Objective-C 2.0 ABI specification

Question

Does documentation for the Objective-C 2.0 ABI exist somewhere on the Internet? The release notes for objc4-493.9 say:

Forthcoming documentation will describe the ABI for the use of compilers and developer tools only.

Has it since been released? The closest such reference is Apple's Objective-C runtime reference, but this only describes the public-facing API rather than the implementation details. In fact, it even mentions the ABI in passing:

In addition, the new Objective-C ABI (not described here) [...]

Unfortunately the new ABI is not hyperlinked in the aforementioned text. :-) Is my only option to grok the source code for the objc4 runtime and Clang's CGObjCNonFragileABIMac code-generation projects?

Answer 1

Nope. Analysis of the clang and runtime source are your only options, aside from perhaps emailing the clang and Apple obj-c lists and seeing if anyone wants to respond. I know several of the people responsible for the GNU runtime subscribe to the clang list, so that may be a start.