build_bug.h

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_BUILD_BUG_H
#define _LINUX_BUILD_BUG_H
 
#include <linux/compiler.h>
 
/*
 * Force a compilation error if condition is true, but also produce a
 * result (of value 0 and type int), so the expression can be used
 * e.g. in a structure initializer (or where-ever else comma expressions
 * aren't permitted).
 *
 * Take an error message as an optional second argument. If omitted,
 * default to the stringification of the tested expression.
 */
#define BUILD_BUG_ON_ZERO(e, ...) \
    __BUILD_BUG_ON_ZERO_MSG(e, ##__VA_ARGS__, #e " is true")
 
/* Force a compilation error if a constant expression is not a power of 2 */
#define __BUILD_BUG_ON_NOT_POWER_OF_2(n)    \
    BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
#define BUILD_BUG_ON_NOT_POWER_OF_2(n)          \
    BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
 
/*
 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
 * expression but avoids the generation of any code, even if that expression
 * has side-effects.
 */
#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
 
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
 
#define BUILD_BUG_ON(condition) \
    BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
 
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
 
#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
 
 
/*
 * Compile time check that field has an expected offset
 */
#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)  \
    BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),    \
        "Offset of " #field " in " #type " has changed.")
 
 
#endif  /* _LINUX_BUILD_BUG_H */