Files

T

ok 2c74222193 Achieve 100% Core compliance, implement CATCH/THROW

Core word set: 0 errors on Gerry Jackson's forth2012-test-suite/core.fr
- Fix POSTPONE for non-immediate words via COMPILE, mechanism
- Fix double-DOES> (WEIRD: pattern) with does-body scanning and
  runtime patching via _DOES_PATCH_
- Implement CATCH/THROW exception handling using wasmtime trap
  mechanism with stack pointer save/restore
- 232 tests passing

2026-03-30 21:26:21 +02:00

2.6 KiB

Raw Blame History

WAFER Project Conventions

What is WAFER?

WAFER (WebAssembly Forth Engine in Rust) is an optimizing Forth 2012 compiler targeting WebAssembly. Currently a working Forth system with 70+ words and JIT compilation.

Architecture

Each Forth word compiles to its own WASM module via wasm-encoder
Modules share memory, globals (dsp/rsp), and a function table via wasmtime imports
IR-based compilation: Forth -> Vec<IrOp> -> WASM codegen -> wasmtime instantiation
Dictionary: linked-list in a Vec<u8> buffer simulating WASM linear memory
Primitives: either IR-based (compiled to WASM) or host functions (Rust closures in wasmtime)

Key Files

crates/core/src/outer.rs -- ForthVM: the main runtime, outer interpreter, compiler, all primitives
crates/core/src/codegen.rs -- IR-to-WASM translation, module generation, wasmtime execution tests
crates/core/src/dictionary.rs -- Dictionary data structure with create/find/reveal
crates/core/src/ir.rs -- IrOp enum (the intermediate representation)
crates/core/src/memory.rs -- Memory layout constants (stack regions, dictionary base, etc.)
crates/cli/src/main.rs -- CLI REPL with rustyline

Adding a New Word

IR primitive (simple stack/arithmetic/logic -- preferred when possible):

self.register_primitive("WORD_NAME", false, vec![IrOp::Dup, IrOp::Mul])?;

Host function (needs Rust logic -- I/O, dictionary manipulation, complex stack access):

let func = Func::new(&mut self.store, func_type.clone(), move |mut caller, _params, _results| {
    // manipulate memory/globals directly
    Ok(())
});
self.register_host_primitive("WORD_NAME", false, func)?;

Special interpreter token (defining words like VARIABLE, CONSTANT, CREATE): Handle in interpret_token_immediate() or compile_token() as a special case.

Code Style

cargo fmt --all and cargo clippy --workspace must pass with no warnings
Every public function needs a doc comment
Use thiserror for error types in core crate, anyhow for CLI
Prefer returning Result over panicking

Testing

Run cargo test --workspace before committing (currently 185 tests)
Forth 2012 compliance: cargo test -p wafer-core --test compliance
Test helper in outer.rs: eval_output("forth code") returns printed output as String
Test helper: eval_stack("forth code") returns data stack as Vec

Key Principles

Correctness first, performance second
Maximize Forth, minimize Rust (self-hosting goal -- not yet started)
Test-driven: if it's not tested, it doesn't work
Every word set at 100% compliance before moving to the next
Never break existing tests

2.6 KiB Raw Blame History