Welcome to the chapters of Let’s Understand Chrome V8.

1. Checkout, Build

1. 1. System Requirements

• win 10 64bit, VS2019 community, Git
• Win 10 64bit, VS2019 community, Git, windows 10 SDK(10.0.19041 and higher)

1.2. depot_tools

Download the depot_tools bundle and extract it somewhere.

Add depot_tools to the start of your PATH (must be ahead of any installs of Python. Note that environment variable names are case insensitive).

Assuming you unzipped the bundle to C:\src\depot_tools, open: Control Panel → System and Security → System → Advanced system settings.

If you have Administrator access, Modify the PATH system variable and put C:\src\depot_tools at the front (or at least in front of any directory that might already have a copy of Python or Git).

If you don’t have Administrator access, you can add a user-level PATH environment variable by opening: Control Panel → System and Security → System → Search for “Edit environment variables for your account”.

Add C:\src\depot_tools at the front. Note: If your system PATH has a Python in it, you will be out of luck.

Also, add a DEPOT_TOOLS_WIN_TOOLCHAIN environment variable in the same way, and set it to 0. This tells depot_tools to use your locally installed version of Visual Studio (by default, depot_tools will try to use a google-internal version).

From a cmd.exe shell, run.

On the first run, gclient will install all the Windows-specific bits needed to work with the code, including msysgit and python.

If you run gclient from a non-cmd shell (e.g., cygwin, PowerShell), it may appear to run properly, but msysgit, python and other tools may not get installed correctly.

If you see strange errors with the file system on the first run of gclient, you may want to disable Windows Indexing.

1.3. Get the Code

• First, configure Git:
• Create a chromium directory for the checkout and change to it (you can call this whatever you like and put it wherever you like, as long as the full path has no spaces):
• Fetch V8
• fetch v8git pull origin master
• At least 10GB of free disk space on an NTFS-formatted hard drive.
• Generate GN project file

cd ~\v8\src> gn gen --ide=vs out\default --args="is_component_build = true is_debug = true v8_optimized_debug = false"

is_debug = true enable V8 debug，v8_optimized_debug = false disenable the optimization that interferes with debug. My args.gn is below:

is_component_build = trueis_debug = truev8_optimized_debug = falsev8_use_snapshot = false

1.4. Build and Run

Compile V8 with VS2019

src\out\default — ->all.sln

Open it,as shown in Figure 1.

In the Solution Explorer, there is the v8_hello_world, right-click it to “Set as Startup Project”, and then build. You can see the compilation process in the output window, as shown in Figure 1.

Figure 2 is the call stack of hello-world.cc.

In summary, if you see strange errors, maybe related to the SDK version or environment path.

2. Where is our starting point

The V8 has huge code, so we need to find an easy way.

The source code of V8 is in src, as shown in Figure 3.

We start to learn from hello-world.cc(it is in the samples directory) as shown in Figure 1.

V8 is the JavaScript engine, the hello-world.cc includes initialization, isolate creation, handle creation, JavaScript compilation, and execution.

Again, the easy way is to debug hello-world.cc one step by one step.

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