[QNX7.1] `std::fs::tests::symlink_hard_link` broken on main

[japaric]

Ferrocene CI has detected that this test was broken by #127897 . Specifically, by the change in library/std/src/sys/pal/unix/fs.rs, shown below:

diff --git a/library/std/src/sys/pal/unix/fs.rs b/library/std/src/sys/pal/unix/fs.rs
index 7fa147c9754..fc9d7e98883 100644
--- a/library/std/src/sys/pal/unix/fs.rs
+++ b/library/std/src/sys/pal/unix/fs.rs
@@ -1717,7 +1717,7 @@ pub fn link(original: &Path, link: &Path) -> io::Result<()> {
     run_path_with_cstr(original, &|original| {
         run_path_with_cstr(link, &|link| {
             cfg_if::cfg_if! {
-                if #[cfg(any(target_os = "vxworks", target_os = "redox", target_os = "android", target_os = "espidf", target_os = "horizon", target_os = "vita", target_os = "nto"))] {
+                if #[cfg(any(target_os = "vxworks", target_os = "redox", target_os = "android", target_os = "espidf", target_os = "horizon", target_os = "vita"))] {
                     // VxWorks, Redox and ESP-IDF lack `linkat`, so use `link` instead. POSIX leaves
                     // it implementation-defined whether `link` follows symlinks, so rely on the
                     // `symlink_hard_link` test in library/std/src/fs/tests.rs to check the behavior.

Test output:

---- fs::tests::symlink_hard_link stdout ----
thread 'fs::tests::symlink_hard_link' panicked at std/src/fs/tests.rs:1473:5:
assertion failed: check!(fs::symlink_metadata(tmpdir.join("hard_link"))).file_type().is_symlink()

Reverting that single line diff fixes the test for the QNX7.1 targets, e.g. arch64-unknown-nto-qnx710 and x86_64-pc-nto-qnx710

@nyurik can the change be reverted or does QNX7.0 need to use link, instead of linkat, here? from looking at libc, it appears that both link and linkat are available on QNX7.0 so reverting the change should at least not cause compilation or linking errors. if the case is the latter, then we should use cfg(target_env = "nto70") in addition to cfg(target_os = "nto").

[nyurik]

@japaric thanks for the report! I will need to re-test it for QNX 7.0, to see if it is a 7.0 requirement (i don't recall why this was required initially, but clearly I ran into some issues with it). I also plan to do a similar automation to ensure 7.0 builds run without problems on our hardware. Is there a list of tests you see failing on 7.1 that are OK to ignore? I see a list here - is this the most relevant one? Thx!

[japaric]

we do not ignore any single unit test at the moment and we run library (e.g. libstd) tests as well as (cross) compilation tests using TEST_DEVICE_ADDR. we don't pass --exclude to x.py but instead pass the list of test suites as arguments.

we currently run these test suites:

$ # run these from the root of the ferrocene/ferrocene repo

$ ferrocene/ci/split-tasks.py test:library
library/alloc library/core library/test

$ ferrocene/ci/split-tasks.py test:library-std
library/std

$ ferrocene/ci/split-tasks.py qnx:compiletest-no-only-hosts
tests/assembly tests/codegen tests/codegen-units tests/coverage tests/crashes tests/debuginfo tests/incremental tests/mir-opt tests/run-make tests/run-pass-valgrind tests/ui

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-low

[nyurik]

fixed in #130248