Not initializing the WASM module

Oct 13, 2025 by wbrum.org 139 views

Introduction

While working with the Monero wallet, developers may encounter various errors, including the infamous "Invalid UTF-8 leading byte" error. This error can be frustrating, especially when it occurs without any clear indication of the cause. In this article, we will delve into the details of this error, explore its possible causes, and provide a step-by-step guide to reproduce and resolve the issue.

Description

The error occurs when trying to create a transaction using the this.Module.prepareTx method in the WABridge.createTransaction function. The error message indicates that an invalid UTF-8 leading byte (0xba) is encountered when deserializing a UTF-8 string in wasm memory to a JS string.

Steps to Reproduce

To reproduce the issue, follow these steps:

Step 1: Install the required packages

First, install the required packages using npm or yarn:

npm install @mymonero/mymonero-lws-client @mymonero/mymonero-monero-client axios

Step 2: Create a test file

Create a new file called test.js and add the following code:

const axios = require("axios")
const LWSClient = require("@mymonero/mymonero-lws-client")
 
const test = async () => {
    // setting variables here
    PRIVATE_LWS_URL = ""
    PRIMARY_ADDRESS = ""
    PRIVATE_VIEW_KEY = ""
    PRIVATE_SPEND_KEY = ""
    PUBLIC_SPEND_KEY = "" 
 
const httpClient = axios.create({ baseURL: PRIVATE_LWS_URL })
const options = {
    httpClient,
    appName: "MyMonero",
    appVersion: "1.1.25",
}
 
const WABridge = await require("@mymonero/mymonero-monero-client")({})
 
const lwsClient = new LWSClient(options)
 
const unspentOuts = await lwsClient.unspentOutputs(PRIVATE_VIEW_KEY, PRIMARY_ADDRESS)
unspentOuts.per_byte_fee = 30000
 
const txOptions = {
  priority: 1,
  address: PRIMARY_ADDRESS,
  privateViewKey: PRIVATE_VIEW_KEY,
  publicSpendKey: PUBLIC_SPEND_KEY,
  privateSpendKey: PRIVATE_SPEND_KEY,
  shouldSweep: false,
  paymentId: "",
  nettype: "TESTNET",
  unspentOuts,
  async randomOutsCb(numberOfOuts) {
    return await lwsClient.randomOutputs(numberOfOuts)
  }
}
 
const tx = await WABridge.createTransaction({
  ...txOptions,
  destinations: [
    {
      send_amount: "0.1",
      to_address: "9tCWVqKUY9t4886T7196doS9GPMzexD9gXpsZJDwVjeRVdFCSoHnv7KPbBeGpzJBzHRCAs9UxqeoyFQMYbqSWYTfJHdcNjL"
    }
  ]
})
 
console.log(tx)
 
}
test()

Step 3: Run the test file

Run the test file using Node.js:

node test.js

Expected Behavior

The expected behavior is that the transaction creation process should complete successfully, and the transaction object should be logged to the console.

Actual Behavior

However, the actual behavior is that the Invalid UTF-8 leading byte error is thrown, and the transaction creation process fails.

Possible Causes

The possible causes of this error are:

UTF-8 encoding issues: The error may occur due to UTF-8 encoding issues in the JSON.stringify method. This can happen when the input data contains non-ASCII characters or when the encoding is not properly set.
WASM memory issues: The error may also occur due to issues with the WASM memory. This can happen when the WASM module is not properly initialized or when there are memory allocation issues.

Resolving the Issue

To resolve the issue, you can try the following:

Check the input data: Verify that the input data is properly encoded and does not contain any non-ASCII characters.
Set the encoding: Set the encoding to utf8 in the JSON.stringify method to ensure that the data is properly encoded.
Check the WASM module: Verify that the WASM module is properly initialized and that there are no memory allocation issues.
Update the packages: Update the packages to the latest version to ensure that you have the latest fixes and improvements.

Conclusion

Q: What is the Invalid UTF-8 leading byte error?

A: The Invalid UTF-8 leading byte error is a common issue that occurs when trying to create a transaction using the this.Module.prepareTx method in the WABridge.createTransaction function. The error message indicates that an invalid UTF-8 leading byte (0xba) is encountered when deserializing a UTF-8 string in wasm memory to a JS string.

Q: What are the possible causes of this error?

A: The possible causes of this error are:

UTF-8 encoding issues: The error may occur due to UTF-8 encoding issues in the JSON.stringify method. This can happen when the input data contains non-ASCII characters or when the encoding is not properly set.
WASM memory issues: The error may also occur due to issues with the WASM memory. This can happen when the WASM module is not properly initialized or when there are memory allocation issues.

Q: How can I resolve the issue?

A: To resolve the issue, you can try the following:

Check the input data: Verify that the input data is properly encoded and does not contain any non-ASCII characters.
Set the encoding: Set the encoding to utf8 in the JSON.stringify method to ensure that the data is properly encoded.
Check the WASM module: Verify that the WASM module is properly initialized and that there are no memory allocation issues.
Update the packages: Update the packages to the latest version to ensure that you have the latest fixes and improvements.

Q: What are some common mistakes that can lead to this error?

A: Some common mistakes that can lead to this error include:

Using non-ASCII characters: Using non-ASCII characters in the input data can lead to UTF-8 encoding issues.
Not setting the encoding: Not setting the encoding in the JSON.stringify method can lead to UTF-8 encoding issues.
Not initializing the WASM module: Not initializing the WASM module properly can lead to WASM memory issues.
Not updating the packages: Not updating the packages to the latest version can lead to outdated code and potential issues.

Q: How can I prevent this error from occurring in the future?

A: To prevent this error from occurring in the future, you can:

Use ASCII characters only: Use ASCII characters only in the input data to avoid UTF-8 encoding issues.
Set the encoding: Set the encoding to utf8 in the JSON.stringify method to ensure that the data is properly encoded.
Initialize the WASM module properly: Initialize the WASM module properly to avoid WASM memory issues.
Update the packages regularly: Update the packages regularly to ensure that you have the latest fixes and improvements.

Q: What are some additional resources that can help me resolve this issue?

A: Some additional resources that can help you resolve this issue include:

Official documentation: Check the official documentation for the WABridge library for more information on how to use the createTransaction method.
Stack Overflow: Check Stack Overflow for similar questions and answers related to this issue.
GitHub issues: Check the GitHub issues for the WABridge library for similar issues and solutions.
Monero community: Reach out to the Monero community for help and support.