[libc++] Implement P2417R2 (A more constexpr bitset)

[jloser]

libcxx/include/__config

846

I'd prefer _LIBCPP_CONSTEXPR_AFTER_CXX20 for consistency and presumably std::bitset will be constexpr still when C++26 is around, so the macro name won't be great at that time.

libcxx/test/std/utilities/template.bitset/bitset.members/right_shift_eq.pass.cpp

68

What about test_right_shift<1000>() in constexpr?

It seems a simpler refactoring is to put the calls into a reusable function, say test and then do

test()
static_assert(test())

What do you think?

libcxx/test/std/utilities/template.bitset/bitset.members/to_string.pass.cpp

130

Similar comment about a reusable test function and why can't we test test_to_string<1000>() in constexpr branch?

[philnik]

libcxx/include/__config

846

I want to avoid the mental burden of forming AFTER_CXX20 to CXX23. I'd actually prefer it a lot if we renamed the other macros. It's also the same naming scheme that we use in the tests. I don't really see how AFTER_CXXab is a better name when we have C++26. IMO it's pretty obvious that _LIBCPP_CONSTEXPR_CXX23 is "it's constexpr since C++23".

libcxx/test/std/utilities/template.bitset/bitset.members/right_shift_eq.pass.cpp

68

test_right_shift<1000>() reaches the constexpr step limit. The other tests combined do the same thing.

libcxx/test/std/utilities/template.bitset/bitset.members/to_string.pass.cpp

130

And the same answer.

[Mordante]

Thanks for working on this!

libcxx/include/__config

846

Thanks for discussing this on Discord.

libcxx/include/bitset

43

Can you add constexpr to all the signatures in the synopsis.

68–72

This one already was constexpr, or wast that changed in C++23 too?

88

Not yours, but N is used in the synopsis for these two operators.

libcxx/test/std/utilities/template.bitset/bitset.cons/char_ptr_ctor.pass.cpp

10

Please update the synopsis and validate the other tests too.

25–26

How about moving this in the #ifndef TEST_HAS_NO_EXCEPTIONS block instead?

libcxx/test/std/utilities/template.bitset/bitset.members/count.pass.cpp

48

Why can't this one be tested constexpr? Due to the default constexpr limit in Clang?
Can you add a comment with the reason?

Do we really need to test 1000 or would something like 513 also suffice?

libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp

64

Please move above to be consistent with the other tests.

libcxx/test/std/utilities/template.bitset/bitset.members/op_xor_eq.pass.cpp

54

Can you improve this to use the typical libc++ constexpr test.

[jloser]

libcxx/include/__config

846

Thanks for the explanation/rationale and discussion on Discord. I'm +1 for this naming now.

libcxx/test/std/utilities/template.bitset/bitset.members/right_shift_eq.pass.cpp

68

Got it - thanks for clarifying.

[philnik]

• Address comments

libcxx/include/bitset

43

AFAIK we normally don't do that when we have // constexpr since C++ab.

68–72

Oops, that one was already constexpr.

libcxx/test/std/utilities/template.bitset/bitset.members/count.pass.cpp

48

The 1000 is special-cased in get_test_cases. I don't think adding a comment makes a lot of sense. The exact same comment would have to be added to almost every bitset test. I think it's especially not useful because the first guess of most people is the correct one.

libcxx/test/std/utilities/template.bitset/bitset.members/op_xor_eq.pass.cpp

54

No, in this case combining them also hits the constexpr limit.

[ldionne]

LGTM with my comments.

libcxx/include/__config

846

I know this has been discussed, but let's use _AFTER_CXX20 until we actually do the rename. I also don't think this will end up being _LIBCPP_CONSTEXPR_CXX23, but probably something like _LIBCPP_CONSTEXPR_IN_CXX23 or _LIBCPP_CONSTEXPR_SINCE_CXX23.

libcxx/test/std/utilities/template.bitset/bitset.members/flip_all.pass.cpp

46

This also applies elsewhere in this patch.

libcxx/test/std/utilities/template.bitset/bitset.members/set_one.out_of_range.pass.cpp

11

Not mandatory, but we could do this while we're at it, since we touch all these lines.

libcxx/test/std/utilities/template.bitset/bitset.members/test.pass.cpp

9

libcxx/test/std/utilities/template.bitset/bitset.operators/stream_in.pass.cpp

15 ↗

(On Diff #451644)

I don't think so?

libcxx/test/std/utilities/template.bitset/bitset.operators/stream_out.pass.cpp

15 ↗

(On Diff #451644)

Same here.

[philnik]

• Address comments

libcxx/docs/FeatureTestMacroTable.rst

.. table:: Current Status
     ``__cpp_lib_allocate_at_least``                   ``202106L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_associative_heterogeneous_erasure``   *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_bind_back``                           *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_byteswap``                            ``202110L``
     ------------------------------------------------- -----------------
+    ``__cpp_lib_constexpr_bitset``                    ``202207L``
+    ------------------------------------------------- -----------------
     ``__cpp_lib_constexpr_cmath``                     *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_constexpr_typeinfo``                  *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_invoke_r``                            *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_is_scoped_enum``                      ``202011L``
     ------------------------------------------------- -----------------

libcxx/docs/ReleaseNotes.rst

 see the `releases page <https://llvm.org/releases/>`_.
 
 What's New in Libc++ 16.0.0?
 ============================
 
 Implemented Papers
 ------------------
 - P2499R0 - ``string_view`` range constructor should be ``explicit``
+- P2417R2 - A more constexpr bitset
 
 Improvements and New Features
 -----------------------------
 
 Deprecations and Removals
 -------------------------
 
 Upcoming Deprecations and Removals

libcxx/docs/Status/Cxx2bPapers.csv

 "`P2278R4 <https://wg21.link/P2278R4>`__","LWG","``cbegin`` should always return a constant iterator","July 2022","",""
 "`P2286R8 <https://wg21.link/P2286R8>`__","LWG","Formatting Ranges","July 2022","",""
 "`P2291R3 <https://wg21.link/P2291R3>`__","LWG","Add Constexpr Modifiers to Functions ``to_chars`` and ``from_chars`` for Integral Types in ``<charconv>`` Header","July 2022","",""
 "`P2302R4 <https://wg21.link/P2302R4>`__","LWG","``std::ranges::contains``","July 2022","",""
 "`P2322R6 <https://wg21.link/P2322R6>`__","LWG","``ranges::fold``","July 2022","",""
 "`P2374R4 <https://wg21.link/P2374R4>`__","LWG","``views::cartesian_product``","July 2022","",""
 "`P2404R3 <https://wg21.link/P2404R3>`__","LWG","Move-only types for ``equality_comparable_with``, ``totally_ordered_with``, and ``three_way_comparable_with``","July 2022","",""
 "`P2408R5 <https://wg21.link/P2408R5>`__","LWG","Ranges iterators as inputs to non-Ranges algorithms","July 2022","",""
-"`P2417R2 <https://wg21.link/P2417R2>`__","LWG","A more ``constexpr`` ``bitset``","July 2022","",""
+"`P2417R2 <https://wg21.link/P2417R2>`__","LWG","A more ``constexpr`` ``bitset``","July 2022","|Complete|","16.0"
 "`P2419R2 <https://wg21.link/P2419R2>`__","LWG","Clarify handling of encodings in localized formatting of chrono types","July 2022","",""
 "`P2438R2 <https://wg21.link/P2438R2>`__","LWG","``std::string::substr() &&``","July 2022","",""
 "`P2445R1 <https://wg21.link/P2445R1>`__","LWG","``forward_like``","July 2022","",""
 "`P2446R2 <https://wg21.link/P2446R2>`__","LWG","``views::as_rvalue``","July 2022","",""
 "`P2460R2 <https://wg21.link/P2460R2>`__","LWG","Relax requirements on ``wchar_t`` to match existing practices","July 2022","",""
 "`P2465R3 <https://wg21.link/P2465R3>`__","LWG","Standard Library Modules ``std`` and ``std.compat``","July 2022","",""
 "`P2467R1 <https://wg21.link/P2467R1>`__","LWG","Support exclusive mode for ``fstreams``","July 2022","",""
 "`P2474R2 <https://wg21.link/P2474R2>`__","LWG","``views::repeat``","July 2022","",""

libcxx/include/__bit_reference

find(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value)
     if (static_cast<bool>(__value))
         return _VSTD::__find_bool_true(__first, static_cast<typename _Cp::size_type>(__last - __first));
     return _VSTD::__find_bool_false(__first, static_cast<typename _Cp::size_type>(__last - __first));
 }
 
 // count
 
 template <class _Cp, bool _IsConst>
-_LIBCPP_HIDE_FROM_ABI typename __bit_iterator<_Cp, _IsConst>::difference_type
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 typename __bit_iterator<_Cp, _IsConst>::difference_type
 __count_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
 {
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
     typedef typename _It::difference_type difference_type;
     const int __bits_per_word = _It::__bits_per_word;
     difference_type __r = 0;
     // do first partial word
friend bool equal(__bit_iterator<_Dp, _IC1>,
                       __bit_iterator<_Dp, _IC2>);
     template <class _Dp, bool _IC>
     _LIBCPP_CONSTEXPR_AFTER_CXX17
     friend __bit_iterator<_Dp, _IC> __find_bool_true(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
     template <class _Dp, bool _IC>
     _LIBCPP_CONSTEXPR_AFTER_CXX17
     friend __bit_iterator<_Dp, _IC> __find_bool_false(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
     template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
                    __count_bool_true(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
     template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
                    __count_bool_false(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
 };
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
 #endif // _LIBCPP___BIT_REFERENCE

libcxx/include/__config

 #    define _LIBCPP_ABI_ENABLE_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1
 
 // Define a key function for `bad_function_call` in the library, to centralize
 // its vtable and typeinfo to libc++ rather than having all other libraries
 // using that class define their own copies.
 #    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 #  endif
 
-#  define _LIBCPP_TOSTRING2(x) #  x
+#  define _LIBCPP_TOSTRING2(x) #x
 #  define _LIBCPP_TOSTRING(x) _LIBCPP_TOSTRING2(x)
 
 #  if __cplusplus < 201103L
 #    define _LIBCPP_CXX03_LANG
 #  endif
 
 #  ifndef __has_attribute
 #    define __has_attribute(__x) 0

 #  endif
 
 #  if _LIBCPP_STD_VER > 17
 #    define _LIBCPP_CONSTEXPR_AFTER_CXX17 constexpr
 #  else
 #    define _LIBCPP_CONSTEXPR_AFTER_CXX17
 #  endif
 
+#  if _LIBCPP_STD_VER > 20
+#    define _LIBCPP_CONSTEXPR_AFTER_CXX20 constexpr
+#  else
+#    define _LIBCPP_CONSTEXPR_AFTER_CXX20
+#  endif
+
 #  if __has_cpp_attribute(nodiscard)
 #    define _LIBCPP_NODISCARD [[nodiscard]]
 #  else
 // We can't use GCC's [[gnu::warn_unused_result]] and
 // __attribute__((warn_unused_result)), because GCC does not silence them via
 // (void) cast.
 #    define _LIBCPP_NODISCARD
 #  endif

libcxx/include/bitset

public:
         operator bool() const noexcept;                  // for x = b[i];
         reference& flip() noexcept;                      // for b[i].flip();
     };
 
     // 23.3.5.1 constructors:
     constexpr bitset() noexcept;
     constexpr bitset(unsigned long long val) noexcept;
     template <class charT>
         explicit bitset(const charT* str,
                         typename basic_string<charT>::size_type n = basic_string<charT>::npos,
-                        charT zero = charT('0'), charT one = charT('1'));
+                        charT zero = charT('0'), charT one = charT('1')); // constexpr since C++23
     template<class charT, class traits, class Allocator>
         explicit bitset(const basic_string<charT,traits,Allocator>& str,
                         typename basic_string<charT,traits,Allocator>::size_type pos = 0,
                         typename basic_string<charT,traits,Allocator>::size_type n =
                                  basic_string<charT,traits,Allocator>::npos,
-                        charT zero = charT('0'), charT one = charT('1'));
+                        charT zero = charT('0'), charT one = charT('1')); // constexpr since C++23
 
     // 23.3.5.2 bitset operations:
-    bitset& operator&=(const bitset& rhs) noexcept;
-    bitset& operator|=(const bitset& rhs) noexcept;
-    bitset& operator^=(const bitset& rhs) noexcept;
-    bitset& operator<<=(size_t pos) noexcept;
-    bitset& operator>>=(size_t pos) noexcept;
-    bitset& set() noexcept;
-    bitset& set(size_t pos, bool val = true);
-    bitset& reset() noexcept;
-    bitset& reset(size_t pos);
-    bitset operator~() const noexcept;
-    bitset& flip() noexcept;
-    bitset& flip(size_t pos);
+    bitset& operator&=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator|=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator^=(const bitset& rhs) noexcept; // constexpr since C++23
+    bitset& operator<<=(size_t pos) noexcept;       // constexpr since C++23
+    bitset& operator>>=(size_t pos) noexcept;       // constexpr since C++23
+    bitset& set() noexcept;                         // constexpr since C++23
+    bitset& set(size_t pos, bool val = true);       // constexpr since C++23
+    bitset& reset() noexcept;                       // constexpr since C++23
+    bitset& reset(size_t pos);                      // constexpr since C++23
+    bitset operator~() const noexcept;              // constexpr since C++23
+    bitset& flip() noexcept;                        // constexpr since C++23
+    bitset& flip(size_t pos);                       // constexpr since C++23
 
     // element access:
-    constexpr bool operator[](size_t pos) const; // for b[i];
-    reference operator[](size_t pos);            // for b[i];
-    unsigned long to_ulong() const;
-    unsigned long long to_ullong() const;
-    template <class charT, class traits, class Allocator>
+    constexpr bool operator[](size_t pos) const;
+    reference operator[](size_t pos);            // constexpr since C++23
+    unsigned long to_ulong() const;              // constexpr since C++23
+    unsigned long long to_ullong() const;        // constexpr since C++23
+    template <class charT, class traits, class Allocator> // constexpr since C++23
         basic_string<charT, traits, Allocator> to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    template <class charT, class traits>
+    template <class charT, class traits> // constexpr since C++23
         basic_string<charT, traits, allocator<charT> > to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    template <class charT>
+    template <class charT> // constexpr since C++23
         basic_string<charT, char_traits<charT>, allocator<charT> > to_string(charT zero = charT('0'), charT one = charT('1')) const;
-    basic_string<char, char_traits<char>, allocator<char> > to_string(char zero = '0', char one = '1') const;
-    size_t count() const noexcept;
-    constexpr size_t size() const noexcept;
-    bool operator==(const bitset& rhs) const noexcept;
-    bool operator!=(const bitset& rhs) const noexcept;
-    bool test(size_t pos) const;
-    bool all() const noexcept;
-    bool any() const noexcept;
-    bool none() const noexcept;
-    bitset operator<<(size_t pos) const noexcept;
-    bitset operator>>(size_t pos) const noexcept;
+    basic_string<char, char_traits<char>, allocator<char> > to_string(char zero = '0', char one = '1') const; // constexpr since C++23
+    size_t count() const noexcept;                     // constexpr since C++23
+    constexpr size_t size() const noexcept;            // constexpr since C++23
+    bool operator==(const bitset& rhs) const noexcept; // constexpr since C++23
+    bool operator!=(const bitset& rhs) const noexcept; // constexpr since C++23
+    bool test(size_t pos) const;                       // constexpr since C++23
+    bool all() const noexcept;                         // constexpr since C++23
+    bool any() const noexcept;                         // constexpr since C++23
+    bool none() const noexcept;                        // constexpr since C++23
+    bitset<N> operator<<(size_t pos) const noexcept;   // constexpr since C++23
+    bitset<N> operator>>(size_t pos) const noexcept;   // constexpr since C++23
 };
 
 // 23.3.5.3 bitset operators:
 template <size_t N>
-bitset<N> operator&(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator&(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <size_t N>
-bitset<N> operator|(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator|(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <size_t N>
-bitset<N> operator^(const bitset<N>&, const bitset<N>&) noexcept;
+bitset<N> operator^(const bitset<N>&, const bitset<N>&) noexcept; // constexpr since C++23
 
 template <class charT, class traits, size_t N>
 basic_istream<charT, traits>&
 operator>>(basic_istream<charT, traits>& is, bitset<N>& x);
 
 template <class charT, class traits, size_t N>
 basic_ostream<charT, traits>&
 operator<<(basic_ostream<charT, traits>& os, const bitset<N>& x);
protected:
     typedef __bit_iterator<__bitset, false>            iterator;
     typedef __bit_iterator<__bitset, true>             const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __bitset() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t __pos) _NOEXCEPT
         {return reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT
         {return const_reference(__first_ + __pos / __bits_per_word, __storage_type(1) << __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t __pos) _NOEXCEPT
         {return iterator(__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t __pos) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t __pos) const _NOEXCEPT
         {return const_iterator(__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator&=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator|=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator^=(const __bitset& __v) _NOEXCEPT;
 
-    void flip() _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY unsigned long to_ulong() const
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void flip() _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long to_ulong() const
         {return to_ulong(integral_constant<bool, _Size < sizeof(unsigned long) * CHAR_BIT>());}
-    _LIBCPP_INLINE_VISIBILITY unsigned long long to_ullong() const
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long to_ullong() const
         {return to_ullong(integral_constant<bool, _Size < sizeof(unsigned long long) * CHAR_BIT>());}
 
-    bool all() const _NOEXCEPT;
-    bool any() const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool all() const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool any() const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_t __hash_code() const _NOEXCEPT;
 private:
 #ifdef _LIBCPP_CXX03_LANG
     void __init(unsigned long long __v, false_type) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     void __init(unsigned long long __v, true_type) _NOEXCEPT;
 #endif // _LIBCPP_CXX03_LANG
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong(false_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong(true_type) const;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(false_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type, false_type) const;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong(true_type, true_type) const;
 };
 
 template <size_t _N_words, size_t _Size>
 inline
 _LIBCPP_CONSTEXPR
 __bitset<_N_words, _Size>::__bitset() _NOEXCEPT
 #ifndef _LIBCPP_CXX03_LANG

 {
 #ifdef _LIBCPP_CXX03_LANG
     __init(__v, integral_constant<bool, sizeof(unsigned long long) == sizeof(__storage_type)>());
 #endif
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
         __first_[__i] &= __v.__first_[__i];
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
         __first_[__i] |= __v.__first_[__i];
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 {
     for (size_type __i = 0; __i < _N_words; ++__i)
         __first_[__i] ^= __v.__first_[__i];
 }
 
 template <size_t _N_words, size_t _Size>
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<_N_words, _Size>::flip() _NOEXCEPT
 {
     // do middle whole words
     size_type __n = _Size;
     __storage_pointer __p = __first_;
     for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
         *__p = ~*__p;
     // do last partial word
     if (__n > 0)
     {
         __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
         __storage_type __b = *__p & __m;
         *__p &= ~__m;
         *__p |= ~__b & __m;
     }
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<_N_words, _Size>::to_ulong(false_type) const
 {
     const_iterator __e = __make_iter(_Size);
     const_iterator __i = _VSTD::find(__make_iter(sizeof(unsigned long) * CHAR_BIT), __e, true);
     if (__i != __e)
         __throw_overflow_error("bitset to_ulong overflow error");
 
     return __first_[0];
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<_N_words, _Size>::to_ulong(true_type) const
 {
     return __first_[0];
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(false_type) const
 {
     const_iterator __e = __make_iter(_Size);
     const_iterator __i = _VSTD::find(__make_iter(sizeof(unsigned long long) * CHAR_BIT), __e, true);
     if (__i != __e)
         __throw_overflow_error("bitset to_ullong overflow error");
 
     return to_ullong(true_type());
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type) const
 {
     return to_ullong(true_type(), integral_constant<bool, sizeof(__storage_type) < sizeof(unsigned long long)>());
 }
 
 template <size_t _N_words, size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type, false_type) const
 {
     return __first_[0];
 }
 
 template <size_t _N_words, size_t _Size>
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<_N_words, _Size>::to_ullong(true_type, true_type) const
 {
     unsigned long long __r = __first_[0];
     for (size_t __i = 1; __i < sizeof(unsigned long long) / sizeof(__storage_type); ++__i)
         __r |= static_cast<unsigned long long>(__first_[__i]) << (sizeof(__storage_type) * CHAR_BIT);
     return __r;
 }
 
 template <size_t _N_words, size_t _Size>
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<_N_words, _Size>::all() const _NOEXCEPT
 {
     // do middle whole words
     size_type __n = _Size;
     __const_storage_pointer __p = __first_;
     for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
         if (~*__p)
             return false;
     // do last partial word
     if (__n > 0)
     {
         __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
         if (~*__p & __m)
             return false;
     }
     return true;
 }
 
 template <size_t _N_words, size_t _Size>
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<_N_words, _Size>::any() const _NOEXCEPT
 {
     // do middle whole words
     size_type __n = _Size;
     __const_storage_pointer __p = __first_;
     for (; __n >= __bits_per_word; ++__p, __n -= __bits_per_word)
         if (*__p)
             return true;
protected:
     typedef __bit_iterator<__bitset, false>            iterator;
     typedef __bit_iterator<__bitset, true>             const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __bitset() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t __pos) _NOEXCEPT
         {return reference(&__first_, __storage_type(1) << __pos);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t __pos) const _NOEXCEPT
         {return const_reference(&__first_, __storage_type(1) << __pos);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t __pos) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t __pos) _NOEXCEPT
         {return iterator(&__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t __pos) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t __pos) const _NOEXCEPT
         {return const_iterator(&__first_ + __pos / __bits_per_word, __pos % __bits_per_word);}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator&=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator|=(const __bitset& __v) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void operator^=(const __bitset& __v) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     void flip() _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong() const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong() const;
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool all() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool any() const _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
     size_t __hash_code() const _NOEXCEPT;
 };
 
 template <size_t _Size>
 inline
: __first_(
         _Size == __bits_per_word ? static_cast<__storage_type>(__v)
                                  : static_cast<__storage_type>(__v) & ((__storage_type(1) << _Size) - 1)
     )
 {
 }
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator&=(const __bitset& __v) _NOEXCEPT
 {
     __first_ &= __v.__first_;
 }
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator|=(const __bitset& __v) _NOEXCEPT
 {
     __first_ |= __v.__first_;
 }
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::operator^=(const __bitset& __v) _NOEXCEPT
 {
     __first_ ^= __v.__first_;
 }
 
 template <size_t _Size>
 inline
-void
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 void
 __bitset<1, _Size>::flip() _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
     __first_ = ~__first_;
     __first_ &= __m;
 }
 
 template <size_t _Size>
 inline
-unsigned long
+_LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long
 __bitset<1, _Size>::to_ulong() const
 {
     return __first_;
 }
 
 template <size_t _Size>
 inline
-unsigned long long
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long
 __bitset<1, _Size>::to_ullong() const
 {
     return __first_;
 }
 
 template <size_t _Size>
 inline
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<1, _Size>::all() const _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
     return !(~__first_ & __m);
 }
 
 template <size_t _Size>
 inline
-bool
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 bool
 __bitset<1, _Size>::any() const _NOEXCEPT
 {
     __storage_type __m = ~__storage_type(0) >> (__bits_per_word - _Size);
     return __first_ & __m;
 }
 
 template <size_t _Size>
 inline
protected:
     typedef __bit_iterator<__bitset, false>            iterator;
     typedef __bit_iterator<__bitset, true>             const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __bitset() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long) _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 reference __make_ref(size_t) _NOEXCEPT
         {return reference(nullptr, 1);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t) const _NOEXCEPT
         {return const_reference(nullptr, 1);}
-    _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 iterator __make_iter(size_t) _NOEXCEPT
         {return iterator(nullptr, 0);}
-    _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 const_iterator __make_iter(size_t) const _NOEXCEPT
         {return const_iterator(nullptr, 0);}
 
-    _LIBCPP_INLINE_VISIBILITY void operator&=(const __bitset&) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY void operator|=(const __bitset&) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY void operator^=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator&=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator|=(const __bitset&) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void operator^=(const __bitset&) _NOEXCEPT {}
 
-    _LIBCPP_INLINE_VISIBILITY void flip() _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 void flip() _NOEXCEPT {}
 
-    _LIBCPP_INLINE_VISIBILITY unsigned long to_ulong() const {return 0;}
-    _LIBCPP_INLINE_VISIBILITY unsigned long long to_ullong() const {return 0;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long to_ulong() const {return 0;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 unsigned long long to_ullong() const {return 0;}
 
-    _LIBCPP_INLINE_VISIBILITY bool all() const _NOEXCEPT {return true;}
-    _LIBCPP_INLINE_VISIBILITY bool any() const _NOEXCEPT {return false;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool all() const _NOEXCEPT {return true;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool any() const _NOEXCEPT {return false;}
 
     _LIBCPP_INLINE_VISIBILITY size_t __hash_code() const _NOEXCEPT {return 0;}
 };
 
 inline
 _LIBCPP_CONSTEXPR
 __bitset<0, 0>::__bitset() _NOEXCEPT
 {
public:
     typedef typename base::reference       reference;
     typedef typename base::const_reference const_reference;
 
     // 23.3.5.1 constructors:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR bitset() _NOEXCEPT {}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
         bitset(unsigned long long __v) _NOEXCEPT : base(__v) {}
     template<class _CharT, class = __enable_if_t<_IsCharLikeType<_CharT>::value> >
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         explicit bitset(const _CharT* __str,
                         typename basic_string<_CharT>::size_type __n = basic_string<_CharT>::npos,
                         _CharT __zero = _CharT('0'), _CharT __one = _CharT('1'));
     template<class _CharT, class _Traits, class _Allocator>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         explicit bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
                         typename basic_string<_CharT,_Traits,_Allocator>::size_type __pos = 0,
                         typename basic_string<_CharT,_Traits,_Allocator>::size_type __n =
                                 (basic_string<_CharT,_Traits,_Allocator>::npos),
                         _CharT __zero = _CharT('0'), _CharT __one = _CharT('1'));
 
     // 23.3.5.2 bitset operations:
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator&=(const bitset& __rhs) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator|=(const bitset& __rhs) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator^=(const bitset& __rhs) _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator<<=(size_t __pos) _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& operator>>=(size_t __pos) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& set() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& set(size_t __pos, bool __val = true);
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& reset() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& reset(size_t __pos);
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset  operator~() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& flip() _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset& flip(size_t __pos);
 
     // element access:
 #ifdef _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR            bool operator[](size_t __p) const {return base::__make_ref(__p);}
 #else
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR const_reference operator[](size_t __p) const {return base::__make_ref(__p);}
 #endif
-    _LIBCPP_HIDE_FROM_ABI                         reference operator[](size_t __p)       {return base::__make_ref(__p);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20 reference operator[](size_t __p)       {return base::__make_ref(__p);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long to_ulong() const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     unsigned long long to_ullong() const;
     template <class _CharT, class _Traits, class _Allocator>
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, _Traits, _Allocator> to_string(_CharT __zero = _CharT('0'),
                                                             _CharT __one = _CharT('1')) const;
     template <class _CharT, class _Traits>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, _Traits, allocator<_CharT> > to_string(_CharT __zero = _CharT('0'),
                                                                     _CharT __one = _CharT('1')) const;
     template <class _CharT>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
         basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> > to_string(_CharT __zero = _CharT('0'),
                                                                                 _CharT __one = _CharT('1')) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     basic_string<char, char_traits<char>, allocator<char> > to_string(char __zero = '0',
                                                                       char __one = '1') const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     size_t count() const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR size_t size() const _NOEXCEPT {return _Size;}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool operator==(const bitset& __rhs) const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool operator!=(const bitset& __rhs) const _NOEXCEPT;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool test(size_t __pos) const;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool all() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bool any() const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY bool none() const _NOEXCEPT {return !any();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20 bool none() const _NOEXCEPT {return !any();}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset operator<<(size_t __pos) const _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
     bitset operator>>(size_t __pos) const _NOEXCEPT;
 
 private:
 
     _LIBCPP_INLINE_VISIBILITY
     size_t __hash_code() const _NOEXCEPT {return base::__hash_code();}
 
     friend struct hash<bitset>;
 };
 
 template <size_t _Size>
 template<class _CharT, class>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>::bitset(const _CharT* __str,
                       typename basic_string<_CharT>::size_type __n,
                       _CharT __zero, _CharT __one)
 {
     size_t __rlen = _VSTD::min(__n, char_traits<_CharT>::length(__str));
     for (size_t __i = 0; __i < __rlen; ++__i)
         if (__str[__i] != __zero && __str[__i] != __one)
             __throw_invalid_argument("bitset string ctor has invalid argument");
 
     size_t _Mp = _VSTD::min(__rlen, _Size);
     size_t __i = 0;
     for (; __i < _Mp; ++__i)
     {
         _CharT __c = __str[_Mp - 1 - __i];
         (*this)[__i] = (__c == __one);
     }
     _VSTD::fill(base::__make_iter(__i), base::__make_iter(_Size), false);
 }
 
 template <size_t _Size>
 template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>::bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
        typename basic_string<_CharT,_Traits,_Allocator>::size_type __pos,
        typename basic_string<_CharT,_Traits,_Allocator>::size_type __n,
        _CharT __zero, _CharT __one)
 {
     if (__pos > __str.size())
         __throw_out_of_range("bitset string pos out of range");
 
for (; __i < _Mp; ++__i)
         _CharT __c = __str[__pos + _Mp - 1 - __i];
         (*this)[__i] = _Traits::eq(__c, __one);
     }
     _VSTD::fill(base::__make_iter(__i), base::__make_iter(_Size), false);
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator&=(const bitset& __rhs) _NOEXCEPT
 {
     base::operator&=(__rhs);
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator|=(const bitset& __rhs) _NOEXCEPT
 {
     base::operator|=(__rhs);
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator^=(const bitset& __rhs) _NOEXCEPT
 {
     base::operator^=(__rhs);
     return *this;
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator<<=(size_t __pos) _NOEXCEPT
 {
     __pos = _VSTD::min(__pos, _Size);
     _VSTD::copy_backward(base::__make_iter(0), base::__make_iter(_Size - __pos), base::__make_iter(_Size));
     _VSTD::fill_n(base::__make_iter(0), __pos, false);
     return *this;
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::operator>>=(size_t __pos) _NOEXCEPT
 {
     __pos = _VSTD::min(__pos, _Size);
     _VSTD::copy(base::__make_iter(__pos), base::__make_iter(_Size), base::__make_iter(0));
     _VSTD::fill_n(base::__make_iter(_Size - __pos), __pos, false);
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::set() _NOEXCEPT
 {
     _VSTD::fill_n(base::__make_iter(0), _Size, true);
     return *this;
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::set(size_t __pos, bool __val)
 {
     if (__pos >= _Size)
         __throw_out_of_range("bitset set argument out of range");
 
     (*this)[__pos] = __val;
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::reset() _NOEXCEPT
 {
     _VSTD::fill_n(base::__make_iter(0), _Size, false);
     return *this;
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::reset(size_t __pos)
 {
     if (__pos >= _Size)
         __throw_out_of_range("bitset reset argument out of range");
 
     (*this)[__pos] = false;
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator~() const _NOEXCEPT
 {
     bitset __x(*this);
     __x.flip();
     return __x;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::flip() _NOEXCEPT
 {
     base::flip();
     return *this;
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>&
 bitset<_Size>::flip(size_t __pos)
 {
     if (__pos >= _Size)
         __throw_out_of_range("bitset flip argument out of range");
 
     reference r = base::__make_ref(__pos);
     r = ~r;
     return *this;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 unsigned long
 bitset<_Size>::to_ulong() const
 {
     return base::to_ulong();
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 unsigned long long
 bitset<_Size>::to_ullong() const
 {
     return base::to_ullong();
 }
 
 template <size_t _Size>
 template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, _Traits, _Allocator>
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
     basic_string<_CharT, _Traits, _Allocator> __r(_Size, __zero);
     for (size_t __i = 0; __i != _Size; ++__i)
     {
         if ((*this)[__i])
             __r[_Size - 1 - __i] = __one;
     }
     return __r;
 }
 
 template <size_t _Size>
 template <class _CharT, class _Traits>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, _Traits, allocator<_CharT> >
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
     return to_string<_CharT, _Traits, allocator<_CharT> >(__zero, __one);
 }
 
 template <size_t _Size>
 template <class _CharT>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<_CharT, char_traits<_CharT>, allocator<_CharT> >
 bitset<_Size>::to_string(_CharT __zero, _CharT __one) const
 {
     return to_string<_CharT, char_traits<_CharT>, allocator<_CharT> >(__zero, __one);
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 basic_string<char, char_traits<char>, allocator<char> >
 bitset<_Size>::to_string(char __zero, char __one) const
 {
     return to_string<char, char_traits<char>, allocator<char> >(__zero, __one);
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 size_t
 bitset<_Size>::count() const _NOEXCEPT
 {
     return static_cast<size_t>(_VSTD::__count_bool_true(base::__make_iter(0), _Size));
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::operator==(const bitset& __rhs) const _NOEXCEPT
 {
     return _VSTD::equal(base::__make_iter(0), base::__make_iter(_Size), __rhs.__make_iter(0));
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::operator!=(const bitset& __rhs) const _NOEXCEPT
 {
     return !(*this == __rhs);
 }
 
 template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::test(size_t __pos) const
 {
     if (__pos >= _Size)
         __throw_out_of_range("bitset test argument out of range");
 
     return (*this)[__pos];
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::all() const _NOEXCEPT
 {
     return base::all();
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bool
 bitset<_Size>::any() const _NOEXCEPT
 {
     return base::any();
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator<<(size_t __pos) const _NOEXCEPT
 {
     bitset __r = *this;
     __r <<= __pos;
     return __r;
 }
 
 template <size_t _Size>
 inline
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 bitset<_Size>::operator>>(size_t __pos) const _NOEXCEPT
 {
     bitset __r = *this;
     __r >>= __pos;
     return __r;
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator&(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {
     bitset<_Size> __r = __x;
     __r &= __y;
     return __r;
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator|(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {
     bitset<_Size> __r = __x;
     __r |= __y;
     return __r;
 }
 
 template <size_t _Size>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX20
 bitset<_Size>
 operator^(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 {
     bitset<_Size> __r = __x;
     __r ^= __y;
     return __r;
 }
 

libcxx/include/version

__cpp_lib_char8_t                                       201907L <atomic> <filesystem> <istream>
                                                                 <limits> <locale> <ostream>
                                                                 <string> <string_view>
 __cpp_lib_chrono                                        201611L <chrono>
 __cpp_lib_chrono_udls                                   201304L <chrono>
 __cpp_lib_clamp                                         201603L <algorithm>
 __cpp_lib_complex_udls                                  201309L <complex>
 __cpp_lib_concepts                                      202002L <concepts>
 __cpp_lib_constexpr_algorithms                          201806L <algorithm>
+__cpp_lib_constexpr_bitset                              202207L <bitset>
 __cpp_lib_constexpr_cmath                               202202L <cmath> <cstdlib>
 __cpp_lib_constexpr_complex                             201711L <complex>
 __cpp_lib_constexpr_dynamic_alloc                       201907L <memory>
 __cpp_lib_constexpr_functional                          201907L <functional>
 __cpp_lib_constexpr_iterator                            201811L <iterator>
 __cpp_lib_constexpr_memory                              201811L <memory>
 __cpp_lib_constexpr_numeric                             201911L <numeric>
 __cpp_lib_constexpr_string                              201907L <string>

 #endif
 
 #if _LIBCPP_STD_VER > 20
 # define __cpp_lib_adaptor_iterator_pair_constructor    202106L
 # define __cpp_lib_allocate_at_least                    202106L
 // # define __cpp_lib_associative_heterogeneous_erasure    202110L
 // # define __cpp_lib_bind_back                            202202L
 # define __cpp_lib_byteswap                             202110L
+# define __cpp_lib_constexpr_bitset                     202207L
 // # define __cpp_lib_constexpr_cmath                      202202L
 // # define __cpp_lib_constexpr_typeinfo                   202106L
 // # define __cpp_lib_invoke_r                             202106L
 # define __cpp_lib_is_scoped_enum                       202011L
 // # define __cpp_lib_move_only_function                   202110L
 # undef  __cpp_lib_optional
 # define __cpp_lib_optional                             202110L
 // # define __cpp_lib_out_ptr                              202106L

libcxx/test/std/language.support/support.limits/support.limits.general/bitset.version.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// WARNING: This test was generated by generate_feature_test_macro_components.py
+// and should not be edited manually.
+//
+// clang-format off
+
+// <bitset>
+
+// Test the feature test macros defined by <bitset>
+
+/*  Constant                      Value
+    __cpp_lib_constexpr_bitset    202207L [C++2b]
+*/
+
+#include <bitset>
+#include "test_macros.h"
+
+#if TEST_STD_VER < 14
+
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
+#elif TEST_STD_VER == 14
+
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
+#elif TEST_STD_VER == 17
+
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
+#elif TEST_STD_VER == 20
+
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
+#elif TEST_STD_VER > 20
+
+# ifndef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should be defined in c++2b"
+# endif
+# if __cpp_lib_constexpr_bitset != 202207L
+#   error "__cpp_lib_constexpr_bitset should have the value 202207L in c++2b"
+# endif
+
+#endif // TEST_STD_VER > 20
+

libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp

/*  Constant                                       Value
     __cpp_lib_byteswap                             202110L [C++2b]
     __cpp_lib_char8_t                              201907L [C++20]
     __cpp_lib_chrono                               201611L [C++17]
     __cpp_lib_chrono_udls                          201304L [C++14]
     __cpp_lib_clamp                                201603L [C++17]
     __cpp_lib_complex_udls                         201309L [C++14]
     __cpp_lib_concepts                             202002L [C++20]
     __cpp_lib_constexpr_algorithms                 201806L [C++20]
+    __cpp_lib_constexpr_bitset                     202207L [C++2b]
     __cpp_lib_constexpr_cmath                      202202L [C++2b]
     __cpp_lib_constexpr_complex                    201711L [C++20]
     __cpp_lib_constexpr_dynamic_alloc              201907L [C++20]
     __cpp_lib_constexpr_functional                 201907L [C++20]
     __cpp_lib_constexpr_iterator                   201811L [C++20]
     __cpp_lib_constexpr_memory                     201811L [C++20]
     __cpp_lib_constexpr_numeric                    201911L [C++20]
     __cpp_lib_constexpr_string                     201907L [C++20]

 # ifdef __cpp_lib_concepts
 #   error "__cpp_lib_concepts should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_constexpr_algorithms
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_constexpr_cmath
 #   error "__cpp_lib_constexpr_cmath should not be defined before c++2b"
 # endif
 
 # ifdef __cpp_lib_constexpr_complex
 #   error "__cpp_lib_constexpr_complex should not be defined before c++20"
 # endif
 

 # ifdef __cpp_lib_concepts
 #   error "__cpp_lib_concepts should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_constexpr_algorithms
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_constexpr_cmath
 #   error "__cpp_lib_constexpr_cmath should not be defined before c++2b"
 # endif
 
 # ifdef __cpp_lib_constexpr_complex
 #   error "__cpp_lib_constexpr_complex should not be defined before c++20"
 # endif
 

 # ifdef __cpp_lib_concepts
 #   error "__cpp_lib_concepts should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_constexpr_algorithms
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_constexpr_cmath
 #   error "__cpp_lib_constexpr_cmath should not be defined before c++2b"
 # endif
 
 # ifdef __cpp_lib_constexpr_complex
 #   error "__cpp_lib_constexpr_complex should not be defined before c++20"
 # endif
 

 
 # ifndef __cpp_lib_constexpr_algorithms
 #   error "__cpp_lib_constexpr_algorithms should be defined in c++20"
 # endif
 # if __cpp_lib_constexpr_algorithms != 201806L
 #   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should not be defined before c++2b"
+# endif
+
 # ifdef __cpp_lib_constexpr_cmath
 #   error "__cpp_lib_constexpr_cmath should not be defined before c++2b"
 # endif
 
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_constexpr_complex
 #     error "__cpp_lib_constexpr_complex should be defined in c++20"
 #   endif

 
 # ifndef __cpp_lib_constexpr_algorithms
 #   error "__cpp_lib_constexpr_algorithms should be defined in c++2b"
 # endif
 # if __cpp_lib_constexpr_algorithms != 201806L
 #   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++2b"
 # endif
 
+# ifndef __cpp_lib_constexpr_bitset
+#   error "__cpp_lib_constexpr_bitset should be defined in c++2b"
+# endif
+# if __cpp_lib_constexpr_bitset != 202207L
+#   error "__cpp_lib_constexpr_bitset should have the value 202207L in c++2b"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_constexpr_cmath
 #     error "__cpp_lib_constexpr_cmath should be defined in c++2b"
 #   endif
 #   if __cpp_lib_constexpr_cmath != 202202L
 #     error "__cpp_lib_constexpr_cmath should have the value 202202L in c++2b"
 #   endif
 # else // _LIBCPP_VERSION

libcxx/test/std/utilities/template.bitset/bitset.cons/char_ptr_ctor.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // template <class charT>
 //     explicit bitset(const charT* str,
 //                     typename basic_string<charT>::size_type n = basic_string<charT>::npos,
-//                     charT zero = charT('0'), charT one = charT('1'));
+//                     charT zero = charT('0'), charT one = charT('1')); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <algorithm> // for 'min' and 'max'
 #include <stdexcept> // for 'invalid_argument'
 
 #include "test_macros.h"
 
 TEST_MSVC_DIAGNOSTIC_IGNORED(6294) // Ill-defined for-loop:  initial condition does not satisfy test.  Loop body not executed.
 
 template <std::size_t N>
-void test_char_pointer_ctor()
-{
-    {
+TEST_CONSTEXPR_CXX23 void test_char_pointer_ctor()
 #ifndef TEST_HAS_NO_EXCEPTIONS
-        try {
-            std::bitset<N> v("xxx1010101010xxxx");
-            assert(false);
-        }
-        catch (std::invalid_argument&) {}
-#endif
-    }
+  if (!TEST_IS_CONSTANT_EVALUATED) {
+#endif
 
-    {
     const char str[] = "1010101010";
     std::bitset<N> v(str);
     std::size_t M = std::min<std::size_t>(v.size(), 10);
     for (std::size_t i = 0; i < M; ++i)
         assert(v[i] == (str[M - 1 - i] == '1'));
     for (std::size_t i = 10; i < v.size(); ++i)
         assert(v[i] == false);
-    }
 }
 
-int main(int, char**)
-{
-    test_char_pointer_ctor<0>();
-    test_char_pointer_ctor<1>();
-    test_char_pointer_ctor<31>();
-    test_char_pointer_ctor<32>();
-    test_char_pointer_ctor<33>();
-    test_char_pointer_ctor<63>();
-    test_char_pointer_ctor<64>();
-    test_char_pointer_ctor<65>();
-    test_char_pointer_ctor<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
+  return true;
+}
+
+int main(int, char**)
+{
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
   return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.cons/default.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test default ctor
+// default ctor
 
 #include <bitset>
 #include <cassert>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_default_ctor()
+TEST_CONSTEXPR_CXX23 void test_default_ctor()
 {
     {
         TEST_CONSTEXPR std::bitset<N> v1;
         assert(v1.size() == N);
         for (std::size_t i = 0; i < v1.size(); ++i)
             assert(v1[i] == false);
     }
 #if TEST_STD_VER >= 11
     {
         constexpr std::bitset<N> v1;
         static_assert(v1.size() == N, "");
     }
 #endif
 }
 
-
-int main(int, char**)
-{
-    test_default_ctor<0>();
-    test_default_ctor<1>();
-    test_default_ctor<31>();
-    test_default_ctor<32>();
-    test_default_ctor<33>();
-    test_default_ctor<63>();
-    test_default_ctor<64>();
-    test_default_ctor<65>();
-    test_default_ctor<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
+  return true;
+}
+
+int main(int, char**)
+{
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
   return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.cons/string_ctor.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset(string, pos, n, zero, one);
+// bitset(string, pos, n, zero, one); // constexpr since C++23
 
 #include <bitset>
 #include <algorithm> // for 'min' and 'max'
 #include <cassert>
 #include <stdexcept> // for 'invalid_argument'
 #include <string>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_string_ctor() {
+TEST_CONSTEXPR_CXX23 void test_string_ctor() {
 #ifndef TEST_HAS_NO_EXCEPTIONS
-    {
-        try {
-            std::string s("xxx1010101010xxxx");
-            std::bitset<N> v(s, s.size()+1, 10);
-            assert(false);
-        }
-        catch (std::out_of_range&)
-        {
-        }
-    }
-    {
-        try {
-            std::string s("xxx1010101010xxxx");
-            std::bitset<N> v(s, 2, 10);
-            assert(false);
-        }
-        catch (std::invalid_argument&)
-        {
-        }
-    }
-    {
-        try {
-            std::string s("xxxbababababaxxxx");
-            std::bitset<N> v(s, 2, 10, 'a', 'b');
-            assert(false);
-        }
-        catch (std::invalid_argument&)
-        {
-        }
-    }
+  if (!TEST_IS_CONSTANT_EVALUATED) {
 #endif // TEST_HAS_NO_EXCEPTIONS
-    {
-        std::string s("xxx1010101010xxxx");
-        std::bitset<N> v(s, 3, 10);
-        std::size_t M = std::min<std::size_t>(v.size(), 10);
-        for (std::size_t i = 0; i < M; ++i)
-            assert(v[i] == (s[3 + M - 1 - i] == '1'));
-        for (std::size_t i = 10; i < v.size(); ++i)
-            assert(v[i] == false);
-    }
-    {
-        std::string s("xxxbababababaxxxx");
-        std::bitset<N> v(s, 3, 10, 'a', 'b');
-        std::size_t M = std::min<std::size_t>(v.size(), 10);
-        for (std::size_t i = 0; i < M; ++i)
-            assert(v[i] == (s[3 + M - 1 - i] == 'b'));
-        for (std::size_t i = 10; i < v.size(); ++i)
-            assert(v[i] == false);
-    }
 }
 
 struct Nonsense {
     virtual ~Nonsense() {}
 };
 
-void test_for_non_eager_instantiation() {
+TEST_CONSTEXPR_CXX23 void test_for_non_eager_instantiation() {
     // Ensure we don't accidentally instantiate `std::basic_string<Nonsense>`
     // since it may not be well formed and can cause an error in the
     // non-immediate context.
     static_assert(!std::is_constructible<std::bitset<3>, Nonsense*>::value, "");
     static_assert(!std::is_constructible<std::bitset<3>, Nonsense*, size_t, Nonsense&, Nonsense&>::value, "");
 }
 
-int main(int, char**) {
-    test_string_ctor<0>();
-    test_string_ctor<1>();
-    test_string_ctor<31>();
-    test_string_ctor<32>();
-    test_string_ctor<33>();
-    test_string_ctor<63>();
-    test_string_ctor<64>();
-    test_string_ctor<65>();
-    test_string_ctor<1000>();
-    test_for_non_eager_instantiation();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.cons/ull_ctor.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset(unsigned long long val);
+// bitset(unsigned long long val); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <algorithm> // for 'min' and 'max'
 #include <cstddef>
 
 #include "test_macros.h"
 
 TEST_MSVC_DIAGNOSTIC_IGNORED(6294) // Ill-defined for-loop:  initial condition does not satisfy test.  Loop body not executed.
 
 template <std::size_t N>
-void test_val_ctor()
+TEST_CONSTEXPR_CXX23 void test_val_ctor()
 {
     {
         TEST_CONSTEXPR std::bitset<N> v(0xAAAAAAAAAAAAAAAAULL);
         assert(v.size() == N);
         std::size_t M = std::min<std::size_t>(v.size(), 64);
         for (std::size_t i = 0; i < M; ++i)
             assert(v[i] == ((i & 1) != 0));
         for (std::size_t i = M; i < v.size(); ++i)
             assert(v[i] == false);
     }
 #if TEST_STD_VER >= 11
     {
         constexpr std::bitset<N> v(0xAAAAAAAAAAAAAAAAULL);
         static_assert(v.size() == N, "");
     }
 #endif
 }
 
-int main(int, char**)
-{
-    test_val_ctor<0>();
-    test_val_ctor<1>();
-    test_val_ctor<31>();
-    test_val_ctor<32>();
-    test_val_ctor<33>();
-    test_val_ctor<63>();
-    test_val_ctor<64>();
-    test_val_ctor<65>();
-    test_val_ctor<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
+  return true;
+}
+
+int main(int, char**)
+{
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
   return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/all.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bool all() const;
+// bool all() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_all() {
+TEST_CONSTEXPR_CXX23 void test_all() {
     std::bitset<N> v;
     v.reset();
     assert(v.all() == (N == 0));
     v.set();
     assert(v.all() == true);
     if (v.size() > 1) {
         v[N/2] = false;
         assert(v.all() == false);
     }
 }
 
-int main(int, char**) {
-    test_all<0>();
-    test_all<1>();
-    test_all<31>();
-    test_all<32>();
-    test_all<33>();
-    test_all<63>();
-    test_all<64>();
-    test_all<65>();
-    test_all<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/any.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bool any() const;
+// bool any() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_any() {
+TEST_CONSTEXPR_CXX23 void test_any() {
     std::bitset<N> v;
     v.reset();
     assert(v.any() == false);
     v.set();
     assert(v.any() == (N != 0));
     if (v.size() > 1) {
         v[N/2] = false;
         assert(v.any() == true);
         v.reset();
         v[N/2] = true;
         assert(v.any() == true);
     }
 }
 
-int main(int, char**) {
-    test_any<0>();
-    test_any<1>();
-    test_any<31>();
-    test_any<32>();
-    test_any<33>();
-    test_any<63>();
-    test_any<64>();
-    test_any<65>();
-    test_any<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/count.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test size_t count() const;
+// size_t count() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_count() {
+TEST_CONSTEXPR_CXX23 void test_count() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         const std::bitset<N> v = cases[c];
         std::size_t c1 = v.count();
         std::size_t c2 = 0;
         for (std::size_t i = 0; i < v.size(); ++i)
             if (v[i])
                 ++c2;
         assert(c1 == c2);
     }
 }
 
-int main(int, char**) {
-    test_count<0>();
-    test_count<1>();
-    test_count<31>();
-    test_count<32>();
-    test_count<33>();
-    test_count<63>();
-    test_count<64>();
-    test_count<65>();
-    test_count<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_count<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/flip_all.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& flip();
+// bitset<N>& flip(); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_flip_all() {
+TEST_CONSTEXPR_CXX23 void test_flip_all() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> v1 = cases[c];
         std::bitset<N> v2 = v1;
         v2.flip();
         for (std::size_t i = 0; i < v1.size(); ++i)
             assert(v2[i] == ~v1[i]);
     }
 }
 
-int main(int, char**) {
-    test_flip_all<0>();
-    test_flip_all<1>();
-    test_flip_all<31>();
-    test_flip_all<32>();
-    test_flip_all<33>();
-    test_flip_all<63>();
-    test_flip_all<64>();
-    test_flip_all<65>();
-    test_flip_all<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_flip_all<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/flip_one.out_of_range.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: no-exceptions
 
-// test bitset<N>& flip(size_t pos);
+// bitset<N>& flip(size_t pos); // constexpr since C++23
 
 // Make sure we throw std::out_of_range when calling flip() on an OOB index.
 
 #include <bitset>
 #include <cassert>
 #include <stdexcept>
 
 int main(int, char**) {

libcxx/test/std/utilities/template.bitset/bitset.members/flip_one.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& flip(size_t pos);
+// bitset<N>& flip(size_t pos); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_flip_one() {
+TEST_CONSTEXPR_CXX23 void test_flip_one() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> v = cases[c];
         if (v.size() > 0) {
             std::size_t middle = v.size() / 2;
             v.flip(middle);
             bool b = v[middle];
             assert(v[middle] == b);
             v.flip(middle);
             assert(v[middle] != b);
             v.flip(middle);
             assert(v[middle] == b);
         }
     }
 }
 
-int main(int, char**) {
-    test_flip_one<0>();
-    test_flip_one<1>();
-    test_flip_one<31>();
-    test_flip_one<32>();
-    test_flip_one<33>();
-    test_flip_one<63>();
-    test_flip_one<64>();
-    test_flip_one<65>();
-    test_flip_one<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_flip_one<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/index.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>::reference operator[](size_t pos);
+// bitset<N>::reference operator[](size_t pos); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_index() {
+TEST_CONSTEXPR_CXX23 void test_index() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> v1 = cases[c];
         if (v1.size() > 0) {
             assert(v1[N/2] == v1.test(N/2));
             typename std::bitset<N>::reference r = v1[N/2];
             assert(r == v1.test(N/2));
             typename std::bitset<N>::reference r2 = v1[N/2];
for (std::size_t c = 0; c != cases.size(); ++c) {
             r.flip();
             assert(r == false);
             assert(v1.test(N/2) == false);
         }
         ASSERT_SAME_TYPE(decltype(v1[0]), typename std::bitset<N>::reference);
     }
 }
 
-int main(int, char**) {
-    test_index<0>();
-    test_index<1>();
-    test_index<31>();
-    test_index<32>();
-    test_index<33>();
-    test_index<63>();
-    test_index<64>();
-    test_index<65>();
-    test_index<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    std::bitset<1> set;
-    set[0] = false;
-    auto b = set[0];
-    set[0] = true;
-    assert(b);
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_index<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/index_const.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test constexpr bool operator[](size_t pos) const;
+// constexpr bool operator[](size_t pos) const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_index_const() {
+TEST_CONSTEXPR_CXX23 void test_index_const() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> const v = cases[c];
         if (v.size() > 0) {
             assert(v[N/2] == v.test(N/2));
         }
     }
 #if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
     ASSERT_SAME_TYPE(decltype(cases[0][0]), bool);
 #else
     ASSERT_SAME_TYPE(decltype(cases[0][0]), typename std::bitset<N>::const_reference);
 #endif
 }
 
-int main(int, char**) {
-    test_index_const<0>();
-    test_index_const<1>();
-    test_index_const<31>();
-    test_index_const<32>();
-    test_index_const<33>();
-    test_index_const<63>();
-    test_index_const<64>();
-    test_index_const<65>();
-    test_index_const<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
   std::bitset<1> set_;
   set_[0] = false;
   const auto& set = set_;
   auto b = set[0];
   set_[0] = true;
 #if !defined(_LIBCPP_VERSION) || defined(_LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL)
   assert(!b);
 #else
   assert(b);
 #endif
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_index_const<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/left_shift.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator<<(size_t pos) const;
+// bitset<N> operator<<(size_t pos) const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_left_shift() {
+TEST_CONSTEXPR_CXX23 void test_left_shift() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         for (std::size_t s = 0; s <= N+1; ++s) {
             std::bitset<N> v1 = cases[c];
             std::bitset<N> v2 = v1;
             assert((v1 <<= s) == (v2 << s));
         }
     }
 }
 
-int main(int, char**) {
-    test_left_shift<0>();
-    test_left_shift<1>();
-    test_left_shift<31>();
-    test_left_shift<32>();
-    test_left_shift<33>();
-    test_left_shift<63>();
-    test_left_shift<64>();
-    test_left_shift<65>();
-    test_left_shift<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_left_shift<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/left_shift_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& operator<<=(size_t pos);
+// bitset<N>& operator<<=(size_t pos); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_left_shift() {
+TEST_CONSTEXPR_CXX23 bool test_left_shift() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         for (std::size_t s = 0; s <= N+1; ++s) {
             std::bitset<N> v1 = cases[c];
             std::bitset<N> v2 = v1;
             v1 <<= s;
             for (std::size_t i = 0; i < v1.size(); ++i)
                 if (i < s)
                     assert(v1[i] == 0);
                 else
                     assert(v1[i] == v2[i-s]);
         }
     }
+    return true;
 }
 
 int main(int, char**) {
-    test_left_shift<0>();
-    test_left_shift<1>();
-    test_left_shift<31>();
-    test_left_shift<32>();
-    test_left_shift<33>();
-    test_left_shift<63>();
-    test_left_shift<64>();
-    test_left_shift<65>();
-    test_left_shift<1000>();
+  test_left_shift<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test_left_shift<0>());
+  static_assert(test_left_shift<1>());
+  static_assert(test_left_shift<31>());
+  static_assert(test_left_shift<32>());
+  static_assert(test_left_shift<33>());
+  static_assert(test_left_shift<63>());
+  static_assert(test_left_shift<64>());
+  static_assert(test_left_shift<65>());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/none.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bool none() const;
+// bool none() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_none() {
+TEST_CONSTEXPR_CXX23 void test_none() {
     std::bitset<N> v;
     v.reset();
     assert(v.none() == true);
     v.set();
     assert(v.none() == (N == 0));
     if (v.size() > 1) {
         v[N/2] = false;
         assert(v.none() == false);
         v.reset();
         v[N/2] = true;
         assert(v.none() == false);
     }
 }
 
-int main(int, char**) {
-    test_none<0>();
-    test_none<1>();
-    test_none<31>();
-    test_none<32>();
-    test_none<33>();
-    test_none<63>();
-    test_none<64>();
-    test_none<65>();
-    test_none<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/not_all.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator~() const;
+// bitset<N> operator~() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_not_all() {
+TEST_CONSTEXPR_CXX23 void test_not_all() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> v1 = cases[c];
         std::bitset<N> v2 = ~v1;
         for (std::size_t i = 0; i < v1.size(); ++i)
             assert(v2[i] == ~v1[i]);
     }
 }
 
-int main(int, char**) {
-    test_not_all<0>();
-    test_not_all<1>();
-    test_not_all<31>();
-    test_not_all<32>();
-    test_not_all<33>();
-    test_not_all<63>();
-    test_not_all<64>();
-    test_not_all<65>();
-    test_not_all<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_not_all<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/op_and_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& operator&=(const bitset<N>& rhs);
+// bitset<N>& operator&=(const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_and_eq() {
+TEST_CONSTEXPR_CXX23 void test_op_and_eq() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             v1 &= v2;
             for (std::size_t i = 0; i < v1.size(); ++i)
                 assert(v1[i] == (v3[i] && v2[i]));
         }
     }
 }
 
-int main(int, char**) {
-    test_op_and_eq<0>();
-    test_op_and_eq<1>();
-    test_op_and_eq<31>();
-    test_op_and_eq<32>();
-    test_op_and_eq<33>();
-    test_op_and_eq<63>();
-    test_op_and_eq<64>();
-    test_op_and_eq<65>();
-    test_op_and_eq<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_op_and_eq<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/op_eq_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // test:
 
-// bool operator==(const bitset<N>& rhs) const;
-// bool operator!=(const bitset<N>& rhs) const;
+// bool operator==(const bitset<N>& rhs) const; // constexpr since C++23
+// bool operator!=(const bitset<N>& rhs) const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_equality() {
+TEST_CONSTEXPR_CXX23 void test_equality() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> const v1 = cases[c];
         std::bitset<N> v2 = v1;
         assert(v1 == v2);
         if (v1.size() > 0) {
             v2[N/2].flip();
             assert(v1 != v2);
         }
     }
 }
 
-int main(int, char**) {
-    test_equality<0>();
-    test_equality<1>();
-    test_equality<31>();
-    test_equality<32>();
-    test_equality<33>();
-    test_equality<63>();
-    test_equality<64>();
-    test_equality<65>();
-    test_equality<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_equality<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/op_or_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& operator|=(const bitset<N>& rhs);
+// bitset<N>& operator|=(const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_or_eq() {
+TEST_CONSTEXPR_CXX23 void test_op_or_eq() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             v1 |= v2;
             for (std::size_t i = 0; i < v1.size(); ++i)
                 assert(v1[i] == (v3[i] || v2[i]));
         }
     }
 }
 
-int main(int, char**) {
-    test_op_or_eq<0>();
-    test_op_or_eq<1>();
-    test_op_or_eq<31>();
-    test_op_or_eq<32>();
-    test_op_or_eq<33>();
-    test_op_or_eq<63>();
-    test_op_or_eq<64>();
-    test_op_or_eq<65>();
-    test_op_or_eq<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_op_or_eq<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/op_xor_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& operator^=(const bitset<N>& rhs);
+// bitset<N>& operator^=(const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_xor_eq() {
+TEST_CONSTEXPR_CXX23 bool test_op_xor_eq() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             v1 ^= v2;
             for (std::size_t i = 0; i < v1.size(); ++i)
                 assert(v1[i] == (v3[i] != v2[i]));
         }
     }
+    return true;
 }
 
 int main(int, char**) {
-    test_op_xor_eq<0>();
-    test_op_xor_eq<1>();
-    test_op_xor_eq<31>();
-    test_op_xor_eq<32>();
-    test_op_xor_eq<33>();
-    test_op_xor_eq<63>();
-    test_op_xor_eq<64>();
-    test_op_xor_eq<65>();
-    test_op_xor_eq<1000>();
+  test_op_xor_eq<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test_op_xor_eq<0>());
+  static_assert(test_op_xor_eq<1>());
+  static_assert(test_op_xor_eq<31>());
+  static_assert(test_op_xor_eq<32>());
+  static_assert(test_op_xor_eq<33>());
+  static_assert(test_op_xor_eq<63>());
+  static_assert(test_op_xor_eq<64>());
+  static_assert(test_op_xor_eq<65>());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/reset_all.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& reset();
+// bitset<N>& reset(); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_reset_all() {
+TEST_CONSTEXPR_CXX23 void test_reset_all() {
     std::bitset<N> v;
     v.set();
     v.reset();
     for (std::size_t i = 0; i < v.size(); ++i)
         assert(!v[i]);
 }
 
-int main(int, char**) {
-    test_reset_all<0>();
-    test_reset_all<1>();
-    test_reset_all<31>();
-    test_reset_all<32>();
-    test_reset_all<33>();
-    test_reset_all<63>();
-    test_reset_all<64>();
-    test_reset_all<65>();
-    test_reset_all<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/reset_one.out_of_range.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: no-exceptions
 
-// test bitset<N>& reset(size_t pos);
+// bitset<N>& reset(size_t pos); // constexpr since C++23
 
 // Make sure we throw std::out_of_range when calling reset() on an OOB index.
 
 #include <bitset>
 #include <cassert>
 #include <stdexcept>
 
 int main(int, char**) {

libcxx/test/std/utilities/template.bitset/bitset.members/reset_one.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& reset(size_t pos);
+// bitset<N>& reset(size_t pos); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 TEST_MSVC_DIAGNOSTIC_IGNORED(6294) // Ill-defined for-loop:  initial condition does not satisfy test.  Loop body not executed.
 
 template <std::size_t N>
-void test_reset_one() {
+TEST_CONSTEXPR_CXX23 void test_reset_one() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         for (std::size_t i = 0; i != N; ++i) {
             std::bitset<N> v = cases[c];
             v.reset(i);
             assert(v[i] == false);
         }
     }
 }
 
-int main(int, char**) {
-    test_reset_one<0>();
-    test_reset_one<1>();
-    test_reset_one<31>();
-    test_reset_one<32>();
-    test_reset_one<33>();
-    test_reset_one<63>();
-    test_reset_one<64>();
-    test_reset_one<65>();
-    test_reset_one<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_reset_one<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/right_shift.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator>>(size_t pos) const;
+// bitset<N> operator>>(size_t pos) const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_right_shift() {
+TEST_CONSTEXPR_CXX23 bool test_right_shift() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         for (std::size_t s = 0; s <= N+1; ++s) {
             std::bitset<N> v1 = cases[c];
             std::bitset<N> v2 = v1;
             assert((v1 >>= s) == (v2 >> s));
         }
     }
+    return true;
 }
 
 int main(int, char**) {
-    test_right_shift<0>();
-    test_right_shift<1>();
-    test_right_shift<31>();
-    test_right_shift<32>();
-    test_right_shift<33>();
-    test_right_shift<63>();
-    test_right_shift<64>();
-    test_right_shift<65>();
-    test_right_shift<1000>();
+  test_right_shift<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test_right_shift<0>());
+  static_assert(test_right_shift<1>());
+  static_assert(test_right_shift<31>());
+  static_assert(test_right_shift<32>());
+  static_assert(test_right_shift<33>());
+  static_assert(test_right_shift<63>());
+  static_assert(test_right_shift<64>());
+  static_assert(test_right_shift<65>());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/right_shift_eq.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& operator<<=(size_t pos);
+// bitset<N>& operator<<=(size_t pos); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_right_shift() {
+TEST_CONSTEXPR_CXX23 bool test_right_shift() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         for (std::size_t s = 0; s <= N+1; ++s) {
             std::bitset<N> v1 = cases[c];
             std::bitset<N> v2 = v1;
             v1 >>= s;
             for (std::size_t i = 0; i < v1.size(); ++i)
                 if (i + s < v1.size())
                     assert(v1[i] == v2[i + s]);
                 else
                     assert(v1[i] == 0);
         }
     }
+    return true;
 }
 
 int main(int, char**) {
-    test_right_shift<0>();
-    test_right_shift<1>();
-    test_right_shift<31>();
-    test_right_shift<32>();
-    test_right_shift<33>();
-    test_right_shift<63>();
-    test_right_shift<64>();
-    test_right_shift<65>();
-    test_right_shift<1000>();
+  test_right_shift<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test_right_shift<0>());
+  static_assert(test_right_shift<1>());
+  static_assert(test_right_shift<31>());
+  static_assert(test_right_shift<32>());
+  static_assert(test_right_shift<33>());
+  static_assert(test_right_shift<63>());
+  static_assert(test_right_shift<64>());
+  static_assert(test_right_shift<65>());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/set_all.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& set();
+// bitset<N>& set(); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_set_all() {
+TEST_CONSTEXPR_CXX23 void test_set_all() {
     std::bitset<N> v;
     v.set();
     for (std::size_t i = 0; i < v.size(); ++i)
         assert(v[i]);
 }
 
-int main(int, char**) {
-    test_set_all<0>();
-    test_set_all<1>();
-    test_set_all<31>();
-    test_set_all<32>();
-    test_set_all<33>();
-    test_set_all<63>();
-    test_set_all<64>();
-    test_set_all<65>();
-    test_set_all<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/set_one.out_of_range.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: no-exceptions
 
-// test bitset<N>& set(size_t pos, bool val = true);
+// bitset<N>& set(size_t pos, bool val = true); // constexpr since C++23
 
 // Make sure we throw std::out_of_range when calling set() on an OOB index.
 
 #include <bitset>
 #include <cassert>
 #include <stdexcept>
 
 int main(int, char**) {

libcxx/test/std/utilities/template.bitset/bitset.members/set_one.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N>& set(size_t pos, bool val = true);
+// bitset<N>& set(size_t pos, bool val = true); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_set_one() {
+TEST_CONSTEXPR_CXX23 void test_set_one() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> v = cases[c];
         if (v.size() > 0) {
             std::size_t middle = v.size() / 2;
             v.set(middle);
             assert(v[middle] == true);
             v.set(middle, false);
             assert(v[middle] == false);
         }
     }
 }
 
-int main(int, char**) {
-    test_set_one<0>();
-    test_set_one<1>();
-    test_set_one<31>();
-    test_set_one<32>();
-    test_set_one<33>();
-    test_set_one<63>();
-    test_set_one<64>();
-    test_set_one<65>();
-    test_set_one<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_set_one<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/size.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test size_t count() const;
+// size_t count() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_size() {
+TEST_CONSTEXPR_CXX23 void test_size() {
     const std::bitset<N> v;
     assert(v.size() == N);
 }
 
-int main(int, char**) {
-    test_size<0>();
-    test_size<1>();
-    test_size<31>();
-    test_size<32>();
-    test_size<33>();
-    test_size<63>();
-    test_size<64>();
-    test_size<65>();
-    test_size<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/test.out_of_range.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: no-exceptions
 
-// test constexpr bool test(size_t pos) const;
+// constexpr bool test(size_t pos) const;
 
 // Make sure we throw std::out_of_range when calling test() on an OOB index.
 
 #include <bitset>
 #include <cassert>
 #include <stdexcept>
 
 int main(int, char**) {

libcxx/test/std/utilities/template.bitset/bitset.members/test.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test constexpr bool test(size_t pos) const;
+// bool test(size_t pos) const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_test() {
+TEST_CONSTEXPR_CXX23 void test_test() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> const v = cases[c];
         if (v.size() > 0) {
             std::size_t middle = v.size() / 2;
             bool b = v.test(middle);
             assert(b == v[middle]);
         }
     }
 }
 
-int main(int, char**) {
-    test_test<0>();
-    test_test<1>();
-    test_test<31>();
-    test_test<32>();
-    test_test<33>();
-    test_test<63>();
-    test_test<64>();
-    test_test<65>();
-    test_test<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_test<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/to_string.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // test:
 
 // template <class charT, class traits, class Allocator>
 // basic_string<charT, traits, Allocator>
-// to_string(charT zero = charT('0'), charT one = charT('1')) const;
+// to_string(charT zero = charT('0'), charT one = charT('1')) const; // constexpr since C++23
 //
 // template <class charT, class traits>
-// basic_string<charT, traits, allocator<charT> > to_string() const;
+// basic_string<charT, traits, allocator<charT> > to_string() const; // constexpr since C++23
 //
 // template <class charT>
-// basic_string<charT, char_traits<charT>, allocator<charT> > to_string() const;
+// basic_string<charT, char_traits<charT>, allocator<charT> > to_string() const; // constexpr since C++23
 //
-// basic_string<char, char_traits<char>, allocator<char> > to_string() const;
+// basic_string<char, char_traits<char>, allocator<char> > to_string() const; // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <memory> // for std::allocator
 #include <string>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <class CharT, std::size_t N>
-void check_equal(std::basic_string<CharT> const& s, std::bitset<N> const& b, CharT zero, CharT one) {
+TEST_CONSTEXPR_CXX23 void check_equal(std::basic_string<CharT> const& s, std::bitset<N> const& b, CharT zero, CharT one) {
     assert(s.size() == b.size());
     for (std::size_t i = 0; i < b.size(); ++i) {
         if (b[i]) {
             assert(s[b.size() - 1 - i] == one);
         } else {
             assert(s[b.size() - 1 - i] == zero);
         }
     }
 }
 
 template <std::size_t N>
-void test_to_string() {
+TEST_CONSTEXPR_CXX23 bool test_to_string() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c = 0; c != cases.size(); ++c) {
         std::bitset<N> const v = cases[c];
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
         {
             std::wstring s = v.template to_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >();
             check_equal(s, v, L'0', L'1');
         }
#endif
             std::string s = v.to_string('0', '1');
             check_equal(s, v, '0', '1');
         }
         {
             std::string s = v.to_string('x', 'y');
             check_equal(s, v, 'x', 'y');
         }
     }
+    return true;
 }
 
 int main(int, char**) {
-    test_to_string<0>();
-    test_to_string<1>();
-    test_to_string<31>();
-    test_to_string<32>();
-    test_to_string<33>();
-    test_to_string<63>();
-    test_to_string<64>();
-    test_to_string<65>();
-    test_to_string<1000>();
+  test_to_string<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test_to_string<0>());
+  static_assert(test_to_string<1>());
+  static_assert(test_to_string<31>());
+  static_assert(test_to_string<32>());
+  static_assert(test_to_string<33>());
+  static_assert(test_to_string<63>());
+  static_assert(test_to_string<64>());
+  static_assert(test_to_string<65>());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.members/to_ullong.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test unsigned long long to_ullong() const;
+// unsigned long long to_ullong() const; // constexpr since C++23
 
 #include <bitset>
 #include <algorithm>
 #include <type_traits>
 #include <climits>
 #include <cassert>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_to_ullong() {
+TEST_CONSTEXPR_CXX23 void test_to_ullong() {
     const std::size_t M = sizeof(unsigned long long) * CHAR_BIT < N ? sizeof(unsigned long long) * CHAR_BIT : N;
     const bool is_M_zero = std::integral_constant<bool, M == 0>::value; // avoid compiler warnings
     const std::size_t X = is_M_zero ? sizeof(unsigned long long) * CHAR_BIT - 1 : sizeof(unsigned long long) * CHAR_BIT - M;
     const unsigned long long max = is_M_zero ? 0 : (unsigned long long)(-1) >> X;
     unsigned long long tests[] = {
         0,
         std::min<unsigned long long>(1, max),
         std::min<unsigned long long>(2, max),
         std::min<unsigned long long>(3, max),
         std::min(max, max-3),
         std::min(max, max-2),
         std::min(max, max-1),
         max
     };
-    for (std::size_t i = 0; i < sizeof(tests)/sizeof(tests[0]); ++i) {
-        unsigned long long j = tests[i];
+    for (unsigned long long j : tests) {
          std::bitset<N> v(j);
         assert(j == v.to_ullong());
     }
     { // test values bigger than can fit into the bitset
         const unsigned long long val = 0x55AAAAFFFFAAAA55ULL;
         const bool canFit = N < sizeof(unsigned long long) * CHAR_BIT;
         const unsigned long long mask = canFit ? (1ULL << (canFit ? N : 0)) - 1 : (unsigned long long)(-1); // avoid compiler warnings
         std::bitset<N> v(val);
         assert(v.to_ullong() == (val & mask)); // we shouldn't return bit patterns from outside the limits of the bitset.
     }
 }
 
-int main(int, char**) {
-//     test_to_ullong<0>();
-    test_to_ullong<1>();
-    test_to_ullong<31>();
-    test_to_ullong<32>();
-    test_to_ullong<33>();
-    test_to_ullong<63>();
-    test_to_ullong<64>();
-    test_to_ullong<65>();
-    test_to_ullong<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+  test_to_ullong<0>();
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test unsigned long to_ulong() const;
+// unsigned long to_ulong() const; // constexpr since C++23
 
 #include <bitset>
 #include <algorithm>
 #include <type_traits>
 #include <limits>
 #include <climits>
 #include <cassert>
 
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_to_ulong() {
+TEST_CONSTEXPR_CXX23 void test_to_ulong() {
     const std::size_t M = sizeof(unsigned long) * CHAR_BIT < N ? sizeof(unsigned long) * CHAR_BIT : N;
     const bool is_M_zero = std::integral_constant<bool, M == 0>::value; // avoid compiler warnings
     const std::size_t X = is_M_zero ? sizeof(unsigned long) * CHAR_BIT - 1 : sizeof(unsigned long) * CHAR_BIT - M;
     const std::size_t max = is_M_zero ? 0 : std::size_t(std::numeric_limits<unsigned long>::max()) >> X;
     std::size_t tests[] = {
         0,
         std::min<std::size_t>(1, max),
         std::min<std::size_t>(2, max),
         std::min<std::size_t>(3, max),
         std::min(max, max-3),
         std::min(max, max-2),
         std::min(max, max-1),
         max
     };
-    for (std::size_t i = 0; i < sizeof(tests)/sizeof(tests[0]); ++i) {
-        std::size_t j = tests[i];
+    for (unsigned long j : tests) {
          std::bitset<N> v(j);
         assert(j == v.to_ulong());
     }
 
     { // test values bigger than can fit into the bitset
         const unsigned long val = 0x5AFFFFA5UL;
         const bool canFit = N < sizeof(unsigned long) * CHAR_BIT;
         const unsigned long mask = canFit ? (1UL << (canFit ? N : 0)) - 1 : (unsigned long)(-1); // avoid compiler warnings
         std::bitset<N> v(val);
         assert(v.to_ulong() == (val & mask)); // we shouldn't return bit patterns from outside the limits of the bitset.
     }
 }
 
-int main(int, char**) {
-    test_to_ulong<0>();
-    test_to_ulong<1>();
-    test_to_ulong<31>();
-    test_to_ulong<32>();
-    test_to_ulong<33>();
-    test_to_ulong<63>();
-    test_to_ulong<64>();
-    test_to_ulong<65>();
-    test_to_ulong<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
 
-    return 0;
+  return true;
+}
+
+int main(int, char**) {
+  test();
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
+
 }

libcxx/test/std/utilities/template.bitset/bitset.operators/op_and.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator&(const bitset<N>& lhs, const bitset<N>& rhs);
+// bitset<N> operator&(const bitset<N>& lhs, const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_and() {
+TEST_CONSTEXPR_CXX23 void test_op_and() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             assert((v1 & v2) == (v3 &= v2));
         }
     }
 }
 
-int main(int, char**) {
-    test_op_and<0>();
-    test_op_and<1>();
-    test_op_and<31>();
-    test_op_and<32>();
-    test_op_and<33>();
-    test_op_and<63>();
-    test_op_and<64>();
-    test_op_and<65>();
-    test_op_and<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_op_and<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.operators/op_not.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator^(const bitset<N>& lhs, const bitset<N>& rhs);
+// bitset<N> operator^(const bitset<N>& lhs, const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_not() {
+TEST_CONSTEXPR_CXX23 void test_op_not() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             assert((v1 ^ v2) == (v3 ^= v2));
         }
     }
 }
 
-int main(int, char**) {
-    test_op_not<0>();
-    test_op_not<1>();
-    test_op_not<31>();
-    test_op_not<32>();
-    test_op_not<33>();
-    test_op_not<63>();
-    test_op_not<64>();
-    test_op_not<65>();
-    test_op_not<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_op_not<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset.operators/op_or.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// test bitset<N> operator|(const bitset<N>& lhs, const bitset<N>& rhs);
+// bitset<N> operator|(const bitset<N>& lhs, const bitset<N>& rhs); // constexpr since C++23
 
 #include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <vector>
 
 #include "../bitset_test_cases.h"
 #include "test_macros.h"
 
 template <std::size_t N>
-void test_op_or() {
+TEST_CONSTEXPR_CXX23 void test_op_or() {
     std::vector<std::bitset<N> > const cases = get_test_cases<N>();
     for (std::size_t c1 = 0; c1 != cases.size(); ++c1) {
         for (std::size_t c2 = 0; c2 != cases.size(); ++c2) {
             std::bitset<N> v1 = cases[c1];
             std::bitset<N> v2 = cases[c2];
             std::bitset<N> v3 = v1;
             assert((v1 | v2) == (v3 |= v2));
         }
     }
 }
 
-int main(int, char**) {
-    test_op_or<0>();
-    test_op_or<1>();
-    test_op_or<31>();
-    test_op_or<32>();
-    test_op_or<33>();
-    test_op_or<63>();
-    test_op_or<64>();
-    test_op_or<65>();
-    test_op_or<1000>();
+TEST_CONSTEXPR_CXX23 bool test() {
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  test_op_or<1000>(); // not in constexpr because of constexpr evaluation step limits
+#if TEST_STD_VER > 20
+  static_assert(test());
+#endif
 
-    return 0;
 }

libcxx/test/std/utilities/template.bitset/bitset_test_cases.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #ifndef LIBCPP_TEST_BITSET_TEST_CASES_H
 #define LIBCPP_TEST_BITSET_TEST_CASES_H
 
 #include <bitset>
 #include <string>
 #include <vector>
 
+#include "test_macros.h"
+
 template <int N>
-std::vector<std::bitset<N> > get_test_cases();
+TEST_CONSTEXPR_CXX23 std::vector<std::bitset<N> > get_test_cases();
 
 template <>
-inline std::vector<std::bitset<0> > get_test_cases<0>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<0> > get_test_cases<0>() {
     std::vector<std::bitset<0> > cases;
     cases.push_back(std::bitset<0>());
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<1> > get_test_cases<1>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<1> > get_test_cases<1>() {
     std::vector<std::bitset<1> > cases;
     cases.push_back(std::bitset<1>("0"));
     cases.push_back(std::bitset<1>("1"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<2> > get_test_cases<2>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<2> > get_test_cases<2>() {
     std::vector<std::bitset<2> > cases;
     cases.push_back(std::bitset<2>("00"));
     cases.push_back(std::bitset<2>("01"));
     cases.push_back(std::bitset<2>("10"));
     cases.push_back(std::bitset<2>("11"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<31> > get_test_cases<31>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<31> > get_test_cases<31>() {
     std::vector<std::bitset<31> > cases;
     cases.push_back(std::bitset<31>("0000000000000000000000000000000"));
     cases.push_back(std::bitset<31>("0000000000000000000000000000001"));
     cases.push_back(std::bitset<31>("1000000000000000000000000000000"));
     cases.push_back(std::bitset<31>("1000000000000000000000000000001"));
     cases.push_back(std::bitset<31>("1000000000000000000001000000001"));
     cases.push_back(std::bitset<31>("0000000000000000111111111111111"));
     cases.push_back(std::bitset<31>("1000000000000000111111111111111"));
     cases.push_back(std::bitset<31>("1111111111111111000000000000000"));
     cases.push_back(std::bitset<31>("1111111111111111000000000000001"));
     cases.push_back(std::bitset<31>("1010101010101010101010101010101"));
     cases.push_back(std::bitset<31>("0101010101010101010101010101010"));
     cases.push_back(std::bitset<31>("1111111111111111111111111111111"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<32> > get_test_cases<32>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<32> > get_test_cases<32>() {
     std::vector<std::bitset<32> > cases;
     cases.push_back(std::bitset<32>("00000000000000000000000000000000"));
     cases.push_back(std::bitset<32>("00000000000000000000000000000001"));
     cases.push_back(std::bitset<32>("10000000000000000000000000000000"));
     cases.push_back(std::bitset<32>("10000000000000000000000000000001"));
     cases.push_back(std::bitset<32>("10000000000000000000111000000001"));
     cases.push_back(std::bitset<32>("00000000000000001111111111111111"));
     cases.push_back(std::bitset<32>("10000000000000001111111111111111"));
     cases.push_back(std::bitset<32>("11111111111111110000000000000000"));
     cases.push_back(std::bitset<32>("11111111111111110000000000000001"));
     cases.push_back(std::bitset<32>("10101010101010101010101010101010"));
     cases.push_back(std::bitset<32>("01010101010101010101010101010101"));
     cases.push_back(std::bitset<32>("11111111111111111111111111111111"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<33> > get_test_cases<33>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<33> > get_test_cases<33>() {
     std::vector<std::bitset<33> > cases;
     cases.push_back(std::bitset<33>("000000000000000000000000000000000"));
     cases.push_back(std::bitset<33>("000000000000000000000000000000001"));
     cases.push_back(std::bitset<33>("100000000000000000000000000000000"));
     cases.push_back(std::bitset<33>("100000000000000000000000000000001"));
     cases.push_back(std::bitset<33>("100000000000000000001110000000001"));
     cases.push_back(std::bitset<33>("000000000000000011111111111111111"));
     cases.push_back(std::bitset<33>("100000000000000011111111111111111"));
     cases.push_back(std::bitset<33>("111111111111111100000000000000000"));
     cases.push_back(std::bitset<33>("111111111111111100000000000000001"));
     cases.push_back(std::bitset<33>("101010101010101010101010101010101"));
     cases.push_back(std::bitset<33>("010101010101010101010101010101010"));
     cases.push_back(std::bitset<33>("111111111111111111111111111111111"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<63> > get_test_cases<63>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<63> > get_test_cases<63>() {
     std::vector<std::bitset<63> > cases;
     cases.push_back(std::bitset<63>("000000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<63>("000000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<63>("100000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<63>("100000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<63>("100000000000000000000000001111100000000000000000000000000000001"));
     cases.push_back(std::bitset<63>("000000000000000000000000000000001111111111111111111111111111111"));
     cases.push_back(std::bitset<63>("100000000000000000000000000000001111111111111111111111111111111"));
     cases.push_back(std::bitset<63>("111111111111111111111111111111110000000000000000000000000000000"));
     cases.push_back(std::bitset<63>("111111111111111111111111111111110000000000000000000000000000001"));
     cases.push_back(std::bitset<63>("101010101010101010101010101010101010101010101010101010101010101"));
     cases.push_back(std::bitset<63>("010101010101010101010101010101010101010101010101010101010101010"));
     cases.push_back(std::bitset<63>("111111111111111111111111111111111111111111111111111111111111111"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<64> > get_test_cases<64>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<64> > get_test_cases<64>() {
     std::vector<std::bitset<64> > cases;
     cases.push_back(std::bitset<64>("0000000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<64>("0000000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<64>("1000000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<64>("1000000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<64>("1000000000000000000000000011111000000000000000000000000000000001"));
     cases.push_back(std::bitset<64>("0000000000000000000000000000000011111111111111111111111111111111"));
     cases.push_back(std::bitset<64>("1000000000000000000000000000000011111111111111111111111111111111"));
     cases.push_back(std::bitset<64>("1111111111111111111111111111111100000000000000000000000000000000"));
     cases.push_back(std::bitset<64>("1111111111111111111111111111111100000000000000000000000000000001"));
     cases.push_back(std::bitset<64>("1010101010101010101010101010101010101010101010101010101010101010"));
     cases.push_back(std::bitset<64>("0101010101010101010101010101010101010101010101010101010101010101"));
     cases.push_back(std::bitset<64>("1111111111111111111111111111111111111111111111111111111111111111"));
     return cases;
 }
 
 template <>
-inline std::vector<std::bitset<65> > get_test_cases<65>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<65> > get_test_cases<65>() {
     std::vector<std::bitset<65> > cases;
     cases.push_back(std::bitset<65>("00000000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<65>("00000000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<65>("10000000000000000000000000000000000000000000000000000000000000000"));
     cases.push_back(std::bitset<65>("10000000000000000000000000000000000000000000000000000000000000001"));
     cases.push_back(std::bitset<65>("10000000000000000000000000011111000000000000000000000000000000001"));
     cases.push_back(std::bitset<65>("00000000000000000000000000000000011111111111111111111111111111111"));
     cases.push_back(std::bitset<65>("10000000000000000000000000000000011111111111111111111111111111111"));
     cases.push_back(std::bitset<65>("11111111111111111111111111111111000000000000000000000000000000000"));
     cases.push_back(std::bitset<65>("11111111111111111111111111111111000000000000000000000000000000001"));
     cases.push_back(std::bitset<65>("10101010101010101010101010101010101010101010101010101010101010101"));
     cases.push_back(std::bitset<65>("01010101010101010101010101010101010101010101010101010101010101010"));
     cases.push_back(std::bitset<65>("11111111111111111111111111111111111111111111111111111111111111111"));
     return cases;
 }
 
-inline std::string str_repeat(std::string s, unsigned int n) {
+TEST_CONSTEXPR_CXX23 inline std::string str_repeat(std::string s, unsigned int n) {
     std::string res = s;
     for (; n != 0; --n)
         res += s;
     return res;
 }
 
 template <>
-inline std::vector<std::bitset<1000> > get_test_cases<1000>() {
+TEST_CONSTEXPR_CXX23 inline std::vector<std::bitset<1000> > get_test_cases<1000>() {
     std::vector<std::bitset<1000> > cases;
     cases.push_back(std::bitset<1000>(std::string(1000, '0')));
     cases.push_back(std::bitset<1000>(std::string(999, '0') + std::string(1, '1')));
     cases.push_back(std::bitset<1000>(std::string(1, '1') + std::string(999, '0')));
     cases.push_back(std::bitset<1000>(std::string(1, '1') + std::string(998, '0') + std::string(1, '1')));
     cases.push_back(std::bitset<1000>(std::string(1, '1') + std::string(400, '0') + std::string(99, '1') + std::string(499, '0') + std::string(1, '1')));
     cases.push_back(std::bitset<1000>(std::string(500, '0') + std::string(500, '1')));
     cases.push_back(std::bitset<1000>(std::string(1, '1') + std::string(499, '0') + std::string(500, '1')));

libcxx/test/support/test_macros.h

 #endif
 
 #if TEST_STD_VER >= 20
 # define TEST_CONSTEXPR_CXX20 constexpr
 #else
 # define TEST_CONSTEXPR_CXX20
 #endif
 
+#if TEST_STD_VER > 20
+#  define TEST_CONSTEXPR_CXX23 constexpr
+#else
+#  define TEST_CONSTEXPR_CXX23
+#endif
+
 #define TEST_ALIGNAS_TYPE(...) TEST_ALIGNAS(TEST_ALIGNOF(__VA_ARGS__))
 
 #if !TEST_HAS_FEATURE(cxx_rtti) && !defined(__cpp_rtti) \
     && !defined(__GXX_RTTI)
 #define TEST_HAS_NO_RTTI
 #endif
 
 #if !defined(TEST_HAS_NO_RTTI)

libcxx/utils/generate_feature_test_macro_components.py

feature_test_macros = [ add_version_header(x) for x in [
     "name": "__cpp_lib_concepts",
     "values": { "c++20": 202002 },
     "headers": ["concepts"],
   }, {
     "name": "__cpp_lib_constexpr_algorithms",
     "values": { "c++20": 201806 },
     "headers": ["algorithm"],
   }, {
+    "name": "__cpp_lib_constexpr_bitset",
+    "values": { "c++2b": 202207 },
+    "headers": ["bitset"],
+  }, {
     "name": "__cpp_lib_constexpr_cmath",
     "values": { "c++2b": 202202 },
     "headers": ["cmath", "cstdlib"],
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_constexpr_complex",
     "values": { "c++20": 201711 },
     "headers": ["complex"],