Upgrade to V8 v4.9

[lewispham]

I'm not sure about the reasons behind this delay. It's been a long time since version v4.6. Please give me some information about the next upgrade of V8. I'll appreciate that.

[bnoordhuis]

We expect to ship node.js v6 with V8 5.0. The V8 version in the current stable and LTS branches won't be upgraded because of API/ABI backwards compatibility issues.

[lewispham]

What about the delay? It's just about this upgrade or the strategy has changed? Why doesn't Nodejs upgrade V8 as soons as possible, just like what it used to do?

[bnoordhuis]

We don't upgrade (only bug-fix) in release lines when it would break the API or the ABI, because that forces everyone to recompile (ABI) or rewrite (API) their native add-ons. With V8, that almost always means you're stuck with a particular version because it changes quite a bit between releases.

Why doesn't Nodejs upgrade V8 as soons as possible, just like what it used to do?

Perhaps you mean io.js? Node.js from before the merger was rather infamous for shipping outdated versions from day zero, never mind upgrades.

Take v0.10: it's still using V8 3.14, last update over three years ago. When v0.10.0 was released, that version of V8 had already been abandoned by upstream for a few months.

[lewispham]

Perhaps you mean io.js?

No. I meant the converged version (Nodejs v4+). You can see the change log for more details. It says:

• 2015-09-08, Version 4.0.0 (Stable)
  • v8: Upgrade to version 4.5.103.30 from 4.4.63.30 (Ali Ijaz Sheikh) deps: update v8 to 4.5.103.30 #2632.
• 2015-09-17, Version 4.1.0 (Stable)
  • v8: Lateral upgrade to 4.5.103.33 from 4.5.103.30, contains minor fixes (Ali Ijaz Sheikh) deps: upgrade V8 to 4.5.103.33 #2870.
• 2015-10-05, Version 4.1.2 (Stable)
  • Upgraded from v4.5.103.33 to v4.5.103.35 (Ali Ijaz Sheikh) deps: upgrade V8 to 4.5.103.35 #3117
• 2015-10-29, Version 5.0.0 (Stable)
  • v8: (Breaking) Upgraded to 4.6.85.25 from 4.5.103.35 (Ali Ijaz Sheikh) Land V8 4.6 onto master #3351.
• 2015-11-17, Version 5.1.0 (Stable)
  • [9ef81ff] - deps: update V8 to 4.6.85.31 (Michaël Zasso) deps: update V8 to 4.6.85.31 #3698

It can be clearly seen that there is no V8 upgrade since 2015-11-17. You can do the math then compare it with the others. That's why I filed this issue and asked for a reason.

If you have no idea about the causes of the delay, please reopen this issue.

[cjihrig]

There are a number of V8 related backports after 2015-11-17, but no version updates because, as @bnoordhuis pointed out, they would be breaking changes. We are still updating V8 (for example see #5494), but it won't be in a release until v6 comes out in April. This is part of the LTS schedule.