utils.h: update ARRAY_SIZEHEADmaster

Update ARRAY_SIZE macro so that we can use it in more places, including
where comma expressions aren't allowed.

1 files changed, 22 insertions, 6 deletions

diff --git a/utils.h b/utils.h
index cb7d795..66430ab 100644
--- a/utils.h
+++ b/utils.h
@@ -15,6 +15,17 @@
 #define static_assert(exp, msg) _Static_assert(exp, msg)
 #endif
 
+/**
+ * BUILD_BUG_ON_ZERO - throws compilation error if true, expressions returns 0.
+ * @cond:	condition
+ *
+ * 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).
+ */
+#define BUILD_BUG_ON_ZERO(cond) ((int)(sizeof(struct { int : (-!!(cond)); })))
+
 #define same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 
 #define container_of(ptr, T, member)                      \
@@ -25,11 +36,16 @@
 		(T *)((void *)(ptr)-offsetof(T, member));         \
 	})
 
-#define ARRAY_SIZE(arr)                             \
-	({                                              \
-		static_assert(!same_type((arr), &(arr)[0]), \
-					  "variable is not an array");  \
-		sizeof(arr) / sizeof(*arr);                 \
-	})
+/**
+ * __ASSERT_IS_ARRAY - throw a compilation error if @arr is not an array.
+ * @arr:	variable to check.
+ */
+#define __ASSERT_IS_ARRAY(arr) BUILD_BUG_ON_ZERO(same_type((arr), &(arr)[0]))
+
+/**
+ * ARRAY_SIZE - return the number of elements in @arr.
+ * @arr:	array of any type.
+ */
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(*arr) + __ASSERT_IS_ARRAY(arr))
 
 #endif