diff --git a/libstdc++-v3/include/debug/bitset b/libstdc++-v3/include/debug/bitset
index 4c0af03c255..9335fe441a3 100644
--- a/libstdc++-v3/include/debug/bitset
+++ b/libstdc++-v3/include/debug/bitset
@@ -141,6 +141,7 @@ namespace __debug
       : _Base(__val) { }
 
       template<typename _CharT, typename _Traits, typename _Alloc>
+	_GLIBCXX23_CONSTEXPR
         explicit
         bitset(const std::basic_string<_CharT, _Traits, _Alloc>& __str,
 	       typename std::basic_string<_CharT, _Traits, _Alloc>::size_type
@@ -152,6 +153,7 @@ namespace __debug
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 396. what are characters zero and one.
       template<class _CharT, class _Traits, class _Alloc>
+	_GLIBCXX23_CONSTEXPR
 	bitset(const std::basic_string<_CharT, _Traits, _Alloc>& __str,
 	       typename std::basic_string<_CharT, _Traits, _Alloc>::size_type
 	       __pos,
@@ -160,10 +162,12 @@ namespace __debug
 	       _CharT __zero, _CharT __one = _CharT('1'))
 	: _Base(__str, __pos, __n, __zero, __one) { }
 
+      _GLIBCXX23_CONSTEXPR
       bitset(const _Base& __x) : _Base(__x) { }
 
 #if __cplusplus >= 201103L
       template<typename _CharT>
+	_GLIBCXX23_CONSTEXPR
         explicit
         bitset(const _CharT* __str,
 	       typename std::basic_string<_CharT>::size_type __n
@@ -173,6 +177,7 @@ namespace __debug
 #endif
 
       // 23.3.5.2 bitset operations:
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       operator&=(const bitset<_Nb>& __rhs) _GLIBCXX_NOEXCEPT
       {
@@ -180,6 +185,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       operator|=(const bitset<_Nb>& __rhs) _GLIBCXX_NOEXCEPT
       {
@@ -187,6 +193,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       operator^=(const bitset<_Nb>& __rhs) _GLIBCXX_NOEXCEPT
       {
@@ -194,6 +201,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       operator<<=(size_t __pos) _GLIBCXX_NOEXCEPT
       {
@@ -201,6 +209,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       operator>>=(size_t __pos) _GLIBCXX_NOEXCEPT
       {
@@ -208,6 +217,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       set() _GLIBCXX_NOEXCEPT
       {
@@ -217,6 +227,7 @@ namespace __debug
 
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 186. bitset::set() second parameter should be bool
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       set(size_t __pos, bool __val = true)
       {
@@ -224,6 +235,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       reset() _GLIBCXX_NOEXCEPT
       {
@@ -231,6 +243,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       reset(size_t __pos)
       {
@@ -238,10 +251,12 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>
       operator~() const _GLIBCXX_NOEXCEPT
       { return bitset(~_M_base()); }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       flip() _GLIBCXX_NOEXCEPT
       {
@@ -249,6 +264,7 @@ namespace __debug
 	return *this;
       }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>&
       flip(size_t __pos)
       {
@@ -259,6 +275,7 @@ namespace __debug
       // element access:
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 11. Bitset minor problems
+      _GLIBCXX23_CONSTEXPR
       reference
       operator[](size_t __pos)
       {
@@ -288,6 +305,7 @@ namespace __debug
 #endif
 
       template <typename _CharT, typename _Traits, typename _Alloc>
+	_GLIBCXX23_CONSTEXPR
         std::basic_string<_CharT, _Traits, _Alloc>
         to_string() const
         { return _M_base().template to_string<_CharT, _Traits, _Alloc>(); }
@@ -295,6 +313,7 @@ namespace __debug
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 396. what are characters zero and one.
       template<class _CharT, class _Traits, class _Alloc>
+	_GLIBCXX23_CONSTEXPR
 	std::basic_string<_CharT, _Traits, _Alloc>
 	to_string(_CharT __zero, _CharT __one = _CharT('1')) const
 	{
@@ -305,6 +324,7 @@ namespace __debug
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 434. bitset::to_string() hard to use.
       template<typename _CharT, typename _Traits>
+	_GLIBCXX23_CONSTEXPR
         std::basic_string<_CharT, _Traits, std::allocator<_CharT> >
         to_string() const
         { return to_string<_CharT, _Traits, std::allocator<_CharT> >(); }
@@ -312,12 +332,14 @@ namespace __debug
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 853. to_string needs updating with zero and one.
       template<class _CharT, class _Traits>
+	_GLIBCXX23_CONSTEXPR
 	std::basic_string<_CharT, _Traits, std::allocator<_CharT> >
 	to_string(_CharT __zero, _CharT __one = _CharT('1')) const
 	{ return to_string<_CharT, _Traits,
 	                   std::allocator<_CharT> >(__zero, __one); }
 
       template<typename _CharT>
+	_GLIBCXX23_CONSTEXPR
         std::basic_string<_CharT, std::char_traits<_CharT>,
                           std::allocator<_CharT> >
         to_string() const
@@ -327,6 +349,7 @@ namespace __debug
         }
 
       template<class _CharT>
+	_GLIBCXX23_CONSTEXPR
 	std::basic_string<_CharT, std::char_traits<_CharT>,
 	                  std::allocator<_CharT> >
 	to_string(_CharT __zero, _CharT __one = _CharT('1')) const
@@ -335,12 +358,14 @@ namespace __debug
 	                   std::allocator<_CharT> >(__zero, __one);
 	}
 
+      _GLIBCXX23_CONSTEXPR
       std::basic_string<char, std::char_traits<char>, std::allocator<char> >
       to_string() const
       {
 	return to_string<char,std::char_traits<char>,std::allocator<char> >();
       }
 
+      _GLIBCXX23_CONSTEXPR
       std::basic_string<char, std::char_traits<char>, std::allocator<char> >
       to_string(char __zero, char __one = '1') const
       {
@@ -351,6 +376,7 @@ namespace __debug
       using _Base::count;
       using _Base::size;
 
+      _GLIBCXX23_CONSTEXPR
       bool
       operator==(const bitset<_Nb>& __rhs) const _GLIBCXX_NOEXCEPT
       { return _M_base() == __rhs._M_base(); }
@@ -366,45 +392,52 @@ namespace __debug
       using _Base::any;
       using _Base::none;
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>
       operator<<(size_t __pos) const _GLIBCXX_NOEXCEPT
       { return bitset<_Nb>(_M_base() << __pos); }
 
+      _GLIBCXX23_CONSTEXPR
       bitset<_Nb>
       operator>>(size_t __pos) const _GLIBCXX_NOEXCEPT
       { return bitset<_Nb>(_M_base() >> __pos); }
 
+      _GLIBCXX23_CONSTEXPR
       _Base& 
       _M_base() _GLIBCXX_NOEXCEPT
       { return *this; }
 
+      _GLIBCXX23_CONSTEXPR
       const _Base&
       _M_base() const _GLIBCXX_NOEXCEPT
       { return *this; }
     };
 
   template<size_t _Nb>
-    bitset<_Nb>
+    _GLIBCXX23_CONSTEXPR
+    inline bitset<_Nb>
     operator&(const bitset<_Nb>& __x, const bitset<_Nb>& __y) _GLIBCXX_NOEXCEPT
     { return bitset<_Nb>(__x) &= __y; }
 
   template<size_t _Nb>
-    bitset<_Nb>
+    _GLIBCXX23_CONSTEXPR
+    inline bitset<_Nb>
     operator|(const bitset<_Nb>& __x, const bitset<_Nb>& __y) _GLIBCXX_NOEXCEPT
     { return bitset<_Nb>(__x) |= __y; }
 
   template<size_t _Nb>
-    bitset<_Nb>
+    _GLIBCXX23_CONSTEXPR
+    inline bitset<_Nb>
     operator^(const bitset<_Nb>& __x, const bitset<_Nb>& __y) _GLIBCXX_NOEXCEPT
     { return bitset<_Nb>(__x) ^= __y; }
 
   template<typename _CharT, typename _Traits, size_t _Nb>
-    std::basic_istream<_CharT, _Traits>&
+    inline std::basic_istream<_CharT, _Traits>&
     operator>>(std::basic_istream<_CharT, _Traits>& __is, bitset<_Nb>& __x)
     { return __is >> __x._M_base(); }
 
   template<typename _CharT, typename _Traits, size_t _Nb>
-    std::basic_ostream<_CharT, _Traits>&
+    inline std::basic_ostream<_CharT, _Traits>&
     operator<<(std::basic_ostream<_CharT, _Traits>& __os,
 	       const bitset<_Nb>& __x)
     { return __os << __x._M_base(); }
diff --git a/libstdc++-v3/testsuite/20_util/bitset/access/constexpr.cc b/libstdc++-v3/testsuite/20_util/bitset/access/constexpr.cc
index 7c39fcadc6c..53bb07f9498 100644
--- a/libstdc++-v3/testsuite/20_util/bitset/access/constexpr.cc
+++ b/libstdc++-v3/testsuite/20_util/bitset/access/constexpr.cc
@@ -27,6 +27,7 @@ test_indexing()
 
 static_assert( test_indexing() );
 
+#if _GLIBCXX_USE_CXX11_ABI
 constexpr bool
 test_to_string()
 {
@@ -35,6 +36,7 @@ test_to_string()
 }
 
 static_assert( test_to_string() );
+#endif
 
 constexpr bool
 test_to_ulong()
diff --git a/libstdc++-v3/testsuite/20_util/bitset/cons/constexpr_c++23.cc b/libstdc++-v3/testsuite/20_util/bitset/cons/constexpr_c++23.cc
index 92bfebe8f66..532fc9dc4d5 100644
--- a/libstdc++-v3/testsuite/20_util/bitset/cons/constexpr_c++23.cc
+++ b/libstdc++-v3/testsuite/20_util/bitset/cons/constexpr_c++23.cc
@@ -24,6 +24,7 @@ constexpr bool test_ntbs()
 
 static_assert( test_ntbs() );
 
+#if _GLIBCXX_USE_CXX11_ABI
 constexpr bool test_string()
 {
   using S = std::string;
@@ -51,3 +52,4 @@ constexpr bool test_wstring()
 }
 
 static_assert( test_wstring() );
+#endif
diff --git a/libstdc++-v3/testsuite/20_util/headers/bitset/synopsis.cc b/libstdc++-v3/testsuite/20_util/headers/bitset/synopsis.cc
index e7ea4f89a4a..ed5604b6b22 100644
--- a/libstdc++-v3/testsuite/20_util/headers/bitset/synopsis.cc
+++ b/libstdc++-v3/testsuite/20_util/headers/bitset/synopsis.cc
@@ -27,17 +27,26 @@
 # define NOTHROW
 #endif
 
+#if __cplusplus > 202002L
+# define CONSTEXPR constexpr
+#else
+# define CONSTEXPR
+#endif
+
 namespace std {
   template <size_t N> class bitset;
 
   // 23.3.5.3 bitset operations:
   template <size_t N>
+    CONSTEXPR
     bitset<N> operator&(const bitset<N>&, const bitset<N>&) NOTHROW;
 
   template <size_t N>
+    CONSTEXPR
     bitset<N> operator|(const bitset<N>&, const bitset<N>&) NOTHROW;
 
   template <size_t N>
+    CONSTEXPR
     bitset<N> operator^(const bitset<N>&, const bitset<N>&) NOTHROW;
 
   template <class charT, class traits, size_t N>
