I was a little surprised to see these disappear. Was there a reason, or just because Cargo isn't using them?

Now that no_std is stable, can we maybe promote this to a 1.0? These functions' signatures are pretty much the definition of stability.

Would you mind tagging commit 5fdc982 as 1.0?

This might be a stretch (and I'm not sure what the Cargo plan for cross-compile stuff is), but as rlibc needs libcore can there be a way to build it?

I've hacked together this https://github.com/bharrisau/rust-libcore, for my mirror of rlibc (https://github.com/bharrisau/rust-librlibc). It should grab the matching source tarball for the rustc version and build libcore when it is missing.

I've discovered that recent rustc nightlies (since January 30 at least) are smart enough to optimize memset and possibly other functions provided here into calls to the corresponding intrinsic which makes them recurse infinitely.

I'm guessing it's related to the switch to LLVM 3.8 in 303892ee15. I'm adopting a workaround with optimized assembly versions of these functions which are opaque to the optimizer, but that's not a portable nor particularly good solution.

Using memset as an example:

    let mut i = 0;
    while i < n {
        *s.offset(i as isize) = c as u8;
        i += 1;
    }
    return s;

Assume usize is a u8 thus isize will be an i8 with a maximum value of 127. If n is between 128 and 255, Bad Things will happen. Scale up as appropriate for the platform's usize.

Doing -C lto will now remove the functions in this crate since they aren't directly used by anything (rust-lang/rust#18134)

Since the end of 2016, the compiler-builtins crate has had its own implementation of the functions in this crate. For some architectures, they are even optimized with inline assembly.

It would make sense to clearly mark this crate as deprecated to prevent people from using it instead of the alternative.

https://github.com/rust-lang/rlibc/blob/1722d04dc38c1b1cf232b1faf152b9c434425799/src/lib.rs#L30

For people who are just trying to use Rust without core and std, this seems like a pretty big restriction. Is it actually needed?