Hey smeenai! I am the author of the MachO linker in Zig. First of, I am closely following your work in LLVM and I am really delighted that someone of your aptitude took over the backend - I definitely intend to take it for a spin soon!
As far as cross-linking is concerned, we do the same thing we do for macOS libc headers - we ship the definitions. You can think of it as effectively shipping a preprocessed version of libSystem.tbd with Zig. This is still early days though, so currently as a workaround for not having a functional yaml parser (so that `zig ld` can link against tbds), every unresolved proxy symbol is simply assumed to come from libSystem. This is of course not ideal since then unresolved symbols are flagged only at runtime rather than at link time.
Anyhow, shipping preprocessed libSystem.tbd makes it possible to cross-compile valid PIE binaries (which is a strict requirement on Apple Silicon anyway).
If you wanna discuss it more, feel free to DM me in Zig's Discord - I'm always game to discuss linkers!
As far as cross-linking is concerned, we do the same thing we do for macOS libc headers - we ship the definitions. You can think of it as effectively shipping a preprocessed version of libSystem.tbd with Zig. This is still early days though, so currently as a workaround for not having a functional yaml parser (so that `zig ld` can link against tbds), every unresolved proxy symbol is simply assumed to come from libSystem. This is of course not ideal since then unresolved symbols are flagged only at runtime rather than at link time.
Anyhow, shipping preprocessed libSystem.tbd makes it possible to cross-compile valid PIE binaries (which is a strict requirement on Apple Silicon anyway).
If you wanna discuss it more, feel free to DM me in Zig's Discord - I'm always game to discuss linkers!