Brainf*ck to LLVM IR Compiler Frontend

A compiler frontend for the Brainf*ck language that outputs code in LLVM Intermediate Representation (IR), which can then be compiled to any desired target architecture with clang.

You can interact with it online here, or in a self-hosted web interface accessed at http://localhost:8080 after running

$ docker compose up

The input validation and parsing functionality is formally verified to be memory safe for inputs up to thirteen commands long. Details are in MODELCHECKING.md.

Dependencies

Ubuntu/Debian

$ sudo apt-get install cmake llvm-dev check expect clang-format cpplint

MacOS (Homebrew)

$ brew install cmake llvm check expect clang-format cpplint

Building

$ cmake -B build
$ cmake --build build

After building, the bfc (compiler) and bfi (interpreter) executables will be in the build directory.

To compile a bf program to a binary executable:

# Generate LLVM IR
$ bfc test/res/helloworld.b > main.ll
# Compile IR to binary
$ clang main.ll -o main
$ ./main
Hello, World!

To execute a bf program with the interpreter:

$ bfi test/res/helloworld.b
Hello, World!

Formatting and Linting

$ cmake --build build --target fmt lint

Documentation

Code docs can be accessed online at benmandrew.com/docs/bf/, or built locally with

$ cmake --build build --target docs

Depends on Doxygen and Sphinx. The generated HTML site is written to build/docs/html/index.html.

Tests

$ cmake --build build --target tests

Fuzzing

You can fuzz test with AFL:

$ docker run -ti -v .:/src benmandrew/bf:fuzz

If there are crashes, the offending inputs will be located in build-fuzz/fuzz_output/default/crashes.

FAQ

Why does ASan fail with malloc: nano zone abandoned due to inability to reserve vm space.?

On MacOS, every ASan-built binary prints this error. This is not an issue with the program, and can be fixed by setting the environment variable MallocNanoZone=0. See google/sanitizers#1666.

Useful Links for Learning the LLVM Intermediate Representation

Compiling to the LLVM IR is a niche topic, and it is hard to find resources for learning. Here are a few useful ones I found:

• Mapping High Level Constructs to LLVM IR (link)
• A Complete Guide to LLVM for Programming Language Creators (link)
• My First Language Frontend with LLVM Tutorial (link)