Build a garbage collector from scratch. Implement mark and sweep, track live objects and reclaim memory like the runtimes you use every day.
Build it in your language
The tester treats your program as a black box: any language works. These are just the most convenient ones for this project.
Project in preparation: we are completing and verifying the implementation path and its tests. The capabilities below describe the project goal; starting the project is not enabled yet.
If you program in a garbage-collected language, there's a component constantly deciding what lives and what dies in your program, and you've never seen it. Here you write it.
You'll build your own heap with its allocator, a mark-and-sweep collector on top of it, and the improvements real runtimes use: generational collection and compaction. And you'll measure the pauses, which is where the hard part lives.
9 stages across 4 phases. Every stage comes with its guide and its tests: you move on when they pass.
Reserve memory, write an allocator, and represent objects with a header.
Roots, traversal of the object graph, marking and freeing.
Free list, fragmentation, and automatic collection triggering.
Generational collection with a nursery, write barriers, and measured compaction.
Build a container runtime from scratch. Isolate processes with namespaces, cgroups and chroot to understand how Docker starts an image.
Go · C · Rust
Build a neural network from scratch. Implement the forward pass, loss functions and gradient descent, then train and run your own model.
Python · TypeScript
Build a POSIX shell from scratch. Use fork, exec, pipes and redirection to write a command interpreter that runs real programs.
C · Rust · Go · Zig