for triple-panics, do not keep printing backtraces #115020

RalfJung · 2023-08-20T08:19:42Z

matthiaskrgr · 2023-08-20T08:25:36Z

Will this change the behavior of -Ztreat-err-as-bug=x ?

RalfJung · 2023-08-20T08:32:36Z

I... don't think so? This is a library patch, that's a compiler flag. How does that flag even relate to triple-panics?

matthiaskrgr · 2023-08-20T09:11:10Z

It can easily cause N-panics. I am not too familiar with this unfortunately, but we used this in #113211 to find panics in nonuwind functions.

RalfJung · 2023-08-20T09:18:03Z

For such cases you can always set RUST_BACKTRACE to get a backtrace as usual. This PR only changes whether a backtrace is printed when that variable is not set.

rustbot · 2023-08-22T13:35:57Z

The Miri subtree was changed

cc @rust-lang/miri

library/std/src/panicking.rs

…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 rust-lang#115020, the 2nd backtrace disappears, hopefully making the "panic in a destructor during cleanup" easier to see. Fixes rust-lang#114954.

bors · 2023-08-25T12:37:48Z

☔ The latest upstream changes (presumably #115045) made this pull request unmergeable. Please resolve the merge conflicts.

…race by default

Amanieu · 2023-08-25T15:57:46Z

I don't think that using the panic count is the right approach here. I would prefer if we specifically disabled backtrace printing when the reason is known to be one where we don't need the additional backtrace. This should be possible now that #115045 has landed.

Note that recursive panics from within the panic hook are already specifically detected by a separate mechanism: those will cause an immediate abort, without even printing the panic message.

RalfJung · 2023-08-25T16:07:25Z

I don't think that using the panic count is the right approach here.

Why not? If the user didn't ask for a backtrace, then printing two (or more) of them is surely not what they were looking for.

I would prefer if we specifically disabled backtrace printing when the reason is known to be one where we don't need the additional backtrace.

Are you saying that PanicInfo should carry another boolean flag that can be used to disable the backtrace?

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 rust-lang/rust#115020, the 2nd backtrace disappears, hopefully making the "panic in a destructor during cleanup" easier to see. Fixes rust-lang/rust#114954.

Amanieu · 2023-08-26T21:21:46Z

Why not? If the user didn't ask for a backtrace, then printing two (or more) of them is surely not what they were looking for.

It could be a perfectly valid case of nested panics (with catch_unwind called from within Drop), where we do want to make sure each panic gets a backtrace printed.

Are you saying that PanicInfo should carry another boolean flag that can be used to disable the backtrace?

That's the best solution I can think of at the moment. At least it's more explicit than just guessing based on the panic count.

RalfJung · 2023-08-27T18:03:26Z

All right. Superseded by #115280.

…trace, r=Amanieu avoid triple-backtrace due to panic-during-cleanup Supersedes rust-lang#115020 Cc rust-lang#114954 r? `@Amanieu`

…trace, r=Amanieu avoid triple-backtrace due to panic-during-cleanup Supersedes rust-lang#115020 Cc rust-lang#114954 r? ``@Amanieu``

…Amanieu avoid triple-backtrace due to panic-during-cleanup Supersedes rust-lang/rust#115020 Cc rust-lang/rust#114954 r? ``@Amanieu``

rustbot assigned Amanieu Aug 20, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Aug 20, 2023

RalfJung mentioned this pull request Aug 21, 2023

when terminating during unwinding, show the reason why #115045

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RalfJung force-pushed the triple-panic branch from f7c774a to 1148ac4 Compare August 22, 2023 13:35

bjorn3 reviewed Aug 23, 2023

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RalfJung added 2 commits August 25, 2023 14:41

for triple-panics, do not keep printing backtraces

8121de1

have a test ensure that a panic-during-cleanup only prints one btackt…

5160ea7

…race by default

RalfJung force-pushed the triple-panic branch from 1148ac4 to 5160ea7 Compare August 25, 2023 12:46

RalfJung mentioned this pull request Aug 27, 2023

avoid triple-backtrace due to panic-during-cleanup #115280

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RalfJung deleted the triple-panic branch August 27, 2023 18:03

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