crate: clean up leftovers from pre-rustc 1.19 without `union`s by dybucc · Pull Request #5351 · rust-lang/libc

dybucc · 2026-08-01T17:29:44Z

Description

This PR tries to address issue #1020. It cleans up a bunch of old ctest skips
over fields and types that were previously (more than six years ago) not proper
unions.

Note as well that _channel_connect_attr in QNX I couldn't check even though it
seems like it may be some left over struct-as-union type. I just coulnd't
get access to the SDK in the QNX site.

Then there's an unnamed field that is itself a union in Haiku targets under
sigaction. I've not changed that one because I don't know of a way of handling
a combination of both unnamed union and unnamed field.

The same applies to cpu_topology_node_info in Haiku targets.

For details on the rest of the changes, see the patch messages.

Checklist

Relevant tests in libc-test/semver have been updated
Commit messages permalink to headers for added or changed API
Placeholder or unstable values like *LAST or *MAX have the standard
doc comment
Tested locally (cargo test -p libc-test --target mytarget);
especially relevant for platforms that may not be checked in CI

@rustbot label +stable-nominated

rustbot · 2026-08-01T17:29:46Z

Some changes occurred in a solarish module

cc @jclulow, @pfmooney

tgross35

Looks like a great cleanup, couple trait requests.

View changes since this review

tgross35 · 2026-08-02T19:25:02Z

+    #[cfg_attr(any(target_arch = "x86", target_arch = "x86_64"), repr(packed(4)))]
+    pub struct epoll_event {
+        pub events: u32,
+        pub data: epoll_data,
+    }
+
+    pub union epoll_data {
+        pub ptr: *mut c_void,
+        pub fd: c_int,
+        pub u32: u32,
+        pub u64: u64,
+    }


Illumos maintainers @jclulow @pfmooney this is a useful change but technically breaking, do you want it in 0.2?

Deciding against this, see #5351 (review)

rustbot · 2026-08-02T19:25:36Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

dybucc · 2026-08-03T06:34:16Z

@rustbot ready
@rustbot label +S-waiting-on-maintainer

tgross35

LGTM, thanks!

I actually don't think we should have the epoll_event changes in 0.2 since we opted out of backporting the fix on Linux (1d10a3f). I'll exclude the relevant commits when picking.

View changes since this review

Remove a check in the Linux routine of build the build script that skipped a field whose type was a `union` upstream but only a specific field of the `union` in Rust. This is a remnant of versions prior to Rust 1.19, where `union`s got introduced. The definition under `unix/linux_like/mod.rs` uses a `union` for that field. The check is redundant now.

Replace field of `epoll_event` that was once only a single field of the upstream `union` with a proper `union`. This was done back before Rust had received support for `union`s, so it's redundant to keep this binding now. The build script also had a skip set in place for this one field, and that now has also been removed.

Remove check in Linux test routine for a field of `sigevent` that was once (pre-Rust 1.19) implemented as a `struct` instead of a `union`. This is no more the case so the check in the build script is redundant.

Remove check for `cpuid_info` as a `union` as that dates back to the times where Rust didn't itself have `union`s so this type had to be implemented as a `struct`. Skipping it in libc-test's build script is redundant. The same applies to `cpu_topology_node_info`.

Replace dummy field for `union` with an actual definition fitting that of the upstream type. The current (pre-patch) field corresponded with the times back when Rust didn't have `union`s. Now it's not necessary anymore to expose only a single field of the `union`. The corresponding skip in libc-test's build script has also been removed.

Remove a skip over `sigaction` in Hexagon QuRT as it seems the separate fields in Rust mentioned in libc-test's build script's skip aligns well with the (also) split fields upstream. See header file `posix/signal.h` under `rtos/qurt/computev81` in the Hexagon SDK.

Remove skip over `sem_t` in Hexagon QuRT as it alleged to this being a `typedef` of an anonymous `struct`, but that also happens in other targets we test against without there being skips for their records. See header file `posix/semaphore.h` under `rtos/qurt/computev81` in the Hexagon SDK for details.

rustbot · 2026-08-03T21:14:44Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

tgross35 · 2026-08-31T11:51:28Z

Excluding b0204f2 from the backport since that would need d255379, which isn't backported.

Remove check for `cpuid_info` as a `union` as that dates back to the times where Rust didn't itself have `union`s so this type had to be implemented as a `struct`. Skipping it in libc-test's build script is redundant. The same applies to `cpu_topology_node_info`. (backport <rust-lang#5351>) (cherry picked from commit 12fe28d)

Replace dummy field for `union` with an actual definition fitting that of the upstream type. The current (pre-patch) field corresponded with the times back when Rust didn't have `union`s. Now it's not necessary anymore to expose only a single field of the `union`. The corresponding skip in libc-test's build script has also been removed. (backport <rust-lang#5351>) (cherry picked from commit 97ad377)

Remove a skip over `sigaction` in Hexagon QuRT as it seems the separate fields in Rust mentioned in libc-test's build script's skip aligns well with the (also) split fields upstream. See header file `posix/signal.h` under `rtos/qurt/computev81` in the Hexagon SDK. (backport <rust-lang#5351>) (cherry picked from commit 96baf11)

Remove skip over `sem_t` in Hexagon QuRT as it alleged to this being a `typedef` of an anonymous `struct`, but that also happens in other targets we test against without there being skips for their records. See header file `posix/semaphore.h` under `rtos/qurt/computev81` in the Hexagon SDK for details. (backport <rust-lang#5351>) (cherry picked from commit 471be3d)

tgross35 · 2026-08-31T11:56:58Z

Similarly skipping 08fa94f which needs 1d10a3f

Replace field of `epoll_event` that was once only a single field of the upstream `union` with a proper `union`. This was done back before Rust had received support for `union`s, so it's redundant to keep this binding now. The build script also had a skip set in place for this one field, and that now has also been removed. (backport <rust-lang#5351>) (cherry picked from commit 3b624ac)