Function causes Lua to die, leaving behind dead threads

Hey all,

I have a program designed to login a person, and let them do things (like open a door, or if root, add users.. etc). My LoadAccounts function is causing ComputerCraft to shutdown the computer, and it seems as though there's a bad pointer somewhere. Lua then leaves a thread open and causes any further running to return the number 25.. then after a while of messing with it it output 16. I don't know what those values mean, but they seem to be error numbers?

Thanks in advance for any help anyone may be able to give.

local accounts={root="e63a0ab2f8e7ecde486b42ebfec16d4434840af4"}

loggedIn = false
name = ""

function Shutdown()
	SaveAccounts()
	print("Shutting down...")
	sleep(2)
	os.shutdown()
end

function SaveAccounts()
	if not fs.exists("data") then fs.makeDir("data") end
	local f = fs.open("/data/accounts", "w")
	for k,v in pairs(accounts) do
		f.writeLine(k.."="..v)
	end
	f.close()
end
function LoadAccounts()
	if not fs.exists("data/accounts") then return end
	local f = fs.open("/data/accounts", "r")
	local line = f.readLine()
	while line do
		local found = line:find("=")
		local key = line:sub(0, found-1)
		local val = line:sub(found+1, -1)

		accounts[key] = val
	end
end

function RawRead()
	local event, p = os.pullEvent("key")
	if event == "key" then
		return p
	end
end

nMenu={"Login", "Shutdown"}
lMenu={"Open Door", "Logout", "Shutdown"}
rMenu={"Open Door", "New User", "Del User", "Save Accounts", "Load Accounts",
			 "Logout", "Shutdown"}

function CUI(m)
	local n=1
	local l=#m
	
	while true do
		term.clear()
		term.setCursorPos(1, 1)
		print("Select an option [arrow up/arrow down]")
		term.setCursorPos(1, 3)
		for i=1, l, 1 do
			if i==n then
				print("["..m[i].."]")
			else
				print(" ", m[i])
			end
		end
		key = RawRead()
		if key==200 and n > 1 then n=n-1 end
		if key==208 and n <= l then n=n+1 end
		if key==28 then break end
	end
	term.clear() term.setCursorPos(1, 1)
	return n
end

function Menu()
	if not loggedIn then
		local opt = CUI(nMenu)
		if opt == 1 then Login() end
		if opt == 2 then Shutdown() end
	else
		if name == "root" then
			local opt = CUI(rMenu)
			if opt == 1 then OpenDoor() end
			if opt == 2 then NewUser() end
			if opt == 3 then DelUser() end
			if opt == 4 then SaveAccounts() end
			if opt == 5 then LoadAccounts() end
			if opt == 6 then Logout() end
			if opt == 7 then Shutdown() end
		else
			local opt = CUI(lMenu)
			if opt == 1 then OpenDoor() end
			if opt == 2 then Logout() end
			if opt == 3 then Shutdown() end
		end
	end	
end

function Login()
	local TextPass = function()
		term.clear()
		term.setCursorPos(1, 1)
		write("Username: ")
		local user = read()
		write("Password: ")
		local pass = read("*")
		pass = StrUtils.SHA1(pass)
		for k,v in pairs(accounts) do
			if user==k and pass==v then
				loggedIn = true;
				name = user
				print("Welcome to 351.10, "..name.."!")
				sleep(2)
				Menu()
			end
		end
		print("ERROR: Bad Username or Password!")
		sleep(3)
		Menu()
	end
	TextPass()
end

function Start()
	--LoadAccounts()
	--For the meantime, just setup two accounts
	accounts["root"] = StrUtils.SHA1("rootpass")
	accounts["bob"] = StrUtils.SHA1("poop")
	Menu()
end

Start()

EDIT: Fixed indent in code. For some reason, 2 space indent wasn't even showing up at the first indentation level

EDIT2: You can substitute the SHA1 function call with your own hashing function.. or just use a plaintext string of any sort.

You got some small indent, but could you add indent to all of the code?

Fixed indent in original post.

Can you add some debug prints and find out exactly where this is happening in your code? LuaJ does crash uncleanly sometimes.

If I had to guess I'd say that your sha function was taking too long - Lua isn't the fastest due to no native binary library (although from 1.43 onwards it has a java side bit library).

Try yielding inside your sha function by doing os.queueEvent("sha") os.pullEvent("sha") - will let your code continue executing with no severe time penalty.

Just calling LoadAccounts caused the server to spit out "05:59:00 [INFO] ComputerCraft: Warning! Failed to abort a Computer. Dangling lua thread could cause errors." and then after rebooting the in-game computer, it says at the top "bios:258: vm error:njava.lang.NullPointerException" (n inserted where a new line is in actual error); is there a way to get more debug output? Should I print after every single line in LoadAccounts until I find the issue?
EDIT: Line 258 in bios.lua is "local meta = getmetatable( _t )" in function "local function protect( _t )"

EDIT2: It seems the loop runs forever. How can I test for EOF? Is there an equiv. to C's feof(file)?

Problem solved. I feel like an idiot, though I am very tired and sick.. I forgot to read more lines in the loop. It looped forever over the first line, so the line variable never was nil so it never ended. Whoops.. still, I don't see why that completely kills Lua; it seems to not catch taking too long sometimes.

Thanks to everyone who took the time to look at this.

Off-topic: Where is the fs API file? I don't seem to have it, yet the API obviously works.

The fs API functions are exposed through the Java code.

You're using an old version too (tekkit) - as the computer thread not being killed is no longer an issue.