fix intermittent crashes when spawning new processes

src/init.lua

@@ -57,7 +57,7 @@ local fillEnv --function(proc:thread, env:table):() -- given a process and an em
 --<https://ocdoc.cil.li/tutorial:custom_oses#what_s_available>
 
 -- _G (through envBase) is used as the base for process environments, so clear it of anything process-specific
-envBase._OSVERSION = 'kitn 0.1.0' --prefer [openloader, openos] "$name $ver" over plan9k "$name/$ver"
+envBase._OSVERSION = 'kitn 0.1.1' --prefer [openloader, openos] "$name $ver" over plan9k "$name/$ver"
 envBase._G, envBase.load = nil
 envBase.coroutine.resume = function(co, ...)
 	checkArg(1, co, 'thread')
@@ -193,7 +193,7 @@ end
 --logic after co_resume(process, ...) returns, in its own function to use varargs instead of table.pack
 local function postResume(co, ok, reason, ...)
 	if co_status(co) == 'dead' then
-		processes[co], runnable[co], schedDeadline[co], schedSignal[co] = nil
+		processes[co], schedDeadline[co], schedSignal[co] = nil
 		--TODO bubble to parent process
 
 		--tostring could run userspace code and even yield, but at this point we're crashing so it doesn't matter
@@ -237,10 +237,26 @@ end
 --goto instead of while-true for vague feeling of performance (TODO benchmark this)
 ::tickScheduler::
 
---clear the run queue
+--[[clear the run queue
+this is a delicate formulation. if proc creates new threads, those are added as new keys to runnable, which
+makes next's behavior undefined*; removing proc before resuming causes the next loop iteration to crash with
+"invalid key to 'next'". unconditionally removing proc after is also wrong, because proc may have rescheduled
+itself immediately. instead we assign proc a value it should never have (false) before, test if it's still set
+to that value after, and remove it if so.
+
+the outer loop is for the occasional case that some of the child processes end up before their parent in next's
+order and so wouldn't be resumed until after another signal was pulled otherwise.
+
+*is this c-like ub that can cause memory corruption and segfaults? the manual doesn't say! (TODO make this not ub)
+]]
+while next(runnable) do
 	for proc, args in pairs(runnable) do
-	runnable[proc] = nil --the process is no longer runnable, unless it reschedules itself
+		runnable[proc] = false
 		postResume(proc, kresume(proc, unpack(args, 1, args.n)))
+		if not runnable[proc] then
+			runnable[proc] = nil
+		end
+	end
 end
 
 local deadline = nil