Compiler hang with incomplete struct literal at end of file · Issue #103451 · rust-lang/rust (original) (raw)

This malformed code (playground) hangs the compiler:

struct R { }

struct S { x: [u8; R

Found by fuzzing with a modified fuzz-rustc.

The bug's edges

• R must be defined as a named-field struct (not a tuple struct or unit struct), although it can have 0 fields.
• R must be the last token to produce the hang:
  • No opening brace (note that braces are required for literals of named-field structs)
  • No closing delimiters
  • Not even a comment

Where it hangs

If I understand mj.sample.txt correctly, the hang occurs in LateResolutionVisitor, with try_lookup_name_relaxed never finishing (while calling various functions such as smart_resolve_context_dependent_help and span_to_snippet)

Additional example

This also hangs. I'm guessing it's the same bug.

Version

rustc --version --verbose:

rustc 1.66.0-nightly (6e95b6da8 2022-10-22)
binary: rustc
commit-hash: 6e95b6da885f42a4e1314595089fa4295e329d11
commit-date: 2022-10-22
host: x86_64-apple-darwin
release: 1.66.0-nightly
LLVM version: 15.0.2

Regression

Bisected with:

cargo-bisect-rustc --start=2022-10-03 --end=nightly-2022-10-23 --preserve --script=./timeout.sh

timeout.sh

#!/bin/bash

This script is wrong in several ways:

- It will try to kill processes that might no longer exist

- It may leave an orphan rustc process after the bisect (because it only kills the shell, not rustc)

But it seems to be good enough for bisection to work

killall rustc outershell=$$ (sleep 5; kill $outershell) & rustc src/main.rs true

• regressed nightly: nightly-2022-10-21
• regressed commit: 53728ff (PR Fix the bug of next_point in source_map #103185)

@rustbot label +regression-from-stable-to-nightly +I-hang