Passing Instance through an Object Literal Causes a runtime error on exit

[torch2424]

Hello!

So I noticed another thing weird with Object literals. If I try to pass a class into my init object, to construct my other class. Everything works fine, but when everything is done, the runtime will throw a memory error.

Here is the test case code:

import {Console} from "as-wasi";

class OtherClass {
  stuff: i32;

  constructor(newStuff: i32) {
    this.stuff = newStuff;
  }
}

class MyClassInit {
  otherClass: OtherClass;
}

class MyClass {
  _myParam: i32;
  _otherClass: OtherClass;

  constructor(param: i32, init: MyClassInit) {
    this._myParam = param;
    this._otherClass = init.otherClass;
  }

  toString(): string {
    return this._otherClass.stuff.toString();
  }
}

export function _start(): void {

  // Make our Other class
  let otherClass = new OtherClass(24);

  // Pass to my class as an object literal
  let myClass = new MyClass(2424, {
    otherClass: otherClass
  });

  // This will all work
  Console.log("Logging myClass.toString() ...\n");
  Console.log(myClass.toString());
  Console.log("\n");

  // Will Error on Exit
  // ~lib/rt/pure.ts:122:13: error: null
}

Here is a reproducable test case: https://github.com/torch2424/as-playground/tree/master/object-literal-pass-instance

cc @dcodeIO or @MaxGraey , if you can point me to where this would be fixed in the compiler (would this object literal be fixed in the same place as #1229 ), I can make this fix 😄

Screenshot

[dcodeIO]

Translated your example to this test case:

class OtherClass {
  stuff: i32;

  constructor(newStuff: i32) {
    this.stuff = newStuff;
  }
}

class MyClassInit {
  otherClass: OtherClass;
}

class MyClass {
  _myParam: i32;
  _otherClass: OtherClass;

  constructor(param: i32, init: MyClassInit) {
    this._myParam = param;
    this._otherClass = init.otherClass;
  }

  toString(): string {
    return this._otherClass.stuff.toString();
  }
}

function start(): void {

  // Make our Other class
  let otherClass = new OtherClass(24);

  // Pass to my class as an object literal
  let myClass = new MyClass(2424, {
    otherClass: otherClass
  });

  trace("Logging myClass.toString() ...");
  trace(myClass.toString());
}
start();

Running this on master, with rtrace enabled, doesn't show any problems. Might this have been fixed since the last release?

[MaxGraey]

Hmm, I don't see any issues in browser (--debug flag turned on):
https://webassembly.studio/?f=xioif2ne2k

It could be problem with wasmtime or as-wasi and Console

[MaxGraey]

@dcodeIO I guess need test with node.js and as-wasi for reproduce full picture.
Also could you check this function?

[MaxGraey]

@torch2424 btw you use pretty old assemblyscript version in your playground: https://github.com/torch2424/as-playground/blob/master/object-literal-pass-instance/package-lock.json#L12

[dcodeIO]

  writeStringLn(s: string): void {
    let s_utf8_buf = String.UTF8.encode(s); // __retain
    let s_utf8_len: usize = s_utf8_buf.byteLength;
    let iov = changetype<ArrayBufferView>(mem256).dataStart;
    store<u32>(iov, changetype<usize>(s_utf8_buf)); // mem256 = [s_utf8_buf]
    store<u32>(iov, s_utf8_len, sizeof<usize>()); // mem256 = [s_utf8_buf, s_utf8_len]
    let lf = changetype<ArrayBufferView>(mem64).dataStart;
    store<u8>(lf, 10); // mem64 = [10]
    store<u32>(iov, lf, sizeof<usize>() * 2); // mem256 = [s_utf8_buf, s_utf8_len, lf]
    store<u32>(iov,  1, sizeof<usize>() * 3); // mem256 = [s_utf8_buf, s_utf8_len, lf, 1]
    let written_ptr = changetype<ArrayBufferView>(mem64).dataStart;
    fd_write(this.rawfd, iov, 2, written_ptr);
    // ^ writes to mem64 at 0 (undefined behavior)
    // __release(s_utf8_buf)
  }

Looks fine from a runtime perspective, with the UB depending on the implementation of fd_write but even then not affecting the runtime.

[torch2424]

Oh Wow that was fast haha! 😄 Thanks y'all!

@dcodeIO

Translated your example to this test case: ... Running this on master, with rtrace enabled, doesn't show any problems. Might this have been fixed since the last release?

So I tried installing the latest master with my example and it didn't work 😢

@MaxGraey

btw you use pretty old assemblyscript version in your playground: https://github.com/torch2424/as-playground/blob/master/object-literal-pass-instance/package-lock.json#L12

Two minors is old? 😂 But thanks for catching that! I updated to 0.9.4 and still no dice 😢

It could be problem with wasmtime or as-wasi and Console

So I replaced out as-wasi and the console logging and it didn't work:

So It may be an issue with Wasmtime? Though, I originally found this bug running AS on Lucet 🤔

@dcodeIO

Looks fine from a runtime perspective, with the UB depending on the implementation of fd_write but even then not affecting the runtime.

I think your responding to Max here, but just in case: I don't think there's anything wrong with the Logging. Because I can totally add some more logs after my testing logs, or do whatever I need to do, and it's fine. I think we may have some dangling memory or something weird after the _start ends? 🤔

[dcodeIO]

In my test, what might have happened is that since I'm not importing as-wasi, static memory contents differ in a way that the bug does not show. Will try to replicate it more closely.

[dcodeIO]

Tried to compile your exact snippet using as-wasi from Git and AS master, but that doesn't compile due to

ERROR AS231: A class with a constructor explicitly returning something else than 'this' must be '@final'.

 export class Descriptor {
              ~~~~~~~~~~
 in ~lib/as-wasi/as-wasi.ts(91,14)

Are you sure you tried with master? I think you should have seen that error as well then.

[dcodeIO]

Updating the snippet to AS 0.10.0 (incl. adding @final to Descriptor)

import "wasi";
import {Console} from "as-wasi";

class OtherClass {
  stuff: i32;

  constructor(newStuff: i32) {
    this.stuff = newStuff;
  }
}

class MyClassInit {
  otherClass: OtherClass;
}

class MyClass {
  _myParam: i32;
  _otherClass: OtherClass;

  constructor(param: i32, init: MyClassInit) {
    this._myParam = param;
    this._otherClass = init.otherClass;
  }

  toString(): string {
    return this._otherClass.stuff.toString();
  }
}

// Make our Other class
let otherClass = new OtherClass(24);

// Pass to my class as an object literal
let myClass = new MyClass(2424, {
  otherClass: otherClass
});

Console.log("Logging myClass.toString() ...\n");
Console.log(myClass.toString());
Console.log("\n");

compiling with

asc assembly/index.ts -b build/optimized.wasm -t build/optimized.wat --runtime half --explicitStart

and then running it in wasmtime v0.16.0

wasmtime build/optimized.wasm

seems to work:

Logging myClass.toString() ...

24

[torch2424]

@dcodeIO

Tried to compile your exact snippet using as-wasi from Git and AS master, but that doesn't compile due to

Oh huh :o I installed from git using like the syntax of:

npm install --save https://git.assemblyscript ....

Maybe that doesn't install master for you? 🤔

Updating the snippet to AS 0.10.0 (incl. adding @Final to Descriptor)

Just tested this, and yep, 0.10.0 fixes this issue! 😄 👍 Thanks very much for making the release that fixed this by proxy haha! 😄 😂

Closing this...