# Libs Meeting 2023-06-07 ###### tags: `Libs Meetings` `Minutes` **Meeting Link**: https://meet.jit.si/rust-libs-meeting-ujepnbwg2lzqgt6wvrndwimi **Attendees**: Amanieu, The 8472, Mara, joboet ## Agenda - Triage - Anything else? ## Triage ### FCPs 1 rust-lang/rust T-libs FCPs - merge rust.tf/104385 *Raise minimum supported Apple OS versions* - (9 checkboxes left) ### (Backports) rust.tf/112292 *Avoid unwind across \`extern "C"\` in \`thread\_local::fast\_local\`* This 'technically UB' doesn't really result in actual issues, it seems. Not a recent regression, so might not be a good backport candidate. Left a comment. ### (Nominated) rust.tf/84187 *Tracking Issue for restructuring \`sys\_common\`* Discussed last time. Still need to respond. Mara to respond. ### (Nominated) rust.tf/110708 *Consider documenting that (parts of?) stdlib must not be used before/after main* Discussed last time. Amanieu replied, saying the main issue is thread::current(), which is only used in a few places. For LocalKey::with we already document it: https://doc.rust-lang.org/stable/std/thread/struct.LocalKey.html#method.with (And also have a try_with.) Only for thread::current() (and a few APIs that use that) we don't provide any panic docs (or a try_current() etc.). Pre-main seems like it's rarely a problem, it's post-main that is more interesting. ### (Nominated) rust.tf/111071 *assert\_eq! message format (take 2a)* Summary: https://github.com/rust-lang/rust/pull/111071#issuecomment-1576734594 Question 1: Change the default panic handler output format? Possible answers: 1. No 2. Yes, as proposed, but only for multi-line messages 3. Yes, as proposed, but for all messages 3 seems like a nice option, because the current "at {message}, {location}" feels flipped/swapped. Crater run could check how widely people depend on the exact output. We can do an FCP to make it show up in TWiR. Split this into a separate PR to focus first on just the panic_handler output, independent from assert_eq. Question 2: Change the panic message of assert_eq? - Put the message on a separate line? - Call it "error" or "message" or "description" or ... ? - Put message on the first line? ``` assertion failed: `left == right` error: message goes here left: `1` right: `2` ``` ``` assertion failed: `left == right`, message goes here left: `1` right: `2` ``` ``` assertion failed: message goes here check: left == right left: 1 right: 2 ``` Leave this for after the PR for question 1. ### (Waiting on team) rust.tf/103126 *Add cfg(no\_128\_bit) to core: removes u128/i128 formatting* Discussed and responded last time. FCP close in progress. Removed label. ### (Regressions) rust.tf/109064 `P-high` *\`+outline\-atomics\` violates "core shall not depend on libc"* Resolutions: Either: - remove outline-atomics, or - allow core to depend on libc. The 'can core depend on libc' discussion is a complicated one, probably needs an RFC for a resolution. Amanieu to write up that RFC. ### (Regressions) rust.tf/112180 *assertion failed: key as usize != KEY\_SENTVAL in DragonFly BSD* Might have already been broken but simply not resulted in a panic. Tier 3, so not high priority.