1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_BUILD_BUG_H
3 #define _LINUX_BUILD_BUG_H
5 #include <linux/compiler.h>
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_NULL(e) ((void *)0)
12 #define BUILD_BUG_ON_INVALID(e) (0)
13 #define BUILD_BUG_ON_MSG(cond, msg) (0)
14 #define BUILD_BUG_ON(condition) (0)
15 #define BUILD_BUG() (0)
16 #else /* __CHECKER__ */
18 /* Force a compilation error if a constant expression is not a power of 2 */
19 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \
20 BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
21 #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
22 BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
25 * Force a compilation error if condition is true, but also produce a
26 * result (of value 0 and type size_t), so the expression can be used
27 * e.g. in a structure initializer (or where-ever else comma expressions
30 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
31 #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); }))
34 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
35 * expression but avoids the generation of any code, even if that expression
38 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
41 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
43 * @condition: the condition which the compiler should know is false.
45 * See BUILD_BUG_ON for description.
47 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
50 * BUILD_BUG_ON - break compile if a condition is true.
51 * @condition: the condition which the compiler should know is false.
53 * If you have some code which relies on certain constants being equal, or
54 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
55 * detect if someone changes it.
57 * The implementation uses gcc's reluctance to create a negative array, but gcc
58 * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
59 * inline functions). Luckily, in 4.3 they added the "error" function
60 * attribute just for this type of case. Thus, we use a negative sized array
61 * (should always create an error on gcc versions older than 4.4) and then call
62 * an undefined function with the error attribute (should always create an
63 * error on gcc 4.3 and later). If for some reason, neither creates a
64 * compile-time error, we'll still have a link-time error, which is harder to
68 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
70 #define BUILD_BUG_ON(condition) \
71 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
75 * BUILD_BUG - break compile if used.
77 * If you have some code that you expect the compiler to eliminate at
78 * build time, you should use BUILD_BUG to detect if it is
81 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
83 #endif /* __CHECKER__ */
85 #endif /* _LINUX_BUILD_BUG_H */