[pypy-dev] PyPy Winter Sprint + cpyext

[Stefan Beyer]

Hey everyone!

Those of you who attended or followed one of the last two winter sprints 
in Leysin might know me, the others probably won't. I'm (still) a 
Master's student writing my thesis on PyPy's current issue with 
cross-heap cycles when using cpyext. The main point is, that they are 
not collected and stay around as floating garbage, even if they are not 
reachable any more. Correct me if I'm wrong, but I didn't notice anyone 
else working on that topic (and/or committing something) since I've 
picked it up two years ago (yeah, I know, that long ago...).

I saw that you would be working on "cpyext performance and completeness" 
during the current winter sprint this week and thought that this might 
also concern my thesis. So I thought I'll give you an update.

I recently pushed my current (non-optimized, breaking-some-tests, but 
more or less working) implementation of the "CPython-style" GC-extension 
for cpyext. It is still in an early stage and not all cases (legacy and 
non-legacy-finalizers, weakrefs) are handled. However, I picked up some 
pace during the last couple of weeks and I'm determined to finish this 
implementation during the following weeks (some quirks with the tests 
have been haunting me, but I think I figured most of them out by now). 
After that, I will implement a second alternative implementation (to 
compare to, mostly for the sake of my thesis), which will take some more 
time. I also added a couple of fancy test cases (the so called 
"dot-tests"), so that we can test complex object graphs a little bit 
easier (and also because it was kind of cool to have another language 
inside PyPy/RPython, even if it was only for the tests...), with more 
test cases to come (the current ones are a bit messy). None of the new 
changes concerning low-latency applications are currently integrated, 
but that should not be too hard.

I guess it won't make much sense for me to join you at this year's 
winter sprint, especially as I won't be able to get there before 
Thursday, but I might be able to join you over the IRC channel (or some 
other form of communication if you like). If there is anything that is 
worth discussing please let me know! Also feel free to comment on my 
code, but beware that I might change some things once I try to do some 
optimizations (probably not many, but at least fix the worst issues) and 
make it a little bit more readable. You can find my code on the 
cpyext-gc-cycle 
branch.<https://bitbucket.org/pypy/pypy/commits/branch/cpyext-gc-cycle>

Looking forward to hearing from you!

Greetings,
Stefan