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WASM Errors

Developers have limited visibility on bb.js errors due to the WASM having the debug symbols stripped out.

We have several tools available to help make it easier to debug and report issues.

Specify WASM​

The environment variable BB_WASM_PATH allows you to replace the WASM that gets loaded into bb.js. You can provide an URL that will "hot swap" the wasm to the debug version in order to get stacktraces. You can see an example of how this is done in the playground here:

bb-wasm-path
// The path to a custom WASM file for bb.js.
// Only the single-threaded file name is needed, the multithreaded file name will be inferred
// by adding the -threads suffix: e.g: /assets/barretenberg.wasm.gz -> /assets/barretenberg-threads.wasm.gz
// Files can be compressed or uncompressed, but must be gzipped if compressed.
BB_WASM_PATH: env.BB_WASM_PATH,
Source code: playground/vite.config.ts#L70-L76

Transaction Profiling​

Transaction profiling combined with serializePrivateExecutionSteps allows devs to generate a msgpack file that can be shared to reproduce issues.

warning

This file may contain private information. This is intended for development and debugging only and should not be exposed to end users. Anyone you share this information with may have access to your secrets, so it is recommended that you do not use sensitive data when developing.

To do this, start by profiling your transaction, getting the execution-steps from the resulting TxProfileResult.

Pass the execution-steps to serializePrivateExecutionSteps from the @aztec/stdlib to get the ivcMessagePack, and download this.

For example:

const profileTx = await tokenInstance.methods
            .transfer_private_to_private(sender, recipient, amount, nonce)
            .profile({ profileMode: "execution-steps" });

const ivcMessagePack = serializePrivateExecutionSteps(profileTx.executionSteps)
const url = window.URL.createObjectURL(new Blob([ivcMessagePack]))

const link = document.createElement("a")
link.href = url
link.download = "ivc-inputs.msgpack"

document.body.appendChild(link)

link.click()