From c5e631cf65f4d6875efcd571275436f2964a8b48 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Sun, 6 May 2007 14:51:05 -0700
Subject: [PATCH] ARRAY_SIZE: check for type
We can use a gcc extension to ensure that ARRAY_SIZE() is handed an array,
not a pointer. This is especially important when code is changed from a
fixed array to a pointer. I assume the Intel compiler doesn't support
__builtin_types_compatible_p.
[jdike@addtoit.com: uml: update UML definition of ARRAY_SIZE]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/um/include/user_util.h | 15 +++++++++++++--
include/linux/compiler-gcc.h | 3 +++
include/linux/compiler-intel.h | 3 +++
include/linux/kernel.h | 3 ++-
4 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/arch/um/include/user_util.h b/arch/um/include/user_util.h
index 73ffea1829fc..b52bc4084830 100644
--- a/arch/um/include/user_util.h
+++ b/arch/um/include/user_util.h
@@ -8,8 +8,19 @@
#include "sysdep/ptrace.h"
-/* Copied from kernel.h */
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+/* Copied from kernel.h and compiler-gcc.h */
+
+/* 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(char[1 - 2 * !!(e)]) - 1)
+
+/* &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])))
+
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
#define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR))
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 9008eabb9c3d..a9f794716a81 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -22,6 +22,9 @@
__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
(typeof(ptr)) (__ptr + (off)); })
+/* &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])))
#define inline inline __attribute__((always_inline))
#define __inline__ __inline__ __attribute__((always_inline))
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index a436eea43912..b769961e6f23 100644
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -21,6 +21,9 @@
__ptr = (unsigned long) (ptr); \
(typeof(ptr)) (__ptr + (off)); })
+/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
+#define __must_be_array(a) 0
+
#endif
#define uninitialized_var(x) x
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index e2f41b051b12..144b615f3a89 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -35,7 +35,8 @@ extern const char linux_proc_banner[];
#define ALIGN(x,a) __ALIGN_MASK(x,(typeof(x))(a)-1)
#define __ALIGN_MASK(x,mask) (((x)+(mask))&~(mask))
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
+
#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
--
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