[PATCH] libstdc++: Define __cpp_lib_stdbit_h and __cpp_lib_stdckdint_h feature test macros.

[Jonathan Wakely]

On Wed, 22 Apr 2026 at 13:12, Tomasz Kaminski <tkaminsk@redhat.com> wrote:
>
>
>
> On Thu, Apr 16, 2026 at 9:53 AM Tomasz Kaminski <tkaminsk@redhat.com> wrote:
>>
>>
>>
>> On Tue, Apr 14, 2026 at 4:43 PM Jonathan Wakely <jwakely@redhat.com> wrote:
>>>
>>> On Tue, 14 Apr 2026 at 15:39, Tomasz Kamiński <tkaminsk@redhat.com> wrote:
>>> >
>>> > This implements LWG4550: Need new feature test macros for <stdckdint.h>
>>> > and <stdbit.h>.
>>> >
>>> > libstdc++-v3/ChangeLog:
>>> >
>>> >         * include/bits/version.def (stdbit_h, stdckdint_h): Define.
>>> >         * include/bits/version.h: Regenerate.
>>> >         * include/c_compatibility/stdbit.h (__cpp_lib_stdbit_h): Define
>>> >         and use it in guards.
>>> >         * include/c_compatibility/stdckdint.h (__cpp_lib_stdckdint_h):
>>> >         Define and use it in guards.
>>> > ---
>>> > Testing on x86_64-linux. Dedicated tests 20_util/stdbit* and 26_numerics/stdckint*
>>> > already passes, so valus seem correct.
>>>
>>> OK. We should backport this to GCC 15 at some point too.
>>
>> Backported to GCC15.
>
> Should I backport it to GCC14? We provide stdbit.h and stdckdint.h there.

Yes please


>>>
>>>
>>>
>>> >
>>> >  libstdc++-v3/include/bits/version.def         | 16 +++++++++++++++
>>> >  libstdc++-v3/include/bits/version.h           | 20 +++++++++++++++++++
>>> >  libstdc++-v3/include/c_compatibility/stdbit.h |  8 ++++++--
>>> >  .../include/c_compatibility/stdckdint.h       |  8 ++++++--
>>> >  4 files changed, 48 insertions(+), 4 deletions(-)
>>> >
>>> > diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
>>> > index 94fc1f85993..13dba4d6378 100644
>>> > --- a/libstdc++-v3/include/bits/version.def
>>> > +++ b/libstdc++-v3/include/bits/version.def
>>> > @@ -1871,6 +1871,22 @@ ftms = {
>>> >    };
>>> >  };
>>> >
>>> > +ftms = {
>>> > +  name = stdbit_h;
>>> > +  values = {
>>> > +    v = 202603;
>>> > +    cxxmin = 26;
>>> > +  };
>>> > +};
>>> > +
>>> > +ftms = {
>>> > +  name = stdckdint_h;
>>> > +  values = {
>>> > +    v = 202603;
>>> > +    cxxmin = 26;
>>> > +  };
>>> > +};
>>> > +
>>> >  ftms = {
>>> >    name = adaptor_iterator_pair_constructor;
>>> >    values = {
>>> > diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
>>> > index 402e67580eb..743f7e29fe2 100644
>>> > --- a/libstdc++-v3/include/bits/version.h
>>> > +++ b/libstdc++-v3/include/bits/version.h
>>> > @@ -2076,6 +2076,26 @@
>>> >  #endif /* !defined(__cpp_lib_stdatomic_h) */
>>> >  #undef __glibcxx_want_stdatomic_h
>>> >
>>> > +#if !defined(__cpp_lib_stdbit_h)
>>> > +# if (__cplusplus >  202302L)
>>> > +#  define __glibcxx_stdbit_h 202603L
>>> > +#  if defined(__glibcxx_want_all) || defined(__glibcxx_want_stdbit_h)
>>> > +#   define __cpp_lib_stdbit_h 202603L
>>> > +#  endif
>>> > +# endif
>>> > +#endif /* !defined(__cpp_lib_stdbit_h) */
>>> > +#undef __glibcxx_want_stdbit_h
>>> > +
>>> > +#if !defined(__cpp_lib_stdckdint_h)
>>> > +# if (__cplusplus >  202302L)
>>> > +#  define __glibcxx_stdckdint_h 202603L
>>> > +#  if defined(__glibcxx_want_all) || defined(__glibcxx_want_stdckdint_h)
>>> > +#   define __cpp_lib_stdckdint_h 202603L
>>> > +#  endif
>>> > +# endif
>>> > +#endif /* !defined(__cpp_lib_stdckdint_h) */
>>> > +#undef __glibcxx_want_stdckdint_h
>>> > +
>>> >  #if !defined(__cpp_lib_adaptor_iterator_pair_constructor)
>>> >  # if (__cplusplus >= 202100L) && _GLIBCXX_HOSTED
>>> >  #  define __glibcxx_adaptor_iterator_pair_constructor 202106L
>>> > diff --git a/libstdc++-v3/include/c_compatibility/stdbit.h b/libstdc++-v3/include/c_compatibility/stdbit.h
>>> > index 1fb691e36c1..fa4ec0414c6 100644
>>> > --- a/libstdc++-v3/include/c_compatibility/stdbit.h
>>> > +++ b/libstdc++-v3/include/c_compatibility/stdbit.h
>>> > @@ -29,7 +29,11 @@
>>> >  #ifndef _GLIBCXX_STDBIT_H
>>> >  #define _GLIBCXX_STDBIT_H
>>> >
>>> > -#if __cplusplus > 202302L
>>> > +#define __glibcxx_want_stdbit_h
>>> > +#include <bits/version.h>
>>> > +
>>> > +#ifdef __cpp_lib_stdbit_h // C++ >= 26
>>> > +
>>> >  #include <bit>
>>> >
>>> >  #define __STDC_VERSION_STDBIT_H__ 202311L
>>> > @@ -577,6 +581,6 @@ _GLIBCXX_STDBIT_FUNC(stdc_bit_floor);
>>> >  _GLIBCXX_STDBIT_FUNC(stdc_bit_ceil);
>>> >  #undef _GLIBCXX_STDBIT_FUNC
>>> >  #endif // !DOXYGEN
>>> > -#endif // C++26
>>> > +#endif // __cpp_lib_stdbit_h
>>> >
>>> >  #endif // _GLIBCXX_STDBIT_H
>>> > diff --git a/libstdc++-v3/include/c_compatibility/stdckdint.h b/libstdc++-v3/include/c_compatibility/stdckdint.h
>>> > index 5bdf4dc7b24..0f0b30cc899 100644
>>> > --- a/libstdc++-v3/include/c_compatibility/stdckdint.h
>>> > +++ b/libstdc++-v3/include/c_compatibility/stdckdint.h
>>> > @@ -29,7 +29,11 @@
>>> >  #ifndef _GLIBCXX_STDCKDINT_H
>>> >  #define _GLIBCXX_STDCKDINT_H
>>> >
>>> > -#if __cplusplus > 202302L
>>> > +#define __glibcxx_want_stdckdint_h
>>> > +#include <bits/version.h>
>>> > +
>>> > +#ifdef __cpp_lib_stdckdint_h // C++ >= 26
>>> > +
>>> >  #include <type_traits>
>>> >  #include <concepts>
>>> >
>>> > @@ -96,6 +100,6 @@ using __gnu_cxx::ckd_sub;
>>> >  using __gnu_cxx::ckd_mul;
>>> >  #endif
>>> >
>>> > -#endif // C++26
>>> > +#endif // __cpp_lib_stdckdint_h
>>> >
>>> >  #endif // _GLIBCXX_STDCKDINT_H
>>> > --
>>> > 2.53.0
>>> >
>>>