Executing bytecode without source in v8 engine

Question

I try to use this source https://github.com/JoseExposito/v8-compiler/blob/master/addon/v8-compiler.cpp in my project. But a function compilation_cache() called from runScript always returns NULL. What can be wrong? What I need to fix in the source to work with the later version of v8? In addition, why is there no flag in the latest version of v8 FLAG_serialize_toplevel?

Answer 1

Two parts here:

First a warning: you should definitely not be writing code using any part of the i (internal) namespace. The APIs in the internal namespace don't always reflect how JS actually runs (due to optimizations), plus they change often and without warning.

In the case of the code you copied from V8 internals, V8 already provides an API to produce and consume "cached data" which is just the bytecode in a serialized form. Here's an example from the source of Node.js for how to produce a code cache.

Secondly your actual question: V8 will always perform a check on bytecode using a special hash (basically V8 version and source text length) and if it doesn't match it won't use the bytecode cache. This is why changing V8 versions causes the bytecode to be rejected.