Challenge Proposal: Floats/Ints (#58)

Author: carolynzech

doc/src/SUMMARY.md

@@ -22,4 +22,5 @@
   - [Contracts for SmallSort](./challenges/0008-smallsort.md)
   - [Safe abstractions for `core::time::Duration`](./challenges/0009-duration.md)
   - [Memory safety of String](./challenges/0010-string.md)
+  - [Safety of Methods for Numeric Primitive Types](./challenges/0011-floats-ints.md)
   - [Safety of NonZero](./challenges/0012-nonzero.md)

doc/src/challenges/0011-floats-ints.md

@@ -0,0 +1,59 @@
+# Challenge 11: Safety of Methods for Numeric Primitive Types
+
+
+- **Status:** Open
+- **Tracking Issue:** [Link to issue](https://github.com/model-checking/verify-rust-std/issues/59)
+- **Start date:** *2024-08-20*
+- **End date:** *2024-12-10*
+
+-------------------
+
+## Goal
+
+Verify the safety of public unsafe methods for floats and integers in `core::num`.
+
+To find the documentation for these methods, navigate first to the [`core::num` documentation](https://doc.rust-lang.org/core/num/index.html), then click on the appropriate primitive type in the left-side menu bar. For example, for `i8::unchecked_add`, click on `i8`.
+
+## Success Criteria
+
+### Part 1: Unsafe Integer Methods
+
+Prove the absence of arithmetic overflow/underflow and undefined behavior in the following methods for each of the listed integer types, given that their safety preconditions are satisfied:
+
+| Method              | Integer Types |
+| :---           |     :---
+| `unchecked_add`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `unchecked_sub`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `unchecked_mul`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `unchecked_shl`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `unchecked_shr`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `unchecked_neg`  |  `i8`, `i16`, `i32`, `i64`, `i128` |
+
+
+### Part 2: Safe API Verification
+
+Now, verify some of the safe APIs that leverage the unsafe integer methods from Part 1. Verify the absence of arithmetic overflow/underflow and undefined behavior of the following methods for each of the listed integer types:
+
+| Method              | Integer Types |
+| :---           |     :---
+| `wrapping_shl`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `wrapping_shr`  |  `i8`, `i16`, `i32`, `i64`, `i128`, `u8`, `u16`, `u32`, `u64`, `u128` |
+| `widening_mul`  |  `u8`, `u16`, `u32`, `u64` |
+| `carrying_mul`  |  `u8`, `u16`, `u32`, `u64` |
+
+
+### Part 3: Float to Integer Conversion
+
+Verify the absence of arithmetic overflow/underflow and undefined behavior in `to_int_unchecked` for `f16`, `f32`, `f64`, and `f128`.
+
+
+## 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):
+
+* Invoking undefined behavior via compiler intrinsics.
+* 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.