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31 lines
1.2 KiB
ReStructuredText
31 lines
1.2 KiB
ReStructuredText
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========
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stdbit.h
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========
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The optional C23 ``stdbit.h`` header provides bit manipulation macros
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(endianness, leading/trailing zeros and ones, count, single-bit test,
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bit width, bit floor, bit ceil). NuttX provides this header only when
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explicitly enabled via Kconfig.
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Configuration
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=============
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- **CONFIG_ARCH_HAVE_STDBIT_H** (bool, selected by arch)
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Architecture indicates it provides ``arch/<arch>/include/stdbit.h``.
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- **CONFIG_ARCH_STDBIT_H** (bool "stdbit.h", depends on ARCH_HAVE_STDBIT_H)
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Use the redirecting header. The build copies
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``include/nuttx/lib/stdbit.h`` to ``include/stdbit.h``; that header
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then includes ``<arch/stdbit.h>`` when this option is set.
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- **CONFIG_LIBC_STDBIT_GENERIC** (bool "stdbit.h (generic C23)")
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Use the generic C23 implementation. The same redirecting file
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``include/nuttx/lib/stdbit.h`` is copied to ``include/stdbit.h``,
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and the generic implementation is used (no arch header). Requires
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compiler builtins (e.g. ``__builtin_clz``, ``__builtin_ctz``,
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``__builtin_popcount``); see ``CONFIG_HAVE_BUILTIN_*`` in
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``nuttx/compiler.h``.
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Either **CONFIG_ARCH_STDBIT_H** or **CONFIG_LIBC_STDBIT_GENERIC** may be
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enabled so that ``#include <stdbit.h>`` is available.
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