Checked arithmetic is wrong for Durations smaller than 100ns on Windows
Open
Nobody has claimed this yet.
C-bug
needs-triage
O-windows
T-libs
- Dominant language
- Rust
- Stars
- 119k
- Forks
- 16.1k
- PR merge metrics
- PR metrics pending
Description
I tried this code:
let system_time: SystemTime = ...;
// Add 1ns.
system_time.checked_add(Duration::new(0, 1)).unwrap();
I expected to see this happen: The unwrap to fail because SystemTime on Windows only has an accuracy of 100ns.
Instead, this happened: The addition "works" by returning some, although the value is unchanged from the original one, meaning an addition of a Duration < 100ns is equivalent of adding Duration::ZERO.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at Rust's SystemTime::checked_add entry point and reproduce the example on Windows, comparing a 1ns duration with the platform's 100ns precision. Done means the sub-100ns addition no longer succeeds as a no-op, with the behavior covered by a regression test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- operating-systems
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100