[PATCH] include: <linux/build_bug.h>: define static_assert

[Ahmad Fatoum]

BUILD_BUG_ON can't be used outside of a function, unlike static_assert.
Import the macro definition.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 include/linux/build_bug.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index 43d1fd50d433..40cd504f63ba 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -80,4 +80,23 @@
 
 #endif	/* __CHECKER__ */
 
+/**
+ * static_assert - check integer constant expression at build time
+ *
+ * static_assert() is a wrapper for the C11 _Static_assert, with a
+ * little macro magic to make the message optional (defaulting to the
+ * stringification of the tested expression).
+ *
+ * Contrary to BUILD_BUG_ON(), static_assert() can be used at global
+ * scope, but requires the expression to be an integer constant
+ * expression (i.e., it is not enough that __builtin_constant_p() is
+ * true for expr).
+ *
+ * Also note that BUILD_BUG_ON() fails the build if the condition is
+ * true, while static_assert() fails the build if the expression is
+ * false.
+ */
+#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
+#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
+
 #endif	/* _LINUX_BUILD_BUG_H */
-- 
2.30.2