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Align os.utime float-to-duration rounding with CPython semantics #6501

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Align os.utime float-to-duration rounding with CPython semantics #6501

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fd73a9c
Initial plan
Copilot Dec 25, 2025
da24a78
Fix duration conversion rounding for os.utime
Copilot Dec 25, 2025
b911e6f
Address review feedback for duration rounding
Copilot Dec 25, 2025
7578fd9
Refine duration conversion constants and checks
Copilot Dec 25, 2025
31765b7
Clarify float nanosecond conversion cast
Copilot Dec 25, 2025
56acf0a
Use checked conversion for float nanoseconds
Copilot Dec 25, 2025
514b716
Add explicit float bounds before nanosecond cast
Copilot Dec 25, 2025
4c3e73f
Streamline duration bounds validation
Copilot Dec 25, 2025
73aa693
Convert float nanoseconds with checked filtering
Copilot Dec 25, 2025
efea81d
Use explicit bounds check before casting nanoseconds
Copilot Dec 25, 2025
a781c0d
Check nanosecond sign before duration bounds
Copilot Dec 25, 2025
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34 changes: 30 additions & 4 deletions crates/vm/src/convert/try_from.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -126,10 +126,7 @@ impl TryFromObject for std::time::Duration {
fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
if let Some(float) = obj.downcast_ref::<PyFloat>() {
let f = float.to_f64();
if f < 0.0 {
return Err(vm.new_value_error("negative duration"));
}
Ok(Self::from_secs_f64(f))
duration_from_f64_floor(f, vm)
} else if let Some(int) = obj.try_index_opt(vm) {
let int = int?;
let bigint = int.as_bigint();
Expand All @@ -149,3 +146,32 @@ impl TryFromObject for std::time::Duration {
}
}
}

fn duration_from_f64_floor(f: f64, vm: &VirtualMachine) -> PyResult<std::time::Duration> {
const NANOS_PER_SEC_U128: u128 = 1_000_000_000;
const NANOS_PER_SEC: f64 = NANOS_PER_SEC_U128 as f64;
// Maximum duration representable by (secs, nanos) with u64 seconds and <1e9 nanoseconds.
const MAX_TOTAL_NANOS: u128 =
((u64::MAX as u128) * NANOS_PER_SEC_U128) + (NANOS_PER_SEC_U128 - 1);

if !f.is_finite() {
return Err(vm.new_value_error("value out of range"));
}
if f < 0.0 {
return Err(vm.new_value_error("negative duration"));
}

let total_nanos = (f * NANOS_PER_SEC).floor();
if total_nanos.is_sign_negative() {
return Err(vm.new_value_error("value out of range"));
}
let total_nanos_u128 = total_nanos as u128;
if total_nanos_u128 > MAX_TOTAL_NANOS {
return Err(vm.new_value_error("value out of range"));
}

let secs = (total_nanos_u128 / NANOS_PER_SEC_U128) as u64;
let nanos = (total_nanos_u128 % NANOS_PER_SEC_U128) as u32;

Ok(std::time::Duration::new(secs, nanos))
}
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