add sections_darwin_rt.d

[WalterBright]

As gdc and ldc compile druntime for OSX AArch64, it is a bit of a mystery why this is not represented in src/rt/sections.d ??

@ibuclaw @kinke please weigh in!

[dlang-bot]

Thanks for your pull request, @WalterBright!

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[ibuclaw]

This doesn't exist?

[WalterBright]

Yes, it does:

https://github.com/dlang/dmd/blob/master/druntime/src/rt/sections_darwin_64.d

Should it exist?

[Herringway]

sections_darwin_64 != sections_darwin_rt

[ibuclaw]

@ibuclaw @kinke please weigh in!

GDC has all logic in its own package gcc.sections.macho, there's likely some duplication, but there's a more that isn't as this code is dependent on how the compiler generates code (i.e: no native TLS in GCC).

[kinke]

And LDC basically uses a generalized rt.sections_elf_shared on all major platforms, incl. Darwin and Windows. Which paves the way for druntime-as-shared-library, but requires compiler support.

[WalterBright]

src/rt/sections.d is in druntime/mak/SRCS, which is fed to Makefile. How does gdc and ldc avoid compiling it?

[kinke]

LDC doesn't use the Makefiles. The whole rt.sections* stuff is quite heavily modified for LDC, primarily the rt.sections_elf_shared. Should all be upstreamed eventually, but that's gonna require compiler support, so the incentive is extremely low.

[WalterBright]

Is there any essential difference between the sections for AArch64 and X68_64 on the OSX?

[kinke]

I don't recall any OTOH, but it's been more than 5 years that LDC comes with a macOS arm64 package, so the memory is anything but fresh.

Edit: I've taken a quick look, and no, I can't spot any diff at all for arm64.

[WalterBright]

@kinke thank you!

[kinke]

Should work fine. FWIW, rt.sections_darwin_64 (LDC only uses that file - I guess it's just the base helpers) uses D_LP64 as inclusion guard. So I think ideally rt.sections_osx_x86_64 would be renamed (to rt.sections_osx_64 or so), to make clear that it's the generic 64-bit implementation for Apple targets.

[WalterBright]

ok I renamed the file