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Auto merge of #117557 - Zoxc:panic-prio, r=petrochenkov
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Make `FatalErrorMarker` lower priority than other panics

This makes `FatalErrorMarker` lower priority than other panics in a parallel sections. If any other panics occur, they will be unwound instead of `FatalErrorMarker`. This ensures `rustc` will exit with the correct error code on ICEs.

This fixes #116659.
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bors committed Nov 9, 2023
2 parents 57fb1e6 + ff1858e commit d8dbf7c
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Showing 3 changed files with 30 additions and 14 deletions.
3 changes: 3 additions & 0 deletions compiler/rustc_data_structures/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,9 @@ impl<F: FnOnce()> Drop for OnDrop<F> {
}
}

/// This is a marker for a fatal compiler error used with `resume_unwind`.
pub struct FatalErrorMarker;

/// Turns a closure that takes an `&mut Formatter` into something that can be display-formatted.
pub fn make_display(f: impl Fn(&mut fmt::Formatter<'_>) -> fmt::Result) -> impl fmt::Display {
struct Printer<F> {
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39 changes: 26 additions & 13 deletions compiler/rustc_data_structures/src/sync/parallel.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,8 @@

#![allow(dead_code)]

use crate::sync::IntoDynSyncSend;
use crate::FatalErrorMarker;
use parking_lot::Mutex;
use std::any::Any;
use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
Expand All @@ -18,14 +20,17 @@ pub use enabled::*;
/// continuing with unwinding. It's also used for the non-parallel code to ensure error message
/// output match the parallel compiler for testing purposes.
pub struct ParallelGuard {
panic: Mutex<Option<Box<dyn Any + Send + 'static>>>,
panic: Mutex<Option<IntoDynSyncSend<Box<dyn Any + Send + 'static>>>>,
}

impl ParallelGuard {
pub fn run<R>(&self, f: impl FnOnce() -> R) -> Option<R> {
catch_unwind(AssertUnwindSafe(f))
.map_err(|err| {
*self.panic.lock() = Some(err);
let mut panic = self.panic.lock();
if panic.is_none() || !(*err).is::<FatalErrorMarker>() {
*panic = Some(IntoDynSyncSend(err));
}
})
.ok()
}
Expand All @@ -37,7 +42,7 @@ impl ParallelGuard {
pub fn parallel_guard<R>(f: impl FnOnce(&ParallelGuard) -> R) -> R {
let guard = ParallelGuard { panic: Mutex::new(None) };
let ret = f(&guard);
if let Some(panic) = guard.panic.into_inner() {
if let Some(IntoDynSyncSend(panic)) = guard.panic.into_inner() {
resume_unwind(panic);
}
ret
Expand Down Expand Up @@ -106,14 +111,20 @@ mod enabled {
parallel!(impl $fblock [$block, $($c,)*] [$($rest),*])
};
(impl $fblock:block [$($blocks:expr,)*] []) => {
::rustc_data_structures::sync::scope(|s| {
$(let block = rustc_data_structures::sync::FromDyn::from(|| $blocks);
s.spawn(move |_| block.into_inner()());)*
(|| $fblock)();
$crate::sync::parallel_guard(|guard| {
$crate::sync::scope(|s| {
$(
let block = $crate::sync::FromDyn::from(|| $blocks);
s.spawn(move |_| {
guard.run(move || block.into_inner()());
});
)*
guard.run(|| $fblock);
});
});
};
($fblock:block, $($blocks:block),*) => {
if rustc_data_structures::sync::is_dyn_thread_safe() {
if $crate::sync::is_dyn_thread_safe() {
// Reverse the order of the later blocks since Rayon executes them in reverse order
// when using a single thread. This ensures the execution order matches that
// of a single threaded rustc.
Expand Down Expand Up @@ -146,11 +157,13 @@ mod enabled {
if mode::is_dyn_thread_safe() {
let oper_a = FromDyn::from(oper_a);
let oper_b = FromDyn::from(oper_b);
let (a, b) = rayon::join(
move || FromDyn::from(oper_a.into_inner()()),
move || FromDyn::from(oper_b.into_inner()()),
);
(a.into_inner(), b.into_inner())
let (a, b) = parallel_guard(|guard| {
rayon::join(
move || guard.run(move || FromDyn::from(oper_a.into_inner()())),
move || guard.run(move || FromDyn::from(oper_b.into_inner()())),
)
});
(a.unwrap().into_inner(), b.unwrap().into_inner())
} else {
super::disabled::join(oper_a, oper_b)
}
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2 changes: 1 addition & 1 deletion compiler/rustc_span/src/fatal_error.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
#[must_use]
pub struct FatalError;

pub struct FatalErrorMarker;
pub use rustc_data_structures::FatalErrorMarker;

// Don't implement Send on FatalError. This makes it impossible to `panic_any!(FatalError)`.
// We don't want to invoke the panic handler and print a backtrace for fatal errors.
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