`CheckStackSize` error with default `operand_stack_size`

[mgord9518]

When running my test, the main file will crash with a CheckStackSize error. If I raise the operand_stack_size to 2048, it appears to fix the issue, but I don't know very much about WASM and I'm not sure if this is actually a good solution.

Stranger yet, when the WASM file is built in any release mode, the issue doesn't happen.

In order to run the test, a couple of the wasi implementation files in this repo have to be updated to 0.12.0, but they're all very small changes (like math.absCast to @abs)

This is the test file built to wasm32-wasi:

const std = @import("std");

pub fn main() !void {
    std.debug.print("All your {s} codebase are belong to us.\n", .{"ligma"});

    const stdout_file = std.io.getStdOut().writer();
    var bw = std.io.bufferedWriter(stdout_file);
    const stdout = bw.writer();

    var i: usize = 0;
    while (i < 100) : (i += 1) {
        try stdout.print("{d}\n", .{i});
    }

    try bw.flush();
}

And the program that loads it:

const std = @import("std");
const posix = std.posix;
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 initHostFunctions(store: *zware.Store) !void {
    try store.exposeHostFunction("wasi_snapshot_preview1", "proc_exit", zware.wasi.proc_exit, &[_]zware.ValType{.I32}, &[_]zware.ValType{});
    try store.exposeHostFunction("wasi_snapshot_preview1", "fd_write", zware.wasi.fd_write, &[_]zware.ValType{ .I32, .I32, .I32, .I32 }, &[_]zware.ValType{.I32});
    try store.exposeHostFunction("wasi_snapshot_preview1", "args_get", zware.wasi.args_get, &[_]zware.ValType{ .I32, .I32 }, &[_]zware.ValType{.I32});
    try store.exposeHostFunction("wasi_snapshot_preview1", "args_sizes_get", zware.wasi.args_sizes_get, &[_]zware.ValType{ .I32, .I32 }, &[_]zware.ValType{.I32});
}

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

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

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

    try initHostFunctions(&store);

    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();

    var in = [0]u64{};
    var out = [0]u64{};

    try instance.addWasiPreopen(0, "stdin", posix.STDIN_FILENO);
    try instance.addWasiPreopen(0, "stdout", posix.STDOUT_FILENO);
    try instance.addWasiPreopen(0, "stderr", posix.STDERR_FILENO);

    try instance.invoke("_start", in[0..], out[0..], .{
        //.operand_stack_size = 2048,
    });
}

[malcolmstill]

Hi @mgord9518,

When running my test, the main file will crash with a CheckStackSize error. If I raise the operand_stack_size to 2048, it appears to fix the issue,

That's interesting, from the posted code I wouldn't have expected particularly deep stack usage. I will say the default of 1024 was chosen without too much thought, maybe the default should just be higher.

Stranger yet, when the WASM file is built in any release mode, the issue doesn't happen.

This wouldn't surprise me too much...by the time you've optimised code there's a good chance the stack usage will not be the same and indeed I'd expect the stack usage to generally go down.

In order to run the test, a couple of the wasi implementation files in this repo have to be updated to 0.12.0, but they're all very small changes (like math.absCast to @abs)

Would you fancy putting in a PR for that? If not I can do it. It would also be good to get the wasi stuff hooked up to some sort of test.

Thanks for raising the issue!

[mgord9518]

@malcolmstill I sent one in, it doesn't have any tests yet but I did add referenceAllDecls, which should hopefully create errors even if a project doesn't reference all of the WASI functions

[malcolmstill]

@mgord9518 great thanks, it's now merged.