V8 VS ChakraCore

V8 GitHub Repository

It's a bit hard to do comparisons without going into threat models and all that _fun_ stuff :shrug:

For example, JS runs in almost every browser on earth too, yet it took V8 devs 2 years to find out that `Math.expm1()` could return -0.0 (https://chromium.googlesource.com/v8/v8.git/+/56f7dda67fdc97...). This is a cherry-picked example, and JS is clearly more complex than WASM, but still.

Just because stuff runs on a lot of devices doesn't mean it's more or less secure.

Linux runs on quite a few devices too, yet we still find bugs, people still don't ship updates to said bugs, yadda yadda yadda.

My point is just that lots of devs often skip the threat modeling and just think "I'll slap it in a WASM thingie an it'll be fine". Well good luck.

Much of the standard library in v8 is written in Torque, a custom language.

https://v8.dev/docs/torque

Example file for array.find(…): https://github.com/v8/v8/blob/5fe0aa3bc79c0a9d3ad546b79211f0...

V8 Docs || V8 Github || Chrome University 2018: Life Of A Script If you like the post then follow me for more and subscribe on youtube Dev Studio

Thank god!

Presumably this new API will fix the fact that JS does in fact know about some time zones, but not most.

Shield your eyes from this monstrosity that will successfully parse some dates using `new Date()` in some select special time zones, but assume UTC in the other cases:

https://github.com/v8/v8/blob/781c20568240a1e59edcf0cb5d713a...

And that happened in 2021.

https://chromium.googlesource.com/v8/v8.git/+/HEAD/include/c...

Due to the nature of web engine workloads migrating objects to being GC'd isn't performance negative (as most people would expect). With care it can often end up performance positive.

There are a few tricks that Oilpan can apply. Concurrent tracing helps a lot (e.g. instead of incrementing/decrementing refs, you can trace on a different thread), in addition when destructing objects, the destructors typically become trivial meaning the object can just be dropped from memory. Both these free up main thread time. (The tradeoff with concurrent tracing is that you need atomic barriers when assigning pointers which needs care).

This is on top of the safey improvements you gain from being GC'd vs. smart pointers, etc.

One major tradeoff that UAF bugs become more difficult to fix, as you are just accessing objects which "should" be dead.

> If that standard library would be written in JS, a new browser (or rather a new JS engine being a part of the browser) could just use some existing implementation

That sounds great, but I'm doubtful of the simplicity behind this approach.

If my understanding is correct, v8 has transitioned to C++[0] and Torque[1] code to implement the standard library, as opposed to running hard-coded JavaScript on setting up a new context.

I suspect this decision was made as a performance optimization, as there would obviously be a non-zero cost to parsing arbitrary JavaScript. Therefore, I doubt a JavaScript-based standard library would be an acceptable solution here.

[0]: https://github.com/v8/v8/tree/main/src/runtime

C++ lets you write anything you can imagine, and the language features and standard library often facilitate that. The committee espouses the view that they want to provide many "zero [runtime] cost," abstractions. Anybody can contribute to the language, although the committee process is often slow and can be political, each release the surface area and capability of the language gets larger.

I believe Hazard Pointers are slated for C++26, and these will add a form "free later, but not quite garbage collection" to the language. There was a talk this year about using hazard pointers to implement a much faster std::shared_ptr.

It's a language with incredible depth because so many different paradigms have been implemented in it, but also has many pitfalls for new and old users because there are many different ways of solving the same problem.

I feel that in C++, more than any other language, you need to know the actual implementation under the hood to use it effectively. This means knowing not just what the language specifies, but can occaissionally require knowing what GCC or Clang generate on your particular hardware.

Many garbage collected languages are written in or have parts of their implementations in C++. See JS (https://github.com/v8/v8)and Java GC (https://github.com/openjdk/jdk/tree/36de19d4622e38b6c00644b0...)

I am not an expert on Java (or C++), so if someone knows better or can add more please correct me.

Edge’s Chakra~ Edge has recently embraced Chromium‘s V8 engine.

Edge’s Chakra

nvs : propose un interpréteur plus évolué et la possibilité de choisir également ChakraCore.