Annotate unstable `*LAST` constants by dybucc · Pull Request #5120 · rust-lang/libc

dybucc · 2026-05-28T10:40:57Z

Description

This PR adds documentation. Some symbols are troublesome. They can change upstream. The Rust change is non-breaking. This requires annotating. It requires usage advice. This patch links to it.

Notes

QNX is untouched. Sources were not found. Their SDK sign up is broken.

Solaris is mostly untouched. Sources were not found. Changes include generic symbols. These were sourced from Illumos.

Sources

FreeBSD manpage detailing how UTXDB_LASTLOGIN is not the type of constant we would want to deprecate.

https://man.freebsd.org/cgi/man.cgi?query=getutxent&sektion=3
DragonFlyBSD sources showing how they define a UTX_DB_LASTLOGX symbol but not a UTX_DB_LASTLOG symbol as we do.

https://github.com/DragonFlyBSD/DragonFlyBSD/blame/59b78e44f96799c5f46fb3d6d616c18d838a75d0/include/utmpx.h#L89
Android sources showing how they use the NF_*_PRI_LAST in much the same manner as the Linux sources (further below.)

https://cs.android.com/search?q=NF_BR_PRI_LAST&ss=android%2Fplatform%2Fsuperproject
https://cs.android.com/search?q=NF_IP_PRI_LAST&sq=&ss=android%2Fplatform%2Fsuperproject
https://cs.android.com/search?q=NF_IP6_PRI_LAST&sq=&ss=android%2Fplatform%2Fsuperproject
Linux sources showing the use of NF_*_PRI_LAST constants as trailing enumeration constants defined in terms of large values.

https://github.com/torvalds/linux/blob/eb3f4b7426cfd2b79d65b7d37155480b32259a11/include/uapi/linux/netfilter_bridge.h#L42
https://github.com/torvalds/linux/blob/eb3f4b7426cfd2b79d65b7d37155480b32259a11/include/uapi/linux/netfilter_ipv4.h#L44
https://github.com/torvalds/linux/blob/eb3f4b7426cfd2b79d65b7d37155480b32259a11/include/uapi/linux/netfilter_ipv6.h#L47
Illumos sources showing how _PC_LAST should be changed when adding new _PC constants.

https://github.com/illumos/illumos-gate/blob/7124a0cccb6ebf2bcffdab36f9bdf8fe4c23d77f/usr/src/uts/common/sys/unistd.h#L336
OpenBSD sources showing how _LC_LAST serves as the "end" value for constants defined prior to it.

https://github.com/search?q=repo%3Aopenbsd%2Fsrc%20_lc_last&type=code

Checklist

Relevant tests in libc-test/semver have been updated
No placeholder or unstable values like *LAST or *MAX are included (see #3131)
Tested locally (cd libc-test && cargo test --target mytarget); especially relevant for platforms that may not be checked in CI

@rustbot label +stable-nominated

rustbot · 2026-05-28T10:41:01Z

Some changes occurred in a NetBSD-like module

cc @semarie

Some changes occurred in an OpenBSD module

cc @semarie

Some changes occurred in a solarish module

cc @jclulow, @pfmooney

Some changes occurred in an Android module

cc @maurer

This patch is a follow up to rust-lang#5120. That PR deprecated the now removed symbols such that it could be included in a stable release. This patch targets the 1.0 release, by altogether removinga the symbols and updating the SemVer-tracking file. See the accompanying PR for more details.

dybucc · 2026-06-09T07:35:19Z

CI actually passes. There seems to be an issue with a glob import that is not used, but this has not
been changed in the patch (it's not even part of it, for that matter.) For some reason, rebasing
onto main with dependabot updates has ended up with a warning across all of my open PRs due to
that one (now apparently unused) import.

This patch is a follow up to rust-lang#5120. That PR deprecated the now removed symbols such that it could be included in a stable release. This patch targets the 1.0 release, by altogether removinga the symbols and updating the SemVer-tracking file. See the accompanying PR for more details.

tgross35

Few nits than lgtm, links should pass now

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tgross35 · 2026-06-24T07:56:11Z

+/// This symbol is prone to change across releases upstream.
+/// See the [usage guidelines](crate::#usage-guidelines) for details and use.


These comments can probably just say "for details", "and use" is kind of redundant since they're called "usage guidelines"

tgross35 · 2026-06-24T08:01:04Z

-pub const SIOCIWFIRST: c_ulong = 0x8B00;
+/// This symbol is prone to change across releases upstream.
+/// See the [usage guidelines](crate::#usage-guidelines) for details and use.
 pub const SIOCIWLAST: c_ulong = SIOCIWLASTPRIV;

+pub const SIOCIWFIRST: c_ulong = 0x8B00;
+


Nit: the previous order matched source order https://cs.android.com/android/platform/superproject/+/android-latest-release:bionic/libc/kernel/uapi/linux/wireless.h;l=65-68;drc=180edefbd287c39caeb9d48784a9a10ac35f3636

tgross35 · 2026-06-24T19:29:50Z

 pub const LC_MESSAGES: c_int = 6;
+
+/// This symbol is prone to change across releases upstream.
+/// See the [usage guidelines](crate::#usage-guidelines) for details.


I guess it still doesn't like these links, does just crate#usage-guidelines work?

View changes since the review

It does. Thanks. Opened #5219. It fixes the same things on #5118 and #5119.

@rustbot ready

tgross35

LGTM but for CI fixes,
@rustbot author

View changes since this review

rustbot · 2026-06-25T06:52:31Z

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.

These symbols are troublesome. They can change upstream. They don't work well with SemVer. Usage advice is needed. This patch links to it.

These symbols are troublesome. They can change upstream. They don't work well with SemVer. Usage advice is needed. This patch links to it. (backport <rust-lang#5120>) (cherry picked from commit 7bb9988)

rustbot added the S-waiting-on-review label May 28, 2026

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This was referenced May 28, 2026

unix: annotate unstable *COUNT constants #5121

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Annotate unstable *MAX constants #5122

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dybucc changed the title ~~refactor deprecate *LAST constants fitting #3131~~ refactor deprecate *LAST constants fitting #3131 May 30, 2026

dybucc mentioned this pull request May 30, 2026

linux_l4re: annotate unstable *NUM constants #5123

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refactor: remove *LAST constants fitting #3131 #5150

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rustbot added the stable-nominated This PR should be considered for cherry-pick to libc's stable release branch label Jun 9, 2026

dybucc force-pushed the _last-deprecation branch from 8e5ad96 to 8c7d21e Compare June 15, 2026 15:26

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dybucc mentioned this pull request Jun 18, 2026

feat: add macro to declare unstable constants #5180

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tgross35 reviewed Jun 24, 2026

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tgross35 changed the title ~~crate: annotate unstalbe *LAST constants~~ crate: annotate unstable *LAST constants Jun 24, 2026

tgross35 changed the title ~~crate: annotate unstable *LAST constants~~ Annotate unstable *LAST constants Jun 24, 2026

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dybucc force-pushed the _last-deprecation branch from 48c1918 to 2934f45 Compare June 25, 2026 06:52

crate: annotate unstable *LAST constants

f52dd42

These symbols are troublesome. They can change upstream. They don't work well with SemVer. Usage advice is needed. This patch links to it.

dybucc force-pushed the _last-deprecation branch from 2934f45 to f52dd42 Compare June 25, 2026 06:56

rustbot added S-waiting-on-review and removed S-waiting-on-author labels Jun 25, 2026

tgross35 added this pull request to the merge queue Jun 25, 2026

Merged via the queue into rust-lang:main with commit 7bb9988 Jun 25, 2026
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This was referenced Jun 25, 2026

linux(uclibc): remove redundant records and explicit linking to libutil #5165

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windows: expose cfg for 64-bit time_t #5062

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Add support for aarch64-unknown-linux-pauthtest target #5065

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dybucc mentioned this pull request Jul 10, 2026

Remove "placeholder constants" #3131

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This was referenced Jul 20, 2026

[0.2] Backports #5293

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[0.2] Backports #5294

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tgross35 added stable-applied This PR has been cherry-picked to libc's stable release branch and removed stable-nominated This PR should be considered for cherry-pick to libc's stable release branch labels Jul 21, 2026

		/// This symbol is prone to change across releases upstream.
		/// See the [usage guidelines](crate::#usage-guidelines) for details and use.

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