I’m confused. The register clobbering is an issue in the compiler, not in the stdlib implementation right? Or are you saying the stdlib has inline assembly in these IO implementations somewhere? I couldn’t find it and I can’t think why you’d need it.

If it’s a compiler frontend-> LLVM interaction bug, I think you are commenting in the spot - it should go in a separate issue not in the PR about io_uring backend. Also, interaction bugs where a compiler frontend triggers a bug in LLVM aren’t uncommon since Rust was the first major frontend other than clang to exercise code paths. Indeed the (your?) fix in LLVM for this issue mentions Rust is impacted too.

I agree with the higher level points about stability and I don’t like Zig not being a safe language in this day and age, but I think your criticism about quality is a bit harsh if your source of this complaint is that they haven’t put a workaround for an LLVM bug.

There is the one issue which I fixed in LLVM, but it should be fixed in Zig as well, because the clobber list in Zig is typed and gives you false impression that adding x30 there is valid. But there is also another issue, x18 is a general purpose register outside of Darwin and Windows and needs to be marked as clobbered on other systems. And yes, look at the linked changes, the stdlib has inline assembly for the context switching.