[PATCH] D59945: [ObjCMetadata] Add support for reading Objective-C metadata

[David Chisnall via Phabricator via llvm-commits]

theraven added a comment.

I am not convinced that there is sufficient abstraction here to handle multiple runtimes without significant code duplication. The Mach-O and LLVM IR parsers both appear to duplicate all knowledge of the runtime's data structures, so if you wanted to add a second runtime you'd then need four classes.  I would expect to see two abstraction layers:

1. Something allowing you to specify a data structure to examine that would load it from some binary (IR, Mach-O, ELF, whatever).
2. Something built on top of this that then queries specific runtime metadata structures.

In clang, we support two broad families of Objective-C runtime: Apple (Legacy and Modern, with version-specific things for macOS, iOS, and so on) and GNU (including GCC, GNUstep / WinObjC, and ObjFW).  These are largely orthogonal to object file formats.  For example, the GNUstep runtime is widely used with both ELF and PE/COFF binaries and can be used with Mach-O (though typically only for testing).  If we wanted to add support for all of these, I suspect that we'd have a code explosion.


Repository:
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https://reviews.llvm.org/D59945