michallenc commented on code in PR #18347: URL: https://github.com/apache/nuttx/pull/18347#discussion_r2762753994
########## include/nuttx/lib/stdbit.h: ########## @@ -0,0 +1,189 @@ +/**************************************************************************** + * include/nuttx/lib/stdbit.h + * + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to you under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +#ifndef __INCLUDE_NUTTX_LIB_STDBIT_H +#define __INCLUDE_NUTTX_LIB_STDBIT_H + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +/* If CONFIG_ARCH_STDBIT_H is defined, then the top-level Makefile will copy + * this header file to include/stdbit.h. In that case the architecture may + * provide arch/<architecture>/include/stdbit.h which will be included below. + * If CONFIG_LIBC_STDBIT_GENERIC is defined (or arch does not provide the + * header), the generic C23 implementation is used. + */ + +#if defined(CONFIG_ARCH_STDBIT_H) && defined(CONFIG_ARCH_HAVE_STDBIT_H) +# include <arch/stdbit.h> +#else + +/**************************************************************************** + * Preprocessor Definitions + ****************************************************************************/ + +/* C23 endianness. Prefer compiler definitions if present. */ + +#ifndef __STDC_ENDIAN_NATIVE__ +# if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) +# define __STDC_ENDIAN_NATIVE__ __STDC_ENDIAN_LITTLE__ +# define __STDC_ENDIAN_LITTLE__ 1 +# define __STDC_ENDIAN_BIG__ 2 +# elif defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__) +# define __STDC_ENDIAN_NATIVE__ __STDC_ENDIAN_BIG__ +# define __STDC_ENDIAN_LITTLE__ 1 +# define __STDC_ENDIAN_BIG__ 2 +# else +# define __STDC_ENDIAN_LITTLE__ 1 +# define __STDC_ENDIAN_BIG__ 2 +# define __STDC_ENDIAN_NATIVE__ 0 +# endif +#endif + +/**************************************************************************** + * Generic C23 stdbit implementation (type-specific macros) + ****************************************************************************/ + +#include <stdint.h> + +#define _STDBIT_WIDTH_UC (sizeof(unsigned char) * 8) +#define _STDBIT_WIDTH_US (sizeof(unsigned short) * 8) +#define _STDBIT_WIDTH_UI (sizeof(unsigned int) * 8) +#define _STDBIT_WIDTH_UL (sizeof(unsigned long) * 8) +#define _STDBIT_WIDTH_ULL (sizeof(unsigned long long) * 8) + +/* Leading zeros: result is width when x == 0 (C23). */ + +#define stdc_leading_zeros_uc(x) ((x) ? (unsigned int)(__builtin_clz((unsigned int)(x)) - (_STDBIT_WIDTH_UI - _STDBIT_WIDTH_UC)) : _STDBIT_WIDTH_UC) Review Comment: NuttX still supports builds with older GNUC where `__builtin_clz` and others might not be defined (look at `nuttx/compiler.h`). We get `CONFIG_HAVE_BUILTIN_CTZ` and other defines that tell us if the builtin is available. We probably don't have to support older GNUC right away, but I think at least some compilation time error could be raised here. ########## Kconfig: ########## @@ -625,6 +625,39 @@ config ARCH_STDARG_H ARCH_STDARG_H=y and providing. If ARCH_STDARG_H, is not defined, then the stdarg.h header file will stay out-of-the-way in include/nuttx/. +config ARCH_HAVE_STDBIT_H + bool + default n + ---help--- + Selected by architecture specific logic if the architecture provides + a stdbit.h header file. + +config ARCH_STDBIT_H + bool "stdbit.h" + depends on ARCH_HAVE_STDBIT_H + default n + ---help--- + There is a redirecting version of stdbit.h in the source tree. It + resides out-of-the-way at include/nuttx/lib/stdbit.h. This is + because you should normally use your toolchain's stdbit.h file if + available (C23). When CONFIG_ARCH_STDBIT_H=y is defined, the + top-level makefile will copy the redirecting stdbit.h header file + from include/nuttx/lib/stdbit.h to include/stdbit.h. The header + will then include the architecture-specific stdbit.h from + arch/<architecture>/include/stdbit.h if the architecture selects + ARCH_HAVE_STDBIT_H. Otherwise a generic C23 implementation is + used. + +config LIBC_STDBIT_GENERIC Review Comment: I am not sure if this belongs here. I suppose it's ok to make `stdbit.h` not mandatory, but maybe it could be done similarly to `libm` and put the configuration option to `libs/libc/stdbit/ `directory? ########## tools/Unix.mk: ########## @@ -222,6 +222,19 @@ include/setjmp.h: include/nuttx/lib/setjmp.h $(Q) cp -f include/nuttx/lib/setjmp.h include/setjmp.h endif +# Target used to copy include/nuttx/lib/stdbit.h. If CONFIG_ARCH_STDBIT_H or +# CONFIG_LIBC_STDBIT_GENERIC is defined, copy stdbit.h to include/ for C23 +# bit utilities. + +ifeq ($(CONFIG_ARCH_STDBIT_H),y) Review Comment: You could do something like ``` ifeq ($(firstword $(filter y,$(CONFIG_ARCH_STDBIT_H) $(CONFIG_LIBC_STDBIT_GENERIC))),y) ``` to get logical OR and avoid unnecessary code duplication. -- This is an automated message from the Apache Git Service. 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