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authorRusty Russell <rusty@rustcorp.com.au>2007-05-06 14:51:05 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-07 12:13:00 -0700
commitc5e631cf65f4d6875efcd571275436f2964a8b48 (patch)
tree1aee9d61560ee369b4a2f077a79e37ab868a4b2d /arch/um/include
parentf34d9d2dcb7f17b64124841345b23adc0843e7a5 (diff)
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>
Diffstat (limited to 'arch/um/include')
-rw-r--r--arch/um/include/user_util.h15
1 files changed, 13 insertions, 2 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))