## the exit handle: waiting for a child to terminate with no polling at all.
##
## sys.popen's slot 4 is a handle that becomes readable when the child exits,
## so it is waited on exactly like a pipe. Where the platform has no such
## facility the slot is nil and this test reports that it was skipped.

fun chk(ok msg) {
	if ok { printf "OK: %s\n" msg } \
	else { printf "ERROR: %s\n" msg }
}

iosem := (core.sem-new)
tmo   := (core.sem-new)
sg    := (core.semgr-new)
core.semgr-add sg iosem
core.semgr-add sg tmo
fin   := (core.sem-new)

p    := (sys.popen "sleep 1; exit 5" "r")
proc := (core.basicAt p 0)
xh   := (core.basicAt p 4)

if (nil? xh) {
	printf "OK: no exit handle on this platform - skipped\n"
	sys.pclose proc
} \
else {
	ticks := 0
	status := -2

	fun waiter() {
		| s |
		core.sem-signal tmo 20 0
		core.sem-signal-on-input iosem xh
		s := (core.semgr-wait sg)
		core.sem-unsignal iosem
		core.sem-unsignal tmo
		if (eqv? s tmo) { status := -1 } \
		else { status := (sys.pwait proc) }
		core.sem-signal fin
		return 0
	}

	fun ticker() {
		## the waiter is parked on the exit handle by now; these ticks only
		## happen if the VM went on scheduling instead of blocking
		while (< ticks 4) {
			ticks := (+ ticks 1)
			core.yield
		}
	}

	chk (integer? xh) "sys.popen hands back an exit handle"
	core.fork waiter
	core.fork ticker
	core.sem-wait fin

	chk (= ticks 4) "other coprocesses ran while the child was alive"
	chk (= status 5) "the exit handle woke the waiter and the status was read"

	## it belongs to the process handle, so pclose takes it away
	sys.pclose proc
	chk true "pclose released the exit handle with the group"
}