Solc require issue

[farooqahmad075]

When I try to include var solc = require('solc'); in my react app I get an error in chrome console that

Uncaught RangeError: WebAssembly.Compile is disallowed on the main thread, if the buffer size is larger than 4KB. Use WebAssembly.compile, or compile on a worker thread.
    at instantiateSync (soljson.js:1)
    at Object.createWasm [as asm] (soljson.js:1)
    at Object.<anonymous> (soljson.js:1)
    at Object../node_modules/solc/soljson.js (soljson.js:1)
    at __webpack_require__ (bootstrap:785)
    at fn (bootstrap:150)
    at Object../node_modules/solc/index.js (index.js:3)
    at __webpack_require__ (bootstrap:785)
    at fn (bootstrap:150)
    at CompileButton.compile (CompileButton.js:10)
    at HTMLUnknownElement.callCallback (react-dom.development.js:188)
    at Object.invokeGuardedCallbackDev (react-dom.development.js:237)
    at invokeGuardedCallback (react-dom.development.js:292)
    at invokeGuardedCallbackAndCatchFirstError (react-dom.development.js:306)
    at executeDispatch (react-dom.development.js:389)
    at executeDispatchesInOrder (react-dom.development.js:414)
    at executeDispatchesAndRelease (react-dom.development.js:3278)
    at executeDispatchesAndReleaseTopLevel (react-dom.development.js:3287)
    at forEachAccumulated (react-dom.development.js:3259)
    at runEventsInBatch (react-dom.development.js:3304)
    at runExtractedPluginEventsInBatch (react-dom.development.js:3514)
    at handleTopLevel (react-dom.development.js:3558)
    at batchedEventUpdates$1 (react-dom.development.js:21902)
    at batchedEventUpdates (react-dom.development.js:1060)
    at dispatchEventForLegacyPluginEventSystem (react-dom.development.js:3568)
    at attemptToDispatchEvent (react-dom.development.js:4267)
    at dispatchEvent (react-dom.development.js:4189)
    at unstable_runWithPriority (scheduler.development.js:653)
    at runWithPriority$1 (react-dom.development.js:11061)
    at discreteUpdates$1 (react-dom.development.js:21918)
    at discreteUpdates (react-dom.development.js:1071)
    at dispatchDiscreteEvent (react-dom.development.js:4168)

What is causing the issue? or how can I fix using WebAssembly?

[chriseth]

Are you able to move this into a worker process?

[farooqahmad075]

@chriseth when I use

var worker = new Worker("wasm_worker.js");
    fetch('solc').then(response =>
      response.arrayBuffer()
    ).then(bytes =>
      WebAssembly.compile(bytes)
    ).then(mod =>
      worker.postMessage(mod)
    );

it shows another error Uncaught (in promise) CompileError: WebAssembly.compile(): expected magic word 00 61 73 6d, found 3c 21 44 4f @+0

[farooqahmad075]

I am totally frustrated, please help me to require solc for my react web app to add solidity compiler in the web.

[chriseth]

It should be enough to use solc-js inside the worker.js - you should not run WebAssembly.compile yourself.

[Aniket-Engg]

@farooqahmad075 Try to use importScripts https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/importScripts inside worker to fetch solc binaries using url like https://solc-bin.ethereum.org/bin/soljson-v0.6.1+commit.e6f7d5a4.js

[Tectract]

Bump. This affects me too.

Uncaught RangeError: WebAssembly.Compile is disallowed on the main thread, if the buffer size is larger than 4KB. Use WebAssembly.compile, or compile on a worker thread. at instantiateSync (soljson-v0.6.9+commit.3e3065ac.js:1) at Object.createWasm [as asm] (soljson-v0.6.9+commit.3e3065ac.js:1) at soljson-v0.6.9+commit.3e3065ac.js:1 instantiateSync @ soljson-v0.6.9+commit.3e3065ac.js:1 createWasm @ soljson-v0.6.9+commit.3e3065ac.js:1 (anonymous) @ soljson-v0.6.9+commit.3e3065ac.js:1 browser-solc.min.js:5 Uncaught TypeError: b.cwrap is not a function

I have code that uses cwrap, it used to work. Sadly no more.

[chriseth]

@Tectract are you sure that cwrap is not available anymore, even if you compile the webassembly code in a worker process?

[r0qs]

Hi, I'm closing this because, as pointed out here: https://github.com/ethereum/solc-js/issues/581 and by this comment: https://github.com/ethereum/solc-js/issues/456#issuecomment-604649453, it is currently required to use a web worker with solc-js in some browsers (chromium-based).

You can see examples of how to accomplish it here: https://github.com/ethereum/solc-js/issues/456#issuecomment-606045994, and here: https://github.com/ethereum/solc-js/issues/627#issuecomment-1243501953

@Tectract, here is an example of how you could use the cwrap if you need to use it directly (works on firefox). However, this is not the recommended way to use library since the underline function signature may vary between compiler versions.

    <script type="text/javascript" src="https://binaries.soliditylang.org/bin/soljson-v0.8.17+commit.8df45f5f.js"
        integrity="sha256-YXgo5jvkhcfMLby91aIrWCtA+vqkEBatWVY3uDyQZWw=" crossorigin="anonymous">
        </script>
    <script  type="text/javascript">
        const soljson = window.Module;
        let compile = null;
        if ('_solidity_compile' in soljson) {
            compile = soljson.cwrap('solidity_compile', 'string', ['string', 'number']);
        }

        const input = {
            language: 'Solidity',
            sources: {
                'test.sol': {
                    content: 'contract C { function f() public { } }'
                }
            },
            settings: {
                outputSelection: {
                    '*': {
                        '*': ['*']
                    }
                }
            }
        };

        const output = JSON.parse(compile(JSON.stringify(input)))
        // do something with the output
    </script>

[Tectract]

thanks for the reference. I'll take a look at my code again.

[sayhicoelho]

I'm receiving an error ReferenceError: window is not defined when importing solc-js in my worker.js

My worker.js:

import solcjs from 'solc-js'

self.addEventListener('message', async e => {
  const version = 'v0.8.23-stable-2023.11.07'

  const compiler = await solcjs(version)

  const sourceCode = `// SPDX-License-Identifier: MIT

  pragma solidity ^0.8.23;

  import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

  contract Example is ERC20 {
    constructor() ERC20("Example", "EXM") {
        _mint(address(this), 1_000 ** 18);
    }
  }`

  const output = await compiler(sourceCode)

  console.log(output)

  self.postMessage({
    success: true
  })
}, false)