[webkit-dev] Towards a unified build system

[Adam Barth]

As we've discussed off-and-on for a while, one of the larger
pain-points in working on WebKit today is the large number of build
systems.  Simple things, like adding, removing, or renaming a file
take a lot more effort than they should.

There are a number of approaches we could take to addressing this
problem.  One of the major constraints is that folks would like to use
familiar IDEs (e.g., Xcode, Visual Studio) to build and debug WebKit.
That means we'll need some sort of meta-build system that can generate
port-specific IDE projects.

Looking around the web, there are a handful of systems that could do
the job.  Dimitri, Eric, and I have started experimenting with one
such system, GYP.  There are various trade-offs between GYP and other
systems, such as CMake, that we've discussed on this list and at the
WebKit meeting last year.  Ultimately, I don't think it really matters
which system we use.  If someone else would like to take over the
project, I'd be happy to let them choose whichever system they'd like
to use.

Our current plan is as follows:

1) Bring up a build of the Apple-Mac port using GYP.  At this stage,
we'll have two ways of building Apple-Mac, the existing xcodeproj
build system and the fancy-pants GYP-generated xcodeproj build system.

2) Replace the manually created xcodeproj files with GYP generated
xcodeproj files.  Ideally, contributors wouldn't even know when this
step occurred.  They can continue to use the generated project files
in exactly the same way they use the manually created project files
today.  This step will help us work out any kinks in the new project
files.

3) Remove the xcodeproj files from svn.webkit.org and integrate the
generation of xcodeproj files with the WebKit build / update scripts.
At this point, contributors will notice that something has changed
because there'll be one less build system to worry about keeping up to
date!

Once we finish these steps, we can repeat them for other build
systems, systematically reducing the number of build systems we need
to maintain.

Currently, we have a fully working build of JavaScriptGlue and a
mostly working build of JavaScriptCore using this system.  Some folks
have asked why we're bothering to convert JavaScriptGlue at all.
Working with JavaScriptGlue has been helpful because it's like a
reduced test case for WebCore.  We might not end up actually changing
its build system in the end (because it's only used by Apple-Mac and
is deprecated), but bringing it up has taught us a lot about how GYP
works, especially for WebKit.

As we get further along towards these milestones, I'll send updates to
webkit-dev, especially if contributors need to change what they're
doing.  If you'd like to follow along in more detail, you're welcome
to CC yourself on the meta bug:

https://bugs.webkit.org/show_bug.cgi?id=55018

Hopefully we'll be able to make this transition as smooth as possible.
 I'm sure there will be some rough spots, and I'd like to thank you
all in advance for bearing with us.

Thanks,
Adam