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SubjectRe: [PATCH] Use more gcc extensions in the Linux headers
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On Sat, 2007-03-10 at 02:04 +0100, Jan Engelhardt wrote:
> Getting back at the macro, how would you like to have it merged?

Well, this is what I sent to Linus and Andrew (many thanks to those who
made appropriately whimsical *or* useful comments):

diff -r 1ccdf46b0f41 include/linux/compiler-gcc.h
--- a/include/linux/compiler-gcc.h Sat Mar 10 09:55:29 2007 +1100
+++ b/include/linux/compiler-gcc.h Sat Mar 10 11:06:35 2007 +1100
@@ -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 -r 1ccdf46b0f41 include/linux/compiler-intel.h
--- a/include/linux/compiler-intel.h Sat Mar 10 09:55:29 2007 +1100
+++ b/include/linux/compiler-intel.h Sat Mar 10 11:06:25 2007 +1100
@@ -21,4 +21,7 @@
__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
diff -r 1ccdf46b0f41 include/linux/kernel.h
--- a/include/linux/kernel.h Sat Mar 10 09:55:29 2007 +1100
+++ b/include/linux/kernel.h Sat Mar 10 11:06:16 2007 +1100
@@ -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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