Can't build on Rust v1.65

[stevenroose]

(TL;DR in the end)

So yesterday I updated my packages in my OS's repo and get Rust to update from 1.60 to 1.65. I'm on a generally considered fast-paced OS so I guess 1.65 must be new right? (It's only 5 months old, so that's kinda really new.)

Then I try to build a Rust project I'm working on. It says libc uses unstable features. Less than 5 months old, really??

error[E0658]: `const extern fn` definitions are unstable
    --> /home/steven/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.141/src/macros.rs:188:17
     |
188  | /                 pub $($constness)* unsafe extern fn $i($($arg: $argty),*
189  | |                 ) -> $ret {
190  | |                     $($body);*
191  | |                 }
     | |_________________^
     |
    ::: /home/steven/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.141/src/unix/linux_like/mod.rs:1521:1

The gist being, this is libc, it's a fundamental crate. Can you please either correctly use semver and publish major releases when breaking compilation or at the very least be more mindful about breaking compilation with older versions?

In our projects we always have an MSRV that is never newer than latest Debian, I think being able to compile a project on all of the major Linux distros should be a reasonable requirement, shouldn't it? The amount of times we had to pin libc specifically because of it or some of its dependencies violating semver is .. simply said, heartbreaking.

[stevenroose]

It turns out the latter problem of the double compilation was an OS issue, so I'll edit that away, the 1.65 build failure still stands though.

[JohnTitor]

Could you provide a reproducible example? I cannot reproduce your issue on my end (a simple code + 1.65). The error message isn't enough to do so, your target, code, toolchain are needed.
And note that MSRV is quite essential to us, we provide support from Rust 1.13.0 to nightly and we've discussed the issue about the most reasonable MSRV here.

[stevenroose]

I cannot reproduce at this time, so I think it was because of some system messup where I was using rustc 1.60 and 1.65 in parallel. Please keep up the commitment to Rust v1.13.0, that's enormously appreciated!