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LuaJIT raw-bytecode decompiler (LJD)

The original name was ljwthgnd as in LuaJIT 'What The Hell is Going On' Decompiler named under the LuaJIT C sources variable naming convention.

WARNING! This code is nor finished, nor tested yet! There is no even slightest warranty that resulting code is even near to the original. Use it at your own risk of the wasted time.

SECOND WARNING! And, BTW, this all is a one huge prototype. Because the "release" version should be written into lua itself. Because it's cool to decompile the decompiler - a great test too!


Python 3.0+ from

How to use it

There is no argument parsing right now, so comment out things in the script and launch it as in path/to/file.luac


There is a lot of work to do, in the order of priority

  1. Logical subexpressions in while statements:

    	while x < (xi and 2 or 3) do
    		print ("Hello crazy world!")

    Logical subexpressions (the subexpressions used as operands in ariphmetic or comparison operations inside other exrpressions) are currently supported only for ifs. To support them for whiles and repeat untils an expression unwarping logic should be moved at the very beginning. But it won't work without all fixes being done in a loop unwarping logic. So we need to split that and move the fixes before expressions before loops before ifs. That's not that easy...

  2. AST Mutations:

    1. Use the line information (or common sense if there is no line information) to squash similar expressions into a single expression.
  3. Formatting improvements

    1. Use the line information (or common sense) to preserve empty lines and break long statements like in the original code.

      This is mostly done, but only in the "common sense" part.

    2. Use method-style calls and definitions for tables.

  4. Features not supported:

    1. GOTO statement (from lua 5.2). All the required functionality is now in place, but that's rather a low-priority task right now.

    2. Local sub-blocks:

    These subblocks are not reflected anyhow directly in the bytecode.
    The only way to guess them is to watch local variable scopes, which
    is simple enough in case of non-stripped bytecode and a bit
    harder otherwise.


LuaJIT raw-bytecode decompiler




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