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Sin's Scheme Compiler

Hi! This is a scheme compiler that I wrote for my Compilers Class: CMSC 430

This is a mostly working compiler from some non-standards compliant Scheme to LLVM IR. For a comprehensive idea on how this works (from scheme to llvm ir), I would recommend you check the class webpage, or ask me to write a blog-post, becuase that sounds like a fun post idea!

Installing Dependencies

Start by installing the threading library in Racket:

$ raco pkg install threading

Then install The Boehm GC, which is what the runtime uses:


I found it on homebrew:

$ brew install libgc

The installed files should be somehwere like /usr/local/Cellar/bdw-gc/. Make sure you set the locations correctly as noted below.


I installed BoehmGC on linux from their page, but my configure command was:

$ ./configure --prefix=/usr/local/ --disable-threads --enable-static

Note: you probably need to edit compiler.rkt to have the correct libgc path. You will see the relevant comment.

If you have easy instructions on how to do it for your platform, please send a PR!!!

Running The Compiler

(right now, we dont clear the build/ folder, so make sure to clear it out once in a while...)

To compile a file hello.sinscm to some file output.ll:

$ racket sinscm.rkt -i hello.sinscm -o output.ll -j scm -t llvm

This .ll file will be the combination of the header and the scheme code. So if you want to store the combined LLVM file, and compile it later, use this option.

To compile that output file to an executable:

$ racket sinscm.rkt -i output.ll -o hello.x -j llvm -t exe

Or you can combine the two steps:

$ racket sinscm.rkt -i hello.sinscm -o hello.x -j scm -t exe

(the CLI args are a bit wonky-named, sorry...)

Anyways, you can run the executable as with any:

$ ./hello.x



We also have a tests.rkt file, you can interact with as so:

$ racket tests.rkt will tell you the tests that you can run.

$ racket tests.rkt TESTNAME will run the test TESTNAME

$ racket tests.rkt all will run all tests.

There is currently something going on with the order tests, making it consume about a Gig of memory for some reason, it also takes forever to run. Good luck with that.

To add a passing test, add it to tests/passing. This test must have the same output value when compiled vs interpreted.

To add a failing test, add it to tests/failing. This test must raise in both compile and interpret mode.

Make sure that the test file-name ends in either .scm or .sinscm!


There is docs in the docs/ folder, currently there is a,, and a, documents a subset of the runtime errors that this language will give you. documents each primitive that this language supports. It also provides documentation for the Hash object implemented in docs/cpp/hash.h (Part 3 Professor...) provides a general guide of the language.

The documentation is hopefully good, and will provide examples of use and some edge cases.

If you would like to contribute documentation feel free :)

I am pretty sure this only works on 64bit machines, so dont try on 32bit.

This was completed as a final project for my undergraduate compilers course. You can find the page here. It was a really fun class, you should take take a look at it!


  • Update documentation on compiler phases and primitives, and everything else...
  • A way to auto-include LibGC without asking users to modify compiler.rkt?
  • Would be nice to revamp the compiler interface.
    • Just default to scm->exe, keep flags the change. still require -i and -o.
  • Rewrite runtime in Rust. Because Rust > C++, fite me.
    • Will require a Rust GC implementation.... FUN!
    • And possibly an extra step to integrate cargo instead of shelling out to clang++ in racket.
  • Rewrite top-level ... ugh.
  • Alter the passes test infra to do what it does now + compile it down to exe and run that too. There are a lot of tests for desugar that I would like to run on LLVM to see what happens.


This Compiler is licensed with the MIT license, so please feel free to use this, and modify the code. If you do use this, please say hi :)

We currently use the Boehm-GC, and code by Thomas Gilray, (particularly utils.rkt and desugar.rkt). I have provided license information in