async_hooks: async hook stack corruption when exception prevents AsyncResource.emitAfter being called. #16156
Description
- Version: 8.2.1, 8.7
- Platform:
- Subsystem: async_hooks
According to async_hooks docs,
If the user's callback throws an exception, emitAfter() will automatically be called for all asyncIds on the stack if the error is handled by a domain or 'uncaughtException' handler.
However, this doesn't seem to work in practice. If I set up a simple AsyncResource to bind a function to its own execution context,
class BoundFunction extends asyncHooks.AsyncResource {
constructor(f) {
super('BOUND_FUNCTION');
this.f = f;
}
run() {
this.emitBefore();
f();
this.emitAfter();
}
}and use it like
const f = () => {
throw new Error('uh ho');
};
const boundF = new BoundFunction(f);
process.nextTick( () => {
try {
boundF.run();
} catch (e) {
console.log('nothing to worry about');
}
});Then I get the following output from node:
$ node src/demonstration.js
nothing to worry about
Error: async hook stack has become corrupted (actual: 5, expected: 6)
1: node::AsyncWrap::PopAsyncIds(v8::FunctionCallbackInfo<v8::Value> const&) [node]
2: v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&)) [node]
3: 0xb8f43c [node]
4: v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*) [node]
5: 0x3aa19890463d
This happens even if I set up handlers for uncaught exceptions and rejections:
process.on('uncaughtException', (e) => { console.log('no worries'); });
process.on('unhandledRejection', (e) => { console.log('relax bro'); });If I change BoundFunction#run to look like
run() {
this.emitBefore();
try {
f();
} finally {
this.emitAfter();
}
}the error goes away. I am fine with my handler looking like that, but it's a bit confusing that the docs seem to say that it shouldn't be required.