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