Missing ICE info after some compiler panics

@lqd

Several panic messages changed recently:

With the panic in ICE with mismatch in trait associated constant #105632, the output now ends immediately after the stack trace. The information about how to report an ICE is missing, and the query stack is also missing.
With the panic in ICE: unwrap on None in find_cycle_in_stack #105321, the output now includes "panic in a function that cannot unwind"

Missing output example

As an example, here's the post-stack-trace output when testing #105632 with an older build:

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.68.0-nightly (657eefe2d 2022-12-11) running on x86_64-apple-darwin

query stack during panic:
#0 [typeck] type-checking `bar`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack

Regression

Seems to be a regression from bdb07a8 (#103647) (@lqd)

Version

rustc 1.68.0-nightly (bdb07a8ec 2022-12-11)
binary: rustc
commit-hash: bdb07a8ec8e77aa10fb84fae1d4ff71c21180bb4
commit-date: 2022-12-11
host: x86_64-apple-darwin
release: 1.68.0-nightly
LLVM version: 15.0.6

@rustbot

Requesting prioritization because affects the quality of bug reports and may interfere with bisection.

@rustbot prioritize

@jruderman

@jruderman do you test on an x86_64 mac? otherwise, I'm curious how you bisected this to #103647.

Yes, this is all on x86_64 mac.

I'm not sure why this would affect ICEs so I've posted the #105646 revert to allow time for some investigation.

Rollup merge of rust-lang#105646 - lqd:revert-thinlto, r=Mark-Simulacrum

This issue isn't platform-specific, and happens on all nightlies built with ThinLTO:

on x64 mac, via Enable ThinLTO for rustc on x86_64-apple-darwin #103647 starting with nightly-2022-12-12 (being reverted in Revert "enable ThinLTO for rustc on x86_64-apple-darwin dist builds" #105646)
on x64 msvc, via Enable ThinLTO for rustc on x64 msvc #103591 starting with the same nightly-2022-12-12
on x64 linux, via Enable LTO for rustc_driver.so #101403 starting with nightly-2022-10-24, and which lands on stable 1.66 in 2 days.

Examples:

On the most recent nightlies, where ThinLTO is enabled on the main targets above: ICE with mismatch in trait associated constant #105632 linked in the OP

#![feature(associated_const_equality)]
#![allow(dead_code)]

trait TraitWAssocConst {
        const A: usize;
}

fn foo<T: TraitWAssocConst<A = 1>>() {}

fn bar<T: TraitWAssocConst<A = 0>>() {
        foo::<T>();
}

fn main() {}

And we can see on the playground that the usual ICE post-trace output is missing.

Note that this ICE was not present on nightly-2022-10-24, and is most useful for bisecting on win/mac, not linux: the following example should be usable for that.

An ICE whose existence crosses the Enable LTO for rustc_driver.so #101403 linux merge date, so you can see the before and after changes (this ICE happens in 1.66 and is fixed in 1.67): ICE: assertion failed: elem.index() < self.domain_size #103748

struct Apple((Apple, Option(Banana ? Citron)));

fn main() {}

We can see the ICE is missing the post trace output on the current beta (1.66.beta.2) on the playground, and the output changed in nightly-2022-10-24, it is present in nightly-2022-10-23.

Since this is useful output for reporting issues, debugging and bisection, should we do something about ThinLTO landing on stable on linux in 2 days (e.g. disabling rust.lto=thin on the x64 linux dist builder on beta) ? I'm not sure anyone will have the time to investigate and land a fix by then.

@rustbot

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-critical

Auto merge of rust-lang#105646 - lqd:revert-thinlto, r=Mark-Simulacrum

#105800 should fix the -Zdylib-lto bug causing this issue, so we shouldn't need to revert the rust.lto = thin config on the dist builders.

Auto merge of rust-lang#105800 - lqd:dylib-thinlto, r=bjorn3

Auto merge of rust-lang#105845 - lqd:revert-thinlto-revert, r=Mark-Si…

Can this be closed now?

Probably. The fix has landed on nightly and beta, but the PR is still stable-nominated. It's not really critical to do such a backport unless someone experiences issues on 1.66 or the triage WG sees too many bug reports they don't like.

@lqd

As @lqd says - the stable backport was discussed but ultimately kept "on hold" to see how the patch behaves in the beta channel. A stable backport sometimes means a point release and that's up to T-infra to decide.

Ok if you prefer to close this issue, we can always re-open if a stable backport will be approved (that will be discussed probably next week)

This is several months old at this point, I think it's safe to say there won't be a stable backport 😄

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Missing ICE info after some compiler panics #105637

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Missing ICE info after some compiler panics #105637

Description

Missing output example

Regression

Version

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jruderman commented on Dec 12, 2022

compiler-errors commented on Dec 12, 2022

jruderman commented on Dec 12, 2022

lqd commented on Dec 13, 2022

lqd commented on Dec 13, 2022

apiraino commented on Dec 13, 2022

lqd commented on Dec 17, 2022

Noratrieb commented on Dec 31, 2022

lqd commented on Dec 31, 2022

apiraino commented on Dec 31, 2022

jyn514 commented on Apr 27, 2023

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