On Sat, Nov 20, 2010 at 00:19, Andrew Morton [off-list ref] wrote:

On Fri, 19 Nov 2010 15:04:11 -0800
Andrew Morton [off-list ref] wrote:

quoted

quoted

Looks good to me.  I posted essentially the same thing some 3 months ago
(http://marc.info/?l=linux-kernel&m8033094822201&w=2) but it then
failed to get any traction.  At any rate, I like your version better as
it seems more readable.

I spose we should document it.   Does this look complete and accurate?

--- a/include/linux/kernel.h~include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit-fix
+++ a/include/linux/kernel.h

@@ -143,6 +143,13 @@ extern int _cond_resched(void);

 #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0)

+/*
+ * abs() handles unsigned and signed longs, ints, shorts and chars.  For long
+ * types it returns a signed long.  For int, short and char types it returns a
+ * signed int.
+ * abs() should not be used for 64-bit types (s64, u64, long long) - use abs64()
+ * for those.
+ */
 #define abs(x) ({                                            \
              long ret;                                       \
              if (sizeof(x) = sizeof(long)) {                \

Well that was a load of bollocks.  2nd attempt:

Yeah, I was just gonna complain "but long _is_ 64-bit on 64-bit platforms"...

After some second thinking, I think this is OK...

In the first patch:

of similarity between video modes.  The arguments of abs() are sometimes
unsigned numbers.  This worked fine until commit a49c59c0 ("Make sure the

The "sometimes" is when the parameter is the difference of 2 numbers, which is a
highly likely use case. Unlike most people's intuitive mathematical
feelings, a difference
is always unsigned in C (that was incorrect in the comment of Michal's
first version).
So I think it's worth mentioning that explicitly.

... and please llet me do the third thinking during the rest of the day ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds