Node.js 12 - V8 version roadmap

[hashseed]

From available release dates for both Node.js and Chromium/V8, we deduce the plan for upgrading V8:

Node.js 12 initial release: 2019-04-23
V8 stable version at that date: 7.4

Node.js 12 LTS start: 2019-10-XX
V8 stable version at that date: 7.7 or 7.8

So at the time of the initial release, we will use V8 7.4, but with a floating patch to be forward-compatible with 7.5. We will then upgrade to 7.5 when it becomes stable. We will later upgrade to 7.6 with a floating patch to be backward-compatible with 7.5.

We stop at 7.6.

So the V8 team will be extra careful between 7.4 and 7.6 wrt ABI stability. Any feature Node.js needs V8 to implement for Node.js 12 will need to land in 7.6 or earlier.

@psmarshall @targos @nodejs/v8-update

[targos]

Isn't off by one version? What I read in the Chromium schedule is that 7.5 will be stable on June 4th, 2019.

[hashseed]

You are right! I read from the wrong table :)

Fixed.

[hassan-dev]

From available release dates for both Node.js and Chromium/V8, we deduce the plan for upgrading V8:

Node.js 12 initial release: 2019-04-23
V8 stable version at that date: 7.4

Node.js 12 LTS start: 2019-10-XX
V8 stable version at that date: 7.7 or 7.8

So at the time of the initial release, we will use V8 7.4, but with a floating patch to be forward-compatible with 7.5. We will then upgrade to 7.5 when it becomes stable. We will later upgrade to 7.6 with a floating patch to be backward-compatible with 7.5.

We stop at 7.6.

So the V8 team will be extra careful between 7.4 and 7.6 wrt ABI stability. Any feature Node.js needs V8 to implement for Node.js 12 will need to land in 7.6 or earlier.

@psmarshall @targos @nodejs/v8-update

cool

[targos]

@hashseed You told me a few months ago that V8 would like to bump the C++ compiler requirement to full C++14 support. It means that Node.js must bump GCC to at least version 5 (we currently support >= 4.9.4).
In yesterday's TSC meeting, concerns were raised that it might be difficult to adapt the build infrastructure for that change before the release of Node 12.
Do you have an idea about which version of V8 would really require full C++14 support? Can we assume that 7.6 will be safe and make the build changes for Node 13 (so, that would be V8 7.7 or 7.8)?

[targos]

Ping @hashseed ^

[hashseed]

The toolchain we test with already supports C++14 if I'm not mistaken, so during development it won't be easy to detect those issues. That said, if they do occur, we can certainly roll offending changes back or work around Node.js' limitations.

[richardlau]

From available release dates for both Node.js and Chromium/V8, we deduce the plan for upgrading V8:

Node.js 12 initial release: 2019-04-23
V8 stable version at that date: 7.4

Not sure if the dates have slipped since this was first posted, but the current https://www.chromium.org/developers/calendar has V8 7.4 estimated going stable in the week of 23 April 2019:

This doesn't seem to line up neatly with the Node.js 12 plan (nodejs/Release#417) -- For example we're aiming to have release candidates from March 23rd so this either means we need to merge V8 7.4 into the Node.js 12 proposal branch before it goes stable or we drop it in at the very last moment which does not sound like a good idea to me.

cc @nodejs/release @BethGriggs

[targos]

I am in favor of merging V8 7.4 before it's stable. But we would need the API compat patch with 7.5 very soon.

[addaleax]

@targos Hey! If you want, I can look into preparing a V8-7.4-to-V8-master compatibility patch today?

[hashseed]

Please loop in @psmarshall!