[rep_lodsb]

But is the "proper UNIX way" a good thing?

Funny that you would be arguing for that (unless I misunderstood the intention), given your many other posts about how C is a horrible broken unsafe language that should not be used by anyone ever. I tend to agree with that, btw, even if not so much with the "memory safety" hysteria.

Should every program, now and in the future, be forced to depend on libc, just because it's "grandfathered in"?

IMO, Linux is superior because you are in fact free to ignore libc, and directly interface with the kernel. Which is of course also written in C, but that's still one less layer of crud. Syscalls returning error codes directly instead of putting them into a thread-local variable would be one example of that.

Should a hypothetical future OS written in Rust (or Ada, ALGOL-68, BLISS, ...) implement its own libc and force userspace appplications to go through it, just because that's "proper"?

[pjmlp]

The problem is the misconception of what libc is.

In traditional UNIX, there is no libc per se, there is the stable OS API set of functions and that's it.

When C was standardised, a subset of the UNIX API became the ISO C standard library, aka libc. When it was proven that wasn't enough for portable C code, the remaining UNIX API surface became POSIX.

Outside UNIX, libc is indeed a thing, because many of those OSes aren't even written in C, just like your language lists example, in those OSes libc ships with C compiler, not the OS per se, as you can check by diving into VMS documentation before it became OpenVMS, or IBM and Unisys systems, where libc is also irrelevant if using PL/I, NEWP, whatever.

Also on Windows, you are not supposed to depend on libc unless you are writing portable C code, there isn't one libc to start with. Just like everyone else, each compiler ships their own C runtime library, and nowadays there is also universal C runtime as well, plenty of libc choices.

If not writing portable C code, you aren't supposed to use memset(), rather FillMemory ().

Same applies to other non-UNIX OSes, you would not be calling memset(), rather the OS API for such service.

[wtetzner]

I don't think GP is arguing that's the best way to design an OS, just that interfacing with non-Linux Unixes is best done via libc, because that's the stable public interface.