1 files changed, 39 insertions, 34 deletions

diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index b7d22d60008a..2cfbb4c65c78 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -1,18 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_BUILD_BUG_H
 #define _LINUX_BUILD_BUG_H
 
 #include <linux/compiler.h>
 
-#ifdef __CHECKER__
-#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
-#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_MSG(cond, msg) (0)
-#define BUILD_BUG_ON(condition) (0)
-#define BUILD_BUG() (0)
-#else /* __CHECKER__ */
+/*
+ * Force a compilation error if condition is true, but also produce a
+ * result (of value 0 and type int), so the expression can be used
+ * e.g. in a structure initializer (or where-ever else comma expressions
+ * aren't permitted).
+ *
+ * Take an error message as an optional second argument. If omitted,
+ * default to the stringification of the tested expression.
+ */
+#define BUILD_BUG_ON_ZERO(e, ...) \
+	__BUILD_BUG_ON_ZERO_MSG(e, ##__VA_ARGS__, #e " is true")
 
 /* Force a compilation error if a constant expression is not a power of 2 */
 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n)	\
@@ -21,15 +23,6 @@
 	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.
@@ -52,23 +45,9 @@
  * 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.
  */
-#ifndef __OPTIMIZE__
-#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
-#else
 #define BUILD_BUG_ON(condition) \
 	BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
-#endif
 
 /**
  * BUILD_BUG - break compile if used.
@@ -79,6 +58,32 @@
  */
 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
 
-#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)
+
+
+/*
+ * Compile time check that field has an expected offset
+ */
+#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)	\
+	BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),	\
+		"Offset of " #field " in " #type " has changed.")
+
 
 #endif	/* _LINUX_BUILD_BUG_H */