1 files changed, 19 insertions, 13 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index 89fb91d0c929..73af37ca472c 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