RUST_BACKTRACE=full panic causes infinite loop on aarch64-pc-windows-msvc

[jrobhoward]

I tried running this code (default cargo new --bin template, changed println! to panic! ):

fn main() {
    panic!("Hello, world!");
}

It builds fine on a aarch64-pc-windows-msvc host, and runs fine with RUST_BACKTRACE env variable:

• left unset
• set to 0
• set to 1

When I run it (on a aarch64-pc-windows-msvc host) with (RUST_BACKTRACE=full), the panic triggers an infinite loop:

    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
     Running `target\debug\arm_panic_test.exe`
thread 'main' panicked at src\main.rs:2:5:
Hello, world!
stack backtrace:
   0:     0x7ff6cb635d24 - std::sys_common::backtrace::_print::impl$0::fmt
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:44
   1:     0x7ff6cb6428d4 - core::fmt::rt::Argument::fmt
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\core\src\fmt\rt.rs:142
   2:     0x7ff6cb6428d4 - core::fmt::write
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\core\src\fmt\mod.rs:1120
   3:     0x7ff6cb634368 - std::io::Write::write_fmt<std::sys::pal::windows::stdio::Stderr>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\io\mod.rs:1846
   4:     0x7ff6cb635b70 - std::sys_common::backtrace::_print
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:47
   5:     0x7ff6cb635b70 - std::sys_common::backtrace::print
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:34
   6:     0x7ff6cb637554 - std::panicking::default_hook::closure$1
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\panicking.rs:272
   7:     0x7ff6cb637208 - std::panicking::default_hook
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\panicking.rs:292
   8:     0x7ff6cb637a04 - std::panicking::rust_panic_with_hook
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\panicking.rs:781
   9:     0x7ff6cb6378a8 - std::panicking::begin_panic_handler::closure$0
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\panicking.rs:651
  10:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  11:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  12:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  13:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  14:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  15:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
  16:     0x7ff6cb6362e8 - std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/7cf61ebde7b22796c69757901dd346d0fe70bd97/library\std\src\sys_common\backtrace.rs:171
...
... repeated indefinitely until I press CTRL^C
...

This also causes unit test execution to hang (e.g. for tokio) if RUST_BACKTRACE=full and a document test contains ````should_panic`.

rustc --version --verbose:

rustc --version --verbose
rustc 1.77.1 (7cf61ebde 2024-03-27)
binary: rustc
commit-hash: 7cf61ebde7b22796c69757901dd346d0fe70bd97
commit-date: 2024-03-27
host: aarch64-pc-windows-msvc
release: 1.77.1
LLVM version: 17.0.6

Additional Info:

• This appears to be unique to aarch64-pc-windows-msvc.
  • The same set of steps runs as expected on aarch64-apple-darwin.
  • The same set of steps runs as expected x86_64-pc-windows-msvc.
• If it matters, VS2022 (not VS2019) was installed.
• It is straightforward to reproduce. If you need me to gather additional info, please let me know.

[workingjubilee]

...huh.

@dpaoliello I know you took a look at all this recently, do you have any insight?

[dpaoliello]

Sure, I can look into it

[dpaoliello]

I have a fix: rust-lang/backtrace-rs#610