[libcxx-commits] [libcxx] [libcxx] Recognize __UEFI__ predefine (PR #139327)

[Prabhu Rajasekaran via libcxx-commits]

Prabhuk wrote:

> > Is this introducing a new target? Are there going to be other changes for that target?
> > libc++ requires pre-commit CI to be set up for any newly supported target/platform, so I'd like to understand whether this falls into that category.
> 
> I introduced a new target triple "x86_64-uefi" in Clang and been incrementally landing changes to support this triple. The `__UEFI__` predefine is set when x86_64-uefi triple is used. This triple does not set `_WIN32` and other windows specific predefines. At this point, this triple is in developmental stage. It will be good to have a pre-commit CI set up when the support is mature. I do not know if we are quite there yet at this point. Thank you.

Adding a little bit more context. The way libcxx is used in the UEFI context I am experimenting with is header-only. We do not rely on the libcxx ABI and the changes I am expecting in the future will be limited to header files only. I would like to add precommit libcxx CI builders for UEFI when the support is mature but the builders will be limited to cover the header only scenarios which will presumably cover the changes I am expecting to land in libcxx. 

https://github.com/llvm/llvm-project/pull/139327