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pycparser is my most widely used open source project (with ~20M daily downloads from PyPI [1] ). It's a pure-Python parser for the C programming language, producing ASTs inspired by Python's own . Until very recently, it's been using PLY: Python Lex-Yacc for the core parsing. In this post, I'll describe how I collaborated with an LLM coding agent (Codex) to help me rewrite pycparser to use a hand-written recursive-descent parser and remove the dependency on PLY. This has been an interesting expe...

One of my oldest open-source projects - Bob - has celebrated 15 a couple of months ago . Bob is a suite of implementations of the Scheme programming language in Python, including an interpreter, a compiler and a VM. Back then I was doing some hacking on CPython internals and was very curious about how CPython-like bytecode VMs work; Bob was an experiment to find out, by implementing one from scratch for R5RS Scheme. Several months later I added a C++ VM to Bob , as an exercise to learn how such ...

"The Origins of Political Order: From Prehuman Times to the French Revolution" by Francis Fukuyama - while reading this book it occurred to me that domains of study like political sciense must be incredibly difficult and frustrating. Imagine trying to match a model onto a set of data; the model has thousands of parameters, but you only have dozens or a couple of hundred of data points. This is what political sciense is like; there's a huge number of parameters and variables, far more t...

mdBook is a tool for easily creating books out of Markdown files. It's very popular in the Rust ecosystem, where it's used (among other things) to publish the official Rust book . mdBook has a simple yet effective plugin mechanism that can be used to modify the book output in arbitrary ways, using any programming language or tool. This post describes the mechanism and how it aligns with the fundamental concepts of plugin infrastructures . mdBook preprocessors mdBook's architecture is pretty simp...

There's an old compiler-building tutorial that has become part of the field's lore: the Let's Build a Compiler series by Jack Crenshaw (published between 1988 and 1995). I ran into it in 2003 and was very impressed, but it's now 2025 and this tutorial is still being mentioned quite often in Hacker News threads . Why is that? Why does a tutorial from 35 years ago, built in Pascal and emitting Motorola 68000 assembly - technologies that are virtually unknown for the new generation of programmers -...

The WebAssembly/tool-conventions repository contains "Conventions supporting interoperability between tools working with WebAssembly". Of special interest, in contains the Basic C ABI - an ABI for representing C programs in WASM. This ABI is followed by compilers like Clang with the wasm32 target. Rust is also switching to this ABI for extern "C" code. This post contains some notes on this ABI, with annotated code samples and diagrams to help visualize what the emitted WASM c...