Auto merge of #115045 - RalfJung:unwind-terminate-reason, r=davidtwco

when terminating during unwinding, show the reason why

With this, the output on double-panic becomes something like that:
```
thread 'main' panicked at src/tools/miri/tests/fail/panic/double_panic.rs:15:5:
first
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'main' panicked at src/tools/miri/tests/fail/panic/double_panic.rs:10:9:
second
stack backtrace:
   0:           0xbe273a - std::backtrace_rs::backtrace::miri::trace_unsynchronized::<&mut [closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/miri.rs:99:5
   1:           0xbe22e6 - std::backtrace_rs::backtrace::miri::trace::<&mut [closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/miri.rs:62:14
   2:           0xbe1086 - std::backtrace_rs::backtrace::trace_unsynchronized::<[closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   3:           0xba3afd - std::sys_common::backtrace::_print_fmt
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:67:5
   4:           0xba2471 - <std::sys_common::backtrace::_print::DisplayBacktrace as std::fmt::Display>::fmt
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:44:22
   5:           0xbcf754 - core::fmt::rt::Argument::<'_>::fmt
                               at /home/r/src/rust/rustc.3/library/core/src/fmt/rt.rs:138:9
   6:           0x9b8f81 - std::fmt::write
                               at /home/r/src/rust/rustc.3/library/core/src/fmt/mod.rs:1094:17
   7:           0x21391d - <std::sys::unix::stdio::Stderr as std::io::Write>::write_fmt
                               at /home/r/src/rust/rustc.3/library/std/src/io/mod.rs:1714:15
   8:           0xba37b1 - std::sys_common::backtrace::_print
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:47:5
   9:           0xba365b - std::sys_common::backtrace::print
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:34:9
  10:           0x143c67 - std::panic_hook_with_disk_dump::{closure#1}
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:278:22
  11:           0x144187 - std::panic_hook_with_disk_dump
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:312:9
  12:           0x143659 - std::panicking::default_hook
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:239:5
  13:           0x1482a7 - std::panicking::rust_panic_with_hook
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:729:13
  14:           0x1475d5 - std::rt::begin_panic::<&str>::{closure#0}
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:650:9
  15:           0xba496a - std::sys_common::backtrace::__rust_end_short_backtrace::<[closure@std::rt::begin_panic<&str>::{closure#0}], !>
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:170:18
  16:           0x147599 - std::rt::begin_panic::<&str>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:649:12
  17:            0x31916 - <Foo as std::ops::Drop>::drop
                               at src/tools/miri/tests/fail/panic/double_panic.rs:10:9
  18:           0x1a2b5e - std::ptr::drop_in_place::<Foo> - shim(Some(Foo))
                               at /home/r/src/rust/rustc.3/library/core/src/ptr/mod.rs:497:1
  19:            0x202bf - main
                               at src/tools/miri/tests/fail/panic/double_panic.rs:16:1
  20:            0xcc6a8 - <fn() as std::ops::FnOnce<()>>::call_once - shim(fn())
                               at /home/r/src/rust/rustc.3/library/core/src/ops/function.rs:250:5
  21:           0xba47d9 - std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:154:18
  22:           0x141a6a - std::rt::lang_start::<()>::{closure#0}
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:166:18
  23:            0xcca18 - std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once
                               at /home/r/src/rust/rustc.3/library/core/src/ops/function.rs:284:13
  24:           0x146469 - std::panicking::try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:524:40
  25:           0x145e09 - std::panicking::try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:488:19
  26:            0x7b0ac - std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>
                               at /home/r/src/rust/rustc.3/library/std/src/panic.rs:142:14
  27:           0x14189b - std::rt::lang_start_internal::{closure#2}
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:148:48
  28:           0x146481 - std::panicking::try::do_call::<[closure@std::rt::lang_start_internal::{closure#2}], isize>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:524:40
  29:           0x145e2c - std::panicking::try::<isize, [closure@std::rt::lang_start_internal::{closure#2}]>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:488:19
  30:            0x7b0d5 - std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#2}], isize>
                               at /home/r/src/rust/rustc.3/library/std/src/panic.rs:142:14
  31:           0x1418b0 - std::rt::lang_start_internal
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:148:20
  32:           0x141a97 - std::rt::lang_start::<()>
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:165:17
thread 'main' panicked at /home/r/src/rust/rustc.3/library/core/src/panicking.rs:126:5:
panic in a destructor during cleanup
stack backtrace:
   0:           0xe9f6d7 - std::backtrace_rs::backtrace::miri::trace_unsynchronized::<&mut [closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/miri.rs:99:5
   1:           0xe9f27d - std::backtrace_rs::backtrace::miri::trace::<&mut [closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/miri.rs:62:14
   2:           0xe9e016 - std::backtrace_rs::backtrace::trace_unsynchronized::<[closure@std::sys_common::backtrace::_print_fmt::{closure#1}]>
                               at /home/r/src/rust/rustc.3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   3:           0xba3afd - std::sys_common::backtrace::_print_fmt
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:67:5
   4:           0xba2471 - <std::sys_common::backtrace::_print::DisplayBacktrace as std::fmt::Display>::fmt
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:44:22
   5:           0xbcf754 - core::fmt::rt::Argument::<'_>::fmt
                               at /home/r/src/rust/rustc.3/library/core/src/fmt/rt.rs:138:9
   6:           0x9b8f81 - std::fmt::write
                               at /home/r/src/rust/rustc.3/library/core/src/fmt/mod.rs:1094:17
   7:           0x4d0895 - <std::sys::unix::stdio::Stderr as std::io::Write>::write_fmt
                               at /home/r/src/rust/rustc.3/library/std/src/io/mod.rs:1714:15
   8:           0xba37b1 - std::sys_common::backtrace::_print
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:47:5
   9:           0xba365b - std::sys_common::backtrace::print
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:34:9
  10:           0x400bd4 - std::panic_hook_with_disk_dump::{closure#1}
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:278:22
  11:           0x144187 - std::panic_hook_with_disk_dump
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:312:9
  12:           0x143659 - std::panicking::default_hook
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:239:5
  13:           0x1482a7 - std::panicking::rust_panic_with_hook
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:729:13
  14:           0x40403b - std::panicking::begin_panic_handler::{closure#0}
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:619:13
  15:           0xe618b3 - std::sys_common::backtrace::__rust_end_short_backtrace::<[closure@std::panicking::begin_panic_handler::{closure#0}], !>
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:170:18
  16:           0x403fc8 - std::panicking::begin_panic_handler
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:617:5
  17:           0xee23e9 - core::panicking::panic_nounwind_fmt
                               at /home/r/src/rust/rustc.3/library/core/src/panicking.rs:96:14
  18:           0xee29e6 - core::panicking::panic_nounwind
                               at /home/r/src/rust/rustc.3/library/core/src/panicking.rs:126:5
  19:           0xee365e - core::panicking::panic_in_cleanup
                               at /home/r/src/rust/rustc.3/library/core/src/panicking.rs:206:5
  20:            0x2028a - main
                               at src/tools/miri/tests/fail/panic/double_panic.rs:13:1
  21:           0x3895ee - <fn() as std::ops::FnOnce<()>>::call_once - shim(fn())
                               at /home/r/src/rust/rustc.3/library/core/src/ops/function.rs:250:5
  22:           0xe61725 - std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>
                               at /home/r/src/rust/rustc.3/library/std/src/sys_common/backtrace.rs:154:18
  23:           0x3fe9aa - std::rt::lang_start::<()>::{closure#0}
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:166:18
  24:           0x389962 - std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once
                               at /home/r/src/rust/rustc.3/library/core/src/ops/function.rs:284:13
  25:           0x4033b9 - std::panicking::try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:524:40
  26:           0x402d58 - std::panicking::try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:488:19
  27:           0x337ff7 - std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>
                               at /home/r/src/rust/rustc.3/library/std/src/panic.rs:142:14
  28:           0x3fe7e7 - std::rt::lang_start_internal::{closure#2}
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:148:48
  29:           0x4033d6 - std::panicking::try::do_call::<[closure@std::rt::lang_start_internal::{closure#2}], isize>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:524:40
  30:           0x402d7f - std::panicking::try::<isize, [closure@std::rt::lang_start_internal::{closure#2}]>
                               at /home/r/src/rust/rustc.3/library/std/src/panicking.rs:488:19
  31:           0x338028 - std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#2}], isize>
                               at /home/r/src/rust/rustc.3/library/std/src/panic.rs:142:14
  32:           0x1418b0 - std::rt::lang_start_internal
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:148:20
  33:           0x3fe9dc - std::rt::lang_start::<()>
                               at /home/r/src/rust/rustc.3/library/std/src/rt.rs:165:17
thread caused non-unwinding panic. aborting.
```
If we also land https://github.com/rust-lang/rust/pull/115020, the 2nd backtrace disappears, hopefully making the "panic in a destructor during cleanup" easier to see.

Fixes https://github.com/rust-lang/rust/issues/114954.

1 files changed, 8 insertions, 5 deletions

diff --git a/tests/ui/backtrace.rs b/tests/ui/backtrace.rs
index 66b378f62d6..95783945529 100644
--- a/tests/ui/backtrace.rs
+++ b/tests/ui/backtrace.rs
@@ -100,14 +100,17 @@ fn runtest(me: &str) {
         let s = str::from_utf8(&out.stderr).unwrap();
         // loosened the following from double::h to double:: due to
         // spurious failures on mac, 32bit, optimized
-        assert!(s.contains("stack backtrace") && contains_verbose_expected(s, "double"),
-                "bad output3: {}", s);
+        assert!(
+            s.contains("stack backtrace") &&
+                s.contains("panic in a destructor during cleanup") &&
+                contains_verbose_expected(s, "double"),
+            "bad output3: {}", s
+        );
 
         // Make sure a stack trace isn't printed too many times
         //
-        // Currently it is printed 3 times ("once", "twice" and "panic in a
-        // function that cannot unwind") but in the future the last one may be
-        // removed.
+        // Currently it is printed 3 times ("once", "twice" and "panic in a destructor during
+        // cleanup") but in the future the last one may be removed.
         let p = template(me).arg("double-fail")
                                     .env("RUST_BACKTRACE", "1").spawn().unwrap();
         let out = p.wait_with_output().unwrap();