chromium VS V8

One of the unexpected use of shadow DOMs for me was a document generated for image resource URLs [1], because the HTML standard apparently specifies the exact DOM structure of the generated document except for the `` element [2].

[1] https://github.com/chromium/chromium/blob/f02ca73/third_part...

[2] https://html.spec.whatwg.org/multipage/document-lifecycle.ht...

Recently my favorite open source mouse gestures extension SmartUp Gestures was taken over by some shady entity (with github no longer being updated of course).

I opened Chrome ticket that they should ask to re-enable extension when ownership changes. They just closed the ticket replying with this link:

https://chromium.googlesource.com/chromium/src/+/main/extens...

:(

Hmm. It looks like files with the .lnk or .pif file extension can only be downloaded on a user gesture: https://chromium.googlesource.com/chromium/src/+/39841e54180...

So it can't be done silently. Although, I do wish the type was marked "DANGEROUS" a la dll files.

On Linux, Chromium uses setuid or user namespaces to restrict the access of sandboxed components and seccomp-bpf to reduce the kernel attack surface.

Check out the Chromium docs on this topic: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/l...

You can also disable JIT in Firefox by setting javascript.options.baselinejit to false in about:config, although you won't get CET.

[1] https://github.com/chromium/chromium/blob/12c232c43ce7324d30...

Chromium targets iOS already: https://chromium.googlesource.com/chromium/src/+/main/docs/i...

For the sake of completeness, I've traced the evolution of the notice over time:

From 2008-07-26: "Going incognito doesn't affect the behavior of other people, servers, or software. Be wary of: / • Websites that collect or share information about you / • Internet service providers or employers that track the pages you visit / • Malicious software that tracks your keystrokes in exchange for free smileys / • Surveillance by secret agents / • People standing behind you" (https://chromium.googlesource.com/chromium/src/+/09911bf300f...)

From 2013-12-07: "Going incognito doesn't affect the behavior of other people, servers, software, or people standing behind you." (https://chromium.googlesource.com/chromium/src/+/c5e36c57178...)

From 2013-12-13: "However, you aren't invisible. Going incognito doesn't hide your browsing from your employer, your internet service provider, or the websites you visit." (https://chromium.googlesource.com/chromium/src/+/70821506825...)

From 2014-02-27: "However, you aren't invisible. Going incognito doesn't hide your browsing from your employer, your internet service provider, governments and other sophisticated attackers, or the websites you visit." (https://chromium.googlesource.com/chromium/src/+/ab54bd65701...)

From 2014-04-29: "Going incognito doesn't hide your browsing from your employer, your internet service provider, or the websites you visit." (https://chromium.googlesource.com/chromium/src/+/eb09a62ef40...)

From 2016-01-15: "However, you aren't invisible. Going incognito doesn’t hide your browsing from your employer, your internet service provider, or the websites you visit." (https://chromium.googlesource.com/chromium/src/+/b7dac1a6a79...)

From 2017-02-27: "Your activity might still be visible to: / • Websites you visit / • Your employer / • Your internet service provider" (https://chromium.googlesource.com/chromium/src/+/cfe102adddc...)

From 2017-03-29: "Your activity might still be visible to: / • Websites you visit / • Your employer or school / • Your internet service provider" (https://chromium.googlesource.com/chromium/src/+/7ca3ccf74e8...)

(Note that some of these were behind a feature flag for a few months.) Also, it looks like they've been intending to modify the new-tab page text for Incognito windows for some time, as part of the "Revamped Incognito NTP" project. You can view the modified text with 'chromium --enable-features=IncognitoNtpRevamp':

From 2021-08-13: "What Incognito doesn't do / Incognito does not make you invisible online: / • Sites know when you visit them / • Employers or schools can track browsing activity / • Internet service providers may monitor web traffic" (https://chromium.googlesource.com/chromium/src/+/e6ae57ba385...)

From 2022-01-25: "What Incognito doesn't do / Incognito does not make you invisible online: / • Sites and the services they use can see visits / • Employers or schools can track browsing activity / • Internet service providers can monitor web traffic" (https://chromium.googlesource.com/chromium/src/+/8b349f6c984...)

Blink can now be compiled for iOS, but without JIT or WASM:

https://chromium.googlesource.com/chromium/src/+/main/docs/i...

https://bugs.chromium.org/p/chromium/issues/detail?id=141170...

I think its weird that Vercel has this limit. There is no practical reason I can think of for having such a limit on URL characters that is so small. Chrome suggests a 2MB limit[0] for example. The platform itself doesn't have one, and Firefox I believe if memory serves (I can't find the source for this claim atm) is 1 MB effectively, and I don't think Safari is any lower than that either (and may well be more inline with Chrome on this, at 2 MB)

[0]: https://chromium.googlesource.com/chromium/src/+/master/docs...

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.

Remember that we earlier established that every source gets parsed into an AST at some point before it gets compiled or interpreted. For example, platforms like Nodejs and chromium-based browsers use Gooogle's V8 engine behind the scenes to run JavaScript and of course, some AST parsing is always involved before the interpreter kicks in. I looked V8's source and I discovered it uses its own internal parser to achieve this.

In the source code of the Node.js opensource project, lib folder contains JavaScript code, mostly wrappers over C++ and function definitions. On the contrary, src folder contains C++ implementations of the functions, which pulls dependencies from the V8 project, the libuv project, the zlib project, the llhttp project, and many more - which are all placed at the deps folder.

Here is the implementation of of Array. prototype.map in V8. It's written in a language called Torque which appears to be a special language just for the v8 engine.

It sounds like you want to know how JavaScript is implemented in the browser. The thing is, there is no universal implementation for JavaScript. JavaScript defines a specification that must be adhered to, and then each browser vendor can implement it in whatever way they see fit, as long as it does the specified things. For example (and I'm not saying this is the case) it's entirely possible for Chrome to implement Array.sort() using merge sort, while Firefox implements it as quick sort. You can try to find the source code for the implementation in a certain browser, but that will not be universal. I imagine you can find out how it works in Chrome somewhere in https://chromium.googlesource.com/v8/v8.git, though I'm not sure exactly where.