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Rollup merge of #85625 - SkiFire13:fix-85613-vec-dedup-drop-panics, r=nagisa

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Prevent double drop in `Vec::dedup_by` if a destructor panics

Fixes #85613
This commit is contained in:
Dylan DPC 2021-05-26 13:32:06 +02:00 committed by GitHub
commit 27899e3887
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2 changed files with 28 additions and 25 deletions
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5
library/alloc/src/vec/mod.rs
View File

@ -1619,6 +1619,8 @@ impl<T, A: Allocator> Vec<T, A> {
let prev_ptr = ptr.add(gap.write.wrapping_sub(1)); let prev_ptr = ptr.add(gap.write.wrapping_sub(1));
if same_bucket(&mut *read_ptr, &mut *prev_ptr) { if same_bucket(&mut *read_ptr, &mut *prev_ptr) {
// Increase `gap.read` now since the drop may panic.
gap.read += 1;
/* We have found duplicate, drop it in-place */ /* We have found duplicate, drop it in-place */
ptr::drop_in_place(read_ptr); ptr::drop_in_place(read_ptr);
} else { } else {
@ -1631,9 +1633,8 @@ impl<T, A: Allocator> Vec<T, A> {
/* We have filled that place, so go further */ /* We have filled that place, so go further */
gap.write += 1; gap.write += 1;
gap.read += 1;
} }
gap.read += 1;
} }
/* Technically we could let `gap` clean up with its Drop, but /* Technically we could let `gap` clean up with its Drop, but

48
library/alloc/tests/vec.rs
View File

@ -2234,48 +2234,50 @@ fn test_vec_dedup() {
#[test] #[test]
fn test_vec_dedup_panicking() { fn test_vec_dedup_panicking() {
#[derive(Debug)] #[derive(Debug)]
struct Panic { struct Panic<'a> {
drop_counter: &'static AtomicU32, drop_counter: &'a Cell<u32>,
value: bool, value: bool,
index: usize, index: usize,
} }
impl PartialEq for Panic { impl<'a> PartialEq for Panic<'a> {
fn eq(&self, other: &Self) -> bool { fn eq(&self, other: &Self) -> bool {
self.value == other.value self.value == other.value
} }
} }
impl Drop for Panic { impl<'a> Drop for Panic<'a> {
fn drop(&mut self) { fn drop(&mut self) {
let x = self.drop_counter.fetch_add(1, Ordering::SeqCst); self.drop_counter.set(self.drop_counter.get() + 1);
assert!(x != 4); if !std::thread::panicking() {
assert!(self.index != 4);
}
} }
} }
static DROP_COUNTER: AtomicU32 = AtomicU32::new(0); let drop_counter = &Cell::new(0);
let expected = [ let expected = [
Panic { drop_counter: &DROP_COUNTER, value: false, index: 0 }, Panic { drop_counter, value: false, index: 0 },
Panic { drop_counter: &DROP_COUNTER, value: false, index: 5 }, Panic { drop_counter, value: false, index: 5 },
Panic { drop_counter: &DROP_COUNTER, value: true, index: 6 }, Panic { drop_counter, value: true, index: 6 },
Panic { drop_counter: &DROP_COUNTER, value: true, index: 7 }, Panic { drop_counter, value: true, index: 7 },
]; ];
let mut vec = vec![ let mut vec = vec![
Panic { drop_counter: &DROP_COUNTER, value: false, index: 0 }, Panic { drop_counter, value: false, index: 0 },
// these elements get deduplicated // these elements get deduplicated
Panic { drop_counter: &DROP_COUNTER, value: false, index: 1 }, Panic { drop_counter, value: false, index: 1 },
Panic { drop_counter: &DROP_COUNTER, value: false, index: 2 }, Panic { drop_counter, value: false, index: 2 },
Panic { drop_counter: &DROP_COUNTER, value: false, index: 3 }, Panic { drop_counter, value: false, index: 3 },
Panic { drop_counter: &DROP_COUNTER, value: false, index: 4 }, Panic { drop_counter, value: false, index: 4 },
// here it panics // here it panics while dropping the item with index==4
Panic { drop_counter: &DROP_COUNTER, value: false, index: 5 }, Panic { drop_counter, value: false, index: 5 },
Panic { drop_counter: &DROP_COUNTER, value: true, index: 6 }, Panic { drop_counter, value: true, index: 6 },
Panic { drop_counter: &DROP_COUNTER, value: true, index: 7 }, Panic { drop_counter, value: true, index: 7 },
]; ];
let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| { let _ = catch_unwind(AssertUnwindSafe(|| vec.dedup())).unwrap_err();
vec.dedup();
})); assert_eq!(drop_counter.get(), 4);
let ok = vec.iter().zip(expected.iter()).all(|(x, y)| x.index == y.index); let ok = vec.iter().zip(expected.iter()).all(|(x, y)| x.index == y.index);