CF Bolz-Tereick

@cfbolz
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PyPy/RPython contributor. Half time teaching at Uni Düsseldorf. Works on dynamic language implementations. Vegan. Love street art and art in public spaces, hiking, reading.
they/them
websitehttps://www.cfbolz.de

@llimllib @eli_oat Thanks! 😄

I see, you might have found it from the IOCCC winners this year. But the author seems to have been working on it for a long time.

This is in the part of the idea space where the build toolchain is complex but the runtime is simple. Though I still have questions: is the binary including all of SDL? Do the terminal programs include an emulator, or simply emit escape codes, and therefore require terminals to be eternal as well 😄

My interest runs more in the direction of making software eternal by making it simple to understand rather than simple to run. Here I think future civilizations don't really have a leg up understanding the programs compared to the emulation based approach.

Still, this seems worth investing in. It improves on the status quo. Somebody build a complete EternalOS distro out of this!

got very thoroughly nerd-sniped by https://github.com/adriancable/eternal today.
I built a jitted rpython version of the VM, it nicely boots linux and runs doom! need to blog about it to get it out of my system

just used memray to find out where my python program was allocating memory and was super impressed by how easy it was to use https://github.com/bloomberg/memray

the steps were just:

1. `memray run python3 my_program.py`
2. copy and paste the snippet it prints out ("memray flamegraph memray-manage.py.37954.bin") to generate a flamegraph
3. open the html flamegraph in my browser

GitHub - bloomberg/memray: Memray is a memory profiler for Python

Memray is a memory profiler for Python. Contribute to bloomberg/memray development by creating an account on GitHub.

GitHub
the nice thing about javascript is that there are so many kinds of scope. truly an embarrassent of riches

Also forgot to mention some small fun with Z3

https://bernsteinbear.com/blog/asm-z3/

Checking assembly with Z3

Short post today. New ZJIT contributor dak2 submitted a PR to fix an overflow bug in fixnum division in ZJIT. We did the division fine, but lied about the type of the result in the case of dividing FIXNUM_MIN by -1. You can see how this is special-cased in CRuby:

Max Bernstein
@regehr @pkhuong here's the variants that I know are used in at least one project. It's all equivalent of course, but mentally switching between them is always annoying
Just blogged: "KnownBits in Lean" https://cfbolz.de/posts/2026-knownbits-in-lean/
KnownBits in Lean

In January I was at the excellent E-Graphs Dagstuhl where I met some really amazing people. One of the things I did during that week was to talk to Marcus Rossel and Andrés Goens about proving the sou

CF Bolz-Tereick's Web Page
Academic peer review is a print-read-eval loop
Verifying EDA and compiler optimizations once and for all
https://samuelcoward.co.uk/blog/2026/parabit/
A Multi-Width Parametric Bitvector Equivalence Solver
https://samuelcoward.co.uk/assets/pdf/Parabit.pdf
CAV 2026
Luigi Rinaldi, John Wickerson, Samuel Coward