1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_BUILD_BUG_H
3#define _LINUX_BUILD_BUG_H
4
5#include <linux/compiler.h>
6
7/*
8 * Force a compilation error if condition is true, but also produce a
9 * result (of value 0 and type int), so the expression can be used
10 * e.g. in a structure initializer (or where-ever else comma expressions
11 * aren't permitted).
12 *
13 * Take an error message as an optional second argument. If omitted,
14 * default to the stringification of the tested expression.
15 */
16#define BUILD_BUG_ON_ZERO(e, ...) \
17 __BUILD_BUG_ON_ZERO_MSG(e, ##__VA_ARGS__, #e " is true")
18
19/* Force a compilation error if a constant expression is not a power of 2 */
20#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \
21 BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
22#define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
23 BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
24
25/*
26 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
27 * expression but avoids the generation of any code, even if that expression
28 * has side-effects.
29 */
30#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
31
32/**
33 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
34 * error message.
35 * @condition: the condition which the compiler should know is false.
36 *
37 * See BUILD_BUG_ON for description.
38 */
39#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
40
41/**
42 * BUILD_BUG_ON - break compile if a condition is true.
43 * @condition: the condition which the compiler should know is false.
44 *
45 * If you have some code which relies on certain constants being equal, or
46 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
47 * detect if someone changes it.
48 */
49#define BUILD_BUG_ON(condition) \
50 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
51
52/**
53 * BUILD_BUG - break compile if used.
54 *
55 * If you have some code that you expect the compiler to eliminate at
56 * build time, you should use BUILD_BUG to detect if it is
57 * unexpectedly used.
58 */
59#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
60
61/**
62 * static_assert - check integer constant expression at build time
63 *
64 * static_assert() is a wrapper for the C11 _Static_assert, with a
65 * little macro magic to make the message optional (defaulting to the
66 * stringification of the tested expression).
67 *
68 * Contrary to BUILD_BUG_ON(), static_assert() can be used at global
69 * scope, but requires the expression to be an integer constant
70 * expression (i.e., it is not enough that __builtin_constant_p() is
71 * true for expr).
72 *
73 * Also note that BUILD_BUG_ON() fails the build if the condition is
74 * true, while static_assert() fails the build if the expression is
75 * false.
76 */
77#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
78#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
79
80
81/*
82 * Compile time check that field has an expected offset
83 */
84#define ASSERT_STRUCT_OFFSET(type, field, expected_offset) \
85 BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset), \
86 "Offset of " #field " in " #type " has changed.")
87
88
89#endif /* _LINUX_BUILD_BUG_H */
90