Closed
Description
use std::{collections::LinkedList, fmt, sync::Barrier, thread};
struct BadDebugBehavior(Vec<&'static i32>, Barrier, Barrier);
impl fmt::Debug for BadDebugBehavior {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let elem = &self.0[0];
self.1.wait();
self.2.wait();
write!(f, "{}", elem)
}
}
fn main() {
let l = Box::leak(Box::new(LinkedList::new()));
l.push_back(BadDebugBehavior(vec![&0], Barrier::new(2), Barrier::new(2)));
let mut i = l.iter_mut();
let r = i.next().unwrap();
let t = thread::spawn(move || {
r.1.wait();
r.0.push(&0);
r.2.wait();
});
dbg!(&i);
t.join().unwrap();
} Compiling playground v0.0.1 (/playground)
Finished dev [unoptimized + debuginfo] target(s) in 1.67s
Running `target/debug/playground`
[src/main.rs:22] &i = IterMut(
[
timeout: the monitored command dumped core
/playground/tools/entrypoint.sh: line 11: 9 Segmentation fault timeout --signal=KILL ${timeout} "$@"
@rustbot label T-libs-impl, A-collections
Caused by violation of safety invariant as documented in IterMut
/// A mutable iterator over the elements of a `LinkedList`.
///
/// This `struct` is created by [`LinkedList::iter_mut()`]. See its
/// documentation for more.
#[stable(feature = "rust1", since = "1.0.0")]
pub struct IterMut<'a, T: 'a> {
// We do *not* exclusively own the entire list here, references to node's `element`
// have been handed out by the iterator! So be careful when using this; the methods
// called must be aware that there can be aliasing pointers to `element`.
list: &'a mut LinkedList<T>,
head: Option<NonNull<Node<T>>>,
tail: Option<NonNull<Node<T>>>,
len: usize,
}yet Debug implementation does
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("IterMut").field(&self.list).field(&self.len).finish()
}
}https://doc.rust-lang.org/nightly/src/alloc/collections/linked_list.rs.html#79
I’m not sure where the list field is really used at all, so maybe it can be replaced by a marker marker: PhantomData<&'a mut Node<T>>, similar to linked_list::Iter’s implementation.