Sample
once_cell 1.21.4: Differentiate lock-free once_cell::race from blocking once_cell::sync across default-features=false configurations, proving race initializers run redundantly under contention while sync initializers run exactly once
Verified sample for cargo once_cell 1.21.4: Differentiate lock-free once_cell::race from blocking once_cell::sync across default-features=false…
sha256:2540d92a67fbf6a1022bea9ae03def3fce5c135fae138bc0e6af3be8d4884445
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
rust linux x64 rust rust cargo
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| rust 1 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-16 |
| rust 1 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · cargo@1 |
2026-08-18 |
Case
HOW- Goal
- Differentiate lock-free once_cell::race from blocking once_cell::sync across default-features=false configurations, proving race initializers run redundantly under contention while sync initializers run exactly once
- Packages
- Symbols
-
- once_cell::race::OnceBox
- once_cell::race::OnceBox::get_or_init
- once_cell::race::OnceNonZeroUsize
- once_cell::race::OnceNonZeroUsize::get_or_init
- once_cell::race::OnceBool
- once_cell::race::OnceBool::get_or_init
- once_cell::race::OnceRef
- once_cell::race::OnceRef::get_or_init
- once_cell::sync::OnceCell
- once_cell::sync::OnceCell::get_or_init
- once_cell::unsync::OnceCell
- Environment
- rust
- Created
- 2026-08-16T08:11:46Z
Contract
- assert once_cell::sync::OnceCell::get_or_init blocks contending threads and executes its closure exactly once, leaving zero losing allocations to drop
- assert once_cell::race::OnceBox::get_or_init executes closures concurrently across all contending threads, discarding and dropping all losing Box allocations while returning the winner
- assert once_cell::race::OnceNonZeroUsize executes its closure redundantly under contention and rejects zero as an invalid sentinel value
- assert once_cell::race::OnceBool manages three distinct states (uninit, false, true) and forbids overwriting once set
- assert once_cell::race::OnceRef initializes static references without heap allocations or destructor overhead
- assert once_cell::unsync::OnceCell is available in core no_std without any cargo feature flags but panics on reentrant initialization
Files
- Cargo.lock
- Cargo.toml
- NOTES.md
- csx.json
- src/lib.rs