Using JSStream and querying persistents crashes in async_wrap

[thlorenz]

This test crashes:

Assertion failed: (cb_v->IsFunction()), function MakeCallback, file ../src/async-wrap-inl.h, line 66.

It actually crashes the moment it is attempting to log res to the console, not when obtaining it.

cc @trevnorris

[thlorenz]

Here is another problematic case related to JSStream.

This one crashes with a segmentation fault:

➝  node test/not-working/08_jsstream.js
TAP version 13
#
jsstream: wrapping a stream via StreamWrap
ok 1 one JSStream
ok 2 the wrapped stream
Segmentation fault: 11

[thlorenz]

So in these cases accessing the properties of the returned Persistent object causes a crash. I hope it's not related to v8 locking down the heap while walking persistents, i.e. I hope the objects aren't somehow invalid once we inspect them.
It would actually be a good thing if all this is pointing out a bug in async_wrap since we (meaning @trevnorris) could fix that.

[thlorenz]

WRT to checking if persistent is empty, I double checked and we are already doing that and ignoring the empty ones, so not sure what we could fix there.

Currently this blocks us from using this attempt at finding handles because this means that in certain situations querying persistents could crash the process.
One workaround I can think of is to just ignore JSStream persistents even though that's kind of a hack.

I'm gonna dig into this more after writing a test for each of the other providers unless you can figure something out by then @trevnorris.

[trevnorris]

Here's the issue. The handle you've created is only partially setup. There's a getter that hasn't been setup yet, thus aborts from a failed CHECK. These should be fully setup by node before you can touch them. So if you've hit that then the program is in a bad place. IOW it's expected.

[trevnorris]

Issue in OP is fixed by nodejs/node#3282.

[trevnorris]

Patch has landed and will be part of the v4.2 release.

[thlorenz]

Thanks, will test again when nsolid rebased on v4.2 and close this once I confirm that things no longer crash.