diff options
| -rw-r--r-- | include/linux/bug.h | 32 |
1 files changed, 19 insertions, 13 deletions
diff --git a/include/linux/bug.h b/include/linux/bug.h index 89fb91d..73af37ca 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -2,6 +2,7 @@ #define _LINUX_BUG_H #include <asm/bug.h> +#include <linux/compiler.h> enum bug_trap_type { BUG_TRAP_TYPE_NONE = 0, @@ -43,25 +44,30 @@ struct pt_regs; * @condition: the condition which the compiler should know is false. * * If you have some code which relies on certain constants being equal, or - * other compile-time-evaluated condition, you should use BUILD_BUG_ON to + * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to * detect if someone changes it. * - * The implementation uses gcc's reluctance to create a negative array, but - * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments - * to inline functions). So as a fallback we use the optimizer; if it can't - * prove the condition is false, it will cause a link error on the undefined - * "__build_bug_on_failed". This error message can be harder to track down - * though, hence the two different methods. + * The implementation uses gcc's reluctance to create a negative array, but gcc + * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to + * inline functions). Luckily, in 4.3 they added the "error" function + * attribute just for this type of case. Thus, we use a negative sized array + * (should always create an error on gcc versions older than 4.4) and then call + * an undefined function with the error attribute (should always create an + * error on gcc 4.3 and later). If for some reason, neither creates a + * compile-time error, we'll still have a link-time error, which is harder to + * track down. */ #ifndef __OPTIMIZE__ #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) #else -extern int __build_bug_on_failed; -#define BUILD_BUG_ON(condition) \ - do { \ - bool __cond = !!(condition); \ - ((void)sizeof(char[1 - 2 * __cond])); \ - if (__cond) __build_bug_on_failed = 1; \ +#define BUILD_BUG_ON(condition) \ + do { \ + bool __cond = !!(condition); \ + extern void __build_bug_on_failed(void) \ + __compiletime_error("BUILD_BUG_ON failed"); \ + if (__cond) \ + __build_bug_on_failed(); \ + ((void)sizeof(char[1 - 2 * __cond])); \ } while (0) #endif |
