kernel_defines.h
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/*
* Copyright (C) 2014 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @addtogroup core_internal
* @{
*
* @file
* @brief Common macros and compiler attributes/pragmas configuration
*
* @author René Kijewski <rene.kijewski@fu-berlin.de>
*/
#ifndef KERNEL_DEFINES_H
#define KERNEL_DEFINES_H
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @def container_of(PTR, TYPE, MEMBER)
* @brief Returns the container of a pointer to a member.
* @details For a struct `TYPE` with a member `MEMBER`,
* given a pointer `PTR` to `TYPE::MEMBER` this function returns a pointer
* to the instance of `TYPE`.
* @details E.g. for `struct my_struct_t { ...; something_t n; ... } my_struct;`,
* `&my_struct == container_of(&my_struct.n, struct my_struct_t, n)`.
* @param[in] PTR pointer to a member
* @param[in] TYPE a type name (a struct or union), container of PTR
* @param[in] MEMBER name of the member of TYPE which PTR points to
* @return Pointer to the container of PTR.
*/
#if __STDC_VERSION__ >= 201112L
# define container_of(PTR, TYPE, MEMBER) \
(_Generic((PTR), \
const __typeof__ (((TYPE *) 0)->MEMBER) *: \
((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER))), \
__typeof__ (((TYPE *) 0)->MEMBER) *: \
((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER))) \
))
#elif defined __GNUC__
# define container_of(PTR, TYPE, MEMBER) \
(__extension__ ({ \
__extension__ const __typeof__ (((TYPE *) 0)->MEMBER) *__m____ = (PTR); \
((TYPE *) ((char *) __m____ - offsetof(TYPE, MEMBER))); \
}))
#else
# define container_of(PTR, TYPE, MEMBER) \
((TYPE *) ((char *) (PTR) - offsetof(TYPE, MEMBER)))
#endif
/**
* @def NORETURN
* @brief The *NORETURN* keyword tells the compiler to assume that the function
* cannot return.
*/
#ifdef __GNUC__
#define NORETURN __attribute__((noreturn))
#else
#define NORETURN
#endif
/**
* @def CONST
* @brief A function declared as *CONST* is #PURE and also not allowed to
* examine global memory. I.e. a *CONST* function cannot even
* dereference a pointer parameter.
*/
#ifdef __GNUC__
#define CONST __attribute__((const))
#else
#define CONST
#endif
/**
* @def PURE
* @brief The function has no effects except the return value and its return
* value depends only on the parameters and/or global variables. Such a
* function can be subject to common subexpression elimination and loop
* optimization just as an arithmetic operator would be.
*/
#ifdef __GNUC__
#define PURE __attribute__((pure))
#else
#define PURE
#endif
/**
* @def UNREACHABLE()
* @brief Tell the compiler that this line of code cannot be reached.
* @details Most useful in junction with #NORETURN.
* Use this if the compiler cannot tell that e.g.
* an assembler instruction causes a longjmp, or a write causes a reboot.
*/
#if ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 5)) || (__GNUC__ >= 5)
#define UNREACHABLE() __builtin_unreachable()
#else
#define UNREACHABLE() do { /* nothing */ } while (1)
#endif
/**
* @def ALIGN_OF(T)
* @brief Calculate the minimal alignment for type T.
* @param[in] T Type to examine
* @returns The minimal alignment of T.
*/
#define ALIGN_OF(T) (offsetof(struct { char c; T t; }, t))
#ifdef __cplusplus
}
#endif
#endif /* KERNEL_DEFINES_H */
/** @} */