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Date: Sat, 10 Sep 2005 14:04:40 +0200
From: "Andi Kleen" <ak@suse.de>
To: akpm@osdl.org
Cc: linux-kernel@vger.kernel.org, jbeulich@novell.com
Subject: [1/2] Make BUILD_BUG_ON fail at compile time.
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Make BUILD_BUG_ON fail at compile time.

Force a compiler error instead of a link error, because they
are easier to track down. Idea stolen from code by Jan Beulich.

Cc: jbeulich@novell.com

Index: linux/include/linux/kernel.h
===================================================================
--- linux.orig/include/linux/kernel.h
+++ linux/include/linux/kernel.h
@@ -307,8 +307,8 @@ struct sysinfo {
 	char _f[20-2*sizeof(long)-sizeof(int)];	/* Padding: libc5 uses this.. */
 };
 
-extern void BUILD_BUG(void);
-#define BUILD_BUG_ON(condition) do { if (condition) BUILD_BUG(); } while(0)
+/* Force a compilation error if condition is false */
+#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
 
 #ifdef CONFIG_SYSCTL
 extern int randomize_va_space;