Stack overflow in rustc, regression from 1.44

[alexcrichton]

First reported to me at rustwasm/wasm-bindgen#2244 I believe the stack overflow is in rustc itself. This code when compiled yields:

$ rustc +1.44.0 foo.rs
$ rustc +stable foo.rs

thread 'rustc' has overflowed its stack
fatal runtime error: stack overflow
zsh: abort (core dumped)  rustc +stable foo.rs
$ rustc +nightly foo.rs

thread 'rustc' has overflowed its stack
fatal runtime error: stack overflow
zsh: abort (core dumped)  rustc +nightly foo.rs

where nightly today is:

$ rustc +nightly -vV
rustc 1.47.0-nightly (d7f945163 2020-07-19)
binary: rustc
commit-hash: d7f94516345a36ddfcd68cbdf1df835d356795c3
commit-date: 2020-07-19
host: x86_64-unknown-linux-gnu
release: 1.47.0-nightly
LLVM version: 10.0

[spastorino]

Assigning P-high as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

[spastorino]

It would be nice to bisect this one if possible ...

@rustbot ping cleanup

[rustbot]

Hey Cleanup Crew ICE-breakers! This bug has been identified as a good
"Cleanup ICE-breaking candidate". In case it's useful, here are some
instructions for tackling these sorts of bugs. Maybe take a look?
Thanks! <3

cc @AminArria @camelid @chrissimpkins @contrun @DutchGhost @elshize @ethanboxx @h-michael @HallerPatrick @hdhoang @hellow554 @imtsuki @kanru @KarlK90 @LeSeulArtichaut @MAdrianMattocks @matheus-consoli @mental32 @nmccarty @Noah-Kennedy @pard68 @PeytonT @pierreN @Redblueflame @RobbieClarken @RobertoSnap @robjtede @SarthakSingh31 @senden9 @shekohex @sinato @spastorino @turboladen @woshilapin @yerke

[kanru]

searched nightlies: from nightly-2020-05-05 to nightly-2020-07-22
regressed nightly: nightly-2020-05-08
searched commits: from 1836e3b to a08c473
regressed commit: 97f3eee

bisected with cargo-bisect-rustc v0.5.1

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc -- check 

cc @oli-obk

[oli-obk]

cc @nagisa

for anyone wanting to fix this, these kind of bugs are very easy to fix. You run rustc in gdb until you get a stack overflow, then you look at the backtrace and look for recursion in there. Then you break the recursion overflow by inserting a use of https://doc.rust-lang.org/nightly/nightly-rustc/rustc_data_structures/stack/fn.ensure_sufficient_stack.html at the recursive call site.