diff --git a/doc/src/SUMMARY.md b/doc/src/SUMMARY.md index 9a8023d63908a..bb064448efe87 100644 --- a/doc/src/SUMMARY.md +++ b/doc/src/SUMMARY.md @@ -18,3 +18,4 @@ - [Pointer Arithmetic](./challenges/0003-pointer-arithmentic.md) - [Memory safety of BTreeMap's `btree::node` module](./challenges/0004-btree-node.md) - [Inductive data type](./challenges/0005-linked-list.md) + - [Contracts for SmallSort](./challenges/0008-smallsort.md) \ No newline at end of file diff --git a/doc/src/challenges/0008-smallsort b/doc/src/challenges/0008-smallsort new file mode 100644 index 0000000000000..b0a4a8f743275 --- /dev/null +++ b/doc/src/challenges/0008-smallsort @@ -0,0 +1,54 @@ +# Challenge 8: Contracts for SmallSort + +- **Status:** Open +- **Tracking Issue:** [Link to issue](https://github.com/model-checking/verify-rust-std/issues/56) +- **Start date:** *2024-08-17* +- **End date:** *2024-12-10* + +------------------- + + +## Goal + +The implementations of the traits `StableSmallSortTypeImpl`, `UnstableSmallSortTypeImpl`, and `UnstableSmallSortFreezeTypeImpl` in the `smallsort` [module](https://github.com/rust-lang/rust/blob/master/library/core/src/slice/sort/shared/smallsort.rs) of the Rust standard library are the sorting +algorithms optimized for slices with small lengths. +In this challenge, the goal is to, first prove the memory safety of the public functions in the `smallsort` module, and, second, write contracts for them to +show that the sorting algorithms actually sort the slices. + +### Success Criteria + +Prove absence of undefined behavior of the following public functions. + +1. `::small_sort` +2. `::small_sort` +3. `::small_sort` +4. `slice::sort::shared::smallsort::swap_if_less` +5. `slice::sort::shared::smallsort::insertion_sort_shift_left` +6. `slice::sort::shared::smallsort::sort4_stable` +7. `slice::sort::shared::smallsort::has_efficient_in_place_swap` + +Write contracts for the following public functions that show that they actually sort the slices. + +1. `::small_sort` +2. `::small_sort` +3. `::small_sort` + +The memory safety and the contracts of the above listed functions must be verified +for all possible slices with arbitrary valid length. + +Note that most of the functions listed above call functions that contain loops. +Function contracts and loop contracts of those callee functions may be required. + +### List of UBs + +In addition to any properties called out as `SAFETY` comments in the source +code, +all proofs must automatically ensure the absence of the following [undefined behaviors](https://github.com/rust-lang/reference/blob/142b2ed77d33f37a9973772bd95e6144ed9dce43/src/behavior-considered-undefined.md): + +* Accessing (loading from or storing to) a place that is dangling or based on a misaligned pointer. +* Reading from uninitialized memory. +* Mutating immutable bytes. +* Producing an invalid value + +Note: All solutions to verification challenges need to satisfy the criteria established in the [challenge book](../general-rules.md) +in addition to the ones listed above.