RuntimeError: memory access out of bounds

[chexiongsheng]

how to reproduce:

1. set up a project named test_proj: https://www.assemblyscript.org/quick-start.html
2. add ue.ts to test_proj/assembly

export declare class Vector {
    constructor(InX: number, InY: number, InZ: number);
    get X(): number;
    set X(val:number);
    get Y(): number;
    set Y(val:number);
    get Z(): number;
    set Z(val:number);
    Set(InX: number, InY: number, InZ: number): void;
}

4.edit test_proj/assembly/index.ts

import { Vector } from './ue';

export function add(a: i32, b: i32): i32 {
  return a + b;
}

export function newVector():Vector {
  return new Vector(1, 2, 3);
}

export function passVector(v:Vector) :Vector {
  return v;
}

5.edit test_proj/index.js

const fs = require("fs");
const loader = require("@assemblyscript/loader");

const v_cache = [];
//(import "ue" "log" (func $log (param i32)))
const imports = { "ue" : 
    {
        "Vector#constructor": function(t, x, y, z) {
            v_cache.push({x:x, y:y, z:z});
            return v_cache.length - 1;
        },
        "Vector#Set": function(t, x, y, z) {
            v_cache[t].x = x;
            v_cache[t].y = y;
            v_cache[t].z = z;
        },
        
        "Vector#set:X": function(t, x) {
            v_cache[t].x = x;
        },
        
        "Vector#get:X": function(t) {
            return v_cache[t].x;
        }
    } 
};
const wasmModule = loader.instantiateSync(fs.readFileSync(__dirname + "/build/optimized.wasm"), imports);
module.exports = wasmModule.exports;

5.edit test_proj/tests/index.js

const myModule = require("..");

let v = myModule.newVector();

console.log(`memory: ${myModule.memory.buffer.byteLength}`)

myModule.passVector(v);

6.build & run test,

npm run asbuild
node tests\index.js

ouput

memory: 0
wasm://wasm/db0e9072:1



RuntimeError: memory access out of bounds
    at passVector (<anonymous>:wasm-function[4]:0xe6)
    at Object.curr.<computed> [as passVector] (D:\learn\assembly_script\test_proj\node_modules\@assemblyscript\loader\umd\index.js:545:20)
    at Object.<anonymous> (D:\learn\assembly_script\test_proj\tests\index.js:8:10)
    at Module._compile (internal/modules/cjs/loader.js:1076:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1097:10)
    at Module.load (internal/modules/cjs/loader.js:941:32)
    at Function.Module._load (internal/modules/cjs/loader.js:782:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    at internal/main/run_main_module.js:17:47

if add some code like this in test_proj/assembly/index.ts, problom resolved.

class BBA {
  i : i32
}

export function newBBA() :BBA {
  const r = new BBA();
  r.i = 100;
  return r;
}

[chexiongsheng]

reason
open test_proj\build\optimized.wat
do not alloc memory
(memory $0 0)
but access *__stack_pointer in passVector

if you add a class and new statement with the class, the module will alloc 1 page
(memory $0 1)

[dcodeIO]

Playing around with this I figured that there simply is no static or dynamic memory to be accessed here. As such, the import of the constructor has no way to actually allocate memory, leading to the situation at hand where calling passVector can never succeed since there cannot be a Vector.

Providing the --exportRuntime command line flag to enable the constructor to allocate memory fixes the problem, since now a Vector can exist. Not considering this a bug anymore, but rather seems that tree-shaking is working as intended.

[chexiongsheng]

I trying interact with a existing javascript lib:

• Assemblyscript call external new, actrually allocate a js object.
• Assemblyscript retain the js object through a array keep a reference for assemblyscript
• And If no reference with the js object in assemblyscript , i expect a notify from assemblyscript, to remove js object from the array.

Is there some kind of similar mechanism?

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in one week if no further activity occurs. Thank you for your contributions!