How to get javascript bytecode from C++ using V8 Engine

Question

I have a following JavaScript code:

class Contract {

// constructor
constructor() {

    // dynamic data
    this.str = '';
    this.count = 0; 
}

// update function
update(_value){
    this.str = _value;
    this.count++; 
   }
}

How can I get bytecode and state of virtual machine using V8 engine?

jmrk · Accepted Answer · 2018-04-27 20:35:28Z

1

Bytecode is not exposed on V8's C++ API.

For human inspection, you can dump it to stdout by using the --print-bytecode flag.

If you're willing to modify V8 for your purposes, you can e.g. look for occurrences of FLAG_print_bytecode in the source to see how the bytecode can be accessed.

answered Apr 27, 2018 at 20:35

jmrk

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5 Comments

Lilit Zakaryan Over a year ago

Thank you. I can parse javascript with V8's C++ to C++ object and get access to properties. So there should be a way for accessing property bytcode

jmrk Over a year ago

Internally, there's SharedFunctionInfo::HasBytecodeArray() and SharedFunctionInfo::GetBytecodeArray(), but as I said, these are not exposed on the embedder API. What do you need the bytecode for?

Lilit Zakaryan Over a year ago

Sorry as I understand this APIs is not public ?

Lilit Zakaryan Over a year ago

I just need to get the byte code and the state of the virtual machine after each call. I mean to have some C++ object which contains byte code. Not just printing

jmrk Over a year ago

Correct, there's no way to access bytecode via the public API. It's an internal implementation detail. Sorry.

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