LuaDecompy/README.md
CPunch 0d947f4f3d Added 'repeat .. until' support
- lines are now tracked by start & end PC
- new config option: annotatedLines. if true line annotations show start & end PC will be emitted
- lundump.py now shows locals for each proto
2022-08-12 17:08:31 -05:00

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# LuaDecompy
An experimental Lua 5.1 dump decompiler (typically dumped using `luac -o <out.luac> <script.lua>`).
You will quickly find that only **extremely** simple scripts are decompiled successfully right now. This is an experimental project and not all opcodes are properly handled for now. If you need a real decompiler I would recommend any of the handful of ones that exist already.
## Why?
Lua has a relatively small instruction set (only 38 different opcodes!). This makes it pretty feasible for a weekend decompiler project. (real) Decompilers are extremely complex pieces of software, so being able to write a simpler one helps show the theory without *much* of the headache.
## Example usage
```sh
> cat example.lua && luac5.1 -o example.luac example.lua
local i, x = 0, 2
repeat
print(i + x)
i = i + 1
until i < 10
> python main.py example.luac
example.luac
==== [[example.lua's constants]] ====
0: [NUMBER] 0.0
1: [NUMBER] 2.0
2: [STRING] print
3: [NUMBER] 1.0
4: [NUMBER] 10.0
==== [[example.lua's locals]] ====
R[0]: i
R[1]: x
==== [[example.lua's dissassembly]] ====
[ 0] LOADK : R[0] K[0] ; load 0.0 into R[0]
[ 1] LOADK : R[1] K[1] ; load 2.0 into R[1]
[ 2] GETGLOBAL : R[2] K[2] ;
[ 3] ADD : R[3] R[0] R[1] ;
[ 4] CALL : R[2] 2 1 ;
[ 5] ADD : R[0] R[0] K[3] ;
[ 6] LT : R[0] R[0] K[4] ;
[ 7] JMP : R[0] -6 ;
[ 8] RETURN : R[0] 1 0 ;
==== [[example.lua's decompiled source]] ====
local i = 0.0
local x = 2.0
repeat
print((i + x))
i = (i + 1.0)
until i < 10.0
```