@@ -4,17 +4,17 @@
#include <linux/compiler.h>
-#ifdef __CHECKER__
-#define BUILD_BUG_ON_ZERO(e) (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 a message as an optional second argument. If omitted, default to
+ * the stringification of the tested expression.
*/
-#define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
-#endif /* __CHECKER__ */
+#define BUILD_BUG_ON_ZERO(e, ...) __BUILD_BUG_ON_ZERO(e, ##__VA_ARGS__, #e)
+#define __BUILD_BUG_ON_ZERO(e, msg) __BUILD_BUG_ON_ZERO_MSG(e, msg " 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) \
__BUILD_BUG_ON_ZERO_MSG(), as introduced in [1], makes it possible to do a static assert while still returning a zero value. The direct benefit is to provide a meaningful error message instead of the cryptic negative bitfield size error message currently returned by BUILD_BUG_ON_ZERO(): ./include/linux/build_bug.h:16:51: error: negative width in bit-field '<anonymous>' 16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); }))) | ^ Get rid of BUILD_BUG_ON_ZERO() bitfield size hack. Instead rely on __BUILD_BUG_ON_ZERO_MSG() (which in turn relies on C11's _Static_assert()). Use some macro magic, similarly to static_assert(), to either use an error message provided by the user or, when omitted, to produce a default error message by stringifying the tested expression. With this, for example: BUILD_BUG_ON_ZERO_MSG(1 > 0) would now throw: ./include/linux/compiler.h:245:62: error: static assertion failed: "1 > 0 is true" 245 | #define __BUILD_BUG_ON_ZERO_MSG(e, msg) ((int)sizeof(struct {_Static_assert(!(e), msg);})) | ^~~~~~~~~~~~~~ Finally, __BUILD_BUG_ON_ZERO_MSG() is already guarded by an: #ifdef __CHECKER__ So no need any more for that guard clause for BUILD_BUG_ON_ZERO(). Remove it. [1] commit d7a516c6eeae ("compiler.h: Fix undefined BUILD_BUG_ON_ZERO()") Link: https://git.kernel.org/torvalds/c/d7a516c6eeae Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> --- include/linux/build_bug.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)