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#ifdef __CHECKER__
8#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
9#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
10#define BUILD_BUG_ON_ZERO(e) (0)
11#define BUILD_BUG_ON_INVALID(e) (0)
12#define BUILD_BUG_ON_MSG(cond, msg) (0)
13#define BUILD_BUG_ON(condition) (0)
14#define BUILD_BUG() (0)
15#else /* __CHECKER__ */
16
17/* Force a compilation error if a constant expression is not a power of 2 */
18#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \
19 BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
20#define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
21 BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
22
23/*
24 * Force a compilation error if condition is true, but also produce a
25 * result (of value 0 and type size_t), so the expression can be used
26 * e.g. in a structure initializer (or where-ever else comma expressions
27 * aren't permitted).
28 */
29#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
30
31/*
32 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
33 * expression but avoids the generation of any code, even if that expression
34 * has side-effects.
35 */
36#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
37
38/**
39 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
40 * error message.
41 * @condition: the condition which the compiler should know is false.
42 *
43 * See BUILD_BUG_ON for description.
44 */
45#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
46
47/**
48 * BUILD_BUG_ON - break compile if a condition is true.
49 * @condition: the condition which the compiler should know is false.
50 *
51 * If you have some code which relies on certain constants being equal, or
52 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
53 * detect if someone changes it.
54 *
55 * The implementation uses gcc's reluctance to create a negative array, but gcc
56 * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
57 * inline functions). Luckily, in 4.3 they added the "error" function
58 * attribute just for this type of case. Thus, we use a negative sized array
59 * (should always create an error on gcc versions older than 4.4) and then call
60 * an undefined function with the error attribute (should always create an
61 * error on gcc 4.3 and later). If for some reason, neither creates a
62 * compile-time error, we'll still have a link-time error, which is harder to
63 * track down.
64 */
65#ifndef __OPTIMIZE__
66#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
67#else
68#define BUILD_BUG_ON(condition) \
69 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
70#endif
71
72/**
73 * BUILD_BUG - break compile if used.
74 *
75 * If you have some code that you expect the compiler to eliminate at
76 * build time, you should use BUILD_BUG to detect if it is
77 * unexpectedly used.
78 */
79#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
80
81#endif /* __CHECKER__ */
82
83#endif /* _LINUX_BUILD_BUG_H */
84