Use Rust union types by kellda · Pull Request #2056 · rust-lang/libc

kellda · 2021-02-04T15:53:32Z

Replace some types with unions now that rustc supports them.

I also found sigevent.sigev_notify_thread_id, siginfo_t.__data and sigaction.sa_sigaction that I think should be unions, but I wasn't sure.

rust-highfive · 2021-02-04T15:53:35Z

r? @Amanieu

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kellda · 2021-02-04T16:02:20Z

Also I had to ignore iffaddrs.ifa_ifu on Linux to pass CI

Amanieu · 2021-02-04T18:47:49Z

Unfortunately I believe this is a breaking change, which means we can't actually do this until we bump the crate version to 1.0.

cc @JohnTitor

kellda · 2021-02-04T19:23:00Z

I'm aware that it is a breaking change and that's not a problem for me to wait until a new major version for this to be merged.

bors · 2021-02-13T22:23:49Z

☔ The latest upstream changes (presumably #1975) made this pull request unmergeable. Please resolve the merge conflicts.

tgross35 · 2024-08-29T03:25:37Z

@kellda main is now intended for libc 1.0. Are you able to rebase this?

@rustbot author

rustbot · 2024-08-29T18:14:28Z

Some changes occurred in solarish module

cc @jclulow, @pfmooney

kellda · 2024-08-29T19:07:44Z

I'm unsure how to find out what's wrong with sigval on emscripten...

kellda · 2024-08-29T19:09:26Z

Btw, I noted (when I originally opened this PR) that the following fields may also be wroth considering turning into unions:

sigevent.sigev_notify_thread_id
siginfo_t.{_pad/__data}
sigaction.sa_sigaction

tgross35 · 2024-10-01T02:50:42Z

I'm unsure how to find out what's wrong with sigval on emscripten...

I also don't know. I'll mark this as review as a reminder that I need to take a look at this.

@rustbot review

Btw, I noted (when I originally opened this PR) that the following fields may also be wroth considering turning into unions:
* sigevent.sigev_notify_thread_id

* siginfo_t.{_pad/__data}

* sigaction.sa_sigaction

Feel free to submit another PR!

tgross35 · 2024-11-19T04:52:07Z

This needs another rebase, feel free to just leave emscripten disabled in build.rs as a FIXME if needed.

Regarding traits: don't add Hash/PartialEq/Eq for unions, or leave them but make the bodies unimplemented!("traits") if some other structs depend on them. We are likely going to drop these in 1.0 so we aren't doing any unsafe union field access.

For Debug, make the unions fmt.debug_struct("type_name").finish_non_exhaustive().

@rustbot author

tgross35 · 2025-02-22T20:25:40Z

@kellda CI should be set!

tgross35 · 2025-03-02T23:41:13Z

@rustbot author, this needs a rebase

kellda · 2025-07-04T16:26:52Z

Yet another inter-semester break, yet another attempt to merge this !

kellda · 2025-07-04T16:49:17Z

libc-test/build.rs

-            // sigval is a struct in Rust, but a union in C:
-            "sigval" => "union sigval".to_string(),
-


This change seems to make freebsd fail, but I'm not sure why or what would be the correct thing to do

The FreeBSD jobs are unfortunately flakey with ctest; I've tried but I can't fix the "spooky action at a distance" response to changes that seem to happen on those.

If you can get the rests of the tests passing (looks like s390x and Solaris are failing) we can hand-review the FreeBSD changes or figure something else out there.

The Solaris tests seems to fail for similar reasons than FreeBSD, or at least similar symptoms.
I'll investigate s390x and emscripten

kellda · 2025-07-05T09:21:18Z

@rustbot ready

tgross35

Sorry this took so long, but it looks great! I have one last request for names then please rebase one last time and I'm happy to merge.

tgross35 · 2025-08-10T03:39:36Z

src/fuchsia/mod.rs

        pub ifa_addr: *mut crate::sockaddr,
        pub ifa_netmask: *mut crate::sockaddr,
-        pub ifa_ifu: *mut crate::sockaddr, // FIXME(union) This should be a union
+        pub ifa_ifu: __c_anonymous_ifa_ifu,


This should be __c_anonymous_ifaddrs_ifa_ifu (struct name + field name)

tgross35 · 2025-08-10T03:41:06Z

src/fuchsia/mod.rs

+    pub union epoll_data {
+        pub ptr: *mut c_void,
+        pub fd: c_int,
+        pub u32: u32,
+        pub u64: u64,
+    }


https://cs.opensource.google/fuchsia/fuchsia/+/main:third_party/llvm-libc/src/include/llvm-libc-types/struct_epoll_data.h;l=12;drc=b47f6213560e67982d8b9d01a78daeb6ec361a5b

tgross35 · 2025-08-10T03:45:26Z

src/unix/linux_like/mod.rs

        pub ifa_addr: *mut crate::sockaddr,
        pub ifa_netmask: *mut crate::sockaddr,
-        pub ifa_ifu: *mut crate::sockaddr, // FIXME(union) This should be a union
+        pub ifa_ifu: __c_anonymous_ifa_ifu,


Same here, could you include the struct name plus the field name?

tgross35

LGTM, thank you for the persistence across the four years since this PR opened!

CI is a bit borked right now but I'll merge this soon

rust-highfive assigned Amanieu Feb 4, 2021

rust-highfive added the S-waiting-on-review label Feb 4, 2021

kellda force-pushed the use-unions branch from 9129c8e to e937f60 Compare February 14, 2021 16:49

JohnTitor added the breakage-candidate label Feb 26, 2021

JohnTitor added S-blocked and removed S-waiting-on-review labels Mar 9, 2021

rustbot added S-waiting-on-author and removed S-blocked labels Aug 29, 2024

tgross35 added this to the 1.0 milestone Aug 29, 2024

kellda force-pushed the use-unions branch from e937f60 to 428814a Compare August 29, 2024 18:14

kellda force-pushed the use-unions branch from 428814a to 1c27eac Compare August 29, 2024 18:43

rustbot added S-waiting-on-review and removed S-waiting-on-author labels Oct 1, 2024

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kellda force-pushed the use-unions branch from 1c27eac to 1f611e1 Compare November 21, 2024 10:34

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rustbot added S-waiting-on-author and removed S-waiting-on-review labels Mar 2, 2025

kellda force-pushed the use-unions branch from 5ea0e70 to 2cf8848 Compare July 4, 2025 16:25

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kellda commented Jul 4, 2025

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kellda force-pushed the use-unions branch 3 times, most recently from c5e2e67 to c10e99f Compare July 5, 2025 08:51

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tgross35 reviewed Aug 10, 2025

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kellda force-pushed the use-unions branch from c10e99f to ef7f85d Compare August 10, 2025 05:24

tgross35 approved these changes Aug 10, 2025

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kellda added 4 commits August 10, 2025 03:17

Make sigval an union

565e0ec

Make ifaddrs.ifa_ifu an union

654db78

Implement epoll_data union

598f7ea

Make fpreg_t an union

978d655

tgross35 force-pushed the use-unions branch from ef7f85d to 978d655 Compare August 10, 2025 08:17

tgross35 added the stable-declined This change is breaking, difficult to backport, low priority, or otherwise not relevant for 0.2 label Aug 10, 2025

tgross35 enabled auto-merge August 10, 2025 08:18

tgross35 added this pull request to the merge queue Aug 10, 2025

Merged via the queue into rust-lang:main with commit 051fa61 Aug 10, 2025
48 of 52 checks passed

rustbot removed the S-waiting-on-review label Aug 10, 2025

yshui mentioned this pull request Aug 11, 2025

Correct the definition of sigval #4637

Closed

3 tasks

		// sigval is a struct in Rust, but a union in C:
		"sigval" => "union sigval".to_string(),

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tgross35 commented Aug 29, 2024 •

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