Re: LLVM-libc FreeBSD Port

On Sunday, May 10th, 2026 at 3:37 PM, Schrodinger ZHU Yifan <[email protected]> wrote:

> Hi all,
>
> I am one of the maintainers of LLVM libc, mainly responsible for its threading support, and I currently daily drive FreeBSD.
>
> LLVM libc is a from-scratch implementation of the C standard library developed as part of the LLVM project. It is designed to be modular, so individual components can be used independently; multiplatform, targeting Linux, GPUs, bare-metal embedded systems, UEFI, macOS, Windows, and more; and written in modern C++ with a focus on correctness, performance, and safety. See also https://libc.llvm.org/ .
>
> We recently had a casual discussion on our Discord about bringing up FreeBSD support. This would be an interesting step toward broadening LLVM libc’s perspective from Linux-only to more general *nix portability, which should also help improve its overall structure. The initial bring-up was fairly straightforward (the PR is a bit outdated but can be fixed without much effort): https://github.com/llvm/llvm-project/pull/124459. This already delivers LLVM libc’s correctly rounded math and mathvec support to FreeBSD.
>
> However, moving toward completeness will require more work. We would also need CI pipelines and stable maintainers before FreeBSD could be added to the list of supported platforms.
>
> Personally, I think bringing a modular libc design with modern features that continue to evolve rapidly would also be a plus for the FreeBSD community, especially given FreeBSD’s close relationship with LLVM. If anyone is interested, please feel free to ping me at i [at] zhuyi [dot] fan.
>
> By the way, the Discord link on your website appears to be broken.
>
> Best,
> Yifan
>
> [image]
> Schrodinger ZHU Yifan, Ph.D. Student
> Computer Science Department, University of Rochester
>
> Personal Email:[email protected]
> Work Email:[email protected]
> Github:SchrodingerZhu

Hi Schrodinger,

Glad to hear that you are working on this project. I'm working on LLDB for FreeBSD, so feel free to reach me out if you have any questions on FreeBSD.

So I want to clarify here: LLVM's libc has its own header and implementation, so it is possible to compile FreeBSD libc on other OSes, right? This also means llvm's libc doesn't use our libsys library but has its own syscall assemblies, which I see from your GitHub PR.

--Minsoo Choo