Bolt is a language with in-built data-race freedom! – mukul-rathi/bolt

What, another programming language?
Yep, this one prevents data races! Concurrent code is hard to get right, so let the language take care of it for you! The best part is that you get more fine-grained concurrency than Rust and this language doesn’t get in the way when you want to write single-threaded code. Want to write Rusty ownership-style code – yep, you can do that in Bolt too!
For a description of the theory, check out the accompanying dissertation.
Alright so what does this language do?
You can already write a lot of Java-esque code – see examples/ in this repo. Bolt already supports inheritance, method overloading and overriding, and generics. Is Bolt missing something? Comment on this issue – I’m all ears.
Two ways Bolt differs from traditional languages – the capability annotations for fields and function/method type signatures, and a structured approach to concurrency – so you know exactly how long your threads live for:
async{ // fork a thread using the async command – you can spawn as many as you like!
… // execute an expression in the forked thread
… // continue executing your code on current thread
} // all forked threads finish executing here
Wait, how did you build this?
A lot of trial-and-error and experimenting with reverse-engineering C++ code! I’ll save you the trouble – step-by-step tutorials for how I built this all are incoming – I’ll tweet about them when they drop so follow me on Twitter.
Unlike your run-of-the-mill compiler tutorials, we’ll be talking about more advanced language features too, like generics, inheritance, method overloading and overriding! More blog posts and live tweets as I develop the language further – let’s see how rich we can get this 🙂
(I also blog about other stuff like this git post and this Facebook internship post)
Getting started
Bolt’s compiler is written in OCaml and C++. You’ll need OCaml and opam installed. You’ll also need to install Bazel, and update llvm.bzl to use the right pre-built LLVM Binary.
Once you have these installed, the Makefile details all the main commands.
To get started run these commands!

  • make install – install dependencies
  • make hook – install the git pre-commit hook
  • make build – build the project

To compile a program:

  • scripts/ <filename> <flag> – run a Bolt program (extension .bolt) – pass in the-help flag to see the list of possible flags you can pass in.
  • alias boltc=./scripts/ >> ~/.bashrc

To compile and run the program:

  • scripts/ <filename> <flag> – run a Bolt program (extension .bolt) – pass in the-help flag to see the list of possible flags you can pass in.
  • alias bolt=./scripts/ >> ~/.bashrc – okay this isn’t strictly necessary, but running bolt <filename> to execute a Bolt program is super cool!

Okay, – the boltc and bolt aliasing isn’t strictly necessary, but running boltc <filename> to compile and bolt <filename> to run a Bolt program is super cool!
Check out the file for more details about the project structure.