Re: CVS commit: syssrc/sys/kern

[Dave Sainty <dave%dtsp.co.nz@localhost>]

Chris Gilbert writes:

> On Wed, 02 Oct 2002 22:14:37 -0700
> Matt Thomas <matt%3am-software.com@localhost> wrote:
> 
> > At 10:06 PM 10/2/2002, itojun%iijlab.net@localhost wrote:
> > > >> Modified Files:
> > > >>         syssrc/sys/kern: kern_resource.c
> > > >>
> > > >> Log Message:
> > > >> check negative arg.  from openbsd
> > > >Due to the `(u_int)' cast -- which I added just about 5 years ago --
> > > >this code already handled negative arguments correctly.  Your change
> > > >is a noop.
> > >
> > >         ok, but isn't it better to explicitly check
> > >                 if (which < 0 || which >= MAX)
> > >                         return EINVAL
> > >         than
> > >                 if ((u_int)which >= MAX)
> > >                         return EINVAL
> > >         from readability/clarity?
> > 
> > No.  It's slower and not if you don't know about signedness/unsigness
> > of number, you shouldn't be doing kernel programming.
> 
> It's not slower (not unless it's got some magic quantum element
> hidden in it 8) as the compiler optimises it to the same thing.  I'd
> prefer readabilty over casting because some thinks it's
> faster. (note I'll happily admit 5 years back it probably was
> faster)

Or if the code doesn't say so itself, at least a comment stating the
implied negative test happens there and is the intention...

With a cast it may be pretty clear what the code does, but it isn't
necessarily clear what the programmers intention was...