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_ZERO(e) (0) 9 #else /* __CHECKER__ */ 10 /* 11 * Force a compilation error if condition is true, but also produce a 12 * result (of value 0 and type int), so the expression can be used 13 * e.g. in a structure initializer (or where-ever else comma expressions 14 * aren't permitted). 15 */ 16 #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) 17 #endif /* __CHECKER__ */ 18 19 /* Force a compilation error if a constant expression is not a power of 2 */ 20 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \ 21 BUILD_BUG_ON(((n) & ((n) - 1)) != 0) 22 #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ 23 BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) 24 25 /* 26 * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the 27 * expression but avoids the generation of any code, even if that expression 28 * has side-effects. 29 */ 30 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) 31 32 /** 33 * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied 34 * error message. 35 * @condition: the condition which the compiler should know is false. 36 * 37 * See BUILD_BUG_ON for description. 38 */ 39 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) 40 41 /** 42 * BUILD_BUG_ON - break compile if a condition is true. 43 * @condition: the condition which the compiler should know is false. 44 * 45 * If you have some code which relies on certain constants being equal, or 46 * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to 47 * detect if someone changes it. 48 */ 49 #define BUILD_BUG_ON(condition) \ 50 BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) 51 52 /** 53 * BUILD_BUG - break compile if used. 54 * 55 * If you have some code that you expect the compiler to eliminate at 56 * build time, you should use BUILD_BUG to detect if it is 57 * unexpectedly used. 58 */ 59 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") 60 61 /** 62 * static_assert - check integer constant expression at build time 63 * 64 * static_assert() is a wrapper for the C11 _Static_assert, with a 65 * little macro magic to make the message optional (defaulting to the 66 * stringification of the tested expression). 67 * 68 * Contrary to BUILD_BUG_ON(), static_assert() can be used at global 69 * scope, but requires the expression to be an integer constant 70 * expression (i.e., it is not enough that __builtin_constant_p() is 71 * true for expr). 72 * 73 * Also note that BUILD_BUG_ON() fails the build if the condition is 74 * true, while static_assert() fails the build if the expression is 75 * false. 76 */ 77 #ifndef static_assert 78 #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr) 79 #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) 80 #endif // static_assert 81 82 83 /* 84 * Compile time check that field has an expected offset 85 */ 86 #define ASSERT_STRUCT_OFFSET(type, field, expected_offset) \ 87 BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset), \ 88 "Offset of " #field " in " #type " has changed.") 89 90 91 #endif /* _LINUX_BUILD_BUG_H */ 92