From: Keir Fraser <keir.fraser@citrix.com>
Date: Wed, 20 May 2009 14:29:25 +0000 (+0100)
Subject: Introduce __must_be_array
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~13897
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=eaa024d29620e08f75090ffc90343c09176c2b12;p=xen.git

Introduce __must_be_array

Cloning the similar construct from Linux, allowing to detect improper
uses of ARRAY_SIZE() at build time.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
---

diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index 95295dce76..909dec0bdf 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -35,6 +35,10 @@
 #define offsetof(a,b) ((unsigned long)&(((a *)0)->b))
 #endif
 
+/* &a[0] degrades to a pointer: a different type from an array */
+#define __must_be_array(a) \
+  BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
+
 #ifdef GCC_HAS_VISIBILITY_ATTRIBUTE
 /* Results in more efficient PIC code (no indirections through GOT or PLT). */
 #pragma GCC visibility push(hidden)
diff --git a/xen/include/xen/config.h b/xen/include/xen/config.h
index b459e80313..9b26d882bb 100644
--- a/xen/include/xen/config.h
+++ b/xen/include/xen/config.h
@@ -11,7 +11,7 @@
 
 #define EXPORT_SYMBOL(var)
 #define EXPORT_SYMBOL_GPL(var)
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]) + __must_be_array(x))
 
 /*
  * The following log levels are as follows:
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index f5c21f64f7..ab76120da6 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -18,6 +18,12 @@ void __warn(char *file, int line);
 /* Force a compilation error if condition is true */
 #define BUILD_BUG_ON(condition) ((void)sizeof(struct { int:-!!(condition); }))
 
+/* 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); }))
+
 #ifndef assert_failed
 #define assert_failed(p)                                        \
 do {                                                            \