Node: Possible bug: instanceof evaluates to true in Node 4 but not Node 6

[wprl]

• Version: 6.3.0:
• Platform: Darwin 15.5.0 Darwin Kernel Version 15.5.0: Tue Apr 19 18:36:36 PDT 2016; root:xnu-3248.50.21~8/RELEASE_X86_64 x86_64:
• Subsystem:

In Node 4, the last statement evaluates to true, but in Node 6 it evaluates to false. Is this a bug?

F = () => {};
F.prototype = {};
Object.create(F.prototype) instanceof F;

Another user verified the behavior on their Windows system: http://stackoverflow.com/questions/38253656/instanceof-evaluates-to-true-in-node-4-but-not-node-6

[mscdex]

/cc @nodejs/v8

[mscdex]

I should note that it returns true in master.

[bnoordhuis]

Looks like a bug to me. v7.0.0-pre (V8 5.1) returns true, which is what I would expect.

[Trott]

All Node.js version 6.x releases that I tried returned the surprising false including 6.0.0.

Version 5.12.0 returned true.

So this would seem to be either a bug in the V8 that shipped with Node.js v6.x or (less likely, I imagine, but still possible) a bug in a patch that we are only floating in v6.x. (I'm not even sure there are any that are in 6.x but not in 5.x or current master.)

[fhinkel]

In d8 version 5.0.71.54 it returns false. So not related to floating patches.

[fhinkel]

This is the commit that fixed it: https://codereview.chromium.org/1810953002/

The patch applies clean on v6.x and fixes this issue. Do we want to float the patch on v6.x or just wait because it's fixed in V8 5.1 anyways?

[Trott]

/cc @nodejs/lts Not strictly an LTS question/issue, but I suspect they'll have an opinion on @fhinkel's question.

[MylesBorins]

Another patch was recently back ported to 5.1 by @bnoordhuis

There is going to be a discussion about maintaining lts release streams directly from V8 to avoid floating patches. Aiming for 6 am estwif anyone wants to join.

[bnoordhuis]

I'm all for back-porting patches that apply cleanly or with minimal wedging.

@fhinkel I see you've done the work already. If you file a pull request and cc me, I'll review it.

[fhinkel]

Fixed in https://github.com/nodejs/node/pull/7638.

Can we close this?

[addaleax]

Yup, works as expected in 6.3.1. Thanks for taking care of this!