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?

Answer 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.

• Lilit Zakaryan: 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: 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: Sorry as I understand this APIs is not public ?
• Lilit Zakaryan: 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: Correct, there's no way to access bytecode via the public API. It's an internal implementation detail. Sorry.