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lazycell.md

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112 lines (86 loc) · 4.95 KB
category description msrv
Data Structure
Similar to RefCell<Option<T>>, but you can keep T borrowed
1.24.0

lazycell

Audit

version thoroughness understanding rating notes
1.2.1 high medium positive Diff review
1.2.0 high medium positive Full review, appears high quality

1.2.1

diff rating notes
.cargo_vcs_info.json ✔️ New
CHANGELOG.md ✔️
Cargo.toml ✔️ Version bump only
Cargo.toml.orig ✔️ Version bump only
LICENSE-MIT ✔️ Copyright year bump only
src/lib.rs ✔️ New clone impls are safe, sane, and well unit tested

1.2.0

file rating notes
src/lib.rs ✔️ MIT OR Apache-2.0
.cargo-ok ✔️
Cargo.toml ❔ MIT/Apache-2.0
Cargo.toml.orig ❔ MIT/Apache-2.0
CHANGELOG.md ✔️ Custom hyperlinks, TIL
LICENSE-APACHE ✔️
LICENSE-MIT ✔️
README.md ❔ MIT and/or Apache-2.0
Other Rating Notes
unsafe ✔️ Used roughly only as much as necessary, with small scopes. All appears to be sound.
fs ✔️ None
io ✔️ None
docs ✔️ Good quality
tests ✔️ LGTM

src/lib.rs

Line Notes
5-9 ✔️ Explicitly "MIT OR Apache-2.0"
63 ✔️ UnsafeCell means LazyCell derives Send, but not Sync (e.g. this is "single threaded" in the sense that there is 1 thread accessing at most at a time.)
76 ✔️ unsafe { ... } appears sound - "single threaded", slot is only modified if it was None, in which case there were no outstanding borrows to the data.
96 ✔️ unsafe { ... } appears sound - &mut self means we have exclusive access, so there should be no outstanding borrows.
110 ✔️ unsafe { ... } appears sound - after the fn returns, there should only be an inner borrow if inner was Some.
119 ✔️ unsafe { ... } appears sound - after the fn returns, there should only be an inner borrow if inner was Some. Also, exclusive access.
119 ✔️ unsafe { ... } appears sound - after the fn returns, there should only be an inner borrow if inner was Some. Also, exclusive access.
204 ✔️ unsafe { ... } appears sound - block is outright unnecessary except for MSRV compatability purpouses
214 ✔️ unsafe { ... } appears sound - after the fn returns, there should be no inner borrow.
226 ⚠️ Despite UnsafeCell, AtomicLazyCell is Send/Sync depending on T
250 ⚠️ unsafe { ... } appears sound, but my acquire/release knowledge here is weak. But I'm fairly sure this is the classic acquire/release pattern.
274 ✔️ unsafe { ... } appears sound - &mut self means we have exclusive access, so there should be no outstanding borrows. This also means updating state need not be atomic.
278 ✔️ Atomic only queried
289 ⚠️ unsafe { ... } appears sound, but my acquire knowledge here is weak. But I'm fairly sure this is a classic acquire.
300 ✔️ unsafe { ... } appears sound - block is outright unnecessary except for MSRV compatability purpouses
311 ⚠️ unsafe { ... } appears sound, but my acquire knowledge here is weak. But I'm fairly sure this is a classic acquire.
317 ✔️ unsafe impl Sync<T: Sync + Send> appears sound. The Send constraint is necessary as fns like fill might be called on a thread other than the one that drops the AtomicLazyCell.
319 ✔️ unsafe impl Send<T: Send> appears sound.
322+ ✔️ skimmed test code

While the use of atomics here is straightforward, in a very classical pattern, and while I'm relatively confident it's all correct, my weakness here downgrades my crev understanding to medium here. This is entirely a reflection on me, and not the code.

TIL

The changelog markdown shows using custom HTML for anchors. I've immediately applied this knowledge to this very review! Doesn't help with VS Code previewing, sadly, but that's a niche need anyways.