bug.h: move BUILD_BUG_* defines to include/linux/bug.h

BUILD_BUG_* macros have been defined in several headers.  It would
be nice to collect them in include/linux/bug.h like Linux.

This commit is cherry-picking useful macros from include/linux/bug.h
of Linux 4.4.

I did not import BUILD_BUG_ON_MSG() because it would not work if it
is used with include/common.h in U-Boot.  I'd like to postpone it
until the root cause (the "error()" macro in include/common.h causes
the name conflict with "__attribute__((error()))") is fixed.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
new file mode 100644
index 0000000000..920e3796c3
--- /dev/null
+++ b/include/linux/bug.h
@@ -0,0 +1,55 @@
+#ifndef _LINUX_BUG_H
+#define _LINUX_BUG_H
+
+#include <linux/compiler.h>
+
+#ifdef __CHECKER__
+#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
+#define BUILD_BUG_ON_ZERO(e) (0)
+#define BUILD_BUG_ON_NULL(e) ((void*)0)
+#define BUILD_BUG_ON_INVALID(e) (0)
+#define BUILD_BUG_ON(condition) (0)
+#define BUILD_BUG() (0)
+#else /* __CHECKER__ */
+
+/* Force a compilation error if a constant expression is not a power of 2 */
+#define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\
+	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
+
+/* Force a compilation error if condition is true, but also produce a
+   result (of value 0 and type size_t), so the expression can be used
+   e.g. in a structure initializer (or where-ever else comma expressions
+   aren't permitted). */
+#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
+#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
+
+/*
+ * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
+ * expression but avoids the generation of any code, even if that expression
+ * has side-effects.
+ */
+#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
+
+/**
+ * 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
+ * some 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 (e.g. not arguments to
+ * inline functions).  Luckily, in 4.3 they added the "error" function
+ * attribute just for this type of case.  Thus, we use a negative sized array
+ * (should always create an error on gcc versions older than 4.4) and then call
+ * an undefined function with the error attribute (should always create an
+ * error on gcc 4.3 and later).  If for some reason, neither creates a
+ * compile-time error, we'll still have a link-time error, which is harder to
+ * track down.
+ */
+#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
+
+#endif	/* __CHECKER__ */
+
+#endif	/* _LINUX_BUG_H */