collector: TempFdArrayIterator unsoundly extends lifetime of owned file_vec data

[korniltsev-grafanista-yolo-vibecoder239]

⚠️ AI-generated issue — requires human investigation before acting on it.

Summary

TempFdArrayIterator in src/collector.rs yields &'a T items where 'a is the lifetime of the buffer slice. Items sourced from file_vec (an owned AVec<u8> inside the iterator) are returned with the same 'a lifetime via an unsafe pointer cast, but file_vec is owned by the iterator — not by the 'a borrow. This is unsound: the compiler cannot enforce that references into file_vec do not outlive the iterator itself.

Location

src/collector.rs, lines 225–243:

impl<'a, T> Iterator for TempFdArrayIterator<'a, T> {
    type Item = &'a T;

    fn next(&mut self) -> Option<Self::Item> {
        // ...
        let ts = unsafe {
            std::slice::from_raw_parts(self.file_vec.as_ptr() as *const T, length)
        };
        // ts has lifetime 'self, but the trait says Item = &'a T
        // the returned reference is coerced to 'a, which can outlive self
        Some(&ts[self.index - self.buffer.len() - 1])
    }
}

Impact

A caller that collects references from this iterator and then drops the iterator would hold dangling references into freed file_vec memory. The pattern iterator.collect::<Vec<_>>() or holding references across iterator advancement would trigger use-after-free.

In the current codebase, try_iter() is consumed immediately via for_each in the report builders, which is safe. But the unsoundness is latent: any future use that holds references across iterator steps or drops the iterator while retaining references is UB.

Expected behaviour

The iterator should either:

1. Store file_vec alongside items decoded from it (e.g., eagerly decode into a Vec<T> and iterate that), or
2. Use a self-referential structure with appropriate lifetime bounds (e.g., pin the vec separately), or
3. Return owned T values rather than references.

The current design exposes a safe-looking iterator API backed by an unsafe lifetime lie.