Coming from wazero

wazy started from wazero’s code (Copyright 2020-2023 wazero authors) and still draws on its WebAssembly semantics, WASI implementation, and compliance and fuzzing test suites. It keeps neither wazero’s API compatibility nor its architecture: the goals are pure Go, performance, and conformance to the standard.

The import path

import "github.com/tetratelabs/wazero"
import "github.com/samyfodil/wazy"

The sub-packages line up: api, experimental, sys, imports/wasi_snapshot_preview1.

The one break: host functions

wazero’s WithFunc takes an interface{} and reflects over it on every call. wazy deleted that path rather than optimizing it.

b.NewFunctionBuilder().
  WithFunc(func(ctx context.Context, x, y uint32) uint32 { return x + y }).
  Export("add")

wazy.HostFunc2(b.NewFunctionBuilder(),
  func(ctx context.Context, mod api.Module, x, y uint32) uint32 { return x + y },
).Export("add")

Two differences to note: the typed helpers always take (ctx, mod, …), and the arity is in the name. HostFunc0–HostFunc16 return one result; HostProc0–HostProc16 return none.

WithGoModuleFunction is unchanged and handles everything the typed helpers do not — multiple results, dynamic signatures.

The payoff for the same workload: 1086 ns and 6 allocations → 74.9 ns and 0.

This is the only compatibility break, and it is behind us — the surface has settled since.

What is the same

Runtime, CompileModule, InstantiateModule, ModuleConfig, FSConfig, api.Module, api.Memory, sys.ExitError, CompilationCache, wasi_snapshot_preview1.MustInstantiate — same names, same shapes. A wazero program that does not register host functions with WithFunc usually compiles after changing the import path.

What is new

• The Component Model, WASI 0.2 and the async ABI — the component package and imports/wasip2. Not targets of upstream wazero.
• Core Wasm 3.0 — api.CoreFeaturesV3, all eight folded-in proposals.
• Performance work — see Performance: 9.1x on instantiate, 12–13x on interruptible loops, geomean −17.8% cumulative.

Release cadence

The API is stable; what keeps moving is everything under it. Performance work lands continuously, guarded by the conformance, differential and fuzzing suites rather than by a release cadence. Those same suites judge a contribution, not its author, machine-generated or human.