Loading WASM modules change the NodeJS unhandled-promise-rejection behavior

[yllan]

Hi.

I don't even know if this is actually an emscripten bug or node's bug. Just observed some strange behavior.

If I load a wasm module compiled by emscripten in NodeJS 12, the unhandled-promise-rejection behavior is changed: if I comment out line 2, the unhandled-promise-rejection will not terminate the node. However, if I uncomment line 2, it immediately crash the node.

Here's a demonstration project:
https://github.com/yllan/unhandled-promise-rejection/

[yllan]

OK. I've found that's because this line:

  process['on']('uncaughtException', function(ex) {
    // suppress ExitStatus exceptions from showing an error
    if (!(ex instanceof ExitStatus)) {
      throw ex;
    }
  });

  process['on']('unhandledRejection', abort);

But why? What will happened if I delete these handler?

[sbc100]

Some version of node will just exit with 0 in this case. I believe we had issues where failures in testing were going unnoticed because tests returning 0 is signal of success.

It could be that recent versions of node have fixed that.. i seem to remember them promising they would do that.

In the mean time I think you can build with -s NODEJS_CATCH_REJECTION=0 to fix this no?

[yllan]

Thanks. It works.