7.7 KiB
This project has history of over 17 years spanning back to Python 1.5
There have been a number of people who have worked on this. I am awed by the amount of work, number of people who have contributed to this, and the cleverness in the code.
The below is an annotated history from talking to participants involved and my reading of the code and sources cited.
In 1998, John Aycock first wrote a grammar parser in Python, eventually called SPARK, that was usable inside a Python program. This code was described in the 7th International Python Conference. That paper doesn't talk about decompilation, nor did John have that in mind at that time. It does mention that a full parser for Python (rather than the simple languages in the paper) was being considered.
This contains a of people acknowledged in developing SPARK. What's amazing about this code is that it is reasonably fast and has survived up to Python 3 with relatively little change. This work was done in conjunction with his Ph.D Thesis. This was finished around 2001. In working on his thesis, John realized SPARK could be used to deparse Python bytecode. In the fall of 1999, he started writing the Python program, "decompyle", to do this.
To help with control structure deparsing the instruction sequence was augmented with pseudo instruction COME_FROM. This code introduced another clever idea: using table-driven semantics routines, using format specifiers.
The last mention of a release of SPARK from John is around 2002.
In the fall of 2000, Hartmut Goebel took over maintaining the code. The first subsequent public release announcement that I can find is "decompyle - A byte-code-decompiler version 2.2 beta 1".
From the CHANGES file found in the tarball for that release, it appears that Hartmut did most of the work to get this code to accept the full Python language. He added precedence to the table specifiers, support for multiple versions of Python, the pretty-printing of docstrings, lists, and hashes. He also wrote test and verification routines of deparsed bytecode, and used this in an extensive set of tests that he also wrote. He could verify against the entire Python library.
decompyle2.2 was packaged for Debian (sarge) by Ben Burton around 2002. As it worked on Python 2.2 only long after Python 2.3 and 2.4 were in widespread use, it was removed.
Crazy Compilers offers a byte-code decompiler service for versions of Python up to 2.6. As someone who worked in compilers, it is tough to make a living by working on compilers. (For example, based on John Aycock's recent papers it doesn't look like he's done anything compiler-wise since SPARK). So I hope people will use the crazy-compilers service. I wish them the success that his good work deserves.
Dan Pascu did a bit of work from late 2004 to early 2006 to get this code to handle first Python 2.3 and then 2.4 bytecodes. Because of jump optimization introduced in the CPython bytecode compiler at that time, various JUMP instructions were classifed as going backwards, and COME FROM instructions were reintroduced. See RELEASE-2.4-CHANGELOG.txt for more details here. There wasn't a public release of RELEASE-2.4 and bytecodes other than Python 2.4 weren't supported. Dan says the Python 2.3 version could verify the entire python library.
Next we get to "uncompyle" and PyPI and the era of public version control. (Dan's code although not public used darcs for version control.)
In contrast to decompyle, uncompyle at least in its final versions, runs only on Python 2.7. However it accepts bytecode back to Python 2.5. Thomas Grainger is the package owner of this, although Hartmut is still listed as the author.
The project exists not only on github but also on bitbucket and later the defunct google code. The git/svn history goes back to 2009. Somewhere in there the name was changed from "decompyle" to "unpyc" by Keknehv, and then to "uncompyle" by Guenther Starnberger.
The name Thomas Grainger isn't found in (m)any of the commits in the several years of active development. First Keknehv worked on this up to Python 2.5 or so while acceping Python bytecode back to 2.0 or so. Then hamled made a few commits earler on, while Eike Siewertsen made a few commits later on. But mostly wibiti, and Guenther Starnberger got the code to where uncompyle2 was around 2012.
In uncompyle2 decompilation of python bytecode 2.5 & 2.6 is done by transforming the byte code into a a pseudo 2.7 python bytecode and is based on code from Eloi Vanderbeken.
This project, uncompyle6, abandons that approach for various reasons. However the main reason is that we need offsets in fragment deparsing to be exactly the same, and the transformation process can remove instructions. Adding instructions with psuedo_offsets is however okay.
Uncompyle6, however owes its existence to the fork of uncompyle2 by Myst herie (Mysterie) whose first commit picks up at 2012. I chose this since it seemed to have been at that time the most actively, if briefly, worked on. Also starting around 2012 is Dark Fenx's uncompyle3 which I used for inspiration for Python3 support.
I started working on this late 2015, mostly to add fragment support. In that, I decided to make this runnable on Python 3.2+ and Python 2.6+ while, handling Python bytecodes from Python versions 2.5+ and 3.2+. (I think I could go back further, but I'd consider doing that only after code is better cleaned up and supports Python 3 better.)
Over the many years, code styles and Python features have changed. However brilliant the code was and still is, it hasn't really had a single public active maintainer. And there have been many forks of the code.
That it has been in need of an overhaul has been recognized by the Hartmut a decade an a half ago:
decompyle/uncompile__init__.py
NB. This is not a masterpiece of software, but became more like a hack.
Probably a complete rewrite would be sensefull. hG/2000-12-27
This project deparses using an Early-algorithm parse with lots of massaging of tokens and the grammar in the scanner phase. Early-algorithm parsers are context free and tend to be linear if the grammar is LR or left recursive.
Another approach that doesn't use grammars is to do something like simulate execution symbolically and build expression trees off of stack results. The two important projects that work this way are unpyc3 and most especially pycdc The latter project is largely by Michael Hansen and Darryl Pogue. If they supported getting source-code fragments and I could call it from Python, I'd probably ditch this and use that. From what I've seen, the code runs blindingly fast and spans all versions of Python.
Tests for the project have been, or are being, culled from all of the projects mentioned.
NB. If you find mistakes, want corrections, or want your name added (or removed), please contact me.