Recent breakage in a Tier 3 platform to the liblibc crate motivated the need for better announcing breakage in liblibc on non-Tier 1 platforms. The conclusion of the libs team was to use a thread on internals for announcing breakage, and this is that thread!
Over time I'll post here with PRs merged to the libc crate which can break existing compatibility on non-Tier 1 targets. For libc itself this means that the target is not on CI and has no verification. Breakage to these targets can happen at any time as definitions are corrected or the platform itself breaks.
The first such change to announce is https://github.com/rust-lang/libc/pull/576, which may break Solaris/Illumos code.