Re: [PATCH] ARM: type casts update_sched_clock cyc_to_sched_clock cyc_to_fixed_sched_clock

[Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>]

On Tue, Apr 05, 2011 at 10:31:44AM +0200, Uwe Kleine-König wrote:
> On Tue, Apr 05, 2011 at 08:56:22AM +0100, Russell King - ARM Linux wrote:
> > On Tue, Apr 05, 2011 at 09:43:21AM +0200, Jan Weitzel wrote:
> > > parameter "u32 mask" type cast befor inversion
> s/befor/before/
> 
> > Nak.  I want a 32-bit all ones quantity.
> > 
> > unsigned long long vali = (unsigned short)~0;
> > unsigned long long vall = ~(unsigned short)0;
> > 
> BTW, the definiton of vall is equivalent to 
> 
> 	unsigned long long valu = ~(unsigned int)0;
> 
> because ~ converts the unsigned short to unsigned int.

No.  The value gets promoted to int not unsigned int.

> > compiles to:
> > 
> > vali:
> >         .word   65535
> >         .word   0
> > 
> > vall:
> >         .word   -1
> >         .word   -1
> I really wonder about that. If I take a value of 0xffffffff (i.e. a 32
> bit wide int == ~0U) and assign that to an 64-bit unsigned long long I'd
> expect it to get the value 0x00000000ffffffffULL, not
> 0xffffffffffffffffULL. What's wrong?

See above.  int not unsigned int.  And it makes a difference:

unsigned long long vals = ~(int)0;
unsigned long long valu = ~(unsigned int)0;

vals:
        .word   -1
        .word   -1
valu:
        .word   -1
        .word   0