"most interesting" process in w(1)

[Benjamin Kaduk]

On Wed, Apr 22, 2020 at 12:09:48AM +0300, Yuri Pankov wrote:
> Looking at how w(1) finds "most interesting" process for terminal, I 
> noticed the following code which looks strange to me (usr.bin/w/w.c, 
> line 360 in HEAD)
> 
> for (ep = ehead; ep != NULL; ep = ep->next) {
>      if (ep->tdev == kp->ki_tdev) {
>          /*
>           * proc is associated with this terminal
>           */
>          if (ep->kp == NULL && kp->ki_pgid == kp->ki_tpgid) {
>              /*
>               * Proc is 'most interesting'
>               */
>              if (proc_compare(ep->kp, kp))
>                  ep->kp = kp;
>              ...
>          }
>      }
> }
> 
> Given the (ep->kp == NULL) check, proc_compare() becomes no-op, it will 
> always select kp, and that's the only place we ever set ep->kp, so the 
> first matching process is always "most interesting".  If that's really 
> what we want, we could do without the proc_compare() call.  What am I 
> missing here?

I suspect it makes more sense as a "!=" than a "==" (with ep->kp = kp;
always occurring for the "== NULL" case).

-Ben