Messages in this thread | | | Subject | Re: [PATCH] bitops: add 8-bit and 16-bit rotation functions | From | Harvey Harrison <> | Date | Tue, 11 Mar 2008 14:15:02 -0700 |
| |
On Tue, 2008-03-11 at 21:59 +0100, Andreas Schwab wrote: > Segher Boessenkool <segher@kernel.crashing.org> writes: > > >> +/** > >> + * rol16 - rotate a 16-bit value left > >> + * @word: value to rotate > >> + * @shift: bits to roll > >> + */ > >> +static inline __u16 rol16(__u16 word, unsigned int shift) > >> +{ > >> + return (word << shift) | (word >> (16 - shift)); > >> +} > > > > This doesn't work for shift values of 0: you get word >> 16, and > > shifts greater than or equal to the word size aren't valid C. GCC > > will warn about this, too. > > On the other hand, a value narrower than int will always be promoted > first, so this is not a problem in this case. >
It's the same way rol32/ror32 is done directly above this section, I saw this as well, but figured that if checking for shift = 0 was wanted, it would have been there.
So...don't do that ;-)
Harvey
| |