Move fd into std::sys

[thaliaarchi]

Move platform definitions of fd into std::sys, as part of #117276.

Unlike other modules directly under std::sys, this is only available on some platforms and I have not provided a fallback abstraction for unsupported platforms. That is similar to how std::os::fd is gated to only supported platforms.

Also, fix the unsafe_op_in_unsafe_fn lint, which was allowed for the Unix fd impl. Since macro expansions from std::sys::pal::unix::weak trigger this lint, fix it there too.

cc @joboet, @ChrisDenton

[rustbot]

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[joboet]

It'd be best left to another PR, but I think we could even move the Windows Handle code in this module and rename FileDesc to something like Object.

[joboet]

Great, thank you!
r=me once #138988 has merged.

@bors delegate+

[bors]

✌️ @thaliaarchi, you can now approve this pull request!

If @joboet told you to "r=me" after making some further change, please make that change, then do @bors r=@joboet

[bors]

☔ The latest upstream changes (presumably #139101) made this pull request unmergeable. Please resolve the merge conflicts.

[thaliaarchi]

@bors r=@joboet

[bors]

📌 Commit 41d6fbf has been approved by joboet

It is now in the queue for this repository.

[bors]

⌛ Testing commit 41d6fbf with merge b15da48...

[rust-log-analyzer]

The job x86_64-gnu-aux failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

test os::raw::tests::same ... ok
test io::tests::test_write_all_vectored ... ok
test os::unix::io::tests::test_raw_fd_layout ... ok
test sync::mpmc::tests::waker_current_thread_id ... ok
error: unsupported operation: can't call foreign function `writev` on OS `linux`
##[error]    --> library/std/src/sys/fd/unix.rs:344:13
     |
344  | /             libc::writev(
345  | |                 self.as_raw_fd(),
346  | |                 bufs.as_ptr() as *const libc::iovec,
347  | |                 cmp::min(bufs.len(), max_iov()) as libc::c_int,
348  | |             )
     | |_____________^ can't call foreign function `writev` on OS `linux`
     |
     = help: if this is a basic API commonly used on this target, please report an issue with Miri
     = help: however, note that Miri does not aim to support every FFI function out there; for instance, we will not support APIs for things such as GUIs, scripting languages, or databases
     = note: BACKTRACE on thread `sys::fd::unix::`:
     = note: inside `sys::fd::unix::FileDesc::write_vectored` at library/std/src/sys/fd/unix.rs:344:13: 348:14
note: inside `sys::fd::unix::tests::limit_vector_count`
    --> library/std/src/sys/fd/unix/tests.rs:11:13
     |
11   |     assert!(stdout.write_vectored(&bufs).is_ok());
     |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside closure
    --> library/std/src/sys/fd/unix/tests.rs:8:24
     |
7    | #[test]
     | ------- in this procedural macro expansion
8    | fn limit_vector_count() {
     |                        ^
     |
    ::: /checkout/library/core/src/macros/mod.rs:1651:5
     |
1651 |     pub macro test($item:item) {
     |     -------------- in this expansion of `#[test]`
note: inside `<{closure@library/std/src/sys/fd/unix/tests.rs:8:1: 12:2} as core::ops::FnOnce<()>>::call_once - shim`
    --> /checkout/library/core/src/ops/function.rs:250:5
     |
250  |     extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: inside `<fn() -> core::result::Result<(), realstd::string::String> as core::ops::FnOnce<()>>::call_once - shim(fn() -> core::result::Result<(), realstd::string::String>)`
    --> /checkout/library/core/src/ops/function.rs:250:5
     |
250  |     extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to 1 previous error

error: test failed, to rerun pass `-p std --lib`

Caused by:
  process didn't exit successfully: `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1/bin/cargo-miri runner /checkout/obj/build/x86_64-unknown-linux-gnu/stage1-std/miri/x86_64-unknown-linux-gnu/debug/deps/std-8311653542201694 --skip 'fs::' --skip 'net::' --skip 'process::' --skip 'sys::pal::' -Z unstable-options --format json` (exit status: 1)
note: test exited abnormally; to see the full output pass --nocapture to the harness.
Build completed unsuccessfully in 0:03:19
make: *** [Makefile:57: check-aux] Error 1
  local time: Sun Mar 30 08:31:27 UTC 2025
  network time: Sun, 30 Mar 2025 08:31:27 GMT
##[error]Process completed with exit code 2.
Post job cleanup.

[bors]

💔 Test failed - checks-actions

[thaliaarchi]

The fix for the CI error is not obvious to me. Miri indeed does not implement readv or writev, but I would have expected an error from that to have been noticed much sooner than now. I didn’t modify any miri gates. Perhaps Miri hardcodes some pal paths?

[jieyouxu]

cc @RalfJung

[RalfJung]

Yeah, we skip the pal tests here:

rust/src/bootstrap/mk/Makefile.in

Lines 72 to 81 in fb04372

	$(Q)MIRIFLAGS="-Zmiri-disable-isolation" \
	$(BOOTSTRAP) miri --stage 2 library/std \
	$(BOOTSTRAP_ARGS) \
	--no-doc -- \
	--skip fs:: --skip net:: --skip process:: --skip sys::pal::
	$(Q)MIRIFLAGS="-Zmiri-disable-isolation" \
	$(BOOTSTRAP) miri --stage 2 library/std \
	$(BOOTSTRAP_ARGS) \
	--doc -- \
	--skip fs:: --skip net:: --skip process:: --skip sys::pal::

So we'll need to come up with a new pattern for this. We already list fs::, maybe just add fd::?