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Prevent array.fromfile reentrancy deadlock in append conversion #6576

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Prevent array.fromfile reentrancy deadlock in append conversion #6576

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4eb77a1
Initial plan
Copilot Dec 29, 2025
c48ff14
Fix array append reentrancy deadlock
Copilot Dec 29, 2025
4e8680f
Refine array reentrancy handling
Copilot Dec 29, 2025
391a83d
rewrite
youknowone Dec 29, 2025
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rewrite
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@youknowone
youknowone committed Dec 29, 2025
commit 391a83d4897f6981d410c2cd92e3d2b45dca8efb
46 changes: 27 additions & 19 deletions crates/stdlib/src/array.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -159,23 +159,22 @@ mod array {
Ok(())
}

// `expected_kind` is captured before acquiring the write lock to ensure the array
// type didn't unexpectedly change between conversion and mutation.
fn push_value(&mut self, expected_kind: ArrayType, value: ArrayElementValue) {
assert_eq!(self.kind(), expected_kind);
match (expected_kind, self, value) {
$((ArrayType::$n, ArrayContentType::$n(v), ArrayElementValue::$n(val)) => {
v.push(val);
fn truncate(&mut self, len: usize) {
match self {
$(ArrayContentType::$n(v) => v.truncate(len),)*
}
}

fn set_or_push(&mut self, index: usize, value: ArrayElementValue) {
match (self, value) {
$((ArrayContentType::$n(v), ArrayElementValue::$n(val)) => {
if index < v.len() {
v[index] = val;
} else {
v.push(val);
}
},)*
(_, array, value) => {
let actual = array.kind();
panic!(
"array element value type {:?} does not match array type {:?} (expected {:?})",
value,
actual,
expected_kind
);
}
_ => unreachable!(),
}
}

Expand Down Expand Up @@ -784,12 +783,21 @@ mod array {
self.read().itemsize()
}

/// Append a new item to the end of the array.
/// Matches `ins1()` in arraymodule.c.
#[pymethod]
fn append(zelf: &Py<Self>, x: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
let kind = zelf.read().kind();
let (n, kind) = {
let r = zelf.read();
(r.len(), r.kind())
};
// First conversion (validation, result discarded)
kind.convert(x.clone(), vm)?;
// Truncate to n+1 if array grew during first conversion
zelf.try_resizable(vm)?.truncate(n + 1);
// Second conversion and store at position n
let value = kind.convert(x, vm)?;
let mut w = zelf.try_resizable(vm)?;
w.push_value(kind, value);
zelf.try_resizable(vm)?.set_or_push(n, value);
Ok(())
}

Expand Down
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