[JoshTriplett]

There's no proposal to stabilize the Rust ABI. There are proposals to define a separate stable ABI, which would not be the default ABI. (Such a separate stable ABI would want to plan for long-term performance, but the default ABI could continue to improve.)

[zozbot234]

There is already a separate stable ABI, it's just the C ABI. There are also multiple crates that address the issue of stable ABIs for Rust code. It's not very clear why compiler involvement would be required for this.

[tialaramex]

Surely it would be nice to be able to specify using the repr mechanism that you explicitly want so-and-such ABI, in the same way that you can for the C ABI.

I haven't looked at the crates you're describing, but presumably they're providing a proc macro or something instead, which is not really the right layer to do this stuff.

[weinzierl]

Thanks, I never had considered that a possibility when hearing about "Rust stable ABI", but it makes a lot if sense.