id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	difficulty
304	coops#subclass? can process abort	Kon Lovett	felix winkelmann	"(use coops)
(subclass? 'not-a-class! <standard-class>) ;=> Bus error (MacOS 10.5)

The `c1' argument is interpreted as a class w/o determining the safety.

Maybe:
((memq c2 (slot-value c1 'class-precedence-list)) #t)
  =>
((and (coops-instance? c1) (memq c2 (slot-value c1 'class-precedence-list))) #t)
"	defect	closed	critical		extensions	4.5.x	fixed	coops