compat: backport BUILD_BUG_ON from recent kernel

This version of BUILD_BUG_ON does not have the following error on an
old kernel version (2.6.32 - 2.6.37):

drivers/net/wireless/iwlwifi/mvm/quota.c:145:24: error: bit-field
'<anonymous>' width not an integer constant

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

diff --git a/include/linux/compat-2.6.38.h b/include/linux/compat-2.6.38.h
index 0aa5d9b7996d983eff742236777eb25228792856..8dfeed63773bd892f93734b2d25d30019c424dec 100644 (file)
--- a/include/linux/compat-2.6.38.h
+++ b/include/linux/compat-2.6.38.h
@@ -139,6 +139,41 @@ static inline int is_unicast_ether_addr(const u8 *addr)
        return !is_multicast_ether_addr(addr);
 }
 
+/* Backport of:
+ *
+ * commit 7ef88ad561457c0346355dfd1f53e503ddfde719
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ * Date:   Mon Jan 24 14:45:10 2011 -0600
+ *
+ *     BUILD_BUG_ON: make it handle more cases
+ */
+#undef BUILD_BUG_ON
+/**
+ * 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
+ * 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
+
 #endif /* (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,38)) */
 
 #endif /* LINUX_26_38_COMPAT_H */