Compiled code could silently move dsp/rsp/fsp out of their stack
regions (e.g. DROP on an empty stack), corrupting later pushes with
no diagnostic -- the addresses stay inside valid linear memory, so
nothing could trap. Host-side checks cannot catch it.
- Guards are emitted at the sp-adjustment choke points (dsp_inc/
dsp_dec, fsp_inc/fsp_dec, rpush/rpop/rpeek, peek, TwoDup/TwoDrop,
promoted prologue/epilogue -- DROP never loads its value, so
guarding pop() alone is not enough). On fault: write the code to
SYSVAR_FAULT_CODE, call _STACK_FAULT_, which THROWs it -- so
guards are CATCHable and print standard messages (-3/-4/-5/-6/
-44/-45).
- The batch/consolidated compile path (all boot primitives) and the
export path are wired too; a thread-local carries the fault index
into the shared emission helpers.
- Config: codegen.stack_guards, default ON. `wafer build` output
defaults OFF (production artifact); WAFER_STACK_GUARDS=0|1
overrides either. Perf comparison lanes run unguarded.
- Measured overhead in release loops: within noise (never-taken
branches).
- toolstest.fth baseline 37 -> 38: line 368's bare interpreted `R>`
used to underflow silently and count as passing; the guard now
correctly reports -6.
sf64 discovery + stdin runner (no -e flag; input lines truncate at
~256 chars, so one statement per line), ucounter-based µs timing —
same wrapper shape as gforth utime. New sf64 + WAFER/sf columns,
informational only (no regression limit). Justfile: bench-compare
target; CARGO_PROFILE_RELEASE_STRIP=none for Darwin 27 dlopen bug.
Rust 1.95 promoted collapsible_match and map_unwrap_or; CI runs
-D warnings so they break the build. Collapse nested `if`s into
match guards across codegen/optimizer/export, and swap
map().unwrap_or(..) for map_or / is_ok_and.
Decouple ForthVM from wasmtime via a Runtime trait so the same outer
interpreter, compiler, and 200+ word definitions work on both native
(wasmtime) and browser (js-sys WebAssembly API) backends.
Runtime trait (runtime.rs):
- HostAccess trait for memory/global ops inside host function closures
- HostFn type: Box<dyn Fn(&mut dyn HostAccess) -> Result<()>>
- Runtime trait: memory, globals, table, instantiate, call, register
NativeRuntime (runtime_native.rs):
- Wraps wasmtime Engine/Store/Memory/Table/Global/Func
- CallerHostAccess bridges HostAccess to wasmtime Caller API
- Feature-gated behind "native" (default)
outer.rs refactor:
- ForthVM<R: Runtime> — generic over execution backend
- All 87 host functions converted from Func::new closures to HostFn
- All memory access via rt.mem_read/write_*, global access via rt.get/set_*
- Zero logic changes — pure API conversion
wafer-core feature gates:
- default = ["native"] includes wasmtime + all native modules
- Without "native": pure Rust only (outer, codegen, optimizer, dictionary)
Browser REPL (crates/web):
- WebRuntime: js-sys WebAssembly.Memory/Table/Global/Module/Instance
- WaferRepl: wasm-bindgen entry point (evaluate, data_stack, reset)
- WebAssembly.Function with Safari fallback (wrapper module)
- Frontend: dark terminal UI, word panel, init code editor, history
- Build: wasm-pack build --target web
All 452 tests pass (431 unit + 1 benchmark + 9 comparison + 11 compliance).
wasmtime 31→43, wasm-encoder/wasmparser 0.228→0.246, rustyline 15→18.
API migrations: F64Const now takes Ieee64 wrapper, wasmtime has own
Error type (wasmtime::bail! in host closures), cache_config_load_default
removed. Add performance regression limits to benchmark tests.
35 behavioral tests across 8 categories verify identical output between
WAFER and gforth. Performance benchmarks compare execution speed for
Fibonacci, Factorial, GCD, NestedLoops, and Collatz workloads.
WAFER-only correctness tests run in CI without gforth; cross-engine
comparison and performance report are opt-in via --ignored.
Oleksandr Kozachuk
ok2