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_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__ */ 17 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)) 23 24 /* 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 28 * aren't permitted). 29 */ 30 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); })) 31 #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); })) 32 33 /* 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 36 * has side-effects. 37 */ 38 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) 39 40 /** 41 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied 42 * error message. 43 * @condition: the condition which the compiler should know is false. 44 * 45 * See BUILD_BUG_ON for description. 46 */ 47 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) 48 49 /** 50 * BUILD_BUG_ON - break compile if a condition is true. 51 * @condition: the condition which the compiler should know is false. 52 * 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. 56 * 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 65 * track down. 66 */ 67 #ifndef __OPTIMIZE__ 68 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) 69 #else 70 #define BUILD_BUG_ON(condition) \ 71 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) 72 #endif 73 74 /** 75 * BUILD_BUG - break compile if used. 76 * 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 79 * unexpectedly used. 80 */ 81 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") 82 83 #endif /* __CHECKER__ */ 84 85 #endif /* _LINUX_BUILD_BUG_H */ 86