[PATCH 03/11] backports: build_bug.h: Add static_assert()

[Hauke Mehrtens <hauke@hauke-m.de>]

Add static_assert() from upstream commit 6bab69c65013 ("build_bug.h: add
wrapper for _Static_assert") which is used by rtw88.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
---
 backport/backport-include/linux/build_bug.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/backport/backport-include/linux/build_bug.h b/backport/backport-include/linux/build_bug.h
index 13ee5d6a..c883e525 100644
--- a/backport/backport-include/linux/build_bug.h
+++ b/backport/backport-include/linux/build_bug.h
@@ -7,4 +7,25 @@
 #include <linux/bug.h>
 #endif /* LINUX_VERSION_IS_GEQ(4,13,0) */
 
+#ifndef static_assert
+/**
+ * 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
+
 #endif /* __BP_BUILD_BUG_H */
-- 
2.20.1

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