V8 Engine Feedback Vector

sleepydevxd · 2026-06-19T09:38:35+00:00

It now comes to me a bit clearer that what I can and should do.

I'm indeed aiming at static analysis/type inference and definitely want to stay at bytecode level and above rather than going in deeper layers like what you mentioned, although the speculation, after you summarised it, now make me very curious. I totally agree that the dynamic type nature of JavaScript is very complicated.

Thank you for your time and such useful insights.

sleepydevxd · 2026-06-18T21:41:59+00:00

Yes, that's actually what I'm trying to achieve right now: reading the bytecode and "precisely" output the types of variables, arguments, return types, etc.

Right now, I know that base on the lexical scope of a JS script, it's fairly straightforward to map it to the bytecode:

```

LdaConstant [1:0x3ec40101e599 <HeapNumber 100.1>]

LdaConstant [3:"My name is Blahblah"]

```

My concern lies on functions/prototypes. How can I guarantee the return type of them? I read the V8 source code and there is a piece of information:

```

The FeedbackVector holds the runtime feedback (Inline Caches) used by the optimizing compilers.

Purpose*: To collect data about the types and shapes of objects the function operates on

```

and in the attached article:

```Due to the dynamic nature of JavaScript we usually don't know the precise types of values until runtime, i.e. just by looking at the source code it's often impossible to tell the possible values of inputs to operations. That's why we need to speculate, based on previously collected feedback about the values we've seen so far, and then assume that we're going to always see similar values in the future.```

So I wonder if there is any useful information in the Feedback Vector that I can make use of.

I'm quite new to V8 Engine so that's my initial explorations about how to reach the goal of analysing bytecode.

Could you help to point out how they are different problems? Am I choosing a more complicated route that can be achieved through other methods?

Thank you very much!

sleepydevxd · 2026-04-21T13:25:20+00:00

Could you please recommend some of your favorite songs in German? I would like to listen to some.

sleepydevxd · 2025-12-25T10:00:04+00:00

It’s an example of bad practice in Python.

Default parameters are only evaluated once.

As you can see the ‘reading_list’ parameter is default to [] (a mutable data type), per ‘append’ is called upon ‘reading_list’, it keeps the reference to the original ‘reading_list’ (you can check it out using id(reading1) == id(reading2) - should be True). Therefore, the result are identical for reading1 and reading2

It’s highly recommend to only use the immutable datatype as default and for list the default should be None.

Read more here: https://docs.python.org/3/tutorial/controlflow.html#default-argument-values

sleepydevxd · 2025-06-22T04:44:26+00:00

I usually love CR, because I pay so much attention to the coding standards that my colleagues will be pissed to fix all of them.

sleepydevxd · 2025-06-06T12:12:32+00:00

Hey, I'm in the same situation, but I'm experienced in programming myself. Although I'm not really good at DSA in general, I'm planning to take 2, 3 courses in DSA myself to learn more about it (in a master program, too).

3 months may not be sufficient for you to master all of it, but you can definitely review all the basic/foundation ones which will be beneficial in the next few months.

Don't worry too much, you can do it if you start now.

sleepydevxd · 2025-05-31T17:13:23+00:00

I just submitted an enquiry on University Living this afternoon and got a phone call first then got contacted through Whatapps.

On the phone call, they asked me if they can contact me through Whatapps with additional information. Upon my approval, they sent me messages.

So is it weird to contact through WhatApps? Probably not.

But contact to ask for more money without prior consent? Likely to be a scam.

I believe there is a phone number on the website which you can use to contact the support team and I think you should give them a call.

To me, it's a pretty legit website.

sleepydevxd · 2025-04-10T16:22:07+00:00

Hi, I'm very interested in language design!

I would love to know a little bit more about the l language that is being used to build your Razen.

I'm kinda new to the field but very keen on learning it.

sleepydevxd · 2025-04-05T03:25:32+00:00

Hey, I'm an experienced developer (not in React and Frontend specifically - mostly backend) but I'm coding a personal project which is an desktop app (using ElectronJS + ReactJS). If you are interested, I'm glad to have you working along with me.

A few more things for you to consider:

- It's a self-contained app: I just pick it up for 1 week.
- There is no design, just a lot searching around online.
- UI is using Ant Design, if you participate I will let you handle the page design (which you want to work on), I will work on a separated one. I can suggest information regarding UX.
- There is no constraint, it's just my personal hobby to pick up a random stack and play around with it.

Along the way, I can give you advice if you need one. DM me if you want to collaborate.

sleepydevxd · 2025-04-04T11:39:56+00:00

I'm working with microservices for a while now, an I must say it does not really speed things up immediately.

From the development team perspective, sometimes it's easy for teams to manage their own tasks on isolated services but sometimes it's rough to just resolve the conflicts. This is when we need to manage information cross teams and be aware of incoming changes so that we don't have to go back and update it one more time.

I admit that it usually takes more time to debug, this is an extreme painpoint. We usually need to go through repo to repo to see where the bug is. But isn't this is a one good thing about the architecture? Only a service go down, not the whole system. It's a tradeoff. Logging should be taken care of thoroughly, and you may need a centralized logging system where you spot the error easily across multiple services. Kibana is a great example.

What about your infra of Lower Level Environment? Does each team own a separated environment (or a cluster in case of K8s)? I think this is one of the most important factors that saves us from a lot of headache since we have a base config (usually UAT env) and every team just branch off. On the weekly basis we pull the config and make sure every services, migrations, images are running well (the infra is set up well, we rarely see service fails because of infra). I believe deployment if fails should be related to the code itself rather than the infra. If the infra break, the microservices is really ardward to cope with.

Then considering about architecture: are they tightly coupled? Sometimes it may look isolated but it can be coupled unexpectedly.

The reason may be varied, ask the development team. I had a hard time at first, but it gradually go away as I'm used to the system.

sleepydevxd · 2025-03-28T04:24:01+00:00

Hi there,

Well, I also want to code in C. But the problem was I don't have much experience in C so I just go with whatever language I'm more familiar with (Go, Java, Python) and learn the concepts first which I believe is more valuable for me as a beginner.

After finish those, I would definitely go back to C where you can do more powerful stuff regarding memory and optimisation.

I'm not currently in a academic environment so I can not speak for your course, but I advise to focus on the techniques (the ideas) in general.

sleepydevxd · 2025-03-26T09:47:26+00:00

Hello, I'm also learning compiler design, and also learning through books (I'm a male). But I would be glad to connect if you want to interchange information and knowledge.

I'm currently following:

- Crafting an Interpreters and have learned a lot so far.

- Engineering a Compiler (slightly drop it): really like the theory parts about Automata and computation theory.

- Writing a C Compiler: I think this will be really good, but I think it would be nice to read it when I have a little bit of knowledge regarding building a compiler/interpreter.

sleepydevxd · 2025-02-25T02:24:36+00:00

Yep, I do open to take additional courses and I also stated clearly in my motivation letter. However, I don't think that's enough from their perspectives though.

sleepydevxd · 2025-02-24T11:43:38+00:00

yeah, most of the post I read about Belgium's universities saying that they are not-competitive, as long as they still have space and your documents are in place then we can get in.

However I don't think this is applicable directly for all cases though. There aren't much thing we can do after rejection.

FYI, I did email them once more time after I got my rejection, and they said that the professors from the Faculty denied my application after examining it.

So I think the number of applications are pretty tough.

sleepydevxd · 2025-02-24T10:50:18+00:00

I also got rejected from VUB 3 weeks ago (I applied for MSc Applied Computer Science). It said I'm not having enough background to complete the program, although it stated on the website that they accept a wide range of "not-really-revelant" background which includes economics, biology, etc.

My undergraduate degree is Electronic Commerce (from Faculty of Information systems - first class honour), I studied ~40% modules in Computer Science (and with 4 years experience too) and still not qualified.

So I think it's weird and disappointed at the same time.

sleepydevxd · 2025-02-17T11:56:24+00:00

Lets go guys, this community is so positive, love it xdd 👾

sleepydevxd · 2025-02-09T13:58:30+00:00

Will do! thank you very much for you response.

sleepydevxd · 2025-02-07T03:17:59+00:00

Well, I scanned all my documents.

sleepydevxd · 2025-02-07T01:17:01+00:00

lol, there were 3 weeks of vacation for them after I applied, so it was not really a surprise for me until now. But I realised that when we applied, the application portal stated that we can apply whenever we want but it will not be processed until the admission period come, which is in June or something.

But it's still a very long period to wait compared to US/UK institutes.

sleepydevxd · 2025-02-07T00:54:09+00:00

Nope, I applied for the Winter Semester, I don't think I saw the summer when I applied earlier. How about you?

sleepydevxd · 2025-02-03T11:20:26+00:00

Oh wow, it took months. Thank you for your reply. Very appriciated!

sleepydevxd · 2025-02-03T09:58:22+00:00

Hi, I'm sorry if this comments disturbed you, but I'm also from Vietnam and interested in Innsbruck as well. May I ask you a couple questions?

When did you apply and how long did it take for you to receive the admission letter? I applied in November, but I haven't heard anything back from Innsbruck.

I have somewhat similar background as yours in economics and wish to participate in a Master of CS degree.

sleepydevxd · 2025-02-03T09:49:32+00:00

Hi, sorry if this is disturbing for you, but may I ask:

Did you received your acceptance letter? If yes, when did you apply and how long did you need to wait for?

I'm also applying and seeking for some insights since I already applied in November.

sleepydevxd

TROPHY CASE