Messages in this thread | | | Date | Fri, 19 Nov 2010 23:28:23 +0100 | From | Michal Januszewski <> | Subject | Re: abs() vs. abs64() (was: Re: [PATCH] fbdev: fix nearest mode search) |
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On Fri, Nov 19, 2010 at 02:07:21PM -0800, Andrew Morton wrote: > On Thu, 18 Nov 2010 07:40:19 +0100 > Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > 'c' will end up with a value of 0xffffffff instead of the expected 0x1. > > > > This happens on 64-bit only, right?
Absolutely, I should have mentioned it in the patch description.
> How does this look? > > [..] > > Reported-by: Michal Januszewski <michalj@gmail.com> > Cc: Rolf Eike Beer <eike-kernel@sf-tec.de > Cc: Geert Uytterhoeven <geert@linux-m68k.org> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > include/linux/kernel.h | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff -puN include/linux/kernel.h~include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit include/linux/kernel.h > --- a/include/linux/kernel.h~include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit > +++ a/include/linux/kernel.h > @@ -143,9 +143,16 @@ extern int _cond_resched(void); > > #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0) > > -#define abs(x) ({ \ > - long __x = (x); \ > - (__x < 0) ? -__x : __x; \ > +#define abs(x) ({ \ > + long ret; \ > + if (sizeof(x) == sizeof(long)) { \ > + long __x = (x); \ > + ret = (__x < 0) ? -__x : __x; \ > + } else { \ > + int __x = (x); \ > + ret = (__x < 0) ? -__x : __x; \ > + } \ > + ret; \ > }) > > #define abs64(x) ({ \ > _
Looks good to me. I posted essentially the same thing some 3 months ago (http://marc.info/?l=linux-kernel&m=128033094822201&w=2) but it then failed to get any traction. At any rate, I like your version better as it seems more readable.
Michal
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