python-uncompyle6/HISTORY.md

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](http://legacy.python.org/workshops/1998-11/proceedings/papers/aycock-little/aycock-little.html). 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](http://pages.cpsc.ucalgary.ca/~aycock/spark/content.html#contributors)
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](https://groups.google.com/forum/#!searchin/comp.lang.python/hartmut$20goebel/comp.lang.python/35s3mp4-nuY/UZALti6ujnQJ). The
first subsequent public release announcement that I can find is
["decompyle - A byte-code-decompiler version 2.2 beta 1"](https://mail.python.org/pipermail/python-announce-list/2002-February/001272.html).

From the CHANGES file found in
[the tarball for that release](http://old-releases.ubuntu.com/ubuntu/pool/universe/d/decompyle2.2/decompyle2.2_2.2beta1.orig.tar.gz),
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](https://packages.qa.debian.org/d/decompyle.html). 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](http://www.crazy-compilers.com/decompyle/) 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](http://pages.cpsc.ucalgary.ca/~aycock/)
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](https://pypi.python.org/pypi/uncompyle/1.1) and the era of
public version control. (Dan's code although not public used
[darcs](http://darcs.net/) 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](https://github.com/gstarnberger/uncompyle) but also on
[bitbucket](https://bitbucket.org/gstarnberger/uncompyle) and later
the defunct [google
code](https://code.google.com/archive/p/unpyc/). 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](https://github.com/gstarnberger/uncompyle/blob/master/uncompyle/__init__.py#L25-L26)

    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](https://code.google.com/p/unpyc3/) and most especially
[pycdc](https://github.com/zrax/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.