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 #ifdef __GENKSYMS__
84 /* genksyms gets confused by _Static_assert */
85 #define _Static_assert(expr, ...)
86 #endif
87 
88 #endif	/* _LINUX_BUILD_BUG_H */
89