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A sneaky preview of ClassBrowser

Let me start with a few admissions. Firstly, I have been computering for a good long time now, and I still don’t really understand compilers. Secondly, work on my GNUstep Web side-project has tailed off for a while, because I decided I wanted to try something out to learn about the compiler before carrying on with that work. This post will mostly be about that something.

My final admission: if you saw my presentation on the ObjC runtime you will have seen an app called “ClassBrowser” where I showed that some of the Foundation classes are really in the CoreFoundation library. Well, there were two halves to the ClassBrowser window, and I only showed you the top half that looked like the Smalltalk class browser. I’m sorry.

So what’s the bottom half?

This is what the bottom half gives me. It lets me go from this:

ClassBrowser before

via this:

Who are you calling a doIt?

to this:

ClassBrowser after

What just happened?

You just saw some C source being compiled to LLVM bit code, which is compiled just-in-time to native code and executed, all inside that browser app.


Well why not? Less facetiously:

  • I’m a fan of Smalltalk. I want to build a thing that’s sort of a Smalltalk, except that rather than being the Smalltalk language on the Objective-C runtime (like F-Script or objective-smalltalk), it’ll be the Objective-C(++) language on the Objective-C runtime. So really, a different way of writing Objective-C.
  • I want to know more about how clang and LLVM work, and this is as good a way as any.
  • I think, when it actually gets off the ground, this will be a faster way of writing test-first Objective-C than anything Xcode can do. I like Xcode 5, I think it’s the better Xcode 4 that I always wanted, but there are gains to be had by going in a completely different direction. I just think that whoever strikes out in such a direction should not release their research project as a new version of Xcode :-).

Where can I get me a ClassBrowser?

You can’t, yet. There’s some necessary housekeeping that needs to be done before a first release, replacing some “research” hacks with good old-fashioned tested code and ensuring GNUstep-GUI compatibility. Once that’s done, a rough-and-nearly-ready first open source release will ensue.

Then there’s more work to be done before it’s anything like useful. Particularly while it’s possible to use it to run Objective-C, it’s far from pleasant. I’ve had some great advice from LLVM IRC on how to address that and will try to get it to happen soon.