Tier 1 Support for x86_64 macOS

[andrewrk]

I just demoted macOS from Tier 1 to Tier 2 support on the support table, because the requirements for Tier 1 say this:

libc is available for this target even when cross compiling.

Here are some of the roadblocks for cross-compiling targeting macOS:

• LLD linker macho code is unmaintained this is actually resolved now
• darwin frameworks (ability to link against darwin frameworks (such as CoreFoundation) when cross compiling #1349)
• Apple has not been careful with the license in their header files and it does not look like we can ship their .h files. So we would need a clean room implementation of darwin libc header files.
• The requirement for applications to be signed causes problems

[robinsoncol]

I couldn't get the latest version of Zig to build on macOS Catalina. Is the build problem that I'm having related to this issue?

Here's the error that I'm getting:

[ 99%] Linking CXX executable zig0
Undefined symbols for architecture x86_64:
  "getPollyPluginInfo()", referenced from:
      (anonymous namespace)::EmitAssemblyHelper::EmitAssemblyWithNewPassManager(clang::BackendAction, std::__1::unique_ptr<llvm::raw_pwrite_stream, std::__1::default_delete<llvm::raw_pwrite_stream> >) in libclangCodeGen.a(BackendUtil.cpp.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [zig0] Error 1
make[1]: *** [CMakeFiles/zig0.dir/all] Error 2
make: *** [all] Error 2

cmake 3.17.0_1
llvm 10.0

[fengb]

@robinsoncol Homebrew’s LLVM is misconfigured: Homebrew/homebrew-core#52352

Edit: I was mistaken. Workaround is -DZIG_PREFER_CLANG_CPP_DYLIB=ON to cmake.

LLVM makes it impossible to configure this in a robust way. Discussion in #4799 (comment) and upstream https://bugs.llvm.org/show_bug.cgi?id=44870

[kubkon]

@andrewrk can we revisit this? Out of the list posted in the issue's description:

• libc is available for this target even when cross compiling
• LLD linker macho code is unmaintained this is actually resolved now
• darwin frameworks (ability to link against darwin frameworks (such as CoreFoundation) when cross compiling #1349)
• Apple has not been careful with the license in their header files and it does not look like we can ship their .h files. So we would need a clean room implementation of darwin libc header files.
• The requirement for applications to be signed causes problems

only the 3rd bullet is still relevant (and probably will be for quite some time); however, the rest seems addressed by now including shipping libc headers for both aarch64-macos-gnu and x86_64-macos-gnu targets. In the light of this plus the fact that the work on self-hosted Mach-O linker is progressing at a steady pace, I'd like to propose we promote macOS back to Tier 1 for x86_64 and introduce arm64 as Tier 2. If there are no objections, I'll be happy to submit relevant changes to the website.

[andrewrk]

I agree, thanks to your diligent work, zig now has tier 1 support for x86_64-macos! Would you like to do the honors of closing this issue?

[kubkon]

I agree, thanks to your diligent work, zig now has tier 1 support for x86_64-macos! Would you like to do the honors of closing this issue?

Oh absolutely, thanks!

[kubkon]

PR upgrading x86_64 to tier 1, and introducing arm64 as tier 2: ziglang/www.ziglang.org#86