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fix: OrderedDict.get() crashes on wasi #8896

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fix: OrderedDict.get() crashes on wasi #8896

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3 changes: 2 additions & 1 deletion crates/vm/src/stdlib/_collections/ordered_dict.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ pub(crate) mod ordered_dict {
last: Option<usize>,
nodes: Vec<Option<ODictNode>>,
free: Vec<usize>,
by_hash: HashMap<PyHash, Vec<usize>>,
by_hash: Box<HashMap<PyHash, Vec<usize>>>,
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jiwahn marked this conversation as resolved.

@youknowone youknowone Sep 29, 2026

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what's happening in wasi? since both Box and HashMap are indirection, this will cause double indirection, which is not very preferred. I'd like to understand how and why this broken in wasi

@jiwahn jiwahn Sep 29, 2026 •
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In wasi, Py<T> has 28 bytes header size and when the T is OrderedDict, the payload requires 8 byte alignment (but the base PyDict has 4 byte align). So accessing an OrderedDict through its PyDict base results to using the wrong payload addrress

@youknowone youknowone Sep 29, 2026

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Thanks, we have to adjust alignment rather than adding a Box.

@1ndahous3 1ndahous3 Sep 29, 2026

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Opened #8905 as a follow-up to #7663 and the layout analysis here. It adds compile-time checks for native subclass payload offsets and object alignment, and aligns PyDict and _IOBase to eight bytes so the affected hierarchies satisfy them without adding a Box.

The original #7663 inherited-getter regression is included. The OrderedDict.get() reproducer passes on wasm32-wasip1 under Wasmtime.

AI assistance: Codex (GPT-6).

@jiwahn jiwahn Sep 29, 2026

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It seems that #8905 fixes this so imma close this one

state: usize,
}

Expand Down Expand Up @@ -573,6 +573,7 @@ pub(crate) mod ordered_dict {
fn __sizeof__(&self) -> usize {
self.dict.__sizeof__()
+ core::mem::size_of::<ODictLinks>()
+ core::mem::size_of::<HashMap<PyHash, Vec<usize>>>()
+ self.links.lock().nodes.capacity() * core::mem::size_of::<Option<ODictNode>>()
}

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