proc_compare() is no-op since rS29310 (almost 23 years ago!), and as everyone seems to be happy with what processes w currently reports, just remove it entirely.
Check w output with/without this change.
Unit Tests Skipped
That revision added a ep->kp == NULL check, which effectively means that first process that we got from proc_compare() is going to stay there. Also, when proc_compare() is called with one argument being NULL (and that is the only case we call it for last 23 years given the check I mentioned previously), you can guess what it would return :-)