blob: b7d22d60008a9004e1f5669aae812cdddb7dddec [file] [log] [blame]
Masahiro Yamada059a4802017-09-16 14:10:44 +09001#ifndef _LINUX_BUILD_BUG_H
2#define _LINUX_BUILD_BUG_H
3
4#include <linux/compiler.h>
5
6#ifdef __CHECKER__
7#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
8#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
9#define BUILD_BUG_ON_ZERO(e) (0)
10#define BUILD_BUG_ON_NULL(e) ((void *)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#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); }))
31
32/*
33 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
34 * expression but avoids the generation of any code, even if that expression
35 * has side-effects.
36 */
37#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
38
39/**
40 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
41 * error message.
42 * @condition: the condition which the compiler should know is false.
43 *
44 * See BUILD_BUG_ON for description.
45 */
46#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
47
48/**
49 * BUILD_BUG_ON - break compile if a condition is true.
50 * @condition: the condition which the compiler should know is false.
51 *
52 * If you have some code which relies on certain constants being equal, or
53 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
54 * detect if someone changes it.
55 *
56 * The implementation uses gcc's reluctance to create a negative array, but gcc
57 * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
58 * inline functions). Luckily, in 4.3 they added the "error" function
59 * attribute just for this type of case. Thus, we use a negative sized array
60 * (should always create an error on gcc versions older than 4.4) and then call
61 * an undefined function with the error attribute (should always create an
62 * error on gcc 4.3 and later). If for some reason, neither creates a
63 * compile-time error, we'll still have a link-time error, which is harder to
64 * track down.
65 */
66#ifndef __OPTIMIZE__
67#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
68#else
69#define BUILD_BUG_ON(condition) \
70 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
71#endif
72
73/**
74 * BUILD_BUG - break compile if used.
75 *
76 * If you have some code that you expect the compiler to eliminate at
77 * build time, you should use BUILD_BUG to detect if it is
78 * unexpectedly used.
79 */
80#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
81
82#endif /* __CHECKER__ */
83
84#endif /* _LINUX_BUILD_BUG_H */