Segfault with -Zprofile test

[io12]

Source: kornelski/deunicode#5 (comment)

I tried this code:

crashy/lib.rs

use std::str::Chars;

pub struct ThisIsNotEvenUsed<'a> {
    never_used: Chars<'a>,
}

impl<'a> Iterator for ThisIsNotEvenUsed<'a> {
    type Item = ();

    fn next(&mut self) -> Option<Self::Item> {
        todo!()
    }

    fn count(self) -> usize {
        // mere existence of this line causes crash!
        self.never_used.count()
    }
}

crashy/tests/crash.rs

use crashy; // unused, but important

#[test]
fn crash() {
    // doesn't crash if the char is ASCII
    let _s = ['\u{80}'].iter().collect::<String>();
}

Compile with:

CARGO_INCREMENTAL=0 RUSTFLAGS='-Zprofile -Cinline-threshold=0 -Clink-dead-code'  cargo test

I expected to see this happen: The test passes.

Instead, this happened: The test SIGSEGVs.

Meta

rustc --version --verbose:

rustc 1.52.0-nightly (f98721f88 2021-03-10)
binary: rustc
commit-hash: f98721f886ab52d32d622ad0a46216ad03f3e525
commit-date: 2021-03-10
host: x86_64-unknown-linux-gnu
release: 1.52.0-nightly
LLVM version: 12.0.0

Backtrace

#0  __memmove_avx_unaligned_erms ()
    at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:287
#1  0x000055555557853e in alloc::vec::Vec<T,A>::append_elements (
    self=0x7ffff7c19660, other=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/vec/mod.rs:1607
#2  <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<&T,core::slice::iter::Iter<T>>>::spec_extend (self=0x7ffff7c19660, iterator=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/vec/spec_extend.rs:80
#3  0x000055555557d29c in alloc::vec::Vec<T,A>::extend_from_slice (
    self=0x7ffff7c19660, other=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/vec/mod.rs:2016
#4  0x000055555557e663 in alloc::string::String::push (self=0x7ffff7c19660, 
    ch=128 '\200')
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/string.rs:1082
#5  0x000055555557ac06 in <alloc::string::String as core::iter::traits::collect::Extend<char>>::extend::{{closure}} (c=128 '\200')
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/string.rs:1778
#6  core::iter::traits::iterator::Iterator::for_each::call::{{closure}} (
    item=128 '\200')
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/traits/iterator.rs:772
#7  core::iter::adapters::map::map_fold::{{closure}} (
    elt=0x555555692120 "\200the test returned a termination value with a non-zero status code () which indicates a failure/rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/test/src/lib.rs\000\000\000", acc=<optimized out>)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/adapters/map.rs:81
#8  core::iter::traits::iterator::Iterator::fold (self=..., init=(), f=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/traits/iterator.rs:2123
#9  0x0000555555577e75 in <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold (self=..., init=(), g=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/ad--Type <RET> for more, q to quit, c to continue without paging--
apters/map.rs:121
#10 0x0000555555577f7f in <core::iter::adapters::cloned::Cloned<I> as core::iter::traits::iterator::Iterator>::fold (self=..., init=(), f=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/adapters/cloned.rs:58
#11 0x0000555555580566 in core::iter::traits::iterator::Iterator::for_each (
    self=..., f=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/traits/iterator.rs:775
#12 <alloc::string::String as core::iter::traits::collect::Extend<char>>::extend (self=0x7ffff7c19660, iter=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/string.rs:1778
#13 0x000055555558097b in <alloc::string::String as core::iter::traits::collect::Extend<&char>>::extend (self=0x7ffff7c19660, iter=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/string.rs:1795
#14 0x0000555555580a42 in <alloc::string::String as core::iter::traits::collect::FromIterator<&char>>::from_iter (iter=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/string.rs:1712
#15 0x0000555555580c19 in core::iter::traits::iterator::Iterator::collect (
    self=...)
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/iter/traits/iterator.rs:1764
#16 crash::crash () at tests/crash.rs:6
#17 0x00005555555794d1 in crash::crash::{{closure}} () at tests/crash.rs:4
#18 core::ops::function::FnOnce::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/ops/function.rs:227
#19 0x00005555555ae096 in core::ops::function::FnOnce::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/ops/function.rs:227
#20 test::__rust_begin_short_backtrace () at library/test/src/lib.rs:567
#21 0x00005555555ac78e in <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/boxed.rs:1546
--Type <RET> for more, q to quit, c to continue without paging--
#22 <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panic.rs:344
#23 std::panicking::try::do_call ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panicking.rs:379
#24 std::panicking::try ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panicking.rs:343
#25 std::panic::catch_unwind ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panic.rs:431
#26 test::run_test_in_process () at library/test/src/lib.rs:589
#27 test::run_test::run_test_inner::{{closure}} ()
    at library/test/src/lib.rs:486
#28 0x000055555558212a in test::run_test::run_test_inner::{{closure}} ()
    at library/test/src/lib.rs:511
#29 std::sys_common::backtrace::__rust_begin_short_backtrace ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/sys_common/backtrace.rs:125
#30 0x000055555558748f in std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}} ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/thread/mod.rs:474
#31 <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panic.rs:344
#32 std::panicking::try::do_call ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panicking.rs:379
#33 std::panicking::try ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panicking.rs:343
#34 std::panic::catch_unwind ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/panic.rs:431
--Type <RET> for more, q to quit, c to continue without paging--
#35 std::thread::Builder::spawn_unchecked::{{closure}} ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/std/src/thread/mod.rs:473
#36 core::ops::function::FnOnce::call_once{{vtable-shim}} ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/core/src/ops/function.rs:227
#37 0x0000555555619f88 in <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/boxed.rs:1546
#38 <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
    ()
    at /rustc/f98721f886ab52d32d622ad0a46216ad03f3e525/library/alloc/src/boxed.rs:1546
#39 std::sys::unix::thread::Thread::new::thread_start ()
    at library/std/src/sys/unix/thread.rs:71
#40 0x00007ffff7f70fa3 in start_thread (arg=<optimized out>)
    at pthread_create.c:486
#41 0x00007ffff7d194cf in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

[tmiasko]

Likely the same root cause as #82833.

FYI: The -C inline-threshold=0, enables inlining with threshold 0, which makes inlining more likely than the default behaviour for -C opt-level=0, which is to only inline functions with #[inline(always)] attribute.

[io12]

Seems like #83030 fixed this.