@ -2093,14 +2227,18 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        void _M_push_front_aux(const value_type&);
>  #else
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   void _M_push_back_aux(_Args&&... __args);
>
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   void _M_push_front_aux(_Args&&... __args);
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        void _M_pop_back_aux();
>
> +      _GLIBCXX26_CONSTEXPR
>        void _M_pop_front_aux();
>        ///@}
>
> @@ -2132,22 +2270,26 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        // insert [__first, __last) at the front, assumes
> distance(__first, __last) is n
>        template<typename _InputIterator, typename _Sentinel>
> +      _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>
> +      _GLIBCXX26_CONSTEXPR
>        void _M_range_append(_InputIterator __first, _Sentinel __last,
>      size_type __n);
>
>        // called by the second insert_dispatch above
>        template<typename _InputIterator>
> + _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>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_range_insert_aux(iterator __pos, _ForwardIterator __first,
>       _ForwardIterator __last, std::forward_iterator_tag);
> @@ -2155,6 +2297,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        // 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).
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_fill_insert(iterator __pos, size_type __n, const value_type&
> __x);
>
> @@ -2192,21 +2335,25 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   deque* _M_this;
>        };
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_insert_aux(iterator __pos, const value_type& __x)
>        { return _M_emplace_aux(__pos, __x); }
>
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   _M_emplace_aux(iterator __pos, _Args&&... __args);
>  #endif
>
>        // called by insert(p,n,x) via fill_insert
> +      _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>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_insert_aux(iterator __pos,
>         _ForwardIterator __first, _ForwardIterator __last,
> @@ -2215,16 +2362,19 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        // Internal erase functions follow.
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_destroy_data_aux(iterator __first, iterator __last);
>
>        // Called by ~deque().
>        // NB: Doesn't deallocate the nodes.
>        template<typename _Alloc1>
> + _GLIBCXX26_CONSTEXPR
>   void
>   _M_destroy_data(iterator __first, iterator __last, const _Alloc1&)
>   { _M_destroy_data_aux(__first, __last); }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_destroy_data(iterator __first, iterator __last,
>         const std::allocator<_Tp>&)
> @@ -2234,6 +2384,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        }
>
>        // Called by erase(q1, q2).
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_erase_at_begin(iterator __pos)
>        {
> @@ -2244,6 +2395,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>        // Called by erase(q1, q2), resize(), clear(), _M_assign_aux,
>        // _M_fill_assign, operator=.
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_erase_at_end(iterator __pos)
>        {
> @@ -2253,23 +2405,28 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   this->_M_impl._M_finish = __pos;
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_erase(iterator __pos);
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_erase(iterator __first, iterator __last);
>
>  #if __cplusplus >= 201103L
>        // Called by resize(sz).
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_default_append(size_type __n);
>
> +      _GLIBCXX26_CONSTEXPR
>        bool
>        _M_shrink_to_fit();
>  #endif
>
>        ///@{
>        /// Memory-handling helpers for the previous internal insert
> functions.
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_reserve_elements_at_front(size_type __n)
>        {
> @@ -2280,6 +2437,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return this->_M_impl._M_start - difference_type(__n);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        _M_reserve_elements_at_back(size_type __n)
>        {
> @@ -2290,9 +2448,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>   return this->_M_impl._M_finish + difference_type(__n);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_new_elements_at_front(size_type __new_elements);
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_new_elements_at_back(size_type __new_elements);
>        ///@}
> @@ -2306,6 +2466,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>         *  actually add the nodes.  Can invalidate _M_map pointers.
>         *  (And consequently, %deque iterators.)
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_reserve_map_at_back(size_type __nodes_to_add = 1)
>        {
> @@ -2314,6 +2475,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>     _M_reallocate_map(__nodes_to_add, false);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_reserve_map_at_front(size_type __nodes_to_add = 1)
>        {
> @@ -2322,6 +2484,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>     _M_reallocate_map(__nodes_to_add, true);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_reallocate_map(size_type __nodes_to_add, bool __add_at_front);
>        ///@}
> @@ -2435,6 +2598,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>    */
>    template<typename _Tp, typename _Alloc>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator==(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>&
> __y)
>      { return __x.size() == __y.size()
> @@ -2454,6 +2618,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>    */
>    template<typename _Tp, typename _Alloc>
>      [[nodiscard]]
> +    constexpr
>      inline __detail::__synth3way_t<_Tp>
>      operator<=>(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>&
> __y)
>      {
> @@ -2511,6 +2676,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
>    /// See std::deque::swap().
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline void
>      swap(deque<_Tp,_Alloc>& __x, deque<_Tp,_Alloc>& __y)
>      _GLIBCXX_NOEXCEPT_IF(noexcept(__x.swap(__y)))
> diff --git a/libstdc++-v3/include/bits/stl_queue.h
> b/libstdc++-v3/include/bits/stl_queue.h
> index 48bd0ebed63..8d73db4b841 100644
> --- a/libstdc++-v3/include/bits/stl_queue.h
> +++ b/libstdc++-v3/include/bits/stl_queue.h
> @@ -115,15 +115,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #endif
>
>        template<typename _Tp1, typename _Seq1>
> + _GLIBCXX26_CONSTEXPR
>   friend bool
>   operator==(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>
>        template<typename _Tp1, typename _Seq1>
> + _GLIBCXX26_CONSTEXPR
>   friend bool
>   operator<(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>
>  #if __cpp_lib_three_way_comparison
>        template<typename _Tp1, three_way_comparable _Seq1>
> + _GLIBCXX26_CONSTEXPR
>   friend compare_three_way_result_t<_Seq1>
>   operator<=>(const queue<_Tp1, _Seq1>&, const queue<_Tp1, _Seq1>&);
>  #endif
> @@ -171,35 +174,43 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #else
>        template<typename _Seq = _Sequence, typename _Requires = typename
>          enable_if<is_default_constructible<_Seq>::value>::type>
> + _GLIBCXX26_CONSTEXPR
>   queue()
>   : c() { }
>
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        queue(const _Sequence& __c)
>        : c(__c) { }
>
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        queue(_Sequence&& __c)
>        : c(std::move(__c)) { }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   explicit
>   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 +218,14 @@ _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 +236,7 @@ _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 +247,7 @@ _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))
>   { }
> @@ -241,12 +256,15 @@ _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
> +      _GLIBCXX26_CONSTEXPR
>        size_type
>        size() const
>        { return c.size(); }
> @@ -256,6 +274,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  element of the %queue.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        front()
>        {
> @@ -268,6 +287,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  element of the %queue.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        front() const
>        {
> @@ -280,6 +300,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  element of the %queue.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        back()
>        {
> @@ -292,6 +313,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  element of the %queue.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        back() const
>        {
> @@ -308,17 +330,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  to it.  The time complexity of the operation depends on the
>         *  underlying sequence.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push(const value_type& __x)
>        { c.push_back(__x); }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push(value_type&& __x)
>        { c.push_back(std::move(__x)); }
>
>  #if __cplusplus > 201402L
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   decltype(auto)
>   emplace(_Args&&... __args)
>   { return c.emplace_back(std::forward<_Args>(__args)...); }
> @@ -332,6 +357,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>  #if __glibcxx_containers_ranges // C++ >= 23
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   push_range(_Rg&& __rg)
>   {
> @@ -353,6 +379,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  data is needed, it should be retrieved before pop() is
>         *  called.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop()
>        {
> @@ -361,6 +388,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        swap(queue& __q)
>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
> @@ -430,6 +458,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator==(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return __x.c == __y.c; }
> @@ -449,6 +478,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return __x.c < __y.c; }
> @@ -456,6 +486,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// Based on operator==
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator!=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return !(__x == __y); }
> @@ -463,6 +494,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// Based on operator<
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return __y < __x; }
> @@ -470,6 +502,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// Based on operator<
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator<=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return !(__y < __x); }
> @@ -477,6 +510,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    /// Based on operator<
>    template<typename _Tp, typename _Seq>
>      _GLIBCXX_NODISCARD
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator>=(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return !(__x < __y); }
> @@ -484,6 +518,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #if __cpp_lib_three_way_comparison
>    template<typename _Tp, three_way_comparable _Seq>
>      [[nodiscard]]
> +    _GLIBCXX26_CONSTEXPR
>      inline compare_three_way_result_t<_Seq>
>      operator<=>(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
>      { return __x.c <=> __y.c; }
> @@ -491,6 +526,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>  #if __cplusplus >= 201103L
>    template<typename _Tp, typename _Seq>
> +    _GLIBCXX26_CONSTEXPR
>      inline
>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>      // Constrained free swap overload, see p0185r1
> @@ -607,22 +643,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _Seq = _Sequence, typename _Requires = typename
>          enable_if<__and_<is_default_constructible<_Compare>,
>   is_default_constructible<_Seq>>::value>::type>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue()
>   : c(), comp() { }
>
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        priority_queue(const _Compare& __x, const _Sequence& __s)
>        : c(__s), comp(__x)
>        { std::make_heap(c.begin(), c.end(), comp); }
>
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        priority_queue(const _Compare& __x, _Sequence&& __s = _Sequence())
>        : c(std::move(__s)), comp(__x)
>        { std::make_heap(c.begin(), c.end(), comp); }
>
> +      _GLIBCXX26_CONSTEXPR
>        priority_queue(const priority_queue&) = default;
> +      _GLIBCXX26_CONSTEXPR
>        priority_queue& operator=(const priority_queue&) = default;
>
> +      _GLIBCXX26_CONSTEXPR
>        priority_queue(priority_queue&& __q)
>        noexcept(__and_<is_nothrow_move_constructible<_Sequence>,
>         is_nothrow_move_constructible<_Compare>>::value)
> @@ -641,32 +683,38 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   explicit
>   priority_queue(const _Alloc& __a)
>   : c(__a), comp() { }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(const _Compare& __x, const _Alloc& __a)
>   : c(__a), comp(__x) { }
>
>        // _GLIBCXX_RESOLVE_LIB_DEFECTS
>        // 2537. Constructors [...] taking allocators should call make_heap
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(const _Compare& __x, const _Sequence& __c,
>          const _Alloc& __a)
>   : c(__c, __a), comp(__x)
>   { std::make_heap(c.begin(), c.end(), comp); }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(const _Compare& __x, _Sequence&& __c, const _Alloc& __a)
>   : c(std::move(__c), __a), comp(__x)
>   { std::make_heap(c.begin(), c.end(), comp); }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(const priority_queue& __q, const _Alloc& __a)
>   : c(__q.c, __a), comp(__q.comp) { }
>
>        template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(priority_queue&& __q, const _Alloc& __a)
>   : c(std::move(__q.c), __a), comp(std::move(__q.comp))
>   { __q.c.clear(); }
> @@ -702,6 +750,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        // 3529. priority_queue(first, last) should construct c with
> (first, last)
>        template<typename _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x = _Compare())
>   : c(__first, __last), comp(__x)
> @@ -711,6 +760,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        // 3522. Missing requirement on InputIterator template parameter
>        template<typename _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x, const _Sequence& __s)
>   : c(__s), comp(__x)
> @@ -722,6 +772,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>        template<typename _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x, _Sequence&& __s)
>   : c(std::move(__s)), comp(__x)
> @@ -736,6 +787,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _InputIterator, typename _Alloc,
>          typename = std::_RequireInputIter<_InputIterator>,
>          typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Alloc& __alloc)
>   : c(__first, __last, __alloc), comp()
> @@ -744,6 +796,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _InputIterator, typename _Alloc,
>          typename = std::_RequireInputIter<_InputIterator>,
>          typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x, const _Alloc& __alloc)
>   : c(__first, __last, __alloc), comp(__x)
> @@ -752,6 +805,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _InputIterator, typename _Alloc,
>          typename = std::_RequireInputIter<_InputIterator>,
>          typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x, const _Sequence& __s,
>          const _Alloc& __alloc)
> @@ -764,6 +818,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>        template<typename _InputIterator, typename _Alloc,
>          typename _Requires = _Uses<_Alloc>>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(_InputIterator __first, _InputIterator __last,
>          const _Compare& __x, _Sequence&& __s,
>          const _Alloc& __alloc)
> @@ -783,18 +838,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         * @{
>         */
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(from_range_t, _Rg&& __rg,
>          const _Compare& __x = _Compare())
>   : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg))), comp(__x)
>   { std::make_heap(c.begin(), c.end(), comp); }
>
>        template<__detail::__container_compatible_range<_Tp> _Rg,
> typename _Alloc>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(from_range_t, _Rg&& __rg, const _Compare& __x,
>          const _Alloc& __a)
>   : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a)), comp(__x)
>   { std::make_heap(c.begin(), c.end(), comp); }
>
>        template<__detail::__container_compatible_range<_Tp> _Rg,
> typename _Alloc>
> + _GLIBCXX26_CONSTEXPR
>   priority_queue(from_range_t, _Rg&& __rg, const _Alloc& __a)
>   : c(ranges::to<_Sequence>(std::forward<_Rg>(__rg), __a)), comp()
>   { std::make_heap(c.begin(), c.end(), comp); }
> @@ -804,12 +862,15 @@ _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
> +      _GLIBCXX26_CONSTEXPR
>        size_type
>        size() const
>        { return c.size(); }
> @@ -819,6 +880,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  element of the %queue.
>         */
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        top() const
>        {
> @@ -834,6 +896,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  The time complexity of the operation depends on the underlying
>         *  sequence.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push(const value_type& __x)
>        {
> @@ -842,6 +905,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push(value_type&& __x)
>        {
> @@ -850,6 +914,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        }
>
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   void
>   emplace(_Args&&... __args)
>   {
> @@ -860,6 +925,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>  #if __glibcxx_containers_ranges // C++ >= 23
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   push_range(_Rg&& __rg)
>   {
> @@ -882,6 +948,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         *  data is needed, it should be retrieved before pop() is
>         *  called.
>         */
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop()
>        {
> @@ -891,6 +958,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        swap(priority_queue& __pq)
>        noexcept(__and_<
> @@ -959,6 +1027,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>  #if __cplusplus >= 201103L
>    template<typename _Tp, typename _Sequence, typename _Compare>
> +    _GLIBCXX26_CONSTEXPR
>      inline
>  #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
>      // Constrained free swap overload, see p0185r1
> diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h
> b/libstdc++-v3/include/bits/stl_uninitialized.h
> index 82e4ba2ff7b..af50649b3e2 100644
> --- a/libstdc++-v3/include/bits/stl_uninitialized.h
> +++ b/libstdc++-v3/include/bits/stl_uninitialized.h
> @@ -975,6 +975,7 @@ _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>
> +    _GLIBCXX26_CONSTEXPR
>      void
>      __uninitialized_default_a(_ForwardIterator __first,
>         _ForwardIterator __last,
> @@ -990,6 +991,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>  #if _GLIBCXX_HOSTED
>    template<typename _ForwardIterator, typename _Tp>
> +    _GLIBCXX26_CONSTEXPR
>      inline void
>      __uninitialized_default_a(_ForwardIterator __first,
>         _ForwardIterator __last,
> diff --git a/libstdc++-v3/include/bits/version.def
> b/libstdc++-v3/include/bits/version.def
> index c7709ba3a07..70c2af36e43 100644
> --- a/libstdc++-v3/include/bits/version.def
> +++ b/libstdc++-v3/include/bits/version.def
> @@ -2317,6 +2317,22 @@ ftms = {
>    };
>  };
>
> +ftms = {
> +  name = constexpr_queue;
> +  values = {
> +    v = 202502;
> +    cxxmin = 26;
> +  };
> +};
> +
> +ftms = {
> +  name = constexpr_deque;
> +  values = {
> +    v = 202502;
> +    cxxmin = 26;
> +  };
> +};
> +
>  // Standard test specifications.
>  stds[97] = ">= 199711L";
>  stds[03] = ">= 199711L";
> diff --git a/libstdc++-v3/include/bits/version.h
> b/libstdc++-v3/include/bits/version.h
> index c72cda506f1..89a9bfb7f9b 100644
> --- a/libstdc++-v3/include/bits/version.h
> +++ b/libstdc++-v3/include/bits/version.h
> @@ -2596,4 +2596,24 @@
>  #endif /* !defined(__cpp_lib_contracts) */
>  #undef __glibcxx_want_contracts
>
> +#if !defined(__cpp_lib_constexpr_queue)
> +# if (__cplusplus >  202302L)
> +#  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) &&
> defined(__glibcxx_want_constexpr_queue) */
> +#undef __glibcxx_want_constexpr_queue
> +
> +#if !defined(__cpp_lib_constexpr_deque)
> +# if (__cplusplus >  202302L)
> +#  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) &&
> defined(__glibcxx_want_constexpr_deque) */
> +#undef __glibcxx_want_constexpr_deque
> +
>  #undef __glibcxx_want_all
> diff --git a/libstdc++-v3/include/debug/deque
> b/libstdc++-v3/include/debug/deque
> index 9fba4ffc499..789ceca4a54 100644
> --- a/libstdc++-v3/include/debug/deque
> +++ b/libstdc++-v3/include/debug/deque
> @@ -106,32 +106,42 @@ namespace __debug
>
>        ~deque() { }
>  #else
> +      _GLIBCXX26_CONSTEXPR
>        deque() = default;
> +      _GLIBCXX26_CONSTEXPR
>        deque(const deque&) = default;
> +      _GLIBCXX26_CONSTEXPR
>        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) { }
>
> +      _GLIBCXX26_CONSTEXPR
>        ~deque() = default;
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        deque(const _Allocator& __a)
>        : _Base(__a) { }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        explicit
>        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) { }
> @@ -145,6 +155,7 @@ namespace __debug
>  #if __cplusplus >= 201103L
>        template<class _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>  #else
>        template<class _InputIterator>
>  #endif
> @@ -157,21 +168,26 @@ namespace __debug
>
>  #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) { }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(const deque&) = default;
>
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(deque&&) = default;
>
> +      _GLIBCXX26_CONSTEXPR
>        deque&
>        operator=(initializer_list<value_type> __l)
>        {
> @@ -184,6 +200,7 @@ namespace __debug
>  #if __cplusplus >= 201103L
>        template<class _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> +      _GLIBCXX26_CONSTEXPR
>  #else
>        template<class _InputIterator>
>  #endif
> @@ -201,6 +218,7 @@ namespace __debug
>     this->_M_invalidate_all();
>   }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        assign(size_type __n, const _Tp& __t)
>        {
> @@ -209,6 +227,7 @@ namespace __debug
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        assign(initializer_list<value_type> __l)
>        {
> @@ -219,6 +238,7 @@ namespace __debug
>
>  #if __glibcxx_containers_ranges // C++ >= 23
>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
> +        _GLIBCXX26_CONSTEXPR
>   void
>   assign_range(_Rg&& __rg)
>   {
> @@ -231,68 +251,81 @@ namespace __debug
>
>        // iterators:
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        begin() _GLIBCXX_NOEXCEPT
>        { return iterator(_Base::begin(), this); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        begin() const _GLIBCXX_NOEXCEPT
>        { return const_iterator(_Base::begin(), this); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        end() _GLIBCXX_NOEXCEPT
>        { return iterator(_Base::end(), this); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        end() const _GLIBCXX_NOEXCEPT
>        { return const_iterator(_Base::end(), this); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reverse_iterator
>        rbegin() _GLIBCXX_NOEXCEPT
>        { return reverse_iterator(end()); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        rbegin() const _GLIBCXX_NOEXCEPT
>        { return const_reverse_iterator(end()); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reverse_iterator
>        rend() _GLIBCXX_NOEXCEPT
>        { return reverse_iterator(begin()); }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        rend() const _GLIBCXX_NOEXCEPT
>        { return const_reverse_iterator(begin()); }
>
>  #if __cplusplus >= 201103L
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        cbegin() const noexcept
>        { return const_iterator(_Base::begin(), this); }
>
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_iterator
>        cend() const noexcept
>        { return const_iterator(_Base::end(), this); }
>
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        crbegin() const noexcept
>        { return const_reverse_iterator(end()); }
>
>        [[__nodiscard__]]
> +      _GLIBCXX26_CONSTEXPR
>        const_reverse_iterator
>        crend() const noexcept
>        { return const_reverse_iterator(begin()); }
>  #endif
>
>      private:
> +      _GLIBCXX26_CONSTEXPR
>        void
>        _M_invalidate_after_nth(difference_type __n)
>        {
> @@ -306,6 +339,7 @@ namespace __debug
>        using _Base::max_size;
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        resize(size_type __sz)
>        {
> @@ -319,6 +353,7 @@ namespace __debug
>     this->_M_invalidate_all();
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        resize(size_type __sz, const _Tp& __c)
>        {
> @@ -347,6 +382,7 @@ namespace __debug
>  #endif
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        shrink_to_fit() noexcept
>        {
> @@ -359,6 +395,7 @@ namespace __debug
>
>        // element access:
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        operator[](size_type __n) _GLIBCXX_NOEXCEPT
>        {
> @@ -367,6 +404,7 @@ namespace __debug
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        operator[](size_type __n) const _GLIBCXX_NOEXCEPT
>        {
> @@ -377,6 +415,7 @@ namespace __debug
>        using _Base::at;
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        front() _GLIBCXX_NOEXCEPT
>        {
> @@ -385,6 +424,7 @@ namespace __debug
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        front() const _GLIBCXX_NOEXCEPT
>        {
> @@ -393,6 +433,7 @@ namespace __debug
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        reference
>        back() _GLIBCXX_NOEXCEPT
>        {
> @@ -401,6 +442,7 @@ namespace __debug
>        }
>
>        _GLIBCXX_NODISCARD
> +      _GLIBCXX26_CONSTEXPR
>        const_reference
>        back() const _GLIBCXX_NOEXCEPT
>        {
> @@ -409,6 +451,7 @@ namespace __debug
>        }
>
>        // 23.2.1.3 modifiers:
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_front(const _Tp& __x)
>        {
> @@ -416,6 +459,7 @@ namespace __debug
>   this->_M_invalidate_all();
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_back(const _Tp& __x)
>        {
> @@ -424,16 +468,19 @@ namespace __debug
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_front(_Tp&& __x)
>        { emplace_front(std::move(__x)); }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        push_back(_Tp&& __x)
>        { emplace_back(std::move(__x)); }
>
>        template<typename... _Args>
>  #if __cplusplus > 201402L
> + _GLIBCXX26_CONSTEXPR
>   reference
>  #else
>   void
> @@ -449,6 +496,7 @@ namespace __debug
>
>        template<typename... _Args>
>  #if __cplusplus > 201402L
> + _GLIBCXX26_CONSTEXPR
>   reference
>  #else
>   void
> @@ -463,6 +511,7 @@ namespace __debug
>   }
>
>        template<typename... _Args>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   emplace(const_iterator __position, _Args&&... __args)
>   {
> @@ -474,6 +523,7 @@ namespace __debug
>   }
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>  #if __cplusplus >= 201103L
>        insert(const_iterator __position, const _Tp& __x)
> @@ -488,10 +538,12 @@ namespace __debug
>        }
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, _Tp&& __x)
>        { return emplace(__position, std::move(__x)); }
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, initializer_list<value_type> __l)
>        {
> @@ -503,6 +555,7 @@ namespace __debug
>  #endif
>
>  #if __cplusplus >= 201103L
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>        insert(const_iterator __position, size_type __n, const _Tp& __x)
>        {
> @@ -524,6 +577,7 @@ namespace __debug
>  #if __cplusplus >= 201103L
>        template<class _InputIterator,
>          typename = std::_RequireInputIter<_InputIterator>>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   insert(const_iterator __position,
>          _InputIterator __first, _InputIterator __last)
> @@ -563,6 +617,7 @@ namespace __debug
>
>  #if __glibcxx_containers_ranges // C++ >= 23
>        template<__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   iterator
>   insert_range(const_iterator __pos, _Rg&& __rg)
>   {
> @@ -572,6 +627,7 @@ namespace __debug
>   }
>
>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   prepend_range(_Rg&& __rg)
>   {
> @@ -580,6 +636,7 @@ namespace __debug
>   }
>
>        template<std::__detail::__container_compatible_range<_Tp> _Rg>
> + _GLIBCXX26_CONSTEXPR
>   void
>   append_range(_Rg&& __rg)
>   {
> @@ -588,6 +645,7 @@ namespace __debug
>   }
>  #endif
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop_front() _GLIBCXX_NOEXCEPT
>        {
> @@ -596,6 +654,7 @@ namespace __debug
>   _Base::pop_front();
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        pop_back() _GLIBCXX_NOEXCEPT
>        {
> @@ -604,6 +663,7 @@ namespace __debug
>   _Base::pop_back();
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>  #if __cplusplus >= 201103L
>        erase(const_iterator __position)
> @@ -630,6 +690,7 @@ namespace __debug
>     }
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        iterator
>  #if __cplusplus >= 201103L
>        erase(const_iterator __first, const_iterator __last)
> @@ -677,6 +738,7 @@ namespace __debug
>     }
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        swap(deque& __x)
>        _GLIBCXX_NOEXCEPT_IF( noexcept(declval<_Base&>().swap(__x)) )
> @@ -685,6 +747,7 @@ namespace __debug
>   _Base::swap(__x);
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        void
>        clear() _GLIBCXX_NOEXCEPT
>        {
> @@ -692,9 +755,11 @@ namespace __debug
>   this->_M_invalidate_all();
>        }
>
> +      _GLIBCXX26_CONSTEXPR
>        _Base&
>        _M_base() _GLIBCXX_NOEXCEPT { return *this; }
>
> +      _GLIBCXX26_CONSTEXPR
>        const _Base&
>        _M_base() const _GLIBCXX_NOEXCEPT { return *this; }
>      };
> @@ -722,6 +787,7 @@ namespace __debug
>  #endif
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator==(const deque<_Tp, _Alloc>& __lhs,
>          const deque<_Tp, _Alloc>& __rhs)
> @@ -734,30 +800,35 @@ namespace __debug
>      { return __x._M_base() <=> __y._M_base(); }
>  #else
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator!=(const deque<_Tp, _Alloc>& __lhs,
>          const deque<_Tp, _Alloc>& __rhs)
>      { return __lhs._M_base() != __rhs._M_base(); }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator<(const deque<_Tp, _Alloc>& __lhs,
>         const deque<_Tp, _Alloc>& __rhs)
>      { return __lhs._M_base() < __rhs._M_base(); }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator<=(const deque<_Tp, _Alloc>& __lhs,
>          const deque<_Tp, _Alloc>& __rhs)
>      { return __lhs._M_base() <= __rhs._M_base(); }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator>=(const deque<_Tp, _Alloc>& __lhs,
>          const deque<_Tp, _Alloc>& __rhs)
>      { return __lhs._M_base() >= __rhs._M_base(); }
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline bool
>      operator>(const deque<_Tp, _Alloc>& __lhs,
>         const deque<_Tp, _Alloc>& __rhs)
> @@ -765,6 +836,7 @@ namespace __debug
>  #endif // three-way comparison
>
>    template<typename _Tp, typename _Alloc>
> +    _GLIBCXX26_CONSTEXPR
>      inline void
>      swap(deque<_Tp, _Alloc>& __lhs, deque<_Tp, _Alloc>& __rhs)
>      _GLIBCXX_NOEXCEPT_IF(noexcept(__lhs.swap(__rhs)))
> diff --git a/libstdc++-v3/include/std/deque
> b/libstdc++-v3/include/std/deque
> index 3899b68e736..f68f57faf35 100644
> --- a/libstdc++-v3/include/std/deque
> +++ b/libstdc++-v3/include/std/deque
> @@ -73,7 +73,7 @@
>
>  #define __glibcxx_want_algorithm_default_value_type
>  #define __glibcxx_want_allocator_traits_is_always_equal
> -#define __glibcxx_want_containers_ranges
> +#define __glibcxx_want_constexpr_deque
>  #define __glibcxx_want_erase_if
>  #define __glibcxx_want_nonmember_container_access
>  #include <bits/version.h>
> @@ -102,12 +102,14 @@ namespace std _GLIBCXX_VISIBILITY(default)
>  _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>    template<typename _Tp, typename _Alloc, typename _Predicate>
> +    _GLIBCXX26_CONSTEXPR
>      inline 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)>
> +    _GLIBCXX26_CONSTEXPR
>      inline 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..d6a14055a6a 100644
> --- a/libstdc++-v3/include/std/queue
> +++ b/libstdc++-v3/include/std/queue
> @@ -63,6 +63,8 @@
>
>  #define __glibcxx_want_adaptor_iterator_pair_constructor
>  #define __glibcxx_want_containers_ranges
> +#define __glibcxx_want_containers_constexpr
> +#define __glibcxx_want_constexpr_queue
>  #include <bits/version.h>
>
>  #include <deque>
> @@ -105,10 +107,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>   { return _M_f.format(__a.c, __fc); }
>
>      private:
> -      // Standard uses formatter<ref_view<_Container>, _CharT>, but
> range_formatter
> -      // provides same behavior.
> -      // _GLIBCXX_RESOLVE_LIB_DEFECTS
> -      // 3881. Incorrect formatting of container adapters backed by
> std::string
> +      // Standard uses formatter<ref_view<_Container>, _CharT>.
>
Any reason to remove _GLIBCXX_RESOLVE_LIB_DEFECTS?

>        range_formatter<_Tp, _CharT> _M_f;
>      };
>
> @@ -147,10 +146,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>   { return _M_f.format(__a.c, __fc); }
>
>      private:
> -      // Standard uses formatter<ref_view<_Container>, _CharT>, but
> range_formatter
> -      // provides same behavior.
> -      // _GLIBCXX_RESOLVE_LIB_DEFECTS
> -      // 3881. Incorrect formatting of container adapters backed by
> std::string
> +      // Standard uses formatter<ref_view<_Container>, _CharT>.
>        range_formatter<_Tp, _CharT> _M_f;
>      };
>
> 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..25c5cd7025f
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
> @@ -0,0 +1,348 @@
> +// { dg-do run { target c++26 } }
> +// { dg-xfail-if "" { *-*-* } { "-D_GLIBCXX_DEBUG } { "" } }
> +
> +#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>
> +
> +template<typename Alloc>
> +constexpr bool ctor_tests()
> +{
> +
> +  Alloc alloc;
> +
> +  std::deque<int> dq1 {};
> +
> +  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};
> +  auto dq5 = std::deque(rg.begin(), rg.end());
> +  VERIFY( dq5.front() == 2 );
> +  VERIFY( dq5.back() == 7 );
> +  VERIFY( dq5.size() == 4 );
> +
> +  auto dq6 = std::deque<int>(std::from_range, rg);
> +  VERIFY(dq6 == dq5);
> +
> +  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;
> +}
> +
> +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;
> +}
> +
> +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;
> +}
> +
> +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;
> +}
> +
> +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;
> +}
> +
> +template<typename Range>
> +constexpr void
> +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 );
> +}
> +
> +constexpr void do_ranges_tests()
> +{
> +  using namespace __gnu_test;
> +  ranges_test<test_forward_range<int>>();
> +  ranges_test<test_forward_sized_range<int>>();
> +  ranges_test<test_sized_range_sized_sent<int,
> forward_iterator_wrapper>>();
> +
> +  ranges_test<test_input_range<int>>();
> +  ranges_test<test_input_sized_range<int>>();
> +  ranges_test<test_sized_range_sized_sent<int, input_iterator_wrapper>>();
> +
> +  ranges_test<test_range<int, input_iterator_wrapper_nocopy>>();
> +  ranges_test<test_sized_range<int, input_iterator_wrapper_nocopy>>();
> +  ranges_test<test_sized_range_sized_sent<int,
> input_iterator_wrapper_nocopy>>();
> +
> +  ranges_test<test_forward_range<short>>();
> +  ranges_test<test_input_range<short>>();
> +
> +  //TODO: this probably needs to be converted to be proper. Needs to
> be r-values?
> +  struct C {
> +    constexpr C(int v) : val(v) { }
> +    constexpr operator int() { return val; }
> +    constexpr bool operator==(int b) { return b == val; }
> +    constexpr bool operator!=(int b) { return b != val; }
> +    int val;
> +  };
> +  using rvalue_input_range = test_range<C, input_iterator_wrapper_rval>;
> +  ranges_test<rvalue_input_range>();
> +}
> +
> +constexpr void do_ctor_tests()
> +{
> +  using namespace __gnu_test;
> +  ctor_tests<std::allocator<int>>();
> +  ctor_tests<SimpleAllocator<int>>();
> +}
> +
> +constexpr bool do_tests()
> +{
> +  do_ctor_tests();
> +  insert_tests();
> +  iterators_tests();
> +  capacity_tests();
> +  nonmember_tests();
> +  // Additional code coverage
> +  do_ranges_tests();
> +  return true;
> +}
> +
> +int main ()
> +{
> +  do_tests();
> +  static_assert( do_tests() );
> +}
> diff --git a/libstdc++-v3/testsuite/23_containers/deque/debug/constexpr.cc
> b/libstdc++-v3/testsuite/23_containers/deque/debug/constexpr.cc
> new file mode 100644
> index 00000000000..0a9552325a1
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/23_containers/deque/debug/constexpr.cc
> @@ -0,0 +1,361 @@
> +// { dg-do run { target c++26 } }
> +// { dg-xfail-if "" { *-*-* } { "-D_GLIBCXX_DEBUG } { "" } }
> +// { dg-require-debug-mode "" }
> +
> +#include <debug/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>
> +
> +constexpr bool ctor_tests()
> +{
> +
> +  using Alloc = __gnu_test::SimpleAllocator<int>;
> +  Alloc alloc;
> +
> +  std::deque<int> dq1 {};
> +
> +  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( dq3.front() == 5 );
> +  VERIFY( dq3.size() == 4 );
> +
> +  auto rg = {2, 3, 5, 7};
> +  auto dq5 = std::deque(rg.begin(), rg.end());
> +  VERIFY( dq5.front() == 2 );
> +  VERIFY( dq5.back() == 7 );
> +  VERIFY( dq5.size() == 5 );
> +
> +  auto dq6 = std::deque<int>(std::from_range, rg);
> +  VERIFY(dq6 == dq5);
> +
> +  std::deque<int> dq7 (dq1);
> +  VERIFY( dq7 == dq1 );
> +  std::deque<int>dq8 (std::move(dq1));
> +  VERIFY( dq8 == dq7 );
> +
> +  std::deque<int, Alloc> dq9 (dq1, alloc);
> +  std::deque<int, Alloc> dq10 (std::move(dq1), alloc);
> +  VERIFY ( dq9 == dq10 );
> +  std::deque<int, Alloc> dq11 (rg, alloc);
> +  VERIFY( dq11 == dq5 );
> +
> +  return true;
> +}
> +
> +static_assert(ctor_tests());
> +
> +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<Range>
> +constexpr void
> +ranges_test()
> +{
> +  using Tp = std::ranges::range_value_t<Range>;
> +  Range rg [] {2, 3, 5, 7}; //TODO: is this optimally clean?
> +
> +  //  Constructor tests
> +
> +  auto dq0 = std::deque(rg.begin(), rg.end());
> +  VERIFY( dq0.front() == 2 );
> +  VERIFY( dq0.back() == 7 );
> +  VERIFY( dq0.size() == 5 );
> +
> +  auto dq1 = std::deque<int>(std::from_range, rg);
> +  VERIFY(dq1 == dq0);
> +
> +  // Insert tests
> +
> +  rg = {1, 2, 3, 4, 5};
> +
> +  std::deque<int> dq1;
> +  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> 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 );
> +}
> +
> +constexpr bool do_tests()
> +{
> +  using namespace __gnu_test;
> +  ranges_test<foo>(bar); // TODO:
> +
> +  ranges_test<test_forward_range<int>>();
> +  ranges_test<test_forward_sized_range<int>>();
> +  ranges_test<test_sized_range_sized_sent<int,
> forward_iterator_wrapper>>();
> +
> +  ranges_test<test_input_range<int>>();
> +  ranges_test<test_input_sized_range<int>>();
> +  ranges_test<test_sized_range_sized_sent<int, input_iterator_wrapper>>();
> +
> +  ranges_test<test_range<int, input_iterator_wrapper_nocopy>>();
> +  ranges_test<test_sized_range<int, input_iterator_wrapper_nocopy>>();
> +  ranges_test<test_sized_range_sized_sent<int,
> input_iterator_wrapper_nocopy>>();
> +
> +  ranges_test<test_forward_range<short>>();
> +  ranges_test<test_input_range<short>>();
> +
> +  struct C {
> +    constexpr C(int v) : val(v) { }
> +    constexpr operator int() && { return val; }
> +    constexpr bool operator==(int b) const { return b == val; }
> +    int val;
> +  };
> +  using rvalue_input_range = test_range<C, input_iterator_wrapper_rval>;
> +  ranges_test<rvalue_input_range>();
> +
> +  ctor_tests();
> +  insert_tests();
> +  iterators_tests();
> +  capacity_tests();
> +  nonmember_tests();
> +  return true;
> +}
> +
> +static_assert( do_tests() );
> diff --git
> a/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
> b/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
> new file mode 100644
> index 00000000000..de1ba25a420
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/23_containers/priority_queue/constexpr.cc
> @@ -0,0 +1,323 @@
> +// { dg-do run { target c++26 } }
> +// { dg-xfail-if "" { *-*-* } { "-D_GLIBCXX_DEBUG } { "" } }
> +
> +#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 <algorithm>
> +#include <ranges>
> +#include <functional>
> +#include <vector>
> +#include <numeric>
> +#include <testsuite_hooks.h>
> +#include <testsuite_iterators.h>
> +#include <testsuite_allocator.h>
> +
> +#include <iostream>
> +
> +struct Gt {
> +  template<typename T, typename U>
> +  constexpr bool operator()(T const& l, U const & r) {
> +    return l > r;
> +  }
> +};
> +
> +template<typename Cont, typename Cmp = std::less<int>>
> +constexpr void 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 );
> +
> +  std::priority_queue<V, Cont, Cmp> pq5 (pq3);
> +  VERIFY( pq5.top() == pq3.top() );
> +  VERIFY( pq5.size() == pq3.size() );
> +
> +  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() );
> +}
> +
> +
> +constexpr bool push_and_pop_test()
> +{
> +  std::priority_queue<int> a;
> +  a.push(1);
> +  a.pop();
> +
> +  return true;
> +}
> +
> +static_assert( push_and_pop_test() );
> +
> +constexpr bool top_test ()
> +{
> +  std::priority_queue<int> a;
> +  a.push(2);
> +  a.push(4);
> +  VERIFY( a.top() == 4 );
> +
> +  return true;
> +}
> +
> +static_assert( top_test() );
> +
> +template<typename Range, typename Cont, typename Comp = std::less<int>>
> +constexpr void push_range_test(Comp comp = Comp())
> +{
> +  using T = std::ranges::range_value_t<Range>;
> +  using V = typename Cont::value_type;
> +  T rg[] {2, 3, 5, 7};
> +
> +  std::vector<T> s(std::from_range, rg);
> +  std::ranges::sort(s, comp);
> +
> +  std::priority_queue<V, Cont, Comp> pq;
> +  pq.push_range(Range(rg, rg+4));
> +
> +  for (auto const& v : s | std::views::reverse) {
> +    VERIFY(v == pq.top());
> +    pq.pop();
> +  }
> +}
> +
> +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());
> +
> +struct S
> +{
> +  int foo;
> +  constexpr S(int i, int j) : foo{i + j} {}
> +  constexpr friend bool operator< (S const &x, S const &y) { return
> x.foo < y.foo; }
> +};
> +
> +constexpr bool emplace_test()
> +{
> +  std::priority_queue<S> pq;
> +  pq.emplace(0, 0);
> +  pq.emplace(1, 0);
> +  VERIFY( pq.size() == 2 );
> +  VERIFY( pq.top().foo == 1 );
> +  pq.pop();
> +  VERIFY ( pq.top().foo == 0 );
> +  return true;
> +}
> +
> +static_assert( emplace_test() );
> +
> +template<typename Container, typename Cmp>
> +constexpr void constructor_tests()
> +{
> +
> +}
> +
> +constexpr bool do_tests()
> +{
> +//  constructor_tests<>();
> +//  swap_test<>();
> +  emplace_test();
> +  return true;
> +}
> +
> +template<typename Range, typename Cont, typename Cmp = std::less<int>>
> +constexpr bool 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>;
> +
> +  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}) );
> +
> +  auto pq2 = std::priority_queue<V, Cont, Cmp>(std::from_range,
> Range(rg, rg+5), alloc);
> +  VERIFY( eq(pq2, {rg, 5}) );
> +
> +  auto pq3 = std::priority_queue<V, Cont, Cmp>(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}) );
> +
> +  return true;
> +}
> +
> +template<typename Range, typename Cont>
> +constexpr void do_ranges_tests_b()
> +{
> +  range_tests<Range,
> +       Cont>();
> +  range_tests<Range,
> +       Cont,
> +       Gt>();
> +}
> +
> +template<typename Cont>
> +constexpr void do_ranges_tests_a() {
> +  using T = typename Cont::value_type;
> +  using namespace __gnu_test;
> +  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>();
> +
> +  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>();
> +}
> +
> +constexpr void do_ranges_tests()
> +{
> +  using namespace __gnu_test;
> +  do_ranges_tests_a<std::vector<int>>();
> +  do_ranges_tests_a<std::vector<int, SimpleAllocator<int>>>();
> +  do_ranges_tests_a<std::deque<int>>();
> +  do_ranges_tests_a<std::deque<int, SimpleAllocator<int>>>();
> +}
> +
> +template <typename Cont>
> +constexpr void do_ctor_tests_a()
> +{
> +  ctor_tests<Cont>();
> +  ctor_tests<Cont, Gt>();
> +}
> +
> +constexpr void do_ctor_tests()
> +{
> +  using namespace __gnu_test;
> +  do_ctor_tests_a<std::vector<int>>();
> +  do_ctor_tests_a<std::vector<int, SimpleAllocator<int>>>();
> +  do_ctor_tests_a<std::deque<int>>();
> +  do_ctor_tests_a<std::deque<int, SimpleAllocator<int>>>();
> +}
> +
> +constexpr bool do_all_tests()
> +{
> +  do_ctor_tests();
> +  push_and_pop_test();
> +  top_test();
> +  swap_test();
> +  emplace_test();
> +
> +  do_ranges_tests();
> +
> +  return true;
> +}
> +
> +static_assert (do_all_tests());
> +
> +int main()
> +{
> +  static_assert( do_all_tests() );
> +  do_all_tests();
> +}
> 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..24ae8d85c63
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/23_containers/queue/constexpr.cc
> @@ -0,0 +1,281 @@
> +// { dg-do run { target c++26 } }
> +// { dg-xfail-if "" { *-*-* } { "-D_GLIBCXX_DEBUG } { "" } }
> +
> +#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>
> +
> +template<typename Container>
> +constexpr void ctor_tests()
> +{
> +  using Tp = typename Container::value_type;
> +  using Alloc = typename Container::allocator_type;
> +
> +  auto eq = [] (std::queue<Tp, Container> 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;
> +  };
> +
> +  Container c0 {};
> +  Alloc alloc0;
> +
> +  std::queue<Tp, Container> q1 (c0);
> +  VERIFY( q1.size() == 0 && q1.empty() );
> +  q1.push(1);
> +  q1.push(2);
> +  VERIFY( q1.size() == 2) ;
> +
> +  Container c1 {1, 2};
> +  std::queue<Tp, Container> q2 {c1}; // q4
> +  VERIFY ( q2 == q1 );
> +  std::queue<Tp, Container> q3 {std::move(c1)}; //q5
> +  VERIFY ( q3 == q1 );
> +
> +  std::queue<Tp, Container> q4 {q1};
> +  std::queue<Tp, Container> q5 {std::move(q1)};
> +  VERIFY ( q4 == q5 );
> +
> +  Tp rg[4] = {2, 3, 5, 7};
> +  std::queue<Tp, Container> q6(std::begin(rg), std::end(rg)); // q3
> +  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();
> +
> +  Container c2 {1, 2};
> +
> +  std::queue<Tp, Container> q7 (alloc0);
> +  q7.push(1);
> +  q7.push(2);
> +  VERIFY( q7.size() == 2 );
> +
> +  std::queue<Tp, Container> q8 (c2, alloc0);
> +  VERIFY( q8 == q7 );
> +
> +  std::queue<Tp, Container> q9 (std::move(c2), alloc0);
> +  VERIFY( q9 == q7 );
> +  VERIFY( c2.empty() );
> +
> +  std::queue<Tp, Container> q10 (q7, alloc0);
> +  VERIFY( q10 == q7 );
> +  VERIFY( q10.size() == q7.size() );
> +  VERIFY( q10.front() == q7.front() );
> +  VERIFY( q10.back() == q7.back() );
> +
> +  std::queue<Tp, Container> q11 (std::move(q7), alloc0);
> +  VERIFY( q11 == q10 );
> +  VERIFY( q11.size() == q10.size() );
> +  VERIFY( q7.empty() );
> +
> +  std::queue<Tp, Container> 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();
> +
> +  auto q13 = std::queue<Tp, Container>(std::from_range, rg);
> +  VERIFY ( eq(q13, rg) );
> +  auto q14 = std::queue<Tp, Container>(std::from_range, rg, alloc0);
> +  VERIFY ( eq(q14, rg) );
> +
> +}
> +
> +template<typename Range, typename Alloc>
> +constexpr void
> +do_ranges_tests_a()
> +{
> +  using Tp = std::ranges::range_value_t<Range>;
> +  Alloc 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;
> +  };
> +
> +  auto q1 = std::queue<Tp>(std::from_range, Range(a, a+4));
> +  std::queue<Tp> q2;
> +  q2.push_range(Range(a, a+4));
> +  VERIFY( eq (q1, q2) );
> +
> +  // TODO: Can check also list when made constexpr.
> +  auto q3 = std::queue<Tp, std::deque<Tp, Alloc>>(std::from_range,
> Range(a, a+4), alloc);
> +  auto q4 = std::queue<Tp>(std::from_range, Range(a, a+4));
> +  VERIFY( eq (q3, q4) );
> +}
> +
> +template<typename Alloc>
> +constexpr void
> +do_ranges_tests()
> +{
> +  using namespace __gnu_test;
> +  using Tp = std::allocator_traits<Alloc>::value_type;
> +
> +  do_ranges_tests_a<test_forward_range<Tp>,
> +      Alloc>();
> +  do_ranges_tests_a<test_forward_sized_range<Tp>,
> +      Alloc>();
> +  do_ranges_tests_a<test_sized_range_sized_sent
> + <Tp, forward_iterator_wrapper>,
> +        Alloc>();
> +
> +  do_ranges_tests_a<test_input_range<Tp>, Alloc>();
> +  do_ranges_tests_a<test_input_sized_range<Tp>, Alloc>();
> +  do_ranges_tests_a<test_sized_range_sized_sent<Tp,
> forward_iterator_wrapper>,
> +        Alloc>();
> +
> +  do_ranges_tests_a<test_range<Tp, input_iterator_wrapper_nocopy>,
> +        Alloc>();
> +  do_ranges_tests_a<test_sized_range<Tp, input_iterator_wrapper_nocopy>,
> +        Alloc>();
> +  do_ranges_tests_a<test_sized_range_sized_sent<Tp,
> input_iterator_wrapper_nocopy>,
> +        Alloc>();
> +}
> +
> +constexpr void push_and_pop_test()
> +{
> +  std::queue<int> a;
> +  a.push(1);
> +  a.pop();
> +}
> +
> +constexpr void push_range_test()
> +{
> +  std::queue<int> a;
> +  const auto rg = {2, 3, 5, 7};
> +  a.push_range(rg);
> +  VERIFY (a.size() == 4);
> +  VERIFY (a.front() == 2);
> +  a.pop();
> +  VERIFY (a.front() == 3);
> +  a.pop();
> +  VERIFY (a.front() == 5);
> +  a.pop();
> +  VERIFY (a.front() == 7);
> +  a.pop();
> +  VERIFY (a.size() == 0);
> +}
> +
> +constexpr void 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 );
> +}
> +
> +struct S
> +{
> +  int foo;
> +  constexpr S(int i, int j) : foo{i + j} {}
> +};
> +
> +constexpr void emplace_test()
> +{
> +  std::queue<S> a;
> +  const S& s = a.emplace(196883, 1);
> +  VERIFY ( a.size() == 1 );
> +  VERIFY ( a.front().foo == 196884 );
> +}
> +
> +constexpr void element_access_tests()
> +{
> +  std::queue<int> a;
> +  a.push(2);
> +  a.push(4);
> +  VERIFY ( a.front() == 2 && a.back() == 4);
> +}
> +
> +constexpr void 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 );
> +}
> +
> +constexpr bool
> +do_tests()
> +{
> +  using namespace __gnu_test;
> +
> +  auto do_modifier_tests = []() {
> +    push_and_pop_test();
> +    push_range_test();
> +    swap_test();
> +    emplace_test();
> +  };
> +
> +  // TODO: Check also list when made constexpr.
> +  auto do_ctor_tests = []() {
> +    ctor_tests<std::deque<int>>();
> +    ctor_tests<std::deque<int, SimpleAllocator<int>>>();
> +  };
> +
> +  do_ctor_tests();
> +  do_modifier_tests();
> +  element_access_tests();
> +  operator_test();
> +
> +  // Additional code coverage
> +  do_ranges_tests<std::allocator<int>>();
> +  do_ranges_tests<SimpleAllocator<int>>();
> +  return true;
> +}
> +
> +int main() {
> +  do_tests();
> +  static_assert( do_tests() );
> +}
> --
> 2.34.1
>
>
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