Stream: t-compiler/meetings

Topic: [weekly meeting] 2021-03-11 #54818


pnkfelix (Mar 11 2021 at 14:14, on Zulip):

Hi @T-compiler/meeting ; we’ll be starting the weekly triage meeting in about 46 minutes.

pnkfelix (Mar 11 2021 at 14:15, on Zulip):

The current agenda, prepared by @WG-prioritization , is here: https://hackmd.io/3dTKNk1_RiK3NOZMfyOldw?view

pnkfelix (Mar 11 2021 at 14:16, on Zulip):

@nikomatsakis and @tmandry , is there anything to report from WG-async-foundations ?

pnkfelix (Mar 11 2021 at 14:16, on Zulip):

and likewise, @nikomatsakis and @Jack Huey , is there anything to report from WG-traits ?

nikomatsakis (Mar 11 2021 at 14:16, on Zulip):

Hmm. :) Yes.

apiraino (Mar 11 2021 at 14:16, on Zulip):

(sorry was about to post the invite)

pnkfelix (Mar 11 2021 at 14:16, on Zulip):

(in either case, feel free to put it directly into the above linked agenda

pnkfelix (Mar 11 2021 at 14:17, on Zulip):

No problem @apiraino , I just happened to be here

pnkfelix (Mar 11 2021 at 15:00, on Zulip):

Hi @T-compiler/meeting , the weekly triage meeting is starting now. Leave a :wave: to show that you're here

pnkfelix (Mar 11 2021 at 15:01, on Zulip):

Lets start off with 8 minutes for

Announcements

pnkfelix (Mar 11 2021 at 15:01, on Zulip):
pnkfelix (Mar 11 2021 at 15:03, on Zulip):

here is "current" list of proposals: https://github.com/rust-lang/compiler-team/issues?q=is%3Aopen+is%3Aissue+label%3Ameeting-proposal+-label%3Ameeting-scheduled (thanks to @Wesley Wiser for posting proposal re sprint retrospective)

pnkfelix (Mar 11 2021 at 15:03, on Zulip):

which reminds me

pnkfelix (Mar 11 2021 at 15:04, on Zulip):
pnkfelix (Mar 11 2021 at 15:04, on Zulip):

I think there was a lot of useful exchange of ideas and gathering of information during the week

pnkfelix (Mar 11 2021 at 15:04, on Zulip):

Not so much to report on concrete action, though some PR's did land that should have an effect.

Wesley Wiser (Mar 11 2021 at 15:05, on Zulip):

Could we try to get a list together of PR's from that week that did land?

pnkfelix (Mar 11 2021 at 15:05, on Zulip):

anyway we can talk about that at the retrospective, assuming it happens

pnkfelix (Mar 11 2021 at 15:05, on Zulip):

Wesley Wiser said:

Could we try to get a list together of PR's from that week that did land?

that would be good

pnkfelix (Mar 11 2021 at 15:05, on Zulip):

(it might have been a good idea to allocate a label on the repo to tag PR's related to the sprint)

pnkfelix (Mar 11 2021 at 15:06, on Zulip):

lets keep going

pnkfelix (Mar 11 2021 at 15:06, on Zulip):

MCPs/FCPs status

pnkfelix (Mar 11 2021 at 15:06, on Zulip):
pnkfelix (Mar 11 2021 at 15:06, on Zulip):
pnkfelix (Mar 11 2021 at 15:06, on Zulip):
pnkfelix (Mar 11 2021 at 15:06, on Zulip):
pnkfelix (Mar 11 2021 at 15:06, on Zulip):
pnkfelix (Mar 11 2021 at 15:06, on Zulip):
nagisa (Mar 11 2021 at 15:08, on Zulip):

(Late announcement: LLVM12 bump landed, with the new and exciting features, fixes and, of course, bugs)

pnkfelix (Mar 11 2021 at 15:09, on Zulip):

WG checkins

pnkfelix (Mar 11 2021 at 15:09, on Zulip):

@WG-async-foundations by @nikomatsakis and @tmandry:

pnkfelix (Mar 11 2021 at 15:09, on Zulip):

@WG-traits by @nikomatsakis and @Jack Huey:

pnkfelix (Mar 11 2021 at 15:09, on Zulip):

This isn't an announcement, as much as a general query:

pnkfelix (Mar 11 2021 at 15:10, on Zulip):

If you have recently used either gdb or lldb to debug a rust program (not necessarily rustc) you recently (within last month lets say) compiled, can you put a :+1: on this comment?

Joshua Nelson (Mar 11 2021 at 15:11, on Zulip):

(should I assume you mean "compiled with rustc"?)

pnkfelix (Mar 11 2021 at 15:11, on Zulip):

Oh yes! That should have been explicitly stated.

pnkfelix (Mar 11 2021 at 15:11, on Zulip):

(I ask because I recently tried to use gdb on what I thought was a relatively simple program, on Linux, and things didn't work as I expected. So I'm trying to find other people who have used it recently so I can pick their brain to figure out what I'm doing wrong.)

Wesley Wiser (Mar 11 2021 at 15:12, on Zulip):

I've been using Windbg recently and the experience is not great there either. So perhaps there are some more general issues that are xplat?

pnkfelix (Mar 11 2021 at 15:12, on Zulip):

(I'll look at the :+1: 's later and ping those people, perhaps in a dedicated zulip topic)

pnkfelix (Mar 11 2021 at 15:12, on Zulip):

(when I say "didn't work as expected", I mean like I wasn't even able to get source code references, so step didn't work, because it didn't have a notion of what the next line of code even was.)

pnkfelix (Mar 11 2021 at 15:13, on Zulip):

I wouldn't be surprised if there are issues, including xplat ones.

pnkfelix (Mar 11 2021 at 15:14, on Zulip):

I just am a bit surprised it got as bad as I observed. I don't yet know if my issue is related to cargo as well, or if it can be narrowed to rustc

pnkfelix (Mar 11 2021 at 15:14, on Zulip):

anyway,I got my list of "people" to bother about this later.

pnkfelix (Mar 11 2021 at 15:14, on Zulip):

so lets move along

pnkfelix (Mar 11 2021 at 15:15, on Zulip):

@nagisa (is there a particularly good or bad time for me to try to get a conversation going with you? Is today good, or tomorrow better?)

pnkfelix (Mar 11 2021 at 15:15, on Zulip):

Oh there's one more announcement worth making

pnkfelix (Mar 11 2021 at 15:15, on Zulip):

the next release will be on march 25th

pnkfelix (Mar 11 2021 at 15:15, on Zulip):

that's two weeks away

pnkfelix (Mar 11 2021 at 15:16, on Zulip):

which makes backport questions all the more important! So lets get to them

pnkfelix (Mar 11 2021 at 15:16, on Zulip):

Backport nominations

pnkfelix (Mar 11 2021 at 15:16, on Zulip):

T-compiler stable / T-compiler beta

nagisa (Mar 11 2021 at 15:16, on Zulip):

pnkfelix said:

nagisa (is there a particularly good or bad time for me to try to get a conversation going with you? Is today good, or tomorrow better?)

I've a 2hr block later today I have preexisting obligations at, but otherwise any time is fine.

pnkfelix (Mar 11 2021 at 15:16, on Zulip):

T-libs-impl stable / T-libs-impl beta

pnkfelix (Mar 11 2021 at 15:16, on Zulip):
pnkfelix (Mar 11 2021 at 15:17, on Zulip):

well, this isn't subtle at all /s

pnkfelix (Mar 11 2021 at 15:19, on Zulip):

This seems fine to me, assuming the performance hit is acceptable for the short term...?

pnkfelix (Mar 11 2021 at 15:19, on Zulip):

(basically I trust alex to make such calls there.)

pnkfelix (Mar 11 2021 at 15:20, on Zulip):

however it hasn't landed on nightly yet. :(

pnkfelix (Mar 11 2021 at 15:20, on Zulip):

I'll just go r+ it now, I think it looks solid, so it has time to bake in nightly

nagisa (Mar 11 2021 at 15:20, on Zulip):

Yeah, I was thinking about it, but there isn't a reason we cannot accept a backport conditional on r+ for nightly.

pnkfelix (Mar 11 2021 at 15:21, on Zulip):

right, we've done so before

pnkfelix (Mar 11 2021 at 15:21, on Zulip):

In terms of the performance impact... is this worth saying rollup=never ?

pnkfelix (Mar 11 2021 at 15:21, on Zulip):

its not going to impact rustc's performance

nagisa (Mar 11 2021 at 15:21, on Zulip):

we don't run perf on wasm, let alone wasi.

pnkfelix (Mar 11 2021 at 15:21, on Zulip):

do wasm developers ever bisect over rustc commit history to investigate performance?

pnkfelix (Mar 11 2021 at 15:21, on Zulip):

right

Joshua Nelson (Mar 11 2021 at 15:22, on Zulip):

pnkfelix said:

In terms of the performance impact... is this worth saying rollup=never ?

#t-infra has been discussing separating "this PR is risky" from "this PR affects perf"

pnkfelix (Mar 11 2021 at 15:22, on Zulip):

So okay, I'm not going to post rollup=never here

Joshua Nelson (Mar 11 2021 at 15:22, on Zulip):

by running perf runs for some prs even if they get rolled up

pnkfelix (Mar 11 2021 at 15:22, on Zulip):

a wasi developer looking into performance should be able to build their own rustc

pnkfelix (Mar 11 2021 at 15:22, on Zulip):

(perf runs won't tell us anything in this case)

pnkfelix (Mar 11 2021 at 15:23, on Zulip):

(this was more a question about what development practices wasi developers are likely to rely on, such as bisecting over the CI-build)

pnkfelix (Mar 11 2021 at 15:23, on Zulip):

It seems like no one is objecting here to a beta backport, but no one is pushing for it either

pnkfelix (Mar 11 2021 at 15:24, on Zulip):

I think we should delegate to libs-impl for the call there

pnkfelix (Mar 11 2021 at 15:24, on Zulip):

cc @Mara

pnkfelix (Mar 11 2021 at 15:24, on Zulip):

(to be fair, libs-impl was not tagged on the issue until yesterday)

pnkfelix (Mar 11 2021 at 15:24, on Zulip):

lets leave it beta-nominated for now

pnkfelix (Mar 11 2021 at 15:24, on Zulip):

can someone leave a note summarizing what I wrote above?

pnkfelix (Mar 11 2021 at 15:25, on Zulip):

moving on

pnkfelix (Mar 11 2021 at 15:25, on Zulip):
pnkfelix (Mar 11 2021 at 15:25, on Zulip):

hmm. I don't think I want to think about back-porting #82804 to stable

pnkfelix (Mar 11 2021 at 15:25, on Zulip):

the release is in two weeks anyway. I don't think it would matter.

apiraino (Mar 11 2021 at 15:25, on Zulip):

:point_up: thats more a question from me (just in case the backport was approved)

pnkfelix (Mar 11 2021 at 15:25, on Zulip):

(unless we don't get it into beta before release)

pnkfelix (Mar 11 2021 at 15:26, on Zulip):

so lets not worry about stable-nomination for now

pnkfelix (Mar 11 2021 at 15:26, on Zulip):

PRs S-waiting-on-team

T-compiler

pnkfelix (Mar 11 2021 at 15:26, on Zulip):
nagisa (Mar 11 2021 at 15:27, on Zulip):

This is waiting a design meeting slot

Mara (Mar 11 2021 at 15:27, on Zulip):

oh hey. reading back

Wesley Wiser (Mar 11 2021 at 15:27, on Zulip):

Ah, ok. I can file a meeting proposal for that.

pnkfelix (Mar 11 2021 at 15:27, on Zulip):

Great, yeah, Lets make a meeting proposal. Thanks @Wesley Wiser !

pnkfelix (Mar 11 2021 at 15:28, on Zulip):

And maybe someone can communicate with the PR filer about the protocol here, in terms of setting expectations about how long it might be before the discussion happens?

pnkfelix (Mar 11 2021 at 15:28, on Zulip):

@Esteban Küber would you be willing to do that? or @nagisa ?

Wesley Wiser (Mar 11 2021 at 15:28, on Zulip):

I'll make sure to post a comment in the thread in #t-compiler

pnkfelix (Mar 11 2021 at 15:28, on Zulip):

okay great, that will do.

Wesley Wiser (Mar 11 2021 at 15:29, on Zulip):

and maybe also try to get some dates that work for the PR author.

pnkfelix (Mar 11 2021 at 15:29, on Zulip):

super :+1: to that

pnkfelix (Mar 11 2021 at 15:29, on Zulip):

T-libs-impl

pnkfelix (Mar 11 2021 at 15:29, on Zulip):

Issues of Note

Short Summary

pnkfelix (Mar 11 2021 at 15:29, on Zulip):

P-critical

T-compiler

pnkfelix (Mar 11 2021 at 15:30, on Zulip):

fudge

nagisa (Mar 11 2021 at 15:30, on Zulip):

This has been investigated and I think there's a fix for that if my memory serves me right.

Esteban Küber (Mar 11 2021 at 15:30, on Zulip):

On our end or llvm?

pnkfelix (Mar 11 2021 at 15:31, on Zulip):

yeah comment thread says LLVM

nagisa (Mar 11 2021 at 15:31, on Zulip):

Not sure if we have a PR to backport the LLVM fix.

nagisa (Mar 11 2021 at 15:31, on Zulip):

the LLVM fix itself has landed upstream.

pnkfelix (Mar 11 2021 at 15:31, on Zulip):

@Nikita Popov any interest in making a backport PR ?

pnkfelix (Mar 11 2021 at 15:31, on Zulip):

its currently assigned to them

pnkfelix (Mar 11 2021 at 15:32, on Zulip):

anyone else want to own just the part of making sure the backport PR happens?

nagisa (Mar 11 2021 at 15:32, on Zulip):

I can look after it, yes.

pnkfelix (Mar 11 2021 at 15:32, on Zulip):

okay great, thanks @nagisa

pnkfelix (Mar 11 2021 at 15:33, on Zulip):

(obviously best to coordinate that with @Nikita Popov )

pnkfelix (Mar 11 2021 at 15:33, on Zulip):

next

pnkfelix (Mar 11 2021 at 15:33, on Zulip):
pnkfelix (Mar 11 2021 at 15:33, on Zulip):

okay so the theory is that this has the same casue

pnkfelix (Mar 11 2021 at 15:34, on Zulip):

(lets get another :tada: for the LLVM 12 upgrade. :laughing: )

Nikita Popov (Mar 11 2021 at 15:34, on Zulip):

pnkfelix said:

Nikita Popov any interest in making a backport PR ?

Yeah, I'm waiting for existing submodule update to land first, to avoid conflicts.

pnkfelix (Mar 11 2021 at 15:34, on Zulip):

awesome

pnkfelix (Mar 11 2021 at 15:34, on Zulip):

next

pnkfelix (Mar 11 2021 at 15:34, on Zulip):

T-libs-impl

pnkfelix (Mar 11 2021 at 15:36, on Zulip):

@Mara is it best to tag such fix PR's with T-libs-impl as well? Or do you all get to them via the issue list anyway?

Mara (Mar 11 2021 at 15:36, on Zulip):

oh yes, having the PR tagged would be great

pnkfelix (Mar 11 2021 at 15:36, on Zulip):

okay. I tagged it already

pnkfelix (Mar 11 2021 at 15:36, on Zulip):

good to know for future

pnkfelix (Mar 11 2021 at 15:37, on Zulip):

I'll assume that T-libs-impl will handle it, and also make judgement call about whether to beta-nominate etc

pnkfelix (Mar 11 2021 at 15:37, on Zulip):

T-rustdoc

pnkfelix (Mar 11 2021 at 15:37, on Zulip):

P-high regressions

P-high beta regressions

pnkfelix (Mar 11 2021 at 15:37, on Zulip):
pnkfelix (Mar 11 2021 at 15:38, on Zulip):

(already discussed, approved for nightly by me, and delegated to T-libs-impl re beta-backport decision)

pnkfelix (Mar 11 2021 at 15:38, on Zulip):

Unassigned P-high nightly regressions

pnkfelix (Mar 11 2021 at 15:38, on Zulip):

Performance logs

2021-03-10 Triage Log

pnkfelix (Mar 11 2021 at 15:38, on Zulip):

A generally positive albeit quiet week though many of the perf improvements were gaining performance back from previous regressions. We'll need to continue to keep an eye on rollups as there were two that caused small performance changes.

Triage done by @rylev.

1 Regression, 4 Improvements, 1 Mixed
2 of them in rollups

pnkfelix (Mar 11 2021 at 15:38, on Zulip):

Regressions

Rollup of 8 pull requests #82929

pnkfelix (Mar 11 2021 at 15:38, on Zulip):

Improvements

pnkfelix (Mar 11 2021 at 15:39, on Zulip):

Mixed

Upgrade to LLVM 12 #81451

pnkfelix (Mar 11 2021 at 15:39, on Zulip):

Nags requiring follow up

No nags for this week and the nag from last week has been resolved by #81458.

pnkfelix (Mar 11 2021 at 15:40, on Zulip):

@rylev: did #81458 resolve something? or did it regress something that was resolved elsewhere?

pnkfelix (Mar 11 2021 at 15:41, on Zulip):

seems like PR #82738 is the followup that resolved the regression injected by #81458

pnkfelix (Mar 11 2021 at 15:41, on Zulip):

Nominated Issues

T-compiler

pnkfelix (Mar 11 2021 at 15:41, on Zulip):
rylev (Mar 11 2021 at 15:41, on Zulip):

pnkfelix said:

seems like PR #82738 is the followup that resolved the regression injected by #81458

That is correct

pnkfelix (Mar 11 2021 at 15:41, on Zulip):

thanks @rylev !

pnkfelix (Mar 11 2021 at 15:42, on Zulip):

Okay so I ensured #81658 was on our docket. Lets try to summarize it quickly.

pnkfelix (Mar 11 2021 at 15:42, on Zulip):

Can someone talk me out of just reverting PR #81473 ?

Wesley Wiser (Mar 11 2021 at 15:42, on Zulip):

Should we "just" revert PR #81473 on beta-alone, and in parallel improve the diagnostic on nightly?

I think this would be a good idea.

Wesley Wiser (Mar 11 2021 at 15:43, on Zulip):

I don't see any reason this "has" to ship in beta and it looks easy to revert.

pnkfelix (Mar 11 2021 at 15:43, on Zulip):

(I'm mentoring Sunjay Varma to fix the issue, and that will be simpler to tell them that we'll focus on nightly.)

pnkfelix (Mar 11 2021 at 15:44, on Zulip):

Okay lets just revert PR #81473 on beta. I can own that.

pnkfelix (Mar 11 2021 at 15:44, on Zulip):

next

pnkfelix (Mar 11 2021 at 15:44, on Zulip):
pnkfelix (Mar 11 2021 at 15:45, on Zulip):

discussion of this might well be worth a design meeting. Maybe.

pnkfelix (Mar 11 2021 at 15:45, on Zulip):

or maybe it just needs an owner. :)

pnkfelix (Mar 11 2021 at 15:46, on Zulip):

(it also might make sense to cc alex crichton on the issue)

pnkfelix (Mar 11 2021 at 15:47, on Zulip):

Okay. I'll self-assign to look at it. I've had some experience messing around with this stuff on OS X

pnkfelix (Mar 11 2021 at 15:48, on Zulip):

next

pnkfelix (Mar 11 2021 at 15:49, on Zulip):

oh, yeah, we tabled this for post-sprint. :)

pnkfelix (Mar 11 2021 at 15:49, on Zulip):

sigh

pnkfelix (Mar 11 2021 at 15:49, on Zulip):

we're not as short on time as we would normally be at this point

pnkfelix (Mar 11 2021 at 15:49, on Zulip):

so maybe lets take a moment for #82151

pnkfelix (Mar 11 2021 at 15:50, on Zulip):

(take a minute to read the bug itself, that is)

nagisa (Mar 11 2021 at 15:51, on Zulip):

This might be an issue in link argument order or lack of #[link(...)] attributes in user code or something like that.

pnkfelix (Mar 11 2021 at 15:51, on Zulip):

lets consider the given MCVE

nagisa (Mar 11 2021 at 15:52, on Zulip):

I recall somewhere else an issue about how cdylib and dylib don't mix well, too.

Wesley Wiser (Mar 11 2021 at 15:53, on Zulip):

https://github.com/rust-lang/rust/issues/65610 maybe?

pnkfelix (Mar 11 2021 at 15:53, on Zulip):

so it seems like the steps here are: 1. identify whether the MCVE is correct code or not (incl how it mixes cdylib+dylib), 2. document options for fixing the MCVE, 3. figure out how to apply those steps to the larger bug (which includes tokio+hyper etc)

nagisa (Mar 11 2021 at 15:54, on Zulip):

Wesley Wiser said:

https://github.com/rust-lang/rust/issues/65610 maybe?

I don't think that's related, but https://github.com/rust-lang/rust/issues/56784 seems to be.

pnkfelix (Mar 11 2021 at 15:55, on Zulip):

I'm willing to allocate some time today for steps 1 (+2, if I can complete 1)

pnkfelix (Mar 11 2021 at 15:56, on Zulip):

I'm debating whether there would be any benefit to trying to engage with people on tokio side. I suppose it will depend on what the answer for what the fixes are

pnkfelix (Mar 11 2021 at 15:56, on Zulip):

I'll self-assign for now

pnkfelix (Mar 11 2021 at 15:56, on Zulip):
pnkfelix (Mar 11 2021 at 15:56, on Zulip):

we already discussed this

pnkfelix (Mar 11 2021 at 15:57, on Zulip):
pnkfelix (Mar 11 2021 at 15:59, on Zulip):

we're almost out of meeting time. I sense that no one is going to volunteer to own this issue this week.

pnkfelix (Mar 11 2021 at 15:59, on Zulip):

We used to have a traits wg

pnkfelix (Mar 11 2021 at 16:00, on Zulip):

but they're focused on foundational question and new trait-solving architectures at this point, right? Not technical artifacts like this?

pnkfelix (Mar 11 2021 at 16:01, on Zulip):

From @Frank Steffahn comment

As to ways this _should_ be fixed: Either disallow all types fn(...) -> R with R: !Sized in general, or at least change the compiler so that they don’t implement FnOnce.

pnkfelix (Mar 11 2021 at 16:02, on Zulip):

That might be a relatively easy fix to put in, in any case. So more a question of whether its a good fix. Maybe a question for T-lang then?

pnkfelix (Mar 11 2021 at 16:02, on Zulip):

I'm going to put that in a comment and retag as T-lang. Nothing like passing the buck.

Esteban Küber (Mar 11 2021 at 16:02, on Zulip):

I can take a look at the impl side of that

pnkfelix (Mar 11 2021 at 16:02, on Zulip):

T-libs-impl

RFC

Esteban Küber (Mar 11 2021 at 16:03, on Zulip):

(Next week)

pnkfelix (Mar 11 2021 at 16:03, on Zulip):

@Esteban Küber don't stress too hard about implementing it though, until after T-lang has had chance to confirm

pnkfelix (Mar 11 2021 at 16:03, on Zulip):

okay good

pnkfelix (Mar 11 2021 at 16:03, on Zulip):

thats our meeting time everyone

pnkfelix (Mar 11 2021 at 16:03, on Zulip):

thanks to everyone in @T-compiler/meeting for attending!

apiraino (Mar 11 2021 at 16:35, on Zulip):

Draft for next week's agenda:
https://hackmd.io/PD1DrtFbSJaLo-hZ0WYc5g?view

Scheduled checkins:

Last update: Jul 29 2021 at 21:45UTC