m2c -Modula-2 to C Compiler

A modern superset of Modula-2 that compiles to fast, portable C. Write safe, modular code with the simplicity of PIM4 Modula-2 -then opt into exceptions, objects, reference types, and concurrency when you need them. The output is plain C that any system compiler can optimize, giving you native performance on every platform clang or gcc supports.

Why Modula-2 in 2026? It's the original systems language designed for modularity and safety. m2c extends it with the features modern applications actually need -TRY/EXCEPT, heap-allocated reference types, vtable-based objects, pthreads concurrency -while keeping the language small and the compiled output readable. No runtime, no garbage collector (unless you want one), no hidden allocations.

Highlights

• Compiles to C -readable output, native speed, runs anywhere clang/gcc does
• Modula-2+ extensions -exceptions, REF types, objects, concurrency, TYPECASE (--m2plus)
• 17 libraries for networking, crypto, graphics, async I/O, and more
• Self-hosted package manager (m2pkg) with registry, dependency resolution, and semver
• Full LSP server with VS Code extension -completions, hover, go-to-definition, call hierarchy
• 500+ tests -unit, integration, adversarial, conformance, with sanitizer coverage

What's in this repository

Component	Location	Description
m2c compiler	src/	Modula-2 to C compiler with built-in LSP server
m2pkg package manager	tools/m2pkg/	Self-hosted package manager (written in Modula-2+)
VS Code extension	tools/vscode-m2plus/	Language support via m2c's LSP server
Libraries	libs/	17 packages for networking, graphics, crypto, and more
Standard library	src/stdlib.rs	InOut, RealInOut, MathLib, Strings, Terminal, etc.
macOS SDK	sdk/macos/v1/	ObjC++ runtime, shaders, M2 library modules

Quickstart

Build from source

cargo build --release
sudo cp target/release/m2c /usr/local/bin/m2c

Hello world

cat > hello.mod << 'EOF'
MODULE Hello;
FROM InOut IMPORT WriteString, WriteLn;
BEGIN
  WriteString("Hello, world!");
  WriteLn;
END Hello.
EOF

m2c hello.mod -o hello && ./hello

Modula-2+ extensions

m2c --m2plus myprogram.mod -o myprogram

Project builds (m2.toml manifest)

m2c build              # compile
m2c run                # compile and run
m2c test               # run tests
m2c clean              # remove artifacts

Package manager

m2pkg init             # create m2.toml
m2pkg resolve          # fetch and lock dependencies
m2pkg build            # compile with all deps
m2pkg run              # build and run

Libraries

All in libs/, installable via m2pkg or usable as local path dependencies.

Library	Description
m2gfx	SDL2-based graphics -windows, drawing, events, fonts, textures, pixel buffers
m2http	HTTP client with DNS resolution and TLS
m2http2	HTTP/2 framing and HPACK compression
m2http2server	HTTP/2 server framework
m2tls	TLS 1.2/1.3 via OpenSSL
m2sockets	TCP/UDP socket abstraction
m2stream	Transport-agnostic byte streams
m2futures	Promises/futures, single-threaded async, pool-based allocation
m2evloop	Event loop with kqueue/epoll polling
m2bytes	Byte buffers, binary codec, hex encoding
m2alloc	Arena and pool allocators (caller-provided buffers, zero malloc)
m2fsm	Table-driven finite state machines, O(1) dispatch
m2auth	JWT HS256 signing/verification, keyring
m2log	Structured logging (no heap allocation in log path)
m2rpc	RPC framework
m2cli	CLI argument parser
m2sys	C shim -file I/O, exec, SHA-256, paths, tar, timestamps

VS Code

cd tools/vscode-m2plus
npm install && npm run compile
ln -s "$(pwd)" ~/.vscode/extensions/m2plus

Restart VS Code and open a .mod or .def file. If m2c is not on your PATH, set m2c.serverPath in settings. Reindex: Command Palette > "Modula-2+: Reindex Workspace".

Tests

cargo test                                  # 141 unit tests
bash tests/run_all.sh                       # 76 integration tests
bash tests/conformance.sh                   # 22 conformance tests
python3 tests/adversarial/run_adversarial.py  # 296 adversarial tests (ASan+UBSan)

Project layout

src/                    Compiler source (Rust)
  main.rs               CLI entry, subcommand routing
  lexer.rs              Tokenizer (case-insensitive keywords)
  parser.rs             Recursive-descent parser -> AST
  ast.rs                AST node types
  sema.rs               Semantic analysis, type checking, scopes
  codegen.rs            C code generation
  driver.rs             Compilation orchestration
  build.rs              Project build system (m2c build/run/test/clean)
  analyze.rs            Analysis-only path (LSP, no codegen)
  project_resolver.rs   Manifest/lockfile parsing
  stdlib.rs             Standard library definitions + C runtime
  lsp/                  LSP server (completions, hover, goto-def, call hierarchy, ...)

tools/
  m2pkg/                Self-hosted package manager (Modula-2+)
  m2pkg0/               Rust bootstrapper for m2pkg
  vscode-m2plus/        VS Code extension (TypeScript)

libs/                   17 libraries (see table above)
tests/                  Integration, conformance, adversarial tests
docs/                   Documentation
sdk/                    Platform SDKs
example_apps/           Example programs

Documentation

• Language support -PIM4 and Modula-2+ feature coverage
• Using the toolchain -compiler, package manager, workflows
• LSP capabilities -features, configuration, troubleshooting
• VS Code integration -extension setup, settings, commands
• Architecture -compiler pipeline, LSP internals
• m2pkg reference -package manager details
• FAQ
• All docs

License

MIT