[PATCHs] Using the MC layer to produce dSYM companion binaries

[Frédéric Riss]

Hi,

I’m directly and indirectly using the MC layer to produce the content of the debug sections in llvm-dsymutil. This works great, except that dsymutil is supposed to produce dSYM companion binaries and not the simple object files MC was designed to produce.

At some point I contemplated making MC generic enough to emit these kind of binaries, but it just feels like a bad fit. Moreover dSYM companion binaries have a number of unique characteristics that I think would fit pretty badly into any kind of generic framework (eg. fake sections that have a size but no contents or VM layout without any loadable sections).

I went the route of writing my own equivalent of the MCObjectWriter in llvm-dsymutil which was easy enough. Today the layout of the sections and the file emission is done inside MCAssembler::Finish(). For my usecase, I want to run only the section layout and do the emission myself. The first attached patch allows that by splitting a layout(MCAsmLayout &) method out of MCAssembler::Finish(). Does this look reasonable?

I also tried to reuse some low-level MachObjectWriter primitives. The second patch attached allows me to do just that by making them a tad more generic.

Both patches should have NFC.


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