Rust nightly doesn't build on armv7-sony-vita-newlibeabihf

[Thomasdezeeuw]

Build error below. From https://github.com/rust-lang/socket2/actions/runs/18309085762/job/52133230573?pr=617#step:5:51

  error[E0425]: cannot find value `_SC_HOST_NAME_MAX` in crate `libc`
   --> /home/runner/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/net/hostname/unix.rs:8:60
    |
  8 |     let host_name_max = match unsafe { libc::sysconf(libc::_SC_HOST_NAME_MAX) } {
    |                                                            ^^^^^^^^^^^^^^^^^ not found in `libc`
  
  For more information about this error, try `rustc --explain E0425`.
  error: could not compile `std` (lib) due to 1 previous error

Meta

rustc --version --verbose:

rustc 1.92.0-nightly (3d8c1c1fc 2025-10-06)
binary: rustc
commit-hash: 3d8c1c1fc077d04658de63261d8ce2903546db13
commit-date: 2025-10-06
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.2

[folkertdev]

Lots of tier-3 targets are failing with this error (see e.g. https://does-it-build.noratrieb.dev/nightly?nightly=2025-10-06).

Introduced in #146937 cc @joboet

[Urgau]

Obligatory reminder that "the Rust project provides no official support for a (tier 3) target"¹, only the armv7-sony-vita-newlibeabihf target maintainers may be able to help here.

@folkertdev Reminder about the "burden on the authors of pull requests" policy:

Do not send automated (or manual) messages or notifications (via any medium, including via @) to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

@rustbot labels -C-bug -needs-triage +C-discussion +A-targets +T-libs

Footnotes

1. https://doc.rust-lang.org/nightly/rustc/target-tier-policy.html#tier-3-target-policy ↩

[workingjubilee]

Many maintainers choose to reuse the "Unix" standard library code. Then when their target doesn't implement common Unix facilities, they fail to build. Part of the point of the standard library refactoring work for std::sys implementations that @joboet has been helping a great deal with has been making the code use of a given platform more intentional, to make this harder to do accidentally.

[ds84182]

Does the Rust standard library define a minimum POSIX version? Because from my investigation _SC_HOST_NAME_MAX is part of POSIX.1-2001 and its predecessor seems to be MAXHOSTNAMELEN.

[workingjubilee]

No. And I can hardly fault maintainers for not including a random symbol in their libc PR that didn't have an obvious practical use at the time.

Anyways: cc @nikarh @pheki @zetanumbers