malcolmstill/zware

---

malcolmstill/zware.json

{
  "createdAt": "2021-02-01T04:27:54Z",
  "defaultBranch": "master",
  "description": "Zig WebAssembly Runtime Engine",
  "fullName": "malcolmstill/zware",
  "homepage": "",
  "language": "Zig",
  "name": "zware",
  "pushedAt": "2025-10-06T17:45:59Z",
  "stargazersCount": 362,
  "topics": [
    "wasm",
    "webassembly",
    "zig",
    "zig-package",
    "ziglang"
  ],
  "updatedAt": "2025-11-17T19:11:15Z",
  "url": "https://github.com/malcolmstill/zware"
}

zware

Zig WebAssembly Runtime Engine

About

zware is a library for executing WebAssembly embedded in Zig programs.

Example

From examples/fib:

const std = @import("std");
const zware = @import("zware");
const Store = zware.Store;
const Module = zware.Module;
const Instance = zware.Instance;
const GeneralPurposeAllocator = std.heap.GeneralPurposeAllocator;
var gpa = GeneralPurposeAllocator(.{}){};

pub fn main() !void {
    defer _ = gpa.deinit();
    const alloc = gpa.allocator();

    const bytes = @embedFile("fib.wasm");

    var store = Store.init(alloc);
    defer store.deinit();

    var module = Module.init(alloc, bytes);
    defer module.deinit();
    try module.decode();

    var instance = Instance.init(alloc, &store, module);
    try instance.instantiate();
    defer instance.deinit();

    const n = 39;
    var in = [1]u64{n};
    var out = [1]u64{0};

    try instance.invoke("fib", in[0..], out[0..], .{});

    const result: i32 = @bitCast(@as(u32, @truncate(out[0])));
    std.debug.print("fib({}) = {}\n", .{ n, result });
}

Requirements

Compile-time

• Zig 0.15.1 (master)

Run-time

• None, zig generates static binaries:

➜  zware git:(master) ✗ ldd fib
        not a dynamic executable

Goals

• Embed WebAssembly programs in other zig programs
• Be fast enough to be useful

Status

• The project is very much alpha quality
• WebAssembly 2.0 supported (apart from the vector / SIMD support which is WIP)
• The WebAssembly official testsuite passes (not including SIMD tests)
• Partial WASI support

Running tests

Use zig build --help to see all the test targets, here’s a summary of the important ones:

zig build test      # Run all the tests (includes unittest and testsuite)
zig build unittest  # Run the library unittests
zig build testsuite # Run all the testsuite tests
zig build test-NAME # Run the NAME testsuite test, i.e. test-type

Does it run doom?

Yes, yes it does

https://github.com/malcolmstill/zware/assets/2567177/c9acdcb2-69e7-495f-b3f1-89cf6b807a43