finalize callback of instance data is not called when error is thrown

[fs-eire]

Version

24.0.2, 22.15.1

Platform

Windows, macOS (linux not tested)

Subsystem

NAPI

What steps will reproduce the bug?

Please check reproduce steps at https://github.com/fs-eire/node-reproduce-instance-cb-not-called

How often does it reproduce? Is there a required condition?

always

What is the expected behavior? Why is that the expected behavior?

finalize callback set by napi_set_instance_data should be always called regardless of whether an uncaught error is thrown. This helps addon to control the lifecycle of native variables.

What do you see instead?

the finalize callback set by napi_set_instance_data is only called when exiting normally. if uncaught error is thrown, it will not be called.

Additional information

See microsoft/onnxruntime#24579 for more details.

[0hmX]

will try to land a PR for this! but will need to investigate;

[fs-eire]

will try to land a PR for this! but will need to investigate;

Thank you! Since it may take a while for the fix to be landed, is there any workaround can be applied?

[mhdawson]

@0hmX thanks for working on this

@fs-eire not sure if it will work, but I wonder if you can add an uncaught exception handler, do some cleanup and then terminate normally and if that might help?

[fs-eire]

you can add an uncaught exception handler

could you please advise how to do this ? I didn't find from N-API documentation.

EDIT: Ah I see. I think you are referring to process.on('uncaughtException', ... This should work for an application but creates new concern for a library to do so.

[fs-eire]

One more thing to mention: napi_add_env_cleanup_hook seems not working in this scenario too. If you are making a change, maybe also fix this.

[johnsonomotunde]

❗ N-API Finalize Callback Not Called on Uncaught Exception

This project reproduces an issue where the finalize callback registered via napi_set_instance_data is not called when the Node.js process exits due to an uncaught exception.

🔁 Reproduction Steps

Install dependencies:

npm ci

Run the test script that throws an error:
bashnode a.js

Observe the output:

TestData constructorC:\code\node-reproduce-instance-cb-not-called\a.js:3
throw new Error('This is a test error')
      ^

Error: This is a test error
    at Object.<anonymous> (C:\code\node-reproduce-instance-cb-not-called\a.js:3:7)

✅ TestData constructor is printed.

❌ TestData destructor is not printed, meaning the finalize callback was never invoked.

Run the normal execution script:
node b.js
Output:
TestData constructor
TestData destructor

This confirms that finalization works only during clean exit.

[0hmX]

This is my initial assessment of the issue. The main problem is that there is no solution to propagate external errors that occur outside of the NodeJS add-on into C++. We will need to build a method that will hook into V8's internal error handling for JS and propagate the error from there!

Would love to get the node API team's thoughts on this! Especially if I am missing something.

[legendecas]

The cleanup hook registered at

node/src/node_api.cc

Line 62 in eaebfab

result->node_env()->AddCleanupHook(

should be ran on every condition a node::Environment destroys. So it will be a bug if this was not ran.

@vmoroz volunteered to take a look on this, thank you!