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Hi all,

We’re planning to contribute a new implementation of LLD for Mach-O, using the same design as the COFF and ELF ports. This design has proven to work very well for those ports, and we’re keen to explore it for Mach-O as well. Our work is based on an initial prototype created by Peter Collingbourne and Rui Ueyama.

Our initial commit is up for review at https://reviews.llvm.org/D75382. We’ve intentionally stripped down this initial commit as much as possible to ease reviewing; we’ve kept it to the absolute minimum needed to produce and test a working macOS x86-64 executable for that prints “Hello World” via a syscall. We have several short-term follow-ups planned to add important functionality, such as linking against archives, universal binaries, dylibs, and tbd files, performing subsection splitting (atomization), and producing dylibs. The follow-ups should give a good sense of the overall design while still keeping each piece easily reviewable and testable individually. Our end goal is to create a full-featured Mach-O linker, and we’ll be working toward that goal over the next several months (and years, in all likelihood). We’d appreciate feedback and reviews.