fix: build-std on 32 bit arm with 64 bit time by guoxe · Pull Request #157609 · rust-lang/rust

guoxe · 2026-06-08T13:22:29Z

Infer target type of tv_usec.

The libc crate has support for building with 64 bit time on 32 bit
platforms, configurable currently via environment variable or cfg directives.
When building using 64 bit time, the tv_usec field will be aliased to __suseconds64_t instead of suseconds_t causing the build-std feature to not be able to build the standard library due to a type mismatch.
Adopting the same convention as in

rust/library/std/src/sys/net/connection/socket/solid.rs

Line 151 in 1b29cfd

    
           let mut timeout = netc::timeval { tv_sec: secs, tv_usec: timeout.subsec_micros() as _ };

fixes the issue, supporting 64 bit time on 32 bit arm platforms.

Another option would be using cfg attributes for this but from what I can tell there are no existing such attributes for time bits in the std and they would essentially duplicate the ones already present in the libc crate https://github.com/rust-lang/libc/blob/e27c7f1e2b281d7c551e6b394b897b4ff0a230e6/build.rs#L16

sertonix · 2026-06-25T13:14:08Z

-                    tv_usec: dur.subsec_micros() as libc::suseconds_t,
+                    // If building 32 bit GNU platforms with 64 bit time, we need to call into here
+                    // since `tv_usec` will in that case be an i64 aliased to __suseconds64_t
+                    tv_usec: (dur.subsec_micros() as libc::suseconds_t).into(),


There is no reason to use as libc::suseconds_t if we ignore it anyways

Suggested change

tv_usec: (dur.subsec_micros() as libc::suseconds_t).into(),

tv_usec: dur.subsec_micros().into(),

View changes since the review

We can not use .into() directly here since subsec_micros returns an unsigned integer.

rustbot · 2026-08-05T14:12:05Z

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @jhpratt (or someone else) some time within the next two weeks.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

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Owners of files modified in this PR: @ChrisDenton, libs
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Random selection from JohnTitor, Mark-Simulacrum, clarfonthey, jhpratt, nia-e

jhpratt · 2026-08-06T04:52:53Z

Stepping away from reviews temporarily.

@rustbot reroll

Mark-Simulacrum · 2026-08-08T13:50:30Z

@bors squash

* fix: build-std on 32 bit arm with 64 bit time The libc crate has support for building with 64 bit time on 32 bit platforms using the `RUST_LIBC_UNSTABLE_GNU_TIME_BITS` environment variable. Convert the tv_usec field to i64 via `into` in this case since `suseconds_t` is still defined as an i32 when this environment variable is set. * Use placeholder as target type This allows us to rely on the compiler to infer the correct target type, mirroring the approach used in `sys/net/connection/socket/solid.rs`.

rust-bors · 2026-08-08T13:50:52Z

🔨 2 commits were squashed into f846f11.

Mark-Simulacrum · 2026-08-08T13:51:07Z

@bors r+ rollup

rust-bors · 2026-08-08T13:51:10Z

📌 Commit f846f11 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…uwer Rollup of 12 pull requests Successful merges: - #160336 (Move attributes out of rustc_hir) - #160715 (ignore tests with the GCC backend if we can't find `libgccjit.so` for the target) - #157609 (fix: build-std on 32 bit arm with 64 bit time) - #160613 (Add regression test for unsized non-last struct field with overlapping impls) - #160658 (miri: implement more restrictive trivial-ABI checks) - #160704 (sort lint names in lint pass declarations) - #160707 (Add regression test for higher ranked fn pointer impl not general enough) - #160713 (Add regression test for #135287) - #160720 (triagebot: add ubiratan to infra-ci) - #160747 (rustc_errors: remove unused code) - #160751 (Add regression test for incremental borrowck ICE with generic const exprs) - #160753 (rustc_lint: remove unused rustc_attrs feature) Failed merges: - #158835 (rustc_passes: lint unused `#[path]` attributes on inline modules)

Rollup merge of #157609 - guoxe:fix_build_std_arm32_gnu_time_bits64, r=Mark-Simulacrum fix: build-std on 32 bit arm with 64 bit time Infer target type of `tv_usec`. The libc crate has support for building with 64 bit time on 32 bit platforms, configurable currently via environment variable or cfg directives. When building using 64 bit time, the tv_usec field will be aliased to `__suseconds64_t` instead of `suseconds_t` causing the `build-std` feature to not be able to build the standard library due to a type mismatch. Adopting the same convention as in https://github.com/rust-lang/rust/blob/1b29cfdbee8ee37333f4b24afb936350eb57e705/library/std/src/sys/net/connection/socket/solid.rs#L151 fixes the issue, supporting 64 bit time on 32 bit arm platforms. Another option would be using cfg attributes for this but from what I can tell there are no existing such attributes for time bits in the std and they would essentially duplicate the ones already present in the libc crate https://github.com/rust-lang/libc/blob/e27c7f1e2b281d7c551e6b394b897b4ff0a230e6/build.rs#L16

…uwer Rollup of 12 pull requests Successful merges: - rust-lang/rust#160336 (Move attributes out of rustc_hir) - rust-lang/rust#160715 (ignore tests with the GCC backend if we can't find `libgccjit.so` for the target) - rust-lang/rust#157609 (fix: build-std on 32 bit arm with 64 bit time) - rust-lang/rust#160613 (Add regression test for unsized non-last struct field with overlapping impls) - rust-lang/rust#160658 (miri: implement more restrictive trivial-ABI checks) - rust-lang/rust#160704 (sort lint names in lint pass declarations) - rust-lang/rust#160707 (Add regression test for higher ranked fn pointer impl not general enough) - rust-lang/rust#160713 (Add regression test for rust-lang/rust#135287) - rust-lang/rust#160720 (triagebot: add ubiratan to infra-ci) - rust-lang/rust#160747 (rustc_errors: remove unused code) - rust-lang/rust#160751 (Add regression test for incremental borrowck ICE with generic const exprs) - rust-lang/rust#160753 (rustc_lint: remove unused rustc_attrs feature) Failed merges: - rust-lang/rust#158835 (rustc_passes: lint unused `#[path]` attributes on inline modules)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 8, 2026

sertonix reviewed Jun 25, 2026

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guoxe force-pushed the fix_build_std_arm32_gnu_time_bits64 branch from dacadfc to 538573a Compare August 5, 2026 12:56

guoxe marked this pull request as ready for review August 5, 2026 14:12

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rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 5, 2026

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rust-bors Bot force-pushed the fix_build_std_arm32_gnu_time_bits64 branch from 538573a to f846f11 Compare August 8, 2026 13:50

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 8, 2026

JonathanBrouwer mentioned this pull request Aug 8, 2026

Rollup of 12 pull requests #160761

Merged

rust-bors Bot merged commit 473809d into rust-lang:main Aug 8, 2026
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rustbot added this to the 1.99.0 milestone Aug 8, 2026

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fix: build-std on 32 bit arm with 64 bit time - #157609

fix: build-std on 32 bit arm with 64 bit time#157609
rust-bors[bot] merged 1 commit into
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	tv_usec: (dur.subsec_micros() as libc::suseconds_t).into(),
	tv_usec: dur.subsec_micros().into(),

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