4 files changed, 32 insertions, 9 deletions
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index a3b148a9187..0b84c61607e 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -249,7 +249,7 @@ static inline enum zone_type gfp_zone(gfp_t flags)
 					 ((1 << ZONES_SHIFT) - 1);
 
 	if (__builtin_constant_p(bit))
-		MAYBE_BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
+		BUILD_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
 	else {
 #ifdef CONFIG_DEBUG_VM
 		BUG_ON((GFP_ZONE_BAD >> bit) & 1);
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d07d8057e44..e2f4d6af212 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -575,12 +575,6 @@ struct sysinfo {
 	char _f[20-2*sizeof(long)-sizeof(int)];	/* Padding: libc5 uses this.. */
 };
 
-/* Force a compilation error if condition is true */
-#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
-
-/* Force a compilation error if condition is constant and true */
-#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))
-
 /* Force a compilation error if a constant expression is not a power of 2 */
 #define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\
 	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
@@ -592,6 +586,32 @@ struct sysinfo {
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
 #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
 
+/**
+ * BUILD_BUG_ON - break compile if a condition is true.
+ * @cond: 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
+ * 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.
+ */
+#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)
+#endif
+
 /* Trap pasters of __FUNCTION__ at compile-time */
 #define __FUNCTION__ (__func__)
 
diff --git a/include/linux/kmemcheck.h b/include/linux/kmemcheck.h
index 08d7dc4ddf4..39f8453239f 100644
--- a/include/linux/kmemcheck.h
+++ b/include/linux/kmemcheck.h
@@ -76,7 +76,7 @@ bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size);
 									\
 		_n = (long) &((ptr)->name##_end)			\
 			- (long) &((ptr)->name##_begin);		\
-		MAYBE_BUILD_BUG_ON(_n < 0);				\
+		BUILD_BUG_ON(_n < 0);					\
 									\
 		kmemcheck_mark_initialized(&((ptr)->name##_begin), _n);	\
 	} while (0)
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 0093dd7c1d6..800617b4ddd 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -109,7 +109,10 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
 				      unsigned int fbit)
 {
 	/* Did you forget to fix assumptions on max features? */
-	MAYBE_BUILD_BUG_ON(fbit >= 32);
+	if (__builtin_constant_p(fbit))
+		BUILD_BUG_ON(fbit >= 32);
+	else
+		BUG_ON(fbit >= 32);
 
 	if (fbit < VIRTIO_TRANSPORT_F_START)
 		virtio_check_driver_offered_feature(vdev, fbit);