malcc

Mal (Make A Lisp) Compiler in C

Overview

Mal is Clojure inspired Lisp interpreter created by Joel Martin.

malcc is an incremental compiler implementation for the Mal language. It uses the Tiny C Compiler as the compiler backend and has full support for the Mal language, including macros, tail-call elimination, and even run-time eval.

malcc can also be used as an ahead-of-time compiler for Mal, producing a single binary file for distribution (though using it this way sacrifices run-time eval functionality since the compiler is not shipped in the resulting binary).

Building and Running

malcc has been tested on Ubuntu 18.04 and macOS 10.14 Mojave.

Prerequisites on Mac:

sudo xcode-select --install
brew install pcre libgc

On Macos 10.14.4, there is a problem building TinyCC. This fixes that:

cd /usr/local/lib
sudo ln -s ../../lib/libSystem.B.dylib libgcc_s.10.4.dylib

Prerequisites on Ubuntu/Debian:

apt-get install libpcre3-dev libedit-dev libgc-dev

Building malcc:

git submodule update --init
make all

Running the REPL:

→ ./malcc
Mal [malcc]
user> (+ 1 2)
3
user> ^D

Running a mal file:

→ ./malcc examples/fib.mal
55
12586269025

Ahead-of-Time compiling a mal file:

→ ./malcc --compile examples/fib.mal fib
→ ./fib
55
12586269025

Speed

malcc is fast! Running the microbenchmarks on my Macbook Pro yields an order-of-magnitude speedup for long-running code vs the C++ implementation:

C++:

→ ../cpp/stepA_mal perf1.mal
"Elapsed time: 1 msecs"
→ ../cpp/stepA_mal perf2.mal
"Elapsed time: 2 msecs"
→ ../cpp/stepA_mal perf3.mal
iters over 10 seconds: 12415

malcc:

→ ../../stepA_mal perf1.mal
"Elapsed time: 0 msecs"
→ ../../stepA_mal perf2.mal
"Elapsed time: 3 msecs"
→ ../../stepA_mal perf3.mal
iters over 10 seconds: 226216

Note: I'm not sure if this is a fair comparison, but I could not coax the C interpreter implementation of mal to run the perf3 test, so I figured the C++ implementation was the next-best thing.

Approach

I followed the Mal guide to implement malcc, using the same steps that any other implementation would follow. Naturally, since malcc is a compiler rather than a straight interpreter, there are some differences from other implementations:

1. Additional functions not specified in the Mal guide are employed to generate the C code that is passed to the TinyCC compiler. These functions all start with gen_ and should be fairly self-explanatory.
2. load-file is implemented as a special form rather than a simple function. This is because macros defined in a file must be found and compiled during code generation--they cannot be discovered at run-time.
3. I chose to publish malcc in a separate repository and have structured it to suit my taste. A copy of the mal implementation of mal and the mal tests were copied into the mal directory to provide test coverage.

Contributing

Contributors are welcome! ❤️

File an issue on GitHub if you find a bug or you want to propose a new feature!

License

This project's sourcecode is copyrighted by Tim Morgan and licensed under the MIT license, included in the LICENSE file in this repository.

The subdirectory mal contains a copy of the Mal language repository and is copyrighted by Joel Martin and released under the Mozilla Public License 2.0 (MPL 2.0). The text of the MPL 2.0 license is included in the mal/LICENSE file.