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

Tomasz Kamiński <[email protected]> Thu, 6 Aug 2026 11:56:30 +0200
Newsgroups gmane.comp.gcc.patches,gmane.comp.gcc.libstdc++.devel
Message-ID <[email protected]>
This patch makes partial progress towards P3372 by marking deque, queue,
and relevant internal helpers to be constexpr when using C++26
(priority_queue was made constexr by r17-1233-g5a6ae2b286a730).

For debug version we use similar approach as is used for vector in
r14-6553-g7d00a59229ee17, and disable safe iterator instrumentation
and checking during constant evaluation, because of mutex locks
and call to non-inline functions.

The __uninitialized_default_a overloads that do not depend on
_Deque_iterator, are marked as _GLIBCXX20_CONSTEXPR for that reason.

libstdc++-v3/ChangeLog:

	* include/bits/deque.tcc (deque): Declare out of line member
	defintions as _GLIBCXX26_CONSTEXPR.
	(std::__fill_a1, std::__copy_move_dit, std::__copy_move_a1)
	(std::__copy_move_a2, std::__copy_n_a)
	(std::__copy_move_backward_dit, std::__copy_move_backward_a1)
	(std::__equal_dit, std::__equal_aux1, std::__lex_cmp_dit)
	(std::__lexicographical_compare_aux1, std::__uninitialized_copy_a)
	(std::__uninitialized_move_a): Declare as _GLIBCXX26_CONSTEXPR.
	* include/bits/stl_algobase.h (std::__fill_a1, std::__copy_n_a)
	(std::__copy_move_a1, std::__copy_move_backward_a1)
	(std::__equal_aux1, __lexicographical_compare_aux1): Declare
	overloads accepting _Deque_iterator as _GLIBCXX26_CONSTEXPR.
	* include/bits/stl_deque.h (std::_Deque_iterator, std::_Deque_base)
	(std::deque): Declare members as _GLIBCXX26_CONSTEXPR.
	(std::operator==, std::operator<=>, std::swap): Declare as
	_GLIBCXX26_CONSTEXPR.
	* include/bits/stl_queue.h (std::queue): Declare members as
	_GLIBCXX26_CONSTEXPR.
	(std::priority_queue): Make _GLIBCXX26_CONSTEXPR placement
	consistient.
	(std::operator==, std::operator!=, std::operator<, std::operator>)
	(std::operator<=, std::operator>=, std::operator<=>, std::swap):
	Declare as _GLIBCXX26_CONSTEXPR.
	* include/bits/stl_uninitialized.h (std::__uninitialized_copy_a):
	Declare overloads accepting _Deque_iterator as _GLIBCXX26_CONSTEXPR.
	(std::__uninitialized_default_a): Declare as _GLIBCXX20_CONSTEXPR.
	* include/bits/version.def (constexpr_deque, constexpr_queue):
	Define.
	* include/bits/version.h: Regenerate.
	* include/debug/deque (__debug::deque): Declare members as
	_GLIBCXX26_CONSTEXPR.
	(__debug::operator==, __debug::operator<=>, __debug::swap)
	(__debug::erase, __debug::__erase_if): Declare as
	_GLIBCXX26_CONSTEXPR.
	* include/std/deque (__cpp_lib_constexpr_deque): Define.
	(std::erase, std::erase_if): Declare as _GLIBCXX26_CONSTEXPR.
	* include/std/queue (__cpp_lib_constexpr_queue): Define.
	(_GLIBCXX_CONSTEXPR_FORMAT): Define locally.
	(std::formatter<priority_queue<...>, _CharT>::format)
	(std::formatter<queue<...>, _CharT>::format): Declare as
	_GLIBCXX_CONSTEXPR_FORMAT.
	* testsuite/23_containers/deque/constexpr.cc: New test.
	* testsuite/23_containers/headers/deque/synopsis.cc: Updated
	declarations.
	* testsuite/23_containers/queue/constexpr.cc: New test.
	* testsuite/23_containers/priority_queue/constexpr.cc: Replace
	existing test with expanded suite.
	* testsuite/std/format/ranges/adaptors.cc: Test at compile
	time.

Co-authored-by: Thor Preimesberger <[email protected]>
Signed-off-by: Thor Preimesberger <[email protected]>
Signed-off-by: Tomasz Kamiński <[email protected]>
---
v3 is recreation of previous patch, as (most likely due mailing
client) all tabs were removed, making it impossible to apply.
I was able to reuse the additional tests.

v3:
- rebases the priority_queue changes, as it was merged
- provides proper support for debug::deque in constexpr,
  by disabling the checks (as for vector)
- expand the patch to cover cosntexpr formatting of the
  containers, as it was merged.
- updates test a bit, to use separate static_assert,
  and have more consistient formatting.

Tested on x86_64-linx and testing on powerpc64-le.
All 23_containers/*ue* and format/ranges/adaptors.cc test
passed in all standard modes, -m32, debug and assertions.
OK for trunk when all test passes?

 libstdc++-v3/include/bits/deque.tcc           |  97 +++--
 libstdc++-v3/include/bits/stl_algobase.h      |  22 +-
 libstdc++-v3/include/bits/stl_deque.h         | 363 ++++++++++--------
 libstdc++-v3/include/bits/stl_queue.h         | 107 +++---
 libstdc++-v3/include/bits/stl_uninitialized.h |   7 +-
 libstdc++-v3/include/bits/version.def         |  18 +
 libstdc++-v3/include/bits/version.h           |  20 +
 libstdc++-v3/include/debug/deque              | 210 ++++++----
 libstdc++-v3/include/std/deque                |   7 +-
 libstdc++-v3/include/std/queue                |  11 +
 .../23_containers/deque/constexpr.cc          | 334 ++++++++++++++++
 .../23_containers/headers/deque/synopsis.cc   |  26 +-
 .../23_containers/priority_queue/constexpr.cc | 253 ++++++++++--
 .../23_containers/queue/constexpr.cc          | 242 ++++++++++++
 .../testsuite/std/format/ranges/adaptors.cc   |  34 +-
 15 files changed, 1370 insertions(+), 381 deletions(-)
 create mode 100644 libstdc++-v3/testsuite/23_containers/deque/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/23_containers/queue/constexpr.cc

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