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I'm not quite sure how to debug this as its happening in a large application, but only some of the devices we have deployed to.
In our code we have an iterator that produces a "BoundingBox" and then we call collect on that BoundingBox.
so we have
filter_map(|| {
// ...
let bbox = BoundingBox {
id: 0,
rect,
score: confidence as f64,
class: mapping.from_detector_class(id),
raw_class: id as usize,
..Default::default()
};
Some(bbox)
})
.collect::<Vec<_>>()
BoundingBox looks like this:
#[derive(Debug, Clone)]
pub struct BoundingBox {
pub id: u64,
pub rect: Rect,
pub score: f64,
pub class: DetectionClass,
pub raw_class: usize,
pub handle: Option<std::sync::Weak<()>>,
}
Where we have a Default impl where handle is None. We noticed that some devices (Rust 1.87.0 and Rust 1.92.0, on Ubuntu Linux x86) were segfaulting so we deployed a debug build and got this trace:
#0 core::sync::atomic::atomic_sub (dst=0x208) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/sync/atomic.rs:4002
#1 core::sync::atomic::AtomicUsize::fetch_sub (self=0x208) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/sync/atomic.rs:3195
#2 <alloc::sync::Weak<T,A> as core::ops::drop::Drop>::drop (self=0x7f85ee5630d8) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/alloc/src/sync.rs:3301
#3 0x0000558f04b2a2eb in core::ptr::drop_in_place<alloc::sync::Weak<()>> () at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/ptr/mod.rs:805
#4 0x0000558f02c66026 in core::ptr::drop_in_place<core::option::Option<alloc::sync::Weak<()>>> () at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/ptr/mod.rs:805
#5 0x0000558f02c62608 in core::ptr::drop_in_place<database::types::bounding_box::BoundingBox> () at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/ptr/mod.rs:805
#6 0x0000558f01cc5719 in core::iter::traits::iterator::Iterator::find::check::{{closure}} (x=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/traits/iterator.rs:2886
#7 0x0000558f01cc5542 in core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut (self=0x7f85ee563188, args=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/ops/function.rs:298
#8 0x0000558f01cce10a in <alloc::vec::into_iter::IntoIter<T,A> as core::iter::traits::iterator::Iterator>::try_fold (self=0x7f85ee567020, accum=(), f=0x7f85ee564e38)
at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/alloc/src/vec/into_iter.rs:351
#9 0x0000558f01cd5537 in <core::iter::adapters::flatten::FlattenCompat<I,U> as core::iter::traits::iterator::Iterator>::try_fold::flatten::{{closure}} (acc=(), iter=0x7f85ee567020)
at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/flatten.rs:563
#10 0x0000558f01cd9074 in core::iter::adapters::flatten::FlattenCompat<I,U>::iter_try_fold::flatten::{{closure}} (acc=(), iter=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/flatten.rs:420
#11 0x0000558f01cde2df in core::iter::adapters::map::map_try_fold::{{closure}} (acc=(), elt=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/map.rs:95
#12 0x0000558f01ceda19 in core::iter::traits::iterator::Iterator::try_fold (self=0x7f85ee566fa0, init=(), f=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/traits/iterator.rs:2427
#13 0x0000558f01cddb50 in <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::try_fold (self=0x7f85ee566fa0, init=(), g=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/map.rs:121
#14 0x0000558f01cdd3de in <core::iter::adapters::fuse::Fuse<I> as core::iter::adapters::fuse::FuseImpl<I>>::try_fold (self=0x7f85ee566fa0, acc=(), fold=...)
at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/fuse.rs:317
#15 0x0000558f01cd881d in <core::iter::adapters::fuse::Fuse<I> as core::iter::traits::iterator::Iterator>::try_fold (self=0x7f85ee566fa0, acc=(), fold=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/fuse.rs:89
#16 core::iter::adapters::flatten::FlattenCompat<I,U>::iter_try_fold (self=0x7f85ee566fa0, acc=(), fold=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/flatten.rs:428
#17 0x0000558f01cd547c in <core::iter::adapters::flatten::FlattenCompat<I,U> as core::iter::traits::iterator::Iterator>::try_fold (self=0x7f85ee566fa0, init=(), fold=...)
at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/flatten.rs:566
#18 0x0000558f01cd52bc in <core::iter::adapters::flatten::FlatMap<I,U,F> as core::iter::traits::iterator::Iterator>::try_fold (self=0x7f85ee566fa0, init=(), fold=...)
at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/flatten.rs:79
#19 0x0000558f01cd7c0c in core::iter::traits::iterator::Iterator::find (self=0x7f85ee566fa0, predicate=0x7f85ee567060) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/traits/iterator.rs:2889
#20 0x0000558f01cf4991 in <core::iter::adapters::filter::Filter<I,P> as core::iter::traits::iterator::Iterator>::next (self=0x7f85ee566fa0) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/core/src/iter/adapters/filter.rs:98
#21 0x0000558f01c93ad0 in <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iterPython Exception <class 'gdb.MemoryError'> Cannot access memory at address 0x8:
(iterator=#22 0x0000558f01c9535e in <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iterPython Exception <class 'gdb.MemoryError'> Cannot access memory at address 0x8:
(iterator=#23 0x0000558f01c9530a in <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter (iter=...) at /rustc/ded5c06cf21d2b93bffd5d884aa6e96934ee4234/library/alloc/src/vec/mod.rs:3689
#24 0x0000558f01cf4b4e in core::iter::traits::iterator::Iterator::collectPython Exception <class 'gdb.MemoryError'> Cannot access memory at address 0x8:
(self=#25 0x0000558f01cc3694 in trt::yolo::parse
(preds=0x7f884e76b380, output_shape=..., classes=44, mapping=0x7f863058ef10, confidence=0x7f863058f028, iou_threshold=0x7f863058f0f8, scaling=0x7f863058f248) at trt/src/yolo.rs:90
It seems that fetch_sub is being called on Weak that was never initialized? I'm not sure when this bug was introduced as our application runs on thousands of devices that are mostly homogenous. However it's not clear to me why drop is called at all for Weak.
I've tried to repro in an example but naturally an isolated example doesn't work; so I'm mainly looking for pointers here on what could be the issue.
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