Is there an alternative to debug.sethook()?
I'm trying to add a little extra safety to a sandbox I've created. On top of doing all the ENV changes, I want to limit CPU and memory usage.
This is some quick and simple Lua code that (mostly) accomplishes that:
local stepLimit = 50 --Maximum instructions
local memLimit = 1000 --Max memory in KB
local count = 0 --Counter for the steps
local function checkMem()
if collectgarbage("count")>memLimit then --If too much mem usage
error("uses too much memory")
end
end
local function step()
checkMem() --check mem usage
count = count+1
if count>stepLimit then -- if too much CPU usage
error("uses too much CPU")
end
end
local code = loadstring("while wait(1) do print('hi') end") --load a chunk
debug.sethook(step, "", 100) --setup this bit of sandboxy stuff
code() --run
However, Roblox uses a modified version of Lua 5.1.4, which lacks debug.sethook() as a function.
Running this code simply gives:
attempt to call field 'sethook' (a nil value)
(Commenting out the debug.sethook() line makes the code run, everything else is fine)
So if I cannot use this, how else can I manage memory and CPU?
1 answer
Thank you to "howmanysmall" on the Lua Learning Discord
Well, rather than be able to set a hook, I can create a thread alongside it.
spawn(function()
while wait() do
local MemUsage = collectgarbage("count")/1000 --(/1000 makes it MB which I prefer)
--print("memUsage:", MemUsage, "(in MB)")
if (MemUsage) > MemLimit then
error('{Code abortion}-"Using too much memory"')
end
end
end)
Not the best (or even close to it), but it does help.
Still no clue how to handle overusing CPU!