1 files changed, 26 insertions, 21 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index b1cf40de847e..7f4818673c41 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,
@@ -12,11 +13,12 @@ enum bug_trap_type {
 struct pt_regs;
 
 #ifdef __CHECKER__
-#define BUILD_BUG_ON_NOT_POWER_OF_2(n)
+#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
 #define BUILD_BUG_ON_ZERO(e) (0)
 #define BUILD_BUG_ON_NULL(e) ((void*)0)
 #define BUILD_BUG_ON_INVALID(e) (0)
-#define BUILD_BUG_ON(condition)
+#define BUILD_BUG_ON_MSG(cond, msg) (0)
+#define BUILD_BUG_ON(condition) (0)
 #define BUILD_BUG() (0)
 #else /* __CHECKER__ */
 
@@ -39,29 +41,37 @@ struct pt_regs;
 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
 
 /**
+ * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
+ *                    error message.
+ * @condition: the condition which the compiler should know is false.
+ *
+ * See BUILD_BUG_ON for description.
+ */
+#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
+
+/**
  * BUILD_BUG_ON - break compile if a condition is true.
  * @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 {                                                    \
-                ((void)sizeof(char[1 - 2*!!(condition)]));      \
-                if (condition) __build_bug_on_failed = 1;       \
-        } while(0)
+#define BUILD_BUG_ON(condition) \
+        BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
 #endif
 
 /**
@@ -71,12 +81,7 @@ extern int __build_bug_on_failed;
  * build time, you should use BUILD_BUG to detect if it is
  * unexpectedly used.
  */
-#define BUILD_BUG()                                             \
-        do {                                                    \
-                extern void __build_bug_failed(void)            \
-                        __linktime_error("BUILD_BUG failed");   \
-                __build_bug_failed();                           \
-        } while (0)
+#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
 
 #endif  /* __CHECKER__ */