[Xen-changelog] [xen-3.2-testing] Fix BUILD_BUG_ON()

["Xen patchbot-3.2-testing" <patchbot-3.2-testing@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1229002605 0
# Node ID 6b4982c3f8588ff80bfb5fa39ffa65457c1ef109
# Parent  51f26d6ebc6c0f581208701e8da629c0a112b21d
Fix BUILD_BUG_ON()

As was noticed on the Linux side, using an array here isn't
appropriate
if the condition is not a compile time constant - gcc allows such
arrays, and hence the intended effect of producing a compiler error is
not achieved in that case. Bit field widths do not know similar
language extensions, and hence always produce a compiler error.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
xen-unstable changeset:   18899:1419a73316e1d75d3e5d7c1530ac6ae7e7bc7fb4
xen-unstable date:        Thu Dec 11 11:19:01 2008 +0000
---
 xen/include/xen/lib.h |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -r 51f26d6ebc6c -r 6b4982c3f858 xen/include/xen/lib.h
--- a/xen/include/xen/lib.h     Wed Dec 10 14:35:38 2008 +0000
+++ b/xen/include/xen/lib.h     Thu Dec 11 13:36:45 2008 +0000
@@ -16,7 +16,7 @@ void __warn(char *file, int line);
 #define WARN_ON(p) do { if (p) WARN(); } while (0)
 
 /* Force a compilation error if condition is true */
-#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2 * !!(condition)]))
+#define BUILD_BUG_ON(condition) ((void)sizeof(struct { int:-!!(condition); }))
 
 #ifndef assert_failed
 #define assert_failed(p)                                        \

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