A New Direction for the Mac Arm64 Code Generator

[Walter Bright]

I had carefully crafted the Mach object file generation according to how the 
default Mac compilers worked. I'd compile bits of code with clang, and dump out 
the object files. Fortunately, there was also a specification for it, and I 
could compare the specification with what was generated.

Enter the arm64 clang. Well, it throws this out the window, and has their own 
undocumented variant of the file format. I've spent a lot of time with AI trying 
to figure out how to make my work still work with the new ld linker.

The AI would give me mostly correct information, but would never quite give me 
the details of how it was supposed to work. (This is the likely result of a lack 
of documentation.) Many of its recommendations just resulted in internal linker 
assert failures. Yes, my object files would crash ld. This is not helpful 
because I don't know why they crashed it. AI finally recommended to me reading 
the LLVM linker source code (it's open source).

Well, looking at that undocumented uncommented hellish snarl of C++ code was a 
moment of unhappy frustration for me.

So I am forced to abandon the documented way to generate object files, and 
reverse engineer the new way. At least one point in my favor is I can use g++ to 
generate sample .o files, and then try to conform to what g++ emits.

It's going to be slow going, though.

Given the frequent erroneous assertions AI has made about the object code 
format, I won't bother trying to use AI to generate the code.