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

[Tomasz Kaminski]

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.

>
>>
>> >
>> >  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
>> >
>>
>>
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