Splice

A Luau compiler and virtual machine, written entirely in Luau.

Features

• Full Luau lexer, parser, and compiler pipeline
• Bytecode serialisation and deserialisation (version 6)
• Stack-based virtual machine supporting all 83 Luau opcodes
• Sandboxed execution with whitelist/blacklist controls, service blocking, and custom global injection
• Upvalue handling, closures, varargs, and coroutine-compatible calling convention

Usage

local Splice = require(path.to.Splice)

Compile and run

local result = Splice.Run([[
    local x = 10
    local y = 20
    return x + y
]])

print(result) --> 30

Compile, serialise, deserialise, execute

local proto = Splice.Compile([[
    local function greet(name)
        return "Hello, " .. name .. "!"
    end
    return greet("world")
]])

local bytecode = Splice.Serialise(proto)

local restored = Splice.Deserialise(bytecode)
local message = Splice.Execute(restored)
print(message) --> Hello, world!

Sandboxed execution

local env = Splice.CreateEnv({
    Whitelist = { "print", "math", "string", "table" },
    BlockedServices = { "HttpService", "DataStoreService" },
    Globals = {
        customLog = function(msg)
            print("[LOG]", msg)
        end,
    },
})

Splice.Run([[
    customLog("running in a sandbox")
    print(math.pi)
]], env)

Sandbox configuration

The CreateEnv function accepts a config table with the following fields:

Field	Type	What it does
Whitelist	{string}?	Only these globals get forwarded from the host
Blacklist	{string}?	These globals get excluded
BlockedServices	{string}?	game:GetService() calls for these services throw an error
Wrappers	{[string]: (any) -> any}?	Functions that wrap specific globals before they enter the sandbox
Script	any?	Overrides the script global inside the sandbox
Globals	{[string]: any}?	Extra globals merged into the environment

Project Structure

init.luau        Entry point and public API
Lexer.luau       Tokeniser (keywords, strings, numbers, interpolation)
Parser.luau      Recursive descent parser producing an AST
Lowerer.luau     AST to bytecode compiler (register allocation, scoping, upvalues)
Opcodes.luau     Opcode definitions, encoding/decoding helpers
Serialiser.luau  Bytecode serialisation and deserialisation
Sandbox.luau     Environment builder with Roblox global forwarding
VM.luau          Stack-based virtual machine

License

MIT