Building V8 Javascript Engine

September 26, 2015

Building V8 Javascript Engine.

Introduction

I was thinking sometime ago about starting hacking with V8, aside from the fact that I work every day with Javascript, is that the Chromium engineers are doing a very good job making V8 fast and efficient and for some task good Javascript code is faster than C++, here is a great talk about the sophisticated JIT generation in Javascript.

After many days of procrastination, I put my hands-on and start the task of downloading the project and prayed that everything would just work, like many things in life it didn't work the first time, here I documented all the steps, if somebody wants to start playing with this, hopefully this will make their life easy.

For my hacking session I just make a VM based in Archlinux, but the same step could apply to other Linux Distributions.

Building.

First we need is to install Git and install the all necessary build tools in others dist is called build-essentials in arch is called base-devel.

$ pacman -Sy base-devel git

Now we need to download from Chromium project their specific tool depot_tools, this will allow us to checkout specifics projects from their repo in this case V8, then we add this directory to our PATH.

$ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
$ export PATH=$PWD/depot_tools:$PATH

If you had python2 by default jump this step, in my case Arch came with Python3 by default so i need to re-direct the global /usr/bin/python to point the /usr/bin/python2.

$ ln -s /usr/bin/python2 /usr/bin/python
$ ln -s /usb/bin/python2-config /usr/bin/python-config

For 64 bits machine like mine i need to made a symlink to libtinfo.so.5

$ ln -s /usr/lib/libncurses.so.5.7 /lib64/libtinfo.so.5

If everything go is fine now you should be able to execute gclient from console.

$ gclient config url-v8-git-project

This make a folder in your root dir named v8, this could be done better but I’m using a virtual machine, so no problem.

go inside the created dir /home/user/v8 in my case.

$ make x64

or if you are in a 32bit machine.

$ make ia32


What to do now ?

You can now execute the V8 REPL and load Javascript files, do profiling, and tons of other stuff. To had global access just add the binary to the system vars.

$ export $PATH:/home/cesar/v8/out/x64.release/d8

Or, what I found more interesting is use VM inside native programs and learn how to take advantage of a high level language like Javascript and give it some new abilities like Socket, Disk, etc. Here you can find a basic Hello World C++ program that run Javascript inside just need to clone it and start hack.

For those interested in how the VM works some useful links:

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