how to compile and use objc runtime from apple's source code?

Question

As is know to us all, objc's runtime is open source and can be downloaded from: http://www.opensource.apple.com/tarballs/objc4/

After I download the tarball an extract it. I open objc.xcodeproj using xcode. However, when I build it, there are many erros, such as, can not find some headers. I googled all the missing headers, download them, put them in /tmp/objc.dst/usr/include. But without luck, still errors.

I searched the internet, but I can find few documents or instructions about:

1. how to compile apple's objc runtime from source code?
2. After compile it , I should get libobjc.A.dylib, how to use it (as a replace of the system's libobjc.A.dylib) ?

I really appreciate any help you can provide.

Answer 1

Compile with no error under 10.10.2(14C1514), Xcode 6.2 (6C131e).

1. You need OSX 10.8 SDK, which you can get from early Xcode install dmg or this repository https://github.com/phracker/MacOSX-SDKs (If you download sdk from this repo, you may need to fix the soft links using this script http://blog.jeswang.org/blog/2014/10/26/fix-slash-soft-slash-links-slash-in-slash-an-slash-archived-slash-file/, you may need to run the script two times for the recursion of references)

2. More the 10.8 sdk to /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs

3. Clone this repository https://github.com/Jeswang/objc4-532.2

4. Compile and Run the debug-objc scheme

5. You can set any breakpoint in the source and debug the whole runtime.