1*4882a593Smuzhiyun #ifndef _LINUX_BUILD_BUG_H 2*4882a593Smuzhiyun #define _LINUX_BUILD_BUG_H 3*4882a593Smuzhiyun 4*4882a593Smuzhiyun #include <linux/compiler.h> 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun #ifdef __CHECKER__ 7*4882a593Smuzhiyun #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0) 8*4882a593Smuzhiyun #define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0) 9*4882a593Smuzhiyun #define BUILD_BUG_ON_ZERO(e) (0) 10*4882a593Smuzhiyun #define BUILD_BUG_ON_NULL(e) ((void *)0) 11*4882a593Smuzhiyun #define BUILD_BUG_ON_INVALID(e) (0) 12*4882a593Smuzhiyun #define BUILD_BUG_ON_MSG(cond, msg) (0) 13*4882a593Smuzhiyun #define BUILD_BUG_ON(condition) (0) 14*4882a593Smuzhiyun #define BUILD_BUG() (0) 15*4882a593Smuzhiyun #else /* __CHECKER__ */ 16*4882a593Smuzhiyun 17*4882a593Smuzhiyun /* Force a compilation error if a constant expression is not a power of 2 */ 18*4882a593Smuzhiyun #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \ 19*4882a593Smuzhiyun BUILD_BUG_ON(((n) & ((n) - 1)) != 0) 20*4882a593Smuzhiyun #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ 21*4882a593Smuzhiyun BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) 22*4882a593Smuzhiyun 23*4882a593Smuzhiyun /* 24*4882a593Smuzhiyun * Force a compilation error if condition is true, but also produce a 25*4882a593Smuzhiyun * result (of value 0 and type size_t), so the expression can be used 26*4882a593Smuzhiyun * e.g. in a structure initializer (or where-ever else comma expressions 27*4882a593Smuzhiyun * aren't permitted). 28*4882a593Smuzhiyun */ 29*4882a593Smuzhiyun #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); })) 30*4882a593Smuzhiyun #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); })) 31*4882a593Smuzhiyun 32*4882a593Smuzhiyun /* 33*4882a593Smuzhiyun * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the 34*4882a593Smuzhiyun * expression but avoids the generation of any code, even if that expression 35*4882a593Smuzhiyun * has side-effects. 36*4882a593Smuzhiyun */ 37*4882a593Smuzhiyun #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun /** 40*4882a593Smuzhiyun * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied 41*4882a593Smuzhiyun * error message. 42*4882a593Smuzhiyun * @condition: the condition which the compiler should know is false. 43*4882a593Smuzhiyun * 44*4882a593Smuzhiyun * See BUILD_BUG_ON for description. 45*4882a593Smuzhiyun */ 46*4882a593Smuzhiyun #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) 47*4882a593Smuzhiyun 48*4882a593Smuzhiyun /** 49*4882a593Smuzhiyun * BUILD_BUG_ON - break compile if a condition is true. 50*4882a593Smuzhiyun * @condition: the condition which the compiler should know is false. 51*4882a593Smuzhiyun * 52*4882a593Smuzhiyun * If you have some code which relies on certain constants being equal, or 53*4882a593Smuzhiyun * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to 54*4882a593Smuzhiyun * detect if someone changes it. 55*4882a593Smuzhiyun * 56*4882a593Smuzhiyun * The implementation uses gcc's reluctance to create a negative array, but gcc 57*4882a593Smuzhiyun * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to 58*4882a593Smuzhiyun * inline functions). Luckily, in 4.3 they added the "error" function 59*4882a593Smuzhiyun * attribute just for this type of case. Thus, we use a negative sized array 60*4882a593Smuzhiyun * (should always create an error on gcc versions older than 4.4) and then call 61*4882a593Smuzhiyun * an undefined function with the error attribute (should always create an 62*4882a593Smuzhiyun * error on gcc 4.3 and later). If for some reason, neither creates a 63*4882a593Smuzhiyun * compile-time error, we'll still have a link-time error, which is harder to 64*4882a593Smuzhiyun * track down. 65*4882a593Smuzhiyun */ 66*4882a593Smuzhiyun #ifndef __OPTIMIZE__ 67*4882a593Smuzhiyun #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) 68*4882a593Smuzhiyun #else 69*4882a593Smuzhiyun #define BUILD_BUG_ON(condition) \ 70*4882a593Smuzhiyun BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) 71*4882a593Smuzhiyun #endif 72*4882a593Smuzhiyun 73*4882a593Smuzhiyun /** 74*4882a593Smuzhiyun * BUILD_BUG - break compile if used. 75*4882a593Smuzhiyun * 76*4882a593Smuzhiyun * If you have some code that you expect the compiler to eliminate at 77*4882a593Smuzhiyun * build time, you should use BUILD_BUG to detect if it is 78*4882a593Smuzhiyun * unexpectedly used. 79*4882a593Smuzhiyun */ 80*4882a593Smuzhiyun #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") 81*4882a593Smuzhiyun 82*4882a593Smuzhiyun #endif /* __CHECKER__ */ 83*4882a593Smuzhiyun 84*4882a593Smuzhiyun #endif /* _LINUX_BUILD_BUG_H */ 85