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9.50 stdbit.h ¶

POSIX :
Not in POSIX yet, but we expect it will be. ISO C23 (latest free draft https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf) section 7.18.

Gnulib module: stdbit

Portability problems fixed by Gnulib:

• This header file is missing on many non-C23 platforms: glibc 2.38, macOS 14, FreeBSD 14.0, NetBSD 10.0, OpenBSD 7.5, AIX 7.3.1, HP-UX 11.31, Solaris 11.4, Cygwin 3.5.3, mingw, MSVC 17, Android 15.

Portability problems not fixed by Gnulib:

• On older non-C23 platforms lacking typeof or equivalent, a call to stdc_bit_floor and stdc_bit_ceil may yield a type that is wider than its argument. Although C23 seems to allow this, it differs from GNU behavior.
• On non-C23 platforms, type-generic functions apply portably only to the standard unsigned integer types specified by C17 or earlier.