From: Michal Schmidt <mschmidt@redhat.com>
Date: Mon, 14 Sep 2015 18:32:17 +0000 (+0200)
Subject: basic: make sure argument of ELEMENTSOF is an array
X-Git-Tag: v227.2^2~36
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=9f8b2124694ac1637198d9a336e2c97e79fd8c23

basic: make sure argument of ELEMENTSOF is an array

Using ELEMENTSOF on a pointer will result in a compilation error.
---

diff --git a/src/basic/macro.h b/src/basic/macro.h
index b9a24f639..e93d7f155 100644
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -124,8 +124,11 @@ static inline unsigned long ALIGN_POWER2(unsigned long u) {
         return 1UL << (sizeof(u) * 8 - __builtin_clzl(u - 1UL));
 }
 
-#define ELEMENTSOF(x) (sizeof(x)/sizeof((x)[0]))
-
+#define ELEMENTSOF(x)                                                    \
+        __extension__ (__builtin_choose_expr(                            \
+                !__builtin_types_compatible_p(typeof(x), typeof(&*(x))), \
+                sizeof(x)/sizeof((x)[0]),                                \
+                (void)0))
 /*
  * container_of - cast a member of a structure out to the containing structure
  * @ptr: the pointer to the member.