Libs Meeting 2025-04-23

tags: Libs Meetings Minutes

Meeting Link: https://meet.jit.si/rust-libs-meeting-ujepnbwg2lzqgt6wvrndwimi
Attendees: Amanieu, JoshS, JoshT, The 8472, Chris Denton, Mara, Sarah Quiñones, Urgau

Agenda

• Triage
• Anything else?

Triage

FCPs

4 rust-lang/rust T-libs FCPs

• merge rust.tf/115746 Print thread ID in panic message - (2 checkboxes left)
• merge rust.tf/137122 Specialize `Iterator::eq{_by}` for `TrustedLen` iterators - (3 checkboxes left)
• merge rust.tf/132484 unix: Relax escaping in `Debug` impl on `Command` - (0 checkboxes left)
• merge rust.tf/135634 stop specializing on `Copy` - (4 checkboxes left)

m-ou-se (2), cuviper (1), the8472 (1), joshtriplett (3), Amanieu (1), thomcc (1)

(Backports) rust.tf/139624 Don't allow flattened format_args in const.

Accepted.

(Prioritization Requested) rust.tf/140020 regression: `error[E0308]: mismatched types` for `is_multiple_of`

As usual: New method vs extension trait in the ecosystem.

Integer trait uses everything by reference. Our new method takes things by copy. Makes sense.

JoshS: We should just acknowledge and accept.

Amanieu: 1000 downloads per month, 9000 downloads per month, ..

JoshS: This should've been warnings, right? The compiler does that?

Amanieu: not sure

(Nominated) rust.tf/140042 Library team consensus on promoting tier 3 riscv32 ESP-IDF targets to tier 2 with std that has processes and signals support stubbed out

JoshT: One of the most stubbed-out targets, other than wasm. It's not just processes and signals.

JoshT: Probably still acceptable..

The 8472: We consider wasm a mistake, though.

The 8472: It is not unix but tries to be?

Amanieu: it has a libc with unix-like apis. it's re-using unix pthreads, filesystem stuff, etc.

The 8472: how about cfg(unix)?

Amanieu: no, it is not cfg(unix).

JoshT: It uses some of the files from sys/unix, but that's internal.

The 8472: that's fine. should not be cfg(unix)

Amanieu: should double check that.

Amanieu: Oh, it is!

JoshT: It does not support processes, but it does support threads?

Amanieu: correct

JoshT: getcwd() always gives "/". chdir() is always unsupported. the kind of thing that makes me stare

JoshT: why does it claim to have that in its libc, rather than just not having that build?

Amanieu: presumably to make it work for programs that don't call it?

Amanieu: Or at the rust level?

Amanieu: we consider it acceptable for any syscall to fail. cfg() would be unportable.

JoshT: seems like the same mistake as with wasm.

Amanieu: problem with wasm is things that don't return Result, like time stuff, and then panic. Not the things that can return Result, and always fail.

Mara: cfg(unix) sounds like posix compliance to me. not the case here, right?

JoshT: is it mostly posix-compliant except exec() etc? or is it more severe?

Amanieu: by some standard, windows is mostly posix-compliant. windows is more unix than this.

Amanieu: emscripten is unix, but wasi is not.

JoshS: emscripten comes with a whole bunch of unix things.

JoshS: might not be our (libs) decision. could be lang or compiler

JoshT to write up a summary of our discussion.

(Waiting on team) rust.tf/134536 Lint on fn pointers comparisons in external macros

(Regressions) rust.tf/119560 `cargo test` performance regression on Windows on version 1.75.0

(Regressions) rust.tf/137971 P-high ReFS volumes on Windows Server 2022 break compilation

Amanieu: fix in progress

Waiting on author

(Regressions) rust.tf/139730 P-high A case of compound x86_64 performance regression caused by LLVM 20 and #124810

(Regressions) rust.tf/139542 Type inference regression in 1.86 stable, due to unstable ByteStr

(Regressions) rust.tf/53340 Performance regression in tight loop since rust 1.25

(Regressions) rust.tf/112180 assertion failed: key as usize != KEY_SENTVAL in DragonFly BSD

(Regressions) rust.tf/124216 P-medium Performance regression: rustc failed to optimize specific x86-64 SIMD intrinsics after 1.75.0

(Regressions) rust.tf/138054 P-low unreachable pub item from portable-simd with target_feature = "avx512f"

(Regressions) rust.tf/130320 P-medium stdlib code size increase in nightly-2024-09-01 for aarch64-linux-android

Actions

• Reply to all issues/PRs discussed in this meeting, or add them to the open action items.

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